Patent US3603846A successfully refreshed from Google Patents.
US3603846A
Expired / Lapsed
US
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Current detector circuit
Assignee: L-Tec Co
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Filing: 1969-05-06
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Granted: 1971-09-07
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Expires: 1989-05-06
Abstract
Abstract A solid-state current-detector circuit capable of detecting the presence of a predetermined magnitude of AC or DC current in a power cable wherein the current may vary over an extended range which includes means for sensing the voltage drop in a relatively short length of cable which means changes its electrical state when said voltage drop exceeds a predetermined level.
Inventors
- 👤 Tibor Endre Toth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:06
CPC Classifications
G; G01; G01R; G01R19/00; G01R19/165; G01R19/16566; G01R19/16571
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
156 words
A welding current detector circuit for detecting the presence of welding current above a predetermined level in a welding power cable comprising: a reference voltage source having a common reference lead connected to the welding power cable and an output lead for supplying a predetermined potential with respect to the reference lead; comparator means having a first input connected to said output lead and a second input connected to said welding cable at a predetermined distance from the connection of said common reference lead, resistance means of very low magnitude connected to said reference lead and to said second input, said comparator means providing a polarity-sensitive output signal in response to the algebraic difference between said predetermined potential and the voltage developed at said second input and sensing means responsive to the polarity of said comparator output signal for indicating the presence or absence of a predetermined level of current flow in the welding power cable.
Claim 2
Dependent Claim
156 words
A welding current detector circuit for detecting the presence of welding current above a predetermined level in a welding power cable comprising: a reference voltage source having a common reference lead connected to the welding power cable and an output lead for supplying a predetermined potential with respect to the reference lead; comparator means having a first input connected to said output lead and a second input connected to said welding cable at a predetermined distance from the connection of said common reference lead, resistance means of very low magnitude connected to said reference lead and to said second input, said comparator means providing a polarity-sensitive output signal in response to the algebraic difference between said predetermined potential and the voltage developed at said second input and sensing means responsive to the polarity of said comparator output signal for indicating the presence or absence of a predetermined level of current flow in the welding power cable.
Claim 3
Dependent Claim
44 words
A welding current detector circuit as defined in claim 1 wherein said comparator means is an operational amplifier, the output polarity of which is controllably alternated between positive and negative saturation in response to the algebraic difference between the first and second inputs thereto.
Claim 4
Dependent Claim
45 words
A welding current detector circuit as defined in claim 2 wherein the output signal of said operational amplifier is of normally positive polarity and reverses to negative polarity when the voltage developed at the second input exceeds the reference potential supplied to the first input.
Claim 5
Dependent Claim
45 words
A welding current detector circuit as defined in claim 3 wherein the reference voltage source is developed by a feedback network connecting the output of the operational amplifier to the first input thereof and to the common reference lead connected to the welding power cable.
Claim 6
Dependent Claim
25 words
A welding current detector circuit as defined in claim 4 wherein the feedback network is resistive and also determines the gain of the operational amplifier.
Claim 7
Dependent Claim
38 words
A welding current detector circuit as defined in claim 1 wherein said sensing means comprises a transistor which is forward biased for a given output polarity of the comparator means and reverse biased for the opposite output polarity.
Claim 8
Dependent Claim
32 words
A welding current detector circuit as defined in claim 6 wherein relay means is connected in series with the collector of said transistor and is actuated when said transistor is forward biased.
Claim 9
Dependent Claim
40 words
A welding current detector circuit as defined in claim 1 wherein said sensing means further includes an integrating circuit for rectifying the alternating changes in the output polarity of the comparator means when said welding power cable carries alternating current.
Claim 10
Dependent Claim
43 words
A welding current detector circuit as defined in claim 1 wherein the output polarity of said comparator means is reversed in response to an input signal thereto of at least 4 mv. representing at least 20 amperes of current in said power cable.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-06 | 1975-03-08 | 1975-09-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-06 | 1979-03-08 | 1979-09-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-06 | 1983-03-08 | 1983-09-07 | $7700.00 | Window Closed / Lapsed |