Apparatus for single cavity injection molding of oil seals

Claim 2

A single cavity injection mold of at least three pieces defining a mold cavity of circular configuration having a common center line, said pieces comprising: i. a mold top defining at least in part a fine orifice into said mold cavity and having an injection conduit connecting said fine orifice with a source of molding composition; ii. a mating mold bottom adapted to accomodate and mate with a center piece; and iii. a center piece extending through said mold bottom, mating therewith and defining at least in part an interior wall of the object to be molded, said center piece having a frusto-conical lower portion serving as a valve and mating with said mold bottom as a valve seat, a conduit connecting an evacuating means with said valve seat, said center piece being moveable a few thousandths of an inch upward into said mold cavity to open said valve and to free the molded article from said mold bottom, said valve including means for maintaining said valve in an open position as said mold cavity is being closed, evacuating means for placing a vacuum on said mold cavity through said valve means for closing said valve for of injection of a molding composition into said mold cavity.

Claim 3

The mold of claim 1 wherein an outer annular shoulder mates with an outer annular wall of said mold top and bottom serving both to align the two and to form a seal against an interior vacuum, which seal is formed before said mold top and bottom are fully seated.

Claim 4

a mold bottom mating therewith and adapted to accommodate and mate with a center piece; and

Claim 5

a mold bottom mating therewith and adapted to accommodate and mate with a center piece; and

Claim 6

a center piece extending through said mold bottom, mating therewith and defining at least in part an interior surface of said lip and at least a portion of said sprue, the upper surface of said center piece having an upwardly opening flash-lock cavity communicating with said injection conduit, said center piece accommodating a flash-lock ejector adapted to seal in the base of said flash-lock cavity to form a seal and to be raised relative to said center piece to allow vacuum to be applied to said mold cavity; said mold including means adapted to apply a vacuum communicating with the underside of said flash-lock ejector seat; and said case having an inner directed annular end wall to which said elastomeric sealing lip is bonded; the improvement comprising: a. a downwardly directed annular cylindrical shoulder on said mold top about said mold cavity the outer cylindrical surface of which is adapted to mate with the inner cylindrical surface of said case and to align the same with respect to said mold cavity, said annular shoulder defining at least in part a surface of said elastomeric sealing lip and ending in a downwardly directed circular knife-edge sealing lip adapted to engage and form a seal with said annular end wall, and b. a portion of the combination of said center piece and said mold bottom underlying said circular end wall having an upwardly directed knife-edge sealing lip adapted to engage and form a seal with said annular end wall, the circles of said knife-edge sealing lips being concentric and slightly radially displaced one from the other. the whole of said mold being adapted to form a vacuum-tight mold cavity with said case with the cylindrical wall of said case being external thereof, and after completion of injection of said molding composition and curing during a cycle, to open first with said mold top being separated from said oil seal, followed by said flash-lock ejector and center piece each being raised to eject the flash-lock along with the cured material in said sprue separated at the tear line created by said fine orifice and to free said oil seal from said mold.

Claim 7

a center piece extending through said mold bottom, mating therewith and defining at least in part an interior surface of said lip and at least a portion of said sprue, the upper surface of said center piece having an upwardly opening flash-lock cavity communicating with said injection conduit, said center piece accommodating a flash-lock ejector adapted to seal in the base of said flash-lock cavity to form a seal and to be raised relative to said center piece to allow vacuum to be applied to said mold cavity; said mold including means adapted to apply a vacuum communicating with the underside of said flash-lock ejector seat; and said case having an inner directed annular end wall to which said elastomeric sealing lip is bonded; the improvement comprising: a. a downwardly directed annular cylindrical shoulder on said mold top about said mold cavity the outer cylindrical surface of which is adapted to mate with the inner cylindrical surface of said case and to align the same with respect to said mold cavity, said annular shoulder defining at least in part a surface of said elastomeric sealing lip and ending in a downwardly directed circular knife-edge sealing lip adapted to engage and form a seal with said annular end wall, and b. a portion of the combination of said center piece and said mold bottom underlying said circular end wall having an upwardly directed knife-edge sealing lip adapted to engage and form a seal with said annular end wall, the circles of said knife-edge sealing lips being concentric and slightly radially displaced one from the other. the whole of said mold being adapted to form a vacuum-tight mold cavity with said case with the cylindrical wall of said case being external thereof, and after completion of injection of said molding composition and curing during a cycle, to open first with said mold top being separated from said oil seal, followed by said flash-lock ejector and center piece each being raised to eject the flash-lock along with the cured material in said sprue separated at the tear line created by said fine orifice and to free said oil seal from said mold.

Claim 8

The mold of claim 1 when adapted to mold a circular oil seal with a metal casing insert, and wherein said center piece is composed of three sections: a stem, an intermediate section, and a top section, said top and intermediate section defining the interior surfaces of said oil seal and the critical oil seal lip, and said intermediate section having the diameter of the largest internal diameter of said oil seal.

Claim 9

The mold of claim 3 wherein An upper edge of said center piece and an inner wall of said mold top form said fine orifice, the same being annular, and wherein said mold top contains an annular accumulation and distribution cavity disposed between said fine orifice and said source of said molding composition, and wherein the mold parts mate to form a flashless joint about the outer circumference of said oil seal.

Claim 10

The mold of claim 4 wherein said top surface of said center piece forms with the under surface of said mold top a disk-shaped distribution conduit connecting said source of molding composition with said accumulation and distribution cavity.

Claim 11

The mold of claim 5 wherein said top section extends through said casing insert, wherein the diameter of said annular orifice lies within the largest diameter of said top section, and wherein the design of said oil seal is such that said oil seal is capable of being stripped off said center peice over said top section.

Claim 12

The mold of claim 3 wherein there are at least three of said fine orifices uniformly spaced about said injection conduit, the same being centrally located, said orifices being individually connected thereto by radial sprues, said critical oil seal lip being positioned in said mold cavity at a point remote from said injection orifices.

Claim 13

The mold of claim 7 wherein said top section of said center piece is recessed to form a flash lock connecting with the material in said sprues, wherein said center piece contains ejecting means for ejecting said flash lock, said flash lock along with the material in said sprues being first extracted from said mold top during mold opening and thereafter being ejected from said center piece with said ejecting means.

Claim 14

The mold of claim 7 wherein said top section of said center piece and the bottom surface of said mold top meet to form a flash-less joint at the inner periphery of said oil seal, and the mold parts are lightly gapped externally and circumferentially about said oil seal to form a flash joint.

Claim 15

The mold of claim 1 comprising in addition a removeable bridge section circular about said center line, inset in said mold top in the face thereof contiguous to said mold cavity, and defining with said mold top at least three radial distribution runners running between said bridge section and mold top from said injection conduit towards the periphery of said mold cavity which runners terminate in orifices downwardly directed into said mold cavity.

Claim 16

In a single cavity injection mold adapted to the repetitive molding of a circular shaft seal having an interior elastomeric sealing lip reinforced with a cylindrical case thereabout, said mold comprising at least three main circular sections having a common center line and defining a mold cavity, viz:

Claim 17

In a single cavity injection mold adapted to the repetitive molding of a circular shaft seal having an interior elastomeric sealing lip reinforced with a cylindrical case thereabout, said mold comprising at least three main circular sections having a common center line and defining a mold cavity, viz:

Claim 18

The mold of claim 11 wherein said upwardly-directed knife-edge sealing lip is located near the annular edge of said center piece and wherein after said mold is closed and the seals are established by said knife-edge sealing lips said ejector is adapted to be in the raised position to permit the application of vacuum through said seat and to be closed upon the commencement of injection.