Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-07-14
2001-07-31
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S179000, C062S225000, C062S526000
Reexamination Certificate
active
06266968
ABSTRACT:
REFERENCES
1. U.S. Pat. No. 5,406,805
2. U.S. Pat. No. 4,459,819
TECHNICAL FIELD
The invention is in the field of vapor compression refrigeration. It is a refrigerator that will efficiently cool multiple cold spaces using only one compressor and one condenser, each cold space being cooled to and maintained at a temperature that can be set by the user.
BACKGROUND ART
The present invention fundamentally improves a refrigerator described in Ref. 1, which uses one compressor, one condenser, and separate thermally insulated freezer and fresh food compartments, each with its own evaporator. As described in Ref. 1, two evaporators are in series, and each is equipped with a fan, which, if not energized, greatly reduces heat transfer to its associated evaporator. Thus, the evaporators may be individually “activated” by energizing one fan and turning off the other. The method disclosed in Ref. 1 advantageously uses a transient effect that occurs in any vapor compression refrigerator in which the refrigerant charge, the bulk of which is in the condenser at high pressure while the compressor is running, is allowed to flow into the low pressure evaporator while the compressor is stopped. The result of such migration of refrigerant is warming of the evaporator, and when the compressor restarts, there is a transient time interval, typically two or three minutes, when the evaporator and the refrigerant it contains are too warm to efficiently cool the cold space. According to Ref. 1, the evaporator of the fresh food evaporator is activated and that of the freezer de-activated during the transient time interval. Since the fresh food compartment is typically about 35F warmer than the freezer, it can be cooled efficiently during the transient time interval.
BRIEF DESCRIPTION OF THE INVENTION
As in prior art Ref. 1, the invention uses one compressor, one condenser, and more than one evaporator, each evaporator being equipped with a fan. However, the present invention does not use the transient effect that, as previously described, is the basis for the method of Ref. 1. Indeed, the transient effect method of Ref. 1 is purposefully prevented in the present invention in order to reduce stop-start loss, by blocking charge migration from condenser to evaporator during compressor-off periods. The present invention uses multiple series evaporators and an expansion valve responsive to superheat measured from the series evaporator inlet to its outlet. The expansion valve automatically adjusts refrigerant flow to match heat transfer from the active evaporator, thus maximizing efficiency regardless of which evaporator is active, and at any condenser pressure within normal limits. Although Ref. 1 refers to an expansion valve (pg. 3, line 50-51, pg. 4, line 25, claims 7 and 13) as an optional alternative to a capillary tube, such references are, in each case, to application of an expansion valve in a multiple evaporator refrigerator based on the transient effect previously described. In the present invention, the transient effect is deliberately avoided to reduce stop-start loss.
If the expansion valve shuts during compressor-off periods, stop-start losses due to charge migration are reduced but pressure equalization of condenser and evaporator pressures is prevented, which may, at ambient temperatures above a certain temperature, cause the compressor motor to overload during restart because of high discharge pressure. To reduce stop-start loss but avoid motor overload, an expansion valve according to the invention may be controlled so that, during compressor-off periods, it shuts only at ambient temperatures low enough to allow the compressor motor to restart without overload.
The number of fan activated series evaporators according to the invention is not limited to two, but may be any integer equal to or greater than two.
According to the invention, the fans that activate each of the multiple evaporators may be controlled so that a particular evaporator fan is only energized if the temperature of the chamber in which it is located is higher than both a set point temperature and the temperature of the series evaporator, thus ensuring that colder compartments are not warmed during refrigeration of warmer 4 compartments.
According to the invention, the compressor motor may be controlled so that it is only energized when at least one evaporator fan is energized.
REFERENCES:
patent: 2026838 (1936-01-01), Koepke
patent: 2133959 (1938-10-01), Buchanan
patent: 2515825 (1950-07-01), Grant
patent: 4459819 (1984-07-01), Hargraves
patent: 5150583 (1992-09-01), Jaster et al.
patent: 5406805 (1995-04-01), Rademacher et al.
Bright Debra A.
Kremblas, Foster Phillips & Pollick
Tanner Harry B.
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