U.S. patent number 3,724,990 [Application Number 05/198,587] was granted by the patent office on 1973-04-03 for photoflash lamp.
This patent grant is currently assigned to General Electric Company. Invention is credited to Lewis J. Schupp.
United States Patent |
3,724,990 |
Schupp |
April 3, 1973 |
PHOTOFLASH LAMP
Abstract
A percussion-ignitable type flashlamp is disclosed which
includes an improved primer material that is more stable in
handling during lamp manufacture and improves performance of the
lamp in operation. Said primer material comprises a mixture in
percentages by weight of 4-50 percent phosphorus, 10-25 percent
potassium chlorate, 4-10 percent sodium chlorate, and the remainder
being titanium, which mixture can be bonded to form a unitary mass
with a polyvinyl alcohol binder. A slurry of the primer material in
an aqueous solution of 87-89 percent hydrolyzed polyvinyl alcohol
remains substantially gel-free for long time periods and provides a
tough and adherent coating in the lamp.
Inventors: |
Schupp; Lewis J. (Chesterland,
OH) |
Assignee: |
General Electric Company
(N/A)
|
Family
ID: |
22733991 |
Appl.
No.: |
05/198,587 |
Filed: |
November 15, 1971 |
Current U.S.
Class: |
431/361; 149/31;
149/44; 149/30; 149/40 |
Current CPC
Class: |
F21K
5/026 (20130101) |
Current International
Class: |
F21K
5/00 (20060101); F21K 5/14 (20060101); F21k
005/02 () |
Field of
Search: |
;431/93,94
;149/30,31 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dority, Jr.; Carroll B.
Claims
What I claim as new and desire to secure by Letters Patent of the
United States is:
1. A flashlamp comprising a hermetically sealed light-transmitting
envelope, a quantity of filamentary combustible material loosely
distributed within said envelope, a filling of
combustion-supporting gas in said envelope, and a
percussive-ignition system secured at one end and in communication
with the interior of said envelope, said percussive-ignition system
including a quantity of primer material which comprises a mixture
in percentages by weight of 4-50 percent phosphorus, 10-25 percent
potassium chlorate, 4-10 percent sodium chlorate, and the remainder
being titanium.
2. A flashlamp as in claim 1 wherein the combined weight percent of
potassium chlorate and sodium chlorate does not exceed 25
percent.
3. A flashlamp as in claim 1 wherein the primer material is bonded
into a unitary mass with a polyvinyl alcohol binder.
4. A flashlamp comprising a hermetically sealed light-transmitting
envelope, a quantity of filamentary combustible material loosely
distributed within said envelope, a filling of a
combustion-supporting gas in said envelope, and a
percussive-ignition system for said lamp comprising a readily
deformable metal ignition tube sealed in and projecting from one
end of said envelope enclosed off at its outer end, a wire anvil of
a high temperature resistant and low thermal-conducting material
disposed within and substantially coaxially with said ignition
tube, said wire anvil being coated with a quantity of primer
material which comprises a mixture in percentages by weight of 4-50
percent phosphorus, 10-25 percent potassium chlorate, 4-10 percent
sodium chlorate, and the remainder being titanium.
5. A flashlamp as in claim 4 wherein the combined weight percent of
potassium chlorate and sodium chlorate does not exceed 25
percent.
6. A flashlamp as in claim 4 wherein the coating of primer material
is bonded to the anvil with a polyvinyl alcohol binder.
7. A flashlamp as in claim 6 wherein the polyvinyl alcohol binder
is approximately 87-89 percent hydrolyzed polyvinyl alcohol.
8. A primer material which comprises a solid mixture having in
percentages by weight 4-50 percent phosphorus, 10-25 percent
potassium chlorate, 4-10 percent sodium chlorate, and the remainder
being titanium which is bonded into a unitary mass with a polyvinyl
alcohol binder.
9. A stabilized slurry of primer material which comprises a solid
mixture containing in percentages by weight of said solid mixture
4-50 percent phosphorus, 10-25 percent potassium chlorate, 4-10
percent sodium chlorate, and the remainder being titanium with said
mixture being suspended in an aqueous solution of polyvinyl
alcohol.
10. A stabilized slurry as in claim 9 wherein the polyvinyl alcohol
is approximately 87-89 percent hydrolyzed.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
A related primer material and flashlamp is described and claimed in
concurrently filed application Ser. No. 198,547 filed Nov. 15, 1971
and filed in the name of the same inventor, entitled "Photoflash
Lamp" and assigned to the assignee of the present invention.
Additionally, an undercoating for the primer material in flashlamps
is described and claimed in a further concurrently filed
application Ser. No. 198,956 filed Nov. 15, 1971 and filed in the
names of Stephen P. Senft and Vaughn C. Sterling, entitled
"Flashlamp Primer Undercoating" and assigned to the assignee of the
present invention.
BACKGROUND OF THE INVENTION
This invention relates in general to photoflash lamps and more
particularly to those of the so-called percussion-ignitable type.
The photoflash lamps in general use at present comprise a
hermetically sealed light-transmitting envelope usually made of
glass and containing a combustion-supporting gas such as oxygen
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. Suitable ignition
means are generally provided in the lamp to initiate the flashing
thereof. In the percussive-ignition type photoflash lamps in
general use at present, the charge of percussively sensitive primer
material is located within a readily deformable metal ignition tube
sealed within and projecting from one end of a length of glass
tubing which forms the lamp envelope and the other end of which is
constricted and tipped off. The ignition tube extends generally
axially of the tubular lamp envelope and opens thereinto, and the
primer material is in the form of a coating on a wire anvil
supported within the ignition tube and extending approximately
axially thereof. Flashing of such constructed percussive type
photoflash lamps is initiated by a forceful mechanical impact or
blow applied against the side of the metal ignition tube to deform
it inwardly against the coating of primer material on the wire
anvil which causes deflagration of the primer material up through
the ignition tube into the lamp envelope where it then ignites the
filamentary combustible material disposed therein.
The known primer materials generally consist of a mixture of a
readily combustible fuel such as phosphorus with an oxidizer
compound for the fuel such as alkali metal chlorates and
perchlorates. The primer material also further generally includes a
powdered combustible incandescable metal such as zirconium,
hafnium, thorium, aluminum, magnesium, boron, silicon or their
alloys which upon being heated spews into the envelope to burn the
filamentary combustible material when the mixture has been
detonated. The known primer materials have been prepared as liquid
suspensions in an organic or aqueous solvent for coating the anvil
member in a percussive type flashlamp, and soluble binders are
generally included to provide adhesion of the coating to the anvil
member. A known organic liquid suspension for the primer material
utilizes nitrocellulose as the binder agent and requires careful
handling during storage and lamp manufacture to avoid accidental
ignition. A less sensitive aqueous suspension of the primer
material which is known uses hydroxyethyl cellulose or methoxy
cellulose as the soluble binder agent.
Various problems exist with the known primer materials both in the
preparation and application as a coating upon the anvil member or
in the operation of a flashlamp having such coatings. The liquid
suspensions have been found unstable in that the suspended material
settled out or aggregated so as to preclude being able to obtain a
uniform liquid coating of the primer material on the anvil member.
In a dip method of coating it was also found that solid materials
from the coating composition adhered to the sides of the container
holding the coating composition with said adhered material proving
to be unwettable when additions of the liquid composition were
supplied to the container. A still different problem encountered
with aqueous suspensions of the primer material which contain a
substantially insoluble constituent such as potassium chlorate
occurs from recrystallization of this constituent to form oversized
lumps in the liquid coating composition. The final solid coatings
obtained with conventional primer materials further lack adequate
adherence to the anvil member and are brittle which has a
deleterious effect upon the lamp operation.
For the solid primer composition to operate satisfactorily when the
lamp is actuated, it becomes necessary for the material to exhibit
both the proper ignition sensitivity as well as to ignite the
filamentary combustible material properly so as to obtain the
desired light output and light peak time. More particularly, the
primer material must be sensitive enough in oxygen or another
combustion-supporting gas to reliably ignite the flashlamp.
Additionally, the blast characteristics of the primer material must
distribute hot burning metal sufficiently for the principal
combustion reaction which produces the light output from the lamp
to take place at a desired light level and time span but without
excessive blast velocity. If the blast velocity of the primer
material is excessive, then the filamentary combustible material
becomes packed in the lamp envelope with subsequent reduction in
light output or slower burning rate.
SUMMARY OF THE INVENTION
An improved primer material has been discovered which can be
applied reliably as a coating for the anvil member in a
percussion-ignitable flashlamp to provide proper ignition
sensitivity and improved blast characteristics in the lamp upon
actuation. The low blast velocity and high impact sensitivity of
the present primer material compared with currently used primers
permits the lamp to flash reliably with a high constant light
output at a primer weight range between 0.5 and 1.2 milligrams. By
reason of the improved efficiency and operational characteristics
of the new primer material, it becomes possible to achieve a mean
light output of approximately 520 zonal lumen-seconds from
flashlamps containing 18 milligrams of a zirconium filamentary
material and 4.5 cc of oxygen compared with the 19 milligrams of
said foil and 5 cc of oxygen being utilized in the conventional
flashlamps.
The improved flashlamp construction of the present invention
comprises a hermetically sealed light-transmitting envelope, a
quantity of filamentary combustible material loosely distributed
within said envelope, a filling of combustion-supporting gas in
said envelope, and a percussive-ignition system secured at one end
and in communication with the interior of said envelope, said
percussive-ignition system including a quantity of primer material
comprising a mixture in percentage by weight of 4-50 percent
phosphorus, 10-25 percent potassium chlorate, 4-10 percent sodium
chlorate, and the remainder being titanium. The combined weight
percent of potassium chlorate and sodium chlorate in the primer
mixture does not exceed 25 percent in the preferred compositions to
maintain a proper balance between safety and handling and
sensitivity in lamp operation to provide the aforementioned
performance advantages. Likewise, the primer mixture is adhesively
bonded to the anvil member with a polyvinyl alcohol binder in the
preferred embodiments which provides a tough, flexible and
abrasion-resistant coating that does not crack or peel off as
readily during lamp manufacture or other handling than was found
with conventional primer formulations.
The coating slurry for the primer materials of the present
invention comprises a suspension of the aforementioned solid
mixture in an aqueous solution of polyvinyl alcohol. More
particularly, the solid mixture can be suspended in equal part by
weight of a 2 percent by weight solution of polyvinyl alcohol in
water. The preferred type of polyvinyl alcohol resin is
approximately 87-89 percent hydrolyzed which provides greater
flexibility and adhesion in the final coating film as well as
greater dispersing power in the aqueous slurry than can be found
with a completely hydrolyzed polyvinyl alcohol. The dispersion
power of polyvinyl alcohol is important in the present coating
compositions by reason of the presence of both potassium chlorate
and sodium chlorate which interact in solution by reason of a
common ion effect. While the greater solubility of the sodium
chlorate serves to reduce the solubility of the potassium chlorate
and minimize recrystallization of the latter material which can
produce large lumps in the coating composition, it becomes
necessary to have these materials uniformly dispersed in the
coating composition for the desired effect to take place.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing, the single FIGURE is a cross-sectional view partly
in elevation of a percussion-type flashlamp of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawing, the flashlamp according to the invention
comprises a glass bulb or envelope 1 which, as shown, may be formed
of a short length of glass tubing, for example, about 3/8 inch
outside diameter, which is constricted and rounded off at one end
as indicated at 2 and closed off thereat by an exhaust tip 3 and is
formed at the other or base end 4 with a fused seal 5 about a
readily deformable metal ignition tube 6 which may comprise a
thin-walled (for example, 0.003-inch wall thickness) tube of a
suitable metallic composition such as a nickel-chromium iron alloy,
for instance. The envelope 1 is made of a glass which is capable of
forming a good hermetic seal to the particular metallic material
employed for the ignition tube 6. As shown, the ignition tube 6
which may have an outside diameter of about one-sixteenth inch, for
example, is sealed into the base end 4 of the tubular lamp envelope
1 in a position extending longitudinally and preferably axially
thereof, and it projects endwise from the envelope end 4 to provide
an exposed section 7. The ignition tube 6 has a closed outer end 8
and an open inner end 9 which opens into the interior space of the
lamp envelope 1 and, as shown, terminates approximately at the
inner wall thereof. A quantity of filamentary combustible material
10 such as a shredded foil of zirconium, aluminum or hafnium, for
example, is loosely distributed within the interior space of the
envelope 1 which also contains a filling of a suitable
combustion-supporting gas such as oxygen.
Disposed within the metal ignition tube 6 and extending
substantially coaxially therethrough is a wire anvil 11 of a
suitable metallic composition of high temperature resistance and
low thermal conductivity such as, for example, a stainless steel.
The wire anvil 11 is suitably held or fastened in place in the
ignition tube 6 as by a circumferential indenture 12 of the tube 6
near its outer end which laps over an enlarged head 13 or other
suitable protuberance on the outer or lower end of the wire anvil.
As shown, the wire anvil 11 is of a slightly smaller diameter in
the inside diameter of the ignition tube 6 so as to be spaced a
slight distance, for example, about 0.05 inch or so from the inside
wall thereof, and it is provided with a thin coating 14 of a
percussively ignitable primer material over an appreciably
lengthwise extent of that portion of the wire anvil located within
the projecting portion 7 of the ignition tube 6. The coating 14 of
primer material is of a thickness such as to be spaced a slight
distance of around a few thousandths of an inch or so, for example,
0.004 inch, from the inside wall of the ignition tube.
To aid in supporting the wire anvil 11 substantially coaxially
within the ignition tube 6 and insure clearance between the coating
14 of primer material in the inside wall of the ignition tube 6,
the wire anvil 11 is formed near the open inner or mouth end of the
ignition tube 6 with three or more protuberances or lobes 15 spaced
apart more or less uniformly around the circumferential extent of
the wire anvil and having, along with the head 13 on the wire
anvil, a close sliding fit within the ignition tube. The anvil
centralizing lobes 15 are of minimal thickness circumferentially of
the wire anvil 11 so as to leave substantially unobstructed the
annular space between the ignition tube 6 and the wire anvil 11 for
the passage therethrough and into the lamp envelope 1 of the
ignited particles of the primer material 14 on ignition and
deflagration thereof. In the particular case illustrated, the anvil
centralizing lobes 15 are formed by flattening the wire anvil 11 at
two closely adjacent points along the length of the anvil and in
two different planes at approximately right angles to one another.
The lamp is also provided with a deflector shield 16 which is
located just inwardly of the open inner mouth end 9 of the ignition
tube 6 on an inwardly extending portion 17 of the wire anvil 11
that extends into the lamp envelope 1 from the mouth opening 9 of
the ignition tube 6. The deflector shield 16 can be constituted by
a glass bead fusion-sealed to the wire anvil 11.
The coating of primer material in the above embodiment can be
applied to the anvil member as a stabilized aqueous suspension of
the present invention in various known ways. For example, the anvil
member can be dipped into the aqueous slurry followed by drying in
air or with heat to remove the liquid and produce a solid adhered
coating having the desired characteristics previously described.
Alternately, the aqueous slurry can be sprayed on the anvil members
and thereafter processed to provide a solid coating exhibiting
comparable performance.
An example of a coating composition made in accordance with the
present invention which is both safe to handle and exhibits the
desired sensitivity in lamp operation is as follows:
Ingredients Parts by Weight Titanium 620 Potassium chlorate 100 Red
phosphorus 180 Sodium chlorate 100 Water (with 2% polyvinyl alcohol
binder) 620
This primer suspension can be mixed in a conventional manner to
produce a smooth, even blend of the constituents which is stable in
storage over long time periods. All solid materials except the
sodium chlorate can have a particle range from a fine mesh size to
a micron size which insures a smooth and uniform primer coating. By
changing the ratio of the solid materials in the primer within the
ratios of the weight ratios above specified, it is possible to make
the final percussively ignitable material more or less explosive
and more or less sensitive in air or oxygen. The formulation can be
varied to make the final primer safer to handle wet or dry and
still be made sensitive enough in oxygen or some other
combustion-supporting gas to reliably ignite the flashlamp.
Consequently, the proper balance between safety and sensitivity
will specify the particular formulation best fitted for a given
application.
Surprisingly, it has been found that raising the phosphorus level
in the primer mixture above the minimum level specified has only
slight effect on light output and variation in light output when
the lamp is actuated. Correspondingly, there is only slight effect
upon light output and time to peak when the potassium chlorate
level is increased above the minimum level hereinbefore specified.
On the other hand, it has also been found that mixtures of the
potassium chlorate and sodium chlorate oxidizers within the weight
ratios specified are significantly more sensitive to impact than
would be an equivalent amount of potassium chlorate alone. Sodium
chlorate cannot be substituted entirely for potassium chlorate in
the primer mixture since the time to peak occurs too quickly in a
flashlamp along with "salting out" of the polyvinyl alcohol binder
in the aqueous slurry at the levels of oxidizer needed.
While the best mode of carrying out the present invention has been
set forth above, it will be understood that additions, changes and
modifications may be made thereto without departing from the spirit
and scope of the invention as defined in the appended claims. For
example, it will be apparent that extenders such as finely divided
silica and suspending agents can be added to the aqueous slurry for
greater stability if the need arises. Likewise, defoamers can be
added to the aqueous slurry which may facilitate more immediate
application of a freshly prepared coating composition. It is
intended to limit the present invention, therefore, only to the
scope of the following claims.
* * * * *