GB2346105A - Metal strip - Google Patents

Abstract

A method of manufacturing metal strip comprising passing longitudinally corrugated strip through the nip of a pair of rolls one of which is in the form of a plain roll and the other of which has axially extending angularly spaced ribs the peaks of which engage across the crests of the corrugations on the face of the strip remote from the first roll, to indent the corrugations at spaced points along the length of the corrugations. The invention further resides in apparatus for manufacturing metal strip comprising a first roll pair defining a nip within which the strip is longitudinally corrugated, and a second roll pair one roll of which is plain and the other of which is axially ribbed, the second roll pair defining a nip within which corrugations on one face of the strip are indented at spaced points along the length of the corrugations.

Description

METALSTRIP This invention relates to a method of manufacturing metal strip, apparatus for manufacturing such strip, metal strip manufactured in accordance with the method, and elongate shaped section or profile produced from the strip.

We have previously proposed a method of manufacturing metal strip suitable for subsequent cold roll forming into an elongate shaped section or profile, the method including stretch forming plain strip to produce therein a plurality of longitudinally extending corrugations and deforming the crests of the corrugations at one face of the strip, at spaced points along the lengths of the corrugations, to provide therein indentations.

In accordance with the present invention there is provided a method of manufacturing metal strip comprising passing longitudinally corrugated strip through the nip of a pair of rolls one of which is in the form of a plain roll and the other of which has axially extending angularly spaced ribs the peaks of which engage across the crests of the corrugations on the face of the strip remote from the first roll, to indent the corrugations at spaced points along the length of the corrugations.

Also in accordance with the present invention there is provided a method of manufacturing metal strip comprising roll forming plain strip in the nip of a first pair of coacting rolls, both rolls having circumferentially extending ribs spaced apart by corresponding circumferentially extending grooves, to stretch the strip across its width to produce a plurality of longitudinally extending continuous corrugations in the strip and, subsequently, passing the corrugated strip through the nip of a second pair of rolls one of which is in the form of a plain roll and the other of which has axially extending angularly spaced ribs the peaks of which engage across the crests of the corrugations on the face of the strip remote from the first roll, to indent the corrugations at spaced points along the length of the corrugations.

The invention further resides in an apparatus for performing the method, the apparatus comprising a first roll pair defining a nip within which the strip is longitudinally corrugated, and a second roll pair one roll of which is plain and the other of which is axially ribbed, defining a nip within which corrugations on one face of the strip are indented at spaced points along the length of the corrugations.

The invention still further relates to metal strip produced by the apparatus and/or in accordance with the method, and elongate shaped section or profile produced from the strip.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic perspective view of a cold roll forming mill ; Figure 2 is a side elevation view of a second pair of rolls of the mill of Figure 1; Figure 3 is an enlarged view of part of Figure 2; Figure 4 is a section view on the line 4-4 of Figure 2; Figure 5 is a side elevation view of a first pair of rolls of the mill of Figure 1, Figure 6 is a section view on the line 6-6 in Figure 5 showing material in the nip of the rolls, Figure 7 is a diagrammatic perspective view of strip material issuing, in use, from the nip of the rolls of Figure 5, and, Figure 8 is a diagrammatic representation of material issuing from the nip of the rolls of Figure 2.

Referring to the drawings, the cold roll forming mill of Figure 1 inclues a de-reeling station 11 supporting a free running reel 12 of plane sheet metal strip 13, conveniently galvanised mild steel strip. The strip 13 is drawn from the reel 12 by the action of the driven rolls of a first roll stand 14 which longitudinally corrugates the strip (as will be described in more detail hereinafter) and which supplies the corrugated strip 13a (Figure 4) to the rolls of a second roll stand 15. After passing through the nip of the rolls of the second stand 15 the strip passes through a plurality of further roll stands 16 which convert the strip into an elongate section (often referred to as a profile) for example a channel-section. The finished section issuing from the last roll pair of the stands 16 passes through a guillotine station 17 which cuts the formed section into appropriate lengths for convenient handling and transport.

As is apparent from Figure 5 the upper roll 18 of the roll pair of the first roll stand 14 is of larger diameter than the lower roll 19 of the pair. It is to be recognised however that this difference in diameter is not of any particular significance, and it will be possible to perform the method of the invention with a roll 18 of the same diameter as, or smaller diameter than, the roll 19.

As is clear from Figure 6, both rolls 18,19 have substantially the same surface profile, in that both rolls have a plurality of equally spaced circumferentially extending ribs 18a, 19a spaced apart along the axis of the rolls by intervening grooves 18b, 19b of V-shaped cross-section. The ribs 18a, 19a have rounded tops and the ribs 18a of the roll 18 align with the grooves 19b of the roll 19 while correspondingly the ribs 19a of the roll 19 align with the grooves 18b of the roll 18. In effect therefore the surface profiles of the rolls 18,19 at the nip of the rolls are the same, but with the pitch of the ribs spaced in the direction of the axes of the rolls by the distance of one half pitch.

As plane strip material 13 passes through the nip of the rolls 18,19 the strip is gripped, across its width, by each rib 18a and the underlying groove 19b, and by each rib 19a and the overlying groove 18b, and each rib 18a, 19a stretches the material of the strip into its opposite groove 19b, 18b so that the plane flat strip is converted into a strip having continuous longitudinally extending corrugations.

It will be recognised that the spacing of the roll 18 from the roll 19 (the gap in the nip of the rolls) is selected in relation to the thickness of the strip material, and the corrugation height which is required. Generally the gap in the nip will be equal to the starting thickness of the strip material 13.

The corrugations are formed by stretching the strip material across its width as is evident from the fact that the overall width of the strip 13a issuing from the roll stand 14 is virtually identical to the width of the plane strip 13 entering the nip of the rolls of the stand 14. The increase in surface area measured across the width of the strip must therefore have been acquired by stretching the strip. It is conceivable that the strip stretches equally over the whole of its width, but it is perhaps more likely that the majority of the stretch occurs in longitudinal bands which correspond to the side walls and/or the crests of the corrugations. The exact mechanism of stretch is not clear without further detailed investigation, but it is clear that the process is one in which the material stretches. It is noted also that there is no loss of length resulting from the corrugation process. Thus the length of material issuing from the nip of the rolls 18,19 is substantially equal to the length of material entering the nip of the rolls 18,19. In practice a very slight increase in length, of the order of one or two percent, has been measured with some mild steel strip materials.

As is apparent from Figure 7 the corrugated material 13a can be thought of as having corrugations projecting upwardly from its top face and intervening corrugations projecting downwardly from its lower face. The corrugated material passes from the rolls 18,19 into the nip of the rolls 21, 22 of the second roll stand 15.

As with the rolls of the first roll stand, the rolls 21, 22 are shown to be of different diameter although this is not essential. The roll 22 is a plane cylindrical roll and the roll 21 has a plurality of axially extending, equi angularly spaced ribs 21 a spaced apart by axially extending V-shaped grooves 21 b. The lower roll 22 therefore presents a plain cylindrical surface 22a to the upper roll 21, the upper roll 21 presenting the axially extending ribs 21 a and intervening grooves 21 b towards the lower roll 22.

The cross-sectional shape of the ribs and grooves of the roll 21 is substantially identical to the cross-sectional shape of the ribs and grooves of the rolls 18,19. Furthermore, the pitch of the ribs around the periphery of the roll 21 is equal to the pitch of the ribs across the width of the rolls 18,19.

It will be recognised that the corrugated strip 13a entering the nip of the rolls 21,22 has an overall thickness (measured between a plane touching the crests of the corrugations protruding from the upper face of the strip, and a parallel plane touching the crests of the corrugations protruding from the lower face of the strip) which is significantly larger than the thickness of the plain strip 13. The gap at the nip of the rolls 21,22 is selected such that with the downwardly protruding corrugations supported on the cylindrical surface of the roll 22, the rounded crests of the corrugations projecting upwardly from the upper surface of the strip are engaged by the rounded tops of the ribs 21a of the roll 21 in such a manner that the ribs indent the upwardly projecting corrugations at equidistantly spaced points along their length. In other words, at equi-distantly spaced points along their length, each corrugation is locally crushed back towards, or even past, the median plane of the corrugated strip.

Figure 8 is not intended to be an accurate visual representation of the form which is produced in the strip issuing from the rolls 21,22. However, it is sufficient to show that the strip has longitudinal corrugations which project downwardly from the lower face of the strip, and which are undeformed, and also has intervening corrugations extending upwardly from the top face of the strip which are indented at equally spaced points along their length, the indentations along the length of each corrugation being aligned widthwise of the strip with the indentations in the parallel corrugations.

Thus the indentations can be considered to be arranged in rows along the length of their corrugations, and in rows transverse to their corrugations, the indentations being spaced apart in both longitudinal and lateral rows by the same distance such that the indentations have the same pitch both longitudinally and laterally of the strip.

It is to be recognised however that if desired the spacing, circumferentially, of the ribs 21 a of the roll 21 could be greater, or less than, the spacing of the ribs 18a, 19a of the rolls 18,19 thereby providing a distribution of indentations where the longitudinal pitch is not equal to the lateral pitch. Furthermore, the gap at the nip of the rolls 21,22 can be varied to vary the depth of the indentations in the crests of the corrugations. Thus the corrugations could be lightly deformed to produce shallow depressions, or could be deeply deformed so that the depressions extend close to, or even below, the median plane of the corrugated strip.

The passage of the corrugated strip 13a through the nip of the rolls 18,19 does not significantly effect either the width, or the length of the strip although it does of course change the physical performance of the strip by virtue of adding locally, to the cold working and thus work hardening, of the strip which occurs during the corrugation of the strip in the nip of the rolls 18, 19.

The rolls 18,19 will be supported on respective shafts one of which is driven, and the other of which is linked to the driven shaft through a gearing arrangement which ensures that the rolls 18,19 rotate the same peripheral speed. A similar arrangement is provided at the rolls 21,22 and if desired the drive to the driven roll of the first roll pair and the drive to the driven roll of the second roll pair could be a common drive arrangement powered from a common prime mover. As an alternative however the rolls 18,19 could have a drive mechanism independent of the drive mechanism of the rolls 21, 22.

In one embodiment of the method and apparatus described above the spacing between the ribs 18a is 4mm as is the spacing between ribs 19a and between ribs 21a. It follows therefor that the spacing between grooves 18b ; 19d ; 21 b; is also 4mm. The height of the ribs, measured radially of the rolls from the apices of the respective grooves to the highest points of the rounded tops of the ribs is 1.5mm and the rounded tops of the ribs are part-circular in section having a radius of 1.25mm.

Conveniently the rolls 18 and 21 are of 143mm diameter and the rolls 19 and 22 are of 102mm diameter. Using these dimensions it is possible to work strip of 0.5 to 1.2 mm thickness. To work material in the range 1.2 to 1.5 mm thickness it would be advantageous to increase the rib and groove pitch to 5mm. To work material in the range 1.5 to 2.0 mm thickness it would be advantageous to increase the rib and groove pitch to 6.5mm. and similarly to work material in the range 2.0 to 2.5 mm thickness it would be advantageous to increase the rib and groove pitch to 8mm.

It will be possible to increase the overall thickness of the strip to about 3.25 times the plain strip thickness although less increase in thickness may be desirable in some applications. Moreover although there is generally little increase in length of the strip as a result of the rolls 18,19 and 21,22 there can in some circumstances be up to 10% increase in length dependent upon the material chosen, its initial thickness, and the depth of forming..

It is believed that the strip issuing from the rolls 21,22 will exhibit at least a 5% increase in yield strength, bending stiffness, bending strength, and compressive strength, measured along or across the strip, by comparison with the plain strip, but much greater increases can be expected in some materials particularly with deeper corrugations and indentations.

The material of the strip is not restricted to mild steel, aluminium and copper strip being examples of other materials which can be strengthened by the above technique.

Downstream of the rolls 21,22 the roll stations 16 and the guillotine station 17 are, in essence, conventional and will be well understood by those skilled in the cold rolling arts. The nature of the section produced by the roll stands 16 is not of significance to the invention, but conveniently may be a rectangular channel-section for use as stud and track members for use in plasterboard partitioning systems. The surface profiling of the material provided by corrugating, and then indenting is ideal for receiving self-drilling/self-tapping screws, the depression providing a location to resist slippage of the screw when first presented to the material, and the work hardening of the material, together with the increase in over all thickness of the material enhancing the resistance of the screw to"pulling-out"of the material when under load.

It is envisaged that the plain cylindrical lower roll 22 will be rigid, not flexing in use. However, a hard resilient material could be used provided the resilience of the material is sufficient to apply a sufficiently large reaction force to the strip to cause the formation of the indentations therein.

In order to guide the strip through the second pair of rolls 21,22, if such guidance becomes necessary, guide means may be provided, conveniently immediately upstream of the second pair of rolls. The guide means may take any suitable form, for example it may take the form of a channel of width substantially equal to the width of the sheet after the corrugations have been formed therein. Such a channel may be in a fixed component through which the strip slides, or may be formed in a roll rotatable about an axis parallel to the strip width, the strip being located in the channel by a second, parallel roll engaging in the channel (such an arrangement usually being referred to as"gated rolls") Alternatively, edge engaging rollers may be used to positively guide the strip.

The first and second roll pairs may be accommodated in a stand-alone, separately driven, device in advance of the remainder of the cold rolling mill if desired.

Certain of the above disclosure is contained also in our British Patent Application 9828363.3 a copy of which is available in the file of this application.

Claims (7)

1. CLAIMS :1. A method of manufacturing metal strip comprising passing longitudinally corrugated strip through the nip of a pair of rolls one of which is in the form of a plain roll and the other of which has axially extending angularly spaced ribs the peaks of which engage across the crests of the corrugations on the face of the strip remote from the first roll, to indent the corrugations at spaced points along the length of the corrugations.
2. 2. A method as claimed in claim 1 wherein said strip is londitudinally corrugated prior to entry into the nip of said rolls by cold roll forming plain strip in the nip of a first pair of coacting rolls, both rolls having circumferentially extending ribs spaced apart by corresponding circumferentially extending grooves, to stretch the strip across its width to produce a plurality of longitudinally extending continuous corrugations in the strip.
3. 3. A method of manufacturing metal strip substantially as hereinbefore described with reference to the accompanying drawings.
4. 4. Apparatus for manufacturing metal strip comprising a first roll pair defining a nip within which the strip is longitudinally corrugated, and a second roll pair one roll of which is plain and the other of which is axially ribbed, the second roll pair defining a nip within which corrugations on one face of the strip are indented at spaced points along the length of the corrugations.
5. 5. Apparatus for manufacturing metal strip substantially as hereinbefore described with reference to the accompanying drawings.
6. 6. Metal strip produced by the apparatus of claim 4 or claim 5 and/or in accordance with the method claimed in any one of claims 1 to 3.
7. 7. Elongate shaped section or profile produced from the strip as claimed in claim 6.