Wheel rim for a pneumatic tire

It relates in particular to a wheel rim of the type disclosed in co-pending European Patent Application No. 88300557.1 which corresponds to U.S. Pat. No. 4,836,260, where a one piece wheel rim is provided having a pair of axially spaced apart tapered bead seats, tire retaining flange located axially outwards of each bead seat and characterised by one flange having a reduced height portion having a length of 0.25 to 0.5 times the bead circumference and the reduced height portion being such that the flange height, measured from the heel point, which is the point of intersection of the nominal diameter and the nominal wheel width, is in the range of 0.15 to 0.6 times the height of the remainder of the flange to allow tire fitting.

The wheel rim of this prior invention may in some circumstances cause chafing of the tire in the bead region adjacent to the cut-away portion of the flange, and it is one object of the present invention to provide a wheel rim of one piece construction which has all the advantages of the previous application but which in addition avoids chafing of the tire bead adjacent to the cut-away region.

According to one aspect of the present invention a one piece wheel rim for a pneumatic tire is provided having a pair of axially spaced apart tapered bead seats, a tire retaining flange located axially outwards of each bead seat, said flange being in its radially inner region at an angle of A degrees to the radial direction of the wheel and being characterised by having a reduced height portion having a length of 0.25 to 0.5 times the bead seat circumference and the reduced height being such that the flange height, measured from the heel point, which is the point of intersection of the nominal diameter and the nominal wheel width is in the range of 0.15 and 0.6 times the height of the remainder of the flange, wherein the portion of the flange which is radially outside the reduced height portion is at an angle B degrees where angle B is greater than angle A to the radial direction so that a tire bead fitted to the wheel rim seats against the flange only to the height of the reduced height portion around the full circumference of the tire.

Preferably the angle B of the radially outer portion of the wheel rim is substantially greater than angle A; for example angle B when measured from the radial direction is preferably in the range of 10 to 75 degrees and more preferably in the range of 60 to 70 degrees.

The overall height of the flange, measured in the radial direction, is preferably similar to the flange height used in a conventional rim.

The resultant assembly, in having the flange cut-away, still allows the wheel to have only a minimal fitting well which is of substantially smaller depth than a normal wheel rim well and thus the wheel rim allows for a greater brake volume than for a conventional wheel rim. As in the case of the previous invention the minimal fitting well may be circumferentially continuous or indeed in some preferred arrangements may be very short in the circumferential direction. The minimal well may comprise only a flat connecting base between the axially inner edges of the tapered bead seats so that in fact the wheel appears to have no well whatsoever.

The reduced height portion of the flange has limited effective thickness so that it projects in the axial direction of the wheel rim only a short distance from the tyre bead contacting flange face. This is to ensure that the necessary skew of the tire as it is fitted with part of the bead in the shallow well does not cause even the reduced height portion to abnormally tension the bead reinforcement on assembly of the tire to the wheel rim.
The reduced height portion, where it joins the portion sloping at angle B, may be smoothly radius from one portion to the other or may have a progressively rising region which has its surface at the angle B but which gradually rises in height until the full flange extension B is provided. Preferably one end of the cut-away portion projects suddenly to the full flange shape at the angle B and at the other end of the cut-away there is a progressive gradual slope in the portion of the flange at angle B.