Patent ID: 7600578

Claim:
A percussion adapter for use with a positive displacement motor and a drill bit, the percussion adapter comprising: a housing; a torque tube, the torque tube having an upper end for engagement to a rotor of a positive displacement motor and a lower end for engagement of a drill bit and being rotationally moveable about its long axis within the housing, a fluid pressure driven piston within the housing configured to be driveable through a cycle including a drive stroke and a charging stroke, the piston drivable through application of fluid to a drive hydraulic chamber to strike the torque tube and drivable through the charging stroke by application of fluid to a charging hydraulic chamber; a fluid passage through the torque tube communicable to the piston; a first port carried on the torque tube, the first port being from the fluid passage openable to the drive hydraulic chamber, when the torque tube is in a first rotational orientation; a second port from the fluid passage openable to the charging hydraulic chamber when the torque tube is in a second rotational orientation, the first port being closed when the torque tube is in the second rotational orientation; and a liner between the drive hydraulic chamber and the torque tube, the liner including a plurality of valving ports therethrough alignable with the first port such that the first port passes over the plurality of ports during a rotation of the torque tube to repeatedly open and close access between the first passage and the drive hydraulic chamber.