an emergency locking seatbelt retractor . the retractor includes a pivoting lock plate which can pivot through a limited arc during activation of a webbing sensor or a vehicle sensor . when the lock plate is in its quiescent position , a pin thereon operates to hold a lock bar out of engagement with ratchet teeth on the webbing spool , thereby allowing free rotation of the spool . if either or both of the webbing sensor and vehicle sensor are activated , the lock plate is caused to pivot , drawing the pin away from the lock bar and allowing the lock bar to engage the ratchet teeth , thereby locking the retractor . additionally , the locking initiation mechanism and the sensors are isolated from webbing withdrawal forces and may therefore be constructed of lightweight , inexpensive materials . the retractor includes a vehicle sensor which is effective in substantially eliminating any vertical motion of the sensor ball . this prevents the retractor from locking when it is subjected to a downward acceleration .