Apparatus for producing stock of synthetic thermoplastic material by continuous molding

Claim 1

In apparatus for continuoUsly molding stock consisting of a foamed, coherent agglutinated core of polymeric material tightly enclosed in a sheet of polymeric material, the combination comprising A. lower and upper endless belts each trained about a head and a tail pulley, the head pulley about which the lower belt is trained being disposed upstream from the head pulley about which the upper belt is trained, and each having a depressed outwardly facing surface area intermediate the opposite side marginal areas thereof, the upper run of the lower belt and the lower run of the upper belt being disposed in mutually overlying relation for movement together away from said head pulleys in the downstream direction at the same rate of speed, and being disposed with the depressed surface areas thereof registering and thereby conjointly defining a continuous open ended mold channel having closed longitudinally extending opposite sidewalls, said mold channel being wide and comparatively shallow in transverse section for production of stock in the form of a flat board, B. rollers underlying, overlying and on each side of said mutually overlying runs of the belts, said rollers being operative for supporting and guiding the same and assuring registration thereof as aforesaid, C. a hopper for continuously feeding unexpanded granules of the polymeric material which is to form the core of said stock into said sheet of polymeric material preliminary to folding the same and thereby forming thereof a sleeve enclosing said granules and preliminary to feeding said sleeve and the granules contained thereby into the upstream end of said mold channel, said hopper having an opening in the bottom thereof through which said material is discharged into a section of the upper run of the lower belt extending between said head pulleys, and having laterally spaced opposed sidewalls with lower sections diverging downwardly and outwardly for having the opposite side marginal areas of said sheet material raised and disposed respectively in overlying relation thereto, D. a steam manifold mounted on the upstream side of said hopper, said manifold being provided with laterally spaced opposed sidewalls respectively coplanar with the laterally spaced opposed sidewall areas of the hopper, and being provided with a bottom wall disposed in close spaced overlying relation to the depressed outwardly facing surface of the underlying belt, and E. a plurality of laterally spaced tubular members extending from said steam manifold into the upstream end of said mold channel and downstream deep into the same and disposed with their central axes in a plane coincident with the interface between the upper run of the lower belt and the lower run of the upper belt, said tubular members being tapered gradually from a large diameter at the upstream end thereof to a smaller diameter at the downstream end thereof, being coated on the outside with polytetra-fluoroethylene, being closed at the downstream end thereof, and being perforated for discharge of steam therefrom into the mold channel directly into the granules of polymeric material contained by said sleeve of sheet material.