US2012582A - Method of making dry system evaporators - Google Patents

Description

Aug. 27,- 1935.

F. G. sLAGEL METHODy oF MAKING DRY SYSTEM EvAPoRAToRs @@@NWQ @,Q. Q

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4METHOD OF MAKING DRY SYSTEM EYAPORATORS l Filed July so, 1932 5 sheets-sheet 2 1W] a .22 WWK?.

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` Patented Aug. -27,l 1935 paire STATES METHOD F MAKING DRY SYSTEM EVAPORATORS j Franklin G. Slag'el, Buffalo, N. Y., assigner to Fedders Manufacturing CompanyJnc., Buffalo,

Application July so, 1.932, serial No. 626,812 sciame. (c1. 11s- 118) This invention relates to the art of mechanical refrigeration, and it has particular reference to the provision of an evaporator made of sheet metal for use in a refrigerating system of the dry or expansion valve type, and to va method of making the same.

In a mechanical refrigerating system, including a compressor, condenser, evaporator, and associated devices for controlling the circulation of a uid refrigerating medium therethrough, the evaporator may be so constructed Vas to receive compressed or liquid refrigerant in a pool, from which it may be delivered to a plurality of tubes connected in multiple, or the evaporator may consist of a coil of pipe into which the refrigerant is admitted by means of an expansion valve. The present invention deals with the last named type of system, and it has as its objects the provision of an evaporator which is formed of sheet metal and a method of making such evaporator, in order to obtain a highly effective and thermally emcient evaporator at a minimum of cost, which serves the dual purpose of providing a sharp freezer for freezing water, and also as a cooling element for a food storage box or refrigerator. V

In order to make an effective evaporator, consideration must be vgiven to the thermal requirements of, good heat transfer between the air or other medium to be cooled and the refrigerant, safety against the possible leakage of the refrigerant, (which in most cases is noxious or highly irritating), and economy in the amount ofl refrigerant required for the system and the proper balance of one part with another. All of these factors, moreover, should be included in the evaporator without prohibitive cost, and without making the unit so large that it occupies an undue amount of the refrigerator space.

In the development of small refrigerating units, such as those adapted for household use, these considerations have, collectively considered, fa

- vored thedevelopment of a flooded type of evaporator, in which a header or boiler is adapted to hold a quantity of liquid refrigerant which boils or evaporates in a number of depending tubes connected in parallel to the header. Evaporators of this type have been made-not only from tubing, but also from sheet or cast metal, but, due to the amount of refrigerant containedin a flooded system, the high pressures which might devolop in the tubes,` and the character of the heat transfer surface, the results obtained with such sheet metal flooded evaporators have not been entirely satisfactory, when considered in the light of the optimum operating conditions, and it has also been found that the cost of making such unit does not warrant the compromise with the defects in operating performance.

In order to obtain effectively the desired objects Yof thermal efficiency and permissible cost in a durable evaporator, the present invention departs from the wet or flooded system of refrigeration, a'nd utilizes the principles of the dry system. In so doing, however, an evaporator is obtained with a greater proportion of heat transfer surface than in the customary dry tubing coil, and one requiring a less amount of refrigerant than in a flooded system of the same capacity, and by making such unit in accordance with the herein de'- scribed method, the objects of low manufacturing cost and a high factor of safety are also realized.

The means whereby these and other objects andv advantages are obtained in practice will be 11n- -derstood from the following description of typical embodiments of the principles of theinvention,

. reference being' had to the accompanying drawings, wherein:

Fig. 1 is an elevation of a deformed outer plate, forming a part of the evaporator, prior to assembly;

Fig. 2 Iis an elevation of the inner plate \of the 2 evaporator prior to assembly;

Fig. 3 is an end view of the integrated inner an outer plates prior to the nal bending operation;

Fig. 4 is an end elevation of the completed evap- 30 orator prior to the final securing operation;

Fig. 5 is a plan view of the completed evaporator; J

Fig. 6 is a section on the lineV 6-6 of Fig. 5; Fig. '7 is a section on the line 'l-l of Fig. 5; Fig. 8 is a side elevation of the evaporator and 'associated units of a refrigeration system.

Inthe drawings, Figs. 1 to 4 illustrate in their' relative order the operations performed in constructing the evaporator device indicated at 20. 40

to provide a continuous serpentine depression 59 having terminal portions and 26 at opposite ends of the plate. Each terminal portion is formed with a raised boss having an nturned ilange 21 adapted to be secured to a conduit or 'pipe line extending from the motive portions of u a refrigerating system. As illustrated in Fig. l, the inturned flange 21 may be screw-threaded, to receive directly a pipe-fitting or the like.

In connection with the outer plate 2|, it is desired to point out that the depressed portions of the plate 23 and 24, as well as the terminal portions 25 and 26 thereof, are disposed wholly with in the marginal portions of the plate, these marginal portions being suiiiciently extensive to permit of the welding or joining of the inner plate to the outer plate, without affecting materially the metal forming the depressions. No openings of any kind are made through the contacting marginal portions of the plates, so that'there are no weak joints which would tend to leak in service. On the contrary, the inlet and outlet to the ser- 'pentine duct are formed in the body portion of the plate, in which the duct terminates, and hence in regions where leak proof joints can be readily made.

The inner plate22 (Fig. 2) is also a'rectangular member of approximately the same length as the plate 2|, but of a slightly greater width, and it is formed with a pair of lateral rows of raised shelf supporting beads 28 and with a pair of stop beads 29 at one extremity of each row oi' beads 28. These beads, in the finished unit, provide means for supporting freezing trays in proper position, and also insure good heat transfer between the refrigerant iiowing in the channel between the plates and the liquid to be frozen.

The plates 2| and 22, with the channels and beads formed as above described, are then superimposed as indicated in dotted lines on Fig. 1, and the protruding longitudinal edges of the plate 22 are rolled over to form reversed flanges encompassing the adjacent margins of the plate 2| as indicated by the numeral 33 (Fig. 3). It will be noted that the plates are longitudinally mismatched, that is, one end of the plate 2 protrudes beyond the plate 22, while the opposite end of the plate 2| is overlapped by the corresponding end of the plate 22. The plates thus connected .are welded together in a suitable welding fixture so that they are substantially integrated to provide a leak proof enclosure for the channels' 23 and 24 of the plate 2|.

Following the above described operations, the assembled plates are inserted in a suitable die and are bent to the form shown in Fig. 4, wherein the,

channels 23 extend transversely about the hous' ing thus formed, and the edge portions of both the plate 2| and the plate 22 are in overlapping relation. When in this position it will be noted that the protruding end portion 3| of the plate 2| is adapted to be inserted in the socket formed by the rolled portions 3|! lof the inner plate to overlie the protruding end portion 32 of the plate 22, thus providing an overlapping Joint, which, when nally secured by welding, as shown in Figs. and 7, not only presents a substantially uninterrupted surface, but provides an extremely rugged connection.

It will be noted that the channels 23 and 24 when enclosed by the plate 22 provide a continuous serpentine refrigerant duct wherein the refrigerant ows about all the walls of the housing in axgeneral lateral direction. In addition to this, the inner plate 22 being formed with the vbeads 28 and 29, provides a mounting means for an ice cube tray 35 and the lo/wer wall 35 of the housing is adapted to act as a shelf for a lower ice cube tray. 'I'here is thus provided, in addition to a dry type of refrigerating coil, a relatively large proportion of heat transfer surface, which, conjointly, provide means for cooling or freezing the refrigerator contents effectively with a minimum of lrefrigerant in `the system.

The application of the evaporator to a refrigerating system of the dry type is illustrated in Fig. 8, in which the evaporator is shown as mounted in a refrigerator box. A motor M, controlled automatically by a thermostat T mountedl adjacent the evaporator, drives a compressor `or pump P for the refrigerant, which medium, after being compressed, is delivered by suitable piping to a condenser C, from which it emerges as a liquid. A pipe line 4|, leading from the condenser or receiver associated therewith, delivers the refrigerant to an expansion valve 42 mounted directly on the evaporator fitting 2B. The valve 42 may assume a number of forms, that herein delineated being of the-type shown in my copending application Serial No. 619,290, iiled June 25, 1932. In passing through the valve 42, the refrigerant is delivered as a vapor, mist, or spray of liquid at a relatively low pressure, and, because of the low pressure and iine division of the refrigerant, cooling 'is rapidly and elciently obtained in passing through theduct 28, all parts of which are, of

course, in good thermal contact with the liquid' to be frozen within the evaporator 20. The discharge terminal of the duct 23 is connected by a return or suction pipe 43 'to the compressor P, to provide a closed cycle. g

The evaporator is supported in the refrigerating chamber by means of a pair of bracket members 45 and 46, the former bracket member having a lower flange 41 conforming to the top wall of the evaporator and being secured thereto and being provided at its upper end with a ange 48 suitably drilled to receive a screw 49 which enters the upper wall of the refrigerating chamber. 'I'he vertical portion vof the bracket 45 is conveniently formed into an instrument mounting panel, as indicated by the numeral 5|, upon the rear of which the various controls of the system, such as the thermostat T, are mounted, and they are adjustable by means of adjusting knobs 53 on the front of the panel. The rear bracket 46 is provided with a longitudinal leg 55 secured by welding or riveting to the body of the evaporator, and with an upper horizontal leg 56 secured to the upper wall of the refrigerating chamber.

From the foregoing description, it will now be understood that the invention provides an eilicient evaporator formed of sheet metal, which embodies the desirable thermal characteristics of the ooded type of system, and also the advantages of the drysystem in simplicity of parts and minimum of refrigerant. The evaporator serves both as a sharp freezer for liquids, and also provides adequate heat absorbing surface in a, compact unit to cool the food contents of the refrigeraton It will also be noted that the method proposed for the manufacture of the evaporator makesfor economy of manufacture, and produces an article in which local weaknesses are avoided.

`It will further be understood that, while the invserpentine depression `having convolutions ex tending longitudinally thereof, superimposing a at plate of similar proportions thereon to cover vsaid depression, said second plate being misform a substantially rectangular tube with opposite edges contacting in overlapping relation, and inally welding the mismatched portions of said edges together.

2. The method of making an evaporator which comprises forming a rectangular plate with a serpentine depression, superimposing a plate of similar proportions thereon to cover said depression, said second plate being mismatched longitudinally relative the rst plate, welding the plates together at contacting surfaces. bending the united plates laterally to form an annulus with the mismatched edges contacting in overlapping relation, andnally welding the mismatched edges together.

3. The method of making an evaporator which comprises forming a Yrectangular plate with a serpentine depression having its convolutions extending longitudinally thereof, superimposing a at plate of similar proportions thereon to cover the depression in the rst plate, said second plate being mismatched longitudinally relative said ilrst plate, rolling the longitudinal edges of the second plate over the similar edges of the irst plate, welding said plates together at contacting portions, bending the assembled plates laterally to form a substantially rectangular tube with the opposite mismatched edges contacting in overlapping relation, and finally welding the mismatched edges together.

FRANKLIN G. SLAGEL.

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