US 2923135 A
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Description (OCR text may contain errors)
Feb. 2, 1960 J. J. PREOTLE OPEN TOP REFRIGERATOR DISPLAY CASE Filed NOV. 23, 1956 2 Sheets-Sheet 1 INVENTOR. 1/0/12; 4/. Preozle Hi5 ATTORNEY Feb. 2, 1960 J. J. PREOTLE OPEN TOP REFRIGERATOR DISPLAY CASE 2 Sheets-Sheet 2 Filed Nov. 23, 1956 INVENTOR. Jolm J. Preofle $4M we Hi5 ATTORNEY United States Patent OPEN TOP REFRIGERATOR DISPLAY CASE John J. Preotle, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application November 23, 1956, Serial No. 623,919 6 Claims. (Cl. 62-157) This invention relates to refrigerating apparatus and more particularly to an open-top refrigerated display case.
One of the big problems in designing an open-top refrigerated display case is that of preventing the accumulation of frost within the open-top storage compartment. Another problem is that of removing frost from the evaporator which cools the air in the storage compartment without unduly increasing the temperature within the storage compartment.
It is an object of this invention to provide an improved arrangement wherein a first refrigerating system continuously refrigerates the walls of the storage compartment and wherein a second refrigerating system, which may be cycled for defrosting purposes, is provided with an overhead evaporator for supplying refrigerated air into the food storage compartment in a manner to prevent the accumulation of frost in the food storage compartment.
Another object of this invention is to provide a simplified control arrangement for the refrigeration equipment.
Still another object of this invention is to provide a novel arrangement of condensers whereby the condenser which supplies refrigerant to the coldest of two evapora tor coils is cooled to a lower temperature than the condenser which supplies refrigerant to the other of the coils.
Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.
In the drawings:
Figure 1 is a vertical sectional view showing the construction and arrangement of a display cabinet constructed in accordance with this invention;
Figure 2 is a horizontal sectional view taken substantially on line 2-2 of Figure 1 and with portions of the condensers broken away;
Figure 3 is a perspective view of a cabinet constructed in accordance with this invention; and
Figure 4 is a fragmentary sectional'view showing the arrangement for holding the defrost heater in place.
Referring now to the drawing, wherein a preferred embodiment of the invention has been shown, reference numeral 143 generally designates an open-top display cabinet of the type which may be used for storing and displaying such products as ice cream and the like which require constant low temperature refrigeration. This cabinet includes a storage compartment 12, a machinery compartment 14 located below the storage compartment 12, and an overhead cooling compartment 16 which is arranged in the upper rear hood or superstructure portion of the cabinet. The compartment 12 consists of an inner liner or tank 20 which is made of metal and which has wrapped therearound refrigerant coils 22 which'serve to refrigerate the liner 20 and consequently the contents of the compartment 12. The bottom, side and end walls.
are surrounded by insulation 24 in accordance with conventional practice.
The coils 22 which serve to refrigerate the walls of the compartment 12 are preferably maintained at a tem-' perature of 30 F. and are supplied with refrigerant from a refrigerant liquefying unit disposed within the machinery compartment 14. This refrigerant liquefying. unit consists of a conventional sealed motor-compressor: unit 26 which is adapted to withdraw vaporized refrigerant from the cooling coil or evaporator 22 and to discharge compressed refrigerant into a condensing coil 28. The flow of liquid refrigerant into the evaporator is controlled by a fixed restrictor 29. The elements 22, 26, 28 and 29 form parts of a conventional refrigeration system which is adapted to operate continuously so as to at all times maintain the walls of the compartment 121 refrigerated.
An insulated hood or super structure 30 overlies the upper rear portion of the compartment 12 so as to form the compartment 16 in which there is disposed a second evaporator 32 which extends the full length of the food compartment and is adapted to be operated at a tem- 2 of the drawings. The flow of refrigerant to the evaporator coil 32, which is arranged for gravity air flow thereover, is controlled by means of an automatic expansion valve 38 which functions in its usual manner to control the flow of liquid refrigerant to the evaporator 32.
The evaporator coil 32 is so arranged with respect to the food storage compartment that a cold blanket of curtain of dry air flows downwardly and forwardly over the products stored in the compartment 12, as indicated by the arrows in Fig. 1 of the drawing. A baffle 42 has been provided adjacent the front edge of the coil 32 so as to form an air return passage 44 at the front of the coil 32 and behind the lamp housing 46, as shown. A condensate drain receptacle 48 is arranged directly beneath the coil 32 for collecting defrost water when the coil 32 is defrosted and for directing the refrigerated air leaving the coil 32 forwardly, as indicated by the arrows. A conventional condensate drain 50 has been provided for draining the condensate water to a point outside the cabinet, in accordance with conventional practice. 3
The gravity air flow coil 32 is purposely operated at a lower temperature than the coil 22 whereby the air leaving the coil 32 and flowing forwardly over the storage compartment will be very dry, whereby it will readily pick up incoming moisture so as to prevent the incoming moisture from depositing on the walls of the tank or liner 20. It has been found that gravity flow can "be relied on for causing the desired circulation of air over the coil 32 and forwardly of the food storage compartment.
An insulating panel 60 which is preferably made of plastic or any other type of material having a low coefiicient of heat transfer, is provided at each end of the Patented Feb. 2, 1960 food storage compartment 12 adjacent the-atop. opening, as shown in Fig. 1 so as to preventexcessive conduction of heat from the upper edge of the tank 20 toward the upper edge of the open top of the cabinet. This reduces the tendency of frost to collect on the upper edges of the end walls of the cabinet. A single glass panel 62 is provide'd adjacent. the upper v front portionof: the cabinet} as shownninFig. l, for directing the refrigerated air away from the front multiple glass panel 64.
Asbest shown in Fig. l ofthe drawings, the condenser 36uwhichsupplies condensed refrigerant to the low temperature evaporator 36 is located above they condenser 28 which supplies condenser refrigerant to the higher temperature evaporator coil 22. The air for. cooling thecondensers 36 .and zslentersthelcabinet through ail-opening 70...wherein there is located a fanu72 for forcefully pulling air intothe condensingcompartrnent. This air is required. to flow. down through thecondensers; 36and 23, asindicated by the arrows in Figs; 1 and2, and leaves the machinery. compartment 14 through outlets 7.4. By virtue of this arrangement it is obvious thatthe coldest incoming'air. contacts the condenser 36 .before contacting thecondenser 28, and that afterthe air leaves the condenser 28=at portion flows out overthe compressor 26 and anotherportion flows. out over thecompressor 34.
The refrigerator cabinet has incorporated therein-the usual low temperature, strip heaters or resistance wires 76 which serve to warm the surfaces adjacent the top opening and also the front glass panel 64 so as toprevent condensation at these points, in accordance with well knownpractice.
There is a tendency for some intermingling of room air with the refrigeratedair in the upper portion of the food storage compartment and the resulting mixture of air tendsto be pulled rearwardly into the-fiue-like passage 44Tand then deposits its excess. moisture on the coil 3.2, hefore flowing over the packages stored in the compartment 1 2. This results in an accumulation of frost on the coilfil which is preferably removed periodically.- For thispurpose, atimer; 80 (see Fig.2) servesto close a defrost heater switch 82 once every twenty-four'hours, and to open the'motor control switch, 83 which stops thg motor compressor unit "34. The switch 82, energizes a. h eater,84 attached to;the lower edges of the fins and-the coil 32 so as to melt the frost on the coil.
A portion of the defrostheater 84.1ies in the defrost water drain pan 48 so as toprevent the defrost water from freezing in the pan 48. A safety thermostat 86 located on the coil 32 serves to open the circuit to the defrost heater when the temperature of thecoil 32 exceeds a predetermined temperature such as 34 P. so as to prevent operation of the heater after the frost has.
all been melted.
As best shown in Fig. 4, the defrost heater 8,4 is held in place within slots 88 formed in the bottom edges of the coil fins. After the heater 84 has been inscrtedin the slots, thefiange material 90 which is left next to the slot when making the slot, is bent so as to hold the heater in firm contact with the fins.- The motor-compressor unit 26 operates continuously and thereforeserves to supply refrigeration to the walls of the tank or inner liner 20 even during the defrosting f the evaporator coil 32. The motor-compressor unit 34 is under control of a switch 92 operated by a-therrnostat 94 located on the suction line 96 which leads from the evaporator 32 to the motor-compressr unit. This switch 92 stops the unit 34 whenever liquid refrigerant starts returning to the compressorin accordance with well-known practice, but this-does notstop the coil 32 from functioning tocoolthe air whichforms the-air curtain at the inlet to the food comparment.
While the form; of embodiment ofthe invention as herein disclosedconstitutes a; preferred form, itis .to be understood that, other forrr1 s,might, be;;adopted, as-may come within the scope of the claims which follow,
. operate. continuously, and controlmeans for operating said second expansion coil at a lower temperature than said first expansion coil including means for starting and stopping the flow of liquid refrigerant to said second expansion coil so as to cyclically cause defrosting of said second expansion coil while saidfirst expansion coil continues to refrigerate said display chamber.
2. A refrigerated display case having a lower display chamber and an upper chamber in communication therewith, a first expansion coil arranged to cool the contents of said lowerchamber, a second expansion coil arranged to cool air. insaid upper chamber, control means. arranged to operate said second coil at a lower temperature thansaid first coil, afirst continuously operating refrigerant liquefyingmeans supplyingtliquid refrigerant to said first expansion coil, and a, second intermittently operating refrigerant liquefyingrneans supplying refrigerant to said second expansion coil,
3. Refrigerating apparatus comprising an open top display case having a front wall, a bottom wall, two end walls, and .a, backwall, said, Walls enclosing an open-top storage compartment ofsubstantially rectangular cross section, said back wall extending up. substantially above the open top of saidcompartment, a first evaporator disposed adjacent the upper portion of said back wall, a thermal insulating hood overlying said evaporator mem: her, said hood opening downwardly into said storage compartment, afirst refrigerant liquefying means, inter: mittently supplying refrigerant to said firstevaporator, a second evaporator arranged; tocool thecontents of said storage compartment and a second refrigerant liquefying means continuously supplying liquid refrigerant tosaid second evaporator.
4. An open-top refrigerated display cabinet for ice creamandthe likecomprising, aframe including insulated'walls forming a product receiving chamber having an open top, means defining an upper chamber having an open bottom communicating with said product receiving chamber, a first refrigerating system supported on said frameand including a first evaporator arranged to refrigerate air within said upper chamber, a second refrigerating System supported on said frame and including a second evaporator arranged to cool the .contents of said product receiving chamber, the relative cooling capacities of said systems being such as to cool the air in the-1 upper chamber to a lower temperature than the temperature in the product receivingchamber;
5. An open-top refrigerated display cabinet for ice cream and the like comprising, a frame including insulated walls forming a product receiving chamber havingan opentoomeans defining an upper chamber having an open bottom communicating with said product receivingchamber, Ya first refrigerating system including a first evaporator arranged to refrigerate air within said upper'chamber, afsecond refrigerating system including a second evaporator arranged to cool the contents of said product receiving chamber, the relative cooling capacities of said systems being such as to cool the air in the upper chamber'to a lower temperature than the temperaturein the product receiving chamber, and means for defrosting said first evaporator. i i
6; An open-top refrigerated display cabinet for ice cream and the like comprising, a frame including insulated walls forming -a-product 'receiving chamber liav mg an open top, means defining an upper chamber having an open bottom communicating with said product receiving chamber, a first refrigerating system including a first evaporator arranged to refrigerate air within said upper chamber, a second refrigerating system including a second evaporator arranged to cool the contents of said product receiving chamber, the relative cooling capacities of said systems being such as to cool said first evaporator to a lower temperature than the temperature of said second evaporator, means for defrosting said first evaporator including means for stopping the operation of said first refrigerating system while continuing the sup ply of refrigerant to said second evaporator.
UNITED STATES PATENTS Anstey Aug. 3, 1926 Knapp Nov. 6, 1934 Ehrlich May 5, 1936 Davis Nov. 4, 1947 Davis July 6, 1948 Brill Sept. 12, 1950 Hoye June 9, 1956 Simmons July 24, 1956 Wallenbrock Oct. 23, 1956