Patent ID: 7089733
Filing Date: 2006-08-15
Classification: F15B,G05D

Abstract:
1. In a hydraulic system having a control valve which controls flow of fluid from a source to a workport connected to a hydraulic actuator, an apparatus for controlling pressure of the fluid supplied to the control valve, wherein the apparatus comprises: a first sensor producing a first electric signal indicating pressure at the workport; a second sensor which produces a second electric signal indicating the pressure of fluid supplied to the control valve; a hydraulic circuit node; a proportional control valve having an inlet for receiving fluid from the source and an outlet connected to the hydraulic circuit node, wherein the proportional control valve is operated by an electric signal applied to a control input; a controller connected to the first sensor and second sensor and having an output that is connected to the control input of the proportional control valve, wherein the controller operates the proportional control valve in response to the first electrical signal and the second electrical signal; and a mechanism which responds to pressure at the hydraulic circuit node by varying the pressure of fluid supplied to the control valve.