US2531220A - Flash lamp - Google Patents

Description

Nov. 21, 1950 J. KAPLAN FLASH LAMP Filed Oct. 17, 1947 J/ICK mPm/v INVENTOR:

Patented Nov. 21, 1950 UNITED STATES PATENT OFFICE 'FLASH LAMP J ack'Kaplan, Brooklyn; N. Y.

Applicationoctober 17, 1947,.Serial No. 780,382

2 Claims.

This invention relates to flash type illuminating devices and is particularly adapted for use in photography.

The invention has for one of its objects the provision of a gas-filled flash lamp which is capable of repeated use, together with an energizing circuit for the lamp'which will produce a short interval flash of high intensity.

A further object of the invention is the provision of an energizing circuit as an electrical source of energy of relatively low capacity.

A further object of the-invention is a provision of electrical circuits suitable for use inobtaining the most effective energization of the flash lamp.

Still another object of the invention is to provide an icnization'type of flash lamp in conjunction with a battery of a relatively low voltage and to include a simple, compact, and efiicient voltage transformation circuit, suitable for energization from the battery which will in turn deliver a high voltage impulse of relatively short duration to the lamp.

Still another-object is to provide a surge. gencrating circuit which is easily controllable, light in weight and small in dimensions, thus being readily portable and economical to manufacture.

Other and further objects will become apparent upon reading the following specification together with the accompanying drawing forming a part thereof.

Referring to the drawing,

Figure 1 shows a front view in elevation of a lamp holder suitable for use in practicing the invention.

Figure 2 shows a form of pulse generating circuit for use in energization of the lamp.

Figures 3, 4, 5 and 6 show various forms of pulse generating circuits for use in energization of the lamp illustrated in Figure 1.

Figure '7 is a graphical representation of time and current relationships in the battery circuit.

Referring to Figure l, a reflector l l is mounted on a handle 12 adapted to receive at its upper end a flash lamp, (not shown) of the ionization type which may be of any desired construction. Lamps of this type are known in the art and accordingly no particular form of lamp has been indicated. Handle 12 may be hollow and may be adapted to receive batteries and other electrical circuit components for energization of the flash lamp. Mechanical means or a pair of conductors in the form of a cord l3 may be extended to auxiliary control contacts suitably coorcli nated with the shutter mechanism of a camera (not shown) with which the lamp may be used. The auxiliary control contacts should be arranged so that the instant of maximum of'camera shutter opening will occur substantially simultaneously with the instant of maximum flash lamp brilliance; correct coordination of these two maxima will produce optimum results.

Referring to Figure 2, a flash lamp Hi of any suitable construction is shown connected in multiple with an inductor I5 and a capacitor [6. A battery I! isconnected to energize inductor l5 upon closure of a switch l8. To limit the surge current upon closure of switch [8, a resistor 19 of small value may beprovided as shown. Upon the closure of switch 18 at a time h the battery current will increase exponentially to a value 12 at-a time t2. At the time t2 there will be energy stored in a magnetic field which may be expressed as Li2 joules where L represents the inductance of the coil in henries and i2 is the cur-rent through the coil in amperes at the time 152.

The energy that can be stored in the electrostatic field'of the'capacitor 15 can be expressed as /;CV where C represents the capacitybf capacitor IS in farads and V is the voltage across the capacitor in volts. Equating the energy stored in the coil to the energy that can be stored in the capacitor will give the maximum voltage that can be developed across flash lamp M which is V=i2 /L/C' if all of the energy stored in the magnetic field is transferred into energy stored in the electrostatic field. The maximum potential generated will be somewhat less than this r ideal value because of loss of energy in the circuit elements such as resistance of the winding of the coil, iron losses in its core, and other effects such as dielectric hysteresis in the capacitor. However, by proper design and selection of circuit components, this loss of energy can be made very small.

From an analysis of the last equation it is readily apparent that as C becomes smaller, V becomes larger and that as C approaches 0, the peak voltage generated will become very large. The minimum value of C which can be obtained will be that due to the inherent self internal capacitance effects within the coil and similar effects necessarily present between conductors interconnecting the circuit elements. By proper selection of the values of L, C and i2 it is possible to generate a sufiicient potential to ionize the lamp and upon ionization thereof the energy stored in the condenser will be discharged into thelamp together with the energy stored in the building up voltage in capacitor [6.

3 coil. The energy distribution throughout the spectrum will depend upon the type of gas in the lamp and this may be selected to give the distribution best suited to the type of use or application of the apparatus.

Figure 3 shows a modification of the arrangement illustrated in Figure 2 in which capacitor [6 is connected across the terminals of switch l8. When switch 18 is open, capacitor 16 is charged to the voltage of batteries H. In order to prevent injury to the switch contacts upon closure thereof, it may be desirable to include in the circuit of capacitor I6 a small resistor I9 of relatively low value which will limit the maximum discharge current upon the closure of switch Hi to a value which will not be injurious to the switch contacts.

When switch I8 is opened, using the modification of Figure 3, the arcing across the switch contacts will be minimized by the action of capacitor IS. The voltage will build up as determined by the charging rate of capacitor 16 and the characteristics of coil I5. When this voltage reaches a sufficient value, the lamp M will ionize and capacitor is will discharge therethrough together with the remaining energy stored in the magnetic field of coil [5.

In Figure 4, a modified arrangement is shown in which three coils l5, l and are connected in the form of a T, capacitor l6 being connected across switch I8 as in Figure 3. This will modify the shape of the voltage pulse produced upon opening switch I8. Coil l5 tends to sustain the battery current after switch 18 is opened, thus Coil l5" does not become effective until after ionization of lamp M. It tends to delay the start of the flash and to extend its duration.

Figure5 illustrates a further modification of the arrangement of the circuit elements in which a further coil I5 in parallel combination with a further capacitor I6 is connected in series with coil [5.

The effect upon the pulse shape will be determined by the relative values of these circuit elements.

In Figure 6, voltage increase or decrease may be obtained by providing a secondary winding I5 inductively coupled to coil 15. The lamp I4 is shown connected directly across secondary winding I5.

Qther modification may be made and circuit elements of various values may be used to obtain the optimum effects with the particular lamp used or the intensity and duration of flash required.

The device operates by closing switch l8 to allow energy storage in the coil l5 and then opening switch l8 to fire the illuminating device.

I have shown what I believe to be the best embodiment of my invention. I do not wish, however, to be confined to the embodiment shown but what I desire to cover by Letters Patent is set forth in the appended claims.

I claim:

1. A flash type illuminating device comprising a source of direct current, a switch and an ionizable flash lamp forming acircuit with the said source of current, an inductor across the said flash lamp and adapted to be energised from the source upon closure of the switch, the said flash lamp being adapted to be energized by the discharge from the inductor upon opening of the said switch, and another inductor in series with the said flash lamp adapted to modify the rate of energization of the lamp by the first mentioned inductor.

2. A flash type illuminating device as set forth in claim 1 and having a capacitor across the switch and adapted to further modify the rate of energization of the lamp.

JACK KAPLAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number

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