Note: Descriptions are shown in the official language in which they were submitted.
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SAFETY HELMET
This invention relates to a safety helmet.
Safety helmets are commonly worn by, for example, horse riders, cyclists and
motor cyclists, with the aim of reducing injury to the wearer's head in the
event that
he falls, crashes or, for horse riders, is thrown. Safety helmets are also
commonly
worn when participating in certain other sports or activities. A typical
safety helmet
design incorporates a layer or pieces of a compressible or deformable material
located such that, in the event of the wearer's head impacting upon an object,
or an
object hitting the helmet, the compressible or deformable material will deform
to
absorb at least some of the impact forces thereby lessening the risk of injury
to the
wearer. As the deformation of the compressible or deformable material can be
pe~ruanent, it is usually recommended that after such an impact has occurred,
the
helmet is disposed of as its ability to absorb future impact forces may be
reduced.
Alternatively, the helmet may be repaired.
Although disposal or repair is recommended, there are often situations where
the wearer may consider the impact to be of insufficient severity to require
the
helmet to be replaced or repaired, and so a helmet may be used which is not
capable
of serving its intended purpose. There are also situations where helmets are
shared
or used by a number of individuals none of whom may know whether an impact has
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occurred whilst the helmet was being used by another. It is an object of the
invention to provide a helmet user with the ability to determine the impact
history
or impact status of a helmet. One way of achieving this is to provide a
mechanism
whereby a record can be kept of the impacts experienced by a helmet.
According to one aspect of the invention there is provided a helmet
comprising an impact sensor and a memory arranged to store impact data from
the
impact sensor.
It will be appreciated that by appropriate interrogation of the memory, a user
can determine whether or not the helmet has been involved in an impact of
magnitude sufficient to impair the subsequent performance thereof.
The memory may be arranged to store the impact information in a range of
ways. For example, it may record the time and magnitude of each impact
experienced by the helmet. Alternatively, some form of filtering may be
applied so
that only data representative of impacts exceeding a pre-determined threshold
value
are recorded. Although the time of the or~each impact may be recorded, there
may
be occasions when this information is not required and so this data may not be
stored. In a simple embodiment, the memory may be bistable and arranged to
switch
between a first, normal, state and a second, warning, state upon the
occurrence of
an impact or series of impacts greater than a pre-determined value.
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The helmet may further include a warning device adapted to be controlled
using the data stored in the memory.
For example, a warning may be triggered in the event that an impact is sensed
the magnitude of which is greater than a predetermined threshold.
The predetermined threshold may be set by, for example, the helmet
manufacturer, so as to be tailored to, for example, the helmet design and the
intended use thereof.
The warning preferably comprises a visible warning, for example an
appropriately controlled liquid crystal display. Alternatively, a warning
light, for
example an LED arranged to be illuminated in the event of the occurrence of a
large
impact, may be provided. However, other warnings could be used. For example,
a light may be switched off in the event of an impact, rendering the helmet
fail-safe.
Another possibility is to provide an audible warning.
The impact sensor may take a range of forms. In one arrangement it
comprises a layer of a material sensitive to the occurrence of an impact.
The said layer of material may be incorporated into the helmet but could,
alternatively, be retrofitted thereto, if desired. Where intended to be
retrofitted, the
layer may be fitted by, a manufacturer or repairer. Alternatively, a suitable
kit may
be supplied to allow the user to fit the layer to the helmet.
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The layer of material conveniently comprises a layer of quantum tunnelling
composite material. The electrical insulating/conducting properties of such a
material vary when the material is pressed, squashed, twisted or stretched
thus by
measuring the electrical resistance across the layer, a measurement of whether
or not
an impact is occurring and the magnitude of any such impact can be made. The
material may be in sheet form or alternatively may comprise granules mixed
with
and incorporated into the material of part of the helmet. The layer is
preferably
continuous, but could alternatively be discontinuous, for example in the form
of a
plurality of isolated regions or pads.
Although the sensor may take the above described form, it will be appreciated
that this need not be the case and a range of other sensors could be used.
For example, the sensor could be capacitance based. In such an arrangement,
a pair of electrically conductive layers are separated by an electrically
insulating
material. In the event of an impact, the electrically insulating material will
deform,
allowing the electrically conductive layers to be forced closer to one another
thereby
changing the capacitance therebetween. A plurality of discrete, self contained
sensor capacitors may be used instead of a single, larger sensor capacitor, if
desired.
Other possibilities, include the use of piezo electric materials, the
application of a
force to which results in a measurable change in the electrical properties
thereof.
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Other forms of strain gauge could also be used.
Although the provision of a suitable sensor and memory allows a user, by
appropriate interrogation of the memory, to ascertain information relating to
impacts
experienced by a helmet and thus determine whether or not he considers it to
be safe
$ for use, it will be appreciated that other techniques are possible.
In accordance with another aspect of the invention, therefore, there is
provided a helmet, and means associated with the helmet capable of providing
an
indication of the impact status or history of the helmet.
The means may take the form of a sensor and memory as described
hereinbefore. Alternatively, the means capable of providing an indication
could
comprise a component the state of which will change in the event of an impact
exceeding a pre-determined threshold, the state of the component being
apparent to
a user of the helmet. By way of example, the component may be arranged to
change
colour in the event of a large impact, the change of colour providing an
indication
1$ to a user that the helmet has been involved in an impact. Alternatively,
the
component may be designed to break, crack, shatter or otherwise deform in the
event
of an impact in such a manner as to provide an indication that an impact has
occurred. Preferably the component is encased, for example within or behind a
suitable transparent material layer, so as to be contained but visible to a
user.
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Another possibility is to provide one or more reservoirs containing an ink or
dye in
the helmet, the reservoirs being arranged to rupture, break, leak or overflow
in the
event of an impact, the escaped ink or dye providing an indication to a user
of the
helmet's involvement in an impact.
The invention will further be described, by way of example, with reference
to the accompanying drawings, in which:
Figures 1 and 2 are views illustrating helmets in accordance with
embodiments of the invention.
Figure 1 illustrates a helmet of the type commonly worn by motor cyclists
which comprises an outer shell 10, an impact absorbing layer 12 and an inner
liner
14. Between the liner 14 and the layer 12 is a layer 16 of a compressible
material
intended to improve the fit of the helinet on the wearer and to improve
comfort.
Although a range of different materials may be used in the helmet, the shell
10 is
typically of a plastics material, for example a fibre reinforced plastics
material. The
impact absorbing layer 12 is typically of a cellular material, for example a
foamed
plastics material. The layer 16 may be of urethane foam.
When the wearer of the helmet experiences an impact which, in the absence
of the helmet would be an impact to the head, the impact absorbing layer 12
deforms, thereby absorbing at least some of the impact force and reducing the
risk
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of injury to the wearer.
In accordance with the invention, in order to allow monitoring of the
occurrence of such impacts, an impact sensor in the form of a layer 18 of a
material
sensitive to the occurrence of such impacts is provided. In the arrangement
illustrated the layer 18 is located between the outer shell 10 and the impact
absorbing layer 12. It will be appreciated, however, that the layer may be
provided
elsewhere, for example on the outside of the outer shell 10.
The layer 18 is formed from a so-called quantum tunnelling composite
material. Such a rizaterial has the quality that its electrical resistance
varies as the
mechanical load applied thereto varies. The electrical resistance across the
layer 18
is, under normal circumstances, high. However, in the event of an impact
resulting
from, for example, the wearer being involved in a road traffic accident and
his head
impacting upon the road surface or another hard object, the impact force will
temporarily squash or compress the layer 18 thus causing a temporary reduction
in
1 S the electrical resistance across the layer 18.
The top, rear part of the helmet is shaped to define a projection 20 adapted
to house a monitoring unit 22. The unit 22 is an electronic unit arranged to
monitor
the electrical resistance across the layer 18. This may be achieved by
providing
electrically conductive layers on each major surface of the layer 18, the
conductive
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layers being isolated from one another by the layer 18, and by providing
electrical
connections between the unit 22 and the conductive layers, the unit 22
monitoring
the electrical resistance between the connections using any suitable
circuitry. The
unit 22 includes a storage device or memory which is used to store data
representative of the measured resistance values, and hence of the impact
state of the
helmet, over time. It will be appreciated, therefore, that by appropriate
interrogation
of the storage device, a history of events or impacts experienced by the
helmet can
be derived. Such interrogation may be achieved by connecting a suitable device
to
the unit 22 to download data from the storage device.
In addition to storage of the resistance data, the unit 22 is arranged to
compare the resistance data with a stored threshold value to determine whether
or
not an impact has occurred of a magnitude sufficient to render the helmet
unsuitable
for further use. The stored threshold value may be set by the helmet
manufacturer
and will depend, to some extent, upon the helmet design and the intended use
thereof. In the event that the comparison of the resistance data with the
stored
threshold indicates that the helmet has experienced an impact great enough to
render
the helmet unsuitable for further use, a warning is triggered. In the
illustrated
arrangement, the warning takes the form of a display device 24 in the form of
a
liquid crystal display which is controlled to display a suitable message. As
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illustrated, the device 24 is located so as to define part of the wall of the
projection
20 so as to be clearly visible. Alternatively, the warning could make use of a
warning light in the form of a LED operable in the event .that an impact has
occurred.
The unit 22 conveniently includes an internal power source in the form of,
for example, a battery. Obviously, where a warning light is used, there is the
risk
that if the battery runs flat, no warning signal is produced. It may be
preferred to
operate on a failsafe system whereby the impact warning is triggered by, for
example, switching off (rather than on) a warning light. In the event of a
flat
battery, no warning light would be illuminated, and so no impression that the
helmet
is safe would be given. A similar operating technique may be used where the
warning is displayed on a liquid crystal display.
Further possibilities include arranging for the warning light or display to be
illuminated or operated only when, for example, a test button is pressed. With
such
an arrangement, a user could test the helmet before use and note whether or
not a
warning indicative of the impact state of the helmet is produced. Further, it
may be
possible to provide an audible warning instead of or in addition to the
visible
warning.
In the arrangement described hereinbefore, the layer 18 is a separate layer.
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However, this need not be the case. Quantum tunnelling composite materials are
available in granular form which can be incorporated into other materials. For
example, the material may be incorporated into the plastics material of the
outer
shell 10, if desired. Further, in the arrangement described hereinbefore the
layer 18
5 is continuous, providing information relating to the occurrence of impacts
on any
part of the helmet. However, provided a reduction in the sensitivity of the
system
is acceptable, the layer 18 may be discontinuous or may comprise a number of
separate sensor regions or "pads".
A further alternative arrangement is shown in Figure 2. In this arrangement,
10 a helmet of conventional form having a shell 10 and layer 12 is modified by
the
fitting thereof of a layer 18 of quantum tunnelling material and a housing 20
containing a monitoring unit 22 and warning device 24. The layer 18, unit 22
and
device 24 may be permanently or semi-permanently secured in position using any
suitable technique, for example by a suitable adhesive, or may be removably
secured
to the helmet, for example using a drawstring, and operate as described
hereinbefore
to allow monitoring of impacts experienced by the helmet.
The helmet impact monitoring techniques described hereinbefore make use
of electronic sensors and memory units, for example using solid state
components.
It will be appreciated that a number of other electrically operated sensor
techniques
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could be used. For example, piezo electric components could be mounted upon
the
helinet and arranged to act like a strain gauge. In the event of an impact,
the
electrical properties of the components would change and this could be used to
indicate that an impact has occurred. Other types of strain gauge could be
used.
Another possibility is to use one or more capacitors to sense the occurrence
of an impact. By way of example, one or more sensor regions of the helmet may
be
provided with a pair of spaced electrically conductive layers, an electrical
insulator
being located between the conductive layers. In the event of an impact, the
layers
will be forced closer together, the insulator deforming to allow such
movement, with
a consequent change in the capacitance between the conductive layers. The
capacitors may take the form of fairly small, discrete, self contained
components,
if desired. Although the capacitance may be continuously monitored and
readings
stored in a memory, the device may be arranged to be inactive whilst in use,
and
arranged to be connected, periodically, to a reader unit arranged to determine
the
1 S measured capacitance and thereby determine whether or not the helmet is
safe for
use.
It will be appreciated that there is a wide range of other possible ways of
enabling a user to determine whether or not a helmet has been involved in an
impact
which could impair the impact absorbing properties thereof. For example, a
number
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of ink or dye containing packets or cells may be incorporated into the helmet
and
arranged to rupture to allow the ink or dye to bleed therefrom in the event of
a large
impact. The ink or dye would then provide an indication to a user that the
helmet
has been involved in an impact. The packets or cells could be provided at or
close
to the surface of the helmet or located within, for example, the shock
absorbing layer
thereof. Where not located at the surface of the helmet, it may be desirable
to
incorporate, for example, a wicking material to allow passage of the ink or
dye to
a location in which it can be viewed. If desired, a transparent element may be
provided in the helmet to allow inspection to determine whether or not the
helmet
is safe for use.
Alternatively, a component may be incorporated into the helmet, the
component being adapted to change state in the event of an impact, the state
of the
component providing an indication to the user of whether or not the helmet has
been
involved in an impact. By way of example, the component may be of a material
arranged to break, shatter, crack or otherwise deform in a noticeable manner
in the
event of an impact. Alternatively, the component may be arranged to undergo a
change of colour in the event of an impact. In such an arrangement, it may be
desirable to encase or enclose the component, for example within or beneath a
layer
of a transparent material.
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As with the electronic arrangements, the components which enable impact
information presentation may be incorporated upon initial manufacture or may
be
subsequently added to the helmet, either by a manufacturer or by the use of,
for
example, a kit of components.
Although the description hereinbefore is primarily of a helinet intended for
use in motor cycling, it will be appreciated that the invention may be
incorporated
into helmets intended for use in a wide variety of applications, such a horse
riding,
cycling, motor racing or other applications in which helinets are worn to
reduce the
risk of head injury.