Internal stroking bumper beam

A bumper structure, for use with an internal frame structure of a vehicle which has a pair of longitudinally extending generally parallel rail members and a cross-beam member attached to and extending transversely of the rail members, including a face bar member which slidingly receives the cross-beam member and provides a cavity between the two members. Energy absorbing material resides within the cavity. Should the frontal portion of the face bar receive an impact load above a predetermined magnitude, the face bar will slide rearward toward the cross-bar member thereby compressing the energy absorbing material and absorbing the impact. Various alternative constructions are included which additionally preclude relative lateral movement of the bumper structure during compression of the bumper beam relative to the frame member, including providing the face bar member with a back-up plate rearward of the cross-beam member and which straddles the respective axially extending rail members.

TECHNICAL FIELD 
This invention relates to vehicle bumpers, particularly energy absorbing 
vehicle bumper structures for cushioning low speed impact. 
BACKGROUND ART 
In recent years, much attention has been paid to developing energy 
absorbing front and rear vehicle bumper structures to absorb low speed 
direct frontal collisions, i.e. in the order of one to five mile per hour. 
These bumper systems are generally supplemental to other passenger 
restraint systems such as seatbelts and steering column mounted expandable 
air bags, with the air bag systems being primarily active for the higher 
speed impacts exceeding the one to five mile per hour range. 
The typical low impact energy absorbing bumper system in popular use is the 
"soft" bumper system. This generally includes a flexible synthetic resin 
front bumper plate enclosing an energy absorbing type foam material, all 
of which may be mounted on a fairly rigid back plate or cross member 
extending transversely of the vehicle and mounted at its ends to axially 
extending vehicle frame members. Such a cross member is usually made of 
steel and is in effect the rigid chromed steel bumper which was so popular 
in the past. Typical of these soft bumper systems are those shown in U.S. 
Pat. Nos. 3,574,379, 4,542,925, 4,569,865 and 4,762,352. 
Additionally, it is known to provide a fairly rigid bumper system with 
axially directed shock absorber members located intermediate the bumper 
structure and the vehicle frame to allow the entire bumper structure to 
yield upon receiving a relatively low energy impact and the return to its 
initial position upon cessation of the impact load. 
Finally, internal stroking type bumper beam constructions are known wherein 
a fairly rigid front bumper plate member is retained on a face plate or 
similar member located at opposite ends of the bumper beam in such a 
manner that the front bumper beam can slide rearward toward the face plate 
upon receiving a frontal impact. An energy absorbing material is located 
between the front bumper beam and face plate to absorb the energy of the 
impact and return the front bumper beam to its original position upon 
cessation of the impact. Such a system has been proposed as an add-on to 
the vehicle frame members, as shown in U.S. Pat. No. 4,460,205. 
Despite the foregoing developments, there exists the need for an energy 
absorbing vehicle bumper system which is designed as an integral part of 
the vehicle frame structure, is simple in construction with a minimal 
number of component parts, provides in the unloaded condition a bumper 
structure having minimal length in the fore-aft axis of the vehicle, and 
is of minimal weight yet capable of resiliently absorbing a maximum amount 
of impact energy per unit stroke. 
SUMMARY OF THE INVENTION 
The present invention contemplates a vehicular energy absorbing bumper 
system capable of absorbing a significant amount of energy at low speed 
impact and returning to its original non-impacted condition. 
The present invention also contemplates a vehicular energy absorbing bumper 
system integrally designed with the vehicle frame structure to thereby 
provide a bumper system of high strength, minimum components, low weight, 
and a minimum fore and aft dimension. 
The present invention further contemplates a vehicular energy absorbing 
bumper system including an energy absorbing foam material positioned 
intermediate a relatively rigid front bumper beam and a rearward 
relatively rigid face plate or cross member integral with the vehicle 
frame structure whereby the front bumper beam can axially collapse 
relative to the rear cross member to thereby depress the energy absorbing 
foam material to absorb the impact of any low speed collision. 
The present invention further contemplates the aforementioned internally 
stroking bumper beam assembly which further includes means for absorbing a 
collision force directed at any acute angle to the front bumper beam and 
for absorbing the transverse load component of any such impact within the 
vehicle frame structure, thereby minimizing shear forces on the energy 
absorbing foam material as well as holding the transverse location of the 
front bumper beam relative to the rear cross member. 
Additionally, the present invention contemplates a unified vehicle chassis 
frame structure and bumper structure wherein (i) the frame structure 
includes a pair of longitudinally extending generally parallel rail 
members, each having a distal end, and a channel member secured to and 
extending traversely between each of the distal ends, and (ii) the bumper 
structure is disposed transversely of the rail members and includes a 
bumper beam, an energy absorbing material member, and an attachment member 
for securing the bumper structure to the frame structure. The bumper 
structure is capable of sliding fore and aft relative to the frame 
structure. The bumper beam and frame member cooperate to define a cavity 
within which is disposed the energy absorbing material member. An impact 
load upon the bumper beam in any rearward direction toward the 
longitudinal axis of the rail members will cause the front portion of the 
bumper beam to slide toward the frame member thereby compressing the 
energy absorbing material and dissipating the impact load over the entire 
length of the bumper beam and frame member. 
In an alternate embodiment, the attachment member of the bumper structure 
is a backing plate member disposed rearward of the traversely extending 
channel member in encapsulating relationship with the rail members to 
preclude relative lateral movement of the bumper structure during fore and 
aft stroking movement of the bumper beam during impact and immediately 
following impact upon cessation of any impact load. 
The above objects and other objects, features, and advantages of the 
present invention are readily apparent from the following detailed 
description of the best mode for carrying out the invention when taken in 
connection with the accompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring to the drawings, FIG. 1 is a general view of the bumper assembly 
2 mounted to the vehicle frame 4 at the front of the vehicle 6 As shown, 
the bumper assembly 2 is covered by a soft flexible plastic material 
forming the ornamental front end of the vehicle. The bumper assembly could 
also be exposed. Further, for purposes of the invention, the bumper 
assembly could be mounted at the front or rear of the vehicle. 
A first embodiment of the present invention is shown in detail in FIGS. 2 
and 3 wherein it is to be noted that the bumper assembly includes three 
basic components, namely a face bar 8, a block of foamed energy absorbing 
material 10 and back plate 12. The bumper assembly 2 is mounted on a frame 
structure comprising a pair of parallel frame rail members 14 (only one of 
which is shown in FIG. 2) and a transversely extending cross-beam 16 which 
is welded or otherwise permanently fixed to the respective ends of the 
frame rails 14 as generally shown at 18. 
These basic components are fairly rigid and made of high strength materials 
such that the low impact loads designed to be absorbed by the assembly 
will not cause permanent deformation of any of its members. For example, a 
suitable design would include a cross-beam member 16 of approximately 2 
millimeters thickness, a face bar 8 of approximately 21/4 millimeters 
thickness made of steel, and a steel back plate 12 of approximately 1.5 
millimeters thickness. Any of the components, but particularly the face 
bar 8, could also be made of a structural composite material, such as a 
resin composite, particularly glass reinforced plastic. 
Suitable materials for the foamed energy absorbing block 10 include most 
any polypropylene or urethane foam, and others such as elastomeric 
honeycomb. As shown in FIG. 2, the foamed energy absorbing material can be 
two separate blocks of material located at the respective ends of the 
cross-beam in alignment with the rail members 14, or it can be a single 
block of material extending the entire length of the cross-beam 16. Where 
separate blocks 10 are used, the space between the blocks allows for the 
possibility of providing aligned slots 19 (shown in dotted line) through 
each of the face bar 8, cross-beam member 16 and back plate 12 to allow 
increased air intake to the conventional radiator placed on the rearward 
side of the back plate 12, thus increasing the cooling capacity of the 
vehicle. 
The face bar 8 is a channel member, being basically C-shaped in 
cross-section, and including a front wall 20 and side walls 22,24. Each of 
the side walls 22,24 includes an outwardly turned flange 26. 
The cross-beam member 16 is also a channel member of basic C-shaped 
cross-section. It includes a vertical base wall 28 and opposed side walls 
30 which form upper and lower flanges 32,34, respectively. 
As seen in FIG. 3, the face bar and cross-member are sized such that the 
cross-beam member is nested completely within the cavity formed by the 
face bar 8. The back plate member 12 is mounted over the frame rail 
members 14 at the rearward side of the cross-beam member and is affixed to 
the face bar flanges 26 by any suitable means such as the rivets 36 shown. 
The foamed energy absorbing block 10 nearly completely fills the cavity 37 
formed between the face bar 8 and cross-beam member 16. Preferably, it is 
sized such that it completely fills the space between the upper and lower 
flanges 32,34 of the cross-beam member and can be held in place during 
assembly by being under slight compression between the two flanges. 
Alternatively, it can be bonded to either or both of the face bar 8 and 
cross-beam member 16. Preferably, in its assembled position as shown in 
FIG. 3, the foamed material will be under slight compression between the 
face bar and cross-beam so that the back plate will be held firmly against 
the cross-beam member 16. 
Further, it is desirable to place a strip or layer of low friction, 
vibration damping material 42 between the interfaces of the upper and 
lower flanges with the side walls of the face bar and between the vertical 
base wall 28 of the cross-beam member and the back plate 12. 
From FIG. 2, it will be noted that the back plate 12 includes a 
rectangularly-shaped cut-out section defined by a pair of side walls 38 
and a third wall 40 which allow the back plate to be mounted over the 
frame rail 14. The depth of the cut-out section is somewhat immaterial, 
however, it is important for reasons explained more fully below that the 
side walls 38 extend the full depth of the frame rail 14 and be positioned 
in close proximity to the frame rail. 
In operation, when the face bar is impacted during a collision at 
relatively low speed, i.e. from 1-5 miles per hour, the face bar will 
slide rearward toward the cross-beam member putting the energy absorbing 
material member 10 in compression and thereby absorbing the impact load. 
The energy absorbed will increase with the stroke of the face bar member 
relative to the cross-beam. When the impact load is absorbed or withdrawn, 
the face bar will return to its original position. The low friction, 
vibration damping material strips 42 disposed between the relative sliding 
surfaces of the cross-beam member and face bar assist in the reciprocal 
sliding action between these two members. Also, if the impact load is 
taken at an angle other than normal to the face bar, there will be 
transverse or lateral component forces which, unless positively 
restrained, would tend to cause the face bars positioned to shift 
laterally relative to the cross-beam. Any such transverse slippage is 
precluded by the walls 38 of the back plate member which act as a guide to 
assure that the sliding action of the bumper assembly is solely along an 
axis coincident with the longitudinal axis of the frame rail members 14. 
Any significant lateral force will cause one side wall 38 or the other to 
abut each respective frame rail member 14. This positively precludes any 
shifting of the face bar member 8 relative to the cross-beam member 16. 
A further embodiment of the present invention is shown in FIG. 4 wherein 
the only notable change is that in the design of the cross-beam member 16. 
The cross-beam 16 is constructed as a hollow composite member comprising a 
vertical base wall 28 to which is welded or otherwise secured a channel 
reinforcement member 44, which is basically C-shaped in cross-section as 
shown in FIG. 4, the reinforcement member 44 includes a front wall 46, 
side walls 48 which diverge outwardly from the front wall and terminate in 
respective flange portions 50 which are welded or otherwise affixed to the 
vertical base wall. The composite cross-beam member includes upper and 
lower edges 52 which may be in contact with or in close proximity to the 
internal surfaces of the face bar side walls 22,24 to provide the means 
for supporting the face bar on the cross-beam member. The cavity between 
the face bar and cross-beam member is completely filled with foamed energy 
absorbing material, which in conjunction with the generally trapezoidal 
cross-sectional shape of the reinforcement member 44 acts to assist in 
supporting the face bar on the cross-beam member. If desired, the foamed 
energy absorbing material may include a series of cavities 49 to adjust 
the compressional characteristics of the foam material to the design 
requirements of the bumper assembly. 
It will further be noted in FIG. 3 from the representation shown in dotted 
line, that the face bar can slide relative to the cross-beam member a 
maximum designed distance 78, at which point the foamed energy absorbing 
block 10 will be under full compression. The bumper may be constructed 
such that the front edge of cross-beam flanges 32 and 34 will, after 
traversing the distance 78, contact the backside of face bar front wall 20 
either directly or indirectly through the fully compressed and expanded 
energy absorbing block 10. 
FIGS. 5 and 6 show yet another alternative embodiment of the present 
invention wherein the back plate member 12 is comprised of three separate 
plate members 54, 56, 58. Each may be secured to the face bar member 8 in 
the manner described above. Alternatively, the side walls 22,24 of the 
face bar may include four raised and internally threaded bosses 60 adapted 
to receive bolts 62 inserted through the vesting holes of each respective 
back plate member 54, 56, 58. The outboard back plate members 54,56 each 
include an inward shoulder 64 in close proximity to the respective outer 
wall of each rail member 14 and act as guide bars for guiding the 
reciprocation of the bumper assembly in the direction of the rail members 
and absorbing at a lateral force placed upon the bumper assembly. 
Likewise, the outboard faces 66,68 of the central back plate unit 58 serve 
the same function. 
Another embodiment of the present invention is shown in FIGS. 7 and 8. The 
previous embodiments each included a back plate member and could be 
referred to as a closed face bar assembly. The embodiment shown in FIGS. 7 
and 8 can be referred to as an open face bar since no back plate member is 
included. The face bar member 8 includes at each end a slot 70 closed at 
each end and longitudinally directed in the direction of the frame rail 
member 14 and having a length at least slightly greater than the internal 
stroke designed into the bumper assembly. A pin 72 passes through the slot 
and is affixed to the upper flange 32 of cross-beam member 16 at locating 
point 76. A similar fastening arrangement can be provided on the opposing 
side wall of the face bar and elsewhere throughout the length of the face 
bar member. The pin and slot arrangement serves the function of attaching 
the bumper assembly components to one another as well as providing a means 
for guiding the stroke of the face bar in a direction parallel to the rail 
members and at the same time having limited capability of absorbing any 
lateral load placed upon the bumper assembly and thereby preventing 
shifting of the face bar member relative to the cross-beam member. 
Although particular embodiments of the present invention have been 
illustrated in the accompanying drawings and described in the foregoing 
detailed description, it is to be understood that the present invention is 
not to be limited to just the embodiments disclosed. Numerous 
rearrangements, modifications and substitutions are possible without 
departing from the scope of the claims hereafter.