Metallic cord and pneumatic tire

Metallic Cord and Pneumatic Tire

The present invention relates to a metallic cord for reinforcing rubber articles such as pneumatic tires in which penetration of rubber into the cord is improved.

Many rubber articles such as pneumatic tires and the like are generally reinforced with steel cords.

As shown in

FIG. 15

, a conventional steel cord is formed by compactly twisting straight steel filaments together. This type of steel cords however have a defect such that closed space not filled with rubber is formed among the filaments and steel filaments are liable to rust and adhesion between the cords and rubber becomes insufficient. As a result, the cord strength greatly decreases and the cord is broken finally.

Recently, in order to improve the penetration of rubber into cords to solve the above-mentioned problems, there have been proposed a steel cord (b) in which straight filaments (f) are loosely twisted as shown in

FIG. 16

, and a steel cord (c) in which spiral filaments (f

1

) and straight filaments (f

2

) are twisted as shown in FIG.

17

.

Such cords however, necessitate a relatively large cord diameter in order to secure stable rubber penetration. Further, such cords tend to show a large initial elongation. As a result, it is difficult to use the cords in order to reinforce a carcass and beads of pneumatic tires.

It is therefore, an object of the present invention to provide a steel cord in which the rubber penetration is improved without increasing the cord diameter and initial elongation.

According to the present invention, a steel cord is formed by compactly twisting steel filaments together, the steel filaments including a plurality of zigzag filaments and optionally a nonzigzag filament, the zigzag filament being zigzaged two-dimensionally and made up of straight segments each extending between the zigzag peak points, the nonzigzag filament being straight. In case the cord is composed of only the zigzag filaments, the zigzag filaments include at least two kinds of zigzag filaments having different zigzag pitch lengths. And at least two kinds of zigzag filaments are first loosely twisted together into a bunch, and then a plurality of bunches are twisted together into the cord. In case the cord is composed of both the zigzag filaments and nonzigzag filaments, some of the zigzag and nonzigzag filaments are first loosely twisted together into a bunch, and then a plurality of bunches are twisted together into the cord. In any case, the zigzag pitch length and zigzag wave height of each zigzag filament are substantially constant along the length thereof.

A Tire comprises a reinforcing layer such as a tread reinforcing belt layer, carcass, bead reinforcing layer and the like made of the above-mentioned steel cords.

Embodiments of the present invention will now be described in detail in conjunction with the accompanying drawings.

FIG.

1

(A) and FIG.

1

(B) show zigzag filaments having different zigzag pitch lengths.

FIG. 2

is a schematic view for explaining a method of making a cord (Embodiment 1) according to the present invention.

FIG.

3

(A) to FIG.

5

(B) are cross sectional views each showing a combination of the number of filaments and the number of filament bunches in Embodiment 1.

FIG.

6

(A) and FIG.

6

(B) are cross sectional views each showing a cord (Embodiment 1) according to the present invention.

FIG. 7

is a graph showing a cord strength reduction and rubber penetration as a function of dXh/Pw value.

FIG. 8

is a schematic view for explaining a method of making a cord (Embodiment 2) according to the present invention.

FIG.

9

(A) to FIG.

10

(D) are cross sectional views each showing a cord (Embodiment 2) according to the present invention.

FIG.

11

(A) and FIG.

11

(B) are cross sectional views each showing a cord (Embodiment 3) according to the present invention.

FIG. 12

is a cross sectional view showing a cord (Embodiment 4) according to the present invention.

FIG. 13

is a cross sectional view showing a tire according to the present invention.

FIG. 14

is a diagram for explaining a coincidence of the zigzag phases of zigzag filaments.

FIG. 15

is a cross sectional view of a conventional compact cord.

FIG. 16

is a cross sectional view of an open cord.

FIG. 17

is a cross sectional view of a cord comprising spiral filaments.

In the drawings, steel cords

1

according to the present invention are each formed by compactly twisting steel filaments

2

together.

The steel filaments

2

include a plurality of zigzag filaments

2

A and optionally a nonzigzag filament

2

B.

The zigzag filament

2

A is, before twisted, zigzaged two-dimensionally or in a plane, and it is made up of straight segments

3

each extending between the zigzag peak points U and D (peak U, dip D) as shown in FIG.

1

(A) and FIG.

1

(B). The distance between the zigzag peak points (D and D) or (U and U) measured in the longitudinal direction of the filament defines a zigzag pitch length Pw. The distance between the adjacent peak points U and D measured normally to the longitudinal direction of the filament defines a zigzag wave height h.

On the other hand, the nonzigzag filament

2

B is straight before twisted.

Preferably, the steel filaments

2

is made of a high carbon steel including 0.65 to 0.88 wt % of carbon. And the steel filaments are plated with a metal or coated with resin to improve the corrosion resistance and adhesion to rubber. If the carbon content is less than 0.65 wt %, the strength of the filament becomes insufficient. If the carbon content is more than 0.88 wt %, the strength of the filament is greatly decreased when bent zigzag.

When the cord

1

is composed of only the zigzag filaments

2

A, the zigzag filaments

2

A should include at least two kinds of zigzag filaments

2

A-

2

An having different zigzag pitch lengths Pw in order to avoid the coincidence of the zigzag phases as shown in

FIG. 14

which lowers the rubber penetration.

When the cord

1

is composed of both the zigzag filaments

2

A and nonzigzag filaments

2

B, some of the zigzag and nonzigzag filaments are first loosely twisted together into a bunch, and then a plurality of bunches are twisted together (last-twist) into the cord, whereby concentration of a cord load on the nonzigzag filaments

2

B can be mitigated. Further, it becomes possible to form spaces between the filaments between the bunches and to avoid the coincidence of the zigzag phases, which further improve the rubber penetration. During last-twisting, it is preferable to twist every bunch itself. (hereinafter, bunch-twist)

In any case, the zigzag pitch lengths Pw and zigzag wave height h of each zigzag filament

2

A are substantially constant along the length thereof. If a zigzag filament has a variable zigzag pitch and a variable zigzag wave height, the strength of the cord has a tendency to decrease.

Code Embodiment 1

This embodiment is designed for a belt reinforcing a tread portion of a pneumatic radial tire, which can be suitably used as a substitute for a conventional steel cord of a 3+9+15 construction widely used in heavy duty radial tires for trucks, buses and the like.

The cord

1

in this embodiment is composed of 8 to 10 zigzag filaments

2

A having a diameter d of from 0.30 to 0.45 mm.

The zigzag filaments

2

A include at least two kinds of zigzag filaments

2

A-

2

An having different zigzag pitch lengths Pw

1

-Pwn.

As shown in

FIG. 2

, the cord

1

is formed by twisting bunches

4

of filaments

2

A together at a twist pitch Pc of 10 to 40 mm (last twist).

Each bunch

4

is formed by twisting together two or three zigzag filaments

2

A including at least two kinds of zigzag filaments

2

A

1

and

2

An at a twist pitch Pf of 3 to 20 times the pitch Pc of the last twist.

In each zigzag filament

2

A, the filament diameter d, zigzag pitch lengths Pw and zigzag wave height h are set to satisfy the following conditions: Pw is 5.0 to 30.0 times d; h is 0.2 to 3.0 times d; and d X h/Pw is 0.014 to 0.028 preferably 0.020 to 0.025.

FIGS.

3

(A) to FIG.

5

(B) show preferable combinations of the number of bunches

4

and the number of filaments

2

A. In FIG.

3

(A), the cord is composed of four bunches

4

A of one zigzag filament

2

A

1

and one zigzag filament

2

An.

In FIG.

3

(B), the cord is composed of two bunches

4

B of one zigzag filament

2

A

1

and two zigzag filaments

2

An and one bunch

4

A of one zigzag filament

2

A

1

and one zigzag filament

2

An.

In FIG.

4

(A), the cord is composed of one bunch

4

B of one zigzag filament

2

A

1

and two zigzag filaments

2

An and three bunches

4

A of one zigzag filament

2

A

1

and one zigzag filament

2

An.

In FIG.

4

(B), the cord is composed of three bunches

4

B of one zigzag filament

2

A

1

and two zigzag filaments

2

An.

In FIG.

5

(A), the cord is composed of five bunches

4

A of one zigzag filament

2

A

1

and one zigzag filament

2

An.

In FIG.

5

(B), the cord is composed of two bunches

4

B of one zigzag filament

2

A

1

and two zigzag filaments

2

An and two bunches

4

A of one zigzag filament

2

A

1

and one zigzag filament

2

An.

Further, FIG.

6

(A) shows a cross sectional view of a cord composed of six zigzag filament

2

A

1

and three zigzag filaments

2

An.

FIG.

6

(B) shows a cross sectional view of a cord composed of five zigzag filament

2

A

1

and three zigzag filaments

2

An.

In the above-mentioned examples shown in FIG.

3

(A) to FIG.

5

(B), the type (B) is more preferable than the type (A) because two or more bunches

4

B of three filaments are included therein.

In the illustrated examples, the direction of twisting the filaments is the same as the direction of twisting the bunches. However, it is also possible to twist in the reverse direction. Further, all the filaments

2

A are the same diameter d, but, they may have two or more different diameters. With respect to the zigzag pitch length Pw and zigzag wave height h, the zigzag filament

2

An is larger than the zigzag filaments

2

A

1

.

If the diameter d is less than 0.30 mm, it becomes difficult to obtain a rigidity required for a belt layer of the heavy duty tires, and the zigzag shape is apt to return to a straight shape during twisting, and the rubber penetration decreases. If the diameter d is more than 0.45 mm, the strength of the filament tends to decrease when shaped into a zigzag, and a suppleness required during making tires is lost.

If the twist pitch Pf is less than 3 times the last twist pitch Pc, the spaces formed between the filaments becomes narrow and the rubber penetration decreases. If the twist pitch Pf is more than 20 times the last twist pitch Pc, the zigzag phases are liable to coincide with each other and the rubber penetration decreases.

It is not necessary for improving the rubber penetration to shorten the twist pitch, and a relatively long pitch 10 to 40 mm can be employed. Thus, the production efficiency of the cord can be improved.

If the zigzag pitch length Pw is less than 5.0 times the diameter d, the strength of the filament tends to decrease when shaped into a zigzag. If more than 30 times, the rubber penetration decreases.

If the zigzag wave height h is less than 0.2 times the diameter d, it becomes difficult to increase the rubber penetration. If more than 3.0 times, the strength of the filament tends to decrease when shaped into a zigzag.

FIG. 7

shows the cord strength reduction (%) and rubber penetration (%) as a function of the dXh/Pw value. As can be seen therefrom, by setting dXh/Pw in the range of 0.014 to 0.028 more preferably 0.020 to 0.025, both the rubber penetration and cord strength are improved.

Comparison Tests

Various experimental steel cords were made, and test tires having a belt layer made of the experimental cords were also made, and the following comparison tests were conducted. The results of the tests are shown in Table 1.

Cord Strength Reduction

In this test, a reduction (%) in the strength of an object cord (Ex.) from a conventional compact cord (Ref.) was obtained, wherein the object cord and the compact cord were the same with respect to the material, number of filaments and last-twist pitch, but the compact cord is composed of nonzigzag filaments only.

Bending Rigidity

The bending rigidity of each cord was measured with a TABER “V-5 Rigidity Tester” (USA).

Rubber Penetration

The cord was took out from the tire together with the surrounding topping rubber, and the topping rubber was carefully removed from the surface of the cord. Then, adjacent two filaments were took out therefrom along 10 cm long using a knife, and the length of a part surrounded by the two took-out filaments and the remaining filaments into which the rubber completely penetrated was measured to obtain the percentage of this length to the total length of 10 cm as the rubber penetration %.

Rust and Reserved Strength

The tire was disassembled after running about 200,000 km, and the steel cords were checked for rust. The results are indicated by an index based on the conventional cord being 100. The smaller the index, the smaller the rust.

Further, the steel cords were took out and the cord strength was measured. The results are indicated in percentage to the original strength.

TABLE 1

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

Ex.

Ex.

Ex.

A1

A2

A3

A4

A5

A6

A7

A8

A9

A10

A11

A1

A2

A3

Filament dia-

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

meter (mm)

Number of filaments

9

9

9

9

9

9

9

9

9

9

9

9

9

Zigzag filament

0

5

0

9

9

9

9

9

9

9

9

9

9

9

Straight filament

9

4

0

0

0

a

0

0

0

0

0

0

0

0

Spiral filament

0

0

9

0

0

0

0

0

0

0

0

0

0

0

Wave height h(mm)

13

0.28

0.45

0.4

0.50/0.40

0.35/0.28

0.35/0.28

0.35/0.30

0.35/0.30

0.06/0.05

1.40/1.20

0.35/0.28

0.35/0.28

0.35/0.28

Wave pitch Pw(mm)

—

5

5

5

6.30/5.00

6.30/5.00

6.30/5.00

1.50/1.30

13.0/12.0

6.30/5.00

6.30/5.40

6.30/5.00

6.30/5.00

6.30/5.00

dXh/Pw

—

0.021

0.034

0.03

0.030/0.030

0.021/0.021

0.021/0.021

0.089/0.088

0.010/0.010

0.004/0.004

0.084/0.084

0.021/0.021

0.021/0.021

0.021/0.021

Number of respective

—

5

9

9

3/6

3/6

316

316

3/6

3/6

3/6

3/6

3/6

3/6

filaments

Structure *1

(5.0*2 + 0

—

—

(6.3*1 +

(6.3*1 +

(6.3*1 +

(1.5*1 +

(13.0*1 +

(6.3*1 +

(6.3*1 +

(6.3*1 +

(6.3*1 +

(6.3*1 +

*1)*2 + (5.0

5.0*1)*3

5.0*2)*3

5.0*2)*3

1.3*2)*3

12.0*2)*3

5.0*2)*3

5.4*2)*3

5.0*2)*3

5.0*2)*3

5.0*2)*3

*1 + 0*2)*1

Last twist pitch (mm)

18

18

18

18

18

8

50

18

18

18

18

18

35

12

Bunch Twist

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

Carbon content (%)

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

Cord characteristics

Diameter (mm)

1.4

1.42

1.53

1.43

1.45

1.46

1.42

1.44

1.43

1/41

1.44

1.43

1.41

1.45

Strength (N/sq. mm)

3013

2630

2980 2561

2570

2953

2970

2420

2965

2970

2530

2953

2967

2938

Strength reduction (%)

0

12.7

2.3

15

14.7

2

1.4

19.7

1.6

1.4

16

2

1.5

2.4

Elongation

0.052

0.057

0.293

0.057

0.059

0.132

0.049

0.173

0.054

0.053

0.199

0.057

0.054

0.071

@ 50N (%)

Cord bending

260

257

249

254

252

256

256

256

256

256

256

256

258

242

rigidity (N cm)

Tire performance

Rubber

0

69

83

72

90

95

89

95

55

43

95

95

93

96

penetration (%)

Rust (index)

100

49

32

43

12

10

25

10

54

62

10

10

15

9

Reserved strength (%)

86

91

92

93

98

98

94

98

89

88

98

98

97

98

Ex.

Ex.

Ex.

Ex.

Ref.

Ref.

Ref.

Ex.

Ref.

Ex.

Ref.

Ex.

Ref.

Ex.

Ex.

Ex.

A4

A5

A6

A7

A12

A13

A14

A8

A15

A9

A16

A10

A17

A11

A12

A13

0.38

0.38

0.38

0.38

0.25

0.50

0.30

0.30

0.45

0.45

0.38

0.36

0.38

0.38

0.36

0.30

9

9

9

9

9

9

9

9

9

9

8

8

10

10

9

9

9

9

9

9

9

9

0

9

0

9

0

8

0

10

9

9

0

0

0

0

0

0

9

0

9

0

8

0

10

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.35/0.28

0.35/0.28

0.42/0.35

0.60/0.51

0.35/0.28

0.35/0.28

0.37/0.24

—

0.37/0.29

—

0.35/0.28

—

0.35/0.28

0.35/0.28

0.37/0.24

6.30/5.00

6.30/5.00

6.00/6.30

11.00/9.60

6.30/5.00

6.30/5.00

—

5.00/3.30

—

8.00/6.30

—

6.30/5.00

—

6.30/5.00

6.30/5.00

5.00/3.30

0.021/0.021

0.021/0.021

0.020/0.021

0.02/10.020

0.021/0.021

0.021/0.021

—

0.022/0.022

—

0.021/0.021

—

0.021/0.021

—

0.021/0.021

0.021/0.021

0.022/0.022

3/6

3/6

3/6

3/6

3/6

3/6

—

3/6

—

3/6

—

3/5

—

4/6

3/6

3/6

(6.3*1 +

(6.3*1 +

(8.0*1 +

(11.0*1 +

(6.3*1 +

(6.3*1 +

—

(5.0*1 +

—

(8.0*1 +

—

(6.3*1 +

—

(6.3*1 +

(6.3*1 +

(5.0*1 +

5.0*2)*3

5.0*2)*3

6.3*2)*2

9.6*2)*3

5.0*2)*2

5.0*2)*2

3.3*2)*3

6.3*2)*3

5.0*2)*2

5.0*2)*2)*3

5.0*2(*3

3.3*2)*3

6.3*1 +

(6.3*1 +

5.0*1)*1

5.0*1)*2

18

16

18

18

18

16

18

18

18

18

18

18

18

18

18

18

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

no

no

0.65

0.88

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.62

0.82

0.82

0.82

0.82

0.82

1.43

1.43

1.45

1.43

0.94

1.88

1.1

1.12

1.68

1.7

1.31

1.33

1.53

1.59

1.48

1.17

2658

3146

2968

2972

2993

2552

3032

2975

2972

2772

3013

2943

3013

2953

2926

2941

1.3

2.4

1.5

1.4

1.8

14.3

0

2.2

0

6.7

0

2.3

0

2

2.9

3

0.057

0.055

0.059

0.064

0.057

0.038

0.078

0.081

0.041

0.044

0.057

0.06

0.05

0.055

0.069

0.089

255

256

252

256

47

749

101

98

500

496

229

225

285

281

232

96

95

95

93

95

83

95

0

94

0

95

0

9s

0

96

92

91

10

11

14

11

34

10

100

13

100

11

100

9

lo0

10

16

17

99

99

98

99

91

98

86

97

86

97

86

97

86

97

96

96

1) For example, (5.0*2+0*1)*2+(5.0*1+0*2)*1 means two bunches of two zigzag filaments whose Pw=5.0 and one straight filament (Pw=0) and one bunch of one zigzag filament whose Pw=5.0 and two straight filaments (Pw=0). (6.3*1+5.0*1)*3 means three bunches of one zigzag filament whose Pw=6.3 and one zigzag filament whose Pw=5.0.

All the cords had a twist pitch Pf of 10 times the last twist pitch Pc. The direction of twisting filaments into a bunch was the same as the last twist. Ref.A

1

, A

14

, A

15

, A

16

A

17

were conventional cords composed of compactly twisted straight filaments. Ref.A

3

was composed of only spiral filaments. Ref.A

4

was composed of one kind of zigzag filaments twisted together without forming any bunch.

Cord Embodiment 2

This embodiment is again designed for a belt reinforcing a tread portion of a pneumatic radial tire, which can be suitably used as a substitute for a conventional steel cord of a 3+6 or 2+7 construction widely used in heavy duty radial tires for trucks, buses and the like.

The cord in this embodiment is composed of a number (n) of steel filaments

2

having a diameter d of 0.25 to 0.45 mm, wherein the number n is 5 or 6.

The steel filaments

2

include at least two but at most (n−3) of zigzag filaments

2

A and the remaining two or three nonzigzag filaments

2

B.

All the zigzag filaments

2

A are the substantially same zigzag pitch length Pw and same zigzag wave height h.

Further, in the illustrated examples, all the steel filaments are the same diameter d.

When a steel filament having a relatively large diameter such as this embodiment is shaped into a zigzag, the strength of the filament tends to decrease. Thus, in this embodiment, in order to provide a strong cord, some of the zigzag filaments are replaced by straight filaments.

The cord

1

is formed by twisting together

(A) a plurality of bunches

4

of filaments or

(B) a nonzigzag filaments

2

B and a plurality of bunches

4

of filaments as shown in FIG.

8

.

In either case (A) or (B), each bunches

4

is formed by twisting together one zigzag filament

2

A and one or two nonzigzag filaments

2

B at a twisting pitch Pf of 3 to 20 times the last-twisting pitch Pc. The last-twisting pitch Pc is in the range of from 10 to 25 mm. The direction of twisting the filaments into a bunch is the same as the last-twisting direction, but it may be reversed.

In this embodiment, also the diameter d, zigzag pitch lengths Pw and zigzag wave height h in each zigzag filament

2

A satisfy the following conditions: Pw is 5.0 to 30.0 times d, preferably 10.0 to 25.0 times d; h is 0.2 to 3.0 times d, preferably 0.5 to 2.0 times d; and dXh/Pw is 0.014 to 0.028, preferably 0.020 to 0.025.

FIG.

9

(A) shows a cord formed by last-twisting one nonzigzag filament

2

B and two bunches

4

C of one zigzag filament

2

A and one nonzigzag filament

2

B.

FIG.

9

(B) shows a cord formed by last twisting one bunch

4

C of one zigzag filament

2

A and one nonzigzag filament

2

B and one bunch

4

D of one zigzag filament

2

A and two nonzigzag filaments

2

B.

FIG.

10

(A) shows a cord formed by last twisting three bunches

4

C.

FIG.

10

(B) shows a cord formed by last twisting two bunches

4

D.

FIG.

10

(C) shows a cord formed by last twisting two bunches

4

C and two nonzigzag filaments

2

B.

FIG.

10

(D) shows a cord formed by last twisting one bunch

4

C, one bunch

4

D and one nonzigzag filament

2

B.

In each of the example cords, all the filaments are the same diameter, but may have two or more different diameters.

If the diameter d is less than 0.25 mm, it becomes difficult to obtain a rigidity required for a belt layer of the heavy duty tires, and the zigzag shape is apt to return to a straight shape during twisting, and the rubber penetration decreases. If the diameter d is more than 0.45 mm, the strength of the filament tends to decrease when shaped into a zigzag, and a suppleness required during making tires is lost.

If the twist pitch Pf is less than 3 times the last twist pitch Pc, the spaces formed between the filaments becomes narrow and the rubber penetration decreases. If the twist pitch Pf is more than 20 times the last twist pitch Pc, the zigzag phases are liable to coincide with each other and the rubber penetration decreases.

It is not necessary for improving the rubber penetration to shorten the twist pitch, and a relatively long pitch 10 to 25 mm can be employed. Thus, the production efficiency of the cord can be improved.

If the zigzag pitch length Pw is less than 5.0 times the diameter d, the strength of the filament tends to decrease when shaped into a zigzag. If more than 30 times, the rubber penetration decreases.

If the zigzag wave height h is less than 0.2 times the diameter d, it becomes difficult to increase the rubber penetration. If more than 3.0 times, the strength of the filament tends to decrease when shaped into a zigzag.

Comparison Tests

Various experimental steel cords were made, and test tires having a belt layer made of the experimental cords were also made, and the following comparison tests were conducted. The results of the tests are shown in Table 2.

Cord Strength Reduction Test

Same as above

Bending Rigidity Test

Same as above

Rubber Penetration Test

Same as above

Rust and Reserved Strength Test

Same as above

TABLE 2

Ref. B1

Ref. B2

Ref. B3

Ref. B4

Ref. B5

Ref. B6

Ex. B1

Ex. B2

Ex. B3

Ex. B4

Ex. B5

Ex. B6

Ex. B7

Ex. B8

Ex. B9

Ref. B7

Filament diameter (mm)

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

0.38

Number of filaments

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

Zigzag filament

0

0

0

1

2

2

2

2

2

2

2

2

2

2

2

2

Straight filament

5

3

5

4

3

3

3

3

3

3

3

3

3

3

3

3

Spiral filament

0

2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Wave height h (mm)

—

0.25

—

0.25

0.4

0.25/0.34

0.25

0.25

0.25

0.25

OA1

0.5

0.25

0.35

0.19

0.05

Wave pitch Pw (mm)

—

5

—

5

5

5.00/6.30

5

5

5

5

8

9.6

5

5

5

0.95

dXh/Pw

—

0.019

—

0.019

0.03

0.019/0.019

0.019

0.019

0.019

0.019

0.02

0.02

0.02

0.027

0.014

0.02

Last twist pitch (mm)

18

18

18

18

18

18

18

18

15

25

18

18

18

18

18

18

Bunch Twist

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

Carbon content (%)

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.65

0.82

0.82

0.82

O,82

0.88

0.82

0.82

0.82

Cord characteristics

Diameter (mm)

1.13

1.25

1.32

1.14

1.17

1.15

1.15

1.15

1.18

1.14

1.18

1.21

1.15

1.16

1.14

1.21

Strength (N/sq. mm)

3015

2973

2954

2984

2563

2683

2946

2651

2887

3004

3005

2966

3241

2849

2999

2966

Strength reduction (%)

0

1.4

2

1

15

i1

2.3

1.8

4.2

0.4

0.3

1.6

2.7

5.6

0.5

0.5

8.7

Elongation @ 50N (%)

0.065

0.132 0.283

0.073

0.123

0.091

0.094

0.095

0.101

0.09

0.121

0.131

0.094

0.103

0.087

0.131

Bending rigidity (N cm)

151

143

137

149

141

143

145

146

142

149

143

142

147

140

148

142

Tire_performance

Rubber penetration (%)

0

87

94

75

85

98

98

98

99

97

98

98

99

94

90

45

Rust (index)

100

21

13

37

25

6

5

6

2

10

6

6

2

12

16

43

Reserved strenght (%)

88

94

98

93

93

97

98

97

99

97

97

97

99

97

94

91

Ref. B8

Ref. B9

Ref. B20

Ex. B10

Ex. B11

Ref.B11

Ex. B12

Ex. B13

Ref. B12

Ref. B13

Ref. B14

Ex. B14

Ex. B15

Ref. B15

Ex. B16

Ref. B16

Ex. B17

Ex. B18

Ex. B19

0.38

0.38

0.25

0.25

0.25

0.45

0.45

0.45

0.17

0.5

0.32

0.32

0.32

0.25

0.25

0.45

0.45

0.38

0.32

5

5

5

5

5

5

5

5

5

5

6

6

6

6

6

6

6

6

6

2

2

0

2

2

0

2

2

2

2

0

2

3

0

2

0

2

2

2

3

3

5

3

3

5

3

3

3

3

6

4

3

6

4

6

4

4

4

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1.5

0.85

—

0.26

0.52

—

0.24

0.57

0.39

0.2

—

0.35

0.35

—

0.32

—

0.38

0.25

0.35

28

16

—

3.3

6.3

—

5

12.8

3.3

5

—

5

5

—

5

—

8

5.

5

0.02

0.02

—

0.02

0.021

—

0.022

0.02

0.02

0.02

—

0.022

0.022

—

0.021

—

0.021

0.019

0.022

18

18

18

18

18

25

25

25

18

25

18

18

18

18

18

25

25

18

18

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

no

no

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

1.15

1.14

0.76

0.78

08

1.36

1.38

1.42

0.53

1.51

0.97

1

1.08

0.78

0.81

1,41

1.43

1.2

1.1

2983

2999

3045

2899

2999

2969

2903

2932

2780

2630

3038

2971

2942

3043

2896

2972

2831

2878

2913

8.7

6.5

0

4.8

1 5

0

2.2

1.2

8.7

10.2

0

2.2

3.2

0

4.8

0

4.7

4.5

4.1

0.094

0.087

0.113

0.126

0.136

0.059

0.071

0.089

0.132

0.065

0.075

0.098

0.119

0.107

0.125

0.056

0.072

0.125

0.137

147

148

28

27

25

277

275

272

6

418

91

89

85

33

31

334

332

141

82

56

67

0

93

82

89

0

99

98

0

98

0

97

93

92

37

31

100

12

15

100

6

1l

25

17

100

3

6

100

7

100

12

14

15

93

96

87

97

96

89

99

97

92

91

88

98

98

87

98

89

96

95

94

Ex.B

1

to Ex.B

9

had a cord structure shown in FIG.

9

(A). Ex.B

14

to

17

had a cord construction shown in FIG.

10

(B). The direction of twisting filaments into a bunch was the same as the last twist. (S direction) The twist pitch Pf was 10 times the last twist pitch Pc.

Ref.B

1

, B

10

, B

11

, B

14

, B

15

and B

16

were conventional compact cords composed of straight filaments. Ref.B

3

was an open cord composed of loosely twisted nonzigzag filaments. Ref.B

6

had two kinds of zigzag filaments.

Cord Embodiment 3

This embodiment is designed as a carcass cord for reinforcing a carcass of a pneumatic radial tire, which can be suitably used as a substitute for a conventional steel cord of a 3+9 or 3+9+15 construction widely used in heavy duty radial tires for trucks, buses and the like.

The cord

1

in this embodiment is composed of 8 to 12 zigzag filaments

2

A. All the filaments are the same diameter d of 0.15 to 0.30 mm.

The zigzag filaments

2

A include at least two kinds of zigzag filaments

2

A

1

-

2

An having different zigzag pitch lengths Pw

1

-Pwn. The number (n) of the kinds is preferably two. The number of zigzag filaments in each kind is at least two, preferably at least three.

The cord

1

is formed by twisting all the zigzag filaments

2

A together at a twist pitch of 10 to 25 mm (last twist). During twisting the zigzag filaments

2

A, the relative positions thereof are changed repeatedly along the length so that a central filament (core filament) is not formed by a specific filament, and all the zigzag filaments

2

A are the substantially same length when measured along the zigzag of each filament. More specifically, the “changing of the relative positions” means that any one of the filaments may be positioned in the center of the cord in a place but in another place positioned on the outside. For example, two of the filaments are interlaced at predetermined intervals along the cord length, wherein the two interlaced filaments are changed or replaced in a predetermined regular or irregular order. As the zigzag filaments

2

A are interlaced, a problem of loosening of the filaments can be solved.

If there is a large difference in the filament lengths, some filaments tends to break out during rubberizing the cords.

In each zigzag filament

2

A, the filament diameter d, zigzag pitch lengths Pw and zigzag wave height h are set to satisfy the following conditions: Pw is 10.0 to 35.0 times, preferably 15.0 to 30.0 times d; and h is 0.5 to 4.0 times, preferably 1.0 to 3.0 times d.

Further, a zigzag filament

2

A

1

having a minimum zigzag pitch Pw

1

and the remaining zigzag filament

2

An having a larger zigzag pitch Pwn satisfy the following condition: hn/Pwn is 0.75 to 1.25 times h

1

/Pw

1

, wherein: h

1

is the zigzag wave height of the zigzag filament

2

A

1

; and hn is the zigzag wave height of the zigzag filament

2

An. However, if there are plural zigzag filaments having the same minimum zigzag pitch lengths Pw

1

but different heights, the minimum height is used as h

1

.

FIG.

11

(A) shows a cord composed of six zigzag filaments

2

A

1

having a small zigzag pitch Pw

1

and three zigzag filaments

2

An having a larger zigzag pitch Pwn, which are twisted together by changing the relative positions.

FIG.

11

(B) shows a cord composed of five zigzag filaments

2

A

1

having a small zigzag pitch Pw

1

and three zigzag filaments

2

An having a larger zigzag pitch Pwn, which are twisted together by changing the relative positions.

If the diameter d is less than 0.15 mm, the zigzag shape is apt to return to a straight shape during twisting, and the rubber penetration decreases. If the diameter d is more than 0.30 mm, it is difficult to provide a suppleness required in a tire carcass, and the fatigue resistance of the cord is lowered.

If the twist pitch is less than 10 mm, the initial elongation of the cord is too large for the carcass of a pneumatic tire, and thus it becomes difficult to keep a stable tire shape. If the twist pitch is more than 25 mm, the filaments are liable to loosen at cut ends, and thus tire durability is liable to decrease.

If the zigzag pitch length Pw is less than 10.0 times the diameter d, the strength of the filament tends to decrease when shaped into a zigzag. If more than 35.0 times, the rubber penetration decreases.

If the zigzag wave height h is less than 0.5 times the diameter d, it becomes difficult to increase the rubber penetration. If more than 4.0 times, the strength of the filament tends to decrease when shaped into a zigzag.

If hn/Pwn is less than 0.75 times h

1

/Pw

1

or more than 1.25 times h

1

/Pw

1

, it becomes difficult to equalize the filament lengths, and thus the cord load is liable to concentrate on a particular filament, and as a result the cord strength is liable to decrease.

Comparison Tests

Various experimental steel cords were made, and test tires having a carcass made of the experimental cords were also made, and the following comparison tests were conducted. The results of the tests are shown in Table 3.

Cord Strength Reduction Test

Same as above

Bending Rigidity Test

Same as above

Rubber Penetration Test

Same as above

Rust and Reserved Strength Test

Same as above

Filament Breaking-Out

During rubberizing a carcass ply for a heavy duty tire, the cords were investigated if the filaments broke out from the cord.

Cord-Cut-End Looseness

In this test, the degree of looseness at cut ends of the cord was evaluated.

TABLE 3

Ref. C1

Ref. C2

Ref. C3

Ref. C4

Ref. C5

Ref. C6

Ref. C7

Ref. C8

Ref. C9

Ex. C1

Ref. C10

Ref. C11

Ex. C2

Filament diameter (mm)

0.20

0.20

0.20

0.20

0.20

0.20

0.20

0.20

0.20

0.20

0.20

0.20

0.20

Number of filaments

9

9

9

9

9

9

9

9

9

9

9

9

9

Zigzag filament

0

s

0

9

9

9

9

9.

9

9

9

9

9

Straight filament

9

4

0

0

0

0

0

0

0

0

0

0

0

Spiral filament

0

0

9

0

0

0

0

0

0

0

0

0

0

Wave height h (mm)

—

0.45

0.65

0.45

0.45/0.45

0.45/0.30

0.45/0.30

0.08/0.05

1.40/1.00

0.45/0.30

0.45/0.30

0.45/0.30

0.45/0.30

Wave pitch Pw (mm)

—

5.00

5.00

5.00

5.00/3.00

1.80/1.20

12.0/8.0

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

h/Pw×100

—

9.0

13.0

9.0

9.0/15.0

25.0/25.0

3.8/3.8

1.6/1.5

28.0/30.3

9.0/9.1

90/91

9.0/9.1

9.0/9.1

Number of respective filaments

—

5

9

9

3/6

3/6

3/6

3/6

3/6

3/6

3/6

3/6

3/6

filament length (cm/100 cm cord)

105.0

106.7

109.3

106.7

106.7/109.7

117.4/117.4

105.3/105.3

105.11/105.0

120.3/122.8

106.7/106.7

105.6/105.6

107.8/107.8

106.7/106.7

Last twist pitch (mm)

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.a

28 0

8.0

23.0

Filament twist

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

Carbon content (%)

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

Cord characteristics

Diameter (mm)

0.71

0.73

0.85

0.78

0.77

0.75

0.75

0.75

0.75

0.75

0.75

0.77

0.75

Strength (N/sq. mm)

3052

2750

2785

3015

2880

2723

3018

3027

2675

3010

3026

2890

3020

Strength reduction (%)

0.0

9.9

8.7

1.2

5.6

10.8

1.1

0.8

12.3

1.4

0.9

5.3

1.0

Elongation @ 50N (%)

0.107

0.112

0.265

0.118

0.125

0.153

0.127

0.118

0.232

0.122

0 118

0.215

0.121

Bending rigidity (N.cm)

22

22

20

21

22

22

22

22

22

22

23

20

23

Tire performance

Rubber penetration (%)

0

76

73

75

95

91

64

53

90

95

92

96

92

Rust (index)

100

45

47

46

10

20

57

68

23

11

14

8

14

Reserved strength (%)

88

94

92

96

99

97

91

90

97

98

98

99

98

Breaking-out

none

some

none

none

few

none

none

none

none

none

none

none

none

Cut-end loose

none

none

none

none

none

none

none

none

none

none

some

none

few

Ref. C

Ref. C

Ref. C

Ref. C

Ex. C3

Ex. C4

Ex. C5

Ex. C6

Ex. C7

Ex. C8

Ref. C12

Ref. C13

14

Ex. 09

15

Ex. C10

16

Ex. C11

17

Ex. C12

Ref. C18

Ex. C13

Ex. C14

0.20

0.20

0.20

0.20

0.20

0.20

0.125

0.35

0.15

0.15

0.30

0.30

0.20

0.20

0.23

0.23

0.20

0.20

0.23

9

9

9

9

9

9

9

9

9

9

9

9

8

8

12

12

9

9

12

9

9

9

9

9

9

9

9

0

9

0

9

0

8

0

12

9

9

12

0

0

0

0

0

0

0

0

9

0

9

0

8

0

12

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.45/0.30

0.45/0.30

0.45/0.30

0.60/0.48

0.45/0.30

0.55/0.41/0.29

0.55/0.37

0.41/0.29

—

0.45/0.32

—

0.64/0.51

—

0.45/0.30

—

0.45/0.30

0.45/0.45

0.45/0.30

0.45/0.30

5.00/3.30

5.00/3.30

5.00/3.30

6.30/5.00

5.00/3.30

6.30/4.70/3.30

4.70/3.30

4.70/3.30

—

4.70/3.30

—

8.00/6.30

—

5.00/3.30

—

5.00/3.30

5.00/3.00

5.00/3.30

5.00/3.30

9.0/9.1

9.0/9.1

9.0/91

9.5/9.6

9.0/9.1

8.7/8.7/8.8

11.7/11.2

8.7/8.8

—

9.6/9.7

—

8.0/8.1

—

8.0/8.1

—

90/91

9.0/15.0

9.0/9.1

9.0/9.1

3/6

3/6

3/6

3/6

6/3

3/3/3

3/6

3/6

—

3/6

—

3/6

—

3/5

—

418

3/6

3/6

418

107.2/107

105.6/105

106.7/106

106.7/106

106.7/10

106.4/106.7/10

108.0/107

106.7/106

104.7

107.0/106

105.4

106.3/106

104.9

106.7/106

105.2

106.7/106

106.7/109

106.7/106

106.7/106

.2

.6

.7

.9

.7

6.6

.6

.6

.9

.2

.7

.7

.7

.7

.7

10.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

0.82

0.65

0.88

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.77

0.75

0.76

0.80

0.78

0.77

0.44

1.24

0.71

0.55

1.09

1.15

0.69

0.74

1.02

1.06

0.77

0.80

1.10

2975

2900

3250

2985

3015

3009

3014

2735

3108

3092

3035

2892

3052

3013

3048

3006

2880

2976

2960

2.5

1.2

1.7

2.2

1.2

1.4

1.0

8.5

0.0

0.5

0.0

5.2

0.0

1.3

0.0

1.4

5.6

2.5

2.9

0.157

0.132

0.137

0.183

0.120

0.123

0.182

0.098

0115

0.153

0.089

0.099

0110

0.145

0.097

0148

0183

0147

0198

20

22

22

19

22

21

3

185

7

6

101

97

18

19

48

47

22

19

45

96

95

95

96

94

97

77

89

0

93

0

96

0

95

0

90

95

90

91

8

10

10

9

13

9

42

17

100

12

100

7

100

10

100

15

10

15

14

99

98

99

95

97

98

91

84

82

97

87

97

86

98

90

98

99

95

98

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

some

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

few

few

Ref.C

1

, C

14

, C

15

, C

16

and C

17

were conventional compact cords composed of straight filaments twisted together without changing the relative positions. Ref.C

2

and C

4

were composed of one kind of zigzag filaments.

Cord Embodiment 4

This embodiment is designed as a cord of a bead reinforcing layer for reinforcing bead portions of a pneumatic radial tire, which can be suitably used as a substitute for a conventional steel cord of a 3+9 or 3+9+15 construction widely used in heavy duty radial tires for trucks, buses and the like.

The cord in this embodiment is composed of nine zigzag filaments

2

A having the same diameter d of 0.17 to 0.25 mm.

The zigzag filaments

2

A include at least two kinds of zigzag filaments

2

A

1

-

2

An having different zigzag pitch lengths Pw

1

-Pwn. The number (n) of the kinds is preferably two. The number of zigzag filaments in each kind is at least two, preferably at least three.

In each zigzag filament

2

A, the filament diameter d, zigzag pitch lengths Pw and zigzag wave height h are set to satisfy the following conditions: Pw is 10.0 to 35.0 times d; and h is 0.5 to 4.0 times d.

Further, a zigzag filament

2

A

1

having a minimum zigzag pitch Pw

1

and the remaining zigzag filament

2

An having a larger zigzag pitch Pwn satisfy the following condition: hn/Pwn is 0.75 to 1.25 times h

1

/Pw

1

, wherein h

1

is the zigzag wave height of the zigzag filament

2

A

1

, and hn is the zigzag wave height of the zigzag filament

2

An. However, if there are zigzag filaments having the same minimum zigzag pitch lengths Pw

1

but different heights, the minimum height is used as h

1

.

The cord is formed by twisting all the zigzag filaments

2

A together at a twist pitch of 10 to 20 mm (last twist). As explained in the formed Embodiment 3, during twisting the zigzag filaments

2

A, the relative positions thereof are changed so that a central filament or core is not formed by a specific filament, and all the zigzag filaments

2

A are the substantially same length when measured along the zigzag of each filament.

In this embodiment, further, a wrapping wire is wound around the resultant bunch

4

of the twisted filaments

2

A. Preferably, the wrapping wire

5

is a single filament made of a high carbon steel including 0.65 to 0.88 wt % of carbon. The diameter of the wrapping wire is 0.13 to 0.17 mm. The winding direction is reverse to the twisting direction, and the winding pitch is 3.0 to 7.0 mm.

If the winding pitch is less than 3.0 mm, the production efficiency is greatly decreased. If the winding pitch is more than 7 mm and/or the diameter of the wrapping wire is less than 0.13 mm, the cord-shape-retaining function decreases to decrease the dimensional accuracy of a rubber reinforcing layer. If the diameter of the wrapping wire is more than 0.17 mm, as the cord diameter and weight increase, it is not preferable. If the carbon content of the steel wire

5

is lower than 0.65 wt %, the strength tends to decrease. If the carbon content is higher than 0.88 wt %, the wire becomes too hard and the bending strength decreases.

FIG. 12

shows a cord composed of six zigzag filaments

2

A

1

having a small zigzag pitch Pw

1

and three zigzag filaments

2

An having a larger zigzag pitch Pwn.

If the filament diameter d is less than 0.17 mm, it becomes difficult to obtain a rigidity required for a bead reinforcing layer of the heavy duty tires, and as a result, tire durability decreases. Further, the zigzag shape is apt to return to a straight shape during twisting, and the rubber penetration decreases. If the diameter d is more than 0.25 mm, it is difficult to provide a bead reinforcing layer with a suppleness required during applying to the bead portion.

If the twist pitch is less than 10 mm, the initial elongation of the cord is too large for the bead reinforcing layer of a pneumatic tire, and thus the reinforcing effect becomes insufficient. If the twist pitch is more than 20 mm, the filaments are liable to loosen at cut ends, and thus tire durability is liable to decrease.

If the zigzag wave height h is less than 0.5 times the diameter d, it becomes difficult to increase the rubber penetration. If more than 4.0 times, the strength of the filament tends to decrease when shaped into a zigzag.

If the zigzag pitch length Pw is less than 10.0 times the diameter d, the strength of the filament tends to decrease when shaped into a zigzag. If more than 35.0 times, the rubber penetration decreases.

If hn/Pwn is less than 0.75 times h

1

/Pw

1

or more than 1.25 times h

1

/Pw

1

, it becomes difficult to equalize the filament lengths, and thus the cord load is liable to concentrate on a particular filament, and as a result the cord strength is liable to decrease.

Comparison Tests

Various experimental steel cords were made, and test tires having a bead reinforcing layer of the experimental cords were also made, and the following comparison tests were conducted. The results of the tests are shown in Table 4.

Cord Strength Reduction Test

Same as above

Bending Rigidity Test

Same as above

Rubber Penetration Test

Same as above

Rust and Reserved Strength Test

Same as above

Filament Breaking-Out

Same as above

Cord-Cut-End Looseness

Same as above

Shape Retention Test

The cord of 1,000 mm long was coiled into a loop of 200 mm diameter. The loop was collapsed gradually in fifteen seconds as follows: the loop was put on a horizontal plane; and one of two oppositely opposed points was fixed, and the other is pressed towards the fixed point so that the two points contact each other. The collapsed state was maintained for ten seconds. Then, the pressing force was decreased gradually in fifteen seconds to allow the loop to return to its original shape. And the distance L between the two points was measured to obtain the shape retention rate E=(L/200)×100. The shape retention rate E of each cord was divided by that of Ex.D

1

and converted into the reciprocal number and further multiplied by 100. The larger the value, the better the shape retention.

Cord Pull-Out Resistance Test

From the tire, a specimen of the bead cord reinforcing layer was cut out, and a force required to pull a cord 15 mm out of the specimen was measured.

TABLE 4

Ref. D1

Ref. D2

Ref. D3

Ref. D4

Ref. D5

Ref. D6

Ref. D7

Ref. D8

Ref. D9

Ref. D10

Ref. D11

Ref. D12

Ref. D13

Cord structure (Ref.) or

1×12×.22

3×.22 +9×.20

1×9×.20

1×9×.20

1×9×.20

1×9×.20

1×9×.20

1×9×.15

1×9×.30

1×9×.20

1×9×.20

1×9×.20

1×9×.20

Filament diameter(Ex.)

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

+1×.15

Number of zigzag filaments

0

0

0

5

9

9

9

9

9

9

9

9

9

Wave height h (mm)

—

—

0.45

0.45

0.45/0.45

0.45/0.30

0.45/0.30

0.45/0.30

0.45/0.30

0.45/0.30

0.08/0.05

1.40/1.00

Wave pitch Pw (mm)

—

—

—

5.00

5.00

5.00/3.00

5.00/3.30

5.00/3.30

5.00/3.30

1.80/1.20

12.0/8.0

5.00/3.30

5.0/3.30

h/Pw×100

—

—

—

9.0

9.0

9.0/15.0

9.0/9.1

9.0/9.1

9.0/9.1

25.0/25.0

3.8/3.8

1.6/1.5

28.0/30.3

number of respective filaments

—

—

—

9

9

3/6

3/6

3/6

3/6

3/6

3/6

3/6

3/6

Filament length (cm)

105.5

105.3

105.0

zigzag

106.7

106.7/109.7

106.7/106.7

106.7/106.7

106.7/106.7

117.4/117.4

105.3/105.3

105.1/105.0

120.3/122.8

per 100 cm long cord

106.7

straight

105.0

Carbon content (%)

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

0.82

Last twist pitch (mm)

15.0

15.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

17.0

Filament Twist

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

Wrapping wire dia. (mm)

0.15

0.15

0.15

0.15

0.15

0.15

0.15

0.15

0.15

0.15

0.15

0.15

0.15

Wrapping wire winding pitch (mm)

3.5

3.5

5.0

5.0

5.0

5.0

9.0

5.0

5.0

5.0

9.0

5.0

5.0

Cord characteristic

Diameter (mm)

1.18

1.09

1.10

1.12

1.12

1.17

1.13

0.85

1.75

1.17

1.13

1.13

1.17

Strength (N/sq. mm)

2916

2935

3035

2635

2927

2735

2925

2955

2873

2732

2925

2945

2673

Strength reduction (%)

—

—

0.0

13.2

3.6

9.9

3.6

2.3

5.3

10.0

3.6

3.0

11.9

Elongation @ 50N (%)

0.089

0.090

0.11g

0.120

0.148

0.137

0.123

0.143

0.104

0.217

0.115

0.117

0.247

Bending rigidity (N cm)

51

41

33

32

30

31

32

9

32

31

32

31

32

Shape retention (index)

98

99

98

96

99

95

85

102

94

96

98

99

94

Tire_performance

Rubber penetration (%)

0

6

0

68

78

91

91

85

91

92

63

58

90

Pullin-out force (N/15 mm)

5

78

128

136

152

173:cord cut

178:cord cut

143

172:cord cut

135

170:cord cut

132

171:cord cut

Rust (index)

100

87

95

50

42

21

20

28

20

17

54

64

12

Reserved strength (%)

89

92

90

92

93

96

97

92

97

92

91

90

97

Filament break-out

none

none

none

some

none

some

none

none

none

none

none

none

none

Cut-end loose

none

none

none

none

none

none

none

none

rione

none

none

none

none

Ref. D14

Ref. D15

Ref. D16

Ref. D17

Ex. D1

Ex. D2

Ex. D3

Ex. D4

Ex. D5

Ex. D6

Ex. D7

Ex. D8

Ex. D9

1×9×.20

1×9×.20

1×9×.20

1×9×.20

0.20

0.20

0.20

0.20

0.20

0.18

0.25

0.25

0.20

+1×.10

+1×.22

+1×.15

+1×.15

9

9

9

9

9

9

9

9

9

9

9

9

9

0.45/0.30

0.45/0.30

0.45/0.30

0.45/0.30

0.45/0.30

0.45/0.30

0.4510.30

0.45/0.30

0.45/0.30

0.45/0.30

0.45/0.30

0.69/0.55

0.45/0.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

5.00/3.30

8.00/6.30

5.00/3.30

9.0/9.1

9.0/9.1

9.0/9.1

9.0/9.1

9.0/9.1

9.0/9.1

9.0/9.1

9.0/9.1

9.0/9.1

9.0/9.1

9.0/91

86/87

90/91

3/6

3/6

3/6

3/6

106.7/106.7

106.7/106.7

106.71106.7

106.71106.7

106.7/106.7

106.5/106.5

107.0/106.9

106.6/106.4

106.7/106.7

106.7/106.7

106.7/106.7

105.6/105.6

107.8/107.8

3/6

3/6

3/6

3/6

3/6

3/6

3/6

3/6

3/6

0.82

0.82

0.82

0.82

0.82

0.65

0.88

0.82

0.82

0.82

0.82

0.82

0.82

17.0

17.0

28.0

8.0

17.0

17.0

17.0

10.0

20.0

15.0

17.0

17.0

17.0

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

no

0.15

0.15

0.15

0.15

0.15

0.15

0.1s

0.15

0.15

0.13

0.17

0.17

0.15

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

3.0

7.0

7.0

5.0

1.13

128

1.13

1.15

1.13

1.13

1.14

1.17

1.11

1.01

1.41

1.45

1.19

2925

2931

3007

2873

2970

2840

3012

2963

3003

3009

2967

2931

2928

3.6

3.4

1.2

5.3

2.1

1.3

2.8

2.4

1.1

0.9

2.2

3.4

3.5

0.129

0.121

0.117

0.208

0.123

0.132

0.130

0.142

0.128

0152

0.115

0.123

0.152

30

35

33

30

32

32

33

30

34

24

59

57

29

82

102

92

98

100

100

100

101

97

101

98

97

93

92

91

88

96

91

95

95

97

91

95

95

91

91

155:cord cut

165:cord cut

163:cord cut

178:cord cut

178:cord cut

170:cord cut

182:cord cut

178:cord cut

180:cord cut

143:cord cut

280:cord cut

270:cord cut

172:cord cut

23

20

28

8

12

9

9

7

13

6

6

13

15

93

89

95

96

97

98

99

98

97

95

98

97

96

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

occurred

none

none

none

none

none

slight

none

none

none

slight

Ref.D

1

and D

3

were conventional compact cords composed of nonzigzag filaments. Ref.D

2

had a layered structure having a specific core filament. Ref.D

4

was formed by twisting one kind of zigzag filaments and nonzigzag filaments together. Ref.D

5

was formed by twisting one kind of zigzag filaments together.

In the cord pull-out resistance test, the filaments of every Example cord were broken without some of them coming out, which shows that the adhesion to the rubber was excellent.

In the cord-cut-end looseness test, Ex.D

5

and D

9

caused slight looseness by which no problem would be causes with tire making processes.

Tire Embodiment

Next, a pneumatic tire according to the present invention is described according to FIG.

13

.

In

FIG.13

, a pneumatic tire T is a radial tire for heavy duty vehicles such as trucks, buses and the like.

The tire T comprises a tread portion

12

, a pair of axially spaced bead portions

13

with a bead core

15

therein, a pair of sidewall portions

13

extending between the tread edges and the bead portions

14

, a carcass C extending between the bead portions

14

, and a belt

17

disposed radially outside the carcass C in the tread portion

12

.

The carcass C comprises at least one ply of radially arranged cords extending between the bead portions through the tread portion and the sidewall portions, and turned up around the bead cores

15

to form two turned up portion and one main portion therebetween. For the carcass cords, the above-mentioned Embodiment 3 is used. Between the turned up portion and main portion in each bead portion

14

is provided with a rubber bead apex

16

.

The belt

17

comprises at least two plies of parallel cords, wherein the cords of one ply cross the cords of the other ply. For the belt cords, the above-mentioned Embodiment 1 or 2 is used.

Each bead portion

14

is provided with a bead reinforcing layer B. The layer B is composed of a single ply of parallel cords. For the bead reinforcing cords, the above-mentioned Embodiment 4 is used. In

FIG.13

, the layer B extends along the axially outside of the carcass ply turned up portion.

Number	Date	Country
10-214116	Jul 1998	JP
10-214117	Jul 1998	JP
10-215560	Jul 1998	JP
10-215561	Jul 1998	JP

Number	Name	Date
4176513	Young et al.	Dec 1979
4389839	Werff	Jun 1983
5287691	Okamoto et al.	Feb 1994
5295346	Bundo et al.	Mar 1994
5337549	Kobayashi et al.	Aug 1994
5502960	Kobayashi et al.	Apr 1996
5609013	Kaneda et al.	Mar 1997
5661966	Matsumaru	Sep 1997
5707467	Matsumaru et al.	Jan 1998
5772809	Yanagisawa	Jun 1998
5784874	Bruyneel et al.	Jul 1998
6098393	Han	Aug 2000

Metallic cord and pneumatic tire

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (4)

US Referenced Citations (12)