High or low fluid flow signalling apparatus

Claim 1

In a signalling apparatus adapted to be installed in a well drilling string for producing signals in a stream of well drilling fluid indicative of the disposition of the drilling string in the well bore, said apparatus comprising: an elongated housing, a shaft longitudinally movable outwardly from and inwardly to an innermost position, said shaft having a free end projecting from said housing, means in said housing for biasing said shaft outwardly from said innermost position, means for limiting outward movement of said shaft to an extent determined by disposition of said housing in the well bore, and signal producing means for producing a number of pressure pulses in the stream of drilling fluid depending upon the extent of outward movement of said shaft, said signal producing means including a knob on the free end of said shaft, seal means carried by said housing for slidably sealing said shaft to said housing substantially where said free end projects from said housing, a pulse tube having a central flow path and axially spaced pulse rings circumscribing said flow path and defining annular spaces between adjacent pulse rings, said pulse rings forming restricted flow paths past said knob when said knob is disposed adjacent said pulse rings, and means positioned inwardly of the last pulse ring for restricting the flow of fluid past said knob following movement of said knob past the last pulse ring during inward movement of said shaft to provide a greater differential fluid pressure acting on said knob to force the shaft to said innermost position, in which the portion of said shaft that is slidably sealed to said housing by said sealing means is protected by said housing from erosive action of the drilling fluid.