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The present invention relates to a mould for injection molding thermoplastic battery containers. It is particularly useful in multicell lead-acid automotive battery containers. However, it is also applicable to single cell batteries. During the molding process, the container is shrunk about a core, which contains a plurality of mandrels. These mandrels are arranged in a rack. They are then melted together by a hot flame. Once this occurs, the innards of the batteries are inserted into the individual cell compartments.
The core of the mold includes a stationary backplate 20 and a forward stationary mounting plate 54. The core-bearing portion 18 of the mold is anchored to the forward stationary mounting plate. The ejector bars 30 of the mandrels are positioned within the mortises 26, and the ejector bar pushes against the top and bottom of the container during the initial stage of stripping.
An ejector bar has a lip at the distal end, which extends to within 0.1 mm of the adjacent wall of the rib-forming cavity. Upon coming out of the mold, the ejector bar retraction is accompanied by a detachable rib.
A thin, angled resilient rib retains the battery innards. The ribs are molded at an angle to the container walls and deflect according to the thickness of the cell elements. When the container is completed, the retainer ribs are substantially detached from the bottom of the container.
A rim 16 of the container is engaged by a stripper plate 66. The hydraulic cylinder 70 advances the stripper plate 66. Similarly, hydraulic cylinders 46 advance the ejector actuating plate 40. Moreover, the ejector actuating plate moves the ejector bars.
The ejector bars of the mandrels, together with the stripper plate, are mated to the stationary/female portion of the mold 74. This part of the mold comprises a main body 76 with a hollow 78, which defines the container-shaped cavity 82. Cam doors 80 slide into hollow 78 to define the container-shaped cavity.
The core-bearing portion of the mold contains a mandrel 24 that includes a plurality of trapezoidal mortises 26. The diverging walls 90 of the ejector bars and the complementary walls of the mortises form a rib-forming cavity. Throughout the molding process, the ejector bars, ejector actuating plate, and the stripper plate move from one side of the rib-forming cavity to the other, while the container shrunk about the core 22.
During the initial stage of stripping, the ejector bars push against the top and bottom of the ribs. Afterward, the container is pushed out of the mandrels. At this point, the container is ready for the molding process.
In order to eliminate the need for separate detachments, the ejector bars and the stripper plate travel with the container. After the molding cycle, the container is positioned in the forward mounting plate, and the ejector bars and the stripper are mated with the forward mounting plate. During the next step, the ejector bars and the ejector actuating plate are moved in the reverse direction.
