Patent ID: 7222640

Claim:
A method of controlling a fluid flow by a three way valve having; (a) an inlet port, (b) first and second outlet ports, (c) a first configuration in which the valve substantially provides a path for fluid flow between the inlet port and the first outlet port but not between the inlet port and the second outlet port, (d) a second intermediate configuration in which the valve provides respective paths for fluid flow between the inlet port and each of the first and second outlet ports; and (e) a third configuration in which the valve substantially provides a path for fluid flow between the inlet port and the second outlet port but not between the inlet port and the first outlet port, the method including the following steps performed sequentially in the order (f) to (l); (f) connecting the inlet port of the three way valve to a source of primary fluid at a first pressure and configuring the three way valve in the first configuration to permit the primary fluid to flow into the inlet port, through the three way valve and out from the first outlet port, (g) connecting a supply of auxiliary fluid at a second pressure to the second outlet port, (h) configuring the three way valve in the second intermediate configuration, (i) discontinuing said supply of auxiliary fluid connected to said second outlet port and connecting a supply of auxiliary fluid at a third pressure to the first outlet port, (j) permitting the primary fluid to flow into the inlet port, through the three way valve and out from the second outlet port, (k) preventing the flow of primary fluid out from the first outlet port by configuring the three way valve in the third configuration, and (l) discontinuing said supply of auxiliary fluid connected to said first outlet port, wherein the second and third pressures are higher than the first pressure, and the primary fluid flow into the inlet port, through the three way valve and out from at least one of the outlet ports is substantially continuously maintained during performance of the above-mentioned steps.