EP1368160B1 - Pneumatic percussive tool with a movement frequency controlled idling position - Google Patents

Description

The invention relates to an air spring hammer mechanism for a percussion and / or Hammer drill according to the preamble of claim 1.

Such an air spring hammer mechanism is known from DE-A-2641070.

Air spring hammer mechanisms have long been in different designs known in which a drive piston back and forth from a crankshaft is moved. There is also a back and forth in front of the drive piston Movable percussion piston, so that between the drive piston and the Percussion piston a cavity is formed to accommodate an air spring serves. This air spring, which acts as an air cushion, transmits the movement of the driven drive piston on the percussion piston, which is the Movement of the drive piston follows with a time delay. The percussion piston finally strikes a shank of a tool or an intermediate one Döpper and releases its impact energy to the tool.

Such air spring hammer mechanisms have been used in practice both with hammers with electromotive drive as well as with internal combustion engines Hammering proven.

In particular, the internal combustion hammers have between one Motor shaft and the crankshaft of the air spring hammer mechanism a centrifugal clutch, which serves to disconnect the percussion drive when the internal combustion engine rotates at idle speed. This should on the one hand a perfect idling of the engine ensured and on the other hand easier engine starting. Such a centrifugal clutch is technically complex, requires installation space and ultimately leads to a relatively expensive, heavy and wear-prone hammer.

The invention has for its object to provide an air spring hammer mechanism, where the benefits of torque transmission and interruption can be maintained by the centrifugal clutch without the described To accept disadvantages.

According to the invention the object is achieved by an air spring hammer mechanism Claim 1 solved. Advantageous further developments of the invention are defined in the dependent claims.

In the air spring hammer mechanism according to the invention is an idle air duct provided, via which the air spring receiving the striking operation Cavity between drive and percussion pistons with a compensation space connected is. The compensation room can e.g. B. the crankcase in which the crankshaft rotates to drive the drive piston. Alternatively the compensation space can also be the area around the air spring hammer mechanism act, making sure that dirt, dust, Moisture or the like does not come from the compensation room and the idle air duct can penetrate into the cavity.

Furthermore, according to the invention, a valve is arranged in the idle air duct, the open and closed position of the frequency of movement of the drive piston depends. It is thereby achieved according to the invention that the Deactivation of the air spring hammer mechanism, i.e. the transition from hammer operation in the idle mode not mechanically in the known manner via a Centrifugal clutch takes place, but via a movement frequency controlled Interruption of the suction effect of the striking mechanism.

In an advantageous embodiment of the invention, the valve is below a predetermined frequency of movement of the drive piston can be opened so that a communicating connection via the idle air duct exists between the cavity and the compensation space. By doing resulting idle operation can also occur in the cavity no air spring if the drive piston continues to oscillate build up more, which leads to the fact that in the field operation of the Air spring driven percussion pistons are now neither driven forward is still sucked back. A reliable interruption of the Field operation is thus guaranteed.

The frequency of movement of the drive piston represents a parameter that as far as the invention is concerned - with a number of further parameters is equivalent. This particularly includes the speed of the drive piston driving crankshaft or wobble shaft and the speed of the a drive motor acting on the drive mechanism. The speed the drive motor in turn can, for. B. by the ignition frequency, so determine the ignition strokes when the drive motor is an internal combustion engine is. With an electric motor, the speed can be adjusted based on the current consumption determine. Because the drive motor always with the drive piston over the drive mechanism is connected, from the movement behavior one of these elements also the movement behavior of the other elements determine. Due to the mostly positive energy transfer from Drive motor to drive piston there is a linear relationship between the individual movement parameters.

The same applies to other drive concepts. If the drive piston z. B. is driven by a linear motor, offer the expert further possibilities due to different operating parameters To determine the frequency of movement of the drive piston.

Accordingly, there is a sensor device for detecting the movement frequency of the drive piston in such a way that they also have a movement parameter can detect that can not be directly assigned to the drive piston is. Then the sensor device is, for. B. able to move frequency of the drive piston by detecting the speed of the Determine drive piston driving crankshaft.

The valve is thus dependent in a preferred embodiment from a signal from a speed sensor detecting the speed of the crankshaft can be opened and closed.

In the broader sense, the speed sensor is also one on the crankshaft arranged, movable centrifugal force weight to view the valve is controllable, the valve depending on a position of the Centrifugal weight can be opened and closed.

In another embodiment of the invention, the speed sensor is used for electrical or electronic recording of the crankshaft speed. His signal is in a suitable manner to the valve, e.g. B. an electromagnetic Valve to deliver.

In a particularly advantageous embodiment of the invention, a additional idling device is provided with which regardless of the frequency of movement of the drive piston or the speed of the crankshaft Cavity in communicating connection with the compensation space is when the percussion piston slides out by one of it Tool from a housing of the hammer and / or hammer drill reaches a front axial position serving as an idle position. Thereby it is possible that the air spring hammer mechanism is independent of the motion frequency or speed-dependent idle operation described above enters an idle state. In this air spring hammer mechanism exist therefore two ways to achieve idle: Firstly idle is automatically set when the movement frequency of the Drive piston or the speed of the crankshaft below the predetermined Value falls. On the other hand, the air spring hammer mechanism also works independently of which in the idle state when the operator removes the tool from the workpiece Stone lifts off and the tool accordingly can slide out of the hammer housing.

The air spring hammer mechanism according to the invention can with different design principles be realized, for. B. in the so-called hollow club impact mechanism, where the drive piston is in a hollow area of the Percussion piston moves, in a hollow piston impact mechanism, in which the drive piston has a hollow area in which the percussion piston is axially is movably received or in a pipe impact mechanism, in which the Percussion piston and the drive piston essentially the same diameter have and are performed together in a percussion tube.

Fig. 1

einen schematischen Schnitt eines als "Hohlschlägerschlagwerk" ausgeführten erfindungsgemäßen Luftfederschlagwerks im Schlagbetrieb;

Fig. 2

das Luftfederschlagwerk von Fig. 1 im Leerlaufbetrieb;

Fig. 3

ein als "Hohlkolbenschlagwerk" ausgeführtes erfindungsgemäßes Luftfederschlagwerk;

Fig. 4

ein als "Rohrschlagwerk" ausgeführtes erfindungsgemäßes Luftfederschlagwerk; und

Fig. 5

ein als "Hohlkolbenschlagwerk" ausgeführtes erfindungsgemäßes Luftfederschlagwerk mit elektronisch angesteuertem Ventil.

These and other advantages and features of the invention are explained in more detail below using an example with the aid of the accompanying figures. Show it:

Fig. 1

a schematic section of an air spring hammer mechanism according to the invention, executed as a "hollow hammer hammer mechanism" in impact operation;

Fig. 2

the air spring hammer mechanism of Figure 1 in idle mode.

Fig. 3

an air spring hammer mechanism according to the invention designed as a "hollow piston hammer mechanism";

Fig. 4

an air spring impact mechanism according to the invention designed as a "pipe impact mechanism"; and

Fig. 5

an air spring hammer mechanism according to the invention, designed as a "hollow piston hammer mechanism" with an electronically controlled valve.

Fig. 1 shows a section through an air spring hammer mechanism according to the invention in field operation.

A crankshaft 1 drives a drive piston 3 axially via a connecting rod 2 and forth. The drive piston 3 is guided in a percussion piston 4, which in turn axially movable back and forth in a tubular striking mechanism housing 5 is.

Such an air spring hammer mechanism is also called a hollow hammer mechanism referred to and is known per se.

In the impact mode, the drive piston 3 moves in the impact piston 4 and forth, whereby in a between the drive piston 3 and the percussion piston 4 trained cavity 6 an air spring is built. When moving forward of the drive piston 3 (in Fig. 1 to the left), the air in Cavity 6 compressed. The energy of the air compressed as an air spring is delivered to the percussion piston 4 and also drives it forward on a schematically illustrated shaft 7 of a chisel tool. Instead of The shaft 7 can also be a not shown, but known per se The striking piston 4 acts on the striker.

After a blow, the drive piston 3 by the rotary movement of the Crankshaft 1 has already started its way back and sucks the from the shaft 7 rebounding percussion piston 4 further back until the Drive piston 3 finally changes into the forward movement and by building up a pressure in the air spring, the stroke cycle starts again.

The cavity 6 is via an idle opening 8, one on the inside of the Percussion mechanism housing 5 formed annular groove 9 and a channel 10 with a serving as compensation chamber crank chamber 11. The crankcase 11 essentially describes the space in which the crankshaft 1 is movable with the connecting rod 2 and the drive piston 3.

The idle opening 8, the annular groove 9 and the channel 10 together form one Idle air channel.

At the crankcase end of the channel 10, a valve 12 is arranged, the is integrally coupled to a centrifugal weight 13. The valve 12 is together with the centrifugal weight 13 against the action of a stop 14 supported spring 15 with respect to the crankshaft 1 radially in a guide 16 mobile.

Fig. 1 shows the impact operation of the air spring hammer mechanism in which the crankshaft 1 with the operating speed of an internal combustion engine, not shown or - if between the internal combustion engine and the crankshaft 1 Gearbox is arranged - with a corresponding to the operating speed Speed is driven. Due to the flyweight 13 and possibly centrifugal force acting on the valve 12 also becomes the valve 12 together with the centrifugal weight 13 against the action of the spring 15 in the Guide 16 held radially outward in the position shown in Fig. 1. The channel 10 is closed by the valve 12.

Fig. 2 shows the same air spring hammer mechanism as Fig. 1, but in idle mode.

The idle mode is a state in which the internal combustion engine, not shown not at operating speed, but at a lower one Speed, especially the idle speed rotates.

Due to the reduced speed of the crankshaft 1, the spring 15 is now strong enough, the centrifugal weight 13 with the valve 12 radially inwards into the Press guide 16. The valve 12 thereby comes into an open position, in which an opening 17 is aligned with the channel 10 and opens it.

This creates a communicating connection between the cavity 6 via the idle opening 8, the annular groove 9 and the channel 10 with the Crank chamber 11. As a result, no air pressure can build up in the cavity 6 and accordingly no longer build an air spring. Although the Drive piston 3 still moves back and forth in the percussion piston 4, remains the percussion piston 4 in its idle position because of lack of Changes in air pressure no longer affect pneumatic forces. The Air spring hammer mechanism is therefore reliably in idle mode.

Only when the engine speed and thus the crankshaft speed increase 1, the effect of the spring 15 is overcome, so that the centrifugal weight 13th slides radially outward with the valve 12 and closes the opening 17. As a result, the cavity 6 is separated from the crank chamber 11 and it can build up an air spring in the cavity 6 again.

The centrifugal weight 13 also serves strictly as a speed sensor, since it detects a change in speed by moving its radial position. The shift in the radial position is in turn to be regarded as a signal depending on which one integrally connected to the centrifugal weight 13 Valve 12 is opened or closed.

The speed of the crankshaft 1 represents in the embodiment described above is the criterion according to which the frequency of movement of the drive piston 3 is determined. Instead of crankshaft speed, however, could also the speed of the drive motor, not shown, by the Flyweight 13 are detected.

Instead of crankshaft 1, it is possible to drive piston 3 by others Drive mechanisms, such as. B. a swashplate in oscillating rear and bring float.

In addition, it is mentioned that through the idle opening 8, a Breakthrough 18 and a channel 19 formed an additional idling device becomes. Via the idle opening 8, the opening 18 and a channel 19 can be used regardless of the connection described above Ring groove 9 and the channel 10 another communicating connection between the cavity 6 and the crank chamber 11. How it works the additional idling device will be explained later with reference to FIG. 3.

3 and 4 show other construction principles for air spring hammer mechanisms according to the invention, the operation of valve 12 and centrifugal weight 13th depending on the crankshaft speed with the air spring hammer mechanism 1 and 2 is comparable. It is therefore only the essentials Differences are explained.

Fig. 3 shows a schematic section also as a hollow piston hammer mechanism designated air spring hammer mechanism according to the invention, in which by the Connecting rod 2, a hollow drive piston 20 is moved back and forth.

Inside the cavity of the drive piston 20 is a solid percussion piston 21 also axially reciprocable.

In the cylindrical side wall of the drive piston 20 there are a number of idle openings 22 is provided, via which a between the drive piston 20 and the impact piston 21 formed cavity 23 with an opening 24 and the channel 10 is connectable.

The channel 10 leads to the crank chamber 11, which serves as a compensation chamber, the valve 12 with the centrifugal weight 13 in that already described above Way is interposed.

The idle openings 22 are arranged axially to one another, so that between the cavity 23 and the opening 24 a permanent connection is ensured in each axial position of the drive piston 20.

In addition, an opening 25 is provided which leads to another channel 26 leads, which is also in communication with the crankcase 11 stands. The opening 25 is of others in the drive piston 20 provided idle openings 27 can be driven over.

In this way, an additional idling device is realized with the regardless of the crankshaft speed described above Idle device of the cavity 23 with the crank chamber 11 in communicating connection can be brought when the percussion piston 21 in his foremost axial position, not shown in FIG. 3. This also as Axial position designated idle position is possible when the operator lifts the chisel off the rock to be machined so that the shaft 7 something slides out of the hammer housing. Then one runs over rear edge 28 of the percussion piston 21 the opening 25 and gives one Connection between the cavity 23 and the opening 25 free. In this Case, the cavity 23 is communicating with the crank chamber 11 Connected so that no air spring build up in the cavity 23 can. This idling device enables independent of the movement frequency dependent Idle operation or the speed of the crankshaft 1 the achievement of an idle state and thus serves as a supplement.

Fig. 4 shows a variant of the invention, also referred to as a pipe impact mechanism Pneumatic spring hammer mechanism.

A drive piston 30 driven by the crankshaft 1 and the connecting rod 2 is axial in a housing part also referred to as percussion tube 31 can be moved back and forth.

In the same percussion tube 31 there is essentially a solid percussion piston 32 same diameter of the drive piston 30 also axially movable arranged.

There is a cavity between the drive piston 30 and the percussion piston 32 33 designed to receive an air spring for driving the percussion piston 32 serves. The cavity is via an opening 34 and the channel 10 33 can be brought into communicating connection with the crank chamber 11, at the end of the channel 10, the valve 12 with the centrifugal weight 13 in the already described manner is arranged.

Here too, the communicating connection between the Cavity 33 and the crank chamber 11 depending on the speed of the Control crankshaft 1.

Furthermore, an opening 35 is provided as an additional idling device, which leads to a further channel 36 and thus to the crank chamber 11.

As already described in connection with Fig. 3, this serves additional Idle device that the striking mechanism then also in an idle state can reach when the percussion piston 32 after lifting the chisel of the rock to be worked and the corresponding sliding out Shaft 7 from the housing in its foremost, not shown in Fig. 4 Position reached. In that case, a rear edge 37 of the percussion piston slides 32 through the opening 35 and gives a connection between the cavity 33 and the channel 36 free.

The additional idling device has the consequence that the striking mechanism too regardless of the engine or crankshaft speed in the idle state can reach.

After placing the tool again on the rock to be machined and accordingly shifting the shaft 7 into the interior of the housing the percussion piston 32 is pushed into the position shown in FIG. 4, whereby the connection between cavity 33 and channel 36 or Crank chamber 11 is closed. As far as the crankshaft 1 on operating speed is located and accordingly the opening 17 on the valve 12 is closed field operation can be resumed.

Fig. 5 shows an air spring hammer mechanism, which works on the same principle as that Air spring hammer mechanism of Fig. 3 works. On a new description of the mechanical interrelationships are therefore dispensed with.

Instead of the valve 12 and the centrifugal weight 13, however, there is a speed sensor 40 arranged in the vicinity of the crankshaft 1. The speed sensor 40 is used to record the speed of the crankshaft 1. It can be work on known principles, such as B. magnetic, optical, inductive etc.

The speed sensor 40 supplies a signal to a controller, not shown, the one in a connecting the cavity 23 with the crank chamber 11 Channel 42 arranged electromagnetic valve 41 depending of the determined speed value. So much for the speed of the crankshaft 1 is above a predetermined value, the valve 41 is closed and interrupts a connection between the cavity 23 and the crank chamber 11. The valve 41 is, for. B. with a 2/2-way valve a valve body that can be swiveled electromagnetically between two positions.

However, if the speed of the crankshaft 1 is below the predetermined value lies, the control opens the valve 41, so that a communicating connection between the cavity 23 via the channel 42 to the crank chamber 11 consists.

The electronic solution shown in Fig. 5 is related to that in context with the mechanical solution presented in FIGS. 1 to 4 the advantage that the "dead spaces", i.e. H. between cavities 6, 23 and 33 and the valve 12, 41 existing space due to the smaller distance are smaller. This enables better sucking back in blow operation.

In all of the embodiments of the invention presented, it has been described that that the cavity between the drive and percussion pistons with the as Compensation chamber serving crankcase is to be connected. alternative other cavities in one can also serve as compensation space Percussion and / or rotary hammers are used which have a certain freedom from dust and thus guarantee cleanliness. In principle, it would also be possible to Cavity in connection with the environment of the percussion and / or hammer drill bring to. In this case, however, provision would have to be made for an air filter be taken to prevent dirt from entering the cavity via the compensation chamber and the idle channel can.

In addition to the mechanical and electromagnetic effects already described Valves 12, 41 can also other types of valves known per se, such as z. B. Piezo valves can be used.

In the above description it is assumed that the speed of the crankshaft 1 is identical to the speed of the internal combustion engine. Of course Variants are also possible in which between the engine and the Crankshaft 1 is a gearbox for speed conversion. Conveniently, is used as the limit for opening and closing the Valve serving predetermined speed value of the crankshaft 1 accordingly adapted to the idle speed of the internal combustion engine.

Instead of determining the crankshaft speed by the sensor device it is also possible to directly determine the frequency of movement of the drive piston, z. B. via a proximity sensor or the movement of the connecting rod 2 to be recorded. There are also numerous possibilities, the movement frequency of the drive piston based on the speed of the drive motor, its Ignition frequency or - if it is an electric motor - the electrical drive frequency or its current consumption.

Claims (15)

1. Pneumatic spring percussive mechanism for an impact hammer and/or a hammer drill, having

   a driving piston (3; 20; 30) which can be moved in a reciprocating manner by a driving mechanism (1);

   a percussion piston (4; 21; 32) which can be moved in a reciprocating manner and is disposed coaxially to the driving piston (3; 20; 30);

   a hollow chamber (6; 23; 33) which is formed between the driving piston (3; 20; 30) and the percussion piston (4; 21; 32) and is intended to receive a pneumatic spring in a striking operation of the pneumatic spring percussive mechanism, and having an idling air duct (8, 9, 10; 22, 24; 34) by means of which the hollow chamber (6; 23; 33) is connected to a compensating chamber (11),

   characterised by

   a valve (12; 41) disposed in the idling air duct (8, 9, 10; 22, 24; 34; 42), the open and closed position of which valve is dependent upon the frequency of movement of the driving piston (3; 20; 30).
2. Pneumatic spring percussive mechanism as claimed in claim 1, characterised in that the valve (12; 41) can be opened if the frequency of movement of the driving piston (3; 20; 30) falls below a predetermined frequency so that a communication connection between the hollow chamber (6; 23; 33) and the compensating chamber (11) is produced via the idling air duct (8, 9, 10; 24; 34) and the pneumatic spring percussive mechanism is in an idling operation.
3. Pneumatic spring percussive mechanism as claimed in claim 1 or 2, characterised in that the frequency of movement of the driving piston (3; 20; 30) can be detected by a sensor device (13; 40).
4. Pneumatic spring percussive mechanism as claimed in claim 3, characterised in that the frequency of movement of the driving piston (3; 20; 30) can be sensed by the sensor device (13; 40) using parameters equivalent to the frequency of movement of the driving piston, namely

   a rotational speed of a wobble shaft or crank shaft (1) appertaining to the driving mechanism and driving the driving piston (3; 20; 30);

   a rotational speed of a driving motor acting upon the driving mechanism;

   an ignition frequency of an internal combustion engine serving as a driving motor; or

   current consumption of an electric motor serving as a driving motor.
5. Pneumatic spring percussive mechanism as claimed in claim 3 or 4, characterised in that the valve (12, 41) can be opened and closed in dependence upon a signal of a rotational speed sensor (13; 40) appertaining to the sensor device and sensing the rotational speed of the crank shaft.
6. Pneumatic spring percussive mechanism as claimed in any one of claims 1 to 5, characterised in that the valve (12) can be controlled by means of a moveable centrifugal weight (13) disposed on the crank shaft (1).
7. Pneumatic spring percussive mechanism as claimed in claim 6, characterised in that the valve (12) can be opened and closed in dependence upon a position of the centrifugal weight (13).
8. Pneumatic spring percussive mechanism as claimed in any one of claims 1 to 7, characterised in that the compensating chamber is a crank chamber (11) allocated to the crank shaft (1) or is the area around the pneumatic spring percussive mechanism.
9. Pneumatic spring percussive mechanism as claimed in any one of claims 1 to 8, characterised in that an additional idling device (18, 19; 25, 26; 35, 36) is provided with which, independently of the frequency of movement of the driving piston (3; 20; 30), the hollow chamber (6, 23; 33) can be brought into a communicating connection with the compensating chamber (11) or with another compensating chamber when the percussion piston (4; 21; 32), by means of a tool, which it acts upon, sliding out of a housing of the impact hammer and/or drill hammer, has come into a forward axial position, which serves as an idling position, so that an idling condition is set independently of the idling operation which is dependent upon the frequency of movement.
10. Pneumatic spring percussive mechanism as claimed in claim 9, characterised in that the additional idling device has at least one idling orifice (25; 35) passing through a side wall of the driving piston (3; 20; 30) or of the striking piston (4; 21; 32).
11. Pneumatic spring percussive mechanism as claimed in any one of claims 1 to 10, characterised in that the percussion piston (4) has at least one hollow region in which the driving piston (3) is received in an axially moveable manner.
12. Pneumatic spring percussive mechanism as claimed in any one of claims 1 to 10, characterised in that the driving piston (20) has at least one hollow region in which the percussion piston (21) is received in an axially moveable manner.
13. Pneumatic spring percussive mechanism as claimed in any one of claims 1 to 10, characterised in that a percussive mechanism pipe (31) is provided in which the percussion piston (32) and the driving piston (30) are guided in an axially moveable manner.
14. Pneumatic spring percussive mechanism as claimed in any one of claims 1 to 13, characterised in that the crank shaft (1) driving the driving piston (3; 20; 30) can be driven by an internal combustion engine.
15. Pneumatic spring percussive mechanism as claimed in claim 14, characterised in that the predetermined frequency of movement of the driving piston (3; 20; 30) substantially corresponds to an idling rotational speed of the internal combustion engine.

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