Attempts have earlier been made, particularly in connection with cross-country vehicles, to design rim constructions which permit running with the tyre under severe loading or heavy duty conditions, and also running with the tyre in a deflated state, commonly referred to as run-flat driving. Examples of known constructions are given in SE-B-317,003, SE-B-362,219, DE-1,505,080, US-A- 2,028,601, US-A-2,409,666, US-A-4,151,870, US-A-3,664,405, US-A-3,669,174, US-A-4,572,265 and SE-B-418,481 (= US-A- 4,016,917).

The construction disclosed in SE-B-418,481 relies on jaws or bead clamps which are elongate and which extend, when in their operative position, in the axial direction of the vehicle wheel to press the tyre beads against the rim flanges. The bead clamps are retained in place by a clamping bolt passing through the rim bottom and mechanic¬ ally pressing the bead clamps against the rim bottom, whereby to obtain a stable and strong engagement. These prior-art bead clamps have proved most useful and reliable for many types of vehicle tyres.

It has however been found that these bead clamps may sometimes tend to rotate about the clamping bolt, particu- larly under heavy duty conditions and especially when using tyres having a large axial width, particularly low- profile tyres for forest machines and other cross-country vehicles. In fact, the purpose of the bead clamps is to mechanically fix the tyre on the rim to prevent it from slipping thereon, also in the case of low air pressure. Another purpose of the bead clamps is to prevent air leakage between the tyre beads and the rim flanges as a result of the tyre beads coming loose from the rim flanges when the tyre is subjected to high lateral stresses. If the bead clamps should rotate about the clamping bolt, the intended fixation of the tyre would be undone.

One object of the present invention therefore is to provide an arrangement in vehicle wheels which reduces or completely obviates the risk of unintentional rotation of the bead clamps. Another object of the invention is to provide an arrangement in vehicle wheels which increases the capacity of the vehicle wheel to take up very high lateral forces. Such lateral forces occur especially in wheels for cross¬ country forest machines. Yet another object of the invention is to provide an arrangement in vehicle wheels which increases the ability of the wheel to ensure air tightness in the areas where the tyre beads engage the rim flanges and the tyre bead seat, also at low air pressures in tubeless tyre designs. A further object of the invention is to improve the device disclosed in SE-B-418,481 (= US-A-4,016,917) and to make it easier to mount and correctly position the bead clamps on the vehicle wheel.

These and other objects of the invention are achieved by means of an arrangement in vehicle wheels as defined in claim 1. The dependent claims recite particularly pre¬ ferred embodiments of the invention.

In the invention, use is made of a number of jaws or bead clamps for securing a pneumatic tyre on the rim. These jaws or bead clamps are elongate and rotatable, and are disposed, when in the operative position, with their longitudinal axis in the axial direction of the vehicle wheel. The jaws or bead clamps are pressed both against the tyre beads in order to apply these against the rim flanges, and against the rim bottom in order to stabilise the jaws or bead clamps and to eliminate or substantially reduce the risk of tilting of the jaws or bead clamps because of heavy impacts in the circumferential direction of the vehicle wheel. The jaws or bead clamps are retained by means of a clamping bolt which is connected to the jaws or bead clamps and extends through a hole in the rim bottom. The clamping bolt is disposed at a location bet-

ween the ends of the jaws or bead clamps, preferably fairly centrally so as to enable requisite pivotal move¬ ment of both ends of the jaw or bead clamp when mounting and dismounting the tyre. To prevent unintentional rota- tion of the jaws or bead clamps about their clamping bolts, the rim bottom has, in accordance with the inven¬ tion, been provided or formed with fixing lugs, against which the jaws or bead clamps abut when mounted.

To prevent unintentional pivotal movement of the jaws or bead clamps, it suffices that each bead clamp or jaw is associated with two fixing lugs or ridges. These two fix¬ ing lugs or ridges may be located on the same side of the associated jaw or bead clamp, however offset in different directions away from the clamping bolt of the jaw or bead clamp. Another option is to use two fixing lugs, one on each side of the jaw or bead clamp at a certain distance from the clamping bolt. For optimum results and for achieving a highly reliable mounting, it is preferred to use four fixing lugs, arranged pairwise on each side of the jaw or bead clamp, the two pairs being disposed on each side of the clamping bolt and at a distance there¬ from.

Within the scope of the invention, it is also poss¬ ible to use fixing lugs which are elongate in the axial direction of the vehicle wheel so as to define a valley between them, in which the jaw or bead clamp is disposed when mounted.

To ensure that the jaws or bead clamps are conveni¬ ently guided into place when being mounted, the top side of the fixing lugs is preferably rounded or bevelled. This can easily be achieved if using fixing lugs formed of metal rods having round or semicircular cross-section, which are welded to the rim bottom.

When the bead clamps or jaws are to be used in a tubeless tyre construction, air tightness is ensured where the clamping bolt passes through the rim bottom by arrang¬ ing a suitable seal of elastomeric material or other seal-

ing material around the clamping bolt between the rim bottom and the jaw or bead clamp.

In the invention, use is preferably made of jaws or bead clamps having a fixed length. Within the scope of the invention, it is however also possible to use jaws or bead clamps of expandable type according to the disclosure of SE-B-418,481. This publication therefore is included in this description by reference.

The invention will be described in more detail here- inbelow in a currently preferred embodiment. Fig. 1 is a radial section of a vehicle wheel according to the inven¬ tion. Fig. 2 is a section taken along the line II-II in Fig. 1. Fig. 3 is a perspective view showing parts of a rim and a bead clamp mounted thereon. Fig. 1 shows a rim 10 having reinforced rim seats 11 and rim flanges 12. The reinforcement consists of a weld¬ ed angle section 13. The rim has a rim disc or spoke structure 14. A vehicle tyre 15 is mounted on the rim, such that the tyre beads 16 engage the rim seats 11 and also the rim flanges 12. The tyre beads are pressed firmly against the rim flanges 12 by means of bead clamps 17 which are arranged in spaced-apart relationship around the rim. In ordinary cases, e.g. six or eight evenly dis¬ tributed bead clamps can be used. Only one of the clamps is however shown in the drawings.

The bead clamp shown in the drawings consists of a welded box girder of sheet metal with a clamping bolt 19 fastened thereon. At the ends of the bead clamp, there are provided clamping surfaces 20 which are pressed against the tyre beads 16, and also abutment surfaces 21 which are pressed against the rim bottom. The bead clamps also have a sealing surface 22 which is pressed against a suitable rubber or plastic gasket 23 engaging the rim bottom so as to ensure air tightness around the clamping bolts 19.

According to the invention, the rim 10 has a number of fixing lugs or ridges 24 which in the illustrated embodiment consist of short round pieces of steel, also having rounded ends and being welded to the rim bottom. The lugs 24 are arranged pairwise on both sides of the bead clamp 17 to prevent it from being unintentionally rotated about the clamping bolt when subjected to high stresses. In this embodiment, one pair of lugs has been disposed adjacent the rim seat 11 while the other pair has been disposed some distance away from the opposite rim seat 11 to make room for one tyre bead when mounting and dismounting the tyre.

One way of mounting the tyre 15 on the rim 10 is to first force one of the tyre beads over one of the rim flanges 12, whereupon the bead clamps are passed into the tyre and into their fixing holes, the bead clamps 17 being so turned that the longitudinal direction of the bead clamps roughly coincide with the plane of rotation of the rim. The bead clamps are thus swung about 60-90° with respect to the position shown in the drawings. After applying the nut on the fixing bolt projecting through the rim bottom, the bead clamp is pressed as far into the tyre as possible while maintaining this orientation. The other tyre bead is thereafter forced over the rim flange, and the tyre is inflated, e.g. to about 500 kPa. The bead clamps are thereafter swung to the position shown in the drawings and pulled down against the rim by tightening the nut. By the provision of the fixing lugs 24, the bead clamp is forcedly guided into its intended operative posi- tion. When the nut has been completely tightened, the tyre beads 16 will be sealingly pressed against the rim flanges 12 and the rim seats 11 at the same time as the gasket 23 is compressed and the abutment surfaces 21 are urged into firm mechanical engagement with the rim bottom 25. As earlier mentioned, the bead clamps may be expand¬ able in the longitudinal direction, as stated in SE-B- 418,481. The same advantages are obtained in this case by the use of the fixing lugs 24.

In the event of a puncture, the bead clamps, as in the device according to SE-B-418,481, will maintain the tyre beads clamped against the rim seats and the rim flanges with a force replacing the clamping force exerted by the air pressure. When using extreme low-profile tyres, as on forest machines, this clamping force brought about by the bead clamps may also supplement the clamping action of the air pressure, so as to give the tyre a considerably improved capacity to withstand high lateral loads as a result of the lugs 24 preventing the bead clamps from turning about the clamping bolts.

Moreover, the clamping of the tyre beads prevents the tyre from slipping on the rim, which in turn means that the tyre can transmit driving and braking forces also when punctured. In this manner, the mobility of the vehicle both under cross-country conditions and on roads will largely remain unaltered, also in the event of a puncture. By the design of the bead clamps, which thus are not to be compared to the known run-flat rings provided on the inner side of the rim, it is possible to achieve sufficient clamping to permit running the tyres at extremely low air pressures in cases where, for example, additional carrying capacity or additional traction is required for driving on very loose ground. Moreover, the clamps permit using tube- less tyres also under cross-country conditions, without the risk of slow leaks because of foreign matter penetrat¬ ing in between the tyre wall and the rim flange. A major advantage gained by the clamp beads being designed to mechanically abut both on the rim bottom and on the tyre beads is that the bead clamps are stabilised and prevented from breaking or tilting or being rotated as a result of the substantial stresses which arise in run-flat driving. If, moreover, use is made of the bead clamps in com¬ bination with a lubricant, it is possible to run punctured tyres over long distances. If the damage to the tyre is only caused by pointed weapons or small-bore arms, it is in fact not necessary to dismount the tyre from the rim

but simply to plug the hole, whereupon the tyre is inflat¬ ed and again becomes functional.

In fact, the bead clamps in the construction accord¬ ing to the invention are so effective that the tyre is retained on the rim even if it were to be blown up by running over a landmine. Since the tyre remains on the rim despite such serious damage, it is possible to continue using the damaged tyre for transmitting driving power and braking forces and imparting carrying capacity to the wheel. Of course, a damaged tyre retained of the rim is better than the rim alone.

Another substantial advantage of the construction according to the invention is that a split rim need not be used for mounting the bead clamps, i.e. these fit both flat-base rims and drop-centre rims.