Eaton Corporation

James K Yip

William John Novacek

Bernard J Larson

Oliver W Johnson

A fluid controller (15) of the type which controls the flow of fluid to an unequal area steering cylinder (25), wherein the controller is of the load reaction type. The controller (15) includes valving (27) which, when it is in neutral (FIGS. 1 and 5), defines a load reaction fluid path (LR) permitting fluid communication between the control fluid ports (21, and 23) through the fluid meter (29) in response to an external load imposed on the cylinder (25). In accordance with the invention, the valving (27) includes a fluid path (97,95,99,71,75) between the load reaction fluid path (LR) and the return port (19), when the valving is in neutral. When the rod end chamber (A) is contracting, fluid is drawn from the return port into the load reaction fluid path (LR), preventing cavitation, and when the head end chamber (B) is contracting, fluid flows from the load reaction fluid path (LR) to the return port (19), preventing pressure intensification.

Load reaction steering unit for unequal area cylinder

An improved fluid controller (17) is disclosed of the type for use in a load sensing hydrostatic steering system. The system includes a load sensing priority flow control valve (15) of the type which operates on a dynamic load signal. The controller includes a spool valve (95) and a sleeve valve (97) which cooperate to define a plurality of orifices including a main variable flow control orifice (71) and a variable orifice (75) through which fluid flows from the return side of a steering cylinder (19) to the return port (25) of the controller. A variable drain orifice (76) communicates between the main flow path, downstream of the main orifice (71) and the return port (25). As the controller valving moves from its neutral position toward an operating position, the orifice (75) begins to open at least as soon as the main orifice (71) and reaches a predetermined flow area before the main orifice (71) reaches that predetermined flow area. In addition, the drain orifice (76) remains open at least until the variable orifice (75) begins to open to reduce undesirable high transition pressures in the controller.

Load sensing system

A closed-center, non load-sensing controller (15) is disclosed for use with an unequal area steering cylinder (17). The controller includes valving comprising a spool (35) and sleeve (37). The sleeve includes an annular groove (65) in communication with the inlet port (29) and cylinder ports (73,75) in communication with the opposite ends of the steering cylinder. The sleeve defines an annular leakage groove (95) which is disposed to interrupt the flow of leakage fluid from the annular groove (65) to the cylinder ports (73,75), to eliminate undesired piston rod extension. When the valving is in neutral, leakage fluid collected in the annular groove (95) is communicated through radial bore (97), axial slots (83), and annular groove (81), axial slots (91), drain bore (99), drain bore (93), and then to the system reservoir.

Closed-center controller for use with unequal area cylinder

A vehicle hydraulic system is disclosed of the type including a steering control valve (29), a brake system (31), and an auxiliary load circuit (65). Fluid flow to these load circuits is controlled by a flow control valve assembly (11) including a priority spool valve (85) which controls the flow of fluid from the inlet port (13) to the priority fluid chamber (75). Fluid flows from the priority fluid chamber to the steering control valve and the brake load system, in parallel, and at equal levels of priority. A shuttle valve assembly (83) receives a steering load signal by means of a load signal line (44) and a brake load signal from the load signal chamber (111), and transmits the higher of the two load signals into the load signal chamber (93) which biases the priority spool valve toward a position to permit a greater flow of fluid into the priority fluid chamber. Therefore, the control valve assembly disclosed herein requires only a single pump to provide sufficient fluid to satisfy the simultaneous demand for fluid by both the steering system and brake system.

Steering valve assembly for steering and brake system

A closed-center controller is disclosed, especially of the type utilized in hydrostatic power steering systems. The controller includes valving which, in the neutral position, defines a bypass passage communicating inlet fluid through the interior of the hollow, primary valve member to the tank port of the controller. The bypass passage includes a variable bypass orifice having a maximum flow area in the neutral position of the valving and decreasing to zero as the valving is displaced from the neutral position. The variable bypass orifice permits the passage of just enough fluid, typically in the range of about 0.25 gpm to about 0.5 gpm, to minimize the temperature difference between the controller valving and the remainder of the hydraulic system, thus minimizing the possibility of thermal seizure of the valving within the controller.

Closed-center controller and neutral bypass arrangement therefor

A system for providing pressurized fluid to a primary load circuit and an auxiliary load circuit, the primary load circuit being of the type which provides a load pressure signal representative of the demand for fluid in the primary load circuit. The system includes first and second fluid pumps feeding first and second priority flow control valves, respectively, each of which has a primary outlet port connected to the primary load circuit and an auxiliary outlet port connected to the auxiliary load circuit. When the flow demand of the primary load circuit can be satisfied by the first pump, any excess flow available is fed by the first flow control valve to the auxiliary load circuit, and all of the flow from the second pump goes to the auxiliary circuit. If the flow demand of the primary load circuit is greater then the capacity of the first pump, all of its flow passes to the primary load circuit with none going to the auxiliary load circuit, and a novel pilot valve arrangement permits the load pressure signal from the primary load circuit to bias the second flow control valve to a position where a sufficient amount of the flow from the second pump is fed to the primary load circuit to meet the demand thereof, with the remainder of the flow going from the second flow control valve to the auxiliary load circuit.

Load sensing steering system with dual power source

A power steering system is disclosed which selectively controls the flow of fluid to a steering motor and an auxiliary device, and may have as its source of pressurized fluid either a fixed displacement pump, a variable displacement pump, or a load sensing pump. The system includes a steering control valve disposed between the pump and the steering motor, and an externally pilot operated flow control valve, specifically, a priority valve, disposed between the pump and the steering control valve, such that the entire system flow enters the priority valve.

Load sensing power steering system

A steering control system is disclosed of the type utilizing a variable fluid delivery source, such as a variable delivery pump, providing fluid to a steering cylinder, the flow to the steering cylinder being controlled by a steering control valve. The steering control valve includes a first orifice which is variable between a minimum orifice area permitting a minimum system flow and a maximum orifice area corresponding to a maximum system flow. The variable fluid delivery source is maintained at a generally constant level above the steering load as the system flow varies between the minimum and maximum flow rates. Disposed in series flow relationship between the fluid delivery source and the steering control valve is a second valve including a valve member defining a second variable orifice operable to maintain a relatively constant pressure drop across the second valve as the system flow varies between the minimum and maximum flow rates. The pressure drop across the second valve may be changed by changing or adjusting the biasing force on the valve member and therefore, the same steering control system may be utilized with any of several different pump control (standby) pressures by changing the pressure drop across the second valve, without the need for changing the configuration of the steering control valve and its variable orifice, because the steering control valve will, in each case, be subjected to approximately the same control pressure differential.

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Richfield, MN, United States of America

James K Yip