ANTI-STRAIN DEVICE FOR ARTILLERY PROJECTILES

Abstract: The present invention relates to a reinforcement device for the tubular shell of an artillery projectile of the type in­ tended to carry a useful load. The portion of the tubular shell to be reinforced is that comprised between the driving band and the base plug of the projectile. The reinforcement device ac­ cording to the invention consists of a metal structure (5) hav­ ing a cylindrical side surface with an outer diameter substan­ tially equal to the inner diameter of the portion of the tubular shell (4) to be reinforced. This metal structure (5) can have several embodiments depending on the useful load contained in the projectile.

Description: Anti-strain device for artillery projectiles The present invention relates to an anti-strain device for the tubular shell of artillery projectiles intended to eject a useful load. It is known that when an artillery projectile is fished, a translation movement and a spin around its axis are simultaneously imparted to it by the pressure exerted by the combustion gases Qf a propellant explosive, which pressure is transmitted through the base plug applied on the tubular shell of said projectile. Said base plug must be separable from the project le when its purpose is to carry on a predetermined target a useful load, for example an illuminating or smoke producing canister, or a set of small bombs; this useful load being ejected from the projectile at the time of splitting up and caused to fall to ground. The maximum operating pressure due to the combustion gases of the explosive causes permanent distorsions in the tubular shell of the projectile, which distorsions, if their amount is higher than allowable, can damage the innercanister or prevent its correct ejection. This leads to defective ope ration or even to disastrous breakage. Generally the more heavily stressed areas are found to be those under the driving band, where the equivalent stresses reach their maximum values. If that area is free to warp, considerable wall displacements can take place, such as to lead even to scraping off of the driving band itself, especially for projectiles with a tubular shell of small thickness. It is the object of the present invention to obviate said inconveniences of the prior art, byprovid- ing an anti-strain device for the portion of the tubular shell between the driving band and the base plug of the projectile. More particularly, the reinforcement device according to the invention for the portion of the tubular shell between the driving band and the base plug is characterized in that it consists of a metal structure having a cylindrical side surface with an outer diameter substantially equal to the inner diameter of the portion of the tubular shell to be reinforced. It is obvious that the metal reinforcing structure according to the invention can have several embodiments, depending particularly on the kind of useful load contained in the tubular shell of the projectile. By using the reinforcement device according to the invention, the strains of the tubular shell are li mited to allowable values, so as to avoid the inconveniences of the prior art. The invention will be better understood from the following description, given merely as an example and therefore in no limiting sense, of three embodiments thereof, referring to the accompanying drawings in which: Fig. 1 is a partial longitudinal sectional view of the end portion of an artillery projectile of a pe intended to carry a useful load which, in this specific case, consists of sub-ammunition, a first embodiment of the invention being shown in the fi gure; Fig. 2 is a plan view of the metal reinforcing structure alone, as shown in Figure 1; Fig. 3 is a vertical cross-sectional view of it, taken along line 3-3 of Figure 2; Fig. 4 is a sectional view similar to that of Figure 1, showing a second embodiment of the invention, for the case in which the useful load is for example an illuminating canister with its associated parachute; ; Fig. 5 is also a sectional view similar to that of Figure 1, showing a third embodiment of the invention for the case in which the useful load consists for example of pyrotechnical mixtures. Referring to Fig. 1 it can be seen that between the driving band 1 of an artillery projectile intended to carry a sub-ammunition load 2, and its base plug 3 there is arranged in contact with the inner wall of the tubular shell 4 a metal reinforcement structure 5 for said tubular shell 4. Said reinforcement structure 5 is better seen in Fig. 2 and 3, where it is shown alone. It should be noted that in Fig. 1 the reinforcement structure 5 is sectioned along a line 1 - 1 indicated in Fig. 2. As is apparent from the figures, the first embodiment shown of the reinforcement structure according to the present invention is particularly suited to the case in which the useful load consists of subammunition 2, in which case a lightweight but particularly strong reinforcement structure 5 is provided which in addition does not take precious space from the useful load. Fig. 2 shows a locating key 6 which can be engaged in a corresponding seat provided on the inner wall of the tubular shell of the projectile to prevent angular displacements of the structure 5 with respect to the projectile during its firing. In the embodiment illustrated said key 6 is fixed to the structure 5 by means of two screws 7. As can be seen in Fig. 2, the reinforcement structure of said first embodiment has a central circular hole and six holes regularly arranged radially around the central hole, all holes having the same diameter. Of course, the diameter of the holes, as well as their number and arrangement depend on the dimensions of the sub-ammunition 2 which represents the useful load of the projectile. A second embodiment of the invention is shown in Fig. 4, in which the metal reinforcement structure consists of a ring formed by a stub pipe 5' within which for example the parachute 2' of an illuminating canister is arranged. In this case the reinforcement structure has been designed so as to leave free the whole space inside the ring 5 he thickness of the ring 5' should be determined in dependance on the type of material, its construction and the stresses which it shall have to withstand without excessive strain of the tubular shell 4. Fig. 5 shows a third embodiment of the metal reinforcement structure according to the invention. In this embodiment the metal reinfocement structure 5" is shaped like an annular box and it also acts as a container, for example for a pyrotechnical mixture. Of course, the wall thickness of the box 5" is to be designed in dtendance on loads and allowable strains. In all three embodiments described the outer diameter of the reinforcement structure can be made slightly smaller than the inner diameter of the tubular shell of the projectile. The clearance so obtained will facilitate an introduction of the reinforcement structure into the tubular shell 4, but it should nevertheless be such as not to allow an eccessive strain of the tubular shell 4 during firing. while some embodiments of the invention have been illustrated and described, it is obvious that a num ber of changes and modifications can be made without departing from the scope of the invention.

Claims: Claims 1. Reinforcement device for a portion of the tubular shell (4) of an artillery projectile of the kind intended to carry a useful load, said portion of the tubular shell (4) being comprised between the driving band (1) and the base plug (3) of the projectile, characteried in that it consists of a metal structure (5) having a cylindrical side surface, with an outer diameter substantially equal to the inner diameter of the portion of the tubular shell (4) to be reinforced. 2. Reinforcement device as claimed in claim 1, characterized in that the metal structure (5) is substantially cylindrical and is provided with a plurality of circular through holes parallel to the axis of the cylinder. 3. Reinforcement device as claimed in claim 2, characterized in that one of the holes of the metal structure (5) is central and the other holes are disposed radially around said central hole. 4. Reinforcement device as claimed in claim 1, characterized in that the metal structure (5) consists of a ring. 5. Reinforcement device as claimed in claim 1, characterized in that the metal structure (5) is shaped like an annular box.

Inventors: ANDREETTA, RODOLFO
Applicants: SIMMEL DIFESA S.R.L.
Application year: 1984
Main classification: F42B12
IPC codes: F42B12