Bumper

The invention relates to a bumper for a vehicle body having two side members (11, 12), said bumper consisting of a bumper bracket (13) extending over the width of the body, with two deformation members (14, 15) projecting at right angles from the back at a distance from one another, said members being integral with bumper bracket (13) and being connectable by bolt connections (20) with side members (11, 12). The deformation members (14, 15) are more resistant to deformation than bumper bracket (13), so that they deform to absorb additional energy only when the ability of bumper bracket (13) to deform is exhausted.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to a bumper, and more particularly to a bumper for a 
vehicle body having two side members, the bumper having a bumper bracket 
extending over the width of the vehicle body with two deformation members 
mounted at a distance from one another on a back side of the bumper 
bracket facing the vehicle body, the deformation members being made more 
resistant to deformation than the bumper bracket so that they deform only 
after the bumper bracket has deformed, 
In a bumper known from German patent document DE 36 26 150 A1, the 
deformation members are made in the form of oval rings of 
glass-fiber-reinforced plastic, with the lengthwise central axis of the 
deformation member extending vertically and the deformation member having 
one wall abutting the side member of the vehicle body and the opposite 
wall abutting the back of the bumper bracket and being mounted releasably 
by bolts. The deformation members thus formed are intended for absorption 
and exhibit the special property of not breaking when overloaded but of 
absorbing energy by delamination of the individual fiber layers. The 
purpose of this property is that the side members can be largely protected 
against damage at impact speeds above the design speed for the bumper. The 
bumper bracket is designed as a box girder with a closed hollow cross 
section and is likewise made of glass-fiber-reinforced plastic, with 
transverse reinforcement being provided by endless fibers or fabric to 
absorb torsion forces and transverse shear. The cavity in the bumper 
bracket can also be filled with foam. In a minor collision, only the 
deformation members are deformed for the most part, so that repair can be 
limited to replacing the deformation members, which can be accomplished 
relatively simply by virtue of the bolt mounting. In a more serious 
collision, both the deformation members and the bumper bracket are 
deformed. In addition, a bumper of the initially described type is known 
from German patent document DE 26 25 724 A1, in which the deformation 
members consist of hollow bodies whose lengthwise central axes are 
extensions of the side members, with the deformation members likewise 
being fastened releasably by bolts to the side members and bumper bracket. 
The bumper bracket consists of a C-profile whose opening facing the side 
members is closed by a flat panel. 
The energy absorption capacity of the bumper described above before the 
side member is damaged is relatively limited, so that damage to the side 
members can only be avoided in collisions at very low speeds, up to 5 km/h 
for example. In addition, the deformation members are insufficiently able 
to absorb energy from diagonal impacts directed at an angle to them. 
A bumper is known from German patent document DE 35 10 590 C2 that is 
assembled from two half shells and is mounted directly on the side members 
of the vehicle body. The legs of the U-shaped half shells decrease in 
width toward the free ends of the bumper, so that the two half shells are 
located opposite one another in their original positions before they are 
joined in such fashion that following endwise contact between the legs in 
the middle of the bumper, a gap remains between them that continuously 
widens toward the ends. For welding, the two half shells are tensioned 
against one another so that the gap is closed. Stresses then develop in 
the half shells which contribute to strengthening the bumper and have a 
favorable effect on its stability under stress. 
The goal of the invention is to provide a bumper of the initially described 
type with much greater energy absorption capacity. 
This and other goals have been achieved according to the present invention 
by providing a bumper bracket which is assembled from half shells which 
abut one another within a separating plane that extends essentially 
horizontally in a mounted position and which are connected to one another 
by flanges, wherein the half shells each have half shell wall parts facing 
the vehicle body which form the two deformation members, the half shell 
wall parts being made in one piece with the half shells and projecting 
transversely therefrom, and the half shell wall parts forming hollow 
bodies integral with the bumper brackets and resistant to deformation when 
in the mounted position. 
The bumper according to the invention has the advantage that it can absorb 
very much greater impact energy without the side members being deformed 
than the known bumper initially described, since the deformation members, 
being stiffer than the bumper bracket, initially keep any impact energy 
from reaching the side members and it is only after the collapse of the 
bumper bracket that the members absorb energy. Hence, impacts that occur 
at vehicle speeds of up to 15 km/h can be absorbed without damaging the 
side members. Inexpensive structural repair of the vehicle following such 
an impact is possible without any welding or straightening work by simply 
replacing the bumper. The fact that the deformation members form one-piece 
deformation-resistant hollow bodies together with the bumper bracket 
permits greater energy absorption because of the larger cross sections 
involved. In addition the requirements for a large-volume and 
bending-resistant structure in designing deformation members that are made 
integral with the bumper bracket, which can be designed to meet the 
requirements in such fashion that energy absorption is largely independent 
of the direction of the stress, so that controlled deformation is possible 
even with diagonal impacts. 
Advantageous embodiments, suitable improvements, and designs of the bumper 
according to the invention are described in the other claims. 
The flanges of the two half shells can run horizontally or vertically, with 
the flanges resting on one another in the horizontal position and with the 
flanges fitting over one another in the vertical direction in the vertical 
position. Alignment of the flanges has the advantage that the half shells 
can be manufactured with a single tool. This applies even when the shapes 
of the half shell wall parts that form the deformation members differ to a 
greater degree in these areas from the remaining area of the bumper 
bracket, for example from its central area. 
By constructing the bumper with reinforcing parts located in the bumper 
bracket and/or the deformation members, the stiffness of the bumper under 
flexure and its resistance to changing shape can be deliberately 
influenced. By arranging a horizontal reinforcing part in the bumper 
bracket to form a two-chambered cross-sectional profile, the bumper 
bracket can be subjected to even higher stresses, for example in the 
bending area between the side member connections. 
By aligning deformation elements in the direction of respective side 
members and abutting the vehicle body at one end, and designing the 
reinforcing parts as profiles, hollow bodies, solid bodies, or vertical 
and horizontal supporting walls, the energy absorption capacity of the 
deformation members can be increased and deliberately influenced in this 
respect depending on the type, shape, and dimensions of the reinforcing 
parts. 
The deformation characteristic of the deformation members and of the bumper 
bracket can be influenced by providing lock beads lock beads are provided 
in the half shells, particularly in the area of the deformation members. 
In one preferred embodiment, the bumper is constructed in a lobular shape. 
This shaping to form the deformation members can also be defined as 
flaring, which serves as a deformation zone and for greater energy 
absorption by larger cross sections, and means that energy absorption by 
large-volume design which is insensitive to bending is largely independent 
of the direction of the load, in other words specific deformation in the 
area of the deformation members is possible even with diagonal impacts. 
In another preferred embodiment, the half shell wall parts of the half 
shells that form the deformation members are designed as lengthwise parts 
projecting approximately at right angles and pointing toward the vehicle 
body. 
In yet another preferred embodiment, the bumper bracket and the deformation 
members are each made as extrusion-molded profiles and wherein the 
extrusion-molded profiles are connected together by bolting, riveting, 
gluing, or welding. By virtue of this design in the form of a box-shaped 
extrusion-molded profile for both the bumper bracket and for the 
deformation members, a much greater energy absorption capacity can be 
achieved, likewise with low cost and weight.

DETAILED DESCRIPTION OF THE DRAWINGS 
The bumper shown in FIGS. 1 and 2 is designed to be attached to a vehicle 
body, specifically to its side members 11 and 12. The bumper can be 
located on the front or rear ends of the two side members 11, 12. The 
bumper has a bumper bracket 13 with two deformation members 14, 15 
projecting transversely therefrom, for example at right angles, said 
members being integral with bumper bracket 13. At the free ends of 
deformation members 14, 15, mounting flanges 16, 17 are provided, e.g. 
molded, said flanges abutting matching flanges 18, 19 on side members 11, 
12 and being firmly connected therewith by bolt connections 20, and being 
disconnectable from said members by said connections. 
The bumper, specifically bumper bracket 13 with the two deformation members 
14, 15 integral therewith, is assembled from two essentially identical 
half shells 21, 22 abutting one another within a separating plane that 
runs horizontally in the mounting position and contacting one another by 
means of surrounding flanges 23, 24 that extend horizontally in the first 
embodiment and are firmly connected to one another by said flanges. The 
two flanges 23, 24 in the first embodiment are aligned parallel to the 
horizontal separating plane. They can also be aligned vertically instead. 
The area of half shells 21, 22 forming respective deformation members 14, 
15 is formed by transversely projecting half shell wall parts 41 and 42, 
said parts forming deformation-resistant hollow bodies when the bumper 
bracket is assembled. Flanges 23, 24 of half shells 21, 22 merge with 
similar flanges 43 and 44 of half shell wall parts 41 and 42. 
The two half shells 21, 22 are made for example from deep-drawn steel or 
light metal sheet, such as aluminum for example. They can also be made of 
cast light metal instead. The firm connection of half shells 21, 22 in the 
vicinity of flanges 23, 24 and 43, 44 is achieved by rivets in particular, 
especially when half shells 21, 22 consist of aluminum. Half shells 21, 22 
can also be connected firmly instead by welding, joining by pressure, 
gluing, bolting, or the like. Spot, laser, or MAG welding can be used as 
welding methods. The assembly composed of the two half shells 21, 22 as 
bumper bracket 13 and deformation members 14, 15 is so designed that 
deformation members 14, 15 are more resistant to deformation than bumper 
bracket 13, so that they deform only when additional energy is absorbed 
after the deformation ability of bumper bracket 13 is exhausted. This 
deformation behavior is conferred by suitable design of the two half 
shells 21, 22. In addition, the stiffness under flexure and resistance to 
change in shape are accomplished by deliberately providing lock beads 25 
in half shells 21, 22 and/or by using preferably galvanized reinforcing 
panels 26 in the vicinity of bumper bracket 13 and/or the two deformation 
members 14, 15. Reinforcing panels 26 run horizontally for example, inside 
the separating plane of half shells 21, 22 and in the plane of flanges 23, 
24, with the shell walls of bumper bracket 13 that are opposite one 
another abutting via reinforcing panels 26 for example. In addition, or 
instead, vertical reinforcing panels or reinforcing parts of another 
design can be provided in bumper bracket 13 and/or deformation members 14, 
15. In the area of deformation members 14, 15 a receptacle, likewise not 
shown in greater detail, can be provided for a bolted towing support. 
In the first embodiment in FIGS. 1 and 2, the two half shell wall parts 41, 
42 of half shells 21, 22 that form deformation members 14, 15 are made in 
the form of lengthwise parts that project from bumper bracket 13 
approximately at right angles and point toward side members 11, 12, so 
that the deformation members are formed as approximately hollow-box-shaped 
supports. In another embodiment, not shown, these deformation members 14, 
15 designed as box-shaped supports can also be modified in such fashion 
that their cross sections change, increasing or decreasing, over their 
length. This is indicated in FIG. 2 by the dashed lines, with the cross 
sections of deformation members 14, 15 tapering from bumper bracket 13 to 
side members 11, 12 or vice versa. In FIG. 2, the dashed lines also 
indicate that an impact absorber 27 made of foamed plastic or the like is 
located on the front of bumper bracket 13, said absorber being mounted for 
example on flanges 23, 24. Impact absorber 27 reduces impact energy by 
deforming, and protects bumper bracket 13 against damage in impacts at 
very low vehicle speeds. After absorbing energy by deformation, impact 
absorber 27 is able to return to its original state. The bumper is so 
designed that in impacts at very low vehicle speeds, energy is initially 
absorbed by deformation of reversible impact absorber 27 located ahead of 
bumper bracket 13. At higher impact energy levels, bumper bracket 13 
initially bends and then deforms. Only higher impact energies are absorbed 
by deformation of deformation members 14, 15, with side members 11, 12 
being deformed only after complete deformation of deformation members 14, 
15 and the overloads that follow. 
In the second embodiment shown in FIGS. 3 to 7, reference numerals 
increased by 100 are used for those parts that correspond to those in the 
first embodiment in FIGS. 1 and 2, so that reference will therefore be 
made to the description of the first embodiment. 
In the second embodiment as well, the two half shells 121, 122 have, on the 
back, facing side members 111, 112 half shell wall parts integral with 
half shells 121, 122 and projecting transversely therefrom, with half 
shell wall parts 141 and 142 forming deformation member 115 in FIG. 6. 
FIG. 5 shows the other two half shell wall parts 145, 146 forming 
deformation member 114. With the bumper assembled, half shells 121, 122 
form bumper bracket 113, half shell wall parts 141, 142 form one 
deformation member 115, and half shell wall parts 145, 146 form the other 
deformation member 114, with deformation-resistant hollow bodies of a 
special design being provided in both deformation members. It is evident 
from FIG. 3 that the hollow body cross section tapers from at least both 
sides toward rear flange 116, 117. Viewed in the other direction, the 
cross section expands approximately in a V-shape starting at flanges 118, 
119. Looking at the cross section of the bumper, starting approximately at 
the middle of bumper bracket 113 and following its course in FIG. 3 to the 
right, it is evident that the front and rear wall parts expand to merge 
with deformation member 115. The special shape of deformation member 114 
or 115 can also be described as flared, viewed starting from side members 
111, 112 and looking in the direction of bumper bracket 113. Flanges 123, 
124 of half shells 121, 122 merge with flanges 143, 144 of half shell wall 
parts 141, 142, as can be seen in deformation member 115 in FIG. 6. 
Flanges 123, 124 and 143, 144 in the second embodiment run transversely 
with respect to the horizontal separating plane, in other words 
approximately vertically. They fit over one another, with flanges 124 and 
144 of lower half shell 122 or of lower half shell wall part 142 being 
gripped by flanges 123, 143 of upper half shell 121 and upper half shell 
wall part 141. Flanges 123, 124, 143, 144 are advantageously permanently 
connected by rivets 147 as shown. 
Reinforcing parts can be mounted in bumper bracket 113 and/or deformation 
members 114, 115 as shown in FIG. 3 by the dashed reinforcing parts 148, 
149 in deformation members 114, 115. Bumper bracket 113 has a horizontal 
reinforcing panel 126 as a reinforcing part, especially in its middle 
area, said panel running inside the horizontal separating plane and 
abutting the opposite shell walls, especially flanges 124. Reinforcing 
panel 126 can have edge parts bent on both sides and internally abutting 
flanges 124, and be fastened to these edge parts together with flanges 
123, 124 by rivets 147. By virtue of reinforcing panel 126, bumper bracket 
113 is designed as a two-chambered profile especially in its middle area, 
as viewed in cross section. 
Reinforcing parts 148, 149 in the vicinity of deformation members 114, 115 
can be designed as deformation elements aligned in the direction of 
respective side members 111, 112 and abutting the vehicle body at one end. 
These reinforcing parts 148, 149 are designed for example as profiles or 
hollow bodies or as solid bodies or vertical and/or horizontal supporting 
walls or the like. In FIGS. 3, 5, and 6, in the embodiment shown therein, 
it is indicated that reinforcing parts 148, 149 can be designed for 
example as horizontally directed tubular profiles. 
In the modified embodiment shown in FIG. 7, reinforcing part 149a is 
designed as an inverted U-shaped profile whose U-base 150 abuts one half 
shell wall part 141 and whose U-legs 151, 152 abut the other half shell 
wall part 142, each in the vertical direction, and are fastened thereto 
for example by rivets or the like. 
In the vicinity of the two deformation members 114, 115, lock beads 125 are 
deliberately provided above and/or below, running approximately parallel 
to the direction of bumper bracket 113, by which the deformation 
characteristic of flared deformation members 114, 115 can be deliberately 
influenced. 
The bumper according to the second embodiment, in the top view according to 
FIG. 3, has the characteristic of a somewhat lobular design viewed for 
example looking from the middle of bumper bracket 113 toward an outer 
side. The arrangement is such that the two half shell wall parts 145, 146 
and 141, 142 of half shells 121, 122 that each form deformation members 
114 and 115, make a transition from an essentially flat and vertical 
mounting surface represented by mounting flange 116, 117, initially 
diagonally or in an arc with convex or concave curvature, to the parts of 
half shells 121, 122 that form bumper bracket 113. This flaring of each 
deformation member 114, 115 that proceeds outward from flange 116, 117 as 
viewed from the front serves as a deformation zone and allows considerable 
energy absorption by virtue of its relatively large cross section. This 
energy absorption, because of the large-volume, bending-insensitive 
design, is largely independent of the direction of the load, in other 
words definite deformation of deformation members 114, 115 is possible 
even in diagonal impacts. In summary, the bumper according to the second 
embodiment is simple in design and therefore economical to manufacture. 
In the first embodiment in FIG. 1, widened areas 30 are indicated on half 
shell flanges 23, 24, said areas having mounting areas 36 for mounting 
additional vehicle assemblies or the like for example. This is also 
possible in the second embodiment shown in FIGS. 3 to 7. For example, 
deformation members 114, 115 can also have a receptacle, not shown in 
greater detail, for a bolted towing support. 
In the third embodiment shown in FIG. 8, a bumper of a different design is 
shown in sections. For parts that correspond to the first embodiment, 
reference numerals that are larger by 200 have been used for the reasons 
given. In FIG. 8, bumper bracket 213 and the deformation members, of which 
only deformation member 215 is shown, are each made separately as 
extrusion-molded profiles and permanently attached to one another, for 
example by bolting, riveting, gluing, or welding. Bumper bracket 213 is 
designed in the middle area as a closed box profile and in the end areas 
as a U-profile open to the vehicle body. Impact absorber 227 made of 
foamed plastic is fastened to the front of bumper bracket 213, facing away 
from the vehicle body. Deformation members 215 are likewise designed as 
extrusion-molded box profiles, with reinforcing ribs 228 possibly being 
provided to influence the resistance under flexure and resistance to 
changing shape, said ribs running horizontally in the installation 
position of the bumper and abutting two opposite profile walls. In order 
to produce a homogeneous deformation process and to reduce the initial 
peak force on folding, reinforcing ribs 228 are cut back in the connection 
area to bumper bracket 213, in other words they end at a distance from the 
end of deformation member 215 mounted on bumper bracket 213. Bumper 
bracket 213 is made with a centrally located horizontal lengthwise rib 
229. 
FIG. 9 shows a fourth embodiment of a bumper, in section and in 
perspective. Bumper bracket 313 here is composed of two identical half 
shells 331, 332, which in the mounting position rest against one another 
by vertical flanges 333 and 334 along a vertical separating plane and are 
firmly connected to one another by means of said flanges. The two 
deformation members, of which only deformation member 315 is shown in FIG. 
9, are designed as box profiles that consist of a U-shaped profile section 
with a closing panel and are fastened endwise to half shell 332 that faces 
the vehicle body by welding, riveting, bolting, gluing, or the like. 
Double tabs 335 are provided at the free ends of deformation members 315 
and serve to receive the bolt connections to the side members. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.