The invention relates to a gripping device for vehicle wheels having elastic tires which are mounted on a rim, the gripping device thereby preventing the wheel from sliding on the ground and comprising at least one cross piece having a fleexiblε, pliable or the like, mid portion and an attachment means arranged at each end thereof , by means of which the cross piece can be attached to rim portions at respective sides of the wheel, and the mid portion hereby is substantially adapting to the cross sectional shape of the tire and brings about an elastic deformation thereof in such a way that the cross piece thereby is heavily tightened.

In the accompanying drawing fig. 1 shows a gripping device of the known type comprising for example a flexible strap having terminal hooks which are adapted to be attached to portions of the rim upon which the tire is mounted. For mounting of the strap one terminal hook thereof is initially attached to the rim near a first wall of the tire, whereupon the strap is laid around the tire in the transverse direction relative to the wheel . As the strap has to be heavily tightened for elastic deformation of the tire, a rod shaped tool is used, one end of which is brought to bear against the rim. The other end is grasped by the hand, and a hook shaped catch which is articulately connected to a mid portion of the rod is hooked onto the strap, for example by inserting its hooked shaped portion into a corresponding hole of the belt adjacent to the free terminal hook thereof .

During the use of the tool, however, only substantially the belt portion being close to the free hook and only the second tire wall adjacent thereto are elastically deformed, while the thread of the tire and the first tire wall are substantially not deformed. Even if the hook which was attached by means of the tool initially exerts a

large force against the rim and apparently is securely attached due to the relatively strong compression of this short tire portion, this tensile force will be reduced after driving for some time, because the strap will be somewhat displaced in its longitttdinal direction and relative to the tire, resulting eventually in a relatively small compression of all sides of the cross section of the tire and a corresponding small tension of the strap, so that the strap then will be relatively loosely connected to the wheel . This may provoke detachment of the strap from the wheel or make it possible for the strap to be moved along the pheriphεry of the wheel , causing a larger wear of the wheel as well as of the gripping device.

The purpose of the invention is to provide a gripping device of the above—mentioned type and which does not suffer from the above— entioned drawbacks.

This is accomplished by a gripping device as defined in the claims.

The invention will now be described in detail by way of example with reference to the drawing, in which:

Fig. 2 and 3 are cross sectional views of an upper portion of a vehicle wheel which is provided with a first embodiment of the device according to the invention;

Fig. 4 and 5 are cross sectional views of an upper portion of a vehicle wheel which is provided with a second embodiment of a device according to the invention;

Fig. <_> is a side elevational view of a beam element;

Fig. 7 is a view in the direction of the arrow A, of the beam element shown in fig. 6.

As shown in fig. 2 a vehicle wheel 1 comprises a tire 2 which is mounted on a rim 3. In order to prevent sliding of the wheel on slippery roads etc., it is provided with a gripping device 4 of the initially mentioned type, having a mid portion 5 and first and second terminal hooks 6 and 7 respectively. The mid portion comprises a beam element S, two opposite side portions of which being connected with one end of respective first and second flexible straps 9 and 10, the beam element being substantially more rigid than the straps.

For the grip device to be mounted, one hook, for example the first hook 6 is hooked onto for example the radially inwards bent portion of one of the rim flanges 11, on which the beads of the tire are resting in the transverse direction, whereupon the mid portion 5 is laid along the first wall 12, the thread 13 and the second wall 14 of the tire. The length of the first strap 9 which is most close to the first hook 6 is such that the beam element δ thereby will be abutting the mutually adjacent portions of the thread and the second wall 14 of the tire, whereby the beam element is inclined relative to the thread 13 as well as the second wall 14 of the wheel.

The second strap 10 which is arranged between the beam element δ and the second terminal hook 7 which is still free, may be provided with a row of holes which are spaced in the longitudinal direction of the strap. The hook shaped portion of a catch 15 of a tool 16 of the abαve- mentioned type is therafter brought into engagement with a suitably positioned hole of the second strap 10, whereupon the tool is swung with its abutment point on the rim as a fulcrum, for tensioning of the gripping device.

The beam element 8 thereby iπitally completely or to a large degree, prevents the portion of the first strap which extends along the thread of the tire, from touching

the thread and the second strap 10 from touching the second wall 14 of the wheel respectively.

The pulling or tensile force which is exerted by the catch 15 of the tool against the beam element δ via the strap 10 hereby tends to tilt the beam element 8 about its abutment point on the tire 2, and the tensile force is thus transferred to the second strap 9, the transferred force substantially being dependenent of the length of the beam element portions at each side of the abLitment point. The beam element thus substantially acts as a lever. Upon continued tilting of the tool 16, initially the thread of the tire and thereafter the second wall of the tire will be deformed, and the beam element will be puilled towards the rim along the wall of the tire until the second hook 7 can be brought into engagement with the adjacent rim flange 11 as shown in fig. 3, whereupon the tool may be removed from the wheel.

In order to obtain elastic deformation also of the first wall 12 of the tire, the mid portion of the gripping device may comprise first and second beam elements 17 and 18 respectively, and first, second and third straps 21, 22 and 23 respectively, as shown in fig. 4 and 5, the first strap 21 being connected to the first hook 6 and one of the two opposite side portions αf the beam element 17, whose other side portion is connected with one end portion of the second strap 22. The second end portion of the strap 22 is connected with one of the two opposite side portions of the second beam element 18, whose second side portion is connected with one end portion of the third strap 23. The second end portion of the strap 23 is connected with the second hook 7, the connection points for the straps, the beam portion and the hooks being marked as black circles or points in the figures.

Like the second strap 10 of the first embodiment of the

gripping device, also the third strap 23 has a row of holes.

For mounting of this gripping device, the first hook 6 is initially hooked onto the rim, whereupon the first strap 21 is laid along the first wall 12 of the tire, the second strap 22 is laid along the thread and the third strap 23 is laid along the second wall 14 of the tire. The mid portion of the first beam element 17 is thereby abutting mutually adjacent portions of the first wall 12 of the tire and the thread 13, and extends substantially inclined relative to this wall of the wheel as well as to the the thread. Further the second beam element lδ is extending in a way similar to the beam element 8 of the above- mentioned, first embodiment, whereby it is extending inclined relative to the thread 13 as well as to the second wall 14 of the tire.

After mounting of the tool 16 and initial tensioning of the gripping device therewith, the beam elements prevent the straps completely or to a large degree from touching the adjacent portions of the tire, so that both walls of the tire and the thread are compressed and deformed elastically upon the further tensioning of the gripping device. In this way it can be ensured that the force which is exerted between the hooks and rim will not be reduced during the following driving.

In place of the gripping device comprising an alternating arrangement of straps and beam elements, the hooks 6,7 can be interconnected by means of only one strap having a row of holes which are evenly spaced in the longitudinal direction of the strap, and the beam element can be separate and adapted to be connected with the strap before the strap is attached to the wheel. As shown in fig. 6 and 7 the beam elements 30 may comprise a rigid, for example plate shaped beam portion 31 having side pins 32 and a

central pin 33 which are projecting away from the plane of the plate and are adapted to introduction into the holes of the strap, the spacing of the pins corresponding to the spacingof these holes.

Prior to the mounting of the strap on the wheel , one or two beam elements 30 whose lengths are equal or unequal, may be arranged between the strap and the tire at positions of the strap corresponding to the positions for the beam elements 8, 17 or 18 of the embodiments of the gripping device described above, the pins being initially introduced into the holes of the strap at these positions. During the mounting and the driving the pins and the holes are ensuring the connection between the strap and the beam element.

For further securing of this connection, the central pin 33 may be lengthened and provided with threads in such a way that its threaded portion extends through the strap and that a nut may be screwed onto this portion. Following the removal of the gripping device from the tire, the beam element will then remain attachded to the strap. Thus, repeted mounting on the same tire or another tire having the same dimentions will be simplified.

In place of the beam elements being symmetrical about a central, transverse plane as shown in fig. 6 and 7, they may be unsymmetrical in such a way that the distances from the pin 33 to the two ends of the beam portion are unequal. Thereby the forces which are exerted against the end portions of the beam element during mounting thereof may be unequal .

The invention is above described for a gripping device having a mid portion comprising a strap. In place of a strap the mid portion may be constituted by for example a chain, the pins of possible separate beam elements then

being adapted to simultaneous introduction into the openings of the chain links.

The end portions of the plate shaped beam portion may be roLinded or bent in such a way that the tire is not liable Ito be damaged by the beam portion upon the tightening of or the driving with the gripping element.

The gripping device is above described as a separate element being mountable across a wheel. It may however of course instead be a similar element which is included in a device having further elements extending along the pheriphery of the wheel .