GB2276579A

GB2276579A - Tool carrier for an electrically operated hammer

Info

Publication number: GB2276579A
Application number: GB9406291A
Authority: GB
Inventors: Karston Blaier
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-04-02
Filing date: 1994-03-30
Publication date: 1994-10-05
Anticipated expiration: 2014-03-30
Also published as: FR2703289A3; FR2703289B3; DE9305034U1; GB2276579B; GB9406291D0; CH688713A5

Abstract

A tool carrier for an electrically operated hammer is rotatable and lockable relative to a housing to enable a tool to be rotatably positioned with respect to the body of the hammer. A hub flange 15 has a number of openings 20 to receive detent means 19. The detent means ordinarily locate in grooves 22 on the outer periphery 21 of part 14 of the tool camper. A locking sleeve 23 encircles the hub flange and is axially movable against spring 24 to reveal recesses (33 fig 2) into which the detent means can temporarily locate. The tool carrier can then be rotated until the detent means are aligned with an appropriate groove and the locking sleeve on release will force the detent means inwards and prevent any further rotary movement. <IMAGE>

Description

Electrically operated hammer Prior art The invention proceeds from an electrically operated hammer according to the preamble of the main claim. Such hammers, having a tool carrier which is rotatable relative to the housing about a tool axis and is lockable in a plurality of detent positions, are known. Such rotatable and arrestable tool carriers have proved useful particularly when working with forming tools because the tool may then be positioned in various working positions.

A commercially known hammer, to said end, has a hub flange which is coupled to the tool carrier via a detent device.

Disposed in the hub flange are radially extending openings, in which a plurality of locking bodies are held with radial play.

Formed opposite the openings in the tool carrier is a plurality of receiving grooves, into which the locking bodies engage for detent purposes. The locking bodies are held in a radial direction in the receiving grooves by means of a locking sleeve. The locking sleeve is coupled in a form-fit manner in a peripheral direction to the tool carrier and is loaded in locking direction by the action of a spring.

To rotate the tool carrier relative to the housing, the locking sleeve is displaced counter to the spring action until it releases the locking bodies, so that the latter in the course of rotation are pressed by the flanks of the receiving grooves radially outwards in the openings and release the receiving grooves.

If the tool carrier is to be locked in another rotary position, it has to be rotated until the locking bodies are situated over the receiving grooves. If the locking sleeve is then released, it slides, operated by spring action, over the locking bodies and presses them into the receiving grooves so that the detent device is locked.

If, however, the locking sleeve is released in a rotary position of the tool carrier in which the locking bodies are not situated precisely over the receiving grooves, locking of the detent device is not possible. In adverse cases, the locking sleeve and the locking bodies may even become jammed, this being particularly undesirable because then a tool change is impossible.

Advantages of the invention In contrast, the hammer according to the invention having the characterizing features of the main claim has the advantage of problem-free locking of the detent device automatically from any rotary position of the tool carrier and, in particular, also from a rotary position in which the locking bodies are not situated over the receiving grooves.

By virtue of the measures outlined in the sub-claims, advantageous developments and improvements of the hammer indicated in the main claim are possible.

Drawings An embodiment of the invention is illustrated in the drawings and explained in greater detail in the following description.

Figure 1 shows a longitudinal section through the tool holder of a hammer constructed according to the invention and Figure 2 is a plan view of a locking sleeve constructed according to the invention.

Description of the embodiment Figure 1 shows merely the tool holder 10 of a known, electrically operated percussion hammer. The tool holder 10 has a hollow cylindrical tool carrier 11, into which a shank 12 of a tool may in a known manner be axially inserted and locked by means of two jewels 13. The end 14 of the tool carrier 11 facing towards a likewise known and therefore not illustrated striking mechanism of the percussion hammer projects into a hub flange 15, which is of a corresponding hollow cylindrical construction.

The hub flange 15 is either formed by a housing of the percussion hammer which surrounds the striking mechanism, or is rigidly connected to said housing. The tool carrier 11 and the hub flange 15 are coupled to one another in a peripheral direction by a detent device 18. The detent device 18 comprises at least one locking body 19. In the embodiment according to Figure 1, a total of four, for example spherical, locking bodies are provided, which are offset by 900 relative to one another and of which only two are shown in section.

Radially extending openings 20, which receive the locking bodies 19 in a radially movable manner, are provided in the hub flange 15. Introduced into the tool carrier 11 at its outer periphery 21 protruding into the hub flange 15 is a plurality of receiving grooves 22, into which the locking bodies 19 engage. The locking bodies 19 are held by a locking sleeve 23, which encircles the front region of the hub flange 15, in the receiving grooves 22 and the openings 20 of the hub flange 15 so that the tool carrier 11 is connected nonrotatably to the hub flange 15 and hence to the housing of the percussion hammer. In the embodiment illustrated in Figure 1, a total of twelve receiving grooves 22 are uniformly distributed over the periphery of the tool carrier 11, with the result that the tool carrier 11 is lockable in increments of 300 relative to the hub flange 15.

The locking sleeve 23 is axially loaded in locking direction by a pressure spring 24. To said end, the pressure spring 24 acts upon lugs 25 rigidly connected to the locking sleeve 23.

At its other end, the pressure spring 24 is supported against the front part of the tool holder 10. At its end remote from the locking bodies 19, the locking sleeve 23 has an inwardly directed radial collar 26 with inwardly directed tongues 26a which engage into corresponding longitudinal grooves 27 in the tool carrier 11, so that the locking sleeve 23 in a peripheral direction is connected in a form-fit manner to the tool carrier 11 but is axially displaceable within the longitudinal grooves 27. When the detent device 18 is locked, the collar 26 of the locking sleeve 23 presses against the front end of the hub flange 15.

The locking sleeve 23 is displaceable counter to the action of the spring 24 by means of an operating sleeve 28. To said end, the operating sleeve 28 acts upon the side of the lugs 25 opposite the spring 24 and receives the lugs 25 in a form-fit manner in a peripheral direction, so that rotation of the operating sleeve 28 in a peripheral direction effects a corresponding rotation of the locking sleeve 23, with simultaneous driving of the tool carrier 11 being effected by the tongues 26a. When the detent device 18 is locked, displacement of the operating sleeve 28 in the direction of the striking mechanism is prevented by a shoulder 29 formed on the hub flange 15.

To unlock the detent device 18, the operating sleeve 28 is displaced towards the tool until it radially releases the locking bodies 19. If the tool holder 10 or tool carrier 11 is then rotated relative to the housing or hub flange 15, the flanks delimiting the receiving grooves 22 in a peripheral direction cause the locking bodies 19 to be pressed radially outwards out of the receiving grooves 22. The tool carrier 11 is then freely rotatable relative to the hub flange 15 about a tool axis 30. The locking bodies 19 are then prevented from falling out in a radial direction by the operating sleeve 28.

Figure 2 shows the locking sleeve 23 according to the invention, on the periphery of which a total of four lugs 25 are disposed offset by 900 relative to one another. At its end facing the tool, the locking sleeve 23 has the inwardly directed radial collar 26 with the inwardly directed tongues 26a, which engage into the longitudinal grooves 27 already described (Figure 1). The tongues 26a have a rounded-off transition 26b to the collar 26 and extend in an axial direction away from the locking sleeve 23, with the result that wear occurring during displacement of the locking sleeve 23 in the longitudinal groove 27 may be reduced.

The locking sleeve 23 has an axial outer edge 32 extending in a, for example, undulating manner in a peripheral direction, which is provided for cooperation with the locking body 19 (Figure 1). The outer edge 32 has axially inward extending, radially continuous recesses 33 of a, for example, parabolic or curvilinear shape. The number and distribution of the recesses 33 corresponds to the number and distribution of the receiving grooves 22 disposed at the outer periphery 21 of the tool carrier 11. The recesses 33 are also disposed so as to lie approximately centrically over the corresponding receiving grooves 22. The undulating shape of the outer edge 32 with the curved recesses 33 enables automatic locking of the detent device 18 even from a rotary position in which the locking bodies 19 do not lie precisely over the receiving grooves 22.

When the operating sleeve 28 is released from such a position, the locking sleeve 23 is pressed eccentrically in the recesses 33, e.g. in a region 34 of the outer edge 32, against the locking bodies 19. The spring force is split at the spherical locking bodies 19 into an axial component and into a component which initiates a rotational movement of the locking sleeve 23 and hence of the tool carrier 11. As a result of the rotational movement, the locking bodies 19 may penetrate axially further into the recesses 33 until-they are situated approximately centrically in the recesses 33. Since the locking bodies 19 are then situated over the receiving grooves 22 in the tool carrier 11, the locking bodies 19 may engage into the receiving grooves 22 and the locking sleeve 23, operated by spring force, slides over the locking bodies 19.

Situated in each case between adjacent recesses 33 is a residual cross-section 35 of the locking sleeve 23 which tapers in locking direction. The residual cross-sections 35 form points 36, which lie approximately centrically between adjacent receiving grooves 22.

In exceptional cases, the locking sleeve 23 with the points 36 may encounter the spherical locking bodies 19 in such a way that the detent device 18 is not lockable. The abovedescribed locking action.of the detent device 18 may then be initiated through a shaking of the hammer, such as occurs, for example, during hammering. For such an eventuality, locking is additionally facilitated by burr-free, slightly rounded-off points 36. The recesses 33 and/or residual cross-sections 35 may alternatively be designed more like saw teeth. Naturally, application of the invention is not restricted specifically to percussion hammers, the invention also being, for example, suitable for use in percussion hammers with rotary drive of the tool holder, which are generally described as drilling hammers.

The locking bodies need not be spherical, as illustrated in the embodiment. Also conceivable are, for example, cylindrical locking bodies which are disposed axially or radially in the receiving groove 22. For functional reasons, the locking bodies should be rounded off at their surfaces facing the locking sleeve 23 and at their surfaces protruding into the receiving groove 22.

The construction of the keyed connection between tool carrier 11 and locking sleeve 23 is not restricted to the design of the tongues 26a indicated in the embodiment. The inwardly directed collar may, for example, alternatively have inwardly directed tabs which, for transmission of the rotational movement, engage into the longitudinal grooves 27.

Claims

1. Electrically operated hammer, in particular a percussion hammer, having a striking mechanism surrounded by a housing and having a tool carrier which is rotatable relative to the housing, is lockable in a plurality of detent positions, projects with its end facing the striking mechanism into a hollow cylindrical hub flange formed by or rigidly connected to the housing and is coupled to said hub via a detent device having at least one locking body, which is disposed with radial play in a radial opening formed in the hub flange and engages for detent purposes into receiving grooves formed at the outer periphery of the tool carrier, the at least one locking body being held in the receiving grooves by means of an axially displaceable locking sleeve, which is loaded in axial locking direction and encircles the hub flange, and the locking sleeve being connected in a peripheral direction in a form-fit manner to the tool carrier, characterized in that the locking sleeve (23), at its axial outer edge (32) provided for cooperation with the locking body (19), has axially inwardly extending, radially continuous recesses (33), whose number and distribution on the periphery of the locking sleeve (23) corresponds to the number and distribution of the receiving grooves (22) on the outer periphery (21) of the tool carrier (11), the recesses (33) each being disposed relative to the associated receiving grooves (22) so that they lie approximately centrically one over the other.

2. Hammer according to claim 1, characterized in that the outer edge (32) of the locking sleeve (23) has an undulating shape.

3. Hammer according to claim 1, characterized in that the recesses (33) are of an approximately parabolic or curvilinear construction.

4. Hammer according to claim 1, characterized in that the at least one locking body (19) is spherical.

5. Hammer according to one of the preceding claims, characterized in that residual cross-sections (35) of the locking sleeve (23) lying between adjacent recesses (33) taper in locking direction and therebyform points (3b).

6. Hammer according to claim 5, characterized in that the points (36) are each disposed approximately centrically between two adjacent-lying receiving grooves (22).

7. Hammer according to claim 5, characterized in that the points (36) are slightly rounded off.

8. Hammer according to claim 5, characterized in that the recesses (33) and/or the residual cross-sections (35) are constructed approximately in the manner of saw teeth.

9. Hammer according to claim 1, characterized in that the form closure provided between tool carrier (11) and locking sleeve (23) is effected by means of tongues (26a), which are disposed on a radially inwardly directed collar (26) of the locking sleeve (23) and project into longitudinal grooves (27) of the tool carrier (11).

10. Hammer according to claim 9, characterized in that the tongues (26a) extend in an axial direction away from the locking sleeve (23) and have a rounded-off transition (26b) to the collar (26).

11. An electrically operated hammer substantially as herein described with reference to the accompanying drawing.