Abstract: A hydraulic breaking hammer and method of supporting a percussion piston is provided. The breaking hammer includes a percussion device provided with a reciprocating piston. The piston is supported on a frame at its end portions by a first piston bearing element and a second piston bearing element. The second piston bearing element includes a collar sealing element facing towards a working collar of the piston. The piston bearing elements are easily mountable and dismountable separate components.

Abstract: An actuator assembly includes a threaded shaft, a threaded nut that is threadably coupled to the threaded shaft, an annular ratchet positioned about the threaded shaft and comprising one or more tracks, and a pin that extends from the threaded shaft and into the one or more tracks. The threaded nut may include a first circumferentially-facing surface, the annular ratchet may include a second circumferentially-facing surface, and the first and second circumferentially-facing surfaces are configured to contact one another to enable the threaded nut to block rotation of the annular ratchet with the threaded shaft. The actuator assembly may enable the threaded nut to move to a limit position and hold full motor torque, but also to break free from the limit position with relatively low torque (e.g., less than the full motor torque; as compared to actuator systems that are devoid of certain features of the actuator assembly).

Abstract: A blowout preventer (BOP) assembly includes a body portion, a bore extending through the body portion, and a ram block assembly. The ram block assembly includes a first ram block being movable into the bore and a second ram block being movable into the bore.

Abstract: An air pump includes a cylinder, a piston rod, and an upper cover. The cylinder forms an opening at a top end thereof and at least one retaining hole adjacent to the opening. The piston rod is configured to be movable within the cylinder and provided with a piston forming a conical lateral face at one end thereof. The upper cover has a top portion forming a hole for the piston rod to penetrate therethrough, at least one extension portion extended from the top portion, and at least one retaining portion extended from the extension portion. The least one extension portion has an abutting edge selectively abutted against the conical lateral face. The retaining portion is engaged with the retaining hole.

Abstract: A power swivel is disclosed that is configured to rotate tubular string and drill bit to form or extend a subterranean borehole. In an embodiment, the power swivel includes a motor, a gear box coupled to the motor, and a lubrication system coupled to the gear box. The lubrication system includes a pump disposed within the gear box, the pump including an outlet. In addition, the lubrication system includes a recirculation line fluidly coupled to the outlet of the pump. Further, the lubrication system includes a first injector fluidly coupled to the recirculation line. The injector is configured to deliver lubricant to one of a bearing and a gear disposed within the gear box.

Abstract: In an embodiment, a system includes a tool that includes an exhaust port and a vacuum. The vacuum also includes an exhaust intake port configured to couple to the exhaust port of the tool. The exhaust intake port may be configured to receive exhaust from the exhaust port. The vacuum includes a vacuum intake port, a vacuum exhaust port opposed to the vacuum intake port, and a mixing chamber between the vacuum intake port and the vacuum exhaust port. The vacuum intake port, the vacuum exhaust port, and the mixing chamber may all be on a same centerline.

Abstract: A retrievable core sampling assembly for latching to or relative to a rotatable tubular housing of a core sampling apparatus to allow the capture and retrieval of a core from a subterranean formation, the assembly comprising or including: a core catcher barrel for a core, the barrel being rotationally isolated from the tubular housing and cooperable with a core taking bit coupled to the rotatable tubular housing to retain a core, and a hammer for providing impact to the core taking bit along a longitudinal impact path that is or is substantially decoupled from the core catcher barrel so that when latched, rotation and impact of the core taking bit captures and passes core material from the formation to the core catcher barrel in manner that isolates a core in the core catcher barrel from rotation and impact forces.

Abstract: A silty floating mud collection device, which includes a drive cylinder, an outer sleeve, a sampler barrel, an lug cover plate, a turning cover, a control ring and a control rod, where the drive cylinder includes a cylinder liner, a piston and a piston rod; the outer sleeve is fixedly connected below the cylinder liner; the sampler barrel is detachably installed inside the outer sleeve; the lug cover plate is fixedly connected to a lower end of the piston rod, and can close an upper-end opening of the sampler barrel; the turning cover is turnably installed at a lower end of the outer sleeve, and can close a lower-end opening of the sampler barrel; the control ring is located below the sampler barrel, and is used to block the turning cover which is in an open state; and an upper end of the control rod is connected to the lug cover plate, and a lower end of the control rod is connected to the control ring.

Abstract: The invention concerns a hydraulic striking tool for application in rock and/or concrete cutting equipment containing a machine housing (100;200) with a cylinder (115;215) with a moveably mounted piston (145;245) which during operation performs a repetitive forward and backward movement relative to the machine housing (100;200) and directly or indirectly strike a rock and/or concrete cutting tool (155;255), and where the piston (145;245) includes a driving part (165;265) which separates a first (120;220) and a second (105;221) driving chamber formed between the piston (145;245) and the machine housing (100;200) and where these driving chambers are arranged to include a pressurized working fluid during operation. The total volume V of the first and second driving chambers is inversely proportional dimensioned to the square of a for the striking tool recommended maximal pressure p, as well as proportional, by a proportionality constant k within the interval 5.3-21.

Abstract: The invention concerns a method to establish communication between the inner cavity of a drill string and the surrounding material down in a drill hole (60) during the use of a down-the-hole drill unit with a drill string (10), a down-the-hole hammer drill (1), and a source of pressurized medium (11) that delivers a medium under pressure to the down-the-hole hammer drill.

Abstract: An impact device and a method of dismounting an impact device from a breaking device is disclosed. The impact device includes a bush having a percussion piston disposed therein. The impact device is arranged inside an impact device space formed in a frame of a breaking device. The percussion piston is provided with a pull shoulder allowing a dismounting force in a return direction to be transmitted from the percussion piston to the bush. Thus, the bush is extracted from the frame by means of the percussion piston.

Abstract: A machine tool is disclosed. The machine tool has a tool receptacle for receiving a tool on a working axis, a housing, and a striking mechanism. An impact stop is provided for a beater or an intermediate beater. An impact absorber has two polymer-based absorber rings that are offset axially to one another and are disposed so that they overlap radially and has two iron-based disks disposed axially between the absorber rings.

Abstract: A pneumatic hammer mechanism is disclosed. The hammer mechanism includes: a flying mass; an impact surface which limits a movement of the flying mass along the impact axis in the impact direction; an exciting piston which limits a movement of the flying mass opposite from the impact direction; a pneumatic chamber between the flying mass and exciting piston; and a drive for periodically moving the exciting piston with a stroke along the impact axis.

Abstract: A pile driver system for installing or removing foundation elements, such as piles, anchors, and conductors, in a subsea ground formation, includes a closed housing defining a cavity, an impact weight accommodated inside the housing, a hydraulic circuit for reciprocating the impact weight, which circuit comprises one or more valves, a cylinder, and a piston accommodated in the cylinder and connected to the impact weight, a pump for withdrawing water from the surroundings of the pile driver and providing pressurized water to the hydraulic circuit, and at least one outlet for returning water to the surroundings. The exhaust of the hydraulic circuit communicates with the cavity and the outlet is located in the wall of the housing.

Abstract: An impact system for a hydraulic hammer is disclosed. The impact system may include a piston, a sleeve disposed co-axial with the piston, and an accumulator membrane disposed external to the sleeve. A first seal may be located at an end of the sleeve, and configured to connect the sleeve to the piston. The accumulator membrane may have an extension configured to engage a recess in the sleeve.

Abstract: Disclosed is a hydraulic breaker.

Abstract: An impulse generator (1) for a percussive tool includes a chamber (3) for receiving a liquid volume and an impulse piston (4) which is arranged for transferring pressure pulses in the liquid volume into stress wave pulses in the tool. The chamber (3) is adapted with respect to its shape such that it forms a resonance chamber for liquid in the liquid volume for forming at least one pressure antinode (11,15,17) inside the chamber. The invention also concerns a method and a hydraulic impulse tool.

Abstract: A pile driving system for driving a pile. The pile driving system comprises a housing assembly, a hammer, a helmet member, and a lifting system. The housing assembly defines at least one vent opening is arranged at a first vent location along the drive axis, and at least one vent opening is arranged at a second vent location along the drive axis. When the hammer drops and is above the first vent location, ambient air flows from the main chamber through the vent openings formed at the first and second vent locations. When the hammer is below the first vent location and above the second vent location, ambient air flows from the main chamber through the vent openings formed at the second vent location. When the hammer is below the second vent location, air within the main chamber is compressed to preload the helmet member.

Abstract: A percussion device has a machine housing (1), a forwards and backwards movable percussion piston (2) in the machine housing, and a reciprocatingly movable valve body (6) in the machine housing. The percussion piston has a first (4) and a second (5) driving surface subjected to pressure to drive the percussion piston (2) forwards and backwards. The valve body (6) has a first end surface (12) and a second end surface (13) for driving the valve body in first and second directions by applied pressure. The valve body (6) is arranged over a channel (7) in the machine housing, to connect at least the second (5) driving surface alternately to a pressure source (8) or to low pressure (9), and the second end surface (13) is alternately connectable by the percussion piston (2) to the pressure source (8) or, over a valve device (11) for creating a counter-pressure, to the low pressure (8).

Abstract: The pneumatic drilling device includes: a ram provided inside a cylindrical body so that the ram can move forward and backward therein; a spindle air motor provided inside the ram; a feed air cylinder mechanism for moving the ram forward and backward; and an air supply port for supplying compressed air to the feed air cylinder mechanism and the spindle air motor through an airflow path. The airflow path includes: a first flow path for driving the spindle air motor; and a second flow path communicating with the feed air cylinder mechanism for moving the ram forward and backward. The first flow path and the second flow path are separately and independently provided in parallel.

Abstract: Pneumatic drill device comprising an outer casing, an assembly of a cylinder and a movable piston actuating a pick element, a device for supplying the cylinder with compressed air, an air exhaust device and an operational control device, wherein the outer casing is formed from two complementary sections adapted to fit into one another in order to enclose, in addition to the cylinder and piston assembly, the said devices for supplying the cylinder, for air exhaust and for operational control.

Abstract: A battering apparatus including a battering element, an air source, a sensing device, a triggering mechanism, and a battering element release mechanism. Engagement of the sensing device activates the triggering mechanism which in turn activated the battering element release mechanism. The battering element is then released, and driven by air from the air source, moved to its extended position, causing the battering head of the battering element to engage an item to be broken.

Abstract: A hydraulic hammer comprising a housing (10) with a longitudinal bore (12), cylinder sleeve (14) supported in the bore (12) a rear and cover (16) closing the bore (12), and a hammer piston (15) reciprocally powered in the cylinder sleeve (14) for delivering blows to a working implement inserted in the guide sleeve (20) mounted at the front end of the bore (12). The hydraulic hammer also comprises a distribution valve (31), for directing pressure fluid to the hammer piston (15), communicating the pressure fluid source and the cylinder sleeve (14). The valve (31) comprises both a clearance seal means (44) and a seat seal (45, 46) for improved tightness.

Abstract: A hand-held power tool includes a motor-driven percussion mechanism. The percussion mechanism includes a guide tube (21) and a reciprocating driving member (22) displaceable in the guide tube (21) for driving, via a gas spring, an impact member (23) likewise displaceable in the guide tube (21). The percussion mechanism further includes a motor-driven eccentric wheel (17) rotatable about an axis (D) which is spaced from the percussion mechanism axis (S) in a direction perpendicular to the percussion mechanism axis (S) by a distance (X). A connection rod (29) is eccentrically supported on the eccentric wheel (17) and connected to the driving member (22) for converting a rotational movement of the eccentric wheel (17) into a reciprocating movement of the driving member (22).

Abstract: A tool assembly such as a hammer assembly, includes a housing defining a chamber and a reciprocating piston arranged in the chamber for cyclical movement in a work stroke and a return stroke. The housing includes a lower housing member, an upper housing member and an engaging structure which permits the engagement of the upper housing member with the lower housing member by relative rotation of the upper and lower housing members, such that each of the lower and upper housing members defines a portion of the chamber. The upper housing member is a precision component which contains the hydraulic components or other drive components necessary to drive the piston, while the lower housing member can be manufactured separately since it does not need to be manufactured to the high tolerances required by the upper housing member. The resulting tool assembly may be more compact than a conventional tie rod tool assembly.

Abstract: A recoilless hammer comprising a moil supported for reciprocal movement along a hammer axis of a housing, a piston moveable within the chamber of an elongate tube extending from the rear of the housing such that it may strike the moil. In a rest position the piston is held forward against the moil by a low pressure air supply delivered from the aft end of the chamber, and the piston is retracted to a charged position at the aft end of the chamber by delivery of high pressure air to act on the fore portion of the piston. Upon actuation of a trigger mechanism, air is vented from the fore end of the chamber to atmosphere causing a pressure unbalance of low magnitude across the piston, such that it accelerates towards and strikes the moil. The chamber is of a length to enable a high energy blow with minimal piston acceleration recoil when the hammer is manually held and operated.

Abstract: According to the invention, the body of the apparatus includes a flow rate adjustment device including a calibrated opening provided on a high-pressure fluid supply circuit, a bore formed in the body and in which is mounted a slider having a first face located in a first chamber connected to a high-pressure fluid supply circuit upstream from the calibrated opening and a second face located in a second chamber connected to the high-pressure fluid supply circuit downstream from the calibrated opening, the bore receiving the slide including an annular groove connected to a low pressure feedback circuit. The slider is adapted for connecting the annular groove to the first chamber when the pressure difference on either side of the calibrated opening increases beyond a predetermined value in order to divert a portion of the fluid flow supplied by the high-pressure fluid supply circuit to the feedback circuit.

Abstract: A pressure fluid operated impact device comprising a frame (2) whereto a tool (3) is mountable movably in its longitudinal direction, and control means (7) for controlling pressure fluid feed to the impact device (1), as well as a method of generating a stress pulse in a pressure fluid operated impact device. The impact device (1) comprises a working chamber (8) and a transmission piston (9) moving therein. Energy charging means for charging energy of pressure fluid and the control means are coupled to allow periodically alternately pressure fluid to flow to the working chamber (8) and, correspondingly, to discharge pressure fluid from the working chamber (8). In the method, pressure fluid is fed to the working chamber (8), which produces a force pushing the transmission piston (9) in the direction of the tool (3), thus generating a stress pulse in the tool (3).

Abstract: A tool assembly such as a hammer assembly, includes a housing defining a chamber and a reciprocating piston arranged in the chamber for cyclical movement in a work stroke and a return stroke. The housing includes a lower housing member, an upper housing member and an engaging structure which permits the engagement of the upper housing member with the lower housing member by relative rotation of the upper and lower housing members, such that each of the lower and upper housing members defines a portion of the chamber. The upper housing member is a precision component which contains the hydraulic components or other drive components necessary to drive the piston, while the lower housing member can be manufactured separately since it does not need to be manufactured to the high tolerances required by the upper housing member. The resulting tool assembly may be more compact than a conventional tie rod tool assembly.

Abstract: Embodiments of systems and methods disclosed herein regard simplifying and improving the performance and reliability of pneumatic actuators operable to actuate surgical cutters or shears. Various embodiments include systems and methods for vitreous cutting apparatuses utilizing self-valving vitreous cutters that actuate at a frequency based on the properties of the vitreous cutter.

Abstract: A percussive device and method having, inside a machine housing (3), a reciprocally moveable percussive piston (2), the movement of which is controlled by a control valve (5), which is arranged to alternatively connect a chamber to a pressure source and to low pressure in dependence on a signal corresponding to the axial position of the percussive piston, and a valve (16) arranged to allow adjustment of the axial position of the percussive piston at which the signal is transmitted, by opening and blocking of a connection between one or more control channels (10, 11, 12, 13) and the control valve.

Abstract: The present invention relates to a control device for an impulse-generating device for inducing a shock wave in a tool, in which said impulse-generating device comprises an impact element for transmitting said shock wave to said tool, a counter pressure chamber acting against the impact element and a device for reducing a pressure in the counter-pressure chamber. The control device comprises control means for regulating the reduction of the pressure in said computer-pressure chamber. The invention also relates to an impulse-generating device.

Abstract: An impulsive unit for a jack hammer or rock drill is adapted to be powered by water, and comprises a piston slidable within a cylinder, and carrying a striker portion thereon. At least a portion of the piston and/or cylinder is coated with ceramic. The ceramic is most suitably an aluminum oxide-titanium dioxide composite, which enables the clearance between the internal diameter of the cylinder and the external diameter of the piston to be reduced to between 8 and 10 micro-meters.

Abstract: A percussion drill, and methods of using the same, including a shank in mechanical alignment with a piston-hammer and a valve in fluid communication with the piston-hammer. The percussion drill further includes an internal hydraulic dampening system for reducing the velocity of the piston-hammer when the shank is forward of a power position relative to the velocity of the piston-hammer when the shank is in a power position. Preferably, the internal hydraulic dampening system includes mechanical alignment of a portion of the piston-hammer with a port in fluid communication with the valve, operable to reduce fluid flow into an area surrounding the valve when the piston-hammer is forward of its position relative to its normal operation.

Abstract: A fluid distributor cylinder is for a percussive drill assembly that includes a casing having an inner circumferential surface defining a central bore, a central axis extending through the bore, a bit movably coupled with the casing and a piston movably disposed within the casing bore. The distributor cylinder includes a generally tubular body disposeable within the casing bore and having first and second ends, a central axis extending generally between the first and second ends, an outer circumferential surface. At least a section of the outer surface is configured to engage with the inner surface of the casing so to form an interference fit between the body and the casing. The cylinder includes an exterior thread and/or a radially-extending shoulder configured to releasably engage with the casing inner surface so as to substantially prevent axial displacement of the distributor body with respect to the casing.

Abstract: A device for impacting a fastener in one embodiment includes a drive channel, a cylinder opening at an end portion to the drive channel, a microcellular polyurethane elastomer (MPE) bumper fixedly positioned at the end portion of the cylinder, the MPE bumper including a drive bore extending therethrough and aligned with the drive channel, and an outer wall defining a plurality of grooves extending radially about the MPE bumper, and a drive mechanism including a drive blade aligned with the drive bore.

Abstract: A pneumatic drive system (1) in which the movement of an output drive unit (7) of a pneumatic drive (2) is controlled by a control valve (25 and 26) which is connected with the working chambers (12 and 13) of the pneumatic drive (2). The control valve (25 and 26) comprises least one air economy setting (30) setting a choke cross section and a high power setting (29) defining a flow cross section larger than it. An actuator serves to ensure that the control valve is switched over, in a fashion dependent on the air pressure obtaining in the at least one working chamber (12 and 13) from the normally assumed air economy setting (30) into the high power setting (29), when the output drive unit (7) meets with an increased resistance to motion.

Abstract: The invention relates to a device and to a method for producing pressure waves of a high intensity. Thereby, a flowable, explosive substance, or flowable components which form an explosive mixture on mixing and are preferably gaseous, are introduced into a pressure-tight container and ignited. The gas pressure arising from the ignition is led away through a previously closed passage. Preferably, a closure is kept closed by way of a spring element until the explosion, wherein the spring element comprises a relief device.

Abstract: A pneumatic hammer mechanism is disclosed. The hammer mechanism includes: a flying mass; an impact surface which limits a movement of the flying mass along the impact axis in the impact direction; a hammer piston which limits a movement of the flying mass opposite from the impact direction; a pneumatic chamber between the flying mass and hammer piston; and a drive for periodically moving the hammer piston with a stroke along the impact axis.

Abstract: The invention relates to an impulse generator (2) for a rock breaking tool, which comprises a propulsion chamber (6) for receiving a pressurizeable liquid volume (8), and an in the propulsion chamber (6) received impulse piston (10), where the impulse piston (10) is arranged for transfer of pressure peaks in the liquid volume (8) into impulses in the tool (12), whereby transfer of energy from a propulsion mechanism (14) into impulses in the tool (12) is effected by volume reduction of the propulsion chamber (6), whereby the impulse piston (10) is driven forward by a pressure peak in the propulsion chamber (6). The invention also relates to a hydraulic impulse tool comprising an impulse generator (2).

Abstract: An improved impact power tool for carving and engraving an article comprises an air delivery system operable to communicate with a pressurized air source; a drive assembly operable to receive air from the pressurized air source via the air delivery system; a hand held device in driven communication with the drive assembly; and a housing for storage of the air delivery system and drive assembly. The tool includes an improved valve design, a throttle bias valve, and an air storage tank housed within the housing, and an improved housing construction. The improved valve design and air storage tank enable greater stroke speeds of a work tool over a wider power range while also improving the crispness and speed of the impact reaction time over the entire range. The throttle bias valve is in communication with an additional exhaust path, such that the bias valve allows improved control of the hand held device and improved operation over a wider range of air pressures.

Abstract: In a valveless percussive drill of the hydraulic type and incorporating a hammer assembly, an “intermediate” shoulder between the head portion and cushion portion of a reciprocating piston engages the end face of a distributor or liner, rather than an interior bearing structure for the piston. This end face can be made harder than the ulterior bearing structure, which may include a surface made of a different material than the piston. Collectively, the result is a percussive drill with the hammer assembly incorporating the piston substantially less susceptible to failure due to galling as the result of contamination in the working fluid.

Abstract: According to the invention, the body of the apparatus includes a flow rate adjustment device including a calibrated opening provided on a high-pressure fluid supply circuit, a bore formed in the body and in which is mounted a slider having a first face located in a first chamber connected to a high-pressure fluid supply circuit upstream from the calibrated opening and a second face located in a second chamber connected to the high-pressure fluid supply circuit downstream from the calibrated opening, the bore receiving the slide including an annular groove connected to a low pressure feedback circuit. The slider is adapted for connecting the annular groove to the first chamber when the pressure difference on either side of the calibrated opening increases beyond a predetermined value in order to divert a portion of the fluid flow supplied by the high-pressure fluid supply circuit to the feedback circuit.

Abstract: A pneumatic impact tool includes a housing, an accumulation chamber, and a piston. The housing defines a longitudinal passageway with a rear end and a front end and a passageway gas port. The accumulation chamber has a accumulation chamber gas port connectable to a gas supply and a inner gas port in fluid communication with the longitudinal passageway. The piston is inserted in the longitudinal passageway and slides between a rest position wherein the piston is juxtaposed to the rear end of the longitudinal passageway and an impact position wherein the piston is juxtaposed to the front end of the longitudinal passageway. The piston moves from the rest position to the impact position when gas is inserted in the longitudinal passageway through the passageway gas port and is propelled therebetween by pressurized gas contained in the accumulation chamber.

Abstract: A method for controlling a fluid operated percussive device, which inside an axially extending cylinder room (3) of a housing (2) of the percussive device includes a to and fro moveable percussive piston (1), which is adapted for performing strikes in a striking direction (A) and which includes a signal portion (4) for controlling a main valve (5), which is adapted to intermittently transmit pressure fluid to at least one driving chamber (7) for the percussive piston. An auxiliary valve (9) is controlled for transmitting fluid contact between at least one auxiliary channel means (13,14) with a channel opening in the cylinder room (3), and the main valve (5) over the signal portion (4), for switching the main valve (5) before the percussive piston, in operation, has reached at least one of said regions. The invention also concerns a percussive device and a rock drilling machine.

Abstract: 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.

Abstract: An object of the invention is to provide an improved technique for lessening an impact force caused by rebound of a tool bit after its striking movement in an impact power tool. The representative impact power tool comprises a tool body, a hammer actuating member, a tool holder, a driving mechanism, a weight placed in contact with the hammer actuating member to move rearward by a reaction force transmitted from the hammer actuating member when the hammer actuating member performs a hammering operation on the workpiece and an elastic element elastically deformed when the weight moves rearward in the tool body to push the elastic element such that the elastic element absorbs the reaction force transmitted to the weight. The weight is defined one or both of the cylinder and the tool holder.

Abstract: 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.

Abstract: Percussion device including a machine housing (1), a forwards and backwards movable percussion piston (2) in the machine housing, and a reciprocatingly movable tubular valve body (6) inside the machine housing, said percussion piston (2) being arranged to subject a tool (3) to impact, and said percussion piston including a first (4) and a second (5) driving surface arranged to be pressurized in order to drive the percussion piston forwards and backwards, said valve body (6) including a first end surface (12) and a second end surface (13), wherein pressurizing the first end surface (12) tends to drive the valve body in a first direction and pressurizing the second end surface (13) tends to drive the valve body in a second direction, whereby the valve body (6) is arranged, over a channel (7) arranged in the machine housing, to connect at least the second (5) of the driving surfaces alternately to a pressure source (8) or to low pressure (9), wherein an inner room (31) in the tubular valve body (6) is continuous

Abstract: A device (1) which includes an elongate body (2) with a movable mass (3) arranged for sliding movement within the body (2), the element (4) being arranged to decelerate toward an end of the body (2) in order to impart forward movement thereto, via momentum transfer, and being arranged to accelerate away from said end in order to further drive the body (2) forward, again using momentum transfer.