Abstract: A simple and economical device is placed in a drill string to provide a pulsating flow of the pressurized drilling fluid to the jets of the drill bit to enhance chip removal and provide a vibrating action in the drill bit itself thereby to provide a more efficient and effective drilling operation.

Abstract: This invention relates to a double-acting drilling jar characterized by a constantly recharged hydraulic system operating in concert with a mechanical brake to actuate the latter and temporarily inhibit extension of the relatively moving parts utilizing a modest fluid pressure multiplied many-fold so as to exert a holding force far in excess of that which the hydraulic system could impose alone without destroying the seals. The invention also encompasses the virtual elimination of heat build-up through the use of drilling mud as the working fluid in a hydraulic system where once-used fluid is discharged downhole before it gets too hot while, at the same time, being replaced by a fresh supply of cool fluid from the surface. By calling upon the hydraulic system to only exert enough force to actuate the mechanical system, none of the fluid seals need be loaded to anywhere near their capacity.

Abstract: In a down hole drilling tool a closed valve is operatively moved downwards by pressurized drilling mud pumped down the drill string, the valve when it attains its lower position being opened and being returned under the influence of a spring or other upwardly urging means acting on the valve to its upper position at which the valve is closed thereby to complete the cycle of operations. The valve is so continuously coupled to a torque member that the downward movement of the valve causes turning of the torque member in one direction, and the upward movement of the valve causes turning of the torque member in the opposite direction. A drill bit mounted on the lower end of a rotor is connected through a one-way clutch to the torque member so that during the downward movement of the valve the rotor and drill bit are rotatably driven by the torque member but are stationary during the upward movement of the valve, the drill bit thus being operatively intermittently rotated.