IE45733B1 - Improvements to tyre and wheel rim assemblies - Google Patents

Description

This invention relates to tyre and wheel rim assemblies and to tyres therefor, and also concerns improvements in or relating to wheel rims for use in such tyre and wheel rim assemblies.

In conventional tyre and wheel rim assemblies the tyre beads are retained on their respective bead seats by means of the internal air pressure and frictional restraint due to the compression in the elastomer under the bead wire when fitted onto the tapered seat of the rim. Lowering the air pressure in the tyre, however, lessens the retention force from internal air pressure and eventually at a sufficiently low internal pressure the assembly reaches an unsafe condition in which the tyre beads may be displaced from their seats by sideways force such as is generated in an accident avoidance manoeuvre.

The European motor industry uses a variety of tests to check bead dislodgement. A typical test is carried out by testing a tyre and wheel rim assembly as the outer front wheel i.e. a left-hand or near side in a right-hand J turn test at 25 mph. The test comprises straight running at 25 mph and then the sudden application of full steering lock. The test is repeated at progressively reducing tyre inflation pressures until dislodgement occurs. Usually the pressure reduction steps are 2 psi. Typical production tubeless radial ply car tyres normally dislodge a bead at air pressures of the order of 5-15 psi in such a test. 43733 Dislodgement of a tyre bead from its seat affects vehicle control. In the use of wheels which include a well to allow tyre fitting there is generally a grave danger of complete separation of the tyre from its wheel rim. in the use of a vehicle, cornering generates sideways [ forces which displace the tread laterally with respect to the wheel rim. These forces are transmitted by the tyre carcass to the tyre bead. In the region of the tyre adjacent to the ground contact area axial forces (i.e. in the direction of the tyre axis) and turning moments (i.e. about a circumferential line through the bead) are generated. In the absence of air pressure these forces may be sufficient to produce lifting of the heel of the bead thus reducing the frictional force between the bead base and the bead,seat on the rim which, in said deflated state, is the only force which retains the bead on its seat. As a result the bead moves down its tapered bead seat laterally inwardly of the rim flange reducing the tension in the bead wire and, very rapidly the residual bead retaining force becomes less than the dislodging forces and the bead leaves its seat and falls into the well.

Previous attempts to solve this problem have centred around the use of wheel rims which do not have a well. The resultant flat-based rim obviates the danger of tyre wheel separation but has the disadvantage that the tyre beads are usually able to move axially between the spaced-apart flanges. Thus the sideways force which can be transmitted between the wheel and the ground changes suddenly from zero when a bead is moving across the rim to a maximum when both beads are 7 3 3 together against a flange. This may, in the extreme, cause loss of control of the vehicle.

This is equally true for a well based rim having a filling device, a wheel rim which has a fitting well closed by crimping after tyre fitting or a divided wheel rim assembly.

A divided wheel rim system requires several extra components with consequent disadvantages in sealing the air chamber of the tyre, increased cost, increased weight and increased complexity for servicing. The well filling system also increases the assembly weight, cost and complicates servicing even though a one-piece wheel rim may then be utilised. None of these previous attempts, however, overcome the problems of side force transmission when a bead moves axially across the rim.

Bead spacer rings which are rigid circumferentially extending rings filling the space between the two beade have been proposed for use with divided wheel rims to hold both beads in place, see for example, U.K. Patent No. 222,768, Such devices provide the required properties but add yet another component to the already complex divided wheel rim assembly.

Another modification to a divided wheel rim having a flat base and no well ie disclosed in . Patent No. 36618 in which a notch is formed between two wheel rim components at the outboard bead side of the flat base rim and an extended rubber toe is provided on the bead which rests freely in the notch. This assembly is still subject to all the complications of divided wheel rims including the air sealing problem and uses a flat based wheel rim for safety in high side force conditions.

Yet another system is shown in U.K. Patent No. 890,959 where a divided wheel rim is proposed in which a fabric reinforced, rubber covered extension of the bead is clamped between the rim parts to seal the assembly. Whilst this may retain the bead, effective sealing depends on accurate assembly and clamping of the bead extension.

The system is also still subject to the general dis10 advantages of divided wheel rims.

One-piece flat based wheel rims are known and one such assembly is disclosed in U.K. Patent No. 1,348,891 where a one-piece wheel rim has provided a well for tyre fitting which is subsequently closed by permanently crimping it closed so as to provide a flat based rim. Such an assembly has the further disadvantage of it being necessary to destroy the rim to repair'the tyre or check the inside for damage.

Still another system is to provide a well in the normal bead seat area at one side of a flat based wheel rim and having fitted the tyre over the flanges using this well to press both beads against the flange furthest from the well and insert a well filler whioh subsequently forms the bead seat. Such a system is disclosed in U.S. Patent No. 3,884,286.

Attempts to overcome the problems of bead retention and yet allow the uee of a normal well in a wheel rim have included small circumferentially extending humps formed in the rim adjacent to the bead. Such humps can be 1.7 mm in 7 3 3 height relative to the bead seat toe diameter but, in any case, these must be limited to dimensions which permit a tyre to be fitted to its seats by inflation pressure without damage. The sideways forces generated by the road when the tyre is deflated greatly exceed the force generated by the inflation pressure and thus any hump which allows tyre fitting cannot prevent bead dislodgement and thus the tyre bead is able to enter the well.

One-piece wheel rims having radially movable stops adjacent to the bead seat are also known but here again to provide the necessary stop movement adds complication, cost and air sealing problems to the assembly.

More'recently in U.S. Patent No. 3,951,192 it has been proposed to provide hook-like extensions formed on the outer lower sidewall areas of the tyre and shaped to engage around the wheel rim flange so as to resist bead movement. However, sideways forces rotate the bead with resulting heel lifting and thus this construction cannot, in our experience, be satisfactory. In addition they are subject to the likelihood of damage from kerbstones.

Thus all known previous attempts to provide for positive bead retention and thus the ability to control a vehicle even when a tyre is deflated have either not provided a solution or have been complex and therefore too costly.

The automobile industry currently fits tyres to rims automatically using firstly a machine which rolls both beads over one flange using the well to give the necessary clearance and secondly a so-called ’explosion’ inflation device which 5733 almost instantaneously inflates the tyre and forces the beads onto their respective bead seats. This means that the industry requires tyre and wheel ritns compatible with this machinery.

We have investigated the phenomena of the forces involved in dislodging the beads of a tyre from a wheel rim when on a vehicle. We have also investigated the phenomena of the forces involved in fitting tyres to and removing tyres from wheel rims. We have found that the road generated * forces· involved in tyre bead dislodgement are quite different from the forces involved in the removal of a tyre from the wheel rim with the wheel tyre assembly removed from the vehicle for tyre replacement or repair. 7 3 3 According to one aspect of the present invention a tyre and wheel rim assembly is provided wherein the tyre comprises a tread portion, sidewalls and a pair of beads each containing a substantially inextensible annular bead core and being seated upon a respective bead seat one at each side of the wheel rim; the wheel rim including a tyre fitting well and being formed axially inward of and adjacent to one bead seat to provide a circumferentially extending groove which axially and radially locates at least the radially inward extremity or tip of an extended toe portion of the associated tyre bead, the said toe portion comprising elastomeric material, extending lengthwise from the annular bead core to the tip in a direction radially and axially inwards of the annular bead core, being flexible in a direction perpendicular to its length to allow tyre fitting and being of a rigidity in the direction of its length such that when an axially inward force at the tread portion is applied to the bead by the tyre sidewall in the ground contacting portion of the tyre circumference, a radially and axially outwardly directed force is generated at the annular bead core in the ground contacting portion of the tyre circumference, the generated force tensioning the annular bead core and retaining the bead.

Preferably the toe rigidity is enhanced by means of a reinforcement layer adjacent to the surface of the toe. The reinforcement layer may extend part of the way around the toe or all of the way around the toe and may comprise one or more plies of material. Preferably the reinforcement ply comprises a fabric which may be cross-woven or knitted.

The elastomeric material of the toe preferably has a hardness measured under laboratory conditions greater than 50° Shore. More preferably the hardness is in the range 60-96° Shore. 43733 It is preferred that the radially inward edge of the bead seat of the wheel rim is smoothly radiused into the circumferential groove and the grooves may have a symmetrical cross-section about a radial line taken through the point of maximum groove depth.

So that the toe will enter into engagement with the groove when the tyre is fitted to the wheel rim the axial length of the bead seat and toe of the ,tyreiwhen the tyre is straightened is preferably less than the distance from the heel point on the rim measured along the bead seat to the nearest point on the axially inboard face of the groove.

Whilst a groove and toe may be provided at either side of the wheel rim and tyre preferably a groove and toe is provided at both sides.

According to another aspect of the present invention a tyre for a tyre and wheel rim assembly comprises a tread portion, sidewalls, and a pair of beads each containing a substantially inextensible annular bead core, one bead having an extended toe portion comprising elastomeric material, extending lengthwise from the annular bead core in a direction radially and axially inwards of the annular bead core, being flexible in a direction perpendicular to its length to allow tyre fitting and being of a rigidity in the direction of its length such that, when the tyre is fitted to a wheel rim including axially inwards of and adjacent to a bead seat a circumferentially extending groove in which at least the radially inward extremity or tip of the toe portion is axially and radially located and an axially inward force at the tread portion is applied to said one bead by the tyre sidewall in the ground contacting portion of the tyre circumference, a radially and axially outwardly directed force is generated at the annular bead core 7 3 3 thereof in the ground contacting portion of the tyre circumference, the generated force tensioning the annular bead core and retaining said one bead.

According to a further aspect of the present invention there is provided a one-piece wheel rim for a tubeless pneumatic tyre wherein the radially outer profile of the wheel rim considered in a plane containing the axis of the wheel rim comprises, in sequence, from one edge of the wheel rim profile:a bead retaining flange; a substantially straight bead seating portion which tapers radially inwardly towards the axially inner region of the wheel rim; an open bead toe locating groove immediately adjacent to said bead seating portion formed by, again in sequence:a radially inwardly curving axially outer groove side portion; an outwardly concave groove base portion; and a radially inwardly curving axially inner groove side portion; a substantially straight flat ledge portion; a tyre-fitting well portion having a base diameter substantially smaller than the ledge portion and arranged to allow tyre fitting over the bead retaining flange; a second open bead toe locating groove formed by, again in sequence:a radially inwardly curving axially inner groove side portion, an outwardly concave groove base portion; and a radially inwardly curving axially outer groove side portion; a substantially straight bead seating portion which tapers radially inwardly towards the axially inner region of the wheel rim; and a bead retaining flange. 9a 7 3 3 Several embodiments of the present invention will now be described, by way of example only, to show the scope of application of the present invention. The embodiments will each be described in conjunction with diagrammatic drawings which relate to each embodiment as £ollowe:The first embodiment is a 180 65 SR 340 radial tyre and wheel rim assembly. A cross-sectional profile of the assembly is shown in Figure 1, a detailed half-section of the tyre is shown in Figure 2 and the rim is shown in detailed cross-section in Figure 5.

The second embodiment is a 180 65 SR 340 'Oenovo' (Registered Trade Mark) run-flat type of tyre/wheel rim assembly and a cross-sectional profile of the assembly is shown in Figure 3, a detailed half-section of the tyre is shown in Figure 4 and the wheel rim is shown in detailed cross-section in Figure 5.

Figures 6, 7, 8, 9, and 10 are shown to assist in the following description of the operation of the invention based on the current understanding of said invention and show respectively a cross-section of a tyre and wheel rim assembly in the ground-contacting area running deflated, an enlarged detail of the bead and wheel rim bead Beat area in the condition of Figure 6, a similar enlarged detail of the bead and wheelxim bead eeat area with a side force applied to the tyre tread, the tyre bead fitting operation and the tyre bead removal operation.

A third embodiment which is a 150/65 SR 320 radial ply tyre and wheel rim assembly is shown in cross-sectional 7 3 3 profile in Figure 11, a detailed half-section of the tyre is shown in Figure 12 and the wheel rim dimensions are to be described in relation to the wheel rim in cross-sectional profile of Figure 13.

A fourth embodiment is a 150/65 SR 320 'Denovo' (Registered Trade Mark) run-flat type tyre and wheel rim assembly. Figure 14 is a detailed half-section of the tyre and the wheel rim profile is again to be described with reference to Figure 13.

A fifth embodiment is a 240/65 395 radial ply tyre wheel rim assembly the cross-sectional profile of which is shown in Figure 15, a detailed half-cross-section of the tyre is shown in Figure 16 and the wheel rim is to be described with reference to Figure 13.

A sixth embodiment is a 240/65 395 'Denovo' (Registered Trade Mark) run-flat type tyre and wheel rim assembly shown in cross-sectional profile in Figure 17.

A detailed half-section of the tyre is shown in Figure 18 and again the wheel rim is to be described with reference to Figure 13.

A seventh embodiment, a 200/50-395 radial ply tyre and wheel rim assembly, is shown in cross-sectional profile in Figure 19, a detailed cross-section of the tyre is shown in Figure 20 and the wheel rim is to be described with reference to Figure 13.

An eighth embodiment is a 560 x 13 tubeless crossply tyre/wheel rim assembly shown in cross-section in Figure 21. The wheel rim of this embodiment is to be described with reference to Figure 13.

Figure 22 shows in cross-section an alternative wheel rim having a substantially straight portion outwardly of the normal flange face.

The ninth embodiment is a radial ply tyre mounted upon the wheel rim of Figure 22 and Figure 23 shows the assembly in eross.-section.

Figure 24 is a cross-section of a tenth embodiment which is a run-flat 'Denovo1 (Registered Trade Mark) tyre mounted upon the wheel rim of Figure 22.

Figure 25 is a cross-section of a final described embodiment which is an alternative radial ply tyre to that of Figure 23 having a construction particularly adapted to suit the wheel rim of Figure 22.

The embodiment of Figure 1 is a 180 65 SR 340 radial ply tyre with a steel breaker and fitted to a 110 mm wide wheel rim having a diameter of 342 mm.

As shown in Figure 2 the tyre has a single radial 5 carcass ply 1 of rayon and a breaker comprising two cut steel plies 2, 3 the cords of which are at 18° to either side of the midcircumferential plane of the tyre. The first ply 2 has an axial width of 126 mm. Each tyre bead wire 4 comprises a 6x6 (strands x turns) winding of 0.038 diameter steel wire coated with rubber. An apex strip 5 is positioned above each bead and has a length of 30 mm and is made from rubber of 80° Shore hardness. A filler 6 of rubber coated nylon tyre fabric is positioned around the bead wire with the nylon cords at 45° to the radial direction. A clinch strip 7 of rubber material is positioned in the outer part of the bead and extends to a radial height of 42 mm. An additional strip 8 of hard rubber material extends radially and axially inwards from the bead wire to form a toe 10. A toe reinforcement strip 9 of cross-woven nylon fabric is positioned with the cords of the fabric at 45° to the radial direction so as to extend from the clinch strip 7 around the outer surface of the bead and the toe 10 as shown in Figure 2.

The tyre is cured using a clip ring shaped to the required toe shape shown in Figure 2 and the completed tyre has an extended toe of hard rubber incorporating a reinforcement strip 9. The bead including the toe has an axial length A* of 20 mm, an end width B* of 5 mm and a radial length C* of 6 mm.

The hard rubber material of the toe strip 8 has a nominal hardness of 80° Shore.

The tyre of the assembly shown in Figure 3 is a 180 65 SR 340 'Denovo' (Registered Trade Mark) type tyre mounted on a 110 mm t wide wheel rim. Such a tyre/wheel rim assembly is designed to be able to run deflated for substantial distances.

The tyre is shown in more detail in Figure 4 and comprises a single radial carcass ply 11 of rayon and a breaker of two cut-steel plies 12,13 the cords of which are 18° to either side of the mid-circumferential plane of the tyre. The inner steel breaker ply has a width of 126 mm. A high resilience rubber composition 14 is used in the shoulder and upper side wall portions of the tyre as described in Irish Patent Specification No. 37065.

The tyre has a lubricant/sealant material coated on the inner surface of the tyre in the region of the tyre crown which provides a sealant to reseal a puncture and a lubricant to avoi,d internal damage and reduce heat build-up when running flat.

The tyre lower sidewall and bead is constructed the same as that for Example 1 and in both cases the tyres are fitted to a llo mm wide wheel rim as shown in Figure 5.

The wheel rim is rolled from .092 thick steel and the dimensions are as followssA llO mm L 21 mm Q ‘41 mm V · 29.5 mm 4i»733 P u B H T 20 mm 37 mm 12 mm 13 mm 5 mmD1 340 mm G 12 mm D 342 mmR9 7 mm radR4 6 mm radR5 4 mm radR8 5 mm rad maxR7 3 mm rad T 5 mm W 5° + 1°R11 9 mm rad The above described tyre/wheel rim assemblies are suitable for a vehicle having an axle load of 1840 lbs.

Figures 6-10 relate to the operation of the bead lock and will be described later.

The tyre/wheel rim assembly of Figure 11 is a smaller tyre/wheel rim assembly being a 15U/55 SR 320 radial ply tyre fitted to a 95 mm wide rim.

The rim dimensions (Figure 13) are as follows:- A 95 mm B 12 mmD1 318 mmD2 320 mm G P 12 nm 18 mm H 13 mm L 20 mm Q 37 .5 mm T 5 mm U 27 mm V 27 mmR4 6 mmR5 4 mmR7 3 mmR8 5 mm Rg 7 mm W 5° + 1° The material thickness is .092.

The radial ply tyre shown in Figure 12 which is that of the assembly shown in Figure 11, comprises a single radial carcass ply 1 of rayon and a breaker comprising two cut-steel plies 2, 3, the cords of which are at 18° to either side of the mid-circumferential plane of the tyre. The first ply 2 has an axial width of 96 mm.

The bead wire 4 comprises a 5 x 4 (strands x turns) winding of .038 diameter steel wire coated with rubber. An apex strip 5 made from hard rubber compound as above is positioned above the bead and has a length of 25 mm. A filler ply 6 of rubber coated weftless nylon fabric is positioned over the bead wires with the nylon cords at 45° to the radial direction and a clinch strip 7 of hard rubber is positioned outwardly overlapping the apex strip 5 and extends to a radial height of 36 mm. *·» < JJ An additional strip of 80° Shore hardness rubber compound is used to form the toe 10 and a toe reinforcement strip of cross-woven nylon fabric to the same specification as the first example is positioned to form the outer toe surface. The toe construction is the same as in the first example except that the axial bead and toe length A* in this case is 18 mm whereas in the first example A* was 20 mm.

The tyre shown in Figure 14 is a run-flat 'Denovo' (Registered Trade Mark) type of tyre of the same overall 150 65 SR 320 dimensions as the tyre in Figure 12. It is fitted to the same rim as the tyre of Figure 12. The tyre differs from the radial tyre of Figure 12 in that the sidewalls are thickened and include a high resilience rubber compound 14 in the shoulder.

A lubricant sealant layer is utilised for run-flat performance. Both these features are the same as for the second embodiment.

The tyres of Figures 10-14 are suitable for small cars having an axle load of 1280 lbs.

The tyre/wheel rim assembly of Figure 15 is a 240/65 - 395 radial ply tyre fitted to a 395 mm diameter rim. The tyre constructional details are shown in Figure 16 and the rim dimensions, using the same nomenclature as Figure 13 are as follows :- A 170 mm B 12 mmD1 393 mm °2 395 mm G 13 mm 43733 P 20 mm H 14 mm L 21 mm Q 47 mm T 7 mm u 50 mm V 33.5 mmR4 8 mmR5 5 mmR7 5 mmR8 8 mm The material thickness is .144.

As shown in Figure 16, the tyre comprises a two ply radial casing 50 15 of rayon and two folded edge steel breaker plies 51. The tyre beads 54 each comprise a 6 x 6 (strands x turns) winding of 0.038 diameter steel wire coated with rubber. An apex strip 55 of 80°‘Shore hardness rubber is provided having a length of 42 mm. A filler ply 56 of rubber coated nylon fabric is positioned around the bead wire and extends to a radial height of 42 mm on the inside of the bead and 28 mm on the outside of the bead. The two carcass pliee 50 are arranged around the bead assembly in the usual manner and a climch strip 57 of 80° Shore hardness rubber compound is positioned outwardly of and overlapping the apex strip 55 so as to extend to a radial height of 48 mm.

The toe 60 is formed from a strip 58 of 80>° Shore hardness rubber compound and a toe reinforcement strip 59 of 7 3 3 cross-woven nylon material as used in the first example is positioned around the outer surface of the toe and bead as shown. The finished tyre has the shape shown in Figure 16 and the axial bead and toe length A* in this case is 20 mm as in the first embodiment.

The tyre and wheel rim assembly of Figure 17 is a 240/65 395 Oenovo' (Registered Trade Mark) type tyre fitted to a 395 mm diameter wheel rim. The tyre construction is shown in Figure 18 and its overall dimensions are the same as the tyre of Figure 16. The wheel rim is also the same as that described for the embodiment of Figures 15 and 16 . The tyre structure is basically tha same as that of the tyre of Figure 16 except that the sidewalls are thickened by a layer 61 of high resilience rubber. The details of the high resilience rubber reinforcement material are the same as for the first example in Figure 4 but in this case the material is 15 mm thick from the carcass ply in the tyre shoulder, 10 mm thick in the mid-sidewall region and tapers to the carcass under the breaker and at the apex strip as shown. The outer sidewall and clinch strip 57 are also thicker than in the radial tyre of Figure 16 the sidewall rubber being 8 mm thick in the mid-sidewall region.

The tyre/wheel rim assemblies of Figures 15-18 are suitable for a vehicle having an axle load of 3200 lbs.

The above described examples are all 65 series tyres i.e. each have an aspect ratio of 65%. The invention has also been applied to other aspect ratio radial tyres and the embodiments of Figures 19 and 20 is a 50 series radial ply tyre having dimensions of 200/50 - 395 and which is fitted i Ί V to a 395 mm diameter wheel rim having the same dimensions as the embodiments of Figures 15-18.

The tyre has a two-ply rayon carcass 61 and two folded ply steel breakers 62 having a width of 150 mm. The bead area is the same as that of Figures 15-18 in relation to construction, dimensions and materials.

The invention has also been applied to a cross-ply tyre one example of which, shown in Figure 21, is a 560/13 tubeless tyre which is mounted on the same wheel rim section as the first embodiment i.e. a 110 mm wide wheel . rim but with a diameter of 13. The tyre carcass comprises two plies 63,64 of rayon.

The bead wires in cross-section are dimensionally the same as the first embodiment and comprise a 6 x 6 (strands x turns) winding of .038 diameter steel wire coated with rubber. An apex strip < of 80° Shore hardness rubber material extends to a length of 30 mm and a clinch strip 71 of 80° Shore hardness rubber compound extending to a radial height of 42 mm is positioned in the outer regions of the bead. The bead toe 73 includes a reinforcement strip of cross-woven material exactly the same as the first embodiment.

Figures 22, 23 and 24 show an alternative wheel rim construction and two assemblies incorporating the rim.

The rim, shown in Figure 22, comprises at each edge a portion 71 which is substantially straight when viewed in cross-section as shown, and which provides a flat Surface which may contact a tyre fitted to the rim.

The remainder of the rim comprises at each side a flange 72 connectihg the straight portion 71 to a bead seat region 73. Immediately inboard of the bead seat region 73 is formed a groove 74 which extends circumferentially around the rim, one groove 74 being provided at either side of the rim. Between the two grooves 74 is provided a well 75 for tyre fitting in the usual manner. Typical rim dimensions are as follows:- A 125 mm B 17.6 mm U 42 mm L 29 mm 0 40 mm V 29.8 mm P 20 mm G 13.5 mm D 395 mmD1 393 mm T 5 mm H 13 mm X 5.7 mm w 5° + 1°R5 4 mm radR4 6 mm radR8 5 mm radR7 3 mm radR11 4 mm rad r^2 7 mm rad R13 45° The tyre and wheel rim assembly shown in Figure 23 comprises a radial ply tyre having a steel breaker 76 and a textile carcass reinforcement 77 fitted to the rim of Figure 22. The tyre is of the same construction as the first embodiment. The textile carcass reinforcement 77 follows the standard shape from the mid-sidewall region to s the bead region i.e. the initial portion A of the textile carcass reinforcement 77 is convex and the second portion B of the textile tarcass reinforcement is concave (both when considered from the outside of the tyre). The tyre has an outer bead profile to correspond with the wheel rim and in particular to the straight portions 71 so that the tyre then matches the wheel rim as shown. Bach tyre bead includes a bead wire 78 and an extended toe 79 which is formed from hard rubber material (for example 70-90° Shore).

The toe shape is such that the assembled tyre and wheel is as shown in Figure 23 and the toe ie the same as that described for the first embodiment.

The tyre and wheel rim assembly shown in Figure 24 is a run-flat version of the assembly shown in Figure 23 and comprises a single radial carcass ply SO of rayon'and a breaker 81 of two out-steel plies. The tyre is of the same construction as the second embodiment and the tyre beads are constructed as described to provide the required toe 79 to engage the grooves 74 in the rim. As described in the previous embodiment, the outer profile of the tyre in the region of the bead and 7 3 3 lower sidewall is moulded so that the tyre again matches the wheel rim as shown in Figure 24.

The assembly shown m Figure 25 comprises a tyre which has a ratio of height to width less than 1.0, in this case 0.65 and a carcass reinforcement having a neutral fibre that follows, at least between the mid-height of each of the sidewalls and their respective bead wire, the natural equilibrium curve of a single ply carcass having no breaker when such a carcass is subjected to inflation pressure. The curve is tangential to the bead wires, passes through the edges of the breaker and passes through the points in the sidewalls at which tangents drawn to the reinforcement are perpendicular to the tyre axis.

The tyre comprises a carcass reinforcement, ply 82 which is folded around each tyre bead wire 83,84 and a breaker structure 85 to reinforce the tread region. The carcass ply 82 in the lower sidewall zone is shaped to remain concave when viewed from outside the tyre until it becomes a tangent to the bead wire 83. Thus the reinforcement ply is concave throughout the zone indicated C. Above the lower sidewall zone C the carcass ply 82 follows the neutral equilibrium curve referred to until in the shoulder zone 86 it is blended to curve smoothly to become a tangent to the breaker structure 85 as shown.

The tyre carcass ply 82 in the lower sidewall zone C is particularly shaped so as to be substantially parallel to the straight portion of the wheel rim 71. Further 43733 details of the tyre carcass are published in U.S. Patent Specification No. 3,910,336.

According to the present invention, however, the lower bead region 87 is shaped the same as in the first embodiment so as to provide a toe 79 which engages the circumferentially extending groove 74 in the wheel rim to provide a bead lock according to the present invention.

As published in U.S. Patent No. 3,910,336 a property of this type of tyre is that the tyre character10 istics may be modified by changing the rim width for a given tyre width. This may be done as long an the flange, bead seat and circumferential groove shapes are maintained as shown without impairing the bead locking. 4S733 The operation of the invention will now be described with reference to the first embodiment. The discussion is for the tyre section in the ground contact area. The bead toe 10 is longer in the radial direction than the groove depth (6 and 5 mm respectively, see Figures 2 and 5) and thus when assembled by the method which will be described later the toe 10 is under a degree of precompression between the groove 15 in the wheel rim and the bead wire 4. The tyre is retained on the wheel rim by the normal bead wire tension force applied to the bead seat and the tyre/wheel rim assembly may be run inflated as normal.

Figure 6 shows the tyre and wheel assembly of Figure 1 in the tyre/ground contact area deflated but with no side force applied. In a cornering or turning manoeuvre a side force SF is developed increasing in intensity as the lateral acceleration increases. This side force distorts the tyre sideways relative to the rim and causes the outboard bead to rotate. As a toe is provided according to the present invention, the centre of rotation of the bead is the end lo of the bead toe which is located axially and radially in the groove 15 formed in the wheel rim and thus the moment is SF x Xj where Xj is the distance measured radially from the tread contact area to the centre of rotation.

The tyre bead is retained against this rotation by the moment of the bead wire tension about the same centre of bead rotation Tj x X2 where X^ = the axial distance of the bead wire from the centre of rotation. It should be noted that there is no retention force due to air pressure as the 4B733 tyre is. being considered in the deflated condition.

Figure 7 shows on an enlarged scale the forces applied to the outboard bead seat on the onset of bead rotation. In the condition shown the fitted bead tension T^ which pre5 compresses the rubber in the area under the bead wire is . sufficient to retain the bead on its seat by frictional grip, any moment due to the precompression force in the toe then being small.

Increased side force generates an increased moment SF χ This initiates the bead rotation and the bead wire begins to move in the direction I inwardly of the wheel rim.

The bead wire 4 is a substantially inextensible hoop around the wheel rim and thus cannot follow the required circular locus to rotate about the centre of rotation. Thus the bead wire 4 rotates and moves axially inwards to the position shown in Figure 8.-> The complete toe of the tyre, whioh has an effective length D1 in Figure 7 is therefore compreesed to a smaller effective length Dg in Figure 8 which shows the position when the tyre is subjected to a degree of side force.

The toe, being made from hard rubber and having a reinforcement ply and being dimensioned to have a substantial compression I stiffness or form stiffness along its length, is.of a rigidity in the direction of its length such that the reaction forces have a resultant force Fg generated by the toe against the bead wire 4 which has an axially outward component F^ and a radially outward component Fg. The force F^ greatly increases the tension in the bead wire 4. The latter tension adds to the tension force T^ an additional component Τ2· Thus the retaining moment T^ x X2 is increased to Tg X3 + T2 X3 and rotation of the bead section has occurred about the centre of rotation to provide a balanced force condition and no further bead movement.

The above force balance occurs in the ground contact area only where the high side force is in fact applied to the tyre by the ground. However, the increased bead wire tension affects the complete hoop of the bead wire 4 and tightens it onto the rim. This increases the grip of the tyre bead to the bead seat of the wheel rim. Bead rotation in the ground contact area may be of the order of 90° when considered as the angle of rotation of the normal bead seating portion 18 of the bead.

The bead toe between the bead wire 4 and the groove 15 may be given the required form stiffness by various means apart from the construction described. It may for example be made entirely from hard rubber composition or other elastomeric compositions and it has been shown that a toe of the same shape but made of rubber having a hardness of greater than 80° Shore gives a satisfactory bead lock. The composition may include known additives for providing the required properties for example fibrous reinforcements which may be linearly or randomly orientated.

The toe may have more than one reinforcement ply 9 and/or in addition the reinforcement ply may comprise separate sections of fabric. The fabric may be woven, non-woven or knitted and made from various reinforcement materials known in the art. The fabric of the reinforcement ply 9 is selected for two purposes, firstly to prevent bulging of the toe and thus contributing to the form stiffness when the toe is under lengthwise compression, and secondly to assist fitting as will be described. It should be noted that the toe materials are not under any substantial load but only a degree of precoropression except in the side force conditions which occur when steering of the vehicle is effected with the tyre deflated or substantially deflated when substantial compression forces may be generated in the toe.

The toe end 10 must be radially and axially inwards of the bead wire 4, so that it comes under increasing ' compression force when the bead is subjected to a rotational moment as described. The moment applied by the side force to the outboard bead may be increased in the ground contact area so as to generate the maximum increased compression and the greatest bead wire tension. The moment may be increased by using a stiffer lower sidewall area for example by a larger bead apex 5 than in conventional tyres and such a stiffened apex is'used in the examples. By lower sidewall is meant the sidewall.between the bead wire and a horizontal line drawn through the widest portion of the tyre when inflated to normal inflation pressure and unloaded.

The shape of the end 10 of the toe is not critical although the flat-ended construction shown in the Figures showing tyres is conveniently manufactured using a modified clip ring and using the moulding diaphragm to form the inner curved toe surface. When assembled to the rim the centre of pressure between the toe end and the groove, moves around the base of the groove 15 so that the toe does not readily buckle when the bead is rotated by the side force. Thus the 57 3 3 preferred groove shape has a radiused base as shown although othe^ shapes may be utilised.

The wheel rim may be rolled by the conventional wheel manufacturing process.

The initial location or grip of the toe end 10 in the groove base 15 before rotation begins may be further improved by means of roughening the groove surface e.g. by knurling although with the above described embodiments this is not necessary.

Tyre fitting to the rim is conventional. The tyre may 10 be fitted over the flanges by hand tools, normal service equipment, or automatic tyre fitting machinery. Upon inflation the bead slides onto its seat under the inflation pressure i.p. as shown in Figure 9. The toe being made of elastomeric material is able to bend to the position shown and when the bead reaches its fully home position on its bead seat 18 the toe is able to snap into the groove using the recovery properties of the rubber of the toe in combination with the reinforcement ply 9 . When fully inflated the toe positively engages in the groove as shown in Figures 1 and 3 so that the toe end 10 is radially and axially located in the groove base 15 and the toe is under a degree of precompression between the groove and the bead wire 4.

To ensure correct fitting the straightened bead base length Hj measured from the heel point H.P.l to the toe end 10 must be lees than the distance from the heel point H.P.2 of the rim along the bead seat 18 and to the nearest point on the inboard face 19 of the groove 15 i.e. the length of the line H2.

Furthermore in the embodiments described to ensure tyre fitting the distance measured in the axial direction from the vertical part of the flange to the centre line of the groove must be at least the same as the axial distance from the end of the toe to the flange contacting vertical part of the bead before the tyre is fitted. These dimensions are both 20 mm in the examples.

Tyre bead removal is shown in Figure 10. Conventional tyre removal tools comprise a spade ended tool 20 which is engaged between the wheel rim flange 21 and is then forced towards the centre of the tyre/wheel rinrassembly in the axial direction. The force does not produoe any substantial bead rotation and the tyre bead can be successfully dislodged with the toe flexing sideways and without any damage to the tyre bead or toe.

The tyre/wheel rim assemblies described-above in relation to Figures 1 -5 were tested as the outer front wheel in a J turn test (i.e. straight running followed by a full steering lock application) with the valve core removed. The test was repeated at successively higher speeds on a high grip tarmac surface. Neither of the embodiments dislodged at 40 mph which represents an applied side acceleration' of the order of 1 g. Higher speeds do not apply greater side force to the tyre since under such conditions the vehicle'slides. In Slalom testing at speeds in excess of 70 mph when the direction of the side force changed bead dislodgement did not occur. The assemblies were similarly proved on all'other wheel positions.

Accordingly the assemblies were absolutely safe from dislodgement at the maximum sideforce available even under extreme test conditions.

Even after the above tests the tyres were readily removed from the rime using a conventional hand-operated tyre demounting machine.

Filmed evidence of the tyre behaviour on the rim confirmed that the tyre bead moves in the ground contact area to lock the tyre to the wheel rim in the manner described.

Different rim widths and tyre sizes have been tested successfully using bead locks according to the present invention. In the case of different rim widths different material thicknesses may be required for wheel rim strength and to allow convenient rolling the groove dimensions are changed accordingly. The tyre toe dimensions are also changed in proportion and the invention operates precisely as in the detailed case described above.

The invention operates with different tyre section 10 widths, aspect ratios and bead diameters and applies to known tyre constructions tubed or tubeless including radial ply tyres, belted bias tyres, cross-ply tyres and runflat 'Denovo' (Registered Trade Mark) type tyres.

The bead lock is preferably applied to both tyre 15 beads although it may be applied to only the inboard or outboard bead.

Claims (54)

1. A tyre and wheel rim assembly wherein the tyre comprises a tread portion, sidewalls and a pair of beads each containing a substantially inextensible annular Bead core and being seated upon a respective bead seat one at each side of the wheel rim; the wheel rim including a tyre fitting well and being formed axially inward of and adjacent to one bead seat to provide a circumferentially extending groove which axially and radially locates at least the radially inward extremity or tip of an extended toe portion of the associated tyre bead, the said toe portion comprising elastomeric material, extending lengthwise from the annular bead core to the tip in a v direction radially and axially inwards of the annular bead core, being flexible in a direction perpendicular to its length to allow tyre fitting and being of a rigidity in the direction of its length such that when an axially inward force at the tread portion is applied to the bead by the tyre sidewall in the ground contacting portion of the tyre circumference, a radially and axially outwardly directed force is generated at the annular bead core in the ground contacting portion of the tyre circumference, the generated force tensioning the annular bead core and retaining the bead.

2. A tyre and wheel rim assembly according to claim 1 wherein t.he toe rigidity is enhanced by means of a reinforcement layer adjacent to the surface of said toe.

3. A tyre and wheel rim assembly according to claim 2 7 33 wherein the reinforcement layer extends from the tip of the toe around the axially inwards surface of the toe to at least the radial height of the centre of the annular bead core.

4. A tyre and wheel rim assembly according to claim 2 wherein the reinforcement layer extends from the bead seat region of the bead around the toe and upwards along the axially inner surface of the, toe to at least the radial height of the centre of the annular bead core.

5. A tyre and wheel rim assembly according to claim 2, 3 or 4 wherein the reinforcement layer comprises at least one ply of material.

6. A tyre and wheel rim assembly according to claim 5 wherein the reinforcement ply comprises a fabric.

7. A tyre and wheel rim assembly according to claim 6 wherein the fabric is a cross-woven fabric.

8. A tyre and wheel rim assembly according to claim 7 wherein the fabric is of nylon.

9. A tyre and wheel rim assembly according to claim 6 wherein the fabric is a knitted fabric.

10. A tyre and wheel rim assembly according to any one of claims 1-9 wherein the elastomeric material of the toe has a hardness when measured under laboratory conditions greater than 50° Shore.

11. A tyre and wheel rim assembly according to claim 10 wherein the hardness is in the range of 60 - 96° Shore.

12. A tyre and wheel rim assembly according to any oneof claims 1-11 wherein the radially inward edge of the bead seat of the wheel rim is smoothly radiused into the 4 5733 circumferential groove and the toe is profiled to a complementary shape.

13. A tvre and wheel rim assembly according to any one of claims 1-12 wherein the groove has a symmetrical crosssection about a radial line taken through the point of maximum groove depth.

14. A tyre and wheel rim assembly according to claim 12 or 13 wherein the groove has a smooth profile.

15. A tyre and wheel rim assembly according to any one of claims 1-14 wherein at least the base of the groove is roughened to increase the grip and thus the initial radial j and axial location of the tip of the toe.

16. A tyre and'wheel rim assembly according to any one of claims 1-15 wherein the axial length of the bead seat and toe of the tyre when the toe is straightened to extend in the axial direction for tyre fitting measured from the tip of the toe to the heel point, which point is the point of intersection of a line along the bead seating portion of the tyre and a line along the flange contacting portion of the bead, is less than the distance from the heel point on the rim measured along the bead seat and to the nearest point on the axially inboard face of the groove so that the toe will enter into engagement with the groove.

17. A tyre and wheel rim assembly according to any one of claims 1-16 wherein the axial distance from the vertical part of the flange to the centre line of the groove is at least as great as the axial distance from the flange contacting vertical part of the tyre bead to the end of the toe measured before the tyre is fitted to the wheel rim so that the toe will enterinto engagement with the groove.

18. A tyre and wheel rim assembly according to claim 17 wherein the said axial distances are in the range of 16-23 mm.

19. A tyre and wheel rim assembly according to claim 17 wherein 5 the said axial distances are both 20 mm.

20. A tyre and wheel rim assembly according to claim 17 wherein the said axial distances are both 18 mm.

21. A tyre and wheel rim assembly according to any one of claims 1-20 wherein a flat ledge is provided between the groove and the well. 10

22. A tyre and wheel rim assembly according to any one of claims 1-21 wherein a groove is provided at either side of the wheel rim and a toe is provided on both tyre beads.

23. A tyre for a tyre and wheel rim assembly comprising a tread portion, sidewalls, and a pair of beads each containing a substantially 15 inextensible annular bead core, one bead having an extended toe portion comprising elastomeric material, extending lengthwise from the annular bead core in a direction radially and axially inwards of the annular bead core, being flexible in a direction perpendicular to its length to allow tyre fitting and being of a rigidity in the 20 direction of its length such that, when the tyre is fitted to a wheel rim including axially inwards of and adjacent to a bead seat a circumferentially extending groove in which at least the radially inward extremity or tip of the toe portion is axially and radially located and an axially inward force at the thread portion is applied 25 to said one bead by the tyre sidewall in the ground contacting portion of the tyre circumference, a radially and axially outwardly directed force is generated at the annular bead core thereof in the ground contacting portion of the tyre circumference, the generated force tensioning the annular bead core and retaining said one bead. 4 8 7 a 3

24. A tyre according to claim 23 wherein the toe portion includes a reinforcement layer extending around and adjacent to the surface of said toe portion.

25. A tyre according to claim 24 wherein the reinforcement layer comprises a woven fabric.

26. A tyre according to claim 25 wherein the fabric is a cross-woven fabric and has both the warp and weft directions substantially at 45° to the radial direction.

27. A tyre according to claim 24, 25 and 26 wherein the reinforcement layer comprises nylon.

28. A tyre according to any one of claims 23-27 wherein the sidewall from the annular bead core towards the mid-sidewall region is reinforced so that said region resists bending.

29. A tyre according to any one of claims 23-29 wherein the tyre is a cross-ply tyre.

30. A tyre according to any one of claims 23-28 wherein the tyre is a radial ply having a radial ply carcass of steel or textile material and a breaker assembly of steel or textile material.

31. A tyre according to any one of claims 23-29 wherein the tyre is a belted bias tyre.

32. A tyre according to any one of claims 29-31 wherein the tyre has an aspect ratio between 50 and 65%.

33. A tyre according to any one of claims 23-32 wherein the tyre is adapted to run in a deflated condition without damage to the tyre.

34. A tyre constructed and arranged substantially as described herein and illustrated in any one of Figures 2, 4, 12 s 14 ,16 , 18, 20, 21 or 25 of the accompanying drawings.

35. A tyre and wheel rim assembly constructed and arranged substantially as described herein and illustrated in any one of 4S733 Figures 1, 3, 11, 15, 17, 19, 21, 23, 24 or 25 of the accompanying drawings.

36. A one-piece wheel rim for a tubeless pneumatic tyre wherein the radially outer profile of the wheel rim considered in a plane 5 containing the axis of the wheel rim comprises, in sequence, from one edge of the wheel rim profile:a bead retaining flange; a substantially straight bead seating portion which tapers radially inwardly towards the axially inner region of the wheel rim; 10 an open bead toe locating groove immediately adjacent to said bead seating portion formed by, again in sequence:a radially inwardly curving axially outer groove side portion, an outwardly concave groove base portion; and a radially inwardly curving axially inner groove side portion; 15 a substantially straight flat ledge portion; a tyre-fitting well portion having a base diameter substantially smaller than the ledge portion and arranged to allow tyre fitting over the bead retaining flange; a second open bead toe locating groove formed by, again in 20 sequence:a radially inwardly curving axially inner groove side portion; an outwardly concave groove base portion; and a radially inwardly curving axially outer groove side portion; a substantially straight bead seating portion which tapers radially 25 inwardly towards the axially inner region of the wheel rim; and a bead retaining flange. 4ii ?33

37. A one-piece wheel rim according to claim 36 wherein each open bead toe locating groove considered in cross-section is symmetrically shaped about a centre line extending radially with respect to the wheel rim through the point of minumum radius of the open locating groove. 5

38. A one-piece wheel rim according to claim 37 wherein said radial centre line is spaced in an axial direction from the bead retaining flange by a distance qf 18 mm.

39. A one-piece wheel rim according to claim 37 wherein said radial centre line is spaced in an axial direction from the bead retaining 10 flange by a distance of 20 mm.

40. A one-piece wheel rim according to claim 37 wherein the radii of curvature of the portions of each groove are, in sequence, 5 mm, 3 mm and 5 mm respectively.

41. A one-piece wheel rim according to claim 37 wherein the radii IS of curvature of the portions of each groove are, in sequence, 8 mm, 5 mm and 8 mm respectively.

42. A one-piece wheel rim according to claim 36 wherein the said bead seating portions have a diameter at the heel point of 320 mm and the axial distance between the spaced apart bead retaining flanges is 20 95 mm.

43. A one-piece wheel rim according to claim 36 wherein the said bead seating portions have a diameter at the heel point of 342 mm and the axial distance between the spaced apart bead retaining flanges is 110 mm. 25

44. A one-piece wheel rim according to claim 36 wherein the said bead seating portions have a diameter at the heel point of 395 mm and the axial distance between the spaced apart bead retaining flanges is 170 mm.

45. A one-piece wheel rim according to claim 36 wherein the said bead seating portions have a diameter at the heel point of 395 mm and the axial distance between the spaced apart bead retaining flanges is 125 mm.

46. A one-piece wheel rim according to claim 36 wherein the 5 radial height of each bead retaining flange is 12 mm and the radial depth of the tyre fitting well is 13 mm.

47. A one-piece wheel rim according to claim 36 wherein the radial height of each bead retaining flange is 13 mm and the radial depth of the tyre fitting well is 14 mm. 10

48. A one-piece wheel rim according to claim 37 wherein the radial height of each bead retaining flange 'is 13.5 mm and the radial depth of the tyre fitting well is 13 mm.

49. A one-piece wheel rim according to any of claims 36 to 48 wherein the radially outer edge of each bead retaining flange is radiused. 15

50. A one-piece wheel rim according to any of claims 36 to 49 wherein the radially outer edge of each bead retaining flange includes a radially and axially outwardly extending portion which is substantially straight and extends at an angle of 45° to the radial direction.

51. A one-piece wheel rim for a tubeless pneumatic tyre constructed 20 and arranged substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.

52. A one-piece wheel rim for a tubeless pneumatic tyre constructed and arranged substantially as hereinbefore described with reference to Figure 13 of the accompanying drawings. >3733

53. A one-piece wheel rim for a tubeless pneumatic tyre constructed and arranged substantially as hereinbefore described with reference to Figure 22 of the accompanying drawings.

54. A one-piece wheel rim according to claim 36 constructed 5 and arranged substantially as hereinbefore described with reference to the accompanying drawings.