US1861421A - Method of making tubing - Google Patents

Description

May 31, 193. F. @188 METHOD OF MAKING TUBING Filed Jan. 25, 1952 5 Sheets-Sheet 1 INVENTOR. flu Tkcmy J? ("1' 5,6

F. CITES 1,861,421

METHQD OF MAKING TUBTW' Filed Jan. 23, 1932 5 Sheets-Sheet 2 May 31, 1932.

6M? ATTORN xi m vm u R t %n May 31, 1952. A. F. was

METHOD OF MAKING TUBING Filed Jan. 25, 1932 3 Sheets-Sheet 3 I N VEN TOR.

Patented May 31, 1932 UNITED STATES PATENT OFFICE ANTHONY F; CIBS, OF CLEVELAND HEIGHTS, OHIO, ASSIGNOR T0 EMIL LINDERME, SR., OF CLEVELAND HEIGHTS, OHIO METHOD OF MAKING TUBING Application filed January 23, 1932. Serial No. 588,338.

This invention relates, as indicated, to a method of and apparatus for making tubing, but has reference more particularly to a method and apparatus which are especially adapted for the rapid. and economical production of tubing from copper coated steel strip, such tubing having a wide application in the automotive industry for gasoline and oil lines, hydraulic brake lines, radiator tubes, etc. i

It has heretofore been proposed to manufacture tubing of the aforesaid type of forming or fashioning a strip or strips of steel having a relatively thick coating of copper into a tube of plural ply hollow cross section, and then heating such tube to fuse the copper coating and cause the plies to adhere together. For the purpose of heating the tube, an electrically heated copper brazing furnace is employed, but such a furnace must necessarily be quite long, and is costly to install and operate, involving constant replacement of heating elements and the services of a number of operators. I

During the passage of the tubing through the brazing furnace, no effort is usually made to maintain the plies in intimate contact with each other, or the edges of the strip or strips in proper abutment. -As a result, the outer strip or ly, which is heated first, and is, by virtue of its relatively thick coating of cop per, to a certain extent bi-nietallic, tends to spring open, leaving a space between the plies. The inner ply then tends to spring open, squeezing some of the molten copper between the plies out of the outer seam. This copper gathers in globular form on the exterior surface of the tubing and some of it drips onto the floor of the furnace. The drippings, as well as the globules on the. surface of the tube must be removed. When the tubing is formed from a single strip of copper coated steel, as by forming a 0g in such strip and curling the edges of the strip into a tube of plural ply hollow cross-section, with the edges of the strip on opposite sides of the jog, the aforesaid difficulti'es appear to be accentuated.

When tubing, which has been heated in the aforesaid manner, is permitted to cool,

it is unreasonable to believe that the tubing will assume its initial contour, and actual visual inspection of such tubing appears to bear out this belief. Such tubing'is not uniform in appearance, but is characterized by such defects as open seams and variations in wall thickness. In order to conceal or minimize these defects, it has been the practice to subject the tubing, after it has passed through the brazing furnace, to sizing and drawing operations, and in some cases, to coat the tubing with solder.

It has also been my observation that tubing made in the aforesaid manner is dilhcult for inexperienced persons to form or bend without fracturing. This probably accounts for the fact that such tubing is formed or bent into the desired finished shape at the factory, and is not generally distributed in straight lengths through retail channels to consumers who desire to form or bend the tubing into the desired finishedshape. Such consumers are usually obliged to purchase higher priced seamless copper tubing, which they can readily bend without danger of fracturing. Since formed tubing necessarily requires more space for shipment than tubing in straight lengths, it is obvious that the aforesaid tubing is relatively expensive to pack and ship, requiring large and strongly reinforced shipping containers.

The present invention has for its primary object the production in a rapid and economical manner of tubing of the type described,

which is characterized by a high degree of uniformity and freedom from the described mechanical and surface defects.

In accordance wlth my invention, I coat steel strip stock with copper, as by depositing the copper thereon electrolytically, or chemically. I am aware that it has been the practice of certain manufacturers to treat such strip stock by electrolytically depositing a heavy coating of copper on the same, form the coated stock into plural ply tub ing, heat the tubing in an electrically heating furnace to a brazing temperature, cool and redraw the tubing. Owing to the thickness of the copper or brazing material in such tubing, I have found that the tubing can be readily disassembled by heating it to a sufiiciently high temperature.

7 In contradistinction to the formation of a relatively thick coating of copper or other brazing material, on the steel strip stock, I form an extremely thin coating on the stock. In practice, I have used a coating approximately one sixty-thousandth of an inch thick, forming a layer of coating material one thirty-thousandth of an-inch thick when two coated surfaces are joined. A coating of such thickness will not flow at the temperatures attained in the electrically heated furnace to which I have referred, and I am therefore compelled to employ a much higher temperature than is attainable in the said furnace, in order to melt the extremely thin film of copper and cause a uniting of the plies of the tube.

At the brazing temperature which I, employ for uniting the plies of the tubing,. I find that an alloying efl'ect takes place, whereby the thin film of copper between the plies of steel forms an iron-copper alloy with the steel, the iron-copper alloy providing an inseparable bond between the plies of steel. Inasmuch as I use only sufficient copper to form the alloy, and have no excess of copper between the plies, it is impossible to separate the plies of material brazed by my process.

I attain the desiredbrazing temperature by passing the'tubing between spaced pairs of electrodes and causing an electriccurrent to traverse the portion of the tubing between thepairs of electrodes. This portion of the tubing thus constitutes a resistance element and is gradually brought up to a' temperature at which the copper coating of the tubing is fused and alloys with the steel. At the same time, the tubing is moved longitudinally at such speed that the temperature of the tubing between the pairs of electrodes is not uniform, but varies, the tubing being gradually brought up to a brazing temperature. By varying the current input and controlling the speed of the tubing, all danger of scorching or melting the tubing is eliminated. If, for example, tubing of a given size and travelling at a given speed requires a certain amount of current to braze the tubing, a larger size tubing travelling at the same speed would, on account of the greater surface area to be welded, require a greater current input. Conversely, if the current input remained the same as in the case of the smaller tubing, the speed of the larger tubing could be decreased and a perfect braze obtained.

The electrodes-also serve to maintain the inner and outer plies of the tubing in intimate contact with each other and the edges of the strip or strips constituting the plies in proper abutment, thereby resisting any tendency for the plies to spring open.

I also preferabl blanket the portion of the tubing which is being brazed with a nonoxidizing gas, such as hydrogen, which prevents oxidation of the copper-iron a loy formed during the heating of the tubing and leaves the tubing with a very bright surface finish, which is also characteristic of tubing made by my process, and is highly desirable. Moreover, the external and internal co periron alloy is resistant to rusting and is highly durable.

Tubing made by my process requires no heat treatment or sizm subsequent to the brazing operation. Ex austive tests have disclosed the fact that the tubing may be bent and twisted to the same extent as seamless steel tubing and to a greater extent than seamless copper tubing without danger of fracture.

In the accompanying drawings, I have i1- lustrated in a more or less diagrammatic manner apparatus which may be employed for brazing tubing of the type hereinbefore described, but it will be understood that the method of the present invention may be practiced with other apparatus, and that the apparatus as shown may be modified for the purpose of brazing products other than tubing.

In said annexed drawings:

Fig. 1 is a View, partly in elevation and partly in section, showing the apparatus employed for making tubing in. accordance with the invention;

Fig. 2 is a view, partly in plan and partly in section of the apparatus shown in Fig. 1;

Fig. 4.- is a longitudinal cdross sectional view through the apparatus, taken on a plane substantially indicated by the line 33 of Fig. 2;

Fig. 4 is a longitudinal cross sectional view through the apparatus, taken on a plane substantially indicated by the line 44 of Fig. 3;

Fig. 5 is a transverse cross sectional view through the apparatus, taken on a plane substantially indicated by the line 5-5 of Figs.

,1 and 4; and

Fig. 6 is across sectional View through tubing formed from two strips which is especially adapted to be brazed and finished in accordance with the present method.

Referring more particularly to the drawings, the tubing shown in Fig. 6 is formed by drawing flat strip stock into tube shape, one

strip of stock being used for the inner ply of the tube and' another strip of stock of slightly greater width than the first strip being used for the outer ply of the tube. The manner in which this tubing is formed is well known to those skilled in the art to which this invention relates, and no further reference need be made thereto, except to point out that the strips, before being formed into tubing, are passed through a plating bath in which a thin film of copper is deposited thereon. The tubing is thus provided with thin internal and external coatings of copper and a thin film of copper between the plies of the tubing.

The tubing which I have designated by the reference character 1 is fed directly from the rolling or forming machine (not shown) into a throat formed by peripheral recesses 2a of roller electrodes 2. The electrodes 2 are connected in parallel to a suitable source of electrical energy 3, as by means of conductors 4. The electrodes 2 are cooled by means of a fluid from valve-controlled pipes 5, the fluid entering annular basins 6 secured to the electrodes and being maintained at a fixed level by means of overflow pipes 7 The overflow is caught in annular basins 8, which are stationarily supported on the table 9, and are disposed directly beneath the basins 6. The basins 6 are provided with drain pipes 10. The tubing then passes into a substantially air-tight chamber 11, which is extended at one end to enclose portions of roller electrodes 12, which are similar to electrodes 2 and are cooled in the same manner. The electrodes 12 are connected tothe other terminal of'the source of electrical energy 3, as by means of conductors 13, and are maintained in spaced adjustable relation by tension means (not shown).

The chamber 11 is provided with peep holes 14 which are covered by windows 15, so that the operator may at all times inspect the tubing and determine the working conditions within the chamber. During the braZ- ing operation, the chamber is kept filled with a suitable non-oxidizing gas, such as hydrogen, which is introduced through a conduit 16 and is ignited, as at vents 17, to prevent inconvenience to the operator.

The tubing, in passing between pairs of electrodes 2 and 12 forms what may be termed a short circuit between the pairs of electrodes, and is heated instantaneously to a brazing temperature. To avoid melting of the tubing, with the resulting breaking of the circuit, the tubing is continuously moved between the pairs of electrodes, thereby pr'esenting successive cold sections of the tubing which are brought up to the desired temperature. Where: the source of energy 3 is direct, the current'input may be varied by means of a rheostat' 18. If alternating current is used as the source of energy, the cur rent density may be varied by means of suitable equipment (not shown) which is already available in the market.

Due to the fact that cold sections of tubing are being constantly introduced between the pairs of electrodes, the temperature of the tubing varies considerably between the pairs of electrodes. At the point a, the tubing is still relatively cool, but as this point in by electrodes 12, it gradually and uniformly attains a brazing temperature. The speed with which the tubing may be brazed is thus limited only by the current input and the distance between the pairs of electrodes.

The brazing operations may be begun without the necessity of preheating the tubing.

The electrodes 12 serve to perform a number of operations, namely, they introduce the brazing current to the tubing, squeeze the plies of the tubing together, size the tubing, cool the tubing and assist in propelling the tubing through the apparatus. The electrodes 12 are preferably so adjusted relatively to each other that they hold the tubing within very close limits to the required inside and outside diameter.

The tubing then passes through a chamber 19 which is cooled by water or other cooling medium. The cooling fluid is introduced through an inlet pipe 20 and is drained through an outlet pipe 21.

here a tinned or other finish is desired on the tubing, the tubing may be passed through a bath 22 of molten tin, or the like. The tubing is completely immersed in the bath by passing through stufiing boxes 23. Additional tin may be supplied to the bath from an ingot 24, which is automatically fed to the bath by means of suitable feeding mechanism 25, so that a fixed level of molten tin is maintained. The bath is electrically heated under thermostatic control, but after production has been started the heat of the tube is sufficient to maintain the tin in molten condition, and the thermostat is automatically cut out.

The tubing is then coiled on a drum 26, which has a slightly tapered surface similar to that of a wire drawing drum, so that successive convolutions of the tubing are forced laterally down the tapered surface of the drum and stored thereon. The electrodes 2 and 12 and the drum 26 may be synchronously driven by a motor 27 secured to the lower surface of the table 9.

The motor 27, through a pinion 28, drives a gear 29, which is fixed on a shaft 30, journalled in bearings 31 secured to the table 9. Secured to the shaft at spaced points are worms 32, which are in driving connection with worm gears 33 secured to drive spindles 34. The spindles 34 are secured to shafts 35 by means of couplings 36 provided with insulating collars 37.

The drum 26 is driven by the shaft 30 through the intermediary of bevel gears 38, 39, 40 and 41.

While I have mentioned the use of coatings of a certain thickness, it will be apparent that the thickness of the coating may be varied, and that coatings, other than copper, may be used, such as lead, tin, or other material having a melting point lower than that of the the tubing moves forwardtothethroat formed -meta1 which its being joined brazed Since the heat or resistance of the portion of the tubing between the pairs of electrodes may be controlled at all times.

Although the invention has been described with particular reference to the making of tubing from plural strips of stock, it will be apparent that tubing made in other ways from single or plural strips of stock may be likewise joined or brazed, and that material other than tubing may be produced, such ascomposite strip stock. In making other material it is only necessary to substitute for the electrode rollers shown, electrodes having the desired peripheral contour. If desired, dies may be employed instead of roller electrodes. It will also be apparent that the apparatus may be used for heat treating instead of brazing, as for example, the heat treatment of wire tubing or strip stock. If the apparatus has been set up to make 4" tubing, no change in the set-up will be required to anneal A" wire. The only adjustment which would be required would be in the speed of the driving motor or an increase or decrease in the current input. In any case, the adjustments may be effected quickly and easily by simple manually operated controls.

After the entire unit has been started, the services of only one man are required, who may operate several of such units. His principal duty is to add new rolls of raw stock and remove the drums of finished material. If the source of energy is direct current, it may be used'to operate a copper plating plant for coating the strip or other stock, thereby materially reducing installation and up-keep' costs.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I therefore particularly point out and distinctly claim as my invention:

1. The method of fabricating plural ply tubing from a plurality of flat strips, the steps: coating at least one of such strips with bonding material, forming such strips into a plural ply tube, progressively passing electrio current longitudinally through successive sections of such tube, and compressing the wall of such tube as the same is brought up to a bonding temperature.

2. In the method of fabricating plural ply tubing from flat stock, the steps: forming such fiat stock into a plural ply tube, progressively passing electric current longitudinally through successive sections of such tube, whereby the contiguous surfaces of said plies are brought up to a bonding temperature.

3. In the method of fabricating plural ply tubing, the steps which consist in progressively passing electric current lon itudinally through successive sections of suc 1 tube and compressing the wall of such tube as the same is brought up to a bonding temperature.

Signed by me this 21st day of January, 1932.

. ANTHONY F. CIBS.

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