Cold roll reduction and forming method
United States Patent [191 Attwood Apr. 15, 1975 1 1 COLD ROLL REDUCTION AND FORMING METHOD [75] Inventor: James W. Attwood, Wayne, Mich.  
 [73] Assignee: Unistrut Corporation, Wayne, Mich.  
 [22] Filed: Aug. 22, 1973 [21] Appl. No.: 390,619  
 [52] US. Cl. 72/177; 72/181; 72/366; 72/234 [51] Int. Cl B2lb 1/12; B2ld 5/08 [58] Field of Search 72/177, 181, 366; 29/155 R [56] References Cited UNITED STATES PATENTS 1,736,331 ll/1929 Townsend 72/181 2,251,967 8/1941 Yoder 1 72/181 X 3,630,059 12/1971 Henkel 72/177 3,638,465 2/1972 Lickliter et a1. 72/181 3,689,970 9/1972 Falkner 29/155 R FOREIGN PATENTS OR APPLICATIONS 1,069,168 11/1959 Germany 72/414 40-1109 l/l965 Japan 72/177 Primary Examiner-Milton S. Mehr Attorney, Agent, or Firm-Haulce, Gifford, Patalidis &amp; Dumont 57 ABSTRACT A method of producing structural members such as angles, channels and tubes from hardened flat strip stock in which the thickness of the initial stock is first reduced, preferably through a cold rolling mill, while simultaneously raising longitudinal ridges from one face and impressing aligned longitudinal depressions into the opposite face, each aligned ridge and depression corresponding in position to a corner of the tobe-formed member. Each ridge consists of a convex radius or a substantially sharp peak intermediate concave radii merging into the remaining flat portions of the stock. Each depression consists of a small concave radius or a substantially sharp groove intermediate convex radii merging into the opposite flat portions of the stock. The stock thus initially reduced and formed is then bent, preferably in a cold roll forming mill, to the desired shape of the member without the risk of cracking, and facilitating the formation of small radius bends at desired corners. 1f the initially formed ridges are sharp, the exterior surface of the member will have substantially sharp corners, which reduces the eccentric loading otherwise encountered with cold rolled members while retaining the strength increased properties of the member effected by the cold roll reduction.  
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  Fig-9A COLD ROLL REDUCTION AND FORMING METHOD BACKGROUND OF THE INVENTION It is well known that cold roll reducing of strip metal stock prior to continuous forming into the crosssectional shape of the desired end product produces a great increase in the yield point of the material. However, in the forming of members such as angles, channels and tubing, it is necessary to bend the corners to certain minimum radii to avoid cracking or otherwise overly stressing the cold reduced material at such corners, and further it is generally not possible to use prehardened material since the bending will either cause cracks or so weaken the material that it stands great risk of failure in use. Also, it is known that structural members having sharp corners are superior for some usage because the sharp angles are subjected to less eccentric loads in use. Normally, members with sharp angles are hot roll formed, thereby losing the advantages obtained through a cold reducing process. Thus, elongated structural members heretofore manufactured have been compromises between ideals, with structural weaknesses compensated for by using thicker stock material, and forming problems overcome by using softer more malleable materials.  
 SUMMARY OF THE PRESENT INVENTION The present continuous method of producing elongated structural members consists in providing hardened material which is cold reduced with a simultaneous formation of longitudinal ridges and depressions on opposite faces of the stock corresponding to the corners of the to-be-formed member, thereby retaining the structural integrity of the strip of material, and then bending the member to shape to form the corners. The method makes possible the forming of small radius bends in hardened material, and the use of hard material having lower elongation factors increases the utility of such members in structural framing and other high stress uses by providing greatly increased yield points.  
 BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention, reference may be had to the accompanying drawings illustrating preferred embodiments of the invention and the formation of various structural members, in which like reference characters refer to like parts throughout the several views and in which:  
  FIG. 1 is a diagrammatic elevational side view of a preferred continuous production line embodying the method of the present invention used in forming elongated members from flat metal stock;  
  FIGS. 2, 2A, and 2B are lateral cross-sectional views illustrating stages in a preferred cold roll reduction of the stock;  
  FIGS. 3, 3A, and 3B are transverse cross-sectional views of a preferred longitudinal angle member in several stages of cold roll forming;  
  FIGS. 4, 4A, and 4B are transverse cross-sectional views of a preferred longitudinal channel member in several stages of cold roll forming;  
  FIGS. 5, 5A, and 5B are transverse cross-sectional views of a preferred longitudinal tube member in several stages of cold roll forming;  
  FIGS. 6 and 7 are transverse cross-sectional views of preferred angle members illustrating the comparison of eccentric loading on corners formed with and without the present preliminary cold reduction method;  
  FIGS. 8 and 8A are cross-sectional views of another preferred angle member illustrating formation thereof following reduction and forming respectively; and  
  FIGS. 9 and 9A are cross-sectional views of yet another preferred angle member illustrating formation thereof following reduction and forming respectively.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates diagrammatically a preferred production line for continuous cold roll reduction and forming of structural members such as angles, channels and tubes from a roll 10 of strip metal stock 12 having an initial predetermined mill guage, although it will be apparent that other production processes may with like advantage make use of the methods hereinafter described.  
  In the preferred method, the strip of stock 12 is first fed to a cold roll reducing mill 16 which has sets of reduction rolls 16a, 16b and (more or less in number as required), which operate to cold reduce the thickness of the stock 12 as indicated, in exaggerated fashion, successively in FIGS. 2, 2A and 2B respectively. The rolls 16a produce an initial stock reduction. The rolls 16b produce a further reduction while simultaneously raising from one face of the stock a continuous longitudinal ridge 12a and impressing into the opposite face a corresponding depression 12b. Finally, the rolls 16c additionally reduce the thickness of the stock 12 while further raising the ridge 12a on the particular roll construction, so that the stock takes the form illustrated in FIGS., 3, 8 or 9. In FIG. 3, the ridge 12a is raised to a substantially sharp peak disposed intermediate concave radii l2c which slope into one flat surface of the stock 12, and the depression 12b consists of a small concave radius intermediate convex radii 12d which slope into the opposite flat surface of the stock 12. The initial thickness of the stock is in the present example preferably reduced by approximately onethird, with the stock material being forged into the ridge and transversely outward to a greater width than the width of the initial stock strip.  
  The cold roll reduced stock 12 is then fed to a continuous cold roll forming station 20 having forming rolls 20a, 20b, 20c, 20d, 20s and 20f (more or less in number as required), which progressively bend the stock 12 along the line of &#39;the ridge 12a and depression 12b into a longitudinal angle member shape as progressively indicated in a FIGS. 3A and 33. It will be apparent that on forming of the stock 12 through successive stages to its ultimate shape, as shown in FIGS. 38, the ridge 12a becomes a small radius or a substantially sharp right angle external corner, and the depression 12b becomes a substantially sharp or very small radius right angle internal corner, while still retaining the structural integrity of the cold reduced material and suppressing any tendency to crack along the corner line, which otherwise makes cold forming of hardened material very difficult, if not impossible.  
  The stock 12 may eventually be passed through the rolls 22a and 22b of a straightening station 22 as indicated in FIG. 1, and thence to a cut-off station 24 where the elongated member is cut into desired lengths.  
  FIG. 4 illustrates a more complex cross-sectional shape taken by a strip of stock 26 after the cold roll reduction step in which a plurality of parallel ridges 26a are raised and corresponding depressions 26b are impressed, being respectively substantially similar to the ridge 12a and depression 12b of FIG. 3. The stock 26 is subsequently formed by progressive stages in the cold roll forming mill 20 through the stage of FIG. 4A to the in-turned edge channel shape member shown in FIG. 4B, in which each of the ridges 26a becomes a small radius or substantially sharp right angle external corner and each of the depressions 26b becomes a small radius or substantially sharp right angle internal corner.  
  FIG. 5 illustrates the cross-sectional shape of another strip of stock 28 in which the cold roll reduction step has raised a plurality of ridges 28a and impressed a plurality of corresponding depressions 28b, being respectively substantially similar to the ridges 12a, 26a and depressions 12b, 26b of FIGS. 3 and 4 respectively. The side edges of the stock 28 have also been forged up in the same reduction step to form half-ridges 280 as indicated.  
  The stock 28 is then progressively formed in the cold roll forming mill 20 through the stage of FIG. 5A to a tubular shape, bringing the edge half-ridges 28c together. The stock 28 passes then through a continuous welding station 30 (FIG. 1) where the side edge surfaces of the stock 28 are welded together, forming a corner welded tube member as illustrated in FIG. 5B, in which each of the ridges 28a becomes a small radius or substantially sharp right angle external corner and each of the depressions 28b becomes a small radius or substantially sharp right angle internal corner, the halfridges 28c becoming a fourth small radius or substantially sharp right angle external corner (after any weld bead has been scarfed).  
  FIG. 8 illustrates the cross-sectional shape of another preferred strip of stock 36 in which the cold roll reduction step has raised a ridge 36a having a convex radius intermediate concave radii 36b which slope into one surface of the stock 36, and has impressed a depression 36c having a concave radius intermediate convex radii 36d which slope into the opposite surface of the stock 36.  
  Upon bending along the line of the ridge 36a and depression 360, an angle member is formed as in FIG. 8A in which the ridge 36a becomes a radiused external corner, the depression 360 becomes a radiused internal corner, and the radii 36b and 36d flatten out to become side planar surfaces.  
  It is noted that the ridge and depression radii 36a and 36c may be chosen to effect almost any desired external and internal radiused corners of the member. The radii 36b and 36d are chosen relative to the thickness and hardness of the stock 36 to flatten out as shown in the forming step without any tendency to crack or be come weakened. Generally, the radii 36b and 36d will be approximately four to ten times the thickness (1) of the stock 36. This is, in fact, the major criteria in the present method to form the various structural members hereinbefore described.  
  FIG. 9 illustrates the cross-sectional shape of a further preferred strip of stock 38 in which the cold roll reduction step has raised a convex radius ridge 38a intermediate concave radii 38b and a substantially sharp depression groove 38c intermediate convex radii 3811. Upon bending, the angle illustrated in FIG. 9A is formed in which the groove 38c becomes a definite sharp internal corner.  
  It will be apparent to anyone skilled in the art of roll forming that unlimited types of geometric crosssectional shapes may be formed by the present process. For example, triangular or pentagonal cross-sectional shapes may be formed and in such cases the ridges would be respectively higher or lower than the ridges for formation of right angle corners, and the depressions would be of respectively lesser and greater radii than the depressions for formation of right angle corners, all depending on the amount of material needed to be forged up for subsequent conversion in the roll forming step to the proper small radius or sharp corners. Also, Z-shaped or other complex shaped members (not shown) may be fabricated with the present method by raising ridges and impressing depressions as described heretofore on the necessary surfaces and along the lines of the to-be-formed corners, each ridge becoming an external corner and each depression be coming an internal corner. Shapes may also be made having both sharp and rounded corners by raising ridges of different degrees of sharpness in the cold reduction step.  
 FIGS. 6 and 7 are intended to illustrate the comparison between an angle member 32 formed by prior roll forming methods and an angle member 34 formed according to that kind of the present method which produces sharp corners. With loading in the plane of a side of the angle member 32 and directed toward the corner, an eccentricity is experienced due to the fact that the corner has a radius whose center is substantially at the point E which is normally at a considerable distance from the plane of the material, whereas the angle member 34 with its sharper corner has its eccentric point close to, if not even directly at, the corner, so that a considerably less eccentric load will be experienced. Thus, the angle member 34 has a greater particular load carrying ability than the angle member 32.  
  In summary, I have described and illustrated a method of forming elongated structural members from flat strip stock which combines the advantages obtained from cold roll reduction processes with the advantageous use of hardened material as well as the advantages obtained from forming members with sharp corners which have greater load bearing capabilities. Structural members so produced have increased tensile strength, increasing the general usability of stressed structures. Further, the use of low alloy steel, for example, may produce structures with the present method which are better than structures using high alloy steels in former methods, because they can now be hardened before roll forming.  
  Although I have described and shown only a few modifications of my invention, it will be apparent to those skilled in the art to which the invention pertains that various changes and modifications may be made therein without departing from the spirit of the invention or the scope of the appended claims.  
 I claim:  
  1. A method of preparing flat stock for subsequent forming to a cross-sectional shape having a bend along a prelocated corner line, comprising:  
 a. providing flat stock of known hardness which normally will not bend to such shape without risk of cracking, either during bending or in subsequent use; and  
 b. cold reducing said stock to diminished thickness while simultaneously raising from one face thereof a ridge and impressing a depression in the opposite side of said stock, said ridge and said depression ex tending on a line corresponding in location to the corner line of the to-be-formed shape flat surfaces of said stock extending from each side of said ridge.  
  2. The method of claim 1 wherein said ridge is raised to a substantially sharp edge.  
  3. The method of claim 1 wherein said ridge is raised intermediate concave radii sloping into the surface plane of said stock.  
  4. The method of claim 3 wherein said radii are in the order of four to ten times the thickness of said stock.  
  5. The method of claim 1 wherein said depression is impressed with a larger radius than said ridge.  
  6. The method of claim 1 wherein said depression is impressed to a substantially sharp groove.  
  7. The method of claim 1 wherein said depression is impressed intermediate convex radii sloping into the surface plane of said stock.  
  8. The method of claim 7 wherein said radii are in the order of four to ten times the thickness of said stock.  
  9. The method of claim 1 wherein said cold reducing step comprises passing said stock between reducing rolls formed to produce said ridge.  
  10. The method of claim 1 wherein said stock comprises a continuous elongated strip and said cold reducing step comprises passing said stock between reducing rolls formed to produce a continuous longitudinal ridge intermediate the longitudinal side edges of said strip.  
  11. The method of claim 10 wherein a plurality of similar parallel spaced ridges are raised along lines corresponding with corner lines of the to-be-formed shape.  
  12. The method of claim 11 wherein the longitudinal edges of said stock are raised to semi-ridges, each being similar to one-half of the other raised ridges for eventual abutment in forming said stock to tubular shape.  
  13. A method of preparing flat stock for subsequent forming to a cross-sectional shape having a bend along a prelocated corner line, comprising:  
 a. providing flat stock of known hardness which normally will not bend to such shape without risk of cracking, either during bending or in subsequent use; and  
 b. cold reducing said stock to diminished thickness while simultaneously raising from one face thereof a ridge and impressing into the opposite face a depression, said ridge and depression being disposed on a line corresponding in location to the corner line of the to-be-formed shape with flat surfaces extending from both sides of said line.  
  14. The method of claim 13 wherein said ridge is raised and said depression is impressed intermediate respective concave and convex radii sloping into the surface planes of said stock.  
  15. The method of claim 14 wherein said radii are in the order of four to ten times the thickness of said stock.  
  16. A method of developing from flat stock a longitudinal member of selected cross-sectional shape bent along a prelocated corner line, comprising:  
 a. providing flat stock of known hardness which normally will not bend to shape without risk of cracking either during bending or in subsequent use;  
 b. cold reducing said stock to diminished thickness while simultaneously raising from one face thereof a ridge and impressing a depression on the opposite face thereof on a line corresponding in location to the corner line of the to-be-formed shape with flat surfaces of the stock extending from opposite sides of said line; and  
 c. subsequently bending said stock along said ridge line to final member shape.  
  17. The method of claim 16 wherein said ridge is raised to a substantially sharp edge, and on bending to final member shape said ridge forms a substantially sharp external corner.  
  18. The method of claim 16 wherein said ridge is raised intermediate concave radii sloping into the surface plane of said stock, and on bending to final member shape said radii increase to form substantially planar surfaces.  
  19. The method of claim 18 wherein said radii are in the order of four to ten times the thickness of said stock.  
  20. The method of claim 16 wherein said depression is impressed with a larger radius than said ridge, and on bending to final member shape said depression forms an internal corner radius.  
  21. The method of claim 16 wherein said depression is impressed to a substantially sharp groove, and on bending to final member shape said depression forms a substantially sharp internal corner.  
  22. The method of claim 16 wherein said depression is impressed intermediate convex radii sloping into the surface plane of said stock, and on bending to final member shape said radii increase to form substantially planar surfaces.  
  23. The method of claim 22 wherein said radii are in the order of four to ten times the thickness of said stock.  
  24. The method of claim 16 wherein said cold reducing step comprises passing said stock between reducing rolls formed to produce said ridge, and said bending step comprises passing said stock between cold forming rolls to form said stock to said selected shape.  
  25. The method of claim 16 wherein said stock comprises a continuous elongated strip, said cold reducing step comprises passing said stock between reducing rolls formed to produce a continuous longitudinal ridge intermediate the longitudinal side edges of said strip, and said bending step comprises passing said stock between cold forming rolls to form said stock to a continuous longitudinal member.  
  26. The method of claim 16 wherein a plurality of similar parallel spaced ridges are raised and said stock is bent therealong to a final member shape having in excess of two planar sides.  
  27. The method of claim 26 wherein said stock is bent to a longitudinal channel shape.  
  28. The method of claim 26 wherein on bending said stock longitudinal edges thereof are abutted to thereby form a tubular member.  
  29. The method of claim 28 including the step of welding said abutted edges together.  
  30. The method of claim 16 wherein said stock is reduced and said ridge is raised progressively and continuously by uni-directional passage between rolls of a cold roll reduction mill.  
  3]. The method of claim 16 wherein said stock is bent along said line progressively and continuously by uni-directional passage between said rolls of a cold roll forming mill.