US 3182467 A
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3,182,467 REliRIGERAI'I0N` SYSTEM WITH DEFROST Sterling Beckwith, Libertyville Township, lll., assignol',l by mesne assignments, to Dual Jet Refrigeration Company, a corporation of Illinois v v Filed May 9, 196,2, Ser. No. 193,483
l 2 Claims. (Cl. 62-256) This invention relates toan improved refrigeration systern characterized by means for defrosting the system in a particularly eicient manner. The invention is particularly directed to devices of the type which are capable of maintaining a refrigerated state within an enclosed space while still providing an opening for access to the contents.
In an application of Hagen et al., Serial `No. 54,077, led September 6, 1960, now Patent No. 3,134,243 granted May 26, 1964 and in the issued Simons Patent No. 2,862,- 369, there are described refrigerated display cabinets which are provided with access openings exposed to the atmosphere while still being capable of maintaining the contents in a rrefrigerated state. Loss of refrigeration from the enclosed space through the access opening is reduced in a highly eifective manner in these constructions by the use of an air curtain which is continuously advanced across the open side from one edge of the opening to the opposite edge. The air curtain in these constructions is adapted to be formed of adjacent panels of air, with the innermost panel comprising a` refrigerated cold air panel, and with one or more outer panels having temperatures approaching the ambient temperature. It has been found that it is desirable to recirculate at least the inner cold air panel, and, at times the adjacent guard panels, to conserve the refrigeration and to maintain the enclosed space in a satisfactory refrigerated state.
In these constructions there are described assemblies which include nozzles extending across the bottom edge of the access opening to direct the air panels upwardly across the opening towards inlets which extend across the top side of the access`opening. As an alternative, the nozzles lare located across the upper edge for projecting the air panels downwardly toward inlets arranged across the bottom edge. It is also contemplated that the air nozzles be located across one of the lateral edges of the opening for directing the corresponding air panels across the opening toward inlets in the opposite edge. Because of the more desirable effect of gravity on the higher density cold air, it has been found preferable to provide the air curtain with a downward movement from nozzles across the top to inlets across the bottom. The following description will refer to this preferred construction, although it will be understood that the concepts to be described are also applicable to other directions of ow.
In applicants copending applications, Serial No. 88,- 879, tiled February 13, 1961, now Patent No. 3,082,612 granted March 26, 1963, and Serial No. 106,805, filed May l, 1961, now Patent No. 3,094,851 granted lune 25, 1963, there are described refrigeration systems of the type referred to above which also employ unique'defrosting means. It is highly desirable to provide defrosting means in refrigeration systems which can provide for rapid and complete defrosting with a minimum of interruption in the refrigerating operation.
It is, therefore, an object of this invention to provide improvements in the structure of refrigeration systems whereby the defrosting of the systems can be carried out with a minimum of interruption in the refrigerating function of the system.
It is an additional object of this invention to provide an improved defrosting means for use in combination with the refrigerating coil structure, the defrosting means being particularly suitable for achieving rapid defrosting of the evaporator plates in this structure.
It is an additional object of this invention to provide an improved defrosting means for use in combination with a refrigerating structure of a particular design whereby the defrosting operation can be accomplished ina rapid and highly efficient manner.
These and other objects of this invention will appear hereinafter and for purposes of illustration, but not of limitation, specific embodiments of this invention* are shown in the accompanying drawingsin which- FIGURE lis a schematic elevation, partly cut away, of a refrigerated enclosure characterized by the features of this invention;
FIGURE 2 is a detail view illustrating in section heating means which are preferably employed in the defroster structure;
FIGURE 3 is an enlarged fragmentary side view of the heating means shown in FIGURE 2; and
FIGURE 4 is a fragmentary cross-sectional view illustrating an alternative form of refrigeration coilsand associated defrosting means.
As indicated, the improvements of this invention are directed to refrigerated enclosures of the type which define an access opening in one wall which is provided for communication with the otherwise enclosed space. The enclosures are provided with a plurality of nozzles arranged in side-by-side relationship across one edge of an access opening and corresponding inlets are located across an opposite edge of the access opening; The inner nozzles and inlets are provided for the passage of reigerated air streams across the access opening, while the outer nozzles and inlets circulate progressively warmer air panels. As indicated, the refrigerated streams are circulated through passages having refrigeration coils or the y like situated therein, and one or more of the outer streams may also be refrigerated.
In applicants aforementioned copending application, means are described which enable operation of the refrigerating function of an enclosure with a minimum of interruption for defrosting purposes. ln accordancey with the present invention, it has been found that the inclusion of certain elements in the area of the refrigeration coils and evaporator plates can provide for a decrease in the time necessary for the defrosting operation. It will be understood that the principles of this invention to be described can be utilized in combination with the systems set forth in the foregoing applications and, furthermore, the invention has utility in combination with other existing refrigeration systems.
The improvements of this invention generally consist in the provision of heating means in the passages communicating the cold air nozzles and inlets. These heating means, which are designed to contact refrigerated streams, are located adjacent the face of the refrigeration means which is exposed to the oncoming stream. The heating means are adapted to be energized during a defrosting operation and, accordingly, the circulating air can be quickly heated and utilized for removal of frost from the evaporator plates in the refrigeration means as well as for the removal of frost throughout the passages through which the heated streams tlow.
It has been found that a more e'icient system is provided if the floor of the passage containing the refrigeration means is placed at an angle with respect to the rest of the enclosure. A drain is located at the lower end of the inclined floor and rapid removal of liquid formed during the defrosting operation is thereby accomplished. A separate heating means is preferably associated with the drain so that any frozen material therein will be quickly removed and thereby acelerate the progress of the defrosting operation. It has also been found that if the drain isy located near the rear face of the refrigerating means-the heater therein functions to accelerate the dcfrosting. of the refrigcrating means.
lt. is desirable to provide a hghdegree of uniformity in the vheated air passing through the refrigerating means during the defrosting operation. In order t'o accomplish this, the heaters employed' are disposed laterally across the face of the refrigerating means and' suspended one l 4 Y internally of the bodyl portion along the' length thereof. Radial tins 62 are formed on the body portion along the length in order that heat will ybev uniformly distributed to the oncoming stream. The heaters 56 are laterally arrangedV one on top of the other between the side walls of the passage 32. Any suitable connecting means can l be employedfor mounting the tubular heaters as long as above the other between the vside walls of the passage. f
The heaters comprise tubular members with internal passages for insertion of electrical resistance means. Radial fins are formed on the outside of the tubular members; and thev high surface area of the fins provides for uniform and highly efficient distribution of heat to theair streams passing in contact with the heaters.
The laccompanying drawings provide an illustration of a refrigerated cabinet which is characterized by the features of thisinvention. The cabinet includes a top wall 12, bottom wall 14, back wall 16, front wall 18 and side walls 20. The front wall 18 defines an opening Z2 lwhich provides access toan enclosed refrigerated space 2d. The .inner wall 26 defines the extent of the refrigerated space.
A pair of partitions 28 and 30 are located intermediate the inner and outer walls and define with these walls passages 32, 34 and 36. These passagesI confine air' streams which are adapted to be circulated through the cabinet. The streams form laminar panels 38, 46 and 42'V which pass acrossl the access opening.
Communicating with the passages are nozzles 44. The
air streams pass through these nozzles toward inlets 46 t communicating with the passages at the opposite edge of the access opening. Screens 48 can be provided over the inlets in order tol prevent entry of insects or other foreign material. These screens can be provided for each of the inlets, however, a heating means 50 can be substituted as the screen for the innermost passage. The' use of a heating means of thistype is describedin copendingapplication Serial No. 198,963, filed May 3l, 1962, Vnow Patent No. 3,128,609' granted April 14, 1964 and entitled Refrigerated Enclosure. The nozzles 44 may comprise honeycomb sections as described in the aforementioned copending applications.
At least the innermost stream of circulating air is adapted to be refrigerated upon its passage about the enclosure. However, more than one of the innermost streams can be refrigerated and fans or other circulating means can be included for each ot" the streams. Although three circulating air panels are illustrated, the concepts of this invention are adaptable for use in combination with systems providing two or more circulating streams.
In the cabinet illustrated, the passage 32 is provided with a circulating fan 52 and a refrigeration means 54. The air panel in this passage is adapted to be circulated by means of the fan into contact with the refrigeration means and is then adapted to pass out through the inner nozzle 44 as a refrigerated air panel 38. The innermost stream is thus the coldest stream and the panels 40 and lare progressively warmer. As explained in the several cases above referred to, this arrangement permits access through the front opening of the cabinet while still providing an extremely efficient refrigerating` operation.
As in most conventional refrigeration systems, frost will build up on the evaporator coils as well as in other locations in the cold air passage. It is, therefore, neces sary to provide for periodic defrosting as otherwise the efliciency of the refrigerating means would be decreased and, furthermore, the accumulation of undue amounts of frost on various portions of the apparatus will disrupt the uniformity of the laminar streams and will, therefore, cause undesirable variations in the temperature conditions.
The heating means 56 located behind the fan 52 Vand across the front face of the refrigerating means 541'comprise an important part of the defrosting system of `this invention. These heating means comprise tobularbody portions 58 with electrical resistance means 60 extending access is providedv for connection'lof the` resistorsA 60 to al source of electricity. y 7 1 With thelde'scribed arrangement, the inner air panel will be forced' into contact with the heaters 56 and then into contact with the coils of the refrigeration unit. If the heaters are not energized, the stream of air will pass through the refrigeration means'and thus serves to maintain the reduced` temperature in the enclosure. If, on the other hand, the refrigeration means is made inoperative and the heating means energized, the streams of air will be rapidly heated due to the large surface area presented by the in's of the heaters. Furthermore, the heated air will pass in a relativelyuniformly heated stream to the refrigeration means since the heaters are distributed over the face of the coils which is exposed to the oncoming stream.
The efficiency of the defrosting operationy is greatly enhanced due to the rapid increase in the temperature of the air stream. This air stream will serve to provide an equally rapid removal of accumulated frost in the refrigerating means as well as in other portions of the inner passage. Since this defrosting operation is carried out quickly with a minimum of' interruption in the refrigerating operation, it is necessary to provide for rapid removal of liquid formed in this operation. Otherwi-se, amounts of liquid' would tendr to freeze in the pas` sage 32 when the refrigerating cycle is again started.
To accomplish removal of the liquid formed during defrosting, the lioor 6'4' of the passage 32 is maintained at an angle with respect to the horizontal position of the cabinet. This incline of the' door permits rapid passage of liquid to the drain 66 located adjacent the rear face of the refrigerating means. It will be noted that the slope is toward the rear of the Ycabinet so that the water drains in the same direction as the air ow. The draining time is decreased in this way, since the air ow aids the waterow rather than retarding it, as would be the case if they moved in opposite directions.
The use of the heating means 56 in combination with the incline cf the passage 32 permits a simplified accomplishment of defrosting. The ydefrosting operation is further facilitated by the provision of a heating means 68 in the drain 66. Thisheating means, which is adapted to operate during the defrosting portion of the cycle, prevents accumulation of solidified products in the drain which would also impede rapid removal of liquid.
The heating means 68 also ser-ves to remove frost from the rear portions of the refrigerating means S4. This is accomplished, since the heating means is located adjacent the rear face of the refrigerating means. In a normal operation, heated air passing through the refrigerating means will be substantially cooled as it performs the defrosting. Accordingly, removal of frost from the rear portions of the refrigeratingmeans would be expected to require a longer time. However, the heating means 68 tends to accomplish removal of at least a part of the frost in the rear portions of the refrigerating means thus compensating for loss in temperature of the heated air` FIGURE 4 illustrates a modied form of the invention wherein a pair of refrigeration coils 70 are located in the inner passage 72 of a cabinet. Heating means 74 are located over the face of each of the coils so that the moving air stream will contact `these means before passing in contact with the adjacent Coils.
In the arrangement shown in`FIGURE 4, the coils 70 may together equal the capacity of a single refrigeration means of the type shown in FIGURE l. The refrigeration portion of the cycle will then be carried out with substantially the same efficiency as in the previous case.
However, with the arrangement of FIGURE 4, the defrosting can be accomplished more rapidly. The overall time required to bring the coil mass to the desired temperature for removing frost is reduced and,` furthermore, the removal of frost is accomplished more efficiently since the distribution of heat through the coil mass is more uniform. This latter factor insures removal of frost from the coils farthest away from the heating means within a reasonable time. Although two separate coils are illustrated, it will be understood that additional coils and associated heating means could be provided.
An additional heater 76 is located in the intake portion of the passage 72 ahead of the fan 78. This heater operates to remove frost which has accumulated in the passage and this removal can be accomplished during the defrosting cycle.
The described system provides an arrangement of elements in a defrosting unit which cooperate to provide material increases in the eiciency of a defrosting operation. It will be appreciated that various modifications may be made in the above described apparatus which provide the characteristics of this invention without departing from the spirit thereof, particularly as defined in the following claims.
l. In a refrigerated cabinet defining an access opening in one wall communicating the otherwise enclosed space with the outside atmosphere, means for circulating a plurality of air panels across said opening and through passages within said enclosure, and means for refrigerating at least the innermost one of said panels, the improvement wherein said refrigeration means comprise spaced apart coils, heating means located over the faces of each of said coils which are exposed to the oncoming air panel, said heating means being adapted to heat substantially all of said oncoming air panel during a defrosting operation whereby heated air-is circulated to said refrigerating means thereby accelerating the defrosting operation, and
additional heating means located between the inlet for the passage confining said innermost panel and the circulatingmeans in said passage, said additional heating means also being adapted to be energized during said defrosting operation.
2. In a refrigerated cabinet dening an access opening in one wall communicating the otherwise enclosed space with the outside atmosphere, means for circulating a plurality of air panels across said opening and through passages within said enclosure, and means for refrigerating at least the innermost one of said panels, the improvement comprising a plurality of heaters arranged adjacent to and across the face of the refrigerating means which is exposed to the oncoming air panel, said heaters comprising tubular members laterally disposed one above the other, said tubular members having electrical resistance elements disposed internally thereof and including radial tins along their lengths which provide for even distribution of heat, the passage conlining said innermost stream and containing said refrigerating means and said heating means being inclined, a drain located at the lower end of this passage, and means for energizing said heaters during a defrosting operation whereby heated air is circulated to said refrigerating means thereby accelerating the defrosting operation and whereby liquid formed during said operation can be quickly passed through said drain.
References Cited by the Examiner UNITED STATES PATENTS 2,952,992 9/ 60 Voorhes 62-256 3,063,253 1 l 62 Dickson 62-419 3,063,254 l 1/ 62 Dickson 62--256 3,063,256 l l/ 62 Lamb 62--256 ROBERT A. OLEARY, Primary Examiner.
WILLIAM L'WYE, Examiner.