Abstract: A process and apparatus for injection molding thin-walled plastic articles having comparatively thick lip portion. The apparatus has a mold cavity and a mold core defining a cavity space in the shape of the article and at least one injection gate adjacent a portion of the cavity space defining the lip portion through which molded plastic is injected into the cavity space. The direct lip gating approaches employed in the apparatus do not sacrifice core/cavity alignment and conventional mold motions along the machine axis and form plastic articles having substantially no gate vestiges on the lip sealing surface or on the outer perimeter of the lip.

Abstract: Apparatus for forming multilayered articles including a nozzle communicating with the mold cavity. The nozzle includes a first nozzle channel for feeding a first thermoplastic material to the mold cavity and a second nozzle channel communicating with the first nozzle channel for feeding a second thermoplastic material to the mold cavity. A metered amount of second material is fed from the second nozzle channel to the first nozzle channel and subsequently to the mold cavity by the first material from the first nozzle channel.

Abstract: A heated injection molding nozzle for use in an injection molding system for injection molding of several different plastic melts in one injection molding cycle. The nozzle has an elongated nozzle body with first and second longitudinal melt passages for two different plastic materials. The second melt passage is a melt bore which extends centrally through the nozzle body. The first melt passage has two outer melt bores which extend through the nozzle body on opposite sides of the second melt passage. The rear end face of the nozzle body has an off center melt inlet recess and two melt branch passages extending to the two outer melt bores.

Abstract: A method of molding a flipper link to reduce or eliminate the tendency of the flipper link to break. The method includes the steps of forming a mold cavity for forming a flipper link having a first end portion, a second end portion and an intermediate necked-down portion. The necked-down portion provides an area between the first and second end portions which more easily twists and absorbs the stress exerted on the flipper link during use. Pins are provided in the cavity for forming an aperture in each of the first and second end portions. Plastic material is injected into the cavity at each end of the first and second end portions such that the plastic material flows into the cavity about the pins and the knit line or lines are formed in the flipper link in a location substantially centrally of the necked-down portion to thereby transfer the stress on the flipper link away from the apertures so as to substantially eliminate the tendency of the flipper link to break about the apertures.

Abstract: A method for manufacturing a three-layered container by injection molding, the method consecutively including steps of:(a) preparing an injection molding apparatus having:an inner injector element having a tubular inner body and a flow path communicating with the inner inlet nozzle and an inner injecting nozzle formed both ends of the body, respectively; andan outer injector element having a tubular outer body including an outer injection nozzle and an outer inlet nozzle, the outer injector element disposed to hold the inner injector element so that a tubular space is formed between the inner and the outer bodies, the inlet nozzle of the outer body communicating with a curved groove formed in the outer surface of the inner injector body; andthe inner surface of the outer body and the outer surface of the inner body are in a form so that the thickness of the tubular space therebetween is smaller at a portion compared to other portions;(b) injecting a first resin from the outer injection nozzle;(c) injecting a

Abstract: Multi-cavity injection molding apparatus to coinject pressurized melt from two or more melt sources. An inner melt passage extends through the central bore of a melt distribution plate and an adjacent heated nozzle. The nozzle has a tapered nose portion which extends into an adjacent heated cavity forming insert having a gate leading to one of the cavities. An outer melt passage is separated by curved conduits on opposite faces of the melt distribution plate into four channels which are radially spaced around the central bore of the nozzle. The four channels lead to a melt funnel duct which extends in the adjacent cavity forming insert around the nose portion of the nozzle. Thus the melt from the outer melt passage is evenly distributed around the melt from the inner melt passage when they join just before entering the gate.

Abstract: An injection mold for forming the halves of a magnetic tape cassette includes stationary and movable molds defining a cavity, and confronting slidable cores disposed in holes extending through the molds. An opaque primary resin is injected into the cavity to form an outer portion of a cassette half with the core faces abutting each other, whereafter the cores are retracted to define a central window cavity in which a transparent secondary resin is injected. A lip surrounds the inner edge of the hole through which one of the cores extends to laterally support and guide the core, and to avoid any jamming or inaccuracy in the retracted position of the core due to thermal expansion.

Abstract: An injection mold unit is provided for an alternate feed, injection molding of parts of a plasticized material and has first and second plasticizing and injection devices, with a respective bores and a mold comprising a heating channel block and a mold cavity. The heating channel has a first passageway connected to the bore of the first plasticizing and injection device, the first passageway having first and second branches in fluid communication with the mold cavity. The heating channel also has as well as a second passageway connected to the bore of the second plasticizing and injection machine and having first and second branches in fluid communication with the mold cavity. One way valves are located in each of the first and second branches of the first and second passageways.

Abstract: Apparatus and method for molding plastic articles including oscillating the molten plastic in the mold cavity. The method and apparatus is particularly suitable for use with a plurality of mold cavities supplied from a single feeding means or extruder. The disclosure teaches alternately feeding molten plastic to the mold cavity from shooting pots while the flow of molten plastic to the mold cavity from the feeding means is discontinued.

Abstract: An integral heated torpedo for use in injection molding has an internal melt distribution chamber which distributes heated melt through multiple melt flow paths onto the exterior surface of the torpedo. The torpedo is formed from a single piece of metal and has an elongate body portion which extends axially from an enlarged end portion and which terminates in tip. The center of the torpedo body portion contains an axial cavity extending between the torpedo tip and the enlarged end portion. The bore is adapted to receive a heating element which includes a coil of resistance wire and a thermocouple which are surrounded by heat insulative material. A plurality of melt flow passages extend axially through the enlarged end portion and are disposed generally around the torpedo bore to provide a series of melt flow paths through the enlarged end portion onto the heated exterior surface of the torpedo body.

Abstract: A bushing used in an injection molding machine and positioned between the nozzle and the sprue thereof includes an adaptor body having a longitudinal axis, a first end and a second end. A first bore extends in the adaptor body parallel to the longitudinal axis from the second end to the first end for accommodating a flow of relatively viscous fluid such as a molten thermoplastic. A bridge extends transversely across the first bore between opposing walls of the bore adjacent the adaptor body first end. Fluid flow is allowed through the first bore around the bridge. A second bore extends from a surface of the adaptor body to a surface of the bridge for accommodating a flow of a relatively non-viscous fluid such as gas. The second bore terminates on the bridge surface so as to be substantially coaxial with the first bore.

Abstract: An apparatus for making a plastic injection molded part with a smooth surface or skin and a hollow core wherein thermoplastic material is injected as a molten stream into the mold cavity through a sprue bushing fixed in the mold. Simultaneously, an unmeasured quantity of inert gas is introduced through an adapter into the molten stream at the sprue bushing substantially coaxially with the melt stream and at a pressure sufficient to penetrate the thermoplastic material to form a gas cavity in the molten material in the mold. For retrofitting an existing mold, an adapter can be added to the existing sprue bushing. During plastic injection and cooling in the mold the gas is maintained at a high pressure, preset, constant and adequate to maintain the plastic against the mold surface until it is self-supporting. The gas is exhausted from the mold, back through the sprue bushing and adapter, before the mold is opened.

Abstract: An injection molding machine has a high volume cylinder with a piston slidably disposed in the cylinder. The piston is formed with channels and check valves for selective communication from the back of the cylinder to the front of the cylinder. A vertically disposed screw plasticizer provides molten thermoplastic material to the back of the cylinder, which material flows to the front of the cylinder with rearward movement of the piston. When the front of the cylinder is filled with thermoplastic material, the piston is moved forewardly to inject the thermoplastic material into a mold. A reciprocating screw plasticizer first assists in filling the front of the cylinder, and then in completing the injection molding under a high pressure. Novel composite thermoplastic products may be produced.

Abstract: A mold for injection molding including a cylindrical outer mold and a columnar inner mold. The inner mold is provided, on its external circumferential surface, with a large number of tooth-shaped grooves extending in the axial direction thereof, and it is placed inside the outer mold to define an annular cavity between the external circumferential surface of the inner mold and the internal circumferential surface of the outer mold. The outer mold is provided with a plurality of runners extending axially near the internal circumferential surface. The runners are arranged at regular annular intervals along the circumference of the outer mold. Furthermore, slit-shaped gates are formed along the full length of the runners, the gates opening into the internal circumferential surface of the outer mold, in such a way that the inflow of molten molding material flowing from each runner into the cavity is gradually reduced along the runner from the upstream side towards the downstream end.

Abstract: A number of heated injection molding nozzles are mounted along the side surface of a melt conveying manifold. In one embodiment of the invention, a connector collar having a tapered flange portion is bolted to the side surface of the manifold to provide each melt bore outlet. Each nozzle has a matching flange portion with a melt bore inlet extending laterally from a side surface. The nozzle is mounted on the manifold by securing the flange portions together by bolting a wedge clamp having two halves over the aligned flange portions. This accurately aligns the inlet with the outlet and allows the nozzle to be rotated to a particular angular position. In another embodiment, a melt conduit member is mounted between the manifold and each nozzle. The melt conduit member is clamped to the manifold after being rotated to a desired angular position about a first axis.

Abstract: A process and apparatus for injection molding of injection molded parts of plasticized material, in particular plasticized liquid crystal polymers, in which the plasticized material is injected into the mold cavity of a closed injection mold having at least two spaced apart infeed gates, separate plastification and injection devices being associated with each of the gates. The plasticized material may be further injected into the mold cavity to compensate for any shrinkage during cooling of the molded material. Injection is carried out by at least one of the devices which causes the material to flow into the cavity via one of the gates associated therewith for filling the cavity and causing the material to partially flow from the cavity via the other of the gates in the direction of the other of the devices associated therewith.

Abstract: A cold runner block (38) has spaced drop holes (54) arranged in a selected pattern for supplying fluid molding material to nozzles (60) connected to the mold gates (62). The drop holes (54) open on nozzle runners (52) in the cold runner block (38) which are in communication with a source of fluid molding material. Close-off rods (68) are selectively positioned in the runners (52) to block the flow of fluid molding material beyond the drop holes (54) communicating with a mold (12) for an object of a particular size and shape. Drop hole plugs (66) are provided for the drop holes (54) which open on the nozzle runners (52) in the section of the runners (52) not blocked by the close-off rods (68).

Abstract: It has been found that when layered preforms are being injection molded utilizing at least two materials, it is possible to maintain the same horizontal and vertical pitch of adjacent cavities as is possible when each mold cavity is being filled with a single material. Most particularly, it has been found that when the percentage of the material to be injected into a mold cavity is relatively high, it is possible to utilize a single metering pot for four adjacent mold cavities. On the other hand, if one of the materials to be injected into a mold cavity constitutes a relatively low percentage of the volume of a mold cavity, it has been found that a small metering pot must be provided for each of the cavities of the four cavity mold.

Abstract: A moulding process including:supplying molten, mouldable material to a mould cavity;subjecting at least a part of the supplied molten material to a shear force;causing the material to solidify while maintaining the shear force; anddemoulding the moulded material.

Abstract: A valve gated injection molding system for making hollow plastic products. A fixed pin extends through an elongated hollow valve member which is reciprocated between a retracted open position and a forward closed position in which the forward end of the valve member is seated in the gate. The fixed pin has a hollow portion for the flow of pressurized gas to a porous portion at the forward end which is centrally located in the gate. In the open position, gas from the fixed pin flows into the hollow center of a stream of melt which flows into the cavity around the forward end of the fixed pin to form a melt bubble in the cavity.

Abstract: A mold assembly having a support member which is moveable in a direction of travel both toward and away from an end plate and supporting individual mold side walls which are slideably moveable along a path of travel from a mold open to a mold closed position; and a locking member is selectively moveable into movement restraining relation relative to the individual mold side walls thereby positioning the individual mold sidewalls in the mold closed position.

Abstract: An apparatus for encapsulating selected portions of the printed circuit board in a pin grid array using transfer molding techniques. In one embodiment for encapsulating only the top surface and side edges of the board, a vacuum is provided in the lower cavity to hold the edges of the bottom surface of the board flush against the mold plate. In a second embodiment for encapsulating all exposed surfaces of the board, the array pins are inserted in holes in the bottom of the cavity and supported by an adjustable block which positions the board in the cavity.

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.

Abstract: In a metal mold for a multi-layer resin molded article for effecting, in injection-molding a cylindrically-shaped part, sandwich molding in which core layer resin is used for the center of the cylinder portion of the cylindrically-shaped part and skin layer resin is used for the portion around the center of the cylinder portion, a mold member provided with a cavity for molding the cylindrically-shaped part has attached thereto a runner plate provided with a plurality of runners for passing the resins therethrough into the cavity, the runner plate has attached thereto a fixed plate provided with a sprue connected to an injection cylinder unit for the core layer resin and an injection cylinder unit for the skin layer resin, the start point of the plurality of runners and the injection port of the injection cylinder unit for the core layer resin are arranged on a straight line, and a runner for the skin layer resin is provided between the injection cylinder unit for the skin layer resin and the start point of th

Abstract: A viscoelastic fluid molding material (50) is injected into a tire tread cavity (32) between the mold (10) and an inflatable tread supporting body (30). The clearance distance (A) between the mold (10) and the inflatable tread supporting body (30) is varied to increase the flow of the initial amount of fluid molding material (50) into remote portions of the tire tread cavity (32) and provide for the flow of the final amount of fluid molding material (50) into gate portions (52) while the tread supporting body (30) is being deflected.Circumferentially spaced gates (76) may be spaced from the centerplane (20"--20") of the mold (10") and have runners (80) extending toward the shoulders of the tread supporting body (30") for increased flow of the initial amount of fluid molding material (50") into remote shoulder portions (52") of the tread cavity (32").

Abstract: This invention relates to a valve gated injection molding system in which a number of melt conveying nozzles leading to a common cavity are releasably clamped to the side surface of an elongated manifold. A cylindrical collar around the inlet to each nozzle is received in a recessed seat around each outlet from the manifold. This structure facilitates assembly and ensures alignment of the inlets and outlets, while permitting for some rotational movement between the nozzles and the manifold due to thermal expansion. The integral nozzles are made by vacuum casting a heating element and vacuum brazing a side member with a sidewards projecting face into a steel main body.

Abstract: This invention relates to a multi-cavity injection molding system in which a number of nozzles are fixed to a common manifold, and valve gating is provided by actuating the manifold and the nozzles together. A pair of hydraulically actuated pistons are mounted to drive the manifold and nozzles between a retracted open position and a forward closed position. Each nozzle has a truncated tip on the forward end portion which seats in a gate in the closed position. Pressurized melt flows through a melt passage which branches in the manifold and extends through each nozzle to a melt receiving space around the forward end portion. A circumferential sealing and locating flange prevents the leakage of melt from this space as the nozzle reciprocates.

Abstract: The injection molding of an elongated thin-walled tubular product such as a medical catheter is accomplished through the mounting of an elongated core pin on the interior of an elongated mold cavity wherein tension is continuously applied to the core pin for the purpose of maintaining it in a predetermined, substantially centered relation to the mold cavity and further maintaining a straight line configuration of the core pin along its length. The plastic material from which the product is formed is introduced into the mold cavity while at the same time overcoming any imbalance in the flow of the plastic melt into the mold cavity and as it travels in surrounding relation to the core pin and along its length by adjusting the position of the core pin relative to the inner surface of the mold cavity.

Abstract: Apparatus for producing an injection moulding of plastics material comprises means for introducing a supply of plastics material, passage means for communicating the supply means to a mould space, and means for introducing a pressurized gas into the plastics material filling the mould space whereby the gas creates a gas containing cavity in the plastics material and for thereafter relieving the gas pressure within the gas containing cavity before the mould is opened.

Abstract: An elongate plastic cylindrical product is molded in one piece including a nozzle extending from an end wall, the flow of plastic being achieved by injecting plastic adjacent the desired end wall so that the plastic flows in one direction to form a cylindrical portion and in another direction to form the end wall and nozzle.

Abstract: In a small-sized and precision injection molding apparatus, a raw material supply means, a raw material plasticization means, an injection plunger means and a melted resin flow passage means are all together incorporated in a mold, thereby a substantial distance from the raw material up to a cavity becomes shorter. Thus, an overall construction of the injection molding apparatus becomes small-size and compact.

Abstract: Apparatus for coinjecting a plurality of thermoplastic materials to mold an article having a layered wall structure using thermoplastic material having different optimum processing temperatures including the maintenance of the optimum temperatures in flow paths individual to each material from its source to a mold cavity.

Abstract: In a molding machine wherein in molding a molded article, the molded article is molded into a so-called sandwich shape in which the central portion of the molded article is molded with core layer resin and the outer surface of the core layer is wrapped with skin layer resin, a valve for changing over and injecting the resins from a first injection cylinder for injecting the core layer resin and a second injection cylinder for injecting the skin layer resin is substantially cylindrical, a cut-away portion for changing over and distributing the resins is formed in the central portion of the valve, and sandwich molding is accomplished with the opening-closing of the cut-away portion and each passageway being effected by rotation of the valve.

Abstract: This invention relates to a valve gated injection molding system in which melt flows through an elongated manifold to a number of spaced nozzles to fill a single non-linear cavity. Each nozzle is mounted against a manifold offset block which is bolted to the side of the manifold. Pressurized melt from the manifold flows through a melt duct in each manifold block and through the central bore of the respective nozzle to a gate into the cavity. Actuating mechanism is mounted to reciprocate a valve pin extending through each manifold block and nozzle. Each manifold offset block can be mounted with a different orientation on the side of the manifold to properly space the gates along the non-linear cavity to ensure it completely fills as quickly as possible. Slight lateral movement of each manifold block relative to the manifold is permitted to avoid melt leakage due to misalignment of the nozzles as a result of thermal expansion of the manifold.

Abstract: Nozzle for synthetic plastic injection molding machines made up of a shaft including a flow channel for plastic material and equipped with a tip. The flow channel is divided so that the plastic flows in two partial channels prior to reaching the tip. The shaft is made of a tube segment. The forward frontal orifice of the tube segment has a small plate tapering into a point. The point protrudes past the shaft. The tube segment at its frontal orifice has both an internal and an external turned recess. The internal recess serves as a seat for the small plate. The external recess serves as a seat for a nozzle cap, which comprises the injector orifice of the nozzle and serves to hold the small plate in place. The small plate has a shoulder at the transition to the tapering area to serve as a contact surface for a corresponding shoulder formed in the nozzle cap.

Abstract: This invention relates to an injection molding system in which melt flows in channels in the outer surface of a heated probe seated in the cavity plate on its way to the gate leading to the cavity. The probe has a tip end in alignment with the gate and the probe is reciprocated between open and closed positions to valve gate the flow of melt to the cavity. According to a preferred embodiment, in a multi-cavity system a number of probes are fixed to a manifold which is actuated to valve gate all of the cavities simultaneously. Hydraulic cylinders are provided to drive the manifold to the closed position, and injection melt pressure acting on the tip ends of the probes is utilized to return them to the open position. Valve gating the heated probes provides the advantage of improved temperature control of the melt in the immediate gate area.

Abstract: In a plastic-surrounded bearing in which a pulley made of plastic wider than the width of the outer race of the bearing and provided with extended portions on the opposite sides of the outer race is integrally coupled to the outer race of the bearing by insert injection molding, the pulley has gates for pouring plastic therethrough in one end surface thereof, recesses are provided at a plurality of circumferential locations between the inner peripheral edge and the outer peripheral edge of the end surface of the extended portion of the pulley, and the plastic portions lying between the recesses are reinforcing ribs, the thickness of the ribs between the adjacent recesses in at least one end surface is made greater in the circumferential direction away from the gates.

Abstract: A press with a plurality of injection plungers, which can be used to enclose integrated circuits in plastics packages, is provided with additional compensating pistons. The lower ends of the compensating pistons and the upper ends of the injection plungers project into a filling pot in which the plastics material is molded. The injection plungers force the plastics material in the injection mold through channels into cavities provided in the mold. When a predetermined pressure P.sub.k is exceeded, the compensating pistons retreat, so that a pressure drop and, thus, pressure limitation occur. In this manner, scrap would be avoided even if too large a quantity of plastics material were placed in the filling pot.

Abstract: Apparatus for making a rigid container by injection molding a parison having plural layers of polymers. The parison is blow molded to the final shape of the container. Control during injection is exercised over each of the plural polymers so as to produce uninterrupted layers extending throughout the walls of the parison and to insure that the interior layers are completely encapsulated within the outer layers.

Abstract: A method and apparatus are disclosed in which a mold plate is provided for defining a mold opening and in which a foraminous member is provided with rows of apertures communicating between an upstream side and downstream side of the member. Narrow slots connect the adjacent apertures in each row. The foraminous member is disposed with the downstream side adjacent the mold plate and has spaced-apart ribs on the upstream side oriented between, and parallel to, the rows of apertures. Pressurized food material is forced from the upstream side of the foraminous member through the apertures to the downstream side of the foraminous member and into the mold opening as discrete extrudate masses which together define a packed array forming the patty. An agitator bar with spaced-apart teeth is disposed on the upstream side of the foraminous member with a tooth disposed between each pair of adjacent ribs.

Abstract: A packaging system for encapsulating an article within a solid foam material. An article to be encapsulated is supported on a base. A wall enclosure is disposed on the base to form a mold cavity. At the top of the base and above the article to be encapsulated is a cover. Expandable plastic foam in liquid form is introduced into an orifice of the base and the expandable plastic foam advances through a passageway in the base and is discharged from an orifice in the base into the mold cavity to encapsulate the article. The foam material in liquid form solidifies into a solid plastic foam material for packaging the article.

Abstract: A method and a mold for fabricating an aerodynamic airframe structure or the like. The method using foam material introduced into the mold having split halves. The mold constructed for receiving a prefabricated stiffener skin. The mold acts as a backup restraint for the airframe structure or any other part being produced. The foam injected into the cavity adheres to the stiffener skin thereby forming an elastic foundation of continuous support for the stiffening element.

Abstract: A device for use with a runner block and a multi-polymer co-injection nozzle having separate rear entrance ports for separate polymer streams, in a multi-coinjection nozzle, multi-polymer injection molding machine, for receiving from the runner block a plurality of separate polymer flow streams and for redirecting them to flow axially out of the forward end of the device into the nozzle rear entrance ports. The device has inlets cut radially into its periphery, each for receiving a polymer flow stream, and has feed channels, each in communication with an inlet and having an inward portion cut toward the device's central axis, and an axial portion communicating with the inward portion, running axially forward and terminating at an exit hole in the device's forward end, the exit holes being in a spaced pattern for feeding the separate polymer flow streams in spaced relation into the nozzle rear entrance ports.

Abstract: Polymer melt material flow stream splitter devices, including runner extensions, T-splitters and Y-splitters are provided, for splitting an incoming flow stream channel for each melt material, into first and second branched flow channels of equal length which communicate with sets of first and second branched exit ports, each set in an axially aligned, spaced pattern in different peripheral surface portions of the respective splitter devices.

Abstract: A process and apparatus for injection-molding a foamed article including a foamed core and an outer solid skin layer of unfoamed synthetic resin are provided. A first molten flow of the unfoaming synthetic resin is at first injected into a mold to form the outer solid skin layer. Subsequently, a second molten flow of a synthetic resin containing a foaming agent is fed into the first molten flow without stopping the first flow and is then mixed and kneaded to form a kneaded mass. The kneaded mass is then injected into the mold to form the core portion. Since the first flow is continuously fed during one operation cycle, the product molded article has no hesitation marks.

Abstract: Hot runner injection molding apparatus for coinjecting two thermoplastic materials sequentially through separate channels to form at least a two-layer sandwich material is provided. There is a valve means for instantaneously switching the flow of thermoplastic material from one channel to the other channel, the valve means preferably comprising a shuttle ball member.

Abstract: An improved device for making plastic articles from resin and an improved runner block assembly for a mold for making plastic articles from resin have been made by providing a runner block assembly having at least one channel wherein the channel has a cross-section with two opposite sides having a length substantially less than the two other sides thereby forming a thin, flat channel sufficient to provide shear resistance resulting from forcing resin through the channel; means for connecting the channel to a plurality of mold cavities, and means for supplying resin to the channel.

Abstract: In an injection mold apparatus for manufacturing molded bodies from two types of plastic, a first and third injection units (4 and 6) are connected to a single mold cavity, and a core piece (15) which is movable back and forth occupies a region of the mold cavity when said core is in the blocking position, and said core in this position separates (by closing off) a first mold cavity region (associated with the first injection unit) and the entrance opening of material coming from the third injection unit (6) into the mold cavity from a second mold cavity region (which is connected to the first injection unit (4), whereby first the second mold cavity region is filled from the first injection unit and then, after the core (15) is drawn back, the region of the mold cavity initially occupied by said core, and the first mold cavity region, are filled from the third injection unit, and whereby the core has a recess, the improvement comprising providing the recess (37) in the blocking region of the core (15), whereb

Abstract: A hot sprue assembly is provided for controlling flow of molten material into the mold cavity of an injection molding machine. The hot sprue assembly is particularly designed for use with an injection molding machine for molding centrally apertured record discs, such as video information discs. The hot sprue assembly includes a hot sprue bushing cooperating with a dispersion head to define an open and relatively narrow annular gate through which molten material is injected into the mold cavity, and a central die plug within the mold cavity for cooperating with the dispersion head to mold a central aperture into the disc. Valving of the molten material through the gate is achieved by heating the sprue assembly to create a temperature differential which, during solidification of the material within the mold cavity, permits the material within the mold cavity to solidify up to the gate without substantial solidification of material within the sprue assembly.

Abstract: An apparatus for injection-molding an insulating liner onto the surface of a metal spool to be included in an electromagnetic flowmeter in which the fluid to be metered is conducted through the lined spool. The spool is composed of a cylindrical body having end flanges and a pair of diametrically-opposed circular bosses disposed midway between the flanges to receive the meter electrodes. To carry out injection molding, the spool is supported within a mold which defines a liner cavity conforming to the inner surface of the cylindrical body and to the faces of the end flanges, the liner cavity communicating with cavities conforming to the inner surface of the electrode bosses. The molding material is injected into a sprue in the mold which runs along the longitudinal axis of the spool toward the hub of a runner extending radially toward an axisymmetric ring gate opening into the liner cavity at a point adjacent the boss cavities.