Device for holding and / or moving a rod-shaped body

Abstract

A device (1) for holding and / or moving a rod-shaped body (2) is proposed, comprising: a fully enclosed housing (3) with a longitudinal axis (L) along which the rod-shaped body (2) is guided or is to be guided; a thrust piston (4) surrounding the rod-shaped body (2), which can be subjected to a first pressure from the outside via a first pressure port (L) through the housing (3) and which can be subjected to a second pressure from the outside via a second pressure port (K) through the housing (3), and which has a first effective surface (5) and a second effective surface (6), which effective surfaces (5, 6) preferably extend in a radial direction, wherein the first effective surface (5) is in fluidic operative connection with the first pressure port (L) and the second effective surface (6) is in fluidic operative connection with the second pressure port (K), wherein the thrust piston (4) has a radially internal recess (7) through which a circumferential free space (8) is formed between the rod-shaped body (2) and an inner surface (9) of the thrust piston (4), which free space (8) has an axial limit (10, 11) on both sides; and at least one clamping sleeve (12) which, with its inner surface (13), defines a central cylindrical area through which the rod-shaped body (2) is guided or can be guided, and which is received in the aforementioned free space (8), extending axially between the two axial limits (10, 11), wherein the clamping sleeve (12) can be subjected to a third pressure from the outside via a third pressure port (V) through the force-pull piston (4) and is designed to deform itself reversibly radially inwards according to the third pressure and to exert a holding force on the rod-shaped body (2).

Description

[0001] The invention relates to a device for holding and / or moving a rod-shaped body with a fully enclosed housing and a longitudinal axis along which the rod-shaped body is guided or to be guided.

[0002] The rod-shaped body will in the following be referred to simply as a rod for the sake of simplicity and as a synonym, which does not imply any limitation of the subject matter of the claim.

[0003] Such and similar devices are known, for example from DE 10 2022 100 222, DE 101 04 652 A1, EP 2 226 513 A2, WO 2010 / 109374 A1, WO 00 / 67987 A1 or EP 3 253 550 B1. They can be used preferably for braking or holding loads or for closing tools, such as presses or molds. The device in question here is therefore also referred to in practice as a mold closing head.

[0004] The predominant operating principle is the use of externally conical clamping cages or clamping jaws that interact with a complementary inner conical shape of the housing or additional sliding wedges arranged in the housing, so that in one direction, with appropriate pressure applied, preferably with a hydraulic fluid, a self-reinforcing clamping effect can be achieved on a rod-shaped body that is guided or to be guided along a longitudinal axis of the device.

[0005] Self-reinforcing mold clamping heads (FSK) present challenges in the manufacturing and procurement of individual components for larger bar diameters starting at approximately 160 mm. In particular, the necessary heat treatment causes distortion of the clamping jaws, which is costly to correct. Assembly is also very complex, due in part to the spring elements used in current technology and the required pressing in of sliding linings. This elaborate design also makes comprehensive maintenance at the FSK's point of use (e.g., press, testing device, or injection molding machine) virtually impossible. The mold clamping head, as designed according to current technology, must be regularly sent back to the manufacturer for servicing.

[0006] Large FSK units have therefore failed so far primarily due to an excessively short service life caused by movements of the aforementioned clamping jaws or wedges on the sliding surface, the implementation of an on-site service concept (due to the given probability of failure in operation), and the procurement of individual parts or their scalability to large forces / rods.

[0007] Specifically, the current state of the art does not readily permit the production of larger units, as the aforementioned distortion of the individual parts is difficult to control, thus limiting the achievable size. The service life of the aforementioned wedge / cone systems is relatively short because the sliding lining necessary for the relative movement makes them susceptible to dirt and wear. Due to the relatively complex design, on-site service / maintenance is only possible to a limited extent. By design, a force thrust (due to the wedge shape and self-reinforcing mechanism) is only possible in one direction, whereas a previously known device opens automatically in the release direction (and in the end position). The retraction of the clamping wedges creates the aforementioned relative movement between the forming head and the rod, which is necessary for clamping. This means that clamping is only possible in a so-called "retracted" state and not at every position along the rod.

[0008] The invention aims to remedy this problem and provide a device of the aforementioned type that has an increased service life, can be serviced on-site, and is also suitable for larger rods, particularly those with a diameter of 160 mm or more, or correspondingly high holding forces. Furthermore, it should allow for force to be applied in both directions along the rod and clamping at virtually any point along the rod.

[0009] This problem is solved by a device with the features of claim 1. Advantageous embodiments of the device according to the invention are defined in the dependent claims. In particular, the invention includes the use of one or more hydraulically and elastically deformable clamping sleeves instead of the aforementioned conical clamping elements.

[0010] A device according to the invention for holding and / or moving a rod-shaped body comprises: a fully enclosed housing with a longitudinal axis along which the rod-shaped body is guided or to be guided;a force-pull piston surrounding the rod-shaped body, which can be subjected to a first pressure from the outside via a first pressure port through the housing and which can be subjected to a second pressure from the outside via a second pressure port through the housing, and which has a first effective surface and a second effective surface, which effective surfaces preferably extend in a radial direction, wherein the first effective surface is in fluidic operative connection with the first pressure port and the second effective surface is in fluidic operative connection with the second pressure port, wherein the force-pull piston has a radially internal recess through which a circumferential free space is formed between the rod-shaped body and an inner surface of the force-pull piston, which free space has an axial limit on both sides;and at least one clamping sleeve, the inner surface of which defines a central cylindrical area through which the rod-shaped body is guided or can be guided, and which is received in the aforementioned free space, extending axially between the two axial limits, the clamping sleeve being subjected to a third pressure from the outside via a third pressure port through the force-pull piston and being designed to deform reversibly radially inwards according to the third pressure and to exert a holding force on the rod-shaped body.

[0011] By using (at least one) clamping sleeve instead of conical clamping systems, a longer service life is achieved due to the elimination of relative movement and a correspondingly reduced abrasion / wear. This also makes it possible to use larger rod diameters without any problems. Because no insertion movement is required, the rod, which is not itself part of the device, can be clamped at virtually any point. Furthermore, a force thrust in both directions along the rod is possible. Last but not least, ease of maintenance is also improved, as will be shown in detail below – especially because the clamping sleeve, unlike the previously used clamping jaws, is designed as a single, manageable unit that remains in the device even after (partial) removal of the rod, whereas the clamping jaws, as separate components, regularly fall out of the device after the rod is removed.

[0012] The following further developments of the device according to the invention have proven to be particularly advantageous in practice: In a further development of the device according to the invention, several clamping sleeves are axially arranged one behind the other in the aforementioned free space and, together with their inner surfaces, define the central cylindrical area.

[0013] In this way, the holding force can be optimally adapted to the given requirements through a modular design.

[0014] In a further development of the device according to the invention, the several clamping sleeves can be pressurized separately.

[0015] This allows the holding force to be flexibly adjusted and controlled.

[0016] In another embodiment of the device according to the invention, the several clamping sleeves can be subjected to pressure together.

[0017] This simplifies the design of the device accordingly.

[0018] In yet another embodiment of the device according to the invention, a first, removable housing cover is provided, which closes the device or the free space at a first end face of the device. After removing the first housing cover in the axial direction, the clamping sleeve(s) can be removed from the aforementioned free space through an opening that opens in the end face, particularly for maintenance purposes.

[0019] This allows maintenance of the clamping sleeve(s) even with the device installed, for example for wear inspection or for replacing corresponding seals.

[0020] In a further development of the device according to the invention, the first housing cover also serves as one of the aforementioned axial limits for the free space that accommodates the clamping sleeve(s), thus enabling a force thrust on the clamped rod (by axially acting on the clamping sleeve(s).

[0021] Preferably, the first housing cover is also sealed inwards against the rod-shaped body, so that a (fluid-)tight seal of the device is created.

[0022] In a further development of the device according to the invention, the housing comprises a circumferential, radially inwardly extending first projection, which is preferably arranged on a side facing the first housing cover. A first pressure chamber is formed between the first projection and the aforementioned first effective surface of the power-push piston. The projection preferably serves as a stop for the power-push piston.

[0023] In this way, the housing ensures a structural cohesion of the device in the axial direction and preferably limits a corresponding stroke movement of the power push piston by means of the projection.

[0024] In another embodiment of the device according to the invention, the first pressure chamber is sealed externally at the force-pull piston against the housing. For this purpose, two circumferential seals can be provided internally on the housing, which are axially spaced apart from each other.

[0025] In a further development of the device according to the invention, one of the aforementioned axial limits, or the other axial limit, is formed integrally with the power thrust piston. In particular, it can be designed as a radially inwardly projecting second projection on the power thrust piston, which preferably extends to the rod-shaped body.

[0026] This results in a particularly stable and compact design of the device.

[0027] In a further development of the device according to the invention, a second housing cover is provided, which closes the housing at a second end face of the device.

[0028] The second housing cover closes off the device to the outside and can advantageously be used - together with the housing - as a fixed element for attaching stationary system components or for fixing the device itself.

[0029] In a further development of the device according to the invention, a second pressure chamber is formed between the second housing cover and the second working surface. This is preferably sealed against the housing and the second housing cover.

[0030] In this way, preferably no hydraulic fluid used in the first and / or second pressure chamber for pressurization reaches the rod, which, among other things, facilitates maintenance.

[0031] In a further development of the device according to the invention, the second housing cover has an axial projection that radially overlaps the thrust piston in the axial direction on the inside. The aforementioned second pressure chamber is sealed against the second housing cover in the overlap area (i.e., in the area of ​​the aforementioned axial projection). Advantageously, one of the seals provided for sealing the first pressure chamber can be used on the outside for this purpose.

[0032] This further emphasizes the aforementioned aspect of improved maintainability. In addition, the axial projection can serve as a stop for the power thrust piston, in the opposite direction to the first projection provided on the housing.

[0033] In yet another embodiment of the device according to the invention, the housing is detachably connected to the second housing cover. The connection is preferably made by means of a number of screw bolts extending axially and accessible from the side of the first housing cover. The housing can also be removed axially from the second housing cover (particularly after loosening the screw bolts). Preferably, after loosening the connection between the housing and the second housing cover, the force-pull piston can then be removed axially, most preferably after prior removal of the housing.

[0034] This greatly improves the ease of maintenance of the device, because practically all components, with the possible exception of the second housing cover, can be removed axially with the rod still mounted, in order to replace existing seals or similar wear parts.

[0035] In a further development of the device according to the invention, the effective surface and pressure ratios or corresponding dimensions are selected or selectable such that, with the rod-shaped body held by the clamping sleeve(s), the force-pull piston, together with the rod-shaped body, is axially movable relative to the housing in one direction when pressure is applied at the second pressure port. Furthermore, it is achieved that, when pressure is applied at the first pressure port, the force-pull piston, together with the rod-shaped body, is axially movable relative to the housing in the opposite direction.

[0036] In this way, the device can execute two opposing types of force thrusts, for example, to close a press and then reopen it. It is important that the holding force of the clamping sleeve(s) is greater than the thrust force along the rod to prevent the rod from slipping through the clamping sleeve(s).

[0037] In a further development of the device according to the invention, a clamping sleeve pressure chamber is defined in the area of ​​the clamping sleeve between the force-pull piston and a radial outer surface of the clamping sleeve. This clamping sleeve pressure chamber is preferably sealed against the force-pull piston by two axially limiting, circumferential seals.

[0038] By applying pressure to the pressure chamber of this clamping sleeve (via the third pressure port from the outside, through the power piston, with the third pressure), the clamping action of the clamping sleeve(s) can be activated. The seal described above ensures that no pressurized medium (e.g., hydraulic fluid or oil) reaches the rod. The seals are easily replaceable if necessary, as already mentioned.

[0039] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the drawing. Fig. Figure 1 shows a longitudinal section through a device according to the invention in two operating states.

[0040] In the Fig. Figure 1 shows a simplified longitudinal section of a device 1 according to the invention for holding and / or moving a rod-shaped body (i.e., in particular a rod) 2. The device 1 has a fully enclosed housing 3 with a longitudinal axis L along which the rod-shaped body 2 is guided or is to be guided. A first operating state of the device 1 is shown above the longitudinal axis L, and a second operating state below.

[0041] The rod 2 itself is not part of the device 1, but belongs to a machine or system (not shown further) in which a desired clamping or holding force is to be generated by means of the device 1 via the rod 2, e.g. an injection molding machine with a corresponding mold.

[0042] The device 1 further comprises a thrust piston 4 surrounding the rod-shaped body 2, which can be pressurized externally via a first pressure port L through the housing 3 and which can be pressurized externally via a second pressure port K through the housing 3. The corresponding pressure medium can, in particular, be a hydraulic fluid. The thrust piston 4 has a first working surface 5 and a second working surface 6, which working surfaces 5, 6 are oriented according to Fig. The first working surface 5 extends radially in the direction of the first pressure port L, and the second working surface 6 extends radially in the direction of the second pressure port K. The power thrust piston 4 has a radially internal recess 7, which defines a circumferential clearance 8 between the rod-shaped body 2 and an inner surface 9 of the power thrust piston 4. This clearance 8 has axial limits 10, 11 on both sides, formed on one side by a removable housing cover 10 (also referred to as the first housing cover) and on the other side by a circumferential radial projection 11 (also referred to as the second projection) on the power thrust piston 4. The aforementioned projection 11 is designed as a radially inwardly projecting projection that extends to the rod-shaped body 2 and is integrally formed with the power thrust piston 4.

[0043] Reference numeral 12 shows a clamping sleeve, of which two are fitted between the aforementioned axial limits 10 and 11. Other numbers of clamping sleeves 12 are possible in principle. The construction of the clamping sleeves 12 will be discussed in more detail below.

[0044] Each clamping sleeve 12 defines a central cylindrical area with its inner surface 13, through which the rod-shaped body 2 is guided. Both clamping sleeves 12 are arranged axially one behind the other and are received in the aforementioned free space 8. The clamping sleeves 12 can be jointly subjected to a third external pressure via a third pressure port V through the force-pull piston 4. They are designed to deform reversibly radially inwards as required by the third pressure and thereby exert a holding force on the rod-shaped body 2.

[0045] The clamping sleeves 12 are preferably formed from a bronze or brass sleeve 14 which has a series of axially extending incisions (which in the Fig. 1 is not recognizable). These incisions ensure improved deformability of the cuffs 14 radially inwards to clamp the rod 2 when the diaphragm 16 is pressurized.

[0046] The cuff 14 has a circumferential, radially outwardly projecting shoulder 15 at each end, between which a (plastic) membrane 16 is arranged, wherein a seal 17 is arranged between the membrane 16 and each of the shoulders 15, which seals a (clamping sleeve) pressure chamber 18 formed between the membrane 16 and the power thrust piston 4.

[0047] On a side of the device 1 furthest from the housing cover 10, a further housing cover 19 is provided, which is also referred to as the second housing cover. The housing cover 10 closes the device 1 and / or the free space 8 at a first end face of the device 1, and the further housing cover 19 closes the device 1 at a second end face. After removal of the housing cover 10 in the axial direction (in Fig. (1 to the right) the clamping sleeves 12 can be removed from the aforementioned free space through an opening on the front side in an axial direction, if necessary after first pushing the rod 2 back to the left and using a suitable tool.

[0048] It has already been pointed out that the housing cover 10 serves as one of the aforementioned axial limits for the clamping sleeves 12. It is sealed inwards against the rod-shaped body 2 by means of a seal 20.

[0049] How to Fig. 1. The housing 3 has a circumferential, radially inwardly extending terminal projection 21 (also referred to as the first projection) located on the side of the device 1 facing the housing cover 10. A first pressure chamber 22 is formed between the projection 21 and the first effective surface 5 of the power-push piston 4, and the projection 21 serves as a stop for the power-push piston 4 when it is in Fig. 1 moved to the right, see the lower part of the figure. The first pressure chamber 22, which is in operative communication with the first pressure port L, is sealed on the outside of the force-pull piston 4 against the housing 3, for which at least two circumferential seals 23, 24 axially spaced apart are provided on the housing 3.

[0050] A second pressure chamber 25 is formed between the second housing cover 19 and the second actuating surface 6 of the thrust piston 4. This chamber is sealed against both the housing 3 (by means of the aforementioned seal 23) and the second housing cover 19. An additional seal is provided on the thrust piston 4 at reference numeral 26. Specifically, the second housing cover 19 also has an axial projection 27 that radially overlaps the thrust piston 4 in an overlap area in the axial direction. The end face of this projection 27 preferably also serves as a stop for the thrust piston 4 in the upper part of the Fig. In the position shown in Figure 1, the second pressure chamber 25 remains at least partially open and pressurizable. The second pressure chamber 25 is sealed in the aforementioned overlap area against the second housing cover 19 by means of the previously mentioned seal 26. On the outside, the same seal 23 is used that also seals the first pressure chamber 22, as already mentioned.

[0051] To simplify maintenance, the housing 3 is detachably connected to the further housing cover 19, in particular by means of a number of screw bolts, which will be discussed in more detail below. These screw bolts preferably extend axially parallel or concentric to the longitudinal axis L through the housing 3 to the further housing cover 19 and are accessed from the sides of the housing cover 10 (i.e., from the right). Fig. 1) accessible. After loosening these screw bolts, the housing 3 is accessible in the axial direction (in Fig. 1 to the right) can be removed from the further housing cover 19 – even with rod 2 present. In this way it is possible, for example, to replace the seals 23, 24. After loosening the housing 3 from the further housing cover 19, the power thrust piston 4 can also be moved axially (to the right). Fig. 1) be removed, preferably by first removing the housing 3 as described, so that the effective surface 5 does not hit the projection 21.

[0052] In this way, the housing cover 10, the clamping sleeves 12, the housing 3 and the power thrust piston 4 can be successively separated axially and serviced with the rod 2 installed, e.g. by replacing the seal 20, the seals 17 and / or the diaphragm 16, the seals 23 and 24 or the seal 26. Other seals not explicitly mentioned here can also be easily replaced in this way.

[0053] As can be seen, due to the chosen sealing geometry or arrangement of the seals, no pressure medium (hydraulic fluid or oil) reaches rod 2, which facilitates the described maintenance.

[0054] It has already been pointed out that in device 1, the effective surface and pressure ratios or the dimensions of the effective surfaces 5, 6 and the pressures at L, K and V are selected or selectable such that, with a rod-shaped body 2 held by the clamping sleeves 12, the force-pull piston 4 together with the rod-shaped body 2 is axially movable relative to the housing 3 in one direction by applying pressure at the second pressure port K, as is shown in the lower part of the Fig. Figure 1 shows that the power piston 4, along with the rod 2 and the clamping sleeves 12, has been moved to the right because a suitable pressure was applied at K. The housing 3 and the further housing cover 19 remained stationary. Conversely, by applying pressure at the first pressure port L, the power piston 4, together with the rod-shaped body 2 and the clamping sleeves 12, can be moved axially relative to the housing 3 and the further housing cover 19 in the opposite direction back into the position in the upper part of the Fig. The position shown in step 1 can be moved back.

[0055] As described above, a clamping sleeve pressure chamber 18 is defined in the area of ​​the clamping sleeves 12 between the power piston 4 and a radial outer surface of the clamping sleeve 12, i.e., the diaphragm 16. This pressure chamber 18 is sealed against the power piston 4 by the aforementioned seals 17 and can be pressurized with a suitable holding / clamping pressure via the pressure port V.

[0056] Reference numeral 28 denotes a screw used for the detachable connection of housing cover 10 and power piston 4. Reference numeral 29 shows one of the previously mentioned screw bolts used for the detachable connection of housing 3 and another housing cover 19.

[0057] Although this is in the Fig.Not shown in Figure 1, it is also possible to provide a distributor attachment for pressurizing the clamping sleeves 12 via their respective third pressure ports V. This attachment preferably has a separate pressure channel for each clamping sleeve 12, branching off from a single, common third pressure port V. In this way, all clamping sleeves 12 can be pressurized to the same pressure. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 100 222

[0003] DE 101 04 652 A1

[0003] EP 2 226 513 A2

[0003] WO 2010 / 109374 A1

[0003] WO 00 / 67987 A1

[0003] EP 3 253 550 B1

[0003]

Claims

[1] Device (1) for holding and / or moving a rod-shaped body (2), comprising: a fully enclosed housing (3) with a longitudinal axis (L) along which the rod-shaped body (2) is guided or is to be guided; a thrust piston (4) surrounding the rod-shaped body (2), which can be subjected to a first pressure from the outside via a first pressure port (L) through the housing (3) and which can be subjected to a second pressure from the outside via a second pressure port (K) through the housing (3), and which has a first effective surface (5) and a second effective surface (6), which effective surfaces (5, 6) preferably extend in a radial direction, wherein the first effective surface (5) is in fluidic operative connection with the first pressure port (L) and the second effective surface (6) is in fluidic operative connection with the second pressure port (K), wherein the thrust piston (4) has a radially internal recess (7) through which a circumferential free space (8) is formed between the rod-shaped body (2) and an inner surface (9) of the thrust piston (4), which free space (8) has an axial limit (10, 11) on both sides; and at least one clamping sleeve (12) which, with its inner surface (13), defines a central cylindrical area through which the rod-shaped body (2) is guided or can be guided, and which is received in the aforementioned free space (8), extending axially between the two axial limits (10, 11), wherein the clamping sleeve (12) can be subjected to a third pressure from the outside via a third pressure port (V) through the force-pull piston (4) and is designed to deform itself reversibly radially inwards according to the third pressure and to exert a holding force on the rod-shaped body (2). [2] Device (1) according to claim 1, in which several clamping sleeves (12) are received axially one behind the other in the said free space (8) and together with their inner surfaces (13) define the central cylindrical area. [3] Device (1) according to claim 2, wherein the multiple clamping sleeves (12) can be pressurized separately. [4] Device (1) according to claim 2, in which the multiple clamping sleeves (12) can be subjected to pressure together. [5] Device (1) according to one of the preceding claims, in which a first, removable housing cover (10) is provided, which closes the device (1) and / or the free space (8) at a first end face of the device (1), after the removal of which in an axial direction the clamping sleeve(s) (12) can be removed from the said free space (8) through an end face opening in an axial direction. [6] Device (1) according to claim 5, wherein the first housing cover (10) serves as one of the aforementioned axial limits and is preferably sealed inwards against the rod-shaped body (2). [7] Device (1) according to one of the preceding claims, wherein the housing (3) comprises a circumferential first projection (21) extending radially inwards, preferably on a side facing the first housing cover (10) according to claim 5, wherein a first pressure chamber (22) is formed between the first projection (21) and the first working surface (5), wherein the projection (21) preferably serves as a stop for the force thrust piston (4). [8] Device (1) according to claim 7, wherein the first pressure chamber (22) is sealed on the outside of the force thrust piston (4) against the housing (4), preferably by means of two circumferential seals (23, 24). [9] Device (1) according to one of the preceding claims, wherein one of the said axial limits (11) is formed integrally with the force thrust piston (4), in particular as a radially inwardly pointing second projection (11) which preferably extends to the rod-shaped body (2). [10] Device (1) according to one of the preceding claims, wherein a second housing cover (19) is provided which closes the housing (3) at a second end face of the device (1). [11] Device (1) according to claim 10, in which a second pressure chamber (25) is formed between the second housing cover (19) and the second working surface (6), which is preferably sealed against the housing (3) and the second housing cover (19). [12] Device (1) according to claim 10 or 11, wherein the second housing cover (19) has an axial projection (27) which overlaps the force thrust piston (4) radially inwards in an axial direction, wherein the second pressure chamber (25) is sealed in the overlap area against the second housing cover (19). [13] Device (1) according to one of claims 10 to 12, wherein the housing (3) is detachably connected to the second housing cover (19), preferably by means of a number of screw bolts (29) extending in an axial direction and accessible from the side of the first housing cover (10), and is axially removable from the second housing cover (19), wherein preferably after detaching the second housing cover (19) from the housing (3) the force thrust piston (4) is axially removable, most preferably after prior removal of the housing (3). [14] Device (1) according to one of the preceding claims, wherein the effective area and pressure conditions are selected or selectable such that, with the rod-shaped body (2) held by the clamping sleeve(s) (12), the force-pull piston (4) together with the rod-shaped body (2) is movable axially relative to the housing (3) in one direction by applying pressure at the second pressure port (K), and that, by applying pressure at the first pressure port (L), the force-pull piston (4) together with the rod-shaped body (2) is movable axially relative to the housing (3) in the opposite direction. [15] Device (1) according to one of the preceding claims, in which a clamping sleeve pressure chamber (18) is defined in the area of ​​the clamping sleeve (12) between the force push piston (4) and a radial outer surface of the clamping sleeve (12), which is preferably sealed against the force push piston (4) by two axially limiting, circumferential seals (17).

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