U.S. patent application number 10/760760 was filed with the patent office on 2006-03-30 for modular energy absorber and method for configuring same.
This patent application is currently assigned to Oakwood Energy Management, Inc.. Invention is credited to Phillip Patrick III Carroll, Joel Matthew Cormier, Paul Gerard Grenier.
Application Number | 20060066134 10/760760 |
Document ID | / |
Family ID | 32966851 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060066134 |
Kind Code |
A2 |
Carroll; Phillip Patrick III ;
et al. |
March 30, 2006 |
MODULAR ENERGY ABSORBER AND METHOD FOR CONFIGURING SAME
Abstract
Abstract of the Disclosure A modular energy absorber 10 that is
tunable. It comprises one or more energy absorbing modules 12. The
energy absorbing modules have means for coordinating energy
absorbing units 16 of the one or more modules. The means 14 for
coordinating position and support the units in relation to each
other before, during and after relative motion between an incident
object and the energy absorber.A crushable member is provided that
has an upper perimeter, a lower perimeter and an intermediate
section extending therebetween. It also includes a number (m) of
breaches defined therein before impact. A method for configuring
the modular energy absorber is also disclosed.
Inventors: |
Carroll; Phillip Patrick III;
(Bloomfield Hills, MI) ; Cormier; Joel Matthew;
(Ferndale, MI) ; Grenier; Paul Gerard; (Lake
Orion, MI) |
Correspondence
Address: |
BROOKS KUSHMAN P.C.
1000 TOWN CENTER
TWENTY-SECOND FLOOR
SOUTHFIELD
MI
48075
US
|
Assignee: |
Oakwood Energy Management,
Inc.
1100 Oakwood Blvd.
Dearborn
MI
48124
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20040178662 A1 |
September 16, 2004 |
|
|
Family ID: |
32966851 |
Appl. No.: |
10/760760 |
Filed: |
January 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10/004,739 |
Dec 15, 2005 |
6752450 |
|
|
10760760 |
Jan 20, 2004 |
|
|
|
09/884,813 |
Dec 15, 2005 |
6682128 |
|
|
10/004,739 |
Dec 4, 2001 |
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09/499,205 |
Jun 19, 2001 |
6247745 |
|
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09/884,813 |
Jun 19, 2001 |
|
|
|
09/328,196 |
Mar 13, 2001 |
6199942 |
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09/499,205 |
Feb 7, 2000 |
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09/018,666 |
Jan 25, 2000 |
6017084 |
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09/328,196 |
Jun 8, 1999 |
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09/617,691 |
Jan 20, 2004 |
6679967 |
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09/018,666 |
Feb 4, 1998 |
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|
Current U.S.
Class: |
296/187.03 |
Current CPC
Class: |
B29C 2791/007 20130101;
B60R 21/04 20130101; B60R 21/0428 20130101; B60R 19/34 20130101;
B60R 2019/1846 20130101; B60R 2021/0435 20130101; B29C 51/12
20130101; F16F 7/12 20130101; F16F 1/376 20130101; B29C 51/14
20130101; B60N 2/4249 20130101; B32B 3/28 20130101; A62B 1/22
20130101; B60N 2/68 20130101; F16F 7/121 20130101; B60N 2/70
20130101; B29C 51/10 20130101; B60R 19/18 20130101; B29L 2031/3044
20130101; B60R 21/045 20130101; B60R 21/02 20130101; B29L 2009/00
20130101; B60R 2019/1866 20130101; B29L 2031/721 20130101; B60R
2021/0414 20130101; B65D 81/127 20130101; B29C 2791/006
20130101 |
Class at
Publication: |
296/187.03 |
International
Class: |
B62D 25/00 20060101
B62D025/00 |
Claims
1. 1. A modular energy absorber comprising: one or more energy
absorbing modules, one or more of which have: means for
coordinating energy absorbing units of the one or more modules, the
means for coordinating having a pre-defined, contoured topography
including a number (n) of apertures defined therein; and one or
more energy absorbing units associated with the means for
coordinating, the means for coordinating positioning and supporting
the one or more units in relation to each other before, during and
after relative motion between an incident object and the energy
absorber, so that impact forces resulting therefrom are at least
partially absorbed, at least some of the units including a
crushable member, with a number (m) of breaches defined therein
before impact and an upper extremity that defines an upper
perimeter, a lower extremity that defines a lower perimeter and a
wall including an intermediate section extending therebetween, the
crushable member at least partially collapsing during absorption to
a crushed configuration.
2. 2. The modular energy absorber assembly of claim 1 further
comprising: a hinge section having leaves, each leaf extending from
one of the one or more energy absorbing modules so that they may be
configured within spatial constraints imposed by an environment
within which the modular energy absorber is positioned, the
environment being selected from the group consisting of a headliner
in a vehicle, a bumper assembly, a knee bolster, and a side-impact
location including a vehicle pillar and a door.
3. 3. The modular energy absorber of claim 1 wherein the number (n)
of apertures equals one.
4. 4. The modular energy absorber of claim 1 wherein the means for
coordinating comprises a form selected from the group consisting of
a web, a tether, a hinge, a planar surface, a rib, a channel, a
non-planar surface, and combinations thereof.
5. 5. The modular energy absorber of claim 1 wherein at least one
of the crushable members is provided with a floor extending at
least partially between opposing faces of the wall.
6. 6. (Withdrawn) The modular energy absorber of claim 5 wherein
the floor is annular.
7. 7. (Withdrawn) The modular energy absorber of claim 5 wherein
the floor extends from the intermediate section of the wall.
8. 8. (Withdrawn) The modular energy absorber of claim 5 wherein
the floor has a configuration that is non-planar.
9. 9. (Withdrawn) The modular energy absorber of claim 5 wherein
the floor is configured as a wedding cake topography with one or
more layers.
10. 10. (Withdrawn) The modular energy absorber of claim 5 wherein
the floor is configured as a volcano type of structure, including
one or more craters defined therein.
11. 11. The modular energy absorber of claim 5 wherein some of the
one or more energy absorbing units have an imaginary axis of
symmetry and at least a segment of the floor is inclined to the
axis of symmetry.
12. 12. The modular energy absorber of claim 1 wherein a released
configuration following rebound is located in substantially the
same position as a pre-impact undeflected configuration.
13. 13. The modular energy absorber of claim 1 wherein at least
some of the crushable members have a wall with a thickness that is
non-uniform between a top edge and a bottom edge of the wall.
14. 14. The modular energy absorber of claim 13 wherein the wall
has an average thickness (t.sub.1) that differs from an average
thickness (t.sub.2) of a wall associated with another energy
absorbing unit.
15. 15. The modular energy absorber of claim 11 wherein each axis
of symmetry defines positioning loci that intersect a given plane,
and a line that joins adjacent loci in that plane describes a
geometrical figure selected from the group consisting of a
segmented line, a circle, an oval, an ellipse, a square, a diamond,
a quadrilateral, and a polygon.
16. 16. The modular energy absorber of claim 1, wherein a lower
perimeter of a crushable member defines a geometric figure that is
selected from the group consisting of a circle, an oval, a polygon,
and an ellipse.
17. 17. The modular energy absorber of claim 1, wherein an upper
perimeter of a crushable member defines a geometric figure that is
selected from the group consisting of a circle, an oval, a polygon,
and an ellipse.
18. 18. The modular energy absorber of claim 1, wherein an
intermediate section of a crushable member defines a geometric
figure that is selected from the group consisting of a circle, an
oval, a polygon, and an ellipse.
19. 19. The modular energy absorber of claim 1 wherein: two or more
of the energy absorbing modules are arranged in a stacked
configuration, the absorber further including means for cooperating
the impact resistance characteristics of the two or more energy
absorbing modules.
20. 20. (Withdrawn) A method for configuring a modular energy
absorber comprising the steps of: selecting one or more energy
absorbing modules according to given spatial constraints and
desired energy absorbing criteria; providing a means for
coordinating energy absorbing units, the means having a pre-defined
contoured topography; locating one or more energy absorbing units
in association with the means for coordinating energy absorbing
units so that the one or more energy absorbing units include one or
more crushable members that are positioned in relation to each
other before, during and after relative motion between an incident
object and the energy absorber; providing a wall within some of the
one or more crushable members of the energy absorbing units so that
the wall provides an upper perimeter, a lower perimeter, and an
intermediate section extending therebetween; defining a number (m)
of breaches within the wall, (m) being an integer selected from the
group consisting of (0, 1, 2, 3, . . . , 100); determining a wall
thickness profile; providing a number (n) of apertures defined
within the means for coordinating energy absorbing units, (n) being
an integer selected from the group consisting of (0, 1,2,3, . . . ,
100); quantifying the resulting modular energy absorbing
characteristics of the absorbing structure; comparing the
characteristics with those desired; and reiterating as
necessary.
21. 21. (Withdrawn) The modular energy absorber of claim 3 wherein
the number (m) of breaches in a crushable member equals zero.
22. 22. (Withdrawn) The method of claim 20 wherein the defining
step comprises defining the number of breaches (m) in a crushable
member to be zero.
23. 23. (Withdrawn) The method of claim 20 wherein the step of
providing a number (n) of apertures in the means for coordinating
comprises providing zero apertures.
24. 24. (Withdrawn) The method of claim 20 comprising the steps of
defining (m) breaches in a crushable member and providing (n)
apertures in the means for coordinating, each comprise selecting an
integer equaling zero.
Description
Detailed Description of the Invention
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Serial No. 10/004,739 filed December 4, 2001 (now U.S.
Patent No. 6,752,450) which is a continuation-in-part of U.S.
application Serial No. 09/884,813 filed June 19, 2001 (now U.S.
Patent No. 6,682,128) which is a continuation-in-part of U.S.
application Serial No. 09/499,205 filed February 7, 2000 (now U.S.
Patent No. 6,247,745), which is a continuation of U.S. application
Serial No. 09/328,196 filed June 8, 1999 (now U.S. Patent No.
6,199,942), which is a continuation-in-part of U.S. application
Serial No. 09/018,666 filed February 4, 1998 (now U.S. Patent No.
6,017,084), the disclosures of which applications are being
incorporated by reference herein. This application is also a
continuation-in-part of U.S. application Serial No. 09/617,691
filed July 17, 2000 (now U.S. Patent No. 6,679,967) which is a
continuation-in-part of U.S. application Serial No. 09/328,196
filed June 8, 1999 (now U.S. Patent No. 6,199,942), which is a
continuation-in-part of U.S. application Serial No. 09/018,666
filed February 4, 1998 (now U.S. Patent No. 6,017,084), the
disclosures of which applications are being incorporated by
reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention generally relates to occupant safety during a
collision, and more specifically to an energy absorber that absorbs
energy imparted by an incident object that impacts the absorber,
and a method for configuring the absorber.
[0004] 2. Background Art
[0005] There have been proposed various ways to protect the
occupant or rider of an automobile when the occupant impacts the A
and B pillars, headliner. or any hard structure during an impact.
Illustrative approaches are described in commonly owned U.S. Patent
No. 6,247,745 and 6,199,942; and U.S. Patent No. 6,443,513, which
issued on September 3, 2002 to Glance.
[0006] It is known, for example, to deploy truncated plastic cones
at rollover stiff points or on door panels for side impacts with
the objective of providing better performance than energy absorbent
foam. Also, such cones may be less expensive to manufacture.
Manufacturing economics have been realized from the raw materials
being melt recyclable. Such structures not only provide weight
savings and a better performance, but also a cost advantage which
may amount to $4-$5 per vehicle.
[0007] The required energy absorption characteristics are defined
in Federal Motor Vehicle Standards 201. To meet the relevant
standards, the industry continues its quest not only for the
physical structures that conform to federally mandated standards,
but also to develop computer modeling protocols that predict head
injury sustained from impacting forces and comparing the results
with head injury criteria. It would be desirable in such
developments to measure actual head impact (of, for example, a
dummy occupant) during in-vehicle testing at selected locations in
the vehicle. Ideally, the actual measurements will approximate the
values predicted by computer dynamic finite element analysis.
[0008] Additionally, the desire to reduce costs while complying
with End of Life Vehicle (ELV) legislation in Europe stimulates the
use of mono-materials in automotive interior soft trim
applications. Related considerations emphasize recyclability of
automotive plastics. The impact or influence of the ELV directive
on automotive interiors will be felt in various ways: e.g., cost
effective use of recycling techniques with environmentally benign
consequences. Most interior modules today are made from a
combination of skin/foam/substrate. Thus, the materials currently
used may present challenges to the recycling task. Such challenges
may be met by more use of energy absorbing modules that are made
from mono-materials. Such materials might, for example, include
polyolefins and melt recyclable polymers, since they show promise
as being versatile alternatives to skin/foam/substrate.
[0009] It is expected that Europe will adopt the U.S. HIC(d)
requirements. This will affect the choice and quantity of materials
used for energy absorbers in headliners. Similar door trim panel
requirements apply to the pelvis and torso (side impact
applications). It is therefore anticipated that there will be an
increase in the usage of energy absorbers that will be incorporated
into the structure of modules such as door trim panel, instrument
panel uppers, and headliners.
[0010] To meet cost reduction goals, there is an increasing desire
to manufacture interior modules using a reduced number of
manufacturing steps.
[0011] In light of these and related approaches, there remains the
desire to absorb as much impact energy in as little crush distance
as possible, with as little weight as possible, yet be capable of
being designed and manufactured under favorable economic
conditions.
SUMMARY OF THE INVENTION
[0012] One object of the present invention is to provide a more
cost effective, efficient energy absorber that can be "tuned" to
produce predefined energy absorption characteristics within spatial
constraints that may be imposed by a particular application.
[0013] The invention includes a modular energy absorber with one or
more energy absorbing modules that are provided with means for
coordinating energy absorbing units therewithin. The coordinating
means has a topography with a variable number (n) of apertures. The
means for coordinating alternatively include a web, a tether, a
hinge, a planar surface, and wings or combinations thereof that
serve to position and support the energy absorbing units in
relation to each other before, during and after relative motion
between an incident object and the energy absorber. The relative
motion causes impact between the energy absorbing units and the
incident object so that forces resulting from the impact are at
least partially absorbed.
[0014] The absorber also has energy absorbing units that have a
crushable member with an upper extremity that defines an upper
perimeter, a lower extremity that defines a lower perimeter, and an
intermediate section extending therebetween. Either the upper or
lower extremities can be presented to the impacting force.
[0015] The crushable member at least partially collapses during
energy absorption to a crushed configuration which in part is
determined by the provision of a number (m) of breaches that are
defined in the crushable member before impact. The breaches may be
defined by slits (no material moved) or slots (material removed to
form an opening).
[0016] To configure the modular energy absorber, the following
steps are taken:selecting one or more energy absorbing modules
according to given spatial constraints and desired energy absorbing
criteria;providing a means for coordinating energy absorbing units
with a pre-defined contoured topography;locating one or more energy
absorbing units in association with the means for coordinating
energy absorbing units so that the one or more energy absorbing
units are positioned in relation to each other before, during and
after relative motion between an incident object and the energy
absorber;providing a wall within some of the one or more energy
absorbing units so that the wall provides an upper perimeter, a
lower perimeter, and an intermediate section extending
therebetween;defining a number (m) of breaches within the wall, (m)
being an integer selected from the group consisting of (0, 1, 2, 3,
. . . , 100); andproviding a number (n) of apertures defined within
the means for coordinating energy absorbing units, (n) being an
integer selected from the group consisting of (0, 1,2,3, . . . ,
100).
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIGURE 1(a) is a top elevational view of a modular energy
absorber constructed in accordance with the present invention,
including two energy absorbing modules linked by a connection;
[0024] FIGURE 1(b) is a quartering side elevational view
thereof;
[0025] FIGURE 1(c) is a cross-sectional view taken along the line
I-I of Figure 1(a);
[0026] FIGURE 2 is a top elevational view of an alternate
embodiment of a modular energy absorber according to the present
invention, in which there is one energy absorbing module with
energy absorbing units that are positioned and supported by means
for coordinating;
[0027] FIGURES 3(a)-(d) are graphs of four factors that influence
energy absorbing characteristics (such as the number of slits,
impact angle, wall thickness, and rib height plotted against peak
filtered pressure (Figure 3a); mean filtered pressure (Figure 3b);
standard deviation of filtered pressure (Figure 3c); and cone mass
(Figure 3d); and
[0028] FIGURES 4(a-c) are schematic illustrations of a crushable
member (pre-impact) that forms one of the energy absorbing units,
enlarged to facilitate an understanding of several of its
characteristics.
[0029] FIGURE 5 is a cross-sectional view of a stacked
configuration of energy absorbing units, including means for
cooperating the impact resistance characteristics of the energy
absorbers;
[0030] FIGURE 6 is a side cross-sectional view of an energy
absorbing unit that illustrates an intersection between means for
coordinating energy absorbing units and the walls of a crushable
member; and
[0031] FIGURE 7 illustrates an alternate embodiment of the
invention wherein an energy absorbing unit is terminated by a floor
that is shaped like an inverted wedding cake or, in a more rounded
form, like a volcano with craters therein;
[0032] FIGURE 8 is a quartering perspective view of a crushable
member 20 having breaches 28 defined therein; and
[0033] FIGURE 9 is a top plan view of a pair of crushable members
20 that have slots and a slit defined within them.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0034] Turning first to Figures 1-2 of the drawings, there is
depicted a modular energy absorber 10 that has one or more energy
absorbing modules 12. Those modules include means 14 for
coordinating energy absorbing units 16 of the energy absorbing
modules. The means for coordinating 14 have a topography that
includes a number (n) of apertures 18 defined therein.
[0035] The energy absorbing units coordinate with each other
through the provision of coordinating means 14 that position and
support the units in relation to each other before, during and
after relative motion between an incident object (not shown) and
the energy absorber 10. That relative motion causes impact between
the energy absorbing units 16 and the incident object so that
forces resulting therefrom are at least partially absorbed. In this
way, the impact forces that are transmitted to an occupant of a
vehicle within which, for example, the modular energy absorber 10
is situated are reduced, together with injuries sustained.
[0036] At least some of the energy absorbing unit 16 include a
crushable member 20 that has an upper extremity or perimeter 22, a
lower extremity or perimeter 24, and an intermediate section 26
extending therebetween.
[0037] Additionally, a number (m) of breaches 28 are defined within
the crushable member 20 before impact. Preferably, the number of
breaches is three where the breach is provided in the form of
slots. As used in this disclosure, the term "slots" 31 (Figure 9)
implies an aperture with facing edges which lacks material or where
material has been removed. As used herein, the term "slits" 29
(Figure 8) implies a cut or gash that is formed without the removal
of material. In the preferred embodiment, the three slots are
inclined to an axis of symmetry of a given crushable member 20, but
lie parallel to the draft angle, in the case where the crushable
member is presented in the form of a cone.
[0038] As depicted in Figure 1(b), the modular energy absorber
includes, in the embodiment depicted, a hinge section 30 having
leaves 32. Each leaf 32 extends from one of the one or more energy
absorbing modules 12 so that they may be configured within the
spatial constraints that are imposed by an environment within which
the modular energy absorber 10 is positioned. The environment (not
depicted) is selected from a group consisting of a headliner in a
vehicle, a bumper assembly, a knee bolster, and a side impact
location including a vehicle pillar and a door, a head rest or seat
back.
[0039] In one embodiment, the modular energy absorber 10 has means
for coordinating 14 the energy absorbing units 16 that may take the
form of a web, a tether, a hinge, a planar surface (as depicted),
and rings, or a combination thereof. In some cases, no apertures
are provided in the energy absorbing coordinating means.
[0040] Figure 6 depicts a floor 40 that extends at least partially
between opposing faces of a wall 38. In one embodiment the floor is
annular. Alternatively, the floor may extend from an intermediate
section 26 of the wall 38. It should be appreciated, that in some
embodiments, the floor may have a configuration that is non-planar.
For example, where the floor 40 is provided proximate an upper
extremity or perimeter 22 of an energy absorbing unit 16, the floor
40 may undulate or be otherwise configured in order to conform the
modular energy absorber 10 to the spatial constraints imposed by
the environment in which the absorber 10 is installed.
[0041] In Figure 7, the floor is configured with a topography that
is akin to a wedding cake with one or more layers. Alternatively,
the floor 40 can be configured in a more rounded form as a volcano
type of structure, including one or more craters defined
therewithin. Continuing with reference to Figure 7, some of the one
or more energy absorbing units 16 have an imaginary axis of
symmetry A-A to which the floor 40 may be inclined at an angle
between zero and 180 degrees.
[0042] It will be appreciated that as a result of tuning the energy
absorber (e.g. dimensional control of wall height, provision of
slits or slots, wall thickness, and material selection), the
configuration following impact is located in substantially the same
position as the pre-impact configuration.
[0043] Continuing with primary reference to Figures 6-7, it will be
appreciated that the wall 38 be characterized by a thickness (t)
which may or may not be uniform between a top edge 22 and a lower
edge 24 of the wall 38. In some configurations, where particular
energy absorbing characteristics are desired or mandated, the wall
38 of a given energy absorbing unit 16 may have an average
thickness (t.sub.1) that differs from an average thickness
(t.sub.2) of a wall associated with another energy absorbing
unit.
[0044] In some embodiments (Figure 6 for example), means of
coordinating 36 may be in the form of a rib or a channel 46,48.
While the means may be located at an intermediate section of a
wall, it will be appreciated that it may also lie proximate its top
or bottom edges.
[0045] Returning now to Figures 1-2, the designer may choose how
best to locate energy absorbing units 16 within a given module. To
facilitate an understanding of positional considerations, it is
helpful to imagine that each energy absorbing unit 16 has an axis
of symmetry which when projected may intersect an imaginary plane
at a loci. An imaginary line can be drawn connecting adjacent loci
in that plane. The energy absorbing unit 16 may be configured so
that the line joining adjacent loci describes a geometrical figure.
The figure may be a segmented line, a circle, an oval, an ellipse,
a square, a diamond, a quadrilateral, and a polygon.
[0046] With reference to Figures 4(a-c), the lower perimeter 24 of
a given energy absorbing unit 16 may describe a circle, an oval, or
an ellipse. Similarly for the upper perimeter and intermediate
section.
[0047] In Figure 5, cooperating means 44 are provided in order to
coordinate the deformation and energy absorbing characteristics of
adjacent energy absorbing modules 12. It will be appreciated that
the cooperating means may take the form of an adhesive, a clip, a
vibration weld, a sonic weld, a heat stake, a "tongue in groove"
arrangement, and the like. It will be appreciated that the stacked
configuration depicted in Figure 5 may be reoriented such that the
energy units 12 may be nested in such a way that the peak of a
given energy unit may lie in a valley (or floor) of the adjacent
energy unit.
[0048] A method for configuring a modular energy absorber comprises
the steps of:
[0049] selecting one or more energy absorbing modules according to
given spatial constraints and desired energy absorbing
criteria;
[0050] providing a means for coordinating energy absorbing units
with a pre-defined contoured topography;
[0051] locating one or more energy absorbing units in association
with the means for coordinating energy absorbing units so that the
one or more energy absorbing units are positioned in relation to
each other before, during and after relative motion between an
incident object and the energy absorber;
[0052] providing a wall within some of the one or more energy
absorbing units so that the wall provides an upper perimeter, a
lower perimeter, and an intermediate section extending
therebetween;
[0053] defining a number (m) of breaches within the wall, (m) being
an integer selected from the group consisting of (0, 1, 2, 3, . . .
, 100);
[0054] providing a number (n) of apertures defined within the means
for coordinating energy absorbing units, (n) being an integer
selected from the group consisting of (0, 1,2,3, . . . 100);
[0055] quantifying the resulting modular energy absorbing
characteristics of the absorbing structure;
[0056] comparing the characteristics with those desired; and
[0057] reiterating as necessary.
[0058] The disclosed energy absorber can be manufactured at
relatively low cost by thermoforming and impact performance can be
optimized without expensive tooling modification at heights below
about 50 millimeters. However, above this height, the base material
thickness required to produce an energy absorber for the
appropriate crush resistance is such that it cannot easily and
inexpensively be produced using in-line thermoforming equipment. In
such circumstances, injection molded absorbers can be produced
perhaps at a lower cost.
[0059] Historically, optimizing crush resistance or the amount of
energy absorbed by injection molded energy absorbers that are
formed from rows of free standing or a lattice of ribs have been
difficult and expensive to modify once the mold has been produced.
Modifying rib thickness is usually accomplished by adding material
to or removing material from the mold by burning, cutting,
inserting and the like.
[0060] It is especially difficult to produce injection molded wall
sections having a thickness less than about 1.25 millimeters. In
such circumstances, multi-drop hot runner systems have been used to
prevent the material from "freezing off" in the thin sections. Cuts
or areas devoid of material have been used to weaken such ribs, but
prove to be less efficient because they may create additional
manufacturing issues. When ribs are integrated into the back side
of class A surfaces (whose appearance is critical), changes in the
ribs can "read through" and result in a product whose appearance is
unacceptable.
[0061] It is therefore essential that an absorber's crush
resistance be "tuned" or "dialed up or down" to provide the
greatest measure of energy management or the highest level of
occupant protection for a given set of impact conditions. Foam
energy absorbers can be tuned by a change in density but have
proven to be less efficient than those composed of metal,
thermoplastic, or composite materials. Metal and composite
absorbers are proven to be more expensive than their plastic
counterparts, such as injection molded and thermoformed energy
absorbers.
[0062] Preferably, the disclosed energy absorbers that include a
structure with recesses in a base sheet produced by injection or
compression molding. The recesses, for example, may have a minimum
wall thickness of about 1.25 millimeters. Small tapered or drafted
areas may have a thickness which is below this thickness.
[0063] The walls of the recesses may be thicker than 1.25
millimeters, but may have areas as thin as 1.25 millimeters to
promote buckling of the recess at a given point.
[0064] Slits, or slots (areas devoid of material) may be provided
which run mostly parallel to the walls of a given energy absorbing
unit. Such breaches may or may not be present, but when present,
the slots may or may not be of varying width. Ribs that protrude
from the interior or exterior of a wall of an energy absorbing unit
may or may not be present.
[0065] When present, the ribs 50 (Figure 6) run mostly parallel to
a wall of a recess, and may have convolutions which promotes the
buckling of a recess at a given point. It will be appreciated that
to produce given energy management characteristics, the ribs may
vary in both height and width.
[0066] Turning now to Figures 3(a-d), there now follows a
disclosure of a series of experiments that were conducted which
involve finite element analysis modeling.
[0067] In order to tune the impact performance, a DOE was performed
via FEA modeling. The results of that DOE are summarized in Figures
3(a-d).
[0068] The minimum wall thickness of 1.25 mm is such that it
promotes material flow within the mold for injection molded designs
with a minimal number of injection ports. Below this thickness,
formed articles have more shear stress caused by forcing the
polymer into a thin section. Thin sections are also difficult to
fill. This involves higher injection molding pressures, larger
equipment, higher utility costs and higher scrap rates. Areas
thicker than 1.25 mm are less prone to these issues. By maintaining
a minimum wall thickness of 1.25 mm, the cost to tool an absorber
is minimized. Also, by increasing or decreasing the wall thickness,
the crush resistance of the absorber can be tuned to optimize the
impact performance.
[0069] The presence of breaches, such as slits, or slots (areas
devoid of material) reduces the crush resistance of the recess. The
number of slits (Figure 1(c)) can also be changed to optimize
impact performance to a lesser degree. Preferably, but not
necessarily, the slits should run the entire length of the recess
wall. By doing so, knit lines (areas where two melt fronts of
plastic come together which have proven to be weak points in the
formed article) are forced toward areas which are less involved in
the energy management - such as the base or the roof of the
recess.
[0070] The presence of ribs, which protrude from either side of the
recess wall (Figure 6), can be added or reduced in size to either
increase or decrease the crush resistance of the structure. When
present, ribs may also provide a channel that promotes material
flow to areas adjacent to the rib. The rib height and width can be
varied to increase or decrease crush resistance. In the preferred
embodiment, the ribs are present on the interior of the recess.
[0071] Injection molds can be manufactured from a solid block of
material or can be composed of a number of inserts. The preferred
embodiment of each recess is a frusto-conical in shape. The
advantage of this design is that it lends itself to both a simple
and inexpensive means of optimizing impact performance through the
use of inserts for the cone interior. These inserts are typically
produced inexpensively on a numerically controlled lathe, rather
than by more expensive methods such as NC machining and EDM
techniques. The wall thickness of the recess can be easily changed
by either modifying or simply replacing the original insert with
one whose profile is different. By changing the wall thickness, the
crush resistance can also be changed as detailed in Figures
3(a-d).
[0072] In summary, the crush resistance of each recess can be
varied in order to optimize the impact performance with a minimal
impact on tooling cost. It also lends itself to high manufacturing
rates and low costs versus current competitive products, while
still providing excellent impact performance.
[0073] The purpose of the experiments (see, the data depicted in
Figures 3(a-d)) was to predict the resistance performance of a
given absorber design, (e.g. made from polypropylene: Basell
Pro-fax SV 152) and efficiently tune or optimize its geometry to
match known benchmarks (up to 80 psi) of given countermeasures for
automotive side impact.
[0074] Among the conclusions were these observations:Performance is
most sensitive to number of slits and wall thicknessCone spacing
could have been a factor in study as pressure on one cone depends
on thisOnce a design is tuned to perform as desired - it may be
advantageous (material usage, uniformity) to determine an
equivalent design by re-spacing cones within reasonable limits and
eliminate slitsCan recalculate pressures for different cone spacing
with raw data if desiredDesign approach ultimately depends on
whether countermeasure interacts with occupant and thus necessity
for load transfer or energy managementBecause impact velocity is
constant, mean pressure directly correlates with energy
absorbed.
Table 1
[0081] Here is a summary of the results: TABLE-US-00001 Impact Wall
Peak Mean Std. Dev. Angle Thickness Rib Height Pressure Pressure
Pressure Cone Mass # of Slits (degrees) (mm) (mm) (PSI) (PSI) (PSI)
(tonnes) 0 0 1.25 0 141.57 86.79 29.53 0.0081 2 27 1.65 1.25 115.42
61.08 16.63 0.0118 2 0 1.25 0 54.01 20.74 12.20 0.0081
[0082] Method: Transient finite element simulation of rigid plane
(oriented normal to cone axis) impacting a single cone at constant
velocity
[0083] Cone Materials modeled: Pro-fax SV152 PP; Cycolac EX75 ABS,
Cycolac MC8800, Cycoloy IP1000
[0084] No strain rate dependency modeled, to reflect quasi-static
performance
[0085] Cone supported by contact with rigid plane
[0086] Cone geometry - 10 degrees draft, 15mm top diameter; no
ribs
[0087] Impact speed = 33 mph (FMVSS214 resultant speed) to reduce
simulation run time
[0088] Area for pressure calculation = maximum area that can be
impacted and only affect one cone. - Assumed area at base of model
(64 mm diameter)
[0089] Raw data filtered with SAE1000 (as other filters smoothed
too much)
[0090] Variables: Impact Angle (0.degree., 14.degree.,
27.degree.)
[0091] Part Thickness (1.25 mm, 1.6 mm, 2.0 mm)
[0092] Number of 75 mm long Slits in Cone Wal l (0, 1, 2, 4)
[0093] Height of Ribs inside Cone (0, 1.25 mm, 2.5 mm)
[0094] Rows: 108 (Full Factorial)
[0095] Measurements: Peak Pressure exerted on impactor
[0096] Mean Pressure exerted on impactor during entire event
[0097] Standard Deviation of Pressure during entire event
[0098] Cone Mass
[0099] Temperature: Room temperature (no temp effects
considered)
[0100] Analysis of results:
[0101] DOE pre and post processing using Altair Hyperworks.RTM.
software suite
[0102] Simulation performed by LS-DYNA3D.RTM. nonlinear finite
element solver
[0103] Analysis of results using JMP statistical software -
[0104] Effects screening for main effects and interactions
[0105] Stepwise Backward Regression for transfer functions
[0106] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *