Puncture preventive sealant

Abstract: A puncture preventive sealant is capable of reducing the content of cellulose fibers for suppressing the cost of the sealant while keeping a high sealing performance due to the cellulose fibers. A sealant 8, which is filled in a sealant chamber 7 defined in a tube 2 adjacently to an air chamber 3, contains synthetic fibers and cellulose fibers in a solvent. The content of the synthetic fibers is in a range of from 75 to 90 wt% and the content of the cellulose fiber is in a range of from 25 to 10 wt%. Since the sealant 8 is filled in the sealant chamber 7 having a capacity significantly smaller than that of the air chamber 3, the separation of the synthetic fibers due to a centrifugal force substantially exert no adverse effect on the characteristics of the sealant, and accordingly, the content of the cellulose fibers can be set at such a minimum value as to block a large puncture hole. As a result, it is possible to reduce the cost by reducing the content of the cellulose fibers.

Description: The present invention relates to a puncture preventive sealant filled in a sealant chamber defined in a tube adjacently to an air chamber. Japanese Patent Laid-open No. Sho 50-72303 discloses a technique in which a sealant containing a fiber component is enclosed in a tire tube of an automobile for repairing a damage of the tube, for example, due to piercing by a nail or the like with the sealant, whereby preventing leakage of air from the tube. This sealant contains short-fibers and a fine crystal powder of cellulose in a liquid polymer or an aqueous solution, wherein the ratio of the fine crystal powder of cellulose is set to be larger than that of the short-fibers for suppressing the flow of the short-fibers in the tube. The above-described sealant has been developed from the viewpoint of the extensive flow of a sealant in a tube, and has been configured that the content of the fine crystal powder of cellulose is set to be larger than that of the short-fibers, whereby suppressing the flow of the short-fibers in the tube. Such a sealant, however, has a problem that since the fine crystal powder of cellulose is produced by processing cellulose fibers and thereby it is higher in cost than the cellulose fibers, with a result that the increased content of the fine crystal powder of cellulose leads to the significantly raised cost. From FR-A-381 166, a puncture preventive sealant filled in a sealant chamber defined in a tube adjacently to an air chamber is known, whereby the sealant comprises asbestos fibers contained in a solvent of caoutchouc. In view of the foregoing, the present invention has been made, and an object of the present invention is to provide a sealant capable of reducing the content of cellulose fibers for suppressing the cost of the sealant while keeping a high sealing performance of the cellulose fibers. To achieve the above object, according to the invention described in claim 1, there is provided a puncture preventive sealant filled in a sealant chamber defined in a tube adjacently to an air chamber, the sealant including a fiber component contained in a solvent, wherein the fiber component includes synthetic fibers and cellulose fibers which are mixed in such a mixing ratio that the weight-content of the cellulose fibers is smaller than that of the synthetic fibers. Therefore, since a sealant is filled in a sealant chamber defined in a tube adjacently to an air chamber, synthetic fibers contained in the sealant is difficult to be separated from a solvent as compared with the case in which the sealant is directly filled in the air chamber. As a result, since the separation of the synthetic fibers from the solvent is not taken into account, the content of expensive cellulose fibers can be set at such a minimum value as to ensure a sealing performance for a large puncture hole, while keeping the flowability of the synthetic fibers. This makes it possible to reduce the cost while keeping a high sealing performance irrespective of the size of a puncture hole. According to the invention described in claim 2, since the content of the synthetic fibers is in a range of 75 to 90 wt% and the content of the cellulose fibers is in a range of from 25 to 10 wt%, it is possible to effectively reduce the cost while keeping a high sealing performance due to the cellulose fibers. Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figs. 1 and 2 show a first embodiment, wherein Fig. 1 is a transverse sectional view of a wheel mounted with a tube tire and Fig. 2 is a flow chart illustrating steps for manufacturing a tube according to the present invention. As shown in Fig. 1, a rim R to be mounted on a wheel used for a motorcycle is connected to a hub (not shown) via wire spokes S. A tube tire T composed of a tire 1 and a tube 2 contained in the tire 1 is mounted on the rim R. The tube 2 has a peripheral wall 4 formed in an annular shape in cross-section, and the peripheral wall 4 is composed of an air chamber side peripheral wall 4i positioned radially inward and a sealant chamber side peripheral wall 4o positioned radially outward. A pair of connection portions for connecting the air chamber side peripheral wall 4i of the peripheral wall 4 to the sealant chamber side peripheral wall 4o thereof are connected to each other by a bulkhead 5 formed integrally therewith. An air chamber 3 formed into an approximately circular shape in cross-section, which is defined between the air chamber side peripheral wall 4i and the bulkhead 5, is filled with an air, and a sealant chamber 7 formed into an approximately arcuate shape in cross-section, which is defined between the sealant chamber side peripheral wall 4o and the bulkhead 5, is filled with a liquid sealant 8 which will be described later. The rim R includes an annular rim main body 11 extending in the circumferential direction of the tube tire T and a pair of flange portions 12, 12 extending radially outward from both the radial ends of the rim main body 11 and holding the inner periphery of the tire 1. An air valve 6 for filling the air chamber 3 formed in the tube 2 with an air, passes through an air valve mounting portion 13 formed at a position in the circumferential direction of the rim main body 11 and is fixed by nuts 14, 15. Since the sealant chamber 7 of the tube 2 is held in a shape following the inner surface of the tire 1 by an air pressure of the air chamber 3, the sealant 8 filled in the sealant chamber 7 is prevented from being shifted on the outer peripheral side of the tube 2 even when the sealant 8 is applied with a centrifugal force due to the rotation of the wheel. Accordingly, even when the tube 2 is pierced with a nail or the like in the radial or sideward direction, the pierced portion is immediately buried with the sealant 8 to be thus repaired, so that it is possible to retard the leakage of air from the air chamber 3. Additionally, since the sealant 8 is held in the sealant chamber 7 and is not allowed to flow on the air chamber 3 side, it does not block the air valve 6 or a pressure gauge touched with the air valve 6. Next, a process of manufacturing the tube 2 will be described. As shown in Fig. 2, the tube 2 is manufactured in accordance with manufacturing steps including a material kneading step, a tube material extrusion molding step, a cutting step, an air valve mounting step, a piercing step, a joining step, a first vulcanizing step, a sealant filling step, a raw rubber sheet sticking step, a second vulcanizing step, and an inspection step. First, a raw rubber kneaded at the material kneading step is extrusion-molded at the tube material extrusion molding step, to form a tube material 2' made of the raw rubber. The tube material 2' continuously extrusion-molded from a nozzle of an extrusion molding machine includes a peripheral wall 4 formed into a circular shape in transverse cross-section and a bulkhead 5 connecting two points positioned along the diameter of the peripheral wall 4. The peripheral wall 4 is divided into an air chamber side peripheral wall 4i and a sealant chamber side peripheral wall 4o with respect to the portions connected to the bulkhead 5. The tube material 2' is cut into a specified length at the subsequent cutting step, and an air valve 6 is mounted at a suitable position of the air chamber side peripheral wall 4i at the air valve mounting step. And, at the piercing step, the sealant chamber side peripheral wall 4o of the tube material 2' are pierced to form sealant filling holes 4 1 , ..., 4 1 . Both the end portions of the tube material 2' are joined to each other at the subsequent joining step, and at the first vulcanizing step, the tube material 2' is inserted in a heating die, and the air chamber side peripheral wall 4i and the sealant chamber side peripheral chamber 4o are brought in close-contact with the heating die and the bulkhead 5 is also brought in close-contact with the sealant chamber side peripheral wall 4o by supplying a heated air or a high temperature steam into the air chamber 3 from the air valve 6. In such a state, vulcanization is performed by heating the heating die. At the subsequent sealant filling step, the sealant 8 is supplied from the sealant filling holes 4 1 , ..., 4 1 to fill the sealant chamber 7. At this time, by expanding the air chamber 3 by supply of an air from the air valve 6 prior to the filling of the sealant 8, the bulkhead 5 is brought in close-contact with the sealant chamber side peripheral wall 4o to perfectly discharge the air in the sealant chamber 7. In such a state, the filling of the sealant 8 is started. The starting of the filling of the sealant 8 in the state that the air in the sealant chamber 7 is perfectly discharged, it is possible to effectively prevent the entrapment of the air in the sealant 8 and hence to fill the sealant chamber 7 with only the sealant 8. Additionally, since the air is supplied into the air chamber 3 using the air valve 6, it is possible to eliminate the need of provision of an air filling hole in the air chamber side peripheral wall 4i. A raw rubber sheet 19 is stuck on the peripheral wall 4 so as to cover the sealant filling holes 4 1 , ..., 4 1 at the raw rubber sheet sticking step, and then the sealant filling holes 4 1 , ..., 4 1 are blocked by local vulcanization of the vicinity of the raw rubber sheet 19 at the second vulcanization step, to finish the tube 2. Since the sealant filling holes 4 1 , ..., 4 1 are blocked using the raw rubber sheet 19 being the same material as that of the tube material 2', it is possible to improve the strength of the blocking portion, and hence to effectively prevent the leakage of the sealant 8. Thus, the finished tube 2 is inspected at the inspection step, to complete the manufacturing steps. Next, the composition of the sealant 8 will be described. The sealant contains synthetic fibers and cellulose fiber in a solvent. As the solvent, there may be used any organic solvent or any mixed solution of an organic polymer, which has an effect of depressing a freezing point and an effect of imparting a suitable viscosity to the sealant. Specific examples of the solvent include a liquid organic polymer such as liquid polyethylene glycol, liquid polypropylene glycol or liquid polybutadiene; a solution of a solid polymer dissolved in an organic solvent such as a solution of methyl vinyl ether-maleic anhydride copolymer dissolved in ethylene glycol; a solution of vinyl acetate-maleic anhydride copolymer dissolved in ethanolamine; a solution of a solid organic polymer dissolved in organic solvent/water such as a solution of methyl hydroxypropyl cellulose dissolved in ethylene glycol/water; an emulsion of a solid organic polymer such as a mixed emulsion of polyvinyl acetate, ethylene glycol and water; and a mixed solution of two or more of the above solutions. As the synthetic fibers contained in the solvent, there may be used short-fibers of polyester, nylon, Vinylon, or acrylic resin. The length of the short-fibers is preferably in a range of from 1 to 7 mm. As the cellulose fibers contained in the solvent, there may be used a natural cellulose such as dissolved pulp, cotton or linen; a regenerated cellulose such as rayon or cellophane; and an oxide thereof. In this embodiment, cotton is used as cellulose fibers. The amount of the fiber component contained in the solvent, that is, the total weight of the synthetic fibers and the cellulose fibers contained in the solvent is set to be in a range of 0.5 to 10% on the basis of the weight of the solvent. And, the content of the synthetic fibers is set to be in a range of from 75 to 90% and the content of the cellulose fibers is set to be in a range of from 25 to 10%. The synthetic fibers are substantially straightened in shape and are excellent in flowability, and thereby they function to be readily inserted in a puncture hole opened in the tube 2 and to block it by a force of the tube 2 applied to contract the puncture hole. On the other hand, the cellulose fibers are softer than the synthetic fibers, and thereby function to be entangled with the synthetic fibers. Accordingly, in the case where the puncture hole is large and the force of the tube 2 applied to contract the puncture hole is small, the cellulose fibers are entangled with the synthetic fibers, to increase the sliding resistance of the entangled fibers with the puncture hole, thereby blocking the puncture hole. In this embodiment, since the sealant 8 is filled in the sealant chamber 7 having a capacity significantly smaller than that of the air chamber 3, the separation of the synthetic fibers from the solvent substantially exert no adverse effect on the characteristics of the sealant even when the sealant is applied with a centrifugal force due to the rotation of the wheel. Accordingly, the content of the cellulose fibers can be selected at such a minimum value as to block a large puncture hole (that is, in a range of 10 to 25% on the basis of the weight of the total fibers), to thereby reduce the cost. Namely, when the ratio of the cellulose fibers is less than 10%, the sealing effect becomes smaller. On the other hand, when the content of the cellulose fibers is more than 25%, the cost is increased, and further, since the flowability of the synthetic fibers is obstructed, the time required for sealing a puncture hole is made longer. Additionally, in this embodiment, since cellulose fibers lower in cost than a fine crystal powder of cellulose are used, the cost can be reduced. The puncture preventive sealant is capable of reducing the content of cellulose fibers for suppressing the cost of the sealant while keeping a high sealing performance due to the cellulose fibers. A sealant 8, which is filled in a sealant chamber 7 defined in a tube 2 adjacently to an air chamber 3, contains synthetic fibers and cellulose fibers in a solvent. The content of the synthetic fibers is in a range of from 75 to 90 wt% and the content of the cellulose fiber is in a range of from 25 to 10 wt%. Since the sealant 8 is filled in the sealant chamber 7 having a capacity significantly smaller than that of the air chamber 3, the separation of the synthetic fibers due to a centrifugal force substantially exert no adverse effect on the characteristics of the sealant, and accordingly, the content of the cellulose fibers can be set at such a minimum value as to block a large puncture hole. As a result, it is possible to reduce the cost by reducing the content of the cellulose fibers.

Claims: A puncture preventive sealant filled in a sealant chamber (7) defined in a tube (2) adjacently to an air chamber (3), said sealant comprising a fiber component contained in a solvent, wherein said fiber component comprises synthetic fibers and cellulose fibers which are mixed in such a mixing ratio that the weight-content of said cellulose fibers is smaller than that of said synthetic fibers. A puncture preventive sealant according to claim 1, wherein the content of said synthetic fibers is in a range of from 75 to 90 wt%, and the content of said cellulose fibers is in a range of from 25 to 10 wt%.

Inventors: TANAKA AKIKO, YAMAGIWA TOSHIO, TANAKA, AKIKO, YAMAGIWA, TOSHIO
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1997
Main classification: B60C17
IPC codes: B60C19, B29C73, C09K3, C08L1, B60C5, B29L23, B29L30