GB2378488A

GB2378488A - Overlatch clutch

Info

Publication number: GB2378488A
Application number: GB0214311A
Authority: GB
Inventors: Karl Frauhammer; Manfred Hellbach; Heinz Schnerring
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-06-25
Filing date: 2002-06-20
Publication date: 2003-02-12
Anticipated expiration: 2022-06-20
Also published as: GB0214311D0; GB2378488B; CN1283423C; DE10130520B4; CN1393323A; DE10130520A1; JP2003062768A; CH695852A5

Abstract

A safety overlatch clutch 14, forming part of a drive train of a hand tool, has two clutch elements, a spur wheel 18 with a detent curve 16 and a clutch disc 20 which are connected to each other by a set of rollers 22. The rollers 22 are pushed out of a groove 28 in the clutch disc 20, by compression springs 30, and jam into the detent curve 16. As the clutch rotates, the detent curves 16 push harder against the rollers 22 until, at a preset torque, the curve 16 pushes the rollers 22 in to the grooves 28 and the spur wheel 18 and clutch disc 20 are disconnected. The torque at which this happens can be varied via a plunger 36 having a tapered surface 56, which can increase or decrease the bias in the compression springs 30 by moving spring plungers 32. The plunger is operated by a rotary lever 46.

Description

5 Hand tool machine Background art

The invention relates to hand tool machines.

In order, in the event of jamming of a drill or drill bit in a wall, to prevent a -. hammer drill held by a user from continuing to rotate in an uncontrolled manner, it is known to connect the drill and/or drill bit to a drive of the hammer drill by a safety clutch, which opens as soon as the drill jams.

From DE 38 32 202 Cl a generic hand tool machine with a safety clutch is known.

The safety clutch, for transmitting a torque, has a first radially inner clutch part enclosed by a second clutch part. The clutch parts are connected to one another by detent elements in the form of rollers. The rollers are guided in the first clutch 20 part in guide channels. Disposed in the guide channels are compression springs, which at their first end are supported against a channel base and with their second end act radially outwards upon the rollers in the direction of the second clutch part and press the rollers into recesses of the second clutch part. If a specific torque is exceeded, the rollers are pressed radially inwards out of the recesses against the 25 compression springs and the safety clutch opens. The rollers then slide over the recesses. The invention proceeds from a hand tool machine having in the drive train at least one safety clutch, which is disposed in a housing and which for transmitting a 30 torque about an axis of rotation comprises at least two clutch elements, which are connected to one another by a detent mechanism comprising at least one detent element, which detent mechanism unlatches when a critical torque is exceeded.

It is proposed that the critical torque is adjustable to various values by means of at 35 least one adjusting, means. Compared to the hand tool machines according to prior

5 art, in which the critical torque is set albeit lower than an ergonomically determined maximum torque but higher than a maximum possible operating torque, this offers the advantage that the critical torque may be set lower for applications of the hand tool machine with a lower possible operating torque, e g.

with standard drills up to 40 mm diameter Maximum possible operating torques 10 arise particularly in the case of applications involving large drill bits in concrete.

Unnecessarily high stressing of the user and the material and/or the detent mechanism may be avoided in the event of jamming in the case of applications involving operating torques lower than the maximum operating torque and safety 15 may be enhanced by avoiding unnecessarily high reaction torques. Wear, particularly in the detent mechanism, may be reduced and it is possible to achieve long tool lives with at least substantially constant critical torques The critical torque may be made adjustable by means of various constructions 20 deemed meaningful by the person skilled in the art, e.g by an adjustable detent contour etc. A solution of a particularly simple design may however be achieved when the critical torque is adjustable by means of a bias of the detent mechanism, which bias is adjustable by the adjusting means. The bias may be of a step-by-step or infinitely adjustable design.

In an advantageous development of the invention, the bias of the detent element is generated by at least one compression spring. It is easily possible to build on standard designs and a low constructional outlay may be achieved.

30 The compression spring is preferably supported at its side remote from the detent element against a spring plunger, which is displaceable via the external contour of the adjusting means. The spring plunger offers the advantage of an optimally adaptable surface of contact with the external contour of the adjusting means. Via the spring plunger the compression spring may therefore be tensioned and released 35 safely, reliably and without material,wear by the adjusting means By means of

5 the spring plunger at its side directed towards the compression spring an advantageous, in particular flat surface of contact with the compression spring may be achieved' with the result that the compression spring is safely guided and jamming, or buckling may be avoided.

10 The adjusting means is advantageously formed by a plunger, against the lateral surface of which at least one spring plunger is supported, and the diameter of which varies in a region of contact with the spring plunger. The adjusting means may be integrated in a space-saving manner into the detent mechanism, and indeed may in particular be aligned at right angles to the spring plunger. A plurality of 15 spring plungers may advantageously be arranged radially around the adjusting means and/or the plunger and adjusted by the adjusting means.

It is further proposed that the compression spring and the spring plunger are guided in a recess of a clutch element, with the result that advantageous guidance 20 may be achieved and canting and jamming of the detent mechanism may be reliably avoided.

The adjusting means is preferably biased towards a cam disk and displaceable via the latter, with the result that in a simple manner a motion of rotation may be 25 converted into an axial displacement of the adjusting means and advantageous transmission may be achieved.

In a further development of the invention it is proposed that the cam disk is rotatable by means of a rotary lever, which is provided externally on a housing of 30 the hand tool machine. With a low constructional outlay easy operation of the adjusting means may be achieved. To enable the adjusting means to be fixed in individual desired positions, the rotary lever may be designed so as to be latchable into various positions.

5 In a preferred embodiment the cam disk is rotatably supported in a sealing screw, which is screwed into the housing of the hand tool machine This offers the possibility of a constructionally simply designed sealing of a rotary leadthrough to the housing interior of the hand tool machine and in particular, during assembly of the sealing screw, it is easily possible to achieve a bias of a spring, which presses 10 the adjusting means towards the cam disk It is further proposed that the adjusting means is actuable by means of an actuator disposed in the housing, with the result that comfort may be enhanced. The actuator may be of a pneumatic, electrical and/or electromagnetic design and be 15 formed e.g by an electric motor or an electrically actuated solenoid.

In a preferred embodiment the actuator is controlled in dependence upon at least one operating parameter. Wrong operation may be reliably avoided and comfort may be further enhanced The operating parameter is advantageously derived from a selected mode of operation, i e. depending on the set mode of operation, an optimized bias of the detent mechanism is adjusted by means of the actuator It is however also possible for the operating parameter to be determined by a sensor For example, depending 2 5 on the position of the drill chuck, i e depending on the diameter of the drill being used, the critical torque may be automatically adjusted in an optimized manner.

With a sensor a particularly flexible adjustment may be achieved Further advantages arise from the following description of the drawings An

embodiment of the invention is illustrated in the drawings The drawings, the description arid the claims contain numerous features in combination The person

skilled in the art will expediently consider the features also individually and combine them into meaningful further combinations.

3 5 The drawings show:

s Pig. 1 a cross section through a hammer drill having an overlatch clutch in the drive train with a strongly biased detent mechanism, Fig. 2 a cross section through the hammer drill according to Fig 1 with a weakly biased detent mechanism, 10 Fig. 3 a section along the line 111-111 in Fig. 1 and Fig. 4 a section along the line IV-IV in Fig. 2.

Fig. I shows a section through a hammer drill (not shown in detail) having a safety clutch 14 in the form of an overlatch clutch disposed in a housing 44 in the drive 15 train The safety clutch 14 has two clutch elements, a clutch spur wheel 16 with a detent curve 18 and a clutch disc 20, which are connected to one another by a detent mechanism comprising detent elements 22 in the form of rollers. The clutch spur wheel 16 is supported rotatably between a shoulder 24 of a pinion 10 of a right-angle gear of the hammer drill and the clutch disc 20, which is pressed 2 0 onto a shaft 26. The pinion I O of the right-angle gear is formed onto the shaft 26 and meshes with a bevel wheel 12 of the right-angle gear.

The clutch disc 20 has at least two opposing grooves 28, each of which receives a roller, a compression spring 30 and a spring plunger 32, wherein the roller and the 25 spring plunger 32 are guided in the groove 28. The biased compression spring 32 presses the roller radially out towards the detent curve 18 and presses the springs plunger 32 radially in towards an adjusting means 36 in the form of a plunger.

The roller projects partially out of the groove 28 and, up to a critical torque, is 30 supported in peripheral direction against a steep flank 34 of the detent curve 18 (Figs. 3 Ed 4). If the critical torque is exceeded, the roller is pressed counter to the action of the compression springs 30 into the groove 287 with the result that the steep flank 34 of the detent curve 18 may move over the roller. The clutch spur wheel 16 with its detent curve 18 rotates relative to the clutch disc 20, the safety 35 clutch 14 is open.

The critical torque, at which the safety clutch 14 opens, is dependent upon the bias of the detent mechanism and/or of the compression springs 30 The spring force is determined by the upsetting of the compression springs 30, i e in the latched state of the roll, by the position of the spring plunger 32, against which the compression 10 spring 30 is supported.

The adjusting means 36 in the form of a plunger is supported in the shaft 26 in the form of a hollow shaft and is pressed away from the pinion I O and towards a cam disk 40 by a spring 38, which is disposed in the shaft 26 at the end directed 15 towards the pinion 10 The cam disk 40 is supported at the side remote from the plunger against a sealing screw 42 screwed into the housing 44, is rotatably supported by a cylindrical region 52 in a through-bore of the sealing screw 42 and extends with a formed-on hexagon insert bit 54 out beyond the sealing screw 42 and the housing 44. For sealing off the through-bore in the sealing screw 42, in 2 0 the cylindrical region 52 of the cam dislc 40 an O-ring 58 is inserted in an annular groove. When the sealing screw 42 is screwed in, the spring 38 is biased via the cam disk 40 and the plunger.

At the housing exterior, on the hexagon insert bit 54 of the cam disk 40 a rotary 2 5 lever 46 with a matching hexagon socket is supported. Rotation of the rotary lever 46, and/or of the cam disk 40 gives rise to a stroke 48 of the plunger. The plunger at the side directed towards the pinion 10 has in a region of contact with the spring plunger 32 a sub- region 56, which tapers towards the pinion 10 30 When the plunger is adjusted via the cam disk 40 in the direction remote from the pinion 10, the spring plungers 32 are displaced radially inwards. The biases of the compression springs 30 and the critical torque are therefore reduced (Figs 2 and 4). The hammer drill is set for an application using a standard drill up to 40 mm.

5 When the plunger is adjusted via the cam disk 40 in the direction of the pinion 10, the spring plungers 32 are displaced radially outwards The biases of the compression springs 30 and the critical torque are therefore increased (Figs I and 3). The hammer drill is set for an application with a drill bit 10 The housing 44 of the hammer drill is partially filled with oil' which passes through a lubricant opening 50 in the pinion 10 into the shaft 26 and into the safety clutch 14.

Claims

5 Claims

1 Hand tool machine having in the drive train at least one safety clutch (14), which is disposed in a housing (44) and which for transmitting a torque about an axis of rotation comprises at least two clutch elements, which are 10 connected to one another by a detent mechanism comprising at least one detent element (22), which detent mechanism unlatches when a critical torque is exceeded, characterized in that the critical torque is adjustable to various values by means of at least one adjusting means (36) .

15 2. Hand tool machine according to claim 1, characterized in that the critical torque is adjustable by means of a bias of the detent mechanism, which bias is adjustable by the adjusting means (36) 3 Hand tool machine according to claim 2, characterized in that the bias of 20 the detent mechanism is generated by means of at least one compression spring (30).

4 Hand tool machine according to claim 3, characterized in that the compression spring (30) at its side remote frond the detent element (22) is 25 supported against a spring plunger (32), which is displaceable via the external contour of the adjusting means (36) 5 Hand tool machine according to claim 4, characterized in that the adjusting means (36) is formed by a plunger, against the lateral surface of 30 which at least one spring plunger (32) is supported, and the diameter of which varies in a region Recontact with the spring plunger (32).

6 Hand tool machine according to claim 4 or 5, characterized in that the compression spring (30) and the spring plunger (32) are guided in a recess 3 (28) of a clutch element.

7 Hand tool machine according to one of the preceding claims, characterized in that the adjusting means (36) is biased towards a cam disk (40) and displaceable via the latter.

10 8, Island tool machine according to claim 7, characterized in that the cam disk (40) is rotatable by means of a rotary lever (46), which is provided externally on the housing (44).

9 Hand tool machine according to claim 8, characterized in that the cam 15 disk (40) is rotatably supported in a sealing screw (42), which is screwed into the housing (44).

10. Hand tool machine according to one of claims l to 7, characterized in that the adjusting means (36) is actuable by means of an actuator disposed 2 O in the housing (44), 11. Hand tool machine according to claim 1O, characterized in that the actuator is controlled in dependence upon at least one operating parameter; 25 12. Hand tool machine according to claim 11, characterized in that the operating parameter is derived from a selected mode of operation, 13. Hand tool machine according to claim 11, characterized in that the operating parameter is determined by a sensor, 14. Hand tool machine substantially as herein described with reference to the accompanying drawings.