US2208988A - Laminated tube - Google Patents

Description

y 194% J. F. LEVAN 2,208,9S8

LAMINATED TUBE Filed July 28, 19338 y INVZIN 113R M BY M WWWZ A 7 TORNEYS.

Patented July 23,1940 8 2,208,988

UNITED STATES! PATENT OFFlCE Curtain Company, Elkhart, Ind., a corporation of Indiana Application July 28, 1938, Serial No. 221,777

1 Claim. (Cl. 138-454) This invention relates to tubes used primarily are substantially coextensive with each other. for rails, hand-holds, uprights, tubular framing Their margins on one side of the line of division for different articles, as for cots, chairs, seats, of said strips are folded reversely and nested to etc., or in any situation where a tube with an form a hook-shaped loop at 5 and the other mar- 5 outer, smooth, polished or lustrous surface is degins of said strips are folded and nested together sired, or to tubes of the type shown in my pendto form a hook-shaped loop 6. The two loops are ing application, Serial No. 187,030, filed Januhooked together to form a lock seam joint conary 26, 1938, and has for its object the formation sisting of layers of stainless steel and the steel of a particularly strong rigid lock seam joint beof softer, tougher metal. The first layer, toward m tween the edges of an outer veneer strip of a finthe center of the tube, being of the softer,

ishing metal, as stainless. steel, which joint is tougher' metal. When so folded and hooked tosnugly wedged in the slot of an internal body gether, the lock seam joint is located in the slot tube and strengthened by internal corrugations of the body I, and as seen in Figure 4, bulges into or internal knurling which so additionally inthe interior of the body 1 beyond the inner surterlocks the laminations of the lock seam joint, face thereof, before the tube is completely formed 15 as to make the joint a substantially rigid rod to into the form shown in Figure 1. Then the resist torsional distortion. joint so consisting of laminations is provided The corrugation or knurling feature is shown with transverse corrugations 1, these being as applied to the tube of my pending applicaformed by a knurling operation with a tool tion referred to. applied to the innermost lamination within the 20 Theinvention also has for its object the method tube, so that the corrugations or knurling are of forming the tube with the corrugated or exposed on the interior of the tube and the out-' knurled joint. side of the tube is smooth. The corrugations, as

The invention consists in the novel features seen in Figure 3, become of less depth and greater and in the combinations and constructions and width from the interior of the tube toward the 25 in the method hereinafter set forth and claimed. outer surface, and there are practically no cor- Indescribing this invention, reference is had rugations in the outer surface of the stainless to the accompanying drawing in which like charsteel tube 2 adjacent the edge 8 of the joint.

acters designate corresponding parts in all the The corrugating or knurling operation comviews. presses the joint and wedges it tightly in the slot 30 Figure 1 is a fragmentary isometric view, on an and also closes up the joint at 8 to the smallest enlarged scale, of a tubing embodying this inpossible crevice. The joint thus formed, and by vention. reason of the corrugations, is particularly strong Figure 2 is a similar view but showing the to resist torsional strains applied to the tube, outside of the joint, after being finished. without welding and the consequent slight dis- Figure 3 is a longitudinal sectional view on coloration of the stainless steel, due to the heat line 3--3, Figure 1. of the welding, and additional operations to Figure 4 is a fragmentary sectional view eliminate such discoloration. through the joint prior to being corrugated or The method consists in performing the corruknurled. gating or knurling operation, after the tube has 40 The tube here illustrated comprises an inner been formed up into the form shown in Figure 4, tubular body I, an outer veneer strip 2 of a metal, the knurling to be applied to the inner face of the as stainless steel, capable of receiving and mainjoint while pressure is applied to the outer face taining a high lustrous finish, and a reinforcing of the joint, causing the joint to be flattened and strip 3 for the veneer strip, this being of a softer, the laminations thereof interlocked by the cortougher metal than the veneer strip. The outer rugations. The tube is formed by passing two 45 strip 2 and the intermediate strip 3 are coextenflat strips which form the layers 2, 3, flatwise on sive and have their margins nested together by each other through rollers or dies which partly a lock seam joint. form them with marginal nested flanges which The body I may be of any suitable thickness of eventually are interlocked and form the lock relatively cheap metal, and is divided or slotted seam joint in the finished article. After the longitudinally with the edges 4 on opposite sides marginal flange forming operation, a flat strip of the division or slot spaced apart to provide a which forms the backing I is fed flatwise onto the recess for the lock seam joint. two strips between the marginal flanges. Then The strips 2, 3 are divided longitudinally and the three strips lying flatwise on each other are fed through a series of dies or rollers which roll them up into tubular form and interlock the lock seam flanges of the layers 2, 3 between the edges of the body I. After this operation, the tube is in the form shown in Figure 4, and then the corrugating or knurling operation is performed which flattens the lock seam joint into the position shown in Figure 2 and firmly wedges and unites it in the lengthwise slot in the backing I, making the whole practically an integral structure. The forming dies and knurling tool are arranged in series and series of operations are performed in a machine in which the flat strips are fed in at an end and the finished tube emerges at the other end.

The tube, due to the corrugations, is stronger" at the joint and resists any torsional strains to which it is subjected in the use thereof, and in fact, the corrugations make the joint practically a solid rod wedged into the slot of the innermost tube 1.

What I claim is:

A tube construction comprising an inner tubular body slotted longitudinally and an outer Veneer strip of a finishing metal having its margins" interlockedtogether in a lock seam joint consisting of layers, the joint being located in the slot and formed with internal transversely extending corrugations exposed on the interior of the tube leaving the outside of the tube smooth.

JOHN F. LEVAN.

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