US2508444A - Igniter - Google Patents

Description

J. P. CATLlN May 23,1950

IGNITER Filed 001'. 27, 1945 Patented May 23, 1950 UNITE S IGNITER John P. Catlin, Fairfield, Conn, assignor to Itemington Arms Company, 1110., Bridgeport, Conn., a corporation of Delaware Application October 27, 1945, Serial No. 625,090

2 Claims.

This invention relates to an improved form of igniting device which has a particularly valuable application to initiating combustion in the fire pot of an automobile torpedo.

The form of automobile torpedo conventionally employed by the naval forces employs a turbine adapted to be driven by the expansion of an elastic fluid. To this turbine is fed a mixture consisting of steam and the products of combustion of a hydro-carbon fuel. This mixture is produced by feeding compressed air and alcohol or other suitable fuel into a combustion pot where the mixture is burned with the injection of water.

The water is injected to aid in controlling comtravels with itto a considerable depth in the form of a large bubble which greatly delays the operation of any water actuated member.

In the use of such torpedoes by military aviation units, it is common practice to launch the torpedo by releasing it from aircraft flown at low altitudes over the water. In carrying out this method, the torpedo is secured by shackles in a position extending substantially longitudinally of the aircraft. The aircraft is flown at a low altitude over the water in the direction of the targetand the torpedo released from the shackles to enter the Water and take up its course in a direction of the target. At the time the torpedo is released from the shackles, valves are actuated for commencing the feeding of air and fuel through the flre pot to the turbine or to the engine of the torpedo. conventionally, the ignition operation has been commenced as discussed above by the action of the water and attempts have also been made to operate the igniters prior I to water entry.

On release from the aircraft, the torpedo will approach the water with a downward velocity due to the acceleration of gravity and with a forward velocity substantially equal to that of the plane.

theorized that if the ignition operation has been commenced prior to this time the shock may snuff out the flame in the fire pot or in the igniter itself, resulting in an undesirable cold-shot, the turbine being driven only by the expansion of the compressed air. It will be seen that it is desirable to delay firing until after water entry to allow the shock problem to be avoided and to secure a better ignition of the fuel, since in the early stages of injection the mixture of air and hydro-carbon has not stabilized at proportions suitable for most effective combustion.

After the torpedo has entered the water, its

' control depends upon the actuation by automatic machinery of suitable steering rudders. At low speeds, these rudders are relatively inefiective in controlling the torpedo. It will be seen,therefore, that if the torpedo is to be brought under control along its course at the earliest possible moment, it is desirable to get the engines underway and secure steerage way as soon as possible after the torpedo has entered the water. It is therefore essential that the torpedo be ignited as soon as possible after entry into the water.

With these factors in mind, it i an object of this invention to provide an improved igniter or aerial torpedo which will not have the undesirable characteristics of the previous igniters.

It is a further object of this invention to provide a torpedo igniter which functions immediately on entry of the torpedo into the water and continues to burn for a period of time adequate to insure that the combustion is well established.

Other objectives are to effect an increase in certainty of functioning and to provide safety means to remove the hazard from storing and handling of such igniters.

This invention contemplates accomplishing these objects by the provision of an inertia actuated igniter which is operated by the deceleration incident to entry of the torpedo into the water.

The exact nature of a particularly desirable form of the invention as well as other objects and advantages thereof will more clearly appear on consideration of the drawing, in which:

Fig. 1 is a longitudinal sectional view through the igniter.

Fig. 2 is a partial sectional view taken in the same plane as Fig. 1 showing the safety or disarming pin in place.

Fig. 3 isa plan view of the mid-section of a typical torpedo, part of the outer skin being broken away to show the location of the fire pot.

Fig. 4 is an elevational view showing substanstraight path in the direction of its intended,

target. During the interval of straight flight, a

torpedo 2 is released from shackles in the torpedo bay of the aircraft and thereafter;controlled by self-contained devices of. relatively well-known construction on its path to the target.

tary and naval forces of the United States, the torpedo 2 to which this invention is shown ape-- plied contains in its mid-section a combustion pot 3.-to whichthereisfed, in the conventional manner; air through tube.;-4,- hydro-carbon. fuel such; asalcohol through. tube 5,; and; water through tube 6.. The r pot 3: issprovidedi with; an opening I in; alignment with a. suitable. access port fl which allows; insertionandremoval-.of the igniter. body 9 from its space :within thertorpedo proper. It will.be-observedthat,the:axis of. the combustion: pot: is at' substantially. a. rig-htangle to a plane including. the; longitudinal. axis of the torpedo. and that theigniter-bodyis inserted into the pot with its axis insubstantialal-ignment'witlr that-of the pot.

Underthe: condition of; launching; illustrated in: Fig. 4; the. torpedo receives'a downward acceleration .due. to, 'tliewforceeof -zgravity f during; the period of 1 free. fall. sincerit will: have; 3 llS'Iibeen released from a-swiftl'y moving plane; it will have a. forward: velocity equal; to: that ofjthe; plane less' a negligible; amount? due; to? friction. The torpedojs; normally: released-from: thexminimum safe altitude;- of operation; of: the aircraft and. the'velocity duezto movementof the plane is a, redominating factor.- As: the: torpedo passes intothe water;v whiohby comparison to the air, is a relatively adense medium; it:;w-i-11- isufier a considerable deceleration: Infact", ak vvalues of several hundredg. have-beenfoundttoberrelatively. commonv at. the; instant of. water entry, The force ofinertia actingon: theapants: of; the torpedo during deceleration maybe-broken; down into two componentswa'lcomponent V dueto, the forward velocity of the forwardtomedo and; a component G due to the downward VBIOCHM'PIQL' duced. by gravitational acceleration: The: former-is: many timesgreatenandthe resultant-decelerational force. will" approximate that: which would be due to a "componentvelocitya such as thatdesignated as Ronthe vector diagram of Fig.1 5.

Referring:particularly/to Fig-.- 1; iti-WillTbQSBEll that a preferredrform of the igniter comprises a. body: 9. which. is. threaded. for: insertion into the. opening. 1? of the combustion pot; The body 9: is; provided with. 3, longitudinally extending cavity in which there may be pressed? a. main burningcharge In; an: i-gniter: charge I1", and a :primer charge 12. It will be noted that the igniter charge is in intimatecontact with the main. burning: charge and that the primer mix.- ture is substantially enclosed. by: the igniter charge. The primer-i2 isaimsnbstantial alignment with an axially extending ignition tube [3 which is threadably. mounted 111;. the. cavity and serves as; a. housing: for'the firing pin 55; Se-

In come mon with most of the torpedoeslusedby the. miliecured near the pointed end of the firing pin is a spring thrust bushing l5 which receives the thrust due to the spring l6 and serves to guide the firing pin in the ignition tube I 3. Seated in an outwardly opening cavity at the opposite end of the body 9 is a shear plate I! which receives the thrust of the spring It on its inner face andengages a sheanpin; 18- passing through the firing pin on its outer face.

Seated against the shear plate l1 and maintaining a predetermined spacing between the shear plate and a thrust plate 23 is an annular spacer bushing 22. Together, the two plates and the-spacen-Zi ,define a cavity in which an inertia weight: 241s received with capacity for relatively free-movement'- in planes normal to the axis of theigniter and, which has only a limited capacity for movement along the axis of the igniter. Thethrust plate I! issealed against the penetration of moisture and the leakage of air or gas from withinthebodyby agasket orsealing ring of. rubberworrubber-like material which. is: compressed and held implace by an.-outer-plug-2.6 which serves to secure theaplateagainst its seat on the. spacer 22;

In armedcondition, a centralopening inthe outer plugdsc-losed by a sealingscrew 21 which sea-ts. upon a gasket 28. To insure that the mechanism will not beinadvertently disas:

.sembled, the outer-"plug may be sealed in place as;by solder;2.9.-

By reference to Fig. 2, it maybe seen that for safety; the sealing screw 21' may be replaced, by asafety screwtdwhichis providedwith apin 31 adapted to. enter-"an appropriatev recess in the inertia weight: 2 and is provided with an arming-pin barflz; It will be-notecl that the bar 32 has a greater lengthwise dimension. than the diameter; of the. wrenchengaging portion of the head of the-b0613 9 Since the igniter canonly be assembled. to the torpedo by use a of; a special socket wrench, it. is: thereby made certain that the igniter cannot beinsertedrwi-thout removing apply an end-wise thrust to the: firing pin- 14.

The-fact that the inertia weight may departf-rom its central positionin any direction and issymmetrically-shaped on its inner face makes the orientation rotationally of. the body an unimportant:- factor. This: avoids the necessity for qualifying the thread which secures the igniter i the firing pot:

* When. the lateral force. tending. to move the inertia weight has exceeded a predetermined minimum; the force. transferred. to the firing. pin will causeshea-ringor the;pin-.,l8. Spring I] will drive the; firing pin inward, thus: firing the primer 1.2:;which, in its turn-,ignitesthe;top-charge H and the maincharge l 0. I

The dimensions of the'cavity; in which the in:- ertia weight. is received are not particularly criticalso long as. no: binding of the-weight is per-- mitted: and. the: weight: is..require.d" to, slide =.in.the

lateral paths without cocking to one side or the other as might be the case if the clearance was excessive. The angle of the coned face and the resistance of the shearing pin are so chosen as to hold under normal shocks such as might be incident to a rough landing of the aircraft and to positively release on water impact incident to launching from aircraft. The preferable construction shown has been found to be safe under accelerational forces of 50 g. and to fire consistently on inertia forces exceeding 100 g.

The heat of combustion and the evolution of gases due to the burning of the charges blows out and fuses the end seal l9. Preferably, the end seal l9 will have been coined to produce an annular zone 34 of reduced thickness which insures that the small center section blows out first. Since the center section is small and is of a readily melted material, it is unlikely to obstruct the turbine nozzle or blading. The relatively heavy outer ring of the end seal gives further support to the igniter charge as it functions and is then melted and blown clear. As a further aid to su porting the charges, annular grooves 35 may be placed in the outside of the ignition tube and will exert considerable holding force on the char e a ter the same has been pressed into the cavit of the body.

The exact composition of the charges employed is not a part of this invention and is not disclosed herein. In order that the skilled pyrotechnist may select suitable mixtures, the essential requirements are:

Igniter mirtura-Ihe primary function of this charge is to ignite readily from the primer flash and in turn to ignite the main burning charge.

Main burning charoe.The mixture must:

1. Be hot enough to ignite and burn to completion under conditions existin in combustion pot; yet

2. Not be so hot that the mixture will detonate; and

8. Be cool enough so that the mixture will burn for a lon time despite the relatively short length of the burning column prescribed by the design limitations;

4. Be stable under severe storage conditions;

and

5. React with complete reliability when set off by the primer flash.

Primer mirture.'lhe primer mixture must be sumciently sensitive to ignite readily when stabbed by the firing pin and must be hot enough to fire the igniter mixture with certainty.

It will be noted that the primer is in direct contact with the igniter mixture and substantially surrounded with that mixture. This makes it certain that the actuation of a properly selected primer will function the igniter mixture even under the most adverse conditions.

From consideration of the foregoing, it will be apparent that the igniter cannot function prior to water impact. Since the release of air and fuel is commenced as soon as the torpedo leaves is present in the fire pot when the igniter does shallow dives on entry into the water.

function and that delivery of a hot mixture of gases to the turbine will commence at once. This ensures that the torpedo will build up steerage way almost immediately and that control will be established in a very short distance. That this does take place is borne out by the fact that torpedoes utilizing this igniter make exceptionally This factor is of great importance in the making of airplane torpedo attacks in shallow coastal and harbor waters where the torpedo might otherwise dive into the bottom.

It is to be understood that the form of my invention herein specificall shown and described is intended only to be illustrative of a preferred embodiment and that various changes and reconstructions may be resorted to without departing from the spirit of the invention as defined in the claims herewith.

I claim:

1. An igniter for a torpedo comprising a body, a pair of flat guide surfaces formed in said body in spaced, facially parallel relationship; an inertia block received in said body between said guide surfaces with capacity for sliding movement parallel to said su faces, the side of said block in en agement with one of said surfaces bein provided with a conical recess: a firing pin slidably mounted in said body and having a terminal end projecting through said one of said surfaces into said conical recess; shearable means retaining said firing pin with said terminal end projecting into the conical recess; spring means in said body tending to withdraw the firing pin from said recess: a primer in position to be struck by said firing pin when same is withdrawn from said recess; a main pyrotechnic charge in said body; means arranged to ignite said pyrotechnic charge as a result Of the functioning of said primer; and safety means comprising a, removable member constructed and arranged to engage said block to positively secure same in a position in which the apex of said cone is in axial alignment with the terminal end of said firing pin.

2. An igniter as described in claim 1, said body being formed with a socket wrench engaging surface, and said removable safety member being provided with a cross bar of greater length than the maximum diametral dimension of the wrench engaging surface. the position of said cross bar being so related to the wrench engaging surface that it is impossible to engage a wrench therewith until said safety member has been removed.

JOHN P. CATLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,068,594 Leavitt July 29, 1913 1,356,633 Kirchhoff Oct. 26, 1920 2,351,474 Berger June 13, 1944 2,405,932 Alderman Aug. 20, 1946 FOREIGN PATENTS Number Country Date 245,528 Italy Mar. 12, 1926

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