GB2044190A - Improvements in or relating to wheel rims for pneumatic tyres - Google Patents

Abstract

An assembly comprising a wheel rim 1 and an annular safety support member 4 mounted on the rim portion 7 between the rim bead seats 6 and extending radially outwards beyond the rim bead retaining flanges 11 to support a tyre 2 mounted on the rim when in a deflated condition. The support member 4 rotates with the rim 1 in the non-load-bearing condition but rotates relative to the rim 1 in the load-bearing condition to compensate for circumferential differences between the tyre tread 14 and the radially outer surface 25 of the support member 4. The confronting surfaces on the support member 4 and rim portion 7 are profiled to axially locate the support member on the rim. Preferably the radially inner surface of the support member is of shallow convex profile and the confronting surface on the rim portion is of shallow concave profile. Preferably the support member comprises a plurality of elongate arcuate elements connected end-to-end. Preferably the rim 1 is well-less. <IMAGE>

Description

SPECIFICAtlON Improvements in or relating to wheel rims for pneumatic tyres This invention concerns improvements in or relating to wheel rims for pneumatic tyres and in particular to an assembly of a wheel rim and an annular safety support member arranged and adapted to become load-bearing and support a pneumatic tyre mounted on the rim when the tyre is in a deflated condition.

It is known from U.K. Patent Specification No.

1,375,415 to provide an assembly of the above type in which the support member rotates with the wheel rim when the tyre is fully inflated but which rotates relative to the wheel rim when the tyre is deflated and supported by the support member. Such relative rotation compensates for the circumferential difference between the tyre tread and the radially outer surface of the support member thereby reducing undesirable heat built-up in the tyre and consequent destruction of the tyre. As a result-the vehicle can be driven to a suitable place of repair with the tyre in a deflated condition.

In such an assembly where the support member is rotatable relative to thewheel rim under load bearing conditions it is important to ensure the correct axial alignment of the support member on the wheel rim is maintained. In the assembly disclosed in U.K. Patent Specification 1,375,415 the wheel rim is a conventional one-piece rim and the support member is located in the usual tyrefitting well. Axial alignment of the support member is achieved by the provision of spaced iugs at intervals around the radially inner peripheral portions thereof so that the support member occupies the full width of the well.

A problem arises in axially locating a support member of the tyre described in U.K. Patent Specification 1,375,415 on a well-less wheel rim, e.g. rims having a detachable flange, since the surface of the rim portion between the bead seats is flat. If the radially inner peripheral portion of the support member is constructed to extend across the entire width of the rim portion between the bead seats the tyre beads engage the support member and considerable frictional resistance to rotation of the support member relative to the rim is produced when the tyre is in a deflated condition. Consequently not only is the efficiency of the support member in compensating for the circumferential difference between the tyre tread and support member reduced but the tyre beads may be damaged necessitating replacement ofthetyre.

In order to overcome this problem it has been proposed in U.K. Patent No. 1,522,028 to provide a bearing ring for the support member. The bearing ring is mounted on the surface of the rim portion between the bead seats and is formed with a channel section groove in which the support member is axially located. The bearing ring is held against rotation relative to the wheel rim by the frictional engagement of the tyre beads while the support member is free to rotate on the bearing ring when the tyre deflates.

The provision of a bearing ring not only increases the number of components of the assembly and hence the cost but also complicates assembly.

It is an object of the present invention to provide a support member, in particular but not exclusively for a well-less wheel rim, which substantially reduces the aforementioned disadvantages.

According to the present invention we provide an assembly comprising a wheel rim and an annular safety support member adapted to become load bearing and support a pneumatic tyre mounted on the rim when the tyre is in a deflated condition, the rim having a pair of axially spaced bead seats, each terminating-at its axially outer edge in an associated bead retaining flange and an annular rim portion between the bead seats, the support member extending circumferentially around said annular rim portion and projecting radially outwards beyond the bead retaining flanges, the radially inner surface of the support member and the confronting surfaces of said annular rim portion defining complementary locating formations constructed and arranged such that, in use, the support member is rotatable relative to said annular rim portion under load-bearing conditions but is retained against movement in an axial direction relative to the wheel rim.

The complementary locating formations may cbmprise an annular rib on one of the wheel rim and support member which engages an annular-groove or recess of complementary cross-section in the other of the wheel rim and support member. Preferably the groove or recess and the rib are of complementary arcuate cross-section. In one preferred construction the annular rim portion extending between the rim bead seats has a shallow concave profile-in cross-section and the confronting surface of the support member has a complementary convex profile in cross-section.

The support member is preferably of the type disclosed in the above-mentioned U.K. Patent Specification No. 1,375,415 and comprises a plurality of elongate arcuate elements attached end-to-end to form an annular hoop. The elements may be made of metal, solid natural or synthetic rubber, or any suitable plastics material or any combination of these materials in sandwich form. The materials may include additives to reinforce the elements and/or provide any other desirable properties.

Preferably means is provided to substantially reduce the friction between the support member and the wheel rim, for example, a lubricant may be provided between the confronting surfaces of the support member and wheel rim during assembly or the lubricant may be contained in containers located in the radially inner surface of the support member and arranged to release the lubricant only when the support member becomes load bearing as described in our co-pending U.K. Patent Application No.

790803 published on 10 October 1979 under Serial No. 2017598A. Alternatively one or both of the confronting surfaces may be coated with a material having a relatively low coefficient of friction, for example Teflon (Registered Trade Mark).

The wheel rim may have a well, but more preferably the rim is well-less. Thus the rim may have a conventional detachable flange to facilitate fitting of the tyre. Alternatively the rim may be of the type disclosed in our co-pending U.K. Patent Application Nos. 7932160,7932161 (serial Nos. 2030086 and 2030087)7932159 (Serial No. 2030085) and 793218 published on under Serial Nos.

respectively.

Where the rim is multi-component sealing means is provided for effecting an air-tight seal at the interface between adjacent rim components. The sealing means may comprise a respective seal element for each interface. Preferably the sealing means comprises a liner member which extends circumferentially around the outer surface of the rim and extends across substantially the entire axial width of the rim. Sealing means comprising a liner member for a multi-component wheel rim is the subject of our co-pending U.K. Application No. published on under Serial No.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings wherein: Figure lisa radial cross-section of an assembly according to the present invention with a tyre mounted on the rim; Figure 2 is an exploded perspective view of the wheel rim shown in Figure 1; Figure 3 is a side elevation of part of the support member shown in Figure 1; Figure 4 is a section on the line A-A of Figure 3, and Figure 5 is a plan view of the attachment means for two successive portions of the support member shown in Figure 3.

The assembly shown in Figure 1 oftheaccom- panying drawings comprises a multi-component well-less wheel rim 1 having a radial ply tyre 2 mounted thereon, sealing means 3 for effecting an air-tight seal at the interface between adjacent rim components and support member 4 for supporting the tyre when in a deflated condition.

The multi-component well-less wheel rim 1, formed by three similar rim components 5 shown in Figure 2, comprises a pair of axially spaced bead seats 6 separated by an annular rim portion 7. The rim profile 7 is of arcuate cross-section having a gentle concave profile. Each bead seat 6 is similar and comprises an annular groove of substantially channel section. Each groove has a base portion 9 and a pair of opposed side portions 10, 11 which extend in a generally radially outwards direction relative to the base portion 9. The axially inner side portion 10 of each groove leads to the rim portion 7 while the axially outer side portion 11 of each groove defines a bead retaining flange and terminates in a rolled over radius 12.An annular attachment flange 13 integral with the base portion 9 of each component 5 provides means for attaching the wheel rim 1 to the usual wheel disc (not shown).

The radial ply tyre 2 has a tread portion 14, a pair of sidewalls 15, and a pair of annular axially spaced tyre beads 16. Each bead 16 is similar and comprises a bead core having a steel wire cable 17 of annular cross-section and a triangular bead apex 18. The bead core is substantially inextensible. A single steel cord ply 19 extends circumferentially around the tyre from one bead to the other bead. The ends of the ply 19 are wrapped around the associated bead core.

Tread reinforcements indicated generally by the reference numerai 20 are provided radially outwards of the ply 19 and reinforce the crown of the tyre.

Each bead 16 is received in a respective one ofthe grooves and the diameter of the substantially inextensible bead cables is less than the maximum diameter of the side portions 10,11 of the associated groove. Consequently the beads are retained in the associated groove both when the tyre is inflated and deflated. A bead retention system of this type forms the subject-matter of our above-mentioned copending U.K. Patent Application No.7932159.

The sealing means 3 for the rim components 5 comprises an elastomeric liner member 21 of airimpermeable material, for example, a rubber such as butyl rubber, moulded to the profile of the rim 1. The liner member 21 extends circumferentially around the wheel rim 1 and provides a lining for each bead seat 6 and the rim portion 7. The liner member 21 is of substantially uniform thickness appart from two resiliently deformable portions 21a of increased thickness each of which lines the axially inner side portion 10 of a respecitve one of the grooves. The portions 21a are resiliently deformable to facilitate insertion of the seal element and tyre bead into the groove during assembly and subsequently to hold the bead under compression in the associated groove and prevent the bead from slipping relative to the groove.

The support member 4, shown in more detail in Figures 3,4 and 5, comprises a plurality of rigid support elements 22 connected end-to-end by elongate links 23 pivotally mounted at their end regions on pivot pins 26 carried by the elements 22. Each support element 22 is similar and is of arcuate profile in side elevation, Figure 3, so that the assembled support elements 22 forms an annular hoop which extends around the rim portion 7. As best shown in Figures 1 and 4 opposed surfaces 24,25 of each support element 22 are of arcuate cross-section having a convex profile, the surface 24 being complementary to the concave profile of the rim portion 7. Consequently when the support means 4 is positioned on the rim 1, the support means 4 is restrained against movement in an axial direction relative to the rim 1. A suitable lubricant (not shown) is provided between the radially inner surface 24 of the support member and the lining member 21 so as to reduce friction therebetween and facilitate relative rotation between the support member and the wheel rim under load-bearing conditions.

Assembly of the wheel rim 1, tyre 2, sealing means 3 and support means 4 is as follows, the support means 4 is assembled and placed inside the tyre 2. A section of the liner member 21 is pushed into position followed by one of the rim components 5.

The tyre 2 is raised to the vertical with the fitted section of the liner member 21 and rim element 5 at the top allowing the support member 4 to hang therefrom. The remaining section ofthe liner mem ber is pushed into position followed by the other two rim elements 5 ensuring that the radially inner surface 24 of the support means 4 is opposite the annular rim portion 7. The usual wheel disc (not shown) is then attached to the flanges 13 to retain the components in position and the tyre inflated via the usual valve (not shown).

As shown in Figure 1 the support member4 extends radially outwards from the rim 1 but is spaced from the crown of the tyre 2 when the latter is inflated. In this condition the support member 4 is non-load-bearing and the dimensions of the support member 4, liner member 21 and wheel rim 1 are such that the support member 4 rotates with the wheel rim 1 i.e. there is no relative rotation.

When the tyre is deflated, the tyre beads 16 remain in the associated groove and the crown of the tyre engages the radially outer surface 25 of the support member4which becomes load-bearing and prevents complete collapse of the sidewa Ils 15so that control of the vehicle can be maintained. In this condition the support member 4 rotates relative to the wheel rim 1.

Rotation of the support member 4 relative to the wheel rim 1 compensates for the circumferential difference between the tyre tread and the radially outer surface of the support member 4 so that the vehicle can be driven to a suitable place of repair with the tyre 2 in the deflated condition without destroying the tyre 2. At the same time the support member 4 is axially located on the rim 1 so that the possibility of the support member 4 engaging the sidewalls 15 and causing destruction of the tyre 2 is substantially eliminated.

It will be understood that the invention is not restricted to the above-described embodiment which may be modified in a number of ways. For example, the annular rim portion 7 may have a convex profile in cross-section and the radially inner surface 24 of the support member 4 a complementary concave profile in cross-section.

The lubricant for reducing friction between the support member 4 and liner member 21 may be contained in containers located in recesses in the radially inner surface of the support member as described in our aforementioned co-pending U.K.

Patent Application No. 7908303. Alternatively the liner member 21 may be made of a material which readily ruptures upon loads being applied to the support member 4 following deflation of the tyre so that the support member 4 rotates on the rim portion 7 and relative rotation is not hindered by the liner member. In this arrangement the radially inner surface 24 of the support member and the annular rim portion 7 may be coated with a material having a low coefficient of friction e.g. Teflon (Registered Trade Mark).

The sealing means 3 may be replaced by individual seal elements which are located between the confronting surfaces of adjacent rim components.

It will be understood that the invention is not restricted to wheel rims of the above-described type in which the bead seats are formed by annular grooves but is applicable to any type of wheel rim having an annular rim portion between the bead seats which can be profiled to co-operate with the radially inner surface of the support member to axially locate the support member and aliow relative rotation between the support member and the wheel rim. Thus the invention is applicable both to assemblies in which the rim is well-less and has a detachable flange to facilitate tyre fitting and to assemblies in which the rim is a single component including a well to facilitate tyre fitting. Where the rim is a single component the sealing means of the abovedescribed embodiment may be omitted.

Finally the invention is applicable to assemblies in which the tyre is a radial ply, cross-ply or belted bias ply tyre.

Claims (17)

1. An assembly comprising a wheel rim and an annular safety support member adapted to become load-bearing and support a pneumatic tyre mounted on the rim when the tyre is in a deflated condition, the rim having a pair of axially spaced bead seats each terminating at its axially outer edge in an associated bead retaining flange and, an annular rim portion between the bead seats, the support member extending circumferentially around the annular rim portion and projecting radially outwards beyond the bead retaining flanges, the radially inner surface of the support member and the confronting surface of the annular rim portion defining complementary locating formations constructed and arranged such that in use, the support member is rotatable relative to said annular rim portion under load-bearing conditions, but is retained against movement in an axial direction relative to the wheel rim.

2. An assembly according to claim 1 wherein the locating formations comprise an annular rib on one of said wheel rim and support member in engagement with an annular groove or recess of complementary cross-section in the other of said wheel rim and support member.

3. An assembly according to claim 2 wherein said locating formations are of arcuate profile in transverse cross-section.

4. An assembly according to claim 2 or claim 3 wherein the rib is on the support member.

5. An assembly according to claim 4 wherein the rib is of shallow convex profile and extends across the entire width of the support member.

6. An assembly according to any one of the preceding claims wherein the support member comprises a plurality of elongate arcuate elements connected end-to-end.

7. An assembly according to claim 6 wherein the adjacent ends of successive elements are connected by releasable attachment means.

8. An assembly according to any one of the preceding claims wherein friction reducing means is provided between the confronting surfaces on the support member and the wheel rim.

9. An assembly according to claim 8 wherein the friction reducing means comprises a liquid lubricant.

10. An assembly according to claim 9 wherein the lubricant is contained in a container located in a recess in the radially inner surface of the support member and arranged to release the lubricant only when the support member becomes load-bearing.

11. An assembly according to any one of the preceding claims wherein the wheel rim is well-less.

12. An assembly according to claim 11 wherein the rim has a detachable flange.

13. An assembly according to claim 11 wherein the rim is formed by three or more arcuate segments.

14. An assembly according to claim 12 or claim 13 including sealing means for effecting an air-tight seal at the interface between adjacent rim components.

15. An assembly according to claim 14 in combination with claim 13 wherein the sealing means comprises a liner member which extends circumferentially around the outer surface of the rim and across substantially the entire axial width of the rim.

16. An assembly according to any one of the preceding claims including a tyre mounted on the wheel rim, the tyre having a pair of axially spaced tyre beads each of which is seated on a respective one of said bead seats.

17. An assembly comprising a wheel rim and an annular safety support member substantially as hereinbefore described with reference to the accompanying drawings.