Surge arrester

A kit of parts for forming a surge arrester, comprising

• (a) a first electrode having (i) a first contact plate with interior and exterior faces and (ii) a first shank projecting from the exterior face of the first contact plate;
• (b) a second electrode having (i) a second contact plate with interior and exterior faces and (ii) a second shank projecting from exterior face of the second contact plate;
• (c) a substantially disk shaped varistor element, capable of forming, in combination with the first and second electrodes, a core assembly wherein the varistor element is sandwiched between the first and second electrodes with the interior faces of the first and second contact plates facing the varistor element and making electrical contact therewith;
• (d) a cup-shaped gasket having a sidewall and a substantially circular base with a through-hole;
• the gasket capable of containing the core assembly, with the exterior face of the first contact plate facing the base of the gasket, the first shank passing through the through-hole of the base, and the second shank extending from the open end of the gasket;
• (e) a housing having a sidewall and a base with a through-hole;
• the housing capable of containing the core assembly and the gasket, with the open end of the gasket facing the base of the housing, the first shank extending from the open end of the housing, and the second shank passing through the through-hole in the base of the housing;
• (f) a sealing element for the through-hole in the base of the housing;
• and (g) a lid with a through-hole, the lid capable of covering the open end of the housing such that the first shank passes through the through-hole in the lid, the lid is engaged and retained in place by an engagement means on the sidewall of the housing, and the lid applies a compressive force to the gasket and the core assembly.

A surge arrester, comprising

• a first electrode having (i) a first contact plate with interior and exterior faces and (ii) a first shank projecting from the exterior face of the first contact plate;
• the first shank being affixed to the first contact plate by an electrically conductive, fusible material;
• (b) a second electrode having (i) a second contact plate with interior and exterior faces and (ii) a second shank projecting from exterior face of the second contact plate, the second shank having an annular groove adjacent to the base thereof;
• (c) a substantially disk-shaped varistor element, the first and second electrodes sandwiching the varistor element therebetween with the interior faces of the first and second contact plates facing the varistor element and making electrical contact therewith, to form a core assembly;
• (d) an O-ring seated into the annular groove of the second shank;
• (e) a cup-shaped gasket having a sidewall, a substantially circular base with a through-hole, and an annular protrusion disposed on the inside of the base of the gasket and surrounding the through-hole therein;
• the gasket containing the core assembly, with the exterior face of the first contact plate facing the base of the gasket, the first shank passing through the through-hole of the base, and the second shank extending from the open end of the gasket;
• (f) a housing having a tapered sidewall and a base with a through-hole;
• the housing containing the core assembly and the gasket, with the open end of the gasket facing the base of the housing, the first shank extending from the open end of the housing, and the second shank passing through the through-hole in the base of the housing;
• the base of the housing having a recess therein, which matingly receives a complementarily sized and shaped registering element in the second electrode, thereby preventing rotation of the second shank;
• (g) a lid with a through-hole, the lid having an annular ridge on the underside thereof and surrounding the through-hole therein, covering the open end of the housing such that the first shank passes through the through-hole in the lid, being engaged and retained in place by an annular groove on the sidewall of the housing, and applying a compressive force to the gasket and the core assembly;
• and
• (h) means for applying a force tending to move the first shank away from the first contact plate, thereby electrically disconnecting one from the other, such force being insufficient to so move the first shank unless the electrically conductive, fusible material is in its fused state;
• the varistor element being sealed from the external environment by seals between the lid and the base of the gasket;
• between the base of the gasket and the first contact plate;
• between the tapered sidewall of the housing and the sidewall of the gasket;
• between the through-hole of the base of the housing and the O-ring;
• and between the second shank and the O-ring.