GB2096045A

GB2096045A - A tool holder

Info

Publication number: GB2096045A
Application number: GB8207603A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1981-04-03
Filing date: 1982-03-16
Publication date: 1982-10-13
Also published as: CH658015A5; DE3205063A1; GB2096045B; DE3205063C2

Abstract

A tool holder 5 for the coupling of percussive and/or rotary tools to hand machine tools is provided in which the shank 13 of the tool is accepted in a coupling sleeve 6 in the tool holder 5. A ball 16 is displaceably arranged in a radial passage 17 in the coupling sleeve 6 the ball engaging in a groove-like recess 15 in the shank 13 closed at both ends in the direction of the rotary axis of the tool. The forward region of the passage 17 remote from the hand machine tool is so covered by a portion 20 of a sliding sleeve 7 located in its rest position that the ball 16 is prevented from moving radially. The ball is held in the said forward region by a spring loaded ring 22. The ring is made as a flat sheet metal ring which contacts the ball over a region situated near to the wall of its bore. The flat sheet metal ring 22 can be tilted away by the ball 16 from a tool shank 13 pushed into the tool holder 5, rearwardly towards the hand machine tool, whereupon the ball arrives in a position in which it can be deflected radially outwards. Thereafter, the tool shank can be pushed completely into the tool holder. Then, the spring loaded ring permits the ball to snap into the recess 15 located in the tool shaft once again and pushes it beneath the portion 20 of the sliding sleeve once again which holds the ball in its rest position. <IMAGE>

Description

SPECIFICATION A tool holder State of the art The invention orginates from a tool holder according to the preamble to the main claim. Such a tool holder is already known which operates satisfactorily. It has certainly been shown that the ring in the known tool holder fashioned more in the form of a sleeve is somewhat impractical and can be inclined to stick. Thus the handling of this known tool holder can be somewhat difficult.

Advantages of the invention As opposed to this, the tool holder in accordance with the invention comprising the characterising featuresofthe main claim has the advantage that the insertion of the tool shank, which takes place without actuating the sliding sleeve, is substantially faciliated. Moreover, a sheet metal ring may, of course, be produced much more cheaply since its outer periphery is produced with a die and the sheet metal ring is then shaped without removing material.

Advantageous further developments and improvements of the tool holder set forth in the main claim are made possible by the measures set forth in the sub-claims. It is of particular advantage that, with a tool holder for coupling a tool on the shank of which, additional to the axially closed recess, is arranged at least one torque transmitting groove opening at the end of the shank the at least substantially radial flanks of which cooperates with associated surfaces on a rib-like rotary driver in the coupling sleeve, the rotary driver is offset with respect to the centre-line of the opening by about 5 in the direction of rotation of the coupling sleeve.

Thereby, the ball serving for the axial locking of the tool shank is not then loaded by the torque transmitted to the tool even when the torque transmitting groove and/or the rotary driver for the tool holder has relatively high wear.

Furthermore, with a tool holder the coupling sleeve of which is axially movably guided over a region on a driving member transmitting the tool movement wherein the region is determined by the axial extension of a recess arranged on the driving member and in which a radially displaceable ball engages in a bore in the coupling sleeve, it has proved to be very advantageous for the ball by abutting the forward end of the recess in the driving member, preferably formed as a rounded corner, to be prevented from moving radially by a track surface which is carried by the coupling sleeve engaging the ball from the rear end facing the hand machine tool and engaging over the ball radially outwardly in the form of a niche.In this way, the tool holder is not released automatically from the driving member even when it is subjected to severe unbraked axial impacts as can act upon it, for example, during percussive hammering during idling.

Drawing Embodiments of the invention are illustrated in the drawing by way of example with the aid of a plurality of figures and are described in detail in the following specification.

Figure 1 shows a tool holder in longitudinal section arranged on the driving member of a hammer drill, Figure 2 is a cross section through the tool holder according to Il-Il in Figure 1, Figure 3 shows a sheet metal ring, Figure 4 is a longitudinal section through a second embodiment of a tool holder, Figure 5 is a cross section through the tool holder according to V-V in Figure 4, Figure 6 is a longitudinal section through a third embodiment of a tool holder according to Figure 1, and Figure 7 is a longitudinal section through a fourth embodiment of a tool holder according to Figure 1.

Description of the embodiments Of a hammer drill (not shown) only its driving member 1 projecting forward out of the housing can be seen in Figure 1. This driving member is in the form of a tool spindle which experiences a percussive and/or rotary movement. At its free end projecting from the housing of the hammer drill, the driving member 1 has a device for torque transmission in the form of an externally splined shaft 2. The externally splined shaft 2 is intersected by an annular groove 3 extending at right angles around the periphery of the forward end of the driving member 1 and which corresponds to the depth of the depth of the grooves of the externally splined section. The end of the driving member 1 carries a flat abutment surface 4.

The tool holder 5 consists essentially of a coupling sleeve 6 made of steel on the outside of which is guided an axially movable sliding sleeve 7. The sliding sleeve can be made of metal or of plastics.

The coupling sleeve 6 has two successive receiving bores of different diameter coaxial to one another: a rear receiving bore 8 of larger diameter facing the hammer drill which changes into a second receiving bore 9 of smaller diameter issuing at the other forward end. An internal spline 10 is arranged on the inner wall of the larger receiving bore 8 and is associated with the external spline 2 on the driving member 1. A radial bore 11, in which a ball 12 in the form of a locking member is displaceably arranged, is arranged at the end region of the coupling sleeve 6 facing the hammer drill (not shown). The ball 12 engages in the annular groove 3 in the driving member 1 and in this way locks the coupling sleeve 6 to the driving member.On its outside, the radial bore 11 is covered by the rear section of the sliding sleeve 7 whereby the ball 12 is prevented from falling out of the radial bore 11. Due to the width of the annular 3, the coupling sleeve 6 has a predetermined degree of axial freedom with respect to the driving member 1.

The smaller receiver bore 9 issuing at the forward end of the coupling sleeve 6 accepts a tool shank 13 of a tool - for example of a drill. At its rear end, the tool shank 13 has a flat abutment surface provided with a chamfer and which sets axially on the abutment surface 4 on the driving member 1. Axial impacts are transmitted from the driving member 1 to the tool shank 13 through these two mutually contacting abutment surfaces. Two groove-like recesses 15 closed at both ends in the axial direction, are arranged on the outer surface of the tool shank 13 at oppositely arranged positions on a diagonal 14.

Two additional opposite torque transmitting grooves 35 open at the end of the shank 13 are arranged on the tool shank 13 on a diagonal 34 perpendicular to the diagonal 14. Their at least substantially radial flanks cooperate with associated surfaces on the rib-like rotary drivers 36 in the receiving bore 9 of the coupling sleeve 6. The rotary drivers 36 are arranged staggered by about 50 in the sense of rotation of the coupling sleeve 6 with respect to the perpendicular 36' to the centre-line 17' of the passage 17. In this way, it is ensured that the ball 16 is not engaged in torque transmission even with considerable wear on the rotary drivers 36. A ball 16 which is arranged for radial and axial displacement in a radial passage 17 in the coupling sleeve 6, engages in the upper recess 15 in Figure 1 of the drawing.The passage 17 is in the form of an axially parallely extending slot which converges towards the tool axis. At least the rear transverse wall 18 of the passage 17 facing the hammer drill is so inclined by an angle a of about 300 with respect to the plane normal to the tool axis, that the passage 17 is widened radially outwards. Viewed in an axial direction (Figure 1), the passage 17 lies substantially centrally in a level milled out portion 19 in the coupling sleeve 6. The milled portion 19 forms a flat surface which, in Figures 1 and 2, lies perpendicular to the plane of the drawing.

In the illustrated embodiments, the diameter of the ball 16 corresponds to the diameter of the ball 12. As is illustrated in Figure 1, the forward region of the passage 17 remote from the hammer drill is covered by a portion 20 of the sliding sleeve 7 located in its rest position. Moreover, the inner diameter of the portion 20 of the sliding sleeve 7 is so calculated that it prevents radial movement of the ball 16 located in its rest position. The ball is retained in the region covered by the portion 20 of the sliding sleeve 6 located in the rest position by a flat sheet metal ring 22 loaded by a spring 21. The sheet metal ring 22 is located in an annular chamber, which is widened in the forward region by the milled out portion 19, formed between the sliding sleeve 7 and the coupling sleeve 6.At the end facing the hammer drill, the annular chamber is bounded by a shoulder 24 on the coupling sleeve 6 and at the other end by an inner shoulder 25 formed in the bore in the sliding sleeve 7. At the inner shoulder 25, the inner diameter of the sliding sleeve 6 is reduced from that of a region permitting radial displacement of the ball 16 out ofthe recess 15 in the tool shank 13 to that of the portion 20 retaining the ball 16 in its rest position.

The end of the portion 20 forming the inner shoulder 25 and the other end of the portion 20 facing the workpieces are each provided with chamfers which are at an angle of about 400 to the axis.

The flat sheet metal ring 22 is held against the inner shoulder 25 on the sliding sleeve 7 by the spring 21 which is supported against the shoulder 24 on the coupling sleeve 6. Thus, on the one hand, the spring 21 holds the flat sheet metal ring 22 in the position illustrated in Figure 1 and on the other hand holds the sliding sleeve directly in the rest position illustrated in Figure 1. In this position, the forward end of the sliding sleeve remote from the hammer drill abuts against a shaped ring 26 inserted in an annular groove at the forward end of the coupling sleeve 7. The shaped ring 26 is formed as a cup-like protective cap on the base portion of which through which the tool shank 13 passes are formed sealing lips 27 making sealing contact with the tool shank.

An annular rib 28 is formed at the outer end of the shaped ring 26 facing the workpiece. In order to seal the interior of the sliding sleeve 6 and to secure the portion of the shaped ring 26 latched in the annular groove, the foremost region of the sliding sleeve remote from the hammer drill overlaps the shaped ring 26 in an axial direction.

As can be seen from Figure 1, the flat sheet metal ring 22 fils the radial dimension of the annular chamber 23 except for a slight movement clearance.

The diameter of the bore 29 in the sheet metal ring is greater than the outer siameter of the coupling sleeve 7 in that region by an amount of substantially 1 mm. At a number of positions 30, the width of the sheet metal ring is widened along a chord which contacts the outer periphery of the coupling sleeve 6 in that region practically tangentially. In this manner, the sheet metal ring is supported on the outer periphery of the coupling sleeve 6 with a slight movement clearance.

As already referred to above, the flat sheet metal ring 22 retains the ball 16 in the region covered by the portion 20 of the sliding sleeve 7. In addition, it must contact the ball 16 over a region situated near to its bore 29. This region is determined by shaped means formed from a buckled portion 31 similar to a clam shell. This buckled portion is so pushed out of the plane of the sheet metal ring that it overlaps at least to some extent the ball 16 in the direction of the tool axis. As can be seen particularly from Figures 1 and 3, the buckled portion is inclined with respect to the plane of the sheet metal ring by an angle a of 35 ; in the assembled condition, the buckled portion 31 engages the side of the sheet metal ring 22 facing the hammer drill.At the position which bears the buckled portion 31, the sheet metal ring is increased to substantially double width along a chord with respect to the width of the remainder of the sheet metal ring 22. This widening is so arranged in the increased portion of the annular chamber 23 produced by milling out 19 that between the chord forming the precise boundary of the widening 32 and the surface of the flat milling out portion 19, an intermediate space of about 0.5 mm remains (Figure 2).

The operation of the tool holder is as follows: If the tool held in the tool holder Sin Figure 1 and 2 is to be removed from the tool holder, then the sliding sleeve 7 must be pushed towards the rear in the direction of the hammer drill against the force of the spring 21. The ball 16 can then be displaced radially outwards into a forward region 33 of the sliding sleeve 7 to such an extent that it can be removed from the recess 15 in the tool shank 13 and release the latter. The sliding sleeve 7 subsequently released by the operator is then pushed by the spring 21 into the rest position illustrated in Figure 1 once again in which the ball 16 is once again pushed into the illustrated position in Figure 1.

During a fresh insertion of a tool shank 13 the rear end of the tool shank 13 entrains the ball 16 projecting into the receiving bore 9 and forces it against the sheet metal ring 22 and into the buckled portion 31 thereof. The ball 16 moves along the passage 17 and urges the sheet metal ring 22 against the force of the spring 21 in the previous manner so that the sheet metal ring 22 is tilted - since indeed only one ball 16 is provided. The tilt axis extends in the representation according to Figure 1 perpendiculay to the plane of the paper and is located somewhat centrally in the shoulder of the cut 22' in Figure 1.

Since the shoulder of the cut 22' remains substantially in its position, the sliding sleeve 7 cannot deviate from its rest position either. Finally, the ball 16 strikes the inclined transverse wall 18 of the passage 17 on which it is forced radially outwards into the annular chamber 23. In this position it may allow the tool shank 13 to pass until the latter finally arrives once again in the position illustrated in Figure 1. Then the force of the spring 21 tilts the sheet metal ring 22 back into its rest position illustrated in Figure 1 whereby the ball 16 in the buckled portion 31 of the sheet metal ring 22 is again forced along moving beneath the portion 20 of the sliding sleeve 7.

The hammer drill is situated once again in its working position in which all parts are locked - tool shank 13 to the coupling sleeve 7 and the coupling sleeve 7 to the driving member 1. If it is desired to remove the entire tool holder 5 from the driving member 1, then the shaped ring 26 must be removed from its annular groove retaining it so that the sliding sleeve 7 can be pushed completely forwards until finally the ball 12 can be deflected radially outwards out of its radial bore 11.

In operation of the hammer drill, the axial impacts from the driving member 1 are transmitted directly to the tool shank through the mutually contacting abutment surface 4 on the driving member 1 and on the tool shank 13. Thetorque istransmitted from the driving member 1 through the splined connection 2, 10 to the coupling sleeve 7 and from the sleeve through the rotary drivers 36 to the tool shank 13.

Because the diagonal 34 on which the rotary drivers 36 are arranged, is arranged staggered by 5" in the sense of rotation of the coupling sleeve with respect to the perpendicular 36' to the centre-line of the passage 17, there is a closure angle of 12" in the embodiment according to Figure 1 without the ball 16 coming into engagement during driving. In other words: the single ball 16 only serves for axial locking of the tool shank 13 in the tool holder 5 and does not even participate in the transmission of torque even after considerable wear on the torque transmitting devices 35, 36.

The second embodiment of a tool holder 45 illustrated in Figures 4 and 5 and of which only the front portion is illustrated, since the rear portion (not shown) corresponds to the first embodiment, is basically similarly constructed as the first embodiment. In this instance, the tool shank 13 certainly has only one recess 15 which is arranged diagonally opposite to a torque transmitting groove 35 open at the end of the shank. As can be seen from Figure 5, the centre-line 54 of the driving member 76 is, in this case, offset in the sense of rotation by an angle of 5" with respect to the associated centre-line 570 of the passage 57.

The further distinction with respect to the first embodiment of a tool holder 5, lies in the fact that the coupling sleeve 46 is suitable for receiving a driving member 41 which has a substantially larger diameter than the driving member 1 of the first embodiment. That of course means that the receiving bore 48 also has a greater diameter. However, in total, the tool holder 45 is of substantially shorter construction than the first embodiment. Thus, with this embodiment, the passage 57 in the coupling sleeve 46 is also in the form of a conical opening and not in the form of an axially parallel slot as in the first embodiment.Nevertheless, in order to achieve a similar mode of operation with this embodiment as with the first embodiment, it has been necessary to form the annular chamber 63, in which the locking element also formed as a ball 56 in this case, can be deflected radially outwards, differently from the annular space 23 of the first embodiment. Also with this embodiment, the ball 56 is retained in its locking position by a flat sheet metal ring 62 the shape of which is substantially the same as the shape of the sheet metal ring 22 of the first embodiment. Moreover, this sheet metal ring 62 also has a buckled portion 71 which is arranged in a widened portion 72 of the sheet metal ring 62.In the rest position illustrated in Figure 4, the sheet metal ring 62 is held against an inner shoulder 65 on the sliding sleeve 57 formed as a plastics moulding, by a spring 61 formed in this instance as a conical compression spring. In this embodiment, the portion of the sliding sleeve 47 covering the passage 57 is formed by a supporting ring 66 of metal or steel which is inserted in an annular chamber 73 in the sliding sleeve 47 directly in front of the sheet metal ring 62 in the axial direction. In so doing, the supporting ring 66 is held through the sheet metal ring 62 by the spring 61 against a resilient abutment bounding the annular chamber 73 at the front end remote from the hammer drill. In the embodiment illustrated in Figure 4, the resilient abutment is formed by a ring 67 of elastic material, preferably foam material. In the expanded condition, the ring 67 has a square cross-section.

The operation of this second embodiment of a tool holder is substantially the same as that of the first embodiment, the difference from the first embodiment lies in the somewhat different operation when inserting a tool shank 13 which is shown in Figure 4.

As in the first embodiment, when inserting the tool shank 13, the ball 56 is pushed outwardly along the wall of the passage 57 facing the hammer drill. In so doing, the ball 56 presses, on the one hand, against the buckled portion 71 of the sheet metal ring 62 which is then tilted forwards slightly, as in the first embodiment, against the force of the spring 61. At the other end, the supporting ring 66, the outer surface 68 of which is rounded to facilitate the operation, is tilted forwards towards the workpiece.

In so doing, the ring 67 consisting of foam material and forming the resilient abutment, which originally had a square cross section, is deformed into the shape illustrated in the upper region of Figure 4. Due to this tilting towards the rear of the sheet metal ring 62 on the one hand and towards the front of the supporting ring 66 on the other hand, a space is then opened into which the ball 56 can be radially outwardly displaced. When the tool shank 13 is finally pushed up to the axial abutment of the driving member 41 in the small receiving bore 49, the ball 56 returns to the locking position in which it engages in the groove 15 in the tool shank 13 (see Figure 1).

With a tensile load outwardly of the tool holder 45 exerted on the tool shank, the supporting sleeve 66 prevents a radial removal of the ball 56.

The third embodiment of a tool holder illustrated in Figure 6 corresponds substantially to the tool holder of the first embodiment. In this embodiment, the difference lies in the fact that the sliding sleeve 87 is made of plastics material. Since, of course, plastics material is not sufficiently resistant to wear a steel insert 88 has been incorporated in the plastics sleeve in which is machined an annular groove 93 into which the ball 12, which locks the tool holder to the driving member 1, can escape in the appropriate position of the sliding sleeve 87.

The embodiment of a tool holder shown in Figure 7 is particularly suitable for hammer drills with highly percussive percussion mechanisms or percussion hammers. It differs from the previous embodiment according to Figure 6 in the fact that the ball 12 which locks the coupling sleeve 116 to the driving member 1 is overlapped by two identical track rings 100, 101 and is thus held in the annular groove 3 the front end 3' and the rear end 3' ' of which are each bounded by a rounded corner. The track ring 100 has a track surface formed as an inner conical surface 102 the forwardly - away from the hammer drill or percussive hammer - opening conical angle P of which amounts to 300. The axial length of the track ring 100 is so determined that it extends forwardly up to the ball centre - with the ball 12 engaging the inner conical surface 102.Moreover, the axial length of the inner conical surface 102 corresponds to the radius of the ball 12. The outer diameter of the track ring 100 is smaller by a slight movement clearance than the inner diameter of the annular chamber 103 in the sliding sleeve 107 consisting of plastics material.

The rear end surface of the second identical track ring 101, which is certainly formed with a rearwardly opening inner conical surface, lies against the forward end surface of the first track ring 100. The two track rings 100, 101 displaceably arranged on the outer diameter of the coupling sleeve 116 with a slight movement clearance, are held in mutual abutment by the spring 105 in front of them supported by the sheet metal ring 106 and the track ring 100 is held at the rear in a supporting abutment against a shoulder 104 on the coupling sleeve 116.

In this embodiment, the portion covering the passage 117 in the coupling sleeve 116 is formed by a separate supporting ring 118 which is arranged in the annular space 103 in the sliding sleeve 107. At its inner diameter, the supporting ring 118 has two 450 chamfers 119; its outer diameter corresponds to that of the track rings 100, 101. The sheet metal ring 106 which corresponds substantially to the sheet metal rings 22, 62 of the previous embodiments, and which is influenced by the spring 105 lies against the rear end surface of the supporting ring 118. The forward end surface of the supporting ring 118, which overlaps the ball 115 - it corresponds to the ball 16, 56 of the previous embodiments - engages the inner shoulder 114 bounding the annular space 103 at the front end remote from the hand machine tool.

The operaton of the form of tool holder illustrated in Figure 7 during the insertion and removal of a tool does not differ substantially from the operation described by way of example in connection with the embodiment according to Figure 1.

When mounting the tool holder on the driving member 1, it is pushed by way of the coupling sleeve 116 over the driving member 1. In so doing, the end surface of the driving member pushes the balls 12 of the three balls 12 provided only a single ball can be seen in Figure 7 - against the track ring 101.

Finally, by considerable axial pressure on the shaped ring 26, the track ring 101 is pushed by the balls 12 axially against the spring 105 but the track ring 100 remains in its position. Then the balls 12 can be deflected radially outwards assisted by the conical formation in this embodiment of the radial bore 111 along the inclination of which they can slide outwardly. As soon as the annular groove 3 on the driving member 1 is pushed under the balls 12, the spring 105 urges the balls back into their initial position. A track ring 100 and the forward end 3' of the annular groove 3 formed as a rounded corner serve as stops between which the balls 12 remain positioned and which limit the axial clearance movement between the tool holder and the driving member 1.

If it is desired to remove the tool holder from the driving member 1, then - as with the first embodiment -the shaped ring 26 must be removed from its annular groove retaining it. Then the sliding sleeve 107 can be pushed completely forwards until finally the balls 12 can move radially outwards between the two track rings 100 and 101.

In normal operation, the function of the radial locking of the ball 12 by means of the track rings 100, 101 does not differ from that of the previous examples. It certainly differs from that of the previous embodiments when the tool holder is subjected strongly to unbraked axial impacts. Such impacts can occur with the tool holders on especially strongly percussive hammer drills or percussion hammers when the percussion mechanism changes from percussive operation into the idling operation.

The idle impacts produced thereby effect increased impacts in the driving member 1 whereby the entire tool holder experiences an acceleration towards the front. This axial displacement of the tool holder with respect to the driving member 1 is then braked abruptly when the balls 12 run against the forward end 3' of the annular groove 3 and are thus wedged in this case against the track surface of the track ring 100 formed as an inner conical surface 103. This occurs because the track surface 102 of the rear end facing the hand machine tool (hammer drill or percussion hammer) overlaps the balls 12 radially outwardly like a niche. Moreover - as described above - the track ring 100 is retained in a radial direction by the coupling sleeve 116 and engages the latter in an axial direction against the shoulder 104.

The described locking effect of the track surface 102 occurs in a particularly favourable manner when the inclination angle p of the track surface 102, at least along the axial contact region with the ball 12, is at least equal or less than the angle of attack of the resulting force on the particular ball 12 when it comes to rest against the forward end 3' of the recess 3.

With the three balls 115 used in this case, it is of course particularly favourable to make the track surface 102 as an inner conical surface. It is however possible - especially when only a single ball 115 is used with a tool holder - to also make the track surface flat. In so doing, it would also be possible, to arrange the track surface not in a track ring but on an extension directly formed on the coupling sleeve 116.

Claims

1. Atool holderforthe coupling of percussive and/or rotary tools to hand machine tools, preferably a hammer drill or percussive hammer, comprising a coupling sleeve which is connected on the one hand to a driving member of the hand machine tool transmitting the working movement and on the other hand receives a tool shank which has a groove-like recess closed at both ends in an axial direction in which a ball displaceably arranged in a radial passage in the coupling sleeve engages wherein, at least in its forward region remote from the hand machine tool, the passage is so covered by a portion of a sliding sleeve located in its rest position that the ball, which is held in the said region by a spring-loaded ring, is prevented from moving radially, characterised in that, the ring is formed as a flat sheet metal ring which contacts the ball over a region situated near to its bore.

2. A tool holder according to claim 1, characterised in that, the region is determined by shaped means which overlap the ball, at least in part preferably in the direction of the tool axis.

3. A tool holder according to claim 2, characterised in that, the shaped means are formed by a shell-like buckled portion of the sheet metal ring which lies on the side of the sheet metal ring facing the hand machine tool.

4. A tool holder according to claim 3, characterised in that, the buckled portion is inclined with respect to the plane of the sheet metal ring at an angle of about 35".

5. A tool holder according to one of the preceding claims, characterised in that, at the position which carries the buckled portion the sheet metal ring is enlarged to somewhat double the width with respect to the remainder of the sheet metal ring along a chord and that the said widening lies in an associated milled out portion from the coupling sleeve.

6. A tool holder according to one of the preced ing claims, characterised in that, the diameter of the bore for the sheet metal ring is larger than the diameter of the coupling sleeve in the region which carries the sheet metal ring by an amount of at least about 1 mm.

7. A tool holder according to claim 6, characte rised in that, the width of the sheet metal ring is increased at a plurality, preferably three, positions along its chord whereby a slight movement clearance remains between the chord and the outer diameter of the coupling sleeve.

8. A tool holder according to one of the preceding claims, in which the sheet metal ring is held by a spring against an inner shoulder on the sliding sleeve, characterised in that, the portion covering the passage is formed by a separate supporting ring which is inserted in an annular space in the sliding sleeve extending in an axial direction until immediately in front of the sheet metal ring and is held by the sheet metal ring against the inner shoulder, preferably with the interposition of a resilient abutment, bounding the annular space at the forward end facing the hand machine tool.

9. A tool holder according to claim 8, characterised in that, the resilient abutment is formed by a ring of elastic material, preferably foam material.

10. A tool holder according to claim 8, characterised in that, the supporting ring which consists of metal, preferably steel, is rounded at its outer peripheral surface.

11. A tool holder, the coupling sleeve of which is axially movably guided over a limited region on a driving member transmitting the tool movement of a hand machine tool, preferably a hammer drill or percussion hammer, wherein the region is determined by the axial dimension of a recess arranged on the driving member, especially an annular groove, in which engages a ball radially displaceable in a bore in the coupling sleeve, especially according to one of the preceding claims, characterised in that, when in abutment with the forward, preferably formed as a rounded corner, end of the recess in the driving member, the ball is prevented from moving radially by a track surface which is carried by the rear end facing the hand machine tool and by overlapping the ball radially from the outside in the form of a niche, by the coupling sleeve.

12. A tool holder according to claim 11,characte- rised in that, at least along the axial contact region with the ball, the track surface has a contour inclined with respect to the axis of the driving member at a forwardly opening angle, preferably of 30".

13. A tool holder according to claim 12, characterised in that, the track surface is formed by an inner cone surface which is arranged in a track ring which is guided on the outer surface of the coupling sleeve and is supported towards the rear at that location against a shoulder.

14. Atool holder according to claim 13,characterised in that, during contact with the ball - viewed in an axial direction - the track ring including the inner cone surface extends forwardly up to the centre of the ball.

15. A tool holder according to claim 14, characterised in that, the ball contacts the inner cone surface over substantially 0.3 to 0.5 of the axial length of the track ring.

16. A tool holder according to one of claims 11 to 15, characterised in that, the end surface of a second, preferably identical, track ring, which is fitted with a rearwardly opening internal cone surface, engages against the front end surface of the track ring.

17. A tool holder according to claim 16, characterised in that, the two track rings are held in mutual abutment by the spring supported by the sheet metal ring.

18. A tool holder according to claim 8 and one of claims 13 to 17, characterised in that, the outer diameter of the track rings and of the supporting ring is the same and is smaller than the inner diameter of the annular space in the sliding sleeve by a slight movement clearance.

19. A tool holder for the coupling of a tool on the shaft of which is arranged, in addition to the recess closed in the direction of the axis, at least one torque transmitting groove open at the end of the tool shank the at least substantially radial flanks of which cooperate with associated surfaces on a rib-like driving member in the coupling sleeve according to one of the preceding claims, characterised in that, the centre-line of the driving member is arranged offset in the sense of rotation of the coupling sleeve by substantially 50 with respect to the centre-line of the associated passage.

20. A tool holdersubstantiallyashereinde- scribed with reference to Figures 1 to 3, Figures 4 and 5, Figure 6 or Figure 7 of the accompanying drawings.