Abstract: In one aspect of the present invention, a drilling assembly has a string of downhole tools connected to a drill bit with a bit body intermediate a shank and a working face. The drill bit is connected to the string of tools at the shank. A continuous fluid passageway is formed within the bit body and the string of tools. A valve mechanism disposed within the fluid passageway is adapted to substantially cyclically build-up and release pressure within the fluid passageway such that a pressure build-up results in radial expansion of at least a portion of the fluid passageway and wherein a pressure release results in a contraction of the portion of the fluid passageway. The expansion and contraction of the portion of the fluid passageway varies a weight loaded to the drill bit.

Abstract: A pressure fluid actuated downhole percussion tool includes a reciprocating piston hammer with differential transverse pressure surfaces cooperable with a cylinder housing, a guide sleeve and a bit carried exhaust tube to form opposed pressure fluid chambers to which pressure fluid may be conducted to deliver repeated impact blows to a bit having circumferentially spaced bosses and replaceable cutting inserts. The bit is drivenly connected to the tool by plural drive pins supported in circumferentially spaced grooves in the bit shank and in a removable sub supported by the tool housing. Improved earth penetration performance is realized utilizing a claw bit with a pressure fluid actuated percussion tool providing rotation as well as selective deliverance of impact blows through the bit.

Abstract: A down-the-hole hammer includes a casing and a piston movable in the casing between a lowermost operating position and an uppermost operating position. A recess is provided between the piston and the casing so that the piston and the casing define an intermediate chamber between a top end of the piston and a bottom end of the piston. A passageway is provided between a source of pressurized fluid and the intermediate chamber such that, at all positions of the piston between the lowermost and the uppermost operating positions, the source of pressurized fluid is in flow communication with the intermediate chamber through the passageway. An opening in the piston at least partially defines the passageway.

Abstract: A bit assembly is for a drill having a casing, a central axis and a hammer movably disposed within the casing. The bit assembly includes a chuck with a tubular body having first and second ends, the first end being connected with the casing such that the second end is spaced axially therefrom, and one or more openings extending generally axially from the second end toward the first end. A bit includes a body with a tubular portion having a cavity and one or more axial lugs, the lug(s) being disposable within the chuck opening(s). A retainer is coupled with the chuck, disposable within the bit cavity and engageable with the bit lug(s) so as to releasably couple the bit with the chuck. The retainer is preferably a deflectable ring sized to receive a portion of the hammer, such that the hammer prevents disengagement of the retainer from the bit.

Abstract: In a reverse circulation down-the-hole hammer assembly a having a axially extending central tube (30) for recovery of drilling debris, the central tube (30) has a downwardly facing abutment (32) and an upwardly facing upper end and is located axially in the hammer assembly by having the part thereof between the downwardly facing abutment and the upper end located between axially spaced complementary abutments, one of which fixed and the other of which is provided by a resiliently longitudinally displaceable member (42) within a casing part providing an upper end of the hammer assembly and which is removably retained in an adjoining part of the hammer assembly. The longitudinally displaceable member engages the upper end of the central tube and thus clamps the central tube in place.

Abstract: A hydraulic jarring tool may be suspended in a well from a wireline, tubular string or drill string, and may be activated to release a tool stuck in the well, or to release the drill string. Each of an upper and lower jarring section include a housing, a piston, a piston biasing member, a fluid metering device and a release mechanism for holding an hammer in a downward position and releasing the hammer to strike an anvil in response to movement of the piston. A timing mechanism results in a timed delay between the impact of one hammer striking the anvil and the other hammer striking the anvil.

Abstract: The invention is a transmission sleeve for the reverse circulation down hole hammer activated by fluid under pressure, the hammer including an outer hammer casing, a drill bit retaining means (17) and a drill bit (10) retaining means (17) and extending forwardly therefrom. The transmission sleeve (25) comprises a transmission sleeve retaining means to retain the transmission sleeve (25) to the hammer, a flange (28) to direct exhaust fluid from the hammer extending from the transmission sleeve retaining means towards the cutting face (14) of the drill bit (10) so that the exhaust fluid is directed towards the cutting face (14) and a chamber (30) that extends circumferentially around the drill bit (10) into which the exhaust fluid flows prior to discharge from the end of the flange (28).

Abstract: A down-the-hole hammer includes a casing and a piston movable in the casing between a lowermost operating position and an uppermost operating position. A recess is provided between the piston and the casing so that the piston and the casing define an intermediate chamber between a top end of the piston and a bottom end of the piston. A passageway is provided between a source of pressurized fluid and the intermediate chamber such that, at all positions of the piston between the lowermost and the uppermost operating positions, the source of pressurized fluid is in flow communication with the intermediate chamber through the passageway. An opening in the piston at least partially defines the passageway.

Abstract: A method and apparatus for boring a hole in the earth including a drill bit assembly including a fluid-powered impact engine contained within a drillpipe sub between an ordinary drillpipe and a modified conventional rotary drill bit. The impact engine is powered by pressurized drilling fluid delivered via the drillpipe which acts on a piston to charge an energy accumulator, preferably in the form of a spring. Periodically, the pressurized drilling fluid in the impact engine is vented, allowing the energy accumulator to rapidly transfer its stored energy to an impact bit which is slidingly housed in a rotary bit to strike and fracture the formation.

Abstract: A hydraulic rotary percussive hammer drill includes a body containing a reciprocating percussion piston sliding under the effect of a main hydraulic supply circuit, this main circuit also being intended to cause the sliding of a roughly annular abutment piston housed in a cavity of the body, and having, on the one hand, a front face in contact with a shank and intended to place this shank a predetermined distance away from the percussion piston and, on the other hand, a rear face facing a rear wall of the cavity, characterized in that an external hydraulic supply circuit is able, when the main circuit is shut down, to introduce fluid under pressure between the rear face of the abutment piston and the rear wall of the cavity so as to maintain a space between these items.

Abstract: The invention provides a down-the-hole drill assembly having exhaust passages from upper and lower chambers past the inner end of a bit and through the body of the bit to exit through the bit face. The construction of the assembly and bit obviates a foot valve tube from the head of the bit and the disadvantages associated with this component.

Abstract: An arrangement by a hydraulic jar device, especially for use in underground wells, where the jar device is installed in a pipe string led down into the well, and designed so that e.g. a stuck object in the well may be loosened or broken up by upward or downward percussions from the jar device. The jar device is actuated by increasing the flow of drill fluid. Alternatively, the device is actuated by compression. A valve (27, 37, 38) closes off the flow of drill fluid, whereby a percussion cycle is initiated. The valve is designed so as also to seal during strong lateral accelerations.

Abstract: A fluid distributor device is for a percussive drill assembly including a generally tubular casing (2) having a longitudinal centerline and a piston (6) disposed within the casing so as to define a reservoir chamber (27) in the casing. The distributor device comprises a generally cylindrical body (12) disposed within the casing and including a central axis, two opposing ends spaced apart along the axis, first and second interior chambers and a port fluidly connecting the two chambers. The body further has a plurality of fluid passages extending between the two ends and fluidly connecting the first chamber with the reservoir chamber and a deflectable retainer portion (16) releasably engaged with the casing so as to retain the body at a desired position with respect to the casing centerline. A valve (7) is disposed within the body and is configured to permit fluid flow through the port and to alternatively prevent fluid flow through the port.

Abstract: The invention concerns a method and a device for directional drilling of a hole, in particular when drilling curved holes for mining, drift mining or similar, whereby a drill support is used in the form of a flexible continuous drill tube with a proximal end and a distal end, that at the end of the drill support distal end is connected a down hole assembly comprising a drill bit for forming a drill string, which is fed into the gradually forming hole. To avoid and minimize the occurrence of “stick slip” during directional drilling, according to the method, the drill support while drilling is taking place is held fixed at its proximal end against rotation outside the borehole and the rotating motion for indexing the drill bit around an axis extending in the direction of drilling is performed in the area between the drill support's distal end and the drill bit while drilling is in progress.

Abstract: Device and method for drilling into geological formations. The device comprises: a rotatable body; drilling cutters arranged on an axial end surface of the rotatable body; a percussion part, which is parallel to the rotating axis reciprocatable arranged on said body; and percussion cutters arranged on an axial end surface of the percussion part. The method comprises the steps of: bringing a percussion part with a percussive movement in contact with the formation in order to crack at least a part of the formation, and scraping the cracked parts of the formation with a drilling part.

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: The invention relates to a method for horizontal ground-boring, in particular for rock-boring, by a rotating and hammering driven ground-boring device, whereby the device is alternately or simultaneously supplied with compressed air and drilling medium and the compressed air and drilling medium are supplied through a channel.

Abstract: A bedrock drilling and excavating apparatus receives power from a rotational power source to drive a drill to strike and shatter bedrock under the gravity of the apparatus and reciprocal vibrations of a pneumatic unit located on the apparatus. The apparatus includes a coupling device to couple with the rotational power source and an air intake vibration structure, a coupling sleeve which has one end coupling with the lower end of a coupling axle and a connector which further couples to the pneumatic unit, and a drill coupling to the pneumatic unit. The pneumatic unit drives the drill to vibrate up and down reciprocally to strike and shatter bedrock. The drill has a drill shell which is alterable according to the diameter of the service shaft without changing the diameter of the pneumatic unit. The drill shell has a plurality of conical drill gimlets mounted thereon in different biased angles to shatter the bedrock and improve drilling and excavating effect.

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: An internal, positive engagement lock that locks a tool, such as a hydraulic drilling jar, in the fully open position when the tool is racked back and when tripping in and out of the hole close to the surface. The lock mechanism is spring biased into a locked position that provides a positive engagement between two axially translatable components, thus preventing any actuation of the tool. As the tool is run in the hole, increasing hydrostatic pressure within the tool will cause the locking mechanism to shift to a disengaged position and the tool will operate normally. The spring-biased locking mechanism will return to the locked position as hydrostatic pressure decreases as the tool is retrieved to the surface.

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: The present invention discloses, in certain aspects, systems and methods for producing cyclical impacts and, in certain aspects for moving a drilling apparatus for drilling a borehole in a formation, the system in certain embodiments including a housing with a longitudinal axis and a movable member movably disposed therein and movable within the housing transversely to the longitudinal axis of the housing and positioned within the housing with a first space on a first side thereof and a second space on a second side thereof, the movable member substantially fluidly isolating the two spaces and movable to compress gas in one of the first space and the second space while decompressing gas in the other space so that a charge of compressed gas exits from the housing to move an impact member; e.g. for impacting a pile to be driven into the earth or for impacting a drill apparatus for drilling a wellbore, the movable member movable continuously to provide a series of impacts.

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: An expandable reamer apparatus and methods for reaming a borehole, wherein a laterally movable blade carried by a tubular body may be selectively positioned at an inward position and an expanded position. The laterally movable blade, held inwardly by blade-biasing elements, may be forced outwardly by drilling fluid selectively allowed to communicate therewith by way of an actuation sleeve disposed within the tubular body. Alternatively, a separation element may transmit force or pressure from the drilling fluid to the movable blade. Further, a chamber in communication with the movable blade may be pressurized by way of a downhole turbine or pump. A ridged seal wiper, compensator, movable bearing pad, fixed bearing pad preceding the movable blade, or an adjustable spacer element to alter expanded blade position may be included within the expandable reamer. In addition, a drilling fluid pressure response indicating an operational characteristic of the expandable reamer may be generated.

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: A percussion apparatus and method of using the percussion apparatus. The apparatus may be used for delivering an impact to a tubular string. The apparatus comprises a cylindrical member having an internal bore containing an anvil and a first guide profile. The apparatus further includes a rotor disposed within the internal bore, and wherein the rotor member comprises a body having an outer circumference with a second guide profile thereon, and wherein the rotor contains a radial hammer face. In a first position, the second external guide profile of the rotor will engage with the first guide profile of the cylindrical member so that the radial hammer face can contact the anvil. In a second position, the second guide profile of the rotor will engage with the first guide profile of the cylindrical member so that the radial hammer face is separated from the anvil shoulder. Multiple rotors and multiple stators may be employed. The rotor may be operatively associated with a stator that directs flow into the rotor.

Abstract: A hydraulic drill string device can be in the form of a percussive hydraulic in-hole drilling machine that has a piston hammer (50) with an axial through hole (51) into which a tube (35) extends. The tube forms a channel for flushing fluid from a spool valve (62) and the tube wall contains channels (40) with ports (41,42) cooperating with the piston hammer for controlling the valve.

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: Method and apparatus for drilling a well bore in a hydrocarbon formation using concentric drill string having an inner pipe and an outer pipe defining an annulus there between. A drilling means such as an air hammer or a rotary drill bit and driving system is provide at the lower end of the concentric drill string and drilling medium is delivered through the annulus or inner pipe for operating the drilling means to form a borehole. Drilling medium, drilling cutting and hydrocarbon are removed from the well bore by extracting the drilling medium, drilling cutting and hydrocarbon through the other of the annulus or inner pipe.

Abstract: A post driving implement for use with a vehicle, such as a tractor or a skid loader, is disclosed. The post driving implement is comprised of a hammer, a hammer channel, and a hammer cylinder. The hammer travels longitudinally within the hammer channel and is lifted by the hammer cylinder mounted to a closed end of the hammer channel. The hammer cylinder and its associated plumbing is of sufficient size to function as a hydraulic reservoir for the post driving implement, thus eliminating the need for a third hydraulic line to the reservoir on the vehicle and to avoiding need for alteration of the vehicle's reservoir. The post driving implement of the present invention may also include a back plate for mounting the implement to a vehicle. Additionally, the post driving implement may include adjustment mechanisms to vary the positional and angular relationship between the vehicle and the implement.

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.

Abstract: A down-the-hole drill hammer comprises a sleeve (46) which defines a cylinder in which a piston is reciprocable. A plurality of axially extending ribs are formed on the outer surface or the sleeve, and conduits are formed in at least one of the fibs for conveying compressed air or another drive fluid to ports in the sleeve, to operate the piston. This arrangement makes it possible to increase the effective diameter of the hammer as a percentage of the bit diameter, which is particularly useful in relatively small drill hammers.

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: Method and apparatus for underground drilling and enlarging of holes, in particular in hard rock, by using a water-driven motor as drive unit.

Abstract: An internal, positive engagement lock that locks a tool, such as a hydraulic drilling jar, in the fully open position when the tool is racked back and when tripping in and out of the hole close to the surface. The lock mechanism is spring biased into a locked position that provides a positive engagement between two axially translatable components, thus preventing any actuation of the tool. As the tool is run in the hole, increasing hydrostatic pressure within the tool will cause the locking mechanism to shift to a disengaged position and the tool will operate normally. The spring-biased locking mechanism will return to the locked position as hydrostatic pressure decreases as the tool is retrieved to the surface.

Abstract: The invention provides a down-the-hole drill assembly having exhaust passages from upper and lower chambers past the inner end of a bit and through the body of the bit to exit through the bit face. The construction of the assembly and bit obviates a foot valve tube from the head of the bit and the disadvantages associated with this component.

Abstract: A hydraulic drill string device can be in the form of a percussive hydraulic in-hole drilling machine that has a piston hammer (50) with an axial through hole (51) into which a tube (35) extends. The tube forms a channel for flushing fluid from a spool valve (62) and the tube wall contains channels (40) with ports (41,42) cooperating with the piston hammer for controlling the valve.

Abstract: A percussion apparatus and method of using the percussion apparatus. The apparatus may be used for delivering an impact to a tubular string. The apparatus comprises a cylindrical member having an internal bore containing an anvil and a first guide profile. The apparatus further includes a rotor disposed within the internal bore, and wherein the rotor member comprises a body having an outer circumference with a second guide profile thereon, and wherein the rotor contains a radial hammer face. In a first position, the second external guide profile of the rotor will engage with the first guide profile of the cylindrical member so that the radial hammer face can contact the anvil. In a second position, the second guide profile of the rotor will engage with the first guide profile of the cylindrical member so that the radial hammer face is separated from the anvil shoulder. Multiple rotors and multiple stators may be employed. The rotor may be operatively associated with a stator that directs flow into the rotor.

Abstract: A downhole tool for generating a longitudinal mechanical load. In one embodiment, a downhole hammer is disclosed which is activated by applying a load on the hammer and supplying pressurizing fluid to the hammer. The hammer includes a shuttle valve and piston that are moveable between first and further position, seal faces of the shuttle valve and piston being released when the valve and the piston are in their respective further positions, to allow fluid flow through the tool. When the seal is releasing, the piston impacts a remainder of the tool to generate mechanical load. The mechanical load is cyclical by repeated movements of the shuttle valve and piston.

Abstract: The invention relates to a method for horizontal drilling with a percussion implement and a percussion head or percussion head element mounted in a movable manner relative to the percussion implement, the percussion impulse being transmitted in at least three steps.

Abstract: The down hole motor is a self-contained radial drive unit that is driven by a linear input, which can be supplied from various sources. As linear motion is applied to the input of the tool, drive pins on a drive shaft follow a helical path, converting the linear motion into radial motion at the attached mandrel end. This may then be utilized in various activities such as drilling, boring and obstruction removal. This tool may also be used in conjunction with jarring mechanisms in order to create an impact drilling device, or a percussion motor.

Abstract: Apparatus for an improved method for drilling earthen boreholes with a fluid powered rotary motor mounted on the downhole end of a non-rotating, fluid conducting drill string has a fluid powered, axially reciprocating hammer coupled to the motor by means of a rotary coupling having freedom for axial movement, so that the hammer will be rotated by the motor and the motor will be axially isolated from the reciprocating hammer as both are powered by fluid conducted from the surface through the drill string.

Abstract: The invention provides a backreaming tool for expanding a pilot bore produced by a drill string, comprising a pneumatic perCussion hammer (1) in combination with a drill string, the drill string being rotatable and reversible through the pilot bore to effect backreaming by the pneumatic perCussion hammer. The pneumatic percussion hammer is longitudinally adjustable relative to the drill string. The arrangement is such that the compressed air supply to the working cylinder of the hammer is cut off when the hammer is longitudinally close to the end of the drill string, then restored as the hammer becomes more distant from the drill string.

Abstract: The invention relates to a method for horizontal ground-boring, in particular for rock-boring, by means of a rotating and hammering driven ground-boring device, whereby the device is alternately or simultaneously supplied with compressed air and drilling medium and the compressed air and drilling medium are supplied through a channel.

Abstract: The invention relates to a method for horizontal ground drilling, in particular for rock drilling, by means of a ground drilling apparatus which can be driven forward in rotation and percussively, the apparatus having compressed air and drilling medium applied to it alternately or simultaneously, and the compressed air and the drilling medium being supplied via one channel.

Abstract: A bi-directional jar with bit turning capability jars down when weight is set down on the tool and pressure is built up on a piston to move the body up while compressing a spring. When spring force opens the valve in the piston, the housing comes down striking an anvil as the flow rushes through the piston before the valve recluses for another cycle. The valve member features a hydraulic brake to slow its movement after the valve is forced open. Clutching action comes from an angled spline acting through a spirally cut cylinder, which reduces in diameter to engage the bit to turn. A single spring acts on a pair of pistons for bi-directional jarring. Modularity allows rapid conversion to uni-directional operation.

Abstract: An arrangement by a hydraulic jar device, especially for use in underground wells, where the jar device is installed in a pipe string led down into the well, and designed so that e.g. a stuck object in the well may be loosened or broken up by upward or downward percussions from the jar device. The jar device is actuated by increasing the flow of drill fluid. Alternatively, the device is actuated by compression. A valve (27, 37, 38) closes off the flow of drill fluid, whereby a percussion cycle is initiated. The valve is designed so as also to seal during strong lateral accelerations.

Abstract: There is provided drilling apparatus (10) comprising a hammer casing (11), a free piston motor piston guide and porting sleeve (12), a drive sub (13), a drill bit (15) splined by shank (16) to the drive sub (13). Below the splined portion (17) the drive sub is relieved at (23) to form an annular air space for motor exhaust air from the splines (16) and (17). The drive sub (13) retains a gauge sleeve (24) via an annular flange (25) between the hammer casing (11) at (26) and a shoulder (27) on the drive sub (13). Below the shoulder (27) the outer diameter of the drive sub (13) is provided with eight grooves that form conduits (30) with the lower portion (31) of the gauge sleeve (24) extending parallel to the drill axis in communication with the space (23) via ports (32). The lower portion (31) extends down the side of the drive sub (13) and terminates with it at (34) adjacent the shoulder (33) at the transition from the bit shank (16) and the bit head (35).

Abstract: A bit retainer for a percussion bit assembly has a bore and upper and lower lips extending into the bore. Multiple slots extend from the lower end of the retainer member to a terminal end disposed intermediate the upper and lower ends, forming multiple cantilever beam segments. The cantilever beam segments are resiliently, radially deflected by the retention shoulder of the percussion bit to mount and retain the bit.

Abstract: A method of freeing stuck objects (16) from a bore (14) comprises running a string (12) into the bore (14), the string (12) including a flow modifier (22), such as a valve, for producing variations in the flow of fluid through the string, and a device (26) for location in the string and adapted to axially extend or contract in response to variations in the flow of fluid through the string. A portion of the string (12) engages the stuck object (16). Fluid is then passed through the string while applying tension to the string, whereby the tension applied to the stuck object varies in response to the operation of the flow modifier and the extending or retracting device.