Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – By mechanically introducing gas into material
Patent
1973-07-24
1976-06-08
Anderson, Philip
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
By mechanically introducing gas into material
264329, 264349, 264DIG5, 264DIG83, B29D 2700
Patent
active
039623874
ABSTRACT:
Plastic molding machine, primarily adapted for generating and molding a closed-cell foam thermoplastic material. The foam is generated by introducing a gas inert to the thermoplastic material into a granular mixture of same so that the gas is thoroughly intermixed among the granular particles. The gas is then held under pressure while the granular particles are reduced to a flowable material, said pressure being sufficient to assure that the gas will not be expelled therefrom during such process. In one preferred embodiment, gas is mixed into the granular thermoplastic in a hopper and held therein under pressure as said granular material is fed into a screw and plasticated thereby.
The plastic material is then conducted at a relatively low pressure, such as that generated by the extrusion machine used for plasticating the material, through a branched system past a check valve in each branch of said system, to an injection assembly. As each injection assembly receives a predetermined amount of plastic material, means are energized preventing more plastic material from entering thereinto but continued operation of the pressure generating device will continue filling other injection assemblies for as long as any thereof are capable of receiving such material. When all injection assemblies are filled, same are actuated simultaneously to drive the plastic material therefrom into the mold cavity. Injection assemblies may supply mold cavities in any pattern, and a single mold cavity may be associated with a given injection assembly or two or more injection assemblies may supply any one given mold cavity.
Local zones, preferably subjected to rapid cooling, are provided with undercut notches connected to the sprue, runners or cavity and filled thereby with plastic. Same is cooled ahead of the cooling of the molded part and provides means for holding the mold closed. This permits removal of the mold from the machine prior to cooling of the molded part and opening of the mold which in turn permits more effective use of multiple molds with a given machine.
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Anderson Philip
Ex-Cell-O Corporation
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