NZ243351A - Weldless, roll formed tubular section, beam or post and method of - Google Patents

Description

24 3 35 1 Patents Form 5 • <o { OO) • * O „vJ J- , _ - „ . ' ' « | r^r;: 6&W§\2o; BSiV&rilo .f'l.'-0.Lr?\\\v C*?; 2 6 JAN 1994 LI I-':: N.Z. No.

NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION N.Z. patent cT"-"" 29 JUN 1992 Receive IMPROVED TUBULAR SECTION fl/St We, STRATCO METAL PTY LTD, -on Australian company»incorporated under the laws of the State of South Australia of Cavan Road, Gepps Cross, South Australia, Australia do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- - 1 - (Followed by 1A) 4 3 3 5 1 This invention relates to an improved tubular or hollow section, and in particular relates to the roll-forming of an improved tubular or hollow section.

There are several conventional tube forming techniques which are widely known and currently used. One comprises the roll-forming of flat sheet into a tubular cross-section, and butt welding the edges which are brought together. Alternatively, the edges may be roll-formed into a lockseam, or may be overlapped and riveted to form a riveted seam.

Roll-formed tubes, regardless of the joining technique, are commonly referred to as rolled hollow sections (RHS).

The use of roll-forming and continuous welding to manufacture 15 an RHS beam is slow. In addition, relatively heavy weight material having wall thicknesses of at least 2 mm is generally used, resulting in a heavy beam, and involving greater forces in roll-forming. Such beams are generally unsuitable for lightweight applications.

Further, if the sheet material used to form the RHS is pre-primed on one of the surfaces, then this coating is likely to be destroyed in any welding or lockseaming process. In addition, corrosion resistant metals such as zinc or 25 aluminium zinc coated steels are also unsuitable for the same reason.

Therefore, RHS sections are normally formed from strip without any form of metallic or decorative coating, and 30 protective coatings are applied after the manufacturing process which obviously adversely affects the efficiency of the manufacture process, and results in a product of increased cost.

In some low load applications, it is possible to use posts and beams which are formed from relatively thin or light gauge material. However, the only means of securing the edges of the roll-formed sheet is to use a lockseam, which results in the seam projecting above the outer planar surface - 1 A — L-\ - t "T 2 -5 of the section formed. Further, the forming of the seam is a complex and costly forming process.

Therefore, it is an object of this invention to provide a 5 hollow section and a means of producing such a hollow section which overcome the abovementioned problems.

In its broadest form, the invention comprises a tubular section that is roll-formed from an elongate sheet of metal 10 material, said section having at least one projecting ridge in said elongate sheet along a first edge thereof so that it is parallel with the longitudinal axis of said elongate sheet and such that it extends away from the plane of said elongate sheet, a turned edge formed by partly folding the second edge 15 of said elongate sheet, and at least one tubular section wall comprising said elongate sheet intermediate of said first and second edges formed about its longitudinal axis so said first and second edges are brought almost together, such that said turned edge may be forced toward and over said projecting 20 ridge, said turned edge and projecting ridge shaped so as to lockably engage thereby holding said first and second edges together and forming a tubular section.

The tubular section wall may comprise a single wall having an 25 arcuate cross-section so as to form a tubular section having a curved cross-section. Alternatively there may be a plurality of section walls formed by an elongate fold between each of said walls so as to form a tubular section having a plurality of planar wall surfaces. In this example, the 30 tubular section may be formed into a right—angled parallelogram such as a square cross-section or a rectangular cross-section.

The projecting ridge may be spaced from the first edge of the 35 elongate strip, such that an intermediate edge portion is formed between the first edge and projecting ridge. The intermediate edge portion may be provided with one or more elongate folds therein so as to allow the second edge to overlap, allowing the turned edge to engage with the ? 4 3 3 5 1 projecting ridge. Preferably, in the case of the tubular section having a right-angled parallelogram cross-section, each corner comprises two folds each fold being spaced from one another either side of an intermediate planar portion. The projecting ridge may be incorporated into or form one of these said two folds and preferably the projecting ridge is incorporated into the second of said two folds which is furthest from the first edge of the elongate strip. The second edge has folds corresponding to the intermediate edge portion so as to allow the two edge portions to overlap. As part of the roll-forming process, the first and second edges of the elongate strip may be formed into a tubular section so that the two edges are brought almost together. This small amount of movement between the sheets is elastic deformation so that as two edges are brought together for the turned edge to engage with the projecting ridge some tension remains. The resulting tension, together with the engagement of the turned edge on the projecting ridge, results in a ridge joint being formed.

To assist in increasing the rigidity of the joint formed, the intermediate edge portion in respect of the right-angled parallelogram cross-sections may be sufficiently wide to overlap one side wall such that the first edge abuts against the adjacent side wall thereby preventing any relative movement of the overlapping portions when the section is subject to torsional loads.

An elongate channel may be formed alongside the projecting ridge on a side opposite to the intermediate edge portion such that the plane of the elongate sheet forming the wall of said tubular section is level with the peak of the projecting ridge. This elongate channel forms a recess into which the turned edge may locate, while at the same time producing a cross-sectional shape where the peak of the projecting ridge is within the periphery of the outer surface of the tubular section. Preferably, the projecting ridge, turned edge and elongate channel have an arcuate cross-section, although as 4 0 0 & 1 an alternative, they may be provided with a triangular or even square cross-sections.

In a further aspect of this invention, the tubular section 5 may comprise two interengaging elongate sheets roll-formed such that each of the sheets has a projecting ridge and turned edge wherein the turned edge of the first elongate sheet engages the projecting ridge of the second elongate sheet, and the seconded turned edge of the second elongate 10 sheet engages the projecting ridge of the first elongate sheet.

In order to improve the torsional rigidity still further, the tubular section may further comprise a second projecting 15 ridge spaced from said second edge of the elongate sheet, and the intermediate edge portion may extend across the section such that the first edge of the elongate sheet locates within and abuts against the inside surface of the second projecting ridge. The concave inner surface of the second projecting 20 ridge hold the first edge captive therein, and thereby prevent separation of the overlapping edge portions when torsional forces are applied to the tubular section.

Further, the torsional rigidity and strength of the section 25 can be further enhanced by locating fasteners through the overlapping portions of the section. Although this may not be used when the tubular section is employed as a post where the fasteners may be unsightly, when the section is used as a beam and roof sheeting is placed across the top of the beam, 30 then fasteners may be used to secure the roof sheeting to the beam, and may pass through both overlapping portions. The use of the threaded fasteners absolutely prevents any relative movement between the overlapping portions.

Further, various fittings such as end caps, elbow joints and in-line connectors may be provided to enable various tubular sections to form a frame. Where the surface of the fitting is visible, then this surface is shaped so as to match the tubular section. A fitting is then provided with male ^ E N '/n ^ o \ // x ^ - 4 - /'v 6 DEC J993 4 3 35 1 portions which locate within the tubular section, and threaded fasteners may be then used to secure the fitting to the tubular section.

In a further aspect of the invention, a method of roll-forming a tubular section comprises, in sequential steps, roll-forming a projecting ridge along a first side of an elongate sheet, roll-forming a turned edge along a second edge of the elongate sheet, roll-forming the elongate sheet 10 such that the first and second edges are brought almost together, and then elastically forcing the turned edge toward an overly projecting ridge, and finally cutting the elongate sheet so as to allow the roll-forming process to form a tubular section of the required length.

In respect of the right-angled parallelogram tubular sections, where two folds are used to form each corner, then the elongate sheet is roll-formed to an intermediate stage where the two folds for each of the two top corners of the 20 tubular section are formed, and one fold for each of the two bottom corners of tubular section are formed so that there is a substantial space between the first and second edges. The partly formed elongate sheet then progresses over a roll-forming mandrel which is suspended via a support post 25 such that the support post is able to locate in the space between the first and second edges. The mandrel, which is elongate has a first roll-forming means on one side of the mandrel that is spaced longitudinally from the support post. This first set of roll-forming means forms the second fold of 30 the bottom corner directly below the projecting ridge thereby bringing that side of the part formed elongate sheet into its final position. The mandrel has a second set of roll-forming means spaced from, and on the opposite side from the first set of roll-forming means which are used to form the second 35 fold of the remaining bottom corner, which results in the turned edge being forced over and locating onto the projecting ridge. Finally, the elongate sheet is cut so as to produce a tubular section of the desired length. '/. ^ o V (U, - 5 - id c'\ /< fc -6 DEC 1993 24 3 3 In respect of the abovementioned method, the two top corners are completed such that the respective surfaces of the tube are at right-angles with respect to one another. By forming only one of the folds in each of the bottom corners, the 5 respective surfaces of the tubular section remain at an obtuse angle thereby allow the partly formed roll-formed section to progress over the mandrel and for the support post to locate in the space between the first and second edges of the elongate sheet. The roll-forming process then 10 progressively completes the remaining folds of the two bottom corners such that the side containing the projecting ridge is completed first, and the other side comes into position where it overlaps a portion of the first side and the turned edge is forced over the projecting ridge.

In order that the invention may be fully understood, preferred embodiments will now be described, but it should be realised that the scope of the invention is not confined or restricted to the precise details of each of these 20 embodiments.

The embodiments are illustrated in the accompanying diagrams in which, Fig 1 shows a perspective end view of a first embodiment, Fig 2 shows a perspective end view of a second embodiment, Fig 3 shows a side view of a roll forming mandrel, Fig 4 shows an underside perspective view of the mandrel, Fig 5 shows a cross-sectional view of a roll-forming mandrel 3 0 with a part formed elongate sheet located around the mandrel, and the first roll-forming means engaging the part formed elongate sheet, Fig 6 shows as a cross-sectional view of the mandrel and the second set of roll-forming means, together with an 35 illustration of the action of the first roll-forming means on one side of the elongate sheet, and Fig 7 shows movement of the other side of the elongate sheet under the action of the second set of roll-forming means. r$ /■ J* La, L-, "Y The first embodiment in Fig 1 shows a rectangular section 10. The section is roll-formed from a single elongate sheet, and comprises a base wall 11, side walls 12 and 13 and overlapping portions 14 and 15 forming a top wall 16.

Although the first embodiment in Fig 1 shows a rectangular section, obviously by varying the length of the walls 11, 12 and 13, and the top wall 16, various configurations can be produced including square and elongate rectangular 10 cross-sectional shapes.

Referring again to Fig 1, a projecting ridge 17 is formed on one side of the elongate sheet at a position spaced from a first edge 18 of the elongate sheet. In addition, an 15 elongate channel 20 is formed adjacent to the projecting ridge 17 on a side opposite to that of the first edge 18.

The second edge 22 of the elongate sheet is folded so as to form a turned edge 23 which is shaped so that the internal 20 surface of the turned edge 23 corresponds to the external surface of the projecting ridge 17.

The tubular section shown in Fig 1 has two folds, a first fold 25 and a second fold 26 forming each corner of the 25 tubular section 10. In addition, the overlapping portions 14 and 15 have corresponding folds 25 and 26 formed therein. So that the inner and outer surfaces of the portions 15 and 14 respectively abut.

Further, three additional elongate channels 27 and three additional projecting ridges 28 are formed in each of the remaining corners of tubular section 10. The formation of these additional elongate channels 27 and projecting ridges 2 8 is to produce a section having a uniform external 35 appearance. In addition, they may be used for locating various fittings on the external surface of the tubular section 10 such that portions of the fittings lie within the channel 27 making it easy for the fitting to be positioned at^ right-angles with respect to the longitudinal axis of the £ N ? // ^ * tubular section 10. // /•"v " 7 " ^ -6 DEC 1993 Op ff - Z4 o 3 5 1 Each of the projecting ridges 17 and 28 are incorporated in the second fold 26 at each of the corners. As seen in Fig 1, each of the projecting ridges 17 and 28 has an arcuate cross-section, and the second fold 26 is formed when the 5 projecting ridge 17 or 28 is formed.

As seen in Fig 1, the overlapping portion 14 extends across the top wall 16 so that the first end 18 projects into the additional projecting ridge 28 on that side of the tubular 10 section 10. The first edge 18 of the elongate sheet either abuts or is extremely close to the inside surface of the additional projecting ridge 28, and therefore limits the amount of torsional deflection and therefore relative movement of the overlapping portions 14 and 15 thereby 15 preventing the overlapping portions from separating under torsional loads.

Fig 2 shows a second embodiment where the tubular section 10 is formed from a first and second elongate sheet 30 and 31. 20 Each of the sheets have a projecting ridge 32 and 33 respectively and each has a turned edged 34 and 35 respectively. As with the previous embodiment, the tubular section 10 has a base wall 11 side walls 12 and 13 and a top wall 16 both the base wall and top wall 11 and 16 have 25 overlapping portions 14 and 15 as with the previous embodiment, the inner overlapping portions extend across the base and top walls respectively so that the ends 35 locate within additional projecting ridges 36, and operate in much the same way as the corresponding components described in the 30 first embodiment.

The tubular section 10 shown in Fig 1 is formed from a flat elongate strip that passes through a sequence of roll formers to arrive at the section shown in Fig 1. The process may 35 commence with either the cutting of an elongate sheet of metal to the desired length, or by simply feeding a roll of elongate sheet material into the first stage of the roll-forming process. The first steps of roll-forming comprise roll-forming the projecting ridges 17 and 28 at the top corners of the tubular section 10, the turned edge 23;f^tN / ~ v P °'" -6DELJ993 the first folds 25 at the top corners of the tubular section 10, and the elongate channels 27 and first folds 25 at the bottom corners of the tubular section 10. This produces a part form elongate sheet as shown in Fig 5. In this part 5 form , there is a space 38 between the first and second edges 18 and 22 A roll-forming mandrel 40 as illustrated in Fig 3 and 4 is then suspended within the part formed section as shown in Fig 10 5. The mandrel 40 has an elongate body 41 which is suspended within the section by support post 42 the mandrel has a first set of roll-forming means which comprises a roller 43 which is spaced longitudinally from the support post 42 and is located on one side of the mandrel 40. A second roll-forming 15 means comprising a roller 44 is located at a point spaced form the first roller 43 and is located on the opposite side of the mandrel 40. As seen in Fig 5, the roller 43 has a corresponding roller 45 which is used to form the additional projecting ridge 28 on the bottom corner below the projecting 20 ridge 17. As seen in Fig 5 this side of the part formed elongate sheet moves into its final position so that the side wall 12 is at right-angles with respect to the base wall 11. This is indicated in Fig 5 by the dotted outline.

Fig 6 shows the forming process in which this first side of the part formed elongate sheet moves into its final position. Fig 6 also shows the second roller 44 and its corresponding roller 46 forming the final additional projecting ridge 28. As shown in Fig 7 as the final projecting ridge 28 is formed, 30 that side of the part formed elongate sheet moves into its final position such that the side wall 13 is at right-angles with respect to the base wall 11. In the process of coming to the final position, the turned edge 23 is forced over and located onto the projecting ridge 17. Although the majority 35 the deformation caused by the final roller set 44 and 46 is plastic deformation, when forming the final projecting ridge 28, there will always be some rebound as the section departs these rollers meaning that the last portion of movement was in fact elastic deformation. This elastic deformation results in the turned edge 23 pulling against the projecting ridge 17 and thereby forming a solid and ridge joint.

Additional torsional rigidity of the tubular section can be 5 obtained by insert self-tapping threaded fasteners through the overlapping portions 14 and 15. This will be the case in respect of tubular section 10 which is used for beams to support roofing sheets, although it should be realised that the tubular section 10 can be used without fasteners and has 10 an added torsional rigidity, particular when it is used as a post.

It can be seen from the above description, the invention provides a means of forming a tubular section having a rigid 15 jointing system. It results in a tubular section having adequate strength that can be produced at minimal cost using thin section material. Further, the forming process enables the use of colour bonded material which is not possible with convention c-shaped sections or rectangular hollow sections 20 that require either welding or seamlock formation. 1

Claims (16)

WHAT WE CLAIM IS:

1. A tubular section that is roll-formed from an elongate sheet of metal material, said section comprising, at least one projecting ridge formed in said elongate sheet along a first edge thereof, so that it is parallel with 5 the longitudinal axis of said elongate sheet and such that it extends away from the plane of said elongate sheet, a turned edge formed by partly folding the second edge of said elongate sheet and a tubular section wall comprising said elongate sheet 10 intermediate of said first and second edges deformed about its longitudinal axis so said first and second edges are brought almost together, such that said turned edge- may be forced toward and over said projecting ridge, said turned edge and projecting ridge shaped so as to lockably engage 15 thereby holding said first and second edges together and forming a tubular section.

2. A tubular section according to claim 1 wherein said deformation comprises an arcuate deformation in said elongate 20 sheet between said first and second edges.

3. A tubular section according to claim 1 wherein said deformation comprises a plurality of elongate folds formed within said elongate sheet between said first and second 25 edges.

4. A tubular section according to claim 3 wherein said folds form a tubular section having a right-angled parallelogram cross-section. 30

5. A tubular section according to either claim 4 wherein said projecting ridge is spaced from said first edge the intermediate edge portion between said first edge and said projecting ridge having at least one elongate fold therein to 35 allow said second edge to overlap and for said turned edge to engage said projecting ridge. \ £ N f ^ '. :;N \ - ii - u ri - 6 DECJ993 i , / VV 4 3 35 1

6. A tubular section according to claim 5 wherein each corner of said cross-section comprises two folds, each fold being spaced from one another either side of an intermediate planar portion.

7. A tubular section according to claim 6 wherein said projecting ridge is incorporated into one of said two folds.

8. A tubular section according to claim 7 wherein said two folds of one corner are located in said intermediate edge portion, and wherein said projecting ridge is incorporated into the second of said two folds which is the furthest from said first edge, and said second edge has folds corresponding to said intermediate edge portion to allow overlapping.

9. A tubular section according to claim 8 further comprising an elongate channel formed alongside said projecting ridge on the side opposite to said intermediate edge portion such that the plane of the elongate sheet forming the wall of said tubular section is level with the peak of said projecting ridge.

10. A tubular section according to claim 9 wherein said projecting ridge, turned edge and elongate channel each have an arcuate cross-section.

11. A tubular section according to claim 8 further comprising a second projecting ridge spaced from said second edge and said intermediate edge portion extending across said section such that said first edge locates within and abuts against the inside surface of said second projecting ridge.

12. A tubular section according to claim 4 comprising two interengaging elongate sheets, each of said sheets having a projecting ridge and turned edge wherei". said turned edge of said first elongate sheet engages said { rejecting ridge of said second elongate sheet, and said turned edge of said u N / ' X - 12 - J \\"" 6 DEC 1993 10 15 0 second elongate sheet engages said projecting ridge of said first elongate sheet.

13. A method for roll-forming a tubular section according to any of the preceding claims comprising in sequential steps, roll-forming a projecting ridge along said first side of said elongate sheet, roll-forming a turned edge along said second edge of said elongate sheet, roll forming said elongate sheet such that said first and second edges are brought almost together, and elastically forcing said turned edge toward and over said projecting ridge, and cutting said elongate sheet to form a tubular section to a required length. 1

14. A method of roll-forming a tubular section according to claim 9 comprising, in sequential steps, roll-forming a projecting ridge and elongate channel along a first side of said elongate sheet, 20 roll-forming a turned edge along said second edge of said elongate sheet, roll-forming said two folds for each of the two top corners of said tubular section and roll-forming one fold for each of the two bottom corners of said tubular section so 25 that there is a substantial space between said first and second edges, suspending a roll-forming mandrel by a support post and locating the part formed tubular section over said mandrel such that said support post is located in said space between 30 said first and second edges, said mandrel having, spaced longitudinally from the support post first roll-forming means on one side of the mandrel to form the second fold of the bottom corner directly below said projecting ridge, and said mandrel having second roll-forming means, spaced and on the 35 opposite side from said first roll-forming means, to form the second fold of the remaining bottom corner, and to force said turned edge over said projecting ridge, and cutting said elongate sheet to form a tubular section to a required length. e n rn v* o\ " \ - 13 - . 'V \ k - 6 DEC 1993

15. A tubular section as hereinbefore described with reference to and as illustrated in the accompanying drawings.

16. A method of roll-forming a tubular section as hereinbefore described with reference to and as illustrated in the accompanying drawings. STRATCO METAL PTY LTD