EP2420681B1 - Hydraulic linear drive device - Google Patents

Description

The invention relates to a hydraulic linear drive according to the preamble of patent claim 1.

Such hydraulic linear drives can be used, for example, to actuate a press ram of a press, a pressing tool being closed via the linear drive, for example in rapid traverse, and the actual pressing process then being carried out with a comparatively large force in a so-called “power stroke”. After the pressing process, the press ram is then quickly moved back to its basic position in the opposite direction. Of course, such linear drives can also be used in other applications, for example punching, machine tools, in production lines, etc.

In the US 5,522,212 a linear drive is shown, in which the feed movement is controlled by a hydraulic cylinder with three pressure chambers. In the known solution, these pressure chambers are designed with different active surfaces, a pressure being applied to a first active surface via a variable displacement pump for the rapid traverse which is carried out with comparatively little force. An effective area in the same direction of a third pressure chamber is pressurized by a hydraulic accumulator, while an effective area in the opposite direction of a second pressure chamber is relieved towards a tank. The pressure medium connection to the variable displacement pump, to the hydraulic accumulator and to the tank is controlled via a valve arrangement, the active surfaces of the first and third pressure chambers then being acted upon by the pump pressure for the power stroke and tank pressure acting on the active surface in the opposite direction of the second pressure chamber, the connection to Is hydraulic accumulator then cordoned off. In the known solution, a separate charge pump is assigned in the hydraulic accumulator, so that it is always charged to a predetermined level.

Such a solution requires a very large expenditure on device technology, since, on the one hand, a complex variable pump is required to control the movements of the hydraulic cylinder and, on the other hand, a further pump must be provided to charge the hydraulic accumulator.

In the DE 10 2008 039 011 A1 discloses a similar linear drive with a hydraulic cylinder designed with three active surfaces, the pressure chambers of which are pressurized for adjustment by means of two parallel variable-speed pumps and a valve arrangement. The control of the two pumps is very complex both in terms of control and in terms of investment costs.

The document shows a generic linear drive NL8105929 , There, a cylinder is controlled in rapid traverse and power stroke with a non-variable-speed pump and two 4/3-way valves.

In contrast, the object of the invention is to create a hydraulic linear drive which has a comparatively simple structure and enables control which is also optimized in terms of energy.

This object is achieved by a hydraulic linear drive with the features of claim 1.

Advantageous developments of the invention are the subject of the dependent claims.

According to the invention, the hydraulic linear drive has a hydraulic cylinder, which is designed with three pressure spaces, each delimited by an effective area, which can be acted upon by a hydraulic machine, preferably a pump and a valve arrangement with high pressure (pump) or a low pressure source, for example with tank pressure, around the hydraulic cylinder To move in rapid traverse or in a power stroke in one direction and in rapid traverse or in power stroke in the other direction. According to the invention, the hydraulic motor is designed with a variable-speed drive, the area ratios of the active surfaces being coordinated such that the drive operates in approximately the same speed range in rapid traverse and in the power stroke.

This design of the area ratios and the drive makes it possible to drive the latter in the optimum torque and speed range and thus with minimal drive power, so that the energy expenditure and the investment outlay are significantly reduced compared to the solutions mentioned at the outset, since a smaller drive motor is used can be. Essentially regardless of whether the hydraulic cylinder is operated with a comparatively high speed and low force (rapid traverse) or with a comparatively low speed and high force (power stroke), the drive always works in its optimal torque / speed range, so that effective control of the Linear drive with minimized drive power is possible. Another advantage is that due to the constant, comparatively low speed of the drive, the sound development of the linear drive is minimal in both working points (rapid traverse, power stroke).

The hydraulic machine can be designed with a constant delivery / displacement volume. In principle, however, hydraulic machines designed for four-quadrant operation are also applicable, in which a reversal of the direction of rotation is possible.

According to the invention, the valve arrangement has a directional control valve which, in a first position, connects a pressure connection of the hydraulic machine via a working line to a first pressure chamber and a second pressure chamber via a further working line to the low-pressure source, for example the tank. In a further, second position, the directional valve shuts off a connection between the second pressure chamber and the low-pressure source.

According to the invention, a control valve is arranged downstream of the directional control valve and, in one position, connects the first pressure chamber to the second pressure chamber, which acts in the opposite direction.

According to the invention, a pressure medium connection of the third pressure chamber to the hydraulic machine is blocked in one position of the control valve.

According to the invention, the third pressure chamber is connected to the low pressure source / tank via a suction line with a check valve opening in the direction of the third pressure chamber.

In one embodiment of the invention, a storage valve is assigned to the low-pressure source, which connects the low-pressure source with a suction side of the hydraulic machine in one position and, in another position, the first-mentioned working line in the area between the directional control valve and the control valve with the low-pressure source.

The first pressure chamber is preferably designed with a larger effective area than the second pressure chamber effective in the opposite direction.

It can be advantageous if the second effective area is again designed to be somewhat smaller than the third effective area.

As already mentioned, it can be advantageous to design the hydraulic machine with reversing the direction of rotation, so that four-quadrant operation is possible.

The hydraulic linear drive can be designed particularly advantageously as a press drive or as the closing axis of an injection molding machine. In principle, the concept according to the invention can be used wherever force and speed are required at different times.

In a variant of the invention, the hydraulic cylinder is designed with a piston with a hollow piston rod into which a rod of the hydraulic cylinder is immersed, so that the first pressure chamber, which is supplied with pressure medium through the rod, is delimited by this and an inner end face of the hollow piston rod.

In such an exemplary embodiment, it is preferred if an annular end face of the piston on the piston rod side delimits the second pressure space and a portion of the annular end surface facing away from the rod delimits the third pressure space.

• Figur 1 ein Schaltschema eines Ausführungsbeispiels eines hydraulischen Linerantriebs für eine Presse;
• Figur 2 eine Einzeldarstellung eines Hydraulikzylinders des Linearantriebs aus Figur 1;
• Figur 3 den Linearantrieb gemäß Figur 1 im Krafthub;
• Figur 4 den Linearantrieb gemäß Figur 1 bei einer Rückbewegung im Eilgang;
• Figur 5 ein gegenüber dem Ausführungsbeispiel gemäß Figur 1 vereinfachtes Ausführungsbeispiel eines Linearantriebs im Eilgang und
• Figur 6 den Linearantrieb gemäß Figur 5 im Krafthub

Preferred exemplary embodiments of the invention are explained in more detail below with the aid of schematic drawings. Show it:

• Figure 1 a circuit diagram of an embodiment of a hydraulic liner drive for a press;
• Figure 2 an individual representation of a hydraulic cylinder of the linear drive Figure 1 ;
• Figure 3 the linear drive according to Figure 1 in the power stroke;
• Figure 4 the linear drive according to Figure 1 when moving back in rapid traverse;
• Figure 5 a compared to the embodiment Figure 1 simplified embodiment of a linear drive in rapid traverse and
• Figure 6 the linear drive according to Figure 5 in the power stroke

The in Figure 1 The linear drive shown can be used, for example, in punching or forming technology, for example in servo presses, pipe and wire bending machines, press brakes, punching and nibbling machines, punching and forming machines, suction transfer or compact suction presses, tire presses, tire building machines, vulcanizing presses, drawing presses, transfer and step presses, Extrusion presses, bending centers, forging presses, scrap presses, injection molding machines, blow molding machines or powder metal presses can be used.

The linear drive 1 has a hydraulic cylinder 2 which, as will be explained in more detail below, is designed with three pressure chambers 4, 6, 8. The pressure medium is supplied via a hydraulic machine 10, preferably a constant pump, which is driven by a variable-speed motor 12. A suction connection of the pump is connected via a low pressure line 14 to a low pressure source 16, for example a hydraulic accumulator or a tank. A pressure connection of the hydraulic machine 10 is connected to a pressure line 18, which leads to the single-port connection of a directional valve 20. In the illustrated embodiment, this is designed as a 4/2-way switching valve, wherein in a basic position (a) shown, the pressure line 18 is connected to a supply line 22, which in turn leads to the input port of a control valve 24, which is also a 4/2-way Switch valve is executed.

In the illustrated basic position (a) of the control valve 24, this connects the supply line 22 to a working line 26, via which the first pressure chamber 4 is supplied with pressure medium. In this switching position, a further connection of the control valve 24 is connected via a regeneration line 28 to a further working line 30, which is connected on the one hand to an outlet connection of the directional valve 20 and on the other hand to the second pressure chamber 6. In position (a) of control valve 24, regeneration line 28 is connected to working line 26 and in position (b) is blocked off from first pressure chamber 4. In the basic position (a) of the directional control valve 20, the connection of the return line to the other working line 30 is blocked. The directional control valve 20 has a return connection, which is connected to the low pressure line 14 via a return line 32. In the switching position (a) of the directional control valve 20, the pressure medium connection between this return line 32 and the further working line 30 is interrupted. This pressure medium connection is opened by switching to the position marked with (b).

According to Figure 1 the third pressure chamber 8 is connected to a further output connection of the control valve 24 via a third working line 34, which is only shown for the purposes of the drawing. This working line 34 can also be combined with the suction line 36, which will be explained below. In the switching position (a) of the control valve 24, this third working line 34 to the supply line 22, the regeneration line 28 and the working line 26 is shut off. By switching the control valve 24 into position (b), the third working line 34 is connected to the working line 26 and the supply line 22.

According to Figure 1 the third pressure chamber 8 is additionally connected to the low pressure line 14 via a suction line 36 with a check valve 38 which is open towards the third pressure chamber 8.

This is connected to an output connection of a storage valve 40, which is designed as a 3/2-way switching valve in the exemplary embodiment. In its basic position (a) shown, the low-pressure source 16 is connected to the low-pressure line 14. By switching over the storage valve 40, the low-pressure source 16 is connected to a line 42 leading into the supply line 22 and the connection to the low-pressure line 14 is blocked. The line 42 is shut off in the position (a) of the storage valve 40 to the low pressure source 16.

Details of the hydraulic cylinder 2 are based on Figure 2 explained. Accordingly, the hydraulic cylinder 2 is designed with a piston 44 which has a hollow piston rod 46 into which a rod 50 supported on the cylinder base 48 dips so that an inner end face 52 of the hollow piston rod 46 and the end face of the rod 50 delimit the first pressure chamber 4. Its pressure supply takes place via a channel 54 which extends through the rod 50 and is connected to the working line 26. A piston rod-side ring end face 56 of the piston 54 delimits in the axial direction the second pressure chamber 6, through which the hollow piston rod 46 passes, and another rod-side ring end surface 58 delimits the third pressure chamber 8, through which the rod 50 passes. The active surfaces of these pressure chambers are shown in Figure 2 marked with the designations A1, A2, A3. The pressure chamber 6 is as based on Figure 1 explained, connected to the further working line 30 and the pressure chamber 8 to the third working line 34 and 36. According to the representation Figure 2 the pressure medium volume flows Q ₁ , Q ₂ , Q ₃ to the pressure chambers 4, 6 and 8 are also shown, which can be set by suitable control of the hydraulic machine 10.

In order to set a rapid extension movement of the hollow piston rod 46 at high speed or high acceleration, the hydraulic machine is to promote a volume flow Q _P with a predetermined pressure, which is to act on a comparatively small area of the hydraulic cylinder 2 which is effective in the extension direction, so that it has a comparatively low volume flow - and the associated low drive power - a high extension speed of the hydraulic cylinder 2 can be effected.

To set the rapid traverse, the directional valve 20 and the control valve 24 are brought into their positions marked with (a). The storage valve 40 is also switched to position (a), so that pressure medium is drawn in from the low pressure source 16 via the hydraulic machine 10 and is conveyed into the first pressure chamber 4 via the supply line 22, the working line 26 and the channel 54. In the position (a) of the control valve 24, the regeneration line 28 is connected to the working line 26, so that the two pressure chambers 4, 6 are also connected to one another. The third pressure chamber 8 is in rapid traverse via the suction line 36 and the check valve 48 opening towards the pressure chamber 8 with the Low pressure line 14 and thus connected to the low pressure source 16. A pressure medium volume flow is supplied to the pressure chamber 4 with the active area A ₁ via the hydraulic machine 10, so that the hollow piston rod 46 extends in the direction of the arrow. The pressure medium is pushed out of the shrinking second pressure chamber 6 and added via the regeneration line 28 to the pressure medium volume flow Q _P conveyed by the hydraulic machine 10. When the hollow piston rod 46 extends in rapid traverse, the third pressure chamber 8 increases, so that pressure medium is sucked in from the low-pressure source 16 via the check valve 48. The hollow piston rod 46 thus extends at a comparatively high speed with a relatively low pressure medium volume flow. In the exemplary embodiment shown, the effective area A _{1 of} the first pressure chamber 4 is made somewhat larger than the effective area A _{2 of} the second pressure chamber, so that only a small pressure medium volume flow Q _p to the pendulum volume flow (quantity ejected from the second pressure chamber 6. needs to be added. Accordingly, the pressure medium volume flow Q _{p to be delivered} by the hydraulic machine 10 is calculated from the formula $${\mathrm{Q}}_{\mathrm{P}.\mathrm{EIL}}={\mathrm{Q}}_1-{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_2$$

$$\mathrm{V}\cdot {\mathrm{n}}_{\mathrm{EIL}}={\mathrm{x}}_{\mathrm{EIL}}\left({\mathrm{A}}_1-{\mathrm{A}}_2\right)$$

berechnet.The volume flows Q ₁ , Q _{2 are} calculated from the product of the extension speed x with the respective effective area A ₁ , A ₂ . The delivery volume flow Q _{p of} the hydraulic machine can be calculated from the product of the speed n of the drive 12 with the delivery / displacement volume V of the _{hydraulic machine} 10, so that the pressure medium _{volume flow} Q _{p, EIL changes rapidly} according to the equations: $${\mathrm{Q}}_{\mathrm{p}\mathrm{,\; EIL}}=\mathrm{x}\left({\mathrm{A}}_1-{\mathrm{A}}_2\right)$$

$$\mathrm{V}\cdot {\mathrm{n}}_{\mathrm{EIL}}={\mathrm{x}}_{\mathrm{EIL}}\left({\mathrm{A}}_1-{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">A</figure-callout>}}_2\right)$$

calculated.

For the power stroke, the hollow piston rod 46 is extended at a comparatively low speed and great force. For this, the hydraulic machine 10 must be in accordance with Figure 3 Promote a pressure medium volume Q _{p force} to the largest possible effective area in order to generate the desired large force. For this purpose, according to Figure 3 the control valve 24 and the control valve 20 switched into their switching positions (b). The storage valve 40 remains in position (a). Accordingly, the first pressure chamber 4 with a comparatively large effective area A _{1 is} supplied with pressure medium. The effective area A _{3 of} the third pressure chamber 8 acting in the same direction is also acted upon by the pressure of the hydraulic machine 10. The effective area A _{2 of} the second pressure chamber 6 acting in the opposite direction is connected via the further working line 30, the directional control valve 20 and the return line 32 to the low-pressure line 14 and thus to the suction side of the hydraulic machine 10 - the hollow piston rod 46 is subjected to great force at low speed x extended. The required pressure medium volume flow Q _{p, force} according to the equation, is then obtained in accordance with the calculation equations explained above $${\mathrm{Q}}_{\mathrm{p}.\mathrm{force}}={\mathrm{<figure-callout\; id="3"\; label="x\; force\; A"\; filenames="imgf0002.png"\; state="\{\{state\}\}">x\; </figure-callout>}}_{\mathrm{force}}\left({\mathrm{A}}_{}\right)\left({\mathrm{}}_3+{\mathrm{A}}_1\right)$$

Assuming that the speeds n in rapid traverse and power stroke should be approximately the same, the factor K of the area ratios must correspond to the reciprocal value of the speed ratio: $$\frac{n_{\mathit{eil}}}{n_{\mathit{force}}}=\mathrm{K}\cdot \frac{x_{\mathit{Eil}}}{{\dot{x}}_{\mathit{force}}}=\frac{Q_{p.\mathit{Eil}}}{Q_{p.\mathit{force}}}$$

For a quick return (rapid traverse), according to the representation in Figure 4 the direction of rotation of the motor 12 reversed. The directional control valve 20 and the control valve 24 each remain in their switching position (b), so that the hydraulic machine 10 conveys the pressure medium volume flow Q _{p, Eil} into the second pressure chamber 6 acting in the retracting direction. The two acting in the opposite direction Pressure chambers 4, 8 are connected to the low pressure source 16 via the directional valve 20 and the control valve 24 as well as the storage valve 40 switched to its switching position (b), so that the pressure medium from these pressure chambers 4, 8 to the low pressure source 16 or to the suction side of the hydraulic machine 10 can flow out - the hydraulic cylinder 2 is retracted at high speed and low force.

According to the above explanations, the active surfaces A ₁ , A ₂ , A _{3 are} designed and interconnectable in such a way that the motor 12 operates at approximately the same speed or with approximately the same torque, both in the power stroke and in the rapid traverse (back and forth), the desired traversing speed x or force (px A) is then achieved by suitable interconnection.

Based on Figures 5 and 6 a second variant, which is simplified compared to the previously described exemplary embodiment, is explained. The only essential difference is in principle that in the Figures 5 and 6 illustrated embodiment is dispensed with the storage valve 40 and the line 42, so that the low pressure line 14 opens directly into the low pressure source 16. Figure 5 shows the linear drive during the power stroke - exactly as in the exemplary embodiment described above, the directional valve 20 and the control valve 24 are adjusted to their switching positions (a), so that the active surfaces A ₁ , A ₃ are acted upon by the pressure at the outlet of the hydraulic machine 10. The second pressure chamber 6 is connected to the low pressure source 16 via the further working line 30, the directional control valve 20, the return line 32 and the low pressure line 14, so that the pressure medium can be pushed out of the third pressure chamber 6.

For the movement of the hollow piston rod 46 in rapid traverse, the directional valve 20 and the control valve 24 are in accordance with Figure 6 adjusted to their positions (b). The first pressure chamber 4 and the second pressure chamber 6 are connected to one another, so that the pressure medium ejected from the latter via the Regeneration line 28 is summed to the pressure medium volume flow flowing to the first pressure chamber 4. During this rapid traverse, pressure medium is sucked in via the suction line 36 and the check valve 38 from the low pressure source into the increasing third pressure chamber 8.

To retract the hollow piston rod 46 in rapid traverse, the directional valve 20 and the control valve 24 are adjusted into their positions (a) (not shown) and the direction of rotation of the hydraulic machine 10 is reversed (see Figure 4 ), so that the two pressure chambers 4, 8 are connected to the suction side of the hydraulic machine 10 and the hydraulic machine 10 conveys pressure medium into the second pressure chamber 6. The pressure medium that was previously removed is then fed to the low-pressure accumulator 16.

Otherwise, this corresponds to the Figures 5 and 6 The exemplary embodiment shown is the exemplary embodiment described at the outset, so that further explanations are unnecessary.

Disclosed is a hydraulic linear drive with a hydraulic cylinder designed with three pressure chambers, the effective surfaces of which are coordinated with one another in such a way that in a rapid traverse and in a power stroke, a drive of a hydraulic machine supplying the hydraulic cylinder with pressure medium operates in approximately the same speed / torque range.

LIST OF REFERENCE NUMBERS

1

linear actuator

2

hydraulic cylinders

4

pressure chamber

6

pressure chamber

8th

pressure chamber

10

hydromachine

12

engine

14

Low-pressure line

16

Low pressure source

18

pressure line

20

way valve

22

supply line

24

control valve

26

working line

28

regeneration line

30

further work management

32

Return line

34

third management

36

suction

38

check valve

40

memory valve

42

management

44

piston

46

Piston rod pipe

48

cylinder base

50

pole

52

Inside face

54

channel

Claims (10)

1. Hydraulic linear drive having a hydraulic cylinder (2) which has three pressure spaces (4, 6, 8) which are delimited by in each case one active face (A₁, A₂, A₃) and can be loaded with high pressure or low pressure via a hydraulic machine (10) and a valve arrangement of the linear drive, in order to move the hydraulic cylinder (2) in a rapid motion or in a power stroke in one direction or in a rapid motion or in a power stroke in the other direction, the valve arrangement having a directional valve (20) which, in a first position (b), connects a pressure connector of the hydraulic machine (10) via a working line (26) to a first one (4) of the pressure spaces (4, 6, 8) and connects a second one (6) of the pressure spaces (4, 6, 8) via a further working line (30) to a low pressure source (16), and, in a second position (a), shuts off the connection of the second pressure space (6) to the low pressure source (16), a control valve (24) being arranged downstream of the directional valve (20) in the pressure build-up direction, which control valve (20), in one position (a), connects the first pressure space (4) to the second pressure space (6) which is active in the opposite direction, and, in the other position (b), connects the first pressure space to the third pressure space (8), and a pressure medium connection of the third pressure space (8) to the hydraulic machine (10) being shut off in the one position (a) of the control valve (24), characterized in that the hydraulic machine (10) has a variable-speed drive (12), and in that the area ratios of the active faces (A₁, A₂, A₃) are adapted in such a way that the drive (12) operates in the same rotational speed range in the rapid motion and in the power stroke, and in that the third pressure space (8) is connected to the low pressure source (16) via a suction line (36) and a check valve (38) which opens in the direction of the third pressure space (8).
2. Hydraulic linear drive having a hydraulic cylinder (2) which has three pressure spaces (4, 6, 8) which are delimited by in each case one active face (A₁, A₂, A₃) and can be loaded with high pressure or low pressure via a hydraulic machine (10) and a valve arrangement of the linear drive, in order to move the hydraulic cylinder (2) in a rapid motion or in a power stroke in one direction or in a rapid motion or in a power stroke in the other direction, the valve arrangement having a directional valve (20) which, in a first position (b), connects a pressure connector of the hydraulic machine (10) via a working line (26) to a first one (4) of the pressure spaces (4, 6, 8) and connects a second one (6) of the pressure spaces (4, 6, 8) via a further working line (30) to a low pressure source (16), and, in a second position (a), shuts off the connection of the second pressure space (6) to the low pressure source (16), a control valve (24) being arranged downstream of the directional valve (20) in the pressure build-up direction, which control valve (20), in one position (a), connects the first pressure space (4) to the second pressure space (6) which is active in the opposite direction, and, in the other position (b), connects the first pressure space to the third pressure space (8), and a pressure medium connection of the third pressure space (8) to the hydraulic machine (10) being shut off in the one position (a) of the control valve (24), characterized in that the hydraulic machine (10) has a variable-speed drive (12), and in that the area ratios of the active faces (A₁, A₂, A₃) are adapted in such a way that the drive (12) operates in the same rotational speed range in the rapid motion and in the power stroke, and in that the third pressure space (8) is connected to a low pressure side of the hydraulic machine (10) via a suction line (36) and a check valve (38) which opens in the direction of the third pressure space (8), and in that an accumulator valve (40) of the linear drive is provided, which accumulator valve (40), in one position (a), connects the low pressure source (16) to the low pressure side of the hydraulic machine (10), and, in the other position (b), connects the low pressure source (16) to a supply line (22) between the directional valve (20) and the control valve (24).
3. Linear drive according to Patent Claim 1 or 2, the hydraulic machine (10) being a machine with a constant delivery volume/displacement.
4. Linear drive according to Claim 1 or Claim 3 in combination with Claim 1, having an accumulator valve (40) which, in one position (a), connects the low pressure source (16) to a low pressure side of the hydraulic machine (10) and, in the other position (b), connects the low pressure source (16) to a supply line (22) between the directional valve (20) and the control valve (24).
5. Linear drive according to one of the preceding patent claims, the first pressure space (4) having a greater active face (A₁) than the second pressure space (6) which is active in the opposite direction.
6. Linear drive according to Patent Claim 5, the active face (A₂) of the second pressure space (6) being somewhat smaller than the active face (A₃) of the third pressure space (8).
7. Linear drive according to one of the preceding patent claims, the variable-speed drive being configured in the form of a motor (12) or the hydraulic machine (10) being configured with rotational direction reversal.
8. Linear drive according to one of the preceding patent claims, it being possible for the said linear drive to be used as a drive of a forming machine or an injection moulding/blow moulding machine.
9. Linear drive according to one of the preceding patent claims, the hydraulic cylinder (2) having a piston (44) with a hollow piston rod (46), into which a rod (50) of the hydraulic cylinder (2) dips, with the result that the first pressure space (4) which is supplied with pressure medium through the rod (50) is delimited axially by way of an inner end face (52) of the hollow piston rod (46) and the end face of the rod (50).
10. Linear drive according to Patent Claim 9, a piston rod-side annular end face (A₂) of the piston (44) delimiting the second pressure space (6) in the axial direction, and a rod-side annular end face (A₃) of the piston (44), which annular end face (A₃) faces away from the said piston rod-side annular end face (A₂), delimiting the third pressure space (8) in the axial direction.

Images