Hot runner system

Claim 2

For a plastic injection mold structure, a hot runner system comprising: a first member located in said mold structure, said first member having a first bore therein of predetermined length; a second member adapted to be located in said mold structure at a position spaced from said first member; a runner member for conducting molten plastic between said first and second members, said runner member having a first tubular end, and a second end adapted to be connected to said second member; a heater coupled to said runner member between said ends to heat said plastic flowing through said runner member; said first end of said runner member being in its entirety adapted to be snugly but slidably fitted into said first bore and having a first portion of length normally less than said predetermined length located in said first bore and a second portion projecting from said first bore, so that when said runner member is heated and expands in a direction parallel to the axis of said first end, said first end of said runner member will slide into said first bore to accommodate such expansion in said direction; said runner member comprising a pair of runner portions oriented at right angles to each other and joined by an integral right angle bend.

Claim 3

Apparatus according to claim 1 wherein said runner portions are substantially tubular and are separated by air gaps from said mold structure over a substantial portion of their length, to reduce heat transfer from said runner member to said mold structure.

Claim 4

Apparatus according to claim 2 including a mounting portion connected to said bend of said runner member and adapted to be connected to said mold structure for supporting said runner member.

Claim 5

Apparatus according to claim 1 wherein said first member is a sprue bushing and said second member is a cavity member having a gate therein for directing plastic into a mold cavity of said mold structure, and wherein at least said first end of said runner member has a thermal coefficient of expansion greater than the thermal coefficient of expansion of said sprue bushing.

Claim 6

Apparatus according to claim 1 wherein said second end of said runner member is tubular, and including a movable stem member slidably mounted at said second end of said runner member, and projecting therefrom, said stem member having an interior passage for plastic and being movable axially of said second end between a first closed position in which it blocks egress of molten plastic from said second member and a second open position in which it permits egress of molten plastic from said second member.

Claim 7

Apparatus according to claim 5 wherein said second member includes a gate therein, said stem member being slidably mounted in said second end, said stem member having a circumferential radially outwardly extending collar, with an elongated closure portion projecting axially from said collar towards said gate, said collar and said elongated portion of said stem member defining with said second member at least a portion of a chamber for plastic, said chamber being closed by said elongated portion blocking said gate when said stem member is in said closed position, the diameter of said collar being such that the area on which plastic presses to move said stem member to said open position is greater than the area on which plastic presses to move said stem member to said closed position, and spring means biasing said stem member to said closed position with preselected pressure, said pressure being such that said stem member will move against the pressure of said spring means to its open position when the pressure of said plastic increases beyond a predetermined level.

Claim 8

Apparatus according to claim 5 wherein said stem member is snugly but slidably mounted in said second end, said second end including a pair of holes in its wall substantially sealed against escape of plastic by said snug fit of said stem member therein, said apparatus further including a pair of pins connected to said stem memBer and protruding through said holes in said second end, a cylindrical piston encircling said second end and connected to said pins, a cylinder encircling and guiding said piston, said piston having a central collar sliding against said cylinder, and means for admitting pressurized fluid to said cylinder on either side of said collar and for removing fluid from said cylinder on the other side of said collar to drive said piston.

Claim 9

Apparatus according to claim 7 wherein said stem member is of a material of very high thermal conductivity.

Claim 10

Apparatus according to claim 4 including a stem member mounted in said second end of said runner member, said stem member having an interior passage directing plastic into said gate, said stem member being of a material of very high thermal conductivity.

Claim 11

Apparatus according to claim 9 wherein said stem member has a substantially cylindrical portion housed in said second end of said runner member, and a narrowed tip, with a substantially radial wall between said cylindrical portion and said tip, said interior passage comprising an axial bore extending part way into said cylindrical portion, and a plurality of smaller passages extending from said axial bore to said radial wall, said smaller passages being spaced around said radial wall.

Claim 12

For a plastic injection mold structure: a tubular member for conducting plastic, said tubular member having an end adapted to be snugly but slidably fitted into a bore in said structure to receive plastic from or deliver plastic to said bore, and a thin cylindrical sleeve at said end projecting from said member, said sleeve being flexible and being joined to said member and having a first portion overlying said member and a second portion projecting from said member, at least a substantial part of said second portion being of diameter equal to a very slightly larger than that of said bore and at least a substantial part of said first portion being of diameter very slightly less than that of said bore, whereby to create a slidable seal between said tubular member and said bore while minimizing heat transfer between said tubular member and said bore.

Claim 13

For a plastic injection mold structure: a tubular member for conducting plastic, said tubular member having an end adapted to be snugly but slidably fitted into a bore in said structure to receive plastic from or deliver plastic to said bore, and a thin cylindrical sleeve at said end projecting from said member, said sleeve being flexible and being joined to said member and having a first portion overlying said member and a second portion projecting from said member, at least a substantial part of said second portion being of diameter equal to a very slightly larger than that of said bore and at least a substantial part of said first portion being of diameter very slightly less than that of said bore, whereby to create a slidable seal between said tubular member and said bore while minimizing heat transfer between said tubular member and said bore.

Claim 14

Apparatus according to claim 11 wherein all of said first portion and a small part of said second portion adjacent said first portion is of diameter slightly less than said bore.

Claim 15

Apparatus according to claim 12 wherein said sleeve is of hardened steel and is fastened to said tubular member by silver solder.

Claim 16

Apparatus according to claim 12 wherein the diameter of said second portion is approximately in the range between the same diameter as that of said bore and .002 inches larger than the diameter of said bore.

Claim 17

Apparatus according to claim 12 wherein said tubular member is a hot runner member.

Claim 18

For a plastic injection mold structure of the type including a cavity plate and a mold cavity bounded at least in part by said cavity plate, the improvement comprising a hot runner member having a first end part adapted to receive plastic and an elongated tubular second end part adapted to discharge plastic, means mounting said second end part in a position spaced from said cavity plate by an air gap so that said second end part is free to expand and contract relative to said cavity plate, a substantially cylindrical gate insert member having a first end portion snugly but slidably fitted into said second end part of said runner member and a second end portion projecting from said second end part of said runner member, said gate insert member having a passage therein to conduct plastic from said runner member to said second end portion of said gate insert member, said second end portion of said gate insert member having an end fitted snugly into said cavity plate and having a gate aperture therein to direct plastic through said cavity plate into said mold cavity, the part of said second end portion immediately adjacent said second end part of said hot runner member also being snugly slidable in said second end parT of said runner member, so that said second end part of said runner member can slide over said gate insert member as said second end part of said runner member expands and contracts with changes in temperature.

Claim 19

For a plastic injection mold structure of the type including a cavity plate and a mold cavity bounded at least in part by said cavity plate, the improvement comprising a hot runner member having a first end part adapted to receive plastic and an elongated tubular second end part adapted to discharge plastic, means mounting said second end part in a position spaced from said cavity plate by an air gap so that said second end part is free to expand and contract relative to said cavity plate, a substantially cylindrical gate insert member having a first end portion snugly but slidably fitted into said second end part of said runner member and a second end portion projecting from said second end part of said runner member, said gate insert member having a passage therein to conduct plastic from said runner member to said second end portion of said gate insert member, said second end portion of said gate insert member having an end fitted snugly into said cavity plate and having a gate aperture therein to direct plastic through said cavity plate into said mold cavity, the part of said second end portion immediately adjacent said second end part of said hot runner member also being snugly slidable in said second end parT of said runner member, so that said second end part of said runner member can slide over said gate insert member as said second end part of said runner member expands and contracts with changes in temperature.

Claim 20

Apparatus according to claim 16 wherein said passage is a straight axial passage through said gate insert member to said gate aperture, said gate aperture being located slightly off the axis of said gate insert member.

Claim 21

Apparatus according to claim 16 wherein said passage is a straight axial passage through said gate insert member to said gate aperture, said apparatus further including a torpedo snugly but slidably fitted into said passage, said torpedo having a narrowed tip cooperating with said gate aperture to control flow of plastic through said gate aperture, said torpedo also having calibrated passages therein to control flow of plastic past said torpedo, and a pin inserted through the walls of said first end portion of said stem member and through said torpedo to retain said torpedo in said gate insert member.

Claim 22

Apparatus according to claim 16 wherein said second end portion of said gate member includes an external circumferential collar therearound, said apparatus further including spring means fitted between said collar and said second end of said runner member to bias said gate member against said mold cavity plate.

Claim 23

Apparatus according to claim 19 including retaining means for retaining said gate insert member in said second end part of said runner member and for limiting sliding movement of said gate insert member within said second end part of said runner member, said retaining means comprising a circumferential groove in said first end portion, and a set screw projecting through the wall of said runner member into said groove, said groove being wider than the width of the end of said set screw to allow said limited sliding movement of said gate insert member.

Claim 24

Apparatus according to claim 20 wherein said set screw projects above the wall of said runner member, the exterior surface of said runner member being adapted to receive a heater, the projecting end of said set screw being adapted to locate the end of said heater.

Claim 25

Apparatus according to claim 21 wherein said spring means is a circular disk spring.

Claim 26

For a plastic injection mold structure of the type including a cavity plate having a gate aperture, and a mold cavity bounded at least in part by said cavity plate and into which said gate aperture opens, the improvement comprising: a hot runner member having a first end adapted to receive plastic and a tubular second end adapted to discharge plastic, a substantially cylindrical stem member having a first end portion snugly but slidably fitted into said second end of said runner member and a second end portion projecting from said second end of said runner member, means retaining said stem member in said second end of said runner member, said stem member having a passage therein to conduct plastic from said runner member to said second end portion of said stem member, said stem member being a valve member and said second end portion of said stem member having an end adapted to cooperate with said cavity plate to direct plastic through said gate aperture into said mold cavity, said stem member forming part of a plastic pressure operated valve and being axially movable between a first position in which said end of said second end portion blocks passage of plastic through said gate aperture and a second position in which said end of said second end portion is withdrawn from said gate aperture to permit passage of plastic therethrough, said first end portion of said stem member having a circumferential radially outwardly extending collar, said collar having an end face defining with said cavity member at least a portion of a chamber for plastic, with said gate aperture in said chamber and said end face closing the end of said chamber remote from said gate aperture, the diameter of said collar being such that the arEa on which plastic presses to move said stem member to said open position is greater than the area on which the plastic presses to move said stem member to said closed position, and spring means biasing said stem member to said closed position with preselected pressure, said pressure being such that said member will move against the pressure of said spring means to its open position when the pressure of said plastic increases beyond a predetermined level.

Claim 27

For a plastic injection mold structure of the type including a cavity plate having a gate aperture, and a mold cavity bounded at least in part by said cavity plate and into which said gate aperture opens, the improvement comprising: a hot runner member having a first end adapted to receive plastic and a tubular second end adapted to discharge plastic, a substantially cylindrical stem member having a first end portion snugly but slidably fitted into said second end of said runner member and a second end portion projecting from said second end of said runner member, means retaining said stem member in said second end of said runner member, said stem member having a passage therein to conduct plastic from said runner member to said second end portion of said stem member, said stem member being a valve member and said second end portion of said stem member having an end adapted to cooperate with said cavity plate to direct plastic through said gate aperture into said mold cavity, said stem member forming part of a plastic pressure operated valve and being axially movable between a first position in which said end of said second end portion blocks passage of plastic through said gate aperture and a second position in which said end of said second end portion is withdrawn from said gate aperture to permit passage of plastic therethrough, said first end portion of said stem member having a circumferential radially outwardly extending collar, said collar having an end face defining with said cavity member at least a portion of a chamber for plastic, with said gate aperture in said chamber and said end face closing the end of said chamber remote from said gate aperture, the diameter of said collar being such that the arEa on which plastic presses to move said stem member to said open position is greater than the area on which the plastic presses to move said stem member to said closed position, and spring means biasing said stem member to said closed position with preselected pressure, said pressure being such that said member will move against the pressure of said spring means to its open position when the pressure of said plastic increases beyond a predetermined level.

Claim 28

Apparatus according to claim 23 wherein said stem member includes a circumferential groove in its exterior surface, said groove being located in said first end portion of said stem member, said runner member having a pair of diametrically opposed slots in its wall over said groove, and a pair of diammetrically opposed springs disposed within said slots and pressing against a wall of said groove to bias said stem member into closed position, said groove being wider than said slots, said springs having outturned ends fitted between said groove and the interior surface of said second end of said runner member to retain said springs in position.

Claim 29

Apparatus according to claim 23 wherein said second end of said runner member has an end surface defining a portion of said chamber, said second end including a seal at its said end surface to seal against said cavity plate.

Claim 30

Apparatus according to claim 23 wherein said passage in said stem member includes an axial bore extending from that end of said stem member located within said hot runner tubular member, and a plurality of smaller passages extending from said axial bore through said collar into said chamber, said smaller passages being spaced around said collar.

Claim 31

Apparatus according to claim 26 wherein said passages are three in number and are spaced at 120* intervals around said collar.

Claim 32

For a plastic injection mold structure of the type including a cavity plate having a gate aperture, and a mold cavity bounded at least in part by said cavity plate and into which said gate aperture opens, the improvement comprising a hot runner member having a first end adapted to receive plastic and a tubular second end adapted to discharge plastic, a substantially cylindrical stem member having a first end portion snugly but slidably fitted into said second end of said runner member and a second end portion projecting from said second end of said runner member, means retaining said stem member in said second end of said runner member, said stem member having a passage therein to conduct plastic from said runner member to said second end portion of said stem member, said stem member being a valve member and said second end portion of said stem member having an end adapted to cooperate with said cavity plate to direct plastic through said gate aperture into said mold cavity, said stem member being axially movable between a first position in which said end of said second end portion blocks passage of plastic through said gate aperture and a second position in which said end of said second end portion is withdrawn from said gate aperture to permit passage of plastic therethrough, the wall of said runner member adjacent said second end including a pair of holes therein substantially sealed against escape of plastic by the snug fit of said first end portion of said stem member in said second end of said runner member, said apparatus further including a pair of pins connected to said stem member and protruding through said holes in said runner member, a cylindrical piston encircling said second end of said runner member and connected to said pins, a cylinder encircling and guiding said piston, said piston having a central collar sliding against said cylinder, and means for admitting pressurized fluid to said cylinder on either side of said collar and for removing fluid from said cylinder on the other side of said collar to drive said piston.

Claim 33

For a plastic injection mold structure of the type including a cavity plate having a gate aperture, and a mold cavity bounded at least in part by said cavity plate and into which said gate aperture opens, the improvement comprising a hot runner member having a first end adapted to receive plastic and a tubular second end adapted to discharge plastic, a substantially cylindrical stem member having a first end portion snugly but slidably fitted into said second end of said runner member and a second end portion projecting from said second end of said runner member, means retaining said stem member in said second end of said runner member, said stem member having a passage therein to conduct plastic from said runner member to said second end portion of said stem member, said stem member being a valve member and said second end portion of said stem member having an end adapted to cooperate with said cavity plate to direct plastic through said gate aperture into said mold cavity, said stem member being axially movable between a first position in which said end of said second end portion blocks passage of plastic through said gate aperture and a second position in which said end of said second end portion is withdrawn from said gate aperture to permit passage of plastic therethrough, the wall of said runner member adjacent said second end including a pair of holes therein substantially sealed against escape of plastic by the snug fit of said first end portion of said stem member in said second end of said runner member, said apparatus further including a pair of pins connected to said stem member and protruding through said holes in said runner member, a cylindrical piston encircling said second end of said runner member and connected to said pins, a cylinder encircling and guiding said piston, said piston having a central collar sliding against said cylinder, and means for admitting pressurized fluid to said cylinder on either side of said collar and for removing fluid from said cylinder on the other side of said collar to drive said piston.

Claim 34

For a plastic injection mold structure, a hot runner system comprising: a first member located in said mold structure, said fIrst member having a first bore therein of predetermined length; a cavity plate located in said mold structure at a position spaced from said first member; a hot runner for conducting molten plastic between said first member and said cavity plate, said hot runner comprising first and second tubular runner members oriented at right angles to each other, and separated from said mold structure and from said cavity plate by air gaps over a substantial portion of their length, and a connecting portion joining said runner members; heater means connected to said runner members to heat plastic flowing through said runner members; said first runner member having a tubular end adapted to be snugly but slidably fitted in its entirety into said first bore and having a first portion of length normally less than said predetermined length located in said first bore and a second portion projecting from said first bore, so that when said runner member is heated and expands in a direction parallel to the axis of said first end, said first end of said runner member will slide into said first bore to accommodate such expansion in said direction; said second runner member having a tubular second end adapted to discharge plastic; means mounting said connecting portion to said mold structure to support said second runner member with said second end spaced from said cavity plate by an air gap so that said second runner member can expand and contract relative to said cavity plate; and means providing a sliding sealed connection between said second end of said second runner member and said cavity plate for allowing expansion and contraction of said second runner member relative to said cavity plate, in a direction parallel to the axis of said second runner member.

Claim 35

For a plastic injection mold structure, a hot runner system comprising: a first member located in said mold structure, said fIrst member having a first bore therein of predetermined length; a cavity plate located in said mold structure at a position spaced from said first member; a hot runner for conducting molten plastic between said first member and said cavity plate, said hot runner comprising first and second tubular runner members oriented at right angles to each other, and separated from said mold structure and from said cavity plate by air gaps over a substantial portion of their length, and a connecting portion joining said runner members; heater means connected to said runner members to heat plastic flowing through said runner members; said first runner member having a tubular end adapted to be snugly but slidably fitted in its entirety into said first bore and having a first portion of length normally less than said predetermined length located in said first bore and a second portion projecting from said first bore, so that when said runner member is heated and expands in a direction parallel to the axis of said first end, said first end of said runner member will slide into said first bore to accommodate such expansion in said direction; said second runner member having a tubular second end adapted to discharge plastic; means mounting said connecting portion to said mold structure to support said second runner member with said second end spaced from said cavity plate by an air gap so that said second runner member can expand and contract relative to said cavity plate; and means providing a sliding sealed connection between said second end of said second runner member and said cavity plate for allowing expansion and contraction of said second runner member relative to said cavity plate, in a direction parallel to the axis of said second runner member.

Claim 36

Apparatus according to claim 29 wherein said means providing a sliding sealed connection comprises: a substantially cylindrical gate insert member having a first end portion snugly but slidably fitted into said second end of said second runner member and a second end portion projecting from said second end of said second runner member, said gate insert member having a passage therein to conduct plastic from said runner member to said second end portion of said gate insert member, said second end portion of said gate insert member having an end fitted snugly into said cavity plate and having a gate aperture therein to direct plastic through said cavity plate into said mold cavity, the part of said second end portion immediately adjacent said second end of said second runner member also being snugly slidable in said second end of said second runner member, so that said second end of said second runner member can slide over said gate insert member as said second runner member expands and contracts with changes in temperature.

Claim 37

A plastic injection mold structure having a cavity plate and a mold cavity bounded at least in part by said cavity plate, said cavity plate having an enlarged aperture therein opening into said mold cavity; said structure further including a hot runner member adapted to receive plastic, said hot runner member having an elongated tubular portion having an end adapted to discharge said plastic; means mounting said tubular portion in a position spaced from said cavity plate by an air gap; a substantially cylindrical discrete gate insert member having a first and second end, a gate aperture at said first end and a passage communicating from said second end to said gate aperture; said gate insert member extending from said end of said tubular portion into said enlarged aperture in said cavity plate, with said first end being located in said enlarged aperture, and said gate insert member forming with said end of said tubular portion and said cavity plate a sliding sealed connection for conducting plastic from said tubular portion into said mold cavity while permitting substantially free axial expansion and contraction of said tubular portion.

Claim 38

A plastic injection mold structure having a cavity plate and a mold cavity bounded at least in part by said cavity plate, said cavity plate having an enlarged aperture therein opening into said mold cavity; said structure further including a hot runner member adapted to receive plastic, said hot runner member having an elongated tubular portion having an end adapted to discharge said plastic; means mounting said tubular portion in a position spaced from said cavity plate by an air gap; a substantially cylindrical discrete gate insert member having a first and second end, a gate aperture at said first end and a passage communicating from said second end to said gate aperture; said gate insert member extending from said end of said tubular portion into said enlarged aperture in said cavity plate, with said first end being located in said enlarged aperture, and said gate insert member forming with said end of said tubular portion and said cavity plate a sliding sealed connection for conducting plastic from said tubular portion into said mold cavity while permitting substantially free axial expansion and contraction of said tubular portion.