Abstract: In a flexible tube for fluid transport, a resin layer is on the outer periphery of an interlocked tube for shielding the fluid flowing within the interlocked tube. An internal-pressure-resistant reinforcing layer is on the outer periphery of the resin layer for reinforcing primarily against internal pressure, etc. of the fluid flowing within the interlocked tube. An axial-force reinforcing layer is on the outer periphery of the internal-pressure-resistant reinforcing layer for primarily suppressing the interlocked tube from deforming in the axial direction of the flexible tube. The axial-force reinforcing layer is formed from alternately winding two layers of reinforcing strips with a long pitch. The reinforcing strips are each configured from a metal strip, a resin layer that covers the strip, and the like. The resin layer is resin to which a microparticulate sulfide-trapping material has been added.

Abstract: An operation method of a reinforcing bar binding machine includes an initializing operation. During the initializing operation, a cutter of a wire cutting mechanism shuts off a wire passageway, a wire is fed by a wire feed mechanism while the wire passageway remains shut off, and the wire feed mechanism is stopped when a leading end of the wire butts against the cutter.

Abstract: A fluid dispensing system including a parent dispenser and a child dispenser, wherein the parent dispenser has a parent body with a parent reservoir containing fluid, a first magnetic coupling member, a passage, a parent pump mechanism and a parent actuator. The parent actuator has an outlet, a second magnetic coupling member, and actuator inlet tube. The actuator inlet tube is removably received within the passage. The first and second magnetic coupling members cooperate to removably couple the parent actuator and the parent body. The child dispenser has a child body with a child reservoir, a child pump mechanism, and a child inlet tube. The child inlet tube is removably received within the passage when the child dispenser is coupled to the parent body. When the child dispenser is coupled to the parent body, the parent pump is actuated to transfer fluid from the parent to the child reservoir.

Abstract: An installation for packaging a gaseous NO/N2 mixture into at least one container from a source (1) of gaseous NO and a source (2) of gaseous nitrogen is disclosed. The installation uses at least one filling system (3) comprising one or more filling stations (24) for gas containers (25). A first gas line (11) is fluidically connected to the source (1) of gaseous NO and to the filling system (3), and a second gas line (12) is fluidically connected to the source (2) of gaseous nitrogen and to the filling system (3). The first gas line (11) and the second gas line (12) each has a mass flow meter (4, 5), each mass flow meter (4, 5) being connected (14, 15) to a control device (6) collaborating with each mass flow meter (4, 5).

Abstract: Medical devices and methods for delivering therapeutic fluids transcutaneously to a body of a patient via a fluid delivery device and an adapter is provided. A Luer slip connector is provided at a first connecting end of the adapter. A therapeutic fluid container is connected with the second connecting end such that the container's neck is received in the second connecting end and a hollow penetrating member provided in the adapter punctures the septum of the container to admit the therapeutic fluid into a needle-less syringe from the container. After, fluid emerges from the tip of the penetrating member, the second connecting end of the adapter is attached to the fluid delivery device, thereby filling the reservoir with the fluid and pushing the syringe plunger forward to inject fluid into reservoir.

Abstract: A tire is described that includes a casing defining a cavity and equipped to receive an object, such as an electronic circuit, for example, through use of a two-part attachment, such as a touch-close attachment, of which a first part is fixed to a wall of the casing and a second part can be joined to the first part when placed in contact with the first part to keep the object on the casing in a service position. The first part of the attachment includes connection elements that are an integral part of the wall of the casing of the tire. The connection elements allow these two parts to have freedom to move relative to each other, thereby limiting the transmission of stresses, which affect the wall of the tire, to the object. The connection elements may be loops of flexible thread formed by the extremities of turns of a coiled thread integrated into the wall of the tire during the tire's manufacture.

Abstract: A pneumatic tire exhibiting high traction performance. A center circumferential groove (14) is provided on the equator (CL) of the tread (12), and between shoulder circumferential grooves (18) on both sides of the center circumferential groove (14) are arranged first lateral grooves (20) formed at a smaller angle relative to the axial direction of the tire than the first lateral groove (20). One end of each first lateral groove (20) and one end of each second lateral groove (22) are made to merge at a shoulder circumferential groove (18), and shoulder lateral grooves (23) are arranged on the outer side of each shoulder circumferential groove (18). Each shoulder lateral groove (23) extends from the merging portion toward a tread end (12E) and is formed at a smaller angle relative to the axial direction of the tire than that of the first lateral groove (20). Because the angle of the shoulder lateral grooves (23) relative to the axial direction of the tire is less, traction performance of the tire increases.

Abstract: Embodiments include a retreaded tire having a precured tread band bonded to a prepared bonding surface of a base portion of the tire. The precured tread band may include a tread groove having a bottom and a top, the top of the groove open to a ground contacting front face of the tread band, the precured tread band further comprising a back face, the back face bonded to a prepared bonding surface of a base portion of the tire. A base groove may be formed in the base portion of the tire and open to the prepared bonding surface of the tire, wherein the tread groove bottom is aligned over a length of the base groove. In some embodiments, the tread groove bottom may be open to the base groove over at least 50% or the entire length of the base groove.

Abstract: Heavy goods vehicle tire including beads, sidewalls and a tread. To deflect the flow of water expelled laterally by this tire while running on a wet road, the tire is provided on each of its sidewalls, and near the tread, with a protuberance. One protuberance is positioned on the tire so as to be effective over a first period of use of the tire and the other protuberance is positioned on the tire so as to be effective after the tread has partially worn away, and after the worn tire has been reversed so as to place such other protuberance to the outside of the vehicle.

Abstract: A labeling machine, comprising a conveyor of containers, each to be labeled with a label taken by cutting from a continuous ribbon wound in a reel, and further comprising feeder elements which are adapted to convey with the appropriate timing the ribbon to a device for the intermittent cutting of each individual label, and elements for locking the label during cutting which are inserted between the cutting device and a drum for transferring the cut label to a container provided on the conveyor.

Abstract: There is described a method for applying foil material (200) onto successive sheets (S), especially sheets of securities. In a first step, individual sheets (S) are transported in succession along a sheet transport path. In a second step, at least one continuous band of foil material (200) is applied onto the individual sheets (S) along a direction substantially parallel to a direction of displacement of the individual sheets, thereby forming a continuous flow of sheets linked to one another by the said at least one continuous band of foil material (200). In a third step, the said at least one continuous band of foil material (200) is cut by means of a laser beam such that the continuous flow of sheets is again separated into individual sheets (S) with portions of foil material (200*) remaining on the sheet. The cutting is performed at positions located on the sheets (S) such that said portions of foil material (200*) remaining on the sheets do not extend beyond leading and trailing edges of the sheets (S).

Abstract: The tire run-flat ring removal and installation machine includes three basic embodiments, each having a tire support table (14) and actuators for removing and/or reinstalling the run-flat ring (R) in the tire (T). The actuators may be hydraulically, pneumatically, or electromechanically powered, and save the technician considerable time and effort in the process.

Abstract: To provide a method and a machine for forming flaskless molds with a shortened cycle time even if many cores are placed, to thereby achieve efficient molding.

Abstract: The invention relates to a method of fabricating a micromechanical part made of a single piece material. According to the invention, the method includes the following steps: a) forming a substrate which includes the negative cavity for said micromechanical part to be fabricated; b) forming a sacrificial layer on one portion of the substrate; c) depositing particles on the substrate intended to form a germ ination layer; d) removing the sacrificial layer so as to selectively leave one portion of the substrate free of any particles; e) depositing a layer of material by chemical vapour phase deposition so that the material is exclusively deposited where the particles remain; f) removing the substrate to release the micromechanical part formed in said negative cavity.

Abstract: The present invention relates to heat exchangers, and more particularly to a heat exchange apparatus configured to operate in a free air stream. In an embodiment, a heat exchange apparatus configured to operate in a free air stream includes a heat exchange structure having a shape configured to conform to a body of a vehicle when in a stowed condition; and a deployment mechanism for moving the heat exchange structure to a deployed condition external to the vehicle. The heat exchange structure has a curved surface that is concave into the air stream when the heat exchange structure is in the deployed condition.

Abstract: An integrated circuit dual-fluid heat exchanger has a housing containing first and second immiscible fluids. A heat-introducing base element contacts the first fluid. A heat-receiving surface on the base element is configured for interfacial contact with a heat-radiating surface of an integrated circuit device. A heat-removing condenser element contacts the second fluid, or is separated therefrom by a gap. The first and second fluids are selected to controllably remove heat from the integrated circuit device by forming heated mass units of the first fluid that migrate through the second fluid and come into contact with the condenser element, where they are cooled and allowed to return to the base element. A heat-expulsion portion on the condenser element is configured to dissipate heat removed by the condenser element to an exterior environment outside the heat exchanger.

Abstract: This invention relates to an internal jet impingement type shell and tube heat exchanger in which the jet cooling tubes and the heating tubes in shell and tube heat exchanger are formed either as a staggered tube bundle or as a square tube bundle, and the orifices on each jet cooling tube are provided according to the arrangement of tube bundle. Thus, the heat transfer performance of jet impingement type shell and tube heat exchanger is remarkably enhanced.

Abstract: Position indication in multiplexed downhole well tools. A method of selectively actuating and indicating a position in a well includes selecting at least one well tool from among multiple well tools for actuation by flowing direct current in one direction through a set of conductors in the well, the well tool being deselected for actuation when direct current flows through the set of conductors in an opposite direction; and detecting a varying resistance across the set of conductors as the selected well tool is actuated, the variation in resistance providing an indication of a position of a portion of the selected well tool.

Abstract: A controlled aperture ball drop includes a ball cartridge that is mounted to a frac head or a high pressure fluid conduit. The ball cartridge houses a ball rail having a bottom end that forms an aperture with an inner periphery of the ball cartridge through which frac balls of a frac ball stack supported by the ball rail are sequentially dropped from the frac ball stack as a size of the aperture is increased by an aperture controller operatively connected to the ball rail.

Abstract: A drilling rig for use in drilling wells having a top drive with a slide assembly configured to engage, slide on, and react torque to a modular torque track assembly. The modular torque track assembly connects between the top of a derrick and lower structure of the drilling rig. The modular torque track assembly can have a top track, one or more middle tracks, and a bottom track allowing the modular torque track to be various lengths for various applications. The torque track sections are connectable with unique locking devices which allow a man in a suspended sling to quickly and safely make or break each connection. There are no loose parts in the design to accidentally drop and hurt a person below.

Abstract: A shear coupling assembly utilizes a second coupling member, a first coupling member and a locking member which is inserted into a bore in the first coupling member to connect between the second coupling member and the first coupling member. In embodiments where a pretension is applied to the shear neck, the locking member maintains the pretension in the shear neck. The bore of the first coupling member has a profiled section which corresponds to a profiled section on the second coupling member which when mated together permit torque to be transferred for co-rotating the second coupling member with the first coupling member for use in rotary pump operations. Advantageously, the profiled portions and the shear neck are encased in the bore of the shear coupling assembly and are protected from corrosive wellbore fluids.

Abstract: A system includes a back pressure valve. The back pressure valve includes a body, a plunger disposed internal to the body, and a friction member disposed about the exterior of the body. The friction member is configured to expand radially to contact an internal surface of a bore. A method includes disposing a back pressure valve into a straight bore and expanding a friction member of the back pressure valve radially into contact with an internal surface of the straight bore.

Abstract: A downhole circulating valve includes a generally tubular outer housing having a generally axially extending internal passageway. At least one generally longitudinally extending circulating passageway is formed through at least a portion of the housing. At least one exterior port and at least one interior port are in fluid communication with the circulating passageway. At least one seal plug is disposed within the circulating passageway. The seal plug has a first position relative to the housing wherein the seal plug is remote from the exterior port and the interior port, thereby allowing fluid flow between the exterior port and the interior port through the circulating passageway. The seal plug has a second position relative to the housing wherein the seal plug is between the exterior port and the interior port and wherein the seal plug forms at least one metal-to-metal seal with the circulating passageway, thereby preventing fluid flow between the exterior port and the interior port.

Abstract: A method of monitoring downhole conditions in a borehole includes receiving sensor data through a network of nodes provided at selected positions on a drill string disposed in the borehole. An inference is made about the downhole condition from the sensor data. A determination is made whether the downhole condition matches a target downhole condition within a set tolerance. At least one parameter affecting the downhole condition is selectively adjusted if the downhole condition does not match the target downhole condition within the set tolerance.

Abstract: An apparatus for determining a property of a downhole formation, the apparatus comprising: an array having a plurality of transmitters and receivers capable of propagating electromagnetic waves through the formation; measuring circuitry for measuring an effect of the formation on the propagating waves; control circuitry arranged to vary the propagating waves as a function of at least one of frequency, spacing and polarization; and processing circuitry arranged to combine the effects of the propagating waves that are varied according to frequency, spacing and polarization for determining the property of the downhole formation.

Abstract: A method of servicing a wellbore extending from a surface and penetrating a subterranean formation is provided. The method comprises placing a assembly in the wellbore, wherein the assembly comprises at least a first downhole tool, a signal receiver subassembly, and a conveyance between the first downhole tool and the surface. The method further comprises the signal receiver subassembly receiving a first signal generated by contact between the wellbore and the assembly and initiating a first function of the first downhole tool based on the first signal.

Abstract: Various disclosed cement slurry monitoring methods include monitoring one or more parameter of the cement slurry at various positions along the borehole during the curing process and responsively identifying a span over which the slurry extends and whether there are any gaps or voids in that span. At least some system embodiments include a distributed sensing arrangement to provide parameter measurements as a function of position and time during the curing process. A computer analyzes the measurements to determine the span of the cement slurry and whether any gaps exist. Contemplated measurement parameters include temperature, pressure, strain, acoustic spectrum, acoustic coupling, and chemical concentration. Individually or in combination, these measurements can reveal in real time the state of the cement slurry and can enable remedial actions to be taken during or after the curing process if needed to address deficiencies in the annular seal being provided by the cement.

Abstract: In one embodiment, a sampling while drilling tool includes a drill collar having a first end, a second end, an outer wall extending between the first and second ends, and at least one opening extending through the outer wall to a cavity within the drill collar. The sampling while drilling tool also includes a sample chamber positionable in the cavity through the opening in the outer wall and a passage for conducting a drilling fluid through the drill collar.

Abstract: A method of heterogeneous proppant placement in a subterranean fracture is disclosed. The method comprises injecting well treatment fluid including proppant (16) and proppant-spacing filler material called a channelant (18) through a wellbore (10) into the fracture (20), heterogeneously placing the proppant in the fracture in a plurality of proppant clusters or islands (22) spaced apart by the channelant (24), and removing the channelant filler material (24) to form open channels (26) around the pillars (28) for fluid flow from the formation (14) through the fracture (20) toward the wellbore (10). The proppant and channelant can be segregated within the well treatment fluid, or segregated during placement in the fracture. The channelant can be dissolvable particles, initially acting as a filler material during placement of the proppant in the fracture, and later dissolving to leave the flow channels between the proppant pillars.

Abstract: A well treatment fluid containing borated galactomannan may be used to isolate a productive zone in a well having multiple productive zones. The fluid is particularly useful in treatment of wells containing a mechanical zonal isolation system in the productive zone of interest. The fluid is pumped into the well in a substantially non-hydrated form. The well treatment fluid is therefore highly effective in preferentially sealing or blocking productive zones in the formation since delayed hydration of the fluid may be controlled for up to several hours.

Abstract: A remotely operated lifting top drive cement head is provided having a high tensile strength, as well as the ability to swivel or rotate about a central vertical axis. The cement head permits selective launching of darts, setting plugs, balls or other objects which can be held in place within the cement head without being damaged or washed away by slurry flow, but which can be beneficially launched into said slurry flow at desired point(s) during the cementing process. The internal components of the cement head can be easily accessed using interrupted thread connections that can be quickly and easy connected and disconnected in the field without requiring specialized equipment. The cement head can be rigged up and remotely operated without requiring the lifting of personnel off the rig floor to actuate the tool or observe tool status.

Abstract: Methods and compositions that protect cement compositions from corrosion, particularly from wet carbon dioxide, are provided. A soluble salt additive is provided to react with reaction products generated during the reactions that occur when cement is exposed to wet carbon dioxide. The soluble salt reacts to form an insoluble salt that forms a protective layer on the surface of the cement that protects it from further corrosion from exposure to wet carbon dioxide.

Abstract: A method of servicing a wellbore in contact with a subterranean formation comprising placing a wellbore servicing fluid comprising a polyuronide polymer within the wellbore, contacting the wellbore servicing fluid with a divalent ion source, and allowing the wellbore servicing fluid to form a gel within the wellbore wherein the divalent ion source is located within the wellbore. A method of servicing a wellbore in contact with a subterranean formation comprising (a) placing a wellbore servicing fluid comprising a polyuronide polymer into the wellbore wherein the wellbore servicing fluid contacts a calcium ion source, (b) shutting the wellbore and allowing the servicing fluid to set into place for a period of time, and (c) repeating steps (a) and (b) until the permeability of a structure within the wellbore is reduced by about 50%.

Abstract: The current application discloses methods and systems for generating high pressure dual phase mixture. In some embodiments, the methods and systems involve mounting a dual phase mixture generator on a transportable platform wherein the dual phase mixture generator comprises a mixing chamber connected with at least a first inlet, a second inlet, and a first outlet. A first container and a first pump are also mounted on the transportable platform wherein the first pump is operably connected with the first container. The transportable platform and the mounted equipments are then deployed at a wellsite. A base fluid is pumped into the first inlet under high pressure, and a gas is pumped into the second inlet under high pressure. The base fluid and the gas is combined in the mixing chamber to generate a high pressure dual phase mixture, which is then discharged via the outlet.

Abstract: A method includes performing a chemical process to create a chemical product and an amount of heat, and transferring the heat to a first fluid. The method further includes hydrating a polymer in the first fluid, and adding the chemical product from the chemical process to the first fluid to create a treatment fluid. The method further includes diluting the treatment fluid with respect to at least one constituent of the treatment fluid. The method includes treating a formation of interest in a wellbore with the treatment fluid. The method includes changing a formulation of the treatment fluid during the treating. The method also includes extending the treating beyond a design amount, or ending the treatment before the design amount and preserving some reagents of the chemical process.

Abstract: A wellhead system comprising a seal with a restraining member adapted to cooperate with a housing to restrict axial movement of the seal. The seal is adapted to form a seal between the housing, such as a wellhead, and a tubular member, such as a casing hanger. The seal has a latch ring that is expanded outward as the seal is installed within the wellhead. Axial movement of the seal is restricted by engagement between the expanded latch ring and the inner profile of the housing. The seal and housing may be adapted so that a portion of the seal is received by a recess in the inner profile of the housing.

Abstract: The segmented ball seat valve is an annular communication valve normally installed in a string of pipe that is to be deployed to a depth within a well. The segmented ball seat valve provides communication between the inside of the pipe and the well bore or casing through open ports. The segmented ball seat valve can be closed to shut off communication by dropping/pumping a ball to the segmented ball seat valve and applying pressure to close the valve. The application of pressure causes the ball seat assembly to move downward into an enlarged portion of the bore. The segments of the seat assembly move outward in the enlarged area to permit passage of the ball.

Abstract: A downhole apparatus is described comprising a body and a sealing arrangement located on the body. The body has a longitudinal axis and the sealing arrangement comprises at least one elongated sealing member with an axis of elongation extending around the longitudinal axis. The sealing member comprises a material selected to expand on exposure to at least one predetermined fluid, such as a hydrocarbon or aqueous fluid encountered in a wellbore. A method of forming the apparatus and methods of use are described. Embodiments of the invention relate to wellbore packers.

Abstract: A dry sprinkler assembly includes a housing, a sprinkler head assembly with a sprinkler head and a trigger assembly, and an actuator assembly. The actuator assembly has a sealing subassembly for sealing the inlet port of the housing and is operatively coupled to the trigger assembly such that the sealing subassembly releases the sealing of the inlet port in response to the trigger assembly releasing its closure at the outlet opening. The sealing subassembly moves in a linear path substantially parallel with the central longitudinal axis of the housing when releasing the sealing of the inlet port wherein the flow of fire suppressant through the inlet port and into the fluid flow passage is substantially unimpeded.

Abstract: A method of firestopping a through-penetration is disclosed, which makes use of a fusible inorganic blended-fiber web. The fusible inorganic blended-fiber web can provide a fire-stopped through-penetration without the use of sealants, intumescent materials, and the like. The fusible inorganic blended-fiber web may comprise a blend of at least first, low melting inorganic fibers and second, high melting inorganic fibers. The fusible inorganic blended-fiber web comprises a bulk density of at least about 7 pounds per cubic foot (0.112 grams/cc).

Abstract: An agricultural row unit having a support frame, a structural support housing coupled to the support frame, and a swing arm having a leading end pivotably coupled to the structural support housing. An agricultural tool is coupled to a trailing end of the swing arm, and a hydraulic actuator is mounted to and fully enclosed within the structural support housing. The hydraulic actuator adjustably urges the agricultural tool downwardly toward a soil surface such that vertical pivoting movement is permitted in response to terrain changes in the soil surface.

Abstract: A hydraulic control apparatus for a foldable farm includes first hydraulic control system is used to control weight transfer to ground engaging tools mounted to a stationary and foldable wing frame sections. A second hydraulic system is used to fold and unfold the wing sections. A hydraulic control is provided that interfaces with both hydraulic systems to control sequencing of the functions provided by the first and second hydraulic systems. The first and second hydraulically systems have mechanically controlled valves to control the flow of hydraulic fluid to various lifting, folding, and down pressure cylinders.

Abstract: A method of operating a rotary tool driven by a brushless motor including a DC brushless motor for rotationally driving a rotary bit, a torque setting clutch mechanism, a drive switch for drive-controlling a drive control circuit of the brushless motor, and a control means to rotationally drive the brushless motor by an operation of the drive switch and wherein the method includes a first step for stop-controlling of the drive control circuit, a second step for rotating forward or in reverse the brushless motor through the control and a third step for control-operating a semiconductor of an inverter circuit provided in the drive control circuit to short-circuit the magnetizing windings of the brushless motor, thus braking the rotor of the brushless motor and stopping the brushless motor.

Abstract: A handheld power tool with a shiftable mechanism, which is adjustable between two operating positions, has a coupling spring that is coupled with an adjustable shifting member of the mechanism. The coupling spring is embodied as a metastable spring.

Abstract: A rotary hammer includes a motor, a spindle coupled to the motor for receiving torque from the motor, a piston at least partially received within the spindle for reciprocation therein, a striker received within the spindle for reciprocation in response to reciprocation of the piston, and an anvil received within the spindle and positioned between the striker and a tool bit. The rotary hammer also includes a retainer received within the spindle for selectively securing the striker in an idle position in which it is inhibited from reciprocating within the spindle, and an O-ring positioned between the retainer and the spindle. The O-ring is disposed around an outer peripheral surface of the anvil. The O-ring is compressible in response to the striker assuming the idle position. The compressed O-ring imparts a frictional force on the outer peripheral surface of the anvil to decelerate the anvil.

Abstract: The present invention provides a pile driver capable of improving operability while preventing breakage and the like of a wire rope by relating a press-in winch and an elevation winch to each other. Solenoid valves are arranged respectively to hydraulic circuits of both of a press-in winch and an elevation winch and an electric circuit is provided to operate the solenoid valves in a related manner so that one winch is to be capable of rotating at semi-engaging when the other winch is set to be in a winding state with automatic brake operated.

Abstract: A feeder holding device used with a rock drilling and/or rock bolting rig, in which the rock drilling and/or rock bolting rig has at least one boom with a first end and a second end, the first end is attached to a carrier, and the second end supports a feed beam by the feeder holding device, and in which the feed beam can be adjusted by the feeder holding device in a first drilling position in a first drilling direction and in a second position. The feeder holding device provides linear movement of the feed beam, in a direction different from the drilling direction, from the first drilling position to the second position, such that the feed beam in the second position is pointed in a direction parallel to the first drilling direction. A rock drilling and/or rock bolting rig is also provided.

Abstract: An auxiliary device for an electrical work machine is provided. The auxiliary device can be attached to the electrical work machine, and the electrical work machine can be equipped with a tool in a tool holder. The auxiliary device comprises a housing comprising a handle and an attaching device. The housing can be attached to the electrical work machine with the attaching device. The housing comprises a handling section, which is disposed next to the attaching device, and which comprises an opening, which allows at least the tool holder to be freely accessible from the sides. The handle is permanently connected to the handling section.

Abstract: The removal of material from the path of a high power laser beam during down hole laser operations including drilling of a borehole and removal of displaced laser effected borehole material from the borehole during laser operations. In particular, paths, dynamics and parameters of fluid flows for use in conjunction with a laser bottom hole assembly.

Abstract: A drilling system and method are provided. The drilling system comprising a tool body, a drill bit, a mechanism for applying weight to the drill bit (“WOB”), and a control system for controlling the rate of rotation of the drill bit (“RPM”) and the weight applied to the bit during drilling. The control system is configurable to a first mode in which RPM and WOB are controlled to maintain power on the drill bit at a predetermined maximum, and a second mode in which RPM and WOB are controlled to maintain a predetermined depth of cut (“DOC”). In use, the control system is adapted to switch between the first and second modes depending on drilling conditions.