METHOD OF MANUFACTURING TIRE TUBES, AND TIRE TUBE

Abstract: The tube material 2' extrusion-molded by the extrusion molding machine has an air chamber peripheral wall 3i, a sealant chamber peripheral wall 3o and a partition wall 4. An air chamber 5 is defined between the air chamber peripheral wall 3i and the partition wall 4, and a sealant chamber 6 is defined between the sealant chamber peripheral wall 3o and the partition wall 4. On the air chamber peripheral wall 3i are protrusively formed a plurality of rib-shaped projections 15 each forming a thick portion for reinforcement. The thickness t 3 of each of the projections is approximately equal to the thickness t 1 of the peripheral wall 3 and the thickness t 2 of the partition wall 4. It is possible to efficiently extrusion-mold the tube material 2' having the thick portions for reinforcement by thus approximately equalizing the thickness of each part of the tube material 2 including the rib-shaped projections 15.

Description: FIELD OF THE INVENTION The present invention relates to a tire tube manufacturing method for molding a tube material by an extrusion process and subsequently for vulcanizing the tube material by a vulcanizing process, and to a tire tube manufactured by the manufacturing method. PRIOR ART When the radial load acts on a vehicle wheel mounted with a tube-incorporated tire, the tire and the tube are subjected to deformation with the load. However, particularly when the tire runs on a hard obstacle such as a rock during off-road traveling, or when the vehicle jumps and touches the ground, the tube is pressed hard between the tire largely deformed and a metal rim, there occurs in some cases the rim-hitting phenomenon that the inner wall surfaces of the tube abut against each other. If the inner wall surfaces of the tube abut against each other because of such rim-hitting phenomenon, the durability of the abutment portion may decrease in some cases. The decrease in the durability of the abutment portion stated above can be prevented, as proposed by Japanese Patent Application Laid-open No. 9-164806, by providing a projection of a thick portion on the wall surface of the tube for reinforcement, which wall surface is likely to be decreased in durability by the rim-hitting phenomenon. It should be noted here that when a tube material is extrusion-molded by the extrusion process in the tire tube manufacturing process, the optimum extrusion speed for extruding each part of the tube material varies with the thickness of the tube material. Therefore, if a projection of a thick portion is provided on the wall surface of the tube for reinforcement, the optimum extrusion speed for the extrusion of the thick portion will differ from the optimum extrusion speed for the other portion, presenting the problem that the extrusion molding of the whole part of the tube material cannot be efficiently accomplished. DISCLOSURE OF THE INVENTION The present invention has been accomplished with the above circumstances in view, and it is an object of the present invention to provide a tire tube manufacturing method which enables manufacture of a tube material having a thick portion for reinforcement to be efficiently carried out. To accomplish the above-described object, according to a first aspect and feature of the present invention, there is provided a tire tube manufacturing method for molding a tube material by an extrusion process and subsequently for vulcanizing said tube material by a vulcanizing process, in which material is extruded through a nozzle that is provided with slits to form a tube body portion of an annular cross section and a plurality of integrally formed, rib-shaped projections extending in the longitudinal direction of and protruding from said tube body portion to reinforce said tube body portion against impact damage with a wheel rim, characterised in that the slits in the nozzle are of approximately equal width so that the thickness of the tube body portion and the thickness of the plurality of rib-shaped projections are set approximately equal to each other in the extruded product. With the above arrangement, not only the provision of the rib-shaped projection can prevent a decrease in tube durability caused by the rim-hitting phenomenon but also the approximate equalization of the thickness of the tube body portion and the thickness of the rib-shaped projection enables extrusion molding of the tube material to be efficiently accomplished. According to a preferred embodiment of the present invention, said material is extruded through a nozzle having a plurality of slits adjacent to each other and of approximately equal width in order to form a plurality of rib-shaped reinforcing projections that are disposed adjacent to each other. Furthermore, two groups of reinforcing projections may be provided, one on each side of the tire tube for protecting the tube body portion against impact damage. With the above arrangement, the plurality of rib-shaped projections can effectively protect a wide range of the tube. According to another preferred embodiment of the present invention, a pair of J-shaped slits are provided in the nozzle for extruding two rib-shaped projections approximately equal to each other for reinforcing the tube body portion against impact damage. These two projections formed by the J-shaped slits in the nozzle may protrude from the inner peripheral surface of said tube body portion, and wherein the base end portions of said rib-shaped projections are disposed at higher level than tip end portions thereof when the tube material is vulcanized and molded by the vulcanizing process. With the above arrangement, since the base end of the two rib-shaped projections is arranged at a higher level than the tip end portion thereof at the time of vulcanization molding of the tube material, it is possible to effectively protect a wide range of the tube by permitting the rib-shaped projections to be suspended by gravitation until they are situated along the inner peripheral surface of the tube body portion. According to a second aspect and feature of the present invention, there is provided a tire tube for use in a tire attached on a wheel rim, having a tube body portion of an annular cross section and a plurality of integral rib-shaped projections extending in the longitudinal direction of and protruding from said body portion to reinforce said tube body portion against impact damage, the thickness of said rib-shaped projections being substantially equal to that of said tube body portion. In a preferred embodiment, the tire tube has two groups of reinforcing projections, one on each side of the tire tube for protecting the tube body portion against impact damage with the wheel rim. According to another preferred embodiment, two rib-shaped projections are provided extending in the longitudinal direction of said tube body portion and protruding from said tube body portion, wherein the rib-shaped projections have been extruded from a pair of J-shaped slits in a nozzle of an extrusion machine, the J-shaped projections being arranged along the same circumferential direction as said tube body portion. Furthermore, the tip ends of the J-shaped projections may be attached to the tube body portion during the vulcanizing process. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 to Fig. 4 show the first embodiment of the present invention, wherein Fig. 1 is a cross-sectional view of a vehicle wheel mounted with a tube-incorporated tire; Fig. 2 is an explanatory view of operation showing the vehicle wheel running on an obstacle; Fig. 3 is a view showing a tube material extrusion process; Fig. 4 is a sectional view of the tube material; Figs. 5 to 10 show the second embodiment of the present invention, wherein Fig. 5 is a cross-sectional view of a vehicle wheel mounted with a tube-incorporated tire; Fig. 6 is an explanatory view of operation showing the vehicle wheel running on an obstacle; Fig. 7 is a view showing the tube material extrusion process; Fig. 8 is a view taken in the direction of an arrow 8 in Fig. 7; Fig. 9 is a sectional view of the tube material; and Fig. 10 is a view showing the tube vulcanizing process; and Fig. 11 is a sectional view of a tube material according to the third embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION The preferred embodiments of the present invention will hereinafter be described with reference to the accompanying drawings. As shown in Fig. 1, on a wheel rim R for a two-wheeled motorcycle is attached a tube-incorporated tire T which comprises a tire body 1 and a tube 2 housed therein. The tube 2 has a peripheral wall 3 of an annular cross section having an air chamber peripheral wall 3i positioned inside in the radial direction and a sealant chamber peripheral wall 3o located outside in the radial direction. A pair of connecting portions for connection between the air chamber peripheral wall 3i and the sealant chamber peripheral wall 3o of the peripheral wall 3 are connected to each other by a partition wall 4 formed integrally with the peripheral wall 3. An air chamber 5 of an approximately round cross section defined between the air chamber peripheral wall 3i and the partition wall 4 is filled with the air. In a sealant chamber 6 having an approximately circular cross section defined between the sealant chamber peripheral wall 3o and the partition wall 4, a known liquid sealant 7 has been charged. The rim R has an annular rim body 11 extending in the circumferential direction of the tube-incorporated tire T and a pair of flanges 12, 12 extending outside in the radial direction from opposite ends in the widthwise direction of the rim body 11 to hold an inner periphery of the tire 1. An air valve 13 through which the air is filled into the air chamber 5 defined within the tube 2 is supported through an air valve mounting section 14 formed in one portion in the circumferential direction of the rim body 11. When the inside wall surfaces of the air chamber 5 abut against each other in case an impact load is applied to the tube-incorporated tire T, a plurality of rib-shaped projections 15 are provided on the inside wall surface of the air chamber peripheral wall 3i of the tube 2 to prevent a decrease in the durability of the tube 2 by the load. The rib-shaped projections 15 projecting toward the center of the air chamber 5 are formed six in each of adjacent positions of a pair of flanges 12, 12 of the rim R, which extend closely to each other, endlessly and in parallel in the circumferential direction of the tube 2. Fig. 3 shows an extrusion molding machine 21 for extruding a tube material 2'. An extrusion nozzle 22 of the extrusion molding machine 21 is provided in a tip end thereof with a round slit 22 1 forming the peripheral wall 3 as the tube body portion, an S-shaped slit 22 2 forming the partition wall 4, and twelve slits 22 3 forming the rib-shaped projections 15. Furthermore, the extrusion nozzle 22 has, in the tip end, a releasing agent supply ports 23, 23 for supplying talc as a releasing agent into the air chamber 5 and the sealant chamber 6. Fig. 4 is a cross sectional view of the tube material 2' extrusion-molded by the extrusion molding machine 21. As is clear from the drawing, the width of each of the slits 22 1 , 22 2 , 22 3 and so forth of the extrusion nozzle 22 is set in order to equalize the thickness of each part of the tube material 2', i.e., the thickness t 1 of the peripheral wall 3 as the tube body portion, the thickness t 2 of the partition wall 4, and the thickness t 3 of the twelve rib-shaped projections 15 will be equal. It is, therefore, possible to perform efficient extrusion molding of each part of the tube material 2' at the optimum extrusion speed by setting the thickness of each part of the tube material 2' equal to one another. The tube material 2' thus extrusion-molded is subsequently subjected to vulcanization and molding in the vulcanizing process after the extrusion process and then the sealant 7 is charged into the sealant chamber 6, thus finishing the tube 2. The sealant chamber 6 of the tube 2 is held in a configuration along the inside surface of the tire body 1 by the air pressure in the air chamber 5. Therefore, if a centrifugal force acts, with the rotation of the vehicle wheel, on the sealant 7 filled in the sealant chamber 6, it is possible to prevent the sealant 7 from gathering to the outer peripheral side of the tube 2. Therefore, if the tube 2 is damaged with a nail or other in a radial direction or from the side, the sealant 7 is instantly filled in the damaged part for mending, thereby delaying air leakage from the air chamber 5. Also the sealant 7, being kept in the sealant chamber 6, will not flow out into the air chamber 5, and therefore will never adversely affect the operation of the air valve 13 and the pressure gage of the air valve 13. Next, as shown in Fig. 2, if the tube-incorporated tire T running on an obstacle 16 on a road receives an impact load, the flanges 12, 12 of the rim R radially compress the tire body 1 and the tube 2 due to the load. At this time, the tire body 1 and the tube 2 are pressed between the flanges 12, 12 of the rim R projecting radially outward and the obstacle 16; however, because of the shock absorbing effect of the rib-shaped projections 15 which are designed to be elastically deformed with ease, the air chamber peripheral wall 3i, sealant chamber peripheral wall 3o and partition wall 4 of the tube 2 can be prevented from decreasing in durability. Furthermore, the provision of the plurality of rib-shaped projections 15 can effectively protect a wide range of the tube 2. Therefore such a simple structure that the rib-shaped projections 15 are formed in a part of the tube 2 can prevent a decrease in the durability of the tube 2, and moreover the weight and the manufacturing cost of the tube-incorporated tire T will not increase. Next, the second embodiment of the present invention will be described with reference to Figs. 5 to 10. As shown in Figs. 5 and 6, a tube 2 of the second embodiment has a pair of rib-shaped projections 17 and 18 in positions corresponding to the rib-shaped projections 15 of the tube 2 (see Fig. 1) of the first embodiment; these rib-shaped projections 17 and 18 have the same function and effect as the rib-shaped projections 15 of the first embodiment, to thereby prevent a decrease in the durability of the tube 2 even in case of rim hitting. As shown in Figs. 7 and 8, a pair of J-shaped slits 22 4 and 22 5 are provided, in place of the twelve slits 22 3 in the first embodiment, in a tip end of an extrusion nozzle 22 of an extrusion molding machine 21 of the second embodiment. Also in the tip end of the extrusion nozzle 22 a pair of small releasing agent supply ports 24, 24 in addition to the pair of releasing agent supply ports 23, 23 are provided correspondingly to tip end portions of the J-shaped slits 22 4 and 22 5 , respectively. As is clear from Fig. 9, a tube material 2' of the second embodiment has a pair of asymmetrical rib-shaped projections 17 and 18 formed by the J-shaped slits 22 4 and 22 5 . These projections 17 and 18 are inclined in the direction along an inside wall surface of an air chamber peripheral wall 3i. A base end portion 17 1 of the rib-shaped projection 17 is in the position of the distance A+B apart from a root 4 1 of a partition wall 4; accordingly, if B represents the height of the rib-shaped projection 17, a tip end portion 17 2 is in the position of the distance A apart from the root 4 1 of the partition wall 4. Therefore, a tip end portion 18 2 of the rib-shaped projection 18 having the height B is in the position of the distance A+B apart from a root 4 2 of the partition wall 4. The pair of rib-shaped projections 17 and 18 are asymmetrically arranged as stated above at the stage of the tube material 2'. Therefore the pair of rib-shaped projections 17 and 18 of the tube 2 after vulcanization and molding are finally arranged in symmetrical positions (see Fig. 1). The width of each of the slits 22 1 , 22 2 , 22 4 and 22 5 of the extrusion nozzle 22 is set so that the thickness of each part of the tube material 2', that is, the thickness t 1 of the peripheral wall 3, the thickness t 2 of the partition wall 4, and the thickness t 4 of the pair of rib-shaped projections 17 and 18 will be equal to one another. Each part of the tube material 2' can be efficiently extrusion-molded at the optimum extrusion speed by thus setting the thickness of each part of the tube material 2' equal to one another. The talc T supplied from the releasing agent supply ports 23, 23 located in the tip end of the extrusion nozzle 22 attaches on inside wall surfaces of an air chamber 5 and a sealant chamber 6 when the tube material 2' is extrusion-molded in the extrusion process. In this case, however, the talc T can hardly enter the spaces of V-shaped section located between an air chamber peripheral wall 3i and the rib-shaped projections 17 and 18. Therefore, it becomes necessary to supply a small amount of talc T through the pair of small releasing agent supply ports 24, 24 so that the talc T will attach on bottoms of the spaces of V-shaped section. The extrusion-molded tube material 2' is cut to a predetermined length and fitted with an air valve 13; then its opposite ends are jointed into an annular form. In the subsequent vulcanizing process, as shown in Fig. 10, the annular tube material 2' is inserted horizontally between an upper die 25 and a lower die 26 of a heating die, which are then heated while supplying high-temperature air (or high-temperature steam) from a hot air supply source 27 through the air valve 13, thus vulcanizing and molding the tube material 2'. At this time, the partition wall 4 is held in firm contact with the sealant chamber peripheral wall 3o by the air pressure supplied from the air chamber 5, but is prevented from jointing with the sealant chamber peripheral wall 3o because of the presence of the talc T which is the releasing agent. The tip end portion 17 2 of the lower rib-shaped projection 17, being located at a lower level than the base end portion 17 1 , automatically abuts against the air chamber peripheral wall 3i with the gravity. At this time, since a small amount of talc T supplied through the small releasing agent supply port 24 is attached to the vicinity of the base end portion 17 1 of the rib-shaped projection 17, only the vicinity of the tip end portion 17 2 of the rib-shaped projection 17 where no talc T is attached is jointed by vulcanization to the air chamber peripheral wall 3i. In the meantime, the tip end portion 18 2 of the upper rib-shaped projection 18, being positioned at a lower level than the base end portion 18 1 , is allowed to be suspended by the gravity a little away from the air chamber peripheral wall 3i, but is pressed into firm contact with the air chamber peripheral wall 3i with the air pressure supplied to the air chamber 5. Accordingly only the vicinity of the tip end portion 18 2 of the rib-shaped projection 18 where no talc T is attached is vulcanized to be jointed to the air chamber peripheral wall 3i. The tube 2 thus completed increases in flexibility to thereby further improve durability because of the presence of a non-jointed portion (see "a" portion in Fig. 6) between the rib-shaped projections 17 and 18 and the air chamber peripheral wall 3i. Fig. 11 shows the third embodiment of the present invention. As is clear from a comparison with Fig. 9 which shows the second embodiment, a tube material 2' of the third embodiment is provided with a pair of rib-shaped projections 17 and 18 protruding to an outside wall surface of an air chamber peripheral wall 3i. Each of the rib-shaped projections 17 and 18 has a form symmetrical to each other. The thickness t 4 of the rib-shaped projections 17 and 18 is set equal to the thickness of other portions of the tube material 2', i.e., the thickness t 1 of a peripheral wall 3 and the thickness t 2 of a partition wall 4; therefore it is also possible to carry out efficient extrusion molding of each part of the tube material 2' at the optimum extrusion speed according to the present embodiment. The provision of a recess, in which the rib-shaped projections 17 and 18 fit, in an upper die 25 and a lower die 26 of the heating die allows projection of the rib-shaped projections 17 and 18 to the outside wall surface of the air chamber peripheral wall 3i of the finished tube 2 at the time of vulcanization molding of the tube material 2' of the present embodiment; and also the provision of flat molded surfaces in the upper die 25 and the lower die 26 of the heating die allows the formation of projections, correspondingly to the rib-shaped projections 17 and 18, on the inside wall surface of the air chamber peripheral wall 3i of the finished tube 2.

Claims: A tire tube manufacturing method for molding a tube material (2') by an extrusion process and subsequently for vulcanizing said tube material by a vulcanizing process, in which material is extruded through a nozzle (22) that is provided with slits (22 1 , 22 2 , 22 3 ) to form a tube body portion (2) of an annular cross section and a plurality of integrally formed, rib-shaped projections (15) extending in the longitudinal direction of and protruding from said tube body portion to reinforce said tube body portion against impact damage with a wheel rim (R), characterised in that the slits in the nozzle are of approximately equal width so that the thickness of the tube body portion and the thickness of the plurality of rib-shaped projections are set approximately equal to each other in the extruded product. A method as claimed in claim 1, in which said material is extruded through a nozzle (22) having a plurality of slits (22 3 ) adjacent to each other and of approximately equal width in order to form a plurality of rib-shaped reinforcing projections (15) that are disposed adjacent to each other. A method as claimed in claim 2, in which two groups of reinforcing projections (15) are provided, one on each side of the tire tube for protecting the tube body portion (2) against impact damage. A method as claimed in claim 1, in which a pair of J-shaped slits (22 4 ,22 5 ) are provided in the nozzle (22) for extruding two rib-shaped projections (17,18) approximately equal to each other for reinforcing the tube body portion (2) against impact damage. A method as claimed in claim 4, in which said two projections (17,18) formed by the J-shaped slits (22 4 , 22 5 ) in the nozzle (22) protrude from the inner peripheral surface of said tube body portion (2), and wherein the base end portions (17 1 ,18 1 ) of said rib-shaped projections are disposed at higher level than tip end portions (17 2 ,18 2 ) thereof when the tube material (2') is vulcanized and molded by the vulcanizing process. A tire tube for use in a tire (1) attached on a wheel rim (R), having a tube body portion (2) of an annular cross section and a plurality of integral rib-shaped projections (15) extending in the longitudinal direction of and protruding from said body portion to reinforce said tube body portion against impact damage, the thickness of said rib-shaped projections being substantially equal to that of said tube body portion. A tire tube as claimed in claim 6, having two groups of reinforcing projections (15), one on each side of the tire tube for protecting the tube body portion (2) against impact damage with the wheel rim (R). A tire tube as claimed in claim 6, in which two rib-shaped projections are provided extending in the longitudinal direction of said tube body portion (2) and protruding from said tube body portion, wherein the rib-shaped projections have been extruded from a pair of J-shaped slits (22 4 , 22 5 ) in a nozzle (22) of an extrusion machine (21), the J-shaped projections (17,18) being arranged along the same circumferential direction as said tube body portion. A tire tube as claimed in claim 8, in which tip ends (17 2 , 18 2 ) of the J-shaped projections (17, 18) have been attached to the tube body portion (2) during the vulcanizing process.

Inventors: YAMAGIWA TOSHIO, YAMAGIWA, TOSHIO, YAMAGIWA, Toshio,
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1999
Main classification: B29D30
IPC codes: B60C5, B29C65, B29D30, B29D23, B29C47