Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
1999-08-19
2001-07-31
Jillions, John M. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
Reexamination Certificate
active
06267314
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a self-locking belt roller with a vehicle-sensitive and/or seat belt-sensitive controllable blocking device, the belt roller being provided with a force limiting device for restricted belt withdrawal when a blocking member is engaged, the force limiting device comprising a torsion rod which is connected on the one hand to the belt winding shaft and on the other hand to the blocking member.
A belt roller having the above features is described in connection with a tightening device in DE 43 31 027 A1; however, the tightening device is not necessary for the function of the force limiting device in the known belt roller. In the known belt roller, the force limiting device is constructed as a torsion rod, so that particularly when used in connection with an airbag, the response of the force limiting device allows for an additional, but decelerated forward displacement of the belted occupant. This is achieved in that, in the event of loading, as the belt unwinds from the belt winding shaft the belt loading of the belt winding shaft blocked by the blocking member is reduced by the torsional rod which yields and allows for further rotation of the belt winding shaft.
The disadvantage associated with the known belt roller is that the acting force is increased by the force limiting device as a result of the cold deformation of the material and the decreasing winding diameter, i.e. as a result of the associated lever arm reduction; the associated force-path characteristic curve is progressive. In this context, further tests have shown that it is, for example, desirable for a higher restraining force to be exerted by the force limiting device at the start of an accident, namely so long as the belted person is not in contact with the airbag, and only to allow a reduced restraining force to be exerted via the belt roller once both safety devices are effective.
It is therefore the object of the invention to use suitable measures to better adapt the force-path curve in a belt roller of the generic type to the special features of the deceleration curve of the vehicle or of the vehicle occupants.
SUMMARY OF THE INVENTION
The idea upon which the invention is based is that, for connecting the torsion rod to the blocking member, a profile head, which is connected to the associated shaft end face and rotates together with the belt winding shaft, is provided as a support for the radially deflectable blocking member, and in the force transmission path between the torsion rod, profile head and shaft an additional energy-dissipating structure is provided for increasing the restraining force prior to the torsion rod becoming effective and for obtaining a stepped and/or degressive force-path characteristic curve. The invention offers the advantage that, prior to the force limiting device constructed as a torsion rod becoming effective, the vehicle occupant still participates as a result of the increased restraining forces in the relatively low initial deceleration of the motor vehicle and later upon contact with the airbag a lower restraining force is exerted via the force limiting device. In this respect, it may be expedient to adjust the force-path characteristic curve so that it decreases in step fashion or is generally degressive. Thus, the path of the chest acceleration or of the HIC index, for example, can be optimized by a degressive force-path characteristic curve of the force limiting device as a function of the deformation behavior of a torsion rod.
In accordance with a first embodiment of the invention, the additional energy-dissipating structure is arranged between the belt winding shaft and the profile head, so that a relative movement between the belt winding shaft and the profile head is made possible by the uncoupling of the blocking member from the belt winding shaft. This relative movement can be exploited for the arrangement of the energy-dissipating structure. In this respect, the energy-dissipating structure according to a first embodiment of the invention is formed by a connection between the shaft end face and the profile head in the form of shearing journals, so that the initial loading is absorbed by the shearing journals and, after the destruction thereof, a reduced force level is adjusted as the torsion rod becomes effective. The arrangement can be adjusted in such a manner that the shearing journals shear off before the torsion rod becomes effective or overlap with the torsion rod.
Alternatively, projections may be provided on the profile head, which engage in corresponding recesses arranged in the belt winding shaft and deforming in the event of a movement of the belt winding shaft relative to the profile head.
According to a further embodiment of the invention, the energy-dissipating structure consists of a division of the torsion rod into two torsion elements, which are arranged one within the other, are connected in a positive-locking manner to one another, and are connected as usual on the one hand to the belt winding shaft and on the other hand to the profile head; the different design of the two torsion elements is selected in such a manner that one of the torsion elements fails at an earlier point in time than the other so that, after the failure of the first torsion element, only the second torsion element is effective.
According to embodiments of the invention, the torsion elements can be made of materials of different ductility, the inner torsion rod preferably being made of a less ductile material. Alternatively, the torsion elements can have different torsion lengths, the “torsion length” being the length of the smallest cross section of the torsion rod.
According to a further embodiment of the invention, in order to adjust an energy-dissipating structure, the torsion rod is constructed as a polygonal tube, whose profile constricts as it absorbs force, so that the polar moment of resistance and therefore carrying capacity of the torsion rod decreases.
In a further development of the invention, the torsion rod can be constructed as a rectangular element having a casing which surrounds the rectangular element and is made of a suitable plastics material. This design offers the advantage that the torsion rod can now be manufactured as a punched part, rather than as the usual turned part in the state of the art, the fitted plastics material casing forming an additional moment of resistance when the torsion rod is twisted, until the casing is blown off as a result of the changing shape within the casing as the torsion rod is twisted. In this context, it is expedient for the rectangular tube to comprise corresponding connection elements having a rectangular cross section at its two ends for the connection of the profile head and the belt winding shaft, and for the casing to extend between the connection elements.
According to an embodiment of the invention, it can be provided that the inner receiving aperture of the belt winding shaft corresponds in its cross section to the dimension of the casing of the torsion rod which can be pushed into the receiving aperture. This results in the following advantage: As the torsion rod is twisted, the plastics material casing fitted over the torsion rod is plastically deformed after being blown off the torsion rod, since the casing cannot escape in the receiving aperture of the belt winding shaft in which it is enclosed.
However, it is also provided in an embodiment of the invention that the torsion rod is constructed as a turned part having a round cross section and is provided with a casing made of a suitable plastics material which is fitted over the torsion rod, the moment of resistance in this embodiment essentially being generated by the friction or cohesion between the torsion rod and the casing.
Finally, it can be provided according to an embodiment of the invention that the belt winding shaft engages around the profile head with a recess and a bending bolt, which deforms when the belt winding shaft moves relative to the profile head, is arranged between the profile head an
Clute Gunter
Singer Klaus-Peter
Witfeld Enno
Autoliv Development AB
Jillions John M.
Robert W. Becker & Associates
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