US Patent 7147816 Method for injection molding of the hollow body

A pair of primary semi-hollow bodies formed by primary injection molding are united together by the molten resin injected for secondary injection molding to fill a joining space defined about the butt ends of the primary semi-hollow bodies having their open ends butted against each other. The molten resin for secondary molding fills the space between the butt ends, or the notch portion, too. Alternatively, the molten resin is compressed after filling the joining space and the space between the butt ends.