Apparatus for forming a paperboard receptacle

Claim 1

An apparatus for drawing a flat paperboard blank to form a dished receptacle having corner areas of maximum stress, during drawing, at the juncture of the receptacle base and sidewall structure, and apparatus comprising: (a) a male die having a central plunger portion for engaging a central portion of the blank and having a peripheral portion for engaging a peripheral portion of the blank; (b) a female die having a peripheral portion for engaging a peripheral portion of the blank and having a central cavity into which a central portion of the blank is drawn; (c) means forming a steam cavity adjacent said female die; (d) means for introducing steam into said steam cavity; (e) a passage extending between said female die cavity and said steam cavity; (f) a reciprocating plunger disposed in said female die cavity, said reciprocating plunger having a portion extending through said passage and into said steam cavity, said reciprocating plunger being removable between first and second positions; (g) means on said reciprocating plunger operable to close said passage when said reciprocating plunger is in said first position; and (h) said male die having means operable when extended into said female die cavity to move said reciprocating plunger to said second position to allow passage of steam into said female die cavity to impinge, upon and thereby plasticize and lubricate areas of the blank which are subject to maximum stress during drawing of the blank.

Claim 2

An apparatus for drawing a flat paperboard blank to form a dished receptacle having corner areas of maximum stress, during drawing, at the juncture of the receptacle base and sidewall structure, and apparatus comprising: (a) a male die having a central plunger portion for engaging a central portion of the blank and having a peripheral portion for engaging a peripheral portion of the blank; (b) a female die having a peripheral portion for engaging a peripheral portion of the blank and having a central cavity into which a central portion of the blank is drawn; (c) means forming a steam cavity adjacent said female die; (d) means for introducing steam into said steam cavity; (e) a passage extending between said female die cavity and said steam cavity; (f) a reciprocating plunger disposed in said female die cavity, said reciprocating plunger having a portion extending through said passage and into said steam cavity, said reciprocating plunger being removable between first and second positions; (g) means on said reciprocating plunger operable to close said passage when said reciprocating plunger is in said first position; and (h) said male die having means operable when extended into said female die cavity to move said reciprocating plunger to said second position to allow passage of steam into said female die cavity to impinge, upon and thereby plasticize and lubricate areas of the blank which are subject to maximum stress during drawing of the blank.

Claim 6

An apparatus for drawing a flat paperboard blank to form a dished receptacle having corner areas of maximum stress, during drawing, at the juncture of the receptacle base and sidewall structure, and apparatus comprising: (a) a male die having a central plunger portion for engaging a central portion of the blank and having a peripheral portion for engaging a peripheral portion of the blank; (b) a female die having a peripheral portion for engaging a peripheral portion of the blank and having a central cavity into which a central portion of the blank is drawn; (c) means forming a steam cavity adjacent said female die; (d) means for introducing steam into said steam cavity; (e) a passage extending and communicating between said female die cavity and said steam cavity with each other; (f) a reciprocating plunger disposed in said female die cavity, said reciprocating plunger having a portion extending through said passage and into said steam cavity, said reciprocating plunger being removable between first and second positions to control the flow of steam into said female die cavity from said steam cavity; (g) means on said reciprocating plunger operable to close said passage when said reciprocating plunger is in said first position; and (h) said male die including means operable when extended into said female die cavity to move said reciprocating plunger to said second position to allow passage of steam into said female die cavity to impinge upon and thereby plasticize and lubricate areas of the blank which are subject to maximum stress during drawing of the blank.

Claim 7

An apparatus for drawing a flat paperboard blank to form a dished receptacle having corner areas of maximum stress, during drawing, at the juncture of the receptacle base and sidewall structure, and apparatus comprising: (a) a male die having a central plunger portion for engaging a central portion of the blank and having a peripheral portion for engaging a peripheral portion of the blank; (b) a female die having a peripheral portion for engaging a peripheral portion of the blank and having a central cavity into which a central portion of the blank is drawn; (c) means forming a steam cavity adjacent said female die; (d) means for introducing steam into said steam cavity; (e) a passage extending and communicating between said female die cavity and said steam cavity with each other; (f) a reciprocating plunger disposed in said female die cavity, said reciprocating plunger having a portion extending through said passage and into said steam cavity, said reciprocating plunger being removable between first and second positions to control the flow of steam into said female die cavity from said steam cavity; (g) means on said reciprocating plunger operable to close said passage when said reciprocating plunger is in said first position; and (h) said male die including means operable when extended into said female die cavity to move said reciprocating plunger to said second position to allow passage of steam into said female die cavity to impinge upon and thereby plasticize and lubricate areas of the blank which are subject to maximum stress during drawing of the blank.