Overvoltage surge arrester for electric meters

Claim 1

An electrical meter of the type having a meter movement enclosed in a case, the case comprising an insulating baseplate through which pass two or more conducting members for supplying electrical current to the movement, and an overvoltage surge arrestor electrically connected between the conducting members and ground potential, wherein the improvement comprises: an overvoltage surge arrestor module mounted substantially inside a receiving well that is open to the outside of the baseplate and sealed from the interior of the meter, the module being demountably inserted in the baseplate receiving well, open end first, the module comprising an insulating cup, a conductive electrode member and a disc-shaped wafer of nonlinear resistance material, the wafer being closely fitted inside the cup with a bottom face substantially parallel to and spaced from the bottom of the cup, said wafer having a conductive contact layer on both faces, said conductive electrode member being fixed to the cup with an end passing through the wall of the cup to within a predetermined distance from the bottom face of the wafer to form an air gap in series with the non-linear resistance material, and a leaf-spring contact mounted in the bottom portion of the well to make a pressure contact with the top face of the wafer in the module.