Wheel rim for pneumatic vehicle tyre

Abstract: A wheel rim for pneumatic tyres comprising a central part having a well and bead receiving regions disposed on both sides of the central part which are bounded towards the outside by rim flanges and merge in the direction towards the well rim into inclined ramp surfaces, wherein a ring like projection or hump which is at least regionally formed in a circumferential direction is provided at least in the transition region between one bead seat and the ramp surface associated with the latter, characterised in that the hump diameter (D H ) at least at the shorter rim side (1) is the same as or larger than the corner diameter (D) of the bead seat surface (3) measured at the base point (5) of the rim flange (4) and in that a ramp surface (7,8) is associated with the hump (6) which, starting from the rim well side, extends at a first steep angle and then subsequently at an angle which is substantially shallower in comparison thereto.

Description: The invention relates to a wheel rim for pneumatic vehicle tyres comprising a central part having a well and bead receiving regions disposed on both sides of the central part which are bounded towards the outside by rim flanges and merge in the direction towards the well rim into inclined ramp surfaces, wherein a ring like projection or hump which is at least regionally formed in a circumferential direction is provided at least in the transition region between one bead seat and the ramp surface associated with the latter. Wheel rims of this kind are known and form, in conjunction with the associated tyre, as a result of the hump that is provided, a retaining system which ensures that even with reduced pressure within the tyre the latter is still held on the rim, and thus that safety is increased. For example such a wheel rim qualifying as prior art under the terms of Articles 54(3) and 54(4) EPC is disclosed by European Patent publication EP-A-0377338. A wheel rim according to the preamble of claim 1 is known from EP-A-0 170 085. It is an object of the invention to further develop a tyre rim of the described kind in a manner which can be simply realised without making it more difficult to install the particular tyre so that the tyre retaining capability of the rim with reduced internal tyre pressure is considerably improved. The rim should also be compatible with all series production tyres. The object is satisfied in accordance with the invention essentially in that the hump diameter (D H ) at least on the outer rim side is the same as or larger than the corner diameter (D) of the bead seat surface measured at the base point of the rim flange and in that a ramp surface is associated with the hump which, starting from the rim well side, has a steeper portion extending at a first steep angle and then subsequently a shallower portion extending at a second angle which is substantially shallower in comparison to the first angle and the transition from the steeper portion to the shallower portion is disposed radially substantially within the line of intersection of the ramp surface and the notional extension of the bead seat surface and the hump is curved and has a radius on the side which is nearest to the rim flange which is smaller than the radius on the side nearest to the well. Preferably the rim shape is used at both bead seats. As a result of this layout of the wheel rim it is possible with series production tyres to reduce the internal tyre pressure at which the tyre is dislodged from the rim by about 40 to 60%, which leads to a considerable increase in safety. It is of particular importance with this arrangement that the fitting or seating pressure which is necessary during installation of the tyre to transfer the tyre bead onto its associated bead seat is not increased despite the increased hump. As a result of the special layout of the ramp surfaces tuis is achieved and thus no danger exists of damaging the tyre or bead reinforcement core on fitting. The steeper section of the ramp surface preferably extends at an angle of approximately 10° to a vertical or circumferential plane of the rim and the shallower portion extends at an angle of 45° relative to a vertical or circumferential plane of thee rim. The hump radius at the side of the rim flange is preferably only half as large as that at the side of the well and a hump free region of preferably about 300 mm is respectively provided on both side of the valve to avoid damage to the tyre beads during tyre removal. In a particularly advantageous embodiment of the invention a circumferentially extending groove is provided at the well side and adjoining the hump associated with the bead set for the accommodation of a tyre bead toe, and in this arrangement the depth of the groove is selected to be smaller, related to the diameter at the base point of the rim flange than 4 mm being in particular 3.3 mm, and this groove is bounded at the rim well side by a second hump with the ramp surface having a steeper and shallower portion being associated with the second hump. By means of this layout of the invention it is possible to maximise the brake space, i.e. the space available within the wheel for accommodating the brake, since the groove which receives the bead toe extends with the largest possible radius but nevertheless fully satisfies the requirements to provide an effective tyre retaining system. In comparison to known tyre retaining systems with circumferentially extending grooves for receiving the bead toe the receiving groove of the invention is, on the one hand formed as a raised shallow groove, which is important to maximise the braking space, and, on the other hand, an elevated hump is provided at the rim well side, the use of which is again possible as a result of the special layout of the ramp surfaces. In this way it is possible to position both conventional tyres and also special tyres which have a special bead toe on the rim with absolute safety, and at the same time to preclude any form of faulty installation and also any danger of loosening and of air loss. The diameter of the further hump is preferably at least substantially the same as the diameter of the hump associated with the bead seat surface, and the radius of curvature of this further hump is preferably smaller than the radius of curvature of the hump associated with the bead seat surface. Further particular advantageous features of the invention are set forth in the subordinate claims. Embodiments of the invention will now be explained, by way of example only, with reference to the drawings in which:- Fig.1. is a schematic representation of the shape of the rim contour at the outer side of the rim and Fig.2. is a schematic representation of the shape of the rim contour in accordance with a second embodiment of the invention in which a circumferential groove is provided to receive a bead toe. Fig.1. shows the outer side of a wheel rim 1 with a rim well 2, a bead receiving surface 3 and a rim flange 4. The rim flange 4 merges at a base point 5, which lies on a diameter D, into the flat bead seat surface 3 which extends at an inclined angle of 5°. A hump 6 which extends at least around the majority of the circumference adjoins the bead seat surface 3 towards the rim well 2. The hump diameter D H is larger than the diameter D at the base point 5. This ensures that with series production tyres the internal tyre pressure at which throw off or dislodgement of the tyre occurs can be reduced by about 40 to 60% compared to a standard wheel rim. In most arrangements the hump (6) extends completely around the wheel rim but, in some embodiments to improve "button-holing" or fitting the tyre of the tyre over the flanges, a short region of the rim may have no hump. This region is preferably opposite the valve in the wheel and is provided at both sides of the wheel. A rim of the kind shown here is compatible with all series production tyres. The hump radius at the side of the rim flange 4 amounts to approximately 4 mm whereas it amounts to approximately 8 mm at the wheel side. the rim well side reduction of the hump radius is advantageous with respect to the operation of this tyre retaining system. The hump diameter D H is increased by at least Jmm in comparison to known arrangements which would lead to a considerable deterioration of the work of fitting the tyres if the ramps were not specially shaped in accordance with the invention, namely in the form of a steeper portion 7 and a shallower portion 8. The steeper portion extends at an angle of 10° relative to the circumferential plane of the tyre, whereas the shallower portion 8 subtends an angle of 45° with this plane. This layout of the ramp surfaces provides for the fitting or installing and correct positioning or seating of all associated kinds of tyres without increasing the fitting pressure required. Fig.2 shows a particular advantageous layout of the invention in which a circumferentially extending groove is provided at the well side adjoining the hump associated with the bead seat surface in order to receive a particular tyre bead toe. The full line shows a configuration which is known, at least in basic concept. In this known basic configuration the hump at the rim well side lies at a substantially smaller diameter than the hump 6. Also the groove 9 which accommodates the tyre toe, has a depth which leads to a substantial restriction of the brake space inside the wheel. In accordance with the invention, which is characterised by the broken line which is shown, the groove 9, is on the one hand, formed as a raised shallow groove and, on the other hand the hump 10 at the rim well side is made substantially higher. This also results in a displacement of both the lowest point of the groove 9 and of the highest point of the hump 10 in the direction of the bead seat surface 3. It is important for the layout of the invention that as result of the groove 9 which lies at a larger radius the space available on the inside of the wheel to accommodate the brake is substantially increased and that through the increased height of the hump 10 the efficiency and functional performance of the entire tyre retaining system is improved. The increased height of the hump 10 is again possible through the special layout of the ramp surfaces which has already described in connection with Fig.1 in the form of a steeper portion and a shallower portion. The functions and advantages described in this respect in conjunction with Fig.1. also apply to the embodiment of Fig.2. Both conventional tyres and also special tyres with retaining toes which engage in the groove 9 can be installed on a rim of the kind shown in Fig.2 and as result of this layout of the rim a reliable seating of the bead is always ensured, no danger of faulty installation or of air loss exists and thus no requirements have to be specified which must be specially observed during tyre fitting. The described layout can be provided both for one side of the rims and also at both sides. In all installed tyres the internal tyre pressure at which the tyre is dislodged is quite substantially lowered, and with tyres with a retaining toe it is indeed possible to reduce this internal tyre pressure at which tyre dislodgement occurs to approximately 0.3 bars.

Claims: A wheelrim for pneumatic tyres comprising a central part having a well and bead receiving regions disposed on each side of the central part which are bounded towards the outside by rim flanges and merge in the direction towards the well rim to inclined ramp surfaces, wherein a ring like projection or hump which is at least regionally formed in a circumferential direction is provided at least in the transition region between one bead seat and the ramp surface associated with the latter, and the hump diameter (D H ) at least at the outer rim side (1) is the same as or larger than the corner diameter (D) of the bead seat surface (3) measured at the base point (5) of the rim flange (4) and in that a ramp surface (7,8) is associated with the hump (6) which, starting from the rim well side, has a steeper portion (7) extending at a first steep angle and then subsequently a shallower portion (8) extending at a second angle which is substantially shallower in comparison to the first angle characterised in that the transition from the steeper portion (7) to the shallower portion (8) is disposed radially substantially within the line of intersection of the ramp surface (7,8) and the notional extension of the bead seat surface (3) wherein the hump (6) is curved and has a radius on the side which is nearest to the rim flange (4) which is smaller than the radius on the side nearest to the well (2). A wheelrim in accordance with claim 1, characterised in that the steeper section (7) of the ramp surface extends at a first angle of approximately 10° relative to a vertical or circumferential plane and the shallower portion (8) of the ramp surface extends at a second angle of approximately 45° relative to a vertical or circumferential plane. A wheelrim in accordance with claim 1 or 2, characterised in that the transition between the steeper portion (7) and the shallower portion (8) is rounded. A wheelrim in accordance with any of the preceding claims, characterised in that the curvature of the hump (6) has a radius on the side which is nearest to the rim flange (4) which is approximately only half as large as the radius on the side nearest to the well (2). A wheelrim in accordance with any of the preceding claims, characterised in that hump free regions are provided at both sides of the valve. A wheelrim in accordance with any of the preceding claims, wherein a peripherally extending groove for receiving a tyre bead toe is provided at the well side of and adjacent to the hump associated with the bead seat, characterised in that the depth of the groove (9) related to the diameter (d) at the base point (5) of the rim flange (4) is smaller than 4mm, in that the groove (3) is bounded at the well side by a further hump (10). and in that the ramp surface with the steeper portion (7) and the shallower portion (8) is associated with this further hump (10). A wheelrim in accordance with claim 6 characterised in that the groove depth is 3.3mm. A wheelrim in accordance with claim 6 or 7 characterised in that the diameter of the further hump (10) is at least substantially the same as the diameter of the hump (6) associated with the bead seat surface (3). A wheelrim in accordance with any of claims 6-8 characterised in that the radius of curvature of the further hump (10) is smaller than the radius of curvature of the hump (6) associated with the bead seat surface (3).

Inventors: GLOTZBACH KLAUS-DIETER, GLOTZBACH, KLAUS-DIETER
Applicants: SP REIFENWERKE GMBH
Application year: 1990
Main classification: B60B21
IPC codes: B60B21