GB2473732A - Hand-held power tool with handle comprising resilient section formed in one piece with base body - Google Patents

Abstract

A hand-held power tool comprises a handle 1 with a base body 2 with a resilient section 6 that is formed in one piece with the base body 2. The base body 2 also carries a flexible coating 3. The resilient section 6 may be axially, transversely and torsionally resilient. The resilient section 6 may be located at the free end 5 of the handle 1, may be spiral-shaped, and may have at least one opening 7. The opening 7 may be rectilinear, rhombus-shaped, and may have angled sections. The coating 3 may penetrate through the opening 7, and may comprise polyamide or glass-fibre. The coating 3 may be injection-moulded onto the base body 2.

Description

Description Title

Hand-held power tool The invention relates to a hand-held power tool having at least one handle which can be fastened to the housing, according to the precharacterising clause of Claim 1.

Prior art

A hand-held power tool in the form of a percussion drill is known from EP 1 449 625 A2, on the housing of which a handle for holding and guiding the percussion drill is arranged, the handle being made of a plastics base body, to which a coating made of damping material is applied. In this way, shocks and impacts occurring during operation of the tool are to be effectively damped.

In the case of the percussion drill described in EP 1 449 625 A2, an auxiliary handle which is prescribed according to legal regulations for such percussion drills is provided. Both the main handle and the auxiliary handle have to withstand loads which arise when the percussion drill strikes the ground when falling from a defined height.

Disclosure of the invention

The object on which the invention is based is to design a hand-held power tool using simple constructional measures such that even high, impulse-like loads do not lead to material failure or breakage.

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

The hand-held power tool has a housing in which a drive motor for driving the tool is accommodated. The drive motor is preferably an electric drive motor, the rotational speed of which is usually transmitted to the tool via gearing.

On the housing there is arranged at least one handle, which is either formed in one piece with the housing or is to be fastened as a separate component to the housing. The handle comprises a base body which is produced, in particular, from a plastics material and carries a flexible coating element, via which oscillations and vibrations which arise during operation of the hand-held power tool are to be effectively damped.

In order to be able to absorb even relatively high, impulse-like loads without breakage of the handle, which loads arise, for example, when the hand-held power tool strikes the ground from a defined height, the base body of the handle is provided with a resilient section which is formed in one piece with the base body and has a resilient structure. The handle thus has, at least in a section, an improved resilience, even if the material of the handle possesses a high modulus of elasticity and thus possesses only a low resilience per Se. The resilient action is thus achieved by the special constructional design of the base body in the region of the resilient section. Owing to the design of the resilient section in one piece with the base body, it is not necessary to provide an additional, separately formed component which has to be connected to the base body in order to achieve the resilient action. A significant constructional simplification is thereby achieved.

The resilient section preferably extends over only a partial length of the base body. In principle, however, it is also possible to provide the base body with a resilient structure over its entire length.

The resilient section possesses an improved resilience, so that high loads, in particular impacts or shocks lead to a corresponding compression of the resilient section without damaging the material of the base body. The damping in the resilient section, which damping is composed of a constructional component and a component with material damping, causes oscillations in the resilient section to die rapidly.

In the embodiment in which the resilient section extends over only a partial length of the base body, the resilient section is preferably located in the region of a free end side of the handle. The handle in this embodiment is fastened by one of its end sides to the housing of the hand-held power tool or formed in one piece with the housing, while the opposite end side projects away from the housing and owing to its exposed position is at increased risk of having to absorb high forces in the event of an impact. Owing to the resilient structure, however, such forces can be absorbed by the handle without material damage.

In the embodiment with a connection of the handle via one end side to the housing of the hand-held power tool, the handle is, in particular, an auxiliary handle, the opposite end side of which projects freely. In principle, however, it is also possible to integrate the resilient section into the base body of a main handle on the hand-held power tool.

Preferably, the resilient section is located at a position of the handle with the greatest distance from the housing.

In the case of a bow-shaped handle which is connected by both end sides to the housing, it may therefore be expedient to place the resilient section at least approximately in the middle of the handle, which is furthest away from the housing of the hand-held power tool.

The resilient section can develop its resilient action in one or more directions. According to a preferred embodiment, it is provided that the resilient section is resilient at least in the direction of the longitudinal axis of the handle, with, additionally or alternatively, a resilient action transversely to the axial direction of the handle or a torsional resilient action also being possible.

Constructionally, the resilient action can be achieved by forming in the resilient section at least one opening which facilitates a compression of the resilient section, but at the same time ensures that when the external load is removed the resilient section springs back into its initial position again. Elastic behaviour is thus involved, where the spring constant is significantly lower in the region of the resilient section than in the other regions of the base body which are not designed as a resilient section and in which a resilient action occurs only on account of the modulus of elasticity of the material of the base body.

Expediently, the resilient section has a plurality of openings distributed both in the axial direction and in the circumferential direction on the resilient section. The openings can be closed upon themselves, having in this embodiment a continuous, closed inner wall bounding the opening. A variety of variants can be used as the geometrical shape for the openings, for example rectilinear, slot-shaped openings with a significantly greater length than width which extend, in particular, in the transverse direction, but optionally also in the longitudinal direction, or with a component both in the transverse and longitudinal direction. Moreover, openings which are of non-rectilinear configuration or composed of a plurality of rectilinear sections oriented at an angle to one another are possible. Furthermore, other geometric designs, for example in the shape of a rhombus, are also possible.

Furthermore, a spiral-shaped structure of the resilient section is also possible, one or more openings likewise having a spiral shape in this case. These openings are formed, with either open or closed design, in the region of the free end side of the handle.

The base body, which is expediently made of a material having a high modulus of elasticity, is advantageously provided with a flexible coating element which enables better and more pleasant holding on the one hand and possesses an oscillation-damping action on the other hand.

Expediently, the flexible coating element is introduced into the at least one opening contained in the resilient section of the base body. This takes place, for example, in such a way that the flexible coating element is injection-moulded onto the base body and penetrates into the at least one opening during application. In this way, an improved connection between the flexible coating element and the base body in the region of the resilient section is achieved.

According to a further expedient embodiment, the flexible coating element penetrates through the at least one opening and forms an undercut on the inside of the resilient section, such that a respective flexible coating element is arranged both on the outside and on the inside of the preferably hollow-cylindrical base body and these two sections of the coating element are connected to one another via a bridge. The inner section of the coating element can likewise be produced by means of injection-moulding-on of the coating element. In this way, the connection between the coating element and the base body in the region of the resilient section is further improved. In particular, the coating element cannot become detached from the base body even in the event of a deformation of the resilient section under high, external forces.

The material used for the base body may be polyamide, in particular PA6, the polyamide optionally having a glass fibre content GF35.

Further advantages and expedient embodiments can be gathered from the further claims, the description of the figures, and the drawings, in which: Fig. 1 shows a handle for a hand-held power tool, comprising a base body, designed as a resilient section in the region of one end side, and a flexible coating element in] ection-moulded onto the base body, Fig. 2 shows the handle without the coating element, Fig. 3 shows the coating element in an individual illustration, Fig. 4 shows a comparative illustration of the handle in the axially compressed state and in the initial state, Fig. 5 to Fig. 11 show the resilient section in the base body of the handle in a variety of variant embodiments, Fig. 12 shows a section through the wall of the base body in the region of the resilient section with an illustration of the flexible coating element on the inside and the outside of the base body, Fig. 13 shows the coating element in an enlarged individual illustration, the sections on the inside and the outside of the base body being connected to one another via an intermediate bridge.

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

In Fig. 1 there is illustrated a handle 1 for a hand-held power tool, in particular for an electric motor-driven percussion drill, the handle 1 being, for example, an auxiliary handle connected to the housing of the hand-held power tool. The handle 1 comprises a base body 2 made of a plastics material having a high modulus of elasticity, for example made of polyamide PA6 having a glass fibre content GF35. At one end side, the handle 1 is connected to the housing of the hand-held power tool via a suitable device.

In the exemplary embodiment, a collar 4 is provided at one end side on the base body 2, via which collar the handle 1 is connected to the housing of the hand-held power tool.

A resilient section 6 is designed in one piece with the base body 2 adjacently to the opposite, free end side 5, which resilient section owing to its special constructional form develops a resilient action significantly exceeding the material resilience of the base body. In the axial region between the end sides, the base body 2 is provided with an outer, flexible coating element 3 which is applied to the outside of the base body 2, in particular by means of injection moulding.

In Fig. 2 the handle 1 is illustrated with the base body 2 being without coating elements. The resilient section 6 adjacent to the free end side 5 extends over only an axial partial length of the base body 2, in the exemplary embodiment over no more than a quarter of the axial length of the base body 2. In the region of the resilient section 6, a plurality of openings 7 are formed in the base body 2, which openings are configured in the shape of slots extending in the circumferential direction and of limited length. Owing to the openings 7, the resilient section 6 possesses a resilient action in the direction of the longitudinal axis of the handle 1. Optionally, the resilient section 6 also possesses a resilient action in relation to flexion and torsion.

Outside the resilient section 6, the base body 2 has a lattice structure with a plurality of relatively small openings. This structure serves for securely and permanently connecting the coating element 3, applied by means of injection moulding, to the base body 2 in that material of the coating element 3 to be applied flows into the openings in the lattice structure. The lattice structure, however, possesses a high rigidity, so that in this section of the base body there is no improved resilient action over the material elasticity. The improved resilient action is only effective in the region of the resilient section 6 arranged adjacent to the free end side 5.

In the base body 2 there is formed a web which extends in the longitudinal direction, is situated in the region of the lattice structure and extends as far as the resilient section 6. The web 8 divides the handle region into two halves, each provided with a coating element 3. The two coating elements 3, which are in the shape of part of a circle, are illustrated in Fig. 3.

In Fig. 4 the handle 1 is illustrated in the axially compressed state and in the initial state. Under the effect of an external force F directed in the axial direction, the handle 1 can contract axially by the amount s owing to the axial elasticity in the resilient section 6. When the external force F is removed, the handle 1 expands axially to its original length again.

In Figs. 5 to 11, a variety of variant constructional embodiments of the resilient section 6 are illustrated.

According to Fig. 5, a plurality of openings 7 spaced apart axially from one another extend in each case in the circumferential direction.

In Fig. 6, a spiral-shaped structure of the resilient section 6 with a corresponding spiral shape of the opening 7 is illustrated.

According to Fig. 7 the openings 7 consist of three individual, rectilinear sections oriented at an angle to one another, in each case only a small angle existing between adjacent sections, so that the openings 7 extend overall in the axial direction. A plurality of openings 7 are arranged parallel to one another in a manner distributed over the circumference.

In Fig. 8 the openings 7 are designed in the shape of a rhombus, the axial extent of each opening 7 being greater than the extent in the circumferential direction. A plurality of rhombus-shaped openings 7 are formed in the resilient section 6 in a manner distributed over the circumference.

According to Fig. 9, a plurality of slot-shaped openings 7 are provided, each having a limited length in the circumferential direction. A plurality of openings 7 are provided both in the circumferential direction and in the axial direction.

In Fig. 10 the openings 7 have a V-shape, the vertex of the V-shape pointing in the axial direction and the free sides being directed to the free end side. A plurality of such openings are provided in each case in the circumferential direction.

According to Fig. 11 the openings 7 are each of rectilinear design, they extend with a component in the circumferential direction and a component in the axial direction. In this exemplary embodiment, too, a plurality of such openings are provided in the circumferential direction.

As can be gathered from Fig. 12, the coating element 3 has an outer section 9 on the outside of the base body 2 and also an inner section 10 on the inner side of the hollow-cylindrical base body 2. The outer section 9 and the inner section 10 of the coating element 3 are connected to one another via a bridge 11 of the coating element. The bridge 11 fills the openings formed in the lattice-shaped structure of the base body 2.

The connection of the outer section 9 and the inner section via the bridge 11 of the coating element 3 enables better adhesion and a more permanent connection of the coating element to the base body. As can be gathered from Fig. 13, a firm connection exists between the coating element 3 and the base body 2 even in the event of bending of the base body 2, for example in the event of a strong, impulse-like external force acting on the handle. The bending of the base body cannot lead to detachment of the coating element, since the inner section 10 of the coating element is accommodated, in the manner of an undercut, in a positive-locking manner inside the base body and the outer section 9 is firmly connected to the captive inner section via the bridge 11.