Abstract: A method and software product for controlling a percussion device belonging to a rock-drilling machine, and a percussion device. The impact frequency of the percussion device is set so that the percussion device forms a new compression stress wave to the tool always when reflected waves from the previous compression stress waves reach a first end of the tool. This requires that the impact frequency be set proportional to the propagation time of the stress wave, whereby the length of the used tool and the propagation velocity of the stress wave in the tool material are to be noted.

Abstract: A portable power drill or hammer drill having a housing (12) which consists in particular of half shells (13, 14) and accommodates a manual gearbox (26), wherein a shift element (59) that can be rotated by hand converts its rotary movement into a shift movement, can be produced cost-effectively and can be easily operated, without lubricant escaping from the housing (12), by the shift element (59) consisting of a shell-like handle part (100) which can be joined together with a further, shell-like shift part (102) in a sealing manner from outside and inside relative to a housing shell (13).

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 percussion mechanism for a repetitively hammering hand power tool in the form of a rotary hammer has a striker movable axially forward and backward in a guide barrel and imparting impacts directly and without any intermediate parts to an end section of a tool bit that is insertable into the hand power tool, a device that exerts pressure on the striker, by which the striker is capable of being set into a forward motion in the direction of the tool bit, a blocking element, with which the striker is blockable in its forward motion, and the striking frequency of the striker is adjustable by controlling the blocking time of the blocking element, so that the striking frequency of the striker depends on how long the blocking element blocks the forward motion of the striker.

Abstract: A superior ram-boring machine “mole”, employing compressed air to drive a reciprocating piston onto either forward or rearward anvils thereby imparting momentum. Wherein a control valve received into the rear of the piston interacts with ports therein determining its stroke characteristics. The end receiving impacts, and hence the direction of action are determined by accurately positioning the control valve forwardly or rearwards. Incorporating a robust, air-on, fail-safe “Rapid Reverse” mechanism, actuated by a small rotation of the air hose. Whereby guide means and an indexing collar incorporating or comprising encompassing spring or elastic means having inter-engaging features deforms by flexing and or compression to disengage and is biased to re-engage with corresponding features to position and lock the control valve into forward and reverse settings; thereby assisting easy switching, location and retention of operating positions.

Abstract: A powered hammer includes a housing, a tool holder coupled to the housing and configured to hold a tool, a motor within the housing, a piston slideably mounted within the housing, a drive mechanism that converts rotary output of the motor into a reciprocating motion of the piston, a ram slideably mounted forward of the piston and that is reciprocatingly driven by the piston, and a beat piece support mounted in the housing forward of the ram. A beat piece is slideably supported by the beat piece support. The beat piece is repetitively struck by the ram and that in turn repetitively strikes an end of a tool when the tool is held in the tool holder to transfer the momentum of the ram to a tool. The beat piece support includes a seal that is slidingly engaged by the beat piece. The seal includes an absorbent material.

Abstract: The invention relates to a percussive tool having an oscillatory drive (3), the force of which is transmitted to a tool bit holder (25) by way of a drive member (17). Extending through the percussive tool is a longitudinal opening that allows a rod-shaped object, such as, for example, a guide wire, to be guided through the percussive tool. The tool bit holder (25) has a seat (34), which can receive the tool bit in different orientations. Moreover, the tool bit holder (25) is made of a combination of light metal and steel, which allows a reduction in acceleration forces and noise generation. A saddle-shaped coupling (24) is provided between the tool bit holder (25) and the drive member (17), which guarantees a tight fit.

Abstract: A rock drilling machine includes a frame, and arranged inside the frame is a drill rod. A hammer gear is arranged to hammer the drill rod rear end. There is arranged around the drill rod a position sleeve and an arrangement to move position sleeve in an axial direction against hammering piston so that a counter surface of the position sleeve meets the counter surface whereby, on continuing the positioning, the drill rod is movable to the point desired. The counter surface by use of a spring element is arranged to flex in regard to the other structure of the position sleeve so that in the drilling position the sleeve is arranged to be freely backing against the front side of the drilling machine, and when in the drilling operation the positioning impact on the position sleeve against the hammering piston is removed.

Abstract: A method and a storage device including a software product for controlling percussive rock drilling, and further a rock drilling rig to which the method is applied. The rotation resistance is monitored, the aim being to keep it below a desired reference value. To adjust the rotation resistance, successive control actions may be carried out, such as decreasing the feed force, decreasing the percussion power and stopping the feed. Control actions are started once a limit set for the control has been exceeded. At least one limit is a time limit determining the time difference between two successive control functions.

Abstract: A mechanical fence post driver for attachment to a lift arm of a standard front-loader which includes a mounting plate, guide tube, and roller latch assembly. The guide tube receives a tee or other fence post inserted therein such that it contacts the mounting plate. The fence post is held in place by a roller latch assembly which compresses the post against the rearward side of the guide tube. Insertion of the fence post into the ground is accomplished by lowering the lift arm while the post is held within the guide cylinder. A rotation plate assembly may be positioned between the mounting plate and guide cylinder to provide a convenient mechanism to rotate the guide cylinder in relation to the mounting plate.

Abstract: Provided are various embodiments of structures that may utilized in a power driver, particularly in a power driver having an optional reciprocating “hammer” action, that may be utilized for retaining an outer bearing during driver assembly and during subsequent operation of the power driver. In particular, the disclosed structures provide one or more surfaces, particularly inner peripheral surfaces, that limit the outward axial movement of the bearing. These structures may include combinations of surfaces defined by retaining members including, for example, one or more flanges, clips and threaded members, an input shaft, biasing mechanisms, typically a spring or other resilient structure, and chuck shield assemblies for positioning the outer bearing within the power driver.

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 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: A multi-purpose beach anchor provides a sturdy base for at least one of a small, medium or large sized beach umbrella as well as for an optional table and an optional tubular holder for a fishing rod. The rigidity of the anchor is secured by an integral hand operable slide hammer mechanism for driving the spike element into the sand for an optimal distance straight down. This slide hammer is used by sliding up and down over a tubular support member atop the spike, wherein the spike has an integral strike collar. A few short strokes of the weighted slide hammer element drives the spike into the sand or other terrain. A hand screw is then used to lock the hammer weight to the tubular support and the spike rigidly. An umbrella shaft can then be directly slid over the support tube and locked in place.

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: A percussion mechanism for a repetitively hammering hand power tool, whose striking frequency and striking intensity are controllable independently of one another, has a striker (2), movable axially forward and backward in a guide barrel (1), and a device (5) exerting pressure on the striker (2), as a result of which the striker can be set into a forward motion in the direction of a tool bit (4) that is insertable into the hand power tool. A blocking element (10) is also provided, with which the striker (2) is blockable in its forward motion, and the striking frequency of the striker (2) is adjustable by controlling the blocking time of the blocking element (10).

Abstract: A pneumatic hammer comprises an elongate hollow casing with operatively upper and lower ends and has a piston slidingly received within the casing and operable to reciprocate within the casing between upper and lower pressure chambers defined within the casing. The hammer further has an axially displaceable bit assembly at the lower end of the casing and a backend assembly at the upper end of the casing. The piston has a striking face at an end thereof proximate the bit assembly, and the piston is operable to impact on a contact surface of the bit assembly in an impact region of the casing. The hammer is characterized in that the piston is shaped and dimensioned at its proximal end to have a snug sliding fit with an interior of the casing in the impact region of the casing.

Abstract: 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.

Abstract: A pneumatically reversible ram boring device includes a percussion piston (8) that is situated in a casing (1) and is movable back and forth by operation air supplied via an operational-air supply via an operational-air line (5), a control pipe (4, 36, 54) having at least one control opening (13), an outer pipe (15, 65), and a control sleeve (10, 60) that can be displaced by compressed air from a control chamber (16, 66). An essentially torsion-resistant operational-air line (5) can be rotatably connected to a rotary valve (4, 40, 70) that supplies the control chamber with operational air or vents air from the chamber.

Abstract: A drive system for driving and/or extracting an elongate member. The drive system comprises a piston drive assembly, a hydraulic system, and a vibration drive assembly. The piston drive assembly comprises a piston member, and the piston member engages the elongate member. The hydraulic system is operatively connected to the piston drive assembly to apply a drive force to the piston member. The vibration drive assembly generates a vibratory force. The vibration drive assembly is operatively connected to the piston drive assembly. The drive system operates in a first mode in which the drive force and the vibratory force are applied to the piston member along a drive axis.

Abstract: A modular signpost including a first section, a second section that mounts onto the first section, and a third section that mounts onto the second section. The first section includes a ground mounting structure, a base tube and a guide tube. The second section includes a bracket for holding a flyer box. The second section includes a body tube that is able to slide over the guide tube on the first section. The third section is slide fit into the second section.

Abstract: An impact tool particularly useful for floor removal material includes an elongated removable rod having an upper end and a lower end. A handle is connected to the upper end of the rod, and an anvil is fixed to the lower end of the rod. A collar is mounted above the anvil with the rod passing therethrough. A replacement blade unit is disposed below the anvil and has an upper portion and a lower portion having a separating blade edge. A pair of guide rods extends between the collar and the upper portion of the blade unit and passes through the anvil on opposite sides of the rod. The guide rods enable sliding movement of the anvil therealong between the collar and the blade unit as the handle and rod are moved up and down. A tubular sheath is telescoped over a portion of the rod, the collar, the anvil and the upper portion of the blade unit, and is connected to the upper portion of the blade unit.

Abstract: A concrete drill for drilling concrete or the like by a diamond bit (5) attached to a front end of a bit drive shaft (4) projected forward from a main body (1) by driving to rotate the bit drive shaft (4) by a drive source (2) contained in the main body (1) in which the main body (1) is provided with a vibrating apparatus (8) for exerting a vibrating force a magnitude which is pulsated to change along the bit drive shaft (4) to the main body (1).

Abstract: A grounding rod driving system for facilitating installation and extraction of a grounding rod includes a sleeve slidably receiving a grounding rod. The sleeve slides along the grounding rod when the grounding rod is being driven into a support surface. A driver is coupled to a top end of the sleeve. The driver impacts the grounding rod to drive the grounding rod into the support surface when the sleeve is slid downwardly onto the grounding rod.

Abstract: A jar mechanism comprises a housing having a fluid chamber therein, a piston encircled by an annular metering sleeve and movably mounted in the fluid chamber for movement between a first position and a second position, and a jar member moveably mounted in the housing such that a pull or push force exerted on the jar member moves the piston from the first position to the second position within the fluid chamber against the resistance of the fluid, and the action of the pull or push force exerted on the jar member actuates a release device. The jar member is releasably coupled to the piston by the release device such that, when the piston is in the first position in the fluid chamber, the jar member is coupled to the piston by the release device for movement therewith. Actuation of the release device enables the jar member to be uncoupled from the piston.

Abstract: 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.

Abstract: The invention represents a new design of a reversible penetrating machine (90) with a pneumatically controlled differential air distributing mechanism. This design eliminates the springs, the rear anvil assembly, and several other components found in the prior machine. The chisel and the tail of the machine are also redesigned to eliminate the need of a special attachment in case of retracting a failed machine. In addition, a simplified modification of the machine for special applications is disclosed in which the rear valve chest with associated parts is replaced by a single flange having appropriate air ducts. Finally, the new design of the chisel causes a reduction of the lateral friction between the body of the machine and soil. All this significantly increases the reliability and efficiency of the machine and results in decrease of the related manufacturing and operating cost.

Abstract: A torque impact wrench having an elongated tubular metal housing. The front end of an impact wrench is secured to the rear end of the housing by a motor mount. The front end of the drive shaft of the impact wrench is inserted into the rear of an impact socket. The rear end of a drive screw is received in the front end of the impact socket. The drive screw has external threads on its rear portion and external threads on its front portion. The drive screw passes through a screw drive nut whose bore is internally threaded. The drive screw is rigidly secured in the steel housing. The front end of the steel housing has a first load disc closing that end and it removably receives the lower crimping die. A second load disc is longitudinally spaced from the first load disc and it also has a crimping die removably secured thereto. A third load disc is screwed onto the front end of the drive screw.

Abstract: 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.

Abstract: A concrete drill for drilling concrete or the like by a diamond bit (5) attached to a front end of a bit drive shaft (4) projected forward from a main body (1) by driving to rotate the bit drive shaft (4) by a drive source (2) contained in the main body (1) in which the main body (1) is provided with a vibrating apparatus (8) for exerting a vibrating force a magnitude which is pulsated to change along the bit drive shaft (4) to the main body (1).

Abstract: Self drilling anchors and related methods and apparatus. In one embodiment an apparatus comprises a drill bit, a hammer mechanism for hammering the drill bit in a first direction and in a second direction, and a selection mechanism for controlling whether, at a given point in time, the drill bit is hammered in the first or second direction.

Abstract: A hydraulic hammer having a sealing bushing includes a percussion piston that delivers strokes to a tool. A lower part of the percussion piston is sealed with respect to a frame by the sealing bushing, which includes one or more lower seals. The sealing bushing does not contribute to the bearing of the percussion piston and it is arranged in place through the lower end of the hydraulic hammer.

Abstract: A post driver is powered by a pair of hydraulic cylinders, one on either side of the hammer to provide a balanced lifting force to the hammer. A post retaining cap is formed to provide a recess for the post. The orientation of the driver may be controlled about a horizontal axis so the post may be driven vertically without regard to the contour of the ground. The post driver is further provided with an extensible beam and foot which is extended to engage the ground and further support the driver.

Abstract: A method of inserting a grounding rod includes providing an elongated grounding rod that has an upper end and a lower end and also providing a hammer drill. An elongated tubular member has an open first end and an open second end. The tubular member includes a first portion and a second portion. A dividing wall is integrally attached to an inner surface of the tubular member and is positioned at a juncture of the first and second portions. Te upper end of the grounding rod is extended into the second portion of the tubular member such that the upper end abuts the dividing wall. The hammer drill is engaged with the first portion of the tubular member. The hammer drill is turned on so that the lower end of the grounding rod is extended into a ground surface.

Abstract: The present invention relates to a drilling hammer comprising a hammer tube (13) that is rotationally drivable inside a housing (10), a striking tool (14) located in the hammer tube (13) and provided with a piston (15) that can driven with a reciprocating motion, and an operating mode change-over switch (35) for the “impact drilling” and “chiseling” operating modes. The hammer tube (13) is decoupled from its rotary drive when in the “impact drilling” operating mode and is secured in the housing (10) in a non-rotative manner when in the “chiseling” operating mode.

Abstract: A post driving device is disclosed. The post driving device slides to a desired position and is essentially locked in place through frictional force. As the post is driven into the ground, the device can be adjusted to a new position along the length of the post.

Abstract: A system and method for applying rotary percussive impacts to a drill bit, according to which an anvil is connected to the bit and a hammer is driven in one direction in the anvil when the bit encounters a relatively large load. Energy is stored during the movement of the hammer in the one direction and the stored energy is released to drive the hammer in a direction opposite the first direction to produce the percussive impacts.

Abstract: An impact drill minimizing transmission of vibration to a handle gripped by a user's hand. A spindle extends through a main frame and is movable in its axial direction and rotatable about its axis. A first ratchet is rotatable and axially movable together with the spindle. A second ratchet is axially movable but unrotatable. In an impact drilling mode, the first ratchet is brought into abutment with the second ratchet so that the spindle is reciprocally moved in the axial direction.

Abstract: An impact tool, comprising: a shaft; a stop on the shaft; a slider movable on the shaft for striking the stop to create an impact force; and a handle on the slider to allow a user to move the slider. The handle isolates the impact force from the user by being movably attached to the slider.

Abstract: A method and apparatus providing a sign post assembly including a stabilizing post member, an outer tubular post and a horizontal post member. The stabilizing post member includes a spike portion and an inner post portion with a blocking portion coupled to the post member above the spike portion. The outer tubular post defines a post bore substantially extending through a length of the outer tubular post with at least a lower open end. The outer tubular post is configured to mate with the inner post portion to substantially extend within the post bore of the outer tubular post. The horizontal post member includes a horizontal post portion and a post coupling portion. The post coupling portion is configured to operatively couple with the inner post portion of the stabilizing post member so that the horizontal post portion extends transverse to the stabilizing post member to hang a sign thereto.

Abstract: A ground piecing tool includes a housing and an air distributing mechanism that reciprocates a striker to impact a chisel shaft in response to a supply of compressed fluid including a fluid inlet tube mounted in the bore of the striker having a radial port, a rear end of the inlet tube being in communication with the distributing mechanism, wherein the housing and chisel shaft cooperate to define a front chamber that decreases in volume as the chisel moves forward relative to the housing, and wherein the chisel shaft has a radial passage therein that conducts compressed fluid from the radial port of the inlet tube to the front chamber, which is configured to form an air spring.

Abstract: The invention relates to a control system for a percussion drive of an earth drilling unit having a housing, a drilling tool, a pulling or thrusting drive, a percussion piston, a pressure chamber belonging to the percussion piston and a pressure medium feed, which can be connected and disconnected, for the operation of the percussion piston, wherein the connecting and disconnecting of the pressure medium feed occurs when the pulling or thrusting drive exceeds or falls below a specific pull or thrust.

Abstract: In a liquid downhole drilling machine, the guiding bushing (31) for the drill bit is rotatably journaled in the housing (11, 12) and, via a one-way coupling (29), coupled to a turning sleeve (22) that has axial ridges (24) that bound a number of chambers (25, 26, 27) and form turning pistons for turning the turnable sleeve to and fro. A number of these chambers are coupled to be pressurized and depressurized simultaneously with said pressure chamber (47) with the piston area (46) for urging the piston hammer (30) forwards. As a result, the drill bit (13) will be indexed a defined angle between each impact so that the button inserts of the drill bit will change contact points with the rock between every impact and fragment the rock efficiently. The drill tube is not rotated.

Abstract: A pneumatic ground piercing tool includes a tail assembly including a tail nut and tail cap, the tail cap having a plurality of discharge ports for exhausting spent compressed air, the discharge ports opening into an annular space between a rearwardly opening recess of the tail cap and an air supply conduit such that the exhaust ports are shielded by a side wall of end cap from plugging when the ground piecing tool is operated in reverse mode.

Abstract: An attachment for an impact hammer for translating the hammer's typical forwardly directed impact force into a rearwardly directed pulling force while still allowing the user to maintain a conventional orientation of the hammer relative to the work piece intended to be pulled. The attachment comprises a housing defining a cavity with a hammer bit axially movable therein and having an impacting head urged rearwardly by a bias structure which responds to a forward impact force by the impact hammer to cause the hammer bit head to exert impact force on the work piece in a rearward direction.

Abstract: A method of the invention uses a pneumatic ground piercing tool having a reversing mechanism with a supplemental air line capable of supplying compressed air for reverse operation to a radial port in the air distributing mechanism. This radial port is located between a pair of bearing surfaces on the step of the air inlet conduit, and when pressurized by the supplemental air line, causes the front pressure chamber to receive compressed air earlier than normal, shifting the stroke of the striker rearwardly so that the tool operates in reverse. Such a method includes the steps of operating the tool in forward mode by supplying compressed air to the first air hose, and operating the tool in reverse mode by supplying compressed air to the second air hose while permitting partial venting of the front pressure chamber through the first air hose.

Abstract: A double-headed tent stake driver and puller having twin release levers for inserting and removing tent stakes, nails and the like is described. The tent stake driver and puller includes a slide hammer and a coupler mounted on the distal end of the slide hammer shaft. The coupler has an elongate body with an open end and a hollow core sized to receive the head of the stake or nail intended for use with the present invention. The coupler includes a pair of retractable keepers slidably received within a corresponding pair of slots. The keepers provide the twofold benefits of retaining the stake once inserted into the coupler, and presenting a surface for imparting the extraction force upon a stake to be pulled from the ground. A pair of spring loaded release levers are provided to enable one-handed retraction of the keepers for receipt of the tent stake. When released, the spring loaded release levers return the keepers to a ciosed position, retaining the stake therein.

Abstract: The invention relates to a demolition hammer and/or hammer drill comprising a percussion generating device having a percussion piston moving axially back and forth. In a main percussion mode, the percussion piston impinges upon a tool which can move along a limited axial path straight into a main percussion direction. In a free percussion mode, the percussion piston indirectly impinges upon a percussion changing device, and by means thereof upon the tool, in a free percussion direction opposite to the main percussion direction. The impact surface of a tool shaft and the impact surface of a free percussion ram are placed opposite an impact surface of the percussion piston in such a way that the free percussion ram is removed from the effective area of the percussion piston by a return spring in the main percussion position.

Abstract: A pneumatic ground piercing tool includes a tail assembly including a tail nut and tail cap, the tail cap having a plurality of discharge ports for exhausting spent compressed air, the discharge ports opening into an annular space between a rearwardly opening recess of the tail cap and an air supply conduit such that the exhaust ports are shielded by a side wall of end cap from plugging when the ground piecing tool is operated in reverse mode.

Abstract: The lower end portion of a pneumatic impact hammer cylinder has at least one upper fluid passage and at least one lower fluid passage. A U-shaped sleeve is mounted in a circumferential groove in the lower end portion of the piston. The sleeve includes a base, upper and lower legs extending radially outward from the base, and a cavity extending axially between the legs. The sleeve has an axial length that is less than the axial length of the piston groove such that the sleeve is slidably movable within the piston groove between an upstroke position and a downstroke position. The upper fluid passage and the lower fluid passage cooperate with the sleeve cavity, as the piston reciprocates between the impact position and the recovery position, to supply pressure fluid to the impact end of the operating chamber for a portion of each upstroke and each downstroke.