Patent ID: 8225883

Claim:
A downhole drill string tool, comprising: a body having an axis and an axial interior chamber formed therein, said interior chamber having an inner surface; a piston element disposed within said interior chamber, said piston element free to slide within said interior chamber, a first face, and a second face spaced apart from said first face, said first face and a first portion of said inner surface defining a first pressure chamber and said second face and a second portion of said inner surface defining a second pressure chamber; at least one first input channel in fluid communication with said first pressure chamber and at least one second input channel in fluid communication with said second pressure chamber; at least one first exit orifice in fluid communication with said first channel, at least one second exit orifice in fluid communication with said second channel, and at least one exhaust orifice; a rotary valve comprising a first disc adapted to be coupled to a driving mechanism, said first disc having at least one through port adapted to receive a pressurized fluid and having at least one exit port in fluid communication with said exhaust orifice and a second disc axially aligned with said first disc, said second disc having at least one first access port in fluid communication with said first channel and at least one second access port in fluid communication with said second channel, said rotary valve configured to selectively align said at least one through port with said at least one first access port and said at least one exit port with said at least one second access port, and selectively align said at least one through port with said at least one second access port and said at least one exit port with said at least one first access port.