Abstract: A hydraulic unit of the type including a cylinder block (19) rotatably disposed adjacent a valve plate (51;61) having inlet ports 41a, 41b, and 41c, and further having outlet ports 43a, 43b, and 43c. Disposed between the individual inlet and outlet ports are web portions, having nominal cross-sections and flow restrictions. In one embodiment (FIG. 3), there is a modified web portion (55) toward the trailing end of the outlet port, and in the other embodiment (FIG. 7), there is a modified web portion (65) toward the leading end of the outlet port. In either case, the web portion has its cross-section or flow restriction modified to move the resultant force on the swashplate (33) in a direction tending to reduce the moments on the swashplate, and therefore, reduce the operator effort required to move or maintain the control lever.

Abstract: A variable displacement axial piston pump (11) having a tiltable swashplate (33) to vary pump displacement by a manual input lever (43). The pump includes a neutral centering device (45) in which a cam member (57) is fixed to the end of one trunnion member (35). The cam member (57) defines three cam surfaces (65), each having a minimum displacement portion (67) and at least one maximum displacement portion (69). In engagement with each of the cam surfaces (65) is a follower element (79) supported by a cam follower holder (73), both of which are biased by a set of Belleville washers (75), toward the cam member (57). The present invention provides a neutral centering device which is balanced and simple to assemble, not requiring any special fixtures or holders for preloading a biasing spring, but which is able to provide a substantially constant return torque.

Abstract: A normally closed high pressure solenoid valve structure including a plunger pin spring-urged against a composite valve seat having a steel reinforcing ring positioned against the seat and backed up by a fixed spacer. The seat has a projecting neck with orifice. The steel reinforcing ring surrounds and contains any radial movement of the seat which is of elastic material softer than the plunger pin which provides a very low leakage level across the valve from either direction. A lost-motion connection between the plunger pin and the solenoid armature provides that the spring load on the plunger pin is retained even with cold flow of the seating material during cycling.

Abstract: A normally closed spool type solenoid-controlled valve which changes its opening in proportion to the amount of current supplied to the solenoid. The spool which blocks the valve opening in an overlapping relation is held in a closed position by a dual spring design having differing spring rates wherein the lighter spring holds the spool in an overlapping closed position.