Injection mold for elongated, hollow articles

• US 4,126,291 A
• Filed: 10/18/1974
• Issued: 11/21/1978
• Est. Priority Date: 10/18/1974
• Status: Expired due to Term

• Current Assignee: Cimco, Inc. (California) (Avient Corp.)
• Original Assignee: California Injection Molding Company Incorporated
• Inventors: Gilbert, Russell T., Pfau, Irwin B.
• Primary Examiner(s): Husar, Francis S.
• Assistant Examiner(s): McQuade, John
• Application Number:
  US05/515,818
• Time in Patent Office: 1,495 Days
• Field of Search: 425/249, 425/250, 425/251, 425/252, 425/134, 425/812, 425/542, 425/556, 425/577, 425/438, 249/122, 249/135, 249/105, 249/176-177, 249/141, 249/63, 264/327, 264/328
• US Class Current: 249/63
• CPC Class Codes: B29C 45/26 Moulds
• CPC Class Codes: B29C 45/261 having tubular mould cavities
• CPC Class Codes: B29C 45/34 having venting means
• CPC Class Codes: B29C 45/36 having means for locating or centering cores
• CPC Class Codes: Y10S 425/812 Venting

Abstract

Thermometer probe covers having an extremely thin wall integral tip for enhanced heat transfer are injection molded by unique mold core construction and venting configuration. A tungsten carbide core minimizes core deflection to maintain improved concentricity of core and cavity. Maintainance of concentricity in quantity production apparatus is improved by a combination of relatively loose cantilevered mounting of an end of the core together with a press fit locking of the core upon closing of the mold. Venting of cavity gas during injection of mold material is precisely controlled through symmetrically distributed vent orifices in both the core and the female mold part. Core venting is controlled by a plurality of orifices and a manifold provided by a water cooled core vent pin within a bore of the core.

Claims

1. 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, and

an elongated rigid core mounted at one end thereof in said second mole part and movable therewith from said mold open position wherein the said core is withdrawn from said cavity, to said mold closed position wherein said core is symmetrically positioned within said cavity to define therewith a thin elongated annular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, said second mold part including first and second relatively movable and mutually connected elements,

means operatively associated with said second mold part for relatively loosely mounting said core in said first and second elements when said mold parts are in open position, and

means operatively associated with one of said elements for rigidly securing and positioning said core with respect to said second element and said second mold part when said mold parts move to said mold closed position.

2. The apparatus of claim 1 wherein said second element of said second mold part includes a stripper ring movably mounted with respect to said first element of said second mold part, said stripper ring and said core having mutually cooperating surfaces constructed and arranged to permit motion of said core relative to said mold parts when said first and second elements of the second mold part are in a first relative position and to securely grasp and position said core with respect to said second mold part when the mold parts are in said closed position and when said first and second elements of said second mold part are in a second relative position with respect to each other.

3. The apparatus of claim 1 wherein said second mold part includes a movable mold element and a stripper ring movably mounted with respect to said element, said core being relatively loosely mounted in said movable element, said stripper ring having a bore circumscribing said core and being movable relative to said movable element and relative to said core when said mold parts are in open position to thereby strip a molded article from said core, said stripper ring and core having mutually engageable locking surface means for firmly grasping and positioning said core with respect to said mold parts and stripper ring when said mold parts are in said closed position.

4. The apparatus of claim 3 wherein said mutually engageable locking surface means comprise a tapered outer surface formed on a section of said core and a mating tapered bore formed in said stripper ring, said stripper ring being positioned with respect to said core and movable mold element to cause said bore to be a press fit upon said tapered surface of said core section when said mold parts are in closed position.

5. The apparatus of claim 4 wherein the relatively loose mounting of said core comprises an aperture formed in said movable mold element loosely receiving an end of said core, and resilient means within said aperture.

6. 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.

7. 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.

8. The apparatus of claim 7 wherein said means for fixedly positioning said core comprises a stripper ring interposed between said first movable mold element and said female mold part, said stripper ring inlcuding means responsive to motion of the ring toward said first movable mold element to securely grasp and position said core.

9. The apparatus of claim 8 including means for venting said annular cavity through said female mold part and through said core.

10. The apparatus of claim 9 wherein said means for venting includes a bore in said core forming a vent aperture and a vent pin in said bore dividing said vent aperture into a plurality of spaced smaller apertures.

11. 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.

12. In apparatus for injection molding elongated thin wall articles having a female mold part defining a mold cavity and having a male mold part carrying an elongated relatively small diameter core adapted to be positioned within said mold cavity to cooperate therewith and define an elongated thin annular cavity space for reception of injected molding material, said male mold part including a first movable mold element movably connected for motion relative to said female mold part, the improvement comprising

means operatively associated with said male mold part for relatively loosely mounting said core to said first movable mold element, and means movable relative to said first movable mold element for selectively fixedly positioning said core relative to said first movable mold element, said last mentioned means comprising a stripper ring interposted between said first movable mold element and said female mold part and loosely retaining said core when said mold parts are moved away from each other, said stripper ring including means responsive to motion of the ring toward said first movable mold element to securely grasp and position said core.

13. The apparatus of claim 12 wherein said means to grasp and position said core comprises a tapered outer surface formed on a section of said core and a mating tapered bore formed in said stripper ring, said stripper ring being positioned with respect to said core and movable mold element to cause said bore to be a press fit upon said tapered surface of said core section when said mold parts are in closed position.

14. 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.