| 摘要 |
PCT No. PCT/US90/05954 Sec. 371 Date Apr. 16, 1992 Sec. 102(e) Date Apr. 16, 1992 PCT Filed Oct. 17, 1990 PCT Pub. No. WO91/06192 PCT Pub. Date May 2, 1991.An underwater transducer assembly (T or P) is mounted on an elongated cylindrical piston (32 or 90) received in a pneumatic cylinder (31 or 91). One or more springs (41 or 92) normally bias the piston (32 or 90) inward into the cylinder (31 or 91) to retract the transducer assembly (T or P) into a sea chest (S'). Air under pressure introduced into the cylinder (31 or 91) is effective to overcome the force of the springs (31 or 91) and project the transducer assembly (T or P) to a position operative for scanning. Force applied to the transducer assembly (T or P) tends to move the piston (32 or 90) inward into the cylinder and thereby increase the pressure of the system. The transducer assembly (T or P) is retracted automatically if the pressure exceeds a predetermined pressure. A separate mechanical sensor is mounted adjacent to the sea chest S' to detect the presence of obstacles or debris and automatically actuate retraction of the transducer assembly (T or P). |
