A subminiature photoflash lamp which includes a pair of pyrotechnic charges centrally disposed in a parallel, spaced relationship within the lamp's plastic, light-transmitting envelope. Each charge is supported on a respective one of the ends of the lamp's ignition wires and is of a disklike, planar configuration. The parallel spacing of the planar charges provides maximum light output from the lamp by permitting "cross-talking" between both charges during simultaneous ignition thereof. The ignition can be accomplished by the application of a firing pulse such as might be provided by a piezoelectric element.

DESCRIPTION 
TECHNICAL FIELD 
The present invention relates to photoflash lamps for use in the field of 
photography, and particularly to such lamps which are of the subminiature 
variety and adapted for being electrically activated. Even more 
particularly, the invention relates to photoflash lamps which utilize 
pyrotechnic light-emitting charges as the desired light source. 
BACKGROUND 
The present invention presents a new and unique concept in the production 
of subminiature photoflash lamps for use in photographic applications. The 
lamps of the instant invention are adapted for use in multilamp devices 
and articles which in turn may be positioned within or atop a camera. 
Examples of such cameras include those of the well known pocket variety as 
manufactured and sold by Eastman Kodak Company, Rochester, New York. 
The subminiature photoflash lamp of the instant invention provides for the 
incorporation of a pair of light-emitting pyrotechnic charges centrally 
disposed within a light-transmitting envelope. The charges are 
electrically ignited by application of a suitable firing pulse (e.g., such 
as may be provided by a piezoelectric element typically associated with 
many of the above cameras) across the two electrical conductors which 
extend from the envelope and constitute part of the ignition means of the 
invention. As will be further defined, the invention can be readily 
produced and operated without the need for many of the components 
typically required in many of today's flashlamps. Specifically, the 
invention can be produced with greater ease and less cost than known lamps 
of the chemical variety. By the term chemical flashlamp is meant one 
having a glass envelope, a combustible material (.e.g., zirconium or 
hafnium shreds) within the envelope, a combustion-supporting atmosphere 
(e.g., oxygen) also within the envelope, and a pair of lead-in wires which 
project through the base of the glass envelope and include a quantity of 
primer material thereon for igniting the shredded combustible material. It 
will be understood from the following that the instant invention may be 
produced without the need for some of the above components, including a 
combustible material such as zirconium or hafnium shreds, a glass material 
for the flashlamp's envelope, and a combustion-supporting atmosphere such 
as oxygen which must be hermetically sealed within the envelope. 
It is believed, therefore, that a subminiature photoflash lamp which is 
capable of being utilized with many of today's cameras and can be 
manufactured without the need for several of the aforementioned components 
heretofore required in chemical flashlamps will constitute a significant 
advancement in the art. 
DISCLOSURE OF THE INVENTION 
It is a primary object of the present invention to provide a new and unique 
subminiature photoflash lamp which possesses the features described above. 
In accordance with a primary aspect of the present invention, there is 
provided a subminiature photoflash lamp which includes a 
light-transmitting envelope, a pair of spaced-apart pyrotechnic charges 
for emitting light through the envelope upon ignition thereof, each of the 
charges spacedly located from the internal walls of the envelope, ignition 
means including a pair of electrical conductors secured within the 
envelope and adapted for electrically igniting both pyrotechnic charges, 
and a pair of support means each adapted for supporting a respective one 
of the pyrotechnic charges within the envelope.

BEST MODE FOR CARRYING OUT THE INVENTION 
For a better understanding of the present invention, together with other 
and further objects, advantages, and capabilities thereof, reference is 
made to the following disclosure and appended claims in connection with 
the above-described drawings. 
With particular reference to FIG. 1, there is shown a subminiature 
photoflash lamp 10 in accordance with the preferred embodiment of the 
invention. Lamp 10 comprises a light-transmitting envelope 11, first and 
second spaced-apart pyrotechnic charges 13 and 14, respectively, each 
located within the envelope at a preestablished distance from the internal 
surfaces thereof, ignition means 15 for providing electrical ignition of 
charges 13 and 14, and first and second support means 17 and 18, 
respectively, each for supporting a respective one of the pyrotechnic 
charges within envelope 11. By the term subminiature is meant a photoflash 
lamp wherein the internal volume of the lamp's envelope is equal to or 
less than about 0.30 cubic centimeters. Understandibly, such lamps are 
extremely small and incorporation of several of these members within a 
singular photoflash device assures that the finished device will be 
extremely small and compact. 
Envelope 11 is preferably of a substantially tubular configuration having 
opposing longitudinal side walls 19 (in cross section), and opposing end 
walls 21. The envelope is manufactured from a light-transmitting plastic 
material (e.g., polypropylene or polyethylene), said material initially in 
the form of an elongated tube having an internal diameter of about 0.33 
centimeters and a thickness of about 0.06 centimeters. The overall 
internal length of envelope 11, as illustrated in the finished 
configuration of FIG. 1, is approximately 2.00 centimeters. 
Ignition means 15 comprises a pair of electrically conductive wires 23 and 
25 which are secured (e.g., heat-sealed) within a first end 21 of the 
envelope and include an end portion which extends within the interior of 
the envelope as illustrated. Each extending end portion is electrically 
coupled to a respective one of the pyrotechnic charges 13 or 14. Each wire 
further includes an opposing end portion which projects from envelope 11 
and is adapted for being electrically connected to the aforementioned 
piezoelectric element or similar power source for effecting ignition of 
lamp 10. A typical piezoelectric element provides a high voltage, low 
energy pulse approaching 5000 volts. The preferred conductive wiring as 
utilized in ignition means 17 is of copper material having an external 
diameter of about 0.025 centimeters. As will be understood from the 
following, each wire as used in the finished product preferably includes 
an insulative coating thereon with portions of the coating removed at the 
desired locations for effecting electrical contact. 
The present invention represents a significant advancement over prior art 
flashlamps which utilize flash-producing charges in that it provides a 
means whereby the light output of the lamp is substantially increased over 
these earlier versions. It will also be understood from the following 
description that the unique arrangement of pyrotechnic charges of the 
instant invention further represents a significant improvement over the 
single charge lamp described in copending application under Ser. No. 
146,574, entitled "Subminiature Photoflash Lamp Having Light-Emitting 
Pyrotechnic Charge" (Inventors: J. A. Scholz et al), filed May 5, 1980. As 
described in Ser. No. 146,574, a singular planar charge is centrally 
disposed within a plastic, light-transmitting envelope in a strategic 
relationship with regard to the internal walls of the envelope so as to 
permit maximum burning of the material. The present invention represents a 
substantial improvement to this arrangement by further providing a second 
charge spaced from the first in a predetermined orientation so as to 
permit "cross-talking" of the charges during the ignition thereof. 
Accordingly, it is possible to obtain greater outputs in the instant 
invention in comparison of those of Ser. No. 146,574. Further description 
of this unique arrangement will be provided below. It is also understood 
that the present invention represents an even greater improvement over 
prior art flashlamps utilizing flash-producing charges in that it 
strategically positions the lamp's charges away from the internal surfaces 
of the walls of the lamp's envelope such that maximum burning capacity of 
both charges and the aforementioned "cross-talking" is assured. To provide 
these features, lamp 10 further includes first and second support means 27 
and 29, each utilized for supporting a respective one of the charges at 
the desired locations. The support means 27 and 29 may each be located on 
a respective one of the extending end portions of wires 23 or 25 or may 
form a part thereof. In a preferred embodiment of the invention, each 
support means comprises an extension of one of the conductive wires such 
that the conductive wire, having the aforedescribed insulative coating 
thereon, forms a substantially annular (coil) element (see FIG. 3). It is 
understood, however, that each support means 27 and 29 may include a 
separate, conductive annular (coil) member which is electrically 
conductive (e.g., metallic) and secured (e.g., soldered) to one of the 
ends of wires 23 and 25. As yet another embodiment, each support means can 
comprise an electrically insulative member (e.g., glass) which is 
positioned on a respective one of the ends of wires 23 or 25 with the 
wires strategically positioned therein or arranged thereabout such that 
the wire may be electrically coupled to the respective charge material. 
With particular regard to FIG. 2, charges 13 and 14 are shown as being 
arranged in a parallel relationship so as to each transverse a respective 
one of the extending wires 23 or 25 to thereby form a substantially 
dislike, planar configuration. Being transverse, each dislike charge lies 
substantially between the respective portions of the wires although it is 
of course understood that the wires are covered by the charge material 
(see FIG. 3). These relationships constitute a significant feature of the 
invention in that they permit a minimum of contact between the conductive 
wiring which supports the charge and the charge material itself. 
Accordingly, the wires do not represent a substantial heat sink for the 
charge material during the burning thereof and thereby assure maximum 
output from each light-emitting charge. In the aforementioned arrangement, 
each charge will include a peripheral portion 41 thereabout (see FIG. 3). 
The respective extending end of the wire which forms the support means for 
each charge will thus occupy or physically contact the charge only at this 
peripheral portion. 
As stated, the positioning of charges 13 and 14 within the envelope is 
deemed critical with regard to the instant invention in order to provide 
maximization of light output from the charges during simultaneous ignition 
thereof. In FIG. 2, the charges are arranged such that a midpoint 
therebetween is centrally disposed within the envelope, lying on the 
geometric center (GC) of the envelope. It is understood from the drawings 
that the envelope's geometric center GC also lies on the central axis 
(CA-CA) of the lamp which in turn is perpendicular to the longitudinal 
axis (LA-LA) of the lamp. More specifically, the central axis of the lamp 
is that axis passing through the geometric center of the lamp's envelope 
and lying substantially normal to the lamp's longitudinal axis. See also 
FIG. 1. It is preferred in this positioning in relationship that the 
geometric centers (GC') of each charge 13 and 14 also lie on central axis 
CA-CA. 
As described, and as illustrated in FIG. 2, the thin planar charges 13 and 
14 are oriented in a parallel relationship such that a midpoint 
therebetween lies at the geometric center of the envelope. When utilizing 
a tubular envelope having the aforementioned dimensions, the charges are 
spaced at a distance (dimension "a") of about 0.13 to about 0.25 
centimeters apart. This distance is also preferred for the parallel 
arrangement depicted in FIG. 4. The illustrated parallel spacing permits 
the two charges 13 and 14 to establish multiple fires such that internal 
regions of each will burn with greater intensity and at increased 
temperatures over a singular charge embodiment, such as defined in Ser. 
No. 146,574. This "cross-talking" between the two charges, as illustrated 
by the directional arrows in FIG. 2, results in a region of high 
brightness between both charges. In addition to this central region, the 
configuration in FIG. 2 also produces on each opposing side of the charge 
a high intensity burning pattern 43. This pattern of particle burning, as 
illustrated, assures maximum ignition of the charge particles as a result 
of the strategic positioning between the respective charge and the spaced 
interior surfaces of the longitudinal walls 19. The embodiment of FIGS. 1 
and 2 possessed a total light output within the range of about 100 lumen 
seconds to about 600 lumen seconds, or approximately twice that of 
copending application Ser. No. 146,574. Surprisingly, the output period 
was approximately one half of that of the singular disklike embodiment and 
ranged from about 1.5 to about 2.0 milliseconds (measured at half peak 
power). It was possible to even further increase peak power and pulse 
duration by the insertion of a Teflon liner (not shown) within envelope 
11. Such a liner is preferably also tubular and has an external diameter 
approximately equal to that of the internal diameter of envelope 11. The 
thickness of such a liner can be equal to that of the envelope's side 
walls 19. The aforementioned increase occurs as a result of the liner's 
increased resistance to charring or discoloration as caused by the burning 
charge material in comparison to the polypropylene or polyethylene 
envelope, thus permitting greater light emission for an extended period. 
It is believed that this increased resistance is due to the greater 
thermal stability of the Teflon. That is, Teflon possesses a substantially 
greater resistance to heat without burning, charring, or similarly 
discoloring. Understandably, liners of other suitable materials could also 
be used for this purpose. 
Each charge 13 and 14 possesses a thickness of only about 0.03 centimeters 
and is positioned at a preestablished distance (dimension "b") of from 
about 0.04 to about 0.10 centimeters from the internal surfaces of walls 
19. As illustrated in FIG. 2, each of these dimensions from the respective 
charge is to a tangent passing perpendicularly through the central axis 
CA-CA of the lamp at an internal surface of the lamp's envelope and also 
parallel to the planes occupied by said charges. It is of course 
understood that the distances between other portions of each charge and 
the internal surfaces will vary accordingly but at no location will either 
charge physically engage the envelope's internal surfaces. 
With particular regard to FIG. 3, there is illustrated an enlarged view of 
one of the support means (27) having the respective pyrotechnic charge 
(13) located thereon. As shown, the support means is substantially formed 
as a part of the respective conductor 23, which in turn includes the 
aforedefined insulative coating (45) thereon. Ignition of charge 13 is 
enhanced by the provision of an arc gap (see FIG. 3) within conductor 23, 
thus resulting in the formation of a third conductor 47 which extends from 
support means 27 to the opposing support means in the manner illustrated 
in FIG. 1. Third conductor 47 thus serves to electrically connect each 
charge and thus assure simultaneous ignition of both charges upon 
application of the aforedefined pulse across conductors 23 and 25. It is 
also understood that a similar arc gap is provided between conductor 47 
and the extending end of conductor 25 which serves to form the second 
support means of the invention. Conductor 47 also preferably includes an 
insulative coating thereon. Each of the arc gaps of the invention is 
approximately 0.025 centimeters wide and is bridged by the respective 
charge material transversely located on the corresponding support means. 
Application of the firing pulse across wires 23 and 25 results in the 
generation of a spark across each gap and subsequent, almost instantaneous 
ignition of the charge materials in physical contact therewith. The 
preferred minimal contact between the round, peripheral portion of charge 
13 an the curvilinear (annular) support means formed by wires 23 and 47 is 
clearly illustrated in FIG. 3. As shown, the wires serve only to engage or 
physically contact the outer portions of the charge. It is understood that 
this positioning relationship is also preferred for charge 14. 
The ignition means and dual support means of the invention are preferably 
manufactured from a singular piece of wire having the described insulation 
thereon. This wire is formed into the dual coil configuration depicted in 
FIG. 1 and the two arc gaps are thereafter provided therein (e.g., by a 
suitable notching tool). It is understood that the provision of these arc 
gaps results in the formation of the three separate wire conductors 23, 
25, and 47 from the originally provided singular wire. The respective 
charge materials (to be described below) are thereafter positioned on the 
support means formed by the above configuration. When utilizing the above 
technique, a suitable holder (not shown) is used to maintain the 
prescribed alignment between the separated third conductor 47 and the 
remainin separate individual conductors 23 and 25. Each of these latter 
conductors is also preferably oriented within the same holder. 
The preferred material for each of the charges 13 and 14 comprises a primer 
composition 51 (FIG. 3) and a fuel mixture 53 (also FIG. 3) located in 
physical contact with the primer. Accordingly, the primer 51 serves as the 
bridging member across the respective arc gaps and is encapsulated by the 
fuel mixture 53. The preferred primer composition for use in the instant 
invention may be selected from any of these presently utilized in the 
state of the art and adapted for being ignited by pulses typically 
provided from such sources as piezoelectric elements. One example of such 
a material is defined in in U.S. Pat. No. 4,059,388 (J. Shaffer), which is 
assigned to the assignee of the present invention. Approximately 0.50 
milligrams of primer 51 is applied across each arc gap and about 5.00 
milligrams of fuel mixture 53 thereafter applied for each charge. The 
preferred fuel mixture is a combination of zirconium and potassium 
perchlorate, with the zirconium comprising approximately 57% by weight of 
the total mixture. Accordingly, the potassium perchlorate comprised about 
43% by weight of the mixture. The particle size of the zirconium is 
approximately 11 microns while that of the perchlorate is only 3 microns. 
Each fuel mixture 53 is dispersed in a nitrocellulose-acetone solution 
yielding a final percentage of 0.5% nitrocellulose in the dried fuel. 
Procedurally, each quantity of charge material is applied to the 
respective coil support means by initially dipping the notched or slotted 
coil within only the primer material, said primer in slurry form. The 
primer covers the respective arc gaps in the manner shown in FIG. 3. The 
dual coiled structure is then removed, the primer composition permitted to 
dry, and the entire structure emersed within the aforementioned fuel 
mixture, said mixture also in slurry form. The structure is then removed 
from the slurry mixture and the fuel permitted to dry. The aforedefined 
technique permits the charge material to transverse the respective coil 
support in the manner indicated. The structure is then oriented within an 
open end of the tubular envelope and the two conductors 23 and 25 heat 
sealed within one of the ends. The second, opposing end 20 of the envelope 
is then sealed. 
The embodiment of FIG. 4 represents still another version of positioning 
the two pyrotechnic charges (13' and 14') within a tubular envelope 11. 
The charges, arranged in a parallel arrangement, are spaced preferably at 
the same distance as charges 13 and 14 in FIG. 1 Accordingly, it is 
possible to achieve the aforedefined "cross-talking" between the two 
charges during simultaneous ignition thereof. In the embodment of FIG. 4, 
the interconnecting third conductor 47' is secured within the same end 
portion 21 of envelope 11 as the two conductors 23' and 25' which form the 
remainder of the invention's ignition means. As illustrated, a pair of arc 
gaps are provided such that each charge can be ignited in the same manner 
as that of the embodiment of FIG. 1. The resulting curvilinear support 
means 27' and 29' formed by the three conductors are each of a 
semicircular configuration, and are therefore not of the substantially 
coiled shape of the support means of FIG. 1. This arrangement, however, is 
understandably more stable than that of the embodiment of FIG. 1 as a 
result of the secured retention of all three conductors within the 
envelope's end portion. 
With regard to FIG. 5, there is illustrated yet another version of 
positioning the planar charges (13" and 14") in a parallel, spaced 
relationship within the envelope 11. In this embodiment, the geometric 
centers (GC') of each chart is oriented along the longitudinal axis LA-LA 
of the envelope. The two conductors 22 and 25 of the invention's ignition 
means are understandably secured within one of the opposing ends (not 
shown) of envelope 11 in much the same manner as that depicted in FIG. 1. 
This orientation also proved to provide substantially the same outputs as 
described for that of FIG. 1, as did the arrangement of FIG. 4. As also 
shown in FIG. 5, the approximate midpoint of the parallel charges is 
located at the point of intersection between the envelope's longitudinal 
axis and central axis (CA-CA). 
With regard to FIG. 6, the preferred positioning relationship between lamp 
10 (FIG. 1) and a reflector 61 (shown in phantom), as might be typically 
provided within many of today's cameras, is shown. In this arrangement, 
the midpoint between the parallel charges 13 and 15 (illustrated as MP) 
will preferably be located at the focal point of reflector 61 and also 
along the reflector's optical axis OA-OA. Accordingly, the planes occupied 
by the disklike charges 13 and 14 will lie substantially parallel to axis 
OA-OA. This arrangement assures maximum forward emission of the light 
generated by both charges upon ignition of lamp 10. It is understood, of 
course that lamp 10 could be arranged in various alternative orientations 
and adequate output still achieved. For example, it is also possible to 
arrange the lamp such that the lamp's axis CA-CA is coaxially aligned with 
optical axis OA-OA. 
Thus there has been shown and described a new and unique photoflash lamp 
adapted for use with many of today's higher speed (e.g., ASA 400) films. 
The invention as defined provides the aforementioned outputs while still 
assuring miniaturization of the lamp's capsule or envelope component. As 
has been described, the invention is fully capable of being successfully 
operated without the need for the aforementioned components associated 
with known chemical flashlamps such as hafnium or zirconium shreds, a 
glass material for the envelope, or a combustion-supporting atmosphere to 
permit successful ignition of said shredded material. As has also been 
described, the invention represents an improvement over the pyrotechnic 
charge lamp of corresponding application Ser. No. 146,574 by providing 
substantially improved outputs and reduced output times. 
While there have been shown and described what are at present considered 
the preferred embodiments of the invention, it will be obvious to those 
skilled in the art that various changes and modifications may be made 
therein without departing from the scope of the invention as defined by 
the appended claims.