EP1646480B1 - Working tool with damped handle - Google Patents

Abstract

The invention relates to a hand-held working tool, comprising a first unit, powered by a vibration on operation and a second unit (2) which may be displaced relative to the first unit (1). A vibration isolation device (3) is arranged between the first and second unit, comprising an actuator (4), for generation of a control force, by means of which the operational force acting in the working direction (A) between the first (1) and the second unit (2) may be at least partly compensated. The actuator (4) is pneumatically operated and comprises an air spring (11) for vibration isolation. A working piston (7) in an air spring percussion device on the working tool serves to supply compressed air for the air spring (11). Alternatively, the compressed air can be supplied by the oscillating relative movement between the first unit (1) and the second unit (2).

Description

The invention relates to a hand-held implement according to the preamble of claim 1 and 2.

Hand-held implements, in particular drills and / or impact hammers (hereinafter referred to as hammer), rammers or the like. Often, a vibration exciting device for generating a vibration required to achieve the desired working effect. In drilling and / or impact hammers this is usually a striking mechanism, with which a striking effect against a tool is achieved. However, the strong vibration should act as little as possible on the operator holding the implement with his hands.

The tools therefore usually have a device with which vibrations, shocks or shocks can be generated. Such devices are referred to collectively below as "vibration exciter".

Many of these implements are hand-guided so that appropriate handles are provided by which an operator can grasp and hold the implement. The vibrations or shock generated in the vibrator of the implement for the performance of the technical function are transmitted to the operator via the handles, which is not only unpleasant, but also harmful to health in the long run. Accordingly, it is desirable to keep the vibrations of the handle as low as possible.

For this purpose, it is known to provide a vibration decoupling device between the handle and the vibration exciter. Usually, such a vibration decoupling device is realized with the aid of passive spring-damper elements. For example, between the handle and the vibrator rubber elements can be used to achieve a certain vibration decoupling. Due to the limited space, the spring elements can only have small spring travel, which limits their suitability for vibration isolation of the handle.

On the other hand, the spring elements can not be made too soft to allow precise guidance of the implement by the operator.

Hammers are known which have anti-vibration systems with passive spring elements, in particular rubber buffers. In order to achieve a good vibration isolation under different conditions of use, low spring stiffnesses and long spring travel are to be striven for in principle, which, however, are disadvantageous for installation space and handling of the working device.

It should be noted in particular that z. B. with hammers with strongly changing Andrückkräften is to be expected. These result, on the one hand, from different reaction forces or recoil forces due to different types of tools or inhomogeneous materials to be processed. On the other hand, the Andrückkräfte change due to different acting weight forces, which are due to the machining direction (down, horizontal, upward) and different tool weights.

It is often problematic to develop suitable spring elements that take into account all conceivable operating conditions, in particular the entire possible range of pressure forces.

In the DE 196 46 622 A1 a work tool that can be guided on a handle is described. The handle is actively damped by an actively controlled or regulated compensation member, wherein the compensation member generates a compensating force or movement in response to the transferable to him, resulting in the implement vibration. By this compensation effect, it is possible to largely compensate for the resulting vibration in the implement, so that the compensation member downstream of the handle is substantially free of vibration. However, the structural and control engineering effort for such a device is not insignificant.

In the DE 101 00 378 A1 a hand tool machine is described, which has a vibration exciter and one between the vibration exciter and having a handle arranged Schwingungstsollereinrichtung. The Schwingungstsoliereinrichtung has an actuator, via which the operating force with a force is at least partially compensated. It is the. Stellkraft largely independent of the actually existing, to be isolated vibration. The vibration itself is compensated by a parallel to the actuator arranged spring element with relatively soft characteristic. In the described working device, the actuator itself thus does not absorb any vibration damping function. Rather, it ensures that the working position of the spring element, ie its bias, always, is within a predetermined range, so that the spring element can compensate for the applied vibration. The actuating force of the actuator is automatically adjusted automatically by the operator as a function of the external operating force, in particular the pressing force. In this respect, one can speak of a "semi-active" vibration isolation. The actuator can be made electrically, electromagnetically or hydraulically, which requires considerable construction effort.

From the DE 101 58 266 A1 a device for vibration damping of a handle of a machine tool is known in which the handle is connected via at least one spring to the housing of the machine tool. With the aid of an actuator acting on the spring, it is possible to keep the distance between the handle and the housing of the machine tool virtually constant, independently of the actuating force exerted on the handle. The actuator has a plunger, which is displaceable by means of an electromagnetic, hydraulic or pneumatic drive.

In the EP 0 206 981 A2 a hand tool with a vibration generating drive device is described. On a housing receiving the drive means, a parallel to the main axis of oscillation between two stops limited displaceable handle is provided. The arranged in the feed direction of the hand tool stop of the handle is designed as an electromagnet which exerts a constant, controllable force both on the handle and on the housing, regardless of the position of the handle relative to the housing. This should be a vibration isolation can be achieved.

The invention has for its object to design a hand-held implement with semi-active vibration isolation such that the Construction costs are minimized. Furthermore, the invention has for its object to provide a device for vibration isolation of a handle in a working device, with a reliable and simple vibration decoupling of the handle, even in different operating conditions, is guaranteed.

According to the invention the object is achieved by a hand-held implement according to claim 1 or claim 2 solved. Advantageous developments of the invention are defined in the dependent claims.

A hand-held implement has a Schwingungsisoliereinrichtung between a vibration generator comprising a first unit and a relative to the first unit in at least one working direction movable second unit. Part of the Schwingungsisoliereinrichtung is an actuator for generating a force, with an acting in the working direction between the first and the second unit operating force, for. B. a pressing force, at least partially compensated. The actuator is operated pneumatically.

It has been found that a pneumatically operated actuator compared to those in the DE 101 00 378 A1 described drive principles for actuators has significant advantages. On the one hand, no additional medium (eg hydraulic oil) is required. Air is available as a medium at any time in sufficient quantity and can be processed without special sealing effort. Possible leakage losses are not critical. On the other hand, the regulatory burden in relation to z. As electric or electromagnetic actuators significantly lower. In addition, the energy consumption for electrical actuators is comparatively high, since the actuators must respond quickly, which is only possible by a corresponding available power.

The handle air spring is so-called, in order to distinguish them conceptually from a particularly in an air spring impact mechanism of a hammer forming, but not further interest here air spring. The handle air spring is variable by different air filling and thus adjustable. In particular, the pressure in the air spring and / or the air volume can be changed. The actuator thus essentially forms a pneumatic spring with adjusting device. In the handle air spring whose filling is variable with compressed air, so that accordingly, the spring characteristics of the handle air spring can be changed.

An air spring has inherently a progressive spring characteristic. The means that the air spring initially has a relatively low spring constant and thus can compensate for vibrations well. Only with a significant increase in the force acting on the air spring force (operating force) increases the spring stiffness, so that the air spring is harder. This prevents the second unit (eg a handle) from being pressed completely against the first unit (eg the housing surrounding the vibration generator), whereby the vibrations could be transmitted to the second unit almost unhindered.

The progressiveness of the air spring can be adjusted by a suitable, explained below spring control device in a corresponding manner.

As already explained in connection with the prior art and explained in more detail later, the actuator has the primary task of compensating the operating force acting between the first and the second unit so that the actual vibration isolation is provided by a spring element arranged parallel to the actuator can be taken. However, since the actuator is pneumatically operated according to the invention, it already has good spring properties due to the compressibility of the air and thus also serves for vibration isolation. A hydraulically powered actuator could not provide such vibration isolation due to the incompressibility of hydraulic fluid. Even electrically operated actuators would always try to counteract a vibration-induced deflection and thus to prevent a spring action.

In a particularly advantageous embodiment of the invention, the implement is a drill and / or percussion hammer (hereinafter referred to as a hammer). The second unit carries a handle on which the operator can guide and hold the implement. In the first unit, a per se known Luftfederschlagwerk is provided which has a driven by a motor drive piston for driving a percussion piston. Between the drive piston and the percussion piston forms an air spring, which transmits the movement of the drive piston on the percussion piston, which in turn strikes against a tool. According to the invention, the drive piston for generating compressed air for Food of the actuator is formed.

In this embodiment, a further advantage of a pneumatically operated actuator becomes clear. The drive piston of the percussion mechanism is in fact already designed to generate compressed air, even if in known striking mechanisms only for driving the percussion piston. According to the invention, the drive piston now has a second function, namely the generation of compressed air for the actuator. However, because the drive piston for this purpose can be used in a simple manner, no additional components for generating a pressure medium, such. B. a hydraulic pump o. Ä., Required. The drive piston z. B. in its return movement, after propelling the percussion piston, displaced air can be supplied to the actuator as compressed air.

It is particularly advantageous if the actuator has a be filled by the drive piston with compressed air compressed air storage. The compressed air reservoir not only serves as a compressed air reservoir for the actuator, from which compressed air can be removed if necessary and fed to the actuator. In addition, the compressed air accumulator even out the compressed by the drive piston due to its reciprocating thrust supplied compressed air.

In a particular embodiment of the invention, the actuator on the compressed air reservoir, a valve device, the handle air spring and a handle piston. In this case, the compressed air reservoir can be connected via the valve device with the handle air spring, while the handle air spring acts on the handle piston, which is connected to the handle. The core of the actuator is thus formed by the handle air spring. Depending on which pressure from the compressed air reservoir, the handle air spring is filled, it moves the acted upon by her handle piston, which in turn is positively connected to the handle and this moves with it. The valve device ensures that only as much compressed air from the compressed air reservoir enters the handle air spring, as required.

Advantageously, the valve means is configured such that when the handle piston is a volume circumscribing the handle air spring Shrunk over a predetermined amount, compressed air from the compressed air reservoir can be tracked in the handle air spring to reach the predetermined level of the volume of the handle air spring again. Thus, when the operator presses against the handle with increased operating force, he shifts the handle and thus the handle piston against the action of the handle air spring. Due to the compressibility of the air, the volume of the handle air spring is reduced until finally a predetermined minimum limit is reached. Thereafter, the valve means opens the connection between the compressed air reservoir and the handle air spring, so that the air pressure in the handle air spring is increased. As a result, the force acting on the handle piston increases and pushes the piston against the action of the operating force again. With appropriate adjustment of the system, it can thus ensure that the handle barely changed its relative position relative to the first unit having the air spring impact mechanism.

In addition, it is expedient if the valve device also has an outlet valve to omit compressed air from the handle air spring, if the volume of the handle air spring exceeds a predetermined maximum value due to a displacement of the handle piston.

This case can z. B. occur when the operator has first pressed with high operating force against the handle and then finally withdraws the operating force, because he wants to lift the device. As a result, the high air pressure in the handle air spring would push the handle piston and thus the handle farther out, which would result in vibration isolation failing to operate in the optimum operating range, particularly if the device were to be reused with less operating force.

To prevent this, the exhaust valve is provided which opens a connection from the handle air spring to the outside, when due to a lowering of the operating force, the handle air spring displaces the handle piston and thereby increases over a predetermined maximum value.

The last described embodiments of the invention can be both purely mechanically as well as mechanically-electronically (mechatronically) realize.

In the mechanical solution, the valve device is preferably coupled to the handle piston. The handle piston is - depending on the pressurization by the handle air spring - between two extreme positions movable. Before these two extreme positions can be defined piston positions corresponding to a minimum value and a maximum value for the volume of the handle air spring. Within these values, no supply or discharge of compressed air to or from the handle air spring should take place. However, as soon as due to a changed operating force, the position of the handle piston exceeds one of the two limit values (maximum value or minimum value), the valve device opens a respective associated valve, d. H. either an inlet valve that connects between the compressed air reservoir and the handle air spring, or the exhaust valve for venting compressed air to the outside. To accomplish this, the valve means has respective intake ports for the intake valve and exhaust ports for the exhaust valve which are opened or closed in response to the position of the handle piston. The channels and their firing or opening mechanisms can be combined in a simple manner with the handle piston.

In the case of the mechatronic solution, it is particularly advantageous if a sensor is provided with which the relative position of the first and the second unit, that is to say the main housing accommodating the percussion mechanism and the drive, and the relatively movable handle can be determined. The sensor should be arranged so that it can detect at least the point of optimal relative position between the two units.

Preferably, the sensor and the valve device are connected to a controller, wherein the valve device is controllable by the controller such that in the handle air spring such a compressed air state prevails that the detected by the sensor relative positions of the first and the second unit in a predetermined fluctuation range being held. The fluctuation range is z. B. by the above-described maximum value and minimum value for the volume of the handle air spring Are defined. With the aid of the sensor, the controller monitors the relative position between the first and the second unit and, if the predetermined fluctuation range is exceeded, can control corresponding countermeasure with the aid of the valve device. On the one hand, it is thus possible to allow compressed air from the compressed air reservoir via the inlet valve to flow into the handle air spring. On the other hand, the controller can also ensure that the handle air spring is relieved via the exhaust valve.

In a particularly advantageous embodiment of the invention, a spring device is arranged parallel to the actuator between the first and the second unit. The spring device may have a softer spring characteristic than the actuator.

Alternatively, it is possible that the spring means has a spring stiffness which is at least so large that the movement of an amplitude of the vibration can be absorbed by the spring means, without a block setting of the spring means occurs.

The force acting between the first unit and the second unit consists essentially of two components: first, the operating force, which is essentially applied by the operator by pressing the handle from the outside, acts. The operating force is superimposed with a force generated by the vibration excited in the first unit. The inventive design, it is possible that the operating force is largely absorbed and compensated by the actuator, the actuator should ideally have the spring stiffness "zero" or a very low spring stiffness. A slight increase in the force acting on the actuator in the low-frequency range would cause a displacement of the actuator plunger without the actuator initially opposes increased counterforce. Only when the limit positions are exceeded would the actuator force be increased.

Superimposed on this is the effect of the spring device which absorbs the force or displacement changes caused by the oscillation amplitude. The oscillation amplitude in turn is not or hardly influenced by the operating force. The spring device must therefore have a spring stiffness have to fully absorb the vibration amplitude can, without blocking occurs, ie without the spring means is compressed so far that corresponding stops come into contact and prevent further compression of the spring. Since the vibration amplitudes occurring during operation are essentially known in advance, the spring device can be designed accordingly.

Incidentally, but the spring stiffness of the spring device should be as low as possible to allow a particularly soft suspension.

Thus, it is possible that the actuator compensates in the manner described above, the operating force acting from the outside on the implement between the first and the second unit, whereby the operating force causes no appreciable deformation of the soft spring means. On the other hand, the spring device is capable of compensating for the higher-frequency vibrations which are caused by the vibration exciter in the first unit, whereby the second unit is substantially isolated from vibrations.

The spring device must therefore not be deformable over the entire range of conceivable operating forces, which would lead to a great length of the spring due to the soft spring characteristic. Rather, it is possible due to the compensation of the operating force by the actuator that the spring device only has to provide a relatively small operating range for the relative movement between the first and the second unit, so that the spring device builds short despite the soft spring characteristic.

In an advantageous further development, the actuating force generated by the actuator is cyclically variable, wherein the change takes place at the same frequency with which the drive piston moves. The vibration generated by the drive piston in the Lüftfederschlagwerk inevitably has exactly the same frequency with which also moves the drive piston. Accordingly, the frequency of the vibration to be isolated is already predetermined by the movement frequency of the drive piston. Now, if the actuator operates at the same frequency, can be caused by the pulsating effect of the actuator in a certain way of the drive piston Compensate for vibration.

Any required phase shifts with respect to the movement of the drive piston and the actuating work of the actuator can be solved by suitable coupling of valves of the valve device and intermediate switching of the compressed air reservoir. So it is z. For example, it is possible for the drive piston to pump air into the compressed air reservoir after it has been acted upon by the percussion piston when the percussion piston is hit and the blow is carried out. In the impact and vibration produced in the next cycle, the valve opens between the compressed air reservoir and the handle air spring to increase the pressure in the handle air spring and thereby increase the force. Upon renewed return movement of the working piston, the handle air spring is emptied while the compressed air reservoir is refilled. This embodiment of the invention enables a particularly skillful and reliable compensation of the unwanted vibration effect on the handle.

As an alternative to the above-described embodiment, in another embodiment of the invention, the maximum actuating frequency of the actuator may be smaller than the frequency of the vibration generated in the first unit, ie in particular as the frequency of movement of the drive piston. This ensures that the actuator only compensates for the external operating force, but does not actively counteract the oscillation. The vibration is instead compensated in the manner described above by the softer spring device or - due to the compressibility of the air - passive also by the actuator.

In another embodiment of the invention, a driven by the drive of the working device compressed air generating device is provided which generates independently of the actual working functions of the device compressed air for the actuator. For this is z. B. a small screw compressor.

The actuating force of the actuator should be adjustable so that a range of fluctuation for the relative positions between the first and the second unit caused by different operating forces is ensured, which is smaller than a fluctuation range that the relative positions between the first and the second unit with equally different operating forces, but without achieving the compensating effect of the actuating force of the actuator. This means that without the action of the actuator, the first and the second unit would be able to move in a considerably larger area relative to each other. The actuator, on the other hand, ensures that this fluctuation range is as small as possible, in order to avoid such fluctuations. B. with the help of the parallel spring device to achieve the best possible vibration isolation.

According to the invention thus a force-generating pneumatic actuator is described, which compensates the averaged over a certain period of contact pressure as in a level control. The actual vibration isolation is achieved either only by the spring characteristic of the air cushion in the handle air spring itself or additionally by the parallel connection of the passive spring device with sufficiently low spring stiffness. This means that the flat spring characteristic is shifted during the oscillation process with changing contact force such that the oscillation ideally oscillates around a fixed point. Even if essentially a semi-active vibration isolation has been described above, it is conceivable, in particular with the mechatronic variant, to achieve fully active compensation in principle the same design, in which case the demands on sensors, control and valves are higher due to the increasing switching frequencies are. Conversely, in semi-active vibration isolation, the requirements for the components are significantly lower because the actual vibration isolation is passive.

The force characteristics of the actuator, which may incidentally also consist of several smaller actuators, as well as the passive spring device, which in turn may also have a plurality of spring elements, are adapted to one another such that at least the maximum conceivable operating force can be compensated. So it is on the one hand possible to combine a strong actuator with a spring device with very soft characteristic, while on the other hand allows a stiffer spring means a weaker design of the actuator.

It is desirable to make the handle air spring as large as possible, because then the relative volume change by the handle movement low and thus the effective force remains almost constant

When the piston area of the handle piston is made sufficiently large, the operating pressure in the handle air spring can be kept low. Thus, the change in the spring stiffness of the air spring against the change in the operating force can be kept low.

According to the invention the object is also achieved by a device according to claim 16.

The vibration isolation device comprises a vibration exciter and a relative to the vibration exciter along a main direction, for. B. the working direction of the implement, movable handle device. Between the vibration exciter and the grip device, a vibration decoupling device is provided, which has a spring device, via which a substantial part of the forces acting between the grip device and the vibration exciter are transmitted. The vibration decoupling device further comprises a spring control device for changing the spring stiffness and / or the bias of the spring device in response to a force acting in the main direction between the grip device and the vibration exciter force, in particular the force exerted by the operator on the grip device in the main direction holding force ,

Because of the clear relationship between force and way in the spring device can also be used as a manipulated variable a position (relative position).

In order to achieve the best possible vibration isolation, as soft as possible a spring, so a spring device with low spring stiffness, to strive for. However, a soft spring has the disadvantage that even small forces can cause a considerable deformation of the spring. With reference to the working device, this means that the gripping device is movable relative to the vibration exciter over greater distances when the spring device arranged therebetween has a soft characteristic. However, this can be disadvantageous in having leadership bring and requires an often unavailable space. In particular, the overall length in the main direction of the implement is significantly increased.

A spring device with a hard characteristic curve, that is to say a stiff spring, permits a minimization of the installation space. At the same time, however, the vibrations of the vibrator are only incompletely held by the handle.

So far, it has only been possible in the prior art to find a compromise between hard and soft characteristics for the spring device. The invention now makes it possible, with the aid of the spring control device, to adjust the spring stiffness or optionally alternatively or additionally also the pretensioning of the spring device to the respective external conditions, in particular the effective force, and to adjust the spring characteristics such that the permissible spring travel and the permissible relative displacement can be exploited between the grip device and vibration exciter.

The force exerted by the operator changes, if at all, only relatively slowly in a low-frequency range. Even a jerky load from the operator occurs at low frequency.

In contrast, the vibrations generated by the vibration exciter in the implement are higher frequency. The force changes between the grip device and the vibration generator caused by the vibrations are not detected by the spring control device. The spring control device thus reacts only to the forces applied by the operator by holding or pressing the implement.

This makes it possible to set the spring device basically to a soft as possible characteristic or a low biasing force. The structurally specified permissible mobility between the grip device and the vibration exciter can then be fully exploited as a vibration path to compensate for the vibrations. Depending on the configuration of the spring device, the spring stiffness in the relevant operating point by changing the bias or the spring characteristic (change the amount of air in an air spring) are influenced.

However, if the operator pushes against the handle device and thus the implement with a stronger holding force, there would be a risk that the grip device touches the vibration exciter. In any case, would - with unchanged spring stiffness of the spring means - the available vibration isolation vibration path is increasingly limited. This is compensated by the spring control device in that, when the holding force of the operator and thus a zero position of the oscillation is static, a displacement of the gripping device relative to the vibration exciter is effected such that the gripping device is in a predetermined desired position.

As the operator pushes the handle assembly with greater force, the spring control increases spring stiffness to compensate for operator force with sufficient spring force. The handle device thus remains - seen statically - in the predetermined desired position. When subjected to the vibration, the grip device can move within a predetermined working range relative to the vibration exciter, because the vibrations caused by the higher-frequency force changes are not compensated.

Advantageously, the relative position of the handle device is held to the vibration exciter by the spring control device in interaction with the force acting in the predetermined working range. The spring control device thus ensures that the relative position always remains within the predetermined working range. In this way, extreme positions and thus z. B. a solid state contact between the grip device and vibration exciter can be avoided by touching, in which the vibrations would be completely transferred to the grip device.

Preferably, the spring control device strives for the grip device to be held substantially in a desired position in the working region even when the holding force changes, which corresponds to a predetermined relative position between the grip device and the vibration exciter.

It is particularly advantageous if the desired position at the same time corresponds to a middle position of the working area, so that the gripping device can be moved forwards and backwards along the main direction from the middle position over substantially equal movement distances to respective limit or end positions. In this way, the grip device can oscillate symmetrically about the center position and thereby compensate for the vibration generated by the vibration exciter.

In a particularly advantageous embodiment of the invention, the spring device can be controlled by the spring control device such that the spring device has an increased stiffness in an idling mode in which the force acting between the grip device and the vibration generator is below a predetermined limit value. It has been found that in particular hammers have a tendency to jump off the Ansetzstelle when starting to a new Bohrstelle. If the spring device has a soft characteristic, the workability of the implement is in principle made more difficult, which still promotes the jumping away. However, if the spring means has an increased rigidity, the implement can be particularly safe when starting when the operator does not press the device with full, so below the predetermined limit force lying.

However, as soon as the implement goes into normal working mode and is held by the operator with a correspondingly higher holding force, which is above a predetermined limit, the stiffness of the spring means by the spring control device can be reduced so that the handle device can be in the desired desired position of the workspace ,

When starting the work process in which the implement is still idling, thus the spring means is stiff to allow good maneuverability. The moment the operator presses against the implement and desires to transition from idle to work, the spring stiffness is reduced to achieve the improved vibration isolation. The spring stiffness will then inevitably not be too low, since the pressure force must be compensated by the operator. Accordingly, good workability of the implement is ensured in the working mode.

In a particularly advantageous embodiment of the invention, the Federeinrichung acting between the handle device and the vibration exciter air spring, which preferably receives air from an air pump.

The air pump can be operated by a drive motor of the implement. For example, the air pump may be coupled to a fan for the drive motor or arranged as an additional pumping element.

The air pump is representative of many other ways to form an air pressure generating device, with the pressurized air can be supplied to the air spring. Accordingly, when subsequently referred to by an air pump, it is also generally understood to mean an air conveying device or an air pressure generating device.

In a particularly advantageous development of the invention, the air pump is operated by the oscillating relative movement between the handle device and the vibration exciter. Due to the required relative to the vibration isolation relative movement of the grip device is a drive movement available, which can be used for the air pump in an advantageous manner.

So z. B. the air pump provided between the grip device and the vibration exciter pump chamber whose volume is constantly changing due to the oscillating relative movement. However, the air pump can also be arranged between the vibration generator and a third mass. Air from the environment can flow into the pumping chamber via a first check valve as the volume of the pumping chamber increases. The air can be conveyed via a second check valve from the pumping chamber into an air spring chamber in which the air spring is formed when the volume of the pumping chamber is reduced with a corresponding countermovement of the gripping device. Due to the interplay between the first and the second check valve, an averaged over the time substantially constant supply air flow is ensured by the air pump to the air spring.

The spring control device has a valve device, by means of which the exhaust air flow from the air spring can be regulated as a function of the relative position of the gripping device. The rigidity of the spring device can thus be adjusted by regulating the exhaust air flow. If more air flows out of the air spring than is supplied by the air pump, the spring stiffness is reduced. Conversely, the spring stiffness can be increased by the exhaust air flow is set lower than the supply air flow, so that in the sum of more air flows into the air spring.

In a particularly advantageous embodiment of the invention, the valve device has a valve opening which can be opened when the gripping device is further away from the vibration exciter. As a result, air can flow out of the air spring, so that the spring stiffness decreases. With unchanged strong pressing force of the operator, this causes the handle device moves closer to the vibration exciter. If the grip device has approached beyond the desired or middle position of the working area beyond the vibration exciter, the valve opening is at least partially closed again. This increases the air pressure in the air spring and the air spring becomes stiffer. Accordingly, the grip device can no longer approach the vibration exciter. Optionally, the grip device is even pushed back by the ever increasing air pressure in the air spring, so that it assumes the desired position desired.

In another embodiment of the invention, the spring control device has a valve device, by means of which the supply air flow to the air spring in dependence on the relative position of the gripping device can be regulated. The exhaust air flow from the air spring is substantially constant. As a result, the air pressure in the air spring can thus be regulated in a manner similar to that already described above.
Of course, a combination solution is possible in which both the supply air flow and the exhaust air flow are regulated. However, a vote of the two air streams is appropriate, which may increase the regulatory burden.

In another embodiment of the invention, the pressure increase is not by supplementing the amount of gas in the spring volume of the air spring achieved, but by reducing the volume at a constant gas volume.

This z. B. by an actuator to be done Stellstellgabe can z. B. take place in that in a coupled to the air spring cavity, a liquid - separated from the actual air volume of the air spring by a membrane or a piston - on or is omitted. Alternatively, a piston or bellows wall may be moved by a mechanical drive and thus alter the volume of air in the air spring. The gas space for the air spring is hermetically sealed in this case. He could therefore be filled with a gas other than air. For example, when using a monatomic gas (noble gas), the adiabatic losses would be lower, so that the "air spring" (here better: gas spring) would be less warm. For this purpose, it is recommended to fill the spring with helium, neon, argon (inexpensive) or krypton.

For such cases of a closed gas volume, the pressure of which can be changed from the outside in the manner described above, the term "air spring" should expressly include gas springs with other fillings than air. The term air spring is thus used only for ease of understanding, but should not be understood in this context to the effect that only spring fillings are detected with air. An air spring is synonymous in this sense with a gas spring.

The gripping device may have at least one, but also two or more handles.

In a preferred embodiment of the invention, an elastic stop is provided between the gripping device and the vibration exciter. At least a portion of the force acting between the handle assembly and the vibrator may be transmitted via the stopper when the spring stiffness of the spring means is insufficient to transmit all of the force. The stop thus corresponds to a classic spring element (eg a rubber spring or a foam element). He only transmits forces in one direction. This can be ensured that z. B. the pressure or holding force of the operator if necessary from the handle device can be transmitted directly over the stop on the vibration exciter. The elastic stop ensures that even in this case a vibration decoupling is possible, albeit less so. Of course, a second stop can be provided for receiving forces in the opposite direction, in particular, when the implement is quickly relieved by the operator or the supporting ground suddenly gives in under the action of the pressing force.

The tools affected by the invention, in particular hammers, are often used in dusty environments (eg in demolition work).
The sucked for the filling of the air spring air should therefore be at least cleaned by a filter. Because of the large proportion of dust, however, it is to be expected that these filters will be quickly occupied, which can result in insufficient maintenance for clogging or throttling of the intake air flow for the air spring, but also for the passage of larger amounts of dust. In this case, increased wear, in particular due to sliding relative movements, can be expected. Therefore, it is advantageous if the air discharged from the air spring in a largely closed space, for. As a bellows or a filter bag, at least partially collected and can be reused from there for the refilling of the air spring. The discharge opening from the air spring and the suction opening of the air pump can then open into this room.

In a further preferred embodiment, accordingly, the air for the air spring from an air reservoir can be fed. It is particularly advantageous if the air discharged from the air spring is traceable into the air reservoir. This means that the air can be buffered in the air reservoir serving as an intermediate reservoir, before it is again injected under pressure into the air spring via the air pump. In this way it is possible to keep the replacement of the air provided for the air spring with the ambient air low, so as to prevent contamination, for. As by dust to minimize. It is thus achieved a substantially closed air circulation, in which only the most unavoidable leakage losses must be compensated by fresh air from the outside.

As an air reservoir or intermediate reservoir z. As a cavity, in particular a bellows or a balloon, the volume of its required Can adjust the amount of air.

The constant compression and decompression of the air (the gas) by the vibration introduction creates losses in the air spring, which lead to a warming of the air (the gas). The heat loss must be dissipated via the walls of the air spring. It may therefore be expedient to provide cooling ribs on the inner and outer surfaces of the space surrounding the air spring.

These and further features of the invention are explained in more detail below by means of examples with the aid of the accompanying figures.

Fig. 1

schematisch eine geschnittene Seitenansicht eines erfindungsgemäßen Arbeitsgeräts;

Fig. 2

das Arbeitsgerät aus Fig. 1, mit teilweise aufgeschnittenem Schlagwerk und erfindungsgemäßem Aktor;

Fig. 3

eine Ausschnittsvergrößerung aus Fig. 2;

Fig. 4

eine Ausschnittsvergrößerung einer weiteren Ausführungsform; und

Fig. 5

einen schematischen Schnitt durch ein Arbeitsgerät mit der erfindungsgemäßen Vorrichtung zur Schwingungsisolation eines Handgriffs.

Show it:

Fig. 1

schematically a sectional side view of a working device according to the invention;

Fig. 2

the work tool off Fig. 1 , with partially cut Schlagwerk and inventive actuator;

Fig. 3

an excerpt from Fig. 2 ;

Fig. 4

an enlarged detail of another embodiment; and

Fig. 5

a schematic section through a working device with the device according to the invention for vibration isolation of a handle.

Fig. 1 shows the example of a drill and / or percussion hammer the basic structure of the working device according to the invention. A first unit 1 and a second unit 2 are connected to each other via a Schwingungsisoliereinrichtung 3.

The Schwingungsisoliereinrichtung 3 has an actuator 4 and a spring means 5.

Furthermore, guide elements 6 are arranged between the first unit 1 and the second unit 2, which are intended to prevent tilting of the two units 1, 2. The guide elements 6 may be made of rubber or plastic and thus also contribute to vibration isolation.

In the first unit 1 is in a known manner - therefore not shown in detail - a drive motor arranged via a crankshaft in an Fig. 2 recognizable drive piston 7 reciprocated. Before the drive piston 7, ie in a working direction A, an unillustrated percussion piston is arranged. As a result of the movement of the drive piston 7, an air spring 8 forms between the drive piston 7 and the percussion piston, which in turn drives the percussion piston so that it strikes against an unillustrated tool end or an interposed anvil. The operation of such air spring impact is known, so that at this point a more detailed explanation is unnecessary.

On the second unit 2, a handle 9 is formed at the rear end.

Because the Fig. 2 and 3 are substantially the same representation, they will be described together below.

The actuator 4 has a compressed air reservoir 10, a handle air spring 11 and a handle piston 12. Part of the actuator is furthermore a valve device which comprises an inlet valve 13 and an outlet valve 14. The inlet valve 13 and the outlet valve 14 essentially consist of a groove milled into a cylinder, which faces a closed cylindrical surface. The function will be explained in more detail later.

The compressed air reservoir 10 is further equipped with an inlet check valve 15 and an outlet check valve 16.

The handle piston 12 is positively connected to the handle 9 in the axial direction. To compensate for any misalignment, lateral movements or angular errors, an annular rubber or foam element 17 is provided. In any case, it is ensured that the axial movement of the handle piston 12 is exactly transferred to the handle 9, and vice versa.

The following explains the functionality:

In operation, the drive piston 7 sucks in a forward movement in the working direction A air from the environment via a check valve 18 in a rear space 19 at. During the subsequent return movement of the drive piston 7 counter to the working direction A, the air is pressed out of the rear space 19 via the inlet check valve 15 into the compressed air reservoir 10. In turn, subsequent forward movement of the drive piston 7 air is then sucked in again via the check valve 18. If an overpressure arises in the compressed air accumulator 10, this can be reduced via the outlet check valve 16.

Now, when the operator presses the hammer on the handle 9 against a rock to be processed, the handle 9 moves relative to the first unit 1 forward in the working direction A. This also penetrates the handle piston 12 with a plunger 20 deeper into the compressed air reservoir 10, to Via a groove 13a of the inlet valve 13, a communicating connection between the compressed air reservoir 10 and the handle air spring 11 is produced. In addition, compressed air from the compressed air reservoir 10 can flow into the handle air spring 11, which acts inter alia against a piston surface 21 and finally the handle piston 12 together with the handle 9 and the second unit 2 back, against the working direction A moves. As a result, the disturbing relative movement between first unit 1 and second unit 2 can be compensated in a very short time.

When the operator presses against the handle 9 with even higher operating force, the above-described procedure is repeated.

On the other hand, if the operator disengages the handle 9 or even lifts the implement on the handle 9, the handle 9 moves with the second unit 2 relative to the first one. Unit 1 to the rear, against the working direction A. Consequently, the handle piston 12 slides back and finally releases the groove 14a on the outlet valve 14, so that compressed air from the handle air spring 11 can flow into the environment until the compressed air in the handle Air spring 11 is completely degraded.

The second unit 2 is at the first unit beyond not shown by stops, z. B. also on the guide elements 6, secured to avoid a complete release of the second unit 2. The stops ensure that the exhaust valve 14 is opened without the handle piston 12 sliding completely out of its guide.

Due to the compressible properties of the compressed air in the handle air spring 11, the actuator 4 is already able to isolate vibrations to a considerable extent. In addition, in the in the Fig. 1 to 3 illustrated embodiment, the spring means 5 arranged in the form of a coil spring with a soft spring characteristic. Without the actuator 4, the spring device 5 would be completely compressed even at low operating force on the handle 9, so that they no longer vibration-isolating effect would have. With the aid of the actuator 4, however, it is possible to maintain the relative position shown in the figures between the first unit 1 and the second unit 2, so that the spring means 5 can still provide a sufficient spring travel. This spring travel is capable of effectively isolating the vibration generated in the first unit 1 from the handle 9.

Fig. 4 shows a second embodiment of the invention. While in the Fig. 2 and 3 a purely mechanical solution has been presented Fig. 4 a mechatronic realization of the invention. If substantially the same components as in the Fig. 2 and 3 are used, the same reference numerals are used. On a new description of these components can be omitted.

A significant difference can be found in the valve device: The air flow to and from the handle air spring 11 is ensured by means of controllable by an unillustrated control valves, namely an inlet valve 22 and an exhaust valve 23.

The controller receives essential information from a sensor 24, with which the relative position between the first unit 1 and the second unit 2 is detected. The sensor 24 may be any proximity sensor, e.g. B. a Hall sensor, act. The sensor 24 should be designed such that it at least the relative position of the two units 1, 2 recorded in the desired optimal range.

If the controller detects a displacement of the second unit 2 due to an operating force acting on the handle 9 with the aid of the sensor 24, it effects a change in the rigidity of the handle air spring 11 by appropriately driving the inlet valve 22 or the outlet valve 23. Accordingly, the handle piston displaces 12 and the handle 9 in the desired manner.

The controller is able to allow a certain range of variation, which depends essentially on the available travel of the spring device 5.

The control frequency of the actuator determined by the control may be smaller than the frequency of the vibration generated in the first unit. As a result, the demands on the controller and the components of the actuator are comparatively low. But it is also possible to choose the control frequency of the actuator higher than the oscillation frequency. Then the actor would be able to actively counteract the vibration. However, this requires a correspondingly fast control and fast valves 23, 24.

FIG. 5 shows a schematic section through a working device with the device according to the invention for vibration isolation of a handle.

In FIG. 5 is a section through an upper or rear, facing away from a tool part of serving as a working hammer blow shown.

The device according to the invention is particularly suitable for hand-held tools in which vibrations or shocks are generated in order to achieve the desired working effect. It is important that the operator guiding or holding the implement is protected from the vibrations and impacts.

A vibration exciter 31 is in the FIG. 5 only schematically shown as a housing box. He points among other things z. As a drive, such as an electric or internal combustion engine, and a motion converter on. The movement conversion device converts the movement, which is usually generated as a rotational movement by the drive, into a slower rotational movement or oscillating reciprocating motion which is suitable for the respective application. So it is z. B. usual to perform the motion conversion device as a transmission with a crank mechanism that drives a percussion. From the percussion shocks are generated by means of a percussion piston, which on a tool, for. As a chisel to be passed.

Except in the FIG. 5 hammer shown hammer, the invention is typically also suitable for rotary hammers or rammers or other tools in which a vibration decoupling of the handle is useful.

As vibration exciter 31 thus the part of the implement is referred to, are generated in the vibrations or shocks. The term is representative of various constellations that can be selected by the skilled person depending on the type of implement.

The vibration generator 31 is connected to one in the FIG. 5 coupled as handle cover handle device 32 coupled. The gripping device 32 may partially surround the vibration generator 31, as in FIG FIG. 5 shown. But it can also be provided spatially separated from the vibration generator 31.

The gripping device 32 is movable relative to the vibration exciter 31 at least along a main direction A. For this is one in the FIG. 5 not shown, known per se guide (eg, by means of parallel rocking) between the gripping device 32 to the vibration exciter 31 is provided. In addition, the gripping device 32 can be movable relative to the vibration exciter 31 in other directions, which deviate from the main direction A, if this is not technically preventable or even desired.

On the grip device 32, two handles 33 are provided, where the operator can hold and run the implement. For the design of the handles 33 numerous variants are also known. In a hammer drill z. B., instead of the two handles 33 a single handle in the form of a pistol or spade handle are used.

At the vibration exciter 31, an air spring piston 34 is attached. The air spring piston is enclosed by a spring cylinder 35 formed by a part of the wall of the grip device 32, so that an air spring chamber 36 is formed in a cavity between the air spring piston 34 and the spring cylinder 35, which accommodates the actual air spring 37. It can be seen that the air pressure in the air spring 37 increases when the grip device 32 is pressed in the direction A closer to the vibration exciter 31. The air spring piston 34, the spring cylinder 35, the air spring chamber 36 and the air spring 37 together form a spring device 38.

On the upper side of the air spring piston 34, an elastic stop 39 is provided, against which the gripping device 32 can strike if the force exerted in the direction A is so great that the air spring 37 is completely compressed or if the air spring 37 contains too little air, to ensure adequate spring action. The elastic stop 39 ensures that a certain vibration isolation of the grip device 32 is ensured even when the grip device 32 is in direct contact with the air spring piston 34 and thus the vibration exciter 31 via the stop 39.

At the vibration generator 31, a pump piston 40 is further provided, which is enclosed by a serving as a pump cylinder 41 part of the wall of the handle device 32. The pump cylinder 41 encloses the pump piston 40 such that a pumping chamber 42 is formed. As a result, an air pump 43 is formed.

Via a one-way valve or first check valve 44, air from the surroundings of the working device can flow into the pumping chamber 42 when the gripping device 32 moves away from the oscillation exciter 31, thereby increasing the volume of the pumping chamber 42. The resulting negative pressure sucks the air via the first check valve 44 into the pumping chamber 42.

In contrast, when the handle 32 is moved in the direction A against the vibration exciter 31, the volume of the pumping chamber decreases 42, so that the pressurized air via a second check valve 45 and an inlet port 46 can flow into the air spring chamber 36. A backflow of air into the environment is prevented by the first check valve 44. As a result, the air pressure in the air spring chamber 36 is increased and the rigidity of the air spring 37 is increased.

Since the vibration generator 31 generates substantially continuous vibrations or continuously recurring shocks and resulting vibrations, the vibration generator 31 tends to reciprocate continuously. By contrast, the grip device 32 held by the operator should remain as stationary as possible. This results in the operation of the working device, a continuous relative movement between the handle device 32 and the vibration exciter 31, which generates averaged over a certain period of time constant air flow with the aid of the air pump 43.

The supply air flow into the air spring chamber 36 comes to a halt when the air pressure generated by the air pump 43 is not higher than the pressure prevailing in the air spring chamber 36 pressure. Then, however, the air spring 37 has reached its maximum possible rigidity. Accordingly, the air pump 43 and the spring device 38 are to be designed so that a separation between, the grip device 32 and the vibration generator 31 is ensured even at theoretical maximum stress (maximum force applied by the operator in the direction A), so that the vibrations occurring in the vibration generator 31 only via the air spring 37, but not over other solid contacts, not even on the stop 39, can be transferred to the handle device 32.

In the wall of the handle device 32, an outlet opening 47 is formed. The outlet opening 47 is positioned such that, depending on the relative position between the gripping device 32 and the vibration generator 31, it is covered or not covered by the air spring piston 34 serving as a slide. As can be seen in the figure, the air spring piston 34 covers the outlet opening 47 serving as the valve opening when the grip device 32 has been approached via a certain point to the vibration generator 31. This will be the case in particular when the operator with correspondingly large holding or pressing force in the direction A suppressed.

In this case, the air pressure in the air spring 37 is increased by the continuous supply air from the air pump 43 until the air spring 37 is strong enough to push the handle 32 against the pressing force of the operator and thus against the direction A. In this case, the grip device 32 is moved back until the air spring piston 34 at least partially releases the outlet opening 47 again. For then air can flow out of the air spring 37 via the outlet opening 47 into the environment, so that the air pressure in the air spring 37 is reduced again. By reducing the air pressure in the air spring 37, in turn, the grip device 32 can again move closer to the vibration exciter 31.

In this way, serving as a spring-regulating device control is ensured, due to the relative position between the handle device 32 and the vibration generator 31 even with changing outer, substantially static forces, such. As the holding force of the operator, always in a defined workspace, preferably even in a desired position, is held. The desired position will usually correspond to a position in which the air spring piston 34 partially covers the outlet opening 47 in the manner shown in the figure. Then, a balance between the supply air flow from the air pump 43 and the exhaust air flow via the outlet port 47 is set, so that the spring force generated by the air spring 37 corresponds to the externally applied force.

As a target position for the control of the air spring 37 is particularly suitable a middle position in which approximately equal movement paths of the gripping device 32 are ensured to the vibration generator 31 out and from the vibration exciter 31 away. As a result, the vibration exciter 31 can swing well relative to the grip device 32.

The regulation of the air spring 37 has a certain intentional inertia. In particular, the vibration frequencies of the vibration generator are significantly greater than the frequencies of the control speed, so that the vibrations cause no or only negligible change in the spring stiffness of the air spring 37. The spring properties are thus predominantly or exclusively by the outside of the grip device 32 and thus the vibration exciter 31 acting force, especially by the holding force of the operator changed.

Accordingly, the air spring 37 compensates for the higher-frequency vibrations of the vibration exciter 31, so that an effective vibration isolation of the grip device 32 takes place.

In another, in the FIG. 5 not shown embodiment of the invention, the exhaust air flow from the air spring 37 is constant, while the supply air flow is controlled or regulated by the air pump to achieve the desired change in the spring characteristics of the air spring 37.

In yet another embodiment, it is possible to control both the supply air flow and the exhaust air flow.

Instead of the air pump described above, other solutions are conceivable with which air can be generated with a certain pressure value. So it is z. B. possible, the compressed air directly in the vibration exciter 31, z. B. from the drive provided there, to produce. These are suitable z. B. corresponding fan wheels.

In another variant, a movable mass oscillator is arranged between the oscillation exciter 31 and the gripping device 32 and is reciprocated by the oscillations of the oscillation exciter.

Of course, the assignment of belonging to the spring device 38 and the air pump 43 components to the grip device 32 and the vibration generator 31 are also easily reversed. The achievable effect remains unchanged.

It is particularly advantageous if the air spring 37 has an increased rigidity when the implement is idling. In particular, in the in the FIG. 5 When hammering a new drilling point, there is a risk that the hammer will jump off the place of attachment. If the air spring 37 is stiff in idling mode, the operator can better guide the hammer and make the tapping. This can z. B. the air spring piston 34 are designed so that it covers the outlet opening 47 in a relative position, in which the grip device 32 is far away, that is pushed back to the vibration exciter 31. Only when the grip device 32 is pressed against the vibration generator 31, the air spring piston 4 releases the outlet opening 47, so that the stiffness of the air spring 37 is initially significantly reduced. As a result, the gripping device 32 can reach the desired desired position (eg middle position) before the air spring piston 34 again closes the outlet opening 47 in the manner described above. To realize this control, 34 corresponding control grooves may be provided in side walls of the air spring piston, which connect the air spring 37 with the outlet opening 47 depending on the relative position.

The fact that the holding force of the operator, in particular the pressing force and caused by the implement and to be held by the operator weight to be compensated, the operating point of the spring characteristic of the air spring 37 can always be maintained in a range of the largest possible vibration of the vibration generator 31 relative to the Grip device 32 allows. As a result, the vibrations and shocks are effectively isolated from the gripping device 32.

In general, there is the problem that with a fresh air supply via the check valve 44 dust and dirt in the interior of the device, in particular in the air pump 43, a corresponding alternative air pressure generating device or in the air spring 37 itself can get. To avoid this, it is desirable to supply the air that has left the air spring 37 via the outlet opening 47 in a closed circuit of the air pump 43 or another air pressure generating device, whereby the air can then be pumped back into the air spring 37. In this way, an air return is achieved in which only the escaped by leakage air must be replaced. Essentially, however, can be used by the return repeatedly the same air for the air spring 37.

An implement according to the invention thus has an air spring between the vibrating first entity and the second unit (eg handle) to be set quietly. The spring properties of the air spring can be changed in vorteihafter way characterized in that the degree of filling of the air spring or the air pressure in the air spring can be changed. For this purpose, proposals for air pressure generating devices and spring control devices have been described above. In a particularly advantageous manner, either the drive of the working device, for. B. via a drive piston of the air spring impact, allow the required air pressure generation. Alternatively, the oscillatory relative movement between the first and second units may be utilized to derive therefrom a pumping motion for the delivery of air and compressed air production. In particular, simple mechanical control devices, it is possible to always adjust the air pressure in the air spring or its air filling the circumstances, ie especially the applied pressure force by the operator.

Claims (15)

1. Handheld working tool, having

   - a first unit (1) excited by vibration during operation;

   - a second unit (2) which is relatively movable at least in one working direction (A) with respect to the first unit (1); and having

   - a vibration isolation device (3) disposed effectively between the first (1) and the second unit (2);

   wherein the vibration isolation device (3) comprises at least one actuator (4) for producing an actuating force, by means of which an operating force acting in the working direction (A) between the first (1) and the second (2) unit is able to be at least partly compensated, and wherein the actuator (4) is pneumatically operated;
   characterised in that

   - the actuator (4) comprises a handle pneumatic spring (11), wherein the filling of which with compressed air is able to be modified; and in that

   - a spring device (5) is disposed in parallel with the actuator (4) between the first (1) and the second unit (2).
2. Handheld working tool, having

   - a first unit (1) excited by vibration during operation;

   - a second unit (2) which is relatively movable at least in one working direction (A) with respect to the first unit (1); and having

   - a vibration isolation device (3) disposed effectively between the first (1) and the second unit (2);

   wherein the vibration isolation device (3) comprises at least one actuator (4) for producing an actuating force, by means of which an operating force acting in the working direction (A) between the first (1) and the second (2) unit is able to be at least partly compensated, and wherein the actuator (4) is pneumatically operated,
   characterised in that

   - the actuator (4) comprises a handle pneumatic spring (11), wherein the filling of which with compressed air is able to be modified; and in that

   - the vibration isolation action is effected substantially by the handle pneumatic spring (11).
3. Working tool as claimed in Claim 1 or 2, characterised in that

   - the working tool is a hammer drill and/or percussion hammer;

   - the second unit (2) comprises a handle (9);

   - in the first unit (1) there is provided a pneumatic spring hammer mechanism having a drive piston (7) driven by a motor for driving an impact piston by means of a pneumatic spring (8) which can be produced between the drive piston (7) and the impact piston; and in that

   - the drive piston (7) is formed for the production of compressed air for supplying the actuator (4).
4. Working tool as claimed in Claim 3, characterised in that the actuator (4) comprises a compressed air storage device (10) which can be filled with compressed air by the drive piston (7).
5. Working tool as claimed in Claim 4, characterised in that

   - the actuator (4) comprises the compressed air storage device (10), a valve device (13, 14; 22, 23), the handle pneumatic spring (11), and a handle piston (12);

   - the compressed air storage device (10) can be connected to the handle pneumatic spring (11) via the valve device (13, 14; 22, 23); and in that

   - the handle pneumatic spring (11) acts on the handle piston (12) which is connected to the handle (9).
6. Working tool as claimed in Claim 5, characterised in that the valve device (13, 14; 22, 23) is formed such that, when the handle piston (12) reduces a volume enclosing the handle pneumatic spring (11) beyond a predetermined value, compressed air can be subsequently guided to the handle pneumatic spring (11) from the compressed air storage device (10) in order to restore the predetermined value for the volume of the handle pneumatic spring (11).
7. Working tool as claimed in Claim 5 or 6, characterised in that the valve device comprises an outlet valve (14) for letting compressed air out of the handle pneumatic spring (11) when the volume of the handle pneumatic spring (11) exceeds a predetermined maximum value due to a displacement of the handle piston (12).
8. Working tool as claimed in any one of Claims 1 to 7, characterised in that a sensor (24) is provided for determining the relative position of the first (1) and the second unit (2).
9. Working tool as claimed in Claim 8, characterised in that

   - the sensor (24) and the valve device (22, 23) are connected to a control unit; and in that

   - the valve device (22, 23) can be controlled by the control unit in such a way that a compressed air state prevails in the handle pneumatic spring (11) such that the relative positions (1) of the first and the second unit (2) which are detected by the sensor (24) are kept within a predetermined range of fluctuation.
10. Working tool as claimed in any one of Claims 1 to 9, characterised in that the spring device (5) has a softer spring characteristic than the actuator (4).
11. Working tool as claimed in any one of Claims 1 to 9, characterised in that the spring device (5) has a spring constant which is at least sufficiently large that the spring device (5) can absorb the movement of an amplitude of the vibration without bottoming out of the spring device occurring.
12. Working tool as claimed in any one of Claims 2 to 11, characterised in that the actuating force produced by the actuator (4) can be modified cyclically, wherein the modification is effected at the same frequency at which the drive piston (7) moves.
13. Working tool as claimed in any one of Claims 1 to 11, characterised in that a maximum actuating frequency of the actuator (4) is smaller than a frequency of the vibration produced in the first unit (1).
14. Working tool as claimed in Claim 1 or any one of Claims 5 to 13 which does not refer back to Claims 3 or 4, characterised in that a compressed air-producing device, driven by a motor of the working tool, is provided in order to produce compressed air for the actuator (4).
15. Working tool as claimed in any one of Claims 1 to 14, characterised in that the actuating force of the actuator (4) can be set in such a way that a range of fluctuation is ensured for the relative positions, caused by different operating forces, between the first (1) and the second unit (2), which range is smaller than a range of fluctuation which the relative positions between the first (1) and the second unit (2) would achieve in the case of equally different operating forces but without the compensating effect of the actuating force of the actuator (4).

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