US 5,215,444 A · System for controlling oil viscosity and cleanliness

Abstract

A system for and a method of establishing and maintaining fluid at desired cleanliness, viscosity and temperature levels in a flow system. The system includes a driven pump that circulates fluid from a fluid source through a hydraulic loading system that includes an unloading valve. As fluid flows through the valve, a pressure drop is created across the valve operator, which restricts flow through the valve. This pressure drop across the valve operator results in the dissipation of heat, increasing the temperature of the fluid flowing through the valve. During operation of the system, if a low temperature condition is sensed in the system, power will be supplied to the pump, which pumps fluid through the valve at a controlled low pressure drop to result in a controlled heating of the fluid. When the fluid is restored to a desired temperature level, power to the pump is discontinued to terminate flow through the valve. The level of heat produced in the fluid may be adjusted by adjusting the degree that the pressure drops as the fluid flows through the valve. This is accomplished by adjusting the degree of the restriction to flow across the valve operator. Additionally, as fluid is circulated through the valve, at least a portion of the fluid is provided to a filter to provide a desired cleanliness level to the fluid.

Claims26

Dependent claims

A method of controlling the cleanliness of hydraulic fluid in a closed hydraulic system having a sump containing hydraulic fluid, a pump, a bypass valve having a valve operator for controlling the flow direction between a low pressure bypass path and a high pressure load path, comprising the steps of:

supplying power to the pump,
pumping high pressure fluid from the sump through the valve along the load path to a load,
advancing the valve operator to redirect flow through the valve to the bypass path,
pumping low pressure fluid from the sump through the valve along the bypass path and returning the fluid to the sump,
coupling a portion of flow through the valve along the bypass path to a filter assembly,
pumping a portion of the low pressure fluid flowing through the valve along the bypass path through the filter assembly, whereby the filter assembly can be constructed to handle only moderate pressures and flow rates, and
returning the fluid to the sump.

4 more elements

A flow system utilizing a bypass valve to control fluid cleanliness, comprising:

a fluid supply,
a pump which pumps fluid from the fluid supply,
the bypass valve having an inlet connected to the pump, a working outlet connected to a high pressure load, and a bypass outlet connected to the fluid supply,
the bypass valve having a loaded position in which fluid flow from the pump is directed to the high pressure load, and a bypass position in which fluid from the pump is directed to a lower pressure high flow rate bypass path for return to the sump,
a filter,
means for coupling the filter in the bypass path for receiving a portion only of the bypass flow to filter said portion and define a filtering path, the filtering path having a low working pressure about equivalent to the pressure in the bypass path and a flow rate lower than the full bypass flow rate, whereby the filter can be constructed to handle only moderate pressures and flow rates, while operating in a high pressure system,
the flow system having at least three operating conditions including:
an off state in which the pump is inactive,
a loaded state in which the bypass valve, after switching to the loaded position, directs fluid flow to the high pressure load, and
a filter state in which the bypass valve is maintained in the bypass condition for circulating and filtering the fluid.

7 more elements

Dependencies are inferred from the claim text.

System for controlling oil viscosity and cleanliness

Life of this patent

System for controlling oil viscosity and cleanliness

Life of this patent

Abstract

Claims26