US2442978A - Refrigeration apparatus having frost localizing means - Google Patents

Description

June` 8; 1948. W. P. JONES 2,442,978

REFRIGERATION APPARATUS HAVING FROST LOCALIZING MEANS Filed March 17; 1944 Patented June 8, 1948 REFRIGERATION APPARATUS HAVING FROST LOCALIZING MEANS Welton Paul Jones, Rydal, Pa., assigner to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application March 17, 1944, Serial No. 526,951

4 claims. 1

This invention relates to refrigeration machines, and is especially concerned with that class of machines which utilize one or more evaporators operating at temperatures below the freezing point of water.

' More speciilcally, the present invention has reference to refrigerators incorporating a relatively low temperature evaporator exposed to moisture laden air within the cabinet structure.

As is well known, moisture present in such refrigerators is gradually deposited upon the evaporator in the form of frost; being carried through the box either by convection currents or moving to the vicinity of the evaporator as the result of the existence of areas of differential vapor pressure. This latter mode of moisture travel is a recognized phenomenon generally referred to as moisture migration; the migration being from areas of relatively high vapor pressure to areas of relatively low vapor pressure. In the presence of such areas of differential vapor pressure moisture will travel through the box even though there are no appreciable convection currents within the refrigerator.

The deposition of the frost upon the evaporator, resulting from moisture travel of the two general types outlined above, tends to insulate the evaporator from the air within the refrigerator, thereby reducing the operating efficiency of the refrigerating system. Because of this reduction in operating eiiiciency periodic defrosting of the evaporator has hitherto been necessary, and such defrosting is not only troublesome, but has created a particular problem in connection with certain refrigerators which have recently come into general use. The refrigerators referred to are those which are adapted for the storage of frozen foods, which foods may be deleteriously affected or even spoiled as a result of the defrosting operation.

The present invention has as a primary object the provision of a refrigerator in which no defrosting ofy the food-storage evaporator means is required.

More particularly, it is an object of the present invention to provide a refrigerating apparatus having novel auxiliary evaporator means upon which the frost deposition is localized.

A more specific object of the invention resides in the provision of such a refrigeration apparatus, in which the auxiliary evaporator means is provided with a portion upon which the frost collection is localized, which portion may be readily removed from the refrigerator cabinet to eect defrosting thereof, without interrupting the operation of the main evaporator system.

The invention also contemplates a construction in which novel means is provided to facilitato ready removal of the frost collecting element from the adjacent cabinet structure.

A further object of the invention resides in the particular construction and mode of association of the main and auxiliary evaporator elements which promote localization of the frost deposition.

These and other objects and advantages will be best understood by consideration of the following description taken in conjunction with thc accompanying drawings in which:

Fig. 1 is a perspective view of a refrigerator embodying the invention, the lower portion of the cabinet structure being broken away for sake of clarity in illustrating the essential elements of the invention;

Fig. 2 is an enlarged sectional view on the line 2-2, in Fig. 1;

Fig. 3 is an enlarged perspective view of the removable portion of the auxiliary evaporator system; and

Fig. 4 is a sectional view of a modication of the apparatus illustrated in Fig. 2.

With reference first to Fig. 1 of the drawings, the reference character 2 designates, generally, a domestic refrigerator of the mechanical type having an outer shell 3, which may be of any well known type and construction, and an inner metal shell or liner member 4 providing the main food storage space indicated generally at 5. This space 5 is preferably fitted with suitable shelves (not shown). Vertical and horizontal breaker strips 6 and 1, respectively, of low thermal conductivity are fitted around the forward marginal edge of the cabinet opening; while thermal insulation, portions of which are indicated at 8, completely surrounds the inner liner member d and the outside surfaces of the evaporator means presently to be described. It will be understood that the cabinet is provided with a door adapted to seat thereagainst in the plane of the breaker strips 6 and 1, said door having been omitted from the drawing for the sake of simplicity in illustration.

As revealed by the broken-away portions of the cabinet structure, there is a machinery compartment 9 located beneath the food storage space, which compartment houses the compressor unit indicated generally at I0. The main evaporator is shown at Il and comprises, generally, a horizontal door portion I2 and vertical side portions 3 I3 and I4. provided with an outwardly turned flange I which is securely connected to the lower edge of inner liner l as by means of the fasteners shown at I6. As illustrated, it is preferable that some suitable insulating material be interposed between the liner 4 and flange I5, along their zone of connection. In the embodiment illustrated, a double thickness partition I1 provides the :door for the main storage compartment, this partition being interposed between the main evaporator and the storage compartment 5 so as to make it possible to operate said compartment,I at relatively high temperatures as compared with the temperature of evaporator I I, and to prevent the frosting-out of moisture present in the compartment. For a purpose which will be made clear hereinafter, wall portion I4 of evaporator II terminates at a level considerably below the upper edge of wall I3, at which level the terminal edge of the wall I I is connected to a laterally extending floor portion I8 which in turn, is provided with an upwardly extending section I9 provided with an out-turned flange adapted for connection by suitable means to the lower edge of liner 4, in a manner similar to that already described with reference to the upper edge of wall I3.

Evaporator II is fitted with shelves 20 and 2| which are preferably equipped with suitable refrigerant receiving tubing, as shown, and which provide an area conveniently arranged for production of ice cubes. A wall 22 extends across the forward portion of evaporator II and terminates below shelf 20 a distance suilicient to permit ready access to the main storage section of said evaporator and its contents. Certain features of the particular evaporator illustrated are disclosed and claimed in the co-pending application of Donald E. Dailey, Serial No. 515,950, filed December 28,

` 1943, which application matured into Patent No.

` Also, and for a purpose which will appear more fully hereinafter, a plurality of apertures 24 serve to permit free passage of air and moisture from the ice freezing space to the vicinity of the horizontally extending floor portion I8.

Although any convenient form of refrigerant circuit may be employed in the main evaporator I I, there has been illustrated an evaporator of the type having a balanced central feed to the bottom wall thereof (through the supply conduit shown at 26) from which the refrigerant passes upwardly through parallel connections to the exhaust headers, one of which is illustrated at 21 in Fig. 1.

In accordance with the present invention, and as best seen in Fig. 2, an auxiliary evaporator 25 is provided just beneath the surface of the laterally extending floor portion I8 which adjoins the main evaporator II. This auxiliary evaporator may conveniently comprise tubing 28 secured to or arranged in good heat exchange relation (as shown) with the lower surface of a removable plate section 29 of the floor member I8. A frame 30, of rubber or the like, surrounds the plate 29, removably securing said plate in spaced relation to the adjacent edge portions of the floor I8. This The upper edge of side wall I3 isa suitable restrictor 3i which delivers the refrigerant from the main evaporator to the auxiliary coils. This restrictor, as shown, takes the form of a capillary tube. and by proper design thereof it is possible to operate the tubing forming the auxiliary evaporator at some temperature considerably below that existing in the main evaporator II. For example, the main evaporator would preferably be operated in the region from 0 to 10 F., while it is desirable to maintain the auxiliary evaporator at temperatures in the neighborhood of 20 below 0 F. It will be understood that a substantial temperature differential is necessary between the main and the auxiliary evaporators, in order to effectively localize the deposition of frost to the vicinity of the plate 29, and also that the auxiliary evaporator must have rsufficient heat exchange surface.

As most clearly appears in Figs. 2 and 3, a platelike element 32 is provided, which is adapted to rest upon the upper surface of the thermally insulated portion 29 of floor I8. This element 32 has a plurality of flanges 33 upstanding therefrom, which serve as additional heat exchange surface, and it will be seen that said plate 32 is substantially coextensive with that portion of plate 29 which lies within the confines of the insulating frame 30, the purpose of this being made clear hereinafter. A release device, generally designated by the reference numeral 3l, is se cured to the upstanding flanges 33, as by means of pins 35. and is provided with cam portions 39 which extend downwardly through apertures 3'I in the plate 32.' Normally, the cam surfaces 38 make contact with or lie slightly above the upper surface of plate 29, and it will be apparent that rotational movement of the release mechanism to the left (as viewed in Fig. 3) will cause the cam portions 36 to bear against the upper surface of said plate, thereby breaking the bond between the removable element 32 and the.plate 29.

If desired, a tray may be employed in place of the plate-like element? 32, and such a modification is illustrated in Fig. 4. In this embodiment, the portion 29 extends downwardly below the plane of floor portion I8, and is of a size to receive the tray 38 snugly therewithin. Although no release mechanism is illustrated in Fig. 4, it will be apparent that an arrangement similar to that described above may be employed, if desired.

As shown, and in order to adapt the apparatus for use with a secondary evaporator arranged in heat exchange relation with the upper food storage compartment 5, theV refrigerant flowing through the auxiliary evaporator is delivered to a small evaporator element 39 (mounted in the upper portion of the cabinet) as by means of the pipe 40. Since the secondary cooling system forms no part of the present invention, per se, it is not illustrated herein, but it will be understood that the small evaporator 39 is utilized to effect condensation of the refrigerant in the secondary system, after which the refrigerant delivered to the evaporator 39 i's returned to the motor-compressor I0 through a suitable suction line, a portion of which is illustrated at 4I. Preferably, the delivery tube 40 presents no substantial restriction to the flow of refrigerant, as there is no purpose in operating evaporator 39 at temperatures lower than those prevailing in the evaporator tubing 28.

The operation of the device is as follows:

As has been set forth, moisture will migrate from areas of relatively high vapor pressure to areas of relatively low vapor pressure, and the novel apparatus of the present invention utilizes thisl phenomenon to'prevent the substantial formation of frost in or upon the main evaporator I l and to provide for the automatic removal of such quantities of frost as may be formed on said evaporator.

The auxiliary evaporator 25, by virtue of the fact that 'it' is operating at the lowest temperature existing within the refrigerator, creates .an area of low vapor pressure as compared with the pressure existing in other portions of the box. Consequently, moisture introduced into the storage space below the shelf l1 will migrate to the removable 'plate.32, and be deposited thereon in the form of frost. In order to facilitate this action, the elongated aperture 23 has been provided in. one side wall of the evaporator Il in relatively close proximity to the low-temperature element 32. In addition, the small apertures 24, described above, serve to permit free passage of moisture'from the ice freezing space between the shelves 20 an-d 2| to the vicinity of plate 32. In view ofthe fact that removable element 32 covers the entire exposed area of plate 29, the frost deposition will be completely localized on said element 32. After a considerable quantity of frost has been built up upon the element 32 and its flanges 33, this element may be released by operation of the cam device v34 and withdrawn from the refrigerator to permit removal of the frost, which may be accomplished by flowing warm water over the plate.

It should be understood that, in practice, small amounts of moisture may become deposited upon the main evaporator il, before reaching the vicinity of the auxiliary low-temperature tubing 28. For example, a portion ofthe moisture which is being carried through the storage space by convection currents may become frosted-out before it has come in contact with the plate 32. However, frost which is so deposited will gradually migrate to the removable plate by a process of sublimation.

From the `foregoing description, it will be apparent that the invention provides a refrigerator in which it is unnecessary to defrost the main storage evaporator. thereby completely eliminating the inconvenience of this operation, and preventing possible spoilage of food stored therein. Moreover, these advantages are realized by an apparatus in which the frost localizing and collecting element may be readily removed from the refrigerator cabinet to eect defrosting thereof, without interrupting the operation of any poryion of the evaporator system.

I claim:

1. In a refrigerator having an enclosed compartment, main evaporator means arranged within said compartment and adapted to operate at sub-freezing temperatures to cool said compartment, auxiliary frost-collecting evaporator means in said compartment and adapted to operate at the lowest temperature prevailing in the refrigerator, said compartment having a metallic wall conductively connected with the main evaporator and extending into proximity to the auxiliary change between said auxiliary evaporator means and the said wall structure, and a removable element upon which the frost deposition is localized, said element being arranged in high heat exchange relation with said auxiliary evaporator means and normally serving to prevent access of moisture to said evaporator means.

3. In a. refrigerator having an enclosed compartment, main evaporator means arranged within said compartment and adapted to operate at sub-freezing temperatures to cool said compartment, auxiliary frost-collecting evaporator means in said compartment and adapted to operate at the lowest temperature prevailing in the refrigerator, said compartment having a me tallic wall conductively connected with the main evaporator and extending into proximity to the auxiliary evaporator, a detachable element constituting substantially the sole effective refrigerat-lng surface of said auxiliary evaporator exposed to the atmosphere in said compartment, and insulating means adapted to prevent substantial heat exchange between said auxiliary evaporator means and the said wall structure.

4. In a refrigerator, a main evaporator adapted to operate at temperatures below the freezing point of water and defining a storage area., and auxiliary evaporator means positioned externally of said storage area and adapted to be maintained at a temperature below that prevailing in said main evaporator so as to establish an area of relatively low vapor pressure with respect to the vapor pressure prevailing in the vicinity of said main evaporator, and means affording free movement of moisture from the said storage area in the interior of said main storage evaporator to the region of said auxiliary evaporator, said auxiliary evaporator including a detachable element constituting substantially the sole eiective refrigerating surface of said auxiliary evaporator exposed to said moisture.

n WELTON PAUL JONES.

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

UNITED STATES PATENTS Number Name Date 1,963,565 Stollsteimer June 19, 1934 2,003,414 Allyne June 4, 1935 2,010,259 Fretter Aug. 6, 1935 2,052,822 Greene Sept. 1, 1946 2,133,958 Kalischer Oct. 25, 1938 2,310,872 Rundell Feb. 9, 1943 2,319,522 Schweller May 18, 1943 2,343,166 Ashbaugh Feb. 29, 1944 2,361,792 Philipp Octl 31, 1944 2,370,267 Starr Feb. 27, 1945

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