Patent ID: 7145834

Claim:
A pulser apparatus for use in wells, in a pipe string, to generate brief pressure changes in a mud stream flowing down the pipe string bore, in response to a down hole instrument, to convey information from the lower end of the pipe string to the surface, the apparatus comprising: a) a housing arranged for selected location in the bore of said pipe string; b) an orifice, having an upstream side and a downstream side, situated in the bore of said pipe string through which at least part of said mud stream flows; c) a poppet situated in said housing and arranged to cooperate with said orifice to comprise a signal valve to vary the resistance to the flow of said mud stream to vary the pressure drop across said orifice; d) a first piston surface on said poppet and an opposed second piston surface on said poppet; e) a first fluid pressure conducting channel arranged to conduct fluid pressure from the downstream side, as defined herein, of said orifice to said first piston surface; f) a second fluid pressure conducting channel arranged to conduct fluid pressure from the upstream side of said orifice to said second piston surface; g) a poppet position controller, intermittently secured to said poppet, responsive to said instrument, to determine at least one controlled position of said poppet relative to said orifice; h) a spring arranged to urge said poppet toward said orifice; i) said piston surfaces and said spring so arranged that said poppet is urged toward said orifice when said pressure drop across said orifice is less than a preselected amount and is urged away from said orifice when said pressure drop across said orifice is more than said preselected amount.