Abstract: An improved electromechanical transducer is provided for use in an acoustic telemetry system. The transducer of this invention comprises a stack of ferroelectric ceramic disks interleaved with a plurality of spaced electrodes which are used to electrically pole the ceramic disks. The ceramic stack is housed in a metal tubular drill collar segment. Thick metal spacer plate are selectively sandwiched between electrodes in order to promote thermal cooling of the ceramic stack. In accordance with an important feature of this invention, the thick metal spacer plates are comprised of a material (such as copper alloys, aluminum alloys or the like) which is softer than the relatively hard, brittle ceramic disks thus reducing the stresses upon the disks when the assembly is subjected to bending, torsion and the like, and thereby minimizing the risk of structural failure of the disks when in operation within a downhole acoustic signal generator.

Abstract: A debris catcher comprising a conical screen (filter) in a drill string which defines an annular accumulation space between the screen and the inner wall of the drill string is presented. The central portion of the screen is open to establish an unimpeded flow path. A centrifugal deflector, impeller or similar device above (upstream from) the screen establishes a helical flow pattern in the drilling mud whereby debris entrained in the mud is forced outwardly by centrifugal action. The debris is then caught in the annular accumulation space between the screen and the drill string wall when the mud flows through the screen. If the accumulator fills or the screen becomes clogged, mud will still flow through the center flow passage. The debris catcher of the present invention is preferably positioned within a drill string upstream of a mud powered turbine or other device in the mud stream, the operation of which may be jeopardized by debris in the mud stream.

Abstract: A flexible electrical connector for borehole telemetry apparatus is presented wherein the electrical connector includes an elongated metal tube having an intermediate section coiled around the exhaust shroud of a mud turbine. Electrical conductors are housed within the metal tube, and the tube is internally pressurized with oil, the pressure of the oil being maintained equal to the drilling mud pressure by a bellows exposed to the drilling mud.

Abstract: A mud pulse telemetry system is presented for transmitting information from the bottom of a well hole to the surface. The mud pulse telemeter is a pilot operated valve which restricts the flow of mud in the drill string to set up pressure waves in the mud stream which can be detected at the surface. The pilot operated mud pulse telemeter uses a small input signal to operate the telemeter valve by pressure differentials created in the mud stream itself.