DE2038562A1 - Process for making pneumatic tires - Google Patents

Description

The invention relates to pneumatic tires, and more particularly to a method of making radial belt pneumatic tires.

It is an object of the invention to provide a radial belted tire to create its tread durability considerably is enlarged without having to accept other disadvantages. Other tasks and advantages of the invention emerge from the following Description of the drawings, namely show:

FIG. 1 is a cross-sectional view of a tire in FIG. a form according to the method according to the Invention, and

Figure 2 is a cross-sectional view of an inflated

Tire made according to the invention.

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As can be seen from the drawings, in particular FIG. 2, a tire 12 according to the invention has a radial ^{ply carcass 11 and a tread n} part 12 which is arranged around the circumference of the carcass 11 radially outside the same. A pair uon belt plies 13 are disposed around the 'JnPang of the carcass 11 around, and zyar below the tread portion 12. The carcass 11 terminates at its radially inner end into a pair vo ^p Uulstgliedern 14. The carcass 11 and the belt plies 13 ueisen per several , substantially parallel tire cords.

Although the carcass 11 is provided with two radial plies 15 and 15 as shown, could only one or several such layers could be used. For the purpose of the invention is intended a radial position also include such a position, the cords of which are at an angle of between 75 ° and 90 ° with respect to the circumferential center line of the tread 12 at this circumferential center line; nylon, rayon, polyester or wire, for example, are specified as suitable material for the cords. For the purposes of this invention, a "circumferential centerline" is used to refer to a circle that extends on the Tread surface in the middle between their Side edges and in one to the axis of rotation of the tire

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vertical plane. This level, which contains the circumferential line, is referred to in the following as " ¹ Jmfancsmittelebe-ic".

Although in the particular "illustrated embodiment." of the tire two belts 13 are shown, You can also use one or more belt layers Find. Extend the cords in each belt ply

ο ο referring to yourself in a uinkei between 10 and 45 on the circumferential center line of the tread on this Line and consist e.g. 5. Made of -clyester, rayon, fiberglass or wire.

As can be seen from FIG. 2, the tire 10 is when it is mounted on a rim and inflated, a Uuistgrundlinie B, which is parallel to the axis of rotation of the tire and is radially from the axis by a distance equal to the de "N'oninal radius of the rim on which the respective tire is to be mounted. For the purposes of this invention, all Cu dimensions are cut of the tire with reference to the cross-section of the tire specified as it appears in a plane within which the axis of rotation of the tire lies. The section width SD of the tire is measured parallel to the axis of rotation of the tire when the tire is on a 70 JJS rim is mounted and inflated on

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the nominal pressure and vsnn the tire is relieved. As indicated for SD, the section width is equal to the distance between the outer surfaces of the tire at its widest point, excluding any decorations, letters or the like. on the tire. For purposes of this invention, the term "nominal pressure" means the internal pressure of a ^{[j r} the tire won the design create & ^ ter norralen working conditions to be inflated. For the purposes of this invention, as a good tire engineer is familiar with, a "7G f ^ - rim" means a rim that has a lateral distance between the inner sides of the rim flanges - measured parallel to the axis of rotation of the tire - which is equal to 70 % of the cutting width SD when the tire is mounted on the rim and inflated to the nominal pressure . The cross-sectional height SH of the tire is indicated at SH in the drawing and is again measured when the tire is mounted on a 70 jS rim, inflated to the nominal pressure and relieved. The cross section height SH is the distance, measured radially to the tire, from the Uulstbaseline B to the radially outermost point of the tread 12 on the circumferential center line of the tread. The tread radius TR is the radius of an arc which coincides with the outer surface 17 of the tread 12 in at least the area of the circumferential center line. A positive one

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The tread radius is one where the center of curvature of the arc, based on the Axis of rotation of the tire, lies radially inward of the tread. A negative tread radius is one that at which the center of curvature of the arc, based on the axis of rotation of the tire, is located radially outward of the tread. Next is for the purposes of this invention the tread arc width TAU the distance between the side edges 18 of the tread, measured in one plane, which contains the axis of rotation of the tire. The "margin" of the tread 18 is the laterally outermost point of the tread, the surface bearing the tread touches when the tire is mounted on a 70 ^ rim, inflated to nominal pressure and statically with the final load is burdened. The "end load", for the purposes of this invention, is the load under which to normally operate the tire is designed.

In the conventional production of radial belted tires, the carcass plies and Uulste are on an approximate Assembled cylindrical tire building drum. the The carcass is made toroidal and the belt plies and tread are laid on. The tire is then in a farm vulcanized to the finished product.

10 9 8 0 8/1453 bad ORiGiNAL

Uie can be seen from Figure 1, a tire 13 is after of the invention vulcanizes while maintaining its tread in an inversely curved shape. This reverse curvature is chosen such that d ° r radial distance from the axis of rotation of the tire to z-jr Tread surface 17 a "i of the circumferential center line is less is as the radial distance from the axis of rotation of the tire to the tread surface 17 on each part a pair of parts 21 located laterally and on opposite sides of the circumferential center line are arranged. With another 'Jorten, the central part 20 of the tread is pressed down between the parts during the molding and curing of the tire 21 of the tread on opposite sides of the central part. This impression forms during the vuicanization of the tire in the Form 19 has a slightly inversely curved part 20 in the central area of the running surface 12.

The depth D of the depression or indentation becomes constant the tire is in the mold 19, on the circumferential centerline measured, i.e. where the indentation is greatest and it is the distance from the surface 17 of the tread 12 at the circumferential center line up to a line which runs parallel to the axis of rotation of the tire and tangential to the parts 21 v /, radially to the axis of rotation

10980 8 / US3

measured on the tire. The point, tangent like runs on each part 21 to the direction parallel to the axis of rotation of the tire line is located at a distance from the Uri ^r angsriittellinie which at least is one third of the distance from the ¹ J ^ fangs "ittelebe ° e to the side edge 18 .

The depth of the depth D is of particular importance and satisfactory results should be obtained if it is kept within certain limits. rope at least 0.013 cn. The * axial depth D ccer D should not be greater

nax

to be more than a distance that is irradiated by the equation

715 TAU -ν 2.54

\ _eff

T (cos. _T

In the above equation, the term TAU means the tread arc width in centimeters, as before Are defined. T is the outermost belt thickness in kilograms in the circumferential direction of the tire, per centimeter of width of the belt. The size of T is determined by Multiply the breaking load or tensile strength in kilograms of a cord in the belt with the total number of cord ends per centimeter in the belt. The breaking load

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of the tire cord is determined immediately before Calendering the material. The total number of cord ends per centireter in the belt is the total of cords in all belt layers, within a one centimeter wide cross-section of the belt, read centrally to the circumferential center line. As mentioned before, are all cross-sectional dimensions with reference to the cross-section of the tire in a plane within which the axis of rotation of the tire lies. AR ^ is the distance ratio of the tire, if this pays for a 70 ^ rim, inflated to nominal pressure and is relieved. The distance ratio is the number that is obtained by dividing the cross-section height SH by the cross-section width SD, or matherra-

SH
Expressed in table: AR = ττττ. Again, uie just

explained, cross-section width and cross-section height determined when the ^D eifen is mounted on a 70 ^ rim, inflated to nominal pressure and relieved. M is the tL · modulus of elasticity of the cords in the belt in grams / denier. The elasticity index of a cord is the angle of inclination of the initially straight part of the tear diagram for the cord when the cord is in the state in which it is normally just before the cord material is calendered. The constant, 715, in the numerator of the first term is given in kilograms per centimeter. The constant 394 in the denominator of the

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second link is given in degrees per centimeter. The 2.54 bar in the numerator of the third link is given in centimeter-grams per denier. oC ** is the angle of the cords in the belt layers and is equal to the angle in degrees that the cords in the belts form with the circumferential center line at this center line when the tire is vulcanized, mounted on a 70 ^ rim, inflated to the nominal pressure and is relieved. If the cord angle varies in the various belt layers, the effective cord angle ⁰ ^ "" must be determined by the equation

Na ₁ + (NI) ₅ C ₂ + (N-2> CC ₃ + ... # _N

^eff 'N + (N-1) + (N-2) + ... 1

Bsi of the above equation, N is the total number of belts in the belt. CC * the cord angle of the belt ply. With the lowest cord angle. oc is the cord angle of the layer with the next lowest cord angle. CX, is the cord angle of the belt layer with the third-thinnest cord angle. OC _n is the Corduinkel of the belt ply with the highest Corduinkel.

If the indentation D during the ulcanization of the Tire in shape within the limits of D. and

min

D is held as described above, so a normal or nominal inflation pressure in the tire,

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if this is not mounted on a rim, generate a sufficient internal force "to remove the indentation D and to expand the LauTlMc ^ e -" with reference to ^c the axis of rotation of the tire radially outwards and thus to form an arc at the circumferential center line, desse ^ center of curvature with respect to the rotation axis of the tire is located radially inwardly of the Lauffiächenoberflache. This will have an improved Lau ^ iächenlebenszeit and W) of the traction neife ^ s result. Optimal results, however, are obtained if the depth D of the indentation during vulcanization of the tire is kept in the shape at approximately ■ * (D + D.).

In the embodiment shown in the drawing is the cross-sectional contour of the indentation D in central part 20 of the tread 12, during the tire is in the Uulkanisierforn, through an "ogen _ defined with a circle whose center is in the circumferential median plane with respect to the axis of rotation of the tire lies radially outward of the tread and in a plane which the Includes axis of rotation of the tire. The cross-sectional contour of each part 21 lying to the side of the central part 20 becomes determined by an arc of a circle, the center of which lies in a plane containing the axis of rotation of the tire and is radially inward of the tread with respect to the axis of rotation of the tire. The distance U by which the

BAD OR in'MyM 109808/1453 ^JAL

Center of curvature of each part 21 from the circumference mid-plane is determined by the equation

U = ^ (TAU - SR - D),

where TAU and D are the arc width bzu. -eindrück'jng si "d cemäes above definition and ucbei SR ^ orn the run ^ lächenschulter-radius, become the ^p in the design of the Psi ens geuählt the tire engineer" ksnr.

The radius of curvature of the Bcrers in central part 20

2 2

R ₁ = D ^ + 'uT

is besti ^ ^m t by's equations ^ c *. Of the

3D

Radius of the Krür '^ - jrc *' of each part 21 is equal to that

1 half of the radius P- of the central part, or R "= γ-

^R 1

This curvature of the central part 20 and of the parts 21 on the opposite sides of the central part 20 is useful, but not critical, and the desired results are obtained in reverse with each other. Curvature of the central portion of the tread which terminates in lateral portions of the tread, each of its radially outermost point 22 is tangent to a common ver parallel to the tire axis of rotation running tangent in a point of the circumferential tread centerline by a distance of at least one third of the distance of the admonished circumferential center line is removed from the side edge. However, it is

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rr Jt

It is important that the depth D of the indentation in the central Area of tread within the prescribed Limits are kept. In the construction of a radial ply tire are the stretch ratio AR, the tread arc width TAU and the shoulder radius SR can be selected and are given by the tire designer. The determination of the materials, the construction 'jnd of the general shape required to make to get a tire that has the desired geometric Has properties is within the ability of one of ordinary skill in the art. Once these variables are determined, they become the depression in the tread part of the mold, the radius of curvature of the central part in the shape and the radius of curvature of the raised parts in the shape towards the top method described.

In a special "exemplary embodiment, FR70-14 Radial layer tires with the same design features manufactured. The main design features of these tires after their completion were:

Belt = 4 layers of 1550/3 rayon with 7.87 ends per centimeter.

Breaking load = 21.1 kg per cord of the rayon cord.

T = 4 layers (7.87 ends per centimeter) (21.1 kg per cord) = 664 kg per centimeter.

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Oi = 12 degrees.

TAU = 15.24 centimeters.

AR = 70

M = 130 g per denier.

The maximum depth D of the indentation was therefore

Max

calculated:

716 (15.24) 12 2.54 i.p.

D = ir ■ * · -; - = 0.300 centimeters.

^maX 664 (C, 973) ° 394 130

Therefore, for optimal outlines, D = 1/3 (0.013 + 0.300) = 0.104 centimeters.

Half of these tires were vulcanized while their tread in the mold had a positive radius of curvature. The remainder of the tires were cured while there was a soft indentation over the tread area, the maximum depth of the indentation being 0.104 cm at the circumferential centerline »by the radius of curvature of the central portion 20 was equal to R ₁ . as defined above. The radius of curvature of each second part or side part 21 was R «as defined above. Each tire was mounted on a 70 ^ rim, inflated to nominal pressure and subjected to a road test for the life of the tread. The average lifespan

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the tread of the tires were vulcanized in a For ^m, nit surfaces in their running a positvien
Radius of curvature was maintained was 48 27C '<r. The average lifetime of La'jfflächen of mz ^ the method of this invention vulcanized
Tires, ie those tires which CISR with the indentation tread of 0.104 cm at the circumferential center line vulcanized were was 64,350 km.

During certain representative embodiments and The details discussed above to explain the invention will be apparent to those skilled in the art Changes and deviations are possible without departing from the scope of the invention.

BATH

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Claims (6)

Claims Method of manufacturing a pneumatic tire of the type with radial ply carcass, a tread part and cord reinforced belt, characterized by vulcanizing the tire in a shape in which the tread has an indentation in cross section in its central part, which is defined by a soft one Curve with a maximum depth between 0.013 cm and Γ 715 TAU OCeff 2.54 "" I - * - + + I cm, where TAU a [_T (cosx _eff ) ^J AR 394 v \ ι Third of the tread arc width, T is equal to the Belt thickness is, Λ., Equal to the effective cord thread angle of the belt, AR is equal to the stretch ratio and Γ1 equal to the modulus of elasticity of the cords in the Belts. 2. The method according to claim 1, characterized in that the tire is vulcanized in a shape that holds the tread in a shape having a pair of raised Has parts, one of which is arranged laterally and opposite one another from the recess, wherein the point at which each raised part is tangent to a common straight tangent that is parallel to the axis of rotation of the tire extends and from the circumferential median plane of the tread 109808 / U53 removed by an amount that is at least one third the distance from the circumferential median plane of the tread to the edge of the page. 3. The method according to claim 2, characterized in that the distance from the circumferential median plane of the tire to
to the tangent point mentioned for each raised part
is defined by equation 1/2 (TAU -SR-D),
where U is equal to the distance eruähnten, TAU equal to the propagation f lächenbogenbreite, D is the indentation and SR equal to the shoulder radius of the die. 4. The method according to claim 3, characterized in that the radius of curvature of the indentation is defined by 2 2 the equation R * = —s4, where R- is equal to the The radius of curvature of the indentation and D is the depth
the indentation on the circumferential median plane and the
The radius of curvature of each of the raised portions is equal to half the radius of curvature of the indentation. 5. The method according to claim 1, characterized in that the impression etua the same 715 TAU α _ff 2.54
j3j- + + + 0.013 T (cosx -) ° AR 394 Π ^l eff Centimeter is 109808 / U53 6. l / experience according to claim 4, characterized in that that the impression is about the same 715 TAU T (cos <* _eff ) ° AR 394 ₃ - _T -SLL + + o, Qi3 Centimeter is 109808 / U53 Blank page