US3801860A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fail-safe lamp filament monitoring circuit
Assignee: Siemens Mobility Ltd
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Filing: 1972-09-22
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Granted: 1974-04-02
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Expires: 1992-09-22
Abstract
Abstract This invention relates to a fail-safe lamp filament monitoring circuit including an a.c. signal source to provide an a.c. signal to the primary of a transformer which, in turn, supplies alternating electrical energy to a lamp filament connected in its secondary, a monitoring device responsive to the current in the primary winding and an auxiliary loading device connected in the secondary. The auxiliary loading device is effective to increase power flow through the transformer to energize the filament to a level where the monitoring device is operated and held operated until the lamp filament is no longer energized at which time the monitoring device is released at the transformer magnetizing current.
Inventors
- 👤 K King
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:15
CPC Classifications
H; H01; H01K; H01K1/00; H01K1/60
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
170 words
A fail-safe lamp filament monitoring circuit comprising, a. transformer means having a primary and a secondary winding, b. an a.c. signal source connected to said primary winding, c. a lamp filament connected in parallel with said secondary winding, said transformer means supplying electrical energy to said lamp filament, d. monitoring means having a first and a second state connected in said primary winding of said transformer and responsive to the current in said primary winding of said transformer, said monitoring means initially in said second state, e. auxiliary loading means connected in parallel with the secondary winding of said transformer means and effective to increase power flow through said transformer means to energize said filament to a preselected energizing power flow level where said monitoring means assumes and is held operated in said first state at said energizing power flow level, said monitoring means resuming said second state at a preselected lower current flow level of said primary winding of said transformer means when said filament is no longer energized.
Claim 2
Dependent Claim
170 words
A fail-safe lamp filament monitoring circuit comprising, a. transformer means having a primary and a secondary winding, b. an a.c. signal source connected to said primary winding, c. a lamp filament connected in parallel with said secondary winding, said transformer means supplying electrical energy to said lamp filament, d. monitoring means having a first and a second state connected in said primary winding of said transformer and responsive to the current in said primary winding of said transformer, said monitoring means initially in said second state, e. auxiliary loading means connected in parallel with the secondary winding of said transformer means and effective to increase power flow through said transformer means to energize said filament to a preselected energizing power flow level where said monitoring means assumes and is held operated in said first state at said energizing power flow level, said monitoring means resuming said second state at a preselected lower current flow level of said primary winding of said transformer means when said filament is no longer energized.
Claim 3
Dependent Claim
31 words
The fail-safe filament monitoring circuit as described in claim 1, wherein said preselected lower current flow level is due to the magnetizing current of said primary winding of said transformer means.
Claim 4
Dependent Claim
20 words
The fail-safe filament monitoring circuit as described in claim 1, wherein said monitoring means is a current responsive electromagnetic means.
Claim 5
Dependent Claim
19 words
The fail-safe filament monitoring circuit as described in claim 3, wherein said electromagnetic means is a current responsive relay.
Claim 6
Dependent Claim
19 words
The fail-safe filament monitoring circuit as described in claim 1, wherein said auxiliary loading means is a resistive device.
References Cited (Backward Citations)
US1788597A
Cited
US2257797A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-04-01 | 1977-10-01 | 1978-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-01 | 1981-10-01 | 1982-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-01 | 1985-10-01 | 1986-04-02 | $7700.00 | Window Closed / Lapsed |