US2067208A - Refrigerating apparatus - Google Patents

Description

1, 1937- s. M. SCHWELLER 2,067,208

REFRIGERATING APPARATUS Original Filed May 28, 1934 2 Sheets-Sheet l l [1-'5 10 13 11 21 16 1 1" T I INVENT OR.

J .8 BY

l ATTORNEYS.

Jan; 12, 1937. 5 SCHWELLEIR 2,067,208

REFRIGERAT I NG APPARATUS Original Filed May 28, 1934 2 Sheets-Sheet 2 y 6 INVENTOR.

Sn. vssrfle M. semvum ll/S ATTORNEYS.

Patented Jan. 12, 1937 UNITED STATES PATENT OFFICE REFRIGERATIN G APPARATUS Original application May 28, 1934, Serial No. 727,942. Divided and this application June 5,

1935, Serial N 25,096

7 Claims This invention relates to refrigerating apparatus and particularly to heat exchangers or evaporators for such apparatus. The present application is a division of my copending application Serial No. 727 ,942 entitled Refrigerating apparatus and filed May 28, 1934.

In the past, evaporators for various types of refrigerating systems have generally been constructed of a plurality of individual pipes formed into various shapes. Evaporators for household refrigerating apparatuses have commonly included a cylindrical tank or header having the ends of a plurality of spaced apart pipes or duct loops secured thereto and extending outwardly and downwardly from the tank, or header to provide a freezing chamber or compartment for the reception of ice-making receptacles. Such evaporators were not neat in appearance and it was, therefore, necessary to conceal the same within a household refrigerator cabinet by some sort of a cover or front plate having a finish thereon which was neat in appearance. In recent years, however, evaporators for household refrigerator cabinets have been constructed of or fabricated from sheet metal plates or shells superimposed upon one another and at least one of which plates or shells was embossed or corrugated to provide refrigerant expansion chambers or passages between the sheet metal plates after the same were welded together. In the production of such sheet metal evaporators from plates or sheets, portions thereof were commonly welded together at certain contiguous points and spaced apart at other points to form a substantially flat double walle structure which was bent or formed, after weldi g, into a shape to provide walls of a freezing chamber or compartment. The structure thus formed was then enameled with a porcelain or the like finish coating so as to render the walls of the evaporator neat in appearance and to eliminate the necessity of employing a cover or front plate in refrigerator cabinet construction.

As far as I am aware, these sheet metal evaporators have been constructed 'of iron or steel sheets or plates which could be readily spot or roll welded together without difiiculty and which were porcelain enameled to isolate the sheet iron or steel from the environment atmosphere and humidity within a refrigerator cabinet to prevent rusting thereof. However, a considerable amount of trouble and expense has been involved in the use of porcelain enameled sheet iron evaporators, since evaporators of refrigerating systems present highly favorable condition for causing corrosion or rusting thereof. For example, evaporators of thus permitting refrigerant to escape from the expansion passages formed between the sheet iron members of which the evaporator is fabricated. A porcelain or the like coating on sheet metal evaporators, being of a refractory substance, also tends to insulate the walls of the evaporator from a the medium to be cooled thereby, thus retarding transference of heat from the medium to the evaporator and consequently refrigerant contained therein. Therefore, sheet iron or steel evaporators having walls thereof covered with a coating of enamel or the like material, which is inherently brittle and easily cracked or chipped merely by the act of removing metal ice trays from or replacing same in the freezing compartment or by striking the porcelain coating on the evaporator with bottles and other objects, have been the major source of trouble to the guarantee and servicing of refrigerators sold by refrigerator manufacturers.

I have recently been striving to overcome the trouble encountered in the use of sheet metal evaporators and have found that an evaporator fabricated from sheets of brass will fully overcome such troubles which render steel evaporators unsatisfactory. Brass sheets suitable for this purpose inherently consist of certain properties to enable fabrication thereof and the application or plating of a metallic coating thereon such as tin or chromium in order to provide a neat and everlasting finish on the evaporator which will not become discolored and unsightly in appearance. Such brass sheets ordinarily consist of approximately 85% copper and 15% zinc. It is well known that brass will resist oxidation, corrosion and/or rusting over a greater interval of time than iron or steel. Brass sheets can also be readily plated with a metallic finish such, for example, as chromium or tin which affords a smooth neat finish that can be readily and easily cleaned with various cleaning compounds without danger of damaging or causing discoloration of the finish. Present known methods of plating tin or chromium on brass provide a metallic finish over the brass which finish inherently has substantially the same coefficient of expansion and contraction as the brass and therefore affords a finish which will not crack under various temperature changes and which is difficult to scratch or chip. For these reasons, such material as brass is preferable for use in fabricating sheet metal evaporators for refrigerating systems wherein existing temperatures and humidity present ideal corrosion and/or rusting conditions. The welding, brazing or bonding of brass sheet portions together, .however, presents many problems to evaporator manufacturers over the comparable simple welding of iron or steel sheets together. For instance, the act of spot or roll welding brass sheets together requires very careful operations on the part of a highly skilled in the art operator in order to prevent burning or scorching of the thin sheets of metal at the welded spots or along the lines of welds. Such spot or roll welding of brass sheets consumes a considerable amount of time and also results in the presence of rough or indented spots or lines along the exterior surfaces of the sheets. These rough spots or lines therefore present surfaces which are very difficult to cover during the plating operation of tin or chromium on the surface of the welded sheets and in addition these spots or lines are rough even after being plated, thereby destroying the smoothness of the exterior surfaces of the evaporator. This prior method of bonding brass sheet portions or plates together is obviously a tedious and expensive procedure and produces a structure which is not entirely satisfactory. My invention is therefore directed to an improved sheet metal heat exchanger or evaporator char-- acterized by the fact that the brass sheets of the evaporator are bonded together in an improved manner;

. One of the objects of the present invention is to provide a fiuid tight evaporator for a refrigerating system constructed of highly conductive sheet metal material having a highly conductive metallic finish thereon.

Another object of the present invention is to provide a fluid tight evaporator for a refrigerating system constructed of sheet material which can be readily plated with a metallic finish which is difiicult to scratch,.crack or chip and which sheet material will resist corrosion and/0r rusting over long periods of time even if exposed to environment atmosphere.

A further object of the invention is to provide an improved evaporator for a refrigerating system fabricated from brass sheet material and characterized by the fact that all of the surfaces of the sheet material to be secured together are bonded by a single heating operation.

Y In carrying out the foregoing objects, it is a still further object of the invention to simultaneously bond all portions of superimposed brass sheet members, to be secured together, to provide fiuid tight passages therebetween by heating the entire article by radiant heat to thereby prevent scorching or burning of portions of the brass sheet members.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 discloses a fiat metal sheet, a corrugated metal sheet and a fiatsheet of spelter material solder or spelter material.

adapted to be superimposed upon one another and secured together to form a double walled substantially flat plate-like assembly;

Fig. 2 is a top plan view of the flat plate-like assembly formed by superimposing the sheets shown in Fig. l;

Fig. 3 is an enlarged sectional view taken on the lines 33 of Fig. 2 and showing the elements of the plate-like assembly before being bonded,

together;

Fig. 4 is an enlarged fragmentary sectional view taken on the lines 44 of Fig. 2 and showing the elements of the double walled plate-like structure after being bonded together;

Fig. 5 is a vertical sectional view through a furnace in which the fiat plate-like assembly shown in Fig. 2 is placed for applying heat thereto;

Fig. 6 is a sectional view of the furnace shown in Fig. 5 and is taken on the lines 6-6 thereof;

Fig. '7 is a front elevational view of a fluid tight heat exchanger or evaporator for a refrigerating system provided by bending the bonded double walled plate-like structure; and

Fig. 8 is a side elevational view of the heat exchanger or evaporator disclosed in Fig. 7.

For the purpose of describing the article as claimed in the appended claims I will illustrate the manufacture of my improved evaporator for a refrigerating system. Referring to Fig. 1 of the drawings for illustration, I have shown a fiat brass sheet or plate l0. Also shown in Fig. 1 is a corrugated or embossed substantially fiat brass sheet or plate II. "In order to bond certain portions of sheets or plates l0 and II together as will hereinafter be more fully described, I show in Fig. 1 a thin fiat sheet l2 of The solder or spelter sheet I2 is placed or superimposed upon .the fiat plate or sheet l0 and. the corrugated sheet or plate II is then placed or superimposed upon the spelter sheet. It will be noted that plate or sheet I0 is slightly larger than the spelter sheet l2 and brass sheet H and has its corners cut away and slit as at I3. The portions of sheet or plate I 0 disposed between its edges and the dot-dash lines designated at M are then bent around the edges and folded over the peripheries of the sheets or plates II and [2 to secure the sheets or plates l0, II. and I2 together to provide the fiat plate-like double walled assembly or structure l5 as shown in-Fig. 2. The brass sheets l0 and II may consist of any desired copper and zinc content and preferably of ap- The proximately copper and 15% zinc. spelter or solder sheet l2 may be of a silver solder composition but is preferably also of brass and consists of a higher zinc content than the sheets "and II, for example, 60% copper and 40% zinc, in order to provide a spelter sheet which will melt at a temperature below that at which brass sheets Ill and II will melt. It is to be understood that the brass sheets and the spelter or solder sheet may consist of various percentages of metallic substances relative to one another so long as the spelter sheet can be melted at a lower temperature than the temperature at which the brass sheets will melt. The melting point of the brass sheets or plates l0 and H described in the present illustration is somewhere in the neighborhood of 1,800 F. while the melting point of the solder or spelter sheet I2 is at approximately 1,650 F. Thus, it is apparent that a temperature of from approximately 1,700 F. to 1,750 F. will cause melting of the spelter ca'te with the manifold chamber I1.

An embossed portion I6 provided in the corrugated brass sheet or plate II forms a header or manifold passage H (see Fig. 3) between the sheets or plates I and II. Corrugated portions I8 form passages I9 (see Figs. 3 and 4) between the plates I0 and II. An opening 2| in embossed portion I6 may be provided therein either before or after the sheets are bonded together. Another opening 22 in the corrugation I8 which extends entirely across the structure I adjacent one end of header I I5 may also be provided either before or after the sheets III and II are bonded together. These openings 2| and 22 are for a purpose to be hereinafter more fully described. It will be apparent, by referring to Fig. 3, that the conduits or passages I 9 communi- The bending of the peripherial portions of sheet or plate I0 around and over the peripherial portions of sheet or plate II, as previously described, clamps or presses certain portions of sheets III, II and I2 into engagement with one another. The substantially fiat double walled assembly I5 is then ready to be heated to cause melting of the spelter sheet I2 and bonding or brazing of the sheets or plates I0 and II together.

The substantially fiat double walled plate-like assembly or structure I5 is placed upon a cart or sled 24, comprising a plurality of cross-beams 25 for supporting the structure I5 at spaced apart points throughout its area, (see Fig. .5 and 6) and this cart or sled 24 together with the structure I5 is then moved into a furnace, generally designated by the reference character 21, through the access door opening 28 which is closed by a door 29. The sheets or plates III, II and I2 of the double walled assembly I5 are preferably forced toward one another during heating thereof in the furnace. Any suitable arrangement may be employed for this purpose. For example, a plurality of weights may be placed or lowered upon the double walled structure I5 or a suction may be created during heating of the structure by an aspirator or pump, in the passages I1 and I9 formed between the sheets or plates of the structure I5. In either event the plates I II and II will be suitably pressed or forced toward one another to cause the spelter material I2 to bond certain portions of the plates together uniformly over lines adjacent the passages I1 and I9. After the double walled structure I5 has been moved into the furnace 21 and after the plates. are suitably pressed toward one another the door 29 of furnace 21 is closed and the fuel supply leading to burners 3|, through pipe 32,- is then turned on to cause the burners to increase the temperature within furnace 21 to a predetermined degree sufficient to cause melting of the spelter or solder sheet I2 by radiant heat. The gas burners 3| or any other suitable source of heat such as electric resistance units or headers may be located wherever desired throughout the interior of the furnace. The structure I5 is permitted to remain in the furnace 21 a predetermined interval of time in accordance with temperatures therein to insure melting of the spelter material I2 and the structure I5 is then removed from the furnace and allowed to cool. It is to be understood that to insure bonding of the brass plates or sheets ID and II by the spelter material I2, any of a wide variety of fluxing compounds may be painted or otherwise applied to the surfaces of the plates to be bonded together. It is to be also understood that the details of construction of the furnace 2I has no bearing on the present invention for the reason that many types of furnaces may be employed to carry out the manufacture of the improved heat exchanger or evaporator herein disclosed so long as the temperature of the entire exchanger or evaporator to be brazed is simultaneously and uniformly increased, which method is esential to insure uniform bonding of portions of thestructure throughout its entire area. For example, the structure may be placed in a furnace in which a reducing gas or atmosphere is present to carry away oxides, etc., formed during heating and melting of the solder or spelter material. In the case of heating the structure in the presence of a reducing gas or atmosphere openings 2| and 22 are provided in the structure prior to applying heat thereto and the use of the fiuxing material mentioned may be dispensed with. I

Referring to Fig. 4 of the drawings wherein I have shown an enlarged cross-section of the double walled structure I5 after the structure, has been heated and brazed, it will be noted that the spelter sheet or material I2 has been deformed by the melting thereof, and that the of the plates I0 and II which are substantially contiguous with one another. It will also be noted that the spelter material has caused the substantially contiguous portions of the brass sheets III and II to be firmly brazed or bonded together. The bonded together substantially flat plate-like double walled structure I5, after having been removed from the furnace and permitted to cool is bent first along the lines designated at A--A and BB in Fig. 2, to form side 'walls of a sharp freezing compartment for the evaporator, and is again bent along the lines designated at CC and DD in Fig. 2 to form a bottom wall of the freezing compartment (see Fig. 8). The ends of structure I5 brought together at the bottom of the freezing compartment are preferably secured together in any suitable manner. The brass evaporator thus formed may be plated in any suitable and well-known manner with a, metallic coating such as tin or chromium to afford a smooth finish on the evaporator which will be neat in appearance and which can be readily and easily cleaned or washed with any of a plurality of cleaning compounds without damage to the finish. The opening 22 leading to pasage I9, formed between the brass plates or sheets I0 and II by the corrugations I8, is adapted to receive one end of a liquid refrigerant supply pipe or conduit 35 having its other end connected to any conventional or well-known refrigerant liquefying and circulating unit (not shown). The gaseous refrigerant return pipe or conduit 36 of the refrigerating system may be secured or attached to opening 2| provided in header I6 of the evaporator I5. Refrigerant admitted to the passages or conduits formed between the double walled evaporator I5 first flows from pipe 35 through the opening 22 and thence to the passages I9 to the bottom wall of the evaporator. Refrigerant flows from the bottom wall of the evaporator I5 upwardly in multiple through the plurality of passages III to the passage H as indicated by the arrows in Fig. 8, from where it flows through opening 2| and pipe 36 back to the refrigerant liquefying and circulating unit.

- spelter material has flown toward those portions From the foregoing, it will be apparent that I have provided an improved evaporator or cooling element for a refrigerating system which is more effective in producing refrigeration due to its being constructed or fabricated of sheet brass and coated or plated with a metallic finish which like the brass is also of high heat conductivity. By increasing the conductivity of walls of the evaporator I insur'e rapid transference of heat from a medium to be cooled by the evaporator to refrigerant contained therein and thereby 'render the refrigerant liquefying and circulating unit of the refrigerating system, in which the evaporator is connected, more efiicient. My improved sheet brass evaporator greatly reduces costs in themanufacture of same. For example, the method of making a sheet brass evaporator as herein disclosed eliminates scorching or buming of the brass sheets, as often occurs in spot or roll welding brass sheets together to form an evaporator, and affords the evaporator with smooth exterior walls which can be readily and easily plated. Moreover, my improved evaporator or cooling element will be of long life even if the metal of the walls thereof should become exposed, or, should the finish thereon have small undetectable pinholes or pits therein extending to the metal of the walls and exposing same to the environment atmosphere, due to the corrosion or rust resisting properties of the walls.

While the form of embodiment of the invention as herein disclosed, constitutes a. preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. An evaporator for a refrigerating system comprising a fluid-tight double walled structure including a brass sheet member superimposed upon an embossed brass sheet member and secured thereto with a bonding material fused between the members by so applying heat uniformly and simultaneously over the entire exposed surfaces of the evaporator as to leave unchanged the original characteristics of said sheet members. i

2. An evaporator for a refrigerating system comprising superimposed brass sheet portions having a fluid-tight refrigerant passage or chamber therebetween characterized by the fact that the brass sheet portions are bonded together with a bonding material by so applying heat uniformly and simultaneously over the entire exposed surfaces of the evaporator as to leave unchanged the original characteristics of said sheet portions. 4

3. An evaporator for a refrigerating system comprising superimposed brass sheet portions having a fluid-tight refrigerant passage or chamber therebetween characterized by the fact that the brass sheet portions are bonded together with a bonding material in a furnace wherein the entire evaporator is exposed to heat within the furnace and the original characteristics of the brass sheet portions are unchanged after being heated.

4. An evaporator for a refrigerating system comprising a double walled structure including a brass sheet member superimposed upon a corrugated brass sheet member and secured thereto with a bonding material fused between the peripheries and the corrugations of the members by so applying heat uniformly and simultaneously over the entire exposed surfaces of the evaporator to provide a plurality of fluid-tight passages within the double walled structure and to leave unchanged the original characteristics of the sheet members.

5. An evaporator for a refrigerating system comprising a double walled structure including a brass sheet member superimposed upon a corrugated brass sheet member and secured thereto with a bonding material fused between the peripheries and the corrugations of the members by so applying heat uniformly and simultaneously over the entire exposed surfaces of the evaporator to provide a plurality of fluid-tight passages within the double walled structure and to leave unchanged the original characteristics of the sheet members, and said double walled structure being bent to provide a plurality of walls of a sharp freezing compartment for said evaporator. I

6. An evaporator for a refrigerating system comprising, superimposed brass sheet portions having parts of the adjacent faces thereof spaced apart to form a refrigerant passage or passages therebetween, certain other parts of the adjacent faces of said superimposed sheet portions being secured together by joints formed of uniformly fluid tight fused bonds, and said sheet portions retaining unchanged their original characteristics and being free from pitted or rough spots after being secured together.

7. An evaporator for a refrigerating system comprising, superimposed brass sheet portions having parts of the adjacent faces thereof spaced apart to form a refrigerant passage or passages therebetween, certain other parts of the adjacent faces of said superimposed sheet portions being secured together with a bonding material by substantially simultaneously and uniformly heating the entire surfaces of the evaporator to'provide uniform fluid tight joints between said sheet portions, and said sheet por-v tions being unburnt and free from pitted or rough spots after being secured together.

SYLVESTER M. SCHWELLER.

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