TOOL HOLDING FIXTURE

Abstract

The invention relates to a tool holding fixture (1) for rotationally driven tools (2), said tool holding fixture comprising a rotationally symmetrical holding body (3) which has a front clamping region (4) having a receiving opening (5) for a tool shank (6) of the tool (2), and a rear holding region (7) to be held in a work spindle of a machine tool. In order to achieve a reduced mass, a lower mass moment of inertia and at the same time high stiffness, a sleeve (11), made of a fiber reinforced plastic, is disposed in at least the front clamping region (4).

Claims

1. A tool holding fixture (1) for rotationally driven tools (2), comprising a rotationally symmetrical holding body (3), the holding body (3) having: (a) a front clamping region (4) with a receiving opening (5) for a tool shank (6) of the tool (2), and (b) a rear holding region (7) to be held in a work spindle of a machine tool, and wherein the tool holding fixture further comprises a sleeve (11), made of a fiber reinforced plastic, disposed in at least the front clamping region (4).

2. The tool holding fixture of claim 1, wherein the sleeve (11) is mounted on the front clamping region (4) of the holding body (11), and wherein the holding body (11) comprises metal.

3. The tool holding fixture of claim 1, wherein the sleeve (11) is shrunk onto the front clamping region (4).

4. The tool holding fixture of claim 1, wherein a positive connection is produced between the holding body (3) and the sleeve (11).

5. The tool holding fixture of claim 1, wherein the tool holding fixture is constructed of several parts in a modular design, and wherein the rotationally symmetrical holding body (3) and the sleeve (11) form at least one module.

6. The tool holding fixture of claim 1, wherein the sleeve (11 is axially prestressed by at least one additional module.

7. The tool holding fixture of claim 1, wherein the sleeve (11) comprises a coolant conducting system (28).

8. The tool holding fixture of claim 7, wherein the coolant conducting system (28) comprises a coolant channel having a course that is composed partly of straight and curved regions.

9. The tool holding fixture of claim 7, wherein the coolant conducting system is partially defined by the holding body (11 and the sleeve (4).

10. The tool holding fixture of claim 1, wherein the sleeve (11) forms the front clamping region (4) and at least one portion of a central region (9) of the holding body (3).

11. The tool holding fixture of claim 10, wherein the rear holding region (7), an outer portion (23) of the central region (9) and a cover member (24) on the front end face of the holding body (3) are made of steel.

12. The tool holding fixture of claim 1, wherein the holding body (3) comprises consists of a thin-walled insert, which is completely enclosed by a sleeve (11), forming the entire outer contour of the tool holding fixture (1).

13. The tool holding fixture of claim 1, wherein the holding body (3) or the sleeve (11) has a receptacle (26) for a screwing-in tool (27).

14. The tool holding fixture of claim 13, wherein the receptacle (26) is designed as a double cone.

15. The tool holding fixture of claim 1, wherein the front clamping region (4) is radially deformable by a clamping element (18), surrounded by the sleeve (11).

16. The tool holding fixture of claim 15, wherein the clamping element (18) is designed as a clamping bushing that can be axially displaced on a conical front portion (12) of the front clamping region (4) and that has a conical inner surface (19) that is adapted to the conical outer surface of the front portion (12).

17. The tool holding fixture of claim 16, wherein the clamping element (18) is adjustable by means of an adjusting ring (20), designed as an inner threaded ring.

18. The tool holding fixture of claim 17, wherein the adjusting ring (20) interacts with an outer thread (21) on the clamping element (18) and with an outer thread (22) on a rear portion (13) on the clamping region (4), with the rear portion having an enlarged diameter.

19. The tool holding fixture of claim 1, wherein the sleeve (11) has one or more cavities in its interior.

20. The tool holding fixture of claim 19, wherein the interior sleeve cavities are formed by a sintering process in a layer, extending longitudinal to the axis of rotation, between two regions made of fiber reinforced plastic.

21. The tool holding fixture of claim 1, wherein the sleeve (1) is applied by a wrapping and/or braiding process.

22. The tool holding fixture of claim 21, wherein the front clamping region (4) has a plurality of needle-shaped and/or pin-shaped elements (31) that penetrate into the sleeve (11) during the winding and/or braiding process.

23. The tool holding fixture of claim 1, wherein the sleeve (11) is made of a plastic, reinforced with carbon fibers, glass fibers or aramid fibers.

Description

[0024] Additional features and advantages of the invention will become apparent from the following description of preferred exemplary embodiments with reference to the drawings. The drawings show in:

[0025] FIG. 1 a first exemplary embodiment of a tool holding fixture in a longitudinal view.

[0026] FIG. 2 a second exemplary embodiment of a tool holding fixture in a longitudinal view.

[0027] FIG. 3 a third exemplary embodiment of a tool holding fixture in a longitudinal view.

[0028] FIG. 4 a fourth exemplary embodiment of a tool holding fixture in a longitudinal view.

[0029] FIG. 5 a fifth exemplary embodiment of a tool holding fixture in a longitudinal view; and

[0030] FIG. 6 a sixth exemplary embodiment of a tool holding fixture in a longitudinal view.

[0031] FIG. 1 shows a tool holding fixture 1, which is provided in this embodiment with an HSK interface, for non-positive holding of drilling, milling, reaming tools or any other rotationally driven tools 2. In the embodiment shown, the tool holding fixture 1 is designed as a thermal chuck and includes a rotationally symmetrical holding body 3, which on its tool-sided front end has a clamping region 4 with a receiving opening 5 for a tool shank 6 of the tool 2 and on its machine-sided rear end has a rear holding region 7, which is conical in this embodiment and has a conical outer clamping surface 8 to be held in a work spindle of a machine tool. Furthermore the holding body 3, made of steel, also has a cylindrical central region 9 with a gripper groove 10 for engagement with a tool changer. A sleeve 11, made of a carbon fiber reinforced plastic (CFRP) or any other fiber reinforced plastic, is disposed on the front clamping region 4 of the holding body 3.

[0032] In the embodiment shown in FIG. 1, the CFRP sleeve 11 is arranged by means of a press fit on the front clamping region 4 of the holding body 3 made of metal. In order to mount the CFRP sleeve 11, the holding body 3 is cooled down to, for example, 180 deg. C. Then the sleeve 11, which is at room temperature, can be mounted on the front clamping region 4 that contracts due to it cooling down. If the holding body 3 is reheated and, as a result, expands, the sleeve 11 is fixed. At the same time the ratio of the inside diameter of the sleeve 11 to the outside diameter of the front clamping region 4 is selected in such a way that the sleeve 11 is held firmly under radial prestress on the front clamping region 4, when, having cooled down, the holding body 3 is heated again to room temperature and expands radially.

[0033] As an alternative or in addition to the formation of a press fit, the holding body 3 and the sleeve 11 may be connected to each other by means of a form fit. In a preferred embodiment the holding body 3 has irregularities, for example, in the form of radially outwardly directed lamellae, into which the sleeve 11 is pressed. In this way a positive connection can be achieved through an elastic deformation of the components. The sleeve 11 has preferably recesses, which correspond to the irregularities of the holding body 3 and which enter into a positive engagement with each other as early as in the unstressed state.

[0034] In another preferred embodiment the sleeve is not slid on as a prefabricated element, but rather is applied in several layers in a wrapping process. For this purpose the holding body 3 has in its clamping region 4 preferably a plurality of needle-shaped and/or pin-shaped elements, which are firmly connected to the holding body and which penetrate into the sleeve during the wrapping process and, in so doing, produce a very stable composite that in the ideal state has enhanced damping properties. It will be clear to the person skilled in the art that the term wrapping process includes a plethora of methods, known from the prior art, such as, for example, weaving, and, in particular, braiding a sleeve of more than one web of fiber reinforced plastic.

[0035] As shown in FIG. 1, the front clamping region 4 is made relatively slim and thin walled compared to the outside diameter of the sleeve 11. In this embodiment the clamping region 4 includes a slightly conical, slender front portion 12 with the receiving opening 5, disposed therein, for the tool shank 6 and a widened rear portion 13. The sleeve 11 extends over the slimmer front portion 12, the widened rear portion 13 and engages with a recess 14 on the front end face of the cylindrical central region 9 of the holding body 3. In the embodiment shown, the tool holding fixture 3 has a continuous opening 15 with an expanded rear cavity 16 in the rear holding region 7. On the inside of the cavity 16 there are clamping surfaces 17 for collets or other clamping elements for internal clamping of the tool holding fixture 1 in a work spindle.

[0036] In contrast to conventional thermal chucks, in which the tool holding fixture 1 is first heated in order to clamp the tools and then has to be cooled down again, in this case for clamping purposes the tool 2 is first cooled down inside the tool holding fixture 1. When the diameter of the tool shank 6 has decreased due to it cooling down, the tool 2 can be inserted into the receiving opening 5. If, after insertion, the tool 2 reaches room temperature again and, in so doing, expands again, then the tool shank 6 is fixed in the receiving opening 5. In this case, too, the ratio of the inside diameter of the receiving opening 5 to the outside diameter of the tool shank 6 is selected in such a way that the tool 2 is firmly held in the receiving opening 5 of the tool holding fixture 1 at the standard operating temperatures.

[0037] In order to release the tool 2, the entire unit consisting of tool holding fixture 1 and tool 2 is cooled down. Depending on the fiber orientation, the inside diameter of the sleeve 11 remains virtually unchanged. At the same time the thin-walled front portion 12 forms with the sleeve 11 an interference fit assembly: in other words, is under radial prestress from the outside. Although the cooling down process in the front portion 12 leads to a reduction in the volume, once the pre-stress is relaxed, the effect is that the receiving opening 5 becomes smaller. Since the diameter of the tool shank 6 is decreased by the cooling process, the diameter of the receiving opening 5 remains the same, the tool 2 can be removed.

[0038] FIG. 2 shows an additional embodiment of a tool holding fixture 1. This tool holding fixture 1 comprises a holding body 3, which is made of steel and which has a front clamping region 4 for clamping the tool 2; and a rear holding region 7 to be held in a work spindle of a machine tool. In this case, too, the front clamping region 4 is formed by a conical, slender front portion 12 and a rear portion 13 with a slightly enlarged diameter. However, in this embodiment the tool 2 is not clamped by shrinking, but rather by radial compression of the conical, slender front portion 12. The radial compression of the front portion 12 is carried out by a clamping element 18 that can be axially displaced on the front portion 12. The clamping element 18, which is designed as a clamping bushing in this embodiment, can be axially adjusted relative to the holding body 3 and has a conical inner surface 19 that is adapted to the conical outer surface of the front portion 12. The bushing-shaped clamping element 18 that is also thin walled in the front region, comprises on its outside a sleeve 11, which is made of CFRP or any other fiber reinforced plastic and which is also used for reinforcement.

[0039] The axial adjustment of the clamping element 18, surrounded by the sleeve 11, relative to the holding body 3 is carried out by an adjusting ring 20, which is designed as a threaded ring. Said adjusting ring interacts with an outer thread 21 on the clamping bushing 18 and with an outer thread 22 on the rear portion of the clamping region 4, with the rear portion having a diameter that is enlarged compared to the front portion 12. The two outer threads have different slopes, so that by rotating the adjusting ring 20, the bushing-shaped clamping element 18 can be moved either to the rear in the direction of the holding region 7 in order to clamp the tool 2 or can be moved to the front in order to release the tool 2. The axial adjustment of the clamping element 18 can be carried out in the manner of a turnbuckle with a right and left hand thread or by means of similar adjustments.

[0040] In the embodiment shown in FIG. 3, almost the entire front clamping region 4 and also a large part of the cylindrical central region 9 is formed by a sleeve 11, made of CFRP or any other fiber reinforced plastic. In this embodiment only the holding region 7, which is highly stressed upon insertion of the tool holding fixture into the work spindle 1; an outer portion 23 of the cylindrical central region 9; and a cover member 24, disposed on the front end face of the tool holding fixture, are made of steel. This tool holding fixture 1 is also designed as a thermal chuck, in which the tool 2 is cooled down for insertion.

[0041] In order to increase the friction between the tool shank 6 and the sleeve 11, both the outer surface of the tool shank 6 and the inner surface of the sleeve 11 can be processed. This processing can be done, for example, by mechanically or chemically roughening the surfaces or by applying a coating. It goes without saying that similar methods can be used to connect the base body 3 and the sleeve 11 to each other.

[0042] FIG. 4 shows another exemplary embodiment of a tool holding fixture 1 that is provided with a sleeve 11 made of fiber reinforced carbon. In this embodiment the holding body 3 consists of a thin-walled insert that is made of metal, which is completely enclosed by a sleeve 11 that is made of fiber reinforced carbon and that forms the entire outer contour of the tool holding fixture 1. The outer contour of the front clamping region 4 and also the outer contour of the rear holding region 7 are formed by the sleeve 11. The holding body 3, which is designed as an insert, also has a slender, thin-walled front portion 12 with a receiving opening 5 for a tool shank 6 of a tool 2. Inserts 25, which are made of metal, can be embedded on the outside of the sleeve 11, in order to form the gripper groove 10.

[0043] In the embodiment shown in FIG. 5, the holding body 3 has in the front clamping region 4 a receptacle 26 for a screw-in tool 27. The receptacle 26 is designed as a double cone in the embodiment shown. The holding body 3 and/or the sleeve 11 is/are provided with a coolant conducting system 28 in the form of boreholes 29, passages 30, grooves, gaps, or the like.

[0044] In the embodiment of FIG. 6, the sleeve 11 is applied by means of a wrapping process. The front clamping region 4 of the holding body 3 has a plurality of needle-shaped and/or pin-shaped elements 31, which penetrate into the sleeve 11 during the winding process. In this embodiment, too, the holding body 3 in the front clamping region 4 comprises a receptacle 26, designed, for example, as a double cone, for a screw-in tool 27.

[0045] In other embodiments, which are not shown separately herein, the tool holding fixture 1 may also be designed as a Weldon tool holder or as a collet chuck. It goes without saying that the invention is not restricted to HSK tool holding fixtures. It is also possible to provide SK, JIS, BT, ABS, Capto or other suitable interfaces in a corresponding manner on the holding body 3.