GB2410916A

GB2410916A - Hand held machine tool having clutch

Info

Publication number: GB2410916A
Application number: GB0502804A
Authority: GB
Inventors: Otto Baumann; Ulrich Bohne; Dietmar Saur
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-02-13
Filing date: 2005-02-10
Publication date: 2005-08-17
Anticipated expiration: 2025-02-10
Also published as: GB2410916B; DE102004007046A1; GB0502804D0; CN1654172A; CN100500386C

Abstract

A hand held machine tool having a striking mechanism 40 and a clutch device 20 which can be engaged and disengaged to produce and interrupt a driving connection of the striking mechanism, where at least part of a drive bearing 18 can be tilted from an idling position to a striking position. Preferably, in the striking position the clutch element may form a support for the drive bearing , the support area being conically tapered in shape. The drive bearing may have a conically tapered face corresponding to that of the clutch element. To produce the striking position, the clutch element can engage in the drive bearing, a wobble drive 46 then promoting the tilting of the drive bearing from an idling position to a striking position, Also claimed is a striking mechanism for a hand held machine tool.

Description

ROBERT BOSCH GMBH; D-70442 Stuttgart Hand-held machine tool

Prior art

The invention takes as its starting point a hand-held machine tool according to the precharacterising clauses of the independent claims.

Hammer drills and/or chisel hammers having pneumatic striking mechanisms are known, which can be activated and deactivated by way of a mechanical friction clutch. If the hammer drill and/or chisel hammer is pressed against a surface for machining by means of a tool, a tool holder holding the tool is guided into a housing of the hammer drill and/or chisel hammer in the direction of the operator. During this, conical friction surfaces of the friction clutch come into contact and the pneumatic striking mechanism is driven by way of a frictional connection. During operation, the striking mechanism generates a compressed-air cushion by means of a piston which is guided in a cylinder and is movable in the axial direction, and the compressed-air cushion accelerates a striking element in the axial direction towards a striking pin. The striking element strikes the striking pin which thus receives momentum. The momentum is transmitted to the tool located in the tool holder If the tool of the hammer drill and/or chisel hammer is lifted off the surface for machining, the friction surfaces of the friction clutch are separated and the driving connection of the striking mechanism is interrupted.

Advantages of the invention The invention takes as its starting point a hand-held machine tool having a striking mechanism and a clutch device which can be engaged and disengaged to produce a driving connection of the striking mechanism.

It is proposed that at least part of a drive bearing be constructed such that it can be tilted from an idling position into a striking position. A stepless transition from the idling position into the striking position is possible. In the idling position, the drive bearing is preferably approximately perpendicular to an axis of rotation of an intermediate shaft and thus enables smooth idling of the hand-held machine tool with little vibration.

Practically no - or only a small - idling path is required for the tool in the tool holder. It is thus possible to achieve a long service life and little wear on the tool holder.

If at least some regions of the clutch element form a support for the drive bearing in a striking position, the actuating force can be set by way of the contact surface.

The clutch element is expediently arranged such that it is axially displaceable relative to the drive bearing. To produce the striking position, the clutch element can engage in the drive bearing. A wobbling movement of a wobble drive here promotes the tilting of the drive bearing from the idling position into the striking position. A favourable starting behaviour for the striking mechanism is enabled since it is possible to accelerate from zero in the idling position to an operating frequency in the striking position.

If a support for the drive bearing is of a conically tapered construction, the actuating force can be controlled or set by way of the cone. The support is preferably of one piece with the clutch element. Alternatively, the support can also be separate from the clutch element. The clutch device is of a very short and compact construction and thus enables the machine to have a small overall length. The clutch device comprises only a few individual parts. The production of the drive bearing, particularly a wobble drive, is simplified. Complex grinding of an oblique recirculating ball path to produce a wobble angle is not required since the necessary wobble angle can be achieved by the cone of the clutch element. The inclined position of the drive bearing increases with the engagement path of the clutch element and enables smooth starting and stopping of the drive. The drive bearing is pressed in the direction of an armature shaft upon compression of the striking mechanism and the forces are absorbed by way of the cone of the clutch element. The forces are thus broken down into an axial and a radial component. The operator only experiences the axial component. This component is small, so the operator need only apply a small pressure force.

If the drive bearing has a face which corresponds to the support, it is possible to achieve a defined tilting of the drive bearing and to support this latter reliably. A strong positive connection can be achieved between the support and the drive bearing.

If, at least in the striking position, the drive bearing dips with a side remote from a support for the drive bearing into a driven spur gear by way of a claw-type connection, it is possible to achieve a slip-free transmission of a rotary movement as a result of the positive connection between the drive bearing and the spur gear. Alternatively, a corresponding positive connection with an intermediate shaft is also possible, which likewise enables a slip-free transmission of the rotary movement.

If the clutch element is arranged on an intermediate shaft, it is possible to achieve a compact clutch device which is of a small construction. A rotary driving element comprising rolling bodies connected in fixed manner to the intermediate shaft is preferably arranged between the clutch element and the intermediate shaft. It is favourable to use balls as the rolling bodies. It is also a possible option to use roller-shaped rolling bodies.

If the clutch element is rigidly coupled to a hammer tube in the axial direction, the clutch element can be moved in the opposite direction to the surface for machining when the tool is pressed against the surface for machining.

The drive bearing can be tilted into the idling position with the aid of an idling-control spring, in that an idling-control spring expands when the tool is removed from the surface for machining and presses the clutch element and a sliding sleeve apart when the idling-control spring is arranged between an annular web of the sliding sleeve and an annular web of the clutch element. It is favourable for the sliding sleeve to be axially fixed on regions of the drive bearing.

If the drive bearing has a recirculating ball path extending perpendicularly to a longitudinal axis of the drive bearing, it is possible to achieve a vibration-free idling of the hand-held machine tool in the idling position. The drive bearing can be perpendicular to the intermediate shaft in the idling position so that the longitudinal axis and an axis of rotation of the intermediate shaft coincide. The manufacture of the drive bearing is simplified since there is no need to produce an oblique recirculating ball path. The necessary wobble angle can be set automatically by the taper angle of the clutch element.

A striking mechanism is furthermore proposed in which at least part of a drive bearing can be tilted from an idling position into a striking position.

Drawing Further advantages are revealed in the following description of the drawing. The drawing shows an exemplary embodiment of the invention. The drawing, the description and the claims contain numerous features combined. A person skilled in the art will also expediently consider the features individually and combine them in other useful ways.

The drawing shows: Fig. 1 a partial section of a preferred hand-held machine tool; Fig. 2 a section through a preferred striking mechanism with a drive and clutch device in the striking position; Fig. 3 an arrangement in the idling position; Fig. 4 the arrangement in Fig. 3 during the transition from an idling position into a striking position; Fig. 5 the arrangement in Fig. 3 in a striking position.

Description of the exemplary embodiment

Fig. 1 shows a partial section of a preferred hand-held machine tool 70 with a striking mechanism 40 and a clutch device 20. A tool 74, which machines a surface for machining in the operating direction 76, is inserted in a tool holder 72 of the hand-held machine tool 70. The operator holds the hand-held machine tool 70 by a curved handle 78 and a handle 80 projecting perpendicularly downwards.

Fig. 2 shows a section through a preferred striking mechanism 40 having a drive constructed as a wobble drive and a clutch device 20 of a hammer drill and/or chisel hammer having an electric motor (not illustrated in more detail) which has an armature shaft 10, the drive being in the striking position. A pinion 12, which meshes with a spur gear 14 arranged on an intermediate shaft 16 extending parallel to the armature shaft 10, is integrally formed on the armature shaft 10. The intermediate shaft 16 has, on a side facing a tool holder (not illustrated), an integrally formed gearwheel 66 by way of which the intermediate shaft 16 meshes with a gearwheel (not illustrated) seated on a hammer tube 64.

The striking mechanism 40, which comprises the wobble drive with a wobble finger 46, is rotatably mounted on the intermediate shaft 16, between the spur gear 14 and the gearwheel 66, by means of a drive bearing 18. Arranged on the outer circumference of the drive bearing 18, there is a recirculating ball path 42 on which balls 44 are guided.

The recirculating ball path 42 is perpendicular to a longitudinal axis 60 of the drive bearing 18 and, like the longitudinal axis 60, is also tilted through an angle a with respect to an axis of rotation 90 of the intermediate shaft 16 in the striking position. The wobble finger 46 therefore experiences a wobbling movement when the intermediate shaft 16 rotates. As a result of the wobbling movement, an air cushion is compressed in a cylinder tube 50, as described above, and momentum is transmitted to a tool (not illustrated) by way of a striking pin 52.

A clutch device 20 is furthermore mounted on the intermediate shaft 16 and can be engaged and disengaged to produce and interrupt a driving connection of the striking mechanism 40. The clutch device 20 has, on that side of the gearwheel 66 which is remote from the tool holder, a clutch element 24 which is mounted on the intermediate shaft 16 such that it is axially displaceable and fixed against rotation. The clutch element 24 has, at its end facing the tool holder, a circumferential groove 36 which extends between an inner web 32 constructed as an annular web and an outer web 34 constructed as an annular web. The inner web 32 constructed as an annular web has a larger radius than the outer web 34 constructed as an annular web.

Engaging in the groove 36, there is a stop ring 68 which extends around the hammer tube 64 and is axially fixed on the hammer tube 64 between two grooves. An axial movement of the hammer tube 64 is therefore transmitted to the clutch element 24. A tool (not illustrated) is held in the hammer tube 64 such that it is axially movable and fixed against rotation.

The clutch element 24 is surrounded by a sliding sleeve 28 which has, on a side facing the spur gear 14, a web 62 constructed as an annular web. Arranged between the web 62 of the sliding sleeve 28, which is constructed as an annular web, and the inner web 32 of the clutch element 24, which is constructed as an annular web, there is an idling- control spring 30 whereof the axial length is greatest in an idling position and shortest in a striking position.

An outer end face of the web 62 of the sliding sleeve 28, which is constructed as an annular web, abuts against the drive bearing 18, the drive bearing 18 being connected with positive fit to the spur gear 14 by way of a claw-type connection 54.

The clutch element 24 has a cone 26 on its side facing the spur gear 14, the diameter decreasing in the direction of the spur gear 14. The clutch element 24 forms a support 56 for the drive bearing 18 with the cone 26. The angle a between a sloping outer face 82 and a linear inner face 84 in a bore of the clutch element 24 is preferably between 5 and 85 , particularly preferably between 10 and 20 . This angle a also corresponds to the angle of inclination a between the longitudinal axis 60 of the drive bearing 18 and the axis of rotation 90.

When the intermediate shaft 16 rotates, the drive bearing 18 is supported on the cone 26 and rotates about the axis of rotation 90 of the intermediate shaft 16. A corresponding face 58 of the drive bearing 18 forms a female taper having a taper angle 2.a, whilst the support 56 forms a male taper having the taper angle 2.a with the cone 26. The clutch element 24 is rotationally driven with positive fit by rolling bodies 22 which are constructed as balls, are connected in fixed manner to the intermediate shaft 16 and are arranged between the clutch element 24 and the intermediate shaft 16.

The hammer tube 64 is axially displaceable with respect to the idlingcontrol spring 30 and is actuated by the operator in that the hand-held machine tool, and therefore the tool - particularly a drilling and/or chiselling tool, - is pressed against that material of the surface for machining which is to be removed. This movement is transmitted to the hammer tube 64 and the clutch element 24 by way of a striking pin 52 supported in conventional manner in the hammer tube 64. This results in the cone 26 of the clutch element 24 being covered by the corresponding inner face 58 of the drive bearing 18, which is described in more detail in the Figures below.

Figs. 3 to 5 show a detail of the arrangement of Fig. 2 in the idling position, during the transition from an idling position into a striking position and in a striking position. Parts which remain substantially the same are essentially denoted by the same reference numerals. It is furthermore possible to refer to the description of the preceding Figures in relation to similar features and functions.

Fig. 3 shows the drive bearing 18 in an idling position in which it is substantially perpendicular to the intermediate shaft 16, a longitudinal axis 60 coinciding with an axis of rotation 90 of the intermediate shaft 16.

The drive bearing 18 has a substantially cylindrical outer contour. On a side facing the spur gear 14, the claw-type connection 54 is provided with the spur gear 14, a driving element (not illustrated in more detail) dipping into the spur gear 14. Diagonally opposite on the side facing the clutch element 24, the drive bearing 18 has a chamfer 86 at the transition between the cylindrical circumference of the drive bearing 18 and a bore having the face 58.

Arranged inside the drive bearing 18, there are bores which extend at an angle to one another and have faces 58, 88 which meet approximately at a centre point of the drive bearing 18 and are arranged substantially pointsymmetrically with respect to the centre point of the drive bearing 18. The face 58 forms the female taper (described in Fig. 2) which abuts against a cone 26 of a clutch element 24. In the idling position, that part of the female taper of the face 58 which is remote from the hammer tube 64 abuts against the intermediate shaft 16 and the part facing the hammer tube 64 extends away from the intermediate shaft 16, whilst the axially adjacent part of the face 88 extends away from the intermediate shaft 16 and that part of the face 88 which faces the hammer tube 64 abuts against the intermediate shaft 16.

The clutch element 24 is located in a position which is at the maximum distance away from the drive bearing 18; the idling-control spring 30 is at its greatest axial length.

The sliding sleeve 28 abuts with its web 62 constructed as an annular web against the lower part of the drive bearing 18, which is remote from the hammer tube 64.

When the spur gear 14 rotates, the drive bearing 18 is driven by way of the positive connection with the spur gear 14, although it does not execute a wobbling movement; the wobble finger 46 projecting into the hammer tube (not illustrated) instead remains stationary as a result of the linearly extending recirculating ball path, since the longitudinal axis 60 and the axis of rotation 90 coincide.

If, when a tool (not illustrated) is pressed against a surface for machining, the clutch element 24 is displaced axially in the direction of the drive bearing 18 as illustrated in Fig. 4, the drive bearing 18 begins to tilt in the direction of the clutch element 24. The tilting movement is facilitated by the commencement of a wobbling movement. The idling-control spring 30 is compressed between the inner annular web 32 of the clutch element 24 moving axially towards the spur gear 14 and the web 62 of the sliding sleeve 28, which is constructed as an annular web, and the web 62 which is constructed as an annular web comes into contact with the chamfer 86 of the drive bearing 18. The claw-type connection 54 between the drive bearing 18 and the spur gear 14 is increased.

If the clutch element 24 is moved into the striking position, as illustrated in Fig. 5, the cone 26 supports the drive bearing 18. At the same time, the drive bearing 18 dips with a maximum depth into the spur gear 14 so that the claw-type connection 54 produces a strong positive connection.

In the striking position, the clutch element 24 forms a support 56 for the drive bearing 18 with the cone 26; the female taper of the drive bearing 18 having the corresponding face 58 lies on the cone 26 of the clutch element 24, which forms a male taper. The chamfer 86 abuts flat against the end face of the annular web 62 of the sliding sleeve 28.

22.01.04 ROBERT BOSCH GMBH; D-70442 Stuttgart List of reference numerals Armature shaft 12 Pinion 14 Spur gear 16 Intermediate shaft 18 Drive bearing Clutch device 22 Rolling body 24 Clutch element 26 Cone 28 Sliding sleeve Idling-control spring 32 Web 34 Web 36 Groove Striking mechanism 42 Recirculating ball path 44 Ball 46 Wobble finger Piston cylinder 52 Striking pin 54 Claw-type connection 56 Support 58 Corresponding face Longitudinal axis 62 Web 64 Hammer tube 66 Gearwheel 68 Stop ring 70 Hand-held machine tool 72 Tool holder 74 Tool 76 Operating direction 78 Handle 80 Handle 82 Sloping outer face 84 Inner face 86 Chamfer 88 Face 90 Axis of rotation a Angle

Claims

22.01.04 ROBERT BOSCH GMBH; D-70442 Stuttgart Claims 1. A hand-held

machine tool having a striking mechanism (40) and a clutch device (20) which can be engaged and disengaged to produce and interrupt a driving connection (54) of the striking mechanism (40), characterized in that at least part of a drive bearing ( 18) is constructed such that it can be tilted from an idling position into a striking position.
2. A hand-held machine tool according to Claim 1, characterized in that, in a striking position, at least some regions of a clutch element (24) form a support (56) for the drive bearing (18).
3. A hand-held machine tool according to Claim 1 or 2, characterized in that a support (56) for the drive bearing (18) is of a conically tapered construction.
4. A hand-held machine tool according to one of the preceding claims, characterized in that the drive bearing (18) has a face (58) corresponding to a support (56) for the drive bearing (18).
5. A hand-held machine tool according to one of the preceding claims, characterized in that, at least in the striking position, the drive bearing (18) dips with a side remote from a support (56) for the drive bearing (18) into a driven spur gear (14) by way of a claw-type connection (54).
6. A hand-held machine tool according to one of Claims 2 to 5, characterized in that the clutch element (24) is arranged on an intermediate shaft (16).
7. A hand-held machine tool according to Claim 6, characterized in that a rotary driving element comprising rolling bodies (22) connected in fixed manner to the intermediate shaft (16) is arranged between the clutch element (24) and the intermediate shaft (16).
8. A hand-held machine tool according to one of Claims 2 to 7, characterized in that the clutch element (24) is rigidly coupled to a hammer tube (64) in the axial direction.
9. A hand-held machine tool according to one of Claims 2 to 8, characterized in that an idling-control spring (30) is arranged between a sliding sleeve (28) and the clutch element (24).
10. A hand-held machine tool according to one of the preceding claims, characterized in that the drive bearing (18) has a recirculating ball path (42) extending perpendicularly to a longitudinal axis (60) of the drive bearing (18).
11. A striking mechanism for a hand-held machine tool (70) having a clutch device (20) which can be engaged and disengaged to produce and interrupt a driving connection (54), characterized in that at least part of a drive bearing (18) is constructed such that it can be tilted from an idling position into a striking position.
12. A striking mechanism for a hand-held machine tool substantially as herein described with reference to the accompanying drawings.
13. A hand held machine tool substantially as herein described with reference to the accompanying drawings.