US 2921521 A
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Jan. 19, 1960 Filed April 25, 1958 2 Sheets-Sheet 1 INVENTORS FRANK LA HAYE DOUGLAS uoRDAHL ATTORN YS Jan. 19, 1 960 F, LA HAYE ETAL GAS GENERATOR ASSEMBLY Filed April 25, 1958 2 Sheets-Sheet 2 INVENTORS FRANK LA HAYE DOUGLAS D.ORDAHL ATT NEYS GAS GENERATOR ASSEMBLY Frank La Haye, Hollister, and Douglas D. Ordahl, China Lake, Calif., assiguors, by mesne asignments, to the United States of America as represented by the Secretary of the Navy Application April 25, 1958, Serial No. 731,065
i 1 Claim. (Cl. 102-39) This invention relates to a unitized gas generator which incorporates into a hermetically sealed unit a solid propellant grain, an igniter, electrical-pressure leads, and a diierential gas exhaust system. The gas generator cousists of a canister open at one end and a header assembly which covers the open end of the canister. The canister is filled with solid, readily burnable material; the header has a gas outlet which is covered by a seal which will rupture when the pressure inside reaches a predetermined value. The header also has an annular skirt wh-ich extends into the canister and an igniter for igniting the solid material in the canister.
An object of the invention is to provide a new and improved gas generator which is hermetically sealed and has a diierential gas exhaust system.
Another object of the invention is to provide a unitized gas generator which incorporates into a sealed unit the propellant grain, igniter, electrical leads and a differential exhaust system.
A further object of the invention is to provide a unitized and sealed igniter containing a positively located primer of a controlled volume and an igniter pellet of controlled size, density, heat release and location.
VA still further object of the invention is to provide an hermetically sealed unitized gas generator.
Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Fig. 1 is a longitudinal cross-sectional view of a preferred embodiment of the gas generator assembly of the present invention;
Fig. 2 is a longitudinal cross-sectional view of another embodiment of the gas generator assembly;
Fig. 3 is a cross-sectional view of the header assembly of the gas generator taken along the line 3-3 of Fig. 1;
Fig. 4 is a cross-sectional view of the gas generator assembly taken along the line 4-4 of Fig. l and showing the slotted end of the solid propellant grain.
Referring now to the drawings, like numerals refer to like parts in each of the iigures.
The unitized gas generator of the present invention consists of a canister 10 open at one end, and contains a solid propellant grain 12 which may be coated with an inhibitor 13. The closed bottom end of canister10 may be provided with a tolerance adjustment dimple 14 which can yield to compensate for ltolerance build-up in the gas generator. This tolerance take-up device is shown in Fig. 1. Solid propellant grain 12 may be provided with slots 16, as shown in Figs. 1, 2 and 4, to allow it to be more readily ignited. The open end of canister 10 is closed and sealed with a header assembly 20. Header assembly 20 consists of a metallic head closure piece 21 of substantially the same outside diameter as canister 10. The head closure is provided wtih a first annular skirt 23 which tits into the open end of canister -10 and has an outside diameter substantially the same as the internal A2,921,521 Patented Jan. 19, 1960 ice 2 i diameter of canister '10, to assure a close t betweenthe canister and the head closure when assembled together. Skirt 23 may be chamfered at 24 to allow easy'it into the open end of canister 10. Annular skirt 23 is also proskirt 27, within annular skirt 23, for containing the igniter pellet 30, and is of substantially smaller diameter than tirst annular skirt 23. Within the second annular skirt is third annular skirt 32, within which is a cavity 33 which is deeper than the length of skirt 32, and a central aperture 34 which passes through head closure 21. An igniter contact pin 35 having a lead end 0f substantially smaller outside diameter than aperture 34 fits within a substantial portion of cavity 33 in skirt 32. The lead end of contact pin 35 passes through aperture 34 to the outer side of head closure 21; contact pin 35 is fixed in position by means of a ceramic material 37 which iills a portion of' cavity 33, insulates contact pin 3X5 from head closure 21 and hermetically seals aperture 34. Contact pin 35 is only partially covered with ceramic 37 and is recessed a substantial distance from the edge of skirt 32. Bridgewire 40 is electrically connected at its -midportion to end 38 of contact pin 35 and at its opposite ends to opposite sides of skirt 32 near the edge of the skirt. Bridgewire 40 may consist of a nickle-chromeiron alloy. The remaining space within skirt 32 is filled with a primer charge 42.
Primer charge `42 may, for example, consist of the following materials, in percentages by weight: Potassium chlorate 45.5, fuse powder 40.0, gallic acid 14.2, and gum yacca or red gum 0.3. Suiiicient binder, consisting of 50 percent lacquer and 50 percent thinner, by weight, is then mixed with the primer charge to bind it together.
Igniter pellet 30 may be in the form of a hollow cylinder 30, as shown in Fig. 1, or cup-shaped 31,v as shown in Fig. 2, and iits ywithin and iills the area within skirt '27. The igniter pellet may, for example, consist o f the following uniform mixture in percentage by weight: Po# tassium nitrate 67.8, sulfur 5.1, carbon 13.5, nitrocellulose 6.8, and dextrin 6.8.
When a hollow cylindrical shaped igniter pellet is used, an illustrated by pellet 30 in Fig. 1, a booster charge 44 ills the remaining portion of the space within the hollow cylindrical pellet not occupied by skirt 32 and primer charge 42. contact with the face of primer charge 412. Booster charge 44 consists of 100 percent black powder, for example.
Igniter pellet 30 or 31, with a booster charge 44 when l pellet of controlled size, density, heat release and location. An igniter closure 46, of aluminum foil or other suitable material, seals the igniter assembly within skirt 527. Igniter closure 46 will burn away upon ignition of the igniter assembly.
Electrical connections are made to contact pin 35 and to metal head closure 21. When a predetermined electrical current is applied to these connections a current will flow through bridgewire 40 heating the bridgewire'until primer charge 42 ignites, activating the igniter assembly, which in turn starts the solid propellant grain 12 burning. The sealed igniter assembly is positively located, as illustrated in the drawings, for eflicient and desirable heat release. Electrical connections may be made to head closure 21 and contact pin 35, as illustrated in Fig. 2, by welding a rst leadwire y50 to head closure 21 at vided with a groove 25 and a sealing ring 26 within groove Head closure 21 is provided with a second annular In this case, booster charge 44 is in direct Vthelbotton ofscavify 49 .on the outer sides of the head 1500 p.s.i. external pressure or at less than 500 p.s.i. in-
ternal pressure. This differential `seal may be obtained by distributingy the force over a differential area between thefoutside and the inside of the gasY generator header. Fig. 1 shows one such differential 'pressure seal. Head closure 21 isprovided with a cylindrical passage 55 which is of larger diameter on the inner side thereof,-forming aseat '56. A nlpturetdisc 58 ts against .seat 56 and is retained- -in place by means 'of a retaining ring 59 which hermetically seals the passage.v f t K Instead of a rupture Vdisc'5'8, head closure`21 may be provided, -as illustrated in Fig. 2, with a passage `65 having a seat ,66 Von the outer side thereof, and a blowout plug 68. The edge of blowout plug 68 fits against seat 66 and is sealingly held in place by tinning or other suit-V able means. When the internal pressure of the gas generator reaches a predetermind value the plug will be blown out.
When header assembly is fitted on to the open end of canister 10, the open end of the canister seats against circumferential seat `69 on head closure 21. Acrimp 76 is then formed in metal canister 10 so that the metal flows into groove against rubber seal ring 26 thereby hermetically sealing the canister and rigidly athxing the canister and header assembly together into a unitized gas generator assembly.
Obviously, many modifications andvariations of the present invention Aare possible in the light of the above teachings.k It is therefore to be understood that within lthe scope vof the appended claim the invention may be practiced otherwise than as specifically described.
What is claimed is:
-lA unitizedy hermetically sealed gas generator for generating .gases V.from solid propellant material, comprising; a cylindrical canister having an integral closed bottom and an open top, a cylindrical grain of solid propellant maf. 2,921,521 k f. f
` terial having an inhibitingl coating von its peripheral'sun face disposedwithinand filling .the crosssection of..said canister, an exposed end of Vthe grain, adjacent the open top of the canister, having a frusto conical radially grooved cavity therein, with exposed surfaces substantially in excess of the cross sectional area of the grain to render the grain more readilyv ignited, a circular header enclosing and hermetically sealing the open top of the canister, said vheader having a iirst cylindrical annular skirt telescopically vtting within the open end of the canister and sealingly connected thereto, Va second annular concentric skirt forming a part of said header and projecting toward the exposed end of said grain forming a lrst annular lspace between it land saidrst skirt, the exposed annular edge of said second skirt terminating in spaced relation to the exposed en'd of said grain, a third annular concentric skirt forming a part of said header and projecting toward the exposed end of said grain having a central borey and forming a second annular space between it and said second skirt, an igniter pellet filling said second annular space, a primer charge disposed within said bore, a bridge wire extending diametrically across saidthird skirt and having opposite outer ends connectedthereto, a contact pin disposed within said bore axially of said third skirt having one end connected to the center of said bridge wire, a ceramic material withinV said bore surrounding said contact pin and engaging sameforipreventing gas leakage along said bore and for preventing blow-out of said pin through said ceramic material, a rupturable closure closing communication between said first named annular space and the outside of said generator, and a diaphragm sealingly closing the annular exposed edge of said second skirt.
vReferences Cited in the file of this patent UNITED STATES PATENTS Marcus June 19,