US2486362A

US2486362A - Acceleration switch

Info

Publication number: US2486362A
Application number: US708388A
Authority: US
Inventors: Laurence A O'brien
Original assignee: US SEC WAR
Current assignee: United States, WAR, Secretary of; US SEC WAR
Priority date: 1946-11-07
Filing date: 1946-11-07
Publication date: 1949-10-25
Anticipated expiration: 1966-10-25

Description

Oct. 25; 1949.

L. A. OBRIEN v ACCELERA'VIIOSWITCH I' 2 Sheets-Sheet 1 v Filed Nov. 7, v194e;

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La-L41: enr: e A, El E11-1an Y om.` 25, l1949.

L- A. O'BREN ACCELERATION SWITCH 2 SheetSJ-Sheet 2 File- Nov'. 74, 1946 lnrucnfor- Laurence 'A E] 'Evian Patented Oct. 25, 1949 ACCELERATION SWITCH Laurence A. OBrien, South Orange, N. J., as-

signor, by mesne assignments, to United States of America as represented by the Secretary of War Application November 7, 1946, Serial No. 708,388

3 Claims. (Cl. 1023-702) This invention relates to an acceleration-responsive safety arming device for delayed arming of electrically operated projectile fuzes, and more particularly, to a combination acceleration switch and powder train interrupter.

The principal object of my invention is toinsure the greatest possible degree of safety against premature explosions in projectiles of the above type. Another object of my invention is to provide arming means for a projectile of the above type, to render the projectile safe against rough handling and dropping, and which cannot explode during or immediately after set-back due to normal firing, as can known fuzes of this type,

if the normal firing mechanism should be damaged or imperfect. If explosion immediately after set-back occurs the projectile may not have travelled a safe distance from its starting point, and may be dangerous to the operator of the weapon. Previously known switches would be in an armed condition immediately after setback, and so could be easily exploded at this point.

In launching a rocket it sometimes happens that shortly after its initial acceleration, which causes the rocket to leave its launcher, the rocket propellant instead of continuing to burn at the correct rate, detonates in a low-order explosion, which imposes a second acceleration impulse on the fuze. It is an object of my improved arming device to prevent this low-order propellant explosion from detonating the main explosive charge of the rocket. I accomplish these objects by providing means for initiating arming of the fuze only when it has been subjected to a set-back force of the same order of magnitude and duration as occurs during normal firing or launching of the projectile, and by completion of the arming a substantial time interval later than initiation thereof. Thus the two events must occur seriatim before the fuze is fully armed so that it can detonate the explosive charge of the projectile.

Other objects will become apparent as the invention proceeds.

More specically, my invention comprises an inertia switch which is latched into circuit-closing position only after sustained set-back, and a rotary powder-train interrupter which is released for movement into its armed position only after the said latching operation is completed. Both of these operations are retarded by the action of an escapement mechanism. The inertia switch is operated by set-back against the action of a driving spring on its shaft, and is released from said shaft by the mechanism which latches it in circuit-closing position. The shaft is then driven by the spring to align the detonator in its armed position, and simultaneously to close a final switch to complete arming of the fuze.

In the drawings:

Figtue 1 is a longitudinal section View of a projectile embodying my invention.

Figure 2 is a longitudinal section View on a plane passing through the longitudinal axis of the projectile and at right angles to Figure 1.

Figure 3 is a schematic perspective view of the main shaft and the elements mounted thereon, prior to setback.

Figure 4 is a perspective of the rotor and inertia member similar to Figure 3, showing the elements at the end of normal setback, but prior to nal arming.

Figure 5 is a view similar to Figure 4, showing the elements at the end of the arming action.

Figure 6 is a detail view showing the manner in which the catch is keyed to the shaft.

Referring to the drawings, shaft I is supported for rotation in frame 2, 2. Eccentric weight 3 is releasably latched to shaft I by latch 4 provided with dog 5, the latch and dog being pivotally fastened to weight 3 by pivot pin 6, and being urged into latching relation with catch 'I on shaft I by spring 8. Catch I is fixed to shaft I for rotation therewith. Spring 9 biases shaft I and weight 3 in a clockwise direction (as viewed in Figures 2 and 3) against stop pin 4I, which acts on Weight 3 to limit its clockwise motion.

Fixed to shaft I for rotation therewith are squib drum I0 and gear wheel I2. Squib drum I0 carries flush on its outer surface arcuate contacts II and I2, from which conductors I4 lead to squib I6. Brushes I8 and 20 bear against drum I0 and are initially out of contact with contacts II and I2, as shown in Figure 3. When drum I0 is in its final position, shown in Figure 5, brushes I8 and 20 engage contacts II and I2 respectively to complete the electrical arming of the squib, although detonation will not normally occur at this time, as the squib energizing circuit is normally completed by a fuze (generally indicated at 32) which may be any known type of electrical fuze.

Gear wheel I2, which is keyed to shaft l, drives an escapement 22 through a reduction gear system generally indicated at 24. The purpose of the escapement device is to retard the rotation of the shaft I in either direction to insure the lapse of a definite time interval between any of 3 the successive stages of operation of the device, as will be described below.

The shaft l is mounted in a projectile having an electrical fuze 32, the aXis of the shaft being perpendicular to the direction of motion of the projectile, as shown in Figure 1. When the projectile is fired or launched, the force of setback acting on eccentric weight 3 forces it toward the rear of the projectile, thus rotating shaft I in a counterclockwise direction. This rotation is retarded by the action of escapement 22. If the set-back force continues for a sufciently long time, weight 3 will ultimately assume the 'posi-` tion shown in Figure 4, wherein spring 26 engages dog 5 of latch 4. Upon cessation of 'setback, spring 9 tends to return the shaft I and weight 3 to the original position. Since dog 5 cannot follow the initial return movement of Weight 3, because it is restrained by spring 2G, the latch 4 disengages from catch l. is thus restrained in the position shown in Figure 4, while shaft l returns clockwise to a position beyond its initial position, as shown in Figure 5, where it is held by a suitable stop, such as stop 34 engaging boss 35 on frame 2. This return rotation is retarded by escapement 22 to provide a definite time delay for this phase of the arming operation.

Weight 3 is provided with a wedge 3S, and in the final position of weight 3, this wedge is inserted between the spring leaves of two switches 3S and 4D to simultaneously close both of these switches, after which they are maintained closed due to the action of spring 2G on latch 4. This will initiate the arming of the fuze by condition- Aing the electric circuits thereof for operation, and iS applicable to any known type of'electri'c fuze.

When shaft l has returned to its final arming position, drum l0 will be vin the position shown in Figure '5 with squib I6 properly aligned with booster Il for detonation, and arcuate contacts Il and l2 in electrical engagement with brushes I8 and 20 respectively. In this position the fuze is fully armed for operation, and when it transmits a 'detonating impulse to the electric circuit, the projectile will be exploded.

It will thus be seen that I have provided an arming device which accomplishes the objects of the invention in a compact, simple unit which 1 can easily be made sufficiently rugged to withstand the setback and other forces to which it is subjected.

In the following claims I use the term setback in the sense in which it is conventionally employed with reference to military projectiles, as denoting a rearward force due to acceleration of the projectile in the direction in which it is red or launched, acting upon free-moving parts in the projectile.

I claim:

1. Arming device for fuzed projectiles comprising a rotary shaft, an inertia element consisting of an eccentric weight latched to said shaft for rotation therewith, first stop means, means biasing said shaft for rotation in one direction to bring said element to bear against said stop means in a position such that setback acting on said weight will tend to rotate the shaft against said biasing means, delay means for retarding rotation of the shaft in either direction, a switch actuated by said inertia element upon sustained setback to initiate arming of said device, means for unlatching said Weight from said shaft upon said sustained setback, thereby rendering said stop means ineiective, a rotary powder train interrupter normally carried by said shaft in unarmed position, and second stop means for stopping said rotary interrupter in armed position against the force of said biasing means a predetermined time interval subsequent to cessation of said sustained setback.

2. An arming device for fuzed projectiles comprising a rotary shaft, means biasing said shaft for rotation in one direction, an escapement geared to said shaft for retarding rotation thereof in either direction, an eccentric weight latched to said shaft and offset therefrom to urge said shaft in the other direction upon setback, first stop means for limiting rotation of said eccentricY weight in said first direction, arming initiation means actuated by said Weight upon rotation thereof in the other direction to a predetermined position, means for unlatching said weight from said shaft upon rotation to said predetermined position to release said shaft for rotation thereof by said biasing means, a rotary interrupter normally carried by said shaft in an unarmed position, second stop means for stopping said rotary interrupter in armed position against the force of said biasing means, and circuit means actuated by nal movement of said rotary powder train interrupter in its final position to complete the arming operation 3. Arming device for fuzed projectiles comprising a rotary shaft, an inertia element consisting of an eccentric weight latched to said shaft for rotation therewith, first stop means, means biasing said Ishaft for rotation in one direction to bring said element to bear against said stop means in a position such that setback acting on said weight will tend to rotate the shaft against said biasing means, delay means for retarding rotation of the shaft, means actuated by said inertia element upon sustained setback to initiate arming of said device, means for unlatching said weight from said shaft upon said sustained setback, thereby rendering said stop means ineffective, a rotary powder train interrupter normally carried by said shaft in unarmed position, and second stop means for stopping said rotary interrupter in armed position against the force of said biasing means a predetermined time interval subsequent to cessation of said sustained setback.

LAURENCE A. OBRIEN.

REFERENCES vClI'lED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,726,325 Varand Aug. 27, 1929 2,149,470 Schenk Mar. 7, 1939 FOREIGN PATENTS Number Country Date 257,335 Great Britain Aug. 27, 1926