RATCHET WHEEL - SPOOL ASSEMBLY FOR A SEAT BELT RETRACTOR

Abstract: Two parts of a seat belt retractor spool sub-assembly are fixed together in an arrangement with plastically deformable formations (6, 7, 9, 12) on either a ratchet wheel (5) or one end of a spool (4) and corresponding deforming formations (10) on either the ratchet wheel (5) or said one end of the spool (4).

Description: RATCHET WHEEL - SPOOL ASSEMBLY FOR A SEAT BELT RETRACTOR The present invention relates to a seat belt retractor. A seat belt restraint comprises a length of webbing that is arranged to pass across the torso of a vehicle occupant. The webbing is wound on a rotatable spool that is mounted in a retractor frame. The spool is biased in a webbing wound direction but is otherwise free to pay out webbing to accommodate normal movement a vehicle occupant . In the event of a crash, the spool is locked against rotation and thus against further payout of webbing and the vehicle occupant is securely restrained against forward motion. Locking of the spool is effected by bringing a toothed locking pawl into engagement with a ratchet wheel fixed to the spool . In high volume assembly lines different sizes of components are handled and this results in a variation in the amount of space between the components. This space is known as the end float and there is currently no way of accurately setting the end float control . According to a first aspect of the present invention, there is provided means for fixing together two parts of a seat belt retractor spool sub-assembly, for example a ratchet wheel and a retractor spool or a spring arbor and the spool . The fixing means comprise plastically deformable formations on one of the ratchet wheels and one end of the spool and corresponding deforming formations on the other of the ratchet wheels and said one end of the spool . Brief Description of the Drawings For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings . FIG. 1 is a cross-sectional schematic view of a retractor sub-assembly and illustrates a fixing means according to one embodiment of the first aspect of the invention and a method of assembly according to the third aspect of the invention. FIG. 2 is a cross-sectional schematic view of a retractor sub-assembly and illustrates a fixing means according to a second embodiment of the invention and an assembly method according to the third aspect of the invention. FIGS .3 and 4 are a plan views and cross- sectional views of various modifications of a part of FIG. 1. FIG. 5 shows plan views and cross-sectional views of a modification of part of FIG.2. FIG. 6 is a cross-sectional axial view of a retractor sub-assembly and illustrates a fixing means according to a third embodiment of the first aspect of the invention. FIG. 7 is a cross-sectional end view of part of FIG. 6. Detailed Description of the Invention In FIGS. 1 and 2 a manufacturing assembly j ig 1 is shown on which is located a retractor frame 2 in abutting contract. The jig incorporates a set table spring loaded stop 3. A spool 4 is inserted into the frame 2 and located against the stop that is set in a predetermined position relative to the jig. A ratchet wheel 5, made of a plastic material, is then pushed onto the end of the spool opposite the spring stop 3 until the ratchet wheel 5 stops against the spool 4. The ratchet wheel is formed in FIG. 1 with extending pegs 6 having crushable ribs around their edges and the spool 4 is formed with corresponding round drafted holes which crush the ribs on pegs 6 and lock the spool to the ratchet wheel 5. In FIG. 2 the ratchet wheel has self-locking ears 7 and the spool has extending pegs 8 that interact to lock the two components together. The setting on the spring-loaded stop 3 controls the amount of spool end float . The plastically deformable formations may be crushable ribs on axially extending pegs or self- locking deformable ears. The corresponding deforming formations may be drafted holes large enough to accommodate the pegs but small enough to deform or crush the ribs. They will have essentially the same shape as the pegs and are preferably round. Alternatively, the deforming formations may be pegs that fit between the ears to deform them and lock the parts together. Various modifications to the means of fixing the ratchet wheel 5 to the spool 4 are shown in FIGS. 3 to 5. FIGS. 3 and 4 show modifications to the crushable rib formations of FIG. 1 and FIG. 5 show modifications to the self-locking ears of FIG. 2. In each figure, line I is a plan view of the peg/ear on the ratchet wheel 5, line II is a cross- sectional view of the fixing formations as the two parts are brought together and line III shows the assembled formations. The crushable ribs may be angled or straight sided and likewise the locking ears may have straight or angled inner edges. The crushable ribs may have angled bottom and straight sides and may incorporate pips on each side of each peg. An additional, a self-locating peg may be provided on one part to aid assembly. In FIG. 3, embodiments A and B show pegs 6 with angled ribs 9 which lock into round drafted holes 10 in the spool 4. In embodiment C the ribs 9 are straight-sided. In embodiment B a self-locating peg is provided in the hole 10 in spool 4 to aid assembly. In FIG. 4, embodiment D has ribs 9 with straight sides and an angled bottom on the peg 6 and the hole 1 has drafted crush locations 11. Embodiment E has ribs 9 also with straight sides and an angled bottom but with pips 12 on each side of each leg and with slightly larger crush locations 11 in the hole 10. In FIG. 5, the self-locking ears 7 on the ratchet wheel have straight inner edges in embodiment F and angled inner edges in embodiment G. The angled inner edges sit more snugly against the spool pegs 8 as can be seen in embodiment G III (FIG. 5) . In FIGS. 6 and 7 the retractor spool 4 has an axial spool spline extension 20 onto which a spring arbor 21 fits. The extension 20 is generally cylindrical with longitudinal shaped ridges on the surface forming deformable crush ribs 22 which are axially oriented around the outer surface of the extension 20. The arbor 21 has corresponding mating shapes 23 on the inside surface. The crush ribs have a slightly bigger angle than the spool splines 20.

Claims: Claims : 1. An arrangement for fixing together two parts of a seat belt retractor spool sub-assembly comprising plastically deformable formations on either a ratchet wheel (5) or one end of a spool (4) and corresponding deforming formations on either the ratchet wheel (5) or said one end of the spool (4) . 2. The arrangement for fixing together two parts of a seat belt retractor spool sub-assembly of claim 1 wherein the plastically deformable formations are crushable ribs (9) on pegs (6) . 3. The arrangement for fixing together two parts of a seat belt retractor spool sub-assembly of claim 1 wherein the plastically deformable formations are self-locking deformable ears (7) . 4. The arrangement for fixing together two parts of a seat belt retractor spool sub-assembly of claim 2 wherein the corresponding deforming formations are drafted holes (10) large enough to accommodate the pegs (6) but small enough to deform or crush the ribs (9) . 5. The arrangement for fixing together two parts of a seat belt retractor spool sub-assembly of claim 4 wherein the drafted holes (10) have essentially the same shape as the pegs (6) . 6. The arrangement for fixing together two parts of a seat belt retractor spool sub-assembly of claim 3 wherein the deforming formations are pegs (6) that fit between the ears (7) to deform them and lock the parts together. 7. The arrangement for fixing together two parts of a seat belt retractor spool sub-assembly of claim 2 wherein the crushable ribs (9) have angled bottoms and straight sides and there are pips (12) on each side of each peg.

Inventors: BLACKADDER DAVID, BOWMAN PAUL, SMITH ALAN GEORGE, BLACKADDER, DAVID, BOWMAN, PAUL, SMITH, ALAN, GEORGE
Applicants: BREED AUTOMOTIVE TECH, BREED AUTOMOTIVE TECHNOLOGY, INC.
Application year: 2000
Main classification: B60R22
IPC codes: B60R22