US2334219A - Evaporator structure - Google Patents

Description

Nov. 16, 1943. 1 Nl RQTH 2,334,219

EvAPoRAToR STRUCTURE Filed May 1'?, 1941 4 sheets-sheet 1 Nov. 16, 1943. J. N. RoTH 2,334,219

EVAPORATOR STRUCTURE F11ed May 17, 1941 Y 4 sheets-sheet 2 Nw; 16, 1943. 1N. RQTH 2,334,219

EVAPORATOR STRUCTURE Filed May 17, 1941 4 Sheets-Sheet 5 Nov. 16, 1943. J. N. ROTH EVAPORATOR STRUCTURE Filed May 17, 1941 v4 sheetsfsheet '4 Watente Nov. 16, `1943 Evarona'ron STRUCTURE `Joseph N. Roth, neming,- Mich.; assignor to Gib- `son Electric Refrigerator Corporation, a corporation of Michigan Application Mey 17,1941, serial N0.3s4,o31

. 'i clame*A (ci. ca -126) This invention relates to an evaporator structure, and more especially to an evaporator structure particularly designed for domestic refrigerators, and 'to an improved method of manu-2y provision of means for fastening a tube in intimate heat exchange relation with a sheet metal plate Aby spot welding, as a rapid factory operation, without danger of burning through 'thin steel tubing; still another feature is. the use of tubing of dierent' internal diameter in different lportions of the evaporator structure, and a particular arrangement of the tubing, to provide smoother freezing action throughoutthe whole of the evaporator structure; and yet another feature is the provision of an improved junction between a capillary tube and an evaporator tube to prevent frosting back through the cabinet wall.

Other features and advantages of this invenv tion-will be apparent from the following specification and the drawings, in which: Y

Figure 1 isa vertical cross-sectional view of the food compartment of a domestic absorption refrigerator: Figure 2 is a top plan view of the evaporator and its connections, the fback insulated wall of the food compartment being shown in dotted lines; Figure 3 is a view along the line t-t of Figure 2; Figure 4 is a back view of the evaporator; Figure 5 is a. bottom view of the structure shown in Figure 2; Figure 6 is a fragmentary detail/viewialong the line" S- of Figure i: Figure 'l isa detail sectional view of the Junction between the capillary tube and the inlet side of the evaporator tube; Figure 8 is a top view of another form of evaporator; Figure 9 is a bottom view of the evaporator shown in Figure 8; and Figure 10 is aside view, partly in section; of this last form of evaporator. f

Shelf or at plate types of evaporators have met with increasing favor -in domestic refrigerators, yet such evaporators present certain problems, particularly with regard to uniform cool- 4upper surface.

and forth in contact with the remaining area of.

arrangement of the.two sets of coils being such that a considerable amount of the refrigerant is forced up-into the upper coils Ain liquid state to complete its vaporization there, so that even at low rates of refrigeration or operation of the refrigerator considerable cooling takes place from above. I have also found that my particular arrangement of evaporator can be best manufactured by welding and forming the.tubing to the desired shape over forms or jigs, separately forming a sheet metal box structure, slipping the tubing over the box structure, and then attaching the two in intimate heat exchange relation by clips or fastening members straddling the tube and spot welded to the sheet metal on each side ofthe tube ata plurality of spaced points. Moreover, I provide a connective arrangement between thel evaporator tubing and capillary tubing such that frosting back through the insu lated food compartment wall is prevented without the necessity of an accumulator.

Referring now to Figures 1 to '7 of the drawings, a domestic refrigerator is shown having' 4a. food compartment I0 with insulated walls II. While my evaporator has advantages in an'y type of domesticrefrigerator, it was designed for a.

continuous absorption refrigerator, wherein its advantages are realized to the fullest. The evaporator is shown in the top of the food compartment I0, and comprises asheet metal box I2 and upper and lower loops of tubing.

Referring now more particularly to Figures 2, 3, 4 and 5, liquid refrigerant delivered to the capillary housing I3 passes through theback insulated wall Il of the food compartment through the tube I 4, the details of this connection being described more fully hereafter. In .Figure 5 it `will be seen that the ow path of the refrigerant' passes along the tube I5 and through the tubes I 6, I1, and I8 to pass substantially entirely around the periphery of the bottom plate I of the evaporat'or box or shell, 'this plate I9 forming a shelf having substantially the same cross-sectional area as that of the food compartment, and adapted to have ice cube trays and the like placed on its The /tubing is then looped back this plate bounded by the above-mentioned tubing, the legs of these loops being here indicated as 20, 2i', 22, 23 and 24. The flow path then con. tinues through the tube 25 to the'back of the evaporator and up throughpthe tube 26 (see Figure 4) to the upper section of the evaporator. Referring more particularly to Figure 2, a top view ofthe evaporatorn it will be seen that when the tubing reaches the upper level it expands in diameter at 21, then extends forwardly to the front edge of the top ofthe evaporator shell andloops back and forth again, the legs of these latter loops being indicated as 28, 29, 30, 3l, 32 and 33. The refrigerant then passes down 4through the tube 35 (also see Figure 4) and out.

through the back wall of the food compartment to `ioin, preferably with a flanged coupling, tothe -pipe 36 leading to part of the refrigerant circuturing convenience this single continuous :Iow

path may be formed by welding together various sections of tubing, in nished form it is in effect a single tube looping back and forth in 'a lower horizontal plane and then passing up to a higher plane parallel to but spaced from the rst-mentioned plane. .By first passing the tubing substantially entirely around the periphery of the freezing shelf or bottom plate of the evaporator shell, and then looping it back and forth over the remaining area, cooling is substantially uniform over the entire area of this shelf. This is important, since heretofore considerable difilculty has been encountered in that an ice tray placed on one side of a freezing shelf might freeze rapidly while an ice tray placed on the, other end of the same shelf might never freeze.

Moreover, although it has been known to be desirable to provide some cooling eifect -above the evaporator shell in these types of evaporators, heretofore the upper tube sections have only been eiective when the refrigerator was operating at a high rate and delivering a considerable amount of liquid refrigerant to the evaporator. caused-a certain amount of the liquid refrigerant to pass on up into the upper section ofthe evaporator even at low refrigeration rates by making the upper and lower portions of tubing of different internal diameter, the tubing of the upper portion preferably having an internal diameter fty per cent or more greater than that of the tubing in the lower portion.V In a particular embodiment of my-invention I find that my desired results are secured by making the lower tubing section of tubing of three-eighths 4inch outer diameter and one-quarter inch internal diameter, and the upper section of tubing of nine-sixteenths inch outer diameter and sevensixteenths inch internal diameter.

In manufacturing an evaporator of the kind here disclosed I flnd it preferably to form and weld the various tubing sections over forms and jigs, forming the vtubing to nished shape. I then separately form the sheet metal box or shell by such bending and welding operations as may be necessary. As may be best seen from Figure 3, the sheet metal shell can then be slipped in between the upper and lower tubing sections, so that the two are brought into finished relation. The tubing is then permanently attached to the shell and held in intimate heat exchange relation with it by the use of clips or fastening members which straddle the tube and are spot welded to the sheet metal on each side.

It will be seen that there are a number of these fastening members overlying the tubing at I have overcome this difficulty and regularly spaced intervals, as about every nve or six inches. Since they are all duplicates only one, here identified as 31, will be described.

Referring more particularly to Figure 6, it will 5 be seen that the fastening member 31 is of strap metal, as thin steel strip, having an arcuate or U- shaped center portion and at outwardly extending end portions identified as 38 and 39. The U- shaped center portion is made with such a curva- '10 ture as to just conform to the outer surface of the tube 33, and of a depth slightly less than the diameter of the tube. 'I'hat is, in their original shape the end portions of the fastening member extend out parallel to the plate 40, but not quite in contact .therewith because of this slight difference between the depth of the center portion and the outer diameter of the tube. The mechanical action of forcing them down into engagement with the plate and spot welding them thereto, therefore, places them under strain so that the tube 33 is pulled down tightly against the plate 40 and held in intimate heat exchange relationship with it.

For a number of reasons it is desirable to use rather thin steel tubing and light sheet metal plates in an evaporator of the type here disclosed. Heretofore tubing has generally had to be brazed or soldered in engagement with the sheet metal, not nearly as rapid and satisfactory as spot welding, because spot welding such light steel tubing directly to the plate frequently burned through the tubing and resulted in openings which caused rejection of the evaporator on inspection, or weak spots which caused leakage after only a short period of use of the evaporator. 'I'he use of fastening members or clips secures all the desirable features of spot welding, such as rapidity and permanence, without any danger of damage to the tubing. Soldering is particularly undesirable, for 4 example, where it is desired to subject the evaporator in nished form to considerable heat, as where enamel is baked on or the structure is hot dip galvanized.

Referring now more particularly to Figure '1, it will be seen that the tube I4 passing through the insulated back wall I I of the food compartment is considerably reduced in internal diameter with respect to the evaporator tube I5 with which it connects. 'Control of the admission of refrigerant to the evaporator is achieved by a capillary tube terminating in a straight portion 4I extending through the back wall and received in a, fairly close fit by the tube I4. The other details of the capillary arrangement are'not illustrated here, forming the subject matter of my copending application Serial No. 361,629, filed November 1'1, 1940. v'I'he capillary is carried by a plate 42 providing a flange adapted to be bolted or otherwise removably sealed to a iiange 43 welded to the outer end of the tube I4. This construction facilitates assembly and disassembly of the parts since the evaporator may be i'lrst located in the cabinet, the capillary 4I slipped into the pipe I4 until the plate 42 contacts the flange 43, and then the parts may be fastened together by bolts. 'I'his enables the final connection to be made from the ass-1,219

cluding: a horizontalmetal plate of an area substantially equal to the cross-sectional area of the food compartment; and a tube adapted to -have the insulated wall to cause frosting of the flange and its associated parts. i

Turning now to Figures 8, 9 and`l0, another form of fiat shelf evaporator is shown which em'- bodies the feature of uniform cooling ofthe shelf surface. .As may be best seen in Figure 8, the refrigerant enters through the tube 45 and then passes substantially entirely around the periphery of the plate through the portions 41, I8 and Il. Thereafter, as in the first described form of my invention, it loops back and forth over the remaining area of the evaporator, the legs of the loops being here indicated as 60, 5I, 52 and 53.

Thereafter the tubing drops down an vinch or so and loops backand forth in the other direction, out of contact with the plate and'slightly below the above-described loops, in loops having legs idened as 5l, 55, 5.5, 51, 58, 50 and l0, the rel frigerant 'then passing out through the outlet pipe 6|. This additional tubing below and out of contact with the plate furnishes further vaporization spacefor the refrigerant when the refrigerator is operating at a high rate. so that frostingnever takes place outside of the food compartment. u

While I have shown and described` certain embodiments of my that it is capabl of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from refrigerant ow therethrough, the tube having a portionilin'fheat exchange relation with the plate and flrst'fpassing substantially entirely around the plate` near the periphery thereof, then-looping in contact with the remaining area of the plate, then extending to and looping. in another plane parallel to saidplate, the internal diameter of the latter portion of the tubenbeing larger than that of the portion in heat, exchange relation with the plate. v

3. Apparatus of the character claimed in claim 2, wherein the two portions are of substantially equal length.

4. Apparatus of the character claimed in claim i 2, wherein the plane in which the latter portion of the tube lies is above that of the plate.

5. Apparatus of the character claimed in claim y 2, wherein the portion of the tube looping back enden, it is to be understood the spirit and scope of the invention as disclosed intheappendedclaims. Y

Iclaim:v

1. In a continuous .absorption refrigerator tact wit'the remaining area of the plate, then extending to and looping Aback and forth in another plane parallel to and above said plate, the

portionfof the tube in the upper plane having a lengt substantially equal te that in the lower plane and having an internal diameter at least 50 %'=la'rger than that of the portion in the lower plane. l Y A 2.-In a continuous. absorption refrigerator and forth makes serpentine bends.

6. In continuous absorption regrlgerator having a food compartment, an evaporator including: a horizontal metalplate of an area substantially equal to the cross-sectional area of the food compartment: and a tube adapted to have refrigerant iiow therethrough, the tube having a first portion in heat exchange relation with the plate and a second portion in another horizontal plane parallel to the plate, the internal diameter of the first portion of the tube being small enough and its arrangement such that the flow of liquid refrigerant through said rst portion is accelerated and there is a. substantially uniform distribution of cooling effect throughout the entire area of said plate at all refrigeration rates, the internal diameter of the second portion being large enough to permit liquid refrigerant to vaporize therein without appreciable acceleration of liquid ow.

7. In a continuous absorption refrigerator having a food compartment, an evaporator including: a horizontal metal' plate of ,an area substantially equal tothe cross-sectional area of the food compartment; and a tube adapted to ing baclaand forth in serpentine bends in conhave refrigerant flow therethrough, the tube having a first portion with at least a part thereof. in heat exchange relation with the plate and a second portion in another horizontal plane parallel to the plate. the construction and arrangement of the tube being such that the iiow of liquid refrigerant throughsaid first portion is accelerated and there is va substantially uniform distribution of cooling effect throughout the entire area of said plate at all refrigeration rates while the ow of liquid refrigerant through the second portion is substantially unaccelerated.

having a food compartment, an evaporator in- J OBEPH N. ROTH.

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