Vacuum circuit interrupter contacts

Claim 1

AN ALTERNATING-CURRENT VACUUM-TYPE CIRCUIT INTERRUPTER HAVING A RATED VOLTAGE OF AT LEAST 7.2 KV. COMPRISING: A PAIR OF CONTACTS THAT ARE RELATIVELY MOVABLE INTO AND OUT OF ENGAGEMENT, SAID CONTACTS BEING SUBSTANTIALLY FREE OF ABSORBED GASES AND SURFACE CONTAMINANTS, AT LEAST ONE OF SAID CONTACTS HAVING CIRCUIT-MAKING AND BREAKING REGIONS FORMED OF AN ALLOY CONSISTING ESSENTIALLY OF A NONREFRACTORY METAL MAJOR CONSTITUENT HAVING A BOILING POINT LESS THAN 3,500*K. AND NON-REFRACTORY METAL MINOR CONSTITUENT THAT (1) HAS AN EFFECTIVE FREEZING TEMPERATURE BELOW THAT OF THE MAJOR CONSTITUENT (2) HAS SUBSTANTIAL SOLUBILITY IN THE MAJOR CONSTITUENT IN THE LIQUID STATE AND (3) IS SOLUBLE IN THE MAJOR CONSTITUENT IN THE SOLID STATE TO A LESSER EXTENT THAN TWO PERCENT BY WEIGHT OF THE ALLOY, CONSIDERED AT A CONTROLLING TEMPERATURE CORRESPONDING TO THE EUTECTIC TEMPERATURE OR TO THE FREEZING TEMPERATURE OF THE MINOR CONSTITUENT IF THERE IS NO EUTECTIC, SAID MINOR CONSTITUENT BEING HIGHLY DISPERSED THROUGHOUT SAID ALLOY AND BEING PRESENT IN AN AMOUNT GREATER THAN THE SOLID STATE SOLUBILITY OF THE MINOR CONSTITUENT IN THE MAJOR CONSTITUENT AT SAID CONTROLLING TEMPERATURE AND IN AN AMOUNT SMALL ENOUGH TO MAINTAIN THE DIELECTRIC STRENGTH OF THE INTERRUPTER ABOVE 95 KV. PEAK IMPULSE VOLTAGE AND 36 KV. R.M.S. 60 CYCLE WITHSTAND VOLTAGE, BOTH VOLTAGES BEING MEASURED ACROSS SAID CONTACTS WHEN FULLY OPEN.