I thought the same thing, but if you keep reading he elaborates later in the patent description:
"Ferrule-tip 12, having a threaded screw 20 discussed below, has a threaded bore to be screwed onto screw 20, as also discussed below. Ferrule tip 12 is a cylindrical member comprising a phenolic ferrule combination, such as a C-grade phenolic. Of course ferrule-tip 12 can alternatively comprise any other resilient material, which can be a plastic such as polyethylene, polypropylene, polycarbonate, acrylic, DELRIN.RTM., acetal, Teflon.RTM., nylon, phenolic, such as C-grade phenolic, ABS, vinyl, PVC, VIVAK.RTM., a hard, rubber, or leather, all of which are conventional in the art. The only time leather would work is if it were very thin and covers a hard ferrule so that the energy being transferred is from the ferrule underneath the leather. Ferrule-tip 12 comprises a cylindrical outer surface 12a having a longitudinal centerline being in alignment with the longitudinal centerline of shaft 14, thereby causing outer surface 14a and outer surface 12a to be aligned. Screw 20 is preferably 1/2 inch long with 5/16--18 threads, and the bore of ferrule tip 12 has mating threads. Ferrule-tip 12 can be permanently affixed to shaft 14 without a threaded screw as well, such as by securing ferrule-tip 12 to a tenon extending upwardly from shaft 12 in the same manner as threaded screw 20 and stabilizing ferrule-tip 12 thereon by any manner conventional in the art, such as by glue. Such a method of permanently securing a ferrule to the shaft is known in the art and so a more detailed description thereof is herewith omitted for the sake of brevity."
Now he does reference a "cylinder", so if you tapered the ferrule tip at all, you come up with a "conic section" which may void the patent. Having said this he does mention having the same centerline as the shaft which may take care of this little loophole as well, it's a little too much for my head this morning.