GB2238513A - Inserts for supporting deflated tyres - Google Patents

Abstract

The insert 14 of closed cell elastomeric material has its inner surface formed of a harder material or bonded to a band 24 of metal, plastics or carbon fibre, which serves to combat centrifugal forces pulling the insert from the wheel during normal running of the wheel and to prevent circumferential slippage of the insert. The insert may be provided with cuts extending radially inwardly from its outer surface and may have axially extending formations to engage in corresponding channels in the wheel. The insert may be covered by a flexible air impermeable membrane. <IMAGE>

Description

Title: Run Flat Tyres, Inserts and Wheels DESCRIPTION The present invention relates to wheels, tyres and inserts on motor vehicles that enable the effects of a puncture or their deflation to be overcome.

Basically, tyre inserts hereof comprise closed cell elastomeric material that, in normally inflated tyres, are substantially free of contact with the interior tyre walls, but, in a punctured or otherwise deflated tyre offer sufficient immediate support to the -tyre side walls to prevent ruinous buckling thereof, and subsequently after being worked by repeated compression/expansion, expand substantially to fill the tyre cavity and support the tyre for a period of "get home" running pending repairs.

Extensive tests have demonstrated the efficiency of such supports, particularly in the form of separable strips installed as rings side-by-side within the tyre on the outer periphery of the wheel, to such extent as readily to afford some tens, even hundreds of miles of near normal running pending repair.

To simplify fitting and servicing of these inserts and tyres, offering positive location of the insert against centrifugal displacement and/or a gas tight seal, it has been proposed to fit such inserts to a separable wheel. Thus, in an annularly separable vehicle wheel, pneumatic tyre and tyre insert assembly, the insert has a base fitting between rims of the wheel and inside beads of the tyre and the base has protrusions serve by cooperation with other formations of the assembly to aid securement of the insert.

It has now been found that the latter arrangement is complicated but that simpler arrangements are not entirely satisfactory as due to the flexibility of the insert material circumferential slippage and centrifugal displacement is still possible and such may interfere with normal running of the tyre.

An object of the present invention is to provide means whereby run flat tyre inserts of the type described above are less susceptible to centrifugal displacement and/or slippage.

According to one aspect of the invention it is proposed, especially for a split or separable wheel assembly, that a run flat tyre insert be stiffened or reinforced around its base or otherwise be retained against slippage or centrifugal displacement.

Various possibilities for stiffening or reinforcing the base of an annular tyre insert are envisaged. One possibility may be to bond the insert to a band of relatively stiff material such as of metal, eg. a spring steel band, or of other suitable material, such as plastics or carbon fibre. Such a band, particularly when sized so as to fit closely over the wheel, a split wheel assembly being essential for this embodiment, may provide the necessary security for the insert to prevent centrifugal forces lifting the insert off the wheel well.

The band may be coated with or have applied to its underside, ie. that side facing the wheel well, a relatively non-slip material, such as of rubber or other elastomeric material.

As an additional or alternative feature, the band and wheel well may be provided with one or more cooperating formations to facilitate location and retention of the insert on the wheel. Preferred formations are mating channels and protrusions axially of the wheel, the wheel preferably having the channels and the band the protrusions.

Alternatively cooperating hook-like formations and slots may be used to facilitate insert location.

Preferably the hook-like formations are on the wheel and the slots formed in or on the insert.

A yet further possibility envisaged by the present invention is for the band to be corrugated axially of the wheel. Such corrugations may be of a smooth undulating type or of an angular type. The corrugations may facilitate fitting of the insert to a wheel by allowing expansion of the metal band for fitting purposes. Also, the corrugated band may by its resilience provide enhanced grip on the wheel well to prevent slippage around the wheel. The flexibility of the corrugated metal band will not, of course, -be such as to permit undue centrifugal displacement of the insert radially from the wheel. Furthermore, a corrugated band formation may provide greater bonding area than a flat band.

Instead of a band it may be possible to achieve a similar effect by bonding to or otherwise treating the tyre insert bottom with a harder material, such as by bonding rubber or other elastomeric strip to the insert or otherwise treating the insert bottom to render same rubberised, such as by dipping the insert bottom into rubber solution. Again cooperating formations of the insert base and wheel well are possible.

The insert itself may be a single strip or a plural strip insert, the latter being either separate strips bonded by the stiffening or reinforcing means or formed from one strip by cutting to near its base to form the separate strips.

According to another aspect of the invention it is proposed that -run flat tyre inserts of the type described be formed as one piece, possibly with parts thereof being partly separable, with their wheel contacting or inner surface formed of a harder material than the remainder of the insert.

The formation of a harder inner surface maybe by particular treatment of the material used to form the inserts say during moulding. Another possibility may be to bond a harder layer of material to the insert. A further possibility may be to coat the inner surface of the inserts with a material that will set to a harder finish than the remainder of the insert.

The preferred harder material is of rubber or other elastomeric material.

Run flat tyre insert of the present invention are preferably not shaped to fit any particular wheel well although they will preferably have a convex bottom so as to fit snugly into any wheel well shape.

The inserts of the invention may be coated or covered entirely with a flexible, resilient, airimpermeable membrane, such as butyl rubber, say by dipping. Such a coating or covering may provide the desired strength for the inserts to resist centrifugal displacement during normal vehicle wheel running, whilst not unduly impairing expansion properties of the insert because of the flexibility and resilience of the coating.

It may be possible to use EPDM but as a mixture with a relatively impermeable rubber, such as butyl rubber.

It may be necessary to make alternative arrangements for pressurising a tyre fitted with an insert of the invention for a preferred insert, which has a base and seperable annular rings integral with the base, inflation of the tyre may be through a valve connected to a vent between two of said rings.

Alternatively, inflation of the tyre could be through a wall of the tyre so as to avoid the insert.

The wheel well is preferably provided with one or more, optionally sealable, vents for pressure equalisation below the tyre insert with atmosphere.

The inserts of the present invention are particularly suitable for unitary wheel constructions as they are easy to fit due to their flexibility.

The invention will now be further described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a section through a wheel, insert and tyre; Figure 2 is a section through a wheel an alternative insert and tyre; Figure 3 is a section through a wheel another alternative insert and tyre; Figure 4 is a section through a wheel, yet another alternative insert and tyre; Figure 5 is a section through a yet further alternative insert for a tyre; Figure 6 is a section through one further alternative insert for a tyre; Figure 7 shows another further alternative for a wheel base; Figure 8 shows an insert for the wheel base of Figure 7; Figure 9 shows detail of interlocking of the insert of Figure 8 on the wheel base of Figure 7; Figure 10 is a section through a wheel, tyre and insert showing another aspect of the invention; and Figure 11 is a section through a wheel, tyre and insert showing yet another aspect of the invention.

Referring to Figure 1 of the accompanying drawings, a vehicle wheel 10 is fitted with a tyre 12 and a run flat insert 14 of closed cell elastomeric material which expands on heating such as caused by working thereof when the tyre runs flat. Expansion of the insert allows "get home" running of the tyre pending repair. The wheel 10 has an integral rim 16 and a detachable rim 18 which is located and secured by bolts 20 to the wheel. The rims 16 and 18 are shaped for retention of the tyre 12 when expanded.

The insert 14 is in one piece and is arranged annularly of the wheel. To its inner surface is bonded a spring steel band 24 that serves to combat centrifugal forces pulling the insert from the wheel during normal running of the wheel and to prevent circumferential slippage of the insert.

To fit the insert to the wheel, the detachable rim 18 has to be first removed. Then, the insert can be pushed over the wheel and the rim 18 reattached.

Turning to Figure 2 of the accompanying drawings, a similar arrangement to that of Figure 1 is shown except that the insert (14') split circumferentially to form rings 28 separate at least over part of their height.

In both Figure 1 and 2, the steel band 24 may be rubberised on its surface that contacts the wheel.

Turning to Figure 3 of the accompanying drawings, the insert 14'' is a single piece insert as in Figure 1 but has a rubberised inner surface for stiffness and to reduce slippage rather than a metal band. In Figure 4, the arrangement is the same as in Figure 3 except that the insert 14''' is of the separable strip type as shown in Figure 2.

The embodiments of Figures 1 to 4 and variations thereon may all be modified to provide for positive location of the insert on the wheel such as by means of cooperating complementary formations, preferably axially of the wheel such as interengaging channels and ribs.

For example, see Figure 5 in which an insert 44 has a steel band or rubberised layer 46 on its inner surface, the band being notched to provide ribs 48 to locate in channels of the wheel rim.

An alternative steel band formation is shown in Figure 6, where the steel band 60 bond to insert 62 is of corrugated formation. Such a band may permit expansion thereof for fitting to the wheel.

Finally Figures 7 and 8 show a wheel base 70 and run-flat insert 72 therefore, in which the wheel base has a plurality of tangential hook members 74 of spring metal. The hook members 74 are formed with a lateral channel 76 intended to locate under corresponding slots 80 of transverse receivers 78 on the inner circumference of the insert 72 (see Figure 9). After fitting the insert 72 and a tyre to the wheel 70 they are turned around the wheel until the hooks and receivers are engaged. The receivers 78 should be such as not to prevent the last tyre bead from entering the wheel well for fitting on well based wheels.

In Figure 10 of the accompanying drawings, a wheel 100 has a well 102 formed between rims 104 and carries a tyre 106. Within the tyre 106 annularly of the wheel is a run-flat tyre insert 108 of closed cell rubber or elastomeric material coated with an air impermeable membrane 110 of butyl rubber.

The insert 108 has a base 112 and four rings 114 integral therewith but separable. The base 112 has a convex surface so as to enable it to fit snugly to any wheel well shape but not necessarily contact it over its entire area.

A valve 116 for inflation of the tyre is fitted to the well 112 and communicates with a space 118 between two of the rings 114. Alternative sites for the valve may be through the tyre wall itself or to communicate with the tyre between the outer surface of insert and the inner tyre wall.

In this embodiment it is intended to hold the insert against displacement by use of differential air pressure although the more resistant material alone might prove sufficient at lower speeds.

Thus in Figure 10 pressure air enters the air space between tyre and insert at say (for example only) 30-psi, through the valve 116. - The insert is sealed against the rim and tyre beads by compression and shaping of the insert and/or tyre beads. The base of the wheel has a vent 126 to atmosphere which may or may not be closed or plugged after inflation of the tyre.

The pressure air now exerts 30 psi on the surface of the insert forcing the insert against the base of the wheel where the pressure is only atmospheric. A resistance to radial displacement of 301bs has now been enacted and the engineered resistance of the insert itself ie.

resistance to stretching.

However, it is believed that with most closed cell elastomeric materials such as EPDM natural rubber etc, a gas under pressure eventually permeates the cells until the pressure within the cells equals that on the surface. Therefore in Figure nowhere the insert has an impermeable skin, the insert is compressed by pressure air against the base of the wheel and at 30 psi to near half its free air size ie. until the gas in the cells reaches 30 psi.

Because of the impermeable skin the insert remains in this state and does not grow to its original free air size as in the case with a normal insert without an impermeable skin. Upon loss of pressure air from the tyre the insert returns to its normal uncompressed or free air size.

Turning to Figure 11 of the accompanying drawings, instead of the insert being entirely coated with an air-impermeable membrane, only the lower surface of the insert has a rubber or other elastomeric coating or layer 120 bonded thereto.

The embodiment shown in Figure 11 has the base of the insert (that portion in contact with the tyre beads and wheel rim or base) only constructed of an impermeable resilient material such as butyl rubber.

Thus in this case pressure air enters the airspace between tyre and insert through the inflation valve 116. The insert is compressed and held against the wheel in the same manner as described in Figure 1.

However over a period of time the insert's closed cell material is permeated by pressure air causing it to "grow" back to its original free air size (Note: in the free air state and before fitting, the pressure in the closed cells is equal to the outside air pressure). At this stage the pressure in the closed cells is equal to the tyre inflations pressure (say 30 psi).

The pressure air is prevented from escaping through the vent 126 or getting below the insert by the impermeable base of the insert and this base still has the pressure 30 psi holding it onto the wheel base and resisting centrifugal force.

On puncture of total loss of pressure air from the tyre the insert will immediately expand to a much greater volume -and probably fill the tyres air cavity and being restricted by the tyre casing from further expansion and the resilient strength of the closed cell walls, a residual pressure is maintained which will be dependent on the amount that the insert fills the tyre in its normal non-run flat condition and the inflation pressure of the tyre.

That could result in near normal or at least a higher tyre configuration on loss of pressure air, resulting in less heat build up and less thermal expansion, perhaps delaying thermal expansion until some of the pressure in the cells of the insert has been lost. This should be largely self governing and may result in extended run flat capability.

Claims (23)

1. A run flat tyre insert comprising closed cell elastomeric material, the insert being stiffened or reinforced around its base or otherwise be retained against slippage or centrifugal displacement.

2. A run flat tyre insert as claimed in claim 1, wherein the insert is bonded to a band of relatively stiff material.

3. A run flat tyre insert as claimed in claim 2, wherein said relatively stiff material is selected from metal, plastics and carbon fibre.

4. A run flat tyre insert as claimed in claims 2 or 3, wherein the band has a layer of relatively non-slip material on its wheel contacting side.

5. A run flat tyre insert as claimed in claim 4, wherein the non-slip material is of rubber or other elastomeric material.

6. A run flat tyre insert as claimed in claim 1, wherein the wheel contacting surface of the insert at least has been coated with rubber or other elastomeric material.

7. A run flat tyre insert as claimed in any one of claims 1 to 6, having one or more cooperating formations for location thereof on a wheel.

8. A run flat tyre insert as claimed in claim 7, wherein the insert has axial protrusion for locating in corresponding channels of the wheel.

9. A run flat tyre insert as claimed in claim 7, wherein the insert has slots for location of hook-like formations of a wheel.

10. A run flat tyre insert as claimed in any one of claims 1 to 5, wherein the band of relatively stiff material is corrugated axially.

11. A run flat tyre insert as claimed in any one of claims 1 to 10, wherein the insert is a single strip.

12. A run flat tyre insert as claimed in any one of claims 1 to 10, wherein the insert is of separate strips bonded together by stiffening or reinforcing means.

13. A run flat tyre insert as claimed in any one of claims 1 to 10, wherein the insert is formed from one strip cut to near its base to form strips.

14. A run flat tyre insert formed from one piece of closed cell elastomeric material with its wheel contacting or inner surface formed of a harder material than the remainder of the insert.

15. A run flat tyre insert as claimed in claim 14, wherein a layer of harder material in bonded to the insert.

16. A run flat tyre insert as claimed in claim 14, wherein the inner surface of the insert is coated with a material that sets to a harder finish than the remainder of the insert.

17. A run flat tyre insert as claimed in claim 14, wherein the insert is coated or covered entirely with a flexible, resilient, air impermeable membrane.

18. A run flat tyre insert as claimed in any one of claims 14 to 17, wherein the insert has parts thereof that are separable.

19. A run flat tyre insert as claimed in claim 18 comprising a base and separable annular rings integral therewith.

20. A run flat tyre insert as claimed in claim 19 having valve means for tyre inflation connected to a vent between two said rings.

21. A wheel fitted with a run flat tyre insert as claimed in any one of claims 1 to 20.

22. A run flat tyre insert substantially as hereinbefore described with reference to and as illustrated in any one of the accompanying drawings.

23. A wheel fitted with a run flat tyre insert substantially as hereinbefore described with reference to and as illustrated in any one of the accompanying drawings.