Method and mould for producing umbrella insulators

A method for producing an umbrella insulator made of plastic material, having a core constructed as a solid body and having umbrellas connected with the core as well as having collars which are molded to the umbrellas and coaxially surround the core, by a mold which reaches coaxially around the core and forms a ring gap with respect to the core at the collar end of the respective umbrella to be molded, the ring gap being sealed off by an elastic seal, and wherein after sealing off, a first pourable material, which cross-links with the core to form a firm electrically insulating body, is poured into the mold and after the cross-linkage and the formation of the respective umbrella a with the collar, the mold with the seal is moved away from the umbrella and in the process, the formed umbrella with the collar is removed from the mold, comprising:

• providing a mold which has at least one laterally arranged valve which extends to a surface of one of the umbrella and the collar coaxially around the core;
• pouring a material into the mold which cross-links with the core to form the insulating body comprising a core, collar and umbrella;
• begin axial moving-away of the mold from the umbrella and collar resulting in a vacuum forming between the mold and the formed insulating body;
• then opening the valve and allowing a gaseous medium to be introduced into a cavity formed between the insulator and the mold so that the pulling-away of the mold is permitted without any unacceptable deformation of the umbrella.