Force-absorbing vehicle bumper

A vehicle bumper includes a hollow tubular wall structure adapted to span the front or rear end of an automotive vehicle so as to absorb crash forces when the vehicle is involved in a crash situation at vehicle speeds above some predetermined speed level, e.g., five miles per hour. The hollow tubular wall structure includes an outer wall disposed to receive the crash force, an inner wall connectable to the vehicle, and four connector walls joining the outer wall to the inner wall. The four connector walls bend at a controlled rate to absorb crash energy. The outer and inner walls have aligned air openings adapted to conduct ram air to the vehicle radiator.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to vehicle bumpers, and particularly to a vehicle 
bumper having force-absorbing capabilities. 
2. Related Prior Developments 
A force-absorbing bumper absorbs some of the crash force applied to it, 
rather than transmitting all of the crash force to the vehicle. The 
advantage of such a bumper is that it minimizes vehicle damage, and also 
reduces potential human injury. 
Force-absorbing bumpers are well known. U.S. Pat. No. 4,018,466, issued to 
S. Norlin, shows a bumper that includes a rigid structural channel having 
several egg-crate energy-absorbing units. Each energy-absorbing unit 
includes a rectangular box having intersecting partitions that form 
individual cells. The cell spaces allow the partitions to collapse so as 
to absorb crash energy. 
U.S. Pat. No. 4,348,042, issued to J. Scrivo, shows a vehicle bumper that 
includes a rigid channel having a thick energy-absorbing elastomeric 
strip. Apparently, the elastomeric strip absorbs crash energy by 
compressing in the direction of the crash force and expanding in a 
direction normal to the direction of the crash force. 
U.S. Pat. No. 4,542,925, issued to G. Huber, shows an energy-absorbing 
bumper that includes a zig-zag leaf spring extending forwardly from a 
rigid support bar. Impact buffer pads are spaced along the support bar to 
cushion the rearward motion of the leaf spring in a crash situation. 
U.S. Pat. No. 5,154,462, issued to R. Carpenter, shows an energy-absorbing 
bumper that includes an elongated rigid tubular support having a thick 
foam rubber strip extending along its front surface. During a crash, the 
foam rubber strip deforms to absorb crash energy. 
SUMMARY OF THE INVENTION 
The present invention relates to an energy-absorbing bumper that includes a 
hollow tubular wall structure adapted to span one end of a vehicle, i.e., 
either the front end or the rear end. The tubular wall structure includes 
an outer wall adapted to receive crash energy and an inner wall adapted to 
be attached to the vehicle or to shock-absorber struts carried by the 
vehicle. 
The outer wall is connected to the inner wall by four separate connector 
walls spaced, one above another, so that the connector walls can deform 
and bend in response to the application of a crash force. The connector 
walls deform, in a controlled fashion, to absorb some of the crash energy. 
The connector walls are constructed so as to be non-bendable until the 
crash energy reaches a predetermined level, e.g. an energy level attained 
by a crash occurring at a relatively low speed, e.g., five to ten miles 
per hour. At higher crash energy levels, the connector walls bend, in a 
controlled manner, to absorb some of the crash energy, thereby at least 
partly protecting the vehicle from damage to the chassis, body or interior 
hardware. 
As an ancillary feature of the invention, the bumper can be formed with air 
openings in its front and rear walls. During operation of the vehicle some 
of the ram air can flow through the air openings. Such air can be used for 
radiator-cooling purposes or for engine combustion purposes. The bumper is 
constructed so that the air openings do not measurably interfere with the 
crash energy-absorbing function of the bumper. 
Further features of the invention will be apparent from the attached 
drawings and description of a preferred embodiment of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
The vehicle bumper shown in FIGS. 1 through 4 includes an elongated hollow 
tubular wall structure 10 adapted to span one end of an automotive 
vehicle, e.g., a car or truck. The ends of tubular wall structure 10 are 
closed by end caps 12. Each end cap has a plug 14 fitting into an end 
opening in tubular wall structure 10, so that the end caps form rigid 
extensions of the tubular wall structure. 
The bumper shown in FIGS. 1 and 2 has aligned air openings 16 and 18 and 
its outer and inner walls, such that the bumper is especially adapted for 
disposition at the front end of a vehicle, i.e., directly in front of the 
air-cooled radiator. However, the same bumper design, without the air 
openings, can be used at the rear end of the vehicle. In either 
disposition of the bumper, the bumper is designed to absorb some crash 
energy at speeds above some predetermined value, e.g., above five or ten 
miles per hour. 
The bumper wall structure 10 includes an outer wall 20 adapted to receive 
the crash impact force, and an inner wall 22 adapted to be attached to the 
vehicle or to shock-absorbing struts carried by the vehicle. As seen in 
FIGS. 3 and 4, walls 20 and 22 are connected together by four connector 
walls 24, 26, 28 and 30 that extend the full length of tubular wall 
structure 10. 
Tubular wall structure 10 can be a one piece aluminum member formed by an 
extrusion process. The slight arcuate plan configuration of wall structure 
10 depicted in FIG. 1 can be achieved by passing the heated extrusion 
through an array of mandrels, as shown, e.g., in U.S. Pat. No. 5,306,058, 
issued to P. Sturrus et al. The air openings 16 and 18 are formed in walls 
20 and 22 after the tubular wall structure has been fully formed to its 
final configuration. 
Connector wall 24 constitutes the upper wall of the tubular wall structure. 
Connector wall 30 constitutes the lower wall of the tubular wall 
structure. For reference purposes, connector walls 26 and 28 will be 
referred to as first and second intermediate connector walls. 
As shown in FIG. 3, connector walls 24 and 30 include first wall sections 
32 extending at right angles from outer wall 20, and second wall sections 
34 extending from wall 22 at an acute angle 36. As shown in FIG. 3, the 
acute angle is, in each case, about fifty degrees. Connector walls 24 and 
30 are mirror images of one another, in that these walls are symmetrical 
around an imaginary mid plane 38 taken through tubular wall structure 10. 
Acute angles 36 are directed away from mid plane 38, such that connector 
walls 24 and 30 will bend away from mid plane 38 when a crash force of 
appreciable magnitude is applied to outer wall 20. 
Connector walls 26 and 28 include first wall sections 40 extending at right 
angles from outer wall 20 and second wall sections 42 extending from inner 
wall 22 at an acute angle 44. As shown in FIG. 3 acute angle 44 is about 
ten degrees. Walls 26 and 28 are equidistant from mid plane 38. The acute 
angles 44 are directed toward mid plane 38, such that walls 26 and 28 will 
bend toward mid plane 38 when a crash force of appreciable magnitude is 
applied to outer wall 20. The cross-sectional spacing between connector 
walls 28 and 26 is greater than the cross-sectional spacing between walls 
24 and 26 and between walls 28 and 30, so that the central chamber 46 
formed by walls 28 and 26 can accommodate the inward bending action of 
walls 28 and 26 in a controlled fashion. 
In one embodiment, the hollow tubular wall structure 10 is designed so that 
the various walls have different wall thicknesses. For example, in a 
hollow tubular wll structure formed of aluminum, and having a height 
dimension 48 of about ninety five millimeters, the thickness dimension for 
wall 20 may be about 0.162 inch, the thickness dimension of wall 22 may be 
about 0.175 inch, the thickness dimension of each wall 24 or 30 may be 
about 0.115 inch, and the thickness dimension of each wall 2 6 or 28 may 
be about 0.100 inch. These thickness dimensions will vary according to the 
weight and crash resistance of the vehicle on which the bumper is used. 
Connector walls 24, 26, 28 and 30 are designed to remain elastically 
deformable with little deformation (as shown in FIG. 3) as long as the 
crash force applied to outer wall 20 remains below a predetermined value, 
e.g., a value associated with a particular vehicle speed such as five or 
ten miles per hour. When the crash force exceeds this predetermined value, 
connector walls 24, 26, 28 and 30 will bend, as shown in FIG. 4. As the 
connector walls bend, they absorb some of the crash energy, thereby 
minimizing damage to the vehicle. 
FIG. 5 shows generally how the connector walls 24, 26, 28 and 30 are 
expected to perform. At crash force values below level 50, the connector 
walls remain substantially undeformed. As the crash force exceeds level 
50, the connector walls begin to deform, as shown in FIG. 4. 
Walls 24 and 26, together with the top portion of front wall 20 define an 
upper chamber and walls 28 and 30, together with a bottom portion of front 
wall 20, define a lower chamber. An intermediate or central chamber is 
defined between walls 26, 28, a central portion of front wall 20 and rear 
wall 22. The rear portions of the upper and lower chambers taper down 
toward the rear wall 22. 
The upper and lower chambers have approximately equal cross-sectional areas 
and the intermediate chamber has a cross-sectional area greater than that 
of the upper and lower chambers. The intermediate chamber flares outwardly 
toward the rear wall along diverging wall sections 42, 42. Air openings 
16, 18 define an air flow path through the intermediate chamber. 
An aim of the invention is to provide each connector wall with the same 
bend resistance so that the connector walls will bend in unison when an 
appreciable crash force is applied to outer wall 20. Walls 20 and 22 will 
remain substantially parallel during a crash event so that any crash force 
transmitted to the vehicle will be in a generally horizontal direction, 
i.e., a direction in which the bumper connection fixtures have the maximum 
strength. 
Each connector wall 26, 28 preferably has a lesser wall thickness than each 
connector wall 24, 30. However, the angulation at 44 is less than 
angulation 36, such that the bend resistance of each connector wall is 
approximately the same. The lesser angulation stiffens the thinner walls, 
whereas the greater angulation tends to weaken the thicker walls. 
As shown in FIG. 4, each connector wall has two distinct flat linear wall 
sections joined together at a distinct bend line 52. This construction is 
preferred to an arcuate wall cross section, in that it promotes a 
predetermined bending action that is more predictable and controlled. 
Approximately the same bending action occurs, wherever the crash force is 
applied along the length of tubular wall structure 10 or along the height 
dimension of wall 20. 
As noted earlier, walls 20 and 22 have aligned openings 16 and 18 designed 
to permit ram air to pass through, as indicated generally by the arrow in 
FIG. 1. As shown in FIGS. 1 and 2, outer wall 20 has two relatively large 
slot-like air openings 16 spaced equidistant from centerpoint 54 of the 
tubular wall structure 10, i.e., a point midway between the ends of wall 
structure 10. 
Each air opening 16 is larger than the aligned air opening 18, to provide 
an accommodation space between walls 20 and 22 for dissipating turbulence 
generated by the pressure drop generated by air flow through each air 
opening 16. The turbulence produces a pressurized cushion alongside 
openings 16 and 18 that enables the air to flow in a relatively smooth 
fashion from each opening 16 through each aligned opening 18. Turbulence 
generated by each opening 16 is dissipated in the space between walls 20 
and 22. 
Each opening 16 has an area that is at least twice the area of the aligned 
opening 18 in order to dissipate the turbulence generated by the air flow 
through each opening 16. If the openings 16 and 18 were to be of the same 
area the turbulence generated by flow through each opening 16 would 
materially interfere with flow through opening 18, such that the total air 
flow would be undesirably reduced. 
In FIG. 3, the height dimension of each slot-type air flow opening 16 or 18 
is designated by numeral 56. The slot opening height is less than the 
height of central chamber 46 so that the air flows only through chamber 
46. Walls 26 and 28 guide the air flow toward each air exit opening 18. 
FIG. 6 shows an alternative form of the invention, wherein the tubular wall 
structure is formed out of steel roll-formed into a cross-sectional 
configuration that is approximately the same as the configuration depicted 
in FIG. 3. The FIG. 6 construction includes a main steel roll-form 59 
jointed to an auxiliary steel stamping 58. Roll-forming 59 includes a 
steel sheet bent into the illustrated cross-sectional configuration, with 
the end edges of the steel welded together at 60. Outer walls 20a of the 
tubular wall structure is thus twice the sheet thickness so as to be 
resistant to deformation forces. 
The inner wall 22a of the tubular wall structure has a greater wall 
thickness than the steel roll-form 59, such that inner wall 22a is 
resistant to bending forces. 
Connector walls 24a, 26a, 28a and 30a are bendable around the bend lines 
52a, so that the FIG. 6 tubular wall deforms in approximately the same 
fashion as the extruded tubular wall structure depicted in FIG. 3. 
In the FIG. 6 construction, the second wall section 42a of wall connector 
wall 26a, 28a are acutely angled to the plane of each inner wall 22a by an 
acute angle that measures approximately ten degrees. The corresponding 
angulations of wall sections 34a relative to wall 22a measure about twenty 
degrees. 
The crash performance of the FIG. 6 tubular wall structure is approximately 
the same as that of the FIG. 3 wall construction. In both cases, the 
bumper deforms substantially only when the crash force exceeds a 
predetermined level, e.g., a crash force associated with vehicle speeds in 
the area of five or ten miles per hour. The energy absorption level is 
preferably at ten g deceleration at a vehicle speed of about thirty miles 
per hour. Clearance openings for rear back-up or fog lamps can also be 
provided in the bumper in a manner similar to clearance holes 16 and 18.