Bumper bar for a motor vehicle

A bumper bar for a motor vehicle comprises a main body portion 1 of moulded plastics material extending transversely across the motor vehicle and having along at least part of its length two opposed walls 4, 5 connected into a box girder structure, and end portions 2 moulded integrally with the main body portion and projecting from each end thereof to extend along the sides of the vehicle; a first pair of transversely spaced connectors 10 for securing the main body portion 1 to the vehicle; a second pair of connectors 35 for securing respective end portions 2 to the vehicle and each comprising a bracket 36 projecting from the end portion to space the end portion transversely from the vehicle and a fastener 44 for securing the bracket to the vehicle; and a third pair of connectors 56 each for securing a respective end portion 2 to the vehicle and comprising a bracket 61 mounted at a desired level on the vehicle, and a locating part 57 fixed to the end portion 2 and forming a snap engagement with the bracket 61.

BACKGROUND OF THE INVENTION 
This invention relates to bumper bars for motor vehicles. 
German Utility Model No. 68105652.4 discloses a bumper bar for a motor 
vehicle comprising a main body portion of moulded plastics material for 
extending transversely across the motor vehicle and end portions moulded 
integrally with the main body portion and projecting from each end thereof 
for extending along the sides of the motor vehicle. The main body portion 
and the end portions have two opposed walls connected together along the 
whole length of the bumper to form a rigid box girder structure. 
Although the box girder construction provides the bumper bar with rigidity, 
the bumper bars are more flexible than conventional metal bumper bars, and 
a problem arises in securing the bumper bar accurately onto the vehicle 
body during assembly. This problem is particularly acute where, for 
reasons of appearance or manufacturing convenience, it is desired to form 
the end portions of the bumper bar not as box girder structures, but from 
single walls of plastics material. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a bumper bar for a 
motor vehicle comprising a main body portion of moulded plastics material 
for extending transversely across the motor vehicle and having, along at 
least part of its length, two opposed walls connected into a box girder 
structure and end portions moulded integrally with the main body portion 
and projecting from each end thereof for extending along the sides of the 
motor vehicle, and means for releasably connecting the bumper bar to a 
motor vehicle body characterized in that the means for releasably 
connecting the bumper bar to the motor vehicle body comprises a first pair 
of transversely-spaced connectors for securing the main body portion to 
the motor vehicle, a second pair of connectors each for securing 
respective end portions to the motor vehicle, and each comprising a 
bracket projecting from the wall of a respective end portion for spacing 
the end portion transversely from the vehicle and a fastener for securing 
the bracket to the vehicle body, and a third pair of connectors each for 
securing a respective end portion to the motor vehicle body, and 
comprising a bracket adapted to be mounted at a desired vertical level on 
the vehicle body and a locating part fixed to the end portion and forms a 
snap engagement with the bracket. 
By securing the end portions to the motor vehicle by two connectors, one of 
which provides the desired transverse spacing between the motor vehicle 
and the end portion, the other of which provides the desired vertical 
height of the end portion, the bumper bar can be mounted accurately on the 
motor vehicle. 
In the preferred embodiment of the invention, the bracket of the second 
connector comprises a wall having an outer surface for abutment with a 
body panel of a motor vehicle, and having an aperture therethrough, and a 
cam surface surrounding the aperture of the inner surface of the wall, and 
the fastener comprises a bolt having a head at one end for engaging the 
inner surface of the body panel, a shank for projecting through an 
aperture in the body panel, and through the aperture in the wall of the 
bracket, and projections extending radially from the end of the shank 
opposite the head for engagement with the cam surface, the cam surface 
being so shaped that rotation of the bolt in one direction moves the bolt 
axially toward the head. 
The head preferably includes a resiliently deformable flange which forms a 
spring washer for biasing the bolt axially away from the bracket. 
The bracket and the fastener are preferably formed of plastics material. 
In the preferred embodiment of the invention, the locating parts of the 
third pair of connectors each comprise a stud having a shank connected at 
one end to the end portion of the bumper bar and projecting therefrom 
toward the motor vehicle body, and a head of larger diameter than the 
shank formed on the other end of the shank, and the brackets each comprise 
means for slidingly receiving the head of the locating part so that the 
locating part can be assembled into the bracket by a simple sliding 
operation. 
In one suitable construction, the brackets each comprise two opposed 
channels mounted on the support for embracing opposite sides of the head 
and preventing movement of the stud in the axial direction, the channels 
being open at one end and terminating in end walls at the other end to 
permit radial sliding movement of the head along the channels, the 
channels being shaped to form a resiliently deformable construction which 
resists such movement of the head. 
In order to secure the brackets to an aperture in a body panel of the motor 
vehicle, the support preferably carries a mounting element comprising a 
shank which terminates in a noncircular flange which is shaped to fit in 
the aperture, which is of complementary noncircular shape. Rotation of the 
bracket in the aperture will secure it to the body panel. 
The brackets and locating parts of the third pair of connectors are also 
preferably formed from plastics material. 
BRIEF DESCRIPTION OF THE DRAWINGS

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring to FIGS. 1 to 3 of the drawings, a rear bumper bar for a motor 
vehicle comprises a main body portion 1 of moulded plastics material 
which, in use, extends transversely across the motor vehicle, and two 
similar end portions, one of which is indicated at 2, moulded integrally 
with the main body portion 1 and projecting forwardly therefrom to lie 
along the sides of the motor vehicle. 
As best seen in FIG. 3, the main body portion 1 comprises two opposed walls 
which will be referred to as the main wall 4, and the supporting wall 5 
connected together to form a box girder structure. The main wall 4 is 
generally channel-shaped and extends across the whole with the main body 
portion 1 and also forms the end portions 2. The supporting wall 5 extends 
along only the central part of the main body portion 1. It is generally 
flat with stiffening ribs on its inside surface, as seen at 6 in FIG. 5. 
The upper and lower edges of the supporting wall 5 include flanges 7, 8, 
which abut the inner faces of the main wall 4 and are connected thereto, 
for example, by friction welding, or any other suitable technique. 
The bumper bar is releasably connected to the motor vehicle by three pairs 
of connectors. The first pair of connectors are spaced transversely from 
each other on the main body portion 1. The position of one of these 
connectors 10 is indicated in broken lines in FIGS. 1 and 2. Since both 
connectors are similar in construction, only one connector 10 will be 
described in detail, with reference to FIGS. 4 and 5. 
The connector 10 comprises two clamping elements formed respectively by a 
rectangular metal plate 11 and an L-shaped metal bracket 12. The plate 11 
lies in contact with the inner side of the supporting wall 5 in a recess 
formed by the ribs 6. The plate 11 includes two holes 13, 14 (FIG. 5) 
through which project stakes 15, 16 of the plastics material from which 
the supporting wall 5 is formed. The stakes 15, 16 are turned over by the 
application of heat to secure the plate 11 permanently to the supporting 
wall 5. Two rectangular apertures 17, 18 in the plate 11 are aligned with 
two circular apertures 19, 20 in the supporting wall 5, and with two 
further elongated apertures 21, 22 in one limb 23 of the bracket 12. The 
other limb 24 of the bracket 12 is provided with a bolt hole 26 by which 
it can be attached to the motor vehicle body. 
The plate and the bracket are held together by two fasteners in the form of 
nuts and bolts. Since the fasteners are identical, only one, indicated 
generally at 27, will be described. The fastener 27 comprises a bolt 28, 
the head of which engages the bracket 12 and the threaded shank of which 
passes through the apertures 22, 19, 17 in the bracket 12, supporting wall 
5 and plate 11. A rectangular pierce nut 30 threaded onto the bolt 28 has 
a flange 31 which engages the inner surface of the plate 11 and a body 32 
of smaller rectangular cross section than the flange 31 which is a 
press-fit in the aperture 17 and which projects through and beyond the 
aperture by a distance marginally less than the thickness of the 
supporting wall 5. As the bolts 28 are tightened into the pierce nuts 30, 
a clamping force is exerted on the bracket 12 and the plate 11 which 
secures the bracket 12 to the supporting wall 5. The maximum compressive 
force exerted on the supporting wall 5 is reached when the body 32 of the 
pierce nut 30 engages the bracket 12. In this condition, metal-to-metal 
contact is established between the two parts of the fasteners, and the 
maximum clamping force thus established is applied to the supporting wall 
5 over the relatively large areas of the plate 11 and bracket 12. 
Consequently, the plastics material of the supporting wall 5 is less 
susceptible to failure under stresses inclined by vibrations. 
The second pair of connectors is provided for securing the respective end 
portions 2 of the bumper bar to the vehicle body and for spacing the end 
portions 2 therefrom by a desired distance. The second pair of connectors 
are attached to the end portions 2 as indicated by the arrow VI in FIG. 1. 
Since the two connectors are identical, only one, indicated generally at 
35, will be described in detail, with reference to FIGS. 6 to 9. 
The connector 35 comprises a U-shaped bracket 36 of plastics material, the 
sides of which terminate in flanges which are heat-staked to the inner 
surface of the supporting wall 5 in a manner similar to the plate 11. The 
outer surface of the bottom wall 37 of the bracket abuts a body panel 38 
of the motor vehicle so that the bracket 36 spaces the end portion 2 of 
the bumper bar laterally from the vehicle by the required amount. 
The bottom wall 37 of the bracket 36 includes an aperture 39, and, as best 
seen in FIGS. 8 and 9, the inner surface of the wall 37 is provided by two 
similar integrally moulded cam surfaces 40, 40 around the aperture 39, 
each of which includes a ramp 41 which leads up to a recess 42. A peg 43 
projects from the wall adjacent the recess 42 to act as a stop. 
The bracket 36 is secured to the body panel 38 by a fastener 44 which is 
also composed of plastics material. As best seen in FIG. 7 the fastener 44 
includes a bolt 45 having a head 46 at one end which includes a 
resiliently deformable flange 47 and a finger grip 48 which enables the 
fastener to be manipulated. A shank 49 extends from the head of the 
fastener and includes radial projections 50, 50 which are shaped and 
positioned to engage with the cam surfaces 40 on the bracket 36. 
The end portions 2 of the bumper bar are connected to the body panel 38 by 
aligning the aperture 39 in the bottom wall 37 of the bracket with a 
corresponding aperture 51 in the body panel 38, inserting the shank 49 of 
the fastener 44 through both apertures, and rotating the fastener 44 
through 90.degree. until the radial projections 50 engage in the recesses 
42 on the cam surfaces. The axial movement of the fastener 44 produced as 
a result of the movement of the radial projections up the ramps 41 is 
resisted by the flange 47, thereby generating a positive retaining force 
in the connector. 
The third pair of connectors is provided for securing the respective end 
portions 2 of the bumper bar and for positioning the terminal end portions 
of the bumper bar at a desired vertical height on the body panel 38. 
The third pair of connectors are attached to the end portions 2 in the 
positions indicated by the arrow X in FIG. 1. Since the third pair of 
connectors are identical, only one, indicated generally at 56 will be 
described, with reference to FIGS. 10 to 13. 
The connector 56 comprises a locating part in the form of a stud 57 of 
plastics material having a shank heat sealed into boss 59 of plastics 
material formed integrally with the supporting wall 5. A disc shaped head 
60 of larger diameter is formed on the free end of the shank. 
The head 60 of the stud 57 is received in a bracket 61 of plastics material 
which is, in turn, mounted in the body panel 38 at a required height. 
As best seen in FIGS. 11 to 13, the bracket 61 comprises a body 62 
carrying, on one side, two opposed channels 63, 64 for embracing opposite 
sides of the head 60 of the stud 57 so that the head 60 can slide along 
the channels in the radial direction (as indicated in FIG. 10), but once 
engaged therewith, cannot move in the axial direction. The channels, which 
are open at one end, terminate in end walls 65, 66 of complementary shape 
to the head 60 and are also shaped to form a resiliently deformable 
constriction 67 which resists the radial movement of the head 60 along the 
channels 63, 64 so that the bracket forms a snap engagement with the stud. 
The other side of the body 62 carries an integral mounting element 68 in 
the form of a stud having a body portion 69 of rounded triangular cross 
section and a flange portion 70 of identical shape but disposed in a 
different radial orientation so that the sides of the stud 69 undercut the 
rounded apices of the flange, as illustrated in FIGS. 12 and 13. The axial 
depth of the flange is equal to the thickness of the body panel 38. The 
bracket 61 is secured to the body panel 38 by inserting the flange 70 into 
an aperture of complementary shape in the body panel and rotating the 
bracket through 60.degree. so that the apices of the flange locate behind 
the panel 38 and the edges of the aperture in the panel 38 cut into the 
plastics material forming the apices of the body portion 69, thereby 
preventing the bracket 36 from moving. The head 60 of the stud 57 is then 
inserted into the bracket 61, as indicated in the arrow in FIG. 10. 
The bumper bar may therefore be mounted on the vehicle quickly and easily, 
with the side portions positioned accurately. Moreover, the connections 
between the bumper bar and the vehicle are resistant to vibrations during 
use. Should the bumper bar become damaged, it can easily be removed and 
replaced.