Abstract: A coupling for connecting downhole tubulars includes a tubular body, and at least one thread of a male screw thread formed on an outer surface of the body, and a female screw thread formed in an inner surface of the body. The at least one thread has a thread-form including a crest, a root, and a pair of flanks. The crest and the root are each cambered about a respective first and second camber radius. Each camber radius is greater than an outer diameter of the coupling.

Abstract: A coupling for connecting downhole tubulars includes a tubular body, and at least one thread of a male screw thread formed on an outer surface of the body, and a female screw thread formed in an inner surface of the body. The at least one thread has a thread-form including a crest, a root, and a pair of flanks. The crest and the root are each cambered about a respective first and second camber radius. Each camber radius is greater than an outer diameter of the coupling.

Abstract: A percussive rock drill bit has a head and a shank in which a plurality of flushing grooves extend radially outward and axially rearward from a front face. The flushing grooves are configured to optimize the axially rearward flow of rock particles and fines entrained in the flushing fluid. In particular, each groove is generally convex relative to a longitudinal axis of the drill bit and is declined continuously relative to the axis from a first groove end to a second groove end.

Abstract: A percussive rock drill bit includes a head having an annular gauge collar and a central island. An annular cutting channel is defined between the collar and the island such that specifically positioned cutting buttons are effective to create an annular ridge in the cut rock face having a reduced rock breaking resistance.

Abstract: A drill bit for rock drilling tools includes a drill bit head having a front surface including a face surface defining a forward-most end of the drill bit head. The face surface has an outer edge, a gauge surrounding the face surface, the gauge having an inner edge, and a transition region that extends in a direction of a longitudinal axis of the drill bit between the outer edge of the face surface and the inner edge of the gauge. An entirety of the face surface from which the cutting surfaces extend is non-flat so that a center of the face surface is axially forward of the outer edge of the face surface. The gauge includes a first gauge surface defining a first angle with the longitudinal axis over a first portion of a circumference of the gauge and a second gauge surface defining a second angle with the longitudinal axis over a second portion of the circumference of the gauge.

Abstract: A percussive rock drill bit includes a head having an annular gauge collar and a central island. An annular cutting channel is defined between the collar and the island such that specifically positioned cutting buttons are effective to create an annular ridge in the cut rock face having a reduced rock breaking resistance to increase the rate of drilling and/or decrease the required power consumption.

Abstract: A percussion drilling apparatus is arranged to affect at least one characteristic of a shock wave produced in a drill string. The apparatus includes an elongate energy transmission adaptor having a shock wave modification sleeve configured with a free end and an attachment end projecting radially from an outer surface of the adaptor.

Abstract: A percussive rock drill bit has a head and a shank in which a plurality of flushing grooves extend radially outward and axially rearward from a front face. The flushing grooves are configured to optimize the axially rearward flow of rock particles and fines entrained in the flushing fluid. In particular, each groove is generally convex relative to a longitudinal axis of the drill bit and is declined continuously relative to the axis from a first groove end to a second groove end.

Abstract: A percussion drilling apparatus is arranged to affect at least one characteristic of a shock wave produced in a drill string. The apparatus includes an elongate energy transmission adaptor having a shock wave modification sleeve configured with a free end and an attachment end projecting radially from an outer surface of the adaptor.

Abstract: A drill bit for rock drilling tools includes a drill bit head having a front surface including a face surface defining a forward-most end of the drill bit head. The face surface has an outer edge, a gauge surrounding the face surface, the gauge having an inner edge, and a transition region that extends in a direction of a longitudinal axis of the drill bit between the outer edge of the face surface and the inner edge of the gauge. An entirety of the face surface from which the cutting surfaces extend is non-flat so that a center of the face surface is axially forward of the outer edge of the face surface. The gauge includes a first gauge surface defining a first angle with the longitudinal axis over a first portion of a circumference of the gauge and a second gauge surface defining a second angle with the longitudinal axis over a second portion of the circumference of the gauge.

Abstract: The present invention relates to a combustion engine, comprising an intake system having a throttle valve controlling an air flow to the combustion engine, a brake booster being in fluid communication with the intake system, downstream the throttle valve, via an evacuation duct for evacuation of air from the brake booster to the intake system, a crankcase being in fluid communication with the intake system, downstream the throttle valve, via a low load duct for conducting crankcase gases to the intake system, a venturi tube forming part of the low load duct, wherein the venturi tube comprises a narrow venturi tube portion forming a flow resistance within the low load duct through which the crankcase gases have to pass, wherein the evacuation duct is also fluidly connected to the venturi tube portion, via a connection duct, for further evacuation of air from the brake booster to the intake system.

Abstract: The present invention relates to a combustion engine, comprising an intake system having a throttle valve controlling an air flow to the combustion engine, a brake booster being in fluid communication with the intake system, downstream the throttle valve, via an evacuation duct for evacuation of air from the brake booster to the intake system, a crankcase being in fluid communication with the intake system, downstream the throttle valve, via a low load duct for conducting crankcase gases to the intake system, a venturi tube forming part of the low load duct, wherein the venturi tube comprises a narrow venturi tube portion forming a flow resistance within the low load duct through which the crankcase gases have to pass, wherein the evacuation duct is also fluidly connected to the venturi tube portion, via a connection duct, for further evacuation of air from the brake booster to the intake system.