Rock drilling machine and drill RIG comprising such a rock drilling machine

Abstract

The disclosure relates to a rock drilling machine comprising an extractor piston arranged radially outside a shank adapter inside an inner housing of the rock drilling machine, the extractor piston being arranged to act on the shank adapter in a backward drilling direction. The inner housing comprises a first chamber which is configured to be provided with a hydraulic fluid to build up a first hydraulic pressure, the extractor piston comprising a first axial surface arranged to face the first chamber such that the first hydraulic pressure will act on the first axial surface to push the extractor piston in the backward drilling direction. A second chamber is arranged in fluid contact via a restriction passage with the first chamber, the extractor piston comprising a second axial surface arranged to face the second chamber such that a second hydraulic pressure present in the second chamber will act on the second axial surface to act on the extractor piston in the backward drilling direction.

Description

[0001] ROCK DRILLING MACHINE AND DRILL RIG COMPRISING SUCH A ROCK DRILLING MACHINE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a rock drilling machine and a drill rig comprising such a rock drilling machine. Specifically, the present disclosure relates to a rock drilling machine with an extractor arranged to loosen a drill string that has become stuck during a drilling operation.

[0004] BACKGROUND

[0005] In the technical field of percussive rock drilling a drill bit may be arranged at an outer end of a drill string comprised of one or more drill rods, wherein a rock drilling machine is arranged to drive the opposite end of the drill string to force the drill bit into the rock. Sometimes, during a drilling operation, the drill bit or another part of the drill string may get stuck inside the drill hole. This may happen both during actual drilling or when the drill string is being retracted after a completed drilling operation.

[0006] In such a case, an extractor is activated to loosen the drill string. The feed force on the rock drilling machine is in such cases reversed, to pull the drill string backwards, opposite to the forward drilling direction. An extractor piston is arranged to act on a flange on the so-called shank adapter, which is the part of the rock drilling machine that is connected to the innermost drill rod of the drill string during a drilling operation.

[0007] After an initial backwards movement of the rock drilling machine, the extractor piston will reach the flange on the shank adapter. Conventionally, the extractor piston is working using a pressurised hydraulic fluid inside a chamber that creates a cushion between the extractor piston and the inside housing of the rock drilling machine.

[0008] The operational performance of the extractor is dependent on the stiffness of the fluid in the chamber. A trade-off must be made between a quick and precise function of the extractor, which is enhanced by a high hydraulic pressure inside the chamber, and the load of the hydraulic pressure acting on the rock drilling housing parts that encloses the chamber, which loads may cause fatigue stress in said housing parts. Further, attention must be made to avoid cavitation damages.

[0009] The mean hydraulic pressure in the chamber is dependent of the reversed feed force, gravity, and the percussion force. A constant fluid flow is supplied to the chamber and a floating position of the extractor is achieved where the pressure drop in the drain opening will equal the pressure inside the chamber.

[0010] It would be advantageous to provide a rock drilling machine overcoming, or at least alleviating, at least one or some of the drawbacks of the prior art.

[0011] SUMMARY

[0012] It is an object of the disclosure to provide a rock drilling machine with an extractor function that is precise in its positioning and stiff when it is required but without causing mechanical fatigue and fluid caused cavitation damages, but which may still be stiff when this is required.

[0013] According to a first aspect, the disclosure relates to a rock drilling machine.

[0014] The rock drilling machine comprises a shank adapter movably arranged along an axis inside the rock drilling machine, the shank adapter facing a drill hammer at a first end, and a drill string at a second, opposite end, the drill hammer being arranged to provide a percussion impact to push the drill string in a forward drilling direction along the axis.

[0015] The rock drilling machine further comprises an extractor piston arranged radially outside the shank adapter inside an inner housing of the rock drilling machine, the extractor piston being arranged to act on the shank adapter in a backward drilling direction along the axis, opposed to the forward drilling direction.

[0016] The shank adapter comprises a circumferential rim and the extractor piston comprises an abutment arranged to abut the circumferential rim of the shank adapter to limit a movement of the shank adapter in a forward drilling direction.

[0017] The inner housing comprises a first chamber which is configured to be provided with a hydraulic fluid to build up a first hydraulic pressure in said first chamber, the extractor piston comprising a first axial surface arranged to face the first chamber such that the first hydraulic pressure will act on the first axial surface to push the extractor piston in the backward drilling direction.

[0018] A second chamber is arranged in fluid contact with the first chamber, via a restriction passage, the extractor piston comprising a second axial surface arranged to face the second chamber such that a second hydraulic pressure present in the second chamber will act on the second axial surface to act on the extractor piston in the backward drilling direction, thereby providing a second force in the backward drilling on the extractor piston.

[0019] The combination of the two chambers provides a quick and precise function of the extractor, while at the same time keeping the loads on the surrounding housing parts at an acceptable level.

[0020] Each of the chambers can be dimensioned to improve functionality. The first chamber makes sure that the operational position is maintained in a best possible way. The second chamber, which is a stiff chamber, may be enclosed within a high quality material such as a hardened steel and is arranged to reduce the extractor position displacement during operation

[0021] The second chamber provides a good damping of rock reflections and helps to reduce the deviation from the extractor working position, which may be quickly restored after any disturbances.

[0022] The pressure in the first chamber balances the feed force, gravity and percussion force of the drilling machine, e.g. by applying a continuous flow through the first chamber.

[0023] In embodiments of the disclosure, the second chamber is smaller than the first chamber.

[0024] The relatively small size of the second chamber, which normally has a larger dynamic pressure response than the first chamber during operation, causes less loads on the surrounding housing parts than what a conventional, bigger chamber would give rise to.

[0025] In embodiments of the disclosure a fluid inlet and a fluid outlet are respectively arranged to and from the first chamber to provide a flow through the first chamber when the extractor piston is in operation.

[0026] The flow through the first chamber is preferably substantially constant, and the pressure will balance the applied feed, gravity, and percussion force around the reference position decided by the position of the outlet channels.

[0027] The stiffness of this chamber can be much less important than the stiffness of the second chamber, and as a consequence, the work pressure in the first chamber will be more stable. The pressure load in the first chamber is much smaller than in the second chamber, thereby keeping the constraints on the surrounding housing at an acceptable level. The stable work pressure is also advantageous as it helps to avoid cavitation, which typically occurs in response to a rapid movement causing a local evacuation of hydraulic fluid.

[0028] In embodiments of the disclosure the extractor piston comprises an edge portion arranged to close a passage from the first chamber to the fluid outlet when the extractor piston is in a forward position with respect to the forward drilling direction, and wherein said passage is open when the extractor piston is in a backward position with respect to the forward drilling direction, such that an equilibrium position, also known as a floating position, is formed between said forward position and said backward position.

[0029] The reference position of the extractor piston is thereby governed by the pressure in the first chamber.

[0030] In embodiments of the disclosure the extractor piston comprises an intermediate rim arranged opposite a step portion of the inner housing, wherein the restriction passage is formed between said intermediate rim and said step portion.

[0031] According to a second aspect, the disclosure relates to a drill rig comprising a rock drilling machine as described above.

[0032] Other embodiments of the disclosure according to the two aspects and advantages thereof will be apparent from the detailed description and the appended drawings.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Below, specific embodiments of the disclosure will be described with reference to the appended drawings, of which:

[0035] Fig. 1 is a very schematic drawing of a rock drilling machine according to an embodiment of the disclosure,

[0036] Fig. 2 is a schematic drawing of the interaction between a shank adapter and an extractor piston inside a rock drilling machine, and

[0037] Fig. 3 shows the extractor piston of Fig. 2 in on an operational floating position.

[0038] DETAILED DESCRIPTION

[0039] In Fig. 1 , a rock drilling machine 10 according to an exemplary embodiment of the disclosure is illustrated in a very schematic manner.

[0040] The rock drilling machine 10 may be said to be comprised of three main parts: • A percussion unit comprising a drill hammer 30 for providing a percussive motion to a drill string 14, of which the position is indicated by an arrow, by repeated hammering on a shank adapter 11 , which is connected to said drill string 14.

[0041] • A damper, comprising a damper piston 29 arranged to dampen the recoil effect from the drill string 14 during drilling, and

[0042] • An extractor comprising an extractor piston 12 arranged to assist when the drill string 14 is retracted from the drill hole by affecting the shank adapter 1 1 , after a completed drilling operation or when the drill string has become stuck inside the drill hole.

[0043] The function of these details is well known to a person skilled in the art and will not be described in detail except for details concerning the embodiments of the disclosure.

[0044] In fig. 2 the extractor unit of a rock drilling machine 10 is shown.

[0045] The rock drilling machine 10 comprises a shank adapter 11 movably arranged along an axis AA extending into the extractor unit of the rock drilling machine 10. As illustrated in Fig. 1 , the shank adapter 1 1 is facing a drill hammer 30 at a first end 16, and a drill string 14 at a second, opposite end 15. The drill hammer 30 is arranged to provide a percussion impact to push the drill string 14 in a forward drilling direction D1 along the axis AA.

[0046] In the extractor unit, an extractor piston 12 is arranged radially outside a portion of the shank adapter 11 inside an inner housing 20 of the rock drilling machine 10. When operated, the extractor piston 12 is arranged to act on the shank adapter 11 in a backward drilling direction D2 along the axial direction AA, opposed to the forward drilling direction D1.

[0047] The shank adapter 11 comprises a circumferential rim 13 and the extractor piston 12 comprises an abutment 17 arranged to abut the circumferential rim 13 of the shank adapter 11 to limit a movement of the shank adapter 11 in the forward drilling direction D1 . Hence, during operation of the extractor, the abutment 17 and the circumferential rim 13 will be in continuous or at least intermittent contact with each other.

[0048] The inner housing 20 comprises a first chamber 21 which is configured to be provided with a hydraulic fluid to build up a first hydraulic pressure P1 in said chamber. The extractor piston 12 comprises a first axial surface 18 arranged to face the first chamber 21 such that the first hydraulic pressure P1 will act on the first axial surface 18 to push the extractor piston 12 in the backward drilling direction D2.

[0049] Further, a second chamber 22 is arranged in fluid contact with the first chamber 21 , via a restriction passage 23. The extractor piston 12 comprises a second axial surface 19 arranged to face the second chamber 22 such that a second hydraulic pressure P2 present in the second chamber 22 will act on the second axial surface 19 to act on the extractor piston 12 in the backward drilling direction D2.

[0050] Hence, both chambers 21 and 22 are arranged to act on the extractor piston 12 in the backward drilling direction D2.

[0051] In conventional extractor designs, the first and second chambers 21 and 22 are one chamber only, without separation formed by the restriction passage 23. With the use of a first, soft chamber 21 and a second, stiff chamber 22, the operation of the extractor will improve. The first chamber 21 is designed to keep a floating position of the extractor piston 12 and the second chamber 22 will prevent rapid movements of the extractor piston 12.

[0052] When the drill hammer 30 strikes the shank adapter 11 , during a retraction operation, a majority of the load will pass into the drill rod, but a part of the load will pass into the extractor piston 12. At his point the second chamber 22 and the restriction passage 23 between the first and second chambers 21 and 22 will prevent large positional deviations of the extractor piston 12, by a pressure response in the second chamber 22. Further, a damping is provided by the leakage flow over the restriction passage 23 from the second chamber 22 to the first chamber 21 . Thereby, the extractor will quickly regain its floating position.

[0053] As visible in the drawing, the second chamber 22 may be smaller than the first chamber 21.

[0054] A fluid inlet 25 and a fluid outlet 26 are arranged to and from, respectively, the first chamber 21 to provide a fluid flow through the first chamber 21 when the extractor piston 12 is in operation.

[0055] The extractor piston 12 comprises an edge portion 27 arranged to close a passage A from the first chamber 21 to the fluid outlet 26 when the extractor piston 12 is in a forward position with respect to the forward drilling direction D1 , and wherein said passage A is open when the extractor piston 12 is in a backward position with respect to the forward drilling direction D1 such that an equilibrium position is formed between said forward position and said backward position.

[0056] In Fig. 3 the extractor piston 12 is in operation and positioned in a floating position. There is a pressure drop over the passage A from the first chamber 21 to the fluid outlet 26 that equals the operating pressure P1 in the first chamber 21 , which is created by the combined pulling force from the rock drilling machine, gravity, and the intermittent percussion force provided the drill hammer 30.

[0057] The extractor piston 12 comprises an intermediate rim 24 arranged opposite a step portion 28 of the inner housing 20, wherein the restriction passage 23 is formed between said intermediate rim 24 and said step portion 28. The restriction passage 28 may open in an outermost position in the backward drilling direction D2. As soon as the shank adapter will be exposed to a pressure acting in the forward drilling direction D1 with respect to the housing 20 of the rock drilling machine 10, the extractor piston 12 will, however, find its way back to the floating position illustrated in Fig. 3.

[0058] Above, the disclosure has been described with reference to specific embodiments. The disclosure is however not limited to these embodiments. It is obvious to a person skilled in the art that other embodiments are possible within the scope of the following claims.

Claims

CLAIMS1 . A rock drilling machine (10) comprising:- a shank adapter (11 ) movably arranged along an axis (AA) inside the rock drilling machine (10), the shank adapter (11 ) facing a drill hammer (30) at a first end (16), and a drill string (14) at a second, opposite end (15), the drill hammer (30) being arranged to provide a percussion impact to push the drill string (14) in a forward drilling direction (D1 ) along the axis (AA),- an extractor piston (12) arranged radially outside the shank adapter (11 ) inside an inner housing (20) of the rock drilling machine (10), the extractor piston (12) being arranged to act on the shank adapter (1 1 ) in a backward drilling direction (D2) along the axis (AA), opposed to the forward drilling direction (D1 ), wherein the shank adapter (11 ) comprises a circumferential rim (13) and the extractor piston (12) comprises an abutment (17) arranged to abut the circumferential rim (13) of the shank adapter (11 ) to limit a movement of the shank adapter (11 ) in the forward drilling direction (D1 ), and wherein the inner housing (20) comprises a first chamber (21 ) which is configured to be provided with a hydraulic fluid to build up a first hydraulic pressure (P1) in said first chamber, the extractor piston (12) comprising a first axial surface (18) arranged to face the first chamber (21 ) such that the first hydraulic pressure (P1) will act on the first axial surface (18) to push the extractor piston (12) in the backward drilling direction (D2), and wherein a second chamber (22) is arranged in fluid contact via a restriction passage (23) with the first chamber (21 ), the extractor piston (12) comprising a second axial surface (19) arranged to face the second chamber (22) such that a second hydraulic pressure (P2) present in the second chamber (22) will act on the second axial surface (19) to act on the extractor piston (12) in the backward drilling direction (D2).

2. The rock drilling machine (10) according to claim 1 , wherein the second chamber (22) is smaller than the first chamber (21 ).

3. The rock drilling machine (10) according to claim 1 or 2, wherein a fluid inlet (25) and a fluid outlet (26) are arranged to and from, respectively, the first chamber (21 ) to provide a fluid flow through the first chamber (21 ) when the extractor piston (12) is in operation.

4. The rock drilling machine (10) according to claim 3, wherein the fluid flow through the first chamber is preferably substantially constant during retraction operation of the rock drilling machine (10).

5. The rock drilling machine (10) according to claim 3 or 4, wherein the extractor piston (12) comprises an edge portion (27) arranged to close a passage (A) from the first chamber (21) to the fluid outlet (26) when the extractor piston (12) is in a forward position with respect to the forward drilling direction (D1), and wherein said passage (A) is open when the extractor piston (12) is in a backward position with respect to the forward drilling direction (D1) such that an equilibrium position is formed between said forward position and said backward position.

6. The rock drilling machine (10) according to any one of the preceding claims, wherein the extractor piston (12) comprises an intermediate rim (24) arranged opposite a step portion (28) of the inner housing (20), wherein the restriction passage (23) is formed between said intermediate rim (24) and said step portion (28).

7. A drill rig (100) comprising a rock drilling machine (10) according to any one of the preceding claims.

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