US4095141A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic flash device
Assignee: Canon Inc
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Filing: 1976-02-13
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Granted: 1978-06-13
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Expires: 1996-02-13
Abstract
Abstract The trigger circuit of an electronic flash device includes a pulse transformer connected to a trigger electrode of a flash tube, a capacitor connected to the pulse transformer, a thyristor connected in the discharge path of the capacitor, and a control circuit for the thyristor. This control circuit is provided with a low-voltage trigger means for applying a trigger pulse to said thyristor and further with a synchronous switch connected therein so that the synchronous switch operates with a low voltage.
Inventors
- 👤 Zenzo Nakamura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 00:11
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/30; H05B41/32
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
198 words
An electric flash device for a camera comprising: (a) flash means for producing a light energy and having trigger and cathode electrodes; (b) a capacitor coupled to said flash means for storing an electrical energy to be converted into the light energy in said flash means; (c) a voltage divider circuit connected in parallel with said capacitor and having an output terminal; (d) trigger pulse producing means coupled to said trigger electrode for supplying a trigger pulse to the trigger electrode of said flash means and including a thyristor having a control electrode; (e) a PNP transistor coupled to the voltage divider circuit for impressing a voltage derived from the voltage divider circuit on the control electrode of said thyristor; the transistor having an emitter electrode connected to an output terminal of the voltage divider circuit, a collector electrode connected to the control electrode of said thyristor and a base electrode; (f) a camera flash synchronizing switch connected to said base electrode of said PNP transistor for actuating the PNP transistor; and (g) a one-way conductive element connected in series with said synchronizing switch to prevent high voltages at the synchronizing switch from appearing at said PNP transistor.
Claim 2
Dependent Claim
198 words
An electric flash device for a camera comprising: (a) flash means for producing a light energy and having trigger and cathode electrodes; (b) a capacitor coupled to said flash means for storing an electrical energy to be converted into the light energy in said flash means; (c) a voltage divider circuit connected in parallel with said capacitor and having an output terminal; (d) trigger pulse producing means coupled to said trigger electrode for supplying a trigger pulse to the trigger electrode of said flash means and including a thyristor having a control electrode; (e) a PNP transistor coupled to the voltage divider circuit for impressing a voltage derived from the voltage divider circuit on the control electrode of said thyristor; the transistor having an emitter electrode connected to an output terminal of the voltage divider circuit, a collector electrode connected to the control electrode of said thyristor and a base electrode; (f) a camera flash synchronizing switch connected to said base electrode of said PNP transistor for actuating the PNP transistor; and (g) a one-way conductive element connected in series with said synchronizing switch to prevent high voltages at the synchronizing switch from appearing at said PNP transistor.
Claim 3
Dependent Claim
220 words
An electric flash device for a camera comprising: (a) a flash tube for producing a light energy and having trigger and cathode electrodes; (b) a capacitor coupled to said flash tube for storing electrical energy to be converted into the light energy in said flash tube; (c) a resistor divider circuit connected in parallel with said capacitor; (d) trigger pulse producing means coupled to said trigger electrode for supplying a trigger pulse to the trigger electrode of said flash tube and including a thyristor having a control electrode; (e) a PNP type transistor coupled to said divider circuit and said pulse producing means for impressing a divided voltage from the resistor divider circuit on the control electrode of said thyristor; the transistor having an emitter electrode connected to an output terminal of the resistor divider circuit, a collector electrode connected to the control electrode of said thyristor and a base electrode; (f) electric energy storage means connected between the base electrode of said PNP type transistor and the cathode electrode of said flash tube; (g) camera synchronizing switch connected in parallel with said electric energy storage means for actuating the PNP type transistor; and (h) a one-way conductive element connected in series with said synchronous switch for preventing high voltage application from the synchronizing switch onto the PNP type transistor.
Claim 4
Dependent Claim
220 words
An electric flash device for a camera comprising: (a) a flash tube for producing a light energy and having trigger and cathode electrodes; (b) a capacitor coupled to said flash tube for storing electrical energy to be converted into the light energy in said flash tube; (c) a resistor divider circuit connected in parallel with said capacitor; (d) trigger pulse producing means coupled to said trigger electrode for supplying a trigger pulse to the trigger electrode of said flash tube and including a thyristor having a control electrode; (e) a PNP type transistor coupled to said divider circuit and said pulse producing means for impressing a divided voltage from the resistor divider circuit on the control electrode of said thyristor; the transistor having an emitter electrode connected to an output terminal of the resistor divider circuit, a collector electrode connected to the control electrode of said thyristor and a base electrode; (f) electric energy storage means connected between the base electrode of said PNP type transistor and the cathode electrode of said flash tube; (g) camera synchronizing switch connected in parallel with said electric energy storage means for actuating the PNP type transistor; and (h) a one-way conductive element connected in series with said synchronous switch for preventing high voltage application from the synchronizing switch onto the PNP type transistor.
Claim 5
Dependent Claim
16 words
An electric flash device according to claim 2, wherein said one-way conductive element is a diode.
Claim 6
Dependent Claim
28 words
An electric flash device according to claim 2, wherein said one-way conductive element includes a diode having an anode electrode connected to the base electrode of said transistor.
Claim 7
Dependent Claim
40 words
An electronic flash device according to claim 2, further comprising a differentiation circuit connected between the collector electrode of said transistor and the control electrode of said thyristor for supplying the thyristor with a differentiation pulse to energize the thyristor.
Claim 8
Dependent Claim
45 words
An electronic flash device according to claim 1, wherein said resistor divider circuit includes a pair of resistors, and further comprising: a Zener diode connected in parallel to one of said resistors of said resistor divider circuit to supply a constant voltage to said transistor.
Claim 9
Dependent Claim
19 words
An electronic flash device according to claim 6, further comprising capacitor means connected in parallel with said Zener diode.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-06-12 | 1981-12-12 | 1982-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-06-12 | 1985-12-12 | 1986-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-06-12 | 1989-12-12 | 1990-06-13 | $7700.00 | Window Closed / Lapsed |