US2754635A US313215A US31321552A US2754635A US 2754635 A US2754635 A US 2754635A US 313215 A US313215 A US 313215A US 31321552 A US31321552 A US 31321552A US 2754635 A US2754635 A US 2754635A Authority US United States Prior art keywords rollers wheel grinding roller end Prior art date 06 Legal status The legal status is an assumption and is not a legal