Compression molding container preforms

Abstract

An apparatus for supplying a mold charge for a mold cavity in accordance with one aspect of the present invention includes a mold charge chamber having a longitudinal dimension and at least two lateral inlets for supplying resin materials to the chamber such that the materials are stratified longitudinally of the chamber. A plunger is movable longitudinally into the chamber to force the stratified materials out of the chamber and thereby provide a stratified mold charge for a mold cavity. The at last two lateral inlets to the chamber preferably are spaced from each other lengthwise of the chamber. In one embodiment, the plunger has a contoured end for imparting a contour to the mold charge as the mold charge is forced from the chamber. A gate preferably is positioned at an end of the chamber remote from the plunger for selectively closing the chamber for filling and opening the chamber for discharge of the mold charge.

1 - 16 . (canceled)  
   
   
       17 . A method of supplying a mold charge to a mold cavity for compression molding a plastic container preform, which includes the steps of: 
 (a) providing a mold charge chamber having a longitudinal dimension and a lateral dimension that is uniform longitudinally of said chamber and having at least two lateral inlets to said chamber that are disposed between longitudinally spaced ends of said chamber and are spaced from each other longitudinally of said chamber,    (b) filling said chamber through said inlets with at least first and second resin materials that are stratified longitudinally of said chamber,    (c) discharging a stratified mold charge from said chamber into a preform mold cavity, and then    (d) compression molding a container preform from said mold charge in said cavity.    
   
   
       18 . The method set forth in  claim 17  wherein said step (a) includes providing a plunger that is movable between a first position that closes an upper end of a chamber and a second position that substantially fills said chamber, and a gate that selectively closes an end of said chamber opposite said plunger, 
 wherein said step (b) is carried out with said plunger in said first position and said gate closed, and    wherein said step (c) is carried out by opening said gate and moving said plunger from said first position to said second position.    
   
   
       19 . The method set forth in  claim 18  wherein said step (a) includes contouring an end of said plunger to impart a contour to said mold charge during said step (c).  
   
   
       20 . The apparatus set forth in  claim 18  further comprising an actuator coupled to said plunger for moving said plunger from said first position to said second position.  
   
   
       21 . The apparatus set forth in  claim 21  wherein said actuator is selected from the group consisting of an electrical servo actuator and a fluid actuator.