Reinforcing hose

Abstract: A reinforced hose, comprising an inner tuber rubber layer (1), a cover rubber layer (5) at least two reinforcing thread layers including an upper thread layer (4) and a lower thread layer (2), and disposed between the inner tube rubber layer (1) and the cover rubber layer (5), and at least the lower thread layer (2) including a polyester thread having the following physical properties: a tensile strength of 8 grams or more per a unit denier, an elongation of (10 ± 1.5) %, and a loaded elongation of (2.7 ± 1.0) % per a unit denier under 3-grams load. With this construction, the reinforced hose satisfies the fatigue resistance and the volume expansion simultaneously.

Description: The present invention relates to a reinforced hose which is used for a passage of a pressurized fluid, e.g., a hydraulic hose, or the like, and in which a reinforcing thread layer is braided at the intermediate portion of the rubber layer. There is known a hose which is used for a passage of a pressurized fluid, e.g., a hydraulic hose, or the like. The hose is required to have such a strength that it can withstand a high pressure. In many cases, since the hose can hardly withstand the high pressure adequately only with the hose which comprises rubber, resin, or the like, the hose usually suffers from an insufficiency in high pressure strength. Accordingly, a hose having a reinforcing thread layer at an intermediate portion of the rubber layer has been used in general. A hose comprising an inner tube ("core") and a reinforcement member comprising one or more layers consisting of fibrous polymeric stands is, for example, known from the document GB-A-1,171,933. The reinforcing thread layer is usually formed of braided reinforcing threads. Moreover, a hose having a single reinforcing thread layer cannot withstand the high pressure satisfactorily in some applications. When such is the case, a hose having a plurality of reinforcing thread layers has been used widely, as also in the above-referenced prior art. As the material of the thread constituting the reinforcing thread layer, there have been Vinylon R (a trademark of polyvinyl alcohol in Japan), polyester, rayon, aramid fiber, and the like. These thread materials are used depending on specific applications and at the same time making the best use of their characteristics. The reinforced hoses using the aforementioned thread materials have different characteristics, respectively. Table 1 below summarizes the difference in the characteristics, e.g., the fatigue resistance and the volume expansion. Here, the fatigue resistance means the durability of the reinforced hoses when they are repeatedly flexed at a high temperature while they are repeatedly subjected to a high pressure. The volume expansion means the variation of the inner volume of the hoses when a highly pressurized fluid is supplied to them, and it is usually preferable that the hoses exhibit a lower value of the volume expansion. Reinforcing Thread Material Fatigue Resistance Volume Expansion Vinylon R Satisfactory Very Small Polyester Excellent Small Rayon Satisfactory Small Aramid Fiber Slightly Poor Very Small As can be summarized in Table 1, there has been no reinforcing thread which satisfies both of the characteristics, i.e., the excellent fatigue resistance and the low value of the volume expansion, simultaneously, and the characteristics are believed to be contradictory phenomena. Therefore, in the reinforcing hose having a plurality of the reinforcing thread layers, the thread materials of the lower thread layer and the upper thread layer are varied with each other in order to reconcile the characteristics. However, such a construction has not satisfactory effected the reconciliation fully yet. The present invention has been developed in view of the above circumstances. It is therefore an object of the present invention to simultaneously satisfy the characteristic of an excellent fatigue resistance and the characteristic of a low value of the volume expansion in the reinforced hose. The present inventors made an extensive research and development on the relationships between the various physical properties of the reinforcing threads and the fatigue resistance as well as the volume expansion of the reinforced hose. As a result, they discovered that a reinforcing thread made from a polyester thread of a specific kind satisfies the fatigue resistance and the volume expansion simultaneously. Further, they revealed that it is advantageous to form at least a lower thread layer of a plurality of reinforcing thread layers, preferably an upper thread layer thereof as well, with the polyester thread in order to further improve the hose's characteristics, and that it is effective to braid at least the lower thread layer with the polyester thread under predetermined braiding conditions in order to furthermore enhance the hose's characteristics. Furthermore, they verified that the lower thread layer formed of the polyester thread so conforms to an upper thread layer formed of polyvinyl alcohol thread that the resulting reinforced hose best satisfies the characteristic of an excellent fatigue resistance and the characteristic of a low value of the volume expansion simultaneously. The present inventors thus completed a reinforced hose according to the present invention. The present reinforced hose comprises: an inner tube rubber layer 1; a cover rubber layer 5; and at least two reinforcing thread layers including an upper thread layer 4 and a lower thread layer 2, and disposed between said inner rubber layer 1 and said cover rubber layer 5; characterized in that at least said lower thread layer 2 includes a polyester thread having the following physical properties: a tensile strength of 8 gram or more per a unit denier; an elongation of (10 ± 1.5)%; and a loaded elongation of (2.7 ± 1.0)% per unit denier under: 3-gram load. In the present reinforced hose, the polyester thread constituting at least the lower thread layer of the reinforcing thread layers is adapted for having a tensile strength of 8 gram or more per unit denier. When the tensile strength per unit denier is less than 8 gram, no sufficient burst strength can be given to the resulting reinforced hose. Further, the polyester thread is adapted for having an elongation of (10 ± 1.5)%. When the elongation is less than 8.5%, no satisfactory fatigue resistance can be given to the resulting reinforced hose. On the other hand, when the elongation is more than 11.5%, the other physical properties of the polyester thread, e.g., the tensile strength per unit denier and the loaded elongation per unit denier under 3-gram load are adversely affected. For instance, the tensile strength of the polyester thread per unit denier becomes less than 8 gram, and accordingly no sufficient burst strength can be given to the resulting reinforced hose. As described below, the loaded elongation of the polyester thread per unit denier under 3-gram load becomes more than 3.7%, the resulting reinforced hose comes to exhibit a larger volume expansion. Furthermore, the polyester thread is adapted for having the loaded elongation of (2.7 ± 1.0) % per unit denier under 3-gram load. When the loaded elongation per unit denier under 3-gram load is more than 3.7%, the resulting reinforced hose comes to exhibit a larger volume expansion. On the other hand, when the loaded elongation per unit denier under 3-gram load is less than 1.7%, the other physical properties of the polyester thread, e.g., the tensile strength per unit denier, the elongation, and the like, are adversely affected. For instance, the tensile strength of the polyester thread per unit denier becomes less than 8 gram, and accordingly no sufficient burst strength can be given to the resulting reinforced hose. If theelongation of the polyester thread becomes less than 8.5%, no satisfactory fatigue resistance can be given to the resulting reinforced hose. In the present reinforced hose, the polyester thread constituting at least the lower thread layer of the reinforcing thread layers needs to satisfy the physical properties requirement, because the characteristics of the reinforced hose depend greatly on the physical properties of the reinforcing thread constituting the lowermost thread layer of the reinforcing thread layers. The polyester thread satisfying the aforementioned physical properties will be hereinafter referred to as the reinforced PE thread. Of course, the other reinforcing thread layers, e.g., the upper thread layer, can be made of the reinforced PE thread as described below. If such is the case, the present reinforced hose comes to have exceptionally good performance accordingly. Moreover, in the present reinforced hose, it is preferred that at least the lower thread layer is braided with the reinforced PE thread under a braiding condition selected from the following 4 braiding conditions: (a) Two (2) continuous strands of said reinforced PE thread are supplied from 20 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 2S-20C braiding condition), (b) two (2) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine a 2S-24C braiding condition), (c) three (3) continuous strands of said polyester thread are supplied from 20 carriers or cheeses disposed circularly on a braiding machine a 3S-20C braiding condition); and (d) three (3) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine a 3S-24C braiding condition). Here, it is particularly preferred to form the lower thread layer with the reinforced PE thread under one of the latter three braiding conditions, e.g., (b) the 2S-24C braiding condition, (c) the 3S-20C braiding condition, and (d) the 3S-24C braiding condition. If such is the case, the resulting present reinforced hose comes to exhibit well balanced fatigue resistance and volume expansion. When the amount of the reinforced PE thread braided is less than the amounts resulting from these braiding conditions, the reinforced hose might sometimes be a bit unsatisfactory in the fatigue resistance, or the like. On the other hand, when the amount is more than the amounts resulting therefrom, the reinforcing thread layer comes to be irregular heavily so that the hose characteristics might be degraded because of the excess amount. Although the braiding condition for the upper thread layer is not specified in the present reinforced hose, it is preferred that the upper thread layer is also formed by braiding the reinforced PE thread under one of the aforementioned braiding conditions for the lower thread layer, e.g., the 2S-24C, 3S-20C and 3S-24C braiding conditions. If such is the case, the resulting present reinforced hose comes to have a further enhanced fatigue resistance. In addition, it is not required that the upper thread layer includes the reinforced PE thread. For example, the upper thread layer can include a polyvinyl alcohol thread, e.g., the Vinylon R thread. When the lower thread layer is formed by braiding the reinforced PE thread under one of the aforementioned 2S-24C, 3S-20C and 3S-24C braiding conditions and the upper thread layer includes a polyvinyl alcohol thread, the resulting reinforced hose comes to have the best balanced fatigue resistance and volume expansion. This results from the facts that the polyvinyl alcohol thread results in an extremely small volume expansion. Namely, in such a reinforced hose, the lower thread layer formed by braiding the reinforced PE thread ensures the fatigue resistance, it suppresses the volume expansion because the reinforced PE thread results in a less volume expansion than the conventional polyester threads do, and the upper thread layer formed by braiding the polyvinyl alcohol thread further suppresses the volume expansion. Thus, the resulting present reinforced hose comes to best satisfy the fatigue resistance and the volume expansion simultaneously. As having been described so far, the present reinforced hose comprises at least the lower thread layer which is formed by braiding the reinforced PE thread, and the reinforced PE thread has the following physical properties: a tensile strength of 8 gram or more per unit denier; an elongation of (10 ± 1.5) %; and a loaded elongation of (2.7 ± 1.0) % load per unit denier under 3-gram. With this construction, the present reinforced hose can be made into one which has the good fatigue resistance and the less volume expansion simultaneously. In particular, the present reinforced hose is superb in the fatigue resistance when it is repeatedly subjected to a high pressure and when it is repeatedly flexed at a high temperature, and accordingly it is remarkably improved in the durability. Moreover, the present reinforced hose varies the volume less when it is subjected to a high pressure, and consequently the present reinforced hose can convey the fluid pressure securely. Thus, the present reinforced hose satisfies the fatigue resistance and the volume resistance simultaneously. A more complete appreciation of the present invention and many of its advantages will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing and detailed specification, all of which forms a part of the disclosure: Figure 1 is a perspective view for illustrating the construction of a First Preferred Embodiment of the present reinforced hose. Having generally described the present invention, a further understanding can be obtained by reference to the specific preferred embodiments which are provided herein for purposes of illustration only and are not intended to limit the scope of the appended claims. First Preferred Embodiment In Figure 1, there is illustrated the First Preferred Embodiment of the present reinforced hose with an end-fitting crimped. The First Preferred Embodiment of the present reinforced hose is adapted to an automotive high pressure hose, and it comprises a tube rubber layer 1, i.e., the innermost layer, a lower thread layer 2 braided on the surface of the tube rubber layer 1, an intermediate rubber layer 3 covered on the surface of the lower thread layer 2, an upper thread layer 4 braided on the surface of the intermediate rubber layer 3, and the cover rubber layer 5 covered on the surface of the upper thread layer 4. Further, an end-fitting 6 is crimped at an end of the reinforced hose. The tube rubber layer 1 was formed of styrene-butadiene rubber (hereinafter simply referred to as "SBR"). The lower thread layer 2 was formed by braiding a 1,500-denier reinforced PE thread under the 2S-20C braiding condition. The reinforced PE thread had the following physical properties: a tensile strength of 9.0 gram per unit denier; an elongation of 10.0%; and a loaded elongation of 2.7% per unit denier under 3-gram load. The intermediate rubber layer 3 was formed of natural rubber (hereinafter simply referred to as "NR"). The upper thread layer 4 was formed by braiding a 1,200-denier Vinylon R thread under the 3S-24C braiding condition. The Vinylon R thread had the following physical properties: a tensile strength of 8.3 gram per unit denier; an elongation of 7.0%; and a loaded elongation of 2.5% per unit denier under 3-gram load. The cover rubber layer 5 was formed of chroroprene rubber (hereinafter simply referred to as "CR"). The thus constructed First Preferred Embodiment of the present reinforced hose was evaluated for the volume expansion, the fatigue resistance and the burst strength, and the results of the evaluations are set forth in Table 2 below. Here, the volume expansion test was carried out in accordance with JIS (Japanese Industrial Standards) No. 2,601. Namely the present reinforced hose was cut to a free length of 305 mm, it was subjected to a pressure of 103 bar (105 kgf/cm 2 ), and it was examined for the variation in the inner volume. The fatigue resistance test was carried out by repeatedly flexing the present reinforced hose at 100 °C while applying a pressure of 98,1 bar (100 kgf/cm 2 ) thereto, and the present reinforced hose was examined how many times it was flexed repeatedly until it was burst. The burst strength test was carried out in accordance with JIS No. 2,601. Namely the present reinforced hose was subjected to a hydraulic pressure which increased at a pressurizing speed of (1716,8 ± 686,7 bar) (1,750 ± 700 kgf/cm 2 ) per a minute, and the present reinforced hose was examined how much the hydraulic pressure it was subjected to when it was burst. Comparative Example No. 1 Comparative Example No. 1 of a reinforced hose was prepared. It had the same construction as that of the First Preferred Embodiment of the present reinforced hose except that the lower thread layer 2 was formed by braiding the 1,200-denier Vinylon R thread under the 2S-20C braiding condition. Comparative Example No. 1 was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 2 below. Comparative Example No. 2 Comparative Example No. 2 of a reinforced hose was prepared. It had the same construction as that of the First Preferred Embodiment of the present reinforced hose except that the lower thread layer 2 was formed by braiding a 1,500-denier polyester thread under the 2S-20C braiding condition, the upper thread layer 4 was formed by braiding the 1,500-denier polyester thread under the 3S-24C braiding condition, and the 1,500-denier polyester thread had the following physical properties: a tensile strength of 8.7 gram per unit denier; an elongation of 14.0%; and a loaded elongation of 4.0% per unit denier under 3-gram load. This polyester thread will be hereinafter simply referred to as a conventional PE thread. Comparative Example No. 2 was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 2 below. 1st Pref. Embodiment Comp. Ex. No. 1 Comp. Ex. No. 2 Lower Thread Layer Thread Material Reinforced PE Vinylon Conventional PE Tensile Strength (gram/D) 9.0 8.3 8.7 Elongation (%) 10.0 7.0 14.0 3 gram-Loaded Elongation (%) 2.7 2.5 4.0 Upper Thread Layer Thread Material Vinylon R Vinylon R Conventional PE Tensile Strength (gram/D) 8.3 8.3 8.7 Elongation (%) 7.0 7.0 14.0 3 gram-Loaded Elongation (%) 2.5 2.5 4.0 Volume Expansion (cm 3 ) 0.18 Good 0.16 Good 0.25 Fair Fatigue Resistance (times) 1-million or more 0.3-million 1-million Burst Strength (kgf/cm 2 ) [N/mm 2 ] 1,050 [102.97] Good 800 [78.45] Good 1,000 [98.07] Good It is understood from Table 2 above that Comparative Example No. 1 whose lower thread layer 2 was formed by braiding the Vinylon R thread had the inferior fatigue resistance of 0.3 million times, and that Comparative Example No. 2 whose lower thread layer 2 was formed by braiding the conventional PE thread had the enlarged volume expansion of 0.25 cm 3 which was fairly larger than 0.2 cm 3 . On the other hand, the First Preferred Embodiment of the present reinforced hose had satisfactory characteristics in both of fatigue resistance and volume expansion, and it had the optimum performance as a high pressure hose. It is apparent that this advantageous effect resulted from the construction that the lower thread layer 2 was formed by braiding the reinforced PE thread having the predetermined physical properties. Second Preferred Embodiment The construction of a Second Preferred Embodiment of the present reinforced hose was basically identical with that of the First Preferred Embodiment illustrated in Figure 1, and it will not be detailed herein except for the following features. Namely, in the Second Preferred Embodiment of the present reinforced hose, the tube rubber layer 1 was formed of ethylene-propylene terpolymer (hereinafter simply referred to as "EPDM"). The lower thread layer 2 was formed by braiding the 1,500-denier reinforced PE thread, which was used to braid the lower thread layer 2 of the First Preferred Embodiment, under the 2S-20C braiding condition. The upper thread layer 4 was formed by braiding the 1,500-denier reinforced PE thread under the 3S-24C braiding condition. The cover rubber layer 5 was formed of EPDM. The thus constructed Second Preferred Embodiment of the present reinforced hose was also evaluated for the volume expansion and the fatigue resistance in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are set forth in Table 3 below. Third Preferred Embodiment A Third Preferred Embodiment of the present reinforced hose was prepared. It had the same construction as that of the Second Preferred Embodiment except that the lower thread layer 2 was formed by braiding the 1,500-denier reinforced PE thread under the 2S-24C braiding condition. The Third Preferred Embodiment was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 3 below. Fourth Preferred Embodiment A Fourth Preferred Embodiment of the present reinforced hose was prepared. It had the same construction as that of the Second Preferred Embodiment except that the lower thread layer 2.was formed by braiding the 1,500-denier reinforced PE thread under the 3S-20C braiding condition. The Fourth Preferred Embodiment was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment section, and the results of the evaluations are also set forth in Table 3 below. Fifth Preferred Embodiment A Fifth Preferred Embodiment of the present reinforced hose was prepared. It had the same construction as that of the Second Preferred Embodiment of the present reinforced hose except that the lower thread layer 2 was formed by braiding the 1,500-denier reinforced PE thread under the 3S-24C braiding condition. The Fifth Preferred Embodiment was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 3 below. Comparative Example No. 3 Comparative Example No. 3 of a reinforced hose was prepared. It had the same construction as that of the Second Preferred Embodiment of the present reinforced hose except that the lower thread layer 2 is formed by braiding the 1,500-denier conventional PE thread under the 2S-20C braiding condition, and that the upper thread layer 4 is formed by braiding the 1,500-denier conventional PE thread under the 3S-24C braiding condition. Comparative Example No. 3 was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 3 below. Comparative Example No. 4 Comparative Example No. 4 of a reinforced hose was prepared. It had the same construction as that of the Second Preferred Embodiment of the present reinforced hose except that the lower thread layer 2 was formed by braiding the 1,200denier vinylon thread under the 2S-20C braiding condition, and that the upper thread layer 4 was formed by braiding the 1,200-denier Vinylon R thread under the 3S-24C braiding condition. Comparative Example No. 4 was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 3 below. Lower Thread Layer Upper Thread Layer Fatigue Resistance (times) Volume Expansion (cm 3 ) Thread Material Braiding Condition Thread Material Braiding Condition 2nd Pref. Embodiment Reinforced PE 2S-20C Reinforced PE 3S-24C 0.6-million 0.21 3rd Pref. Embodiment Reinforced PE 2S-24C Reinforced PE 3S-24C 1.5-million 0.20 4th Pref. Embodiment Reinforced PE 3S-20C Reinforced PE 3S-24C 4.5-million 0.20 5th Pref. Embodiment Reinforced PE 3S-24C Reinforced PE 3S-24C 5.4-million 0.18 Comp. Ex. No. 3 Conventional PE 2S-20C Conventional PE 3S-24C 0.4-million 0.25 Comp. Ex. No. 4 Vinylon R 2S-20C Vinylon R 3S-24C 0.25-million 0.16 It is understood from Table 3 above that only the Second through Fifth Preferred Embodiments had the satisfactory characteristics in both of fatigue resistance and volume expansion, and that they had the optimum performance as a high pressure hose. In particular, the Third through Fifth Preferred Embodiments were exceptionally good in the fatigue resistance. It is apparent that this advantageous effect resulted from the construction that the lower thread layer 2 was formed by braiding the reinforced PE thread having the predetermined physical properties under one of the predetermined braiding conditions, and that the upper thread layer 4 was also formed by braiding the reinforced PE thread. Sixth Preferred Embodiment The construction of a Sixth Preferred Embodiment of the present reinforced hose was basically identical with that of the First Preferred Embodiment illustrated in Figure 1, and it will not be detailed herein except for the following features. Namely, in the Sixth Preferred Embodiment of the present reinforced hose, the tube rubber layer 1 was formed of EPDM. The cover rubber layer 5 was formed of EPDM. The thus constructed Sixth Preferred Embodiment of the present reinforced hose was also evaluated for the volume expansion and the fatigue resistance in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are set forth in Table 4 below. Seventh Preferred Embodiment A Seventh Preferred Embodiment of the present reinforced hose was prepared. It had the same construction as that of the Sixth Preferred Embodiment except that the lower thread layer 2 was formed by braiding the 1,500-denier reinforced PE thread under the 2S-24C braiding condition. The Seventh Preferred Embodiment was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 4 below. Eighth Preferred Embodiment An Eighth Preferred Embodiment of the present reinforced hose was prepared. It had the same construction as that of the Sixth Preferred Embodiment except that the lower thread layer 2 was formed by braiding the 1,500-denier reinforced PE thread under the 3S-20C braiding condition. The Eighth Preferred Embodiment was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 4 below. Ninth Preferred Embodiment A Ninth Preferred Embodiment of the present reinforced hose was prepared. It had the same construction as that of the Sixth Preferred Embodiment except that the lower thread layer 2 was formed by braiding the 1,500-denier reinforced PE thread under the 3S-24C braiding condition. The Ninth Preferred Embodiment was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 4 below. Comparative Example No. 5 Comparative Example No. 5 of a reinforced hose was prepared. It had the same construction as that of the Sixth Preferred Embodiment of the present reinforced hose except that the lower thread layer 2 was formed by braiding the 1,500-denier conventional PE thread under the 2S-20C braiding condition. Comparative Example No. 5 was also evaluated for the characteristics in the same manner described in the above "First Preferred Embodiment" section, and the results of the evaluations are also set forth in Table 4 below together with those of aforementioned Comparative Example No. 4 for reference. Lower Thread Layer Upper Thread Layer Fatigue Resistance (times) Volume Expansion (cm 3 ) Thread Material Braiding Condition Thread Material Braiding Condition 6th Pref. Embodiment Reinforced PE 2S-20C Vinylon R 3S-24C 2.5-million 0.18 7th Pref. Embodiment Reinforced PE 2S-24C Vinylon R 3S-24C 4.0-million 0.17 8th Pref. Embodiment Reinforced PE 3S-20C Vinylon R 3S-24C 6.0-million 0.17 9th Pref. Embodiment Reinforced PE 3S-24C Vinylon R 3S-24C 7.0-million 0.16 Comp. Ex. No. 5 Conventional PE 2S-20C Vinylon R 3S-24C 1.0-million 0.19 Comp. Ex. No. 4 Vinylon R 2S-20C Vinylon R 3S-24C 0.25-million 0.16 It is understood from Table 4 above that only the Sixth through Ninth Preferred Embodiments had the exceptionally good characteristics in both of fatigue resistance and volume expansion, and that they had the best performance as a high pressure hose. It is apparent that this advantageous effect resulted from the construction that the lower thread layer 2 was formed by braiding the reinforced PE thread having the predetermined physical properties under one of the predetermined braiding conditions, and that the upper thread layer 4 was formed by braiding the Vinylon R thread. In addition, in the First through Ninth Preferred Embodiments described above, the tube rubber layer 1, the intermediate rubber layer 3 and the cover rubber layer 5 were formed of either SBR (Styrene-Butadiene Rubber) or EPDM (Ethylene-Propylene terpolymer), NR (natural rubber) and either CR (chloroprene rubber) or EPDM (Ethylene-Propylene terpolymer), respectively. However, the tube rubber layer 1, the intermediate rubber layer 3 and the cover rubber layer 5 can be formed of SBR (Styrene-Butadiene Rubber), NR (natural rubber) and EPDM (Ethylene-Propylene terpolymer), respectively.

Claims: A reinforced hose comprising an inner tube rubber layer (1), a cover rubber layer (5) and at least two reinforcing thread layers including an upper thread layer (4) and a lower thread layer (2) and disposed between said inner rubber layer (1) and said cover rubber layer (5), characterized in that at least said lower thread layer (2) includes a polyester thread having the following physical properties: a tensile strength of 8 gram or more per unit denier; an elongation of (10 ± 1.5) %; and a loaded elongation of (2.7 ± 1.0) % per unit denier under 3-gram load. The reinforced hose according to claim 1, wherein said upper thread layer (4) and said lower thread layer (2) include said polyester thread. The reinforced hose according to claims 1 and 2, wherein at least said lower thread layer (2) is formed by braiding said polyester thread under one of the following conditions: Two (2) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 2S-24C braiding condition); three (3) continuous strands of said polyester thread are supplied from 20 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 3S-20C braiding condition); and three (3) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 3S-24C braiding condition). The reinforced hose according to any of the claims 1 to 3, wherein said upper thread layer (4) is further formed by braiding said polyester thread under one of the following braiding conditions: Two (2) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 2S-24C braiding condition); three (3) continuous strands of said polyester thread are supplied from 20 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 3S-20C braiding condition); and three (3) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 3S-24C braiding condition). The reinforced hose according to any of the claims 1 to 4, wherein said inner tube rubber layer (1) includes SBR, and said cover rubber layer (5) includes CR. The reinforced hose according to any of the claims 1 to 4, wherein said inner tube rubber layer (1) includes SBR, and said cover rubber layer (5) includes EPDM. The reinforced hose according to any of the claims 1 to 4, wherein said inner tube rubber layer (1) and said cover rubber layer (5) include EPDM. The reinforced hose according to any of the claims 1 to 7, further comprising an intermediate rubber layer (3) disposed between said upper thread layer (4) and said lower thread layer (2). The reinforced hose according to claim 8, wherein said intermediate rubber layer (3) includes natural rubber (NR). The reinforced hose according to any of the claims 1 to 9 wherein said upper thread layer (4) is formed by braiding a polyvinyl alcohol thread. The reinforced hose according to claim 10, wherein at least said lower thread layer (2) is formed by braiding said polyester thread under one of the following conditions: Two (2) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 2S-24C braiding condition); three (3) continuous strands of said polyester thread are supplied from 20 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 3S-20C braiding condition); and three (3) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 3S-24C braiding condition). The reinforced hose according to claim 10 or claim 11, wherein said upper thread layer (4) is formed by braiding said polyvinyl alcohol thread under one of the following braiding conditions: Two (2) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 2S-24C braiding condition); three (3) continuous strands of said polyester thread are supplied from 20 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 3S-20C braiding condition); and three (3) continuous strands of said polyester thread are supplied from 24 carriers or cheeses disposed circularly on a braiding machine (hereinafter simply expressed as a 3S-24C braiding condition). The reinforced hose according to any of the claims 10 to 12, wherein said inner tube rubber layer (1) includes SBR, and said cover rubber layer (5) includes CR. The reinforced hose according to any of the claims 10 to 12, wherein said inner tube rubber layer (1) includes SBR, and said cover rubber layer (5) includes EPDM. The reinforced hose according to any of claims 10 to 14, wherein said inner tube rubber layer (1) and said cover rubber layer (5) include EPDM. The reinforced hose according to any of claims 10 to 15, further comprising an intermediate rubber layer (3) disposed between said upper thread layer (4) and said lower thread layer (2). The reinforced hose according to claim 16, wherein said intermediate rubber layer (3) includes natural rubber (NR).

Inventors: IKEDA FUMIO, KITAOKA KATSUSHI, MIZUTANI SATOSHI, IKEDA, FUMIO, KITAOKA, KATSUSHI, MIZUTANI, SATOSHI, Ikeda, Fumio, c/o Toyoda Gosei Technical Center, Kitaoka, Katsushi, c/o Toyoda Gosei Techn. Center, Mizutani, Satoshi, c/o Toyoda Gosei Techn. Center
Applicants: TOYODA GOSEI KK, TOYODA GOSEI CO., LTD.
Application year: 1993
Main classification: F16L11
IPC codes: F16L11