EP2470742B1 - Ram boring device - Google Patents

Description

The invention relates to a ram boring apparatus according to the preamble of claim 1 and to a method for operating a corresponding ram boring apparatus according to the preamble of claim 13.

Such ram boring devices are known from the prior art and are used in particular for the production of horizontal wells. In general, such Rammbohrvorrichtung has a percussion piston, which is oscillating (reciprocating) within the housing and thereby, depending on the desired direction of movement of the ram boring device, bounces on a front or rear impact surface of the housing. The transmitted kinetic energy of the percussion piston ensures an acceleration of the ram boring device within the soil.

Such Rammbohrvorrichtung is for example from the DE 39 09 567 A1 known. The local ram boring device has a control tube with a percussion piston movably mounted thereon. The control tube is fixed at its rear end with a compressed air supply and further connected both longitudinal axial and rotationally movable via a prestressed coil spring with a housing-fixed component. The spring forces the head tube into a forward position (pre-run position) and locks it in this position by a quarter turn in a locking groove. For reversing the device, the control tube is unlocked by a quarter turn of the compressed air supply against the spring bias, so that the control tube under the influence of compressed air and against the longitudinal axial spring force in a rear position (return) is moved. At the same time the middle position of the percussion piston is displaced within the housing, so that in the return position, a rear impact surface is acted upon by the percussion piston. As in the forward position, the control tube locks in the return position under the influence of the rotationally biased spring in a second locking groove. A renewed reversing of the ram boring device in the flow position is carried out by a quarter turn of the control tube, at the same time the amount of pressure of the supplied compressed air is reduced, so that the forces applied by the prestressed spring forces exceed the pressure forces and the control tube is moved back into the forward position ,

The device of DE 39 09 567 A1 thus discloses two operating positions in which either a front or a rear impact surface of the housing is acted upon.

The invention is based on the object of improving a ram boring device such that the impact frequency and / or the impact intensity can be influenced.

This object is achieved by the subject matter of the independent claims. Advantageous embodiments are claimed in the subclaims and will become apparent from the following description of the invention.

The invention provides a ram boring device for creating horizontal bores of the type mentioned above to be provided with a device which allows a displacement of the central position of the percussion piston such that a variation of the frequency of the percussion piston movement and / or the impact intensity.

By "ram boring" is meant, in particular, any device which is moved intermittently in an existing or to-be-created channel to create or expand a bore or destructively or non-destructively replace or clean an existing pipe, conduits in existing pipes or other long bodies as well as all devices for construction work of underground tunneling.

The ram boring device according to the invention is not limited to underground earthworks. Thus, for example, lines in which a Erdbohrgerät is operated, run above ground.

The term "horizontal drilling" in the sense of the present invention covers in particular any type of existing or to be created, preferably horizontal Ducts in a body, in particular earth channels including earth bores, rock holes or earth pipes and underground or above-ground pipelines and sewers, which can be produced, widened, destroyed, cut or cleaned by using a corresponding ram boring.

"Middle position" of the percussion piston is understood in the context of the invention, the position which is located centrally between the two reversal points of the oscillating movement of the percussion piston.

In an advantageous embodiment of the device according to the invention, this has, in addition to the housing and a percussion piston, which is displaced via a supplied pressurized fluid, thus a gas or a liquid, in an oscillating movement taking place within the housing, further comprising a control sleeve which is movable within the Impact piston is arranged. Furthermore, the percussion piston is characterized by at least one control opening in its jacket, wherein the position of the control opening before, above and behind the control sleeve causes the alternating ventilation of a pressure chamber located between the housing and the percussion piston. The displacement of the central position of the percussion piston can be effected by a change in length (extension, shortening) of the control sleeve and / or by a displacement of the position of the control sleeve within the housing.

One way to change the position of the control sleeve may be to use the control sleeve with a back side, i. to connect in the direction of the connection for a pressurized fluid supply with a guide sleeve, which itself is either extended / shortened or displaced within the housing in order to achieve via the connection with the control sleeve, the inventive displacement of the central position of the percussion piston.

In an alternative embodiment, the position of the control sleeve can also be changed in that it is displaced via the connecting element relative to the guide sleeve.

According to the invention, it is not necessary for the "control sleeve" or the "guide sleeve" to be tubular. Rather, any shape is possible through which the intended function can be fulfilled.

A length-adjustable control or guide sleeve may have at least two sub-sleeves which are movable relative to each other in at least longitudinal axial direction and define by their position relative to each other, the length of the control or guide sleeve. Preferably, the sub-sleeves are formed such that one of the sub-sleeves is slidably mounted on another sub-sleeve. For this purpose, the second part of a sleeve Having reduced outer diameter portion which substantially corresponds to the inner diameter of the first sub-sleeve.

Advantageously, a device for adjusting the relative position of the two sub-sleeves can be further provided to each other. This can allow adjustment in both directions (shortening and extension of the control or guide sleeve) or only in one direction. In the second case, elastic means are preferably provided, which are arranged between the two sub-sleeves and cause a restoring force against the adjusting force of the device. However, the elastic means may e.g. be arranged on the opposite side of one or both sub-sleeves and cause a corresponding force that moves the sub-sleeves toward or away from each other. Particularly preferably, the device also allows to adjust the two sub-sleeves to each other during the beating operation.

The function of the adjusting device can be based on various physical principles. In particular, the adjusting force can be generated by hydraulic, pneumatic or magnetic means. Likewise, purely mechanical adjustment options are possible, for example via a driven relative rotation in conjunction with a thread-shaped connection of the two sub-sleeves. Of course, combinations of the above adjustment can be used.

Preferably, the length-adjustable control or guide sleeve is designed or fixed such that a change in length of the control sleeve only causes a displacement of the sleeve edge, which faces away from the impact surface of the housing acted upon. The control sleeve edge, which is located on the side of the impact surface of the housing is thus arranged (in an operating position (forward / backward) of the ram boring device) fixed within the housing.

A device according to the invention for displacing the position of the control or guide sleeve within the housing preferably comprises a control tube, which extends at least in one section within the control or guide sleeve and is movable in at least longitudinal axial direction. A movable to the control sleeve trained control tube is preferably fixedly connected to the housing.

In a preferred embodiment of the present invention, in which the control tube (at least in the longitudinal axial direction) connected to the control sleeve and movably mounted within the guide sleeve, whereby a displacement of the control tube relative to the guide sleeve leads to a displacement of the control sleeve, the relative position of Control ear in the guide sleeve fixed in several positions, whereby different defined operating position can be generated. Further preferably, the control tube can be biased by elastic means both in the longitudinal axial direction and in the direction of rotation with respect to the guide sleeve, wherein the bias in the longitudinal axial direction, a displacement of the control sleeve within the housing forward, ie in the direction of the flow, and the bias in the direction of rotation Engaging (at least) one locking element in a corresponding undercut causes; the latter leads to a fixation of the relative position of the control tube to the guide sleeve. For example, the locking element may be formed as a projection provided on the control tube, which can be screwed into a corresponding recess in the guide sleeve.

Another way to obtain a relative movement of the control or guide sleeve to the head tube, may be that the head tube and the control or. Guide sleeve together form a pressure chamber whose size is defined by the relative position of the two components to each other. For example, the outer surface of the guide tube and the inner surface of the control or guide sleeve with correspondingly arranged, annular edges form an annular pressure chamber which is filled by a pressurized fluid. For fixing or varying the size of the pressure chamber, the height of the pressure of the fluid can be varied as a function of the external pressure or of another counterforce, for example a spring force.

Of course, the pressure chamber next to the ring shape may have any other shape. In particular, the pressure chamber can be formed only by a partial circle of the outer or the inner circumference of the guide tube or the control or guide sleeve.

The size of the pressure chamber defined by the position of the sleeve edges of the control sleeve, the average position of the oscillating percussion piston in the housing. Displacement or lengthening / shortening of the control sleeve within the housing causes the center position of the percussion piston to also be displaced. As a result, the impact frequency of the percussion piston can be changed and at the same time the impact intensity can be influenced.

In one embodiment, the pressure chamber can be supplied with the pressure fluid via an additional line, which runs, for example, within the control tube. It may be compressed air, which is also preferably used as a drive medium for the percussion piston and is preferably guided by the control tube into the interior of the piston. Another embodiment may provide for the supply of a pressurized fluid. For example, this liquid can be added at the same time be used in the area of the drill head or elsewhere in the soil to positively influence the drilling progress. In these cases, drilling fluids can be used whose properties can be adapted to the respective drilling conditions by adding additives.

Preferably, the length and / or the position of the control or guide sleeve can be changed continuously in a certain adjustment range. As a result, a particularly good adaptation of the beat frequency / intensity to the given drilling conditions can be achieved. However, it is possible to define a plurality of positions within the adjustment range that allow graduated adjustment.

An alternative embodiment of a Rammbohrvorrichtung invention may have a control sleeve which is movably disposed within the percussion piston, and at least two control openings in the shell of the percussion piston, wherein the alternate positioning of the control openings in front of and behind the control sleeve, the ventilation of a between the housing and causes the impact piston located pressure chamber. The at least two control openings are offset in this embodiment in the longitudinal direction of the percussion piston to each other.

By means of a device for covering or releasing one of the control openings on demand, it can be achieved that a specific control opening is responsible for the ventilation and venting of the pressure chamber. Due to the distance between the control openings in the longitudinal direction of the percussion piston can be achieved by a corresponding covering or releasing individual control openings different stroke paths of the percussion piston.

Preferably, the percussion piston is constructed in two parts, for example, with a further (partial) sleeve which is movably disposed within the (residual) percussion piston and by a defined rotation and / or translation within the (residual) percussion piston for a corresponding release or Covering one or more of the control openings ensures.

The device according to the invention makes it possible to operate a ram boring device of the type described above in such a way that the frequency of the percussion piston movement and / or the impact intensity is changed via a displacement of the middle position of the percussion piston. Thus, both the frequency and the intensity of the blows can be adapted to the given soil conditions. This can be carried out particularly advantageously during the drilling operation.

Fig. 1:

eine geschnittene Seitenansicht einer erfindungsgemäßen Rammbohrvorrichtung in einer ersten Ausführungsform;

Fig. 2:

eine Detailansicht der Steuerhülse der Fig. 1 einschließlich der angrenzenden Bauteile;

Fig. 3:

einen Ausschnitt aus einer erfindungsgemäßen Rammbohrvorrichtung in einer zweiten Ausführungsform;

Fig. 4:

eine geschnittene Seitenansicht einer erfindungsgemäßen Rammbohrvorrichtung in einer dritten Ausführungsform; und

Fig. 5:

die Steuerungselemente einer erfindungsgemäßen Rammbohrvorrichtung in einer vierten Ausführungsform.

The invention will be explained in more detail with reference to an embodiment shown in the drawings. In the drawings shows:

Fig. 1:

a sectional side view of a ram boring device according to the invention in a first embodiment;

Fig. 2:

a detailed view of the control sleeve of Fig. 1 including the adjacent components;

3:

a section of a ram boring device according to the invention in a second embodiment;

4:

a sectional side view of a ram boring device according to the invention in a third embodiment; and

Fig. 5:

the control elements of a ram boring device according to the invention in a fourth embodiment.

In the Fig. 1 illustrated embodiment of a ram boring device according to the invention consists essentially of a housing 1, in which a drill head 2 is screwed. A percussion piston 3 reciprocates under the influence of compressed air in the housing 1, whereby the percussion piston 3 impinges on either a front impact surface 5 or a rear impact surface 6 within each period, depending on the position of a control sleeve 4.

As in particular in Fig. 2 can be seen, the control sleeve 4 consists of two sub-sleeves 7, 8. The partial sleeve 8 shown in the drawing on the right side has a portion having a reduced outer diameter, which substantially corresponds to the inner diameter of the left part of the sleeve 7. The sleeve 4 is connected via an intermediate element 9 with a control tube 10, which in turn for reversing the direction of movement of the ram boring device in the longitudinal axial direction within the housing displaceable and in two positions - one for the flow and one for the return of the device - can be fixed. The Umsteuern takes place in exactly the same way as in the introductory part of the description with reference to in the DE 39 09 567 A1 disclosed ram boring device is described.

For the operation of the ram boring device compressed air via a compressed air hose 11, which is connected to the rear end of the hollow head tube 10, passed into the pressure chamber 12 of the percussion piston 3. In the illustrated position of the percussion piston is a pressure equalization between the pressure chamber 12 and the Pressure chamber 14, which is formed by the outer surface of the percussion piston 3 and the inner surface of the housing 1, via the control openings 13 instead. Due to the larger effective area of the pressure chamber 14 compared to the pressure chamber 12, the resulting pressure force causes a rearward movement of the percussion piston third

As soon as the control openings 13 completely exceed the front (left) edge of the control sleeve 4, pressure equalization no longer takes place between the pressure chamber 12 and the pressure chamber 14. Although the pressure in the pressure chamber 14 steadily decreases due to its magnification with the backward movement, the percussion piston 3 moves back so far due to its inertia, until the control openings 13 exceed the rear (right) edge of the control sleeve 4. Thereupon, pressure equalization takes place between the pressure chamber 14 and the atmosphere outside the drilling device via the control openings 13 and the ventilation openings 15.

After releasing the overpressure in the pressure chamber 14, the compressive force generated by the pressure chamber 12 causes the percussion piston 3 to be decelerated and then accelerated in the opposite direction, i.e., in the opposite direction. towards the front to the drill head. The thus initiated forward stroke is terminated by the impact of the percussion piston 3 on the front striking surface 5. At this time, the control openings 13 have already exceeded the front (left) edge of the control sleeve 4 again, so that a new cycle begins.

The control bushing 4, consisting of the partial bushes 7 and 8, can be changed in length by an adjusting device (not shown), wherein the adjusting device brings about a pushing together and thus a shortening of the bush 4 against a spring force of the spiral spring 16.

The front part bush 7 is fixedly connected in the longitudinal axial direction with the control tube 10, so that a change in the bushing length causes no change in the position of the front control edge. Depending on the length of the sleeve 4, the control openings 13 thus exceed the rear control edges of the socket 4 at different positions within the housing, ie the longer the control bushing 4, the later there is a reversal of the direction of movement of the control piston, so that this the rear reversal point to the front striking surface 5 must cover a longer path. This reduces the impact frequency of the piston. At the same time, however, causes the longer path to the face 5 a longer-lasting acceleration of the percussion piston 3, so that the speed and thus the kinetic energy when hitting the percussion piston 3 on the club face 5 is greater than in a short control sleeve 4. It thus becomes a Increased impact intensity achieved.

In the Fig. 3 an alternative embodiment of a length adjustable control sleeve 104 is disclosed. This may instead of in the Fig. 2 shown control sleeve 4 in a Rammbohrvorrichtung according to Fig. 1 come into use. The control sleeve 104 of Fig. 3 It also consists of a front partial sleeve 107 and a rear partial sleeve 108. These form a pressure chamber 117, which is supplied via a pressure medium line 118 which extends within a portion of the wall of the control tube 110, with a pressurized fluid. By increasing the pressure in the pressure chamber 117, the rear sub-sleeve 108 is in the direction of the rear end of the ram boring device (in the Fig. 3 shifted to the right), whereby the total length of the control sleeve formed from the two sub-sleeves 107 and 108 extends and - since the front part of sleeve 107 is firmly connected to the control tube 110 - the rear control edge of the control sleeve 104 is moved backwards; As a result, a delayed reversal of the direction of movement of the percussion piston 103 within the housing 101 is achieved. The displacement of the rear sub-sleeve 108 causes a compression of a spring arranged between the sub-sleeves 107, 108, whereby their bias voltage is increased. If the pressure in the pressure chamber 117 is reduced again, this bias causes the total length of the control sleeve 104 to reduce again.

The in the Fig. 4 Rammbohrvorrichtung shown is based on changing the beat frequency and / or the impact intensity by shifting the relative position of the control sleeve within the housing 201. In this case, a small displacement of the control sleeve 204 defined in its length results in a change of the beat frequency and / or the impact intensity, while a larger displacement leads to a reversal of the direction of movement of the ram boring machine, since the percussion piston 203 no longer impacts on the front striking surface 205 impinges on the rear impact surface 206.

For changing the position of the control sleeve 104, a pressure medium line 218 is provided, which is guided within the compressed air supply line 211 to the ram boring device and extends in this through the control tube 210 and further into the tip of the drill head 202. A fitting 219 supplies an annular pressure chamber 217, which is formed by the outer surface of the control tube 210 and an inner surface of the control sleeve 204, with a fluid from the pressure medium line 218. About the pressure in the pressure chamber 217 in conjunction with the back pressure within the pressure chamber 212 acts on the control sleeve 204, and possibly in conjunction with a counterforce, which can be applied for example by a spring, the relative position of the control sleeve 204 can be changed and fixed within the housing 201.

As in the embodiment of Fig. 1 and 2 causes a displacement of the control sleeve 204 in the direction of the rear end of the ram boring device that the reversal of the direction of movement of the percussion piston 203 also in a Rear offset middle position of the percussion piston 203 takes place. The distance to be traversed by the percussion piston 203 between the reversal point and the front impact surface 205 is thus longer, which reduces the impact frequency of the percussion piston 203.

When the control sleeve 204 moves sufficiently far toward the rear end of the ram boring apparatus, the control piston 203 abuts against the rear striking surface 206, while at the same time the forward striking surface 205 is not touched during the forward stroke. This results in a reversal of the direction of movement of the ram boring device, so that it can be recovered, for example, when hitting an obstacle from the borehole.

The Fig. 5 shows an embodiment of a ram boring device according to the invention, which differs substantially from the embodiments described above in that the control sleeve 304 is fixedly connected to the control tube 310 and a displacement of the entire control sleeve and thus the central position of the percussion piston by a displacement of the control tube 310 within of the housing takes place.

In the Fig. 5 only the control elements of the ram boring device are shown; These can, for example, with the other components (in particular housing, percussion piston, drill head, etc.) in the Fig. 1 to 3 Rammbohrvorrichtungen shown are combined.

The control tube 310 is slidably mounted within a guide sleeve 320, which is fixedly disposed via elastic connecting elements 321 in a rear portion of the housing. The control tube 310 forms three successive grooves 322, wherein depending on the longitudinal axial relative position of the control tube 310 to the guide sleeve 320 formed on the inside of the guide sleeve projection 323 can engage in one of the grooves 322. In the section of the control tube 310 receiving the grooves 322, this has a cross-section which allows the projection 323 to engage the guide sleeve 320 in the grooves 322 at a certain rotational relative position of the control tube 310 (locking position), whereby a longitudinal axial relative displacement is prevented, and at least a second rotational relative position (switching position), which is preferably offset by 90 ° to the first, no engagement of the projection 323 is provided in one of the grooves 322, and therefore a longitudinal axial relative displacement is possible. Corresponding cross sections of the control tube 310 and the corresponding guide sleeve 320 are in the DE 39 09 567 A1 , especially in the Fig. 3 to 5 and in the description in column 4, lines 1 to 22; This disclosure is incorporated herein by reference.

Via a spring 324, which is defined between the guide sleeve 320 and the front end of the control tube 310, the control tube 310 is biased relative to the guide sleeve 320 both in the longitudinal axial direction and in the direction of rotation; in such a way that the control tube 310 relative to the guide sleeve 320 forward (in the Fig. 5 to the left) and simultaneously moved to the locking position.

About a rotation of a compressed air hose of the ram boring device, which is connected via an adapter piece 325 fixed to the head tube, the control tube can be rotated from the locking position to the switching position. If the pressure chamber formed by the control tube 310 and the percussion piston would then be subjected to a high pressure, this pressure, which acts on the front surfaces of the control tube 310 and the associated control sleeve 304, would exceed the spring forces of the spring 324 and the control tube 310 including Control sleeve 304 relative to the guide sleeve 320 to the rear (in the Fig. 5 to the right). Of course, this can also be done without or with little pressure by exerting tensile forces on the compressed air hose. Upon release of the rotational forces on the compressed air hose, the projection 323 of the guide sleeve 320 could then engage in one of the front grooves 322, whereby either the frequency and the intensity of the impacts on the front striking surface is changed or the direction of movement is reversed from the first position the striking piston only strikes a rear striking surface.

In the Fig. 5 the control tube 310 is fixed in its foremost position; this corresponds to an engagement of the projection 323 in the rear of the grooves 322. In this position, the control tube 310 and thus also the control sleeve is positioned as close as possible to the front striking surface of the housing. This causes a short stroke of the percussion piston with a relatively small intensity but high beat frequency.

If the projection 323 engages in the middle of the grooves 322, the ram boring device is still in its forward position, the percussion piston but by a displacement of the control sleeve and thus the middle position of the percussion piston to the rear at each stroke cycle exerts a longer stroke with higher intensity; At the same time, a lower beat frequency is achieved.

Upon engagement of the projection 323 in the front groove 322, the center position of the percussion piston is offset so far back that the percussion piston no longer impinges on the front impact surface of the ram boring device, but on the rear, whereby a reversal of the direction of movement of the ram boring device can be achieved can.

The grooves 322 (in particular, the two front grooves) may be (rotationally) staggered with respect to each other, which can be made to switch gradually between the individual switching positions. This can be prevented that, instead of switching between the two switch positions for the lead, unintentionally switched directly from, for example, the rear groove in the front groove, whereby the direction of movement of the ram boring would be reversed.

Claims (16)

1. Percussion drill for creating horizontal drill holes, having a housing (1; 101; 201) and a striking piston (3; 103; 203) which is set into an oscillating movement by way of a supplied compressed fluid and transfers its kinetic energy to one or more striking surfaces (5, 6; 205, 206) in the process, characterised by a device for moving the middle position of the striking piston (3; 103; 203) to vary the frequency of the striking piston movement and/or the striking intensity.
2. Percussion drill according to claim 1, characterised in that a control sleeve (4; 104; 204; 304) is movably arranged inside the striking piston (3; 103; 203), wherein at least one control opening (13; 113; 213) is constructed in the casing of the striking piston (3; 103; 203), and the alternating positioning of the control opening(s) (13; 113; 213) in front of and behind the control sleeve (4; 104; 204; 304) causes the aeration and deaeration of a pressure chamber (14; 114) located between the housing (1; 101; 201) and the striking piston (3; 103; 203), wherein the frequency and/or the striking intensity is changed by a change in the length of the control sleeve (4; 104) and/or a displacement of the position of the control sleeve (204; 304) inside the housing (1; 101; 201).
3. Percussion drill according to claim 2, characterised in that the control sleeve is connected to a guide sleeve arranged in the back of the housing, wherein the control sleeve is displaced by a change in the length of the guide sleeve and/or a displacement of the position of the guide sleeve inside the housing.
4. Percussion drill according to claim 2 or 3, characterised in that the control sleeve (304) is connected by a control tube (310) to a guide sleeve (320) arranged in the back of the housing (301), wherein the control sleeve (304) is displaced inside the housing by a movement of the control tube (310) relative to the guide sleeve (320).
5. Percussion drill according to any one of claims 2 or 4, characterised in that the control sleeve (4; 104) or the guide sleeve comprises at least two part sleeves (7, 8; 107, 108) which can be moved toward each other at least in the longitudinal axial direction and by way of the their position relative to each other define the length of the control sleeve (4; 104) or the guide sleeve.
6. Percussion drill according to claim 5, characterised by an adjustment device for changing the relative position of the two part sleeves (7, 8; 107, 108).
7. Percussion drill according to claim 6 or 7, characterised by elastic means which are arranged between the two part sleeves (7, 8; 107, 108) and cause a restoring force counter to the adjusting force applied by the adjustment device.
8. Percussion drill according to any one of claims 2 to 6, characterised by a control tube (210; 310) which runs at least in one section inside the control sleeve (204) or the guide sleeve (320) and can be moved in at least the longitudinal axial direction thereto, and means for adjusting the relative position between control or guide sleeve and control tube (210; 310).
9. Percussion drill according to any one of claims 2 to 8, characterised in that the control tube (310) is connected to the control sleeve (304) and is movably mounted inside the guide sleeve (320), wherein the position of the control tube (310) relative to the guide sleeve (320) can be fixed in a plurality of positions.
10. Percussion drill according to any one of claims 2 to 9, characterised in that the control tube (310) is pre-stressed with respect to the guide sleeve (320) by elastic means in both the longitudinal axial direction and the direction of rotation, wherein the pre-stressing in the longitudinal axial direction causes a forward displacement of the control sleeve (304) inside the housing and the pre-stressing in the direction of rotation causes an engagement of a locking element in a corresponding undercut, whereby the position of the control tube (310) relative to the guide sleeve (320) is fixed.
11. Percussion drill according to any one of claims 2 to 10, characterised by a pressure chamber (217) between the control sleeve (204) or guide sleeve and the control tube (210), the size of which defines the relative position of control sleeve (204) and control tube (210).
12. Percussion drill according to any one of claims 1 to 4, characterised by an additional supply line (118; 218), which is independent of the supply line (211) of the driving fluid of the percussion drill, for a hydraulic fluid for pressurising the pressure chamber (217).
13. Percussion drill according to claim 1, characterised in that a control sleeve is movably arranged inside the striking piston, and at least two control openings are constructed in the casing of the striking piston, wherein the alternating positioning of the control openings in front of and behind the control sleeve causes the aeration and deaeration of a pressure chamber located between the housing and the striking piston, and the at least two control openings are arranged mutually offset in the longitudinal direction of the striking piston and a device for temporarily covering one of the control openings is provided.
14. Percussion drill according to claim 13, characterised by a further sleeve which is movably arranged in the longitudinal direction and/or rotatably arranged inside the striking piston and covers none, one or a plurality of the control openings of the striking piston as a function of its position inside the striking piston.
15. Method for operating a percussion drill, wherein a striking piston (3; 103; 203) is set into an oscillating movement by way of a compressed fluid and at least some of its kinetic energy is transferred via one or more contact face(s) (5, 6; 205, 206) to a housing (1; 101) of the drill in the process, characterised in that the frequency of the striking piston movement and/or the striking intensity is changed by a movement of the middle position of the striking piston (3; 103; 203).
16. Method according to claim 15, characterised in that, during operation, the frequency and/or the striking intensity is adjusted to the composition of the ground.

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