Base plug with differentiated masses for artillery projectiles.

The present invention relates to base plugs for artillery projectiles intended to eject a useful load at a given point of their trajectory.

It is well known that when an artillery projectile is fired, a movement of translation and spin around its axis is imparted to it by the pressure exerted by the combustion gases of a propellant explosive, which pressure is transmitted through the base plug applied on the tubular portion of the projectile. Said base plug must be separable from the projectile when its purpose is to carry on a predetermined target a useful load, for example an illuminating or smoke producing canister, which is ejected from said projectile at the time of splitting up and falls to ground generally suspended to a parachute.

It is therefore desirable that the base plug, once separated from the projectile, does not go to interfere with the trajectory of the useful load because in such a case the load could be damaged. As a result, arrangements have been devised to avoid that such a disadvantage may occur.

In particular, base plugs of a composite structure have been provided comprising a separable centering element inserted in a cavity provided in the base plug itself. This element can be either slidable but not separable, or totally separable. This assembly has a symmetrical distribution of the masses and therefore does not cause any disturbance in the trajectory of the projectile. At the time of splitting, the components of the base plug are either thrown each in a different direction by the centrifugal force or, because of the eccentricity of the center of gravity due to their mutual movement, they are deviated, so that they go out from the trajectory of the useful load.

These known base plugs are, however, rather complex and therefore expensive.

A base plug with eccentric structure is also known, in which a portion of material is missing in a side zone (that is, the center of gravity of the base plug is not on the axis of the projectile) and therefore at the time of splitting up the base plug is moved away from the trajectory of the useful load by the centrifugal force.

The base plugs with eccentric structure, due to the .. fact that their center of gravity is on the axis of the projectile, may cause disturbances in the trajectory of the projectile, it being, however, possible to keep these disturbances within acceptable limits. Nevertheless, the forging process of the blank of base plugs having an eccentrical structure is rather complicated.

It is an object of the present invention to provide a base plug whose center of gravity is eccentric with respect to the axis of the projectile, although its geometrical center is on said axis of the projectile, and which is, in addition, simple and inexpensive to manufacture.

More particularly the base plug according to the invention, having its geometric center on the axis of the projectile, is characterized in that it has a center of gravity eccentric with respect to the axis of the projectile because of the pressure of masses incorporated in the base plug having a different density with respect to the remainder of the material of the base plug.

The invention will be better understood from the following detailed description given merely as an example and therefore in no limiting sense, of some embodiments thereof, referring to the accompanying drawings, in which: <ul id="ul0001" list-style="none"><li>Fig. 1 is a side view, partly cross-sectional, of a first embodiment of the invention, with a single excentric mass;</li><li>Fig. 2 is a top plan view of it;</li><li>Fig. 3 is a side view, partly cross-sectional, of a second embodiment of the invention, also provided with a single excentric mass;</li><li>Fig. 4 is a top plan view of it;</li><li>Fig. 5 is a side view, partly cross-sectional, of a third embodiment of the invention, with two excentric masses; and</li><li>Fig. 6 is a top plan view of it.</li></ul>

In the embodiment of the invention shown in Figures 1 and 2 the base plug 1 is provided with a blind hole 2 drilled in the side facing toward the inside of the projectile. This hole is filled with a threaded plug 3 having a different mass with respect to that of the base plug 1. It is apparent that the connection between plug 3 and plug 1 may be provided, besides by screwing, by other well known means, each as by welding, glueing and the like.

It is also apparent that the blind hole 2 may be drilled, instead of from the side of the base plug facing the inside of the projectile, also from the side facing outwardly.

Figures 3 and 4 show a second embodiment of the base plug according to the invention, in which the base plug 1' has been provided with a blind hole 2' drilled from the side of the base plug 1' facing the inside of the projectile. This hole 2' has thereafter been fitted by pouring into it a suitable material 3' of a density different from that of the base plug 1, for example a resin.

Also in this case it is apparent that the blind hole 2' might be provided in the portion of the base plug l' facing the outside of the projectile.

A third embodiment of the invention is shown in Figures 5 and 6. This embodiment is similar to that shown in Figures 3 and 4, except that two blind holes are provided, symmetrically disposed with respect to an X-X centerline.

By changing the number of holes, their dimensions and shapes and the type of filling material of these holes, it will be possible to obtain eccentricity of the center of gravity of the base plug assembly such as not to disturb excessively the stability of the projectile still reaching the result of deviating the base plug from the trajectory of the useful load of the projectile after its splitting up.

While some embodiments of the invention have been illustrated and described, a number of modifications and changes can be made without departing from the scope of the invention.