Making perforated dimpled sheet, for e.g. washing machine drums, involves relating rotation of dimpling and backing rollers to position of holes

摘要

Drum (1) of perforated material (1a) is dimpled by passing it between a roller (2) with projections (3) and a backing roller (4) with a flexible, e.g., rubber, covering (4a). The drives (A2,A3) to the rollers are controlled to give a precise positioning relative to the holes in the material (1a). The principle can also be used on flat continuous sheet with a repeating hole pattern. Independent claims are also included for the following: (a) an arrangement where the flexible covering (4a) has recesses to correspond with the position of the holes in the material (1a); and (b) the manufacture of a washing machine drum with the dimples arranged at the holes in the material.