US2462305A

US2462305A - Explosive device

Info

Publication number: US2462305A
Application number: US564748A
Authority: US
Inventors: John P Catlin
Original assignee: Remington Arms Co LLC
Current assignee: Remington Arms Co LLC
Priority date: 1944-11-23
Filing date: 1944-11-23
Publication date: 1949-02-22
Anticipated expiration: 1966-02-22

Description

Feb. 22, 1949." J. P. CATLIN 2,462,305

EXPLOSIVE DEVICE Filed Nov. 23, 194

INVENTOR. n Catlin.

Patented Feb. 22, 1949 UETE 2,462,305 EXPLOSIVE DEVICE Application November 23, 1944, Serial No. 564,748

2 Claims.

This invention relates to torpedo igniters of the general type shown in the patent to Moore, No. 1,935,126, November 14, 1933, and has for its object the improvement of the igniter shown in saidpatent, with a view to overcoming certain defects and inadequacies which have been found to be inherent in the patented construction.

The torpedo igniter may be described as a device for insertion in the wall of the combustion pot of a torpedo for the purpose of igniting the liquid fuel and air mixture which begins to be injected into the combustion pot at the time the torpedo is launched and which builds up considerable pressure in the pot before the igniter is fired. At least two factors are known to affect the ignition of the fuel and air mixture adversely, and hence to render the operation of the torpedo uncertain. The launching of torpedoes, particularly from the air, may impose repeated severe shocks and strains thereon. The torpedo may be dropped a distance of several feet through the air onto the surface of water while it is moving forward with considerable velocity. There is a substantial impact when the torpedo first strikes the water, and the torpedo may thereafter repeatedly skip, producing additional severe shocks. On initial impact with the water, a suitable trigger or trip lever of the torpedo is actuated to initiate firing of the igniter. If the firing mechanism is complicated or improperly designed, the force of this initial impact may disable or otherwise render the firing mechanism inoperative. Or the flame of combustion which may have been initiated in the combustion pot by a properly operating igniter may be extinguished by the shock of such impacts. Secondly, the torpedo igniter is adapted to deliver its flame directly into the combustion chamber or pot in which considerable air pressure has been already built up as hereinafter described. The igniter is provided with a seal to protect its firing device from this pressure prior to ignition, but,if this seal has been rendered defective through gassing, that is to say, the development of gas pressure within the igniter itself due to decomposition of the igniter mixtures over long periods of storage or because of pin point leaks or punctures, then the air pressure within the combustion chamberwill act against the firing device before ignition has been initiated, and hence interfere or prevent the operation of the igniter.

It is necessary, therefore, for successful operation that the firing mechanism of an igniter be designed to operate positively eve-n though subiected to severe impact forces and that an igniter furnish a flame which will not .be extinguished by shock and will continue to burn continuously for a time of the order of one minute to insure continuance of the combustion necessary to propulsion of the torpedo; and that the operation of the igniter shall be made certain by positively sealing its firing device against back pressure from the combustion pot.

In the drawing:

Fig. 1 is a sectional side elevation of the improved torpedo igniter embodying the present invention. 5

Fig. 2 is a transverse section on line 22 of Fig. 1.

Referring to the drawing, the igniter embodying this invention comprises a cylindrical body indicated generally at it! having an extension II of reduced diameter provided with exterior screw threads l2 by which the igniter may be threadedly secured in the wall of the combustion chamber of a torpedo as described fully in the aforementioned Moore patent. The upper end of the igniter has a head l3 of greater diameter than the body In and is provided with internal threads M for securing a plug l5 in the open end of the head, the base 16 of the plug beingthreaded externally as at H f-or'this-purpose. A nipple l8 extends upwardly from the plug and is threaded externally to provide means for securing a fitting thereto for connecting the igniter to a compressed air line. A set screw i9 is shown for locking the plug 15 in the head 13 of the igniter.

The plug I5 is adapted to secure a pressure responsive device such as the diaphragm 20 in the open end of the head I3. The diaphragm is preferably formed of cartridge brass and annealed to a dead soft condition. Since the life of the diaphragm is only one cycle, it is possible to use working stresses well over the yield point of the metal and thus to securerelatively large movement of, the diaphragm. Moreover, the specific'contour of the diaphragmf-shown also provides. for.reIatiVeIylarge movement for the purpose hereinafter described r The periphery 21 of the outer edge, 22" of'the diaphragm is bent atsubstantially right-angles,

as shown, andcircumscribes theperiphery of a Washer 23 which in the present embodiment comprises soft annealed copper. The latter seats on an internal shoulderZ L of the head ,l3 and is adapted to supportthe outer edge 22 of the diaphragm. A second washer comprising a fiber insulating material isshown at 25'seated" on the top surface of the outer edge 22 of the diaphragm. By screwing the plug l5 down into the head [3,

ignition tube hereinafter described. The upper surface of the bridge 2! is provided with a central boss 29 concentric with the aperture 28. The boss is adapted to support a shear die 39 =whichi-comprises a disk having a central a'perture 31 anda concentric counterbore 32 in its top surface. Thecentral aperture 3| is flared-slightly at its-lower.

end, as shown, so as to provide angular clearance to prevent any binding between thewall's-"of'the aperture and a striker or firing pin 33 which passes through theapertureand'which is supportedth'erein by a shear 'pin 34; The angular clearance of" the dieaperture also obviatesany frictional drag which might otherwise occur-as the-- severedf portion' of the shear pin passes through the die aperture.

Asshown; the'shear pin'34 passes through a transverse hole 35 of the-firing pin, the opposite ends of the shear pin extending substantially equal distan'ce's on opposite sides of'the firing pin 33' and'being supported 0n the bottom of the counterbore 32. By this construction, the shear pin is"locatedsubstantially' centrally with respect to the diaphragm 2B and firing pin 33.

Thefiring pin is provided witha thrust disk 36 whi-ch is shown secured-to the upper end of thefiring pin and' concentric with its longitudinal axis by a rivet 31' or 'othersimilarfastening means; The firing pinis adapted to be supported within-theigniter by the aforedescribed means SO-T'thilt the thrust disk 36is'in direct and positiveengageinent with the underside'of the-dia-phragm whenthe latter is" in its normal or: unstresse'dposition, the longitudinal axis of the ofthediaphragm, the latter corresponding to the point of'maximum' displacement thereof. The firing pin comprises a substantially cylindrical sterrr, the lower end of which is provided'with aitapered point'38 having a roundedapex. For optimum performance, thepoint 38 is heat treated for hardness.

Theshank'of the firing pin isguided by and' has a smooth sliding fitin the cylindrical bore 39"ofr'an ignition tube. which is rigidly fastened in.'tlie lgniter by threadedly securing the. upper end'of-theltube in the aperture 280i the bridge 292 The threaded'fconnection between the ignition tube" ,39fand'. bridge 29' is" sealed: by means Of a gasketfirwhich may be: copper or. other suitable materialfithe. gasket being,compressedltighfly be tiveennthunderside; of the; bridge-'29 and a shoulder 431 of the ignition .tube Aflfwhenthe; latter is, screwed .-lup intothe;v aperture: oft-he bridge. 'Ifli'e..ignitij tube-.isnonuniform. inlcross; section, its.oi1ter-. '-surface beingprovided with a. series of annular. shoulders 44. whichar-e adapted to pro.- vide means for preventing an ignition. mixture 45.-from. being displaced longitudinally within the igniter. Moreover, the. overall diameter of the shank. of; the ignition tube isless than the diame-ter'of the-aforesaid shoulder. 43 so thatthe opposite side of; the shoulder presents. apressure surface 43 Thus, in; the event gas develops in 4 the igniter due to leakage or powder decomposition, it will act against the pressure surface 43 of the ignition tube and tighten the gasket 42 against'its seat.

The ignition mixture or main burning charge s5 is a composition comprising substantially 18% potassium perchlorate, 47% barium nitrate, 22% powdered shellac; 6% wood-rflour-and,7% hexachloral benzine, and is tightly packed in the annular space between the smooth cylindrical inner walls 66 of the body ifi and extension H of the igniteri and the outershouldered surface of the ignition tube 40. The specific ignition mixture describedhas' along-burning time and liberates sumcient heattoignite the fuel in the combustion chamber of thetorped o with certainty.

The lower end of the bore 39 of the ignition tube 46 is reduced in diameter to provide an annular restriction 41, an annular shoulder 48 and a relatively short axial flash passage 69 which terminates in aclosed end 50 short of theend or the ignition tube 68. The. shoulder 48.. is adaptedto support a percussionprimer 52which has a. relatively tight fitin the restriction, 41 of the bore- 39 so asto be heldfirmly; on L'the shoulder. 38. The-flash passage'49j isintersected adjacent its lower end bya transverse passage whieh'isformed through the lower end ot the tube-coaxial .with a diameter thereof andat right angles totheiflash passage 49;

The transversepassage 53=is sealed at-its outer endsby means of a: cap 54- which comprises-a relatively thin extruded or drawn zine cup dimensioned to makeasnug fit: over the lower. end of theignitiontube 4e. The length' ofthe cup is such that'its lip 54' isadapted toabutthe lowest shoulder 44 of the ignition tubewhile the closed end of the cup fits closelyover the end. of the ignitionx-tube. The cap' is firmlysecured to the tube: by applying solder 55 or other equivalent fasteningmeansto. the junction of theshoulder 44:01 the tubeand thelip 54f of.the-cup. The cup thus providesmeans for positively-sealing the interior of'the ignition tubeso.thattheignition strikerorfiring pin being coaxial with the center that iS'tO y; the diaphragm.- 2G. firing pin 33Tand primer" 5-2? are sealed against external pressure such as-might-occur by a gassing of the ignition-mixture 45over long periods of storage or-as the result ofarpuncture of theend closure 'or .seal hereinafter described.

The'ignition mixture AS'isignitedby an igniter charge Sfiwhich is a composition adaptedto be the igniter such as powdered shellac. 'The'igniter charge is packed relatively loosely in the'endbf the igniter against the end. of tlie ignition mixture :35. As shown in Fig; l; ,theig'niter mixture surrounds the ignitiontubesealing cap- 54 but-is. separatedgtheres fromby aniannular'spacebfl; v r 1 The igniter mixture 55 -andiignitionmixturerdfi specified" above provide; combination which;

7 when fired, is hot zenough to burn to completion even though completely immersed in water; but will not detonate. These ignition mixtures are alsocharacterized by along burning time, st 1 bility under severe storage'conditionsand com-:

plete reliability when setofi 'by the. primer-flame.

The igniter is closed'by'a frangible end seal, the function of whichisto resist, without leaking, external pressure of the order of, two hundred poundsper squareqinch which may develop in the the igniter extending outside of the pot.

torpedo combustion chamber prior tothe operation of the igniter. Moreover, it is desirable that the end closure or seal break up into relatively small particles or even melt when the igniter is fired and at a definite pressure. An end seal having these characteristics is shown in the drawing and comprises a disk 58 of zinc substantially 0.010 inch thick and provided with a concentric coined annulus 59 substantially 0.004 inch thick which forms a concentric central disk 58. The end seal is seated on an annular shoulder 50 formed on the inside wall I I of the igniter and is preferably separated from the igniter charge 55 by a paper disk 62, both sides of the latter being shellacked. The zinc end seal 58 is held securely in place both by roll crimpin the end of the extension ll of the igniter as shown at $3 and by applying solder 64 to the joint. Inasmuch as it is usually neces sary to tin the end seal and the crimp metal, the latter is tinned before crimping. By fastening the end seal in the end of the igniter in this manner, it is held firmly in place and will not be blown out prematurely either by the primer explosion or during the initial burning of the igniter charge. Moreover, it is impossible for the seal to bulge or creep, and hence to leak due to internal pressure caused by a gassing of the ignition charges.

In operation, the igniter is secured in an aperture in the wall of the combustion pot of a torpedo by its threaded portion 12, the upper end of The threaded nipple it of the plug !5 is connected by a suitable fitting to an air line which supplies compressed air to the igniter. When the starting lever of the torpedo is tripped, which occurs when the torpedo is released, compressed air is automatically admitted to the combustion pot. In the brief interval between the time the torpedo is released and the time it strikes the water (which may be as long as ten seconds) air pressure builds up in the combustion pot, thereby subjecting the end seal of the igniter to considerable pressure. However, by providing the improved end seal and sealing cap for the ignition tube as described above, the firing mechanism of the igniter is protected from this pressure. As soon as the torpedo hits the water, a suitable trip is actuated which admits air pressure to the igniter through the plug I5 to the top of the diaphragm 2G. The latter tends to be displaced downwardly from its normal unstressed position by the pressure exerted thereon. This pressure slowly builds up on the thrust plate 36 of the firing pin 33 until the force exerted on the shear pin 35 approximates one hundred to one hundred and twenty five pounds per square inch whereupon the pin shears abruptly. Since the diaphragm is designed for and is capable of relatively large movement, the firing pin, and more particularly its nose 38, is driven down violently and without restraint onto the primer 52, all of the energy of the firing pin being concentrated on a single primer. The ignition of the primer is thus positively insured. The relative simplicity and symmetry of design of the firing mechanism precludes any liability of failure due to the severe shock sustained on impact of the torpedo with the water. The hot flame from the primer passes down through the relatively short passages c9 and 53, burns through the exposed wall of the zinc sealin cap 54 and blasts a cavity in the igniter composition 55 thereby creating broken up particles readily amenable to ignition. Moreover, since the primer is located in the lower end of the ignition tube, the primer flame is relatively short and contacts the ignition mixture 56 while the flame is still extremely hot which circumstance further insures positive ignition of the adjacent igniter composition. The latter thereupon ignites the ignition mixture 45 and the combined pressure and heat of the burning ign'iter and ignition mixtures breaks out the center 58 of the sealing disk 58. In the embodiment shown, the thin annulus 59 of the sealing disk is designed to rupture and free the central disk 58 at a pressure of approximately two hundred and fifty pounds per square inch. This expedient introduces a time delay which insures positive burning of the igniter and ignition charges before the sealing disk has been completely blown out and the powder charges subjected to the high pressure of the combustion pot. Moreover, by allowing the small central disk 58' of the seal to blow out before the entire seal is blown off of the end of the igniter, the igniter charge 56 is effectively retained in the igniter casing for complete combustion. After the sealing disk has been ruptured, the flame of the burning powders bursts "into the combustion pot and ignites the combustion charge therein. This r flame will continue to burn uninterruptedly for a period of substantially one minute, and hence insure continuance of the combustion necessary to the successful propulsion of the torpedo.

What is claimed is:

1. An igniter comprising an elongated body constructed and arranged to define two oppositely extending tubular chambers separated by an intermediate partition; a generally axially arranged ignition tube communicating between a first one of said chambers and the remote end of the second of said chambers; a percussion primer seated in the end of said ignition tube remote from said first chamber; a firing pin in said ignition tube in alignment with said primer; shearable means releasably holding said firing pin in spaced relation to said primer; pressure responsive means in said first chamber in operative engagement with the end of said firing pin; explosion removable seal means separating the primer containing end of said ignition tube from the second of said chambers; a pyrotechnic charge loaded in said second chamber surroundin said ignition tube in position to receive a primer flame when said seal means has been blown from said ignition tube; and a heat removable closure for the end of said second chamber.

2. An igniter comprising an elongated tubular casing separated between its ends by a partition to define a first chamber and a second chamber; an ignition tube secured to said partition and extending axially substantially through the second one of said chambers; a percussion primer seated in said ignition tube at a point remote from said partition; flash passages communicating between said primer and the exterior of said ignition tube; seal means removable by the primer explosion closing said flash passages; an igniter charge in said second chamber in surrounding relation to the igniter tube; an ignition mixture in contact with said igniter charge surrounding the seal means over said flash passages; an end seal releasably closing the end of the second chamber of said casing over said ignition mixture; a firing pin slidably mounted in said ignition tube in alignment with said primer; shearable means restraining said firing pin against movement toward said primer; and pressure responsive means in operative engagement with the end of said firing pin, said pressure responsive means being mounted in the; first chamber; ofisaidicasingand isolated Number. bysaid seaL means; iron direct communication 1,163,937 with said second chamber. y 1 1 J JQHN T N 5 1,514,743 REFERENCES CITED khezfollowing referencesazre ofirecord in the 2:423:83? file of 'this patent; 2,349,980

UNITED STATES PATENTS 10 Number Name" Date; Number 42,4:23 Bloem May 25, 1835 4:

8 r 7 Name 1 Date, Macomber .:Dec.,14, 1915 Woodberry May 3,1921 Pape j Nov. 20, ,1923 Taylor" Nov. 11-, 1924 Guillemet' Dec. 30;- 1924 Barker Nov. 8, 1927 Martin July15, 1927 Moore May 30; 1944 FOREIGN PATENTS Gountry Date; Germany June 3., 191-9