Heat transfer unit

L. M. MILLER

HEAT TRANSFER UNIT

April 12, 1960

Filed Oct. 3, 1957

2,932,491

Sheets-Sheet 1

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ATTORNEY

L. M. MILLER

HEAT TRANSFER UNIT

April 12, 1960

Filed Oct. 3, 1957

2,932,491

Sheets-Sheet 2

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<img file="US2932491A_D0003.tif" />

ATTORNEY

April 12, I960

Filed Oct. 3, 1957

L. M. MILLER

HEAT TRANSFER UNIT

2,932,491

Sheets-Sheet 3

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INVENTOR.

Lester M. Miller

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April 12, 1960

Filed Oct. 3, 1957

L. M. MILLER

HEAT TRANSFER UNIT

2,932,491

Sheets-Sheet 4

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Lester M. Mill er

<img file="US2932491A_D0007.tif" />

ATTORNEY

L. M. MILLER

HEAT TRANSFER UNIT

April 12, 1960

Filed Oct. 3, 1957

2,932,491

Sheets-Sheet 5

<img file="US2932491A_D0008.tif" />

April !2, I960

2,932,491

L. M. MILLER

HEAT TRANSFER UNIT

Filed Oct. 3, 1957

Sheets-Sheet 6

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<img file="US2932491A_D0010.tif" />

L. M. MILLER

HEAT TRANSFER UNIT

April 12, 1960

Filed Oct. 3, 1957

2,932,491

Sheets-Sheet 7

<img file="US2932491A_D0011.tif" />

ATTORNEY

United States Patent Office „ , ²’^932,491

Patented Apr. 12, 1960

2,932,491

HEAT TRANSFER UNIT 5

Lester M. Miller, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware

Application October 3, 1957, Serial No. 688,042 jo 7 Claims. (CI. 257—256)

This invention pertains to refrigerating apparatus and 15 especially to heat exchange structures such as evaporators and condensers and other fluid heat transfer applications.

In heat transfer apparatus, it is desirable to provide at the lowest cost extended passages carrying one heat transfer medium enclosed in walls having on their outer sur- 20 faces maximum contact with another heat transfer medium throughout. Expanded metal provides an open network of connected strands at a low cost.

It is an object of this invention to provide an inexpensive expanded metal structure containing connected 25 heat transfer passages extending throughout the strands.

These and other objects are attained in the various forms shown in the drawings by first bonding the metal sheets together and, secondly, hydraulically expanding an open network of passages between the bonded sheets. 30 After this, the structure is slitted in the spaces between the passages and bent apart either by the guillotine method or by dies or by scalloped rotary cutters to form an expanded metal structure containing the heat transfer passages. 35

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the invention are clearly shown.

In the drawings: 40

Figure 1 is a view taken substantially along the line 1—1 of Figure 4 directly in alignment with the flow of air through a heat transfer structure embodying one form of my invention;

Figure 2 is an enlarged transverse sectional view taken ⁴⁵along the line 2—2 of Figure 1;

• Figure 3 is a fragmentary perspective view of a modified form of the invention;

Figure 4 is a diagrammatic view showing one of the structures used as a condenser and another as an evap- ⁵⁰orator in an air conditioning refrigerating system;

Figure 5 is a plan view illustrating the pattern of stop weld material provided between an assembled sheet structure to be forge welded in the first step of manufacture of the heat transfer structure;

Figure 6 is a diagrammatic view illustrating the roll forge welding process applied to the sheet assembly shown in Figure 5;

Figure 7 is a plan view of the elongated sheet structure as it issues from the roll forge welding step shown ⁶⁰in Figure 6;

: Figure 8 is a diagrammatic vertical sectional view illustrating the hydraulic expansion of the passages within the sheet structure shown in Figure 7 between flat surfaced dies; 65

Figure 9 is a plan view of the sheet structure following the expansion illustrated in Figure 8;

Figure 10 is a sectional view taken substantially along the line 10—10 of Figure 11 showing diagrammatically a guillotine type machine for forming the structure shown 70 in Figure 9 into the expanded metal structure with openings in the spaces between the passages;

Figure 11 is a right end view of the guillotine type machine shown in Figure 10;

Figure 12 is a view of a roll forge welded sheet structure containing two outer sheets and a lower melting point bonding sheet welded in between;

Figure 13 shows a heated forming die arrangement for hydraulically expanding passages between the outer sheets of the structure shown in Figure 12;

Figure 14 is a view illustrating the expanded structure issuing from the expansion die shown in Figure.13;

Figure 15 is a side view, partly diagrammatic, showing a slitting die for slitting the structure shown in Figure 14 between the passages;

Figure 16 is a plan view of one of the dies shown in Figure 15;

Figure 17 is a view of the scalloped rollers for slitting and expanding the structure shown in Figure 14 by a scalloped roller process; and

Figure 18 is a vertical sectional view taken along the line 18—18 of Figure 17.

Referring now more particularly to Figs. 1 and 2, there is shown one form of my improved, simple, inexpensive expanded metal heat transfer structure composed of two sheets 20 which are forge welded together throughout excepting where the upper header 22, the lower header 24 and the network of passages 26 extend between the headers 22 and 24 within the sheets. The portions of the sheets between the passages are slit and bent apart in opposite directions to form the openings 28 along the upper header 22, the openings 30 along the lower header 24 and the openings 32 between the passages in the remaining portions of the sheet structure 20; The passages 26 extend in a zig-zag arrangement and have fin structures 34 and 36 extending on opposite sides thereof. These fin structures are preferably coined, stretched or otherwise thinned and extended either in a wavy edge pattern 38 as shown in Fig. 2 or by the coined fin extensions 40 shown in Fig. 3.

The structure may be used for various sorts of heat transfer uses, one of which is shown in Fig. 4, in which a sealed motor-compressor unit 42 supplies compressed refrigerant through the conduit 44 to the top of the inclined heat transfer unit 46. This compressed refrigerant flows through the passages 26 in the structure 46 which is substantially identical to the structure shown in Fig. 1. The fan 48 driven by the electric motor 50 discharges the air through a duct or shroud 52 through the openings 32 in the structure 36. These openings 32 as well as the greater portion of the strands are aligned substantially parallel to the air flow within the shroud 52. The portion of the metal between the openings are termed strands which together form a network containing the passages 26 between the headers 22 and 24.

The refrigerant condenses in the structure 46 by being cooled by the air flow through the openings 32 and around the strands and collects in the lower header 24. It is conducted by the conduit 54 to a suitable refrigerant expansion device 56 which may be either a restrictor or an expansion valve. The refrigerant expands as it issues from the expansion valve 56 and is carried by the conduit 58 to the lower header 24 of the inclined structure 60, preferably like the. structure shown in Fig. 1. The liquid refrigerant flows upwardly through the passages in the strands surrounding the openings 32, removing heat from the air until it evaporates and flows into the upper header 22. The fan 62 driven by the electric motor 64 forces air through the shroud or duct 66 substantially parallel to the openings 32 and the strands and passages 26 of a structure 60 identical to that shown in Fig. 1. This air is cooled by the evaporation of the refrigerant within the passages 26 in the. strands as it flows through the openings 32. The evaporated refrigerant: flows into

2,932,481

If the structure 20 should be too far to the right, the passage portion 135 will depress the feeler member 131 and close the switch 143, while the feeler pin 141 will move upwardly to the left of the passage portion 137 to close the switch 149 to energize the solenoid 125 to push the structure 20 to the left until it reaches its proper position.

The structure 20 is advanced to proper position in the tranvserse direction by a solenoid or other electrical operating means 155 acting through a bent lever latch member 157 having saw teeth 159 for engaging the passage portions of the structure 20. A light spring 161 keeps the lever member 157 in contact with the structure 20. The pivot 163 between the lever 157 and the plunger 165 of the solenoid 155 is sufficiently offset from the line of saw teeth 159 that the pivoting force will tend to keep the saw teeth 159 in contact with the structure 20 when the solenoid 155 is energized. The solenoid 155 is controlled by a feeler member 167 pressed upwardly by the spring 169 into the space between the passage portions 171 and 173. This feeler member 167 is provided with a spring-pressed Contact 175 which is pressed downwardly to closed position when any one of the passage portions is over the feeler member 167 to depress it. The supply conductor 177 connects to the switch 175 which, in turn, connects to the conductor 179 connecting with the solenoid 155. To start the movement of the structure 20 forwardly, a shunt switch 181 may be momentarily closed to initiate the movement when the switch 175 is in the open position. The movement continues until the feeler member 167 moves up into the space between the passage portions 171 and 173 to reopen switch 175. By operating the switch 181 in response to the cutter member 185, this may be synchronized with the cutting so that the 35 cutting and forming operation may proceed automatically.

The cutting and forming may be done by a combined guillotine cutting and forming operation in which there is a lower stationary die member 183 and a vertically reciprocating combined cutting and forming die member _ ____ „ * recesses 187 throughout for the passage portions 22, 24 and 26. In addition, on the opposite sides of the recesses 187, there are provided forming serrations 189 to provide the coined wavy edge portion 38 to provide a fin surface. A movable reciprocating knife edge 191 is

The re15 the upper header 22 and returns to tire compressor 42 through the suction conduit 68.

• The expanded metal structure shown in Figs. 1 to 4 may be made by several different processes. In one, two sheets of metal such as aluminum or brass may be placed together as indicated by the reference character 70 in Fig. 5 with stop weld material 72 in between in a zig-zag arrangement. This structure is roll forge welded together into a single sheet by the roll force welding process illustrated diagrammatically in Fig. 6 and described in more detail in Patent 2,662,273 issued December 15, 1953, and Patent 2,690,002 issued September 28, 1954. ’ suiting structure is shown in Fig. 7 in which the sheet structure 70 is greatly elongated.

An opening ir> made extending to the stop weld material 72 betweb a the sheets. The structure 70 is placed by the flat surfaced dies 74 and 76 as illustrated in Fig. 8 and the entrance passage 80 is connected to a hydraulic pump 78. By forcing hydraulic liquid into the entrance passage 80, the passages 22, 24 and 26 are opened and expanded into contact with the opposed flat surfaces of the dies 74 and 76. The edges of the sheets are then trimmed close to the passages to provide a structure substantially like that shown in Fig. 9 in which the upper header 22 extends across the top the lower header 24 extends across the bottom, and the zig-zag passages 26 extend between the upper and lower headers 22 and 24, respectively. To form the hydraulically expanded structure shown in Fig. 9 into an expanded metal structure like that shown in Figs. 1 to 3, it is necessary that the structure be slit along the dotted lines 82 between the passages and the adjacent edges and the adjacent portions of the passages being bent apart to form the openings 32.

This can be done by several different forms of machines in slightly different processes. As one particular example, there is shown a form of guillotine machine and method in Figs. 10 and 11 in which the hydraulically expanded .sheet 20 is placed upon a suitable bed or table 121. This structure 20 is laterally positioned by the left and right _____r_______„-----solenoids 123 and 125 or some other electrical operating ₄₀ 185. Each of these die members have complementary means. These solenoids have fingers 127 and 129 en- ' ' ' gaging the left and right edges of the structure 20 for laterally moving the structure 20 to the proper position. This lateral movement is controlled by a feeler member 131 which is spring-pressed upwardly by the spring 133 -------------- —_ and is of such a size that it fits between the passage por- ⁴⁹ moved upwardly and downwardly by a suitable cam 193. tions 135 and 137 when the structure 20 is in its proper lateral location. On each side of the feeler 131 are the left and right feeler pins 139 and 141, also spring-pressed upwardly. ______________________ .

The feeler member 131 is provided with a spring- 60 _teetfj 159. The protruding passage portion 195 is sepmounted switch 143 connected in series with the supply conductor 145 so that whenever the structure 20 is in the proper lateral position, the switch 143 will be open.

When the structure 20 is not in the proper lateral posi- _r_____________________ tion, one of the passage portions 135 or 137, for example, 65 pjg_ jq This insures the proper location of the strucwill push the feeler member 131 down to the position *“ ' ” ------- ^J----------^J’ where the spring-pressed contact 143 will be closed. This will allow current to flow to either the switch 147 closed tween the passage portion 173 and 195 first in the dotted by the upward movement of the feeler pin 139 or the _____ ,------________ switch 149 closed by the upward movement of the feeler 60 full-line position at 195. At the same time, the serrapin 141. The switch 147 connects through the conductor 151 to the solenoid 123 or other electrical operating means. 153 to means.

By virtue of this ararngement, if the structure 20 should be too far to the left, the switch 143 will be pushed downwardly by the passage portion 137 while the pin 139 will be pushed upwardly to the right of the passage portion 135 to close the switch 147. This will energize the 70 solenoid 123 to move the structure 20 to the right until the feeler pin 139 is depressed to open the switch 147. .At substantially the same time, the feeler member 131 will move upwardly into the space between the passages 135 and 137 to deenergize both solenoids 125 and 123. 75

This supports the passage portion 173 and the fin extension thereof during the cutting or shearing operation. It is lowered when the member 185 is in its upper position to permit the advancement of -the structure 20 by the saw arated from the passage portion 173 by the cutters 185 and 191 to make the cut 82. The switch 181 is closed momentarily to advance the structure 20 until the passage portion 195 is in the dotted line position shown in ture 20 before the die moves downwardly. This upper die shears the metal substantially at the mid-portion beline position and moves the portion 195 downwardly to tions 189 form the wavy, fin surface on the edges of the tubing to provide extending contact with the air.

This operation continues progressively with the trigger (not shown) actuated when the die 185 reaches its uppermost position to momentarily close the switch 181 so as to advance the structure 20 so that the next row of passages 173 is moved to the position 195 While the proper lateral shift is provided by the solenoids 125 and 123 under the control of the feeler members 131, 139 and 141. By virtue of this arrangement, a heat exchange structure of substantially any width and length may be made automatically at a relatively low cost. The size, thicknesses and wall structures may be varied to suit the particular application desired.

The switch 149 connects through the conductor the solenoid 125 or other electrical operating

2,932,491

The heat exchange structure may be manufactured Using other bonding processes. For example, in Fig. 12 there is shown a thin, flat laminated sheet member 220 which is composed of two sheets of a higher melting temperature metal bonded together by an ultra-thin sheet of a lower melting temperature metal. A hydraulic passage 222 extends between the outer sheets to the portion containing the lower melting metal. To form and hydraulically expand the passageways within the sheet structure 220, the structure is placed between upper and lower forming dies 224 and 226 which are provided with electrical heaters 228 and 230 or other form of heaters to keep the dies at a temperature above the melting temperature of the bonding sheet but the temperature is not sufficiently high to melt the outer sheets. A hydraulic pump 232 is connected to the hydraulic conduit 222 to force hydraulic liquid between the outer sheets as soon as the bonding sheet is melted to expand the outer sheets into the passage grooves formed in the upper and lower dies 224 and 226 to form the structure 220 with the passageway configurations 234 shown in Fig. 14. As is evident, the structure resulting is substantially like that shown in Fig. 9 with the outer sheets being held bonded together between the passageways by raised portions of the upper and lower dies until the cooling is sufficient to rebond the laminated sheet between the passageways. In this process, the passageways 234 are very accurately located so that the metal between the passageways may be slit accurately in a punch press operation illustrated in Fig. 15. The structure 220 rests upon the lower cutting die 236. The upper cutting die 238 is provided with slitting knives 240 which cooperate with the cutting edges 242 upon the lower die 236. The knives 240 and 242 cooperate in a scissors-type cutting action. The location of the passage portions 234 is shown in dot-and-dash lines superimposed upon the lower die 236. The structure 220, after being slit as shown in Fig. 15, is stretched by any suitable form of pulling device which grips the upper and lower edges of the structure 220 as indicated by the arrows 224 and 246 in Fig. 14. This will form a structure substantially like that shown in Figs. 1 to 4. Subsequent forming operations may be used to provide either the wavy edge such as is shown in Fig. 2 or the extruded coined fins shown in Fig. 3.

In Fig. 17 there is shown another form of cutting and bending operation which may be applied to the structure 220. In this form, the sheet 220 is fed between alternate pairs of scalloped cutting and bending rolls, with the rolls 248 and 250 constituting one opposite pair. In this arrangement the projections of the scalloped cutter 248 extend into the recesses of the scalloped cutter 250 and vice versa. These cutters have recessed portions 252 for the passages. The cutter 248 rotates upon the bearing 254 mounted eccentrically upon the stationary shaft 256, while the cutter 250 rotates upon the eccentric bearing portion 258 upon the stationary shaft 260. At the side of the cutters 248 and 250 are a second set of cutters 262 and 264 rotatably mounted upon eccentric bearings 266 and 268. These scalloped rollers provide cooperating scissors-type cutting edges for the rollers 248 and 250 and also serve to provide the opposite bends of the passage portions 234 as shown in Fig. 18 to form the structures shown in Figs. 1 to 4.

A sufficient number of rollers are provided to extend entirely across the passage portion of the sheet 220. The rollers or cutters 270 and 272 are located alongside the cutters 262 and 264 and cooperate with them. They, however, have the same axis of rotation as the cutters 248 and 250. Alongside the cutters 270 and 272 are the cutters 274 and 276 which rotate upon the same axis as the cutters 262 and 264. In this process the structure 220 is drawn or forced through the in-between cutters as illustrated in Fig. 17. The cutters may be either idlers or they may be power-driven.

By virtue of these methods and machines, the heat ex6 change structure may be manufactured rapidly at a relatively low cost.

While the embodiments of the present invention as , herein disclosed constitute preferred forms, it is to be 5 understood that other forms might be adopted, as may come within the scope of the claims which follow.