US2789486A - Capacitor photoflash circuit - Google Patents

Description

April 2-3, 1957' S. D. EILENBERGER CAIACITOR PHOTOFLASH CIRCUIT Filed April 10, 1953 0 Cameru Shutter Contacts "W 00mm (HIE s r l4 (:1

INVENTOR. Stanley D. Eilentqerger ATTORNEY United States Patent ce CAPACITOR PHOTOFLASH CIRCUIT Stanley D. Eilenberger, Kittredge, Colo., assignor, by

mesne assignments, to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application April 10, 1953, Serial No. 347,996 2 Claims. (Cl. 95--11.5)

This invention relates to improvements in photographic flash circuits and more particularly to the type of flash equipment utilizing ordinary flash bulbs and commonly referred to as battery-capacitor operation where energy is taken from a battery, stored in a capacitor, and then discharged through a flash bulb. This type of operation is well known to those skilled in the art and many commercial devices of this type have been on the market for several years. One disadvantage of the present devices of this type is the mismatching of load to stored energy when a solenoid is used for remote tripping of a camera and when one or more sidelights or extension lights are used in addition to the flash bulb initially placed in the flash gun.

My invention, in its more specific aspects, relates to improvements in circuits for use in battery-capacitor operated flash units where one or more'sidelights are used in conjunction with the main lamp in the flash gun, and where a solenoid is also used to remotely trip the camera.

A principal object of the invention is to provide a circuit where operation of the solenoid is independent of the load placed on the energy storage capacitor by all of the flash bulbs in the circuit.

A further object of the invention is to provide a circuit where operation of one or more sidelights will have no effect on operation of the flash bulb initially installed in the flash gun and in this manner eliminate the necessity of all flash bulbs used in the sidelights or extension lights of the same class as the one used in the flash gun, or the further necessity of having all of these lights operate in series, as has been prior practice.

A further object of this invention is to eliminate the need for self-closing series contacts on the outlets provided for the sidelights or extension lamps which cause the introduction resistance in the circuit and also mechanical operating difliculties.

A further object of this invention is to provide a means for remotely tripping a camera by means of a solenoid while all of the flash bulbs in the circuit are fired by provided built-in contacts on the camera shutter.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawings in which the single figure is a wiring diagram showing photoflash circuits in which my invention is embodied.

I have discovered that if each circuit of the photoflash equipment, to which my invention is related, is treated individually and each circuit supplied with its own energy storage capacitor, these circuits may be operated independently without interference. From the viewpoint of space requirement or cost this is not a disadvantage, inasmuch as the total capacity required at any given voltage and for any given load will be the same whether the capacitance is supplied as three independent units or as a single unit. The amount of capacity required in each unit is strictly dependent upon the type of load contemplated and these values are well known to 2,789,486 Patented Apr. 23, 1957,

those skilled in the art. By way of example, if the primary battery has an initial voltage of 22 /2 volts, then an energy storage capacitor which will be used to flash only one flash bulb may be on the order of microfarads, the capacitor used to trip the camera solenoid may be on the order of 300 to 500 microfarads, depending upon solenoid design and stiffness of the shutter, and the capacitor intended to flash remote extension lamps in series would also be on the order of 300 to 500 microfarads, depending upon the number of lamps it is desired to flash at one time.

Referring now to the single figure representing a gen eral circuit diagram of a complete battery-capacitor operated flash unit making use of my invention, the primary battery, usually of the dry cell type, is indicated at 1 and is permanently connected across capacitors 5, 6 and 7 in series with resistors 2, 3 and 4 where capacitor 5 is charged in series with resistor 3; capacitor 6 is charged in series with resistor 4 and capacitor 7 is charged in series with resistor 2. In the ordinary commercial battery-capacitor unit the purpose of the series resistor is simply to limit the surge current drawn from the battery. Resistors 2, 3 and 4 also serve this same purpose and in addition they serve to isolate the three circuits where the value of resisors 2, 3 and 4 is relatively high, as compared to the resistance value of the load circuit associated with each resistor-capacitor combination. By way of example, the load resistance of the ordinary flash bulb will be on the order of 4 ohms. For five sidelights operated in series, the resistance would be on the order of 20 ohms. The average solenoid used for tripping the camera also has a relatively low resistance, usually less than 20 ohms. Therefore, the value of resistors 2, 3 and 4 should be relatively high in comparison to 20 ohms. This value is not critical and may be in the range of 1000 to 3000 ohms, it being understood that values higher or lower than this may be used without departing from the principles disclosed by this invention.

Energy storage capacitor 5 is associated only with flash bulb 12 which represents the flash bulb initially installed in the flash gun at the camera. Energy storage capacitor 6 is associated only with an outlet 9 which is an outlet provided for one or more extension or side lamps which may be flashed in series or parallel. It is usually considered advantageous to flash these lamps in series, inasmuch as the capacitor is charged to 22 /2 volts in the example given, and therefore more efficient operation will be obtained from a series circuit. The sidelights are shown at S in series and a plug A cooperates with outlet 9. Energy storage capacitor 7 is associated only with an outlet 13 which is supplied for a plug T and connections to a solenoid 14 which is attached to the camera shutter and may be of any standard type normally used for tripping a camera shutter. Switch 10 is a single-pole, single-throw switch in the circuit, as shown, and is normally in the closed positions. Another single-pole, single-throw switch 11 is in a circuit parallel with outlet 8, as shown, and it is normally open. Outlet 8 receives a plug C for connecting the circuit to the built-in camera shutter contacts of well known construction and therefore not shown.

Assuming that switch 10 is in the closed or operated position as above indicated and shown on the figure, then closure of switch 11 will close all circuits simultaneously, thus operating solenoid 14, flash bulb 12 installed in the flash gun, and any and all extension flash bulbs connected in series (or parallel) to outlet 9. With outlet 8 in parallel with switch 11 for connecting into the circuit, the built-in shutter contacts on the camera, it will be possible to control the lamps by the contacts, which contacts will be under the control of the solenoid tripper.

greener;

3 To accomplish such a control the switch 19 will be left open, as indicated in dashed lines in the figure. Now, when switch 11 is closed, solenoid 14 will be tripped to operate the shutter and in turn close its associated contacts and energize all the flash bulb circuits and cause all the lamps to be fired.

It will be noted that operation of each or" the three circuits having the flash gun bulb 12, the side lamps S and the tripping solenoid 14 is completely independent of the other. Therefore, the class or number of extension lamps used has no effect on the firing of the lamp initially installed in the flash gun and neither the lamp installed in the flash gun nor the number of extension lamps used has any effect on solenoid operation. Any synchronizing adjustment, whether mechanically or electrically made, to synchronize solenoid 14 to the operating peak of a particular class of flash bulb will be permanent and not affected by class or number of flash bulbs installed in the circuits. This is not true in the case of present equipment. Thus, for example, if the solenoid is synchronized for use in present equipment as, for example, a class M No. or press 25 flash bulb, then the same synchronizing adjustment will not hold for class F bulb commonly designated as SP or SM. Likewise, in prior circuits now being used, synchronization is eflected by the number of flash bulbs operating in extension lamps. With my improved circuits the above disadvantages are no longer present.

1 have disclosed in the specific photoflash circuit a resistor in series with each capacitor, but a system embodying my invention can be satisfactory by using any two resistors if they are of the right value in consideration with other elements of the circuit. It is also not necessary to embody the invention with a photoflash circuit having side lamps, as it can be employed where only a flash gun lamp or equivalent alone is used with the tripper solenoid. Also, two or more separate flash lamp circuit capacitors can be controlled by built-in shutter contacts where the shutter may be manually controlled.

Being aware of the possibility of modification in the particular circuit combination disclosed by Way of example, all without departing from the fundamental principles of my invention, I desire it to be understood that the scope of my invention is not to be limited except in accordancewith the appended claims.

What is claimed is:

l. A photoflash circuit for use with a camera having shutter contacts and having a flash gun with a flash lamp clement, an auxiliary or side flash lamp element, and a solenoid operated camera shutter tripper element, said circuit comprising; a source of direct current voltage, a first, second and third capacitor, circuit means connecting said capacitors in parallel to said source of voltage to charge all of said capacitors, a first control switch connected in series between said third capacitor and the shutter tripper element to cause said third capacitor to be discharged to operate the shutter tripper element, a second control switch having a first and a second position, second circuit means controlled by said second control switch in said first position and including said first con- 4 trol switch operatively connected in series between said first capacitor and the flash lamp element and in series between said second capacitor and the auxiliary lamp element to cause said first and second capacitors to be discharged to operate the flash lamp element and auxiliary lamp element under the direct control of said first control switch and simultaneously with operation of the shutter tripper element, and third circuit means controlled by said second control switch in said second position and including the camera shutter contacts operatively connected in series between said first capacitor and the flash lamp and in series between said second capacitor and the auxiliary lamp element to cause said first and second capacitors to be discharged to operate the flash lamp element and auxiliary lamp element under the direct control of the camera shutter contacts following operation of the shutter tripper element.

2. A photoflash circuit for use with a camera having shutter contacts and having a flash gun with a flash lamp element, an auxiliary or side flash lamp element, and a solenoid operated camera shutter tripper element, said circuit comprising; a source of direct current voltage, a first capacitor and. a first resistor connected in series, a second capacitor and a second resistor connected in series, a third capacitor and a third resistor connected in series, circuit means connecting said series connected capacitors and resistors in parallel to said source of voltage to charge all of said capacitors, a first control switch connected in series between said third capacitor and the shutter tripper element to cause said third capacitor to be discharged to operate the shutter-tripper elemenga second control switch having a first and a second position, second circuit means controlled by said second control switch in said first position and including said first control switch operatively connected in series between said first capacitor and the flash lamp element and in series between said second capacitor and the auxiliary lamp element to cause said first and second capacitors to be discharged to operate the flash lamp element and auxiliary lamp element under the direct control of said first control switch and simultaneously with operation of the shutter tripper element, and third circuit means controlled by said second control switch in said second position and including the camera shutter contacts operatively connected in series between said first capacitor and the flash' lamp and in series between said second capacitor and the auxiliary lamp element to cause said first and second capacitors to be discharged to operate the flash lamp element and auxiliary lamp element under the direct control of the camera shutter contacts following operation of the shuttertripper element.

References Cited in the file of this patent UNITED. STATES PATENTS 2,464,188 Spinks Mar. 8, 1949 2,553,662 Marsal May 22, 1951 2,590,069 Robinson Mar. 18, 1952 2,664,795 Tone Jan. 5, 1954

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