Lock mechanism for webbing retractor

A lock mechanism for a webbing retractor employed in a seatbelt system for a vehicle to prevent an occupant restraining webbing from being unwound when an emergency situation of the vehicle occurs, which comprises:

• (a) a frame secured to the vehicle;
• (b) a take-up shaft rotatably supported by said frame for winding up said webbing from one end thereof by means of a biasing force;
• (c) a lock wheel rotatably supported on one end portion of said take-up shaft which rotates substantially in unison with said take-up shaft in a direction which said webbing is unwound, said lock wheel and said take-up shaft being connected together by a biasing means interposed therebetween, said lock wheel having ratchet teeth formed around the outer peripheral porton thereof;
• (d) a pawl lever activated by the action of an acceleration sensor to move toward the ratchet teeth on said lock wheel so as to engage with said ratchet teeth, thus causing the rotation of said lock wheel to be delayed with respect to the rotation of said take-up shaft;
• (e) lock means for locking the rotation of said take-up shaft in the webbing unwinding direction when the rotation of said lock wheel is delayed with respect to the rotation of said take-up shaft;
• (f) a rotary wheel secured to an end face of said one end portion of said take-up shaft so as to rotate together with said take-up shaft;
• and
• (g) follower means including a spring member having a substantially V-shaped portion and an extended portion defined by one end of said V-shaped portion which is bent to extend toward the other end of said V-shaped portion, and a substantially triangular-shaped arm connected to the distal end of said extended portion of said spring member, said spring member frictionally engaging the take-up shaft at three discrete points to rotate therewith, said three points including points at both sides of said V-shaped portion and said extended portion, respectively, and wherein said spring member pushes said arm against said pawl lever in a direction to make said pawl lever inoperative when the take-up shaft rotates in a direction to wind-up the webbing;
• whereby, when the vehicle is running on a rough road, said webbing is prevented from being gradually wound up onto said take-up shaft.

A lock mechanism for a webbing retractor employed in a seatbelt system for a vehicle to prevent an occupant restraining webbing from being unwound when an emergency sitution of the vehicle occurs, which comprises:

• (a) a frame having a pair of leg plate portions and secured to the vehicle;
• (b) a take-up shaft retaining one end of said webbing and extending through the leg plate portions of said frame so as to be rotatably supported at two longitudinal ends thereof by said leg plate portions, respectively;
• (c) a spiral spring-operated retractor interposed between one end portion of said take-up shaft and the leg plate portion closer to said end portion and adapted to bias said take-up shaft so as to rotate in a direction in which said webbing is wound up;
• (d) a lock wheel rotatably supported on the other end portion of said take-up shaft and having ratchet teeth formed on the outer peripheral portion thereof;
• (e) a rotary wheel secured to the end face of said other or second end portion of said take-up shaft in such a manner as to rotate together with said take-up shaft;
• (f) a torsion coil spring interposed between said lock wheel and said rotary wheel to bias said lock wheel so as to rotate substantially in unison with the rotation of said take-up shaft in a direction in which said webbing is unwound;
• (g) an acceleration sensor supported by the leg plate portion closer to the second end portion of said take-up shaft and having a conical recess which receives a ball, such that, when acceleration acts, said ball goes up said conical recess;
• (h) a pawl lever pivotally placed on said ball in such a manner that, when said ball goes up said conical recess, said pawl lever is engaged with the ratchet teeth of said lock wheel, thus causing the rotation of said lock wheel to be delayed with respect to the rotation of said take-up shaft;
• (i) lock means including an internallytoothed ratchet wheel rigidly secured to the leg plate portion closer to the second end portion of said take-up shaft in such a manner as to be disposed around said take-up shaft, and a pair of lock plates having a substantially C-shaped cross-section and disposed in such a manner as to clamp the outer peripheral portion of said take-up shaft so as to rotate together with it, said lock plates being adapted such that, when the rotation of said lock wheel is delayed with respect to the rotation of said take-up shaft, said lock plates are caused by said lock wheel to move toward said internally-toothed ratchet wheel so as to be engaged therewith;
• and
• (j) follower means including a spring member having a substantially V-shaped portion and an extended portion having a distal end that is defined by one end of said V-shaped portion which is bent to extend toward the other end of said V-shaped portion, and a substantially triangular-shaped arm connectable to the distal end of said extended portion of said spring member, said spring member frictionally engaging the take-up shaft at discrete points to rotate therewith, said three pints including points at both sides of said V-shaped portion and said extended portion, respectively, and wherein said spring member pushes said arm against said pawl lever in a direction to make said pawl lever inoperative when the take-up shaft rotates in a direction to wind-up the webbing;
• whereby, when the vehicle is running on a rough road, said webbing is prevented from being gradually wound up onto said take-up shaft.