US2267315A - Method of making heat exchange units - Google Patents

Description

1941- R. M. STIKELEATHER- 2,267,315

METHOD OF MAKING HEAT EXCHANGE UNITS Original Filed Feb. 15, 1939 tubes.

Patented Dec. 23, 1941 Robert M. Stikeleather, Dedham, Mass., assignor to B. F. Sturtevant Company, Boston, Mass.

Original application February 15, 1939, Serial No. 256,475. Divided and this application July 15.

1940, Serial No. 345,475

2 Claims.

This invention relates to heat exchange tubes and relates more particularly to methods and apparatus for anchoring heat exchange tubes in end plates extending transversely of the tubes,

This application is adivision of my copending application Serial No. 256,475, filed Feb. 15, 1939.

For the conditioning of air it is convenient to provide heat exchange tubes such, for example, as refrigerant condensers and air cooling refrigerant evaporators in units including several horizontal rows of tubes, each row containing several tubes. The tubes are usually connected in a series-parallel circuit with respect to interior fluid flow, by return bends at the ends of adjacent tubes. It is also usual to provide vertically extending end plates at the ends of the tubes, the end plates containing circular openings through which the tubes extend, with the end plates between the ends of the tubes and the return bends. The end plates serve as air tguliding passages and to support and align the n es.

Heretofore it has been the practice to either solder or braze the end plates directly to the tubes. Neither practice has proved satisfactory. For duties such as for railroad cars where considerable motion and vibration is present, the

end plates move relative the tubes and loosen the soldered joints. To braze the end plates to the tubes requires that the end plate and tubes be raised to thebrazing temperature. Sucli high temperatures result in the relatively thin fins adjacent the end walls, always used on this type of tube, being burned and weakened.

According to this invention tubular bushings are expanded into the circular openings in the end walls and the outer ends of the bushings are brazed to the ends of the tubes while simultaneously the ends of the tubes are brazed to the return bends. The end walls and the bushings protect the extended-surface fins from the high brazing temperatures.

An object of the invention is to improve the method of securing end Another objectof the invention is to anchor end plates more securely to heat exchange tubes without damaging the tubes.

Other objects of the invention will be apparent from the drawing and the following description.

The invention will now be described with reference to the drawing, or which:

plates to heat exchange exchange tube assembly embodying the invention, and

Fig. 2 is a sectional view along the line 2-2 of Fig. 1.

tinned in the circular apertures with solder.

Tubular copper bushings 8 have portions adapted to fit. into the apertures 6 correspondingly tinned and the bushings are then' placed within the apertures and are expanded into the end plate by a suitable tool to take the shape chosen by Fig. l of the drawing. The expanded bushings have recessed portions 9 which fit into the circular apertures G and have the raised shoulder portions I0 and II on each side of each recessed portion 9.

The plate 5 is then placed on the tubes and its position is regulated by the shoulders ll contacting at their inner edges the outer edges of the innermost fins [2 which thus space properly the position of the tube ends with respect to the outer ends of the bushings '8. The outer ends l3 of the tubes are then flared as illustrated by Fig. 1 with the outer ends of the bushings 8 so as to tightly contact same. The return bend I4 is then placed in position as shown by Fig. 1,withits two ends within the flared portions l3 of the tubes.

After the above described assembly operations have taken place, heat is applied. to the outer portions of the bushings 8 and the flared portions ll of the tubes, brazing compound is flowed in between the bushings 8 and the flared portions l3 of the tubes and between the ends of the return bend and the flared portions l3, and the bushings are brazed to the flared portions of the tubes and the flared portions of the tubes are brazed to the ends of the return bend. Sumcient heat is also transmitted through the bush- I Fig. l is a side elevation insection of a heat should be understood that the invention is not limited to the exact apparatus and arrangements of apparatus shown as modifications may suggest themselves to those skilled in the art without said return. bend.

ing said bushing to said tube and said tube to 15 2. The method oi? attaching an end plate to a -,tube which comprisesaperturing the plate, tinning the periphery ofthe aperture with solder, tinning an intermediate exterior portion 01' a 5 tubular bushing with solder, placing the tinned portion of the bushing within the aperture, expanding the bushing into the aperture, placing the plate over the tube with the outer end of the bushing around one end of the tube, and

10 brazing the bushing to the tube while simultaneously through. the conduction of heat through the bushing, sweatingthe tinned areas of the bushing and the plate together.v

, ROBERT M. STIKELEA'I'HER.

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