Untitled record

FRENCH REPUBLIC

MINISTRY OF INDUSTRY

INDUSTRIAL PROPERTY SERVICE

PATENT

PV n ° 797.394 1.237.762

International classification: As / - ",? B 62 gi

_ <· A

Improvements to rubber bandages.

SOCIETE ANONYME DES PNEUMATIQUES DUNLOP resident in France (Seine).

Requested on June 12, 1959, at 16 "35", in Paris.

Issued June 27, 1960.

(2 patent applications filed in Great Britain on June 14, 1958 and May 22, 1959, in the name of the so-called Company: Dunlop Rubber Company Limited.)

This invention relates to rubber tires, and more particularly to rubber tires intended for traction on loose or not very resistant ground, for example those which are mounted on agricultural tractors.

Bandages intended for this use generally have a sculpture on their tread formed by bars in relief on the crown of the bandages, these bars forming acute angles with the equatorial circle of the bandage. These bars do not protrude laterally outside the bandage.

A disadvantage of this type of tire lies in the fact that when the tread pattern bars are driven into the ground by the weight of the vehicle, the spaces between the bars tend to fill with packed soil. This tendency is accentuated by the phenomenon which occurs when a flat surface, like that of a bar of the sculpture, is partially sunk in the ground and is moved parallel to the surface of the ground in a perpendicular direction, or inclined compared to itself: the earth is first compacted, then it is pushed upwards by the flat surface which continues to move. Thus, during the periods during which a bar of the sculpture moves relative to the ground, that is to say before the attachment of the tire is sufficient to move the vehicle forward or when this attachment decreases and there is a sliding, there is an increased tendency for the spaces between the bars to fill with soil, and therefore the bandages become practically smooth and lose their grip. To reduce this tendency, the bars can be tilted relative to the equatorial circle of the tire, thus providing the ground with a way to escape from between the bars during their movement relative to the ground.

If the above mentioned drawback did not exist, the maximum traction would be obtained by the use of tread bars perpendicular to the equatorial circle of the bandage, but a compromise is necessary, the angle of the bars with the equatorial circle having to be large enough that traction is as great as possible, and small enough that the tread can be cleaned automatically.

Sometimes, to increase the available tensile force, removable or retractable metal pallets are used which form large angles with the equatorial circle, but they are expensive, long to install and wear out quickly. In addition, they must be removed, or at least retracted, when the vehicle on which they are mounted is traveling on a gravel road.

An object of the present invention is to provide a rubber tire providing a high tensile force on loose or weakly resistant surfaces.

According to the invention, a rubber bandage comprises a body, a tread, and several ears intended to increase the traction effect, which start from at least one shoulder of the body of the bandage and clearly protrude axially.

Preferably, the ears extend axially over the body of the bandage by an amount comprised between. 9.5 mm and 76 mm.

Although the invention relates above all to bandages with a total width of between 20 and 35 cm, it is possible to manufacture bandages in accordance with the invention, the total width of which is less than 20 cm or greater than 35 cm, and can use in this

- 41450

Price of the booklet: 1 NF [1,237,762] - case of the ears extending axially from the body of the. bandaging less than 9.5 mm or more than 76 mm.

Preferably, also, each of the aforementioned ears forms a body with a bar of the sculpture on the crown of the bandage, this bar being inclined and forming an acute angle with the equatorial circle of the bandage. The bar of the sculpture may extend from the ear to the equatorial circle of the bandage, or only over part of this distance, or it may extend from one side to the other of the crown of the bandage. The ears can, however, be separated from the bars of the tread pattern.

The description which follows with reference to the appended drawing, given by way of nonlimiting example, will make it clear how the invention can be implemented, the particular features which stand out both in the drawing and in the text forming, of course, part of said invention :

Figure 1 is a perspective view of a portion of a bandage;

Figure 2 is a developed plan view of a portion of the tire, part of which is shown in Figure 1;

Figure 3 is an axial section of two tires and a wheel with twin rims for carrying these two tires.

A tire casing 1 (see fig. 1 and 2), having a maximum width of 14 cm and intended to be mounted on a rim 71 cm in diameter, comprises a tread 2 carrying a sculpture formed of bars 3 which, from the equatorial circle XX, go alternately towards one side and towards the other of the bandage, each bar being inclined by 45 ° on the equatorial circle XX of the bandage, the successive bars 3 being inclined alternately in opposite directions. Ears 4, each in one piece with a bar of the sculpture, extend outwards from the shoulders 5 of the pneumatic envelope, each ear 4 having a face which extends transversely to increase the effect traction. These ears each make an angle of 90 ° with the equatorial circle of the bandage, and each of them protruded outward 63.5 mm from the side wall 6 of the bandage. The ears have a thickness, measured parallel to the circumference of the bandage, of approximately 25 mm, and their attachment to the shoulders and to the higher lateral parts of the bandage is reinforced by rounds with large radius 7 at the junction of the surfaces of the ear with the pneumatic cover.

In service, the tire is mounted, with an inner tube, on an ordinary rim with a hollow base, 71 cm in diameter, having the bead seats at the desired spacing for the narrow casing.

As the width of the tread is determined to a large extent by factors such as the space available on the vehicle for which the tire is intended, or the maximum permissible width for passage through the furrows in agricultural use , a bandage according to the invention will often be used to carry the same load as a bandage having the same total width and the envelope of which has practically the same width as the tread.

The narrower envelope of the bandage according to the invention will therefore have to be inflated to a higher pressure, and will therefore have to be stronger than the envelope of a normal bandage.

The bars of the bandage sculpture described above being fixed to the crown of the bandage in the usual way, it is desirable that they form acute angles with the equatorial circle, to improve the effect of automatic cleaning, to provide a rolling soft on hard surfaces, and increase the wear resistance of the tire tread. Automatic cleaning is also improved by the reduced length of the sculpture bars.

The ears protruding axially from a bandage according to the invention provide, on loose or weakly resistant surfaces, a much better grip than that of an ordinary bandage. The upward flow of the earth between the ears is not prevented by the casing, as happens with an ordinary bandage, and the compaction of the earth between the bars of the band sculpture is thus avoided. of rolling which would occur if the bars were perpendicular to the equatorial circle of an envelope of normal width, and the bandage maintains its traction in conditions which would cause an ordinary bandage to slip. The bandage according to the invention has, compared to an ordinary bandage provided with removable metal pallets, the advantage of being able to be used on a gravel road without it being necessary to remove the pallets.

Although a tire casing has been described with reference to the drawing, the invention also applies to solid or semi-pneumatic rubber tires.

In an alternative embodiment of the invention, shown in Figure 3, an assembly may be constituted by two or more bandages according to the invention. The tires 8 and 9 are mounted on rims 10 and 11 axially spaced and fixed to the same wheel hub 12, thus forming an assembly having a large effective width and allows the earth to flow upward as well at its central part only at its edges, thus providing a very significant pulling effect.