AT526711B1 - Hydraulic drive unit for a forming machine - Google Patents

Abstract

Shaping machine, in particular injection molding machine, with a hydraulic drive unit comprising a piston (4) arranged in a cylinder (3) so as to be linearly displaceable and a pressure chamber (5) in the cylinder (3) delimited by the piston (4), at least one pressure sensor (6) which is designed to detect a signal characteristic of the pressure in the pressure chamber (5), and a computing unit (7) which is signal-connected to the at least one pressure sensor (6) in order to receive the characteristic signal, wherein the computing unit (7) is designed to determine a kinematic parameter, preferably a position and/or a change in position, of the piston (4) on the basis of the signal characteristic of the pressure in the pressure chamber (5), wherein the pressure chamber (5) cooperates with a constant pressure medium mass, preferably hydraulic fluid mass, at least during the measurement of the characteristic signal.

Description

Description

[0001] The present invention relates to a forming machine with a hydraulic drive unit having the features of the preamble of claim 1, a method for monitoring a forming machine with a hydraulic drive unit and a computer program product for monitoring a forming machine with a hydraulic drive unit.

[0002] Shaping machines can be understood to mean injection molding machines, transfer presses, presses and the like. Shaping machines in which the plasticized molding compound is fed into an open mold are also quite conceivable.

[0003] In the following, the state of the art will be outlined using an injection molding machine as an example. The same applies generally to molding machines.

[0004] Generic hydraulic drive units for an injection molding machine comprise

- a piston arranged in a cylinder so as to be linearly displaceable and a pressure chamber in the cylinder delimited by the piston,

- at least one pressure sensor which is designed to detect a signal characteristic of the pressure in the chamber and

- a computing unit which is signal-connected to the at least one sensor for receiving the characteristic signal.

[0005] Embodiments known from the prior art are disclosed, for example, in DE 10310300 A1, US 2015/167700 A1, DE 10 2020 200104 A1, DE 10 2007 024794 A1 or DE 10 2014 004879 A1.

[0006] In injection molding machines, drive movements are often implemented by hydraulic drive units, which are usually realized via hydraulic cylinders.

[0007] For this purpose, it is almost always necessary to detect or know in some way the position of the injection molding machine part moved by the hydraulic drive unit.

[0008] For simple applications, it is usually sufficient to detect the end position of a movement axis via limit switches, whereby a limit switch detects exactly one position (usually the end position) of the injection molding machine part or the drive unit.

[0009] However, this only allows two functions to be implemented and monitored, whereby on the one hand it can be detected whether the injection molding machine part has reached a certain position and on the other hand whether the injection molding machine part remains in this position during the ongoing monitoring.

[0010] Such limit switches usually have to be mounted externally and are usually actuated by the moving injection molding machine part.

[0011] However, for many movements it is necessary to detect and monitor the constant and accurate knowledge of the absolute position, whereby various types of displacement sensors are usually known from the state of the art.

[0012] By means of appropriate displacement sensors, the following feedback is provided to an injection molding machine control and/or the following options are created for the injection molding machine:

- reaching a desired target position,

- Monitoring of specific positions,

- Speed regulation and/or control depending on a position, and

- Force regulation and/or control depending on the position.

[0013] Typically, clean acceleration and/or deceleration profiles as well as precise positions can be realized in such systems.

[0014] In most cases, linear displacement sensors must be parallel to the moving injection

casting machine part (or the drive unit) and sensor elements must be arranged over the entire length of movement in order to be able to detect the position.

[0015] However, corresponding position measuring systems are complex to install and are associated with high costs due to the high manufacturing effort and material expenditure.

[0016] A further disadvantage is that corresponding position measuring systems require space for corresponding hydraulic drive units and are therefore often difficult to access in even small installation spaces, which makes them difficult to assemble, disassemble and maintain.

[0017] In addition, these position measuring systems, which are arranged externally on the hydraulic drive units, are exposed to environmental influences, which means that the very precise measuring systems in particular are exposed to an increased risk of damage.

[0018] The object of the present invention is to provide a hydraulic drive unit which enables a kinematic parameter of the hydraulic drive unit to be recorded more easily and/or has a smaller space requirement and/or requires less maintenance, installation or disassembly work and/or is easier to manufacture and/or enables a kinematic parameter recording of the hydraulic drive unit due to fewer components.

[0019] This object is achieved according to the invention by a shaping machine with a hydraulic drive unit having the features of claim 1, a method for monitoring a shaping machine with a hydraulic drive unit having the features of claim 14 and a computer program product for monitoring a shaping machine with a hydraulic drive unit having the features of claim 15.

[0020] According to the invention, it is provided that a shaping machine, in particular

an injection molding machine with a hydraulic drive unit comprising:

- a piston arranged in a cylinder so as to be linearly displaceable and a piston chamber in the cylinder delimited by the piston,

- at least one pressure sensor which is designed to detect a signal characteristic of the pressure in the pressure chamber and

- a computing unit which is signal-connected to the at least one sensor for receiving the characteristic signal,

wherein the computing unit is designed to calculate, on the basis of the pressure in the pressure chamber

characteristic signal a kinematic parameter, preferably a position and/or

a change in position of the piston, whereby the pressure chamber is at least

during the measurement of the characteristic signal with a constant pressure media mass, preferably

preferably hydraulic fluid mass and/or a gas.

[0021] When the piston changes its position, the volume of the pressure chamber formed by the piston and the cylinder is changed, resulting in a change in pressure of a pressure medium mass, fluid and/or hydraulic oil present in the pressure chamber. Due to this pressure change and the known behavior of the pressure medium mass, fluid and/or hydraulic oil present in the pressure chamber (for example the compressibility), the change in volume can be calculated via the pressure variation.

[0022] Since the piston and the cylinder have known geometric dimensions, a linear displacement of the piston can be calculated taking into account the change in volume, whereby the kinematic parameter, preferably a position and/or a change in position, of the piston can be determined by the computing unit.

[0023] Thus, it is no longer necessary to provide position measuring systems, limit switches or similar sensors in order to detect a kinematic parameter of the piston, since the kinematic parameter can be calculated simply by arranging a pressure sensor on or in the pressure chamber.

[0024] This has the enormous advantage that significantly fewer parts, components or modules of the sensor system are required to determine the kinematic parameters of the piston, which not only reduces costs but also the effort required for assembly, disassembly and/or maintenance.

[0025] Furthermore, an advantage is created in that the installation space can be significantly reduced since no separate sensors have to be arranged on the hydraulic drive unit.

[0026] A pressure sensor can be integrated and/or screwed into the hydraulic drive unit, whereby the pressure sensor is also protected from environmental influences and is not exposed to external damage.

[0027] The pressure in the pressure chamber is therefore particularly preferably measured directly.

[0028] A hydraulic medium can be present in the pressure chamber, the pressure of which is measured by means of the pressure sensor. In other embodiments, a gas or another compressible fluid can be present in the pressure chamber, the pressure of which is detected by means of the pressure sensor (for example in embodiments in which the pressure chamber itself is an integrated hydraulic accumulator).

[0029] A device according to the invention and a method according to the invention can be used and subsequently installed by their use in already known embodiments of the prior art, as described for example in the introduction to the description.

[0030] Shaping machines can be understood to mean injection molding machines, transfer presses, presses and the like. Shaping machines in which the plasticized molding compound is fed into an open mold are also quite conceivable.

[0031] The computing unit may be physically part of the hydraulic drive unit or may be connected to the hydraulic drive unit via a remote data transmission connection.

[0032] In the latter case, the computing unit could be realized by a computer server or a set of computers (distributed computing).

[0033] The same applies to a control or regulating device of a forming machine. [0034] Advantageous embodiments are defined by the dependent claims.

[0035] It can be provided that a hydraulic fluid mass, preferably a hydraulic oil, or also a gas mass (for example nitrogen, air or other gases) is used as the pressure medium mass.

[0036] Preferably, it can be provided that at least during the measurement of the characteristic signal, the pressure chamber in the cylinder is closed and preferably encloses a constant pressure medium mass.

[0037] It can be provided that during the measurement of the characteristic signal the pressure chamber is connected to a hydraulic accumulator via a connecting line, preferably wherein a constant pressure medium mass is enclosed by the pressure chamber, the connecting line and the hydraulic accumulator.

[0038] Thus, it can preferably be provided that during the measurement of the characteristic signal, a pressure loading or pressure relief of a precisely defined pressure medium mass is carried out, so that the volume variation of the pressure medium mass and thus a kinematic parameter of the piston can be determined in a simple manner via the pressure variation during the measurement by means of the pressure sensor.

[0039] It could of course also be provided that the pressure chamber cooperates with a non-constant pressure medium mass, whereby the kinematic parameter can still be determined by precisely defining the system, whereby, however, the variations of the system can be determined by complex processes due to flow conditions for the pressure medium mass (for example

pressure variation taking into account passage cross sections and flow velocities).

[0040] Even designs in which reference pressures for defined kinematic parameters are first determined and stored, whereby the computing unit uses the corresponding stored kinematic parameter when a pressure is measured, are quite conceivable.

[0041] However, it can be particularly preferably provided that the pressure chamber is connected to a hydraulic accumulator, for example a bladder accumulator, wherein the pressure chamber and the hydraulic accumulator (of course together with the connecting line of these) inject a constant pressure medium mass, wherein in the event of a pressure variation of the pressure medium mass, taking into account a compression behavior of the pressure medium mass, it is possible to deduce in a simple manner a volume change and thus a kinematic parameter of the piston.

[0042] By providing a hydraulic accumulator, in particular a bladder accumulator, the compression behavior of the system can be influenced, whereby, for example, when using hydraulic fluid, the limited compression capacity of the fluid can be expanded to the extent that larger volume changes in the pressure chamber are permitted by escaping into the hydraulic accumulator, so that the method according to the invention and/or the device according to the invention can also be used, for example, in hydraulic cylinders with high freedom of movement - drive movements.

[0043] It can be provided that the computing unit is designed to determine the kinematic parameter by means of a relationship with the pressure stored in the computing unit, preferably taking into account a stored compression behavior of the drive unit.

[0044] The compression behavior of the drive unit may relate to the compressibility of the printing media mass, alternatively or additionally taking into account the geometric dimensions of the volumes in which the printing media mass is enclosed.

[0045] When providing a hydraulic accumulator, the compression behavior, the compression ratio of the system between two measurements and/or the back pressure of the hydraulic accumulator can also be taken into account in the compression behavior of the drive unit.

[0046] It can be provided that the drive unit has a hydraulic accumulator, preferably a bladder accumulator and/or diaphragm accumulator, particularly preferably with a variable compression ratio and/or variable back pressure.

[0047] It can be provided that the hydraulic accumulator is designed as a mechanical, preferably spring-operated, and/or fluid-operated hydraulic accumulator.

[0048] A fluid-operated hydraulic accumulator (for example a bladder accumulator) can preferably have a gas (particularly preferably nitrogen, air or other gases) as the actuating medium.

[0049] Preferably, it can be provided that the piston divides the cylinder into the (first) pressure chamber and a second pressure chamber.

[0050] It can be provided that the drive unit has a pressure source, in particular at least one pump, preferably which pressure source is connected or connectable to the second pressure chamber in order to apply the pressure to the second pressure chamber.

[0051] It can be provided that the pressure source is connected to the second pressure chamber via a valve, preferably which valve can be controlled or regulated by a control or regulating device.

[0052] It can be provided that the computing unit is signal-connected to a control or regulating device of the pressure source and/or is designed as an integral component of the control or regulating device, wherein the kinematic parameter can be used as an actual value by the control or regulating device for controlling or regulating the pressure source.

[0053] It can be provided that the cylinder with the piston arranged therein is designed as a double-acting piston-cylinder unit.

[0054] Preferably, it can be provided that the pressure chamber is designed as a rod-side chamber of a piston-cylinder unit.

[0055] It can be provided that the at least one drive unit is designed to drive a locking nut relative to a bar and/or as a pressure cushion for building up the closing force.

[0056] Furthermore, protection is sought for a method for monitoring a forming machine with a hydraulic drive unit, preferably a hydraulic drive unit according to the invention, which hydraulic drive unit comprises a piston arranged to be linearly displaceable in a cylinder and a pressure chamber delimited by the piston in the cylinder, wherein a pressure in the pressure chamber is measured and a kinematic parameter, in particular a position and/or a position change, of the piston is determined via the pressure, preferably a determined pressure change, wherein the pressure chamber cooperates with a constant pressure medium mass, preferably hydraulic fluid mass and/or a gas, at least during the measurement of the characteristic signal.

[0057] Protection is also sought for a computer program product for monitoring a

Forming machine with a hydraulic drive unit, preferably an inventive

hydraulic drive unit comprising commands that instruct a computer to

executing the program to perform the following steps:

- Receiving a characteristic signal for a pressure in a pressure chamber and

- Determining a kinematic parameter, preferably a position and/or a change in position, of a piston of the pressure chamber on the basis of the signal characteristic of the pressure in the pressure chamber.

[0058] Further advantages and details of the invention emerge from the figures and the associated figure description.

[0059] Fig. 1 shows a first embodiment of a drive unit, [0060] Fig. 2 shows a second embodiment of a drive unit, [0061] Fig. 3 shows a third embodiment of a drive unit, [0062] Fig. 4 shows a fourth embodiment of a drive unit, [0063] Fig. 5 shows a fifth embodiment of a drive unit, [0064] Fig. 6 shows an embodiment of a forming machine and [0065] Fig. 7 shows an embodiment of a closing unit.

[0066] The embodiment of a hydraulic drive unit 1 shown in Fig. 1 has a piston 4 arranged to be linearly displaceable in a cylinder 3, wherein the piston 4 divides the cylinder 3 into a pressure chamber 5 and a second pressure chamber 10.

[0067] Such a cylinder (3) - piston (4) arrangement is also called a double-acting piston-cylinder unit.

[0068] In order to supply the pressure chambers 5, 10 with a pressure medium mass, preferably a hydraulic fluid, they are connected to the valve 13 via the connecting lines.

[0069] The valve 13 is designed, for example, as a 4/3-way valve, which can be switched between the individual valve positions via a control or regulating device 14.

[0070] The valve 13 is designed to connect the pressure chambers 5, 10 selectively to the pressure source 11 or the tank 18 in order to selectively apply a pressure to the pressure chamber 5 or the pressure chamber 10 and/or to discharge a pressure medium mass into the tank 18.

[0071] The pressure source 11 of this embodiment is formed by a pump 12 which is driven by a motor drive unit, wherein the drive unit can be controlled or regulated by the control or regulating device 14.

[0072] The control or regulating device 14 further comprises a computing unit 7, which is designed as an integral component of the control or regulating device 14 of the hydraulic drive unit 1.

[0073] The signal-conducting connections of the control or regulating device 14 with the individual components of the hydraulic drive unit 1 are shown in Fig. 1 as dashed lines.

[0074] The computing unit 7 is connected to the pressure sensor 6 in a signal-conducting manner (shown by the dashed line), wherein a characteristic signal for a pressure present in the pressure chamber 5 can be detected by the pressure sensor 6 and can be fed to the computing unit 7 via the signal-conducting connection.

[0075] Furthermore, a valve 17 is provided, which is designed as a shut-off valve and via which the pressure chamber 5 can be shut off.

[0076] In order to carry out a measurement of a kinematic parameter of the piston 4, the pressure chamber 5 can be shut off via the valve 17 during the movement of the piston 4 and pressure medium mass can be supplied to the pressure chamber 10 via the valve 13 with the aid of the pressure source 11, whereby a higher pressure can be built up in the pressure chamber 10 than in the pressure chamber 5.

[0077] Alternatively or additionally, the piston 4 can of course also be moved via a machine part which is connected to the piston 4 via the piston rod.

[0078] As a result of the increasing pressure in the pressure chamber 10, the piston 4 is moved in the direction of the pressure chamber 5, whereby the shut-off pressure chamber 5 - more precisely: the constant pressure medium mass which is present in the pressure chamber 5 - is compressed and the pressure in the pressure chamber 5 increases.

[0079] This pressure increase in the pressure chamber 5 can be fed to the computing unit 7 as a characteristic signal via the pressure sensor 6, whereby the computing unit 7 can determine a kinematic parameter, preferably a position and/or a change in position, of the piston 4 on the basis of the signal characteristic of the pressure in the pressure chamber 5.

[0080] In the same way, of course, a kinematic parameter for the piston 4 could also be determined in the event of a pressure drop.

[0081] This determination and/or calculation of the kinematic parameter of the piston 4 can be carried out by calculating the stroke volume, whereby the compression volume AV can be calculated via the pressure variation Ap and the output volume Vo of the pressure chamber 5 using the following formula.

1

[0082] K compression modulus of the pressure media mass [0083] Vo output volume in the pressure chamber [0084] AVx compression volume of the pressure chamber [0085] Ap pressure variation in the pressure chamber

[0086] The compression modulus K, which is also required in the formula, is a dependent quantity of the pressure medium mass and can be determined from tests and/or data sheets of the pressure medium mass (for example the hydraulic fluid).

[0087] Subsequently, a change in position of the piston 4 can be calculated using the compression volume AVxk and the known geometrical sizes of the piston 4 and/or the cylinder 3 and/or the pressure chamber 5, whereby, taking into account the

Starting position of piston 4 allows an instantaneous position of piston 4 to be determined.

[0088] It can be provided that the computing unit 7 transfers the determined kinematic parameter of the piston 4 to the control or regulating device 14, wherein the control or regulating device 14 uses the kinematic parameter of the piston 4 as the actual size of the piston 4 in the control or regulating of the valve 13, the valve 17 and/or the pressure source 11, so that the piston 4 can be adjusted to a desired position.

[0089] Of course, this procedure can also be applied to a speed and/or acceleration of the piston 4.

[0090] Alternatively or additionally, it can also be provided that the determination of the kinematic parameter of the piston 4 takes place via a calibration process, whereby a measurement of the position of the piston 4 is carried out at different pressures in the pressure chamber 5 and, for example, a reference curve is created for the kinematic parameter of the piston 4 as a function of a pressure in the pressure chamber 5 (and an initial position of the piston 4).

[0091] Subsequently, as previously explained, a pressure can be measured via the pressure chamber 10 when the pressure chamber 5 is closed and, taking into account the measured pressure in the pressure chamber 5, a kinematic parameter for the piston 4 can be determined via the calibrated reference curve.

[0092] Due to the limited compressibility of common pressure media masses, only limited position changes of the piston 4 can be determined in the embodiment of Fig. 1, whereby usually only smaller strokes of the piston 4 can be determined via the pressure sensor 6 and the computing unit 7 due to the compression of the pressure chamber 5.

[0093] However, in order to be able to determine larger travel distances of the piston 4, the method can, for example, be carried out several times in succession, with several kinematic parameters of the piston 4 being measured and calculated one after the other if necessary.

[0094] However, it can also be provided that the compressibility of the system is increased by connecting the pressure chamber 5 to a hydraulic accumulator 9, whereby significantly larger travel distances and strokes of the piston 4 can be determined.

[0095] Such embodiments are shown in Figures 2 and 3.

[0096] In these embodiments, a pressure medium mass of a pressure source 11 can again be supplied to the second pressure chamber 10 via a valve 13, wherein the pressure chamber 5 can be shut off during this time and thus forms a constant pressure medium mass during the measurement with the hydraulic accumulator 9 and the connecting line 8.

[0097] A hydraulic accumulator 9 of this or a similar type may be provided in some embodiments anyway, for example to save energy through recuperation.

[0098] If the hydraulic accumulator 9 is designed, for example, as a bladder accumulator (as shown in Fig. 2 or 3), the compression behavior can be varied considerably by a suitable choice of the counter pressure in the bladder accumulator, whereby higher compression volumes AVx« are also made possible in order to detect larger position changes of the piston 4.

[0099] The hydraulic accumulator 9 shown in Figures 2 and 3 is designed as a fluid-operated bladder accumulator which has a gas (for example nitrogen, air or other gases) as the actuating medium.

[00100] The determination of the kinematic parameter in the piston 4 by the computing unit 7 can again - as previously described - be carried out via a previous calibration and determination of a reference curve or also by calculating the compression volume, whereby the following formula can be used in the embodiments of Figs. 2 and 3,

to determine not only the compressibility of the print media mass, but of the entire system.

take into account: n [69 *- 69° 0 [AD P2

AV = K Ca

[00101] n polytropic exponent

[00102] % effective gas volume of the hydraulic accumulator [00103] AVx/ compression volume

[00104] vo Gas filling pressure of the hydraulic accumulator

[00105] 91 Pressure at the start of the measurement in the pressure chamber 5 [00106] 2, Pressure at the end of the measurement in the pressure chamber 5 [00107] CC. Correction factor for adiabatic change of state

[00108] For the present case (in the case of adiabatic changes of state) the polytropic exponent n = 1.4.

[00109] The compressibility of the hydraulic fluid is negligible due to its small size and was not taken into account in the calculation.

[00110] The embodiments of a hydraulic drive unit 1 explained by Figures 1 to 3 can, for example, be used as a hydraulic drive unit 1 for individual movements in a forming machine 2, preferably an injection molding machine.

[00111] Preferably, an embodiment of a hydraulic drive unit 1 according to the invention can be used to drive a locking nut 19 relative to a bar 15 and/or as a pressure cushion 20 for building up the closing force in a closing unit 16.

[00112] Fig. 4 shows a fourth embodiment of a hydraulic drive unit 1, which has a mechanically operated hydraulic accumulator 9, wherein the counter pressure can be varied and/or adjusted via the spring element 33 (suitable choice of the spring element 33).

[00113] The remaining features of the embodiment of Fig. 4 correspond essentially to those of Fig. 2.

[00114] Fig. 5 shows a fifth embodiment of a hydraulic drive unit 1, wherein the pressure chamber 5 is integrated into the piston-cylinder unit and forms a hydraulic accumulator.

[00115] The pressure medium in the pressure chamber 5 can be implemented, for example, by nitrogen, air or another gas.

[00116] When the pressure medium in the pressure chamber 5 is compressed, a kinematic parameter of the piston 4 can be determined taking into account the compressibility of the pressure medium and the pressure in the pressure chamber 5 (which can be determined via the pressure sensor 6).

[00117] The remaining features correspond essentially to those of Fig. 3.

[00118] The molding machine 2 shown as an example in Fig. 6 is an injection molding machine and has an injection unit 21 and a closing unit 16, which are arranged together on a machine frame 22. The machine frame 22 could alternatively also be designed in several parts.

[00119] The clamping unit 16 has a fixed mold clamping plate 23 and a relatively

for this purpose, a movable mold clamping plate 24 is provided.

[00120] Alternatively, variants with a front plate 21 are also possible. Such closing units are also referred to as three-plate closing units.

[00121] The movable mold clamping plate 24 can be moved relative to the machine frame 22 via a closing drive (not shown here). The closing drive and the closing unit 16 are explained in more detail by an exemplary embodiment in Fig. 6.

[00122] Mold halves of a mold 25 can be clamped or mounted on the fixed mold clamping plate 23 and the movable mold clamping plate 24 (shown in dashed lines).

[00123] The fixed mold clamping plate 23 and the movable mold clamping plate 24 are supported and guided relative to each other by the bars 15.

[00124] The mold 25 shown closed in Fig. 6 has at least one cavity. An injection channel leads to the cavity, via which a plasticized mass can be fed to the plasticizing unit 26.

[00125] Fig. 6 shows a molding machine 2 with an injection unit 21, wherein the injection unit 21 shown in this embodiment has an injection screw, which is also used for plasticizing a material to be plasticized.

[00126] The injection screw is mounted in the mass cylinder 27 so as to be axially displaceable along a longitudinal axis.

[00127] These movements are driven by a schematically shown drive unit 28.

[00128] Preferably, this drive unit 28 comprises a hydraulic rotary drive for the rotary movement and a linear hydraulic drive for the axial injection movement.

[00129] The plasticizing unit 26 (and thus the injection unit 21) is in signal-technical connection with the central control or regulating device 14.

[00130] The central control or regulating device 14 can therefore simultaneously be the control or regulating device 14 of the hydraulic system 1.

[00131] In alternative embodiments, the control or regulating device 14 of the hydraulic system 1 and the forming machine is designed separately.

[00132] Analogously, the computing unit 7 can be designed separately or integrally with the control or regulating device 14.

[00133] Control commands are issued from the central control or regulating device 14, for example, to the plasticizing unit 26, the injection unit 21 or to the closing unit 16.

[00134] The central control or regulating device 14 can be connected to an operating unit 29 and/or a display device 30 via a signal-conducting connection or can be an integral part of such an operating unit 29.

[00135] The computing unit 7 can be signal-connected to the central control or regulating device 14 of the forming machine 2 and/or be designed as an integral component of the central control or regulating device 14.

[00136] Fig. 7 shows a side view of a closing unit 16 of a forming machine 2 - in this case an injection molding machine.

[00137] The clamping unit 16 of the embodiment is again designed as a two-plate clamping unit, wherein a movable mold clamping plate 24 is linearly movable on the machine frame 22 relative to a fixed mold clamping plate 23.

[00138] To implement this linear movement of the movable mold clamping plate 24, the rapid stroke drive 31 on the one hand and the pressure pads 20 on the other hand are provided.

[00139] In the following, the usual movement sequence of such a closing unit 16 will be explained using a closing movement. The same applies in the opposite direction for opening the closing unit 16.

[00140] Thus, two mold halves of a mold 25 (not shown in this figure for reasons of clarity), which are arranged on the mold clamping plates 23, 24, are first brought closer to each other via the rapid stroke drive 31 designed as a piston-cylinder unit, until they rest against each other or are close to doing so.

[00141] The locking nuts 19 are then locked with their inner profile to a corresponding outer profile of the bars 15, whereby the locking nuts 19 firmly connect the movable mold clamping plate 24 to the bars 15 by engaging the inner profile with the outer profile of the bars 15.

[00142] After locking the locking nuts 19, the movable mold clamping plate 24 is pulled over the bars 15 towards the fixed mold clamping plate 23 via the pressure pads 20 until the mold halves of the molding tool 25 lie against each other and then an additional pressure is built up between the movable mold clamping plate 24 and the fixed mold clamping plate 23 (via the molding tool 25 arranged between them), which pressure serves as the closing force of the closing unit 26.

[00143] The actuation of the locking nuts 19 as well as the pressure pads 20 of this embodiment are implemented by embodiments of a hydraulic drive unit 1 according to the invention, whereby the kinematic parameters of the pistons 4 can be determined by a computing unit 7 and thus an actual position, a speed, an acceleration and/or a change in position of the locking nuts 19 and/or the pressure pads 20 can be determined.

LIST OF REFERENCE SYMBOLS:

1 drive unit

2 forming machine 3 cylinder

4 pistons

5 Pressure chamber

6 Pressure sensor

7 Computing unit

8 Connecting cable

9 Hydraulic accumulator

10 second pressure chamber 11 pressure source

12 Pump

13 Valve

14 Control or regulating device 15 Beam

16 Locking unit

17 Valve

18 tanks

19 Locking nut

20 pressure pads

21 Injection unit

22 Machine frames

23 fixed mold clamping plate 24 movable mold clamping plate 25 mold tool

26 Plasticizing unit

27 mass cylinders

28 Drive unit

29 Control unit

30 Display device

31 Rapid stroke drive

32 Spring element

Claims (15)

Patent claims 1. Forming machine, in particular injection moulding machine, with a hydraulic drive unit comprehensive - a piston (4) arranged to be linearly displaceable in a cylinder (3) and a pressure chamber (5) delimited in the cylinder (3) by the piston (4), - at least one pressure sensor (6) which is designed to detect a signal characteristic of the pressure in the pressure chamber (5), and - a computing unit (7) which is signal-connected to the at least one pressure sensor (6) for receiving the characteristic signal, characterized in that the computing unit (7) is designed to calculate the for the pressure in the pressure chamber (5) characteristic signal a kinematic pa- parameter, preferably a position and/or a position change, of the piston (4) wherein the pressure chamber (5) is at least during the measurement of the characteristic signal with a constant pressure medium mass, preferably hydraulic fluid mass, cooperates. 2, Forming machine according to claim 1, wherein at least during the measurement of the characteristic signal the pressure chamber (5) in the cylinder (3) is closed and preferably encloses a constant pressure medium mass. 3. Shaping machine according to claim 1, wherein at least during the measurement of the characteristic signal the pressure chamber (5) is connected to a hydraulic accumulator (9) via a connecting line (8), preferably wherein a constant pressure medium mass is enclosed by the pressure chamber (5), the connecting line (8) and the hydraulic accumulator (9). 4. Shaping machine according to one of the preceding claims, wherein the computing unit (7) is designed to determine the kinematic parameter by means of a relationship with the pressure stored in the computing unit (7). 5. Shaping machine according to one of the preceding claims, wherein the drive unit (1) has a hydraulic accumulator (9), preferably a bladder accumulator and/or diaphragm accumulator, particularly preferably with variable counterpressure. 6. Shaping machine according to claim 5, wherein the hydraulic accumulator (9) is designed as a mechanical, preferably spring-actuated, and/or fluid-actuated hydraulic accumulator (9). 7. Forming machine according to one of the preceding claims, wherein the piston (4) divides the cylinder (3) into the (first) pressure chamber (5) and a second pressure chamber (10). 8. Shaping machine according to claim 7, wherein the drive unit (1) has a pressure source (11), in particular at least one pump, preferably which pressure source (11) is connected or connectable to the second pressure chamber (10) in order to apply a pressure to the second pressure chamber (10). 9. Forming machine according to claim 8, wherein the pressure source (11) is connected to the second pressure chamber (10) via a valve (13), preferably which valve (13) is controllable or regulatable by a control or regulating device (14). 10. Shaping machine according to claims 8 or 9, wherein the computing unit (7) is signal-connected to a control or regulating device (14) of the pressure source (11) and/or is designed as an integral component of the control or regulating device (14), wherein the kinematic parameter can be used as an actual value by the control or regulating device (14) for controlling or regulating the pressure source (11). 11. Shaping machine according to one of the preceding claims, wherein the cylinder (3) with the piston (4) arranged therein is designed as a double-acting piston-cylinder unit. 12. Shaping machine according to one of the preceding claims, wherein the pressure chamber (5) is designed as a rod-side chamber of a piston-cylinder unit. 13. Shaping machine according to one of the preceding claims, wherein the at least one drive unit (1) is designed to drive a locking nut (19) relative to a bar (15) and/or as a pressure cushion (20) for building up the closing force. 14. Method for monitoring a shaping machine (2) with a hydraulic drive unit (1), preferably a shaping machine (2) with a hydraulic drive unit (1) according to one of claims 1 to 13, which hydraulic drive unit (1) comprises a piston (4) arranged to be linearly displaceable in a cylinder (3) and a pressure chamber (5) delimited in the cylinder (3) by the piston (4), wherein a pressure in the pressure chamber (5) is measured and a kinematic parameter, in particular a position and/or a position change, of the piston (4) is determined via the pressure, preferably a determined pressure change, wherein the pressure chamber (5) cooperates with a constant pressure medium mass, preferably hydraulic fluid mass, at least during the measurement of the characteristic signal. 15. A computer program for monitoring a forming machine (2) with a hydraulic drive unit (1) according to one of claims 1 to 13, comprising instructions which cause the forming machine (2) to carry out the following steps when the program is executed on a computer: - Receiving a characteristic signal for a pressure in a pressure chamber (5) and - Determining a kinematic parameter, preferably a position and/or a change in position, of a piston (4) of the pressure chamber (5) on the basis of the signal characteristic of the pressure in the pressure chamber (5). 5 sheets of drawings