Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2000-03-07
2001-10-09
Nguyen, John Q. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
C242S381400, C280S805000, C280S807000
Reexamination Certificate
active
06299092
ABSTRACT:
The present invention relates to a retractor for a vehicle safety restraint and in particular to a retractor which comprises web locking wedges which grip the seat belt webbing, under certain predetermined load conditions, so as to more securely restrain the vehicle occupant. Gripping wedges of this sort are particularly advantageous since they arrest forward movement of the vehicle occupant immediately, at the beginning of a crash pulse. A retractor without a web locker often allows an unacceptable movement of the occupant, even after the retractor mechanism has locked, because of the so-called spool film effect whereby slack in the webbing already wound on the spool is taken up as the webbing is tightened on the spool under load crash conditions. In high speed crashes, this can result in the vehicle occupant moving so far forward as to risk impact with some part of the vehicle interior, with resultant injuries to the occupant.
However, it has recently become evident, that arresting the motion of the vehicle occupant too abruptly, in a high speed crash situation, can itself cause injury to the vehicle occupant via the seat belt webbing itself. Thus it is required to introduce some load limiting arrangement into modern retractors so as to allow a limited and controlled pay out of webbing at the beginning of the crash pulse. Load limiting mechanisms have been suggested. For example, crushable spools, torsion bars placed in the force path between the spool and the retractor locking mechanism, and crushable nuts mounted on the spool shaft.
In web locking retractors it has been suggested to incorporate some load limiting by connecting the web locker wedges together by plastically deformable connectors, as described in EP 0 556 719. Alternatively DE 195 47 576 suggests that the wedges deform a plastic element on the frame of the retractor as they move up to grip the webbing. GB 2 288 527 uses a few longer teeth, arranged amongst normal sized teeth, on the wedges. The longer teeth shear at a certain load.
It is an object of the present invention to provide an improved weblocking retractor.
According to one aspect of the present invention there is provided a web locking retractor comprising a spool on which seat belt webbing is wound and which is lockable under predetermined crash conditions to prevent rotation of the spool in a webbing pay out direction, and a web locking arrangement comprising a wedge housing and at least one wedge mounted in the housing so as to move, under certain load conditions, to grip the webbing against further pay out, the wedge being arranged with a gripping surface having a predetermined co-efficient of friction relative to the seat belt webbing so that, at a predetermined loading, the webbing slips past the friction surface of the wedge.
This may be achieved by using a double thickness seat belt webbing over a predetermined portion of the belt. Alternatively a different coating for the webbing may be used over a different portion of the belt.
Another alternative is to use an erodible material coating the inside surface of the wedge. Such an erodible material will wear away due to friction from the webbing moving past it under a predetermined load and will reveal a surface with a higher coefficient of friction which will grip the webbing. For example the wedges may comprise teeth on their inner surface and the soft erodible material may cover these teeth, until it is worn away.
Alternatively, the wedges may comprise teeth on their inner surface and the webbing may be coated with the erodible material which is cut into and eroded by the teeth.
According to a second aspect of the present invention there is provided a weblocking retractor comprising a spool on which seat belt webbing is wound and which is lockable under predetermined crash conditions to prevent rotation of the spool in a webbing pay out direction, and a web locking arrangement comprising a wedge housing and at least one wedge mounted in the housing so as to move, under certain load conditions, to grip the webbing against further pay out, the wedge being arranged with a gripping surface having a predetermined co-efficient of friction relative to the seat belt webbing so that, at a predetermined loading, the webbing slips past the friction surface of the wedge wherein the wedge comprises a cylindrical drum shaped member mounted in the wedge housing, the wedge having an outer curved surface formed as a gripping surface for the webbing and having a torsion bar arranged along its axis wherein the torsion bar is fixed against rotation at at least one end to the wedge housing and is fixed at a point spaced from said one end, to the cylindrical wedge.
Under crash conditions the cylindrical wedge slides up in the tapered wedge housing and its outer surface impinges on the webbing and grips it against the inside surface of the housing. The load on the webbing causes a rotational torque on the cylindrical wedge which in turn imparts a twisting force on the torsion bar. Thus, under particularly high loads, the webbing is allowed to pay out as the torsion bar twists and thus the instantaneous load felt by the vehicle occupant is limited in a predetermined and controlled manner and the risk of injury to the vehicle occupant from the seat belt webbing is reduced.
Preferably the cylindrical wedge has teeth arranged around its outer surface so as to grip the webbing more securely. The torsion bar may be held in the wedge housing by one or both ends being profiled, for example being in the form of a hexagonal nut fitting in a corresponding hexagonal hole in the wedge housing.
REFERENCES:
patent: 5436065 (1995-07-01), Kukamoto et al.
patent: 34 21 837 (1985-12-01), None
patent: 44 26 479 (1996-02-01), None
patent: 195 47 476 (1996-04-01), None
patent: 196 04 483 (1997-03-01), None
patent: 196 02 267 (1997-07-01), None
patent: 0 487 760 (1992-06-01), None
patent: 0 556 718 (1993-02-01), None
patent: 2 093 523 (1972-01-01), None
patent: 2 652 323 (1991-03-01), None
patent: 2 288 527 (1995-04-01), None
“Energy Absorbing Webgrabber—Concept B”—Research Disclosure No. 363, Jul. 1, 1994, p. 370 XP000461318, Emsworth, GB.
Bell John
Harte Joseph Patrick
Laidlaw Darren
Rees Elizabeth
Smithson Alan George
Breed Automotive Technology Inc.
Nguyen John Q.
Seitzman Markell
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