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Патент USA US3077087

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Feb. 12, 1963
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United drietjes Patent hice
Keith tC. lonas, Minneapolis, Minn, assigner to Minneap=
olie-Honeywell Regulator Company, Minneapolis,
Minn., a corporation ol Delaware
Filed luly ll, 1959, Ser. No. $24,323
6 Claims. (Cl. till-_39.470
This invention relates to pyrotechnic accumulatore
wherein hot gas is generated and used to pressurize a
stored quantity of hydraulic fluid, and more particularly,
to a hot gas generator wherein the gas is developed by
the regulated burning of a quantity of solid propellant
Patented Feb. l2, 1953
laut is ignited, it supplies hot gases at three thousand
pounds per square inch pressure behind a piston 6l (FlG
URE l) which forces hydraulic oil in chamber 6b out of
the device at the required flow rate. Exhaust gases also
pass around the solid propellant assembly and down its
full length by way of longitudinal grooves 56 (see FIG
URE 3) and are then exhausted through a relief valve 4t)
(FlGURE l). This relief valve dumps all excess exhaust
gases not required by the hydraulic demand, and regu
lates the three thousand pound per square inch operating
pressure. The details of this operation will be best un
derstood from the following more complete description.
over a predetermined period of time so as to maintain
Detailed Description
pressure on said hydraulic iluid throughout said time in
In FIGURE l, it is apparent that the main structural
member is a body, or internal housing 22. This member
has the form of a cylindrical tube provided with male
threads at both ends, an outwardly extending circular
flange Sil, a plurality of ports 7h', arranged. about a cir
cular groove e9 formed in the inner wall of housing 22,
and an inwardly extending circular ilange d'7. An an
nular gap or chamber, 6h, for hydraulic iluid is formed
by a pair of annular end closure members 71 and 23,
the outer wall of body 22, and the inner wall of an outer
Pyrotechnic auxiliary power units using either liquid or
solid fuels have been in existence for some time, and are
well known in the art. These units have been, for the
most part, designed around a high-speed turbine, driving
an alternator and/or hydraulic pump through one or
more stages of gear reduction, and the resultant corn
piexity, weight, size and relatively high cost make this
type of power unit undesirable for many applications.
Another problem in this type of device is that of inhibit
ing the solid propellant so that it burns at one end-surface
only, since the gas production rate cannot be controlled
unless the area of the burning surface is controlled. This
latter problem becomes particularly acute when the design
pressure for the device is in the order of 3,600 pounds per
square inch, since high pressures tend to increase the
tendency of the fuel to instantly ignite on all surfaces and,
essentially, explode.
Consideration of these problems
in the past has, for the most part, led to the use of a
separate gas generator and a separate gas~to-hydraulic
pressure converter, and this type of construction has
further increased the complexity, weight, size and cost
as mentioned above.
It is therefore a principal object of my invention to
housing member 35. Member 35 is concentrically
located around body 22, and tits snugly against a shoulder
'72 of end closure member' 7l, and a shoulder 26 of end
closure member 23. The components making up this
hydraulic chamber are held in fixed relation by a lock nut
ll, which threads onto body 22 and compresses elements
Z3, 35, and 7l against shoulder 3l) of body Z2. It should
be noted that Q-ring seals 2d, 25, 73 and 74 are provided
to prevent hydraulic and gas leaks between these mem
bers, and that a safety valve ’i5-_76 is provided in mem
ber 7l.
A free-heating ring-type piston el is located in chamber
6i?, and is shown in its normal position at the right end of
the chamber. Piston 6l rits snugly against the inner wall
of member 35 and tre outer wall of member 22, and is
provide a simple and compact device containing hydraulic 40 designed to move toward end-closure member 23 under
:duid and solid fuel, wherein said fluid is highly pres
the induence of pressurized gas impinging on its right face.
surized over a predetermined time interval by gases gen
(1i-ring seals 64 and 65 are provided to prevent leakage
erated through controlled burning of said fuel.
between the surfaces, and a plurality of pressure balance
A further object of my invention is to provide such
rings 63 are provided to minimize locking of the pistou in
a device in a relatively small and compact design, having
chamber oil and thereby impart greater lubricity to piston
relatively light weight, and being relatively low in cost.
movement. It should be noted that a male llange 62 on
A further object of my invention is to provide such a
piston nl is designed to engage a female opening 3d in
device wherein a novel structure and method is employed
end-closure member 23, so that all of the hydraulic fluid
to inhibit the burning of said fuel.
in chamber et? can be exhausted except that remaining in
These and other objects of my invention will become
a fluid line 3l and a port 32 threaded at 33.
apparent upon consideration of the following description,
In addition to holding the hydraulic chamber compo
taken in conjunction with the accompanying single sheet
nents in fixed relation, loclt nut lll is also efectivo to sup~
of drawing wherein:
port a portion of the pressure regulating assembly of my
FIGURE l is a sectional View of. the hot gas generator
device. This pressure regulating assembly includes an
forming my invention,
55 inner porting nut 13 having ports le therein, a set screw
FIGURE 2 is an enlarge sectional view of the ignitor
l5 which threads into nut 13, a spring retainer Zd, a spring
assembly used to ignite the solid fuel, and
2l, a spring seat 3d, and a valve dll. Valve ell includes
FlGURE 3 is an exploded isometric view of my solid
propellant assembly.
General Description
My hot gas generator is made operative by ignition
taking place in the ignition assembly shown in FIGURE
a pivot dll, a spool 45, and a sleeve ¿il which is provided
with ports such as ft2 and e3. Valve ¿S6 also has male
60 threads ed which engage female threads in flange 47. The
compression of spring 2l, and therefore the relief pressure
of the assembly, is established by set screw lâ which can
be turned by means of a tool (not shown) inserted through
opening l2 in lock nut ll. When suiîicient pressure has
2. This is initated by at least one of two “squibs” lill
and lill, that are normally connected in parallel. These 65 been generated in the system, gas is ported through sleeve
squibs ignite a booster charge of fast burning smokeless
4l from the right (in a manner to be described below),
powder lilià. The ignition charge is contained long
enough to build up to a pressure which insures a fast
ignition burn. When the necessary elevated pressure
is reached, a diaphragm 97 ruptures and releases the burn
ing ignition gases through the ports 96' and across the
face of the solid propellant 53. After the solid propel~
and against the right end face of spool d5, forcing the
spool 455 and pivot ‘le to the left so as to compress spring
2l. Gas is thereby released through ports 42 and 43 in
sleeve 4l, ports le in porting nut 13, and through a center
opening l2 in hydraulic lock nut ll.
The solid propellant fuel assembly is located tothe right
of llange 47, within body 22. An insulator washer 5@ is
mounted at the left end thereof, and a gas porting end
being subjected to 29S pounds per square inch pressure,
for a minimum of sixteen hours.
The pressure is an
essential step in the process, since it forces the poly
5l provides
a pathwill
for be
to flow
urethane against the propellant and into the pores therein,
which compensates for slight dimensional changes in the
by reference to FlGUP-,E 3, where it is shown in greater
stick caused by temperature change. The resultant in
detail. This assembly consists
a solid propellant stick
hibitor has been found to adhere well to the propellant
53, and a tube :lo housing an end closure 52 and consisting
stick and form a cohesive layer between the stick and the
of an epoxy material reinforced with fiberglass, which
sleeve, this layer having suliicient strength and resilience
serves the dual function of housing the propellant stick
and also providing a support member for a bonding layer lí) to maintain the desired end-burning of the propellant.
lgnitor assembly 99 consists of a header 93 which is
53 of polyurethane which is injected and cured under
provided with female threads at the left end thereof to
pressure between tube Se and propellant stick 53. A steel
receive a nut 95, perforations 96 being provided therein.
sleeve 55, with splined grooves 55 therein, holds the -liber
glass and propellant potted assembly in position, and also
provides porting passages to the relief valve. Although
grooves Se are shown, it should be understood that a
number of dii‘îerent types of depressions would be equally
Nut 95 and header 93 deiine an internal chamber, or
ignition cavity, llltl,
smokeless powder, a
and 162 being also
smokeless powder is
which is filled with a fast-burning
pair of electrically tired squibs N1
mounted therein as shown. The
held in this chamber by a plastic
effective to port the exhaust gas to the valve. Another
membrane 97 glued to the inside of nut 95 as shown. A
steel sleeve 57', having thread-like grooves out in its out~
side diameter, lits concentrically between sleeve
and as seal is provided between body 22 and header @3 by 0
the inside of body Z2. Sleeve S7 provides the necessary
heat insulation due to the dead air space in the grooves
and the minimum contact with housing 22, to protect th
hydraulic accumulator from the temperature or the hot
gases ñowing around the propellant assembly.
At the right end of propellant stick 53, l have provided
ring 94, and header 93 is held against the end of body Z2
by lock nut 115, which is provided with female threads to
engage the male threads c‘ll on the right end of body 22.
Positive ignition is achieved by the use of two squibs,
25 lill. and N2, each of which contains a small charge, and
by the booster charge in chamber îllltl. The two squibs
are identical, and are connected in parallel, to provide
ignition redundancy in case one of them should fail to
a propellant
55 £4?,
lits snugly
92. tube
Cap end
ignite. Each squib consists of a small charge encased in
of the polyurethane between propellant 53 and sleeve 5d, 30 a cardboard cover, this small charge being ignited respon
to protect the sleeve and the bonding layer from the hot
gases generated as the propellant 53 burns.
Flanges S5
on cap tid act as spacers, and permit the combustion gases
to how to the piston and pressure-regulation mechanism.
A shield 32 fits snugly into housing 22, and between sleeve
57 and insulator washer 92 and has ports d3 that are
aligned with groove oil in housing 2.2. The inside diam
sive to an electric current Flowing through a small resist
ance-wire ûlarnent mounted therein (not shown). Upon
receipt of an appropriate electrical signal, the squibs lire
and ignite the booster charge of smokeless powder, to
thereby raise the pressure in the ignition cavity ltlll.
After the pressure has risen to approximately 1000 pounds
per square inch, the membrane 97 ruptures, allowing the
gases to expand from the ignition cavity through perfora
eter of shield S2 is greater than the outside diameter of
tions h6 in perforated nut 95 onto the end of propellant
propellant cap 8d, and the annular opening therebetween
carries the combustion gases to the right end of spline-:l 40 stick 53. The expansion or” the gases from the ignition
cavity to the face of the stick is restricted by the pressure
grooves 56 in sleeve 55.
drop through holes 96 in perforated disc 95 of ignition
The solid propellant stick or body was potted as shown,
cavity lill), thus maintaining the elevated pressure within
in order to obtain end-burning thereof. End-burning was
the ignition cavity and allowing the continuation of fast
chosen as the means for prescribing and maintaining con
stant burn area on the solid propellant, and this makes it 45 burn of the remainder of the smokeless powder. This
permits fast and positive burning of the ignition charge,
necessary to coat the sides and bottom of the solid propel~
and assures positive ignition of the propellant stick. The
lant with a burn inhibiting potting material. A virtually
energizing leads for squibs lill and 162 are schematically
air tight, tough, resilient inhibition coating was necessary,
shown as leads 105 and lilo, encased in a tubing llld
clue to the explosive nature of the propellant and the
resulting tendency of the burn area to expand into the 50 extending to squib lill, and leads lll and 1212 are en
cased in a tubing il?) which extends to squib 162. Plugs
slightest opening in the potting material. The problem
w3 and ll@ are iirmly mounted in header 93, and provide
was aggravated by the tendency of the propellant mate
a positive seal around the lead wires and tubes idd and
rials to resist adhesion due to the oils and residual
3113, to prevent the escape of gas therearound.
solvents contained therein, by the tendoney ot certain
potting materials to shrink as they cure, and by the ex
tremely high coeflicient of expansion of the propellant
materials. This expansion characteristic made it impos
sible to use a potting material requiring elevated tempera~
When squibs lill and ltlZ are tired, and powder lo@ is
ignited, the adjacent end of propellant stick 53 is also
ignited and begins to burn from the end in much the
ture cure, or an exothermic potting material such as epoxy
resin, since the heat would cause the inhibitor to
onto 60 same manner as a cigarette, although considerably faster.
an expanded propellant stick, and the stick would then
The burning rate is determined by the propellant material
shrink away from the inhibitor as it cooled.
that is used, and the area of burn is determined by the
outer casing and potting that is used to contain the pro
pellant stick, as described above. For this application, I
have sized the propellant stick, and chosen a propellant, to
lt is also
essential to choose a compatible potting material, that is,
one that does not include components aiiectcd by or hav
ing an adverse effect on the solid propellant material.
I have found it possible to solve these problems by
using a thermo-setting material with good adhesion char
acteristics, such as one of the class of compounds known
as polyurethanes. One such material found suitable for
the purpose is a urethane manufactured by the Coast
Froseal Mfg. Co. and marketed under code number
XWC45~4L The material is drawn into the space between
provide a pressure versus burn-rate curve that has a some
what Íiattened plateau range close to the desired operat~
ing pressure of 3000 pounds per square inch. This per
mits a closer maintenance of a desired operating pressure,
without the necessity of exhausting large variations in
quantities or" gas through the regulating valve assembly.
stick 53 and tube 54 with a minimum of 4 millimeters
of mercury vacuum, and is then slowly cured at room
As the pressure builds up, the gases llow between
flanges 85 on cap 8d, into the annular groove between
cap @d and shield 82, through ports S3 to groove 69,
temperature, approximately 70 degrees Farenheit, while
through ports 7€), and between end closure member 7l and
piston '61. Piston 61 is thereby forced to the left, against
the hydraulic liuid in chamber 60. Suliicient propellant is
provided to maintain the operating pressure of 3,000
`tubular portion extending therefrom towards said second
end closure; a solid propellant stick substantially filling
said lining means and positioned for ignition by said com
pounds per square inch behind piston 61 until all of the
bustion initiating means to produce gas by end-burning
lluid has been exhausted from chamber 60, and shoulder
at the end nearest thereto; and means including said lining
62 is seated in groove 30. Thus, hydraulic fluid is forced
means providing a passage for gas between said end clo
into groove 30, and through fluid line 31, and from there
out of port 33 to the operated device. "the propellant is
4. In a pyrotechnic accumulator, in combination: a tir
sized to burn in approximately five seconds, but when
ing chamber adapted to receive an elongated propellant
hydraulic fluid is not being used, pressure will remain at 10 stick and comprising an open end, a closed end, and an
the operating value of 3,000 pounds per square inch for
elongated barrel having gas conducting channel means
an additional one to two seconds before the temperature
outwardly therethrough near said open end; gas
of the gas drops to a value below that required for main
pressure regulating means in said closed end; an end clo
tenance of operating pressure.
for said open end including inwardly acting combus
There is considerable di?liculty in predicting the precise 15 sure
means; a first, heat insulating liner within
burning rate of the solid propellant, and even greater dif
said barrel including end portions apertured for coopera~
ficulty in anticipating the rate at which hydraulic fluid will
tion with said pressure regulating means and said combus
be used, and it therefore becomes necessary to provide la
tion initiating means, and a tubular intermediate portion
pressure relief mechanism to prevent a build-up of pres
apertured for cooperation with said channel means; and a
sure that could possibly destroy the overall device. Thus, 20 second liner having internal dimensions substantially the
when pressure builds up due to the burning of propellant
same as the external dimensions of said propellant stick,
stick 53, some of the gases ilow from the annular space
said liners being formed to cooperate for providing passage
between elements 82 and 84, into longitudinal grooves 56,
means for gas from end to end of said chamber, said pas
between spacer :31 and insulator Washer 50, through
sage means communicating with the apertures in said first
Washer 50 and sleeve 4d, and against the right hand face 25 liner.
of spool 45, as viewed in FIGURE 1. When the pressure
5. In a pyrotechnic accumulator, in combination: a
on spool 45, which is equal to the hydraulic pressure in
tiring chamber adapted to receive an elongated propellant
chamber 6i), exceeds the predetermined maximum setting
stick and comprising an open end, a closed end, and an
of the valve, spool 45 moves to the left. This permits gas
elongated barrel having gas conducting channel means
to new through ports 42 `and 43, and from there through 30 passing outwardly therethrough near said open end; gas
ports 14 and 12 to be exhausted from the device.
pressure regulating means in said closed end; an end clo
What has been described is considered to be the pre
sure for said open end including inwardly acting combus
Íerred embodiment of my invention. However, it should
tion-initiating means; lining means within said barrel hav
be understood that various changes and modifications
ing internal dimensions substantially the same as the ex
thereof may be made without departing from the spirit and 35 ternal dimensions oi said stick, and external dimensions
`scope or" the invention, as defined in the appended claims.
substantially the same as the internal dimensions of said
What is claimed is:
barrel; and passage means defined by said lining means
1. in combination: =a propellant stick including an elon
for conducting gas between the ends of said chamber, said
gated charge of pyroteuhnical material, a housing therefor
passage means communicating with the apertures in said
of heat insulating material open at one end, and combus 40 first liner.
tion inhibiting bonding means joining said charge to said
6. In a pyrotechnic accumulator, in combination: a
housing in flexible, air tight relation to prevent lany com
firing chamber adapted to receive an elongated propellant
bustion of said charge except end-burning at the end there
rstick and comprising an open end, a closed end, and an
of nearest the open end >of said housing; an elongated fir
elongated barrel; gas pressure regulating means in said
ying chamber, having a body and end closures, for receiv 45 closed end; end closure for said opening end including in
ing said stick; gas pressure regulating means associated
wardly acting combustion initiating means; a first, heat
with one of said end closures; ignition means associated
with the other of said end closures, adjacent to the end of
insulating liner within said barrel including end portions,
open ends and a wall with gas conducting channel means
to end of said chamber.
apertured for cooperation with said pressure regulating
said stick at which said end-burning is to take place; and
means and said combustion initiating means, and a tubular
sleeve means between said stick and the body of said 50 intermediate portion; `and a second liner having internal
chamber and formed to provide passage for gas between
dimensions substantially the same as the external dimen
the ends of said chamber.
sions of said propellant stick, said liner being formed to
2. In combination: an elongated firing chamber having
cooperate for providing passage means for gas from end
passing laterally therethrough; a first end closure for said 55
chamber including gas pressure regulating means; a second
end closure for said chamber including inwardly directed
combustion initiating means; chamber lining means in
oluding an end portion next to said first end closure and
a tubular portion extending therefrom towards said second 60
end closure and having lateral passage means extending
therethrough and positioned for alignment with said chan
nel means in said chamber; a solid propellant stick sub
stantially filling said lining means and positioned for igni
tion by said combustion initiating means to produce gas 65
by end-burning at the end nearest thereto; `and means in
cluding said lining means providing a passage for gas be»
tween said end closures.
3. In combination: an elongated firing chamber having
a wall and open ends; a ñrst end closure for said chamber 70
including gas pressure regulating means; a second end
end closure for said chamber including inwardly directed
combustion initiating means; chamber lining means in
cluding an end portion next to said first end closure and a 75
References Cited in the file of this patent
Lansing _____________ __ Nov. 14,
Lansing _____________ __ Apr. 18,
Crutchfield et al ________ __ Ian. 30,
Goddard ______________ __ Mar. 6,
Nardone _____________ __ Dec. 9,
Roy _________________ __ Mar. 9,
Ramberg _____________ __ May 1,
Thomann et al. __________ ._ Ian. 7,
Dennis ______________ _.. Dec. 23,
Fox ________________ __ Mar. 17,
Rabern et al ___________ __ lune 28,
Kimmel et al. _________ _.. Sept. 20,
Kobbeman ___________ __ Oct. 25,
Rice _________________ __ Apr. 4, 1961
Alden _______________ __ June 27, 1961
Cohen _______________ _.. Iuly 4, 1961
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