US 3004877 A
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Description (OCR text may contain errors)
Oct. 17, 1961 'r. s. SIMMS ETAL 3,004,377
HEAT-INSULATING UNITS FOR REFRIGERATOR CABINETS Filed Oct. 8, 1957 FIG. 3
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2/0 Fur/ KRAFT PAPER United States PatentO "ice 3,004,877 HEAT-INSULATING UNITS FOR REFRIGERATOR CABINETS Thomas S. Simms,;Bensenville, andArthur J. Harder, 112, Franklin Park, 111., assignors to General Electric Company, a corporation of New York Filed Oct. 8, 1957, Ser.No. 688,977 4 Claims. (Cl. 154-45) The present invention relates to heat-insulating units for refrigerator cabinets, and more particularly to an improved heat-insulating unit of the general character of that disclosed in the copending application of Thomas S. Simrns and Arthur J. Harder, 112, Serial No. 504,248, filed April 27, 1955, now abandoned.
It is a general object of the invention to provide an improved heat-insulating unit of the type including an hermetically sealed bag enclosing both a porous mass of solid poor heat-conducting material and a charge of a gas having a coefiicient of thermal conductivity lower than that of air and thoroughly permeating the porous mass of material, wherein the bag is constructed of a flexible multi-ply laminate provided with an intermediate ply of kraft paper having a high tear strength, an inner ply of organic resin having a low permeability and an outer ply of organic resin having a high abrasion resistance. Another object of the invention is to provide a heat insulating unit of the character noted, wherein the materials of the laminate are of improved construction and arrangement and lend themselves to ready and economical manufacture and assembly.
A further object of the invention is to provide a heatinsulating unit of the type noted, that is of improved and simplified construction and arrangements, that is economical to manufacture, and that has a long life in use;
Further features of the invention pertain to the particular arrangement of the elements of the heat-insulating unit, whereby the above-outlined and additional operating features thereof are attained.
The invention, both as to its organization and method of operation, together with further objects and adv-antages thereof, Will best beunderstood by reference to the following specification taken in connection with the accompanying drawing, in which:
FIGURE 1 is a fragmentary front view of the upper left-hand portion of a household refrigerator cabinet incorporating a heat-insulating unit embodying the present invention;
FIG. 2 is a fragmentary vertical sectional view of the refrigerator cabinet, taken in the direction of the arrows along the line 22 in FIG. 1;
FIG. 3 is a reduced plan view of one of the heatinsulating units incorporated in the refrigerator cabinet shown in FIGS. 1 and 2;
FIG. 4 is a reduced side view of the heat-insulating unit shown in FIG. 3;
FIG. 5 is an enlarged fragmentary vertical sectional view of the heat-insulating unit, taken in the direction of the arrows along the line 55 in FIG. 3; and
FIG. 6 is a greatly enlarged fragmentary sectional view or" a wall of the bag of the heat-insulating unit, taken in the direction of the arrows along the line 66 in FIG; 5.
Referring now to FIGS. 1 and 2 of the drawing, there is illustrated a cabinet 1! for a household refrigerator,
or the like,'embodying thefeatures of the present invention, and comprising a metal outer shell 11 and a metal innerliner 12, both of box lik e form, the metal inner liner 12 being arrangedin nested relation within the metal outer shell 11. The cabinet comprises a por tion of a household refrigerator, as previously noted,
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and cooperates with a refrigerating machine, not shown, that includes a refrigerant evaporator that is operatively associated with a food storage space 13 defined within the inner liner 12. For example, the refrigerant evaporator may be arranged in any suitable manner within the storage space 13 for the purpose of effecting the required cooling of the food, or the like, stored therein. A substantially rectangular heat-insulating frame strip 14, usually formed of a suitable molded plastic material, is arranged about the open front of the cabinet, 10 and joiningt eboun'dary edges of the outer shell 11 and the inner liner 12. As shown in FIG. 2, the boundary edges of the walls of the outer shell 11 may be provided with inturned flanges and the boundary edges of the walls of the inner liner 12 may be provided with outturned flanges, which flanges are joined together by the frame strip 14 in order to close the space between the shell 11 and the liner 12, the securing means for the frame strip 14 being entirely conventional.
Arranged within the space defined between the outer shell 11 and the inner liner 12 are a number of heatinsulating units 20 of pillow-like construction; which heat-insulating units 20 are designed nicely to fit between the outer shell 11 and the inner liner 1'2 and substantially completely to fill up the space disposed between the elements 11 and 12. For example, the space between the outer shell 11 and the inner liner 12 may be nicely filled by a pair of cooperating and differently constructed ones of the heat-insulating units 20, a first of these heatinsulating units being deformed into a substantial U shape and arranged to fill the top and side portions of the space noted, and a second of these heat-insulating units being deformed into a substantial L shape and arranged to fill the bottom and rear portions of the space noted. v
Referring now to FIGS. 3 to 5, inclusive, of the drawing, the heat-insulating unit 2% there illustrated is of substantially pillow-like form and of substantially rectangular configuration; the unit 26 comprising a pair of complementary sheets 21a and 21b disposed on opposite sides of a slab or mattress 22 of heat-insulating material; which sheets 21a and 2112 are drawn down around the mattress 22 and sealed about the meeting marginal edges thereof, as indicated at 23, thereby to define an hermetically sealed bag enclosing the mattress 22. Also the bag of the unit 2% comprises a charge (indicated by the reference character 24) of gas thoroughly permeating the porous mass of the mattress 22 and having a substantially lower thermal conductivity than that of air. Accordingly, and hermetically sealed envelope or bag of the unit 20 comprises the two complementary sections of substan tially rectangular dish-like configuration and including the air of opposed facing walls respectively defined by the pair of sections and the connecting marginal wall jointly defined by the pair of sections. I
Preferably the sheets 21a and 21b are identical, each comprising a flexible sheet-like wall formed of low thermal conductivity materials and constituting a unitary multi-ply laminate. Specifically, as shown in FIG. 6, the sheet 21a comprises an intermediate ply 25 of kraft paper having a high tear strength, an outer ply 26 of organic resin having a high abrasion resistance, and two inner plies 27 and 28 of organic resin having a low permeability to gas and air and water vapor. In the laminate 21a, the outer-ply 26- is intimately bonded to the intermediate ply 25 by a layer of" adhesive 31, the inner ply 27 is intimately bonded to the intermediate ply 25 by a layer of adhesive 32, and the inner ply 28 is intimately bonded to the inner ply 27 by a layer'of adhesive 33. V p
In a first example of the laminate 21a: the P13 25 comprises a sheetofsupercalendered kraft paper of 40# gauge; the ply, 26 comprises a film of polyethylene having; a thickness of about 2 mils; and'each of the plies 27 and- 28 comprises a'film of Saran having a thickness of about 1 mil. The material Saran essentially comprises vinylidene chloride copolyrners, one form of this material comprising vinylidene chloride and vinyl chloride copolymers resin, and another form of this materialcornprising vinylidene chloride and acrylonitrile copolymers resin. The kraft paper ply 25 is supercalendered so that it will not abrade or puncture the adjacent plies 27 and 28; and in passing, it is mentioned that 40# gauge kraft paper designates the weight of a ream thereof (500 sheets-24" X 36"). Accordingly, the ply 24 of kraft paper has a thickness in the general range 4 to 5 mils.
Preferably the adhesive of the layers 31, 32 and 33 essentially comprises a Hycar rubbercement or adhesive that consists essentially of 'copolymers of butadiene and acrylonitrile. This adhesive normally contains a few percent of phenolic resin, as well as a plasticizer (normally dioctylphthalate). This Hycar adhesive is manufactured by B. F. Goodrich Co. and possesses the desirable quality that after it sets-up it maintains its flexibility and materially reduces the permeability of the composite laminate, presumably by plugging or closing any small pinholes, or the like, that might be present therein.
In a second example of the laminate 21a, the plies 25, 27' and 28 are identical to those previously described, while the ply 26 comprises a film of Mylar having a thickness of about /2'mi1. The material Mylar essentially comprises a polyester of ethylene glycol and terephthalic acid. Also, in this arrangement, the adhesive layers 31, 32 and 33 are the same as previously described. In this arrangement, the outer ply 26 of ethylene glycol terephthalate resin has an abrasion resistance'that is superior to that of polyethylene and can accordingly comprise a thinner film, as noted above.
4 the gas enclosed in the bag; whereby the facing walls of the bag are normally pressed by atmospheric pressure into firm engagement with. the adjacent faces of the slab or mattress 22.
Moreover, since the sheets 21a and 21b are heat-sealed adjacent to the marginal edges'thereof, about the perimeter of the bag, as indicated at 23, one end of the mattress 22 is spaced about 6 from the corresponding end of the bag, soas to provide a normally collapsed expansion pocket, indicated by the reference character 35, at theleft-hand end of the bag, as shown in FIGS. 3 and 4. This normally collapsed expansion pocket 35, together with the normal elasticity of the walls of the bag, accommodate the required expansion of the confined charge 24 of gas as the temperature thereof is increased within the normal operating'temperature range of the unit so that the normal operating pressure within the bag in the a normal operating temperature range thereof (30 F.
to +150 F.) does not ordinarily exceed atmospheric pressure. Accordingly the bag of the unit 20 is not ruptured, punctured or subjected to undue strain, within the normal operating pressure range of the confined charge of gas 24 in the normal operating temperature range thereof.
The composite structure of the laminate 21a is very advantageous in that the kraft paper ply 26 lends great tear strength thereto, while the polyethylene or Mylar outer ply 26 lends great abrasion resistance thereto,
' whereas the inner plies 27 and 28 of Saran lend low In the unit 20,'the mattress 22 may be formed of a number of suitable heat-insulating materials, but it preferably comprises a mass or slab of loosely packed glass fibers, the glass fibers being suitably matted to render the hat or mattress 22 sufiiciently self-supporting and integrated to accommodate ready handling thereof. Likewise the charge 24 of gas may take the form of a number of suitable heavy gases having a thermal conductivity lower than that of air, but it preferably essentially comprises dichlorodifluoromethane, as this material is very advantageous,'having a thermal conductivity that is substantially lower than air, and having a boiling point that is well below the normal operating temperature range of the unit 20. g
It is noted that when the refrigerator cabinet 10 is employed in the storage of food in a frozen condition, the temperature of the refrigerator space 13 may be as low as -30 F.; whereas, when the refrigerator cabinet 10 is not in use and is involved in railway transportation or in warehouse storage, the temperature of the space 13 may be as high as +150 F. Hence the charge 24 of gas confined within the bag of the unit 20 may be-subjected to any temperature within the so-called operating temperature range extending from about '-30 F. to about 77 +l50 F. Thus hereinafter, the expression: operating-temperature range of the charge 24 of gas confined within the bag of the unit 20 refers to the total temperature range to which it may be subjected and not merely to the temperature range involved in the normal operation of the refrigerator cabinet 10 when it is used in the refrigeration of food.
Again referring .to FIGS. 3, 4 and S of the drawing, in the preferred embodiment of the unit 20 the bag is substantially rectangular in plan having a length of about 32" and a width of about 17 and a thickness of about 1%"; while the mattress 22 has a length of about'25 /2", a width of about 14" and a thickness of about 1%". When the charge 24 of CCl F is introduced into the bag of the unit 20, it has a pressure of about 730 mm. of mercury at a temperature of about.l20 F., so that there is a slight subatmospheric pressure of the charge 24 of permeability thereto with respect 'to the gases involved. More particularly, the composite laminate 21a is practically impervious to the charge 24 of CCl F confined in the hermetically sealed bag and highly impervious to ordinary light atmospheric gases, including water vapor. Furthermore, the inner plies 27 and 28 of Saran of the laminate 21a are admirably suited to heat-sealing in the manufacture of the unit 20. I
In heat-sealing the bag of the unit 20, the marginal edges of the two sheets 21a and 21b are subjected to heat and pressure therethrough, so that the inner plies 27 and 28 of the'two sheets in facing relation with each other fuse and bond together, producing the seal indicated at 23, about the perimeter of the bag. In this step, the paper plies 25 of the two sheets absorb with their re silient thickness the variation in the thickness of the Saran plies 27 and 28 in the two sheets, as well as other. sources of misalignment, thereby eliminating microscopic; bridges through the welds and unfused areas in the Welds.
, More particularly, these paper plies effect a more uniform pressure along the entire length of the seam in fusing the liquid interfaces. Moreover, these paper plies distribute some of the force of the sealing electrodes laterally, so that the plastic material adjacent to the weld zone is compressed, thereby preventing excessive upsetting of the plastic material. Thismaterially improves the tear resistance of the plastic material adjacent to the weld and prevents any reduction in thickness through which excessive permeation might occur. Hence, the important structural advantages of the bag of the unit 20 flow not only from the individual elements or plies of the sheets thereof, but also from the cooperation therebetween and from the essentially new characteristics imparted to the plastic plies by the paper plies, both in the final structure of the bag and in the fabrication thereof.
When the unit 20 is in place in the refrigerator cabinet 10, it nicely fills the space between the cabinet walls 11 and 12; and in placing the unit 20 in this space, it is deformed to conform thereto, the mattress 22 and the walls 21a and 21b accommodating the required deformation. In the operation of the unit 20, the mattress 22 of glass fibers breaks up the charge 24 of gas confined in the bag thereof so as to minimize or prevent substantial convection currents within the bag. In the assembly of the refrigerator cabinet :10, the required heat-insulating units 29 are placed between the cabinet walls 11 and 12 for the insulating purpose. M
In the present construction of the improved heat-ins lating unit 20, a thermal conductivity (k) is obtained that has a value of about 0.12 Btu. per hour per square foot per inch of thickness per F.; whereas corkboard has a corresponding value of k of 0.33 and expanded vermiculite has a corresponding value of k of 0.48. Thus the thermal conductivity of the improved heat-insulating unit 2%) is only about /3 of that of these good heat-insulating materials named that are frequently used in refrigerator cabinets; whereby the substitution of the heat-insulating units 21} of the present invention renders it feasible to reduce by about /2 the normal spacing between the outer shell 11 and the inner liner 12 of the refrigerator cabinet so as materially to increase the useful volume of the refrigerator space 13 within the inner liner 12, utilizing the outer shell 11 of given dimensions. Moreover, the weight of these heat-insulating units is substantially less than that of conventional units thereby effecting a corresponding reduction in the overall weight of the composite household refrigerator.
In view of the foregoing, it is apparent that there has been provided a heat-insulating unit of improved construction and arrangement for ready incorporation into a refrigerator cabinet in the space between the metal outer shell and the metal inner liner thereof, thereby accommodating a substantial reduction in the wall thickness of the cabinet between the outer shell and the inner liner thereof and contributing materially to compactness and reduction in the weight of the cabinet.
While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.
What is claimed is:
1. In combination, a deformable porous mass of solid poor heat-conducting material, an hermetically sealed bag enclosing said material, and a charge of a gas having a coefiicient of thermal conductivity lower than that of air also enclosed in said bag and thoroughly permeating said porous mass of solid poor heat-conducting material, the walls of said bag being substantially impervious to said gas confined therein and also to atmospheric gases and to water vapor and being formed of a flexible multi-ply laminate, said laminate including an intermediate ply of calendered kraft paper having a thickness of about 5 mils to provide a high tear strength and an inner ply of vinyl idene chloride copolymer resin having a thickness of at least about 1 mil to provide a low permeability to said gas and to atmospheric gases and to water vapor and an outer ply of polyethylene resin having a thickness of about 2 mils to provide a high abrasion resistance, said intermediate ply being respectively adhered to said inner ply and to said outer ply by inner and outer adhesive layers, each of said adhesive layers being flexible after setting thereof and having a low permeability to said gas and to atmospheric gases and to water vapor.
2. The combination set forth in claim 1, wherein each of said adhesive layers comprises copolymers of butadiene and acrylonitrile.
3. The combination set forth in claim 1, wherein said mass of material essentially comprises a self-supporting slab of glass fibers, said gas essentially comprises dichlorodifiuoromethane, and said bag essentially comprises a pair of facing walls disposed on opposite faces of said slab, the facing walls of said bag being normally pressed by atmospheric pressure into firm engagement with the adacent faces of said slab by virtue of a slight subatmospheric pressure of the charge of said gas enclosed in said bag.
4. The combination set forth in claim 3, wherein the charge of said gas enclosed in said bag is productive of a pressure of about 730 mm. of mercury at a temperature of about F.
References Cited in the file of this patent UNITED STATES PATENTS 2,067,015 Munters Jan. 5, 1937 2,268,462 Sachsenroder et al Dec. 30, 1941 2,354,855 Emanuel Aug. 1, 1944 2,673,826 Ness Mar. 30, 1954 2,686,744 Cornwell Aug. 17, 1954 2,817,123 Jacobs Dec. 24, 1957 2,817,124 Dybvig Dec. 24, 1957 2,863,179 Gaugler Dec. 9, 1958 OTHER REFERENCES Protective Packaging of Frozen Foods, by I. G. Woodroof et al., in Refrigerating Engineering, for February 1954, pages 45-48, page 46 relied on.