WO2021078983A1

WO2021078983A1 - Helmet

Info

Publication number: WO2021078983A1
Application number: PCT/EP2020/079966
Authority: WO
Inventors: Maximilian Edward Vereker WAKEFIELD
Original assignee: Wakefield Maximilian Edward Vereker
Priority date: 2019-10-25
Filing date: 2020-10-23
Publication date: 2021-04-29
Also published as: WO2021078983A9; GB2588463B; GB2588463A; GB201915548D0

Abstract

The present disclosure describes a helmet (10) comprising a liner (20), a shell (22) attached to the liner, and a damage detector for detecting damage to the helmet from an impact, wherein the damage detector comprises: a first conductor (26) on an interior surface of the shell; and a second conductor (28) on an exterior surface of the liner, wherein in an intact state, the first and second conductors are separated by a separation distance to form an open circuit, and in an impacted state, the first and second conductors form a closed circuit at a point of impact to the shell.

Description

HELMET

Field

The present disclosure relates to improvements in helmets that protect a wearer in the event of an impact with a foreign object.

Background

The term “helmet” may be used interchangeably with the term “headgear”, and generally covers protective articles to be worn on a user’s head to protect the user from an impact with a foreign object. After an impact, it is not always possible to determine whether the helmet is safe for use.

The present disclosure aims to improve on the prior art.

Summary

According to an aspect of the present disclosure, there is provided a helmet comprising a liner, a shell attached to the liner, and a damage detector for detecting damage to the helmet from an impact, wherein the damage detector comprises: a first conductor on an interior surface of the shell; and a second conductor on an exterior surface of the liner, wherein in an intact state, the first and second conductors are separated by a separation distance to form an open circuit, and in an impacted state, the first and second conductors form a closed circuit at a point of impact to the shell.

The term “impacted” may be used herein to define a state of the helmet that is potentially degraded and may not be safe for use. The helmet may not necessarily be damaged but may at least require an investigation to determine if it is safe for use. Providing an open circuit for the intact state and a closed circuit for the impacted state reduces the power consumption required to implement the damage detector.

The first conductor and/or the second conductor may each comprise a conductive coat substantially covering respectively the interior surface of the shell or the exterior surface of the liner. In this way, almost complete coverage can be provided such that impacts almost anywhere on the shell can be detected. The conductive coat may be formed by metallic spray deposition. As a result, the manufacturing burden may be reduced since metallic spray deposition is a comparatively quick and easy way to apply the first and second conductors.

The helmet may comprise a separator between the shell and the liner to maintain a separation distance between the first and second conductors in the intact state, wherein the separator may be made from an electrically insulating material. The separator reduces the risk of false indications that the helmet is an in an impacted state. The separation distance may be constant (or substantially constant) across the entire helmet. Alternatively, the separation distance may vary depending on the location on the helmet in order to provide more or less sensitivity to impacts at more sensitive areas, for instance the temple area.

The separator may include a plurality of elongate fibers displaced from one another across the liner. The elongate fibres provide a comparatively simple structure that is easier to manufacture than other forms of separator.

The separator may include a plurality of pads. Pads are another simple structure that can be used alternatively to or in addition to the elongate fibres. Using the pads in addition to the elongate fibres enables more control over the sensitivity of detecting that the helmet is in an impacted state since more resistance to shell deformation can be provided in certain areas and less resistant in other areas.

The plurality of fibers may be made from a material having a hardness greater than the liner to penetrate the liner in the impacted state. The separator being able to penetrate the liner in the impacted state helps to reduce rotation of the head. This is achieved since the fibres penetrate the liner but provides a bearing function where the shell can slip over the separator so that increased rotation of the impact is absorbed between the shell and the liner, rather than being transmitted to the head of the wearer.

The plurality of fibres may be made from a material having a hardness less than or equal to the liner to at least partially absorb the impact in the impacted state. The fibres having a hardness less than or equal to the liner enables them to absorbed at least partially the impact in the impacted state to help reduce damage to the liner. The plurality of pads may be made from a material having a hardness less than or equal to the liner to at least partially absorb the impact in the impacted state.

The damage detector may comprise a temperature sensor arranged to provide a signal for indicating that the helmet is in an impacted state in response to detecting a temperature of below about -20°C and/or above about +50°C. Below about -20°C and above about 50°C would render the helmet potentially unsafe due to material degradation outside this range.

The helmet may further comprise a chin strap connected to the helmet at one end by a fastener, wherein the damage detector comprises an electrical switch coupled to the fastener, the electrical switch having an intact state when the fastener is connected to the helmet, and an impacted state when the faster has been removed from the helmet, wherein the electrical switch is arranged to transition between a closed circuit and an open circuit in response to transitioning from the intact state to the impacted state. In this way, it can be determined whether or not the helmet is safe for use depending on whether or not the chinstrap is still attached to the helmet. Having an open circuit in the intact state and a closed circuit in the impacted state is preferable from an energy consumption perspective.

The separation distance may be between about 0.2mm and about 0.8mm. This range of separation distance is able to detect severe enough impacts to warrant further investigation of the helmet and precludes impacts that are not severe enough.

The separation distance may be between about 0.3 and about 0.5mm.

One or more of the first and second may comprise aluminium. Aluminium is preferable to other conductors, for example copper, due to corrosion resistant properties. Corrosion resistance is important since the helmet will be used in a corrosive environment and also next to the head of the wearer perspiring use.

The helmet may further comprise an indicator arranged to provide an indication in response to detecting the impacted state. The indicator may include a visual indicator arranged to provide the indication at decreasing frequency from a time at which the impacted state has been detected. Decreasing the frequency of visual indication reduces power consumption over time. Furthermore, it is more likely that a user will check the integrity of the helmet immediately after an impact so increased frequency of indication is advantageous immediately after impact.

According to a further aspect of the present disclosure, there is provided a method of manufacturing a helmet as described above, the method comprising forming the damage detector by: applying a first conductor to an interior surface of the shell; applying a second conductor to an exterior surface of the liner; and coupling the shell to the liner such that the first conductor is separated from the second conductor by the separation distance.

The helmet may further comprise depositing the first and/or the second conductors by spray

The first and/or second conductors each may be provided as sets of substantially parallel wires instead of the conductive coat. Parallel wires on the liner may be formed at substantially right angles to parallel wires provided on the shell to form a grid structure. A grid structure may enable location of the damage to be detected increased accuracy.

As a further alternative, one of the conductors may be provided as a conductive coat whereas the other conductor may be provided as substantially parallel wires. The damage detector may be arranged to locate the damage based on which wire forms a closed circuit. Increased accuracy of location detection may also be achieved by using conductive coat as a variable resistor.

It will be appreciated that further embodiments may be provided without departing from the scope of the appended claims.

Brief Description of the Drawings

• Figure 1 shows an illustration of a helmet according to an embodiment of the present disclosure; • Figure 2A shows a cross-section view of the helmet from Figure 1 , and Figures 2B to 2D show manufacturing stages of the helmet;

• Figure 3 shows a cross-sectional view of the helmet of Figure 1 according to another embodiment, and Figures 3B to 3E show manufacturing stages of the helmet;

• Figure 4A and Figure 4B show the helmet from Figure 1 during manufacture;

• Figure 5 shows a cross-section view of the helmet from Figure 1 during operation receiving an external impact;

• Figures 6A and 6B show cross-section view of a section of the helmet from Figure 1 during operation when receiving an impact;

• Figures 7 A to 7B show similar views to Figures 6A and 6B according to further embodiment during operation when receiving an impact;

• Figures 8A and 8B show similar view to Figures 6A and 6B according to a further embodiment during operation when receiving an impact;

• Figure 9 shows a block diagram of a damage detector as shown on the helmet from Figure 1 ;

• Figure 10A shows schematic of a first conductor or a second conductor from a further embodiment of the helmet from Figure 1, and Figures 1B to 10D show similar views to Figures 6A and 6B of the helmet during operation receiving an impact;

• Figure 11 shows the first and second conductors from Figure 10A arranged in a grid pattern;

• Figure 12 shows a block diagram of a damage detector for the embodiment of the helmet from Figure 10A; and

• Figure 13A and 13B show cross-section views of a section of an embodiment of a helmet from Figure 1 in operation when removing the chinstrap from the helmet.

Detailed description

It is noted that that the various embodiments described below are provided for illustrative purposes. Various features from the embodiments may be modified and incorporated into other embodiments without departing from the scope of the disclosure. With reference to Figure 1, a helmet 10 is provided for protecting a head of a wearer in the event of an impact. The helmet 10 includes a chinstrap 12 and a damage indicator 14 the damage indicator is shown with broken lines since it may appear at the rear of the helmet on an exterior face rather than an interior surface. The indicator 14 may include one or more visual indicators 16. In this embodiment, three visual indicators 16 are shown. However, the number of visual indicators 16 may be more or less but preferably there are a plurality thereof the visual indicators 16 may include lights, which may be in the form of light emitting diodes (LED). The LEDs may be provided in different colours. For instance, the LEDs may include a green LED, an amber LED, and a red LED. The green, amber, and red LEDs may be illuminated independently depending on the state of the helmet. Alternative forms of indication are also possible. For instance, one or more LEDs may be provided that flash intermittently when in an impacted state. The frequency of flashing may reduce over time to conserve energy since a user is most likely to check the helmet 10 immediately after an impact.

With reference to Figure 2A the helmet 10 includes a liner 20, a shell 22 attached to the liner 20 and a separator 24. The separator is between the liner 20 and the shell 22 to maintain a separation distance between them.

The liner 20 is used to absorb an impact. The shell 22 is arranged to spread the load of an impact over the surface of the liner 20. The liner 20 may be made from a foam material, which may be a polymeric foam. Example materials may include extended polystyrene (EPS). The shell 22 may be made from a hard plastics material. Example materials may include acrylonitrile butadiene styrene (ABS), polycarbonate plastic, or even a composite material with layers of fibres laid up in an epoxy. The fibres may be made from fibreglass or even Kevlar.

The helmet 10 may also include damage detector. The damage detector may include a first conductor 26 on an interior surface of the shell 22 and a second conductor 28 on an exterior surface of the liner 20. The first and second conductors 26, 28 may be provided as a metallic material. The metallic material may be aluminium. Other conductor materials may be used. However, aluminium is selected here for its corrosion resistant properties. The first and second conductors 26, 28 are of opposite polarity. In this embodiment, the first conductor 26 has negative polarity and the second conductor 28 has positive polarity. However in other embodiments the opposite may be true.

With reference to Figure 2B, the liner 20 has the second conductor 28 applied as a conductive coat substantially covering the exterior surface of the liner 20.

With reference to Figure 2C, the separator 24 is attached to the second conductor 28 on the exterior surface of the liner 20. The separator 24 includes a plurality of elongate fibres 30 displaced from one another around the liner 20. The fibres 30 may have an origin in the vicinity of the crown of the helmet 10. The fibres 30 may be unconnected. In particular, the fibres 30 may allow a crown detection region having an area dictated by the point of origin of the fibres 30. Alternatively, the fibres 30 may be connected at or near the crown to ease the manufacturing burden. In any case, the fibres 30 extend from an origin at or near the crown region and extend toward a rim of the helmet 10.

The separator 24 may be made from an electrically insulating material. In this way, a separation distance between the first and second conductors 26, 28 may be maintained by the separator 24 leaving the first conductor 26 and the second conductor 28 to form an open circuit. The separation distance may be substantially constant around the helmet or may be variable depending on the degree of sensitivity to impacts that is required in different portions of the helmet. For instance, the separation distance may be between about 0.2 mm and about 0.8 mm, or more preferably between about 0.3 mm and about 0.5 mm. To achieve this separation distance, the thicknesses of the fibres 30 is controlled such that the thickness of the fibres 30 is substantially equal to the separation distance at any given point.

With reference to Figure 2D, the shell 22 is shown having the first conductor 26 applied to an interior surface thereof. The first conductor 26 may be provided as a conductive coat substantially covering the interior surface of the shell 22. In this way, almost the entire interior surface may be covered by the first conductor 26. The shell 22 is then attached to the liner 20 such that the first conductor 26 contacts the separator 24. With reference to Figure 3A, a further embodiment is shown which is similar to that shown in Figure 2A. The embodiment of Figure 3A shares many features in common with that shown in Figure 2A unless otherwise described below.

The separator 24’ includes fibres 30’ and pads 32’. There may be a plurality of pads 32’. The pads 32’ may have a thickness substantially equal to the separation distance.

With reference to Figure 3B, the second conductor 28 is applied to the exterior surface of the liner 20.

With reference to Figure 3C, the fibres 30’ are elongate and are displaced from one another around the liner 20.

With reference to figure 3D, the pads 32’ are arranged between the adjacent fibres 30’. The pads 32’ may be used to strengthen the helmet 10 in certain areas. Where both the fibres 30’ and the pads 32’ are used in combination, different materials may be used such that the fibres 30’ and the pads 32’ provide difficult functions. For instance, as described in more detail below, if the pads 32’ or fibres 30’ are made from a material having a hardness greater than the liner 20, the pads 32’ or fibres 30’ may penetrate the liner to reduce rotation of the head of a wear during a collision that has a high degree of rotation. However, if the fibres 30’ or pads 32’ are made from a material having a hardness less than or equal to that of the liner 20, the fibres 30’ or pads 32’ may help to absorb the impact to reduce damage to the liner 20. Using materials of different hardness for the pads 32’ and fibres 30’ incorporates both the liner damage reduction and the reduced rotation features. In a case of a hybrid separator including pads having a comparatively low hardness and the fibres having a comparatively high hardness, the pads may have a thickness greater than fibres. For instance, the fibres 30, 30’ may have a thickness of less than the separation distance, and the pads 32, 32’ may have a thickness of substantially equal to the separation distance. The same is true for the converse situation where the fibres 30, 30’ have a comparatively low hardness and the pads 32, 32’ have a comparatively high hardness. In this case, the fibres 30, 30’ have a thickness substantially equal to the separation distance, and the pads 32, 32’ have a thickness less than the separation distance. In this way, the component of the separator 24 having comparatively low hardness can function to absorb the impact and the comparatively hard component can then function to absorb the rotation. In other embodiments, fibres 30, 30’, and pads 32, 32’ may be made from materials that both have either a hardness that is greater than the liner 20 or is substantially equal to or less than the liner 20.

With reference to Figure 3E, the pads 32’ may be used independently from the elongate fibres 30’ such that the separator 24 comprises the pads 32’ to maintain the separation distance between the first conductor 26 and the second conductor 28.

With reference to Figure 4A, the first conductor 26 may be applied to the shell as a conductive coat formed by metallic spray deposition. Similarly, with reference to Figure 4B, the second conductor 28 may be applied as a conductive coat on the exterior surface of the liner 20 by metallic spray deposition.

With reference to Figure 5, during use the helmet 10 may experience an impact from a foreign object 34. Prior to impact, the helmet 10 is in an intact state. In the intact state, the first and second conductors 26, 28 are separated by the separation distance. In this way, the first and second conductors 26, 28 may act as the switch, and form an open circuit. Once hit, the helmet 10 is in an impacted state. In the impacted state, the first and second conductors 26, 28 may move together as a result of the separation distance reducing when the shell 22 deforms towards, and potentially against, the liner 20. In the event of an impact that is of sufficient force, the first and second conductors 26, 28 may contact each other and form a close circuit at point of impact on the shell 22. If the impact is large enough, the closed circuit may be permanent, or may be temporary if the impact is not quite as severe.

With reference to Figure 6A and Figure 6B, there is shown a detailed section view representing the impact from Figure 5.

Figure 6A shows the shell 22 in a non-impacted state where the first and second conductors 26, 28 have a separation distance “S” therebetween. The separation distance S is maintained by the separator 24.

With reference to Figure 6B there is shown the shell 22 during, or after, the impact. The shell 22 is shown deformed such that the first conductor 26 is in contact with the second conductor 28 between the adjacent parts of the separator 24, which in this case may be fibres 30, 30’ (see Figures 2C and 3C). In this case, the fibres 30, 30’ have a material having a hardness less than or equal to that of the liner 20. In this way, the fibres 30, 30’ at least partially absorb the impact in the impacted state. In this way damage to the liner 20 is reduced. Whilst Figures 6A and 6B are shown with reference to the fibres 30, 30’, the same operation will be true if the separator 24 were to use the pads 32’ alone, or in addition to, the fibres 3030’.

Figure 7 A and 7B show similar views to those in Figures 6A and 6B. Figure 7A shows a view of the helmet 10 in an intact state were a separation distance S is maintained between the first and second conductors 26, 28.

With reference to Figure 7B, the shell 22 is shown during, or after, the impact and has deformed toward the liner 20. The deformation is between adjacent portions of the separator 24 which in this case may be adjacent fibres 30, 30’. In this instance, the fibres 30, 30’ may be made from a material having a hardness greater than that of the liner 20. In this way, the fibres 30, 30’ may be able to penetrate the liner 20 in the impacted state. Penetration of the liner 20 by the separator 24 may help to reduce rotation of the head of the wearer. Whilst Figures 7 A and 7B have been described with the separator 24 made up of fibres 30, 30’, the same operation could be achieved by using pads 32’ instead of, or in in addition to, the fibres 30, 30’. In this way, the plurality of pads 32’ may be made from a material having hardness less than or equal to the liner 20 to at least partially absorb the impact. Alternatively, the pads 32’ may have a material having a hardness greater than that the liner 20 to penetrate the liner 20 during an impact and act as a bearing surface for the shell 22 to slide over.

It will be appreciated, that whilst the fibres 30, 30’ and pads 32’ when used in combination may be made from materials having similar properties or different properties of hardness. For instance, the fibres 30, 30’ may be made from a material having hardness greater than that the liner 20 and the pads 32, 32’ may be made from a material having a hardness less than or equal to that of the liner 20. In this way, the separator may both reduce damage the liner 20 in certain areas and reduce rotation of the head of a wearer.

Specific materials may be any material to achieve the hardness requirements. For instance, the comparatively hard material may be a plastics material, and may be a polymer. The material may be acrylonitrile butadiene styrene (ABS), polycarbonate plastic, or even a composite material with layers fibres laid up in an epoxy, may be used. The fibres may include fibreglass or even Kevlar fibre. For the material having comparatively low hardness, a foam material may be used. For instance, the foam may be a polymeric foam. The foam may be extruded polystyrene (EPS) or a polyurethane foam.

Figures 8A and 8B show similar views to those of 6A and 6B. In Figure 8A the shell 22 is provided with a plurality of recesses 36 that sink into the interior surface. The first conductor 26 need not be provided within the recesses 36. Instead, the recesses 36 accommodate the separator 24. The liner 20 may also include protrusions 38 rising from the exterior surface. The protrusions 38 may be sized to complement the recesses 36. The protrusions 38 may have substantially parallel sides like the recesses 36 and may have a clearance distance therebetween. The second conductor 28 need not be provided on the protrusions 38, but on the exterior surface of the liner 20 from which the protrusions 38 protrude. In this way, an outermost surface of the protrusions is further away from a head of a wearer than the exterior surface of the liner 20. The separator 24 may be attached to the outer surface of the protrusions 38.

With reference to Figure 8B, the helmet 10 is shown in an impacted state. In particular, the shell 22 has deformed towards the liner 20 and the separator 24 has been deformed to have a reduced thickness such that the separation distance S has reduced to substantially zero. In this way, the first second conductors 26, 28 are in contact with each other to form a closed circuit.

Operation of the damage detector may be described best with reference to Figure 9.

The damage detector may include a detection circuit 40, a processing module 42, and the indicator 14 (Figure 1). The damage detector may be formed as one unit or may be formed as separately unit.

The detection circuit 40 may include a power supply 44, a first input terminal 46 and a second input terminal 48. The first input terminal 46 may be a negative input terminal and may be connected to the first conductor 26. The second input terminal 48 may be a positive input terminal may be connected to the second conductor 28. However, the present embodiment is not limited to this particular polarity since the opposite may be true.

The detection circuit 40 may also include a resistor 50. The resistance of the resistor 15 is known. The detection circuit 40 may also include a voltmeter 52. The voltmeter 52 may provide an input to the processor device 42. The processor 42 may include its own memory or may be connected to an external memory 54. The processing device 42 may be arranged to process instructions stored on a non-transitory computer readable medium to determine whether or not the helmet 10 is in the intact state or the impacted state depending on a reading from the voltmeter from the detection circuit 40. In the even that an impact is only temporary, the impact is stored in the memory 54. In this way, the indictor 14 can provide an indication of the impact following the impact even if the first and second conductors 26, 28 revert back to forming an open circuit. A severe impact resulting in a permanently closed circuit between the first and second conductors 26, 28 need not use the memory 54.

Whilst the detection circuit 40 has been described in the foregoing manner, other similar an alternative circuits may be used provided they realise the same purpose of detecting whether the switch provided by the first and second conductors 26, 28 is open or closed.

The damage detector may comprise a temperature sensor 56. The temperature sensor 56 may be integral with the processing device 42 for ease of assembly. The temperature sensor 56 may be arranged to provide a signal for indicating that the helmet 10 is in an impacted state or the intact state. A normal temperature threshold for the helmet 10 may be considered to be anywhere within the range of about -20°C and above about 50°C. Within this range, the helmet 10 may be considered to be in an intact state. Outside of this range and helmet may be considered to be in an impacted state.

An alternative embodiment to the foregoing embodiment is described with reference to Figures 10A to 12. Many of the features of the helmet 10 from this embodiment are the same as those described previously so any feature other than those described below should be assumed to be the same. With reference to Figure 10A, the first and the second conductors 26, 28 may be provided as substantially parallel wires. The wires may be provided as a single continuous wire having loops at ends thereof and substantially straight portions therebetween. Figure 10A shows a cross-section line AA for use in interpreting Figures 10B to 10D.

Figure 10B shows the shell 22 having the first conductor 26 attached to an interior surface thereof. The first conductor 26 may be provided as a plurality of parallel wires or may be provided as a conductive coating applied substantially to the entire interior surface of the shell 22. The liner 20 may include the second conductor 28 formed as the parallel wires. An exterior surface of the liner 20 may include a plurality of raised regions 56 and recessed regions 60. The raised regions 58 may include a notched exterior surface having an indent 62 therein. The recessed region 60 includes a lump 64 and a depression 66 surrounding the lump 64. The lump 64 is provided with the second conductor 28 which loops around the raised regions 58 as shown in Figure 10A.

With reference to Figure 10C, an impact from the foreign object 34 causes the shell 22 to deform against the liner 20. In this way, the first conductor 26 contacts the second conductor 28 at a point of impact forming a closed circuit. The indent 62 enables the raised region 58 to deform laterally during the impact to allow the first conductor 26 to contact the second conductor 28. With reference to Figure 10D, after the impact the shell 22 may revert to its original position prior to the impact. However, the first conductor 26 may remain in contact with the second conductor 28 if the impact is large enough. However, if the impact is of a lower force, it may be the case that the first conductor 26 only temporarily contacts the second conductor 28 and returns to its original position with the shell 22.

With reference to Figure 11 , it may be the case that the first conductor 26 is provided also as a series of substantially parallel wires. Accordingly, Figure 11 shows the first conductor 26 and the second conductor 28 each as a set of substantially parallel wires intersecting substantially at right angles to form a grid with respect to each other.

Operation of this embodiment is best described with reference to the block diagram shown in Figure 12. The processor 42 may receive inputs from the first conductor 26 and the second conductor 28 by monitoring each of the wires thereof. The processor 42 may be configured to process instructions able to identify which wire of the respective first and second conductors 26, 28 formed the close circuit. In this way, it may be possible to identify a location of the impact.

With reference to figures 13A and 13B, a cross-section view of a section of the helmet 10 is shown.

In Figure 13A, the chinstrap 12 is shown attached to the helmet using a fastener 70. The fastener 70 may be a rivet. Other forms of fastener 70 may be used but fasteners 70 that may be forced into the helmet are preferred. The fastener 70 may be specifically attached to an interior surface of the liner 20. The helmet 10 may also include a third conductor 72 and a fourth conductor 74 attached to an interior surface of the liner 20 or embedded therewithin. An electrical switch 76 may be provided between, and connected to, the third and fourth conductors 72, 74. The electronic switch 76 may be coupled to the fastener 70. lin particular, when the fastener 70 is inserted into the liner 20 the fastener 70 contacts the switch 76 and maintains the switch in an open position to form an open circuit between the third and fourth conductors 72, 74. This configuration is more energy efficient. However, it will be appreciated that the fastener 70 may contact the electrical switch 76 to maintain the switch 76 in a closed position forming a closed circuit with the third and fourth conductors 72, 74.

When the chinstrap 12 is connected to the helmet 10, the switch 76 is said to have an intact state. With reference to Figure 13B, when the chinstrap 12 is removed from the helmet 10 the fastener 70 is removed. The fastener 70 may be removed by an exterior force. When the fastener 70 has been removed from the helmet 10 the switch 76 is said to be an impacted state. In this embodiment, in the impacted state the switch 76 is in a closed position such that the third and fourth conductors 72, 74 form a closed circuit. It will be appreciated that the electrical switch 76 is arranged to transition between the close circuit and the open circuit in response to transitioning from the intact state of the impacted state.

It will be appreciated that providing the first and second conductors 26, 28 with the separation distance S therebetween results in an open circuit when the helmet 10 is in an intact state and a close circuit when the helmet 10 is an impacted state. It will be appreciated that the intact state associated with the open circuit between the first and second conductor 26, 28 is a more energy efficient form of damage detection since no power is consumed unless the helmet 10 is considered to be in an impacted state. The indicator 14 (Figure 1) may be arranged to provide an indication in response to detecting the impacted state. The indicator may include the visual indicator 16 to provide the indication. The indication may occur as a constant illumination of light or may occur as intermittent flashes of light. Intermittent flashes of light may be provided at a constant frequency reducing frequency to save battery power.

It will be appreciated that the foregoing embodiments are by no way limiting and that the scope of protection is defined by the following claims.

Claims

CLAIMS:

1. A helmet comprising a liner, a shell attached to the liner, and a damage detector for detecting damage to the helmet from an impact, wherein the damage detector comprises: a first conductor on an interior surface of the shell; and a second conductor on an exterior surface of the liner, wherein in an intact state, the first and second conductors are separated by a separation distance to form an open circuit, and in an impacted state, the first and second conductors form a closed circuit at a point of impact to the shell.

2. The helmet of Claim 1 or Claim 2, wherein the first conductor and/or the second conductor each comprises a conductive coat substantially covering respectively the interior surface of the shell or the exterior surface of the liner.

3. The helmet of Claim 2, wherein the conductive coat is formed by metallic spray deposition.

4. The helmet of any preceding claim, wherein the helmet comprises a separator between the shell and the liner to maintain a separation distance between the first and second conductors in the intact state, wherein the separator is made from an electrically insulating material.

5. The helmet of Claim 4, wherein the separator includes a plurality of elongate fibers displaced from one another across the liner.

6. The helmet of Claim 4 or Claim 5, wherein the separator includes a plurality of pads.

7. The helmet of Claim 5 or Claim 6, wherein the plurality of fibers are made from a material having a hardness greater than the liner to penetrate the liner in the impacted state.

8. The helmet of Claim 5 or Claim 6, wherein the plurality of fibres are made from a material having a hardness less than or equal to the liner to at least partially absorb the impact in the impacted state.

9. The helmet of Claim 6, or any claim dependent thereon, wherein the plurality of pads are made from a material having a hardness less than or equal to the liner to at least partially absorb the impact in the impacted state.

10. The helmet of Claim 6, or any claim dependent thereon, wherein the plurality of pads are made from a material having a hardness of greater than the liner to penetrate the liner in the impacted state.

11. The helmet of any preceding claim, wherein the damage detector comprises a temperature sensor arranged to provide a signal for indicating that the helmet is in an impacted state in response to detecting a temperature of below about - 20°C and/or above about +50°C.

12. The helmet of any preceding claim, wherein the helmet further comprises a chin strap connected to the helmet at one end by a fastener, wherein the damage detector comprises an electrical switch coupled to the fastener, the electrical switch having an intact state when the fastener is connected to the helmet, and an impacted state when the faster has been removed from the helmet, wherein the electrical switch is arranged to transition between a closed circuit and an open circuit in response to transitioning from the intact state to the impacted state.

13. The helmet of any preceding claim, wherein the separation distance is between about 0.2mm and about 0.8mm.

14. The helmet of any preceding claim, wherein the separation distance is between about 0.3 and about 0.5mm.

15. The helmet of any preceding claim, wherein one or more of the first and second comprises aluminium.

16. The helmet of any preceding claim, further comprising an indicator arranged to provide an indication in response to detecting the impacted state.

17. The helmet of Claim 16, wherein the indicator includes a visual indicator arranged to provide the indication at decreasing frequency from a time at which the impacted state has been detected.

18. A method of manufacturing a helmet according to any preceding claim the method comprising forming the damage detector by: applying a first conductor to an interior surface of the shell; applying a second conductor to an exterior surface of the liner; and coupling the shell to the liner such that the first conductor is separated from the second conductor by the separation distance.

19. The method of Claim 17, further comprising depositing the first and/or the second conductors by spray.