Abstract: The invention relates to a drive system, in particular a downhole drilling assembly (10). In the preferred embodiment, a bearing mechanism (14,24) of the assembly (10) is isolated from a gear mechanism (20) of the assembly (10), to prevent failure of the bearing mechanism (14, 24) due to vibration and heat generated by the gear mechanism (20) in use. A lower bearing unit (24) of the bearing mechanism (24) is coupled to the gear mechanism (20) by a shock eliminating coupling assembly (22), which prevents the transmission of shock loads to the gear mechanism (20). Also, the gear mechanism (20) is coupled through a shock eliminating coupling assembly (18) to a turbine (16) and thus to an upper bearing unit (14). Sealing assemblies (60, 116) are provided for the gear mechanism (20) and the upper bearing unit (14) to prevent drilling fluid ingress and consequent damage. The assembly (10) may also carry a torsionally flexible drive shaft (46).

Abstract: In one aspect, a downhole assembly has a downhole tool string component with a bore adapted to accommodate drilling mud. A fluid barrier is disposed within the bore and has a cylindrical portion substantially aligned with the bore. A drive shaft is sealed within and substantially coaxial with the cylindrical portion and has a first magnet disposed on its outer surface. A turbine assembly is disposed around the cylindrical portion of the fluid barrier and has an inner diameter and outer surface. The outer surface of the turbine assembly has a plurality of turbine blades. The inner diameter of the turbine assembly has a second magnet disposed within a region defined by the turbine blades and is in magnetic communication with the first magnet of the drive shaft, wherein when the drilling mud engages the turbine blades the first and second magnets rotate the drive shaft with the turbine assembly.

Abstract: In one aspect of the present invention a tool string comprises a jack element substantially coaxial with an axis of rotation. The jack element is housed within a bore of the tool string and has a distal end extending beyond a working face of the tool string. A rotary valve is disposed within the bore of the tool string. The rotary valve has a first disc attached to a driving mechanism and a second disc axially aligned with and contacting the first disc along a flat surface. As the discs rotate relative to one another at least one port formed in the first disc aligns with another port in the second disc. Fluid passed through the ports is adapted to displace an element in mechanical communication with the jack element.

Abstract: The invention relates to a drive system, in particular a downhole drilling assembly (10). In the preferred embodiment, a bearing mechanism (14, 24) of the assembly (10) is isolated from a gear mechanism (20) of the assembly (10), to prevent failure of the bearing mechanism (14, 24) due to vibration and heat generated by the gear mechanism (20) in use. A lower bearing unit (24) of the bearing mechanism (24) is coupled to the gear mechanism (20) by a shock eliminating coupling assembly (22), which prevents the transmission of shock loads to the gear mechanism (20). Also, the gear mechanism (20) is coupled through a shock eliminating coupling assembly (18) to a turbine (16) and thus to an upper bearing unit (14). Sealing assemblies (60, 116) are provided for the gear mechanism (20) and the upper bearing unit (14) to prevent drilling fluid ingress and consequent damage. The assembly (10) may also carry a torsionally flexible drive shaft (46).

Abstract: Apparatuses and methods for generating fluid pressure pulses are disclosed. An example apparatus may include a chamber that can collect fluid and an upstream ported disc coupled to a downstream end of the chamber. The upstream ported disc may rotate about a central axis. The upstream ported disc includes an upstream eccentric port that rotates about the central axis as the upstream ported disc rotates. The example apparatus may include a downstream ported disc coupled to a downstream end of the upstream ported disc such that the downstream ported disc remains substantially rotationally fixed relative to the upstream ported disc. The downstream ported disc includes a downstream eccentric port that may align with the upstream eccentric port to form a passageway for fluid to exit from the chamber to outside of the apparatus, at some time in a rotation cycle of the upstream ported disc.

Abstract: A hydrostatic mechanical seal assembly includes a locally deployed pump for pressurizing a lubricant fluid between the opposing faces of a mating ring and a sealing ring. In one exemplary embodiment, such pressurization may be achieved via a device that converts the rotational motion of a drive shaft into fluid pressure. The locally deployed pump is intended to advantageously provide a stable positive pressure on the sealing interface between the mating and sealing rings, which may provide improved sealing characteristics, especially in demanding downhole environments.

Abstract: A downhole motor arrangement for a directional drilling comprises a first motor component (22), a second motor component (24) encircling at least part of the first motor component (22), and a third motor component (26) encircling at least part of the second motor component (24), the first and second motor components (22, 24) having surfaces associated therewith adapted to define isolated cavities, the application of fluid under pressure thereto causing relative rotation between the first and second motor components (22, 24), the second and third motor components (24, 26) having surfaces associated therewith adapted to define isolated cavities, the application of fluid under pressure thereto causing relative rotation between the second and third motor components (24, 26).

Abstract: A general housing encloses a drilling motor that can be disabled to permit optimum rotary drilling practice. A mode selector responds to manipulation of the drilling fluid flow rate and permits activation of the drilling motor to drive a drill bit. The general housing is a two part arrangement that is connected by a deflection arrangement that is activated by start-up of the motor. A one-way clutch allows the lower housing to drive the drill bit when the motor is disabled and the clutch, with drill bit rotation resistance, changes the deflection arrangement for straight rotary drilling when the drill string is rotated.

Abstract: An active differential pressure device (APD device) in fluid communication with a returning fluid creates a differential pressure across the device, which controls pressure below the APD Device. In embodiments, a control unit controls the APD Device to provide a selected pressure differential at a wellbore bottom, adjacent a casing shoe, in an intermediate wellbore location, or in a casing. In one arrangement, the control system is pre-set at the surface such that the APD Device provides a substantially constant pressure differential. In other arrangements, the control system adjusts an operating parameter of the APD Device to provide a desired pressure differential in response to one or more measured parameters. Devices such as an adjustable bypass can be used to control the APD Device. In other embodiments, one or more flow control devices coupled to the return fluid reduce the effective pressure differential provided by the APD Device.

Abstract: A hydrostatic mechanical seal assembly includes a locally deployed pump for pressurizing a lubricant fluid between the opposing faces of a mating ring and a sealing ring. In one exemplary embodiment, such pressurization may be achieved via a device that converts the rotational motion of a drive shaft into fluid pressure. The locally deployed pump is intended to advantageously provide a stable positive pressure on the sealing interface between the mating and sealing rings, which may provide improved sealing characteristics, especially in demanding downhole environments.

Abstract: A technique that is usable with a well includes running a motor into the well and actuating the motor to turn a drill bit. The motor is used to pump well fluid from the well.

Abstract: A downhole drilling motor bearing assembly includes a tubular mandrel adapted to connect to a rotational power output of downhole motor. The bearing assembly includes a mandrel having: an upper end proximal to the downhole motor, a lower end with a pin connection distal from the motor, and a longitudinal passage through the mandrel from the upper end to the lower end. The assembly further includes at least one circumferential ring projecting radially outward from an other surface of the tubular mandrel. The ring has and upper shoulder and a lower shoulder and a radial surface. A circumferential upper thrust bushing contacts the upper shoulder of the ring and a circumferential lower thrust bushing contacts the lower shoulder of the ring. An upper thrust bearing contacts the upper thrust bushing and a lower thrust bearing contacts the lower thrust bushing. A tubular bearing housing includes a longitudinal passage from an upper end of the housing to a lower end of the housing.

Abstract: A hydraulic motor for use in subterranean drilling operations in which a drive fluid within a first reservoir is forced through the motor by a high pressure working fluid, such as drilling mud, the drive fluid entering a second reservoir upon exiting the motor. Upon a change in valving, the drive fluid in the second reservoir is forced through the motor by the high pressure working and back into the first reservoir.

Abstract: System for coupling two tubular ends for use in a well bore, the system comprising a first tubular end, a second tubular end for inserting into the first tubular end in axial alignment thereof, thereby forming an annular space between the first tubular end and the second tubular end, and a connecting assembly for axially coupling the first tubular end with the second tubular end whereby the connecting assembly at least partly reaches in the annular space.

Abstract: A thrust bearing assembly in which each thrust pad is individually mounted on a deflection element. An embodiment of the invention comprises a rotating bearing runner having a wear resistant face and a stationary bearing carrier defining a plurality of cavities disposed annularly around the carrier. A deflection element, such as a Belleville washer, is disposed in a cavity of the plurality of cavities and a pad is disposed over the deflection element. The pad is at least partially disposed within the cavity. The wear resistant face of the rotating bearing runner contacts the pad.

Abstract: A tubing string rotator for rotating a tubing string in a well having a downhole pump. The tubing string rotator includes a housing having a first portion and a second portion. At least the second portion of the housing is adapted to be operatively connected to the end of a length of the tubing string such that rotational torque applied to the tubing string through the operation of the pump is transferred to the second portion of the housing. The rotator further includes means to permit the controlled rotation of the second portion, together with the tubing string connected thereto, relative to the first portion of the housing when the ability of the first portion to rotate is retarded or eliminated, and when rotational torque is supplied to the tubing string through the operation of the pump.

Abstract: Apparatus and methods for establishing electrical communication between an instrument subsection disposed below a mud motor and an electronics sonde disposed above the mud motor in a drill string conveyed borehole logging system. Electrical communication is established via at least one conductor disposed within the mud motor and connecting the instrument sub section to a link disposed between the mud motor and the electronics sonde. The link can be embodied as a current coupling link, a magnetic coupling ling, an electromagnetic telemetry ling and a direct electrical contact link. Two way data transfer is established in all link embodiments. Power transfer is also established in all but the electromagnetic telemetry link.

Abstract: A down hole drilling motor includes a stator housing having an exterior surface, an upper end, a lower end, an upper vane mounting region at the upper end and lower vane mounting region at the lower end. An upper mounting sleeve engages the upper vane mounting region, such that rotation during use brings the upper mounting sleeve into contact with an upper contact shoulder. A lower mounting sleeve engages the lower vane mounting region, such that rotation during use brings the lower mounting sleeve into contact with a lower contact shoulder. A plurality of vanes are secured to each of the upper mounting sleeve and the lower mounting sleeve.

Abstract: A reverse-circulation drilling method and system includes a drill bit, a drill string having drill rods, and a rotary table or power swivel for bringing the drill bit into rotation by means of the rods. The system includes a positive-displacement pump made up of a stator and of a rotor, the stator being inserted in the drill rods, and the rotor being assembled to operating rods arranged within the drill rods.

Abstract: A downhole drilling motor comprising a housing and a shaft extending within the housing, wherein the shaft is movable relative to the housing. Further, a conducting path extends within the housing between a first axial position and a second axial position. The conducting path comprises a housing conductor associated with the housing and a shaft conductor associated with the shaft, wherein the shaft conductor is capable of a movement relative to the housing conductor. An assimilating connector is interposed between the housing conductor and the shaft conductor for conductively connecting the housing conductor with the shaft conductor and for assimilating the movement of the shaft conductor relative to the housing conductor. The assimilating connector includes one or more of a rotary movement assimilating connector, a longitudinal movement assimilating connector and a transverse movement assimilating connector.

Abstract: A drilling motor is housed in the upper portion of a housing, with a drive shaft extending through a lower portion of the housing. The two portions are coupled by bearing that has an axis of rotation that is tilted a small amount relative to the axes of both portions. The lower portion is rotationally coupled to the lower housing until a small amount of drilling fluid flow, or a preselected amount of motor torque, forces a clutch to disengage the motor, rotationally, from the lower housing. The lower portion is allowed limited rotation relative to the upper portion. At one rotational limit, the housing is in the straight configuration. At the other limit, the housing is in the deflected configuration. Conversion to the straight configuration is achieved, while drilling fluid flows, when the drill string is rotated, by formation drag, which rotates the lower portion to the straight configuration.

Abstract: The invention comprises a downhole jet motor, and a method of using same, that can be utilized to drill or to clean a well bore or tubing. The jet motor comprises a power shaft partially surrounded by a control sleeve defining a blind annular space, closed at the upper end and open at the lower end to allow fluid discharge. At least one opening is provided in the drive shaft wall extending radially within the annulus region. Drilling or cleaning fluid pressure is directed to the at least one opening in the power shaft. The control sleeve provides a reaction structure in relation to fluid discharged from the at least one opening producing rotation of the drive shaft in relation to the control sleeve.

Abstract: In one aspect of the invention, a method for drilling a bore hole includes the steps of deploying a drill bit attached to a drill string in a well bore, the drill bit having an axial jack element with a distal end protruding beyond a working face of the drill bit; engaging the distal end of the jack element against the formation such that the formation applies a reaction force on the jack element while the drill string rotates; and applying a force on the jack element that opposes the reaction force such that the jack element vibrates and imposes a resonant frequency into the formation.

Abstract: In one aspect of the present invention a tool string comprises a jack element substantially coaxial with an axis of rotation. The jack element is housed within a bore of the tool string and has a distal end extending beyond a working face of the tool string. A rotary valve is disposed within the bore of the tool string. The rotary valve has a first disc attached to a driving mechanism and a second disc axially aligned with and contacting the first disc along a flat surface. As the discs rotate relative to one another at least one port formed in the first disc aligns with another port in the second disc. Fluid passed through the ports is adapted to displace an element in mechanical communication with the jack element.

Abstract: A filter assembly including a primary flow passageway having at least one filter deployed therein and a secondary flow passageway having a bypass filter deployed therein is provided. The filter assembly further includes a bypass valve assembly configured to selectively open and close the secondary flow passageway when a fluid pressure is respectively above and below an adjustable, predetermined threshold value. Exemplary embodiments of this invention may be coupled to a drill string and advantageously utilized to filter drilling fluid downhole. Such embodiments tend to advantageously improve the filtering efficiency and safety of drilling operations.

Abstract: Self-blocking fishing device to be used in petroliferous well drilling tools, wherein said tools are preferably Positive Displacement Downhole Drilling Motors, Drilling mud motors, and the similar. The device includes a substantially cylindrical and hollow rod, and a sliding piece which includes an orifice for said rod to pass through, wherein the rod includes an end screwed portion for connecting the tool, whereas in a distal portion from said screwed end, said rod includes a reducing diameter zone, presenting the sliding piece an internal diameter slightly larger than the outer diameter of said rod, wherein in an lower portion of said sliding piece the inner diameter increases, including said widening at least one liquid flowing opening, being said rod and said sliding piece mutually fixed by a transversal bolt.

Abstract: A lockable motor assembly for use in a well bore comprises a stator, a rotor rotatably mounted within the stator, and a selectively removable flow restriction means. The lockable motor assembly may further, comprise holding means for rotationally fixing the rotor to the stator. The flow restriction means limits the flow rate of fluid downstream of the rotor, thereby substantially balancing hydraulic pressure above and below the stator.

Abstract: The invention relates to gerotor mechanisms for screw downhole motors used for drilling oil and gas wells, to screw pumps for producing oil and pumping fluids and to general purpose screw motors. The profiles of a rotor (3) and stator (1) are outlined in the end cross section thereof in the form of the envelop of the initial contour of a rack-type tool, which is formed by conjugation of circle arcs when said initial contour of the rack-type tool is run without sliding along corresponding tool circles. The arc radii of the circle arcs of the initial contour are calculated according to determined relations. Said invention makes it possible to improve energy characteristics, increase a life service and producibility, to reduce hydromechanical losses and costs.

Abstract: A downhole tractor is provided that includes a motor, at least one rotatable screw powered by the motor, and a chain engageable with the at least one rotatable screw, whereby rotation of the at least one rotatable screw moves the chain.

Abstract: A turbine is disclosed which includes a turbine blade housing having an inner facing portion of a first material having a first coefficient of expansion, and a turbine blade body having an outer facing portion of a second coefficient of expansion greater than said first coefficient. In a preferred embodiment, the blade housing comprises a number of steel shroud rings and the turbine blade body comprises a number of stators and rotors of a thermoplastic material. An interference fit between stator blades and the shroud rings is enhanced in use due to the difference in thermal and/or hydrophilic coefficients of expansion of the first and second materials.

Abstract: Rotary jetting tool including a rotor with axially-opposed pressure-balanced mechanical face seals. Vented upper mechanical face seal enables the rotor to be operated with the relativity low starting torque achievable using reaction forces from offset jets energized with a pressurized fluid. When rotor is displaced axially due to set-down conditions, a pressure chamber exerts a pressure imbalance on the rotor, forcing the rotor to return to a normal operating position. Alternate structure to achieve low starting torque includes a volume disposed adjacent to a lower mechanical face seal, the volume being coupled in fluid communication with the pressurized fluid. Mechanical face seal surfaces are fabricated from ultra-hard materials, such as tungsten carbide, silicon carbide, and diamond. A gage ring designed to ensure the jets remove all of the material from the gage of the protective housing before the tool can advance can be incorporated.

Abstract: A bottom hole assembly is rotatably adapted for drilling directional boreholes into an earthen formation. It has an upper stabilizer mounted to a collar, and a rotary steerable system. The rotary steerable system has an upper section connected to the collar, a steering section, and a drill bit arranged for drilling the borehole attached to the steering section. The steering section is joined at a swivel with the upper section. The steering section is actively tilted about the swivel. A lower stabilizer is mounted upon the steering section such that the swivel is intermediate the drill bit and the lower stabilizer.

Abstract: An underreamer for forming a cavity within a well bore includes a fluid motor having a first body and a second body arranged about a longitudinal axis. The first body is adapted to rotate about the longitudinal axis in relation to the second body when fluid is passed between the first and second bodies. The fluid motor further defines a longitudinal tubing passage adapted to allow passage of the fluid motor over a tubing string. At least one cutting arm is coupled to rotate with the first body, and radially extendable into engagement with an interior of the well bore to form the cavity.

Abstract: According to one embodiment of the invention, a system for directional drilling within a wellbore includes a drill string having an upper portion, a lower portion, a bent motor coupled to the lower portion, and a drill bit coupled to bent motor, and a clutch assembly disposed between the upper and lower portions. The clutch assembly is operable to disengage the upper and lower portions of the drill string and allow the upper portion to rotate while the lower portion does not rotate.

Abstract: Methods and control systems are provided for a wellbore drilling system having an active differential pressure device (APD device) in fluid communication with a returning fluid. The APD Device creates a differential pressure across the device, which reduces the pressure below or downhole of the device. In embodiments, a control unit controls the APD Device to provide a selected pressure differential at a wellbore bottom, adjacent a casing shoe, in an intermediate wellbore location, or in a casing. In one arrangement, the control system is pre-set at the surface such that the APD Device provides a substantially constant pressure differential. In other arrangements, the control system measures one or more parameters (e.g., wellbore pressure, formation parameters, BHA parameters, etc.) and adjusts an operating parameter of the APD Device to provide a desired pressure differential. Devices such as an adjustable bypass can be used to control the APD Device.

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: The present invention provides an apparatus for the communication of power or data signals across the rotating gap of two tubular members, such as the stator and rotor of a mud motor, and between said rotating members of a drill string through inductive couplers located axially along the drill string.

Abstract: A lockable motor assembly for use in a well bore comprises a stator, a rotor rotatably mounted within the stator, and a selectively removable flow restriction means. The lockable motor assembly may further comprise holding means for rotationally fixing the rotor to the stator. The flow restriction means limits the flow rate of fluid downstream of the rotor, thereby substantially balancing hydraulic pressure above and below the stator.

Abstract: A wellbore drilling system has an umbilical that carries a drill bit in a wellbore. Drilling fluid pumped into the umbilical discharges at the drill bit bottom and returns through an annulus between the umbilical and the wellbore carrying entrained drill cuttings. An active differential pressure device (APD device), such as a jet pump, turbine or centrifugal pump, in fluid communication with the returning fluid creates a differential pressure across the device, which alters the pressure below or downhole of the device. The APD device can be driven by a positive displacement motor, a turbine, an electric motor, or a hydraulic motor. A controller controls the operation of the APD device in response to programmed instructions and/or one or more parameters of interest detected by one or more sensors. A preferred system is a closed loop system that maintains the wellbore at under-balance condition, at-balance condition or over-balance condition.

Abstract: A flow control valve is disclosed for controlling the rotation of a hydraulic motor, such as a turbine, a mud motor, for example, having an element that rotates in response to power fluid. The valve disclosed may include a valve housing and a valve piston, each having a port, moveable relative to one another. When the ports at least partially align, bypass flow is generated which acts to decrease the speed of rotation of the element, such as a turbine shaft. An energizer, such as a pump assembly, is further described which is adapted to move the valve housing or the valve piston in response to the speed of rotation, such that bypass flow is a function of the motor speed (i.e. speed of rotation of the element). A bottom hole assembly including a flow control valve and a method of controlling the rotation of a downhole tool are also described.

Abstract: An apparatus and related method are useful for compensating the pressure of drilling fluid in a drill collar disposed in a borehole. The apparatus includes a stator adapted for being secured within the drill collar against rotation relative to the drill collar, and a shaft rotatably carried within the stator so as to define a fluid-conducting annular gap between the shaft and the stator. The shaft has a fluid-conducting channel extending axially therethrough. A rotor is secured about the shaft for rotation therewith. A portion of the rotor is disposed adjacent a portion of the stator so as to define an inlet between the rotor and stator portions through which drilling fluid in the drill collar will be conducted. The rotor portion further cooperates with the stator and the shaft to define a first annular cavity that fluidly communicates with the gap and the inlet. A rotary seal is disposed in the first cavity for isolating the gap from the inlet.

Abstract: A retaining apparatus is provided for preventing the separation and loss of a down-hole drive motor and associated drill bit from the drill string due to gyroscopic precession of the motor housing resulting from counter torque produced by the drill bit. The retaining apparatus includes a collet, an expander with interchangeable nozzles and a fluid bypass flange.

Abstract: An inverted motor with a drilling utensil attached to or integrated as part of an outer motor housing that rotates around a fixed non-rotating shaft or tube. The non-rotating shaft or tube is attached to a fixed base and can extend to the end or past the end of the drilling utensil. A rotary motor is positioned between the outer rotating housing and center fixed shaft and imparts force and motion to the housing and drilling utensil. A channel traverses through the length of the shaft or tube to allow fluids or wires to fully or partially bypass the motor.

Abstract: The present invention is a cylindrical linear fluid motor comprising a plurality of reciprocating rotary piston sleeve intermediate an inner coaxial hollow drive shaft and an outer coaxial cylindrical housing. Rotating disc valves at both ends of the sleeve piston control the sequential flow of high-pressure and low-pressure fluid through ports in both the drive shaft and the housing. High-pressure fluid acts on one end of the sleeve piston causing the piston to travel laterally along the drive shaft, with an inner set of roller balls in linear raceways ensuring no rotation between each piston and the drive shaft. The linear motion simultaneously affects exhausting of low-pressure fluid at the other end of the piston. Outer balls are seated in the housing and a sinusoidal circumferential raceway of each piston, to affect rotation in the piston from the lateral motion.

Abstract: A rotary valve assembly for a rotary steerable tool is disclosed for directing flow of an abrasive laden drilling fluid; the valve assembly has a first sealing surface rotatably engaging a second sealing surface. At least one of the surfaces has at least about 5% of its area comprising interconnecting voids to an average depth of at least 0.02 mm. The interconnected voids allow fluid pressure to equalize between the sealing faces by flowing through the interconnecting voids to the sealing surfaces. Because the fit of the sealing surfaces of the valve is less than perfect, and because the voids on mating surfaces do not necessarily overlap, the 5% of the surface area comprising interconnected voids can easily translate to a 10% or more reduction in sealed area when both sealing surfaces have the interconnecting voids. The additional reduction in surface area subjected to differential pressure has substantially eliminated the hydraulic lock problem previously encountered upon startup.

Abstract: An inverted motor with a drilling utensil attached to or integrated as part of an outer motor housing that rotates around a fixed non-rotating shaft or tube. The non-rotating shaft or tube is attached to a fixed base and can extend to the end or past the end of the drilling utensil. A rotary motor is positioned between the outer rotating housing and center fixed shaft and imparts force and motion to the housing and drilling utensil. A channel traverses through the length of the shaft or tube to allow fluids or wires to fully or partially bypass the motor.

Abstract: The present invention provides a speed governor (5) suitable for use in a fluid driven down-hole tool (3). The speed governor comprises an actuator (7) operatively coupled to a motive fluid flow control valve (6). The actuator is and arranged so as to be activatable, directly or indirectly, in response to the running speed of the tool (3), for opening of the control valve (6) with increasing rotational speed of the motor (3) above a predetermined speed limit thereby to limit the rotational speed of the downhole tool (3).

Abstract: The invention provides apparatus for drilling trenches in the ground, the apparatus comprising a frame and a drilling assembly having a horizontal support plate connected to the bottom end of the frame, said plate supporting drilling tools disposed beneath said plate, said trench being filled with a drilling mud. The periphery of said plate has resilient sealing means for co-operating with the walls of the trench so as to provide at least partial sealing between said plate and the walls of the trench, and means for adjusting drilling mud flow rates from the portion of the trench situated above said plate to the portion of the trench situated beneath said plate, and also in the opposite direction.

Abstract: The present invention is a cylindrical linear fluid motor comprising a plurality of reciprocating rotary piston sleeve intermediate an inner coaxial hollow drive shaft and an outer coaxial cylindrical housing. Rotating disc valves at both ends of the sleeve piston control the sequential flow of high-pressure and low-pressure fluid through ports in both the drive shaft and the housing. High-pressure fluid acts on one end of the sleeve piston causing the piston to travel laterally along the drive shaft, with an inner set of roller balls in linear raceways ensuring no rotation between each piston and the drive shaft. The linear motion simultaneously affects exhausting of low-pressure fluid at the other end of the piston. Outer balls are seated in the housing and a sinusoidal circumferential raceway of each piston, to affect rotation in the piston from the lateral motion.

Abstract: A downhole mud motor (100) is disclosed which has an improved bearing mandrel (107) and a bearing stop (105) to transfer a larger percentage of the weight of a drill string to the bit. Also improved sealing systems (113) (114) (220) (515(706) for the transmission section and bearing section (116) (310) (117) (118) (119) prevent drilling mud from entering critical components. A piston stop is provided to prevent the piston from damaging other parts as the piston moves under pressure. Compensating pressure assembly (204) preferably including a disk (1408) is placed in the lower housing (108) to prevent pressure from building up in the bearing section (308). A combination of grooved ball seats (130) and circumferentially spaced balls (127) are provided in the transmission section (200) (207) to allow for greater flow of lubricant around the ball bearings.