Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-05-21
2001-09-04
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S339100
Reexamination Certificate
active
06283185
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a traveling assembly for vehicles, which assembly is intended to be able to travel after a consequent and unexpected loss of pressure of the tire of the assembly, the tire being more particularly either a tubeless tire of the heavy-vehicle type or a tire for a passenger car, the H/B aspect ratio generally being at most equal to 0.8 in both cases. The assembly, apart from the tire and the mounting rim, comprises a supporting means for the tread of the tire when there is a loss of pressure. The invention also relates to the supporting means.
Although tires having a radial carcass reinforcement and crown reinforcement are less and less subject to slow or rapid deflation, and to becoming flat, whatever the cause(s) of said flat, the fact remains that there are still accidents and that a loss of pressure can result in many disadvantages, depending on the position of the tire on the vehicle and the rapidity of deflation. The most widespread disadvantages remain the loss of control of the vehicle, the replacement of the tire under conditions which are not always the most suitable, and practically in all cases deterioration of the properties of the tire, which deterioration may be partial or total.
Many proposals have been made to obtain a traveling assembly which is capable of traveling despite the loss of pressure of the tire of the assembly, and it would be tedious to list all the patent applications and/or patents relating to solutions for the problem. There will be discussed only the conventional, universally known means for solving said problem.
A supporting ring for a tread, which may be of one piece or of several pieces, either formed of a single material, generally a metallic material, or formed of two materials, metal and rubber, possibly being of different geometrical shapes, is inserted into the tire cavity such that the inner wall of the crown of the tire can make contact with the radially upper wall of the supporting ring. One such example of a supporting ring is described in U.S. Pat. No. 5,450,887.
It is also possible to use rings made of foam or cellular material, which under the normal pressure conditions of the tire occupies a certain volume of the tire cavity and which dilates when the internal pressure decreases, until the total volume of said cavity is occupied.
Another solution consists in inserting into the inner cavity of the tire a second, so-called inner tire, having a structure comparable to that of the first tire. The inner tire, which is of smaller dimensions, is then inflated to a pressure greater than the pressure existing in the inner cavity of the first tire, or at least in the free space between the inner wall of the outer tire and the outer wall of the inner tire, such that the outer tire comes to bear on the inner tire in the event of deflation of the outer tire. Japanese application 74/111,303 of Oct. 23, 1974 describes an inner tire of this type.
Whatever the solution adopted, it has disadvantages: a tread supporting ring made of metal or of two materials is costly, heavy and difficult to manipulate despite its lack of height, compared with that of the tire into which it is inserted. It does not enable the tire of the assembly to travel, after deflation, with a deflection compatible with good resistance to internal deterioration of the tire. The same is true of inner tires, which, although less heavy, are just as difficult to handle individually. As for rings of foam or cellular material, they cannot be used for all dimensions of tire because of the high cost of the traveling assembly, while not having any particular advantage from the point of view of assembly and manipulation compared with the use of an inner tire. Quite the contrary, the increase in the internal heating of the tire due to the presence of an inner foam body practically prevents use thereof in a tire of large dimensions.
SUMMARY OF THE INVENTION
In order to be able to use a traveling assembly, formed of an outer tire mounted on its operating rim, and a supporting means for the tread of said tire, when the latter is subject to deflation, said means making it possible to alleviate or even to do away with the disadvantages caused by the known devices referred to above, the invention proposes the use, as a supporting means for a tread, of a toric membrane of reinforced rubber, inflated to a pressure p
o
greater than the pressure p
1
of the cavity of the tire, and having, in the inflated state, a crown radius R
M
less than the loaded radius R
E
of the tire used at its recommended pressure, said membrane being reinforced, at least in its crown, by a crown reinforcement formed of at least one ply of cords or cables which are parallel to one another in each ply and form an angle &agr; with the circumferential direction such that 50°≦&agr;≦90°, said crown of said membrane furthermore comprising a hooping reinforcement composed of at least one ply of cords or cables oriented circumferentially and having a breaking force per cm of ply firstly at least equal to the product of the crown radius R
M
and the pressure, per cm
2
of surface of said ply, resulting in a tension per cm of ply equivalent to the tension due to the maximum centrifugal force to which the tire can be subjected, and secondly at most equal to the product of the crown radius of said ply and the pressure p
1
, such that the cords or cables break when the difference in pressure p
o
−p
i
increases following the decrease in p
1
.
The breaking force per cm of ply, measured perpendicular to the circumferential cords or cables of the ply, will preferably be the product of the crown radius R
M1
of said ply and a linear function of the inflation pressure p
1
of the tire, the angular coefficient of which is between 0.05 and 0.5 and the ordinate at the origin of which is precisely the corresponding pressure at the maximum centrifugal force. For example, for the range of so-called heavy-vehicle tires, this pressure is selected to be equal to 0.3×10
5
Pa, whereas for the range of tires for passenger cars this pressure will be 1.2×10
5
Pa.
The toric membrane may be closed or open. It is said to be closed when the cross-section thereof has a continuous contour, that is to say, one resembling a section of an inflated inner tube; it is said to be open if the contour of its cross-section is discontinuous, for example when the sidewalls of said membrane have ends joined by a suitable means to the beads of the tire into which said membrane is inserted.
The internal pressure po of said membrane, measured in the cold state, that is to say at 20° C., is greater than the pressure p
1
of the inner cavity of the tire by a quantity generally between 0.5×10
5
Pa and 5.0×10
5
Pa, depending on the dimensions of the tire in question. Given that the crown radius R
M
of the toric membrane is preferably between 0.80 and 0.95 times the loaded radius R
E
of the tire, mainly for reasons of the heating of said tire, an excessive pressure difference would risk adversely affecting a certain number of properties of the tire itself, for example the strength of the carcass reinforcement of said tire, while requiring an excessively large hooping reinforcement.
The crown reinforcement is preferably formed of two plies of cords or cables which are parallel to one another in each ply and are crossed from one ply to the next, forming an angle of between 50° and 75° with the circumferential direction. The cables or cords are advantageously textile cables or cords for reasons of lightness, flexibility and good corrosion resistance, and are preferably of aromatic polyamide. The axial ends of the two plies are preferably located in the sidewalls of the membrane, such that, if S is the maximum axial width of the carcass reinforcement of the tire, the width of the plies is preferably between S and 1.30 S.
The toric membrane, according to the invention, may comprise sidewalls each reinforced by at least one ply of radial cords or cables. It may also comprise, radiall
Baker & Botts L.L.P.
Compagnie Generale des Etablissements Michelin - Michelin & Cie
Johnstone Adrienne C.
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