Patent Publication Number: US-11639844-B2

Title: Penetrating and explosive projectile with stabilizing fin assembly

Description:
The technical field of the invention is that of fin assembly-stabilized projectiles, and more particularly that of explosive and penetrating projectiles. 
     Explosive projectiles that also have penetrating capability are intended to penetrate armored protection and explode behind the protection. 
     To achieve this, the body of the projectile has a reinforced warhead and the fuze ensuring the firing of the explosive charge is located at a rear part (or base) of the projectile so as not to be destroyed by the impact. 
     However, the fin assembly of the projectiles always forms a mass that remains behind the fuze and may disrupt the operation of the fuze on impact. 
     The aim of the invention is therefore to propose a penetrating and explosive projectile with an architecture that does not disturb or destroy the fuze on impact on a target. 
     The invention thus relates to a penetrating and explosive projectile provided with a trajectory-stabilizing fin assembly which is secured to a body of the projectile by a mechanical connection, the fin assembly including a tapped tube which engages on a threaded rear cylindrical shank of a tail connected to the projectile body, thereby forming a threaded mechanical connection between the fin assembly and the body, the projectile being characterized in that it includes means ensuring the fragilization of the threaded connection on impact on a target, the fin assembly then separating from the projectile body. 
     In a particular embodiment, the projectile has a fuze arranged at a rear part of the projectile and the tail carrying the fin assembly includes a conical portion which connects to the body of the projectile. 
     The fin assembly may also include fragilization means consisting of breakage initiators arranged on the tube of the tail, between the fins of the consisting of, wherein said breakage initiators are made as longitudinal grooves that ensure a thinning of the thickness of the tube, the inertial advance motion of the fin assembly on the conical portion, upon impact of the projectile on a target, causing the grooves to break. 
     Each fin may include a conical front part cooperating with the conical portion of the tail. 
     The front part of the tube may also include a conical part in continuation of the conical front parts of the fins. 
    
    
     
       The invention will be better understood upon reading the following description of various embodiments, description made with reference to the annexed drawings in which: 
         FIG.  1    shows a schematic longitudinal section of an embodiment of a projectile according to the invention; 
         FIG.  2    shows the fin assembly alone in perspective; 
         FIG.  3    shows the deformation of the fin assembly upon impact on a target. 
     
    
    
     Referring to  FIG.  1   , a projectile  1  according to an embodiment of the invention includes a body  2  enclosing an explosive charge  3 . The body  2  is closed at its front part by a tip  4  made of dense material, such as a steel with high mechanical characteristics or a tungsten alloy, and which is intended to enable penetration of a target. 
     The explosive charge  3  is intended to be initiated by a detonation relay  5  which is itself initiated by a fuze  6  which is arranged in a base  7  secured to the rear part of the body  2 , for example by a thread. 
     The projectile  1  also includes a stabilizing fin assembly  8  which is secured to the body  2  of the projectile by means of a threaded mechanical connection that includes a tail  9 . This tail  9  includes a rear cylindrical shank  10 , extended at the front by a conical portion  11  which connects to the body  2  of the projectile at a threaded bearing surface  12  of the base  7 . 
     The cylindrical shank  10  includes a thread on which is screwed a tapped tube  14  that carries the fins  15  of the fin assembly  8 . The thread of the shank  10  and the tapped hole of the tube  14  form the threaded connection  13 . 
     As can be seen in  FIG.  1   , the tube  14  carries an internal partition  16  which separates a front chamber  17  and a rear chamber  18 . The rear chamber  18  is intended to receive a pyrotechnic tracer. 
     According to the invention, the projectile  1  includes means ensuring the fragilization of the threaded connection  13  between the thread of the shank  10  and the tapped hole of the tube  14  upon impact of the projectile on a target. 
     Thus, the inertial forces exerted on the fin assembly  8  at the impact will cause the fragilization means to break, thus ensuring the separation of the fin assembly  8  and the body  2  of the projectile  1 . 
     For example, a simple transverse groove on the shank  10 , between the threaded part and the conical portion  11 , could be defined as fragilization means. 
     This groove will weaken the shank  10  which will break upon impact on a target. 
     The fin assembly  8  will then detach from the projectile  1  and will not interfere with the operation of the fuze. 
     It should be noted that the external profile of the conical portion  11  also ensures a deflection of the fin assembly  8 , thus protecting the fuze  6  against the impacts caused by the latter. 
     It can be seen in  FIG.  1    that the tail  9  has a conical portion  11 . 
     Therefore, if the fins  15  or the fin assembly  8  hit the projectile body  2 , the impact will occur at a distance from the fuze  6  and will not disrupt the operation of the fuze. 
     In a particular embodiment of the invention, it is noted in  FIG.  2    that the fin assembly  8  includes longitudinal grooves  19  which extend longitudinally along substantially the entire length of the tube  14  and which are arranged between each pair of fins  15  of the fin assembly, midway between two adjacent fins  15 . Here, there are two parallel longitudinal grooves  19  arranged between each pair of fins  15 . 
     These grooves  19  ensure a thinning of the thickness of the tube  14  and constitute breakage initiators for the wall of the tube  14 . It is also noted that each fin  15  includes a front part with conical profile  20  which is intended to cooperate with the conical portion  11  of the tail  9 . This front part with conical profile  20  also extends at the front part of the tube  14  which is also conical. 
     As can be seen in  FIG.  3   , upon impact of the projectile  1  on a target  21 , the projectile  1  is strongly decelerated. The decelerated  8  advances, due to inertia (arrow E), towards the conical portion  11 , causing the threaded connection  13  to be sheared off. 
     This advance motion of the fin assembly  8  leads to a sliding of the conical part  20  of each fin  15  (and of the tube  14 ) on the profile of the conical portion  11  of the tail  9 . This results in a radial stress leading to an enlargement of the internal diameter of the tube  14 . This stress causes the grooves  19  to break and the fins  15  to move away from each other (arrows A 1  and A 2 ). 
     Each fin  15  thus follows a trajectory that moves it away from the fuze  6 . 
     Such an arrangement makes the breakage of the threaded connection  13  more reliable and ensures that the impacts that the fin assembly  8  could cause on the fuze  6  are reduced to a minimum.