GB2239483A

GB2239483A - Clamping device for a part displaceable on a guide

Info

Publication number: GB2239483A
Application number: GB9025976A
Authority: GB
Inventors: Guenter Schaal; Albert Kleider
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1989-12-28
Filing date: 1990-11-29
Publication date: 1991-07-03
Anticipated expiration: 2010-11-29
Also published as: GB9025976D0; DE3943134A1; GB2239483B; DE3943134B4

Abstract

The clamping device for a part (4) displaceable on a channel-section-shaped part (1) is constructed in such a way that the displaceable part (4) carries at least one curved leaf spring (9, 11) which extends with at least one end up close to a wall of the channel-section-shaped part (1) and that the curvature of the leaf springs (9, 11) can be varied. Thus the chord length of the springs changes allowing releasable clamping of the spring ends into the internal walls of the guide. The guide may be a channel or a tube. <IMAGE>

Description

- 1 Clampina device for a part displaceable on a guide

Prior Art

The invention starts from a clamping device according to the generic category of Claim 1.

European Patent 204,023 discloses a longitudinal guide in particular for a circular saw. The longitudinal guide is a component part of a guide bar. A channelsection centre piece of an adaptor for the circular saw is to be guided free of play in the channel-section longitudinal guide. In order to reduce the play of the channel-section centre piece in the channel-section longitudinal guide. an expanding device is arranged in the channel-section centre piece. This expanding device is based on the action of wedge faces displaceable relative to one another. Here, a bolt having a cone point as an expanding member is axially displaced, for example by turning in a screw thread. It is supported with its cone point on the cone points of two thrust bolts which are arranged normal to the axis of the expanding member. The thrust bolts are thereby axially displaced and in turn displace the legs of the channel-section centre piece outwards as a result.

The play on the channel-section centre piece in the channel-sectionshaped longitudinal guide can be reduced according to the displacement of the expanding member.

The known expanding device consists of relatively heavy parts which are expensive to machine. it is suitable for small. sensitive expansions. but not for large expansions or for clamping purposes in which long t is displacement motions are to be achieved with a short adjusting distance. The known expanding device has no catch in the clamping and release position.

Further clamping devices are known which work according to the screwing principle and have either short adjusting distances and as a result only develop a small locking force or provide a high locking force at long adjusting distances, that is. they respond slowly.

The effort involved in assembling the known clamping and expanding devices is considerable.

In known clamping devices for turnbuckles of protective hoods for powered hand tools, the clamping lever is always located on the protective hood. This has the disadvantage that the clamping lever shifts along with the protective hood when the latter is turned and then the operator has to look for it.

Advantages of the Invention

Claims

Against this background. the clamping device according to the invention, having the characterizing features of Claim 1, has the advantage of rapid response as a result of short adjusting distances. Catches in the clamping and release position facilitate the operation. In addition, the construction of the clamping device isdistinguished by low weight and low machining and assem- bly costs. Further. advantageous designs of the invention follow from the subclaims. A further advantage of the invedtion results for the exemplary embodiment of a turnbuckle for protective hoods of powered hand tools in that the adjusting lever is always located at the same position relative to the machine irrespective of the position of the protective hood. Drawing An exemplary embodiment is explained in greater detail in the following description and in the associated drawing. In the drawing, Figure 1 shows a clamping device -1 in the release position, Figure 2 shows a clamping device in the clamping position, Figure 3 shows a cross-section of the clamping device according to Figure 2, Figure 4 shows a longitudinal section of the clamping device according to Figure 21 Figure 5 shows an exemplary embodiment of the invention as a turnbuckle on a protective hood of an angle grinderi Figure 6 shows the partially sectioned plan view of the exemplary embodiment according to Figure 5. and Figure 7 shows an individual leaf spring according to Figures 5 and 6. Description of the exemplary embodiment The clamping device shown in Figure 1 shows a sectional plan view of a channel - s ection- shaped part 1 between whose legs 2, 3 a part 4 displaceable like a slide sits in such a way as to be secured against falling out. The displaceable part 4 has a central hollow space 5. The hollow space 5 is cylindrical and is interrupted tangentially by two slots 7. 8 running through the displaceable part 4 essentially in parallel and transversely to the guide L. At their ends, the slots 7, 8 narrow funnel-like. Two leaf springs 9,, 11 sit in a curved manner in the slots 7, 8, which leaf springs 9, 11 extend over the entire length of the slots 7. 8 or over the width of the displaceable part 4. With their convex sides, the leaf springs 9. 11 face one another and are in each case fixed at their centre to one guide plate 10. 12 each. The guide plates 10. 12 are displaceably mounted in a central longitudinal slot 6 extending over the hollow space 5 and point towards the centre of curvature of the curves of the leaf springs 9, 11. They secure the leaf springs 9. 11 against uncontrolled shifting in their slots 7,, 8 transversely to the channel-section-shaped part 1 and prevent them from inadvertently jamming or tilting on the walls of the legs 2. 3. In the hollow space 5 there is seated between the leaf springs 9, 11 an adjusting dog 13 which catches in the release position and is in the form of a square, the is flanks of which are arched inwards like a cylinder segment and which is rotatable about its centre or the axis of the hollow space 5. In each case two opposite flanks of the square determine one catch position each of the adjusting dog 13 with regard to the leaf springs 9, 11, the release and clamping position. The displaceable part 4 is positionally secured in a longitudinal aperture 14, interrupted by stabilising webs 20, in the wall of the channel-section-shaped part 1 in the area between the legs 2, 3. Instead of the guide plates 10, 12, the leaf springs 9. 11 can each be provided with a V-shaped centre area (not shown) which is bent out spikelike and is guided in the longitudinal slot 6 in such a way as to point towards their centre of curvature or they can be provided with a recess into which a dog of the displaceable part engages. In Figure 2, unlike Figure 1, the adjusting dog 13 is rotated through 90 degrees into the clamping position and is supported in this catch position on the convex sides of the leaf springs 9, 11. The leaf springs 9, 11 are thereby expanded like a toggle lever so that their transverse extent in the slots 7. 8 increases and they are supported with their spring ends 16, 18 on the legs 2. 3 of the channel-section-shaped part 1. A cross-section in accordance with Figure 2 is shown in Figure 3. Here, as in Figure 2, the adjusting dog 13 catches in the clamping position. A rotary knob 15 with which the clamping or release position can be adjusted by hand is fixed to the upper extension of the adjusting dog 13. At its lower end. the adjusting dog 13 sits in an opening of a guiding plate 17. The latter sits in the longitudinal aperture 14 and partly overlaps the underside of the channel -section- shaped part 1. A snap ring 19 in an annular groove 21 at the free end of the adjusting dog 13 retains the adjusting dog 13 in an axially securing manner on the guiding plate 17. A longitudinal section in accordance with Figure 2 is shown in Figure 4. Here, toot the adjusting dog 13 catches in the clamping position, the rotary knob 15 being disposed parallel to the channel-section-shaped part 1. The guiding plate 17 is connected to the dis placeable part 4 via two screws 23, 25. It can be seen from Figures 1 to 4 that the adjusting dog 13 catches in the release position when the rotary knob 15 is disposed transversely to the channel section-shaped part 1 and that it catches in the clamping position when the rotary knob 15 is disposed lengthwise relative to the channel-section-shaped part 1. The displaceable part 4 in the exemplary embodi ment described above can always only be displaced from one stabilising web 20 up to the other. In the present case, the distance between the stabilising webs 20 must correspond to the necessary displacements of the dis placeable part 4. In another exemplary embodiment (not shown) of the invention, the guide is designed, for example, as a longitudinally slit tube. This tube surrounds the dis placeable part in such a way that it cannot move trans versely but only longitudinally in the tube and can only be inserted or removed at the ends of the tube. The rotary knob, with which the displaceable part can be moved without interruption over the entire length of the slit tube and can be locked at any location, can project from the longitudinal slit. Depending on the use, the displaceable part 4 can also serve as guide and the channel-section-shaped part 1 can be the guided part. Instead of a raillike channel section, a pro filed groove, for example on the periphery of a circular disc. can also accommodate the displaceable part. In a further exemplary embodiment (not shown). the displaceable part can be designed in such a way that it surrounds from three sides, for example with a pro filed groove,. a rail of rectangular section. In this arrangement. the slot for guiding the leaf spring is only to be open towards the side facing the rail so that the 1 is leaf spring can be supported laterally with one spring end on the rail in the clamping position of the adjusting dog. Another exemplary embodiment (not shown) of the displaceable part can be configured in such a way that two leaf springs are arranged so as to face away from one another with their convex sides. In this position, the clamping position, the spring ends of t.he leaf springs are supported on the walls of the channel-section-shaped part without the adjusting dog touching the leaf springs. Here, the adjusting dog must be designed in such a way that. when catching in the release position, it touches the concave sides of the leaf springs and reduces their expansion. Particularly advantageous is the design of the adjusting dog 13 of rectangular hollow section having concavely arched flanks and rounded edges as a dog roller. The adjusting dog 13 is thereby adapted to the curved shape of the leaf springs 9. 11. This improves the wear behaviour and handiness of the clamping device. Instead of the mechanical adjusting dog 13. hydraulic, pneumatic or electromagnetic means can be used for expanding the leaf springs. In a further exemplary embodiment (not shown). the axis of rotation of the adjusting dog can run transversely to the guide. The clamping device can be used especially advantageously for stop slides, rapid adjustments on machine beds, work benches, drill stands or in particular as turnbuckle on protective hoods as described in German Offenlegungsschrift 3.636,500. But it can also be used wherever lockable parts adjustable in guides are provided. e.g. even in lamps and search lights displaceable in rails. If there is only one leaf spring or a plurality of leaf springs running parallel to one another, a slip clutch like a freewheel can be realised in a modification of the exemplary embodiment in Figures 1 to 4. On the channel-section-shaped part. in the clamping position of 4 N C is the adjusting dog, this slip clutch permits displacement of the displaceable part away from the centre of curvature of the leaf springs, but catches in the opposite direction. A further exemplary embodiment of the invention is described below with reference to Figures 5 to 7. In Figure 5, an angle. grihder 30 is shown in lateral section. The angle grinder 30 has a machine housing 31 and a gearbox 32. On one side, the gearbox 32 forms a clamping neck 33 which surrounds tube-like an output spindle 35 serving to drive a grinding disc 34. A control ring 37 having an adjusting lever 38 sits in a rotatable manner in a channel-sectionshaped annular groove 36 located at the end face or axially in the free end of the clamping neck 33. which control ring 37 is secured by a lid 39 to prevent falling out of the annular groove 36. The plan view of Figure 5 is shown in partial section in Figure 6. Here, the adjusting lever 38 is located in the release position. The clamping position of the adjusting lever 38 is shown by chain lines. Passing through the clamping neck 33 and the annular groove 36 are three slots 40, 41, 42 running symmetrically to one another in a curved shape from the periphery of the clamping neck to its centre and back again to the periphery. Sitting in the slots 40, 41, 42 are three leaf springs 43. 44r 45 with their free ends close to the periphery of the clamping neck 33. With a central curved area, the leaf springs 43, 44F 45 touch the outer periphery 46 of the control ring 37 at its curved, deep recesses 47, 48, 49, adjacent to each of which a shallow recess 50. Sir 52 is in each case arranged on outer periphery 46. Sitting on the clamping neck 33 is a protective hood 53 which. with its flange 54, concentrically surrounds the clamping neck 33 with slight clearance. A radial dog 55. pointing inwards. on the inner periphery of the flange 54 in a radially encircling groove 56 on the outer periphery of the clamping neck 33 secures the is protective hood 53 against unintentional release from the angle grinder 30. The bayonet-catch principle of the dog 55 and the groove 56 on the protective hood 53 is revealed, for example, in German Offenlegungsschrift 3,636j601. In its release position shown in Figure 6, the protective hood 53 can be rotated as desired on the clamping neck 33 or can be completely released axially from the clamping neck 33. In the process, the clamping neck 33 forms a curved guideway. The deep recesses 47, 48, 49 catch on the leaf springs 43, 44, 45. As a result, the free ends of the latter are at a distance from the wall of the flange 54, cannot touch this wall and also do not exert any braking force. - If. according to Figure 6. the adjusting lever 38 is shifted into the position drawn in chain lines, the control ring 37 is consequently rotated counterclockwise. As soon as the shallow recesses 50. 51, 52 catch on the leaf springs 43, 44, 45, the latter are expanded. As a result of the increased longitudinal extentr their free ends are pressed like a toggle lever against the wall of the flange 54. They thereby exert a braking force and thus lock the protective hood 53 on the clamping neck 33 via the flange 54. In this catch position of the control ring 37, the protective hood 53 can no longer be rotated on the clamping neck 33 or released from the latter. Figure 7 shows the side view of one of the three identical leaf springs 43, 44, 45 having one central, lateral catch recess 57 each. In the assembly position, the leaf springs 43. 441 45 sit with their catch recesses 57 on one centring dog each (not shown) in the slots 40, 41, 42 and are thereby secured against unintentional shifting from their centre position inside the slots 40. 41r 42. Consequently, the free ends of the leaf springs 431 44r 45 cannot come to bear on the wall of the flange 54 in the release position. Thus unintentional restraining actions in the release position are impossible.

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Instead of being effected via the adjusting lever 38, the change between the clamping and release position can also be effected, for example, via a toothed pushbar (not shown) or via Bowden cables which convert their longitudinal displacement into a rotary movement of the control ring 37.

- 10 Claims 1. Clamping device f or sub-assemblies andlor attachments in particular of electrical powered hand tools, in which two parts (1, 4), mounted so as to be movable relative to one another on a curved or straight guideway. can be-locked against one another, characterized in that the locking force is applied by changing the curvature and thus the chord length of at least one curved leaf spring (9, 11).

2. - Clamping device according to Claim 1, characterized in that the leaf spring (9 r 11) is arranged in only one of the parts (1, 4).

3. Clamping device according to Claim 2, characterized in that one leaf spring (9, 11) each is arranged in both parts (1, 4).

4. Clamping device according to Claim 3,, characterized in that the leaf spring (9, 11) is supported on one side in the part (1, 4), while the other end of the leaf spring (9, 11) is guided in a longitudinally movable manner.

5. Clamping device according to Claim 3, characterized in that both ends of the leaf spring (9, 11) are guided in a longitudinally movable manner.

6. Clamping device according to Claim 4 or 5, characterized in that the curvature can be varied via adjusting means designed as adjusting dog (13) or the like, and in that at least one end of the leaf spring (9, 11) extends in the release position only up close to the guideway and in the clamping position is supported like n Z:

1 a toggle lever on the guideway.

7. Clamping device according to Claim 1, characterized in that the part (4) is designed so as to be displaceable like a slide and sits in a groove of the part (1), which groove forms a guideway.

8. Clamping device according to Claim 1,, characterized in that the displaceable part (4) can be split up into at least two individual parts, of which at least one, in a positive-locking manner, secures the displaceable part (4) against falling out of the part (1).

g. Clamping device according to Claim 8, characterized in that the part (1) is a fixed. channel -sectionshaped rail whose legs (2, 3) form the guideway and which has a longitudinal aperture (14) which runs essentially symmetrically between the legs (2, 3) and is interrupted by safdty webs (20).

10. Clamping device according to Claim 8 or 9, characterized in that the displaceable part (4) has an open hollow space (5) in which the adjusting dog (13) sits and through which two leaf springs (9, 11) extend, the adjusting dog (13), in a first adjusting position, being at a distance from the leaf springs (9, 11) and. in a second adjusting position, expanding the leaf springs (9, 11), which are thereupon supported on the legs (2, 3) in the expanding direction.

11. Clamping device according to Claim 10. characterized in that. in one catch position, the adjusting dog (13) touches the leaf springs (9, 11) on their convex sides.

12. Clamping device according to Claim 11. characterized in that the convex sides of the leaf springs (9, 11) face one another.

13. Clamping device according to Claim 12. characterized in that the leaf springs (9, 11) sit in slots (7, 8) which merge into the hollow space (5).

14. Clamping device according to Claim 13. characterized in that centring means designed as guide plates (10,, 12) hold the leaf springs (9,, 11) in the hollow space (5) or in the slots (7, 9).

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15. Clamping device according to Claim 14 j characterized in that the adjusting dog (13) is designed as rectangular sectional body which can be rotated rollerlike about the centre of its section, and in that its edges are rounded and its flanks are of concave shape.

16. Clamping device according to at least one of the preceding claims, in particular for an angle grinder (30) having a protective hood (53), characterized in that the at least one curved leaf spring (43, 441 45) is mounted in the clamping neck (33) of the powered hand tool or the angle grinder (30), which leaf spring (43, 44, 45), with both ends, is closely adjacent to a flange (54) of the protective hood (53), which flange (54) is arranged so as to be rotatable relative to the clamping neck (33) and surrounds the latter in an annular manner, and in that, when the at least one leaf spring (43, 441 45) is expanded, its two ends are pressed like a toggle lever onto the surrounding wall of the flange (54).

17. Clamping device according to Claim 16. characterized in that a rotatable control ring (37) which runs essentially parallel to the grinding disc (34), is located on the clamping neck (33) and has a handle designed in particular as an adjusting lever (38), can expand the leaf springs (43, 441 45), in the course of which the latter are touched by shallow recesses (50, 51, 52) on the outer periphery (46) of the control ring and can be held in a first catch positions [sic], and in that the control ring (37) can hold the leaf springs (43. 44r 45) in a relieved manner in its second catch position in its deep recesses (47, 48r 49).

18. Any of the clamping devices substantially as herein described with reference to the accompanying drawings.

Published 1991 atThe Patent 0Mce. State House. 66171 HighHolbom. London WC1R47P. Further copier, maybe obtained from Sales B. Unit 6. Nine Mile Point Cwmfelinfach. Cross Keys. Newport NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.

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