公开(公告)号：US4969345A

公开(公告)日：1990-11-13

申请号：US306161

申请日：1989-02-06

Applicant: Louis M. Zonneveld ,  Friedrich W. Thoolen

Inventor： Louis M. Zonneveld ,  Friedrich W. Thoolen

IPC: B21D19/04

CPC classification number: B21D19/043 ,  Y10S72/702

Abstract: An upstanding collar is formed around a hole in a sheet metal blank by means of a converter tool which converts an edge region bordering the hole into the collar, while the blank is rotated relative to the converter tool. This method comprises (i) in a first stage, converting a portion of the blank into a first turned-up rim, (ii) after the first stage, converting a further portion of the blank into a second turned-up rim, (iii) in at least one further stage repeating step (ii) successively converting each time a further portion of the blank into another turned-up rim, until the whole of the edge region has been converted, wherein (a) in at least one of the stages the conversion takes place on free air, and (b) in all these stages the conversion takes place in the same direction relative to the blank. A converter tool increasing stepwise in diameter may be used.