US 757592 A
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bPAV'I'ENTED APBn 19, 1904- y. No. 757,592.
- F. ATWooD.
PROCESS 0F BBNDING TUBES.
APPLIOATION FILED JULY 11, 1902.'.
2 SHEETS-SHEET 1,
a Y 1 Way PATENTED APR. 19, 1904.
G. SQA'TW'UOD. PROCESS 0F BBNDNG TUBES.
APPLICATION FILED JULY 1l, 1902.
2 SHEETS-SHEBT 2.
Nrrsn STATES segr avenants com Patented April 19, 1904.
GEORGE Ff ATIVOOD, OF HOBOKE, NEW JERSEY, ASSIGN-OR TO WEST- EBN ELECTRIC. COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF .ncLnyols PFioor-:Ss oF BENDlNe TUBES.
` srEcIFleA'rIoN forming part of Letters Patent No. 757,592, dated April 19, 1904.
Application filed July 11,1902. serial No. 115,107. (No specimens.)
To all whom t may concern.:
Beit known that I, GEORGE F. A'rwool), a
citizen of the United States, residing at Hobeken, in the lcounty of Hudson and State of N ew Jersey, have invented a. certain new and useful Improvement in Machines forBending Tubes, of which the following is a full, clear, concise, and exact description.
My invention relates to a process for bending tubes, and isuseful more particularly in bending tubing of rectangular cross-'section'- such, for instance, as that used in a wellknown pneumatic'tube system for distributing toll-tickets in telephone-exchanges.
The problem of bending a rectangular tube presents much greater diiculties than the bending of round tubes, and it has been found' that the methods heretofore employed for the latter will not attain the desired results with rectangular tubing. It is frequently required to bend the rectangular tube on a radius of three or four inches without distortion .or wrinkles, and in such a case the outer wall and` the two edges must stretch a very considerable distance more than theinner wall. In attem ptin g to bend a thin rectangular tube by the methods heretofore employed it is found that before vthe outer wall will-stretch the required amount the inner wall will be buckled and distorted. The lilling of sand ordinarily used may prevent the metal from buckling inward; but it will then buckle outward, which no filling will eflectually prevent.
A ln accordance with my invention the tube is iirst subjected toa longitudinal tensile stress sutiicient to stretch the metal, and then the tube is bent while such tensile strain is maintained. 'Prefer-abi y the tube is stretched to approximately the elastic limit of the metal, and this stress is gradually increased as the tube is bent. I have found that by this process a perfectly regular and symmetrical curve or twist without the slightest distortion or wrinkle can be produced.
A machine for practicing the process in question is shown in the accompanying drawings, in connection with which 1 will more particularlydescribe my invention. The machine 1s made the subject-matter of another' application for patent, Serial No. 115, 108, filed July '11, 1902. l
Figure 1 is a view'of the machine in elevation. Fig. 2 is a sectional plan View thereof on line Q 2 of Fig.' 1. Fig. 3 is an end elevation. Fig. 4 is a sectional plan view similar to Fig. 2, but showing the parts in an alternative position. ing how the tube may be given a twist or quarter-turn. Figs. 6 and 7 are detail views showing. how the tube is plugged at the points where it is clamped,`,so tllat it will not collapse.
The same letters of reference designate the same parts Wherever they'areshown.
The rigid framework a', which may be supported on legs or standards has a threaded bearing c at one end, through which the longitudinal screw c is passed. The .inner end of said screw carries a liead or cin'ck d, which is mounted thereon so that the screw can rotate independently thereof. A removable cross-bar t' is fitted upon pins carried by the chuck (Z and projects above and below the same alongside the horizontal bars of the `framework, so that when said cross-bar is in place the chuck cannot rotate, but will merely slide forward or backward as the screw is turned; iVhen thc cross-bar is removed, the chuck may be rotated by the aid of a wrenchbar-thrust into one of theholesflj3 in its periphery- At the other end of the framework mis mounted a vertical shaft e', which carries the bending mandrel f, the shaft being so disposed that the curve of the mandrel will be approximately tangent lto a line projected along the longitudinal axis of the screw.
'lhe head or chuck (Z is provided with jaws ai f, which are adapted to grasp one end of the tl'lbing, said jaws being tightened by means of bolts di d2. Clamps g (7, tightened by bolts g1 y, are placed upon the other end of the tubing, and these clamps are seated against lugsf' f', which project from the top and bottom of the bending-mandrel. Plugs t /L are inserted in the tube at the points where it is clamped to preventcollapse. The tubo is also lilled with sand or other filling in accordance with tlle'usual practice.
'.lhc screw c has-a' long keyway c', along Fig. 5 is a detail view showy supported upon the lugsy" f of the bendingperiphery of the mandrel will move slightly which a pinion c2 is adapted to slide, said pinm ion being thus thrown into or out of mesh with a spur-gear le, as may be desired. The spur-gear'o is fixed upon one end of the shaft le', the other end whereof carries a worm k2, which engages a worm-wheel r, fixed upon the Vertical shaite' of the lbending-mandrel.
The operation of the machine is as follows: A tube of suitable length is plugged and filled with sand and one end clamped between the jaws d d of thechuck d, while the 4clamps g g, whichare placed on the other end, are
mandrel, as shown in Figs. 1 vand The pinion c2 is now removed from mesh with the spur-gear it', and the screw c is turned backward by a crank or -other means to put a longitudinal tensile stress on the tube, the mandrel f being held immovable by the worm-gear and the h e'ad or chuck OZ being retracted by the screw. When this stress-is suiiicient to elongate the tube', the pinion c2 is thrown into mesh with the spur-gear s, and the screw c is then turned forward. Now as the screw is rotated the pinion c drives the bending-mandrel f through the gearing before described; which is preferably so proportioned that the faster than the chuck d, whichis advanced by the screw. By this means not only the initial x stress on the tube is Ikept up, but the stress i is gradually increased as the bend is made. l Fig. 4 shows the position of the mandrel in l finishing a bend of ninety degrees. The stress upon the tube is so ygreat that the inner wall can not buckle while the'outer wall is stretched, and a perfectly regular and smooth bend is thus secured.
Wrhen desired, the tubes may be given a twist, as shown in Fig. 5. This may be done by removing the cross-bar t' from the chuck.
d, so leaving the latter free to turn, and then rotating saidchuck through the required are by means of a wrench-bar thrust into one of' the holes d.
i claim as my inventionl. The herein-described process of bending metal tubes which consists in first subjecting the tube to a longitudinal tensile stress sutiicient to stretch the tube approximately to the elastic limit of the instal, and then bending the tube while maintaining such a tensile stress.
2. The herein-described process of bending metal tubes which consists in subjectingthc vtube to a longitudinal tensile stress suiicient