Winding prevention belt retractor for passive shoulder belt system

摘要

The invention provides an inertia locking seat belt retractor for winding a shoulder belt having one end mounted on the vehicle door so that door movement moves the belt between stowed and restraining positions. The retractor has a winding prevention mechanism including a pawl and ratchet operable by a prior known control means to selectively lock the retractor against belt winding to hold the belt extended at a set slackened length with respect to the occupant. The improvement is comprised of a cam member which is rotatably mounted and has a cam surface which blocks movement of the pawl to the locked condition irrespective of the control means. The cam member also has a notch which allows the pawl to move to the locked condition with the ratchet. The cam member is coupled to the reel by a reduction gear set which causes the cam member to revolve less than one revolution during a plurality of reel revolutions upon movement of the belt between the fully wound and fully unwound conditions. The reduction gear set synchronizes the rotation of the cam member to align the circumferentially extending notch portion with the pawl only when the extent of belt unwinding is within the range of unwound length indicative of the belt having assumed an effective restraining length relative the occupant. Accordingly, the pawl is blocked from possible engagement with the ratchet and a previously engaged pawl will be disengaged from the ratchet whenever the door is opened.