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Figure #1 illustrates the critical aspects of the three seal design. The figure also depicts the position of the lid as it approaches the container during closing. The hinged design positions the lid at the appropriate angle to ensure proper closure. |
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The first seal is formed by the union of the lid valve (figure #2) with the inside surface of the container wall. The integrity of this seal is obtained by forcing the top of the container into a small space between the valve and the wall of the lid. The structural interference encountered during closing and the shrinkage that occurs during the curing stage create the airtight seal. |
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The second seal is formed by the union of the top edge of the container wall (figure #3) and the inside wall of the lid. Similar to the first seal, it is a combination of structural interference and shrinkage that guarantees the integrity of the seal. This feature's primary function is to provide a leakproof seal that prevents fluids from entering or exiting the container. |
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The third seal is formed by the union of the outer wall of the container (figure #4) and the undercut around the inside wall of the lid. This seal provides another layer of protection against fluid ingress and egress and also determines the amount of internal air pressure the container will withstand. The level of internal air pressure is controlled by the ratio of surface contact to undercut. |
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Capitol Vial’s Molding & Curing Process for Flip-Top Vials— |
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The critical aspect of Capitol Vial’s injection molding technology is its ability to close the container before the material is fully set. By closing the container while the part is still hot, Capitol Vial uses the natural curing properties of the plastic to help form the seals inherent in the container design. The process for closing the container in the mold is shown in the figures below.
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The mold consists of two sides, the cavity and the core. The container can be closed in the mold because the cavity that forms the lid is located in a movable piece of the mold called the flipper. Plastic is injected into the mold from the bottom of the body cavity and forms around the cores. The hinge of the container provides the pathway for the plastic to flow from the body to the lid cavity. As depicted in step 1, the container remains in the cavity after the cores have retracted. This differs from many injection molding processes where the part is usually removed from the cavity by the retracting core. |
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With the core side retracted, the flipper is free to rotate upwards. Step 2 illustrates the flipper moving the lid towards the body of the container. The flipper rotates 180º until the lid is closed. Since the container is still hot, the plastic flexes and allows the seal to form without distortion. |
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As the flipper returns to its home position in step 3, the lid is secured to the body of the container and the normal shrinkage process continues. Along with the airtight seals, shrinkage creates the “living hinge” of the container. The hinge is molded in the open position and as a result acquires memory for this orientation. The hinge also obtains memory in the closed position. This “dual memory” creates a robust “living hinge” which maintains its integrity indefinitely. |
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Once the flipper is fully retracted, the container is ejected from the mold in step 4 with the use of a mechanical pin and air pressure. The container continues to cool until it reaches ambient temperature, providing a hermetic seal. |
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For additional information, please contact us directly.
Capitol Vial, Inc. ISO 9001 Certified Company
Toll-Free Customer Service: 800.772.8871
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