US2958934A

US2958934A - Method of making refrigerating apparatus

Info

Publication number: US2958934A
Application number: US302748A
Authority: US
Inventors: Leonard J Mann
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1952-08-05
Filing date: 1952-08-05
Publication date: 1960-11-08
Anticipated expiration: 1977-11-08

Description

N v- 19 L. J. MANN 2,958,934

METHOD OF MAKING REFRIGERATING APPARATUS Filed Aug. 5, 1952 2 Sheets-Sheet 1 4 INVENTOR.

Leonard J. Mann,

Nov. 8, 1960 L. J. MANN 2,958,934

METHOD OF MAKING REFRIGERATING APPARATUS Filed Aug. 5, 1952 2 Sheets-Sheet 2 FIT JNVENTOR. Leonard J. Mann,

2,958,934 Patented Nov. 8, 1960 METHOD OF MAKING REFRIGERATING APPARATUS Leonard J. Mann, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Filed Aug. '5, 1952, Ser. No. 302,748

1 Claim. 01. 29-1572 This invention relates to refrigerating apparatus and more particularly to heat exchangers and the method. of making the same.

This invention is particularly intended to utilize a process wherein apair of weldable metal sheets are roll welded together and wherein the one sheet is precoated with a stop-weld material in a definite pattern so as to prevent the welding of the two sheets throughout the coated area whereby it is possible to separate the sheets throughout the coated area by the application of hydraulic pres sure between the sheets so as to form internal passages.

The pressure required for hydraulically dilating the passages in a roll welded sheet metal heat exchanger are so great that it is essential to limit the size of the passages thus formed and it is also essential to limit the degree of expansion of even the smaller passages by means of heavy protective plates or blocks placed on opposite sides of the sheet metal during the process of dilating the passages. Due to the process used in forming the passages, the location of the passages varies considerably from one pair of plates to another and therefore it is impractical, if not impossible, to use protective blocks which have recesses corresponding to the final shape of the passages to be formed. This then complicates the problem of forming heat exchangers and the like wherein some of the internal passages or chambers are larger than others. The high pressures required for di lating the smaller passages and the irregularity in the pat tern of the smaller passages each present different prob lems.

It is an object of this invention to provide a heat ex changer design and a method of making heat exchang ers which makes it possible to hydraulically dilate the relatively small fluid passages even though they connect onto a relatively large header which could not be formed by dilating a portion of the roll welded sheets,

One object of this invention is to form the header separately from the main body of the heat exchanger and to weld the two together while the main body of the heat exchanger is still perfectly flat.

More particularly it is an object of this invention to provide a heat exchanger and a method of making the heat exchanger which makes it possible to weld the header to the main body before the internal passages of the heat exchanger body have been dilated.

Still another object of this invention is to provide an improved method of manufacturing heat exchangers and the like wherein chambers of difierent sizes are formed by a process which does not require stretching the metal forming the Walls of the larger chambers.

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:

Figure 1 is a plan view showing a heat exchanger a sembly in an intermediate stage of manufacture just prior to the formation of the fluid passages and header chamber;

Figure 2 is a side elevational view of the structure shown in Figure 1 on a slightly enlarged scale;

Figure 3 is a view similar to Figure 2 but showing the shape of the heat exchanger after the fluid passages have been dilated;

Figure 4 is a fragmentary plan view showing the relationship of the header to the fluid passages after the dilation of the various fluid passages and the header chamber;

Figure 5 is a vertical sectional view showing the plates which are used for limiting the extent of dilation;

Figure 6 is a fragmentary elevational view showing a modified header construction;

Figure 7 is an end elevational view for illustrating the manner in which the header is formed;

Figure 8 is a vertical sectional view through the header in an intermediate stage of manufacture; and

Figure 9 is a view similar to Figure 8, but showing the manner in which the header is attached to the main body of the heat exchanger prior to the dilation of the refrigerant passages.

Figure 1 of the drawings shows an illustrative forgewelded composite plate 10 having stop-weld material 12 arranged in a pattern so as to establish the location of predetermined passages within the plate. The individual sheets used for forge-welding are preferably made of .070" thick weldable bronze of the following specification:

Copper92-94% Iron-2. 1-2.6

Zinc substantially all the remainder Iron/ zinc minimum .30

Tensile strength 44,000 lbs. per sq. in. minimum Elongation-in 2 inches 31% minimum Hardness Rockwell H 96-103 The above specification is merely illustrative as any other type of weldable material such as copper, brass, or aluminum could be used in place of the bronze.

The sheets which are used in forming the main body of the heat exchanger are cut to approximately the same width as the width of the final product but are approximately /3 shorter than the length of the final product desired. As explained hereinabove stop-weld material 12 is applied to the one sheet so as to prevent the adjacent shects from adhering to oneanother at those places where the stop-weld coating is present. This stop-weld material maybe applied by printing, rolling, painting or spraying the stop-weld material in fluid or solid form. In this example, the stop-weld material is in the form of a water suspension of colloidal graphite and sodium silicate which serves as a binder.

The one portion of the stop-weld material extends to one edge of the plates as indicated by the reference numeral 1-4. After the stop-weld coating has beenplaced on the one sheet and another sheet laid thereon with the coating then being disposed between the two sheets, the edges of the two sheets are inert gas welded so as to hold them together in the desired relationship and so asto prevent the admission of air between the sheets during the subsequent roll-forging or welding operation. The.

process to the same extent of the elongation of the sheets as they were rolled into one composite sheet. Several cold-rolling passes may follow the initial hot-rolling pass to bring the final composite sheet to approximately the desired length. The final length in this example is about 2.92 times the original. length. The thickness of the single composite sheet is allowed to vary between .045 and .048 inch. Following the final rolling operation the composite sheet is annealed. The rolling and the annealing causes the line of separation between the two sheets to disappear and recrystallization and grain growth extends across the former line of separation so that the two sheets have been completely forge-welded into one composite sheet except where stop-weld material has been provided.

The inert gas welded edges of the sheets are cut away so as to expose the stop-weld material at the one end of the plate and at 14 and so as to form a product having straight, clean-cut edges with the finished outer dimensions of all of the heat exchangers thus formed being absolutely uniform.

By inspection of the trimmed edges of the composite plate it is possible to determine the area where the stop-weld material 14 extends to the edge of the sheet and at this point the sheets are mechanically forced apart so as to make it possible to introduce fluid under pressure for separating the sheets throughout the area covered by the stop-weld material. However, before this separation or dilation of the sheets is undertaken a folded sheet member 16 is slipped over the one end of the plate 10 as best shown in Figures 1 and 2 and is inert gas welded to the plate 10 as indicated at 18. Since the plate member 10 is still a perfectly flat plate, it is a simple matter to provide a good welded joint between the

members

10 and 16. The ends of the folded member 16 are also inert gas welded so as to seal the same as indicated by the reference numeral 20.

After the element 16 has been properly secured to the element 10, the assembly is placed between a pair of heavy rigid plates or

block members

30 and 52. The plates or

block members

30 and 32 may be held in a press (not shown) or otherwise held against separation so as to firmly grip the edges of the plate 10. The

members

30 and 32 are provided with spaced

fiat surfaces

34 and 36, respectively, which overlie the main body of the plate 10 wherein the fluid passages are to be formed and are cut away as indicated at 38 and 40 so as to allow for dilation of the folded plate 16 so as to form a header element 42. The depth and shape of the

cuts

38 and 40 are such that the dilation of the header is stopped before the walls of the header are stretched any appreciable amount. Since the folded plate portion 16 has not been produced by the roll-forging operation, all of these plates 16 may be made of exactly the same size and shape with the result that all of the headers will be of the same shape and in the same relative location with respect to the main body of the heat exchanger.

After the heat exchanger assembly has been inserted between the

blocks

30 and 32, fluid under pressure is used for hydraulically dilating or expanding all of the passages which are to be formed. The hydraulic pressure required for properly expanding the heat exchanger is 10,000 pounds per square inch or higher. By using rigid flat surfaces for limiting the expansion or dilation of the smaller passages, the rupturing of the walls of the passages is prevented and the entire main body of the heat exchanger remains uniformly flat.

Experience shows that passages formed by hydraulically expanding the same while the roll-forged plate is held between flat blocks have uniformly flat top and bottom surfaces 48 which are particularly desirable in refrigerant evaporators, for example. These flat surfaces provide excellent contact for ice trays and other vessels which may be placed on the surface of an evaporator.

By virtue of the fact that the passages are expanded by the substantially flat blocks rather than complex dies which have recesses exactly corresponding to the final outer contour of the entire heat exchanger, it is obvious that any unevenness in the location or length of the smaller fluid passages does not present any problem.

Upon completion of the dilating process the composite device may be removed from between the heavy plates or blocks 30 and 32 and then bent into any desired shape.

Although one specific example has been given it should be understood that the arrangement of the fluid passages as well as the types of materials which are used could be varied. By virtue of the method used in manufacturing the heat exchanger it is possible to weld the header sec tion to the main body of the heat exchanger at a time when the joint between the two may be easily made even though the final joint assumes much more intricate shape as indicated in Figure 4 of the drawing. Thus, as shown in Figure 4 of the drawing, the various passages formed in the main plate 10 extend up into the header in the finished form.

In Figures 6 through 9 of the drawing there is shown a modified type of header construction wherein the header 52 is formed by taking a cylindrical tank like element 54 as shown in Figure 7 and crimping it adjacent one edge throughout its major length until it assumes a shape like the dot-dash shape shown in Figure 7. The bottom end 56 of the crimped portion is cut away so as to make it possible to insert a forge-welded heat exchanger element 60 between the flanges 62 of the header 52. The main body of the heat exchanger element 60 may be made similar in every respect to the heat exchanger element 10 described hereinabove.

The element 60 is assembled between the flanges 62 before any of the fluid passages are dilated whereby a straight flat seam is provided between the element 60 and the flanges 62. The flanges 62 then are inert gas welded or otherwise fused or brazed to the plate 60 so as to provide an absolutely gas-tight joint between the flanges 62 and the outer walls of the element 60. After the flanges of the header element 52 have been properly secured to the element 60, the assembly is placed between a pair of blocks such as the

blocks

30 and 32 which would be provided with a preformed cavity for receiving the header 52 so as to prevent any further deformation of the header 52 during the process of dilating the fluid passages in the element 60. Fluid for dilating the passages in the element 60 may be introduced through the conduit 64 which connects to the header 52 as shown in Figure 6. Upon introduction of the dilating fluid, preferably a liquid, the fluid passages 66 are formed in the main body member 60. It will be noted that in forming the passages 66 the flanges 62 are also reshaped and that the walls of the passages are flat sided. It is obvious that it would be much more diflicult to provide a fluid tight welded joint between the header 52 and the main body 60 of the heat exchanger if the welding operation were to be performed after the fluid passages in the element 60 were dilated. By virtue of the method and construction used in each of the above described heat exchangers it is obvious that the element which forms the header portion may be made separately from the roll-forged body of the heat exchanger and that the connection between the header portion and the body portion may be made before the final shaping of the fluid passages.

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, as may come within the scope of the claim which follows.

What is claimed is as follows:

The method of manufacturing heat exchangers and the like wherein chambers of dilferent sizes are formed without stretching the metal forming the walls of the larger of the chambers which comprises roll forging into one. composite sheet apair of metal sheets having stop 5 weld material therebetween in the pattern of fluid passages some of which extend to one edge of said sheets, forming a relatively large header chamber by folding a flat third sheet member over onto itself and slipping those fiat edges of the folded sheet member which are opposite the fold over onto said one edge of said roll forged sheets while the outer sides of said rol-l forged sheets are still flat, inert gas welding the edges of the folded sheet member to the roll forged sheets, inert gas welding the ends of the folded sheet member so as to seal the same, dilating said passages and said header by subjecting the interior of said passages and said header to a fluid pressure and limiting the extent of dilation by placing the header and composite sheet between a pair of spaced confining dies having flat faces opposite said fluid passages and having cuts opposite said header chamber, the depth and shape of said cuts being such that the dilation of the header chamber is stopped before the walls of the header are stretched any appreciable amount.

References Cited in the file of this patent UNITED STATES PATENTS Re. 18,182 Booth Sept. 8, 1931 6 Holmes July 24, Evans Oct. 29, Litle May 7, Rosenqrist Aug. 6, Keig-hley Aug. 18, Hastings June 29, Sendzimir Aug. 20, Booth Aug. 27, Nickolas Sept. 5, Davis Jan. 9, Hytte May 26, Long Dec. 15, Grenell Sept. 28, Simmons Apr. 3, Heidorn July 31, Adams et a1. Oct. 9,

FOREIGN PATENTS Great Britain Mar. 27, Denmark Apr. 16,