A multiple photoflash system is provided which employs a high voltage type flashlamp construction, including a shorting primer material. Said primer material is converted to a conductive residue upon ignition of flashlamp to provide a short circuit path between spaced apart inleads of the lamp. Further series connection of the individual lamps in the flashlamp system which are operatively associated with switching devices to provide an open circuit condition upon flashing of the associated lamps permits sequential flashing. The particular primer material which enables the flashlamp system to be operated in this manner comprises a solid mixture of a combustible metal fuel and an oxidizer for the fuel such as alkaline metal chlorates and perchlorates, and which further contains particular proportions of various combustion supporting oxides.

CROSS REFERENCE TO RELATED APPLICATIONS 
A related primer material composition and high voltage type flashlamp 
construction is disclosed in co-pending patent application, Ser. No. 
508,107 filed Sept. 23, 1974 in the name of Lewis J. Schupp and assigned 
to the assignee of the present invention. In said high voltage lamp 
construction, however, the lamp desirably provides an "open circuit" 
condition after flashing. Co-pending patent application, Ser. No. 448,671, 
filed Oct. 22, 1973, and U.S. Pat. No. 3,937,946, in the name of K. H. 
Weber and assigned to the assignee of the present invention, further 
describes a multiple photoflash lamp system having connector tabs 
permitting insertion of the unit into the camera socket in different 
orientations. In said lamp system, the lamps are electrically connected to 
said connector tabs so that only the group of lamps relatively farthest 
from the lens axis will be flashed. The individual lamps in this system 
are also of the "open circuit" type and are arranged to operate with 
associated short circuiting switch devices to provide the desired firing 
sequence. 
BACKGROUND OF THE INVENTION 
The general field of the present invention is a high voltage actuated 
multiple flashlamp system utilizing a high voltage low energy electrical 
power source to ignite the flashlamps in sequence. Said multiple flashlamp 
system can be of the planar array type which is provided with plug-in 
connector tabs at each end of the unit to fit into the socket of a camera. 
Such flash lamp unit can be provided with an upper array of flashlamps 
which are electrically connected to a lower plug-in tab by means of an 
associated electrical circuit board so that only the upper lamps in the 
array will be flashed when the lower tab has been inserted into the camera 
socket. By turning the flashlamp unit top to bottom and reinserting the 
remaining tab in the camera socket, it becomes possible to flash a second 
group of flashlamps which are now oriented farthest away from the axis of 
the camera lens. This is made possible by means of a different circuit 
path on the associated circuitboard which electrically interconnects said 
lamps with the connector tab now inserted in the camera socket. The above 
generally described lamp sequencing arrangement eliminates or reduces the 
undesirable "red-eye" effect since only the lamps of the array that can 
flash are grouped relatively farthest from the axis of the camera lens. 
The already known high voltage type flashlamps employed in such multiple 
flashlamp systems require a short duration pulse of approximately 1,000 or 
2,000 volts at a low current value. Although the firing pulse is sometimes 
called a "voltage pulse", it is primarily the energy of the pulse, 
comprising the combination of voltage, current and time duration, that 
causes an individual lamp to flash when a firing pulse is applied across 
the spaced apart inleads of an unflashed lamp in the circuit. The firing 
pulse source may comprise a suitable battery-capacitor discharge and 
voltage step-up transformer type of circuit, or may employ a compact 
piezoelectric element arranged to be impacted or stressed in 
synchronization with opening of the camera shutter, so as to produce a 
firing pulse with a voltage of approximately 1,000 or 2,000 volts and of 
sufficient energy to fire a single flash lamp. An example of a high 
voltage flashlamp and a firing pulse source comprising a piezoelectric 
element synchronized with the camera shutter is described in U.S. Pat. 
Nos. 2,972,937 and 3,106,080, both to C. G. Suits. 
A flashlamp construction of the all glass type that can be actuated by a 
high voltage pulse in the above described type multiple photoflash lamp 
systems further contains a combustion-supporting gas such as oxygen within 
a hermetically sealed glass envelope together with a loosely distributed 
filling of a suitable light producing combustible material such as 
shredded foil of zirconium, aluminum or hafnium, for example, which upon 
ignition produces a high intensity flash of actinic light. In typical high 
voltage flashlamp constructions, a fulminating type primer material is 
employed as a mass electrically connected directly across and between a 
pair of inlead wires extending into the lamp glass envelope. The primer 
material may be positioned and carried in the lamp on top of a glass or 
ceramic insulating member through which the inlead wires extend, or may be 
carried in a cavity provided in such a member. Ignition of said primer 
material responsive to the firing pulse desirably provides a sufficient 
blast that the inleads remain spaced apart in an open circuit condition. 
The known primer materials for such flashlamp constructions also desirably 
produce a non-conductive residue upon combustion to further help avoid 
establishing any low resistance shorting path between the spaced apart 
inleads after the lamp has been flashed. 
A known primer material of this type which is disclosed in the above 
referenced patent application Ser. No. 508,107 comprises a solid mixture 
of a combustible fuel and an oxidizer for the fuel such as alkaline metal 
chlorates and perchlorates, and which further contains a 
combustion-supporting oxide of the type which is converted to a lower 
oxide upon combustion of the mixture. Combustion-supporting oxides already 
found suitable in the primer material can be selected from the group 
consisting of Co.sub.3 O.sub.4, BaCrO.sub.4, Fe.sub.2 O.sub.3, and higher 
oxides of nickel by reason of not converting to form a conductive residue 
after the primer has been ignited. In contrast thereto, other metal oxides 
found not suitable include CuO, PbO, SnO.sub.2, TiO.sub.2 and ZnO which 
are said to form conductive residues hence have proven unsatisfactory for 
an "open circuit" type lamp construction. 
SUMMARY OF THE INVENTION 
It has now been discovered that a particular type primer material can be 
employed in a high-voltage flashlamp construction so as to reliably 
provide short circuiting of the lamp after flashing. More particularly, a 
shorting primer material for a high voltage actuated flashlamp has been 
discovered which comprises a solid mixture containing in weight percent 
about 40-90% powdered combustible metal fuel, 5-15% of an oxidizer for 
said combustible metal fuel, 5-15% of a combustion supporting oxide which 
is converted to a non-conductive residue upon combustion of the mixture, 
and 10-20% of a combustion supporting oxide which is converted to a 
conductive residue upon combustion of the mixture. The operational 
characteristics of this primer material produces an after-flash residue 
remaining between the spaced apart inleads to establish a sufficient 
conducting path across said inleads for the shorted lamp to function 
thereafter as a conducting element in the flash sequencing circuit. 
Briefly, the present high voltage actuated multiple flashlamp unit 
comprises a base, a reflector unit mounted on said base having a plurality 
of outwardly facing reflector cavities disposed in a matrix arrangement 
and facing outwardly in the same direction, a plurality of flashlamps 
including a first group of flashlamps and a last flashlamp mounted on said 
base with each one of said lamps being positioned within a respect of one 
said reflector cavities, and a circuitboard member operatively associated 
with said lamps to flash the lamps in sequence by providing a series 
circuit including said lamps adapted to be connected to the energy source, 
a low resistance switching device connected in series with each lamp of 
said first group across the energy source and switching to open the 
circuit upon flashing of its associated lamp, said flashlamps each 
comprising a hermetically sealed light transmitting envelope, a quantity 
of filament recombustible material distributed within said envelope, and 
flash ignition means within said envelope which includes a pair of spaced 
apart inleads having a mass of primer material connected between said 
inleads to form a conductive residue upon combustion and provide an 
electrical path to succeeding lamps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the preferred flashlamp design of the present invention, a mount 
construction is employed for assembly of the inlead wires and primer 
material to provide the flash ignition means. Said flashlamp mount 
construction comprises a glass bead or other electrically-insulated member 
provided over an end of the pair of inlead wires. An opening is provided 
to the bead member between and in communication with both of the inlead 
wires, and primer material is provided in the opening and electrically 
bridges across the inlead wires. Preferably, said opening extends fully 
through the bead member in a direction parallel to the inlead wires. Also, 
preferably, a portion of the bead member extends above and overlies at 
least a portion of the ends of the inlead wires. The underside of the bead 
member may also be sleeved or shaped to provide increased electrical 
insulation between the inlead wires. It is also within contemplation of 
the present invention, however, to provide different support means for the 
required conductive primer residue in forming this type electrical path 
interconnecting the inleads. 
Referring to FIG. 1, the preferred lamp construction has the same general 
features described in the aforementioned co-pending application Ser. No. 
508,107 which comprises a tubular envelope 11 preferrably made of a 
borosilicate glass or other suitable light-transmitting vitreous material 
such as lead glass and having a stemmed press seal 12 at one end thereof 
through which a pair of inlead wires 13 and 14 extend from the exterior to 
the interior of the bulb 11 in a generally mutually parallel spaced apart 
manner and form part of a mount 15. The bulb 11 is partially filled, above 
the mount 15, with a loose mass of filamentry or shredded metal foil or 
wire 16, of zirconium or hafnium, or other suitable combustible metal. Air 
is exhausted from the bulb 11, and the bulb is filled with oxygen at a 
pressure of at least several atmospheres, such as about 5 to 10 
atmospheres or greater and the bulb is sealed off at an exhaust tip 17 at 
the other end thereof from the stem press seal 12. The lamp may be coated 
with the usual lacquer or plastic protective coating. 
To further enhance the reliability of afterflash electrical shorting in the 
flashlamp, an excess quantity of the filamentry combustible material is 
employed with respect to the available quantity of combustion supporting 
atmosphere beyond that necessary for a stoichiometric combustion reaction 
to take place. Thus, while it has proven generally desirable to maintain 
an excess stoichiometric ratio between oxygen and the combustible metal 
foil in the already known "open circuit" type lamp constructions 
previously mentioned, it is desirable for the present shorting type lamp 
construction to reduce said stoichiometric ratio to about 90-100% for 
enhanced shorting reliability. This can be accomplished simply by 
increasing the weight of the combustible metal foil in the lamp while 
maintaining the oxygen pressure at the conventional levels already 
employed. 
As further described in the aforementioned co-pending application Ser. No. 
508,107, the preferred mount construction can take the form of a glass 
bead shaped to form a pocket for containment of the afterflash conductive 
primer residue between the spaced apart inlead wires 13 and 14. Thus, the 
glass bead can be sealed over and around an end of said inlead wires and 
be provided with an opening which is located between and in communication 
with both of the inlead wires. The glass bead may be formed by placing a 
ring of glass around the ends of the inlead wires and heating for a 
suitable time and at suitable temperature so as to cause the glass ring to 
shrink into molten contact with the open portion of the inlead wires, 
leaving a slot-like or other shape opening which preferably extends fully 
through the electrically insulative member in a direction parallel to the 
inlead wires. As shown, the opening is at least partially filled with a 
solid mixture of the primer material which can be deposited in the opening 
by various known means such as with a syringe, or by daubing, or by 
dipping the inverted mount member in a liquid primer slurry. The small 
cross-sectional area of the opening and the opening being open at both 
ends causes a capillary action effect which aids in drawing the liquid 
primer slurry into the opening. 
The present primer material providing the desired short circuited condition 
in the lamp upon flashing comprises a solid mixture containing in weight 
percent about 40-90% powdered combustible metal fuel, 5-15% of an oxidizer 
for said combustible metal fuel, 5-15% of a combustion supporting oxide 
which is converted to a non-conductive residue upon combustion of the 
mixture, and 10-20% of a combustion supporting oxide which is converted to 
a conductive residue upon combustion of the mixture. In said primer 
material, the afterflash shorting condition is believed attributable to 
using combustion supporting oxides which when reduced by loss of oxygen 
become conductive oxides or are converted to the metallic state along with 
using excess ratios of the combustible metal fuel with respect to the 
oxidizer constituents beyond that necessary for the stoichiometric 
combustion reaction to take place. By reason of the latter feature, not 
all of the metal fuel constituent is reacted upon ignition of the primer 
material and the afterflash residue can be in the form of a slag 
containing the partly reacted metal powder which may have become partially 
converted to a conductive metal oxide. 
The electrical characteristics of the afterflash primer residue in 
providing a conductive path are significant since they differ considerably 
from the conductivity that would result if the metal inleads were directly 
short circuited by physical contact therebetween. More particularly, 
direct physical contact between said inleads would provide an absolute 
short circuit path having only a few ohms resistance value whereas the 
afterflash resistance of the primer connected inleads can be as high as 
10,000 ohms and still provide the necessary conductive path in the present 
flashlamp system. Even if the electrical resistance of the primer residue 
exceeds this value it would still be possible to provide an electrical 
path thereafter between the spaced apart inleads with application of a 
successive firing pulse since the applied voltage levels range from 
approximately 1,000 volts to as high as 2,500 volts or greater. The 
desired conductive path can be maintained with a successive firing pulse 
at these applied voltage levels by maintaining a breakdown voltage level 
of around 200 volts for the primer residue as deposited in the spaced 
apart leads. A satisfactory conductive path would still result although 
physical discontinuities in the primer residue or other abnormalities 
produce an electrical resistance across the spaced apart inleads exceeding 
10,000 ohms. 
The fuel in the present primer material is a powdered combustible 
incandescible metal such as zirconium, hafnium, titanium, thorium, 
aluminum, magnesium, boron, silicon or other alloys which upon ignition by 
the high voltage firing pulse ignites the filamentary combustible 
material. Suitable oxidizers for the combustible metal fuel include alkali 
metal and alkaline earth metal chlorates, as well as perchlorates 
including soidum perchlorate, potassium perchlorate, barium chlorate, 
sodium chlorate, and potassium chlorate. As has been previously pointed 
out, the above defined proportions for the fuel and oxidizing constituents 
in the present primer material are controlled to provide reliable ignition 
with incomplete combustion of the fuel constituent which further leads to 
a low-blast characteristic for greater retention of primer residue between 
the inlead wires after the lamp has been flashed. Useful combustion 
supporting oxides in the primer material which are converted to a 
non-conductive residue upon combustion of the mixture can be selected from 
the group consisting of Co.sub.3 O.sub.4, BaCrO.sub.4, Fe.sub.3 O.sub.4 
and higher oxides and nickel while the combustion supporting oxides which 
are converted to a conductive residue upon combustion of the mixture 
include CuO, PbO.sub.2, SnO.sub.2 and ZnO. BaCrO.sub.4 has been found to 
be a particularly useful combustion supporting oxide in the primer mixture 
in providing the desired afterflash characteristics through disassociation 
into its BaO and Cr.sub.2 O.sub.3 constituents. 
Referring to FIG. 2, there is illustrated a preferred linear or planar type 
multiple flashlamp unit of the present invention which is provided with 
plug-in connector tabs at each end of the unit to fit into the socket of 
the camera (not shown). Said lamp array is provided with an upper group of 
flashlamps which are electrically connected to the lower plug-in tab by 
means of an associated electrical circuitboard so that only the upper 
lamps in the array will be flashed when the lower tab has been inserted in 
the camera socket. By turning the flash unit top to bottom and inserting 
the remaining tab into the camera socket it becomes possible to flash a 
second group of flashlamps which are not oriented farthest away from the 
axis of the camera lens. This is made possible by means of a different 
circuit path on the associated circuitboard which electrically 
interconnects said lamps with the connector tab now inserted in the camera 
socket. Said planar type multiple flashlamp unit 20 is of the same general 
type described in the above cross-referenced co-pending Weber application. 
Accordingly, said flashlamp unit generally comprises a reflector unit 22 
mounted upon an elongated molded plastic base supporting member 24 which 
further supports an electrical circuitboard member 26 along with 
transparent cover means 28 which is secured to said base as shown. The 
individual reflector cavities of said reflector unit are suitably provided 
with a specular reflective coating of a suitable metal such as aluminum, 
as by well-known metal vaporisation vacuum deposition processes or other 
suitable techniques. Individual flashlamps 30 are mounted within 
respective reflector cavities 32 also as shown to rest upon the baseboard 
member 24. The electrically fired flashlamps of said unit are electrically 
connected to the circuitboard member 26 so that the unit can be plugged 
into a camera socket in different orientations whereby only a group of 
said lamps relatively furthest away from the camera lens axis will be 
flashed so as to reduce the likelihood of the undesirable "red-eye" effect 
previously mentioned. The detail features of said electrical connections 
are disclosed in the above cross-reference Weber application, hence need 
only be further defined herein as relates to the series circuit connection 
between said lamps which further includes connection of the switching 
devices to provide a particular open circuit condition with respect to 
operatively associated flashlamps. The cover member 28 physically 
interlocks with the base supporting member 24 so as to contain the 
circuitboard member 26 having a plurality of flashlamps 30 attached 
thereto. 
Referring to FIG. 3, a schematic electrical diagram 34 is shown which 
represents the particular circuit configuration being employed for one 
group of four lamps in the above flashlamp unit. Accordingly, lamps 36, 
38, 40 and 42 are serially connected in the circuit 44 to have the 
high-voltage low energy firing pulse applied across the inlead terminals 
46 and 48 of the circuit from a suitable electrical energy source which 
can be located in a camera (not shown). As further shown in said diagram, 
the above described shorting lamps are operatively associated with low 
resistance type switching devices 50, 52 and 54 which are connected in 
series with flashlamps 36, 38 and 40, respectively, to avoid short 
circuiting of the energy source when successive lamps are flashed in the 
firing sequence. The desired result is accomplished when the switching 
devices successively produce an open circuit condition in the branch 
circuits of the first group of flashlamps 36-40 and it should be noted 
that the last flashlamp 42 in the series does not have a corresponding 
switching device connected across the energy source. 
Low resistance switching devices are employed in the circuit to produce a 
minor voltage drop when the firing pulse is applied across an unflashed 
lamp so that a major portion of the available energy serves to ignite the 
flashlamp in accordance with voltage division considerations. The 
particular electrical characteristics for suitable switching devices in 
the above described circuit are also significant since these devices can 
be actuated in different ways when the associated flashlamps are ignited. 
More particularly, locating said switching devices adjacent to the 
flashlamps permits receipt of radiant energy therefrom in the form of 
light and heat when the lamps are ignited. This can be accomplished with a 
switching material being deposited on the circuit-board between a pair of 
terminals in the electrical circuit. Upon actuation by the radiant energy 
when the adjacent flashlamp is ignited produces a physical alteration in 
the switch material to provide the desired open circuit condition between 
said electrical terminals. Thermally fusable metals can be employed in 
this manner as well as combustible materials exhibiting electrical 
resistance less than around 1000 ohms before the switch opens and the 
desired protection of the energy source is accomplished when the open 
switches have a resistance greater than about 1,000,000 ohms. It is 
further desirable for the switch material in the foregoing type switch 
device to exhibit a relatively low breakdown voltage so that a firing 
pulse can be applied across the associated flashlamp in the event that the 
switch material does not make good electrical contact with the electrical 
terminals. Thus, a firing pulse can still be applied across the unflashed 
lamp, at the previously mentioned applied voltage levels when an unopened 
switch exhibits a breakdown voltage level of around 200 volts or less. On 
the other hand, a breakdown voltage level of at least around 2000 volts is 
required for an open switch to provide the desired protection in a circuit 
employing flashlamps having after-flash electrical characteristics as 
hereinbefore reported. From a comparison of these after-flash breakdown 
voltage and resistance characteristics in the associated flashlamps and 
switching devices it can also be seen that both values are desirably 
maintained at much higher levels in the switching devices. 
It will be apparent from the foregoing description that various other 
embodiments and modifications of the present invention will be apparent to 
persons skilled in the art. For example, the invention can also be 
embodied in planar type multiple flashlamp units having a different number 
of lamps than herein specifically disclosed and to even include a unit 
having a group of lamps and reflectors arranged to illuminate in one 
direction with another group of lamps and reflectors being arranged to 
illuminate in the opposite direction. Still further modifications of the 
particular circuit configuration are contemplated such as that described 
in connection with FIG. 3 of the U.S. Pat. No. 3,532,931 which is assigned 
to the assignee of the present invention. It is intended, therefore, to 
limit the present invention only by the scope of the following claims.