Abstract: A mold apparatus and method is used to form a solid injection molded plastic part having no internal voids, a Class A finish, a sink-free exterior appearance surface, and unevenly distributed structural detail extending from the opposite surface, the detail including free-standing reinforcement ribs, attachment bosses, and the like. A charge of hot melted thermoplastic and pressurized gas are sequentially injected into a mold cavity defining the shape of the desired part, the plastic not filling the cavity and being simultaneously received in shaped recesses and grooves which form the structural detail. The pressurized gas forces the hot plastic from one mold half against the other mold half, and into the recesses and grooves, and is maintained during cooling. A gas seal is formed by the plastic to prevent gas in the mold cavity from reaching the finished exterior surface of the part during shrinkage of the plastic.

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 mold apparatus and method is used to form a solid injection molded plastic part having no internal voids, a Class A finish, a sink-free exterior appearance surface, and unevenly distributed structural detail extending from the opposite surface, the detail including free-standing reinforcement ribs, attachment bosses, and the like. A charge of hot melted thermoplastic and pressurized gas are sequentially injected into a mold cavity defining the shape of the desired part, the plastic not filling the cavity and being simultaneously received in shaped recesses and grooves which form the structural detail. The pressurized gas forces the hot plastic from one mold half against the other mold half, and into the recesses and grooves, and is maintained during cooling. A gas seal is formed by the plastic to prevent gas in the mold cavity from reaching the finished exterior surface of the part during shrinkage of the plastic.

Abstract: A mold apparatus and method is used to form a solid injection molded plastic part having no internal voids, a Class A finish, a sink-free exterior appearance surface, and unevenly distributed structural detail extending from the opposite surface, the detail including free-standing reinforcement ribs, attachment bosses, and the like. In the method the mold portions of the mold apparatus are closed, charges of molten thermoplastic and pressurized gas are sequentially injected into a mold cavity defining the shape of the desired part, and the mold portions are sequentially separated and closed. The pressurized gas forces the hot plastic away from one mold half and against the other mold half, and separation of the mold portions ensures uniform distribution of the pressurized gas behind the hot plastic, which pressure is maintained during cooling.

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 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.

Abstract: A process and apparatus for injection molding and a plastic article having a hollow rib portion is formed utilizing a spill cavity. The 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 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.

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 pressurized fluid reservoir having a variable working volume includes a cylinder body having a fixed storage volume and a first inlet and exhaust structure for allowing a compressible fluid to enter and leave the cylinder. A second inlet and exhaust structure is also provided for allowing a substantially incompressible fluid to enter and leave the cylinder. A first charge mechanism pumps the compressible fluid into the cylinder. A second charge mechanism pumps the substantially incompressible fluid into the cylinder to reduce the cylinder fixed storage volume to a desired working volume into which the compressible fluid can be pumped by the first charge mechanism.

Abstract: A method and system for the injection molding of plastic articles in an injection molding system including a pneumatically operated gas compression unit having a high pressure gas receiver. The injection molding system includes a resin injection nozzle and a mold having an injection aperture and mold cavity for receiving molten resin from the nozzle. The gas compression unit includes a gas booster which pressurizes a first charge of gas to the pressure setting of a pressure switch. The gas receiver stores the first charge of pressurized gas at a pressure level within a predetermined range of pressures. At least one fluid pressure reducing valve reduces the pressure of the gas as it is communicated from the fluid receiver to an orifice in the mold to an acceptable level for molding the article. The gas compression unit is capable of servicing a plurality of injection molding machines and corresponding molds when a like plurality of pressure reducing valves are provided.

Abstract: A method of gas-assisted injection molding in which: (1) a first amount of plastic is injected into an article-defining cavity of a mold so that it flows therein; (2) a second amount of plastic continues to be injected into the cavity simultaneous with the injection of a charge of pressurized gas wherein the pressurized gas prevents the flow of plastic in the cavity from stopping; and (3) the charge of pressurized gas continues to be injected after the second amount of plastic is injected to distribute the total amount of molten plastic resin in the cavity. The ratio for the first amount of plastic to the total amount of plastic required for the preparation of the article is in the range of 0.2 to 0.7. Also, the pressurized gas has a pressure between approximately 1000 psi and 5000 psi. These steps prevent imperfections on the exterior surface of the plastic article. The gas charge is maintained under pressure within the article until the article has set up in the article-defining cavity.

Abstract: A process for injection molding hollow plastic articles includes the steps of sequentially injecting fluent plastic and gas into a mold cavity. A quantity of fluent plastic is initially injected to substantially fill the mold cavity. A charge of pressurized gas is then injected into the mold cavity to displace a portion of the still fluent plastic into a spill cavity flow coupled to the mold cavity. The article may be formed with an internal wall by introducing first and second gas charges into the mold cavity at separate entry points. In one embodiment, the first and second charges are introduced substantially simultaneously. In a second embodiment, the charges are introduced sequentially. After the hollow plastic article has solidified, the gas is vented.

Abstract: A method of gas-assisted injection molding in which a first charge of pressurized gas is injected into the mold, but not into the article-defining cavity. The gas charge is of a predetermined pressure sufficient to assist in filling out the article-defining cavity with resin and promoting surface quality. A second charge of pressurized gas may be introduced into the mold at a location remote from a first resin flow path by which the resin entered the article-defining cavity. The second charge of gas is of a pressure and quantity sufficient to enter the article-defining cavity but not into the first resin flow path. In the embodiment of FIGS. 9 and 10, the second charge of gas is directly introduced into the article-defining cavity. In the embodiment of FIGS. 4 through 8, the second charge of gas is introduced into a resin reservoir in communication with the article-defining cavity by a second resin flow path.

Abstract: A pressurized fluid reservoir having a variable working volume includes a cylinder body having a fixed storage volume an a first inlet and exhaust structure for allowing a compressible fluid to enter and leave the cylinder. A second inlet and exhaust structure is also provided or allowing a substantially incompressible fluid to enter and leave the cylinder. A first charge mechanism pumps the compressible fluid into the cylinder. A second charge mechanism pumps the substantially incompressible fluid into the cylinder to reduce the cylinder fixed storage volume to a desired working volume into which the compressible fluid cna be pumped by the first charge mechanism.

Abstract: A method and apparatus for injection molding plastic articles with gas-assistance wherein the injected molten plastic is depressurized by a controlled amount prior to gas injection to facilitate the penetration of the gas into the molten plastic within the article-defining cavity of the mold.

Abstract: A method of gas-assisted injection molding in which a charge of pressurized gas is injected into the mold, but not into the article-defining cavity. The gas charge is of a predetermined quantity and pressure sufficient to assist in filling out the article-defining cavity with resin and promoting surface quality. In another feature, the gas pressure within the resulting molding may be relieved by separating the mold halves and permitting the gas-containing portion of the molding to self-rupture, or by means well known in the art.

Abstract: A process for molding a thermoplastic material includes the aspect of venting fluid through a bore in a valve member of a nozzle body through which thermoplastic material flows. The nozzle body is communicated with a mold space into which the thermoplastic material flows. The mold space is defined by mold surfaces. Then the valve member is actuated to allow thermoplastic material to flow through the nozzle body into the mold space. Subsequently, pressurized fluid is allowed to flow through the valve member bore into the thermoplastic material in the mold space to form a cavity in the thermoplastic material. Then the valve member is actuated to terminate the flow of thermoplastic material through the nozzle body. The pressurized fluid is allowed to flow through the valve member bore into the fluid cavity. Finally, the pressurized fluid is vented from the fluid cavity to the valve member bore.

Abstract: 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.

Abstract: A method and associated apparatus for the injection molding of plastic articles of enhanced surface quality using fluid pressure. The method involves the initial step of injecting molten plastic at a nominal injection pressure from an injection molding machine through a flow path to a mold cavity defining the shape of the molded article. A charge of fluid pressurized at a predetermined level no greater than the nominal plastic injection pressure is communicated to the plastic flow path through an orifice of sufficiently small dimension to resist entry of the molten plastic against the pressure of the fluid charge. The pressurized charge of fluid responds to a reduction of the pressure in the plastic flow path below the predetermined level upon substantial completion of plastic injection and enters the flow path and passes into the mold cavity. The fluid is contained within the mold cavity under pressure until the article has set up, and is thereafter vented to atmosphere.