The invention relates to a motor-driven hand tool as per the preamble of claim 1, to a handgrip arrangement of a motor-driven hand tool of said type as per the preamble of claim 11, and to a coupling arrangement as per the preamble of claim 12.

Numerous motor-driven hand tools, in the operational state thereof, generate vibrations in a machine body, which vibrations are transmitted via a handgrip arrangement to the user of the machine. Such vibrations are generated for example in the case of percussive tools such as a percussion drill, a hammer drill, a chisel hammer or the like. As a result of the percussive and possibly simultaneously rotational engagement with the respective item to be drilled, vibrations are generated in the machine body, which vibrations are transmitted via the handgrip arrangement to the user of the machine.

The above vibrations may be considerably detrimental to health. One example of this is so-called "white finger syndrome" caused by damaged nerves and cells.

In the present case, the expression "vibrations" is to be understood very generally to mean mechanical vibrations which are perceptible via the human hand. Such vibrations may include linear and non-linear vibration components.

The known hand tool (EP 1 533 084 B1) on which the invention is based is in the form of a percussion drill. In the operating state, linear and non-linear vibrations of innumerable frequencies and directions are generated, said vibrations being transmitted differently to the machine operator depending on the handgrip arrangement.

In the case of the known hand tool, it has been identified that the machine-side vibrations include a dominant vibration component with a preferential direction which can be determined statistically. To prevent said vibration component "arriving" at the handgrip of the percussive tool, a damping arrangement composed of rubber or cellular foamed material is provided between the handgrip and the machine body of the hand tool. The mode of operation of the damping arrangement is based on the conversion of vibration energy into deformation energy.

Other approaches are based on the principle of a "vibration absorber" in which the disturbing vibrations excite an additional mass-spring oscillator, whereby vibration energy is extracted from the machine body (DE 20 2010 002 296 U1, DE 20 2010 002 297 U1).

The invention is based on the problem of configuring and refining the known hand tool such that the vibrations transmitted to the handgrip in the operational state are further reduced.

The above problem is solved in the case of a hand tool as per the preamble of claim 1 by means of the features of the characterizing part of claim 1.

What is essential is a special embodiment of the coupling arrangement for coupling the handgrip to the machine body, such that the handgrip is substantially isolated from the machine body with respect to machine-side vibrations.

According to the proposal, it has been identified that particularly good isolation of the handgrip with respect to the transmission of machine-side vibrations is ensured by virtue of the machine-side vibrations being conducted in a very specific manner via at least two coupling strands of the coupling arrangement. Here, it is in turn essential that the coupling strands are of different configuration such that the force effects which are channeled out at the handgrip side via the individual coupling strands and which are attributed to vibrations introduced at the machine side into the individual coupling strands at least partially cancel one another out.

The individual coupling strands of the coupling arrangement are preferably assigned different transmission functions, such that the resulting force effects at the handgrip correspondingly at least partially cancel one another out.

According to the invention, provision is made of a first coupling strand for the substantially in-phase transmission of machine-side vibrations and a second coupling strand for the substantially anti-phase transmission of machine-side vibrations. The anti-phase condition is realized in a particularly simple manner by means of a mass-spring oscillator.

"Substantially in-phase" and "substantially anti-phase" means that, owing to deformation and friction, an ideal in-phase condition and an ideal anti-phase condition will scarcely occur in practice. In this respect, these two expressions are to be interpreted broadly, and encompass angular deviations of up to +/- 10°.

The mass-spring oscillator is excited by the machine-side vibrations such that the force effects channeled out of the second coupling strand cancel out the force effects channeled out of the first coupling strand. This, in effect, constitutes an active reduction of vibrations at the handgrip. Of interest here is the fact that the mass-spring oscillator may also serve as a vibration absorber for the machine body.

The particularly preferred embodiments as claimed in claims 3 to 7 relate to variants for the configuration of the mass-spring oscillator. Particular emphasis should be given here, with regard to design, to the embodiment, in which the oscillator mass is simply connected between the two spring elements of the oscillator spring arrangement.

In the further preferred embodiment as claimed in claim 7, the coupling between the oscillator mass and the oscillator spring arrangement has, in any case in the operational state, a certain degree of play in a movement direction of the mass-spring oscillator. Of interest here is the fact that the play between the oscillator mass and the oscillator spring arrangement is generally associated with an additional phase offset between the machine-side vibration and the force effect channeled out of the second coupling strand. This is advantageous because, with the mass-spring oscillator alone, the desired precise anti-phase condition is scarcely attained in practice owing to damping influences.

According to a further teaching as per claim 11, which is of independent significance, a handgrip arrangement for a hand tool according to the proposal is claimed independently. Reference may be made to all statements suitable for describing the handgrip arrangement.

According to a further teaching as per claim 12, which is likewise of independent significance, a coupling arrangement as described above is claimed independently. What is essential here is the fact that the force effects which are channeled out at one end via the individual coupling strands and which are attributed to vibrations introduced at the other end into the individual coupling strands at least partially cancel one another out. Here, the expressions "at one end" and "at the other end" relate to the two sides of the coupling arrangement. In this regard, reference may be made to the statements regarding the two former teachings. All of the features and advantages explained with regard to the two former teachings may be applied to the latter teaching. Here, it must be taken into consideration that the coupling arrangement according to the proposal can be used in a wide variety of applications. For example, the coupling arrangement may be incorporated in a drivetrain of an electric machine or in the suspension arrangement of a washing machine.

The invention will be explained in more detail below on the basis of a drawing, which illustrates merely one exemplary embodiment. In the drawing:

figure 1

shows a hand tool according to the proposal in a perspective, partially disassembled overall view,

figure 2

shows a partially sectional detail view of the hand tool as per figure 1 in the region of the coupling arrangement for the handgrip, and

Figure 3

is a highly schematic illustration of the coupling arrangement for the handgrip as per figure 1a) in the region of one full excursion of the machine-side vibration and b) in the region of the opposite full excursion of the machine-side vibration.

The hand tool 1 illustrated in the drawing is preferably a percussion drill, as will be explained in more detail. This is to be understood merely as an example. The expression "motor-driven hand tool" also encompasses other tools, in particular percussive tools, machine tools and the like.

The hand tool 1 is equipped with a machine body 2 and with a handgrip arrangement 3, wherein the handgrip arrangement 3 has a handgrip 4 and a coupling arrangement 5 for coupling the handgrip 4 to the machine body 2.

The machine body 2 is the unit which provides the motor function of the hand tool 1. In the operational state, the machine body 2 vibrates, in this case primarily as a result of the percussive mechanism of the percussion drill and as a result of the cutting engagement between the respective drilling tool and the material to be drilled. The expression "machine body" is to be understood in a broad sense and encompasses all components linked in the broadest sense to the motor function of the hand tool 1. The machine body 2 thus has a motor, gearing, percussive mechanism, drill chuck, housing parts, electrical or electronic components, switches or the like.

In the illustrated and, in this respect, preferred exemplary embodiment, the handgrip 4 is of substantially U-shaped configuration and is coupled to the machine body 2 via an upper coupling arrangement 5 and a lower coupling arrangement 5a. The lower coupling arrangement 5a provides a pivotable mounting of the handgrip 4 on the machine body 2. The lower coupling arrangement 5a is assigned elastic damping rings 6 which generate a first vibration damping action. The focus will hereinafter be on the upper coupling arrangement 5, via which the major part of the actuation forces introduced by the user via the handgrip 4 is transmitted into the machine body 2. Figure 2 shows the construction of the upper coupling arrangement 5 according to the proposal.

A central element of the coupling arrangement 5 is a machine-side coupling plate 7 which is fastened at one end to the machine body 2 and which, at the other end, has latching hooks 8 which engage into the handgrip 4 in the assembled state illustrated in figure 2. The basic design of said latching means is described in the European patent EP 1 533 084 B1, which belongs to the applicant and the content of which is in this respect incorporated in the subject matter of the present application.

What is essential for the latching means is the fact that a tensile load on the handgrip 4 counter to its actuation direction 21, downward and to the right in figure 2, has the effect that the latching hooks 8 come into blocking engagement, by way of a detent stop 9, with the handgrip 4. Loading of the handgrip 4 in the actuation direction 21, to the left and upward in figure 2, has the effect that the handgrip 4 comes into blocking abutment with a counterpart stop 10. The upper coupling arrangement 5 thus permits a certain adjustment of the handgrip 4, wherein the lower coupling arrangement 5a ensures that said adjustment is a pivoting adjustment.

It need not be explained any further that the machine body 2 of the hand tool 1, which in this case and preferably is in the form of a percussion drill, vibrates in the operational state. With the solution according to the proposal, it is possible, as explained above, to attain good isolation of the handgrip 4 with respect to said vibrations. For this purpose, the coupling arrangement 5 has at least two parallel coupling strands 11, 12, in this case and preferably exactly two parallel coupling strands 11, 12, which are of different configuration in the illustrated and, in this respect, preferred exemplary embodiment.

In the illustrated and, in this respect, preferred exemplary embodiment, the two coupling strands 11, 12 are realized independently of one another. This means that the two coupling strands 11, 12 do not influence one another aside from the in this case common coupling points.

In a way which will be explained, the two coupling strands 11, 12 are realized on the basis of springs, and provide a certain transmission of force between the machine body 2 and the handgrip 4 at all times. The two coupling strands 11, 12 are now of different configuration such that the force effects which are channeled out at the handgrip side via the individual coupling strands 11, 12 and which are attributed to vibrations introduced at the machine side into the individual coupling strands 11, 12 at least partially cancel one another out.

Of interest in the exemplary embodiment illustrated is firstly the fact that all machine-side vibrations are introduced into the coupling arrangement 5 via an end region 13 of the coupling plate 7, and are channeled out of the coupling arrangement 5 via a sleeve 14. Of interest here is the fact that both the end region of the coupling plate 13 and also the sleeve 14 are formed in each case in one piece. This means that the machine-side vibrations are initially "split up" between the individual coupling strands 11, 12 of the coupling arrangement 5 and are subsequently merged again at the sleeve 14. Owing to the parallel arrangement of the coupling strands 11, 12, this results in a superposition, at the sleeve 14, of the force effects attributed to the machine-side vibrations. With the configuration according to the proposal, this has the result that the force effects attributed to vibrations introduced at the machine side into the individual coupling strands 11, 12 at least partially cancel one another out.

In the illustrated and, in this respect, preferred exemplary embodiment, the coupling arrangement 5 is suitable for the isolation of a one-dimensional vibration. This is also appropriate because the machine-side vibrations in this case include, in a manner inherent to the system, a dominant vibration component with a preferential frequency which, in a particularly preferred configuration, constitutes a substantially harmonic vibration. In the case of a percussion drill, said preferential vibration is generated by the percussive mechanism, wherein the preferential frequency is in this case and preferably in the range between approximately 10 Hz and approximately 100 Hz, and is in particular approximately 50 Hz. The preferential vibration also has a preferential direction 1a, which in the case of a percussion drill, is defined by the percussion direction. In a way which will be explained, the coupling arrangement 5 is aligned with the preferential direction 1a of the hand tool 1.

Numerous advantageous variants are conceivable for the embodiment of the two coupling strands 11, 12. The structural design of the two coupling strands can be seen from a juxtaposition of figures 2 and 3.

The coupling strand 11 illustrated on the left in figure 2 and at the bottom in each case in figure 3 is equipped with a transmission element 15 for the substantially in-phase transmission of machine-side vibrations, said transmission element being coupled here at one side via the coupling plate 7 to the machine body 2 and at the other side via the sleeve 14 to the handgrip 4, wherein it is also possible in principle for merely a facility for coupling to be provided. The transmission element 15 is preferably a spring element, in particular a helical compression spring. In this respect, the embodiment of said coupling strand 11 corresponds to a conventional design.

Of particular interest is the design of the other coupling strand 12, illustrated on the right in figure 2 and at the top in each case in figure 3. Said coupling strand 12 provides a mass-spring oscillator 16 which can be excited by a machine-side vibration and which, in the excited state, generates a handgrip-side force effect which is phase-offset and substantially in anti-phase, with respect to the machine-side vibration.

With suitable configuration, it is then the case that the first coupling strand 11 has a transmission element 15, in this case and preferably a spring element 15, for substantially in-phase transmission of machine-side vibrations and that the second coupling strand 12 has the mass-spring oscillator 16 for the phase-offset and substantially anti-phase transmission of machine-side vibration. As a result of the fact that the resultant force effects introduced via the individual coupling strands 11, 12 are phase-offset and even substantially in anti-phase, said force effects at least partially cancel one another out. This applies in particular to vibrations at a preferential frequency, as described above, for which the coupling arrangement 5 is to be correspondingly configured.

In a particularly preferred embodiment, it is the case that the mass-spring oscillator 16 is at least slightly detuned, in particular toward lower frequencies, with respect to the above-described preferential frequency of the machine-side vibrations. With suitable configuration, this has the effect that a machine-side vibration with the preferential frequency is converted by means of the mass-spring oscillator 16 into a substantially anti-phase handgrip-side force effect. Precise tuning of the mass-spring oscillator 16 to the preferential frequency of the machine-side vibrations is expressly not desired because, in this way, a phase offset of only 90°, and not the desired 180° (anti-phase condition), is attainable.

The mass-spring oscillator 16 is equipped with an oscillator spring arrangement 17 which is coupled to the machine body 2 and which is in this case and preferably coupled to the handgrip 4. Furthermore, the mass-spring oscillator 16 has an oscillator mass arrangement 18 which is coupled to the oscillator spring arrangement 17. In the exemplary embodiment illustrated, coupling of the oscillator mass arrangement 18 to the transmission element 15 is not provided but is conceivable. Numerous advantageous variants are conceivable for the embodiments of the oscillator spring arrangement 17 and of the oscillator mass arrangement 18.

The mode of operation of the coupling arrangement 5 according to the proposal will be explained below on the basis of the illustration in figure 3.

In figure 3, it is assumed that a user actuation in an actuation direction 21 and a machine-side vibration with the preferential frequency discussed above are present, wherein figures 3a) and 3b) show the two opposite full excursions of the machine-side vibration. In both figures, the mass-spring oscillator 16 is in the excited state. Dashed lines indicate the positions of the full excursions not presently assumed.

It can be seen from the illustrations of figures 3a) and 3b) firstly that the vibration is conducted from the coupling plate 7 to the sleeve 14 via the transmission element 15, in this case the spring element 15. A substantially in-phase transmission of the vibration is to be expected here.

A different situation is encountered in the case of the second coupling strand 12 which is equipped with the mass-spring oscillator 16. While the coupling plate 7, that is to say the machine body 2, is situated at the right-hand full excursion in figure 3, the oscillator mass arrangement 18 reaches its left-hand full excursion in figure 3.

The situation encountered after one half of the period length of the vibration is shown in figure 3b). Here, the coupling plate 7, that is to say the machine body 2, is situated at the left-hand full excursion in figure 3, while the oscillator mass arrangement 18 reaches its right-hand full excursion in figure 3.

It can thus be seen from a juxtaposition of figures 3a) and 3b) that the machine-side vibration is converted into an anti-phase vibration of the oscillator mass arrangement 18. By virtue of the fact that the oscillator mass arrangement 18 is coupled to the sleeve 14 via the oscillator spring arrangement 17, the anti-phase condition has the effect that the resultant handgrip-side force effects cancel one another out.

In the illustrated and, in this respect, preferred exemplary embodiment, it must be taken into consideration that the coupling arrangement 5 provides a transmission of force between the machine body 2 and the handgrip 4 at all times. Here, and preferably, this takes place via the transmission element 15, which is in the form of a helical compression spring, and via the oscillator spring arrangement 17, which in this case and preferably is likewise in the form of a helical compression spring arrangement.

According to the proposal the oscillator spring arrangement 17 of the mass-spring oscillator 16 has two spring elements 19, 20, specifically a first spring element 19 coupled to the machine body 2, in this case to the coupling plate 7, and a second spring element 20 coupled to the handgrip 4, in this case to the sleeve 14, wherein, the two spring elements 19, 20 are connected in series. The oscillator mass arrangement 18 is, as illustrated in figure 3, coupled to the oscillator spring arrangement 17 as a whole at the connection point between the two spring elements 19, 20. For this purpose, the oscillator mass arrangement 18 has, in this case and preferably, a fastening web 18a which extends between the two spring elements 19, 20.

In an embodiment which can be realized in a particularly simple manner, the two spring elements 19, 20 of the mass-spring oscillator 16 are sections of a single spring element. It is however also conceivable for more than two spring elements 19, 20 to be assigned to the oscillator spring arrangement 17.

A particularly compact embodiment of the coupling arrangement 5 is attained in that, in this case and preferably, the machine-side spring element 19 assigned to the oscillator mass arrangement 18 is aligned with regard to its spring action, and in this case also with regard to its shaping, with the handgrip-side spring element 20 assigned to the oscillator mass arrangement 18. The two spring elements 19, 20 in the form of helical compression springs are thus arranged coaxially with respect one another. Furthermore, it can be seen from a juxtaposition of figures 2 and 3 that the spring elements 19, 20 of the oscillator spring arrangement 17 are aligned parallel to the spring element 15.

Other arrangements and embodiments of the coupling strands 11, 12 are possible. In this connection, one particularly advantageous embodiment would be for the oscillator spring arrangement 17 to be configured coaxially with respect to the transmission element 15, in particular for the spring elements 19, 20 in the form of helical compression springs to be configured coaxially with respect to the transmission element 15 in the form of a helical compression spring. It would thus be ensured that the connection points of the two coupling strands 11, 12 are situated particularly close to one another, which would simplify the desired cancelling-out of the channeled-out force effects.

In the illustrated and, in this respect, preferred exemplary embodiment, the oscillator mass arrangement 18 is coupled to the oscillator spring arrangement 17 without play. It may however also be advantageous for the coupling between the oscillator mass arrangement 18 and the oscillator spring arrangement 17 to have, in any case in the operational state, a degree of play in a movement direction of the mass-spring oscillator 16. Such a degree of play, the extent of which is considerably less than 1 mm, can, as explained above, assist in generating a substantially anti-phase handgrip-side force effect.

For the desired cancelling-out of the force effects channeled out via the individual coupling strands 11, 12, it is advantageous for the coupling points of the individual coupling strands 11, 12 to the machine body 2 and/or to the handgrip 4 to be situated adjacent one another as illustrated in figure 2, or to even be identical. As an alternative or additional measure, which is provided in the embodiment as per figure 2, the coupling points of the individual coupling strands 11, 12 to the machine body 2 and to the handgrip 4 are arranged on a respective machine-side and handgrip-side coupling part 7, 14 which is common to the coupling strands 11, 12, in this case and preferably on the end region 13 of the coupling plate 7 and on the sleeve 14 respectively.

In the present case, the appropriate alignment of the coupling arrangement 5 with regard to the coupling forces thereof is of very great significance. Here, and preferably, it is provided that the coupling arrangement 5 is aligned, with regard to its coupling forces, substantially with the preferential direction 1a of the hand tool 1.

If the hand tool 1 is in the form of a percussion drill with a drilling tool, the preferential direction 1a of the hand tool corresponds, as already indicated, to the percussion direction of the hand tool 1. In a particularly preferred embodiment, the line of force action of the coupling forces lies in the direct vicinity of the line of force action of the percussion mechanism of the percussion drill, that is to say substantially in the direct vicinity of the geometric axis of the respective drilling tool. Accordingly, it is also appropriate for the vibration direction of the mass-spring oscillator 16 to correspond to the preferential direction 1a of the hand tool 1.

Figure 2 shows that the handgrip 4 is preloaded counter to the user actuation direction 21 by means of the coupling arrangement 5, in particular by means of the spring elements 15, 19, 20, and can be deflected in the user actuation direction 21. The handgrip 4 is thus, in the non-actuated state, preloaded against a machine-side stop, in this case against the detent stop 9 discussed above, wherein the handgrip 4, in the event of a predetermined user-imparted actuation force being exceeded, abuts against a further machine-side stop, in this case against the counterpart stop 10 discussed above.

The above statements show that the two coupling strands 11, 12 may be of relatively rigid configuration, without excessive vibrations occurring at the handgrip 4. The reason for this is the fact that the force effects channeled out via the individual coupling strands 11, 12 cancel one another out. It can thus be ensured that the handgrip 4 comes into contact with the counterpart stop 10 only in the event of an exceptional actuation force. This is advantageous because the contact with the counterpart stop 10 results in a direct transmission of the machine-side vibrations to the handgrip 4.

It is also pointed out that the solution according to the proposal serves primarily as an isolator for the handgrip 4 with regard to the transmission of machine-side vibrations. However, it must also be emphasized that, in an advantageous manner, the mass-spring oscillator 16 may in principle also serve as a vibration absorber because it extracts from the machine body 2 a part of the vibration energy thereof.

According to a further teaching which is of independent significance, the handgrip arrangement 3 for a hand tool 1 according to the proposal is claimed independently. Reference may be made to all statements regarding the hand tool according to the proposal which are suitable for describing the handgrip arrangement 3.

According to a further teaching which is likewise of independent significance, the coupling arrangement 5 with the two coupling strands 11, 12 is claimed independently. It has already been pointed out that the coupling arrangement 5 according to the proposal may be used in a wide variety of applications. Furthermore, reference may be made to the statements regarding the two former teachings. All of the features and advantages explained with regard to the two former teachings may be applied to the latter teaching.