Note: Descriptions are shown in the official language in which they were submitted.
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PROTECTIVE HELMET FOR MITIGATION OF LINEAR
AND ROTATIONAL ACCELERATION
Cross Reference to Related Applications
[0001] The present application claims priority to U.S. Patent Application
No.
13/803,962, filed March 14, 2013, entitled "PROTECTIVE HELMET FOR
MITIGATION OF LINEAR AND ROTATIONAL ACCELERATION," which claims
priority to U.S. Patent Application No. 61/670,258, filed July 11, 2012,
entitled
"PROTECTIVE HELMET FOR MITIGATION OF LINEAR AND ROTATIONAL
ACCELERATION," the entire disclosures of which are hereby incorporated by
reference in their entirety.
Technical Field
[0002] Embodiments herein relate to the field of protective helmets and,
more
specifically, to helmets designed to protect the head from linear and
rotational
acceleration
Background
[0003] Helmets protect the head from injury during a direct impact. An
impact
to the head can cause skull fracture and/or traumatic brain injury (TBI), and
TBI is
the leading cause of death and long-term disability in the US among people
under
45. 90% of traumatic brain injuries occur without the presence of a skull
fracture,
and TBI can be induced by rotational acceleration alone. Despite the
vulnerability of
the brain to rotational acceleration, contemporary bicycle helmets are
primarily
designed and tested to mitigate linear acceleration. Most contemporary helmets
have two principal shortcomings: first, they have limited means to absorb
rotational
acceleration, and second, elastic helmet liners may store energy during
impact, and
release of the stored energy may induce a rebound after impact that may
contribute
to the severity and duration of rotational head acceleration.
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Brief Description of the Drawings
[0004] Embodiments will be readily understood by the following detailed
description in conjunction with the accompanying drawings. Embodiments are
illustrated by way of example and not by way of limitation in the figures of
the
accompanying drawings.
[0005] Figure 1 illustrates a cross-sectional mid-sagittal view of an
example of
a helmet, shown in an unloaded, non-deformed configuration, in accordance with
various embodiments;
[0006] Figure 2 illustrates a cross-sectional mid-sagittal view of a
helmet
shown during impact in a loaded, partially deformed configuration, and
depicting
relative translation between the outer and inner layers, accommodated by in-
plane
compression and tension of the intermediate layer, in accordance with various
embodiments;
[0007] Figures 3A and 3B illustrate non-elastic, plastic deformation of an
example of a honeycomb membrane, shown in non-deformed (Figure 3A) and
deformed (Figure 3B, with cut-away) states, in accordance with various
embodiments;
[0008] Figures 4A and 4B illustrate schematic drawings of a planar segment
(Figure 4A) and a spherically shaped segment (Figure 4B) of an exemplary
honeycomb configuration that enables spherical, three-dimensional shaping, in
accordance with various embodiments;
[0009] Figures 5A, 5B, and 5C depict a schematic drawing of a honeycomb
layer segment with alternate fixation points, shown in unloaded (Figure 5A)
and
loaded, deformed conditions (Figure 5B), and a perspective view of the
honeycomb
layer in a loaded, deformed condition (Figure 5C), in accordance with various
embodiments;
[0010] Figure 6 illustrates a cross-sectional mid-sagittal view of an
exemplary
helmet shown in conjunction with additional layer segments adjacent to the
intermediate layer to facilitate sliding of the intermediate layer relative to
the inner
and outer layers, in accordance with various embodiments;
[0011] Figure 7 illustrates a cross-sectional mid-sagittal view of one
embodiment of a helmet, shown during impact in a loaded, partially deformed
configuration, in accordance with various embodiments; and
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[0012] Figure 8 illustrates a cross-sectional view of a section of another
embodiment, wherein the outer layer and inner layer are perforated with a
multitude
of holes, which may allow for ventilation through the honeycomb cells, in
accordance
with various embodiments.
Detailed Description of Embodiments of the Invention
[0013] In the following detailed description, reference is made to the
accompanying drawings which form a part hereof, and in which are shown by way
of
illustration embodiments that may be practiced. It is to be understood that
other
embodiments may be utilized and structural or logical changes may be made
without
departing from the scope. Therefore, the following detailed description is not
to be
taken in a limiting sense, and the scope of embodiments is defined by the
appended
claims and their equivalents.
[0014] Various operations may be described as multiple discrete operations
in
turn, in a manner that may be helpful in understanding embodiments; however,
the
order of description should not be construed to imply that these operations
are order
dependent.
[0015] The description may use perspective-based descriptions such as
up/down, back/front, and top/bottom. Such descriptions are merely used to
facilitate
the discussion and are not intended to restrict the application of disclosed
embodiments.
[0016] The terms "coupled" and "connected," along with their derivatives,
may
be used. It should be understood that these terms are not intended as synonyms
for
each other. Rather, in particular embodiments, "connected" may be used to
indicate
that two or more elements are in direct physical with each other. "Coupled"
may
mean that two or more elements are in direct physical or electrical contact.
However, "coupled" may also mean that two or more elements are not in direct
contact with each other, but yet still cooperate or interact with each other.
[0017] For the purposes of the description, a phrase in the form "A/B" or
in the
form "A and/or B" means (A), (B), or (A and B). For the purposes of the
description,
a phrase in the form "at least one of A, B, and C" means (A), (B), (C), (A and
B), (A
and C), (B and C), or (A, B and C). For the purposes of the description, a
phrase in
the form "(A)B" means (B) or (AB) that is, A is an optional element.
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[0018] The description may use the terms "embodiment" or "embodiments,"
which may each refer to one or more of the same or different embodiments.
Furthermore, the terms "comprising," "including," "having," and the like, as
used with
respect to embodiments, are synonymous.
[0019] Embodiments herein provide protective helmets designed to lessen the
amount of harmful acceleration (both straight linear and rotational) that
reaches the
brain of a wearer during an impact to the head. In various embodiments, the
helmets may include a multilayer construction for both cushioning and
absorbing
impact and rotational energy, thus reducing peak acceleration or deceleration
of a
wearer's head in an impact. In various embodiments, this reduction in head
acceleration and deceleration may result in a corresponding reduction in the
magnitude of acceleration or deceleration experienced by the brain, reducing
the risk
and/or severity of traumatic brain injury (TB!).
[0020] In various embodiments, the helmets disclosed herein may include a
suspension of a compressible intermediate layer suspended between generally
non-
compressible inner and outer layers. In various embodiments, the suspension of
the
compressible intermediate layer may mitigate transfer of rotational
acceleration from
the outer layer to the inner layer. In various embodiments, the suspension may
be
created by coupling the compressible intermediate layer, such as a honeycomb
layer, through discrete, alternate (e.g., non-opposing) fixation sites, to the
outer and
inner helmet layers in a manner that allows substantially tangential
translation of the
outer layer relative to the inner layer. Thus, in various embodiments,
translation of
the outer layer relative to the inner layer may induce in-plane compression
and
tension in the intermediate layer, rather than shearing.
[0021] In various embodiments, in addition to providing a suspension
between
the inner and outer layers, the intermediate layer also may crumple and/or
compress
in an essentially non-elastic manner to mitigate linear acceleration by
depleting
impact energy and minimizing elastic rebound, which can otherwise contribute
to
linear and rotational head acceleration. As such, in various embodiments, the
disclosed helmets may allow tangential impact components to be absorbed by in-
plane compressive or tensile deformation of the intermediate layer, and
perpendicular impact components to be absorbed by non-elastic
crumpling/compression of the intermediate layer.
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[0022] In various embodiments, the intermediate layer may include a
honeycomb, such as a honeycomb formed from any material having little or no
elastic rebound. For example, in various embodiments, the honeycomb may be
formed from compressible aluminum elements. Although the examples illustrated
herein use aluminum honeycombs, one of skill in the art will appreciate that
other
lightweight, compressible materials may be employed that have little or no
elastic
rebound, such as cardboard or paper pulp, various natural or synthetic foams
(such
as aluminum foam), plastic, non-elastic polymers, and the like.
[0023] In various embodiments, the layered construction of the helmets
disclosed herein may be used to construct any type of protective headgear,
such as
safety helmets, motorcycle helmets, bicycle helmets, ski helmets, lacrosse
helmets,
hockey helmets, football helmets, batting helmets for baseball and softball,
headgear
for rock and mountain climbers, headgear for boxers, construction helmets,
helmets
for defense and military applications, and headgear for underground
activities. In
other embodiments, the layered technologies disclosed herein may be adapted
for
use in other types of protective gear, such as elbow pads, knee pads, shoulder
pads,
shin guards, and the like.
[0024] Figure 1 illustrates a cross-sectional mid-sagittal view of an
example of
a helmet, shown in an unloaded, non-deformed configuration, in accordance with
various embodiments. In the illustrated embodiment, the helmet 101 has an
aerodynamic shape designed for use by bicyclists. As illustrated, helmet 101
may
include an outer layer 104, an inner layer 105, and an intermediate layer 102.
In
various embodiments, intermediate layer 102 may be made from a honeycomb
material, such as an aluminum honeycomb material, and may be coupled to the
outer and inner layers 104, 105 at alternate fixation sites 103a, 103b, 103c.
As
defined herein, the term "alternate fixation sites" refers to attachment
points between
the outer and intermediate layers, or the intermediate and inner layers, that
are
spaced apart such that the outer and intermediate layers are not coupled
together at
a point directly above (e.g., across a thickness dimension of the helmet) a
fixation
site between the intermediate and inner layers. The term "alternate fixation
sites"
does not require that each fixation site alternates with respect to adjacent
sites along
a length of a layer. In embodiments, there may be, for example, two fixation
sites
adjacent to each other between the intermediate layer 102 and the outer layer
104
and one or more fixation sites between the intermediate layer 102 and the
inner layer
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105 further in one direction along the layers. In various embodiments, these
alternate fixation sites 103a, 103b, 103c may be positioned such that
intermediate
layer 102 is not coupled to both the outer and inner layers 104, 105 at
opposing
locations of intermediate layer 102, so that, for example, a fixation site
103b between
intermediate layer 102 and outer layer 104 is not directly opposed to a
fixation site
103a, 103c between intermediate layer 102 and inner layer 105, and vice versa.
In
various embodiments, this alternate fixation may leave portions of
intermediate layer
102 that are coupled to neither outer layer 104 nor inner layer 105, enabling
stretching and/or compression of intermediate layer 102 between alternate
fixation
sites 103a, 103b, 103c, thus enabling translation of outer layer 104 relative
to inner
layer 105, as described in greater detail below.
[0025] In various embodiments, outer helmet layer 104 may be sufficiently
stable, rigid, and/or non-compressible to distribute impact forces over an
extended
area. One of skill in the art will appreciate that the shape depicted in
Figure 1 is
merely exemplary, and that the helmet shape can vary depending on the
particular
sporting event or activity for which the helmet is designed. Furthermore,
helmets in
accordance with the present disclosure may include additional features, such
as a
cage for a hockey helmet, a face mask for a football helmet, a visor for a
motorcycle
helmet, and/or retention straps, chin straps, and the like. Although not shown
in the
illustrated embodiment, inner, intermediate, and/or outer layers 105, 102, 104
may
include one or more ventilation openings to permit air flow for cooling the
wearer's
head.
[0026] In the illustrated embodiment, intermediate layer 102 may include
an
aluminum honeycomb, arranged with its cells oriented generally perpendicular
to the
outer layer 104 of the helmet. In various embodiments, inner layer 105 may be
applied to at least a portion of the intermediate layer 102 interior surface.
In
embodiments, the inner layer covers most if not all of the intermediate layer.
The
inner layer may be comprised of a singular component, of multiple, partially
overlapping components, or of multiple components that are joined together in
a
flexible manner (e.g., like the sewn patches of a soccer ball). As described
above, in
various embodiments, intermediate layer 102 may be coupled to outer layer 104
and
inner layer 105 at discrete and alternate fixation sites 103a, 103b, 103c so
as to
provide a suspension between outer layer 104 and inner layer 105. For example,
in
some embodiments, outer layer 104 may be coupled to intermediate layer 102 at
the
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helmet crown 103b, and inner layer 105 may be coupled to intermediate layer
102 at
the helmet periphery 103a, 103c. Without being bound by theory, this
configuration
may reduce the rotational head acceleration caused by the impact component
acting
tangential to the helmet surface, and it also may reduce linear head
acceleration
caused by the impact component acting perpendicular to the helmet surface, as
described in greater detail below. Other configurations/arrangements may be
used
in other embodiments.
[0027] Figure 2 illustrates a cross-sectional mid-sagittal view of a helmet
201
shown during impact in a loaded, partially deformed configuration, and
depicting
relative translation between the outer and inner layers 204, 205, accommodated
by
in-plane compression and tension of the intermediate layer 202, in accordance
with
various embodiments. In the illustrated embodiment, as described above,
intermediate layer 202 may be suspended between inner layer 205 and outer
layer
204 via coupling to both layers 204, 205 at alternate fixation sites 203a,
203b, 203c.
In use, when helmet 201 is exposed to a primarily tangential impact, this
impact
induces relative translation between outer layer 204 and inner layer 205,
accommodated by in-plane compression 206 and tension 207 (e.g., expansion) of
intermediate layer 202.
[0028] In various embodiments, the suspension of intermediate layer 202
between inner layer 205 and outer layer 204 also may allow for small amounts
of
translation of inner layer 205 perpendicular to and away from outer layer 204.
In
various embodiments, this increase in separation between outer layer 204 and
inner
layer 205 may accommodate tangential translation between outer and inner
layers
204, 205 in an ovoid, non-spherical shape of helmet 201. Without being bound
by
theory, in various embodiments, a primary benefit of translation between the
outer
and inner layers 204, 205 during impact may be mitigation of rotational head
acceleration. In some embodiments, an additional benefit may be that
translation
distributes the impact over a larger segment of intermediate layer 202, which
may
increase absorption of the impact force component perpendicular to the outer
layer
204 by controlled crumpling of the honeycomb of the intermediate layer 202 in
a
direction perpendicular to the honeycomb elements. In some embodiments, a
surface of inner layer 205, outer layer 204, or intermediate layer 202 may
include
one or more indicators that show the amount of translation 208 between the
outer
and inner layers 204, 205 in response to an impact to estimate impact
severity. For
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example, such indicators may be comprised of graded color bands 209, 210 that
circumscribe the periphery of the inside of outer layer 204, whereby increased
exposure of color bands 209, 210 indicates an increased impact force.
[0029] In some embodiments, the intermediate layer may include two or more
layers of honeycomb materials having different stiffness, such that the less
stiff
layers protect the brain during mild impacts, and the stiffer layers protect
the brain
during severe impacts. In other embodiments, the honeycomb cells may be
entirely
or partially filled with an additional energy absorbing material, such as an
expanded
foam. In particular embodiments, the additional energy absorbing material may
be of
non-uniform thickness, and may be configured, for example, such that the
intermediate layer becomes progressively stiffer as it is crushed in the
direction
tangential to the outer layer, and/or in the direction perpendicular to the
outer layer.
In still other embodiments, the additional energy absorbing material also may
form a
solid layer on the inner and/or outer surface of the honeycomb.
[0030] Figures 3A and 3B illustrate non-elastic, plastic deformation of an
example of a honeycomb layer, shown in non-deformed (Figure 3A) and deformed,
partially cut-away (Figure 3B) states, in accordance with various embodiments.
In
various embodiments, an impact force acting perpendicular to the outer helmet
surface in excess of the compressive strength of the honeycomb layer may
induce
plastic, permanent compression of the honeycomb layer by means of crumpling of
honeycomb cells. In various embodiments, the plastic, non-recoverable
crumpling of
honeycomb cells may absorb an impact by depleting a portion of the impact
force.
Thus, this crumpling may reduce or eliminate rebound after impact, which may
otherwise induce rotational head acceleration subsequent to a primary impact.
In
some embodiments, in order to minimize an initial peak force required to
initiate
crumpling, the honeycomb layer may be pre-crushed to a certain degree, such as
about 1-20% of its thickness, or about 5-15% in various embodiments.
[0031] Figures 4A and 4B illustrate schematic drawings of a planar portion
(Figure 4A) and a spherically shaped portion (Figure 4B) of an example
honeycomb
configuration that enables spherical, three-dimensional shaping, in accordance
with
various embodiments. In the illustrated example, this honeycomb configuration
404
enables conforming of an aluminum honeycomb into the spherical, three-
dimensional shape of a helmet, while retaining a substantially symmetric shape
of
honeycomb elements without buckling of honeycomb elements.
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[0032] Figures 5A, 5B, and 5C depict a schematic drawing of a honeycomb
layer segment with alternate fixation points, shown in unloaded (Figure 5A)
and
loaded, deformed conditions (Figure 5B), and a perspective view of the
honeycomb
layer in loaded, deformed condition (Figure 5C), in accordance with various
embodiments. Figure 5A illustrates an example of a non-deformed honeycomb 502,
with some fixation sites 510 attached to an inner helmet layer, and other
fixation
sites 511 attached to an outer helmet layer. In various embodiments, honeycomb
502 may include void sections 512 for ventilation, which may correspond to
similar
void sections in the inner and outer helmet layers. Figure 5B illustrates
honeycomb
502 under tangential loading, whereby honeycomb segments between alternate
fixation points 510 and 511 are deformed to accommodate suspension and
translation between the inner and outer helmet layers. Figure 5C illustrates
again
the deformed shape of honeycomb 502 due to tangential force introduction
through
fixation point 511.
[0033] In some embodiments, the alternate fixation sites between the
respective layers may include non-permanent connections, such as hook-and-loop
connections, and may allow for replacement of the inner, outer, or
intermediate layer
if damaged. In other embodiments, the inner layer may be attached to the outer
layer with an elastic material, and wherein the elastic material holds the
inner layer in
place during normal wearing, but allows relative displacement between the
inner
layer and outer layer in an impact.
[0034] Figure 6 illustrates an example of a helmet 601 having an
intermediate
layer 602 in suspension between outer layer 604 and inner layer 605, wherein
intermediate layer 602 is coupled to the inner and outer layers via alternate
fixation
sites 603. In the illustrated embodiment, helmet 601 also includes a padding
layer
608 on the inside of inner layer 605 to improve comfort and help attenuate
impacts.
In various embodiments, padding layer 608 may include a single layer or may be
comprised of multiple sections. In some embodiments, one or more glidable
interface layers 607 may be added between at least a part of intermediate
layer 602
and outer layer 604. In some embodiments, one or more glidable interface
layers
606 may be added between at least a part of intermediate layer 602 and inner
layer
605. In some embodiments, these interface layers 606 and 607 may reduce
friction
to enhance tangential displacement between the inner and outer layers during
an
oblique impact. In addition, in some embodiments, inner layer 605 may be
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configured with perforations or alternative means to reduce its in-plane
stiffness in
order to enhance tangential displacement between the inner and outer layer
during
an oblique impact. In further embodiments, intermediate layer 602, and/or
inner 605
layer or outer 607 layer, may be provided with a colorimetric indicator that
indicates
the severity of impact when the helmet sustains an impact force. In some
embodiments, the severity of impact may be shown as the degree of displacement
of
the outer layer 607 relative to the inner 605 and/or intermediate 602 layers.
[0035] Figure 7 illustrates a cross-sectional mid-sagittal view of another
embodiment of a helmet 701 shown during impact in a loaded, partially deformed
configuration. In this embodiment, some or all of the fixation points 703a,
703b,
703c are not rigid connections (703b), but rather are unidirectional couplings
703a,
703c that locally couple the layers together upon tangential forces in one
direction,
while allowing free relative displacement upon tangential forces in another
direction.
For example, in the illustrated embodiment, relative translation between the
outer
layer 704 and inner layer 705 is accompanied by in-plane compression of the
intermediate layer 702 on one side 706, but the other side 707 remains
undeformed
in the in-plane direction. In the illustrated embodiment, the inner layer 705
is held in
place in the undeformed configuration by elastic connections 708, and in
various
embodiments, these elastic connections may allow for relative displacement
between the outer layer 704 and inner layer 705 in an impact. In practice,
this
embodiment may allow for greater control of the in-plane stiffness of the
intermediate
layer 701.
[0036] Figure 8 illustrates a cross-sectional view of a section of another
embodiment, wherein the outer layer 801 and inner layer 802 are perforated
with a
multitude of holes 803, which may allow for ventilation through the honeycomb
cells
in intermediate layer 804. Although a particular hole size is illustrated, one
of skill in
the art will appreciate that a range of hole sizes is contemplated, for
example, from
about 1 mm to about 3 cm, such as about 0.5-2 cm, or about 1 cm, depending on
the
application. The holes may be ordered in an array or random in placement, and
different portions of the helmet may have holes of different sizes and/or
placement,
depending on the ventilation needs of the particular application. It will be
appreciated that it may be advantageous to supply the helmet with a multitude
of
small ventilation holes in order to prevent the gaps in protection that may
result from
the larger ventilation holes used in most conventional helmets. Additionally,
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providing a multitude of small holes may enable the helmet to have a more
streamlined, smooth shape, which in turn may reduce the chance that a helmet
contour may "catch" on an obstacle or obstruction during a fall or other head
impact,
which could increase rotational impact forces.
[0037] Although certain embodiments have been illustrated and described
herein, it will be appreciated by those of ordinary skill in the art that a
wide variety of
alternate and/or equivalent embodiments or implementations calculated to
achieve
the same purposes may be substituted for the embodiments shown and described
without departing from the scope. Those with skill in the art will readily
appreciate
that embodiments may be implemented in a very wide variety of ways. This
application is intended to cover any adaptations or variations of the
embodiments
discussed herein. Therefore, it is manifestly intended that embodiments be
limited
only by the claims and the equivalents thereof.
