GB2408476A

GB2408476A - Power tool with switching device for reversing the direction of rotation of an electric motor

Info

Publication number: GB2408476A
Application number: GB0425850A
Authority: GB
Inventors: Willy Braun; Axel Kuhnle; Karl Frauhammer; Gerhard Meixner; Heinz Schnerring
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-11-28
Filing date: 2004-11-24
Publication date: 2005-06-01
Anticipated expiration: 2024-11-24
Also published as: CN100436076C; DE10355812A1; GB2408476B; JP2005161517A; GB0425850D0; CN1621205A

Abstract

A power tool comprises an electric motor disposed in a housing (10, fig 1), a tool held within a tool holder (12, fig 1), and a switching device for reversing the rotational direction of the tool. The switching device comprises a transmission, by means of which the tool can be driven in either rotational direction, where the rotational direction of the electric motor remains unchanged. The power tool may have various modes of operation including drilling only, hammer drilling (fig 5), and chiselling (fig 6). Preferably a main bevel gear 26 and a reverse bevel gear 28 are provided, on opposite sides of a bevel gear pinion 24. At least one switch sleeve 40 may also be provided, which may be coupled to the main bevel gear or the reverse bevel gear.

Description

R.305045 17.11.03 Electric power tool

Prior art

The invention proceeds from an electric power tool according to the preamble of Claim 1.

In the case of electric power tools, both drilling and hammer-drilling are normally effected by right-turning. A left-turning function, particularly in the case of rotary hammers, is therefore limited to the unscrewing of screws or any drill bits, for example, jammed in a concrete reinforcement, for the purpose of their removal. Left- turning in this case is realized by changing the rotational direction of the electric motor of the electric power tool.

The simplest way of changing the rotational direction is to reverse the polarity of the supply of electric power to the motor by means of an electric changeover switch. The series-wound motors normally used in electric power tools have a preferred rotational direction since, in order to minimize electromagnetic losses, the armature windings are skewed at a certain angle relative to the field windings, in order that a commutation can take place in a range of small magnetic field strengths. In the case of stationary carbon brushes, therefore, an optimum interconnection can only operate in one rotational direction, so that the opposite rotational direction, normally left-turning, is connected through pure reversal of the motor current, due to the poor commutation with losses of power. Further

L

R.305045 disadvantages are a high thermal load, a pronounced wearing of the carbon brushes, and problems in radio interference suppression due to increased brush sparking. In order to reduce the thermal load of the electric motor in the case of a high power capacity, there is a need for effective air cooling. However, adequately high air throughputs can only be achieved with fans whose blades are of an appropriate curved shape and therefore, in principle, have a preferred rotational direction. Consequently, the rotational direction of the electric motor that is opposite to the preferred rotational direction is subject to additional thermal disadvantage.

Advantages of the invention The invention proceeds from an electric power tool having an electric motor which is disposed in a housing and by means of which an accessory disposed in a tool holder can be driven at least in a rotating manner, and having a switching device for reversing the rotational direction of the accessory.

It is proposed that the switching device comprise a transmission by means of which the accessory can optionally be driven in the one or other rotational direction, with the rotational direction of the electric motor being unchanged. A reversal of the rotational direction of the accessory can be realized through purely mechanical means.

The electric motor and a fan can be optimized for operation with a single rotational direction, thereby improving the motor efficiency and cooling. There is thus available a greater nominal motor output which can be used for both t I R.305045 rotational directions of the accessory. The useful life of the carbon brushes of the electric motor is prolonged. The mechanical switching device for reversing the rotational direction is robust, and less liable to failure than an electrical changeover of the rotational direction of the electric motor. The invention is applied with particular preference in hand-held electric power tools, and may be preferentially applied in L-type electric power tools. L- type means that the drive shaft of the electric motor is arranged perpendicularly to the direction of working. The invention may be applied with particular preference both in L-type rotary hammers in which the percussion mechanism is driven by a wobble shaft, and in L-type rotary hammers in which the percussion mechanism is driven by an eccentric.

If the switching device has at least one switch sleeve which can be positioned in dependence on a selected operating mode, the different operating modes of the electric power tool can be set in a convenient and user friendly manner by means of only one operating-mode selector knob. In particular, in the case of a preferred rotary hammer, the four hammer operating modes, of left- turning, right-turning, hammer-drilling and chiselling, can be set by means of only one operating-mode selector knob.

Thus, incorrect operation, i.e., hammer operation or chiselling operation during left-turning, can be easily prevented. The switch sleeve can be displaced by means of, for example, a switch rod, according to the adjustment of the operating-mode selector knob.

In a preferred embodiment, the switching device has a second switch sleeve which can likewise be positioned in r, R.305045 dependence on a selected operating mode. The switch sleeve can be rotatably accommodated in a switch gate which, in the various positions of the operating-mode selector knob, runs in a recess of the switch rod and is axially driven along only in the case of a left-turning position and, accordingly, causes a left-turning motion, while the first switch sleeve which, in this embodiment, effects the right- turning motion, is in a neutral position.

The first and the second switch sleeves preferably have actuating means which, depending on the position of the switch sleeve, can either be brought into active coupling to a drive means for the one or other rotational direction, or into at least one rotationally neutral position.

Operating modes such as left-turning and right-turning, as well as hammerdrilling and chiselling, can thereby be realized in that the switch sleeves can be brought into a position defined for a respective operating mode.

If the switching device comprises a reversing bevel gear which can be driven, together with a main bevel gear, by a bevel-gear pinion, the invention can be realized particularly easily in an electric power tool in which a drive shaft of an percussion mechanism and an electric motor shaft form an approximately right angle. In conventional electric power tools of such type, a bevel gearing is normally used to redirect the rotary motion of the motor to an percussion-mechanism drive, with the result that the redirecting device according to the invention can be easily integrated into such an electric power tool.

R.305045 If the main bevel gear and the reversing bevel gear are disposed on opposite sides of the bevel-gear pinion, two drive means, rotating in opposite directions, for the one or other rotational direction, are created in a very simple manner.

The reversing bevel gear is preferably disposed so as to be rotatably movable on a supporting sleeve, thereby enabling a compact structure of the switching device to be achieved.

Expediently, the main bevel gear is firmly joined to the supporting sleeve, and the axial length of the supporting sleeve is available as a displacement path of the switch sleeve. This arrangement is particularly suitable for L- type rotary hammers in which the percussion mechanism is driven by a wobble shaft.

In an alternative development, the reversing bevel gear is disposed on a hammer tube. This arrangement is particularly suitable for L-type rotary hammers in which the percussion mechanism is driven by an eccentric drive.

The reversing bevel gear is preferably disposed on a hammer tube so as to be longitudinally displaceable, in such a way that it can be brought into engagement and out of engagement with the bevel-gear pinion. In the case of this development, the main bevel gear and the reversing bevel gear are only simultaneously in engagement with the bevel- gear pinion in the left-turning operating mode. It is thereby possible to prevent friction losses of the counter rotating bevel gears during the main operating mode, in right-turning.

R.305045 If the second switch sleeve can be coupled to the reversing bevel gear, the first and the second switch sleeve can be moved in a coordinated manner via a common switch rod.

While the first switch sleeve can effect a coupling of the main bevel gear to the hammer tube, the second switch sleeve can remain in a neutral position, the reversing bevel gear being able to remain in a position in which it is out of engagement with the bevel-gear pinion. When the switch rod is in an appropriate position, the first switch sleeve can be positioned so that the main bevel gear does not have a driving function, while the second switch sleeve indirectly or directly couples the reversing bevel gear to the hammer tube.

If the reversing bevel gear has, in an axial bore, a recess in which a radially biased annular spring is disposed, the reversing bevel bear can be coupled to the hammer tube by the second switch tube via the annular spring. A secure, frictional-force contact can be produced which can be realized with a reliable mechanism.

If the first and the second switch sleeve are guided so as to be rotatably movable and axially movable, both a rotatory motion in both rotational directions and a translational motion for travelling a switching path can be executed. In a preferred development, the first switch sleeve is guided in the supporting sleeve and in a bearing, particularly a needle bearing, running in the wobble shaft.

Here, a single switch sleeve is sufficient to couple both the main bevel gear and the reversing bevel gear to the actuating means.

R.305045 If an intermediate shaft is provided which is mounted so as to be axially movable in a transmission housing and in the wobble shaft, the intermediate shaft can be axially displaced, via a bearing, by the operating-mode selector knob, and the different desired operating modes can thus be set. Instead of a wobble shaft, a person skilled in the art will also consider other suitable percussion mechanism drives which appear appropriate.

If a switch bearing is provided via which the intermediate shaft can be axially displaced by the selector means, an actuation, particularly a turning of the selector means, can cause the intermediate shaft to be axially displaced.

If a compression spring is provided which couples the switch sleeve to the intermediate shaft, it can be ensured, due to its axial force, that a rotary coupling between the switch sleeve and the intermediate shaft is maintained in different axial positions of the intermediate shaft and switch sleeve.

If a common selector means for operating modes is provided for both rotational directions, incorrect operation can be prevented. All operating modes of the electric power tool can be set on the central selector means, in particular, on an operating-mode selector knob.

Drawing Further advantages are disclosed by the following description of the drawing. The drawing shows three R.305045 exemplary embodiments of the invention. The drawing, the description and the claims contain numerous features in combination. A person skilled in the art will also expediently consider the features individually, and combine them to form further meaningful combinations.

In the drawing: Fig. 1 shows a preferred rotary hammer, Fig. 2 shows an operating-mode selector knob of the preferred rotary hammer, Fig. 3 shows a portion of a longitudinal section through a preferred rotary hammer according to a first exemplary embodiment, in left-turning, without percussion, Fig. 4 shows a portion of a longitudinal section through a preferred rotary hammer, in right turning, without percussion, Fig. 5 shows a portion of a longitudinal section through a preferred rotary hammer, in the operating mode percussion drilling, Fig. 6 shows a portion of a longitudinal section through a preferred rotary hammer, in the operating mode chiselling.

Fig. 7 shows a portion of a longitudinal section through a preferred rotary hammer according to R.305045 a second exemplary embodiment, in the operating mode drilling / hammer-drilling.

Fig. 8 shows a portion of a longitudinal section through the preferred rotary hammer, in the operating mode vario-lock.

Fig. 9 shows a portion of a longitudinal section through the preferred rotary hammer, in the operating mode chiselling.

Fig. 10 shows a portion of a longitudinal section through the preferred rotary hammer, in the operating mode left-turning.

Fig. 11 shows a portion of a longitudinal section through a preferred rotary hammer according to a third exemplary embodiment, in the operating mode drilling / hammer-drilling.

Fig. 12 shows a portion of a longitudinal section through the preferred rotary hammer, in the operating mode vario-lock.

Fig. 13 shows a portion of a longitudinal section through the preferred rotary hammer, in the operating mode chiselling.

Fig. 14 shows a portion of a longitudinal section through the preferred rotary hammer, in an engagement phase for the operating mode left turning.

R.305045 Fig. 15 shows a portion of a longitudinal section through the preferred rotary hammer, in the operating mode left-turning.

Description of the exemplary embodiments

Fig. 1 shows a rotary hammer as a preferred hand tool, having a housing 10 in which an electric motor, not shown, is disposed. By means of the electric motor, an accessory, not shown, which is disposed in a tool holder 12 can be driven at least in a rotating manner about an axis 18. The electric power tool can be held by means of a vertical handle 14 attached to the housing, and switched on by means of a switching latch disposed on the said handle. A selector means 16 is used to change over between different operating modes of the electric power tool. A rotatable operating-mode selector knob 16 is preferably the central selector means 16 for all operating modes. A switching device, which is represented in greater detail in the following figures, is provided for reversing a rotational direction of the accessory. In the figures, parts which are the same or similar are in principle denoted by the same reference numerals.

The operating-mode selector knob 16 is shown in greater detail in Fig. 2. It can be turned to successively set an operating position 20 to different operating modes A, B. C, D, thus for example, left-turning without percussion (A), right-turning without percussion (B), hammer- drilling (C) and chiselling (D). In this case, a pin 22 within the R. 305045 housing 10 cooperates with the switching device, for example, via a toothed rack, in order to reverse the rotational direction of an accessory or to activate different operating modes.

Fig. 3 to Fig. 6 shows a first exemplary embodiment.

Fig. 3 shows a longitudinal section through a portion of the rotary hammer from Fig. 1 and explains the structure of a mechanical switching device, particularly of a left turning function of the rotary hammer without percussion.

A bevel-gear pinion 24 of an armature shaft of the electric motor engages simultaneously in a main bevel gear 26 and in a reversing bevel gear 28. The main bevel gear 26 and the reversing bevel gear 28 are disposed on opposite sides on the circumference of the bevel-gear pinion 24. The main bevel gear 26 is firmly pressed on by a supporting sleeve 32 which, in turn, is firmly guided, via a supporting ball- bearing 34, in a setting cover 38.

The reversing bevel gear 28 is seated so as to be rotatably movable on the supporting sleeve 32, so that, in the case of the represented rotational direction of the bevel-gear pinion 24, the main bevel gear 26, as viewed by an operator standing behind the rotary hammer, executes a right rotation, while the reversing bevel gear 28 executes an opposing left-rotation. The right-rotation corresponds to the usual main rotational direction of the rotary hammer.

In the operating mode shown, an internal toothing 30 of the reversing bevel gear 28 engages in an external toothing 44 of a switch sleeve 40, so that the latter also rotates to the left. The switch sleeve 40 is guided so as to be R.305045 rotatably movable and axially movable in the supporting sleeve 32 and in a needle bearing 72 running in a wobble shaft 62. It is possible for the switch sleeve 40 to move substantially in parallel to the axis 18 (Fig. 1). The wobble shaft 62 is coupled, by a wobble finger 64, to a piston guided in a hammer tube.

The switch sleeve 40 has further external Loathings 42, 46 which, in other axial positions of the switch sleeve 40, are used as actuating means 42, 44, 46 which, depending on the position of the switch sleeve 40, can either be brought into active coupling to a drive means 26, 28, in particular, the main bevel gear 26 or the reversing bevel gear 28, for the one or other rotational direction, or into at least one rotationally neutral position in which only the percussion mechanism is driven.

In the shown axial position of the switch sleeve 40, an internal toothing 36 of the supporting sleeve 32 can rotate freely, next to the external toothing 42, in a bore of the switch sleeve 40. The torque supplied by the electric motor is transferred by an internal toothing 48 of the switch sleeve 40 to an intermediate shaft 50. The intermediate shaft 50 is mounted, preferably on needle bearings 66, 68, 70, 72, so as to be axially movable in a transmission housing and in the wobble shaft 62. Via a switch bearing 56, the intermediate shaft 50 can be moved axially in a defined manner by the operating-mode selector knob 16, e.g., through active coupling to the pin 22 of the operating-mode selector knob 16. Via a straight-cut spur toothing, a rotary motion is transferred, via a toothed wheel 52 of the intermediate shaft 50 and a spur gear 54, R. 305045 to the hammer tube and ultimately to the accessory. There is a rotary driving between the switch sleeve 40 and the intermediate shaft 50, in that an external toothing 74 of the intermediate shaft 50 engages with an inner toothing 48. The rotary coupling between the switch sleeve 40 and the intermediate shaft 50 is supported by a compression spring 60.

Fig. 4 shows the structure in the operating mode "right running without percussion". Turning of the operating-mode selector knob 16 causes the intermediate shaft 50 to be moved to the left. Due to the axial force of the compression spring 60, the switch sleeve 40 also moves together with the intermediate shaft 50, so that the rotary coupling between the two is maintained. At the same time, the rotary driving to the reversing bevel gear 28 goes out of engagement, and a rotary driving from the switch sleeve to the supporting sleeve 32 goes into engagement, in that the external toothing 44 of the switch sleeve 40 disengages from the internal toothing 30 of the reversing bevel gear 28 and the external toothing 42 of the switch sleeve 40 engages in the internal toothing 36 of the supporting sleeve 32. The right-rotating main bevel gear 26 is now coupled to the intermediate shaft 50, and hence to the accessory. The rotary driving between the switch sleeve 40 and the intermediate shaft 50 is maintained in that the external toothing 74 of the intermediate shaft 50 engages with the internal toothing 48.

The structure in the operating mode "hammer-drilling" is represented in Fig. 5. Further turning of the operating- mode selector button 16 (Fig. 2) causes the intermediate R.305045 shaft 50 and the switch sleeve 40 to move one further step to the left. The rotary driving via the main bevel gear 26 to the switch sleeve 40 and further to the intermediate shaft 50 remains in engagement, in that the internal toothing 36 of the supporting sleeve 32 continues to engage with the external toothing 42 of the switch sleeve 40. In addition, the front external toothing 46 of the switch sleeve 40 has engaged in an internal toothing 76 of the wobble shaft 62, as a result of which a percussion mechanism, not shown, in the hammer tube can be driven via the wobble shaft 62. The external toothing 74 of the intermediate shaft 50 continues to be in engagement with the internal toothing 48 for the purpose of rotary driving.

The chiselling position is represented in Fig. 6. Turning of the operating-mode selector knob 16 to the end position D (Fig. 2) causes the intermediate shaft 50 to be moved into its left stop in a locking plate 80, where it is fixed in a torsionally rigid manner for the purpose of locking a chisel, not shown, in position. Since the switch sleeve 40 in the wobble shaft 62 strikes on a bearing 78, it cannot participate in this further displacement. The rotary driving between the switch sleeve 40 and the intermediate shaft 50 thus goes out of engagement, in that the external toothing 74 of the intermediate shaft 50 disengages from the internal toothing 48 of the switch sleeve 40, so that only the wobble shaft 62 continues to be driven by the switch sleeve 40 by the engagement of the external toothing 46 of the switch sleeve 40 with the toothing 76 of the wobble shaft 62.

R.305045 Fig. 7 to Fig. 10 show a second exemplary embodiment of an Ltype rotary drill in which the percussion mechanism is driven by an eccentric. The direction of working is represented by a broken line.

Fig. 7 shows a portion of a longitudinal section through a preferred rotary hammer having an eccentric drive, not shown, according to a second exemplary embodiment of the invention. In the figure, the eccentric drive, not shown, acts from the right side on a tool, not shown, which in the figure is disposed on a left side of a hammer tube 108.

The arrangement represented corresponds to an operating mode drilling / hammer-drilling in right-turning.

A main bevel gear 26 and a reversing bevel gear 28 now sit on the hammer tube 108 and are in continuous engagement with a bevel-gear pinion 24 which is disposed perpendicularly to the hammer tube 108 and is driven by an electric motor, not shown. The main bevel gear 26 and the reversing bevel gear 28 are disposed on opposite sides of the bevel-gear pinion 24. Between them, a ring 184 is disposed on the hammer tube 108 for the purpose of fixing in position.

A first and a second toothed sleeve 102, 160 are respectively disposed on the side of the bearing gears 26, 28, along the hammer tube 108, which is not in engagement.

The first toothed sleeve 102, an internal toothing 104 of which engages in longitudinal grooves 110 of the hammer tube 108, is disposed to the side of the main bevel gear 26. An external toothing 106 enables the first toothed sleeve 102 to be coupled, via a non-represented driving R.305045 toothing of a first switch sleeve 140, to an external toothing 112 of the main bevel gear 26. Additionally attached along the hammer tube 108 is a stationary friction bearing 120 having an external toothing 122. The first switch sleeve 140 engages circumferentially in a gripper 118 of a switch rod 100 and is axially displaced by the switch rod 100. The switch rod 100 is connected to an actuating means, not shown, for example, an operating-mode selector knob 16, as described in Fig. 2. Actuation of the actuating means causes the switch rod 100 to be displaced along the hammer tube 108, the first switch sleeve 140 or possibly a second switch sleeve 150 being driven along, in dependence on position.

A second toothed sleeve 160, an internal toothing 162 of which likewise engages in the longitudinal grooves 110 of the hammer tube 108, adjoins the reversing bevel gear 28 along the hammer tube 108. The second toothed sleeve 160 can be coupled to an external toothing 114 of the reversing bevel gear 28 via an external toothing 164, via a driving toothing 152 of the second switch sleeve 150, when the second switch sleeve 150, through its driving toothing 152 in an appropriate position, engages both in the external toothing 114 of the reversing bevel gear 28 and in the external toothing 164 of the second toothed sleeve 160.

The second toothed sleeve 160 is axially fixed on the hammer tube 108 by a fixing element 166 disposed in a groove of the hammer tube 108.

The second switch sleeve 150 engages, by means of a circumferential driver 154, in a pocket 176 of a switch gate 174. The switch gate 174 runs in a recess 116 of the R.305045 switch rod 100 and is held on a housing part 170 by means of a compression spring 172.

The main bevel gear 26 is coupled, by means of its external toothing 112, and via the driving toothing, not visible in the Figure, of the first switch sleeve 140, to the first toothed sleeve 102, the internal toothing 104 of which engages in the longitudinal grooves 110 of the hammer tube 108, so that a right-turning rotary motion of the hammer tube 108 ensues in the case of a left-turning bevel-gear pinion 24. The reversing bevel gear 28 rotates loosely on the hammer tube 108 in the direction opposite to that of the main bevel gear 26, since the second switch tube 150 only engages, by means of the driving toothing 152, in the loosely rotating second toothed sleeve 160.

If the actuating means, preferably the operating-mode selector knob 16 (Fig. 2) is turned to the next step, the switch rod 100 is displaced axially along the hammer tube 108 and comes into a position of the so-called vario-lock, as shown in Fig. 8. Vario-lock means that the hammer tube 108 is rotatable, but not driven, and is used, for example, for manually setting a suitable angular position for a chisel.

In respect of the functionality and description of the individual components, reference is made to the preceding Fig. 7. Due to the axial displacement of the switch rod 100, towards the left in the figure, the first switch sleeve 140 now engages fully in the external toothing 106 of the first toothed sleeve 102 and goes out of engagement in the case of the external toothing 112 of the main bevel R.305045 gear 26. The second switch sleeve 150 continues to be coupled only to the second toothed sleeve 160. The main bevel gear 26 and the reversing bevel gear 28 can therefore rotate freely, without driving the hammer tube 108. The hammer tube 108 can be turned independently of the drive This operating mode constitutes a transition between the operating modes drilling and chiselling.

If the actuating means, preferably the operating-mode selector knob 16 (Fig. 2) is turned to the next step, the switch rod 100 is displaced axially further to the left.

This is represented in Fig. 9, which illustrates the previously described arrangement in the operating mode chiselling. In respect of the functionality and description of the individual components, reference is made to the preceding Fig. 7. Upon the axial displacement of the switch rod 100, its gripper 118 drives the first switch sleeve 140 along and positions it in such a way that its internal toothing engages both in the external toothing 106 of the first toothed sleeve 102 and in the external toothing 122 of the stationary friction bearing 120. The first toothed sleeve 102 is thereby fixed in position, and its internal toothing 104 also causes the hammer tube 108 to be fixed in position. The main bevel gear 26 and the reversing bevel gear 28 can rotate freely.

This is represented in Fig. 10, which illustrates the previously described arrangement in the operating mode left-turning. In respect of the functionality and R.305045 description of the individual components, reference is made to the preceding Fig. 7. The gripper 118 of the switch rod pushes the first switch sleeve 140 on to the stationary friction bearing 120, so that the first toothed sleeve 102 can rotate freely. At the same time, in the case of this switching operation, the second switch sleeve 150 has been driven along by the switch rod 100 and moved to the left, since a switch gate 174 at the end of the recess 116 of the switch rod 100 is shifted, against the pressure of a compression spring 172, into the direction of motion of the switch rod 100. The second switch sleeve 150 is shifted, by means of its driving toothing 152, into the external toothing 114 of the reversing bevel gear 28, and simultaneously engages in the external toothing 164 of the second toothed sleeve 160. The reversing bevel gear 28 and the second toothed sleeve 160 are now coupled, and the hammer tube 108 is also coupled on, via the internal toothing 162 of thetoothed sleeve 160 engaging in the longitudinal grooves 110.

Fig. 11 to Fig. 15 show a third exemplary embodiment of a preferred rotary hammer having a percussion mechanism driven by an eccentric drive. The components and the switching sequences correspond largely to those of the preceding Figs. 7 to 10. In respect of the functionality and description of the individual components, reference is made to the preceding figures.

In contrast to the first and second exemplary embodiments, the preferred embodiment has a reversing bevel gear 28 which is only in engagement with a bevel-gear pinion 24 in the operating mode left-turning.

R.305045 In the development shown in Fig. 11, a switch rod 100 is again switched as in Fig. 7; the rotary hammer is in the operating mode drilling / hammer-drilling.

The reversing bevel gear 28 is disposed so as to be axially displaceable on a hammer tube 108, and its internal toothing 30 engages in longitudinal grooves 110 of the hammer tube 108. A second toothed sleeve 160 for coupling the reversing bevel gear 28 on to the hammer tube 108, via the toothed sleeve 160, as described in Figs. 7 to 10, can be omitted in this case.

In an axial bore of the reversing bevel gear 28 is a recess 182 in which is located a radially biased annular spring 156. The annular spring 156 lies on the hammer tube 108. Running in the bores of the reversing bevel gear 28 are locking pins 158 which, internally, bear on the annular spring 156 and, externally, bear on a conical inner face of a second switch sleeve 150. The second switch sleeve 150, in turn, is rotatably accommodated in a switch gate 174 which is held on a housing part 170 by a compression spring 172. As before, in the operating positions hammerdrilling, vario-lock and chiselling, the switch gate 174 also runs in a recess 116 of the switch rod 100 and is only driven along when leftrunning is operated.

Fig. 12 shows a portion of a longitudinal section through the preferred rotary hammer in the operating mode vario- lock. This arrangement corresponds to that in Fig. 8. In respect of the functionality and description of the R.305045 individual components, reference is made to the preceding figures. The switch rod 100 has been moved axially further to the left and engages, by means of a gripper 118, in an external toothing 106 of the first toothed sleeve 102, the internal toothing 104 of which engages in the longitudinal grooves 110 of the hammer tube 108.

Fig. 13 shows a portion of a longitudinal section through the preferred rotary hammer, in the operating mode chiselling. This arrangement corresponds to that of the second exemplary embodiment in Fig. 9. In respect of functionality and description of the individual components, reference is made to the preceding figures. The switch rod has again been moved axially further to the left and engages, by means of the gripper 118, both in an external toothing 106 of the first toothed sleeve 102 and in an external toothing 122 of a stationary friction bearing 120.

If the switch rod 100 is moved axially further to the left through actuation of an actuating means, in particular, an operating-mode selector knob 16 (Fig. 2), a phase commences, shown in Fig.14, in which the reversing bevel gear 28 shifts into engagement with the toothing of the bevel-gear pinion 24 for the operating mode left-turning.

The reversing bevel gear 28 is axially displaced via the switch rod 100, the switch gate 174 and the second switch sleeve 150. In this case, an oblique face 180 of the second switch sleeve 150 bears on the locking pins 158 which, initially, cannot yet shift radially inwards due to the fact that the annular spring 156 is still lying on the hammer tube 108. If the reversing bevel gear 28 adjoins in its end position, further displacement of the second switch R.305045 sleeve 150 causes the locking pins 158 to be pressed inwards, until the annular spring 156 sinks into an annular groove 186 in the hammer tube 108. Due to the radial sinking of the locking pins 158, the second switch sleeve 150 can be moved as far as the stop 188 on the reversing bevel gear 28. This is represented in Fig. 15 for the operating mode left-turning. In respect of the functionality of the individual components, reference is made to the preceding figures.

The internal toothing 30 of the reversing bevel gear 28 bears on the annular spring 156, so that the reversing bevel gear 28 lies axially fixed on the hammer tube 108.

R. 305045 References housing 56 switch bearing 12 tool holder 60 compression spring 14 handle 62 wobble shaft 16 operating-mode selector 64 wobble finger knob 18 axis 66 bearing, intermediate shaft operating position 68 bearing, intermediate shaft 22 pin 70 bearing, intermediate shaft 24 bevel-gear pinion 72 needle bearing, wobble shaft 26 main bevel gear 74 external toothing, intermediate shaft 28 reversing bevel gear internal toothing, 76 toothing, wobble shaft reversing bevel gear 78 bearing 32 supporting sleeve 80 locking plate 34 supporting ball-bearing 100 switch rod 36 internal toothing, 102 toothed sleeve supporting sleeve 104 internal toothing 38 setting cover 106 external toothing switch sleeve 108 hammer tube 42 external toothing 110 longitudinal groove 44 external toothing 112 external toothing 46 external toothing 114 external toothing 48 internal toothing 116 recess intermediate shaft 116 gripper 52 toothed wheel, 120 friction bearing intermediate shaft 54 spur gear 122 external toothing R.305045 switch sleeve switch sleeve 152 driving toothing 154 driver 156 annular spring 158 locking pin toothed sleeve 162 internal toothing 164 external toothing 166 fixing element element 172 spring 174 switch gate 176 pocket oblique face 182 recess 184 ring 186 annular groove 188 stop

Claims

R.305045 Claims 1. Electric power tool having an electric motor which is

disposed in a housing (10) and by means of which an accessory disposed in a tool holder (12) can be driven at least in a rotating manner, and having a switching device for reversing the rotational direction of the accessory, characterized in that the switching device comprises a transmission (24, 26, 28, 32, 40, 140, 150) by means of which the accessory can optionally be driven in the one or other rotational direction, with the rotational direction of the electric motor being unchanged.
2. Electric power tool according to Claim 1, characterized in that the switching device has at least one switch sleeve (40, 140) which can be positioned in dependence on a selected operating mode.
3. Electric power tool according to Claim 2, characterized in that a second switch sleeve (150) is provided.
4. Electric power tool according to either of Claims 2 or 3, characterized in that the first and the second switch sleeves (40, 140, 150) have actuating means (42, 44, 152) which, depending on the position of the switch sleeves (40, 140, 150), can either be brought into active coupling to a drive means (26, 28) for the one or other rotational direction, or into at least one rotationally neutral position.

R.305045
5. Electric power tool according to any one of the preceding Claims, characterized in that the switching device comprises a reversing bevel gear (28) which can be driven, together with a main bevel gear (26), by a bevel-gear pinion (24).
6. Electric power tool according to Claim 5, characterized in that the main bevel gear (26) and the reversing bevel gear (28) are disposed on opposite sides of the bevel-gear pinion (24).
7. Electric power tool according to either of Claims 5 or 6, characterized in that the reversing bevel gear (28) is disposed so as to be rotatably movable on a supporting sleeve (32) .
8. Electric power tool according to either of Claims 5 or 6, characterized in that the reversing bevel gear (28) is disposed on a hammer tube (108).
9. Electric power tool according to Claim 8, characterized in that the reversing bevel gear (28) is disposed so as to be longitudinally displaceable, in such a way that it can be brought into engagement and out of engagement with the bevel-gear pinion (24).
10. Electric power tool according to either of Claims 8 or 9, characterized in that the second switch sleeve (150) can be coupled to the reversing bevel gear (28).

R.305045
11. Electric power tool according to any one of Claims 8, 9 or 10, characterized in that the reversing bevel gear (28) has, in an axial bore, a recess (182) in which a radially biased annular spring (156) is disposed.
12. Electric power tool according to any one of the preceding Claims, characterized in that the first and the second switch sleeve (40, 140, 150) are guided so as to be rotatably movable and axially movable.
13. Electric power tool according to any one of the preceding Claims, characterized in that an intermediate shaft (50) is provided which is mounted so as to be axially movable in a transmission housing and in a wobble shaft (62).
14. Electric power tool according to Claim 13, characterized in that a switch bearing (56) is provided via which the intermediate shaft (50) can be axially displaced by the selector means (16).
15. Electric power too according to either of Claims 13 or 14, characterized in that a compression spring (60) is provided which couples the first switch sleeve (40) to the intermediate shaft (50).
16. Electric power tool according to any one of the preceding Claims, characterized in that a common selector means (16) for operating modes is provided for both rotational directions.

R.305045
17. An electric power tool substantially as herein described with reference to the accompanying drawings.