Expansion chuck

Abstract

Expansion chuck (1) for receiving and clamping a shank tool, with a clamping part (10) extending along a longitudinal central axis (2) of the expansion chuck (1), which has a central receiving opening (3) for receiving a tool shank and a chamber system that can be subjected to fluid pressure, which comprises at least one pressure chamber (30) that is separated in the radial direction from the receiving opening (3) by an expansion wall that is elastically flexible under the fluid pressure, can be subjected to fluid pressure via a pressure channel (31) and can be vented via a vent channel (32), characterized in that the pressure channel (31) and the venting channel (32) lead to the at least one pressure chamber (30) diametrically opposite one another in relation to the longitudinal central axis (2), wherein the pressure channel (31) and the venting channel (32) wind at least in sections around the longitudinal central axis (2).

Description

[0001] The invention relates to an expansion chuck for receiving and clamping a shank tool according to the preamble of claim 1.

[0002] Such an expansion chuck, also referred to by those skilled in the art as a hydro or hydraulic expansion chuck, is known, for example, from WO 2017 / 093280 A1. The expansion chuck specified in WO 2017 / 093280 A1 has a shank portion with a so-called HSK (short for: hollow shank taper) shank for coupling to a module of a modular tool system or to a machine spindle, and a clamping portion axially adjacent to the shank portion, which extends along a rotational or longitudinal center axis of the expansion chuck and has an (axially extending) central receiving opening for receiving a tool shank and a chamber system that can be pressurized with fluid pressure. The chamber system comprises two pressure chambers arranged at an axial distance from one another, each extending annularly around the receiving opening and being separated radially from the receiving opening by an expansion wall that is elastically flexible under the fluid pressure.The two pressure chambers are fluidically connected to one another and can be pressurized with fluid via a pressure channel running through the clamping part, which opens into the pressure chamber located closer to the shaft part. The fluid pressure is generated by a pressure generating device (consisting of a clamping screw, a clamping piston, etc.) arranged in the shaft part. The pressure channel leading from the pressure generating device to the pressure chamber is composed of bores running longitudinally or transversely to the rotational or longitudinal center axis. A filling or (hereinafter:) venting channel with a smaller cross-sectional area, which is formed from a bore running transversely to the rotational or longitudinal center axis and originates from a venting device (consisting of a vent screw, etc.), opens into the pressure channel in an area between the pressure generating device and the pressure chamber.

[0003] The aforementioned venting channel serves to vent the chamber system and pressure channel and subsequently fill them with a suitable pressurized fluid, in particular oil. The chamber system is regularly filled with fluid while the pressure channel is fluid-tightly closed by the pressure-generating device, and by applying a negative pressure to the chamber system (including the pressure and venting channels connected to the chamber system) via the venting device. After the vented chamber system has been filled with fluid, the venting channel is fluid-tightly closed by the venting device. In this state, the pressure channel, the chamber system, and the venting channel form a fluid-tight, closed system, allowing the chamber system to be pressurized via the pressure-generating device.

[0004] Due to their eccentric arrangement, uneven design, etc., the pressure channel, the venting channel, the pressure generation device, and the venting device result in an asymmetrical mass distribution with respect to the rotational or longitudinal center axis. This can lead to imbalances when the expansion chuck is driven in rotation. These imbalances become increasingly greater the higher the speed at which the expansion chuck is operated. Furthermore, when the chamber system is pressurized, the eccentrically located pressure channel leading to the chamber system and the eccentrically located venting channel opening into the pressure channel cause an asymmetrical stress distribution in their surroundings in the clamping part body with respect to the rotational or longitudinal center axis. This can lead to a slight but noticeable bending deformation of the clamping part.Particularly in the case of an expansion chuck with an axially elongated clamping part whose axial extension is significantly greater than its diametrical extension, the above-mentioned imbalances and the stress-induced bending deformation can lead to an undesirable concentricity error of the tool clamped in the clamping part, especially at the high tool speeds that are now common.

[0005] In light of this problem, EP 1 737 594 B1 proposes an expansion chuck in which the pressure is applied to a chamber system consisting of a single pressure chamber via a pressure channel. Unlike a pressure channel formed from a bore or bore sections, this pressure channel is designed as a closed, annular gap or annular channel running concentrically with respect to the rotational or longitudinal center axis. When the chamber system is pressurized, the closed annular shape of the pressure channel may result in a stress distribution in the clamping part that is rotationally symmetrical with respect to the rotational or longitudinal center axis.Especially in the case of the expansion chuck mentioned above with an axially elongated clamping part, the axial extension of which is significantly greater than its diametrical extension, the considerable axial length of the annular pressure channel from a pressure generating device to the chamber system results in a reduced rigidity of the clamping part, so that concentricity errors can occur due to external torsional and transverse forces which are transmitted to the expansion chuck via a clamped tool during machining.

[0006] The subsequently published document DE 10 2017 004 994 A1 discloses an expansion chuck according to the preamble of claim 1.

[0007] Based on WO 2017 / 093 280 A1, the invention is based on the object of creating an expansion chuck which is characterized by high rigidity and high concentricity.

[0008] This object is achieved by an expansion chuck having the features of claim 1. Advantageous further developments are the subject of dependent claims.

[0009] An expansion chuck according to the invention has the function of holding and clamping a shank tool, e.g. a drilling, milling or reaming tool.

[0010] Analogous to the expansion chuck known from WO 2017 / 093280 A1, an expansion chuck according to the invention has a clamping part extending along a rotational or longitudinal center axis of the expansion chuck, which has an (axially extending) central receiving opening for receiving a tool shank of the shank tool and a chamber system that can be subjected to fluid pressure. The chamber system comprises at least one pressure chamber, which is radially separated from the receiving opening by an expansion wall that is elastically flexible under the fluid pressure, can be subjected to fluid pressure via a first channel, referred to below as the pressure channel, and can be vented and filled with pressurized fluid via a second channel, referred to below as the venting channel.

[0011] The at least one pressure chamber can extend in a closed ring around the receiving opening, similar to the expansion chuck known from WO 2017 / 093280 A1. However, this is not absolutely necessary. To clamp a shank tool in the central receiving opening, it is generally sufficient for the expansion wall of the at least one pressure chamber to expand under the fluid pressure against a shank tool received in the receiving opening. This can also be achieved, for example, if the at least one pressure chamber extends in the form of an open ring around the central receiving opening or is formed from fluidically interconnected pressure chamber sections distributed in a ring around the central receiving opening.

[0012] Furthermore, the chamber system can be formed from a clamping part manufactured entirely using a generative manufacturing process (i.e. generally using a 3D printing process, e.g., using selective laser melting or selective laser sintering). In this case, the expansion wall that separates the at least one pressure chamber from the central receiving opening can be an integral part of the clamping part. The clamping part can thus be formed in one piece. Alternatively, the clamping part can be formed from a clamping part body and an expansion bushing arranged in the clamping part body, and the chamber system can be formed between the clamping part body and the expansion bushing. In the latter case, the expansion bushing forms the expansion wall that separates the at least one pressure chamber from the central receiving opening. Of course, in this case too, the clamping part can be manufactured using generative manufacturing, at least in sections.Additive manufacturing can be particularly advantageous when the chamber system and / or the pressure channel or vent channel have a complex design / arrangement.

[0013] In contrast to the expansion chuck known from WO 2017 / 093280 A1, in which only the pressure channel leads to the pressure chamber, while the venting channel opens into the pressure channel, in an expansion chuck according to the invention, both the pressure channel and the venting channel lead separately from one another (from a pressure generating device or venting device) to the at least one pressure chamber, and the pressure channel and the venting channel are arranged diametrically opposite one another with respect to the longitudinal center axis, i.e., offset by substantially 180°. In particular, the pressure channel and the venting channel can be arranged such that one of the two channels can be brought into alignment with the other channel by a 180° rotation around the longitudinal center axis.If the pressure channel and the vent channel have different cross-sections, the diametrical arrangement of the pressure channel and the vent channel refers to the respective cross-sectional centers. In other words, in each cross-section of the expansion chuck, a connecting line runs from the cross-sectional center of the pressure channel to the cross-sectional center of the vent channel, at least essentially through the longitudinal center axis.

[0014] The pressure channel and the venting channel, which thus run eccentrically, are fluidically connected to one another via the at least one pressure chamber, whereby when pressure is applied to the pressure channel, the fluid pressure generated in the chamber system is transferred to the venting channel. The diametrically opposed arrangement of the two channels ensures that when pressure is applied to the chamber system, the clamping part not only experiences stress-induced deformation in the area in which the pressure channel runs due to the pressure in the pressure channel, but also experiences stress-induced deformation in the diametrically opposite area in which the venting channel runs. By an appropriate arrangement, e.g. in every cross section of the expansion chuck at at least substantially equal radial distances from the longitudinal center axis, and an appropriate design, e.g.By means of channel cross-sections of at least substantially equal size, the two channels can be used to aim for or achieve at least substantially symmetrical stress states in the clamping part with respect to the rotational or longitudinal center axis, resulting in a higher concentricity than with the expansion chuck known from WO 2017 / 093 280 A1.

[0015] In this regard, the already mentioned generative manufacturing offers the possibility of forming the pressure channel and the venting channel from a pressure generating device or a venting device separately from each other and individually configurable towards the at least one pressure chamber.

[0016] It should be noted that the pressure channel and the venting channel, in contrast to the annular channel known from DE 20 2004 005 321 U1, are each formed by an eccentrically running channel with preferably a cylindrical, in particular round, channel cross-sectional area.

[0017] Furthermore, the pressure channel and the venting channel can each extend linearly, e.g. as a bore, or at least partially non-linearly, e.g. with a twist around the longitudinal center axis, through the clamping part to the at least one pressure chamber.

[0018] With the above-mentioned linear course of the pressure channel and vent channel, when pressure is applied to the chamber system, the clamping part experiences stresses or stress-induced deformations along the rotational or longitudinal center axis in diametrically opposite areas, while the areas lying circumferentially between the two channels remain stress-free or almost stress-free. According to the invention, the pressure channel and the vent channel wind at least in sections around the longitudinal center axis. The twist around the rotational or longitudinal center axis means that when pressure is applied to the chamber system, the stresses resulting from the pressure in the pressure channel and in the vent channel are distributed circumferentially around the rotational or longitudinal center axis in the clamping part. This stress distribution can contribute to greater concentricity, in particular when a tool clamped in an expansion chuck is used for machining a workpiece, e.g.B. during milling, a feed is made transverse to the rotational or longitudinal center axis.

[0019] The pressure channel and the vent channel can, in particular, wind around the rotational or longitudinal center axis in a spatial spiral or (hereinafter referred to as:) spiral, helical, or helix shape. With a spiral course, the radial distance to the longitudinal center axis changes along the longitudinal center axis, whereas with a helical or helix course, the radial distance along the longitudinal center axis remains the same. The aforementioned generative manufacturing allows for various options in this regard. With regard to the radial distance to the longitudinal center axis, it should be noted that the radial distance of the pressure channel from the longitudinal center axis and the radial distance of the vent channel from the longitudinal center axis are preferably at least substantially the same for one and the same cross-section of the expansion chuck.Depending on the design of the two channels, the radial distances to the longitudinal center axis can also be different for one and the same cross-section of the expansion chuck.

[0020] In the interest of achieving the same stress states as possible, the pressure channel and the vent channel can have the same cross-sections and lengths and, as already mentioned, can be arranged with respect to the longitudinal center axis in such a way that one of the two channels can be aligned with the other channel by a 180° rotation around the longitudinal center axis.

[0021] The aforementioned pressure generation device, to which the pressure channel connects, and the venting device, to which the venting channel connects, can be arranged in the clamping part. The aforementioned additive manufacturing is suitable for complex internal structures that accommodate the pressure generation device and venting device.

[0022] In the preferred embodiment, the clamping part can be attached axially to a shaft part for coupling the expansion chuck to a module of a modular tool system or to a machine spindle. In this case, the aforementioned pressure generating device, to which the pressure channel is connected, and the venting device, to which the venting channel is connected, are preferably arranged in the shaft part, and the pressure channel and venting channel each have an opening located at the end of the clamping part on the shaft part side, which is connected to the pressure generating device or venting device by a connecting channel on the shaft part side. This embodiment allows for a relatively slim design of the clamping part. The joint between the clamping part and the shaft part can be permanent, e.g., by a material bond, or detachable, e.g., by screwing.

[0023] As already mentioned, the fluid pressure is generated by the pressure generating device, which is arranged, for example, in the shaft part and can comprise a clamping screw, a clamping piston, etc., as in WO 2017 / 093 280 A1 discussed above. The pressure generated by the pressure generating device is transmitted to the pressure chamber exclusively via the pressure channel leading from the pressure generating device and, if applicable, the aforementioned connecting channel to the pressure chamber. The aforementioned venting channel, which leads from the pressure channel to the pressure chamber separately from the venting device, serves only to vent the chamber system and pressure channel and fill it with a suitable pressure fluid, in particular oil.The chamber system is regularly filled with fluid while the pressure channel is fluid-tightly closed by the pressure generation device, and while the chamber system (including the pressure and vent channels connected to the chamber system) is subjected to a vacuum. After the vented chamber system has been filled with fluid, the vent channel is fluid-tightly closed by the vent device. In this state, the pressure channel, the chamber system, and the vent channel form a fluid-tight, closed system, allowing the chamber system to be pressurized via the pressure generation device.

[0024] The shaft part can be manufactured separately from the clamping part. In particular, as already mentioned, the clamping part can be manufactured entirely or at least partially using additive manufacturing, while the shaft part can be manufactured conventionally. In this case, the clamping part and the shaft part can be joined together, e.g., by a material bond.

[0025] To ensure high concentricity, the chamber system can comprise two or more pressure chambers arranged at an axial distance from each other. This allows clamping forces to be applied to the tool held in the central receiving opening at an axial distance(s).

[0026] In this case, the two or more pressure chambers can be fluidically connected to one another for pressure transmission, e.g., through one or more axial channels, and the pressure channel, e.g., specifically a pressure channel, and the vent channel, specifically a vent channel, can lead to one of the two pressure chambers, e.g., to the axially closest pressure chamber. The clamping part can have multiple pressure chambers, specifically one pressure channel, and one vent channel, for pressurizing.

[0027] Alternatively, the two pressure chambers can also be fluidically separated from each other, each capable of being pressurized with fluid pressure via an associated pressure channel and vented and filled via an associated vent channel. In this case, the clamping part can have one pressure channel and one vent channel for each pressure chamber.

[0028] Preferred embodiments of an expansion chuck according to the invention are described below with the aid of the accompanying drawings. The drawings show: Fig. 1 a side view of an expansion chuck according to the invention according to a preferred embodiment; Fig. 2 a longitudinal section BB along the rotational or longitudinal center axis of the expansion chuck; Fig. 3 a cross-section AA of the expansion chuck; Fig. 4 a front view of the expansion chuck; Fig. 5 a perspective side view of the expansion chuck; Fig. 6 a partially sectioned side view of the clamping part of the expansion chuck; Fig. 7 a front view of the clamping part; Fig. 8 a rear view of the clamping part; and Fig. 9 a perspective side view of the clamping part.

[0029] The Fig. 1 to 9 show various views and sections of an expansion chuck 1 according to the invention according to a preferred embodiment. The expansion chuck 1 according to the invention has the function of receiving and clamping a shank tool not shown in the figures, e.g., a drilling, milling, or reaming tool.

[0030] As particularly in Fig. 1 and Fig. 2, the expansion chuck 1 has an essentially axially two-part structure with a clamping part 10 and a shaft part 20. The clamping part 10 is joined to the shaft part 20 at its shaft-side end at a joining surface 11.

[0031] The shank part 20 has an HSK (hollow shank taper) shank for coupling to a module (not shown) of a modular tool system or to a machine spindle.

[0032] The clamping part 10 extends along a rotational or longitudinal central axis 2 of the expansion chuck 1 and has an axially extending central receiving opening 3 for receiving a tool shank of the shank tool and a chamber system to which fluid pressure can be applied. In the preferred embodiment, the chamber system comprises two pressure chambers, a first pressure chamber 30 and a second pressure chamber 40, which are separated in the radial direction from the central receiving opening 3 by an expansion wall that is elastically flexible under the fluid pressure. The clamping part 10 is manufactured using additive manufacturing. This means that the expansion wall, which separates the pressure chambers 30, 40 from the central receiving opening 3 for receiving the shank tool, is an integral component of the clamping part 10. In other words, the clamping part 10 is formed in one piece. The pressure chambers 30, 40 each extend in a closed ring around the receiving opening 3.

[0033] The first pressure chamber 30 can be pressurized with fluid via a first pressure channel 31 and vented and filled with pressurized fluid via a first vent channel 32. The second pressure chamber 40 can be pressurized with fluid via a second pressure channel 41 and vented and filled with pressurized fluid via a second vent channel 42. The two pressure channels 31, 41 each have an opening located in a kidney-shaped groove 51 formed within the joining surface 11. Likewise, the two vent channels 32, 42 each have an opening located in a kidney-shaped groove 52 formed within the joining surface 11.

[0034] In the preferred embodiment, the rotary chuck 1 has a pressure channel 31 or 41 and a vent channel 32 or 42 for each pressure chamber 30 or 40. For the sake of simplicity, only the arrangement of the first pressure chamber 30, the first pressure channel 31, and the first vent channel 32 will be explained below. The arrangement of the second pressure chamber 40, the second pressure channel 41, and the second vent channel 42 essentially corresponds in terms of structure and function to the arrangement of the first pressure chamber 30, the first pressure channel 31, and the first vent channel 32 and is therefore not described separately.

[0035] As in Fig. 1 and 5 to 9, in the expansion chuck 1 according to the invention, the pressure channel 31 leads from the kidney-shaped groove 51 and the venting channel 32 leads from the kidney-shaped groove 52 to the pressure chamber 30. The pressure channel 31 and the venting channel 32 are separate from one another and are arranged diametrically opposite one another with respect to the longitudinal center axis 2. The diametrically opposed arrangement of the pressure channel 31 and the venting channel 32 ensures that when pressure is applied to the chamber system, the clamping part 10 not only experiences stress-induced deformation in the region in which the pressure channel 31 runs, due to the pressure in the pressure channel 31, but also experiences stress-induced deformation in the diametrically opposite region in which the venting channel 32 runs.By appropriately designing the two channels, at least substantially symmetrical stress states in the clamping part 10 can be aimed for or achieved with respect to the longitudinal center axis 2, resulting in a high concentricity.

[0036] In the preferred embodiment, the pressure channel 31 and the vent channel 32 have identical, particularly round, cross-sections and lengths. Due to the round cross-sections of the pressure channel 31 and the vent channel 32, one of the two channels can be aligned with the other channel by rotating it 180° around the longitudinal center axis 2. In their course from the kidney-shaped grooves 51, 52 to the pressure chamber 30, the pressure channel 31 and the vent channel 32 each wind around the longitudinal center axis 2. As shown particularly in Fig. 7 and Fig. 8, the courses are each spiral, i.e. the radius to the longitudinal center axis 2 decreases starting from the kidney-shaped groove 51, 52 towards the pressure chamber 30. The resulting twist around the longitudinal center axis 2 has the effect that, when the chamber system is pressurized, the stresses in the clamping part 10 resulting from the pressure in the pressure channel 31 and in the venting channel 32 are distributed axially in the circumferential direction around the longitudinal center axis 2. This stress distribution can contribute in particular to greater concentricity when a tool clamped in the expansion chuck 1 for machining a workpiece, e.g. during milling, experiences a feed transverse to the longitudinal center axis 2.

[0037] In the preferred embodiment, in which the rotary chuck 1 has a pressure channel 31 or 41 and a venting channel 32 or 42 for each pressure chamber 30 or 40, the two pressure channels 31 or 41 and the two venting channels 32 or 42 are each arranged at equal distances in the circumferential direction around the longitudinal center axis 2, as shown in Fig. 9 can be seen.

[0038] As in Fig. 1 to 5, the expansion chuck 1 has a pressure generating device 60 and a venting device 70 at the clamping part end of the shaft part 20. As shown in Fig. 2, the pressure generating device 60 has a clamping screw 62 and a clamping piston 63 actuated by the clamping screw 62. The clamping piston 63 is arranged in a cylinder bore 61 formed in the shaft part 20 transversely to the longitudinal center axis 2. As shown in Fig. 5, the cylinder bore 61 is connected via a first connecting channel 53 to the kidney-shaped groove 51 and thereby to the pressure channel 31 and the pressure chamber 30 as well as to the pressure channel 41 and the pressure chamber 40. The venting device 70 has a vent screw 71 and a ball seal 72. The ball seal 72 seals a cylinder bore 73 formed transversely to the longitudinal center axis 2 from the atmosphere by being pressed by the vent screw 71 against an opening of the cylinder bore 73. As shown in Fig. 5, the cylinder bore 73 is connected via a second connecting channel 54 to the kidney-shaped groove 52 and thus to the vent channel 32 and the pressure chamber 30, as well as to the vent channel 42 and the pressure chamber 40. Therefore, simultaneous pressurization of the two pressure chambers 30, 40 is achieved via the connecting channel 53 and the groove 51.

[0039] Before commissioning the expansion chuck 1, the contiguous volume of the cylinder bore 61, the first connecting channel 53, the pressure channel 31, the pressure chamber 30, the pressure channel 41, the pressure chamber 40, the venting channel 32, the venting channel 42, the second connecting channel 54, and the cylinder bore 73 is first vented with the pressure generating device 60 closed and the venting device 70 open, and then filled with oil as the pressure fluid. The fluid filling takes place, in particular, by applying a vacuum to the chamber system and the channels connected to the chamber system. After the fluid filling, the venting device 70 is closed in a fluid-tight manner. In this state, the chamber system and the channels connected to the chamber system form a fluid-tight, closed system that can be pressurized via the pressure generating device 60 in a conventional manner.Due to the pressure application, the elastically flexible expansion wall between the pressure chamber 30 and the central receiving opening 3 as well as the elastically flexible expansion wall between the pressure chamber 40 and the central receiving opening 3 deform radially in the direction of the central receiving opening 3, whereby a tool inserted into the receiving opening 3 can be clamped in a force-fitting manner.

[0040] The invention is, of course, limited to the preferred embodiment discussed above. Thus, in a further embodiment not shown in the drawings, an expansion chuck according to the invention can, for example, have precisely one pressure channel and precisely one vent channel leading to the pressure chamber closest to the shaft part. To enable pressurization of two pressure chambers, they can be fluidically connected to one another, for example, by one or more axial channels.

[0041] Further modifications arise from the claims and the introductory part of the description.

Claims

[1] Expansion chuck (1) for receiving and clamping a shank tool, with a clamping part (10) extending along a longitudinal central axis (2) of the expansion chuck (1), which has a central receiving opening (3) for receiving a tool shank and a chamber system which can be subjected to fluid pressure and which comprises at least one pressure chamber (30) which is separated in the radial direction from the receiving opening (3) by an expansion wall which is elastically flexible under the fluid pressure, can be subjected to fluid pressure via a pressure channel (31) and can be vented via a vent channel (32), characterized by , that the pressure channel (31) and the venting channel (32) lead to the at least one pressure chamber (30) diametrically opposite one another in relation to the longitudinal central axis (2), wherein the pressure channel (31) and the venting channel (32) wind at least in sections around the longitudinal central axis (2). [2] Expansion chuck (1) according to claim 1, characterized by that the pressure channel (31) and the vent channel (32) run in a spiral or helical manner. [3] Expansion chuck (1) according to one of the preceding claims, characterized by that the pressure channel (31) and the vent channel (32) have the same cross-sections and lengths. [4] Expansion chuck (1) according to one of the preceding claims, characterized by that the at least one pressure chamber (30) runs in a ring shape around the central receiving opening (3). [5] Expansion chuck (1) according to one of the preceding claims, characterized by that the clamping part (10) is manufactured generatively at least in sections. [6] Expansion chuck (1) according to one of the preceding claims, characterized by , that the clamping part (10) is attached axially to a shaft part (20) for coupling the expansion chuck (1) to a module of a modular tool system or to a machine spindle, and the pressure channel (31) and the venting channel (31) each have an opening located in a shaft-side end face of the clamping part (10). [7] Expansion chuck (1) according to claim 6, characterized by that the shaft part (20) is manufactured separately from the clamping part (10). [8] Expansion chuck (1) according to claim 6 or 7, characterized by that the shaft part (20) has a pressure generating device (60) connected to the pressure channel (31) and a venting device (70) connected to the venting channel (32). [9] Expansion chuck (1) according to one of the preceding claims, characterized by that the chamber system comprises two pressure chambers (30, 40) which are arranged at an axial distance from one another. [10] Expansion chuck (1) according to claim 9, characterized bythat the two pressure chambers (30, 40) are fluidically connected to one another for pressure transmission, and the pressure channel (31) and the vent channel (32) lead to one of the two pressure chambers (30, 40). [11] Expansion chuck (1) according to claim 9, characterized by that the two pressure chambers (30, 40) are fluidically separated from one another for pressure transmission and can each be subjected to fluid pressure via an associated pressure channel (31, 41) and can be vented and filled via an associated venting channel (32, 42).

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