Importance

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Abstract

Low refrigerant charge is detected in a refrigeration system under thermal expansion valve control with a valve stem stroke measurement switch. The switch includes a first contact mounted on the valve stem of the thermal expansion valve and a second contact mounted on the valve casing. The two contacts are aligned in the direction of valve stem motion and are relatively positioned so as to be normally closed but to open when the valve stem reaches its full stroke position. At least one of the contacts is mounted to its respective structure by a flexible member to accommodate the motion of the valve stem. The switch is connected to the compressor clutch to deactivate the compressor when opened. A timer can be provided to delay deactivation of the compressor in instances where the valve stem is just momentarily at full stroke. Alternatively, the valve stem stroke measurement switch can be configured to be normally open but to close at full stroke, or the switch can include three contacts in which a first contact engages one of other contacts at full stroke and engages the remaining contact when the valve stem is not at full stroke.

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First Claim