WO2005032747A1

WO2005032747A1 - Clamping device with radially movable clamping segments

Info

Publication number: WO2005032747A1
Application number: PCT/SE2004/001381
Authority: WO
Inventors: Mats ÅSBERG
Original assignee: Sandvik Intellectual Property Ab
Priority date: 2003-10-07
Filing date: 2004-09-27
Publication date: 2005-04-14
Also published as: SE0302644L; SE527239C2; SE0302644D0

Abstract

The present invention relates to a clamping device (1) for a tool holder (5), which comprises a tubular shaft (17) having at least two concave, abutment surfaces (18a) facing away from the free end of the tubular shaft (17), the clamping device (1) and the tool holder (5) being intended to be received from separate directions in a first through hole (20) of a coupling unit (3), and that the clamping device (1) comprises a drawbar (7) as well as means (10) for imparting the drawbar (7) an axial displacement in relation to the coupling unit (3). Characteristic of the clamping device (1) according to the present invention is that the clamping device (1) comprises at least two clamping segments (16), which are formed to move radially outwards or inwards upon a relative motion between the drawbar (7) and the clamping segments (16), and that the clamping segments (16) have convex abutment surfaces (33) that have a shape mating to the concave abutment surfaces (18a).

Description

CLAMPING DEVICE

Technical Field of the Invention The present invention relates to a clamping device for a tool holder, which comprises a tubular shaft having at least two concave abutment surfaces facing away from the free end of the tubular shaft, the clamping device and the tool holder being intended to be received from separate directions m a first through hole of a coupling unit, and that the clamping device comprises a drawbar as well as means for imparting the drawbar an axial displacement m relation to the coupling unit

Prior Art By US-A-4 726 268 a clamping device is previously known, which is intended to clamp a tool holder having a tubular shaft, the shaft being provided with two diametrically arranged concave, cylindrical abutment surfaces. For this purpose, the device comprises two radially displaceable clamping jaws, which may be brought to move to or from each other. The displacement of the clamping jaws is effected by rotation of an element, which is threaded in two directions and is received in threaded holes in the respective clamping jaw. The rotation is normally carried out manually by means of a hex socket wrench. Upon displacement radially outward of the clamping jaws, these will come to engagement with the concave, cylindrical abutment surfaces, whereby a clamping of the tool holder takes place. In that connection, the clamping jaws move purely radially, I e , no axial displacement of the clamping jaws takes place in connection with the clamping operation. By US-A-5 466 102 a clamping device is previously known, which is intended to clamp a tool holder having a tubular shaft, the shaft being provided with an internal conical abutment surface, which extends around the entire internal circumference of the shaft. The clamping device comprises two diametrically arranged clamping jaws, which are displaceable radially outward during influence of a sphere that is displaced in the direction of the tool holder. In this case, therefore, it is not a question of two diametrically arranged concave, abutment surfaces, which is a prerequisite for the clamping device according to the present invention.

Objects and Features of the Invention A primary object of the present invention is to provide a clamping device of the kind defined in the introduction, said clamping device providing a substantially more stable clamping of the tool holder than the known technique that employs spherical elements in the clamping mechanism. Another object of the present invention is that the clamping device should fit to a tool holder available on the market and marketed under the denominations KM 40 and VM-40. At least the primary object of the present invention is realised by means of a clamping device having the features defined in the subsequent independent claim 1. Preferred embodiments of the invention are defined in the dependent claims .

Brief Description of the Drawings Below, an embodiment of the invention will be described, reference being made to the accompanying drawings, where: Fig. 1 shows an exploded view in perspective, obliquely from the front, of a clamping device according to the present invention, a coupling unit as well as a tool holder; Fig. 2 shows an exploded view in perspective, obliquely from behind, of the components included in Fig. 1 ; Fig. 3 shows an exploded view in perspective, obliquely from the front of solely a clamping device according to the present invention; Fig. 4 shows a perspective view of a clamping segment included in the clamping device; Fig. 5 shows a perspective view, from another direction, of the clamping segment according to Fig. 4 ; Fig. 6 shows a side view of the clamping device according to Fig. 3 in an assembled state; Fig. 7 shows a perspective view, obliquely from the front, of the clamping device according to Fig. 6; Fig. 8 shows a section through the clamping device according to the present invention, the coupling unit and the tool holder, the clamping device being in an inactive state and received m a housing; and Fig. 9 shows a section corresponding to Fig. 8, the clamping device being in an active state.

Detailed Description of a Preferred Embodiment of the Invention In Figs. 1 and 2, a clamping device 1 according to the present invention, a coupling unit 3 as well as a tool holder 5 are shown. The clamping device 1 and the tool holder 5 are intended to be inserted in the coupling unit 3 from opposite directions, and then a coupling of the tool holder 5 and the clamping device 1 takes place. The clamping device 1 comprises a drawbar 7, which, in the area of the end thereof facing away from the coupling unit 3, is provided with a through opening 9, which extends transverse to the axial extension of the drawbar 7. A cam 10 is intended to cooperate with the opening 9 m order to displace the drawbar 7 axially. In the clamping device, a whole ring 11 as well as two ring halves 12 are also included, each one of the ring halves 12 having an axially directed flange 12a, which is intended to cooperate with the inside of the whole ring 11 when the ring halves 12 are mounted in the active position. The constructive design of two ring halves 12 is due to mounting-technical reasons. Adjacent to the whole ring 11, a spring package 13 included in the clamping device 1 is arranged, one end of the spring package 13 abutting against the whole ring 11 while the other end of the spring package 13 abuts against an abutment 14 of the drawbar 7, see Fig. 6. In the clamping device 1 according to the present invention, two circular cylindrical segments 15 are also included, said segments 15 being intended to abut against an intermediate portion 6 of the drawbar 7, said intermediate portion 6 being defined by an external first circular-cylindrical surface. Together, the segments 15 do not surround the drawbar 7. In the gaps being present between the circular cylindrical segments 15, in the direction of circumference of the intermediate portion 6, two clamping segments 16 are arranged, said clamping segments 16 being described more in detail below. As is most clearly seen in Fig. 2, the drawbar 7 also has a head 4, which is located at the opposite end of the drawbar 7 m relation to the end where the opening 9 is situated. The head 4 has a greater diameter than the intermediate portion 6, the transition between the head 4 and the intermediate portion 6 consisting of a first conical surface 8. The tool holder 5 is only schematically shown m Figs. 1 and 2, i.e., the tool carried by the tool holder 5 is omitted. The tool holder 5 is of the type that has a tubular shaft 17, said shaft 17 being externally slightly conical. The shaft 17 is provided with two diametrical openings 18, only one of which being visible n Fig. 1 while both are visible m Fig. 2. In the part of each opening 18 facing the free end of the tubular shaft 17, a second concave, circular-cylindrical surface 18a is formed, which is facing away from the free end of the tubular shaft 17. The tool holder 5 also comprises two slots 19, which intersect the free end of the tubular shaft 17. The slots 19 are diametrically arranged in the tubular shaft 17 and preferably one individual slot 19 is located halfway between the openings 18 m the direction of circumference of the tubular shaft 17. The coupling unit 3 has a first through hole 20, in which the clamping device 1 and the tool holder 5 are intended to be inserted from separate directions when the clamping device 1 and the tool holder 5 shall be coupled together. The coupling unit 3 also comprises an abutment surface 21, see Fig. 2, adjacent to the first through hole 20, the abutment surface 21 facing the drawbar 7 and being intended to cooperate with the ring halves 12 of the drawbar 7. The coupling unit 3 is also provided with means for adjusting the cutting edge height, see Fig. 1, said means comprising a guide 22 as well as a screw 23, which is received inside the guide 22. The guide 22 has two axially spaced-apart portions 24 and 25, the portion 25 defining the free end of the guide 22 being eccentric in respect of a longitudinal centre axis of the guide 22 In the embodiment illustrated, the guide 22 is provided with cross recesses 26, wherein the guide 22 may be rotated by means of a screwdriver or the like when the guide 22 is introduced into a second through hole 27 of the coupling unit 3. When the guide 22 has been rotated to the desired position, the guide 22 is fixed by means of the screw 23, which expands the guide 22 in the second hole 27. In Figs. 4 and 5, a clamping segment 16 is shown more in detail, the clamping segment 16 having a third circular-cylindrical surface 30, which, when the clamping segment 16 is in the inactive position, is intended to abut against the first circular-cylindrical surface that constitutes the intermediate portion 6 of the drawbar 7. The clamping segment 16 also comprises a fourth circular-cylindrical surface 31, which has an axially shorter extension than the third circular-cylindrical surface 30 The fourth circular-cylindrical surface 31 extends between the third circular-cylindrical surface 30 and a first free end of the clamping segment 16. In the active position, the fourth circular-cylindrical surface 31 is intended to cooperate with the first circular-cylindrical surface 6 of the drawbar 7. The imaginary centre axes assigned to the two circular-cylindrical surfaces 30, 31 intersect each other at a certain angle. The clamping segment 16 also comprises a second conical surface 32, which extends between the third circular- cylindrical surface 30 and a second free end of the clamping segment 16. In the active position, the second conical surface 32 is intended to cooperate with the first conical surface 8 of the drawbar 7. The third circular-cylindrical surface 30, the fourth circular-cylindrical surface 31 and the second conical surface 32 are all concave and located on the same side of the clamping segment 16. The clamping segment 16 also comprises a fifth convex, circular-cylindrical surface 33, which in the active position is intended to cooperate with the second circular-cylindrical surface 18a of each one of the openings 18. The fifth convex, circular-cylindrical surface 33 starts from one end of the clamping segment 16 and extends a distance in the axial direction of the clamping segment 16. The clamping segment 16 also comprises an intermediate first protruding portion 34, which is located approximately at the middle of the clamping segment 16, as seen in the axial direc- tion thereof, the protruding portion 34 generally extending transverse to the axial extension of the clamping segment 16. The clamping segment 16 also comprises a second protruding portion 35, which is arranged in the area of the end of the clamping segment 16 that is facing away from the fifth circular-cylindrical surface 33. The second protruding portions 35 generally have an extension transverse to the axial extension of the clamping segment 16. The two protruding portions 34 and 35 are located at some distance from each other in the axial direction of the clamping segment 16. The fifth circular-cylindrical surface 33, the first protruding portion 34 and the second protruding portion 35 are all located on the same side of the clamping segment 16, said side being opposite the side where the third circular-cylindrical surface 30, the fourth circular-cylindrical surface 31 and the second conical surface 32 are located. The cam 10 included in the clamping device 1 according to the present invention is rotationally fixedly carried on a shaft or the like, a socket head 40 being carried on one end of the shaft By means of a hex socket wrench, the shaft and thereby also the cam 10 can be turned. Adjacent to the socket head 40, a cam stop 41 is arranged, the cam stop, formed as a pulley 41, cooperating with a groove in the socket head 40. The cam stop 41 enables the socket head 40 to be rotated an angle of 180°, i.e., half a revolution. In Figs. 6 and 7, a side view and a perspective view, respectively, are shown of the clamping device 1 in the assembled state. In that connection, the ring halves 12 form a whole ring that cooperates with the whole ring 11. The ring 11 and the ring halves 12 surround the clamping segments 16 as well as the circular cylindrical segments 15. The ring halves 12 and the clamping segments 16 have a force-transferring cooperation that will be described more m detail m connection with Figs. 8 and 9. This enables a mutual conveying to take place between the clamping segments 16 and the ring halves 12 when the ring halves 12 are displaced in the axial direction. In the assembled state of the clamping device 1 shown in Figs. 6 and 7, the spring package 13 abuts against the whole ring 11 and aims to displace the same, and also the ring halves 12 to the left in Fig. 6, the ring 11 m the position shown in Fig. 6 being displaced maximally towards the left, which is indicated by the clamping segments 16 assuming the radially outer^¬ most, active positions thereof. In Figs. 8 and 9 a section through a housing 45, through the clamping device 1 that is received in the housing 45, through the coupling unit 3 and through the tool holder 5 is shown. In that connection, the coupling unit 3 is fixed at the housing 45. The second protruding portion 35 of the clamping segments 16 is received in an internal groove 12b, see Fig 3, in the ring halves 12 when the clamping segment 16 is mounted on the drawbar 7. In that connection, the clamping segment 16 may either assume an inactive position according to Fig. 8, l e , when the second circular-cylindrical surface 30 of the clamping segment 16 abuts against the first circular-cylindrical surface 6 of the drawbar 7. In Fig. 9, the clamping segment 16 assumes an active position, i.e., the fourth circular- cylindrical surface 31 abuts against the first circular-cylindrical surface 6 of the drawbar 7 and the first conical surface 8 abuts against the second conical surface 32 of the clamping segment 16. In the position shown in Fig. 8, the cam 10 has displaced the drawbar 7 maximally towards the left, which means that the ring halves 12 have come to abutment against the abutment surface 21 of the coupling unit 3. In that connection, the clamping segments 16 assume the radially innermost positions thereof, the third circular-cylindrical surface 30 of the clamping segment 16 abutting against the first circular-cylindrical surface 6. As is seen in Fig. 8, the retracted positions of the clamping segments 16 entail that the tubular shaft 17 of the tool holder 5 may be pushed into the first hole 20 of the coupling unit 3 In that connection, the guide 22 of the coupling unit 3 will be received in one of the slots 19 of the tubular shaft 17. Thereby, the tubular shaft 17 assumes a correct position in the first through hole 20 of the coupling unit 3 and the diametrically located openings 18 are exactly opposite the end of the clamping segments 16 that is facing the head 4 of the drawbar 7. In Fig. 9 the clamping device 1 according to the present invention is shown in the active state. In order to transfer the clamping device 1 from the inactive state according to Fig. 8 to the active state according to Fig. 9, the cam 10 is rotated approximately half a revolution, the drawbar 7 being displaced towards the right in Fig. 9. In that connection, the intermediate portion 6 of the drawbar 7 will be displaced m relation to the clamping segments 16, since the spring package 13 exerts a resisting force on the clamping segments 16, via the whole ring 11 and the ring halves 12. The first conical surface 8 of the drawbar 7 will in that connection cooperate with the second conical surface 32 of the clamping segment 16, the relative displacement between the drawbar 7 and the clamping segments 16 resulting in the fifth convex, circular-cylindrical surface 33 of each one of the clamping segments 16 coming to abutment against the second concave, circular-cylindrical surface 18a of each one of the diametrical openings 18. Since the fifth circular-cylindrical surface 33 and the second circular-cylindrical surface 18a have a shape mating to each other, in principle a surface contact takes place between said surfaces. Generally, the fifth circular-cylindrical surface 33 and the second circular-cylindrical surface 18a have the same radius of curvature, however the tolerances are so chosen that the clamping segment 16 does not get caught in the opening 18. In connection with the above-described co-operation between the fifth circular-cylindrical surface 33 and the second circular-cylindrical surface 18a being established, the first protruding portion 34 of the clamping segment 16 will come to abutment against the inside of the tubular shaft 17, see Fig. 9, it being guaranteed that the clamping segment 16 assumes a correct position so that a satisfactory surface contact is established between the fifth circular-cylindrical surface 33 of the clamping segment 16 and the second circular-cylindrical surface 18a of the opening 18. Upon continued axial displacement of the drawbar 7 towards the right in Fig. 9, which displacement is effected by additional rotation of the cam 10, the clamping segments 16 will convey the tubular shaft 17, and thereby the entire tool holder 5, m said axial displacement. Thereby, it is guaran- teed that a satisfactory shoulder stop is established between the tool holder 5 and the coupling unit 3. Thereby, the coupling of the tool holder 5 with the clamping device 1 is completed. When the tool holder 5 should be detached from the clamping device 1, it is proceeded in the converse way, i.e., the drawbar is displaced from the position shown in Fig. 9 to the position shown in Fig. 8, the clamping segments 16 changing from the active position to the inactive position, which allows the tool holder 5 to be removed from the coupling unit 3.

Feasible Modifications of the Invention In the above-described embodiment, the tool holder 5 is provided with two concave, circular-cylindrical surfaces 18a and the clamping device 1 has two clamping segments 16, which have convex, circular-cylindrical surfaces (33), which are intended to cooperate with the concave, circular-cylindrical surfaces 18a. However, within the scope of the invention, it is also conceivable that the tool holder has more than two concave, circular-cylindrical surfaces 18a and that the number of clamping segments 16, each having a convex, circular- cylindrical surface 33, is adapted to the number of concave, circular-cylindrical surfaces 18a. In the above-described embodiment, a plurality of surfaces are circular cylindrical, while it is within the scope of the invention feasible that, for instance, the co-operating surfaces of the tool holder and the clamping segments are not circular cylindrical but adapted to each other for a satisfactory co-operation.

Claims

1. Clamping device (1) for a tool holder (5), which comprises a tubular shaft (17) having at least two concave, abutment surfaces (18a) facing away from the free end of the tubular shaft (17) , the clamping device (1) and the tool holder (5) being intended to be received from separate directions in a first through hole (20) of a coupling unit (3) , and that the clamping device (1) comprises a drawbar (7) as well as means (10) for imparting the drawbar (7) an axial displacement in relation to the coupling unit (3), c h a r a c t e r i z e d in that the clamping device (1) comprises at least two clamping segments (16) , which are formed to move radially outwards or inwards upon a relative motion between the drawbar (7) and the clamping segments (16) , and that the clamping segments (16) have convex abutment surfaces (33) that have a shape mating to the concave abutment surfaces (18a) .

2. Clamping device (1) according to claim 1, c h a r a c- t e r i z e d in that the convex abutment surfaces (33) of the clamping segments (16) have substantially the same radius of curvature as the concave abutment surfaces (18a) of the tool holder (5) .

3. Clamping device (1) according to claim 1 or 2 , c h a r a ct e r i z e d in that the abutment surfaces (33) of the clamping segments (16) and the abutment surfaces (18a) of the tool holder (5) are circular cylindrical.

4. Clamping device (1) according to any one of the preceding claims, c h a r a c t e r i z e d in that it comprises resilient means (13), which aim to displace the clamping segments (16) in relation to the drawbar (7) to a radially outermost position of the clamping segments (16) .

5. Clamping device (1) according to any one of the preceding claims, c h a r a c t e r i z e d in that the clamping segments (16) are received in a part of the drawbar (7) that has a reduced diameter.

6. Clamping device (1) according to any one of the preceding claims, c h a r a c t e r i z e d in that ring-shaped means (11, 12) surround the clamping segments (16) in a portion (35) that principally does not move radially.

7. Clamping device according to claim 6, c h a r a c t e ri z e d in that the ring-shaped means (11, 12) and the clamping segments (16) have a force-transferring co-operation in the axial direction of the drawbar (7) .

8. Clamping device (1) according to any one of the preceding claims, c h a r a c t e r i z e d in that the means for imparting the drawbar an axial displacement consists of a cam (10) .

9. Clamping device (1) according to claim 8, c h a r a c- t e r i z e d in that the cam (10) is assigned a rotation lim- iter (41) .