Ball-point pen with knife blades - has blades masked by ball-point when used for writing

摘要

The ballpoint pen or pen cartridge has knife blades to allow easy opening of cartons etc. One or more blades (2) are so mounted on the tip of the cartridge (1) that they are masked by the ballpoint (3) when this is used for writing. Alternatively, a blade can slide in a guide rail in the pen clip, being guarded when not in use.