Vehicle fenders – Buffer or bumper type – Bumper having impact force absorbing means directly...
Reexamination Certificate
2000-03-02
2001-08-07
Pape, Joseph D. (Department: 3612)
Vehicle fenders
Buffer or bumper type
Bumper having impact force absorbing means directly...
C293S133000, C188S371000
Reexamination Certificate
active
06270131
ABSTRACT:
The present invention relates to a partitioned impact absorber made of two interfitting blocks, and to a bumper beam including such an impact absorber.
BACKGROUND OF THE INVENTION
Partitioned impact absorbers are already known, being honeycomb-type structures comprising an array of partitions extending parallel to a predetermined “impact” direction, and which deform in the event of an impact, thereby absorbing the energy thereof.
By way of example, such impact absorbers are used for mounting bumper beams to vehicle structures or they are mounted directly to the structure of the vehicle. When the impact absorber is subjected to an impact directed substantially along the axis of the vehicle, the bumper beam moves towards the inside of the vehicle and the energy transmitted by the bumper beam is absorbed by the impact absorbers so as to protect the remainder of the vehicle and above all its passengers.
Until now, partitioned impact absorbers have generally been obtained by extrusion or by injection.
When obtained by injection, there is a lower limit on the pitch of the array of partitions, i.e. on the distance between two adjacent partitions in the array, because the injection mold and in particular the cores which separate the partitions, must present at least some minimum thickness below which they would not withstand the very high injection pressure that needs to be exerted in order to fill completely the cavities in the mold between the cores and defining the volume in which said partitions are made.
With injection, the pitch of the array must also be larger with increasing depth of the partitions in the impact direction. Unfortunately, this correlation between partition depth and array pitch as imposed by the injection process is particularly unfavorable to the effectiveness of the absorber.
Ideally, in order to be effective during a high-energy impact, the depth of the partitions should be large and simultaneously the size of the cells, i.e. the pitch of the array, should be small.
In addition, there is another characteristic of injected absorbers that reduces their effectiveness: the fact that the partitions must be of tapering thickness towards the ends of the cores so as to enable the absorber to be unmolded. The consequence of this characteristic is that the resistance opposed by the absorber increases with increasing depth of compression, which phenomenon is referred to as the taper phenomenon, whereas more energy would be absorbed if the resistance opposed by the absorber was at its maximum from the beginning of its deformation.
As a result, previous molded impact absorbers provide energy absorption conditions that are not satisfactory because of the relatively low density of their arrays of partitions and because their efficiency is diminished by the taper effect.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention seeks to provide a solution whereby partitioned impact absorbers can be made by molding, while nevertheless having a high-density array of partitions and a taper effect that is limited.
The present invention provides a partitioned impact absorber comprising an array of partitions extending parallel to a given impact direction, the absorber being constituted by at least two mutually-engageable blocks, each block having partitions, the partitions of each block interfitting between the partitions of the other block so as to build up the array of partitions of the absorber.
In other words, the present invention consists in making two blocks each having its own array of partitions at relatively low density, thus enabling them to be made by molding, and in interfitting the two blocks one in the other so that their partitions are interleaved, thereby effectively doubling the density of the resulting partition array.
In a preferred embodiment of the invention, each block comprises a number of partitions that is substantially half the total number of partitions constituting the array of partitions of the absorber, said array in a direction perpendicular to the impact direction comprising, in alternation, a partition from one block and a partition from the other block.
In a particular embodiment of the invention, the thickness of the partitions of each block tapers towards the other block, which enables the block to be made by molding and which enables each partition to be given a taper that facilitates unmolding of the block.
Given that the two blocks are interfitted in mutually opposite directions, the thin ends of the partitions in each block are adjacent to the thick ends of the partitions in the other block, such that at any cross-section of the absorber, the average thickness of the partitions is constant.
In this way, the absorber is caused to be very uniform, thus giving rise to optimum efficiency in the face of impact, given that the resistance opposed by the absorber is substantially constant while it is being compressed.
This characteristic makes it possible to eliminate the phenomenon referred to as the taper effect.
In a preferred embodiment of the invention, the partitions of each block are split over half their length so as to enable them to be interlocked with the partitions of the other block.
Thus, two perpendicular partitions, one belonging to the first block and the other to the second block, can hold each other mutually, with the slot in each partition receiving the unslotted portion of the other partition, and vice versa.
In a variant of this embodiment, on the border of its slot, each partition has stiffening ribs having the function of compensating for the weakening due to the presence of the slot and of keeping the partition and the partition that engages in the slot mutually perpendicular. This partition can additionally include ribs on either side of its region that is to be held captive in the slot, so as to prevent said region in the slot from moving and so as to keep the partitions mutually perpendicular.
In a particular embodiment of the invention, the absorber is constituted by:
a first block having a first set of partitions;
a second block having a first side carrying a second set of partitions suitable for interfitting with the first set of partitions by the first block being engaged in the first side of the second block, and a second side opposite from its first side and carrying a third set of partitions; and
a third block having a fourth set of partitions suitable for interfitting with the third set of partitions by the third block engaging in the second side of the second block.
Such a three-block absorber can also be defined as being constituted by two impact absorbers each comprising two mutually-engaged blocks, with one of the blocks of the first impact absorber being secured back to back with one of the blocks of the second impact absorber so as to form the second block as defined above.
Such a three-block impact absorber presents the advantage of being capable of extending over a relatively long distance in the impact direction, because the length of each of its partitions is, in fact, only half the total length of the absorber.
The present invention also provides a bumper beam including an integrated impact absorber, the bumper beam including a portion constituting one of the blocks of the impact absorber as defined above.
In a particular embodiment, the beam is associated with a block additional to that constituted by a portion of the beam, and this additional block presents, on its front face opening towards the front of the vehicle, a staircase-shaped wall comprising only portions that are perpendicular to the partitions of the block, which portions are interconnected by portions parallel to the partitions of the blocks.
The staircase-shape enables the front wall of the additional block to follow substantially the curvature of the front face of the beam while preserving the blocks from the oblique stresses that would impede proper effectiveness of the absorber.
Such a beam can include, in particular, a three-block impact absorber. In which case, the block which is integrally formed with the beam is the second bl
Cornet Olivier
Martinez Bernard
Chenevert Paul
Compagnie & Plastic Omnium
Oliff & Berridg,e PLC
Pape Joseph D.
LandOfFree
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