Load leveling system

Claim 1

In a semi-trailer, a system for maintaining the trailer load bed horizontal during raising and lowering that end of the trailer carried by the tractor comprising: at least a pair of hydraulic cylinders equally spaced from a vertical plane through and including the longitudinal axis of said semi-trailer and suitably disposed to raise and lower said semi-trailer; a source of pressurized fluid for operating said cylinders; a valve for controlling the operation of said cylinders, said valve comprising a housing formed with a bore therethrough and with two transverse bores intersecting said through bore equidistant from but on opposite sides of a plane through and parallel to the axis of elongation of said through bore and communicating with said hydraulic cylinders and with a transverse intersectIng bore along said plane communicating with said source of pressurized fluid; said valve further comprising a shaft rotatably mounted within said through bore on which is formed a flat registering with said third transverse bore and in which are formed two transverse bores extending from said flat through said shaft; means for axially retaining said shaft in said through bore; means for sealing said through bore and means exterior of said housing to rotate said shaft between a position in which said flat registers with said transverse intersecting bore and said transverse bores in said shaft respectively equally register with said transverse bores in said housing and positions in which registration between said transverse bores in said shaft and in said housing are not in equal registration whereby the rate of operation of said cylinders is equal in said first mentioned position of said shaft and the rate of operation of said cylinders is equal in said first mentioned position of said shaft and the rate of operation of one of the cylinders is inversely proportional to the rate of operation of the other cylinder at other positions of said shaft.