Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-03-31
2001-11-27
Walberg, Teresa (Department: 3742)
Refrigeration
Automatic control
Refrigeration producer
C062S126000, C062S230000
Reexamination Certificate
active
06321548
ABSTRACT:
DESCRIPTION
1. Field of Invention
This invention relates generally to cooling systems, such as comfort cooling and refrigeration systems, and in particular to apparatus for closing a refrigerant expansion valve used in such cooling systems in response to a loss of system electrical power.
2. Background Art
Space cooling systems, including both comfort cooling and refrigeration systems, typically include an evaporator in heat exchange relationship with a space to be cooled, a condenser external to the space, a compressor for circulating a heat transfer medium (e.g., a phase change refrigerant) between the evaporator and the condenser, and an expansion valve located between the condenser outlet and the inlet to each evaporator. The expansion valve is positionable at various positions between fully opened and fully closed to regulate the flow rate of the heat transfer medium through the evaporator. An indoor fan is typically included to provide air flow across the evaporator and outdoor fan is provided for cooling the condenser.
In some cooling systems, an electrically operable solenoid valve is located between the condenser outlet and the expansion valve. The solenoid valve typically includes a spring which biases the solenoid valve toward a closed position in the absence of electrical power being supplied to the solenoid valve. In the event of a loss of electrical power to the cooling system, the spring closes the solenoid valve to prevent migration of refrigerant in the system.
In other types of cooling systems, however, there is no solenoid valve to help prevent refrigerant migration after a loss of electrical power. In such cases, the expansion valve will usually remain in the same position as it was when power was lost. Therefore, unless the expansion valve was fully closed at the time that power is lost, refrigerant may migrate in the system through the open expansion valve, which can cause damage to the compressor upon restart when electrical power is restored.
There is therefore a need for an improved apparatus for preventing refrigerant migration in a cooling system when there is a loss of electrical power.
SUMMARY OF INVENTION
In accordance with the present invention, apparatus is provided for automatically closing an electrically operable expansion valve located between an outlet side of a condenser and an inlet side of an evaporator in a cooling system, in response to a substantial loss of electrical power. The apparatus comprises a capacitor coupled to an electrical power source for being charged by the power source, a regulator intermediate the power source and the capacitor for regulating voltage across the capacitor within a predetermined limit, a detector for detecting a substantial loss of electrical power from the power source and for generating an electrical signal indicative thereof, and a controller responsive to the electrical signal for generating a control signal to control an electrically operable device to close the expansion valve. The capacitor is operable to automatically discharge in response to a substantial loss of electrical power to provide electrical power to the controller and to the electrically operable device to close the expansion valve.
In accordance with one embodiment of the invention, the regulator is comprised of a booster power supply for maintaning voltage across the capacitor within the predetermined limit when electrical power is being supplied from the power source. In the preferred embodiment, the booster power supply includes a switching regulator and an inductor for storing electrical current.
In accordance with a feature of the invention, the apparatus includes another regulator for maintaining voltage supplied to the controller within another predetermined limit. The other regulator is intermediate the capacitor and the controller, such that when said capacitor discharges in response to a substantial loss of electrical power from the power source, the other regulator is operative to maintain the voltage input to the controller within the other predetermined limit.
In accordance with another feature of the invention, the apparatus further includes a driver device electrically coupled between the controller and the electrically operable device. The driver device is operative in response to the control signal from the controller to supply power to operate the electrically operable device to close the expansion valve. In the preferred embodiment, the electrically operable device is a step motor, which is operable to open and close the expansion valve in predetermined increments, whereby the expansion valve is positionable in various positions between fully opened and fully closed.
In accordance with the present invention, improved apparatus is provided for automatically closing a cooling system expansion valve in response to a loss of system electrical power without the need for an electrically operable solenoid device. By closing the expansion valve upon loss of system electrical power, refrigerant migration in the system after power loss is substantially inhibited.
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Clarke Raynald C.
Cornish David R.
Dahbour Fadi H.
Heatcraft Inc.
McCord W. Kirk
Walberg Teresa
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