GB2080178A

GB2080178A - Apparatus for forming heat exchanger fins

Info

Publication number: GB2080178A
Application number: GB8024555A
Authority: GB
Original assignee: Covrad Ltd
Current assignee: Covrad Ltd
Priority date: 1980-07-26
Filing date: 1980-07-26
Publication date: 1982-02-03
Also published as: GB2080178B

Abstract

The conventional roll pairs used for forming fin material having openings and louvres for beat exchangers are modified for ease of manufacture and for improving the resulting fin material. The rolls are made up of discs and the discs have alternating radial slots 10 and teeth 11. The edges of the teeth 11 are formed with bevels 19 at an acute angle relative to the disc axis and the outer ends 18 of the slots 10 diverge outwards. One roll has knives 15 mounted in the slots 10. <IMAGE>

Description

SPECIFICATION Apparatus for forming heat exchanger fins This invention relates to apparatus for forming heat exchanger fins, the fins being of the kind formed of thin thermally conductive material, such as metal foil, and having louvres and openings for receiving tubes.

Hitherto heat exchanger fin has been rolled from metal foil using a pair of rolls made up of an assembly of discs. The outer peripheries of the discs are shaped to provide louvrecutting teeth and radial slots. Each disc is formed so that the discs when assembled give the desired pattern of louvres and tube openings. A typical fin material is shown in Fig. 6.

For the illustrated form of fin some of the discs are provided with louvre-forming teeth and slots and other discs are provided only with slots. Other discs may be provided to serve as spacers effecting no louvre-forming or hole forming function. In the present application we are concerned primarily with discs which are provided with louvre-forming teeth and slots. Such discs have hitherto been formed by a series of complex machining operations. For example the prior disc may have an outer periphery of the form shown in Fig. 5 in which slots 50 are circumferentially spaced apart by teeth members 51. The teeth members 51 have louvre-forming cutting edges 52 extending only partially across the teeth 51 and extending outwardly of outer edges of the members 51.The edges 52 are each individually precision ground, as shown in Fig. 5A, to an angle a during manufacture of the discs and the circumferential extent of the edges 52 is restricted by the need to maintain an adequate amount of material along the outer edges of the slots 50.

In this previous arrangement each tooth on each disc has to be individually ground which makes for a time consuming and inefficient manufacturing process and it is an object of the invention to provide an improved construction of disc for forming heat exchanger fins.

According to the invention apparatus for forming heat exchanger fins comprises a disc having circumferentially spaced, alternating radial slots and louvre-forming teeth, the teeth having their outer edges bevelled or angled at an acute angle relative to the axis of the disc along their length between the slots, and the outermost portions of the sides of the slots being outwardly divergent.

The outwardly divergent sides of the slots provide the run out angles for the ends of the louvres.

With this arrangement the slots and their divergent portions can be formed in the disc in one operation and, as a single further operation, the outer edges of the teeth may be angled by grinding, for example by a rotary grinding operation.

Further features of the invention will appear from the following description given by way of example only and with reference to the drawings in which: Figure 1 is a side elevation of part of a disc for rolls for rolling heat exchanger fins, Figure 2 is a perspective view of part of the disc of Fig. 1, Figure 3 is a sectional view on the line 3-3 in Fig. 2, Figure 4 is a plan view of heat exchanger fin produced by rolls incorporating the disc of Figs. 1-3, Figure 5 is a side elevation of part of a prior art disc for forming heat exchanger fins, Figure 5A is a section on the line 5A-5A of a tooth of the disc of Fig. 5, and Figure 6 is a plan view of heat exchanger fin produced by the disc of Figs. 5 and 5A.

Referring to Figs. 1-3 a thin metal disc is shown which has a series of alternating radial slots 10 and teeth 11 circumferentially arranged about the periphery of the disc.

Discs such as that shown in Figs. 1-3 are assembled onto a shaft (not shown) to form a first laminar roll and a similar roll is used cooperating with the first roll to form fin material having louvres 13 and holes 14, such as shown in Fig. 4. In forming such fin material thin metal foil or other suitable thermally conductive material is fed between the rolls for the louvres 13 and the holes 14 to be cut and shaped, in known manner.

The slots 10 in the disc are for forming the holes 14 and this is achieved by locating knives 15 (Fig. 1) in the slots 10 on one of the rolls which engage in the slots on the other of the rolls.

The teeth 11 are for forming the louvres 13 which each have a run-out portion at each end and the teeth on one roll are arranged to mate with the teeth on the other roll to form the louvres 1 3.

The slots 10 are parallel-sided over their radially inner portions 17 and towards the radially outer ends of the slots are formed outwardly divergent portions 18 which provide the run-out angle for the ends of the louvres. The portions 18 are at an angle ss to the tangential direction.

The teeth 11 each have their outer edges bevelled or angled at an acute angle of a to the axis of the disc, the depth of the bevel being greater than the depth of the divergent portion 18 of the slot. The teeth thus each have a bevelled surface 19 which extends the full length of each tooth.

The disc of Figs. 1-3 can be made by a two stage process in a first stage of which a disc blank or a plurality of blanks are formed with an alternating slot and tooth profile around its outer periphery and in a second stage the disc has its teeth formed with the angled surfaces 19 by, for example, a rotary grinding process.

The discs thus produced give rise to an improved form of fin material, as shown in Fig. 4, in that the lengths of the louvres 13 between the tube openings 14 can extend over the full width of the gaps between the tubes thereby enabling a fin material to be produced which has better performance than prior fin material. The fin material 1 4A which is displaced to form the openings lies transverse to the plane of the material so as to surround the opening. Due to the provision of the portions 18 the louvres run out at the edges of the openings 14 but do not extend into the transversely extending portion 1 4A of the fin. The fin material of Fig. 4 produced by the discs of the invention can be compared with the material of Fig. 6 produced by the prior discs of Figs. 5 and 5A which have louvres of relatively short length.

Claims

1. Apparatus for forming heat exchanger fins comprising a disc having circumferentially spaced, alternating radial slots and louvreforming teeth, the teeth having outer peripheral edges extending between the slots which edges are bevelled or angled at an acute angle relative to the axis of the disc, and the outermost portions of the sides of the slots being outwardly divergent.

2. Apparatus for forming heat exchanger fins comprising a pair of rolls between which fin material is fed to form openings and louvres in the material, each roll including a plurality of discs, the discs comprising circumferentially spaced, alternating radial slots and louvre-forming teeth, the teeth having outer peripheral edges extending between the slots which edges are bevelled or angled at an acute angle relative to the axis of the disc, and the outermost portions of the sides of the slots being outwardly divergent, knives being located in the slots of the rolls to form the openings in the fin material, and the teeth on the rolls cooperating to form the louvres in the fin material.

3. Apparatus according to claim 1 or 2 wherein the bevelled or angled edge of each tooth extends the full length of the peripheral edge and the depth of the bevel is greater than the depth of the divergent portions of the adjacent slots.

4. Apparatus for forming heat exchanger fins substantially as described with reference to Figs. 1-4 of the drawings.