EP1896222A1

EP1896222A1 - Percussive mechanism with an electrodynamic liner drive

Info

Publication number: EP1896222A1
Application number: EP06754612A
Authority: EP
Inventors: Rudolf Berger; Otto W. Stenzel; Wolfgang Schmid
Original assignee: Wacker Construction Equipment AG
Current assignee: Wacker Neuson Produktion GmbH and Co KG
Priority date: 2005-06-29
Filing date: 2006-06-28
Publication date: 2008-03-12
Also published as: JP2008544871A; US20100236802A1; CN101203359A; JP5130207B2; DE102005030340B3; US8534377B2; CN101203359B; WO2007000344A1

Abstract

A percussive mechanism, which is provided in the form of an, e.g. pneumatic spring percussive mechanism, comprises an electrodynamic linear drive, a drive piston (1), which can be reciprocally moved inside a percussive mechanism housing (9) by the linear drive, and a percussive piston (3). An additional hollow space (14, 17) is provided in front of and/or behind the drive piston (1) and can be isolated at least in part from the surrounding area so that a pneumatic spring can be created in the additional hollow space (14, 17). The pneumatic spring slows the drive piston (1) at its returning points and facilitates a returning motion without loading the electrodynamic linear drive.

Description

Impact mechanism with electrodynamic linear drive

The invention relates according to the preamble of claim 1 a striking mechanism with an electrodynamic linear drive.

Drilling and / or impact hammers (hereinafter referred to as hammers) are usually driven by electric motors in which a rotor rotates a drive shaft. The rotary motion is converted into an oscillating linear motion, which is fed to a drive element in a striking mechanism. In particular, an air spring impact mechanism in which a drive piston serving as a drive element is reciprocated is suitable as impact mechanism.

From DE 102 04 861 Al a Luftfederschlagwerk for a hammer is known in which a drive piston can be driven by an electrodynamic linear drive. The drive piston is coupled to a rotor of the linear drive, so that the linear reciprocating motion of the rotor is transmitted to the drive piston. The movement of the drive piston, in turn, is transmitted via an air spring to a percussion piston, as is usual with air spring impact devices, which strikes against a tool end or an interposed anvil in a known manner.

In such a linear electromagnetic drive system, the rotor and the drive piston coupled thereto must each be braked when they reach their extreme position in order to change the direction of movement can. Only then is an oscillating impact mode possible. During deceleration, a part of the kinetic energy can be fed back into a DC link as electrical energy. However, in the coils of the stator surrounding the rotor, there is lost heat, which degrades the efficiency of the impact system. In addition, the heat loss must be dissipated by means of a suitable cooling device.

It is therefore advantageous to interpose the kinetic energy of the drive unit consisting of the rotor and the drive piston in a spring so that it is available for the countermovement after reversing the direction of movement and supports the electromagnetic drive force of the linear drive. EP 0 718 075 A1 and DE 24 19 164 A1 each disclose an electrodynamic drive for a striking mechanism, in which a return movement of a striking piston is absorbed by a mechanical helical spring as an end stop. During the renewed forward movement of the impact piston, the coil spring releases the stored energy and thus supports the forward or impact movement. However, the percussion mechanisms described are not air spring impact devices and have no separation between a drive piston and a percussion piston.

The coil springs also have the disadvantage that they can break due to the high impact speeds. In addition, not inconsiderable vibration noises arise. In addition, in a too weak sizing of the coil spring at a correspondingly high abutment speed of the percussion piston locking the spring can be achieved, which can lead to damage to the percussion.

The invention has for its object to provide a striking mechanism with an electrodynamic linear drive, in which a serving for reversing the direction of movement of a linearly moving drive unit electromagnetic magnetic drive is supported, without the disadvantages occurring in other types of percussion must be taken into account.

According to the invention the object is achieved by a striking mechanism according to claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

An impact mechanism according to the invention has an electrodynamic linear drive, a drive element which can be moved back and forth by the linear drive in a striking mechanism housing, a striking element for striking against a tool and a coupling device acting between the drive element and the striking element, via which the movement of the drive element can be transmitted to the striking element is. According to the invention, the percussion mechanism is characterized in that, seen in the direction of impact, in front of and / or behind the drive element, a reversing cavity is provided, and that the reversing cavity is at least temporarily separable from the environment, such that in the reversing cavity a reversing air spring acting against the drive element and / or against the striking element can be generated.

Accordingly, the invention provides that before and / or behind the drive element during operation of the impact mechanism, an air spring can be generated. This so-called reversing air spring is charged or "stretched" or compressed by the movement of the drive element when the drive element moves in the direction of the air spring or the receiving them reversing cavity. When the linear motion of the drive element is reversed, the air pressure then prevailing in the reversing air spring causes a force on the drive element which supports the reversal of the direction of movement and accelerates the drive element in the opposite direction.

It is not absolutely necessary that the reversing air spring is actually arranged spatially axially in front of or behind the drive element. The actual location of the reversing air spring located in the reversing cavity is rather arbitrary. However, it is important that the force effect of the reversing air spring on the drive element (or the Schlage- Lement) can be transferred or that, conversely, the charging of the reversing air spring by the drive element (impact element) is possible.

Air spring systems have proven themselves in the impact area and have a very high reliability. With appropriate design, they have a good efficiency. A complete compression of the air spring and thus a shock-like solid-state load of the relatively moving, the cavity-forming components can be avoided due to the Professivity of the spring characteristic (especially in the end). The overall length of the reversing air spring can accordingly be shorter than with linear metal spring systems (coil springs). In addition, air springs produce less sound.

In a particularly advantageous embodiment of the invention, the drive element is connected to a rotor of the linear drive and forms an integrated drive unit with the rotor. In particular, it is advantageous if the drive element carries the runner or is substantially completely formed by the runner, so that the runner simultaneously Function of the drive element takes over.

The linear motor may be a switched reluctance motor (SR motor) and has several drive coils (stator) in the range of movement of the rotor, which are switched according to the desired movement of the drive element. It should be noted that as a linear motor in connection with the invention, an electrodynamic drive, for. B. in the form of a single electromagnetic coil, which serves as a drive coil for the drive element. The return movement of the drive element can then be achieved, for. B. exclusively via a reversing air spring, which can be generated in a present before the drive element reversing cavity.

In one embodiment, the coupling device is formed by a stop acting between the drive element and the striking element. By the stop directly the drive movement of the drive element can be transmitted to the striking element. In this case, a variant is possible in which the coupling device is formed by two stops which reciprocate the striking element according to the movement of the drive element.

Preferably, the coupling device is designed as an effective between the drive element and the impact element in at least one direction elastic, in particular resilient element. This makes it possible to reduce the noise emission and the mechanical loads of the components involved. As an elastic element, a later-explained coupling air spring can be used. Alternatively, the attacks described above can be supplemented by an elastic element or provided with an elastic layer to develop a spring-elastic-see effect.

In a preferred embodiment, the reversing cavity is arranged at the end face to the drive element between the drive element and the percussion mechanism housing, in particular between the drive unit and the percussion mechanism housing. The reversing cavity can accordingly also be arranged on the front side of the runner coupled to the drive element. Due to the frontal arrangement, it is possible that the in the reversing cavity producible reversing air spring acts directly on the drive unit and thus on the drive element.

It is particularly advantageous that the reversible air spring which can be produced in the reversing cavity at least temporarily counteracts a movement of the drive element. In this way, the drive element can compress or charge the reversing air spring during its movement. After a reversal of the direction of movement of the drive element, the reversing air spring releases its stored energy and supports the countermovement of the drive element.

Advantageously, the reverse air spring, which can be produced in the reversing cavity, counteracts the movement of the drive element at least shortly before a reversal of the direction of the drive element. In this way, the reversing air spring contributes to a deceleration of the drive element just before its reversal. Depending on the dimensions of the linear drives and the reversing air spring can thereby possibly even be achieved that a return movement of the drive element is effected solely by the reversing air spring, while the linear drive is switched off. It is also possible that the linear drive controls the return movement of the drive element only with low power. Optionally, this is to provide a sensor that always determines the exact location of the drive element or the rotor and controlled in this way the effect of the reversing air spring. The linear drive can be controlled with the aid of the sensor system and a corresponding control so that the drive element and the rotor take a predetermined course of motion.

In a particularly advantageous embodiment of the invention, the reverberation cavity is a "first" cavity, which is provided in front of the drive element, wherein the first cavity is penetrated by a part of the impact element.

It is particularly advantageous if, alternatively or in addition to the first cavity, a reversing cavity is provided as the "second" cavity behind the drive element and the reversible air spring which can be generated in the second cavity is directed in an opposite direction to the direction of impact Return movement of the drive element at least over a movement path of the drive element of mehT than 30 percent, but in particular of more than 50 percent of the total return path of the drive element is effective.

While it has been defined above that a reversing cavity is arranged as a "first cavity" in front of the drive element, the reversing cavity behind the drive element is referred to as "second cavity". This different, unambiguous name only serves to improve understanding and is of no significance in terms of function. Both the first cavity in front of the drive element and the second cavity behind the drive element serve as a "reversing cavity" for receiving a reversing air spring, which supports the respective direction reversal of the drive element and the corresponding acceleration in the opposite direction. The first and second cavities may alternatively or jointly be provided in the striking mechanism.

The relatively long-lasting effectiveness of the reversing air spring in the second cavity means that the reversing air spring lying behind the drive element builds as long as possible, so that the drive unit has to exert force almost over its entire return path against this reversing air spring in order to compress it. While in the forward direction of the drive unit is striving in the direction of impact, that as much of the drive energy is transmitted to the striker and thus is available as impact energy, there is a certain surplus of energy in the return movement of the drive unit, because just run in the return movement no shock got to. This excess energy can now be used to load the existing behind the drive element reversing air spring over the longest possible way. The energy stored in the reversing air spring is then available during the renewed forward movement and supports the effect of the linear drive for impact generation. In this way, the linear drive can be dimensioned smaller, so that the applied power loss is reduced in the stator coils.

The driving force generated by the coils is proportional to the current flowing through them, while the power dissipation in the coils is square of the current is proportional. The impact energy is proportional to the product force times way. Extending the path of the drive element, one can reduce the drive from the linear, ie the stator coils, to generate force to obtain the same energy effect. This increases the efficiency. Even if the air spring itself generates losses, the overall balance remains positive in comparison with an electrical intermediate storage of the electrical braking energy in a DC link.

Preferably, a temporary closable ventilation opening is provided between the reversing cavity and the environment. Via the ventilation opening there is a possibility of air compensation between the reversing air spring in the reversing cavity and the surroundings in order to compensate for gap losses, which inevitably occur during the compression phases.

Preferably, the ventilation opening is provided in the hammer mechanism housing in a region which is run over by the drive element or the drive unit in a beating cycle. The opening and closing of the ventilation opening can be taken over in this way directly by the drive element or the drive unit itself, without the need for an additional control mechanism.

Accordingly, it is particularly advantageous if the ventilation opening can be opened or closed depending on the position of the drive element and / or the drive unit during a beating cycle.

Particularly advantageous is an embodiment in which the striking mechanism is realized as a pneumatic spring impact mechanism. For this purpose, the drive element is designed as a drive piston and the impact element as a percussion piston. The coupling device is formed by an effective in a coupling cavity between the drive piston and the percussion piston coupling air spring. The coupling air spring ensures the energy transfer from the drive piston to the percussion piston and gives the "air spring striking mechanism" its name in a known manner. Air spring impact devices are known from the prior art in many ways. New according to the invention, however, is the possibility of decelerating the drive piston and / or the percussion piston by the additional reversing air spring. The coupling air spring can also be considered as the main air spring, because a considerable part of the impact energy is transmitted through them.

In a particularly advantageous embodiment of the invention, the drive piston surrounds the percussion piston substantially. The impact piston has a piston head, wherein - in relation to the forward direction of impact - the coupling cavity is arranged with the coupling air spring for transmitting the impact energy to the percussion piston behind the piston head. Before the piston head, a further cavity for a return air spring is formed between the drive piston and the percussion piston. Such a hollow piston percussion with double-acting air spring is known per se. The drive piston thus has a cavity in which the percussion piston can reciprocate. The return air spring ensures a controlled return movement of the percussion piston after impact. The percussion piston is thereby necessarily connected with the movement of the drive piston during its return movement.

So that the hollow space for the return air spring can be formed in front of the piston head, it is necessary for the drive piston to surround the percussion piston not only in the rear area, namely in the region of the main air spring, but also in the front area, in front of the piston head , Only one of the piston head extending shaft of the percussion piston can be led out of the drive piston.

In a preferred embodiment, the reversing air spring acts only against the drive piston, but not against the percussion piston. The percussion piston is thus freely movable and receives all its kinetic energy via the coupling with the drive piston.

In another embodiment of the invention, however, the Revers air spring acts at least in one direction of movement of the percussion piston or even exclusively against the percussion piston. In this variant, the percussion piston, in particular during its return movement, can run against the reversing air spring and charge it, so that the reversing air spring, which is not coupled to the drive piston, assists the subsequent forward movement of the percussion piston.

In such an embodiment, it may be advantageous if the Impact piston is positively connected to a reversing piston, so that the reversing piston acts against the reversing air spring. It is then possible to arrange the reversing air spring at a location remote from the percussion piston.

In another embodiment of the invention, the reversing air spring acts at least temporarily axially against the drive element or the striking element, wherein the reversing cavity is provided in a region which is not arranged axially to the drive element. Therefore, a transmission device is provided with which the drive element can be force-coupled with the reversing air spring formed in the reversing cavity. The reversing cavity can in this way, for. B. laterally next to the drive element or in another area of the impact mechanism or driven by this hammer.

This embodiment allows the free arrangement of the reversing air spring at a location where it is suitable place. Thus, the reversing cavity with the reversing air spring z. B. arranged next to the drive element.

These and other advantages and features of the invention are explained in more detail below by means of examples with the aid of the accompanying figures. Show it:

Fig. 1 is a schematic representation of a section through a

Air spring impact mechanism realized impact mechanism according to a first embodiment of the invention, with a drive unit in the rear extreme position;

2 shows the air spring impact mechanism of Figure 1, with the drive unit in the middle position.

FIG. 3 shows the air spring impact mechanism of FIG. 1, with the drive unit in front extreme position; FIG.

Fig. 4 is a schematic representation of a section through a

Air spring impact mechanism realized impact mechanism according to a second embodiment of the invention, with a drive unit in the rear extreme position; 5 shows the air spring impact mechanism of FIG. 4, with the drive unit in the center position; FIG.

6 shows the pneumatic spring impact mechanism of FIG. 4, with the drive unit in the front extreme position;

Fig. 7 is a schematic representation of a section through a

Schlagwerk according to a third embodiment of

Invention; and

Fig. 8 is a schematic representation of a section through a

Schlagwerk according to a fourth embodiment of the

Invention.

Figures 1 to 3 and 4 to 6 show two different embodiments of the invention, realized as a pneumatic spring impact mechanism percussion in a greatly simplified sectional view. In particular, known components, such as electrical connections and sensors, are omitted since they do not affect the invention. The impact mechanism according to the invention can be used particularly advantageously in a rotary hammer and / or percussion hammer. In this case, different types of percussion can be realized, of which in particular air spring impact devices are particularly suitable.

FIGS. 1 to 3 show a first embodiment of the invention with an air spring impact mechanism driven by an electrodynamic linear drive. In this case, a drive unit explained later is in an illustration in FIG. 1 in an upper / rear extreme position, in FIG. 2 in a middle position and in FIG. 3 in a lower / front extreme position.

The air spring impact mechanism has a drive piston 1, which encloses a piston head 2 of a percussion piston 3. The percussion piston 3 extends with a shaft 4 through a front side of the drive piston 1 in a percussion piston guide 5 and can strike in its foremost position against a tool end 6, as shown in Fig. 3. Instead of the tool end 6, an intermediate header can also be provided in a known manner be.

Between the drive piston 1 and the percussion piston 3, a first cavity 7 is formed, in which a main air spring 8 acts. In the case of a forward movement of the drive piston 1, which can be axially moved back and forth in a percussion mechanism housing 9, a pressure builds up in the main air spring 8, which drives the percussion piston 3 forwards, so that it finally abuts against the tool end 6 can.

In a return movement of the drive piston 1 is formed in the main air spring 8, a negative pressure, which sucks the percussion piston 3 with its piston head 2. The return movement of the percussion piston 3 is also supported by the impact reaction at the tool end 6. Furthermore, as seen in the direction of impact, in front of the piston head 2, a return air spring 10 is formed in a further cavity, which comes into effect during the return movement of the drive piston 1. It also supports the return movement of the percussion piston 3.

To compensate for air losses in the air springs 8, 10 a plurality of air compensation pockets 1 1 are provided on the inner wall of the drive piston 1. Their operation is known from the prior art, so that at this point a more detailed description is unnecessary. Instead of the air compensation pockets 1 1, other air ducts are known which allow ventilation of the air springs 8, 10 in order to compensate for air losses caused by the compression can.

The oscillating, linear reciprocating movement of the drive piston 1 is effected by an electrodynamic linear drive. For this purpose, the drive piston 1 is coupled to a rotor 12 of the linear drive. The rotor 12 may be formed by a plurality of stacked electrical sheets and is reciprocated by alternating magnetic fields generated by a stator 13 of the linear drive. The operation of such a linear drive is known and z. B. in DE 102 04 861 Al described. In the linear motor, it may, for. B. may be a reluctance motor with external stator.

The rotor 12 and the drive piston 1 form a one-piece drive unit. Ness.

Before the drive piston 1, an additional, second cavity 14 is formed between the drive piston 1 and the percussion mechanism housing 9, which communicates with the environment in the positions shown in FIGS. 1 and 2 via ventilation openings 15.

In the position of the drive unit shown in FIG. 3, the rotor 12 has moved the drive piston 1 so far forward that the drive piston 1 has passed over the ventilation openings 15. As a result, the ventilation openings 15 are closed and the second cavity 14 is separated from the environment. Accordingly, an air spring is formed in the second cavity 14, which acts against the drive piston 1 and slows down its movement in the forward or impact direction.

In order that the air spring can be generated in a suitable manner in the second cavity 14 and in particular does not act against the percussion piston 3, which is intended to hit the tool end 6 as unhindered as possible, the drive piston 1 forms on its front side a piston surface 16. The piston surface 16 compresses the air spring in the second cavity 14th

Depending on the dimensions, it is possible that at the time when the ventilation opening 15 is closed by the drive piston 1, the stator 13 is de-energized. The braking of the existing drive piston 1 and the rotor 12 drive unit is then carried out exclusively by the air spring in the second cavity 14. Since the compressed air spring then wants to relax again, it also pushes the drive unit against the direction of impact. Then, if necessary, the stator 13 can be excited again in order to support the return movement.

The air spring in the second cavity 14 should be positioned or dimensioned such that the drive unit is intercepted at the lower reversal point before the percussion piston 3 strikes the tool end 6.

According to the air spring in the second cavity 14 is on the opposite side, behind the drive piston 1 and behind the entire Drive unit, a third cavity 17 between the drive piston 1 and the drive unit and the impact mechanism housing 9 is formed. The striking mechanism housing 9 is shown only schematically in the figures. Of course, the percussion mechanism housing 9 may be assembled from different building dements or have a different design than that shown in the figures.

The third cavity 17 is in the positions shown in FIGS. 2 and 3 of the drive unit via ventilation openings 18 in communication with the environment.

In the position shown in Fig. 1, however, the drive unit has overflowed the ventilation openings 18 and thus closed. Accordingly, the third cavity 17 is separated from the environment, so that it can form an air spring in it, as shown in particular in Fig. 1. This air spring slows down the movement of the drive unit during its return movement. Depending on the dimensions of the air spring in the third cavity 17 may be strong enough to completely decelerate the return movement and to convert into a counter-movement, namely a movement in the direction of impact. Again, the stator 13, similar to the effect of the air spring in the second cavity 14, switched off or switched on only as needed.

The air spring in the third cavity 17 should be constructed as long as possible so that it is compressed over a longer path of movement of the drive unit. In the return movement of the drive unit relatively little energy is required compared to the impact movement, which can then be stored in the air spring in the third cavity 17. The stored energy is then available during the forward movement of the drive piston 1 in order to move it against the percussion piston 3. The stored energy in the air spring of the third cavity 17 thus supports the linear drive, which can either be dimensioned smaller or with which a significantly higher impact energy can be achieved.

Figs. 4 to 6 show a second embodiment of the invention, with regard to the design of the electrodynamic linear drive of the differs in the first embodiment shown in Figs. 1-3. Identical components are identified by the same reference numerals. 4 shows the drive unit in an upper / rear extreme position, FIG. 5 in a middle position and FIG. 6 in a lower / front extreme position.

Such a linear drive can, for. B. be realized by a magnetic motor.

The drive piston 1 carries a rotor 19 in the form of two sword- or plate-shaped projections 20. On the extensions 20 magnets 21 are attached from rare earth, which are reciprocating in a stator 22 and forth.

The rotor 19 may alternatively be provided in another, not shown embodiment of the invention with an annular projection which is movable in a likewise annular stator.

Behind the drive piston 1, a third cavity 23 is formed in cooperation with the impact mechanism housing 9, in which an air spring can be generated. As already explained above, the term drumming housing 9 is to be understood broadly. It is only important that in cooperation with the drive piston 1 or the drive unit formed from the drive piston 1 and the rotor 19, a cavity can be generated in which an air spring can form.

In the rotor 19, a ventilation opening 24 is formed, which is brought in the position shown in Fig. 5 with a present in the striking mechanism housing 9 ventilation opening 25 in coverage, so that air from the environment in the third cavity 23 can flow to the previously to replenish lost air during the compression of the air spring. In the positions shown in Figs. 4 and 6, the ventilation openings 24 and 25 are not superimposed, so that the third cavity 23 is separated from the environment.

The interaction of drive piston 1 and percussion piston 3 as well as the operation of the second cavity 14 corresponds to the first embodiment, so that a further description is omitted. Fig. 7 shows a schematic section through a third embodiment of the invention. In contrast to the Luftfederschlagwerken described above with reference to FIGS. 1 to 6, the third embodiment of FIG. 7 relates to a striking mechanism, in which the energy for the impact movement can not be transmitted by an air spring. Accordingly, this striking mechanism can not be called an air spring impact mechanism.

The percussion mechanism is driven by an electrodynamic linear drive in a manner similar to the above-described air spring impact devices. It has a drive unit 30, which combines the functions of a drive element and a rotor of the linear drive with each other. The drive unit 30 is shown only schematically in FIG. So z. B. the structure of the rotor is not shown in detail. With regard to the rotor, however, the details described above for the rotor 12 (FIG. 1) or the rotor 19 (FIG. 4) apply.

The drive unit 30 is analogous to the manner described above in a tubular percussion gear housing 9 reciprocable, wherein the movement is effected by the stator 13.

The drive unit 30 is of sleeve-shaped construction and has in its interior a hollow region in which the percussion piston 3 forming a striking element can be moved back and forth. The percussion piston 3 then hits in a known manner against the tool, not shown in Fig. 7.

To transmit the movement of the drive unit 30 to the percussion piston 3, a coupling device is provided. The coupling device has a driver 31 carried by the percussion piston 3, in particular by the piston head 2 of the percussion piston 3, which can be moved back and forth in recesses of the drive unit 30 in the working direction of the percussion mechanism. The driver 31 may, for. B. by a piston head 2 of the percussion piston 3 penetrating transverse pin are formed, as shown in Fig. 7.

The recesses in the drive unit 30 are formed by two axially extending longitudinal grooves 32, which penetrate the wall of the hollow cylindrical drive unit 30. At the end faces of the longitudinal grooves 32 lower stops 33 and upper stops 34 are formed, which limit the longitudinal movement of the driver 31 in the longitudinal grooves 32.

In a reciprocating motion of the drive unit 30 thus the percussion piston 3 is forcibly guided over the respective stops 33, 34 and the driver 31. During a forward movement of the drive unit 30 (downwards in FIG. 7) in the direction of the tool (working direction), the upper stops 34 press the catch 31 downwards with the percussion piston 3, the percussion piston 3 shortly before striking the tool or tool . should fly freely between the intermediate striker to avoid damaging repercussions on the drive unit 30 and the catch 31. In the subsequent subsequent return movement of the drive unit 30, the lower stops 33 come into contact with the driver 31 and pull the rest of the rebounding piston of the rest of the tool 3 against the working direction. Thereafter, the duty cycle is repeated by the drive unit 30 with the upper stops 34 accelerates the percussion piston 3 again against the tool.

The coupling device is thus not formed by an air spring, but by the longitudinal grooves 32, the stops 33, 34 and the driver 31 in this embodiment. Of course, the structure described is merely illustrative. There are numerous other possibilities for the skilled artisan, as the movement of the drive unit 30 can be transferred to the percussion piston 3.

Fig. 8 shows a schematic representation of a section through a striking mechanism according to a fourth embodiment of the invention.

The basic structure of the impact mechanism is identical to the percussion mechanism according to FIG. 7. In addition, the piston head 2 of the percussion piston 3 is positively coupled via a piston rod 35 with a reversing piston 36. The reversing piston 36 is in a z. B. belonging to the percussion mechanism housing 9 reversing cylinder 37 according to the movement of the percussion piston 3 back and forth.

The reversing piston 36 and the reversing cylinder 37 rewrite one Reversing cavity 38 in which a reversing air spring 39 is formed.

Similar to the reversing air spring in the reversing cavity 17 in the first embodiment shown in Figs. 1 to 3 braking a return movement of the drive piston 1 shown there and later supports a forward movement, the reversing air spring 39 shown in Fig. 7 at a return movement of the percussion piston 3 stretched so that they can support a forward movement of the percussion piston 3 below.

The compensation of air losses of the reversing air spring 39 is carried out in a similar manner as in the embodiments described above, so that it is possible to dispense with a new detailed description at this point.

Also applies to the reversing air spring 39, that it may be particularly useful when it is charged over a longer path of movement of the percussion piston 3. Compressing the reversing air spring 39 takes place particularly reliably in the fourth embodiment shown in FIG. 8, because the forced movement of the percussion piston 3 is achieved by the form-fitting coupling between the drive unit 30 and percussion piston 3 effected by the coupling device.

Due to the invention, it is possible to increase the efficiency of a linearly driven electrodynamic impact mechanism. By buffering energy in the air springs, a more uniform electrical power consumption with low peak loads can be achieved. In addition, shock loads on the hammer housing in the reversal points of the drive unit are avoided. By striking mechanism according to the invention a greater demolition performance can be achieved, at the same time lower hand-arm vibrations.

Claims

Patent claims

1. Schlagwerk, with an electrodynamic linear drive (12, 13, 19, 22); - One of the linear drive (12, 13, 19, 22) in a striking mechanism housing (9) reciprocable drive element (1); a striking element (3) for striking against a tool (6); a coupling device (8) which acts between the drive element (1) and the striking element (3) and via which the movement of the drive element (1) can be transmitted to the striking element (3); characterized in that seen in the direction of impact, in front of and / or behind the drive element (1), a reversing cavity (14, 17, 23) is provided; and that the reversing cavity (14, 17, 23) is at least temporarily separable from the environment, such that in the reversing cavity (14, 17, 23) a against the drive element (1) and / or against the Impact element (3) acting reversing air spring can be generated.

2. striking mechanism according to claim I _1, characterized in that the drive element (1) with a rotor (12) of the linear drive is connected and with the rotor (12) forms a drive unit.

3. impact mechanism according to claim 1 or 2, characterized in that the coupling device between the drive element (1) and the striking element (3) effective stop (33, 34).

4. striking mechanism according to one of claims 1 to 3, characterized in that the coupling device between the drive element (1) and the striking element (3) in at least one direction effective elastic element (8).

5. striking mechanism according to one of claims 1 to 4, characterized in that the reversing cavity (14, 17, 23) frontally to the drive element (1) between the drive element (1) and the striking mechanism housing (9), in particular between the drive unit and the percussion gear housing (9) is arranged.

6. striking mechanism according to one of claims 1 to 5, characterized in that in the reversing cavity (14, 17, 23) producible Re- 1 versier air spring at least temporarily a movement of the drive element (1) is counteracting.

7. striking mechanism according to one of claims 1 to 6, characterized in that in the reversing cavity (14, 17; 23) producible Reverse-air spring at least shortly before a reversal of direction of the drive element (1) the movement of the drive element (1 ) is counteracting.

8. striking mechanism according to one of claims 1 to 7, characterized in that

10. the reversing cavity is a first cavity (14) arranged in front of the drive element (1); and that the first cavity (14) is penetrated by a part of the striking element (3).

, _j -

9. striking mechanism according to one of claims 1 to 8, characterized in that the reversing cavity is behind the drive element (1) arranged second cavity (17; 23); in the case of a return movement of the drive element (1) directed counter to the direction of impact at least over a movement path of the drive element (1) of more than 30 percent, in particular more than 50 percent, of the drive element (1) that can be generated in the second cavity (17; entire return path of the drive element (1) is effective.

10. impact mechanism according to one of claims 1 to 9, characterized marked records 25 that a temporarily closable ventilation opening (15, 18, 24,

25) is provided between the reversing cavity (14, 17, 23) and the environment.

1 1. striking mechanism according to claim 10, characterized in that the

Ventilation opening (15, 18, 24, 25) in the percussion mechanism housing (9) in one

30 area is provided, which is run over in a beating cycle of the drive element (1) or the drive unit.

12. striking mechanism according to claim 10 or 11, characterized in that the ventilation opening (15, 18; 24, 25) depending on the position of the drive

35 elements (1) and / or the drive unit is open or closed during a beating cycle.

1 13. striking mechanism according to one of claims 1 to 12, characterized in that the striking mechanism is a Luftfederschlagwerk; the drive element is designed as a drive piston (1); the impact element is designed as a percussion piston (3); and in that the coupling device has an in a coupling cavity (7) between the drive piston (1) and the percussion piston (3) effective coupling air spring (8).

14. impact mechanism according to claim 13, characterized in that

10 - the drive piston (1) substantially surrounds the percussion piston (3); the percussion piston (3) has a piston head (2); with respect to the direction of impact of the coupling cavity (7) with the coupling air spring (8) behind the piston head (2) is arranged;

-. c - in front of the piston head (2) between the drive piston (1) and the

Impact piston (3) a further cavity for a return air spring (10) is formed.

15. Impact device according to claim 13 or 14, characterized in that the reversing air spring acts only against the drive piston (1) is not ^0, however, against the percussion piston (3).

16. striking mechanism according to claim 13 or 14, characterized in that the reversing air spring acts at least in a direction of movement of the percussion piston only against the percussion piston (3).

25

17. striking mechanism according to one of claims 13 to 16, characterized in that the percussion piston (3) with a reversing piston (36) is positively connected; and that the reversing piston (36) acts against the reversing air spring (39). 30

18. impact mechanism according to any one of claims 1 to 17, characterized in that the reversing air spring acts at least temporarily axially against the drive element (1) or the striking element (3);

35 - the reversing cavity is not arranged axially to the drive element; and that a transmission device is provided for the power-driven Coupling of the drive element with the reversing air spring formed in the reversing cavity.