TECHNICAL FIELD

The invention relates to a safety indicator device. The invention relates particularly, though not necessarily, to a safety indicator device for mounting onto a polygonal fastener, such as a wheel nut, or other component having a multi-angular peripheral surface.

BACKGROUND

Safety indicator devices are widely used on heavy goods vehicles to indicate the occurrence of loosening of individual wheel nuts. Such devices are described in earlier patent specifications. For example, GB2242720A describes a safety indicator device comprising a body having a bore formed with a plurality of equispaced grooves. The grooves enable the device to be mounted onto a wheel nut in a manner that inhibits relative rotation of the device and the wheel nut. Corners of the wheel nut engage with the grooves, so the device only rotates upon rotation of the wheel nut, such as when the wheel nut loosens, thereby indicating rotation. More recently, GB2560950A describes a safety indicator device comprising a body having a pair or deformable tapered regions. Like the grooves, the tapered regions enable the device to be mounted onto a wheel nut in a manner that inhibits rotation of the device and the wheel nut relative to one another. The tapered regions allow the safety indicator device to fit snuggly over the wheel nut, thus gripping the wheel nut.

Safety indicator devices may also be used to indicate overheating of a wheel or parts thereof. Overheating may be caused by a fault within a braking system. Various problems may arise as the result of overheating of the wheel, including increased tyre wear, increased tyre pressure, carbonisation of the tyre, damage to the tyre valve (which may cause air to leak from the tyre) and component failures. Known devices may fall off the wheel nut in the event of overheating of the wheel, so that a missing device indicates overheating. A problem with this solution is that a missing device may have been inadvertently knocked off or otherwise removed from the wheel nut, rather than having fallen off due to overheating.

It is an object of embodiments of the invention to at least mitigate one or more problems associated with known arrangements.

SUMMARY OF THE INVENTION

According to the invention, there is provided a safety indicator device for mounting onto a fastener, such as a wheel nut, the device comprising first and second parts fixable in relation to one another at least when the first part is mounted onto the fastener, the first part having a body through which extends a bore configured to releasably mount the first part onto the fastener such that movement of the first part relative to the fastener is inhibited and the first part being meltable at a higher temperature than the second part. The device may be used to indicate loosening of a wheel nut of a vehicle. Additionally, or alternatively, the device may be used to indicate overheating of a wheel of a vehicle upon melting of the second part or at least a portion thereof.

In certain embodiments, the second part, including a portion thereof, may be receivable within the bore when the first part is mounted onto the fastener. This may fix the first and second parts in relation to one another. In other words, the first and second parts may be configured to allow receipt of the second part, including a portion thereof, within the bore when the first part is mounted onto the fastener. The second part may contact the fastener when the first part is mounted thereon, which may facilitate the conduction of heat from the fastener to the second part.

The second part may comprise a trunk, a head and a neck. The neck may connect the trunk to the head and at least a part of the neck may have a smaller cross-sectional area than that of each of the trunk and the head. The neck may comprise a hinge about which the second part is predisposed to bend. The head may extend away from the bore, at least when the first and second parts are fixed in relation to one another. Optionally, the first part may comprise a recess to receive at least a portion of the head. The recess may comprise a periphery having at least one chamfered or curved edge region to facilitate removal of the head from the recess.

In certain embodiments, the second part may comprise a plurality of spaced apart grooves, or splines, for engaging with a peripheral surface of the fastener when the first part is mounted onto the fastener. The second part may be shaped to conform to at least a region of the periphery of the bore. Additionally, or alternatively, the second part may be deformable to conform to at least a region of the periphery of the bore.

The first and second parts may be coupleable to one another. The second part may comprise a spigot receivable within an aperture of the first part to couple the first and second parts to one another. The spigot may extend from the head and/or the aperture may be a through-hole extending through the first part. In certain embodiments, the spigot may comprise an enlarged end. A length of the spigot between the head and the enlarged end may be greater than a thickness of the first part through which the aperture extends. Additionally, or alternatively, the device may comprise a bonding agent to couple the first and second parts to one another.

Optionally, the first part may be meltable at a temperature of at least 150 °C. The second part may be meltable at a temperature less than 150 °C. The second part may be meltable at a temperature of at least 100 °C.

In certain embodiments, the device may comprise at least one tapered region extending around at least a portion of a periphery of the bore, each of the at least one tapered regions being resiliently deformable to mount the first part onto the fastener. In certain embodiments, one or more of each of the at least one tapered regions may extend around the entirety of the periphery of the bore. The device may comprise a plurality of equispaced grooves or splines extending around at least a portion of a periphery of the bore to mount the first part onto the fastener. The device may comprise a pointer coupled or integral to the body and extending from a side of the body of the first part. The first part may be formed of a resilient material, such as a silicone rubber material. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures, in which:

Figure 1 is a perspective view of a safety indicator device according to an embodiment of the invention;

Figure 2 is a cross-sectional perspective view of the safety indicator device shown in Figure 1 ; Figure 3 is a perspective view of a second part of the safety indicator device shown in Figures 1 and 2; and

Figure 4 is a perspective view of a second part of a safety indicator device according to a further embodiment of the invention.

DETAILED DESCRIPTION

Figures 1 to 3 show a safety indicator device 10 according to an embodiment of the invention. The device 10 is particularly suitable for releasable attachment to a wheel nut to indicate rotation thereof. The device 10 comprises a first part 12 and a second part 14. The first part 12 comprises a body 16 having a bore 18 extending axially through a central region of the body 16. As shown in the illustrated embodiment, the body 16 may be at least substantially annular. Additionally, or alternatively, the bore 18 may be at least substantially annular. A pointer 20 may extend laterally from a side of the body 16. The pointer 20 may to help indicate rotation of the wheel nut. The pointer 20 may be triangular, although other shapes are contemplated, such as trapezoidal and rectangular. The bore 18 is configured to allow the body 16 to be mounted onto the wheel nut. The bore 18 may be configured to allow the body 16 to be mounted onto the wheel nut in any angular orientation relative thereto. In certain embodiments, this is possible owing to a pair of tapered regions 22a, 22b extending circumferentially around a periphery of the bore 18, i.e. the tapered regions extend from the body 16 into the bore 18. Each of the tapered regions 22a, 22b may extend around a portion of the periphery of the bore 18 or may extend around the entirety of the periphery of the bore 18. Each of the tapered regions 22a, 22b varies a diameter of the bore 18 axially, i.e. in a direction that the bore 18 extends through the body 16, to provide a narrowing of the bore 18. Thus, each of the tapered regions 22a, 22b provides a restricted diameter of the bore 18. In the illustrated embodiment, the restricted diameter is defined by respective apexes 24a, 24b of each of the tapered regions 22a, 22b. To this end, a profile of each of the tapered regions 22a, 22b may be substantially triangular. However, other shapes are contemplated, for example trapezoidal. As shown in the illustrated embodiment, the restricted diameter may be constant about a circumference of the bore 18.

Each of the tapered regions 22a, 22b may be formed of a resilient material, such that the tapered regions 22a, 22b are sufficiently deformable to allow the bore 18 to fit snuggly over a peripheral surface of the wheel nut. As such, each of the tapered regions 22a, 22b may be resiliently, i.e. elastically, deformable. At least the tapered regions 22a, 22b may be made from a resilient rubber material, for example a silicone rubber material. The inherent resilience of the tapered regions 22a, 22b may cause each to impart a gripping force on the wheel nut when the wheel nut is received in the bore 18, to securely mount the first part 12 onto the wheel nut. The tapered regions 22a, 22b allow for mounting of the first part 12 onto the wheel nut such that a rotation of the device 10 relative to the wheel nut is substantially prevented or is at least inhibited. Thus, the position of the pointer 20 relative to the wheel nut should remain the same as that selected by a user when mounting the device 10 to the wheel nut. Thus, the direction in which the pointer 20 points will only change if the wheel nut rotates, as will occur if the wheel nut loosens. In certain embodiments, the whole of the first part 12 may be formed from the resilient rubber material. As such, the first part 12 may be made as a single piece.

Figure 3 shows the second part 14 removed from the first part 12. The second part 14 is fixed in relation to the first part 12, at least when the first part 12 is mounted onto the wheel nut. As shown in the illustrated embodiment, the second part 14 may be receivable within the bore 18 when the first part 12 is mounted onto the wheel nut. To this end, the second part 14 may be insertable between the periphery of the bore 18 and the wheel nut, enabling the second part 14 to be wedged therebetween. Subsequently, the second part 14 may be fixed in relation with the first part 12 by the gripping forced imparted by the tapered regions 22a, 22b. As such, the second part 14 may be fixed in relation with the first part 12 by mounting of the first part 12 on to the wheel nut. The second part 14 may be shaped to conform to at least a region of the periphery of the bore 18 (best shown in Figure 2), as this may help the second part 14 to maintain fixed relation with the first part 12 and/or inhibit distortion of the first part

12 when the second part 14 is received within the bore 18 and the first part 12 is mounted onto the wheel nut. As shown in the illustrated embodiment, the second part 14 may comprise a protrusion 26 receivable between the tapered regions 22a, 22b, the protrusion 26 being shaped to conform to the tapered regions 22a, 22b. Additionally, or alternatively, the second part 14 may deformable, including but not limited to resiliently deformable, flexible, to conform the to conform to at least a region of the periphery of the bore 18 and/or a peripheral surface of the wheel nut.

In certain embodiments, at least a region of the second part 14 may comprise a plurality of spaced apart grooves 28 for engaging with the peripheral surface of the wheel nut. As such, each of the grooves 28 may extend axially over a region of the second part 14 that is exposed to the wheel nut when the second part 14 is received within the bore 18. The grooves 28 may help maintain the relative position of the device 10 and the wheel nut. The first and second parts 12, 14 are meltable at different temperatures, respectively. The first part 12 is meltable at a higher temperature than the second part 14. The first part 12 may be meltable at a temperature of at least 150 °C, e.g. the first part 12 may be meltable at a temperature of approximately 165 °C. The second part 14 may be meltable at a temperature less than 150 °C, e.g. the second part 14 may be meltable at a temperature of approximately 125 °C. In certain embodiments, the second part 14 may be meltable at a temperature of at least 100 °C. However, as the skilled reader will appreciate, the specific temperatures at which each of the first and second parts 12, 14 will melt is not crucial to the invention, only that the second part 14, or at least a portion thereof, will melt before the first part 12. The difference in melting temperatures of the first and second parts 12, 14 may be at least 10 °C. In certain embodiments, the difference in melting temperatures of the first and second parts 12, 14 may be at least 25 °C. The melting temperatures of the first and second parts 12, 14 will be determined by the specific application of a given embodiment of the invention.

The second part 14 may comprise a trunk (or body) 30 and a head 32 (best shown in Figure 3). The second part 14 may further comprise a neck 34 (best shown in Figure 3) connecting the trunk 30 to the head 32. The neck 34, or at least a part thereof, may provide a region of the second part 14 of reduced cross-sectional area, relative to respective cross-sectional areas of the trunk 30 and the head 32. Thus, as the skilled reader will appreciate, the neck 34 may provide a weak or frangible region of the second part 14, relative to the remainder of the second part 14. As such, in use, when the second part 14 experiences a temperature at which it will melt, or at least begin to melt, the second part 14 may divide at the neck 34. In certain embodiments, division of the second part 14 at the neck 34 may cause the head 32 to fall away from the device 10, thereby indicating overheating of the wheel. As shown in the accompanying figures, the head 32 may extend laterally from the trunk 30, i.e. in a direction away from the bore 18, when the first and second parts 12, 14 are fixed in relation to one another. However, in certain embodiments, this may not be the case. At the very least, in embodiments of the invention, the head 24 provides a region of the second part 24 that is visible in use, such that the absence, or alteration in appearance, thereof may indicate the overheating of the wheel.

The second part 14 may comprise a spigot 36 configured to couple the first and second parts 12, 14 to one another. The first part 12 may comprise an aperture 38 to receive the spigot 36. As shown in the illustrated embodiment, the aperture 38 may be a through-hole. However, in certain embodiments, the aperture 38 may be a blind hole. To effect coupling of the first and second parts 12, 14 to one another, the spigot 36 may achieve a friction fit within the aperture 38. The spigot 36 may have an enlarged end 40, which may help to provide the friction fit. In embodiments where the aperture 38 is a through-hole, the spigot 36 may extend through the first part 12 when the first and second parts 12, 14 are coupled to one another. The spigot 36 may extend from the head 24. As such, a length of the spigot 36 extending between the head 32 and the enlarged end 40 may be at least equal to a thickness of the first part 12 through which the aperture 38 extends. The enlarged end 40 may have a width or a diameter greater than a diameter of the aperture 38. As such, the enlarged end 40 may help to couple the first and second parts 12, 14 to one another, by inhibiting pull-through as the enlarged head 40 may provide a shoulder 40a (best shown in Figure 3) to abut a periphery of an opening of the aperture 38. The length of the spigot 36 extending between the head 32 and the enlarged end 40 may achieve a clearance fit within the aperture 38. In certain embodiments, the spigot 36 may retain the head 32 on the device 10 in the event of division of the second part 14 at the neck 34, while allowing the head 32 to hang from the device 10, thereby indicating overheating of the wheel. This means that the first and second parts 12, 14 may be coupleable to one another in a manner that may not fix the first and second parts 12, 14 in relation with one another. Although, in certain embodiments, coupling the first and second parts 12, 14 to one another may fix the first and second parts 12, 14 in relation to one another. The first and second parts 12, 14 may be adhered to one another by an adhesive. More specifically, the trunk 30 of the second part 14 may be adhered to the periphery of the bore 18. The head 24 may be receivable within a recess 42 of the first part 12. This may offer some protection to the head 32, which may help to prevent the head 32 from being inadvertently damaged and/or removed from the device 10. The recess 42 may be shaped to complement the shape of the pointer 20. As such, the head 24 may also be shaped to complement the shape of the pointer 20. However, the head 24 may be shaped to complement the shape of the pointer 20 regardless of whether the recess 42 is provided. As shown in the illustrated embodiment, a chamfered or curved edge region 44 may extend around a periphery of the recess 42. The edge region 44 may inhibit the head 24 from being held in the recess in the event the second part 14 is divided at the neck 34, to help indicate overheating of the wheel. The edge region 44 may help the head 32 to fall free from the recess 42 in the recess in the event the second part 14 is divided at the neck 34, to help indicate overheating of the wheel. To the same end, the head 32 may comprise a complementary edge region 46.

In certain embodiments, the length of the spigot 36 extending between the head 32 and the enlarged end 40 may be greater than the thickness of the first part 12 through which the aperture 38 extends. This may provide an amount of play, i.e. freedom of movement, of the spigot 36 when the spigot 36 is received in the aperture 38. The play may help the head 32 to fall free from the recess 42 and/or hang from the device 10 in the event the second part 14 is divided at the neck 34, to help indicate overheating of the wheel.

The second part 14 may be a different colour to that of first part 12, to help identify the absence, or alteration in appearance, thereof and thus help identify overheating of the wheel.

In use, the user may mount the first part 12 to the wheel nut by insertion of a head of the wheel nut into the bore 18. The second part 14 may be received in the bore 18 prior to insertion of the head of the wheel nut into the bore 18. However, the user may insert the second part 14 into the bore once the first part 12 is mounted onto the wheel nut. This may be helped by the user grasping the pointer 20 and pulling the pointer 20 in a direction away from the bore 18, thus stretching the first part 12 and widening the bore 18 to create a space for receiving the second part 14. The user may align the pointer 20 with a reference mark to help identify rotation of the device 10 and hence rotation of the wheel nut. The reference mark may be a pointer of an adjacent device.

The skilled reader will understand that the dimensions of the device 10 will be determined by the size of the fastener upon which the device 10 is to be mounted. Wheel nuts, for example, are available in different sizes. Two commonly used wheel nut sizes used on heavy goods vehicles are 32mm and 33mm, measured across the flats of the head of the wheel nut. While less common, wheel nut sizes of 30mm, 31 mm and 34mm are also used. Due to the resiliency of the resilient material, the device 10 may be capable of being mounted upon wheel nuts of a range of sizes, e.g. wheel nut sizes ranging from 30mm to 38mm. To this end, the restricted diameter of the bore 18 may be between 29mm and 30mm.

Figure 4 shows the second part 114 according to an alternative embodiment of the invention, to which the foregoing description of the embodiment illustrate in Figures 1 to 3 to 3 applies with like features denoted using reference numerals offset by a factor of 100. As shown in Figure 4, the neck 134 may comprise a hinge 148 to allow bending of the second part 114 for insertion between the periphery of the bore 18 and the wheel nut. The hinge 148 may be the part of the neck 134 that provides the region of the second part 114 of reduced cross-sectional area (i.e. the weak or frangible region). Such an arrangement may improve the ease of manufacture of the second part 114. The terms“fastener” and“wheel nut” may be used interchangeably, although it is to be understand that fastener encompasses more than wheel nuts and includes, but is not limited to, bolts, nuts, Allan bolts and the like. The term“coupleable” is to be understood to mean coupleable by any suitable means, including, but not limited to, push fit, snap fit, friction fit, bonding, adhering and coating. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including in the accompanying claims and drawings). For example, rather than the tapered regions 22a, 22b, the device 10 may comprise a plurality of equispaced grooves or splines extending around at least a portion of a periphery of the bore to mount the first part onto the fastener. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims. Each feature disclosed in this specification (including any accompanying claims and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.