Patent ID: 7430153

Claim:
A downhole tool for generating a fluid pressure pulse, the tool comprising: a fluid actuated flow restrictor; a first fluid flow path for flow of actuating fluid to actuate the flow restrictor; a second fluid flow path for flow of actuating fluid to actuate the flow restrictor; a control member movable between a first closed position where the first fluid flow path is closed and the second fluid flow path is open, and a discrete second closed position where the first fluid flow path is open and the second fluid flow path is closed, for controlling actuation of the flow restrictor; and an intermediate member in fluid communication with the flow restrictor, wherein the first fluid flow path is for fluid flow to the intermediate member and the second fluid flow path is for fluid flow from the intermediate member, the control member serving for controlling fluid flow to and from the intermediate member, which in turn controls actuation of the flow restrictor, wherein the intermediate member comprises a piston mounted in a cylinder.