Sprue bushing for a single cavity or center sprued mold

Claim 2

An improved sprue bushing adapted to be inserted into a mold for directing a plastics material into a mold cavity, said sprue bushing comprising an elongated body having a base portion and a nose portion, a seat on the end of said base portion for receiving the end surface of a nozzle of an in-line plastic injection molding machine, a tip surface on the end of said nose portion and forming part of the mold cavity, means defining an injection orifice within said tip surface, means defining an axially extending chamber within said body and connected to said orifice, an elongated valve member disposed within said chamber and having a reduced tip portion, means defining an axially extending opening within said valve member, an electrical heating element extending within said opening, means supporting said valve member and said heating element for axial movement within said chamber between a closed position with said tip portion of said valve member closing said orifice and an open position with said tip portion retracted inwardly from said orifice, said reduced tip portion of said valve member having an end surface positioned substantially flush with said tip surface of said nose portion when said valve member is in said closed position, spring means located within said chamber for urging said valve member toward said closed position, said Valve member being movable to said open position in response to a predetermined pressure of plastic material within said chamber around said valve member, means defining at least one passage extending within said body from said seat to said chamber and around said spring means for conducting plastics material from said seat to said chamber, and electrical conductor means extending through said base portion of said body to said valve member and said heating element.

Claim 3

A sprue bushing as defined in claim 1 wherein said body includes a forward cylindrical section and a rearward cylindrical section having the same outer diameter, and an electrical heating element extending around both said sections of said body.

Claim 4

A sprue bushing as defined in claim 1 wherein said base portion of said body includes forward and rearward sections, means for securing said sections together, said passage includes a first portion which extends outwardly and forwardly from said seat and converges with a second portion which extends outwardly and rearwardly from said chamber.

Claim 5

An improved sprue bushing adapted to be inserted into a mold for directing a plastics material into a mold cavity, said sprue bushing comprising an elongated body having a base portion and a nose portion, a seat on the end of said base portion for receiving the end surface of a nozzle of an in-line plastic injection molding machine, a tip surface on the end of said nose portion and forming part of the mold cavity, means defining an injection orifice within said tip surface, means defining an axially extending chamber within said body and connected to said orifice, an elongated valve member disposed within said chamber and having a reduced tip portion, means defining an axially extending elongated opening within said valve member, an electrical heating element extending within said opening, means supporting said valve member and said heating element for axial movement within said chamber between a closed position with said tip portion of said valve member closing said orifice and an open position with said tip portion retracted inwardly from said orifice, said reduced tip portion of said valve member having an end surface positioned substantially flush with said tip surface of said nose portion when said valve member is in said closed position, a plurality of spring washers located within said chamber for urging said valve member toward said closed position, said valve member being movable to said open position in response to a predetermined pressure of plastic material within said chamber around said valve member, means defining a plurality of passages extending within said body from said seat to said chamber and around said spring washers for conducting plastics material from said seat to said chamber, and electrical conductor means extending through said base portion of said body and said spring washers to said valve member and said heating element.

Claim 6

An improved sprue bushing adapted to be inserted into a mold for directing a plastics material into a mold cavity, said sprue bushing comprising an elongated body having a base portion and a nose portion, a seat on the end of said base portion for receiving the end surface of a nozzle of an in-line plastic injection molding machine, a tip surface on the end of said nose portion and forming part of the mold cavity, means defining an injection orifice within said tip surface, means defining an axially extending chamber within said body and connected to said orifice, an elongated valve member disposed within said chamber and having a reduced tip portion, means defining an axially extending elongated opening within said valve member, an electrical heating element extending within said opening, means supporting said valve member and said heating element for axial movement within said chamber between a closed position with said tip portion of said valve member closing said orifice and an open position with said tip portion retracted inwardly from said orifice, said reduced tip portion of said valve member having an end surface positioned substantially flush with said tip surface of said nose portion when said valve member is in said closed position, a plurality of spring washers located within said chamber for urging said valve member toward said closed position, said valve member being movable to said open position in response to a predetermined pressure of plastic material within said chamber around said valve member, means defining a plurality of passages extending within said body from said seat to said chamber and around said spring washers for conducting plastics material from said seat to said chamber, and electrical conductor means extending through said base portion of said body and said spring washers to said valve member and said heating element.

Claim 7

An improved sprue bushing adapted to be inserted into a mold for directing a plastics material into a mold cavity, said sprue bushing comprising an elongated body having a cylindrical base portion and a cylindrical nose portion of reduced diameter, said base portion including a forward section and a separate rearward section, means for securing said sections together, a seat on the end of said rearward section of said base portion for receiving the end surface of a nozzle of an in-line plastic injection molding machine, a tip surface on the end of said nose portion, means defining an injection orifice within said tip surface, means defining an axially extending chamber within said forward and rearward sections of said body and connected to said orifice, an elongated valve member disposed within said chamber and having a reduced tip portion, means defining an axially extending opening within said valve member, an electrical heating element extending within said opening, means supporting said valve member and said heating element for axial movement within said chambEr between a closed position with said tip portion of said valve member closing said orifice and an open position with said tip portion retracted inwardly from said orifice, said reduced tip portion of said valve member having an end surface positioned substantially flush with said tip surface of said nose portion when said valve member is in said closed position, spring means located within said chamber for urging said valve member toward said closed position, said valve member being movable to said open position in response to a predetermined pressure of plastic material within said chamber around said valve member, means defining passages extending forwardly and radially outwardly within said rearward section from said seat and then forwardly and inwardly around said spring means for conducting plastics material from said seat to said chamber, and electrical conductor means extending through said base portion of said body to said valve member and said heating element.

Claim 8

An improved sprue bushing adapted to be inserted into a mold for directing a plastics material into a mold cavity, said sprue bushing comprising an elongated body having a cylindrical base portion and a cylindrical nose portion of reduced diameter, said base portion including a forward section and a separate rearward section, means for securing said sections together, a seat on the end of said rearward section of said base portion for receiving the end surface of a nozzle of an in-line plastic injection molding machine, a tip surface on the end of said nose portion, means defining an injection orifice within said tip surface, means defining an axially extending chamber within said forward and rearward sections of said body and connected to said orifice, an elongated valve member disposed within said chamber and having a reduced tip portion, means defining an axially extending opening within said valve member, an electrical heating element extending within said opening, means supporting said valve member and said heating element for axial movement within said chambEr between a closed position with said tip portion of said valve member closing said orifice and an open position with said tip portion retracted inwardly from said orifice, said reduced tip portion of said valve member having an end surface positioned substantially flush with said tip surface of said nose portion when said valve member is in said closed position, spring means located within said chamber for urging said valve member toward said closed position, said valve member being movable to said open position in response to a predetermined pressure of plastic material within said chamber around said valve member, means defining passages extending forwardly and radially outwardly within said rearward section from said seat and then forwardly and inwardly around said spring means for conducting plastics material from said seat to said chamber, and electrical conductor means extending through said base portion of said body to said valve member and said heating element.

Claim 9

A sprue bushing as defined in claim 5 wherein said base portion has a diameter of approximately 2 inches and said nose portion has a diameter of approximately 1 inch, and said spring means comprise spring washers having an outer diameter smaller than the outer diameter of said nose portion.

Claim 10

An improved sprue bushing adapted to be inserted into a mold for directing a plastics material into a mold cavity, said sprue bushing comprising an elongated body having a cylindrical base portion with a diameter of about two inches and a cylindrical nose portion with a diameter of about 1 inch, a seat on the end of said base portion for receiving the end surface of a nozzle of a plastic injection molding machine, a tip surface on the end of said nose portion and forming part of the mold cavity, means defining an injection orifice within said tip surface, means defining an axially extending chamber within said body and extending to said orifice, an elongated valve member disposed within said chamber and having a reduced generally cylindrical tip portion, means defining an axially extending opening within said valve member, an electrical heating element extending within said opening, means supporting said valve member and said heating element for axial movement within said chamber between a closed position with said tip portion of said valve member closing said orifice and an open position with said tip portion retracted inwardly from said orifice, said reduced tip portion of said valve member having a flat end surface positioned substantially flush with said tip surface of said nose portion when said valve member is in said closed position, spring means located within said chamber for urging said valve member toward said closed position, said valve member being movable to said open position in response to a predetermined pressure of plastics material within said chamber around said valve member, means defining at least one passage extending within said body from said seat to said chamber and around said spring means for conducting plastics material from said seat to said chamber, and electrical conductor means extending through said base portion of said body to said valve member and said heating element.

Claim 11

An improved sprue bushing adapted to be inserted into a mold for directing a plastics material into a mold cavity, said sprue bushing comprising an elongated body having a cylindrical base portion with a diameter of about two inches and a cylindrical nose portion with a diameter of about 1 inch, a seat on the end of said base portion for receiving the end surface of a nozzle of a plastic injection molding machine, a tip surface on the end of said nose portion and forming part of the mold cavity, means defining an injection orifice within said tip surface, means defining an axially extending chamber within said body and extending to said orifice, an elongated valve member disposed within said chamber and having a reduced generally cylindrical tip portion, means defining an axially extending opening within said valve member, an electrical heating element extending within said opening, means supporting said valve member and said heating element for axial movement within said chamber between a closed position with said tip portion of said valve member closing said orifice and an open position with said tip portion retracted inwardly from said orifice, said reduced tip portion of said valve member having a flat end surface positioned substantially flush with said tip surface of said nose portion when said valve member is in said closed position, spring means located within said chamber for urging said valve member toward said closed position, said valve member being movable to said open position in response to a predetermined pressure of plastics material within said chamber around said valve member, means defining at least one passage extending within said body from said seat to said chamber and around said spring means for conducting plastics material from said seat to said chamber, and electrical conductor means extending through said base portion of said body to said valve member and said heating element.