Patent US3643247A successfully refreshed from Google Patents.
US3643247A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for detecting open-circuit condition
Assignee: Lockheed Martin Corp
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Filing: 1969-12-22
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Granted: 1972-02-15
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Expires: 1989-12-22
Abstract
Abstract Apparatus for detecting an open-circuit condition in a circuit element such as an indicator lamp irrespective of whether the circuit is switched on or off. A trickle current flowing through the circuit element is interrupted if the element becomes open, and this trickle current controls a suitable indicator.
Inventors
- 👤 David J Ratcliffe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 14:08
CPC Classifications
G; G08; G08B; G08B5/00; G08B5/22; G08B5/36
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
151 words
An electrical circuit including apparatus for evaluating the continuity of the circuit, comprising: a first series circuit including an electrical device the continuity of which is being evaluated and a switch means connected to a source of electrical potential; resistance means connected between said series circuit and a voltage source of a polarity to establish current flow in a second series circuit including said electrical device and said resistance means irrespective of the operation of said switch means; first diode means connected in said first series circuit to permit current flow through said first series circuit when said switch means is closed and to prevent current from flowing through said switch means into said second series circuit; and means connected to be responsive to the voltage across said resistance means to provide a signal indicating that said electrical device is nonconductive when no current is flowing in said second series circuit.
Claim 2
Dependent Claim
151 words
An electrical circuit including apparatus for evaluating the continuity of the circuit, comprising: a first series circuit including an electrical device the continuity of which is being evaluated and a switch means connected to a source of electrical potential; resistance means connected between said series circuit and a voltage source of a polarity to establish current flow in a second series circuit including said electrical device and said resistance means irrespective of the operation of said switch means; first diode means connected in said first series circuit to permit current flow through said first series circuit when said switch means is closed and to prevent current from flowing through said switch means into said second series circuit; and means connected to be responsive to the voltage across said resistance means to provide a signal indicating that said electrical device is nonconductive when no current is flowing in said second series circuit.
Claim 3
Dependent Claim
21 words
Apparatus as in claim 1, wherein the resistance of said resistance means is greater than the resistance of said electrical device.
Claim 4
Dependent Claim
51 words
Apparatus as in claim 1, wherein said electrical device comprises a source of illumination, and the resistance of said resistance means limits the current flowing in said second series circuit when said switch means is open to an amount which does not produce any perceptible illumination of said source of illumination.
Claim 5
Dependent Claim
116 words
Apparatus as in claim 1, wherein: said last-mentioned means includes second diode means connected to be responsive to the voltage developed across said resistance means by current flowing through said second series circuit, said second diode means being connected to be maintained in a substantially nonconductive state by said voltage developed across said resistance means and to be rendered conductive in the absence of said voltage; and signal means connected to be responsive to the conductive state of said second diode means to give an indication of an open-circuit condition of said electrical device when the absence of current through said second series circuit results in the absence of said voltage developed across said resistance means.
Claim 6
Dependent Claim
79 words
Apparatus as in claim 4, wherein: a first element of said second diode means is connected to receive said voltage developed across said resistance means; a second element of said second diode means is connected to be responsive to a voltage source of polarity opposite the polarity of the voltage source to which said resistance means is connected; and said signal means is connected to be responsive to conduction through said second diode means to give said open-circuit indication.
Claim 7
Dependent Claim
51 words
Apparatus as in claim 4, wherein said electrical device comprises a source of illumination and the resistance of said resistance means limits the current flowing in said second series circuit when said switch means is open to an amount which does not produce any perceptible illumination of said source of illumination.
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) | 1975-02-14 | 1975-08-16 | 1976-02-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-02-14 | 1979-08-16 | 1980-02-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-02-14 | 1983-08-16 | 1984-02-15 | $7700.00 | Window Closed / Lapsed |