Low refrigerant charge detection using thermal expansion valve stroke measurement
First Claim
1. A thermal expansion valve comprising:
- a casing;
a valve stem disposed in said casing which is movable in a longitudinal direction; and
a switch having first and second states, wherein said switch changes from said first state to said second state whenever said valve stem reaches full stroke.
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Accused Products
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.
93 Citations
24 Claims
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1. A thermal expansion valve comprising:
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a casing; a valve stem disposed in said casing which is movable in a longitudinal direction; and a switch having first and second states, wherein said switch changes from said first state to said second state whenever said valve stem reaches full stroke. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A low refrigerant charge detection circuit for a refrigeration system including a compressor and a thermal expansion valve having a casing and a valve stem which is movable in a longitudinal direction, said circuit comprising:
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a first contact mounted on said casing; and a second contact mounted on said valve stem and aligned with said first contact in the longitudinal direction, said second contact being movable between a first position contacting said first contact and a second position not contacting said first contact, said first and second contacts being relatively positioned so that said second contact changes position whenever said valve stem reaches full stroke. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of determining low refrigerant charge in a refrigeration system having a thermal expansion valve having a movable valve stem, said method comprising the steps of:
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monitoring the position of the valve stem; and producing a signal in response to said valve stem reaching full stroke. - View Dependent Claims (22, 23, 24)
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Specification