Monitoring assembly, clamping system with monitoring assembly, and method for monitoring a clamping device with a monitoring assembly - Patents.com

Abstract

To provide a monitoring assembly for monitoring clamping quality of a workpiece carrier or a workpiece clamped on a clamp device.SOLUTION: The invention relates to a monitoring assembly (12) for monitoring clamping quality of a workpiece carrier clamped in a clamping device (3, 40, and 49) as well as a clamping system including the clamping device (3, 40, and 49) and such a monitoring assembly (12). The monitoring assembly comprises at least two sensors (A1 to A4) for independent detection of the clamping quality of a clamped workpiece carrier or a workpiece. The monitoring assembly also comprises a transmitting device (14) and a receiving device (21), where the transmitting device (14) is constituted such that it transmits a determined or calculated parameter or parameters redundantly to the receiving device (21).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The invention relates to a monitoring assembly as constructed according to claim 1, to a clamping system as constructed according to claim 14 comprising the monitoring assembly, as well as to a method according to claim 21 for monitoring a clamping device by means of a monitoring assembly. [Background technology]

[0002] In a monitoring assembly of the type described herein, the clamping devices are monitored in particular with regard to whether the workpiece carriers (pallets) clamped by the respective clamping devices or the workpieces clamped in the clamping devices are correctly and securely clamped or not, and preferably information in particular regarding the clamping quality can be deduced, the measured parameters being wirelessly transmitted to a receiver.

[0003] From EP 3 391 991 A1 a chuck is known which is adapted to clamp a pallet provided with a clamping spigot. The chuck is provided with a positioning hole for the clamping spigot and a clamping means comprising a clamping element for clamping the clamping spigot in the positioning hole. At least one sensor is arranged on the chuck by means of which at least one parameter related to the chuck and / or at least one parameter related to the interaction of the pallet with the chuck and / or at least one parameter related to the pallet. The chuck is provided with a transmitter for wirelessly transmitting the parameters determined by the at least one sensor. By means of a first sensor the clamping force acting on the clamping spigot can be determined. For this purpose the first sensor is arranged on the chuck and is adapted to measure the material elastic deformation of the chuck when the pallet is clamped. The chuck can further be provided with a second sensor capable of detecting the attachment of the pallet to the chuck.

[0004] From EP 1998932 a chuck is known which comprises a clamping head with three clamping jaws. The chuck comprises a rotationally symmetrical base body with a conical positioning bore for receiving the clamping head. A draw tube, which is part of the machine spindle, is provided for drawing the chuck into the positioning bore. Such a chuck is used in particular in lathes. A first sensor is provided on the outer surface of the chuck body, a second sensor is arranged in a recess on the outer surface of the chuck body. Finally, a third sensor is arranged in the draw tube. These sensors are configured as strain gauges and each has an integrated signal processing unit. Each signal processing unit is assigned a transmitting device for wireless transmission of the measured values. With this embodiment of the chuck the clamping force of the chuck can be determined. If a minimum clamping force is reached, maintenance of the chuck must be performed. The axial positioning of the workpiece is not monitored and cannot be determined. No message is issued regarding the presence of a workpiece. Furthermore, possible errors during wireless transmission are not detected.

[0005] From EP 2 052 808 A1 a clamping device is known which comprises a chuck for releasably clamping a workpiece carrier. The chuck is provided with a locking mechanism which comprises a number of clamping elements which, in the locked position, engage on clamping spigots connected to the workpiece carrier. Each clamping element is provided with a through hole which is closed at one end when the respective clamping element is correctly locked. Alternatively or additionally, an actuating element provided with a through hole is assigned to each clamping element which is closed at one end when the respective clamping element is correctly locked and / or unlocked. Each clamping element or each through hole of the actuating element is connected to a pneumatic source via a common connecting line. In the connecting line at least one sensor is provided for detecting the air flow. By means of this sensor it is possible to detect whether the clamping element is correctly unlocked or locked. The sensor is connected to an electronic control and evaluation device.

[0006] Furthermore, a clamping device for a machine tool is known from EP 2 759 372 A1. The machine tool comprises a rotatable spindle with a tool holder for a tool. A clamping device is provided for clamping the tool. To detect correct or incorrect clamping of the tool in the tool holder, the clamping device is equipped with force sensors at different measuring points, so that the clamping forces acting on the different measuring points are detected. The force sensors are arranged on an annular seating surface of the tool holder. The sensors protrude above the seating surface so as to be compressed when the tool is clamped. This makes it possible to detect the clamping force and whether the tool is clamped correctly or whether misalignment and / or incorrect positioning occurs. AOW sensors (surface acoustic wave sensors) are used as force sensors. The force sensors are arranged on the seating surface rotationally symmetrically around the central axis of the machine tool. When the tool is positioned correctly, each force sensor detects the same clamping force, whereas when the tool is clamped at an angle, each force sensor detects a different clamping force. The electrical signals of each sensor are wirelessly transmitted to a transceiver unit and evaluated in the evaluation unit.

[0007] EP 2 093 016 A1 describes an intelligent multi-part clamping device. The clamping device consists of several clamping jaws arranged on a base plate, with the fixed and displaceable clamping jaws forming a kind of vice. A workpiece attachment sensor or a ram air workpiece attachment control is arranged in the clamping jaws, the former being connected by a cable to a wireless module. Whether the workpiece is correctly inserted in the clamping jaws is monitored by the sensor.

[0008] EP 3028804 A1 describes a transmission assembly, in particular a transmission assembly for transmitting energy and / or signals and for use in machining centers. In this case, signals and voltages are inductively transmitted from a fixed machine frame to a rotating chuck (not only in the direction of the chuck but also in the opposite direction). Each chuck has clamping jaws which are displaceable by an electric motor and supported on the chuck body. The electric motor is switched off when a predefined actual position is reached and the clamping jaws are stopped by a spring assembly and a mechanical friction brake. The electric motor compresses the spring assembly during the clamping process, which exerts a clamping force on the clamping jaws. After the electric motor is switched off, slippage or release of the clamping jaws is prevented by the mechanical friction brake. Furthermore, the position of the clamping jaws is permanently monitored during the machining process in order to detect machining errors or release of the clamped workpiece. For permanent monitoring of the operating state and the position of the clamping jaws and / or the electric motor, these are assigned a number of measuring sensors which generate corresponding measurement data and transmit these via an inductive transmission device. The inductive transmission device is made up of two parts, one of which is arranged on the rotating chuck and the other on the stationary support frame. The two transmission devices are arranged coplanar with each other and spatially separated, so as to enable the rotation of the chuck and at the same time the inductive transmission of measurement signals, measurement data and / or voltages for operating the electric motor.

[0009] EP 3 620 248 A1 discloses a coupling device with which data can be inductively transmitted from a rotatable part to a non-rotatable part. In particular, the chuck, which rotates during operation, can be connected to a customer-side control device and monitored by the coupling device. The chuck has radially displaceable clamping jaws for clamping the workpiece. Each clamping jaw is driven by an assigned electric motor. To supply energy to the rotating chuck during the machining process of the clamped workpiece, the chuck is provided with a first transmission device, which is connected by electric lines to the electric motor and to a measuring sensor. The position of the clamping jaws and the voltage of the electric motor or the speed of the electric motor are measured by the measuring sensor. A second transmission device, which is arranged non-rotatably, is attached to the support frame. The measurement data is inductively transmitted from the rotatable first transmission device to the non-rotatably arranged second transmission device. The second transmission device is connected by electric lines to a programmable interface. In a variant of the chuck, the chuck is provided with two interfaces, which are connected to the second transmission device. Both interfaces receive the measurement data sets of the measuring sensors independently of each other and evaluate them: if the measurement results at the two interfaces coincide, the control receives a release signal, whereas if the measurement results differ the machining process is interrupted or not released.

[0010] Finally, EP 2 457 688 A1 discloses a method for positioning and fixing a workpiece, the process steps of which make it possible to check the presence or absence of a workpiece or a workpiece carrier. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] European Patent Application Publication No. 3391991 [Patent Document 2] European Patent No. 1998932 [Patent Document 3] European Patent Application Publication No. 2052808 [Patent Document 4] European Patent Application Publication No. 2759372 [Patent Document 5] European Patent Application Publication No. 2093016 [Patent Document 6] European Patent Application Publication No. 3028804 [Patent Document 7] European Patent Application Publication No. 3620248 [Patent Document 8] European Patent Application Publication No. 2457688 Summary of the Invention [Problem to be solved by the invention]

[0012] The object of the present invention is to provide a monitoring assembly belonging to the technical field mentioned at the beginning for monitoring the clamping quality of a workpiece carrier or a workpiece clamped in a clamping device, which can reliably detect one or more parameters, in particular parameters from which information about the secure clamping of the clamped workpiece carrier or workpiece can be deduced, on the one hand, and reliably transmit them to a receiver without a data line on the other hand. [Means for solving the problem]

[0013] The solution to this problem is defined by the features of claim 1. According to the invention, a monitoring assembly for monitoring the clamping quality of a workpiece carrier or a workpiece clamped in a clamping device comprises at least two sensors for independently detecting the clamping quality of the clamped workpiece carrier or workpiece, the transmitting device being configured to redundantly transmit the determined or calculated parameters to the receiving device. If at least two sensors are provided for independently detecting the clamping quality of the clamped workpiece carrier or workpiece, possible errors provided by one sensor can be detected, for example, by mutual comparison of the measurement data. Redundant transmission of the measurement data from the transmitting device to the receiving device allows errors on the transmission link to be detected and, if necessary, eliminated.

[0014] Preferred embodiments and configurations of the monitoring assembly are set out in the dependent claims 2-13.

[0015] In a preferred embodiment, it is envisaged that the monitoring assembly comprises at least one sensor module, which digitalizes the measured values ​​of the sensors and transmits them to a transmitting device. Such processing of the measured data increases the reliability and facilitates the transmission of the measured values ​​to the transmitting device. Furthermore, each sensor module can be used to power one or more sensors, as required.

[0016] In a particularly preferred embodiment of the monitoring assembly, the transmitter device is provided with two independent microprocessor units, which are arranged for independent and redundant processing of the measured values ​​transmitted by each sensor module. On the one hand, this arrangement contributes to immediately detecting errors in the messages and, if necessary, to checking whether the measurements are valid. On the other hand, the different, independent microprocessors can also be programmed differently, which is advantageous with regard to the detection and processing of redundant measured data.

[0017] The transmitting device preferably has at least one transmitting antenna for transmitting the measurement data processed by the two independent microprocessor units. The measurement data can be wirelessly transmitted by the transmitting antenna to the receiving device, and the above-mentioned components can be grouped together in a compact and power-saving component.

[0018] Particularly preferably, the monitoring assembly comprises at least two sensors which are arranged in such a way that their measured values ​​are positively correlated with one another, so that the measured values ​​can be compared with one another and therefore particularly easily checked for accuracy.

[0019] The monitoring assembly particularly preferably comprises at least two sensors, which are constructed and arranged to measure the material elastic deformation of the chuck or vice in the clamping device during clamping of the workpiece carrier or workpiece, the sensors being in particular strain gauge sensors (DMS). DMS sensors are characterised by high precision and excellent long-term stability, so that with the above-mentioned sensor arrangement information about the actual clamping force can be deduced very easily.

[0020] A preferred embodiment of the monitoring assembly monitors a clamping device with at least one chuck, which at least one chuck includes in its interior space an actuating piston displacing in the Z direction a clamping element for clamping a clamping spigot. In this case, the monitoring assembly comprises at least two sensors operating without contact, by means of which at least two positions of the actuating piston can be detected independently of one another, preferably three positions. This embodiment makes it possible by means of two sensors to reliably monitor different states of the chuck, and it is particularly preferred that inductively actuated sensors are used.

[0021] In a further preferred embodiment, the monitoring assembly comprises at least one further sensor capable of detecting the attachment of the workpiece carrier to the clamping device, such that it can be detected whether the workpiece carrier is in fact directly in position on the Z support of the clamping device or whether it is on a contaminant such as debris and is therefore incorrectly positioned in the Z direction.

[0022] In a further embodiment of the monitoring assembly, a clamping device is provided with a clamping device. The clamping quality of the workpiece is monitored and in this preferred embodiment the monitoring assembly comprises at least two further sensors capable of detecting the mounting of the workpiece in each guide block in the vice, thereby making it possible to detect whether the workpiece is clamped correctly or, for example, at an angle.

[0023] Furthermore, a preferred embodiment of the monitoring assembly provides for the monitoring assembly to be provided with a further sensor capable of detecting the position of the element for activating the clamping element, this embodiment being particularly important for the automatic supply or removal of the workpiece carrier by a robot, since in order to supply or remove the workpiece carrier, the aforementioned element for activating the clamping element must be in the initial or open position.

[0024] In a particularly preferred embodiment, the monitoring assembly comprises a receiving antenna for receiving the data transmitted by the transmitting device and a gateway connected to the receiving antenna, the gateway being provided with two independent microprocessor units for further processing the received data independently and redundantly, the gateway being connected to a machine control device of the processing machine. This embodiment contributes to data being reliably received and transmitted by the gateway to the machine control device of the processing machine.

[0025] In a particularly preferred embodiment of the monitoring assembly, the gateway processes the measured values ​​transmitted by the transmitting device in such a way that, if a coincidence of the detected measured values ​​is confirmed and a predefined measured value in the machine control is reached, a signal is redundantly output to the machine control regarding a correctly clamped workpiece carrier or a correctly clamped workpiece and / or a reliable operation of the machine tool, thereby ensuring a reliable operation of the processing machine, since a release signal is only present when the workpiece carrier or workpiece is reliably and correctly clamped.

[0026] A further object of the present invention is to provide a clamping system comprising a clamping device for clamping a workpiece carrier or a workpiece and a monitoring assembly configured according to any one of claims 1 to 13, which makes it possible to reliably detect whether the workpiece carrier or workpiece is securely clamped or not.

[0027] This problem is solved by a clamping system according to claim 14, in that the monitoring assembly of the clamping system comprises at least two sensors arranged on the clamping device for independently detecting the clamping forces acting on the clamped workpiece carrier or the clamped workpiece, so that the measured values ​​related to the secure clamping of the workpiece carrier or the workpiece are detected twice independently of each other, which provides the basic prerequisite for being able to reliably detect whether the workpiece carrier or the workpiece is securely clamped or not.

[0028] Preferred embodiments of the clamping system are defined in the dependent claims 15-20.

[0029] The clamping system is preferably configured such that the transmitter of the monitoring assembly has a radio transmitter arranged on the clamping device and the receiver has a radio receiver arranged remotely from the radio transmitter, the transmitter having two independent microprocessor units that process the measured values ​​transmitted from each sensor module independently and redundantly and check their validity by comparing the measured values ​​with each other, thereby allowing redundant pre-processing of the validity of the measured data to be performed already on the transmitting side, i.e. in or on the clamping device.

[0030] In a particularly preferred embodiment of the clamping system, a strain gauge is used as the sensor, which is frictionally engaged and / or rigidly bonded to the chuck or vice of the clamping device so that its signal is substantially proportional to the clamping force.DMS is particularly suitable for providing accurate information about the clamping force acting on the workpiece carrier or workpiece, and thus about the clamping quality, by measuring the deformation of the material in the chuck or vice, due to its high accuracy and excellent long-term stability.

[0031] In a further preferred embodiment of the clamping system, the clamping device of the clamping system comprises at least one chuck for clamping the workpiece carrier, which has a sensor arranged in the upper area for detecting the attachment of the workpiece carrier, such a sensor making it possible to determine the Z position of the workpiece carrier exactly, which is important, for example, with regard to possible contamination in the Z support area.

[0032] In a particularly preferred embodiment of the clamping system, the clamping system comprises a chuck for clamping a workpiece carrier provided with a clamping spigot, the chuck having an actuating piston displaceable between an initial position and a locked position for actuating a clamping element which clamps the clamping spigot, the chuck being provided with a further sensor for monitoring the position of the actuating piston, detecting the position of the actuating piston being particularly important in connection with the automatic mounting of the clamping system by a handling robot, in particular in order to avoid causing undesired damage.

[0033] In a particularly preferred embodiment of the clamping system, the clamping system comprises at least two chucks for clamping a workpiece carrier with a number of clamping spigots corresponding to the number of chucks, each chuck having an actuating piston displaceable between an initial position and a locked position for actuating a clamping element clamping the respective clamping spigot, and at least one chuck is provided with a further sensor for monitoring the position of the actuating piston, by means of which the position of the at least one actuating piston can be deduced information regarding whether the workpiece carrier is essentially ready to be fed or removed.

[0034] In an alternative embodiment of the clamping system, the clamping device is configured as a vice with two clamping jaws, each of which is assigned a sensor for determining the clamping force of the clamped workpiece, which is determined by both clamping jaws, allowing information to be inferred as to whether the workpiece is securely clamped or not.

[0035] Finally, a further object of the present invention is to provide a method for monitoring a clamping device in a processing machine by means of a monitoring assembly constructed according to one of claims 1 to 14, in which way it can be reliably and easily determined whether the clamping quality of a clamped workpiece carrier or a workpiece meets certain requirements or not and, on the basis of the measured values, the control of the processing machine and / or the associated handling robot can be influenced.

[0036] This problem is solved by a method according to claim 21. Reliability can be ensured during processing of a workpiece clamped on a processing machine by a clamping device or a workpiece carrier, in that the clamping quality of a workpiece carrier or a workpiece clamped on the clamping device is determined by at least two independent sensors, the measurement data determined by each sensor are compared with one another and checked for plausibility, the determined or calculated parameters are redundantly transmitted by a transmitting device to a receiving device, and the control of the processing machine is influenced on the basis of the detected measured values.

[0037] Preferred embodiments of the inventive method are defined in the dependent claims 22-25.

[0038] In a particularly preferred method, the plausibility check comprises checking the agreement of the determined and compared parameters after processing by two independent microprocessor units in the transmitting device, whereby a redundant evaluation as well as a double detection of the measured values ​​relevant for positive clamping is also performed.

[0039] In a particularly preferred embodiment of the invention, the determined or calculated parameters are redundantly transmitted by the transmitting device to the receiving device in the form of data packets, and the transmitted data are checked at the receiving side for validity, so that errors on the radio link can be detected.

[0040] In a further preferred embodiment, it is provided that if the determined and compared parameters coincide and a predefined measured value is reached, a release signal for a reliable operation is generated by the gateway and redundantly transmitted to the control device of the processing machine. In this way, the release signal is only present if the prerequisites necessary for a reliable operation of the processing machine are fulfilled, i.e. the workpiece carrier or the workpiece is securely clamped.

[0041] Finally, in a particularly preferred embodiment of the invention, it is provided that the gateway emits a release signal in the form of a binary signal, which takes the value 1 if the measured value is valid and reaches a predefined value, and which takes the value 0 if the detected measured value is invalid or does not reach a predefined value. Thus, a positive reliability can be achieved, since the release signal only takes the value 1 if the workpiece carrier or the workpiece are correctly and securely clamped. In the event of a fault, such as a power failure, the release signal automatically takes the value 0, which is immediately detected by the machine control and the machine is stopped or at least an error message is output.

[0042] Further advantageous embodiments and feature combinations of the invention will become apparent from the following detailed description and the entire claims. [Brief description of the drawings]

[0043] [Figure 1] 1 is a schematic diagram showing a first clamping device together with a monitoring device. [Diagram 2] FIG. 2 is a perspective view of the second clamping device together with the individual components of the workpiece carrier and the monitoring device. [Diagram 3]Figure 3a shows a cross-sectional view of the clamping device in Figure 2 with a workpiece carrier in a raised position, Figure 3b shows a cross-sectional view of the clamping device in Figure 3a with a workpiece carrier clamped thereon, and Figure 3c shows a further cross-sectional view of the clamping device in Figure 2 without a workpiece carrier. [Figure 4] FIG. 13 is a perspective view of a third clamping device configured as a vice together with individual components of the monitoring device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] FIG. 1 shows a schematic representation of a clamping device 3 together with a monitoring device 12. A first rectangle 1 diagrammatically represents a machine space in which a processing machine is arranged and on which the clamping device 3 is placed for use. A dashed line 2 represents a clamping system, which comprises the clamping device 3 and part of the monitoring device 12. The clamping device 3 shown is a so-called quadruple chuck, in which four chucks 6, 7, 8, 9 are arranged on a base plate 5. Each chuck comprises a central locating hole (not shown) for receiving and clamping a clamping spigot arranged on a workpiece carrier (not shown). In order to clamp the clamping spigot in the locating hole, each chuck 6-9 is provided with a clamping mechanism. The upper sides of the four chucks form the X-Y plane of the chuck, to which the so-called Z axis is perpendicular. Since such chucks are known in principle, for example from DE 10 2013 014 036 A1, the respective chuck will only be represented diagrammatically and only certain features relevant to the present invention will be described.

[0045] Besides a number of sensors for detecting the clamping quality of the clamped workpiece carrier, the monitoring device 12 comprises a transmitter device 14 and a receiver device 21, represented by dashed lines. In the illustrated embodiment, each chuck 6-9 is assigned three sensors A1, B1, C1; A2, B2, C2; A3, B3, C3; A4, B4, C4, the function of which will be explained in more detail below. The three sensors A1-C1; A2-C2; A3-C3; A4-C4 in each chuck 6-9 are connected respectively to a sensor module 34, 35, 36, 37, in which the processing of the measured values ​​measured by each sensor takes place. Each sensor module is on the one hand responsible for the feeding of the sensors (strain gauges or Wheatstone bridge circuits, inductive sensors, etc.). On the other hand, an A / D converter is integrated which digitizes the analog measurement signals so that these measurement data can be digitally transmitted to the transmitting device 14 via a relatively small number of lines L1-L4, ideally one line per sensor module 34-37. The transmitting device 14 is provided with two independent microprocessor units 15, 16 which perform pre-processing of the measurement data. The two microprocessor units 15, 16 are preferably provided with different microprocessors in order to ensure independent and redundant processing of the measurement data. The transmitting device 14 is further provided with a radio module (radio transmitter) and a transmitting antenna 17 for wireless transmission of the measurement data. In the illustrated embodiment, a transmitting antenna 17 is provided for transmitting the measurement data processed by the two microprocessor units 15, 16. Furthermore, the clamping system 2 is provided with an acceleration sensor 18 which can be arranged in the area of ​​the transmitting device 14 as shown.

[0046] To supply the transmitting device 14, a power supply 19 in the form of a battery or accumulator is preferably used, which may for example be accommodated in a separate battery compartment in the clamping device 3 (neither battery nor battery compartment shown). If required, a power pack, an inductive power supply or a device for converting energy from the environment (energy harvesting) may also be provided.

[0047] The receiving device 21 (radio receiver), arranged remotely from the clamping device 3, comprises besides the receiving antenna 22 a gateway 24 for processing the data. The generally known technical term gateway refers to a switching device, in particular a transfer point as a switching device in a computer network. In computing, a gateway is understood to mean a component (hardware and / or software) that establishes a connection between two systems. The gateway 24 also comprises two independent microprocessor units 25, 26 for evaluating the received data. Again, the two microprocessor units 25, 26 are preferably provided 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 increases reliability.

[0048] The receiving antenna 22 is connected via a first cable 23 to a gateway 24, which is in turn connected via a second cable 27 to a machine control 28. The machine control 28 is connected via a third cable 29 to a handling robot 30. The gateway 24 is also connected via a fourth cable 31 to a service tool 32. The illustrated gateway 24 is represented outside the line 2 representing the clamping system, but is essentially a component of the monitoring device 12 and is assigned to the clamping system. The handling robot 30 allows the clamping device 3 to be fed with workpiece carriers or workpieces and to be removed from the clamping device 3. The machine control 28 controls the processing machine on which the clamping device 3 is mounted and used. Finally, the service tool serves as a tool for calibration and diagnosis. The illustrated cables 23, 27, 29, 31 described above are only diagrammatically represented as lines, but the term cable in this context is understood to mean any kind of electrical connection, encompassing single-core and multi-core electrical lines as well as several independent lines. Thus, the gateway 24 is, for example, connected to a machine controller 28 via at least two lines, as will be described in more detail below.

[0049] The gateway 24 receives and evaluates the digitally transmitted data from the transmitting device 14 by means of the antenna 22. For wireless data transmission, it is preferred to use standardized interfaces such as, for example, Bluetooth®, ZigBee® or a proprietary radio transmitter in the 2.4 GHz frequency range, and it is particularly preferred to use the Bluetooth Low Energy (BLE) radio technology, as will be explained in more detail below.

[0050] Based on the transmitted data, the gateway 24 can detect the state of the clamping device, e.g. chuck open, no pallet present, pallet in place, pallet clamped, pallet clamped at 10 kN, etc., and relay it to the machine control 28 or to a process control system connected to the machine control 28. The machine control 28 or to a process control system can send commands to the handling robot 30, e.g. to transfer a workpiece carrier to the clamping device 3 or to remove the workpiece carrier from the clamping device 3. In case of a malfunction or if an insufficient mechanical clamping is detected, the respective processing machine can be stopped immediately, especially even during processing of a workpiece carrier clamped in the clamping device 3. In any case, based on the measured values ​​at the sensors, the control of the processing machine and / or the associated handling robot can be influenced.

[0051] Of the three sensors in each of the chucks 6-9, each first sensor A1, A2, A3, A4 serves to measure the clamping force with which the clamping spigot is clamped in the respective clamping chuck. For this purpose, preferably a strain gauge based sensor (hereinafter referred to as DMS) is used, which is able to measure the material elastic deformation of the chuck, in particular the housing. This allows information to be deduced about the force with which the clamping spigot is drawn into or clamped in the respective chuck.

[0052] Each further sensor B1, B2, B3, B4 serves on the one hand to check the presence of the workpiece carrier. On the other hand, each sensor B1-B4 also makes it possible to determine the exact Z-position of the workpiece carrier. For this purpose, inductively actuated sensors are preferably used which are arranged in the upper area of ​​the chucks 6-9 to detect the presence or attachment of the workpiece carrier.

[0053] Each of the further sensors C1, C2, C3, C4 serves to monitor the position of an actuating piston for actuating the clamping element. The actuating piston presses the clamping element (clamping ball) for clamping the clamping spigot radially inwards, so that the clamping element abuts against the clamping spigot in a frictional engagement manner. When the actuating piston presses the clamping element radially inwards, the actuating piston is in the actuating position. If the actuating piston is pressed into the initial position, the clamping element is in the open position or at least can be pressed back into the open position. Thus, in the open position of the actuating piston, the clamping spigot can be introduced into or removed from the chuck, whereas in the locked position of the actuating piston, the clamping element is in the clamping position and the clamping spigot is clamped in the chuck. When the actuating piston is in the locked position, the clamping spigot cannot be introduced into or removed from the chuck. For such chucks, the actuating piston is usually pneumatically actuated and moved pneumatically into the open position, whereas it is pressed into the locked position by spring action and remains in the locked position by self-retaining force. This has the advantage that the chuck locks even without compression, so that the workpiece carrier is reliably clamped and remains so even in the absence of compressed air.

[0054] It goes without saying that it is not necessary to provide three sensors for each of the chucks 6-9, but depending on the requirements one, two or three sensors may be sufficient. In some cases it is sufficient to provide sensors only for two of the four chucks. In such a case, preferably two chucks 6,8 or 7,9 diagonally opposite each other are provided with sensors, which can measure the clamping force with which each clamping spigot is clamped in the chuck.

[0055] Furthermore, the acceleration sensor 18 is used to determine the position of the clamping device 3. In addition, the movement of the clamping device 3 can also be monitored by the acceleration sensor 18. Thus, vibrations occurring, for example, during machining of a workpiece can be continuously monitored and the machining process can be stopped immediately if limit values ​​are detected to be exceeded.

[0056] The Bluetooth Low Energy (BLE) technology, which is particularly preferably used for wireless transmission, requires very little energy for transmission and has a transmission range of about 10 meters. Furthermore, BLE is an internationally standardized radio interface and can therefore be used worldwide at a frequency of 2.4 GHz. Since BLE is also used, for example, in smartphones, corresponding components are produced in great numbers and are therefore available at advantageous costs. Thus, for example, a smartphone can also communicate with the chuck. This gives the technology many advantages over inductive transmission, as disclosed, for example, in Patent Document 6.

[0057] In the following, several possible functional modes of the monitoring device are described. EXAMPLES

[0058] In this example, it is assumed that only one sensor is provided per chuck 6-9, namely DMS sensors A1, A2, A3, A4, to measure the clamping force present.

[0059] After the workpiece carrier (not shown) has been clamped in the clamping device 3, the data measured by the DMS sensors A1-A4 and digitized in the sensor modules 34, 35, 36, 37 are processed in parallel in the two microprocessor units 15, 16 in the transmitting device 14. In this case, the measurement data of the various sensors are processed independently of one another by the two microprocessor units 15, 16 and their plausibility is checked by mutual comparison. The measured values ​​of the DMS sensors A1-A4 may differ from one another by at most a predefined value. If the determined measured values ​​are within predefined tolerance ranges, the measured values ​​are transmitted by the transmitting device 14 to the receiving device 21. However, if the measured values ​​differ significantly from one another, it is already detectable on the transmitting side that an error exists and, if necessary, an error message can be output. In this case, the measured values ​​can be transmitted to the receiving device 21 despite the error.

[0060] Apart from the above-mentioned mutual comparison of measured values, in which the validity of the measured values ​​is determined, absolute measured values ​​are of course also used to determine whether the workpiece carrier or the workpiece is correctly clamped with the required clamping force.

[0061] The measured or determined data is preferably checked for validity before being transmitted and again after being transmitted.

[0062] Due to the fact that the measurement data, which are positively correlated with each other, such as the clamping forces measured by the DMS sensors A1-A4, are compared and checked for plausibility in the two microprocessor units 15, 16, the measurement data can already be pre-processed in the transmitting device 14 and, if necessary, can be transmitted in a reduced data volume to the receiving device 21. If the measurement data are valid, they are transmitted from the transmitting device 14 to the receiving device 21, whereas if it is detected that the measurement data are invalid, an error message is transmitted. In addition to the error message, if necessary, the measurement data can also be transmitted. The actual measured value, i.e. the clamping force with which the respective clamping spigot is clamped in the chuck, can be transmitted or, alternatively, a reduced data volume can be transmitted in the sense of "clamping OK" if the measured value is valid. In some cases, it is sufficient to only detect the measured values ​​from the two diagonally arranged sensors and check the plausibility of the measured values. However, if the data of all four DMS sensors A1, A2, A3, A4 have been determined and checked for plausibility, it can also be guaranteed that all four clamping spigots are present on the workpiece carrier and that none are missing.

[0063] Appropriate measures must be taken to avoid possible transmission errors over the radio link, such as corrupted messages, unintentional repetition of messages, incorrect ordering of messages, message loss, time delays in messages, insertion of incorrect information due to, for example, malfunctions or fraudulent senders, etc.

[0064] The measurement data is preferably transmitted redundantly in the form of digital data packets, each of which can be subjected to a confusion-safe coding so that a corresponding allocation can be made at the receiving end.

[0065] At the receiving side, the data packets are received by an antenna and evaluated in two microprocessor units 25, 26 in the gateway 24. The transmitted measurement data is preferably checked for validity by mutual comparison also at the receiving side. Apart from the mutual comparison, absolute measurement values ​​must also be used to determine whether the clamping is correct or not.

[0066] To ensure reliability, if a correct clamping is detected, the gateway 24 generates a clamping signal (release signal), which is monitored by the machine control. Correct clamping means, on the one hand, that the validity of the measured values ​​is detected by mutual comparison and, on the other hand, that a predefined minimum clamping force is reached. The gateway preferably emits the release signal in the form of a binary signal, which takes the value 1 if the measured values ​​are valid and reach the predefined value, and the release signal takes the value 0 if the detected measured values ​​are not valid or do not reach the predefined value. If both microprocessor units 25, 26 detect a correct clamping, two release signals with a value of 1 are generated independently of each other by the two microprocessor units 25, 26 in the gateway 24. The machine control is connected to the gateway 24 via two lines to transmit the release signals, and a correct clamping is detected by the machine control 28 only if the release signals on both lines take the value 1. In this way, the release signal is transmitted redundantly (twice) to the machine control 28.

[0067] If the gateway 24 detects that an unacceptable error has occurred on the transmission link, an error is also generated and the release signal takes the value 0, which causes the machine controller to stop the processing machine. In the event of a receiving device (electronics) defect or other malfunction, such as a power failure or invalid measurements, the release signal also takes the value 0, which also causes the machine controller 28 to stop the processing machine.

[0068] Particularly preferably, the data is enriched with redundant information in the wireless transmission in order to detect corruption and / or errors, by taking such measures errors and / or corruption can be detected earlier rather than at the end.

[0069] The transmitting device 14 and the receiving device 12 have been described above, but data is not only transmitted in one direction from the transmitting device 14 to the receiving device 21, but data can also be transmitted in the opposite direction as described above.

[0070] In any case, the measurement data or parameters relevant for positive clamping are detected twice, i.e. redundantly, in the monitoring device constructed according to the invention, these measurement data are checked for plausibility by cross-comparison using two independent microprocessor units 15, 16 on the sending side and then redundantly transmitted, and on the receiving side are again double-checked and redundantly evaluated using two independent microprocessor units 25, 26 in the gateway 24 and finally redundantly transmitted again to the machine control device 28. Thus, at each of these steps, a double safety is built in, ensuring a reliable functioning of the entire measurement chain, including the radio transmission. EXAMPLES

[0071] In this example, the measurement data of all sensors in the clamping device 3 are recorded. Preferably, the data of sensors of the same type are compared with one another and checked for plausibility. On the one hand, the clamping quality of the clamped workpiece carrier can be determined as described above by means of the DMS sensors. In principle, safety-relevant measured values ​​are always compared with one another.

[0072] On the other hand, the presence of the workpiece carrier and its exact position can be determined by means of further sensors B1, B2, B3, B4. Inductive sensors B1-B4 arranged in the upper area of ​​each chuck 6-9 can measure the exact distance of the workpiece carrier from the respective sensor. This makes it possible to detect, in particular, whether the workpiece carrier rests flat on the clamping device 3 or on the Z-support of the respective chuck 6-9 and whether there is an undesired distance between the Z-support and the corresponding support on the workpiece carrier, which would adversely affect the machining accuracy of the workpieces clamped on the workpiece carrier, for example due to contamination. This makes it possible to detect, for example, whether debris is clamped under the pallet and therefore the pallet does not rest above the relevant point by, for example, 0.1 mm. If it is detected that the workpiece carrier is incorrectly attached, an error message is output and the release signal takes on the value 0.

[0073] Further sensors C1, C2, C3, C4 are used to monitor the position of the working piston for actuating the clamping elements. Based on the position of the working piston, information can be deduced as to whether the working piston is in the open or locked position. This information can be used as to whether the clamping spigot can be introduced into or removed from the respective chuck. This of course also makes it possible to determine whether the workpiece carrier can be fed or removed by the robot. However, feeding or removing the workpiece carrier must only take place when the working piston is in the open position.

[0074] Furthermore, the position of the clamping device 3 can be determined by an acceleration sensor 18. The movement of the clamping device 3 can also be monitored by the acceleration sensor 18.

[0075] 2 shows a further embodiment of a clamping device 40 in a perspective view together with the workpiece carrier 45 and the individual components of the monitoring device. The clamping device shown is configured as a single chuck 41. The chuck 41 is provided with a central positioning hole 42 for receiving a clamping spigot 46 arranged on the workpiece carrier 45. In the example shown, the monitoring device comprises, besides the transmitting device 14 arranged on the clamping device 40 and the receiving device 21 arranged remotely from the transmitting device 14, two sensors for determining the clamping force, a third sensor 43 for determining the position of the workpiece carrier 45, a fourth sensor for monitoring an actuating piston for actuating the clamping elements and a fifth sensor for determining the position of the clamping device 40, the sensors other than the third sensor 43 being not shown in FIG. 2.

[0076] The two first sensors, serving to measure the clamping force, are configured as DMS sensors, by means of which the material elastic deformation of the chuck 41 can be measured. The third sensor 43 is an inductive sensor arranged on the upper side of the chuck 41, by means of which the presence or correct mounting of the workpiece carrier 45 can be determined. The fourth sensor is an inductive sensor arranged inside the chuck, by means of which the position of the actuating piston for actuating the clamping elements, i.e. whether the actuating piston is in the open or locked position. Finally, the fifth sensor is an acceleration sensor arranged on the clamping device 40, by means of which the position and / or the movement of the chuck 41 can be detected.

[0077] The transmitter 14 and the receiver 21 are basically constructed as shown in Fig. 1, but as clearly shown in Fig. 2, it can be seen that the gateway 24 is provided with a multi-core cable 27 via which the release signal can be redundantly relayed to a machine control (not shown). In addition to the multi-core cable 27 for redundantly transmitting the release signal, further lines are preferably also provided between the gateway 24 and the machine control for transmitting additional information to the machine control, for example: chuck open, pallet not present, pallet in place, pallet clamped, pallet clamped with 10 kN, etc.

[0078] The difference between the monitoring device shown in Fig. 2 and the monitoring device shown in Fig. 1 is that the monitoring device shown in Fig. 2 comprises only two DMS sensors arranged on a single chuck 41 for measuring the clamping force. The two DMS sensors are arranged on the chuck 41 in such a way that they detect measured values ​​that are positively correlated with each other. For this purpose, the two DMS sensors are attached to the upper area of ​​the chuck 41 in such a way that they allow an accurate and repeatable detection of the material elastic deformation, i.e. of the chuck 41, when the workpiece carrier 45 is clamped. This allows the correct clamping of the workpiece carrier 45 on the clamping device 40 to be reliably and reliably monitored by the two DMS sensors.

[0079] The two DMS sensors mentioned above are in principle sufficient to monitor whether the workpiece carrier 45 is securely clamped in the chuck 41, since a defined elastic deformation in the chuck 41 only occurs when a sufficiently large clamping force acts on the clamping spigot 46. If a defined clamping force acts on the clamping spigot 46, it can be assumed that the workpiece carrier 45 is securely clamped. If the workpiece carrier 45 is not clamped or clamped incorrectly, it can be detected by the two DMS sensors, since the elastic deformation of the chuck 41 is smaller when the workpiece carrier 45 is not clamped correctly than when it is clamped correctly. Measurement values ​​indicating correct clamping are determined by test measurements and calibration of the system and are stored. The measurement values ​​of the DMS sensors are preferably already checked for plausibility by mutual comparison in the transmitting device 14. If the measurement value seems plausible, it is transmitted by the transmitting device 14 to the receiving device 21, and if the measurement value seems invalid, an error message is transmitted. In addition to the error message, the measurement value can also be transmitted if necessary. The error message is received by the receiving device 21 and accordingly a signal with a value of 0 is present at both outputs of the gateway 24, which is detected by the machine control device. When the release signal takes on the value 0, an ongoing machining process is interrupted or cannot even be started.

[0080] If the measured value appears to be valid, it is transmitted by the transmitting device 14 to the receiving device 21, where it is evaluated by the two microprocessor units 25, 26. In this case, the measured value is compared with a specified value (set value). If both microprocessor units 25, 26 detect that the set value has been reached, a correct clamp is detected and the release signal takes on the value 1. This release signal is preferably transmitted redundantly via a separate line to the machine control. Once the release signal has taken on the value 1, the machining process can be started or continued.

[0081] On the other hand, if at least one of the two microprocessor units in the receiving device 21 detects that the set value has not been reached, an incorrect clamp is detected and the release signal assumes the value 0, which is also detected by the machine control. In this case too, the release signal is redundantly transmitted to the machine control. As soon as the release signal assumes the value 0, the ongoing machining process is interrupted or cannot even be started.

[0082] In summary, correct clamping is only detected if the measured values ​​are valid and reach the set value. In any case, the release signal takes the value of 1 only if a large or predetermined measured value is present at the sensor and the measured values ​​differ from each other by at most a predetermined value. It is important that the release signal is sent redundantly, regardless of the physical configuration of the lines / cables.

[0083] Besides the correct clamping of the workpiece carrier 45, further states of the clamping device 40 or of the chuck 41 can be ascertained by using further sensors. By means of a third sensor, it can be detected whether the workpiece carrier 45 is mounted on the chuck 41 or not. As mentioned above, based on the magnitude of the measurement signal of the third sensor 43, the position of the workpiece carrier 45 relative to the chuck 41 can also be determined. By means of a fourth sensor, the position of the actuating piston for actuating the clamping elements (clamping balls) can be determined. In particular, it is possible to determine whether the actuating piston is in the initial position or in the locked position. In the locked position, the clamping elements are pressed radially inwards so that they abut or can abut frictionally against the clamping spigot. If the actuating piston is pressed into the initial position, the clamping elements are in the open position or can at least be pushed back into the open position. In the open position, the clamping spigot 46 of the workpiece carrier 45 can thus be introduced into or removed from the positioning hole 42 of the chuck 41. The detection of the respective positions of the actuating piston is important in particular in connection with the automatic mounting of the clamping device 40 by a handling robot. This is because it can be inferred whether the workpiece carrier 45 can be fed or removed without damaging the clamping device 40. Finally, the position of the clamping device 40 can be determined by a fourth sensor configured as an acceleration sensor. If necessary, the clamping device 40 can also be monitored with respect to swings / vibrations by the fourth sensor during processing of the workpiece.

[0084] The measurement data of the various sensors can be transmitted redundantly by the transmitting device 14 to the receiving device 21, as mentioned above. It goes without saying that it is not necessary for there to be five sensors and, even if there are five sensors, it is not necessary to transmit all measured values, or at least not all measured values ​​always, to the receiving device 21. To detect reliable clamping of the workpiece carrier, it is in principle sufficient to evaluate the data of two DMS sensors.

[0085] Figure 3a shows in cross section the chuck 41 of the clamping device from figure 2 together with the workpiece carrier 45 in the raised position. In figure 3a an actuating piston 65 arranged inside the chuck 41 is clearly visible, which serves to actuate a spherically shaped clamping element 66 by means of which the clamping spigot 46 fixed to the workpiece carrier 45 can be clamped in the chuck 41.

[0086] In the embodiment shown, the monitoring assembly comprises two inductive sensors 43, 44 arranged on the upper side of the chuck 41 and two DMS sensors 69, 70 arranged in the upper housing part of the chuck 41 as well as two sensors 71, 72 arranged inside the chuck 41 with non-contact operation, by means of which at least two positions of the working piston 65 can be detected. The two sensors 71, 72 are located diametrically opposite each other and measure the distance to the working piston 65. Preferably, inductively operated sensors 71, 72 are used, by means of which at least two different positions of the working piston 65 can be detected, preferably three different positions. The two inductive sensors 43, 44 arranged on the upper side of the chuck 41 make it possible to detect the presence or attachment of the workpiece carrier 45, whereas the two DMS sensors 69, 79 make it possible to measure the elastic deformation of the chuck housing, by means of which the actually existing clamping force can be deduced. Sensors 71, 72 arranged inside the chuck 41 measure the distance to the upper side of the fixed and displaceable working piston 65. If the workpiece carrier 45 is in the raised state, a relatively large distance Y1 exists between the underside of the workpiece carrier 45 and two inductive sensors 43, 44 arranged on the upper side of the chuck 41, so that the two sensors 43, 44 detect that the workpiece carrier 45 is not attached.

[0087] In order to move the working piston 65 to the initial position of FIG. 3a, the working piston is moved upwards pneumatically against the compression spring force. For this purpose, an overpressure is applied to the annular space arranged below the working piston 65. In this initial position, the working piston 65 rests against an upper stop formed by the upper housing part. The chuck 41 is thus in an open position in which the clamping spigot 46 of the workpiece carrier 45 can be introduced into or removed from the chuck 41. In the initial / open position of the working piston 65, the distance X1 between the working piston 65 and the respective sensors 71, 72 is minimal and can lie, for example, between about 0.5 mm and several mm. In this state, the measured values ​​of the respective sensors 71, 72 are detected during calibration and stored as "open position". The measured values ​​of the two DMS sensors are also stored as "open position". Furthermore, the measurements of the two inductive sensors 43, 44 arranged above the chuck 41 are stored as indicating that the workpiece carrier is "not attached" or "not present".

[0088] FIG. 3b shows the chuck 41 according to FIG. 3a in a cross-sectional view with the workpiece carrier 45 clamped thereon. The working piston 65 is in the locked position, in which it is displaced downwards towards the chuck base under a compression spring force (no overpressure is applied to the annular space 68). When the working piston 65 moves downwards, the clamping ball 66 is pressed inwards into the central bore 68 of the chuck 41 by the pressure surface arranged on the inside and widening slightly conically downwards, until it rests against the shoulder of the clamping spigot 46. The displacement path of the working piston 65 towards the chuck base is therefore limited by the clamping ball 66 resting against the pressure surface of the clamping spigot 46. The working piston 65 is held in the illustrated locked position by the spring force, whereas the clamping spigot 46 is held by a self-retaining force.

[0089] In the locked position of the working piston 65 shown in FIG. 3b, the distance X2 between the working piston 65 and the respective sensors 71, 72 is much larger than in the initial position, for example by about 1-4 mm. In this state, the measured values ​​of the respective sensors 71, 72 are again detected during calibration and are stored as “correctly clamped”. When the workpiece carrier 45 is clamped, the clamping force exerted by the clamping balls 66 on the clamping spigot 46 causes an elastic deformation of the chuck housing, which can be measured accurately and repeatedly by the two DMS sensors. Furthermore, the measured values ​​of the two inductive sensors 43, 44 arranged on the upper side of the chuck 41 are stored as the workpiece carrier being “present” or “attached”. This is because there is a relatively small distance Y2 between the underside of the workpiece carrier 45 and the two inductive sensors 43, 44 arranged on the upper side of the chuck 41.

[0090] FIG. 3c shows the chuck 41 from FIG. 3a again in a cross-sectional view, but without a workpiece carrier. Since in this case the clamping spigot is not received in the central bore 68 of the chuck 41, the clamping ball 66 is pressed into the central bore 42 by the working piston 65, so that the working piston 65 can be moved completely downwards under the action of the compression spring 67 to its end position. A prerequisite for this is that the space 68 below the working piston 65 is not pneumatically loaded with a predefined overpressure. In this state, the distance X3 between the working piston 65 and the respective sensor 71, 72 is relatively large, for example approximately 1-4 mm larger than in the locked position. In this state, the measured value at the respective sensor 71, 72 is again detected during calibration and saved as "not clamped correctly" or "no workpiece carrier present".

[0091] The values ​​measured by the sensors 71, 72 can be assigned to the three chuck states mentioned above, so that each state of the chuck can be reliably and repeatedly detected. For this purpose, the two sensors 71, 72 are preferably calibrated in three deliberately and precisely brought about states of the chuck 41. In each state of the chuck 41, the two sensors 71, 72 must measure at least approximately identical values ​​or calibration values ​​so that an unambiguous assignment of the chuck state can be made. The measurement data of the two sensors are preferably processed independently of each other by two microprocessor units, as mentioned above, and their plausibility is checked by mutual comparison of the measurement data, so that an unambiguous assignment of the chuck state can be made.

[0092] In some cases, the measured values ​​of the two sensors 71, 72 do not have to be identical, for example if the two sensors 71, 72 measure at different points of the working piston 65, but must correspond to values ​​measured in a calibration state. In any case, the sensors 71, 72 can also be arranged at different distances from the working piston 65. The only important thing is that at least two, preferably three, operating states of the chuck 41 are assigned clear values ​​by the two sensors 71, 72 and that the operating states can be clearly distinguished. The three operating states to be distinguished are in particular: - The chuck is open. - The chuck is closed and the workpiece carrier is correctly clamped. - The chuck is closed, there is no workpiece carrier or clamping spigot present.

[0093] However, each operating condition is not assigned a fixed single value, but rather a predetermined range of tolerances.

[0094] It goes without saying that it is possible to provide both a single chuck as well as a clamping device with different combinations of the above-mentioned sensors. In the simplest case, it is necessary to provide two sensors whose measured values ​​are positively correlated with each other. That is to say, it may be sufficient to provide two DMS sensors for determining the elastic deformation of the chuck housing or two sensors for monitoring the position of the working piston 65 in order to deduce reliable information regarding the clamping / operating state of the chuck. Combinations of the above-mentioned sensors are of course also possible, in which case an inductive sensor may additionally be provided which is arranged above the chuck and provides information regarding the position of the workpiece carrier.

[0095] In any event, in chuck operation, a "chuck open" or "chuck closed and workpiece carrier properly clamped" release signal is generated only if the measurements at the two sensors are within predetermined ranges.

[0096] To monitor the correct operation of the chuck, two sensors for monitoring the position of the working piston can be provided instead of the DMS sensor described at the beginning, although if necessary it is also possible to combine two DMS sensors and two sensors for monitoring the position of the working piston, possibly with two inductive sensors arranged above the chuck.

[0097] 4 shows a perspective view of a further clamping device 49, which together with a monitoring device (not shown) also constitutes a clamping system. The clamping device 49 is a vice 50 known per se, which is provided with two displaceable clamping jaws 51, 52 (the clamping jaw 51 shown is elevated). The two clamping jaws 51, 52 are actuated by a spindle 60. Between the two clamping jaws 51, 52 a workpiece 64, which is represented diagrammatically, can be clamped. The two clamping jaws 51, 52 can be fixed on guide blocks 53, 54 by means of screws. To fix a workpiece in the vice 50, the workpiece is clamped between the two clamping jaws 51, 52. The vice 50 comprises a stable base 55, on the upper part of which two parallel-running guide rails 56, 57 are provided for guiding the two displaceable guide blocks 53, 54. The vice 50 is provided with a clamping spigot 63 secured to the underside of the base 55, by which it can be secured to a chuck, as shown in Figure 2. Of course, the vice 50 can be secured to the machine tool in other ways.

[0098] The clamping device 49 is provided with a transmitting device (not shown), as mentioned above. In order to monitor the clamping quality of the workpiece clamped between the clamping jaws 51, 52, a DMS is arranged on each of the two guide rails 56, 57 (only one DMS 61 is shown in FIG. 3). In order to protect the DMS from external influences, a cover cap 62 is provided. Each DMS is arranged on the guide rails 56, 57 at a point where high forces and correspondingly high elastic material deformations occur during clamping of the workpiece, which deformations can be measured by the DMS. Due to the arrangement of the DMS sensors on the guide rails 56, 57, the clamping forces can be measured by these sensors regardless of the clamping jaws used, so that the clamping jaws 51, 52 can be exchanged without any changes to the DMS sensors.

[0099] Each guide block 53, 54 is also provided with a respective sensor 58, 59 for detecting the position of the clamped workpiece. The respective sensor 58, 59 is arranged in the outer area of ​​the guide block 53, 54 so as to measure perpendicularly upwards to the displacement direction of the clamping jaws 51, 52, i.e. in the Z direction, and thus detects the distance between the underside of the clamped workpiece and the respective guide block 53, 54. The two sensors 58, 59 are arranged diagonally to each other. The sensors 58, 59 for detecting the position are preferably inductively actuated sensors in the form of inductive proximity switches, which can advantageously detect, for example, workpieces clamped at an angle. The arrangement of the position detection sensors 58, 59 on the guide blocks 53, 54 allows the measurement to be performed by these sensors regardless of the clamping jaws used.

[0100] In addition to the transmitter and receiver, the four sensors mentioned above also form part of the monitoring device. The transmitter is preferably accommodated in a recess arranged in the lower half area of ​​the vice. The transmitter and receiver are basically identical in construction to those shown in FIG. 1 and will not be described in detail here. The two position detection sensors 58, 59 are arranged on the movable part (guide block) of the vice 50 and are therefore connected via a movable cable to the transmitter accommodated in the base body 55. The two DMS sensors are connected to the transmitter via conventional cables. By mutually comparing the measurement data of the two DMS sensors, the validity of the measurement data can also be mutually checked. Thus, by means of the two DMS, the clamping quality of the clamped workpiece can be redundantly monitored as described above. In addition to the four sensors mentioned above, it is also possible to provide additional sensors, such as an acceleration sensor arranged in the vice, which allows not only the position of the vice but also, if necessary, the movement of the vice to be detected. Furthermore, a sensor for measuring the distance between the two guide blocks 53, 54 may be provided.

[0101] It goes without saying that the above-mentioned embodiments are not definitive or exhaustive. Thus, for example, the transmitting and receiving devices can be provided with two independent transmitters and receivers for redundant transmission of measured values. Additional sensors can also be provided in the chuck or in each clamping device to monitor further parameters. For example, temperature sensors can be used. The data of the further sensors can be transmitted wirelessly using the transmitting device. Instead of the inductive sensors 71, 72, for example ultrasonic, capacitive or optical sensors can also be provided to determine the position of the working piston.

[0102] A "simpler" variant of the monitoring device constructed according to the invention is also conceivable. In this case, for example, only the clamping force is redundantly monitored by two sensors, which does not necessarily have to be detected with absolutely high resolution, and in some cases it is sufficient to detect and / or monitor the clamping force, for example, in 2 to 10 steps and transmit it by the transmitting device. Also, bidirectional data exchange is possible between the transmitting device and the receiving device. This allows, for example, software updates to be transmitted from the receiving device to the transmitting device.

[0103] The term clamping quality is understood in this specification to mean the ratio between the required clamping force (depending on the part size and the processing forces acting on the workpiece during processing) and the actual measured clamping force or measured value.

[0104] Some advantages of a monitoring system constructed in accordance with the present invention are briefly summarized below. - The clamping quality between the workpiece carrier / workpiece and the clamping device can be reliably monitored and wirelessly transmitted to a remote location. - The transmitted data can be detected, stored and externally evaluated. The clamping quality of the clamped workpiece carrier or workpiece can be monitored reliably and reliably with only two sensors. - The parameters can be continuously monitored. - The measurement of certain parameters increases the reliability of the process. In particular, the clamping force or the retraction force of the clamping spigot can be continuously monitored to obtain useful safety-related data. - By providing two different microprocessors in the transmitter and receiver, the measurement data can be processed independently and redundantly. The entire measurement chain, including the transmission and evaluation of the measurement data, is designed to be reliable and redundant. [Explanation of symbols]

[0105] 1 Machine space 2 Clamping System 3 Clamping device 4 5 Base plate 6 First chuck 7 Second Chuck 8. Third Chuck 9. 4th Chuck 10 11 12 Surveillance Assembly 13 14 Transmitting device 15 First Microprocessor Unit 16 Second microprocessor unit 17 Transmitting Antenna 18 Acceleration Sensor 19 Power supply 20 21 Receiving device 22 Receiving antenna 23 First Cable 24 Gateway 25 1st Microprocessor Unit 26 Second Microprocessor Unit 27 Second Cable 28 Machine Control Device 29 3rd Cable 30 Handling Robot 31 4th Cable 32 Service Tools 33 34 First Sensor Module 35 Second Sensor Module 36 3rd Sensor Module 37 4th Sensor Module 38 39 40 Clamping device 41 Chuck 42 Central hole 43 Sensor Presence Palette 44 45 Workpiece carrier (pallet) 46 Clamp spigot 47 48 49 Clamping device 50 Vice 51 Clamp jaw 52 Clamp jaw 53 Guide block 54 Guide block 55 Base 56 Guide rail 57 Guide rail 58 First position sensor 59 Second position sensor 60 Spindle 61 DMS 62 Cover 63 Clamp spigot 64 Workpieces 65 Working piston 66 Clamp ball 67 Compression Spring 68 Circular Space 69 1st DMS sensor 70 Second DMS sensor 71 First induction sensor (operating piston) 72 Second induction sensor (operating piston) L1~L4 lines (sensor module) A1~C4 Sensors

Claims

1. A monitoring assembly for monitoring a clamping quality of a workpiece carrier or a workpiece clamped in a clamping device (3, 40, 49), comprising at least two sensors (A1-C4) arranged in said clamping device (3, 40, 49) for independently detecting said clamping quality of a clamped workpiece carrier or workpiece, and a transmitting device (14) for wirelessly transmitting a plurality of parameters measured by the sensors (A1-C4) and positively correlated with each other to a receiving device (21), A monitoring assembly, characterized in that the transmitting device (14) is configured to transmit the measured parameters to the receiving device (21).

2. 2. The monitoring assembly according to claim 1, characterized in that the monitoring assembly (12) comprises at least one sensor module (34, 35, 36, 37), which digitizes the measured values ​​of the sensors (A1-C4) and transmits them to the transmitting device (14).

3. 3. A monitoring assembly according to claim 2, characterized in that the transmitting device (14) is provided with two independent microprocessor units (15, 16) configured for independent and redundant processing of the measurement values ​​transmitted by each of the sensor modules (34, 35, 36, 37).

4. 4. A monitoring assembly according to claim 3, characterized in that the transmitting device (14) comprises at least one transmitting antenna (17) for transmitting measurement data processed by the two independent microprocessor units (15, 16).

5. 5. A monitoring assembly according to claim 1, characterized in that the at least two sensors (A1-A4) are constructed and arranged to measure a material elastic deformation of a chuck (6, 7, 8, 9, 41) or a vice (50) in the clamping device (3, 40, 49) during clamping of a workpiece carrier or a workpiece, the sensors being in particular strain gauge sensors (DMS).

6. 6. A surveillance assembly according to claim 1, wherein the clamping device comprises at least one chuck (41) including an actuating piston (65) for displacing in the Z direction a clamping element (66) for clamping a clamping spigot (46), The monitoring assembly comprises at least two sensors (71, 72) operating without contact, and the at least two sensors (71, 72) are capable of detecting at least two positions of the working piston (65) independently of each other.

7. 7. The monitoring assembly of claim 6, wherein the sensor is an inductively actuated sensor (71, 72) capable of detecting at least one of an open position and a closed position of the actuating piston (65).

8. A monitoring assembly for monitoring the clamping quality of a workpiece carrier clamped by the clamping device (3, 40) according to any one of the preceding claims, comprising:

2. A monitoring assembly, characterized in that the monitoring assembly comprises at least one further sensor (B1-B4, 43) capable of detecting the attachment of the workpiece carrier to the clamping device (3, 40).

9. 6. A monitoring assembly according to claim 1, for monitoring the clamping quality of a workpiece clamped in a vice (50) of a clamping device (49), in which the vice (50) is provided with two guide blocks (53, 54), on each of which a clamping jaw (51, 52) for clamping a workpiece is fixed, the monitoring assembly comprising at least two further sensors (58, 59) capable of detecting the attachment of a workpiece to each of the guide blocks (53, 54) in the vice (50), The at least two further sensors (58, 59) are arranged in outer areas of the guide blocks (53, 54) so ​​as to measure upwards perpendicular to the displacement direction of the clamping jaws (51, 52) and detect the distance between the underside of the clamped workpiece and the guide blocks (53, 54).

10. A monitoring assembly according to any one of the preceding claims, characterized in that the monitoring assembly is provided with further sensors (C1-C4) capable of detecting the position of an element for actuating the clamping element.

11. A monitoring assembly according to any one of claims 1 to 10, comprising a receiving antenna (22) for receiving data transmitted by the transmitting device (14) and a gateway (24) connected to the receiving antenna (22), the gateway (24) being provided with two independent microprocessor units (25, 26) for further processing the received data independently and redundantly, the gateway (24) being connected to a machine control device (28) of a processing machine.

12. 12. A monitoring assembly according to claim 11, characterized in that the gateway (24) processes the measured values ​​transmitted by the transmitting device (14) in such a way that, if a coincidence of the detected measured values ​​is confirmed by the two independent microprocessor units (25, 26) and a predefined measured value in the machine control is reached, a signal is redundantly output to the machine control device (28) regarding a correctly clamped workpiece carrier or a correctly clamped workpiece and / or a reliable operation of the machine tool.

13. A clamping system (2) comprising a clamping device (3, 40, 49) for clamping a workpiece carrier or a workpiece and a monitoring assembly constructed according to any one of claims 1 to 10, 1. A clamping system comprising: a clamping device having a clamping force detecting means for detecting a clamping force acting on a clamped workpiece carrier or a clamped workpiece, the clamping device comprising: a clamping device configured to detect a clamping force acting on the clamped workpiece carrier or a clamped workpiece;

14. 14. A clamping system (2) according to claim 13, characterized in that the transmitting device (14) of the monitoring assembly (12) comprises a radio transmitter arranged on the clamping device (3, 40, 49) and the receiving device (21) comprises a radio receiver arranged remotely from the radio transmitter, the transmitting device (14) comprising two independent microprocessor units (15, 16) arranged for independently and redundantly processing the same measurement values ​​transmitted from each sensor module (34, 35, 36, 37) and for checking the validity of the measurement values ​​by comparing them with each other.

15. 15. The clamping system (2) according to claim 13 or 14, characterized in that the sensors (A1-A4) are strain gauge sensors frictionally engaged and / or rigidly bonded to a chuck or vice of the clamping device (3, 40, 49) such that its signal is substantially proportional to the clamping force.

16. 16. Clamping system (2) according to any one of claims 13 to 15, characterized in that the clamping device (3, 40) comprises at least one chuck (6, 7, 8, 9, 41) for clamping a workpiece carrier, the chuck (6, 7, 8, 9, 41) having a sensor (B1-B4, 43) arranged in its upper area for detecting the attachment of the workpiece carrier.

17. A clamping system (2) comprising a clamping device (3, 40, 49) for clamping a workpiece carrier or a workpiece and a monitoring assembly configured according to claim 6, the monitoring assembly (12) comprises at least two sensors (A1-A4) arranged on the clamping device for independently detecting the clamping force acting on a clamped workpiece carrier or a clamped workpiece, The clamping system comprises a chuck (41) for clamping a workpiece carrier (45) provided with a clamping spigot (46), the chuck (41) having an actuating piston displaceable between an initial position and a locked position for actuating a clamping element which clamps the clamping spigot (46), The clamping system is characterized in that the chuck (41) is provided with a further sensor for monitoring the position of the working piston, in particular, that the chuck (41) is provided with at least two sensors (71, 72) operating without contact, and by means of the at least two sensors (71, 72), at least two positions of the working piston (65) can be detected independently of one another.

18. A clamping system (2) comprising a clamping device (3, 40, 49) for clamping a workpiece carrier or a workpiece and a monitoring assembly configured according to claim 6, the monitoring assembly (12) comprises at least two sensors (A1-A4) arranged on the clamping device for independently detecting the clamping force acting on a clamped workpiece carrier or a clamped workpiece, The chuck (6, 7, 8, 9, 41) comprises a first chuck (6, 7, 8, 9) and a second chuck (41), the first chucks (6, 7, 8, 9) are adapted to clamp a workpiece carrier having a number of clamping spigots corresponding to the number of chucks, each of the first chucks (6, 7, 8, 9) having an actuating piston displaceable between an initial position and a locking position for actuating a clamping element for clamping each of the clamping spigots, A clamping system characterized in that at least one chuck is provided with further sensors (C1-C4) for monitoring the position of the working piston, and in particular that the second chuck (41) is provided with at least two sensors (71, 72) operating without contact, by means of the at least two sensors (71, 72) at least two positions of the working piston (65) can be detected independently of one another.

19. A clamping system (2) comprising a clamping device (3, 40, 49) for clamping a workpiece carrier or a workpiece and a monitoring assembly configured according to claim 9, the monitoring assembly (12) comprises at least two sensors (A1-A4) arranged on the clamping device for independently detecting the clamping force acting on a clamped workpiece carrier or a clamped workpiece, A clamping system, characterized in that each clamping jaw (51, 52) is assigned a sensor for determining the clamping force of the clamped workpiece.

20. A method for monitoring a clamping device in a processing machine by means of a monitoring assembly constructed according to any one of claims 1 to 12, comprising the steps of:

1. A method according to claim 1, further comprising the steps of: determining the clamping quality of a workpiece carrier or a workpiece clamped in the clamping device by means of at least two independent sensors (A1-A4), comparing the measurement data determined by each of the sensors (A1-A4) with one another and checking them for plausibility by two independent microprocessor units (25, 26), and redundantly transmitting the determined or calculated parameters by a transmitting device (14) to a receiving device (21) and by a gateway (24) to a control device (28) of the processing machine.

21. 21. The method according to claim 20, characterized in that the sensors (A1-A4) are strain gauge sensors (DMS) and that the plausibility check comprises checking the agreement of the determination and the parameters compared with each other after processing by two independent microprocessor units (15, 16) in the transmitting device (14).

22. 22. A method according to claim 21, characterized in that the determined or calculated parameters are redundantly transmitted by the transmitting device (14) to the receiving device (21) in the form of data packets and the validity of the transmitted data is checked at the receiving side.

23. 23. The method according to claim 22, wherein the receiving device (21) comprises a gateway (24), the gateway (24) generates a release signal for a secure operation and redundantly transmits it to a control device (28) of the processing machine if the determined and compared parameters coincide and reach a predetermined measured value.

24. 24. The method according to claim 23, characterized in that the gateway (24) emits the release signal in the form of a binary signal, the release signal taking a value of 1 if the measured value is valid and reaches a predetermined value and the release signal taking a value of 0 if the detected measured value is not valid or does not reach a predetermined value.

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