US2675049A - Process for the manufacture of tubular l's - Google Patents

Description

C. J. MARTIN April 13, 1954 PROCESS FOR THE MANUFACTURE OF TUBULAR ELLS 2 Sheets-Sheet 1 Filed Aug. 31, 1946 Nil. 45

rllll mms\ INVENTOR C2 ma/ MART/N C. J. MARTIN April 13, 1954 2 Sheets-Sheet 2 Filed Aug. 51, 1946 m m H NM 1 in M V. B a 0 M 5 I wwf/ w Patented Apr. 13, 1954 PROCESS FOR THE MANUFACTURE OF TUBULAR L S Clyde J. Martin, Bradford, Pa., assignor to Dresser Industries, Inc., Cleveland, Ohio, a corporation of Pennsylvania Application August 31, 1946, Serial No. 694,324

The present invention relates to the manufacture of tubular L's, the term L" being used generically to comprise not only ninety degree turns, but also turns of other angles, for example forty-five degree Us or reverse bends.

Many methods have been used for forming L's, among which are: bending a blank of pipe or tubing around an external mandrel to any desired angle; drawing the tubing over an internal mandrel having eccentric portions to simultaneously bend and expand the tubing into the desired shape; using various combinations of external dies and internal mandrels such as bending the blank by external dies while simultaneously moving internal dies within the blank; forcing a straight piece of tubing in an endwise direction through an external die having a curved passageway; and using an internal segmented mandrel to support and shape the interior of the blank while forming the exterior of the blank between opposed dies as disclosed in my copending application Serial No. 593,931, filed May 15, 1945, now Patent No. 2,528,315.

Among the disadvantages of the prior methods is the large amount of power required to form the blank into the desired shape. In the prior methods, the forming is done in presses which are of large size in proportion to the size of the L and are comparatively slow in operation. Another. disadvantage in the use of the prior methods is that the L may be buckled, wrinkled or collapsed during the forming of the L.

The present invention aims to overcome the foregoing disadvantages by providing an improved method of forming tubular Us. By this method a short radius tubular L is formed from a straight blank of tubular stock in three steps or operations. In the first operation the straight blank of cylindrical stock is flattened to a blank of generically elliptical cross section. The term ellipticaP' or "obrotund is used herein to mean not only true elliptical shapes, but also to include shapes approximating a pure ellipse such as an oval shape, all having a generally arcuate edge and in which one principal axis is longer than any other axis. The first step may be performed, for example, by passing the blank between opposed rollers of suitable cross section, by pressing the blank between opposed flat surfaces. or preferably, by pressing the blank be tween opposed die sections cooperating to form a die cavity straight in longitudinal section and elliptically shaped in cross section. In the second operation the straight elliptically shaped blank is curved into an elliptically shaped L of the desired radius. This step is performed by position- 3 Claims. (c .15s 4s ing a segmented mandrel of elliptical cross section in the elliptical blank and pressing the blank with the mandrel therein between opposed die sections having cooperating die cavities corresponding in contour to the shape of the desired L. In the third or finishing operation the elliptically shaped L is formed into an L of circular cross section. This step may be performed by passing the elliptically shaped L between opposed rollers, by pressing the L between opposed fiat surfaces, or preferably, by pressing the blank between opposed die sections having cooperating die cavities corresponding in shape to the desired L.

The methods in accordance with the invention are advantageous in that bending of the L is accomplished more easily with less distortion of the wall section. Buckling or wrinkling is eliminated because of the comparatively small differences in radius between the inner and outer surfaces of the elliptical blank as compared with the larger difierences in radius between the inner and outer surfaces of a cylindrical blank. The L's produced by the present method are accurately formed and are free of wrinkles, radius errors and other imperfections.

An object of the present invention is to provide a more economical method of forming tubular Us The economy results from the reduced power requirements in the bending operation. This is of particular importance in forming US of short radius in which larger amounts of power are required than in the making of Us of longer radius.

Another object of the invention is to provide a method of forming Ls with lesser danger of buckling, wrinkling or collapsing of the blank during the forming operation. This is particularly important in the forming of Us of short radius and having relatively thin walls. By the method of the invention, the stresses on the blank during the bending operation are materially reduced.

A further object of the invention is to provide a method of forming tubular L's which is particularly advantageous in cold forming of the L and makes it possible to use cold forming in many instances where hot forming would otherwise be necessary. While the method of the invention is particularly useful in this respect, it is not to be limited to cold forming, as in the forming of L's beyond certain limits in diameter or wall thickness, or in the forming of Us or certain materials, the heating of the blank maybe desirable.

Apparatus for carrying out the method in acoperating dies for bending an elliptical blank in accordance with the invention, a. blank being shown in position in the open die and a mandrel being shown in theblank.

Fig. 3 is a, view similar to Fig. 2 but showing the dies closed and the blank formed into an L.

Fig. 4 is a plan view of the mandrel, the sections of which are shown separated for the sake of clarity. Fig. 5 is a cross section. through the mandrel taken along the line 5-5 of Fig. 4.

Fig. 6 is a cross section through the mandrel taken along the line 6-5 of Fig. 4.

7 is a plan View of the two sections, of a finishing die laid side by side with the .die cavities of both sectionsfacing up. J

- Fig. 8 is. a cross sectional-vi w of the finishing dies in closed position with the formed L therein, the section being taken along the line 8-% of Fig. '7.

Fig. 8a is a section like Fig. 8 but showing a modification, corresponding parts being designated by the same reference numbers as Fig. 8 with the addition of 100. V

Fig; 9 is a side view and end view of a blank before forming.

Fig. 10 is a side View and end view of a blank after the first forming operation in which the blank has been given an elliptical cross sectional shape.

Fig. 11 is a side view and end'view of a blank after it has been formed into an elliptically shaped L of the desired curvature or radius.-

Fig. 12 is a side view and end view of an L of circular cross section after it has been formedby the finishing operation. 5

7 Referring to the drawings there is shown in- Figure 1 a cross'sectional viewof an elliptical forming die -10 which is used to form a straight cylindrical blank l2 (Fig. 9) intoa straight blank of elliptical cross section i3 (Fig. 10) which,- in turn, is formed'in bending dies 51 and 52 (Figs. 2 and3) into a'curved L [5 or elliptical cross-section (Fig.1l). The elliptical L I5 is then formed in finishing dies it into an L of circular cross section I? (Fig. 12).

The ellipticalfonning die l0 (Fig. 1) comprisesa pair of cooperating sections 29 and 2! having cooperating-die cavities 22 and 23 which together form a cavity 25 having a contour which is straight along its longitudinal axis and elliptically shaped in cross section. V V I It has'been foundpreferable inpracticing the method of the invention, to form the cavity of the forming die with a cross section in which the minor axis is fifty percent to seventy-five percent of the major axis, although these limits may vary depending upon the various possible combinations of wall thickness, diameter and material of the blank'and radius of the L; It is understood, however, that the elliptical forming die it may not be necesary in all cases, it being possible to fornrthe elliptical blank l3 (Fig. 10) by applying the cross section of the members is in the'line' 4 a force approximately perpendicular to the longitudinal axis of the blank, such as by applying pressure to blank I2 between flat opposed surfaces, or by passing the blank between opposed rollers of suitable cross section.

Figs. 2 through 6 illustrate apparatus which is utilized in performing the second or bending operation in accordance with the invention. Referring to Fig. 2, there is shown a segmental mandrel ordie of elliptical cross-section 56 in placewitliin'anelliptical blank l3 in position between two opposed die sections 5! and 52 having -c oope'r-ating die cavities which together form a cavity corresponding in contour to the dsired elliptical L. The upper die section it is pro vided on. its lowerfaoe with a die cavity 53 which is approximately semi-elliptical in cross-section and curved to the radiusof the desired L. in longitudinal section. For convenience of manufacture, the diemay be made up of a pluralityof parts removably secured to a base portion 55 b means of bolts 56 or the like.

The lower die section 52 has a die cavityfid complementing the die cavity 53 to form a cavity corresponding in contour to the desired elliptical L. The lower die section may also be made up oi'a plurality of parts removably'secured to a base portion 5'! by means of bolts 58 or the like.

The die sections may be moved together to form the blank by any suitable means such as a hy draulic press. The upper and lower die sections cooperate with the segmental mandrel to form a curved L of elliptical cross-section. V

The segmental mandrel 50 (Fig. 4)- which cooperates with the opposeddie-sections in formin'g the-blank to the desired shape comprises a plurality'of sections which are pivoted relative to one another to form-an articulated structure. The mandrel conforms to the inner surface of the blank and 'afiords substantially continuous support throughout the portion acted upon by the die. The mandrel 50 comprises a plurality of spaced end sections 62 and53 and an intermediate or central section 64. The end sections are substantially straight and are elliptical in crosssection, asshown in'F'ig. 5, so that the mandrel will fit into the elliptical blank l3 snugly without binding The intermediate or centralsection 6 3 is elliptical in central cross section, the outer portion being a cuate or curved longitudinally corresponding to the curvature of the desired L while the inner-portion is straight longitudinally. The section thus has a surface-of double curvature. erably split along an inclined plane indicated,

for example by the line 65 to facilitate removal from the L. The ends of the central section are cut off at an angle, thus forming l -shaped ends 66 and 6! which are received in V-shaped recesses 68 and 69 in the end sections 62 and 63.

. In forming an elliptical blank intoan elliptical L with the apparatus shown in Figs. 2th'rough 6,

a straight blank [3 (Fig. 10) is positioned inthe cavity of the opposeddies and the-segmental mandrel 50 is positioned-in the blank, as shown in Fig. 2, so that the minor axis of the ellipse of of action of the dies. The die sections are then brought together by the press. 7 of the mandrel 50 permits itto bend as the blank is progressively formed by the cooperation of V the forming die sections 5! and 52 and the elliptical'mand'rel 50, the mandrel affording studport to substantially the entire inner surface-oi the blank and corresponding-withthe-die sections The central section 84' is"p ref-' The articulation in the forming operation. The straight end sec tions of the mandrel maintain the ends of the blank straight and thus a tubular L may be formed in accordance with this method, having straight ends of any desired length.

After the blank has been formed into the elliptical L, as described above, the finishing die 16 (Figs. 7 and 8) is used for forming the L of elliptical cross section into an L of circular cross section. The die is divided into two halves or sections 36 and 31, which are similar but op-' posed to one another, the line of division being in the plane-of the longitudinal curvature of the formed blank or L. The cooperating die sections 3E5 and 31 have opposed die cavities 38 and 39 which together form a cavity corresponding in shape to the shapeof the completed L. The central portion of each die cavity is arcuate or curved in a longitudinal direction, corresponding to the desired curvature of the L while the end portions of each die cavity are straight, being tangential to the curved central portion. Each of the dies is shown as made up of a plurality of parts or elements removably secured to base plates ii) and ll, for. example by suitable screws 42 or other retaining means. The straight portions of the die cavities can be of any desired lengths. Means is provided for forcing the dies toward one another to operate on ablank positioned in the die cavity. For this purpose the dies are shown provided with suitable lugs GB for adjustably securing the dies to the platens of a suitable press in proper alignment and operative position relative to one another.

In some instances, for example when forming Ls of particularly resilient material, it may be found desirable to perform more work on the blank in the finishing operation, in order to compensate for the amount the metal springs back and thereby produce a more accurately formed L. This result is accomplished as illustrated in Fig. So by making the cooperating die section cavities 38 and 139 with an elliptical cross section, the minor axis of the cross section of the die cavity being perpendicular to the minor axis of the cross section of the curved elliptical L prior to the finishing operation.

In forming a tubular L with the apparatus shown in Figs. 1 to 8, a straight blank of tubular stock i2 is positioned in the elliptical forming die Hi. It is preferred in the case of short Ls that the edges be precut with inclined ends, as shown in Fig. 9, as by using a blank with an edge of the proper angle the finished L will have I square ends. Thus, there will be no material wasted in finishing the edges. The proper angle for the edge of the straight blank may be determined by experience, as it varies with different diameters, lengths and angles of the Us. If an inclined edged blank is used, it is positioned in the forming die so that the shortened side faces the top section of the die (Figure 1). Pres- Slll'G is then applied, forming the elliptically.

shaped blank 13. The segmental mandrel 50 is positioned in the blank and the blank is placed between the bending dies 51 and 52. The blank is positioned with its shortened side facing the die 55. Pressure is then applied forming the curved elliptical L IS. For some purposes the L may now be considered a finished product. However, as it is generally required that the L have a circular cross section, a further operation is necessary. The elliptically shaped curved L is is then positioned in the finishing die l6 and the two sections of the die are moved toward one another in a direction transverse to the.

blank and approximately perpendicular to the plane of curvature. The direction of movement of the finishing diesrelative to the movement of the blank is thus approximately at right angles.

to the direction of movement of the elliptical forming die. The operationof the finishing dies changes the cross section of the curved blank from an elliptical shape to a circular shape. While the longitudinal curvature remains approximately the same, any slight deviation is corrected.

While certain forms of apparatus for carrying out my invention have been described, it will be understood that the invention is in no way lim-.

ited to this specific apparatus or to the particular steps described, but is subject to various modifications and variations. For instance, a greater number of dies may be employed, each set of dies performing a portion of the forming operation.

The method is equally applicable to tubular Ls, of circular or other cross section, and the straight.

tubular blank may be either square ended or provided with inclined ends as shown in Figure 9. Still other embodiments and variations of the invention within the scope of the appended claims will be obvious to persons skilled in the art.

What Iclaim and desire to secure by Letters Patent is:

l. A method of forming a tubular L. of circular cross-section from a straight cylindrical blank, which comprises providing a cylindrical blank with an elliptical crossesectional shape, positioning in the elliptical blank an articulated mandrel of elliptical cross-section and having straight longitudinal end portions and a central portion having an arcuate lower surface and. a substantially straight upper surface in a longitudinal porting the end portions and central portion of.

said elliptical blank both interiorly and exteriorly and thereby maintaining the elliptical cross-section, removing the blank from between said dies and removing said mandrel from the blank, placing the blank thus formed between dies having cooperating die cavities corresponding to the shape of the finished L and moving said dies toward one another to impart to said blank a substantially circular cross-section.

2. A method of forming a tubular L from a straight cylindrical blank, which comprises forming a straight blank with an elliptical crosssectional shape, pressing a central portion of one side wall of said elliptical blank between a rigid die surface disposed inside the blank, said surface being convexly arcuate in a longitudinal direction and convexly semi-elliptical in cross-section and a mating rigid die surface outside the blank, said outer die surface being concavely arcuate in a longitudinal direction and concavely semi-elliptical in cross-section, the pressure being exerted in a direction substantially perpendicular to the longitudinal axis of the elliptical blank and perpendicular to the major axis of the elliptical cross-section of the blank, the cross-sectional elliptical curvature of said inner and outer die surfaces being substantially the same as the crosssectional curvature of the inner and outer surfaces respectively of said elliptical blank, simultaneously pressing the opposite side wall of said elliptical blank in the same direction between a rigid die surface inside the blank, said latter surfaces being substantially straight in a longitudinal direction and semi-elliptical in cross-section and an opposed rigid die surface outside the blank which is concavely arcuate in a longitudinal direction and concavely semi-elliptical in cross-section and simultaneously pressing each end portion of said elliptical blank between an inner rigid die surface which is rectilinear in a longitudinal direction and convexly elliptical in cross-section and opposed outer rigid die surfaces each of which is rectilinear in a longitudinal direction and concavely semi-elliptical in cross-section and thereafter pressing the blank thus formed between opposed rigid die surfaces each. of which in an axial direction is arcuate with straight end portions and in cross-section is substantially semi-circular, the last mentioned pressing being in a direction perpendicular to the minor axis of the elliptical cross-section of said blank.

3. A method of making a tubular L from a straight cylindrical blank of deformable material having inherent resiliency, which comprises forming a straight blank with an elliptical crosssectional shape and with ends out on at symmetrically opposite anglesso that the end edges lie approximately in planes which converge at a point on an extension of the minor axis of the central cross-section of said blank, the blank thus having a longer side and a shorter side, pressing a central portion of the longer side of said elliptical blank. between a rigid die surface disposed inside the blank, saidsurface being convexly arcuate in a longitudinal direction and convexly semi-elliptical in cross-section and. a mating rigid die surface outside the blank, said outer die surface being concavely arcuate in a longitudinal direction and concavely semi-elliptical in.cross-section, the pressure being exerted in a direction substantially perpendicular to the longitudinal axis of the elliptical blank and perpendicular to the major axis of the elliptical cross-section of the blank, simultaneously pressing the shorter side of said elliptical blank in the same direction between a rigid die surface inside the blank, said latter surface being substantially straight in a longitudinal direction and semi-elliptical in cross-section and an opposed rigid die surface outside the blank which is concavely arcuate in a longitudinal direction and concavely semi-elliptical in cross-section and simultaneously pressing each end portion of said elliptical blank between an inner rigid die surface which is rectilinear in a longitudinal direction and convexly elliptical in cross-section and opposed outer rigid die surfaces each of which is rectilinear in a longitudinal direction and concavely semi-elliptical in cross-section and thereafter pressing the blank thus formed between opposed rigid die surfaces each of which in an axial direction is arcuate with straight end portions and in cross-section is semi-elliptical with the minor axis of said semi-elliptical surface perpendicular to the minor axis of the elliptical cross-section of the blank, the last mentioned pressing being in a direction perpendicular to the minor axis of the elliptical cross-section of said blank and being continued slightly beyond the point at which the cross-section of the blank becomes circular so that due to the inherent resiliency of the material the blank springs back to circular cross-section when pressure is relieved.

teferences Cited in the file Of this patent UNITED STATES PATENTS Number Name Date 953,253 Brinkman Mar. 29, 1910 1,136,364 Powell Apr. 20, 1915 1,225,788 Dies May 1 1917 1,875,954 Taylor Sept. 6, 1932 1,888,837 Schutt Nov. 22, 1 32 2,044,322 Oliver June 16, 1936 2,179,530 Townsend et al. Nov. 14, 1939 2,267,774 Wall Dec. 3 1941 2,336,611 Hill et al Dec. 14, 1943 2,413,547 Davidson -1. Dec. 31, 1946 2,449,423 Timmons Sept. 4, 48 2,528,315 Martin Oct. 3 1950 FOREIGN PATENTS Number Country Date 5,019 Great Britain 1 1 ,278 Great Britain Mar. 29, 1923 570,251 Germany Feb. 13, 1933 469,004 Great Britain July 16, 1937

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