GB2326123A

GB2326123A - Hammer drill with dust seal for tool holding assembly

Info

Publication number: GB2326123A
Application number: GB9811280A
Authority: GB
Inventors: Karl Frauhammer; Gerhard Meixner; Heinz Schnerring
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-06-11
Filing date: 1998-05-26
Publication date: 1998-12-16
Anticipated expiration: 2018-05-26
Also published as: FR2764541B1; CH692608A5; GB2326123B; DE29724927U1; DE19724532A1; GB9811280D0; FR2764541A1

Abstract

A hammer drill 9 has a tool holder 10 for locking a tool shaft 13 into a spindle sleeve 11. An annular actuating sleeve 22 is axially movable to allow a locking element 15 to be displaced radially from engagement with a groove 20 of the tool shaft. The actuating sleeve is sealed at the front by a dust seal cap 29. The locking mechanism is sealed at the rear by a seal ring 45 having inner and outer O-rings 51,50 engaging the spindle sleeve and actuating sleeve respectively and thus creating a chamber 40.

Description

1 Hand-guided drilling _. n machine tool State of the art 2326123 The

invention is based on a hand-guided drilling or percussion machine tool according to the preamble of claim 1. A drilling machine tool is already known (DE 32 05 063 C2), which comprises locking devices both for securing a tool holder on a drill spindle and for securing a tool in the tool holder. The locking devices each comprise a locking ball, which engages in positive-locking fashion in parts which are to be connected to one another and is held in this position by an actuating sleeve. The actuating sleeve can be adjusted into an unlocking position, in which the locking balls are released radially, so that they disengage from at least one of the parts which. can then be separated. The actuating sleeve encloses the section of the drilling machine tool facing the tool and is axially displaceably guided on a base element of the tool holder. In order to protect against the penetration of drilling dust a dust protection cap is provided, which seals the tool holder relative to a tool shaft fitted therein.

A hammer drill with a tool holder is known from EP 0 668 127 Al. This hammer drill comprises an elongate locking element for locking a tool shaft, which is also held in its locking position by an axially displaceable actuating sleeve. This tool holder is also provided with a dust protection cap at the end facing the tool.

A further hammer drill with a tool holder is known firom EP 0 494 400 B 1. In this hammer drill the tool holder is also sealed at the end facing the tool by a dust protection cap. The actuating sleeve in this hammer drill is both displaceably and rotatably arranged in order to release the locking devices.

2 What is common to both known drilling or percussion machine tools is that the actuating sleeve, in its rear section facing the machine, comprises a displacement gap relative to other parts of the machine or tool holder in order to allow for displaceability. In this respect, the displacement gap can be designed with a greater or lesser width. For dust sealing of the tool holder, only a dust protection cap is provided at the end facing the tool. Until now, it has clearly been the assumption that additional measures to prevent the penetration of drilling dust via the movement gap are unnecessary.

Advantages of the invention The hand-guided drilling or percussion machine tool according to the invention having the features of claim 1 has the advantage of comprising substantially improved wear behaviour in the region of the tool accommodation as compared with known machine tools. This is attained by the provision of at least one separate sealing element in the region of the actuating sleeve facing the machine and lying behind the locking element. As a result, the penetration of fine drilling dust, which is not prevented from penetrating the tool holder through the movement gap, is effectively prevented. In long-duration tests, the positive influence of the measure according to the invention resulted m an unexpectedly high reduction in the wear of parts which are moved relative to one another, such as locking elements, rotary drive strips, etc.. This occurred in spite of the fact that problems resulting from drilling dust were not anticipated on account of the relatively large distance from the dust- producing site and the relatively narrow displacement gap.

The measures described m the dependent claims allow for advantageous further developments of, and improvements to, the machine tool according to the invention.

3 Drawings An embodiment of the invention is illustrated in the drawings and is explained in further detail in the following description. The single drawing shows part of a longitudinal section through a hammer drill according to the invention.

Description of the embodiment

In the drawing, the reference 10 designates a tool holder of a hammer drill 9, which is arranged at the end of a spindle sleeve I I of the hammer drill 9. To this end, the spindle sleeve I I forms a receiving aperture 12 at its end facing the tool, into which receiving aperture the shaft 13 of a tool can be inserted and locked therein by means of a locking device 14. The locking device 14 comprises a spherical locking element 15, which sits in a recess 16 in the spindle sleeve 11. When the tool shaft 13 is inserted, the locking element 15 engages in an axially closed groove 20 M the tool shaft 13. In this locking position, the locking element 15 is covered radially on the outside by a securing ring 2 1. The securing ring 21 is axially displaceably mounted on the spindle sleeve 11. The securing ring 21 can be displaced axially backwards towards the machine by meansof an actuating sleeve 22 against the force of a compression spring 23 into an unlocking position, in which a cavity 24 in the securing ring 21 allows the locking element 15 to escape radially from the groove 20 in order to release the tool shaft 13.

In the region of the receiving aperture 12, rotary drive strips 27 are also provided in the spindle sleeve 11, which rotary drive strips engage in associated rotary drive grooves 28, open at the back, in the tool shaft 13 when the tool shaft 13 is inserted. A dust protection cap 29 is arranged at the end of the spindle sleeve 11 facing the tool and seals a region between the actuating sleeve 22 and the tool shaft 13 in a dustproof manner.

4 The spindle sleeve 11 is mounted in a bearing site 30 so as to rotate relative to a machine housing 3 1. The machine housing 31 is formed by a housing core 3 la of metal, which is enclosed by a housing casing 3 lb of plastics material. At least one percussion element 34, which strikes axially against the tool shaft 13 in known manner, is axially displaceably mounted in the spindle sleeve 11. The spindle sleeve 11 acts as a guide tube for the percussion element 34. A lubricant seal 35 seals an intermediate space 36 between the machine housing 31 and the spindle sleeve 11, so that lubricant is prevented from escaping firom the interior of the hammer drill 9.

The actuating sleeve 22 engages around an end 37 of the machine housing 31 facing the tool with a sleeve-shaped extension 22a. In order to ensure the displacement of the actuating sleeve 22 relative to the machine housing 3 1, an annular gap 3 8 is formed between the extension 22a and the machine housing 3 1. In this respect, the actuating sleeve 22, by way of its extension 22a, defines a chamber 40 on the outside, which lies axially between the locking element 15 and an end 41 of the actuating sleeve 22 facing the machine and which is defined on the inside by the spindle sleeve 11. The chamber 40 is protected against dust at the tool end by the dust protection cap 29. At the end facing the machine, the chamber 40 is protected against the penetration of drilling dust by a sealing element 44.

The sealing element 44 comprises a support ring 45, which is used to support the compression spring 23 at the end facing the machine and to this end comprises a cylindrical guide extension 46 for the compression spring 23. In the exemplary embodiment the support ring 45 is axially secured at the end facing the machine to a shoulder 47 of the spindle sleeve 11. Disposed on the inner circumference and outer circumference of the support ring 45 are circumferential grooves 48, 49 respectively, in which a sealing ring 50, 51 is arranged in each case. The outer scaling ring 50 arranged in the outer circumferential groove 48 provides sealing between the actuating sleeve 22 and the support ring 45, whilst the inner sealing ring 51 sitting in the inner circumferential groove 49 provides sealing between the spindle sleeve 11 and the support ring 45. Drilling dust, which penetrates the annular gap 38 past the machine end 41 of the actuating sleeve 22, is prevented from penetrating the chamber 40 and therefore from reaching the locking element 15 by means of the sealing element 44. The tool holder 10 is thereby also effectively protected against the penetration of fine drilling dust in its rear machine-end section, so that abrasive wear in the inner tool holder region can be reduced as a whole. As an additional positive secondary effect, the friction work (heat generation) is reduced, so that the temperature in the inner tool holder region is lowered, thereby increasing the service life of the sealing elements 44. The service life of the sealing elements 44 can also be increased by a reduction in the relative movement of these seals, as is provided, for example, by the provision of the known automatic locking in the tool holder 10. A relative displacement of the sealing element 44 is then unnecessary when the tool shaft 13 is inserted, so that a wear-generating actuation of the actuating sleeve is then unnecessary for unlocking.

The invention is not limited to the illustrated embodiment. The invention can also be advantageously used in cases where the locking device is used for removing the tool holder or comprises an actuating sleeve which is locked or released by rotation. Of course, more than one locking element can also be arranged distributed over the circumference of the spindle sleeve 11. The spindle sleeve 11 can also be of multi-part construction. The sealing element 44 can also be arranged on the inside of the actuating sleeve 22.

6

Claims

1. Hand-guided drilling or percussion machine tool, with at least one locking device (14), which comprises at least one locking element (15) for positive-locking engagement in parts which are to be connected, and which comprises at least one actuating sleeve (22), which is manually displaceable from a locking position, in which the at least one locking element (15) is held in its engaged position with the parts to be connected, into an unlocking position, in which the at least one locking element (15) is radially released, characterised m that a chamber (40), which is defined on the outside by the actuating sleeve (22), lies axially between the at least one locking element (15) and an end (4 1) of the actuating sleeve (22) facing the machine and is defined on the inside by a spindle sleeve (11) of the hammer drill (9), is sealed by at least one sealing element (44) to prevent drilling dust penetrating past the machine-side end (4 1) of the actuating sleeve (22) in the direction of the at least one locking element (15).

2. Drilling or percussion machine tool according to claim 1, characterised in that the at least one sealing element (44) comprises at least one separate sealing member made of elastic, flexible material.

Drilling or percussion machine tool according to claim 2, characterised m that the sealing element is formed by a sealing ring (50).

4. Drilling or percussion machine tool according to claim 3, characterised in that the sealing ling (50) is arranged in a circumferential groove (58) on the outer circumference of a support ring (45), 7 which acts as an abutment on the side facing the machine for the compression spring (23) acting upon the actuating sleeve.

5. Drilling or percussion machine tool according to claim 4, characterised in that the support ring (45) is mounted so as to be displaceable relative to the spindle sleeve (11) and is sealed on the inside by means of a second sealing ring (5 1) relative to the spindle sleeve (11) to prevent drilling dust from penetrating the chamber (40).

6. Drilling or percussion machine tool according to one of the preceding claims, characterised in that the actuating sleeve (22) is axially displaceable relative to the sealing element (44).

7. A hand-guided drilling or percussion machine tool substantially as herein described with reference to the accompanying drawing.