Refrigeration – Processes – Defrosting or frost inhibiting
Reissue Patent
2000-04-27
2002-04-09
Tapolcai, William E. (Department: 3744)
Refrigeration
Processes
Defrosting or frost inhibiting
C062S199000, C062S217000, C062S255000
Reissue Patent
active
RE037630
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the commercial refrigeration art, and more particularly to improvements in food product merchandisers and temperature control systems therefor.
2. Description of Prior Art
Great advances have been made in the last forth years in the field of commercial food merchandising with the improved insulation materials, better refrigerants, more efficient air handlers and condensing unit systems, better lighting and the universal use of ambient air temperature and humidity control in food stores and the like. A long checklist of important factors influence the construction and manufacture of food merchandisers including refrigeration requirements and performance, structural engineering for strength, durability and safety as well as insulation effect, servicing capability, product merchandising potential, and both manufacturing and operating costs.
In today's marketplace a wide variety of food merchandisers are used to best market different types of food products as well as meet their cooling needs. In the low temperature field, frozen food merchandisers maintain product display temperatures at about 0° F. and ice cream cases operate at about −5° F. to −10° F. Frozen foods are best protected in reach-in coolers (with glass front doors), but open front, multi-deck merchandisers best display various food products. Similarly, in the medium temperature field of 28° F. to 50° F. product temperature range, glass front deli merchandisers are generally preferred for the marketing of freshly cut meats, cheeses, salads and other deli items, but open front multideck merchandisers are widely used for packaged meat and dairy products and single deck cases are preferred for fresh produce. Thus, even with some industry standardization at eight (8′) foot and twelve (12′) foot lengths for merchandisers, the manufacture of each commercial refrigerator fixture has remained in hand built operation.
In the past, most commercial merchandisers have utilized evaporator coils of the fin and tube type, which extend the full length of the merchandiser to best achieve uniform air cooling from end-to-end throughout the length. In some applications the evaporator coil was divided into two or more full length sections connected in series refrigerant flow relationship and typically arranged in tandem in the bottom section and/or immediately adjacent in the lower back wall of the merchandiser cabinet. Such coils and the control valving therefor were generally accessible only from the inner lower well area of the product zone for maintenance or service. Furthermore, although such a location does not interfere with the structural soundness of a coffin-type merchandiser, it has been discovered that a back wall evaporator coil location limits the structural support capability for internal vertical frames in multi-deck merchandisers, and the cantilever suspension of glass front panels in a deli merchandiser. The commonly assigned co-pending application Ser. No. 08/057,980 of Michael Grassmuck discloses improvements in hinging and structural supports for glass front panels for deli and reach-in merchandisers, and accommodated the development of the air cooling and control system of the present invention.
Also in the past, pressure regulating valves have been interposed in the evaporator-to-compressor suction line to regulate the refrigerant vapor out-flow from the evaporator coil and for the purpose of establishing and maintaining a certain evaporator suction pressure (relative to the compressor) and producing a corresponding saturated refrigeration temperature within the evaporator coil. One class of these valves have generally only been responsive to the evaporator pressure, or the pressure differential between the evaporator and the compressor—and, additionally, many prior art valves have been controlled by a second pilot valve. Representative of such prior art are:
Hanson U.S. Pat. No. 3,303,664
Another class of back pressure regulating valves have been responsive to temperature—as it affects pressure sensors and triggers pressure responsive diaphragm control of a valve element. Representative of such valves are:
Quick U.S. Pat. No. 3,316,731
Another class of evaporator pressure regulating valves have been designed to be responsive to both temperature and pressure acting through a pilot valve. Representative of this class are:
Pritchard U.S. Pat. No. 2,161,312
Dube U.S. Pat. No. 2,401,144
Boyle U.S. Pat. No. 2,993,348
Miller U.S. Pat. No. 3,242,688
SUMMARY OF THE INVENTION
The invention is embodied in an air cooling and control system for a refrigerated food merchandiser having an insulated cabinet with a product zone, plural modular evaporator coil sections of substantially equal heat exchange potential and being of predetermined length and arranged in horizontal, spaced, predetermined disposition, first refrigerant metering means for controlling liquid refrigerant flow on the high (inlet) side of the evaporator sections, second refrigerant metering means for controlling suction pressure and refrigerant vapor flow on the low (outlet) side of the evaporator sections, and electronic control means sensing exit air temperatures downstream of the evaporator sections and operating the second metering means in response thereto. The invention is further embodies in the method of operating an electronic evaporator pressure regulating (EEPR) valve during the refrigeration and defrost modes of the controlled evaporator and in response to sensed air temperatures.
It is a principal object of the present invention to provide a novel modular evaporator coil that facilitates modular design and fabrication of different refrigerated fixtures, that provides increased coil capacity with a smaller coil size having a reduced refrigerant charge and improved efficiency; that produces better product temperatures; that eliminates return bends and evaporator coil joints and minimizes refrigerant leaks; that can be used in multiple, parallel-piped sections with one or more liquid metering controls; that is responsive to both liquid and suction controls; and that accommodates ease of manufacture, installation and service. Another feature of the invention is in controlling the operation of commercial refrigerator evaporators to maintain preselected food zone temperatures at substantially constant values. Another object is to provide an EEPR valve for suction control of the associated evaporator means during refrigeration and defrost modes and in response to sensed and projected exit air temperatures. Still another object is to provide an improved apparatus and control strategy for regulating the suction pressure of refrigeration evaporators to achieve operating temperatures and maintain exit air and display zone temperatures. These and still other objects and advantages will become more apparent hereinafter.
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pat
Heywood Richard G.
Hussmann Corporation
Tapolcai William E.
LandOfFree
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