GB2315438A

GB2315438A - Speed selection for an electric handtool

Info

Publication number: GB2315438A
Application number: GB9714799A
Authority: GB
Inventors: Manfred Buck; Gerd Mueller; Juergen Schmidt; Siegfried Fehrle
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1996-07-23
Filing date: 1997-07-14
Publication date: 1998-02-04
Anticipated expiration: 2017-07-14
Also published as: GB2315438B; GB9714799D0; JPH1086007A; CH692976A5; DE19629623A1

Abstract

A electric handtool having a workspindle 12 carries a tool holder 15 for a rotary tool 10 and is driven via a multi-speed indexing mechanism 13 by a rotating drive shaft 14. To provide automatic speed or gear selection for the rotary tool 10 the indexing mechanism 13 includes a shift mechanism 38, which by means of an indexing pin disposed on the rotary tool 10 automatically selects a desired operating speed of the workspindle 12. The automatic speed selection may be manually overridden by means of a switch.

Description

2315438 Tool machine

Background art

The invention proceeds from a tool machine, in particular an electric handtool machine which is guided manually or held stationary, of the type defined in the preamble of claim 1.

In a known handtool machine for a rotary tool, the speed specified for the rotary tool has to be looked up in the tool information and adjusted manually by means of the operating knob for speed or gear selection. Such speed specifications are to be found particularly in the case of drilling tools which have a diamond bit.

Advantages of the invention In contrast the tool machine according to the invention havirig the characten g features of claim 1 has the advantage that the sensing plunger preferably disposed in the centre of the spindle automatically senses an indexing device provided for speed selection purposes on the tool upon insertion of the rotary tool into the tool holder and, in dependence upon the sensing position of the sensing plunger, the shift mechanism automatically selects the reduction stage which delivers the appropriate speed at the workspindle. It is therefore no longer necessary for the operator to look up the speed specified for the rotary tool, e.g. in the operating instructions, or adjust the tool machine in the appropriate manner. Every rotary tool is reliably driven at the required speed. Speed adjustment errors as a result of selecting the wrong gear are ruled out.

2 By virtue of the measures described in the finther claims, advantageous developments and improvements of the tool machine indicated in claim I are possible.

According to a preferred embodiment of the invention, a plurality of output wheels, each associated with one reduction stage and having spacer rings positioned in between, are disposed next to one another in a freely rotating manner on the workspindle and the drive wheels may be nonrotatably coupled to the workspindle by means of sliding keys which are pushable radially out of the workspindle. The shift mechanism comprises a sliding key holder, which is disposed displaceably in the hollow workspindle and contains the sliding keys, and a restoring spring in the form of a compression spring, which applies the sliding key holder in a fliction-locked manner against the sensing plunger likewise lying coaxially in the hollow workspindle. When there is no tool in the tool holder, the sensing plunger is supported under the action of the restoring spring against a stop formed on the workspindle. The arrangement of the sliding keys relative to one another and of the drive wheels relative to one another is such that, in accordance with the displaced position of the sliding key holder, in each case one of the sliding keys moves into radial alignment with a radial counterbored hole in the cylindrical inner wall of the output wheels. The displaced position of the sensing plunger is determined by the length of an indexing pin on the rotary tool so that, as the tool is inserted into the tool holder, the sensing plunger is displaced by a defined distance which ensures the correct association of sliding key and output wheel through displacement of the sliding key holder.

For rotary tools with no indexing, according to an advantageous embodiment of the invention an output wheel of a medium-speed reduction stage is coupled to the workspindle, this being ensured by an appropriate arrangement of the stop for the 3 sensing plunger inside the hollow workspindle. From then on, flirther speed or gear selection may be effected manually by means of the operating knob.

In order in a simple manner to enable manual speed or gear selection upon insertion of a rotary tool with no indexing into the tool holder, according to a fluther embodiment of the invention the operating knob, which has a plurality of positions for manual speed or gear selection and one position for automatic speed selection, in the manual speed selection positions is coupled to the sliding key holder by means of an axially displaceable shift gate and a shift element disposed displaceably on the workspindle. In the automatic speed selection position of the operating knob, said coupling is cancelled.

In order, upon insertion of a tool with speed indexing different from the automatic speed setting, also to be able to effect a manual correction of the speed, according to an advantageous embodiment of the invention the shift mechanism comprises a coupling element, which is disposed in an axially displaceable manner in the hollow workspindle between sensing plunger and sliding key holder, and a decoupling spring in the form of a compression spring, which is supported between the sensing plunger and the coupling element and the spring bias of which is very much greater than that of the restoring spring. The operating knob is coupled by a second axially displaceable shift gate and a second shift element to the coupling element in such a way that, in the manual speed selection positions of the operating knob, the coupling element by compression of the decoupling spring cancels a displaced position of the sliding key holder brought about by the sensing plunger via the decoupling spring and the coupling element.

Drawings 4 There follows a detailed description of an embodiment of the invention which is illustrated in the drawings. The drawings show:

Fig. 1 in a cutout manner, a longitudinal section of an electric handtool machine with a drilling tool attached, Fig. 2 a longitudinal section of a drilling tool with a speed indexing pin, Fig. 3 a plan view of an operating knob for speed selection on the handtool machine in Fig. 1, Figs. 4-7 in each case a selection mechanism for manual speed selection coupled to the operating knob in Fig. 3 in side view (above) and in plane view (below) in four different positions of the operating knob.

Description of the embodiment

The electric handtool machine, which is illustrated in a cutout manner in the longitudinal section in Fig. 1 and is intended for a rotary tool 10 which m the present case takes the form of a diamond bit, comprises a workspindle 12 rotatably supported m a machine housing 11 and driven via a three-speed indexing mechanism 13 by the drive shaft 14 of an electric motor which is not shown here. At its end projecting from machine housing 11, the workspindle 12 carries in a non-rotatable manner a tool holder 15 for the rotary tool 10 comprising a threaded portion 16, onto which a hollow shank 101 of the drilling tool 10 provided with an internal thread 17 may be screwed.

The mechanism 13 comprises three output wheels 18, 19, 20 in the form of gear wheels, which are each associated with one reduction stage and are arranged next to one another, with spacer rings 21 - 24 positioned in between, in a freely rotating manner on the workspindle 12. The two outer spacer rings 21 and 24 lying adjacent to the end faces of the outer-lying output wheels 18, 20 are locked by means of lock washers 25 and 26 against axial displacement on the workspindle 12. The output wheel 18 is part of the reduction stage (I st gear), which delivers the lowest speed of the workspindle 12, and the output wheel 20 is part of the reduction stage (3rd gear) which produces the highest speed of the workspindle 12. The output wheel 19 (2nd gear) is part of the medium-speed reduction stage. The output wheels 18, 19, 20 are meshed with gear wheels 18a, 19a, 20a which may be rotatably driven by the drive shaft 14. In each case one of the output wheels 18 - 20 may be non-rotatably connected by one of two sliding keys 27, 28 to the workspindle 12 so that said output wheel sets the workspindle 12 in rotation while the other output wheels, which are likewise driven by the drive shaft 14, rotate freely on the workspindle 12.

Selection of the output wheel 18 - 20 to be coupled to the workspindle 12 is effected by means of a sliding key holder 29, which is disposed in an axially displaceable manner in the hollow workspindle 12 and carries two radial pockets 30, 3 1. Inserted in each pocket 30 or 3 1 is a sliding key 27 or 28 and a push-out spring 32 or 33. The push-out spring 32 or 33 is supported between the sliding key 27 or 28 and the base of the pocket 3 0 or 3 1 and pushes the sliding key 27 or 28 radially outwards. Provided in the inner wall of each output wheel 18 - 20 is a counterbored hole 34 or 35 or 36, into which the sliding key 27 or 28 engages under the action of the push-out spring 32 or 33 as soon as the sliding key 27 or 28 is in radial alignment with the relevant counterbored hole 34 or 35 or 36. Otherwise, the sliding keys 27, 28 are pressed by the push-out springs 32, 33 6 against the spacer rings 21 - 23. Bevels at the top ends of the sliding keys 27, 28 make it possible for the sliding keys 27, 28 to be lifted out of the counterbored holes 34 - 36 and for the sliding keys 27, 28 to dip under the spacer rings 21 - 23. Extending over the displacement range of the sliding key holder 29 in the spidle wall of the hollow workspmdle 12 is an axial slot 37, through which the sliding keys 27, 28 may pass radially towards the spacer rings 21 - 23 and the output wheels 18 - 20.

The sliding key holder 29 having the sliding keys 27, 28 is part of a shift mechanism 38 which additionally comprises a restoring spring 39 in the form of a compression spring, a coupling element 40, a decoupling spring 41 in the form of a compression spring and a selection mechanism 42 for manual speed selection. The shift mechanism 38 moreover comprises a sensing plunger 43, which is likewise disposed displaceably in the hollow workspindle 12 and together with the latter projects coaxially into the tool holder 15. The decoupling spring 41, the spring bias of which is far greater than that of the restoring spring 39, is supported between the end face of the sensing plunger 43 remote from the tool holder 15 and the coupling element 40 lying adjacent to the one end face of the sliding key holder 29. Supported against the opposite end face of the sliding key holder 29 is the restoring spring 39, the bias of which is adjustable by means of an adjusting screw 44 screwed into an internally threaded bore in the workspindle 12. When there is no tool in the tool holder 15, the sensing plunger 43 is supported under the action of the restoring spring 39 - which acts Via the sliding key holder 29, the coupling element 40 and the decoupling spring 49 upon the sensing plunger 43 against a stop 45 on the workspindle 12, which stop in the present case is formed by an annular shoulder inside the hollow workspindle 12. Said stop 45 is spatially disposed in the workspindle 12 in such a way that, when the sensing plunger 43 rests against the stop 45, the rear sliding key 28 is radially aligned with the 7 counterbored hole 35 m the output wheel 19 of the middle reduction stage (2nd gear) and is therefore pushed by the push-out spring 33 into the counterbored hole 35 so that the output wheel 19 is non-rotatably connected to the workspindle 12.

For certain rotary tools 10, operating speeds or speed ranges are specified, which have to be observed in order to achieve the best results. Thus, for example, drill bits for a handtool machine with a three-speed indexing mechanism are divided into three diameter ranges. Smalldiarneter drill bits are to be operated in third gear, i.e. at maximum speed. Large-diameter drill bits, on the other hand, are to be operated in first gear, i.e. at the lowest speed. Second gear is specified for medium-diameter drill bits. The small- and large-diameter rotary tools 10 are therefore provided with an indexing pin 46 (Fig. 2), which clearly indicates the specified speed to the handtool machine. For instance, small-diameter drill bits have a long indexing pin 46 and large-diameter drill bits have a short indexing pin, such as is shown in Fig. 2. Mediumdiameter drill bits have no indexing pm. Upon insertion of the rotary tool 10 into the tool holder 15, the indexing pin 46 is pushed by its front end into the hollow workspindle 12 and in accordance with its length effects a displacement of the sensing plunger 43. The displaced position subsequently assumed by the sensing plunger 43 is transmitted to the shift mechanism 38, which converts said displaced position of the sensing plunger 43 into a gear speed change such that the reduction stage delivering a desired operating speed of the rotary tool 10 is applied onto the workspindle 12. Thus, when the rotary tool 10 with the short indexing pin 46, which is shown in Fig. 2 and is to be operated in the 1 st gear of the handtool machine, is inserted into the tool holder 15, the indexing pin 46 displaces the sensing plunger 43 by the length of the indexing pin 46. The displacement of the sensing plunger 43 is transmitted via the stifF coupling spring 41 and the coupling element 40 to the sliding key holder 29 which shifts, while simultaneously compressing the restoring spring 39, 8 to such an extent that the rear sliding key 28 leaves the counterbored hole 35 in the output wheel 19 and is pushed under the spacer ring 23, while the firont sliding key 27 moves into radial alignment with the counterbored hole 34 of the output wheel 18 for the I st gear, is pushed by the push-out spring 3 2 into the counterbored hole 34 in the output wheel 18 and so couples the latter non-rotatably to the workspMdle 12. When, on the other hand, a small-diameter rotary tool 10 (not shown here), which is to be operated in the highest gear and has a correspondingly long indexing pin 46, is inserted into the tool holder 15, the sliding key bolder 29 is displaced by the longer indexing pin 46 to such an extent that the rear sliding key 28 moves into radial alignment with the counterbored hole 36 in the output wheel 20 of the reduction stage for the 3rd gear and couples said output wheel 20 to the workspindle 12. During said displacement of the sliding key holder 29 effected by the sensing plunger 43, the decoupling spring 41 remains stiff, i.e. is not pressed in, because its bias is much greater than that of the restoring spring 39. In Fig. 1, a medium-diameter rotary tool 10, which according to its specification is to be operated in the 2nd gear of the handtool machine, is inserted into the tool holder 15. Said rotary tool 10 has no indexing pin, with the result that the sensing plunger 43 is not influenced by the rotary tool 10 and maintains the same basic position as if there were no tool in the tool holder 15, in which position the output wheel 19 of the reduction stage for 2nd gear is coupled to the workspindle 12 M the manner shown in Fig. 1.

In order, when a rotary tool 10 has no indexing, to enable a manual speed adjustment of the handtool machine or, when a gear has been automatically selected by the rotary tool 10, to enable the speed of the handtool machine to be varied according to individual requirements, an operating knob 47 of the type shown in Fig. 3 is provided on the machine housing 11. The operating knob 47 is seated non-rotatably on an operating shaft 48 (Figs. 4 - 7) and has one position "A" for automatic gear or speed selection and three positions "2", " 1 " and "3 " for 9 manual gear or speed selection, in which it is coupled by the selection mechanism 42 already described to the shift mechanism 38. In position "A", said coupling is cancelled. In particular, the selection mechanism 42 to be seen in side and plan view in Fig. 4 comprises two shift gates 51, 52, which are displaceable parallel to the workspindle 12 m the machine housing 11, and two shift elements 53, 54 which are axially displaceable on the workspindle 12. Shift element 53 is firmly connected by an alignment pin 55 to the sliding key holder 29 and shift element 54 is firmly connected by an alignment pin 56 to the coupling element 40. The two alignment pins 55, 56 project through two diametrical axial slots 57, 58 and 59, 60 in the workspindle 12. The length of the axial slots 57 is slightly greater than the maximum displacement distance of the sliding key holder 29 for a gear speed change. Each shift gate 51, 52 comprises a sliding plate 511, 521 with a gate window 512, 522 left open therein and with a shift fork 513, 523 jutting out at right angles therefrom. The two sliding plates 511, 521 are guided with play parallel on one another, their shift forks 513, 523 lying on sides of the sliding plates 511 and 521 which are remote from one another. Disposed on the operating shaft 48 are two operating cams 49, 50 which are rotated through an angle at circumference of 90' relative to one another. The operating cams 49, 50 project radially from the operating shaft 48 and are axially offset so that the operating cam 49 lies in the plane of the gate wiridow 512 and the operating cam 50 lies in the plane of the gate window 522. For displacement of the shift gates 519 52, the operating cams 49, 50 act upon the boundary edges of the gate windows 512, 522 aligned at right angles to the direction of displacement of the shift gates 51, 52. As Fig. 1 reveals, the shift forks 513, 523 engage over the workspindle 12, the shift fork 513 coming to lie next to the shift element 53 connected to the sliding key holder 29 and the shift fork 523 of the shift gate 52 coming to he next to the shift element 54 firmly connected to the coupling element 40. When the shift gate 51 is displaced, the shift fork 513 displaces the shift element 53 and hence the sliding key holder 29 to the right in Fig. 1, with simultaneous compression of the restoring spring 39. When the shift gate 52 is displaced, its shift fork 523 displaces the shift element 54 and hence the coupling element 40 to the left in Fig. 1, with simultaneous compression of the decoupli g spring 4 1.

In position 'W' of the operating knob 47, the selection mechanism 42 assumes the position shown in Fig. 4, in which the, in Fig. 4, right transverse edge of the gate window 512 of the shift gate 51 rests against the operating cam 49 and the left transverse edge of the gate window 522 of the shift gate 52 rests against the operating cam 50. The shift forks 513 and 523 assume the position shown in Fig. 1. The coupling of the operating knob 47 to the shift mechanism 38 by the selection mechanism 42 is cancelled. Depending on the length of the indexing pin 46 of the rotary tool 10 inserted into the tool holder 15, the sensing plunger 43 may displace the sliding key holder 29 to an extent which allows engagement of either the sliding key 27 in the counterbored hole 34 in the output wheel 18 or the sliding key 28 in the counterbored hole 36 in the output wheel 20. The shift element 53 and 54 which are simultaneously moved in the process do not come into contact with the shift forks 513 and 523.

Fig. 5 shows the position of the selection mechanism 42 once the operating knob 47 has been moved into position '7' for manual speed adjustment (2nd gear). By means of the operating cam 50, the shift gate 52 is displaced by the radial length of the operating cam 50 to the let with the result that the shift fork 523 is applied against the shift element 54 and so the coupling element 40 is locked against a displacement - in Fig. 1 - to the right. As Fig. 1 shows, 2nd gear of the handtool machine is therefore selected. A displacement of the sliding key holder 29 by the sensing plunger 43 is not possible. By moving the operating knob 47 into its 11 position " 1 ", the selection mechanism 42 is moved into the position shown in Fig. 6. The cam 49 displaces the shift gate 51 to the right with the result that the shift fork 513 displaces the shift element 53 in Fig. 1 so far to the right, with simultaneous compression of the restoring spring 39, that the sliding key 27 drops into the counterbored hole 34 of the output wheel 18 and at the same time the sliding key 28 is lifted out of the output wheel 19. Since the shift gate 52 is pressed with its gate window 522 against the cam 50 by the decoupling spring 41 via the coupling element 40, the shift element 54 and the shift fork 523, the shift gate 52 follows the swivelling motion of the cam 50 and moves - in Fig. 6 slightly to the right.

When the operating knob 47 is then moved into its position "Y, the selection mechanism 42 assumes the position shown in Fig.7. The operating cam 49 via the gate window 512 displaces the shift gate 5 1, which in turn via the shift fork 513 displaces the shift element 53, which via the alignment pin 55 displaces the sliding key holder 29 by such a displacement distance that the rear sliding key 28 drops into the counterbored hole 36 m the output wheel 20 and so 3rd gear of the handtool machine is selected. Since, as before, the shift gate 52 is pressed by the decoupling spring 41 against the operating cam 50, the shift gate 52 follows the swivelling motion of the cam 50 and moves - in Fig. 7 further to the right. The shift element 53 firmly connected to the coupling element 40 assumes the position shown by the dashed lines M Fig. 1.

The operating knob 47 may also be used, in the case of automatic speed ad ustment by the indexing pin 46 of a rotary tool 10, to effect a speed or gear j correction. When, for example, a rotary tool 10 with a long indexing pin 46 specifying 3rd gear of the handtool machine is inserted into the tool holder 15, then - in the manner described - the indexing pin 46 displaces the sensing plunger 12 43 and the sensing plunger 43 displaces the sliding key holder 29 to such an extent that the rear sliding key 28 drops into the counterbored hole 36 in the output wheel 20 of the reduction stage for 3rd gear. When, for exatriple, the operating knob 47 is then turned to its position '7' for 2nd gear, the operating cams 49, 50 assume the position shown in Fig. 5. Thus, the operating cam 50 displaces the shift gate 52, and the shift fork 523 of the latter via the shift element 54 displaces the coupling element 40 counter to the action of the decoupling spring 41 to the left m Fig. 1 so as to create between the coupling element 40 and the sliding key holder 29 a gap for displacement of the sliding key holder 29. Thus, the restoring spring 39 may displace the sliding key holder 29 to such an extent that the rear sliding key 28 leaves the counterbored hole 36 in the output wheel 20, moves into radial alignment with the counterbored hole 35 in the output wheel 19 and couples said output wheel 19 non- rotatably to the workspindle 12. The same process occurs when, for example, the rotary tool 10 shown in Fig. 2 and having the short indexing pin 46 for selecting 1 st gear of the handtool machine is inserted into the tool holder 15 and the operating knob 47 is moved out of its position 'W' into its position "2".

13

Claims

1. Tool machine, in particular an electric handtool machine which is guided manually or held stationary, having a workspindle (12) which carries a tool holder (15) for a rotary tool (10), having a rotatably drivable drive shaft (14), and having a multi-speed indexing mechanism (13) which is disposed between drive shaft (14) and workspindle (12) and transmits the rotation of the drive shaft (14) to the workspindle (12) at a speed ratio determined by the effective reduction stage, characterized in that the indexing mechanism (13) has a shift mechanism (38) which converts a mechanical sensing of an indexing device (46), which is disposed on the rotary tool (10) and selects a desired operating speed of the workspindle (12), into a gear speed change in such a way that a reduction stage of the indexing mechanism (13) associated with the desired operating speed of the workspindle (12) is applied onto the workspindle (12).

2. Machine according to claim 1, characterized in that the shift mechanism (38) comprises a sensing plunger (43), which is guided in an axially displaceable manner in the workspindle (12) and projects into the tool holder (15) for sensing an indexing pin (47), which selects the recommended operating speed of the rotary tool (10) actually in use.

3. Machine according to claim 2, characterized in that a plurality of output wheels (18 - 20), each associated with one reduction stage and having spacer rings 14 (21 - 24) positioned in between, are disposed next to one another in a freely rotating manner on the workspindle (12), that the shift mechanism (38) comprises a sliding key holder (29), which is disposed displaceably in the hollow output shaft (12) and has sliding keys (27, 28) pushable radially outwards for non-rotatable coupling of the output wheels (18 - 20), and a restoring spring (39) in the form of a compression spring which applies the sliding key holder (29) in a friction-locked manner against the sensing plunger (43) which, when there is no tool in the tool holder (15), is supported under the action of the restoring spring (39) against a stop (45) formed on the workspindle (12), and that the arrangement of the sliding keys (27, 28) and of the output wheels (18 - 20) is such that, depending on the displacement distance of the sliding key holder (29), in each case one of the sliding keys (27, 28) moves into radial alignment with a radial counterbored hole (34 - 36) in the inner wall of the output wheels (18 - 20) which rests on the workspindle (12).

4. Machine according to claim 3, characterized in that, when the sensing plunger (43) rests against the stop (45), the sliding key holder (29) assumes such a displaced position that a sliding key (28) lies with the counterbored hole (35) in an output wheel (19) of a reduction stage which preferably drives the workspindle (12) at a medium speed.

5. Machine according to claim 3 or 4, characterized in that the sliding keys (27, 28) are accommodated in radial pockets (30, 3 1) which are introduced at an axial distance parallel to one another in the sliding key holder (29), that a push-out spring (32, 33) is supported in each case between the sliding keys (27, 28) and the base of the pockets (30, 3 1) and that the hollow workspindle (12) over the displacement range of the sliding key holder (29) has an axial slot (37), which penetrates the spindle wall and through which the sliding keys (27, 28) may pass radially.

6. Machine according to one of claims 1 - 5, characterized in that an operating knob (47) is additionally provided for adjusting the reduction stage which determines the desired operating speed.

7. Machine according to claim 6, characterized in that the operating knob (47) has a plurality of manual gear or speed selection positions (1, 2, 3), in which it is coupled by an axially displaceable shift gate (5 1) and a shift element (5 3), which is axially displaceable on the workspindle (12), to the sliding key holder (29) for the purpose of axial displacement of the latter, and has an automatic gear or speed selection position (A), in which said manual coupling is cancelled.

8. Machine according to claim 7, characterized in that the shift element (53) is connected, preferably by an alignment pin (55) projecting through diametrical axial slots (57, 58) in the workspindle (12), firmly to the sliding key holder (29) and lies under the action of the restoring spring (39) against the shift gate (5 1) and that the operating knob (47) has an operating cam (49) which is so designed that, in every manual speed selection position of the operating knob (47), it displaces the shift gate (5 1) counter to the action of the restoring spring (39) by a defined displacement distance, which via the shift element (53) selects the displacement distance of the 16 sliding key holder (29) in such a way that one of the sliding keys (27, 28) is in radial alignment with the counterbored hole (34 - 36) of the output wheel (18 - 20) of the reduction stage corresponding to the manually selected speed.

9. Machine according to claim 8, characterized in that the shift gate (5 1) has a gate window (512), in which an operating cam (49) of the operating knob (47) lies for the purpose of displacement of the shift gate (5 1) by defined displacement distances in the individual manual gear or speed selection positions of the operating knob (47).

10. Machine according to one of claims 7 - 9, characterized m that the shift mechanism (38) comprises a coupling element (40), which is disposed in an axially displaceable manner in the hollow workspindle (12) between sensing plunger (43) and sliding key holder (29), and a decoupling spring (41) in the form of a compression spring, which is supported between the sensing plunger (43) and the coupling element (40) and the spring bias of which is very much greater than that of the restoring spring (39), and that the operating knob (47) is coupled by a second axially displaceable shift gate (52) and a second shift element (54), which is axially displaceable on the workspindle (12), to the coupling element (40) in such a way that in the manual gear or speed selection positions of the operating knob, the coupling element (40) through compression of the decoupling spring (41) cancels a displaced position of the sliding key holder (29) which is brought about by the sensing plunger (43) Via the decoupling spring (4 1) and the coupling element (40).

17

11. Machine according to claim 10, characterized in that the second shift element (54) is connected, preferably by an alignment pin (56) projecting through diametrical axial slots (59, 60) in the workspindle (12), firmly to the coupling element (40) and that the operating knob (47) has a second operating cam (50) which is so designed that, in every manual gear or speed selection position of the operating knob (47), it displaces the second shift gate (52) counter to the action of the decoupling spring (41) by a defined displacement distance which adjusts such a gap between coupling element (40) and sliding key holder (29) that the sliding key holder (29) is movable by the restoring spring (39) into a displaced position with radial alignment of a sliding key (27, 28) with the counterbored hole (34 - 36) in the output wheel (18 - 20) of the reduction stage corresponding to the manually selected speed.

12. Machine according to claim 11, characterized in that the second shift gate (52) has a gate window (512), in which the second operating cam (50) of the operating knob (47) lies for the purpose of displacement of the shift gate (52) by defined displacement distances in the individual manual gear or speed selection positions of the operating knob (47).

13. Machine according to claim I I or 12, characterized in that the operating knob (47) is seated non-rotatably on an operating shaft (48) and that the operating cams (49, 50), rotated through an angle at circumference of 90' relative to one another, project radially from the operating shaft (48) and he at the operating shaft (48) in an axially offset manner in each case in the plane of a rectangular gate 18 window (512, 523) and act upon the boundary edges of the gate windows (512, 523), which edges are aligned at right angles to the direction of displacement of the shift gates (51, 52).

14. Machine according to one of claims 10 - 13, characterized in that each shift gate (51, 52) comprises a sliding plate (511, 512), which contains the gate window (512, 522), and a shift fork (513, 523) which projects, preferably integrally, at right angles from the sliding plate (511, 521), engages diametrically over the workspindle (12) and lies against the associated shift element (53, 54), and that the two shift gates (51, 52) lie, with their sliding plates (511, 521) aligned parallel to one another, mirror-symmetrically one on top of the other such that the shift forks (513, 523) lie on sides of the sliding plates (511, 521) which are remote from one another.

15. Machine having a three-speed mechanism according to claim 5, characterized in that three output wheels ( 18, 19, 20) are seated on the workspindle (12) and the sliding key holder (29) has two radial pockets (30, 3 1), in each of which a sliding key (27, 28) is radially displaceable, and that the axial distance of the output wheels (18, 19, 20) from one another and of the blind holes (30, 3 1) from one another as well as the arrangement of the stop (45) for the sensing plunger (43) in the hollow workspindle (12) are such that, when the sensing plunger (43) rests against the stop (45), the rear sliding key (28) lying remote from the sensing plunger (43) is radially aligned with the counterbored hole (35) in the middle output wheel (19) and, when the sliding key holder (29) is displaced counter to the action of the restoring spring (39), first the front sliding key (27) 19 moves into radial aligrunent with the counterbored hole (34) In the front output wheel (18) lying, in displacement direction, In front of the middle output wheel (19) and then the rear sliding key (28) moves into radial alignment with the counterbored hole (36) in the rear output wheel (20) lying behind the middle output wheel (19).

16. Tool for a tool machine according to one of claims I - 15, characterized by an indexing device (46), which may be sensed by a shift mechanism (3 8) of the machine, the nature and arrangement of the latter being an index of the recommended operating speed of the tool (10).

17. Tool for a tool machine according to claim 16, characterized by a coaxial indexing pin (46), which projects from the rear end and which either has a length corresponding to the displacement distance of the sliding key holder (29) up to radial alignment of the front sliding key (27) with the counterbored hole (34) of the front output wheel ( 18) or has a length corresponding to the displacement distance of the sliding key holder (29) up to radial alignment of the rear sliding key (28) with the counterbored hole (36) in the rear output wheel (20), in each case starting from the basic position of the sliding key holder (29) when there is no tool in the tool holder (15), in which position the rear sliding key (28) is radially aligned with the counterbored hole (3 5) in the middle output wheel (19).

18. A tool machine substantially as herein described with reference to the accompanying drawings.

19. A tool for a tool machine, the tool being substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.