| 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. |
Step 1
|
| 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 onto the body of the container.
Since the container is still hot, the plastic flexes and allows the seal
to form without distortion. |
Step 2
|
| 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 also 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. |
Step 3
|
| 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. |
Step 4
|
| Figure #5 shows the distortion that occurs when the lid is closed
after the material has cooled and has fully set.
Since shrinkage has occurred, the plastic is less flexible and
the first and third seal areas are distorted upon closure.
This distortion damages the integrity of the seals and prevents
the container from being airtight or leak-proof.
Capitol Vial's
unique closing processes prevent the plastic from cooling
excessively before closure and ensure a perfect seal. |
