Patent Publication Number: US-4220091-A

Title: Delay fuze for explosive charge

Description:
GOVERNMENTAL INTEREST 
     The invention described herein may be manufactured, used and licensed by or for the government for governmental purposes without payment to us of any royalty thereon. 
    
    
     BRIEF SUMMARY OF THE INVENTION 
     The present invention relates to delay fuzes for explosive devices, and particularly for hand grenades. 
     In accordance with the invention, an explosive device is provided with a novel delay fuze including a housing, a barrier plate having an eccentric hole at one end of the housing, a first member fixed in the housing, spaced from the barrier plate, having a first elongated passage out-of-line with the barrier plate hole, a second member in the housing, between the barrier plate and the first member, having a second elongated passage aligned in a first position with the first passage and movable to a second position in alignment with the barrier plate hole, a unitary combustible delay cord extending through both passages and initially preventing relative movement of the two members, means for igniting the end of the cord remote from the barrier plate, and spring means for moving the second member to the second position after the cord has burned to the junction of the two passages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an axial section view, taken along the angled line 1--1 of FIG. 2, of a hand grenade embodying the present invention. 
     FIG. 2 is a top plan view of a portion of the grenade of FIG. 1. 
     FIG. 3 is a side view, partially cut-away, of the fuze of FIG. 1. 
     FIG. 4 is a transverse section view of a central portion of the fuze of FIG. 1 taken on line 4--4. 
     FIG. 5 is a side elevation view of FIG. 4, taken in the direction 5--5. 
     FIG. 6 is a transverse section view taken along line 6--6 of FIG. 1. 
     FIG. 7 is a transverse section view taken along the line 7--7 of FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 through 7 illustrate a hand grenade 1 embodying an example of the present invention. Grenade 1 comprises a hollow shell 3, which may be generally spherical, as shown in FIG. 1, having a single opening 5, surrounded by an outwardly-extending, internally-threaded hub 7. A generally cylindrical delay fuze 9 embodying the invention is axially mounted in the opening 5. 
     Fuze 9 includes a tubular housing 11 comprising an externally-threaded outer portion 13 threaded into the hub 7 and terminating in a flange 15, and an inner portion 17. The inner surfaces of parts 13, 15 and 17 constitute a continuous cylindrical bearing surface 19. The inner end of portion 17 is reduced in diameter at 21 and closed by a transverse barrier plate 23 and a booster charge cup 25 to form a booster charge cavity 27 therebetween. Barrier plate has a single eccentric hole 29, located on the right side in FIG. 1. Contiguous to the barrier plate 23 is a mandrel 31 comprising a cylindrical inner end 33 rotatable in the tubular portion 17, in bearing 19, and a reduced cylindrical extension 35. The extension 35 extends through and also rotates in a bushing 37 which is fixed within the tubular portion 17 by a pin 39. The mandrel is biased to rotate counter-clockwise relative to the bushing 37 by a torsion spring 40. As shown in FIG. 7, this rotation is limited to about 90° by an axial pin 41 in the mandrel and an arcuate groove 42 in the bushing 37. A flange plate 43 is attached to the end of extension 35 by a screw 44 and keyed with a radial pin 45 in the plate engaging a radial notch 47 in the extension 35. Prior to firing the grenade, rotation of plate 43 with respect to the bushing 37 is prevented by an axial safing pin 49, the inner end of which engages two mating semi-cylindrical grooves 53 and 55 in the plate and bushing. The safing pin 49 extends through a cylindrical body 57 held in the hub 7 by a screw 59. Pin 49 is biased outwardly by a spring 61 recessed into body 57 and engaging a flange 63 on the pin, and held in locking position, against spring 61, by a manually-held safety spoon 65. The spoon 65 comprises a top plate 67 having two side flanges 69 detachably hinged by angled slots 71 and a dowel pin 73 mounted in hub flange 15, and a handle 75. A detachable safety pin 81 may be used to lock the spoon 69 to the flange 15. The travel of safing pin 49 is restricted by a pin stop leaf spring 77 which is staked at 79 to the outer face of body 57. The space between the shell 3 and the fuze 9 is filled with high explosive material 82. 
     The firing train of the fuze comprises a detonator 83 housed in the mandrel 31 on the left side of FIG. 1, which is angularly displaced from the barrier plate hole 29 by 90° (with the angled section line 1--1). A unitary elongated lead-cased PDC (pyrotechnic delay cord) 85 extends from the detonator 83, through aligned passages 87 and 89 in the mandrel 31 and bushing 37, to an igniter or flash stem 91, such as a &#34;Magicube&#34;, located near the body 57. The igniter 91 is initiated, after release of the spoon 69 and safety pin 81, by a cocked spring wire striker 93 (see FIGS. 4 and 5) which is staked at 95 in a groove 97 in the body 57. 
     In operation, the spoon handle 79 is manually held against the grenade shell 3 while the safety pin 81 is removed, and the grenade is then thrown at the target in the usual manner. Upon release of the handle 79, the spoon is removed by the pin 49 and its spring 61. As the pin 49 moves outward, it releases the plate 43 an mandrel 31 for rotation, and simultaneously releases the cocked striker 93 to ignite the flash stem 91, which in turn starts the combustion of the PDC 85. Rotation of the mandrel 31 by the torsion spring 40 is prevented by the body of the PDC 85 until the latter burns therealong to the junction of the mandrel 31 and the bushing 37, in the transverse plane 99. The PDC 85 disintegrates at plane 99, allowing the spring 40 to rotate the mandrel 31 through 90°, which aligns the burning inner portion of PDC 85 and the detonator 83 with the barrier plate hole 29, thereby initiating the booster charge 27 a predetermined delay time after the grenade is thrown. 
     The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, because obvious modifications will occur to a person skilled in the art.