When designing and manufacturing a fragmentation grenade (a pressed explosive inside a rugged steel case), there are several practices to be avoided. Pre-assembly of the case followed by explosive insertion and closure by welding is dangerous and can alter the metallurgical properties of the case. Threading a two piece design together is also dangerous as threads can press on stray material and trigger a charge. Additionally, rotating explosive material creates friction and is bad practice. Navy researchers have investigated “press fit” designs but these have struggled to attain a necessary ruggedness standard.
Additional work on the design has produced a two-piece, snap-fit interlocking structure requiring relatively little force to assemble; but, a large force to pull apart. It snaps together similarly to a two-piece plastic egg. No adhesive bonding is needed. The design represents an ideal balance between fragmentation capacity, ruggedness, and safe manufacturability. The exterior of the case is a series of tiles separated by interconnecting grooves. The tiles and grooves may have different widths and depths respectively. With regard to applications, this is primarily a military grenade but it may also be configured as a bullet, missile, other ammunition, or any other device meant to fragment into components – lethal or non-lethal. Non-military applications may include police use in riot suppression (loaded with rubber balls) or as a computer hard drive or an electrical component enclosure designed to fragment under predetermined conditions.
US patent 9,738,948 is related to US patent 9,738,947.
- Hardness of the steel can be varied down to a point of brittleness
- Assembly can be performed under loads achievable with a common, hand operated Arbor press
- Prototypes, CAD drawings, results data available
- US patents 9,738,947 and 9,738,948 available for license
- Potential for collaboration with Navy researchers