This invention relates generally to explosive cartridges, and more particularly to a cartridge which is manufactured to explode a predetermined number of seconds or fraction of a second after firing. In its preferred form, the invention includes a train of pressure-consolidated ignitable charges containing metal and metallic oxide which serves as a fuse leading from a primer and an initial shock chamber to an explosive propellant adapted to deliver a work output on some device such as a parachute assembly.
The cartridge of the present invention provides a reliable means for opening a parachute a precise interval of time after an object has been dropped from an airplane. Heretobefore, the most widely used means for opening a parachute on a dropped object has been by means of a rip cord line extending from the plane, and of a length believed to be great enough to avoid entanglement of the parachute by the plane or the air currents produced by it. The rip cord line itself has been a cause of erratic performance and accident, however. Sometimes it became entangled with the plane or dropped object, or with other planes or parachutes engaged in the same dropping operation. The time lapse before opening of the parachute could not be controlled with accuracy. The lines and mechanical connections added useless weight and were subject to deterioration and damage even prior to use.
The delayed firing cartridge eliminates the need for any connection between the plane and the dropped object. It and the operating mechanism by which it opens the parachute are very reliable in operation, small in size, and light in weight. Moreover, the cartridge can be fabricated to discharge at precisely the desired interval after firing, without being subject as rip cord lines are to variations in time arising out of different flying and dropping conditions.
The present cartridge may be used in other applications in which a time fuse is required, particularly for delivering a few foot pounds of work after the lapse of a few seconds. It can be used in aircraft ejector seats, missile mechanism, submarine emergency devices, fire alarm systems, etc. In larger sizes the time delay and energy output can be greatly increased. In such sizes, it can be used for small blasting purposes, and in devices for lifting heavy objects into position.