GB2445238A

GB2445238A - Vibration decoupling of power tool handle

Info

Publication number: GB2445238A
Application number: GB0724180A
Authority: GB
Inventors: Jochen Krauter
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2006-12-15
Filing date: 2007-12-11
Publication date: 2008-07-02
Anticipated expiration: 2027-12-11
Also published as: GB2445238B; DE102006059348A1; GB0724180D0

Abstract

The invention relates to a hand-held power tool (2) having a housing (4) and a handle (12) which is separated from the housing (4) in the extension of a main vibration axis (22) of the housing (4) by an intervening space (23) for the purpose of vibration uncoupling and is connected to the housing (4) at a lateral distance from the main vibration axis (22). The handle (12) is integrally moulded on the housing (4) via a material bridge (30). In preferred embodiments, the material bridge may be formed from a different material. Furthermore, the material bridge may also contain a spring for further damping of vibrations.

Description

Description Title

Hand-held power tool having a vibration-uncoupled handle The invention relates to a hand-held power tool according to the precharacterising clause of Claim 1.

Particularly in the case of hand-held power tools having a percussive drive, such as for example drilling hammers, chiselling hammers and the like, the hand-held power tool can be subjected to considerable vibrations. If these vibrations are transmitted to a handle serving for pressing the hand-held power tool against a workpiece, this is not only found to be unpleasant by the operator, but on prolonged exposure may even result in damage to health.

Prior art

A hand-held power tool of the type mentioned at the outset is known from the applicant's DE 100 36 078 Al. The known hand-held power tool, in particular a drilling or chiselling hammer, has a housing, a tool holder and a bow-shaped handle on the side of the housing facing away from the tool holder. For the purpose of vibration uncoupling, the handle is separated there at its upper end from the housing in the extension of a tool axis forming the main vibration axis of the drilling hammer by an intervening space and is supported against the housing via a spring element arranged in the intervening space, while it is connected at its lower end at a distance from the main vibration axis to the housing by a joint which enables relative movement between the handle and the housing. -2

However, the outlay involved with the vibration damping and the linking of the handle to the housing is quite considerable, since the housing and the handle are produced from separate parts and then, on assembly, have to be connected to one another with insertion of the spring element as well as further components, such as stops, guide elements, joint bushes, etc. With this as the starting point, the object on which the *invention is based is to improve a hand-held power tool of the type mentioned at the outset such that the outlay involved with the vibration damping and the attachment of the handle to the housing can be reduced.

Disclosure of the invention

This object is achieved according to the invention in that the handle is integrally moulded on the housing via a material bridge, so that it can be produced, on production of the housing, together with the latter in one operation by injection moulding from plastic.

The invention preferably makes use not only of the elastic deformability of the material bridge, in order to enable the relative movement between housing and handle which is required for the vibration uncoupling, but also the bending stiffness of the material bridge, in order, on the one hand, to lead the pressing force applied to the handle by the operator into the housing via the material bridge and, on the other hand, to damp the oscillations or vibrations arising from the housing or prevent their transmission into the handle by the material bridge.

Furthermore, the solution according to the invention has the advantages that it enables a very compact construction of the hand-held power tool and is largely insensitive to dust, since ingress of dust into the intervening space does not result in any functional impairment, unlike known hand-held power tools with vibration uncoupling, such as the hand-held power tool from DE 100 36 078 Al mentioned at the outset.

A particularly preferred configuration of the invention provides that the housing and the handle are composed of two half-shells formed in one piece, and in that the material bridge is formed by integral parts of the half-shells. In this way, each half-shell comprising one half of the housing, handle and material bridge can be produced in one piece in a single injection mould and then the two half-shells are mounted on the hand-held power tool, while hitherto required additional parts, such as spring, pivot joint, bearings, bushes, stops and guide elements, can be dispensed with, whereby the outlay involved with fabrication and assembly can be further reduced.

Preferably, the material bridge formed as a unit with a half-shell consists of the same plastics material as the half-shell itself, so that the entire housing including handle and material bridge can be fabricated in one injection operation. Alternatively, the material bridge can, however, also consist of a plastics material moulded jointly with the half-shells and connected in one piece with the half-shells, the material being injected between the housing and the handle and expediently possessing a different stiffness or elasticity to the plastics material of the housing and of the handle, so that vibration damping properties can be improved.

Expediently, the material bridge is separated as far as possible from the main vibration axis of the housing, so that some of the vibrations are damped already between the main vibration axis and the material bridge in the housing itself. At the place where the handle and the housing define a gripping opening, the material bridge is therefore expediently arranged on the side of the gripping opening opposite the intervening space and the main vibration axis, in the case of drilling or chiselling hammers expediently at the outermost end of the handle.

In the case of battery-operated hand-held power tools, which frequently have a battery holder integrally moulded on the underside of the housing in front of the handle, it may be preferable to connect the handle in one piece with the battery holder via the material bridge. Alternatively, however, it is also possible to form the handle and the battery holder jcintly as a unit and to integrally mould it on the housing, or connect it in one piece with the housing, via the material bridge, in which case the material bridge is expediently arranged above the battery holder.

In order to enable also large pressing forces applied to the handle by the operator to be led into the housing via the material bridge or in order to alter the vibration damping properties of the material bridge, it may optionally be expedient to arrange inside the material bridge an additional bending spring which can expediently -5 be embedded in one of the two half-shells during the injection moulding.

In order that contact between the parts of the housing and of the handle arranged on both sides of the intervening space is avoided also in the case of large pressing forces applied to the handle by the operator, an additional compression spring can be provided within the intervening space between the handle and the housing, which spring is supported on the handle and on the housing, so that at least some of the pressing forces applied to the handle can be led into the housing via the compression spring without the vibrations of the housing being transmitted into the handle via the compression spring.

In order to prevent dust or other impurities from getting inside the housing through the intervening space, and reliably preclude injuries to an operator by catching limbs in the intervening space, the intervening space can, according to two further advantageous configurations of the invention, either contain an elastically flexible material, which optionally also ensures transmission of pressing forces while at the same time ensuring vibration damping, instead of a compression spring, or alternatively can be surrounded by bellows fitted by its ends on the handle and on the housing.

Preferably, the invention is used in drilling and/or chiselling hammers, the main vibration axis of which coincides with the longitudinal axis of a drill bit, chisel bit or chisel inserted into a tool holding fixture of the drilling and/or chiselling hammer.

Brief description of the drawings

The invention is explained in more detail below with the aid of some embodiments illustrated in the drawing, in which: Fig. 1: shows a side view of a drilling hammer according to the invention; Fig. 2: shows a side view of a battery-operated drilling hammer according to the invention; Fig. 3: shows a side view of another battery-operated drilling hammer according to the invention.

Embodiments of the invention The hand-held power tools in the form of a small drilling hammer 2 which are illustrated in the drawing consist essentially of a housing 4, a tool holder 6 for receiving a tool 8 in the form of percussion drill bit, and a drive device (not illustrated) for the rotational and percussive driving of the tool 8 inserted into the tool holder 6.

While the drilling hammer 2 illustrated in Fig. 1 can be connected to a power supply network via a power cable (not illustrated), the drilling hammers 2 illustrated in Figs. 2 and 3 have a receiving shaft 10 for a battery pack (not illustrated) serving as the power source.

The housing 4 is provided, at its end facing away from the tool holder 6, with a handle 12 which, together with an auxiliary handle 16 detachably fitted on the housing 4 in the vicinity of the tool holder 6 at 14, serves for gripping and holding the drilling hammer 2. The handle 12 encloses together with the housing 4 a gripping opening 18 for a hand of an operator and facilitates the firm holding and guiding of the drilling hammer 2 particularly in vertical operation, i.e. when the working direction A is vertical and the tool 8 directed downwards, while the auxiliary handle 16 is used preferably when the working direction A is horizontally oriented or at a small inclination. On its side facing the gripping opening 18, the handle 12 is provided with a switch 20, by which the drilling hammer 2 can be switched on and off without letting go of the handle 12 in doing so.

The drive device accommodated inside the housing 4 comprises, in a manner known per Se, an electric drive motor, which rotationally drives the tool holder 6 via a reduction or change-speed gear, and a percussion mechanism, which is likewise driven by the drive motor and by which the tool 8 in the tool holder 6 can be subjected, via a plunger, to an intermittent percussive force acting along a tool axis 22 in the working direction A of the drilling hammer 2.

If the drilling hammer 2 is pressed against a workpiece in chiselling mode or combined drilling and chiselling mode, however, an intermittent recoil force opposite the percussive force is also led into the housing 4 due to the rebound of the plunger, and despite damping measures this results in the housing 4 being subjected to considerable vibrations along a main vibration axis Coinciding with the tool axis 22.

In order to avoid the transmission of these vibrations to the handle 12 as well, which is found to be unpleasant by an operator and on prolonged exposure may even result in damage to health, the handle 12 is separated from the housing 4 behind the housing 4, i.e. on the side of the latter facing away from the tool holding fixture 6, in the extension of the tool axis and main vibration axis 22, by an intervening space 23 running at least partly transversely to this axis 22. As a result, the housing 4 can move there in the direction of the tool axis and main vibration axis 22 with respect to an upper part 24, situated behind the housing 4, of the handle 12 without touching the latter, whereby the handle 12 can be uncoupled from the vibrations of the housing 4 in this region. The intervening space 23 can be open towards the upper side and the longitudinal sides of the drilling hammer 2, as illustrated in Fig. 3. In order to avoid penetration of dust or other impurities into the intervening space 23, it is, however, preferably surrounded by bellows 26, as illustrated in Fig. 1, or by a reversibly deformable vibration-damping elastomer material or foam material 28, as illustrated in Fig. 2.

To connect the handle 12 to the housing 4, the handle 12 is integrally moulded on the housing 4 at a distance from the main vibration axis 22 via a slender material bridge 30 and is thereby connected in one piece with the housing 4. In order to ensure vibration uncoupling between the housing 4 and the handle 12 in the region of the material bridge 30 as well, the mass of the upper part 24 of the handle 12 situated on the other side of the material bridge 30, the length of a part 32 of the handle 12 (Fig. 2), or of parts 32, 34 of the handle 12 and of the housing 4 (Fig. 1), adjoining the material bridge 30 and oriented substantially transversely to the main vibration axis 22, and also the spring stiffness of the material bridge 30 are coordinated with the vibration frequencies of the percussion mechanism or of the vibrations of the housing 4 in such a way that these vibrations are not transmitted, or are transmitted only to a very small extent, into the handle 12 over the material bridge 30. At the same time, however, the bending stiffness of the material bridge 30 is such that a pressing force applied to the handle 4 by the user during the operation of the drilling hammer 2 is led into the housing 4 via the material bridge 30 without parts of the housing 4 and of the handle 12 adjoining the intervening space 23 on both sides touching one another.

In order to give the handle 12 a high degree of lateral guiding stability, it is designed relatively stiff in a direction perpendicular to the longitudinal mid-plane of the drilling hammer 2, so that the bending of the material bridge 30 owing to the pressing forces, and the vibration damping or vibration uncoupling occurs in a plane parallel to the longitudinal mid-plane of the drilling hammer 2.

In the case of the drilling hammers 2 illustrated in the figures with the tool axis and main vibration axis 22 oriented horizontally and the handle 12 projecting downwards (Fig. 1) or with the combination of battery pack-receiving shaft 10 and handle 12 projecting downwards (Figs. 2 and 3), the material bridge 30 is arranged in each case below the tool axjs and main vibration axis 22. In the case of the drilling hammers 2 illustrated in Figs. 1 and 2, it is situated at the greatest possible distance from the main vibration axis 22 on the lower side of the gripping opening 18 opposite the intervening space 23, the material bridge connecting the handle 12 to the downward-projecting part 34 of the housing 4 (Fig. 1) and to the lower end of the batter pack-receiving shaft 10 (Fig. 2).

In contrast to this, in the case of the drilling hammer 2 illustrated in Fig. 3, the intervening space 23 does not extend from the upper side of the housing 4 to the gripping opening 18, as in the case of the drilling hammers 2 in Figs. 1 and 3, but is prolonged obliquely downwards and forwards at a distance above the gripping opening 18, 50 that the entire battery pack-receiving shaft 10 together with the handle 12 above the battery pack-receiving shaft is integrally moulded on the housing 4 via the material bridge 30. As a result, in the case of the latter drilling hammer 2, not only the handle 12 but also the battery pack-receiving shaft 10 is vibrationally uncoupled from the housing 4.

In the case of all the drilling hammers 2 illustrated, the entire housing 4 including the handle 12 and, where present, the battery pack-receiving shaft 10 comprises two substantially mirror-symmetrical half-shells which are produced by injection moulding from plastic and which, on assembly of the drilling hammer 2, are mounted on the opposite longitudinal sides of the latter and meet at a parting line in the longitudinal mid-plane of the drilling hammer 2, as is customary with electric hand-held power tools. Each of the two half-shells moulded as a unit extends over the material bridge 30, which is thus formed by opposite sub-regions of the half-shells and can optionally be supplemented inside the half-shells by a bending spring designed as a leaf spring (not illustrated), which allows the stiffness of the material bridge 30 and hence the degree of deflection of the handle 12 to be altered in dependence on a pressing force applied to the handle 12.

Besides the already-mentioned parameters for influencing the spring stiffness of the material bridge 30, such as increasing or reducing the mass of the upper part 24 of the handle 12, shortening or lengthening the part 32 of the handle adjoining the material bridge 30 (Fig. 2) or the parts 32, 34 of the handle 12 and of the housing 4 adjoining the material bridge 30 (Fig. 1), the spring stiffness and/or bending stiffness of the material bridge can furthermore also be influenced by changing its cross-sectional shape and/or the wall thickness of the hollow half-shells in the region of the material bridge 30, and optionally also by virtue of the fact that the material bridge 30, although moulded as a unit with the half-shells in an injection mould, is so from a different plastics material, the stiffness of which differs from that of the half-shells in the region of the housing 4 and of the handle 12.

Claims

Claims 1. Hand-held power tool having a housing and a handle which is

separated from the housing in the extension of a main vibration axis of the housing by an intervening space for the purpose of vibration uncoupling and is connected to the housing at a lateral distance from the main vibration axis, characterised in that the handle (12) is integrally moulded on the housing (4) via a material bridge (30).
2. Hand-held power tool according to Claim 1, characterised in that the housing (4) and the handle (12) are composed of two half-shells, formed in one piece, made of a plastics material, and in that the material bridge (30) is formed by integral parts of the half-shells.
3. Hand-held power tool according to Claim 2, characterised in that the material bridge (30) consists of the same plastics material as the two half-shells.
4. Hand-held power tool according to Claim 2, characterised in that the material bridge (30) consists of a plastics material moulded jointly with the half-shells and connected in one piece with the half-shells, the material possessing a different stiffness to the plastics material of the housing (4) and of the handle (12).
5. Hand-held power tool according to one of the preceding claims, characterised in that the handle (12) and the housing (4) define a gripping opening (18), and in that the intervening space (23) and the material bridge (30) are arranged on opposite sides of the gripping opening (18).
6. Hand-held power tool according to one of the preceding claims, characterised in that a battery holder (10) integrally moulded on the handle (12) is connected to the housing (4) via the material bridge (30).
7. Hand-held power tool accordingto Claim 6, characterised in that the material bridge (30) is arranged above the battery holder (10).
8. Hand-held power tool according to one of the preceding claims, characterised by a bending spring arranged inside the material bridge (30)
9. Hand-held power tool according to one of the preceding claims, characterised by a compression spring arranged within the intervening space (23) between the handle (12) and the housing (4).
10. Hand-held power tool according to one of the preceding claims, characterised in that the intervening space (23) contains an elastically flexible material (28).
11. Hand-held power tool according to one of the preceding claims, characterised by bellows surrounding the intervening space (23) and fitted on the handle (12) and on the housing (4).
12. Hand-held power tool according to one of the preceding claims, characterized in that it is a drilling and/or chiselling hammer (2), the main vibration axis of which coincides with the longitudinal axis (22) of a drill bit, chisel bit or chisel inserted into a tool holding fixture (6) of the drilling and/or chiselling hammer. --14
13. A hand-held power tool substantially as herein described with reference to the accompanying drawings.