GB2444401A

GB2444401A - Hand machine tool with vibration isolating spring in region of swivel joint

Info

Publication number: GB2444401A
Application number: GB0723330A
Authority: GB
Inventors: Bernhard Hegemann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2006-12-01
Filing date: 2007-11-28
Publication date: 2008-06-04
Anticipated expiration: 2027-11-28
Also published as: DE102006056854A1; CN101224572B; GB0723330D0; GB2444401B; CN101224572A

Abstract

The invention relates to a hand tool machine, in particular a hammer drill and/or paving breaker 2, having a housing 4, and a handle 10 that is connected by a swivel joint 28 to the housing so as to be pivotable to a limited extent. A spring 34 is provided for vibration isolation between the handle and the housing, in the region of the swivel joint. Preferably, the spring is a bent spring wire or bar, a helically wound middle portion of which surrounds the swivel joint.

Description

I

Description Title

Hand tool machine with pivotably connected, vibration-isolated handle The invention relates to a hand tool machine according to the preamble of claim 1.

Especially in hand tool machines with a percussion mechanism, such as for example in hammer drills, chisel hammers and the like, the hand tool machine may be subject to considerable vibrations. If these vibrations are transmitted to a handle used to press the hand tool machine towards a workpiece, this is not only an unpleasant sensation for the operator but may also, given prolonged exposure, result in damage to his health.

Background art

From DE 100 36 078 Al of the applicant, a hand tool machine of the initially described type is known. The known hand tool machine, in particular a hammer drill or chisel hammer, comprises a housing, a tool holder, and at the end of the housing remote from the tool holder a bow-shaped handle, which is connected at a first end remote from a tool axis by a swivel joint and at a second end facing the tool axis by a compliant isolating device to the housing.

The isolating device there comprises a biased helical compression spring for vibration isolation, which acts by its one end upon the handle and by its other end upon the housing.

This style of construction with a linear spring guide of the handle, whilst effecting good vibration isolation of the handle from the housing, does however both in working direction of the hand tool machine and transversely of the working direction take up a relatively large amount of installation space between handle and housing, thereby leading in this region to a not inconsiderable increase of the length and width of the hand tool machine.

The same applies to leaf-spring multi-joint guides, which are used in some hand tool machines likewise for vibration decoupling and/or vibration isolation of handles.

Against this background, the underlying object of the invention is to improve a hand tool machine of the initially described type in such a way that the installation space for the spring used for vibration isolation may be reduced.

Disclosure of the invention

According to the invention this object is achieved in that the spring is disposed in the region of the swivel joint.

There, the spring may be accommodated in a space-saving manner in the housing and in the handle, in particular if the spring according to a preferred development of the invention is a biased torsion-or spiral spring, which during operation of the hand tool machine is subject to a bending stress if the handle in the event of vibration or oscillation of the housing is swivelled while simultaneously approaching the housing.

In the context of the present invention the term, swivel joint, denotes not only a joint in the literal sense, whereby two parts are pivotable relative to one another about a defined swivelling axis, but also a deformable element between the handle and the housing that allows a limited swivelling motion of the handle in relation to the housing.

A particularly preferred development of the invention provides that the torsion-or spiral spring is formed by a bent spring wire or spring bar, the middle part of which advantageously extends in one or more helical turns around the swivel joint so that the spring wire or spring bar is held firmly in position by the swivel joint. The two end parts advantageously take the form of elongate limbs and project into the interior of the handle and the housing respectively, where they are supported in each case against an abutment.

The abutments of the handle and the housing are preferably formed by inner surfaces of the handle and the housing that are directed towards a handle aperture of the hand tool machine that is delimited by the handle and the housing, wherein the abutment in the housing in the case of a cordless hammer drill may be disposed for example in the vicinity of a passage leading to the battery mounting.

According to a further preferred development of the invention, the spring has a defined spring stiffness so that it enables a defined decoupling or compliance of the relative movement between the handle and the housing, wherein the spring action exerted by the spring on the handle is in a defined relationship to the swivel angle of the handle.

To allow swivelling of the handle, there is disposed between an end part of the handle remote from the swivel bearing and an adjacent part of the housing an intermediate space, which is either bridged at least partially by an elastically compliant material or may be surrounded by a compliant guard, for example in the form of bellows, in order to prevent dirt from penetrating between the handle and the housing and to prevent an operator from injuring himself as a result of getting his finger or thumb caught between handle and housing.

Inside the intermediate space a further guide device may additionally be provided, which effects additional guidance of the swivelling motion of the handle about the swivelling axis of the swivel joint.

While the swivel joint preferably comprises two parts, which are rigidly connected to the handle and the housing respectively and are twistable relative to one another along two seating faces, which are coaxial with the swivelling axis, of a swivel journal and a locating bush, the swivel joint may alternatively comprise a material bridge of a reversibly deformable material, such as for example an elastomer or a thermoplastic elastorner, which connects the handle to the housing, wherein the material bridge allows a swivelling of the handle in relation to the housing. In this case, the spring may advantageously be moulded into the deformable material, wherein the free ends of the spring project from the deformable material such that they may be supported against corresponding abutment faces in the handle and/or housing, which are made of hard plastics material.

Brief description of the drawings

The invention is described in detail below with reference to an embodiment that is represented in the drawing. The single figure shows a part-sectional side view of a tool machine according to the invention.

Embodiment of the invention The hand tool machine in the form of a hammer drill 2 that is represented in the drawing substantially comprises a housing 4, a tool holder 6 for receiving a tool 8 in the form of a percussion drill bit, as well as a drive device (not shown) enclosed by the housing 4 for setting the tool 8 inserted into the tool holder 6 in rotational and percussive motion.

The drive device in a known manner comprises an electric drive motor, which via a reduction-and/or change speed gear sets the tool holder 6 in rotation, as well as a percussion mechanism, which is likewise driven by the drive motor and by means of which the tool 8 in the tool holder 6 may be loaded with an impact force acting in a working direction A of the hammer drill 2.

The housing 4 at its end remote from the tool holder 6 is provided with a handle 10, which together with an additional handle 14 detachably mounted on the housing 4 at 12 in the vicinity of the tool holder 6 is used to grasp and support the hammer drill 2. The handle 10 together with the housing 4 surrounds a handle aperture 16 for a hand of an operator and particularly during vertical operation, i.e. in the case of a vertical working direction A and a downwardly directed tool 8, makes it easier to tightly hold and guide the hammer drill 2, while the additional handle 14 preferably comes into operation in the case of a horizontally oriented or slightly inclined Both the housing 4 and the handle 10 each comprise two half-shells 18, 20 and 22, 24 respectively, which are connected in pairs to one another along a longitudinal centre line of the hammer drill 2. At its side facing the handle aperture 16 the handle 10 is provided with a switch 26, by means of which the hammer drill 2 may be switched on and off without letting go of the handle 10.

The bow-shaped handle 10 at its bottom end is pivotably connected by a swivel joint 28 to the housing 4 so as to be capable of swivelling to a limited extent relative to the housing 4 about a swivelling axis of the swivel joint 28 that extends at right angles to the longitudinal centre line of the hammer drill 2. In order to allow the swivelling of the handle 10, an upper end part of the handle 10 at its side facing the housing 4 is separated from the housing 4 by a wedge-shaped intermediate space 30.

Furthermore, the half-shells 18, 20 of the housing and the half-shells 22, 24 of the handle overlap one another in the region of the swivel joint 28.

The swivel joint 28 comprises a hollow-cylindrical journal 36, which projects from the one 24 of the two half-shells 22, 24 of the handle 10 into the hollow interior of the handle 10 and delimits a cylindrical opening 32. During assembly of the housing 4 and the handle 10, there is inserted into the opening 32 a correspondingly dimensioned cylindrical bolt 38, which projects from the half-shell 18 of the housing 4 that lies opposite the half-shell 24 of the handle 10.

In order to prevent vibrations of the housing 1 thit are caused for example by the percussion mechanism of the hammer drill 2 from being transmitted to the handle 10, which is not only an unpleasant sensation for the operator but may also, given prolonged exposure, result in damage to his health, a biased spring 34 used for vibration isolation is provided in the vicinity of the swivel joint 28.

The spring 34 comprises a bent spring bar or spring wire, the middle part 40 of which is helically wound, wherein one or more turns thereof surround the journal 30 of the swivel joint 28, and the two opposite end parts 42, 44 of which project in the form of two elongate limbs into the interior of the handle 10 and the housing 4 respectively. In the interior of the handle 10 and housing 4 the biased end parts 42, 44 are supported in each case against an abutment that is formed by an inner side, facing the handle aperture 16, of an outer boundary wall part, remote from the handle aperture 6, of the half-shell 20 and 24 respectively. As the middle part 40 of the spring 34 extends around the journal 36 of the swivel joint 28, the biased spring 34 is held firmly in position by the journal 36.

The spring 34 has a defined spring stiffness, so that the spring action exerted by the spring 34 on the handle 10 is in a defined relationship to the swivel angle of the handle 10. The spring action in this case increases in dependence upon the swivel angle of the handle 10 with a defined gradient when the handle 10 is swivelled in an anticlockwjse direction about the swivelling axis of the swivel joint 28, so that the top end of the handle 10 approaches the housing 4 with a simultaneous reduction in the size of the intermediate space 30.

To prevent dirt from collecting in the intermediate space 30 between the upper end part of the handle 10 and the adjacent part of the housing 4 or to prevent the user from injuring himself by getting a finger or thumb caught in the intermediate space 30, the intermediate space 30 is at least partially filled with an elastomeric material 46, which upon swivelling of the handle 10 about the swivelling axis of the swivel joint 28 deforms in an elastically compliant manner and in said case effects additional vibration damping and noise reduction.

Alternatively, for the same purpose the intermediate space might be surrounded by an annular protective enclosure in the form of bellows made of an elastically compliant material.

Claims

R. 316642 Claims 1. Hand tool machine, in particular a hammer drill

and/or paving breaker, having a housing, a handle that is connected by a swivel joint to the housing so as to be pivotable to a limited extent, as well as a spring disposed for vibration isolation between the handle and the housing, characterized in that the spring (34) is disposed in the region of the swivel joint (28)
2. Hand tool machine according to claim 1, characterized in that the spring (34) is subject to a bending stress upon swivelling of the handle (10) with a simultaneous approach of the housing (4).
3. Hand tool machine according to claim 1 or 2, characterized in that the spring (34) has a defined spring stiffness in dependence upon a swivel angle of the handle (10) in relation to the housing (4)
4. Hand tool machine according to one of the preceding claims, characterized in that the spring (34) is biased.
5. Hand tool machine according to one of the preceding claims, characterized in that the spring (34) comprises a bent spring wire or spring bar, the end parts (42, 44) of which extend from the swivel joint (28) out into the interior of the handle 10) and the housing (4) respectively.
6. Hand tool machine according to claim 5, characterized in that the two end parts (42, 44) of the spring wire or spring bar are supported in the interior of the handle (10) and the housing (4) in each case against an abutment.
7. Hand tool machine according to claim 6, characterized in that the abutment comprises a seating face that is directed towards a handle aperture (16) delimited by the handle (10) and the housing (4)
8. Hand tool machine according to one of the preceding claims, characterized in that the spring (34) comprises a bent spring wire or spring bar, the helically wound middle part (40) of which surrounds the swivel joint (28).
9. Hand tool machine according to one of the preceding claims, characterized in that disposed between an end part of the handle (10) remote from the swivel joint (28) and an adjacent part of the housing (4) is an intermediate space (30), which allows the swivelling of the handle (10)
10. Rand tool machine according to claim 9, characterized in that the intermediate space (30) contains an elastically compliant material (46)
11. Hand tool machine according to claim 9 or 10, characterized in that the intermediate space (30) is at least partially surrounded by a compliant protective enclosure.
12. Hand tool machine according to one of the preceding claims, characterized in that the housing (4) and the handle (10) each comprise two half-shells (18, 20; 22, 24), which overlap one another in the vicinity of the swivel joint (28)
13. Hand tool machine according to one of claims 1 to 12, characterized in that the swivel joint (28) comprises two parts (36, 38), wherein one of the parts is connected rigidly to the handle (10) and the other is connected rigidly to the housing (4) and wherein the two parts (36, 38) have seating faces, which are coaxial with the swivelling axis.
14. Hand tool machine according to one of claims 1 to 12, characterized in that the swivel joint (28) comprises a material bridge of a reversibly deformable material, which connects the handle (10) to the housing (4).
15. A hand tool machine substantially as herein described with reference to the accompanying drawing.