Importance

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Abstract

A safety apparatus for preventing the traveling block of a drilling rig from being drawn into the top of the rig and also for preventing the traveling block from falling downwardly below a predetermined bottom position. A high position limiting valve has an air inlet and an air outlet with a valve stem providing communication between the inlet and the outlet when a predetermined amount of cable is spooled onto the drum. A low position limiting valve has an air inlet and an air outlet with a stem yieldably urged at all times into engagement with the cable for actuation and providing communication between the inlet and the outlet when a predetermined amount of cable is spooled off of the drum. An air supply is connected to the inlets of the valve and the outlets of the valves supply air to stop the actuation of the cable drum. The longitudinal axis of the valves are positioned generally perpendicular to the surface of the cable drum and their stems are longitudinally movable.

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First Claim