Roll formed metal members may be used for a variety of purposes, as either structural load bearing members, or as beams of various kinds, or in many non-load bearing applications.
Such members may be of a variety of cross-sections. One typical member has a generally C shaped cross-section. Other members may have a cross-section similar to a Z, and other members may be of a T shaped cross section or an I shaped cross section to name only a few.
In all cases, however, it is desirable that whatever the section of the member, it should have certain characteristics.
It should be strong enough to carry the load for which it is designed, in the case of a load bearing member, and even in the case of such members which are strictly speaking non-load bearing members, it shall at least have sufficient strength to withstand the forces to which it will be subjected in normal use.
It should be capable of being fabricated at high speed by roll forming to minimise production costs.
It should use a minimum quantity of metal, for a given length, in order to both minimise cost and reduce weight.
Numerous proposals have been made in the past for designing such metal members having both reduced weight, and increased strength, as compared with a plain unformed section.
Such proposals are almost too numerous to mention, but are usually based on some form of combination of openings formed through the member, or some form of indentations, or flanges, formed in the member so as to increase its strength and thus permit the thickness of metal to be reduced, for a given load or application. One of the principal problems with most of the earlier proposals of this type is that it was simply impossible to manufacture them by known manufacturing techniques, in an economical manner.
Continuous cold roll forming techniques for forming longitudinal formations in sheet metal, and hot rolling were not capable of both the piercing of openings through the metal, and also forming indentations or flanges. For many years, no equipment was known which was capable of carrying out these functions on a continuously moving piece of metal moving along a forming line. Accordingly, most of these earlier proposals have been impractical, since they could only be made on a typical stationary press. Recent developments in rotary forming apparatus are disclosed in U.S. Re. Pat. No. 33,613 entitled Rotary Apparatus, Inventor E. R. Bodnar, and U.S. Pat. No. 5,040,397 entitled Rotary Apparatus and Method, Inventor E. R. Bodnar.
Using this type of apparatus, it is now possible to manufacture a wide variety of different products, in which openings can be pierced or formations formed, in a continuously moving bar or strip of material. Examples of continuously formed strip sheet metal products are shown in U.S. Pat. No. 4,909,007 entitled Steel Stud and Precast Panel, Inventor E. R. Bodnar and U.S. Pat. No. 4,793,113 entitled Wall System and Metal Stud Therefor, Inventor E. R. Bodnar.
Using these new manufacturing techniques, it has been found possible to produce structural load bearing and non-load bearing sheet metal products having both transverse formations, openings, flanges, and longitudinal formations. A combination of some or all of these formations greatly increases the strength capacity of the structural member and consequently enables the thickness of the sheet metal to be reduced. For example, in the structural member shown in U.S. Pat. No. 4,793,113, the member is formed with generally triangular or trapezoidal shaped openings, which openings define between them generally diagonal struts. Edge flanges were formed along either side of the struts and around the sides of the openings. Roll formed continuous angle formations were formed along either side of the member. In this way, it was possible to provide for example, a light weight structural member for use in interior construction in buildings such as the supporting of interior walls and the like, using thin gauge sheet metal. The uses of the invention described in that patent are in no way limited to such a thin gauge material, but the invention had particular utility in that connection, since it also provided generally transverse indentations alongside the struts, and in the angle formations. These transverse indentations reduced the tendency of the roll formed angle portions to flex.
It was also surprisingly found that these formations also reduced the flexibility of the web portion of the structural member, between the roll formed longitudinal angle formations, and this factor still further enhanced the resistance of the stud to flexing. This surprising and unexpected result has led to further developments to still further enhance the rigidity both of thin gauge structural members and also of much heavier gauge structural members of various widths, for heavy duty load bearing uses.
While up to this point, the characteristics of metal products described above, have generally speaking been formed of strip sheet metal in cold forming processes, it has now further been determined that by the use of some, or all of the inventive features about to be described, the performance of both cold rolled and hot rolled metal members may be substantially improved. In the past, hot rolled metallic members typically being flat steel bars, girders, joists, lipped angles, and plain channels, and the like have been hot rolled from a heated billet usually of steel (and/or ferrous and non-ferrous metals), and then allowed to cool, and then cut to length. These products generally had relatively primitive continuous sections described above, typically, having a continuous planar web, and one or more edge formations.
Such hot rolled structural members are formed in various thicknesses and dimensions for various different applications. Clearly, the same observations apply namely that if the hot rolled members can be increased in strength by certain formations, which are formed in them, then the thickness of metal in the member may be reduced thereby reducing its weight and its cost.