GB2478187A

GB2478187A - External damper for power tool

Info

Publication number: GB2478187A
Application number: GB1102999A
Authority: GB
Inventors: Elmar Buckenmaier; Michael Weiss
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2010-02-23
Filing date: 2011-02-21
Publication date: 2011-08-31
Also published as: CN102161196A; DE102010002262A1; GB201102999D0

Abstract

An oscillation damper 1 comprises an equalising mass 3, and is reversibly attachable to the outside of an electric power tool housing (22, Fig 2). The equalising mass 3 provides a counter-oscillation that counteracts an oscillation of the housing (22, Fig 2) of an electric tool (2, Fig 2). The damper 1 may comprising fastening means 41, 411, 42, which may replace the tool fastening means (21, Fig 3). The equalising mass 3 may be fastened to an elasticity 5, and may be guided by guide means 6. The equalising mass 3 and/or the elasticity 5 may be fastened in an exchangeable manner within an interior space 13 of the damper housing 12.

Description

Description Title

External damper

Prior art

The present invention relates to an oscillation damper, comprising an equalizing mass, which is provided to exert a counter-oscillation that counteracts a housing oscillation of an electric tool, and to an electric tool having an oscillation damper according to the invention.

As a result of the entry into force of the legal requirement that, in the use of electric tools, the daily allowable workload be linked to the physical load acting upon the operator, the topic of vibration is becoming increasingly important in the case of electric tools, particularly in the case of hammer drills and percussion hammers.

In the case of hammer-drilling and chiselling by means of a hammer, a very large physical load upon the operator emanates from the housing oscillation produced by the percussion mechanism. Particularly in the case of large hammer drills and percussion hammers, the vibrations are very pronounced, owing to the high percussion energy.

Without further measures, therefore, the allowed working time for operators of such machines is reduced considerably. However, even in the case of smaller electric tools intended, for example, for private use, the operating comfort can be improved considerably by reducing the housing oscillation.

A housing oscillation that generates vibration has a multiplicity of frequency components, which are caused by differing vibration sources. Possible causes include, amongst others, the play between the individual components, non-linear elasticity characteristics, non-linear impulse actions, only approximately harmonic reaction forces from a percussion mechanism, impulse and recoil actions of a percussion chain, or unequalized mass forces of the drive.

Frequently, however, the main frequency is caused in a determinant manner by a single vibration source. Thus, in the case of electric tools having a percussion mechanism, for example, the main frequency is derived substantially from the periodic acceleration of the striker. In the case of such electric tools, a very good reduction of the housing oscillation is already achieved in that a vibration reduction system counteracts the determinant vibration source as exactly as possible.

In practice, the generation of counterforces that counteract the housing vibrations is effected, for example, through the use of dampers or counter-oscillators. A damper is a spring-mass system having a fixed resonant frequency, by means of which a significant reduction in oscillation can be achieved in a range close to the resonant frequency. In the case of the counter-oscillator, an equalizing mass is coupled to the drive of the electric tool and driven in such a way that the reaction force resulting from the drive of the counter-oscillator counteracts the vibration source as well as possible.

Solely because of the coupling of the counter-oscillator to the drive of the electric tool, however, even in the case of dampers, in order that the force flow path between the vibration source and the oscillation reduction system is kept short and a high efficiency is achieved as a result, the embodiments known hitherto have in common the fact that they are built into the electric tool.

Disclosure of the invention

The object of the invention is to create an oscillation reduction system for an already produced electric tool, which system can be retrofitted and nevertheless allows an effective reduction of the housing oscillation of the electric tool, in particular for differing operating modes of the electric tool.

The object is achieved with an oscillation damper comprising an equalizing mass, which is provided to exert a counter-oscillation that counteracts a housing oscillation of a housing of an electric tool, the oscillation damper being reversibly attachable to the outside of the housing of the electric tool. Since the oscillation damper can be attached to the outside of the housing, it can be attached to an electric tool that has already been produced, without any resource-demanding modification of the inside of the electric tool and/or without any alteration of the functioning of the electric tool. Preferably, the electric tool can also be retrofitted with the oscillation damper according to the invention, without any alteration of the housing of the electric tool. This applies both to an electric tool for professional application and to a hand-held power tool for private use, such that, in both cases, it is possible for the housing oscillation of the already provided electric tool to be reduced retroactively in an effective manner through attachment of the oscillation damper according to the invention.

The oscillation damper is preferably provided as close as possible to a determinant vibration source, such that the force flow path between the vibration source and the oscillation reduction system is short. Likewise preferably, it is provided such that it does not impair the handling of the electric tool, particularly during its operation.

In a preferred embodiment, the oscillation damper has an outer contour, delimiting the same, which corresponds at least partially to a housing contour of the housing that delimits the electric tool, such that the oscillation damper, when in a state of having been attached to the electric tool, bears at least partially on the latter.

The oscillation damper preferably comprises at least one fastening means, by means of which it can be fastened to the electric tool. In a preferred embodiment, the fastening means is a clamping means, by means of which the oscillation damper can be wedged on the housing of the electric tool. Likewise preferably, a plurality of fastening means, in particular differing fastening means, are provided. In a further preferred embodiment, the fastening means is an adhesive, a screw or a rivet, a snap-on fastener and/or a hook-and-loop fastener. Likewise preferably, depending on the respective fastening means, a counter-fastening means, which corresponds to the fastening means and with which the fastening means acts in conjunction, is provided, if necessary, on the electric tool. The fastening means allows simple and rapid attaching of the oscillation damper, in particular by means of a conventional tool or even without a tool. Preferably, the oscillation damper, after having been attached to the electric tool, is fixedly connected to the latter, enabling the forces to be transferred satisfactorily. Persons skilled in the art understand that it is also possible to use other fastening means, by means of which the oscillation damper can be fixedly connected to the electric tool.

Preferably, the counter-fastening means of the tool that acts in conjunction with the fastening means has a further technical function. For example, the counter-fastening means has the further function of a connecting means for two housing parts of the electric tool. Particularly preferably, the counter-fastening means is a receiving boss.

In a preferred embodiment, the fastening means replaces an electric-tool fastening means, for example a fastening means for connecting a first housing part of the electric tool to a second housing part of the electric tool, in particular a screw or a rivet, and/or an electric-tool fastening means can be used simultaneously for fastening the oscillation damper to the electric tool.

Preferably, the oscillation damper comprises a damper housing, the equalizing mass being arranged in an interior space that is delimited, at least partially, by the damper housing. Likewise preferably, the housing of the electric tool delimits the interior space, at least partially.

The equalizing mass is preferably fastened so as to be elastically movable in the interior space, in particular by means of a spring. The elastic fastening of the equalizing mass in the interior space allows a counter-oscillation of the equalizing mass. In a preferred embodiment, the natural frequency of the oscillation damper is provided so as to be alterable, in particular through alteration of the weight of the equalizing mass and/or of the spring characteristic and/or of the spring constant and/or of the spring bias, for example through use of a non-linear spring characteristic. Likewise preferably, the spring is provided so as to be exchangeable and/or a plurality of equalizing masses and/or a plurality of springs are provided in the oscillation damper, in particular so as to be exchangeable. As a result, the counter-oscillation of the oscillation damper can be adapted, in particular in dependence on the operating mode of the electric tool.

Also preferably, a guide means is provided, by means of which the equalizing mass is guided. The equalizing mass is preferably provided in the oscillation damper in such a way that it oscillates to and fro in an oscillation direction. Also preferably, the oscillation direction of the counter-oscillation of the equalizing mass is provided so as to be alterable, for example in that the alignment of the equalizing mass can be turned round.

Preferably, there are provided, alternatively or additionally, a plurality of oscillation dampers, whose natural frequency and/or oscillation direction differ, in particular for the purpose of adaptation to differing operating modes. Moreover, the adaptation of the natural frequency and/or of the oscillation direction of the oscillation damper, or the replacement of the oscillation damper by an oscillation damper of a different natural frequency and/or oscillation direction, makes it possible to equalize also, if necessary, a housing oscillation caused by further vibration sources.

Also preferably, the equalizing mass extends substantially flatly, such that it occupies little space, and the oscillation damper can made so as to be small, in particular very flat.

The object is further achieved by an electric tool having an oscillation damper according to the invention. The electric tool can preferably be retrofitted with the oscillation damper, without structural alterations being made on the tool, in particular on the housing.

The invention is described in the following with reference to figures. The figures are merely exemplary, and do not limit the general concept of the invention.

Fig. 1 shows an oscillation damper according to the invention, Fig. 2 shows, in a perspective view, a portion from an electric tool having the oscillation damper of Fig. 1 attached to the housing of the electric tool, and Fig. 3 shows, in a side view, a portion from the electric tool having the oscillation damper of Fig. 1 attached to the housing of the electric tool.

Fig. 1 shows an oscillation damper 1 according to the invention. Provided in an interior space 13 constituted by a damper housing 12 of the oscillation damper 1 there is an equalizing mass 3, which is fastened in the interior space 13 by means of two elasticities 5. The elasticities 5 are realized, for example, as plastic bodies or as springs.

They provide for a counter-oscillation of the equalizing mass 3 that counteracts a housing oscillation of an electric tool 2 (see Fig. 2) . The equalizing mass 3 is guided along two guide means 6, which are realized here as guide bars. In the present embodiment, the guide bars 6 are routed through lead-throughs 31 in the equalizing mass 3. The elasticities 5 and the guide means 6 are arranged parallel to an oscillation direction in which the equalizing mass 3 oscillates, the oscillation direction being indicated here by an arrow 7.

The damper housing 12 has an outer contour 11 that corresponds to a housing contour 221 of a housing 22 of the electric tool 2 (see Fig. 2), such that the oscillation damper 1, when in a state A of having been attached to the electric tool 2 (see Fig. 2), bears on the latter through its damper housing 12. Moreover, the damper housing 12 has a housing cover 121, which, here, is fastened to the damper housing 12 by means of screws 122. The fastening means 6 and the elasticities 5 are mounted in recesses 123 of the damper housing 12, such that, after removal of the housing cover 121, they can be taken out of the interior space 13 together with the equalizing mass 3. The equalizing mass 3, the elasticities 5 and/or the guide means 6 are thus provided in an exchangeable manner in the interior space 13 of the oscillation damper 1.

As fastening means 41, 42 of the oscillation damper 1 on the housing 22 of the electric tool 2, the oscillation damper 1 represented here has two snap-on fasteners 42, which are integrally formed onto the damper housing 12.

Moreover, it has two clamping means 41, likewise integrally formed onto the damper housing 12. The oscillation damper 1 represented here is substantially rectangular in form, and the fastening means 41, 42 are each arranged at the corners 124 of the oscillation damper 1 and enable the oscillation damper 1 to be fixedly connected to the housing 22 of the electric tool 2.

The clamping means 41 are realized here as bosses, and have a slit 412, such that they can be splayed by means of a splaying means 411, in particular a wedge or a screw.

Figure 2 shows, in a perspective view, a portion from an electric tool 2 having the oscillation damper 1 of Fig. 1.

The oscillation damper 1 is arranged on the outside of the electric tool 2.

The damper housing 12 has an outer contour 11 that corresponds to the housing contour 221 of the electric tool 2. Here, the housing 22 of the electric tool 2 has a convex curvature, and the damper housing 12 has a concave curvature, which correspond with one another in such a way that the damper housing 12 bears on the housing 22 of the electric tool 2.

-10 -The housing 22 of the electric tool 2 has a first housing part 24 and a second housing part 25. Two first receiving bosses 211 are formed onto the first housing part 24, and two second receiving bosses 212 are formed onto the second housing part 25, a first receiving boss 211 being respectively adjacent to a second receiving boss 212. The first housing part 24 can be connected to the second housing part 25 by means of two electric-tool fastening means 21, namely, two screws (see Fig. 3), in that the first receiving boss 211 is screwed, respectively, onto the adjacent second receiving boss 212.

The oscillation damper 1 can be fastened to the electric tool 2 in that the two snap-on fasteners 42 are pushed or snapped onto the second receiving bosses 212 in such a way that a snap-on fastener 42 bears, respectively, on a second receiving boss 212, and the oscillation damper 1 is then displaced in such a way that a clamping means 41 is introduced, respectively, into a first receiving boss 211, or the clamping means 41 are first introduced into the first receiving bosses 211 and the snap-on fasteners 42 are then snapped onto the second receiving bosses 212. The clamping means 41 are then splayed by means of a splaying means 411, here a screw, such that they become wedged on an inner wall 2111 (see Fig. 3) of the first receiving boss 211 and can no longer be displaced.

Here, therefore, the first receiving bosses 211 are used as counter-fastening means for the clamping means 41, while the second receiving bosses 212 are used here as counter-fastening means for the snap-on fasteners 42.

-11 -Fig. 3 shows, in a side view, a portion from the electric tool 2 having the oscillation damper 1 of Fig. 1. Fig. 3 shows, respectively, one of the fastening means 41, 42 and, respectively, one of the counter-fastening means 211, 212, in a sectional representation.

It can thus be seen that the screw, which is used as an electric-tool fastening means 21 and which connects the first housing part 24 of the electric tool 2 to the second housing part 25 of the electric tool 2, need not be removed for the purpose of attaching the oscillation damper 1.

Rather, the oscillation damper 1 can be attached to the finished electric tool 2 without alteration of the housing 22, in that the clamping means 41 are arranged in a receiving region 20 of the first receiving boss 211 that remains free after the first housing part 24 has been connected to the second housing part 25.

After the oscillation damper 1 has been put in place, therefore, in order for the oscillation damper 1 to be fixedly connected to the electric tool 2 it is necessary only to splay the clamping means 41 by means of the two screws 411 used as splaying means. The splaying causes the clamping means 41 to become wedged on the inner wall 2111 of the first receiving boss 211, such that the oscillation damper 1 is fixedly connected to the electric tool 2. The oscillation damper 1 can therefore be attached to the electric tool 2 in a very rapid and easily reversible manner.