Two-level depth controllers for seismic streamer cables

Claim 1

In a controller for controlling the depth of a body between a first predetermined depth level and a second predetermined level while it is being towed below the free surface of a water medium, the controller having a frame removably coupled to said body and including: depth-sensing means responsive to the water''s pressure and defining a chamber having a movable wall for containing a gas whose pressure is adjusted for a predetermined depth level, a pair of rotatable surfaces symmetrically disposed relative to the longitudinal axis of said frame and laterally extending therefrom, and torque-producing means coupling said surfaces to said movable wall to rotate said surfaces by an amount and in a direction dependent on said body''s depth variation from said predetermined depth level, the improvement comprising: a source of high-pressure gas in said frame; an inflatable member in said chamber, said member when said controller is in use being inflated by said source or deflated by exhausting the gas from said member into the surrounding water; and gas-conduit means including electrically controllable valve means coupling said source with said member and with said surrounding water to selectively maintain said member deflated or inflated, thereby allowing said controller to selectively maintain said body at said first predetermined level and upon actuation of said valve means to move said body to said second predetermined level.