Faster cycling sprue method and apparatus for injection molding plastic optical disks

Claim 1

A method of injection molding plastic optical disks in a moldset maintained in fluid communication through a nozzle tip with an injection molding machine at least while plastic melt flow into the moldset is desired, the moldset containing a sprue bushing assembly having a female member and a male member co-axially aligned with the nozzle tip so as to form a melt passageway from the nozzle tip on an upstream end to an annular gate to a disk mold cavity on a downstream end such that the melt passageway between its ends defines a length and a shape of a sprue to be formed between the nozzle tip on the upstream end to the annular gate to a disk mold cavity on the downstream end, the male member having a spreader die contour of a generally conically-tipped torpedo-shape, the male member protruding substantially into the female member cavity's length and the male member being separated from the female member cavity in a first position to form at least substantially upstream from the gate an annular open aperture between the male and female members wherein a hollow sprue may be molded, the hollow sprue having both inside and outside surfaces, the male and female members being capable of axial motion therebetween to a second position of the moldset wherein the male and female members are less separated than in the first position, and at least the male member being maintained at a temperature below the solidification temperature of the plastic by a mass transport cooling mechanism, comprising the steps of: (a) injecting plastic melt into the moldset in the first position to form the molten hollow sprue and disk therein; (b) urging together axially the male and female members while the hollow sprue is still molten until the second position of the moldset is reached, wherein the male and female members are less separated than in the first position, (c) cooling the molten hollow sprue by concurrent contact on the inside surface with the male member and contact on the outside surface with the female member, while concurrently the molten disk is also being cooled to below its solidification temperature; (d) ejecting the molded hollow sprue and solidified disk out of the moldset.

Claim 2

A method of injection molding plastic optical disks in a moldset maintained in fluid communication through a nozzle tip with an injection molding machine at least while plastic melt flow into the moldset is desired, the moldset containing a sprue bushing assembly having a female member and a male member co-axially aligned with the nozzle tip so as to form a melt passageway from the nozzle tip on an upstream end to an annular gate to a disk mold cavity on a downstream end such that the melt passageway between its ends defines a length and a shape of a sprue to be formed between the nozzle tip on the upstream end to the annular gate to a disk mold cavity on the downstream end, the male member having a spreader die contour of a generally conically-tipped torpedo-shape, the male member protruding substantially into the female member cavity's length and the male member being separated from the female member cavity in a first position to form at least substantially upstream from the gate an annular open aperture between the male and female members wherein a hollow sprue may be molded, the hollow sprue having both inside and outside surfaces, the male and female members being capable of axial motion therebetween to a second position of the moldset wherein the male and female members are less separated than in the first position, and at least the male member being maintained at a temperature below the solidification temperature of the plastic by a mass transport cooling mechanism, comprising the steps of: (a) injecting plastic melt into the moldset in the first position to form the molten hollow sprue and disk therein; (b) urging together axially the male and female members while the hollow sprue is still molten until the second position of the moldset is reached, wherein the male and female members are less separated than in the first position, (c) cooling the molten hollow sprue by concurrent contact on the inside surface with the male member and contact on the outside surface with the female member, while concurrently the molten disk is also being cooled to below its solidification temperature; (d) ejecting the molded hollow sprue and solidified disk out of the moldset.

Claim 30

A method of injection molding plastic optical disks in a moldset, the moldset having a stationary moldhalf and a movable moldhalf, the moldset being maintained in fluid communication through a nozzle tip with an injection molding machine at least while plastic melt flow into the moldset is desired, the moldset containing a sprue bushing assembly having a female member housed within the stationary moldhalf and a male member housed within the movable moldhalf, the male member opposing the female member such that both members are co-axially aligned with the nozzle tip and also the male member is protruding through a plane in which lie the annular gate and the disk mold cavity when the moldset is in a first position, the male member being separated from the female member cavity in the first position to form at least substantially upstream from the gate an annular open aperture between the male and female members wherein a hollow sprue may be molded, the hollow sprue having both inside and outside surfaces in contact with the male and female members respectively, such that a contact area of the inside and outside surfaces summed together substantially exceed all surface contact area of a solid conical sprue of an equal length, and co-axially aligned with the nozzle tip so as to form a melt passageway therebetween from the nozzle tip on an upstream end to an annular gate to a disk mold cavity on a downstream end such that the melt passageway between its ends defines a length and a shape of a sprue to be formed between the nozzle tip on the upstream end to the annular gate to a disk mold cavity on the downstream end, the male member having a spreader die contour of a generally conically-tipped torpedo-shape, the male member protruding through a plane in which lie the annular gate and the disk mold cavity, and substantially into the female member cavity's length and the male member being separated from the female member cavity in a first position to form at least substantially upstream from the gate an annular open aperture between the male and female members wherein a hollow sprue may be molded, the hollow sprue having both inside and outside surfaces, the male and female members being capable of axial motion to a second position of the moldset wherein the male and female members are separated by at least a same distance as in the first position but the annular gate is now closed, and at least the male member being maintained at a temperature below the solidification temperature of the plastic by a mass transport cooling mechanism, comprising the steps of: (a) injecting plastic melt into the moldset in the first position to form the molten hollow sprue and disk therein; (b) cooling the molten hollow sprue by concurrent contact on the inside surface with the male member and contact on the outside surface with the female member, while concurrently the molten disk is also being cooled to below its solidification temperature; (c) urging axially both the male and female members after the hollow sprue is substantially solidified, until a second position of the moldset is reached, wherein the male and female members are separated by at least the same distance as in the first position, and the hollow sprue is now separated from the disk before the moldset is opened; (d) ejecting the molded hollow sprue and solidified disk out of the moldset.

Claim 31

A method of injection molding plastic optical disks in a moldset, the moldset having a stationary moldhalf and a movable moldhalf, the moldset being maintained in fluid communication through a nozzle tip with an injection molding machine at least while plastic melt flow into the moldset is desired, the moldset containing a sprue bushing assembly having a female member housed within the stationary moldhalf and a male member housed within the movable moldhalf, the male member opposing the female member such that both members are co-axially aligned with the nozzle tip and also the male member is protruding through a plane in which lie the annular gate and the disk mold cavity when the moldset is in a first position, the male member being separated from the female member cavity in the first position to form at least substantially upstream from the gate an annular open aperture between the male and female members wherein a hollow sprue may be molded, the hollow sprue having both inside and outside surfaces in contact with the male and female members respectively, such that a contact area of the inside and outside surfaces summed together substantially exceed all surface contact area of a solid conical sprue of an equal length, and co-axially aligned with the nozzle tip so as to form a melt passageway therebetween from the nozzle tip on an upstream end to an annular gate to a disk mold cavity on a downstream end such that the melt passageway between its ends defines a length and a shape of a sprue to be formed between the nozzle tip on the upstream end to the annular gate to a disk mold cavity on the downstream end, the male member having a spreader die contour of a generally conically-tipped torpedo-shape, the male member protruding through a plane in which lie the annular gate and the disk mold cavity, and substantially into the female member cavity's length and the male member being separated from the female member cavity in a first position to form at least substantially upstream from the gate an annular open aperture between the male and female members wherein a hollow sprue may be molded, the hollow sprue having both inside and outside surfaces, the male and female members being capable of axial motion to a second position of the moldset wherein the male and female members are separated by at least a same distance as in the first position but the annular gate is now closed, and at least the male member being maintained at a temperature below the solidification temperature of the plastic by a mass transport cooling mechanism, comprising the steps of: (a) injecting plastic melt into the moldset in the first position to form the molten hollow sprue and disk therein; (b) cooling the molten hollow sprue by concurrent contact on the inside surface with the male member and contact on the outside surface with the female member, while concurrently the molten disk is also being cooled to below its solidification temperature; (c) urging axially both the male and female members after the hollow sprue is substantially solidified, until a second position of the moldset is reached, wherein the male and female members are separated by at least the same distance as in the first position, and the hollow sprue is now separated from the disk before the moldset is opened; (d) ejecting the molded hollow sprue and solidified disk out of the moldset.