EP0646056B1 - Process and device for actuating a percussive tool by means of compressed air - Google Patents

Abstract

PCT No. PCT/EP93/01193 Sec. 371 Date Nov. 15, 1994 Sec. 102(e) Date Nov. 15, 1994 PCT Filed May 13, 1993 PCT Pub. No. WO93/23211 PCT Pub. Date Nov. 25, 1993In a rotary compressor unit an inner and an outer rotor turn in an intermeshed rotation, a compression space and a suction space being formed alternately on radially offset sides of the inner rotor. A piston moves axially back and forth within a hollow space of the inner rotor. The inner rotor has a hollow space which has front and rear control channels which are alternately connected to the compression and suction spaces to drive the piston back and forth. The piston is used to actuate a percussion tool.

Description

The invention relates to a method for actuating an impact drilling tool and an impact mechanism for a striking or rotary impact tool according to the preamble of claim 1 and claim 5.

Such a method or percussion mechanism is described in Charcut, W .: Drucklufthandbuch, 2nd edition, Vulkan-Verlag Essen, 1979, pages 246 to 247, ISBN 3-8027-2647-2. For the reciprocating movement of the percussion piston, the compressed air must be fed in and out in a controlled manner depending on the path in the cylinder spaces in front of and behind the piston. This control is basically possible in two different ways: namely via a self-controlling percussion piston, the stroke movement of the percussion piston being controlled by the air supply and removal by the piston opening and closing the air supply and exhaust air control channels, or via a valve body. Valveless striking mechanisms are used because of the simple construction and the robust construction considered advantageous, but the impact energy is low, since the flying piston is required to open and close the control channels and can therefore only perform a small stroke, so that the piston speed reached is low and thus the impact energy, which is proportional to the square of the speed . In the publication it is expressly stated that an increase in the piston travel is only possible if the control of the compressed air supply is transferred to special control members.

Another conventional method or striking mechanism of this type is based on the principle that, by means of a pressure piston which is moved back and forth in a cavity and is designed as a reciprocating piston, a percussion or flying piston is moved back and forth to advance a drilling tool or chisel. Such impact hammers are known in particular as electropneumatic impact hammers. The electric motor actuates the pressure piston via a bevel gear set or a self-aligning ball bearing, which causes considerable vibrations in the hammer.

DE 34 39 268 A1 describes an impact drilling machine in which a cylinder space guiding the impact piston is acted upon alternately on different sides of the impact piston by a pressure medium in order to produce the reciprocating movement. For this purpose, outgoing channels from a pressure medium source are controlled by means of valves.

The invention is based on the object of a method for actuating an impact drilling tool or chisel or a valveless impact mechanism for a striking or to provide rotationally working tool with which a high impact energy can be achieved.

This object is achieved with the features specified in claims 1 and 5, respectively.

With these measures it is achieved that without separate control valves and without mediation of the flying piston, the compressed air is supplied and discharged solely by the rotation of the inner rotor and outer rotor in order to move the flying piston. In this way, the flight path can be increased considerably compared to conventional valveless thrusters and can be varied within wide limits. Due to the relatively large stroke of the flying piston, high impact energy can be achieved even with a relatively light flying piston.

Advantageous refinements of the method and the striking mechanism with regard to the structure and mode of operation are the subject of the subclaims.

To transfer the energy of the flying piston to a tool, it can be provided, for example, that a firing pin is present, with which a striking or rotationally striking tool can be coupled and which is axially displaceably guided in a firing pin guide provided on the front end face of the inner rotor, and that Firing pin axially aligned with the flying piston and actuated by it.

In the case of a rotary hammer which uses the striking mechanism or the method, it is provided that a firing pin which can be rotated by means of a drive is provided, with which a drilling tool can be coupled and which is in one on the front Front side of the inner rotor provided firing pin guide is axially displaceable, and that the firing pin is axially aligned with the flying piston and can be actuated by this.

A striking tool on the basis of this device or the method is characterized in that a firing pin is provided, into which a chisel can be inserted and which is guided axially displaceably in a firing pin guide provided on the front end face of the inner rotor, and that the firing pin axially on the Flight piston aligned and actuated by this.

The rotary lobe compressor principle presented here is known in particular from the extensive work of Wankel, who has proposed various types and shapes of rotary lobe compressors. According to the invention, this principle is now modified so that it is suitable for generating the lifting movement of the flying piston, whereby not only a simple construction and drive, but also a largely vibration-damped suspension of the drive motor is possible, for example a bevel gear set that is difficult to adjust compared to conventional rotary hammers or a self-aligning ball bearing is unnecessary. The construction that is made possible with few components and a favorable arrangement of the same further enables simple assembly with small dimensions and low weight. The flight length of the flying piston is not tied to the stroke length of a crank mechanism.

In a special embodiment, the speed ratio between the inner and outer rotor is 1: 2, and the compression and the suction space are on themselves diametrically opposite partial surfaces of the outer circumference of the inner rotor are formed.

It can be provided in the various configurations - as is known per se - that when the flying piston assumes its front end position facing the tool to be actuated, the cavity between the first and the second control channels is flowed through freely by the compressed air, as a result of which an idling blow occurs is avoided, and that the movement of the flying piston is started by pushing it into the cavity between the first and the further control channels by inserting the tool to be actuated.

Another advantage is that on the return flight of the flying piston behind the other, i.e. rear control channels, as is also known per se, an air cushion can be formed through which the impact is damped.

A favorable form of the inner rotor is such that the outer contour of the inner rotor cross-section is symmetrical to its small and large outer diameter and consists of two circular sections whose radius of curvature corresponds approximately to the larger radius of curvature of the elliptical interior, which is based on the DKM 53 from Wankel. Various designs provide that the cavity of the inner rotor and the flying piston are cylindrical, that the outer circumference of the outer rotor is circular, and that the electric motor used to generate the rotational movement is arranged parallel to the inner and outer rotor and that the drive is via pulleys and belts, in particular toothed belts or V-ribbed belts, or via gears.

In the rotary hammer using the principle of the rotary piston compression unit described, for example the firing pin is held in a rotatingly driven drilling shaft. The drilling shaft can also be driven via a pulley and a belt or via gears by means of the electric motor.

Fig. 1

einen Längsschnitt einer Drehkolben-Verdichtungseinheit als Preßluft-Flugkolbenbetätigungseinheit,

Fig. 2

einen Querschnitt einer Drehkolben-Verdichtungseinheit als Preßluft-Flugkolbenbetätigungseinheit,

Fig. 3A und B

Stellungsbilder von Innen- und Außenläufer der Preßluft-Flugkolbenbetätigungseinheit gemäß den Fig. 1 und 2,

Fig. 4

ein Schlagbohrgerät im Längsschnitt mit einer Preßluft-Flugkolbenbetätigungseinheit nach den Fig. 1 bis 3 und

Fig. 5

einen Querschnitt der Preßluft-Flugkolbenbetätigungseinheit in dem Schlagbohrgerät nach Fig. 4.

The invention is explained in more detail below using an exemplary embodiment with reference to the drawing. Show it:

Fig. 1

2 shows a longitudinal section of a rotary piston compression unit as a compressed air / flying piston actuation unit,

Fig. 2

3 shows a cross section of a rotary piston compression unit as a compressed air / flying piston actuation unit,

3A and B

Positional images of the inner and outer rotor of the compressed-air piston actuation unit according to FIGS. 1 and 2,

Fig. 4

a hammer drill in longitudinal section with a compressed air-piston actuation unit according to FIGS. 1 to 3 and

Fig. 5

4 shows a cross section of the compressed air / flying piston actuation unit in the impact drill according to FIG. 4.

The basic structure of a device or the mode of operation for generating the compressed air by means of a rotary piston compression unit 12 and actuation of a flying piston 4 of an impact device, such as e.g. a hammer drill or a hammer bit is illustrated in FIGS. 1 to 3.

1 shows the rotary piston compression unit 1 as a compressed air / flying piston actuation unit with an external rotor 3, which has an eccentrically arranged interior 3.4 with an elliptical cross section that is constant over its entire longitudinal extent and in which an internal rotor 2 is accommodated. The inner rotor 2 has, for example, a cylindrical cavity 2.8, in which the flying piston 4 is displaceably guided to and fro.

Near the two end faces of the inner rotor 2 there are one on radially opposite sides or several first (front) and further (rear) control channels in the form of control bores 2.1 and 2.2. The first control bore 2.1 located at the front end of the compressed air-flying piston actuation unit is arranged so far from the front end that the cavity 2.8 between the front and rear control bore 2.1 or 2.2 is free when the flying piston 4 is fully advanced, whereby an idle position is defined and avoiding an idle blow.

The outer cross-sectional contour of the inner rotor 2 has a large and a small outer diameter and is symmetrical to both, whereby it is composed of two identical circular sections, the radius of curvature of which is adapted approximately to the radius of curvature of the interior 3.4 of the outer rotor 3. The large diameter almost corresponds to the small diameter of the interior 3.4. The control bores 2.1 and 2.2 are arranged diametrically opposite one another in the area of the small diameter, but axially offset in the front and rear area of the inner rotor 2. If control channels other than the control bores mentioned are provided, their openings are arranged accordingly on the compression or suction space.

The outer rotor 3 and the inner rotor 2 have eccentric axes of rotation 3.5 and 2.9, respectively, about which they rotate in the same direction during operation at a speed ratio of 2: 1. This alternately forms on the side of the first (front) and further (rear) control bores 2.1 and 2.2, ie In the area of the corresponding partial areas A and B of the outer circumference of the inner rotor 2 and the facing inner wall of the elliptical interior 3.4, a compression space and a suction space. The compressed air is alternately pressed into the control bore just facing the compression chamber and drives the flying piston 4 in the direction of the other control bore through which air is sucked in, as a result of which the desired reciprocating movement of the flying piston is achieved. The described mode of action can be understood on the basis of the position pictures a to p shown in FIG. 3.

During the return stroke of the flying piston 4, the impact is dampened by an air cushion on the rear face. The idle stroke is avoided in that the flying piston 4 overflows the front control bore (s) 2.1 and now the air can freely circulate through the cylindrical bores 2.8 through the control bores 2.1 and 2.2. If a plurality of front and / or rear control bores are provided, these can be distributed radially or axially insofar as the assignment to the respective partial areas on the outer circumference of the inner rotor is retained.

Even if the large outer diameter of the inner rotor 2 is slightly shorter than the smaller diameter of the interior 3.4, a compression that is still sufficient to drive the flying piston 4 can be achieved. However, if a higher compression is desired, sealing means can be provided on the lateral surfaces of the interior 3.4 and inner rotor 2 sliding past one another, as are known, for example, from conventional rotary piston machines.

The compressed air-flying piston actuation unit or rotary piston compression unit 12 can be made of aluminum. With a so-called HART-COAT coating it can be made wear-resistant and with a surface impregnation made of Teflon (PTFE) an optimal dry lubrication can be achieved if strong heating is prevented. Other advantages are: low weight, simple assembly, few components, small dimensions and, due to the special design, high impact energy. The rotating parts can be balanced and the drive motor can be mounted in a vibration-damped manner, so that vibrations are suppressed in the entire device.

The preferred rotary piston compression unit described above is based on the rotary piston system DKM 53 ("Moon Maiden") proposed by Wankel. However, any other rotary piston compression system can also be used, as long as it alternately achieves a compression and suction effect on the radially and axially offset control bores.
The cross-sectional shape of the cavity 2.8 in the inner rotor 2 need not be circular, but can have other geometric shapes, such as elliptical or polygonal.

In order to achieve a pulse-like pressing and suction effect, a fixed sleeve, which is concentric with the axis of rotation 2.9 of the inner rotor and fits into the cavity 2.8, can be provided in the rotating inner rotor 2, into which the front and rear control bores 2.1 and 2.2 coordinated bores are incorporated, which always coincide with the control bores when the strongest compression or suction state is reached.

A moving sleeve can also be provided in the cavity 2.8, in which there are corresponding bores or openings which are connected to the suction space or the compression space.

The device described in the form of the compressed air-flying piston actuation unit with rotary piston compressor 12 is particularly suitable for use in electropneumatic rotary hammers or chisels.

An exemplary embodiment of a striking device 1 in the form of an electropneumatic hammer drill is shown in FIGS. 4 and 5.

4 and 5, the above-described piston actuation unit 12 with a rotary piston compression unit is accommodated in a guide bush 5.1 of a receiving device 5. A front or rear receptacle 5.2 and 5.3 for the outer rotor 3 are arranged at the front and rear of the guide bush 5.1, in which the outer rotor 3 is rotatably mounted by means of ball bearings 9, thermal expansion being taken into account. Front and rear pulley mounts 3.1 and 3.2 are provided for driving by means of belts and pulleys 3.3. Gears can also be used for the drive.

A pulley, in particular toothed belt pulley 2.4, is also coupled to the inner rotor 2 via a shaft 2.3, so that this too can be driven from the outside.

To drive the inner and outer rotor, an electric motor 8 is provided, which is arranged in parallel next to the rotary piston compression unit 12.

In the front area, in a firing pin guide 2.6, which is coupled to the inner rotor 2, a firing pin 11 with a tool holder is provided, into which a tool 7 can be inserted. The firing pin 11 is held in a rotationally driven drilling shaft 6, which can also be driven by the electric motor 8 via a pulley 6.1 and a belt 6.2.

In the idle position, the firing pin 11 is pushed all the way forward. If the tool 7 is placed on a base, the firing pin 11 is pushed back and with it the flying piston 4 enters the cavity between the front and rear control bores 2.1 or 2.2, so that it is driven back and forth by means of the rotary piston compressor 12. For softer contact in the inserted position, the firing pin 11 has an O-ring 10. Lock nuts 2.5 are screwed on behind the pulley 2.4 and on the firing pin guide.

The device shown in Fig. 4 is accommodated in a housing, not shown, which is advantageously formed from two half-shells.

Another possible use, not shown, of the compressed air / flying piston actuating unit with a rotary piston compressor is for a striking chisel device, in which there is also a striking pin in the front area which receives the chisel. Except for the rotating drive of the drilling shaft, the structure corresponds essentially to the hammer drill described above. In both devices, firing pin 11 and flying piston 4 are axially aligned with one another.

Further application possibilities arise wherever an axial impact operation is carried out.

Claims (16)

1. Method of actuating a percussion drilling tool or chisel of a drilling or chiselling hammer by means of a free piston (4), which is moved to and fro in a cavity (2.8) by compressed air, characterised in that the compressed air is produced by means of an elongate rotating outside rotor (3) and an elongate inside rotor (2), which rotates in said outside rotor about an eccentric axis of rotation (2.9) at a relative speed, a compression chamber and a suction chamber being formed by the rotation alternately between radially offset, axially extended partial areas (A, B) of the external periphery of the inside rotor (2) and a facing portion of the internal wall of the outside rotor (3), the compression chamber being produced at one partial area, while the suction chamber is produced at the other partial area, and in that the air from the compression chamber is urged into the axially orientated cavity (2.8) in the interior of the inside rotor (2) through at least a first guide channel situated on the facing partial area of the external periphery of the inside rotor (2) close to its one axial end, while air from the cavity (2.8) is drawn into the suction chamber through at least an additional guide channel situated at the radially offset partial area of the external periphery of the inside rotor (2) close to its other axial end, whereby the free pis6ton (4) is moved to and fro between the first guide channel (2.1) and the additional guide channel (2.2).
2. Method according to claim 1, characterised in that the inside rotor (2) and outside rotor (3) rotate with a speed ratio of 1:2, and in that the compression chamber and the suction chamber are formed on diametrically opposed partial areas (A, B) of the external periphery of the inside rotor (2).
3. Method according to claim 1 or 2, characterised in that the inside rotor (2) and outside rotor (3) are electrically driven.
4. Method according to one of the preceding claims, characterised in that an air cushion is formed during the return stroke of the free piston (4) behind at least the one additional guide channel, and the impact is reduced by said cushion.
5. Striking mechanism for a striking or rotationally striking tool, having a component part with a cavity in which a to-and-fro displaceable free piston (4) is guided, at least one guide channel (2.1, 2.2) terminating in the cavity (2.8) close to its axial ends, characterised in that the component part is configured as a rotatingly driven inside rotor (2), which is disposed in an outside rotor (3), which is rotatingly driven at a relative speed relative to the inside rotor (2), in that the axes of rotation (2.9, 3.5) of the inside rotor (2) and outside rotor (3) are disposed parallel and eccentrically to each other, and in that the external configuration of the inside rotor (2) and the internal configuration of the outside rotor (3) are so adapted to each other that, during the rotation, the guide channels (2.1, 12.2), which are situated close to the axial ends of the inside rotor (2), are alternately connected to a compression chamber, which is formed between the external configuration of the inside rotor (2) and the internal configuration of the outside rotor (3), and a suction chamber thereby being formed.
6. Striking mechanism according to claim 5, characterised in that the speed ratio between inside rotor (2) and outside rotor (3) is 1:2, and in that the compression chamber and the suction chamber are formed on diametrically opposed partial areas of the external configuration of the inside rotor (2).
7. Striking mechanism according to claim 5 or 6, characterised in that the cross-section (3.4) of the outside rotor (3) has an elliptical configuration, its central axis being offset parallel to the axis of rotation (3.5) of the outside rotor (3), in that the inside rotor (2) has a small external diameter and a large external diameter, so that the large external diameter almost corresponds to the smaller internal diameter of the elliptical cross-section (3.4) of the outside rotor (3), while the small external diameter is so selected that one of the two partial areas (A, B) of the external configuration of the inside rotor (2) associated therewith lies close to the wall of the outside rotor (3) when the direction of the small external diameter corresponds with the direction of the eccentric offset arrangement of the two axes of rotation (2.9, 3.5).
8. Striking mechanism according to claim 7, characterised in that the external configuration of the inside rotor (2) is symmetrical and comprises two segments of a circle.
9. Striking mechanism according to one of claims 5 to 8, characterised in that the cavity (2.8) of the inside rotor (2) and the free piston (4) are cylindrical.
10. Striking mechanism according to one of claims 5 to 9, characterised in that a striking pin (11) is provided, with which a striking or rotationally striking tool (7) can be coupled, and which is axially displaceably guided in a striking pin guide means (2.6), which is provided on the front end face of the inside rotor (2), and in that the striking pin (11) is axially aligned with the free piston (4) and is actuatable thereby.
11. Striking mechanism according to one of claims 5 to 10, characterised in that an electric motor (8) is provided to produce the rotational movement of the inside rotor (2) and the outside rotor (3).
12. Striking mechanism according to claim 11, characterised in that the electric motor (8) is disposed parallel to the inside rotor (2) and outside rotor (3), and in that the drive is effected via belt pulleys (3.3, 2.4) and belts, more especially toothed belts, or via toothed wheels.
13. Use of the striking mechanism according to one of claims 5 to 12 with a drilling hammer, wherein a striking pin (11) is provided, which is rotatable by means of a drive (8), a drilling tool (7) can be coupled with said pin, and said pin is axially displaceably guided in a striking pin guide means (2.6) provided on the front end face of the inside rotor (2), and wherein the striking pin (11) is axially aligned with the free piston (4) and is actuatable thereby.
14. Use according to claim 13, wherein the striking pin (11) is retained in a rotatingly driven drilling shaft (6).
15. Use according to claim 14, wherein the drilling shaft (6) is drivable, via a belt pulley (6.1) and a belt (6.2) or via toothed wheels, by means of an electric motor (8).
16. Use of the striking mechanism according to one of claims 5 to 12 with a percussion chiselling apparatus, wherein a striking pin is provided, into which a chisel is insertable, and which is axially displaceably guided in a striking pin guide means (2.6) provided on the front end face of the inside rotor (2), and wherein the striking pin (11) is axially aligned with the free piston (4) and is actuatable thereby.

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