Abstract: There is disclosed a double-acting hydraulic jar having upper and lower detent pressure chambers having upper and lower restrictions, respectively, formed on the inner diameter of its outer tubular member and through which upper and lower detent means carried about the outer diameter of the inner tubular member may be moved in order to impart either an up or down jar.

Abstract: A hydraulic breaking hammer (10) has a machine housing (11) in which a percussion motor (15) which includes a reciprocatingly movable percussion piston (17) delivers impacts to a breaking tool (13) in the front of the machine housing (11). The machine housing (11) is carried by a surrounding carrier support (18) via intermediate walls (24, 25, 26). The carrier support has the form of a shell (18) which is attached at the rear adjacent connecting devices (19), to a carrier, such as a hydraulic digging machine which aligns the machine housing (11) while the manner (10) is at work. The machine housing (11) is constructed without joints in its axial direction along the length of the housing and includes a guide passage (21) in which a percussion motor (15) is carried, this percussion motor having the form of an insert cartridge which can be clamped from the rear.

Abstract: A down-the-hole rock drill includes a top sub, a driver sub having a bore therein, and a piston case extending between and detachably connected to the top sub and the driver sub. A piston is located within the piston case, and a drill device is detachably connected to the driver sub. The drill device includes a shank and a head. The drill device also has a central passageway for a flushing medium. A tube is secured in the central passageway at a free end of the shank. The tube extends beyond the free end of the shank, and the piston has a central piston passageway that receives the tube. The piston is slidably movable relative to the tube. A first portion of the shank located closest to the head has a cross section, normal to a longitudinal center axis of the shank, in the shape of a multi-lobed figure that is continuously non-concave, and the bore of the driver sub is of a matching cross-sectional shape.

Abstract: In an underground borer with down hammer having a vehicle body 1, a guide stilt 2 standing on the vehicle body, and a rotary machine 4 having its bottom coupled with a screw shaft 3 and a down hammer B, a supply unit 5 is interposed between the rotary machine 4 and the screw shaft 3, a fluid conduit 6 is formed centrally of the screw shaft 3, compressed air conduits 7 and 7' are formed to surround the fluid conduit 6, and a fluid jetting pipe 8 is arranged centrally of the down hammer B to extend until the inside of a bit body 9 so that water may be discharged, along with high-pressure compressed air, from a central portion of the bottom surface of the bit body during boring to cool the bit body, promote anti-wear properties, suppress powdery dirts, reduce noises and increase the boring speed.

Abstract: There is disclosed a tool for enhancing the impact delivered to an object stuck in a well bore by means of a jar having a first tubular member connected to the object and a second tubular member having a hammer arranged to deliver an upward blow to an anvil on the first member in response to raising and a downward blow in response to lowering of the second tubular mandrel member with respect to the first member, the tool comprising a first tubular member having a lower end adapted to be connected to the second tubular member of the jar for raising and lowering therewith, a second tubular member vertically reciprocable with respect to the first member to form on annular space between them and having an upper end adapted to be connected to a well pipe string above it, and first and second sets of upper and lower longitudinally spaced seal rings within the annular space and sealably slidable with respect to equal diameter portions of each of the tubular members to form upper and lower fluid chambers between the

Abstract: A reverse percussion device for use with hydraulic percussive drills is provided. The reverse percussion device includes a cycling piston, valve and anvil. The piston and valve move in opposing directions between low and high pressure passages automatically until a lodged drill bit is freed, thereby facilitating removal of the drill bit from the drilled hole and eliminating alternate loosening and tightening of drill string threads. The reverse percussion device preferably includes an automatic disabling feature which causes the reverse percussion operation to cease when the bit is free to retract normally.

Abstract: The present invention provides a pneumatically operated impact-action self-propelled mechanism for driving holes in the earth, comprising a cylindrical housing assembly (1) with an anvil member (2) located at a forward end thereof; and a pneumatically-operated impact piston (3) reciprocal in the housing to deliver successive impacts to the anvil member (2) and forming with the housing a forward chamber (6) of variable volume. The mechanism includes a head chamber (22) forward of the anvil member (2), a head piston (23) reciprocal in the head chamber (22) and connected at its forward end to the head (24) of the mechanism, and compressed air supply member (29, 30) communicating between the forward chamber (6) and the head chamber (22) to the rear of the head piston (23) so as to cause the head piston to travel forwards.

Abstract: A hydraulic jar device for use in through-tubing drilling and fishing operations which consists of an elongate tube having an upper hammer sub, a kelly cylinder and a hydraulic cylinder with central restrictor secured therebelow. A lower sub connects to the bottom end of the hydraulic cylinder. The sliding interior components are an upper mandrel secured to an anvil sub which, in turn, is fastened to an axial plunger, all of which are slidable down within the elongate tube. A metering ring retained on the plunger interacts with the central restrictor of the hydraulic cylinder to control force effected up and down jars that occur when the mandrel strikes the hammer sub on the down stroke, and when the anvil sub strikes the hammer sub bottom on the up stroke.

Abstract: A method and an arrangement for controlling the supply of air into a rock drilling machine. In the method, the air supply of an air compressor in a power unit operated by a diesel engine is adjusted so that when the percussion pressure of the percussion device of the rock drilling machine is high, the amount of air supplied by the compressor is small, and vice versa. In the arrangement, the pressure fluid pump of the hydraulic motor of the compressor is an adjustable-displacement pump, the volume flow of the pressure fluid supplied by the pump being adjusted inversely proportionally to the pressure of the supply conduit of the percussion device of the rock drilling machine.

Abstract: A down-the-hole hammer drill having a reverse circulation system which conducts pressurized air downwardly to a lower cutting face of a drill bit. The air travels across the cutting face and upwardly through a central exhaust passage. The air is conducted to the cutting face through longitudinal and lateral passages in the bit which are kept isolated from the environment surrounding the bit so that no appreciable amount of pressurized air can escape, and so that the passages do not become clogged with dirt. The drill bit comprises upper and lower pieces. Upper sections of the longitudinal passages are formed in the upper piece, and lower sections of the longitudinal passages are formed in the lower piece.

Abstract: An apparatus for a percussive, down-hole drill, for positioning a split retaining ring against an internal surface of a drill casing including a chuck with a tapered top surface, a bit bearing with a tapered bottom surface, and a reversible split retaining ring sandwiched therebetween, the split ring having a tapered top and bottom surface, each tapered surface subtending an angle between 5.7 and 25 degrees, as measured from a perpendicular to a drill longitudinal axis, whereby a portion of any longitudinal load on the split ring is developed into a preselected maximum and minimum amount of radial load, to position the split ring in the casing, without damaging the casing.

Abstract: An impact tool having an air-operated hammer for impacting against an anvil in the body of the tool to cause the tool to tunnel through the ground, and having passages and conduits opening to the front region of the tool to pass water to lubricate the tool and wet the soil proximate the front of the tool, to ease the passage of the tool through the soil during the propulsion of the tool.

Abstract: Hammer device comprising a machine housing (1) with a hammer piston (2) movable to-and-fro. The movement to-and-fro of the hammer piston is controlled by a valve body (6) movable to-and-fro in the machine housing. In order to speed up the turning of the hammer piston at its rear end position the machine housing is provided with a room (10) which by the hammer piston is separated from connection with the valve body (6) at the same time as the rear end surface (5) is supplied with pressure fluid via a connection (11) opened by the hammer piston to the pressure source (8) when the hammer piston approaches its rear end position.

Abstract: A plurality of rods each having a bit at a front end are disposed in parallel to one another so that adjacent bits are displaced to some extent forward and backward, and a striking device operatively connected to each of the rods includes a striking block. The striking block includes a single cylinder block having a plurality of cylinder tubes, and a striking piston is slidably fitted into each of the cylinder tubes. The striking block further includes a change-over valve for changing over between a forward movement and a backward movement of each striking piston. A rear end of each rod is connected through an adapter to a shank rod which is connected to the striking device. In the striking device, a spring is provided between a bearing holder which holds the shank rod rotatably and the adapter to push the rod in a forward direction. When the bit is not reached the rock, the rod is pushed forward by the spring to hold the shank rod at a position before the striking point.

Abstract: The weight of a pneumatic ground piercing tool of the type having a stepped air inlet is reduced and tool power increased by providing the tool body with a dual diameter. The tubular tool body has a front section and a rear section which has a greater inner and outer diameter than the front section, thereby reducing overall tool weight. In a preferred embodiment, the rear end portion of the striker likewise has a greater outer diameter than the front end portion thereof. The bearing of the front end portion of the striker remains in sliding contact with the interior of the front body section during tool operation, and the bearing of the rear end portion of the striker likewise remains in sliding contact with the interior of the rear body section. In this manner, the power of the tool is enhanced because the tool has less weight and the air distributing mechanism, located in the rear body section, is the same size as in a conventional tool wherein the entire body has a uniform diameter.

Abstract: Rock drilling device comprising a backhammer unit (10) in which a hammer piston (9) is movable to-and-fro for automatically exposing a tube string (4) to impacts in a direction away from a drill bit (8) in the tube string. The backhammer unit comprises a housing (13) and a springloaded tube part (14). The housing and the tube part form between them a first valve (16) and a second valve (17). At drilling the first valve which controls the supply of driving medium to said hammer piston is closed and the second valve which controls the flushing medium flow is open. At backwards feeding of the rock drilling machine (2) along the feed beam (1) with a force which exceeds a predetermined value the first valve is open and the second valve is closed.

Abstract: Down-the-hole drill comprising a housing (1), a hammer piston (6) movable to-and-fro in the housing and intended for impacting a drill bit (5). A back piece (3) provided with an extension (12) with a valve part (17) cooperates with a part (8) of a central channel in the hammer piston. This part of the central channel comprises a zone (16) with larger diameter than adjacent parts at an intermediate part of this part. This results in that pressure medium can pass the valve part when it is situated at the zone and that the valve part and the hammer piston sealingly cooperate when the valve part is on either side of the zone.

Abstract: A down-the-hole hammer includes a drill bit and a piston reciprocating therebehind to periodically strike the drill bit. The drill bit includes front and rear portions of difference impedance, and the piston includes front and rear portions of difference impedance. In the drill bit, the front portion has a larger impedance than the rear portion. In the piston, the rear portion has a larger impedance than the front portion.

Abstract: An air percussion hammer drill is disclosed for operation in an earthen formation. The air compression hammer mechanism comprises a piston that reciprocates while simultaneously rotating within its housing. A hammer drill bit slidably keyed to the bottom of the piston transfers the impact energy to the formation and rotates during operation independent of an attached drill string. The air percussion hammer assembly is therefore ideally suited to directional drilling activities.

Abstract: A pressure sensitive valve for a fluid-actuated percussive drill includes passageways for fluid flow to expose a valve surface to a burst of short-interval, high pressure fluid from a drive chamber to cause early closing of the valve.

Abstract: A method and apparatus for enlarging a straight or arcuate pilot bore hole and the insertion of tubing in the enlarged bore is disclosed, in which the pilot bore hole 10 is enlarged by advancing a larger diameter housing with a conical enlarging head by impacting of a striking body mounted within a housing against the inside of the enlarging head at the forward end of the housing. Fluid jet cutting action is also employed and the pilot hole boring device may be coupled to exert a steady pull on the housing as it is advanced through the pilot bore. The housing may thus be connected to the pilot bore drilling device, with an interposed cushioning device. The fluid jets may be created by nozzle openings in the enlarging head or in a separate device mounted forward of the enlarging head.

Abstract: A hydropneumatic hammer operated by a reciprocal action of a percussive piston and a directional control valve, comprising a piston having steps of larger and smaller diameters separating the interior of a piston chamber intended for admitting said piston into four chambers, a first chamber communicating by way of a first passage with a pressure line, the second chamber being defined by a step of middle portion of said piston connecting to a discharge line, the third one being defined by a step formed on an upper portion of said piston, and the fourth one defining a gas chamber separated from the third chamber by a seal retainer, a valve chamber intended for admitting a valve system, being arranged parallel to said piston chamber, a passage for converting a pressure line of fluid or oil into a discharge line and connecting said valve chamber with the second chamber, a passage for returning an exhausted fluid or oil being converted into depressurized condition after working, a first passage intened for deliver

Abstract: In a percussion drilling apparatus, an impact block assembly is provided for sequentially driving drill rods into a subterranean formation, the impact block assembly including an impact block member aligned with one or more rows of drill rods and a combustion operated piston is arranged above the impact block assembly for sequentially driving each of the impact members downwardly into engagement with the aligned drill rods.

Abstract: An impact borer, a connector, a method for embedding lines and an improved method for sinking geothermal wells. The impact borer has a shell, which has a longitudinal bore. An anvil closes one end of the bore. A ram is reciprocally slideable within the bore, against and away from the anvil. The ram divides the bore into front, rear, and ram chambers. A director is joined to the shell. The director is monolithic. The director isolates the front and rear chambers in alternation upon reciprocation of the ram. The director defines an inlet passage communicating with the ram chamber and an outlet passage communicating with the rear chamber.

Abstract: An impact borer having a shell and an air drive within the shell. The air drive includes a ram for reciprocation within the shell and a manifold joined to the shell. The manifold defining an inlet passage delivering air to the air drive and an outlet passage exhausting air from the air drive, and a duplicate passage interconnecting the inlet and outlet passages within the manifold.

Abstract: An uphole hammer is provided comprising a substantially tubular housing which is closed at a first end and supports a substantially centrally located fluid supply tube at the first end. The fluid supply tube extends axially through the housing and is adapted to be mounted at its other end to a drill string, the fluid supply tube being adapted to receive fluid being directed to the hammer by the drill string. The housing further supports a drill bit at or towards its other end which is slidably received about the fluid supply tube, a piston also being slidably supported about the fluid supply tube in the housing for reciprocation between the drill bit and the first end of the housing.

Abstract: A self-propelled, pneumopercussive, cyclic action, ground penetrating machine (200) has decreased energy consumption and increased average working velocity compared to conventional machines. This is obtained in part by a valve-operated air-distribution mechanism (203) having separate forward and reverse compressed air supply lines (35, 37), which mechanism (203) does not limit the length of the forward and backward strokes of the striker (202). This mechanism allows the backward stroke chamber (75) to be connected with the atmosphere during the entire forward stroke of the striker (202). This eliminates generation of an air buffer in the backward stroke chamber (75) and, consequently, the striker (202) does not lose part of its kinetic energy before impact.

Abstract: A fluid-activated, percussive, down-the-hole drill having a reversible bearing and bit combination for altering the volume of return reservoir exhaust fluid between a larger amount for deep hole drilling and a smaller amount for shallow hole drilling.

Abstract: A forward and rearward running ramming device includes: a housing having a percussion head in which a percussion piston a axially displaced by compressed air; a control device for controlling the compressed air so that, during forward running the percussion piston strikes a front side of the housing, and during rearward running the percussion piston strikes a rear side of the housing, the control device interacting with control openings in the percussion piston, which control advancing movement and returning movement of the percussion piston, the control device being seated in a the housing and being connected, through the housing, to an air supply hose; an arresting device, which fixes the control device relative to the housing in individual switching positions, which are set by turning the air supply hose, wherein the arresting device is also a damping device, at least one air chamber, variable in size, being provided as arresting and damping element, the air chamber being bounded at end faces by rear and f

Abstract: An impact borer, a connector, a method for embedding lines and an improved method for sinking geothermal wells. The impact borer has a shell, which has a longitudinal bore. An anvil closes one end of the bore. A ram is reciprocally slideable within the bore, against and away from the anvil. The ram divides the bore into front, rear, and ram chambers. A director is joined to the shell. The director is monolithic. The director isolates the front and rear chambers in alternation upon reciprocation of the ram. The director defines an inlet passage communicating with the ram chamber and an outlet passage communicating with the rear chamber.

Abstract: A downhole oil well tool uses impact, reciprocal drilling and an improved rotating bit or like working member, receiving both fluid pressure and weight from an elongated pipe string with a flow bore in order to drive the tool. A valve within tool housing controls fluid pressure to the working end so that the tool pressures up, then releases pressure through the working member allowing the pipe string to load the bit, creating impact. A clutch rotates the working member during drilling to prevent imprint upon the formation. A bias spring is provided to control and adjust the amount of weight on the bit independent of pipe weight.

Abstract: The present invention relates to a sacrificial transmission sleeve for a reverse circulation down hole hammer of the percussive type actuated by a fluid under pressure, including an outer sleeve, a drill bit retained in retaining means, the transmission sleeve comprising a body and an annular flange extending from the body towards the drill bit, wherein the transmission sleeve has an outer diameter greater than that of the outer sleeve and substantially the same as the drill bit.

Abstract: A ram boring machine having a striking piston that is axially displaceable in a housing, of which the forward and backward movement is controlled by a control sleeve connected to a supply hose and which engages in a cylinder chamber of the striking piston, and by one or more corresponding control openings in the striking piston, wherein the control sleeve is loaded both axially and torsionally, has axial and rotational stops and is rotatable and axially displaceable in a guide sleeve arranged at the rear end of the housing.

Abstract: A device for use adjacent to a down-the-hole percussive drillhead, for removing debris from a drillhole, includes a separator for removing water and other matter from the percussive fluid prior to the percussive fluid entering the drillhead. The water and other matter are ejected into the drillhole to remove the debris, and the separator includes a one-way flow valve to prevent backflow of debris and water into the drillhead during periods when the percussive fluid flow ceases.

Abstract: A method for removing debris from a drillhole, includes positioning a separator adjacent to a down-the-hole percussive drillhead, for removing water and other matter from the percussive fluid prior to the percussive fluid entering the drillhead. The water and other matter are ejected into the drillhole to remove the debris, and backflow of debris and water into the separator and drillhead is prevented, during periods when the percussive fluid flow ceases.

Abstract: A pneumatic percussion hammer for attachment to a drill tube is coaxially constructed about an outflow tube which is mounted therein for axial removal and replacement when worn. A cylindrical piston moves axially between a top sub wherein a drill stem is screwed, and an anvil of a bit at the bottom. A casing and the piston are configured to valve the flow of pressurized air therethrough for reciprocating motion of the piston and an outflow that carries debris through the outflow tube and drill stem.

Abstract: An excavation tool, in which a device is provided which receives the striking force of a hammer and the rotational force of a hammer cylinder, in a bottom surface of which at least three axle holes are provided displaced from a center of the device and at equivalent angular intervals in the circumferential direction, block axles are inserted in the axle holes in a freely rotatable manner, blocks which are roughly fan-shaped and have bits embedded in the lead end surfaces thereof are provided at lead end parts of the block axles, so that left- and right-side faces of said blocks are in mutual opposition and arc parts of all blocks together form roughly a circle shape; and when said device is rotated in the direction of excavation, said blocks rotate as a result of the resistance to excavation of the bottom part of the excavation hole, one intersection part of the side faces and the arc part of each block protrudes beyond the outer circumferential surface of the device by a predetermined excavation amount, and

Abstract: A percussion boring machine for destructive replacement of buried pipelines, having an opening-out cone at the back of the machine housing and cutters spaced in front of said cone, wherein the cutters form part of a breaking-up head slipped on to the housing and the opening-out cone is likewise slipped on to the housing.

Abstract: A valveless-type down-the-hole hammer drill which has an inner tube extending from the upper end of the hammer body into a central opening in a cutter bit reciprocably mounted in a chuck on the opposite end of the hammer body. High pressure fluid is supplied to the interior of the inner tube and a piston surrounding the inner tube has internal surfaces controlling connection of a port to chambers above and below the piston. The external surface of the piston controls connection of these chambers to an exhaust port. A valve sleeve on the chuck coacts with the piston in this respect.

Abstract: An excavation tool, having a pair of insertion holes placed in the bottom surface of a device, which receives the impact force of a hammer and the rotational force of a hammer cylinder, at positions separated in a radial direction from the center of the device and symmetrical around this center as a center of rotation, also having block axles, one end of each of which is freely rotatably inserted into one of the insertion holes, and having blocks, which have a roughly semicircular shape with a diameter roughly equal to that of the device, into the lead end surfaces of which are set bits, and which have straight edge surfaces which are flat surfaces vertical with respect to the lead end surfaces, provided at the other end of the block axles and with the straight edge surfaces in mutual opposition; in an extended diameter state of the blocks, the blocks are moved in opposite directions along a radius of the device by rotating the blocks around the block axles, and the distance between the centers of the inserti

Abstract: An impact borer is disclosed for embedding lines and for sinking geothermal wells. The impact borer has a shell, which has a longitudinal bore. An anvil closes one end of the bore. A ram is reciprocally slideable within the bore, against and away from the anvil. The ram divides the bore into front, rear, and ram chambers. A director is joined to the shell. The director is monolithic. The director isolates the front and rear chambers in alternation upon reciprocation of the ram. The director defines an inlet passage communicating with the ram chamber and an outlet passage communicating with the rear chamber.

Abstract: In a water driven down-the-hole rock drill, the rearward end of an associated hammer is provided with a drive piston reciprocable in a cylinder located adjacent the rear of the drill. The front end of the hammer is guided for reciprocation in a bearing located adjacent an anvil of a drill bit. Between the cylinder and the bearing the hammer is elongated and enlarged diametrically relative to the piston. The enlarged hammer portion reciprocates freely in a chamber formed by an outer casing of the drill. Drive water is expelled from the cylinder and flushes the hole drilled by the bit. An open ended tubular valve reciprocates to control a duct connecting the interior of the valve to coaxial through-flushing channels in the hammer and the drill bit.

Abstract: In a process for laying underground service lines without excavation by means of a ram boring machine, old pipe lines already buried underground are replaced by new service lines without having to tear up the ground or destroy the old pipe line. To enable the new line to be laid accurately in position and to be accurately targeted the ram boring machine is provided with a guiding bore passing axially through the casing and is guided on the old line.

Abstract: In a device for controlling a pneumatic pile-driving or ram drilling apparatus having an internal, reciprocating ram, the control is effected in a forward stroke phase, a reverse stroke phase, and a subsidiary phase for the supply of air via a control device to a ram. The subsidiary control phase is a delay phase, in which subsidiary compressed air is fed to the front of the ram via time-delay means to take effect with an interval after that flow begins whereby to be substantially effective only in extending the reverse stroke of the ram. An apparatus is provided having a housing, in which the ram is reciprocated and compressed air admission is controlled by the control device which projects into the rear face of the ram and cooperates with the control ports in the ram to control the forward and reverse stroke movements of the ram. At least one supplementary control port, provides a time-delay device with which subsidiary compressed air is additionally fed on to the front of the ram.

Abstract: A hydro-mechanical device for underground drilling for use with a drilling rig comprises a container having a combustion chamber, an ignition system, inlets for introducing a fuel, an oxidizer, a liquid into the combustion chamber, a nozzle for discharging combustion products, a piston slidably mounted in the container and a reamer connected to the piston. The ignition system provides electro-discharges in the fuel, oxidizer, liquid mixture. Each electro-discharge has an explosive nature and produces combustion products having a high pressure. Combustion products are ejected through the circular nozzle surrounding the container to provide a thermal drilling action. The movable piston is pushed downwardly by the products of electro-discharge and causes the reamer to penetrate rocks or a frozen ground to provide a percussion drilling action. By the use of combined effect of thermo-percussion drilling, holes of significant depth can be drilled and rocks or frozen ground of high hardness can be pierced.

Abstract: A fluid actuated percussion rock drill comprising a hollow wear sleeve and a piston slidingly disposed within the wear sleeve. Drive and return pressure surfaces bias the piston between drive and return positions, respectively. A high pressure port is included. A return chamber is exposed to the return pressure surface. A drive chamber is exposed to the drive pressure surface. A pressure sensitive valve is movable between an open and a closed position. When the valve is in the open position, the high pressure port is connected to the drive chamber. The valve includes a first valve pressure surface for exposure to the drive chamber and a second pressure surface for exposure to the high pressure port. A third valve pressure surface is exposed to an outlet pressure port. The volume of fluid travels between the high pressure port and the drive chamber when the valve is in an open position can be limited as desired for different drill applications.

Abstract: A downhole hammer having a fluid inlet controlled by a check valve. The valve assembly is used to remove subsidence from a bore hole to prevent problems caused by bore hole collapse. The valve assembly contains a housing and fluid inlet and outlet. A valve is positioned in the housing between the fluid inlet and outlet. A bypass passageway is also provided in the housing between the fluid inlet and the bore hole exterior.

Abstract: A ram boring machine having a striking piston that is axially displaceable in a housing, of which the forward and backward movement is controlled by a control sleeve connected to a supply hose and which engages in a cylinder chamber of the striking piston, and by one or more corresponding control openings in the striking piston, wherein the control sleeve is loaded both axially and torsionally, has axial and rotational stops and is rotatable and axially displaceable in a guide sleeve arranged at the rear end of the housing.

Abstract: A self-propelled, pneumopercussive, cyclic action, ground penetrating machine (200) has decreased energy consumption and increased average working velocity compared to conventional machines. This is obtained in part by a valve-operated air-distribution mechanism (203) having separated forward and reverse compressed air supply lines (35, 37), which mechanism (203) does not limit the length of the forward and backward strokes of the striker (202). This mechanism allows the backward stroke chamber (75) to be connected with the atmosphere during the entire forward stroke of the striker (202). This eliminates generation of an air buffer in the backward stroke chamber (75) and, consequently, the striker (202) does not lose part of its kinetic energy before impact.

Abstract: In a water driven down-the-hole rock drill, the rearward end of an associated hammer is provided with a drive piston reciprocable in a cylinder located adjacent the rear of the drill. The front end of the hammer is guided for reciprocation in a bearing located adjacent an anvil of a drill bit. Between the cylinder and the bearing the hammer is elongated and enlarged diametrically relative to the piston. The enlarged hammer portion reciprocates freely in a chamber formed by an outer casing of the drill. Drive water is expelled from the cylinder and flushes the hole drilled by the bit. An open ended tubular valve reciprocates to control a duct connecting the interior of the valve to coaxial through-flushing channels in the hammer and the drill bit.