Method for forming a strain-hardenable plastic container
AssigneeContinental PET Technologies, Inc.
InventorsWayne N. Collette, Suppayan M. Krishnakumar
Life of this patent
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Abstract
A method of making a blow-molded container from a strain-hardenable polymer, the container having deep recesses for secure "post mold" attachment of a handle. The container is formed in a modified blow mold having retractable blades. The blades are partially extended for blow molding partial recesses, and then further extended for mechanically forming the deep handle recesses. The mechanical forming operation overcomes the stretch limits imposed by strain-hardening of the plastic material during blow molding, and the "post-mold" attachment of the handle provides a reduced cycle time and lower level of defects compared to the known "in-mold" handle forming operations.
Claims13
A method of forming a strain-hardenable plastic container with handle comprising:
- stretch blow molding a strain-oriented container from a preform in a cavity of a blow mold, the preform being made of a strain-hardenable thermoplastic material, the mold having at least one extendable projection forming a partial recess of a first depth in the container as the material is blow molded over the projection at a forming temperature above T.sub.g of the thermoplastic material, the first depth of the partial recess being limited by strain hardening of the thermoplastic material during the stretch blow molding such that the partial recess has a depth-to-width ratio of up to about 2:1;
- then mechanically extending the first depth of the partial recess to a greater second depth by extending the projection further into the recess to form a handle recess of the second depth and having a depth-to-width ratio of at least about 3:1;
- mechanically retracting the extendable projection and removing the container with the handle recess from the blow mold;
- and
- attaching a handle to the container by engaging an attachment member on the handle with the handle recess.
Dependencies are inferred from the claim text.