SERVO VALVE FOR WELL-LOGGING TELEMETRY

摘要

A monostable valve for insertion in a drill string used in forming a borehole such as an oil well. In an open position, the valve vents drilling fluid flowing in the drill string to an annulus in the borehole for return flow to the surface, thus generating a surface-detectable negative fluid-pressure pulse. A valve closure member is supported for horizontal movement to provide significant isolation from vertical accelerations occurring during drilling, and the closure member and associated valve seat are field replaceable. Primary power for valve actuation is drawn from the drilling-fluid hydraulic energy as controlled by a low-power solenoid-actuated pilot valve.