INSULATOR TYPE GAS BREAKER

A porcelain clad gas circuit interrupter is disclosed which includes: an arc extinguishing porcelain tube defining therein an arc extinguishing chamber in which a stationary and a movable contact are disposed, the arc extinguishing chamber being filled with an insulating gaseous medium; and a hollow support porcelain tube supporting the arc extinguish porcelain tube and communicating with the arc extinguishing chamber. An insulating operation rod having its opposite ends formed hollow is disposed in the support porcelain tube and adapted to operate the movable contact for closing and opening thereof against the stationary contact. A pair of shield members are received in the opposite hollow ends of the insulating operation rod and have their base end mounted on the opposite ends of the insulating operation rod and their distal end configured into a gradually curved shape such as a semi-spherical shape whereby the distribution of potential at the distal ends of the shield members can be improved to materially reduce the electric field strength along the surface of the support porcelain tube, thus enhancing the voltage-withstanding property thereof without increasing the size or diameter of the support porcelain tube. Preferably, each of the shield members is of a cylindrical configuration and has a positioning projection formed at its side surface for abutting engagement with the inner surface of the support porcelain tube.