Page 2 - us2995088

United States Patent Office 2,995,088
Patented Aug. 8, 1961

1 2
creases expense and sometimes introduces sources of
2,995,088 failure.
MULTI-STAGE IGNITER CHARGE A practical .form for the igniter charge material is in
Robert K. Asplund, Newhall, Calif., assignor to Bermite pellets rather than in powder. However, some failures
Powder Company, Saugus, Calif., a corporation of Cali- 5 in the past have been traced -to attrition of said pellets
fornia
Filed June 29, 1959, Ser. No. 823,586 · within the igniter housing, during transport and storage
1 Claim. (Cl. 102-70) prior to use. Although some of this attrition can be
avoided by the introduction of cushioning materials, cush-
This invention relates generally to igniters of the type ioning alone has proven ineffective to avoid substantial
having an igniter charge within a housing of sufficient 10 attrition, and failures resulting therefrom.
strength to resist rupture during ignition combustion, and Other proposals have involved the use of slow burning
also having one or more nozzles for discharging igniting powders, delayed ignition structures, various types of
gases from said housing; such igniters are generally used fuses, etc., but all have proven rather complicated and
for igniting bodies of solid propellant supported within expensive for the purpose intended.
rocket housings. 15 It is a major object of the present invention to provide
More particularly, this invention is concerned with an an igniter producing propellant-igniting gases of con-
igniter of the type descri:bed in which the duration and trolled duration and limited pressure, by means of a novel
pressure of the jets of igniting gas are controlled, at least structure of the combustible igniter material itself.
,in part, by an ignition charge comprised of an initial It is another object of the invention to provide an ig-
stage of rapid burning igniter material enclosed in or 20 niter charge structure which achieves the results of two
surrounded by a main ignition charge made up at least or more stages of combustion, with extremely simple and
in major part of ignition pellets enveloped in slow burning economical arrangements of the charge materials, and the
or combustion resistant material. use in most instances of only one or two readily available
In the preferred species of the invention, the main ig- combustible materials.
niter charge is annular in shape and surrounds a core of 25 It is still another object of the invention to provide an
initial igniter charge, into which a squib means discharges, igniter in which the ignition charge or charges are largely
with or without the aid of confining or directing barrier protected from attrition, without interfering with their
walls. quick and reliable ignition by standard squib ignition
· In wckets or missiles in which solid propellant is used, means.
the propellant is ordinarily supported in a chamber inside 30 The foregoing and other objects are accomplished with
a housing or case with free space around the propellant standard igniter materials. Any of the solid igniter ma-
material. The means of support may be a spider or the terials ordinarily used in granular or pelletized form may
like, but the present invention is not concerned with the be employed in the practice of the invention. Such
nature of the propellant or of its support, or general struc- igniter materials are generally much more readily ignited
ture, but only with the need for igniting it by means of 35 than the propellant employed as rocket fuel, which is to
hot igniting gases. be ignited by the igniter. Also, such igniter materials
It is important for suitable ignition that the igniting ordinarily have a burning rate which is much higher than
gases be projected at or on the solid propellant in a de- that of propellant materials or certain other solid oxidant
sired manner for a suitable igniting time of a few milli- compositions which can be used in association with the
seconds. It is desirable for reliable ignition, without fail- 40 rapidly burning igniter materials.
ure and without irregular and improper burning of the In the present invention, at least two stages of igniter
propellant, that the igniting gases are supplied in a very combustion are approximated by pellets of the same
roughly constant fashion for the brief but perceptible ig- rapidly burning igniter material, some of said pellets
niting period. Of course, the pressure of the gases will being uncoated and unshielded from the squib ignition,
change substantially during the igniting period, but it is 45 and others being enveloped by a coating or a solid matrix
desirable to avoid very high peak pressures which then bed of relatively slow burning material, which may be a
trail off to much lower pressures early in the ignition slower burning igniter material, propellant material, or
period. even a mere coating of combustible ibut combustion re-
One excellent solution for the problem has been to sistant material.
5
provide a strong igniter housing for the igniter charge, o The application of the invention is illustrated by two
with a plurality of nozzle openings directed toward the very different specific embodiments described herein in
propellant, and adapted to project a number of jets of hot connection with the accompanying drawings, in which:
igniting gases from the igniter housing, across the inter- FIGURE 1 is a sectional view through the housing of
• vening space within the rocket or missile housing, to an igniter constructed according to the present invention,
the exposed surfaces of the solid propellant. Such an 55 in one of its simplest forms; and
igniter housing may be in the form of an ignition charge FIGURE 2 is a cross-sectional view of a rocket hous-
container mounted in the end of the rocket housing, and ing, and an igniter constructed according to the invention
provided with an electrically controlled squib igniting in a somewhat more elaborate form, approximating three-
means in its outer end, external to said rocket housing. stage ignition burning.
The present invention uses such a housing but only as 60 In FIGURE 1, an igniter indicated generally by the
one coacting part of a combination, the principal novel numeral 10 is enclosed in a two-piece igniter housing 11,
parts of which are the combustible igniter materials them- which is generally cyiindrical in shape, and is comprised
selves, which are shaped into charges providing sustained of a lower cup 12 on to which is threaded an inverted cup
and controlled ignition burning. shaped cover 13.
In the past, the igniter housing has had to be made 65 The lower cup container 12 may be threadably received
heavy enough to withstand high peak pressures, or has into the end of a rocket housing, in the same manner as
been constructed of light materials which would blow out is illustrated in FIGURE 2 for cup 32 which is received
upon ignition, with resultant inferior quality of ignition. in a rocket housing 60 _
Control of pressure and duration of ignition flame has
" been attempted by making use of heavier and more com- 70 Also, the cup 12 may be surrounded at its base with
, plex igniter housings, with more comp!ex and expensi_ve an outwardly projecting flange 14 which may serve to seat
, nozzle arrangements. Such complexity naturally m- against an O-ring recessed in the end of the rocket hou~-