Ratchet device having a stopper member for preventing excessive rotation of ratchet wheel, and tape feeding apparatus using the ratchet device

摘要

A ratchet device is disclosed which includes a body, a ratchet wheel rotatably supported by the body, a feed pawl having an engaging portion engageable with teeth of the ratchet wheel, a support member for holding the feed pawl, a member for biasing the feed pawl toward the wheel teeth, and a drive device for moving reciprocating the support member between two positions to place the feed pawl alternately in its fully advanced and retracted positions, so as to rotate the ratchet wheel a predetermined angle in one direction. The ratchet device further includes a stopper member for contact with the feed pawl when the pawl is placed in the fully retracted position, to thereby prevent the engaging portion of the pawl from disengaging from the teeth of the ratchet wheel. Further, the engaging portion of the feed pawl is shaped so that it engages mutually opposed faces of the ratchet wheel when the feed pawl is in contact with the stopper member, to thereby lock the ratchet wheel against clockwise and counterclockwise rotations thereof. Also disclosed is a tape feeding apparatus which utilizes the ratchet device.