| 摘要 |
A two-way thermally activated valve is configured within a valve body having a bore therethrough which communicates with an inlet port, an outlet port and an exhaust port. A valve spool is disposed within the bore. The valve spool has a relieved portion which permits continual communication between the inlet port and outlet port regardless of the position of the valve spool. When the valve spool is in a first mode, the exhaust port is in communication with the bore and, when the valve spool is a second mode, the exhaust port is blocked. Since the inlet and outlet ports are never blocked, pressure builds at the outlet port as the exhaust port closes. The valve is shifted from the first position to the second position as a thermally expandable wax element pushes the spool axially against the bias of a coil spring. The two-way thermally activated valve is used to cause high pressure fluid to operate a fan driven by a hydraulic motor when the exhaust port of the valve is closed by allowing the high pressure fluid to flow to the tank only as exhaust from the motor when the temperature level is sufficient to expand the wax plug. When the wax plug is unexpanded because the oil is cooled, the oil flows through the exhaust port of the valve to tank and, therefore, does not allow sufficient pressure to build in the outlet port of the valve to drive the motor.
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