Patent ID: 7540299

Claim:
Apparatus for cooling a clutch of a motor vehicle, said apparatus comprising: a unitary valve having a housing through which a coolant circuit is coupled with a pump circuit, wherein the valve includes a unitary control piston that is movable within the housing at least a distance sufficient to effectuate a connection between the coolant circuit and the pump circuit, wherein the control piston includes first and second opposite ends and only first, second, and third axially spaced cylindrical sections between the first and second opposite ends and that are operative with respect to respective connection conduits located in the valve housing for controlling flow through the valve to and from the coolant circuit and the pump circuit; a first connection conduit provided in the valve housing as a supply conduit of the pump circuit and with which the first cylindrical section of the control piston is operatively associated: a second connection conduit provided in the valve housing as a return conduit of the coolant circuit and with which the second cylindrical section of the control piston is operatively associated: a third connection conduit provided in the valve housing and operative as a first supply conduit of the coolant circuit, and a fourth connection conduit provided in the valve housing and operative as a second supply conduit of the coolant circuit, wherein the third cylindrical section of the control piston is operatively associated with the third connection conduit; wherein the second cylindrical section of the control piston has a diameter that is smaller than a diameter of each of the first and third cylindrical sections of the control piston and is positioned between the first and the third cylindrical sections; and wherein transition regions between the second cylindrical section and the first and third cylindrical sections have a rounded shape.