Abstract: A breathing system is described for underwater diving system which is particularly useful in emergency, "bailout" situations where the diver's external support is terminated. The invention is particularly characterized by a gas recirculation and purification system which is entirely contained within the helmet and which functions to purify and recirculate exhaled gas within the helmet and to preserve heat generated by the reaction whereby CO.sub.2 is purged from exhaled gas. The invention, further, conserves human respiratory heat by minimizing breathing gas exposure to cold surfaces.

Abstract: In an improved diving helmet, or diving helmet assembly, of the type having a seal characterized as a flexible diaphragm, usually an annular diaphragm which seals about the diver's neck to close off the helmet and provide an interface between the water and the diver's breathing gas, improvements characterized as means associated with said flexible diaphragm for sensing changes in the physical position of said diaphragm caused by the differential pressure between said ambient water pressure and said helmet pressure, and actuating means responsive to said sensing means for opening and closing a valve to regulate helmet gas pressure. The said actuating means is located in said gas supply inlet for regulating the flow of breathing gas into the helmet or in said gas exhaust outlet for regulating the flow of exhaust gas from the helmet, or both, such that the ingress or egress of gas to or from the helmet is regulated and directly proportioned to the differential pressure sensed by the flexible diaphragm.

Abstract: A spring loaded accumulator is carried by a diver and is positioned within the gas circuit of a push-pull system wherein the diver is supplied with breathing gas from a remote source and exhaust gas is returned back to the source. The accumulator positioned in the return line reduces umbilical hose and pump capacity requirements. A regulator within the accumulator is positioned to limit the maximum differential pressure on the diver side of the return line.

Abstract: A hand held electronic calculator which includes a grip for attaching the calculator to the hand of the user to make it fully operable with one hand while reducing the danger of damage by dropping. The concept is equally applicable to any hand held device having a keyboard, such as various telephone handsets and to remote control devices wherein the keyboard consists of one or more switches.

Abstract: Described is a diving helmet which includes a relatively inexpensive adapter unit custom fitted to an individual diver. The assembly includes a standardized helmet body having an inner surface generally conforming to the surface of the adapter unit so as to be capable of being worn by any diver. A sealing arrangement is provided around the base portion of the helmet body and lift off forces are directly communicated to the diver's head.

Abstract: Described is a diving helmet having receptacles for receiving insertable modular valves or plugs for governing gas flow. The receptacles are diametrically opposed on the helmet and are connected by gas conducting conduits. Gas may be supplied to the diver by way of a main supply duct which discharges the gas against the helmet window for defogging purposes. A sealing arrangement is provided with the diver, and particular valves or plugs are inserted into the receptacles in accordance with a particular gas supply system being utilized.

Abstract: Breathing gas from a remote source is supplied directly to a diver's helmet, without the requirement of a demand valve. Exhaust gas is returned back to the remote source through a series arrangement of a normally open fail-safe valve and an exhaust control valve which maintains the helmet pressure within predetermined limits relative to the ambient water pressure. Should the exhaust control valve fail in the open position, the fail-safe valve will actuate to insure that the helmet pressure does not decrease to a dangerous level. Valve actuation is a function of diver orientation so as to maintain helmet pressure within a range to minimize diver breathing effort, for the various positional orientations.The helmet includes ducting for the exhaust gas and the valves are constructed and arranged to sense the helmet pressure directly for comparison with the ambient water pressure acting on the respective valves.

Abstract: Breathing gas from a remote source is supplied directly to a diver's helmet, without the requirement of a demand valve. Exhaust gas is returned back to the remote source through a series arrangement of a normally open fail-safe valve and an exhaust control valve which maintains the helmet pressure within predetermined limits relative to the ambient water pressure. Should the exhaust control valve fail in the open position, the fail-safe valve will actuate to insure that the helmet pressure does not decrease to a dangerous level. Valve actuation is a function of diver orientation so as to maintain helmet pressure within a range to minimize diver breathing effort, for the various positional orientations.

Abstract: Underwater breathing apparatus which includes means for reducing the power required to operate the pumps that effect flexible-hose interchange of breathing gas to and from a diver and a diving bell. This is accomplished primarily by maintaining a substantially constant differential between the supply and return pressures.

Abstract: Underwater breathing apparatus including a diver worn back pack having a hard outer shell and a soft flexible undersurface to conform to the diver's back. Breathing bags positioned between the undersurface and outer shell are connected to the undersurface so as to extend down the diver's back and be coextensive with his lungs. Gas circuit components are mounted on the inside of the shell. The apparatus makes contact with the diver's back, at a small area on the upper portion of his back, and, at the lower portion of the diver's back two extending projections from the shell receive a transverse strap which contacts the diver in the vicinity of the small of his back.