In this connection, the ends of a safety tyre liner are coupled together and releasably attached for permitting fixing of the safety liner to the wheel rim of an inflatable tyre. Such liners allow continued operation of the tyre in the event that the tyre is deflated.

In this regard, it can often prove highly desirable to provide a such a safety liner within an inflatable tyre and wheel rim assembly. Such safety liners generally comprise two or more arcuate segments which are joined together and releasably attached to an outer peripheral surface of the rim by way of a coupling means. If during operation of the tyre it becomes deflated, the arcuate segments become load bearing and the deflated tyre engages the arcuate segments such that they rotate on the outer peripheral surface of the rim.

During normal inflated operation of the tyre, rotation of the arcuate segments on the rim is undesirable since this can lead to the tyre and wheel rim assembly becoming unbalanced.

In addition, relative movement of the arcuate segments on the wheel rim will cause heat to be generated within the tyre and wear on the engagement surfaces of the arcuate segments and rim.

Accordingly it is desirable to provide a coupling means for accurate and controlled fastening of the arcuate segments on a wheel rim surface.

In this regard, it is known from UK patent specification GB-A-1,375,415 to provide a coupling at each end of a two- piece tyre safety liner comprising a bolt passing through overlapping edges thereof. A problem associated with this type of arrangement is that the circumference of the safety

tyre liner cannot be adjusted to accommodate variations in manufacturing tolerances of the wheel rim on which the liner is secured. Manufacturing tolerances of up to +/-2% are common for wheel rims so that the liner will potentially be either too tightly or too loosely fitted on the wheel rim with the above-mentioned disadvantages.

Such a problem is partly overcome by the arrangement shown in European patent specification EP-A-0,100,013. In this arrangement two semi-circular liner segments are joined at each of their ends by adjustable coupling means. The two segments are joined together by means of a moveable link which is positioned in accordance with a cam setting when the two segments are joined together. The cam is moveable to release the segments from the wheel rim. A major disadvantage with this arrangement is that the cam only allows a small range of adjustment and is furthermore only moveable between discreet points such that the coupling can only be adjusted by certain fixed amounts. In addition, the entire load acting on the coupling is transmitted through a relatively weak link element.

Accordingly it is an object of the present invention to provide a robust coupling which is adjustable over a readily wide range and which overcomes the above drawbacks.

According to the first aspect of the invention there is provided a coupling for use between adjacent ends of a safety liner provided in an inflatable tyre and wheel rim assembly, said coupling comprising: first and second overlapping members provided at respective ends of a safety tyre liner, said overlapping members being movable relative to one another; fastening means for fastening said overlapping members together, said fastening means being provided on the second overlapping member and comprising a movable slide member

arranged to engage a surface of said first overlapping member; wherein the coupling is arranged such that the relative position of the overlapping members in a generally longitudinal direction can be altered by relative movement of the slide member and the first overlapping member. In this respect the safety liner's circumference can be readily adjusted by movement of the fastening means to a desired position.

Preferably, said slide member is a wedge member having a surface inclined relative the longitudinal direction of the overlapping members, and wherein said inclined surface engages a corresponding inclined surface provided on said first overlapping member. The provision of inclined surfaces on the wedge member and the first overlapping member allows the fastening means to be readily accessed from the side of the coupling. The provision of inclining surfaces also enhances the sensitivity of the fastening means.

In preferred embodiments, said wedge member is movable along said corresponding inclined surface in a dedicated slot in said first overlapping member. This provides a reliable and positive movement of the wedge member.

Conveniently, said fastening means comprises a bolt extending within said slot, said bolt having a first end which engages said wedge member and a second end which is threadedly mounted in said second overlapping member. In this way, the fastening means can be readily moved to a position corresponding to the desired separation of the arcuate segments.

Preferably, said bolt passes through the inclined surface of the wedge member.

Preferably, the bolt extends substantially normally to the longitudinal direction of the first and second

overlapping members. Further, the inclined engaging surfaces are preferably at substantially 45° to the longitudinal direction of the first and second overlapping members. The provision of a bolt as an actuator in such an arrangement allows for the use of torque setting apparatus to accurately apply the correct loading on the rim by the liner.

Conveniently, said bolt is a first bolt and the fastening means comprises a second bolt spaced from said wedge member, and wherein said second bolt has a first end which engages said first overlapping member and a second end which engages said second overlapping member.

In preferred embodiments, the first and second overlapping members are slidably engaged. This provides for a mechanically compact arrangement.

Preferably, the overlapping members are provided at respective ends of adjacent arcuate segments of the safety tyre liner.

Conveniently, the overlapping members are provided at opposing ends of a split annular safety tyre liner.

According to a second aspect of the present invention there is provided a coupling for use between adjacent ends of a safety liner provided in an inflatable tyre and wheel rim assembly, said coupling comprising: first and second overlapping members provided at respective ends of a safety tyre liner, said overlapping members being movable relative to one another; fastening means for clamping said overlapping members in abutting engagement, said fastening means comprising an actuator provided on the second overlapping member and movable through a continuous range of clamping positions, and a slide means provided between said actuator and said first overlapping member to effect relative movement of said first and second overlapping members in the longitudinal direction

of said overlapping members when said actuator is moved within said range, thereby to alter the relative positions of said overlapping members.

According to a third aspect of the present invention there is provided a safety liner for an inflatable tyre and wheel rim assembly comprising a coupling as set out above.

Preferably, said liner comprises a pair of semi-circular segments joined together by said coupling means. This provides a simple two-piece liner requiring only two coupling means.

Conveniently, said liner comprises a split annular member joined at its respective ends by said coupling means.

In preferred embodiments, the extent of said relative movement of said overlapping members of said coupling means is sufficient to accommodate +/-2% expansion of the safety tyre circumference. This provides sufficient expansion within the liner to accommodate variations in manufacturing tolerances of the wheel rim on which it is to be mounted.

Examples of the present invention will now be described with reference to the accompanying drawings wherein:- Figure 1 is an exploded view of a two-piece safety liner in accordance with the present invention; and Figure 2 is a sectional view along line 1,1 of Figure 1 showing in detail a coupling between adjacent segments of the liner in an assembled condition; Figure 3 is a sectional view similar to that of Figure 2 showing a modified coupling arrangement.

Referring to Figure 1, a two-piece liner 10 for releasable attachment to an outer peripheral engagement surface of a wheel rim centre section comprises two arcuate semi-circular segments 12 & 14. The segments may be constructed from any suitable material including metal, rubber or plastic capable of supporting the weight normally

carried by an inflated tyre within which the liner is to be mounted. The segments 12 & 14 have at opposite ends thereof flat co-planar surfaces 16 & 18 which are cut away from the main section of the segments to provide overlapping engagement members 20 & 22 at opposite ends thereof.

Referring now to Figure 2, the arcuate segments 12 & 14 are joined together in overlapping sliding engagement.

Figure 2 shows the detail at one adjoining end of the arcuate segments, the other end being identical. As shown, the first of the arcuate segments 12 is cut away at its end to provide a flange 24 which defines the co-planar surface 18 and the overlapping engagement member 22. A second of the segments 14 is similarly cut away at its end to provide a flange 26 which defines the co-planar surface 16 and the overlapping engagement member 20. The overlapping members 20 and 22 are held in mutual abutting engagement along part of their respective co-planar surfaces 16 and 18 by way of fastening means provided in the form of a bolt 28. The bolt 28 passes through a wedge shaped member 30 positioned in a slot 32 in the flange 24 and is rotatably mounted in an aperture 34 having a threaded portion 36 extending part way along its length to an external surface 37 of the flange 26. The bolt 28 is rotatable within the threaded portion 36 so that it may be moved within the slot 34 along its axis 38.

The slot 32 extends from one side of the flange 24 to the other and has a generally rectangular section and includes a surface 40 inclined relative to the longitudinal direction of the overlapping members to provide a ramped recess into a main region 44 of the slot.

The wedge shaped slide element 30 includes a rectangular portion 46 and a triangular portion 48 having an inclined surface 50 which corresponds to and engages with the inclined surface 40.

As shown, the flanges 24 and 26 are positioned such that the flange 24 defines a gap 52 between its remote end 54 and the arcuate segment 14 and similarly the flange 26 defines a gap 56 between its remote end 58 and the arcuate segment 12.

In the position shown, a circumference defined by the two arcuate members may be adjusted by drawing the flanges 24 and 26 into the regions defined by the gaps 54 and 56. The gaps 54 and 56 are caused to close by rotation of the bolt 28. As the bolt moves along its axis, the slide element 30 is caused to follow the bolt towards the surface 16 of the flange 26. This movement imparts a reaction force on the inclined surface 40 of the ramp recess portion, so that the flanges 24 and 26 move relative to one another in the longitudinal direction of the arcuate segments. The bolt 28 may be moved through a range of positions defined from the position shown to that where wedge element 30 engages the co- planar surface 16. Thus as the wedge element 30 moves along the inclined surface 40 towards the co-planar surface 16, the relative movement of the flanges 24 and 26 closes the gaps 52 and 56 so as to reduce the overall circumference of the assembled safety liner.

In the arrangement of Figure 3, the bolt 28 is arranged to pass through the inclined surface 50 of the wedge shaped member. The flange 24 is provided with slot 32, inclined in part, through which bolt 28 extends.

A secondary bolt 62 may be provided extending from a clamping plate 64 which bridges the flange 24 and the wedge member 30. The secondary bolt passes through an aperture 66 provided in the flange 26. Bolts 28 and 62 secure the flanges together by means of fastening nuts 60. Nut movement restrictors 70 may be provided to prevent rotation of the nuts on tightening of bolts to thereby facilitate fastening of the liner on to the wheel rim from one side. In this

connection, the fastening means, however provided, is configured to be readily accessible from a side of the liner.

Where a secondary bolt is provided, the respective bolts are suitably spaced apart within the slot 32 in the longitudinal direction of the overlapping members 20 and 22.

In this arrangement, bolt 28 operates as previously described to reduce the circumference of the safety liner when it is being fitted to a wheel rim. The secondary bolt 62 provides for greater security of the coupling by providing a direct clamping load between the overlapping members 20 and 22 once the bolt 28 has been tightened and the circumference of the safety liner adjusted on the wheel rim. In this regard, the bolt 62 enhances the clamping force generated by the first bolt, thereby locking the coupling in position once adjusted but also provides for fail safe operation in the event of the bolt 28 breaking or otherwise becoming dislodged.

The above described embodiments concern providing the liner in two separate sections connected at the appropriate points using corresponding couplings. However, the present invention encompasses an arrangement where the liner comprises a single annular member, split at one point, with a coupling provided at that point. The liner would in this regard be required to have sufficient flexibility to allow fixing onto the wheel rim. Moreover, it will be appreciated that the present invention can also be used in safety liner arrangements comprising more that two arcuate segments.

It will be understood therefore that in the arrangements described, the bolt 28 may be moved to any position within its range of travel to obtain a desired degree of clamping according to the circumference of the wheel rim to which the liner is to be attached. Further, by use of known torque setting apparatus in conjunction with the coupling fastening an appropriate engagement force can be accurately applied on

the rim to thereby prevent slippage of the liner during normal inflated tyre operation.

It will be further understood that the arrangement could be modified to provide greater degrees of adjustment simply by altering the angle of the inclined surface 40 relative to the co-planar surfaces 16 and 18 and increasing the gaps 52 and 56 accordingly.

It will be understood that the embodiment illustrated shows an application of the invention in one form only for the purposes of illustration. In practice, the invention may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.

For example, whilst the wedge member may be formed of metal, plastics or rubber, any suitable alternative materials may also be used. In addition, the safety tyre may be a split resilient annular member having a gap between adjacent ends thereof, wherein the coupling is provided between the two ends of the annular member to join the two ends together.