DE10123642A1 - Device for application of pressing force has pressure relief facility which when predetermined pressure acting upon piston has been reached opens up return path for pressure medium to reservoir - Google Patents

Abstract

The device for the application of a pressing force includes a working piston (35) operated by a pressurized medium stored in a reservoir (29), and operating elements on the piston for the pressing elements. The device has a pressure relief facility (48) which when a predetermined pressure acting upon the piston has been reached opens up a return path for the pressure medium to the reservoir. The pressure relief facility has an overpressure valve which is flow-connected to the pressure chamber in front of the working piston.

Description

The invention relates to a device for applying a press force according to the preamble of claim 1.

For example, when connecting pipes, it is known to be firmly connected by a pressing process. With the front direction is the required with a corresponding pressing tongs Pressing force applied. For this purpose, the pressing elements with the Ar beitskolben shifted to actuate pressing jaws of the pressing tongs At the end of the pressing process, the pressing elements and so that the working piston can be moved back to the press jaw to be able to remove the compressed pipe connection.

The invention has for its object the generic before Train direction so that the piston in constructively simple cher way and reliably after the pressing process in its off current situation is reduced.

This task is invented in the generic device appropriately with the characterizing features of claim 1 solved.

In the device according to the invention, the pressure relief ensures device for that inevitably after the pressing process, the working piston  pushed back towards its starting position can be. As soon as the pressure of the Media exceeds a specified value, the Return flow path for the pressure medium to the reservoir is automatically opened net, so that the print medium back towards the memory can flow. As a result, the pressure in the pressure medium decreases, so that the working piston can be pushed back easily and reliably can.

Further features of the invention result from the other An sayings, the description and the drawings.

The invention is illustrated by two in the drawings Exemplary embodiments explained in more detail. Show it

Fig. 1 in a section, a device according to the invention for crimping workpieces,

Fig. 2a shows a longitudinal section through the device according to FIG. 1, in which a control piston of a pressure relief device is in a closed position,

FIG. 2b shows the control piston according to Fig. 2a in an open position,

Fig. 3 shows a cross section through the device of FIG. 1 along the line III-III in Fig. 1,

Fig. 4 shows the control piston according to Fig. 2a in its closed position in an enlarged scale;

FIG. 5a in a representation corresponding to Fig. 2a, the Druckentla of the inventive device stungseinrichtung with a diffuser,

Fig. 5b, the pressure relief device of Fig. 2b with a diffuser,

Fig. 6 shows a longitudinal section through a second embodiment ei ner inventive device,

Fig. 7 is a radial section through the device according to FIG. 6,

Fig. 8 is a section along the line VIII-VIII in Fig. 7.

With the device described in detail below, the mainly used in the sanitary sector, pipes, Pipe pieces and the like are inextricably linked. in this connection there is a plastic deformation process through which the fixed connection is established. The pipes put together, Pipe pieces, fittings and the like become radial in the plug-in area pressed, creating the positive connection between them Sharing is achieved.

The device is designed as a portable tool that can be carried comfortably by the operator. The device has a housing 1 , which advantageously consists of two releasably interconnected housing shells. The housing 1 can also be composed of more than two housing parts. As Fig. 1 shows, the housing 1 is formed approximately pistol-shaped and has elongated egg NEN housing part 2, in which a hydraulic part 3 of a drive to 4 is accommodated. From the housing part 2 is a handle part 5 which is part of the housing 1 and in which an electrical / electro-African part 6 of the drive 4 is housed. The longitudinal axis of the handle part 5 lies at an obtuse angle to the longitudinal axis of the housing part 2 . The handle part 5 is preceded by a hollow web 7 which extends approximately parallel to the longitudinal axis of the handle part 5 and is at a distance from it. As a result, a handle opening 8 is formed between the handle part 5 and the web 7 . The web 7 and the handle part 5 ge hen via a cross piece 9 into each other, which is also advantageously formed as a hollow part.

During the pressing process, the device is preferably held on the grip part 5 , the user embracing the grip part 5 and reaching through the grip opening 8 with his hand. The web 7 protects the hand of the user during the pressing process. At the transition from the grip part 5 into the grip opening 8 , a switch 10 protrudes into the grip opening, which can be comfortably pressed with the index finger when reaching around the grip part in order to switch on the drive 4 . The switch 10 can be designed so that it must be kept pressed during the pressing process. As soon as the switch 10 is released, the drive 4 is switched off. This ensures that the tool does not continue to run when it is put down by the user. But it is also possible to design the switch 10 so that it must be pressed to switch on the drive 4 and pressed a second time to switch it off. This design has the advantage that the operator does not have to keep the switch 10 pressed during the pressing process. In this case in particular, the device can also be held and gripped such that one hand of the operator comprises the grip part 5 and the other hand the web 7 . In order to give the hand a secure grip in this case too, part of the web 7 and the adjoining region of the housing part 2 are provided with recessed grips 11 .

The crosspiece 9 of the housing 1 can be designed as a receptacle for at least one rechargeable battery 12 or a battery. The device can also be operated with mains power. In this case, a power cord (not shown) is led out of the housing 2 , preferably out of the cross piece 9 .

The electric / electronic drive part 6 of the drive 4 is accommodated in the narrow handle part 5 in a space-saving manner. About him a mechanical drive part 13 is switched on or off. He has an electric motor 14 , the axis 15 is parallel to the longitudinal axis of the housing part 2 . A motor shaft 17 protruding from a motor housing 16 is coupled to a downstream reduction gear 18 , which is advantageously a planetary gear. The reduction gear 18 is advantageously designed at least in two stages. The preferred use of a planetary gear as a reduction gear 18 has the advantage that it requires little space with a high reduction ratio. Therefore, the reduction gear 18 can be accommodated in the housing part 2 to save space. The Längach se 19 of the reduction gear 18 is advantageously aligned with the longitudinal axis 15 of the motor 14th

An output shaft 20 of the reduction gear 18 carries outside a housing 21 of the reduction gear 18, an eccentric piece 22 , on which an elliptical ring 23 is mounted directly or with the interposition of an intermediate ring or a roller bearing, such as a needle bearing. The longitudinal axis of this elliptical ring 23 extends perpendicular to the axis of the output shaft 20 or perpendicular to the plane of the drawing, while the minor axis lies in the plane of the drawing according to FIG. 1. The eccentric piece 22 or the round ring sitting on it lie on the inner wall of the sections of the ring 23 extending perpendicular to the plane of the zei. If the drive shaft 20 is rotated about its axis, the elliptical ring 23 is moved up and down in the direction of the double arrow 24 in FIG. 1 in the plane of the drawing via the eccentric piece 22 . Such an eccentric drive is known and is therefore not described in detail.

The elliptical ring 23 carries a piston 25 , which is advantageously formed integrally with the ring 23 , but can also be attached to it. The piston 25 protrudes with all-round play from a housing 26 accommodating the eccentric drive 20 , 22 , 23 in a piston chamber 27 , which is advantageously formed by a bore in a hydraulic block 28 . It is housed in the housing part 2 and supported on the housing 26 of the eccentric drive 20 , 22 , 23 and fastened on it. At one end of the hydraulic block 28 there is a reservoir 29 for hydraulic medium, preferably hydraulic oil. In the bottom 30 of the reservoir 29 opposite the hydraulic block 28 , a closable filling opening 31 is provided, through which the hydraulic medium can be introduced into the reservoir 29 . In the memory 29, a check valve 32 which closes an axis perpendicular to the piston space 27 bore 33 against the reservoir 29 protrudes. The smaller cross section than the piston 25 having bore 33 opens into the piston chamber 27 at the drive from the eccentric 20 , 22 , 23 facing away from the end. The bore 33 extends beyond the piston chamber 27 and opens into a pressure chamber 34 in which a working piston 35 is accommodated. The working space 35 is closed against the bore 33 by a check valve 36 .

The working piston 35 is sealed in a cylinder chamber 37 leads and is under the force of at least one compression spring 38 , preferably before a helical compression spring which surrounds the working piston 35 . It protrudes sealed from the cylinder space 37 and carries before partially rolling pressure rollers 39 , 40 , with which press jaws (not shown) of a pressing tongs for radial pressing of the pipes, pipe pieces, fittings and the like are operated in a known manner.

The cylinder space 37 is provided in the hydraulic block 28 . The longitudinal axis of the cylinder space 37 extends in the longitudinal direction of the hydraulic block 28 and parallel to the axis 15 of the engine 14 .

Fig. 1 shows the working piston 35 in its starting position, in which it rests with its end face 41 facing the accumulator 29 against a bottom 42 of the pressure chamber 34 . The press rollers 39 , 40 are then most retracted.

The tool has at least one connection opening 43 , to which, in a known manner, the pressing tongs (not shown) with the two pressing jaws pivotable relative to one another are connected. These press jaws are also formed and arranged in a known manner so that by moving the working piston 35 in Fig. 1 to the left, the press rollers 39 , 40 get between the press jaws and press them together at the appropriate feed rate of the working piston 35 so that the between the Press jaws located pipes, pipe sections, fittings and the like are pressed radially ver.

In order to initiate the pressing process, the switch 10 to the drive 4 is switched on. Via the motor 14 and the reduction gear 18 , the output shaft 20 is rotatably driven. The Exzen terantrieb 20 , 22 , 23 moves the piston 25 in the piston chamber 27 back and forth. Due to the oscillating movement of this pump piston 25 , the check valves 32 , 36 are opened alternately by negative or positive pressure in the bore 33 . If the Rückschlagven valve 32 is opened when the pump piston 25 moves back due to the negative pressure that arises in the bore 33 , the hydraulic medium in the reservoir 29 can enter the bore 33 and part of the piston chamber 27 . The other check valve 36 remains closed in the bore 33 at negative pressure. If the pump piston 25 is moved again in the opposite direction, the hydraulic medium located in the bore 33 and in the pump chamber 27 is pressurized, as a result of which the check valve 32 is closed. The pressurized hydraulic medium opens the check valve 36 so that the hydraulic medium can get into the pressure chamber 34 in front of the working piston 35 . By ständi ge pumping movement of the piston 25 such a high pressure in the hydraulic medium is applied in the pressure chamber 34 that the working piston 35 against the force of the compression spring 38 in the direction of arrow 44 in the cylinder space 37 is moved. The pressure rollers 39 , 40 carried by the working piston 35 are thereby also displaced in a known manner in the direction 44 , whereby they swivel the pressing jaws of the pressing tongs connected to the work against one another and thereby cause the radial pressing.

The working piston 35 can be moved at most until it comes to rest against a stop 45 lying opposite the bottom 42 of the cylinder space 37 . It is advantageously formed by a ring inserted into the cylinder space 37 , which is supported on the base 46 of the cylinder space 37 opposite the base 42 . As soon as the working piston 35 reaches this stop 45 , a correspondingly high pressure builds up in the pressure chamber 34 .

During the pressing process, the working piston 35 often does not come up to the stop 45 because, due to the plastic deformation of the corresponding workpieces or the structural design of the pressing pliers ge via the pressing rollers 39 , 40, a strong back pressure is built up so that the working piston 35 does not move any further can push ver 44 .

The tool is now designed so that when a given pressure in the pressure chamber 34 is reached, the pressure builds up automatically. To achieve this, a bore 47 ( FIG. 2) opens into the pressure chamber 34 , which is separated by a pressure relief valve 48 from a drilling 49 . The pressure relief valve 48 is seated in a bore 50 ( FIG. 3) which extends transversely to the bore 47 . The pressure relief valve 48 has a valve body 51 which is under the force of at least one compression spring 52 . The biasing force of the compression spring 52 can be set before geous with a threaded sleeve 53 which is screwed radially from the outside into the hydraulic block 28 . The spring force is set so that the pressure relief valve 48 only opens at a pressure in the pressure chamber 34 which is established when the working piston 35 abuts the stop 45 or the pressure rollers 39 , 40 have pressed the workpieces to the maximum. Since the bore 47 opens into the pressure chamber 34 , the same pressure prevails in the bore 47 as in the pressure chamber 34 . As soon as it becomes greater than the force exerted by the compression spring 52 on the valve body 51 , the pressure relief valve 48 opens, so that the flow connection from the bore 47 to the bore 49 is released. As shown in FIG. 2, 49 opens the bore in one end face of the hydraulic unit 28, which is also the base of Spe I Chers 29 (Fig. 1). The bore 49 is closed at this end by a locking element 54 , such as a threaded pin.

A bore 55 with a smaller diameter branches off from bore 49 ( FIG. 2) and opens into a cylinder space 56 . Its axis is parallel to the axis of the bores 47 , 49 and, like this, is provided in the hydraulic block 28 .

The valve body 51 of the pressure relief valve 48 lies in the closed position under the force of the compression spring 52 on a sealing seat 57 ( FIG. 3). The bore 55 radially penetrates the cylinder space 56 , in which a control piston 58 of a backflow valve 58 A ( FIGS. 2a, 4) can be displaced in a sealed manner. The bore 55 opens into the outer surface of the hydraulic block 28 and is closed with a closure element 59 , preferably before a threaded pin.

The control piston 58 has an axial bore 60 which is open in the direction of the piston 35 ( FIG. 2a). The bore 60 is penetrated by a diametric bore 61 ( FIG. 4), which is provided near the other end of the control piston 58 . The piston head 62 having the diametral bore 61 has a slightly smaller diameter than the cylinder space 56 . As a result, an annular space 63 is formed between the inner wall of the cylinder space 56 and the outer surface of the piston head 62 , into which the diametral bore 61 opens. The piston head 62 has a frustoconical end and tapers towards its free end. The end face 64 of the piston head 62 is thereby smaller diameter than the piston head 62 subsequent to the piston part 65th It passes at a distance from the piston head 62 into a piston part 66 of reduced outer diameter, in the end face 67 of which the axial bore 60 opens centrally. The end face 67 faces the pressure chamber 34 in front of the working piston 35 ( FIG. 2a). The piston part 66 is sealed over a part of its length in a bore 68 , which passes into the cylinder space 56 via at least one shoulder 69 and opens into the Bo 42 of the pressure chamber 34 . Paragraph 69 limits the displacement of the control piston 58 . Due to the paragraph 69 , a receiving space 85 is formed in the hydraulic block 28 , in which we at least one (not shown) compression spring is housed, which surrounds the control piston 58 and loads it to the right in Fig. 4. At least one vent hole 86 opens into the receiving space 85 , which extends to the outside of the hydraulic block 28 and enables the control piston 58 to be moved without problems.

From the end face 64 of the control piston 58 is a Dros selelement 70 centrally, which is initially cylindrical in connection with the end face 64 and at the end merges into a conically tapering end portion 71 . The throttle element 70 is advantageously formed in one piece with the control piston 58 .

The cylindrical part of the throttle element 70 projects into an axial bore 72 which projects into an insert body 73 inserted into the cylinder space 56 . It is screwed with an end threaded part 74 into the cylinder space 56 and lies sealed against the inner wall of the cylinder space 56 .

The bore 72 in the insert body 73 has a larger diameter than the cylindrical part of the throttle element 70 , so that an annular flow space 75 for the hydraulic medium is formed between the inner wall of the bore 72 and this cylindrical throttle element. At a distance from the free end face of the insert body 73 , the bore 72 merges into a bore 76 of smaller internal diameter. The cylindrical part of the throttle element 70 projects into it. The inner diameter of the bore 76 is only slightly larger than the outer diameter of the cylindrical throttle element part. As a result, an annular throttle chamber 77 is formed, which is connected to the substantially larger flow cross-section having flow chamber 75 .

The bore 76 has a bottom 78 at its end facing away from the bore 72 , into which a bore 79 with a small diameter opens centrally, which is provided in the insert body 73 and connects the bore 76 to a channel 80 which enters the memory 29 for the hydraulic medium opens. The conical end part 71 projects into the thin bore 79 with its conical tip. Depending on the axial position of the control piston 58 and thus of the throttle element 70 , an annular throttle gap 81 is formed between the conical tip of the end part 71 and the bore 79 .

When the pressure relief valve 48 opens in the manner described, the hydraulic medium under high pressure reaches the pressure chamber 34 in front of the working piston 35 via the bores 47 , 49 , 55 into the flow chamber 75 , into which the bore 55 opens. Due to the throttle chamber 77 and the throttle gap 81 , a pressure can build up in the flow chamber 75 , with which the annular end face 64 of the control piston 58 is acted upon. This actuated control surface 64 is larger than the opposite end face 67, which is acted upon by the hydraulic medium in the pressure chamber 34 . The differential force ensures that the control piston 58 is moved from the closed position shown in FIG. 2a, in which it has distance from the working piston 35 , in the open position shown in FIG. 2b. The control piston 58 thereby lifts with its conical outer surface 82 of its piston head 62 from a sealing seat 83 at the end of the insert body 73 lying in the cylinder 56 . As a result, the hydraulic medium located in the pressure chamber 34 can pass through the axial bore 60 and the diametral bore 61 in the control piston 58 into the annular space 63 and from here into the flow chamber 75 . Via the throttle chamber 77 , the bore 76 , the throttle gap 81 , the drilling 79 and the channel 80 , the hydraulic medium can thus flow back from the pressure chamber 34 into the reservoir 29 . The control piston 58 is pushed back so far that a throttling effect is not exerted on the hydraulic medium. The working piston 35 is pushed back by the force of the compression spring 38 . He then comes with his end face 41 to the end face 67 of the control piston 58 to the plant and takes the control piston 58 accordingly and pushes it back into the closed position according to FIG. 2a.

The pressure relief valve 48 closes as soon as the pressure in the pressure chamber 34 is again below the predetermined pressure, so that the flow connection between the two bores 47 and 49 is broken. The hydraulic medium is thus returned from the pressure chamber 34 to the accumulator 29 exclusively via the control piston 58 in the manner described.

So that the control piston rests 58 in the initial or closed position according to Fig. 2a, by force on the sealing seat 83, and thus the access of the hydraulic medium prevents into the flow space 75, which is acted upon by the hydraulic medium in the pressure chamber 34 end face 67 is greater than that in the range Between the sealing seat 83 and the transition into the cylindrical jacket of the piston head 62, the surface of the control piston 58 that can be acted upon. As a result, the force exerted in the direction of the closed position of the control piston 58 is greater than the counterforce which the hydraulic medium exerts on the jacket surface 82 in the closed position of the control piston 58 . This ensures that the control piston 58 reliably closes the flow chamber 75 in the closed position.

In the manner described, the working piston 35 will automatically move back to the starting position shown in FIG. 1 after the pressing operation, the pressing rollers 39 , 40 also being inevitably moved back to the starting position. The operator therefore does not have to perform a separate switching or actuation process to return the press rollers 39 , 40 to the starting position after the pressing process.

The end face 41 of the working piston 35 is slightly conical, preferably with a cone angle of 3 °. This is sicherge provides that the hydraulic medium in the pressure chamber 34 can also flow into the axial bore 60 of the control piston 58 when it rests on the end face 41 of the working piston 35 . The end face 67 of the control piston 58 is flat, so that in connection with the kegelförmi gene end face 41 ensures that the hydraulic medium can flow into the axial bore 60 even when the control piston 58 is in contact.

Instead of the conical design of the end face 41 , the end face 67 can also be provided with at least one groove or notch, which enables the hydraulic medium to enter the axial bore 60 in the closed position of the control piston 58 . Then both end faces 41 , 67 can be flat.

Since the hydraulic medium is under pressure when flowing back from the pressure chamber 34 via the control piston 58 , the medium flows through the various bores and channels at high speed. So that the hydraulic medium does not flow into the accumulator 29 at a high flow rate and leads to problems, a diffuser 84 ( FIG. 5) is provided at the end of the channel 80 , with which the flow rate is reduced when entering the accumulator 29 .

The tool described enables the pressing process to run inevitably. In the starting position according to FIG. 2 a, the control piston 58 closes, supported by the hydraulic medium pressure acting on it, the flow space 75 in the direction of the accumulator 29 . The pressure relief valve 48 is also in its closed position. Thus, when the tool is switched on via the eccentric drive 20 , 22 , 23, the pump piston 25 is moved back and forth in the manner described, whereby the hydraulic medium arrives from the accumulator 29 via the two check valves 32 , 36 in the pressure chamber 34 and the working piston 35 pressures. It is moved against the force of the compression spring 38 , where by the pressure rollers 39 , 40 in the manner described press the Pressbac ken press tool connected to the tool to radially press the workpieces. As soon as the working piston 35 strikes the stop 45 or the pressing process is completed and a corresponding counterpressure acts on the pressing rollers 39 , 40 , the working piston 35 can no longer be moved in the direction 44 ( FIG. 1). As a result, the pressure of the hydraulic medium in the pressure chamber 34 increases until it exceeds the pressure exerted by the pressure spring 52 of the pressure relief valve 48 on the valve body 51 ( FIG. 3). The pressure relief valve 48 inevitably opens, so that the hydraulic medium can flow through the bore 47 and the open pressure relief valve 48 into the bores 49 and 55 . In the manner described, this hydraulic medium leads to the control piston 58 being moved out of its closed position according to FIG. 2 a in the direction of the working piston 35 . By moving the control piston 58 , the tapered surface 82 of the Kolbenkop fes 62 lifts off from the sealing seat 83 . As a result, the hydraulic medium located in the pressure chamber 34 can flow back via the axial bore 60 and the diamond bore 61 in the control piston 58 into the flow chamber 75 and from here into the reservoir 29 in the manner described. As a result, the pressure in the pressure chamber 34 is reduced. This leads to the fact that the compression spring 38 can push the control piston 58 back into the closed position via the working piston 35 , whereby the flow connection between the bores 60 and 80 in the hydraulic block 28 , 73 is interrupted. The working piston 35 finally returns to the starting position in which it rests on the bottom 42 of the cylinder space 37 or on the control piston 58 . The control piston 58 is pushed back into its closed position according to FIG. 2a.

In order to enable the described forced return of the working piston 35 in an emergency, the tool is provided with an emergency trigger 88 ( FIG. 3). With it, the valve body 51 of the pressure relief valve 48 can be brought manually into the release position, so that, as described in detail above, the working piston 35 is inevitably pushed back into its starting position ( FIG. 1). The emergency stop solver 88 is a two-armed lever in the exemplary embodiment, which is pivotally mounted on the hydraulic block 28 . The shorter arm 89 engages with its free end on an end head 90 of the Ventilkör pers 51 . The longer arm 91 of the emergency release 88 serves as a hand to manually move the valve body 51 to the release position. The arm 91 lies within the housing part 2 and can be actuated from the outside through an opening 92 in the housing part 2 . If the arm 91 is pressed inwards, the head 90 of the valve body 51 is adjusted against the force of the compression spring 52 by the arm 89 in the release position, so that the hydraulic medium in the manner described from the pressure chamber 34 in front of the working piston 35 through the holes 47 , 49 can reach the control piston 58 . It is then, as described above, moved into its open position, so that the working piston 35 is forced to be pushed back due to the pressure reduction in the pressure chamber 34 .

FIGS. 6 to 8 show an embodiment in which the breather tung bore 86 does not open into the outer side of the hydraulic block 28, but includes a transverse bore 87 in the hydraulic block 28, which opens into the memory 29. The transverse bore 87 is parallel to the cylinder chamber 56 , in which the control piston 58 is placed. Since the memory 29 is depressurized, it is ensured even with such a design that the control piston 58 can be reliably moved in the manner described. The hydraulic block 28 has, as Fig. 7 shows, corresponding to the previous form of circular cross-section. The vent hole 86 has a substantially smaller cross section than the cross hole 87 , which in turn has a smaller cross section than the cylinder space 56 .

Otherwise, the embodiment according to FIGS. 6 to 8 is formed the same as the embodiment according to FIGS. 1 to 5.

Claims (33)

1. Apparatus for applying a pressing force, with a housing in which a drive is housed, with a working piston which can be acted upon with pressure medium and carries actuating elements for pressing elements, and with at least one memory for the pressure medium, characterized in that the device a Druckentla stungseinrichtung ( 48 , 58 A), which opens a return flow path ( 60 , 61 , 75 , 79 , 80 ) for the pressure medium to the memory ( 29 ) when a predetermined pressure on the working piston ( 35 ) acting on the pressure medium. 2. Device according to claim 1, characterized in that the pressure relief device ( 48 , 58 A) has a pressure relief valve ( 48 ) which is in flow connection with a pressure chamber ( 34 ) in front of the working piston ( 35 ). 3. Apparatus according to claim 2, characterized in that the pressure relief valve ( 48 ) switches a flow path ( 47 , 49 , 55 ) to a backflow valve ( 58 A). 4. The device according to claim 3, characterized in that the flow path ( 47 , 49 , 55 ) has at least one in the pressure chamber ( 34 ) in front of the working piston ( 35 ) opening ( 47 ). 5. Apparatus according to claim 3 or 4, characterized in that the backflow valve ( 58 A) has a control piston ( 58 ) with which a flow path ( 75 , 79 , 80 ) to the memory ( 29 ) can be closed. 6. The device according to claim 5, characterized in that the control piston ( 58 ) has at least one bore ( 60 , 61 ) which is fluidly connected to the pressure chamber ( 34 ) in front of the working piston ( 35 ). 7. Apparatus according to claim 5 or 6, characterized in that the control piston ( 58 ) is provided with at least a throttle element ( 70 ). 8. The device according to claim 7, characterized in that the throttle element ( 70 ) from the end face ( 64 ) of the control piston ( 58 ) protrudes. 9. Apparatus according to claim 7 or 8, characterized in that the throttle element ( 70 ) is integrally formed with the control piston ( 58 ). 10. Device according to one of claims 7 to 9, characterized in that the throttle element ( 70 ) has a ko tapered end portion ( 71 ). 11. Device according to one of claims 7 to 10, characterized in that the throttle element ( 70 ) projects into a passage ( 76 ) of an insert body ( 73 ). 12. Device according to one of claims 7 to 11, characterized in that the throttle element ( 70 ) has a smaller external cross section than the control piston ( 58 ). 13. The device according to one of claims 7 to 12, characterized in that the throttle element ( 70 ) in the connection to the end face ( 64 ) of the control piston ( 58 ) is cylindrical. 14. The apparatus according to claim 13, characterized in that between the cylindrical part of the throttle element ( 70 ) and the inner wall of the passage ( 76 ) of the insert body ( 73 ) an annular flow space ( 75 ) for the pressure medium flowing back to the reservoir ( 29 ) is formed , 15. The apparatus according to claim 14, characterized in that the annular flow chamber ( 75 ) via at least one throttle point ( 77 , 81 ) with the flow path ( 79 , 80 ) for the back-flowing pressure medium is connected ver. 16. The apparatus according to claim 15, characterized in that the throttle point ( 77 ) is an annular gap between the cylindrical part of the throttle element ( 70 ) and the inner wall of a reduced diameter Drosselrau mes ( 77 ). 17. The device according to one of claims 10 to 16, characterized in that the conical end part ( 71 ) projects into a bore ( 79 ), forming a throttle gap ( 81 ), which is part of the return flow path of the pressure medium. 18. Device according to one of claims 14 to 17, characterized in that by moving the control piston ben ( 58 ) from a closed position of the annular flow chamber ( 75 ) via at least one transverse bore ( 61 ) in the control piston ben ( 58 ) with at least one axial Bore ( 60 ) of the control piston ( 58 ) is to be brought into flow connection. 19. Device according to one of claims 5 to 18, characterized in that the control piston ( 58 ) has a working piston ( 35 ) facing, pressurized with bare end face ( 67 ). 20. The apparatus according to claim 19, characterized in that in the end face ( 67 ) of the control piston ( 58 ) opens the axial bore ( 60 ). 21. The apparatus of claim 19 or 20, characterized in that in the closed position, the pressure chamber ( 34 ) in front of the working piston ( 35 ) facing the end face ( 67 ) of the control piston ( 58 ) has a larger area than the opposite, outside a sealing seat ( 83 ) lying and pressurized with free medium end face ( 63 , 82 ). 22. Device according to one of claims 5 to 21, characterized in that the displacement path of the control piston ( 58 ) is stop-limited. 23. Device according to one of claims 18 to 22, characterized in that the transverse bore ( 61 ) of the control piston ( 58 ) in an annular space ( 63 ) between a piston head ( 62 ) and the inner wall of a receiving space ( 56 ) for the control piston ( 58 ) ends. 24. The device according to claim 23, characterized in that the annular space ( 63 ) with the flow chamber ( 75 ) in the insert body ( 73 ) is fluidly connected. 25. The apparatus of claim 23 or 24, characterized in that the piston head ( 62 ) has a conical surface ( 82 ) with which it bears in the closed position of the control piston ( 58 ) on the sealing seat ( 83 ). 26. The apparatus according to claim 25, characterized in that the sealing seat ( 83 ) on the insert body is provided by ( 73 ). 27. The apparatus of claim 25 or 26, characterized in that at the moment of opening of the control piston ( 58 ), the effective, pressurizable end face of the control piston ( 58 ) is larger than the working piston ( 35 ) facing end face ( 67 ) the control piston ( 58 ). 28. Device according to one of claims 5 to 27, characterized in that the control piston ( 58 ) can be pushed back into its closed position by the working piston ( 35 ). 29. Device according to one of claims 1 to 28, characterized in that the working piston ( 35 ) can be pushed back into its starting position by a restoring force, preferably by spring force. 30. Device according to one of claims 1 to 29, characterized in that the displacement of the working piston ( 35 ) is stop-limited. 31. The device according to one of claims 1 to 30, characterized in that the control piston ( 58 ) facing end face ( 41 ) of the working piston ( 35 ) is weakly conical. 32. Device according to one of claims 11 to 32, characterized in that the return flow path ( 75 , 77 , 79 , 80 ) is provided for the pressure medium in the insert body ( 73 ). 33. Device according to one of claims 11 to 32, characterized in that the insert body ( 73 ) in the receiving space ( 56 ) of the housing ( 1 ) can be screwed.