Abstract: A hydraulic lift valve system for fork lift trucks comprising a three way valve including a spool in a bore having a first neutral position, a second lift position and a third lower position. In the second lift position, the spool functions to apply fluid from a source to a cylinder for lifting the fork of the truck only after the pressure exceeds the load pressure and a predetermined value as established by a first poppet valve. Upon shifting to the third position the spool functions to permit exhaust of the fluid in the cylinder and therefore lowering the fork only after a predetermined pressure is established in a pilot valve which permits the first poppet valve to open, thereby insuring that the fork of the lift truck is not lowered unless there is a predetermined load on the fork. By this arrangement, the problem of uncontrolled descent of the fork upon engagement of the fork with an object is obviated.

Abstract: A directional valve assembly for use in hydraulic power systems such as are used on fork lift trucks has a plurality of sliding spool directional valves and a balanced relief valve mounted in the body formed of a plurality of sections bolted and gasketed together. The main lift section has a load-holding check valve of special design together with means on the spool for opening the check valve to lower the load. Means are provided in the assembly for preventing interflow from one valve spool to another when two or more spools are simultaneously shifted. This includes a system of restrictors, check valves and passages causing the main relief valve to act as a pressure compensator responsive to the pressure requirement of the smallest load.