PRODUCTION OF CLOSED BOTTOM SHELLS

摘要

The present invention provides in a machine which forms shells of can dimension from a blank by moving the blank through a deforming means including a die and in which the blank is of a material having given electromagnetic properties, the combination of (a) a punch of material having different electromagnetic properties, on which the shell is supported on emerging from the deforming means, (b) an electromagnetic field sensor positioned to create an electromagnetic field in an area corresponding to the free end of a shell of correct length, and (c) means to discriminate between the field altered by the punch element alone, not supporting a shell of correct length, and the field altered by a shell of correct length on the punch.