Method of and apparatus for increasing the fin density of heat exchanger sheet material

This invention relates to a method of and apparatus for increasing the fin density of corrugated sheet material having a plurality of fins for use as primary surface plates of heat exchangers.

Apparatus for corrugating relatively thin deformable sheet material for use as the primary surface plates of fixed type heat exchangers or recuperators for gas turbines is known. In one technique, as disclosed in U.S. Patent Specification No. 3,892, 119, the corrugating apparatus receives substantially flat and relatively thin deformable sheet material which is then shaped into a relatively narrowly grooved corrugated configuration having a determined number of fins per inch, the configuration being serpentine. The apparatus is such that the corrugations in the sheet material are formed individually in a sequential manner to minimize any stretching or tearing of the material.

More particularly, the flattened material is transported to a fin shaping station which has a plurality of forcing blades on either side of the material. These blades are moved sequentially into contact with the flattened sheet material to form one fin of the corrugated sheet. After forming this one fin, the blades are moved away from the sheet and the latter indexed or moved one fin position so that the blades again can be actuated to contact the sheet and form another fin.

For example, with such prior corrugation apparatus, a first lower blade is raised into contact with one side of the flattened sheet material and then a second upper blade on the other side of the material is lowered into a groove of a previously formed fin to act as a clamp for the forming of the next fin. These two blades are on opposite sides of one wall of the previously formed fin. Next a third, upper, blade is lowered into contact with the flattened material to fold such material around the first blade and thereby form a wall of the fin being formed. Finally a fourth, lower, blade is raised to fold the material around the third blade, and thereby form another wall of the fin being formed.

It is desirable to obtain as high a fin density as possible. With more fins per inch, there will be a greater surface area per unit volume, resulting in greater neat transfer because of the increased surface area. The above-described apparatus is capable of producing about 40 fins per inch, which is a significant improvement over other known apparatus which can form the sheet material into corrugations providing only about 25 fins per inch.

According to the present invention a method, for increasing the fin density of a serpentine sheet having a plurality of spaced-apart fins each fin having two spaced apart sides, comprises continually carrying out the steps of clamping one side of a fin at a work station;bringing closer together the two sides of the fin;unclamping the side;and moving a further fin to the work station for compression thereat.

The invention also includes apparatus for increasing the fin density of a serpentine sheet having a plurality of spaced-apart fins, each fin having two spaced-apart sides connected at one end, the apparatus comprising clamping means for releasably engaging the sides of a fin, including first means for contacting one. side of the first fin and second means for contacting the other side of the first fin, and means for bringing closer together said first and second contacting means.

Although the above-mentioned prior 40 fin-per- inch forming apparatus is capable of producing even a higher fin density corrugated sheet, this would involve using narrower or thinner forming blades which would thereby reduce the width of the grooves of the fins; however, there is a limit to the minimum thickness of the forming blades. If these blades are made too narrow, this will increase the wear of the blades, thereby requiring that they be replaced more often. Also, the relatively thinner blades are more fragile, which means that they are more susceptible to breakage. Furthermore, the more narrow the blade, the more expensive it is to manufacture, thereby increasing the cost of the fin forming apparatus. In addition, the more narrow blades will be lighter and this reduces the speed of formation of the fins because of inertia problems with the lighter blades.

With the method and apparatus of the present invention, all of the advantages of the prior 40 fin- per-inch corrugating apparatus are maintained while not requiring the use of relatively thin blades for forming the serpentine sheet. The prior apparatus can still operate at its relatively high fin formation speed and with relatively thick blades which will not wear quickly or be unduly flexible. At the same time, with the present invention the serpentine sheet can be modified into a higher fin density sheet of about 45 to 90 fins per inch depending on the requirements of, for example, a heat exchanger.

• Figures 1 and 2 are enlarged diagrammatic views which together show essentially an embodiment of the fin compressing technique of the present invention.
• Figure 3 is a side elevational view of an embodiment of the fin compressing apparatus of the present invention.
• Figure 4 is an end elevational view of the fin compressing apparatus of the present invention.
• Figure 5 is an enlarged vertical sectional view S-5 of the apparatus circled in Figure 6.
• Figure 6 is a side elevational view, partly in section, showing details of the apparatus of Figure 3.
• Figures 1 and 2 illustrate the steps for increasing the fin density of a serpentine sheet by compressing the respective fins. Figure 1 illustrates a fin which is about to be compressed, while Figure 2 illustrates the fin after it has been compressed.

A serpentine sheet 10 which includes a plurality of succeeding fins 14a, 14b and 14c which are to be compressed is supplied to a fin compressing work station 12. The work station 12 outputs a sheet 10 having a plurality of compressed fins 14'.

As represented by fin 14a, each uncompressed fin includes a first side 16 and a second side 18 connected together at one end 20, there being a first space or groove 22 between the two diverging sides 16 and 180 Side 16 has a second end 24 opposite the one end 20 while side 18 has a second end 25. A second space or groove 26 lies between each two adjacent fins such as fins 14a and 14b.

A sheet clamping means 28 is employed to compress the uncompressed fins. The clamping means 28 includes a pair of movable blocks 30 and 32 on opposite surfaces or sides A and B, respectively, of the sheet 10, for holding or gripping or clamping the opposite ends 24 and 20, respectively, of one side 16 of the fin 14a. The block 30 has a recess 30a conforming to the end 24 and is movable vertically into contact with such end 24, while the block 32 has a recess 32a conforming to the end 20 and is also movable vertically into contact with such end 20.

The clamping means 28 also includes a pair of blades 34 and 36, on opposite surfaces A and B, respectively, of the sheet 10. The blade 34 is movable vertically into the space 22 of the fin 14b to contact or engage one side 16 of fin 14b intermediate the ends of this one side. The blade 36 is movable vertically into the space 26 between fins.14a and 14b to contact or engage the side 18 of the fin 14a intermediate its ends. As shown in Figure 2, the blades 34 and 36 are also movable horizontally to bring the side 18 of fin 14a closer to the side 16 of fin 14a while the side 16 is held stationary by the blocks 30 and 32.

In operation, once fin 14a is in the work compressing station 12, the block 30 and blade 34 on the one hand, and the block 32 and blade 36 on the other hand, are moved simultaneously from their dotted line positions shown in Figure 1 into their full line positions shown in Figure 1. Thus, prior to compressing the fin 14a, one side 16 is held stationary within the receptacles 30a and 32a of the respective blocks 30 and 32, while blade 34 contacts side 16 in fin 14b and blade 36 contacts side 18 of fin 14a. Then, as shown in Figure 2, the blades 34 and 36 are moved simultaneously horizontally a predetermined distance towards stationary blocks 30 and 32 to move side 18 of fin ₁4a into a substantially vertical position, thereby compressing fin 14a. At the same time, side 16 of fin 14b is brought into a substantially vertical alignment. After this horizontal movement, the blocks 30 and 32 and the blades 34 and 36 are withdrawn simultaneously vertically cut of contact with the sheet 10 so that the fin 14b can be indexed or moved into the work station 12 to be compressed in the same manner as fin 14a. After this withdrawal, blades 34 and 36 will also be moved horizontally to the start position shown in phantom lines in Figure 1 prior to compressing fin 14b.

Figure 3 illustrates in further detail the apparatus for performing the method described in connection with Figures 1 and 2. Block 38 represents a known apparatus for corrugating sheet material having a fin density of about 40 fins per inch. The output of this apparatus 38 is the serpentine material 10 that is fed to apparatus 40 which compresses the fins in the manner shown in Figures 1 and 2. The apparatus 38 may be that described in the above-noted U.S. Patent Specification No.3,892,119.

Apparatus 40 includes a frame assembly 42 in which there is a path 44 for the movement of sheet material 10 therethrough. The clamping means 28 is shown on both sides A and B of this path 44. On side A, and supported by frame 42, is a hydraulic cylinder 46 and a cylinder rod 48 which is connected to a slide support 50. This support 50 is slidable vertically and supports a slide plate 52 which is movable laterally. Another hydraulic cylinder 54 has a cylinder rod 56 coupled to plate 52 to slide the latter laterally. Cylinder 54 and rod 56 are connected to.support 50 to move vertically with this support while being able to move plate 52 laterally. The block 30 shown in Figure 1 is connected to support 50 to move only vertically, while the blade 34 is coupled to plate 52 to move both vertically and laterally.

On side B of the path 44 is a hydraulic cylinder 58 having a cylinder rod 60 coupled to another support 62 to move the latter vertically. The support 62 supports a slidable plate 64^*which is movable laterally by a cylinder 66 and a cylinder rod 68 which are also supported by the support 62. Support 62 carries the block 32 shown in Figure 1 for movement only vertically, while plate 64 carries the blade 36 for movement both vertically and laterally.

Also illustrated in Figure 3 is a mechanism 70 for holding the corrugated sheet 10 while one of the fins 14a, 14b, 14c etc. is being compressed by the clamping means 28. This mechanism 70 includes plates 72 and 74 on opposite sides A and B, respectively, of the path 44. Plate 74 is fixed while plate 72 is movable vertically in relation to plate 74 by a hydraulic cylinder means 76 as will be shown more clearly in Figure 6. Prior to compressing one of the fins, plate 72 is moved downwardly so that sheet material 10 is sufficiently held on its upper and lower sides by the plates 72 and 74. This will prevent "fishtailing" of the sheet 10 when one of the fins is being compressed. After compression of the fin, plate 72 is elevated to enable the sheet 10 to be moved forward one fin position for compressing another fin.

The output of apparatus 40 is the corrugated sheet 10 having the compressed fins 14'. This sheet is fed to a take-up reel 80 which is rotatably supported on a frame 82. The compressed sheet is thereby stored on reel 80 for use later in the manufacture of, for example, heat exchangers.

Figure 4 shows further detail of the apparatus 40. Rod 48 of cylinder 46 is coupled to the support 50 by a pin connection 84 and, similarly, rod 6₀ of cylinder 58 is coupled to support 62 by a pin connection 86. Support 50 is slidable in vertically extending side guide rails 87 and 88, and support 62 is slidable in vertically extending side guide rails 90 and 92. A stop member 94 is connected between the ends of guide rails 87 and 90 while another stop member 96 is connected between the ends of guide rails 88 and 92. The support 50 has two respective protrusions 98 and 100 which come in contact with one end of respective stop members 94 and 96. The support 62 likewise has two respective protrusions 102 and 104 which come in contact with the other end of stop members 94 and 96, respectively. Stop members 94 and 96, and protrusions 98 and 100 are positioned so that support 50 will be stopped on its downward movement when block 30 and blade 34 are in the full line positions shown in Figure 1. Similarly, stop members 94 and 96 and protrusions 102 and 104 are positioned so as to stop the upward movement of support 62 when block 32 and blade 36 are in the full line positions shown in Figure 1. In this manner, the blades 34 and 36 are prevented from cutting through the sheet material 10, and blocks 30 and 32 are prevented from deforming the ends 24 and 20 of the material 10.

As also shown in Figure 4, the cylinder 54 is bolted to the support 50 by four bolts 106 extending through flanges 108 and 110 of the cylinder 54. Similarly, the cylinder 66 is connected to the support 62 by four bolts 112 extending through flanges 114 and 116 of the cylinder 66. The slide plate 52, movable horizontally with the use of cylinder 54 and rod 56, has flanges 118 and 120, and support 50 has brackets 122 and 124 aligned with these flanges 118 and 120, respectively. A dowel 126 extends from flange 118 and into an elongate opening 128 of bracket 122, and another dowel 130 extends from flange 120 and into an elongate opening 132 of the bracket 124. In this manner, plate 52 is connected to support 50 so as to move vertically therewith, while dowels 126 and 130 are slidable laterally along openings 128 and 132 to enable the plate 52 to move horizontally an relation to support 50, as described in connection with Figure 3.

Slide plate 64, movable horizontally with the use of cylinder 66 and rod 68, is coupled to support 62 in a similar manner as plate 52 is coupled to support 50. Plate 64 has flanges 134 and 136 aligned with brackets 138 and 140 of support 62. A dowel 142 extends from flange 134 into an elongate opening 144 of bracket 138 and another dowel 146 extends from flange 136 into an elongate opening 148 of bracket 140. Thus, plate 64 can move vertically with block 62 and move laterally in relation to support 62 as described in Figure 3 by the sliding of dowels 142, 146 in openings 144, 148.

Two springs 150 and 152 are coupled between plate 52 and support 50 to cushion the relative movement of those two members, and two springs 154 and 156 are coupled between plate 64 and block 62 to cushion the relative movement of these two members. A number of head sockets 158 connect block 30 to support 50 and a number of head sockets 160 connect block 32 to support 62. Blades 34 and 36 may be similarly connected to plates 52 and 64, respectively.

Figure 5 shows in more detail the manner in which blades 34 and 36 are movable laterally towards blocks 30 and 32, respectively, to compress a fin of sheet 10. The plate 52 is spaced from the support 50 with the spring 150 extending therebetween, the spring 150 being disposed within respective openings 162 and ₁64 of plate 52 and support 50. The rod 56 of cylinder 54 extends through support 50 and plate 52 via respective openings 166 and 168. Rod 56 is slidable through opening 166 but is rigidly connected to plate 52 by a nut 168^t and washer 170.

Plate 64 also is spaced from support 62 as shown in Figure 5. Rod 68 of cylinder 66 extends through an opening 172 of support 62 and an opening 174 of plate 64. Rod 68 is slidable through support 62 and fixed to plate 64 by a nut 176 and washer 178. A rod 180 is fixedly connected to support 62 by a nut 182 and extends partially from the support towards the plate 64. Plate 64 has a protrusion 184 which functions as a stop member to stop the movement of the plate 64 towards support 62, when the rod 180 and protrusion 184 come into contact. With this stop member, one side 18 of fin 14a is brought closer to the other side 16 of fin ₁₄a by a pred_ete_rmined amount, thereby preventing the fin 14a from being compressed beyond a desired amount.

For purposes of simplifying the drawings,Figure 5 shows only the spring 150 coupled between the plate 52 and support 50. However, as indicated in 4, the plate 64 and support 62 similarly have the spring 154 connected therebetween. Springs 152 and 156 are coupled to plate 64 and support 62 in the same manner, respectively, as spring 150 and 154. Also, for the same purpose, only one stop member including rod 180 and protrusion 184 is shown between plate 66 and support 62. However, a similar stop member is situated between plate 52 and support 50 to prevent the compressing of a fin beyond a desired amount.

The relative positions (shown in Figure 5) of the blade 34 and block 30 on the one hand, and the blade 36 and block 32 on the other hand, are as shown in the full lines in Figure 1. When hydraulic fluid is introduced into cylinders 54 and 66 to compress fin 14a, rods 56 and 58 will be retracted into their respective cylinders, carrying plates 52 and 64 with them. This will cause the springs 150, 152, 154 and 156 to compress and bring the side 18 of fin 14a towards the stationary side 16 of the fin until the protrusion 184 comes into contact with rod 180. Then, hydraulic fluid will be introduced into cylinders 46 and 58 to retract their respective rods 48 and 60, thereby removing blocks 30 and 32 and blades 34 and 36 from contact with the sheet 10. Then, hydraulic fluid is discharged from the cylinders 54 and 66 to move plates 52 and 64, and hence blades 34, 36 away from the respective blocks 30 and 32 under the force of springs 150, 152, 154, and 156 to the dotted line positions of Figure 1.

Figure 6 shows in more detail the holding mechanism 70 shown in Figure 3. The hydraulic mechanism 76 includes a hydraulic cylinder 186 and a cylinder rod 188. Rod 188 is fixedly connected to a movable plate 190 by a nut 192 and extends through a fixed plate 194 having a hole 196 through which rod 188 is slidable. Fixed plate 194 is coupled to a fixed plate 198 by two guide rails 200 and 202. A pair of springs 204 and 206 are coupled between guide rail 200 and guide rail 202, respectively, and plate 190 through plate 194. Two lift bolts 208 and 210 are fixedly connected at one end to plate 190 by nuts 212 and 214, respectively. These bolts 208 and 210 extend through plate 194, respective guide rails 200, 202 and plate 198 to a plate 216 which is movable in a vertical direction. Bolts 208 and 210 are coupled to this plate 216 by nuts 218 and 220_«

Plates 198 and 216 define one part of the path 44 over which the uncompressed serpentine sheet material 10 is transported. Another plate 222 constitutes a table on which the compressed fins 14' are transported out of the apparatus 40 and also defines part of the path 44.

The normal relative position of the plates 216 and 198 is a shown in Figure 6. That is these two plates are normally in a position such as to hold the sheet material 10 on either side A and B to prevent it from being moved forwardly over path 44. Thus, when a fin is being compressed, these two plates will be in their normal state to prevent "fishtailing" of the material. After the fin compressing operation, hydraulic fluid is introduced into cyliner 186 to raise rod 188 and with it, plate 190, to move the latter towards fixed plate 194. This movement also raises lift bolts 208 and 210, along with plate 216, so that the sheet material 10 is now free to move one fin position for compressing another fin. Then, the hydraulic fluid is discharged from the cylinder 186 and the plate 190 allowed to descend with a force provided by the compressed springs 204 and 206, thereby moving plate 216 downwardly and holding firmly the sheet material 10 in'anticipation of another fin compressing operation.

While not described herein, one type of mechanism for moving the sheet material 10 the one fin position is disclosed in U.S. Patent Specification No. 3,892,119. Such a mechanism may sequentially feed a predetermined amount of material 10 into the apparatus 40 to position a fin at the fin compressing work station 12 prior to compressing the fin.