US2680353A - Evaporator for refrigerators - Google Patents

Description

June 8, 1954 B. BAXTER 2,680,353

EVAPORATOR FOR REFRIGERATORS Filed Nov. 16, 1951 3 Sheets$heet 2 o o o June 8, 1954 B. BAXTER EVAPORATOR FOR REFRIGERATORS 3 Sheets-Sheet 3 .FTg-5- Filed Nov. 16, 1951 mwzxva BY A 44L ATYWKNZZ Patented June 8, 1954 EVAPORATOR Foa REFRIGERATORS Bruce L. Baxter, Louisville, Ky., assignor to Reyn olds Metals Company, Richmond, Va., a corporation of Delaware Application November 16, 1951, Serial no. 256,765

2 Claims.

The present invention relates more particularly to evaporators used in household refrigerators, wherein leaks are most dangerous.

Welded joints in evaporator tubing have always been one of the major trouble sources in household refrigerators wherein the tubing connected to the accumulator consists of both aluminum and copper sections with welded joints. The elimination of even a single joint greatly minimizes potential future leaks in the system. By eliminating two welded joints from the system and furthermore, by elimination of all manual operations in making the remaining welded joints, a far superior quality evaporator with greater dependability will result. Production would also be materially facilitated by substitution of the simple butt flash welding for the much longer manual Hell-arc welding. This is accomplished by means of the invention-which also enables elimination of the copper tubing sections entirely.

The invention will be described with reference to the accompanying drawings, in which- Fig. 1 is a plan view taken at one major side of an evaporator embodying the invention.

Fig. 2 is a plan view showing the opposite major side of the evaporator.

Fig. 3 is a View in elevation showing the back plate of the evaporator with the accumulator in position and its circulatory tubing.

Fig. 4 is a plan view showing one minor side of the evaporator.

Fig. 5 is a perspective view.

Fig. 6 is a detail schematic View, partly broken away, showing one of the welds long considered as normal and sought to be avoided by the invention.

Fig. '7 is a detail view showing one end of the accumulator and its swaged reduced arcuate extension according to the invention.

Referring to the drawings, and particularly Fig. 5, it will be seen that the evaporator consists of a casing or shell, having two major walls I, two narrower connecting walls 2, and a back plate 3, which carries the accumulator 4, having conical or funnel shaped longitudinal ends of substantial length. Tubing 5, 5a leads to the accumulator suction end, and tubing 6, Ba abuts the shell, tubing 611 being formed in a plurality of loops for extended passage of the refrigerant. Shell tubing 6a, leads to the capillary end of the assembly and to capillary tube containing section I customarily of copper. Also, suction tube member 5 is customarily of copper. The accumulator and the shell tubing are formed of aluminum.

A flash weld connecting aluminum elements 6 and Ea, a flash weld connecting aluminum and copper elements 5 and 5a, and a flash weld connecting aluminum and copper elements 6a and l are each indicated by the reference W.

We now come to the prime characteristic of the invention. It is to be noted that suction tubular element 5a and shell tubular element 6 are arcuate integral members of the accumulator itself and wholly eliminate the welds at such points long found essential.

In the former practice, five welds on the evaporator, improved by the present invention, consist of three manual Heli-arc welds and two butt flash welds. The three Heli-arc welds are located at each end of the accumulator and capillary end of the aluminum tubing. The twobutt flash welds are used in joining short copper sections to the ends of the suction and capillary end of the tubing respectively after arcuate formation of the said swaged and tubular formed ends of the accumulator, as shown at 5a and 6.

In my evaporator there are no welds whatsoever within the bend radii. Hence the probability of there being a strain on the weld duringjthe bending operations, and thus causing possible subsequent fracture, is eliminated.

The three butt flash welds to be made on the evaporator when both aluminum and copper tubing sections are employed are: First, flash welding the suction integral longitudinal tubular extension of the accumulator 5a to the copper tubing 5. This weld is made first in order to facilitate the drilling of the flash on the inside of the tube of this small sub-assembly, which can be made and preinspected before bending said accumulator tubular extension into arcuate form. Secondly, flash welding the copper tubing '5 to the shell tubing 6, since this weld is a more accessible weld. Thirdly, the final operation of flash welding the accumulator 4 to the shell tul ing 6a. Since the other two flash welds have already been drilled and tested, this last welding operation leaves only one drilling operation to be performed on the complete assembly, thereby reducing to a minimum possible entrapment of foreign material. The internal flash of all three welds is removed by drilling against 40 lbs. of air back pressure. Thus, the chips are removed by this air pressure as the drilling operation is being performed.

A special and self centering drill is preferred, having a rounded cutting lip that will virtually eliminate any possibility of cutting the flash out in a solid ring or washer, which may be pushed ahead of the drill, thereby remaining in the tube and proving diificult to remove. This type of drill will assure concentricity of the bore and will cut up the chips in small pieces, which may easily be dislodged by a highly turbulent air stream. The drill bit may be welded to a semi-flexible shank which will permit it to run concentric within the tube even though the tube may be slightly bent or out of line. This will eliminate the possibility of cutting into the side of the tube or cutting into the shoulder of the accumulator.

The invention eliminates two Hell-arc welds and substitutes one butt flash weld for the three Heli-arc welds. One of the principal sources of trouble and major reason for leaks in household refrigerator evaporators has thereby been eliminated. Butt flash welding has a great many advantages over Heli-arc welding, in that the butt flash weld eliminates the human element, which is inherent to Hell-arc welding. Each Hell-arc weld depends on the manual skill of each operator. Further, Hell-arc welding anneals the tubing by approximately 1 in each direction from the joint, and considerable care must be taken to prevent fracture of the tubing in this adjacent area where the metal is of a cast structure and has a low fatigue strength. The butt flash weld on the other hand is a matter of machine setting. Microscopic examination of the: butt flash welds, both aluminum to aluminum and aluminum to copper indicates complete homogeneity of the weld with no porosity or entrapment of oxide material.

By means of my invention, copper tube sections heretofore considered necessary for weld connection directly to the accumulator ends may be entirely eliminated by reason of the swaged integral arcuate tubular end formations of the accumulator, itself. In such case the presently used five welds will thereby be reduced to a single weld connecting the arcuate shell end of the accumulator to the shell tubing.

It will be noted, particularly from Fig. 5, that the reduced projecting tubular ends of the accumulator body extend therefrom offset from the longitudinal axis of the said body. In fact, the outer surface of each of said accumulator projecting tubular ends may be a straight extrusion of the outer wall of the accumulator body. This adapts the accumulator for all conditions of control of the volume of refrigerant in the accumulator. Thus, referring to Fig. 5, when the accumulator body is turned to bring it horizontal with the tubular extrusions 5a and 6 uppermost the accumulator will have full working capacity.

4 In the use of the accumulator as part of a defrosting assembly, this feature is particularly valuable.

Having described my invention, what I claim and desire to secure by Letters Patent is as follows:

1. A continuous tube evaporator comprising a core shell having an open front wall, a continuone tube disposed about said shell and having a plurality of return bends disposed in opposed relation upon a single wall of said shell, an integral weld-free accumulator of larger diameter than said tube and having a pair of elongated tapered ends, said accumulator being obliquely secured to the back of said shell, both of said tapered ends being bent, one of said tapered ends being butt welded to one end of said continuous tube and the other of said tapered ends being doubly bent to form a U-shaped configuration and welded to a suction conduit, the other end of said continuous tube being welded to a capillary tube element and disposed adjacent said suction conduit disposed on the back of said shell.

2. An evaporator for refrigerators comprising a rectangular shell container having a back wall, a top wall and an open front, a unitary weldfree accumulator obliquely secured to said back wall and having a singly bent lower elongated tapered tubular end and a doubly bent upper elongated tapered tubular end, a continuous tube having the diameter of the tubular ends butt welded at the lower tapered tubular end of said accumulator, said continuous tube being windingly disposed upon the walls of said shell and having opposed return bends disposed in spaced relation on the top wall of said shell and having the second end of said continuous tube disposed in spaced relation adjacent to the back wall of said shell, said second end being welded to a capillary conduit and said upper tapered tubular end of said accumulator being welded to a suction conduit.

References Cited in the file of this patent Hebard Sept. 2, 1952

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