US3501939A - Apparatus for and method of forming long tangent elbows - Google Patents

Description

March 24, 1970 M. E. REMUS ET AL 3,501,939

APPARATUS FOR AND METHOD OF FORMING LONG TANGENT ELBOWS Filed Sept. 15, 1967 2 Sheets-Sheet 1 46 Inveniora mewmzffiems,

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APPARATUS FOR AND METHOD OF FORMING LONG TANGENT ELBOWS Filed Sept. 15, 1967 March 24, 1970 us ET AL 2 Sheets-Sheet 2 United States Patent O 3,501,939 APPARATUS FOR AND METHOD OF FORMING LONG TANGENT ELBOWS Melvin E. Remus, Park Ridge, and Joseph F. Staroba, Des Plaines, Ill., assignors to Taylor Forge Inc., Bellwood, III., a corporation of Illinois Filed Sept. 13, 1967, Ser. No. 667,502 Int. Cl. B21d 22/00 US. Cl. 72-343 8 Claims ABSTRACT OF THE DISCLOSURE A die having an arcuate cavity of circular cross section, and an arcuate mandrel of circular cross section disposed in the cavity in radially spaced relation. One end of a tubular blank is forced through the cavity and about the mandrel whereby to form an elbow at the end of the tubular blank to produce a long tangent elbow.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates generally to the forming of pipe and more particularly to apparatus for and a method of cold forming an elbow at one end of a tubular blank to produce a long tangent elbow.

Description of the prior art Heretofore, various techniques have been proposed for forming a tubular blank into an elbow. Apparatus of the prior art has in general comprised a die with an arcuate cavity, and an articulated mandrel extending into the cavity concentrically thereof. To form an elbow, a short tubular blank, while hot or in some cases cold, is forced lengthwise into the arcuate cavity and over the mandrel.

Elbows formed in the foregoing manner have a number of shortcomings. There occurs undesirable thinning in various portions of the elbow wall; there is a considerable variation in wall thickness throughout the elbow; and there is a substantial differential in thickness at the crotch and back wall of the elbow relative to the remaining wall areas. Furthermore, the techniques of the prior art, not only are deficient in regard to the forming of conventional elbows, but also are not readily adaptable to the forming of long tangent elbows.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a die having an arcuate cavity of circular cross section presenting an entrance and an exit. An arcuate mandrel of circular cross section is disposed in the cavity with one end terminating at the entrance and with the other end extending outwardly of the exit. The mandrel is allowed to float in the die cavity, but is prevented from being ejected, and is positioned lengthwise of the cavity, by means of reaction means which is spaced from the die and is engaged by the other end of the mandrel.

Preferably, ring members are disposed loosely in the cavity about the mandrel for positioning the latter radially, the radius of curvature of the centerline of the mandrel is greater than the radius of curvature of the centerline of the cavity, the diameter of the cavity increases slightly from the entrance to the exit, guide means projects from the die and is formed with a cylindrical bore that communicates with the entrance end of the cavity, and a cylindrical mandrel extension is disposed in the bore and has one end engaging the one end of the arcuate mandrel.

In operation, one end portion of a tubular blank is moved lengthwise through the cylindrical bore and over the cylindrical mandrel, and is then forced through the arcuate cavity and over the arcuate mandrel during which time the ring members are pushed outwardly of the exit end of the cavity. In this manner, an elbow is formed at one end of the tubular blank to produce a long tangent elbow. To complete the operation, the cylindrical mandrel is removed from the tangent and bore, the reaction means is removed, the arcuate mandrel is forced out of the elbow, and the resultant long tangent elbow is removed from the die and cylindrical bore.

As contrasted with prior art techniques, the apparatus and method of the present invention are especially adapted for forming or producing long tangent elbows. Also, with regard to the elbow portions of long tangent elbows formed in accordance with the present invention, thinning of the wall areas is minimized, greater uniformity in wall thickness is attained, and the differential in wall thickness at the crotch and back wall is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is an elevational view of a die assembly incorporating the principles of the present invention;

FIGURE 2 is a plan view of the die assembly of FIGURE 1;

FIGURE 3 is a sectional view, taken substantially along the line 3-3 in FIGURE 2, looking in the direction indicated by the arrows, and shows a tubular blank in position for forming; and

FIGURE 4 is a sectional view, corresponding generally to FIGURE 3, but shows the blank after it has been formed into a long tangent elbow.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is indicated generally by the reference numeral 10 a die assembly which includes a main die 12 and a die extension 14.

The die 12 comprises two opposed sections 16 and 18 which are provided with appropriately formed recesses that together serve to define an arcuate cavity 20 of circular cross section. The cavity 20 presents an entrance 22 opening through one side of the die, and an exit 24 with a flared mouth portion 26 opening through a second side of the die 12. The diameter of the cavity 20 preferably increases slightlyin the order of .001 inch per inch of length of the axis of the cavity 20from the entrance 22 to the exit 24. The die sections 16 and 18 are secured together in a conventional manner, either by bolts or by quick release clamp means, with the mating faces of the die sections lying in the plane of the centerline of the cavity 20.

The die extension 14 is in the form of a guide sleeve 28 having a cylindrical bore 30 with a diameter corresponding to that of the cavity 20 at the entrance 22. The sleeve 28 is provided with a flange 32 which is secured to the die 12, either by bolts 34 or by quick release clamp means, with the bore 30 communicating at one end with the cavity entrance 22. If desired, the die extension 14 may be split lengthwise into two parts, and each part may be formed integrally with the respective die sections 16 and 18.

Disposed in the cavity 20 is an arcuate mandrel or horn 36 adapted to be positioned with one end terminating at the entrance 22 and with the other end extending outwardly of the exit 24. The radius of curvature of the centerline of the mandrel 36 is greater than the radius of curvature of the centerline of the cavity 20, and the difference in radii of curvatures is about A inch for a cavity of 3 /2 inches in diameter. A cylindrical mandrel extension 38 is disposed in the bore 30. One end of the mandrel extension 38 engages the end of the mandrel 36 at the entrance 22 and is centered thereon by a central axial projection 40 that seats in a recess 42 in the mandrel 36. The mandrel extension 38 is allowed to tip, swivel or float relative to the mandrel 36, and the outer end is bevelled as at 44.

Arranged about the die 12 is a yoke assembly 46 comprised of a front reaction bar or plate 48, a rear bar or plate 50, spacer blocks 52, and tie-bolts 54 extending between and through the ends of the bars 48 and 50. The yoke assembly 46 is clamped about the die 12 and secured in position by nuts 56 threaded onto the ends of the tiebolts 54. In clamped position, the front reaction bar 48 is spaced from the exit 24 of the die 12 by the spacer blocks 52, and is engaged by the end of the mandrel 36 which extends outwardly of the exit 24. Thus, while the mandrel 36 is allowed to float in the cavity 20, it is prevented from being ejected, and is positioned lengthwise of the cavity, by means of the reaction bar 48. Also, ring members 58 and 60 (FIGURE 3) are preferably arranged loosely in the cavity 20 about the mandrel 36 for initially positioning the latter radially.

The above described die assembly is adapted to be positioned on the base 62, and beneath the ram 64, of a hydraulic press or the like. In forming a long tangent elbow, a tubular blank is prepared by cutting the tube to correct length and then cutting the leading end at an angle of approximately 30 degrees relative to the plane normal to the axis. The tubular blank is then coated, both interiorly and exteriorly, with a suitable lubricant such as a phosphate coating. The thus prepared tubular blank 66, as shown in FIGURE 3, is inserted in the bore 30 of the guide sleeve 28 with the short side aligned with the short side of the cavity 20. By means of the ram 64, the tubular blank 66 is forced downwardly, and the lower end portion thereof is first moved through the confined cylindrical space of generally annular cross section between the wall of the bore 30 and the mandrel extension 38 and is then forced through the confined elongated arcuate space of generally annular cross section between the wall of the cavity and the mandrel 36 to the position shown in FIGURE 4. As the lower end portion of the tubular blank 66 is forced through the cavity 20, the ring members 58 and 60 are successively engaged and pushed outwardly of the cavity exit 24. In this manner, the tubular blank 66 is formed with an elbow 68 at the end of a tangent 70 to produce a long tangent elbow.

While the elbow 68 is being formed, the floating mandrel 36 and mandrel extension 38 prevent the walls of the tube blank 66 from collapsing and seek their own location to accommodate variations in wall thickness as bending occurs, the slight increase in the diameter of the cavity 20 from the entrance 22 to the exit 24 accommodates movement of the lower end of the tubular blank 66 therethrough, and the differential in the radii of curvatures of the centerlines of the cavity 20 and the mandrel 36 allows for a differential in the wall thickness of the elbow 68 at the crotch and back wall thereof. In the latter respect, the radial width on the short side of the arcuate space occupied by the crotch of the elbow is greater than the radial width on the long side of the arcuate space occupied by the back wall of the elbow. By reason of the use of the floating mandrel 36 and mandrel extension 38, thinning of the wall areas of the elbow 68 is minimized, greater uniformity in wall thickness is attained, and the dilferential in wall thickness at the crotch and back wall relative to the remaining wall areas is reduced. While the elbow 68 illustrated in FIGURE 4 is a 90 degree elbow, it will be appreciated that the radius of curvature of the centerline of the cavity 20 may be varied to form elbows of different angles. Finally, the apparatus and method of the present invention is adapted for cold forming or producing long tangent elbows from tube blanks either of ferrous or non-ferrous material.

After the elbow 68 has been formed, the ram 64 is retracted, the mandrel extension 38 is removed from the .4 top of the guide sleeve 28, and the yoke assembly 46 is removed from about the die 12. Then, a series of balls, or any other suitable flexible pusher means, are inserted in the tangent 70 and forced, by any suitable pressure producing means, against the end of the mandrel 36 for pushing the latter out of the elbow 68 as indicated in dotted lines in FIGURE 4. Thereafter, the guide sleeve 28 is removed from the die 12 and the die sections 16 and 18 are separated so that the completed long tangent elbow may be removed. To prepare the die assembly 10 for forming another long tangent elbow, the die sections 16 and 18 are assembled together, the guide sleeve 28 is attached to the die 12, the mandrel 36 and ring members 58 and 60 are inserted in the cavity 20, the yoke assembly 46 is clamped about the die 12, and the mandrel extension 38 is inserted in the bore 30 of the guide sleeve 28. The die sections 16 and 18, the die extension 14, the horn 36, the horn extension 38, and the yoke assembly 46 may be arranged to be assembled and disassembled either manually or automatically.

While there has been shown and described a preferred embodiment of the present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. For use in forming a long tangent elbow, the combination of a die having an arcuate cavity of circular cross section presenting an entrance and an exit, an arcuate mandrel of circular cross section fioatingly disposed in said cavity with one end terminating at said entrance and with the other end extending outwardly of said exit, reaction means spaced from said die and being freely engaged in compression by said other end of said mandrel to position said mandrel lengthwise of said cavity, and ring members arranged loosely in said cavity about said mandrel for positioning the latter radially.

2. The combination of claim 1 wherein the radius of curvature of the centerline of said mandrel is greater than the radius of curvature of the centerline of said cavity.

3. The combination of claim 2 wherein the diameter of said cavity increases slightly from said entrance to said exit.

4. The combination of claim 3 including die extension means projecting from said die and formed with a cylindrical bore communicating at one end with and having the same diameter as said entrance, and further including a cylindrical mandrel extension disposed in said bore and having one end engaging said one end of said arcuate mandrel.

5. The combination of claim 4 wherein said mandrel extension is allowed to swivel relative to said arcuate mandrel.

6. For use in forming a long tangent elbow, the combination of a die having an arcuate cavity of circular cross section presenting an entrance and an exit, an arcuate mandrel of circular cross section floatingly disposed in said cavity with one end terminating at said entrance and with the other end extending outwardly of said exit, the radius of curvature of the centerline of said arcuate mandrel being greater than the radius of curvature of the centerline of said cavity, ring members arranged loosely in said cavity about said arcuate mandrel for positioning the latter radially, reaction means spaced from said die and being freely engaged in compression by said other end of said mandrel to position said mandrel lengthwise of said cavity, die extension means projecting from said die and formed with a cylindrical bore communicating at one end with and having the same diameter as said entrance, a cylindrical mandrel extension disposed in said bore and having one end engaging said one end of said arcuate mandrel, and said mandrel extension being allowed to swivel relative to. Said arcuate mandrel.

7. The combination of claim 6 wherein said die is comprised of two sections having mating faces lying in the plane of the centerline of said cavity, and wherein said die extension means is comprise of a guide sleeve secured to said die.

8. A method of forming a long tangent elbow comprising the steps of moving one end portion of a tubular blank lengthwise through a cylindrical bore in a die assembly and over an interior cylindrical mandrel, forcing the tubular blank through an arcuate cavity in the die assembly and over an arcuate mandrel positioned radially by ring members which are pushed from the arcuate cavity as the tubular blank progresses through the latter whereby to form an elbow at one end of the tubular blank to produce a long tangent elbow, removing said cylindrical mandrel from the tangent of said long tangent elbow, removing said arcuate mandrel from said elbow, and removing said long tangent elbow from said die assembly.

References Cited UNITED STATES PATENTS 454,186 6/1891 Rosenfield 72-343 5 1,908,373 5/1933 Loepsinger 29157 1,996,838 4/1935 Snell 72356 2,936,019 5/1960 Miller 72-343 FOREIGN PATENTS 10 48,289 6/1966 Germany.

RICHARD J. HERBST, Primary Examiner US. Cl. X,R. 15

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