IMPROVEMENTS TO VEHICLE WHEELS

Abstract: A vehicle wheel rim comprising a pair of bead seats (1) and axially inwards of and adjacent to each bead seat a circumferentially extending tyre toe engaging groove (3) characterised by a secondary bead retaining means (6,8) between the bead seat (1) and the groove (3) comprising a hump having a height measured radially from the bead seat surface adjacent to the hump of 1 to 3.0 mm. The hump preferably has a steep surface on its axially outer edge. The resultant wheel still correctly seats a normal tyre with the toe engaging the hump when the tyres is deflated and correctly engages in TD type of tyre with the toe in the groove.

Description: This invention relates to vehicle wheels and in particular to wheel rims of the type described in UK Patent Specification No. 1584554 which provides a wheel rim having adjacent to and axially inwards of each bead seat a circumferentially extending, continuous groove. The groove is designed to accommodate a special toe of the tyre for which the wheel rim is designed and together they provide an assembly with a very high degree of bead retention and resultant vehicle safety even in the event of a tyre deflation. Such tyres and wheel rims are available in some countries with the designation "TD" on the rim and tyre. A problem with this type of wheel is that if a normal tyre without the "TD" toe but of the same nominal bead seating diameter is fitted to the rim, whilst full "inflation" is readily achieved, improper air retention occurs in some service conditions. In particular when cornering with the tyre only slightly deflated the bead can rock on its seat into the groove and allow further air loss. This has resulted in tyres and wheel of the "TD" type being limited to non-standard bead seat diameters to avoid dangerous mismatching. The present invention overcomes the above problem with such wheels and provides a wheel rim suitable for use with a tyre having a bead retaining toe as well as with normal tyres. According to the present invention a wheel rim is provided comprising a pair of spaced apart bead seats and axially inwards of each bead seat and adjacent thereto a circumferentially extending tyre toe engaging groove whereby a secondary bead retaining means between the bead seat and the groove is provided, comprising a hump having a height in the radial direction of between 1.0 and 3.0mm. The hump is preferably less than 3mm in width. Preferably the edge of the hump on the outside, axially of the wheel, has a face which is substantially perpendicular to the bead seat to present a toe engaging face to the tyre of a standard tyre. By substantially vertical is meant at 80 degrees or more to the axial centreline of the wheel rim. The hump may be cast integrally with a cast wheel rim but for a rolled wheelrim the hump may be attached to the rim after rim manufacture. Such attachments may be by welding etc. The hump may be rectangular section or a round or circular section member. Preferably it comprises a circumferentially continuous hump although it may be formed by several short components positioned end to end or spaced apart around the wheel rim. The hump may be adjacent to the groove or may be on the edge or shoulder part of the groove. Further aspects of the present invention will be apparent from the following description, by way of example only of one embodiment in conjunction with the attached diagramatic drawings in which:- Fig.1. is a cross section of one bead seat of a wheel rim. Fig.2. is a cross section of one alternative wheel rim shape with a standard tyre & Fig.3. is a cross section of the wheel rim of Fig.1. with a TD tyre bead fitted. The wheel shown in Fig.1. comprises a tapered bead seat 1 having a tyre retaining flange 2 axially outwards of the bead seat 1. A tyre bead receiving groove 3 is positioned adjacent to the bead seat 1 and this groove is of the "TD" type as described in UK Patent Specification No. 1 584 554. The groove 3 has smoothly curved axially outer and axially inner groove sides 4, 5 which are radiused such that the wheel rim may be made by conventional rolling techniques. A steel ring 6 is welded to the upper edge of the axially outer groove side 4 as shown. The ring 6 has a circular cross-section and projects in the radial direction above the bead seat surface adjacent to the ring 6. The ring 6 therefore provides a low hump with a steep surface 7 on the axially outer side. The wheel rim shown in Fig.2. is a cast wheel rim having a narrow hump 8 cast integrally with the wheel rim and having a steep surface 7 at an angle greater than 80 degrees to the axial direction of the wheel rim AX. The ring 6 or hump 8 may have a cross section other than those shown including rectangular cross sections so long as the step surface 7 is provided as it is important to retain standard tyre that this surface is at 80° or more. The height of the ring may be from 1.0 - 3mm for car wheel rims and higher with larger diameter rims. However, the height must not be enough to prevent satisfactory fitting of the bead to its seat or to stretch or damage the bead reinforcement. In use on a vehicle the wheel rim may carry a TD type tyre as shown in Fig.3 in which case the hump 6,8 has no effect on the bead retention properties which are, however, maintained as those now well known with TD tyres and wheels.If desired the "TD" tyre may be modified by providing a small groove or notch to fit over the ring or hump 8, 6 and still further improve the fit of the tyre to its rim. The bead toe engaged in the groove generates bead retention forces when the bead is rotated quite unhindered by the hump 6, 8. The wheel rim, however, when fitted with a standard tyre as shown in figure 2 provides an assembly where the conventional bead is given conventional bead retaining properties. In this case the steep surface 7 is engaged by the toe 9 of the tyre. The steepness of the hump 6,8 provides bead retention to a similar degree as that with a conventional flat ledge wheel rim or indeed a conventional wheel rim with hump. Thus the resultant wheel rim may be used either with TD tyres or conventional tyres thus overcoming one of the problems with present TD wheels to which conventional tyres may not be safely fitted.

Claims: A vehicle wheel rim comprising a pair of spaced apart bead seats (1) and axially inwards of each bead seat (1) and adjacent thereto a circumferentially extending tyre toe engaging groove (3) characterised by a secondary bead retaining means (6,8) between the bead seat (1) and the groove (3) comprising a hump having a height measured radially from the bead seat surface adjacent to the hump of 1.0 to 3.0mm. A wheel rim according to claim 1 characterised in that the hump (6,8) has a width in the axial direction of the wheel rim of not more than 3mm. A wheel rim according to claim 2 characterised in that the hump (6,8) provides on its axially outer edge (7) a tyre contacting face which is sufficiently steep in relation to the bead seat (1) to engage the toe of a conventional tyre fitted to the wheel rim when said tyre toe is moved inwardly. A wheel rim according to claim 3 characterised in that the hump (6,8) provides on the axially outer edge a tyre contacting face which is at an angle of 80 degrees or more to the axial direction of the wheel rim. A wheel rim according to claim 3 or 4 characterised in that the hump comprises a circular cross section member (6) A wheel rim according to any of claims 1 - 5 characterised in that the hump (6) is positioned on the shoulder of the axially outer side of the groove (3). A wheel rim according to any one of claims 1 - 6 characterised in that the hump (6) is attached to the wheel rim subsequent to wheel rim manufacture. A wheel rim according to claim 7 characterised in that the hump (6) is welded to the wheel rim. A wheel rim according to any one of claims 1 - 8 wherein the hump (6,8) is circumferentially continuous.

Inventors: GRIFFITHS, PHILLIP NEWELL, HOLMES, THOMAS
Applicants: SP TYRES UK LIMITED
Application year: 1987
Main classification: B60B21
IPC codes: B60B21