Press forming process and apparatus for plastic foam and plastic foam product

A forming press for shaping an article of required shape from a flat workpiece of thermoplastic foam, comprising:

• a frame,
• a compliant female mold member,
• a rigid male form punch defining the inside shape and dimensions of said article,
• a pair of rollers disposed side by side in said frame, said rollers having at each end extended central shafts supported in slots provided in said frame,
• an elastomeric belt serving as a compliant forming surface of said female mold member and disposed across the top side of each of said rollers and wrapping partially around each of said rollers and extending downward from each of their outward sides,
• said compliant female mold member being initially stretched flat, disposed and supported by said rollers such that the workpiece, when heated above its forming temperature and placed thereon, may be deflected along with the compliant mold member by pressure from the form punch so as to urge said workpiece to progressively wrap itself around said form punch, thus forming said workpiece to the required shape.

A forming press for shaping an article of required shape from a flat workpiece of thermoplastic foam, comprising:

• an elastomeric belt, serving as the forming surface of said compliant female mold member, disposed across the top side of each of said rollers and wrapping partially around each of said rollers and extending downward from each of their outward sides,
• said compliant female mold member initially stretched flat, disposed and supported by said rollers such that the workpiece, when heated above its forming temperature and placed thereon, may be deflected along with the compliant mold member by pressure from the form punch so as to urge said workpiece to progressively wrap itself around said form punch, thus forming said workpiece to the required shape,
• a rigid male form punch defining the inside shape and dimensions of said article, and
• a pair of rollers disposed side by side in said frame, said rollers having at each end extended central shafts supported in inclined slots located in said sidewalls,
• spring fastening means disposed at each end of said belt,
• a plurality of coil springs attached between said spring fastening means and corresponding attachment means located on the main frame of said forming press so as to hold said belt in tension, urging it against said rollers,
• a plunger assembly comprising a form punch shaped in accordance with the required shape of the article to be formed,
• guidance means on said plunger assembly and on said sidewalls allowing said form punch to move vertically while constraining it horizontally, midway between said rollers,
• hoisting means enabling said plunger assembly to be raised so as to lift said form punch clear of said belt, and
• pressure means capable of acting downwardly on said plunger assembly so as to urge said form punch against said belt,
• wherein said inclined slots are sized and positioned to allow said rollers to separate sufficiently to allow said form punch to be forced downward between the rollers, as permitted by flexure of said belt and extension of said springs whereby, said workpiece, when placed within a special heat-retaining envelope and heated to forming temperature in an oven, may then be placed on said belt, and then formed by pressing said form punch downward so as to urge said enveloped workpiece against said belt and deflect them downward together in a forming action which progresses uniformly while the heat-retaining envelope holds the workpiece above its forming temperature until the form punch has been pressed downward to a final position between said rollers;
• whereby said workpiece becomes formed to the required shape, and hardens in the required shape upon cooling.