Positioning device

Abstract

The present invention relates to a positioning device comprising a base body (1) and an actuating element (2) spanning a front end face (1a) of the base body (1), such that a pressure chamber (3) is formed between the base body (1) and the actuating element (2). The wall of the actuating element (2) is designed as an elastic membrane such that pressurizing the pressure chamber (3) via a hydraulic channel causes the actuating element (2) to move axially away from the front end face (1a) of the base body (1), at least in its central region. The hydraulic channel (6) is closed by a clamping screw (7, 8) which is operatively connected to a piston (9, 10) slidably arranged in the hydraulic channel (6), so that the piston (9, 10) can be moved inwards by rotating the clamping screw (7, 8) and thereby increasing the pressure in the pressure chamber (3).

Description

[0001] The present invention relates to a positioning device comprising a base body defining a longitudinal axis and an actuating element held on the base body, wherein the actuating element spans a front end face of the base body, such that a pressure chamber is formed between the front end face of the base body and the actuating element, which can be pressurized with a pressure medium via at least one fluid channel formed in the base body, and wherein the wall of the actuating element is designed as an elastic membrane such that pressurization of the pressure chamber causes the actuating element to deform elastically and thus be moved purely axially away from the front end face of the base body, at least in its central region coinciding with the longitudinal axis of the base body.

[0002] Positioning devices of this type are known from DE 20 2013 003 488 U1. They have a base body that can be fixedly positioned, for example, clamped to the table of a machine tool, and defines a longitudinal axis. Furthermore, the positioning device includes an actuating element that is fixed to the base body and spans a front end face of the base body, so that a pressure chamber is formed between the front end face of the base body and the actuating element. This chamber can be pressurized with a pressure medium via a fluid channel formed in the base body. The wall of the actuating element is designed as an elastic membrane that is elastically deformed when the pressure chamber is pressurized, so that the actuating element is moved axially away from the front end face of the base body, at least in its central region which coincides with the longitudinal axis of the base body.

[0003] A tensile-type expansion clamping device is known from CN 112059678 A. This device has a base body that defines a clamping surface on its outer surface for clamping a component. An annular pressure chamber is formed within the base body, extending over the area of ​​the clamping surface. It is arranged such that only a very thin wall exists between the pressure chamber and the clamping surface. This thin wall can be deformed outwards by pressurizing the pressure chamber to clamp the component. The pressure chamber is connected to a hydraulic channel in the base body, which is closed at its end furthest from the pressure chamber by a clamping screw. By turning the clamping screw in one direction or the other, the pressure in the hydraulic channel / pressure chamber can be increased or decreased to clamp the component.

[0004] The established positioning devices have proven their worth in practice. However, efforts are focused on increasing positioning accuracy. Once a predetermined position is reached, it should be able to be maintained without problems over an extended period.

[0005] The object of the present invention is therefore to design a positioning device of the type mentioned above in such a way that a high axial positioning accuracy can be achieved and a desired position can also be maintained.

[0006] This problem is solved in a positioning device of the type mentioned above by the characterizing features of claims 1 and 2.

[0007] According to the invention, the fluid channel is thus designed as a hydraulic channel. Accordingly, the hydraulic channel and the pressure chamber are filled with a hydraulic fluid such as oil. The end of the hydraulic channel facing away from the pressure chamber is closed by a clamping screw, which is operatively connected to a piston slidably arranged within the hydraulic channel. By rotating the clamping screw, the piston can be moved into the base body, thereby increasing the pressure in the pressure chamber. It has been shown that by using a hydraulic fluid and a clamping screw that can be moved into the pressure chamber by increasing the pressure, highly precise elastic deformation of the diaphragm-like actuating element can be achieved, thus enabling the central area of ​​the actuating element to be positioned axially with high precision.

[0008] According to a first aspect of the invention, a single hydraulic central channel is provided which, at its end region pointing away from the pressure chamber, transitions into two branch channel sections, each of which is closed at its end pointing away from the pressure chamber by a clamping screw, wherein each clamping screw is operatively connected to a piston slidably arranged in the respective branch channel section, so that the piston can be moved inwards by turning the clamping screw while increasing the pressure in the pressure chamber.

[0009] In this configuration, the hydraulic central channel branches into two two-channel sections, each closed by a clamping screw. The pressure in the pressure chamber can be increased by tightening one or the other clamping screw into the respective branch channel section. The clamping screws that close the branch channel sections have different thread pitches and / or the branch channel sections have different flow cross-sections. By selecting the appropriate thread pitches / flow cross-sections, one clamping screw can be used for coarse adjustment, while the other clamping screw is used for fine adjustment of the axial position.For example, if the clamping screws have different thread pitches, the clamping screw with the larger thread pitch is used for coarse adjustment, and the clamping screw with the smaller thread pitch is used for fine adjustment. Similarly, in the branch channel section with the smaller flow cross-section, less hydraulic fluid is displaced towards the pressure chamber with one turn of a clamping screw than in the branch channel section with the larger flow cross-section, so the branch channel section with the smaller flow cross-section is used for fine adjustment.

[0010] According to a second aspect of the invention, it is provided that several hydraulic channels are formed in the base body, each opening into a central area of ​​the pressure chamber and each closed at its end pointing away from the pressure chamber by a clamping screw, wherein each clamping screw is operatively connected to a piston slidably arranged in the respective hydraulic channel, so that the piston can be moved inwards by turning the clamping screw while increasing the pressure in the pressure chamber, and that the clamping screws have different thread pitches and / or the hydraulic channels have different flow cross-sections.

[0011] Functionally, this embodiment corresponds to the previously described embodiment in which the pressure medium channel transitions into two branch channel sections, except that in the present embodiment two separate hydraulic medium channels are provided.

[0012] According to one embodiment of the invention, it is provided that a hydraulic central channel opens centrally into the pressure chamber at its front axial end and runs in its axially front end region in particular coaxial to the longitudinal axis.

[0013] According to one embodiment of the invention, the actuating element has a greater wall thickness in its central region, which coincides with the longitudinal axis of the base body, than in the laterally adjacent regions, where the actuating element has a comparatively thinner wall to achieve deformation. In particular, the actuating element can be designed as a solid body in the central region. The wall of the actuating element can be curved starting from the central region coinciding with the longitudinal axis, with the wall initially approaching the end face of the base body and then moving away from it again as its distance from the longitudinal axis increases. The bending forms a kind of solid-body hinge and represents the material or...The wall length is provided that is required to move the central area of ​​the actuating element axially away from the base body without having to substantially stretch the wall of the actuating element. Preferably, the wall of the actuating element has a thin wall thickness at the end of the bend, so that the actuating element is selectively deformed, i.e., bent open, at this point when the pressure chamber is acted upon. The tapered area then acts as a kind of solid-state hinge.

[0014] According to a further embodiment of the present invention, the actuating element is designed in a cap-like form, encompassing a cylindrical section of the base body that defines the front end face. The actuating element can be screwed onto the cylindrical section of the base body. Alternatively, the cap-like actuating element can have a circumferential mounting flange at its rear free edge and be fixed to the base body via this flange, in particular by screwing it in place. An annular gap between the cap-like actuating element and the circumferential wall of the base body is preferably sealed. The cap-like design of the actuating element allows for simple fixation to the base body, and in particular, fixation by means of a screw connection.

[0015] The actuating element is preferably symmetrical to the longitudinal axis, i.e. rotationally symmetrical, which allows for very uniform deformation, and furthermore the actuating element is preferably made of steel and / or titanium.

[0016] In a further embodiment of the invention, an attachment body is provided on the front of the base body, which is connected to the base body, in particular screwed on, a central, in particular cylindrical, receptacle is formed in the attachment body, and a positioning element, in particular piston-like, is inserted into the receptacle and guided axially displaceably therein, wherein the actuating element defines a contact surface on the front of its central area, which comes into contact with a corresponding contact surface on the underside of the positioning element, such that the positioning element is axially adjusted when the pressure chamber is actuated by the actuating element.

[0017] In this embodiment, an attachment body is provided on the base body, within which a positioning element is guided for axial displacement. A contact surface is provided on the underside of the positioning element, which comes into contact with a corresponding contact surface on the front of the actuating element, so that the positioning element is axially adjusted when the pressure chamber is pressurized. In other words, an axial deformation of the actuating element is converted into an axial displacement of the positioning element within the attachment body. Preferably, a contact surface is formed on the front / top of the positioning element, onto which a component to be machined can be placed. Because the positioning element is guided axially within the attachment body, unwanted angular misalignments are avoided.

[0018] In this embodiment, the positioning element can have a recess on its rear side in which the contact surface for the actuating element is formed, with the actuating element engaging in the recess.

[0019] Furthermore, restoring means may be provided which push the positioning element backwards to ensure contact between the contact surfaces of the actuating element and the positioning element, even when the pressure chamber is relieved, wherein, in particular, the restoring means have a compression spring which is held in a bore of the mounting body.

[0020] Preferably, clamping devices are provided which are designed to fix the positioning element in a predetermined axial position on the attachment body. The clamping devices can, for example, be designed as magnetic clamping devices. However, according to a preferred embodiment, the clamping devices are designed as hydraulic clamping devices and comprise an expansion sleeve which is inserted into the central receptacle of the attachment body, particularly from its front end face. At least one pressure chamber is formed between the inner circumferential wall of the receptacle and the expansion sleeve, which can be pressurized via a pressure medium channel formed in the attachment body to elastically deform the wall of the expansion sleeve inwards towards the positioning element and thus fix the positioning element. In this embodiment, the positioning element is guided in the receptacle by the expansion sleeve.

[0021] In a further embodiment of this design, it is advantageously provided that the pressure medium channel is closed at its end furthest from the pressure chamber by a clamping screw, wherein the clamping screw is operatively connected to a piston arranged to be slidable into the pressure medium channel, so that the piston can be moved inwards into the pressure medium channel by turning the clamping screw while increasing the pressure in the pressure chamber.

[0022] The pressure chamber can extend in a ring shape around the expansion sleeve. Alternatively, several pressure chambers can be provided, evenly distributed along the circumference of the expansion sleeve.

[0023] Regarding further embodiments of the invention, reference is also made to the dependent claims and the following description of an exemplary embodiment with reference to the accompanying drawing. The drawing shows Fig. 1 an embodiment of a positioning device according to the present invention in perspective view, Fig. 2 the positioning device Fig. 1 in front view, Fig. 3 the positioning device Fig. 1 in longitudinal section and Fig. 4 the positioning device Fig. 2 on average along line IV-IV.

[0024] The drawing shows an embodiment of a positioning device according to the present invention. This device comprises a base body 1 of cylindrical shape, which defines a longitudinal axis X. The positioning device also includes an actuating element 2, which is held on the base body 1 and spans the front end face 1a of the base body 1, so that a pressure chamber 3 is formed between the front end face 1a of the base body 1 and the actuating element 2. In the illustrated embodiment, the actuating element 2 is cap-shaped, encompassing a cylindrical section 1b of the base body 1 that defines the front end face 1a. At its axially rear end, the actuating element 2 has a mounting flange 2b, which rests on a corresponding radially outwardly projecting shoulder 1c of the base body 1.The annular gap formed between the circumferential wall of the cylindrical section 1b of the base body 1 and the actuating element 2 is sealed by a sealing element in the form of an O-ring 4, which is inserted into an annular groove 5, which is located axially in the outer circumferential wall of the cylindrical section 1b between the front end face 1a and the radial shoulder 1c.

[0025] The base body 1 also includes a hydraulic channel 6 through which the pressure chamber 3 can be pressurized to axially push the central area of ​​the actuating element 2, which is coaxial with the longitudinal axis X, away from the front end face 1a of the base body 1. For this purpose, the central area of ​​the actuating element 2 is designed to be rigid so that it does not deform. Specifically, the central area of ​​the actuating element 2 defines a solid body 2a that is to be axially adjusted. Starting from the central area / solid body 2b of the actuating element 2, which coincides with the longitudinal axis X, the wall of the actuating element 2 is curved, with the wall approaching the front end face of the base body with increasing distance from the longitudinal axis X or from the central area, and then moving away from it again.In the bending region, the wall has a substantially constant thickness, thinner compared to the central region. At the end of the bend, the wall thickness is reduced further, making it particularly easy to bend in this thinned area when the pressure chamber 3 is pressurized. The actuating element 3 is symmetrical to the longitudinal axis X, ensuring that the bending is uniform and that the central region of the actuating element 2 moves purely axially. In the illustrated embodiment, the hydraulic center channel 6 opens centrally into the pressure chamber 3 and runs coaxially to the longitudinal axis X at its front end. As shown in particular... Fig. As can be seen from Figure 4, the hydraulic central channel 6 branches at its rear end region pointing away from the pressure chamber 3 into two branch channel sections 6a, 6b. Each of these two-channel sections 6a, 6b is closed at its end pointing away from the pressure chamber 3 by a clamping screw 7, 8, wherein each clamping screw 7, 8 is operatively connected to a piston 9, 10 which is slidably arranged in the respective branch channel section 6a, 6b, so that the pistons 9, 10 can be moved inwards in the respective branch channel section 6a, 6b by turning the clamping screws 7, 8 and thereby increasing the pressure in the pressure chamber 3.

[0026] It is not apparent from the drawing that the two clamping screws 7, 8 have different thread pitches. In the present example, the one in Fig. 4 left clamping screw 7 a larger thread pitch than the one in Fig. 4. The clamping screw 8 shown. If the left clamping screw 7 is turned one turn into the base body 1, correspondingly more hydraulic fluid is displaced than if the right clamping screw 8 is turned one turn. In this respect, the clamping screw 8 shown in the Fig. 4 left clamping screw for coarse adjustment of the axial position of the actuating element 2 and the right clamping screw 8 for fine adjustment of the axial position.

[0027] The positioning device further comprises an attachment body 11, which is provided on the front of the base body 1 and connected to it, here by screws. Specifically, the rear end of the attachment body 11 surrounds the actuating element 2 and is placed on its mounting flange 2b. Through holes 12 are provided in the base body 1, the mounting flange 2b of the actuating element 2, and the attachment body 11, through which the three components can be screwed together and clamped to a plate or machine table.

[0028] The attachment body 11 has a central, cylindrical receptacle 13. A piston-like positioning element is provided in this receptacle and guided axially for displacement. The actuating element 2 defines a contact surface 15 on the front of the solid body 2a, which comes into contact with a corresponding contact surface 16 on the underside of the positioning element 14, such that the positioning element 14 is axially adjusted by the actuating element 2 when the pressure chamber 3 is pressurized. Specifically, the positioning element 14 has a recess 17 on its rear side, in which the contact surface 16 for the actuating element 2 is formed, with the solid body 2a of the actuating element 2 engaging in the recess 17.

[0029] To ensure continuous contact between the contact surfaces of the actuating element 2 and the positioning element 14, even when the pressure chamber 3 is relieved, restoring means are provided which push the positioning element 14 backwards to ensure contact between the contact surfaces 15, 16. In this case, the restoring means comprise a compression spring 18, which is held in a bore 19 of the attachment body 11 and supported on the upper side of a radially outwardly projecting shoulder 20 of the positioning element 14.

[0030] Finally, clamping devices are provided, which are designed to fix the positioning element 14 in a predetermined axial position on the mounting body 11. In this case, the clamping devices are designed as hydraulic clamping devices and comprise an expansion sleeve 21, which is inserted into the central receptacle 13 of the positioning element 14 from its front end face in such a way that a pressure chamber 22 is formed between the inner circumferential wall of the receptacle 13 and the expansion sleeve 21, extending annularly around the expansion sleeve 21. The positioning element 14 passes through the expansion sleeve 21 and is guided axially displaceably within it.The pressure chamber 22 can be pressurized, for example, with a hydraulic medium via a pressure medium channel 23 formed in the attachment body 11, in order to elastically deform the wall of the expansion sleeve 21 radially inwards in the direction of the positioning element 14 and thus fix the positioning element 14 in the attachment body 11.

[0031] For this purpose, the pressure medium channel 23 is closed at its end furthest from the pressure chamber 22 by a clamping screw 24, wherein the clamping screw 24 is operatively connected to a clamping piston 24 which is slidably arranged in the pressure medium channel 23, so that the clamping piston 24 can be moved inwards into the pressure medium channel 23 by turning the clamping screw 24 and increasing the pressure in the pressure chamber 22.

[0032] In operation, the positioning devices according to the invention are used to align a component to be machined on a machine table. For this purpose, several, in particular three, positioning devices are clamped to the machine bed by suitable fastening means. The positioning devices are then actuated so that the front end faces 14a of their positioning elements 14 lie in a horizontal plane. For this purpose, the axial position of the support surface of the respective positioning device is adjusted. Here, the clamping system for fixing the positioning element 14 in the mounting body 11 is relieved of tension, i.e., the clamping screw 24 is turned outwards, so that the pressure chamber 22 is relieved of tension and the positioning element 14 is axially displaceable in the expansion sleeve 21. The pressure chamber 3 is initially pressurized by the Fig. 4. The left clamping screw 7 is screwed into the left branch channel section 6a of the hydraulic center channel 6 for coarse adjustment of the axial position of the positioning element 14. This increases the pressure in the pressure chamber 3, causing the actuating element 2 to deform elastically, which presses its central section against the positioning element 14 and lifts or moves it forward. For fine adjustment of the axial position, the Fig.Four right-hand clamping screws 8 are screwed into the cylinder section 6b until the desired axial position of the positioning element 14, or rather of its front axial end face, is reached. The axial position of the positioning element 14 is then fixed in the attachment body 13 and thus relative to the base body 1. For this purpose, the pressure chamber 22 is hydraulically pressurized so that the wall of the expansion sleeve 21 is elastically deformed against the positioning element 14. To pressurize the pressure chamber 22, the clamping screw 24 is screwed into the pressure medium channel 23. Reference symbol list 1 Basic body 1a front face 1b cylindrical section Paragraph 1c 2 Actuating element 2a solid body 2b Mounting flange 3 pressure chamber 4 O-rings 5 ring groove 6 Hydraulic center channel 6a, 6b branch canal sections 7 Tensioning screw 8 clamping screws 9 pistons 10 pistons 11 attachment bodies 12 through holes 13th entry 14 Positioning element 14a Support surface 15 Plant area 16 Plant area 17 Exclusion 18 compression spring 19 bore Paragraph 20 21 expansion bushing 22 Printing room 23 Pressure medium channel 24 Tensioning screw

Claims

[1] Positioning device comprising a base body (1) defining a longitudinal axis (X) and an actuating element (2) held on the base body (1), wherein the actuating element (2) spans a front end face (1a) of the base body (1) such that a pressure chamber (3) is formed between the front end face (1a) of the base body (1) and the actuating element (2), which can be pressurized with a pressure medium via at least one fluid channel formed in the base body (1), and wherein the wall of the actuating element (2) is designed as an elastic membrane such that pressurization of the pressure chamber (3) causes the actuating element (2) to deform elastically and thus be moved purely axially away from the front end face (1a) of the base body (1), at least in its central region which coincides with the longitudinal axis (X) of the base body (1). characterized bythat the at least one fluid channel is designed as a hydraulic intermediate channel (6) which is closed at its end pointing away from the pressure chamber (3) by a clamping screw (7, 8), wherein the clamping screw (7, 8) is operatively connected to a piston (9, 10) slidably arranged in the hydraulic intermediate channel (6), so that the piston (9, 10) can be moved inwards by turning the clamping screw (7, 8) thereby increasing the pressure in the pressure chamber (3), that a single hydraulic intermediate channel (6) is provided which transitions at its end region pointing away from the pressure chamber (3) into two branch channel sections (6a, 6b), each of which is closed at its end pointing away from the pressure chamber (3) by a clamping screw (7, 8), wherein each clamping screw (7, 8) is operatively connected to a piston (9, 10) slidably arranged in the respective branch channel section (6a, 6b). is, so that the piston (9, 10) is moved by turning the clamping screw (7,8) is displaceable inwards under increased pressure in the pressure chamber (3), and that the clamping screws (7, 8) which close the branch channel sections (6a, 6b) have different thread pitches and / or that the branch channel sections (6a, 6b) have different flow cross-sections. [2] Positioning device comprising a base body (1) defining a longitudinal axis (X) and an actuating element (2) held on the base body (1), wherein the actuating element (2) spans a front end face (1a) of the base body (1) such that a pressure chamber (3) is formed between the front end face (1a) of the base body (1) and the actuating element (2), which can be pressurized with a pressure medium via at least one fluid channel formed in the base body (1), and wherein the wall of the actuating element (2) is designed as an elastic membrane such that pressurization of the pressure chamber (3) causes the actuating element (2) to deform elastically and thus be moved purely axially away from the front end face (1a) of the base body (1), at least in its central region which coincides with the longitudinal axis (X) of the base body (1). characterized by, that the at least one fluid channel is designed as a hydraulic medium channel (6), which is closed at its end pointing away from the pressure chamber (3) by a clamping screw (7, 8), wherein the clamping screw (7, 8) is operatively connected to a piston (9, 10) slidably arranged in the hydraulic medium channel (6), so that the piston (9, 10) can be moved inwards by turning the clamping screw (7, 8) thereby increasing the pressure in the pressure chamber (3), and that several hydraulic medium channels are formed in the base body (1), each opening into a central area of ​​the pressure chamber (3) and each closed at its end pointing away from the pressure chamber (3) by a clamping screw (7, 8), wherein each clamping screw (7, 8) is operatively connected to a piston (9, 10) slidably arranged in the respective hydraulic medium channel (6), so that the piston (9, 10) can be moved inwards by turning the clamping screw (7,8) is displaceable inwards by increasing the pressure in the pressure chamber (3), and that the clamping screws (7, 8) have different thread pitches and / or the hydraulic center channels have different flow cross-sections. [3] Positioning device according to claim 1 or 2, characterized by , that a hydraulic median channel (6) opens centrally into the pressure chamber (3) at its front axial end and runs in particular coaxially to the longitudinal axis (X) in its axially front end region. [4] Positioning device according to one of the preceding claims, characterized by , that the actuating element (2) has a greater wall thickness in its central area which coincides with the longitudinal axis (X) of the base body (1) than in the laterally adjoining areas and is in particular designed as a solid body (2a). [5] Positioning device according to claim 4, characterized by, that the wall of the actuating element (2) is curved starting from the central area which coincides with the longitudinal axis (X), wherein the wall, with increasing distance from the longitudinal axis (X), first approaches the end face of the base body (1) and then moves away from it again. [6] Positioning device according to claim 5, characterized by , that the wall of the actuating element (2) has a thinning in wall thickness at the end of the bend. [7] Positioning device according to one of the preceding claims, characterized by , that the actuating element (2) is cap-shaped, encompassing a cylindrical section (1b) of the base body (1) defining the front end face (1a). [8] Positioning device according to claim 7, characterized by , that the actuating element (2) is screwed onto the cylindrical section (1b) of the base body (1). [9] Positioning device according to claim 7, characterized by, that the cap-shaped actuating element (2) has a circumferential mounting flange (2b) at its rear free edge and is fixed to the base body (1) via the mounting flange (2b), in particular by being screwed in place. [10] Positioning device according to one of claims 7 to 9, characterized by , that an annular gap between the cap-like actuating element and the circumferential wall of the base body (1) is sealed. [11] Positioning device according to any of the preceding claims, characterized by that the actuating element is symmetrical to the longitudinal axis (X) and / or is made of steel and / or titanium. [12] Positioning device according to any of the preceding claims, characterized by, that an attachment body (11) is provided on the front of the base body (1), which is connected to the base body (1), in particular screwed on, that a central, in particular cylindrical, receptacle (13) is formed in the attachment body (11), and that a positioning element (14), in particular piston-like, is inserted into the receptacle (13) and guided axially displaceably therein, wherein the actuating element (2) defines a contact surface (15, 16) on the front of the central area, which comes into contact with a corresponding contact surface (15, 16) on the underside of the positioning element (14), such that the positioning element (14) is axially adjusted when the pressure chamber (3) is actuated by the actuating element. [13] Positioning device according to claim 12, characterized by, that the positioning element (14) has a recess (17) on its rear side, which forms the contact surface (15, 16) for the actuating element, wherein the actuating element engages in the recess (17). [14] Positioning device according to one of claims 12 and 13, characterized by that restoring means are provided which push the positioning element (14) backwards to ensure contact between the contact surfaces (15, 16) of the actuating element and the positioning element (14), even when the pressure chamber (3) is relieved, wherein, in particular, the restoring means have a compression spring (18) which is held in a bore (19) of the attachment body. [15] Positioning device according to one of claims 12 to 14, characterized by , that clamping devices are provided which are designed to fix the positioning element (14) in a predetermined axial position on the attachment body. [16] Positioning device according to claim 15, characterized by that the clamping devices are designed as magnetic clamping devices. [17] Positioning device according to claim 15, characterized by , that the clamping means are designed as hydraulic clamping means and comprise an expansion sleeve (21) which is inserted into the central receptacle (13) of the positioning element (14) in particular from its front end face, wherein at least one pressure chamber (22) is formed between the inner circumferential wall of the receptacle (13) and the expansion sleeve (21), which can be acted upon via a pressure medium channel (23) formed in the attachment body (11) in order to elastically deform the wall of the expansion sleeve (21) inwards in the direction of the positioning element (14) and thus fix the positioning element (14). [18] Positioning device according to claim 17, characterized by, that the pressure medium channel (23) is closed at its end furthest from the pressure chamber (22) by a clamping screw (24), wherein the clamping screw (24) is operatively connected to a clamping piston arranged to be slidable into the pressure medium channel (23), so that the clamping piston can be moved inwards into the pressure medium channel (23) by turning the clamping screw (24) while increasing the pressure in the pressure chamber (22). [19] Positioning device according to claim 17 or 18, characterized by , that a pressure chamber (22) is provided which extends in a ring shape around the expansion sleeve (21), or that several pressure chambers are provided which are positioned evenly distributed along the circumference of the expansion sleeve (21).

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