Injection mold bushing

Claim 2

A hot sprue bushing adapted to be mounted in a mold part, said bushing having a head portion at the rearward end thereof, a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; and heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said head portion and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the rearward terminal portions of said annular space and of said heater means extending into said head portion but terminating short of the rearward end of the latter, said head providing a relatively large metallic mass having substantial strength to withstand forces imposed thereon in use by material in said passage and said head further adapted to be heated in use by the portion of said heater means disposed therein and defining a heat sink for heating the portion of said passage and material therein extending axially rearwardly beyond said heater means, the forward terminal portions of said annular space and of said heater means at least partially overlapping said tapered section, and the portion of said bushing disposed forwardly of said heater and of said annular space providing a direct radial heat flow path between the mold and said orifice whereby to permit coolant conventionally circulated through the mold to freeze material in said orifice during removal of a part from said mold while permitting said heater to maintain material in said outlet behind said orifice and in said passage in a fluid condition.

Claim 3

The sprue bushing as defined in claim 1 wherein the forward terminal portions of said annular space and of said heater means overlap at least a substantial portion of said tapered section.

Claim 4

A sprue bushing as defined in claim 1 wherein said head portion is provided with a duct extending radially outwardly from substantially the rearward end portion of said annular space to accommodate electric leads for said heater means.

Claim 5

A sprue bushing as defined in claim 1 including means defining a second elongate, annular, heat insulating space surrounding said first mentioned heat insulating space and said material passage.

Claim 6

The sprue bushing as defined in claim 1 wherein the portion of said bushing extending forwardly of said head portion comprises an inner shank, and a removable outer tubular body, said shank and said tubular body being spaced radially apart for at least a portion of their length and defining said annular heat insulating space, the outer tubular body being provided at the forward end thereof with a radially inwardly extending annular flange disposed radially in-line with the outlet of said material passage, said annular flange receiving and snugly fitting said shank and defining said radial heat flow path, the outer radial surface of said flange being disposed substantially flush with the end surface of said shank, and the mentioned surface of said flange being adapted to be positioned contiguous to the wall of the mold cavity adjacent to the hole in which said bushing is mounted, whereby the mentioned surface of said flange and said shank collectively form a portion of said cavity wall.

Claim 7

A sprue bushing as defined in claim 1 wherein the portion of said bushing extending forwardly of said head portion comprises an inner shank, and a removable outer tubular body, said shank and said tubular body being spaced radially apart for at least a portion of their length and defining said annular heat insulating space.

Claim 8

The sprue bushing as defined in claim 6 wherein said outer tubular body is provided at the forward end thereof with a radially inwardly extending annular flange disposed radially in-line with the outlet of said material passage that receives and snugly fits said shank, and wherein said flange defines said radial heat flow path.

Claim 9

A hot sprue bushing adapted to be mounted in a mold, said bushing having a head portion at the rearward end thereof, a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said head portion and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the rearward terminal portions of said annular space and of said heater means extending into said head portion but terminating short of the rearward end of the latter and the forward terminal portions of said annular space and of said heater means overlapping at least a portion of the tapered section of said material passage, said head providing a relatively large metallic mass having substantial strength to withstand forces imposed thereon in use by material in said passage and said head further adapted to be heated in use by the portion of said heater means disposed therein and defining a heat sink for heating the portion of said passage and material therein extending axially rearwardly beyond said heater means; cooling means disposed axially forwardly of said annular heat insulating space and radially outwardly of said orifice providing a direct radial heat flow path between the mold and said orifice; and means including the combination of said heater means and said cooling means and the relationship thereof to each other and to said outlet adapted to permit coolant conventionally circulated in use through the mold to freeze material in said orifice during removal of a part from said mold while maintaining said material in fluid condition in said outlet behind said orifice and in said passage.

Claim 10

A hot sprue bushing adapted to be mounted in a mold, said bushing having a head portion at the rearward end thereof, a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said head portion and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the rearward terminal portions of said annular space and of said heater means extending into said head portion but terminating short of the rearward end of the latter and the forward terminal portions of said annular space and of said heater means overlapping at least a portion of the tapered section of said material passage, said head providing a relatively large metallic mass having substantial strength to withstand forces imposed thereon in use by material in said passage and said head further adapted to be heated in use by the portion of said heater means disposed therein and defining a heat sink for heating the portion of said passage and material therein extending axially rearwardly beyond said heater means; cooling means disposed axially forwardly of said annular heat insulating space and radially outwardly of said orifice providing a direct radial heat flow path between the mold and said orifice; and means including the combination of said heater means and said cooling means and the relationship thereof to each other and to said outlet adapted to permit coolant conventionally circulated in use through the mold to freeze material in said orifice during removal of a part from said mold while maintaining said material in fluid condition in said outlet behind said orifice and in said passage.

Claim 11

A hot sprue bushing adapted to be mounted in a mold, said bushing having a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, said material passage having an inlet opening through the rearward end of said bushing and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing; an annular heat insulating space surrounding and spaced radially outwardly from said passage; heater means in said annular space in heat exchange relation with the inner annular wall thereof and at least partially overlapping said tapered section at the forward end thereof; means disposed forwardly of said annular heat insulating space and radially outwardly of said orifice providing a direct radial heat flow path between the mold and said orifice; and means including the combination of said heater means and said last mentioned means and the relationship thereof to each other and to said outlet being adapted to permit coolant conventionally circulated in use through the mold to freeze material in said orifice during removal of a part from said mold while maintaining said material in said outlet behind said orifice and in said passage in fluid condition.

Claim 12

A hot sprue bushing adapted to be mounted in a mold, said bushing having a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, said material passage having an inlet opening through the rearward end of said bushing and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing; an annular heat insulating space surrounding and spaced radially outwardly from said passage; heater means in said annular space in heat exchange relation with the inner annular wall thereof and at least partially overlapping said tapered section at the forward end thereof; means disposed forwardly of said annular heat insulating space and radially outwardly of said orifice providing a direct radial heat flow path between the mold and said orifice; and means including the combination of said heater means and said last mentioned means and the relationship thereof to each other and to said outlet being adapted to permit coolant conventionally circulated in use through the mold to freeze material in said orifice during removal of a part from said mold while maintaining said material in said outlet behind said orifice and in said passage in fluid condition.

Claim 13

A hot sprue bushing adapted to be mounted in a mold, said bushing having a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; and heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said bushing and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the forward terminal portion of said bushing providing a direct radial heat flow path between the mold and said orifice which subjects material in said orifice to the effect of coolant conventionally circulated through the mold, the forward end of said heater means being disposed rearwardly of said orifice and at least partially overlapping said tapered section but sufficiently close to said orifice so that the combined effects of said heater means and of said coolant acting on the material in said outlet through said forward terminal portion of said bushing and said heat flow path freezes the material in said orifice during removal of a part from said mold while maitaining said material in said outlet behind said orifice and in said passage in a fluid condition.

Claim 14

A hot sprue bushing adapted to be mounted in a mold, said bushing having a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; and heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said bushing and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the forward terminal portion of said bushing providing a direct radial heat flow path between the mold and said orifice which subjects material in said orifice to the effect of coolant conventionally circulated through the mold, the forward end of said heater means being disposed rearwardly of said orifice and at least partially overlapping said tapered section but sufficiently close to said orifice so that the combined effects of said heater means and of said coolant acting on the material in said outlet through said forward terminal portion of said bushing and said heat flow path freezes the material in said orifice during removal of a part from said mold while maitaining said material in said outlet behind said orifice and in said passage in a fluid condition.

Claim 15

A hot sprue bushing adapted to be mounted in a mold, said bushing having a head portion at the rearward end thereof, a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said head portion and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the rearward terminal portions of said annular space and of said heater means extending into said head portion but terminating short of the rearward end of the latter, said head providing a relatively large metallic mass having substantial strength to withstand forces imposed thereon in use by material in said passage and said head further adapted to be heated in use by the portion of said heater means disposed therein and defining a heat sink for heating the portion of said passage and material therein extending axially rearwardly beyond said heater means, the forward terminal portion of said bushing providing a direct radial heat flow path between the mold and said orifice which subjects material in said orifice to the effect of coolant conventionally circulated through the mold, the forward end portion of said heater means being disposed rearwardly of said orifice and at least partially overlapping the tapered section of said material passage but sufficiently close to said orifice so that the combined effects of said heater means and of said coolant acting on the material in said outlet through said forward terminal portion of said bushing and said heat flow path freezes the material in said orifice during removal of a part from said mold while maintaining said material in said outlet behind said orifice and in said passage in a fluid condition.

Claim 16

A hot sprue bushing adapted to be mounted in a mold, said bushing having a head portion at the rearward end thereof, a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said head portion and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the rearward terminal portions of said annular space and of said heater means extending into said head portion but terminating short of the rearward end of the latter, said head providing a relatively large metallic mass having substantial strength to withstand forces imposed thereon in use by material in said passage and said head further adapted to be heated in use by the portion of said heater means disposed therein and defining a heat sink for heating the portion of said passage and material therein extending axially rearwardly beyond said heater means, the forward terminal portion of said bushing providing a direct radial heat flow path between the mold and said orifice which subjects material in said orifice to the effect of coolant conventionally circulated through the mold, the forward end portion of said heater means being disposed rearwardly of said orifice and at least partially overlapping the tapered section of said material passage but sufficiently close to said orifice so that the combined effects of said heater means and of said coolant acting on the material in said outlet through said forward terminal portion of said bushing and said heat flow path freezes the material in said orifice during removal of a part from said mold while maintaining said material in said outlet behind said orifice and in said passage in a fluid condition.

Claim 17

The sprue bushing as defined in claim 11, the portion of said bushing extending forwardly of said head portion comprising an inner shank portion, and a removable outer tubular body portion, said shank and said tubular body portion being spaced radially apart for at least a portion of their length and defining said annular heat insulating space.

Claim 18

The sprue bushing as defined in claim 12 further provided with means for providing a second elongate, annular heat insulating space between said outer tubular body portion and said mold part.

Claim 19

A hot sprue bushing adapted to be mounted in a mold part, said bushing having a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; and heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said bushing and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the forward terminal portions of said annular space and of said heater means overlapping at least a portion of the tapered section of said material passage and terminating behind but adjacent to said discharge orifice whereby heat from said terminal portion of said heater means overlaps at least a portion of said tapered section, the portion of said bushing disposed forwardly of said heater and of said annular space providing a direct radial heat flow path between the mold and said orifice whereby coolant conventionally circulated through the mold freezes material in said orifice during removal of a part from said mold while permitting said heater to maintain material in said outlet behind said orifice and in said passage in a fluid condition.

Claim 20

A hot sprue bushing adapted to be mounted in a mold part, said bushing having a material passage extending in substantially a straight path entirely therethrough from the rearward end to the forward end thereof, and an annular heat insulating space surrounding and spaced radially outwardly from said passage; and heater means in said annular space in heat exchange relation with the inner annular wall thereof, said material passage having an inlet opening through the rearward end of said bushing and an outlet having a tapered section terminating in a material discharge orifice opening through the forward end of said bushing, the forward terminal portions of said annular space and of said heater means overlapping at least a portion of the tapered section of said material passage and terminating behind but adjacent to said discharge orifice whereby heat from said terminal portion of said heater means overlaps at least a portion of said tapered section, the portion of said bushing disposed forwardly of said heater and of said annular space providing a direct radial heat flow path between the mold and said orifice whereby coolant conventionally circulated through the mold freezes material in said orifice during removal of a part from said mold while permitting said heater to maintain material in said outlet behind said orifice and in said passage in a fluid condition.

Claim 21

The sprue bushing as defined in claim 14 wherein the forward terminal portions of said annular space and of said heater means overlap at least a substantial portion of said tapered section.