HYDRAULICALLY OPERATED VARIABLE LENGTH TOP GUIDE COUPLING MEMBER

摘要

A hydraulically operated variable length top guide coupling member for use in three point linkage couplings for attaching agricultural implements to farm tractors includes a cylinder and a main piston with piston rod carried for longitudinal movement within the cylinder to thereby vary the length of the coupling member. Articulation means are carried at one end of the cylinder and at the other end of the piston rod for connecting the coupling member between a tractor and an agricultural implement. A pair of hydraulic lines provide communication between a source of hydraulic fluid and cylinder spaces on opposite sides of the main piston. A one-way valve is located in the path of communication between each of the hydraulic lines and the respective cylinder spaces. A control piston is carried between the two one-way valves for controlling opening of the valves. Application of hydraulic pressure to one of the hydraulic lines will open its respective one-way valve to permit hydraulic fluid to flow into the cylinder space on one or the other side of the main piston. Hydraulic pressure also acts on the control piston causing it to open the other one-way valve and permit hydraulic fluid to flow out of the other cylinder space into the other hydraulic line. Hydraulic pressure acting on the main piston will thus cause it to move within the cylinder to vary the length of the coupling member. A means for immobilizing the main piston within the cylinder to fix the length of the coupling member to a desired position is also provided.