A pressure limiting propellant activating system for simultaneously limiting the output force while maintaining a constant output pressure from the combustion chamber is described. The propellant actuated system includes an outer barrel, outer housing and a combustion chamber. A main piston is movable in the barrel housing when gas pressure is developed in the combustion chamber. A relief piston is concentrically mounted and fixedly movable with the main piston when gas pressure is exerted from the combustion. A relief piston has a force-activated separation mechanism for limiting the output force while simultaneously maintaining constant output pressure on the main piston from the combustion chamber

Murphy, D. W.

Reese, P. B.

English

NASA Technical Reports Server

United States Patent 1191 
Reese et al. 
I1 11 4,183,217 
1451 Jan. 15, 1980 
[54] PRESSURE LIMITING PROPELLANT 
[75] Inventors: Paul B. Reese, Los Angeles; David 
ACTUATING SYSTEM 
W. Murphy, Garden Grove, both of 
Calif. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[73] Assignee: The United States of America as 
[21] Appl. No.: 933,218 
[22] Filed: Aug. 4, 1978 
[51] Int. C l . 2  .............................................. FOlR 29/08 
[52] U.S. CI. ...................................................... 60/632 
[58] Field of Search .......................... 601'632, 636, 638 
1561 References Cited 
U.S. PATENT DOCUMENTS 
2,815,008 12/1957 Hirt ........................................ 60/636 
2,979,904 4/1961 Royer ..................................... 60/632 
3,031,845 5/1912 Ludwig .................................. 60/632 
3,645,091 2/1972 Ivanov et al. .......................... 60/632 
Primary Examiner-Wendell E. Burns 
Attorney, Agent, or Firm-Carl 0. McClenny; John R. 
Manning; Marvin F. Matthews 
WI ABSTRACT 
A pressure limiting propellant actuating system includes 
an outer barrel housing having a combustion chamber 
formed therein. A main piston is movable in the barrel 
housing when a pressure is developed in the combustion 
chamber. A relief piston. is concentrically mounted and 
fixedly movable with the main piston when the gas 
pressure is exerted thereon from the combustion cham- 
ber. The relief piston includes a separation mechanism 
for limiting the output force and simultaneously, main- 
taining output pressure from the combustion chamber. 
5 Claims, 3 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19800009832 2020-03-21T02:48:13+00:00Z
U.S. Patent ~m. 15,1980 Sheet 1 o f 2  4,183,2 17 
U.S. Patent ~m. 15,1980 Sheet 2 of 2 4,183,217 
-‘M- 
i 
1 
4,183,217 
2 -
PRESSURE LIMITING PROPELLANT 
ACFUATING SYSTEM 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; 45 U.S.C. 2457). 
BACKGROUND O F  THE INVENTION a main piston 22 a predetermined distance outside of the open end of the barrel 16. The exterior end of the piston 
1. Field of the Invention 22 is coupled to an output foot 24. As illustrated in FIG. 
The field of art to which the invention pertains in- 15 1 the output foot contains a curved surface 26 which 
abuts a member 28 (shown in dotted lines). The member 
28 in turn is moved as the output foot 24 moves due to 
the sliding action of the main piston 22. The second 
cludes the field of propellant actuating systems, particu- 
IarIy with respect to a non-venting pressure relief piston 
that allows equivalent thruster output force when either 
DESCRIPTION OF THE PREFERRED 
EMBODIMENTS 
Referring now to the drawings there is shown in 
FIG. 1 a pressure limiting actuation system constructed 
in accordance with principles of the invention. Propel- 
lant actuating devices are housed in first cartridge 12 
and a second cartridge (not shown in FIG. 1) at one end 
of a housing barrel 16. When the propellant actuating 
devices are fired, gas pressure in the adjacent combus- 
tion chamber 18 of the housing barrel is utifized to move 
of a plurality of pressure cartridges are fired. 
2. Description of the Prior Art 
In conventional pyrotechnic thruster designs, redun- 
dant design requires that dual cartridges be utilized. 
However, the firing of a single cartridge must accom- 
plish the intended function. When a dual firing occurs, 
which normally would produce double the normal re- 
quired thruster output force, this additional force is 
normally absorbed by the mechanism being actuated. 
However, where the pressure exerted by the thruster on 
the mechanism must be within a specified range, and the 
pressure must be maintained on the mechanism subse- 
quent to actuation, conventional techniques such as 
venting of excess pressure cannot be utilized since the 
thruster force must be maintained on the mechanism by 
the gas pressure developed by the thruster. 
Known prior act includes U.S. Pat. Nos. 3,656,296; 
3,557,550; 3,484,846; 3,112,670; 3,03 1,845; and 
3,024,749. 
SUMMARY OF THE INVENTION 
The present invention provides a propellant actuating 
system including an outer barrel outer housing having a 
combustion chamber formed therein. A main piston is 
movable in the barrel housing when gas pressure is 
developed in the combustion chamber. A relief piston is 
concentrically mounted and fmedly movable with the 
main piston when the gas pressure is exerted thereon 
from the combustion chamber. The relief piston has a 
separation mechanism for limiting the output force and 
simultaneously maintaining the output pressure on the 
main piston from the combustion chamber. 
The advantages of this invention, both as to its con- 
struction and mode of operation, will be readily appre- 
ciated as the same becomes better understood by refer- 
ence to the following detailed description when consid- 
ered in connection with the accompanying drawings in 
which like reference numerals designate like parts 
throughout the Figures. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a longitudinal sectional view of the actuat- 
ing system prior to firing of a pyrotechnic device. 
FIG. 2 is a cross sectional view of the device of FIG. 
1 where one of the pyrotechnic devices have been fired; 
and 
FIG. 3 is a cross sectional where both of the pyro- 
technic devices have been fired. 
cartridge is identical to and is positioned directly behind 
The present invention utilizes dual cartridges which 
are redundant, the firing of a single cartridge accom- 
plishing the intended function of moving the main pis- 
ton 22, and hence, member 28 a desired distance. In 
25 conventional prior art redundant designs, the excess 
pressure generated by the additional propellant actuat- 
ing device can normally be bled off. However, in the 
present application it is necessary that the member 28 be 
retained in a predetermined position by the output foot 
30 24 once the propellant actuating devices have been 
fired. Therefore, gas pressure bleeding techniques can- 
not be utilized. 
Referring now to FIG. 1 in greater detail, the housing 
barrel 16 contains a first fued mounting lug 32 at the 
35 housing barrel closed end 34 adjacent combustion 
chamber 18. The other end 36 of the housing barrel 16 
is open enabling slidable movement of the main piston 
22 therefrom. The barrel open end 36 contains an en- 
larged diameter threaded bore portion 38 which termi- 
40 nates at a shoulder 42 facing the barrel open end. A 
reduced diameter bore 44 extends from the shoulder 42 
to the barrel closed end 34. The portion of the reduced 
diameter bore 44 adjacent the closed end defines the 
combustion chamber 18. A second fmed mounting lug 
45 46 extends from the outer surface of the housing barrel 
16 adjacent the enlarged diameter threaded bore 38. 
Additional mounting lugs, of course, could be secured 
to the housing barrel 16, if necessary. 
The main piston 22 is formed of a cylindrical sleeve 
50 48 having an outer diameter slightly less than the barrel 
reduced diameter bore 44. The main piston cylindrical 
sleeve 48 as an end wall 52 at its portion extending 
beyond the barrel open end 36. A flange 54 extends 
from the end wall and is utilized to secure the main 
The other end of the main piston terminates in an 
outwardly turned flange 48 whose outer edge 62 diame- 
ter is approximately equal to the diameter of the hous- 
ing barrel 16 reduced diameter bore 44. A groove 64 
60 formed in the flange edge 62 has an O-ring 66 positioned 
therein which forms a dyamic seal for preventing gas 
leakage from the combustion chamber 18 to the atmo- 
sphere. A longitudinally extending slot 68 is formed on 
the outer surface of the the main piston cylindrical 
65 sleeve and extends from the flange 58 to a shoulder 72 
adjacent the piston end wall 52. When the main piston 
22 is loaded into the housing barrel 16, a retaining sleeve 
74 is threadably secured in the barrel enlarged diameter 
20 the first cartridge 12, when viewed in FIG. 1. 
55 piston 22 to the output foot 24 by means of a bolt 56. 
4,183,217 
3 4 
bore 38. The retaining sleeve 74 contains an anti-rota- wall 96. The honeycomb acts as a attenuator SO that 
tion pin 76 which is slidably movable in the main piston when the relief piston 92 fractures, it will not hit the 
slot 68 and prevents rotation of the main piston 22. main piston end wall 52 with such force as to damage 
A groove 78 is formed in the main piston outer sur- the output foot 24 or the member 28. It should be noted 
face intermediate the piston end wall 52 and the slot 5 that when the relief piston 92 fractures, the volume 
shoulder 72. An O-ring environmental seal 82 is posi- adjacent the combustion chamber 18 is increased suffi- 
tioned in the piston groove 78 which is adjacent the ciently so that additional volume is provided for gas 
retaining sleeve 74 in the initial position of FIG. 1. expansion in the combustion chamber. 
To maintain the relief pressure necessary when both FIG. 2 illustrates the movement of the main piston 
actuating devices fire, a relief piston 92 is positioned in 10 and the relief piston when only a single actuating device 
the main piston 22 adjacent to the combustion chamber has fired. In such an instance the relief piston 92 remains 
18. The relief piston 92 is formed of a cylindrical sleeve intact and the main piston 22 is forced out of the barrel 
94 whose outer diameter is slightly less than the inner 16 until the main piston flange 54 abuts the retaining 
diameter of the main piston. The relief piston sleeve 94 sleeve 74. FIG. 3 illustrates the fracturing of the relief 
is substantially shorter than the main piston sleeve 48 15 piston 92, forming an additional volume and, thus, re- 
and is positioned therein adjacent the combustion cham- lieving pressure adjacent the combustion chamber 18, as 
ber. The cylindrical sleeve 94 contains an end wall 96 at when both pyrotechnic devices fire. It should be noted 
its end communicating with the interior of the main that the honeycomb 114 is crushed intermediate the 
piston sleeve 48 and is open adjacent the combustion relief piston end wall 96 and the main piston end wall 
chamber 18. An outwardly extending flange 98 is 20 52. However, the main piston 22 has travelled the same 
formed at the open end of the relief piston cylindrical distance as the main piston flange 58 abuts the retaining 
sleeve 94 and extends to the interior surface of the bar- sleeve 74. 
re1 reduced diameter bore 44. The relief piston flange 98 We claim: 
abuts the main piston flange 58 on one side thereof and 1. A pressure limiting propellant actuating system 
has a reduced thickness portion 102 formed on the other 25 comprising; 
side thereof adjacent the combustion chamber. The an outer barrel housing having a combustion chamber 
portion 102 enables a compression spring 104 to be therein; 
positioned in the combustion chamber intermediate the a main piston movable in said barrel housing when 
barrel interior end 34 and portion 102. When the main gas pressure is developed in said combustion cham- 
piston 22 moves due to the gas pressure in the combus- 30 ber; 
tion chamber, the compression spring 104 provides a a relief piston concentrically mounted and fixedly 
force sufficient that the main piston 34 moves the de- movable with said main piston when said gas pres- 
sired distance out of the housing barrel 16. In this regard sure is exerted thereon from said combustion cham- 
it should be noted that the retaining sleeve 74 forms a ber, said relief piston having separation means for 
stop for the main piston flange 58 along the plane of the 35 limiting the output force and, simultaneously, 
barrel shoulder 42. maintaining a predetermined gas pressure from said 
A plurality of gas ports 106 are formed in the relief combustion chamber. 
piston cylindrical sleeve 94 and extends from the inte- 2. A pressure limiting propellant actuating system in 
rior of the sleeve to adjacent the interior surface of the accordance with claim 1 wherein said separation means 
main piston sleeve 48 and flange 54. The gas ports 106 40 enables a portion of relief piston to move with respect to 
enable a predetermined amount of gas to leak in the said main piston for increasing the volume of the cavity 
surface area intermediate the outer surface of the relief formed between main piston and said combustion cham- 
piston sleeve 94 and the inner surface of the main piston ber. 
sleeve 48. A groove 108 formed on the outer surface of 3. A pressure limiting propellant actuating system in 
the sleeve piston sleeve 94 contains an O-ring 112 45 accordance with claim 2 wherein means are provided 
therein. The dimensions of the groove 108 are chosen for impeding the travel of said relief piston portion 
such that when gas pressure leaks through the ports 106, within said main piston for controlling the rate of gas 
the relief piston 92 fractures along the groove 108 plane expansion in said cavity. 
at a predetermined pressure which is exceeded only 4. A pressure limiting propellant actuating system in 
when both actuating devices contained in the cartridges 50 accordance with claim 3 wherein said impeding means 
fire. Fracturing of the relief piston 92 along the plane of includes a honeycomb. 
groove 108 causes separation of the end wall 96 and the 5. A pressure limiting propellant actuating system in 
adjacent portion of the sleeve 94. The gas pressure then accordance with claim 3 wherein said separation in- 
forces this portion of the relief piston 92 towards the cludes gas ports formed in said relief piston for enabling 
main piston end wall 52. A crushable honeycomb is 55 gas in said gas chamber to exert a pressure on a groove 
positioned in the area of the main piston intermediate formed on said relief piston. 
the main piston end wall 52 and the relief piston end * * * * *  
60 
65 


Pressure limiting propellant actuating system

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