Abstract: An acoustic isolator for use with tubular assemblies such as drillpipe or production tubing comprising an acoustic wave transmitter, the acoustic isolator comprising, in series, an odd integer ?/4 multiple tuning bar of first acoustic impedance adjacent the acoustic wave transmitter, an odd integer ?/4 multiple reflector tube of second acoustic impedance, and a snubber of third acoustic impedance, wherein there is an acoustic impedance mismatch between the odd integer ?/4 multiple tuning bar and the odd integer ?/4 multiple reflector tube and an acoustic impedance mismatch between the odd integer ?/4 multiple reflector tube and snubber, such that a “down” wave propagated toward the isolator is reflected back substantially in phase with an “up” wave propagated from the acoustic wave source away from the isolator.

Abstract: A shaft protection washer to protect a rotating shaft in a “measurement while drilling” (MWD) tool. Use of the shaft protection washer renders the rotating shaft less susceptible to erosion from the drilling fluid flowing between the rotating component and the stationary component.

Abstract: A direct current electric motor brush and brush housing arrangement, comprising means to significantly reduce the effect of brush lift in a brushed motor containing viscous fluid. The means enable viscous fluid to avoid momentum transfer into the brushes by providing two or more pressure relief channels that provide the fluid with direct means of radial exit along the direction of the brush, potentially reducing the brush lift due to the fluid being forced between a rotating commutator and its associated brushes. The pressure relief channels may be located in the housing immediately adjacent to the brush, being radially disposed to the leading face (or leading and trailing faces) of each brush, or in the leading face (or leading and trailing faces) of each brush itself, and may comprise additional channels in the housing near but not immediately adjacent the brushes.

Abstract: A rotatable plug and socket for establishing electrical communication in a hazardous environment, each of said plug and socket having biased slidable protective members covering electrical contacts on each of said plug and socket, which are each slidably displaced during mating engagement of the plug with the socket. The slidable protective members ensure protection of the electrical contacts on each of the plug and socket members when such plug and socket connectors are not engaged, or not fully engaged.