US 3081795 A
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March 19, 1963 B. R. LESSER RECTANGULARLY BENT "SQUARE" TUBING Filed July 21, 1961 BERTQAND R. LESSER m T m V m United States Patent 3,031,795 RECTANGULARLY BENT SQUARE TUBING Bertrand R. Lesser, 24- Stonewall Lane, Mamaroneclr, N.Y.
Filed .luly 21, 1961, Ser. No. 125,763 3 Qiaims. (Cl. 138177) The invention herein disclosed relates to the bending of tubing used in the manufacture of chairs and other furniture.
Objects of the invention are to utilize so-called square tubing in place of the circular cross section tubing ordinarily used for such purposes.
The square cross section tubing has certain advantages but introduces difliculties in the fabrication thereof, particularly in the matter of bending the same to meet different requirements.
It has been diflicult to obtain a sharp right angle bend without considerable radius of curvature.
An object of the present invention is to obtain a sharp right angle bend of square tubing with no radius of curva ture at the inside of the bend.
This has been accomplished by first transversely indenting opposite sides of the tubing to locate the bend and then bending the tubing at opposite sides of the indentations to first extrude a bulging portion of the inner Wall of the tubing and to then fold projecting portions of such extrusion up into the body of the tubing so as to permit the opposing portions of the inner wall to come together in a sharply defined perpendicular relation. During this operation the outer wall of the tubing under tension aids in bringing the companion inner wall sections into the de sired, sharply defined, rectangular corner defining relation.
Other desirable objects and the novel features and operative steps of the invention are set forth and will appear in the course of the following specification.
The drawing accompanying and forming part of the specification illustrates present embodiment of the invention but structure and mode of operation may be modified and changed as regards the immediate illustration, all within the true intent and scope of the invention as hereinafter defined and claimed.
FIG. 1 in the drawing is a perspective view of a section of square tubing such as comprehended in the present invention.
FIG. 2 is a side or front elevation showing the firstor initial step of transversely indenting the front and back walls of the tubing to establish the line of bending.
FIG. 3 is a plan view of the tubing as transversely in dented on opposite sides.
FIG. 4 is a front elevation showing the tubing started on the bending movement with the material at the inside of the bend constituting the inner wall of the tubing being projected as a bulging extrusion.
FIG. 5 is a View of the inside of the bend showing the extruded bulging lower wall portion ready to be collapsed between the approaching angled side sections of the tube.
FIG. 6 is a front elevation of the completed right angle bend with the side sections of the tube brought together in adjoining rectangular relation.
FIG. 7 is a view of the inside of the completed bend showing the excess bulged material folded fully into the confines of the tubing.
FIG. 8 is an elevation of the completed bend viewed on the line of the arrow 3 in FIG. 7 illustrating the arching of the outer wall effected in the completion of the bend.
FIG. 9 is a broken sectional detail on the plane of line 99 of FIG. 7, showing how the metal of the inner wall is folded and compacted in the body of the tubing.
FIG. 10 is a broken sectional detail on substantially the plane of line 1tl1tl= in FIG. 7 illustrating disposal of excess material in the corner formed by the bend.
3,081,795 Patented Mar. 19, 1963 'ice FIG. 1 illustrates a length of tubing such as this invention is concerned with having what may be considered front and back, top and bottom side walls 12, 13, 14 and 15. This tubing may be of aluminum or other such work able metals or materials.
FIGS. 2 and 3 illustrate the first step or steps involving impressing into opposed walls, such as front and back walls 12, 15 the aligned transversely extending straight indentations 16, 17.
The indenting of the front and back walls causes a foreshortening of the top and bottom walls 14,. 15 creating upstanding or outstanding ridges 18, 19.
In the next stage or phase of operations the sections of tube 20, 21, FIG. 2, at opposite sides of the transverse indentations are pressured toward each other as in FIG. 4 bending in consequence on the line of the ridge 18 at the outside and causing the ridge portion 19 at the inside of the bend to bulge inwardly in a somewhat angled extrusion 22 of the bottom wall 15.
In this transformation the indentations 16, 17 in the opposite side walls sink further into the side walls practically as shown in FIG. 5.
On further bending of the tube sections toward each other the bulged portion 22 of the inner wall 15 is forced up into the body of the tube until it practically or wholly disappears as shown in FIG. 6, this action being assured by the outer wall 14 of the tube arching as a tension ele- 'rnent 23, FIG. 9, holding the tube sections to the desired right angled relation. In stretching to this limiting arch formation the outer wall sinks at the center to the transversely curved formation shown at 23, FIGS. 8 and 9, forming a rigid truss maintaining the angled portions of the tube in perpendicular relation.
The final result is a sharply angled corner having no radius of curvature at the inside and having a smooth rounded exterior radius with the inside point of the angle as a center.
This rectangular corner structure is internally reinforced by the originally extruded portion projecting from the inner wall and then folded up into the body of the tube and externally by the arch 23 of the outer wall stressed about the corner.
This fully reinforced sharp corner is particularly desirable for chairs and other furniture since there is no bulk such as results from the large radius bending of circular cross section tubing commonly used in this art. This right angle bend is more stable and enables filling in of covering material such. as webbing fully up into the corners. In addition to greater comfort and safety the invention also provides desirable and attractive design and appearance features.
The square tubing is light, strong and rigid and the square corners provide added strength and in the final structure reduce the size and afford a more compact structure.
The transverse indenting of opposite sides raises transverse ridges on the other two sides in line with and connecting the indentations. The tubing then will bend readily on the line of the ridge which is to be at the outside of the bend. In the preliminary stages of this bending the ridge which is at the inside of the bend constitutes an amount of excess which extrudes first as a bulge projecting from the inner wall of the tube and then as the bend is completed this bulging portion is doubled and folded up within the hollow of the bend where, as indicated in FIGS. 6 and 9, it constitutes an internal reinforcement of the bent tube.
These steps or stages may constitute different phases of a single continuing operation or be accomplished in separate steps and may be effected by relatively simple tools, equipment or machinery.
Under stress the outer wall collapses to an extent into a transversely curved arch and this transverse curvature gives the bend a further degree of stability and strength.
What is claimed is:
1. A tubular frame'member for furniture or other purpose comprising square tubing having a right angle bend therein,
said tubing having parallel inner and outer walls connected by parallel side Walls,
the inner Wall formed at said bend in a substantially continuous, sharp, ninety degree angle and the outer Wall at said bend being curved in an arch over said sharp angle in the inner Wall,
said side walls being indented beneath and into supporting engagement with said arched portion of the outer Wall and the inner wall having excess material at said sharp angle therein projecting into the tubing and into engagement with said indented portions of the side walls, and
whereby said included portions of the tubing mutually reinforce each other.
2. The invention according to claim 1 in which said arched portion of the outer wall is transversely, concavely curved into the tubing into engagement with said indented portions of the side walls.
3. The method of forming a sharply angled right angle bend in square tubing with no radius curvature at the inside of the bend, comprising indenting opposite sides of the tubing on oppositely located transverse lines and thereby forcing the material of the two other opposite sides of the tubing into transverse ridges in line with and connecting the indentations in the first two mentioned opposite sides and then bending the tubing in line with the ridge at the inner side of the bend and obtruding excess material from said ridge at the inside of the bend and forcing such obtruded material within the tubing and into supporting engagement with the originally indented portions in the first mentioned sides of the tubing.
References Cited in the file of this patent UNITED STATES PATENTS 615,701 Higgins Dec 13, 1898 1,913,417 Ulrich June 13, 1933 2,077,454 Almdale Apr. 20, 1937 2,551,871 Briggs May 8, 1951 2,748,455 Draper et al June 5, 1956 FOREIGN PATENTS 581,106 Germany July 21, 1933 763,296 France Feb. 12, 1934 767,481 Great Britain Feb. 6, 1957