Controlled buoyancy system for seismic streamer sections

Claim 1

An automatic buoyancy controlled streamer section for controlling the depth of adjacent portions of an elongated expansible flexible marine seismic detection streamer having serially connected sections containing a plurality of hydrophones therein and each filled with a buoyancy control liquid of different density from the density of the sea water in which the streamer is to be immersed to be towed continuously at a predetermined depth of submersion through the sea water by a vessel, the streamer section comprising an elongated hollow outer tubular jacket having a pressure sensing switch assembly located within the jacket of the streamer section including a pressure sensing device having a movable wall which has a first surface exposed to a reference pressure and an opposite surface exposed to the water pressure at the depth of the streamer to move in response to changes in water pressure of the sea water at the depth of the streamer section, first and second pairs of electrical contacts in the streamer section forming first and second switches, a first contact of each contact pair being a fixed contact and the second contacts of each contact pair being rigidly interconnected together for corresponding movement along a switch axis and being directly connected to said movable wall of said pressure sensing device to be actuated thereby, said contact pairs being in normally open condition and said first contacts of said contact pairs being spaced in opposite directions from their companion second contacts for electrically closing said first and second contact pairs respectively upon movement of the interconnected second contacts in first and second relatively opposite directions, a buoyancy control liquid supply line extending through the streamer section from a pressurized source of the buoyancy control liquid, a normally closed electrically operated inlet valve and a normally closed electrically operated exhaust valve disposed within the streamer section for admitting an additional quantity of the buoyancy control liquid from said supply line to the streamer for increasing the buoyancy thereof and for discharging the buoyancy control liquid from the streamer section for decreasing the buoyancy thereof respectively, and electrical circuit connections from an electrical power source through said first and second electrical contact pairs to said inlet valve and exhaust valve respectively by direct connections wholly located within the section between the contact pairs and said valves to operAte said inlet valve and exhaust valve respectively responsive to closure of said first or second contact pairs by the movable wall of said pressure sensitive element upon downward or upward deviation respectively of the streamer depth from said predetermined depth.