| 摘要 |
<p>A dimensionally stable plastic canning ring for securing vacuum sealing lids to food containers during processing is fabricated of thermoplastic material reinforced with fibers. The fibers are circumferentially aligned in the plastic media whereby the canning ring exhibits thermal expansion which is lowest in the direction of fiber alignment, i.e., circumferentially. The circumferential thermal coefficient of expansion substantially matches that of a glass container with which the canning ring is utilized. Due to the similarity of thermal coefficients of expansion, relative dimensional differences between the plastic ring and the glass container occurring during processing are negligible. The ring is manufactured by an injection molding process. The mold cavity includes a single gate disposed generally adjacent its periphery. Injection of the plastic and fiber material into the mold through the single gate causes laminar circumferential flow about the mold cavity and alignment of the fibers with the circumferential flow streamlines.</p> |
