Device for Hardening a Mechanical Propulsion System Connection for a Mortar Round and Round Comprising Such a Connection

Abstract

A self-propelled munition having a munition rear body of circular cylindrical shape of diameter D 1 , along axis ZZ′. A propulsion system of the munition has a tubular casing of circular cross section, has an axis of revolution coincident with axis ZZ′, has an internal surface of diameter D 1 able to slide over said munition rear body, and contains a pyrotechnic propulsion chamber. The munition includes a mechanical connection between the propulsion system and the munition using shear pins evenly distributed about axis ZZ′, a hardened mechanical connection having a ring groove around the munition rear body in a plane perpendicular to axis ZZ′, another ring groove on the internal surface of the propulsion system casing, a retaining ring inserted in the ring groove configured to expand into the other ring groove from diameter D 1 to a diameter greater than diameter D 1 to secure the propulsion system to the munition.

1 . A self-propelled munition intended to be fired against a target, comprising:
 a munition having a munition body extended by a munition rear body of circular cylindrical shape of diameter D 1 , along a longitudinal axis ZZ′, a propulsion system of the munition having a casing in the form of a tube of circular cross section of diameter D 2 , of axis of revolution coincident with the longitudinal axis ZZ′, the casing, having an internal surface of the same diameter D 1  as the munition rear body, being able to slide over said munition rear body along said longitudinal axis ZZ′, the casing containing a pyrotechnic propulsion chamber intended to be activated upon firing, wherein it comprises at least two mechanical connections each able to adopt an activated state that secures the propulsion system to the munition or a deactivated state that releases the propulsion system from the munition,   the first mechanical connection comprising several shear pins, evenly distributed about the longitudinal axis ZZ′, inserted into the casing of the propulsion system and into the munition rear body, said first mechanical connection moving from an activated state to a deactivated state through the breakage of the shear pins, and   the second mechanical connection having a ring groove around the munition rear body in a plane perpendicular to the longitudinal axis ZZ′, another ring groove on the internal surface of the propulsion system casing, a retaining ring inserted in the ring groove, the retaining ring being configured to expand into the other ring groove from the diameter D 1  to a diameter D 4  that is greater than the diameter D 1 , and place said second mechanical connection in the activated state.   
     
     
         2 . The self-propelled munition as claimed in  claim 1 , wherein, in a storage phase, the first mechanical connection is in the activated state, the intact pins securing the propulsion system to the munition in terms of rotational and translational movement. 
     
     
         3 . The self-propelled munition as claimed in  claim 1 , wherein, in a munition firing phase, a sliding of the casing over the munition rear body toward said munition body places the first mechanical connection in the deactivated state by the breakage of the shear pins, the second mechanical connection in the activated state through the expanding of the retaining ring into the other ring groove which comes to face the ring groove during said sliding of the casing over the munition rear body. 
     
     
         4 . The self-propelled munition as claimed in  claim 1 , wherein, during a propulsion system deconfinement phase, a sliding of the casing over the munition rear body away from the munition body through an increase in pressure caused by the gases of combustion in the pyrotechnic chamber, places the first mechanical connection in the deactivated state by the breaking of the shear pins and the pyrotechnic chamber in contact with the external surroundings in order to release the combustion gases. 
     
     
         5 . The self-propelled munition as claimed in  claim 1 , wherein the munition rear body comprises, on each side of the longitudinal axis ZZ′, two notches and the propulsion system casing comprises two pegs, one peg being inserted into one respective notch on each side of said longitudinal axis ZZ′ to secure the munition and the propulsion system in terms of rotation about the longitudinal axis ZZ′. 
     
     
         6 . The self-propelled munition as claimed in  claim 1 , wherein the casing is delimited, on the munition side, by a casing edge in a plane perpendicular to the longitudinal axis ZZ′. 
     
     
         7 . The self-propelled munition as claimed in  claim 1 , wherein the munition body, of circular cylindrical shape having the same outside diameter D 2  as the casing of the propulsion system, is extended inside said casing by the munition rear body in the form of a cylinder of circular cross section of diameter D 1  forming an annular shoulder in a plane perpendicular to the longitudinal axis ZZ′, the munition rear body ending in the casing in the form of an end surface in another plane perpendicular to the longitudinal axis ZZ′. 
     
     
         8 . The self-propelled munition as claimed in  claim 1 , wherein the casing contains a pyrotechnic chamber containing a propellant pyrotechnic charge, the pyrotechnic chamber comprising walls affording thermal protection to the pyrotechnic charge, one thermal protection wall in the form of a tube, in contact with the internal surface of the casing and closed, on the munition side, by another thermal protection wall perpendicular to the longitudinal axis ZZ′. 
     
     
         9 . The self-propelled munition as claimed in  claim 8 , wherein the casing of the propulsion system comprises, at the same end as the other thermal protection wall of the pyrotechnic chamber, a circular cylindrical moving end wall of the same diameter D 1  as the internal surface of the casing, of axis of revolution coincident with the longitudinal axis ZZ′, having two faces in planes perpendicular to the longitudinal axis ZZ′, one face in contact with the thermal protection wall and another face on the munition rear body side having a circular recess for keeping a coil spring along the longitudinal axis ZZ′, the spring being inserted between said moving end wall and the end surface of the munition rear body in order to ensure a distance L 1  forming a clearance J 1  between the other face of the moving end wall and the munition rear body. 
     
     
         10 . The self-propelled munition as claimed in  claim 6 , wherein the casing of the propulsion system comprises holes near the casing edge in a plane perpendicular to the longitudinal axis ZZ′, the munition rear body having other respective holes in the same plane perpendicular to the longitudinal axis ZZ′ facing the holes in the casing of the propulsion system for the forcible insertion of the pins, the positions of the holes near the casing edge and those of the other holes in the munition rear body being such that when the pins are inserted into the respective holes in the casing and the munition rear body, the shoulder of the munition body and the casing edge are separated by a distance L 2  to form a clearance J 2 . 
     
     
         11 . The self-propelled munition as claimed in  claim 10 , wherein the clearance J 2  is smaller than the clearance J 1  so that when the pins have sheared upon firing, the casing edge and the shoulder coming into contact, there is still a space between the munition rear body end surface and the other face of the moving end wall. 
     
     
         12 . The self-propelled munition as claimed in  claim 1 , wherein the shear strength of the second mechanical connection is greater than the shear strength of the first mechanical connection. 
     
     
         13 . The self-propelled munition as claimed in  claim 1 , wherein the shear pins and the retaining ring are secured to the munition by a propulsion system end wall which is itself secured to the propulsion system. 
     
     
         14 . The self-propelled munition as claimed in  claim 13 , wherein the propulsion system end wall is in the form of a collar closed by an end wall in a plane perpendicular to the longitudinal axis ZZ′, the circular cylindrical exterior surface of the end wall comprises the shoulder, the holes for the pins, the groove containing the retaining ring and the groove containing the body sealing gasket, the face of the end wall on the propulsion system side having the same role as the end surface. 
     
     
         15 . The self-propelled munition as claimed in  claim 14 , wherein a circular cylindrical internal part of the propulsion system end wall has a screw thread for the screw-fastening of the munition rear body which likewise has a screw thread that can be screwed onto the screw thread of the propulsion system end wall. 
     
     
         16 . The self-propelled munition as claimed in  claim 1 , wherein during its storage, transport and maintenance phase, it is fitted with a belt that locks the first mechanical connection in the activated state. 
     
     
         17 . The self-propelled munition as claimed in  claim 16 , wherein the locking belt, in the form of a tube with an outside diameter D 5  greater than the diameter D 2  of the external surface of the propulsion system, partially surrounding the munition body and the casing, comprises an interior part in the form of a collar inserted between the casing and the munition body to prevent them from moving closer to one another. 
     
     
         18 . The self-propelled munition as claimed in  claim 7 , wherein the casing of the propulsion system comprises holes near the casing edge in a plane perpendicular to the longitudinal axis ZZ′, the munition rear body having other respective holes in the same plane perpendicular to the longitudinal axis ZZ′ facing the holes in the casing of the propulsion system for the forcible insertion of the pins, the positions of the holes near the casing edge and those of the other holes in the munition rear body being such that when the pins are inserted into the respective holes in the casing and the munition rear body, the shoulder of the munition body and the casing edge are separated by a distance L 2  to form a clearance J 2 . 
     
     
         19 . The self-propelled munition as claimed in  claim 8 , wherein the casing of the propulsion system comprises holes near the casing edge in a plane perpendicular to the longitudinal axis ZZ′, the munition rear body having other respective holes in the same plane perpendicular to the longitudinal axis ZZ′ facing the holes in the casing of the propulsion system for the forcible insertion of the pins, the positions of the holes near the casing edge and those of the other holes in the munition rear body being such that when the pins are inserted into the respective holes in the casing and the munition rear body, the shoulder of the munition body and the casing edge are separated by a distance L 2  to form a clearance J 2 . 
     
     
         20 . The self-propelled munition as claimed in  claim 9 , wherein the casing of the propulsion system comprises holes near the casing edge in a plane perpendicular to the longitudinal axis ZZ′, the munition rear body having other respective holes in the same plane perpendicular to the longitudinal axis ZZ′ facing the holes in the casing of the propulsion system for the forcible insertion of the pins, the positions of the holes near the casing edge and those of the other holes in the munition rear body being such that when the pins are inserted into the respective holes in the casing and the munition rear body, the shoulder of the munition body and the casing edge are separated by a distance L 2  to form a clearance J 2 .