초록 ▼

A system for molding elongated ribbon-like products from thermoplastic materials utilizing a plurality of molds which are moved in tandem along a production line. As the molds are moved along the line at successive stations they are, while open, thermally adjusted to a temperature suitable for formi

A system for molding elongated ribbon-like products from thermoplastic materials utilizing a plurality of molds which are moved in tandem along a production line. As the molds are moved along the line at successive stations they are, while open, thermally adjusted to a temperature suitable for forming the product to be molded and then a ribbon of plastic is deposited in them. They are then closed and cooled and reopened and the molded product removed. The system utilizes only enough molding pressure to assure distribution of the plastic to all parts of the mold cavity and shaping of the molded product to the geometric design of the mold. The system includes a transfer means for the molds which returns the emptied molds for recycling through the molding process.

대표청구항 ▼

The method for forming an extruded product of thermoplastic material by low pressure molding including the steps of providing a plurality of molds each having a base and a cover which when closed form a closed internal cavity shaped to form the top, sides and ends of the product, continuously transp

The method for forming an extruded product of thermoplastic material by low pressure molding including the steps of providing a plurality of molds each having a base and a cover which when closed form a closed internal cavity shaped to form the top, sides and ends of the product, continuously transporting the molds in sequence around a closed circuit, preparing each mold to receive a charge of moldable thermoplastic material, sequentially moving each mold beneath a source of plastic material, while the mold is open flowing a charge of extruded thermoplastic material into each mold, removing each mold from the source of the plastic material, by means of the cover simultaneously closing and sealing the cavity in the mold while applying at least sufficient pressure to distribute the plastic material throughout the mold cavity whereby all areas of the mold are filled with plastic and the plastic will accuratedly reproduce the configuration of the cavity, cooling the mold sufficiently that the molded product can be removed without distortion of its molded configuration; as the mold and plastic are being cooled further closing the mold data rate to progressively compensate for thermal shrinkage of the plastic; precisely measuring the volume of plastic material discharged into the mold such that the mold cavity when initially sealed will hold the entire change of plastic delivered into the mold and such amount will be equal to the volume of the mold cavity when the plastic material has cooled to a temperature at which the molded product can be removed from the mold. A system for molding elongated ribbon-like plastic strips from a thermoplastic material, said system comprising: a plurality of stations, a plurality of molds each having a base portion and a cover portion at least one of which has a mold cavity recess therein shaped to form the strip when the mold is closed, said mold being made of a non-ferrous material, transport means interconnecting all of the stations; at least one of the stations having means for preparing the molds to receive a charge of moldable thermoplastic material; another station having means under which the molds pass in tandem for flowing a ribbon of precise and predetermined volume of hot thermoplastic material into each mold as it passes through the station; mold controlled means for controlling the discharge of the plastic material such that the length and volume of the discharged ribbon is commensurate with the length and volume of the mold cavity; means or closing the mold and sealing the mold cavity, pressure exerting means for engaging the mold and solely by pressure exerted by said means on the cover pressurizing the plastic material at least to that necessary to cause the mold cavity to be entirely filled with the plastic material and be impressed with the configuration of the mold cavity said pressure exerting means including means to limit the closing pressure only to that necessary to positively fill the mold cavity with the material and to thereafter continue to progressively reduce the size of the mold cavity at a rate commensurate with the rate of shrinkage of the plastic as it cools to cause adequate material migration within the cavity to prevent sink formation or other distortion during cooling; and means for removing the molded strip after it has cooled until it can be removed without distortion of its physical shape.