GB2276578A

GB2276578A - Hammer drill and/or percussion hammer

Info

Publication number: GB2276578A
Application number: GB9404663A
Authority: GB
Inventors: Karston Blaier; Karl Frauhammer; Gerhard Meixner; Heinz Schnerring; Frank Mueller; Ulrich Muetschele
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-04-02
Filing date: 1994-03-10
Publication date: 1994-10-05
Also published as: ITMI940636A0; GB9404663D0; ITMI940636A1; DE4310835A1; CH687965A5; IT1273412B; FR2703279A1

Description

Hammer drill and/or percussion hammer

Prior Art

2276578 The starting point of the invention is a hammer drill and/or percussion hammer according to the preamble of Claim 1. From DE 35 06 008 Al (= GB 2171340) a similar drill or hammer is known in which the toolholder nevertheless comprises numerous individual component parts, which have to be assembled, and is not very suitable for heavy drills or hammers of the 10kg class. The guides f or the locking members are expensive to manufacture and under heavy loading are subject to wear, which may lead to a jamming or even to the loss of the locking members.

Advantages of the Invention The hammer drill and/or percussion hammer according to the invention having the characterizing features of the independent claim has in contrast thereto the advantage that the toolholder, while of simple construction, also durably withstands heavy loading by powerful percussion mechanisms. This is in particular achieved by improved mounting and guiding of the locking members, whereby the high kinetic energy of the tool during the idling stroke can be effectively dissipated without damage to the locking members, tool shanks and the toolholder.

The measures specified in the dependent cl IMS permit advantageous developments and improvements of the hammer drill and/or percussion hammer indicated in the independent claims. For the axial displacement of the locking members it is particularly advantageous to suspend them in an index ring. The actuating elements can R. 26074 act on the latter at radially far outward points without dispensing with important guide surfaces at the ends of the locking members. The selected position of the actuating elements provides space in the interior for the installation of a securing device for the toolholder.

The guiding of the locking members prevents a tilting of said members, particularly in the case of hard idling strokes. It is also particularly advantageous that the locking members are supported, both radially outwards and forwards, against a guide element mounted resiliently with axial elasticity. Wear on the closed grooves of the tool shank is thereby avoided. In particular a formation of burrs at the ends of the grooves, which otherwise would make it impossible to extract the tool from the toolholder, is prevented.

Drawing One exemplary embodiment of the invention is illustrated in the drawing and explained in greater detail in the following description. Figure 1 shows a partial section through a hammer drill without handles, Figure 2 a longitudinal section through a toolholder of the hammer drill, Figure 3 a cross-section through the mounting sleeve on the line III-III in Figure 2, and Figure 4 a side view of the index ring viewed in the direction IV in Figure 2.

Description of the Exemplary Embodiment

Figure 1 shows an electrically operated hammer'l having a casing 2 and a motor 3 disposed at the rear. The motor 3 drives a percussion mechanism 5 by means of a shaft 4. Said mechanism has a connecting rod 6 which reciprocatingly drives a piston 8 guided in a hammer tube 7. By means of an air cushion the piston 8 drives a striker 9 acting via a punch 10 on a tool which is received at the front in a toolholder 11 and the shank 12 of which, shown in Figure 2, is held in a mounting sleeve 1 -1 R.26074 13. The Punch 10 is shown in a rear position in the top halves of the sections in Figures 1 and 2, and in ' the bottom half of each section is shown in a forward position. Instead of a connecting rod, the percussion mechanism may however also be driven for example by swash plates or eccentrically mounted springs or the like. In addition, a rotary drive, not shown in the examplary embodiment, may be provided for the hammer tube 7, and the hammer 1 may be constructed as a hammer drill and/or percussion hammer.

In Figure 2 the toolholder 11 is shown on a larger scale. By means of a securing device 14 the mounting sleeve 13 can be joined to the casing 2 so as to be non-rotatable relative to the latter. For this purpose locking balls 16 engage in both parts and are movable radially outwards on actuation of a sleeve 15, so that the mounting sleeve 13 is then rotatable relative to the casing 2.

For the rotational driving of the tools the mounting sleeve 13 has striplike rotational drivers 17 which project into corresponding rotational drive grooves formed in the tool shank 12. The tools inserted are locked for example by means of two axially movable locking members 18 which engage in radial through-slots 19 which are cut smooth, with a constant width, in the mounting sleeve 13 and are longer than the locking members 18, so that the latter have considerable axial play. In the axial direction of the mounting sleeve 13 the locking members 18 have an elongated, somewhat parallelepipedal shape, while their inwardly pointing side is cylindrical and rounded at the ends. In the front region 20 of the locking members 18 two wings 21 disposed opposite one another project out laterally, preventing deeper penetration of the locking members 18 into the slots 19 and guiding the looking members 18 in the axial direction on the mounting sleeve 13 (see also Figure 3). In the rear region an actuating arm 22 projects radially outwards and is inserted into an opening 23 provided in an axially projecting tab 24a on an index ring 24 bent R.26074 over at right angles (see Figure 4). Between the actuating arm 22 and the wing 21 the locking member 1.8 is notched to make room f or a driving bow 24b of the tab 24a of the index ring 24. The locking members 18 are preferably precision castings or made by the metal injection moulding (mim) process, in which metal powder is poured into an injection moulding machine and then subjected to sintering treatment.

The index ring 24 lies against a sliding sleeve 25, which can be moved by hand in the axial direction against the force of a compression spring 26 bearing against the rear face of the index ring 24. By its other end the compression spring 26 is supported against the sleeve 15 and therefore against the casing 2.

The locking members 18 are supported radially against a sleeve-like guide element 28. The latter has a widened support portion 29 against which the actuating arms 22 lie radially, and also a support portion 30 which is narrower than said widened portion and against which lies, at least partially, the radially outwardly directed outer surface 27 (Figure 3) of the wings 21. The outer surface 27 and the actuating arms 22 accordingly form support points 22a, 27a for the radial support of the locking members 18 by the support portions 29, 30 of the guide element 28. In addition, the locking members 18 lie with their bevelled front end face 31 against the guide element 28 in the axial direction. The guide element 28 is axially movable within limits, since at the front it is supported against an annular damping element 32 of elastomer material. Said damping element is in turn supported at the front against a washer 33 and a circlip 34 inserted into the mounting sleeve 13. The damping element 32 reduces the mechanical loadings on the locking members 18 and the tool shank 12. In particular, during idling the hard blow between the closed grooves 35 in the tool shank 12 and the rear edges 36 of the locking members 18 is damped.

The axial mounting of the locking members 18 by means of the wings 21, in conjunction with their radial 6:

11 q k R.26074 support in the support portions 29, 30 of the guide element 28, prevents a tilting of the locking members 18. By means of the greatest possible axial distance between the support points 22a. 27a of the locking members 18. the guiding of the locking members 18 can be controlled in an advantageous manner.

The locking members 18 are installed by tilting them inwards by their ends on the side of the actuating arms 22, with the sliding sleeve 25 pulled back against the compression spring 26, and inserting them from the inside into the openings 23. The guide element 28 and the other parts are then pushed onto the mounting sleeve 13.

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Claims

1. Hammer drill and/or percussion hammer comprising a motor (3) housed in a casing (2), a percussion mechanism (5) guided in a hammer tube (7), and a toolholder (11) having a mounting sleeve (13) into which a shank (12) of a tool can be inserted,, said mounting sleeve (13) having openings for the insertion of axially movable locking members (18), characterized in that the openings are in the form of through-slots (19) which are cut smooth and into which the locking members (18) penetrate, "and in that the looking members (18) have wings (21) which project laterally out of the mounting sleeve (13) and which guide the locking members (18) axially on the mounting sleeve (13)..

2. Hammer drill and/or percussion hammer according to Claim 1, characterized in that the slots (19) are longer than the locking members (18) and the latter are mounted, by means of a damping element (32), elastically forwards in the- axial direction in such a manner as to dissipate energy.

3. Hammer drill and/or percussion hammer according to Claim 1 or 2, characterized in that the locking members (18) are supported at the front and radially outwards against a likewise axially movable guide element (28).

4. Hammer drill and/or percussion hammer according to one of the preceding claims, characterized in that the locking members (18) each have an actuating arm (22) projecting radially outwards and cooperating with a sliding sleeve (25) to open the toolholder (11).

S. Hammer drill and/or percussion hammer according to Claim 4, characterized in that for the movement of the locking members (18) the actuating arm (22) is inserted into an opening (23) in an axially projecting tab (24a) r, R.26074 of an axially movable index ring (24).

6. Hammer drill and/or percussion hammer according to Claim 4, characterized in that the index ring (24) lies against the sliding sleeve (25) on one side and is loaded by a compression spring (26) on the other side.

7. Hammer drill and/or percussion hammer according to one of the preceding claims, characterized in that the looking members (18) are supported radially at support points (22a, 27a) in order to prevent tilting.

8. Hammer drill and/or percussion hammer according to Claim 7, characterized in that the support points (22a, 27a) are spaced at an axial distance from one another.

9. Hammer drill and/or percussion hammer according to one of the preceding claims, characterized in that the locking members (18) are produced by the metal injection moulding (mim) process.

10. A hammer drill and/or percussion hammer sub- stantially as herein described with reference to the accompanying drawings.