The present invention relates to a runflat device for use with a tyre, and associated methods.

Puncture or deflation of a pneumatic tyre of a vehicle can lead to a loss of support and stability which can render a vehicle un-driveable. Devices that are fixed to a wheel inside a pneumatic tyre cavity to support a deflated tyre are variously known as runflat devices or inserts. These devices are annular in shape and typically designed to be located within the wheel and tyre assembly so that a part of the runflat device rests in the drop-centre or‘well’ of the wheel. They can be formed from a number of segments.

When a pneumatic tyre deflates, the tyre wall collapses and the treaded part of the tyre is forced towards the drop-centre of the wheel, where the runflat device is located, to rest on said runflat device. The runflat device therefore prevents the tyre wall from compressing fully and prevents the treaded part of the tyre from coming into contact with the wheel rims and wheel centre. As such, a wheel and tyre assembly containing a runflat device is still able to offer support and thus driveability to the vehicle to which it is fitted even when there is a partial or total loss of air pressure in the tyre. A tyre which has deflated is supported by the runflat device fitted around the circumference of the wheel. More specifically, the treaded part of the tyre is supported by the runflat device. In these circumstances, a runflat condition has been achieved and the runflat device enables the vehicle to continue driving with a loss of tyre pressure, albeit at a reduced speed. This is known as running-flat.

As is known in the field, considerable friction occurs between the inner surface of the treaded part of a tyre, and the supporting surface of a runflat device or insert when a tyre is running- flat (a runflat condition). In order to reduce this friction and resultant heat this generates, and therefore prevent premature wearing of the tyre which would otherwise cause the tyre to break up, the contact surfaces of the runflat device and the tyre are lubricated. Conventional runflat systems typically require lubricant to be manually applied within the inner tyre cavity when fitting the runflat device. There are many disadvantages to this conventional method of lubricating a runflat system. Lubricant applied in this manner tends to cover the entire inside surface of the tyre, the runflat device and inside of the wheel, meaning the runflat device and wheel must be cleaned of any lubricant before re-fitting a tyre and/or a runflat device. This is an extremely messy operation which some fitters refuse to handle due to the laborious nature of the operation and concerns over the potentially hazardous nature of lubricant which has been in contact with the tyre over a prolonged period of time. As lubricant applied in this manner covers the entire inner surface of the tyre, repair of tyre punctures by ordinary methods is also precluded, meaning punctured tyres generally have to be discarded.

Once this cleaning operation has taken place, it is necessary for a fitter to replace the lubricant before refitting the runflat device and/or tyre. Some fitters will choose not to do this, either because they do not have lubricant available or because of the inconvenience and potential health hazards of having to clean the runflat device and wheel if the tyre requires replacement in future. As a result, it is common that the runflat system is fitted without any accompanying lubrication, causing the tyre to fail prematurely when in a runflat condition thus presenting considerable danger when the vehicle is being driven.

Also known in the art is a runflat system which attempts to resolve some of the issues posed by the above conventional method of applying lubricant to a runflat system, by affixing bags containing lubricant to the outer surface of a runflat device. This system is designed such that, upon achieving a runflat condition, the bags burst under the weight of a vehicle, thereby releasing lubricant into the cavity between the runflat device and the inner surface of the tyre. A runflat system of this design provides some control over the release of lubricant into a runflat system, however the extent of this control is limited by a number of design constraints.

As the runflat system is designed to release lubricant instantaneously upon achieving a runflat condition, as a direct result of the vehicle load being applied to the runflat system, there is potential for lubricant to be released into the system under circumstances where lubrication is not required. An example of such a circumstance is when a tyre deflates whilst the vehicle it is supporting is stationary, and there is no requirement for the vehicle to travel to an alternative destination for repair. In such a circumstance, the release of lubrication into the runflat system is particularly undesirable as it complicates the process of replacing the tyre, and precludes repair of the tyre by ordinary methods. Furthermore, the runflat system releases all contained lubricant in one instance. Releasing lubricant in such a manner may be considered undesirable as the lubricant tends to dry out over time, therefore limiting the distance to which a runflat device may be capable of supporting a vehicle. Also, the bags containing lubricant are, by design, vulnerable to breakage. Unfortunately, this means they commonly release lubricant prior to the runflat system requiring lubrication. This may occur, for example, whilst the runflat device is being handled by a fitter.

For a runflat device to operate efficiently, it is conventional that the height of a runflat device exceeds half of the height of the tyre cavity. This leaves limited space for the bags of the known runflat system, and therefore limits the volume of lubricant which can be contained therein. This limitation is particularly significant as there must be a margin of space between the bags and the inner tyre to enable the tyre to deform without exerting pressure on the bags, which would otherwise cause them to burst undesirably. In practice, this renders such a runflat system incompatible with non-military sized tyres and low profile tyres, and even with larger military tyres when the pressure is reduced, as is often done to increase traction of the tyre in certain conditions. This prior art system is inappropriate for use in low-pressure applications and where central tyre inflation systems are used, as the deformation of the tyres which results inevitably results in the tyre exerting pressure on the bags containing lubricant, causing them to release lubricant prematurely (i.e. where no runflat condition exists).

Furthermore, undesirable release of lubricant into the runflat system, prior to a runflat condition being achieved, can result in an imbalance on the wheel, which subsequently effects handling of the vehicle and the stability of the wheel.

It is an object of the present invention to avoid the problems mentioned above in relation to prior art runflat devices.

One aspect of the present invention provides a runflat device for a pneumatic tyre, the device comprising a lubricator, the lubricator comprising a container for containing lubricant, and a release system for selectively releasing said lubricant from the interior of the container to the exterior of the container in response to a runflat condition of the tyre being achieved.

It will be understood that lubricant is only released from the container into the cavity between the wheel and tyre when a runflat condition is achieved. Lubrication is only required when a runflat condition is achieved, and the present invention provides lubrication when there is a demand for it. At other times, when lubrication is not required (there is no demand), lubrication is contained and the aforementioned disadvantages with certain prior art devices are avoided. In the present invention, the disadvantages of introducing lubricant into the runflat system are only of concern once a runflat condition has been achieved. Prior to achieving a runflat condition, the inner parts of the runflat system, including the tyre cavity, runflat device and wheel are not exposed to lubricant. Therefore a tyre and/or runflat device which has not experienced a runflat condition may be replaced without a fitter having to endure the extensive cleaning operation and subsequent reapplication of lubricant that is traditionally required. Furthermore, if a tyre has suffered a puncture but the release system has not been activated because, for example, the vehicle which it is supporting has not since been driven or deflation of the tyre has not been so extensive as to achieve a runflat condition, then the tyre may be repaired by conventional methods as lubricant will not yet have been released from the container and come into contact with the tyre. It will also be understood that the function of containing lubricant is performed by the container and the function of selectively releasing said lubricant is performed by a release system. The two functions are performed by different aspects of the lubricator. The container and release system are different, which allows them to be positioned in different locations and specifically gives freedom as to where the container is positioned. So, the container may be positioned in a location where it is not vulnerable to damage during ordinary use of the tyre (i.e. use not involving a runflat condition). Damage to the container, and premature release of lubricant and consequential unbalancing of the wheel assembly, can therefore be avoided.

A runflat device may further comprise a lubricant director for directing lubricant released from the container to a surface of the runflat device to be lubricated. Optionally, the lubricant director comprises a flow channel. The flow channel may comprise a tubular flow passage. Furthermore, in a runflat device, the surface to be lubricated may be one which, during a runflat condition achieved in use, presses against a flat tyre.

Also, in a runflat device, the release system optionally comprises at least one sacrificial element which, when removed, provides fluid communication between the interior of the container and the exterior of the container.

Also, in a runflat device, the release system optionally comprises a plurality of sacrificial elements which, when removed, provide fluid communication between the interior of the container and the exterior of the container.

The or each sacrificial element may be located adjacent a surface of the runflat device to be lubricated. The or each sacrificial element may be spaced from the container. In a runflat device, the surface to be lubricated may be one which, during a runflat condition achieved in use, presses against a flat tyre.

Furthermore, in a runflat device, the location of the or each sacrificial element adjacent said surface optionally is such that the or each sacrificial element protrudes from said surface and is abutted and removed by a flat tyre pressing against said element during use.

The or each sacrificial element may be configured to be either worn away or broken by a flat tyre during a runflat condition, and thereby removed by the flat tyre. The or each sacrificial element may be configured to be either worn away or broken by friction with a flat tyre during a runflat condition, and thereby removed by the flat tyre.

In a runflat device, the or each sacrificial element may close the end of a respective flow passage extending from the container. Furthermore, the or each flow passage optionally extends through an aperture in the runflat device, the passage extending from a first side of the runflat device where the container is located to a second side of the runflat device where said surface is located. Flow passages may be tubular.

In a runflat device, the release system may comprise at least two sacrificial elements which, when removed, provide two fluid communication passages between the interior of the container and the exterior of the container, one of which receives lubricant flowing from the container and the other of which receives ambient air or fluid flowing into the container.

In a runflat device, the release system may comprise at least one sacrificial element which, when removed, provides a fluid communication passage between the interior of the container and the exterior of the container, and may further comprise a flow passage projecting within the container from one interior surface of the container to a location adjacent a second interior surface of the container opposite the first interior surface, the flow passage being open at both ends thereof to provide fluid communication passage between the interior of the container and the exterior of the container.

One of the open ends of the flow passage may be located in a recess in said second interior surface of the container. This has the consequence of allowing a convenient reduction or minimising of the volume of lubricant in the container which can flow through the flow passage. So, even if the container is full of lubricant, with the recess also full of lubricant, only the small amount of lubricant located in the recess over the open end can possibly flow through the flow passage.

In a runflat device, the sacrificial elements may be separate plugs or caps retain in position with a friction fit. In a runflat device, the sacrificial elements may be integrally moulded.

In a runflat device, the container may be selectively removable from the remainder of the runflat device.

A runflat device may comprise a plurality of segments arranged end to end so as to form an annulus, each segment being provided with a separate lubricator.

A runflat device may comprise a releasable fastener for releasably fastening the container to the remainder of the runflat device.

In a runflat device, the release system may comprise a lubricant flow restrictor which allows a restricted release of lubricant from the container. The lubricant flow restrictor may comprise a reduction in flow area for the lubricant. This reduction in flow area may be an orifice. For the given lubricant characteristics (e.g. viscosity) and operating conditions (e.g. temperature, and the pressure differential generating the flow of lubricant), the flow restrictor is configured to produce the required pressure loss in lubricant fluid flow necessary to ensure lubricant dispenses from the container over a desired period of time. The greater the pressure losses produced, the greater the time taken for the container to be emptied of lubricant (i.e. the lower the rate of release of lubricant from the container). The required pressure loss may be achieved by appropriate selection of the diameter of a flow passage.

The runflat device comprises a pair of legs which are resiliently and elastically flexible, and the fastener fastens the container to the remainder of the runflat device at locations between the pair of legs. This fastening location allows flexing of the pair of legs to be unimpeded by the fastening of the container to the remainder of the runflat device. The container may be spaced from the release system.

A second aspect of the present invention provides an assembly comprising a wheel, tyre and runflat device, wherein the runflat device is as described above in relation to the first aspect of the present invention.

An assembly may further comprise lubricant contained in the container and wherein a reduction in flow area for the lubricant is such that the container is emptied of lubricant only after 50 kilometers of use (in a runflat condition) at a speed of 50 kilometers an hour.

An assembly may comprise a plurality of lubricators and may be rotationally balanced with the amount of lubricant contained in each container of said plurality of lubricators. In this case, rather than balancing the assembly with balance weights for that specific purpose, the assembly can be balanced by adjusting the volume (and hence weight) of lubricant in the containers. The gear and tensioning system of some prior art runflat devices create a asymmetric weight in an assembly which may be balanced with a container of lubricant positioned diametrically opposite said gear and tensioning system.

A third aspect of the present invention provides a method of assembling a runflat device as described above in relation to the first aspect of the present invention, the method comprising the steps of: filling the container with a lubricant; and fastening the container to the remainder of the runflat device. The container may be fastened with a releasable fastener.

With regard to the third aspect of the present invention, the container may be filled with lubricant whilst separate from the remainder of the runflat device and, as such, the filling of the container is made more convenient than would be the case if the container was together with the remainder of the runflat device. By itself, the container is less bulky than when located with the remainder of the runflat device.

A fourth aspect of the present invention provides a method of assembling a wheel, tyre and runflat device wherein the runflat device is as described above in relation to the first aspect of the present invention, the method comprising the step of filling the or each container with an amount of lubricant which rotationally balances the assembly of the wheel, tyre and runflat device.

A fifth aspect of the present invention provides a method of reducing wear between a surface of a runflat device and a tyre operating in a runflat condition, the method comprising the steps of: storing lubricant in a container; locating the container spaced from said surface of the runflat device; and releasing lubricant from the interior of the container to the exterior of the container in response to a runflat condition being achieved.

In a method of reducing wear, the step of locating the container may comprise locating the container radially inward of said surface of the runflat device along a radial extending through the point about which the tyre rotates in use. So, in this way, when the tyre rotates, lubricant in the container tends to move radially outward from the centre of rotation and, hence, in the general direction of the surface in need of lubrication.

A method may further comprise the step of directing any lubricant released from the container to said surface of the runflat device. This direction may be achieved by a step of deflecting a flow of lubricant to said surface. A method may further comprise the step of restricting release of lubricant from the container. Restricting release of lubricant may comprise providing a flow area for the lubricant such that the container is emptied of lubricant only after 50 kilometers of use at a speed of 50 kilometers an hour.

The runflat device may be as described above in relation to the first aspect of the present invention.

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

Figure 1 shows a cross-sectional view of a portion of a runflat device fitted to a wheel and inside a pneumatic tyre;

Figure 2 shows an isometric view of the bottom of a lubrication device of the present invention; Figure 3 shows an isometric view of the top of the lubrication device of Figure 2;

Figure 4 shows an isometric view of the interior of the lubrication device of Figure 2;

Figure 5 shows an isometric view of an end of the lubrication device of Figure 2 housed within the runflat segment of Figure 1 ;

Figure 6 shows an isometric view of the top of the lubrication device of Figure 2 housed within the runflat segment of Figure 1 ;

Figure 7 shows an isometric view of the interior of the lubrication device of Figure 2 housed within the runflat segment of Figure 1 ;

Figure 8 shows an isometric cross-section view of the lubrication device of Figure 2 housed within a runflat segment, the cross-section being taken along a transverse axis of the lubrication device;

Figure 9 shows an isometric cross-section view of the lubrication device of Figure 2 housed within a runflat segment, the cross-section being taken along a first longitudinal axis of the lubrication device;

Figure 10 shows an isometric cross-section view of the lubrication device of Figure 2 housed within a runflat segment, the cross-section being taken along a second longitudinal axis of the lubrication device.

Referring firstly to Figure 1 , there is shown the upper portion, in cross-section, of a standard single-piece drop centre wheel 19 to which a runflat device 20 and pneumatic tyre 24 have been fitted. The pneumatic tyre 24 is shown fitted to the wheel 19 with the runflat device 20 enclosed in a cavity formed by the tyre 24 and the wheel 19. The runflat device 20 is made up of a body having a plurality of uniform or identical segments 12.

Each segment 12 of the body of the runflat device 20 is seated on tyre bead retention humps 21 of the wheel 19 so as to span the wheel well 22. Tyre beads 25 of the tyre 24 are located in the gap provided between each wheel rim 23 and the outside edge 26 of feet of the segments 12 of the runflat device 20. The pneumatic tyre 24 has a tyre tread 28 on its circumference and tyre walls 29 which extend from the edge of the tyre tread 28 to the beads 25 of the tyre 24. The depth of the tyre tread 28 is thicker than that of the tyre walls 29, as is usual for pneumatic tyres in the field.

Each segment 12 has a top plate 16 having a generally rectangular cross-section and a part- arcuate length which, in use, forms part of the circular circumference of a complete runflat device. From the underside (radially inward side) of the top plate 16 a pair of legs 17 extend. Each leg 17 runs the entire length of the top plate 16, and extends at an oblique angle, away from the centre of the width of the top plate 16 such that the legs 17 form an inverted‘V’ in cross-section with the apex near the centre of the width of the top plate 16. The ends of the legs 17 distal from the top plate 16 provide each segment 12 with a pair of feet or base edges 18 which rest on the bead retention humps 21.

Referring to Figures 2-4, there is shown an embodiment of the present invention. A lubrication device or lubricator 1 is shown. The lubrication device 1 has a container 27 having a general shape of a trapezoidal prism with rounded vertices. The volume of the container 27 forms an enclosure for containing and storing lubricant. The largest generally rectangular side of the container 27 is formed of a closure 3, and the remainder of the container 27 constitutes a container body 2. The smallest generally rectangular side of the container 27, which forms the base 30 of the container body 2, is outwardly curved, forming an arch which spans the space between its shortest sides, the maximum height of the arch being at the midpoint of its shortest sides. Correspondingly, the generally rectangular sides 31 of the container 27 which span the space between the base 30 of the container body 2 and the closure 3 each have a curved edge which matches and adjoins the arch of the base 30. The closure 3 has two grooves 6,1 1 which extend within the perimeter of its generally rectangular shape. The grooves are centred about the midpoint of the shortest sides of the closure 3. Correspondingly, the generally rectangular sides 31 of the container 27 which span the space between the base 30 of the container body 2 and the closure 3 each have a groove 32,33 which matches and adjoins grooves 6, 1 1 respectively. The grooves 6,1 1 ,32,33 function to position and retain the lubrication device 1 within a runflat segment 12 and fit around apertures in the segments which receive cables linking the segments together and allowing the segments to be drawn against a wheel when tensioned (as is known for runflat devices).

The container closure 3 and container body 2 are attached to one another by way of a groove along the perimeter of the closure 3, the outermost part of the groove providing a lip 15 which extends over the outer surface of the container body 2 (and over an upper edge defining an opening of the container body 2) to thereby form a resilient snap fit of the closure 2 to the body 3. The groove may receive a seal (not shown) disposed on its inner surface to enhance the sealing engagement of the closure 3 with the container body 2.

The closure 3 is symmetrical about its midpoint, meaning the direction in which it is oriented onto the container body 2 is irrelevant. This simplifies the assembly of the lubrication device 1. The closure 3 has a first aperture 13 and a second aperture 14 arranged so as to align with a first hollow post 4 and a second hollow post 5 extending from the base 30 of the container body 2 through the enclosure/interior of container 27. This arrangement enables the container, as a whole, to be releasably fastened to the remainder of the runflat device by way of inserting a fixture, such as a screw threaded bolt (not shown), through each of the first and second apertures 13, 14 and into the first and second hollow posts 4,5 respectively. In so doing, container closure 3 is also further secured to the container body 2.

The first and second apertures 13, 14 are circular holes, each having a raised circular wall 38,39 disposed thereabout with four reinforcing members 34,35,36,37 radiating therefrom. The reinforcing members 34 extend from circular walls 38,39 to meet one another near a first edge 39 of the closure 3 at the midpoint between its two shortest sides. Reinforcing members 35 extend in the same manner as reinforcing members 34 but meet one another at a second edge 40 of the closure 3 at the midpoint between its two shortest sides. Reinforcing members 36,37 extend from circular walls 38,39 to meet each vertex of the closure 3. This arrangement of reinforcing members distributes the load which is applied when a fixture is inserted into apertures 13, 14 evenly across the closure 3 to encourage its secure attachment to the container body 2, and to minimise the presence of stressors in the closure 3 which could lead to breakage of the closure 3 (particularly adjacent the first and second apertures 13, 14) and leakage of lubricant from container 27. The closure 3 also has two closed shallow cylinders 45,46 extending from its surface. These two cylinders 45,46 each allow for the provision of a recess in the interior surface of the closure 3, and therefore in the interior surface of the container, the purpose of which shall be described below. Connected to and extending away from the base 30 of the container body 2 in a direction perpendicular to the surface of the closure 3, are three lubricant directors 7,8,9. The arrangement of the directors is such that, when the runflat device is assembled with a wheel and tyre, the directors extend radially outwardly from the base 30 (the radial extending through the point about which the assembly rotates in use). Each director is a tube which defines a tubular flow path. Each of the lubricant directors 7,8,9 is in fluid communication with the interior of the container 27 and is closed with a sacrificial element at their free end (i.e. the end radially outermost and distal to the end adjacent the base 30). The lubricant directors may be made from a material (e.g. a frangible material) which would wear or break after making contact with the inside surface of a tyre, thus opening the free ends of the lubricant directors 7,8,9. In this way, the runflat device is provided with a release system for selectively releasing said lubricant from the interior of the container to the exterior of the container in response to a runflat condition of the tyre being achieved. The container and directors are made from a plastics material and the container body and directors are of a one piece moulding. Sacrificial elements closing the free ends of the directors are of the same moulding, and hence are of the same material.

An air director 10 having a tubular flow path, extends through the closure 3, and through the enclosure/interior of the container 27 so as to terminate beyond the base 30 of the container body 2. The air director 10 runs generally parallel to lubricant directors 7,8,9 and may also be closed at the end proximate to the free ends of the lubricant directors 7,8,9.

The open top of the air director 10 is located within one of the recesses formed by the two closed cylinders 45,46 depending on the way in which the closure 3 has been orientated onto the container body 2. This arrangement is more clearly demonstrated in figure 8. Locating the top of the air director 10 within a recess in this way enables air to enter container 27 via the air director 10 whilst preventing or limiting lubricant from exiting via the same flow path. This keeps the flow path open for its intended use: to allow air to enter container 27 as lubricant exits via the lubricant directors 7,8,9 and to thereby prevent the formation of a vacuum within the container 27 which would otherwise hinder the release of lubricant.

Figures 5-10, show the lubrication device 1 of figures 2-4 located adjacent a segment 12 of a runflat device.

The top plate 16 of the segment 12 has four apertures 42,43,44,45 extending therethrough. The three lubricant directors 7,8,9 and the air director 10 extend through the apertures 42,43,44,45 respectively when the lubrication device is located adjacent the runflat segment 12, such that their free ends extend beyond the base of the runflat segment 12.

When a runflat condition of the tyre is achieved as a result of, for example, the tyre suffering a puncture, the closed ends of lubricant directors 7,8,9 and air director 10 come into contact with the inside surface of the pneumatic tyre 24. Whilst the vehicle is being driven, wheel 19 continues to rotate, generating friction between the closed ends of the lubricant directors 7,8,9 and the inside surface of the pneumatic tyre 24. This causes the ends of the lubricant directors to wear and/or break. Lubricant is then released from the interior of the container 2 to the exterior of the container 2, flowing through the directors 7,8,9 under the action of gravity and/or the forces resulting from the rotation of the wheel 19. The rate of release depends on the size and shape of the lubricant flow path from the container and the associated pressure losses, and this is arranged so that the lubricant does not immediately empty from the container but is dispensed/released from the container flover time so as to continually feed the lubricant to the required surfaces. In this regard, the diameter of the flow passages is selected having reference to the lubricant characteristics (for example, viscosity) and operating conditions (for example, temperature, and speed of wheel rotation). In an alternative embodiment, an orifice may be used in each flow passage in order to restrict flow of lubricant.

The now open free ends of the directors 7,8,9 are located adjacent the surface of the top plate 16 which needs lubricating, and so lubricant is released between this surface and the tyre and thereby reduces wear of the tyre as a consequence of its contact with said surface.

When assembling a runflat device with the lubricator 1 , the container is first filled with lubricant by removing the container closure, filling the container body, and then replacing the closure on to the body. The full container is then fastened to a segment of the runflat device as described above. The segments of the runflat device are then secured to a wheel in a conventional manner so as to form an annular support structure for a vehicle in the event of a runflat condition. One or more (optionally, all) of the segments are provided with a container of lubricant.

If a tyre becomes worn through use, it may be replaced without the need to remove lubricant from the tyre or wheel because, unless a runflat condition had been achieved, lubricant will have remained housed within the container.

The present invention is not limited to the specific embodiments described above. Alternative arrangements, methods and suitable materials will be apparent to a reader skilled in the art. For example, the sacrificial elements closing the free ends of the lubricant directors may be provided as plugs/caps located in the directors and therefore separate from the lubricant directors themselves. The sacrificial elements may be integral with (i.e. of the same material and moulding) the surface of the runflat device or insert requiring lubrication. In this case, the directors are, at least in part, passages defined in the top plate 16 and opening onto the surface requiring lubrication. Also, the free end of the air director does not need to be closed, although it is desirable for it to closed otherwise there is the possibility of gradual leakage of lubricant via the air director.

The volume/weight of lubricant in the container or containers may also be used to rotationally balance the assembly of wheel, tyre and runflat device/insert.

For the avoidance of doubt, the present invention may be used in relation to two-piece and multi-piece wheels, and flat centre wheels.