Discharge pipe line locator

Claim 2

An electronic locator for tracing the course of a metallic discharge line which is disposed below ground comprising: reel means having a frame, said reel means storing a length of flexible, hollow cable operable when rotated to drive the free end of the cable into said metallic discharge line, An audio frequency signal generator to generate a signal of less than about 800 Hz located on said frame and in which said audio frequency signal generated by said generator has a frequency periodically varying in the range of about 400 to about 800 Hz, a transmitter antenna attached to the free end of the cable, conductors extending through said cable for electrically connecting said audio frequency signal generator to said transmitter antenna, and a directional receiver means for detecting the audio frequency signals generated by said audio frequency signal generator and radiated by said transmitter antenna.

Claim 3

The invention in accordance with claim 1 including: a thermistor attached to the transmitter antenna, and a bridge circuit on the frame of the real means, wherein the audio frequency generator is connected by one of said conductors and the cable itself to the transmitter antenna, and wherein the thermistor is connected by another of said conductors and the cable itself to form one side of said bridge circuit.

Claim 4

The invention in accordance with claim 1 including means for converting said audio frequency signals received by said directional receiver means to a corresponding audible tone.

Claim 5

An audio frequency generator circuit for an electronic locator used for tracing the course of a metallic discharge line which is disposed below ground, said audio frequency signal generator circuit being connected by conductors extending through a length of hollow flexible cable to a transmitter antenna which is inserted by the cable into the metallic discharge line and operates to radiate the audio frequency signal generated by said circuit, said circuit including: an oscillator for providing periodic pulses, means responsive to said periodic pulses to provide square wave pulses, means for converting said square wave pulses to sawtooth pulses, a voltage controlled oscillator operable in response to the slopes of said sawtooth pulses to provide varying audio frequency signals of frequency less than about 800 Hz, a gating means for gating said audio frequency signals, means responsive to said periodic pulses for momentary closing said gating means, means for amplifying said audio frequency signals, and a current transformer for coupling the audio frequency signals via said conductors to said transmitter antenna.

Claim 6

An audio frequency generator circuit for an electronic locator used for tracing the course of a metallic discharge line which is disposed below ground, said audio frequency signal generator circuit being connected by conductors extending through a length of hollow flexible cable to a transmitter antenna which is inserted by the cable into the metallic discharge line and operates to radiate the audio frequency signal generated by said circuit, said circuit including: an oscillator for providing periodic pulses, means responsive to said periodic pulses to provide square wave pulses, means for converting said square wave pulses to sawtooth pulses, a voltage controlled oscillator operable in response to the slopes of said sawtooth pulses to provide varying audio frequency signals of frequency less than about 800 Hz, a gating means for gating said audio frequency signals, means responsive to said periodic pulses for momentary closing said gating means, means for amplifying said audio frequency signals, and a current transformer for coupling the audio frequency signals via said conductors to said transmitter antenna.

Claim 7

The invention in accordance with claim 4 wherein said sawtooth pulses provide for controlling said voltage controlled oscillator whereby during each cycle of said sawtooth pulse the frequency of the audio frequency signals generated varies from approximately 400 Hz to 800 Hz and then back down to 400 Hz.

Claim 10

The apparatus of claim 6 in which said means to periodically modulate said signal includes means to form a series of spaced pulses in which the frequency in said pulses is not more than about 800 Hz.

Claim 11

The apparatus of claim 7 in which said frequency in said pulses varies in the range of about 400 to about 800 Hz.

Claim 12

The apparatus of claim 6, a temperature responsive device mechanically connected to said radiator, means including said device to detect the change in temperature to which said device is responsive.

Claim 15

The apparatus of claim 10 in which the pulses vary in frequency from about 400 Hz to about 800 Hz followed by a pulse in which the frequency decreases from 800 to 400 Hz.

Claim 18

The method of claim 12 in which said radiated signal in each pulse is of a frequency in the range of about 400 Hz to about 800 Hz.

Claim 19

The method of claim 12 modulating the frequency of said radiated signal to vary the frequency in a series of pulses each varying in frequency in the range from about 400 to about 800 Hz.

Claim 20

The method of claim 14 in which said modulation increases the frequency from about 400 to about 800 Hz and then from about 800 to about 400 Hz in a series of spaced pulses.

Claim 21

An audio frequency generator circuit for an electronic locator used for tracing the course of a metallic discharge line which is disposed below ground, said audio frequency signal generator circuit being connected by conductors to a transmitter antenna which is inserted by the cable into the metallic discharge line and operates to radiate the audio frequency signal generated by said circuit, said circuit including: an oscillator for providing periodic pulses, means responsive to said periodic pulses to provide square wave pulses, means for converting said square wave pulses to sawtooth pulses, a voltage controlled oscillator operable in response to the slopes of said sawtooth pulses to provide varying audio frequency signals of frequency less than about 800 Hz, a gating means for gating said audio frequency signals, means responsive to said periodic pulses for momentary closing said gating means, means for amplifying said audio frequency signals, and a current transformer for coupling the audio frequency signals via said conductors to said transmitter antenna.

Claim 22

An audio frequency generator circuit for an electronic locator used for tracing the course of a metallic discharge line which is disposed below ground, said audio frequency signal generator circuit being connected by conductors to a transmitter antenna which is inserted by the cable into the metallic discharge line and operates to radiate the audio frequency signal generated by said circuit, said circuit including: an oscillator for providing periodic pulses, means responsive to said periodic pulses to provide square wave pulses, means for converting said square wave pulses to sawtooth pulses, a voltage controlled oscillator operable in response to the slopes of said sawtooth pulses to provide varying audio frequency signals of frequency less than about 800 Hz, a gating means for gating said audio frequency signals, means responsive to said periodic pulses for momentary closing said gating means, means for amplifying said audio frequency signals, and a current transformer for coupling the audio frequency signals via said conductors to said transmitter antenna.