CA1315652C - Pneumatic tire - Google Patents
Pneumatic tireInfo
- Publication number
- CA1315652C CA1315652C CA000544941A CA544941A CA1315652C CA 1315652 C CA1315652 C CA 1315652C CA 000544941 A CA000544941 A CA 000544941A CA 544941 A CA544941 A CA 544941A CA 1315652 C CA1315652 C CA 1315652C
- Authority
- CA
- Canada
- Prior art keywords
- belt
- reinforcing layer
- tire
- laterally
- hooped
- 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 - Lifetime
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Abstract
Abstract of the Disclosure A pneumatic tire comprising a carcass having two opposite beads and extending from one bead to the other bead, a tread portion disposed radially outwardly of the carcass and extending in a circumferential direction of the tire, a belt of steel cord material disposed between the carcass and the tread portion, the belt having two laterally opposite end portions, and a reinforcing layer disposed between the tread portion and the belt. The reinforcing layer is formed by spirally hooping a continuous ribbon material on the belt. The continuous ribbon material is composed of a plurality of nylon cords covered with rubber. The reinforcing layer is varied in cord density laterally of the tire by varying a hooping pitch of the ribbon material laterally of the tire and hooping the ribbon material in two or more layers.
Description
~ 3 ~ 2 The present invention relates to a pneumatic tire and in particular to a radial pneumatic tire which is used at high speeds and which includes a belt reinforcing cap or layer between the tread portion and the belt portion.
A conventional radial pneumatic tire which is used at high speeds includes a belt reinforcing layer consistin~ of two layers each having a predeter-mined width and disposed radially outwardly of a lateral end portion of a belt. Each reinforcing layer is composed of cords. The cords extend substantially in the circumferential direction of the tire and are covered with rubber. The lower reinforcing layer is hooped around the belt, and then the longitudinal end portions are overlapped with each other. Likewise, the upper reinforcing layer is hooped on the lower reinforcing layer previously hooped on the belt, and the lon~itudinal end portions are overlapped with each other and vulcanized. Thus, the reinforcing layers of 2~ the conventional tire form overlapped portions, respectively. Another conventional radial pneumatic tire which is used at high speeds includes a belt reinforcing cap of a predetermined width disposed radially outwardly of a belt and covering a full width of the belt. The reinforcing cap is composed of cords.
The cords extend substantially in the circumferential direction of the tire and are covered with rubber. The reinforcing cap is hooped around the belt, and then the '~ ~
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, ~31~2 longitudinal end portions are overlapped with each other and vulcanized. Thus, the rein~orcing cap of the conventional tire also forms an overlapped portion.
In both cases of the reinforcing layer and the reinforcing cap, at least one overlapped portion is formed on the circumference of the tire, and therefore the longitudinal end portions of the overlapped portions slip relative to each other and loosen, thereby weakening the tightening effect of the reinforcing layer and cap. Also, the reinforcing layer and the reinforcing cap are increased in thickness due to the overlapped portions, thereby reducing a uniformity level of the tire and degrading a comfortable riding performance. Furthermore, in the lateral end portion of the belt, the width of the upper reinforcing layer can be reduced to a width smaller than a full width of the lower reinforcing layer in order that the belt is tightened by the reinforcing layer, but if different layers of narrow and wide widths are used, two kinds of reinforcing layers different in width must be prepared. Furthermore, if the reinforcing cap is further used, the cap of the width must also be prepared in addition to the two kinds of layers. As a result, there is the disadvan-tage that various kinds of belt reinforcing layers and caps are required.
It is accordingly an important object of the present invention to provide an improved pneumatic tire .
' : .
- 13~ 2 which prevents and overcomes the a~orementioned disadvantages attendant with the prior art.
In accordance with an important aspect of the present invention, there is provided a pneumatic tire comprising a carcass having two opposite beads and extending from one bead to the other bead, a tread portion disposed radially outwardly of the carcass and extending in a circumferential direction of the tire, a belt of steel cord material disposed between the carcass and the tread portion, the belt having two laterally opposite end portions, and a reinforcing layer disposed between the tread portion and the belt.
; The reinforcing layer is formed by spirally hooping a continuous ribbon material on the belt. The continuous ribbon material is composed of a plurality of nylon cords covered with rubber. The reinforcing layer is varied in cord density laterally of the tire by varying a hooping pitch of the ribbon material laterally of the tire and hooping the ribbon material in two or more layers.
The drawbacks of a prior-art pneumatic tire and the features and advantages of a pneumatic tire according to the present invention will be more clearly understood from the following description taken in ; conjunction with the accompanying drawings in which:
Fig. 1 is a part-sectional view of a first embodiment of the pneumatic tire in accordance with the ~- present invention;
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--- 131~2 - 4a -Fig. 2 is an enlarged sectional view of the ribbon-like material and the belt shown in Fig. l;
: Fig. 3 is an enlarged sectional view showing cord ' :
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. . - - . - .
13~6~2 materials of the ribbon-like material shown in Fig. 2;
Fig. 4 is a part-sectional view showing a belt reinforcing layer of a ribbon-like material hooped on a belt in accordance with a second embodiment of the present invention;
Fig. 5 is a part-sectional view showing a belt reinforcing layer of a ribbon-like material hooped on a belt in accordance with a third embodiment of the present invention;
Fig. 6 is a part-sectional view showing a belt reinforcing layer of a ribbon-like material hooped on a belt according to a fourth embodiment of the present invention;
Fig. 7 is a view showing the manner in which a belt reinforcing layer of a ribbon-like material is hooped on a belt in accordance with a fifth embodiment of the present invention;
- Fig. 8 is a view showing the manner in which two belt reinforcing layer of a ribbon-like material are hooped on a belt in accordance with a sixth embodiment of the present invention;
Fig. 9 is a part-sectional view showing a pneumatic tire of the prior art, two belt reinforcing layers being hooped on a laterally end portion of the belt;
Fig. 10 is a side sectional view, taken from an arrow B of Fig. 9, showing that longitudinal end portions of the reinforclng layers are overlapped with each other;
Fig. 11 is a part-sectional view showing a pneumatic tire of the prior art wherein the belt reinforcing cap is . . : . , :
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:J 3 ~ 2 hooped over a full width of the belt;
Fig. 12 is a side sectional view, taken from an arrow s of Fig. 11, showing that longitudinal end portions of the reinforcing cap are overlapped with each other;
Fig. 13 is a view showing the manner in which a belt reinforcing layer of a ribbon-like material is hooped on a belt in accordance with a seventh embodiment of the present invention; and 10Fig. 14 is a view showing the manner in which a belt reinforcing layer of a ribbon-like material is hooped on a belt in accordance with an eighth embodiment of the present invention.
Referring to Figs. 9 and 10, there is shown a conventional radial pneumatic tire which is used at high speeds and which includes a belt reinforcing layer 1 consisting of two layers la and lb each having a ` predetermined width Wl and disposed radially outwardly of a lateral end portion 2a of a belt 2. Each reinforcing layer is composed of cords. The cords ~; extend substantially in the circumferential direction of the tire and are covered with rubber. The lower ; reinforcing layer lb is hooped around the belt 2, and then the longitudinal end portions lbl (Fig. 10) are overlapped with each other. Likewise, the upper reinforcing layer la is hooped on the lower reinforcing layer lb previously hooped on the belt 2, and the longitudinal end portions lal (Fig. 10) are overlapped ; ~ , E3 ~.. ,, . :
~L31~52 with each other and vulcanized. Thus, the reinforcing layers la and lb of the conventional tire form overlapped portions 4, respectively. In Figs. ll and 12, there is shown another conventional radial pneumatic tire which is used at high speeds and which includes a belt reinforcing cap 7 of a predetermined width W7 disposed radially outwardly of a belt 9 and covering a full width Wg of the belt 9. The re-inforcing cap 7 is composed of cords. The cords extendlO substantially in the circumferential direction of the tire and are covered with rubber. The reinforcing cap 7 is hooped around the belt 9, and then the longitudinal end portions 7a (Fig. 12) are overlapped with each other and vulcaniæed. Thus, the reinforcing cap 7 of the conventional tire also forms an overlapped portion ll.
In hoth cases of the reinforcing layer l and the reinforcing cap 7, at least one overlapped portion 4 or ll is formed on the circumference of the tire, and therefore the longitudinal end portions lal, lbl and 7a of the overlapped portions 4 and ll slip relative to each other and loosen, thereby weakening the tightening effect of the reinforcing layer and cap. Also, since the reinforcing layer l and the reinforcing cap 7 are increased in thickness due to the overlapped portions 4 and ll, thereby reducing a uniformity level of the tire and degradin~ a comfortable riding performance.
Furthermore, in the lateral end portion 2a of the belt .
.
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2 shown in Fig. 9, the width of the upper reinforcing layer la can be reduced to a width Wlc smaller than a full width wl of the lower reinforcing layer lb in order that the belt 2 i~ tightene~ by the reinforcing layer 1, but if different layers of narrow and wide widths are used, two kinds of reinforcing layers different in width must be prepared. Furthermore, if the reinforcing cap 7 as shown in Fig. 11 is further used, the cap of the width W7 must also be prepared in addition to the two kinds of layers. As a result, there is the disadvantage that various kinds of belt reinforcing layers and caps are required.
Referring to Fig. 1 of the drawings, a radial pneumatic tire according to a first embodiment of the present invention is generally designated by reference numeral 21. The radial pneumatic tire 21 comprises a carcass 23 made up of layers of cord materials and extending from one bead to the other bead, a tread portion 25 disposed radially ou~wardly of ;~ 20 the carcass 23 and extending in a circumferential direction of the tire, a belt 27 disposed between the carcass 23 and the tread portion 25, and a belt reinforcing layer 30 disposed between the tread portion 25 and the belt 27. The reinforcing la~ver 30 is formed by hooping a continuous ribbon-like material 36, which is composed of one to twelve cord materials 32 covered with rubber 34, on the belt 27 spirally in the circumferential direction o~ the tire. In this embodi-, .~
, , "
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;
~ 3 ~ 2 g ment, the cord materials 32 of the ribbon-like material 36 comprises two nylon cords as shown in Fig . 3. When the ribbon-like material 36 of two cord materials 32 is used, there is the advantage that the number of hoops of the continuous ribbon-like material 36 can be reduced by half as compared with a ribbon-like material of one cord, thereby enhancing an efficiency of production. The continuous ribbon-like material 36 forming the belt reinforcing layer 30 is capable of being hooped with a variable hooping density in a lateral direction of the tire indicated by an arrow A
in Fig. 2. More particularly, the reinforcing layer 30 of a laterally outer end portion 27a of the belt 27 comprises an outer reinforcing layer 30a and an inner reinforcing layer 30b, and in the outer reinforcing layer 30a, the ribbon-like material 36 is hooped in two lay~rs, and in the inner reinforcing layer 30b, the ribbon-like material 36 is hooped in one layer. Thus, the hooping density of the hooped ribbon-like material 36 is reduced at the inner reinforcing layer 30b than at the outer reinorcing layer 30a.
The operation of the aforementioned first embodiment according to the present invention will be hereinafter described.
As mentioned above, the continuous ribbon-like material 36 forming the belt reinforcing layer 30 is capable of being spirally hooped with a variable hooping density in the lateral direction of the tire, ~` , ; `
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and therefore, the hooping density can be increased gradually toward the outer end portion 27a of the belt 27 which should be more tightened, and decreased gradually toward a mid-circumferential portion E of the belt 27 which should be less tightened. Furthermore, the reinforcing layer 30 is ~ormed by hooping spirally many times the continuous ribbon-like material 36 composed of one to twelve cord materials 32 covered with rubber 36, and therefore there is no overlapped longitudinal end portions which are formed in the aforementioned prior art. As a consequence, the belt reinforcing layer 30 according to the present invention is effectively prevented from slipping and loosening, thereby considerably enhancing the tightening effect of the belt and the tire durability performance at high speeds. In addition, since the continuous ribbon-like material 36 is hooped spirally, the leading and trailing end portions thereof are effectively prevented from being overlapped ~ith each other and therefore a ~0 uniformity level of the tire cannot be reduced and a comfortable riding performance of the tire cannot be degraded. Furthermore, since a narrow reinforcing layer and a wide reinforcing layer can be made by varying the hooping density of the continuous ribbon-like material 36, only one kind of a material is required to make the ribbon-like material 36, thereby considerably reducing the cost of production.
;
Referring to Fig. 4, there is shown a belt reinforcing layer 40 of a ribbon-like material 46 ~pirally hooped on a belt 27 in accordance with a second embodiment of the present invention. The reinforcing layer 40 comprises a laterally inner reinforcing layer 42 which is spixally hooped on a laterally outer end portion 27a of the belt 27 with a predetermined spacing in the lateral direction of the tire, and a laterally outer reinforcing layer 44 which is hooped on the laterally outer end portion 27a of the belt 27 without the spacing. As a result, the hooping density of the continuous ribbon-like material 46 forming the reinforcing layer 40 is reduced from the outer reinforcing layer 44 toward the inner reinforcing layer 42. Other members are substantially identical in construction and operation to those of the first - embodiment and therefore the description will be hereinafter omitted.
Referring to Fig. 5, there is shown a third embodiment of the present invention. In this embodi-ment, a reinforcing layer 50 is used as a cap. That is, a continuous ribbon-like material 52 forming the reinforcing layer 50 is hooped over the full width o~
the belt 27 so that the spacing between the adjacent looped portions is gradually reduced from a mid-circumferential portion E of the tire toward opposite outer end portions 27a of the belt 27. More parti-cularly, at the opposite outer end portions 27a, the .~ ~
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ribbon-like material 52 is spirally hooped without the spacing between the adjacent looped portions thereof.
When the reinforcing layer is one layer at the outer end portion of the belt as shown in Figs. 4 and 5, it is desirable that the width of the ribbon-like material 52 be between 4 mm and 6 mm. If the width is less than 4 mm, the cost of production is increased, and if the width is more than 6 mm, the ribbon-like material of the reinforcing layer protrudes from the lateral end of the belt when it i5 hooped, so that cracks occur at the protruded portion. Other members are substantially identical in construction and operation to those of the second embodiment and therefore the description will be hersinafter omitted.
Referring to Fig. 6, there is shown a fourth embodiment of the present invention. A reinforcing layer 60 is provided over the full width of the belt 27. A continuous ribbon-like material 62 forming the reinforcing layer 60 is spirally hooped so that the spacing between the adjacent looped portions thereof is gradually reduced from a mid-circumferential portion E
of the tire toward the opposite outer end portion 27a of the belt 27. At the outer end portion 27a, the ribbon-like material 62 is hooped in two layers without the spacing between the adjacent looped portions thereof. Thus, in this embodiment, the hoopin~ density is increased at the opposite outer end portion 27a than the third embodiment shown in Fig. 5. When the ,~
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- llb -reinforcing layer is hooped in two layers at the outer ~nd portion of the belt as shown in Fig. 6, it is desirable that the width of the ribbon-like material be between 4 mm and 11 mm. If the width is less than 4 mm, the cost of production is increased, and if the width is more than 11 mm, the ribbon-like material of the reinforcing layer protrudes from the lateral end of the belt when it is hooped, so that cracks occur at the protruded portion. Other members are substantially identical in construction and operation to those of the third embodiment and therefore the description will be hereinafter omitted.
Referring to Fig. 7, there is shown the manner in which a belt reinforcing layer 70 of a ribbon-like material 72 is spirally hooped on the belt 27 in accordance with a fifth embodiment of the present invention. The ribbon-like material 72 is first hooped leftward of Fig. 7 from a position B to a lateral left end C. At the lateral end C, the hooping direction of ~O the ribbon-like material 72 is turned to the position B
so that the ribbon material can be hooped in two layers. The reinforcing layer 70 becomes one layer from the positon B and the hooping density is gradually decreased toward the mid-circumferential positon E.
After passing the mid-circumferential position E, the ribbon-like material 72 is hooped so that the hooping density is gradually increased toward a lateral right end D. At the lateral right end D, the ribbon-like ;
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-- llc --material 72 is again turned back to the mid-circumferential position E to be in two layers, and the hooping is completed at a position F. Thus, the ribbon-like material 72 is hooped with a locus of a generally inverted letter ~ indicated by the arrow in Fig. 7. As a result, the reinforcing la~er 70 as shown in Fig. 7 can be easily formed continuously by a single ribbon-like material 72.
Referring to Fig. 8, there is shown a sixth embodiment according to the present invention. The sixth embodiment is identical to the fifth embodiment of Fig. 7 except that two ribbon-like materials 82 forming a reinforcing layer 80 are used. The two ribbon-like materials 82 are hooped in opposite direc-tions from the mid-circumferential position E to opposite ends D and D, and turned back at the ends D
and D toward the mid-circumferential position E, and the hooping of the two ribbon-like materials 82 are completed at positions F and F. In this embodiment, two ribbon-like materials are used, but the reinforcing layer 80 aan also be ~.~
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',: '. ' . ,; ' " ' ' :
', ' ' ' , ' ' easily formed.
Fig. 13 shows the manner in which a belt reinforcing layer 90 of a ribbon-like material 92 is hooped on the belt 27 in accordance with a seventh embodiment of the present invention. The ribbon-like material 92 is flrst hooped laterally outward from a position H to the lateral edge of the belt 27, and turned back toward the mid-circumferential position E and turned back again at the other lateral edge of the belt 27 and terminated at a postion G. It is noted that two ribbon-like materials 92 may be hooped from the positions H and E at the same time.
Fig. 14 shows the manner in which a belt reinforcing layer 100 of a ribbon-like material 102 is hooped on the belt 27 in accordance with an eighth embodiment of the present invention. In this embodiment, the ribbon-like material 102 is hooped so as be three layers at the opposite outer end portions 27a of the beIt 27. It is noted that two ribbon-like materials ln2 may be hooped from positions K and L at the same time.
While certain representative embodiments and details have been shown for the purpose of illustrating the invention, i~t will be apparent to those skilled in this art that various changes and modifications may be made therein without departing rom the spirit or scope of the invention.
2;
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A conventional radial pneumatic tire which is used at high speeds includes a belt reinforcing layer consistin~ of two layers each having a predeter-mined width and disposed radially outwardly of a lateral end portion of a belt. Each reinforcing layer is composed of cords. The cords extend substantially in the circumferential direction of the tire and are covered with rubber. The lower reinforcing layer is hooped around the belt, and then the longitudinal end portions are overlapped with each other. Likewise, the upper reinforcing layer is hooped on the lower reinforcing layer previously hooped on the belt, and the lon~itudinal end portions are overlapped with each other and vulcanized. Thus, the reinforcing layers of 2~ the conventional tire form overlapped portions, respectively. Another conventional radial pneumatic tire which is used at high speeds includes a belt reinforcing cap of a predetermined width disposed radially outwardly of a belt and covering a full width of the belt. The reinforcing cap is composed of cords.
The cords extend substantially in the circumferential direction of the tire and are covered with rubber. The reinforcing cap is hooped around the belt, and then the '~ ~
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. .
: :
.
, ~31~2 longitudinal end portions are overlapped with each other and vulcanized. Thus, the rein~orcing cap of the conventional tire also forms an overlapped portion.
In both cases of the reinforcing layer and the reinforcing cap, at least one overlapped portion is formed on the circumference of the tire, and therefore the longitudinal end portions of the overlapped portions slip relative to each other and loosen, thereby weakening the tightening effect of the reinforcing layer and cap. Also, the reinforcing layer and the reinforcing cap are increased in thickness due to the overlapped portions, thereby reducing a uniformity level of the tire and degrading a comfortable riding performance. Furthermore, in the lateral end portion of the belt, the width of the upper reinforcing layer can be reduced to a width smaller than a full width of the lower reinforcing layer in order that the belt is tightened by the reinforcing layer, but if different layers of narrow and wide widths are used, two kinds of reinforcing layers different in width must be prepared. Furthermore, if the reinforcing cap is further used, the cap of the width must also be prepared in addition to the two kinds of layers. As a result, there is the disadvan-tage that various kinds of belt reinforcing layers and caps are required.
It is accordingly an important object of the present invention to provide an improved pneumatic tire .
' : .
- 13~ 2 which prevents and overcomes the a~orementioned disadvantages attendant with the prior art.
In accordance with an important aspect of the present invention, there is provided a pneumatic tire comprising a carcass having two opposite beads and extending from one bead to the other bead, a tread portion disposed radially outwardly of the carcass and extending in a circumferential direction of the tire, a belt of steel cord material disposed between the carcass and the tread portion, the belt having two laterally opposite end portions, and a reinforcing layer disposed between the tread portion and the belt.
; The reinforcing layer is formed by spirally hooping a continuous ribbon material on the belt. The continuous ribbon material is composed of a plurality of nylon cords covered with rubber. The reinforcing layer is varied in cord density laterally of the tire by varying a hooping pitch of the ribbon material laterally of the tire and hooping the ribbon material in two or more layers.
The drawbacks of a prior-art pneumatic tire and the features and advantages of a pneumatic tire according to the present invention will be more clearly understood from the following description taken in ; conjunction with the accompanying drawings in which:
Fig. 1 is a part-sectional view of a first embodiment of the pneumatic tire in accordance with the ~- present invention;
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- ' ,' ': ' :
' .
--- 131~2 - 4a -Fig. 2 is an enlarged sectional view of the ribbon-like material and the belt shown in Fig. l;
: Fig. 3 is an enlarged sectional view showing cord ' :
.`;~ .
. . - - . - .
13~6~2 materials of the ribbon-like material shown in Fig. 2;
Fig. 4 is a part-sectional view showing a belt reinforcing layer of a ribbon-like material hooped on a belt in accordance with a second embodiment of the present invention;
Fig. 5 is a part-sectional view showing a belt reinforcing layer of a ribbon-like material hooped on a belt in accordance with a third embodiment of the present invention;
Fig. 6 is a part-sectional view showing a belt reinforcing layer of a ribbon-like material hooped on a belt according to a fourth embodiment of the present invention;
Fig. 7 is a view showing the manner in which a belt reinforcing layer of a ribbon-like material is hooped on a belt in accordance with a fifth embodiment of the present invention;
- Fig. 8 is a view showing the manner in which two belt reinforcing layer of a ribbon-like material are hooped on a belt in accordance with a sixth embodiment of the present invention;
Fig. 9 is a part-sectional view showing a pneumatic tire of the prior art, two belt reinforcing layers being hooped on a laterally end portion of the belt;
Fig. 10 is a side sectional view, taken from an arrow B of Fig. 9, showing that longitudinal end portions of the reinforclng layers are overlapped with each other;
Fig. 11 is a part-sectional view showing a pneumatic tire of the prior art wherein the belt reinforcing cap is . . : . , :
~,' ; . , `
` ':
:J 3 ~ 2 hooped over a full width of the belt;
Fig. 12 is a side sectional view, taken from an arrow s of Fig. 11, showing that longitudinal end portions of the reinforcing cap are overlapped with each other;
Fig. 13 is a view showing the manner in which a belt reinforcing layer of a ribbon-like material is hooped on a belt in accordance with a seventh embodiment of the present invention; and 10Fig. 14 is a view showing the manner in which a belt reinforcing layer of a ribbon-like material is hooped on a belt in accordance with an eighth embodiment of the present invention.
Referring to Figs. 9 and 10, there is shown a conventional radial pneumatic tire which is used at high speeds and which includes a belt reinforcing layer 1 consisting of two layers la and lb each having a ` predetermined width Wl and disposed radially outwardly of a lateral end portion 2a of a belt 2. Each reinforcing layer is composed of cords. The cords ~; extend substantially in the circumferential direction of the tire and are covered with rubber. The lower ; reinforcing layer lb is hooped around the belt 2, and then the longitudinal end portions lbl (Fig. 10) are overlapped with each other. Likewise, the upper reinforcing layer la is hooped on the lower reinforcing layer lb previously hooped on the belt 2, and the longitudinal end portions lal (Fig. 10) are overlapped ; ~ , E3 ~.. ,, . :
~L31~52 with each other and vulcanized. Thus, the reinforcing layers la and lb of the conventional tire form overlapped portions 4, respectively. In Figs. ll and 12, there is shown another conventional radial pneumatic tire which is used at high speeds and which includes a belt reinforcing cap 7 of a predetermined width W7 disposed radially outwardly of a belt 9 and covering a full width Wg of the belt 9. The re-inforcing cap 7 is composed of cords. The cords extendlO substantially in the circumferential direction of the tire and are covered with rubber. The reinforcing cap 7 is hooped around the belt 9, and then the longitudinal end portions 7a (Fig. 12) are overlapped with each other and vulcaniæed. Thus, the reinforcing cap 7 of the conventional tire also forms an overlapped portion ll.
In hoth cases of the reinforcing layer l and the reinforcing cap 7, at least one overlapped portion 4 or ll is formed on the circumference of the tire, and therefore the longitudinal end portions lal, lbl and 7a of the overlapped portions 4 and ll slip relative to each other and loosen, thereby weakening the tightening effect of the reinforcing layer and cap. Also, since the reinforcing layer l and the reinforcing cap 7 are increased in thickness due to the overlapped portions 4 and ll, thereby reducing a uniformity level of the tire and degradin~ a comfortable riding performance.
Furthermore, in the lateral end portion 2a of the belt .
.
' ., :
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2 shown in Fig. 9, the width of the upper reinforcing layer la can be reduced to a width Wlc smaller than a full width wl of the lower reinforcing layer lb in order that the belt 2 i~ tightene~ by the reinforcing layer 1, but if different layers of narrow and wide widths are used, two kinds of reinforcing layers different in width must be prepared. Furthermore, if the reinforcing cap 7 as shown in Fig. 11 is further used, the cap of the width W7 must also be prepared in addition to the two kinds of layers. As a result, there is the disadvantage that various kinds of belt reinforcing layers and caps are required.
Referring to Fig. 1 of the drawings, a radial pneumatic tire according to a first embodiment of the present invention is generally designated by reference numeral 21. The radial pneumatic tire 21 comprises a carcass 23 made up of layers of cord materials and extending from one bead to the other bead, a tread portion 25 disposed radially ou~wardly of ;~ 20 the carcass 23 and extending in a circumferential direction of the tire, a belt 27 disposed between the carcass 23 and the tread portion 25, and a belt reinforcing layer 30 disposed between the tread portion 25 and the belt 27. The reinforcing la~ver 30 is formed by hooping a continuous ribbon-like material 36, which is composed of one to twelve cord materials 32 covered with rubber 34, on the belt 27 spirally in the circumferential direction o~ the tire. In this embodi-, .~
, , "
.... ~
;
~ 3 ~ 2 g ment, the cord materials 32 of the ribbon-like material 36 comprises two nylon cords as shown in Fig . 3. When the ribbon-like material 36 of two cord materials 32 is used, there is the advantage that the number of hoops of the continuous ribbon-like material 36 can be reduced by half as compared with a ribbon-like material of one cord, thereby enhancing an efficiency of production. The continuous ribbon-like material 36 forming the belt reinforcing layer 30 is capable of being hooped with a variable hooping density in a lateral direction of the tire indicated by an arrow A
in Fig. 2. More particularly, the reinforcing layer 30 of a laterally outer end portion 27a of the belt 27 comprises an outer reinforcing layer 30a and an inner reinforcing layer 30b, and in the outer reinforcing layer 30a, the ribbon-like material 36 is hooped in two lay~rs, and in the inner reinforcing layer 30b, the ribbon-like material 36 is hooped in one layer. Thus, the hooping density of the hooped ribbon-like material 36 is reduced at the inner reinforcing layer 30b than at the outer reinorcing layer 30a.
The operation of the aforementioned first embodiment according to the present invention will be hereinafter described.
As mentioned above, the continuous ribbon-like material 36 forming the belt reinforcing layer 30 is capable of being spirally hooped with a variable hooping density in the lateral direction of the tire, ~` , ; `
' -: ' ' : . ~ .
~ 3 ~
and therefore, the hooping density can be increased gradually toward the outer end portion 27a of the belt 27 which should be more tightened, and decreased gradually toward a mid-circumferential portion E of the belt 27 which should be less tightened. Furthermore, the reinforcing layer 30 is ~ormed by hooping spirally many times the continuous ribbon-like material 36 composed of one to twelve cord materials 32 covered with rubber 36, and therefore there is no overlapped longitudinal end portions which are formed in the aforementioned prior art. As a consequence, the belt reinforcing layer 30 according to the present invention is effectively prevented from slipping and loosening, thereby considerably enhancing the tightening effect of the belt and the tire durability performance at high speeds. In addition, since the continuous ribbon-like material 36 is hooped spirally, the leading and trailing end portions thereof are effectively prevented from being overlapped ~ith each other and therefore a ~0 uniformity level of the tire cannot be reduced and a comfortable riding performance of the tire cannot be degraded. Furthermore, since a narrow reinforcing layer and a wide reinforcing layer can be made by varying the hooping density of the continuous ribbon-like material 36, only one kind of a material is required to make the ribbon-like material 36, thereby considerably reducing the cost of production.
;
Referring to Fig. 4, there is shown a belt reinforcing layer 40 of a ribbon-like material 46 ~pirally hooped on a belt 27 in accordance with a second embodiment of the present invention. The reinforcing layer 40 comprises a laterally inner reinforcing layer 42 which is spixally hooped on a laterally outer end portion 27a of the belt 27 with a predetermined spacing in the lateral direction of the tire, and a laterally outer reinforcing layer 44 which is hooped on the laterally outer end portion 27a of the belt 27 without the spacing. As a result, the hooping density of the continuous ribbon-like material 46 forming the reinforcing layer 40 is reduced from the outer reinforcing layer 44 toward the inner reinforcing layer 42. Other members are substantially identical in construction and operation to those of the first - embodiment and therefore the description will be hereinafter omitted.
Referring to Fig. 5, there is shown a third embodiment of the present invention. In this embodi-ment, a reinforcing layer 50 is used as a cap. That is, a continuous ribbon-like material 52 forming the reinforcing layer 50 is hooped over the full width o~
the belt 27 so that the spacing between the adjacent looped portions is gradually reduced from a mid-circumferential portion E of the tire toward opposite outer end portions 27a of the belt 27. More parti-cularly, at the opposite outer end portions 27a, the .~ ~
~ ;,' ' ~' ~L 3 ~ 2 - lla ~
ribbon-like material 52 is spirally hooped without the spacing between the adjacent looped portions thereof.
When the reinforcing layer is one layer at the outer end portion of the belt as shown in Figs. 4 and 5, it is desirable that the width of the ribbon-like material 52 be between 4 mm and 6 mm. If the width is less than 4 mm, the cost of production is increased, and if the width is more than 6 mm, the ribbon-like material of the reinforcing layer protrudes from the lateral end of the belt when it i5 hooped, so that cracks occur at the protruded portion. Other members are substantially identical in construction and operation to those of the second embodiment and therefore the description will be hersinafter omitted.
Referring to Fig. 6, there is shown a fourth embodiment of the present invention. A reinforcing layer 60 is provided over the full width of the belt 27. A continuous ribbon-like material 62 forming the reinforcing layer 60 is spirally hooped so that the spacing between the adjacent looped portions thereof is gradually reduced from a mid-circumferential portion E
of the tire toward the opposite outer end portion 27a of the belt 27. At the outer end portion 27a, the ribbon-like material 62 is hooped in two layers without the spacing between the adjacent looped portions thereof. Thus, in this embodiment, the hoopin~ density is increased at the opposite outer end portion 27a than the third embodiment shown in Fig. 5. When the ,~
': , .
~ 3 ~
- llb -reinforcing layer is hooped in two layers at the outer ~nd portion of the belt as shown in Fig. 6, it is desirable that the width of the ribbon-like material be between 4 mm and 11 mm. If the width is less than 4 mm, the cost of production is increased, and if the width is more than 11 mm, the ribbon-like material of the reinforcing layer protrudes from the lateral end of the belt when it is hooped, so that cracks occur at the protruded portion. Other members are substantially identical in construction and operation to those of the third embodiment and therefore the description will be hereinafter omitted.
Referring to Fig. 7, there is shown the manner in which a belt reinforcing layer 70 of a ribbon-like material 72 is spirally hooped on the belt 27 in accordance with a fifth embodiment of the present invention. The ribbon-like material 72 is first hooped leftward of Fig. 7 from a position B to a lateral left end C. At the lateral end C, the hooping direction of ~O the ribbon-like material 72 is turned to the position B
so that the ribbon material can be hooped in two layers. The reinforcing layer 70 becomes one layer from the positon B and the hooping density is gradually decreased toward the mid-circumferential positon E.
After passing the mid-circumferential position E, the ribbon-like material 72 is hooped so that the hooping density is gradually increased toward a lateral right end D. At the lateral right end D, the ribbon-like ;
'' : ., .
' ' ' .
... .
~ 3 ~
-- llc --material 72 is again turned back to the mid-circumferential position E to be in two layers, and the hooping is completed at a position F. Thus, the ribbon-like material 72 is hooped with a locus of a generally inverted letter ~ indicated by the arrow in Fig. 7. As a result, the reinforcing la~er 70 as shown in Fig. 7 can be easily formed continuously by a single ribbon-like material 72.
Referring to Fig. 8, there is shown a sixth embodiment according to the present invention. The sixth embodiment is identical to the fifth embodiment of Fig. 7 except that two ribbon-like materials 82 forming a reinforcing layer 80 are used. The two ribbon-like materials 82 are hooped in opposite direc-tions from the mid-circumferential position E to opposite ends D and D, and turned back at the ends D
and D toward the mid-circumferential position E, and the hooping of the two ribbon-like materials 82 are completed at positions F and F. In this embodiment, two ribbon-like materials are used, but the reinforcing layer 80 aan also be ~.~
:
~ -~- ' , , , ' .
',: '. ' . ,; ' " ' ' :
', ' ' ' , ' ' easily formed.
Fig. 13 shows the manner in which a belt reinforcing layer 90 of a ribbon-like material 92 is hooped on the belt 27 in accordance with a seventh embodiment of the present invention. The ribbon-like material 92 is flrst hooped laterally outward from a position H to the lateral edge of the belt 27, and turned back toward the mid-circumferential position E and turned back again at the other lateral edge of the belt 27 and terminated at a postion G. It is noted that two ribbon-like materials 92 may be hooped from the positions H and E at the same time.
Fig. 14 shows the manner in which a belt reinforcing layer 100 of a ribbon-like material 102 is hooped on the belt 27 in accordance with an eighth embodiment of the present invention. In this embodiment, the ribbon-like material 102 is hooped so as be three layers at the opposite outer end portions 27a of the beIt 27. It is noted that two ribbon-like materials ln2 may be hooped from positions K and L at the same time.
While certain representative embodiments and details have been shown for the purpose of illustrating the invention, i~t will be apparent to those skilled in this art that various changes and modifications may be made therein without departing rom the spirit or scope of the invention.
2;
.~ . . . .
, , ' . ~ : ` , :
Claims (7)
1. A pneumatic tire comprising:
a carcass having two opposite beads and extending from one said bead to the other said bead;
a tread portion disposed radially outwardly of said carcass and extending in a circumferential direction of said tire;
a belt of steel cord material disposed between said carcass and said tread portion, said belt having two laterally opposite end portions; and a reinforcing layer disposed between said tread portion and said belt;
said reinforcing layer being formed by spirally hooping a continuous ribbon material on said belt;
said continuous ribbon material being composed of a plurality of nylon cords covered with rubber; and said reinforcing layer being varied in cord density laterally of said tire by varying a hooping pitch of said ribbon material laterally of said tire and hooping said ribbon material in two or more layers.
a carcass having two opposite beads and extending from one said bead to the other said bead;
a tread portion disposed radially outwardly of said carcass and extending in a circumferential direction of said tire;
a belt of steel cord material disposed between said carcass and said tread portion, said belt having two laterally opposite end portions; and a reinforcing layer disposed between said tread portion and said belt;
said reinforcing layer being formed by spirally hooping a continuous ribbon material on said belt;
said continuous ribbon material being composed of a plurality of nylon cords covered with rubber; and said reinforcing layer being varied in cord density laterally of said tire by varying a hooping pitch of said ribbon material laterally of said tire and hooping said ribbon material in two or more layers.
2. A pneumatic tire as set forth in claim 1, wherein:
said belt has lateral edges which are completely covered.
said belt has lateral edges which are completely covered.
3. A pneumatic tire as set forth in claim 1, wherein:
said continuous ribbon material has ends which do not overlap each other.
said continuous ribbon material has ends which do not overlap each other.
4. A pneumatic tire as set forth in claim 1, wherein:
said continuous ribbon material has a rectangular transverse cross-section.
said continuous ribbon material has a rectangular transverse cross-section.
5. A pneumatic tire as set forth in claim 1, wherein:
said reinforcing layer comprises:
a laterally inner reinforcing layer which is hooped on a laterally inner end portion of said belt with a predetermined spacing laterally of said tire, and a laterally outer reinforcing layer which is hooped on said laterally outer end portions of said belt without said spacing.
said reinforcing layer comprises:
a laterally inner reinforcing layer which is hooped on a laterally inner end portion of said belt with a predetermined spacing laterally of said tire, and a laterally outer reinforcing layer which is hooped on said laterally outer end portions of said belt without said spacing.
6. A pneumatic tire as set forth in claim 1, wherein:
said continuous ribbon material is hooped over the full width of said belt so that spacing between adjacent looped portions thereof is gradually reduced from a mid-circumferential portion of said tire toward laterally opposite outer end portions of said belt.
said continuous ribbon material is hooped over the full width of said belt so that spacing between adjacent looped portions thereof is gradually reduced from a mid-circumferential portion of said tire toward laterally opposite outer end portions of said belt.
7. A pneumatic tire as set forth in claim 6, wherein:
the width of said continuous ribbon material is between 4 mm and 6 mm.
the width of said continuous ribbon material is between 4 mm and 6 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000544941A CA1315652C (en) | 1987-08-20 | 1987-08-20 | Pneumatic tire |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000544941A CA1315652C (en) | 1987-08-20 | 1987-08-20 | Pneumatic tire |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1315652C true CA1315652C (en) | 1993-04-06 |
Family
ID=4136308
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000544941A Expired - Lifetime CA1315652C (en) | 1987-08-20 | 1987-08-20 | Pneumatic tire |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1315652C (en) |
-
1987
- 1987-08-20 CA CA000544941A patent/CA1315652C/en not_active Expired - Lifetime
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| MKEX | Expiry |