US3896333A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic flash device
Assignee: Canon Inc
•
Filing: 1973-05-09
•
Granted: 1975-07-22
•
Expires: 1993-05-09
Abstract
Abstract The device controls the amount of light emitted by a flash illumination tube by interrupting the energization of the tube during a flash discharge. A main condenser is charged to a predetermined voltage from a suitable source, and is arranged to be discharged through the flash illumination tube when a thyristor, connected in series with the flash illumination tube, is triggered conductive responsive to actuation of a camera element. A discharge preventing condenser is also charged from the source and is arranged to be discharged through a switch element connected in series therewith responsive to a flash preventing trigger signal. When the flash preventing condenser is thus discharged, it triggers the thyristor non-conductive to block discharging of the flash illumination tube. A charging signal trigger circuit and a charging thyristor, having its gate connected to the charging signal trigger circuit, are connected in parallel with the illumination or discharge preventing condenser. The charging signal trigger circuit is activated responsive to discharge of the illumination preventing condenser to trigger the connected thyristor conductive for a rapid recharging of the illumination preventing condenser. Thereby, the delay in the resetting of the circuit for a subsequent flash operation, as in conventional electronic flash devices, is eliminated.
Inventors
- 👤 Zenzo Nakamura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:47
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/30; H05B41/32; H05B41/325
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
379 words
An electronic flash device for a photographic camera, operable to control the amount of light emitted by a flash tube by interrupting the discharge of a flash tube after initiation of the discharge thereof, said electronic flash device comprising, in combination, a source of electric potential; a first capacitor connected across said source for charging thereby; a flash tube having one terminal connected to one terminal of said first capacitor; a first switching means connected in series to the other terminal of said flash tube, at a junction point, and to the other terminal of said first capacitor, and operable to effectively connect and disconnect said flash tube from said first capacitor; trigger means connected to said first switching means and operable to trigger said first switching means conductive for discharging said first capacitor through said flash tube; impedance means; a second capacitor; said impedance means connecting one end of said second capacitor with one terminal of said source of electric potential; the other end of said second capacitor being connected to said junction point of said first switching means and said flash tube, and to the other terminal of said source of electric potential, for charging of said second capacitor through said impedance means; signal generating means operable to generate a signal for interrupting flashing of said flash tube; first means connecting one end of said second capacitor to a terminal of said source of potential and to said first switching means, and connected to said signal generating means for operation responsive to a flash interrupting signal to be conductive for a predetermined time by the flash interrupting signal so as to reverse the potentials at the opposite ends of said second capacitor and to trigger said first switching means non-conductive; whereby said second capacitor is discharged; and a second means connected in parallel with said impedance means and electrically connected to said first means; said second means being triggered conductive for a predetermined time responsive to discharge of said second capacitor, to form a charging circuit for said second capacitor in parallel with said impedance means and bypassing said impedance means; said second means being triggered conductive after said first means has been triggered conductive and then triggered non-conductive responsive to termination of said flash interrupting signal.
Claim 2
Dependent Claim
379 words
An electronic flash device for a photographic camera, operable to control the amount of light emitted by a flash tube by interrupting the discharge of a flash tube after initiation of the discharge thereof, said electronic flash device comprising, in combination, a source of electric potential; a first capacitor connected across said source for charging thereby; a flash tube having one terminal connected to one terminal of said first capacitor; a first switching means connected in series to the other terminal of said flash tube, at a junction point, and to the other terminal of said first capacitor, and operable to effectively connect and disconnect said flash tube from said first capacitor; trigger means connected to said first switching means and operable to trigger said first switching means conductive for discharging said first capacitor through said flash tube; impedance means; a second capacitor; said impedance means connecting one end of said second capacitor with one terminal of said source of electric potential; the other end of said second capacitor being connected to said junction point of said first switching means and said flash tube, and to the other terminal of said source of electric potential, for charging of said second capacitor through said impedance means; signal generating means operable to generate a signal for interrupting flashing of said flash tube; first means connecting one end of said second capacitor to a terminal of said source of potential and to said first switching means, and connected to said signal generating means for operation responsive to a flash interrupting signal to be conductive for a predetermined time by the flash interrupting signal so as to reverse the potentials at the opposite ends of said second capacitor and to trigger said first switching means non-conductive; whereby said second capacitor is discharged; and a second means connected in parallel with said impedance means and electrically connected to said first means; said second means being triggered conductive for a predetermined time responsive to discharge of said second capacitor, to form a charging circuit for said second capacitor in parallel with said impedance means and bypassing said impedance means; said second means being triggered conductive after said first means has been triggered conductive and then triggered non-conductive responsive to termination of said flash interrupting signal.
Claim 3
Dependent Claim
29 words
An electronic flash device, as claimed in claim 1, in which said second means is a second switching means triggered conductive responsive to the output of said second capacitor.
Claim 4
Dependent Claim
18 words
An electronic flash device, as claimed in claim 2, in which said second switching means is an SCR.
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) | 1978-07-21 | 1979-01-20 | 1979-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-21 | 1983-01-20 | 1983-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-21 | 1987-01-20 | 1987-07-22 | $7700.00 | Window Closed / Lapsed |