US2529734A - Defrosting system in refrigerated locker - Google Patents

Description

Nov. 14, 1950 R. E. LEHMANN 2,529,734

DEFROSTING SYSTEM IN REFRIGERATED LOCKER Filed Feb. 18, 1947 J'nyen/ar Patented Nov. 14, 1950 DEFROSTING SYSTEM IN REFRIGERATED LOCKER Ralph E. Lehmann, Felton, Calif.

Application February 18, 1947, Serial No. 729,265

This invention relates to improvements in refrigeration, and particularly to refrigeration systems and methods operating at or below C.

Conventional refrigerating and freezing systems utilize expansion coils which are externally exposed to free air which air is constantly renewed through thermal or forced circulation. Particularl if the coils are operated at below freezing temperatures, they constantly extract moisture from the circulating air, the moisture freezes on the coils and gradually encrusts the coils with frost until the thickness becomes so great as to almost terminate transfer of heat. For this reason expansion coils must be frequently de-frosted. Any frost encrustation lowers the efficiency of the unit, and the relatively long time customarily required for de-frosting allows the temperature in the refrigerated compartment or room to rise considerably so that considerable power and time is again required to return the room to its prescribed temperature. Furthermore, the warmed air because of its increased temperature will take u a new supply of moisture which immediately starts to condense on the coils.

Thus, with the conventional refrigerating system, particularly where temperatures below freezing are normally maintained, hours may be required to de-frost the coils because no de-frosting occurs until the temperatures of coils and room 5 Claims. (Cl. 62-102) 2 can be almost exactly maintained, one which requires so relatively short a time for de-frosting as not to appreciably affect the room temperature, and because of de-frosting at below-freezing temperatures in the room re-humidification of the air cannot occur.

The system is suitabl for an and all types of refrigeration including conventional locker freezing installations, refrigerated packing house and meat market cold rooms and lockers, ice-cream and other frozen food freezers, and all similar installations.

The objects and advantages of the invention are as follows:

First, to provide a refrigeration system which is de-frostable at will under sub-freezing room temperatures.

Second, to provide a refrigerating system in which defrosting can be completed in a relatively very short time without transfer of heat to the room in which the refrigerating system is installed.

rise above 0 C. After de-frosting has been completed, the temperature of the room and coils must again be lowered to the normal operating temperature which again takes a considerable length of time. During the de-frosting period the air in the room has taken up a great deal of additional moisture which starts depositing in the form of frost on the coils as soon as the freezing point is reached, immediately reducing the efiiciency of the system and greatly shortening the periods between de-frostings. Thus there is an almost continuous sequence of humidification and de-humidification of the air, and regular room temperature changes.

My invention overcomes the above-mentioned disadvantages and provides a system which operates at the highest possible emciency, with defrosting rapidly carried-out, and with an entire absence of re-humidification of air because it is never necessary to allow the temperature of the room to rise to any noticeable degree, de-frosting being carried out irrespective of the room temperature, within a matter of minutes.

It thus provides a system of refrigeration which is dependable, one in which room temperatures Third, to provide a refrigerating system with selective refrigerating and heating means for quickly de-frosting the refrigerating means at will.

Fourth, to provide a refrigerating system in which the cooling coils and heating means are enclosed within a sealed cabinet and including forced air circulating means for continuously circulating the same body of air for uniform cooling to eliminate all frosting of the cooling coils, with the heating means manually controllable for defrosting the cabinet exterior through heat delivered from the interior of the cabinet.

Fifth, to provide a refrigerating system in which the cooling coils are sealed within an enclosure to eliminate all possibility of frosting of the coils.

Sixth, to provide a refrigerating system in which the cooling coils are mounted within a sealed enclosure containing a body of inert gas such as air and with the enclosure provided with forced circulating means, and with heating means, with the cooling coils and heating means individually controllable, with the entrapped body of gas limiting frosting of coils and interior surfaces of the walls of the enclosure to its moisture content, and with the exterior surfaces of the walls de-frostable at will by terminating operation of the cooling coils and initiating operation of the heating means.

Seventh, to provide a system as outlined in which the enclosure is provided with sealed recesses, open to the exterior for storage of pack- 3 ages or extreme cooling or freezing of selected products.

Eighth, to provide a system as outlined in which the enclosure includes a series of lockers with the spaces between the walls of the lockers forming circulator paths for the enclosed body of air.

In describing the invention reference will be made to the accompanying drawings in which:

Fig. 1 is a top plan view of the invention partly shown in section with the section corresponding to a line l--l of Fig. 2.

Fig. 2 is a front elevation of Fig. 1 and showing a portion with the doors removed and another portion in section to illustrate the interior construction.

Fig. 3 is a modification showing a unit for installation in a conventional cold room such as a refrigerator for meat markets and the like.

Figs. 4 and 5 are alternative sections taken on a line 4-4 of Fig. 3, one being a modification of the other.

Fig. 6 is an enlarged fragmentary section showing the double door seal and the sealing of the locker cans to the walls of the enclosure.

Fig. 7 is a fragmentary view showing the invention as adapted to display cases.

As is well known, the conventional refrigerating system consists of a compressor unit which umps the expanded gas, compresses and reliquifies the gas and delivers it to a cooling coil under control of a thermostat, the gas as released through the thermostatic control discharging and expanding in cooling coils or expansion chamber, the coils or expansion chamher being exposed to constantly changing air exteriorly, the cold de-humidified air escaping and fresh humid air entering the refrigerated space each time the door is opened. The exposed cooling coils immediately start condensing the moisture in the new air on their surfaces, freezing it, with the coils eventually becoming thickly coated with ice and frost.

As the frost builds up on the coils they become less and less efficient in the transfer of heat because of the insulating properties of the ice and frost, and particularly because of the frost because of its porosity. Unless this frost and ice is removed, the refrigerating system will almost cease operating and the temperature of the cold room will consequently rise. This defrosting is accomplished by shutting down the compressor system and allowing the temperatures of the coils and of the cold room to rise above the freezing point, below which no defrosting occurs, and, to complete the ole-frosting may require several hours.

Such methods are detrimental particularly with freezing units in which the temperature should be constantly maintained below 0 centigrade. The refrigerating system gradually lowers in eflicien'cy as the frost develops, then the room is allowed to slowly warm up to eliminate the frost from the coils, endangering the products subject to refrigeration, then the refrigerating system is again started and will require a considerable length of time, in some cases several hours to return the room to its below-freezing temperature, and when again started the coils immediately begin to remove the moisture from the re-humidified warmed air with immediate re-frosting resulting. It should also be noted that the superficial area of a conventional cooling coil is quite small in relation to the space refrigerated.

My invention almost completely eliminates and prevents the previously mentioned objectionable and detrimental features and operates with maximum efficiency, and consists of the conventional compressor and reliquification unit l0 and cooling or expansion coils ll, the compressor and re-liquification unit being conventionally installed in any convenient location.

The cooling coils however are enclosed within a sealed enclosure having end walls l2 and I3, top and bottom walls [4 and I5, and back and front walls It and H, and also scaled within the same enclosure is a blower or fan l8 and a heating unit l9, the enclosure or cabinet being sealed against ingress or escape of air, so that the original body of air is sealed within the enclosure.

The trapped air may to advantage be dehumidified by any conventional means, such as by introduction of a relatively small amount of dry calcium chloride when the enclosure is ready to be sealed. This will eliminate any possibility of even the minutest frosting of the coils.

The heating unit l9, fan l3 and compressor unit I0 are selectively controllable through the respective switches 29, 2| and 22, and a shutofi valve 23 is provided for the supply of refrigerant to the cooling coils.

In operation, the cooling coils can never become frosted and therefore will always transfer heat at maximum efficiency, and for which reason far less coil area is required in comparison to conventional systems. The same regarding frosting applies to the inside surfaces of the walls of the enclosure.

The exterior surface of the cabinet obviously will frost but the area is so great that elapsed times between defrosting periods will increase in proportion to the relative areas of the conventional cooling coil installation and the exterior area of the enclosure, in the neighborhood of ten to twenty times for the same buildup of frost.

However, this system is so easily and quickly de-frosted, and since it does not cause any rise in temperature of the room, de-frosting can be carried out at relatively frequent intervals for maximum cooling, operating, and power emciency.

At any time when frost has built up on the outside surfaces of the enclosure, the compressor unit is stopped, the valve 23 is closed to terminate delivery of refrigerant to the coils, and the heating unit is set in operationthe fan operating continuously. Since there is no frost on the coils the heat from the heating unit is circulated throughout the interior of the enclosure, heating the walls and causing the frost and ice to lose its adherence and break away and fall off. This requires only a few minutes even when the room temperature is below freezing, since the frost insulates the walls against this low temperature while the warmed walls thaw the und'ersurface of the frost.

As soon as the frost falls off the enclosure walls, the heating is discontinued and the compressor unit is again set in operation with the valv 23 open.

Thus, with only a few minutes for de-frosting and no transfer of heat to the interior of the cold room, the cold room temperature is substantially maintained and the refrigerating system kept operating at maximum efiiciency.

The unit illustrated in Figs. 1 and 2 is of the '75 locker type freezer or cold storage, and consists of the conventional enclosure .in which s'o-called locker cans 24extendinto the enclosure and. are perfectlyi sealed in their openings as indicated at '25, and since in this type of installation all heat transfer is to be confined to the lockers, the exterior of the enclosure is heavily insulated as indicated at 26 and provided with an exterior enclosure 21 which inturn is provided with doors 28 which are double-sealed as indicated fat 29 and 30. v

With this type ofinstallation, becauseiofthe insulation of the exterior, frosting will occur only onthe interior surfaces of the lockers, .but. these are quickly and easily defrosted aspreviously explained. These interiors are just as subject to frosting as the exterior walls of the conventional cabinet with th exception that because of the double seal, frosting occurs selectively in the lockers onlyin relation to the number oftimes a,door is opened, admitting fresh humidified lair, and since locker doors are opened only at infrequent intervals, long periods will elapse before de-frosting becomes necessary, and when it is required, all are simultaneously de-frosted, requiring only a few minutes and leaving the frost in the form of loose broken ice in the locker instead of water as in the conventional systems. The loose ice is easily and quickly scraped or brushed out and cannot in any way damage any products contained in the locker, because the insidetemperature of the locker is not noticeably increased during de-frosting.

The modifications illustrated in Figs. 3, 4 and 5 are suitable for meat market and similar refrigeration installations, and also for ice-cream and cold drink cabinets and refrigerated display cases.

For meat market and similar refrigerators the enclosure is made relatively shallow so as not to take up excessive space. It has no exterior insulation and is to be installed with the back wall l6 about four inches from the wall of the refrigerated room to provide for air circulation, and need not be more than six inches deep from front to back if the fan section I8 is made large enough to clear the fan blades, or if the fan or blower is mounted in a separate compartment.

When there is ample room, the most desirable form is similar to that shown in which recesses 3| or through passages 32 are formed to simultaneously increase the superficial area of the exterior walls to decrease the volume of frost per unit area, and to provide storage space for packages or special relatively small portions of merchandise which ar to be kept particularly cold or frozen. The walls 33 of these recesses or passages are sealed to the walls of the enclosure as indicated, and they are spaced as indicated to provide circulation of air and contact thereof with all of the walls.

Both of these types are suitable for display cases, that illustrated in Fig. 4 being suitable for self-help installations, and that in Fig. 5 for installations for display to the customer, permitting the customer to see the merchandise from one side, and for the merchant to remove it from the other side. Obviously these constructions, particularly for display cases, could be modified as illustrated in Fig. 7, in which the walls 34 are inclined and the through passages 35 formed level for display of trays 36 of merchandise.

I claim:

1. A- refrigerator comprising; a refrigerating unit; a cabinet having outside walls and inside walls spaced apart with intervening insulation and including'front, back, top, bottom and'side walls, and having a multiplicity .of spaced open,- ings formed through the front wall, and a locker can for each opening and, each having its open end sealed in its opening to the front wall of the cabinet and the other end extendingreare wardly to a point in slightly spaced relation to the rear wall, and having a refrigerating .unit compartment and a closure and sealingzmeans therefor for completely sealing the cabinet against ingress or egress of air having rear, top,'bottom andv side walls with all walls of all lockercans and said compartment spaced apart and from the top, bottom, rear and side walls of the cabinet to provide circulatory paths about all locker cans and said compartment; said compartment includ-'- ing a-deflector and being open at the top for deflecting refrigerated air over the tops of the uppermost cans; and an expansion coil and an electrical heating unit in said compartment and mounted in spaced relation and having. a fan located therebetween, and control means for said fan, for said heating unit, and for said expansion coil; and a door and sealing means for each locker can; whereby refrigerated air is confined in said sealed cabinet to maintain the expansion coils against frosting, and defrosting of the interiors of the lockercans may be carried out at will through the medium of said control means, whereby complete'sealing of said cabinet against ingress or egress of air limits frosting to the interior walls of the locker cans through interchange of air when the doors are opened.

2. A refrigerator comprising; a cabinet having top, bottom, front, back and end walls; a plurality of locker cans sealed to said front Wall and opening therethrough and extending rear- Wardly in spaced relation to said rear wall and peripherally spaced from each other and from the top, bottom and end walls to provide circulatory paths about each locker can; and a door for each locker can and including sealing means; one of said locker cans having openings for inlet and discharge of air and having a refrigerating unit therein including air circulating means, and also including heating means; and manual control means for selectively controlling said refrigerating unit and said heating means for refrigeration, and for rapid defrosting of the inside walls of the locker cans at will; said cabinet containing a supply of entrapped air at substantially atmospheric pressure for forced circulation about said refrigerating coils and heating means and said circulatory paths by said air circulating means.

3. A refrigerator comprising; a refrigerating unit including a refrigeration coil and air circulating means, a cabinet having top, bottom, front, rear and side walls and having locker cans spaced from each other and from the rear, top, bottom and end walls to provide circulatory paths about all walls of the locker cans with the open ends of the locker cans opening through and sealed to the front wall of the cabinet, said cabinet having a compartment in which said coils and air circulating means are installed with said compartment having an intake opening at one end and a discharge opening at the top and being included in said circulatory paths and discharging into the upper of said paths, and sealing means for said compartment to provide a sealed cabinet with air entrapped therein; heating means in said compartment and control means for said heating means and refrigerating unit, for controlling heating of said entrapped circulating air for rapidly defrosting the interior walls of the locker cans and for return to refrigeration when defrosting has been completed, and whereby frosting of the cooling coils and interior of the cabinet is limited to the moisture contained in said entrapped air, for negligible frosting, and defrosting of the interiors of the locker cans is accomplished with a minimum of heat transfer to the interiors of the locker cans, said locker cans in,- creasing the interior superficial area of the cabinet to reduce the volume of frosting per unit of area to an absolute minimum, and to serve as storage and refrigerating spaces and supports for merchandise.

4. A refrigerator comprising; a refrigerating unit including a compressor and re-liquification unit and a cooling coil; a cabinet having said cooling coil mounted therein; said cabinet containing a supply of air and said cabinet being sealed against ingress or escape of air, whereby frosting of the cooling coil and interior of the cabinet is limited to the moisture content of the entrapped air; said cabinet having a front wall; a plurality of locker cans spaced apart and projecting into said cabinet through openings formed insaid front wall and spaced from the walls of said cabinet other than said front wall and having their open front ends peripherally sealed to the front wall of said cabinet and each having a door and locking and sealing means therefor to provide access to the respective locker cans at Cir will while maintaining the cabinet against ingress or escape of air, and providing circulatory paths about all walls of all locker cans and between the walls of the cabinet and the walls of the locker cans for the entrapped air, whereby normal frosting is limited to the interior walls of the locker cans.

5.- A structure as defined in claim 4; a heating unit and forced air circulating means within said cabinet and control means therefor, for heating and circulating the entrapped air through all circulatory paths about the locker cans to rapidly defrost the interior walls of the locker cans with a minimum transfer of heat to the interiors of the locker cans.

. I RALPH E. LEHMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,908,573 Sulzberger May 9, 1933 1,921,865 Curtis 1 Aug. 8, 1933 2,126,285 Schaaf Aug. 9, 1938 2,252,237 Stiles Aug. 12, 1941 2,311,000 Smith et a1 Feb. 16, 1943 2,322,882 Raskin June 29, 1943 2,437,215 Wheeler et al Mar. 2, 1948

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