1. Field of the Invention
The invention relates to a method of forming a cup-shaped metal object of special cross sectional configuration from a flat sheet metal disc. More particularly, the invention relates to the method of roller spinning a dynamically balanced cup-shaped metal stage blank for subsequent use in spinning a V-grooved pulley, in which a reversely angled conical flange is roller spun in the disc blank adjacent a cylindrical side wall, which conical flange forms a portion of final V-groove of a spun pulley.
2. Description of the Prior Art
Many procedures have been used and are known for the formation of cup-shaped metal blanks from flat sheet metal discs, which blanks in turn are used in the manufacture of V-grooved pulleys, or similar articles. Many of these procedures involve stamping, drawing and slitting operations, examples of which are shown in U.S. Pat. Nos. 1,766,098, 2,330,228, 2,493,053 and 3,080,644.
Cup-shaped stage blanks for V-grooved pulleys produced by such prior stamping and drawing methods are not balanced dynamically since the blanks are formed by a series of progressive die steps on a non-rotating blank.
Other procedures and apparatus have been known for directly spinning cup blanks and V-groove pulleys from flat metal discs for producing dynamically balanced V-grooved pulleys, as shown in U.S. Pat. No. 1,728,002. The equipment and dies required, however, involves headstock dies with sliding and movable members which considerably increase the cost of pulley manufacture with such apparatus.
Likewise, these dies require means on the machine for controlling movement of the disc components which contribute to the increased costs and involve maintainence problems. Also, considerable tooling costs are involved to provide various dies from which to produce a variety of cup blanks, since a different die size and configuration is required for each type of cup blank produced.
Several other known procedures for spinning objects from flat sheet metal blanks are known, such as the procedure in U.S. Pat. No. 3,195,491 for spinning rounded bowl-like blanks from discs in producing tapered disc wheels. Conical-shaped metal objects are produced by roller spinning procedures in U.S. Pat. No. 3,104,640. The disc wheel or conical shaped metal objects produced by such methods have tapered or curved side walls which are not suitable for V-grooved pulley manufacture. U.S. Pat. No. 3,282,078 uses tubular-shaped blanks instead of flat metal discs to spin grooved objects. This procedure flows the metal by thinning the sidewalls of the tubular blank to form an enlarged curved end groove.
Such prior art equipment and processes appear to be satisfactory for their intended use especially where vast quantities of cup-shaped blanks and finished spun products are made at high production rates. Such vast quantities spread the cost of the equipment, dies and tooling which is expensive over the large numbers of units produced.
It is desirable in certain situations and locations to be able to produce a relatively small quantity of cup-shaped metal blanks for subsequent use in spinning V-grooved pulleys with inexpensive, low volume producing equipment and methods. Furthermore, it is desirable to be able to change the size and configuration of the cup-shaped blank produced with a minimum tooling cost, so that small quantities of various sizes and configurations of cup-shaped blanks can be produced by a relatively low initial and replacement cost for equipment, tooling and dies.
The cup-shaped metal stage blanks for V-groove pulley manufacture produced by known drawing, die stamping and similar forming procedures preferably have flat bottom walls or hub connecting portions. The bottom wall is connected with a cylindrical side wall by an angled conical flange groove or annular shoulder formation such as shown in the cup-shaped pulley blanks of U.S. Pat. Nos. 3,826,804, 3,869,223 and 2,892,431. The conical flange, cylindrical side wall and shoulder formations, broadly may be termed a reentrant conical flange which provides an annular flange portion of one of the V-grooves in the finished pulley spun from the stage blank shown in these patents.
No known method of which I am aware enables the production of relatively small quantities of various sizes and configurations of cup-shaped metal stage blanks by roller spinning flat sheet metal discs on a usual and simple type of metal spinning machine, for use in the subsequent spinning of V-groved pulleys; which cup-shaped blanks are dynamically balanced due to their formation by roller spinning, and in which an annular groove or conical reentrant flange formation which provides a portion of the final pulley groove flange is formed during the spinning procedure in the cup-shaped stage blank.