TIRE DEVICE

Abstract: An arrangement relating to pneumatic tubeless tires which are fitted with a tire bead (12) in sealing abutment with a rim seat (13) inwardly from a rim edge (14) on each side of an undivided rim (11). The tire is provided with an internal seal (16) which is made of rubber or some like elastic material and which extends inwardly from the tire bead (12) along the rim seat (13). The outer part of the internal lip seal (16) that lies proximal to the rim edge (14) is fastened to the tire bead (12) at a distance from its end. The inner part of the internal seal (16) that lies proximal to the centre of the rim (11) has a circumference that is slightly smaller than the circumference of the rim (11) at this location. The seal (16) is adapted to seal at least around the region in which the tire bead (12) is in abutment with the rim seat (13) through the influence of the pneumatic pressure in the tire (10).

Description: TIRE DEVICE The invention relates to pneumatic tubeless tires, which are fitted with a bead that lies in tight, sealing abutment with a rim seat inwardly of a rim edge on each side of an undivided rim. The invention is particularly suitable for use with tubeless tires for forestry service vehicles, for instance forest vehicles or forest machines, particularly those that are equipped with a bogey. At present, tires used with forestry service vehicles and with vehicles for similar advanced use include air-filled tubes, since pneumatic tubeless tires, i.e. tires inflated without the use of an inner tube, lose air as a result of the heavy mechanical stresses and strains to which they are unavoidably subjected when driving over rough terrain, such as those often encountered in forests, for instance in clear-felled areas and similar areas. One cause in this respect resides in the heavy lateral movements that occur when negotiating curves, par- ticularly in the case of bogey-equipped vehicles, therewith causing the walls of the tires to be pressed into contact with stones, logs and like obstacles in the terrain, wherewith the tire bead, i.e. that part of the tire which is in abutment with the rim seat can, in both instances, be forced loose from the rim seat over a longer or shorter time period. This results in an instantaneous leakage of air from the tire, and occurs so often that a short working shift is sufficient for the tire to be deflated to such an extent as to lose its function as a tire. It will be realised that this problem does not apply to tube-equipped tires, and consequently such tires are used exclusively for forestry service use, as far as we are aware. Tube-equipped tires, however, do not fulfil present-day requirements relating to high pro- ductivity and limited costs in forestry work, since tube-equipped tires are prone to be pinched in the sides of the tire when passing over stones, rocks and stubs, resulting in repeated puncturing of the tubes and also in financial losses on the part of the users, in the form of the costs entailed by tire changes and repeated idling times necessitated by repair requirements. These problems are particularly troublesome in the case of tires that have extremely low profiles, which are the most common and most expedient type of tire for forestry work. For reasons of a manufacturing nature, the tubes in low profiled tires cannot be produced with an optimal profile/cross-section, which involves extra high stretch levels of more than 50% against a normal 30%. This high degree of stretch exacerbates the tube pinching problem and also problems caused by fatigue. Although various solutions to similar types of problems relating to tubeless tires have been proposed, none of these solutions has been found useful in respect of tires intended for forestry service or similar advanced terrain applications. Although the proposed solutions dif- fer quite considerably from one another, a common primary feature of the solutions is directed towards pressing the tire bead mechanically against the rim seat. For instance, US-A-2,731 ,063 proposes the use of an insert ring, principally in the form of a rubber-covered metal ring, adapted to press a respective tire bead against the tire rim on respective sides of the ring, said rim being a split ring in this particular case. In this case, one rim edge can be removed so as to enable the insert ring to be pushed in on the rim seat with the rim edge removed and thereafter adapted so as to clamp between the two tire beads and the rim edge. As will be understood, such an insert ring cannot be fitted to undivided rims, as distinct from the object of the present invention. DE-B-1 024 384 proposes the use of a closed ring-shaped diaphragm or membrane which is connected to the bead of the tire so as to lie folded around the bead, and is pressed firmly between the bead and the rim seat. The diaphragm is folded double inwardly of the tire edge and therewith is pressed down against the central path of the rim by the tire pressure. This solution is intended for car tires and is not believed to be useful in the case of heavy tires, because the diaphragm will quickly be worn out when subjected to the heavy loads that are exerted between the edge of the tire and the rim in the case of heavier tires. WO 98/21056 proposes a similar construction for bicycle tires, with the same problems as those mentioned with the use of heavy tires. Finally, DE-A-2 356 097 proposes the use of an inflatable ring-shaped so-called pressure bag which is inflated separately when placed in position. This solution is intended primarily for tires of large diameter used with agricultural appliances and road working appliances with which heavy torque shall be transferred and for which the normal air pressure is not sufficient to prevent the tire from sliding on the rim. The object of the present invention is to provide a pneumatic tubeless tire arrangement with which problems caused by the leakage of air resulting from driving in rough terrain and being subjected to the mechanical influence of obstacles such as stones, rocks, tree stubs, ruts and ditches, are eliminated. This object is achieved with an inventive arrangement having the features set forth in the accompanying Claims. Thus, the inventive tire is provided with a lip seal made of rubber or some similar elastic material that extends internally and inwardly from the bead of the tire and along the rim seat. That part of the internal seal that lies proximal to the edge of the rim is fastened to the tire bead at a distance from its end. The circumference of that part of the internal seal which lies proximal to the centre of the rim is somewhat smaller than the circumference of the rim at this position and the seal is adapted to seal at least in the region around the abutment of the tire bead with the rim seat by virtue of the action of the pneumatic pressure in the tire. The outer part of the internal lip seal is suitably glued to the bead of the tire, although it may alternatively be fastened in some other way that will effectively hold the seal against the tire bead. Thus, the join between the seal and the tire bead need not be sealing in itself. The lip seal will preferably be comprised of a material of such softness that the seal will lie sealingly against its supporting surface throughout essentially the whole of its extension when subjected to the pneumatic pressure prevailing in the tire when inflated. Alternatively, the lip seal may be made of a relatively rigid elastic material and adapted so that at least its inward part will lie sealingly against the rim. In this case, the seal will not always lie against the underlying surface along the full length of the seal, but primarily only at its end portions. This can be suitable when tire pressures are extremely high. The lip seal is conveniently fastened at its outer edge at a distance of about 50-70 mm from the end of the bead. The lip seal will often have a skirt-like shape with its inner part resting loosely on the rim, such a tire also being referred internally to as a "skirt tire", although it lies within the scope of the invention to give the seal some other shape and also to fasten the inner part of the seal to the rim in the same manner as it is secured to the bead of the tire should this be found desirable for some reason or another. The inner edge of the lip seal may be formed as a so-called selvage that stretches towards the rim and may be glued thereto or fastened in some other way. The inventive arrangement may be used beneficially with low profile tires, particularly tires that are used on forestry vehicles or forestry machines equipped with bogeys, although it can also be used generally with all types of tubeless tires. The invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 is a cross-sectional view of a tire and an associated rim in a non-assembled state; and Figure 2 is a similar cross-sectional view of an inflated tire assembly. Figure 1 illustrates a tubeless tire 10 and a rim 11, which are shown in an unassembled state for the sake of illustration. The rim 11 includes a rim seat 13, a rim edge 14 and a ridge 15 on each side of its centre part. The tire 10 includes a bead 12 which when the tire is fitted lies against the rim seat 13 from the edge 14 of the rim to the ridge 15 and therewith seal against the rim 11 so that air pumped into the tire 10 will not escape therefrom. A lip seal 16 is glued or otherwise affixed to the bead 12 in the region 17 thereof. Although the illustrated embodiment of the invention includes a rim 11 that is provided with a ridge 15, it will be understood that rims which lack such a ridge may also be used within the scope of the invention. Figure 2 shows the tire 10 and the rim 11 assembled and the tire inflated. The air pressure inside the tire 10 causes the lip seal 16 to lie sealingly against the rim 11 in the region outwardly of the rim seat 13, i.e. towards the ridge 15 and the inwardly located parts of the rim 11 facing towards the centre of said rim. Should the bead 12 of the tire be loosened inwardly from the rim seat 13 as a result of external forces for a shorter or longer period of time, the air pressure in the tire 10 will cause the lip seal 16 to remain in abutment with both the bead 12 and the rim 11 and therewith reseal any gap that may occur therebetween. If an object, such as a wood chip, stone or the like, wedge between the edge 14 of the rim and the bead 12 and therewith result in a more permanent gap between the edge 14 and the bead 12, the lip seal 16 will still provide an effective seal that prevents air from escaping from the tire 10.

Claims: CLAIMS 1. An arrangement relating to pneumatic tubeless tires that are fitted with a tire bead (12) in sealing abutment with a rim seat (13) inwardly from a rim edge (14) on each side of an undivided rim (11), characterised in that the tire is provided with an internal lip seal (16), which is made of rubber or some like elastic material and which extends along the rim seat (13) inwardly from the tire bead (12); in that the outer part of the internal seal (16) proximal to the rim edge (14) is fastened to the tire bead (12) at a distance from its end; in that the inner part of the internal seal (16) proximal to the centre of the rim (11) has a cir- cumference which is slightly smaller than the circumference of the rim (1 1) at this location; and in that the seal (16) is adapted to seal at least in the region of the abutment of the tire bead (12) with the rim seat (13) through the influence of the pneumatic pressure in the tire (10). 2. An arrangement according to Claim 1, characterised in that the outer part of the lip seal (16) is glued to the tire rim (2). 3. An arrangement according to Claim 1 or 2, characterised in that the lip seal (16) comprises a material of such softness as to cause the seal to lie in sealing abutment with its underlying supporting surface essentially along the whole of the extension of the seal. 4. An arrangement according to Claim 1 or 2, characterised in that the lip seal (16) is comprised of a relatively rigid elastic material and is adapted to lie in sealing abutment with the rim (11) at least at the inward part of said seal. 5. An arrangement according to any one of Claims 1-4, characterised in that the lip seal (16) is fastened with the edge of its outer part spaced from the end of the tire bead (12) by at least 50-70 mm. 6. An arrangement according to any one of Claims 1-5, characterised in that the lip seal (16) has a skirt-like configuration with the inner part of said seal resting loosely on the rim (11). 7. An arrangement according to any one of Claims 1-6, characterised in that the inner edge of the lip seal (16) has the form of a so-called selvage. 8. The use of the arrangement according to Claims 1-7 in low profile tires, preferably low profile tires intended for forestry service.

Inventors: NILSSON TOMAS, NILSSON, TOMAS
Applicants: NILSSON TOMAS, TRELLEBORG IND AB, NILSSON, TOMAS, TRELLEBORG INDUSTRI AB
Application year: 2000
Main classification: B60C5
IPC codes: B60C5, B60C15