DE102014002528B4 - Display device for the optical display of a clamping state of a clamping device and clamping system - Google Patents

Abstract

Display device (1, 8-10) for the optical display of a clamping state of a fluidically controlled mechanical clamping device for clamping components, with a) a first fluid connection (32) a1) wherein the first fluid connection (32) for receiving the on the clamping device acting fluid pressure, a2) wherein the display device (1, 8-10) shows the state of the clamping device purely mechanically as a function of the fluid pressure applied to the first fluid connection (32), a3) wherein the first fluid connection (32) is a hydraulic connection, at which a hydraulic pressure is applied, which acts on the clamping device, a4) the hydraulic pressure applied to the hydraulic connection (32) being used to release the clamping device, the clamping device releasing a component when the hydraulic pressure is high, b) a second fluid connection (22), b1 ) wherein the second fluid connection (22) for supplying a further F, which represents the clamping state of the clamping device fluid pressure is used, andb2) wherein the display device (1, 8-10) also purely mechanically displays the state of the clamping device as a function of the fluid pressure applied to the second fluid connection (22), b3) wherein the second fluid connection (22) is a pneumatic connection, at which a pneumatic pressure is applied, b4) the pneumatic pressure applied to the pneumatic connection (22) being a control pressure which is provided by the clamping device depending on its clamping state, and c) a movable display element (15), the position of which reflects the clamping status of the clamping device , characterized in, d) that the display device (1, 8-10) has a control piston (20) which is slidably mounted in the display device (1, 8-10) and is subjected to the fluid pressure which is applied to the second fluid connection and in the display device (1, 8-10) in a first pressure chamber (23) acts on the control piston (20), and e) that the control piston (20) is mechanical is coupled to the movable display element (15), f) that the control piston (20) is displaceable between a release position and a blocking position, f1) wherein the release position indicates that a component is clamped in the clamping device and released for processing, f2) whereas the blocking position indicates that machining of the component is blocked because the component is not clamped, andg) that the control piston (20) is prestressed into the blocking position by a first prestressing spring (21), h) that the display device (1, 8 -10) has a locking device (26-31) for locking the control piston (20) in the release position, and i) that the display device (1, 8-10) has a venting device (34-40) for venting the first pressure chamber (23) for the control piston (20), the venting device (34-40) being actuated by the fluid pressure at the first fluid connection (32).

Description

The invention relates to a display device for the optical display of a clamping state of a mechanical clamping device and a clamping system.

Clamping devices are known from the prior art which can be used to clamp components for subsequent machining in a machine tool. Such clamping devices can be controlled hydraulically, for example, in order to release the clamping device and release the clamped component. Furthermore, it is known per se to poll the clamping state of such a clamping device pneumatically via control units. It is desirable here to visually indicate the clamping state of the clamping device so that the respective machine operator can recognize whether the component to be clamped is properly clamped and released for subsequent machining in the machine tool. So far, such display devices for displaying the clamping state of a clamping device function electronically with pressure switches, but this is relatively complex.

Out DE 100 22 227 A1 a clamping drive for driving a workpiece clamping system is known, a pressure indicator showing the clamping force. However, the pressure indicator does not make it possible to distinguish between a release position and a blocking position. The release position here is the clamping state of the clamping device in which a component is properly clamped so that machining of the component is enabled, for example by a machine tool. The blocking position, on the other hand, is the clamping state of the clamping device in which the clamping device is not yet properly clamping the component, so that machining of the component is blocked.

Furthermore, reference should be made to the state of the art DE 25 27 958 A1 , DE 198 38 306 B4 , DE 10 2013 012 183 A1 , EP 0 579 017 A1 , DE 102 24 042 A1 , DE 101 35 295 B4 , DE 25 48 172 A1 , DE 24 47 023 A1 , DE 22 31 967 B2 , DE 28 01 677 C2 and DE 100 05 213 A1 . However, these documents do not relate to clamping devices.

Also disclosed CH 498 686 A a hydraulic clamping device that shows the clamping status.

Finally revealed DE 10 2005 052 780 A1 a display device according to the preamble of claim 1. However, this known display device is not yet completely satisfactory.

The invention is therefore based on the object of creating a correspondingly improved display device for the optical display of a clamping state of a clamping device.

This object is achieved by a display device according to the invention according to the main claim.

The invention encompasses the general technical teaching of creating a display device which optically displays the clamping state of a clamping device and thereby works purely mechanically, i.e. without electrical or electronic components.

In this context it should be mentioned that the invention is not limited to display devices which do not contain any electrical or electronic components. However, the invention is limited to display devices in which no electrical or electronic components are required for the optical display of the clamping state. However, within the scope of the invention it is possible for the display device to contain electronic or electrical components that serve other purposes.

The display device according to the invention has a fluid connection, a fluid pressure (release pressure for releasing the clamping device) being detected at the fluid connection, which fluid pressure acts on the clamping device. The display device then evaluates this fluid pressure present at the fluid connection and displays the clamping state of the clamping device as a function thereof.

According to the invention, this first fluid connection is a hydraulic connection to which a hydraulic pressure is applied, which acts on the clamping device.

According to the invention, this hydraulic pressure is used to release the clamping device, the clamping device releasing a component at high hydraulic pressure (release pressure).

In addition, the display device comprises a second fluid connection (pneumatic connection for control pressure) for supplying a further fluid pressure (control pressure) which reflects the clamping state of the clamping device and which is provided by the clamping device via valves. The display device then evaluates the fluid pressures present at the two fluid connections and displays the clamping state of the clamping device as a function thereof.

According to the invention, this second fluid connection is one Pneumatic connection at which a pneumatic pressure is applied, which is provided by the clamping device via valves (e.g. control units).

According to the invention, the pneumatic pressure applied to the pneumatic connection is a control pressure which is provided by the clamping device via control units as a function of its clamping state.

The actual evaluation of the fluid pressures present within the display device is carried out, among other things, by means of a control piston which is mounted displaceably in the display device and is subjected to the fluid pressure that is applied to the second fluid connection (pneumatic connection) and in the display device in a first pressure chamber on the control piston works. The fluid pressure (control pressure) applied to the second fluid connection (pneumatic connection) of the display device thus reaches the first pressure chamber of the display device and acts there on the control piston, the control piston being pretensioned by a first biasing spring which acts against the pressure in the first pressure chamber.

The control piston is connected to a movable display element, the position of which reflects the clamping state of the clamping device. A displacement of the control piston according to the fluid pressure (control pressure) in the first pressure chamber and at the second fluid connection (release pressure) thus leads to a corresponding displacement of the movable display element and thus to a visual display of the clamping state of the clamping device.

In addition, a movable actuating element (e.g. query pen) can also be provided in order to actuate an external sensor. The movable actuating element is also mechanically connected to the movable control piston and is therefore moved in the first pressure chamber or at the second fluid connection as a function of the fluid pressure (e.g. control pressure). The control piston can therefore move the movable display element on the one hand and the movable actuation element (e.g. query pen) on the other in order to enable an optical display or a sensor query.

According to the invention, the control piston can be displaced between a release position and a blocking position. The control piston is in the release position when the clamping device properly clamps a component so that the component is released for subsequent machining, for example in a machine tool. In contrast, the control piston is in the locked position when machining of the component to be clamped is blocked because the component is not yet properly clamped. According to the invention, the first biasing spring, already briefly mentioned above, biases the control piston in the direction of the blocking position.

In addition, the display device has a locking device which can lock the control piston in the release position, wherein the lock can be released.

The locking device preferably has a displaceable locking piston to which the fluid pressure (e.g. hydraulic pressure or release pressure) is applied, which is applied to the first fluid connection (e.g. hydraulic connection) and acts on the locking piston in the display device in a second pressure chamber. The locking piston is preferably displaceable transversely to the control piston and engages laterally in the control piston to lock the control piston, in particular in an annular groove in the lateral surface of the control piston. When a hydraulic release pressure is applied to the first fluid connection, this hydraulic release pressure thus acts on the locking piston and thus releases the locking of the control piston. This in turn has the consequence that the first prestressing spring acting on the control piston pushes the control piston out of the release position into the blocking position, whereupon the display device visually indicates that the clamping device is in the blocking position.

In the preferred embodiment, a locking pin is slidably mounted in the locking piston, which engages laterally in the control piston to lock the control piston, in particular in an annular groove in the lateral surface of the control piston. In this exemplary embodiment, the locking piston does not itself directly and directly engage in the control piston in order to lock the control piston. Rather, the actual locking takes place by the locking pin in the locking piston.

Here, the locking piston itself is preferably biased by a second biasing spring in the direction of the control piston, while the locking pin is biased by a third biasing spring with respect to the locking piston in the direction of the control piston. The second preload spring for the locking piston preferably has a significantly stiffer spring characteristic than the third preload spring for the locking pin. This is advantageous so that the control piston can push away the locking pin laterally when it is moved from the locking position to the release position, which only works easily if the preloading spring for the locking pin does not exert a particularly large spring force on the locking pin. The locking piston itself is against it exposed to the hydraulic release pressure, so that the associated second preload spring for the locking piston must have a much more rigid spring characteristic. The division between two preload springs for the locking piston on the one hand and for the locking pin on the other hand enables both a slight lateral evasion of the locking pin and a suitable response of the locking piston to the hydraulic release pressure.

In addition, the display device according to the invention has a venting device in order to be able to vent the first pressure chamber for the control piston, the venting device being actuated by the fluid pressure at the first fluid connection (e.g. hydraulic release pressure).

In the preferred embodiment of the invention, the venting device has a displaceable venting piston to which the fluid pressure applied to the first fluid connection (e.g. hydraulic connection) and acting in the display device in a third pressure chamber acts on the venting piston. The fluid pressure (e.g. hydraulic release pressure) at the first fluid connection thus acts both on the locking piston and on the venting piston. If a sufficiently high hydraulic pressure is applied to the first fluid connection, then both the locking piston is released and the venting piston is displaced so that the first pressure chamber for the control piston can be vented. This has the consequence that the control piston is displaced by its preloading spring from the release position into the blocking position, since the lock is released and the first pressure chamber of the control piston is vented. In the preferred exemplary embodiment, the first fluid connection (e.g. hydraulic connection or release pressure connection) is therefore connected both to the second pressure chamber for the locking piston and to the third pressure chamber for the venting piston.

It should also be mentioned that the ventilation piston is preferably prestressed by a fourth prestressing spring into a position in which the first pressure chamber for the control piston is not vented. The ventilation piston is therefore preferably pressed by the fourth preload spring into a sealing seat in which it prevents the first pressure chamber from being vented for the control piston.

For this seal, the vent piston can have a seal at its free end, which can be designed as a separate component and can seal the sealing seat when the vent piston is pressed into the sealing seat by the fourth pretensioning spring.

The venting piston and the locking piston are preferably displaceable transversely to the control piston, specifically preferably at right angles thereto. This means that the venting piston and the locking piston can preferably be displaced parallel to one another. It should be mentioned here that the control piston, the venting piston and the locking piston are preferably displaceable in a common plane.

Finally, it should also be mentioned that the invention not only claims protection for the above-described display device according to the invention as a single component. Rather, the invention also claims protection for a clamping system with at least one clamping device for clamping components and at least one display device for visually displaying the clamping state of the clamping device.

In a preferred exemplary embodiment of the invention, the clamping system has numerous clamping devices which can be divided into groups of several clamping devices, each group of the clamping device being assigned a display device. The display device then shows the clamping states of the clamping device in the respective group.

• 1 eine Perspektivansicht einer erfindungsgemäßen Anzeigeeinrichtung von schräg unten,
• 2 eine Querschnittsansicht der Anzeigeeinrichtung aus 1 in einer Freigabestellung, die anzeigt, dass die zugehörige Spannvorrichtung ein Bauteil ordnungsgemäß einspannt, so dass die Bearbeitung des Bauteils freigegeben ist,
• 3 die Querschnittsansicht gemäß 2 in einer Sperrstellung, die anzeigt, dass die Spannvorrichtung ein Bauteil nicht ordnungsgemäß spannt, so dass die Bearbeitung des Bauteils gesperrt ist,
• 4 die Querschnittsansicht aus 3, jedoch ohne hydraulischen Lösedruck,
• 5 eine andere Querschnittsansicht durch die Anzeigeeinrichtung aus 1 zur Verdeutlichung von Druckräumen und Kanälen in der Anzeigeeinrichtung,
• 6 eine Detailansicht aus den Querschnittsansichten gemäß den 2 bis 4 im Bereich eines Entlüftungskolbens,
• 7 eine Detailansicht aus den Querschnittsansichten gemäß den 2 bis 4 im Bereich eines Arretierungskolbens,
• 8 eine Explosionsdarstellung der Anzeigeeinrichtung aus 1, sowie
• 9 eine Perspektivansicht eines erfindungsgemäßen Spannsystems mit zahlreichen Spannvorrichtungen und vier Anzeigeeinrichtungen.

Other advantageous developments of the invention are characterized in the subclaims or are explained in more detail below together with the description of the preferred exemplary embodiment of the invention with reference to the figures. Show it:

• 1 a perspective view of a display device according to the invention from obliquely below,
• 2 a cross-sectional view of the display device 1 in a release position, which indicates that the associated clamping device is properly clamping a component so that machining of the component is enabled,
• 3 the cross-sectional view according to 2 in a locked position, which indicates that the clamping device is not properly clamping a component, so that machining of the component is blocked,
• 4th the cross-sectional view 3 , but without hydraulic release pressure,
• 5 shows another cross-sectional view through the display device 1 to clarify pressure spaces and channels in the display device,
• 6th a detailed view from the cross-sectional views according to FIG 2 to 4th in the area of a venting piston,
• 7th a detailed view from the cross-sectional views according to FIG 2 to 4th in the area of a locking piston,
• 8th an exploded view of the display device 1 , such as
• 9 a perspective view of a clamping system according to the invention with numerous clamping devices and four display devices.

The 1 to 8th show different views of a display device according to the invention 1 that are in a clamping system 2 according to 9 can be used to indicate the clamping state (release position or blocking position) of clamping devices, the clamping devices themselves in 9 are not shown. Rather shows 9 a clamping system 2 with a tower with four sides, with four cylindrical receptacles on each side 3 are arranged for one clamping device each. The clamping system 2 thus has four groups of four clamping devices each, with each group of clamping devices each having a hydraulic connection 4th or. 5 for a release pressure and a pneumatic connection 6th or. 7th is controlled for a control pressure.

The 1 to 8th show the structure of the display device 1 at the top of the clamping system 2 . In addition, the clamping system 2 however, other display devices 8th , 9 , 10 that are identical.

It is still off 9 seen that in the recordings 3 a control unit for each of the clamping devices 11 is arranged, which pneumatically polls the associated clamping device and generates a pneumatic control signal, which is then transmitted by the display devices 1 , 8-10 can be evaluated, as will be described in detail.

The display devices 1 , 8-10 thus each indicate the clamping state (release position or blocking position) of the associated four clamping devices, which are arranged below.

The term “release position” used in the context of the invention means that a component is properly clamped in the associated clamping device, so that this component is released for subsequent processing.

In contrast, the term “locked position” used in the context of the invention means that the machining of a workpiece is still locked because this component has not yet been properly clamped.

In the following, with reference to the 1 to 8th the structure and mode of operation of the display device 1 described.

The display device 1 has a housing 12th on that on the actual clamping system 2 according to 9 is put on, as can be seen from the drawing.

The housing has on its front 12th the display device 1 a viewing window 13th to the clamping state (release position or blocking position) of a clamping device through the viewing window 13th to display through. The viewing window 13th is located in a cover plate 14th into a case opening on the front of the case 12th is screwed in. Behind the cover plate 14th is a slide indicator 15th slidably arranged, the indicator slide 15th through a pane of glass 16 from the cover plate 14th is separated. The indicator slide carries on its left side 15th a green display area 17th while the indicator slider 15th on its right side a red display area 18th wearing.

In the in 2 The display slide is located in the release position shown 15th far right, so that the green display area 17th through the viewing window 13th is visible from the outside.

In the in 3 and 4th The display slide is in the locked position shown 15th on the other hand, on the far left, so that the red display area 18th through the viewing window 13th is visible from the outside.

The indicator slider 15th is about a straight pin 19th with a control piston 20th connected to that in the housing 12th the display device 1 is movable. When the control piston is displaced 20th takes the control piston 20th so the indicator slide 15th accordingly with so that the position of the control piston 20th also the position of the indicator slide 15th certainly.

The control piston 20th is done by a preload spring 21 towards the in the 3 and 4th shown locking position biased.

The actual drive of the control piston 20th takes place pneumatically by means of control air, which is supplied via a pneumatic connection 22nd at the bottom of the case 12th is fed. The control air is used by the control units 11 provided, which in turn query the associated clamping devices, so that the control air indicates the clamping state of the associated clamping device. The control air comes from the pneumatic connection 22nd in a pressure room 23 on the left face of the control piston 20th so that the control pressure in the pressure chamber 23 the control piston 20th against the pre-tensioning force of the pre-tensioning spring 21 pushes to the right.

In addition, the control piston is 20th with an interrogation pen 24 connected, which enables, for example, the control of an external sensor. In the in 2 The interrogation pin protrudes as shown in the release position 24 therefore from the side of the housing 12th the display device 1 out to control an external sensor.

The control piston 20th is here in a hole in the housing 12th the display device 1 displaceable, with this hole in the finished state through a stopper 25th is locked.

In addition, the display device 1 a locking device that enables the control piston 20th in the in 2 to lock the release position shown.

For this purpose, the locking device has a locking piston 26th on that in the case 12th the display device 1 perpendicular to the direction of movement of the control piston 20th is movable.

The locking piston 26th is cup-shaped on its top and contains an insert there 27 , being a biasing spring 28 on the insert 27 and thereby the locking piston 26th biased downwards.

It is also located in the locking piston 26th a coaxially displaceable locking pin 29 , that of another preload spring 30th is biased downwards.

In the in 2 The locking pin engages in the release position shown 29 in an annular groove 31 in the lateral surface of the control piston 20th a, causing the control piston 20th is locked.

The drive of the locking piston 26th takes place hydraulically, in that the hydraulic fluid provided for releasing the associated clamping device is via a hydraulic connection 32 at the bottom of the case 12th in a pressure room 33 and there on the locking piston 26th works.

If the associated clamping device is therefore subjected to a sufficiently high hydraulic pressure to release the clamping device, this hydraulic pressure is also applied to the hydraulic connection 32 the display device 1 and thereby also acts in the pressure chamber 33 on the locking piston 26th , causing the locking piston 26th is pushed up in the drawing.

In addition, the display device 1 a ventilation device, which makes it possible to remove the pressure chamber 23 for the control piston 20th to vent.

The ventilation device essentially consists of an axially displaceable ventilation piston 34 , which has a sealing element at its free end 35 carries that in the in 2 The release position shown rests in a valve seat and thereby seals it, which means that the pressure chamber is vented 23 for the control piston 20th prevented. The bleed piston 34 is supported by a preload spring 36 preloaded in the sealing seat.

The actual drive of the vent piston 34 also takes place hydraulically through the on the hydraulic connection 32 supplied hydraulic fluid, which in a pressure chamber 37 and there on the venting piston 34 works. With a sufficiently high hydraulic pressure at the hydraulic connection 32 this hydraulic pressure is therefore also in the pressure chamber 37 and acts there on the bleeding piston 34 , causing the vent piston 34 is lifted out of the sealing seat and thereby the venting of the pressure chamber 23 for the control piston 20th releases. The compressed air can then out of the pressure chamber 23 via a vent screw 38 at the bottom of the case 12th escape.

From the detailed view in 6th it can be seen that the vent piston 34 several sealing rings 39 , 40 having, the sealing ring 40 the pneumatic area separates from the hydraulic area, while the sealing ring 39 the pressure room 37 seals upwards.

From the detailed view in 7th it can also be seen that the locking piston 26th several sealing rings 41 , 42 has to the pressure chamber 33 for the locking piston 26th to seal.

It can also be seen from the drawings that the bores in the housing 12th for the locking piston 26th and for the vent piston 34 each through a sealing plug 43 , 44 are locked.

Out 5 it can also be seen that the hydraulic connection 32 at the bottom of the case 12th via hydraulic channels 45 , 46 , 47 with the two pressure rooms 33 , 37 connected is.

It should also be mentioned that the compression spring 28 for the locking piston 26th has a much stiffer spring characteristic than the preload spring 30th for the locking pin 29 . This is advantageous because of the control piston 20th Must be able to use the locking pin 29 to push away upwards without great counterforce when the control piston 20th from the locked position according to 3 and 4th to the right in the release position according to 2 is pressed. On the other hand, the preload spring must 28 offer a sufficiently large counter pressure compared to the hydraulic pressure applied.

List of reference symbols

1

Display device

2

Clamping system

3

Holders for clamping devices

4th

Hydraulic connection for release pressure

5

Hydraulic connection for release pressure

6th

Pneumatic connection for control pressure

7th

Pneumatic connection for control pressure

8th

Display device

9

Display device

10

Display device

11

Control unit for querying the clamping device

12th

Housing of the display device

13th

Viewing window

14th

Cover plate

15th

Indicator slide

16

Pane of glass

17th

Green display area

18th

Red display area

19th

Straight pin

20th

Control piston

21

Preload spring for control piston

22nd

Pneumatic connection for control pressure

23

Pressure chamber for control piston

24

Inquiry pin on the control piston

25th

Sealing plug for control piston bore

26th

Locking piston

27

Insert for locking piston

28

Preload spring for locking piston

29

Locking pin in the locking piston

30th

Preload spring for locking pin

31

Ring groove in the control piston

32

Hydraulic connection for release pressure

33

Pressure space for locking piston

34

Bleeding piston

35

Sealing element of the venting piston

36

Preload spring for vent piston

37

Pressure space for the venting piston

38

Vent screw with vent outlet

39

Sealing ring for ventilation piston

40

Sealing ring for ventilation piston

41

Sealing ring around locking piston

42

Sealing ring around locking piston

43

Sealing plug for locking piston bore

44

Sealing plug for venting piston bore

45

Hydraulic duct

46

Hydraulic duct

47

Hydraulic duct

Claims (6)

Display device (1, 8-10) for the optical display of a clamping state of a fluidically controlled mechanical clamping device with a specific fluid pressure for clamping components, with a) a first fluid connection (32) a1) wherein the first fluid connection (32) for receiving the Clamping device acting fluid pressure is used, a2) wherein the display device (1, 8-10) shows the state of the clamping device purely mechanically as a function of the fluid pressure applied to the first fluid connection (32), a3) wherein the first fluid connection (32) is a hydraulic connection , at which a hydraulic pressure is applied, which acts on the clamping device, a4) the hydraulic pressure applied to the hydraulic connection (32) serving to release the clamping device, the clamping device releasing a component at high hydraulic pressure, b) a second fluid connection (22), b1) wherein the second fluid connection (22) for supplying a white reproducing the clamping state of the clamping device tere fluid pressure is used, and b2) wherein the display device (1, 8-10) also purely mechanically indicates the state of the clamping device as a function of the fluid pressure applied to the second fluid connection (22), b3) wherein the second fluid connection (22) is a pneumatic connection to which a pneumatic pressure is applied, b4) the pneumatic pressure applied to the pneumatic connection (22) being a control pressure which is provided by the clamping device as a function of its clamping state, and c) a movable display element (15) whose position indicates the clamping state reproduces the clamping device, characterized in that d) that the display device (1, 8-10) has a control piston (20) which is slidably mounted in the display device (1, 8-10) and is subjected to the fluid pressure that is applied to the second fluid connection and in the display device (1, 8-10) acts in a first pressure chamber (23) on the control piston (20), and e) that the control piston (20) is mechanically coupled to the movable display element (15), f) that the control piston (20) is displaceable between a release position and a blocking position, f1) the release position indicating that a component is clamped in the clamping device and released for processing, f2) whereas the blocking position indicates that the processing of the component is blocked because the component is not clamped and g) that the control piston (20) is biased into the blocking position by a first biasing spring (21), h) that the display device (1, 8-10) has a locking device (26-31) for locking of the control piston (20) in the release position, and i) that the display device (1, 8-10) has a venting device (34-40) for venting the first pressure chamber (23) for the control piston (20), the venting device (34 -40) is actuated by the fluid pressure at the first fluid connection (32). Display device (1, 8-10) according to Claim 1 , characterized in that a) that the locking device (26-31) has a displaceable locking piston (26), and b) that the locking piston (26) is subjected to the fluid pressure which is applied to the first fluid connection (32) and in the display device (1, 8-10) acts in a second pressure chamber (33) on the locking piston (26), and / or c) that the locking piston (26) can be displaced transversely to the control piston (20) and to lock the control piston (20) engages laterally in the control piston (20), in particular in an annular groove (31) in the lateral surface of the control piston (20). Display device (1, 8-10) according to Claim 2 , characterized in that a locking pin (29) is slidably mounted in the locking piston (26) and engages laterally in the control piston (20) to lock the control piston (20), in particular in an annular groove (31) in the lateral surface of the control piston ( 20). Display device (1, 8-10) according to Claim 3 , characterized in that a) that the locking piston (26) is pretensioned by a second preloading spring (28) in the direction of the control piston (20), b) that the locking pin (29) by a third preloading spring (30) opposite the locking piston (26) is biased in the direction of the control piston (20), and c) that the second biasing spring (28) for the locking piston (26) has a significantly stiffer spring characteristic than the third biasing spring (30) for the locking pin (29). Display device (1, 8-10) according to one of the preceding claims, characterized in that a) that the venting device (34-40) has a displaceable venting piston (34) to which the fluid pressure applied to the first fluid connection (32) is applied and acts in the display device (1, 8-10) in a third pressure chamber (37) on the venting piston (34), and / or b) that the first fluid connection (32) both with the second pressure chamber (33) for the locking piston (26) as well as with the third pressure chamber (37) for the vent piston (34), and / or c) that the vent piston (34) is biased by a fourth biasing spring (36) into a position in which the first pressure chamber (23) is not vented for the control piston (20), and / or d) that the vent piston (34) has a seal (35) at its free end and engages with the seal (35) in a sealing seat, and / or e ) that the vent piston (34) transversely to the steering rkolben (20) and parallel to the locking piston (26) is displaceable. Clamping system with a) at least one clamping device for clamping components for subsequent machining of the components in the clamped state, and b) at least one display device (1, 8-10) according to one of the preceding claims, wherein the display device (1, 8-10) displays the clamping state of the clamping device.

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