Title: Wheel Construction Description of Invention

This invention relates to a wheel construction and more particularly but not exclusively to a wheel construction for agricultural vehicles or light construction machines or the like.

Wheel constructions for agricultural vehicles and the like off-road vehicles, are known which include a circular wheel rim which provides respective axially inner and outer flanges which each provide a seat for a tyre bead of a floatation tyre which is fitted to a radially outer, or "tyre side" of the rim. In the example of US-A-5560686, such a wheel construction is disclosed which further includes a disc by means of which the wheel is securable to a hub of the vehicle, the disc being connected to a radially inner side of the rim and the disc and rim being separable. The invention is though applicable to wheels in which the rim and disc are permanently connected together e.g. by welding.

In this specification, by "floatation tyre" we mean a wide (axially long) tyre which spreads loads thus reducing, e.g. soil, compaction, when the tractor is driven on a non-road surface.

Agricultural vehicle wheel constructions are known which include a wheel rim with axially inner and outer portions which each provide a tyre bead seat flange, and an adjoining frusto-conical connecting surface which extends axially towards the mid-portion where there is central well. The tyre bead seat flange, and typically at least a part of the connecting surface, together provide a seat for the tyre. The connecting surface adjoins a circumferentially

extending convex surface, and a frusto-conical side part adjoins the convex surface, and the mid-portion of the rim.

It has been found that with such existing rims, the service life of the rims may be insufficient because structural stresses which occur in the area where the side parts adjoin the mid-region, can lead to premature failures of the rims.

According to one aspect of the present invention we provide a wheel construction which includes a wheel rim which in use, at a tyre side of the rim, receives a tyre, the rim being circular and having axially inner and outer portions, and a mid-portion between the axially inner and outer portions, the mid-portion including a circumferential well where the radius of the wheel rim is a minimum, and each axially inner and outer portion providing a flange, a connecting surface adjoining the flange and extending axially towards the mid portion, the flange and part of the connecting surface providing a seat for a bead of the tyre, and there being a side part between the connecting surface and the mid portion, and wherein for at least one of the inner and outer portions, the connecting surface is a frusto-conical having an axial end of greatest radius and an axial end of least radius, the connecting surface, at its axial end of greatest radius, adjoining the flange, and the axial end of least radius adjoining a circumferentially extending convex surface, when viewed from the tyre side of the rim, the convex surface at the tyre side of the rim extending radially outwardly of the wheel axis beyond the end of least radius of the adjoining frusto-conical connecting surface, and the side part of the at least one of the axially inner and outer portions including a generally frusto-conical region and a curved region, the frusto-conical region at its end of greatest radius adjoining the convex surface, and the curved region including first and second axially spaced circumferentially extending concave surfaces, when viewed from the tyre side of the rim, the curved region adjoining the end of least radius of the frusto-conical region and the mid-portion.

The present invention enables the structural stresses which occur in the area where the side part of the at least one of the inner and outer portions adjoins the mid-region to be decreased, and this has been found to lead to structural failures in this area to be at least reduced. This enables the service life of the rim to be increased compared with prior proposals, and moreover, the thickness of the rim material can be reduced without compromising the structural integrity of the rim, thus reducing weight and the cost of production. Preferably the first concave surface of the curved region is located radially outwardly of the second concave surface, and preferably the second concave surface continuously adjoins the mid-region and the first concave surface continuously adjoins the frusto-conical region, but the curved region may include a frusto-conical formation between the second concave surface and the mid region and/or the first concave surface and the frusto-conical region, if required.

Between the first and second concave surfaces there may be a convex formation, when viewed from the tyre side of the rim. Preferably this convex formation continuously melds with the adjacent first and second concave surfaces to provide a continuously undulating curved region, but in another example, between the first and second concave surfaces there may be one or more frusto-conical or cylindrical connecting formations.

The first and second concave surfaces, and the convex formation between the first and second curved surfaces, where provided, may each be of a local respectively internal and external, radius of between 10mm and 25mm, and more typically about 18mm. By "local" radius we mean the actual radius of the surface rather than the radial distance of the surface from the wheel axis.

The convex surface of the at least one of the inner and outer portions of the rim, may be of a local external radius which varies between about 11mm

adjacent where the convex surface adjoins the end of least radius of the connecting surface, to about 23mm where the convex surface adjoins the side part. Desirably the convex surface of the at least one inner and outer portion of the rim extends radially from the wheel axis such that the distance between a tangent of the convex surface which is parallel to the frusto-conical connecting surface at the tyre side of the rim, and the connecting surface itself, is at least 3mm and more preferably about 4.5mm. Preferably the convex surface of the at least one of the inner and outer portions of the rim, continuously melds with the end of least radius of the frusto-conical connecting surface, with a local internal local radius where they meld, of between 3mm and 8mm, and more typically 5mm.

The frusto-conical region of the side part may subtend and angle between 15° and 50°, and more preferably about 40°, to a radial plane which is perpendicular to the wheel axis. Thus the cone angle of the frusto-conical region may be about 100°.

The frusto-conical connecting surface of the at least one of the inner and outer regions may subtend an angle to a plane which is perpendicular to the wheel axis, of between 72° and 78° and typically about 75°. Thus the cone angle of the frusto-conical connecting surface may be about 30°.

In another example though the frusto-conical connecting surface of the at least one of the inner and outer regions may subtend an angle to a plane which is perpendicular to the wheel axis, of between 94° and 96° and typically about 95°. Thus the cone angle of the frusto-conical connecting surface may be about 10°.

Conventionally the flanges of the inner and outer portions are provided by circumferentially extending curved formations at the axial ends of the rim, each

curved formation including a convex surface, when viewed from the tyre side of the rim which extends radially outwardly of the wheel axis to where the radius of the wheel rim is a maximum, and the flange terminating at the axial end of the rim at a position radially outwardly of the convex surface adjoining the end of minimum radius of the frusto-conical connecting surface and the side part. Desirably though in the construction of the present invention the flange of the at least one of the inner and outer portions terminates at a position radially inwardly of the convex surface adjoining the end of minimum radius of the frusto-conical connecting surface and the side part, to add additional stiffness at the axial end of the rim.

If desired the wheel rim may be symmetrical about a central plane of the mid portion which is perpendicular to the wheel axis, in which case both of the inner and outer portions of the rim may have the features of the invention identified above, but in another example the rim may be asymmetrical with the axially outer portion i.e. the portion of the rim which is axially outermost of the vehicle on which the wheel is in use mounted, may have the features of the invention identified above.

In this latter case, the inner portion of the rim may include a frusto-conical connecting surface adjoining the flange, and a convex surface when viewed from the tyre side of the rim, and a side part including a frusto-conical region and a curved region which includes first and second concave surfaces, when viewed from the tyre side of the rim, between the convex surface and the mid portion. The side part of the inner portion of the rim may additionally include a generally cylindrical region between the frusto-conical region and the convex surface.

Embodiments of the invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is an illustrative axial end view of a wheel for an agricultural or light construction vehicle, in accordance with the present invention; FIGURE 1A shows a modified flange detail;

FIGURE 2 is a partial cross sectional view on l-l of figure 1 , showing the general wheel construction;

FIGURE 3 cross detailed sectional view of an axially outer portion of a prior art wheel construction;

FIGURE 4 is a view similar to figure 3 but of part of a wheel construction in accordance with the present invention, and slightly enlarged for clarity.

Referring to figures 1 and 2 there is shown a wheel construction 10 which includes a wheel rim 11 which in use, at a tyre side 12 of the rim 11 receives a tyre 14. The position of the tyre 14 is indicated only in figure 3.

The rim 11 is circular and in this case is asymmetrical, having axially inner 16 and axially outer 15 portions, and a mid-portion 18 between the axially inner and outer portions 15, 16.

Each axially inner and outer portion 16, 15 provides a flange 22, a frusto- conical connecting surface 23, and side parts 19, 20 between the mid portion 18 and each respective flange.

Each flange 22 and an adjacent part of the connecting surface 23 in use, provide a seat for a bead of the tyre 14.

The configuration of the axially outermost portion 15 of the rim 11 i.e. the portion of the rim 11 which is use is axially outermost of the vehicle on which the wheel 10 is mounted, will now be described in detail, with additional reference to figure 4.

The generally frusto-conical connecting surface 23 has an axial end 24 of greatest radius and an axial end 25 of least radius, the connecting surface 23, at its axial end 24 of greatest radius, adjoins the flange 22, and the connecting surface 23 extending inwardly of the rim 11 towards the mid-portion 18. The axial end 25 of the frusto-conical connecting surface 23 of least radius adjoins a circumferentially extending convex surface 26, i.e. a surface which is convex when viewed from the tyre side 12 of the rim 11.

The convex surface 26 at the tyre side 12 of the rim 11 extends radially outwardly of the wheel axis A beyond the end 25 of least radius of the adjoining frusto-conical connecting surface 23.

The mid-portion 18 includes a circumferential well where the radius of the wheel rim 11 is a minimum.

Referring now to figure 3, parts corresponding to the wheel construction 10 already described, and parts to be described, are all indicated by the same references.

The side part 20 in the figure 3 prior art wheels, includes a frusto-conical region 28 which at its end 31 of greatest radius, adjoins the convex surface 26 of the outer portion 15 and the frusto-conical region 28 also adjoins, at its end 27 of least radius, the mid portion 18 of the wheel rim 11.

It has been found that with such a proposal, as the wheel rim 11 is formed, typically by a cold forming or pressing operation, the area where the end 27 of least radius of the frusto-conical region 28 adjoins the mid-portion 18 is formed with structural stresses which can lead to premature failure of the wheel rim 11 in this area.

Also, the flanges 22 at the axial ends of the wheel construction 10 which provide the tyre 14 bead seats have been found to be insufficiently insubstantial. In this prior art proposal (and as indicated in figure 1 ) the flanges 22 of the inner and outer portions 15, 16 are provided by circumferentially extending curved formations 35 at the axial ends of the rim 11 , each curved formation 35 including a convex surface 36, when viewed from the tyre side 12 of the rim 11 which extends radially outwardly of the wheel axis A to where the radius of the wheel rim 11 is a maximum. The flanges 22 terminate at the axial ends of the rim at positions 30 radially outwardly of the convex surface 26 adjoining the end 25 of minimum radius of the frusto-conical connecting surface 23, and the respective side parts 19, 20.

Referring now to figure 4 the contrast of the arrangement of the present invention compared with the prior art rim 11 of figure 3 can readily be seen.

The side part 20 is of a modified configuration compared to the side part 20 of the figure 3 prior proposal. Particularly the side part 20 includes both a frusto- conical region 28 and a curved region 40. By providing the side part 20 with particularly the curved region 40, the stresses present in the figure 3 proposal in the area where the end 27 of least radius of the frusto-conical region 28 adjoins the mid-portion 18 are avoided during manufacture thus improving the service life of the wheel 10.

The frusto-conical region 28 subtends an angle B of about 40° to a plane P which extends perpendicularly to the wheel axis A but the frusto-conical region 28 may in other examples, typically subtend an angle of between 15° and 50°.

The curved region 40 is provided by a first circumferentially extending concave surface 41 and a second circumferentially extending concave surface 42 (both when viewed from the tyre side 12 of the rim 11 ), the first and second concave

surfaces 41 , 42 being axially separated in this example, by a convex formation 44 (when viewed from the tyre side 12 of the rim 11 ).

In this example, the first concave surface 41 of the curved region 40 is located radially outwardly (relative to the wheel axis A) of the second concave surface, 42, and the second concave surface 42 continuously adjoins the mid-region 18.

The convex formation 44 between the first and second concave surfaces 41 , 42 continuously melds with the adjacent concave surfaces 41 , 42 so that the curved region 40 is continuously undulating, but if desired, there may be a frusto conical or cylindrical region between the convex formation 44 and one or other of the concave surfaces 41 , 42.

In the example of figure 4, the first and second concave surfaces 41 , 42, and the convex formation 44 between them, each are of a local respectively internal and external, radius R1 , R2, R3 respectively, of about 18mm, but in any event preferably between 10mm and 25mm. The radii R1 , R2, R3 need not all be the same, as in the example, but at least one of the concave surfaces 41 , 42 may have a local radius different to at least one of the other of the other concave surface 42, 41 and the convex formation 44 as desired.

The convex surface 26 of the outer portion 15 of the rim 11 in the example, may have a varying local radius of between 11 mm as shown at R4, and 23mm at R5, where R4 is axially outwardly beyond radius R5.

It can also be seen that the convex surface 26 of the outer portion 15 of the rim 11 extends radially from the wheel axis A such that the distance D between a tangent T to the convex surface 26 which is parallel to the frusto- conical connecting surface 23 at the tyre side 12 of the rim 11 , and the

connecting surface 23 itself, is in the example about 4.5mm but is preferably always at least 3mm.

It can be seen in the example that the convex surface 26 of the outer portion 15 of the rim 11 also continuously melds with the end 25 of least radius of the frusto-conical connecting surface 23, with a local internal local radius where they meld R6, of typically about 5mm, but desirably in the range 3mm to 8mm.

The frusto-conical connecting surface 23 of the outer region 15 may subtend an angle C to the plane P which is perpendicular to the wheel axis A, of 75° as in the example shown, but preferably between 72° and 78° so that the cone angle of the frusto-conical connecting surface 23 may be about 30°.

In another example, if desired, the frusto-conical connecting surface 23 of the outer region 15 may subtend an angle C to the plane P which is perpendicular to the wheel axis A, of 95° as in the example shown, or at least is between 94° and 96° so that the cone angle of the frusto-conical connecting surface 23 may be about 10°.

In the wheel construction 10 in the example of figure 4 (and figure 1A) the flanges 22 of the inner and outer portions 15, 16 each terminate at a respective position 30 inwardly radially relative to the wheel axis A of the convex surface 26 adjoining the end 25 of minimum radius of the frusto-conical connecting surface 23 and the respective side part 19, 20. Thus the flanges 22 are more substantial than in the prior art proposal and add additional stiffness at the axial ends of the rim 11 , as well as adding stiffness to the rim 11 generally. In the example, the convex surface 36 of each flange 22, when viewed from the tyre side 12 of the rim 11 , has a radius R8 of about 12.7mm, and the flange 22 adjoining the end 24 of maximum radius of the frusto-conical connecting surface 23, with a radius R7 in the order of 8mm.

By adopting the present invention, a rim 11 is provided in which the material thickness of the rim 11 can be reduced compared with comparable rims which do not incorporate the invention.

Various modifications are possible without departing from the scope of the invention.

In the example shown in figures 1 , 2 and 4, the rim 11 is asymmetrical about a central plane P of the mid region 18 which is perpendicular to the wheel axis A. In the example, the side part 19 of the axially inner region 16 of the rim 11 includes a generally cylindrical region 50 between the frusto-conical region 28 and the convex surface 26 so that the wheel rim 11 extends axially further from the mid region 18 towards the vehicle on which the wheel 10 is in use mounted, than the rim 11 extends axially outwardly. Otherwise in the example of figure 2, both inner and outer portions 15, 16 of the rim 11 include side parts

19, 20 with substantially similar but mirrored, frusto conical 28 and curved regions 40 as described.

In another example, at least one of the side parts 19, 20 may include, between the second concave surface 42 and the mid region 18 and/or the first concave surface 41 and the frusto-conical region 28, a frusto-conical formation, if desired.

Further, although in the example described with reference to the drawings, the convex formations 44 of each of the side parts 19, 20 continuously meld with the adjacent first and second concave surfaces 41 , 42 to provide a continuously undulating curved region 40, in another example, between the first and second concave surfaces 41 , 42 of at least one of the side parts 19,

20, these may include one or more frusto-conical or cylindrical connecting formations.

In another example, the wheel rim 11 may be symmetrical about the central plane P which is perpendicular to the wheel axis A.

Although the wheel construction described is that of a floatation wheel for use on an agricultural vehicle such as a tractor, or a light construction vehicle such as an excavating and/or loading machine,, the invention may be applied to another wheel construction.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.