A hydraulic system may include multiple hydraulic loads, each of which may have different flow and pressure requirements that can vary over time. The hydraulic system may include a pump for supplying a flow of pressurized fluid to the hydraulic loads. The pump may have a variable or fixed displacement configuration. Fixed displacement pumps are generally smaller, lighter, and less expensive than variable displacement pumps. Generally speaking, fixed displacement pumps deliver a definite volume of fluid for each cycle of pump operation. But depending on the configuration of the pump and the precision with which the pump is manufactured, the flow output of the pump may actually decrease as the system pressure level increases due to internal leakage from the outlet side to the inlet side of the pump. The output volume of a fixed displacement pump can be controlled by adjusting the speed of the pump. Closing or otherwise restricting the outlet of a fixed displacement pump will cause a corresponding increase in the system pressure. To avoid over pressurizing the hydraulic system, fixed displacement pumps typically utilize a pressure regulator or an unloading valve to control the pressure level within the system during periods in which the pump output exceeds the flow requirements of the multiple hydraulic loads. The hydraulic system may further include various valves for controlling the distribution of the pressurized fluid to the multiple loads.
USPTO Backgrounds
USPTO Backgrounds