Mold-masters Limited

Harald H Schmidt

Jobst U Gellert

Rory McDowall

Henry John Rozema

Michael C McEnroe

A multi-cavity valve gates injection molding system. The pneumatic actuating mechanism to reciprocate each elongated valve member includes a piston which reciprocates in a cylindrical opening through a cylinder plate. A sealing bushing which is mounted around each valve member has a flanged portion which bridges an insulative air gap between the manifold and the cylinder plate. Thus, the sealing bushing forms part of the piston cylinder as well as sealing against melt leakage around the reciprocating valve member. The piston has a circumferential outer band formed of a graphite alloy seated in a groove formed between a front portion and a removable rear plate portion.

Pneumatic actuating mechanism for injection molding

A thermocouple assembly and method of making it wherein a pair of wires formed of dissimilar metals extend through electrical insulating material in a thin flexible stainless steel sheath. A forward portion of the sheath containing the wires is snugly received in a nickel alloy casing which is then bent to form an opening to receive a screw therethrough to accurately secure the forward end of the thermocouple assembly in place. The casing is made strong enough to maintain the circular shape and bending the sheath and casing together securely retains the sheath in the casing.

Thermocouple construction

An injection molding heated manifold having a melt passage with a longitudinal portion to convey melt from a molding machine to a number of different nozzles. The steel manifold has a pair of cooling bores extending parallel to and equally spaced on opposite sides of the longitudinal portion of the melt channel. A cooling fluid, such as air, flows through the cooling bores to quickly cool the manifold after the system is shut down to minimize deterioration of the melt in the melt channel. The air flows helically around spiral vanes which are mounted in the cooling bores to avoid temperature stratification along the melt passage.

Injection molding manifold having a pair of cooling bores on opposite

An injection molding system having at least one insulation gate seal extending outwardly to bridge an insulative air space between a heated nozzle and the adjacent cooled cavity plate. Each seal has a central bore therethrough to convey pressurized melt from the nozzle to the aligned gate. The outer end of each seal has a circular groove extending between a central portion and a surrounding flange portion. The flange portion is substantially larger in diameter than the gate and extends outwardly past the face of the central portion into sealing contact around the gate against the surrounding surface of the cavity plate. The combination of the clearance provided between the face of the central portion and the surrounding surface of the cavity plate and the distance between the gate and the surrounding flange portion limits the temperature of the cavity plate immediately around the gate, while still providing the necessary seal.

Injection molding system with flanged insulating gate seal

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.

Injection molding system with gas flow through valve gate

This invention relates to an injection molding system having two heated nozzles mounted in tandem. The rearward nozzle is considerably longer than the forward nozzle and has a melt bore which is considerably larger in diameter than the melt bore of the forward nozzle. The smaller forward nozzle has a backplate secured to its rear end with a thin flanged portion which extends outwardly and rearwardly into bearing contact against a rearward mold core to secure the forward nozzle in position in a well in a forward mold core. The rear face of the backplate has a seat extending around the melt bore to receive a cylindrical forward portion of a gate insert mounted on the forward end of the rearward nozzle. Thus thermal expansion of the larger rearward nozzle is taken up by the forward portion of the gate insert sliding in the seat. The smaller forward nozzle has a portion of the electrical heating element extending into a forwardly extending nose portion which provides sensitive temperature control in the gate area.

Injection molding system with nozzles in tandem

This invention relates to an injection molding system having a number of nozzles conveying melt from an elongated manifold to a common cavity. In the preferred embodiment, each heated nozzle has a melt channel which is offset from a central valve pin bore for conveying the melt to the gate. The melt channel extends through a side portion of the nozzle which is bolted to the side surface of the manifold. The bolts provide a seal against leakage of the pressurized melt, while at the same time allow slight lateral movement between the manifold and the nozzle. This provides for thermal expansion of the manifold relative to the nozzle which is accurately located in a well in the core. The system is used for large cavities which require large flow volumes and avoids the difficulty of accurate machining of the large molds to provide sealing.

Injection molding system having manifold with side mounted nozzles

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.

Injection molding system having clamped rotatable nozzles and method

This invention relates to an improved injection molding nozzle having an integral electrical heating element. The nozzle has an elongated nose portion extending to a forward end from a cylindrical central portion. The heating element is brazed in a spiral channel around a central melt bore in the central portion of the nozzle, and extends into the nose portion to a forward end which is grounded by brazing it in nickel adjacent a high speed steel insert portion at the forward end of the nozzle. This forms a pointed tip at the forward end of the nozzle which is corrosion and wear resistant and can be heated to a predetermined temperature. In alternative embodiments, the forward end of the heating element can be brazed in nickel adjacent the forward end without the high speed steel insert portion and/or the nose portion can be inclined with the forward end of the heating element being grounded adjacent an end gate rather than a separate gate. The mass of the central portion and the elongated tapered shape of the nose portion which permits relatively rapid temperature changes of the melt in the gate area enable the nozzle having a single heating element to be used for temperature assisted gating.

Injection molding nozzle having grounded heating element brazed into

This invention relates to a valve gated single cavity injection molding system wherein the valve pin actuating mechanism is cooled by circulating hydraulic fluid through it. The cylinder is mounted in a cylinder housing inside a dome portion of a heated manifold housing. The cylinder housing has a wing portion extending out openings in each side of the manifold housing. Each wing portion has an inlet duct and an outlet duct for hydraulic fluid across which a pressure differential is applied. The ducts connect to circumferential channels which extend around the outside of the cylinder and lead to respective openings into the cylinder. Thus, the application of hydraulic fluid pressure during operation circulates hydraulic fluid through the actuating mechanism. The cooling which results extends the operating life of the mechanism, particularly the seals and O-rings.

Fluid cooled hydraulic actuating mechanism for single cavity injection

This invention relates to a multi-cavity valve gated injection molding system wherein a continuous flow of hydraulic fluid through the actuating mechanism provides additional cooling. A pair of hydraulic fluid lines are drilled in the mold back plate to apply a minimum pressure differential across the cylinder chamber on one side of the piston. In the preferred embodiment, this pressure differential is also applied to opposite sides of a circular cooling chamber extending through the cylinder to provide additional cooling near a high pressure seal. Additional cooling is very advantageous to avoid system malfunctions and inferior product, particularly when molding high performance engineering resins at a high temperature.

Fluid cooled hydraulic actuating mechanism for injection molding

This invention relates to sealing and support bushings which are located between the manifold and the mold back plate to encircle each valve pin in a multi-cavity valve gated injection molding system. Each bushing is bolted through the manifold to a respective heated nozzle with central bores in alignment to receive the valve pin therethrough. The bushing has an outer flanged portion which extends to contact the mold back plate and forms a leakage containment chamber between them. Thus, the bushings retain the manifold in place, seal against substantial melt leakage around the reciprocating valve pins and collect any melt which does escape to prevent it entering the insulative air space between the hot manifold and the cooled mold back plate. Location of the bushing between the manifold and the mold back plate also enables the use of a standard manifold having longitudinal and transverse bores without requiring diagonal bores.

Sealing and retaining bushing for injection molding

This invention relates to a manifold housing for a valve gated single cavity injection molding system. The heated manifold housing has a dome portion and a base portion which is secured to a heated nozzle with aligned central bores through which the valve pin extends. Hydraulic actuating mechanism is mounted inside the manifold housing to reciprocate the valve pin between open and closed positions. The melt duct in the manifold branches from a central inlet into two separate arms with smoothly curved bends which extend to join the central bore on opposite sides of the valve pin. Providing two streams of melt which meet at the valve pin avoids the problem of streaking and slow melt flow on one side of the valve pin.

Dual feed single cavity injection molding system

This invention relates to an improved valve pin bushing for a multi-cavity, injection molding system. The valve pin bushing has a central bore through which the valve pin extends. The melt duct extends through the bushing to join an enlarged portion of the central bore around the valve pin. In the bushing according to the invention, the melt duct branches into two arms with smoothly curved bends which lead to opposite sides of the valve pin. This avoids the problem of streaking and slow melt flow on the opposite side of the valve pin.

Dual feed bushing for multi-cavity injection molding

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.

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Georgetown, Canada

Harald H Schmidt