Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
1999-05-20
2001-07-17
Rivera, William A. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
C242S376000, C242S613400, C242S577100, C297S472000
Reexamination Certificate
active
06260782
ABSTRACT:
DESCRIPTION
The present invention relates to a retractor spool for a vehicle safety restraint.
A retractor spool generally consists of a cylindrical bobbin with a circular cross-section. Seat belt webbing is attached to and wound around the spool and the spool is mounted on a spool shaft to be rotatable in the retractor to wind in webbing under action of a retractor spring and to pay out webbing under the influence of relatively gentle forwardly directed inertia of a vehicle occupant, for example to allow for normal movement associated with vehicle occupancy such as reaching forwards to activate in-car controls (for a radio or a window) or to reach a glove compartment or door pocket. In the event of a crash situation, the more extreme momentum of the occupant activates a crash sensor which locks the spool against rotation and thus prevents forward motion of the occupant and injury due to occupant collision with the interior fixtures of the vehicle such as the steering wheel, dashboard or windscreen.
However, this sudden locking of the seat belt spool under crash conditions can itself sometimes cause injury to the occupant due to sudden impact of the torso with the belt webbing. This is particularly true in high velocity crashes.
In recent years this problem has been recognized and some solutions proposed.
One solution has been to rely on natural elongation of the webbing under high loads, and on the spool film effect (natural tightening of the webbing wound on the spool under high loads), to produce a load limiting effect.
Another known proposal has been described in EP 0 297 537 A, wherein force limiting is effected by interposing a plastically deformable member between the spool and the innermost winding of the belt webbing or by interposing an elastic member such as a spring rubber member or resin member between an end flange of the spool and the latch plate. This allows a pay-out of webbing in proportion to the inertia of the vehicle occupant at the moment of a crash condition being sensed. This pay-out lessens the otherwise severe restraining forces on the occupant at high vehicle speeds especially during the initial moments of the crash. It thus reduces the injurious effects of the seat belt in a crash.
The present invention proposed improved load limiting arrangements for retractors.
According to one aspect of the present invention there is provided a seat belt retractor comprising:
a spool mounted on a spool shaft for rotation in the retractor,
a length of seat belt webbing wound on the spool for retraction or pay-out depending on the rotation direction of the spool;
means for locking the spool shaft against rotation when a crash condition is sensed;
force limiting means for allowing further pay-out of the seat belt webbing after the spool shaft has locked, under the influence of an occupant's forward momentum in the crash condition,
wherein the force limiting means is provided by a plurality of fins provided on the outer surface of the spool, each fin having a section which extends in a generally radial direction and a section which extends circumferentially, the circumferentially extending section of one fin overlapping the circumferentially extending section of an adjacent fin and are supported by the radial extending section of that adjacent fin, so that a force tending to tighten the webbing on the spool, acts in a direction to crush the radial sections of the fins and to slide the circumferential sections over each other, thus reducing the effective outer circumference of the spool.
The circumferentially extending fin parts may be stepped so as to provide a stop for the sliding movement of the fins and to provide a minimum crushed spool size, i.e. a maximum load limiting force, at which pay out is allowed.
The fins may be fixed in place, in the undeformed spool, by shear elements. This provides a minimum force at which the load limiting comes into effect. It also provides a visual indication of when the force limiting has been deployed, alerting the owner to effect the necessary replacement for safety reasons before further use of the retractor.
The shear elements may be formed of small ribs, pins or clips which fracture at a predetermined load, and with suitable choice of material an aural signal may also be generated.
According to a second aspect of the invention the force limiting means comprises an energy absorbing member connecting the spool to the spool shaft, the connection being rigid below a predetermined force, and above the predetermined force there being relative rotation of the spool with respect to the spool shaft to allow pay out of belt webbing.
According to the second aspect of the invention the energy absorbing member of the force limiting means may comprise a slipping clutch connecting the spool to the spool shaft co-axial of the spool.
In one embodiment the spool is hollow and the clutch comprises a plurality of interposed clutch plates extending alternately, on the one hand inwardly from the inside surface of the spool casing, and on the other hand outwardly from the spool shaft, within the hollow spool.
In a second embodiment the slipping clutch comprises co-operating clutch plates at one or both ends of the spool shaft by means of which the spool is clamped.
The force limiting load is determined by the slipping torque of the clutch plates and this may be controlled by the position of a nut on the spool shaft acting to apply tension to the clutch, either directly or via a spring or one or more Belville washers between the nut and the clutch, or an elastically or plastically deformable member.
The clutch plates may be generally planar with surfaces having circular inter-connecting ribs, for example of trapezoidal or sinusoidal profile. Alternatively a cone clutch design as is well known in the art could be used, at one or both ends of the spool shaft.
Preferably a non-circular hole is used to avoid the clutch plates spinning on the shaft.
According to a preferred embodiment of the second aspect the nut is linked to the spool so that as the clutch slips under load limiting conditions, allowing rotation of the spool relative to the shaft, then the nut rotates and moves along the shaft, increasing or decreasing the tension on the clutch plates accordingly. This acts as an automatic load control feedback system.
Another variation of the second embodiment is to use a friction clutch whereby friction material is arranged between the spool and the clutch plate at one or both ends of the spool. The clutch plate may be a combined locking ratchet or a separate component. The friction coefficient of the friction material will control the slipping torque and thus the limiting load. The material could be keyed, attached or chemically bonded to one of the adjacent surfaces. The flexibility and surface properties of the material help to compensate for any manufacturing variations in the adjacent surfaces. A suitable friction material would be the proprietary material Jurid® 850 or 851.
The friction material may be tensioned by a locking nut on the spool shaft and/or by washers, for example Belville washers or an elastically or plastically deformable member.
According to a third embodiment of this aspect of the invention, the energy absorbing member of the force limiting means may comprise a deformable member. This may be a crushable or deformable tube mounted on the rotation shaft of the spool and means for applying a compressive load to the deformable tube axially with respect to the shaft, when a high load is applied to the retractor under crash conditions. The tube may be mounted on the shaft at one end of the spool, or within a hollow spool.
Preferably the deformable tube is deformable outwardly in a radial direction under an axial compressive load, for example, one end may splay radially outward or the middle region of the tube may bulge outward.
The compressive load may be applied by a nut abutting the deformable tube and mounted on the spool shaft, and which rotates to apply force to the deformable tube when a high crash load is detected. It ca
Blackadder David
Martellini Carlo
Palliser Martyn
Park Andrew
Smithson Alan G.
Breed Automotive Technology Inc.
Rivera William A.
Seitzman Markell
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