DE102014110007B4 - Clamping unit and chuck unit of a clamping device and method for performing a clamping or releasing movement for clamping or releasing a workpiece - Google Patents

Abstract

The invention relates to a clamping device (10), which consists of a machine-side clamping unit (11) and a thus mechanically and fluidically connectable clamping chuck unit (12). The clamping chuck unit (12) has a clamping cylinder (20) for moving clamping jaws (19), one working chamber (23) of which has a first clamping cylinder line (30) with a first chuck connection (28) and its other working chamber (24) second clamping cylinder line (31) with a second chuck terminal (29) is fluidly connected. In the two clamping cylinder lines (30, 31) is seated in each case a pilot-operated check valve (36, 37) which is unlocked when hydraulic medium from the associated working chamber (23) or (24) to be removed. When the fluidic connection between the chuck unit (12) and the clamping unit (11) is established, the two clamping cylinder lines (30, 31) are each fluidically connected to an associated hydraulic line (70) or (71). Each hydraulic line (70, 71) is associated with a separately controllable and switchable working valve device 68, 69. Only when both working valve devices (68, 69) via a control unit (66) from the neutral position N in a defined switching position (Z) or (R) are switched, a movement of the clamping jaws (19) is possible.

Description

The invention relates to a clamping unit, a fluidically and mechanically connectable to the clamping unit chuck unit, a clamping device consisting of the clamping unit and the chuck unit and a method for performing a clamping or releasing movement of clamping jaws of the chuck unit.

In some applications for machining workpieces, the workpieces are clamped in a chuck unit and prepared, for example, at a set-up station for processing. In this case, the chuck unit is fluidically and mechanically connected to a clamping unit of the set-up station in order to move the clamping jaws of the chuck unit and clamp the workpiece inside or outside. The chuck unit keeps the clamping force even after separating the chuck unit from the chuck unit. The workpiece can thus be transported in the clamped state from the set-up station to a processing machine and there again connected to a clamping unit of the machine tool. After processing, the workpiece can be transported together with the chuck unit again from the processing machine, for example, back to the set-up station or to a subsequent processing machine. About the respective clamping unit of the setup station or the machine tool, it is possible to clamp or loosen the workpiece and to change the clamping force. The clamping unit is thus part of the processing machine or the setup station. The clamping unit can be arranged to be movable or stationary relative to a machine frame of the processing machine or the set-up station in at least one translational degree of freedom. Via a turntable, the clamping unit can also be moved in a rotational degree of freedom.

A clamping device with a clamping unit and a chuck unit is for example off DE 20 2006 015 097 U1 known. The hydraulic clamping device described therein for the internal and external clamping of workpieces has manually operable changeover valves in the chuck unit, with which the movement of the clamping jaws for internal or external clamping can be specified. The chuck unit also has a clamping cylinder with two working chambers, wherein a clamping cylinder line is connected to each working chamber. The piston rod of the clamping cylinder is mechanically coupled in movement with the clamping jaws of the chuck unit, so that a movement of the piston rod causes a corresponding movement of the clamping jaws. When a fluidic connection of the chuck unit with the clamping unit is established, hydraulic medium is fed into a working chamber via a working valve device of the clamping unit and removed from the other working chamber when a movement of the clamping jaws is to be caused. The working valve device is fluidly connected to the two clamping cylinder lines for this purpose.

DE 10 2004 011 120 A1 discloses a clamping unit with a connecting device having a hydraulic first working port and a hydraulic second working port, wherein by means of the connecting device a separate chuck unit with a first working chamber and a second working chamber having hydraulic clamping cylinder is mechanically and fluidly connectable to the clamping unit. The clamping unit has a first working valve device, the output of which is fluidically connected to supply or discharge hydraulic medium into and out of the first working chamber of a chuck unit connected to the clamping unit. The clamping unit also has a second working valve device, the output of which is fluidically connected to supply or discharge hydraulic medium into and out of the second working chamber of a chuck unit connected to the clamping unit. The working valve devices are each connected to an inlet with a supply line and at another input with a return line for hydraulic medium. The two working valve devices can be switched independently of each other in an inlet position or a return position and in the inlet position of the respective output to the supply line and in the return position of the respective output to the return line is fluidly connected.

With the help of such hydraulic tensioners very large workpieces with a total weight of up to about 4 tons can be clamped. During machining, these workpieces are rotated at speeds of up to 1000 revolutions per minute. Accelerating and moving such large masses during processing requires the highest level of safety. Accidental loosening or loosening of the workpiece in the chuck unit can cause considerable damage to the machine tool and is a great danger to the operator.

It can therefore be regarded as an object of the present invention to make the known chuck device safer.

This object is achieved by a clamping unit with the features of claim 1, by a chuck unit with the features of claim 13 and a method having the features of claim 17.

The clamping unit according to the invention can be present at a set-up station or a processing machine. The clamping unit has a connection device which is adapted to be mechanically and hydraulically connected to a separate chuck unit. A connected chuck unit can be actuated via the clamping unit, so that a workpiece can be clamped in the chuck unit or detached from the chuck unit or the clamping force can be changed.

The chuck unit has for clamping the workpiece movably mounted clamping jaws. The clamping jaws are mechanically coupled with a movable piston of a hydraulic clamping cylinder. The movement coupling can take place arbitrarily and optionally provide a translation or reduction of the piston movement. The piston of the clamping cylinder divides the cylinder interior into a first working chamber and one of them fluidically separated second working chamber. The first working chamber is hydraulically connected to a first clamping cylinder line and the second working chamber to a second clamping cylinder line. The present invention also relates to a clamping device with such a chuck unit of the clamping unit according to the invention.

The connecting device of the clamping unit has a first hydraulic working connection for the fluidic connection to the first clamping cylinder line and a second hydraulic working connection for the fluidic connection of the second clamping cylinder line. A first working valve device of the clamping unit has an output, which is connected by means of a first hydraulic line to the first working port. Therefore, a hydraulic medium can be supplied into the first working chamber or removed from the first working chamber via the first hydraulic line and the first working port. Accordingly, a second working valve device is present, the output of which is connected by means of a second hydraulic line to the second working port, so that hydraulic medium can be supplied to the second working chamber or discharged from the second working chamber. The two working valve devices are independently switchable in at least two switching positions, namely an inlet position and a return position. In the inlet position, the outlet of the relevant working valve device is fluidically connected to a supply line, which provides pressurized hydraulic medium and which is connected to an input of the working valve device. In the return position, the output of the respective working valve device is fluidly connected to another input of the working valve device, to which a return line for the hydraulic medium is connected, which leads, for example, to a tank or reservoir.

For switching the two working valve devices in the different switching positions, for example, electrically actuated valve drives can be provided. The switching of the two working valve devices takes place independently of one another and can be initiated, for example, by a control device which controls the valve drives.

By providing two independently switchable working valve devices for each hydraulic line, safety is increased. In particular, it can be achieved that a movement of the clamping jaws can only be performed when both working valve devices occupy a predetermined switching position. For example, movement of the clamping jaws of the chuck unit is only possible if the one working valve device is in the feed position and the other work valve device is in the return position. An accidental loosening or tightening the jaws or the workpiece by a simple error is avoided in this way. The failure of a working valve device or an associated valve drive for switching thus does not lead to a safety-critical state.

Preferably, the two working valve devices are identical.

The first and / or the second working valve device in each case has a directional control valve with a working output and a control output. The work outlet is fluidly connected to the respective working valve device associated first and second hydraulic line.

In this case, the first and / or the second working valve device in each case one arranged in the respective hydraulic line, via a control input unlocked check valve. The control input of the pilot-operated check valve is fluidically connected to the control output of the associated directional valve of the working valve device. In the blocking state, the check valve prevents a hydraulic flow in the direction of the directional control valve and allows a hydraulic flow from the working output of the directional control valve to the relevant working connection of the clamping unit.

In the inlet position of one of the two working valve devices, the control output of the respective directional control valve can be fluidically connected to the return line. In the return position of the first or second working valve device, the Control output of the directional control valve to be connected fluidly to the supply line. About the directional valve, the associated unlockable return valve is therefore unlocked in the return position and only then is a backflow from the hydraulic fluid from the associated working port through the working valve device in the return line to the reservoir possible.

Preferably, the first directional control valve of the first working valve device and / or the second directional control valve of the second working valve device is designed as a 4/3-way valve. It thus has, in addition to the inlet position and the return position to a third switching position, which is preferably designed as a neutral position. In the neutral position, for example, both the work output and the control output of the directional control valve are fluidically connected to the return line. In this neutral position, the respectively associated unlockable check valve can not be unlocked and a flow of hydraulic fluid through the relevant working valve device in the return line is prevented.

Preferably, the first directional control valve and / or the second directional control valve are mechanically biased in the neutral position. For this purpose, for example, one or more spring means may be present. The neutral position can be performed in one embodiment as the center position of the directional control valve between the inlet position and the return position.

The first directional control valve and / or the second directional control valve preferably has two independently operable valve drives, wherein the one valve drive for switching the directional control valve from the neutral position into the inlet position and the respective other valve drive for switching the directional control valve from the neutral position to the return position. Two independent valve actuators for switching the directional valve from the neutral position to the inlet position and into the return position, the safety of the clamping unit can be further increased. It is advantageous if the switching movements of the two valve drives take place in opposite directions.

It is advantageous if the clamping unit has a control valve device. The output of the control valve device can be fluidly connected to a control connection of the connection device by means of a third hydraulic line. The control valve device is switchable between a control position and a rest position and preferably mechanically biased into the rest position. In the control position of the control port is fluidly connected through the control valve means with the return line.

In one embodiment, the check valve means may comprise a directional control valve having a control output and a control output, the control output being fluidly connected to the third hydraulic line. The check valve device may also include a pilot operated check valve disposed in the third hydraulic line and, in the locked state, inhibiting hydraulic flow from the control port to the directional control valve. The control input for unlocking the pilot-operated check valve is preferably fluidically connected to the control output of the directional valve of the control valve device. In particular, the control output of the directional control valve in the control position is fluidically connected to the supply line, while the control output is fluidically connected to the return line. Thus, in the control position hydraulic fluid can flow from the control port via the control valve device in the return line. About the control port can be carried out in a fluidically connected to the clamping unit chuck unit a short-term pressure reduction, regardless of the switching position of the two working valve devices, which can be used for example for testing pressure sensor signals.

It is also advantageous if the clamping unit has an unlocking valve device. The output of the Entsperrventileinrichtung can be fluidly connected by means of a fourth hydraulic line with an unlocking connection of the connecting device. The Entsperrventileinrichtung can be switched between an unlocking and a rest position. In the unlocked position, the output of the unlocking valve device is connected to the supply line and / or a hydraulic supply line, the hydraulic supply line providing hydraulic medium or at least the same hydraulic pressure as the supply line. About the Entsperranschluss a there existing pilot-operated check valve can be unlocked in a connected chuck unit. Preferably, a hydraulic pressure from a supply line is used, which is greater than the hydraulic pressure in the supply line.

The connecting device of the clamping unit can also have a pneumatic connection. This can be connected or connected via a pneumatic line with a pneumatic pressure source. The pneumatic pressure in the pneumatic line can be evaluated via a pressure sensor. For example, a connected chuck unit in the event of an inadmissible or unscheduled operating state, this chuck unit vent the pneumatic connection (fluidly connect to the environment) and in this way the state of the tension unit transmit state information.

It is also advantageous if one, several or all hydraulic lines of the clamping unit are each connected to a pressure sensor to determine the prevailing fluid pressure there. As explained, the pneumatic line can also be connected to a pressure sensor.

In an exemplary embodiment of the chuck unit according to the invention, a coupling device is provided, which cooperates in particular with the connecting device of the clamping unit in order to mechanically and fluidically couple the clamping unit to the chuck unit. The chuck unit has a plurality of mutually toward and away from each other movably mounted jaws. A workpiece can be clamped inside or outside via the clamping jaws. To move the jaws, a hydraulic clamping cylinder with a first working chamber and a second working chamber is present. The first working chamber is fluidically connected to a first clamping cylinder line and the second working chamber is fluidically connected to a second clamping cylinder line. In each clamping cylinder line in each case a releasable chuck check valve is arranged, which prevents in its blocking state leakage of hydraulic fluid from the respective working chamber. To unlock, each chuck check valve has a control input. The first clamping cylinder line fluidly connects the first working chamber to a first clamping chuck closure of the coupling device. Accordingly, the second clamping cylinder line fluidly connects the second working chamber with a second chuck terminal of the coupling device. The control input of the first chuck check valve in the first clamping cylinder line is fluidly connected to the second chuck terminal. Analogously, the control input of the second chuck check valve in the second clamping cylinder line is fluidly connected to the first chuck terminal. By pressurizing one of the two clamping cylinder lines with hydraulic medium thus the outflow of hydraulic medium from the other working chamber via the other clamping cylinder line is made possible by the unlocked chuck check valve. If the two clamping cylinder lines are depressurized, the position of the clamping jaws is maintained, whereby, for example, the clamping state of a workpiece can be maintained, even if the clamping unit is separated from the clamping unit or if, for example, the hydraulic supply fails.

Optionally, the chuck unit may also include one or two hydraulic accumulators. In one embodiment, each pressure accumulator is fluidly connected to one of the two clamping cylinder lines. Thereby, the maintenance of the pressure in the clamping cylinder can be improved when the chuck unit is fluidically separated from the clamping unit.

In addition, the coupling device of the chuck unit has a hydraulic monitoring connection. This monitoring port is fluidly connected to a hydraulic monitoring line. The monitoring line has two parallel branches, wherein one branch is fluidly connected to the first chuck terminal via a check valve and the other branch is fluidly connected to the second chuck terminal via a further check valve. The check valves in the two branches each prevent hydraulic flow from the monitoring line to the associated chuck port. If the hydraulic pressure in the monitoring line is smaller than at a chuck port, hydraulic fluid flows from the chuck port into the monitoring line, reducing the pressure there. By this measure, the hydraulic pressure can be lowered in a pressurized clamping cylinder line, for example, during a predetermined period of time, whereby a test or monitoring of a pressure sensor signal can be performed.

In addition, the coupling device may have a hydraulic drive connection. The drive connection can be fluidically connected to an unlock line. The unlock line may be fluidly connected to the control input of the first chuck check valve and / or the control input of the second chuck check valve. About the Entsperrleitung thus the associated chuck check valve can be unlocked.

In a preferred embodiment, the unlocking of a chuck check valve may be accomplished both by the pressure in an associated chucking cylinder conduit and by the pressure in the release conduit. For this purpose, a shuttle valve with two inputs can be connected to the control input of each chuck-check valve, via which a logical OR function is realized. On the input side, the shuttle valve with the Entsperrleitung and a clamping cylinder line and the output side is fluidly connected to the control input of the relevant chuck check valve.

In the installation position in the chuck unit, the optionally present shuttle valves are arranged such that the movable valve elements under centrifugal force - during the rotation of the workpiece - are moved away from the input to which a clamping cylinder line is connected, so that under centrifugal force a fluidic connection between the connected clamping cylinder line and the control input of the chuck check valve connected to the shuttle valve and thus the unlocking is not affected.

Advantageously, the coupling device of the chuck unit has a pneumatic test connection. The test connection is pneumatically connected to a vent by means of a pneumatic test line. In the test line a test valve is arranged. The pneumatic connection between the test port and the vent is inhibited when an evaluation means of the chuck unit associated with the check valve indicates that the jaws are within a predetermined position range. If the jaws are not within this position range, but in an inner and / or outer end zone of their maximum range of motion, the test port is vented through the vent. The pneumatic pressure in the pneumatic test line can be evaluated, for example via a pressure sensor in the clamping unit. If the clamping jaws are not within a permissible position range, a faulty or insufficient clamping is detected by a pressure drop.

With the help of the clamping unit and a fluidically connected chuck unit, the jaws can perform a clamping or releasing movement. In particular, the procedure is as follows:
Depending on the desired direction of movement of the jaws towards or away from one another, either the first working chamber or the second working chamber of the clamping cylinder is subjected to hydraulic pressure and discharged from the other working chamber hydraulic medium. For this purpose, one of the two working valve devices of the clamping unit is switched to the inlet position and the respective other working valve device in the return position. Only when both working valve devices occupy the relevant switching position, hydraulic medium can be fed into a working chamber and discharged from the other working chamber.

Optionally, in the case of clamping a workpiece after the end of the clamping movement of the jaws, so after clamping a workpiece, the pressure in the pneumatic test line is controlled. If a pneumatic pressure is applied there, the clamping jaws are in the permissible position range. For pressure testing, the pneumatic test line is subjected to a pneumatic pressure via the clamping unit. If the jaws are outside the permissible range, the pneumatic test line is or is vented and the clamping unit detects an error during clamping.

It is further contemplated, after the termination of the clamping movement of the jaws on the control valve means to lower the hydraulic pressure in the control line during a predetermined control period. As a result, the hydraulic pressure in the clamping cylinder line or first or second hydraulic line coupled to the supply line also drops. The pressure value measured in the clamping cylinder line or the hydraulic line must follow the pressure drop in the control line - slightly delayed in time. In this way, it can be checked whether the pressure sensor is working properly in a tensioning cylinder line or in a first or second hydraulic line connected thereto or whether one of the two tensioning cylinder lines of the tensioning chuck unit is properly providing a hydraulic pressure. This eliminates sensors in the chuck unit.

If the hydraulic pressure fails during operation of the tensioner, the tensioning pressure or force remains through the pilot operated check valves in the tensioner unit. For example, if a leak occurs in the tension cylinder line between a chuck port and the pilot operated check valve, the clamping pressure is maintained. This pressure loss can be detected by pressure sensors. In the case of such a pressure loss or even in the event of the loss of electrical energy, the valve devices of the clamping unit are switched over to the mechanically preset switching positions. The same applies if an emergency stop in the processing machine is triggered by an operator.

Advantageous embodiments of the invention will become apparent from the dependent claims, the description and the drawings. Hereinafter, preferred embodiments of the invention will be explained in detail with reference to the accompanying drawings. Show it:

1 a schematic, simplified schematic representation of a clamping device with a chuck unit and a clamping unit,

2 a schematic plan view of a portion of a connecting device of the clamping unit 1 according to arrow II,

3 a fluid circuit diagram of the chuck unit 1 .

4 to 6 different switching positions of a test valve of the chuck unit 3 .

7 a fluid circuit diagram of an embodiment of the clamping unit 1 .

8th and 9 the fluid circuit diagram according to 7 , wherein the existing valve means of the clamping unit are in different switching positions,

10 and 11 in each case only an exemplary, greatly simplified time course of control signals for switching over the valve devices of the clamping unit and of pressure sensor values for the clamping unit according to FIGS 7 to 9 ,

In 1 is schematically a tensioning device 10 with a clamping unit 11 and a chuck unit 12 illustrated. The clamping unit 11 and the chuck unit 12 are fluidly and mechanically connected to each other. For this purpose, the clamping unit 11 a connection device 13 and the chuck unit has a coupling device 14 on, which cooperate to produce the mechanical and fluidic connection.

About the chuck unit 12 can be a workpiece 15 be clamped and held. The chuck unit 12 has towards each other and wegbewegbare clamping jaws 19 on. Preferably, the jaws 19 in a common plane radially to a longitudinal center axis of the chuck unit 12 movable inwards or outwards. The chuck unit 12 can a palette 25 have the chuck unit 12 carries and when made connection with the clamping unit 11 is interposed in particular for mechanical connection. The pallet 25 Can be handled with the chuck unit 12 be releasably connected, so that a jointly manageable unit is formed.

With the help of the clamping jaws 19 can be a workpiece 15 be stretched inside or outside. In 1 is schematically an externally clamped workpiece 15 illustrated.

To move the jaws 19 serves a hydraulic clamping cylinder 20 that has a movable piston 21 having. The piston 21 is over the piston rod 22 and optionally further mechanical transmission parts with the clamping jaws 19 motion-coupled. This can cause a piston movement in a movement of the jaws 19 be implemented. The piston 21 divides the interior of the clamping cylinder 20 fluidly into a first working chamber 23 and a second working chamber 24 , By supplying a hydraulic medium in one of the two working chambers 23 or 24 and discharge of hydraulic medium from the other working chamber 24 respectively. 23 can be a movement of the piston 21 and therefore a movement of the jaws 19 be generated. About the hydraulic pressure in the working chambers 23 . 24 can the clamping force between the jaws 19 and the workpiece 15 be set or changed.

The coupling device 14 Provides hydraulic connections to hydraulic fluid from the tensioner 11 feed or to the clamping unit 11 dissipate. In the embodiment, this four hydraulic connections and a pneumatic connection to both the coupling device 14 as well as at the connection device 13 present, which will be discussed in detail later in connection with the fluid circuit diagrams. In the schematic representation after 1 the fluid lines and the valve devices and pressure accumulator or pressure sources are omitted for clarity.

In 3 is the fluid circuit diagram of an embodiment of the chuck unit 12 illustrated. The coupling device 14 the chuck unit 12 has a hydraulic first chuck port 28 and a hydraulic second chuck port 29 on. The first chuck connection 28 is via a hydraulic first tension cylinder line 30 fluidic with the first working chamber 23 and the second chuck port 29 via a hydraulic second clamping cylinder line 31 fluidic with the second working chamber 24 connected. In both tension cylinder lines 30 . 31 is in each case a throttle valve arrangement 32 arranged. Each throttle valve assembly 32 has one over a throttle 33 throttled flow path 34 on. By adjusting the throttle 33 can cause a jerky movement of the piston 21 and therefore the jaws 19 at a hydraulic medium supply to one of the two working chambers 23 . 24 be prevented. Parallel to the throttled flow path 34 is a backwash path 35 in which a check valve is arranged, which is a hydraulic flow to the associated chuck terminal 28 respectively. 29 allowed and an oppositely directed hydraulic flow in the direction of the clamping cylinder 20 in derogation. About the backwash path 35 becomes the flow path 34 during the outflow of hydraulic medium to a chuck connection 28 respectively. 29 shorted and the choke 33 is not effective.

Between the throttle valve assembly 32 and the clamping cylinder 20 is in the first tension cylinder line 30 a releasable first chuck check valve 36 and in the second tension cylinder line 31 a releasable second chuck check valve 37 arranged. The chuck check valves 36 . 37 prevent in their locking state a hydraulic flow from the associated working chamber 23 respectively. 24 , To unlock the chuck check valves 36 . 37 is each a control input 36s respectively. 37s available. When a hydraulic pressure at the control input 36s respectively. 37s is applied, is the relevant chuck check valve 36 . 37 unlocked, allowing a hydraulic flow from the relevant working chamber 23 respectively. 24 is possible.

The control inputs 36s respectively. 37s are controlled by way of example via two separate hydraulic lines. To enable this is the control input 36s of the first chuck check valve 36 with the output of a first shuttle valve 38 and the control input 37s of the second chuck check valve 37 with the output of a second shuttle valve 39 fluidly connected. Each shuttle valve 38 . 39 has two entrances. If a hydraulic pressure is applied to at least one of the two inputs, then this is via the output of the shuttle valve 38 . 39 to the assigned control input 36s respectively. 37s created.

The one input of the first shuttle valve 38 is fluid with the second clamping cylinder line 31 connected while the one input of the second shuttle valve 39 fluidly with the first clamping cylinder line 30 connected is. The connection between the shuttle valves 38 . 39 and the respective clamping cylinder line 31 respectively. 30 are preferably between the throttle valve assembly 32 and the chuck check valve 36 . 37 arranged.

The other entrance of the shuttle valves 38 . 39 is fluidic with an unlock line 40 connected. The unlock line 40 is fluidic to a hydraulic drive connection 41 the coupling device 14 connected.

The coupling device 14 also has a hydraulic monitoring port 42 on, with which a hydraulic monitoring line 43 is fluidically connected. The monitoring line 43 is over a first branch 43a fluidly with the first clamping cylinder line 30 and over a second branch 43b fluidic with the second clamping cylinder line 31 connected. In each of the branches 43a . 43b a non-return valve is arranged, which is a hydraulic flow from the monitoring line 43 in the respective clamping cylinder line 30 . 31 in derogation.

Optionally, the chuck unit 12 also one or two hydraulic pressure accumulators 44 exhibit. At the in 3 illustrated embodiment is in each case a pressure accumulator 44 as a buffer memory fluidly with an associated working chamber 23 respectively. 24 and / or an associated clamping cylinder line 30 respectively. 31 connected. This allows pressure losses through hydraulic leakage currents to be buffered when the chuck unit 12 from the clamping unit 11 is fluidically isolated. The accumulators 44 are without the interposition of valves or other hydraulic control components with the respective associated working chamber 23 respectively. 24 fluidly connected. According to the example, each accumulator is 44 between the clamping cylinder 20 and the respective chuck check valve 36 . 37 to the associated clamping cylinder line 30 31 connected.

The coupling device 14 also has a pneumatic test port 45 on. A pneumatic test line 46 connects the test port 45 fluidic with a vent 47 , Between the vent 47 and the test port 45 is a pneumatic check valve 48 into the test line 46 used. A movable valve member 49 of the test valve 48 depends on the position of the jaws 19 positioned. For this purpose, a mechanical movement coupling between at least one of the clamping jaws 19 or a motion coupled element and the valve member 49 be present, this coupling is schematically in 3 by a coupling element 50 is illustrated.

In the 4 to 6 are different positions of the valve member 49 depending on the position of the clamping jaws 19 illustrated. In 4 are the jaws 19 in the region of a first end zone E1 following the radially inner stop of the movement of the clamping jaws 19 available range of motion. In 6 are the jaws 19 in the region of a second end zone E2 following the radially outer end stop. When the jaws 19 located in one of the two end zones E1, E2, so there is the valve member 49 a fluidic connection between the vent 47 and the test port 45 free ( 4 and 6 ). Are the jaws 19 within a permissible for the clamping position position B between the two end zones E1, E2, so the valve member locks 49 the fluidic connection between the test port 45 and the vent 47 off ( 5 ).

As in 3 the coupling device can be illustrated 14 one connection check valve at each fluid connection 14a to drain the fluidic conduit connected to the respective port after disconnecting the chuck unit 12 from the clamping unit 11 to avoid. The connection check valve 14a For example, they can be opened mechanically when the chuck unit 12 with the clamping unit 11 is connected.

The clamping unit 11 has a pressure source 60 for the hydraulic medium, to which a hydraulic supply line 61 connected. The pressure source 60 is in 7 only schematically illustrated and may include a pressure accumulator and / or a motor-pump unit for filling the pressure accumulator. In the supply line 61 the hydraulic medium is provided at a pressure of, for example, about 80 bar. To the stock management 61 is a pressure control unit 62 connected, for example, a controllable or controllable pressure control valve. About a control unit 66 can by means of a Druckeinstellsignals D a working pressure in a to the pressure control unit 62 connected supply line 63 be set. The working pressure in the supply line 63 is at most as large as the pressure in the supply line 61 , In the exemplary embodiment, the working pressure in the supply line is set in the range between 10 and 60 bar.

The clamping unit 11 has a reservoir 64 for hydraulic medium on, with a return line 65 is fluidically connected. Via a motor-pump unit of the pressure source 60 can hydraulic fluid from the reservoir 64 put under pressure and in the supply line 61 to be provided.

The clamping unit 11 has a first working valve device 68 and a second working valve device 69 on. To the first working valve device 68 heard a first way valve 68a and a pilot-operated first check valve 68b , Accordingly belongs to the second working valve device 69 a second directional valve 69a and a pilot-operated second check valve 69b , The first and the second directional valve 68a . 69a are each designed as a 4/3-way valve. On the input side, the first and the second directional valve 68a . 69a with an input to the supply line 63 and with another input to the return line 65 fluidly connected. The first and the second directional valve 68a . 69a each have a control output 68c respectively. 69c on, with an unlocking control input 68s respectively. 69s the respectively associated unlockable check valve 68b respectively. 69b is fluidically connected. In addition, the first and the second directional control valve 68a . 69a one work exit each 68d respectively. 69d on that with an associated first hydraulic line 70 or a second hydraulic line 71 is fluidically connected. In the first hydraulic line 70 is the first check valve 68b and in the second hydraulic line, the second check valve 69b arranged. The first hydraulic line leads from the work exit 68d of the first way valve 68a over the first check valve 68b to a first work connection 72 the connection device 13 , Accordingly, the second hydraulic line leads 71 from the work exit 69d of the second directional valve 69a over the second check valve 69b to a second work connection 73 the connection device 13 , In the locked state prevent the check valves 68b . 69b a hydraulic flow from the respective associated working port 72 respectively. 73 through the respective hydraulic line 70 respectively. 71 to the directional valve 68a , respectively. 69a out.

The working valve devices 68 . 69 are about the control unit 66 switchable between at least two and example according to three switch positions. The directional valves are used for this purpose 68a . 69a the working valve devices 68 . 69 , In a neutral position, the control output is in each case 68c . 69c or as well as the work exit 68d . 69d with the return line 65 fluidly connected. The supply line 63 will be blocked. The two way valves 68a . 69a are biased in the embodiment by mechanical spring means in the neutral position N ( 7 ). From this neutral position N, the first directional control valve 68a via a first drive signal M1a for the first directional control valve 68a into an inlet position Z ( 8th ) and by a second drive signal M1b for the first directional control valve 68a in a return position R ( 9 ) are switched. Accordingly, the second directional control valve 69a via a first drive signal M2a for the second directional control valve 69a into an inlet position Z ( 9 ) and a second drive signal M2b for the second directional control valve 69a in a return position R ( 8th ) are switched. For switching to the inlet position Z and in the return position R, each directional control valve 68a . 69a two independently controllable valve actuators 75 on, which are executed as an example according to electromagnetic valve actuators. Starting from the neutral position N, the relevant directional valve 68a . 69a via the one valve drive 75 in the inlet position Z and on the other valve drive 75 be switched in the opposite direction in the return position R.

In the inlet position Z connects the respective directional control valve 68a . 69a the control output 68c respectively. 69c with the return line 65 and the work exit 68d respectively. 69d with the supply line 63 , In the return position R connects the respective directional control valve 68a . 69a the control output 68c respectively. 69c with the supply line 63 and the work exit 68d respectively. 69d with the return line 65 ,

To the first hydraulic line 70 is a first pressure sensor 76 and to the second hydraulic line 71 a second pressure sensor 77 fluidly connected. The first pressure sensor 76 generates a first pressure signal P1, and the second pressure sensor 77 generates a second pressure signal P2. The pressure signals P1, P2 become the control unit 66 transmitted.

About the control unit 66 are therefore the two working valve devices 68 . 69 independently controllable and switchable to the respective inlet position Z or return position R. Without the presence of a relevant drive signal M1a, M1b, M2a, M2b, the two working valve devices are located 68 . 69 in the neutral position N ( 7 ).

The connection device 13 has a hydraulic control connection 80 on, by means of a third hydraulic line 81 fluidic with a control valve device 82 connected is. To the control valve device 82 belongs, for example, a third-way valve 82a and a pilot operated third check valve 82b , The third directional control valve is designed, for example, as a 4/2-way valve. An entrance of the third way valve 82a is with the supply line 61 and the other input to the return line 65 fluidly connected. The third way valve 82a has a control output 82c that with a control input 82s of the third check valve 82b is fluidly connected to unlock this can. The third way valve 82a has a control output 82d fluidly via the third check valve 82b with the third hydraulic line 81 connected is. The third way valve 82a is biased by a spring means in a rest position S ( 7 ), in which both the control output 82c , as well as the control output 82d fluidic with the return line 65 are connected. Via a third drive signal M3, a valve drive 75 of the third directional control valve to the third directional control valve 82a from the rest position S to a control position in which the control output 82d fluidic with the return line 65 and the control output 82c fluidic with the supply line 61 connected is.

A third pressure sensor 83 is fluidic with the control port 80 or the third hydraulic line 81 connected and generates a third pressure signal P3, the control unit 66 is transmitted.

The connection device 13 also has a hydraulic Entsperranschluss example according 85 on, over a hydraulic line 86 fluidic with a Entsperrventileinrichtung 87 connected is. The Entsperrventileinrichtung 87 is in the embodiment by a fourth directional control valve 87a formed, which is designed as a 4/2-way valve. With one input is the fourth directional control valve 87a to the supply line 61 and with another input to the return line 65 fluidly connected. The output of the Entsperrventileinrichtung 87 or the fourth directional valve 87a is fluid with the fourth hydraulic line 86 connected. In a rest position S connects the Entsperrventileinrichtung 87 the fourth hydraulic line 86 fluidic with the return line 65 , The fourth directional valve 87a is via a spring means in the rest position S ( 7 ). Via a fourth control signal M4 of the control unit 66 can be a valve drive 75 of the fourth directional valve 87a be controlled to the fourth directional valve 87a to switch from the rest position S to an unlocked position in which the supply line 61 fluidsch with the fourth hydraulic line 86 and therefore the unlock connection 85 connected is.

A fourth pressure sensor 88 is fluidsch with the Entsperranschluss 85 or the fourth hydraulic line 86 connected and generates a fourth pressure signal P4, the control unit 66 is transmitted.

In addition to the four hydraulic connections, the connecting device 13 also a pneumatic connection 90 on, over a pneumatic line 91 with a pneumatic pressure source 92 connectable or permanently connected. To the pneumatic line 91 is fluidly a fifth pressure sensor 93 connected, which generates a fifth pressure signal P5 and to the control unit 66 transmitted. The pneumatic pressure source 92 can generate a pneumatic pressure of a few bar - for example 6 bar - and at the pneumatic connection 90 provide.

According to the example, the pneumatic connection between the pneumatic pressure source 92 the clamping unit 11 and the monitoring line 46 the chuck unit 12 only in a given rotational position of the connecting device 13 having turntable of the set-up station or the processing machine made. In 2 is an example of the arrangement of the fluidic connections 72 . 73 . 80 . 85 . 90 the connection device 13 illustrated. By way of example, the pneumatic connection is 90 provided on a mandrel, which in a corresponding recess on the coupling device 14 engages the pneumatic test port 45 represents. An outlet on the mandrel and an inlet on the recess allow a pneumatic connection between the pneumatic port 90 the clamping unit 11 and the test port 45 the chuck unit 12 getting produced. Optionally, this pneumatic connection only in one or more predetermined rotational positions of the connecting device 13 opposite the coupling device 14 be produced.

When manufactured fluidic connection between the clamping unit 11 and the chuck unit 12 both at standstill and when turning the turntable is the first work connection 72 with the first chuck connection 28 , the second work connection 73 with the second chuck connection 29 , the control terminal 80 with the monitoring connection 42 , the unlock connection 85 with the control connection 41 and the pneumatic connection 90 with the test connection 45 fluidly connected.

The interaction of the clamping unit 11 with the fluidically connected chuck unit 12 in the preferred embodiment described here is as follows:
It is assumed that for clamping a tool from the outside (as in 1 illustrated) of the first working chamber 23 Hydraulic medium supplied and from the second working chamber 24 Hydraulic medium should be dissipated to a corresponding movement of the piston 21 and therefore the jaws 19 for clamping the workpiece 15 to reach. In 10 are schematically illustrated the control signals and pressure signals generated depending on the time t illustrated. At a first time t1, the first operating valve device M1a is activated via the first activation signal M1a 68 switched to the inlet position Z ( 8th ). The second drive signal M1b for the first working valve device 68 it remains equal to zero, so that a control of the corresponding valve drive 75 not taking place. By way of example, at the first time t1, the second operating valve device M2b is activated via the second actuation signal M2b 69 a switching of the second working valve device 69 in the return position R causes ( 8th ). The first drive signal M2a for the second working valve device 69 it stays zero.

By this switching is hydraulic medium via the first hydraulic line 70 and the first tension cylinder line 30 in the first working chamber 23 promoted. About the fourth control signal M4 for the Entsperrventileinrichtung 87 is at the first time t1 at Entsunranschluss 85 and therefore in the unlock line 40 generates a hydraulic pressure at the control input 37s of the second chuck check valve 37 is applied and this unlocked, so that hydraulic medium from the second working chamber 24 can drain away.

At a second time t2 reach the jaws 19 in contact with the workpiece 15 , whereby the hydraulic pressure in the first clamping cylinder line 30 or the first hydraulic line 70 increases, which is registered by the first pressure signal P1. When the desired hydraulic pressure is reached, the workpiece is 15 between the jaws 19 clamped (according to the second time t2, for example). At the second time t2, the position of the movable valve member 49 of the test valve 48 be in the allowable predetermined position range B. This can be done via the pressure signal P5 of the fifth pressure sensor 93 be controlled, which is approximately the pressure of the pneumatic pressure source 92 must correspond.

After the second time t2, ie after clamping the workpiece 15 In the preferred embodiment, a check routine is performed. For this purpose, at a third time t3, a third control signal M3 for the control valve device 82 generated to switch them to the control position. In the control position is the control connection 80 with the return line 65 fluidly connected, so that the pressure in the first hydraulic line 70 or the first clamping cylinder line 30 over the first branch 43a the monitoring line 43 is reduced. The control valve device 82 is held in the control position for a control period TK. At a fourth time t4 during the control period TK, the pressure loss is detected by the first pressure signal P1 and in the control unit 66 displayed. Accordingly, at the fourth time t4, the hydraulic pressure in the third hydraulic line also decreases 81 or the monitoring line 43 which is indicated by the third pressure signal P3.

At a fifth time t5, the control period TK is completed. The control valve device 82 is switched back to the rest position S by falling of the third drive signal M3. Thereupon, at a sixth point in time, the pressure in the monitoring line increases 43 or the first clamping cylinder line 30 and accordingly in the third hydraulic line 81 or the first hydraulic line 70 again, which is detected by the first pressure signal P1 and the third pressure signal P3.

With the help of this method, the functionality of the pressure sensors can be tested. It is thereby ensured that the pressure detected by the first pressure sensor also bears and the pressure sensor is not defective.

In 11 is analogous to the sequence after 10 an example method for the internal clamping of a workpiece described. The difference is that with the two working valve devices 68 . 69 the other valve drive 75 is activated, so that the first working valve device 68 in the return position R and the second working valve device 69 be switched to the inlet position Z, as it is in 9 is illustrated.

The invention relates to a clamping device 10 consisting of a machine-side clamping unit 11 and a thus mechanically and fluidically connectable chuck unit 12 consists. The chuck unit 12 is in the preferred embodiment free of directional control valves. It has one for the movement of jaws 19 equipped clamping cylinder 20 on, whose one working chamber 23 via a first clamping cylinder line 30 with a first chuck connection 28 and its other working chamber 24 via a second clamping cylinder line 31 with a second chuck connection 29 is fluidically connected. In the two tension cylinder lines 30 . 31 each seated a pilot-operated check valve 36 . 37 , Unlocking the check valve 36 respectively. 37 takes place when hydraulic medium from the assigned working chamber 23 respectively. 24 should be dissipated to a movement of the jaws 19 permit. When established fluidic connection between the chuck unit 12 and the clamping unit 11 are the two tension cylinder lines 30 . 31 each with an associated hydraulic line 70 respectively. 71 fluidly connected. Every hydraulic line 70 . 71 is a separately controllable and switchable working valve device 68 . 69 assigned. The working valve devices 68 . 69 are preferably mechanically held in a neutral position N, in which a movement of the clamping jaws 19 is prevented. Only when both working valve devices 68 . 69 via a control unit 66 From the neutral position N are switched to a defined switching position Z or R, is a movement of the clamping jaws 19 possible.

LIST OF REFERENCE NUMBERS

10

jig

11

clamping unit

12

Chuck unit

13

connecting device

14

coupling device

14a

Connection Rückschlagvetil

15

workpiece

19

jaw

20

clamping cylinder

21

piston

22

piston rod

23

first working chamber

24

second working chamber

25

palette

28

first chuck connection

29

second chuck connection

30

first tension cylinder line

31

second clamping cylinder line

32

Throttle valve assembly

33

throttle

34

throttled flow path

35

return path

36

first chuck check valve

36s

Control input of the first chuck check valve

37

second chuck check valve

37s

Control input of the second chuck check valve

38

first shuttle valve

39

second shuttle valve

40

unblocking

41

drive terminal

42

monitor terminal

43

monitoring line

43a

first branch

43b

second branch

44

accumulator

45

pneumatic test connection

46

pneumatic test line

47

vent

48

check valve

49

valve member

50

coupling element

60

pressure source

61

supply line

62

Pressure control unit

63

supply line

64

reservoir

65

Return line

66

control unit

68

first working valve device

68a

first way valve

68b

first check valve

68c

Control output of the first directional control valve

68d

Outgoing work of the first directional valve

69

second working valve device

69a

second way valve

69b

second check valve

69c

Control output of the second directional valve

69d

Working output of the second directional control valve

70

first hydraulic line

71

second hydraulic line

72

first work connection

73

second work connection

75

valve drive

76

first pressure sensor

77

second pressure sensor

80

control port

81

third hydraulic line

82

Control valve means

82a

third directional valve

82b

third check valve

82c

control output

82d

control output

83

third pressure sensor

85

Entsperranschluss

86

fourth hydraulic line

87

Entsperrventileinrichtung

87a

fourth directional valve

88

fourth pressure sensor

90

pneumatic connection

91

pneumatic line

92

Pneumatic pressure source

93

fifth pressure sensor

B

Positinsbereich

D

Druckeinstellsignal

E1

first end zone

E2

second end zone

M1a

first drive signal for the first directional control valve

M1b

second drive signal for first directional control valve

m2a

first drive signal for second directional control valve

M2b

second drive signal for second directional control valve

M3

third drive signal

M4

fourth drive signal

N

neutral position

P1

first pressure signal

P2

second pressure signal

P3

third pressure signal

P4

fourth pressure signal

P5

fifth pressure signal

R

Return position

S

rest position

t1

first time

t2

second time

t3

third time

t4

fourth time

t5

fifth time

t6

sixth time

TK

Control period

X

unlocked

Z

inlet position

Claims (17)

Clamping unit ( 11 ), with a connection device ( 13 ), which has a hydraulic first working connection ( 72 ) and a hydraulic second working connection ( 73 ), wherein by means of the connecting device ( 13 ) a separate chuck unit ( 12 ) with a first working chamber ( 23 ) and a second working chamber ( 24 ) hydraulic clamping cylinder ( 20 ) mechanically and fluidically with the clamping unit ( 11 ) is connectable, wherein the clamping unit ( 11 ) a first working valve device ( 68 ) whose output by means of a first hydraulic line ( 70 ) with the first work connection ( 72 ) for supplying or discharging hydraulic medium into or out of the first working chamber ( 23 ) one with the clamping unit ( 11 ) associated chuck unit ( 12 ) is fluidly connected, wherein the clamping unit ( 11 ) a second work valve device ( 69 ) whose output by means of a second hydraulic line ( 71 ) with the second working connection ( 73 ) for supplying or discharging hydraulic medium into or out of the second working chamber ( 24 ) one with the clamping unit ( 11 ) associated chuck unit ( 12 ) is fluidically connected, wherein the first working valve device ( 68 ) and the second working valve device ( 69 ) each at an input with a supply line ( 63 ), which provides pressurized hydraulic medium, and at another input with a return line ( 65 ) are hydraulically connected for hydraulic medium, wherein the two working valve devices ( 68 . 69 ) are each independently in an inlet position (Z) or a return position (R) can be switched and in the inlet position (Z) of the respective output to the supply line ( 63 ) and in the return position (R) of the respective output with the return line ( 65 ) is fluidically connected to the first and / or the second working valve device ( 68 . 69 ) in each case a directional control valve ( 68a . 69a ) with a work exit ( 68d . 69d ) and with a control output ( 68c . 69c ), the work exit ( 68d . 69d ) with the associated first or second hydraulic line ( 70 . 71 ) is fluidically connected, and wherein the first and / or the second working valve device ( 68 . 69 ) one each in the respective hydraulic line ( 70 . 71 ), via a control input ( 68s . 69s ) non-return valve ( 68b . 69b ), which in the blocking state, a hydraulic flow in the direction of the directional control valve ( 68a . 69a ), whereby the control input ( 68s . 69s ) with the control output ( 68c . 69c ) of the directional valve ( 68a . 69a ) of the working valve device ( 68 . 69 ) is fluidly connected. Clamping unit according to claim 1, characterized in that in the inlet position (Z) of the first or the second working valve device ( 68 . 69 ) the respective control output ( 68c . 69c ) of the directional valve ( 68a . 69a ) with the return line ( 65 ) is fluidically connected and / or that in the return position (R) of the first or the second working valve device ( 68 . 69 ) the respective control output ( 68c . 69c ) of the directional valve ( 68a . 69a ) with the supply line ( 63 ) is fluidly connected. Clamping unit according to claim 1 or 2, characterized in that the first directional control valve ( 68a ) and / or the second directional control valve ( 69a ) has a further switching position, which represents a neutral position (N), in which the working output ( 68d . 69d ) and the control output ( 68c . 69c ) of the directional valve ( 68 . 69 ) with the return line ( 65 ) are fluidly connected. Clamping unit according to claim 3, characterized in that the first directional control valve ( 68a ) and / or the second directional control valve ( 69a ) is held mechanically in the neutral position (N). Clamping unit according to claim 3 or 4, characterized in that the first directional control valve ( 68a ) and / or the second directional control valve ( 69a ) by means of a valve drive ( 75 ) from the neutral position (N) to the inlet position (Z) and by means of a further valve drive ( 75 ) from the neutral position (N) in the return position (R) is switchable. Clamping unit according to one of the preceding claims, characterized in that a control valve device ( 82 ) is present whose output by means of a third hydraulic line ( 81 ) with a control connection ( 80 ) of the connection device ( 13 ) is fluidly connected, wherein the control valve device ( 82 ) between a control position and a rest position (S) is switchable and in the control position the control port ( 80 ) with the return line ( 65 ) fluidly connects. Tensioning unit according to claim 6, characterized in that the control valve device ( 82 ) a directional valve ( 82a ) with a control output ( 82d ) and a control output ( 82c ), the control output ( 82d ) with the third hydraulic line ( 81 ) is fluidically connected, and that the control valve device ( 82 ) in the third hydraulic line ( 81 ), via a control input ( 82s ) non-return valve ( 82b ), which in the blocking state, a hydraulic flow in the direction of the directional control valve ( 82a ), whereby the control input ( 82s ) with the control output ( 82c ) of the directional valve ( 82a ) of the control valve device ( 82 ) is fluidly connected. Clamping unit according to one of the preceding claims, characterized in that an unlocking valve device ( 87 ) is present whose output by means of a fourth hydraulic line ( 86 ) with an unlock connection ( 85 ) of the connection device ( 13 ) is fluidically connected, wherein the Entsperrventileinrichtung ( 87 ) is switchable between an unlocked position and a rest position (S). Tensioning unit according to one of claims 6 to 8, characterized in that the control valve device ( 82 ) and / or the Entsperrventileinrichtung ( 87 ) each at an input to the return line ( 65 ) and at another entrance either with supply line ( 63 ) or with a hydraulic supply line ( 61 ) is fluidly connected, wherein the supply line ( 61 ) Provides hydraulic medium under at least the same hydraulic pressure as the supply line ( 63 ). Clamping unit according to one of the preceding claims, characterized in that the connecting device ( 13 ) a pneumatic connection ( 90 ), which by means of a pneumatic line ( 91 ) with a pneumatic pressure source ( 92 ) is connectable or connected. Clamping unit according to one of the preceding claims, characterized in that with the first hydraulic line ( 70 ) and / or with the second hydraulic line ( 71 ) and / or with the third hydraulic line ( 81 ) and / or with the fourth hydraulic line ( 86 ) and / or with the pneumatic line ( 91 ) each a pressure sensor ( 76 . 77 . 83 . 88 . 93 ) is fluidly connected. Clamping unit according to one of the preceding claims, characterized in that the supply line ( 63 ) via a pressure control unit ( 62 ), in particular a proportional valve, with a pressure source ( 60 ) connected is. Chuck unit ( 12 ) for hydraulic clamping and holding a workpiece ( 15 ), with a coupling device ( 14 ), for the mechanical and fluidic connection with a clamping unit ( 12 ) of a processing machine or a set-up station, wherein the coupling device ( 14 ) a hydraulic first chuck terminal ( 28 ) and a hydraulic second chuck connection ( 29 ), with a plurality of mutually towards and away from each other movably mounted jaws ( 19 ) for engaging the workpiece ( 15 ), with a hydraulic clamping cylinder ( 20 ), which has a movable piston ( 21 ) having a first working chamber ( 23 ) and a second working chamber ( 24 ) fluidly separated from each other and with the clamping jaws ( 29 ) is mechanically coupled, with a hydraulic first clamping cylinder line ( 30 ) fluidly connected to the first working chamber ( 23 ) and the first chuck connection ( 28 ), wherein in the first clamping cylinder line ( 30 ) a releasable first chuck check valve ( 36 ) is arranged, which in its blocking state, a hydraulic flow from the first working chamber ( 23 ), whereby a control input ( 36s ) for unlocking the first chuck check valve ( 36 ) fluidly with the second chuck terminal ( 29 ) is connected to a second hydraulic clamping cylinder line ( 31 ) fluidly connected to the second working chamber ( 24 ) and the second chuck connection ( 29 ), wherein in the second clamping cylinder line ( 31 ) a releasable second chuck check valve ( 37 ) is arranged, which in its blocking state, a hydraulic flow from the second working chamber ( 24 ), whereby a control input ( 37s ) for unlocking the second chuck check valve ( 37 ) fluidly with the first chuck terminal ( 28 ), the coupling device ( 14 ) a hydraulic monitoring connection ( 42 ) provided with a hydraulic monitoring line ( 43 ) is fluidically connected, wherein the monitoring line ( 43 ) two parallel branches ( 43a . 43b ), of which one branch ( 43a ) via a check valve fluidly with the first chuck terminal ( 28 ) and the other branch ( 43b ) via a further check valve fluidly with the second chuck terminal ( 29 ), wherein the check valves a hydraulic flow from the monitoring line ( 43 ) to the first and second chuck terminals ( 28 . 29 ) prevent. Clamping unit according to claim 13, characterized in that the coupling device ( 14 ) a hydraulic drive connection ( 41 ) provided with an unlock line ( 40 ) is fluidically connected to the control input ( 36s ) of the first chuck check valve ( 36 ) and / or the control input ( 37s ) of the second chuck check valve ( 37 ) is fluidly connected. Clamping unit according to claim 13 or 14, characterized in that the coupling device ( 14 ) a pneumatic test connection ( 45 ), which by means of a pneumatic test line ( 46 ) fluidly with a vent ( 47 ), whereby in the test line ( 46 ) a test valve ( 48 ) is arranged, the pneumatic connection between the test port ( 45 ) and the vent ( 47 ) locks when the jaws ( 19 ) are within a predetermined position range (B). Chuck unit according to one of claims 13 to 15, characterized in that at least one pressure accumulator ( 44 ) present with the first working chamber ( 23 ) or the second working chamber ( 24 ) is fluidly connected. Method for performing a clamping or releasing movement of clamping jaws ( 19 ) using a tensioning device ( 10 ) with a clamping unit ( 11 ) mechanically and fluidically with a separate chuck unit ( 12 ) is connectable, wherein the chuck unit ( 11 ) the jaws ( 19 ), for clamping or releasing a workpiece ( 15 ) are mounted on each other and movable away from each other, and a hydraulic clamping cylinder ( 20 ) with a movable piston ( 21 ) having a first working chamber ( 23 ) and a second working chamber ( 24 ) fluidly separated from each other and with the clamping jaws ( 19 ) is mechanically coupled, wherein the first working chamber ( 23 ) with a hydraulic first tensioning cylinder line ( 30 ) and the second working chamber ( 24 ) with a hydraulic second clamping cylinder line ( 31 ) is fluidically connected, wherein the first clamping cylinder line ( 30 ) with a first working valve device ( 68 ) of the clamping unit ( 11 ) and the second clamping cylinder line ( 31 ) with an independent of the first working valve device ( 68 ) operable second working valve device ( 69 ) of the clamping unit ( 11 ) is fluidically connected, and wherein the clamping unit ( 11 ) a pressurized hydraulic medium supply line ( 63 ) and a return line ( 65 ) for discharging hydraulic medium, wherein the chuck unit ( 12 ) a hydraulic control line ( 43 ), which via a check valve with the first clamping cylinder line ( 30 ) and via a check valve with the second clamping cylinder line ( 31 ) and via a control valve device ( 82 ) of the clamping unit ( 11 ) either with the return line ( 65 ) or with the supply line ( 63 ) or another pressurized hydraulic medium supply line ( 61 ) is connectable, with the following steps: - connecting the first or second clamping cylinder line ( 30 . 31 ) with a supply line ( 63 ) to the hydraulic medium source ( 60 ) by switching the associated first or second working valve device ( 68 . 69 ) in a feed position (Z) and connecting the other clamping cylinder line ( 31 . 30 ) with the return line ( 65 ) by switching the associated second or first working valve device ( 68 . 69 ) in a return position (R); Performing the following steps after clamping a workpiece ( 15 ): - measuring the pressure at least in the tensioning with the supply line ( 63 ) connected first or second clamping cylinder line ( 30 . 31 ) or a fluidically connected hydraulic line ( 70 . 71 ), - connecting the control line ( 43 ) with the return line ( 65 ) during a specified control period (TK) - Check that the pressure measured decreases after the start of the control period (TK) and rises again after the end of the control period (TK).

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