US1715099A - Metal tube and method of making same - Google Patents

Description

MayZS, 1929- I W. J. lawslimlsolv 1,715,099

METAL TUBE AND METHOD OF MAKING SAME Filed Nov. 2o. 1922 4 shets-sheet 1 l 77x25 ivmey May 228, 1929. w. J. ROBINSON METAL TUBE AND METHOD OF MAKING SAME Filed NOV. 20. 1.922 4 Sheets-Shea?l 2 May 28, 19x29. W, J, ROBlNsON 1,715,099

METAL TUBE AND METHOD 0F MAKING SAME Filed Nov. 20. 1922 4 Sheets-Sheet 3 May 28, 1929. Y w, J, RQ'BlNSON 1,715,099

METAL TUBE AND METHOD OF MAKING SAME Filed Nov. zo. 1922 '4 sheets-sheet 4 named' May 2s, 1929.

UNITED sTATEs WILLIAM J. nonrNsoN,

MENTS, To wmcnnsrnn BEPEATING Amas company,

CUT, A CORPORATION F DELAWARE.

0F LOWELL, MASSACHUSETTS, ASSIGNOR, BY HESNE ASSIGN- or :mw mvaN, commeri- METAL TUBE AND :BETH-0D 0F MAKING' SAIE.

Application led November 20, 1922. Serial No. 802,289.

This invention relates to metal tubes and more particularly to thin metal, usually coper tubes, for the radiators of automobiles,

and other heat exchangers, the `walls of such ,5 tubes having a thickness of the order of fivethousandths of an inch.

Heretofore it has been customary to make radiator tubes and other thin'l tubes from sheet copper stock by stamping a disc from the stock and then bending up the margin of the disc to form a cupped'blank which 1s then annealed and thereafter extruded into the form of the tube by the single stroke of an extruding plunger. I have found this method unsatisfactory in many respects and I believe the followino' to be -a substantially correct explanationoiP the reasons therefor.

In cupping a flat disc the center becomes the bottom of the cup and the surrounding part becomes the side-wall or rim of the cup. The metal in the latter part is condensed, whereas at the corner between the side wall and bottom it is bent and therefore to some extent stretched. This bending produces incipient fractures which persist throughout subsequent operations and is' so pronounced especially in cups intended for the extrusion of small diameter tubes as to` prohibit their manufacture on a commercial basis.

Thin tubes made from sheet stock as above described frequently have wrinkled walls and often display cracks in the walls. Moreover, such tubes have a tendency to develop leaks or fractures in subsequent manipulations. For example, in making radiator tubes it is desirable to hex the ends of the tubes for assembly into groups and also to indent the walls to form air baies within the tubes. When usin tubes made from sheet material as describe the hexing and indenting is not uniform and the tubes are frequently dis-- torted and cracked in these operations. Also the making of the cups involves a considerable waste of metal because the pieces of metal in- 45. tervening between the round discs in the flat sheet are necessarily lost as waste.

In making tubes from cast blanks there are. dificulties due, I believe, to the fact that the blanks do not consist of homogeneous metal nor of equal amounts of metal and therefore are not well suited to flow uniformly under` extrusion by impact pressure.

Theprincipal obj ects of the present invention are to overcome the aforesaid disadvantages and diflculties, to make tubes by hammer-stroke extrusion which are stronger and morel uniform, to extrude tubes more economically both with respect to the elimination of Wastage and the wear on the dies, to extrude the metal into tube form without need of heatin the metal and so as to make thin walled tues, especially tubes about a quarter inch diameter and about nine inches long, which are substantially free v:from internal stresses, which will not wrinkle, and which will not readily crack when indented or otherwise shaped for radiator orother uses.

My improved method involves the cutting of a rod into sections to form cylindrical blanks, having substantially parallel grain throughout and causing the metal to flow by impact extrusion in a direction which 1s parallel to the axis and grain of the blank, into the form of a tube. The lmetal is extruded cold, that is without preheating. The cylindrical form and parallel arrangement of the grain of the blank is secured by usin a section of a rod which is formed preferably by an extrusion process or other process adapted to produce lines of flow vapproximately parallel to each other and to the axis of the rod. lThe rod from which the blanks are cut is circular in section and may be a tubular rod, in which case the rod sections may be extruded without any preliminary sha ing. However, if the rod is a solid rod, tge rod sections are preferably provided with axial openings before being extruded. The axial openings may extend entirely through the blanks so as to form hollow cylindrical blanks or rod sections or they may be in the form of indentations extending only part way through so as to form hollow cup-shaped blanks or rod sections. When vthese openings are formed by punches they are preferably produced in two stages, the first stage producing an axial dent in one end of the blank and the second stage extending the opening either wholly or substantially through the blank. The outer lsurfaces of the blanks are kept smooth and true in these indenting operations, by conflning the blanks in dies of suitable diameter while being punched.

If the blanks are formed with axial openings extending entirely therethrough, the resultant tubes are open at both ends which is preferred. If the axial openings extend only part way through the blanks, tubes open at both ends may bottom of the culpped blank by the former of the extruding p unger in the initial state of the extrusion o eration. v

In an case I ave ascertained that the rod from w ich the blank is cut must be homo.

geneous in respect to its crystalline structure and in respect to the distribution vthrough the metal of such impurities as may be present. Any rod stock is suitable which complies with these requirements. Any extruded rod is generally found to do s o, because such rod is produced from a large sized lngot, generall quite pure. Rolled stock is apt to be.4

nonomogeneous if it is rolled from an ingot that was poured in a horizontal mould, because in such case the impuritles tend to `rise during the cooling so as to occupy the upper part of the in ot after it has set. When such an ingot is ro led into rod, the lmpurlties therein willbe found more on one side than the other, but the use of rolled rod' stock is nevertheless satisfactory and within the 1nvention and can be produced of sufficiently homogeneous condition to avoid much of the waste that has heretofore been incident to the impact extrusion of tubes from sheet stock.

My improved method results in tubes whose metallurgical structure is strong and smooth, whose walls are of uniform thickness, and which are adapted to be indented or otherwise Shaped without fracturing. The crinkled condition found in prior tubes, indieating strained and over-worked metal, is entire] to be ue to the use of blanks cut from rod stock, and in some measure to the use of a blank having substantially parallel grain throughout and to the working of the metal longitudinally of the axis of the blank in each stage of the process.

According to the present invention, in-

i volving the use of rod stock, there is praci for cutting the rods tieally no Waste material, each rod-section blank being substantiallywholly converted into tubular form. This is a marked advantage over the prior methods using sheet stock where about one-third of the stock is Wasted in stamping out the disc blanks.

IIn order more clearly to set forth the invention certain concrete examples have been illustrated in the accompanying drawings, in which Fi 1-is a diagrammatic view of one method o making rods for use according` to the present invention;

Fig. 2 is a sectional view of the machine into sections;

Fig. 3 is a perspective View of a rod section;

Fig. 4 is a diagrammatic illustration of one step 1n forming the blank;

Fig. 5 is a sectional view of the blank as shaped in the step shown in Fig. 4;

be formed by puncturing the absent. These advantages I believev Fig.' 6 is a diagrammatic illustration of the next step in forming the blank;

Fig. 7 is a sectional view. of the blank after the forming step shown `in Fig. 6;

' Fi 8 shows another method of forming the rod or use according to the present invention, this rod being tubular;

Fig. 9 is a section of the rod formed as illustrated in Fi 8; l

Fig. 10 is a dlagrammatic illustration of the extrusion of the blank into the form of a tube; i

Fig. 11 is a similar view stage of the process;

lFig. 12 is an elevation of, the resulting tu e;

Figs. 13 and 14 are perspective views of dies for indenting walls of the tube for radi`- ator purposes;

Fig. 15 is a developm-cnt'of the operative faces of the dies, showing the distribution of the indenting elements;

Fig. 16 illustrates, matically, the method of simultaneously hexing the ends of the tube and indenting gig. 17 is a side view of the finished tube; an

Fig. 18 is an ond radiator tube.

In Fig. 1, I have shown, more or less dia# grammatically a common Way of forming copper rod, namely by forcing a mass of pure copper M softened by heat through a restricted round opening into the form of a rod R, D representing the die through which the metal is forced, and P the plunger which is hydraulically'operated. The rod R is cut olf in lengths and passed through sizing or straightening rolls and is then ready to be cut up into sections to form blanks.

Fig. 2 illustrates suitable means for cutting the rod R into sections, rapidly and uniof a succeeding elevation of the finished formly and without deforming the structure r of the rod. This machine comprises a `bed plate 1, a vertically reciprocating head 2 and the cam roll 5 against the cam 4. The head 2 also carries a plunger 7 adapted to force the rod sections from the machine after being severed. The rod R is fed downwardly through an opening 8 into the opening of an annular die 9 carried by the slide 3. As the slide is forced to the left by the cam 4, a section of the rod is severed along the dotted line 10 and is then carried into alignment with the opening 11 and the plunger 7. Upon further descent of the head 2, the plunger 7 forces the rod section Y from, the die 6 through the opening 12. The rolling of the rod in the process of manufacture produces a slightlyhardened surface thereon which truding plunger,

grammatically, ways of forming the axialV opening in the rod section. In Fig. 4 D1 represents a die, P1 a plunger, and A a bottom or ejector plunger. -The severed rod section, after bein first annealed,I -is placed in the die D1 wit the plun er A held in the position indicated, and t e plunger l?1 is thenf' forced down into the rod section until the rod section is formed substantially into the shape indicated at C in Figs. 4 and 5, the plunger P1 is then withdrawn and the plunger A advanced to remove the 4blank from the die. The blank is then placed after another annealing, `in die D2, Fig. 6, with the plunger A2 in the Iposition indicated, whereupon the lunger 2 is advanced until the blank is ormed into substantially the shape indicated at B in Figs. 6 and 7 .The plunger P2 is then withdrawn and the plunger A2 advanced to re# move the blank from the die.

In each of the operations illustrated in Figs. 4 and 6, the ow of metal is along the axis of the rod blank, the surrounding dies restraining the metal against later al flow as the plun ers advance. axially into the blanks, and the isplacement of the metal is equal in every radial direction, so that the metal in the resulting blank is' of uniform condition on all sides of its longitudinal axis.

In the operation shown in Fig. 6, the formingplunger may pass either entirely through the lunger so as to leave a small axial opening inthe base of the cup'Bl or it may be ad' vancedonlyto, the point where the base of the cup B is very thin as shown in Fig. 7.

Fig. 8 illustrates, more or less diagrammatically, the method of extruding a hollow rod section, or blank, in which the grain is longitu'dinal of the rod. In this figure, Da represents an extrudin die, Is the hydraulic ex- 2 a mass of hot copper and B the resultlng tubular rod. Fig. 9 represents a section of this blank on a larger scale.

Fig. 10 illustrates the operation of extruding ythe blank into the form of a thin tube ladapted for radiator purposes or other uses. Inthis figure, D* represents the die, P* the extruding lunger, and T the resultinv tube. With the p unger P4 retracted the blark (for example th'e blank B of Fig. 7 or the blank B of F ig'. 9) isl placed in the die D4 and the plunger P4 is caused to strike it a sharp blow which squirts or extrudes the metal through the restricted annular orifice formed between the lip at the bottom of the die cavity and the reduced diameter extension, or former, on the end of the plunger P". This orifice gives the shape to the tube which then projects or hangs therefrom by the unextruded portion, or flange, still remaining 'in the die cavity. It will be understood that the extrusion is done the metal in a cold orA normal temperature and that the blank is flooded with oil at u `the moment of plunger impact. Thefextru sion operation may be carried on in any suitable apparatus, such for exampleas that shown in Hooker Patent No. 918,154 and such apparatus is commonly used in an-ordinary crank type press running at a speed of about 120 operations a minute, as customary for the Yimpact extrusion process. The blank, when ready for introduction into the extrusion die is shaped to fit the same snugly Aand the indentationtherein is carefully made so as to be central of the blank and to fit the former on the extruding plunger. Preferably the copper in the blankis of the grade known as electrolytic, althou h the process is applicable to any metal which offers substantially the' same resistance to cold extrusion as coppor and copper alloys. If it is desired to' make an open end tube from ac'losed bottom cup blank such as shown in Fig. plunger P4 may be pointed to puncture the base of the blank before extrusion begins.

After the plunger' P2 has made its stroke into the position shown in Fig. 10, it is retracted and a trimming plunger such as shown at P5 in Fig. 11, is advanced into the die D2. The plunger P5 hasV an annular shoulder, G which severs the flanged upper end of the-tube to trim and release the tube T, the severed angebeing carried out of the die by the shoulder G as the plunger P5 is retraeted. f i

The resulting tube T shown in Fig. 12 is extremely thin and at the same time stron g and uniform. In the case of radiatpr -tubesfor example, the tubes are commonly .268 inches in diameter and 4have a wall thickness of .006 inch. Such tubes can not be commercially .produced from sheet stock by cold impact extrusion as far as I am aware. For the purposes of illustration it has been necessary to show the walls of the tubes disproportionately thick. They are commonly about nine and a half `inches long and for automobile radiators they are then cut in two or more sections.

The indenting dies D5 and Dl shown in Figs. 13 and 14 have opposing semi-cylindrical recesses in which are provided indenting die el'ements a, b, c and d, these die elements being distributed both axially and circumferentially of the recesses. FigaV 15 shows an effective distribution of these dieelements, it

7, the forward end of being understood that the indentations pro-v the tube, the semi-cylindrical recesses engag- A ing the tube on all sldes of each die element to prevent the tube from being-distorted or collapsed. After the die elements have been rfully advanced, so that they entirely surround the tube, end formin plungers P". and Pfare advanced Vinto the en s of the tubes, the plungers havin hexagonal ends adapted to cooperate w1th hexagonal dies Bland D8 to hex the ends of the tubes. Inv this operation die elements a, b, c and d, which are intruded into the Walls of the tube, hold the tube against longitudinal movement, thereby insuring that the tube is hexed the salne axial distance at both ends. l

Figs. 17 and 18 illustrate the resulting tube T having nthe hexed ends H and the baffle indentations a', b', o anda?. By forming the tubes as herein described, these indentations can be formed uniformly and Without cracking or deforming the tubes.`

yof a hollow rod, cutting olf a section of the rod to form a hollow cylindrical blank, and extruding the unheated metal longitudinally of the blank intothe form of a thin t'ube.

3. The method of making metal tubes which comprises forming a rod by causing a body of metal when cold to flow longitudinally of the axis of the rod, cutting a section from the rod to form a blank, and causing the unheated metal of the blank to flow longitudinally of said axis into the form ofa tube.

4.. The method of making radiator tubes which comprises flowing metal into the form of a tube from a. blank having substantially parallel grain throughout, the flow being lon-v gitudinal of the grain of the blank, and inp denting the tube transversely of the grain.

y 5. The method of making radiator tubes which comprises extruding metal into the form of a tube ironia blank having substantially parallell grain throughout, the extrusion being longitudinal ofthe grain of the blank, and forming bales in the tube by indenting thewall of the tube transversely of the grain.

6. The improvement in the-art of making` v tubes by cold impact extrusion out of copper, which consists in making a copperv blank with longitudinal grain parallel to the axis of said blank and then subjecting said blank, unheated, to the impact of an extruding plung- `erV in the direction of said axis and thereby extruding the metal through an annular orifice.

'7. The process of making tubes which comprises as steps forming a cylindrical rod of eleetrolytic copper of substantially homogeneous character and having its grain running parallel to its axis, cutting said rod transversely to form a cylindrical blank,

axially indenting one end of the blank, placing the blank in the die of an extruding press with the indented end of the blank opposed tothe press plunger, and actuating the plunger to extrude the blank in an axial direction into a. thin Walled tube. v

. Signed by me at Lowell, Mass., this 17th day of November, 1922.

WILLIAM J. ROBINSON.

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