U.S. patent application number 13/700045 was filed with the patent office on 2013-11-21 for helmet.
The applicant listed for this patent is Anirudha Surabhi. Invention is credited to Anirudha Surabhi.
Application Number | 20130305435 13/700045 |
Document ID | / |
Family ID | 42799899 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130305435 |
Kind Code |
A1 |
Surabhi; Anirudha |
November 21, 2013 |
Helmet
Abstract
A head protection helmet comprises an impact resistant shell
comprising a cavity for accommodating a user's head and an array of
crushable bodies having a hollow closed configuration, e.g. flutes
in corrugated material. The crushable bodies each having an axis
that extends outwardly from the cavity to absorb impact forces
exerted along the direction of the axis.
Inventors: |
Surabhi; Anirudha; (London,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Surabhi; Anirudha |
London |
|
GB |
|
|
Family ID: |
42799899 |
Appl. No.: |
13/700045 |
Filed: |
May 26, 2011 |
PCT Filed: |
May 26, 2011 |
PCT NO: |
PCT/GB11/00814 |
371 Date: |
March 7, 2013 |
Current U.S.
Class: |
2/414 |
Current CPC
Class: |
A42B 3/06 20130101; A42B
3/124 20130101; A42B 3/063 20130101; A42B 3/065 20130101; A42B
3/067 20130101; A42B 3/322 20130101 |
Class at
Publication: |
2/414 |
International
Class: |
A42B 3/06 20060101
A42B003/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 26, 2010 |
EP |
10250978.3 |
Claims
1. A head protection helmet comprising an impact resistant shell
comprising: a cavity for accommodating a user's head and an array
of crushable bodies having a hollow closed configuration, the
crushable bodies each having an axis that extends outwardly from
the cavity to absorb impact forces exerted along the direction of
the axis.
2. A helmet as claimed in claim 1, wherein the crushable bodies are
cells formed by intersecting arc-shaped ribs overlying the cavity,
wherein the ribs extend outwards from the cavity.
3. A helmet as claimed in claim 2, wherein the intersecting
arc-shaped ribs are formed of crushable sheet material.
4. A helmet as claimed in claim 2, wherein the crushable sheet
material is a single sheet.
5. A helmet as claimed in claim 3, wherein the ribs are each made
of multiple sheets of a crushable board, the sheets of each rib
being connected together.
6. A helmet as claimed in claim 5, wherein the sheets of each rib
are connected together by connector bodies that have an axis that
lies generally orthogonal to the plane of the ribs.
7. A helmet as claimed in claim 5, wherein the sheets of each rib
are connected together by an array of honeycomb cells, the cells
being of at least square, rectangular or hexagonal shape.
8. A helmet as claimed in claim 5, wherein the sheets of each rib
are connected together by at least one connector body having an
axis and wherein said axis extends generally tangentially with
respect to the cavity.
9. A helmet as claimed in claim 5, wherein the sheets of each rib
are connected together by crushable bodies having a hollow closed
configuration, e.g. the crushable bodies each having an axis that
extends outwardly from the cavity to absorb impact forces exerted
along the direction of the axis.
10. A helmet as claimed in claim 1, wherein the crushable bodies
are flutes in corrugated material.
11. A helmet as claimed in claim 10, wherein the corrugated
material is in the form of arc-shaped ribs overlying the cavity,
wherein the ribs extend outwards from the cavity.
12. A helmet as claimed in claim 11, wherein the flutes in some of
the ribs extend generally horizontally and the flutes in others of
the ribs extend in a direction having at least a vertical
component.
13. A helmet as claimed in claim 2, wherein the array of ribs
comprises ribs extending axially between the front and the back of
the head cavity and ribs extending laterally between two opposed
sides of the head cavity, the axial and lateral ribs intersecting,
e.g. at crossed halved joints.
14. A helmet as claimed in claim 1, wherein the shell includes a
rim encircling the head cavity, the rim including said crushable
bodies.
15. A helmet as claimed in claim 1, wherein the crushable bodies
are tubes that are arranged in an array, the tubes each having an
axis that is directed outwardly away from the cavity.
16. A helmet as claimed in claim 15, wherein the crushable bodies
are frusto-cones with the larger surface facing outwards so that
the axes of the frusto-cones extend outwardly from the cavity in
different directions.
17. A helmet as claimed in claim 15, wherein the tubes include a
line of weakness in the walls of the tubes and are such that they
crumple within their own diameters when impacted.
18. A helmet as claimed in claim 15, wherein the tubes are formed
by intersecting arc-shaped ribs overlying the cavity, wherein the
ribs extend outwards from the cavity.
19. A helmet as claimed in claim 1, wherein the crushable bodies
have outwardly facing parts that are covered by a waterproof layer,
which waterproofing layer is made of a material that has a
stiffness coefficient higher than that of the material of the
crushable bodies.
20. A helmet as claimed in claim 19, wherein the waterproofing
layer is an outer shell and optionally includes ventilation
openings therein.
21. A helmet as claimed in claim 1, which includes an inner shell
which inner shell is in direct or indirect contact with the cavity
of the impact absorbent shell and which is releasably connected
thereto.
22. A helmet as claimed in claim 1, which includes padding arranged
to be next to the user's head and straps capable of extending under
the chin of a user.
23. An impact absorbent shell for a head protection helmet
comprising: a cavity for accommodating a user's head and an array
of crushable bodies having a hollow closed configuration, the
crushable bodies each having an axis that extends outwardly from
the cavity to absorb impact forces exerted along the direction of
the axis, the shell comprising: a cavity for accommodating a user's
head and an array of crushable bodies having a hollow closed
configuration, the crushable bodies each having an axis that
extends outwardly from the cavity to absorb impact forces exerted
along the direction of the axis; wherein the crushable bodies are
cells formed by intersecting arc-shaped ribs overlying the cavity,
wherein the ribs extend outwards from the cavity.
24. A head protecting helmet comprising a shock indicator, that
gives an indication when the helmet has been subject to a shock in
excess of a threshold value, thereby indicating that the helmet or
at least a shock absorbing part of the helmet should be replaced,
which indicator comprises a chamber and at least 5 flasks spaced
around the chamber, each flask having a space containing a colored
liquid and each flask including a capillary bore that provides
communication between the space of that flask and the chamber,
wherein each capillary bore is capable of allowing the liquid in
the space adjacent to it to pass into the chamber when the
respective flask is subjected to a shock of at least said threshold
value.
Description
TECHNICAL FIELD
[0001] The present invention relates to a helmet. The helmet is
primarily intended as a cycling helmet to provide head protection
in the event of a cycling accident. However, it also finds
application at any time when head protection is needed, for example
ice skating, roller skating, skateboarding, caving, climbing, e.g.
indoor climbing or mountain climbing, skiing, baseball, American
football, ice hockey and head protection at work or when working at
heights, e.g. in the construction industry.
TECHNICAL BACKGROUND
[0002] Most bicycle helmets available have (a) a thin outer layer,
which may be made, for example, out of polypropylene that is able
to absorb initial peak impact forces, (b) a shell within the thin
layer and composed of expanded polystyrene that absorbs both
initial and subsequent impact forces and (c) padding within the
expanded polystyrene shell both to provide comfort to the user and
to adjust the shape of the internal cavity within the shell for
different shaped and sized heads.
[0003] In general, a cycling helmet should fit closely over the
cyclist's head so that any impact force is spread over as wide an
area of the head as possible. The impact forces are absorbed by the
thin polypropylene layer and the expanded polystyrene shell. In
addition, some helmets fracture under impact, which also absorbs
energy and reduces the energy transferred to the head.
[0004] Cycling helmets are often treated roughly and such rough
treatment can impair the effectiveness of the helmet. However,
there is often no outward visible sign of such impairment.
[0005] As mentioned, cycling helmets and helmets for other uses are
generally made of synthetic plastics. Although it would be
desirable to make the helmets at least partly out of natural
material that could be recycled, it is counter-intuitive to use
such materials in applications requiring the resistance of such
strong forces.
[0006] Helmets should generally be light to be acceptable to
wearers. Sports protective helmets should also be well ventilated
so that sweat does not accumulate around the user's head and so
that body heat generated due to the exertion of cycling or other
sport can be displaced through the head.
[0007] Although the materials used for making the cycling helmets
are not particularly expensive, it would advantageous to use
cheaper materials, if possible.
DISCLOSURE OF THE INVENTION
[0008] The present invention uses the strength of flutes or hollow
tubes, e.g. hollow cylinders, hollow cells and hollow frusto-cones,
in a helmet to resist impact and also to crumple on impact, such
crumpling absorbing significant energy which is thereby not
transferred to the user's head.
[0009] In one embodiment, the flutes may be those present in
corrugated material, e.g. corrugated fibre board can be used to
absorb impact energy. In this case, an impact resistant shell of
the helmet of the present invention can be made of such corrugated
material, which may be in the form of intersecting arc shaped ribs
overlying a head cavity of the helmet and extending outwards,
optionally radially outwards, from the cavity. In this case, the
arc-shaped ribs may be arranged to extend generally axially (front
to back) and laterally (side to side). The arrangement of the
flutes may be such that at the front, top and sides of the helmet,
at least some of the flutes extend radially outwards from the
cavity (e.g. forwardly and optionally also upwardly at the front
and sideways and optionally also upwardly at the respective sides).
The positioning of the flutes can be brought about by suitably
locating the arc-shaped ribs and by selecting the direction of the
flutes within those ribs.
[0010] However, sufficient impact resistance can be achieved using
the above intersecting arc-shaped ribs but without the use of
flutes. The arc-shaped ribs may each be made of one or more sheets.
When two or more such sheets are present in a single rib, they will
generally lie parallel to each other and may be joined together in
a spaced apart relationship. When each rib has three or more
sheets, each spaced may be apart from, and connected to, its
neighbouring sheet. The material joining the sheets together and
maintaining the sheets in a parallel spaced-apart configuration may
be composed of cells. Such cells may be formed by a corrugated
sheet, as discussed above, or by cells having walls and or axes
that extend generally orthogonal to the planes of the sheets. For
example, the sheets may be connected by an array of honeycomb cells
where the individual cells are hexagonal, square or rectangle in
cross-section. The honeycomb cells, which are connected to the
sheets overlying them, increase the resistance to flexing of the
ribs and thereby make them stiffer. They also maintain the sheets
in a parallel spaced-apart configuration, which means that the
sheets themselves can absorb greater impact forces than if the
sheets were connected together by flutes that have lower ability to
maintain the sheets in parallel.
[0011] The sheets are preferably semi-rigid, where the term
"semi-rigid" material is used in the present specification in
relation to a sheet to denote a material that will remain in a
planar configuration but can be crumpled by a substantial force
applied within the plane of the sheet. The force it can withstand
before crumpling will depend on the nature of the ribs, and the
arrangement of the sheets within each rib and the number and
arrangement of the ribs within a helmet. The semi-rigid material
should be such that the helmet overall can withstand the force
required for the application concerned and the various standard
that apply to these helmets. Typical materials include cardboard
and stiff but flexible plastics.
[0012] The arc-shaped ribs may together form an intersecting array
or lattice, with ribs extending axially between the front and the
back of the head cavity and laterally between the two opposed sides
of the head cavity; they can also extend diagonally. Naturally, the
ribs will intersect in such an arrangement and, at the intersection
point, the ribs preferably form crossed halved joints, which are
made by forming a groove in the lower part of one rib and another
groove in the upper part of the other rib so that the two ribs can
be slotted into each other without severing either rib completely.
The joint can be an interference fit between the two ribs or
adhesive can be used to cement the two ribs at the joint.
Alternatively, some of the grooves in the ribs may be larger than
is necessary to accommodate the intersecting ribs, partly to make
manufacture easier and partly to allow a limited amount of movement
or play between the ribs, which helps absorb energy in a crash.
[0013] As mentioned above, when corrugations are provided, the
corrugations provide the impact strength along the direction of the
flutes. Therefore, at the centre of each arc-shaped rib, it is
preferred that the flutes extend either parallel to the edge of the
rib or at right angles to the edge of the ribs. The latter
arrangement absorbs impact forces exerted on the centre of the rib
at a right angle to the edge. The former arrangement provides
strength at the ends of the rib rather than in the centre and can
absorb impact forces exerted at right angles of the ends of the
ribs. The flutes in adjacent ribs need not be parallel to each
other and indeed it may be advantageous if that is not the case so
that adjacent ribs can absorb impact forces applied from different
directions. Thus, for example, the flutes of one arc-shaped rib can
extend at right angles to the flutes on the adjacent rib.
[0014] The helmet may include a rim encircling the head cavity that
may also be made of the same material as the ribs; if made of
corrugated material containing flutes, the flutes preferably extend
from the front to the back of the head cavity so as to absorb front
impact forces.
[0015] Although the corrugated material may be made of plastic, it
is preferred to use fibre board (e.g. corrugated cardboard) since
the materials for making fibre board are natural and the helmet can
be recycled after use. Corrugated fibreboard can be obtained
commercially in a large number of different qualities but all
qualities are relatively cheap. Honeycombed fibreboard can be made
by forming a layer of honeycomb cells and adhering to this layer to
the face sheets.
[0016] In a second embodiment, instead of flutes in corrugated
boards, the strength of the impact resisting shell may be provided
by an array of hollow tubes, e.g. cylinders or frusto-cones,
typically made from sheet material, especially paper and cardboard.
The ends of the cones or cylinders should point outwardly from the
head cavity so that they are able to absorb impact and also crumple
under that impact, thereby absorbing energy and reducing the force
that is transmitted to the user's head in the event of an
accident.
[0017] Cylinders, when packed together in a dome-shaped array, may
not present a smooth external surface or a smooth inner surface
that outlines the head cavity. In order to address this, it is
possible to machine the external or internal surfaces to provide
such a smooth domed shape. However, it is not necessary to produce
a smooth dome shape to the outside surface.
[0018] Furthermore, an uneven dome shape within the cavity of the
impact resistant shell can be tolerated if an inner shell is
provided that has a matching outer surface; the inner shell may
then provide a smooth domed inner surface. The role of the inner
shell will be discussed below. A domed shape can be achieved more
easily by using hollow frusto-cones instead of cylinders with the
larger end face of the cones pointing outwardly while the smaller
faces point inwardly.
[0019] The tubes (hollow frusto-cones or cylinders) can be held in
a bundle or array with each tube being in contact with a
neighbouring tube. A mixture of cones and cylinders can be used.
Alternatively, the tubes can be held in position by a matrix
material in which they are captured within the matrix material.
[0020] Hollow cylinders can be made by winding strips of flexible
sheet material into a closed shape and retaining the closed shape,
for example, by adhesive. The strips used to form such tubes will
generally extend helically around the axis of the tube. The
manufacture of hollow cylinders is widely practiced in the
manufacture of the cores of paper rolls. Frusto-conical shapes can
also be made by a similar winding technique.
[0021] The greater the number of tubes (cylinders or frusto-cones)
used to make up the impact resistant shell, the greater is the
impact strength of the shell. Therefore, the outside diameter of
the cylinders or frusto-cones will generally not exceed 4 cm and,
for example, will generally not exceed 3 cm. On the other hand, a
greater number of tubes will increase the complexity of
manufacturing the shell and accordingly the outside diameter of the
cylinder should preferably be at least 0.5 cm, e.g. 1 cm. In the
case of frusto-cones, the mean diameter of the cones should
generally lie in the above ranges.
[0022] The tubes (cylinders or frusto-cones) should crumple on
impact. In order to control the degree of crumpling, a line of
weakness may be provided in the walls of the hollow tubes along
which they can collapse. The lines of weakness are preferably
helical in shape so that the crumpling will occur within the
boundary of the tubes and the lines of weakness may be provided in
the form of holes or openings spaced along the line of
weakness.
[0023] As is the case in the first embodiment, cheap material used
to make the tubes, which material may be plastic but preferably is
paper or cardboard. Cork could also be used.
[0024] In fact, the distinction between the first embodiments and
the second embodiment is not clear-cut since the above-described
arrangement of intersecting ribs can also be seen as falling within
the scope of the second embodiment since the intersecting ribs form
an array of cells that are tubes having a 4-sided
cross-section.
[0025] In order to waterproof the helmet of the present invention,
at least the outside edge regions of the crushable bodies may be
covered with a waterproofing material, although optionally an outer
shell may be provided that will provide such waterproofing, in
which case it is preferred that ventilation openings are provided
in the outer shell. The waterproofing material/outer shell is
preferably made of a material having a stiffness coefficient higher
than that of the material used for forming the crushable bodies so
that it is less elastic. In this way, it can assist in resisting
the peak force exerted on impact. The preferred materials are
polypropylene, acrylic or ABS.
[0026] The helmet may include an inner shell, which may perform a
number of functions. Firstly, it can add extra impact resistance to
the impact resistant shell of the present invention, for example it
could be made of moulded expanded polystyrene. Secondly, it can be
used to tailor the helmets to the size of a particular user's head.
This can be achieved by making the cavity within the impact
resistant shell of the present invention in one standard size and
providing an inner shell with an outside that matches the size of
the impact resistant shell cavity and an inside that has a head
cavity that is matched to the size of a user's head; thus a number
of inner shells could be manufactured having variously sized
internal cavities to fit various head sizes and shapes. Padding may
also be provided for additional comfort and/or ensuring that a
tight or snug fit is maintained between the user's head and the
helmet, e.g. using insertable padding that can be adhered to the
inside surface of the inner shell cavity, as is widely practiced
with cycling helmets currently available.
[0027] A further use of the inner shell is to dissipate the impact
forces that are transmitted to the inner ends of the crushable
bodies, i.e. the ends lying in the head cavity, so they are not
transmitted directly on the user's head. In addition, the shape of
the cavity within the impact resistant shell may not be uniformly
smooth and the outer surface of the inner shell can, as discussed
above, be shaped to match the uneven surface of the cavity in the
impact resistant shell. This avoids having to shape the head cavity
of the impact resistant shell in an expensive manner. The inner
shell may be permanently attached to the impact resistant shell of
the present invention or may be releasable attached, e.g. using
loop-and-hook fastenings, e.g. Velcro.RTM., so that the impact
resistant shell of the present invention is replaceable if
dented.
[0028] Instead of a continuous inner shell, a series of pads may be
used that lie between the array of crushable bodies and the user's
head. Such pads may be made of relatively rigid foam material to
provide a cushion between the crushable bodies and the user's head.
The series of pads may be viewed as a discontinuous inner
shell.
[0029] Generally, because the outside surface of the impact
resistant shell (even with the waterproofing layer or outer shell),
is made up of an array of crushable bodies rather than a uniform
smooth surface, it will be more evident when the impact resistant
shell has been damaged and therefore needs replacing.
[0030] The impact resistant shell can be recycled, if made of fibre
based materials, such as paper or cardboard. The strength of the
crushable bodies will depend on the nature and thickness of the
sheet material used and so it is possible to adjust the impact
strength and crumpling properties of the helmet by the choice of
the sheet material used. in the present specification, the term
"outer" shell does not necessarily mean that it forms the outermost
layer of the helmet (although it can) and likewise the term "inner"
shell does not necessarily mean that it forms the innermost layer
of the helmet (although again it can). However, the outer shell
will always lie outside the impact resistant shell and any inner
shell in the helmet will always lie inside the impact resistant
shell.
[0031] According to a further aspect of the present invention,
there is provided a head protecting helmet comprising a shock
indicator that gives it an indication when the helmet has been
subject to a shock in excess of a threshold value, thereby
indicating that the helmet or at least the shock absorbing part of
the helmet should be replaced. Often, for convenience, the
magnitude of a shock, which is a force exerted as a result of
acceleration or deceleration, is stated as a multiple of the
acceleration caused by earth's gravity, which is indicated by the
symbol "G". During a bicycle accident, the helmet can suffer shocks
of 150 G and after any shock of 150 G should preferably be
replaced.
[0032] The accelerometer contains at least five tubes or flasks
each containing a viscous coloured liquid held in a chamber of the
flask by a wall having a capillary bore extending through it that
normally retains the liquid within the chamber as a result of the
surface tension of the liquid and the small size of the bore.
However, if a sufficient force is exerted on the liquid due to
shocks, the liquid passes through the capillary into a further
chamber; the presence of the coloured liquid in the further chamber
indicates that the accelerometer has suffered a shock in excess of
a threshold value. The at least five tubes or flasks communicate
with a common further chamber and so the present of the coloured
liquid in the common further chamber indicates that the helmet
needs replacing. Tubes or flasks of the above type are already
known and sold under the trademark "Shockwatch". The viscosity of
the liquid and the size of the capillary bore are preferably
designed to allow the liquid to pass into the common chamber when
subjected to a threshold shock that is selected from the range of
75-100 G.
[0033] We have found that at least five such tubes or flasks are
needed to ensure that shock exerted in any direction on the helmet
is captured and triggers the release of liquid into the common
chamber and the use of a larger number is preferred, e.g. six,
eight or more.
[0034] The common chamber may be located behind a magnified lens,
which could be clear or diffusing, thereby making it easier to
detect the triggering of accelerometer.
BRIEF DESCRIPTION OF DRAWINGS
[0035] There will now be described, by way of example only, several
embodiments of the present invention by reference to the
accompanying drawings in which:
[0036] FIG. 1 shows part of a helmet, that is to say an impact
resistant shell in accordance with the present invention, viewed
from the front and one side;
[0037] FIG. 2 shows the helmet of FIG. 1 viewed from below;
[0038] FIG. 3 is an end view of corrugated fibre board that may be
used in the helmet of FIGS. 1 and 2;
[0039] FIG. 4 is a partly cutaway view of part of an arc-shaped rib
made of fibre board having a honeycomb core that may be used in the
helmet of FIGS. 1 and 2;
[0040] FIG. 5 shows the joint between two arc-shaped ribs used in
the helmet of FIGS. 1 and 2.
[0041] FIG. 6 is a schematic view of a helmet in accordance with
the present invention using the shell shown in FIGS. 1 and 2;
[0042] FIGS. 7 and 8 show, schematically, an alternative
arrangement to the impact resistant shell of FIGS. 1 and 2; and
[0043] FIGS. 9a and 9b shows schematically a shock indicator for
use as a helmet.
DETAILED DESCRIPTION
[0044] The helmet of the present invention includes an impact
resistant shell that is able to absorb some of the forces exerted
on a helmet during a collision with another object, which may be
the road, a pavement, a pedestrian or another vehicle. As mentioned
above, the present invention is not limited to a cycling helmet but
cycling will be used to exemplify the diverse applications for
which the helmet may be used, some of which are set out above.
[0045] Referring initially to FIGS. 1 and 2, which show the shell
from one side and from below, respectively, the impact resistant
shell 10 of the helmet includes a rim 12 made of a solid fibre
board. The rim may be made in a single piece or in multiple pieces
(as shown in FIGS. 1 and 2) that are joined together at connection
13, which is most clearly shown in FIG. 2. The joint 13 is a simple
tongue-and-groove joint that includes a tongue 13a on one piece of
the rim that slots into a groove 13b cut into the end of a second
piece of the rim.
[0046] The rest of the impact resistant shell 10 is made up (a) of
series of axial ribs 14 extending between the front 18 and the back
19 of the helmet and (b) a series of lateral ribs 16 extending
between the two sides 20 of the helmet. As can be seen, the ribs
are arranged in planes that extend radially outwards from the
helmet and form an intersecting lattice of shock absorbing ribs;
the lattice can be seen as an array of 4-sided shock-absorbing
cells 23. The axial ribs 1 of FIGS. 1 and 2 come together at the
front 18 and the rear 1 of the helmet. Likewise, the lateral ribs
16 come together at the two sides 20 of the helmet. The ends of the
ribs 14, 16 slot into grooves 21 in the rim 12. They may be held in
the grooves 21 by adhesive.
[0047] The ribs 14,16 are arc shaped and the insides of the ribs
forms a head cavity 30. As is clear from FIGS. 1 and 2, the ribs
14, 16 intersect with each other. The joints at these intersecting
points are shown in an exploded view in FIG. 5. The axial ribs 14
have a groove 34 cut in the concave side of the rib while the
lateral ribs 14 have a groove 32 cut in their convex faces. The
grooves 32, 34 can then be slotted into each other together to form
a halved cross joint, which means that neither of the ribs 14, 16
is cut completely through in order to provide the intersection. The
grooves in the ribs 14,16 can extend radially from the centre of
the cavity 30. In FIG. 5, the grooves 32,34 are shown to extend at
right angles to the plane of the respective ribs but, as can be
seen in FIG. 1, the groove may extend in a non-orthogonal direction
to the plane of the ribs that forming an intersection. The sizes of
the grooves 32, 34 should accommodate the other rib and the ribs
may be held in place either by friction or by adhesive or by a
mechanical element. As can be seen in FIG. 1, some of the grooves
34 in the ribs 14 (as indicated by the reference number 34a in FIG.
1) are larger than necessary to accommodate the corresponding
lateral ribs 16 and this provides some play between the ribs which
can therefore absorb more impact energy in the case of an accident.
Furthermore, it assists in assembling the shell 10.
[0048] The ribs 14, 16 may be made of corrugated fibre board, as
shown in FIG. 3. Corrugated fibreboard includes at least one
undulating section 28 sandwiched between flat fibre board layers 31
to form a series of flutes 29. It possible to build up a number of
such layers in a unitary corrugated fibre board (FIG. 3 includes
two such undulating sections). The thickness of the material
forming the undulations 28 and the thickness of the flat board 1
should be chosen to give the degree of shock resistance and
crumpling need to absorb the type of forces exerted during a
collision.
[0049] Alternatively, the ribs can be made from honeycomb
fibreboard, which is shown in FIG. 4 and has a pair of fibreboard
face sheets 31; only one face sheets is shown in FIG. 4 and that
face sheet is shown partly cut away so that the internal honeycomb
array 33 is visible. The honeycomb connects together the face
sheets 31 and may be made of plastic or paper or cardboard. It is
glued to the face sheets 31 in a known manner. Again, it possible
to build up a number of sheets and honeycomb layers in a unitary
corrugated fibre board so that three or more sheets 31 are included
in each rib, each adjacent pair of sheets sandwiching between them
a honeycomb layer.
[0050] Turning back to FIGS. 1 and 2 and dealing with the case in
which the ribs are made of corrugated fibreboard, the flutes 29 in
the ribs may extend in horizontal, vertical, axial or lateral
directions or diagonally within the helmet. The flutes in alternate
lateral ribs 1 extend horizontally (i.e. in the direction between
the two sides of the helmet) and such flutes resist especially
lateral forces on the helmet. The flutes in the other lateral ribs
16 extend vertically and such flutes resist vertically acting
forces. Likewise in some of the axial ribs 14, the flutes extend
horizontally which are resistant to forces impacting on the front
or rear of the helmet while the flutes on the other ribs extend
vertically and such flutes resist vertically acting forces.
Generally, alternate ribs should have vertically-extending flutes
and the remaining ribs should have horizontally-extending flutes,
although the two central axial ribs 14 may have vertically
extending ribs to resist forces exerted down onto the crown of the
helmet.
[0051] When the ribs are made of the honeycomb material shown in
FIG. 4, the honeycomb cells will extend at right angles to the
plane of the ribs.
[0052] The impact resistant shell shown in FIGS. 1 and 2 can absorb
impact forces from any direction and can crumple as a result,
thereby absorbing the energy of the impact and protecting the
user's head.
[0053] In order to provide waterproofing to the fibre board, an
outer shell or layer 50 (see FIG. 6) can overlay the shell 10 shown
in FIGS. 1 and 2 and which can be fastened to the shell 10, either
permanently or temporary. The outer shell 50 should be provided
with ventilation holes (not shown) that preferably line up with the
spaces between the ribs 14, 16 of the shell 10. In addition, the
cardboard used to make the shell 10 may be waterproof by the
application of a waterproofing or water resistance layer (not
shown).
[0054] The outer shell 50 may be made of acrylic material but it
could also be made of other materials for example, polypropylene or
ABS having a stiffness coefficient higher than that of the material
used to make the impact resistant shell 10 and so absorbs part of
the initial shock waves when an impact occurs. Slots 52 may he
provided in the outer shell in order to attach straps (not shown)
that can be secured under the user's chin to hold the helmet on the
user's head
[0055] An inner shell 55 may be provided between the user's head
and the cavity 30 within the impact resistant shell 10 in order to
provide comfort to the user, to dissipate forces being transmitted
through the edges of the ribs 14, 16 directly to the user's head
and to ensure that the helmet fits snugly. The inner shell may be
made of padding, for example a layer of foam and or woven or
non-woven fabric.
[0056] As is evident from the discussion above, the impact
resistant shell 10 shown in FIGS. 1 and 2, when made with the ribs
of corrugated fibreboard, provides strength and impact resistance
by means of the flutes within corrugated material. In addition
impact strength is provided by holding the ribs in a fixed array of
4-sided cells 23, each cell having an axis that extends away from
the inner cavity 30 of the helmet and generally radially outward
from the cavity. In the case of the ribs being made of the
honeycomb material shown in FIG. 4, the strength of the helmet will
mostly be provided by this array of 4-sided cells, with the
honeycomb pattern within the ribs resisting the collapse of the
ribs and thereby maintaining the face sheets 31 in a space-apart
parallel configuration, which increases the impact resistance of
the individual ribs. In a variant of the cellular structure just
described, the shell 10 may be made of an array of cylindrical
tubes (see FIGS. 7 and 8) that are arranged in a dome shape and the
under surface (not shown) forms a head cavity. The tubes 100 are
collected in array with the inner ends of the tubes lying at
different elevations in order to provide the shell with a hollow
dome-shape. The axis of the various tubes shown in FIG. 9 all
extend vertically and are intended to resist vertical forces.
However, they can be embedded in a matrix so that they extend in
different directions from the head in order to provide protection
against forces from different directions.
[0057] The tubes, instead of being cylindrical, may be
frustoconical, which has the advantage that, when the tubes are
gathered together with the larger faces .phi.x (see FIG. 8)
pointing outwardly and the smaller faces .phi.y pointing inwardly,
the axes of the frusto cones point in different radial
directions.
[0058] The tubes 100 are hollow and are generally made of fibre
board such as paper or cardboard. Tubes made of this configuration
can be incredibly strong and can transmit an impact force directly
to the user's head without absorbing it. In order to provide some
measure of impact absorption, a crumple zone may be introduced in
the side walls of the tubes. So that the tubes crumple within their
own diameter, it is preferred that the crumple zone is helical in
shape and may be formed, as can be seen in FIG. 8, by helically
arranged holes 102.
[0059] The tubes 100 formed into an impact resistant shell may be
incorporated into a helmet with an outer shell 50 and padding 55
(see FIG. 6).
[0060] The outside and inside surfaces of an impact resistant shell
formed from an array of tubes 100 may be sanded to provide the
hollow dome shape.
[0061] Turning finally to FIGS. 9a and 9b, an arrangement is shown
that can detect when a helmet has been subject to impact forces (or
shock) exceeding a threshold, indicating that the helmet should be
replaced or at least the impact resistant shell 10 should be
replaced. As shown in FIG. 9a, which shows the whole shock
indicator; the indicator includes a central chamber 124 having a
number of shock indicator flasks 120 spaced around it and
preferably evenly spaced around it. FIG. 9b, is a schematic drawing
showing one of the flasks 120 and part of the central chamber 124.
Each flask includes a space 122 that is filled with coloured liquid
that communicates with the central chamber 124 via a capillary bore
128. The common chamber 124 is initially empty. Because of the size
of the capillary bore 128 and the viscosity of the liquid, the
liquid is generally retained within the space 122. However, if a
particular flask is subject to an acceleration or deceleration (in
the case of the orientation shown in FIG. 9a in the vertical
direction), the coloured liquid can be forced through the capillary
bore into the previously empty common chamber 124. The presence of
the coloured liquid within the chamber 124 indicates that the flask
has been subject to excessive shock and that the helmet therefore
needs replacing. The liquid may be such that it adheres to the
walls in the common chamber 124 thereby clearly showing that one of
the flasks 120 has been subject to an excessive shock. The
indicator of FIGS. 9a and 9b can be incorporated into a holder that
fits into a cavity within the helmet (not shown) and is held within
that cavity by latches (again not shown). The indicator 120 can be
small (of the order of a few centimetres) and so it can easily be
accommodated in a relatively small cavity within a helmet. The
common chamber 124 can be smaller than shown. A transparent or
translucent lens (not shown) may be provided on the outside of the
helmet to view the common indicator chamber 124; the magnification
makes it easier to see whether or not liquid is located within the
chamber 124.
* * * * *