RESIN HOSE MANUFACTURING METHOD

Abstract: A resin hose manufacturing method which is capable of omitting a burr removing finishing step by preventing the leakage of a material, which causes burrs to occur on a final product, during the blow molding of a hose body and the injection molding of a joint member, which molding methods are used to omit a polishing process for obtaining a proper shape of the inner surface of a joint member at which a resin hose is connected to a mate tube body, and improving the dimensional accuracy of the product, and which is also capable of preventing the occurrence of chipping during the injection molding operation. To attain this object, in the present invention, a thermoplastic resin is blow molded to form a hose body (12), and this hose body (12) is then set in an injection mold (20) which includes an inner mold member (24) and an outer mold member (22). A material is then injected into a molding cavity (26) adjacent to an opening portion of the hose body (12) with the inner mold member (24) fitted closely and liquid-tightly in the opening portion of the hose body (12) via seal means (28, 30, 40, 42), to mold a joint member of the resin hose with respect to the mate tube body and combine the joint member with the hose body (12) unitarily.

Description: The present invention relates to a process for producing a resin hose according to the preamble of claim 1. Such a process is optimum for producing air duct hoses, filler hoses or the like for automobiles. In a field of hoses, for instance, air duct hoses, filler hoses or the like for automobiles, it has been tried to replace rubber hoses with hoses made of resin recently. Some of the rein hoses have been put into actual applications. The resin hoses have advantages in that they have light specific gravities compared to those of the rubber hoses, they can be lightweighted, they can make an integrally formed product comprising soft portions and hard portions, and they allow a high degree of freedom in designing the configurations or the like. In the resin hoses, hard resinous materials are used for portions which require hardness, and soft resinous materials are used for portions which require softness. When forming the hoses, the hard and the soft portions can be formed integrally with the two materials, e.g., the hard and the soft resinous materials. However, in the rubber hoses, it is difficult to constitute the hard and the soft portions with an integrally formed product. Usually, in the rubber hoses, metallic pipes make the portions which require hardness, rubber hoses make the other portions which require softness and flexibility, and they are assembled together. In the resin hoses, the soft and the hard portions can be made with the integrally formed product. Hence, the number of the component parts can be decreased, and the production costs can be reduced. In the resin hoses, the phrase, "the high degree of freedom in designing the configurations or the like," means that the hose are limited less configurationally because they fully resist negative pressures. On the other hand, in the rubber hoses, when the rubber hoses are formed in a flattened shape in cross-section at a portion thereof and they are subjected to negative pressure, they are likely to deform at the portion. Consequently, compared to the resin hoses, the rubber hoses allow a lower degree of freedom in designing the configurations or the like. By the way, in the resin hoses, blow molding processes are employed preferably as a process for forming the resin hoses. In the blow molding processes, a tubular or bag-shaped parison is usually expanded by blowing air thereinto, and it is adhered to inner surfaces of a forming mold, thereby being formed into a predetermined configuration. Accordingly, the outer surfaces of the formed products can be formed into predetermined shapes accurately with the forming mold. However, the inner surfaces of the formed products are not formed with the mold surfaces, but they are formed in the free states. Hence, the inner surfaces are inevitably inferior in terms of the configurations and the dimensional accuracy. However, the hoses are usually connected by fitting a mating member, e.g., a metallic pipe or the like, into the inside of them at the end which usually makes the connecting portion, and at the same time it is necessary to securely provide a sealing property at the connecting portion. If such is the case, when the inner surfaces of the connecting portion of the hoses are inferior in terms of the configurations and the dimensional accuracy, for example, when the hoses have fluctuating inside diameter dimensions or thickness, uneven thickness and convexities and concavities on the inner surfaces, the sealing property cannot be fully secured at the connecting portion between the hoses and the mating member. Therefore, in the resin hoses made by the above-described blow molding processes, the inner surfaces of the connecting portion are finished to predetermined shapes and dimensions by grinding. However, when the grinding is carried out onto the hoses, not only the number of the hose production processes increases, but also there remain ground chips at the processed portions and the peripheries. Consequently, it is necessary to employ a washing process for removing the ground chips, thereby further increasing the number of the hose production processes and resulting in increasing production costs. Hence, the present inventors invented a process for producing a resin hose and proposed it in the prior patent application (JP-A-3-39,145). According to this process, a hose body is formed of a thermoplastic resin by blow molding, and thereafter a connecting portion to be connected to a mating member is formed and integrated with the hose body by injection molding while the hose body is set in a forming mold for injection molding. Figure 15 illustrates one of the preferred embodiments according to the JP-A-3-39 145. In the process illustrated in the drawing, a hose body 100 is first obtained by blow molding with a thermoplastic resin. The hose body 100 is then set in a forming mold 102 for injection molding. Thereafter, a material is injected into the cavity and cured therein, thereby forming a connector end 104 to be connected to a mating member and integrating it with the hose body 100. When blow molding the hose body, the inner surfaces are formed in the free states as aforementioned, namely they are formed without receiving any direct restrictions from the forming mold. Accordingly, the inner surfaces fluctuate dimensionally. Hence, as schematically illustrated in Figure 16, when the blow-molded hose body 100 is set with respect to the injection molding mold and an inner mold (e.g., a mandrel) 106 is fitted into the opening of the hose body 100, there might arise a clearance between the inner surface of the end opening or the neighboring portion of the hose body 100 and the inner mold 106. If such is the case, when the material is injected into the cavity formed between the inner mold 106 and an outer mold 108, there arises the problem in that the material leaks through the clearance and produces a flash 110. When the flash 110 is produced in a greater amount, the material is supplied insufficiently for the connector end 104 and the neighboring portion to be connected to the mating member, and there might arise fears for the failures such as the material shrinkage or the like. On the contrary, when the diameter of the inner surface of the opening of the hose body 100 is smaller than the outside diameter of the inner mold 106, it is difficult to insert the inner mold 106 into the opening of the hose body 100. Consequently, the operational efficiency deteriorates. A generic process for producing a resin hose is known from DE-A-1 108 421. This reference shows that a hose body is placed in an injection mold including an inner mold and an outer mold. The inner mold is adhered to an opening portion of the hose body and is formed with a sliding member which is slidable in an axial direction with respect to a body of the inner mold. Moreover, the sliding member is provided with a portion whose outside diameter is larger than that of other portions thereof. After having placed the hose body in the injection mold, an elastic member is compressed between the sliding member and the body of the inner mold, thereby expanding towards the outside, coming into contact with the opening portion and sealing a forming cavity. Subsequently, a material is injected into the forming cavity formed neighboring around the opening portion while the adhered state of the inner mold is maintained. Thereby, a connecting portion is formed to be connected to a mating member in the form of a cap. GB-A-1 595 692 relates to a coupling of pipes made of glazed or unglazed clay, pitch-fiber, asbestos cement or concrete. A frusto-conical rubber seal covers the frusto-conical surface of a sliding member. This frusto-conical rubber seal is held in position by a lip trapped in a circumferential groove defined between two fixedly arranged members. The sealing is thus established between non-movable elements which are pressed by the sliding member. Moreover, the rubber seal is designed to abut against the side opening of the pipe. A method for producing a resin tube is known from FR-A-1 300 212. Just as according to DE-A-1 108 421, an elastic member is axially compressed without being moved in the axial direction so as to extend in the radial direction for abutting against an inner surface of a tube body in order to seal a forming cavity. It is an object of the present invention to further develop the process according to the preamble of claim 1 such that a sealing of the forming cavity can easily and reliably be performed. This object is achieved by the features of claim 1. Advantageous further developments are set out in the dependent claims. According to the present invention, it is possible to produce the advantageous effects similar to those produced by the method disclosed in JP-A-3-39 145. Namely, according to the present invention, simultaneously with the forming of the hose, the longitudinal end or the like, i.e., the connecting portion to be connected to the mating member, can be formed into predetermined configurations and dimensions. Accordingly, it is not necessary to carry out the grinding onto the inner surface of the connecting portion after forming the hose, grinding which has been required conventionally. Hence, not only it is possible to obviate the grinding process, but also it is unnecessary to carry out the washing process for removing the remaining ground chips. Thus, the overall number of the processes is decreased, and consequently the production costs can be reduced. In addition, when the connecting portion of the hose is formed by injection molding in accordance with the present invention, the inner surface of the connecting portion can be formed with higher accuracy than the case where the inner surface of the connecting portion is ground after forming the hose. Accordingly, the sealing property is improved in terms of the reliability when the metallic pipe or the like, i.e., the mating member, is connected to the connecting portion. Further, in accordance with the present invention, there arises an advantage in that the hose body and the connecting portion can be constituted with a hard resinous material and a soft resinous material, respectively. For instance, in air duct hoses for automobiles, since negative pressures are applied to the hoses during service, the hose bodies deform when they are formed of soft materials, and thereby the air sucked by way of the hoses decreases in amount to cause the incomplete combustion in the engines. If the whole hoses are formed of hard materials in order to prevent this failure, the sealing property is damaged when the mating member is connected to the connecting portion. On the other hand, when the hose body is formed of a hard resinous material and the connecting portion is formed of a soft resinous material in accordance with the present invention, the mechanical strengths, such as the negative pressure resistance or the like, can be given to the hose, and the sealing property can be provided satisfactorily at the connecting portion. Of course, it is possible to partially form a bellows portion in the hose body, and it is further possible to constitute this bellows portion with a soft resin so as to properly give flexibility to the hose. In the present invention, the inner mold and the opening portion of the hose body, for example, at a predetermined portion in the inner surface of the opening portion, are sealed in a fluid-proof manner. Consequently, there scarcely occurs the flashes resulting from the material leakage when injecting the fluidic material into the forming cavity neighboring around the opening portion. Therefore, it is not necessary to carry out the deflashing process for removing the flashes thereafter. Further, there scarcely arises the problem of the ground chips remaining around the processed portions which results from the deflashing process. Furthermore, it is not needed to carry out the washing process for removing the ground chips. Moreover, since there hardly arises the flashes, the material can be fully filled into the cavity in a prescribed amount. Hence, there occurs no failure, such as the material shrinkage or the like in the connecting portion. In accordance with the present invention, when fitting the inner mold into the opening portion of the hose body, the portion of larger outside diameter is brought into contact with the inner surface of the opening portion by pushing the sliding member, and thereby the cavity is sealed securely at an end. Under the circumstance, the connecting portion can be formed by injection molding. As a result, there scarcely occurs the problem that the fluidic material leaks out to produce the flashes during the injection molding of the connecting member. Hence, it is not necessary to carry out the deflashing process thereafter. Further, it is not needed to carry out the washing process for removing the ground chips after the deflashing process. Furthermore, there occurs no failure, such as the material shrinkage or the like, in the connecting portion, failure which results from the flashes produced in a large amount. In accordance with the present invention, a projection is formed on the inner mold side, and the projection is brought into contact with the diameter-increasing portion, disposed on the inner surface of the opening portion of the hose body, during the fitting of the inner mold into the opening portion of the hose body. With this arrangement, the cavity is sealed in a fluid-proof manner. Accordingly, the flashes can be inhibited from producing when the connecting portion is formed by injection molding under the circumstances. Further, it is possible to obtain the same advantageous effects described above, for example, it is possible to improve the insertability of the inner mold or the like. Figure 1 is an explanatory view on a comparative example for a process for producing a resin hose; Figure 2 is a cross-sectional view on a major portion of a resin hose produced by the process; Figure 3 is an explanatory view on a preferred embodiment according to the present invention; Figure 4 is an enlarged view on a major portion of Figure 3; Figure 5 is an explanatory view on a further preferred embodiment according to the present invention; Figure 6 is an explanatory view on a still further preferred embodiment according to the present invention; Figure 7 is an explanatory view on a further preferred embodiment according to the present invention; Figure 8 is an explanatory view on a still further preferred embodiment according to the present invention; Figure 9 is an explanatory view on a moreover preferred embodiment according to the present invention; Figure 10 is an explanatory view on a still moreover preferred embodiment according to the present invention; Figure 11 is an explanatory view on a yet further preferred embodiment according to the present invention; Figure 12 is an explanatory view on a yet still further preferred embodiment according to the present invention; Figure 13 is an explanatory view on a yet moreover preferred embodiment according to the present invention; Figure 14 is an explanatory view on a yet still moreover preferred embodiment according to the present invention; Figure 15 is an explanatory view of a process for producing a resin hose known from prior art; and Figure 16 is an explanatory view on the problems to be solved by the present invention. Preferred embodiments according to the present invention will be hereinafter described with reference to the drawings. In Figure 2, a resin hose which can be favorably used for an air duct hose for automobile is designated at 10. A hose body which is formed of a hard resinous material by blow molding is designated at 12, it has a large-diameter portion 16 at a longitudinal end, and connecting concave is formed on the inner surface of the large-diameter portion 16. Further, at the root on the inner surface of the base of the large-diameter portion 16, there is formed a diameter-increasing portion 17 which enlarges diametrically toward the opening end. In addition, it is possible to constitute the hose body 12 with a hard resinous material at the ends only. A connecting end which is to be connected to a mating member and which is integrated with the hose body 12 by injection molding a soft resinous material is designated at 14. This connecting end 14 has a tubular connecting convex 18, and this connecting convex 18 is welded and bonded to the aforementioned connecting concave. In particular, as the hard resinous material for constituting the hose body 12, a polypropylene resin (e.g., "EC-9B" produced by MITSHUBISHI YUKA Co., Ltd.) having a Rockwell hardness of 94 (in "R" scale) can be exemplified. As the soft resinous material for constituting the connecting end 14, a polymer alloy containing a polypropylene resin and EPDM and having a Shore "A" hardness of 75 (e.g., "SANTOPLAIN 101-75" produced by NIHON MONSANTO Co., Ltd.) can be exemplified. Figure 1 illustrates a comparative example of a process according to the present invention along with a forming mold for injection molding the connecting end 14. This forming mold 20 has an outer mold 22 and an inner mold (e.g., mandrel) 24, and it further has a cavity 26 for forming the connecting end 14 therebetween. In the inner mold 24, a portion to be fitted into the end opening of the hose body 12 comprises a metallic core body 28 and a rubber layer 30 covering the outer peripheral surface of the core body 28. The core body 28 is joined to a main body 34 of the inner mold 24 with thread, and, with the thread joining force, an end 32 of the rubber layer 30 is pressed by the main body 34 and the core body 28. Into the core body 28, a bolt 36 having a large-diameter head is threaded, and thereby the other end 38 of the rubber layer 30 is pressed by the head of the bolt 36 and the core body 28. These ends are thus pressed, thereby sealing between the outer peripheral surface of the core body 28 and the rubber layer 30 in an air-tight or a fluid-proof manner. In the main body 34 and the core body 28 of the inner mold 24, there is formed a passage 40 for a fluid such as air, oil or the like. Further, in the core body 28, there is disposed a porous member 42 for introducing the fluid flowing in the passage 40 to the outer peripheral surface. In particular, the outside diameter of the rubber layer 30 is designed to be smaller by a predetermined dimension than the smallest inside diameter of the end opening among all of the hose bodies 12 obtained by the blow molding. In this comparative example of the hose production process, the hose body 12 is first formed of a hard thermoplastic resin (or a resin mainly containing a hard resin) by blow molding. Then, the blow-molded hose body 12 is set in the forming mold 20 for injection molding, and a front end of the inner mold 24, specifically speaking, the portion constituted with the core body 28 and the rubber layer 30 is fitted into the end opening of the hose body 12. At this moment, the inner mold 24 can be inserted into the hose body 12 with ease. This results from the arrangement that the outside diameter of the rubber layer 30 is designed in advance to be smaller than the inside diameter of the end of the hose body 12 obtained by blow molding. Then, the fluid, e.g., pressurized air, oil or the like, is supplied through a supply port 25. Accordingly, the rubber layer 30 covering the outer peripheral surface of the core body 28 is expanded by the pressure to increase the diameter. In this state, the aforementioned connecting end 14 can be formed by injecting a predetermined resin material into the cavity 26, and it can be simultaneously welded and bonded integrally to the hose body 12. According to this process, when the pressurized fluid is not supplied, the inner mold 24 can be inserted into the hose body 12 or removed therefrom with ease. Further, since the inner mold 24 can be securely adhered to the inner surface of the end opening of the hose body 12 by introducing the pressurized fluid, it is possible to inhibit the flashes, resulting from the material leakage through the cavity 26, from producing. Figure 3 illustrates a preferred embodiment according to the present invention. In this preferred embodiment, the inner mold 24 is formed into a sliding member 56 at the front end portion which includes the portions to be fitted into the opening portion of the hose body 12. This sliding member 56 is driven by a predetermined driving means (not shown in the drawing), such as a cylinder or the like, by way of a shaft 58, and thereby it is pushed out of a main body 60 of the inner mold 24 or it is retracted toward the main body 60. This sliding member 56 has a forming surface 62, which extends straight in the axial direction, and a swollen portion 64, which is disposed at an end of the forming surface 62. Its outer peripheral surface extending from the swollen portion 64 to the front end is formed into a tapered end 62. In this preferred embodiment of the hose production process, the hose body 12 is first formed of a hard thermoplastic resin (or a resin mainly containing a hard resin) by blow molding. Then, the blow-molded hose body 12 is set in the forming mold 20 for injection molding, and the front end portion of the inner mold 24, is fitted into the end opening portion of the hose body 12, starting at from the longitudinal end of the hose body 12. Namely, the sliding member 56 of the inner mold 24 is pushed out of the main body 60, thereby fitting the front end portion into the hose body 12. At this moment, the swollen portion 64, which is positioned at the base end of the tapered surface 66 of the sliding member 56, is brought into contact with the diameter-increasing portion 17 of the hose body 12 so as to press the same portion, thereby sealing an end of the cavity 26 in a fluid-proof manner. In this state, the aforementioned connecting end 14 can be formed by supplying a fluidized resin material into the cavity 26, and it can be simultaneously bonded integrally to the hose body 12. According to this process, it is possible to inhibit the flashes, resulting from the material leakage through the cavity 26, from producing during the forming of the connecting end 14. Therefore, it is not necessary to carry out the subsequent deflashing process and the washing process for removing the ground chips resulting from the deflashing. Thus, the hose connecting process is simplified, and the production costs are reduced. In addition, the reliability on the hose qualities is improved as well. In particular, in this preferred embodiment, as shown in Figure 4 which illustrates the major portions in an enlarged manner, the swollen portion 64 is formed in the sliding member 56, and thereby the outer peripheral surface of the front end portion is formed in the tapered surface 66. However, it is possible not to form the swollen portion like this, but it is possible to directly extend the tapered surface 66 out from an end of the forming surface 62. With this arrangement, it is possible to seal the forming cavity 26 at an end in a fluid-proof manner. Figure 6 illustrates a further preferred embodiment according to the present invention. In this preferred embodiment, the inner mold 24 is provided with a projection 68 which has an annular shape and a wedge-shaped cross-section. During the fitting of the inner mold 24 into the hose body 12, this projection 68 is pressed onto the diameter-increasing portion 17, and part of it is intruded thereinto. Thus, it is possible to seal the forming cavity 26 and to obtain the same advantageous effects as aforementioned. Figure 7 illustrates a further preferred embodiment according to the present invention. In this preferred embodiment, a hose body end 70 is designed to have the same diameter as the other portions of the hose body 12, and this hose body end 70 is disposed in a cavity 74 so as to form a predetermined clearance 72 around the outer peripheral surface thereof. While, the sliding member 56 of the inner mold 24 is provided with a tapered stepped portion 76, and the tapered stepped portion 76 is brought into contact with the chamfered front end inner peripheral rim of the hose body end 70. In particular, as illustrated in Figure 7 (B), the front end surface of the hose body end 70 can be formed in an end surface which is perpendicular to the hose axis, and the stepped portion 76 can be brought into contact with the circumferential edge of this end surface. In this preferred embodiment as well, it is possible to carry out the injection molding with a resin material, during which the cavity 74 is sealed at an end in a fluid-proof manner, and accordingly it is possible to prevent the injected material from leaking into the hose body 12 and producing flashes. Figure 8 illustrates a still further preferred embodiment according to the present invention. In this preferred embodiment, the hose body end 70 is formed in a diameter-increasing portion 78, which is slightly flared diametrically, at the front end. The tapered stepped portion 75 of the sliding member 56 is brought into contact therewith, thereby sealing the cavity 74 at an end in a fluid-proof manner. Figure 9 illustrates a moreover preferred embodiment according to the present invention, wherein the sliding member 56 is provided with a swollen portion 80 which is swollen outwardly in the radial direction, and this swollen portion 80 is brought into contact with the front end inner peripheral rim of the hose body end 70, thereby carrying out the sealing in a fluid-proof manner. Figure 10 illustrates a still moreover preferred embodiment according to the present invention, wherein a diameter-increasing portion 78 is disposed on the hose body end 70, while a swollen portion 80 is formed in the sliding member 56 of the inner mold 24, and they are brought into contact with each other. Figure 11 illustrates a yet further preferred embodiment according to the present invention, wherein an annular-shaped projection 68, disposed on the inner mold 24, intrudes into the front end inner peripheral rim or the diameter-increasing portion 78 of the hose body end 70, thereby sealing a cavity 74 at an end. Figure 12 illustrates a yet still further preferred embodiment according to the present invention, wherein the sliding member 56 is provided with an O-ring groove 81, an O-ring 82 is installed thereto, and this O-ring 82 is adhered to the inner peripheral surface of the hose body end 70, thereby carrying out the sealing. Figure 13 illustrates a yet moreover preferred embodiment according to the present invention, wherein the O-ring 82 is brought into contact with the aforementioned diameter-increasing portion 17 of the hose body 12, thereby carrying out the sealing. Additionally, Figure 14 illustrates a yet still moreover preferred embodiment according to the present invention, wherein the sliding member is provided with a wedge-shaped groove 84 or 86, and, a rubber layer 88 or 90 are integrally bonded by vulcanization thereto in a burying state, instead of installing an O-ring thereto. Having now fully described the preferred embodiments according to the present invention, they are one of the exemplifications. For instance, the present invention is applicable for injection molding branched portions which are extended out from the hose body in a direction perpendicular to the axis or with a predetermined angle, and which are designed for introducing blowby gases or achieving the other objects. Further, it is applicable to hoses whose hose bodies are forked in two branches or more. Moreover, it is possible to constitute a part of the injection molding mold for forming the connecting portion by utilizing a part of the blow molding mold for forming the hose body. Thus, without departing from the scope of the present invention defined in the claims, the present invention can be carried out in modes which are modified variously according to the knowledge of one of ordinary skill in the art.

Claims: A process for producing a resin hose, comprising the steps of forming a hose body (12) of a thermoplastic resin by blow molding, setting said hose body (12) in an injection molding mold including an inner mold (24) and an outer mold (22), wherein said inner mold (24) is formed with a sliding member (56) being slidable with respect to a body (60) of said inner mold (24) in an axial direction, the sliding member (56) being provided with a portion (64; 66; 68; 76; 80; 82; 88, 90) whose outside diameter is larger than that of other portions thereof, pushing said sliding member (56) for sealing a forming cavity (26; 74) formed neighbouring around said opening portion (16; 70) by adhering said inner mold (24) from the inside against an opening portion (16; 70) of said hose body (12), injecting a material into said forming cavity (26; 74) while maintaining the adhered state, thereby forming a connecting portion (14) to be connected to a mating member and integrating it with said hose body (12), characterized in that said portion (64; 66; 68; 76; 80; 82; 88, 90) of larger outside diameter of said sliding member (56) is moved in the axial direction integrally with said sliding member (56) when this is pushed into said opening portion (16; 70), thereby fitting said portion of larger outside diameter into said opening portion (16; 70) free of an abutment on an open end surface of the opening portion (16; 70) of said hose body (12) for sealing said cavity (26; 74). A process for producing a resin hose according to claim 1, characterized in that an outer diameter of a portion of said sliding member (56) located in pushing direction in front of said portion (64; 66; 68; 76; 80; 82; 88, 90) of larger diameter decreases gradually or stepwise from a rear end to a front end thereof and is pushed into said opening portion (16; 70) of said hose body (12). A process for producing a resin hose according to claim 1 or 2, characterized in that said portion of larger diameter is formed into a swollen portion (64; 80; 82; 88; 90) or a projection (68) to be fitted into said opening portion (16; 70) by said movement integral with said sliding member (56). A process for producing a resin hose according to any of the preceding claims, characterized in that said portion (64; 66; 68; 76; 80; 82; 88, 90) of larger outside diameter of said sliding member is pushed against a portion (17) of said opening portion (16) the inner diameter of which increases in the axial direction toward a free end (16) of said opening portion (16) abutting against said cavity (26) such that said free end (16) is covered by said injected material from its inner side. A process for producing a resin hose according to any of the claims 1 to 3, characterized in that said opening portion (70) of said hose body (12) is designed to have the same diameter as the other portions of said hose body (12) and is set in said cavity (74) so as to form a predetermined clearance (72) around the outer peripheral surface thereof to be filled by the injected material.

Inventors: ISHIGURO HIROMASA, KAWASAKI MINORU, ISHIGURO, HIROMASA                             ., KAWASAKI, MINORU, ISHIGURO, HIROMASA TOKAI RUBBER INDUSTRIES, LTD., KAWASAKI, MINORU TOKAI RUBBER INDUSTRIES, LTD.
Applicants: TOKAI RUBBER IND LTD, TOKAI RUBBER INDUSTRIES, LTD.
Application year: 1993
Main classification: B29C65
IPC codes: B29C49, B29C45, B29C57, B29C33, B29C70