Patent Publication Number: US-2002011173-A1

Title: Pyrotechnic impact fuse

Description:
[0001] The invention concerns a pyrotechnic impact fuse as set forth in the classifying portion of claim 1.  
       [0002] A pyrotechnic percussion or impact fuse is known from DE 196 51 169 A1. Disposed in a ballistic cap of a high explosive shell on a so-called anvil is a secondary explosive  28  which is commercially available but which is made especially fireable or detonatable. That secondary explosive is not defined in greater detail.  
       [0003] There the object of the invention is to propose an explosive which explodes upon impact on a target.  
       [0004] That object is attained in accordance with claim 1.  
       [0005] Advantageous developments of the invention are set forth in the appendant claims.  
       [0006] In accordance with the invention, the impact detonating or firing means is a conventional explosive but with uniformly distributed, defined cavities. Due to those cavities of a diameter of from 0.2 -1.2 mm, the sensitivity of the explosive is below the sensitivity of tetryl. Tetryl is referred to as a secondary explosive and does not require any special mechanical safety means, as is required in the case of conventional explosive, fitted in fuses.  
       [0007] The cavities in the primary explosive are defined in a simple manner by glass balls, styropor balls, addition of polyurethane, the addition of gas in the casting or moulding procedure or by virtue of bores which are disposed transversely with respect to the main axis of the explosive body.  
       [0008] The invention is based on the operative principle that, upon impact of the projectile, shock wave initiation of explosive occurs due to imploding pores or cavities in the explosive mixture. 
     
    
    
     [0009] Embodiments of the invention are described hereinafter and illustrated in the drawing in which:  
     [0010]FIG. 1 is a view in longitudinal section of a high explosive shell, FIG. 2 is a phase illustration, and FIG. 3 is a simplified view of an explosive charge. 
    
    
     [0011] Referring to FIG. 1, a high explosive shell  1  comprises a casing  2  with a guide band  3 , a base-screw  4 , a main charge  5  of explosive and a cap  6 .  
     [0012] The cap  6  and an anvil  7  are connected to a screw threaded ring  8  on the shell side.  
     [0013] The anvil  7  has a plurality of firing or detonation passages  10 . They connect a space  11  at the cap side, to a conical recess  12  of the anvil  7 .  
     [0014] The firing passages  10  are closed by foils  9  of metal such as aluminium.  
     [0015] A structured explosive  13 ,  15  of PETN, nitropenta, with cavities  16 , is disposed in the space  11  and likewise the conical recess  12 . A conventional explosive can also be arranged in the recess  12 . The cavities  16  are defined by suitable bodies of styropor.  
     [0016]FIG. 2 shows the firing or detonation progression of the explosive  13  which is structured in accordance with the invention, upon on-target impact  17  of the shell  1 .  
     [0017] A shockwave  20  which is shown by way of example produces firing or detonation potentials  21  in the phase  1  which is identified by reference  22 , in the structured explosive  13 , and causes partial firing  17  in the cavities  16 , due to shockwave initiation.  
     [0018] In phase  2 , see reference numeral  23 , the fire sources  17 . 1  have expanded and form a detonation front  25  which extends in the space  11 , see also FIG. 1.  
     [0019] When the detonation front  25  reaches the foils  9  at the firing passages  10 , the procedure then involves firing through to the explosive charge  15  in the conical recess  12 . That then causes detonation of the main charge  5  which breaks up the casing  2  into fragments (not shown).  
     [0020] As shown in FIG. 3, a test body  30  of PHX, plastic-bound explosive, has bores  32  which are disposed transversely with respect to its longitudinal axis  31 . Conversion of the explosive into detonation energy occurs in the direction of the arrow  33 . That takes place in the same manner as described with reference to FIG. 2.  
     [0021] All military explosives are suitable as the explosives.