US3666394A - Multiflash lamp unit - Google Patents

Abstract

A DEVICE FOR THE SERIES IGNITION OF COMBUSTIBLE FLASHBULBS WHICH ARE ESSENTIALLY CONNECTED IN PARALLEL WITH ONE ANOTHER. EACH FLASBULB IS IN SERIES WITH A SWITCHING ELEMENT WHICH RESPONDS TO THE ENERGY EMITTED DURING FLASHING OF SAID FLASHBULB, AND PERMANENTLY INTERRUPTS THE ELECTRIC CONNECTION BETWEEN THE BULB AND THE CIRCUIT.

Description

United States Patent 3,666,394 MULTIFLASl-l LAMP UNIT Johannes Gerardus Bok and Wilhelmus Polycarpus de Graaf, Emmasingel, Eindhoven, Netherlands, assignors to [1.5. Philips Corporation, New York, N.Y.

Filed May 18, 1970, Ser. No. 37,976 Claims priority, application Netherlands, May 30, 1969, 6908333 Int. Cl. F21k /02 US. Cl. 431-95 2 Claims ABSTRACT OF THE DISCLOSURE A device for the series ignition of combustible flashbulbs which are essentially connected in parallel with one another. Each flashbulb is in series with a switching element which responds to the energy emitted during flashing of said flashbulb, and permanently interrupts the electric connection between the bulb and the circuit.

The invention relates to a multiflash lamp unit comprising photoflash lamps and an electric circuit in which the flashlamps are essentially connected in parallel to one another and which flashlamps will be ignited one at a time and one after the other each time the shutter mechanism is actuated.

Several types of multiflash lamp units for such series ignition are known. A number of these units have in common that the current conductors of the flashlamps are connected to the voltage source by means of the electric circuit across one or more switches one of which cooperates with the shutter mechanism, which lamps remain connected or are connected to said voltage source when the next lamp is ignited, also after they have been flashed.

It is found that this may cause difliculties in practice. It was found that the resistance between the current conductors after flashing is only approximately 1 ohm in approximately 25% of the common photoflash lamps. This implies the formation of current bridges due to combustion products in the flashed lamp.

Common photoflash lamps are understood to mean flashlamps wherein ignition means comprising two current conductors interconnected by a filament is present within a transparent envelope filled with a combustible metal wire filling and a combustion supporting gas such as oxygen or nitrofluoride/NF An ignition mass is provided on the terminals of the current conductors which mass explosively burns after it has reached a given temperature and thereby initiates the actinical reaction between the metal wire filling and the oxidizing gas.

The formation of current bridges does not only occur in this type of lamps, but also in so-called high-voltage photoflash lamp wherein the ignition means comprises two current conductors which are electrically connected together within the bulb only by means of an ignition mass no ignition filament being present. When applying a high voltage an electric breakdown succeeded by a resistive heat development in the ignition mass takes place upon which an explosive combustion of the ignition mask starts and the actinical reaction between metal wire filling and oxidizing gas is initiated.

If flashed lamps having a relatively low resistance between the current conductors are present in an electric circuit including in-flashed lamps such flashed bulbs completely or partly take up the supplied energy when it is attempted to ignite one of the unflashed lamps. The result is that none of the in-flashed lamps, can be flashed under such circumstances.

This phenomenon particularly occurs when not all flashlamps in the circuit are flashed one after the other. As is known cracks occur during flashing in the envelopes of 3,666,394 Patented May 30, 1972 most fiashlamps, which envelopes normally consist of glass. As a result the contents of the envelope come in open communication with the atmosphere. Thus combustion products which initially do not conduct or conduct in an unharmful manner can become highly conducting due to attracting moisture from the atmosphere and can constitute current bridges between the current conductors in flashed lamps.

The object of the present invention is to obviate these drawbacks. To this end a multiflash lamp unit provided with photoflash lamps which can be ignited one after the other and are connected together in an electric circuit is characterized in that each flashlamp is electrically connected in series to its own switching element which interrupts the electric connection between at least one of the current conductors of the lamp and the circuit under the influence of the energy emitted during flashing.

The switching element may consist of, for example, an electrically conducting wire or strip incorporated in the circuit which wire or strip melts under the influence of the energy emitted by the associated flashlamp and permanently interrupts the electric connection between at least one of the current conductors of this flashlamp connected in series with the switching element and the circuit.

According to a preferred embodiment of the invention the switching element consists of a locally blackened wire or strip of an alloy or metal preferably melting at a temperature of not more than 400 C. but more than approximately C.

Metals suitable for this purpose are, for example, bismuth, cadmium, indium, lead, tin and alloys of these metals melting between approximately 85 C. and approximately 400 C. and/or alloys of these metals and the metals silver, copper, zinc, aluminium, silicon, magnesium, antimony, nickel, thallium and gold.

Particularly suitable for the desired purpose is a strip of a known solder alloy of tin and lead (60:40) having a melting point of 180: A strip having a section of 2 mm. x 0.014 mm. melts when it is at a distance of 15 mm. to 20 mm. from the wall of the envelope of a burning flashbulb and when it has been blackened by means of soot.

The switching element which is used according to the invention must of course not be actuated by the energy which is emitted by a flashbulb not connected in series with the switching element. If this condition and the condition that the melting point of the material of which the switching element consists, can be reached under the influence of the energy emitted during flashing are satisfied the location of the element does not further play an important role. The switching element may be provided on the outer wall of the envelope or on or in the reflector operating with the flashlamp or in the vicinity of the base of the flashlamp, for example, on or in a holder for the flashlamp.

In order that the invention may be readily carried into effect, a few embodiments thereof will now be described in detail by way of example with reference to the accompanying diagrammatic drawing, which shows three systems for series ignition of combustible flashbulbs.

FIG. 1 relates to a multiflash lamp unit provided with high voltage flashlamps.

FIGS. 2 and 3 relate to units provided with common photo flash lamps.

FIG. 1 shows a principal circuit diagram of a circuit suitable for photoflash lamps wherein ignition is induced by applying for a short period a voltage which increases to a high value within a short time, for example, within several microseconds up to a value of several thousands volts. Upon reaching the voltage value which corresponds to the breakdown voltage of the flashlamp having the lowest breakdown voltage in the multiflash lamp unit, this flashlamp is ignited. The next time when a flashlamp is to be ignited, the flashlamp which then has the lowest breakdown voltage of the unflashed lamps in the unit is ignited.

In the figure the reference numerals 1, 2 and 3 denote combustible fiashlamps. More than three lamps may be present in the circuit. Each lamp is connected in series through one of its current conductors 9 with a switching element 4 consisting of a locally blackened strip of a leadtin alloy (40:60) having a section of 1 mm. x 0.014 mm. The fiashlamps 1 to 3 are mutually connected in parallel by means of the current conductors 7 and 8. The lamps are connected by means of these conductors to a high voltage source, not shown, which supplies a voltage increasing to a high value within a short period when the shutter mechanism of the camera is actuated. The current conductors 9 and 10 of the fiashlamps are connected within the envelope by an ignition mass comprising a mixture of zirconium powder and potassium perchlorate and furthermore the mixture comprises approximately 30 vol. percent of approximately 1% by weight of strontium containing lanthanum cobaltite which is a semiconducting material and a binder. The fiashlamps contain zirconium wire filling 5 and oxygen. When flashing a lamp the strip 4 which is located at a distance of approximately 5 mm. from the wall of the envelope of the lamp melts, so that the connection between the lamp and the current conductor 8 is completely and permanently interrupted. Each lamp has its own reflector (diagrammatically shown by broken line circles 11) which may also be used to shield the switching element 4 from irradiation by flashbulbs not associated therewith.

FIG. 2 shows a principal circuit diagram of a circuit suitable for common fiashlamps provided with an ignition filament connecting the current conductors within the envelope and an ignition mass in the vicinity of said filament. This ignition mass comprises, a mixture of zirconium powder, potassium perchlorate and a binder (29).

The circuit includes the fiashlamps 21, 22 and 23. The circuit is not limited to this number. The lamps 21, 22 and 23 are series-arranged with switching elements 24 which upon flashing of the fiashlamps interrupt the connection between the relevant flashlamp and the current conductor 25 under the influence of the emitter energy. The flashlamp 22 and 23 are also series-arranged with a switching element 27 which upon flashing of the previous lamp establishes the electrical connection between the next flashlamp and the current conductor 26. The switching elements 27 are provided in the system in such a manner that they can only be operated by a previous flashlamp, for example, by accommodating them possibly jointly with the switching element 24 in the reflectors (diagrammatically denoted by the broken line circles 28). Furthermore the fiashlamps are connected by means of the current conductors 25 and 26 to a device, not shown, which provides a current during a short period when the shutter mechanism of the camera is actuated. Such devices are known to the art. If flashlamp 21 is ignited, the connection between this lamp and the current conductor 25 is interrupted and the connection between flashlamp 22 and the current conductor 26 is established.

FIG. 3 shows a principal circuit diagram of a circuit which is suitable for common fiashlamps wherein the fiashlamps are essentially connected mutually in parallel and in series with resistors the resistances of which increase in the sequence of ignition.

The reference numerals 31 to 34 denote fiashlamps of the common type wherein the current conductors 35 and 36 are interconnected within the envelope of the flashlamp by means of a filament 37. The envelope furthermore contains zirconium wire filling 79 and oxygen. The fiashlamps 31 to 34 are connected across switching elements 38 to 41 to the current conductor 42, and the fiashlamps 32 to 34 are connected across resistors 43 to 45 to the current conductor 46. The resistance of the resistor 45 is then higher than that of the resistor 44 and the resistance of the resistor 44 is in turn higher than that of the resistor 43. The mutual ratio of the resistances may, for example, always be chosen to be 2:1 in the given sequence.

The circuit can be connected by means of the current conductors 42 and 46 to a device not shown which supplies current during a short period when the shutter mechanism of the camera is actuated; such devices are known to the art.

Each flashlamp has its own reflector (diagrammatically shown by the broken line circles 47) which may also be used to shield the switching elements 39, 40 and 41 from irradiation by a previously flashed lamp which is not series-arranged with the switching element.

If a current is applied to the circuit by means of the previously mentioned device, flashlamp 31 is first ignited and the connection between the current conductor 35 and the current conductor 42 is interrupted by the switching element 38 under the influence of the emitted energy. The next time when a current is applied to the circuit, flashlamp 32 is ignited and the switching element 39 interrupts the connection between the current conductor 48 and the current conductor 31 under the influence of the emitted energy.

The relative magnitudes of the resistances have been chosen to be such that the combustible fiashlamps ignite in the given sequence and that two or more fiashlamps are not simultaneously ignited.

The switching elements 38 to 41 may comprise a strip of a lead-tin alloy (40:60) as mentioned in the previous example.

The present invention provides a simple and reliable, yet inexpensive step by which these drawbacks relating to the use of circuits for series flashing wherein fiashlamps are essentially connected in parallel can be surmounted, which drawbacks consist in the circuit not further functioning it one of the fiashlamps has a relatively low resistance after flashing.

What is claimed is:

1. In a multiflash lamp unit sequential ignition of fiashlamps of the type having a plurality of fiashlamps connected in parallel with each other and means to sequentially ignite said fiashlamps wherein the improvement comprises a plurality of switching elements included in said sequential ignition means, each of said switching elements being in series with a corresponding flashlamp for interrupting the igniting means for said fiashlamp after said flashlamp is ignited, said switching elements comprising an electrically conducting, locally blackened strip of material having a melting point between substantially C. and 400 C., said strip of material further being positioned in the vicinity of said flashlarnp.

2. A unit as claimed in claim 1 wherein said material is selected from the group consisting of bismuth, cadmium, indium, lead, tin, and lead tin (40:50) alloy.

References Cited UNITED STATES PATENTS 3,443,875 5/1969 Herrmann 431- 3,459,487 8/1969 Glenn 43l95 3,518,487 6/1970 Tanaka et a1. 431-95 X 3,532,931 10/1970 Cote et al 431 9s X FOREIGN PATENTS 1,192,047 4/ 1965 Germany 431-95 EDWARD J. MICHAEL, Primary Examiner 753? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3666394 Dated May 13, 1972 I en (s) JOHAN'NES GERADUS BOK ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 27, "31" should read -42- Column 4-,. line 59, (4-0 :50) should read (40:60)

Signed and sealed this 5th day of September 197-2.

(SEAL) Attest:

ROBERT GOTTSCHALK Commissioner of Patents EDWARD M.FLETCHER,JR. Attesting Officer

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