Land vehicles – Wheeled – Attachment
Reexamination Certificate
1998-04-23
2001-10-09
Luong, Vinh T. (Department: 3682)
Land vehicles
Wheeled
Attachment
C280S805000, C280S741000, C297S480000, C060S638000, C074S500500
Reexamination Certificate
active
06299211
ABSTRACT:
TECHNICAL FIELD
The invention relates to a tensioner for a safety belt.
BACKGROUND OF THE INVENTION
Hereto known belt tensioners have a piston/cylinder unit, which comprises a cylinder and a piston arranged in its interior, and a compressed gas source, on the activation of which the piston is displaced. A belt engagement means which engages the safety belt is connected by a traction transfer means to the piston. A damping means provides for the absorption of energy on deceleration of the movement of the belt engagement means.
Tensioners for safety belts must be constructed as small as possible owing to the small space available in the vehicle. Inside or outside the cylinder, usually a damping means is provided, having a negative influence on the axial length of the tensioner, which damping means brakes the piston at the end of the tensioning way and in so doing absorbs energy, thus reducing load peaks. Owing to the length of the tensioning way and damping way necessary hitherto, known tensioners have such an axial overall length that they cannot be installed in the vehicle without a cable deflector.
BRIEF SUMMARY OF THE INVENTION
The invention provides a tensioner which, with the same tensioning way compared with known tensioners, is distinctly shorter in axial direction, without this being achieved at the expense of a poorer damping effect.
The tensioner according to the invention has a piston/cylinder unit, which comprises a cylinder with a cylinder jacket delimiting an interior of the cylinder and a piston arranged in the interior, and a compressed gas source, on the activation of which a tensioning process is initiated and the piston is displaced in a tensioning direction. Further, it comprises a belt engagement means which engages the safety belt, a traction transfer means which connects the piston to the belt engagement means, and at least one damping means for the absorption of energy on deceleration of movement of the belt engagement means. The cylinder has a first end nearer to the belt engagement means and a second end further away therefrom. The piston consists of at least two piston parts, namely of a first, radially outer piston part and a second, radially inner piston part. The second piston part is uncoupled from the first piston part on deceleration of the piston at the end of the tensioning process.
By uncoupling the piston parts on deceleration of the piston, it is possible to decelerate the piston parts independently from each other and to provide for their damping independently from each other. Accordingly, two or more damping means can be provided which, owing to uncoupling the two masses of the piston parts, can be constructed relatively small, because the mass which is to be decelerated or damped is smaller than with a piston having a single part. In addition, the tensioning process can proceed more quickly, because the damping ways for both piston parts which are to be decelerated are shorter than has been the case hitherto. Depending on when the damping of the second piston part occurs, the second piston part can run through the entire tensioning way also undamped and only be subsequently damped and decelerated. The first piston part, having a small mass, can be decelerated immediately before the end of the tensioning way on a short distance, so that the damping ways for the deceleration of the piston parts lie almost exclusively outside the tensioning way, therefore chronologically after the complete tensioning way has been covered by the piston parts.
In the preferred embodiment, at least one stop is provided for each of the first and the second piston parts each, the stop for the second piston part decelerating the latter chronologically after the impact of the first piston part. This means that the first piston part is already decelerated whilst the second piston part is still moving in the tensioning direction. When the second piston part is coupled with the traction transfer means and hence also with the belt engagement means, the mass of the first piston part, on braking, cannot exert any stress on the unit consisting of second piston part, traction transfer means and belt engagement means, so that, as a whole, the load peaks occurring in the traction transfer means can be kept small.
The stop for the first part can be formed by the end wall of the cylinder at the second end, a projection protruding on the inner side from the cylinder jacket or, according to a further preferred embodiment, by an jacket section of the cylinder, tapering conically, at its second end.
The stop for the second part, viewed spatially, can be provided in the tensioning direction after the stop for the first piston part or in front of it. In the latter case, a part connected to the traction transfer means strikes against the stop, which, for example, is the end wall at the first end of the cylinder. By a stop which is constructed in such a way, the second part and, if the traction transfer means and also the belt engagement means are fastened to it, the entire resulting unit can be damped, i.e. not decelerated abruptly.
According to one embodiment of the invention, the second piston part, the traction transfer means and the belt engagement means move on, after the deceleration of the first piston part, by a damping way and after the deceleration thereof, move back by at least a portion of the damping way contrary to the tensioning direction.
This return movement of the unit comprised of second piston part, traction transfer means and belt engagement means can occur by the forward movement of the vehicle occupant relative to the vehicle after the tensioning process or, when the vehicle occupant is not wearing his belt, by an elastic spring element which can be arranged inside the cylinder and moves the second piston part and thereby the belt engagement means back contrary to the tensioning direction at least by a partial distance after running through the damping way. The spring element has a dual function by having on the one hand a damping effect and, on the other hand, a restoring effect for the second piston part. When the belt engagement means is constructed as a belt buckle, it must be ensured after the tensioning is completed that the vehicle occupant can still actuate the release button of the belt buckle. This can be a problem when the belt buckle for example has dipped too deep between the back part and the seat part of a vehicle, as can be the case with tensioners for rear occupants of vehicles. The elastic spring element moves the belt buckle back by a certain distance, whereby the vehicle occupant can actuate the release button. The spring element offers a desired resistance to the pressing of the release button, so that the belt buckle assumes a stable position and is not displaced.
In the preferred embodiment, the end wall on the second end of the cylinder has an opening or it is completely open, so that an actual end wall is no longer present. After the second piston part is uncoupled from the first piston part, the traction transfer means and/or the second piston part extend into the opening or even to outside the piston, so that axial construction space can be saved. As the tensioner is usually arranged a few millimeters or even centimeters in front of a component on the vehicle side, which is usually formed by the floor of the vehicle or a carpet on the floor of the vehicle, in the case of restraint this intermediate space can be further utilized as a whole for extending the tensioning way. The traction transfer means or the second part can partially project into this intermediate space and fill it, so that a portion of the damping way can lie outside the cylinder and the tensioning way to be covered within the cylinder by the piston can be extended.
Owing to the saving of space which is able to be achieved by the invention, it is possible to accommodate the belt tensioner in the vehicle without a cable deflector.
The tensioner according is further characterized in that the sleeve is made of steel and the cone is made of a light metal or of a non-ferr
Luong Vinh T.
Tarolli, Sundheim, Covel Tummino & Szabo L.L.P.
TRW Occupant Restraint Systems GmbH & Co. KG
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