Power line fault indicating system employing a neon lamp oscillator

Claim 2

An a.c. power line fault indicating device comprising respective phase, neutral and ground conductors, an indicator circuit branch including a capacitor and a resistor connected in series and a discharge lamp connected across the capacitor to form an oscillator, circuit means including a rectifier connecting said indicator circuit branch across said phase and neutral conductors, switch means connected across said resistor, means to close said switch means to disable the oscillator when said phase, neutral and ground conductors are connected to corresponding supply terminals of a three-wire a.c. power supply system free of wiring faults, whereby to illuminate said discharge lamp steadily, and means opening said switch means responsive to the presence of a wiring fault condition in the power supply system, whereby to allow the oscillator to function and to cause periodic illumination of said discharge lamp, wherein the switch means comprises an electrically operated switch device and the means responsive to the presence of a wiring fault condition comprises a wiring fault-sensitive control circuit operatively connected between said ground conductor and said electrically operated switch device.

Claim 3

The fault indicating device of claim 1, and wherein the means responsive to the presence of a wiring fault condition includes means responsive to the presence of phase voltage between said neutral and ground conductors.

Claim 4

The fault indicating device of claim 1, and wherein the means responsive to the presence of a wiring fault condition includes means responsive to the presence of a relatively high impedance between said neutral and ground conductors.

Claim 5

The fault indicating device of claim 1, and wherein the means responsive to the presence of a wiring fault condition includes means responsive to the presence of a substantial voltage between said neutral and ground conductors.

Claim 6

The fault indicating device of claim 1, and wherein the means responsive to the presence of a wiring fault condition includes means responsive to leakage current in said ground conductor.

Claim 7

The fault indicating device of claim 1, and wherein said electrically operated switch device comprises a switch transistor having its collector and emitter connected to opposite terminals of the resistor, and wherein said control circuit is connected to the base of said transistor, and wherein the means to disable the oscillator comprises voltage divider circuit means in said control circuit arranged to furnish an inhibit signal to said base to render the transistor conductive in the absence of wiring fault conditions in the power supply system and arranged to substaNtially remove said inhibit signal in the presence of a power supply wiring fault condition.

Claim 8

The fault indicating device of claim 6, and wherein said voltage divider circuit means comprises first and second impedances connected in series, a control transistor connected across the second impedance, d.c. supply means connected to said voltage divider circuit means, circuit means connecting the junction of the impedances to said base, and means to turn on said control transistor responsive to the presence of a power supply wiring fault condition, said inhibit signal normally appearing across said second impedance.

Claim 9

The fault indicating device of claim 7, and wherein said second impedance includes a delay means connected across said control transistor to impose a time delay in the triggering of said switch transistor.

Claim 10

The fault indicating device of claim 8, and wherein said delay means comprises a capacitor connected across the control transistor.

Claim 11

The fault indicating device of claim 8, and circuit means responsive to the condition of the ground conductor to connect said d.c. supply means at times to the base of said control transistor.

Claim 12

The fault indicating device of claim 8, and circuit means including a zener device connecting said d.c. supply means to the base of said control transistor, and means responsive to a power supply wiring fault condition to render said zener device conductive.

Claim 13

In combination, an artificial kidney machine having respective phase, neutral and ground power input conductors adapted to be connected to corresponding terminals of a three-wire a.c. power supply system, an indicator circuit branch including a capacitor and a resistor connected in series and a discharge lamp connected across the capacitor, to form an oscillator, circuit means including a rectifier connecting said indicator circuit branch across said phase and neutral conductors, switch means connected across said resistor, means to close said switch means to disable the oscillator when said phase, neutral and ground conductors are connected to corresponding supply terminals of a three-wire a.c. power supply system free of wiring faults, whereby to illuminate said discharge lamp steadily, and means opening said switch means responsive to the presence of a wiring fault condition in the power supply system, whereby to allow the oscillator to function and to cause periodic illumination of said discharge lamp, wherein the switch means comprises an electrically operated switch device and the means responsive to the presence of a wiring fault condition comprises a wiring fault-sensitive control circuit operatively connected between said ground conductor and said electrically operated switch device.

Claim 14

In combination, an artificial kidney machine having respective phase, neutral and ground power input conductors adapted to be connected to corresponding terminals of a three-wire a.c. power supply system, an indicator circuit branch including a capacitor and a resistor connected in series and a discharge lamp connected across the capacitor, to form an oscillator, circuit means including a rectifier connecting said indicator circuit branch across said phase and neutral conductors, switch means connected across said resistor, means to close said switch means to disable the oscillator when said phase, neutral and ground conductors are connected to corresponding supply terminals of a three-wire a.c. power supply system free of wiring faults, whereby to illuminate said discharge lamp steadily, and means opening said switch means responsive to the presence of a wiring fault condition in the power supply system, whereby to allow the oscillator to function and to cause periodic illumination of said discharge lamp, wherein the switch means comprises an electrically operated switch device and the means responsive to the presence of a wiring fault condition comprises a wiring fault-sensitive control circuit operatively connected between said ground conductor and said electrically operated switch device.

Claim 15

The structural combination of claim 12, and wherein the means responsive to the presence of a wiring fault condition includes means responsive to leakage current in said ground conductor.