GB2409422A

GB2409422A - Connecting a tool to a drive unit without the use of auxiliary tools

Info

Publication number: GB2409422A
Application number: GB0427034A
Authority: GB
Inventors: Steffen Wuensch
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-12-10
Filing date: 2004-12-09
Publication date: 2005-06-29
Anticipated expiration: 2024-12-09
Also published as: CN1626311A; GB2409422B; DE10357652A1; GB0427034D0; CN100553882C

Abstract

Means for locking a tool (19, Fig. 1) onto a driver 22 of a hand-held electric machine tool comprises at least two laterally protruding pegs 224, 225 on the driver 22 and a spring plate 24 fixed around a central opening of the tool (19, Fig. 1). Slots 27 corresponding to the number of pegs 224, 225 are formed in the spring plate 24, with a cam 25 rising up transverse to the plane of the spring plate 24 from each slot 27. The cams 25 are arranged around the circumference of a circle which is concentric with the central opening of the tool. The tool (19, Fig. 1) is locked to the driver 22 by passing the pegs 224, 225 through the slots 27, rotating the tool (19, Fig. 1) to move the pegs 224, 225 along the cams 25 and into depressions 26 thereon. Deformation of the spring plate 24 holds the tool (19, Fig 1) in place when it is locked onto the driver 22. Used to lock a grinding platen to an eccentric or rotary grinder or a circular blade to a rotary saw.

Description

ROBERT BOSCH GMBH, 70442 Stuttgart Electric hand-held machine tool,

particularly an eccentric grinder

Prior art

The invention takes as its starting point an electric hand- held machine tool, particularly an eccentric grinder, according to the precharacterising clause of Claim 1.

A known grinding wheel for a hand-held grinding machine (EP 0 557 773 B1) is coupled to a driven shaft of a drive unit by way of a driver. On its side facing the grinding wheel, i the driver widens into a plate-type toothed carrier having three teeth arranged evenly over its circumference, and is provided with a central threaded bore into which a screw pushed through the grinding wheel can be screwed. On its side facing the driver, the grinding wheel has tooth- engagement bores into which the teeth of the driver dip so that the grinding wheel is fixed on the driver with form fit in the direction of rotation. The screw securing the axial position on the driver is screwed in by means of a key or a screwdriver, it being necessary to tighten the screw with the required torque for secure fixing of the grinding wheel. To replace the grinding wheel, the central screw is released and the grinding wheel is pulled axially off the driver.

The grinding wheel is replaced when the application necessitates the use of grinding wheels having an appropriate hardness, or in the event of wear on the grinding wheel.

Advantages of the invention The inventive hand-held machine tool, particularly eccentric grinder, having the features of Claim 1 has the advantage of rapid and secure replacement of the tool without the use of an auxiliary tool such as a spanner, screwdriver or the like. The quickacting closure enables simple push-on assembly of the tool, in which case only a simple rotary movement of the tool in opposite directions of rotation is required to close and open the quick-acting closure. Auxiliary assembly means, such as a screw which can fall out, are not used.

The quick-acting closure according to the invention can be advantageously used in eccentric grinders for which frequent replacement of the grinding wheel is undertaken in order to provide the optimum hardness of the grinding wheel for the particular application. However, it can also be used in other electric hand-held tools having a rotating tool, e.g. in a hand-held circular sawing machine for fixing the circular saw blade on the drive element, in which the direction of rotation for closing the quickacting closure is directed in opposition to the direction of rotation of the circular saw blade.

Advantageous further developments and improvements of the electric handheld machine tool indicated in Claim 1 are possible as a result of the measures described in the further claims.

According to a preferred embodiment of the invention, one closure part is a closure pin constructed on the driver and the other closure part is a closure spring which is incorporated in the tool and latches against the closure pin and then generates an elastic tensile stress on the closure pin. The closure pin has at least two laterally protruding transverse pegs and the closure spring has a spring plate having at least two cams which protrude axially therefrom and are mutually offset by the same angle of rotation as the transverse pegs. Each cam is provided with a rising ramp and a latching depression, adjoining this latter, for the transverse pegs. As a result of this constructive design, after pushing the tool onto the closure pin, a latching of the tool is already achieved by twisting the tool through a maximum of 90 . At the same time, the spring plate holds the latched-in tool under high axial pre-tension. When the electric hand-held machine tool is constructed as an eccentric grinder in which the grinding wheel can assume any direction of rotation, this has the advantage that the closure does not open at any time during the grinding operation since the counter torques produced on the grinding wheel during the grinding operation are always smaller than the retrotorque of the grinding wheel required to open the quick-acting closure.

Drawing The invention is explained in more detail in the

description below, with reference to an exemplary

embodiment illustrated in the drawing, which shows: Fig. 1 a longitudinal section through part of an eccentric grinder having the grinding wheel thereon; Fig. 2 an enlarged section through part of the grinding wheel having a quick-acting closure comprising two closure parts for fixing the grinding wheel on the eccentric grinder of Fig. 1; Fig. 3 an enlarged illustration of the quick-acting closure in Fig. 2; Figs. 4 to 6 one closure part of the quick-acting closure in a to 6respective plan view, side view and perspective illustration; Figs. 7 to 9 the other closure part of the quick-acting closure in a respective plan view, side view and perspective illustration; Fig. 10 a longitudinal section through part of an eccentric grinder according to a further exemplary embodiment.

Description of the exemplary embodiment

As an exemplary embodiment for a general electric hand-held machine tool having a rotating tool, the eccentric grinder (illustrated in part in a longitudinal section in Fig. 1) has an electric motor 10 having a driven shaft 11 on which a fan impeller 13 of a extractor fan is placed in torsion- resistant manner on its end portion. A rotary bearing 17 having a bearing axis which is eccentric to the axis of the driven shaft 11 is held in the fan impeller 13 and has a driver 12 connected in fixed manner to the grinding wheel 14 mounted therein. The driver 12 can be displaced in a circular movement which is concentric with the axis of the driven shaft 11 by a drive unit comprising an electric motor 10, driven shaft 11 and fan impeller 13, the grinding wheel 14 at the same time rotating about the bearing axis as a result of the bearing of the driver 12 in the rotary bearing 17. The rotation can be effected in both directions and is arbitrary. The electric motor 10, driven shaft 11, fan impeller 13 and driver 12 are received in a housing 15, the eccentric journal 12 projecting partially out of the housing 15. The driven shaft 11 is supported in the housing by means of a ball bearing 16. The grinding wheel 14 has, in known manner, a carrying part 18 on which a grinding plate 19, which is made of foam and whereof the free surface is covered by a touch-and-close fastening material 20, is fixed. The touch-and-close fastening material 20 cooperates in known manner with the velour rear side of an abrasive sheet (not illustrated here) and fixes the abrasive sheet in torsion-resistant manner on the grinding plate 19.

The torsion-resistant connection between the grinding wheel 14 and the driver 12 is effected by means of a quick-acting closure 21. The quick-acting closure 21 shown in a perspective and sectional illustration on an enlarged scale in Figs. 2 and 3 comprises two closure parts 211 and 212 which can be brought in and out of engagement with one another without the use of auxiliary tools. The closure part 211 is constructed on the driver 12 and the closure part 212 is integrated in the grinding wheel 14. Fig. 2 shows a cross-section through the closure parts 211 and 212 in the engaging position and Fig. 3 shows a perspective illustration of the closure parts 211, 212 in the engaging position. The separated closure parts 211, 212 are illustrated in Figs. 4 to 6 and 7 to 9, and more precisely in a respective plan view (Fig. 4 and Fig. 7), side view (Fig. 5 and Fig. 8) and perspective view (Fig. 6 and Fig. 9).

The closure part 211 illustrated in Figs. 4 - 6 is designed as a closure pin 22 which is integrally formed on the driver 12 and is therefore a onepiece component of the driver 12. The closure pin 22 dips into a central opening 23 in the carrying part 18 of the grinding wheel 14 by means of a pin body 221 and reaches over the upper side of the carrying part 18 in the edge region of the opening 23 by means of a radial flange 222 (Fig. 2). A pin neck 223 of reduced diameter is constructed on the free end face of the pin body 221. Adjacent to the free end of the pin neck 223, two diametrical transverse pegs 224, 225 protrude radially from the pin neck 223, the transverse pegs 224, 225 being constructed in one piece with the pin neck 223.

The closure part 212 illustrated in Figs. 7 to 9 is constructed as a closure spring 24 which is incorporated in the opening 23 of the carrying part 18 and held therein.

The closure spring 24 is constructed such that the closure pin 22 can be latched therein and generates an elastic tensile stress after latching against the closure pin 22.

In detail, the closure spring 24 constructed in one piece has a spring plate 241 and two cams 242 which protrude axially from the spring plate 241 and are mutually offset through an 180 angle of rotation corresponding with the transverse pegs 224, 225 on the closure pin 22. The cams 242 here are arranged on a graduated circle which is concentric with the axis of the spring plate 241 and are of an identical construction. Each cam 242 has a rising ramp 25 and a latching depression 26 adjoining this latter.

The rising ramp 25 has an arcuate course, its axial height increasing from the spring plate 241 to the latching depression 26. In relation to the direction of rotation of the driven shaft 11, the axial height increases in its direction of rotation. In front of each rising ramp 25, a radial cutout 27 is provided in the spring plate 241. The cutouts 27 are arranged diametrically and serve for pushing through the transverse pegs 224, 225 of the closure pin 22.

The closure spring 24 is constructed as an insert part and is inserted into the injection mould during injection moulding of the carrying part 18 - which is manufactured from plastics material - of the grinding wheel 14, so that, during injection moulding, the plastics material of the carrying part 18 reaches over the outer edge region 241a of the spring plate 241 (Fig. 2).

During assembly, the grinding wheel 14 is placed on the closure pin 22 in such a rotational position that the transverse pegs 224, 225 on the closure pin 22 can pass through the cutouts 27 in the spring plate 241 of the closure spring 24. The grinding wheel 14 is then pushed axially onto the closure pin 22 until the carrying part 18 strikes the radial flange 222 of the closure pin 22. The grinding wheel 14 is now rotated manually in opposition to the direction of rotation of the driven shaft 11 of the electric motor 10. During this, the transverse webs 224, 225 on the closure pin 22 slide over the rising ramps 25 in order to then latch in the latching depressions 26 under the spring pre-tension of the spring plate 241. In the latching position, an axial bracing between the grinding wheel 14 and the closure pin 22 is achieved as a result of the elastic deformation of the spring plate 241. The removal of the grinding wheel 14 from the eccentric grinder is in turn effected by rotating the grinding wheel 14 through 90 , this time in the opposite direction of rotation. Under the pressure of the torque applied to the grinding wheel 14, the transverse pegs 224, 225 slide out of the latching depression 26 and down the rising ramps 25 into the cutouts 27. If the grinding wheel 14 is rotated until the transverse pegs 224, 225 are congruent with the cutouts 27 in the spring plate 241, the grinding wheel 14 can be pulled axially off the closure pin 22 and replaced for example by another grinding wheel 14 having a different hardness of the grinding plate 19.

In the modified eccentric grinder illustrated in part in a longitudinal section in Fig. 10, the rotary bearing 17 is integrated in the carrying part 18 of the grinding wheel 14 so that the grinding wheel 14 is mounted in freely rotational manner. The driver 12 is seated in torsion- resistant manner on the driven shaft 11 with an axis which is eccentric to the axis of the driven shaft 11. In this case, the radial flange 222 on the closure pin 22 integrally formed on the driver 12 is omitted and the closure pin 22 dips into the opening 23 in the carrying part 18 without bearing against the carrying part 18. Upon closing the quick- acting closure 21, the closure spring 24 then braces the grinding wheel 14 against the closure pin 22 by way of the rotary bearing 17 whereby, when the rotary bearing 17 is constructed as a deep groove ball bearing, the ball-bearing play is eliminated and the grinding wheel 14 is prevented from wobbling.

The invention is not restricted to the exemplary embodiment of the eccentric grinder described. It is thus also the case in a hand-held circular saw machine that the circular saw blade can be fixed on the driven element of a speed- transforming gear by means of a quick-acting closure 21. In this case, the driver 12 is a component of the driven element without being connected thereto in torsion- resistant manner. The closure spring 24 is fixed in the central opening in the circular saw blade with the edge of its spring plate 241 against the circular saw blade. The rising ramps 25 of the cams 242, 243 are aligned such that they rise in the direction of rotation of the driven element; therefore, to close the quick-acting closure 21, the circular saw blade has to be rotated inversely to the direction of rotation of the driven element. /

Claims

Claims 1. An electric hand-held machine tool, particularly an eccentric

grinder, having a tool, particularly a grinding wheel (14), which can be driven in a rotational and/or orbital movement by means of an electric drive unit, and having fixing means for fixing the tool in torsionresistant manner on a driver ( 12) which is in active communication with the drive unit, characterized in that the fixing means have a quickacting closure (21) which is operated without the use of auxiliary tools and has two closure parts (211, 212) of which one is arranged on the driver ( 12) and one is arranged on the tool.
2. An electric hand-held machine tool according to Claim 1, characterized in that the one closure part (211) is a closure pin (22) connected in torsion-resistant manner to the driver (12) and the other closure part (212) is a closure spring (24) which is incorporated in the tool, can be latched in torsion-resistant manner with the closure pin (22) and generates an elastic tensile stress on the closure pin (22) upon latching.
3. An electric hand-held machine tool according to Claim 2, characterized in that the closure pin (22) has at least two laterally protruding transverse pegs (224, 225) and the closure spring (24) has a spring plate (241) and at least two mutually offset cams (242, 243) which rise up axially from the spring plate at the same angle of rotation as the transverse pegs (224, 225) and each have a rising ramp (25) and, adjoining this latter, a latching depression (26) for the transverse pegs (224, 225).
4. An electric hand-held machine tool according to Claim 3, characterized in that the cams (242, 243) are arranged, preferably equidistant, on a graduated circle concentric with the wheel axis and the rising ramps (25) rise in the circumferential direction of the graduated circle.
5. An electric hand-held machine tool according to one of Claims 2 - 4, characterized in that the closure pin (24) is a one-piece component of the driver ( 12) .
6. An electric hand-held machine tool according to one of Claims 2 - 5, characterized in that the closure spring (24) is fixed in a central opening (23) of the tool.
7. An electric hand-held machine tool according to Claim 6, characterized in that the closure spring (24) is clamped in the tool at the edge side by means of its spring plate (241).
8. An electric hand-held machine tool according to Claim 7, characterized in that the tool has a plastics part and the closure spring (24) is an insert part incorporated with form fit in the plastics part.
9. An electric hand-held machine tool according to one of Claims 1 - 8, characterized in that the tool is a grinding wheel ( 14) and in that the driver ( 12) is mounted in a rotary bearing (17) having a bearing axis which is eccentric to the axis of a driven shaft (11) of the drive unit, and the rotary bearing (17) is coupled in torsion- resistant manner to the driven shaft (11), preferably received in a fan impeller (213) of a extractor fan, which is seated in torsion-resistant manner on the driven shaft (11) .
10. An electric hand-held machine tool according to one of Claims 1 - 8, characterized in that the tool is a grinding wheel (14) and in that the driver (12) is seated in torsion-resistant manner on a driven shaft (11) of the drive unit with an axis which is eccentric to the shaft axis and is mounted in a rotary bearing (17) received in the grinding wheel (14).
11. An electric hand-held machine tool substantially as herein described with reference to the accompanying drawings.