Forming catch tabs on paperboard food container components for retaining containers and lids in releasable attachment

Abstract

A die set apparatus for forming catch tabs on a flange of a first paperboard container component, such as a lid, while the paperboard is being pressed between a pair of mating dies. A plurality of cavities are formed in and circumferentially spaced around a first die, each cavity opening toward a second die and having a shearing edge. A plurality of radial passages extend through a second die, each passage in registration with one of the cavities. A plurality of catch punches are mounted for radial movement through a radial passage and into its associated cavity. Each catch punch also has a shearing edge aligned to closely slide past the shearing edge of its associated cavity. An actuator drives the catch punches into the cavities to shear a slit in the interposed paperboard and drive an adjacent segment of paperboard into the cavity to preform the catch tabs. As the dies are separated, each catch tab is caught on the edge of the cavity and bent inwardly, tearing the paperboard at opposite ends of the slit so that the tears form opposite sides of the catch tabs.

1 . A method for forming catch tabs on an axially extending flange of a first paperboard container component part during the pressforming of the first container component between a pair of mating dies, the container component part having a closed end and an open end for engaging a second container component part, the method comprising: 
 (a) shearing a plurality of circumferentially spaced slits through the axially extending flange; and    (b) radially punching the paperboard adjacent each slit to deform a segment of the paperboard adjacent the slit in a radial direction to form the catch tabs.    
   
   
       2 . A method in accordance with  claim 1  and further comprising shearing the spaced slits along a circumferential direction and punching and radially deforming the paperboard on the open end side of the slit.  
   
   
       3 . A method in accordance with  claim 2  wherein the shearing and punching operations are performed in a single operation by driving a shearing punch member radially through openings in said dies.  
   
   
       4 . A method in accordance with  claim 3  wherein the shearing punch member is driven in a radially inwardly direction to perform the punching and shearing operation and then withdrawn.  
   
   
       5 . A method in accordance with  claim 1  or  2  or  3  or  4  and further comprising catching each catch tab on an edge formed on one of the dies as the dies are separated and bending the catch tab toward the open end of the container component part.  
   
   
       6 . A method in accordance with  claim 5  and further comprising tearing the paperboard at opposite ends of the slit during the bending step so that tears form opposite sides of the catch tab.  
   
   
       7 . A paperboard container component having catch tabs made in accordance with the method of  claim 1  or  2  or  3  or  4   
   
   
       8 . A die set apparatus for forming catch tabs on an axially extending flange of a first paperboard container component part having an open end for engaging a second container component part, the catch tabs being formed while a sheet of paperboard is being pressed to form the first container component between a pair of mating dies, the mating dies including a male die portion for pressforming the interior surface of the axially extending flange and a female portion for pressforming the exterior surface of the axially extending flange radially outwardly from the male portion, the apparatus comprising: 
 (a) a plurality of cavities circumferentially spaced around a first one of said die portions, each cavity opening toward the second of said die portions and having a shearing edge;    (b) a plurality of radial passages extending through the second of said die portions, each passage in registration with one of said cavities;    (c) a plurality of catch punches, each punch mounted for radial movement through a radial passage and into an associated one of the cavities, each catch punch including a shearing edge aligned to closely slide past the shearing edge of its associated cavity; and    (d) an actuator drivingly linked to each catch punch for driving the catch punches into the cavities and thereby shearing a slit in the interposed paperboard and driving an adjacent segment of paperboard into the cavity to form the catch tab.    
   
   
       9 . An apparatus in accordance with  claim 8  wherein the shearing edges of the catch punch and the cavity are positioned on the respective edges of both each catch punch and each cavity that are closer to the closed end of the container component part.  
   
   
       10 . An apparatus in accordance with  claim 9  wherein a cavity entering end of each catch punch has a beveled end and a distally protruding edge of the beveled end forms a knife edge as the shearing edge of the punch.  
   
   
       11 . An apparatus in accordance with  claim 8  or  9  or  10  wherein the first portion having the cavities is inward of the second portion having the radial passages and wherein the catch punches are retractable outwardly where they are disengaged from the cavities and are extendible radially inwardly into the cavities to form the catch tabs.  
   
   
       12 . An apparatus in accordance with  claim 8  or  9  or  10  wherein the cavities are formed by segments of a continuous groove extending around the first die portion.  
   
   
       13 . An apparatus in accordance with  claim 8  or  9  or  10  wherein each cavity is formed into an inclined surface of the first die portion, the inclined surface being inclined toward the axial center of the dies as the inclined surface approaches the mating die, the shearing edge of the cavity being formed on the cavity edge nearest the mating die but spaced radially inwardly from an opposite edge of the cavity less than the distance of protrusion of the catch tabs so that, upon separation of the die portions, the shearing edge of the cavity will catch and bend the catch tabs toward the open end of the container component part.  
   
   
       14 . An apparatus in accordance with  claim 8  or  9  or  10  wherein each cavity has a bending edge axially opposite the shearing edge and wherein the catch punch has an axial thickness that is less than the axial distance from the shearing edge of the cavity to the bending edge of the cavity to avoid shearing the paperboard at both edges.  
   
   
       15 . An improved container component part having at least one axially extending flange with catch tabs protruding from the flange, wherein the improvement comprises: 
 the container component part being formed of a unitary sheet of pressformed paperboard.