Friction welded seal caps for grenade casings - involving thin coatings pref. of polyvinylidene fluoride or chloride

摘要

Chamber of an explosive or smoke grenade or shell is sealed by rotary friction welding a cap on to a suitable annular land at the chamber mouth, both the cap and the land having a thin coating of thermoplastic material. The component surfaces may be pretreated to improve anchorage of their respective thermoplastic coatings. Pref. the coatings are only a few tengths of a mm thick. Pref. the coatings are of polyvinylidene-fluoride or -chloride. The rotary motion may be oscillatory. Pref. the seal and/or land interfaces are ribbed. This provides a better long term seal for protective sensitive contents, such as a charge of TNT, than a mechanically clamped seal with or without an ancillary seal profile such as a rubber 'O' ring. The quantity of heat necessary for fusing thin coatings is small enough not to affect the casing body of its contents significantly.