CA1200185A

CA1200185A - Tire having a body without reinforcement structure in the sidewalls and in the crown, and a crown reinforcement

Info

Publication number: CA1200185A
Application number: CA000432081A
Authority: CA
Inventors: Jean-Pierre Cesar
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 1982-07-08
Filing date: 1983-07-08
Publication date: 1986-02-04
Also published as: AU1665783A; DE3369486D1; ZA835003B; AR231414A1; DK316683D0; ES281459U; FR2529834B1; ATE25218T1; OA07488A; EP0098459A1; JPH0336681B2; JPS5920702A; DK316683A; EP0098459B1; BR8303672A; AU555087B2; FR2529834A1; ES281459Y

Abstract

ABSTRACT OF THE DISCLOSURE

A tire having a body and a crown reinforcement arranged on the body, the body having two sidewalls and a crown, the crown of the body being formed of three zones located below the crown reinforcement, namely, two side zones close to the edges of the crown reinforcement and a central zone adjacent to the side zones, the body being without reinforcement structure in the sidewalls and in the crown, the concavity of the sidewalls facing the inside of the tire, characterized by the following features:
(a) the thickness e0 of the body along the edges of the crown reinforcement and the thickness e1 of the body at any point in each of the side zones are related by the relationship: e1 > 0.6 e0;
(b) the width ?1 of each side zone and the width L of the crown of the body are related by the relationship:
0.02 L ? ?1 ? 0.30 L;
(c) the average thickness of the body in the central zone and the thickness e0 of the body along the edges of the crown reinforcement are related by the relationship:

Description

~2~ 5 The present invention concerns tires. More particularly, the invention concerns tires having a body which is without reinforcement structure in its sidewalls and in its crown. Such tires having an unreinforced body have a part which is intended to reinforce the crown and is arranged on the body. This part will be referred to as acrown reinforcement in the following description but it may also be called, for instance, ~<txead reinforcement in the tire industry. These tires with an unreinforced body have the advantage that they are simple to manuracture, these tires being manufactured, for instance, by producing the body by molding from one or more polymers, for instance, by the molding of polyurethanes.
It is already known to produce tires having the above-described unreinforced body in such a manner that the sidewalls of said bodies have a concavity which faces the outside of the tires.

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The sidewalls of these tires must be made of substantial thickness in order to resist the compressive force caused by the inflation pressure.
These tires have the drawback of being of high weight and they are furthermore characterized in operation by excessive resistance to rolling and excessive heating.
It is furthermore known to produce tires having an unreinforced body in sucn a manner that the sidewalls of said bodies have a concavity which faces the inside of the tires. These tires have bodies with thinner side-walls than the tires which were previously described.
Thus, their resistance to rolling and their heating can be decreased, but these tires still require a s~lbstantial amount of rubber and therefore are of high cost.
The object of the invention is to eliminate these disadvantages.
Accordingly, the tire of the invention which has a body and a crown reinforcement arranged on the body, the body having two sidewalls and a crown, the crown of the body being formed of three zones located below the crown reinforcement, namely, two side zones close to the edges of the crown reinforcement and a central zone adjacent the side zones, the body being without reinforcement structure in the sidewalls and 2S in the crown~ the concavity of the sidewalls facing the inside of the tire, is characterized by the following features:
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(a) the thic]cness eO of the body along the edges of the crown reinforcement and the thickness el of the body at any point in each of the side zones are related - by the relationship: el > 0.6 e0;
(b) the width ~l of each side ~one and the width L of the crown of the body are related by the relationship:
0.02 L < ~l < 0.30 L;
(c) the average thickness e2m of the body in the central zone and the thickness e0 of the body along the edges of the crown reinforcement are related by the relationship: e 2m < 0-5 e0.
The invention will be easily understood from the following e~amples and the igures referrin~ to the examples. Of these figures, all of which are schematic:
- Fig. 1 shows a tire according to the invention, seen in radial cross section;
- Fig. 2 shows in part, seen in top plan view, the crown reinforcement of the tire shown in Fig. 1, the tread being assumed removed;
- Fig. 3 shows the crown of the tire shown in Fig. l, seen in radial cross section;
- Fig. 4 shows a portion of the crown shown in Fig. 3, seen in radial cross section;
- Fig. 5 shows the crown of another tire according to the invention, seen in radial cross section.
Fig. 1 shows a tire in accordance with the invention.
This tire 1 has a body 2 formed of two beads 3, two sidewalls 4 and a cro~n 5. Each of the beads 3 has a reinforcing bead ring 6, these beads 3 making it possible to mount the tire 1 on a rim 7. However, one can also contemplate beads 3 without bead rings, as known per se. One can even contemplate tires without a bead. The body 2 has no reinforcement structure in the sidewalls 4 or in the crown 5, that is to say it is without reinfo.rcing wires or cables at these places, but the body 2 may possibly have short reinforcing fibers, for example metal fibers, inorganic fibers, particularly glass fibers, organic fibers, particularly cellulose fibers or fibers of synthetic polymers such as, for example, aromatic or nonaromatic polyamide fibers and polyester fibers. The body 2 has been prQdu~ed, fo- example, by molding from one or more polymers in paste or liquid form, for example, one or more polyurethanes, these polymers containing, if desired, various additives known per se, for example, the aforementioned short rein-forcing fibers.
The concavity of the sidewalls ~ faces the inside 8 of the tire 1.
The tire 1 furthermore has a tread 9 and a crown reinforcement 10 arranged on the body 2 namely on the outside of said body. The c.rown reinforcement 10 may ~e either arranged directly on the body 2 or, for example, wi~h the interposition of a connecting layer, in particular a rubber which is in solid or liquid condition at the time of its use. The tire 1 is produced, for example, by arran~ing the crown reinforcement 10 on the molded body 2 and then molding the tread 9 on the body 2 and the crown reinforcement 10, this crown reinforcement 10 being thus arranged between the body 2 and the tread 9.
The molding of the tread 9 is effected with one or more materials, particularly one or more polyurethanes. It goes without saying that other methods of manufacture are possible, for example, by applying a separately prepared tread 9 of different rubbers, pa.rticularly natural rubber, r ~5712 ~L~`r,?~8~i onto the body 2 and the crown reinforcement lO. It goes without saying, also, that one can possibly provide a connecting layer between the tread 9, on the one hand, and the body 2 and/or cxown reinforcement 10, on the other hand, and that the crown reinforcement 10 can be applied to the body 2 at the same time as the tread 9, these two parts 9, 10 then forming, for example, a single part.
The assembly formed by the crown 5 of the body

2, the tread 3 and the crown reinforcement 10 constitutes the crown lOQ of the tire l. The crown reinforcement 10 is formed, for example, of two pli.es 11, 12 referred to as "crown plies" which are arranged one above the other~
the ply 11 ~eing the inner ply, that is to say the ply closest to the body 2. The ply 11 has cables 110 which are parallel to each other, each of these cables forming an angle ~ with the equatorial plane of the tire 1, that is to say the plane perpendicular to the axis of the tire 1 and passing through the middle of the crown 5. Likewise, the ply 12 has cables 120 which are parallel to each other, each of these cables formin~ an angle ~2 with the equatorial plane of the tire 1. These angles ~l and ~2 have been shown in Fig. 2, the equatorial plane being represented by the line PP' and the axis of the tire 1 by th~ line XX'. The angles ~1 and ~2 are each equal to at most 90 and will be described in greater detail below.
For the sake of the clarity of the drawing, the outer ply 12 has been assumed in Fig. ~ to be partiall~
removed and in each of the plies 11, 12 the cables 110 and 120 have been shown further apart than they actually are, the tread 9 being assumed removed.

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It goes without saying that instead of using cables one could also possibly use unitary wires. The cables 110, 120 are made, for e~ample, of metal, particularly steel, possibly covered with a layer of a different metal such as, for example, zinc or brass. In each ply 11, 12 the cables 110, 120 are, for example, covered with rubber in known manner. It goes without saying that the unitary wires or cables llO, 120 of the crown reinforcement lO can be made of nonmetallic materials, fo.r example, inorganic materials, and particularly glass, or organic polymers, particularly synthetic polymers, such as, for example, the aromatic or nonaromatic polyamides and the polyesters.
Fig. 3 shows the crown lO0 of the tire l in greater detail, Figs. l and 3 being radial cross sections, that is to say sections taken along planes containing the axis XX' of the tire 1. The inner ply 11 has been shown wider than the outer ply 12 but it goes without saying that the invention applies, for e~ample, to cases in which the plies 11, 12 have the same width and to cases in which the outer ply 12 is wider than the inner ply ll. At the crown 5, the body 2 has two faces: an outer face 13, arranged on the side of the reinforcement 10, and an inner face 14 opposite the reinforcement 10.
The radial cross section of the crown 5 of the body 2 is formed of three zones located below the crown reinforcement lO, namely, two side zones Zl and a central zone Z 2 which is adjacent to the side zones Z1. Each side zone Zl is bounded on the one side by a straight line Nl~ and on the other side by a strai~ht line Nl 6 the two straight lines Nl 6 being arranged between the ~q.~ S

two straigh~ lines Nls. The central zone Z 2 is bounded by the two straight lines N 16 . Each of these straight lines N1s, Nl 6 iS perpendicular to the outer face 13 of ~ the body 2 at the point where it passes through the outer face 13. By definition, the straight lines Nls are such that the entire crown reinforcement 10 is arranged between these straight lines and limited by them, the points 15 of the crown reinforcement 10 which are located on these straight lines being referred to as the "edges of the crown reinforcement 10."
In the example shown in ~ig. 3, the edges 15 of the crown reinforcement 10 correspond to the edges of the inner ply 11, the edges 12b of the outer ply 12 being closer to the equatorial plane than the edges 15, the equatorial plane being schematically indicated by the straight line EE'. If the edges 15 of the crown reinforce-ment 10 were to correspond, for example, to a ply other than the ply 11, the above definitions would apply with respect to such other ply, the crown reinforcement 10 possibly also comprising a number of plies other than two. The side zones Z1 are close to the edges 15 of the crown reinforcement 10.
The width Q1 of each side zone Z1 corresponds to the distance between the straight lines N1s, Nl6 which define each side zone Zl. The width Q 2 of the central zone Z 2 corresponds to the distance between the two straight lines N1 6 which define the central æone Z 2 . The width L of the crown 5 of the body 2 corresponds to the distance between the two straight lines N15 ~ that is to say it is equal to the sum of the two widths Ql and the width Q 2 -All of these width measurements are made along the outer ~2~ t3S

face 13 of the body 2 and in a radial plane which is, for example, the plane of Fig. 3.
The thickness e0 of the body 2 along each edge 15 is measured by definition along the straight line Nls passing through the edge 15. The thickness el of the body 2 at any point in each side zone Zl and the thickness e2 of the body 2 at any point in the central zone Z2 are measured along a straight line N perpendicular to the outer face 13 of the body 2 and passing through said point, these thickness measurements being made in a radial plane which is, for example, the plane of Fig. 3.
The average thickness e2m of the body 2 in the central zone Z 2 iS defined by the relationship:
e = S 2 S2 being the value of the surface (that is to say the area) of the zone Z 2 measured in a radial plane which is, for example, the plane of Fig. 3.
For purposes of simplification, the average thickness e has not been shown in the drawing.
2m In accordance with the invention, the thicknesses e , el, eam and the widths Ql/ L satisfy the following relationships:
el > 0.6 eO; 0.02 L < Ql ~ 0.30 L; e2m ~ 0~5 e0.
Preferably one applies at least one of the following relationships:
0.6 eO ~ el < 1.2 eO; 0.05 L C Ql ~ 0.20 L; e2m ~ 0 3 e0;
and advantageously one has 0.6 e0 < el < e0. One can even contemplate embodiments in which the central zone Z 2 iS without any material, that is to say e 2 may be zero or prac~ically zero over a part or all of the central zone Z 2 -The crown reinforcement 10 is made in such a manner that after inflation it can withstand the forces transmitted by the sidewalls 4, despite the thinning of the crown 5. As previously described, this crown rein-forcement may, for example, comprise at least two plies,each ply having cables or unitary wires parallel to each other, the angle of each ply being defined by the angle which the cables or the wires of that ply form with the equatorial plane. In this case, it is preferable for the crown reinforcement 10 to be in accord with one of the following two embodiments:
(1) the crown reinforcement 10 has two plles and the angle of each ply is at least equal to the minimum value ~m and at most equal to a maximum value ~M such that ~ = 2 cos ~M = 0 9 cos ~0 the angle ~o being defined by the relationship:

2 R 2 ( 1 - ~ Rs 2 - Re 2 in which:
~ Ps represents the radius of curvature of the ply in question, this radius beirlg determined in a radial plane, at the intersection of that ply with the equatorial plane or in the vicinity of that intersection; Fig. 3 represents in part the radius Ps relati~e to the ply 11;
- Rs represents the distance of the ply in question from the axis XX' of the tire, this distance being determined in the equatorial plane; Rs is represented in part in Fig.

3 in regard to the ply 11;

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- Re represents the distance from the axis XX' of the tire of the points A, B where the body has the greatest width in radial section, the curvature of the body at these points being assumed uniform, that is to say without protuberance or depression at these points;
the width of the body is determined along the straight line A,B parallel to the axis XX'; the distance Re is represented in part in Fig. 1.
The definitions given above for Ps, Rs~ Re correspond to the tire 1 assumed not under load, mounted on its rim 7 and inflated to its rated pressure with air at ambient temperature (about 20C.).
In this case, the angles ~ 2 of the two plies are crossed, that is to say the angles ~l and ~2 have ~opposite orientations with respect to the equatorial plane p~', as shown in Fig. ~.
When the angle of each ply is less than the minimum value ~m defined above, excessive axial flow of the body takes place causing an increase of its width in radial section. When the angle of each ply is greater than the maximum value ~M~ there is an excessive increase in the outside diameter of the tire at the time of travel.
These two defects then make the use of the tire uncertain.
(2) the crown reinforcement 10 has at least three plies crossed in such a manner as to form a triangula-tion, the angles of the three plies being different from each other. In this case, the angles of these plies may vary within wide limits.
The use of a crown reinforcement lO limited to two plies, in accordance with the first embodiment above, however, is preferredr because it makes it possible to produce relatively light tires.

The angle ~ is de~ined by each straight line Nls and the inner face 14 of the body 2, this angle being measured, in a r~dial plane, outside the body 2 - and in the direction towards the side zone Zl defined by the straight line Nls (Fig. 4). This angle ~, called the "inner connection angle" is preferably defined by the relationship 70 < ~ < 130, so as to facilitate the transmission of the forces between the sidewalls 4 and the crown reinforcement lO. The angle ~ for this purpose is advantageously defined by the relationship 90 < ~ < 110.
The thinning shown in Fig. 3 is practically discontinuous, that is to say the thicknesses el, e~
are practically constant except in the vicinity of the straight lines ~16 where these thicknesses suddenly vary.
However, one can contemplate cases in which the decrease of the thickness of the body s~a~tincJ from the straight lines N 15 is progressive in the direction towards the equatorial plane EE' over at least a portion of the crown 5, shown in ~ig. 5. This solution can have the advantage of favoring the uniformity of the transfer of the forces between the sidewalls 4 and the crown rein-forcement 10.
The advantages of the invention are the followin~:
- the decrease in the thickness at the crown results in a decrease in Ihe weight of material and thus in a lower cost of manufacture, without diminishing the performance of the tire;
- the thlnning at the crown makes it possible to decrease the resistance to rolling of the tire.

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By way of example, two tires of size 135-13 were compared, each having an unreinforced body in the sidewalls and at the crown, the body being made by the molding of polyurethanes. Each of these tires furthermore has a tread as well as a crown reinforcement arranged on the body between the body and the tread, the rubber used for the tread and the crown reinforcement being natural rubber. The value Re is the same for both bodies, namely, 220 mm.
These two tires are identical except at the crown where one has a body of constant thickness and the other a thinned body in accordance with the invention.
I~he crown reinforcement of each tire is formed of two plies of steel cables, the arrangement of which is similar to that of the plies 11, 12 which have been described above. The inner ply 11 has a width of 86 mm and the outer ply 12 has a width of 78 mm, these widths being measured in a radial plane along the ply in question.
The width L of the crown of the body is practically equal to 86 mm. The characteristics Ps~ Rs are practically the same for both plies, namely, Ps = 200 mm, Rs = 262 mm.
The plies are crossed, each of the angles ~ 2 being between 18 and 29, for example, practically equal to 23.
The crown of each body has the following characteristics:
- for the tire of known type, the thickness of the body is constant at the crown and equal to 5 mm;
- for the tire in accordance with the invention, ec is equal to 5 mm, el varies from 5 mm to 3 m~ over S

a corresponding width Ql of 15 mm, el decreasing in the direction towards the equatorial plane, e2m is equal to 1.5 mm over the central width Q2i Q2 = L - 2 Ql - 56 mm, that is to say there is the relationships: 0.6 eO < el < eO;
Ql = 0.17 L; e2m = 0 3 eO-The invention makes it possible in this embodiment to effect a saving in weight of 25% with respect to the weight of the body, namely, a saving in weight of about 12% with respect to the -tota].weight of the tire, and a decrease in the resistance to rolling of 5~.
Of course, the invention is not limited to the embodiments which have been described above. Thus, for example, the tire in accordance with the invention may have parts known per se, which have not been described above for purposes of simplification, which parts may, in particular, be reinforcing or protective rubbers or plies, and the crown reinforcement may comprlse at least one folded ply.

Claims

WHAT IS CLAIMED IS:

1 A tire having a body and a crown reinforcement arranged on the body, the body having two sidewalls and a crown, the crown of the body being formed of three zones located below the crown reinforcement, namely, two side zones close to the edges of the crown reinforcement and a central zone adjacent to the side zones, the body being without reinforcement structure in the sidewalls and in the crown, the concavity of the sidewalls facing the inside of the tire, characterized by the following features:
(a) the thickness e0 of the body along the edges of the crown reinforcement and the thickness e1 of the body at any point in each of the side zones are related by the relationship: e1 ? 0.6 e0;
(b) the width ?1 of each side zone and the width L of the crown of the body are related by the relationship:
0.02 L ? ?1 ? 0.30 L;
(c) the average thickness of the body in the central zone and the thickness e0 of the body along the edges of the crown reinforcement are related by the relationship: .

2. A tire according to claim 1, characterized by the fact that it has at least one of the following relationships:
.

3. A tire according to claim 1, characterized by the fact that it has the relationship: 0.6 e0 ? e1 ? e0.

4. A tire according to claim 1, characterized by the fact that the thicknesses e1 and/or e2 decrease progressively in the direction towards the equatorial plane over at least a portion of the crown, e2 being the thickness of the body at any point in the central zone.

5. A tire according to claim 1, characterized by the fact that the crown reinforcement has at least two plies, each ply having cables or unitary wires which are parallel to each other.

6. A tire according to claim 5, characterized by the fact that the crown reinforcement has two crossed plies, the angle of each ply being at least equal to a minimum value of .alpha.m and at most equal to a maximum value of .alpha.M such that ;
the angle .alpha.0 being defined by the relationship in which ?S represents the radius of curvature of the ply in question, RS represents the distance of said ply from the axis of the tire, Re represents the distance from the axis of the tire of the points A, B where the body has the greatest width in radial section, the straight line A,B being parallel to the axis.

7. A tire according to claim 5, characterized by the fact that the crown reinforcement has three crossed plies so as to form a triangulation.

8. A tire according to claim 1, characterized by the fact that the inner connection angle .beta. is defined by the relationship 70° ? .beta. ? 130°.

9. A tire according to claim 8, characterized by the fact that the inner connection angle .beta. is defined by the relationship 90° ? .beta. ? 110°.