[0001] This invention relates to metal sheeting.
[0002] Metal profiled sheets are frequently used as roof panels and for other building cladding
purposes. It is well known to provide a metal sheet which is pre-formed with integral
ribbing so that it may readily be interlocked at adjoining edges with a similar sheet
and which may be fastened to a support without the fastening means being exposed to
the environment or being on the visible side of the sheet. These products may include
separate fixing clips and involve on site roll forming to close the interlocking seams.
All such products are usually referred to as "raised seam cladding". Many examples
of such profiled sheets are known and they are frequently roll-formed from an aluminium
alloy as well as other metallic materials. Usually each sheet has a first upstanding
hook formation along one edge and a second upstanding formation along an opposite
edge of the sheet with a hook receiving part and a valley in the plane of the sheet
through which fasteners can be passed. When the sheets are interlocked the first formation
of one sheet hooks on to the hook receiving part of an adjoining sheet and covers
the valley and its fasteners. From their outer surfaces the sheets then present a
generally flat appearance having spaced apart upstanding ribs with no fasteners visible.
These ribs are usually referred to as "raised seam".
[0003] In general, when used as roof panels, the sheets need to be fully supported on a
pre-prepared flat surface and are not strong enough to span any worthwhile distance
between supporting purlins. It is however clearly desirable to provide sheets that
can be supported at intervals, as between spaced apart purlins, and it is further
desirable that the sheet should be wider so that the spacing between the raised seams
is increased. In addition the sheets should be strong enough to support snow loads,
wind loads both in pressure and suction and so that, for example, operatives can walk
on them.
[0004] We have found that there are conflicting factors between, on the one hand, increasing
the strength and stiffness of the sheet and, on the other hand, ensuring adequate
locking against suction forces under high wind conditions.
[0005] It is therefore an object of the present invention to provide an improved interlocking
metal sheet which has good strength characteristics and improved interlocking formations.
[0006] According to the present invention there is provided a metal sheet having a first
upstanding hood formation along one edge and a second, upstanding hook receiving formation
and a valley along an opposite edge the arrangement being such that the sheet can
be fastened directly to a support without the interposition of separate clips and
so that the first formation of one sheet can hook over the second formation of an
adjoining sheet and cover its valley characterised by latching means acting between
the formations so that after interlocking the sheets said one sheet can be rotated
about the hook receiving formation of the other sheet through at least 25° before
the formations can be disengaged.
[0007] The rotation preferably occurs without significant distortion of the material of
either sheet.
[0008] Preferably upon said relative rotation the latching action ceases to function, and
further rotation through at least 10° is required before the formations can be disengaged.
[0009] The above and other aspects of the present invention will now be described with reference
to the accompanying drawing in which:-
Fig. 1 is a transverse section through a metal sheet,
Fig. 2 is a view similar to Fig. 1 showing part of two sheets distorted by suction
forces, and
Fig. 3 is a similar section, to a larger scale, of an interconnection between two
metal sheets.
[0010] Referring to Fig. 1 a roll-formed aluminium alloy sheet 1 has along one side edge
2 a first, hook, formation indicated generally at 3 which is upstanding from the outer
surface 4 of the sheet. At its other side edge 5 the sheet has a second, hook receiving,
formation indicated generally at 6 and a valley 7. The formations 3 and 6 are separated
by a web 8 which is coplanar with the floor 9 of the valley 7. A number of stiffening
ribs 8
b may be formed in the sheet.
[0011] The hook formation 3 comprises a sloping part 10, a wall 11 approximately at right
angles to the web 8, a flat 12 and downwardly and inwardly projecting parts 13 and
14 constituting a hook having a curved part 15. As shown the outer end of the part
14 is curved to be approximately parallel with the wall 11 and to allow run-out on
the edge of the sheet material on roll forming.
[0012] The hook receiving formation comprises a sloping part 16 the upper end 16
b of which is approximately at right angles to the web 8 and is then folded at a part
17 which, together with the wall 16
b defines a hook receiving formation as will be described later. The lower end of the
folded part 17 is formed as a hollow bead 18 and the rolled material of the sheet
is then formed as a platform 19 with a recess 20, a side wall 21 approximately at
right angles to the web 8 leading to the valley 7, the floor 9 of which has an upwardly
turned part 22 and a lip 23 at the same angle to the web 8 as the sloping part 10.
The lip 23 allows run out of the edge of the sheet material on roll forming.
[0013] Fig. 3 shows how the hook formation 3 engages over the hook receiving part 6 of an
adjoining sheet. In Fig. 3 the same reference numerals have been used except that
for the "adjoining" sheet suffixes "a" have been added to each reference numeral.
[0014] It will be assumed that the sheet 1
a is already mounted on suitably spaced-apart purlins (not shown) and secured thereto
through the valley floor 9
a. The fixings used can be conventional and may be arranged to accommodate longitudinal
expansion of the sheet 1
a. The sheet 1 is then held with its web 8 approximately vertically and its hook formation
3 engaged around the bead 18
a. The sheet 1 is then pivoted to the position shown in cross-hatched lines in Fig.
3 and secured to the purlins. In this position the sloping part 10 engages with the
lip 23
a and the wall 11, the flat 12, the part 13 and the curved part 15 respectively embrace
the upper part of the side wall 21
a, the platform 19
a, the part 17
a and the curved part 15
a. Sealing material (not shown) may be disposed in the recess 20
a. The dimensions of the formations 3 and 6 are such that the upper part of the formation
2 is a "latching fit" over the upper part of the formation 6.
[0015] As mentioned above we have found that conflicting requirements exist in increasing
the strength of the sheets without at the same time increasing the risk that suction
forces under high wind conditions will tear off one of the sheets. When the sheets
are mounted on spaced-apart purlins this reduces the number of edge fastenings that
can be used.
[0016] Although innately higher strength aluminium alloys than are usually employed can
be used this does not, of itself, increase the strength of the sheets sufficiently.
Increasing the height of the "raised seams" constituted by the formations 3 and 6
does significantly increase the strength of the sheets and enables them to be unsupported
across suitably spaced purlins. However such a change significantly alters the pattern
of distortion of the "other" sheet 1
a raised by suction forces on the web 8
a resulting from wind flow across the outer surfaces 4 and 4
a of the sheets. This change tends to make easier the lateral separation of the formations.
[0017] As shown in Fig. 2, wind flow across the outer surfaces 4 and 4
a can cause high suction forces to be applied to the webs of the sheets and lift these
webs so that their formations 3 and 6 distort and move laterally to disengage the
formations 3 and 6.
[0018] With the present invention the close, "latching fit", engagement between the upper
parts of the formations ensures that the wall 11 constitutes latching means for the
hook by its close fit against the upper part of the side wall 21
a. As shown in Fig. 3 the edge of the sheet 1 can rotate about the bead 18
a through successive positions indicated at A, B, C and D before reaching the postion
E shown as a solid line. During the movement A to approximately C the wall 11 rides
up the side wall 21
a and retains its latching action. At the approximate position C the corner between
the sloping part 10 and the wall 11 rides over the corner between the side wall 21
a and the platform 19
a. As a result of the "latching fit" referred to above this transition occurs suddenly.
In positions D and E the hook still remains engaged since the outer end of the part
14 remains in engagement with a part of the bead 18
a which extends parallel with the upper end of the sloping part 16. Once a sheet has
been distorted to the extent represented in position E the strains to which it is
subjected are extremely complex and not readily predictable. However it would be expected
that position E represents the point at which the edge of the sheet 1 will move laterally
and the formations will disengage.
[0019] In position C the chain line 25 represents the angle between the edge of the web
8 and the line of the web 8
a. The angle defined is G.
[0020] In position E the chain line 24 represents the angle between the edge of the web
8 and the line of the web 8
a. The angle defined is F. The precise angle F reached for position E is determined
by the detailed dimensions of the upper parts of the formations 3 and 6, the width
of the web 8 and the thickness of the sheet. We have found the following criteria
achieve good results:-
[0021] Height of the formations 3 and 6 a minimum of 10% (preferably 12.5%) of the total
sheet width. This is to achieve a basic stiffness to the whole profile so as to allow
it to support the imposed loads.
[0022] Length of the vertical wall 11 between 20% to 30% (preferably 24%) of the height
of the rib formation 3 and 6.
[0023] Centre of radius of tip of the hook receiving formation in the range 10 to 20% (preferably
14%) below the top of the rib formation 6.
[0024] Distance of centre of radius of tip of hook receiving formation to vertical wall
11 when assembled in the range 3.75% to 6.25% (preferably 5%) of the total formation
width.
[0025] Sheet thickness lies in the range of 0.15% to 0.25% of total formation width.
[0026] The angle G is in the range 25° to 30° (preferably 28°).
[0027] The angle F is in the range 10° to 35° greater than angle G (preferably 30°).
[0028] By using a high strength aluminium alloy such as 3105 or 3004 in standard roofing
sheet thicknesses and tempers and by increasing the height of the raised seams the
basic strength of sheets 500 mm wide can be increased sufficiently to enable the sheets
to span purlins with spacings in excess of 2.0 m and still readily support snow and
wind loads both in pressure and suction and carry the weight of an operative between
the purlins. By utilising the latching feature of the present invention the disadvantages
of increasing the height of the seams can be obviated and increased protection given
against suction induced by wind force.
[0029] It will be understood that with the interlocking formations described above then
should the sheet 1 be rotated through an angle significantly greater than the angle
F (position E) the sheets will again interlock as the part 14 extends upwardly behind
the folded part 17. Depending upon the dimensions of these parts this re-engagement
is likely to occur with an angle F of about 75°.
1. A metal sheet (1) having a first upstanding hook formation (3) along one edge (2)
and a second, upstanding hook receiving formation (6) and a valley (7) along an opposite
edge (5) the arrangement being such that the sheet can be fastened directly to a support
without the interposition of separate clips and so that the first formation of one
sheet can hook over the second formation of an adjoining sheet and cover its valley
characterised by latching means (11, 12, 13, 14, 15 and 16b, 17, 19, 21) acting between the formations so that after interlocking the sheets
said one sheet can be rotated about the hook receiving formation of the other sheet
through at least 25° before the formations can be disengaged.
2. A metal sheet according to claim 1 in which said rotatin occurs without significant
distortion of the material of either sheet.
3. A metal sheet according to claim 1 in which upon said relative rotation the latching
action ceases to function, and further rotation through at least 10° is required before
the formations can be disengaged.
4. A metal sheet according to any one of claims 1 to 3 in which the first upstanding
hook formation (3) comprises a sloping part (10) extending upwardly away from the
sheet (1), a wall (11) at the outer end of the sloping part being approximately at
right angles to the sheet, a flat (12) extending away from the wall and generally
downwardly and inwardly projecting parts (13, 14) constituting a hook having a lower
curved part (15).
5. A metal sheet according to claim 4 in which the outer end of said parts (14) is
curved to be approximately parallel with the wall so as to allow run-out on the edge
of the sheet material when the latter is roll formed.
6. A metal sheet according to claim 4 in which when the sheets are interlocked the
base of the sloping part (10) of the sheet (1) abuts the valley (7) of the second
formation of the adjoining sheet.
7. A metal sheet according to any one of the preceding claims in which the second
upstanding hook receiving formation (6) comprises a sloping part (16) the upper end
(16b) of which is approximately at right angles to the sheet and is then folded (17) so
that the folded part and the upper end define a hook.
8. A metal sheet according to claim 7 in which, above the hook the sheet is formed
with a platform (19) having a side wall (21) approximately at right angles to the
sheet which side wall extends downwardly to form said valley.
9. A sheet according to claim 8 in which the floor (9a) of the valley is in the same
plane as the sheet.
10. A sheet according to claim 9 in which the floor has an upwardly tuned part (22a)
and a lip (23a) at the same angle to the sheet as the sloping part.