U.S. Patent Specifications

A two‐pipe‐lino liquid pressure remote control system comprising a transmitter unit and a receiver unit, a pair of cylinders in each unit, pistons in the cylinders, coupling means between the pistons of each unit to produce simultaneous movement of said pistons in opposite senses, two pipe‐lines each connecting one cylinder of the transmitter unit to one cylinder of the receiver unit, stops limiting the movement of the pistons in both the transmitter and the receiver units, resilient means supporting the stops for the receiver pistons, and a reservoir, a valve adapted to at times connect each of the cylinders in said receiver unit to the reservoir, and means other than said stops to open either of said valves when the piston in the cylinder which that valve connects to the reservoir is moved beyond the position defined by its stop.