Abstract This invention relates to an improved seal for injection molding mechanism. The lower nozzle portion of a heater with the reciprocal valve pin extending centrally therethrough extends downwardly to the gate in the mold. The generally cylindrical seal is horizontally located in an outward upward flare of the air space between the lower nozzle portion and the mold. The seal has a V-shaped lower surface which provides inner and outer circumferential lips which prevent the pressurized melt from flowing upward past the seal. The outer wall of the seal extends across the flare of the air space with only a portion of the outer lip abutting on the mold, thus substantially reducing heat loss from the heater through the seal to the cooled mold. The seal is located sufficiently far from the gate that the reduced heat loss through it is not from the direct gate area but sufficiently close that the melt which is injected into the remaining accessible air space is sufficiently small to be drawn into the cavity on each successive injection to avoid a color streaking problem. The outer lip is thicker than the inner lip to avoid it rupturing into the flare of the air space.
In an injection molding valve-gated mechanism having a vertical valve pin which reciprocates in a passage bore in a heater located in a mold to control flow of molten plastic from a molding machine to a cavity, the heater having a lower nozzle portion which is separated from the surrounding mold by a circumferential air space and through which the valve pin projects to provide a valve in a gate to the cavity, the improvement comprising a generally cylindrical seal having a vertical inner wall, a vertical outer wall and a lower surface, said seal being horizontally located in the air space between the lower nozzle portion of the heater and the wall of a recess in the mold, said seal being located where the air space flares outwardly upward, the lower surface extending upwardly from the mold across the air space to an overhanging shoulder on lower nozzle portion of the heater, the lower surface having a uniform V-shaped cross section formed by a first face extending diagonally outwardly upward from the inner surface and a second face extending diagonally inwardly upward from the outer surface, the lower surface forming an inner lip defined between the inner surface and the first diagonal face and an outer lip defined between the outer surface and the second diagonal face, the seal being positioned so that only a portion of the outer lip abuts on the mold to reduce heat transfer through the seal from the lower nozzle portion of the heater to the mold.
Claim 2
Dependent Claim
253 words
In an injection molding valve-gated mechanism having a vertical valve pin which reciprocates in a passage bore in a heater located in a mold to control flow of molten plastic from a molding machine to a cavity, the heater having a lower nozzle portion which is separated from the surrounding mold by a circumferential air space and through which the valve pin projects to provide a valve in a gate to the cavity, the improvement comprising a generally cylindrical seal having a vertical inner wall, a vertical outer wall and a lower surface, said seal being horizontally located in the air space between the lower nozzle portion of the heater and the wall of a recess in the mold, said seal being located where the air space flares outwardly upward, the lower surface extending upwardly from the mold across the air space to an overhanging shoulder on lower nozzle portion of the heater, the lower surface having a uniform V-shaped cross section formed by a first face extending diagonally outwardly upward from the inner surface and a second face extending diagonally inwardly upward from the outer surface, the lower surface forming an inner lip defined between the inner surface and the first diagonal face and an outer lip defined between the outer surface and the second diagonal face, the seal being positioned so that only a portion of the outer lip abuts on the mold to reduce heat transfer through the seal from the lower nozzle portion of the heater to the mold.
Claim 3
Dependent Claim
21 words
The improvement claimed in claim 1 wherein the inner lip is substantially lesser in height and width than the outer lip.
Claim 4
Dependent Claim
36 words
The improvement claimed in claim 2 wherein the angle between the inner wall and the first diagonal face is approximately 10° and the angle between the outer wall and the second diagonal face is approximately 30°.