GB2459190A

GB2459190A - Hand-held power tool with protector part

Info

Publication number: GB2459190A
Application number: GB0906491A
Authority: GB
Inventors: Sinisa Andrasic; Marcus Schuller
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-04-18
Filing date: 2009-04-15
Publication date: 2009-10-21
Anticipated expiration: 2029-04-15
Also published as: GB2459190B; GB0906491D0

Abstract

A hand-held power tool comprises a housing 1, on the outside of which at least one separate protector part 5 is arranged. The protector part has at least one deformation section 6, 7, which possesses an increased deformability in relation to the housing wall of the housing. Preferably, the deformation section consists of a material with greater elasticity than the housing, and may be a two-component part, the two parts having different degrees of deformability. The protector part may be fastened detachably to the outside of the housing by a catch connection. The at least one deformation section may consists of a material with greater elasticity than the housing. Preferably, a wall of the at least one deformation section has regions of reduced wall thickness, and may be configured in a wave shape or with a plurality of depressions and elevations.

Description

Description Title

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

Prior art

Hand-held power tools, such as, for example, angle grinders, which have in a housing an electric drive motor for driving a tool, are known. The housing of the hand-held power tool is subjected to considerable loading during operation, including vibrations which arise when the motor is running as a result of the rotating motor parts or gearbox parts for driving the tool. Loading may also arise during the machining of the workpiece, for example as a result of shocks. The housing of the hand-held power tool has to withstand loading of this kind over a long operating time.

In addition, the housing also has to withstand individual shocks or impacts which occur, for example, if the hand-held power tool is inadvertently dropped. The housing also has to withstand these shocks, up to a certain extent, without breaking.

Disclosure of the invention

The object on which the invention is based is to design a hand-held power tool using simple measures such that the housing of the hand-held power tool can also withstand increased loading.

This object is achieved according to the invention by the features of Claim 1. The subclaims specify expedient developments.

The hand-held power tool according to the invention, which is in particular an electrically operated hand-held power tool, such as, for example, an angle grinder, has a housing, in which the components required for the drive, such as the drive motor, gearbox unit and tool shaft, are accommodated. For protection against increased shocklike loading, such as, for example, impacts, a covering part is arranged on the outside of the housing, which is designed as a separate component and is connected to the housing.

This covering part is formed as a protector part and has at least one deformation section, which possesses an increased deformability in relation to the housing wall of the housing.

The protector part performs essentially a protective function for protecting the underlying housing wall. Owing to the increased deformability of the deformation section in the protector part, the shock energy or impact energy acting on the hand-held power tool is converted into deformation energy through deformation of the deformation section, so that the underlying housing does not undergo high, shocklike loading any more, but only a considerably reduced force action, which does not usually lead to damage of the housing any more, even if the protector part itself were to be damaged.

The protector part may be provided with an additional function, for example with air apertures, in order to enable an inflow and/or outflow of cooling air into or out of the housing. What is essential, however, is the protective function of the protector part, which function may be utilised once or more than once depending on the design of the protector part and the degree of loading acting on the protector part.

It may be expedient to fasten the protector part on the outside of the housing using simple measures, in particular in such a manner that it is possible to replace the protector part, that is to say detach it from and fasten it to the housing, quickly and without problems and in particular without auxiliary tools. In order to accomplish this, the protector part is preferably connected to the housing via a catch connection, for example a clip connection or the like, so that the protector part can be replaced simply and in a short time as a quick-change element. Alternatively or additionally, it is also possible to provide a form-fitting connection between protector part and housing, the form fit existing transversely to the assembly direction, so that a firm connection is obtained between protector part and housing in the transverse direction. The form fit exists, for example, in the form of a so-called dovetail guide having two corresponding elements on the protector part and on the housing, which taper in the assembly direction, whereby a self-centring action is achieved. In the fully assembled state, the protector part is fixed securely and permanently in its position relative to the housing via the form-fitting connection, even in the event of shocklike loading acting on the protector part.

A further possible form-fitting connection is a groove-and-web connection between protector part and housing, the groove direction running, transversely to the direction of expansion of the protector part in the event of loading acting from outside. This ensures that the protector part does not yield laterally at its edge sections under loading and thereby lose contact with or connection to the housing of the hand-held power tool. The groove-and-web connection is also a form-fitting connection.

The deformation in the protector part is produced by the fact that the deformation section, which is a constituent part of the protector part, has an increased deformability, which is achieved either by an appropriate material choice and/or via an appropriate structural configuration. For example, it is possible to choose a material for the deformation section with greater elasticity than the housing, so that a force action from outside on the protector part leads to a correspondingly greater elastic deformation of the deformation section. In principle, however, instead of elastic deformations, plastic deformations are also possible, which is likewise achieved either via an appropriate material choice and/or a structural configuration.

The increased deformability may be achieved by structural measures, for example by the fact that regions of reduced wall thickness are present in the deformation section, it optionally being possible to provide a plurality of depressions and elevations lying one behind the other, which lead, by way of example, to a wave shape of the deformation section. In the event of a force action on the appropriately structurally configured deformation section, the latter will expand or contract in the wave direction, thereby dissipating the shock energy. Optionally, a combination of structural measures with an appropriate material choice is also possible.

According to a further advantageous embodiment, the deformation section is formed as a two-component part, it being possible for the two components of which the deformation section consists to have different material properties. On combination of the two components, desired properties can be produced, for example restitution after comparatively large deformations.

The aforementioned measures for increasing the deforrnability relate at least to the deformation section within the protector part. The deformation section forms at least one part of the protector part, although optionally embodiments in which the protector part is formed completely by the deformation section are also possible.

Further advantages and expedient embodiments can be found in the further claims, the description of the figures and the drawings, in which: Fig. 1 shows a perspective illustration of a gearbox housing as a constituent part of the housing of a hand-held power tool, Fig. 2 shows the gearbox housing with an attached protector part, which has a greater deformability than the gearbox housing, Fig. 3 shows the protector part in a perspective view from inside, Fig. 4 shows a detail of the gearbox housing having a screw centring dome, around which the protector part is placed, Fig. 5 shows the detail from Fig. 4, additionally illustrated with the protector part, Fig. 6 shows a detail view of the protector part, seen from inside, Fig. 7 shows a further perspective view of the protector part, Fig. 8 shows a still further perspective view of the protector part.

In the figures, identical components are provided with the same reference symbols.

Fig. 1 illustrates a gearbox housing as a constituent part of the housing of a hand-held power tool. The gearbox housing is flanged to a motor housing, in which an electric drive motor is accommodated, whereas gearbox components including a tool shaft driven by the drive shaft of the drive motor are accommodated in the gearbox housing. The gearbox housing 1 consists of metal, preferably of aluminium. Situated on the upper side of the gearbox housing 1 are two spaced-apart screw centring domes 2, which serve to receive a screw for connection to the motor housing. Situated between the screw centring domes 2 is a bridging crosspiece 3, which is formed integrally with the gearbox housing, as are the screw centring domes 2, and has an outward curvature. A trapezoidal groove 9 is provided centrally in the crosspiece 3. The curved crosspiece 3 spans a recess in the gearbox housing and also an air outlet opening 4, which in the assembled state serves to lead cooling air away from the interior of the housing.

Fig. 2 illustrates the gearbox housing 1 including an attached protector part 5. The protector part 5 preferably consists of a plastics material, which preferably possesses a greater deformability than the gearbox housing 1, and in particular of a material with a greater elasticity. The protector part 5 covers the crosspiece 3 (Fig. 1) and also the lateral screw centring domes 2 and is adapted to the 20.contour of the crosspi.ece and of the screw centring domes.

Just as the gearbox housing, the protector part 5 is connected to the motor housing via the screws to be inserted into the screw centring domes 2. The protector part 5 has a central section 6 and lateral dome sections 7, the central section 6 being adapted to the crosspiece 3 and having the same curvature as the latter, and the dome sections 7 being formed to correspond to the contour of the screw centring domes 2. In the front part, the protector part 5 has air apertures 8, which communicate with the air outlet opening 4 of the gearbox housing 1 and allow air to escape from the housing. The lateral dome sections 7 of the protector part 5 form deformation sections, which are deformable in a particular manner in the event of high loading acting from outside. Advantageously, the central section connecting the lateral dome sections also forms a deformation section with increased deformability.

As can be seen in Fig. 3, the deformability in the dome sections 7 is achieved, in addition to by the choice of a material with increased deformability, by a particular geometrical or structural configuration, in that the inside of the dome sections 7 is formed by successive depressions and elevations in a wave shape with a wall thickness changing continuously in the peripheral direction. This wave shape of the wall in the dome sections 7 promotes the deformability in the event of high, external loading.

Additionally in Fig. 3 there can be seen a trapezoidal web 10, which is arranged on the transversely extending section 6 of the protector part 5 and rises above the upper side of the section 6. The trapezoidal web 10 is adapted to the contour of the trapezoidal groove 9 in the crosspiece 3 of the gearbox housing 1 and can be pushed into the trapezoidal groove 9 in such a manner that the protector part 5 is connected in a form-fitting manner to the gearbox housing 1 both in the transverse direction and in the vertical direction.

In Fig. 4, at the transition between the screw centring dome 2 and the large-area section of the gearbox housing 1, there is provided in the housing wall a fixing groove 11 which serves to receive a corresponding fixing web 12 on the protector part 5 (Figs. 6 to 8) . The groove direction of the fixing groove 11 and also correspondingly the direction of extension of the fixing web 12 lie transversely to the direction of expansion of the protector part in the event of loading acting on the protector part from outside. In this situation, the protector part 5 endeavours to expand transversely to the shock direction, that is to say transversely to the groove direction and web direction of the fixing groove 11 and the fixing web 12, respectively. Owing to the form fit between fixing groove 11 and fixing web 12, an expansion in the transverse direction beyond the fixing groove 11 is prevented, so that the outer edges of the protector part 5 retain their relative position in relation to the gearbox housing. The shock compensation takes place rather through a deformation in the region, above all, of the dome section 7 and optionally also of the central section 6 connecting the dome sections 7.

In Figures 5 and 6 as well as 7 there can be seen furthermore the wave-shaped, approximately tooth-shaped course of the inner wall of the dome section 7 in the protector part 5. The recesses and the elevations of the dome section 7 provided with an outward curvature correspond to the curvature of the screw centring dome 2 and have in each case approximately the same length and depth. In the exemplary embodiment, three successive elevations are provided on the inside of the dome section 7, and are respectively preceded and followed by recesses in each case.