Abstract: A method and system for injection molding plastic articles which utilize a spill area whose volume varies within an article-defining mold cavity. In one embodiment, the volume increases during introduction of pressurized gas into the mold cavity. In another embodiment, the volume of the spill area varies during a plastic injection which fills the mold cavity. A core reciprocally mounted within the mold cavity partially defines the variable volume of the spill area. An air spring is utilized to control pressure on the core which counters the pressure of the plastic at an end face of on the core. In one embodiment, the end face of the core is non-flat to create an area where fluid plastic can exert pressure against the end face within the mold cavity during plastic injection and/or during introduction of pressurized gas.

Abstract: A method and system for injection molding plastic articles which utilize a spill cavity whose volume varies. In one embodiment, the volume varies during introduction of pressurized gas into a mold cavity flow coupled to the spill cavity. In another embodiment, the volume of the spill cavity varies during a plastic injection which fills the mold cavity. A piston reciprocally mounted within a cylinder defines the variable volume of the spill cavity. In one embodiment, a pneumatic control circuit controls the pressure on a lower surface of the piston to thereby control the position of the piston within the cylinder and therefore the volume of the spill cavity. In another embodiment, an air spring is utilized to control pressure on the piston which counters the pressure of the plastic on the piston. In one embodiment, a stop pin connected to the piston prevents the piston from leaving the cylinder when the mold is opened and solidified plastic in the spill cavity is to be ejected therefrom.

Abstract: A method and system for injection molding plastic articles which utilize a spill cavity whose volume varies. In one embodiment, the volume varies during introduction of pressurized gas into a mold cavity flow coupled to the spill cavity. In another embodiment, the volume of the spill cavity varies during a plastic injection which fills the mold cavity. A piston reciprocally mounted within a cylinder defines the variable volume of the spill cavity. In one embodiment, a pneumatic control circuit controls the pressure on a lower surface of the piston to thereby control the position of the piston within the cylinder and therefore the volume of the spill cavity. In another embodiment, an air spring is utilized to control pressure on the piston which counters the pressure of the plastic on the piston. In one embodiment, a stop pin connected to the piston prevents the piston from leaving the cylinder when the mold is opened and solidified plastic in the spill cavity is to be ejected therefrom.

Abstract: A system for injection molding a hollow plastic article utilizing a secondary resin flow path which communicates one portion of an article-defining cavity with a second portion of the article-defining cavity. The second portion of the article-defining cavity is typically the hardest-to-fill area of the article-defining cavity. The secondary resin flow path is outside of the article-defining cavity and the normal flow of plastic resin.

Abstract: A method and system for the injection molding of plastic articles in an injection molding system including a chamber in a mold of the system which stores a charge of pressurized gas immediately prior to use. The mold has an injection aperture and a mold cavity for receiving molten resin. A resin flow path fluidly communicates the injection aperture and the mold cavity within the mold. An orifice in the mold opens the chamber to the mold. A gas receiver initially stores the charge of pressurized gas and a fluid circuit selectively introduces the charge of pressurized fluid into the chamber. A valve mechanism in the chamber selectively fluidly communicates the chamber to the flow path under control of a controller. When communicated to the flow path, the charge of gas distributes the molten plastic within the mold cavity in one embodiment of the invention.

Abstract: A method and system are disclosed for locally introducing fluid, such as a gas, at a predetermined location into molten resin downstream from a resin injection aperture to form a hollow part. The gas is utilized at the localized area to distribute the molten resin, to eliminated molded in stress and to prevent formation of sink marks in the part during resin solidification. An overflow reservoir outside of the mold cavity is filled with the resin during resin injection and then the gas is introduced into the reservoir through a fluid aperture and into the part. The reservoir creates a cocoon of solidified material to act as a seal to prevent gas leakage. One hollow body formed by the method and system includes a substantially endless hollow body portion with a fluid opening for communicating the interior of the hollow body portion with the locally introduced fluid. The hollow body provides an internal gas manifold and means for greater structural integrity.

Abstract: A method and system are provided for controlling a pressurized fluid such as nitrogen gas which may be initially stored at a pressure as high as 20,000 psi. The pressurized nitrogen gas may be utilized in high pressure gas systems such as in gas-assisted injection molding systems or low pressure gas systems such as robotic control and actuators. A valve assembly is utilized in the method and system and includes an electric proportioning device such as a pneumatic servovalve and a pair of pneumatic, fluidly-coupled valves which are piloted by the servovalve to regulate the pressure of the pressurized nitrogen gas. In the method and system, the servovalve operates in a closed loop fashion by utilizing feedback from a feedback device such as a pressure transducer. A controller in the closed loop is responsive to a pressure signal from the pressure transducer and a preset reference signal to provide an error control signal to the servovalve.

Abstract: A method and system for injection molding a hollow plastic article utilizing a secondary resin flow path which communicates one portion of an article-defining cavity with a second portion of the article-defining cavity. The second portion of the article-defining cavity is typically the hardest-to-fill area of the article-defining cavity. The secondary resin flow path is outside of the article-defining cavity and the normal flow of plastic resin.

Abstract: Apparatus for injection molding a plastic article having a hollow rib portion utilizing a spill cavity. A process includes the steps of sequentially injecting fluent plastic and gas into a mold cavity having a space defining at least one wall portion of the article and a channel defining a rib portion of the article. A quantity of fluent plastic is initially injected to substantially fill the mold cavity. A charge of pressurized gas is then injected into the channel of the mold cavity to displace a portion of the still fluent plastic into the spill cavity which is flow coupled to the channel. Preferably, the thickness of the rib portion in cross section is at least twice as large as the thickness of the wall portion in cross section along the entire length of the rib portion. Also, preferably, the channel is tapered along its length. The rib portion may be either internal or external to the article.

Abstract: A system is disclosed for locally introducing fluid, such as a gas, at a predetermined location into molten resin downstream from a resin injection aperture to form a hollow part. The gas is utilized at the localized area to distribute the molten resin, to eliminated molded in stress and to prevent formation of sink marks in the part during resin solidification. An overflow reservoir outside of the mold cavity is filled with the resin during resin injection and then the gas is introduced into the reservoir through a fluid aperture and into the part. The reservoir creates a cocoon of solidified material to act as a seal to prevent gas leakage. One hollow body formed by the method and system includes a substantially endless hollow body portion with a fluid opening for communicating the interior of the hollow body portion with the locally introduced fluid. The hollow body provides an internal gas manifold and means for greater structural integrity.

Abstract: A method and system for the injection molding of plastic articles of enhanced surface quality using pressurized fluid introduced into the article defining cavity or runner of a mold by a sealed pin or valve having an orifice therein and movable between open and closed positions to inject gas into a subgate of the mold. In one embodiment, the fluid is a gas which is injected through the subgate between a pair of seals. The seals and the subgate prevent gas leakage around the periphery of the pin. The fluid is prevented from contaminating the molten resin in a nozzle from which it was injected to eliminate splay by either using a shut-off valve with the nozzle or by introducing the pressurized fluid into the molten resin parallel to its direction of flow. 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.