Abstract: A constant tension hoisting system is provided for raising and lowering an object between a platform and a surface undergoing vertical motion relative to the platform, such as raising and lowering a lifeboat from a seagoing vessel to the sea in rough weather. The system operates in a normal hoisting mode to raise or lower the object, and in a constant tension mode when the object is supported on the surface. The system is changed from the normal hoisting mode to the constant tension mode at the moment when the object being lowered is first supported by the surface, and a slack condition exists in the cable. The changeover from the normal hoisting mode to the constant tension mode, is performed by a solenoid-operated mode selector responsive to a proximity switch operated by a lever arm engaging the cable. The hoisting system is operated by a single, manually-actuated control lever, which mechanically activates the proximity-type control switches.

Abstract: A constant tension hoisting system is provided for raising and lowering an object between a platform and a surface undergoing vertical motion relative to the platform, such as raising and lowering a lifeboat from a seagoing vessel to the sea in rough weather. The system operates in a normal hoisting mode to raise or lower the object, and in a constant tension mode when the object is supported on the surface. The system is changed from the normal hoisting mode to the constant tension mode at the moment when the object being lowered is first supported by the surface, and a slack condition exists in the cable. The changeover from the normal hoisting mode to the constant tension mode, is performed by a solenoid-operated mode selector responsive to a proximity switch operated by a lever arm engaging the cable. The hoisting system is operated by a single, manually-actuated control lever, which mechanically activates the proximity-type control switches.