Take-up spool latch

Abstract

A take-up spool latch for a seat belt retractor of the type comprising a spool journalled for rotation in a spool frame and incorporating a torsion spring for retracting a seat belt, the latch having a clutch member and a brake member with means between them limiting relative movement, both the clutch and brake members having cam surfaces thereon which are engaged by a pawl which co-operates with a ratchet on the spool and is so arranged that: A. upon retraction of a seat belt which has been withdrawn from the spool the cam surfaces retain the pawl out of engagement from the ratchet teeth, B. upon initial further withdrawal and during the limited rotation between the brake and clutch member the pawl is released by the cam surfaces and engage the ratchet teeth thereby preventing retraction, C. upon still further withdrawal the cam surfaces again engage the pawl and retain it out of engagement from the ratchet teeth, so that full retraction can again take place.

What I claim is: 
     
       1. In a seat belt retractor having a spool frame, a spool journalled for rotation in the spool frame, and a torsion imparting spring operably connected between the spool and the spool frame arranged for retracting a belt when carried on the spool, a take-up spool latch comprising: a clutch member coaxial with the spool and in frictional engagement with the spool,   a brake member coaxial and rotatable with respect to the spool and in frictional engagement with the spool frame,   interengaging means between the clutch and brake members limiting relative rotation therebetween,   cam surfaces on both the clutch member and the brake member,   a ratchet having ratchet teeth on the spool, and   a pawl pivoted to the spool frame for engaging the cam surfaces of both the clutch and brake members and the ratchet teeth, the cam surfaces controlling the engagement of the pawl with the ratchet teeth such that: a. upon retraction of a seat belt which has been withdrawn from the spool, the cam surfaces pivot the pawl out of engagement with the ratchet teeth,   b. upon initial further withdrawal and during said limited relative rotation between the clutch and brake members, the pawl is released by the cam surfaces and pivots to engage the ratchet teeth thereby preventing retraction, and   c. upon further withdrawal to and beyond said limited relative rotation accomplished by the interengaging means, the cam surfaces again engage the pawl and pivot it out of engagement with the ratchet teeth.     
     
     
       2. A take up spool according to claim 1 wherein the clutch member and brake member are both discoid members, said cam surfaces being peripheral surfaces of said respective said discoid members. 
     
     
       3. A take up spool according to claim 2 wherein the spool includes an end plate and each said discoid member is provided with an annular friction pad, the friction pad of said clutch member bearing against said end plate of the spool, the friction pad of said brake member bearing against the spool frame, the effective mean radius of the friction pad of the clutch member being greater than the effective mean radius of the friction pad of the brake member, and a spring between the clutch and brake members effecting said frictional engagements. 
     
     
       4. A take up spool according to claim 2 wherein said interengaging means between the clutch and brake members includes a spigot outstanding from a face of one said members movable in a circumferential recess in the periphery of the other said member. 
     
     
       5. A take up spool according to claim 2 wherein said pawl is a double lobe pawl, one lobe extending over the peripheries of both said discoid members, the other lobe being that portion of said pawl which is releasably engageable in the said ratchet teeth. 
     
     
       6. A take up spool according to claim 2 further comprising a brake lug projecting from a face of the brake disc, and an arcuate slot in the spool frame, the brake lug being movable in the arcuate slot but said movement being limited by the ends of said slot. 
     
     
       7. In a seat belt retractor having a spool frame, a spool journalled for rotation in the spool frame, and a torsion imparting spring operably connected between the spool and the spool frame arranged for retracting a belt when carried on the spool, a take up spool latch comprising: a clutch disc and a brake disc both coaxial and rotatable with respect to the spool,   a spring between said discs urging the clutch disc into frictional engagement with the spool and the brake disc into frictional engagement with the spool frame,   interengaging means between the brake disc and the spool frame limiting rotary movement of the brake disc,   a radially inwardly extending pawl recess in the periphery of the brake disc, a radially inwardly extending recess in the periphery of the clutch disc of greater circumferential length than the pawl recess, said peripheries and recesses forming co-operating cam surfaces,   a spigot outstanding from a face of one of the discs, and co-operable limit means on the other disc engageable by the spigot to thereby limit relative rotation of discs to a degree exceeding said limited rotary movement of the brake disc,   a ratchet having ratchet teeth on the spool,   a pawl pivoted on the spool frame arranged to engage the ratchet teeth and also to engage the cam surfaces, the inter-relation of said interengaging means, cam-forming recesses and limit means being so arranged that: a. upon retraction of a seat belt which has been withdrawn from the spool, the clutch disc is urged to rotate owing to said frictional engagement with the spool and the brake disc is urged by the spigot to rotate, whereby the pawl recess moves into alignment with the pawl but the cam surface of the clutch disc pivots the pawl out of engagement with the ratchet teeth,   b. upon initial further withdrawal of the seat belt from the spool and during said limited relative rotation between said clutch and brake discs the clutch disc is urged to rotate in a reverse direction to place its radially inwardly extending recess into alignment with the pawl, whereby the pawl pivots to engage the teeth of the ratchet, and,   c. upon further withdrawal beyond the limit of said limited relative rotation of the discs, the spigot of the clutch disc imparts rotation to the brake disc and the cam surface of the brake disc lifts and pivots the pawl out of engagement with the ratchet teeth.     
     
     
       8. A take up spool lug according to claim 7 wherein said clutch disc has a clutch friction pad thereon in frictional engagement with said spool; said brake disc has a brake friction pad thereon in frictional engagement with said spool frame, the clutch friction pad being displaced further from the spool axis than the brake friction pad whereby the clutch friction pad transmits more drive torque than the brake friction pad and upon spool rotation the clutch disc causes rotary movement of the brake disc. 
     
     
       9. A take up spool lug according to claim 7 wherein said spigot is outstanding from a face of the clutch disc and lies within a further radially inwardly extending recess in the brake disc, the ends of which recess constitute with the spigot said co-operable limit means. .Iadd. 10. In a seat belt retractor having a spool frame, a spool journalled for rotation in the spool frame, and a torsion imparting spring operably connected between the spool and the spool frame arranged for retracting a belt when carried on the spool, a take-up spool latch comprising: a clutch member journalled for rotation relative to the spool,   a brake member journalled for rotation relative to both the spool and clutch member,   drive means between the clutch member, spool and brake member,   interengaging means between the clutch member and brake member limiting relative rotation therebetween,   cam surfaces on both the clutch and brake members,   a ratchet, having teeth, on the spool,   a pawl carried by and movable with respect to the spool frame for engaging the ratchet teeth, and cam engaging means coupled to the pawl and engaging the cam surfaces of both the clutch and brake members, the cam surfaces controlling the engagement of the pawl with the ratchet teeth such that: a. upon retraction of a seat belt which has been withdrawn from the spool at least one of the cam surfaces engages the cam engaging means and holds the pawl out of engagement with the ratchet teeth,   b. upon initial further withdrawal spool rotation causes cam movement which in turn allows the pawl to engage the ratchet teeth thereby preventing retraction, and   c. said cam surfaces of the clutch and brake members co-operate to move and to hold the pawl out of engagement with the ratchet teeth during further     
     
     
        withdrawal and subsequent retraction. .Iaddend..Iadd. 11.  In a seat belt retractor having a spool frame, a spool journalled for rotation in the spool frame, and a torsion imparting spring operably connected between the spool and the spool frame arranged for retracting a belt when carried on the spool, a take-up spool latch comprising: a clutch member journalled for rotation relative to the spool,   a brake member journalled for rotation relative to both the spool and clutch member,   drive means between the clutch member, spool and brake member,   interengaging means between the clutch member and brake member limiting relative rotation therebetween,   cam surfaces on both the clutch and brake members,   a ratchet having teeth on the spool,   a pawl, pivot means on the spool frame supporting the pawl for pivotal movement, cam engaging means coupled to the pawl and engaging the cam surfaces of both the clutch and brake members so that the pawl is pivoted into or out of engagement with the ratchet teeth upon rotational movement of the clutch and brake members, such that: a. upon retraction of a seat belt which has been withdrawn from the spool, the pawl is out of engagement with the ratchet teeth,   b. upon initial further withdrawal and during said relative rotation between the clutch and brake members, the pawl pivots into engagement with the ratchet teeth thereby preventing retraction, and   c. upon further withdrawal the cam surfaces again pivot the pawl out of     
     
     
        engagement with the ratchet teeth. .Iaddend..Iadd. 12.  A take-up spool latch according to claim 11 wherein said clutch member is co-axial with and in frictional engagement with said spool, said frictional engagement forming said drive means between the clutch member and spool. .Iaddend..Iadd. 13. A take-up spool latch according to claim 12 wherein said interengaging means between the clutch and brake members includes means outstanding from one said member and engaging the other said member, and forms at least part of said drive means between the members. .Iaddend..Iadd. 14. In a seat belt retractor having a seat belt carried on a spool, a torsion imparting spring arranged for retracting the belt on the spool and an emergency locking means for preventing belt withdrawal upon sudden change in vehicle inertia, a take-up spool latch means for relieving tension on the belt when withdrawn from the spool and placed in use which acts independently of said emergency locking means, comprising: ratchet means associated with said spool and having ratchet teeth inclined in a direction to prevent retraction of said spool;   pawl means engageable with said ratchet teeth; and   means frictionally driven by said spool for holding said pawl means out of engagement with said ratchet teeth during retraction of said belt on said spool and for allowing said pawl means to engage said teeth in response to spool rotation imparted by a retraction movement of a withdrawn seat belt followed by a subsequent limited further withdrawal movement of said belt said frictionally driven means including means for causing said pawl means to release said ratchet means and allow retraction of said belt on said spool automatically by the urging of said torsion imparting spring upon a still further withdrawal movement of said belt beyond said limited further withdrawal of said belt. .Iaddend..Iadd. 15. The take-up spool latch means of claim 14 wherein said frictionally driven means comprises:   a clutch member frictionally driven by said spool and having a first cam surface engaging said pawl means, said first cam surface including a clutch recess therein;   a brake member having a second cam surface engaging said pawl means, said second cam surface including a brake recess therein;   interengaging means between said members allowing limited relative rotation therebetween but otherwise effecting concurrent rotation; whereby   after withdrawal of a seat belt on said spool said retraction movement of said belt moves one of said members into a position where its recess is in alignment with said pawl means and said subsequent limited further withdrawal movement of said belt moves the other of said members relative to the first said member to place said recess of the other said member also in alignment with said pawl means allowing said pawl means to engage said ratchet teeth. .Iaddend..Iadd. 16. In a seat belt retractor having a spool frame, a spool journalled for rotation in the spool frame, and a torsion imparting spring operably connected between the spool and the spool frame arranged for retracting a belt when carried on the spool, a take-up spool latch means comprising:   a clutch member frictionally driven by said spool and having a first cam surface;   a brake member driven by said clutch member, interengaging means between said members allowing only limited relative rotation therebetween, said brake member having a second cam surface;   a retraction preventing ratchet and pawl means associated with said spool and cam surfaces for selectively preventing retraction of said spool on alignment of said members in predetermined manner relative to said ratchet and pawl means; and   means for mounting said members for limited movements under the drive of said spool for bringing said members into said alignment in response to spool rotation imparted by a retraction movement of a withdrawn belt followed by a subsequent limited further withdrawal movement of said belt   
     
     
        thereby engaging said pawl means with said ratchet. .Iaddend. .Iadd. 17. In a seat belt retractor having a seat belt carried upon a take-up spool, a spool retracting spring for normally biasing said spool in a belt retracting direction and thereby normally imparting tension to the seat belt when it is placed in use, and a spool locking means for locking the spool against belt withdrawal under emergency conditions, the improvement comprising the provision of: pawl and ratchet means associated with said spool independent of said spool locking means for preventing retraction of said belt under urging of said spring; and   means driven by rotation of said spool for operating said pawl and ratchet means to prevent belt retraction under urging of said spring in response to spool rotation imparted by a retraction movement of a withdrawn belt followed by a subsequent further limited withdrawal movement of said belt, said driven means including means for de-activating said pawl and ratchet means to allow retraction of said spool under the urging of said spring in response to a still further withdrawal movement of said belt beyond said limited withdrawal of said belt. .Iaddend. .Iadd. 18. In a seat belt retractor having a seat belt carried on a take-up spool which is rotatable in a frame, a spool retracting spring for normally biasing said spool in a belt-retracting direction and thereby normally imparting tension to the seat belt when it is placed in use, the improvement comprising:   pawl and ratchet means operatively interconnecting said frame and spool for preventing retraction of said belt under urging of said spring,   a clutch member driven by said spool;   a brake member driven by said clutch member with means for allowing limited relative movement therebetween; and   cam means on both said members for selectively locating the pawl in operative and inoperative positions, each said member having first and second positions, the cam means being such that if either one or the other or both of said members are in said first positions said pawl is located in said inoperative position and when both said members are in said second positions said pawl is located in said operative position, and wherein spool rotation in response to retraction movement of a withdrawn belt moves said brake member to said second position and said clutch member to said first position, subsequent spool rotation in response to further belt withdrawal moves said clutch member relative to said brake member to said second position, whereby said pawl is operated to prevent belt rotation. .Iaddend. .Iadd. 19. The improvement in seat belt retractor of claim 18 wherein:   friction means are provided in association with said clutch member for driving it off of frictional contact with a portion of said spool. .Iaddend.