Our Ref: STBOO5NZ
Patents Form No. 5
S ACT 1953
Complete After Provisional No. 597341
Filed 22 er 2011
COMPLETE SPECIFICATION
ROOFING OR CLADDING SHEET AND METHOD OF FORMING
We, Steel & Tube Holdings Limited, a New Zealand company of 15—17 Kings Cres,
Lower Hutt, New Zealand, 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:
ROOFING OR CLADDING SHEET AND METHOD OF FORMING
FIELD OF THE INVENTION
The invention s to roofing or cladding materials, in particular to ribbed roofing
or cladding materials.
BACKGROUND TO THE INVENTION
Metal roofing materials such as steel, copper and the like are widely used. Steel
roofing is often coated, e.g. by galvanising or with a zinc-aluminium alloy.
Various profiles are used for different applications. These s include simple
ated profiles and ribbed profiles, and are usually roll-formed. Figure 1 shows
an existing ribbed profile. This profile consists of trapezoidal ribs 1 ted by so-
called “pans” 2. The pans 2 generally define a plane and the ribs 1 extend from that
plane. The roofing material is attached to supporting purlins by g roofing
screws through the top of the ribs. The screws extend into the purlins that lie
beneath the plane defined by the pans.
Each rib includes two side portions, known as “webs" 3, and a top portion, known as
a “crest” 4. The profile has a “pitch" defined as the distance 6 between the same
point on adjacent ribs and a depth that is the distance from the highest point to the
plane of the pans.
Roofing sheets are generally installed side by side, with the partial side ribs 8 of
adjacent sheets overlapping.
Ribbed roofing sheets include standard or low rib , and high rib sheets. High
rib sheets are used, usually in industrial buildings, where the span between
supporting purlins is large. The higher rib shape provides greater strength and
rigidity, allowing these longer spans to be covered. High rib roofing sheets have a
depth greater than 35mm.
Ribbed sheets can be contrasted with standing seam roofing material, in which
vertical elements at the sides of adjoining panels are joined by a physical rolling or
seaming process after the al is positioned on the roof. Standing seam material
is usually attached by non-penetrating clips and does not provide structure over long
spans. In fact standing seam roofing is usually ted by d or similar
material over its entire coverage area.
Ribbed materials may also be used in cladding the walls of buildings. In this
specification the term "cladding" means wall cladding, not roof cladding. Roof
cladding is included in the term “roofing”.
Reference to any prior art in this specification does not constitute an admission that
such prior art forms part of the common general knowledge.
It is an object of the invention to provide an improved ribbed roofing or cladding
material, or at least to provide the public with a useful choice.
SUMMARY OF THE INVENTION
In a first aspect the invention provides a ribbed roofing or cladding sheet including: a
plurality of ribs extending along the roofing or cladding sheet; one or more pans
n the ribs; wherein: in cross-section, each rib includes two opposing webs,
each web having a first inclined section that extends upwards from a pan on an
angle towards a mid-point of the rib and a second inclined section that s
upwards from the top of the first inclined section on an angle towards the mid-point
of the rib, the first and second inclined sections er forming a lly concave
web e with a bend between the first and second inclined sections ing
along the length of the generally concave web surface; and each rib further includes
a crest extending between the tops of the two opposing webs, wherein the crest, in
cross section, es: two opposing outer sections, each outer section extending
inwards s the mid-point of the rib from the top of one of the ng webs
and then upwards; and an inner cap that extends between the two outer sections.
Preferably the first ed section extends at an obtuse angle to the pan from which
it extends. Preferably the first inclined section extends at an obtuse angle of
between 120 and 135 degrees to the pan from which it extends. Preferably the first
inclined section extends at an obtuse angle of between 120 and 132 degrees to the
pan from which it extends. Preferably the first inclined section extends at an obtuse
angle of around 127 degrees to the pan from which it s.
Preferably the second ed section extends at an obtuse angle to the first inclined
section. ably the second inclined section extends at an obtuse angle of
between 160 to 175 degrees to the first inclined section. Preferably the second
inclined section extends at an obtuse angle of between 162 to 174 degrees to the
first inclined section. ably the second ed section extends at an obtuse
angle of around 168 degrees to the first inclined section.
Preferably each rib further includes a crest extending between the tops of two
opposing webs, and wherein the crest, in cross section, includes: outer sections that
extend inwards from the tops of the opposing webs and then upwards; and an inner
cap that extends between the two outer sections.
Preferably the inner cap is convex. Preferably the inner cap has a radius of curvature
between 50 and 150 millimetres. Preferably the inner cap has a radius of curvature
between 50 and 100 millimetres. Preferably the inner cap has a radius of curvature
of around 75 millimetres.
Preferably the ribs include: a partial rib at each side of the roofing sheet configured,
when installed, to overlap with a partial rib of an adjacent roofing or cladding sheet;
and one or more full ribs between the l ribs.
Preferably the full ribs are symmetric.
Preferably the sheet is a high rib sheet wherein the ribs are high ribs.
Preferably the sheet is a roofing sheet.
In a second aspect the invention provides a method of g a ribbed roofing or
cladding sheet, including: providing a sheet material, and roll-forming the sheet
material to form: a plurality of ribs extending along the roofing or cladding sheet; and
one or more pans between the ribs; wherein in cross-section, each rib includes two
opposing webs, each web having a first inclined section that extends upwards from a
pan on an angle towards a mid-point of the rib and a second inclined section that
extends upwards from the top of the first inclined section on an angle towards the
mid-point of the rib, the first and second inclined sections together forming a
generally concave web surface with a bend between the first and second inclined
ns extending along the length of the generally e web surface; and
each rib further includes a crest extending between the tops of the two opposing
webs, wherein the crest, in cross section, includes: two opposing outer sections,
each outer section extending s towards the int of the rib from the top of
one of the opposing webs and then upwards; and an inner cap that extends n
the two outer sections.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example only, with reference to the
accompanying drawings, in which:
Figure 1 is a cross-section through a prior art roofing sheet;
Figure 2 is a perspective view of a roofing sheet according to one embodiment;
Figure 2A is an expanded view of part of the roofing sheet of Figure 2;
Figure 3 is a section through the roofing sheet of Figure 2;
Figure 3A is an expanded view of part of the roofing sheet of Figure 4;
Figure 3B is a similar view to Figure 3A illustrating certain dimensions of one
embodiment of roofing sheet;
Figure 4 shows how two adjacent roofing sheets overlap; and
Figure 5 shows a number of roofing sheets fixed to a supporting structure.
DETAILED DESCRIPTION
Figure 2 is a ctive view of a high rib roofing sheet 10 according to one
embodiment. Figure 2A is an expanded view showing the high rib profile of Figure 2.
The roofing sheet has a generally trapezoidal high rib profile. However, as
sed below the rib profile is more complex and stronger than in prior high rib
roofing.
The roofing sheet 10 may be roll-formed from any suitable material, ing steel
with any suitable coating, such as galvanised steel or zinc-aluminium alloy coated
steel. The sheet may also have an organic coating, such as an c paint coating
and/or may be coloured by any suitable s.
The high rib roofing sheet 10 is shown in cross-section in Figure 3. The roofing
sheet 10 includes a number of high ribs 11 separated by pans 12.
The pans may include low ridges or swages 13, but these form no part of the
invention.
The shape of the high ribs 11 is shown in detail in Figure 3A. Each side or web 15 of
the rib 11 is formed in two sections. A lower inclined section 16 extends upwards
from the pan 12 at an obtuse angle 9. The lower inclined section 16 is angled in
towards a mid-point of the high rib, indicated by the dashed line in Figure 3A. An
upper inclined section 17 extends upwards from the top of the lower inclined section
16 at an obtuse angle a. The upper inclined n 17 is also angled towards a
mid-point of the high rib, indicated by the dashed line in Figure 3A.
The lower and upper inclined sections 16, 17, together define a generally concave
web due to the angle a between them. The bend 18 between these two sections
extends along the length of the rib, as can be seen in Figure 2.
A crest 19 extends between the upper points of the two opposing webs 15. The
crest 19 includes outer sections 20 that are each formed in two parts. These outer
sections e a first portion 21 extending inwards from the top of the web 15 and a
second portion 22 extending upwards from the first portion 21. A cap 24 extends
between the two second portions 22.
The cap 24 is preferably slightly convex. The cap may have a radius of curvature
between 50 and 150 mm preferably between radius of curvature n 50 and
150 mm, ideally around 75 mm.
In some embodiments the second portions 22 and cap 24 may be formed in a single
continuous curve.
The angle 6 may be between 120 and 135 degrees, ably between 120 and 132
degrees, ideally around 127 degrees.
The angle a may be between 160 to 175 degrees, ably n 162 to 174
degrees, ideally around 168 degrees.
The high rib may have an overall height H (Figure BB) of between 35 and 55 mm,
preferably between 41 and 51 mm, ideally around 46mm. The bend 18 may be
positioned above the pan by a distance H1 that is between 16 and 27 mm, ideally
around 22 mm.
The height H2 of the outer crest section 20 may be around 2mm to 10mm. ideally
around 5 to 6 mm. The three bends 20a, 20b, 200 e 3a) in the outer crest
n 20, as well as the bend 12a where the high rib meets the pan, may have
bend radii between 1 and 5 mm, preferably around 2-3mm.
The overall width W of the high rib may be between 80 and 100mm, preferably
between 85 and 96 mm, ideally around 91mm.
The width W1 of the crest’s inner cap 24 may be between 15 and 35 mm, preferably
between 20 and 30mm, ideally around 25mm.
The width W2 of the outer crest section, measured perpendicular to the upper
ed section 17, may be around 2 to 10mm, ideally around 4mm.
The pitch of the roofing profile is not critical, but may be around 320mm in some
embodiments.
Figure 4 shows how the sides of two adjacent roofing sheets 10 overlap. As shown
in Figure 3 a partial high rib is formed at each side of the roofing sheet 10. The
partial high rib 30 includes an outer element 31 that is formed at an angle to fit inside
the opposite partial high rib 32 of an adjacent sheet. A roofing screw can be driven
h both partial high ribs 30, 32 thereby fixing the two roofing sheets 10
together.
Figure 5 shows a number of roofing sheets 10 fixed to an underlying structure. The
roofing sheets 10 are laid over a number of purlins 35, with the high ribs running
transverse to the s of the purlins 35. A roof underlay and/or support netting
and/or safety mesh may be laid between the roofing sheets and the purlins, as
required for the application or building code. Roofing fasteners 36 (usually screws,
although other methods of fixing may be used) are led through the tops of the
high ribs and into the s 35. Washers 37 are positioned between the heads of
the fasteners and the roofing sheet to limit ingress of water.
The ant’s profile provides improved strength over traditional high rib profiles.
The shape of the e web 15 contributes to this increased strength. The
effective length of the web is decreased by dividing it in two. Buckling resistance
decreases in a manner proportional to the square of increasing web length. The
1O bend 18, which extends along the length of the concave web 15, provides increased
buckling resistance over a straight web, by effectively dividing the web in two. This
significantly raises the critical buckling load of the panel, helping to prevent local
panel buckling, which is often the onset of instability and ultimate collapse of a
roofing section.
The outer ns 20 of the crest connect to the steeper upper inclined section 17 of
the web 15. The bend 20a is more acute that would be the case if the web 15 were
simply a flat panel with the same average angle as the two inclined sections 16, 17.
This contributes to increased bending stiffness in this region. The series of bends
20a, 20b, 20c at this junction also contributes to increased bending ess.
The neutral axis of the rib is relatively close to the plane in which the pans lie. This
means that the peak stresses will be towards the top of the profile. The profile shape
helps to resist these stresses in the upper regions of the profile.
On the other hand the lower sections of the rib profile are well supported by the
s and close to the neutral axis of the rib. The stresses on these regions are
therefore lower and there is not the same need for local stiffness.
These improvements provide a stronger panel than in conventional high rib roofing.
The Applicant’s roofing sheet is capable of ng large distances between
purlins, up to around 4000 mm. Furthermore, the increased strength makes the
profile less ive to local imperfections in the material or introduced in
manufacturing.
The roofing sheet may be manufactured in any desired length or cover width.
While described mainly in the context of a high rib material, the Applicant's profile
may also be applied in other ribbed material, including standard or low rib roofing
materials. Furthermore, in some applications the Applicant’s material may be used
as a cladding rather than a roofing material.
While the t invention has been illustrated by the description of the
embodiments thereof, and while the embodiments have been described in detail, it is
not the intention of the Applicant to restrict or in any way limit the scope of the
appended claims to such detail. onal advantages and modifications will readily
appear to those skilled in the art. Therefore, the invention in its r aspects is
not limited to the specific details, representative apparatus and methods, and
illustrative examples shown and described. Accordingly, departures may be made
from such details without departure from the spirit or scope of the ant’s general
ive concept.