1. Field of the Invention
The present invention relates to an improved fuze initiation device to allow faster warhead detonation, and more particularly, to such a device for use in the M759 or similar stab upon impact type fuzes.
2. Background Art
The AH-64 Apache is a four-blade, twin-engine attack helicopter with a tandem cockpit for a crew of two, whose mission involves close air support to fulfill that mission; regarding which mission; the Apache is provided with an M230 chain gun with 1,200 rounds of 30 mm ammunition. The M230 Chain Gun is a single-barrel electrically operated, automatic cannon that was developed by Hughes and is currently manufactured by Alliant Techsystems. The M230 is a formidable weapon that is electrically primed, has a chamber pressure measured at 40,600 to 44,950 psi, and a muzzle velocity of 2,640 feet per second for both target practice (TP) and high-explosive dual purpose (HEDP) type ammunition. The “dual purpose” of the HEDP ammunition is its design for both anti-materiel and anti-personnel purposes. This HEDP ammunition has an aluminum cartridge, and a steel body loaded with 27 grams of PBXN-5 high explosive charge. Each HEDP round, or cartridge, or projectile, incorporates a spin compensated shaped charge liner, to help compensate for the 60,000 rpm terminal spin, and has a dual function, type M759 fuze. The fuze arms while the projectile is in flight and initiates detonation of the projectile's explosive fill upon a direct impact that causes immediate loss of velocity/momentum (i.e. dual mode action). The shaped charge liner collapses upon detonation creating an armor piercing jet with an estimated penetration performance which is in excess of 50 mm rolled homogeneous armor (RHA) at 2,500 meters. Fragmentation of the projectile body also occurs upon detonation thereby producing significant antipersonnel effects.
The current M759 fuze design incorporates as an initiation feature a generally cylindrical nylon probe with a surrounding aluminum confinement cap that moves rearward upon target impact to trigger the firing pin, i.e. point detonation (PD). This generally cylindrical nylon probe, which is located in the fuze at the nose of the 30 mm cartridge, has an integral cylindrical shoulder extending from the lower section thereof; which nylon shoulder, abuts a ledge within the aluminum o-give section of the fuze, which ledge is located toward the front of the cartridge. When the cartridge is fired, the probe is subjected to an acceleration, or setback load, of up to 100,000 g's and the subject nylon shoulder is forced, in a rearwards direction against the ledge. However, this nylon shoulder is designed to resist this setback level of force and will therefore keep the probe from moving rearward and triggering the firing pin, until the cartridge impacts a hard target and abruptly stops. Upon such a sudden stop, the force rearward imparted to the probe and its aluminum confining cup, causes the nylon shoulder to shear away against the aluminum ledge, allowing the probe to move rearwards within the fuze, thereby impacting the firing pin to initiate the detonation chain, i.e. the firing pin hits the sensitive primary explosive within the fuze (a “stabbing” type effect), which detonates and in turn ignites the secondary explosive in the body of the cartridge.
The design of the current nylon shoulder probe system is such that the nylon shoulder will not reliably shear away when the cartridge hits a soft target, such as sandy ground or plowed fields, or hits a glancing blow, where the cartridge does not immediately stop. Therefore, there is a need in the art for an initiation mechanism within the M759, or similar stab upon impact type fuzes, that will reliably allow the detonation of the cartridge upon impacting either a hard or soft target, directly or glancing. Such an initiation mechanism will afford increased lethal effect over the prior art, when utilized against soft targets in anti-personnel applications, while expending fewer cartridges.
The present invention relates to a simple, reliable, and relatively inexpensive initiation mechanism to initiate the detonation upon and only upon impact of M759 or similar stab upon impact type fuzes—impact that may be directly or tangentially against a hard target, or soft target. In the present invention a generally cylindrical target sensing probe, preferably manufactured of a light weight metal, is provided within a generally cylindrical channel located immediately behind the windscreen in the nose of the fuze, the target sensing probe has an annular section extending from and running along a length of its middle, which section touches and rides against the cylindrical interior of the channel to keep the target sensing probe centered as it moves within the cylindrical channel. The target sensing probe is provided with an anti-setback spin clip, which clip prior to firing is generally horse shoe shaped, with its open end forced about and lodged in a grove within and about the body of the generally cylindrical target sensing probe, but extending partially therefrom. Adjacent to the extending portion of this clip, and just rearward within the fuze therefrom, is a ledge within the aluminum o-give; which ledge extends inward toward the center line of the cartridge, so as to support the portion of the clip extending from the grove—such that during firing, and setback, this overlap will keep the clip and the target sensing probe, within which it is crimped, from moving rearward within the fuze and from impacting the firing pin. After firing, with the onset of spin, the clip will expand away from, out of, and clear of the grove within the target sensing probe and into the cylindrical channel. Due to a thinned area in the middle or apex of the horse shoe shaped clip, the expansion of the clip will be a plastic deformation and the clip once opened/expanded will remain open/expanded. The expanded clip, as stated, will be moved entirely clear of the grove within the target sensing probe, there being adequate space/clearance between the wall of the cylindrical channel and the target sensing probe—such that when the target sensing probe impacts its target, the obstructed forward travel of the target sensing probe will force it rearwards in the fuze (there being now no impediment to such a motion). The target sensing probe will impact the piston assembly, which houses the firing pin, located immediately rearward thereof within the fuze; thereby, forcing the firing pin rearward and initiating the firing train of the fuze, and subsequently, igniting the secondary explosive within the cartridge to cause detonation thereof.
The target sensing probe in the subject invention is preferably manufactured of light weight metal, preferably aluminum, or of a filled polymeric material; as, such obvious alternative materials as unfilled Lexan® (a brand of unfilled polycarbonate resin thermoplastic used in making bullet proof glass applications), or acrylonitrile butadiene styrene (ABS) (a common thermoplastic used to make light, rigid, molded products such as piping) were found inadequate under the subject setback and rotation forces. Applications experiencing lesser setback and rotation forces may allow the use of unfilled materials.
The subject metallic target sensing probe is preferably designed to be of comparable mass to that of the prior art nylon probe and confinement cup—so as to provide comparable flight stability. Therefore after significant experimentation, an aluminum metallic target sensing probe was designed, with a cylindrical boring along the longitudinal axis to reduce its mass to the desired level. The preferred aluminum probe has a front face adjacent to and open toward the windscreen at the front of the fuze and the rear face located rearward within the fuze, which second end is closed, i.e. a blind hole. Alternatively, other light weight metals, such as magnesium may suffice; however, their configuration may require tweaking to obtain the required mass.
Further features and advantages of the present invention will be set forth in, or apparent from, the detailed description of preferred embodiments thereof which follows.
For reference purposes, shown in
In contrast to the prior art of
The target sensing probe 50 of the fuze 200 of the present invention is also provided with an anti-setback spin clip 30, manufactured of cartridge brass or a similar metal. Initially, i.e. prior to firing of the subject cartridge, the clip 30 which is generally horse shoe shaped, is crimped in a groove 40 toward the rear of the body of the subject probe 50; but extending partially out of the groove 40 (a position not shown in
After firing of the cartridge, with the onset of spin and under the centripetal force generated thereby, the anti-setback spin clip 30 will expand away from and out of the grove 40 in the direction of the arrows A, and lodge against the wall of the cylindrical channel 45. As shown in
Continuing to refer to
Although the invention has been described above in relation to preferred embodiments thereof, it will be understood by those skilled in the art that variations and modifications can be effected in these preferred embodiments without departing from the scope and spirit of the invention as claimed.
The inventions described herein may be manufactured, used and licensed by, or for, the U.S. Government, for U.S. Government purposes.
Number | Name | Date | Kind |
---|---|---|---|
2137983 | Remondy | Nov 1938 | A |
3956992 | Tari | May 1976 | A |
4013013 | Davis | Mar 1977 | A |
4466351 | Strobush | Aug 1984 | A |
5243912 | Ziemba | Sep 1993 | A |
7357081 | Zinell et al. | Apr 2008 | B2 |