Abstract: An oilfield tool can include a composite structure that includes a reactive shape-memory alloy element disposed at least in part in a filler material.

Abstract: Apparatus and methods for decreasing pressure of drilling fluid within a region between an impeller and a housing of a power generation module (PGM). The apparatus comprises a shaft extending from and rotatable relative to the housing; The impeller is coupled with the shaft external to the housing and includes a group of blades that rotate the impeller as the drilling fluid flows past the PGM. The impeller further includes another group of blades that decrease the pressure of the drilling fluid within the region between the impeller and the housing when the impeller is rotating.

Abstract: A debris management assembly including a housing, a mandrel disposed within the housing, a debris sump defined between the mandrel and the housing, and a debris diverter operably connected to the mandrel and positioned to direct debris that encounters the debris diverter into the debris sump.

Abstract: The present disclosure relates generally to the field of variable geometry guide vanes for gas turbine engines. More specifically, the present disclosure relates to a plastic variable inlet guide vane for a gas turbine engine.

Abstract: Multimodal rock disintegration by non-contact thermal effect, spallation, melting, evaporation of a rock through a movable electric arc, arc thermal expansion and subsequent shock pressure wave allows in comparison with currently available and known technologies to drill into the rock by direct action of the electric arc and heat flows generated by the electric arc. The principle of the disintegration is based on the electric arc generation, force action to it and pressing it towards the rock intended to disintegrate, which causes heating of the rock so that a phase change and thermal disintegration of the rock occurs. Subsequently, the crushed rock is transported by a fluid streams, which are involved in stabilizing and guiding of the electric arc, from the area between the rock and the electric arc, which is the area of the rock disintegration.

Abstract: A wellbore apparatus and method comprising a first wellbore tool having a primary flow path and at least one secondary flow path and a second wellbore tool having a primary flow path and secondary flow path. A radial center of the primary flow path in the first wellbore tool is offset from a radial center of the primary flow path in the second wellbore tool which comprises a crossover joint connecting the first wellbore tool to the second wellbore tool having a primary flow path fluidly connecting the primary flow path of the first wellbore tool to the primary flow path of the second wellbore tool, and at least one secondary flow path fluidly connecting the at least one secondary flow path of the first wellbore tool to the at least one secondary flow path of the second wellbore tool.

Abstract: A method of controlling fluid flow between two tubulars includes disposing a sealing member in an annular area between two tubulars, wherein the two tubulars partially overlap; moving the sealing member to a lower position where it is not in contact with one of the tubulars, thereby allowing fluid flow through the annular area; and moving the sealing member to an upper position where it is in contact with both of the tubulars, thereby preventing fluid flow through the annular area.

Abstract: A downhole tool for removing debris from a wellbore comprises a mandrel and a shroud disposed around a portion of the mandrel. The mandrel includes at least one mandrel port in fluid communication with a mandrel bore. The shroud includes a cavity and a shroud port. Debris laden fluid is pulled into the shroud cavity by flowing fluid through the mandrel bore, out the mandrel port, into the shroud cavity, and through the shroud port. The debris-laden fluid is pulled into the shroud cavity due to a pressure differential created by the flow of the fluid through the mandrel port and out of the shroud port. As the debris laden fluid flows into the shroud cavity, the debris is captured within the tool.

Abstract: Methods and apparatus are described to drill and complete wellbores. Such wellbores include extended reach horizontal wellbores, for example in shales, deep subsea extended reach wellbores, and multilateral wellbores. Specifically, the invention provides simple threaded subassemblies that are added to existing threaded tubular drilling and completion equipment which are used to dramatically increase the lateral reach using that existing on-site equipment. These subassemblies extract power from downward flowing clean mud, or other fluids, in an annulus to provide additional force or torque on tubular elements within the wellbore, while maintaining circulation, to extend the lateral reach of the drilling equipment and completion equipment. These added elements include combinations of The Leaky Seal™, a Cross-Over, The Force Sub™ and The Torque Sub™. The use of such additional simple elements allow lighter drilling equipment to be used to reach a given lateral distance, therefore reducing drilling costs.

Abstract: A mud motor radial bearing, a combination flow diverter and integral radial mud motor bearing, and a mud motor bearing assembly including the combination. The flow diverter includes a body defining threaded box ends, a concentric longitudinal bore, a generally cylindrical outer surface, and a longitudinal axis. The longitudinal bore fluidly connects the first and second threaded box ends. The first threaded box end connects to a pin of a transmission of a mud motor rotor, and the second threaded box end connects to a pin of a mandrel. A portion of the generally cylindrical outer surface of the body in a region of the second threaded box end has bonded thereto a bearing material. The bearing material includes a plurality of tungsten carbide portions surrounded by a hard metal alloy matrix binder.

Abstract: A drill string tubular component for use in an oil or gas well, in the form of a tubular having a central bore and a mechanism for mobilising drill cuttings comprising at least one radial impeller (30) configured to apply radial thrust cuttings passing it, the radial impeller being located between first and second axial impellers (10, 20) configured to apply axial thrust to the fluids in opposite directions. Typically helical components of the first and second axial impellers extend in respective opposite directions, typically toward the radial impeller. Fluids are thus diverted radially away from the outer surface of the tubular component, and thereby enter a more turbulent region of the annulus, there reducing the tendency of the drill cuttings to settle out of suspension.

Abstract: A drilling sub assembly adapted to be coupled between a drill bit of a drilling rig and a drill pipe, the drilling sub assembling including a turbine unit directly coupled to the drill bit via a mandrel, such that passage of a drilling fluid through the drilling sub assembly rotates the turbine unit which in turn directly rotates the drill bit coupled thereto. The present invention further relates to a baffle for controlling and reducing debris present within a drilling fluid used in combination with the drilling sub assembly.

Abstract: The method of controlling the load on a drill bit drilling a hole by providing differential pressure across a seal area on a drilling assembly to increase the bit load and providing a relief valve from the annular area above the seal to the bore returning fluid to the surface to limit the maximum differential pressure to limit the maximum load allowed.

Abstract: A baffle device for use in a drilling sub assembly, the baffle device including an upper chamber for receiving a drilling fluid, the upper chamber having a window through which the drilling fluid exits the upper chamber, the window being in fluid communication with a fluid channel forming a groove on an outer surface of the baffle, the fluid channel having an exit though which the drilling fluid exits the baffle. In general, the exit of the fluid channel is aligned with a downstream turbine unit, such that the turbine unit is rotated by the drilling fluid exiting the baffle. The present invention further includes various modifications to control the velocity at which the drilling fluid exits the baffle.

Abstract: A device for boring a well is provided, the device being attached to a motor having a power shaft for imparting rotational movement responsive to a fluid flow. The device includes a driver operatively connected to the power shaft, the driver having a tubular body with an internal bore for accommodating fluid flow, a first bit connected to the driver at a first end so that rotational movement of the driver is imparted to the first bit, and an inner bore. A second bit is attached to housing about the first bit. A nozzle communicating the internal portion of the tubular body with an outer portion thereof, the nozzle being oriented to deliver a portion of the fluid flow to the second bit.

Abstract: A fluid channeling device (10) is for a down-hole drill assembly (1) having a central axis (1c) and advanceable into a hole in a downward direction (D) along the axis (1c). The assembly (1) includes a drill member (2) with an inner surface (2a) bounding a central bore (2b) and an outer surface (2c). The channeling system includes at least one passage (12) provided within the drill member (2) so as to extend generally between the drill member inner (2a) and outer surfaces (2c). A generally annular channeling member (14) is disposeable about a portion of the drill member (2) and has at least one inlet port (20), at least one discharge port (16), and a passage (12) extending between the inlet (20) and discharge ports (16). The inlet port (20) is fluidly connectable with the drill member passage (12) to fluidly couple the central bore (2b) with the discharge port (16).

Abstract: A method and apparatus for changing the speed of a drill bit down hole in a fluid-actuated motor, including a positive displacement motor and a hydraulic motor, is disclosed. The apparatus comprises a bypass valve installed in the motor for controlling flow through and around the power section of the motor. When closed, the bypass valve forces all fluid to flow through the power section of the motor, imparting maximum speed to the drill bit. When opened, a portion of the fluid flow is allowed to flow around the power section of the motor, thereby reducing the speed of the drill bit. The bypass valve may be opened or closed mechanically, electrically, hydraulically, pneumatically, or by any other means, including a removable plug.

Abstract: The present invention generally relates to an apparatus and method for use in a wellbore. In one aspect, a downhole tool for use in a wellbore is provided. The downhole tool includes a housing having a shaped inner bore, a first end and a second end. The downhole tool further includes a rotor having a plurality of extendable members, wherein the rotor is disposable in the shaped inner bore to form at least one chamber therebetween. Furthermore, the downhole tool includes a substantially axial fluid pathway through the chamber, wherein the fluid pathway includes at least one inlet proximate the first end and at least one outlet proximate the second end. In another aspect a downhole motor for use in a wellbore is provided. In yet another aspect, a method of rotating a downhole tool is provided.

Abstract: A method and apparatus for controlling fluidic torque in a downhole tool is provided. One or more rotatable components of the downhole tool comprise a deformable material, such as rubber or SMA, selectively deformable in response to the flow of fluid through the downhole tool. The rotatable components may include a rotor and/or a turbine of a generator in the downhole tool. Non-rotatable components, such as the stator of the generator, may also be deformable. The rotor, the stator, and/or turbine may comprise a deformable material capable of selectively deforming in response to the flow of drilling mud through the generator. The desired deformation and/or the desired torque may be controlled by adjusting the parameters of the components.

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: The drilling motor is provided that operates pursuant to the Moineau principle for drilling deep holes or wells in the ground. A helically extending rotor is disposed in a stator having a rigid shell that is provided on the inside with an inwardly helically extending lining of elastomeric material for receiving the rotor. The shell has essentially cylindrical end sections having an inner thread for securement of connection elements of the drilling motor. The portion of the shell disposed between the end sections extends helically in conformity with the lining such that at least the lining has an essentially uniform thickness over the length of this portion, which has an outer diameter that is less than that of the end sections. Between the end sections, the shell has a thickness that is less than that of the end sections.

Abstract: Improvements for a downhole flexible drive system for drilling high angle well holes or curved holes from the vertical to the horizontal with an ultra short radius to drill a horizontal drain hole. The improvements include a flexible shaft that connects the drive train of the system to a swivel joint attached inside the uphole tool joint of the system, that provide the drive train of the system the capability to carry part or all the tension loads on the system. An exhaust collar is provided with deflectors that direct excess drilling fluid up a well hole. A pump section is provided to insure drilling fluid flow over the face of a drill bit and the transport of cuttings. To increase flexibility and limit the length of inflexible sections of the system, a flexible tube to carry drilling fluids connects the bearing pack to the system.

Abstract: A self-advancing drilling system comprising a drilling apparatus, the drilling apparatus, the drilling apparatus having at least one leading fluid cutting nozzle, means on the drilling apparatus to provide forward movement to the drilling apparatus, the drilling system further comprising a drill string formed from recoverable flexible hose.

Abstract: Hydraulic drilling apparatus and method in which a hole is formed with a series of drill heads and strings of successively smaller diameter. After each section of the hole is formed, the drill head is withdrawn back through the string, leaving the string in place in the hole to serve as a casing for the well. The next smaller size drill head and string are then introduced through the strings which have already been placed, and the process is repeated until the hole has reached the desired length. The course of the hole can be changed, e.g. from vertical to horizontal, without interruption of the drilling process by selective application of the drilling fluid to the nozzles in the drill head to steer the advancing string. Multiple laterals are formed by introducing a module having a plurality of extensible drilling tubes with drill heads at the distal ends thereof into the string and applying the pressurized drilling fluid to the module to advance the tubes from the string.

Abstract: A drillstring pressure-modulation valve which is usable in combination with a downhole drilling motor and a drillstring thruster to compensate for changes in pressure drop through the drilling motor which normally occur during drilling. When conditions change during drilling, which in turn changes the pressure drop through the drilling motor, the drillstring pressure-modulation valve compensates for such changes to minimize the effect of such changes on the operation of the thruster and the resulting WOB created by the thruster. The modulation valve has a feature which allows it to find automatically a balanced preload condition for the main needle valve, the primary functional element within the modulation valve, each time the rig pumps are turned off and then turned on. The modulation valve is fully self-contained, and is assembled as part of the bottomhole assembly.

Abstract: An apparatus for creating a pulling force on a bottom hole assembly contained within a bore hole is disclosed. Generally, the apparatus comprises a housing, a piston having a first section and a second section, and a venturi member, operatively associated with the piston, adapted for creating a zone of low pressure. In one embodiment, the housing is attached to a work string and the piston is attached to a bottom hole assembly. The first section of the piston and the housing forms a first chamber. The second section of the piston and the housing forms a second chamber. The venturi member contains a first passageway for communicating the zone of low pressure created by the venturi member with the first chamber; and a second passageway for communicating the inner diameter of the venturi means with the second chamber.

Abstract: A device for use within the backhead of a down hole percussive drill, for removing debris from a drillhole, includes a flow control member in the drill backhead for inducing cyclonic flow of percussive fluid, to concentrate the heavier water and other matter away from the lighter percussive gases, a separator in the backhead that separates the water and other matter, passageways in the backhead for ejecting the separated water and other matter, a sealing member for sealing the backhead passageways against back flow of debris from the drillhole annulus, and an indexing member for positioning the separator so as to permit a pre-selection of flow amounts of removed water and other matter.

Abstract: A drilling column has a percussive drilling head attached to a lower end thereof. The drilling column includes a skirt extending downwardly from a lower end thereof in surrounding relationship to the drilling head. The skirt is disposed in eccentric relationship to the drilling head, so that an enlarged space is formed at one side of the drilling head. An air duct arrangement extends through the drilling column for supplying compressed air to the drilling head. That compressed air exits the drilling head through a front face thereof and then flows upwardly through the enlarged space in the skirt and then travels through a discharge channel arrangement formed in the drilling column. In that way, cuttings entrained in the compressed air are removed upwardly from the drill hole. The drilling column is sealed-off with respect to the upper open end of the drill hole by a chuck pipe, enabling compressed air or liquid to be introduced from above ground into a gap surrounding the drilling column.

Abstract: A method and apparatus for enlarging an inverted arcuate underground path between two surface locations is disclosed, where the cuttings from the enlarging are removed. After the drilling of a pilot borehole, and possibly after some reaming operations, a reamer and hole cleaner are pulled through the path, with the reamer rotating as the drill string in the path rotates. The rotation of the drill string also powers a positive displacement pump inside of the hole cleaner, which pumps fluid and entrained cuttings to the surface behind the hole cleaner. Fluid may also be pumped into the reamer from behind the hole cleaner, preferably by way of an inlet pipe which surrounds the outlet from the pump. The hole cleaner includes an agitator, also powered by the rotation of the drill string, which agitates the fluid and cuttings while the drill string is rotated but is not being pulled to the surface.

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: Apparatus for pressurized cleaning of well flow conductors. The apparatus has a non-rotating inner mandrel, an adapter to connect the inner mandrel to a work string, a rotating housing on the exterior of the inner mandrel, and a nozzle body attached to the housing. An alternative embodiment of the invention allows cleaning tools to be attached to a modified nozzle body and rotated therewith. Fluid pressure flowing through the inner mandrel will cause the housing to rotate relative to the inner mandrel. Rotation is used to direct fluid jets in the nozzle body towards different portions of the interior of the flow conductor. Rotation of a cleaning tool can also be used for combined mechanical and hydraulic drilling to remove deposits from within a well flow conductor.

Abstract: To divert sufficient fluid flow through an unsealed bearing section of a downhole drilling motor, a flow control apparatus is provided for insertion between the power section of the motor and the bottom of a drill bit which is to be turned by the motor. The flow control apparatus includes a variable flow channel having a selectable effective cross-sectional area preferably embodied by a valve. A selected effective cross-sectional area is chosen by a control mechanism, such as a snap ring or a spring used to control the position of a valve member of the valve in response to different flow rates of fluid pumped through the valve depending upon whether the drill bit is on-bottom or off-bottom. In one embodiment the apparatus is incorporated within the interior of a drill bit which has angled flow channels to direct flushing fluid flow to side wall locations where reaming occurs. Flow through these outlets is controlled by positioning of the valve member.

Abstract: A new and improved air motor operated rotary earth drilling tool for use with a source of high pressure, high volume compressed air has a circulation control housing, a motor housing, a reduction gear housing, and a bearing housing connected longitudinally in series. The circulation control housing is connected to high pressure, high volume, compressed air and has an outlet opening into the motor housing, and an exhaust opening for discharge of compressed air for flushing cuttings and debris from a bore hole which is controlled by longitudinal movement of an inlet tube. The motor housing has a motor chamber and a sliding vane rotor with a rotary shaft extending into the reduction gear housing. A planetary reduction gear receives the rotor shaft and has a low speed, high torque output shaft extending into the bearing housing. A passageway conducts compressed air around the planetary reduction gear for cooling.

Abstract: A drill string has a bulge equipped with a system of n injection ducts connecting the interior of the string surrounding annular space and opening upwardly into the space to divert a part of the drilling fluid supplied to the bit. This arrangement makes it possible to produce below the bulge a pressure decrease H markedly greater than 10 meters of water by setting the flow of drilling fluid in the system of injection ducts at a value, expressed in m.sup.3 /s, equal to approximately: .sqroot.10H.times.S.times.s33 n, S and s being the cross-sections, expressed in m.sup.2, respectively, of a part of the portion of the annular space included between the periphery of the bulge and the drill string and of the group of n injection ducts.

Abstract: A down hole hammer comprising a substantially cylindrical casing having a top sub at one end and a drill bit support at the other; a central passageway extending through the top sub, casing and drill bit support; a central tube coaxial with the casing and extending from the bottom of the top sub to the top of the bit support thereby defining an annular space between its outer surface and the internal face of the casing, its inner bore forming part of the central passageway; an annular piston reciprocatively accommodated within the annular space for movement between an impact position at which said piston abuts the drill bit support, and a raised position at which said piston is spaced from the drill bit support; fluid porting being provieded to said annular space to effect the reciprocation of the piston between the raised and impact positions, the exhaust from the annular space during reciprocation of the piston being exhausted into the central passageway; a fluid by-pass extending between the top sub and th

Abstract: A drill string is made flexible near the lower marginal end thereof, and a pneumatic turbine motor is located at the lower terminal end thereof. The pneumatic turbine is connected to a planetary gear reduction system for rotating a drill bit. The diameter and the length of the pneumatic turbine motor, gear reduction system, and bit is of a size which enables the entire assembly to negotiate a sharp bend in the borehole, so that the borehole can be formed to extend downwardly along a relatively straight vertical line towards a payzone, where the borehole then sharply bends laterally towards the payzone, and then continues in another relatively straight line horizontally through the payzone. The pneumatic turbine motor includes reaction ports arranged to force the drill bit against the formation being penetrated, and to counteract the bit torque.

Abstract: In a borehole forming operation, the flow of gas through a downhole pneumatic motor is regulated to eliminate horsepower variations due to variations in bottom hole pressure. The pneumatic motor is connected to the lower end of a tubing string and an orifice is placed within the entrance and exit gas passageways leading to and from the pneumatic motor. The uphole source (i.e., compressors) of gas pressure and gas flow rate is maintained as a constant value which assures that sonic flow conditions exist at the lower orifice. The employment of gauged orifices placed within the inlet and exit passageways of the gas motor assures that sonic flow conditions exist at the lower orifice and as the bottom hole pressure varies, there is no resultant change in the motor output horsepower since constant flow rate and pressure drop ratio through the motor is maintained. This is the case so long as the bottom hole pressure does not increase to the critical ratio.

Abstract: Drilling means of the type having a pilot bit, a reamer and a guidemember mounted in the bottom end of the casing tube, and which transmits impacts to the casing. The guide member is snugly enclosed in the thickened mouth portion of the casing tube and has a plurality of channels which are segments of a spiral through which the drilling debris is discharged upwardly to the casing tube.

Abstract: Apparatus by which a vertical borehole is curved to a new angle and extended through a production reservoir. A vertical borehole of a suitable diameter is extended downhole to the proximate depth of the production reservoir. A Zublin drill guide apparatus is employed to drill a curved section of the hole, thereby turning the borehole to a desired angle so that the lower marginal end of the borehole is directed laterally away from the vertical part of the borehole. A drill pipe string is positioned within the vertical part of the borehole. A flexible pipe is fitted to the downhole end of the drill pipe string, and a Zublin straight drill guide assembly is fitted to the end of the flexible pipe. A motor, such as an expansible gas turbine motor, for example, is connected to the end of the straight drill guide assembly. A suitable drill bit is connected to be rotated by the turbine motor.

Abstract: Drilling means of the type having a pilot bit, a reamer and a guidemember mounted in the bottom end of the casing tube, and which transmits impacts to the casing. The guide member is snugly enclosed in the thickened mouth portion of the casing tube and has a plurality of channels which are segments of a spiral through which the drilling debris is discharged upwardly to the casing tube.

Abstract: A skirted crossover sub for joining an air hammer to a string of dual concentric drill pipe is characterized by passageways for directing air from the pipe string annulus to operate the hammer and for directing exhaust air and cuttings from the hammer bit to the inner pipe of the string. A tubular skirt at the downhole end of the sub surrounds the hammer and channels the flow of exhaust air therebetween. A packer and uphole reamer may be included, as well as valves for air lift and for providing proper air flow direction in the borehole annulus.

Abstract: A pneumatically operated impact drilling tool for earth drilling, includes a reciprocating hammer, an anvil positioned under the hammer and a feeder tube extending through the hammer. The drilling tool is connected to a string of drilling pipe and high pressure compressed air or other pneumatic fluid is introduced to operate the tool. The feeder tube directs the flow of fluid through ports in the hammer to alternate pressure on opposite sides of the hammer to move the same upward and downward relative to the anvil. An elastomeric check valve is positioned inside the upper end of the feeder tube. The air inlet end of the tube is also provided with air jet passages extending upward and outwardly and having check valves operated in the outflow direction. A flow controlling washer may also be provided at the inlet to the check valve in the feeder tube.

Abstract: A mining system for extraction of coal or the like from narrow seams has a conduit system for pneumatic conveyance of mined material. A leading section of apparatus comprises a cutter head assembly driven by an air motor which exhausts into the conduit system. The leading section includes further an anchoring means which is changeably mounted thereon to permit advance of the leading section and cutter head assembly, and ground contact means for pivoting of the cutter head from side-to-side.

Abstract: The device features its housing carrying the soil sampling ing socket and the striker arranged coaxially to said socket, and adapted to act thereupon and establish some chambers in said housing, which are alternatively communicated, through the inlet fitting and the piping connected thereto, with a source of compressed air for the striker to perform forward and return strokes. The piping portion immersed in water is essentially a rigid pipe joined with the inlet fitting by way of an axially spring-loaded sleeve whose one end is rigidly connected to said pipe. Arranged along said pipe is another pipe rigidly coupled thereto and serving for used-up gas to discharge from said chambers to the water surface.Such a device is applicable for soil sampling at depths amounting to several scores of meters.

Abstract: An airhammer and core bit apparatus including a housing and a hammer piston reciprocable in the housing for delivering repeated impact blows to an anvil secured to or forming part of a core bit which produces a core in a bore hole being drilled. A central core receiving tube extends through the housing and hammer piston, through which the core formed by the bit is conducted upwardly and through the hammer piston to the top of the bore hole, part of the compressed air supplied to the airhammer being diverted to the central tube for elevating the core therewithin toward the top of the bore hole.