Method for manufacturing composite insulators

A method of manufacturing a composite insulator including a core rod, a sheath covering the core rod over substantially the entire length thereof, and a plurality of sheds projecting radially outwards from the sheath and spaced from each other in a longitudinal direction of the core rod, the core rod having a longitudinal end portion provided with a seat which is integral with the sheath and to which a metal fitting can be fixedly secured, wherein said method comprises the steps of:

• placing the core rod in a mold cavity of a mold assembly which is comprised of a pair of mold halves, with a seat forming member detachably fitted to the end portion of the core rod and arranged between the mold halves such that a space is formed between an inner surface of the seat forming member and an outer surface of the core rod, which space is in communication with the mold cavity;
• venting the mold cavity through at least one longitudinal groove formed in an outer surface of the seat forming member;
• and
• introducing an electrically insulating polymeric material into the mold cavity to form the sheath and sheds, while admitting the polymeric material into said space so as to form the seat for the metal fitting.