This invention relates to a method for manufacturing elongate metal
strip strip according to the preamble of claims 1 and 2 (see for example EP-A-0
Background of Invention
It is known to enhance the resistance to bending of metal strip along
its length by forming the strip with longitudinally extending ribs. It is also
known to alter the plain surface finish of metal strip by knurling to produce
a regular array of indentations in the surface of the strip for example to roughen
or otherwise provide the strip surface with a 'key' to improve its frictional performance.
It is an object of the present invention to provide a strip which has improved
resistance to bending in more than simply a longitudinal plane and which also has
a 'textured' surface, such properties being particularly advantageous when the
strip is formed into elongate shaped section. An elongate shaped section can, in
its simplest form, be strip bent along a longitudinal line to produce two planar
regions disposed at an angle to one another. Particularly, but not exclusively,
the invention is concerned with elongate channel sections for use inter alia as
stud and/or track for partitioning constructions.
Summary of the Invention
In accordance with the first aspect of the present invention there
is provided a method for manufacturing elongate metal strip according to claim
The invention still further resides in an alternative method of manufacturing
elongate metal strip as defined in claim 2.
Preferably the pitch of the corrugations and the pitch of the transverse
deformations are substantially equal.
Brief Description of the Drawings
In the accompanying drawings:-
Details of the Preferred Embodiments
- Figure 1 is a simplified diagrammatic perspective view of elongate metal strip
manufactured in accordance with one example of the method of the present invention,
- Figure 2 is a sectional view along the crest of a corrugation of the strip of
- Figure 3 is a sectional view along the trough of a corrugation of the strip
of Figure 1,
- Figure 4 illustrates diagrammatically a pair of rolls for use in the manufacture
of strip in accordance with a second example of the method of the present invention,
- Figure 5 is a developed diagrammatic view illustrating the form on the surface
of the rolls of Figure 4,
- Figure 6 is a front view of a pair of rolls used in the production of a strip
in accordance with a third example of the method of the present invention,
- Figure 7 is an end view of the rolls of Figure 6,
- Figure 8 is an enlarged sectional view of part of the rolls of Figure 6,
- Figure 9 is a diagrammatic plan view of strip manufactured in accordance with
the third example of the method of the invention produced using the rolls of Figure
- Figure 10 is an enlarged sectional view of the line 10-10 in Figure 9,
- Figure 11 is a view in the direction of arrow X in Figure 9 and
- Figure 12 is a diagrammatic perspective view of the strip of Figure 9 inverted
to reveal its underside.
Referring first to Figures 1, 2 and 3, which are simplistic representations,
plane, elongate, mild steel strip is corrugated to produce rectilinear corrugations
extending longitudinally of the strip, the corrugations being of part-circular
transverse cross-section. The exact shaping of the corrugations is not of major
significance to the invention, and the corrugations can be such that the troughs
12 and crests 13 of the corrugated strip 11 have the same radius of curvature and
the same width. Alternatively, as shown in Figure 5, the crests may have a larger
radius of curvature and width than the radius of curvature and width of the troughs.
At equally spaced points along each of the crests 13 the crest is
deformed to produce a part-cylindrical depression 14 extending downwardly towards,
or in some applications beyond, the median plane of the corrugated strip 11. The
part-cylindrical depressions 14 have their axes extending transverse to the length
of the corrugations, preferably at right angles to the corrugation length, and
the depressions 14 are aligned transversely of the strip. The troughs 12 are also
subject to deformation at a spacing along their length equal to the spacing of
the depressions 14 in the crests. However, the troughs are deformed upwardly towards,
or beyond, the median plane of the strip 11 to form projections 15 the projections
15 being disposed along the troughs mid-way between the positioning of adjacent
depressions 14 in the adjacent crests. The projections 15 are of part-cylindrical
form and are the mirror image of the depressions 14. Thus the projections 15 have
their axes extending transverse to the length of the corrugations and are aligned
transversely of the strip. In the embodiment shown in Figure 1 the height of the
projections 15 is equal to the depth of the depressions 14. The provision of corrugations
in the strip, with deformations in the corrugations is believed to enhance the
rigidity of the strip material, more particularly when the strip material has subsequently
been cold roll formed to an angle or channel section. It follows from this, that
when rigidity rather than load supporting strength is the primary requirement of
a cold rolled section, then using strip as described above increases the rigidity,
and thus permits the use of thinner, and therefore cheaper, material to achieve
the same rigidity. It is contemplated that such a strip material. will find particular
use in the manufacture of cold rolled channel sections, both plane C sections,
and lipped-C sections for use as stud and/or track in the partitioning industry.
It will be recognised that the spacing of the depressions and projections
along the length of the corrugations can be varied to achieve different physical
properties. Similarly, the depth and curvature of the depressions and projections
can also be changed to alter the physical properties. In some embodiments it may
be desirable to provide depressions 14 deeper, or less deep, than the height of
the projections 15. Moreover, it is contemplated that in some applications either
the depressions 14, or the projections 15 may be omitted.
In one embodiment of the strip illustrated in Figure 1 the spacing
of depressions 14 along the crests 13, and the equivalent spacing of projections
15 along troughs 12 is equal to the spacing of adjacent crests 13 across the width
of the strip.
The strip 11 may be manufactured by a pressing operation in which
plane strip is fed stepwise between upper and lower corrugating tools.
The upper and lower tools are mirror images of one another and are
shaped to produce the pattern of corrugations extending longitudinally of the
strip. After each stroke of the press the strip is fed by an amount equal to the
tool length so that the next press stroke continues the previously formed corrugations
along the length of the strip. After a predetermined length of strip has been formed
with longitudinally extending corrugations the corrugated strip is fed through
the press again, but after rotating the upper and lower press tools through 90°.
Moreover, the stroke and pressure applied by the press is controlled so that the
corrugation forms on the press tools, which of course now are extending transversely
at right angles to the preformed corrugations, produce the depressions 14 and projections
15 in the preformed crests 13 and troughs 12 respectively.
In an alternative method of manufacture the corrugations 12, 13 are
produced in the elongate strip by a first pair of matching rolls between which
the strip passes. Each of the rolls of the pair has ribs and grooves, corresponding
to the troughs and crests, extending circumferentially around the rolls. The strip
is then passed through the nip of a second pair of rolls, the rolls of the second
pair having ribs and grooves extending axially of the rolls. The second set of
rolls produces the depressions 14 and projections 15 in the corrugations formed
by the first pair of rolls, and the depth and height of the depressions 14 and
projections 15 are controlled by the shaping of the ribs on the rolls of the second
pair and the loading applied by the rolls to the corrugated strip.
It will be recognised that the rolls of each pair will be geared together
so as to ensure that the forms on the mating pairs of rolls remain in registration
during rolling of the strip material.
Where the troughs and crests have the same curvature troughs become
crests simply by inverting the strip but the understanding of crests and troughs
and the roll shapes which produce them is more critical where crests and troughs
have different radii of curvature in cross section.
Figure 4 illustrates a pair of rolls 16, 17 where the ribs and grooves
for producing corrugations in the strip extend helically on the surface of the
rolls. The roll 17 is a mirror image of the roll 16 and thus mates therewith when
rolling strip material. As mentioned above the rolls 16, 17 will be geared together
to ensure registration during roiling. The helix angle of the ribs and grooves
on the rolls 16, 17 is 45°, and thus when plane elongate strip is fed between the
rolls the rolls produce corrugations extending at 45° to the length of the strip.
In order to produce the depressions 14 and projections 15 in the 45°
corrugations the corrugated strip can be inverted before being passed through
the nip of the rolls 16, 17 again. During the second pass the spacing of the rolls
is increased to determine the depth of the depressions 14 and height of the projections
15, it being recognised that by inverting the corrugated strip the corrugations
of the strip will then lie at 90° to the form on the rolls 16, 17 so that the rolls
16, 17 will, in the second pass, produce the projections 15 and depressions 14.
As an alternative however a second pair of rolls similar to the rolls
16, 17, but with their formations extending in an opposite helix, can be used
to produce the projections 15 and depressions 14 upon corrugated strip issuing
from the rolls 16, 17.
As a further alternative a press operation of the kind described above
can produce 45° corrugations.
Corrugations at angles other than 45° to the strip length can be formed
It will be recognised that if desired the corrugations can extend
transverse to the length of the strip with the axes of the projections 15 and
depressions 14 extending longitudinally of the strip.
Figure 5 illustrates the developed form of the ribs and depressions
on the rolls 16, 17, and it is to be understood that this could be the developed
form of any of the rolls or press tools. The overall amplitude of the corrugations
is A and the pitch of the corrugations is B. The radius of curvature
of the crests is C while the radius of curvature of the troughs is
D. In one example of the invention the mild steel is galvanised mild steel
strip and its thickness is 0.3-2.0mm. A = 0.35mm; B = 4.643mm;
C = 2.8mm and D = 1.4mm.
In a further embodiment the strip again is galvanised mild steel strip
and in this instance its thickness is 0.3-2.0mm. A = 0.75mm; B =
6.5mm; C=4.75mm and D = 2.53mm.
As mentioned above there can be embodiments where C = D.
In a further alternative a single pair of rolls as illustrated in
Figures 6 to 7 is utilized, one roll 21 having circumferential ribs and grooves
which correspond to a mirror image set of grooves and ribs on the other roll 22
so that strip material is formed with longitudinal corrugations as it passes through
the nip of the rolls. However, the roll 22 is also formed with axial grooves intersecting
the circumferential ribs, the axial grooves having the pitch and transverse curvature
of the circumferential grooves of the roll such that a developed side elevation
of a circumferential rib of the roll would be substantially identical to an axial
sectional view of the periphery of the either roll. The strip material (Figures
9 to 12) produced by the rolls has longitudinal corrugations the troughs of which
have regular, part cylindrical projections corresponding to the axial grooves in
said one roll. Thus the effect is that only troughs (or the crests) of the corrugations
are deformed in this example, but in practice of course the deformations take place
simultaneously and it is incorrect to assume that corrugations are formed first
and are subsequently deformed. In essence the roll with circumferential and axial
grooves has a series of circumferential rows of teeth which deform the strip into
the circumferential grooves of the other roll to produce longitudinal corrugations
and transverse deformations simultaneously, the teeth having the same cross-section
both axially and circumferentially of the roll 22. In a modification both rolls
can have axial grooves. The rolls can be geared if desired so as to retain registration
between depressions and projections longitudinally of the strip.
It can be seen in Figure 8 that the circumferential grooves in the
rolls 21,22 are V-shaped while the ribs defined between them are rounded, having
part cylindrical crests. The axial grooves in the roll 22 are similarly V-shaped,
the crests of the ribs defined between the axial grooves being rounded by machining
during formation of the axial grooves such that their radius of curvature circumferentially
of the roll 22 is substantially equal to the radius of curvature axially of the
The circumferentially extending grooves and ribs are conveniently produced by a
turning operation whereas the axially extending grooves and corresponding rounding
of the intervening crests is effected by spark erosion techniques. In some applications
the grooves, both circumferential and axial were radiused in section to mirror
the intervening crests. However it was found that in many cases the strip being
deformed did not reach the bottom of the grooves and thus their bottom shaping
was largely irrelevant, hence the choice of V-shaped grooves as these are easier
and more economic to machine.
As is apparent from Figures 9 to 12 which illustrate a preferred
embodiment the shaping of the strip produced by the rolls 21,22 is complex. In
one example the circumferential ribs of the rolls 21, 22 were of 101mm diameter
(50.5mm radius of curvature), the V-shaped grooves (both circumferential and axial
in the roll 22) were of 89° included angle and the height of each rib crest above
the bottom of the adjacent grooves was 1.50mm. The pitch of the ribs/grooves measured
axially of the rolls (and also circumferentially in the case of the roll 22) was
4.00mm and the crests of the ribs were of 1.25mm radius of curvature (both axially
and circumferentially in the case of the roll 22). Such rolls produced the deformation
illustrated in Figures 9 to 12 in galvanised mild steel strip of 1.5mm thickness,
the rolls spacing, rotational speed, and the roll pressure being set by trial and
error to accommodate variables such as strip hardness, to produce well defined
shaping of the strip, having longitudinal corrugations 23 the troughs of which
have transverse deformations 24 similar to corrugations and merging into the corrugations
It will be recognised that in all of the above examples the longitudinal
corrugations are continuous across the width of the strip in the sense that there
is no undeformed strip separating adjacent corrugations as would be the case with,
for example, discrete parallel ribs. In the example of Figures 2 and 3 the transverse
deformations are spaced apart but in the preferred example of Figures 9 to 12 it
can be seen that the transverse deformations flow into one another lengthwise of
the strip in a manner similar to that in which the lengthwise corrugations flow
into one another across the strip. In all cases the whole of the strip is deformed
from its planar configuration in at least one direction.
Mild steel strip deformed as described above, is then cold rolled
to produce the necessary shaped section. The cold rolling does not significantly
alter the corrugated form of the strip although of course high points of the strip
and at sharp, for example right angle, bends in the strip, the shaping may become
flattened. The strip is not restricted to use in standard track for partitioning
and may find use in other box, channel and like sections or angle for example for
building purposes and/or reinforcement of UPVC window frames.
The shaping of the strip material with depressions and/or projections
is of particular benefit where a self tapping screw or the like is screwed through
the strip as the provision of corrugations with depressions and/or projections
assists location of the screw during initial insertion and significantly increases
the "pull-out" resistance of the engagement of the screw in the strip material.