Method and apparatus for inertial spinwelding of thermoplastic container ends

摘要

A thermoplastic end is inertially spinwelded onto the paperboard sidewall of a container body, the end having an annular grove for snugly receiving the sidewall and a wall configuration which minimizes the forces exerted on the bond by liquid contents which would tend to dislodge the end portion. The end portion has strengthening ribs positioned generally within the region of U-shape and additional radial ribs imparting strength and rigidity to the container end. The paperboard sidewall may be internally lined with a layer of thermoplastic material or may be unlined. During spinwelding, a sidewall supporting mandrel 28 having an expandable engaging portion is inserted into the sidewall and subsequently expanded to define a cylindrical surface of a diameter equal to that of the specified internal diameter of the sidewall. A seating member at the end of the sidewall supporting mandrel establishes the depth to which the container end is inserted into the sidewall and is provided with a low-friction member which contacts and aligns the rotating container end with the container sidewall; Figs 4-9 and 13 (not shown).