Metal deforming – With indication of condition or position of work – product,... – Work drawn or extruded through die
Patent
1990-06-05
1992-01-14
Larson, Lowell A.
Metal deforming
With indication of condition or position of work, product,...
Work drawn or extruded through die
72 49, 29407, B21C 5100, B21C 3712
Patent
active
050799380
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for producing a helically-seamed pipe from a flat band of material that is fed in at angle to the pipe, marked and wound, any deviation from the nominal value of the circumference length being detectable by changing relations of mark positions so that a corrective procedure can be initiated.
Problems connected with maintaining the correct diameter of the pipe can arise when such pipes are helically wound without the use of a core, from a strip of material, and the edges of the strip are joined continuously with each other. These problems arise sometimes when the diameter of the cross-sectional area of the first winding is being determined; this is generally bent by hand, when a section of the strip of material that is of equal length to the length of the circumference of the desired pipe is fed through the winding rollers, bent to form a loop, and then the beginning is passed once again to the bending or joining rollers. It is extremely difficult to establish the diameter of the pipe accurately in this way, since only in the rarest cases, when cylindrical pipes are involved, is the first, hand-bent loop of a circular cross-section, or of the desired angular cross-section area when angular pipes are involved.
In the same way, however, it is also extremely difficult to maintain the desired circumference length. If the long edges are seamed, for example, one long edge may have a bent web and the other may have a U-shaped fold, these being guided into each other, the connector rollers folding and flattening the seam. This causes an offset of the material sections of between 0.7 and 1.3 mm per winding. The reasons for the resulting inaccuracies may be that the folded web of the section of the material strip that bends undergoes a stretching that increases radially, and this can only be partially compensated by upsetting when the seam is bent, since the folded web within the bent seam comes to rest at a distance from the outer surface of the last winding that equals the thickness of the strip of material, since it is encompassed by the U-shaped seam. For this reason, the length of the U-shaped seam is approximately equal to the length of the stretched web, so that the diameter of the pipe increases with each winding. A number of possibilities to eliminate these deficiencies have already been suggested for cylindrical pipes. For this purpose, for example relations of mark positions are controlled (U.S. Pat. No. 4,287,739, U.S. Pat. No. 2,301,092 and JP-A-58/192617). According to U.S. Pat. No. 4,287,739 a sheet metal strip is at each edge provided with a number of marks being spaced from each other by the same distance which is chosen at random. When the strip is being wound, the distance which results between a mark of the one edge and a mark of the other edge of the preceding winding should not change when the circumference length is constant. It cannot be seen directly if the constant circumference length corresponds to the desired circumference length. Occuring changes in the distance are recognized by the operators, whereupon suitable corrective procedures can be initiated. U.S. Pat. No. 2,301,092 and JP-A-58/192617 also use two rows of marks at constant distances which are chosen at random, in these cases the additional criterium is set that at the distance of the desired circumference length from each mark at the one strip side a mark is provided at the other strip side. Hence, during the winding process the marks of the one edge coincide with the marks of the other edge of the preceding winding only if the circumference length corresponds to the desired circumference length and if the circumference length is constant. In this case, too, changes are recognized by the operators so that corrective steps can be taken. Problems arise in connection with arranging and comparing adjacent edge marks, when the windings are seamed, since the marks may become unrecognizable through the seam formation and, moreover, they may move for the reasons mentioned at the beginning of t
REFERENCES:
patent: 4287739 (1981-09-01), Campbell
patent: 4615094 (1986-10-01), Kai et al.
Larson Lowell A.
McKeon Michael J.
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