Method for making seamless wheel rims

A method for forming seamless tubular workpieces, such as vehicular wheel rim components. In the method, a flat circular blank having a central aperture is expanded into the interior of a hollow mandrel using a mushroom-shaped spinning roller. In this expansion operation, the blank is caused to take on a tubular shape having an exterior contour which conforms to the interior contour of the hollow mandrel.

FIELD OF THE INVENTION
 This invention relates generally to methods for forming metal workpieces
 and, more particularly, to methods for forming seamless tubular
 workpieces, such as wheel rim components.
 BACKGROUND OF THE INVENTION
 Seamless aluminum wheel rims for automobiles and other vehicles have become
 very popular. Such seamless wheel rims are generally held to be both
 structurally and aesthetically superior to conventional wheel rims.
 Unfortunately, previously-known methods of making seamless wheel rims are
 unduly expensive, because such seamless wheel rims are either extruded or
 machined using external mandrels which produce large amounts of scrap
 metal waste.
 Accordingly, there is a need for an improved method of forming seamless
 wheel rims without the problems associated with prior art processes.
 SUMMARY
 The invention satisfies this need. The invention is a method and an
 apparatus for forming a hollow annular work piece, such as a wheel rim
 component. The method comprises the steps of (a) providing a hollow
 mandrel with a forward end, a rearward end, a longitudinal axis and an
 internal surface typography, the forward end having a substantially
 circular cross-section with an internal diameter, the internal surface
 typography being the reverse of the desired typography, (b) providing a
 disc-shaped metallic blank having a centralized aperture, the centralized
 aperture having a center, (c) securing the blank to the forward end of the
 mandrel such that the center of the centralized aperture is aligned with
 the longitudinal axis of the mandrel, and (d) rotating the mandrel about
 the longitudinal axis of the mandrel while pressing the blank against the
 interior surface of the mandrel with a spinning roller, the spinning
 roller having a smooth rounded surface, the pressing of the blank against
 the interior surface of the mandrel being continued until the blank takes
 on a hollow annular shape having an external surface with the desired
 typography.

DETAILED DESCRIPTION
 The following discussion describes in detail one embodiment of the
 invention and several variations of that embodiment. This discussion
 should not be construed, however, as limiting the invention to those
 particular embodiments. Practitioners skilled in the art will recognize
 numerous other embodiments as well.
 The invention is a method and apparatus for forming a hollow annular
 workpiece 20. The apparatus 10 comprises a hollow mandrel 12, a mandrel
 retaining assembly 14, a spinning roller 16 and a spinning roller carriage
 18.
 The invention can be used to manufacture hollow annular workpieces 20, such
 as wheel rim components 22. A typical wheel rim 24 is illustrated in FIGS.
 1 and 2. The wheel rim 24 illustrated in FIGS. 1 and 2 is commonly termed
 a "three-piece" wheel rim because it comprises a forward moiety 26, a
 rearward moiety 28 and a center plate 30. Both the forward moiety 26 and
 the rearward moiety 28 have end flanges 32 to facilitate their connection
 to each other and to the center plate 30. The three pieces are typically
 fastened together with bolts 34 (as illustrated in FIG. 2) or are welded
 together to form a completed wheel rim 24. The apparatus of the invention
 10 can be used to manufacture the forward moiety 26 of the wheel rim 24
 and the rearward moiety 28 of the wheel rim 24. In another embodiment of
 the invention, the apparatus of the invention 10 can be used to
 manufacture one-piece integral combinations 36 of the forward moiety 26
 and the rearward moiety 28. Such integral combinations 36 can be assembled
 with a center plate 30, usually by welding. Such combination 36 is
 commonly termed a "two-piece" wheel rim. The forward moiety 26, the
 rearward moiety 28 and the integral combination 36 of the forward and
 rearward moieties 26 and 28 are referred to herein as "wheel rim
 components 22." All such wheel rim components 22 have an external surface
 38 with a desired typography.
 The mandrel 12 is most conveniently seen in FIGS. 6 and 7. The mandrel 12
 comprises a forward portion 39 having a forward end 40, a rearward portion
 41 having a rearward end 42 and a longitudinal axis 44. The forward end 40
 has a substantially circular cross-section with a forward end internal
 diameter between about 10 inches and about 24 inches. The rearward portion
 41 is also substantially circular with a rearward portion internal
 diameter. In a typical embodiment, the mandrel 12 is made from steel.
 The internal surface 46 of the mandrel 12 has an internal surface
 typography which is the reverse of the desired typography of the workpiece
 20. In some embodiments, the internal surface typography of the mandrel 12
 defines a smooth right circular cylinder. In other embodiments, the
 internal surface typography can be a non-smooth, non-cylindrical surface,
 termed herein as a "contoured surface."
 The mandrel retaining assembly 14 allows the mandrel 12 to be rotated at a
 rate of rotation which is typically between about 100 rpm and about 800
 rpm, most typically between 400 rpm and about 500 rpm.
 The spinning roller 16 is disposed proximate to the forward end 40 of the
 mandrel 12 on a spinning roller shaft 48. The spinning roller 16 is
 rotatable by the spinning roller shaft 48 at rates of rotation typically
 between about 50 rpm and about 1000 rpm, most typically between about 300
 rpm and about 500 rpm. The spinning roller shaft 48, in turn, is retained
 on the spinning roller carriage 18. The spinning roller carriage 18
 maintains the spinning roller shaft 48 in a spinning roller plane 50 which
 contains the linear extension 52 of the longitudinal axis 44 of the
 mandrel 12. Typically, the spinning roller plane 50 is a substantially
 horizontal plane, although it can also be a vertical plane or a plane
 disposed neither horizontally or vertically.
 The spinning roller carriage 18 is moveable between a forward most
 position, wherein the spinning roller 16 is disposed within the hollow
 mandrel 12, and a rearward most position wherein the spinning roller 16 is
 disposed external of the mandrel 12. The spinning roller carriage 18 is
 also capable of moving the spinning roller shaft 48 laterally within the
 spinning roller plane 50. Preferably, the spinning roller carriage 18 is
 capable of "canting" the spinning roller shaft 48 with respect to the
 linear extension 52 of the longitudinal axis 44 of the mandrel 12. In a
 typical embodiment, the spinning roller shaft 48 can be canted to angles A
 between about -5.degree. and about +30.degree. with respect to the linear
 extension 52 of the longitudinal axis 44 of the mandrel 12.
 In the embodiment illustrated in the drawings, the spinning roller carriage
 48 includes a pair of longitudinal opposed track members 54 for allowing
 the movement of the spinning roller 16 between the forward most position
 and the rearward most position. The spinning roller carriage 48 further
 comprises a pair of lateral track members 56 for allowing movement of the
 spinning roller shaft 48 in opposed lateral directions.
 The apparatus 10 is capable of spin forming disk-shaped metallic blanks
 into the completed annular workpieces 20. FIG. 4 illustrates a typical
 disk-shaped metallic blank 58. The blank 58 has a centralized aperture 60
 with a center 62. The blank 58 can be substantially flat across its entire
 diameter (as illustrated in FIG. 4) or it can have a non-flat perimeter
 64, such as illustrated in FIGS. 5, 6 and 7. Such non-flat perimeters 64
 are typically provided in a preliminary machining or forging operation.
 The blank 58 can have a substantially uniform thickness, but this is not
 necessary. In some applications, the blanks 58 are non-uniform in
 thickness. In the formation of wheel rim components 22, the thickness of
 the blank 58 is typically between about 0.2 inch and about 1.5 inches.
 The blank 58 is typically made from a material comprising aluminum or
 aluminum alloy. In many applications, the blank 58 will consist
 essentially of aluminum or aluminum alloy. The apparatus 10 and the method
 of the invention can also be used with other metals. The centralized
 aperture 60 is typically circular and has a diameter between about 4
 inches and about 16 inches. In most applications, the optimum diameter of
 the centralized aperture 60 will depend upon the thickness and the
 ductility of the blank 58 and upon the thickness of the workpiece 20 to be
 formed from the blank 58.
 Blanks 58 made from aluminums or other materials having high elongation
 characteristics are often preferred in the invention because such
 materials are less likely to crack during fabrication.
 The blank 58 can be conveniently manufactured from inexpensive cast
 material, such as 7-inch diameter billets of cast material. Such cast
 material can then be machined into a substantially planar shape using, for
 example, a rotary forge.
 The spinning roller 16 has a smooth, rounded surface 66, such as the
 "mushroom-shaped" spinning rollers 16 illustrated in the drawings.
 In the method of the invention, hollow annular workpieces 20 having an
 external surface 38 with a desired typography are formed in the following
 steps. A disk-shaped metallic blank 58 is secured to the forward end 40 of
 the hollow mandrel 12 using a mechanical clamp 68 or equivalent device.
 The center 62 of the centralized aperture 60 of the blank 58 is aligned
 with the longitudinal axis 44 of the mandrel 12. The mandrel 12 is then
 rotated about the longitudinal axis 44 of the mandrel 12 while the
 spinning roller 16 (rotating on the spinning roller shaft 48) is slowly
 pressed against the rotating blank 58. The initial pressure applied to the
 blank 58 by the spinning roller 16 is made proximate to the centralized
 aperture 60 of the blank 58. Using the forward/backward and lateral
 movement of the spinning roller carriage 18, the spinning roller 16 can be
 moved forward and rearward as well as left and right within the spinning
 roller plane 50. Also, the spinning roller shaft 48 can be canted with
 respect to the linear extension 52 of the longitudinal axis 44 of the
 mandrel 12, so that the pressure of the spinning roller 16 on the blank 58
 can be applied obliquely.
 The entire operation can, in many instances, be carried out in a single
 "pass." In other operations, two or more passes are used.
 The operation is continued until the blank 58 is formed into a hollow
 annular workpiece 20 having an external surface 38 with the desired
 typography.
 Typically, the blank is at ambient temperature during the operation. With
 certain metals and with certain thicknesses of metals, the operation is
 preferably carried out after the blank has been preheated up to about
 650.degree. F.
 FIGS. 6A and 6B illustrate an embodiment of the invention 10 wherein a
 rearward moiety 28 of a wheel rim 24 is formed. The spinning roller 16 is
 pressed against the blank 58 until the centralized apertured 60 is
 expanded to substantially the same diameter as the rearward portion
 internal diameter and the blank 58 is expanded into an annular tubular
 configuration having a contoured external surface 38 which is the reverse
 of the internal contoured typography 46 of the mandrel 12. In the
 embodiment illustrated in FIGS. 6A and 6B, an end flange 32 is provided on
 the rearward moiety 28 by pressing the blank 58 against an annular stop
 ring 70 disposed within the mandrel 12.
 FIG. 7 illustrates another embodiment of the invention. In this embodiment,
 an integral wheel rim combination 36 is formed. In a most typical
 embodiment, the internal typography 46 of the mandrel 12 defines a smooth,
 right circular cylinder. The spinning roller 16 presses the blank 58
 against the internal typography 46 of the mandrel 12 until the blank 58 is
 expanded into an annular tubular configuration having a smooth exterior
 typography 38 in the shape of a right circular cylinder. Thereafter, the
 completed workpiece 20 is removed from the mandrel 12 and is machined in a
 separate post-invention step into the final configuration of the integral
 wheel rim combination 36, typically by spin forming or press forming.
 In an alternative embodiment, the integral wheel rim combination 36 can be
 wholly formed within the mandrel 12. In this embodiment, the mandrel 12
 must be separable along edges parallel with the longitudinal axis 44 so
 that the completed integral wheel rim combination 36 can be removed from
 the mandrel 12. In one such embodiment, the mandrel 12 is separable in
 "clam-shell" fashion. In another embodiment, the mandrel 12 is separable
 in "chuck-like" fashion.
 The invention 10 can be used to manufacture seamless wheel rims 24 in an
 efficient and far less expensive manner than methods and apparatuses of
 the prior art. The invention 10 is contrasted with methods and apparatuses
 110 of the prior art for manufacturing seamless wheel rims 24 as
 illustrated in FIG. 3. In such prior art methods and apparatuses 110, a
 substantially flat blank 158 is machined into a wheel rim component 22 by
 pressing the blank 158 against the outside typography 180 of an external
 mandrel 112. As can be readily appreciated, the flat blanks 158 used in
 such prior art methods must be considerable larger in diameter than blanks
 58 used in the invention 10. For example, in forming a 17-inch wheel rim
 24, a typical blank 58 used in the invention 10 is 19 inches in diameter,
 whereas a typical blank 158 used in prior art methods 110, such as
 illustrated in FIG. 3, would be about 221/2 inches in diameter. Since the
 circular blanks 58 and 158 in both cases are most conveniently cut from
 square sheets, it can be seen that the amount of waste material created in
 the preparation of a 221/2 inch diameter blank 158 is considerably more
 than that which results from the creation of a 19-inch diameter blank 58.
 Moreover, in methods of the prior art, the centralized aperture 160 of the
 blank 158 must be considerably larger than the centralized aperture 60 in
 blanks 58 used in the invention 10. Accordingly, the method of the
 invention 10 entails a second considerable savings stemming from less
 wasted scrap metal from the formation of the centralized aperture 60 of
 the blank 58.
 Having thus described the invention, it should be apparent that numerous
 structural modifications and adaptations may be resorted to without
 departing from the scope and fair meaning of the instant invention as set
 forth hereinabove and as described hereinbelow by the claims.