Standoff munition
This invention relates to a standoff munition, and more particularly an improved such munition with simple but reliable standoff firing mechanism. 
     It is a primary object of the present invention to provide a standoff munition, adapted to be projected alone by hand or weapon, or as one of a group particularly by weapon, in which standoff firing is achieved by simple, compact, inexpensive, mechanical mechanism with great reliability and regardless of wide variation in the angle of approach of the munition to the ground. It is a further object to provide such a munition which makes improved provision for safety against firing not only prior to being projected, but during flight (and prior to reaching the height above ground at which firing is predetermined), again by simple and reliable mechanical means. It is a further object to provide such a mechanism capable of meeting military specifications, including requirements thereof as to tests for out-of-line safety, jolt and jumble, shipping vibration, operational vibration, shipping shock, muzzle shock (acceleration and deceleration), storage temperature extremes, and salt spray, humidity, and fungus environments. 
     The invention features use of a probe that is flexible until after the munition is projected, so that it may be folded up and compactly stored despite considerable length, but is fairly rigid as the munition descends toward earth, and cooperates with other mechanism to explode the munition when the end of the probe engages an obstruction such as the ground. 
    
    
     Other objects, features, and advantages will appear from the following description of preferred embodiments thereof, taken in conjunction with the attached drawings thereof, in which: 
     FIG. 1 is an isometric view of the presently preferred embodiment of the unprojected munition; 
     FIG. 2 is a vertical generally sectional view therethrough, taken at 2--2 of FIG. 1; 
     FIG. 3 is a sectional view taken at 3--3 of FIG. 2; 
     FIG. 4 is a view corresponding to FIG. 2, but showing the munition after projection and arming, and in mid-air approaching the ground; 
     FIG. 5 is a partial isometric view detailing the firing pin lever and the manner in which the upper end of the probe cooperates therewith; 
     FIG. 6 is a partial isometric view detailing the configuration of the fuze and high explosive containers, cords and beads being shown in their falling-toward-earth relationship therewith; 
     FIG. 7 is an exploded isometric view of the bore lock safety element and the detonator holder; 
     FIG. 8 is an isometric view of a modified bead useful in probes of munitions of the invention; and 
     FIG. 9 is an isometric view of another modified bead so useful. 
    
    
     Referring now in more detail to the drawings, there is shown in FIG. 1 a standoff munition indicated generally at 10. 
     A pair of symmetrical cover elements 12 cooperate with generally rectangular O-ring (type in cross-section) gasket 14 to provide a sealed outer case, the elements 12 being held in position by a pair of shear pins 16, each extending through aligned holes in tongues protruding from the cover elements (the tongues and pin 180° opposite to those shown in FIG. 1 are not shown). The cover ribs 18 and 20 provide added strength. 
     Inside the outer case is a folded parachute 22 attached to cord 24 running over pulley 26 borne on shaft 28 journaled in walls 30 of the fuze container indicated generally at 32. Pivotally mounted on pin 34 also journaled in walls 30 is firing pin lever 36, through which extends cord 24, and which carries toward its inner end a generally downwardly extending firing pin 38. The firing pin lever includes a clevis portion 40 which carries, extending therebetween, pin 42 over which cord 24 passes between pulley 26 and the outer portions of the probe, indicated generally at 44 and defined by beads 46 strung on the cord 24. 
     Seated on plate 50, which also defines the upper portion of the high explosive housing 92, is detonator holder support and booster carrier 52 which carries press fitted therein pin 54, which by virtue of head 56 secures detonator holder 58 down on support 52 for rotatably (about pin 54) slidable movement thereon. Spring 59 has ends which cooperate respectively with the support 52 and detonator holder 58 to urge the latter toward rotation about pin 54 relative to support 52. Prior to arming of the munition, as illustrated for example in FIGS. 2 and 6, this rotation is prohibited by clevis portion 60 of bore lock safety 62, which engages the sides of extension 64 of detonator holder 58. The inner tip 66 of the bore lock safety holds the firing pin 38 of the unarmed munition down in detent 68 of detonator holder 58. 
     Cord 24 extends from parachute 22 through a gap in a layer of beads 46, a hole in fuze cover plate 70, and a one-way opening defined by points 72 in firing pin lever 36, over pulley 26, pin 42, and then through member 74 and a multiplicity of beads 46. The cord is continuous, and all the beads in the munition are successively strung on it, but sufficient slack is left that in unarmed condition, the cord may be bent between the beads to permit folding up for storage of the beads above and alongside the fuze container defined by fuze cover plate 70 and side walls 30. The cord may suitably be provided at its end with knot 71 to prevent movement thereby of the lowest (in armed flight toward the ground) bead 46. 
     The member 74 has a shoulder 76 that cooperates with projection 78 of member case 80 to limit downward movement of the member 74. The member case 80 cooperates with the member 74 to provide for limited longitudinal movement of the latter, thus. In unarmed condition a second, upwardly directed shoulder 82 rests against the lower surface of pin 42. A third, and transversely, facing shoulder 84 of the member 74 is positioned to engage one lower edge 85 of firing pin lever 36 to hold it against rotation for safety should the member 74 move downwardly relative to the rest of the munition. 
     In operation, the shear pins 16 are first sheared by centrifugal force in firing, for example as one of a group of munitions in a container opening in the air. (If the munition is projected by hand, the pins may be first pulled.) The cover elements 12 thereafter drop away from the rest of the munition. The parachute 22 then unfolds and catches the air, while the beads 46, previously confined by the cover elements, begin to drop. The bore lock safety 62 falls away through the hole 32a; it may if preferred be secured to one of the cover elements 12 to fall away therewith. By the time the drag of the parachute has taken all the slack out of the cord 24, as shown in FIG. 4, the beads have been pulled by it into a probe of some length, in the preferred embodiment much more than the greatest dimension of the unarmed munition, say for example 20 feet. Firing pin lever 36 is caused by the movement of cord 24 to rotate clockwise (as shown in FIG. 4) about pivot 34 until its inner tip is stopped by fuze cover plate 70. With removal of the bore lock safety and lifting of firing pin 38 from detent 68, detonator holder 58 rotates about pin 54 so that detonator 84 moves into position over booster 86, as shown in FIG. 4. The points 72 in firing pin lever 36 permit the cord 24 to move upwardly through the firing pin lever easily, as slack is taken out by the parachute&#39;s drag, but do not permit movement of the cord downwardly therethrough. (Other means to provide one-way movement, for example employing a ratchet, may suitably be used.) 
     Ordinarily, firing then occurs at the predetermined standoff position when the munition is a distance above the ground corresponding to the length of the semi-rigid column or probe 44. If the munition falls in such a way that the probe receives from the ground a force with a longitudinal component, the effect is to move the probe upwardly relative to the rest of the munition, with the consequences that the shoulder 82 of member 74 upwardly urges the outer end of firing pin lever 36, pivoting the same about shaft 34 to drive firing pin 38 into detonator 84, which fires through booster 86 high explosive 90 in high explosive container 92. If the probe 44 has impact at an angle, the longitudinal component pressing upwardly on the lower portion of the firing pin lever 36 is supplemented by a downward pull in cord 24 through the probe, produced by bending of the probe. This downward force, because the cord 24 cannot move downwardly through the points 72 in the firing pin lever 36, also urges the firing pin down into the detonator 84, tending to pivot the firing pin lever about shaft 34. If the probe strikes at an extreme angle, this firing mechanism may become controlling, and thus of especial importance. In the unlikely event the probe should fail to fire the munition, firing upon impact of the main body of the munition with the ground nevertheless occurs, inertia driving the firing pin 38 then into the detonator. 
     Firing in mid-air is ordinarily prevented by the tension put by the parachute 22 and the probe 44 of the cord 24, holding the firing pin 38 away from the detonator 84 through moments about pin 34. In the event a shock wave for example should tend to drive the main body of the munition upwardly relative to the probe in mid-air, however, the member 74 drops to interpose shoulder 84 between the firing pin lever 36 and the wall 94, the distance therebetween being just sufficient to accept the end of the member 74 carrying said shoulder, so that firing pin lever 36 is jammed against rotation for in-flight safety against accidental firing. 
     The bead of FIG. 8 may be used in a probe in which increased rigidity is wished, while the bead of FIG. 9, successive beads in the probe being oppositely longitudinally directed as indicated, may be used if increased response to bending of the probe is desired. 
     The art has been thus provided with a novel munition filling the objects above set forth. Other embodiments of the invention as claimed hereinafter will occur to those skilled in the art.