Relay type automotive tachometer with time delay circuitry for the relay to enable operation at high engine speeds

Claim 1

IN AN ELECTRICAL TACHOMETER FOR USE WITH AN AUTOMOTIVE IGNITION SYSTEM HAVING A PRIMARY CIRCUIT INCLUDING BREAKER POINTS FOR GROUNDING THE SAME, THE COMBINATION COMPRISING A RELAY HAVING A COIL AND ARMATURE, CONTACTS ON SAID RELAY INCLUDING A CENTRAL CONTACT AND RELATIVELY STATIONARY CHARGING AND DISCHARGING CONTACTS ALTERNATIVELY ENGAGEMENT BETWEEN THE CENTRAL CONTACT AND THE DISCHARGENGAGEMENT BETWEEN THE CENTRAL CONTACT AND THE DISCHARGING CONTACT, A CHARGING CIRCUIT INCLUDING A BATTERY OF CONSTANT VOLTAGE CONNECTED TO THE CHARGING CONTACT, A DISCHARGING CIRCUIT INCLUDING AN INDICATING METER CONNECTED TO THE DISCHARGING CONTACT, A FIRST CAPACITOR CONNECTED TO THE CENTRAL CONTACT SO THAT THE CAPACITOR IS ALTERNATIVELY CHARGED ACROSS THE BATTERY AND DISCHARGE THROUGH THE INDICATING METER, A RESISTOR CONNECTED IN SERIES WITH THE RELAY COIL SO THAT AN IR DROP IS DEVELOPED ACROSS THE RESISTOR DEPENDING UPON THE CURRENT IN THE COIL, MEANS FOR CONNECTING THE RELAY COIL AND ITS SERIES-CONNECTED RESISTOR ACROSS THE BREAKER POINTS SO THAT THE RELAY IS SUPPLIED WITH CURRENT FROM THE PRIMARY CIRCUIT BY DIRECT CURRENT FLOW THROUGH SAID RESTRICTOR WHEN THE POINTS ARE OPEN AND SO THAT THE RELAY IS CONNECTED TO FORM A SHORT-CIRCUITING LOOP CIRCUIT WITH SAID RESISTOR WHEN THE POINTS ARE CLOSED DURING