Seat belt retractor spool and torsion bar

Details Seat belt retractor spool and torsion bar Seat belt retractor spool and torsion bar

2000-01-12

2001-10-09

Walsh, Donald P. (Department: 3653)

Winding, tensioning, or guiding

Reeling device

With spring motor

C242S371000, C242S379000

Reexamination Certificate

active

06299091

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a seat belt retractor spool of the type, which employs a torsion bar to reduce the belt loading on a vehicle occupant in the event of a crash. The invention also relates to a torsion bar for use with the spool.
BACKGROUND OF THE INVENTION
A known seat belt retractor spool comprises a spool body with a bore formed therethrough. A ratchet wheel is arranged on one end of the spool body so as to be rotable relative to the body. A torsion bar is arranged within the spool and comprises an elongate bar having a toothed peripheral surface portion formed adjacent each end of the bar. One of the toothed peripheral surface portions is drivingly engaged with a cooperating toothed surface on an inner part of the ratchet wheel. The other toothed peripheral surface is drivingly engaged with a cooperating toothed surface in the bore at the opposite end of the spool from the ratchet wheel. Thus, under normal circumstances the spool rotates with the ratchet. In the event of a crash, the seat belt retractor locking mechanism locks the ratchet wheel, preventing rotation thereof. As the seat belt begins to pay out further due to the forward motion of the occupant, the spool body is caused to rotate. As the ratchet wheel cannot rotate and the spool body rotates, the torsion bar, which is connected between the spool body and ratchet wheel, is twisted. The torsion bar deforms plastically in torsion. The plastic deformation of the torsion bar reduces the seat belt loading on the occupant, which in turn lessens the chance of the occupant receiving an injury from the seat belt.
A disadvantage of the prior art arrangement is that the torsion bar engages the ratchet wheel and spool body by means of a toothed peripheral surface portion. In view of the forces involved, the toothed portion must take up a substantial length of the torsion bar. That reduces the length of the bar able to be given over to plastic torsion and deformation and this reduces the amount of force that can be taken up by the torsion bar.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a seat belt retractor spool comprising a spool body having opposite end faces, a ratchet wheel arranged for rotation relative to the spool on one end face of the spool body and a torsion bar coupled to the ratchet wheel, the torsion bar extending through the spool body and having a spool-coupling formation on the end thereof spaced from the ratchet wheel, the end face of the spool body spaced from the ratchet wheel having a cooperating formation for cooperation with the spool-coupling formation on the torsion bar so as to couple the torsion bar to the spool body for rotation therewith.
According to a second aspect of the invention there is provided a torsion bar for a seat belt retractor spool comprising an elongate body having a ratchet wheel coupling formed in a peripheral portion towards one end of the body and a spool-coupling formation comprising a projection projecting transversely from the other end of the body.
According to a third aspect of the invention there is provided a method of manufacturing a torsion bar for a seat belt retractor spool comprising the steps of providing an elongate rod of a suitable torsion bar material, cutting a length of the rod, to form a bar forming a ratchet wheel coupling surface in a peripheral portion of the bar towards one end thereof and forging the other end to form a spool-coupling formation in the form of a projection projecting transversely from said other end of the bar.
According to a fourth aspect of the invention there is provided a method of assembling a torsion bar in accordance with the invention into a seat belt retractor spool in accordance with the invention comprising the steps of inserting a torsion bar in accordance with the invention into a bore in a seat belt retractor spool, which bore is arranged to receive the torsion bar, the inserting step comprising inserting the end of the bar which includes the ratchet wheel coupling into the bore at the end of the spool spaced from the end which receives the ratchet wheel, coupling the spool-coupling formation on the bar with the cooperating formation on the end face of the spool, coupling the ratchet wheel coupling surface on the bar with the ratchet wheel, whereby part of the end of the bar protrudes from the ratchet wheel, and working the protruding end of the bar to form and end cap to retain the bar in the spool.


REFERENCES:
patent: 5820058 (1998-10-01), Hirzel et al.
patent: 5961060 (1999-10-01), Brambilla et al.
patent: 6029924 (2000-02-01), Ono et al.
patent: 6105893 (2000-08-01), Schmidt et al.

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