Underwater transducer with depth compensation

Claim 1

A sealed underwater transducer comprising: a plurality of electrostrictive elements and spacer elements arranged to form a driving ring, said elements having opposed surfaces axially of the ring, said ring surrounding a space radially internally of the same, said driving ring being expandable radially in response to an applied voltage; a pair of flexible diaphragms closing off said space axially of said ring, said diaphragms each being formed with a plurality of extensions extending radially outwardly, said extensions being connected to said opposed surfaces of the elements so as to prevent mechanical bending stresses peripherally of the diaphragms from being transferred to the electrostrictive elements; a closeable gas inlet means for injecting a compressed gas into said space; a water bladder assembly within said driving ring, including a water bladder in said space, said water bladder having water inlet means in communication with the exterior of the transducer, said water bladder being collapsable by injection of a compressed gas at a predetermined pressure into said space via said gas inlet means, said water bladder being expandable from said collapsed condition to a condition substantially fill-ing said space thereby to protect the diaphragms against collapse under excessive ambient water pressures; and a pair of supports positioned in said space between said bladder and said diaphragms such that at a predetermined operating depth, when the external water pressure exceeds the internal gas pressure the bladder expands and is supported by said supports such that said water bladder is prevented from touching the diaphragms thus impeding the operation of said transducer, and hence extending the operating depth range.