A rock drill includes a shank. A percussion piston is arranged to hit the back end of the shank. Further, a pulling element is arranged around the shank, to which a pulling force can be directed in such a manner that the shank can, by the pulling force, be moved toward the percussion piston, when stuck drilling equipment is freed. During rock drilling, a push force is arranged to act on the pulling element, the push force being opposite with respect to the pulling force. The push force is designed in such a manner that during drilling the pulling element moves due to the push force toward the front section of the drill to be at a predefined distance from the position corresponding to the impact point of the shank.
This application is a continuation of international PCT application Ser. No. PCT/FI02/00506, filed Jun. 11, 2002, which was published in English as WO 02/101192 A1 on Dec. 19, 2002, and which is incorporated by reference.
A percussion device for a rock drilling machine or the like, which comprises means for providing an impact, i.e. a stress pulse, to a tool connected to the percussion device. The means for proving the stress pulse include a stress element (4) of liquid, which is supported to a body (2) of the percussion device and means for subjecting the stress element to pressure and correspondingly for releasing the stress element (4) abruptly, whereby the stress energy is discharged as a stress pulse to the tool in direct or indirect contact with the stress element.
A percussion device for a rock drilling machine or the like, which includes providing an impact, i.e. a stress pulse, to a tool connected to the percussion device. The the stress pulse is provided by way of a stress element of liquid, which is supported to a body of the percussion device. The stress element is subjected to pressure and correspondingly the stress element is released abruptly, whereby the stress energy is discharged as a stress pulse to the tool in direct or indirect contact with the stress element.
An impact device includes a frame to which a tool is connectible, and a stress element that is supported on the frame and disposed between the frame and the tool. A hydraulic control system leads pressurized hydraulic fluid into and out of a hydraulic fluid space such that the stress element causes a stress pulse in the tool. The hydraulic control system includes a rotatingly installed control valve that has control openings for intermittently leading the hydraulic fluid out from the hydraulic fluid space.
An axial bearing includes a first piston and a second piston. Axial contact surfaces between the pistons are arranged in the same pressure space. The same pressure fluid fed to the axial bearing acts on the contact surfaces and on working pressure surfaces of the pistons. A rock drilling machine is also provided with such an axial bearing.
A percussion device (1) with a reciprocating percussion piston (3), includes a first chamber (5) that can be pressurized for forward driving of the percussion piston (3) and a second chamber (8) that can be periodically pressurized for back-driving of the percussion piston (3). The percussion device includes at least one driving piston (7) arranged for actuating the back-driving of the percussion piston (3) wherein a portion of said driving piston (7) is arranged to enter into the second chamber (8) for pressure actuating on a driving surface of the driving piston by pressure medium being present in this chamber in the direction of back-driving, wherein the driving piston (7) includes means for back-driving co-operation with the percussion piston (3), and wherein the driving piston (7) is free for axial movement with respect to the percussion piston (3), opposite the direction of back-driving. The invention also concerns a method and a rock drilling machine.
