Vehicle fenders – Buffer or bumper type – Shiftable between operative and inoperative positions other...
Reexamination Certificate
1999-10-13
2001-01-16
Pape, Joseph D. (Department: 3612)
Vehicle fenders
Buffer or bumper type
Shiftable between operative and inoperative positions other...
C293S119000, C293S132000, C293S135000
Reexamination Certificate
active
06174008
ABSTRACT:
The invention relates to a bumper arrangement for a motor vehicle with a bumper which is mounted in such a way that it can be moved between a rest position and an operating position, a spring energy store which acts on the bumper and is prestressed in the rest position of the bumper, a locking device which holds the bumper in the rest and/or operating position, a control unit which actuates the locking device as a function of signals from an accident-cetection sensor system, and means for returning the bumper from the operating position to the rest position, the spring energy store being designed in such a way that, when the locking device is unlocked, it moves the bumper abruptly into an operating position, in which the bumper absorbs in a purely elastic manner impact loads resulting from relative velocities of up to 8.1 km/h between the motor vehicle and an obstacle
German Offenlegungsschrift DR 41 13 031 A1 has disclosed a bumper arrangement of the generic type with a resiliently mounted bumper. The bumper arrangement has a drive device which moves the bumper from a rest position into an operating position, and a control device which activates the drive device in a manner dependent on a dangerous situation. The drive device comprises a hydraulic damping device with a piston which can be moved in a cylinder, is firmly connected to the bumper and can be moved together with the latter into the rest position by means of a hydraulic pump. The damping device is capable of absorbing impact loads resulting from speeds of 15 km/h without damage. Extension times of less than one second are achieved, in particular, by means of a spring energy store in the form of an additional extension spring with an assisting action which is arranged in the hydraulic cylinder.
DE 38 08 813 A1 discloses an impact device for commercial vehicles, in which a bumper can be extended forwards from the vehicle and, in conjunction with an energy-absorbing structure, has an energy-absorbing effect in this position. The extension process can be performed either explosively by converting potential energy stored in a system into kinetic energy or by means of conventional thrust mechanisms, which are activated in an appropriate manner before an impact. In this case, the thrust mechanisms are activated by signals from a measurement and distance sensor.
U.S. Pat. No. 1,642,233 has disclosed a bumper which can be pushed forwards by a compression spring when required to prevent pedestrians from getting under the front wheels of the vehicle.
In another known system (JP 07 144 587 A), a bumper arrangement of a motor vehicle is extended forwards into an elastically flexible state in order thereby to achieve greater elastic flexibility in the event of corresponding impact loads.
German Patent DE 44 26 090 C2 has disclosed a safety device for a motor vehicle which has a bumper bar fitted with preloading elements that can be triggered pyrotechnically. The bumper bar can be extended with the aid of the preloading elements into an operating position in which it offers a higher energy absorption capacity. It can be brought back into its original position after being triggered. It is triggered by means of an impact sensor system comprising proximity sensors such as infra-red and/or magnetic-field sensors.
German Offenlegungsschrift DE 44 14 432 A1 has disclosed an impact protection unit for a motor vehicle, this unit having a body part which can be extended on a linkage and, if the vehicle is involved in a collision, is moved into an operating position hydraulically or by means of an airbag together with the body parts, the airbag and/or the holding mechanism represents an enlarged, plastically deformable crumple zone for the motor vehicle.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a bumper arrangement of the type stated at the outset in which the bumper can be returned to its rest position by means which are as simple as possible while providing a high energy absorption capacity and rapid extension of the bumper into its operating position.
This object is achieved by virtue of the fact that the means for returning the bumper have a shape-memory spring arrangement which can be converted by an activation unit to a special configuration, in which the shape-memory spring arrangement forces the bumper into its rest position. In the operating position of the bumper, the spring energy store can assume a position in which it is completely relaxed and thus has its maximum energy absorption capacity. While retaining otherwise customary spring characteristics of known bumper arrangements, the energy absorption capacity of the spring energy store is significantly increased thanks to a considerable increase of the spring displacement. When needed, it is available without any significant delay by rapid extension In the rest position, the energy absorption capacity of the spring energy store is reduced in favour of space-saving accommodation. The shape-memory spring arrangement can preferably be embodied in such a way that, in the special configuration, it has a reduced length compared with a standard configuration and, in this special configuration, pulls the bumper into a rest position, in which it likewise has a reduced extent, and, in the standard configuration, acts in parallel with the bumper. This means that, once the spring energy store has reached its prestressed state, and the bumper has been locked in its rest position, the shape-memory spring arrangement can be transferred to its standard configuration, in which it likewise prestressed.
As a refinement of the invention, the shape-memory spring arrangement can be converted to the special configuration as a function of temperature, and the activation unit is designed as an energy source that can be actuated by the control unit. Here, the shape-memory spring arrangement preferably assumes its standard configuration at customary ambient temperatures, while it assumes its special configuration at an activation temperature that deviates significantly from a customary ambient temperature. The activation temperature is introduced by resistance heating.
As a further refinement of the invention, the spring energy store and the shape-memory spring arrangement are arranged to form a coaxial spring assembly. Particularly when it takes the form of a helical spring assembly, the spring assembly represents a particularly space-saving possibility for arranging the spring energy store and the shape-memory spring arrangement. Force is transmitted between the spring assembly, on the one hand, and the bumper, on the other hand, in a precisely defined manner along the axis of the spring assembly.
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Kramer Johann
Schroder Bernd
Tebbe Martin
Daimler-Chrysler AG
Pape Joseph D.
Patel Kiran
Shurupoff Lawrence J.
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