Technical Field

This invention relates to metal strip, to methods of and apparatus for manufacturing such strip, and to elongate shaped sections produced from the strip.

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 elongate metal strip having a plurality of substantially rectilinearly extending corrugations, the troughs and/or crests of the corrugations being deformed at predetermined points spaced along their length, towards or beyond the median plane of the corrugations.

Preferably the pitch of the corrugations and the pitch of the transverse deformations are substantially equal.

Conveniently the strip is formed by passing plain strip through the nip of a pair of rolls both of which have corresponding circumferential ribs and grooves, and one of which has similarly shaped axial grooves.

The invention further resides in an elongate shaped section comprising a length of strip as specified above bent along its length to provide first and second regions having their planes disposed at an angle less than 180° to one another.

Desirably said elongate shaped section is an elongate channel section comprising a length of strip as specified above bent along at least two parallel rectilinear lines extending lengthwise of the strip.

The invention still further resides in a method of manufacturing elongate strip comprising passing cold, substantially undeformed metal strip through the nip of a pair of rolls having corresponding circumferential grooves and ribs, one of said rolls also having axially extending grooves of similar shape to its circumferential grooves.

Brief Description of the Drawings

In the accompanying drawings:-

Figure 1 is a simplified diagrammatic perspective view of elongate metal strip in accordance with one example of the present invention,

Figure 2 is a sectional view along the crest of a corrugation of the strip of Figure 1 ,

Figure 3 is a sectional view along the trough of a corrugation of the strip of Figure 1 ,

Figure 4 illustrates diagrammatical ly a pair of rolls for use in the manufacture of strip in accordance with a second example 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 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 in accordance with the third example of the invention produced using the rolls of Figure 6,

Figure 10 is an enlarged sectional view of the line 10-10 in Figure 9,

Figure 1 1 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.

Details of the Preferred Embodiments

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 1 1 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 1 1 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 rolling. 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

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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 if desired.

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. Omm. 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. Omm. 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 circumferential ly 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 roll 22. 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 101 mm 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 23.

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.