GB2346100A - Spindle brake - Google Patents

Abstract

A device for arresting a shaft 10 rotatably mounted in a housing 11, eg the tool spindle of a hand-held electrical machine tool, has two arresting members 12,13 which can be brought into mutual engagement and of which the first is disposed in the housing in a non-rotatable manner while the second is disposed on the shaft in a rotation-proof manner. The first member 12 is a radially displaceable button with a detent 31 for engagement with grooves 35 in the second member 13. The second member 13 is axially displaceable on the shaft 10 and has an end profile 381,382 which co-operates with a spring loaded pin 36 on the button 12 to so displace the second member when the shaft is rotating as to move the grooves 35 out of range of the detent 31 and hence prevent the brake operating.

Description

Device for arresting a shaft Prior art The starting point of the invention is a device, of the type defined in the precharacterising clause of claim 1, for arresting a shaft rotatingly mounted in a housing, in particular the tool spindle of a hand-held electrical machine tool, such as a hand-held drill, battery screwdriver or the like.

When used in a hand-held electrical machine tool, for example, as a so-called "spindle-locking function", such arresting devices arrest the tool spindle when the machine is not in operation, in order to permit the tightening or undoing of a single-sleeve tool chuck.

In a known arresting device for a hand-held electrical machine tool of this kind (DE 43 05 967 A I), use is made, for the purpose of implementing the so-called "locking function", of a spindle gearwheel, as a second arresting member, which is seated on the tool spindle in a rotation-proof manner and meshes with a driving wheel on the output shaft of the electric motor and which is provided, for this purpose, with a plurality of axial recesses. The first arresting member is constructed as an arresting switch which is equipped with a recessed grip on its upper side and is displaceable parallel to the tool spindle and which carries an arresting bar which is capable of insertion, in a form-locking manner, in one of the recesses in the spindle gearwheel and thereby secures the tool spindle to the housing in a non-rotatable manner. In order to prevent the locking function being brought into operation, when the machine is running, by actuation of the arresting slide, and damage thus occurring in the machine, measures are adopted which block displacement of the arresting switch when the electric motor is switched on.

These measures consist in the fact that the arresting bar is guided backwards as far as the electrical switching region of the motor and is there coupled with a sliding piece which is released, for displacement purposes, by a positioning ring only when a brush-shifting device is located in the central position which is currentless for the electric motor.

In an arresting device for a percussion drill, which device is likewise known (DE 195 28 924 Al), a manual switch-over lever for the"drilling"and"percussion drilling"operating modes has a third pivoting position in which the locking function is implemented. In this pivoting position of the switch-over lever, an arresting pin which is integral with the housing and displaceably mounted is displaced against the restoring force of a restoring spring and engages in the same way, in a form-locking manner, in one of a number of axial recesses in a spindle gearwheel via which the tool spindle is driven by an electric motor. Here too, in order to avoid malfunctions, the conveying of the switch-over lever into its third switching position takes place with tensioning of a restoring spring which immediately resets the switch-over lever again if the said lever is released. This ensures that the locking function is immediately discontinued again after toolchanging and, when the electric motor is switched on, one of the"drilling"or "percussion drilling"operating modes is set, gearing-wise. Advantages of the invention The arresting device according to the invention having the characterising features of claim 1 has the advantage that manual execution of the locking function is not blocked at any point in time, but at the same time it is ensured, by means of relatively little constructional outlay, that no damage to the device or shaft can occur as a result of the triggering of the locking function ; since the separating means according to the invention, which are active only when the shaft is rotating, force the separation of the arresting members if the latter come into engagement, or threaten to reach engagement, as a result of triggering of the locking function.

This eliminates all the complicated measures which blocking of the locking function against manual actuation requires.

Advantageous further developments of, and improvements to, the device indicated in claim 1 for arresting the shaft are possible through the measures set out in the other claims.

Preferred forms of embodiment of the invention for achieving a configuration of the arresting device which is advantageous in terms of design are presented as alternatives in claims 7,13 and 15.

Drawings The invention is explained in greater detail in the following description with the aid of exemplified embodiments represented in the drawings, in which: figure 1 represents, in detail form, a longitudinal section, along the sectional line 1-1 in figure 2, through a device for arresting a shaft which is rotatably mounted in a housing, figure 2 shows a section along the line II-II in figure 1, figure 3 shows the same representation as in figure 1 of an arresting device according to a second exemplified embodiment, figure 4 shows a section along the line IV-IV in figure 3, figure 5 shows, in detail form, a cross-section through an arresting device according to a third exemplified embodiment, and figure 6 shows, in detail form, a cross-section through an arresting device according to a fourth exemplified embodiment.

Description of the exemplified embodiments The device, which is represented in figures 1 to 6 in various sections and exemplified embodiments, for arresting a shaft 10 rotatingly mounted in a housing 11 is preferably used in hand-held electrical machine tools, such as a hand-held drill, battery screwdriver or the like, and serves to secure the tool spindle representing the shaft 10 in position when the machine is not in operation, in order to tighten or undo, for tool-changing purposes, a single-sleeve clamping chuck for receiving the tool, such as a drill or screwdriver bit, which chuck is connected to the tool spindle in a rotation-proof manner. Under these circumstances, the housing 11 represents the machine housing of the hand-held electrical machine tool. In principle, all the exemplified embodiments of the arresting device which are represented in the drawings have two arresting members 12,13 which can be brought into engagement with one another and of which the first arresting member 12 is disposed in the housing 11 in a non-rotatable manner while the second arresting member 13 is disposed on the shaft 10 in a rotation-proof manner. The two arresting members 12,13 are brought into engagement by manual actuation of the first arresting member 12 which is disposed in the housing 11 and, for actuation purposes, partly protrudes from the said housing 11. If the two arresting members 12,13 are in engagement, the shaft 10 is secured to the housing 11 in a non-rotatable manner. In order to prevent damage occurring to the motor, the arresting device or the shaft 10 with the switching-on of the drive for the shaft 10, that is to say, in the example of the hand-held electrical machine tool, when the electric motor is switched on, separating means are provided which bring about constrained separation of the two arresting members 12,13 when the shaft 10 rotates. In the various exemplified embodiments according to figures 1 and 2,3 and 4 or 5 and 6, the said separating means are embodied in different ways according to the different constructions of the arresting members 12,13.

In the first exemplified embodiment of the arresting device, which is represented in different sections in figures I and 2, the first arresting member 12 has a detent ring 14, the said ring enclosing the shaft 10, being displaceably guided in the housing 11 and having detents 15 constructed on one of its annular sides, and also has an actuating member 16, which protrudes on the housing 11, for displacing the detent ring 14 on the shaft 10. As can be seen from figure 2, the detent ring 14 is guided by two diametral guide noses 17 in two guide rails 18 which are constructed in the housing 11, extend in an axial manner, parallel to the axis of the shaft, and are U-shaped in cross-section. Likewise constructed on the second arresting member 13, on that end face of the latter which faces towards the detent ring 14, are detents 19 which correspond with the detents 15 on the detent ring 14 and come into engagement with one another as a result of displacement of the detent ring 14 in the guide rails 18. For the axial displacement of the detent ring 14, the actuating member 16 acts upon a transmission ring 20 which is mounted in front of the detent ring 14 and is seated loosely on the shaft 10. Between the transmission ring 20 and the detent ring 14 there are disposed, in a manner uniformly distributed over the periphery, a number of pressure springs 21 having spring axes directed parallel to the axis of the shaft. The ends of the pressure springs 21 are received in a form-locking manner in axial depressions 22 in the detent ring 14 and axial depressions 23 in the transmission ring 20, which axial depressions are introduced from end faces of the detent ring 14 and transmission ring 20 which face towards one another.

The actuating member 16 comprises a displacing button 24, which is displaceably guided in the housing 11 radially to the shaft 10, and a displacing wedge 25 which continues the displacing button 24 in one piece in the direction of displacement of the said button and engages over the shaft 10 in a fork-shaped manner.

Constructed on the displacing wedge 25 is a wedging face 26 which is set in such a way in relation to the axis of the displacing button 24 that, when there is an inward movement of the displacing button 24, which movement is directed towards the shaft 10, the wedging face 26 gives rise to a displacing movement of the transmission ring 20 and detent ring 14 which is directed towards the second arresting member 13. To this end, the transmission ring 20 abuts, by way of a bevel 27 which is constructed on its end face that faces towards the displacing wedge 25, and which runs parallel to the wedging face 26, on the said wedging face 26 under the pressure of the pressure springs 21. Associated with the displacing button 24 are restoring springs 28 which are supported on the said displacing button 24 on the one hand, and on the housing 11 on the other, and are tensioned when the displacing button 24 is moved radially inwards.

If the displacing button 24 is now pressed manually, the displacing wedge 25 moving towards the shaft 10 displaces, via its wedging face 26 and via the bevel 27 on the transmission ring 20, the said transmission ring 20 towards the left in figure 1, as a result of which the detent ring 14 is displaced via the pressure springs 21, and the detents 15,19 on the detent ring 14 and second arresting member 13 are brought into engagement with each other. The separating means initially touched upon, which bring about a constrained separation of the two arresting members 12,13 when the shaft 10 is rotating, and thus avoid damage, are here formed by an over-detent moment provided between the detents 15,19. The size of the over-detent moment is determined by the structure of the detents 15,19 and by the hardness of the pressure springs 21 and is so designed that, when the shaft 10 is stationary, the over-detent moment is smaller than a torque which acts upon the shaft 10 and is produced, for example, when the tool chuck of a tool spindle is being undone. When the shaft 10 is rotating, the over-detent moment permits ratcheting between the detent ring 14 and second arresting member 13, so that the shaft 10 is able to turn in spite of the pressed-in displacing button 24.

In the case of the arresting device sketched in various sections in figures 3 and 4, the first arresting member 12 has a displacing button 30 for manual actuation which is displaceably guided in the housing 11 radially to the shaft 10 and which carries a detent cam 31 on its end face which faces towards the said shaft 10. Associated with the displacing button 30 are restoring springs 32 which are supported on the said displacing button 30 on the one hand, and on the housing 11 on the other, and which are tensioned when the displacing button 30 is moved radially inwards. The second arresting member 13 is secured on the shaft 10 in a rotation-proof but axially displaceable manner by means of a groove-and-tongue joint 33. In this case, the axial displacement takes place against the force of pressure spnngs 34 which are supported between the second arresting member 13 and the housing 11 with their spring axes orientated parallel to the shaft 10.

Constructed on an axial section of the second arresting member 13 are detent grooves 35 which are disposed in a manner uniformly distributed over the periphery and correspond with the detent cam 31 on the displacing button 30.

When the second arresting member 13 is in its basic position on the shaft 10, the said detent grooves 35 lie in the displacement path of the detent cam 31, so that, when the displacing button 30 is pressed manually into the housing 11 against the force of the restoring springs 32, the advancing detent cam 31 engages in one of the detent grooves 35 in a form-locking manner in the peripheral direction and thereby secures the second arresting member 13 and the shaft 10 to the housing 11 in a non-rotatable manner.

In this exemplified embodiment, the separating means for the constrained separation of the two arresting members 12,13 when the shaft 10 is rotating have a pin 36 which is associated with the first arresting member 12 and a shaft section 37 which is constructed on the second arresting member 13 and has a shaft profile 38. The pin 36 is displaceably guided in the displacing button 30 and is subjected to the force of a pressure-applying spring 39 which presses the pin 36 against stops 301 on the displacing button 30, radially in relation to the shaft 10 and far beyond the detent cam 31, the said pin ending at a small radial distance in front of the shaft section 37. When the displacing button 30 is pressed into the housing 11, the pin 36 thereby comes into engagement with the shaft profile 38 very much earlier than the detent cam 31 does with the detent grooves 35. Now the shaft profile 38 is constructed in such a way that the pin 36, which is inserted when the shaft 10 is rotating, displaces the second arresting member 13 against the force of the pressure springs 34 to an extent such that the detent grooves 35 now lie outside the displacement path of the detent cam 31 and the said detent cam 31 is thereby not able, at the end of the inward movement of the displacing button 30, to give rise to detent as a result of engagement in the detent grooves 35. To be specific, the shaft profile 38, which has shaft peaks 381 and shaft troughs 382, is cut, for this purpose, into the shaft section 37 of the second arresting member 13 in such a way that the shaft peaks 381 are flush with the annular end face 371 of the shaft section 37, so that the inserted pin 36 runs up, when the shaft 10 is rotating, onto the end face 371 and engages behind the shaft section 37 in such a way that its superficies abuts on the end face 371 and, as a result of this, the second arresting member 13 is kept displaced against the force of the pressure springs 34. In order to achieve adequate displacement of the second arresting member 13, the depth of the shaft profile 38, that is to say the distance between the shaft peaks 381 and the shaft troughs 382, is of slightly larger dimensions than that displacement travel of the second arresting member 13 which is necessary for guiding the detent grooves 35 out of the displacement path of the detent cam 31. If the shaft 10 is stationary, the pin 36 likewise impinges upon the shaft profile 38 when the displacing button 30 is moved inwards. If the said pin is not able to enter any intermediate space on the shaft profile 38, it is moved inwards, against the force of the pressure-applying spring 39 in the displacing button 30, so that the displacing movement of the displacing button 30 can be continued until the detent cam 31 is inserted in the detent groove 35 and the shaft 10 is thereby immobilised.

In the third exemplified embodiment of an arresting device, which is represented in figure 5, the second arresting member 13, which is disposed on the shaft 10 in a rotation-proof manner, carries external toothing 40 and the first arresting member 12 has two locking levers 41 of identical construction which are pivotably mounted on the housing 11 and engage, by way of a detent nose 42, in the external toothing 40 and which thereby secure the second arresting member 13 to the housing 11 in a non-rotatable manner. Seated on each locking lever 41 is a leg spring 43 which loads the said locking lever 41 in the direction of engagement, so that the detent noses 42 are always located, under the spring force of the leg springs 43, in gaps between the teeth of the external toothing 40.

In this exemplified embodiment, the separating means for the constrained separation of the two arresting members 12,13 when the shaft 10 is rotating have two electromagnets 44, of which one electromagnet 44 is associated with a locking lever 41 in each case. When current is supplied to the exciter winding of the electromagnet 44, which winding is indicated by 45, the associated locking lever 41 is attracted and thereby pivoted, under which circumstances the detent nose 42 lifts out of the external toothing 40. Control electronics 46, which sense the on/off position of a switch for driving the shaft 10, that is to say the switched-on and switched-off condition of the electric motor in the case of a hand-held electrical machine tool, ensure that, with closure of the switch for driving the shaft, current is supplied to the exciter windings 45 of both the electromagnets 44 and, as a result of the lifting of the detent noses 42 out of the external toothing 40, the two arresting members 12, 13, which are interlocked with one another when the electromagnets 44 are currentless, are separated from one another, so that the shaft 10 is able to turn in an unhindered manner.

In a simplifie embodiment of the arresting device represented in figure 5, one of the two locking levers 41 and electromagnets 44 can be eliminated.

In the fourth exemplified embodiment of an arresting device, which is sketched diagrammatically in cross-section in figure 6, the second arresting member 13 again carries external toothing 50, whereas the first arresting member 12 comprises a locking lever 51 with a detent nose 52, which locking lever is pivotably mounted in the housing 11, and also a displacing button 53 which is displaceably mounted in the said housing 11 and can be displaced manually inwards into the latter. Acting upon the locking lever 51 is a leg spring 54 which loads the said locking lever 51 in figure 6 in the anticlockwise direction and applies it against the displacing button 53. When the displacing button 53 is not actuated, it is applied against a stop 111 on the inner wall of the housing 11 by the pre-tensioned locking lever 51. In this position, the detent nose 52 of the locking lever 51 is disengaged from the external toothing 50 in the second arresting member 13 and can be conveyed again, by inward movement of the displacing button 53, into the detent position represented in figure 6, in which the two arresting members 12,13 are connected to one another in a rotation-proof manner.

In this case, the separating means for bringing about constrained separation of the two arresting members 12,13 when the shaft 10 is rotating have a cam plate 55 with a radially protruding cam 56, which cam plate is seated on the shaft 10 in a frictionally engaged manner, and also a lifting-out curve 57 constructed on the locking lever 51, on the underside facing towards the said cam plate 55, which lifting-out curve interacts with the cam 56 and is delimited by a stop 58 for the said cam 56. The lifting-out curve 57 has an approximately cosine-shaped curve section 571, the distance of which from the cam 56 is so dimensioned that the detent nose 52 of the locking lever 51 is capable of dropping into the external toothing 40 (as is represented in figure 6) when the cam 56 is located at the lowest point on the curve section 571, and is lifted out of the external toothing 50 when the cam 56 is located at the highest point. The stop 58 is disposed at the end of the highest point on the curve section 571, viewed in the direction of turning of the cam 56. The direction of turning of the shaft 10 is indicated by the arrow 59.

Under these circumstances, the cam plate 55 with the cam 56 is always kept between the detent nose 52 and the stop 58.

If, when the shaft 10 is rotating, the locking lever 51 is pivoted inwards by the operator via the displacing button 53, so that its detent nose 52 arrives in the vicinity of the external toothing 50, the locking lever 51 is blocked when the cam 56 rolls along on the lifting-out curve 57. Under these circumstances, the cam 56 strikes against the stop 58 after a certain degree of twisting and the cam plate 55 slips on the shaft 10, so that insertion of the detent nose 52 into the external toothing 51 when the shaft 10 turns is prevented. When the shaft 10 is stationary, the operator is able to twist the shaft 10 slightly by hand, so that the cam plate 55 releases the locking lever 51 again and the shaft 10 can be arrested by pressing the displacing button 53.

Claims (8)

1. Claims 1. A device for arresting a shaft rotationally mounted in a housing, said device comprising two arresting members which can be brought into engagement with one another, the first arresting member being disposed in the housing in a non-rotatable manner, while the second arresting member is disposed on the shaft in a rotation-proof manner, and separating means for bringing about constrained separation of the two arresting members when the shaft is rotating, wherein the first arresting member has a displacing button which is displaceably guided in the housing, radially to the shaft, and can be actuated manually and which carries, on its end face that faces towards the shaft, and a detent cam which can be inserted in grooves constructed on the periphery of the second arresting member, the said second arresting member being disposed on the shaft in an axially displaceable manner and the separating means have a spring loaded pin which is associated with the first arresting member, is guided so as to be displaceable in the displacing button in the direction of displacement of the said first arresting member and protrudes on the displacing button radially to the shaft, and a shaft section constructed on the second arresting member and the shaft profile of which is constructed in such a way that the pin, which is inserted radially in the shaft section when the shaft is rotating, displaces the second arresting member against spring force to an extent such that the detent grooves lie outside the displacement path of the detent cam.
2. 2. A device according to claim 1, wherein the shaft peaks of the shaft profile are flush with the annular end face of the shaft section, so that the pin runs up, when the shaft is rotating, onto the end face of the shaft section and engages behind the said shaft section.
3. 3. A device according to claim 2, wherein the axial depth of the shaft profile is of greater dimensions than that displacement travel of the second arresting member which is necessary for conveying the detent grooves out of the displacement path of the detent cam.
4. 4. A device according to any one of claims 1 to 3, wherein the second arresting member is supported, by way of its end face which faces away from the shaft section, on the housing via pressure springs.
5. 5. A device according to any one of claims 1 to 4, wherein the pin protruding on the displacing button is applied, by means of a pressure-applying spring, against at least one stop constructed on the said displacing button, and that the displacement travel of the pin against the pressure-applying spring is of greater dimensions than the displacement travel of the detent cam until it is inserted in the detent grooves.
6. 6. A device according to any one of claims 1 to 5, wherein there are associated with the displacing button restoring springs which are supported on the said displacing button and on the housing and can be tensioned when there is radial inward movement of the said displacing button.
7. 7. A device according to any one of the preceding claims, wherein the device is an electric hand held machine tool.
8. 8. Device for arresting a shaft substantially as herein described with reference to the accompanying drawings.