Abstract: An apparatus for multiplexing a first hydraulic cylinder and a second hydraulic cylinder. Each cylinder has a head end port and a rod end port. The apparatus includes a tank, a pump connected to the tank, and a control valve having an inlet port connected to the pump, an outlet port connected to the tank, and first and second control ports. The apparatus also includes at least two two-position valves each having at least one port connected to a corresponding at least one of the first and second control ports and at least one other port connected to a corresponding one of the head end and rod end ports of the first and second hydraulic cylinders, the at least two two-position valves being operable to selectively divert hydraulic fluid from the respective first and second control ports of the control valve to one of the first and second hydraulic cylinders.

Abstract: A system for controlling an independent metering valve having a pair of independently controlled electrohydraulic displacement controlled spool valves for controlling pump-to-cylinder communication between an inlet port and a pair of control ports and another pair of independently controlled electrohydraulic displacement controlled spool valves for controlling cylinder-to-tank fluid flow between the control ports and an outlet port. The spool valves of the independent metering valve are calibrated to provide the required fluid flow.

Abstract: In machines having a bucket that is capable of carrying a load of material, it is well known that when the machine encounters a bump or other obstacle that the effects thereof may result in a shock or jolt being subjected to the machine due to the sudden change in forces acting on the actuator of the lift mechanism. In the subject invention, an accumulator arrangement is connected through a first valve mechanism to the loaded end of an actuator to provide a cushion or damping of the sudden changes in the forces. The first valve mechanism controls the magnitude of the damping in response to the rate of flow between the actuator and the accumulator arrangement. This is accomplished by sensing the pressure drop across a flow restriction mechanism located upstream of the first valve mechanism and controlling the degree of fluid communication between the actuator and the accumulator arrangement in response thereto.

Abstract: A method and apparatus for providing control of multiple actuators with a single control lever is provided. The method and apparatus is adapted for use in an electro-hydraulic system having a microprocessor, multiple actuators, respective electro-hydraulic directional control valves for each actuator, and individual control levers operatively associated with the microprocessor for controlling movement of the respective electro-hydraulic directional control valves. The method and apparatus is accomplished by providing a switch on each of the control levers that is operational to condition the microprocessor to direct simultaneous signals to the respective electro-hydraulic directional control valves to control each of the multiple actuators in proportion to the degree of movement of the one actuator when the switch thereon is depressed.

Abstract: A method is provided for controlling the bounce of a work implement attached to a machine having an electro-hydraulic system. The method comprises the steps of sensing the operating pressure in an actuator arrangement connected between the frame of the machine and the work implement, monitoring an upper and a lower operating pressure level in the actuator arrangement to establish a threshold pressure level and altering the pressure level in the actuator arrangement in the event the threshold level is exceeded to re-establish the threshold pressure level. Once the original threshold level is attained, the system is reset. This effectively eliminates the bounce of the work implement at the initial onset of the bounce and resets the system to react to future bounces.

Abstract: An apparatus and method for controlling a variable displacement motor of a hydrostatic transmission is provided. The apparatus includes an engine, and a hydraulic pump mechanically coupled to the engine. The variable hydraulic motor includes an output shaft. The apparatus monitors rotational speed of the output shaft. The apparatus and method control motor displacement and detect and/or predict the occurrence of an overspeed condition. The displacement of the motor is modified if an overspeed condition is predicted and/or detected.