Abstract: A pressure regulating device for fluidtight, fluid-filled apparatus comprises a solid body with a shallow recess in a surface enclosed by a flexible diaphragm. A narrow passage, preferably of capillary dimensions, connects the recess to the interior of the apparatus and the diaphragm is flexible enough to be deformed without injury so as to enter the recess and reduce its volume substantially and preferably practically to zero. The recess contains a volume of air which for optimum performance should be equal to the amount by which the volume can be reduced by movement of the diaphragm and also equal to the volume expansion of the fluid (or if more than one device is fitted its share of the fluid) from atmospheric conditions to mean working temperature (less the volume of any air occluded elsewhere in the apparatus). By this means, the diaphragm is substantially unstressed both under atmospheric conditions and under mean working conditions, since the gas will be compressed to a negligible volume.

Abstract: A separable electric connector for use "downhole" in the oil industry or else where when large pressure changes are encountered comprises a socket part which, prior to the assembly of the part, can be filled with a viscous insulating fluid. The corresponding plug part has a tubular member which is closed at one end and surrounds the socket part with a clearance when the connector is assembled. A male member which forms or carries contacts is upstanding from the closed end of the tubular member to enter the socket part and make the required contact or contacts. A passage is provided to allow flow of the fluid from the socket member into the space within the tubular member. A sleeve member subsequently enters the tubular member, whereupon the fluid flows mainly between the sleeve member and the tubular member until a seal is formed, for instance by a sealing ring. An escape path is formed, as between the socket member and the sleeve member, to allow the subsequent escape of excess fluid.