Patent ID: 6223790
Filing Date: 2001-05-01
Classification: F01M,F16H

Abstract:
A method of exchanging fresh fluid from a fresh fluid source for used fluid from an accessed hydraulic fluid circuit having an outlet port and an inlet port, said method comprising the steps of:providing a pump assembly having a pump body and a movable pump member disposed relative the pump body, said pump assembly defining at least a first and a second working chamber each having a port for communicating with the used fluid and at least a first and a second pumping chamber each having a port for communicating with the fresh fluid;providing a control structure in communication with the fresh fluid and the used fluid and the pump assembly, said control structure having at least a first control condition and a second control condition;for a first predetermined period of time, providing the control structure in the first control condition, wherein the first working chamber is fluidly coupled to the outlet port of the accessed hydraulic circuit, and the second working chamber is fluidly coupled to a used fluid receptacle, and the second pumping chamber is fluidly coupled to the fresh fluid source, and the first pumping chamber is fluidly coupled to the inlet port of the accessed hydraulic fluid circuit, thereby providing a flow of used fluid from the outlet port of the accessed hydraulic circuit into the first working chamber, a flow of used fluid from the second working chamber into the used fluid receptacle, a flow of fresh fluid from the fresh fluid source into the second pumping chamber, and a flow of fresh fluid from the first pumping chamber into the inlet port of the accessed hydraulic circuit;after said first predetermined period of time, providing the control structure in the second control condition for a second predetermined period of time, wherein the second working chamber is fluidly coupled to the outlet port of the accessed hydraulic circuit, and the first working chamber is fluidly coupled to the used fluid receptacle, and the first pumping chamber is fluidly coupled to the fresh fluid source, and the second pumping chamber is fluidly coupled to inlet port of the accessed hydraulic fluid circuit, thereby providing a flow of used fluid from the outlet port of the accessed hydraulic circuit into the second working chamber, a flow of used fluid from the first working chamber into the used fluid receptacle, a flow of fresh fluid from the fresh fluid source into the first pumping chamber, and a flow of fresh fluid from the second pumping chamber into the inlet port of the accessed hydraulic circuit;after said second predetermined period of time, establishing a cycle by returning the control structure to the first control condition for said first predetermined period of time; andrepeating the cycle to achieve the fluid exchange.