Injection molding apparatus having a melt bore through the front end of the pin
AssigneeMold-Masters Limited
InventorsJobst Ulrich Gellert, Denis L. Babin
Life of this patent
Estimating the term…
Abstract
Multi-cavity injection molding apparatus for three layer molding having elongated pins for fixed pin gating or valve gating. Each elongated pin has a central melt bore extending rearwardly from its front end to a number of laterally extending bores. A low viscosity barrier material such as EVOH or nylon flows through these bores to the gate leading to the cavity. This allows coinjection with fixed pins and sprue gating in one embodiment and by valve gating in another embodiment.
Claims20
A method of continuously injection molding three layer products in a multi-cavity injection molding apparatus having a front melt distribution manifold spaced from a rear distribution manifold with a plurality of heated nozzles mounted in a mold, each heated nozzle having a rear end abutting against the front melt distribution manifold and a front end adjacent a gate leading to a cavity in the mold, each heated nozzle having a central melt channel extending therethrough from the rear end to the front end and an annular melt channel extending around the central melt channel to the front end, an elongated pin having a rear end, a front end and an outer surface extending in the central melt channel in each heated nozzle in alignment with the gate leading to the cavity in the mold, each pin having a central melt bore extending rearwardly from its front end to a plurality of lateral melt bores which extend outwardly to the outer surface of the pin, comprising the steps of:
- (a) injecting a first molten material from a first melt source into the cavities through a first melt passage which branches in the front melt distribution manifold and extends through the annular melt channel in each heated nozzle through the gate,
- (b) after a predetermined quantity of the first molten material has been injected into the cavities, simultaneously injecting a second molten material from a second melt source into the cavities through a second melt passage, which branches in the rear melt distribution manifold, and flowing the second molten material along each elongated pin through the central melt channel of each of the heated nozzles, and then flowing the second molten material to the gates through the lateral melt bores and then through the central melt bore of each pin to form an inner layer of the second material between two outer layers of the first material in each of the cavities,
- (c) when the cavities are nearly full, discontinuing the injection of the second material through the second melt passage, while continuing the injection of the first material through the first melt passage until the cavities are full,
- (d) after a cooling period, opening the mold and ejecting the molded products, and
- (e) closing the mold after ejection of the molded products.
A method of injecting two materials into a mold cavity through an injection nozzle located in a hot runner mold comprising the steps of:
- (a) directing a first molten material to a first melt channel formed in the injection nozzle to form an annular stream of said first molten material within the injection nozzle,
- (b) injecting only a certain amount of said annular stream of said first molten material into said cavity,
- (c) directing a second molten material into a second melt channel formed in the injection nozzle, and flowing the second molten material along said second melt channel, and dividing the second molten material in said second melt channel into a plurality of separate streams after the second molten material flows along said second melt channel, and then combining said separate streams into a single central stream within the injection nozzle and flowing the second molten material toward the cavity centrally of the annular stream of said first molten material,
- (d) simultaneously injecting both of said molten materials into the cavity, and
- (e) discontinuing injection of said second molten material and injecting only said first molten material until the cavity is full, thereby forming a multi-layered product of said first material and said second material.
A method of injecting different materials into a mold cavity through an injection nozzle, comprising the steps of:
- providing an annular melt channel in the injection nozzle;
- providing a central melt channel in the injection nozzle;
- providing a pin in the central melt channel, wherein a front portion of the pin has a central melt bore and lateral melt bores that communicate with the central melt bore and the central melt channel;
- flowing an annular stream of a first molten material through the annular melt channel;
- flowing a stream of second molten material through the central melt channel along the pin and then through the lateral melt bores to divide the second molten material into a plurality of separate streams, and then through the central melt bore to combine the separate streams into a single central stream;
- injecting the first molten material into the mold cavity;
- injecting the central stream of the second molten material flowing from the central melt bore into the mold cavity;
- simultaneously injecting both the first and second molten materials into the cavity;
- and
- injecting only the first molten material until the cavity is full, thereby forming a composite product of the first and second materials.
Dependencies are inferred from the claim text.