DE20313182U1 - Coordinate measuring machine safety device has capacitive switch in remote control levers to stop moving parts immediately - Google Patents

Abstract

A coordinate measuring machine (10) safety device has a capacitive sensor in the remote control (38) levers (40, 42) with switch to stop the moving parts (14, 16, 18) when the control is not in use and so immediately enter a predetermined rest state.

Description

WITTE, WELLER & PARTNER

Patent attorneys

Rotebühlstraße 121 D-70178 Stuttgart

Applicant:

Carl Zeiss 89518 Heidenheim Germany

July 1, 2003
6409G100 - AW/ad

Coord inatenmes s device

The innovation concerns a coordinate measuring machine with movement units, with a manually deflectable control lever for controlling the travel path of the movement units, and with a safety device for stopping the movement units when the control lever is in a predetermined rest state.

·

·

DE 198 09 690 A1 describes a coordinate measuring machine with a gantry design. In this known coordinate measuring machine, the movement units, i.e. the gantry, the cross slide and the spindle, are moved in the three usual coordinate directions y, x and z, depending on a control console that is equipped with control levers that can be deflected by hand.

With such coordinate measuring machines, it is common practice to convert the respective deflection of the control lever into a speed of the corresponding movement unit that is proportional to the deflection.

Especially with coordinate measuring machines where the movement units are controlled by means of manually deflectable control levers located on an external console, it can happen that the control lever is deflected unintentionally, for example if a person walking past the console accidentally bumps into the control lever. In this case, the corresponding movement unit would immediately start moving, which in turn could lead to an accident if someone happens to be in the immediate vicinity of this movement unit. In addition, damage can occur in this way if the corresponding movement unit collides with a workpiece or another stationary object as a result of an unintentional deflection of a control lever.

In order to prevent such unintentional movement of the movement units and in particular of the sensitive probe, and to avoid endangering persons, safety

safety devices on such coordinate measuring machines. In known safety devices, the function of the control levers is switched off via software and the speed of the movement units is set to zero if no change in the movement speed of the coordinate measuring machine's probe head is detected within a defined time (so-called "time-out"). If the movement units have been stopped after the defined time has elapsed, any subsequent deflection of the control levers has no effect, regardless of whether this is intentional or unintentional. The coordinate measuring machine's probe head can then no longer be set in motion. Instead, in order to be able to move the probe head again, the control levers must be reactivated by the user. This is done by a predetermined action by the user, for example pressing a defined button.

These known safety devices have several disadvantages. Firstly, the above-mentioned reactivation after a previous shutdown is generally perceived by users as not very ergonomic and therefore annoying. Secondly, the concept of known safety devices described above can lead to an unintentional shutdown of the movement units. If the deflection of the control lever is converted into a speed proportional to the deflection in the manner already mentioned, a user must constantly hold the control lever at maximum deflection if the probe is to be moved from one end of a long axis to the opposite end, i.e. over a long distance. Since the travel speeds of the movement units are relatively low,

This long travel distance may also require a long period of time, which may be longer than the specified "time-out". However, since the probe is moved at a constant, i.e. unchanging, speed during this time, the safety device detects a safety case and switches off the movement units.

Another control unit for an industrial robot is known from DE 33 21 796 C2. In this known unit, a control lever is used to control a movement of the robot. Next to the control lever there is a cover plate on which the user places his hand when he operates the control lever. The cover plate is equipped with a microswitch, strain gauges or a capacitive sensor. The arrangement is such that the function of the control lever is blocked if the user's hand is not resting on the cover plate, for example by interrupting the power supply to the drive systems for the robot's drive motors.

However, this known arrangement has the disadvantage that it requires the user's hand to be in a certain position. In order to be able to control the robot over a longer period of time using the control lever, the user must constantly rest his hand on the cover plate in order to keep the microswitch or similar constantly activated. This leads to tension in the user's hand, especially when working for a longer period of time, and is therefore not ergonomic.

The innovation is based on the task of developing a coordinate measuring machine of the type mentioned above in such a way that the disadvantages mentioned above are avoided. In particular, a much more ergonomic safety circuit for a coordinate measuring machine is to be achieved, which is derived directly from the user's actions without forcing him to adopt an unnatural position in the area of his hand.

In a coordinate measuring machine of the type mentioned at the outset, this object is achieved according to the innovation in that the safety device contains a sensor arranged in the control lever and a switching unit controlled by the sensor, wherein the sensor generates a first signal when the control lever is grasped by a user and the switching unit releases the movement units when the first signal occurs.

The innovation has the advantage that the control lever is no longer reactivated by pressing a specific button or similar, but rather by touching the control lever with the user's hand. The safety device also responds immediately in that when the user removes their hand from the control lever, the activation of the movement units is terminated and they are thus brought to a standstill. In contrast to the state of the art explained above, a "time-out" does not have to elapse before the safety function is activated.

Because a touch of the control lever itself is sufficient, it does not matter how the user holds his hand when touching the control lever, so that the hand does not cramp because a specific hand position is not required.

In practical implementations of the innovation, two alternatives are preferred.

According to a first alternative, the control lever contains switching means for generating a second signal corresponding to its deflection, wherein the switching means are connected to an input of the switching unit and the second signal is forwarded to the movement units only when the first signal occurs at an output of the switching unit.

This design has the advantage that conventional control levers of coordinate measuring machines can be easily replaced in order to achieve the advantages of the innovation. It is therefore not necessary to intervene in the control software of the coordinate measuring machine.

This is especially true if the switching unit is integrated into the hand lever.

In this case, all that really needs to be done is to replace the hand lever to transform a conventional coordinate measuring machine into an innovative coordinate measuring machine.

According to the second of the two variants mentioned, the control lever contains switching means for generating a second signal corresponding to its deflection, wherein the switching means are connected to a drive control for the movement units, and the switching unit enables the drive control only when the first signal occurs.

This measure has the advantage that various safety functions can be implemented by intervening in the control software, for example a delayed response and the like, although this involves a certain amount of additional effort.

In this second embodiment, it is preferred if the switching unit is integrated into the drive control.

This measure has the advantage that the switching unit can be implemented either as hardware or as software to realize various safety functions.

Within the scope of the innovation, it is further preferred if the hand lever has a hollow handle and a sensor of the sensor is arranged in a hollow space of the handle.

This measure has the advantage that the "hand lever gripped" state can be reliably detected through simple structural measures.

Although a wide variety of sensors can be used within the scope of this innovation, it is preferred if the sensor is a capacitive sensor.

This measure is particularly advantageous if an electrode insulated from the handle is arranged in the cavity and the sensor has means for measuring a current between the electrode and the handle, which current is generated by charge displacement when the handle is touched.

This measure has the advantage that it is possible to distinguish with a high degree of certainty between a touch by a person and a touch by an object. While touching the handle with the user's hand results in a charge current flowing as a result of the leakage resistance of the human hand, this is not the case if the control lever is accidentally touched and deflected by an object moving past, for example.

Finally, according to the innovation, it is particularly preferred if the sensor is adjustable in its sensitivity.

This measure has the advantage that the safety function mentioned can be adapted to different users. It is also possible to clearly differentiate whether a user touches the hand lever with their bare hand, with a thin glove or - usually accidentally - with their elbow when it is covered with a normal piece of clothing, such as a suit jacket. In this case, by adjusting the sensitivity, a certain range can be defined within which the sensor still responds (bare skin or bare skin covered with thin fabric on the one hand and skin covered with thick fabric on the other).

Further advantages are apparent from the description and the attached drawing.

It is understood that the features mentioned above and those to be explained below are not only available in the combination specified, but also in other combinations

or can be used alone without departing from the scope of the present innovation.

An example of the innovation is shown in the drawing and is explained in more detail in the following description. Shown are:

Fig. 1 is a highly schematic, perspective view of an embodiment of a coordinate measuring machine according to the invention;

Fig. 2 shows, on a scale greatly enlarged compared to Fig. 1, a side view, in section, through a hand lever as can be used in a coordinate measuring machine according to the innovation.

In Fig. 1, 10 designates a coordinate measuring machine in a conventional gantry design. The coordinate measuring machine 10 has a measuring table 12 on which a gantry 14 can move longitudinally along a y-axis. On top of the gantry 14 there is a cross slide 16 which can be moved along an x-axis. The cross slide 16 in turn carries a spindle which allows movement in the z-direction. By means of incremental scales 20, 22, 24 and travel drives (not shown), a movement in the three coordinate directions y, x and z can be represented.

At the lower end of the sleeve 18 there is a probe unit 26 with a probe head 28 and a probe 30 formed at its lower end.

The coordinate measuring machine 10 is used to measure a workpiece 32, which is attached to the measuring table 12, for example via a pallet 34.

A control unit 36 is used to control the aforementioned movement units, namely the portal 14, the cross slide 16 and the sleeve 18, which in turn is supplied with control signals from a control panel 38. The control panel 38 has one or more control levers 40, 42.

By deflecting the control levers 40, 42, the movement units 14, 16 and 18 can be moved in the three coordinate directions y, x and z. This is usually done by forming a value proportional to the deflection of the control lever 40 and converting it into a travel speed of the movement units 16, 18 and 20 that is also proportional to it.

The purpose of this innovation is to prevent an unintentional actuation of the control levers 40, 42 from triggering an equally unintentional movement of the movement units 14, 16 and 18.

For this purpose, the control levers 40, 42 are designed as shown in Fig. 2 on an enlarged scale and very schematically for the control lever 40.

The control lever 40 is provided at its upper end with a handle 50, for example in the shape of a ball. The handle 50 is connected to a tube 52 which is held in a gimbal suspension 54 for approximately half of its length.

A double arrow 55 indicates that the control lever 40 can be pivoted from right to left and vice versa in the plane of the drawing in Fig. 2, but also in a direction perpendicular to the plane of the drawing or obliquely thereto.

At the lower end of the tube 52 there is a sensor 56 which works together with several sensors 58a, 58b. The sensors 58a, 58b are fixed to the housing, as is the gimbal 54. The structure consisting of the sensor 56 and sensors 58a, 58b can be of any type, i.e. inductive, capacitive, optical or similar. The purpose of this arrangement is to obtain a signal proportional to the deflection of the control lever 40.

The handle 50 is hollow. In its hollow space 60 there is an electrode 62, which is also almost spherical in shape. The electrode 62 is electrically insulated from the handle 50. A cable 64 leads from the electrode through the tube 52 and then laterally out of the tube 52 to an evaluation unit 66. The evaluation unit 66 is connected via a line 67 to a control input of a switching unit 68. An input of the switching unit 68 is connected via the line 69 to the sensors 58a, 58b. A further line 70 leads from the output of the switching unit 68 to a central control of the coordinate measuring machine 10.

The operation of the arrangement according to Fig. 2 is as follows:

If a user touches the handle 50 with his bare hand, it is connected to ground via the resistance of the user's body. A differential current then flows.

· t ·

The application current is passed through the electrode 62 and the cable 64 to the evaluation unit 66. As long as the user holds the handle 50 with his bare hand, a certain signal level is present at the output of the evaluation unit 66. This signal level is sufficient to control the switching unit 68 via the line 67 in the sense that a switch is closed. When the switch is closed, the signals generated by the sensors 58a, 58b, which are proportional to the deflection of the control lever 40, can be forwarded to the central control for the movement units 16, 18 and 20 of the coordinate measuring machine 10.

As soon as the user releases the handle 50 of the control lever 40, the level of the evaluation unit 66 drops back to zero and the switch in the switching unit 68 is opened. The signal flow from the sensors 58a, 58b to the central control unit is then interrupted and the travel units 14, 16 and 18 remain stationary.

The sensitivity of the arrangement of handle 50 and electrode 62 with the evaluation unit 66 is preferably adjustable, so that the arrangement can also be set so that the switching unit 68 is released even if the user is wearing a thin glove, for example, while on the other hand no release occurs if the user touches the handle 50 with his elbow, for example, while wearing a jacket or a sweater. In this way, certain states can be differentiated precisely.

It is understood in this context that the arrangement shown in Fig. 2 with a handle 50 and an electronic

trode 62 is only to be understood as an example. In this area, sensors of the most varied types can of course be used. Particularly preferred are sensors of a type that automatically detect the gripping piece 50 without, for example, a switch having to be operated. This can also be done inductively, by optical reflection or the like.

For the processing of the two signals, namely from the electrode 62 and from the sensors 58a, 58b, essentially two concepts are preferred:

In a first concept, the entire arrangement shown in Fig. 2 is integrated into the control lever 40. This creates a unit in which the signals proportional to the deflection of the control lever 40 are only emitted (via line 70) when the control lever 40 is deflected in a defined manner, i.e. usually by grasping it with the bare hand. This alternative makes it possible to simply replace the control lever in existing coordinate measuring machines in order to implement the advantages achievable through this innovation.

In a second alternative, the evaluation unit 66 and the switching unit 68 are located in the central control unit, for example the control unit 36 according to Fig. 1, in which case the evaluation unit 66 and the switching unit 68 are preferably located in the control panel 38. The signal from the electrode 62 is then processed by software. If the control lever 40 delivers a signal that corresponds to a deflection, the software recognizes from the presence or absence of a signal from the electrode 62 whether the deflection of the control lever is due to the

The signals are then linked via software that allows for different security concepts, such as delayed response, response tailored to the user, and so on. However, with this second variant, the control of the coordinate measuring machine must be intervened in, which is not the case with the first variant.

Claims (9)

1. Coordinate measuring machine with movement units ( 14 , 16 , 18 ), with a manually deflectable control lever ( 40 , 42 ) for controlling the travel path of the movement units ( 14 , 16 , 18 ), and with a safety device for stopping the movement units ( 14 , 16 , 18 ) when the control lever ( 40 , 42 ) is in a predetermined rest state, characterized in that the safety device contains a sensor ( 62 , 64 ) arranged in the control lever ( 40 ) and a switching unit ( 68 ) controlled by the sensor ( 62 , 64 ), wherein the sensor ( 62 , 64 ) generates a first signal when the control lever ( 40 ) is grasped by a user and the switching unit ( 68 ) stops the movement units ( 14 , 16 , 18 ) is activated. 2. Coordinate measuring machine according to claim 1, characterized in that the control lever ( 40 ) contains switching means ( 56 , 58a , 58b ) for generating a second signal corresponding to its deflection, that the switching means ( 56 , 58a , 58b ) are connected to an input of the switching unit ( 68 ), and that the second signal is forwarded from an output of the switching unit ( 68 ) to the movement units ( 14 , 16 , 18 ) only when the first signal occurs. 3. Coordinate measuring machine according to claim 2, characterized in that the switching unit ( 68 ) is integrated into the hand lever ( 40 ). 4. Coordinate measuring machine according to claim 1, characterized in that the control lever ( 40 ) contains switching means ( 56 , 58a , 58b ) for generating a second signal corresponding to its deflection, that the switching means ( 56 , 58a , 58b ) are connected to a drive control for the movement units ( 14 , 16 , 18 ), and that the switching unit ( 68 ) enables the drive control only when the first signal occurs. 5. Coordinate measuring machine according to claim 4, characterized in that the switching unit ( 68 ) is integrated into the drive control. 6. Coordinate measuring machine according to one or more of claims 1 to 5, characterized in that the hand lever ( 40 ) has a hollow handle ( 50 ), and that a sensor of the sensor ( 62 , 64 ) is arranged in a hollow space ( 60 ) of the handle ( 50 ). 7. Coordinate measuring machine according to one or more of claims 1 to 6, characterized in that the sensor ( 62 , 64 ) is a capacitive sensor. 8. Coordinate measuring device according to claim 6 and 7, characterized in that an electrode ( 62 ) insulated from the handle ( 50 ) is arranged in the cavity ( 60 ) and that the sensor ( 62 , 64 ) has means for measuring a current between the electrode ( 62 ) and the handle ( 50 ), which current is generated by charge displacement when the handle ( 50 ) is touched. 9. Coordinate measuring machine according to one or more of claims 1 to 8, characterized in that the sensor ( 62 , 64 ) is adjustable in its sensitivity.