US3270670A - Impact fuzes for spinning explosive projectiles and more particularly basedetonatingfuzes of the type equipped with a mechanical auto-destruction device - Google Patents

Description

Sept. 6, 1966 w. GUERNE IMPACT FUZES FOR SPINNING EXPLOSIVE PROJECTILES AND MORE PARTICULARLY BASE-DETONATING FUZES OF THE TYPE EQUIPPED WITH A MECHANICAL AUTO-DESTRUCTION DEVICE Filed Feb. 18, 1964 2 SheetsSheet l Sept. 6, 1966 w. GUERNE 3,270,670

IMP C FUZES FOR SPINNING EXPLOSIVE PROJECTILES AND MORE FA CULARLY BASE-DETONATING FUZES OF E TYPE EQUIPPED WITH A MECHANICAL AUTO-DESTRUC N DEVICE Filed Feb. 18, 1964 2 Sheets-Sheet 2 1? L IQT United States Patent This invention relates to those impact fuzes for explosive projectiles spinning about their longitudinal axis particularly small-caliber projectiles (of the order of 20 to 50 mm.) for anti-aircraft or aircraft-mounted automatic weapons-which are equipped with a mechanical auto-destruction device comprising, in addition to other components, centrifugal locking means which are maintained in a locking position so long as the rotational speed of the projectile about its axis remains above a predetermined value, said locking means temporarily restraining an intermediate member in an inoperative position, which member is adapted when released and in response to elastic means to trip the fuze, usually by the plunging movement of a firing pin. The invention is more particularly though not exclusively applicable to so-called base-detonating fuzes, which are designed to be fitted to the base end of explosive projectiles.

It is the chief object of the present invention to provide an improved impact fuze of the above-mentioned type that is notably characterized by its attenuated sensitivity.

The present invention relates to an impact fuze of this type comprising a mechanical auto-destruction device having a first rearwardly directed surface against which bear the centrifugal locking means of said auto-destruction device so long as the rotational speed of the projectile remains above a predetermined value, below which elastic means controlling a centrifugal-lockingmeans-supporting intenmediate member become preponderant and cause percussion of the fuze by a longitudinal forward movement of said intermediate member, characterized in that there is provided, along the axipetal paths which said centrifugal locking means are constrained to follow in their housings in order to escape from said first surface, a second forwardly directed surface supported by a longitudinally movable weight which is free to move rearwardly relative to said centrifugal-locking-means-supporting intermediate member in response to the pressure exerted on said second surface by said centrifugal locking means as the same follow their axipetal escape path, the movement along this path being thus restrained in the event of an impact since said centrifugal locking means are then constrained to overcome the forwardly directed inertia force of said weight in order to escape from said first surface, and it will therefore be manifest that this restraining effect has an attenuating influence on the sensitivity of the fuze.

The description which follows with reference to the accompanying non-limitative exemplary drawings will give a clear understanding of how the invention can be carried into practice.

Referring to the drawings filed herewith:

FIGURE 1 shows in side elevation, in fragmental longitudinal section and with cutaway portions, a base-detonating fuze with mechanical auto-destruction device for fitting to a spinning explosive projectile, as executed in ac cordance with the invention, the component parts thereof being shown in the inoperative or safe configuration, and

FIGURES 2 to 4 show the basic components of the auto-destruction device of said fuze in the positions they occupy when the round is fired subsequent to arming of the fuze, and subsequent to an impact of sufiicient force to trip the fuze, respectively.

Referring to the accompanying drawings, there is shown thereon a base-detonating fuze with mechanical autodestruction device for a small-caliber spinning explosive projectile of up to 30 mm., say, and it will of course be understood that the fuze as a whole, with the exception of the mechanical auto-destruction device, may be devised in any convenient manner provide-d that it comprises an intermediate member, hereinafter assumed to be a firing pin adapted to be longitudinally slidable forwardly whereby to detonate the priming charge of the fuze.

Referring first to FIGURE 1, there is shown thereon a base-detonating fuze case 1 having therein an axial bore 2 into which is fitted a socket 3 comprising a transverse wall 3a embodying a central cylindrical hole for slidably receiving therein a forwardly pointing firing pin 4, said firing pin being urged forwardly by a spring 5 bearing against the rear end closure of said fuze case and being adapted to coact, in the event of an impact or autodestruction, with a primer (not shown) positioned ahead of said transverse wall 3a. In order to restrain the firing pin 4 in its retracted position until the round is fired (fuze in safe configuration), provision is made for centrifugally releasable locking means comprising two half-rings 6 inseited between the wall 3a and a flange 4a provided at the rear of firing pin 4, said half-rings being surrounded by a spiral strip 7 and a split sleeve 8 which spreads apart under the effect of centrifugal force and thereby enable half-rings 6 to spread apart in turn whereby to release said firing pin 4 (fuze armed).

Referring still to FIGURE 1, the mechanical autodestruction device comprises, in the manner well known per se, in addition to the firing pin spring '5 referred to, centrifugal locking means consisting of balls 9 disposed within radial housings embodied in the flange 4a of firing pin 4. In response to centrifugal force, said balls 9 bear against a first rearwardly directed frusto-conical surface 10 which is positioned substantially level with said flange when the firing pin is locked in its retracted position (fuze in safe configurationsee FIGURE 1)..

Before proceeding with a description of the principal feature of the present invention, it is thought necessary, for a proper appreciation of this specific feature and of the advantages stemming therefrom, to explain forthwith the manner of operation of the assembly hereinbefore describe-d, firstly after the round is fired, secondly in the event of an impact, and thirdly in the event of operation of the auto-destruction device (if no impact occurs).

Immediately upon emerging from the gun barrel, and in response to the centrifugal force engendered by the spin imparted to the projectile, the balls 9 are pressed firmly against the surface 10, thereby temporarily preventing any forward motion of the firing pin 4. This centrifugal force in addition causes spreading open of split sleeve 8, loosening of spiral strip 7 and spreading open of half-rings 6, thereby releasing the firing pin 4 which, though urged forwardly by spring 5, is restrained in its retracted position by balls 9.

The fuze is then ready to trip in the event of an impact occurring, which tripping takes place when the forwardly exerted inertia forces set up, at the instant of impact, in the movable compound comprising firing pin 4 and balls 9 are sufiicient to overcome the restraining force exerted by said balls.

If no impact occurs, automatic destruction of the projectile will take place when the centrifugal force acting upon the balls 9 is no longer sufficient to offset the urge exerted by spring 5. Said spring 5 will then first constrain the balls 9 to retract into their radial housings and subsequently constrain the consequently released firing pin 4 to move forwardly and strike the fuze priming charge, whereby to cause auto-destruction of the projectile.

As a result of the functional arrangement described hereinabove, the sensitivity of the fuze to impact is all the greater as the mass of the movable compound comprising firing pin 4 and balls 9 is greater; for, all other things being equal, the inertia forces which urge said movable compound forwardly and which must overcome the restraining force exerted by the locking balls 9 are proportional to the mass of said movable compound.

In some instances, however, it may be preferable to attenuate the sensitivity of a fuze of this type in order to preclude its tripping when the projectile passes through comparatively thin, low-resistance obstacles and thereby ensure that it remains armed and ready to be tripped by a subsequent more violent impact.

It might well be thought that such attenuation could readily be achieved by merely lightening the firing pin 4. Although theoretically sound, this solution is in fact impracticable, due to the fact that the firing pin must posses adequate mechanical strength to withstand the shock loadings it sustains when the projectile is fired, which in turn prohibits any substantial lightening of the firing pin for a given type of fuze.

The principal feature of the present invention provides a ready solution to the problem referred to precedingly, to wit that of attenuating the sensitivity of a basedetonating fuze with sliding firing pin and ball-type autodestruction device as hereinbefore described, without entailing any modification of the basic fuze components and, above all, without lightening the firing pin or modifying the auto-destruction device thereof.

Provision is accordingly made, along the axipetal paths followed by the balls 9 in their housings, for a second forwardly directed surface 11 provided on a weight 12 mounted in a bore provided therefore in the flange 4 whereby to be axially movable rearwardly relative to firing pin 4, when the same moves forwardly, and, by reason of a small axial clearance provided between said balls 9 and said second surface 11, initially also when the weight 12 bears against the end closure of its housing.

Thus, when an impact occurs, the balls 9 are urged forwardly by firing pin 4 under the effect of its inertia; however, in order to escape from the first surface 10 on reaching the end of their axipetal movement, said balls must thrust the weight 12 rearwardly of the firing pin, and this must be done against the countering inertia force of the weight 12 which applies the second surface 11 against the balls 9 and thereby restrains their axipetal movement.

Thus, all other things being equal, the presence of the weight 12 will attenuate the sensitivity of the fuze and most significantly, this will have been achieved Without the need to dangerously lower the mechanical strength of its firing pin and without affecting its auto-destruction characteristics, in respect of which the additional weight will have virtually no effect.

All other things being equal, the weight 12 can be rendered more effective by constituting it from a material such as brass of a density greater than that of the material used for the firing pin 4 (light alloy, for example).

It will readily be appreciated from the foregoing that the sensitivity of the fuze can be effectively adjusted in the assembly stage by operating in particular on the mass of the additional weight 12 and possibly also on the slope of the surface 11. It will also be seen that a basedetonating fuze devised as hereinbefore disclosed has its sensitivity attenuated without affecting the resistance to motion of the firing pin itself.

Reference is next had to FIGURES 1 to 4 for a detailed explanation of the relative positions of the moving parts of the fuze at certain specific moments of the fuze operation.

In its inoperative position, the firing pin 4 is locked as shown in FIGURE 1.

When the round is fired, said firing pin is thrust by inertia into pressure contact against the weight 12, which weight is in turn thrust into pressure contact against the end closure of its housing, while the balls 9 are urged outwardly (position shown in FIGURE 2).

At this stage, the firing pin is released and, due to the deceleration of the projectile, the weight 12 lifts slightly off the end closure of its housing and applies its surface 11 against the balls 9, which balls are clamped, as it were, between the surfaces 10 and 11 (position shown in FIG- URE 3).

In the event of an impact of force greater than the sensitivity threshold of the fuze, the firing pin urges the balls 9 forwardly, which balls, having thrust the weight 12 rearwardly, leave the surface 10, whereupon no further substantial force subsists to counter the percussion stroke of the firing pin 4 (position shown in FIG- URE 4).

In a general manner, while the above description discloses what is deemed to be a practical and efficient embodiment of the present invention, said invention is not limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the invention as comprehended within the scope of the appended claims.

What I claim is:

1. An impact fuze for a spinning propectile which comprises, in combination, a fuze case fixed with respect to said propectile and having a longitudinal axis of rotation, a firing pin slidable longitudinally in said case in the direction corresponding to firing in response to the stopping of said projectile by an obstacle, spring means in said fuze case operatively connected with said firing pin for urging it longitudinally with respect to said case in said direction, locking means for yieldingly preventing said firing pin from moving in said direction as long as the speed of revolution of said projectile is above a given value, said locking means comprising, on the one hand, a surface of said fuze case of revolution about said axis, said surface having generatrices oblique to said axis and converging in said direction, and, on the other hand, adapted to cooperate with said surface by sliding engagement therewith, rounded centrifugal members guided in said firing pin radically and transversely to said axis, whereby an inward movement of said centrifugal members toward the axis of said fuze case takes place when the speed of revolution of said fuze case about said axis drops below said given value, and an inertia part slidable longitudinally in said firing pin and having a surface thereof, of revolution about said axis and converging in the same direction as said first mentioned surface, in engagement with said centrifugal members, whereby said inertia part is pushed longitudinally in a direction opposed to the first mentioned direction with respect to said fuze case in response to a movement of said centrifugal members toward said axis.

2. An impact fuze according to claim 1, wherein said centrifugal members are balls.

3. An impact fuze according to claim 1 wherein said firing pin is provided with a longitudinal bore, said inertia part being slidably guided in said bore.

4. An impact fuze according to claim 1 wherein said inertia part is made of a material of a density greater than that of the material of which said firing pin is made.

References Cited by the Examiner UNITED STATES PATENTS 2,167,197 7/1939 Brandt 102-79 2,871,788 2/1959 Guerne 10271 2,945,440 7/1960 Vogt 10216 BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner.

Claims (1)

1. AN IMPACT FUZE FOR A SPINNING PROPECTILE WHICH COMPRISES, IN COMBINATION, A FUZE CASE FIXED WITH RESPECT TO SAID PROPECTILE AND HAVING A LONGITUDINAL AXIS OF ROTATION, A FIRING PIN SLIDABLE LONGITUDINALLY IN SAID CASE IN THE DIRECTION CORRESPONDING TO FIRING IN RESPONSE TO THE STOPPING OF SAID PROJECTILE BY AN OBSTACLE, SPRING MEANS IN SAID FUZE CASE OPERATIVELY CONNECTED WITH SAID FIRING PIN FOR URGING IT LONGITUDINALLY WITH RESPECT TO SAID CASE IN SAID DIRECTION LOCKING MEANS FOR YIELDINGLY PREVENTING SAID FIRING PIN FROM MOVING IN SAID DIRECTION AS LONG AS THE SPEED OF REVOLUTION OF SAID PROJECTILE IS ABOVE A GIVEN VALUE, SAID LOCKING MEANS COMPRISING, ON THE ONE HAND, A SURFACE OF SAID FUZE CASE FOR REVOLUTION ABOUT SAID AXIS, SAID SURFACE HAVING GENERATRICES OBLIQUE TO SAID AXIS AND CONVERGING IN SAID DIRECTION, AND, ON THE OTHER HAND, ADAPTED TO COOPERATE WITH SAID SURFACE BY SLIDING ENGAGEMENT THEREWITH, ROUNDED CENTRIFUGAL MEMBERS GUIDED IN SAID FIRING PIN RADICALLY AND TRANSVERSELY TO SAID AXIS, WHEREBY AN INWARD MOVEMENT OF SAID CENTRIFUGAL MEMBERS TOWARD THE AXIS OF SAID FUZE CASE TAKES PLACE WHEN THE SPEED OF REVOLUTION OF SAID FUZE CASE ABOUT SAID AXIS DROPS BELOW SAID GIVEN VALUE, AND AN INERTIA PART SLIDABLE LONGITUDINALLY IN SAID FIRING PIN AND HAVING A SURFACE THEREOF, OF REVOLUTION ABOUT SAID AXIS AND CONVERGING IN THE SAME DIRECTION AS SAID FIRST MENTIONED SURFACE, IN ENGAGEMENT WITH SAID CENTRIFUGAL MEMBERS, WHEREBY SAID INERTIA PART IS PUSHED LONGITUDINALLY IN A DIRECTION OPPOSED TO THE FIRST MENTIONED DIRECTION WITH RESPECT TO SAID FUZE CASE IN RESPONSE TO A MOVEMENT OF SAID CENTRIFUGAL MEMBERS TOWARD SAID AXIS.

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