Abstract: A magnetic drive device couples the drive motor of a depth control device or bird, with the axle of the depth control wings. The magnetic drive includes a plurality of permanent magnet pieces mounted in respective drive blocks on either side of a magnetically permeable membrane of the main body of the drive mechanism. The magnet pieces are mounted side by side in alternating polarity to capture as much of the magnetic flux of the magnets as possible to minimize stray flux from escaping the drive. Pole pieces either side of the drive blocks also serve to capture stray flux. To the maximum extent possible within the constraints of mechanical durability, the drive mechanism is made of non-magnetic or non-ferrous materials which would interfere with the heading sensor of the bird. Thus, this invention avoids reducing the accuracy of the heading sensor of the bird, while eliminating a major source of seawater inleakage into the bird.

Abstract: A battery charging apparatus and method permits the recharging of the batteries of a seismic streamer depth control device or bird without access to the interior of the bird. In a preferred embodiment, a battery pack includes a coil within the bird that is capable of receiving a charging field from a charging unit by inductive coupling. The coil provides power to a regulated power supply comprising a voltage regulator and rectifier, and direct current is provided to charge battery cells. Thus, the batteries within the bird a charged by induction from outside the casing of the bird. Alternatively, the battery pack may be detached from the rest of the bird, but the battery pack remains scaled against the elements. The battery pack may include an electrical connector which attaches to the main body of the bird, and the electrical connector includes one or more pins for charging purposes.