RU2846009C2 - Monitoring system, clamping system with monitoring system and method for monitoring clamping device using monitoring system - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: group of inventions relates to machine building and can be used in clamping quality control systems clamped in clamping device workpiece holder, as well as in clamping system with clamping device and such control system. Control system includes at least two sensors for independent registration of clamping quality of clamped workpiece holder or workpiece itself. Besides, monitoring system has transmitting device and receiving device, wherein the transmitting device is configured in such a way that it transmits the detected or calculated parameter or detected or calculated parameters with redundancy to the receiving device. Invention covers also the method of control over clamping device.

EFFECT: use of inventions improves reliability and safety of clamping.

25 cl, 4 dwg

Description

The present invention relates to a control system made according to claim 1 of the invention, to a clamping system with a control system made according to claim 12 of the invention, and to a method for checking a clamping device using a control system according to claim 19 of the invention.

With the aid of a monitoring system of the type specified here, in particular the clamping devices must be monitored to ensure that the workpiece holder - pallet - clamped by the corresponding clamping device or the workpiece clamped in it is clamped correctly and safely. In particular, it must be possible to make a judgment about the quality of the clamping, whereby the measured parameter or parameters must be transmitted wirelessly to the receiver.

From EP 3 391 991 A a clamping chuck is known which is designed for clamping pallets provided with a clamping pin. The clamping chuck is provided with a receiving opening for the clamping pin and a clamping device having clamping members for clamping the clamping pin in the receiving opening. At least one sensor is arranged on the clamping chuck, by means of which at least one parameter of the clamping chuck and/or the interaction between the pallet and the clamping chuck and/or the pallet can be recorded. The clamping chuck is provided with a transmitter for wirelessly transmitting the parameters detected by the sensor or sensors. The clamping force acting on the clamping pin can be detected by means of the first sensor. For this purpose, the first sensor is designed and arranged on the clamping chuck in such a way that elastic deformations of the material of the clamping chuck can be measured when the pallet is clamped. The clamping chuck can also be provided with a second sensor, by means of which the application of the pallet to the clamping chuck can be detected.

A chuck with a clamping head having three clamping jaws is known from EP 1 998 932 B1. The chuck has a rotationally symmetrical main body with a conical receiving bore for receiving the clamping head. In order to draw the chuck into the receiving bore, an exhaust pipe is provided, which is part of the machine spindle. Such chucks are used in particular on lathes. A first sensor is provided on the outer surface of the chuck body, while a second sensor is located in a recess on the outer surface of the chuck body. Finally, a third sensor is located on the exhaust pipe. The sensors are designed as strain gauges and are provided in each case with an integrated signal processing unit. A transmitter for wireless transmission of the measured values is matched to each signal processing unit. With this design of the chuck, it must be possible to detect the clamping force of the chuck. When the minimum clamping force is reached, maintenance of the chuck must be carried out. The positioning of the workpiece in the axial direction is not monitored and also cannot be determined. There is no message about the presence of the workpiece. In addition, errors that may occur in any case during wireless transmission are not detected.

From EP 2 052 808 A1 a clamping device with a clamping chuck for detachably fixing a workpiece holder is known. The clamping chuck is provided with a locking mechanism which comprises several clamping elements which, in the locked position, act on a clamping pin connected to the workpiece holder. Each clamping element is provided with a through-hole which is closed on one side when the respective clamping element is correctly locked. Additionally or alternatively, an actuator provided with a through-hole is assigned to each clamping element, the through-hole of which is closed on one side when the respective clamping element is correctly locked and/or released. The through-holes of the clamping elements and the actuators are connected to an air source via a common connecting line. At least one sensor for recording the air flow is provided on the connecting line. The sensor can be used to detect whether the clamping elements have been correctly released or locked. The sensor is connected to an electronic control and evaluation device.

Furthermore, a clamping device for a machine tool is known from EP 2 759 372 A1. The machine tool has a rotatable spindle with a tool holder. A clamping device is provided for clamping the tool. In order to detect whether the tool is clamped correctly or incorrectly in the holder, the clamping device has force sensors at various measuring points in order to record the clamping forces that are active in each case at the various measuring points. The force sensors are arranged on a ring-shaped support surface of the holder. The sensors project above the support surface in such a way that they are compressed when the tool is clamped. Thus, on the one hand, it must be possible to record the clamping force and it must be detected whether the tool is clamped correctly or whether there is an incorrect orientation and/or incorrect positioning. SAW sensors (surface acoustic wave sensors) are used as force sensors. The force sensors are arranged on the support surface symmetrically with respect to the central axis of the machine. When the tool is correctly oriented, the force sensors register clamping forces of the same magnitude, while when the tool is clamped at an angle, the force sensors register clamping forces of different magnitudes. The electrical signals from the sensors are transmitted wirelessly to the receiving and transmitting unit and are evaluated in the evaluation unit.

An intelligent multi-element clamping device follows from EP 2 093 016 A1. The clamping device consists of a plurality of clamping jaws arranged on a base plate, wherein in each case one fixed and one movable clamping jaw form a kind of clamping vice. The clamping jaws contain workpiece contact sensors or workpiece contact controllers with forced air, wherein the former are connected via cables to the radio module. The sensors must be able to monitor the correct placement of the workpieces in the clamping jaws.

EP 3 028 804 A1 describes a transmission system, in particular for transmitting energy and/or signals and for use in a machining centre. In this case, signals and voltages are transmitted inductively from a stationary machine bed to a rotating clamping chuck, both in the direction of the clamping chuck and vice versa. The corresponding clamping chuck has clamping jaws, which are supported in the chuck body so that they can be moved by means of an electric motor. The electric motors are switched off when a specified actual position is reached, while the clamping jaws are stopped by means of spring packs and mechanical friction brakes. The electric motors compress the spring packs during the clamping process, so that they apply a clamping force to the clamping jaws. After the electric motors have been switched off, the mechanical friction brakes prevent the clamping jaws from slipping or loosening. In addition, the positions of the clamping jaws are constantly monitored during the machining process in order to detect machining errors or even loosening of the clamped workpiece. In order to be able to continuously monitor the respective operating states or positions of the clamping jaws or electric motors, a plurality of measuring sensors are matched to them, which generate the respective measured data and transmit them by means of inductive transmitters. The inductive transmitters consist of two parts, on the one hand in the rotating clamping chuck and on the other hand in the fixed supporting frame. Both transmitters are aligned coaxially with respect to each other, so that due to the spatial separation of both transmitters, rotation of the clamping chuck is possible, and at the same time measuring signals, measured data and/or voltages for operating the electric motors can be inductively transmitted.

EP 3 620 248 A1 shows a connection device by means of which data can be inductively transmitted from a rotating part to a non-rotatably arranged part. In particular, a clamping chuck rotating during operation must be able to be connected to a control device on the customer's side and monitored by means of the connection device. The clamping chuck has radially movable clamping jaws in order to clamp the workpiece with them. Each clamping jaw is driven by a coordinated electric motor. In order to supply the clamping chuck rotating during the machining process with energy for the clamped workpiece, a first transmission device is provided in the clamping chuck, which is connected via electrical lines to the electric motors and measuring sensors. The position of the clamping jaws and the voltage of the electric motors and their rotational speed are to be measured by means of the measuring sensors. A second non-rotatably arranged transmission device is arranged on the support frame. The measured data are transmitted inductively from the first rotating transmitter to the second transmitter, which is arranged without the possibility of rotation. The second transmitter is connected via electrical lines to the programmable interface. In the version of the clamping chuck, it is provided with two interfaces connected to the second transmitter. Both interfaces receive blocks of measured data from the measuring sensors independently of each other and evaluate them. If the measurement results of both interfaces coincide, the control unit receives a release signal, while in the case of different measurement results, the processing is interrupted or not released.

Finally, EP 2 457 688 A1 discloses a method for positioning and fixing a workpiece. The presence or absence of workpieces or workpiece holders can be determined by means of the steps of the method.

The task of the invention is to create a control system related to the initially indicated field of technology for monitoring the quality of clamping of a workpiece holder clamped in a clamping device or of the workpiece itself, creating conditions for one or more parameters, in particular such parameters that allow a conclusion to be made about the safe clamping of the clamped workpiece holder or of the workpiece itself, on the one hand, to be reliably recorded, and on the other hand, to be reliably transmitted to the receiver without data transmission lines.

The solution to the problem is determined by the features of claim 1 of the invention formula. According to the invention, a monitoring system for monitoring the quality of clamping of a workpiece holder clamped in a clamping device or of the workpiece itself includes at least two sensors for independently recording the quality of clamping of the clamped workpiece holder or of the workpiece itself, wherein the transmitting device is designed in such a way that it transmits the detected or calculated parameter or detected or calculated parameters with redundancy to the receiving device. Due to the fact that at least two sensors are provided for independently recording the quality of clamping of the clamped workpiece holder or of the workpiece itself, errors that could be produced by a single sensor can be detected, for example, by means of a cross-comparison of the measured data. Due to the redundant transmission of the measured data by means of the transmitting device to the receiving device, errors on the transmission path can also be detected and, if necessary, eliminated.

Preferred embodiments and improvements of the control system are described in dependent claims 2-13 of the invention.

Thus, in a preferred development, it is provided that the monitoring system has at least one sensor module, by means of which the measured values present on the sensors are digitalized and transmitted to the transmitting device. Such processing of the measured data increases the reliability and simplifies the transmission of the measured values to the transmitting device. In addition, the corresponding sensor module can, if necessary, also be used to supply a sensor or several sensors.

In the most preferred development of the monitoring system, the transmitting device is provided with two independent microprocessor units, which are configured to independently and redundantly process the measured values transmitted by the respective sensor module in each case. On the one hand, this design helps to immediately detect errors in the measurement and, if necessary, to check whether the measurement is plausible. On the other hand, the different and independent microprocessors can also be programmed differently, which is advantageous with respect to redundant recording and processing of the measured data.

Preferably, the transmitting device includes at least one transmitting antenna for transmitting the measured data processed by two independent microprocessor units. By means of the transmitting antenna, the measured data can be wirelessly transmitted to the receiving device, and the said components can be combined in a compact and energy-saving structural element.

Most preferably, the monitoring system includes at least two sensors that are arranged in such a way that their measured values are positively correlated with each other. This makes it possible to check the measured values in terms of their reliability in the simplest possible way, since the recorded measured values can be compared with each other by means of a cross-comparison.

Most preferably, the monitoring system comprises at least two sensors, which are designed and arranged in such a way that, when the workpiece holder or the workpiece itself is clamped, the elastic deformations of the material of the clamping chuck or the clamping jaw of the clamping device can be measured, wherein the sensors are in particular strain gauge sensors (DMS). Strain gauge sensors are characterized by their high accuracy and good long-term stability, so that, thanks to the said arrangement of the sensors, conclusions can be drawn very easily regarding the clamping force actually present.

A preferred development of the monitoring system serves to monitor a clamping device with at least one clamping chuck, which has a control piston movable in the Z-direction inside for actuating the clamping members for clamping the clamping pin, wherein the monitoring system has at least two sensors operating in a contactless manner, by means of which at least two positions, preferably at least three positions, of the control piston can be recorded independently of one another. This design makes it possible to reliably monitor different states of the clamping chuck by means of two sensors, wherein inductive sensors are used most preferably.

In a particularly preferred development, the monitoring system comprises at least one additional sensor, by means of which the application of the workpiece holder to the clamping device can be detected. By means of such a sensor, it can be detected whether the workpiece holder actually rests in the intended position directly on the Z-supports of the clamping device, or whether it rests on contamination, such as chips, and is therefore incorrectly positioned in the Z-direction.

A further embodiment of the monitoring system serves to monitor the quality of the clamping of the workpiece clamped in the clamping vice of the clamping device, wherein the monitoring system comprises in this preferred example at least two additional sensors, by means of which the positioning of the workpiece on the corresponding guide slide of the clamping vice can be detected. In this way, it can be detected whether the workpiece is clamped correctly or, for example, at an angle.

A further development of the control system also provides for it to be equipped with an additional sensor, by means of which the position of the element used to actuate the clamping members can be detected. This design is particularly important with regard to the automatic approach or automatic retraction of the workpiece holder by the robot, since the said element for actuating the clamping members must be in the initial or open position, so that the workpiece holder can be advanced or retracted.

In the most preferred development, the monitoring system has a receiving antenna for receiving data transmitted by means of a transmitting device and a network gateway connected to the receiving antenna, wherein the network gateway is provided with two independent microprocessor units, by means of which the received data are independently and redundantly further processed in each case, and wherein the network gateway is connected to the control system of the processing machine. This design helps to ensure that the data can be reliably received and transmitted to the control system of the processing machine by means of the network gateway.

In the most preferred development of the monitoring system, the network gateway processes the measured values transmitted by the transmitting device in such a way that, when a match is established between the recorded measured values and when the specified measured values are reached in the machine control system, a signal for a correctly clamped workpiece holder or for a correctly clamped workpiece and/or for safe operation of the processing machine is redundantly transmitted to the machine control system. As a result, safe operation of the processing machine can be ensured, since the enabling signal only occurs if the workpiece holder or the workpiece itself is securely and correctly clamped.

A further object of the invention is to improve the clamping system with a clamping device for clamping a workpiece holder or the workpiece itself and a monitoring system implemented in accordance with one of the preceding claims of the invention in such a way that it can be reliably detected whether the workpiece holder or the workpiece itself is securely clamped.

This problem is solved by means of a clamping system according to claim 14 of the invention formula. Due to the fact that the monitoring system of the clamping system is provided with at least two sensors arranged on the clamping device for independently recording the clamping force acting on the clamped workpiece holder or on the clamped workpiece, the measured values relevant for the safe clamping of the workpiece holder or the workpiece itself are recorded twice and independently of each other. This creates the basic prerequisite that it can be reliably detected whether the workpiece holder or the workpiece itself is safely clamped.

Preferred improvements of the clamping system are defined in dependent claims 15-20 of the invention formula.

Preferably, the clamping system is designed in such a way that the transmitting device of the monitoring system includes a radio transmitter located on the clamping device, and the receiving device a radio receiver located at a distance from it, wherein the transmitting device has two independent microprocessor units, which are configured in order to independently and redundantly process the measured values transmitted by the respective sensor module and to check their plausibility by means of a cross-comparison of the measured data. Thus, already on the side of the transmitter, i.e. in or on the clamping device, a redundant pre-processing of the measured data with respect to their plausibility can be carried out.

According to a particularly preferred embodiment of the clamping system, strain gauges are used as sensors, which are arranged with a force and/or material closure on the clamping chuck or clamping vice of the clamping device in such a way that their signal is essentially proportional to the clamping force. Since strain gauges have a high accuracy and good long-term stability, they are particularly suitable for making an accurate judgment about the clamping force acting on the workpiece holder or the workpiece and thus about the quality of the clamping by measuring the deformation of the material on the clamping chuck or clamping vice.

In a further preferred embodiment of the clamping system, its clamping device has at least one clamping chuck for clamping the workpiece holder, wherein the clamping chuck includes a sensor arranged in the region of the upper side for detecting the overlay of the workpiece holder. With the aid of such a sensor, the exact Z-position of the workpiece holder can be detected, which is important, for example, with regard to possible contamination in the region of the Z-supports.

The most preferred development of the clamping system is provided with a clamping chuck for clamping a workpiece holder provided with a clamping pin, wherein the clamping chuck is provided with a control piston movable between a starting position and a locking position for actuating the clamping members for clamping the clamping pin, and the clamping chuck is provided with an additional sensor for monitoring the position of the control piston. Detection of the position of the control piston is important in particular with regard to the automatic loading of the clamping system by means of a robot manipulator, in particular in order not to cause unwanted damage.

The most preferred embodiment of the clamping system comprises at least two clamping chucks for clamping a workpiece holder, provided with a number of clamping pins corresponding to the number of clamping chucks, wherein each clamping chuck is provided with a control piston movable between a starting position and a locking position for actuating the clamping members for clamping the corresponding clamping pin, and wherein at least one clamping chuck is provided with an additional sensor for monitoring the position of the control piston. Due to the fact that the position of at least one control piston is monitored, a judgment can also be made as to whether the workpiece holder can in principle be advanced or retracted.

In an alternative design of the clamping system, the clamping device is designed as a clamping vice with two clamping jaws, with each clamping jaw being matched with a sensor for detecting the clamping force of the clamped workpiece. Due to the fact that the clamping force is detected by both clamping jaws, a judgment can be made as to whether the workpiece is clamped safely or not.

Finally, a further object of the invention is to improve the method for monitoring the clamping device of a machine tool using a monitoring system implemented in accordance with one of claims 1 to 14 of the invention in such a way that it can be reliably and simply determined whether the quality of the clamping of the clamped workpiece holder or the workpiece itself satisfies a certain specified value, whereby on the basis of the measured values an effect can be exerted on the control system of the machine tool and/or the coordinated robot manipulator.

This problem is solved by means of a method according to claim 21 of the invention formula. Due to the fact that the quality of the clamping of a workpiece holder clamped in a clamping device or of the workpiece itself is detected by means of at least two independent sensors, that the measured data detected by means of the corresponding sensor are compared with each other and checked for plausibility, and that the detected or calculated parameter or parameters are transmitted with redundancy to a receiving device by means of a transmitting device, and that the control system of the processing machine is influenced on the basis of the available measured values, safety can be ensured during the processing of a workpiece clamped on the processing machine by means of a clamping device or a workpiece holder.

Preferred improvements of the method are defined in dependent claims 22-25 of the invention formula.

In the most preferred method, the plausibility check includes a check for the coincidence of the detected and compared parameters after their processing by two independent microprocessor units of the transmitting device. As a result, in addition to the double registration of the measured values relevant for reliable clamping, a redundant evaluation can also be ensured.

In the most preferred improvement of the method, the detected or calculated parameter or the detected or calculated parameters are transmitted by means of a transmitting device with redundancy and in the form of data packets to a receiving device, whereby a check is performed on the receiving side to determine whether the transmitted data are reliable. As a result, it should be possible to detect errors on the radio communication line.

A further preferred method provides that when the detected and compared parameters match and when the specified measured values are reached, a release signal for safe operation is generated by means of a network gateway and is redundantly transmitted to the control system of the processing machine. The release signal therefore only occurs if the conditions necessary for safe operation of the processing machine are met, namely the workpiece holder or the workpiece itself is securely clamped.

Finally, in a particularly preferred development of the method, it is provided that the network gateway issues an enable signal in the form of a binary signal, wherein the enable signal takes the value 1 if the recorded measured values are plausible and reach the setpoint value, and wherein the enable signal takes the value 0 if the recorded measured values are either not plausible or do not reach the setpoint value. In this way, positive safety can be achieved, due to the fact that the enable signal takes the value 1 only if the workpiece holder or the workpiece itself is correctly and securely clamped. In the event of a fault, such as a power failure, the enable signal automatically takes the value 0, which is immediately detected by the control system of the machine and leads to a stop of the machine or at least to an error message.

From the following detailed description and the claims, further preferred embodiments and combinations of features of the invention follow.

The figures used to explain the examples of the drawing implementation show:

Fig. 1 - the first clamping device together with the control device in a schematic representation;

Fig. 2 - the second clamping device together with the workpiece holder and individual components of the control device in a perspective view;

Fig. 3a - section of the clamping device according to Fig. 2 together with the workpiece holder shown in the raised position;

Fig. 3b - a cross-sectional view of the clamping device according to Fig. 3a together with the workpiece holder clamped in it;

Fig. 3c - additional section of the clamping device according to Fig. 2 without the workpiece holder; and

Fig. 4 - a third clamping device, designed in the form of a clamping vice, together with individual components of the testing device in a perspective view.

Fig. 1 shows the clamping device 3 together with the testing device 12 in a schematic representation. The first rectangle 1 schematically indicates the machine room in which the processing machine is located, on which the clamping device 3 is used. The dotted line 2 schematically indicates the clamping system, which includes the clamping device 3 and also part of the testing device 12. The clamping device 3 in this example is a so-called quadruple clamping chuck, in which four clamping chucks 6, 7, 8, 9 are arranged on the base plate 5. Each clamping chuck has a central receiving opening (not shown) for receiving and clamping a clamping pin located on a workpiece holder (not shown). For clamping the clamping pin in the receiving opening, each clamping chuck 6, 7, 8, 9 is provided with a clamping mechanism. The upper side of the four chucks forms the X-Y plane of the chuck, while the so-called Z axis runs perpendicular to it. Since such chucks are known in principle, for example, from EP 3391991 A or DE 102013014036 A1, the corresponding chucks are only shown schematically, and only a few features relevant in connection with the invention are discussed.

The control device 12 includes, in addition to several sensors for recording the quality of clamping of the clamped workpiece holder, a transmitting device 14, as well as a receiving device 21 indicated by a dotted line. In this example, three sensors A1, B1, C1; A2, B2, C2; A3, B3, C3; A4, B4, C4 are matched to each clamping chuck 6, 7, 8, 9, the function of which is explained in even more detail below. The three sensors A1-C1, A2-C2, A3-C3, A4-C4 of each clamping chuck 6, 7, 8, 9 are connected in each case to a sensor module 34, 35, 36, 37, in which the values measured by the corresponding sensors are prepared. Each sensor module is responsible on the one hand for supplying the sensors (strain gauges or Wheatstone measuring bridge, inductive sensors, etc.). On the other hand, an analog-to-digital converter is integrated, which digitizes the analog measuring signals, so that these measuring data can be transmitted digitally via a comparatively small number of lines L1-L4, ideally one line per sensor module 34, 35, 36, 37, to the transmitting device 14. The transmitting device 14 is provided with two independent microprocessor units 15, 16, which perform preliminary processing of the measuring data. Both microprocessor units 15, 16 are preferably provided with different microprocessors, in order to ensure independent and redundant preparation of the measuring data. The transmitting device 14 is further provided with a radio module - a radio transmitter - and a transmitting antenna 17 for wireless transmission of the measuring data. In this example, one transmitting antenna 17 is provided for transmitting the measuring data prepared by both microprocessor units 15, 16. In addition, the clamping system 2 is provided with an acceleration sensor 18, which, as shown here, can be located in the region of the transmitting device 14.

For power supply of the transmitting device 14, a power source 19 is used, preferably in the form of batteries or accumulators, which can be accommodated, for example, in a separate battery compartment in the clamping device 3, whereby neither the batteries nor the battery compartment are shown in more detail. If necessary, a network power supply unit, an inductive power source or a device for converting energy from the environment (energy harvesting) can also be provided.

The receiving device 21, a radio receiver, which is located at a distance from the clamping device 3, includes, in addition to the receiving antenna 22, a network gateway 24 for processing the data. The generally known and used term network gateway denotes a transmission point in the form of a switching device, in particular in the form of a switching device in computer networks. In computer science, a network gateway is understood to be a component (hardware and/or software) that establishes a connection between two systems. The network gateway 24 also has two independent microprocessor units 25, 26 for evaluating the received data. Here, too, the two microprocessor units 25, 26 are preferably equipped with different microprocessors in order to ensure independent and redundant processing of the received measurement data. The different and independent microprocessors can also be programmed with different software, which again serves for reliability.

The receiving antenna 22 is connected via a first cable 23 to a network gateway 24, which in turn is connected via a second cable 27 to a machine control system 28. The machine control system 28 is connected via a third cable 29 to a handling robot 30. The network gateway 24 is also connected via a fourth cable 31 to a service tool 32. Although the network gateway 24 is shown here outside the line 2 symbolizing the clamping system, it also forms a component part of the testing device 12 overall and is matched to the clamping system. With the aid of the handling robot 30, workpiece holders or the workpieces themselves can be fed to or removed from the clamping device 3. The machine control system 28 controls the processing machine on which the clamping device 3 is used. Finally, the service tool serves as a calibration and diagnostic tool. Although the said cables 23, 27, 29, 31 are in advance schematically shown in each case by only one line, the term cable means in this context any type of electrical connection, and it should be understood as both single-core and multi-core electrical lines, as well as several independent lines. Thus, for example, the network gateway 24 is connected by at least two lines to the control system 28 of the machine, as will be explained in more detail below.

The network gateway 24 receives the data transmitted in digital form by the transmitting device 14 via the antenna 22 and evaluates them. For wireless data transmission, a standardized interface is preferably used, such as Bluetooth, ZigBee, or a proprietary radio transmitter in the 2.4 GHz frequency range, whereby Bluetooth Low Energy (BLE) radio technology is most preferably used, as will be explained in more detail below.

On the basis of the transmitted data, the network gateway 24 can recognize the state of the clamping device, such as chuck open, pallet missing, pallet placed, pallet clamped, pallet clamped with a force of 10 kN, etc., and transmit it further to the machine control system 28 or the process control system connected thereto. The machine control system 28 or the process control system can transmit commands to the handling robot 34, for example to move the workpiece holders to the clamping device 3, or to remove the workpiece holders from the clamping device 3. In the event of a malfunction or detection of insufficient mechanical clamping, in particular also during the processing of a workpiece holder clamped on the clamping device 3, the corresponding processing machine can be stopped immediately. In any case, on the basis of the measured values available on the sensors, the control of the processing machine and/or the associated handling robot can be influenced.

Of the three sensors on the clamping chuck 6, 7, 8, 9, the first sensor A1, A2, A3, A4 in each case serves to detect the clamping force with which the clamping pin is clamped in the respective clamping chuck. For this purpose, a sensor based on a strain gauge, hereinafter referred to as DMS, is preferably used, with the aid of which the elastic deformations of the material of the clamping chuck, in particular the housing, can be measured. As a result, a conclusion can be drawn regarding the force with which the clamping pin is drawn into the respective clamping chuck and is correspondingly clamped in it.

In each case, the additional sensor B1, B2, B3, B4 serves on the one hand as a presence monitor for the workpiece holder. On the other hand, the exact Z-position of the workpiece holder can also be detected by means of the corresponding sensor B1, B2, B3, B4. For this purpose, an inductively operating sensor is preferably used, which is arranged in the area of the upper side of the clamping chuck 6, 7, 8, 9 in such a way that it detects the presence or application of the workpiece holder.

In each case, an additional sensor C1, C2, C3, C4 serves to monitor the position of the control piston, which serves to actuate the clamping members. By means of the control piston, the clamping members, the clamping balls, which serve to clamp the clamping pin can be moved radially inward, so that they are applied to the clamping pin with a force lock. If the clamping members are moved radially inward by the control piston, the control piston is in the locking/working position. If the control piston is moved into the starting position, the clamping members are in the opening position, or they can at least be moved back into the opening position. In the opening position of the control piston, the clamping pin can therefore be inserted into the clamping chuck and removed from it, while in the locking position of the control piston, the clamping members are in the clamping position, in which the clamping pin is clamped in the clamping chuck. If the control piston is in the locked position, the clamping pin can neither be inserted into nor removed from the clamping chuck. In such clamping chucks, the control piston is usually driven pneumatically, whereby it is moved pneumatically into the opening position, while it is moved into the locked position by means of a spring force and is held there by self-locking. This has the advantage that the clamping chuck is locked in a state without air pressure, so that the workpiece holder remains securely clamped even without compressed air.

It should be understood that, of course, three sensors should not be provided for the clamping chuck 6, 7, 8, 9, but it may be sufficient to provide one, two or three sensors per clamping chuck according to the requirements. If necessary, it is even sufficient to provide only one sensor in each case on two of the four clamping chucks. In such a case, one sensor would preferably be located on two diagonally opposite clamping chucks 6, 8 or 7, 9 in each case, with the help of which the clamping force with which the corresponding clamping pin is clamped in the clamping chuck can be measured.

Finally, the acceleration sensor 18 serves to determine the position of the clamping device 3. In addition, the movements of the clamping device 3 can also be monitored using the acceleration sensor 18. Thus, for example, vibrations that occur during the processing of the workpiece can be continuously monitored, and if a threshold value is detected to be exceeded, the processing process can be stopped immediately.

The Bluetooth Low Energy (BLE) technology, which is most preferably used for radio transmission, requires very little energy for transmission and has a range of approximately 10 meters. In addition, BLE is an internationally standardized and therefore worldwide applicable radio interface with a frequency of 2.4 GHz. Since BLE is also used, for example, in smartphones, the corresponding components are manufactured in very large series and can therefore be purchased inexpensively. As a result, for example, a smartphone could also communicate with a chuck. This technology therefore has, for example, also many advantages compared to the inductive transmission used in EP 3 028 804 A1.

Some possible operating principles of the control device are explained below.

Example 1

In this example, it is assumed that only one sensor is provided for the clamping chuck 6, 7, 8, 9 in each case, namely the DMS sensor A1, A2, A3, A4 for measuring the existing clamping force.

After the workpiece holder (not shown) has been clamped in the clamping device 3, the data measured by the DMS sensors A1, A2, A3, A4 and digitized in the sensor modules 34, 35, 36, 37 are processed in parallel in both microprocessor units 15, 16 of the transmitting device 14. In this case, the measurement data of the different sensors are processed by both microprocessor units 15, 16 independently of one another and are checked for plausibility by means of a cross-comparison of the measurement data. The measured values available on the four DMS sensors A1, A2, A3, A4 may differ from one another in each case by a maximum of a specified value. If the detected measured values are within a specified tolerance window, the measured values are transmitted by the transmitting device 14 to the receiving device 21. However, if the measured values differ from each other too much, then it can already be detected on the transmitting side that there is an error and, if necessary, an error message can be issued, whereby the measured values can still be transmitted to the receiving device 21.

In addition to the above-mentioned cross-comparison of the measured values, by means of which the reliability of the measured values is determined, the absolute measured value is, of course, also used in order to determine whether the workpiece holder or the workpiece itself is clamped correctly and with the necessary clamping force.

Preferably, the measured or detected data are checked for plausibility before transmission and checked again for plausibility after transmission.

By comparing the positively correlated measurement data, such as the clamping forces measured by the DMS sensors A1, A2, A3, A4, and checking them for plausibility by means of the two microprocessor units 15, 16, a pre-processing of the measurement data can already be carried out in the transmission device 14 and, if necessary, a reduced volume of data can be transmitted to the receiving device 21. If the measurement data are plausible, they are transmitted by the transmission device 14 to the receiving device 21, while an error message is transmitted if plausible measurement data is detected. If necessary, measurement data can also be transmitted in addition to the error message. Either the actual measured values, in particular the clamping force with which the respective clamping pin is clamped in the clamping chuck, can be transmitted, or alternatively a reduced volume of data in the sense of clamping - ok can also be transmitted if the measured values are plausible. If necessary, it may also be sufficient to record and check for plausibility only the measured values of two diagonally opposite sensors. However, due to the fact that the data of all four DMS sensors A1, A2, A3, A4 are detected and checked for plausibility, it can also be established that the workpiece holder has all four clamping pins and none of them is missing.

In order to prevent errors in radio transmission which may arise, for example, due to message corruption, unintentional repetition of messages, incorrect message sequence, loss of messages, time delays in messages, insertion of incorrect information, for example due to a failure or the wrong sender, appropriate precautions must be taken.

Preferably, the measurement data are transmitted redundantly and in the form of digital data packets. In this case, each data packet can be provided with a uniquely identifiable coding, so that the corresponding recognition can be carried out on the receiving side.

On the receiving side, the data packets are received by the antenna and evaluated by both microprocessor units 25, 26 of the network gateway 24. Preferably, the transmitted measurement data are also checked for plausibility on the receiving side by means of a cross-comparison. In addition to the cross-comparison, absolute measurement values must also be used in order to decide whether the clamping is correct or not.

In order to ensure positive safety, in the event of correct clamping being detected, a clamping signal - an enable signal - is generated by the network gateway 24, which is monitored by the machine control system. Correct clamping means that, on the one hand, the plausibility of the existing measured values is detected by means of a cross-comparison, and on the other hand, a specified minimum clamping force is achieved. Preferably, the network gateway issues the enable signal in the form of a binary signal, wherein the enable signal takes the value 1 if the recorded measured values are plausible and reach the specified value, and wherein the enable signal takes the value 0 if the recorded measured values are either not plausible or do not reach the specified value. By means of the two microprocessor units 25, 26 of the network gateway 24, two enable signals with the value 1 are generated independently of one another, if both microprocessor units 25, 26 detect correct clamping. The machine control system is connected by two lines for transmitting the enable signal to the network gateway 24, and only if the enable signal of both lines takes the value 1, the machine control system 28 detects the correct clamping. In this way, the enable signal is transmitted redundantly - twice - to the machine control system 28.

If the network gateway 24 detects that impermissible errors occur on the transmission line, an error is also generated and the enable signal takes the value 0. This would then lead to the machine control system stopping the processing machine. In the event of a fault in the receiving device - the electronics - or another disturbance, such as a power failure or unreliable measured values, the enable signal would also take the value 0, as a result of which the machine control system 28 would stop the processing machine again.

Most preferably, data during wireless transmission is enriched with redundant information in order to detect distortions and/or errors. Thanks to the measures taken, distortions and/or errors can be detected already at an early stage, and not for the first time at the very end.

Although the transmitting device 14 and the receiving device 21 are mentioned in each case, not only is there a one-way transmission of data from the transmitting device 14 to the receiving device 21, but data can also be transmitted in the opposite direction, as explained above.

In any case, by means of the monitoring device according to the invention, the measurement data or parameters relevant for reliable clamping are duplicated, i.e. recorded redundantly, these measurement data are checked on the transmitting side by both independent microprocessor units 15, 16 by means of a cross-comparison for plausibility, then transmitted redundantly, on the receiving side they are again cross-checked and redundantly evaluated by both independent microprocessor units 25, 26 of the network gateway 24 and finally transmitted again redundantly to the control system 28 of the machine. In this way, double security is established at each of these steps, so that ultimately the entire measurement chain, including the wireless transmission, works safely and reliably.

Example 2

In this example, the measurement data of all sensors of the clamping device 3 are recorded. Preferably, in each case, the data of identical sensors are compared with each other and checked for plausibility. Using the DMS sensors, the clamping quality of the clamped workpiece holder can be determined on the one hand in the manner described above. The fundamental point is that the safety-relevant measured values are always compared with each other.

On the other hand, the presence and exact position of the workpiece holder can be detected by means of additional sensors B1, B2, B3, B4. The inductive sensors B1, B2, B3, B4, which are arranged in the region of the upper side of each clamping chuck 6, 7, 8, 9, can measure the exact distance from the workpiece holder to the respective sensor. In this way, it can be detected in particular whether the workpiece holder rests on the clamping device 3 or the Z-support of the respective clamping chuck 6, 7, 8, 9 along the plane, and whether, for example, due to contamination, there is an undesirable distance between the Z-support and the respective support of the workpiece holder, which impairs the machining accuracy of the workpiece clamped on the workpiece holder. In this way, for example, it can be detected whether chips are stuck under the pallet, and as a result the pallet does not rest on the corresponding place, for example by 0.1 mm. If an incorrect workpiece holder placement is detected, an error message is generated and the enable signal is set to 0.

In each case, the additional sensor C1, C2, C3, C4 serves to monitor the position of the control piston used to actuate the clamping elements. Based on the position of the control piston, a conclusion can be drawn as to whether the control piston is in the opening position or the locking position. This information can be used to determine whether the clamping pin can be inserted into the corresponding clamping chuck and/or removed from it. As a result, it can naturally also be decided whether the workpiece holder can be fed in and/or removed by means of the robot. The feeding in and removal of the workpiece holder can only be carried out completely if the control piston is in the opening position.

Finally, the position of the clamping device 3 can be determined using the acceleration sensor 18. In addition, the vibrations of the clamping device 3 can also be monitored using the acceleration sensor 18.

Fig. 2 shows a further embodiment of the clamping device 40 together with the workpiece holder 45 and the individual components of the testing device in a perspective view. The clamping device is designed here in the form of a single clamping chuck 41. This clamping chuck 41 is provided with a central receiving opening 42 for receiving a clamping pin 46 arranged on the workpiece holder 45. In this example, the testing device includes, in addition to the transmitting device 14 arranged on the clamping device 40 and the receiving device 21 arranged at a distance from it, two sensors for detecting the clamping force, a third sensor 43 for detecting the position of the workpiece holder 45, a fourth sensor for monitoring the control piston used to actuate the clamping members and a fifth sensor for detecting the position of the clamping device 40, whereby, apart from the third sensor 43, none of the sensors are visible in the image according to Fig. 2.

The first two sensors used to determine the clamping force are designed as DMS sensors, by means of which the elastic deformations of the material of the clamping chuck 41 can be measured. The third sensor 43 is an inductive sensor located on the upper side of the clamping chuck 41, by means of which the presence or correct application of the workpiece holder 45 can be detected. The fourth sensor is an inductive sensor located inside the clamping chuck, which detects the position of the control piston used to actuate the clamping members, in particular whether the control piston is in the open position or the locked position. Finally, the fifth sensor is an acceleration sensor located on the clamping device 40, by means of which the position and, if necessary, the movement of the clamping chuck 41 can be detected.

The transmitting device 14, as well as the receiving device 21, are designed in principle in the same way as these devices in Fig. 1, whereby it can be seen from this representation that the network gateway 24 is provided with a multi-core cable 27, via which the enable signal can be transmitted further with redundancy to a machine control system, which is not shown. In addition to the multi-core cable 27 for the redundant transmission of the enable signal, additional lines are preferably provided between the network gateway 24 and the machine control system in order to transmit, for example, additional information, such as the chuck is open, the pallet is missing, the pallet is positioned, the pallet is clamped, the pallet is clamped with a force of 10 kN, to the machine control system.

The difference between the testing device according to Fig. 2 and the testing device in Fig. 1 is that it has only two DMS sensors for determining the clamping force, which are arranged on a single clamping chuck 41. Both DMS sensors are arranged on the clamping chuck 41 in such a way that they record measured values that are positively correlated with each other. For this purpose, both DMS sensors are arranged in the region of the upper side of the clamping chuck 41 in such a way that they can repeatedly and accurately record elastic deformations of the material, in particular elastic deformations of the material of the clamping chuck 41, when clamping the workpiece holder 45. In this way, the correct clamping of the workpiece holder 45 on the clamping device 40 can be reliably and safely monitored with the help of both DMS sensors.

In order to monitor the reliable clamping of the workpiece holder 45 on the clamping chuck 41, both of the mentioned DMS sensors are in principle sufficient, since the specified high elastic deformation of the clamping chuck 41 occurs only if a sufficiently high clamping force acts on the clamping pin 46. In any case, if a specified high clamping force acts on the clamping pin 46, it can be safely assumed that the workpiece holder 45 is securely clamped. If the workpiece holder 45 is not clamped or is clamped incorrectly, this can be detected by both DMS sensors, since with incorrect clamping of the workpiece holder 45, the elastic deformation of the clamping chuck 41 is smaller than with correct clamping. The measured values that signal correct clamping can be determined by means of test measurements and calibration of the system and saved. Preferably, the measured values of the DMS sensors are already checked for plausibility in the transmitting device 14 by means of a cross-comparison. If the measured values are valid, they are transmitted by the transmitting device 14 to the receiving device 21. Otherwise, i.e. if the measured values are invalid, an error message is transmitted. If necessary, in addition to the error message, the measured values can also be transmitted. The error message is received by the receiving device 21, and accordingly a signal with the value 0 occurs at both outputs of the network gateway 24, which is detected by the machine control system. If the enable signal takes the value 0, then a possible ongoing machining process is interrupted or cannot be started at all.

If the measured values are plausible, they are transmitted by the transmitting device 14 to the receiving device 21 and evaluated there by both microprocessor units 25, 26. In this case, the existing measured values are compared with a specified value - the calculated value. If both microprocessor units 25, 26 detect that the calculated value is reached, the correct clamping is recognized and the enable signal takes the value 1. This enable signal is transmitted redundantly to the machine control system, preferably via separate lines. If the enable signal takes the value 1, the machining process can be started or continued.

If at least one of the microprocessor units of the receiving device 21 detects that the calculated value is not reached, an incorrect clamping is recognized and the enable signal takes the value 0, which is again detected by the machine control system. In this case, too, the enable signal is transmitted redundantly to the machine control system. As soon as the enable signal takes the value 0, a possible ongoing machining process is interrupted or cannot be started at all.

Thus, in summary, it can be stated that correct clamping is only recognized if the measured values are both reliable and reach the calculated value. In any case, the enable signal only takes the value 1 if both sensors have correspondingly high or specified measured values that differ from each other by a maximum of the specified value. Regardless of the physical design of the lines/cables, it is important that the enable signal is transmitted redundantly.

In addition to the correct clamping of the workpiece holder 45, further states of the clamping device 40 or the clamping chuck 41 can be determined by means of additional sensors. By means of the third sensor 43, it can be detected on the one hand whether the workpiece holder 45 is placed on the clamping chuck 41. In addition, the position of the workpiece holder 45 relative to the clamping chuck 41 can be detected by means of the magnitude of the measuring signal of the third sensor 43, as has already been explained above. By means of the fourth sensor, the position of the control piston used to actuate the clamping members - the clamping balls - can be determined. In particular, it can be detected whether the control piston is in the starting position or the locking position. In the locking position, the clamping members are shifted radially inward, so that they are or can be applied to the clamping pin with a force lock. If the control piston is shifted to the initial position, the clamping members are in the opening position, or they can at least be moved back to the opening position. In the initial position, the clamping pin 46 of the workpiece holder 45 can therefore be inserted into the receiving opening 42 of the clamping chuck 41 or removed from it. The detection of the respective position of the control piston is important in particular in connection with the automatic assembly of the clamping device 40 by means of a handling robot, since a conclusion can be drawn from this whether the workpiece holder 45 can be fed in or removed without damaging the clamping device 40. Finally, the position of the clamping device 40 can be determined by means of a fourth sensor, which is designed as an acceleration sensor. If necessary, the clamping device 40 can also be monitored for existing oscillations/vibrations during the processing of the workpiece by means of the fourth sensor.

The measurement data of the various sensors can be transmitted in the above-described manner with redundancy to the receiving device 21 by means of the transmitting device 14. It should be understood that five sensors do not necessarily have to be present, or that, if five sensors are present, not all measured values, or at least not always all measured values, have to be transmitted to the receiving device 21. In order to recognize a secure clamping of the workpiece holder, it is fundamentally sufficient to evaluate the data of both DMS sensors.

Fig. 3a shows a section through the clamping chuck 41 of the clamping device according to Fig. 2 together with the workpiece holder 45 shown in a raised position. In this representation, a control piston 65 arranged inside the clamping chuck 41 can be seen, which serves to actuate the clamping members 66 designed as balls, by means of which the clamping pin 46 fixed to the workpiece holder 45 can be clamped in the clamping chuck 41. The control piston 65, which can be moved in the Z-direction between the initial position shown and the locking position, is loaded by compression springs in the direction of the locking position, in particular in the direction of the bottom of the clamping chuck.

In this example, the monitoring system has, in addition to two inductive sensors 43, 44 arranged on the upper side of the clamping chuck 41 and two DMS sensors 69, 70 arranged on the upper part of the housing of the clamping chuck 41, two sensors 71, 72 arranged inside the clamping chuck 41 and operating in a contactless manner, by means of which at least two positions of the control piston 65 can be detected. Both sensors 71, 72 are diametrically opposed to each other and measure the distance to the control piston 65. Preferably, inductively operating sensors 71, 72 are used, by means of which at least two, preferably three different positions of the control piston 65 can be detected. By means of the two inductive sensors 43, 44 arranged on the upper side of the clamping chuck 41, the presence or application of the workpiece holder 45 can be detected, while the two DMS sensors 69, 79 measure the elastic deformations of the chuck body and thus make it possible to draw conclusions about the clamping force actually present. The sensors 71, 72 located inside the chuck 41 are fixed and measure the distance to the upper side of the movable control piston 65. Since, when the workpiece holder 45 is raised, there is a comparatively large distance Y1 between the lower side of the workpiece holder 45 and the two inductive sensors 43, 44 located on the upper side of the chuck 41, both inductive sensors 43, 44 detect that the workpiece holder 45 is not mounted.

In order to shift the control piston 65 into the starting position shown in Fig. 3a, it is moved pneumatically upwards against the force of the compression springs. For this purpose, the annular space 68 located below the control piston 65 is loaded with a corresponding excess pressure. In this starting position, the control piston 65 is in contact with the upper stop formed by the upper part of the housing. The clamping chuck 41 is thus in the opening position, in which the clamping pin 46 of the workpiece holder 45 can be inserted into the clamping chuck 41 or removed from it. In the starting position/opening position of the control piston 65, the distance X1 between the control piston 65 and the corresponding sensor 71, 72 is minimal and can be, for example, approximately 0.5 to several millimetres. In this state, the measured value available at the corresponding sensor 71, 72 is recorded in the calibration process and stored as the “opening position”. On both DMS sensors there is a measured value, which is also stored as the “opening position”. Finally, on both inductive sensors 43, 44, located on the upper side of the clamping chuck 41, there is a measured value, which is stored as the workpiece holder “not applied” or “missing”.

Fig. 3b shows the clamping chuck 41 according to Fig. 3a together with the workpiece holder 45 clamped therein in a section. The control piston 65 is here in its locking position, in which it is displaced downwards in the direction of the bottom of the clamping chuck by the force of the compression springs, wherein there is no excess pressure in the annular space 68. When moving downwards, the control piston 65 pushes the clamping balls 66 with its pressure surface located on the inside and slightly conically expanding downwards inwards into the central opening 68 of the clamping chuck 41 until they rest against the shoulder of the clamping pin 46. Thus, the displacement path of the control piston 65 in the direction of the bottom of the clamping chuck is limited by the clamping balls 66 adjacent to the pressure surface of the clamping pin 46. The control piston 65 is held by the force of the springs in the shown locking position, while the clamping pin 46 is held by self-locking.

In the locking position of the control piston 65 shown in Fig. 3b, the distance X2 between the control piston 65 and the respective sensor 71, 72 is significantly larger than the initial position, for example by approximately 1-4 millimetres. In this state, the measured value present on the respective sensor 71, 72 is again recorded in the calibration process and stored as the “correct clamping”. When the workpiece holder 45 is clamped, an elastic deformation of the chuck body is caused by the clamping force acting from the clamping balls 66 on the clamping pin 46, which can be measured repetitively and precisely by both DMS sensors. Finally, at both inductive sensors 43, 44 located on the upper side of the clamping chuck 41, there is a measured value which is stored as the workpiece holder “present” or “on”, since there is a comparatively small distance Y2 between the lower side of the workpiece holder 45 and the two inductive sensors 43, 44 located on the upper side of the clamping chuck 41.

Fig. 3c again shows a section through the clamping chuck 41 according to Fig. 3a without the workpiece holder. Since the clamping pin is not accommodated in the central bore 68 of the clamping chuck 41, the clamping balls 66 can be moved inward by the control piston 65 into the central bore 42 of the clamping chuck 41, so that the control piston 65 can move completely downwards into its end position under the action of the compression springs 67. The prerequisite for this is that the space 68 below the control piston 65 is not pneumatically loaded with a specified excess pressure. In this state, there is a comparatively large distance X3 between the control piston 65 and the corresponding sensor 71, 72, which is larger than the locking position, for example, by approximately 1-4 millimetres. In this state, the measured value present at the respective sensor 71, 72 is again recorded in the calibration process and stored as “incorrect clamping” or “workpiece holder missing”.

With the three shown states of the clamping chuck, the measured values by the sensors 71, 72 can be matched in such a way that the conditions are created for a repeatedly reliable detection of the respective state of the clamping chuck. Preferably, both sensors 71, 72 are calibrated/adjusted for this purpose in three intentionally and precisely achieved states of the clamping chuck 41. In each state of the clamping chuck 41, both sensors 71, 72 must measure at least approximately the same values or reference values, so that an unambiguous matching of the state of the clamping chuck can be made. The measurement data of both sensors are processed independently of one another preferably in the above-described manner by both microprocessor units and are checked for their plausibility by means of a cross-comparison of the measurement data, so that an unambiguous matching of the state of the clamping chuck can be made.

If necessary, the measured values available on both sensors 71, 72 also do not have to be identical, for example in the case where both sensors 71, 72 measure at different locations on the control piston 65, and the measured values must correspond to the values measured in the calibration state. In any case, the sensors 71, 72 could also be arranged at different distances from the control piston 65. The only and extremely important thing is that at least two operating states, preferably three operating states of the clamping chuck 41, can be matched with unambiguous values from both sensors 71, 72, and the operating states can be unambiguously differentiated. The three operating states that must be differentiated are in particular the following:

- the chuck is open,

- the chuck is closed and the workpiece holder is correctly clamped,

- the chuck is closed, the workpiece holder or clamping pin is missing.

However, each operating state is associated not with a fixed individual value, but with a given tolerance window.

It should be understood that both the individual clamping chuck and the clamping device can be provided with various combinations of the above-mentioned sensors. In the simplest case, only two sensors should be provided, the measured values of which are positively correlated with each other. In particular, it may be sufficient to provide two DMS sensors for detecting the elastic deformation of the clamping chuck body or two sensors for monitoring the position of the control piston 65, so that an unambiguous conclusion about the clamping state/operating state of the clamping chuck is possible. Naturally, combinations of the above-mentioned sensors are also possible, whereby inductive sensors located on the upper side of the clamping chuck can also be provided, which transmit information about the position of the workpiece holder.

During operation of the chuck, the enable signal for “chuck open” or “chuck closed and workpiece holder correctly clamped” is generated one way or another only if the measured value of both sensors is within a specified window.

Two sensors for monitoring the position of the control piston can be provided instead of the above-described DMS sensors in order to monitor the safe operation of the clamping chuck. However, if necessary, a combination of two DMS sensors and both sensors serving to monitor the position of the control piston is also possible. If necessary, both inductive sensors located on the upper side of the clamping chuck can also be combined with this.

Fig. 4 shows a further clamping device 49 in a perspective view. The clamping device together with a control system, not shown, again forms a clamping system. The clamping device 49 is here a clamping vice 50, which is essentially known, and which is provided with two movable clamping jaws 51, 52, wherein one clamping jaw 51 is removed in this illustration. The two clamping jaws 51, 52 are driven by a lead screw 60. A workpiece 64, shown schematically, can be clamped between the two clamping jaws 51, 52. The two clamping jaws 51, 52 can be fixed with screws in each case on guide slides 53, 54. In order to fix the workpiece in the clamping vice 50, it is clamped between the two clamping jaws 51, 52. The clamping vice 50 has a stable main body 55, which is provided with two parallel guide rails 56, 57 in the upward direction for guiding the two movable guide slides 53, 54. The clamping vice 50 is provided on its side with a clamping pin 63, fixed to the underside of the main body 55, by means of which it can be fixed on the clamping chuck, as shown in Fig. 2. It should be understood that the clamping vice 50 can also be secured in another way on the processing machine.

The clamping device 49 is provided with a transmitting device (not shown), which has already been explained above. In order to monitor the quality of the clamping of the workpiece clamped between the clamping jaws 51, 52, a DMS is arranged on both guide rails 56, 57 in each case, wherein only one DMS 61 is visible in this illustration. In order to protect the DMS from external influences, a protective cap 62 is provided. Each DMS is arranged at a location on the guide rail 56, 57 in which, when the workpiece is clamped, high forces and correspondingly high elastic deformations of the material occur, which can be measured by DMS sensors. Due to the fact that the DMS sensors are arranged on the guide rails 56, 57, the clamping force can be measured by means of these sensors independently of the clamping jaws used, so that the clamping jaws 51, 52 can be changed without having to change anything in the DMS sensors.

Each guide slide 53, 54 is additionally provided in each case with a sensor 58, 59 for detecting the position of the clamped workpiece. Each sensor 58, 59 is arranged in the outer region of the guide slide 53, 54 in such a way that it measures at right angles to the upward movement direction of the clamping jaws 51, 52, i.e. in the Z-direction, so that the distance between the underside of the clamped workpiece and the respective guide slide 53, 54 can be recorded. Both sensors 58, 59 are arranged diagonally opposite each other. Preferably, the sensors 58, 59 for detecting the position are inductively operating sensors in the form of inductive proximity switches. In this way, it should be possible, for example, to detect workpieces that are clamped at an angle. Due to the fact that the position recognition sensors 58, 59 are arranged on the guide slides 53, 54, the measurement can be carried out with these sensors independently of the clamping jaws used.

The four sensors mentioned, together with the transmitter and the receiver, again form part of the monitoring device. The transmitter is preferably accommodated in a recess arranged in the region of the lower half of the clamping vice. The transmitter and the receiver are designed in principle in the same way as these devices in Fig. 1, so that they will not be discussed in more detail here again. Since the two position recognition sensors 58, 59 are arranged on a movable part - the guide slide - of the clamping vice 50, they are connected by movable cables to the transmitter arranged in the base body 55. The two DMS sensors are connected by normal cables to the transmitter. By means of a cross-comparison of the measurement data available on the two DMS sensors, they can again be mutually checked for plausibility. In this way, with the aid of the two DMS sensors, the quality of the clamped workpiece can be redundantly monitored in the manner described above. In addition to the four sensors mentioned, additional sensors could also be provided, such as, for example, an acceleration sensor located on the clamping vice, with the help of which the position and, if necessary, the movement of the clamping vice can be detected. Additionally, for example, another sensor could also be provided for measuring the distance between the two guide slides 53, 54.

It should be understood that the above-mentioned embodiment examples are not to be regarded as exhaustive or comprehensive. For example, both the transmitting device and the receiving device could be provided with two independent transmitters or receivers for redundant transmission of measured values. For monitoring further parameters, additional sensors can also be provided on the clamping chuck or the corresponding clamping device. For example, a temperature sensor could also be used. The data of the additional sensors could also be transmitted wirelessly by means of the transmitting device. Instead of sensors 71, 72 operating on an inductive basis, ultrasonic sensors, capacitive or optical sensors could, for example, also be provided for detecting the position of the control piston.

On the other hand, “simpler” variants of the monitoring device according to the invention are also entirely possible, in which, for example, only the clamping force is redundantly monitored by two sensors, wherein the clamping force does not necessarily have to be recorded in absolute values and with high resolution, but if necessary it may be sufficient to record and/or monitor the clamping force and transmit it by the transmitting device in stages, for example from two to ten stages. Bidirectional data exchange between the transmitting device and the receiving device is also possible. Thus, for example, software updates can be transmitted from the receiving device to the transmitting device.

In this context, the term clamping quality refers to the relationship between the required clamping force (depending on the dimensions of the part and the machining forces acting on the workpiece during its processing) and the actually measured clamping force or the available measured value.

Some advantages of the control device constructed according to the invention are briefly summarized below:

- The clamping quality between the workpiece holder/workpiece and the clamping device can be reliably monitored and transmitted wirelessly to a remote location;

- The transmitted data can be recorded, stored and evaluated externally;

- With only two sensors, the clamping quality of the clamped workpiece holder or the clamped workpiece can be reliably and safely monitored;

- Parameters can be continuously monitored;

- Measuring certain parameters increases the safety of the production process, in particular continuous monitoring of the clamping force or the retraction force of the clamping pin provides convincing and safety-relevant data;

- By providing two different microprocessors in the transmitting and receiving devices, independent and redundant preparation of measurement data can be ensured;

- The entire measurement chain, including the transmission and evaluation of measurement data, is made reliable and redundant.

LIST OF REFERENCE POSITIONS

1 machine room

2 clamping system

3 clamping device

4

5 base plate

6 first chuck

7 second chuck

8 third chuck

9 fourth chuck

10

11

12 control system

13

14 transmitting device

15 first microprocessor unit

16 second microprocessor unit

17 transmitting antenna

18 acceleration sensor

19 power supply

20

21 receivers

22 receiving antenna

23 first cable

24 network gateway

25 first microprocessor unit

26 second microprocessor unit

27 second cable

28 machine control system

29 third cable

30 manipulation robot

31 fourth cable

32 service tool

33

34 first sensor module

35 second sensor module

36 third sensor module

37 fourth sensor module

38

39

40 clamping device

41 chuck

42 center hole

43 sump presence sensor

44

45 workpiece holder (pallet)

46 clamping pin

47

48

49 clamping device

50 clamping vice

51 clamping jaws

52 clamping jaw

53 guide rails

54 guide rails

55 main body

56 guide rail

57 guide rail

58 first position sensor

59 second position sensor

60 lead screw

61 DMS

62 protective cap

63 clamping pin

64 blank

65 control piston

66 clamping balls

67 compression springs

68 annular space

69 first DMS sensor

70 second DMS sensor

71 first inductive sensor (control piston)

72 second inductive sensor (control piston)

L1-L4 lines (sensor modules)

A1-C4 sensors

Claims (26)

1. A control system intended for monitoring the quality of clamping of a workpiece holder clamped in a clamping device (3, 40, 49) or of the workpiece itself, comprising at least one sensor (A1-C4) located on the clamping device (3, 40, 49) and a transmitting device (14) for wirelessly transmitting the parameters detected by the sensor (A1-C4) to a receiving device (21), characterized in that it has at least two sensors (A1-A4) for independently recording the quality of clamping as the ratio between the required and actually measured clamping force of the clamped workpiece holder or of the workpiece itself, and the transmitting device (14) is designed with the possibility of transmitting the detected or calculated parameter or detected or calculated parameters with redundancy to the receiving device (21). 2. The control system according to claim 1, characterized in that it has at least one sensor module (34, 35, 36, 37) designed with the ability to digitize and transmit to the transmitting device (14) the values measured by the sensors (A1-C4). 3. The control system according to paragraph 2, characterized in that the transmitting device (14) is equipped with two independent microprocessor units (15, 16), which are designed with the possibility of processing independently and with redundancy the measured values transmitted by the corresponding sensor module (34, 35, 36, 37). 4. The control system according to item 3, characterized in that the transmitting device (14) includes at least one transmitting antenna (17) for transmitting measured data processed using two independent microprocessor units (15, 16). 5. A control system according to any one of paragraphs 1-4, characterized in that at least two sensors (A1-A4) are arranged in such a way that their measured values positively correlate with each other. 6. A control system according to any one of paragraphs 1-5, characterized in that at least two sensors (A1-A4) are designed and located with the possibility of measuring elastic deformations of the material of the clamping chuck (6, 7, 8, 9, 41) or the clamping vice (50) of the clamping device (3, 40, 49) when clamping the workpiece holder or the workpiece itself, wherein the sensors are, in particular, strain gauge sensors (DMS). 7. A control system according to any one of paragraphs 1-6, characterized in that it has at least two sensors (71, 72) operating in a contactless manner, configured to independently register at least two positions of a control piston (65) located inside at least one clamping chuck (41) of the clamping device and movable in the Z-direction to actuate the clamping members (66) to clamp the clamping pin (46). 8. The control system according to item 7, characterized in that the sensors (71, 72) are made in the form of inductive sensors with the ability to register at least one opening position and a locking position of the control piston (65). 9. A control system according to any one of paragraphs 1-8, characterized in that it has at least one additional sensor (B1-B4, 43) for monitoring the quality of clamping of the workpiece holder clamped using the clamping device (3, 40), designed with the possibility of detecting the application of the workpiece holder to the clamping device (3, 40). 10. A control system according to any one of paragraphs 1-6, characterized in that it has at least two additional sensors (58, 59) for monitoring the quality of clamping of a workpiece clamped in a clamping vice (50) of a clamping device (49), equipped with two guide slides (53, 54), on each of which a clamping jaw (51, 52) is fixed for clamping the workpiece, designed with the possibility of detecting the imposition of the workpiece on the corresponding guide slides (53, 54) of the clamping vice (50). 11. A control system according to any one of paragraphs 1-10, characterized in that it is equipped with an additional sensor (C1-C4) designed with the possibility of detecting the position of the element used to actuate the clamping organs. 12. A control system according to any one of paragraphs 1-11, characterized in that it has a receiving antenna (22) for receiving data transmitted using a transmitting device (14) and a network gateway (24) connected to the receiving antenna (22), wherein the network gateway (24) is provided with two independent microprocessor units (25, 26) designed with the possibility of independent and redundant processing of the received data, wherein the network gateway (24) is designed with the possibility of connection to the control system (28) of the processing machine. 13. The control system according to item 12, characterized in that the network gateway (24) is designed with the possibility of processing the measured values transmitted by the transmitting device (14) in such a way that, upon establishing a match between the registered measured values and upon reaching the specified measured values in the machine control system, a signal for a correctly clamped workpiece holder or for a correctly clamped workpiece and/or for the safe operation of the processing machine is redundantly issued to the machine control system (28). 14. A clamping system (2) comprising a clamping device (3, 40, 49) for clamping a workpiece holder or the workpiece itself and a control system (12) made according to any one of paragraphs 1-13, which has at least two sensors (A1-A4) located on the clamping device for independently recording the clamping force acting on the clamped workpiece holder or on the clamped workpiece. 15. The clamping system (2) according to claim 14, characterized in that the transmitting device (14) of the control system (12) includes a radio transmitter located on the clamping device (3, 40, 49), and the receiving device (21) - a radio receiver located at a distance from it, wherein the transmitting device (14) has two independent microprocessor units (15, 16), which are designed with the possibility of independently and redundantly processing the measured values transmitted by the corresponding sensor module (34, 35, 36, 37) and checking them for reliability by means of cross-comparison of the measured data. 16. The clamping system (2) according to claim 14 or 15, characterized in that the sensors (A1-A4) are strain gauge sensors which are placed with force closure and/or material closure on the clamping chuck or clamping vice of the clamping device (3, 40, 49) in such a way that their signal is essentially proportional to the clamping force. 17. A clamping system (2) according to any one of claims 14-16, characterized in that the clamping device (3, 40) has at least one clamping chuck (6, 7, 8, 9, 41) for clamping the workpiece holder, which includes a sensor (B1-B4, 43) located in the region of the upper side for detecting the application of the workpiece holder. 18. A clamping system (2) according to any one of paragraphs 14-17, characterized in that it includes a clamping chuck (41) for clamping a workpiece holder (45) provided with a clamping pin (46), wherein the clamping chuck (41) is provided with a control piston movable between an initial position and a locking position for actuating the clamping members for clamping the clamping pin (46), wherein the clamping chuck (41) is provided with an additional sensor for monitoring the position of the control piston, in particular, the clamping chuck (41) is provided with at least two sensors (71, 72) operating in a contactless manner, by means of which at least two positions of the control piston (65) can be recorded independently of each other. 19. A clamping system (2) according to any one of claims 14 to 17, characterized in that it includes at least two clamping chucks (6, 7, 8, 9) for clamping a workpiece holder provided with a number of clamping pins corresponding to the number of clamping chucks, wherein each clamping chuck (6, 7, 8, 9) is provided with a control piston movable between an initial position and a locking position for actuating the clamping members for clamping the corresponding clamping pin, wherein at least one clamping chuck is provided with an additional sensor (C1-C4) for monitoring the position of the control piston, in particular, at least one clamping chuck (41) is provided with at least two sensors (71, 72) operating in a contactless manner, by means of which at least two positions of the control piston (65) can be recorded independently of one another. 20. A clamping system (2) according to any one of paragraphs 14-17, characterized in that the clamping device is made in the form of a clamping vice (50) with two clamping jaws (51, 52), wherein each clamping jaw (51, 52) corresponds to a sensor for detecting the clamping force of the clamped workpiece. 21. A method for monitoring a clamping device of a processing machine, including the use of a monitoring system implemented according to any of paragraphs 1-13, wherein by means of at least two independent sensors (A1-A4) the quality of clamping of the workpiece holder clamped in the clamping device or the workpiece itself is detected, the measured data detected by means of the corresponding sensor (A1-A4) are compared with each other and checked for plausibility, and the detected or calculated parameter or the detected or calculated parameters are transmitted by means of the transmitting device (14) with redundancy to the receiving device (21) and through the network gateway (24) to the control system (28) of the processing machine. 22. The method according to paragraph 21, characterized in that the verification of authenticity includes a verification of the coincidence of the parameters identified and compared with each other after their processing by two independent microprocessor units (15, 16) of the transmitting device (14). 23. The method according to paragraph 22, characterized in that the detected or calculated parameter or detected or calculated parameters are transmitted using the transmitting device (14) with redundancy and in the form of data packets to the receiving device (21), while the authenticity of the transmitted data is checked on the receiving side. 24. The method according to item 23, characterized in that the receiving device (21) includes a network gateway (24), wherein in the event of a coincidence of the detected and compared parameters and upon reaching the specified measured values, an enabling signal for safe operation is created using the network gateway (24) and is redundantly transmitted to the control system (28) of the processing machine. 25. The method according to claim 24, characterized in that a network gateway (24) is used, which issues an enabling signal in the form of a binary signal, wherein the enabling signal takes the value 1 if the registered measured values are reliable and reach a specified value, and wherein the enabling signal takes the value 0 if the registered measured values are either not reliable or do not reach a specified value.