초록 ▼

A method, system and device utilized therein for the injection molding of plastic articles of enhanced surface quality using pressurized fluid. The fluid is prevented from contaminating the molten resin in the nozzle from which it was injected to thereby eliminate splay. The method involves the init

A method, system and device utilized therein for the injection molding of plastic articles of enhanced surface quality using pressurized fluid. The fluid is prevented from contaminating the molten resin in the nozzle from which it was injected to thereby eliminate splay. The method involves the initial step of injecting molten resin at a nominal injection pressure from the nozzle of an injection molding machine through a resin injection aperture at an upstream position in a mold. The resin travels along a resin flow path in the mold to a mold cavity defining the shape of the molded article at a downstream position. The device at least partially defines the resin flow path in the mold. A charge of fluid pressurized at a predetermined level is communicated to the resin flow path through an orifice in the device which opens to the resin flow path. During or after resin injection the pressurized charge of fluid enters the flow path at the orifice and passes into the mold cavity to distribute the molten plastic within the mold cavity. The fluid is contained within the mold cavity under pressure until the article has set up, and is thereafter vented to the atmosphere. The device prevents the pressurized fluid from traveling back along the resin flow path and through the injection aperture. The device thereby prevents contamination of the molten resin in the nozzle.

대표청구항 ▼

An apparatus for the injection molding of plastic articles comprising: an injection molding machine for injecting molten plastic through a nozzle into a flow path at a nominal injection molding pressure; a mold having a cavity defining the shape of the molded article and at least one plastic entry p

An apparatus for the injection molding of plastic articles comprising: an injection molding machine for injecting molten plastic through a nozzle into a flow path at a nominal injection molding pressure; a mold having a cavity defining the shape of the molded article and at least one plastic entry point coupled to the plastic flow path; fluid charge means for pressurizing a charge of fluid at a predetermined level no greater than the nominal injection pressure; and fluid circuit means, interconnecting the flow path and the fluid charge means, for communicating the charge of fluid to the flow path during plastic injection and responding to a pressure reduction in the flow path below the predetermined level of pressure to introduce the fluid charge into the flow path wherein the fluid circuit means interconnects the flow path downstream of the nozzle of the injection molding machine and proximate a mold sprue communicative with the flow path and wherein the machine nozzle communicates with a bushing in the sprue, and the fluid charge is communicated to an orifice in the sprue bushing. A method for the injection molding of a plastic article in an injection molding system including a resin injection nozzle and a mold having an injection aperture for receiving molten resin from the nozzle at an upstream position, a mold cavity at a downstream position and a resin flow path for fluidly communicating the injection aperture and the mold cavity between the upstream and downstream positions, the method comprising the steps of: pressurizing a charge of fluid at a predetermined pressure level; injecting a quantity of molten plastic from the injection nozzle through the injection aperture and the flow path and into the mold cavity at a nominal plastic injection pressure; communicating the charge of pressurized fluid to an orifice opening to the resin flow path in the mold between the upstream and downstream positions; introducing the fluid charge into the flow path from the orifice to distribute the molten plastic within the mold cavity; preventing the introduced fluid charge from traveling from the flow path, through the injection aperture and into the injection nozzle; containing the fluid under pressure within the article until it has set up in the mold cavity; and venting the fluid to ambient wherein the mold includes valve means movable between fluid open and fluid closed positions, the valve means allowing the fluid charge to travel through the orifice and into the flow path in the fluid open position and preventing the flow of the fluid charge through the orifice and into the flow path in the fluid closed position.