Injection mold for elongated, hollow articles

Apparatus for molding elongated thin wall articles comprising

• a first mold part having a cavity formed therein with a length several times greater than its maximum cross-sectional dimension, a second mold part movably connected to said first mold part,
• means operatively associated with said mold parts for moving said first and second mold parts between mold open and mold closed positions, an elongated rigid core mounted at one end thereof in said second mold part and movable therewith from said mold open position wherein the said core is withdrawn from said cavity, to said mold closed position wherein said core is symmetrically positioned within said cavity to define therewith a thin elongated annular cavity space for reception of injected molding material, said core having a length several times greater than its maximum cross-sectional dimension and being supported by said second mold part independently of the mold cavity when said mold parts are in closed position, means for venting said elongated annular mold cavity space through said core comprising
• a core bore extending longitudinally through said core and having a vent aperture at the free end of said core,
• a core vent pin positioned in said core bore and having an end cooperating with said vent aperture to define orifice means symmetrically positioned about said vent aperture for passing gas from said elongated annular cavity space to the core bore, said core pin having a generally cylindrical cross-section with a maximum dimension substantially equal to the interior diameter of said vent aperture in said core, said generally cylindrical cross-section having a plurality of flat surfaces each cooperating with the wall of said core bore to define an individual vent orifice, said core pin further including manifold means for providing a vent manifold in communication with said orifice means, and means for providing a vent conduit between said core pin and said core bore from said manifold means toward a fixed end of said core, said manifold means comprising a section of said core pin immediately adjacent said orifice means, said core pin section having a relatively decreased diameter, said means for providing a vent conduit between said core pin and said core bore comprising a flat formed on the surface of said core pin between said section of decreased diameter and another portion of said core pin that is more remote from said orifice means than is said section of decreased diameter, said vent conduit flat extending in a spiral path.

In apparatus for injection molding elongated thin wall articles having a female mold part defining a mold cavity with a length several times greater than its maximum cross-sectional dimension and having a male mold part movably mounted to the female mold part and carrying an elongated relatively small diameter core adapted to be positioned within said mold cavity to cooperate therewith and define a long thin annular cavity for reception of injected molded material, said core having a length several times greater than its maximum cross-sectional dimension and a diameter at portions therof that is slightly less than the diameter of the cavity at corresponding portions so as to define a long thin annular cavity, the improvement comprising

• means operatively associated with said male mold part for cantilevering said core from said male mold part to support said core solely by said male mold part independently of said mold cavity,
• said core being formed of a material having a high modulus of elasticity whereby the core will have a decreased magnitude of bending deflection in the presence of lateral forces of pressurized material being injected even though the core is supported solely from the male mold part during the injection, said male mold part including a first movable element mounted for motion relative to said female mold part, and
• including means operatively associated with said male mold part for relatively loosely mounting said core to said first movable element, and means operatively associated with said first movable element and movable relative thereto for selectively fixedly positioning said core relative to said first movable mold element when said mold parts are in closed position and for loosely retaining said core when said mold parts are in open position.

In apparatus for molding elongated thin wall articles, said apparatus having a cavity in one mold part and an elongated core secured to a second mold part and having a free end, said core and cavity defining an elongated annular cavity space for receiving injected material, the improvement wherein said core comprises

• an elongated body having a core bore extending longitudinally through said core and having a vent aperture at the free end of said core,
• a vent pin positioned in said core bore and having an end cooperating with said vent aperture to define orifice means symmetrically positioned about said vent aperture for passing gas from said elongated annular cavity space to the core bore,
• said pin having a generally cylindrical cross-section with a maximum dimension substantially equal to the interior diameter of said vent aperture in said core end,
• said cylindrical cross section having a plurality of flat surfaces each cooperating with the wall of said core aperture to define an individual vent orifice, said core pin including manifold means for providing a vent manifold in communication with said orifice means, said manifold means comprising a section of said core pin immediately adjacent said orifice means, said core pin section having a relatively decreased diameter,
• means for providing a vent conduit between said core pin and said core bore from said manifold means away from said free end of said core,
• said means for providing a vent conduit between the core pin and the core bore comprising a flat formed on the surface of said core pin between said section of decreased diameter and another portion of said pin that is more remote from said orifice means than is said section of decreased diameter,
• said vent conduit flat extending in a spiral path.

Apparatus for molding elongated thin wall articles comprising,

• a first mold part having a cavity formed therein having a length several times greater than its maximum cross-sectional dimension,
• a second mold part movably connected to said first mold part,
• means operatively associated with said mold parts for moving said first and second mold parts between mold open and mold closed positions,
• an elongated rigid core mounted at one end thereof in said second mold part and movable therewith from said mole open position wherein said core is withdrawn from said cavity, to said mold closed position wherein said core is symmetrically positioned within said cavity to define therewith an elongated annular cavity space for reception of injected molding material, said annular cavity space having at least a portion with a thickness of less than 0.060 inches, said core being formed of a material having a high modulus of elasticity,
• said core having a length several times greater than its cross-sectional dimension and being cantilevered to said second mold part and supported thereby independently of and free of contact with the mold cavity and said first mold part when said mold parts are in closed position, to thereby provide an unobstructed and continuous cavity around the sides and the other end of said core,
• said second mold part including first and second relatively movable elements,
• means operatively associated with said second mold part for relatively loosely mounting said core at said one end thereof to said first element for motion with said first element relative to said first mold part, said second element including means responsive to movement of said mold parts to mold closed position for firmly and precisely positioning said core and responsive to movement of said mold parts to mold open position for releasing such firm and precise positioning of the core.