GB2322602A

GB2322602A - Bumper assemblies for motor vehicles

Info

Publication number: GB2322602A
Application number: GB9703251A
Authority: GB
Inventors: John Peter Thorp
Original assignee: Lin Pac Mouldings Ltd
Current assignee: Linpac Mouldings Ltd
Priority date: 1997-02-17
Filing date: 1997-02-17
Publication date: 1998-09-02
Also published as: FR2759655A1; GB9703251D0; DE19806541A1; IT1298583B1; ITMI980243A1

Abstract

A bumper assembly for a motor vehicle has a shell 5 supported by support means providing a progressively increasing force on impact. The shell 5 contains layers of plastics foam 8,9 of different densities. Displacement of the shell 5 relative to a body part 7 in response to the impact causes progressive resistance by the foam layers, firstly that of lighter density 8 and subsequently that of heavier density 9 to progressively decelerate the shell. The shell 5 is mounted on the body 7 through pin and slot linkages 12, 13, 14 (Fig 2), which resist initial displacement of the shell 5. Alternatively, the initial displacement of the shell may be resisted by friction dampers, springs and air bags. Following an impact with a pedestrian the shell 5 may be displaced and/or deformed to present an inclined facia by which the pedestrian is directed upwardly.

Description

1 is 2322602

TITLE "A Bumper Assembly" TECHNICAL FIELD & BACKGROUND ART

The present invention relates to a bumper assembly and is primarily concerned with such an assembly for motor vehicles.

It is recognised that automobile bumper or fender assemblies should be capable of withstanding relatively small impact forces without unreasonable or unacceptable damage occurring to either the bumper assembly or vehicle. To assess this the vehicle may be subjected to a socalled "parking test" where, during slow parking manoeuvres an impact may be applied to the bumper assembly so that, within reason, it can be determined that the impact can be absorbed without damage. Generally impacts caused during slow parking manoeuvres result from collision between the bumper assembly and another vehicle or a solid object.

However, if the impact results from the collision between the bumper assembly and a pedestrian, it is unlikely that the bumper assembly of a slow moving vehicle will be damaged by the impact but it is likely that the pedestrian will be injured. It is well known to provide bumper assemblies constructed of a heavy duty rubber or similar resilient material which is not damaged when subjected to small impact forces during the "parking test" (as the resilience of the material absorbs the impact shock) but such a bumper assembly could cause severe damage to a pedestrian even when colliding with the pedestrian at slow speeds associated with parking manoeuvres. It is an object of the present invention to provide an improved bumper assembly which will satisfy the aforementioned "parking test" requirements and will alleviate the likelihood of injury to a pedestrian in collision with the 2 bumper assembly at relatively slow speeds usually associated with automobile parking manoevures.

STATEMENT OF INVENTION & ADVANTAGES

According to the present invention there is provided a bumper assembly comprising a shell part and support means for the shell part, said support means restraining deformation of the bumper assembly in response to an impact on the shell part which effects in displacement of that part, and wherein the support means provides a progressively increasing force to restrain said displacement of the shell part and deformation of the assembly and which force progressively increases the deceleration of the shell part as that part is progressively displaced following the impact thereon.

The progressive deceleration by the support means to the shell part may be a stage-wise deceleration or a continuous deceleration. Also the impact force applied to the shell part may initially cause displacement of that shell part in the bumper assembly substantially without deformation of that part or may be intended to initially deform the shell part during its displacement to provide initial deceleration. However, irrespective of whether or not the shell part is deformed initially following an impact by the slow moving vehicle, it is intended by the present invention that the support means initially provides a light restraining force against the displacement of the shell part. The intention of this is that during an impact with a pedestrian in the "parking test", the shell part is displaced against the light restraining force of the support means to provide a relatively slow deceleration for the pedestrian relative to the vehicle following the collision to alleviate the likelihood of injury to the pedestrian. However, this initial light restraining is 3 force progressively increases as the displacement of the shell part increases in response to the impact to progressively increase the deceleration between the impacted body and the vehicle.

Preferably the bumper assembly is arranged so that following the initial deformation or displacement of the shell part in response to an impact with a pedestrian, the bumper assembly deforms to present to the pedestrian an inclined facia by which it is intended that the pedestrian impacted will be guided upwardly relative to the moving vehicle, possibly onto a bonnet or hood of that vehicle (where it is believed that the pedestrian is unlikely to suffer such serious injury as that which is likely to be caused by the pedestrian being run over by the vehicle).

The aforementioned light force restraining initial displacement of the shell part in response to an impact may be provided by mechanical linkages between the shell part and a f irm body part of the bumper assembly or of the vehicle chassis. These mechanical linkages can conveniently serve to mount the shell part in the bumper assembly or on the chassis and conveniently comprise springs, friction dampers or co-operating slot and pin components which are displaceable relative to each other to exhibit resistance to displacement of the shell part following the initial impact thereon. The support means may also comprise compressible plastics foam material or gas bags or dampers. A preferred support means for restraining displacement of the shell part comprises plastics foam which is intended to be compressed as the shell part is displaced (following an impact and with or without distortion of the shell part). It is further preferred that at least two layers of plastics foam are provided and which layers have different densities so that 4 following an impact and displacement of the shell part that displacement is f irst restrained by compression of the lighter density foam and thereafter by compression of the heavier density foam to progressively decelerate the shell part during its displacement.

Preferably the shell part of the bumper assembly is formed as a plastics moulding.

DRAWINGS Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings.

DETAILED DESCRIPTION OF DRAWINGS

In the drawings Figure I diagrammatically illustrates an automobile having a front bumper assembly 1, road wheels 2, front lights 2a and a hood or bonnet 3. There will hereinafter be described different structures for the bumper assembly I in accordance with the present invention and the illustrations for those structures will generally be shown, possibly in part section, in the direction A - A of Figure 1.

The embodiment of bumper assembly 1 shown in Figure 2 has a plastics moulded trough-shaped shell 5 having a channel 6 which is received on a rail 7 that is secured relative to a chassis of the vehicle. Located within the channel 6 is a layer 8 of low density plastics foam and an adjacent layer 9 of relatively high density plastics foam. Provided in opposed walls 10 and 11 of the shell is a spaced array of slots 12 which extend in the general longitudinal direction of the vehicle. The slots 12 receive pins 13 which mount the shell 5 and its foam layers 8 and 9 to the rail 7. The pins 13 are located at one end of their respective slots 12 and are captured at that end by a waisted region 14 of the slots in which they are received. The position of the pins 13 in their respective slots 12 when the bumper assembly is originally mounted on the vehicle is shown in Figure 2A. If the bumper assembly is subjected to a minor collision causing a relatively light impact on its shell 5, the shell may be displaced as a whole causing the pins 13 to move through the waisted regions 14 of their respective slots to provide relatively light forces which restrain displacement of the shell 5 (possibly whilst lightly compressing the plastics layer 8 between the shell 5 and the rail 7). This initial displacement of the shell 5 consequently causes a light deceleration of the body such as a pedestrian that is impacted by the moving vehicle. Following such an impact the pins 13 may move to the ends of the slot remote from the waisted regions 14 as shown in Figure 2B. When the bumper assembly is subjected to a heavy impact sufficient to displace the slots 12 over the pins 13 to the position shown in Figure 2B, the shell 5 may be deformed during its continued displacement to progressively compress the foam layer 8 and thereafter the denser foam layer 9 so progressively increasing the restraining force which is applied. As an alternative, or in addition to restraining initial displacement of the shell 5 by use of the co-operating slot and pin mountings shown in Figure 2, the shell 5 may be coupled to the vehicle chassis or a body part of the bumper assembly by use of a friction damper as shown at 10 in Figures 3 and 3A. Legs 11 and 12 of the damper 10 are coupled between the shell 5 and the vehicle chassis or bumper body part so that relative rotation between those legs restrains initial displacement of the shell part 5 relative to the rail 7 following an impact.

The restraining force provided by the friction damper 10 is variable by adjustment of a wing nut 13 which determines 6 is the frictional characteristics presented by co-operating frictional components which slide relative to each other during relative rotation between the damper legs.

In the arrangement of Figure 4 the initial displacement of the shell 5 of the bumper assembly is restrained by a leaf spring 15 which reacts between the shell part and a chassis part 7A of the vehicle.

Conveniently the leaf spring 15 is moulded integrally with the shell part 5. The bumper assembly in Figure 4 includes a stiffening rod 16 that is coupled to the vehicle chassis and is intended to take the force of an impact on the bumper assembly when that bumper assembly has collapsed substantially in response to a heavy impact force so that the stiffening rod 16 (which will extend across the width of the vehicle) may alleviate excessive damage to a substantial part of the vehicle such as its engine components.

In the embodiment of the bumper assembly shown in Figure 5 the shell 5 has extending therefrom a probe 20 which tapers to progressively reduce as it approaches a distal end 21. The distal end of the probe is presented to a port 22 in a wall 23 carried by, or secured relative to, the vehicle chassis 7A. Either or both the wall 23 and the probe 20 are deformable, preferably resiliently so. Provided over the longitudinal extent of the probe are laterally extending projections 24. In response to an impact on the shell 5 which is sufficient to displace the shell, the distal end 21 of the probe 20 moves through the aperture 22 of the wall 23 causing resilient deformation of either the probe or the wall. Continued displacement of the shell 5 will eventually cause a leading projection 24 and then trailing projections 24 which progressively increase in size laterally to be forced sequentially 7 through the port 22 along with the tapered body of the probe 20 thereby progressively increasing the restraining force which is applied to the displacement of the shell 5. It will be appreciated that the orientation of the probe 20 and wall 23 may be reversed so that the wall 23 is displaceable with the shell 5 whilst the probe 20 and its projections 24 are secured relative to the vehicle chassis. The probe 20 is not necessarily tapered and also may be replaced by rods or the like which progressively engage different sized ports in the wall 23 to provide the required progressive restraining force to displacement of the shell 5.

In the embodiment shown in Figure 6 the shell 5 is a relatively thin plastics moulding and a cavity 13 is provided immediately behind the shell, between the shell 5 and layers of low density plastics foam 8 and high density plastics foam 9 which are housed in the shell 5 adjacent to a vehicle chassis cross member 7. In response to a light impact being applied to the shell 5, such as that as may be caused by collision with a pedestrian during a slow parking manoeuvre, the shell 5 is intended to deform and collapse over the cavity 30 and against the low density foam layer 8 as shown in Figure 6A. Upon such initial collapse of the bumper assembly, the shell 5 presents to the pedestrian that is subjected to the impact an inclined facia indicated at 31 in Figure 6A which is intended to guide the pedestrian upwardly relative to the vehicle and onto the bonnet 3 (as indicated by the arrow 32) where it is believed the pedestrian is likely to have greater control of body movements and is likely to suffer less injury than if directed to the ground and be run over by the vehicle.

If the impact of force on the shell 5 as shown in Figure 6A is excessive it will be appreciated that the foam layers 8 8 and 9 will be progressively compressed against the chassis cross member 7 to provide progressive deceleration forces on the impacted body.

Figure 7 shows an arrangement of the bumper assembly 1 that is similar to that shown in Figure 6 in the sense that the assembly will present the guidance facia 31 in response to an initial impact on its shell 5. However, in the arrangement of Figure 7 and in response to the initial impact, the shell 5 is displaced as a whole (in the direction of arrow 40 in Figure 7) and substantially without deformation until it commences compression of a foam layer 8 when the inclined facia condition 31 is presented by the bumper assembly (with the shell displaced to the position shown at 5a in Figure 7). The initial displacement of the shell 5 in Figure 7 -may be lightly restrained simply by frictional displacement between foam layers 8 or otherwise, for example by use of air bags or the mechanical dampers or restraints discussed with reference to the previously described Figures.

Ck

Claims

CLAIMS:

1. A bumper assembly comprising a shell part and support means for the shell part, said support means restraining deformation of the bumper assembly in response to an impact on the shell part which effects in displacement of that part, and wherem the support means provides a progressively increasing force to restrain said displacement of the shell part and deformation of the ' assembly and which force progressively increases the deceleration of the shell part as that part is progressively displaced following the impact thereon.

2. An assembly as claimed in claim 1 in which the support means proVides stage-wise progiessive deceleration to displacement of the shell part.

3.An assembly as claimed in either claim 1 or claim 2 in which the support means permits initial displacement of the shell part in response to an impact on that part substantially without deformation of the shell part.

4. An assembly as clairned in any one of the preceding claims in which the shell part is arranged so that following an initial impact thereon it tdeforms the assembly and presents on the assembly an inclined facia wWch, in use, is intended to guide a body that is impacted by the assembly in an upward direction.

1

5. An assembly as claimed in any one of the preceding claims in which a force restraining initial displacement of the shell part in response to an impact thereon is provided by a mechanical linkage between the shell part and a firm body part.

6. An assembly as claimed m claim 5 m which the mechanical linkage serves to mount the shell part in the bumper assembly.

7. An assembly as claimed in either claim 5 or claim 6 in which the mechanical linkage comprises at least one of a spring, a ffiction damper to device and a co-operating pm and slot which are displaceable relative to each other to exhibit resistance to said displacement of the shell part.

8. An assembly as claimed m any one of claims 5 to 7 in which the mechanical linkage is adjustable for varying the restraining force which it provides.

9.An assembly as claimed in any one of the preceding claims in which the support means comprises at least one of a compressible plastics foam material and a gas bag or damper.

1 O.An assembly as claimed in claim 9 in which the support means comprises at least two layers of said foam material and said layers have different densities so that following an unpact and displacement of the shell part that displacement is first restrained substantially by compression of the lighter density foam material and thereafter substantially by compression of the heavier density foam material to progressively decelerate the shell part during its displacement.

11. A motor vehicle having a bumper assembly as claimed in any one of the preceding claims.

12. A vehicle as claimed m claim 11 when appendant to claim 5 in which said firm body part is provided by a chassis of the vehicle.

13. A vel-ficle as claimed in claim 12 in which the mechanical linkage serves to mount the shell part on the chassis.

14. A vehicle as claimed m any one of claims 11 to 13 when appendant to claim 4 in which the bumper assembly is arrancs, ged so that said mclined facia directs a body impacted thereby upwardly and over the vehicle.

15. A bumper assembly as claimed m claim 1 and substantially as herein described with reference to the accompanymg illustrative drawings.

lk

16. A motor vehicle which mcludes an assembly as claimed in claim 15.