Patent ID: 7033536
Filing Date: 2006-04-25
Classification: B29C,B29L

Abstract:
1. In a method for thermoforming parts from preheated sheet material using a mold cavity having a lip projecting therefrom and a plug assist advanced from a retracted position into said preheated sheet to force said material of said sheet into said cavity and thereafter drawing said heated sheet material against said mold cavity and said projecting lip by fluid pressure, the improvement comprising: recessing said plug assist into a well in said retracted position of said plug assist aligned with said mold cavity; advancing said preheated sheet across a clamping ring recessed into said well and surrounding said plug assist but having an end projecting above an end of said plug assist with said plug assist in said retracted position to engage said preheated sheet and create a sealing of said well with said preheated sheet spaced slightly from said plug assist end; applying a vacuum in said sealed well to draw said sheet slightly into said well and against said end of said plug assist just prior to advance of said plug assist and engagement of said clamping ring with structure adjacent said mold cavity and subsequent forming of a part in said mold cavity.