Process for closing metal cans

Abstract

A process for closing a metal can body, suitable for containing an edible product, with a can lid, to provide a metal can suitable for heating in a retort. The process comprises: placing a metal lid over and in contact with an open end of a metal can body; applying an inwardly directed mechanical force to the lid such that at least a central portion of the lid is deformed into the interior space of the metal can body; and seaming the lid to the can body to form an airtight seal between the lid and the can body.

1 . A process for closing a metal can body, suitable for containing an edible product, with a semi-rigid can lid, to provide a metal can suitable for heating in a retort, the process comprising the steps of:
 placing a metal lid over and in contact with an open end of a metal can body;   applying an inwardly directed mechanical force to the lid such that at least a central portion of the lid is deformed into the interior space of the metal can body; and   seaming the lid to the can body to form an airtight seal between the lid and the can body.   
     
     
         2 . A process as claimed in  claim 1 , further comprising providing a seaming apparatus which comprises a seaming chuck and seaming rolls. 
     
     
         3 . A process as claimed in  claim 2 , in which the step of applying an inwardly directed mechanical force to the lid is provided by moving the seaming chuck into contact with the lid and maintaining that contact throughout the remainder of the step of seaming the lid to the can body. 
     
     
         4 . A process as claimed in  claim 1 , wherein, for a filled metal can body with a closed bottom, the step of seaming the lid to the can body is carried out after the step of applying an inwardly directed mechanical force. 
     
     
         5 . A process as claimed in  claim 4 , wherein the central portion of the lid is deformed inwardly to the extent that the headspace volume inside the metal can is reduced by between 50% and 100%. 
     
     
         6 . A process as claimed in  claim 4 , wherein the metal can is cylindrical and the lid is circular. 
     
     
         7 . A process as claimed in  claim 4 , wherein the lid is deformed by the inwardly directed force from a generally flat shape to a generally dished shape. 
     
     
         8 . A process as claimed in  claim 1 , wherein the lid comprises one or more beads extending across the surface. 
     
     
         9 . A process as claimed in  claim 1 , comprising, prior to a seaming step, the step of holding a seaming panel of the lid off a flange at the upper edge of the can body by a plurality of dimples disposed around the seaming panel. 
     
     
         10 . A process as claimed in  claim 1 , wherein, prior to being deformed, the lid is capable of passing horizontally through a slot with a height of less than 6 mm for a lid of nominally 153 mm diameter.