GB2413105A

GB2413105A - Percussion mechanism with impulse force opposite to working direction

Info

Publication number: GB2413105A
Application number: GB0507412A
Authority: GB
Inventors: Achim Duesselberg; Kurt Sieber
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-04-14
Filing date: 2005-04-12
Publication date: 2005-10-19
Anticipated expiration: 2025-04-12
Also published as: GB2413105B; CN100553891C; CN1683117A; FR2868977B1; DE102004017940A1; FR2868977A1; GB0507412D0

Abstract

A percussion mechanism for a hand-held power tool 10, in particular for a hammer drill and/or chisel hammer which is provided to transmit impact pulses to a percussion unit 14 which comprises a tool 12. It is proposed that the impact pulses are oriented counter to a working direction 16 of the tool 12. The percussion mechanism may comprise at least two latching bodies 18, 20 which can move relative to one another. The latching bodies may comprise a saw tooth profile at least in one direction.

Description

Percussion Mechanism for a Hand-held Power Tool

Prior Art

The invention is based on a percussion mechanism for a hand-held power tool according to the preamble of claim 1.

It has already been proposed to integrate a percussion mechanism in a hand-held power tool and namely, in particular, in a hammer drill and/or chisel hammer. Such percussion mechanisms are provided to transmit impact pulses to a percussion unit which comprises a tool, the impact pulses being oriented in a working direction in order to be able to transmit impacts to a workpiece by means of the tool. In this connection, hammer drills and/or chisel hammers frequently comprise pneumatic percussion mechanisms, whereas percussion drills comprise arresting impact mechanisms with locking discs.

Advantages of the invention The object of the invention is to provide a percussion mechanism which assists an operator when releasing a jammed tool from a workpiece.

The invention is based on a percussion mechanism for a hand-held power tool, in particular for a hammer drill and/or chisel hammer which is provided to transmit impact pulses to a percussion unit which comprises a tool.

It is proposed that the impact pulses are oriented counter to a working direction of the tool. As a result, it can be ) advantageously achieved that the percussion mechanism assists an operator with releasing a jammed tool from the workpiece. The invention may be particularly advantageously used in hammer drills and/or chisel hammers and namely, in particular, when drilling in workpieces made from damp concrete or masonry, as in such applications the drill bit or chisel bit easily jams. The impact pulses exerted by the percussion mechanism counter to the working direction can, therefore, advantageously release the jamming. Similar advantages can be revealed when the solution according to the invention is used to release tools jammed on the In this connection, the terms 'designed' and 'equipped' are to be understood by the term 'provided'. The percussion mechanism can comprise a switching element for switching the percussion mechanism between operating modes with different orientations of the impact pulses or for allowing a single orientation of the impact pulses. Therefore, the orientation of the impact pulses is to be considered as counter to the working direction when the orientation comprises at least one component counter to the working direction.

The design of the percussion mechanism can be of particularly simple construction with at least two latching bodies which can move relative to one another, continuous operation being possible when the latching bodies are configured as locking discs. An advantageously high frequency and directional stability of the impact pulses may be achieved when the locking discs respectively comprise at least three notches. )

Particularly powerful impact pulses may be achieved when the latching body comprises a saw tooth profile at least in one direction.

A separate spring mechanism for producing the impact pulses can be dispensed with when the impact pulses are derived from an operator pulling force. As a result, the operator can also advantageously control the strength of the impact pulses. In this connection, the percussion mechanism can be biased against the operator pulling force. By means of an abrupt release of the biasing, it can be achieved that the operator pulling force accelerates masses, for example, an operator pulling weight, and absorbs them on an abutment element.

A specific application of the percussion mechanism can be achieved when the percussion mechanism comprises a spring element to create a pulling force threshold. In this connection, the percussion mechanism can be particularly advantageously activated with a pulling force above the pulling force threshold and deactivated below the pulling force threshold. Embodiments of the invention are conceivable in which the percussion mechanism comprises a switching device independent of the pulling force to activate and/or deactivate the percussion mechanism.

A particularly cost-effective spring element can be achieved when the spring element is designed as a spring blade.

If the percussion mechanism comprises at least two stable configurations which may be at least substantially

N

elastically converted from one to another, operating modes which are respectively associated with one of the stable configurations can be particularly reliably converted from one to another and maintained.

Drawings Further advantages are revealed from the following description of the drawings. Embodiments of the invention are shown in the drawings. The drawings, description and claims contain numerous features in combination. A person skilled in the art will expediently also consider the features individually and combine them into appropriate further combinations.

In the drawings: Fig. 1 is a section of a hand-held power tool with two percussion mechanisms, Figs. 2-4 are diagrammatic views of a functioning mode of the second percussion mechanism from Figure 1, Fig. 5 is a diagrammatic view of a percussion mechanism of an alternative hand-held power tool with a chiselling function with a rotary switch, Fig. 6 is a further alternative hand-held power tool with a bistable spring element in a first configuration and ) Fig. 7 is the hand-held power tool from Fig. 6 in a second configuration.

Description of the embodiments

Figure 1 shows a section of a hand-held power tool 10 configured as a drill with two percussion mechanisms. The first percussion mechanism is a known mechanical percussion mechanism equipped with a striker 26 that is axially movable in a hammer tube 24 and which is provided to transmit an impact pulse to an impact head 28 during a movement axially oriented in a working direction 16 and which is also axially movably mounted in the hammer tube 24. The impact head 28 transmits the impact pulse in the working direction 16 as a shock wave to the tool 12.

The tool 12 is, to a certain extent, axially movably mounted in the hammer tube 24, the extent being determined by the length of a recess extending in the axial direction on the shank of the tool 12 and in which a locking ball 30 engages. The locking ball 30 simultaneously engages in an elongate recess on the hammer tube 24 and, in a force-free configuration, is pushed via a retention tab 32 of a spring 34 in the direction of a front edge 36 of the recess on the hammer tube 24. The locking ball 30 is prevented from deflecting radially by an annular safety device 38. An operator can displace the safety device 38 counter to the working direction 16 and against the force of the spring 34 via a sleeve-shaped actuation element 40 attached to the safety device 38 and, as a result, radially release the locking ball 30 to remove and exchange the tool 12. In addition to the locking ball 30 the tool 12 comprises further rotary drive elements, in particular grooves, in which complementary elements of the hammer tube 24 engage.

During operation of the hand-held power tool 10, the hammer tube 24 is rotated continually by a motor, not shown, about its longitudinal axis and displaces the tool 12 by means of the rotary drive elements in a rotary movement 44 which is superimposed by abrupt axial movements in the working direction 16 produced by the first percussion mechanism.

The second percussion mechanism according to the invention is configured as a reverse arresting impact mechanism and comprises two latching bodies 18, 20 configured as locking discs with circumferential saw tooth profiles.

The first latching body 18 is rigidly connected to the hammer tube 24 and secured in the axial direction by means of two snap rings on the hammer tube 24. The hammer tube 24 itself may be displaced in the axial direction 16 and rotatably mounted about a tool axis in a housing 42 of the hand-held power tool 10.

The second latching body 20 enclosing the hammer tube 24 is rigidly connected to the housing 42 and in the resting position of the hammer tube 24 is spaced approximately 1 cm from the first latching body 18, so that the saw tooth profiles of the latching bodies 18, 20 do not engage in one another in the resting position of the hammer tube 24. In this connection, the second latching body 20 is annular and has an internal diameter which is approximately 2 mm greater than an external diameter of the hammer tube 24.

If the tool 12 is tightly or axially jammed in a workpiece, but can nevertheless rotate, an operator can therefore exert a pulling force F on the housing 42. As a result, the tool 12 is firstly displaced in the hammer tube 24 in the working direction 16 until the locking ball 30 bears against one edge 60, opposing the working direction 16, of the recess in the tool shank and transmits thereto a counter force, compensating the operator pulling force, in the working direction 16 via the edge 36 of the recess in the hammer tube 24. The hammer tube 24 is displaced in the working direction 16 from its resting position by the pulling force F and by the counter force which also acts on the workpiece by jamming the tool 12. If the pulling force exceeds a threshold value of approximately 10 N. the saw tooth profiles of the latching bodies 18, 20 become engaged.

Figures 2 - 4 illustrate diagrammatically a functioning mode of the second percussion mechanism configured as a reverse arresting impact mechanism. If the operator exerts a pulling force F of more than 10 N on the hand-held power tool 10, the latching bodies 18, 20 engage in one another with their saw tooth profiles, in a first configuration shown in Figure 2.

By means of the rotary movement 44 the flat sides of the saw tooth profiles of the latching bodies 18, 20 slide over one another and pull the hand-held power tool 10 in the working direction 16 whilst, because of the jammed tool 12, the spacing of the hammer tube 24 to the tool remains substantially unaltered (Figure 3). \ )

If one end of the flat sides of the saw tooth profiles of the latching bodies 18, 20 is reached, the latching bodies 18, 20 engage once again, the hand-held power tool 10 being accelerated by the pulling force F counter to the working direction 16 (Figure 3), as is an arm of the operator acting on the hand-held power tool 10. At the end of the latching movement the flat sides of the saw tooth profiles of the latching bodies 18, 20 strike one another and the pulse created by the acceleration is transmitted as an impact pulse, counter to the working direction 16 via the latching body 18 fastened to the hammer tube 24, to a percussion unit 14 comprising the hammer tube 24 and the tool 12. The tool 12 j ammed in the workpiece jolts, which can lead to the release of the jamming.

Figures 5 and 6 show alternative embodiments of the invention. In this connection, similar components are denoted by the same reference numerals. A detailed description is substantially given of the differences to the embodiment shown in Figures 1 - 4 and, with regard to features remaining the same, reference is made to the

description of the embodiment in Figures 1 - 4.

In the embodiment shown in Figure 5, a hand-held power tool comprising a percussion mechanism configured as a reverse arresting impact mechanism is configured as a hammer drill or chisel hammer. The hand-held power tool, not shown in more detail, comprises a driving spur gear 46 which encloses a hammer tube 24 of the hand-held power tool and is rotatably mounted on the hammer tube 24. The hammer tube 24 comprises a snap ring 48 for axially fixing the driving ) spur gear 46 in the working direction 16 and a peripheral shaping 50 in the opposing direction.

A saw tooth-shaped toothing facing the working direction 16 is formed on the driving spur gear 46, which toothing forms a latching body 18 configured as an integral part of the driving spur gear 46 and designed as a locking disc. A second latching body 20 is, as in the embodiment of Figures 1 - 4, rigidly connected to a housing, not shown in more detail, of the hand-held power tool. On the face opposing the latching body 18, facing away from the working direction 16, the driving spur gear 46 comprises a plurality of rotary drive lugs 52 which can engage in corresponding lugs of an annular rotary drive element 54.

On an outer contour, the driving spur gear 46 additionally comprises a further toothing in which a gear wheel, not shown here, connected to a motor of the hand-held power tool can engage and displace the driving spur gear 46 in a rotary movement 44.

The rotary drive element 54 can be axially displaced by an operator of the hand-held power tool 10, being guided in the axial direction by guide rails 56, 56 ' which are formed on the hammer tube 24. In a first position, the rotary drive lugs 52, 52 ' of the driving spur gear 46 engage in the corresponding lugs of the rotary drive element 54, whilst this is not the case in a second position of the rotary drive element 54. In the first position, associated with a hammer drill mode, the rotary movement 44 of the driving spur gear 46 is transmitted via the rotary drive lugs 52, 52 ' to the rotary drive element 54 and therefrom via the guide rails 56, 56 ' to the hammer tube 24, which rotates with the driving spur gear 46. In the second position, associated with a chiselling mode, the rotary drive lugs 52, 52' do not engage with the corresponding lugs on the rotary drive element 54 and the hammer tube 24 remains fixed in its rotary position.

The embodiment shown in Figures 6 and 7 relates to a spring element 22 to define resting positions of a hammer tube 24.

A hand-held power tool 10 comprises the hammer tube 24 which comprises two annular disc-shaped bearing elements 58, 58 ' rigidly connected to the hammer tube 24. Located between the bearing elements 58, 58 ' is an inner edge of the annular disc-shaped, bistable spring element 22, of which the internal diameter is approximately 2mm smaller than an external diameter of the bearing elements 58, 58 ' . The bistable spring element 22 forms a spring mechanism and is connected to a housing 42 of the hand-held power tool 10 and, in a first configuration (Figure 6) in which a percussion mechanism is deactivated, is curved in a direction which is counter to a working direction 16.

If an operator exerts a pulling force F on the housing 42, this is transmitted, when the tool 12 is jammed, via the bearing element 58 to the bistable spring element 22 of which the curvature is deformed when it reaches a threshold force of approximately ION. As a result, the spring element 22 is substantially elastically converted into a second configuration, in which latching elements 18, 20 of the percussion mechanism configured as locking discs engage and can act as a reverse arresting impact mechanism. \)

In the second configuration, if the operator exerts a thrust force on the hand-held power tool 10 in the working direction 16, this thrust force is assisted via the bearing element 58 on the bistable spring element 22 and when a threshold value is reached the bistable spring element 22 is deformed into the first configuration, whereby the percussion mechanism is deactivated.

List of Reference Numerals Hand-held power tool 12 Tool 14 Percussion unit 16 Working direction 18 Latching body Latching body 22 Spring element 24 Hammer tube 26 Striker 28 Impact head Locking ball 32 Retention tab 34 Spring 36 Edge 38 Safety device Actuation element 42 Housing 44 Rotary movement 46 Driving spur gear 48 Snap ring Shaping 52 Rotary drive lug 54 Rotary drive element 56 Guide rail 58 Bearing element Edge F Pulling force

Claims

Claims 1. Percussion mechanism for a hand-held power tool (10), in

particular for a hammer drill and/or chisel hammer which is provided to transmit impact pulses to a percussion unit (14), which comprises a tool (12), characterized in that the impact pulses are oriented counter to a working direction (16) of the tool (12).
2. Percussion mechanism according to claim 1, characterized by at least two latching bodies (18, 20) which can move relative to one another.
3. Percussion mechanism according to claim 2, characterized in that the latching bodies (18, 20) are configured as locking discs.
4. Percussion mechanism according to claim 3, characterized in that the latching bodies (18, 20) respectively comprise at least three notches.
5. Percussion mechanism, at least according to claim 2, characterized in that the latching bodies (18, 20) comprise a saw tooth profile at least in one direction.
6. Percussion mechanism according to any of the preceding claims, characterized in that the impact pulses are derived from an operator pulling force (F). \
Percussion mechanism according to any of the preceding claims, characterized by a spring element (22) to create a pulling force threshold.
8. Device according to claim 6, characterized in that the spring element (22) is designed as a spring blade.
9. Percussion mechanism according to any of the preceding claims, characterized by at least two configurations which may be at least substantially elastically converted from one to another.
10. Hand-held power tool (10), in particular hammer drill and/or chisel hammer with a percussion mechanism for transmitting impact pulses to a percussion unit (14) comprising a tool (12), characterized in that the impact pulses are counter to a working direction (16) of the tool (12).
11. A percussion mechanism for a hand-held power tool, substantially as herein described with reference to the accompanying drawings.
12. A hand-held power tool comprising a percussion mechanism as defined in any one of claims 1 to 9 or 11.