EP0906175A1

EP0906175A1 - Manually driven machine

Info

Publication number: EP0906175A1
Application number: EP97942809A
Authority: EP
Inventors: Manfred Kirn; Manfred Bleicher; Gerd Hahn; Justus Lamprecht; David Matzo; Herbert Faerber; Andreas HÖLDERLIN; Jörg DEHDE; Leon Bujalski; Alex Gawron; Michael Holzer, Jr.
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1996-11-29
Filing date: 1997-09-06
Publication date: 1999-04-07
Anticipated expiration: 2017-09-06
Also published as: EP0906175B1; US6148526A; DE19649514A1; JP2000504282A; DE59706502D1; WO1998023410A1

Abstract

The present invention relates to a manually driven machine (10) provided with a rotatively driven disk-type tool (22), for example a circular saw, a cage (12) accomodating a propulsion engine and a spindle (17) bearing a tool between an attaching nut, a clamping screw (19), or a similar item, and supporting bridles (21, 23), of which the one (23) facing the spindle (17) is easily workable, can rotate without using any tool and takes its bearing against the tool (22) without much friction. The securing and releasing efficiency of the tool results from the fact that adjustment means (35) coupled with the supporting bridle (22) cause the latter to be axially shifted by a torque, including through the tool, in the direction of the latter (22) when they start rotating relative to the tool spindle (17), thereby increasing the clamping force exerted on the tool (23), and tend, when the tool (22) is idle, to cause the supporting bridle (23) to axially shift away from the tool (22), thereby bringing about a release of the clamping force.

Description

Handwerkzeuαmaschine

State of the art

The invention relates to a handheld power tool according to the preamble of claim 1.

A hand-held grinding tool known from DE-OS 44 21 480 carries a grinding wheel on its output shaft between two clamping flanges. The outer clamping flange can be clamped against the grinding wheel via a thread. The inner flange is mounted so that it can be rotated with little friction with respect to the output spindle using a solid lubricant. When turning the outer clamping flange in the loosening direction, the inner clamping flange can be easily rotated together with the grinding wheel. This means that the outer clamping flange can be loosened with little force and the grinding wheel can be changed easily.

This solution has the disadvantage that when the grinding spindle abruptly brakes, the outer flange tries to loosen and there is a risk that the grinding wheel will be thrown away with high energy from the grinding spindle, with a corresponding risk of injury to persons in the vicinity. Since the previous self-tightening effect could be so strong that the clamping screw could be loosened by the saw blade so that the clamping screw could not be removed by hand, but only by means of an auxiliary tool, an auxiliary tool had to be carried and used in most cases to change the saw blade. This resulted in a correspondingly high amount of time.

From EP 0 231 500 quick release systems are easy

Loosening grinding wheels, saw blades or the like from hand-held power tools known to work satisfactorily, but which do not automatically reduce the clamping torque when the tool shaft is at a standstill so that the tool can be easily released by turning the outer clamping flange.

Advantages of the invention

The hand tool according to the invention with the characterizing features of claim 1 has the advantage that when the tool shaft is at a standstill, the outer clamping flange or clamping bolt can be easily released by hand without any additional auxiliary tool. Because the self-releasing or tensioning clamping mechanism is arranged inside the hand-held power tool, it is captive and safe from contamination by dust and chips. It also makes it possible to use an inexpensive mass or standard part as a clamping screw or outer clamping flange.

Because the tensioning mechanism essentially consists of a pair of disks with rolling elements arranged in between, which are held in a certain position by a torsion spring, assembly as an assembly is particularly easy to accomplish. The fact that the clamping mechanism can be prefabricated as a structural unit with the drive pinion for the tool shaft means that the assembly effort is low.

The flat head of the cap screw and the particularly flat outer flange prevent a reduction in the depth of cut for miter cuts of more than 45 ° compared to straight cuts because, despite the inclined position of the saw shaft, the axially outermost part of the cap screw or the outer flange does not hit the workpiece before reaching for straight cuts greatest depth of cut threatens.

A particularly large bearing dimension can be selected by arranging the saw shaft bearing on the outer circumference of the sleeve region of the outer disk. Such a large needle bearing behaves more wear-resistant than needle bearings of comparable smaller diameter.

The time required to change the saw blade is reliably reduced in any case. In addition, the previous risk is eliminated that the saw blade unintentionally detaches from the saw shaft when the saw shaft stops suddenly.

Another advantage of the invention is that the depressions in the pair of disks can be contoured so that the rolling elements pass through a noticeable pressure point, from which the clamping torque no longer increases. This simplifies the handling of the clamping device because the operator receives clear information when the clamping position has been reached and that the clamping is finished.

drawing

An embodiment of the invention is in the follow he explains the description with reference to the accompanying drawing.

FIG. 1 shows a spatial representation of a circular saw according to the invention, FIG. 2 shows a partial longitudinal section of the circular saw according to FIG. 1 in the area of the saw shaft with the clamping mechanism, FIGS. 3, 4, 5, 6 exemplary embodiments for the design possibility of the pair of discs in FIG 7, the special contour of a rolling element bearing in one of the disks, which causes a noticeable pressure point as soon as the clamping position is reached.

Description of the embodiment

The hand-held circular saw 10 shown in FIG. 1 has a housing 11 with a handle 12 which contains an on / off switch 13 and an electrical connection cable 14. The housing 11 is pivotably arranged on a base plate 15 on a joint 16. The housing 11 contains a motor, not shown. This drives a saw shaft 17 via a drive pinion 28 (FIG. 2) of a motor shaft. This is rotatably mounted about an axis 18. A head screw 20 which can be screwed into an internally threaded section 19 (FIG. 2) of the saw shaft 17 and has a particularly flat head 19 "axially clamps a particularly flat outer flange 21 against a saw blade 22.

The saw blade 22 is encompassed by a saw blade housing 24 in its area arranged above the base plate 15 and emerges from the bottom through a through slot 25 arranged in the base plate.

FIG. 2 shows the sectional view of the hand-held circular saw 10 in the area of the saw shaft 17. This is in the housing 11 via saw shaft bearings 32, 34 rotatably and axially immovable. The saw shaft 17 is driven by a pinion

28 of the motor shaft, which is mounted in a motor bearing 29 in the housing 11 and which is arranged parallel to the saw shaft 17.

The pinion 28 is in engagement with an output pinion 30, which sits on the saw shaft 17 in a rotationally fixed manner. The output pinion

30 carries an inner disk 36 of a disk pair 35 on its end face on the left in the viewing direction.

An outer disk 37 of the pair of disks 35 adjoins the inner disk 36 axially, with a plurality of rolling elements 38 spaced apart from one another being rotatably mounted between the inner and outer disks 36, 37 or being supported and guided such that they can be passed around their respective axis of rotation 39.

The inner and outer disks 36, 37 are biased relative to one another via a torsion spring 40, which engages axially in the disks 36, 37 with legs that are not described in more detail.

The outer disk 37 continues in a sleeve-like shaft 37 ', which is positively coupled on the end face to the right end face of the inner flange 23 in the viewing direction, the saw shaft bearing 34, which is a needle bearing with a large, seated on the outside of its cylindrical surface

Diameter is. The outer disc 37 is rotatably mounted together with the inner flange 23 relative to the saw shaft 17. The saw blade 22 is supported on the left side of the inner flange 23 in the viewing direction, preferably with increased friction, e.g. through areas of increased roughness.

The saw shaft 17 has in its left end in the viewing direction an internally threaded section 19 into which the threaded shaft 19 ′ of the cap screw 20 engages in a screwed manner. The head screw 20 is supported axially with its head 19 ″ against the outer flange 21, which, with a central polygonal hole 46, closely engages around the outside of the end of the saw shaft 17, which is designed as a flat surface, one flat side of which can be seen as a flattening 44. The outer flange 21 is thereby held against rotation against the saw shaft 17.

The variants shown in FIGS. 3, 4, 5 and 6 show pairs of disks 35 rotated by 90 ° according to the sectional arrows X-X according to FIG. 2 with differently contoured recesses for receiving the rolling elements 38.

Figure 3 shows that the inner disc 36 has a recess 49 with an inclined surface 48 and rounded flanks on which the rolling element 38 can roll as on an inclined plane, delimited on the left and right by rounded flanks. A recess 50 arranged in the outer pane 37 with an angular contour and without an inclined surface holds the rolling element 38 in a cage-like manner, so that it can only change its position with respect to the outer pane 37 minimally.

Figure 4 shows the reverse arrangement compared to Figure 3, i.e. H. the inner pane 36 carries a flat recess 149 and the outer pane 37 a recess 150 provided with a bevel 151 and with rounded flanks.

In FIGS. 5 and 6, the inner and outer disks 36, 37 carry offset and oppositely arranged depressions 49, 150 with inclined surfaces 48, 151. In addition, the rolling element 38 in FIG. 6 is guided in a separate, disk-like cage 53. In FIG. 7, an oblique depression 249 with an unevenness 260 is arranged which, when rolled over by the rolling element 38, causes a pressure point on the tensioning device, from which the tensioning torque no longer increases and which facilitates handling of the tensioning device. The unevenness is to be dimensioned such that rolling the rolling elements 38 back into the loose position can always be carried out easily. The tensioning device according to the invention works in the following way: the cap screw 20 is turned by hand with respect to the saw shaft 17, the outer flange 21 being axially supported on the saw blade 22, which is thereby pressed against the inner flange 23 with increasing axial force. The inner flange 23 is supported axially to the right in the viewing direction against the outer disk 37 of the disk pair 35 and via the rolling elements 38 against the inner disk 36, the driven pinion 30 and the bearing 32.

The torsion spring 40 is preloaded in such a way that it attempts to turn the pair of disks 35 against one another in such a way that the rolling bodies 38 at the lowest point of the recesses 50 or

Recess 49 are mounted and that the axial distance between the inner and outer disks 36, 37 is minimal. If the motor and thus the motor shaft 28 are set in motion by actuating the on / off switch 13, the saw shaft 17 rotates together with the driven pinion 30, the pair of discs 35, the rolling elements 38, the inner flange 23, the saw blade 22 and the outer flange 21 and the screw 20. As a result of the screw 20 being tightened only by hand, there is initially a relatively large amount of slip between the saw blade 22 and the inner and outer flanges 21, 23. Because of its inertia, the saw blade 22 tries to stop relative to the saw shaft 17. The saw blade 22 also tries to hold or delay the inner and outer flange 23, 21. This is only possible with respect to the inner flange 23 because it rotates with respect to the saw shaft 17. is cash. In the case of the outer flange 21, a delay with respect to the saw shaft 17 is not possible because there is a positive fit between the outer flange 21 and the saw shaft 17 via the double surface 19 'and the polygonal recess. As a result, only the inner flange 23 together with the outer disk 37 is decelerated relative to the saw shaft 17. This leads to a relative rotation between the outer disk 37 and the inner disk 36, the rolling elements 38 rolling in the recesses 49 or the recesses 50 into elevated positions and thus trying to enlarge the axial distance between the inner and outer disks 36, 37. As a result, the outer disk 37 is moved axially together with the inner flange 23 in the direction of the saw blade 22 or against the outer flange 21. This leads to an increase in the clamping torque between the flanges 21, 23 and the saw blade 22.

If the rotating saw blade 22 is now guided against a workpiece and comes into machining engagement with it, the saw blade 22 is again decelerated with respect to the saw shaft 17, so that the automatic tensioning just described is now repeated or continued by frictional entrainment.

The clamping torque of the saw blade 22 has thus reached a maximum. If the drive motor or the motor shaft 28 is now switched off via the on / off switch 13, the reverse process occurs, as previously described for starting the machine or during machining of the workpiece. This effect is further enhanced if a spindle stop is actuated, which abruptly stops the saw shaft 17 by positive engagement. By doing so in reverse

In the same direction as the inertial forces of the saw blade 22 which act when starting, the inner flange 23 is rotatably entrained, the axial spacing of the disk pair 35 decreasing to its minimum. Supported by the torsion spring 40, the clamping torque drops to a minimum value. Because of the shape Conclusion between the outer flange 21 and the saw shaft 17 there is no risk that the cap screw 19 is loosened by an inertial force of the saw blade 22 acting in the loosening direction. An unwanted loosening of the saw blade or tool from the saw shaft 17 can thus be ruled out and a considerable gain in occupational safety in connection with a manually operated quick-action clamping or loosening device for a hand-held circular saw or a disk grinding machine or the like. reached .

Claims

Expectations

1.Handheld power tool (10) with a rotationally driven, disk-like tool (22), for example a hand-held circular saw, cut-off machine or the like, with a housing (12) which receives a drive motor and a tool shaft (17) which between a clamping nut, clamping screw ( 19) or the like. And support flanges (21, 23) carries tensionable tool (22), whereby the support flange (23) is easy to turn relative to the tool shaft (17), can be rotated without auxiliary tools and is supported on the tool (22) with high friction, thereby characterized in that adjustment means (35) are coupled to the support flange (23), which, when rotated relative to the tool shaft (17) as a result of rotary driving, in particular by the tool (22) when the hand-held power tool (10) is operated, towards the tool (22) move axially - and thus clamp the tool (22) with increasing force - and which automatically move the support flange (23) away from the tool (22) when the tool (22) is at a standstill ial try to move - and thus reduce the tension.

2. Hand tool according to claim 1, characterized in that the clamping screw (19) or the like. Opposite the tool shaft (17) is secured against rotation.

3. Hand tool according to claim 1, characterized in that the adjusting means (35) consist of a pair of disks (35), the disks (36, 37) of which are supported against one another via axial inclined surfaces (48, 151) and via a spring (40 ) biased against each other, try to take a position with a minimal axial dimension of the pair of disks (35) and, when twisted mutually, move out of this position to a specific, maximum axial dimension, one disc (37) being rotatable and coupled to the support flange (23) in a rotationally driving manner and wherein the other disc (36) is rotatably coupled to the saw shaft (17).

4. Hand tool according to claim 1, characterized in that between the pair of discs (35) rolling elements (38) are arranged rollable.

5. Hand tool according to claim 3, characterized in that at least the axial inclined surfaces (48, 151) of one of the disks (36, 37) serve to receive the rolling elements (38).

6. Hand tool according to claim 3 or 4, characterized in that the axial inclined surfaces (48, 151) for receiving the rolling elements (38) in recesses (49) of the axial surfaces of the disks (36, 37) are arranged.

7. Hand tool according to claim 3 or 4, characterized in that the axial inclined surfaces (248) uneven Wear units (260) to create a pressure point when tensioning or releasing the tensioning device.

8. Hand tool according to claim 3, 4 or 5, characterized in that the outer disc (37) with an axial sleeve (37 ') on the saw shaft (17) is arranged, the outer periphery of which forms the bearing seat for a saw shaft bearing (34).