US3725728A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fail-safe lamp filament monitoring circuit
Assignee: Siemens Mobility Ltd
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Filing: 1970-09-04
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Granted: 1973-04-03
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Expires: 1990-09-04
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
2026-11-01 08:08
CPC Classifications
H; H01; H01K; H01K1/00; H01K1/60
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
255 words
A fail-safe lamp filament monitoring circuit comprising, a. transformer means having a primary and a secondary winding, an a.c. signal source connected to said primary winding, b. a lamp having at least a first and a second filament portion serially connected together, said transformer means supplying electrical energy to said lamp filament, c. current responsive monitoring means having a first and a second electrical state connected in the circuit of 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 electrical state, d. auxiliary loading means connected to the secondary winding of said transformer means and effective to increase power flow to a preselected energizing power flow level through said transformer means to energize said filament thus operating said monitoring means in said first electrical state, said monitoring means resuming said second electrical state at a preselected lower current flow level in said primary winding of said transformer means when said filament is no longer energized. e. a load control relay having a contact means for connecting the junction between one lead of each of said first filament and said second filament portions to said secondary winding of said transformer means, the other lead of said first filament portion connected to said secondary winding of said transformer means, and said contact means of said load control relay connecting the other lead of said second filament por-tion to said secondary winding of said transformer means when said first filament portion fails.
Claim 2
Dependent Claim
255 words
A fail-safe lamp filament monitoring circuit comprising, a. transformer means having a primary and a secondary winding, an a.c. signal source connected to said primary winding, b. a lamp having at least a first and a second filament portion serially connected together, said transformer means supplying electrical energy to said lamp filament, c. current responsive monitoring means having a first and a second electrical state connected in the circuit of 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 electrical state, d. auxiliary loading means connected to the secondary winding of said transformer means and effective to increase power flow to a preselected energizing power flow level through said transformer means to energize said filament thus operating said monitoring means in said first electrical state, said monitoring means resuming said second electrical state at a preselected lower current flow level in said primary winding of said transformer means when said filament is no longer energized. e. a load control relay having a contact means for connecting the junction between one lead of each of said first filament and said second filament portions to said secondary winding of said transformer means, the other lead of said first filament portion connected to said secondary winding of said transformer means, and said contact means of said load control relay connecting the other lead of said second filament por-tion to said secondary winding of said transformer means when said first filament portion fails.
Claim 3
Dependent Claim
40 words
The fail-safe filament monitoring circuit as described in claim 1, wherein said preselected lower current flow level occurs when the power supplied by said primaRy winding of said transformer means and drawn by said secondary winding of said transformer decreases.
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
78 words
The fail-safe filament monitoring circuit as described in claim 1, wherein an auxiliary load control means having a first and a second electrical state is serially connected to said filament assuming said first electrical state whenever said filament is energized, and assuming said second electrical state whenever said filament is no longer energized, said auxiliary loading means effective to increase the power flow through said transformer whenever said auxiliary load control means is in said first electrical state.
Claim 7
Dependent Claim
21 words
The fail-safe filament monitoring circuit as described in claim 5, wherein said auxiliary load control means is a current electromagnetic device.
Claim 8
Dependent Claim
51 words
The fail-safe filament monitoring circuit as described in claim 1, wherein a supplemental filament is positioned and connected to said secondary winding to maintain said monitoring means in said first electrical state and hold said monitoring means at said energizing power flow level when said lamp filament is no longer energized.
Claim 9
Dependent Claim
51 words
The fail-safe filament monitoring circuit as described in claim 5, wherein a supplemental filament is positioned and connected to said secondary winding to maintain said monitoring means in said first electrical state and hold said monitoring means at said energizing power flow level when said lamp filament is no longer energized.
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) | 1976-04-02 | 1976-10-02 | 1977-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-02 | 1980-10-02 | 1981-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-02 | 1984-10-02 | 1985-04-03 | $7700.00 | Window Closed / Lapsed |