Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SHOCK ABSORBERS FOR PROTECTIVE BODY GEAR
TECHNICAL FIELD
[0001] The present invention relates generally to shock absorbers for use
in protective
structures such as body gear.
BACKGROUND
[0002] During sports and other physical activity, individuals are often
exposed to impact
forces that, if not at least partially attenuated, can cause severe injury.
Therefore, they usually
wear protective sporting gear, such as helmets, shields, elbow and knee pads,
etc. Such
protective gear typically includes impact-attenuating structures that deform
elastically and/or
plastically in response to an impact force, thereby mechanically attenuating
the impact. For
example, many helmets have a crushable foam layer disposed between a rigid or
semi-rigid outer
shell and an inner liner that conforms the helmet to the wearer's head.
[0003] Foams are generally customized to respond optimally to a specific
range of impact
energies, but outside this range, their effectiveness is significantly
reduced. For impact energies
exceeding the high end of the range, the foam is too soft and "bottoms out" ¨
i.e., reaches
maximum compression ¨ before the impact is fully attenuated, resulting in the
transfer of high
impact forces to the body. For impact energies below the optimal range, on the
other hand, the
foam is too hard to compress, or "ride down," sufficiently to adequately
prolong the distance and
time over which deceleration occurs following impact, resulting in sudden,
high peak forces.
The only way to improve the impact-attenuating capability of a foam layer is,
typically, to
decrease the density of the foam (i.e., make it softer) and increase the
thickness of the layer,
which results in an undesirable increase in the amount of material used.
Exacerbating this trade-
off, the maximum ride-down distance for most foams is only about 30-40% of the
original
height. Thus, about 60-70% of the foam layer add to the bulk and weight, but
not the impact-
absorption capacity, of the protective structure. In addition, the performance
of many foams
degrades rapidly with repeated impacts. Other conventional impact-absorbing
layers exhibit
similar problems and limitations.
[0004] More recent helmet designs feature, in place of a continuous layer,
discrete
compression cells, which attenuate the impact with their side walls and/or by
resistively venting
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a fluid through an orifice of the cell enclosure. These cells generally have
ride-down distances
close to their height, exhibit superior durability, and adapt to a wide range
of impact energies.
Furthermore, they provide opportunities for tailoring the impact-absorption
characteristics of the
helmet (or other protective structure) via the cell design. Such customization
opportunities,
however, have rarely been exploited.
SUMMARY
[0005] The present invention provides shock absorbers for integration into
protective
structures, such as, for example, helmets and other protective body gear, as
well as dashboards,
shock-absorbing seating, and safety padding in vehicles, sporting equipment,
and machinery.
The shock absorbers generally take the form of hollow, fluid-filled (e.g., air-
filled), compressible
cells, and typically absorb the impact in multiple stages. In various
embodiments, different
portions and features of the cell enclosure contribute to shock-absorption at
different times
throughout the impact by resistively yielding in response thereto. In
addition, in some
embodiments, the cell enclosure includes one or more small orifices, or vents,
through which the
fluid (e.g., air or water) resistively vents, providing an additional impact-
attenuating mechanism
that operates in conjunction, simultaneously or in sequence, with resistive
yielding of the
enclosure. For example, in some embodiments, the cell attenuates impact forces
by resisting
compression at least initially through both the enclosure (or walls) and the
fluid, and following
an initial stage of the impact, the walls may yield to allow the remainder of
the impact to be
attenuated via resistive fluid-venting. In alternative embodiments, an opening
in the cell
enclosure that allows fluid to escape is so large as to have no (or no
significant) impact-resisting
effect. Various embodiments of the present invention are directed to improving
the energy
management characteristics of the shock absorbers by tailoring the structure
and shape of the
enclosure, and/or the size and shape of the vents.
[0006] The compression cells may include top, bottom, and side walls, and
may (but need
not necessarily) be symmetrical around an axis through the center points of
the top and bottom
walls. For example, the cells may be disk-shaped or cylindrical. The side
walls may be of
uniform or varying thickness, and may be, without limitation, straight,
angled, curved, or frusto-
conical, depending on the impact absorption profile desired for the particular
application. In
certain embodiments, two frusto-conical portions of the side walls are
arranged back-to-back
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such that the walls toe in toward a medial plane, accelerating the reduction
of the inner volume
as the cell collapses. In other embodiments, the frusto-conical portions are
arranged such that
their larger ends meet at the medial plane. The exterior shape of the cell may
be adjusted to the
protective structure in which it is integrated. For example, shock absorbers
for use in helmets
may have rounded (rather than planar) top walls to better fit between the
interior liner and the
shell, and/or side walls that taper toward one side to better accommodate the
narrow space along
the periphery of the helmet.
[0007] The top wall may include one or more corrugations that may contact
the opposing
wall during a late stage of compression, thereby effectively increasing the
number of vertical
walls that contribute to impact absorption. These corrugations may form rings
surrounding a
central portion of the top wall. In some embodiments, the central portion is
raised above the
height of the side wall, providing a separate mechanism that contributes to
impact absorption
initially, prior to buckling of the side wall. In various embodiments,
depression of the central
portion of the top wall, buckling of the side wall, and buckling of the
corrugation(s) upon contact
with the bottom wall start sequentially, forming three impact-absorption
stages (which may
partially overlap).
[0008] Accordingly in a first aspect, the invention pertains to a
compressible cell for
attenuating impact forces imparted thereto in three stages. The cell includes
a hollow enclosure
having (a) a top wall with a raised central portion and one or more
corrugations around a
periphery of the raised central portion, (b) a bottom wall, and (c) a side
wall extending between
the top and bottom walls, the corrugation(s) descending to a depth below half
a height of the side
wall. Impact forces imparted on the cell are attenuated in a first stage by
resistive yielding of
part of the at least one corrugation to allow for depression of the central
portion (in other words,
by partial resistance to such depression), in a second stage by resistive
yielding of the side wall
(i.e., by partial resistance to compression and/or buckling of the side wall),
and in a third stage,
upon contact of the at least one corrugation with the bottom wall, by
resistive yielding of the at
least one corrugation. The enclosure may be configured to cause overlap in
time between any
combination of the first, second, and third stages. In some embodiments, the
side wall includes
two frusto-conical wall portions meeting at an intermediate plane (e.eg., at
about half the height)
of the cell. The inner surfaces of the two frusto-conical wall portions may
include an obtuse
angle. The cell may further include an orifice in the top wall for resistively
venting fluid from an
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interior of the cell. The enclosure may be substantially cylindrically
symmetric. The
corrugation(s) may form two ring walls meeting at a trough of the corrugation.
[0009] In another aspect, the invention relates to a method for staged
attenuation of impact
forces imparted on a compressible cell including a hollow enclosure having a
top wall with at
least one corrugation around a periphery of a raised central portion of the
top wall, a bottom
wall, and a side wall extending between the top and bottom walls, the at least
one corrugation
extending to a depth below half a height of the side wall. The method includes
attenuating the
impact forces by resistively yielding to depression of the central portion of
the top wall; when a
height of the central portion has reached the height of the side wall,
attenuating the impact forces
with the side wall by resistive yielding thereof; and when the at least one
corrugations contacts
the bottom wall, attenuating the impact forces with the at least one
corrugation by resistive
yielding thereof. The enclosure may have an orifice (e.g., in the top wall),
and the method may
further include attenuating the impact forces at least partially by
resistively venting fluid from an
interior of the enclosure through the orifice.
[0010] In another aspect, the present invention pertains to a compressible
cell for attenuating
impact forces imparted thereto. The cell includes a hollow (e.g.,
cylindrically symmetric)
enclosure having a top wall including a corrugation (or multiple corrugations)
defining a
periphery around a central portion of the top wall, a non-corrugated bottom
wall, and a side wall
extending between the top and bottom walls; the corrugation descends to a
depth below half a
height of the side wall. The corrugation(s) may form two ring walls meeting at
a trough of the
corrugation. The center portion of the top wall may be higher than the side
wall. The top wall,
side wall, and corrugation(s) may cooperate to attenuate impact forces
imparted on the top wall.
In some embodiments, the side wall includes two frusto-conical wall portions
meeting at an
intermediate plane of the cell (e.g., at about half the height of the side
wall). The inner surfaces
of the two frusto-conical wall portions may include an obtuse angle. The cell
may further
include an orifice in the top wall for venting fluid from an interior of the
cell.
[0011] In another aspect, the invention relates to a compressible cell for
attenuating impact
forces imparted thereto. In various embodiments, the cell comprises an
enclosure defining an
inner chamber for containing a fluid; the enclosure includes a side wall,
extending and varying in
thickness between a top wall and a bottom wall, that resistively yields in
response to an impact
imparted to the top wall. The side wall may increase or decrease in thickness
from the top to the
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bottom wall. The resistance of the yielding side walls may increase with
increasing energy of
the impact and/or increased compression of the side wall. The cell may shear
in response to a
non-perpendicular impact force. In various embodiments, the cell further
comprises at least one
orifice in the enclosure for resistively venting fluid from the inner chamber
so as to at least
partially attenuate the impact when the side wall yields.
[0012] In another aspect, the invention relates to a method involving a
safety article that
comprises a compressible cell including an enclosure defining an inner chamber
and having a
side wall extending and increasing in thickness between a top wall and a
bottom wall, where the
safety article is worn on a body with the bottom wall closer to the body than
the top wall. The
method is directed toward protecting the body from damage due to impacts and
comprises, in
various embodiments, attenuating an impact imparted on the top wall at least
partially with the
side wall by resistively yielding, where resistance to yielding increases with
increased
compression of the side wall. In various embodiments, the enclosure has an
orifice and the
method further comprises attenuating the impact at least partially by venting
fluid from the inner
chamber through the orifice.
[0013] In a further aspect, the invention relates to a method involving a
safety article that
comprises a compressible cell including an enclosure defining an inner chamber
and having a
side wall extending and decreasing in thickness between a top wall and a
bottom wall, where the
safety article is worn on a body with the bottom wall closer to the body than
the top wall. The
method is directed toward protecting the body from damage due to impacts and
comprises, in
various embodiments, attenuating a tangential component of an impact imparted
on the top wall
at least partially by shearing, and attenuating a normal component of the
impact imparted on the
top wall at least partially with the side wall by resistively yielding. In
some embodiments, the
enclosure has an orifice and the method further comprises attenuating the
impact at least partially
by venting fluid from the inner chamber through the orifice.
[0014] In another aspect, the invention pertains to a compressible cell for
attenuating impact
forces imparted thereto. In various embodiments, the cell comprises an
enclosure defining an
inner chamber for containing a fluid; the enclosure comprises a top wall
including one or more
corrugations defining a periphery around a central portion of the top wall, a
bottom wall, and a
side wall extending between the top and bottom walls. The side wall and
corrugation(s) of the
top wall resistively yield in response to an impact imparted to the top wall
so as to attenuate
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impact forces while allowing the cell to compress. In various embodiments, the
cell further
comprises at least one orifice in the enclosure for resistively venting fluid
from the inner
chamber so as to at least partially attenuate the impact. The corrugation(s)
may increase
resistance to compression of the cell as they contact the bottom wall. In
various embodiments,
the top wall is configured to allow lateral movement of a center region
thereof relative to a
periphery thereof. Furthermore, the side wall may vary in thickness between
the top wall and the
bottom wall.
[0015] The cell may be configured for use between an exterior shell and an
interior liner of
an impact-attenuating helmet, in which case the top wall may be domed so as to
conform to the
inner surface of the exterior shell. Moreover, the enclosure may be tapered at
the top wall so as
to fit between the shell and the liner in a peripheral region of the helmet.
[0016] In still a further aspect, the invention relates to a method
involving a safety article that
comprises a compressible cell including an enclosure defining an inner
chamber, a top wall
having one or more corrugations defining a periphery around a central portion
of the top wall, a
bottom wall, and a side wall extending between the top and bottom walls. The
safety article is
worn on a body with the bottom wall closer to the body than the top wall. The
method is
directed toward protecting the body from damage due to impacts and comprises,
in various
embodiments, attenuating an impact imparted on the top wall at least partially
with the side wall
and the corrugation(s) of the top wall by resistive yielding thereof In some
embodiments, the
enclosure has an orifice and the method further comprises attenuating the
impact at least partially
by venting fluid from the inner chamber through the orifice.
[0017] In yet another aspect, the invention pertains to a compressible cell
for attenuating
impact forces imparted thereto, and which, in various embodiments, comprises
an enclosure
defining an inner chamber for containing a fluid; the enclosure comprises at
least one side wall
extending between a top wall and a bottom wall, and the side wall(s)
resistively yield in response
to an impact imparted to the top wall so as to allow the cell to compress. The
top wall and/or the
bottom wall comprises one or more vertically extending features that increase
resistance to
compression of the cell as the top wall approaches the bottom wall. In some
embodiments, the
cell further comprises at least one orifice in the enclosure for resistively
venting fluid from the
inner chamber so as to at least partially attenuate the impact. The feature(s)
may comprise one or
more corrugations defining a periphery around a central portion of the top
wall and/or a plurality
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of concentrically arranged ridges on the bottom wall. In some embodiments, the
side wall varies
in thickness between the top wall and the bottom wall. The cell may be
configured for use
between an exterior shell and an interior liner of an impact-attenuating
helmet, with the top wall
being domed so as to conform to the inner surface of the exterior shell. The
enclosure may be
tapered at the top wall so as to fit between the shell and the liner in a
peripheral region of the
helmet.
[0018] In still a further aspect, the invention relates to a method
involving a safety article that
comprises a compressible cell including an enclosure defining an inner
chamber, a side wall, and
top and bottom walls at least one of which includes one or more vertically
extending features.
The safety article is worn on a body with the bottom wall closer to the body
than the top wall.
The method is directed toward protecting the body from damage due to impacts
and in various
embodiments comprises, in response to an impact imparted to the top wall,
attenuating the
impact at least partially with the side wall by resistive yielding thereof;
and attenuating the
impact at least partially with the vertically extending feature(s) as the top
wall approaches the
bottom wall. The enclosure may have an orifice, and the method may further
comprise
attenuating the impact at least partially by venting fluid from the inner
chamber through the
orifice.
[0019] In a further aspect, the invention pertains to a compressible cell
for attenuating impact
forces imparted thereto, and which, in various embodiments, comprises an
enclosure defining an
inner chamber for containing a fluid; the enclosure compresses in response to
an impact. The
cell also includes at least one orifice in the enclosure for resistively
venting fluid from the inner
chamber during the compression so as to at least partially attenuate the
impact, and a valve for
partially obstructing the orifice so as to increase resistance to the
compression. In various
embodiments the enclosure comprises top and bottom walls, and the resistance
to the
compression of the cell is increased by the partial obstruction of the orifice
as the top wall
approaches the bottom wall. Some or all of the walls may resistively yield in
response to the
impact, thereby partially attenuating the impact while allowing the cell to
compress. In various
embodiments, the valve comprises a pin protruding from the bottom wall
opposite the orifice,
where the pin, in a compressed state of the cell, engages the orifice so as
restrict fluid venting
therethrough. Alternatively, the valve may comprise a tubular protrusion
extending downward
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from the top wall and surrounding the orifice. The tubular protrusion self-
restricts the orifice due
to increased fluid turbulence.
[0020] Yet another aspect of the invention relates to a method involving a
safety article that
comprises a compressible cell that includes an enclosure defining an inner
chamber and having
an orifice and a valve therein. The method is directed toward protecting the
body from damage
due to impacts and comprises, in various embodiments, attenuating an impact
imparted on the
enclosure at least partially by resistively venting fluid from the inner
chamber through the
orifice, whereby the enclosure compresses, during compression of the
enclosure, increasing a
resistance to compression by partially and increasingly obstructing the
orifice with the valve.
[0021] Still another aspect of the invention pertains to a compressible
cell for use between an
exterior shell and an interior liner of an impact-attenuating helmet. In
various embodiments, the
cell comprises an enclosure comprising a top wall, a bottom wall, and at least
one side wall that
resists yielding in response to an impact at least during an initial phase
thereof, the enclosure
defining an inner chamber for containing a fluid; and at least one orifice in
the enclosure for
resistively venting fluid from the inner chamber so as to at least partially
attenuate the impact
after the initial phase, wherein the top wall is domed so as to conform to an
inner surface of the
exterior shell.
[0022] In yet another aspect, the invention relates to a protective helmet
comprising an
exterior shell, an interior liner placed inside the shell, and, disposed
between the shell and the
liner, at least one compressible cell comprising (i) an enclosure defining an
inner chamber and
comprising a top wall, a bottom wall, and side walls that resist yielding in
response to an impact
at least during an initial phase thereof, the top wall being domed so as to
conform to an inner
surface of the exterior shell, and (ii) at least one orifice in the enclosure
for resistively venting
fluid from the inner chamber so as to at least partially attenuate the impact
after the initial phase.
[0023] In a further aspect, the invention pertains to a compressible cell
for use between an
exterior shell and an interior liner of an impact-attenuating helmet. In
various embodiments, the
cell comprises an enclosure including a top wall, a bottom wall, and side
walls that resist
yielding in response to an impact at least during an initial phase thereof,
the enclosure defining
an inner chamber for containing a fluid; and at least one orifice in the
enclosure for resistively
venting fluid from the inner chamber so as to at least partially attenuate the
impact after the
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initial phase, wherein the enclosure is tapered at the top wall so as to fit
between the shell and
liner in a peripheral region of the helmet.
[0024] In another aspect, the invention relates to a protective helmet
comprising an exterior
shell; an interior liner placed inside the shell, where the distance between
the exterior shell and
the liner decreases in a peripheral region of the helmet; and disposed between
the shell and the
liner, at least one compressible cell comprising (i) an enclosure defining an
inner chamber and
comprising a top wall, a bottom wall, and side walls that resist yielding in
response to an impact
at least during an initial phase thereof, the enclosure being tapered at the
top wall so as to fit
between the shell and the liner in the peripheral region of the helmet, and
(ii) at least one orifice
in the enclosure for resistively venting fluid from the inner chamber so as to
at least partially
attenuate the impact after the initial phase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The foregoing will be more readily understood from the following
detailed
description, in particular, when taken in conjunction with the drawings, in
which:
[0026] FIG. 1A is a schematic cross-sectional view of a shock absorber
enclosure in
accordance with one embodiment, which features side walls including an
exterior obtuse angle
and increasing in thickness toward the bottom plate;
[0027] FIG. 1B is a schematic cross-sectional view of a shock absorber
enclosure in
accordance with one embodiment, which features side walls including an
exterior obtuse angle
and decreasing in thickness toward the bottom plate;
[0028] FIG. 1C is a schematic cross-sectional view of a shock absorber
enclosure in
accordance with one embodiment, which features side walls of uniform thickness
that include an
interior obtuse angle;
[0029] FIG. 2 is a schematic cross-sectional view of a shock absorber
enclosure in
accordance with one embodiment, which features a corrugation in the top wall;
[0030] FIGS. 3A and 3B are a side view and a cut-away view, respectively,
of a shock
absorber enclosure with a deep corrugation in accordance with various
embodiments;
[0031] FIGS. 4A-4E are cut-away views of the shock absorber of FIGS. 3A and
3B,
illustrating multiple compression stages in accordance with various
embodiments.
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[0032] FIG. 5 is a schematic cut-away view of a shock absorber enclosure in
accordance
with one embodiment, which features nested cylindrical walls protruding from
the bottom wall;
[0033] FIG. 6A is a is a schematic cross-sectional view of a shock absorber
enclosure in
accordance with one embodiment, which features a pin protruding from the
bottom wall opposite
an orifice through the top wall;
[0034] FIG. 6B is a schematic cross-sectional view of a shock absorber
enclosure in
accordance with one embodiment, which features a tubular protrusion extending
from the top
wall and surrounding an orifice therethrough;
[0035] FIG. 7 is an elevational view of a protective helmet with multiple
distributed
compression cells in accordance with one embodiment.
[0036] FIGS. 8A is a perspective sectional view of a shock absorber
enclosure in accordance
with one embodiment, side walls of varying thickness, a rounded top wall, and
corrugations
along the circumference of the top wall;
10037] FIG. 8B is a perspective sectional view of a shock absorber
enclosure similar to that
of FIG. 8A, which further tapers off toward one side so as to better fit into
peripheral space of a
protective helmet; and
[0038] FIG. 8C is a sectional view of a shock absorber enclosure in
accordance with another
embodiment, which features varying wall thickness, corrugations along the
circumference of the
top wall, and a valve protruding from the top wall.
DETAILED DESCRIPTION
[0039] Shock absorbers in accordance herewith can be fabricated from a
variety of elastic
and semi-elastic materials, including, for example, rubbers, thermoplastics,
and other moldable
polymers. A particularly suited material, due its durability, resiliency, and
amenability to blow
molding or injection molding, is thermoplastic elastomer (TPE); commercially
available TPEs
include the ARNITEL and SANTOPRENE brands. Other materials that may be used
include,
for example, thermoplastic polyurethane elastomers (TPUs) and low-density
polyethylene
(LDPE). In general, the material selection depends on the particular
application, and can be
readily made, without undue experimentation, by a person of skill in the art
based on known
material properties. Further, the desired shape and configuration of the shock
absorber enclosure
can generally be created using any of a number of well-known manufacturing
techniques, such
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as, e.g., blow molding or injection molding. The shock absorber may be
manufactured in one
piece, or in two or more parts that are subsequently bonded together to form a
fluid-tight
enclosure. Bonding may be accomplished, for example, with an adhesive (such as
glue), or
using a thermal bonding process. Mechanically interlocking features, clamps,
or similar devices
may be used to assure that the multiple parts remain affixed to each other.
[0040] FIG. lA schematically illustrates an exemplary shock absorber cell
100 in accordance
with various embodiments. The cell includes a flat bottom plate 102 and,
secured thereto, a cap
104 forming the top wall 106 and side walls 108 of the structure. An orifice
or vent 110 through
the top wall 106 allows fluid to exit from the interior chamber 112 formed by
the cell enclosure
as the cell is compressed during an impact, as well as to enter the chamber as
the cell returns to
its original shape following the impact. Although only one orifice is shown,
various
embodiments use multiple orifices of the same or different shapes and sizes.
The orifice(s) need
not go through the top wall, but may generally be located in any portion of
the cell enclosure.
Further, instead of being simple holes or slits, the orifices may be equipped
with valve structures
that regulate flow therethrough. For example, in some embodiments, check
valves that allow
only inflow are provided at the bottom wall of the cell, and check valves that
permit only outflow
are included in the top wall, or vice versa. Alternatively, in some
embodiments, the enclosure
includes a larger opening that allows air to flow in and out of the cell
substantially without
encountering resistance; in this case, the impact is absorbed largely
mechanically through
deformation of the enclosure. In still other embodiments, the enclosure does
not allow for fluid-
venting at all such that fluid compression in the cell contributes to the
cell's overall resistance to
compression.
[0041] Returning to FIG. 1A, the side walls 108 form two back-to-back
frusto-conical
portions that meet with their narrower end at a horizontal plane located
between the top and
bottom walls 106, 102, such that they define an obtuse exterior angle a. Thus,
when the cell 100
collapses, the side walls 108 move inward toward a central axis 114 of the
cell, thereby reducing
the volume of the cell and further compressing the air therein. This may
result in increased
turbulence of the air escaping through the orifice 110 and, thus, in increased
resistance to
compression. Further, as shown, the side walls 108 increase in thickness
between the top and
bottom walls. As a result, the resistance that the walls 108 themselves
provide to the impact
increases steadily throughout the duration of the compression. As will be
readily apparent to one
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of skill in the art, variations of the wall thickness along its height can
generally be used to tailor
the temporal energy management profile of the cell, as characterized, for
example, in terms of
the residual force transmitted through the cell as a function of time.
[0042] FIG. 1B illustrates an alternative compression cell 120, in which
the thickness of the
side walls 128 increases toward the top wall 106. (Other than that, the cell
120 is similar to the
cell 100 depicted in FIG. 1A.) The thin portion 130 of the wall 128 near the
bottom plate 102
constitutes a "weak spot" of the cell enclosure, which allows the cell to
initially shear in response
to an impact force that includes a component parallel to the top surface
(i.e., a tangential force),
thereby dissipating tangential forces. During later phases of the impact,
energy is absorbed via
compression of the thicker wall portions near the top wall 106.
[0043] FIG. 1C shows yet another shock absorber structure 140, which
includes walls of
substantially uniform thickness. In this embodiment, the side walls 148 are
angled so as to
define an interior obtuse angle 13, and, consequently, they collapse
outwardly. Accordingly, the
cell enclosure provides somewhat lower resistance to collapse then that of the
cells 100, 120 with
inverted walls depicted in FIGS. lA and 1B. These and other cell wall designs
may be combined
with additional features as described below.
[0044] In some embodiments, the top and/or bottom walls of the shock
absorber are not flat
(as depicted in FIGS. 1A-1C), but include one or more corrugations or features
vertically
protruding therefrom. Such features can provide increased resistance during
late stages of cell
compression. For example, FIG. 2 shows a shock-absorber cell 200 with a "V-
shaped"
corrugation 202 in the top wall 204 defining a circular periphery around the
center portion of the
top wall 204. As the cell is 200 compressed, the top wall 204 approaches the
bottom wall 206,
and the lowest points 208 of the corrugation 202 eventually contact the bottom
wall 206.
Effectively, this increases the number of side walls against which the impact
forces work and,
thus, inhibits further compression of the cell 200. As a result, the shock
absorber cell 200 can
withstand larger impact forces before it bottoms out. Moreover, flexure of the
corrugation 202
facilitates lateral motion of the center region of the top wall 204 relative
to the periphery in
response to shear forces. Thus, in addition to increasing the cell's
resistance to normal forces,
the corrugation 202 helps dissipating shear forces.
[0045] The contribution of the corrugation(s) in the top wall to the
overall impact-absorbing
characteristics of the shock absorber can be tailored via the number and
dimensions of the
A/75749937 1 12
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corrugation(s). The depth of the corrugation(s), in particular, affects the
point in time during
compression at which the corrugation(s) start significantly resisting
compression due to contact
with the bottom surface. In various advantageous embodiments, the
corrugation(s) descend
down below half the height of the side wall, preferably down to below 40% of
the height. FIG.
3A illustrates an exemplary embodiment of such a shock absorber (showing only
the cap 300 and
omitting the bottom wall). As shown, the top wall 302 of the shock absorber
may include a
(typically circular) central portion 304 that is raised above the height of
the side walls 306; this
features is also illustrated in FIG. 3B in a side view of The V-shaped
corrugation 308 forms a
periphery around this central portion 304. The trough 310 of the corrugation
308 (i.e., the tip of
the "V") is positioned significantly below a medial plane 312, where the two
frusto-conical
portions forming the side wall 306 of the depicted shock absorber meet.
[0046] FIGS. 4A-4E illustrate various compression stages of the shock
absorber cap 300.
FIG. 4A shows the shock absorber in the uncompressed state. FIG. 4B
illustrates the first
compression stage, in which the central portion 304 of the top wall is
depressed due to impact
forces imparted thereon. The interior walls 500 of the corrugation buckle to
allow for such
depression. Once the central portion 304 has been lowered to about the height
of the side wall
306, the side wall 306 begins to buckle (outwardly, in the depicted
embodiment), as shown in
FIG. 4C; this side-wall yielding attenuates the impact throughout the second
compression stage,
which lasts until the trough 310 of the corrugation 308 contacts the bottom
surface (shown in
FIG. 4D). Following contact, which marks the beginning of the third
compression stage, the side
wall 306 of the enclosure and the interior and exterior walls 500, 502 of the
corrugation 308
jointly absorb the impact by buckling further. In effect, the compression cell
now has three
approximately concentric vertical walls; each additional corrugation would add
another two
effective walls. In embodiments where the side wall 306 of the cell encloses
an interior obtuse
angle and, therefore, collapses outwardly (as shown), the walls 500, 502 of
the corrugations tend
to likewise move outwardly. For cells with side walls that toe in at the
medial plane (as
illustrated in FIGS. lA and 1B, the walls of the corrugation would, instead,
tend to move
inwardly.
[0047] Impact absorption in multiple stages may serve to increase the range
of impact forces
over which the shock absorber is effective. Small impacts may be absorbed, to
a large extent, by
depression of the central portion 304 of the top wall 302 and the accompanying
buckling of the
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inner wall 500 of the corrugation, whereas larger impacts may quickly proceed
to the second
and/or third stages, where the side walls 306 and both walls 500, 502 of the
corrugation resist
compression. As will be readily appreciated by one of skill in the art, the
shock absorber can be
designed to absorb impact forces in more than three stages, e.g., by addition
of more
corrugations. Conversely, a two-stage absorber may be constructed by using a
top wall 302 that
is, apart from the corrugation, flat, i.e., does not include a raised portion.
Additional features and
shock-absorbing mechanisms, e.g., as described herein, may be incorporated
into a shock
absorber with deep corrugations. For instance, as shown in FIG. 3A, the shock
absorber may
include a fluid-venting orifice 314. Resistive fluid-venting may provide an
impact-absorbing
mechanism that works in parallel with the structural resistance via the
enclosure. Alternatively,
the shock absorber may form an enclosure without any openings, resulting in
pressure increase
inside the shock absorber as it is compressed, or an enclosure with an opening
that allows free
fluid flow in and out of the shock absorber, eliminating any fluid-dynamic
resistance to
compression.
[0048] FIG. 5 illustrates another design for a shock-absorbing cell 500, in
which a plurality
of concentric circular ridges 502 are arranged on the bottom wall 504. When
the top wall
reaches these ridges 502 during compression of the cell 500, the ridges 502
begin contributing to
the absorption of the impact, resulting in a higher overall resistance of the
shock absorber to
compression. The above-described corrugations and vertically protruding
features are merely
examples; corrugations and protrusions of different shapes and configurations,
attached to the
top wall, the bottom wall, or both, may likewise be used to achieve similar
effects.
[00491 FIGS. 6A and 6B illustrate shock absorbers in which the
configuration of the orifice
and, consequently, the rate of fluid flow therethrough change depending on the
compression state
of the cell. For example, FIG. 6A shows a compression cell that includes a
long, conical pin 602
protruding from bottom wall 604 opposite an orifice 606 through the top wall
608. Once the cell
600 has been sufficiently compressed in response to the impact (e.g., to about
half its original
height as shown in the figure), the pin 602 is received within and penetrates
the orifice 606,
thereby reducing the area through which fluid can escape. Eventually the pin
602 completely
obstructs the orifice, preventing any further fluid-venting. Thus, the orifice
606 and pin 602
together function as a valve.
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[0050] FIG. 6B shows an alternative embodiment 620, in which valve-like
behavior is
created by a tubular protrusion 622 that extends vertically downward from the
top wall 624 and
includes a lumen 626 therethrough. The tubular protrusion 622 can restrict
fluid-venting via two
mechanisms. As can be readily seen, fluid venting through the lumen 626
requires the fluid to
enter the tube 622 at the end 628 close to the bottom wall 630. Accordingly,
as this end 628
contacts the bottom wall, venting is precluded or at least inhibited. In
addition, and generally
more importantly, the tube 622 can be made of a thickness and material that
allows it to constrict
and self-restrict the orifice in response to increased fluid turbulence, much
like a balloon that
releases air through the opening.
[0051] Shock absorbers as described above may employed advantageously in a
variety of
applications, including, for example, protective body gear, vehicle dash
boards, and shock-
absorbing seats. FIG. 7 illustrates, as one exemplary application, a
protective helmet 700
including multiple compression cells 702 distributed between a shell and a
helmet liner. The
shock absorbers 702 may include any combination of the features described
above. Further, they
may be shaped to accommodate the space between the shell and liner. For
example, FIG. 8A
shows a shock absorber cap 800A (omitting the bottom wall) that has an
elevated, rounded top
wall 802 with a curvature complementary to that of the interior surface of the
helmet shell.
Further, the shock absorber features one or more "V-shaped" corrugations 502
around the
periphery of a center portion of the top wall 802, and inwardly angled side
walls 805 with that
increase in thickness toward the bottom. The rounded top wall and
corrugation(s) cooperate to
allow the cell top to shift laterally in response to shear forces.
[0052] FIG. 8B illustrates a shock absorber 800B suitable for use in areas
of the helmet that
curve back in toward the head, e.g., the occipital lock area on the back of
the helmet and the
areas on the lower sides. The shock absorber 800B has an elevated, rounded top
wall 802 with a
curvature complementary to that of the interior surface of the helmet shell.
Further, the shock
absorber features one or more "V-shaped" corrugations 802 in the top wall 802,
and inwardly
angled side walls 805 that increase in thickness toward the bottom. The
enclosure of this shock
absorber tilts toward one side, i.e., the side wall height decreases across a
diameter of the shock
absorber such that, properly placed, it sits flush against the shell. The
shock absorber 8008
includes a tubular protrusion 622 that extends vertically downward from the
top wall 802 and
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includes a lumen therethrough. The radial grooves illustrated in FIGS. 8A and
8B are vents that
permit air to travel over the surface of the shock absorber upon impact.
[0053] FIG. 8C illustrates another shock-absorbing cell 800c having side
walls whose
collective height decreases across a diameter of the shock absorber to conform
to a space of non-
uniform height. This cell combines side walls 802 toeing in toward a medial
plane and
increasing in thickness toward the bottom, corrugations 802 in the top wall,
and a plurality of
concentric circular ridges 502 arranged on the bottom wall 806. These features
cooperate to
increase the cell's resistance to compression as a highly compressed state is
reached and, thus,
collectively increase the energy levels that can effectively be absorbed
without increasing the
height of the shock absorber structure.
[0054] Certain embodiments of the present invention are described above. It
is, however,
expressly noted that the present invention is not limited to those
embodiments; rather, additions
and modifications to what is expressly described herein are also included
within the scope of the
invention. Moreover, it is to be understood that the features of the various
embodiments
described herein are not, in general, mutually exclusive and can exist in
various combinations
and permutations, even if such combinations or permutations are not made
express herein,
without departing from the spirit and scope of the invention. In fact,
variations, modifications,
and other implementations of what is described herein will occur to those of
ordinary skill in the
art without departing from the spirit and the scope of the invention. As such,
the invention is not
to be defined only by the preceding illustrative description.
[0055] What is claimed is:
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