Properties of the continuous linear winches
Two movable grippers
The continuous linear winch consists of two grippers mounted in a frame. Both grippers move back and forth (extend and retract) through the actions of two sets of hydraulic main cylinders. When moving, the grippers pull a steel wire rope, that is passed through the machine.
Load holding wedges
The grippers can pull since each gripper is fitted with wedges. These wedges will clamp onto the steel wire rope. When a gripper is pulling, the wedges in this gripper hold the wire rope, moving the rope while it slides through the wedges of the other gripper. The wedges can be opened and closed by hydraulicly powered wedge cylinders inside the gripper.
Continuous motion is reached since during the pull of one gripper (extension), the other gripper moves back to the starting position (retraction), allowing this gripper to start the next pull immediately after the current pull is finished. The wire rope pull-in is usually automatically controlled, and a winch operator can adjust the pull speed and the load. The movement of the grippers can be sequenced to either pull-in or pay-out. In manual mode the grippers can be independently controlled.
Fail to safe
In both the manual and automatic modes, one of the gripper wedges always maintains contact with the wire rope. Since the load-holding wedge is automatically locked and cannot be opened, control of the load is always maintained. Only when there is no load or when the load is released after a pull operation, both wedges can be opened. This allows for inserting and removing wire. The system is “Fail to Safe”. In other words, when a sudden pressure drop occurs, for example when the emergency engine stop is activated, springs will automatically close the wedges and the wedges will hold on to the steel wire rope.