IL44178A - Manufacture of tubular metal members of polygonal cross-section by rolling - Google Patents

Abstract

1433431 Making polygonal tubing; bending AFRICAN GATE & FENCE WORKS Ltd 8 Feb 1974 [14 Feb 1973] 05916/74 Headings B3A and B3E A method of making tubular members of polygonal cross-section from strip material comprises bending the strip by rolling to form the desired cross-sectional shape so that its edges abut along a corner of the member and welding the edges together at the corner, the longitudinal edge portions of the strip being the first to be bent and welding being effected only when the final cross-sectional shape has been formed. The strip passes through a series of roller pairs, the first pair 23 being alignment rollers, the second pair 2 bending each strip edge to form a fraction of a completed corner of the tubular member, and the remaining pairs 4, 7, 8, 11, 12 bend the strip into rectangular or other polygonal crosssection. The rollers comprise hard steel and sections (30), Fig. 10 (not shown), and mild steel spacing sections (31) which may be added or removed to vary the cross-sectional dimensions of the piping being formed. The strip edges are welded together at a high-frequency welding station 24 and a cutting blade 25 trims the weld. Lengths of the formed tube may be subsequently cut off. [GB1433431A]

Description

Manufacture of metal membere of polygonal crose-eection by rolling African Gate and Pence Works Limited THIS INVENTION relates to a method and apparatus. for manufacturing tubular members, more particularly of the type having a polygonal cross-section.

Tubular members of polygonal cross- section are usually extruded. Alternatively, the desired cross-section is shaped from a tube or pipe of circular cross-section.

It has been proposed to manufacture such tubes or pipes from a strip of sheet metal by rolling the strip to the desired shape and welding the side edges together. The edges of the strip are abutted and welded in the middle of a side of the polygonal cross-section. This method of manufacture has the disadvantages in that the ridge of a seam weld is visibly on one of the external sides of the tubular member and the abutting of the two edges of the strip is inhibited by ^the "waving" or "bias" of the strip caused by rolling-Good abutment of the side edges is necessary not only to provide a pipe with an even side but also to ensure a strong weld particularly if/ a high frequency welding process is used.

It is therefore the object of this invention to provide a relatively simple method of manufacturing tubular members of polygonal cross-section from strip material in which an effective weld is provided and in which the external weld ridge is largely eliminated and to provide apparatus to effect the manufacture of such tubular members.

According to this invention there is provided a method of manufacturing tubular members of polygonal cross-section from strip material, said method comprising the steps of rolling strip to form the desired cross-sectional shape so that the edges thereof abut along a corner of the member and welding the edges together at the corner* From British Patent Specifications Noe. 997089 and 1251175 there are known processes for the production of tubes. However in said process the edges of the strip of metal are bevelled whereas in the method according to the present invention the bevelling is avoided in that the edges of the strip are rolled to form partly bent corners, which when abutted will form a substantially completed corner suitable as is described herein for welding and in particular for high frequency welding.

Further features of the invention provide for the edges to be bent by rolling to form a fraction of a completed corner of the tubular member before the strip is rolled into the desired shape, for the rolling operation to be cold rolling and for the Still further features of the invention provide for the fraction of a corner to be a half of the completed corner and for the method to include the step of severing at least part of the external protruding weld ridge from the welded seam of" the formed tubular member .

The invention also provides a tubular member of polygonal cross-section, said member being welded along one of the corners thereof.

The invention further provides apparatus for effecting the method of manufacturing tubular members defined above, the apparatus comprising a support for a coil of metal strip material, a series of roller p¾irs arranged in line and adapted, in turn, to bend the longitudinal edges of a length of strip material to form a fraction of a completed corner and to form the strip into a tubular member having the desired cross-sectional dimensions and shape such that the bent edges abut each other on a corner and a welding station located adjacent the final pair of rollers adapted to weld said edges together. -k- Further features of this aspect of the invention provide for each of said rollers to comprise a plurality of abutting annular spacing sections releasably attached together to form the desired width and cross-sectional shape of the roller, and for the apparatus to include a cutting blade adapted to sever at least part of the externally protruding weld ridge from the tubular member.

A preferred embodiment of the invention will be described below by way of example, reference being made to the accompanying drawings in which: Fig. 1 to 7 are diagrammatic representations of the steps of forming a tube or pipe of square cross-section and of the various roller pairs used in this formation; Fig. 8 is an oblique projection of a tube prior to cleaning, Fig. is a diagrammatic representation of a tube forming apparatus, and Fig. 10 is a radial cross-sectional view of a roller included in the apparatus.

In this embodiment of the invention a strip of sheet metal is to be formed into a tube of square cross-section. However, it is to be understood that tubes of any other polygonal cross-section may be formed by the same method and furthermore that the polygonal cross-section may opti.onally be irregular.

It is to be appreciated that in practice a corner of a polygonal tubular member is not a sharp edge but is rounded and hence reference is made to "part" or a "fraction" of a corner in the specification to mean "part", or a "fraction" of the rounded edge when viewed in cross-section.

The steps of the tube forming process and the rollers used therein are shown diagrammatically in Figures 1 to 7. A strip 1 of metal has its side edges bent in the same direction in a cold rolling operation utilizing a complementary roller pair 2 vertically disposed as shown in Figure 2. Each of the bent edges forms a small lip 3 corresponding in cross-section to half a corner of a tube such that when the two side edges are subsequently brought together a complete rounded corner will be formed by the two abutting lips. -6- /...

A roller pair then bends the outer sections 5 of the metal strip . upwardly so that the angle between each outer section and the connecting web 6 is approximately 135° as shown in Figure 3· The width of each bent outer section is approximately one quarter of the width of the strip.

■ A further roller pair 7 (Figure ) bends the outer sections such that the angle between each section and the web 6 is approximately 100°. The bent strip is passed through another pair of rollers 8 (Figure 5) one of which 9 has an inverted "Vee" shape portion in diametric cross- section . The angle between the inclined surfaces of this roller is approximately 120° and the other roller 10 of this pair 8 has an acute "Vee" shape and the apex thereof is located centrally with respect to the roller 9· The strip is thus bent centrally and subsequent pairs of complementary and horizontally disposed rollers 11 and 12 (Figures 6 and 7) force the edges of the strip together from the outside thereof such that the strip forms a tubular member of square cross- section.

The side edges are then welded by a high frequency welding process indicated at 13 in Fig. pressure being applied transversely to the weld axis simultaneously with the welding operation by the final pair of rollers 12.

The weld ridge formed above the join between the edges is removed by a cutting blade and when the tube is thus "cleaned" externally it is difficult to distinguish the welded corner from a bent corner.

In cases where relatively thick strip metal is used it is preferable to include two or more pairs of rollers similar to the pair 8 in order to effect the central bend in the strip metal in a professional manner.

It will be appreciated that as the strip is initially lipped, the side edges can be correctly aligned before welding and therefore abut evenly when pressed together. As a consequence, a strong, even weld will result. The forming of the lips provides rigidity to the strip and consequently a pipe may be formed from ;tbinner strip metal than is possible at present.

Figure 8 shows a section of the pipe formed by the method outlined above and in Figure the pipe forming apparatus is illustrated diagrammatically.

Basically, the apparatus comprises a support 20 for a coil.21 of strip sheet metal and a series of pairs of · rollers arranged in line and spaced apart. ■ The roller pairs are rotatably mounted in conventional manner with respect to cold rolling technique in supports 22 therefor and the coil is rotatably mounted in its support. The first roller pair 23 are alignment rollers and the subsequent complementary pairs 2, h , 7, 8, 11 and 12 correspond to the rollers outlined above with reference to Figure.1. A further roller 27 acts as a guide for the strip between the coil and the alignment rollers.

A high frequency welding station 2 is located adjacent the final pair of forming rollers 12 and is adapted to weld the abutting edges of the formed strip 1 as described above. A cutting blade 25 supported in a mounting 26 is located near the final pair of forming rollers and the blade projects downwardly and rearwardly to the level of the welded seam of the formed tube.

In operation, strip metal is drawn off the coil by the rollers and passed through the series of rollers to be shaped as described above. The abutting edges are welded together and the cutting blade trims the weld ridge such that the formed tube appears approximately uniform when viewed externally. Lengths of the formed tube may be subsequently cut off.

With reference to Figure 10 a convenient roller construction for use in the above apparatus is now described. This roller corresponds to one of the rollers of the pair but it is to be understood that the construction outlined may be used with any one of the roller pairs included in the tube forming apparatus where appropriate.

The roller comprises hard steel end sections 30 and four mild steel annular spacing sections 31 located between the end sections, all the above components being located on a shaft 32. This construction allows the dimensions of the roller to be relatively easily varied according to the desired cross-sectional dimensions of the piping to be formed. Spacing sections may be removed or added to accomplish the variation.

Furthermore, the construction reduces the cost of the .apparatus since separate rollers for different pipe dimensions need not be provided.

The invention is not confined in scope to the manufacture of square tubing and suitable rollers -10- •f may be provided to form a pipe having any desired polygonal cross-sectio .

In all cases, however, the invention provides a relatively simple method and apparatus for producing a well formed and strong tubular member.

Claims (12)

metal

1. A method of manufacturing/ tubular members of from strip material polygonal cross-section /said method comprising the steps of rolling the strip to form the desired cross-sectional shape so that the edges thereof abut along a corner of the member and welding the edges together at the corner.

2. A method as claimed in claim 1 in which the edges of the strip are bent by rolling to form a fraction of a completed corner of the tubular member, before the strip is rolled into the desired shape. 44178/2 - 13 - *

3. A method as claimed in either of claims 1 or 2 in vhich at least part of the external protruding veld ridge is severed from the welded seam of the formed tubular member.

4. A method as claimed in any of the preceding claims in which the edges of the strip are bent by rolling to form half of a completed corner of the tubular member before the strip is rolled into the desired shape ·

5. · A method as claimed in any of the preceding claims in which the rolling operation is a cold rolling operation.

6. A method as claimed in any of the preceding claims in which the welding operation is a high frequency welding operation.

7. A tubular member of polygonal cross-section, made by the method according to any of claims 1 to 6, said member,, being welded along one of the corners thereof.

8. · Apparatus for effecting the method of manufacturing tubular members according to any of claims 1 to 6, the apparatus comprising a support for a coil of metal strip material, a series of roller pairs arranged in line and adapted, in turn, to bend the longitudinal edges of a length of strip material to form a fraction of a completed corner and to form the strip into a tubular member having the desired cross-sectional dimensions and shape such that the bent edges abut each other on a corner, and a welding station located adjacent the final pair of rollers adapted to weld said edges together.

9. Apparatus as claimed in claim 8 in which said rollers comprise a plurality of abutting annular sections releasabl attached together to form the desired width and cross-sectional shape of the rollers.

10. Apparatus as claimed in either of claims 8 or 9 in which a cutting blade is included which is adapted to sever at least part of the externally protruding weld ridge from the tubular member.

11. A method of manufacturing tubular members of polygonal cross-section substantially as herein described with reference to. the accompanying drawings. -Ik-

12. Apparatus for ©iffecting . the method of manufacturing tubular members as claimed in claim 11 with reference to the accompanying drawings. For the. Applican s Dr.Yitzhak Hess