WO1988004975A1

WO1988004975A1 - Clamping device for releasably holding a tool, in particular a disk

Info

Publication number: WO1988004975A1
Application number: PCT/DE1987/000552
Authority: WO
Inventors: Winfried Helm; Manfred Stäbler
Original assignee: Robert Bosch Gmbh
Priority date: 1986-12-24
Filing date: 1987-11-28
Publication date: 1988-07-14
Also published as: DE3644440A1; DE3770641D1; EP0336930A1; EP0336930B1; JPH02501128A; BR8707952A

Abstract

A clamping device for portable grinding machines has a back flange (16) axially movable on the spindle (10) but able to transmit torque and capable of being relieved of the clamping pressure for the grinding wheel (15) by means of an annular piece (22). The annular piece (22) is axially supported by the spindle (10) and rotates therewith. The flange (16) can axially move and turn within certain limits relative to the annular piece (22). Both have left-hand inclined faces (32, 33) axially facing each other and axially adjacent. When the rotation of the annular piece (2) with the spindle (10) is blocked, the flange (16) can axially move and turn within certain limits relative to the annular piece (22). Both have left-hand inclined faces (32, 33) axially facing each other and axially adjacent. When the rotation of the annular piece (22) with the spindle (10) is blocked, the flange (16) can be moved with the inclined faces (33) in the direction of the tapering of the inclined faces (32) of the annular piece (22), approaching the same and relieving the clamping nut (18) from the clamping pressure, by turning the grinding wheel (15) anti-clockwise with the flange (16). With this clamping device, it is possible to change the grinding wheel quickly, safely and without any tools.

Description

Clamping device for releasably fastening a tool, in particular a disk

State of the art

The invention is based on a clamping device for releasably fastening a tool, in particular a disk, according to the generic preamble of the main claim. Clamping devices for, in particular, disk-shaped tools are particularly suitable for portable hand-held machine tools, and here in particular for grinding machines. A clamping device is known (DE-PS 30 12 836), in which the one flange, which is arranged on the side of the tool facing the housing of the hand-held power tool, is displaceable relative to the spindle and is coupled to this in a torque-transmitting manner. This rear support flange is supported against axial displacement in an axial end position via a shoulder of the spindle which forms a support element therefor. The other flange, which can be screwed onto the end of the spindle, consists of a nut with a in cross section approximately hat-shaped, separate clamping element, which is supported axially via a helical spring against the flange of the clamping nut. When screwing and tightening this clamping nut, the hat-shaped clamping element is pressed axially against the tool via the axially compressed spring, thereby tightening the tool against the spindle-side flange, the end face of a cylinder shoulder of the clamping nut coming into direct contact with a facing axial side of the rear flange and at further tightening the clamping nut, this rear, spindle-side flange is tightened together with the clamping nut, possibly until the rear flange comes to rest axially on the shoulder surface of the spindle forming the supporting element. The aim of this is to clamp the grinding wheel with a defined contact pressure in an angle grinder and to ensure this contact pressure. This clamping device is also intended to enable the grinding wheel to be replaced quickly and easily and at the same time to avoid overloading the hand-held power tool, in particular the angle grinder. If the torque applied to the grinding wheel becomes too large, the grinding wheel stops, while the rear flange and the clamping nut with the clamping element execute a relative movement. This clamping device counteracts the effect that the clamping nut continues to tighten during operation, which otherwise makes it considerably more difficult to loosen the clamping nut when changing the grinding wheel. Nevertheless, loosening the clamping nut is only possible with the help of a special auxiliary tool, and depending on the design of the machine, the spindle must be countered accordingly with a second auxiliary tool, for example a wrench. Advantages of the invention

In the tensioning device according to the invention with the characterizing features of the main claim, the following advantages result. A tool change is made possible without any auxiliary tool, which, moreover, can be carried out quickly and safely. Another advantage is that existing handheld power tools can be converted without major modifications. For this, e.g. a simple exchange of the existing rear support flange for a ring part with an adapted flange. The front clamping nut is unchanged in a known manner, so that standardized, inexpensive parts can be used here. At the same time, it can still be used for particularly stubborn cases, e.g. if the clamping nut is rusty, a key is attached to it and the clamping nut is loosened with this auxiliary tool. The rear part of the ring has a non-rotatable molded part with the spindle, so that relevant regulations are met. It is also advantageous that the clamping device is not arranged on the working side of the tool, but in the area between the tool and the housing-side bearing flange, so that any risk of damage, e.g. by rubbing against the workpiece. This also prevents any axial overhang on the working side of the tool, which may impair work.

Advantageous further developments and improvements of the clamping device specified in the main claim are possible due to the features listed in the subclaims.

The full wording of the claims is not reproduced above solely to avoid unnecessary repetition, but instead only by

Naming the claim number referred to, whereby however, all of these claims have to be expressly disclosed at this point and are essential to the invention. All of the features mentioned in this description and those that can be inferred solely from the drawing are further components of the invention, even if they are not particularly emphasized and are not mentioned in the claims.

drawing

An embodiment of the invention is shown in the drawings and explained in more detail in the following description. Show it:

1 shows a schematic, axial longitudinal section of a clamping device as part of an angle grinder with a clamped grinding wheel,

Fig. 2 is a schematic side view of a

Detail of the clamping device with the tool clamped on a larger scale,

3 shows a schematic side view corresponding to that in FIG. 2, but with the tool loosened,

FIG. 4 shows a schematic plan view with a partial section along the line IV-IV in FIG. 3.

Description of the embodiment

In Fig. 1 the lower part of a e.g. as

Angle grinder designed, portable hand tool shown, which has a motor-driven and gearbox-driven spindle 10, which at the end merges via an annular shoulder 11 into a cylindrical shoulder 12 of smaller diameter and then into an end threaded shoulder 13 with an external thread 14. The spindle 10 serves to drive a tool 15 which, for example, consists of the indicated grinding wheel or another tool wheel, a rubber plate or the like. The tool 15 is axially clamped and clamped between two flanges 16 and 17. Of this, the flange 17 seated at the spindle end is designed as a conventional clamping nut 18 which adjoins the flange. Has hub part 19 and is provided on the inside with a continuous internal thread 20 with which the clamping nut 18 is screwed onto the threaded shoulder 13. On the outer circumferential surface of the

Hub part 19 is the center of the tool 15 when fastened

The other flange 16 is displaceable relative to the spindle 10 and coupled to the spindle 10 in a manner to be transmitted in a torque-transmitting manner. It is secured against axial displacement via a support element 21 and can be relieved of the clamping pressure for the tool 15. The support element 21 consists of a ring part 22 with a bottom 23 and a cylinder part 24, which is approximately inverted in cross-section. With the bottom 23, the ring part 22 is axially supported on the ring shoulder 11 and centered radially on the cylindrical shoulder 12. By matching shaped surfaces, e.g. two mutually parallel flats, on the spindle 10 and in the bottom 23, the ring part 22 has a non-rotatable positive connection with the spindle 10, from which it is rotatably carried in the direction of rotation according to arrow 25 when the motor is switched on.

The flange 15 consists essentially of a relatively flat disc. It is relative to the spindle 10 on the outer peripheral surface of the hub part 19 Ring part 22 axially displaceable and rotatable within limits. The ring part 22 and the flange 15 are coupled by means of a spring 26, which is designed here as a torsion spring, one end 27 of which engages the ring part 22 and the other end 28 of the flange 16. For clarification, a spring is only indicated schematically in FIGS. 2 and 3, which engages with the end 28 on the flange 16 and acts on it in the direction of the indicated arrow 29 in a resilient manner relative to the ring part 22.

The ring part 22 and the flange 15 have several, e.g. three, in the circumferential direction successive, left-rising inclined surfaces 32 and 33, with which the flange 16 and the ring member 22 axially abut. The inclined surfaces 32 of the ring part 22 are located on the end face 30 of the cylinder part 24 facing the flange 15.

The wedge angle of both inclined surfaces 32, 33 is chosen to be large enough that it lies in the area of self-locking. At the respective inclined surface 32 of the ring part 22 there is an axially parallel stepped surface 34 at the wedge upward end. During the movement of the flange 15 relative to the ring part 22 wedge-downward of the inclined surfaces 32, 33 and the associated axial relief from the clamping pressure, the flange 16 strikes the step surfaces with the step surfaces 34 assigned to the step surfaces while limiting the pivoting angle. This state is shown in FIG. 3, in which the clamping device is released and thus the screwed-on flange 17 is relieved of the axial clamping pressure acting on the tool 15 from the flange 16.

The flange 15 has an axially parallel connection to the end of the respective inclined surface 33 located downstream of the wedge Directional locking lugs 36, the front surface of which is adjacent to the inclined surface 33 and is each formed as a locking surface 35. The opposite end face of each locking lug 36 of the flange 16 is designed as an approximately parallel driving surface 37. The ring part 22 has, in the circumferential direction of each inclined surface 32, upstream, approximately axially parallel driver surfaces 38 which, when the tool 15 (FIG. 2) is clamped, abut against an associated driving surface 37 of the locking lug 36 while driving the flange 16.

The Stepped surfaces 34 and circumferentially spaced driving surfaces 38 of the ring member 22 are formed by the two end faces of respective locking recesses 39, which consist of openings in the wall of the cylinder member 24. The locking recesses 39 adjoin the upward wedge end of each inclined surface 32 and are open axially and in the direction of the flange 16. The opening width of each latching recess 39 measured in the circumferential direction is larger than the width of each locking lug 36 engaging therein.

As shown in FIG. 4 in particular, rolling elements 40 are arranged between the axially adjacent inclined surfaces 32 and 33 of the ring part 22 and the flange 16, respectively, which make the sliding friction between the inclined surfaces 32, 33 a rolling friction and thus substantially reduce the friction. The rolling elements 40 here consist of balls which are inserted into recessed grooves 41 in the inclined surfaces 32.

The flange 16 is fastened to a cylinder sleeve 42 surrounding it, for example screwed into it. The cylinder sleeve 42 also extends axially over the cylinder part 24 of the ring part 22, which is in the form of an axial stop at the end facing away from the tool 15 an annular shoulder 43 is overlapped. In this way, the flange 16, together with the cylinder sleeve 42, is secured on the ring part 22 against detachment in the axial direction which faces away from the ring part 22. The flange 16 and the ring part 22 are held together by means of the cylinder sleeve 42.

The tensioning device also has at least one releasable locking device 44, via which the flange 16 in the position shown in FIG. 2, in which the tool 15 is clamped, is positively secured with respect to the ring part 22. The locking device 44 has a tongue 45 which is fastened at one end to the ring part 22 by means of screw 46, to be precise on the side which points towards the flange 16. The tongue 45 is directed approximately radially. It acts approximately like a spring leaf and is additionally pressed down by means of a spring 47 in the form of a cylindrical coil spring in FIGS. 2 and 3. The tongue 45 contains a recess 48 for holding and centering the end of the spring 47. The spring 47 engages at a relatively large radial distance from the fastening point of the tongue 45 by means of the screw 45. The tongue 45 is dimensioned with respect to the cross-sectional thickness so that it is bent downwards under the action of the relaxing spring 47 in the manner of a spring tongue in FIGS. 2 and 3 and can be bent in the opposite direction by means of manual actuation with compression of the spring 47. It is understood that the tongue 47 is also shaped, e.g. bent, can be that it is tension-free and relieved in the position shown in Fig.2, brought down in the axial direction and can be lifted axially upwards against the action of the spring 47 in the position shown in Fig. 3.

The tongue 45 rests in a recess 49 which runs in the foot region of the latching recess 39 and in the region the spring 47 is provided with a recess 50 receiving and centering this end.

The width of the tongue 45 and the locking lug 36 together is chosen approximately as large as the total width of the locking recess 39, so that the locking lug 36 and the tongue 45 can be found side by side within the locking recess 39 in the clamped state of the tool 15 according to FIG. 2. The tongue 45 thus engages in the locking position 39 in the position of the flange 16 clamping the tool, between the step surface 34 and the locking surface 35 of the locking lug 36. In this way, the tongue 45 secures in this position (FIG. 2) the contact of the locking lug 36 with its driving surface 37 on the driving surface 38 of the ring part 22. If the spindle 10 is driven in the working direction according to arrow 25, and thus in the same way the ring part 22, it takes over the driving surface 38, which is on the driving surface 37 the locking lug 36 also strikes the flange 16. The ring part 22 and the flange 16 have slid up along the inclined surfaces 32, 33 and are thereby pressed apart axially. This axial spreading position (Fig. 2) is secured by the tongue 45, even if e.g. the motor of the hand machine tool is switched off and the spindle 10 is stopped relatively suddenly, while the momentum still acting on the tool 15 in the same direction according to arrow 25 could tend to the tool 15 together with both flanges 15, 17 and relative to the ring part 22 in To drive direction according to arrow 25 with accompanying, unwanted loosening of the tool 15. This is prevented by the tongue 45, which supports the locking lug 36 with respect to the step surface 34 of the ring member 22.

If no tool 15 is clamped, the spring 26 additionally causes the flange 16 and of the ring part 22 relative to each other so that both parts slide up on the inclined surfaces 32, 33 and are thereby pressed axially apart.

If the tool 15 is to be removed and replaced, the ring part 22 is rotationally blocked by suitable means, which can be achieved by appropriately blocking the spindle 10 e.g. can be done by means of a spindle locking device integrated in the hand tool. Under certain circumstances, the friction in the transmission up to the motor is sufficient to prevent the spindle 10 from rotating in the direction of the arrow 25, at least within limits. Here, by attacking the graspable end of the tongue 45, this is raised with one hand against the action of the spring 47 into the position shown in Fig. 3, in which the tongue 45 enters the recess 49, which is deep enough that the Tongue 45 now releases the locking lug 36, which can drive over the tongue 45 with its axially facing end. Then the tool 15 is rotated by hand in the same direction according to arrow 25, thus counterclockwise. The flange 17 and the flange 16 are also entrained via the friction. The rotation of the flange 16 in this direction causes its inclined surfaces 33 to slide downward on the inclined surfaces 32 of the rotationally blocked ring part 22, this sliding movement becoming a rolling movement with reduced rolling friction due to the rolling bodies 40. During this relative rotation of the flange 16 with respect to the ring part 22 wedge-downward of the inclined surfaces 32, the flange 16 moves axially in the direction of the ring part 22, which leads to a corresponding axial relaxation. The clamping nut 18 can then be easily unscrewed by hand. The sliding movement of the flange 16 with the inclined surfaces 33 wedge down the inclined surfaces 32 is limited in that the locking surfaces 35 on one side of the locking lugs 36 on the

Stepped surfaces 34 on the associated side of the respective Attach the notch (Fig. 3). As soon as the loosening torque is reduced to zero when the tool 15 is loosened, the spring 26 is able to rotate the flange 16 relative to the ring part 22, so that the inclined surfaces 33 of the flange 16 slide upwards on the inclined surfaces 32 of the ring part 22 and the two parts 15, 22 are axially pushed apart again. This movement is limited by the stop of the locking lugs 36 with their driving surfaces 37 on the facing driving surfaces 38 of the respective locking recess 39. Then each locking lug 36 is in the position according to FIG. 2, in which the tongue 45 previously blocked by the locking lug 36 under the action of the relaxing spring 47 automatically moves out of the recess 49 into the space between each step surface 34 and locking surface

35 can snap. This pressed-apart position is thus positively secured. In this position, a new tool 15 can be inserted and clamped. It is sufficient to slightly tighten the clamping nut 18 and thus to tighten the new tool 15 slightly, since the tool 15 will tighten itself during operation when the motor is subsequently switched on.

The rolling bodies 40 arranged between the inclined surfaces 32, 33 have the advantage that the fore-end friction between the two is reduced to rolling friction and is thus practically negligible.

The clamping device described is simple, inexpensive and fast, safe and easy to use. It enables a quick and safe change of the tool 15 without the need for additional special tools. Another advantage is that existing hand tool machines, in particular grinding machines, can also be retrofitted without any major changes Conversion can be equipped with this clamping device. For this purpose, as a rule, only the existing rear flange has to be exchanged for the unit consisting of the ring part 22 and flange 16, held together via the cylinder sleeve 42. The existing, for example standardized, clamping nut 18 in other machines is retained unchanged, as is the fact that the part supporting the tool 17 with the spindle 10 has a non-rotatable form fit. This complies with the relevant regulations. Due to the clamping nut 18 used, it is possible in particularly stubborn cases, for example in the rusted state, to loosen the clamping nut .18 in the usual way by means of an auxiliary tool. The clamping device is not limited to grinding wheels as a tool 15. Rather, other tools, for example cup wheels, brushes, rubber plates or the like, can be clamped in the same way without tools.

Claims

Expectations

1. Clamping device for releasably fastening a tool (15), in particular a disk, on a driven spindle (10) with two flanges (16, 17) between which the tool (15) can be axially clamped, a flange (16) which is displaceable relative to the spindle (10) and coupled to the spindle in a torque-transmitting manner, is secured against axial displacement by a support element and can be relieved of the clamping pressure for the tool (15), characterized in that the support element (21) consists of a ring part (22) . Is formed, axially supported on the side of the flange (16) facing away from the tool (15) on the spindle (10) and coupled to this in a torque-transmitting manner, that the flange (16) is axially displaceable and rotatable relative to the ring part (22) is held and that the ring part (22) and the flange (16) on the axially facing end faces (30, 31) have a plurality of successive left-handed inclined surfaces (32, 33) in the circumferential direction point with which the flange (16) and the ring part (22) lie axially against one another.

2. Clamping device according to claim 1, characterized in that the ring part (22) with the flange (16) by means of a spring (26), in particular a torsion spring, is coupled, of which one end (27) on the ring part (22) and the other End (2B) engages the flange (16).

3. Clamping device according to claim 1 or 2, so that the wedge angle of the inclined surfaces (32, 33) is chosen so large that it lies in the area of self-locking.

4. Clamping device according to einεm of claims 1-3, characterized in that at the respective inclined surfaces (32) of the ring part (22) at the wedge upward end approximately axially parallel stepped surfaces (34) connect, to which the flange (16) with each pull orderly locking surfaces (35) while limiting the angle of rotation of the flange (16) relative to the ring part (22) when moving downward wedge and in axial relief from the clamping pressure.

5. Clamping device according to claim 4, characterized in that the flange (16) on the wedge-down end of the respective inclined surface (33) has adjoining, approximately axially parallel locking lugs (36), the front surface of which is adjacent to the inclined surface (33) each as a locking surface (35 ) is trained.

6. Clamping device according to one of claims 1-5, characterized in that the ring part (22) in the circumferential direction of each inclined surface (32) has upstream, approximately axially parallel driver surfaces (38) which with the tool (15) clamped the associated driving surfaces (37) of the flange (16) while turning them.

7. tensioning device according to claims 5 and 6, d a d u r c h g e k e n n e e c h n e t that the respective locking surface (35) opposite end face of each locking lug (36) of the flange (16) is designed as a driving surface (37) this.

8. Clamping device according to one of claims 1-7, characterized in that the ring part (22) in each case at the wedge-upward end of each inclined surface (32) has adjoining locking recesses (39) which are open axially and towards the flange (16) and one of which The end face forms a step surface (34) and the other end face forms a driving surface (38)

9. Clamping device according to claim 8, d a d u r c h g e k e n n z e i c h n e t that the circumferentially measured opening width of each locking recess (39) is larger than the width of each locking lug (36) of the flange engaging therein.

10. Clamping device according to one of claims 1-9, characterized in that the ring part (22) is of approximately inverted cup-shaped cross section and its inclined surfaces (32) on the flange (16) facing end face (30) of its cylinder part (24) are arranged.

11. Clamping device according to claim 10, characterized in that the latching recesses (39) consist of openings in the wall of the cylinder part (24).

12. Clamping device according to one of claims 1-11, d a d u r c h g e k e n n z e i c h n e t that between the axially adjacent inclined surfaces (32, 33) of the ring member (22) and the flange (16) rolling body (40), e.g. balls inserted into recessed grooves (41) are arranged.

13. Clamping device according to one of claims 1-12, so that the flange (16) is fastened to a cylinder sleeve (42) enclosing this, which is secured with an axial stop, e.g. an annular shoulder (43) on the ring part (22) is secured against detachment in the axial direction directed towards the tool (15).

14. Clamping device according to one of claims 1-13, at least one detachable, the flange (16) in its position ready for clamping the tool (15) in a form-fitting manner. locking device (44) securing the ring part (22).

15. Clamping device according to claim 14, characterized in that the locking device (44) has an approximately radially directed, spring-loaded tongue (45) on the ring part (22), which in the ready for clamping the tool (15) position of the flange (16) in the locking recess (39) between the step surface (34) and the engaging locking lug (36) engages and secures the relative rotational position between the flange (16) and the ring member (22) and which moved axially towards the ring member (22) from which Path of the locking lug (36) moved out, ineffective position, the locking lug (36) releases and can be overlapped by the locking lug (36) in the circumferential direction.

16. Clamping device according to claim 15, so that the width of a tongue (45) and locking lug (36) together is chosen approximately as large as the width of a locking recess (39).

17. Clamping device according to claim 15 or 16, so that the locking recess (39) on the foot side contains a recess (49) receiving the tongue (45).