Fin array for heat transfer assemblies and method of making same

Abstract

A fin array for a heat exchanger and method of forming same are disclosed. The fin array is an elongated one piece element that includes a plurality of fins. The fins include connected staggered top segments and bottom segments. A top bend axis extends continuously across a plurality of the top segments.

Description

RELATED APPLICATIONS

The present patent document is a continuation of PCT Application Serial No. PCT/US03/20653, filed Jun. 30, 2003, designating the United States and published in English, which claims the benefit of the filing date under 35 U.S.C. § 119(e) of Provisional U.S. Patent Application Ser. No. 60/392,075, filed Jun. 28, 2002, both of which are hereby incorporated by reference.

BACKGROUND

The present invention relates generally to the field of heat exchanger assemblies. More specifically, the present invention relates to an improved design and method of manufacturing a fin array for use in a heat transfer assembly.

Fin arrays have been previously produced using a louvered design. The louvered fin array is folded in a serpentine pattern to form a series of alternating rounded upper and lower crests with a plurality of individual fins. Each of the individual fins may include a plurality of louvers. This fin array is manufactured from strips of metal, such as copper or aluminum, that are driven through rotary cutting dies that cut the openings in the strip and shape the louvers by pushing them inward or outward from the strip. The fins are then folded using a “star wheel” style roller which imparts rounded bends to the fin stock. This approach has certain disadvantages. For example, the louvered fin arrays do not provide the maximum heat flux between the fins and the ambient air as a consequence of air by-pass in the rounded fin areas. In addition, the angled louver designs create unwanted pressure drop differentials through the coil assembly. Also, these fin arrays can be expensive to manufacture as a consequence of the high tooling costs associated with shear cutting of the fin material.

Alternative approaches to the louvered design have been proposed in order to overcome some of the problems previously encountered. For example, the use of a one-piece elongated serpentine fin array design has been proposed. The fin array includes top and bottom portions connected together by fins extending between adjacent ones of the top and bottom portions. The fins have side edges facing generally perpendicular to the longitudinal length of the one-piece fin member. The side edges of the completed fins are also offset with respect to each other in order to improve heat flux with the passing air. While this serpentine fin array design improved heat transfer capabilities, it has other disadvantages associated with its manufacture.

The one-piece serpentine design can be manufactured by scoring fin stock using a crush cut method (chisel and anvil). After the fin stock is scored or cut, it is driven through a pair of star wheels. The star wheels bend the fin stock so that the top portion extends in a common top plane, the bottom portion extends in a common bottom plane, and the fin stock extends between and connects adjacent ones at the top and bottom portions. Because the fin stock is uncompressed, it is placed in a compression device that urges the ends together in order to complete manufacture of the fin array. This manufacturing approach has been problematic. For example, the machinery, such as the star wheels, can be very slow moving, and complicated. More specifically, it has been found that the use of star wheels requires that the fin material be folded and gathered with many small angle changes in a multiplicity of staged and synchronized wheel combinations. This procedure results in an expensive manufacturing process that is difficult to set up and maintain while also being slow moving.

Therefore, there is a need for an improved fin array design that can be easily and rapidly manufactured while having the same advantageous heat transfer capabilities of the previous serpentine design.

BRIEF SUMMARY

The present invention is directed to an improved fin array and method of making same. More specifically, the present invention is directed to a fin array that has significant heat transfer capabilities, such as those found in the previous serpentine design, while capable of being easily and rapidly manufactured.

According to a first aspect of the invention, a fin array is provided having a plurality of fins. The fin array is an elongated one piece element. The fins include connected staggered top segments and bottom segments. A top bend axis extends continuously across a plurality of the top segments.

According to a second aspect of the invention, a fin array is provided having a plurality of fins. The fin is an elongated one piece element. The fins include a plurality of connected staggered top segments and bottom segments. Upper and lower bend axes extend continuously through a plurality of the top segments and bottom segments, respectively. A plurality of staggered fin bend axes extend on both sides of the top bend axis and the bottom bend axis.

According to a third aspect of the invention, a method of forming a fin array is provided. The method includes the step of providing a sheet of fin stock. The method also includes the step of positioning and passing the fin stock through a cutting roller which produces a one-piece fin member including a plurality of fins. The fins include connected staggered top segments and bottom segments. The one piece fin member has top and bottom bend axes extending continuously through the top and bottom segments. The one piece fin member also includes staggered fin bend axes on both sides of the top and bottom bend axes. The method also includes the step of bending the fin stock along the top and bottom bend axes such that the top and bottom segments form a generally flat surface.

The present invention, together with attendant objects and advantages, will be best understood with reference to the detailed description below in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a folded fin array in accordance with an embodiment of the present invention;

FIG. 2 is a schematic view of an embodiment of the folding process of the fin stock that ultimately forms the fin array shown in FIG. 1;

FIG. 3 is a top plan view illustrating fin stock after having been passed through cutting rollers;

FIG. 4 is an enlarged view of forming wheels and fin stock passing outward therefrom;

FIGS. 5A-H are side views and enlarged portions of the star wheels that form a portion of the forming wheels; and

FIG. 6 is a perspective view of the fin array after having passed through the forming wheels.

DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED EMBODIMENTS

The present invention is directed to an improved fin array and heat transfer assembly and method of making same. It will be understood by those of ordinary skill in the art that the fin array of the present invention can be used with a wide variety of heat exchanger assemblies and in various applications. For example, a fin array of the present invention could be used in air conditioning condenser coils or automotive radiators

FIG. 1 illustrates a fin array 10 in accordance with a first embodiment of the present invention. The fin array 10 has a generally serpentine pattern and is preferably formed from a single piece of fin stock. Materials such as aluminum, particularly rolled aluminum fin stock, or copper or other known materials may be used to form the fin array 10. The fin array 10 includes a plurality of fin sets 14 formed from fins 18. The fin sets 14 include top and bottom portions 22, 24. The top portions 22 extend in a common flat top plane and bottom portions 24 extend in a common flat bottom plane. The top and bottom portions 22, 24 maximize surface contact area with an associated heat exchanger tube thereby maximizing heat transfer between the fins 18 and the associated heat exchanger tube. In addition, each fin 18 runs continuously from tube to tube surface giving enhanced heat transfer close to the tubes where the temperature differential between fins 18 and air is greatest.

The top and bottom portions 22, 24 are elongated flat sections that extend generally perpendicular to the running length of the fin array 10. The top and bottom portions 22, 24 form a plurality of top and bottom staggered segments 28, 29 generally having a staggered rectangle shape. However, it should be recognized by those of ordinary skill in the art that other shapes may be implemented.

In the embodiment illustrated in FIG. 1, the fin array 10 includes four fin sets 14. The fin sets 14 include seventeen fins 18 in the illustrated embodiment. It should again be recognized by those of ordinary skill in the art that more or less than four fin sets 14 may be implemented and that more or less than seventeen fins 18 may be implemented. For example, a single fin 18 might be as wide as the fin strip itself or as narrow as 0.002 inches. Fin strips can be of any width but are typically in the range of 0.5 inches to 6.0 inches in width. The number of fins 18 in each fin set 14 (or repeated pattern) is defined by the fin pitch (the spacing of fins in the completed folded fin) and the fin offset (the staggered spacing of fins across the fin). The number of fins 18 in a fin set 14 (pattern repeat) will be not greater than the fin pitch divided by the fin offset. Fin pitch may vary from as little as 0.020 inches to as much as 0.500 inches. Fin offset may vary from as little as 0.010 inches to as much as 0.500 inches depending on the application. Fin height may also vary greatly from as little as 0.100 to as much as 6.0 inches typically.

Each of the fins 18 includes top and bottom edges 30A, 30B. The top and bottom edges 30A, 30B define sides 32A, 32B. The sides 32A, 32B interconnect the top and bottom portions 22, 24. The fins 18 are offset from one another to provide a gap 38 that maximizes the heat transfer of the fins 18 by allowing ambient air ready access to fins 18. The sides 32A, 32B extend perpendicular to the longitudinal or abyssal length of the fin array 10 in order to further maximize air flow.

The fin array 10 includes a top or ordinential bend axis 40 that extends across the top segments 28. In the illustrated embodiment, the top bend axis 40 extends continuously along the top portion 22. The bottom or ordinential bend axis 44 extends along the bottom portion 24 or bottom segments 29. In the illustrated embodiment, the bottom bend axes 44 extend continuously along the bottom portion 24. As explained herein, the use of the term “continuous” is not intended to suggest that the associated cutting of the fin stock has to be “continuous.” Indeed it cannot be continuous or the fin would fall apart during assembly operations. Rather, the cuts are sufficient to cause the material to bend easily and in precise alignment yet remain attached while the bend axes extend continuously through the material forming the top and bottom portions 22, 24.

FIG. 2 is a schematic view of an embodiment of the manufacturing method of the present invention 60. The manufacturing process includes using a conventional rotary cutting device (not shown) to cut or score the fin stock 62 into the pattern as best shown in FIG. 3. The cut fin stock 62 is passed into the folding rollers 68 which fold the cut fin stock 62 into the folded fin pattern 70 best illustrated at FIG. 6. The folded fin pattern 70 is passed into a conventional compression device 72 that compresses the ends of the folded fin stock pattern 70 into the fin array 10 illustrated in FIG. 1.

The cut fin stock 62 is best illustrated in FIG. 2. In the preferred embodiment, two cutting rollers and two pinch rollers are provided. The cutting rollers cut the fin stock into the pattern illustrated in FIG. 2 using a conventional crush cut (chisel and anvil) technique. It should be recognized that the cuts forming the bend axes 40, 44 are longer than the cuts used to form the fins 18 thereby resulting in an inherently greater weakness in the bending of these areas. Two pinch rollers are provided to assist by flattening out the cut fin stock after each cutting step. Reference is made to U.S. Pat. No. 6,247,527 issued on Jun. 19, 2001 to Roger Paulman, for a further description of the cutting process and other related manufacturing steps, the disclosure of which is hereby incorporated by reference. It should be noted that other known methods of cutting fin stock may be implemented so as to produce the cut fin stock 62.

Referring back to FIG. 2, after the cut fin stock 62 is produced, it is passed into the folding rollers 68. The folding rollers 68 serve to separate the fins 18 and fold the fin pattern 70 along the bend axes 40, 44. In particular, the folding rollers mechanically force apart the fins 18 of the fin sets 14 and bend each fin set at the bend axes 40, 44 as illustrated in FIG. 6. Because the bend axes 40, 44 extend across the top and bottom portions 22, 24 of each fin set 14, the fin stock material is weakened substantially in order to provide for easy bending and re-flattening along the associated bend axes. It should be noted that with some materials the crush cutting technique yields small spurs or burrs along the cut edges of the material. These spurs or burrs, when run through the flattening rollers, which are a part of this process, often become entangled and consequently must subsequently be forced apart using mechanical force.

The folding rollers 68 include a plurality of sets of star wheels 90, 92, 94, 96. The star wheels 90-96 are formed in sets of four wheels 90-96 with four sets shown to form each folding roller in the illustrated embodiment. The star wheels 90, 92, 94, 96 are best illustrated in FIGS. 5A-H. Each star wheel 90, 92, 94, 96 includes associated teeth 90A, 92A, 94A, 96A. The teeth 90A, 92A, 94A, 96A are best illustrated in the enlarged views of FIGS. 5B, 5D, 5F, 5H. Each of the teeth 90A, 92A, 94A, 96A is sized differently to produce the offset pattern of teeth as best seen in FIG. 4. The teeth 90A-96A produce the fins 18 by pressing into the cut fin stock 62. In addition, the top portions 90B-96B and bottom portions 90C-96C are used to bend the fin sets 14 along the bend axes 40, 44.

After passing through the folding rollers 68, the folded fin pattern 70 is produced. The folded fin pattern 70 includes a plurality of fin sets 14 with individual fins 18 formed and partially bent along the bend axes 40, 44. A conventional compression device 72 compresses the edges of the folded fin pattern 70 in order to produce the fin array 10 illustrated in FIG. 1. Because the cuts associated with the bending axis 40 extend across each fin set 14, the material is weaker in these areas thereby allowing for the folded fin pattern 70 to be readily bent to produce fin array 10. The folded fin pattern 70 is produced by urging it into a box against a backwards force. More specifically, the present invention overcomes previous problems by positively folding (using opposing wheels) two approximately 90 degree bends (the bottom bend axes 44) along with an approximately third 90 degree bend (the bending axis) which is subsequently flattened back to the straight or nearly straight condition in the box. This third bend is made such that the fin material holding the fin together at the bend is much narrower than that of the other bends which are expected to remain at about 90 degrees in the final formed fin array. As a consequence of the built-in relative “weakness” the third bend will re-flatten itself back to near flat condition without changing the two 90 degree bends on either side of it thus resulting in a near perfect “square” final fin configuration.

The embodiments described above and shown herein are illustrative and not restrictive. The scope of the invention is indicated by the claims rather than by the foregoing description and attached drawings. The invention may be embodied in other specific forms without departing from the spirit of the invention. For example, the shape and size of the fins of the fin array may be designed in a manner other than as specifically illustrated in the figures. Accordingly, these and any other changes which come within the scope of the claims are intended to be embraced herein.

It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.

Claims

1. A fin array for a heat exchanger assembly comprising:

an elongated one piece fin array including a plurality of fins, the fin including connected staggered top segments and bottom segments, and a top bend axis extending continuously across a plurality of the top segments.

2. The fin array of claim 1 wherein a fin material used to form the fin member is cut to generally define the top bend axis.

3. The fin array of claim 2 further comprising a bottom bend axis that extends continuously across a plurality of the bottom segments.

4. The fin array of claim 3 wherein the fin material is cut to generally define the bottom bend axis.

5. The fin array of claim 4 further comprising staggered fin bend axes on both sides of the top bend axis.

6. The fin array of claim 5 further comprising staggered fin bend axes on both sides of the bottom bend axis.

7. The fin array of claim 6 wherein the cuts used to form the top bend axis and the bottom bend axis are not continuous.

8. The fin array of claim 7 wherein the staggered segments have a generally rectangular shape.

9. The fin array of claim 8 wherein the top and bottom bend axes are weaker than the staggered fin bend axes.

10. A fin array for a heat exchanger assembly comprising:

an elongated one piece fin array including a plurality of fins, the fins including connected staggered top segments and bottom segments, and a top bend axis and a bottom bend axis that extend continuously through a plurality of the top segments and bottom segments, respectively, and staggered fin bend axes on both sides of the top bend axis and bottom bend axis.

11. The fin array of claim 10 wherein the top and bottom bend axes are weaker than the staggered fin bend axes.

12. The fin array of claim 11 wherein the top and bottom bend axes extend across a width of the fin.

13. The fin array of claim 12 wherein a group of fins forms a fin set with the top and bottom bend axes extending across each fin set.

14. The fin array of claim 13 wherein the top and bottom bend axes extend straight through the top and bottom segments.

15. A method of making a fin array for a heat exchanger assembly comprising:

a) providing a sheet of fin stock;

b) positioning and passing the fin stock through a cutting roller which produces a one piece fin member including a plurality of fins, the fins including connected staggered top segments and bottom segments, and the one piece fin member having the top and bottom bend axes extending continuously through the top and bottom segments, and staggered fin bend axes on both sides of the top and bottom bend axes; and

c) bending the fin stock along the top and bottom bend axes such that the top and bottom segments form a generally flat surface.

18. The method of claim 17 wherein the bend axes are formed by cutting the fin stock.

19. The method of claim 18 wherein the bending of the fin stock requires a bending and a re-bending of the fin stock.

20. The method of claim 19 wherein the top and bottom bend axes are weaker than staggered fin bend axes.