Tubular substance and manufacturing method therefor

Abstract: The invention concerns a durable and good-operability fishing rod which is highly strong and is improved in specific rigidity by preventing excessive resin, reinforced fibers from leaning to one side, and resin pools. The fishing rod has a main layer (12) formed by winding a first prepreg provided by impregnating highly strong fibers with resin so that weight percentage becomes 25% or less so that the fibers are oriented in an axial length direction and a reinforcement layer (14, 16) formed by winding a second prepreg provided by impregnating highly strong fibers with resin so that the fibers are oriented in a direction crossing the fiber orientation of the main layer (12) on at least one side of the inside and outside of the main layer (12). The reinforcement layer (14, 16) is formed thinner than the main layer (12), and resin impregnation percentage of the second prepreg is set to substantially the same as that of the first prepreg.

Description: BACKGROUND OF THE INVENTION This invention relates to a fishing rod and a method of manufacturing a pipe-shaped part for a fishing rod by winding a plurality of prepreg layers provided by impregnating reinforcing fibers aligned or oriented mainly in one direction with thermosetting resin wherein an inner layer has bubbles therein and pressurizing and heating it, and a manufacturing method therefor. Therefore, it can be used for rod pipes of fishing rods, shafts of golf clubs, etc. Fishing rods need to be lightweight because they are held for long hours and from the viewpoint of improvement in operability and further need to be improved in strength because they receive a large bend force of strong pulling of fish, etc. Golf clubs also need to have light and highly strong nature. Thus, fishing rods and shafts of golf clubs need to satisfy compatibility of antithetic properties of lightweight and high strength. Therefore, hitherto, lightweight and strong tubular substances have been made by impregnating highly strong and lightweight fibers such as carbon fibers with synthetic resin such as epoxy resin for forming prepreg and winding, pressurizing, and heating the prepreg. In this case, the fact that the weight percentage of resin in the prepreg generally is 35% to 40% is disclosed in Japanese Patent Publication No.Hei 2-44492. The Publication specifies the relationship between the resin impregnation amount of the first prepreg of the innermost layer of a rod pipe and that of the second prepreg for the main layer of an outer layer from the viewpoints of conformability with the mandrel and coherency of the layers, wherein the fact that the resin impregnation amount of the prepreg of the innermost layer is 50% or less and that of the outer layer is 30% or less is disclosed. However, the weight increases because the resin amount is large as a whole. Further, because the above-disclosed resin amount is too much with respect to fibers, the formation of a resin layer or resin pool (portion with no or few fibers) where delamination or crack easily occurs is observed from photomicrographs. A resin flow occurs during molding, and thus fibers also move easily in association with the resin flow to meander or lean to one side, whereby lowering of strength or unintentional bending easily occurs. Particularly, if the resin amount of the prepreg for the main layer exceeds about 25 wt%, when the prepreg is wound and thereafter tightened with tape and heat-molded, circumferential shift of the prepreg material occurs during the molding depending on the tightening condition and molding failure often occurs. However, if prepreg impregnated evenly with a small amount of resin is used, coherency on boundaries of wound layers worsens and voids occur on the boundaries. Particularly on the prepreg-wound layer boundaries of fibers oriented in the length direction of the mandrel, the voids easily occur continuously in the length direction, causing the strength to lower due to delamination. Japanese Utility Model Laid-Open Publication No.Hei 6-7923 discloses the fact that heating and molding in a state in which a resin flow from an inner layer to surface layer is suppressed is a point to be considered. On the other hand, this publication also discloses the fact that an inner reinforcement layer contains a larger resin impregnation amount than the main layer for conformity with a mandrel and that an outer reinforcement layer contains a larger resin impregnation amount than the main layer for discharging air pools. However, if the resin percentages of the reinforcement layers are set larger than that of the main layer for conformity with the mandrel and for pushing out air pools of the outer reinforcement layer, the resin flow from the inner layer to the outer layer is not completely suppressed. The conformity with the mandrel may be achieved, for example, by adjusting the molding temperature and pressurization force instead of setting the large amount of resin. Air pools can be pushed out by another method instead of setting the large amount of resin for preventing air pools from being produced at prepreg molding. However, the lightweight of the molded rod pipe and improvement in the specific rigidity can be accomplished only by adjusting the resin amount. SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a fishing rod which is highly strong and has excellent durability without impairing the lightweight and a manufacturing method of a pipe-shaped part therefore. Said objective is performed by the features of claims 1 and 11. In an embodiment of the invention, preferably an end of the fiber reinforced prepreg on the outermost layer of the rod pipe is formed with a thickness adjustment part for absorbing the level difference caused by the thickness difference. Preferably, an end of the fiber reinforced prepreg on an intermediate layer of the rod pipe is formed with a thickness adjustment part for absorbing a level difference caused by a thickness difference. Preferably, fiber reinforced prepreg provided by impregnating reinforced fibers aligned, and oriented in a direction different from the axial length direction with resin is made to intervene between the layers. In the invention, the bubbles existing in the outermost layer and/or layer interface are set fewer than those existing in the inner layer; at least they need to be fewer than the bubbles existing in the inner layer and preferably fewer bubbles exist in the outermost layer and/or layer interface. The inner layer means a layer wound inside the outermost layer. In an embodiment of the invention, preferably the weight percentage of the resin to the total weight of the reinforced fibers and the resin is as small as possible, for example, about 20 wt% or less to improve the specific strength and specific elasticity of the fishing rod as much as possible. In an embodiment of the invention, if the thickness adjustment part is provided, bubbles need not exist in a plurality of layers or layer interface. The fishing rod of the invention is made of a rod pipe comprising a plurality of layers formed by winding fiber reinforced prepreg provided by impregnating reinforced fibers with resin. The inner layer of the layers has bubbles and the bubbles existing in the outermost layer and/or layer interface are fewer than the bubbles existing in the inner layer. In the fishing rod having the structure, the portion where strength reduction is comparatively hard to occur, namely, the inner layer of the layers contains bubbles and bubbles scarcely exist in portions where bending stress largest acts and the strength comparatively easily reduces, namely, the outermost layer and the layer interface. Therefore, while the strength can be prevented from reducing on the outermost layer and layer interface and damage to the portions is prevented, the resin impregnation amount is decreased in the inner layer, thereby providing a lightweight and highly strong fishing rod. The end of the fiber reinforced prepreg on the outermost layer of the rod pipe is formed with a thickness adjustment part for absorbing the level difference caused by the thickness difference, whereby stress concentrating on the level difference is spread if a large load is applied, thus delamination, a crack, or the like can be prevented from occurring on the end. The end of the fiber reinforced prepreg on the intermediate layer of the rod pipe is formed with a thickness adjustment part for absorbing the level difference caused by the thickness difference, whereby the reinforced fibers can be prevented from being abutted directly against the end and broken with the end as a supporting point. The fiber reinforced prepreg provided by impregnating reinforced fibers pulled, aligned, and oriented in a direction different from the axial length direction with resin is made to intervene between the layers, whereby crush or buckling can be prevented and in the bubble existing portions, delamination of the reinforced fibers can be prevented. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partially broken-away side view of a fishing rod for explanatory purposes. Figure 2 is a partially enlarged view of Figure 1. Figure 3 is a fragmentary sectional view of a pipe-shaped part for explanatory purposes. Figures 4(a) and 4(b) are sectional views of two types of prepregs forming a pipe-shaped part. Figure 5 is a schematic drawing of the transverse section of a conventional pipe-shaped part. Figure 6 is a polymerization end enlarged view corresponding to Figure 5. Figure 7 is a polymerization end enlarged view of a main layer of the pipe-shaped part said view being for explanatory purposes only. Figure 8 is an enlarged view of an embodiment of part A in Figure 3. Figure 9 is an enlarged view of another embodiment of part A in Figure 3. Figure 10 is a fragmentary longitudinal sectional view of a pipe-shaped part for explanatory purposes. Figure 11 is an enlarged view of part A in Figure 10. Figure 12 is an enlarged view of part B in Figure 11. Figures 13(a) to 13(d) are illustrations showing a manufacturing method of the pipe-shaped part. Figure 14 is a fragmentary sectional view showing an example of a fishing rod of the invention. Figure 15 is a fragmentary sectional view showing another example of a fishing rod of the invention. Figure 16 is a sectional view showing a structure in the vicinity of the end in an outermost layer of the fishing rod of an embodiment of the invention. Figure 17 is a sectional view showing a structure in the vicinity of the end in an intermediate layer of the fishing rod of an embodiment of the invention. It is to be noted that only Figures 14-17 (inclusive) as well as the corresponding description belong to the present invention; the remaining Figures and description have been retained purely for explanatory purposes. Figure 1 is for explanatory purposes a fragmentary sectional view of a fishing rod pipe 10. The rod pipe 10 may be a shaft of a golf club, a ski stock, a bicycle frame, or the like. In Figure 2, the rod pipe 10 has a main layer 12 made by winding prepreg provided by impregnating a bundle of carbon fibers 18 pulled and aligned in one direction with epoxy resin so that the carbon fibers 18 are oriented in the length direction of the rod pipe 10, and heating and hardening the prepreg. The carbon fibers 18 are one example of highly strong fibers and may be glass fibers, boron fibers, etc., and the epoxy resin is one example of thermosetting resin and may be polyester resin, phenol resin, etc., throughout the specification. Reinforcement layers 14 and 16 thinner than the main layer 12 are formed on the inside and outside of the main layer 12 respectively. For the reinforcement layers 14 and 16, prepreg provided by impregnating a bundle of carbon fibers pulled and aligned in one direction with epoxy resin is wound so that the fibers are oriented in the circumferential direction of the rod pipe 10, and is heated together with the main layer 12 for hardening, thereby forming the rod pipe 10. The reinforcement layers are provided for preventing a crush or destruction which would occur if the main layer 12 only existed; the reinforcement layer may be formed only on either the inside or the outside. Preferably, the reinforced fibers are the same as the reinforced fibers 18 of the main layer 12, but can also be made different from them. Generally, the reinforced fibers are oriented in the circumferential direction, but may be oriented in a slant direction between the length direction and the circumferential direction. Numeral 22 is a protective layer of epoxy resin, etc. Considerations of a manufacturing method of the layers 12, 14, and 16 will be discussed later. The weight percentage of the resin of the prepreg of which the main layer 12 is formed is 25% or less and the weight percentage of each resin impregnation amount at the prepreg stage of each reinforcement layer 14, 16 is also 25% or less. Moreover, the main layer 12 and the reinforcement layers are set to substantially the same resin percentage in the prepreg; substantially the same resin percentage is set within the error range of about 5%, preferably within the range of about 3%. From the viewpoint of bonding the fibers to each other, the lower limit of the weight percentage of the synthetic resin is about 10%, preferably about 15%. According to photomicrographs of the rod pipe 10 manufactured by setting the resin percentage of the prepreg of which each layer is formed as the embodiment to 20%, it is not found that fibers meander or lean to one side, and resin pools are not observed in each layer or layer interface. In contrast, if the resin percentage of the prepreg of which the main layer is formed is set to 25% and that of which each reinforcement layer is formed is set to 40%, fiber leaning to one side and resin pools are observed. This indicates that the fishing rod pipe according to the invention is strong. Considerations on a rod pipe manufacturing method when the rod pipe 10 and the main layer 12 shown in Figure 1 are formed as a multilayer will be discussed. To mold prepreg of each layer, one end of the length direction of the carbon fibers pulled and aligned in one direction is impregnated with epoxy resin or one end of either the surface or rear of a fiber bundle sheet is impregnated so as not to produce air pools. In the former, bubbles are pushed out from the opposed end of the length direction of the fibers and are hard to remain as compared with the case where both ends of the fibers are impregnated. In the latter, bubbles are hard to remain as compared with the case where both ends are impregnated, as in the former, and the workability is also improved as compared with the former. In both the former and latter, since resin used for pushing out bubbles at heating and molding becomes unnecessary, the amount as much as the resin can be lessened. Before the substance is laminated, heated, and hardened, the layers are brought into intimate contact with each other by sufficiently pressurizing, and bubbles are excluded from in the layer interfaces. Further, conformity with a mandrel can be improved by adjusting the heating and molding temperatures and increasing the pressurization force, as described above. Without rapidly rising to a hardening temperature at heating, preferably heat is previously applied at a resin softening temperature lower than the hardening temperature and the whole is made to adapt itself with the temperature held from the viewpoint of preventing bubbles from occurring. Further, since the substance contains a small resin percentage, preferably a pressurization force is made higher than that at conventional molding in large resin percentage for improving adhesion between fibers. Although the main layer 12 is a single layer with fibers pulled and aligned in one direction in the embodiment, a layer pulled and aligned in the length direction of the rod pipe 10 and a thin layer pulled and aligned in a direction perpendicular or slant to that layer may be disposed and laminated alternately for forming the main layer 12. Also in this case, the weight percentage of resin of each prepreg of which the main layer 12 is formed is set to substantially the same value (in the embodiment, 20%) in the range of 25% or less. Preferably, the layers are made of the same type of reinforced fibers, but may be made of different types of reinforced fibers. Since the main layer 12 of the rod pipe 10 of the embodiment in Figure 1 has not necessarily sufficient shock resistance strength, a thermoplastic resin layer having a good vibration absorption property may be formed on the outside of the reinforcement layer 16 of the outermost layer, namely, the lower part of the protective layer 22 or if the outer reinforcement layer 16 does not exist, may be formed directly on the outside of the main layer 12. As an example of the thermoplastic resin layer, if polyamide fibers or film is wound on the layer formed by winding prepreg described above and in this state, the above-mentioned heat process for hardening is executed, the polyamide fibers or film softens and is formed like a layer depending on the temperature. This softening may be incomplete. As seen from the description made so far, the resin percentage is made small, thus the lightweight is achieved, specific rigidity is improved, and operability becomes good. Since the layers are set to substantially the same resin percentage in addition to the small resin percentage, resin does not flow, fibers do not meander or lean to one side, and resin pools do not occur. Therefore, a durable and good-operability fishing rod which is highly strong can be provided. Figure 3 is a fragmentary sectional view of a laminated pipe-shaped part 110. The pipe-shaped part 110 has a main layer 112 made by a proper number of times winding sheet-like prepreg provided by impregnating a bundle of carbon fibers pulled and aligned so as to be oriented in one direction with epoxy resin so that the carbon fibers are oriented in the substantial length direction of the pipe-shaped part 110, and pressurizing and heating the prepreg. The epoxy resin is one example of thermosetting synthetic resin; it may be polyester resin, phenol resin, etc. Reinforcement layers 114 and 116 thinner than the main layer 112 are formed on the inside and outside of the main layer 112 respectively. For the reinforcement layers 114 and 116, prepreg provided by impregnating a bundle of carbon fibers pulled and aligned so as to be oriented mainly in one direction with epoxy resin is wound so that the fibers are mainly oriented substantially in the circumferential direction of the pipe-shaped part 110, and is pressurized and heated together with the main layer 112 for hardening, thereby forming the tubular substance 110. Although the carbon fibers of the main layer 112 are oriented in the length direction of the tubular substance 110, a reinforcement layer consisting essentially of fibers oriented crossing the direction, for example, in the above-mentioned circumferential direction may be mixed between wound layers oriented in the length direction. To form such sheet-like prepreg, for example, a thermosetting synthetic resin film is placed along one side of a bundle of carbon fibers TS pulled and aligned and they are processed or a thermosetting synthetic resin film is placed along both sides of the carbon fiber bundle and they are inserted between a pair of rollers for pressing. The prepreg formed by the former method becomes as shown Figure 4(a) schematically showing the cross sections of prepreg; the prepreg formed by the latter method becomes as shown in Figure 4(b). That is, in Figure 4(a), a rich resin amount area RA containing a relatively large amount of epoxy resin as thermosetting synthetic resin capable of preventing voids from occurring if it is heated and hardened in the resin impregnation state exists on one side, a poor resin amount area PA containing a small amount of resin causing voids to occur if it is heated and hardened in the resin impregnation state exists on the opposed side, and a medium resin amount area MA exists between them. On the other hand, in Figure 4(b), a rich resin amount area RA exists on both sides, a poor resin amount area PA exists in the center, and a middle resin amount area MA exists between the areas RA and PA. As shown in the figures, the arrangement form of carbon fibers TS of the poor resin amount area PA is mainly a triangular layout and that of the rich resin amount area RA is mainly a quadrangular layout. If the cross section of each fiber is formed like a circle and the size is the same, the resin amount becomes the minimum in the triangular layout and the fibers can be impregnated with more resin in the quadrangular layout. The average synthetic resin impregnation amount of prepreg thus formed is in the range of 10 wt% to 20 wt%; it is fairly smaller than the conventional amount. This produces the effect of preventing a resin pool from occurring, etc., as described below. Sheet-like prepreg is wound a proper number of times in such a direction that at least one layer of adjacent wound layers with a boundary between has a rich resin amount area RA faced to the boundary, and is pressurized and heated, then a layer to be made the main layer 112 after being pressurized and heated is formed. While being pressurized, it is heated and hardened together with layers corresponding to reinforcement layers 114 and 116 outside and inside the layer, thereby forming the pipe-shaped part 110. The resin amount of the inner reinforcement layer 114 is set to a similar amount to that of the main layer 112. If the outer reinforcement layer 116 is pressurized with tightening tape, an air pool caused by tape polymerization remains between the tightening tape and the reinforcement layer 116. To discharge the air pool, the reinforcement layer 116 is impregnated with a larger amount of resin than the main layer 112. The reinforcement layer may be placed only on either of the inside and the outside or be placed between wound layers in the main layer 112 depending on the necessity for reinforcement. It is feared that the layer formed as described above to be made the main layer 112 may have a small amount of resin causing coherency failure of the boundary between the wound layers. However, the resin amounts in each wound layer are uneven and at least one layer has a rich resin amount area RA faced to the boundary, thus providing coherency. The fact that some small voids remain in addition to a resin shift from rich area RA to poor area PA at pressurizing, heating, and molding is not a problem. The layer corresponding to the outer reinforcement layer 116 contains a considerably large amount of resin, but is thin and the absolute amount of resin is small. The resin is used to discharge an air pool caused by tightening tape and can little move to the inside of the layer corresponding to the main layer 112; it penetrates only the adjacent contact area. If the resin amount of the inner reinforcement layer 114 is increased, it is a thin layer and the absolute resin amount is small; the resin penetrates only the adjacent contact area. This is also applied when the reinforcement layer is disposed between the wound layers in the main layer. Thus, here, the resin amount is proper, preventing fibers from shifting, meandering, or leaning to one side. Further, the lightweight is achieved, wound layer boundary coherency is improved, molding failure is hard to occur, and the specific strength of the tubular substance is improved. In addition, this technique also has the effect of preventing resin pool J discussed below from occurring: Figure 5 is a schematic drawing of the cross section of a pipe-shaped part made by winding prepreg having a conventional resin amount after the pipe-shaped part is pressurized, heated, and hardened. It comprises an inner reinforcement layer 114', a main layer 112', and an outer reinforcement layer 116'. The main layer 112' has an inner layer 112A formed of a first sheet-like prepreg and an outer layer 112B formed of a second sheet-like prepreg. In such a case, the wind start end and termination end of each sheet-like prepreg are polymerized; in such polymerization end regions, hitherto, resin pool J has easily occurred and delamination has often occurred from here. Figure 6 is an enlarged view of the polymerization end region, wherein resin pool J contains few fibers TS and thermosetting synthetic resin occupies most of the resin pool J. In comparison with Figure 6, the polymerization end region of a main layer formed using a sheet-like prepreg having the resin amount does not contain resin pool J and has carbon fibers TS dispersed properly as shown in Figure 7. Thus, here, the resin pool is prevented from occurring and the strength of the tubular substance is improved. If prepreg with uneven distribution of synthetic resin percentage in the thickness direction as shown in Figure 4(a) or 4(b) is used to form a pipe-shaped part by heating, although the percentage changes, the uneven distribution state of the synthetic resin percentage remains in the thickness direction in each wind formation layer provided by heating and hardening each wound layer. For example, as shown in Figure 8, an enlarged view of part A in Figure 3, if three layers each with uneven distribution of resin percentage in such a manner that one side of each of wind formation layers making up the main layer 112 is rich area RA and that the other side is poor area PA are aligned in orientation in the prepreg state and are overlapped so that the rich and poor areas are made adjacent to each other, coherency of each layer boundary is improved and the resin amount can be reduced as a whole as compared with the case of even resin percentage, achieving the lightweight. Therefore, the specific strength is also improved. The resin percentage in each of the inner and outer reinforcement layers 114 and 116 of the embodiment is substantially even and is set to the same resin percentage as the rich area RA of the main layer 112 or more. The boundaries with the main layer 112 are prevented from being lacking in resin, and provide a good contact formation property. The reinforcement layers are thin and the absolute amount of resin is small; the entire tubular substance is not contrary to the lightweight. In Figure 9, an enlarged view of part A of another embodiment in Figure 3, a main layer 112 is made up of two layers with their rich areas RA faced to each other. Also in the embodiment, the resin percentage in each of reinforcement layers 114 and 116 is substantially even and is set to the same resin percentage as the rich area RA of the main layer 112 or more. Therefore, the boundaries with the main layer 112 are also prevented from being lacking in resin, and provide a good contact formation property. The reinforcement layers are thin and the absolute amount of resin is small; the entire tubular substance is not contrary to the lightweight. If either surface is not formed with a reinforcement layer, the resin percentage is increased on the surface of the main layer. In doing so, the carbon fibers oriented substantially in the length direction are protected from a scratch, providing a highly durable tubular substance. If the main layer is formed of one layer and inner and outer reinforcement layers have the same degree of resin percentage, the main layer side high in resin percentage is made adjacent to the outer reinforcement layer for helping the action of pushing out surface air by a resin flow caused by pressurization of tightening tape. If the inner and outer reinforcement layers differ in resin percentage, the main layer side high in resin percentage is made adjacent to the reinforcement layer having a small resin percentage for supplying resin to this reinforcement layer. The reinforced fibers of the reinforcement layer cross the main reinforced fibers (carbon fibers) of the main layer oriented substantially in the length direction and normally are oriented substantially in the circumferential direction, and the fibers cross largely each other on the interface between the reinforcement layer and the main layer, thus voids easily occur at molding. Therefore, preferably the side high in resin percentage is faced to the interface side, preventing delamination or damage from occurring on the interface for achieving the lightweight. The experiment results for the bend strength of material required particularly for fishing rod pipes and shafts of golf clubs are as follows: The bend strength of four-point bend of a tubular test substance having inner diameter 10 mm and being 600 mm long (with supporting point spacing 500 mm and load spacing 150 mm) was measured. A conventional product was made as follows: Overlapped on a main layer prepreg formed by impregnating carbon fibers pulled and aligned in one direction with 25-wt% epoxy resin was a backed reinforcement prepreg formed by impregnating carbon fibers pulled and aligned in the direction perpendicular to the fiber orientation of the main unit prepreg with 40-wt% epoxy resin (thickness of about one fifth of the main layer prepreg), and four turns were made. In the product, the main layer prepreg was formed by impregnating carbon fibers with 20-wt% epoxy resin and other points such as backing were as described above. Although the four test substances of the conventional products and the four test substances of the products as described hereinbefore differ slightly in thickness, they are shown by comparing thickness (mm), tare (gw), breaking load (kgw), and specific strength (kgw/gw): No. Thickness Tare Breaking load Specific strength Conventional products 1 0.63 20.13 73.8 3.67 2 0.64 20.21 75.2 3.72 3 0.64 20.31 70.6 3.48 4 0.64 20.22 71.6 3.54 Average value 0.64 20.22 72.8 3.60 Products described here 1 0.58 19.04 73.5 3.86 2 0.59 19.08 77.0 4.04 3 0.59 19.24 75.8 3.94 4 0.59 19.12 73.5 3.85 Average value 0.59 19.12 75.0 3.92 As seen in these experiment results, the products described above are improved in specific strength as compared with the conventional products, namely, are lightweight, high in strength, and easy to handle. The point to note in the manufacturing method of the tubular pipe-shaped part is that without rapidly rising to a hardening temperature at heating, preferably heat is previously applied at a resin softening temperature lower than the hardening temperature and the whole is made to adapt itself with the temperature held. Further, since the pipe-shaped part contains a smaller resin amount than the conventional one, preferably a pressurization force higher than that at conventional molding is applied for improving adhesion between fibers. Since the main layer 112 of the pipe-shaped part 110 of the embodiment in Figure 3 has not necessarily sufficient shock resistance strength, a thermoplastic resin layer having a good vibration absorption property may be formed on the outside of the reinforcement layer 116 of the outermost layer or formed directly on the outside of the main layer 112. As an example of the thermoplastic resin layer, if polyamide fibers are wound on the layer formed by winding prepreg described above and in this state, the above-mentioned heat process for hardening is executed, the polyamide fibers soften and are formed like a layer depending on the temperature. This softening may be incomplete. In doing so, durability increases particularly in shafts of golf clubs, etc. As the resin amount is properly adjusted with respect to the fiber amount, that prepreg material shear is hard to occur during molding and molding failure can be prevented. Since the prepreg to form the main layer contains different resin impregnation percentages in the thickness direction and at least one layer has a rich resin amount area faced to the wound layer boundary, wound layer boundary coherency becomes good and voids are prevented from occurring on the boundaries for its small average resin amount. Since the absolute amount of resin is small, resin pools are also prevented from occurring. Further, resin percentage is also unevenly distributed in the thickness direction of each layer of the molded tubular substance and the resin amount is increased only on the necessary side, whereby the total resin amount of the tubular substance can be reduced. Therefore, the lightweight, highly elastic, and highly strong tubular substance can be formed owing to the small resin amount. Particularly, specific strength (strength per unit weight) is improved. Figure 10 is a partially cutaway view of another pipe-shaped part. Figure 11 is an enlarged view of part A in Figure 10. Figure 12 is an enlarged view of part B in Figure 11. The pipe-shaped part 210 comprises a thin outer reinforcement layer 212 and a thin inner reinforcement layer 216 disposed on the outer surface and inner surface of a thick intermediate layer (main layer) 214 formed of a prepreg provided by impregnating highly strong fibers with synthetic resin. Further, an extra-thin thermosetting synthetic resin coat 218 is formed on the inside of the inner reinforcement layer 216. Most of the highly strong fibers of the intermediate layer 214 are oriented in the length direction and most of the reinforcement layers 212 and 216 are oriented in the circumferential direction. A manufacturing method of the pipe-shaped part 210 will be discussed with reference to Figures 13(a) to 13(d). A mandrel 220 is like a loose taper of about 3/1000 or less or is straight and made of a hard material such as metal. A releasing agent is applied to the surface of the mandrel 220. Fluorine-family resin or silicone-family resin is used as the releasing agent. An extra-thin coat of thermosetting synthetic resin is put on it. In the embodiment, a coat of epoxy resin is applied with a spray 22, Figure 13(a). Then, heat is applied for hardening or semi-hardening of the epoxy resin coat. Then, as shown in Figure 13(b) and later, prepreg is wound for molding the tubular substance. At this time, if the (semi-) hardened epoxy resin coat and the prepreg insufficiently adhere to each other, a coat of viscous epoxy resin is furthermore put on the coat. The pipe-shaped part is formed of prepregs provided by impregnating highly strong fibers such as carbon fibers, glass fibers, alumina fibers, or aramid fibers with thermosetting synthetic resin such as epoxy resin, phenol resin, or unsaturated polyester resin. In the embodiment, carbon fibers and epoxy resin are used. A pulled and aligned sheet 216A with fibers oriented in the circumferential direction is disposed on the inside of the prepreg P1 and a pulled and aligned sheet 214A with fibers oriented in the length direction is disposed on the outside. A small sheet 224 provided by overlaying a pulled and aligned sheet oriented in the circumferential direction on a scrim sheet is disposed on the inside of the pulled and aligned sheet 216A at the tip of prepreg P1 for reinforcing the end of the pipe-shaped part, Figure 13(b). After the prepreg P1 is wound, prepreg P2 is wound; a pulled and aligned sheet 214B oriented in the length direction is disposed on the inside of the prepreg P2 and a pulled and aligned sheet 212A oriented in the circumferential direction is disposed on the outside and further a cloth-like small sheet provided for reinforcing the end of the tubular substance is disposed on the outer margin of the sheet 12A, Figure 13(c). Last, the substance is tightened and pressurized with tightening tape 228, Figure 13(d), and heated and hardened. An external mold may be used instead of the tightening tape for pressurizing. After molding, the tightening tape 228 is removed and the mandrel is drawn out. The substance is worked to desired length, dimensions, etc. Further, painting or printing can also be put on the outer peripheral surface for decoration and protection. The winding steps of the prepregs P1 and P2 are not limited to those in the embodiment and the number of prepreg sheets and fiber orientation combinations are arbitrary. As shown in Figure 12, the inside of the tubular substance 210 thus made is formed with the thermosetting synthetic resin coat 218 so as to protect highly strong fibers oriented in the circumferential direction of the inner reinforcement layer 216. As understood from the discussion with reference to Figures 13(a) to 13(d), the internal surface of the coat 218 coming in contact with the surface of the mandrel 220 is rubbed with minute asperities on the mandrel surface when the mandrel 220 is drawn out, and minute asperities 218A occur. However, the highly strong fibers of the reinforcement layer 216 are protected by the coat 218 against damage, providing the tubular substance 210 which is highly strong and has excellent durability. The reinforcement layer 216 is 50 microns or less thick and preferably 30 microns or less thick. The weight percentage of resin is 50% or less and preferably a low resin amount percentage of the same degree as the main layer is set for achieving the lightweight. The extra-thin coat 218 is made thicker than the asperities on the surface of the mandrel 220 and equal to or thinner than the average diameter of the highly strong fibers of the innermost side of the reinforcement layer 216. Therefore, normally the coat 218 is about 10 microns or less thick, which is as thin as possible within the thickness range in which the highly strong fibers are prevented from being rubbed with the asperities on the mandrel surface when the mandrel 220 is drawn out. Therefore, the weight of the pipe-shaped part 210 little increases and protection of the highly strong fibers can be achieved compatibly with the lightweight. Since the coat 218 is formed of epoxy resin of the same family as the epoxy resin used for the prepreg, it has high coherency and when the mandrel is drawn out or the temperature changes in the operating environment, delamination or strength degradation is hard to occur. When the prepreg uses a polyester family resin, if the coat 218 is also formed of a polyester resin of the same polyester family, high coherency is provided. The coat 218 in the embodiment is made of epoxy resin, but may be formed of thermoplastic resin as well as such thermosetting synthetic resin as epoxy resin. For example, particles or short fibers may be mixed therein. If particles or short fibers smaller in diameter than the highly strong fibers of the reinforcement layer 216 are used or a material softer than the highly strong fibers is used for the mixed particles or short fibers, when the mandrel is drawn out, the mixed particles or short fibers can prevent the highly strong fibers of the reinforcement layer from being scratched or pressed and bent, etc. Expandable particles, hollow particles, and other synthetic resin particles can be used as the mixed particles; expandable or hollow particles contribute to achieving the lightweight. Substantially spherical form is preferred from the viewpoint of scratch prevention; if ceramic particles are used, the tubular substance is improved in resistance to abrasion. If talc particles, Teflon particles, or silicon particles are used, slipperiness is improved and when the mandrel is drawn out, drawing-out property is also improved. If flat material is used for the particles, it is pressurized at pressure molding and is aligned so that the wide face is arranged along the length direction, and the coat can be formed thin. Further, the short fibers may be whiskers, but need not be highly strong fibers. If whiskers are mixed, resistance to abrasion is improved. The particles or short fibers are mixed 50% or less as volume . percentage and normally may be mixed 35% or less. The effect of the reinforcement layer 216 on the highly strong fibers can be lowered by increasing the resin amount. If the particles or short fibers are thus mixed, when prepreg is heated, a resin flow in the portion corresponding to the coat is suppressed although the portion does not harden; the portion is held like a layer and during the molding, the highly strong fibers of the reinforcement layer 216 can be prevented from coming in contact with the mandrel. The primary purpose of the extra-thin coat 218 is to prevent damage to the highly strong fibers of the innermost layer of the main portion of the tubular tube, and the coat 218 need not be formed in the wind area of the small sheet 224 or 226 for reinforcement. As seen from the discussion made so far, since an extra-thin coat is molded integrally on the inner side of the inner surface of the inner thin reinforcement layer made of prepreg with highly strong fibers oriented substantially in the circumferential direction, the highly strong fibers of the reinforcement layer can be prevented from coming in direct contact with the mandrel. Although the mandrel is drawn out in a direction traversing the highly strong fibers oriented in the circumferential direction of the reinforcement layer, the highly strong fibers are not scratched or cut, thus providing a highly strong tubular substance. If it is used for a long term, scratches of the highly strong fibers are not enlarged, providing excellent durability. Since the coat exists inside the tubular substance, if a foreign member such as a fishing line, a small-diameter tube, or parts strikes the inside, the highly strong fibers can be protected by the coat, thus providing durability. Further, since the coat is extremely thin, the lightweight is not impaired. In the manufacturing method, the hardened or semi-hardened coat, which is previously formed, exists between the wound prepreg and the mandrel. If the mandrel is drawn out after heating and molding, the coat prevents the highly strong fibers of the prepreg from being damaged owing to minute asperities on the mandrel surface. The above-mentioned pipe-shaped part can be easily manufactured. Figure 14 is a fragmentary sectional view showing the fishing rod of the invention made by winding prepreg provided by impregnating reinforced fibers pulled and aligned with resin, wherein numeral 311 is an innermost layer made of a fiber reinforced prepreg with reinforced fibers pulled and aligned in the circumferential direction. Laminated on the innermost layer 311 is a first intermediate layer 312 made of a fiber reinforced prepreg with reinforced fibers pulled and aligned in the axial length direction. Bubbles 313 exist in the first intermediate layer 312. Laminated on the first intermediate layer 312 is a second intermediate layer 314 made of a fiber reinforced prepreg with reinforced fibers pulled and aligned in the circumferential direction. Further, laminated on the second intermediate layer 314 is an outermost layer 315 made of a fiber reinforced prepreg with reinforced fibers pulled and aligned in the axial length direction. The outermost layer 315 and layer interface contain few bubbles 313. In the structure, a method of adjusting the amount of resin with which the reinforced fibers of the fiber reinforced prepreg of which each layer is made are impregnated is possible as a method of making bubbles 313 exist in the first intermediate layer 312 and few bubbles 313 exist in the outermost layer 315 and layer interface. For example, a method of adjusting a resin impregnation amount when fiber reinforced prepreg is prepared is possible. In this case, preferably the weight percentage of the resin to the total weight of the reinforced fibers and resin in the first intermediate layer 312 is 15%-20% and that in the outermost layer 315 and layer interface is 18%-25%. However, the percentage in the first intermediate layer 312 needs to be set smaller than that in the outermost layer 315. In the fiber reinforced prepregs, carbon fibers, glass fibers, aramid fibers, etc., can be used as the reinforced fibers, and epoxy resin, phenol resin, polyester resin, etc., can be used as the resin with which the reinforced fibers of the prepregs are impregnated. Since few bubbles exist in portions where bending stress largest acts and the strength comparatively easily reduces, namely, the outermost layer 315 and the layer interface (particularly, interface between laminated fiber reinforced prepregs different in orientation of the reinforced fibers), the strength can be prevented from reducing on the outermost layer 315 and layer interface and damage to the portions can be prevented. The portion where strength reduction is comparatively hard to occur, namely, the first intermediate layer 312 contains a small resin impregnation amount to such a degree that bubbles 313 partially exist, and is very lightweight. Therefore, the fishing rod is not broken under a large load; it is highly strong and moreover lightweight. The fishing rod of the invention can adopt a structure as shown in Figure 15. That is, first and second intermediate layers 322 and 323 made of fiber reinforced prepreg with the reinforced fibers pulled and aligned in the axial length direction are laminated on an innermost layer 321 made of fiber reinforced prepreg with the reinforced fibers pulled and aligned in the circumferential direction, and an outermost layer 324 made of fiber reinforced prepreg with the reinforced fibers pulled and aligned in the circumferential direction is laminated on the second intermediate layer 323. Bubbles 325 exist in the first and second intermediate layers 322 and 323; they exist a comparatively great deal at the center of the region extending across the first and second intermediate layers 322 and 323. To make the bubbles 325 exist a comparatively great deal at the center of the region extending across the first and second intermediate layers 322 and 323, the resin impregnation amount is adjusted when fiber reinforced prepreg is prepared, as described above. The bubbles 325 are thus made to exist a comparatively great deal at the center of the region extending across the two layers (portion hard to be affected by bending stress), whereby the fishing rod can be made more lightweight while strength reduction is suppressed. Also in such a structure, bubbles 325 scarcely exist in portions where bending stress largest acts and the strength comparatively easily reduces, namely, the outermost layer 324 and the layer interface, thus the strength can be prevented from reducing on the outermost layer 324 and layer interface and damage to the portions can be prevented. The portions where strength reduction is comparatively hard to occur, namely, the first and second intermediate layers 322 and 323 contain a small resin impregnation amount and bubbles 325, thus are very lightweight. Therefore, the fishing rod is not broken under a large load; it is also highly strong and moreover lightweight. Figures 14 and 15 show the cross sections in the circumferential direction; similar structures to those in Figures 14 and 15 are also taken in the cross sections in the axial length direction. Each of the structures may be adopted for the whole or a part of a fishing rod. Figure 16 is a sectional view showing a structure in the vicinity of the end in an outermost layer of the fishing rod of the invention. In the structure in the vicinity of the end, an outermost layer 332 is laminated on a main layer 331 made of a fiber reinforced prepreg and a reinforcement lug 333 exists on the outermost layer 332. An end 333a of the reinforcement lug 333 is formed with a fiber reinforcement part 334 as a thickness adjustment part. The fiber reinforcement part 334 has a cross section formed like a moderate slope or curved face for absorbing the level difference caused by the thickness of the reinforcement lug 333. The fiber reinforcement part 334 may be formed by winding a different fiber reinforced prepreg from the fiber reinforced prepreg of which the main layer 331 (containing the outermost layer 332) is made; some of the reinforced fibers of the fiber reinforced prepreg of which the main layer 331 or the reinforcement lug 333 is made may be used. Since stress concentrating on the end 333a is spread by means of the fiber reinforcement part 334 thus formed if a large load is applied, delamination, a crack, or the like can be prevented from occurring on the end 333a. Figure 17 is a sectional view showing a structure in the vicinity of the end in an intermediate layer of the fishing rod of the invention. In the structure in the vicinity of the end, an intermediate layer 342 is laminated on an innermost layer 341 made of a fiber reinforced prepreg, a reinforcement lug 343 exists between the intermediate layer 342 and the innermost layer 341, and further a main layer 344 is laminated on the intermediate layer 342. An end 343a of the reinforcement lug 343 is formed with a resin pool 345 as a thickness adjustment part. The intermediate layer 342 and the innermost layer 341 are made of fiber reinforced prepreg with reinforced fibers pulled and aligned in the axial length direction. A resin pool 345 can be formed, for example, by a method of coating with resin of the same kind as the resin of the fiber reinforced prepreg or winding a film of the resin before the intermediate layer 342 is wound or a method of increasing the resin impregnation amount of the fiber reinforced prepreg of which the reinforcement lug 343 is made (for example, 40 wt% or more) or increasing about 20 wt% greater than the resin impregnation amount of the fiber reinforced prepreg of which the main layer 344 is made and using the resin. Preferably, the length L of the resin pool 345 is three times or more the thickness t of the reinforcement lug 343. In setting so, the fibers pulled and aligned in one direction can be prevented from being bent or meandering. The resin pool 345 thus formed can prevent the reinforced fibers of the intermediate layer 342 from being abutted directly against the end 343a and broken with the end 343a as a supporting point. Next, evaluation for clarifying the effect of the fishing rod of the invention will be discussed. Specifically, a 4-point bending test was executed for the fishing rod material of the invention having the structure shown in Figure 14 and as a control example, a fishing rod material using a laminated substance with the weight percentage of resin to the total weight of reinforced fibers and the resin being 10%-20%. As a result, the specific strength and the specific elasticity of the fishing rod material of the invention were larger than those of the fishing rod material of the control example. Delamination from the end of the outermost layer and damage from the end of the intermediate layer were not confirmed for the fishing rod material of the invention. On the other hand, delamination from the end of the outermost layer and damage from the end of the intermediate layer were partially confirmed for the fishing rod material of the comparison example. The invention is not limited to the embodiments, but by the scope of the appended claims, and the number of turns of fiber reinforced prepreg, the thickness of each layer, and the resin impregnation amount are adjusted appropriately in response to applications and specifications. However, the resin impregnation amount needs to be made 25 wt% or less in the fiber reinforced prepreg with the reinforced fibers pulled and aligned in the axial length direction. As we have discussed, the fishing rod of the invention is made of a rod pipe comprising a plurality of layers formed by winding fiber reinforced prepreg provided by impregnating reinforced fibers with resin. The inner layer of the layers has bubbles and the bubbles existing in the outermost layer and/or layer interface are fewer than the bubbles existing in the inner layer. Therefore, the portions where strength reduction easily occurs are reinforced and the fishing rod has excellent specific strength and specific elasticity although it contains a small resin impregnation amount of fiber reinforced prepreg. In the fishing rod of the invention, the end of the fiber reinforced prepreg on the outermost layer or intermediate layer of the rod pipe is formed with a thickness adjustment part for absorbing the level difference caused by the thickness difference, whereby the strength of the fishing rod can be furthermore improved.

Claims: A fishing rod comprising a rod pipe (10) having a plurality of layers (311,312,313,314,315;321,322,323,324) made of fiber-reinforced prepreg which, in turn, are composed of resin impregnated fibers pulled and aligned in an axial length direction of the fishing rod, characterized in that the weight percentage of resin impregnation is less in an inner layer (311,322) of said fiber-reinforced layers than that of the outer layer (315,323) and/or inner layer interface, so that said inner layer (311,322) comprises a greater number of bubbles than those bubbles contained in said outer layer (315,323) and/or outer layer interface thereof. Fishing rod according to claim 1, wherein said plurality of layers including an intermediate layer (312) having a weight percentage of resin to the total weight of the reinforced fibers and resin in said first intermediate layer (312) in the range of 15% to 20% by weight. Fishing rod according to claim 2, wherein an end of said fiber-reinforced prepreg on an outermost layer is formed with a thickness adjusting part for absorbing a level difference caused by a thickness difference. Fishing rod according to claim 2 or 3, wherein fiber-reinforced prepreg having reinforcing resin-impregnated fibers oriented in a direction different from the axial length direction of the fishing rod is interposed between said plurality of layers. Fishing rod according to claim 4, wherein adjacent layers contain reinforcing fibers of axial and circumferentially oriented directions. Fishing rod according to one of the preceding claims 1 to 5, comprising an innermost layer (311) made of a fiber-reinforced prepreg with said fibers being oriented in a circumferential direction, with a first intermediate layer (312) made of a fiber-reinforced prepreg having the reinforcing fibers oriented in an axial length direction of the fishing rod being laminated thereon, with a second intermediate layer (314) made of a fiber-reinforced prepreg having the reinforcing fibers oriented in the circumferential direction being laminated thereon, and with an outermost layer (315) made of a fiber-reinforced prepreg having the reinforcing fibers oriented in the axial length direction of the fishing rod. Fishing rod according to claim 6, wherein the weight percentage of fiber-impregnating resin is to be smaller in the first intermediate layer (312) than in the outermost layer (315). Fishing rod according to one of the preceding claims 2 to 7, wherein the weight percentage of the fiber impregnating resin in the outermost layer (315) and the layer interface amounts to 18% to 25% by weight. Fishing rod according to claim 1, wherein an innermost layer (321) made of fiber-reinforced prepreg with the reinforcing fibers extending in a circumferential direction is provided with said first and second intermediate layers (322,323) having their reinforcing fibers oriented in the axial length direction being laminated thereon, and an outermost layer (324) comprising resin impregnated reinforcing fibers oriented in the circumferential direction being laminated on said second intermediate layer (323). Fishing rod according to claim 9, wherein the bubbles (325) are concentrated in the area of the center region extending across the first and second intermediate layers (322,323) defining an area where the bending stress is relatively low contributing to render the fishing rod more lightweight while strength reduction is suppressed. A method of manufacturing a pipe-shaped part for a fishing rod according to claim 1 comprising the steps of: preparing a first prepreg by impregnating carbon fibers with thermosetting synthetic resin in the range of approximately up to 25 wt%; and adjusting the amount of resin impregnation so as to have a smaller weight percentage resin amount area and a greater weight percentage resin amount area in a circumferential direction, so that a greater number of bubbles exist in an inner layer of fiber-reinforced layers; winding said first prepreg with the carbon fibers mainly orientated in an axial length direction of a mandrel, so that the greater weight percentage resin amount is located at least in one of the adjacent layers at a wound layer boundary, to thereby form a relatively thick layer corresponding to a main layer; winding a second prepreg provided by impregnating reinforced fibers with thermosetting synthetic resin so that its main fiber orientation crosses at an angle the carbon fibers mainly orientated in the axial length direction of said first prepreg, prior to, simultaneously with and/or subsequently to the winding of said first prepreg, for forming at least one relatively thin layer corresponding to a reinforcement layer; pressurizing the layers corresponding to the reinforcement layer and the main layer by a tightening substance from the outside and heating them; and removing the mandrel and the tightening substance. Method according to claim 11, comprising the steps of: applying a releasing agent to a mandrel; putting a coat of material consisting essentially of thermosetting synthetic resin on said releasing agent for forming a hardened or semi-hardened extra-thin coat; winding prepreg provided by impregnating highly strong fibers with synthetic resin around an outside of said coat; preparing a pressurizing member; pressurizing from an outside of said prepreg with said pressurizing member and heating and hardening; and removing said pressurizing member and drawing out said mandrel.

Inventors: KAMEDA KENICHI, NAITOU HIDEYUKI, SUZUE HIROYASU, TAKAMATSU NOBUAKI, TSURUFUJI TOMOYOSHI, KAMEDA, KENICHI, NAITOU, HIDEYUKI, SUZUE, HIROYASU, TAKAMATSU, NOBUAKI, TSURUFUJI, TOMOYOSHI
Applicants: DAIWA SEIKO INC, DAIWA SEIKO INC.
Application year: 1995
Main classification: A01K87
IPC codes: B29C53, B29C70, A01K87, A63B53