EXPLOSIVE TUBE APPARATUS FOR PRETENSIONER AND MANUFACTURING METHOD THEREOF

PURPOSE: A gunpowder pipe unit for a safety belt and a manufacturing method thereof are provided to reduce insertion interference of gunpowder in bending of an uniform diameter of a steel pipe and stand pressure due to explosion of gunpowder by expanding the steel pipe. CONSTITUTION: A steel pipe(100) used for pre-tensioner is cut to a desired length. One end of the cut steel pipe is expanded and thus the diameter of an original steel pipe(110) becomes different from that of an expanded steel pipe(120). The original steel pipe is bent. The expanded steel pipe is shear-deformed to the bent original steel pipe in one direction. For powder(200) to be able to be put into, the diameter of the original steel pipe deformed by the bending is relatively increased.