EP2448720A1

EP2448720A1 - Hydraulic press unit

Info

Publication number: EP2448720A1
Application number: EP10727433A
Authority: EP
Inventors: Egbert Frenken
Original assignee: Gustav Klauke GmbH
Current assignee: Gustav Klauke GmbH
Priority date: 2009-07-02
Filing date: 2010-07-01
Publication date: 2012-05-09
Anticipated expiration: 2030-07-01
Also published as: AU2010268021A1; US20120160065A1; BRPI1015945A2; RU2012103481A; ES2411881T3; CN102481689B; US8844436B2; RU2532224C2; MX2012000079A; AU2010268021B2; KR101821238B1; CN102481689A; PL2448720T3; KR20120052957A; WO2011000907A1; EP2448720B1; DE102009026273A1

Abstract

The invention relates to a hydraulic press unit (1) having a fixed part (2) and a moving part (3), wherein the moving part is moved relative to the fixed part (2) by means of a hydraulic piston (4) and can be moved back into an initial position by means of a restoring spring (5), wherein furthermore, the return movement can be triggered as a function of a predetermined pressing pressure by means of the response of a return valve (6), wherein furthermore a control valve (7) is provided which, in addition to the return valve (6), opens up a hydraulic medium outlet (8) in the open state and has a hydraulic medium inflow and outflow side. To provide a hydraulic press unit of said type which is of advantageous design with regard to the response of the control valve, it is proposed that, when the return valve (6) opens, the control valve (7) is acted on by the pressure of the returning hydraulic medium on the inflow and outflow sides, wherein the pressure on the inflow side is lower as a result of throttling.

Description

Hydraulic pressing device

The invention relates to a hydraulic pressing device with a fixed part and a moving part, wherein the moving part is moved by a hydraulic piston relative to the fixed part and by means of a return spring in an initial position zurückbewegbar, wherein further the return movement in response to a predetermined pressing pressure can be triggered by addressing a Return valve, wherein, in addition, a control valve is provided which, in addition to the return valve in the open state, a hydraulic liqueur drain free and has a hydraulic fluid inflow and outflow side.

Such pressing devices are known in various configurations. For example, reference should be made to WO 99/19947. In addition, also to WO 98/24570, relating to an application as a punching device, WO 02/62504, relating to an application as a widening tool and WO 02/00368, relating to an application as a riveting tool.

Such a pressing device is also known for example from DE 20 2004 000 215 Ul. The control valve arranged here in a hydraulic line leading from the hydraulic fluid pump to the hydraulic piston receiving hydraulic cylinder is penetrated by the hydraulic fluid delivered by the pump according to a design as a check valve from the inflow side to the outflow side. When the hydraulic fluid pump is switched off, the fluid pressure acting on the downstream side, together with a biasing spring acting in the same direction, causes the control valve to move to the open position, thereby releasing the hydraulic fluid discharge associated with the downstream side. Since, in addition, the control valve does not open at higher system pressure, there is still no opening of the control valve at the beginning of the hydraulic fluid return when the return valve has opened after the pressing operation has taken place. Based on the above-described prior art, the invention is in one aspect with the task of making such a hydraulic pressing device with regard to the response of the control valve advantageous. Another aspect relates to an advantageous arrangement of the control valve.

A possible solution in any case of said first aspect is given by a first inventive concept by the subject-matter of claim 1, wherein it is based on the control valve is acted upon by the pressure of the returning hydraulic fluid on the arrival and downstream side with the return valve open, wherein the Throttling pressure is lower on the upstream side. With the return valve open, the control valve is exposed to the pressure of the hydraulic medium in the return area, albeit differently, on both sides. The resulting due to the throttling pressure difference acts in the opening direction of the control valve and thus causes or in any case supports a rapid opening. This effect can be additionally supported by a spring bias of the control valve in the open position. On the other hand, however, in preferred embodiments of the subject of the invention, this is not the above design criterion for an optionally selected spring preload. After opening the return valve results in almost immediately, possibly even in conjunction with the opening of the return valve, an opening of the control valve and thus a dual drainage possibility for the hydraulic fluid. As a result, a desired fast return of the hydraulic piston can obviously be achieved. On the other hand, there are also applications in which the setting is made so that only a very small amount of the hydraulic fluid via the return valve runs. A possible solution, in particular the further indicated aspect of the problem, is also given by the subject matter of claim 2, the latter being geared to providing a hydraulic pump, from which pump a (first) hydraulic fluid flow path leads to the control valve and another (second) hydraulic fluid flow path leads directly to the return valve. The hydraulic fluid supply line leading from the hydraulic fluid pump to the control valve and preferably also to a hydraulic cylinder receiving the return piston is also provided directly from the hydraulic fluid pump to the control valve. The said hydraulic fluid flow paths can also partially coincide. It is essential that, due to the direct connection, the hydraulic fluid flows through the supply line to the control valve or to the return valve without initially flowing, for example with respect to the return valve, via the control valve. As a result, with respect to the two valves, a parallel circuit is provided starting from the hydraulic fluid pump. Hydraulic fluid inlet (from the pump) and hydraulic fluid drain through the (opened) return valve are located hydraulically on the same side of the control valve. The connection to the cylinder chamber (moving part) is located hydraulically on the other side of the control valve (or in the bypass for this purpose). Seen from the moving part, the return valve may be arranged hydraulically after the control valve or, at least in addition, in parallel with the control valve. Essential is the possible compact arrangement of said valves and the hydraulic lines.

The biasing the control valve in the open position spring can be formed with a relatively low spring force. Thus, no opening of the control valve is given even when stopping the pump in the course of the initiation of the compression process or in an already more advanced compression. Rather, the control valve moves only in its open position, if in addition, according to the open return valve, a negative pressure of the control valve or an admission pressure difference sets. In the case of a hydraulic hand press device, which is the preferred method here, the compression is actuated triggering of the pump, which is preferably driven by an electric motor achieved. If the depression of a corresponding switch is interrupted, the pump also stops running. Press jaws of a pressing device remain in a certain position. In the embodiment described here, the resumption of the operation allows the injection process to be continued without further ado. There is no running back of the hydraulic piston. Not even with a very low system pressure or (over) pressure level in the hydraulic cylinder at the beginning of a grouting process.

The term "control valve" is chosen for a clear conceptual separation.Other characteristics of the invention are described below, also in the description of the figures, often in their preferred assignment to the claim concept already explained above but also in an assignment to only one or more features of this claim or independently or in another overall concept of importance.

It is further preferred initially that the control valve is designed as a seat valve. By driving against a seat stop, the valve closes the hydraulic fluid drain. The opening closed by the seat valve runs (in relation to an axis of the opening) in the direction of displacement of the control valve. There is no Abschieberung, but a closure of a drain opening whose opening area in coverage of the control valve, based on a projection in the direction of movement of the control valve is located.

Associated therewith, though not necessarily connected, is the fact that the closed control valve is affected by one of the pressure in the hydraulic fluid reservoir and the pressure in the hydraulic fluid supply line applied differential force is applied. Since in almost all operating conditions, the pressure in the hydraulic fluid supply line is higher than the pressure in the hydraulic fluid reservoir, this results in a locking force of the control valve when it is in the closed position. Although initially a higher pressure is required to move the control valve in the closed position, then, when it is in the closed position, also a lower pressure in the hydraulic medium supply line, as long as this pressure is still sufficiently higher than that Pressure in the hydraulic fluid reservoir. The pressure in the hydraulic fluid reservoir may correspond to the ambient pressure or may even be lower than the ambient pressure, that is to say a negative pressure. The latter especially if the pump works at high flow rate. The higher pressure which serves to displace the control valve into the closed position results from the pressure loss of the flowing hydraulic fluid via the control valve, seen from the inflow side to the outflow side. It is, as it were, a dynamic pressure due to the movement of the hydraulic fluid or the pressure difference resulting from the control valve. The control valve responds to the direction of flow of the hydraulic fluid. The pressure in the hydraulic medium supply line increases accordingly in the

Triggering a pressing operation from ambient pressure (or slightly above) to the pressing triggering pressure. Such a trigger pressure can for example be between 300 and 700 bar. After pressing, when the return valve has opened, the pressure is in the hydraulic fluid supply line, which then depending on the configuration, as described below, hydraulic fluid runs back into the reservoir, for example, 10 and 0.5 bar (pressure) , In this case, all intermediate values, in particular in steps of 0.1 bar, are included in the disclosure. The hydraulic fluid pump delivers via a delivery line into a first branch line leading to the control valve and a second branch line leading to the return valve. When a conventional grouting operation is triggered, the return valve is closed or is closed, for example, by releasing an opening detent in the course of this triggering. The hydraulic fluid is therefore only in this branch line, but does not flow. However, it then flows via the control valve and the hydraulic fluid supply line into the cylinder chamber. In addition, a bypass can be provided directly in the cylinder chamber. The promotion to the return valve is carried out according to line or not only via the control valve, but, if appropriate, in parallel thereto. The return valve is hydraulically connected in parallel to the control valve with respect to the hydraulic fluid delivery. Further, it is preferably also provided in this context that when the return valve is opened via the return valve, the hydraulic fluid flowing out initially, preferably as a whole, flows via the control valve. In this case, the return valve is hydraulically connected downstream of the control valve at draining hydraulic fluid. But it can also be provided that it flows only partially through the control valve. On the other hand, it can flow through a line leading directly from the cylinder to the return valve, this line furthermore preferably having a throttle point. It may also flow in total via said separate line from the cylinder space to the return valve. Even in the latter case, however, it is provided that this leading to the return valve line is in line connection with the control valve, and to the upstream side of the control valve. Also in this structural design, therefore, in the case of the return of hydraulic fluid, the respective pressurization is given on the upstream side of the control valve. The control valve may be biased by a spring in its open position. This bias is preferably chosen to be lower in this case than corresponds to a force acting on the control valve by a spring action of the return piston force. The caused by the spring action of the return piston in the case of the return in the hydraulic medium supply line pressure, which, as stated, for example, between 0.5 and 5 bar can, corresponding to the hydraulically effective surface of the control valve to a force acting thereon. Regardless of the possibly additionally supportive acting lower pressure or even negative pressure in the hydraulic fluid reservoir, the said force exerted by the spring action of the return piston force is greater than that corresponding to the force acting on the control valve in the opening direction spring force. A realistic size for the force of this spring acting on the control valve in the opening direction is, for example, between 0.1 and 1 Newton, more preferably between 0.2 and 0.4 Newton, in which ranges also all intermediate values, in particular in 1 / 10 Newton steps are included.

As an alternative to the configuration described above, in the case of opening the return valve, hydraulic fluid at least partially flows via the control valve to the return valve, it can also be provided that the control valve in its open position at the same time the hydraulic fluid supply line, via which otherwise Hydraulic fluid can flow to the return valve locks. Whereby this blocking may preferably also be given in the sense of a seat valve. The outflow can then be provided via an example provided direct line connection from the hydraulic cylinder to the return valve, as already mentioned. However, the outflow via the return valve can thereby be completely interrupted. The return valve goes in this case, because of the associated pressure drop, immediately in its closed position. The return valve is set to the highest pressure, the pressure to be achieved. The control valve allows due to the (further) pressure drop resulting from its opening an automatic control of the return valve in the closed position, with simultaneous opening of a (further) discharge path for the hydraulic fluid. This can be achieved in the desired manner in the course of carrying out a pressing process first, take each intermediate position and then continue the pressing process. After the Verpressvorganges can be achieved by simply re-actuation of the pump stopping the moving part, so usually the return piston, and made from this position from the next pressing.

The control valve consists in detail of a valve closure body, which cooperates with a - fixed to the housing - valve seat. In this regard, it is preferably provided that the valve closure body passes through a compensating part that accompanies the movement of the valve closure body. The compensation part thus moves with the valve closure body from the closed position to the open position and vice versa. The compensating part is designed such that the valve closure body can move transversely to its direction of movement when moving from the closed position to the open position or vice versa. For this purpose, the valve closure body is also preferably received in the hydraulic medium supply line with a corresponding play. This mobility of the valve closure body ensures that even with not exactly aligned alignment of the valve seat with the valve closure body results in a reliable closure of the control valve. The valve closure body accordingly has sufficient movement possibility with respect to possible manufacturing tolerances.

The compensating part may be formed, for example, in the form of a washer. Also, the compensation part, for example, specifically the washer, is preferably not sealing in the further preferred at least in this area cylindrically shaped hydraulic fluid supply line fitted. On the contrary, it is also possible here to suitably retain a radial gap, albeit a very small one, which allows a certain flow of hydraulic fluid through it. In any case, such a gap allows, at rest, the pressure equalization over the compensation part. A realistic size for such a gap is about 1/100 to 2/100 mm. In contrast, the possibility of movement of the valve closure part transversely to the direction of movement with respect to an Öffnungsbzw. Closing process be 2/100 to 10/100 or more hundredths of a millimeter, for example, up to a 1/2 mm.

The invention is further explained below with reference to the accompanying drawing, which, however, represents only exemplary embodiments. Hereby shows:

Fig. 1 is a partially sectioned, representation of a front

Part of a pressing device;

Fig. 2 is an enlargement of the range 2-2 in Figure 1, with the control and return valve closed. 3 shows an illustration according to FIG. 2, with the control valve open; FIG.

4 shows a representation according to FIG. 2 with additional throttle opening; 5 shows an illustration according to FIG. 4, with a modified throttle opening; and

Fig. 6 is an enlarged view of the control valve relative to the area VI - VI in Fig. 3, with compensation part. Illustrated and described, first with reference to Fig. 1, a hydraulic pressing device with a fixed part 2 and a moving part 3. The moving part 3 is by means of a hydraulic piston 4 relative to the fixed part 2, which can also be regarded as the entire housing moves , The hydraulic piston 4 can be moved back into its initial position by means of a restoring spring 5 and, in the non-use state, is thereby biased into the starting position. The return movement of the hydraulic piston 4 can be triggered by the response of a return valve 6 at the end of a pressing operation. In the exemplary embodiment, this return valve 6 is designed and operates in the manner described in EP 0 944 937 B1. The disclosure of this document is hereby incorporated by reference in its entirety into the disclosure of the present application with regard to the design of this return valve and the corresponding mode of operation, also to include one or more of the features known therein in claims of this application.

Furthermore, a control valve 7 is provided which influences the closure characteristic of the return valve 6. Because preferably, the return valve 6 is no longer open until complete return of the hydraulic piston 4. According to the control valve 7 results in the opening state of this control valve 7 such a strong pressure drop before the return valve 6, that it prematurely in this sense, before the hydraulic piston 4 reaches its end-return position closes. A further return movement of the hydraulic piston 4 then takes place only by the outflow of hydraulic fluid via the discharge opening 8 released from the control valve 7 in the opening state into the hydraulic fluid reservoir 9.

In detail, the control valve 7 has an inflow side 10 and an outflow side 11. The inflow side 10 refers to the fact that the control valve 7 is acted upon by the hydraulic medium on this side during the conveyance of hydraulic fluid by means of the hydraulic fluid pump 12. About the downstream side 11, the hydraulic fluid flows through the hydraulic fluid line 13 into the hydraulic cylinder 14 in which the hydraulic piston 4 is received. The hydraulic pump 12 may be a piston pump as shown. But it may also be, for example, a screw pump. The latter has the advantage that it is pumped with a continuous pressure. When pumping hydraulic fluid through the open control valve 7, which is associated with this, but also practically immediately displaced into the closed position, resulting throttling effect, a pressure drop of, for example, 1 bar, which causes said shift to the closed position.

The path of the returning hydraulic fluid, to which reference is also made in detail in Fig. 2, is given at the beginning, at the opening of the return valve 6, via the control valve 7, according to a circumferentially continuous gap 15 let hydraulic fluid flow past. Since this passage gap 15 is relatively small, it can be seen that this results in throttling, which leads to a pressure drop across the control valve 7. On the inflow side 10, which is actually a downstream side in this state, there is correspondingly then a lower pressure than on the downstream side 11. In addition, a certain back pressure on the outflow side may additionally result. By this pressure difference and supported by the control valve 7 biasing in the open position compression spring 16, the control valve 7 is moved very quickly in the open position shown in FIG.

In a conventional design, but it actually does not need the compression spring 16 to move the control valve 7 in the open position. Due to the self-adjusting flow through the discharge opening 8, however, a suction effect on the open control valve 7 may result, which is counteracted by means of the compression spring 16. The opening position shown in FIG. 3 can be provided on the one hand so that a dense or nearly dense valve seat 17 results. An opening seat section 18 of the control valve 7 cooperates sealingly with the housing wall 36, which has a valve seat with ausformende constriction in this area. As a result, in the formation of the control valve as a shuttle valve, wherein the control valve in one position (closed position) closes the drain opening 8 and in the other position (with respect to the final position 8: open position) closes the flow to the return valve 6 results a closing of the return valve 6 even in the event that it should have such a large hysteresis that it would otherwise remain in the open position during the entire return of the hydraulic piston. Thus, even after opening the return valve given enough time to turn off the hydraulic pump, so that the control valve is not immediately closed again when the return valve closes and the pump would still promote. The design can also be provided so that even in the opening state of the control valve 7 according to FIG. 3, a flow of hydraulic fluid to the return valve 6 remains. With increasing retraction of the hydraulic piston 4, the spring 5 relaxes and the pressure exerted on the hydraulic fluid pressure is reduced. Correspondingly, the return valve 6 can then also be moved into a closed position, if a required critical pressure, which is necessary to maintain the opening state of the return valve 6, is exceeded.

Here, too, then, the closure position of the return valve 6 is reached before the hydraulic piston 4 is fully returned to its final position. However, the setting can also be made such that, in order to achieve the fastest possible retraction of the hydraulic piston, the control valve 7, as well as the return valve 6, remain in the open position until reaching the end position. In the illustrated embodiment, the setting is provided so that the return valve 6 immediately moves into its closed position when the control valve 7 opens. The flow of the hydraulic fluid then takes place only through the drain opening 8, which is formed in the valve seat of the control valve 7. In addition to the path of the hydraulic means when triggering a pressing operation via the control valve 7, a conveying path 19 provided in the bypass for this purpose, see FIGS. 4, 5, may be formed. This is preferably formed as a throttle point. According to FIG. 5, it can also be closed by a check valve 20 so that hydraulic fluid flows through the delivery path 19 only when pumping hydraulic fluid through the pump 12.

In the embodiment according to FIG. 4, even after the return valve 6 has been triggered, hydraulic fluid flows through the delivery path 19 into the space 21 and from there, with the return valve 6 open, via the return valve 6 into the hydraulic fluid reservoir 9.

The embodiment described here is of particular advantage in various respects.

If, after initiation of a pressing operation by appropriate switch operation, the running of the pump 12, which is driven for example via an electric motor, is triggered, the control valve 7 is immediately moved to the closed position. The return spring 16, which acts on the control valve 7 in the open position, in this case is designed so that even after a successful initiation of the pressing operation interrupting the pump, such as by the switch is no longer pressed, acting on the control valve 7 closing pressure is sufficient to keep the control valve 7 in the closed position. Then there is no return of the hydraulic piston 4. By pressing the release switch again then the pressing process can be continued, at the same position of the hydraulic piston 4, this has taken on interruption of the pumping operation. If, nevertheless, a return of the hydraulic piston 4 is desired, this can additionally be triggered via the manual switch 21, which acts on the return valve 6, see, for example, FIG. 4. On the other hand, the design of the control valve 7 is made so that the pressure drop described in the case that the return valve 6 triggers, each shift the control valve 7 in the open position. Due to the bias by means of the spring 16, the control valve then remains in this opening position.

During a return of the hydraulic piston 4, which then takes place, the pump 12 can be actuated again at any time by a switch actuation. Immediately, the control valve 7 moves in the closed position, whereby the hydraulic piston 4 is stopped at the then reached position in the hydraulic cylinder 14. Without a complete retraction is required, then from this position, the next compression can be performed. The control valve 7 is seen to be formed in further detail with a front cone-shaped seating area 22, which merges via a cylinder portion 23 into an enlarged flange area 24. At the end of this flange region 24, a throttling region 25 adjoins. When the control valve 7 is displaced in the mentioned manner in the open position, this is a very fast, practically instantaneous process. Due to the fact that the throttle region 25 dips into the passage opening 26, which is only a little larger, this results in a desired deceleration and a gentle abutment of the region 24 on the wall of the housing. Following this, an elongate shaft 27 is formed, which extends with an extension 29 into an inlet bore 28 of the return valve 6. The inlet bore 28 continues in a right angle extending continuation 30, in which the return valve 6 is arranged. The shaft 27 passes through the space 21, which is first reached by pumped by the pump 12 hydraulic fluid. This space 21 apparently branches into an inlet to the Control valve 7 and an inlet to the return valve 6. In addition, in the bypass line 19, if this is provided.

Associated with the discharge opening 8, a baffle 31 is provided on the supply chamber side. Even with a small diameter of the drain opening 8, a thin, strong hydraulic fluid jet caused thereby can not lead to damage of the opposite wall 32 of the storage space 9. Especially since the wall 32 is preferably formed by a resilient rubber material. The baffle 31 is formed in detail by a T-tube, wherein a portion of the T-tube is formed as Einschraubabschnitt, the end forms the seat for the control valve 7 and the other portion of the T-tube forms said baffle.

With reference to FIG. 6, it can be seen that the valve body of the control valve 7, which has the seating area 22, the cylinder section 23 and the flange area 24, passes through a compensation part 33. The compensation part 33 is designed as an annular body having an inner diameter Di which is smaller than an outer diameter Da of the flange region 24. The compensating part 33 is seated on the seat area side of the flange region 24, ie in the embodiment of the cylinder section 23, penetrated by the valve closure body. The inner diameter Di of the compensation part 33 leaves a gap s with respect to the said cylinder part 23. This gap s allows the valve closure body to move transversely to its longitudinal extent. This automatically results in a certain transverse displacement when, for example, the counter-valve seat forming bore 34 of the here formed by the T-tube valve seat portion 34 should not be aligned with a longitudinal center axis of the valve body.

As can also be seen in the following also about Fig. 2 and the above description, goes from the hydraulic fluid pump 12, a flow path through the space 21 and the line branching from this line 35 directly to the return valve 6. Hydraulically speaking, ie in terms of at least theoretical way, the hydraulic fluid travels during the flow, the hydraulic fluid supply, in the form of the hydraulic fluid pump 12 and the immediately subsequent conduction path, and the return valve 6 are arranged hydraulically on the same side, namely the upstream side of the control valve 7.

All disclosed features are essential to the invention. The disclosure of the associated / attached priority documents (copy of the prior application) is hereby also incorporated in full in the disclosure of the application, also for the purpose of including features of these documents in claims of the present application. The subclaims characterize in their optional sibling version independent inventive development of the prior art, in particular to make on the basis of these claims divisional applications.

LIST OF REFERENCE NUMBERS

1 hydraulic pressing device

2 hard part

3 movement part

4 hydraulic pistons

5 return spring, spring

6 return valve

7 control valve

8 drain opening / hydraulic fluid drain

9 (hydraulic fluid) storage room

10 upstream side 11 outflow side

12 hydraulic fluid pump

13 hydraulic fluid line

14 hydraulic cylinders

15 pass gap

16 compression spring / return spring

17 valve seat

18 opening seat section

19 conveying path / bypass line

20 check valve

21 room / hand switch

22 seating area

23 cylinder section

24 flange area

25 throttle area

26 passage opening

27 shaft

28 inlet bore

29 extension

30 Continuation

31 baffle

32 Wall of the storage room 9

33 compensation part

34 bore / seat part

35 bore section / line section

36 housing wall

Claims

1. Hydraulic pressing device (1) with a fixed part (2) and a moving part (3), wherein the moving part by a hydraulic piston (4) relative to the fixed part (2) is moved and by means of a return spring

(5) can be moved back into a starting position, wherein further the return movement in response to a predetermined pressing pressure can be triggered by response of a return valve (6), wherein in addition a control valve (7) is provided which in addition to the return valve (6 ) in the opening state releases a hydraulic fluid outflow (8) and has a hydraulic fluid inflow and outflow side, characterized in that the control valve (7) acts upon opening of the return valve (6) by the pressure of the returning hydraulic fluid on the inflow and outflow side is, wherein the pressure on the upstream side due to throttling is lower.

2. Hydraulic pressing device according to claim 1 with a fixed part (2) and a moving part (3), wherein the moving part by a hydraulic piston (4) relative to the fixed part (2) is moved and by means of a return spring (5) is moved back into an initial position , wherein further the return movement in response to a predetermined pressing pressure can be triggered by responding a return valve (6), wherein in addition a control valve (7) is provided which releases in addition to the return valve (6) in the open state a hydraulic fluid drain (8) and a hydraulic fluid inflow and outflow side, further comprising a hydraulic fluid pump (12), from which pump a hydraulic fluid flow path leads to the control valve, characterized in that a hydraulic fluid flow path directly from the hydraulic fluid pump Return valve (6) leads.

3. Press according to one of the preceding claims or in particular according thereto, characterized in that the control valve (7) is designed as a seat valve.

4. Press device according to one or more of the preceding claims or in particular according thereto, characterized in that the control valve (7) is arranged in a leading to a hydraulic piston (4) receiving the hydraulic cylinder (14) leading supply line.

5. Press device according to one or more of the preceding claims or in particular according thereto, characterized in that the closed control valve is acted upon by a differential force formed by the pressure in the hydraulic medium supply chamber and the hydraulic medium supply line.

6. Press device according to one or more of the preceding claims or in particular according thereto, characterized in that the leading from the pump to the cylinder hydraulic fluid supply line both has a direct connection to the return valve as to the control valve.

7. Press device according to one or more of the preceding claims or in particular according thereto, characterized in that via the return valve draining hydraulic fluid first flows through the control valve.

8. Press device according to one or more of the preceding claims or in particular according thereto, characterized in that a force acting on the control valve biasing force in the open position less is as it corresponds to a force acting on the control valve by a spring loading of the return piston force.

9. Press device according to one or more of the preceding claims or in particular according thereto, characterized in that the control valve in the open position blocks a hydraulic reflux to the return valve.

10. Press device according to one or more of the preceding claims or in particular according thereto, characterized in that the control valve has a closure body which passes through a movement of the valve closure body mitvollziehendes compensation part.