AU2001265696A1 - Improvements in roll-forming sheet material - Google Patents

Description

TITLE: IMPROVEMENTS IN ROLL-FORMING SHEET MATERIAL

FIELD OF THE INVENTION

This invention relates to the prevention or alleviation of distortions in sheet metal products having complex cross-sectional profiles, which products are produced by roll- forming a substantially planar sheet metal workpiece to the required cross-sectional profile. For brevity's sake the term profile is used below to indicate a cross-sectional profile in every instance.

BACKGROUND OF THE INVENTION

The invention is a development and improvement of the invention described in International Patent Application PCT/AU89/00403 (Publication No. WO 90/03233, which is included herein by reference).

Briefly stated, the invention subject of that earlier application consists in a method of roll-forming a sheet metal workpiece of the kind comprising passing the workpiece through at least one stage of forming rolls to produce at least one longitudinally extending fold in the workpiece, characterised by the step of plastically straining a narrow elongated fold zone coinciding with the fold position in a manner causing localised elongation thereof to an extent substantially equalising the longitudinal contraction of the fold zone induced by the forming of the fold therein, thereby to substantially eliminate oil-canning defects in the finished work.

The term "fold zone" as used in the earlier publication WO 90/03233, and as used herein, refers to a narrow longitudinal zone of the workpiece, which is plastically deformed during the roll-forming so as to acquire and retain the curved or angulated profile of a longitudinal fold in the finished work.

The term "protective zone" is used herein to indicate a narrow longitudinal zone of the workpiece which is plastically strained in a manner causing elongation of the protective zone, which elongation may compensate in whole or in part for the aforesaid longitudinal contraction of an associated fold zone. The term "protective straining" is used herein to indicate the straining applied to a protective zone.

Publication WO 90/03233 did not use the terms "protective zone" or "protective straining". However the invention described therein could be succinctly summarised, using that terminology, as requiring the protective zone and the associated fold zone to be superimposed so that their respective edges are in register. That is to say the two zones are constituted by one and the same strip of workpiece material.

Thus the prior art comprised a process wherein the alleviation of oil canning is effected on a fold by fold basis, and wherein each fold zone is intentionally plastically elongated to compensate for the longitudinal contraction of the fold zone inevitably accompanying the formation of the fold therein.

By contrast the present invention arises from an appreciation of the fact that effective compensation for fold zone shortening may be provided by protectively straining protective zones that are associated with the respective fold zones but not necessarily in substantially exact edge to edge registration therewith. The invention is based on the further appreciation that the effects of plural protective zones are cumulative, so that more than one protective zone may be associated with a single fold zone to ensure adequate compensation. On the other hand the effects of plural fold zones are also cumulative and in some instances compensation for the combined effect of two fold zones may be provided by a single protective zone.

To recapitulate, defects arising from multiple folds in a workpiece, including but not restricted to oil canning, depend on the cumulative effects of the several folds. In particular the relative positions of the individual folds and any variations in their respective radii of curvature (and the corresponding degrees of plastic strain required for their production) should be taken into consideration. These matters are profile dependent, that is to say the deleterious result of fold zone shortening will vary from one product to another, but the same may be said in respect of the beneficial effect of protective straining of protective zones.

It may be true that virtually eliminating fold zone shortening, by treating each fold zone as proposed by the above mentioned prior art, would eliminate defects. However such treatment of a fold zone is sometimes difficult to achieve in practice. If, as suggested in one version of the prior art, zones of the flat workpiece corresponding to the fold zones of the finished work are pre-strained by an additional initial stand of ironing rolls, it is difficult to achieve sufficiently accurate tracking of the flat workpiece through the ironing rolls to achieve the desired result. On the other hand the suggested prior art alternative of providing ironing formations coinciding with the fold zones on the forming rolls themselves, frequently interferes with the formation of the fold or places undesirable limits on the extent of the folding possible at a single pass.

DISCLOSURE OF THE INVENTION

According to the invention, based upon the better appreciation of the need to consider the cumulative effects of fold zone shortening and the deliberate extension of protective zones of the workpiece in relation to the whole profile, the nexus between the fold zones and the protective zones may be relaxed to some extent.

This enables a wider and more strategic choice of the positions, widths and number of the protective zones and of the intensities of the protective straimng of each of them to be exercised. This, in turn allows other considerations, for example the complexity of the combined forming and ironing rolls and the pressure between the ironing formations and the workpiece, to be better taken into account.

Therefore, the invention consists in a method of continuously roll-forming substantially flat strip material, to form an elongate product having a non-planar profile, by imparting a curved or angled profile to each of a plurality of longitudinally extending fold zones of the strip, and straining each of a plurality of longitudinally extending protective zones so as to elongate each protective zone and thereby alleviate defects in the product due to longitudinal contraction of the fold zones, characterised in that at least one edge of each protective zone is out of register with either edge of its associated fold zone.

While the exact superimposition of the protective zones upon the fold zones that was a necessity of the prior art is abandoned by the present invention, there is still an association between protective zones and fold zones in methods according to the invention. In general, where the profile is such that a plurality of fold zones are disposed in an array that is symmetrical about a longitudinal centre line of that array, then the protective zone or zones nullifying the effect of those fold zones will also preferably be arranged substantially symmetrically about that centre line. On the other hand where the protective zone or zones is or are concerned with nullifying the effect of one fold zone, it or they will be disposed substantially symmetrically about the centre line of that fold zone.

By way of example, several arrangements conforming to the invention, and differing from the prior art, are described below. (a) In relation to a single fold zone, a protective zone may be used that overlies the fold zone so that the two centre lines of the zones are substantially in register, but wherein the protective zone is somewhat wider than the fold zone. Thus the protective zone covers the fold zone and has longitudinal margins disposed one on each side of the fold zone. This enables the protective stiaining of the protective zone to be less intense than would otherwise be the case, so that it may be achieved with lighter and cheaper ironing rolls than heretofore, or with less damage to the surface finish of the product.

(b) There may be two protective zones disposed one on either side of a single associated fold zone. The two protective zones may be equally spaced laterally from the fold zone or they may be contiguous therewith. In either instance the two protective zones may be substantially identical. Alternatively, if product profile makes it more convenient one protective zone may be narrow and mtensely strained and the other wider and less intensely strained, so as to substantially equalise their effect on the fold zone positioned between them. (c) There may be a plurality of spaced apart protective zones disposed on each side of an associated fold zone, in an overall array which is preferably substantially symmetrical about the centre line of fold zone. However it would not be essential for the protective zones on each side of the fold zone to be identical, they may be of various widths and straining intensity so as to substantially equalise the effect of each plurality on the fold zone. Furthermore the protective zones may be so narrow and intensely strained as to remain visible in the finished product, so that to the uninstructed observer they may appear as a decorative feature.

(d) In relation to a fold zone, there may be one or more narrow intensely strained protective zones located within or partly within the ambit of the fold zone. This possibility is attractive when the "fold" profile has a large radius of curvature.

(e) In relation to two closely spaced fold zones, a single protective zone disposed between, possibly extending laterally from one to the other, may be appropriate. (f) In relation to two widely spaced fold zones in an otherwise, flat pan or the like, two associated protective zones respectively adjacent to the fold zones and positioned either between or outboard of the two fold zones, may be appropriate.

Many other possibilities will be apparent in relation to specific profiles, and although a degree of trial and error may be needed, an appropriately skilled addressee should have no need of further instruction, to enable a strategic choice of protective zones and the degree of protective straining of each to be made.

The present invention admits of the possibility of the protective straining of the, or each, protective zone being effected after at least some of the folding of one or more of the fold zones has occurred. This is in contrast to the prior art wherein the protective straining was necessarily applied to the workpiece prior to roll-forming by dedicated ironing rolls, or at the onset of folding by ironing formations on the first met pair of forming rolls. The present invention may also be effected in that way, but it is not limited to that way as a matter of necessity. Preferably, ironing formations on the forming rolls are utilised in embodiments of the present invention, but the forming roll in question is not necessarily a roll in the first met stage of forming rolls. It may be, and preferably is, a roll in a later met stage, preferably the second forming stage of a particular bend. This preference arises because it has been found that it enhances the tracking of the workpiece through the ironing stage to more accurately position the protective zone(s) relative to the fold zones.

Another advantage of the present invention is that it may be applied to the correction or alleviation of defects other than oil-canning which are also due to the contraction of fold zones during the roll-forming operation. Such other defects may include longitudinal bowing, twisting, camber and wavy edges. For example, a channel- sectioned product is prone to longitudinal bow because of the contraction of the fold zones at the junction of the floor and sidewalls. This defect may be rectified by a protective zone in each wall immediately above the floor. Likewise oil canning in the channel floor may be alleviated by two protective zones in the floor respectively adjacent the side walls. Furthermore, the fact that in methods according to the invention the protective straining in relation to a particular fold does not necessarily precede, or is not necessarily simultaneous with, the start of the formation of that fold, enables the ironing formations to be selectively positioned in forming rolls that may be spaced apart along a multi-stand roll- forming line. This frequently facilitates the manufacture of the forming rolls, and permits individual ironing formations to be targeted at different defects. For example, one roll stand may be formed to reduce oil canning defects likely to arise from particular folds and another roll stand may be formed to reduce longitudinal bow likely to arise as a result of other folds in the finished product. BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:-

Figures 1 to 5 illustrate profiles of typical roll-formed products; Figure 1 shows the simplest formed profile, namely an angle section with one fold zone;

Figure 2 shows the profile of a roof gutter section with a large radius "fold";

Figures 3 and 4 show part profiles of panels with multiple closely spaced folds in edge margins of the panel; Figure 5 is part profile of a roof or wall cladding panel along with a detail profile of one stiffening rib therein;

Figures 6(a) to 6(n) show a series of views, each representing a transverse strip from an elongate product, and collectively illustrating various possible locations and configurations of protective zones in relation to an associated fold zone; Figure 7 is diametral section showing two forming rolls with ironing formations causing compression of the protective zone, in a configurations corresponding to the product represented by section (j) of figure 6; and

Figure 8 is a view similar to figure 7 but corresponding to section (f) of figure 6.

PREFERRED EMBODIMENTS OF THE INVENTION

Referring to the drawings, the invention provides a method of continuously roll- forming substantially flat strip material 1, to form an elongate product 2 having a non- planar profile, by imparting a curved or angled profile to each of a plurality of longitudinally extending fold zones 3. For each fold zone 3, at least one longitudinally extending protective zone 5 is formed by localised straining of the sheet material. This straining process elongates the sheet in the protective zone, and thereby avoids or alleviates defects in the finished product due to longitudinal contractions of the fold zones. While the concept of protective straining is known, the present invention is characterised in that at least one longitudinal edge 10 of the protective zone 5 is out of register with one or other edge 11 of an associated fold zone. This was hitherto thought not to be effective, or technically feasible without introducing further distortions or defects. Accordingly, the efficacy of the present invention is a surprising and unexpected result. In all of figures 1 to 5, wherein similar features are denoted by corresponding reference numerals, partial envelopes are shown, each covering a protective zone that would be protectively strained in accordance with the present invention. In each instance, the protective zone has a central longitudinal axis which coincides with that of the fold zone with which it is associated. However, it will be appreciated that the protective zone is wider than that fold zone. This is of course merely one option and it will be apparent from the earlier description that many other options are available, all of which would be in accord with the invention.

For example, in another embodiments, two protective zones may be disposed one on either side of a single associated fold zone. Alternatively, two protective zones of substantially equal width may be spaced laterally from the associated fold zone, or be substantially contiguous therewith. In a variation of this arrangement, one of the two protective zones may be substantially narrower and correspondingly more intensely strained than the other of the two protective zones, such that the effects on the associated fold zone positioned between them are substantially equal. In a further variation, a plurality of spaced apart protective zones can be disposed on each side of an associated fold zone. Optionally, the protective zones of this plurality may be substantially equal in width, and form an array that is generally symmetrically disposed about the centre of the associated fold line. It should be appreciated, however, that this is not essential and alternatively, the plurality of protective zones may be unequal in width and varyingly strained so as to substantially equalise the effect on either side of the fold zone.

In one particularly advantageous form of the invention, one or more of the protective zones is sufficiently narrower and intensely strained so as to be visible, and thereby constitute a decorative or aesthetic feature in the finished product. The resultant decorative bands may be located within or outside the associated fold zone. One attractive variation on this embodiment makes use of a symmetrical array of decorative strain bands within the ambit of a fold profile having a relatively large radius of curvature.

A further variation makes use of at least two closely spaced fold zones, and at least one single protective zone disposed between them, optionally with the protective zone extending laterally from one fold zone to the other. Alternatively, the two fold zones may be spaced relatively widely apart, with a substantially flat region between them. In this case, the two protective zones would be positioned closely adjacent and either between or outwardly of the respective fold zones. Several of these variations are illustrated in figure 6, which is a diagram showing various possible protective zone locations in relation to a fold zone. Each section of the diagram, referenced (a) to (n) respectively, represents a transverse strip of a long product. In all sections, the broken lines delineate the edges of the fold zone and the blocked in areas correspond to associated protective zones. Section (a) shows a section before roll-forming has begun, where there is no protective zone shown. Section (c) is included for comparison purpose. It shows the prior art in which the protective zone and fold zone were coincident. The remaining sections show various new arrangements, including a number of those outlined above, all made possible by virtue of, and within the scope of, the present invention.

In accordance with the method of the present invention, the straining of the protective zones may advantageously be effected either prior to or after the fold zones are formed in the workplace. This aspect adds considerable flexibility and versatility to the production process. In the preferred embodiment, the fold zones are formed progressively in the sheet material by forming rolls, while the protective zones are progressively formed by means of ironing formations. Normally, at least some of the forming rolls will also incorporate ironing formations.

Ideally, a multistage process is used, wherein the ironing formations on the respective forming rolls are positioned downstream of a first stage of forming rolls for each particular fold or bend, noting that in some configurations, it will be feasible to form an several folds substantially simultaneously. It has been found that by incorporating the ironing formations into a second downstream forming stage for a particular fold or bend, the tracking of the work piece through the ironing stage is enhanced. This in turn facilitates more accurate positioning of the protective zone relative to the associated fold zone. Optimally, the ironing formations are selectively positioned in respective forming rolls disposed in spaced apart relationship along a multi-stand roll-forming line, thereby permitting specific ironing formations to be targeted toward selected defects. The invention also provides an apparatus, part of which is represented diagrammatically in figures 7 and 8, for continuously roll-forming substantially flat strip material to form an elongate product having a non-planar profile, of the type illustrated. The apparatus includes forming rolls 15 and ironing formations 20 of the type described, configured such that at least one edge of each protective zone is out of register with either edge of an associated fold zone, as described.

The invention thus provides a mechanism to correct or substantially alleviate a diverse range of defects that are commonly produced in roll-formed products of this type, including canning, longitudinal bowing, twisting, cambering and undulating edging, in a manner which is more flexible, versatile, efficient and accurate than can be achieved using previously known protection and compensation techniques. Accordingly, the invention represents a practical and commercially significant improvement over the prior art.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims (24)

CLAIMS:-

1. A method of continuously roll-forming substantially flat strip material, to form an elongate product having a non-planar profile, by imparting a curved or angled profile to each of a plurality of longitudinally extending fold zones of the strip, and straining each of a plurality of longitudinally extending protective zones so as to elongate each protective zone and thereby alleviate defects in the product due to longitudinal contraction of the fold zones, characterised in that at least one edge of each protective zone is out of register with either edge of an associated fold zone.

2. A method according to claim 1, wherein a single protective zone is formed so as to overlie at least one of the fold zones, whereby the centre lines of the respective zones are substantially in register, but wherein the protective zone is substantially wider than the fold zone, such that the protective zone has longitudinal margins disposed one on each side of the fold zone.

3. A method according to claim 1 or claim 2, wherein two protective zones are disposed one on either side of a single associated fold zone.

4. A method according to claim 3, wherein the two protective zones are substantially equal in width, and are either equally spaced laterally from the associated fold zone or are substantially contiguous therewith.

5. A method according to claim 3, wherein one of the two protective zones is substantially narrower and correspondingly more intensely strained than the other of the two protective zones, such that the effects on the associated fold zone positioned between them, are substantially equal.

6. A method according to any one of the preceding claims, wherein a plurality of spaced apart protective zones are disposed on each side of an associated fold zone.

7. A method according to claim 6, wherein said spaced apart protective zones are substantially equal in width and form an array that is substantially symmetrically disposed about the centre line of the associated fold zone.

8. A method according to claim 6, wherein said spaced apart protective zones are unequal in width and varyingly strained so as to substantially equalise the effect of each plurality on either side of the fold zone.

9. A method according to any one of the preceding claims, wherein one or more of the protective zones are sufficiently narrow and intensely strained so as to be visible, and thereby constitute a decorative feature in the finished product.

10. A method according to any one of the preceding claims, wherein one or more relatively narrow and intensely strained protective zones are located within or partly within the associated fold zone.

11. A method according to claim 10, wherein a plurality of said relatively narrow protective zones are provided within the. ambit of a fold profile having a relatively large radius of curvature.

12. A method according to any one of the preceding claims, incorporating at least two closely spaced fold zones, and at least one single protective zone disposed therebetween.

13. A method according to claim 12, including two closely spaced fold zones and a single protective zone disposed therebetween, with the protective zone extending laterally from one fold zone to the other.

14. A method according to any one of the preceding claims, including two relatively widely spaced fold zones with a relatively flat region therebetween, and two associated protective zones disposed adjacent the respective fold zones, with the protective zones being positioned either between or outwardly of the associated fold zones.

15. A method according to any one of the preceding claims, wherein the stiaining of at least one of the protective zones is effected prior to the fold zones being formed in the workpiece.

16. A method according to any one of the preceding claims, wherein the straining of at least one of the protective zones is effected after at least some of the folding of one or more of the fold zones has occurred.

17. A method according to any one of the preceding claims, wherein the fold zones are progressively formed by means of forming rolls.

18. A method according to any one of the preceding claims, wherein the protective zones are progressively formed by means of ironing formations.

19. A method according to claim 18, wherein at least some of the forming rolls incorporate ironing formations.

20. A method according to claim 19, wherein the ironing formations on the respective forming rolls are positioned downstream of a first stage of forming rolls for a particular fold or bend.

21. A method according to claim 20, wherein the ironing formations on the forming rolls are incorporated into a second forming stage for a particular fold or bend, so as to enhance tracking of the workpiece through the ironing stage and thereby facilitate more accurate positioning of the protective zone relative to the associated fold zone.

22. A method according to any one of the preceding claims, wherein the ironing formations are selectively positioned in respective forming rolls disposed in spaced apart relationship along a multi-stand roll-forming line, thereby permitting specific ironing formations to the targeted toward selected defects.

23. A method according to any one of the preceding claims, wherein the protective zones are positioned and strained relative to the fold zones and in relation to one another so as to correct or alleviate one or more defects selected from a group comprising oil- canning, longitudinal bowing, twisting, cambering, and undulating edging.

24. An apparatus for continuously roll-forming substantially flat strip material to form an elongate product having a non-planar profile, said apparatus including forming rolls disposed to impart a curved or angled profile to each of a plurality of longitudinally extending fold zones of the strip, and ironing formations disposed to strain each of a plurality of corresponding longitudinally extending protective zones so as to elongate each protective zone and thereby alleviate defects in the product due to longitudinal contraction of the fold zones, characterised in that the ironing formations are configured and positioned relative to the forming rolls such that at least one edge of each protective zone is out of register with either edge of an associated fold zone.