GB2319974A

GB2319974A - Machine tool spindle lock

Info

Publication number: GB2319974A
Application number: GB9725285A
Authority: GB
Inventors: Albert Kleider
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1996-12-05
Filing date: 1997-11-28
Publication date: 1998-06-10
Anticipated expiration: 2017-11-28
Also published as: JPH10156760A; IT1296583B1; ITMI972649A1; GB9725285D0; DE19650364A1; GB2319974B

Abstract

A machine tool such as an angle grinder has a spindle lock (25) for locking the operating spindle (13) against rotation, which spindle lock comprises a grooved rim (27) arranged on the clamping flange (19) with at least one groove (28). A hand lever (29) has a locking cam (32), which can engage in the at least one groove (28). The spindle lock (25) can releasably engage with the operating spindle (13) in the operating direction of rotation and can only be coupled in hooking fashion in the opposite direction. Engagement of the locking cam (32) in the groove (28) is ruled out during rotation so long as its rear end edge (38) has not reached the groove flank (42).

Description

1 Manual machine tool State of the art 5' 2319974 The invention is based

on a manual machine tool with a rotating tool accordmig to the generic type of claim 1.

A generic manual machine tool is known according to DE-OS 44 32 973 (PCT DE 95/01083), whose spindle lock can be actuated via a rotary bolt operable by means of a hand lever, a locking cam arranged on the rotary bolt having a semi-circular cross section. The locking cam is provided for engagement in oppositely disposed, semi-circular grooves in the grooved rim of a clamping flange. The locking cam enters these semi-circular grooves in the outwardly pivoted operating position of the hand lever by being driven so as to rotate.

This known spindle lock can be simply manufactured and operates reliably. However, in the event of faulty actuation of the spindle lock whilst the machine is (still) running, the force acting between the grooves and the locking cams is so great that disturbing vibrations can be generated.

Advantages of the invention In contrast to the above state of the art, the manual machine tool according to the invention having the characterising features of claim 1 offers the advantage that in the event of faulty actuation, the locking cam only allows minimal force to be transferred from the hand lever to the clamping flange. In the event of faulty operation of the spindle lock e.g. whilst the machine is running, there is therefore no danger of the locking cam or grooves be Mig deformed. In addition, the locking function in both directions of rotation of the operating spindle is differentiated and more reliably ensured than mi the known locking device, e.g. when the clampmg nut is to be tightened using an auxiliary tool.

2 As a result of the fact that the rear end face of the locking cam-slides upon the grooved rim until the locking cam can engage 'm the groove, and as a result of the fact that the cam end face of the locking cam is 1 to 3 min shorter than the width of the groove, the entry of the locking cam is only possible during safe low rotation of the operating spindle.

As a result of the fact that the locking cam and the groove have acuteangled contours at one end and rounded contours at the other designed for reciprocal engagement the retaining force between the spindle and the spmdle lock is less in an operating direction of rotation than when the clamping nut is tightened.

As a result of the fact that the groove flanks are inclined relative to a radial in the opposite direction to the operating direction of rotation of the operating spindle, so that the first flank in the operating direction of rotation extends through a, more particularly sharp-edged, retaining edge and the second flank extends in curved fashion through a rounded section into the contour of the grooved rim, and as a result of the fact that the locking cam comprises a cam end face which can engage m the manner of a hook over the retaining edge of the flank when the clamping nut is released, as well as a rounded end contour, against which the groove flank can be supported, the locking groove being approximately 1 to 2 mm smaller than the groove, the intended difference mi the retaining force can be particularly reliably attained, more particularly mi that the groove has a depth of approximately 3 to 5 mm, a width of approximately 5 to 10 mm and radii of approximately 0.5 to 1.2 mm, the rounded section having a radius of curvature of approximately 1.2 to 1.8 mm, and mi that the locking cam has a length which is 1/3 to 1/2 shorter than that of the hand lever.

A further improvement mi the retaining fimction of the spindle lock is obtained in that the cam end face of the locking cam is micImied relative to the groove base during engagement in the groove and when resting upon the rounded end contour, since this increases the surface pressure between the engaging parts.

3 The retaining effect in the clamping direction of the clamping nut is improved Mi that the cam end face has a V-shaped recess, whose contour substantially matches the contour of the groove flank in the region of the retaining edge.

As a result of the fact that the rotary bolt and the hand lever are two parts which can engage with one another in a fork-like manner, the rotary bolt supporting the locking cam in the manner of an attached fork and the hand lever supporting a gripper plate made of plastics material, an expedient, light-weight manufacture of the acting device from stamped parts is possible.

As a result of the fact that the rotary bolt is mounted ad. oining the locking cam in a metal bush and in the region of the hand lever in plastics material, the service life of the actuating device for the spindle lock is increased.

Drawings is The invention will be explained in further detail in the following description by way of an embodiment illustrated in the drawings, in which:

Figure 1 is a partial longitudinal section through an angle grinding machine, Figure 2 is a plan view (from below) of the angle grinding machine 2 0 according to the arrow II in Figure 1 without the clamping nut, grinding disc and protective hood, Figure 3 is a perspective rear view of the clamping flange, Figures 4 to 7 show the spindle lock as a detail 'm four different operating positions, and Figure 8 is an exploded view of the hand lever with rotary bolt and locking cam.

Description of the embodiment

4 The angle grinding machine 9 shown in longitudinal section mi -Figure 1 comprises a housing 10, which accommodates an electric drive motor, not shown, with a drive shaft 11, an angle gearing 12 and an operating spindle 13. The operating spindle 13 is rotatably mounted 'm a ball bearing 14 and a needle bearing 15, both constructed as radial bearings. The needle bearing 15 is accommodated by the machine housing 10 and the ball bearing 14 by a bearing flange 16 made of plastics material. The bearing flange 16 is flanged onto the machine hous Mig 10 and an angle grinder protective hood 161 is mounted on the outer circumference of the bearing flange referred to as the neck 160.

With its free end 13 1, the operating spindle 13 projects axially beyond the bearing flange 16. Mounted on this free end 131 is a clamping device 17, which receives a tool 18 in the form of a cutting or grinding disc.

The clamping device 17 comprises a clamping flange 19, which is fitted onto the free end 131 of the operating spindle 13 and is non-rotatably and radially is and axially non-displaceably connected therewith, and a clamping nut 20. The clamping nut 20 can be screwed onto a threaded section 2 1 of the free end 13 1 of the operating spindle. The tool 18 can be fitted in a posifive-locking manner with a central centring aperture 22 onto a receiving Journal 23 formed on the end face of the clwnpmg flange 19 and can be pressed in a non-posifive locking manner by means of the clamping nut 20 against the annular end face 191 of the clamping flange 19.

A washer 24 is fitted between the clamping nut 20 and the tool 18.

The operating spindle 13 can be locked against rotation by way of a spindle lock 25 by actuating the hand lever 29 thereof To this end, the spindle lock comprises a grooved rim 27 formed on the outside of the clamping flange 19 with a plurality of radial grooves 28 offset relative to one another with equal angle of rotation spacing and having a rectangular cross section, and a locking carn 32, which cooperates with the grooved rim 27 and whose cain end face 37 has a hook- like contour. The contour of the grooves 28 and the profile of the locking cam 32 match one another in such a manner that, when the locking cam 32 engages 'm the groove 28 when the operating spindle 13 is inoperative or merely rotating at a low velocity, i.e. in the most desirable case, said locking cam locks the clamping flange 19 and therefore the operating spidle 13, and in an undesirable case, i.e. actuation of the spindle lock whilst the motor is running, the locking cam 32 is deflected with minimal force and low vibration away from the grooved rim 27 and cannot lock the locking spindle 13. This matching is attained by the slight width difference between the cam support surface 337 and the width of the groove 28 of only approximately 1 min. Consequently, with the rotation of the operating spindle 13 in the operating direction of rotation and with the actuation of the hand lever 29, the locking cam 32 has insufficient time to pivot so far towards the groove base 45 that it can engage in a locking manner in the groove 28 and can bring the grooved rim 27 together with the operating shaft 13 to a standstill.

The grooves 28 of the grooved rim 27 comprise substantially parallel flanks 42, 44 inclined relative to a radial passing through the centre of the operating spindle 13 according to Figure 2, and a substantially flat groove base 45. In the viewing direction, the flanks 42, 44 are inclined to the right, i.e. in the opposite direction to the direction of rotation indicated by the arrow 50 and relative to a radial passing through the centre of the operating spmdle 13 (Figure 2).

The locking cam 32 is an elongate lever arm with a straight or rounded contour on the radially outer side facing away from the clamping flange 19, which contour extends in the manner of a beak or nose on the radially inner side remote from the hand lever 29 and facing the clamping flange 19 through a rounded end edge 38 with a small radius of curvature into a flattened, cam end face 37, which is preferably concavely curved with the same radius of curvature as the grooved rim 27 and has a rear end edge 38', and then extends into a V-shaped recess 39. The recess 39 substantially corresponds to the contour of the left flank 42 of the groove 28 in the region of an acute-angled retaining edge 4 1, which is formed from the transition of the groove flank 42 into the circumferential curvature of the grooved rim 27.

6 The locking cam 32 is constructed at the free end of a rotary holt 3 1, which is rotatably mounted in the bearing flange 16. The pivot axis 30 of the rotary bolt 31 extends parallel to the operating spindle 13. Rotationally-nigidly connected to the rotary bolt 31 is a hand lever 29 projecting at a right angle, the hand lever 29, the rotary bolt 31 and the lockmg cam 32 being manufactured separately, more particularly from plastics material.

The hand lever 29 is arranged mi the vicinity of the end of the rotary bolt 3) 1 facing away from the locking cam 3 2, an end-face rotary bolt section 3 11 extending axially beyond the hand lever 29 and being mounted in the bearing flange lo 16.

Fitted onto the end-face rotary bolt section 3 11 is a restoring spn rig 3 3, which is constructed as a torsion spring with one spring end fixed to the bearing flange 16 and the other spring end fixed to the rotary bolt 3 1. The restoring spring 33 is constructed in such a manner that it attempts to rotate the rotary bolt into a basic position, mi which the locking cam 32 is fully pivoted out of the groove 28 and lies directly radially Mi front of and at a distance from the grooved rim 27 on the clampmg flange 19. This basic position of the rotary bolt 31 or locking cam 32 is determined by an abutment 34 which is formed on the clamping flange 16 and against which the hand lever 29 rests (Figure 2). The hand lever 29 projects through an opening 35 in the bearing flange 16 to extend radially slightly beyond said bearing flange and at one end supports a gripper plate 29 1.

If the tool 18 is to be changed, it is firstly necessary to release the clamping nut 20 by means of a spanner, not shown. In order to lock the operating spindle 13 during this process, the operator places a finger on the gripper plate 291 of the hand lever 29 and pivots the hand lever 29 in the direction of the arrow 29 according to Figure 2. The rotary bolt 3 1 is thereby rotated in a clockwise direction against the force of the restoring spring 33. The locking cam 32 is thereby pivoted into one of the grooves 28 'm the grooved rim 27. The rounded end edge 38 of the locking cam 32 is supported against the right-hand groove flank 44 or the rounded 7 section 46 thereof of the clamping flange 19. The rounded section 46 and the end edge 38 are dimensioned in such a manner that the degree of locking of the locking cam 32 against the flank 44 increases with the increase in the release moment at the clamping nut 20.

By way of the positive locking connection between the groove 28 and the locking cam 32, the clamping flange 19 and therefore the operating spindle 13 are locked against rotation when the hand lever 29 is held. The clamping nut 20 can then be easily released by means of a spanner.

FoHowing a replacement of the tool 18, an actuation of the spindle lock 25 is also advantageous when tightening the clamping nut 20. In order to clamp the clamping nut 20, the hand lever 29 is pivoted in the direction of the actuating arrow 26. If the clamping nut 20 is then rotated in the clamping direction relative to the operating spm'dle 13, i.e. in the opposite direction to tile operating direction of rotation, the clamping nut 20 thereby rotates the operating spindle 30, with a clear degree of slip. Consequently, the grooved rim 27 rotates together with the groove 28 relative to the locking cam 3 2 so that the cam end face 3 7 engages with the recess 3 9 over the retaining edge 41. The clamping flange 20 and together therewith the operating spindle 13 are thereby locked, counter to the clamping direction of the clarnpingnut20. In other words, the rear end edge 38'of the cam end face 37 locks the retainffig edge 41 'm the manner of a hook.

When the operator releases the hand lever 29 following the tightening of the clamp mig nut 20, the restoring spring 33 rotates the rotary bolt 31 according to Figure 2 mi an anti-clockwise direction or in the opposite direction to the arrow 26, until the hand lever 29 abuts against the abutment 34 on the bearing neck 16. During this rotary movement of the rotary bolt -3) 1, the locking cam 32 is reliably fully pivoted out of the groove 28 and the'clamping flange 19 can rotate freely.

The clamping flange 19 shown in a rear perspective view in Figure 3 comprises a through opening 36' constructed as an internal hexagon for engagmig in a rotationally locking manner over the free end 131 of the operating spindle 13, 8 which is provided with a matching external hexagon 36. Also clear from this drawing is the design of the grooves 28 with the overall rounded contour, the arrangement of the groove flanks 42, 44, the rounded section 46 and the retaining edge 4 1.

The detailed views of the spindle lock 25 in Figures 4 to 6 in different operating positions show, mi Figure 4, the neutral position of the locking cam 32 relative to the groove 28 of the grooved rim 27 with the spindle lock 25 unactuated, by way of the enlarged form of the hand lever 29, the locking cam 32 and the grooved rim 27.

Figure 5 shows the locking cam 32 during faulty actuation, i.e. with actuation of the spindle lock 25 whilst the output shaft 13 is rotating at high speed, immediately following deflection from entry into the groove 28. In this case, it is clear that the slightly rounded end edge 38 has slid off the rounded section 46 of the groove flank 44, so that entry of the locking cam 32 mito the groove 28 is prevented.

Also clear are the almost corresponding sizes of the locking cam 32 and the groove 28. Consequently it is clear that, upon actuation of the spindle lock 25, the locking cam 32 can only enter the groove 28 firom its abutment position on the radially outer edge of the grooved rim 27 if the retaining edge 41 has reached the recess 39.

However, owing to the fact that the rounded section 46 lies only approximately 1 nun away from the end face 38 in this position, the retaining edge 41 and the recess 39 meet before the end edge 38 has reached the groove base 45 and can come to rest against the groove edge 44. Thus, after a relatively short futile pivoting stroke, the locking cam 32 is deflected at the rounded section 46 and experiences a similarly short, deflecting return stroke. This results mi a soft, low-vibration reaction 'm the event of faulty operation of the spindle lock 25 with a corresponding increase 'm operational reliability. Accordmigly, the operating spindle 13 can only be locked when its rotational speed is sufficiently low.

9 Figure 6 shows the position of the lockmg cam 32 engaged-in the groove 28 so as to stop the operating spindle 13 slowly rotating in the operating direction of rotation, the rounded end edge 38 being supported against the groove flank 44 without sliding off. In this case, it is clear that the clamping nut 20 can be released, without having to hold the spMidle lock 25 in the actuated position, so long as the end edge 38 abuts mi a self-locking manner against the groove flank 44 as a result of the release moment at the clamping nut 20.

Thus it is clear that the operating spindle 13 is rotated together with the groove rim 27 in the reverse direction to that shown in Figure 6 when the clamping nut 20 is tightened, and that the recess 39 of the end face 38 of the locking cam 32 can engage in the manner of a hook over the retaining edge 41 of the grooved rim 27 and thereby prevent further rotation of the operating spindle 13 under the action of the tightening torque at the clamping nut 20.

As a result of the fact that the elongate locking cam 32 is only insignificantly shorter than the actuating lever 29 and the end face 38 is only slightly shorter than the width of the locking groove 28, the locking cam 32 can be pivoted with relatively little force and can therefore only enter the groove 28 at a low rotational speed of the grooved rim 27. The reason for this is that in cases where the locking cam 32 can pivot into the groove 28, there is only approximately 1 nun clearance between the end edge 38 and the rounded section 46, during which the locking cam 32 has to reach the groove base 45 in its locking stroke. At the operating speed of the grooved rim 27, this 1 mm is covered long before the end edge 38 can reach the groove base 45 and can come to rest against the steep region of the groove flank 44. As a result of the fact that it reaches the rounded section 46 of the flirther rotating groove flank 44 after only a short pivoting stroke which can be triggered with relatively low force, it is reliably deflected, only low vibrations and noises being generated which cannot irritate the operator.

The spindle lock 25 illustrated Mi Figure 7 shows its position during tightening of the clamping nut 20. As a result of the tightening torque at the clamping nut 20, the operating spindle is rotatably driven, with the grooved rim 27 following. If the hand lever 29 is then held 'm the actuated position, the rear end edge 3 8 of the locking cam 3 2 can engage in a hooking manner under the groove flank 42 beneath the retaining edge 41, so that when the clampmg nut 20 is tightened the locking cam 32 is held in the groove 28 without flirther actuation of the hand lever 29.

The detailed exploded view mi Figure 8 of the hand lever 29, the rotary 10bolt 3 1, the locking cam 32 and the metal bush 54 shows the assemblyfriendly, cost- effective, multi-part design of the spindle lock 25, which is arranged in the plastics material bearing flange 16 so as to be particularly protected against wear.

A fork-shaped recess 58 'm end of the hand lever 29 facig the rotary bolt 3 1 can be non-detachably fitted onto the rotary bolt 3 1 via a double notching 59 15on the shaft of the rotary bolt 3 1. A torsion spring 33 according to Figure 1 engages with one end in an axial groove 60 'm the rotary bolt 3 1. In addition, on its lower region directly adjacent the locking cam 32, the rotary bolt 31 supports a collar 55 having an enlarged shaft diameter, which, mounted in a metal bush 54, is particularly suited to receivmg high forces.

Claims

1. Manual machine tool with a disc-shaped tool (18) and with a machine housing (10), which receives an operating spindle (13), which on its free end (13 1) clamps the tool (18) between a clamping flange (19) forming a clamping device (17) and a clamping nut (20), and with a spindle lock (25) for locking the operating spindle (13) against rotation, which spindle lock comprises a grooved rim (27) arranged on the clamping flange (19) with at least one groove (28) and a hand lever (29) with a locking cam (32), which is arranged on the hand lever (29) and can 10 engage in the at least one groove (28) with groove flanks (42, 44), characterised in that the spindle lock (25) can releasably engage with the grooved rim (27) on the clamping flange (19) of the operating spindle (13) in the operating direction of rotation and can be coupled in hooking fashion in the opposite direction, an engagement of the locking cam (32) in the groove (28) being ruled out by the shape and dimensions of the groove (28) so long as the rear end edge (38) of the locking cam (32) has not reached the groove flank (42).

2. Machine according to claim 1, characterised in that the rear end edge (38) of the locking cam (J3 M slides upon the grooved rim (27) until the locking cam (J3 M can enter the groove (28), and the cam end face (37) of the locking cam (32) is 1 to

3 min shorter than the width of the groove (28).

Machine according to claim 1, characterised in that the locking cam (32) and the groove (28) have acute-angled contours at one end and rounded contours 2 5 at the other end for reciprocal engagement.

4. Machine according to claim 1, characterised in that at least the rear of the two groove flanks (42, 44) is inclined relative to a radial mi the opposite direction to the operating direction of rotation (26) of the operating spindle (13), the first flank 12 (42) in the operating direction Of rotation (26) extending through a, more particularly sharp-edged, retaining edge (4 1) and the second flank (44) extending in curved fashion through a rounded section (46) into the contour of the grooved rim (27), and the locking cam (32) comprises a cam end face (37) engaging in the manner of a hook over the retaining edge (41) of the flank (42) when the clamping nut (20) is released as well as a rounded end face (38), against which the second groove flank (44) can be supported, the locking cam (32) being approximately 1 to 2 mm narrower than the groove (28).

is

5. Machine according to claim 2, characterised in that the groove (28) has a depth of approximately 3 to 5 nun, a width of approximately 5 to 10 nun and radii of approximately 0.5 to 1.2 mm, the rounded section (46) having a radius of curvature of approximately 1.2 to 1. 8 mm.

6. Machine according to claim 1 or 2, characterised in that the locking cam (32) is constructed as a lever arm havmg a length which is 1/3 to 1/2 that of the hand lever (29).

7. Machine according to claim 1 or 2, characterised in that the cam end face (37) of the locking cam (32) extends inclined relative to the groove base (45) during locking in the groove (28) and when resting upon the rounded end contour (38).

2s

8. Machine according to claim 1 or 2, characterised in that the cam end face (37) has a V-shaped recess (39), whose contour matches the contour of the groove flank (42) in the region of the retaining edge (4 1).

13

9. Machine according to claim 1 or 2, characterised in that a rotary bolt (3 1) and the hand lever (29) are parts which can engage with one another in a fork like manner, the rotary bolt (3 1) supporting the locking cam (32) and the hand lever (29) supporting a gripper plate (29 1).

10. Machine according to claim 1 or 2, characterised 'm that the rotary bolt (3 1) is mounted adjoining the locking cam (32) Mi a metal bush (54) and in the region of the hand lever (29) mi plastics material.

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