AU767942B2

AU767942B2 - Further improved tubular section

Info

Publication number: AU767942B2
Application number: AU35054/99A
Authority: AU
Inventors: Michael Roy Stenhouse
Original assignee: Stratco Metal Pty Ltd
Current assignee: Stratco Metal Pty Ltd
Priority date: 1992-06-29
Filing date: 1999-05-26
Publication date: 2003-11-27
Anticipated expiration: 2012-06-29
Also published as: AU3505499A

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 PATENT OF ADDITION

ORIGINAL

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0* Name of Applicant: STRATCO METAL PTY LTD Actual Inventor: MICHAEL ROY STENHOUSE Address for Service: MADDERNS, 1st Floor, 64 Hindmarsh Square, Adelaide, South Australia, Australia Invention title: "FURTHER IMPROVED TUBULAR SECTION" The following statement is a full description of this invention, including the best method of performing it known to us.

This application is a patent of addition based on Australian Patent No. 649335 (18644/92) entitled "Improved Tubular Section".

The above mentioned earlier specification described an improved tubular or hollow section that was formed by roll forming elongate sheet metal. It also shows a means of roll forming folds and projections which are used to lock together the two edges of a metal strip so that a useful tubular section is produced.

This specification describes an improvement to the invention described in the earlier specification.

In its broadest form, the improved tubular section, formed by folding an elongate sheet of metal, comprises: a first fold along a first longitudinal edge of said elongate sheet where said first edge is folded through an angle greater than 900, and a further fold or folds that form a tubular section, said fold or one of said further folds comprising a corner formed along said tubular section that is shaped and positioned so that said first folded edge locates over said corner with the inner surface of said first folded edge and is contiguous with said corner so that said first o-20 folded edge locks with respect to said corner to form a tubular section.

It will be understood that the term folded edge or fold will include bends which result in the minimum possible radius between the folded surfaces as well as corners which comprise a substantial arcuate portion. It will be understood that a fold will also include any deformation of the elongate metal strip from its original planar S form.

S Preferably, the tubular section will be either rectangular or square in cross section and will have corners with substantial radii. Accordingly, the first fold will also be of S 30 a similar radius to the corner over which it locates. The corner will be formed so that the first fold, which extends through an angle greater than 900, can locate over the corner in a manner that will lock the first edge in relation to that corner. Obviously, the fold extending through an angle greater than 900 will result in a positive locking or location of the fold with respect to the corner.

The first fold may also comprise a sharply radiused fold with planar sections either side of the fold line. In this case, the corner would be shaped accordingly. With both a substantial radius or a sharp bend, the first fold will lock to the corner in either case as a result of it being formed through greater than 900. This means that there would need to be some outward deformation of the first folded edge before the joint could be released.

In both cases, as the first fold is folded through an angle greater than 900, the corner will also need to be folded through angle greater than 90'. A return fold will be required to form a planar side that is aligned with the outer edge of the corner. This will result in a recess in the sides of the tubular section in the form of a channel.

15 Preferably, the corners will comprise a first radius of greater than 90' followed by a second radius of opposite curvature to produce a channel below each of the corners.

This provides the necessary relief for the outer edge of the first fold to locate fully over the corner. Alternatively, the sides of the tubular section may be spaced inwardly from the corners to accommodate the first fold.

The other longitudinal edge of the metal sheet may extend from the corner engaged by the first fold so that it abuts against an opposite side or corner. This prevents the corner flexing away from the first fold which might otherwise occur if a compressive force is applied below the corner. This results in a double thickness of metal between the first fold and the opposite side or corner.

The method of forming the tubular section according to the present description can be similar to that described in the earlier Australian Patent No. 649335. This process uses a series of roll forming stages which gradually bring the first edge and corner together. The last operation pushes the first edge and corner together. The final fold does not result in permanent deformation, so there is obviously some remaining tension which holds the fold and corner together. Alternatively, the first fold may be formed last in a roll forming operation where it is formed around the fold or corner to which it locks. Some degree of over-folding may be required to ensure that the surfaces of the first fold and corner remain in contact to an acceptable extent.

In order to fully understand the invention, a preferred embodiment will now be described but it should be realised that the scope of the embodiment is not to be confined or restricted to the precise terms of this embodiment. This embodiment is illustrated in the accompanying drawing (Fig 1) which shows a cross-sectional view of a tubular section.

The illustration shows a rectangular tubular section 10 which is roll formed from a single elongate sheet of metal. It comprises a base wall 11 side walls 12 and 13 and overlapping portions 14 and 15 that form a top wall 16. Each corner 19 is formed by a curved portion and a second curved portion 20 is provided which has a direction of curvature opposite to that of the first curve 19. This results in the second curve forming a pair of elongate channels on each side wall 12 and 13.

9 Obviously, the length of the side walls 12 and 13 and base wall 11 and top wall 16 can be varied to produce tubular sections with different cross sectional sizes.

The first edge 22 is folded so that it overlaps a corner 19. The degree of fold of the first edge 22, from the top wall 16, is through an angle that is greater than 900. This prevents the first edge 22 from disengaging from the corner 19. The provision of the outermost edge of the first edge 22 locates within the channel formed by the second curves 20. In this manner, width between the side walls 12 and 13 is the same as the width of the base wall 11 and top wall 16 as seen in Fig 1.

The overlapping portion 14 which extends from the corner 19 has an end that abuts within the inside radius of the opposite corner 19. This end is formed by the second edge of the elongate sheet and is folded into a curved edge 24 which is folded through 1800. The external radius of curvature is the same as the internal radius of curvature of the corner 19.

The location of the edge 24 within the corner 19 prevents the side wall 12 from flexing towards the side wall 13. If this were to occur, there would be a possibility of the first edge 22 disengaging from the corner 19.

Although not required, the formation of each corner 19 is identical which results in a tubular section having a uniform cross section and a uniform external appearance.

Additional torsional rigidity of the tubular section will be obtained by inserting self tapping thread fasteners through the overlapping portions 14 and 15. This will occur where tubular sections are used for beams to support roofing sheets which are attached via self tapping screws. However, in other cases, fasteners can be added where additional torsional rigidity is required.

iii The method of roll forming the tubular section described above could be the same as that described in the earlier Australian Patent No. 649335. Alternatively, the first edge 22 could be formed last in the roll forming operation by it being formed around corner 19. A degree of over-rolling may be used to ensure contact of the inside surface of first edge 22 with the corner 19.

a a.

Claims

1. A tubular section, formed by folding an elongate sheet of metal, comprising: a first fold along a first longitudinal edge of said elongate sheet where said said first edge is folded through an angle greater than 900, and a further fold or folds that form a tubular section, said fold or one of said further folds comprising a comer formed along said tubular section that is shaped and positioned so that said first folded edge locates over said corner with the inner surface of said first folded edge and is contiguous with said corner so that said first folded edge locks with respect to said corner to form a tubular section.

2. A tubular section according to claim 1 wherein said first folded edge comprises a planar surface either side of said fold.

3. A tubular section according to claim 1 wherein said first folded edge is arcuate in cross-section where the angle of curvature of said arcuate section is greater than

4. A tubular section according to any one of the preceding claims wherein said tubular section is a right-angled parallelogram in cross-section.

5. A tubular section according to any one of claims 1 to 3 wherein said tubular S" section has a substantially rectangular cross-section.

S6. A tubular section according to either claim 4 or 5 wherein the second longitudinal edge of said sheet of metal opposite said first longitudinal edge locates against an opposite comer of sald tubular section to prevent movement of said corner away from said first fold. *e

7. A tubular section according to claim 3 wherein said tubular section has a e rectangular cross-section with a pair of sides having a shorter width than the other sides 30 and where each corner of said rectangular cross-section comprises a first radius of eee* greater than 900 that extend from the shorter width sides and a second radius of opposite curvature to the first said radii that produce a channel in the larger width sides spaced away from each said corner.

8. A tubular section according to claim 7 wherein said first folded edge comprises one of said first radii referred to in claim 7.

9. A tubular section according to claim 8 wherein a portion of said sheet of metal adjacent said second longitudinal edge is overlapped by a portion of metal adjacent said first longitudinal edge so that said second longitudinal edge locates into and abuts against a comer opposite said first fold.

10. A tubular section according to claim 9 wherein said second longitudinal edge is formed with a radius that locates into said adjacent comer.

11. A method of roll forming a tubular section from a continuous flat strip of metal according to any one of claims 6 to 10 comprising, in sequential steps: partly forming said first fold and fully forming folds in said second longitudinal edge; folding said sheet at two locations to form a base wall between two comers; folding said second longitudinal edge to form an upper comer; and folding said first longitudinal edge over said corner and completing said first fold.

12. A method according to claim 11 wherein said last step comprises over-folding S said first fold to ensure contact between the inner surface of said first fold and said corner.

13. A tubular section as hereinbefore described and with reference to and as illustrated in the accompanying drawings. Dated this 26 th day of September, 2003 STRATCO METAL PTY LTD S" by its Patent Attorneys MADDERNS cV_-_MW