Abstract: This invention relates to an improved method of manufacturing a heater nozzle for an injection molding system. The heater nozzle has a helical heating element which is cast into an outer portion around an inner liner through which the melt flows. The outer portion is formed of a conductive material such as a beryllium copper alloy and the inner liner is formed of a durable corrosion resistant material such as stainless steel to provide an excellent combination of these characteristics. The heater nozzle is made by positioning the heating element around a pre-heated solid threaded liner in a mold and pressure casting the beryllium copper outer portion around them. The elongated liner is very accurately located in the mold by having the lower end received in a seat in the mold and the upper end received in an aperture through the plunger as it closes.

Abstract: An improved hot tip nozzle seal for use in a sprue gated injection molding system and a method of manufacture. The nozzle seal has a cylindrical outer portion, an elongated central pin portion and a number of ribs extending therebetween to define a number of apertures through the nozzle seal. The outer portion is seated in both the heated nozzle and the cavity plate to bridge the insulative air gap between them. The central pin portion of the seal has a tip portion which extends downstream into the gate and a head portion which extends upstream into the nozzle bore. The central pin portion has an inner conductive portion formed of copper and an outer protective casing formed of steel.

Abstract: This invention relates to an improved connector assembly for an electrically heated injection molding sprue bushing and a method of making the same. The sprue bushing has a helical portion of the heating element extending around a central core portion which conveys pressurized melt from a molding machine to a cavity in the mold. It is formed by filling the space between the stainless steel core portion and a stainless steel outer sleeve by a highly conductive copper alloy. The heating element has a lead portion which extends out through an aperture. The aperture provides a seat which receives two split washers with central openings therethrough for the lead portion. The washers are each formed of two half washers which are oriented so that the divisions therebetween are not aligned. A connector sleeve is inserted over the projecting lead portion with a flared end which is received in the aperture against the washers. The washers and connector sleeve are brazed in position in a vacuum furnace.

Abstract: This invention relates to an improved method of installing an elongated heater such as a cartridge heater in a molding member such as an injection molding manifold member. First, a bore is drilled into an elongated portion of the manifold member to extend generally parallel to the hot runner passage extending through it and a filler duct is drilled from the top to intersect the bore along its length. The cartridge heater is then inserted into the bore and a filler tube with a base is set on the top in alignment with the filler duct. A brazing paste is then applied around the base of the filler tube and around the terminal portions of the cartridge heater extending from the bore. The manifold member is then heated in a vacuum furnace which brazes the filler tube in position and seals the outer end of the duct against leakage.

Abstract: This invention relates to a spacer clip for an injection molding electric heating element. A number of clips, each formed of a continuous band, are slipped over one end of the heating element and slid along to predetermined positions. Each clip is then crimped to the heating element in that position which forms a finger which extends radially from the heating element in a predetermined orientation. The heating element with the spacer clips attached is located in a suitable mold for casting and the fingers of the clips locate each coil of the element with sufficient clearance from the mold and the other coils. The thickness of the conductive heater cast around the heating element is important to provide uniform heat transfer. The spacer clips are formed of a material such as stainless steel which has sufficient pliability to be securely crimped to the heating element, but sufficient strength to reliably retain the heating element in position.

Abstract: This invention relates to an improved valve pin bushing for use in a multi-cavity valve gated injection molding system and a method of manufacture. Each valve pin bushing has a main body portion which is positioned between the end of a manifold plate arm and the heated nozzle, and a collar portion which projects from the main body portion with clearance beyond the end of the manifold plate arm. The melt passage 34 extending through the manifold plate joins a melt duct extending diagonally through the main body portion and the valve pin is snugly received in a bore in the bushing. The bore has an enlarged portion which receives the melt from the diagonal duct which then flows through the heated nozzle around the valve pin. The valve pin bushing has a peripheral flange which laterally locates it in the cavity plate to offset frictional forces from thermal expansion of the manifold plate.

Abstract: This invention relates to an improved valve pin for an injection molding system and a method of making the same. The elongated valve pin has a tip end portion which extends from a larger driven end portion into the flow of melt to the cavity. The elongated tip end portion is provided with a desired combination of strength and thermal conductivity by having a copper core inside a steel casing. The casing is made by brazing a tip end cap member to a hollow sleeve. A predetermined quantity of copper wire is then inserted into the casing and melted in a vacuum furnace to form an integral construction. The excess sleeve is then cut off and the end is brazed into a well in the driven end portion of the valve pin. The tip end cap member is then machined to provide a tip end of a desired shape.

Abstract: This invention relates to an improved connector assembly for an electrically heated injection molding sprue bushing and a method of making the same. The sprue bushing has a helical portion of the heating element extending around a central core portion which conveys pressurized melt from a molding machine to a cavity in the mold. It is formed by filling the space between the stainless steel core portion and a stainless steel outer sleeve by a highly conductive copper alloy. The heating element has a lead portion which extends out through an aperture. The aperture provides a seat which receives two split washers with central openings therethrough for the lead portion. The washers are each formed of two half washers which are oriented so that the divisions therebetween are not aligned. A connector sleeve is inserted over the projecting lead portion with a flared end which is received in the aperture against the washers. The washers and connector sleeve are brazed in position in a vacuum furnace.

Abstract: This invention relates to an improved method of making a sprue bushing for injection molding and the improved sprue bushing made thereby. The runner passage extends through a corrosion resistant inner core portion with an outer surface around which a helical electrical heating element is located. A stainless steel outer sleeve extends between an enlarged front portion which provides the opening to the gate and an enlarged back collar portion which provides for connection to the heating element leads. The space around the heating element is filled by a highly conductive material such as a beryllium copper alloy in a vacuum furnace which causes the beryllium copper to fuse with the adjacent materials. This improves the transfer of heat from the heating element to the melt and the outer sleeve substantially reduces the costly machining required to produce the finished product as well as provides additional strength.

Abstract: This invention relates to an integral heated probe for plastic injection molding and a method of making the same. The probe has an elongated steel outer body with a cylindrical well extending to a pointed tip end. An electrical cartridge heater member positioned in the well with the leads extending out the open end. The space adjacent the pointed tip end and all around the cartridge heater is filled with copper to improve heat transfer between the heater member and the outer body. The copper fusing is performed by two-stage heating in a vacuum furnace. First a slug of copper is inserted into the well and heated to melt it into the pointed tip end. Then the heater member is inserted into the well through a sleeve of copper at the top and heated to melt the copper. The copper flows down around the heater member and fuses to it, the outer body and the previously inserted copper.

Abstract: This invention relates to an improved method of making a sprue bushing for injection molding and the improved sprue bushing made thereby. The runner passage extends through a corrosion resistant inner core portion with an outer surface around which a helical electrical heating element is located. A stainless steel outer sleeve extends between an enlarged front portion which provides the opening to the gate and an enlarged back collar portion which provides for connection to the heating element leads. The space around the heating element is filled by a highly conductive material such as a beryllium copper alloy in a vacuum furnace which causes the beryllium copper to fuse with the adjacent materials. This improves the transfer of heat from the heating element to the melt and the outer sleeve substantially reduces the costly machining required to produce the finished product as well as provides additional strength.

Abstract: This invention relates to an edge gated injection molding system. An electrically heated sprue bushing is seated in a well in the cavity plate with a centrally extending melt runner passage which branches radially outward with separate channels leading to a number of edge gates in the cavity plate. An air gap is provided to insulate the hot sprue bushing from the surrounding cooled cavity plate and a hollow seal is provided at each gate to convey the melt across the air gap. Each seal is in alignment with one of the channels and one of the gates, and has its inner end seated in a recess in the sprue bushing and its outer end abutting against the curved wall of the cavity plate. The outer ends of the seals are dome shaped so that they are slightly resiliently deformable. A portion of the wall of the cavity plate is slightly inwardly tapered so that at the gates, the effective combined diameter of the sprue bushing and the seals is slightly larger than that of the well.

Abstract: This invention relates to mechanical double acting mechanism for actuating valve pins in a valve gated injection molding system. A number of valve gate units are aligned with a pneumatically driven toothed rack member. The rack member engages a hollow rotatable pinion member which is secured in each unit against transverse movement. The driven end of the valve pin is fixed in a bushing which extends through the pinion member and threadably engages it. The valve pin is actuated between the open and closed positions by longitudinally driving the rack member which rotates the pinion member and the bushing. In addition to providing a reliable and relatively inexpensive actuating mechanism, provision is made for relative axial adjustment of the valve pins prior to the commencement of operation which provides accurate valve seating without unduly high manufacturing tolerances.

Abstract: This invention relates to an improved valve-gated injection molding system. The hot runner passage through which the melt flows to the cavity is divided into three spiral-shaped channels which converge again immediately before the gate, thereby imparting a curving motion to the melt as it flows outward from the gate in the cavity. This avoids unidirectional molecular orientation of the melt, thereby providing a stronger molded product. In a preferred embodiment of the invention, the melt channels reduce in helical diameter and cross sectional area as they approach the gate, thereby accelerating the swirling motion of the melt.

Abstract: This invention relates to a nozzle seal for valve-gated injection molding. The hollow seal is seated in the nozzle portion of the heater cast and extends across the insulative air gap and into a gate aperture in the cavity plate. The inner bore of the nozzle seal is tapered to form the gate which receives the tip end of the valve pin in the closed position. The nozzle seal is formed of a poor conductive metal such as titanium alloy which conducts sufficient heat to provide a clean closing gate without resulting in unacceptable heat loss to the surrounding cavity plate.

Abstract: This invention relates to an improved injection molding filter assembly to be located between the molding machine and the mold. The assembly has an elongated inner torpedo member with a generally cylindrical outer surface which is centrally located in a passage through a hollow outer member. The passage is defined by a generally cylindrical inner wall which is interrupted by an even number of inwardly opening longitudinally extending channels. Inlet channels extending from the inlet of the assembly and dead ending adjacent the outlet alternate with outlet channels extending from the outlet of the assembly and dead ending adjacent the inlet. Filtering apertures are formed between the outer surface of the torpedo member and the lands between the inlet and outlet channels through which the melt flows from the inlet channels to the outlet channels.

Abstract: This invention relates to a hot tip seal located between the nozzle and the gate in an injection molding system. The seal has a generally cylindrical hollow outer portion which is seated in the nozzle and extends to abut on the cavity plate around the gate. Three ribs extend radially from the outer portion to an elongated central pin portion and define apertures therebetween. Pressurized melt flows from a central passage in the nozzle, through the apertures around the central pin portion, and into the cavity. The nozzle seal prevents direct contact between the heated nozzle and the cooled cavity plate to reduce heat loss, while at the same time improves heat transfer to the gate area by conducting heat downstream to a tip of the central pin portion which extends into the gate. In one embodiment, the central pin portion is enlarged and formed of a more conductive material to improve this process.

Abstract: This invention relates to an improved injection molding filter assembly to be located between the molding machine and the mold. The assembly has an elongated inner torpedo member with a generally cylindrical outer surface which is centrally located in a passage through a hollow outer member. The passage is defined by a generally cylindrical inner wall which is interrupted by an even number of inwardly opening longitudinally extending channels. Inlet channels extending from the inlet of the assembly and dead ending adjacent the outlet alternate with outlet channels extending from the outlet of the assembly and dead ending adjacent the inlet. Uniform width elongated filtering slits are thus formed between the outer surface of the torpedo member and the lands between the inlet and outlet channels. The melt flows into the inlet channels, through the adjacent filtering slits, and out the outlet channels.

Abstract: This invention relates to injection molding and particularly to a melt transfer system for stack molding. According to the invention, a novel combination of known melt flow control valve units are arranged and operated to control the flow of pressurized melt from the stationary platen adjacent the molding machine to a manifold in the center moving platen. One control valve unit is located in the stationary platen in alignment with another control valve unit located in the moving platen. When the moving platen is in the closed position adjacent the stationary platen, the gates of the two control valve units abut and when the valve pins of the two control valve units are actuated to the open position, pressurized melt will flow through the gates from the stationary platen to the moving platen. The hot runner passage extends from the molding machine through the control valve unit located in the stationary platen.

Abstract: This invention relates to an improved electrically heated sprue bushing for injection molding. The sprue bushing has a central runner passage for conveying melt from the molding machine or manifold to the cavity. The runner passage extends through an elongated inner core portion having an undulating outer surface in the form of a helical ridge with a rounded cross section. A single element electrical heating element with a helical configuration is located over the core portion and an outer shell portion is cast over them to form the sprue bushing as an integral unit. The inner core portion is formed of a high strength material such as a beryllium nickel alloy and the outer shell portion is formed of a highly conductive material such as a beryllium copper alloy. The coils of the heating element are separated from each other and threaded in the opposite direction to the helical ridge on the outer surface of the core portion.