Abstract: A sprue and valve assembly (22) delivers a curable liquid material to a mold cavity (26) and thereafter is easily cleaned of the cured residual core (52) remaining from the liquid material. A sprue (34) having a flow passage (36) extends between the exterior surface of a mold (24) and a runner (30) in the mold (24). A valve body (54) is connected to the exterior face of the sprue (34). A coin slide type closure element (56) within the valve body (54) is controlled by a lever mechanism to selectively open or close the flow passage (36) to the curable liquid material flow. The flow passage (36) is tapered to permit easy removal of the cured residual core (52). PTFE seals (74) are disposed on opposite sides of the closure element (56). A bayonet fitting permits quick connection and disconnection of a supply line (18) to the valve body (54).

Abstract: A metal mold device for molding a substrate includes a fixed metal mold, a movable metal mold mounted facing the fixed metal mold for being moved towards and away from the fixed metal mold and for defining a mold cavity between it and the fixed metal mold, a stamper mounted on at least one of the fixed metal mold or the movable metal mold and arranged within the mold cavity, a positioning unit provided on the metal mold on which the stamper is mounted for positioning the loading position of the stamper, and a stamper supporting unit provided on the metal mold on which the stamper is mounted for supporting the stamper by suction. The stamper is positioned by the positioning member and held under suction by the stamper suction unit so that it may be mounted in position on the fixed metal mold or the movable metal mold to permit a disc substrate to be molded highly accurately.

Abstract: A molding flask structure for molding close tolerance articles, such as prosthetic dental devices. The flask structure includes upper and lower flask members that each include cup-recesses adapted to face each other to define therebetween a mold cavity when the flask members are connected together. Assembly of the flask members is effected by a plurality of connecting bolts to securely hold the flask members together. Vent passageways are provided in the flask members to extend from the mold cavity to permit excessive internal pressures to be relieved to the exterior of the flask member. A sprue opening defined by semi-cylindrical recesses in contacting faces of each of the flask members extends from the mold cavity to the exterior to permit the introduction of molding material into the mold cavity. The sprue opening is partially threaded and partially unthreaded.

Abstract: A system of injection-molding a super-precision product by an injection machine with a mold comprises conventional fundamental steps including a material plasticizing and metering step, an injection step and a material pressure-holding step, with additional features in that a nozzle passage, enlarged in volume, extending from a machine body to a cavity gate is interrupted midway therealong by a valve from communication with the interior of the body, after the injection step but while the pressure-holding step is being carried out. The pressure-holding step is carried out at least using the valve for exerting an internal pressure on a forward portion of the injected material separated due to the passage interruption, and compacted in a fixed closed space limited by the valve including a mold cavity, during which step a next plasticizing and metering step is commenced.

Abstract: A method and 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 exisiting 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: Single and double injection molding using a single molding machine is made possible by providing two injection units, each having an injection nozzle, and a stationary platen three insertion holes into which the nozzles can fit. For double injection, the injection units are moved transversely of the stationary platen so as to orient both injection nozzles with a respective one of the insertion holes. For single injection, the injection units again are moved transversely of the stationary platen so as to orient one of the injection nozzles with one of the insertion holes, with the other nozzle not being so oriented.

Abstract: A highly reliable hot sprue bushing for use in controlling the temperature of plasticized material while it flows from the nozzle to the runner or sprue system in an injection molding machine. Advantageously, the hot sprue bushing is adjustable in length so that it can be used with a full range of standard or custom mold plate thicknesses or other required lengths.

Abstract: In the plasticizing cylinder the plasticized plastic material is transported by a rotating feed screw into a space which is in front of the feed screw and the plastic material is subsequently injected into the injection mold of the injection molding machine by an axial discharge stroke of the feed screw. During that stroke a backflow-preventing valve is effective to seal a high-pressure space from a low-pressure space, which contains the feed screw. The plasticizing cylinder is composed of a cylinder head, which always completely encloses the high-pressure space and the backflow-preventing valve, and a cylinder shank, which encloses the low-pressure space and the feed screw. Even when the feed screw is in its rearmost initial position will the high-pressure space not be adjoined by a joint which leads to the outside of the plasticizing cylinder so that the problems previously encountered in connection with the sealing of the high-pressure space are avoided.

Abstract: A flask used with a method for making resin dental plates includes a splittable flask body having an upper lid member, a tray member and a lower lid member, all formed of a material through which microwaves are transmittable, an injection attachment to be mounted in place through a mounting hole between the tray member and the lower lid member and having an axial resin injection hole, and a sprue-opening closure member to close up the resin injection hole in the injection attachment, the flask body being provided in the vicinity of its side edge with at least two through-holes through which bolts of tightening mechanism are to be inserted. The tightening mechanism includes bolts and nuts, each formed of a material through which microwaves are transmittable, and the injection attachment having its outside shaped to fit into a recess formed at one end of the cylinder filled therein with a pasted resin.

Abstract: A modular manifold system is described. A plurality of generally cylindrical manifold components engage a melt distribution element. The manifold components each have a generally cylindrical body which has an annular cavity formed therein which axially extends with the component body for a predetermined length which separates the component body from a component inner core. A melt runner passage extends axially through the inner core. A heating element in the form of a ceramic insulator sleeve occupies a portion of the annular cavity with a particulate refractory material occupying the remainder of the annular cavity.

Abstract: An injection molding apparatus includes a screw housed in a heating cylinder, a rotator for rotating the screw, a linear mover for moving the screw linearly, a motor for driving the rotator, a driver for driving the linear mover, and a base member for supporting the screw, the rotator, the linear mover, the motor and the driver. The screw, the linear mover and the rotator are supported by the base member along a vertical line against the ground. In the injection molding apparatus is a nozzle touch mechanism which includes a support member mounted on the base member, and a member for mounting a die member mounted on the support member to support the die member. The die member is mounted by the member for mounting the die member so that a molding material entrance port of the die member engages an injection port of the heating cylinder.

Abstract: A method and apparatus for providing gas assistance in a resin injection molding process of the type in which hot resin is injected into a mold, gas is injected into the mold to displace a portion of the resin in the mold, the resin cools, the gas is vented, and the mold is opened to remove the molded part. The apparatus includes a high pressure gas storage system, a plurality of pressure control assemblies set at varying pressures and interposed between the high pressure gas storage system and the injection nozzle, and a control system which is operative to selectively communicate each of the pressure control assemblies with the injection nozzle so as to allow the delivery of gas at varying pressures to the mold to facilitate the creation of an individualized gas pressure profile to suit the particular molding requirement.

Abstract: A device to position a mold is shaped like a doughnut having a tapered edge with four standardly positioned holes to fit a standard mold. The apertures in the mold having a narrow portion in the thick portion and a wider portion in the tapered portion of the ring. The ring material has lubricated 6/10 style of nylon having glass fiber loading, a type 6 nylon high impact modified nylon, a type 66 nylon which is mineral filled, a acrylonitrile butadiene styrene copolymer, a chemical blowing agent and a wax slipping agent.

Abstract: A cast manifold for distributing pressurized melt in an injection molding system. The melt is received at a central inlet on the rear surface of the manifold to an inlet portion of a melt passage. Four identical outlet portions of the melt passage branch radially outward from the inlet portion to equally radially spaced outlets on the forward surface of the manifold. Each outlet portion extends around a first smoothly curved bend from the inlet portion, along a radial portion, and then around a second smoothly curved bend to the outlet. By casting on a removable ceramic mold, the bends in the melt passage are very smoothly curved and do not all have to extend in a common plane. Furthermore, the radial portions angle a substantial distance rearwardly as they extend outwardly which allows the thickness of the manifold to be reduced.

Abstract: The sprue bushing is mounted within a support housing for an injection molding machine. Melt viscosity of plastic employed is controlled by moving water through the bushing inner tube during the presence of the plastic. The bushing has an outer sleeve containing a longitudinal central bore. An inner tube is mounted within the bore, but spaced apart from an inner wall of the bore. Baffles mounted on opposite sides of an outer wall of the inner tube prevent water movement around an upper portion of the tube. A lower portion of the tube having a smaller outer diameter than the upper portion permits the water to flow under the baffles and through the bushing.

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: A method and 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 ata 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 for producing plastic parts from chemical materials includes a mold mounting plate divided into two parts in a direction transverse to a closing direction of the parts. A quick-acting clamping device holds the parts together with a closing force. At least one of the parts is laterally movable on guide spars after releasing the clamping device. A melt guide system is disposed between the parts. Adapters are disposed in a cassette holder opening formed in at least one of the parts. Mold halves in the form of cassette plates have surfaces facing the melt guide system. At least one of the cassette plates is disposed on the adapters in the opening formed in the at least one part. There is a device disposed on the surface of the at least one cassette plate facing the melt guide system for transferring the closing force.

Abstract: Injection molding machines for making plastic articles having a stack mold arrangement frequently suffer from the problem of unbalanced forces. Various novel techniques for counteracting and/or avoiding the production of these forces are disclosed. These techniques include the use of latches to lock an injection nozzle to a sprue bar, the use of shutters to lock the sprue bar to a stationary platen, the use of a force compensator in a moving stack mold half, and the use of an injection nozzle axially offset from the sprue bar.

Abstract: In a device for making shaped objects from plastic refuse plasticized in a roller extruder under pressure and ejected from the nozzle of the extruder a plurality of molds are provided transported to the extruder, filled thereby and transported therefrom. Each mold has at the end face a plate having a filling opening. During the filling process this plate sealingly overlaps the surface surrounding the nozzle so that the mold can be filled with plasticized plastic under the pressure generated in the roller extruder.

Abstract: Apparatus operative to reduce molten plastic drool when the injection unit is separated from the runner system. The apparatus includes access means for closing the runner system when the injection unit is disengaged therefrom and for opening the runner system for engagement with the injection unit, wherein the injection unit is operative to move the access means away from the runner system for engagement of the injection unit with the runner system.

Abstract: A metal mold for injection molding tubular or columnar products is provided in which those portions of matching surfaces of the metal mold members close to end portions of an annular or cylindrical cavity are provided with grooves extending continuously or intermittently so as to surround the cavity's end portions.

Abstract: A quick set sprue bushing for use in combination with injection molding apparatus. The bushing is made from a beryllium-free alloy that will rapidly dissipate heat. The alloy is of the copper, nickel type and reduces the cure time by between 15% and 20%. The significance of being beryllium-free is that it has been established that beryllium is a carcinogen and endangers workers. A bushing of this type results in the sprue or tail of the molten plastic type cooling as rapidly as possible for removal of the molded product from the mold. The bushing is elongated and has a generally conical passageway along its longitudinal centerline axis that diverges in the direction of the flow of material therethrough, and is further provided with a stainless steel bushing insert at the end that receives the injection mold apparatus nozzle such that the bushing will not conduct heat from the injection apparatus to the mold but will dissipate heat from the mold that comes from the molten material.

Abstract: An injection molded plastic article is produced by introducing a stream of molten plastic material from an injection molding machine cylinder into an article forming mold space. Pressurized gas is supplied into the interior of the molten plastic material to form a gas containing cavity therein. The plastic material is then allowed to solidify and cool sufficiently so that the article can itself sustain the form dictated by the mold surface. The cavity is vented to reduce the pressure within the cavity to ambient pressure prior to opening of the mold.

Abstract: A nozzle touch sprue bushing device for a unit-type injection metal mold which includes a molding body such as a metal mold including an inner mold element which is removably mounted on an outer frame mounted on an injecting molding machine, wherein a sprue bush has a nozzle touch provided at a rear end thereof for fitting with an end of a nozzle of an injecting machine, and has a front end formed in such a fitting configuration as to allow fitting engagement thereof with a material admitting portion of a metal mold.

Abstract: To avoid contaminating the sprue runner which leads from the mixing device to the molding cavity of a molding tool for the production of molded plastic, especially foam plastic, parts, an insertable lining is placed in the sprue runner and can be removed along with the molded part.

Abstract: A stack injection molding system for conveying melt from an upstream heated nozzle seated in a fixed mold platen to an aligned downstream heated nozzle in a movable mold platen. The upstream dowstream nozzles each have a nose portion with a forward face which abuts against each other in the parting line in the closed position. The melt passage extends through aligned central melt bores in the nozzles which taper inwardly adjacent the forward faces to form a sprue gate where they join. While both nozzles have an integral electrical heating element, only the heating element of the upstream nozzle has a circular forward portion which is brazed in the nose portion to encircle the melt bore and provide more heat and better control adjacent the sprue gate. Before the mold is opened along the parting line for ejection during the injection cycle, power to the heating elements of the nozzles is turned off to avoid drooling of melt from the open sprue gate.

Abstract: The present invention provides in a stack mold with back to back centrally located mold cavities a multiple sprue bar arrangement including a pair of sprue bars balanced on opposite sides of the mold and connecting bridge across the sprue bars for interfacing to a plastic injector. At least one of the sprue bars provides a plastic flow path from the connecting bridge to the mold cavities.

Abstract: A process for applying tension to the extending ends of a thin wire core of a mold to apply tension to the core during the molding process to maintain alignment of the core at all times during the molding process. Also included is apparatus for carrying out the process. Also included is a generally tubular part having a fine diameter hole therethrough.

Abstract: This invention relates to an injection molding system having an axially aligned forward and rearward heated nozzle mounted in tandem. The rearward nozzle is seated in a fixed position, while the forward nozzle reciprocates between a retracted open position and a forward closed position to provide valve gating. The forward nozzle has a rearwardly extending sleeve portion which projects into the rearward nozzle to connect the melt bores of the nozzles as the forward nozzle reciprocates. The forward nozzle has a heated nose portion with a tip which seats in the gate in the closed position. A pneumatically actuated piston bears against the rear end of the forward nozzle to drive it to the closed position. Injection melt pressure around the nose portion drives the forward nozzle back to the open position.

Abstract: An injection mold having a fixed mold member and a movable mold member, a sprue bushing assembly mounted in the fixed member containing an automatically actuated gate slidably mounted therein for opening and closing the sprue hole in response to the positioning of the mold members.

Abstract: In a vent type injection molding machine of the type comprising a heating cylinder, injection nozzle means having a vent port and connected to the front end of the heating cylinder and a reciprocatable screw for metering a predetermined quantity of resin to be injected, the injection nozzle means comprises a first injection nozzle connected to the heating cylinder, a second injection nozzle coaxial with the first injection nozzle, a spring for urging the second injection nozzle against a stationary metal mold and a housing surrounding the first and second injection nozzles. The vent port is provided through the housing at a point communicating with a space in the housing between the first and second injection nozzles.

Abstract: A mold assembly for manufacturing composite plastic products includes a mold cavity part and a lid, which is joined to form a cavity for foam precursors. The precursors expand in the cavity in a known manner to fill the cavity with a suitable layer of foamed material, such as foamed urethane. The mold cavity supports an exterior shell and the lid supports an insert for reinforcing a finished composite product. A sleeve is integrally formed on the preformed shell and it in turn is located within an access port formed through wall of the cavity part to define a slideway for receipt of a pour head extension. The extension is selectively clamped and unclamped with respect to the shell sleeve by an inflatable seal clamp which is formed as an annular ring with a pressurizable passage connected to a source of selectively applied pressure.

Abstract: An injection molding machine includes an injection molding unit which has a plasticizing unit formed of a plasticizing cylinder and a feed screw rotatably and axially shiftably received in the plsticizing cylinder, a supply block having a central passage adapted to receive an end portion of the plasticizing cylinder and a hopper or chute communicating with the passage.

Abstract: An injection molding machine has an exchangeable working unit including an injection mold assembly and a plasticizing unit. The latter has a plasticizing cylinder and a feed screw. The machine further has a drive, including a spindle for imparting a rotation and a periodic axial shifting motion to the feed screw. There is further provided a coupling assembly for operatively connecting the feed screw to and disconnecting it from the spindle. The coupling assembly has radially displaceable locking bolts, springs urging the locking bolts into a locking position, a radially guided expander wedge driving the locking bolts away from one another into a releasing position, a radially oriented piston-and-cylinder unit for moving the expander wedge between the locking bolts and an axially displaceable radial coupling. The feed screw shaft has a circumferential groove into which the locking bolts project in their locking position, for axially immobilizing the feed screw relative to the spindle.

Abstract: A locking ring for use in an injection molding machine and for securing a sprue bushing in place with respect to a mold plate assembly such that the sprue bushing is retained in place with respect to movement in the direction of the longitudinal axis of the sprue bushing bore, and from rotating in the bore.

Abstract: Moulding equipment in which cooperable male and female connectors of a mould and a dispensing container for mouldable material have means to lock them together. This includes a locking member which is manually moveable in pivotal fashion upon one connector into and out of a locking position with the other connector.Opposing surfaces of the locking member and the other connector relatively move across each other during movement of the locking member while offering sufficiently low resistance to movement to allow for manual operation. During transfer of the material into the mould, the opposing surfaces are urged together by moulding pressure to increase resistance to movement of the locking member out of the locking position. In preferred constructions, the locking member has a cam surface which ensures the need for a progressively increasing unlocking force to enable release of the locking member during transfer of the mouldable material.

Abstract: A device and method for flash suppression in a molding with rotation system having a non-rotating mating surface capable of venting gases during the molding process while simultaneously suppressing flash. Flash is directed inwardly and away from the mating surface and contained between a mandrel and mandrel housing in a low pressure reservoir which is completely separate from the mating surface. A cooling fluid is utilized to carry away flash particles from the low pressure reservoir and thereby further prevent contamination of the mating surface.

Abstract: The present invention relates to a mould for making articles of expanded plastics material and to a machine adapted to receive such a mould. The mould according to the invention comprises a finned body whose central bore constitutes a cavity. The latter is closed in its lower part by a plunger while the top of this mould comprises a support provided with a guide in which a slide element moves longitudinally. The latter comprises a perforation intended for the injection of matter into the cavity, and a hole for ejection of the moulded piece after translation of the slide element.

Abstract: The invention relates to a mold for the production of dishes from powdered ceramic materials wherein two coaxial cylindrical dies are displaceable to generate with their end facing walls a cavity to be filled with the powdered ceramic materials, said cavity being peripherally completed by a displaceable die-box provided with a vertical conduit through which the ceramic material is fed into said cavity. An auxiliary die-box is provided sideways on said die-box, displaceable at least along one of said cylindrical dies, the lateral facing walls of said die-box and of said auxiliary die-box (16) being provided with annular grooves that in the closed condition of said lateral walls generate an annular cavity that may be registered in correspondence with said first-mentioned cavity of the mold, radially prolonging the latter and forming the peripheral border of the dish to be produced.

Abstract: In an injection molding apparatus in which an injection device imposes a touching force on an injection mold in a direction perpendicular to the direction of the clamping force for closing the mold cavity, an apparatus is provided which imposes a force on the injection mold of an equal magnitude an in an opposite direction to the injection device touching force. The apparatus can be a hydraulic ram which is driven by fluid from the same line that supplies fluid to drive the touching motion of the injection device.

Abstract: A gate member for admitting plastic material into a mold which comprises a hollow member defining a bore having a longitudinal axis and an inner wall for separating the bore from a mold chamber positioned between mold halves. Aperture means extends through the inner wall, being peripherally spaced from the longitudinal axis and preferably defining an angle of essentially 30.degree. to 60.degree. to the longitudinal axis, diverging outwardly in the direction of the mold chamber. Also, preferably, the inner wall defines a centrally-positioned peak pointing toward the bore and having sloping sides, to assist in directing molten plastic toward the peripherally spaced aperture means. Also, rib means may be provided, pointing inwardly and extending radially from the central portion of the inner wall toward the periphery thereof, to reinforce the inner wall.

Abstract: An injection mold bushing which is mounted on the mold and is adapted for sprueless molding. The construction comprises an inner shank and an outer body between which is mounted a heating element for independently controlling the heat at each gate. The material passage is straight and centrally located, minimizing the likelihood of material collecting and degrading in the passage, and making it simple to clear this passage if material build-up occurs. The location of the heater and insulating construction around the bushing insures that the mold will be uniformly cool relative to the material, minimizing distortion of the molded parts.

Abstract: A sprue bushing for an injection molding machine comprising a body surrounding a core. The core has a central passageway for flow of the plastic from the nozzle of the machine to the mold and has on its exterior surface longitudinal grooves. Assembly of the body and core forms fluid channels with the grooves. The temperature of the bushing is controlled by the flow of water through the channels.

Abstract: A die stem for an extrusion press connected at its one end to a die holder including a first connecting construction such as a screw or a bayonet provided in the inner bore of the end portion of a sleeve received by the inner bore of the die stem, and a second connecting construction such as a screw or a bayonet provided at the rear end projection of the die holder, the second connecting construction being adapted to cooperate with the first connecting construction, whereby the compression stress at the connecting portion thereof due to the extrusion force is prevented from taking place.

Abstract: In a method for the injection molding of a plastic blind rivet of the type essentially consisting of a shank and a rivet body such that an upward slide of the shank relative to the rivet body causes the leading end of the rivet body to expand outwardly and the outward expansion of the rivet body enables the rivet to be fastened to a panel, the improvement which comprises forming a ring gate in the lower end of the cavity of a second die used for molding a rivet body around a shank molded in advance in a first die, whereby the molten plastic material for the rivet body is allowed to flow through the ring gate into the rivet-body cavity of the second die with high uniformity, whereby the rivet body is produced free from a weld line and consequently from the possibility of sustaining cracks under the force exerted thereon when the shank is slid upwardly therein.

Abstract: Voluminous products of plastics are made by providing between a filling cylinder of the injection part and the mould a transfer chamber with a piston, the axis of which does not coincide with the axis of the filling cylinder.

Abstract: An injector mounted on a carriage having an elevator is movable along a row of conventional mold press units each having an article mold, and is movable vertically to register with a selected mold. The press units and the molds therein are separate and independent of one another. Injection parameters are preset and activated upon registry of the injector with a selected mold, independently of the mold-to-mold sequence selected. Conventional mold press units (clamps) are simply modified to cooperate with the injector. The foregoing abstract is not to be taken as limiting the invention of this application, and in order to understand the full nature and extent of the technical disclosure of this application, reference must be made to the accompanying drawing and the following detailed description.

Abstract: An apparatus for injection molding synthetic resin materials comprises means for injecting the material to be molded, mold means having a cavity for receiving the material from said injecting means, entrance passage means connecting said injecting means with the cavity of said mold means and valve means disposed in said entrance passage means for closing it to shut off the flow of material in said entrance passage means, said valve means having a fluid passage communicating at its one end with only the cavity of said mold means when said valve means is closed, said fluid passage having the opposite end thereof adapted to connect with another source of pressurized fluid.

Abstract: A machine and method for injecting structural foam or other thermoplastic materials into one or more mold cavities. The machine comprises at least one mold-mounted shut-off bushing having a material delivery chamber formed between an outer body and a shank, with a shut-off pin slidably mounted in the shank, a heater being disposed between the pin and shank so as to heat the material passage as well as the shut-off pin tip. Closing of the shut-off bushings is independent of material pressures and is carried out from the space between a mold half and its platen by a cylinder operated cam rod.