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A downhole mud pressure change signal generator has a signal valve to variably resist the flow of mud down the drill string bore. The valve is powered by a bias driver and controlled by a holding magnet that is in turn controlled by a downhole instrument. The bias driver has a spring opposed fluid p

A downhole mud pressure change signal generator has a signal valve to variably resist the flow of mud down the drill string bore. The valve is powered by a bias driver and controlled by a holding magnet that is in turn controlled by a downhole instrument. The bias driver has a spring opposed fluid powered piston that moves in response to changes in fluid pressure drop across the signal valve. The valve in normally biased closed. The bias driver is resiliently connected to the valve such that when the piston moves the bias driver in response to fluid pressure that overcomes the spring, the valve is urged toward an open position. When the valve is open and signal pressure across the valve is low the spring exerts more force than the piston and the driver urges the valve toward a closed position. The valve is urged to move but not compelled and is subject to latching in desired positions without losing the power needed to move later. The bias driver is used to power a latch that holds the valve open or closed. The energy is invested in springs that move the latch when holding magnets permit the latch to respond to the bias. The holding magnets never depend upon a flux gap because they hold positions the springs have provided.

대표청구항 ▼

Apparatus for the generation of drilling fluid pressure change signals, for well bore telemetry, in a stream of drilling fluid being circulated through the bore of a drill string, the apparatus comprising: (a) a housing comprising a length of drill string with fluid tight means at one end for attach

Apparatus for the generation of drilling fluid pressure change signals, for well bore telemetry, in a stream of drilling fluid being circulated through the bore of a drill string, the apparatus comprising: (a) a housing comprising a length of drill string with fluid tight means at one end for attachment to an upwardly continuing portion of the drill string and means at the other end for fluid tight attachment to a downwardly continuing portion of the drill string; (b) an orifice, with an upstream side and a downstream side, situated in the bore of said drill string and arranged to accept at least part of said drilling fluid stream therethrough; (c) a poppet mounted for reciprocating movement in said housing between a first position near said orifice to produce a signal pressure drop therethrough and a second position farther from said orifice to produce a pressure drop lower than said signal pressure drop; (d) actuator means situated in said housing comprising a fluid power cylinder with a piston resiliently connected by a first bias means to said poppet such that said piston and said poppet are urged to move in sympathy; (e) first fluid channel means in said housing to conduct fluid from the drilling fluid stream upstream of said orifice to said cylinder on one side of said piston and second fluid channel means to conduct fluid from said drilling fluid stream downstream of said orifice to the other side of said piston, said two channel means arranged such that increasing pressure across said orifice increasingly urges said poppet away from said orifice; (f) position latch means in said housing arranged to releasably secure said poppet in at least one of said two positions in response to movement of a latch control member between a first and a second latch control position; (g) second bias means arranged to urge said actuator means and said latch control member to move in sympathy; (h) holding means situated to releasably engage said latch control member in at least one of said two latch control positions in response to a first signal from a downhole instrument and to release said latch control member in response to a second signal from said downhole instrument.