US2850885A - Method of and means for refrigerating with dry ice - Google Patents

Description

Sept. 9, 1958 E. H. MOHR EI'AL 3 3 I um'non OF AND ms FOR REFRIGERATING wrm DRY ICE Filed Nov. 25, 1956 I... v mm-2|" qkum mgmmn y METHOD OF AND MEANS FOR REFRIGERA'IING WITH DRY ICE Edgar H. Mohr and Ernest G. Hutcheson, Tampa, Fla.

Application November 23, 1956, Serial No. 623,894

2 Claims. (Cl. 62372) The present invention relates to a method of and means for refrigerating various articles, for example, food, bottled beverages, etc., through the use of compressed carbon dioxide, commonly known as Dry Ice.

The concept of refrigerating through the use of Dry Ice is of course very old, in and of itself, but heretofore, considerable restrictions have been placed on the use of this refrigerating medium, particularly so far as insulated containers, such as those designed as portable coolers used on picnics, hunting trips, etc., are concerned.

Heretofore, it has been proposed to provide portable coolers or refrigerators, using Dry Ice. So far as is known, however, those devices previously conceived along this line have not found commercial favor. This may be due in some instances to the relative complexity of the construction, which militates against its being put on the market at a cost sufliciently low to attract purchasers. In other instances, the lack of commercial success may be due to the inability of the device to be used economically to produce a maximum freezing action while at the same time utilizing a refrigerant-confining compartment sufficiently small in relation to the compartment in which the food or other articles to be cooled are kept.

We are aware, for example, of prior art devices utilizing natural or water ice, such as one wherein a food chamber fails to maintain contact betweenthe walls of the chamber and the refrigerant during melting or evaporation of the refrigerant. Further, we are aware of the suggestion that the refrigerating means be placed directly in the compartment in which the food or other articles to be cooled are kept, this having the disadvantage that instability of the refrigerated commodity results, thus rendering the refrigerator somewhat impractical for its intended purposes.

We are also aware that in many instances, the principle of convection, rather than conduction, has been utilized. In carrying out the present invention, the cooling is effected entirely by conduction with high efficiency, as distinguished from the principles employed in the prior art devices.

Still further, devices heretofore conceived have, in general, required special designs for outer containers, so that it has not been possible to make use of existing outer containers already in use, such as the conventional portable cooler hereinbefore referred to.

In carrying out the present invention, we propose to eliminate the deficiencies which have been noted in the prior art, through the provision of a method of and means for refrigerating various articles, which will make use of a principle of refrigeration that will be readily adaptable to any size or shape of existing portable or stationary refrigerating devices, through the introduction of a specially designed insert and seal, insertable in a selected refrigerating device and adapting said device for the use of Dry Ice as the refrigerating medium.

Another object is to provide a construction of the character described that will effect self sealing of the insert Patented Sept. 9, 1958 within the outer insulated casing, responsive merely to lowering of the insert into said outer casing.

Another object is to provide a device of the character stated which will eliminate the drainage of water, air circulation or similar characteristics which have been present in prior art devices and have prevented full and efiicient utilization of said devices.

Still another object is to provide a refrigerating device as stated that will have greater refrigerating ability in direct proportion to lesser area occupied by the refrigerant, thus to in turn afr'ord greater commodity storage area while eliminating considerable weight owing to the type of refrigerant used.

Another object is to provide, in a device of the char-' acteristics stated, a perforated or expanded metal false 1 bottom on the insert, of simple design, which without anything more converts the device from a freezing to a cooling device, that is, by introduction of the false bottom the commodities confined in the device will be merely cooled but will not be frozen solid with the removal of the false bottom causing the articles to thereafter be frozen solid if desired.

Another object is to provide a device of the character described which will make use entirely of the principle of refrigeration by conduction rather than by convection or by a combination of these two refrigerating principles.

It is a further object to provide a method and means as previously described herein such that the principles can be applied not only to portable coolers, but also to refrigerator truck bodies, partly fishing vessels having fish boxes that are to be refrigerated, and any of various other stationary or portable structures.

Still another object is to provide a method of refrigerating that will keep the contents of the receptacle in which the food or other commodity is stored wholly dry, and will require far less space for the refrigerant than is true when conventional or natural ice is used.

A further object is to provide a refrigerating device as stated which will have a much needed advantage over conventional type cooling in that the device is adapted to maintain extremely low temperatures over an extended period of time, with this desirable result being achieved entirely through the previously mentioned thin sheet of perforated metallic material.

Still another object is to provide a refrigerating device as stated in which the conduction will occur directly through the metal bottoms or sides of thepreviously mentioned insert, and will in turn be transmitted directly to the contents of the insert or food receptacle.

A further object is to so form the insert that there will be a greater retardation of the escape of carbon dioxide gas liberated by evaporation of the Dry Ice, which retardation creates a lower evaporation of the refrigerant. It is proposed, in this regard, that the gasket or sealing means he so designed as not to form a tight seal, with the construction being, rather, such that the food container or insert will automatically gravitate to continuallylower positions as the evaporation of the refrigerant proceeds, thereby keeping the metallic body of the insert in full contact with the refrigerant. I

A further object is to so design the construction thatof portable coolingand refrigerating embodied in the in-' vention will eliminate the possibility of food spoilage through contact with water, such as occurs when natural ice is used, eliminating as well the necessity for bailing -or draining water from the food container.

Other objects will appear from the following description, the claims appended thereto, andfrom the annexed drawing, in which. like reference characters designate like parts throughout the several views, and wherein:

Figure 1 is a perspective view of a refrigerating device according to the present invention, a portion of the lid being broken away;

Figure 2 is a longitudinal sectional view, on an enlarged scale, substantially on line 22 of Figure l; and

Figure 3 is an exploded perspective view of the insert per se and its perforated false bottom.

Referring to the drawings, in detail, designated generally at is an outer or main receptacle which lncludes an open top, and whichis completely insulated over the area of its bottom, side, and end walls. Thus, the receptacle includesthe bottom 12 which may be of double-walled construction with insulation between the wall portions (see Figure 2). Integral with the bottom wall 12 are upwardly projecting end walls 14 and side walls 16, all of which are also of double-walled, insulated construction.

A bail-type handle 18 is provided in the illustrated example, the ends of the handle being pivotally engaged in the end walls 14. Of course, other handles, or no handle at all, are possible.

Closing the outer receptacle 10 is an insulated lid 20, which may be engaged in place by latch means 22 shown in Figure 1.

It will be observed that up to this point, the construction illustrated and described is basically conventional in a portable cooler. The construction, in fact, is similar to that employed in the food containers used on picnics, hunting trips, fishing trips, etc., for the purpose of keeping foods or beverages cool. Such a container normally makes use of natural ice, which is often deposited directly within the container with the food being supported in the same container with the natural ice. This has the undesirable results noted in the objects and preliminary discussion of this application.

A feature of the invention, in this regard, is its adaptability for incorporation in an otherwise conventional cooler such as is illustrated and described hereinbefore. This reduces considerably the cost of applying the principles of the invention for the purpose of refrigerating various products, since the insert and false bottom shown in Figure 3 can be associated with a conventional, lidprovided, insulated, portable cooler of the character shown.

In any event, lid is readily removable, to provide access to the contents of the device, and to permit inser' tion and removal of an insert 24 constituting part of the present invention. 7

The insert 24 is so shaped as to conform generally to the configuration of the outer casing, although the transverse and longitudinal dimensions of theinsert are smaller than the corresponding inner dimensions of the outer container or casing, as shown in Figure 2. This provides a space between the walls of the insert and the corresponding walls of the insulated container, having characteristics which will. be. described hereinafter in full detail.

The insert or inner receptacle. 24 is formed of a relatively thin but strong metallic material havinga high rate of thermal conductivity. At its upper end, the insert is formed with an outwardly directed flange 26 lying in the plane of the open top of the insert, and extending continuously through the full periphery of the insert. Embraceably receiving the flange and correspondingly e?- tending through the full periphery of the insert, is a sealing gasket 28 of .C-shaped cross section, which is formed of any suitable, sealing. material having the desired characteristics of compressibility for effecting a sealing action. Soft rubber is wholly satisfactory for the desired purpose, it has beenfound in practice.

Adapted to be positioned in the bottom of the insert is a planiform, forarninous spacer plate or false bottom 30. This may be'formed of expanded metal, or alter- 4. natively, may comprise a metallic sheet freely perforated over its entire area.

In any event, the spacer plate 30 corresponds in length and width to the corresponding inner dimensions of the insert 24, and is adapted to be removed from the insert whenever desired, for a purpose to be made presently apparent. When the spacer plate is disposed within the insert, it is in face-to-face contact with the flat bottom wall of the insert or inner receptacle, as will be noted from Figure 2. This is an important characteristic of the invention, furthering the application of the principle of refrigerating wholly by conduction, rather than by convection or by a combination of convection and conduction.

The inner receptacle is of a depth substantially less than the depth of the outer receptacle 10, so that the bottom walls of the respective receptacles will be spaced apart as shown in Figure 2, to define therebetwcen a relatively shallow compartment, extending over the full bot tom areas of the respective receptacles, in which a quantity of Dry Ice 32 is deposited. Preferably, the Dry Ice is so disposed Within the inner receptacle as to define a flat top surface on the Dry Ice, so that the bottom wall of the inner receptacle will be in full contact, over its complete area, with the refrigerant as shown in Figure 2.

The Dry Ice extends over the bottom wall only of the inner receptacle, and does not extend upwardly into the relatively narrow, continuous chamber 34 that extends about the side wall of the inner receptacle. It will be noted that the chamber 34 is completely closed at its upper end by the gasket-provided flange of the inner receptacle, so that in effect the space 34 is substantially sealed. In actuality, the sealing action of the gasket 28 is not a full and complete sealing action, and intentionally, a small amount of escape of the gas resulting from evaporation of the Dry Ice is permitted. The gas so escaping, it should be noted, is harmless and noncombustible, and has no adverse effects on food packed within the insert.

In use of the device, and assuming that it is desired to refrigerate but not completely freeze food products within the insert, a quantity of Dry Ice 32 is deposited in the outer receptacle. Thereafter, the spacer plate is positioned in the bottom of the insert, and the food products are packed in the insert to any extent desired. The insert is positioned within the outer receptacle, with the gasket 28 in slidable contact with the inner side and end surfaces of the outer casing. The insert rents directly on the refrigerant 32, in face-to-face contact lli'lBlCWlill, so that there is direct conduction through the metal of the bottom wall of the insert, and through the spacer plate 30 to the food product, thus refrigerating the product.

An important characteristic resides in the use of a spacer plate formed and arranged as shown. The spacer plate, being of expanded metal or otherwise freely perforated, is in contact, for the purpose of conduction, with the bottom wall of the insert only over that part of the 'area of the spacer plate that remains when one subtracts from the area of the bottom plate the total area occupied by the apertures thereof.

This leaves only a comparatively small area of the spacer plate in direct contact with the bottom wall of the inner receptacle or insert 24 but it is important to note that such area of the spacer plate that remains in contact with the bottom wall of the insert constitutes the full area of the spacer plate less the area thereof occupied by its openings. Therefore, the effect of the conduction is reduced in direct proportion to the extent that the total area of metal in the spacer plate 30 is reduced by the openings thereof. In this connection, the spaces or openings in the spacer plate act as a buffer, and the final result is that the refrigerating action is tempered to the extent that the food or other commodity will be suitably refrigerated, while not being fully frozen.

If, however, it is desired to fully freeze the commodity IE un it? within the inner receptacle, it is merely necessary that the spacer plate 30 be removed. In these circumstances,

conduction or heat transfer, from the commodity being refrigerated to the refrigerant, passes directly from said commodity through the imperforate bottom wall of the insert, to the refrigerant which is in contact with the bottom wall of the insert over the full area over said bottom wall. It has been found in practice that this causes full freezing of the material within the inner receptacle. The net result is that in a simply formed device as shown, one can selectively either fully freeze the confined product or alternatively, refrigerate the product While maintaining the temperature thereof above freezing.

An important characteristic of the construction resides in the fact that the inner receptacle is in actuality mounted within the outer receptacle for gravitational sliding movement, with said sliding movement being restrained only by the refrigerant, which extends as a solid between the bottom wall of the outer casing and the bottom wall of the inner receptacle. It follows that as the refrigerant evaporates over a period of time, the overall thickness thereof will be reduced progressively, so that the inner receptacle slowly moves downwardly within the outer receptacle to maintain its full contact with the surface of the refrigerant.

The refrigerating or freezing action thus remains constant as long as there is refrigerant underlying the full area of the bottom wall of the inner receptacle, and the continually decreasing thickness does not affect adversely or vary the refrigerating or freezing action. This is due to the fact that the cooling action occurs entirely by conduction, with said conduction occurring over the full area of the bottom wall of the inner receptacle regardless of the thickness of the supply of refrigerant. The constant and fully eiiicient cooling action further results from the fact that the insert is self-adjusting in respect to the supply of refrigerant, continually moving downwardly as the supply of refrigerant decreases to remain in complete contact with the top surface of the refrigerating medium. The gasket 28 is in slidable contact with the inner surface of the outer receptacle, and provides the mentioned seal at the upper end of the space 34 in which the gasket moves responsive to the evaporation of the refrigerant. While the gasket maintains the mentioned sealing action, it still permits the free gravitational movement of the insert 24 downwardly within the outer casing until the supply of refrigerant is exhausted.

In prior art devices of which we have knowledge, as the supply of solid refrigerant decreases there is an ever-increasing space formerly occupied by the refrigerant. This space becomes occupied by air or (in the case of natural ice) water. Thus, there is a corresponding, progressive decrease in efficiency of the refrigerant, having a direct relationship to the extent that the refrigerant melts or decreases in'size.

It has been found by experimentation, in this regard, that maximum refrigerating efficiency, when Dry Ice is used, is obtained by actual physical contact of the Dry Ice with the surface being cooled. In'any device in which the exterior physical contact is reduced on account of evaporation of the Dry Ice, there is, as will be understood, a corresponding loss in full refrigerating efficiency.

This problem has been overcome in the illustrated device by maintaining full physical contact between the bottom wall and the refrigerant, over the full area of the bottom wall, even during the continuous evaporation of the refrigerant. Said contact is maintained as long as there is any refrigerant left in the container suflicient to completely overlie the bottom of the outer casing. The results are achieved by providing for the free gravitational movement of the insert, restrained only by the refrigerant itself, so that the full physical contact previously referred to is continuously maintained automatically.

It is to be noted, in this regard, that the entire cooling action is by conduction, directly between the refrigerant, the bottom wall of the insert, and the product. When the spacer plate is used, of course, the conduction occurs also through the spacer plate to prevent full freezing of the product. At no time is there a reduction of the area of the insert that is in physical contact with the solid refrigerant, and the refrigerating action remains constant, regardless of the steadily decreasing thickness of the refrigerating medium.

A further important characteristic of the invention resides in the fact that the refrigerant occupies only a comparatively small amount of the total area of the cooler, leaving a substantially larger area for packing of the commodity to be cooled. This is accompanied by a reducillustrative of the principles of operation and the means presently devised to carry out said principles, it being considered that the invention comprehends any minor change in construction that may be permitted within the scope of the appended claims.

What is claimed is:

1. A refrigerating device using Dry Ice as a refrigerant, comprising an outer receptacle including a bottom and a wall extending upwardly from the bottom; and inner receptacle for holding a product to be cooled, said inner receptacle including a bottom, a wall extending upwardly therefrom, and an outwardly directed flange formed on the inner receptacle wall and slidably contacting the outer receptacle wall, for gravitational movement of the inner receptacle within the outer receptacle to maintain contact between the bottom of the inner receptacle and a quantity of Dry Ice confined between the bottoms of said receptacles; and a sealing gasket covering said flange to provide a seal between the flange and the wall of the outer receptacle.

2. A refrigerating device using Dry Ice as a refrigerant, comprising an outer receptacle including a bottom and a wall extending upwardly from the bottom; an

inner receptacle for holding a product to be cooled, said inner receptacle including a bottom, a wall extending upwardly therefrom, and an outwardly directed flange formed on the inner receptacle wall and slidably contacting the outer receptacle wall, for gravitational movement of the inner receptacle within the outer receptacle to maintain contact between the bottom of the inner receptacle and quantity of Dry Ice confined between bottoms of said receptacles; and compressible sealing means interposed between said flange and the wall of the outer receptacle.

References Cited in the file of this patent UNITED STATES PATENTS 1,595,385 Cusak Aug. 10, 1926 1,731,578 Kennedy Oct. 15, 1929 1,817,605 Belt et a1. Aug. 4, 1931 2,068,384 Newport et a1. Ian. 19, 1937 2,216,330 St0ver Oct. 1, 1940

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