CA1058494A - Pneumatic rubber tire for off-road vehicles - Google Patents
Pneumatic rubber tire for off-road vehiclesInfo
- Publication number
- CA1058494A CA1058494A CA284,985A CA284985A CA1058494A CA 1058494 A CA1058494 A CA 1058494A CA 284985 A CA284985 A CA 284985A CA 1058494 A CA1058494 A CA 1058494A
- Authority
- CA
- Canada
- Prior art keywords
- tire
- breaker
- cords
- carcass
- reinforcing element
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
- B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
- B60C9/28—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers characterised by the belt or breaker dimensions or curvature relative to carcass
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
- B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
- B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
- B60C9/2003—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords
- B60C9/2006—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords consisting of steel cord plies only
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
- B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
- B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
- B60C9/2003—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords
- B60C9/2009—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords comprising plies of different materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C2200/00—Tyres specially adapted for particular applications
- B60C2200/14—Tyres specially adapted for particular applications for off-road use
Abstract
Abstract of the Disclosure A pneumatic rubber tire for off-road vehicles comprising a multi-layered carcass and a breaker circumfer-entially superimposed about the carcass is disclosed. The carcass is composed of rubberized plies each containing cords formed of organic fiber and inclined at a given angle with respect to the circumferential direction of tire. The cords of approximately one-half of the carcass plies extend in an opposite direction to the cords associated with the remaining plies to define a bias construction. The breaker is composed of at least two rubberized layers containing reinforcing elements with different properties embedded therein. The reinforcing element in one of the breaker layers is composed of a helically formed filament of material having a tensile strength of not less than 140 kg/mm2 or a bundle thereof together without twisting and has a modulus of elasticity of 0.6 to 70 times higher than that of the organic fiber cords of the carcass ply. The reinforcing element in another breaker layer is composed of a stranded cord of metallic filaments each having a tensile strength equal to or larger than that of steel and inclined in the circumferential direction of tire at an angle of not larger than 8° and not smaller than 15° with respect to the given angle of the cords in the carcass plies which are aligned with the stranded cord.
Description
105~494 This invention relates to pneumatic rubber tires, and more particularly to pneumatic rubber tires suitable for off-road vehicles (hereinafter referred to as a tire), which are adapted for use in construction vehicles such as dump truck, scraper, loader and so on, agricultural vehicles such as log skidder, log forward and so on, or industrial vehicles such as fork lift, platform truck, trailer and so on.
In general, the tires of this type run on off-road area where obstructions such as sharp rocks, metal pieces, glass pieces, stubs after felling and the like are scattered thereon under a heavy load per tire. Therefore, such tire is required to have a large resistance against damages due to cut failure and a good durability for use in a long ~ime.
In this type of tire, a resistance to damage due to tire cuts (hereinafter referred to as cut resistant property), a resistance to separation of rubber around a reinforcing layer in crown and other portions of the tire (hereinafter referred to as separation resistant property), and a wear resistance are most important requirements.
Heretofore, there have been made a few attempts for improving the cut resistant property of the tire, but these attempts are not always satisfactory. Besides, the separation resistant property in the crown and other portions may be considerably degraded. As a result, it is very difficult to provide tires having a practical durability by any of these attempts.
For instance, a first type of the conventionally proposed pneumatic tires is so-called wire-under-tread type tires (hereinafter referred to as W.T.U. tire), wherein a rubberized layer containing thin metallic filaments of about
In general, the tires of this type run on off-road area where obstructions such as sharp rocks, metal pieces, glass pieces, stubs after felling and the like are scattered thereon under a heavy load per tire. Therefore, such tire is required to have a large resistance against damages due to cut failure and a good durability for use in a long ~ime.
In this type of tire, a resistance to damage due to tire cuts (hereinafter referred to as cut resistant property), a resistance to separation of rubber around a reinforcing layer in crown and other portions of the tire (hereinafter referred to as separation resistant property), and a wear resistance are most important requirements.
Heretofore, there have been made a few attempts for improving the cut resistant property of the tire, but these attempts are not always satisfactory. Besides, the separation resistant property in the crown and other portions may be considerably degraded. As a result, it is very difficult to provide tires having a practical durability by any of these attempts.
For instance, a first type of the conventionally proposed pneumatic tires is so-called wire-under-tread type tires (hereinafter referred to as W.T.U. tire), wherein a rubberized layer containing thin metallic filaments of about
- 2 -: -- .
105849~l 10 mm length embedded therein is arranged between a tread rubber and a carcass body so as to prevent growth of the damage due to cuts started from the tire tread into the interior portion of ~he tire. The W.U.T. tire has been tried to be sold in market. In practice, however, this first type tire has such drawbacks that if an amount of the metallic filaments enough to improve the cut resistant property is embedded in rubber, the premature separation failure frequently occurs inside the W.U.T. layer or between the W.U.T. layer and the tread rubber or between the W.U.T. layer and the carcass body before the tire will attain its advantageous feature due to its large cut resistant property, while if the amount of the metallic filaments used is decreased to such an extent that the premature separation failure is not caused, the aimed cut resistant property cannot be achieved. Thus, the W.U.T. tires have not yet been put to practical use.
A second type of the conventional pneumtic tire is tires provided with a steel cord breaker. As is well-known, the steel cord for tire is prepared by twisting a plurality of strands, each strand being formed by twisting a plurality of elongated steel filaments each having a filament diameter of about 0.15 to 0.3 mm. In this second type tire, the breaker is formed by embodding such steel cords at equal intervals in rubber and arranged between the carcass body and the tread rubber so as to prevent growth of cut failure passing through the crown portion of the tire. However, the second type tire having such a steel cord breaker has an unavoidable drawback that the separation failure is apt to be caused at steel cord ends and the like.
It is, therefore, an object of the invention to .
. .
eliminate the above mentioned drawbacks of the conventional pneumatic tire. That is, the invention is to provide a pneumatic rubber tire suitable for off-road vehicles having improved cut resistant property, separation resistant property and wear resistance.
According to the invention, there is provided a pneumatic rubber tire for off-road vehicles, comprising a - multi-layered carcass composed of rubberized laminated plies, the cords of which are formed of organic fiber and ` 10 inclined at a given angle with respect to the circumferential direction of tire, the cords of approximately one-half of said carcass plies extending in an opposite direction to the cords associated with the remaining plies to define a bias construction, and a breaker circumferentially superimposed about said multi-layered carcass and composed of at least two rubberized layers containing reinforcing elements with different properties embedded therein; said reinforcing element in one of said breaker layers being composed of a helically formed filament of material having a tensile strength of not less than 140 kg/mm2 or a bundle thereof together without twisting and said heli.cally formed filament having a modulus o elasticity of 0.6 to 70 times higher than that of said organic fiber cords of said carcass ply;
sai.d reinforcing element in said another breaker layer being composed of a stranded cord of metallic filaments each having a tensile strength equal to or larger than that of steel and inclined in the circumferential direction of tire at an angle of not larger than 8 and not smaller than 15 with respect to said given angle of the cords in said carcass plies which are aligned with said stranded cord.
105849~
In a preferred embodiment of the invention 7 the reinforcing element composed of the helically formed filament or bundle thereof in one of the breaker layers is inclined at an angle of not larger than 5 and not smaller than 10 with respect to the angle of the stranded cord as the reinforcing element in another breaker layer.
The breaker layer containing the helically formed filament or bundle thereof as the reinforcing element may be terminated at suitable positions in the widthwise direction of the tread, but the end portion of the breaker layer containing the stranded cord as the reinforcing element is not located at a hump portion of the tire.
According to the invention, the carcass is a multi-layered bias structure composed of rubberized laminated plies ;....................................................................... . .
lS each containing cords formed of organic fiber and inclined at a given angle, preferably an angle of 23 to 45, with respect to the circumferential direction of tire, provided that the cords of approximately one-half of the carcass plies extend in an opposite direction to the cords associated with the remaining plies.
The formation of a tire body comprising such multi-layered bias carcass is substantially followed by the prior - art in the fundamental construction as a so-called bias type tire. However, the invention is particularly aimed at to adapt such tire for travel on off-road under peculiar and severe service conditions.
In such multi-layered bias carcass, if the cord angle of the carcass ply is smaller than 23, it is difficult to deform the carcass into a toroidal shape in the tire building step. On the contrary, if the cord angle of the . , .
- .
~584g4 carcass ply is larger than 45, an undesirable flexibility is given to the side portions of the tire so that the stability and safety of the tire are degraded.
According to the invention, as the breaker circum-ferentially superimposed about the carcass there are used at least two rubberized layers each containing a reinforcing element embedded therein. The reinforcing element used in one of the breaker layers is composed of a helically formed filament or a bundle thereof together without twisting.
A tensile strength required for such helically formed filament is defined by a balanced resistance to cuts penetrating into the tire which resistance is present in the tire immediately before the tread cut is produced by sharp rocks and the like when the tire rides on or is urged against these rocks.
The tensile strength of the filament is made at least 1~0 kg/mm2 preferably at least 170 kg/mm2 when the tire is used under such condition that a comparatively mild tread cut is produced, and at least 200 kg/mm2 when a maximum cut resistant property is required.
As the breaker for the tire according to the invention, the rubberized layer containing the reinforcing element composed of the above mentioned helically formed filament or bundle thereof is used together with a rubberized layer containing a reinforcing element composed of a stranded cord of metallic filaments each having a tensile strength equal to or larger than that of steel. The reason why such two rubberized layers are used as the breaker is as follows.
Heretofore, there was used a steel cord breaker composed of a rubberized layer containing steel cords embedded therein. As mentioned above, such steel cords are 1058~94 prepared by twisting a plurality of strands, each strand being formed by twisting a plurality of thin steel filaments each having a filament diameter of about 0.15 to 0.3 mm.
Since the steel cord has a very high modulus of elasticity and a high flexural rigidity, if the crown portion of the tire as a whole is largely deformed during ; the running under a load, the steel cord intends to hold linearity and original length of the crown portion. On the contrary, the rubber surrounding the steel cord is small in the modulus of elasticity and flexible. As a result, a large shearing strain is caused between the steel cord and the tread rubber contacting therewith. Especially, the shearing strain becomes maximum at ends of the steel cord and hence the damage due to separation occurs at an early ; 15 time in use. If the tire is repeatedly used for a long time in such a damaged state, the range of the damage due to separation becomes wide and the use of such tire becomes : ~ impossible . ' The term "modulus of elasticity" used herein means a value calculated from the following equation on the basis of a relationship between an elongation and a force obtained by drawing the organic fiber cord or the reinforcing element composed of steel cord or helically formed filament or bundle of such filaments under a tension;
ModuIus of elasticity = S [kg/mm2], wherein F
represents a force ~kg) at an elongation of 1%, S represents a sectional area (mm2) of a material to be drawn and Q ~ ;
represent an elongation of 1%. According to this equation, .
the modulus of elasticity of the nylon cord is about ;~
. . - ~ - - . :
- :. ~ ~ .
1.2 x 102 kg/mm2 and that of the steel cord is about 200 x 102 kg/mm2.
According to the invention, a helically formed thin filament of a metal such as steel and the like having a filament diameter of 0.1 to 1.0 mm, preferably about 0.13 to 0.5 mm, or a bundle obtained by gathering a plurality of such helically formed filaments together without twisting is used as a new reinforcing element having an improved cut resistant property for use in a rubberized breaker layer.
This reinforcing element composed of the helically formed filament has a modulus of elasticity within a range of 0.2 x 102 to 80 x 102 ~kg/mm2), preferably 0.7 x 102 to 60 x 102 (kg/mm2), which is very close to the value of the organic fiber cord and is fairly smaller than the value of the steel cord commonly used. That is, the modulus of elasticity of the reinforcing element composed of the helically formed filament is 0.6 to 70 times higher than that of the organic fiber cord used in the carcass ply, while the modulus of elasticity of the steel cord is about 200 times higher than that of the organic fiber cord.
According to the invention, the modulus of elasticity of the reinforcing element composed of the helically formed filament is so selected that a ratio in modulus of elasticity of such reinforcing element to the organic fiber cord is within a range of 0.6 to 70, preferably 0.6 to 50. If such a ratio is larger than 70, a difference between the modulus of elasticity of the reinforcing element and that of the tread rubber becomes considerably large, and as a result, the shearing strain between the reinforcing element and the adjoining tread rubber becomes large during the rotation of 1C~58494 the tire and the damage due to separation is liable to be caused When the modulus of elasticity of the reinforcing element comes near that of the organic fiber cord, the damage due to separation hardly occurs. However, if the ratio is smaller than 0.6, the rigidity of the reinforcing element becomes excessively small, so that the tire is apt to be deformed more and hence the wearing of the tread rubber is accelerated.
According to the invention, by using at least two rubberized layers each containing the different reinforcing element as the breaker, there is provided pneumatic rubber tires for off-road vehicles which prevent occurrence of the damage due to separation, which was liable to be caused in the conventional steel cord breaker, sufficiently utilize a high cut resistant property inherent to steel and have excellent wear resistance and high durability as compared with those of the breaker using only the helically formed filament. That is, the rubberized layer containing steel cords as the reinforcing element for the breaker according to the invention is not effective to a certain special cut but exhibits an excellent cut resistant property against general cuts. ~urther, this breaker layer increases the rigidity of the crown portion and hence exhibits an excellent wear resistance owing to its high modulus of elasticity.
However, such a high modulus of elasticity causes a large relative strain between the steel cord and the adjoining tread rubber and as a result, the separation resistant property is considerably degraded. Therefore, it is obliged to considerably limit the position, number and the like of this breaker layer in use. On the other hand, the rubberized g ~ 05~494 layer containing the helically formed filament or bundle thereof as the reinforcing element for the breaker according to the invention considerably decreases the relative strain between the reinforcing element and the adjoining tread rubber as compared with the case of using the steel cord hecause the modulus of elasticity of this reinforcing element is lower than that of the steel cord and as a result, such a layer exihibits not only a very high separation resistant - property but also a considerably improved cut resistant ,~ 10 property against any kind of cuts. Therefore, there is no limitation relating to the position, number and the like of the layer in use.
The inventors have confirmed from many experimental results that a synergetic effect is developed by optionally combining the steel cord reinforced layer with the helically formed filament reinforced layer as the breaker and as a result, very excellent properties are given to the tire for ; use in off-road vehicles.
That is, the invention makes it possible to combine the rubberized layers containing two different reinforcing elements in various forms in practice. For instance, a first rubberized layer containing the helically formed filament or bundle thereof as the reinforcing element is arranged outside a second rubberized layer containing the steel cord as the reinforcing element, and vice versa.
Furthermore, the second rubberized layer is sandwiched between the two first rubberized layers, and vice versa.
In any case the number of each of the first and second rubberized layers used may be one or more. Such modified constructions of the breaker are optionally selected , 10 1~358494 depending upon matters for tire design inclusive of use conditions of tire, production cost and the like. Moreover, an additional rubberized layer containing fiber cords made of a suitable material as a reinforcing element may be used in the breaker besides the first and second rubberized layers. Alternatively, such fiber cords may be incorporated into any one of the first and second rubberized layers as a part of the reinforcing element, if necessary.
According to the invention, the rubberized layer containing the steel cords as the reinforcing element for the breaker should be arranged in the circumferential direction of tire so that its steel cord angle is not larger than 8 and not smaller than 15 with respect to the given angle of the cords in the carcass plies which is aligned with the steel cord.
In the rubberized layer containing the helically formed filament or bundle thereof as the reinforcing element, the modulus of elasticity of the reinforcing element is very small as compared with that of the steel cord and comes near that of the tread rubber. Thus, it will be anticipated that the rigidity of this rubberized layer as a whole becomes small due to the decrease of the modulus of elasticity and hence the wear resistance of the tread rubber is degraded.
Therefore, in order to approach the rigidity of the helically formed filament reinforced layer to that of the steel cord reinforced layer to thereby improve the wear resistance of the tread rubber, the helically formed filament reinforced layer is arranged in the circumferential direction of tire so that the angle of the helically formed filament reinforce-ment is not larger than 5 and not smaller than 10 with .
1~358494 respect to the angle of the steel cord used as the reinforcing element for the breaker.
In order to prevent growth of the damage due to cuts started from the tread portion in the pneumatic bias tire for off-road vehicles, it has been the common practice to arrange the breaker composed of two or more steel cord reinforced layers between the carcass ply and the tread rubber wherein one of the steel cord layers has a width somewhat larger than the tread width and also the other steel cord layer near the tread portion has a width narrower than the tread width. In such a bias tire, it has been well-known that the radius of that portion of the tire which makes contact with ground ~effective rotational radius) becomes small during the rotation of tire under a load and at the same time the cread width of said portion becomes narrow, while when that portion of the tire which makes contact with ground is not subjected to the load in the course of the rotation, the radius becomes large and at the same time the tread width is turned to the original width.
Upon the observation of such phenomenon, particularly behavior in the internal portion of tread, it has been confirmed that the angle of the organic fiber cord used in the carcass ply ; as well as the angle of the steel cord used in the breaker at that portion of the tire which makes contact with ground under a load are variously changed. Such change of cord angles is indefinitely repeated until the tire becomes useless. On the other hand, the modulus of elasticity of the steel cord is considerably higher than that of the tread rubber. This considerably large difference between the modulus of elasticity of the steel cord and that of the ~ 058494 tread rubber results in occurrance of large shearing strain between the steel cord and the tread rubber contacting therewith when that steel cord which makes contact with ground under a load is forced to be subjected to change of cord angle. This pnenomenon has been examined in detail with respect to the damaged tires provided with the steel cord breaker to recognize the followings; that is, the damage due to separation is not observed at end portions of the breaker extending near the side portions over the tread width because the shearing strain between the steel cord and the adjoining tread rubber during the rotation of tire under ~-a load becomes gradually increased from a crown center to a hump portion, and is maximum at the hump portion and becomes rapidly decreased beyond the hump portion. On the contrary, at end portions of the steel cord terminated at the hump portion there is caused a considerably large shearing strain ~ -between the steel cord and the adjoining tread rubber due to the change of the steel cord angle as described above, and as a result, the damage due to separation is caused and gradually spreaded by repeating such phenomenon. Therefore, -; there have been frequently seen the case that the steel cord ; breaker tires become useless at a relatively early time in use though they possess a considrably high cut resistant property. On the basis of such recognition, according to the invention, th0 breaker composed of at least two rubberized layers is so arranged that the breaker layer containing steel cords as the reinforcing element is arranged so as not to be located at the hump portion where is liable to cause the damage due to separation, while the breaker layer contaiDing the helically formed filament or bundle thereof ' ,:
~058494 as the reinforcing element may be located at any position because such layer itself does not cause the damage due to separation as mentioned above.
The term "tread width" used herein means a distance on tread surface between the most thick portions o-f tread rubber gauge a~ both ends of the crown portion when the tire is cut along a plane including a rotational axis of tire.
The term "hump line" used herein means a normal line drawn from the tread surface having the most thick portion of the tread rubber toward the carcass ply, and hence the term "hump portion" used herein means a vicinity of a point intersecting the hump line with the outermost ply of the carcass plies or the tread rubber near the carcass plies.
The inventors have already confirmed from experi-mental results relating to the filament diameter of thehelically formed filament that when the helically formed filament of the same material is used as the reinforcing element against any type of cuts, the cut resistant property as a tire depends upon the total sectional area of the filaments included in the section of the tire due to cut failure but does not depend upon a size of sectional area or diameter of each filament. Therefore, it is preferable that the filament diameter of the helically formed filament becomes small as far as possible in order to make internal stress of the filament uniform. In this connection, according to the invention, there are used helically formed filaments having a filament diameter of 0.1 mm to 1.0 mm.
If the filament diameter is smaller than 0.1 mm, - the filament is frequently breaked in allowable extent in the step of forming the helically formed filament. As a result, it is clear that the use of such thin filament is not economical. On the contrary, if the filament diameter is larger than 1.0 mm, the internal stress produced in the step of forming the helically formed filament becomes excessive.
In addition, the torsional shearing stress produced when the force for expanding or contracting the filament is applied thereto in its lengthwise direction is concentrated toward the outer portion of the filament. As a result, in order to ;~
give the filament a strength necessary for withstanding the same exterior force, a total sectional area of the large diameter filament must be larger than that of the thin filament, so that a more greater amount of the material is required. Hence, it is clear that the use of such large ;~
diameter filament is not economical. As seen from the above reasons, the filament diameter should lie within the above mentioned range of 0.1 mm to 1.0 mm.
In the practice of the invention, the breaker of ,,'J the above mentioned construction is usually arranged between the tread rubber and the carcass ply. Further, the breaker may be arranged in the tread rubber or in the carcass plies near the tread in dependence with the use of tires. Moreover, the breaker may be divided at suitable intervals in its widthwise direction.
According to the invention, the breaker is not t 25 always symmetrical with respect to the equatorial plane oftire and may be unsymmetrical in dependence with the use of tires.
In addition, at least one rubberized layer of cords made of an organic fiber such as nylon and the like ~breaker protect layer) may be arranged as a cut protect by ' ' ~05849~
superimposing it outside the breaker (near the tread) with a width larger than that of the breaker or along both side edges of the breaker so as to improve a recap property of the tire.
According to the invention, the organic fiber cord used in the carcass ply and the breaker protect layer may be made of rayon, vinylon, polyester or the like in addition to nylon. As the helically formed filament and the stranded cord composed of metallic filaments constituting the rein-forcing element for the breaker, there is preferably used filament materials having a good adherence to rubber or subjected to a treatment for adhering to rubber, for example, a brass plated steel filament, an aromatic polyamide fiber having a high modulus of elasticity, a glass fiber and the like.
The invention will now be described in greater detail with reference to the accompanying drawings, wherein:
Fig. 1 is a cross-sectional view of one-half of a tire embodying the invention;
Fig. 2 is a graph illustrating experimental test results of separation resistant property of tires according to the invention compared with those of conventional tires;
and Figs. 3 to 5 are cross-sectional views of modified forms of a tire embodying the present invention, respectively.
Pneumatic tires for construction vehicle wheels embodying the invention will now be described with reference to Examples.
Example 1 In Fig. 1 is shown a radial cross-sectional view 105~494 of one-half of a tire embodying the invention, the section containing the rotational axis of tire. This tire is of 17.5-25 12PR in size (12PR indicates the size on the basis of cotton yarn). In the present example, a bead member 1 is composed of two sets of bead cores la, lb. A carcass 2 is composed of 8 plies in total, each ply being composed of nylon cord of 1,260 denier/two strands.
~ our plies 2a of the total 8 plies of the carcass 2 are wound around the bead core la from the inside toward the outside thereof and secured to the bead member 1. The other two plies 2b are wound around the bead core lb from the inside toward the outside thereof and secured to the bead member 1. The remaining two outside plies 2c are extended from the outside toward the inside of the bead cores la, lb along their lower surfaces and secured at their ends to a toe portion lc of the bead member 1.
The cords of each ply of the carcass 2 are inclined at an angle of about 36 with respect to the circumferential direction of tire as measured at a center of a tire crown portion. These cords of the carcass plies are alternately extended along two opposite directions symmetrically inclined at about 36 with respect to the circumferential direction of the tire crown portion.
In the crown portion 3 of the tire, about the outside of the carcass 2 is superimposed a breaker 4 of two-layered structure. In the breaker 4, a layer 4a is composed of a rubberized fabric containing a plurality of stranded steel cords having a strand construction of 1 x 4 + 6 x 4 + 1 ~the filament diameter is 0.175 mm and the cord diameter is 1.26 mm) embedded therein as a reinforcing element.
' - . .
~05~494 The number of steel cords per 5 cm is approximately 18 and these cords are inclined at an angle of about 36 with respect to the circumferential direction of tire. Another layer 4b for the breaker is composed of a rubberized fabric containing a plurality of bundles made of helically formed filaments ~the filament diameter is 0.25 mm and the number of filaments is 14) embedded therein as a reinforcing element.
The number of the bundles per 5 cm is approximately 18 and these bundles are inclined at an angle of about 36 with - -respect to the circumferential direction of tire.
In Fig. 2 are shown improved separation resistant property and durability of the tire built as above described manner. This figure shows an examples of experimental tests obtained by an indoor drum testing machine by plotting running time in hour on abscissa and plotting load speed per hour in ton-kilometer per hour on ordinate. In the present ' experimental test, the tire was pressurized to the standard internal pressure of 3.5 kg/cm2, the speed was made constant as 11 km/hr, and the load was increased from 60% to 170% in a stepwise manner as shown in Fig. 2. In this case, 100%
load corresponds to 6.135 kg (standard load for 17.5-25 tire as defined according to JIS).
In Fig. 2, a point A represents a test result of a conventional steel breaker tire, a point B a test result of a conventional nylon breaker tire, and a point C a test ` result of the tire according to the example 1 of the invention.
As shown by the point A, the conventional steel breaker tire exceeded its limit temperature at the third load step, thus resulting in the breaker end separation. On the contrary, as shown by the point C, the tire according to the example 1 . ~
~051~494 of the invention safely passed the third load step and arrived at the fifth load step where the tire exceeded its limit temperature and caused separation at the breaker due to overheating. In this case, there was not observed the occurrence of separation at ends of each bundle made of the helically formed filaments in the breaker layer 4b.
The above experimental tests have yielded the - surprising result ~hat the invention brings the same effectas the conventional nylon breaker tire which causes separation at the point B of the fifth load step although the steel cords liable to cause the separation in itself are used as the reinforcing element for the breaker.
Example 2 In Fig. 3 is shown a radial cross-sectional view of one-half of a tire having the same structure as described in Example 1, except that the breaker 4 is composed of two t layers 4a and two layers 4b and the arrangement of the breaker layers 4a, 4b is reversed to the case of Example 1.
The tire of the present example gave the substan-tially same result as the tire of Example 1 when the durability of the tire is examined by an indoor drum testing machine in the same manner as described in Example 1.
In the examples of Figs. 1 and 3, the modulus of elasticity of the nylon cord used in each ply of the carcass 2 was 1.2 x 102 kg/mm2, and that of the reinforcing element composed of the bundle of helically formed steel filaments in the breaker layer 4b was 2.5 x 102 kg/mm2. Further, the tensile strength of the helically formed steel filament was 27n kg/mm2.
In Fig. 4 is shown another embodiment of the tire , .. . .
~058494 according to the invention. In this embodiment, the arrange-ment of the breaker 4 composed of an outer layer 4a and an inner layer 4b is the same as in Fig. 3 except that both ends of the breaker 4 are not located in the vicinity of hump portions 5 of the tire, and further an additional reinforcing layer 6 is arranged between the breaker layers ~` 4a and 4b. This additional reinforcing layer 6 is composed of a rubberized ply containing 40 stranded nylon cords per 5 cm, the stranded nylon cord being composed of 1,260 denier/
two strands. These cords are inclined at the same angle as ` that of the breaker 4, but extended in a direction opposite ~ to the breaker layer 4b.
r In Fig- 5 is shown a further embodiment of the tire according to the invention. In this embodiment, the arrangement of the breaker 4 composed of an inner layer 4a and an outer layer 4b is the same as in Fig. 1 except that the ends of the breaker layer 4a are not located in the vicinity of the hump portions 5 of tire but the ends of the breaker layer 4b are terminated in the vicinity of the hump portion 5.
In Figs 4 and 5, a dot-dash-line represents a hump line of tire.
As stated hereinbefore, according to the invention, the cut resistant property, separation resistant property and wear resistance of pneumatic rubber tire for off-road vehicles can be improved remarkably.
. . :
- .
105849~l 10 mm length embedded therein is arranged between a tread rubber and a carcass body so as to prevent growth of the damage due to cuts started from the tire tread into the interior portion of ~he tire. The W.U.T. tire has been tried to be sold in market. In practice, however, this first type tire has such drawbacks that if an amount of the metallic filaments enough to improve the cut resistant property is embedded in rubber, the premature separation failure frequently occurs inside the W.U.T. layer or between the W.U.T. layer and the tread rubber or between the W.U.T. layer and the carcass body before the tire will attain its advantageous feature due to its large cut resistant property, while if the amount of the metallic filaments used is decreased to such an extent that the premature separation failure is not caused, the aimed cut resistant property cannot be achieved. Thus, the W.U.T. tires have not yet been put to practical use.
A second type of the conventional pneumtic tire is tires provided with a steel cord breaker. As is well-known, the steel cord for tire is prepared by twisting a plurality of strands, each strand being formed by twisting a plurality of elongated steel filaments each having a filament diameter of about 0.15 to 0.3 mm. In this second type tire, the breaker is formed by embodding such steel cords at equal intervals in rubber and arranged between the carcass body and the tread rubber so as to prevent growth of cut failure passing through the crown portion of the tire. However, the second type tire having such a steel cord breaker has an unavoidable drawback that the separation failure is apt to be caused at steel cord ends and the like.
It is, therefore, an object of the invention to .
. .
eliminate the above mentioned drawbacks of the conventional pneumatic tire. That is, the invention is to provide a pneumatic rubber tire suitable for off-road vehicles having improved cut resistant property, separation resistant property and wear resistance.
According to the invention, there is provided a pneumatic rubber tire for off-road vehicles, comprising a - multi-layered carcass composed of rubberized laminated plies, the cords of which are formed of organic fiber and ` 10 inclined at a given angle with respect to the circumferential direction of tire, the cords of approximately one-half of said carcass plies extending in an opposite direction to the cords associated with the remaining plies to define a bias construction, and a breaker circumferentially superimposed about said multi-layered carcass and composed of at least two rubberized layers containing reinforcing elements with different properties embedded therein; said reinforcing element in one of said breaker layers being composed of a helically formed filament of material having a tensile strength of not less than 140 kg/mm2 or a bundle thereof together without twisting and said heli.cally formed filament having a modulus o elasticity of 0.6 to 70 times higher than that of said organic fiber cords of said carcass ply;
sai.d reinforcing element in said another breaker layer being composed of a stranded cord of metallic filaments each having a tensile strength equal to or larger than that of steel and inclined in the circumferential direction of tire at an angle of not larger than 8 and not smaller than 15 with respect to said given angle of the cords in said carcass plies which are aligned with said stranded cord.
105849~
In a preferred embodiment of the invention 7 the reinforcing element composed of the helically formed filament or bundle thereof in one of the breaker layers is inclined at an angle of not larger than 5 and not smaller than 10 with respect to the angle of the stranded cord as the reinforcing element in another breaker layer.
The breaker layer containing the helically formed filament or bundle thereof as the reinforcing element may be terminated at suitable positions in the widthwise direction of the tread, but the end portion of the breaker layer containing the stranded cord as the reinforcing element is not located at a hump portion of the tire.
According to the invention, the carcass is a multi-layered bias structure composed of rubberized laminated plies ;....................................................................... . .
lS each containing cords formed of organic fiber and inclined at a given angle, preferably an angle of 23 to 45, with respect to the circumferential direction of tire, provided that the cords of approximately one-half of the carcass plies extend in an opposite direction to the cords associated with the remaining plies.
The formation of a tire body comprising such multi-layered bias carcass is substantially followed by the prior - art in the fundamental construction as a so-called bias type tire. However, the invention is particularly aimed at to adapt such tire for travel on off-road under peculiar and severe service conditions.
In such multi-layered bias carcass, if the cord angle of the carcass ply is smaller than 23, it is difficult to deform the carcass into a toroidal shape in the tire building step. On the contrary, if the cord angle of the . , .
- .
~584g4 carcass ply is larger than 45, an undesirable flexibility is given to the side portions of the tire so that the stability and safety of the tire are degraded.
According to the invention, as the breaker circum-ferentially superimposed about the carcass there are used at least two rubberized layers each containing a reinforcing element embedded therein. The reinforcing element used in one of the breaker layers is composed of a helically formed filament or a bundle thereof together without twisting.
A tensile strength required for such helically formed filament is defined by a balanced resistance to cuts penetrating into the tire which resistance is present in the tire immediately before the tread cut is produced by sharp rocks and the like when the tire rides on or is urged against these rocks.
The tensile strength of the filament is made at least 1~0 kg/mm2 preferably at least 170 kg/mm2 when the tire is used under such condition that a comparatively mild tread cut is produced, and at least 200 kg/mm2 when a maximum cut resistant property is required.
As the breaker for the tire according to the invention, the rubberized layer containing the reinforcing element composed of the above mentioned helically formed filament or bundle thereof is used together with a rubberized layer containing a reinforcing element composed of a stranded cord of metallic filaments each having a tensile strength equal to or larger than that of steel. The reason why such two rubberized layers are used as the breaker is as follows.
Heretofore, there was used a steel cord breaker composed of a rubberized layer containing steel cords embedded therein. As mentioned above, such steel cords are 1058~94 prepared by twisting a plurality of strands, each strand being formed by twisting a plurality of thin steel filaments each having a filament diameter of about 0.15 to 0.3 mm.
Since the steel cord has a very high modulus of elasticity and a high flexural rigidity, if the crown portion of the tire as a whole is largely deformed during ; the running under a load, the steel cord intends to hold linearity and original length of the crown portion. On the contrary, the rubber surrounding the steel cord is small in the modulus of elasticity and flexible. As a result, a large shearing strain is caused between the steel cord and the tread rubber contacting therewith. Especially, the shearing strain becomes maximum at ends of the steel cord and hence the damage due to separation occurs at an early ; 15 time in use. If the tire is repeatedly used for a long time in such a damaged state, the range of the damage due to separation becomes wide and the use of such tire becomes : ~ impossible . ' The term "modulus of elasticity" used herein means a value calculated from the following equation on the basis of a relationship between an elongation and a force obtained by drawing the organic fiber cord or the reinforcing element composed of steel cord or helically formed filament or bundle of such filaments under a tension;
ModuIus of elasticity = S [kg/mm2], wherein F
represents a force ~kg) at an elongation of 1%, S represents a sectional area (mm2) of a material to be drawn and Q ~ ;
represent an elongation of 1%. According to this equation, .
the modulus of elasticity of the nylon cord is about ;~
. . - ~ - - . :
- :. ~ ~ .
1.2 x 102 kg/mm2 and that of the steel cord is about 200 x 102 kg/mm2.
According to the invention, a helically formed thin filament of a metal such as steel and the like having a filament diameter of 0.1 to 1.0 mm, preferably about 0.13 to 0.5 mm, or a bundle obtained by gathering a plurality of such helically formed filaments together without twisting is used as a new reinforcing element having an improved cut resistant property for use in a rubberized breaker layer.
This reinforcing element composed of the helically formed filament has a modulus of elasticity within a range of 0.2 x 102 to 80 x 102 ~kg/mm2), preferably 0.7 x 102 to 60 x 102 (kg/mm2), which is very close to the value of the organic fiber cord and is fairly smaller than the value of the steel cord commonly used. That is, the modulus of elasticity of the reinforcing element composed of the helically formed filament is 0.6 to 70 times higher than that of the organic fiber cord used in the carcass ply, while the modulus of elasticity of the steel cord is about 200 times higher than that of the organic fiber cord.
According to the invention, the modulus of elasticity of the reinforcing element composed of the helically formed filament is so selected that a ratio in modulus of elasticity of such reinforcing element to the organic fiber cord is within a range of 0.6 to 70, preferably 0.6 to 50. If such a ratio is larger than 70, a difference between the modulus of elasticity of the reinforcing element and that of the tread rubber becomes considerably large, and as a result, the shearing strain between the reinforcing element and the adjoining tread rubber becomes large during the rotation of 1C~58494 the tire and the damage due to separation is liable to be caused When the modulus of elasticity of the reinforcing element comes near that of the organic fiber cord, the damage due to separation hardly occurs. However, if the ratio is smaller than 0.6, the rigidity of the reinforcing element becomes excessively small, so that the tire is apt to be deformed more and hence the wearing of the tread rubber is accelerated.
According to the invention, by using at least two rubberized layers each containing the different reinforcing element as the breaker, there is provided pneumatic rubber tires for off-road vehicles which prevent occurrence of the damage due to separation, which was liable to be caused in the conventional steel cord breaker, sufficiently utilize a high cut resistant property inherent to steel and have excellent wear resistance and high durability as compared with those of the breaker using only the helically formed filament. That is, the rubberized layer containing steel cords as the reinforcing element for the breaker according to the invention is not effective to a certain special cut but exhibits an excellent cut resistant property against general cuts. ~urther, this breaker layer increases the rigidity of the crown portion and hence exhibits an excellent wear resistance owing to its high modulus of elasticity.
However, such a high modulus of elasticity causes a large relative strain between the steel cord and the adjoining tread rubber and as a result, the separation resistant property is considerably degraded. Therefore, it is obliged to considerably limit the position, number and the like of this breaker layer in use. On the other hand, the rubberized g ~ 05~494 layer containing the helically formed filament or bundle thereof as the reinforcing element for the breaker according to the invention considerably decreases the relative strain between the reinforcing element and the adjoining tread rubber as compared with the case of using the steel cord hecause the modulus of elasticity of this reinforcing element is lower than that of the steel cord and as a result, such a layer exihibits not only a very high separation resistant - property but also a considerably improved cut resistant ,~ 10 property against any kind of cuts. Therefore, there is no limitation relating to the position, number and the like of the layer in use.
The inventors have confirmed from many experimental results that a synergetic effect is developed by optionally combining the steel cord reinforced layer with the helically formed filament reinforced layer as the breaker and as a result, very excellent properties are given to the tire for ; use in off-road vehicles.
That is, the invention makes it possible to combine the rubberized layers containing two different reinforcing elements in various forms in practice. For instance, a first rubberized layer containing the helically formed filament or bundle thereof as the reinforcing element is arranged outside a second rubberized layer containing the steel cord as the reinforcing element, and vice versa.
Furthermore, the second rubberized layer is sandwiched between the two first rubberized layers, and vice versa.
In any case the number of each of the first and second rubberized layers used may be one or more. Such modified constructions of the breaker are optionally selected , 10 1~358494 depending upon matters for tire design inclusive of use conditions of tire, production cost and the like. Moreover, an additional rubberized layer containing fiber cords made of a suitable material as a reinforcing element may be used in the breaker besides the first and second rubberized layers. Alternatively, such fiber cords may be incorporated into any one of the first and second rubberized layers as a part of the reinforcing element, if necessary.
According to the invention, the rubberized layer containing the steel cords as the reinforcing element for the breaker should be arranged in the circumferential direction of tire so that its steel cord angle is not larger than 8 and not smaller than 15 with respect to the given angle of the cords in the carcass plies which is aligned with the steel cord.
In the rubberized layer containing the helically formed filament or bundle thereof as the reinforcing element, the modulus of elasticity of the reinforcing element is very small as compared with that of the steel cord and comes near that of the tread rubber. Thus, it will be anticipated that the rigidity of this rubberized layer as a whole becomes small due to the decrease of the modulus of elasticity and hence the wear resistance of the tread rubber is degraded.
Therefore, in order to approach the rigidity of the helically formed filament reinforced layer to that of the steel cord reinforced layer to thereby improve the wear resistance of the tread rubber, the helically formed filament reinforced layer is arranged in the circumferential direction of tire so that the angle of the helically formed filament reinforce-ment is not larger than 5 and not smaller than 10 with .
1~358494 respect to the angle of the steel cord used as the reinforcing element for the breaker.
In order to prevent growth of the damage due to cuts started from the tread portion in the pneumatic bias tire for off-road vehicles, it has been the common practice to arrange the breaker composed of two or more steel cord reinforced layers between the carcass ply and the tread rubber wherein one of the steel cord layers has a width somewhat larger than the tread width and also the other steel cord layer near the tread portion has a width narrower than the tread width. In such a bias tire, it has been well-known that the radius of that portion of the tire which makes contact with ground ~effective rotational radius) becomes small during the rotation of tire under a load and at the same time the cread width of said portion becomes narrow, while when that portion of the tire which makes contact with ground is not subjected to the load in the course of the rotation, the radius becomes large and at the same time the tread width is turned to the original width.
Upon the observation of such phenomenon, particularly behavior in the internal portion of tread, it has been confirmed that the angle of the organic fiber cord used in the carcass ply ; as well as the angle of the steel cord used in the breaker at that portion of the tire which makes contact with ground under a load are variously changed. Such change of cord angles is indefinitely repeated until the tire becomes useless. On the other hand, the modulus of elasticity of the steel cord is considerably higher than that of the tread rubber. This considerably large difference between the modulus of elasticity of the steel cord and that of the ~ 058494 tread rubber results in occurrance of large shearing strain between the steel cord and the tread rubber contacting therewith when that steel cord which makes contact with ground under a load is forced to be subjected to change of cord angle. This pnenomenon has been examined in detail with respect to the damaged tires provided with the steel cord breaker to recognize the followings; that is, the damage due to separation is not observed at end portions of the breaker extending near the side portions over the tread width because the shearing strain between the steel cord and the adjoining tread rubber during the rotation of tire under ~-a load becomes gradually increased from a crown center to a hump portion, and is maximum at the hump portion and becomes rapidly decreased beyond the hump portion. On the contrary, at end portions of the steel cord terminated at the hump portion there is caused a considerably large shearing strain ~ -between the steel cord and the adjoining tread rubber due to the change of the steel cord angle as described above, and as a result, the damage due to separation is caused and gradually spreaded by repeating such phenomenon. Therefore, -; there have been frequently seen the case that the steel cord ; breaker tires become useless at a relatively early time in use though they possess a considrably high cut resistant property. On the basis of such recognition, according to the invention, th0 breaker composed of at least two rubberized layers is so arranged that the breaker layer containing steel cords as the reinforcing element is arranged so as not to be located at the hump portion where is liable to cause the damage due to separation, while the breaker layer contaiDing the helically formed filament or bundle thereof ' ,:
~058494 as the reinforcing element may be located at any position because such layer itself does not cause the damage due to separation as mentioned above.
The term "tread width" used herein means a distance on tread surface between the most thick portions o-f tread rubber gauge a~ both ends of the crown portion when the tire is cut along a plane including a rotational axis of tire.
The term "hump line" used herein means a normal line drawn from the tread surface having the most thick portion of the tread rubber toward the carcass ply, and hence the term "hump portion" used herein means a vicinity of a point intersecting the hump line with the outermost ply of the carcass plies or the tread rubber near the carcass plies.
The inventors have already confirmed from experi-mental results relating to the filament diameter of thehelically formed filament that when the helically formed filament of the same material is used as the reinforcing element against any type of cuts, the cut resistant property as a tire depends upon the total sectional area of the filaments included in the section of the tire due to cut failure but does not depend upon a size of sectional area or diameter of each filament. Therefore, it is preferable that the filament diameter of the helically formed filament becomes small as far as possible in order to make internal stress of the filament uniform. In this connection, according to the invention, there are used helically formed filaments having a filament diameter of 0.1 mm to 1.0 mm.
If the filament diameter is smaller than 0.1 mm, - the filament is frequently breaked in allowable extent in the step of forming the helically formed filament. As a result, it is clear that the use of such thin filament is not economical. On the contrary, if the filament diameter is larger than 1.0 mm, the internal stress produced in the step of forming the helically formed filament becomes excessive.
In addition, the torsional shearing stress produced when the force for expanding or contracting the filament is applied thereto in its lengthwise direction is concentrated toward the outer portion of the filament. As a result, in order to ;~
give the filament a strength necessary for withstanding the same exterior force, a total sectional area of the large diameter filament must be larger than that of the thin filament, so that a more greater amount of the material is required. Hence, it is clear that the use of such large ;~
diameter filament is not economical. As seen from the above reasons, the filament diameter should lie within the above mentioned range of 0.1 mm to 1.0 mm.
In the practice of the invention, the breaker of ,,'J the above mentioned construction is usually arranged between the tread rubber and the carcass ply. Further, the breaker may be arranged in the tread rubber or in the carcass plies near the tread in dependence with the use of tires. Moreover, the breaker may be divided at suitable intervals in its widthwise direction.
According to the invention, the breaker is not t 25 always symmetrical with respect to the equatorial plane oftire and may be unsymmetrical in dependence with the use of tires.
In addition, at least one rubberized layer of cords made of an organic fiber such as nylon and the like ~breaker protect layer) may be arranged as a cut protect by ' ' ~05849~
superimposing it outside the breaker (near the tread) with a width larger than that of the breaker or along both side edges of the breaker so as to improve a recap property of the tire.
According to the invention, the organic fiber cord used in the carcass ply and the breaker protect layer may be made of rayon, vinylon, polyester or the like in addition to nylon. As the helically formed filament and the stranded cord composed of metallic filaments constituting the rein-forcing element for the breaker, there is preferably used filament materials having a good adherence to rubber or subjected to a treatment for adhering to rubber, for example, a brass plated steel filament, an aromatic polyamide fiber having a high modulus of elasticity, a glass fiber and the like.
The invention will now be described in greater detail with reference to the accompanying drawings, wherein:
Fig. 1 is a cross-sectional view of one-half of a tire embodying the invention;
Fig. 2 is a graph illustrating experimental test results of separation resistant property of tires according to the invention compared with those of conventional tires;
and Figs. 3 to 5 are cross-sectional views of modified forms of a tire embodying the present invention, respectively.
Pneumatic tires for construction vehicle wheels embodying the invention will now be described with reference to Examples.
Example 1 In Fig. 1 is shown a radial cross-sectional view 105~494 of one-half of a tire embodying the invention, the section containing the rotational axis of tire. This tire is of 17.5-25 12PR in size (12PR indicates the size on the basis of cotton yarn). In the present example, a bead member 1 is composed of two sets of bead cores la, lb. A carcass 2 is composed of 8 plies in total, each ply being composed of nylon cord of 1,260 denier/two strands.
~ our plies 2a of the total 8 plies of the carcass 2 are wound around the bead core la from the inside toward the outside thereof and secured to the bead member 1. The other two plies 2b are wound around the bead core lb from the inside toward the outside thereof and secured to the bead member 1. The remaining two outside plies 2c are extended from the outside toward the inside of the bead cores la, lb along their lower surfaces and secured at their ends to a toe portion lc of the bead member 1.
The cords of each ply of the carcass 2 are inclined at an angle of about 36 with respect to the circumferential direction of tire as measured at a center of a tire crown portion. These cords of the carcass plies are alternately extended along two opposite directions symmetrically inclined at about 36 with respect to the circumferential direction of the tire crown portion.
In the crown portion 3 of the tire, about the outside of the carcass 2 is superimposed a breaker 4 of two-layered structure. In the breaker 4, a layer 4a is composed of a rubberized fabric containing a plurality of stranded steel cords having a strand construction of 1 x 4 + 6 x 4 + 1 ~the filament diameter is 0.175 mm and the cord diameter is 1.26 mm) embedded therein as a reinforcing element.
' - . .
~05~494 The number of steel cords per 5 cm is approximately 18 and these cords are inclined at an angle of about 36 with respect to the circumferential direction of tire. Another layer 4b for the breaker is composed of a rubberized fabric containing a plurality of bundles made of helically formed filaments ~the filament diameter is 0.25 mm and the number of filaments is 14) embedded therein as a reinforcing element.
The number of the bundles per 5 cm is approximately 18 and these bundles are inclined at an angle of about 36 with - -respect to the circumferential direction of tire.
In Fig. 2 are shown improved separation resistant property and durability of the tire built as above described manner. This figure shows an examples of experimental tests obtained by an indoor drum testing machine by plotting running time in hour on abscissa and plotting load speed per hour in ton-kilometer per hour on ordinate. In the present ' experimental test, the tire was pressurized to the standard internal pressure of 3.5 kg/cm2, the speed was made constant as 11 km/hr, and the load was increased from 60% to 170% in a stepwise manner as shown in Fig. 2. In this case, 100%
load corresponds to 6.135 kg (standard load for 17.5-25 tire as defined according to JIS).
In Fig. 2, a point A represents a test result of a conventional steel breaker tire, a point B a test result of a conventional nylon breaker tire, and a point C a test ` result of the tire according to the example 1 of the invention.
As shown by the point A, the conventional steel breaker tire exceeded its limit temperature at the third load step, thus resulting in the breaker end separation. On the contrary, as shown by the point C, the tire according to the example 1 . ~
~051~494 of the invention safely passed the third load step and arrived at the fifth load step where the tire exceeded its limit temperature and caused separation at the breaker due to overheating. In this case, there was not observed the occurrence of separation at ends of each bundle made of the helically formed filaments in the breaker layer 4b.
The above experimental tests have yielded the - surprising result ~hat the invention brings the same effectas the conventional nylon breaker tire which causes separation at the point B of the fifth load step although the steel cords liable to cause the separation in itself are used as the reinforcing element for the breaker.
Example 2 In Fig. 3 is shown a radial cross-sectional view of one-half of a tire having the same structure as described in Example 1, except that the breaker 4 is composed of two t layers 4a and two layers 4b and the arrangement of the breaker layers 4a, 4b is reversed to the case of Example 1.
The tire of the present example gave the substan-tially same result as the tire of Example 1 when the durability of the tire is examined by an indoor drum testing machine in the same manner as described in Example 1.
In the examples of Figs. 1 and 3, the modulus of elasticity of the nylon cord used in each ply of the carcass 2 was 1.2 x 102 kg/mm2, and that of the reinforcing element composed of the bundle of helically formed steel filaments in the breaker layer 4b was 2.5 x 102 kg/mm2. Further, the tensile strength of the helically formed steel filament was 27n kg/mm2.
In Fig. 4 is shown another embodiment of the tire , .. . .
~058494 according to the invention. In this embodiment, the arrange-ment of the breaker 4 composed of an outer layer 4a and an inner layer 4b is the same as in Fig. 3 except that both ends of the breaker 4 are not located in the vicinity of hump portions 5 of the tire, and further an additional reinforcing layer 6 is arranged between the breaker layers ~` 4a and 4b. This additional reinforcing layer 6 is composed of a rubberized ply containing 40 stranded nylon cords per 5 cm, the stranded nylon cord being composed of 1,260 denier/
two strands. These cords are inclined at the same angle as ` that of the breaker 4, but extended in a direction opposite ~ to the breaker layer 4b.
r In Fig- 5 is shown a further embodiment of the tire according to the invention. In this embodiment, the arrangement of the breaker 4 composed of an inner layer 4a and an outer layer 4b is the same as in Fig. 1 except that the ends of the breaker layer 4a are not located in the vicinity of the hump portions 5 of tire but the ends of the breaker layer 4b are terminated in the vicinity of the hump portion 5.
In Figs 4 and 5, a dot-dash-line represents a hump line of tire.
As stated hereinbefore, according to the invention, the cut resistant property, separation resistant property and wear resistance of pneumatic rubber tire for off-road vehicles can be improved remarkably.
. . :
- .
Claims (3)
1. A pneumatic rubber tire for off-road vehicles, comprising a multi-layered carcass composed of rubberized laminated plies, the cords of which are formed of organic fiber and inclined at a given angle with respect to the circumferential direction of tire, the cords of approximately one-half of said carcass plies extending in an opposite direction to the cords associated with the remaining plies to define a bias construction, and a breaker circumferentially superimposed about said multi-layered carcass and composed of at least two rubberized layers containing reinforcing elements with different properties embedded therein; said reinforcing element in one of said breaker layers being composed of a helically formed filament of material having a tensile strength of not less than 140 kg/mm2 or a bundle thereof together without twisting and said helically formed filament having a modulus of elasticity of 0.6 to 70 times higher than that of said organic fiber cords of said carcass ply; said reinforcing element in said another breaker layer being composed of a stranded cord of metallic filaments each having a tensile strength equal to or larger than that of steel and inclined in the circumferential direction of tire at an angle of not larger than 8° and not smaller than 15°
with respect to said given angle of the cords in said carcass plies which are aligned with said stranded cord.
with respect to said given angle of the cords in said carcass plies which are aligned with said stranded cord.
2. A pneumatic rubber tire for off-road vehicles as claimed in claim 1, wherein said reinforcing element composed of said helically formed filament or bundle thereof is inclined at an angle of not larger than 5° and not smaller than 10° with respect to said angle of said stranded cord as the reinforcing element in said another breaker layer in the circumferential direction of tire.
3. A pneumatic rubber tire for off-road vehicles as claimed in claim 1, wherein end portion of said breaker layer containing said stranded cord as the reinforcing element is not located at a hump portion of the tire.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9815176A JPS5330502A (en) | 1976-08-19 | 1976-08-19 | Pneumatic rubber tire with different cut resisting material for running rough ground |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1058494A true CA1058494A (en) | 1979-07-17 |
Family
ID=14212163
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA284,985A Expired CA1058494A (en) | 1976-08-19 | 1977-08-18 | Pneumatic rubber tire for off-road vehicles |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5330502A (en) |
| AU (1) | AU499247B1 (en) |
| CA (1) | CA1058494A (en) |
| ES (1) | ES461729A1 (en) |
| GB (1) | GB1573231A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2419181A1 (en) * | 1978-03-10 | 1979-10-05 | Michelin & Cie | IMPROVEMENTS TO RADIAL CARCASE TIRES |
| FR2419182A1 (en) * | 1978-03-10 | 1979-10-05 | Michelin & Cie | RADIAL CARCASS TIRE, ESPECIALLY FOR CIVIL ENGINEERING VEHICLES |
| FR2419184A1 (en) * | 1978-03-10 | 1979-10-05 | Michelin & Cie | LARGE WIDTH RADIAL CASING PNEUMATIC |
| FR2419180A1 (en) * | 1978-03-10 | 1979-10-05 | Michelin & Cie | RADIAL CASING PNEUMATIC |
| FR2426580A1 (en) * | 1978-05-24 | 1979-12-21 | Michelin & Cie | RADIAL CASING PNEUMATIC |
| JPS5843803A (en) * | 1981-09-11 | 1983-03-14 | Bridgestone Corp | Pneumatic radial tire for heavy load |
| JPS5889694U (en) * | 1981-12-14 | 1983-06-17 | 三菱農機株式会社 | Lubricating device for agricultural machinery |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2082137A5 (en) * | 1970-03-04 | 1971-12-10 | Englebert |
-
1976
- 1976-08-19 JP JP9815176A patent/JPS5330502A/en active Granted
-
1977
- 1977-08-08 AU AU27717/77A patent/AU499247B1/en not_active Expired
- 1977-08-11 GB GB3371777A patent/GB1573231A/en not_active Expired
- 1977-08-18 ES ES461729A patent/ES461729A1/en not_active Expired
- 1977-08-18 CA CA284,985A patent/CA1058494A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5618406B2 (en) | 1981-04-28 |
| ES461729A1 (en) | 1978-05-01 |
| AU499247B1 (en) | 1979-04-12 |
| JPS5330502A (en) | 1978-03-22 |
| GB1573231A (en) | 1980-08-20 |
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