Hydraulic priority circuit

A hydraulic priority circuit for a fork lift truck or the like including a primary work system comprising a hydraulically operated steering means, and comprising a secondary work system comprising hydraulically operated means for raising and lowering load carrying forks on a mast and for tilting said mast, said hydraulic priority circuit comprising:

• variable output fluid pump means;
• a motor operatively coupled to said pump means for driving said pump means at one of a plurality of speed such that said pump means output is controlled thereby;
• valve means for regulating the flow of fluid from said pump means to said primary work system and said secondary work system on a priority demand basis, said valve means including first pressure compensated flow control orifice means for providing a minimum fluid flow from said pump means to said primary work system, means for automatically responding to a pressure differential between the fluid pressure in said primary work system and the fluid pressure of the fluid flow from said pump means such that any excess fluid flow not needed by said primary work system is directed to said secondary work system, sequence valve means responsive to an increased fluid pressure in said primary work system for supplying an increased fluid flow from said pump means to said primary work system, said sequence valve means further including second pressure compensated flow control orifice means for limiting the fluid flow from said pump means to said primary work system to a preset maximum amount, and indicator means for indicating said demand for an increased level of fluid flow to said primary work system, said indicator means actuated upon detecting from said primary work system an increased fluid pressure;
• and
• means for coupling said demand indication to said motor to cause the speed of said motor to increase thereby.