US2685837A

US2685837A - Igniter

Info

Publication number: US2685837A
Application number: US481653A
Authority: US
Inventors: Bruce H Sage; Mcmorris John; Glen W Miller
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1943-04-02
Filing date: 1943-04-02
Publication date: 1954-08-10
Anticipated expiration: 1971-08-10

Description

Allg. 10, 1954 B. H. SAGE ETAL IGNITER 2 Sheets-Sheet l Filed April 2, 1943 FIG. l.

INVENTORS ,/0 25 26a/was H. SAGE GLENN MILLER Aug. l0, 1954 B, H. SAGE: ETAL IGNITER 2 Sheets-Sheet 2 Filed April 2, 1945 FIG. 4.

Patented Aug. 10, 1954 UNITED STATES PATENT OFFICE IGNITER Application April 2, 1943, Serial No. 481,653

8 Claims. 1

This invention relates to igniters and more particularly to a novel igniter for powder grains, and the like, which comprises a casing containing an electrically operable squib and an auxiliary charge adapted to be fired by the squib. The new igniter may be made in a simple and compact form and is positive and reliable in operation.

The igniter of our invention may be employed for various purposes but may be used to particular advantage for ignting the powder grain in a rocket motor. It has been proposed heretofore to propel a rocket motor by means of a single grain of powder mounted in the motor body so that the grain burns simultaneously on its external surface and on an internal surface formed by an axial passage in the grain, as disclosed in a copending application of C. C. Lauritsen, Ser. No. 481,644, filed April 2, 1943, now Patent No. 2,464,181. In such rockets, it is desirable to ignite the powder by an igniter at one end of the grain, whereby the blast from the igniter is communicated simultaneously to the internal and external surfaces of the grain.

One object of the present invention, therefore, resides in the provision of a novel igniter for use in motors of the type described, which occupies a relatively small space in the motor body and directs a blast instantaneously in a form suitable for igniting the internal and external surfaces of the grain simultaneously. An igniter made in accordance with my invention comprises a casing for receiving an electrically operable squib, and an auxiliary powder charge compressed in the casing adjacent the squib. The auxiliary charge is preferably in the form of flash powder or black powder, or both, and is arranged to fracture the casing, when fired by the squib, and provide a blast which is directed both radially and endwise with respect to the powder grain.

Another object of the invention is to provide an igniter in which the casing has a hollow boss for receiving the squib and adapted to t into the axial passage in the grain. In the preferred construction, the boss has longitudinal, external ribs for strengthening it, and the main body of the casing contains the auxiliary charge and is provided with means for spacing the main body from the end of the powder grain to form an annular chamber in the motor through which the blast is communicated to the external surface of the grain.

Still another object of the invention is to provide a novel igniter including a generally cupshaped casing for receiving the squib and auxili- Cl. M12-70.2)

ary charge, and a closure member for use in compressing the charge in the casing against the squib and which is automatically locked in position upon release of the compressing force.

These and other objects of the invention may be better understood by reference to the accompanying drawings, in which Fig. 1 is a longitudinal sectional View of one form of the new igniter;

Fig. 2 is a rear end View of the igniter shown in Fig. 1;

Fig. 3 is a longitudinal sectional view of part of a rocket motor embodying the igniter;

Figs. 4 and 5 are sectional and end views, respectively, of a modified form of the igniter;

Fig. 6 is a front end View of still another form of the igniter, and

Fig. 7 is a sectional View on the line 'I-I in Fig. 6.

Referring to the drawings, the igniter shown in Figs. 1 and 2 comprises a casing having a main body portion Il) containing a charge of black powder II. The body Iii, as shown, is generally cup-shaped in form and may be spun from a sheet of metal. The black powder II is compressed inthe main body by a closure disc I2 around which the edges of the body II) are crimped, as shown at Ila. It will be noted the tighter the crimping is done, the more compressed the black powder will become. In its central portion, the disc I2 is provided with a hollow boss I3 extending outwardly from the disc, the disc and boss being preferably molded from a plastic material, such as cellulose acetate.

An electrically operable squib I4 fits closely in the outer end of the boss I3, and the latter has an opening through which wires I5 extend from the squib for conducting current thereto. The inner end portion of the boss I3 contains a charge of flash powder IS which is compressed in the boss against the squib I4, and a disc I1 may be placed over the inner end of the boss to separate the powder charges Ii and I6. The boss I 3 is provided with longitudinal reenforcing ribs I8 on its external surface, the ribs I8 merging with ribs I9 integral with the closure disc I2 and extending radially from the boss.

The igniter is adapted for use in a rocket motor (Fig. 3) comprising a hollow cylindrical body 2i which is internally threaded at its front end, as shown at 2Ia, for connection to a suitable pay load (not shown). Within the motor body is a cylindrical powder grain 22, which may be made of ballistite, having an axial passage 23. On its outer cylindrical surface, the grain 22 is provided with spaced longitudinal ribs 22a which t closely against the inner wall of the motor body, the ribs 22a serving to support the powder grain in the body 2| with a substantial clearance between the external surface of the grain and the inner wall of the body. Accordingly, the grain has an internal combustion surface, dening the passage 23, and an external combustion surface between the ribs 22a, whereby the grain is adapted to burn simultaneously on both surfaces. Preferably, the grain is formed with radial passages 24 spaced along its length, as disclosed in the above-mentioned application of C. C. Lauritsen, Ser. No. 481,644.

Near its front end, the motor body 2i has a closure disc which may be secured in the body by a sealing compound 25. The disc 25 is spaced from the adjacent end of the powder grain to provide a chamber for receiving the igniter casing I6. As shown, the igniter is mounted at the front end of the powder grain with the hollow boss I3 projecting into the axial passage 23 in the grain and with the wires I5 extending through the passage to a suitable current source (not shown). In this position of the igniter, the radial ribs 2S serve to space the main body of the igniter from the front end of the powder grain and thereby form an annular chamber around the base of the boss I3. The main body I0 is substantially smaller in diameter than the interior of the motor body so as to provide an annular chamber around the body I 0. It will be apparent that the annular chamber around the igniter body I0 and around the base of the boss I3 communicates with the external combustion surfaces between the grain ribs 22a and also communicates through the spaces between the ribs I8 and I9 with the axial passage 23 in the grain. As a result, when the squib I4 is energized, it fires the black powder I I through the ash powder I6, and the resulting blast shatters the igniter casing and is communicated into the grain passage 23 and into the external combustion spaces between the grain ribs 22a. The igniter ribs I8 and I8 serve the dual function of strengthening the hollow boss I3 and directing the blast toward the combustion surfaces on the powder grain.

The igniter shown in Figs. 4 and 5 comprises an electrically operable squib 28 which is seated at one end in a charge of flash powder 2S. The squib and the ash powder, in turn, are embedded in a charge of black powder 30 compressed in a generally cylindrical casing 3|, the squib and powder charges being sealed in the casing by a closure member 32 around which the edges of the container are crimped, as shown at Bla. In the central portion of the closure disc is an opening through which wires 33 extend to the squib for energizing the same.

In the use of the igniter shown in Figs. 4 and 5, the casing 3I is mounted at one end of the powder grain with the wires 33 extending through the axial passage 23 to the current source (not shown). When the squib 23 is energized, it res the flash powder 29 which, in turn, res the black powder 30, the latter producing a blast which is communicated to the internal and external combusticn surfaces on the powder grain. Preferably, the powder charges 28 and 30 are compressed in the casing 3l to a substantial pressure by the closure disc 32.

A mcdied form of the igniter casing is illustrated in Figs. 6 and '7. As there shown, the casing comprises a generally cup-shaped body 35,

the inner wall of which flares outwardly toward the open end of the body, as shown at 36. Preferably, the body is provided on its outer surface with longitudinal reenforcing ribs 31 merging with transverse ribs 31a on the closed end of the body. The body 35 with its external ribs may be molded from a suitable plastic material and is adapted to receive an electrical squib and an auxiliary powder charge similar to those shown in Figs. 2 and 4. In its closed end, the body 35 is formed with a passage 38 through which wiring may extend to the squib.

In assembling the igniter parts in the casing 35, the parts are placed in the casing and the auxiliary powder charge is compressed by forcing a closure disc 39 into the casing. The disc 39 is flexible and may be made of bre, or the like. When the powder charge has been sufficiently compressed by pressing inwardly on the central portion of the disc 39, the pressure on the disc is released and the latter snaps outwardly at `its central portion and is locked by the wedging action of the ared surface 36. The powder charge is thus maintained under adequate pressure in the igniter casing, and the casing is sealed by the disc 39.

While we have described and illustrated three forms of the new igniter, it will be understood that they invention is not limited to these forms but is susceptible of various modifications within its scope. All oi the illustreated forms of the igniter afford the advantage of providing a uniform, reproducible action because of their accurately controlled geometrical arrangement, in contrast to the prior forms of igniters employing cloth bags for the igniting charge.

If desired, a suitable substance, such as cement or wax, may be used to hold the squb in position and to seal the wires. While the external ribs on the boss I3 (Fig. 1) increase the strength of the igniter, it will be understood that they serve primarily to support the igniter on the powder grain 22.

We claim:

l. An igniter for powder grains, which comprises a casing having a main body portion and a hollow boss on the body, means on the boss for spacing it from the grain, a squib in the boss, and an auxiliary powder charge compressed in the main body and ignitible by the squib.

2. An igniter for powder grains, which comprises a casing having a main body portion and a hollow boss on the body, ribs on the body extending radially from the boss for strengthening the boss and spacing the body from the powder grain, a squib in the boss, and an auxiliary powder charge compressed in the body and ignitible by the squib.

3. An igniter for powder grains, which comprises a casing having main and closure sections, a hollow boss on the closure section, a squib in the outer end portion of the boss, a charge of black powder in the main section, and a charge of flash powder in the boss between the squib and said first charge, the edges of the main section being crimped over the closure section to compress the charges.

4. An igniter for powder grains, which comprises a casing having a main body portion and a hollow boss on the body, radial ribs on the boss and the body, a squib in the boss, and an auxiliary powder charge compressed in the body and ignitible by the squib.

5. In combination, an igniter for a powder grain comprising a casing adapted to receive a squib and an auxiliary powder charge, the casing being generally cup-shaped with its inner wall aring outwardly near the open end of the casing, longitudinal ribs on the casing to separate it from the powder grain, and a flexible closure member fitted closely in said flared portion for compressing the auxiliary charge when flexed and being locked in the casing when returned to normal shape.

6. An igniter for a powder grain comprising a casing having a main body portion and a hollow boss on the body extensible into an axial passage of a powder grain, spacing means on the main body abuttable with one end of the grain to space said body from the grain, a squib located in the boss so as to come within the confines of the powder grain, and an auxiliary powder charge in said main body but distanced from said grain end because of the spacing means and ignitible by the squib.

7. An igniter for powder grains comprising a body section, a boss section, a closure separating said sections, an electric squib in the boss section, a ash powder in the boss section ignitible by the References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,313,801 Doran Aug. 19, 1919 1,360,602 Van Deuren Nov. 30, 1920 2,150,374 Johnson Mar. 14, 1939 FOREIGN PATENTS Number Country Date 24,270 Great Britain of 1906