Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
1999-11-24
2001-10-09
Jillions, John M. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
C060S632000
Reexamination Certificate
active
06299090
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a seat belt for use in a vehicle, and more specifically to a device for restraining a seat belt.
BACKGROUND OF THE INVENTION
A seat belt is wound on a belt reel, for example an automatic belt retractor. A belt tightener can be brought into driving connection with the belt reel in order to eliminate belt slack from the wound seat belt and/or the belt webbing extending across the vehicle occupant. For example in the event of a crash the belt tightener assures that the seat belt rests firmly on the vehicle occupant's body and excessive forward displacement is prevented. A driving part of the belt tightener is activated by a propellant gas which acts in a pressure chamber and has a specific working pressure so that the driving part is moved in the driving direction and the belt reel and the seat belt are driven in a retraction direction. A load limiter allows decelerated extraction of belt webbing with energy consumption after tightening of the seat belt and during blocking of the belt reel, can also be connected to the belt reel. An excessive load due to the applied seat belt on the vehicle occupant's body during this forward displacement is therefore avoided, as the seat belt protracts due to the decelerated extraction of belt webbing.
In the prior art, the activation of the pretensioner can on occasion adversely interfere with the normal operation of the blocking process of the belt reel and the operation of the load limiter of the seat belt. If the retensioning process is initiated early, for example ignition of the propellant gas within 6 ms after the crash, the piston is able to complete the working stroke, and the residual pressure in the guide tube neither influences the blocking process nor operation of the load limiter. During normal initiation (for example normal ignition) within a period of up to about 15 ms after the crash, the driving part, for example the linearly driven piston, can not complete the stroke and hence a residual gas is remaining in the guide tube. The residual pressure results in a force that additionally acts on the force limiter and can cause an unacceptable high load of the belt webbing on the body of the vehicle occupant during his forward displacement. If the working pressure is initiated even later, for example due to ignition of a propellant gas within a period of about 15 ms to 25 ms after the crash, preliminary and/or principal locking of the blocking device can occur prior to tightening but is eliminated again on tightening. If a principal blocking pawl is used, it is removed again from the blocking teeth of the belt reel during tightening. The vehicle occupant's body begins to be displaced forwardly owing to the late initiation of the tightening process and therefore exerts an increased force via the belt webbing and the belt reel on the driving part counter to the retensioning direction. The working stroke of the driving part is limited so that an excessive build-up of pressure is brought about at its rear in the pressure chamber by the propellant gas. This can lead to rupture of the tightener drive system resulting in a rapid drop in pressure and, owing to the forward displacement of the vehicle occupant, the rotation of the belt reel is accelerated such that it is no longer possible to control the preliminary and principal blocking. The webbing is then unwound without deceleration during the forward displacement of the vehicle occupant. The risk of rupture of the tightener drive system also arises if the working pressure is initiated later, i.e. after 25 ms after the crash. A high load which can be as much as 1 kN and higher is applied to the driving part owing to the forward displacement of the vehicle occupant's body. An excessive working pressure is then created in the smallest space, since the driving part hardly moves or only slightly. A rapid reversal of the direction of rotation of the belt reel also occurs here. Therefore, control of the principal locking of the blocking device is no longer possible and the belt webbing is also extracted without deceleration.
DISCUSSION OF THE PRIOR ART
DE 295 20 307 U1 teaches a linear drive consisting of a piston and a cylindrical tube. The piston is driven in the cylindrical tube by a pyrotechnic propellant charge during tightening of the seat belt. To improve protection against rupture of the cylindrical tube, a rupture disc, located in the end wall of the piston, provides a means to decrease the pressure in the interior of the cylindrical tube after the tightening movement.
Furthermore, DE 93 08 273 U1 discloses a linear tightener in which the driving movement of the piston is transmitted via a toothed rack provided on the piston directly onto a gear wheel resting non-rotatably on the winding shaft. An effective linear drive of extremely simple design is thus created for tightening a seat belt.
DE 44 26 479 C2 teaches a load limiter optionally integrated in the belt reel of the retractor (i.e. torsion bar) which can limit forces exerted on the forwardly displaced body of the vehicle occupant.
SUMMARY OF THE INVENTION
The present invention provides a restraint device wherein, irrespective of the moment of release or ignition of the propellant gas, the restraint function of the belt retractor is reliably ensured after tensioning of the belt.
With the present invention, the working pressure in the pressure chamber is reduced optionally by a dampened blowout a specific time after initiation of the retensioning process, more specifically within a minimum period of time to ensure actuation of blocking of the belt reel, and optionally actuation of the load limiter. After the blocking of the belt reel, or of a part of the belt reel to be secured during the load limiting function, the driving part of the tightener remaining in a driving connection with the rotatable part of the belt reel can be moved counter to the driving direction. With the present invention, it is not necessary to release the driving part of the tightener, which may be a rotary piston, a linearly moved piston or the like, from the belt reel, for example by an uncoupling process, after the drive movement during tightening of the belt. The driving part can remain in a driving connection with the belt reel. This driving connection can be produced by a clutch which is actuated on activation of the tightener or can be ensured by engagement of the driving part with a rotary drive part, for example pinion, connected to the belt reel. The pressure is reduced by blowing out of the gas remaining in the pressure chamber after tightening until the driving part can be moved counter to the tightener drive direction.
The pressure-reducing device can be provided on the movable driving part or in a stationary limit of the pressure chamber. The pressure-reducing device can be activated after expiry of a specific period of time beginning with initiation of the working pressure. The belt reel or the part of the belt reel, which is to be secured during load limitation, is blocked for this period of time. The reduction in pressure can be produced, for example, by burning which is ignited on initiation of the working pressure and leads to a gradual reduction in pressure. The pressure-reducing device can also be designed as a weak point in the wall of the pressure chamber on the piston and/or the piston guide device. The weak point is opened after a predetermined minimum amount of time on attainment of a specific pressure value, optionally owing to the flow properties of the material at the weak point. This weak point is preferably provided on the driving part that can be designed as a linearly movable piston. The working pressure for tightening can be supplied, for example, by a pyrotechnically produced propellant gas, for example from a gas generator, or from a compressed gas source in which the propellant gas is kept on standby, for example from a hybrid gas generator.
The invention provides a compact tightener construction with few components, wherein only one driv
Marshall Steve
Specht Martin
Breed Automotive Technology Inc.
Drayer Lonnie
Jillions John M.
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