Electronic flash unit for cameras adapted to receive flashbulbs

Claim 2

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger capacitor for initiating a flash-firing operation, a flash firing capacitor for producing a sustained flash following flash-firing initiation, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including input means for coupling said flash unit to a camera having a shutter and a flash lamp firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera in timed relation to operation of the camera shutter, the improvement comprising: a. circuit means, coupled to said input means, having (1) a non-conductive state for electrically isolating said input means from said trigger circuit and (2) a conductive state for producing a time-delay signal a predetermined time interval following the occurrence of the energization signal, said time interval being functionally related to the timed relation between the flash lamp energization signal and operation of the camera shutter; b. switch means responsive to (1) said firing capacitor being charged to a level sufficient to flash said flashtube, and (2) the occurrence of the energization signal for switching said circuit means into its conductive state; and c. switching means responsive to said timedelay signal for permitting said flashtube trigger circuit to trigger said flashtube ON.

Claim 3

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger capacitor for initiating a flash-firing operation, a flash-firing capacitor for producing a sustained flash following flash-firing initiation, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including an electrical input circuit for electrically coupling said flash unit to a camera having a shutter and a flash lamp firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera prior to operation of the camera shutter, the improvement comprising: a. circuit means interconnecting said electrical input circuit and said trigger circuit, said circuit means having (1) a first non-conductive state for electrically isolating said input circuit from said flashtube trigger circuit to prevent the energization signal from rendering said trigger circuit effective to trigger said flashtube ON, and (2) a second conductive state for producing a control signal a predetermined time interval following the initiation of the flash lamp energization signal, said time interval being proportional to the time period between the occurrence of the flash lamp energization signal and operation of the camera shutter; b. flash-ready switch means responsive to the charge on said firing capacitor and having (1) a first, non-conductive state for maintaining said current means in said non-conductive state while said firing capacitor is charged to a level insufficient to flash said flashtube and (2) a second, conductive state in response to said firing capacitor being charged to a level sufficient to flash said flashtube for permitting said circuit means to assume its conductive state in response to the occurrence of the flashlamp energization signal; and c. electronic switching means responsive to said control signal for rendering said flashtube trigger circuit effective to trigger said flashtube ON.

Claim 4

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger capacitor for initiating a flash-firing operation, a flash-firing capacitor for producing a sustained flash following flash-firing initiation, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including an electrical input circuit for electrically coupling said flash unit to a camera having a shutter and a flash lamp firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera prior to operation of the camera shutter, the improvement comprising: a. circuit means interconnecting said electrical input circuit and said trigger circuit, said circuit means having (1) a first non-conductive state for electrically isolating said input circuit from said flashtube trigger circuit to prevent the energization signal from rendering said trigger circuit effective to trigger said flashtube ON, and (2) a second conductive state for producing a control signal a predetermined time interval following the initiation of the flash lamp energization signal, said time interval being proportional to the time period between the occurrence of the flash lamp energization signal and operation of the camera shutter; b. flash-ready switch means responsive to the charge on said firing capacitor and having (1) a first, non-conductive state for maintaining said current means in said non-conductive state while said firing capacitor is charged to a level insufficient to flash said flashtube and (2) a second, conductive state in response to said firing capacitor being charged to a level sufficient to flash said flashtube for permitting said circuit means to assume its conductive state in response to the occurrence of the flashlamp energization signal; and c. electronic switching means responsive to said control signal for rendering said flashtube trigger circuit effective to trigger said flashtube ON.

Claim 5

An electronic flash unit as set forth in claim 2 wherein said flash-ready switch means further includes means for optically signaling that the charge on said firing capacitor is sufficient to flash said flashtube.

Claim 6

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger operation for initiating a flash-firing operation, a flash firing capacitor for producing a sustained flash following flash-firing initiation, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including input means for coupling said flash unit to a camera having a shutter and a flash lamp firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera in timed relation to operation of the camera shutter, the improvement comprising: a. means operatively associated with said input means for producing a control signal having a particular parameter a predetermined time interval following the initiation of the flash lamp energization signal; b. voltage-sensitive switching means responsive to the voltage across said flash firing capacitor for rendering said control signal producing means conductive when the firing capacitor voltage is adequate to flash said flashtube; c. electronic switching means responsive to said control signal for rendering said flashtube trigger circuit effective to trigger said flashtube ON; and d. second voltage-sensitive switching means responsive to the discharge of said flash firing capacitor for rendering said control signal producing means non-conductive.

Claim 7

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger operation for initiating a flash-firing operation, a flash firing capacitor for producing a sustained flash following flash-firing initiation, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including input means for coupling said flash unit to a camera having a shutter and a flash lamp firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera in timed relation to operation of the camera shutter, the improvement comprising: a. means operatively associated with said input means for producing a control signal having a particular parameter a predetermined time interval following the initiation of the flash lamp energization signal; b. voltage-sensitive switching means responsive to the voltage across said flash firing capacitor for rendering said control signal producing means conductive when the firing capacitor voltage is adequate to flash said flashtube; c. electronic switching means responsive to said control signal for rendering said flashtube trigger circuit effective to trigger said flashtube ON; and d. second voltage-sensitive switching means responsive to the discharge of said flash firing capacitor for rendering said control signal producing means non-conductive.

Claim 8

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger capacitor for initiating a flash-triggering operation, a flash firing capacitor for producing a sustained flash following flash-firing energization, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including input means for coupling said flash unit to a camera having a shutter and a flash lamp firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera in timed relation to operation of the camera shutter, the improvement comprising: a. first electronic switching means having a gate electrode operatively associated with said flashtube trigger circuit for controlling triggering of said flashtube; and b. circuit means interconnecting said input means and said first electronic switching means, said circuit means including: i. means having a resistor and timing capacitor for producing a control signal having a particular amplitude in a time interval following initiation of the flash lamp energization signal proportional to the product of the resistance and capacitance value; ii. first voltage-sensitive means for producing a signal to render said control signal producing means effective to produce said control signal once said firing capacitor is charged above a predetermined level; iii. second electronic switching means having a gate electrode electrically coupled to said input means for permitting said timing capacitor to charge following initiation of the flash lamp energization signal; and iiii. second voltage-sensitive means having a nonconductive state for rendering said circuit means non-conductive, said second voltagesensitive means assuming said non-conductive state during a flashtube-firing operation to effectively open circuit said resistor and capacitor combination.

Claim 9

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger capacitor for initiating a flash-triggering operation, a flash firing capacitor for producing a sustained flash following flash-firing energization, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including input means for coupling said flash unit to a camera having a shutter and a flash lamp firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera in timed relation to operation of the camera shutter, the improvement comprising: a. first electronic switching means having a gate electrode operatively associated with said flashtube trigger circuit for controlling triggering of said flashtube; and b. circuit means interconnecting said input means and said first electronic switching means, said circuit means including: i. means having a resistor and timing capacitor for producing a control signal having a particular amplitude in a time interval following initiation of the flash lamp energization signal proportional to the product of the resistance and capacitance value; ii. first voltage-sensitive means for producing a signal to render said control signal producing means effective to produce said control signal once said firing capacitor is charged above a predetermined level; iii. second electronic switching means having a gate electrode electrically coupled to said input means for permitting said timing capacitor to charge following initiation of the flash lamp energization signal; and iiii. second voltage-sensitive means having a nonconductive state for rendering said circuit means non-conductive, said second voltagesensitive means assuming said non-conductive state during a flashtube-firing operation to effectively open circuit said resistor and capacitor combination.

Claim 10

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger capacitor for initiating a flash-firing operation, a flash firing capacitor for producing a sustained flash following flash-firing initiation, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including input means for coupling said flash unit to a camera having a shutter and a flash-firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera in timed relation to operation of the camera shutter, the improvement comprising: a. means defining an electrical circuit interconnecting said input means and said flashtube trigger circuit and having first and second parallel branches, said first branch comprising a voltage-sensitive switching element in series with a resistor, said first branch having a first, non-conductive state and a second, conductive state for producing a control signal, said conductive state occurring when a charge exists on said firing capacitor above a predetermined level, said second branch comprising first electronic switching means a resistor, a capacitor, second electronic switching means, and means for interconnecting said first and second electronic switching means, said resistor and said capacitor in a series configuration, said first electronic switching means having controllable gate means connected to said first branch for rendering said second branch conductive with the occurrence of said control signal, said second electronic switching means having controllable gate means coupled to said input means for rendering said second branch effective to charge said capacitor upon the presence of the flash lamp energization signal; and b. third electronic switching means having a gate electrode responsive to the voltage across said capacitor for rendering said trigger circuit conductive to effect a flash-firing operation.

Claim 11

In an improved electronic flash unit having a flashtube, a flashtube trigger circuit including a trigger capacitor for initiating a flash-firing operation, a flash firing capacitor for producing a sustained flash following flash-firing initiation, and means for connecting said trigger and firing capacitors to a source of electrical potential for controllably charging said trigger and firing capacitors, said electronic flash unit further including input means for coupling said flash unit to a camera having a shutter and a flash-firing mechanism of the type which produces a flash lamp energization signal in response to actuation of the camera in timed relation to operation of the camera shutter, the improvement comprising: a. means defining an electrical circuit interconnecting said input means and said flashtube trigger circuit and having first and second parallel branches, said first branch comprising a voltage-sensitive switching element in series with a resistor, said first branch having a first, non-conductive state and a second, conductive state for producing a control signal, said conductive state occurring when a charge exists on said firing capacitor above a predetermined level, said second branch comprising first electronic switching means a resistor, a capacitor, second electronic switching means, and means for interconnecting said first and second electronic switching means, said resistor and said capacitor in a series configuration, said first electronic switching means having controllable gate means connected to said first branch for rendering said second branch conductive with the occurrence of said control signal, said second electronic switching means having controllable gate means coupled to said input means for rendering said second branch effective to charge said capacitor upon the presence of the flash lamp energization signal; and b. third electronic switching means having a gate electrode responsive to the voltage across said capacitor for rendering said trigger circuit conductive to effect a flash-firing operation.

Claim 12

An electronic flash unit as set forth in claim 6 wherein said electrical circuit defining means further includes means interconnecting said first and second branches for permitting said first electronic switching means to remain electrically conductive while said second electronic switching means is nonconductive.

Claim 13

An electronic flash unit as set forth in claim 7 wherein said second branch further includes voltage-sensitive switching means for rendering said first electronic switching means non-conductive when the firing capacitor voltage is below a particular level.