Emergency lock safety belt retractor with lock-up release mechanism

Abstract

An emergency lock safety belt retractor is designed to facilitate release from an inadvertent lock-up which may occur after full-speed retraction of the seat belt. This undesired lock-up is due to a latch mechanism which locks a belt spool in response to either excessively abrupt onset of extraction, such as may occur in front-end automotive accidents, or excessively abrupt cessation of retraction. This latch mechanism has two separate latches: a simple latch pawl biased away from its latched position and a more complicated lock wheel. The latch pawl is mounted on a rotary drum and in its latched position engages teeth on a stationary drum. The lock wheel is coupled for rotation with the belt spool but is free to move axially through three regimes. The lock wheel is biased toward a first axial regime in which it couples the rotary drum to the belt spool. In the second regime, it couples the belt spool to both the rotary drum and a set of stationary latch teeth, thus locking the belt spool and the rotary drum against rotation in the direction of extraction of the belt. In the third regime, the belt spool and latch teeth remain coupled while the rotary drum is released. The coupling between the lock wheel and the belt spool causes the lock wheel to move from the first to the second to the third regime as the belt is extracted slightly after the latch pawl is engaged.