WO2008104730A1

WO2008104730A1 - Improved run-flat device

Info

Publication number: WO2008104730A1
Application number: PCT/GB2007/000678
Authority: WO
Inventors: Trevor John Chandler; John Bemard Savage
Original assignee: Runflat International Ltd
Current assignee: Runflat International Ltd
Priority date: 2007-02-27
Filing date: 2007-02-27
Publication date: 2008-09-04
Anticipated expiration: 2009-08-27

Abstract

A run-flat device (13) for fitting on the outer circumference of a wheel (11) inside an inflatable tyre, said device (13) comprises an annular ring (14) made up of a plurality of arcuate segments (15) having a flange at each end that overlaps circumferentially the corresponding flanges (26, 27) by clamping means (23) equally spaced around the ring (14) that imparts to each segment (15) a circumferential clamping force and an axial clamping force to urge the segments (15) circumferentially and axially towards each other wherein the clamping means comprises a first and second clamping bolts (23a, 23b) which pass through a pair of spaced holes formed in the adjacent flanges, characterised in that the clamping bolts are used in association with anti-vibration locking washers.

Description

IMPROVED RUN-FLAT DEVICE

This invention relates to vehicle wheels provided with inflatable tyres and in particular the invention is concerned with devices fitted on the internal rim of a wheel inside the tyre enabling the wheel to run with a deflated tyre. Such devices have become known as "run-flat devices". The present invention is concerned with improved clamping means and parts for more securely, reliably and accurately, clamping together segments of a segmented ring run- flat device.

With conventional wheels not fitted with run-flat devices, if the tyre suddenly deflates the tyre is almost always irrepairably damaged and can become shredded or thrown off the metal wheel rim. This can cause the vehicle to which the wheel is fitted to lose control, endangering the occupants and other road users. At best, the vehicle can be stopped and the wheel replaced with a spare wheel, or the puncture repaired, or a new tyre fitted to the existing wheel. For commercial vehicles, such as lorries, this is both time consuming and costly because of the need to mobilise independent breakdown or repair services to effect a repair or replacement and return the vehicle to normal use. Whereas a punctured tyre on a typical passenger car can be replaced by a spare wheel, usually by just one capable person, given a truck or large van, or heavy duty commercial lorry replacement by one person is not normally possible.

With lorries, military vehicles, carriers, such as bullion carriers, security vehicles, or other vehicles where tyre deflation effectively halts the vehicle, and exposes the vehicle to danger from an external threat, it is highly desirable to be able to continue the vehicle journey destination despite the inconvenience of a deflated tyre. When a tyre deflates partially or completely, the effective diameter of the corresponding wheel decreases compared with the wheels with inflated tyres. Therefore, the frictional engagement of the deflated tyre on the road causes the peripheral speed of the deflated tyre to increase to match the peripheral speed of the inflated tyres. Simultaneously, any differential gearbox in the transmission drive path to a wheel with a deflated tyre will divert torque away from the driven wheels that have inflated tyres to the wheel with the deflated tyre. This in turn causes rotation of the deflated tyre relative to the metal wheel, particularly where the metal wheel is a driven wheel.

Run-flat devices that fit on the rim of the metal wheel inside the tyre are well known, and usually comprise an annular body on to which that part of the outer circumferential wall of the tyre that is in contact with the ground or road can contact. The annular body is usually made in two parts that are clamped to the outer rim of the metal wheel and the annular body is designed to slip circumferentially on the metal rim when the tyre deflates. This slippage is important because it allows the tyre to slip on the wheel rim whilst ensuring little or no slippage of the tyre relative to the outer circumference of the annular body.

In a prior known device, the annular body comprises two semi-circular segments that are pivotally connected together at each end by a single clamping bolt that clamps the two segments together. Radial clamping of the segments onto the metal wheel is achieved by a cylindrical band extending around the circumference of the segments that can be tightened to pull the segments together prior to tightening the pivot bolts. In this case the pivotal connection at one end of the segments has an elongate slot through which the clamping bolt passes that allows circumferential movement of the segments relative to each other during clamping them on to the rim of the metal wheel. The bolt is accessible for tightening from only one side of the segments. In a second prior known form of run-flat device having two segments, a single circumferential clamping means is used at one end of the segments. At the other end a simple pivot is provided. The clamping means comprises a slot in one of the segments, and the slot has an inclined surface. A tapered wedge is provided in the slot and engages the inclined surface. A single bolt (accessible from one side) passes through holes in each end of adjoining segments. At least one of the holes is elongated to allow relative circumferential movement of the segments. By tightening the single clamping bolt, the two ends of the segments are pulled together by the wedge to clamp them on to the rim of the metal wheel.

A problem with both of these known types of segmented run-flat devices is that because a single bolt is used at at least one end of the segments, each segment can pivot relative to the other and move out of alignment radially relative to the other segment. This can cause damage to the inside surface of the outer circumferential wall of the tyre when the tyre becomes deflated. This is particularly more of a problem with the prior known run-flat devices that do not use circumferential clamping bands because the two segments tend to open up like jaws under centrifugal and centripetal loads. At worst, even when the tyre is inflated, the leading edge of one segment can protrude beyond the circumference of an adjoining segment of the protruding segment and release the frictional engagement of the annular body on the rim of the metal wheel, allowing ^'relative rotational slippage of the run-flat device on the rim of the metal wheel. Consequently, excessive wear on the run-flat device and the rim of the metal wheel is caused and the wheel becomes unbalanced during normal running. When the tyre deflates, the protruding edges of the displaced segments exacerbate the damage to the inside of the tyre and can cause the annular body to twist out of alignment with the plane of rotation of the wheel. This may lead to the tyre coming off the metal wheel altogether. A further disadvantage of known segmented run-flat devices is that each segment has a single captive bolt that is only accessible from one side of the segments, and the segments are of an asymmetric shape, with the design of one end of each segment being different from the other end of the same segment. This means that two different sets of segments have to 5 be made depending on whether the segments are to be fitted to the left-hand side or to the right-hand side of the vehicle. This adds to the complexity and cost of manufacture and means that extra spare sets have to be carried by puncture repairers or breakdown personnel. For a review of known constructions, attention is drawn to the disclosures of WO- A-9911476 and WO-A-03106198. I O

An object of the present invention is to provide a run-flat device comprising a plurality of segments inter-connected by clamping means that even more reliably and securely limits or prevents relative pivotal movement between the segments; and which prevents movement of the coupled segments relative to the wheel or to a sleeve if present, until required by the 15 event of a tyre deflation.

This object can be met by a run-flat device according to Claim 1. Preferred features of the device are provided within the sub-claims. 0 The present invention will now be described, purely by way of non-limiting example, with reference to the accompanying drawings in which:

Figure 1 shows a cross-sectional view through a wheel fitted with a run-flat device incorporating the present invention; 5

Figure 2 is a side elevation showing a segmented ring and inner sleeve of the run-flat device of Figure 1 ; Figure 3 is a schematic perspective view of the run-flat device of Figure 1;

Figure 4 shows a cross sectional view through the ends of two adjacent segments of the run flat device of Figure 2 and shows in greater detail the clamping means of the present invention;

Figure 5 shows a schematic cross-sectional view of an inner sleeve of the run-flat device of Figure 2; and

Figure 6 shows a run flat device of Figures 1 to 5 fitted to a two part wheel.

Referring to Figure 1 , there is shown schematically a cross-section through a wheel assembly of a lorry. The wheel assembly 10 comprises a metal wheel 11 adapted to be fixed to a wheel hub of a vehicle (not shown) by way of conventional studs and nuts (not shown), or threaded studs (not shown). An inflatable tyre 12 is mounted on the rim of the metal wheel in a conventional manner. The metal wheel is of a single piece construction of the type in widespread use, and is provided with a conventional inflation valve (not shown). The metal wheel could be made of a well-known two-part construction that has a removable rim as shown in Figure 6.

Mounted on the rim of the wheel 11 inside the tyre 12 is a run-flat device 13 comprising an annular body 14 made of three modified nylon segments 15 that are either clamped directly to the outer diameter of the wheel rims, or, as is preferred, clamped to the outer circumference of an inner modified nylon sleeve 16 split to permit the inner sleeve 16 to be opened and snapped in place around the outer diameter of the wheel 11. The said segments are preferably constructed from a modified nylon material that has elastomeric properties and enhanced ballistic and shock absorption. The inner sleeve 16 is also preferably made of a modified nylon, but modified in the sense of having enhanced lubricity and bearing functions. In other less preferred constructions it could be constructed with a nylon central band 17 and polyurethane edge bands 18 as shown in Figure 5. The central band has a dove-tail shaped recess 17(a) on each side face and polyurethane side bands 18 if used would each have a dove-tail shaped side member 18(a) that fits into one of the recesses 17(a). The central band 17 provides rigidity to resist side-loads of the side walls as they collapse inwards whilst integrally formed side bands of the same modified nylon material 18 provide rigidity with flexibility or resilience to cushion the contact between the beads of the side-walls of the tyre 12 to avoid damage to the tyre 12 when the tyre deflates.

The outer circumference of the central band 17 has a recess 41 and the inner circumference of the segments 15 have a flange 42 that locates in the recess 41. A high temperature grease lubricant is preferably liberally applied to the outer circumference of the inner sleeve 16 and the inner circumference of the segments 15 which form a rotatable roller assembly. In order to provide a reservoir of applied grease, the outer circumference of the sleeve 16 may be provided with peripheral grooves.

It will be appreciated that at high rim speeds, the run-flat device 13 is subject to centripetal and centrifugal forces which tend to loosen the circumferential grip of the run-flat device 13 on the metal wheel 11. A shear pin 43 may be provided (as shown in Figure 5) for each segment 15 to accommodate this radial movement whilst restraining the segments 15 circumferentially until the pins 43 are sheared by the deflated tyre contacting the segments 15 and causing the segments 15 as a complete ring to rotate. The shear pin 43 is inserted through a hole in the central part of the rim of the wheel and through the inner sleeve 16.

The inner circumference of the inner sleeve 16 may be profiled to match the profile of a specific metal wheel, or could simply bridge across the recesses or wells of the metal wheel 11 between the surfaces 12(a), 12(b) on which the beads of the side walls of the tyre 12 sit. The inner sleeve 16 must be shaped so as not to impede the fitting of the tyre because it is necessary to provide gaps or circumferential recesses that allow each side wall of the tyre 12 to fit as the tyre is slipped over the front rim of the metal wheel 11 prior to inflation, The inner sleeve 16 functions as a tyre bead retainer that stops the sidewalls of the tyre 12 collapsing inwards when the tyre is deflated.

Referring now to Figure 6 there is shown a second type of metal wheel 11 fitted with a run- flat device 13 of the present invention. In this design of wheel, the metal wheel 11 is in two parts 44 and 45. The main part 44 of the wheel constitutes the rear rim 46 and central rim 47 of the wheel 11 on to which the rear wall of the tyre 12 is fitted and the second part 45 constitutes the front rim 48 that retains the front side wall of the tyre 12. The second part 45 is bolted to the main part 44 of the wheel prior to inflation of the tyre 12. The run-flat device 13 is of a similar construction to that described and shown in Figures 2 to 5.

It will be appreciated that the inner sleeve 16 shown in Figure 1 effectively blocks off the deep wells formed in the rim of the metal wheel and serves to stop the side wails of the tyre falling into the deep wells when the tyre deflates. Clearly in those designs of metal wheel that do not have deep wells and those that have cylindrical or slightly conical central rims with in-built bead retaining features (such as for example similar to that shown in Figure 6) the inner sleeve 16 may be dispensed with but in this case a bead retaining, device may be needed or the inner periphery of the segments modified to form a bead retaining device. We prefer to keep the inner sleeve 16 as the bead retainer.

Referring in greater detail to Figures 2 and 3, the three segments 15 are symmetrical about a radial plane orthogonal to the axis of rotation of the wheel and are of identical shape whether for a left-hand wheel or a right-hand wheel. Each segment is a segment of a hollow cylinder with a concave end 20 and a convex end 21. The convex ends 21 are of a complementary shape to the concave ends 20 so that the convex end 20 of each segment 15 nestles into the concave end 21 of an adjacent segment 15. The segments 15 are assembled inside the tyre 12 with the convex ends 21 constituting the leading edge relative to the direction of rotation of the tyre 12 when it is running wholly deflated. Each segment 15 has an arcuate recess 22 on each side to lighten the segments.

At each end of the segments 51 there is provided a clamping means 23 constructed in accordance with the present invention in the form of two parallel bolts 23(a), 23(b) each associated with a pair of anti-vibration washers (not shown). The most preferred type of anti- vibration washers are those where opposed mating surfaces are provided with upstanding inter-engagable formations such as serrated edges which mutually interact to prevent slippage of those washers. The shape of the ends of adjacent segments 15 and details of the clamping means is best seen in Figure 3.

Referring to Figures 2, 3 and 4, the concave end 20 of each segment has a flange 26 of half the thickness of each segment and two circumferentially spaced holes 24, 25 are drilled through the flange 26. The holes 24 are of a slightly larger diameter than that of the bolts 23(a) and 23(b) to allow relative movement of the end 20 relative to end 21. The convex end 21 of each segment has a flange 27 that overlaps the flange 26 in a circumferential direction. The flange 27 is provided with an elongate slot 28 that has inclined surfaces 29 that face away from the concave end 20 of the adjacent segment 15.

A wedge 31 having an inclined face 32 that abuts the inclined face 29 of the slot 28 in the convex end 21 of the segment 15 is placed in the slot 28 with the inclined face of the wedge 31 in contact with the inclined faces 29, The angle of the wedge surface is preferably such as to permit optimum subsequent clamping force of the roller assembly on the wheel directly in the case of one piece wheels, or upon the sleeve in the case of two or three part wheels. The wedge 31 has a hole 31 (a) through which one of the dome-headed clamping bolts 23(a) is passed. Prior to usage, the bolt and preferably all six such bolts, have a thread adhesive applied to the thread in the region where the corresponding nut will be applied thereto. It is preferred to use thread lock adhesive as sold under the 'LOCTITE¹ brand. The ends 21 of the segments have two spaced holes 33, 34 that align with the holes 24, 25 in ends 20. Two captive nuts 35 are mounted on a retaining plate 36 and the nuts 35 are inserted into the holes 33, 34 in the flanges 27. By tightening the first bolt 23(a) the wedge 31 urges the ends of the segments together in a circumferential direction. A second dome headed clamping bolt 23(b) is passed through a hole 37 in a clamping plate 38, through the slot 28 and holes 34 and screwed into the second captive nut 35.

The clamping plate 38 bridges the slot 28 and is shaped so as not to interfere with bolt 23(a). When bolt 23(b) is tightened the clamping plate 38 engages a sidewall of the segment (15) and pulls the two flanges 26, 27 axially together in a direction parallel to the axis of rotation of the wheel 11.

To fit the run-flat device 13, the rear side wall of the tyre 12 is levered on to the front rim of the metal wheel 11 and then the inner sleeve 16 is prised open and fitted over the rim of the metal wheel inside the deflated tyre 12. The slit 39 in the inner sleeve 16 is positioned to align with the inflation valve of the wheel (not shown). The rear wall of the tyre is then pushed over the sleeve 16 on to the rear rim. The segments 15 are inserted into the cavity of the deflated tyre from the front and are loosely assembled around the inner sleeve 16 with the heads of the bolts 23(a), 23(b) facing outwards. The wedges 31 are then tightened down by tightening the bolts 23(a) evenly to an appropriate torque setting as will permit rotation of the roller assembly in the run-flat mode, whilst preventing unwanted rotation of the roller assembly directly on the internal wheel rim or on the sleeve where fitted. This tightening to desired torque causes the wedges 31 to pull the segments 15 together and thereby clamp the segments 15 firmly to the inner sleeve 16 (where fitted) and clamp the inner sleeve 16 (where fitted) to the internal rim of the metal wheel 11. With the run-flat device 13 clamped on to the internal rim of the metal wheel 11 the bolts 23(b) are fully tightened to an appropriate torque value effective to clamp the flanges 26 and 27 together axially. The outer sidewall of the tyre 12 is then levered over the front rim of the metal wheel 11 and the tyre 12 inflated.

In use, when the tyre 12 deflates, the tyre 12 collapses onto the outer circumferential surface of the run-flat device 13 in the region where the tyre 12 contacts the ground or road. This causes the run-flat device 13 to slip circumferentially on the rim of the metal wheel 11. This slippage between either the segments 15 and the rim of metal wheel (where no inner sleeve 16 is fitted) or between the segments 15 and the inner-sleeve 16 (where a sleeve 16 is fitted), ensures that there is little or no relative rotation between the tyre 12 and the run-flat device 13 and consequently little or no damage to the tyre 12. The beads of the sidewalls of the tyre 12 are prevented from collapsing inwards by the inner sleeve 16 that acts as a bead retainer when the tyre deflates.

It will be appreciated that at high rim speeds, the run-flat device 13 is subject to centripetal and centrifugal forces, which, in the absence of the second bolt 23(b) would loosen the circumferential grip of the run-flat device 13 on the metal wheel 11 by allowing the segments 15 to pivot relative to each other. By using two parallel bolts 23(a), 23(b) pivotal movement of the segments relative to each other is restricted or prevented. The bolts 23(a), 23(b) also provide both clamping in the circumferential direction and clamping in the axial direction (in a direction along the axis of rotation of the wheel) and prevent the segments twisting out of alignment with the wheel 11 when the deflated tyre contacts the outer circumference of the run-flat device 13,

In order to facilitate tracking and monitoring of the manufactured and supplied run-flat assemblies, a non-electronic security mark can be incorporated into appropriate non-bearing surfaces of the component parts, especially the segments. For example, a unique geometric profile can be incorporated into one or more segments that can act as a unique identity profile associated with the manufacturer and may further be associated with manufacturing and/or other production or test data ascribed uniquely to each relevant assembly.

In the case of embodiments of the invention where the roller assembly, consisting of the interconnected segments, is used in conjunction with the aforementioned sleeve nested within the internal rim of the wheel, such as in 2-piece (bolt together) or 3-piece (loose flange) wheels, the sleeve can be prevented from rotating relative to the wheel by using a transverse block sited within a gap in the periphery of the sleeve. For example, a solid block of steel, alloy, nylon or other deformation resistant material can be bolted, welded or otherwise affixed to the internal rim of such wheel to prevent rotation of the sleeve in inflated and deflated modes.

Such a block is desirable to enhance the 'run-flat' performance of the assembly especially in 'run-flat', i.e. tyre deflated mode. The transverse block (not shown) can be e.g. various shapes, such as rectangular or machined to accommodate opposing ends defining a peripheral gap at a circumferential location. A principal advantage of the present invention is that unlike other run-flat systems which necessitate the tyre fitter placing his hands inside the interior of the tyre during the fitting procedure, an assembly method is possible wherein the fitter can avoid placing either or both hands inside the tyre. For example, it is possible to use a cord, strap or rope to bring the ends of the assembly together and to install the fixing bolts without insertion of hands into the interior of the type. This can help to reduce or avoid accidental injury during the installation procedure.

Claims

1. run-flat device (13) for fitting on the outer circumference of a wheel (11) inside an inflatable tyre, said device (13) comprises an annular ring (14) made up of a plurality of arcuate segments (15) having a flange at each end that overlaps circumferentially the corresponding flanges (26, 21 ) by clamping means (23) equally spaced around the ring (14) that imparts to each segment (15) a circumferential clamping force and an axial clamping force to urge the segments (15) circumferentially and axially towards each other wherein the clamping means comprises a first and second clamping bolts (23a, 23b) which pass through a pair of spaced holes formed in the adjacent flanges, characterised in that the clamping bolts are used in association with anti-vibration locking washers.

2. A device as claimed in Claim 1 wherein first and second bolts are each provided with a pair of said washers in which opposing surfaces of such washers in contact have interengageable formations.

3. A run-flat device as claimed in Claim 1 or 2, wherein the clamping bolts are threaded and provided with a thread adhesive prior to fastening.

4. A run-flat device according to any of Claims 1 to 3, wherein there is provided a lubricant between the bearing underside of the segments and the bearing surface of the internal rim of the wheel or of a sleeve if present.

5. A run-flat device according to Claim 4, wherein the bearing underside of the segments and/or the bearing surface of the sleeve if present is provided with reservoir means to contain said lubricant.

6. A run-flat device according to Claim 4 or Claim 5, wherein the lubricant is a high temperature grease.

7. A run-flat device according to any preceding Claim wherein the clamping bolts are associated with fastening means and are tightened to a predetermined torque value or range.

8. A run-flat device according to any preceding Claim, wherein the segments are constructed from a modified nylon having elastomeric properties and enhanced ballistic and shock absorption.

9. A run-flat device according to any preceding Claim and including a sleeve having a bearing surface upon which the under-surface of the joined segments is adapted to bear and said sleeve is constructed from a modified nylon elastomer having a greater lubricity than that of the material of the said segments.

10. A run-flat device according to any one of the preceding Claims, wherein at least one said segment and/or the sleeve if present is provided with an integrally formed identity mark in the form of a predetermined geometric profile.

11. A vehicle wheel to which has been fitted a run-flat device according to any preceding claims.

12. A wheel as claimed in Claim 1 1 , which is selected from a 1 -part wheel, a 2-part wheel or a 3-part wheel.

13. A 2-part or 3-part wheel as claimed in Claim 12, comprising an inner sleeve with a circumferential bearing surface, the sleeve being split apart at a peripheral location and wherein a fastening block is affixed to the wheel within the region of said peripheral location and which abuts opposing edge portions of said sleeve such as to resist rotation of said sleeve relative to the wheel.