TUBE FIXING STRUCTURE OF A BICYCLE

Abstract: A tube fixing structure of a bicycle includes a tube (4) constituting the bicycle and a portion (1a) to be fitted into the tube. A space (4a) is formed between the tube and the portion to be filled with a bonding agent (13) and communicates with a bonding agent pouring inlet (11). The space communicates with an air exhaust outlet (12) so as to exhaust air in the space when the bonding agent (13) is poured into the space.

Description: FIELD OF THE INVENTION The invention relates to a tube fixing structure of a bicycle including a tube constituting the bicycle and a portion to be fitted in the tube, said tube and said portion are to be assembled together by a bonding agent which is to be poured into a space formed between said tube and said portion so that said space is filled with said bonding agent, said fixing structure further comprises a bonding agent inlet communicating with said space and an air exhaust outlet also communicating with said space. Furthermore the invention relates to a method for manufacturing a tube fixing structure of a bicycle including a tube constituting the bicycle and a portion to be fitted in the tube for assembling said tube and said portion together by a bonding agent, said method comprising the steps of (a) forming a space between said tube and said portion, (b) forming a bonding agent inlet which communicates with said space, (c) forming an air exhaust outlet which communicates with said space, and (d) pouring the bonding agent into said space so that said space is filled with said bonding agent. In such tube fixing structure and method a tube constituting a frame of a bicycle is fitted onto a portion such as a lug projecting from a head tube and is fixedly joined to the portion with a bonding agent. BACKGROUND OF THE INVENTION Heretofore, when a tube constituting a frame of a bicycle is fixedly mounted to a head tube to which a handlebar stem is attached, a bonding agent is applied to an outer periphery of a lug projecting from the head tube and an inner periphery of an end of the tube, and the lug is fitted into the end of the tube so that both of them are fixedly joined to each other (refer to Japanese Utility Model Application No. 8191/1982). The bonding agent for fixedly joining the tube utilizes an epoxy thermosetting resing having a relatively large viscosity. Accordingly, any brush cannot be used for applying the bonding agent, and heretofore a spatula is used to extend the bonding agent and apply it to the lug and the tube. However, such a manner in which the spatula is utilized to extend the agent and apply it to the lug and the tube requires much labor and time. Further, in such a case as the bonding agent is extended and applied by the spatula, the bonding agent is applied more than a required thickness (0.05 to 0.15 mm) and hence extra bonding agent overflows from the joining portion. Accordingly, since it is necessary to wipe off the overflowed agent with a cloth additionally, the operation efficiency is reduced and the amount of used bonding agent is much to thereby be expensive. Moreover, when the bonding agent is extended and applied, air is introduced into the agent and air bubbles are produced within the agent. Accordingly, the air bubbles are expanded upon thermohardening of the agent and the joining area is reduced substantially. Consequently, a joining force of only about 245.25 bar is obtained and hence it is necessary to extend the length of the fitted portion of the tube. Furthermore a tube fixing structure and a method of manufacturing of the types mentioned in the beginning are disclosed in EP-A-0 275 797. In this tube fixing structure the space for the bonding agent is provided by forming an annular recess of considerable axial length in said portion which is to be fitted in the tube. Further the tolerance of fitting said portion into the tube must be made small and accordingly the assembling of the tube and said portion cannot be performed easily. A similar tube fixing structure is described in FR-A-2 523 541 wherein the portion to be fitted in the tube is a tube piece also formed with an annular recess of considerable axial length and which must be fixed, e.g. by brazing to that part which is to be connected in the tube. Finally, FR-A-1 114 386 discloses also a similar tube fixing structure wherein however only one opening connects the space for the bonding agent with the outside. Furthermore this tube fixing structure requires either special deforming or welding operations for providing the space for the bonding agent. SUMMARY OF THE INVENTION It is an object of the present invention to provide a tube fixing structure of a bicycle capable of fixedly joining a tube and a portion to be fitted therein with a predetermined amount of bonding agent strongly. According to the present invention there is provided a tube fixing structure of the type mentioned in the beginning, which is characterized in that said space is further formed by at least one annular seal member disposed between said tube (4, 5) and said portion to keep said space airtight. Furthermore the invention provides a method of the type mentioned in the beginning, which is characterized by further forming said space by at least one annular seal member by disposing said annular seal member between said tube and said portion to keep said space airtight. According to one embodiment of the tube fixing structure said inlet and said outlet are provided in said tube or said portion. Furthermore the tube fixing structure can be designed such that said outlet includes a cavity formed in the periphery of the end of said portion to communicate with said space. According to another construction said outlet includes a gap formed between an inner periphery of said tube and an end of said portion having a diameter which is slightly smaller than that of said inner periphery. Since the space filled with a bonding agent is formed between a tube and a portion to be fitted therein and the bonding agent is poured into the space through a bonding agent pouring inlet communicating with the space while air in the space is exhausted from an air exhaust outlet, the tube can be fixedly joined strongly to the portion to be fitted therein by a predetermined amount of bonding agent with stable strength and high operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a whole structure of a frame of a bicycle; Fig. 2 is a sectional view showing part of the frame of Fig. 1; Fig. 3 is a sectional view showing an embodiment of the present invention; and Figs. 4(A), (B) and (C) are sectional views showing modifications of the embodiment of Fig. 3, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are now described in detail with reference to the drawings. Referring to Fig. 1, there is shown a frame structure of a bicycle which includes a head tube 1 formed of aluminum. The head tube 1 includes lugs or projections 1a and 1b which are integrally formed at upper and lower portions thereof, respectively, as shown in Fig. 2. Further, the frame includes a seat bracket 2 and a botton bracket 3. The seat bracket 2 includes lugs 2a and 2 b integrally formed therewith and the bottom bracket 3 also includes lugs 3a to 3c integrally formed therewith. The lug 3a of the bottom bracket 3 is forcedly inserted into a lower end of a down tube 5 and the lug 2a of the seat bracket 2 is also forcedly inserted into an end of a top tube 4. The lug 2b of the seat bracket 2 and the lug 3b of the bottom bracket 3 are forcedly inserted into upper and lower ends of a vertical tube or seat tube 6, respectively, and the lug 3c of the bottom bracket 3 is forcedly inserted into an end of a chain stay 7. A lug not shown of a coupling member 8 is forcedly inserted into the other end of the chain stay 7, and the other lug of the coupling member 8 and a lug not shown having a small diameter of the seat bracket 2 are forcedly inserted into both ends of a back fork or a seat stay 9, respectively. As shown in Figs. 1 and 3, the lug 1a (1b) of the head tube 1 is fitted into the other end of the top tube 4 (down tube 5). An annular cavity 10 is formed around an inner periphery of the top tube 4 (down tube 5) so that a space 10 filled with a bonding agent 13 is formed between the inner periphery of the top tube 4 (down tube 5) and an outer periphery of the lug 1a (1b) when the lug 1a (1b) of the head tube 1 is fitted into the other end of the top tube 4 (down tube 5). Further the top tube 4 (down tube 5) includes a bonding agent pouring inlet 11 formed to penetrate a wall of the top tube 4 (down tube 5) in the thickness direction or in the radial direction thereof and communicating with the space 10. In the embodiment of Fig. 3 the lug 1a (1b) is formed with a small diameter over the whole length thereof and is formed at its outer periphery near both ends thereof with annular grooves 17 having a substantially semicircular shape in section. Annular seal members 18 are fitted into the annular grooves 17 and the lug 1a (1b) is fitted into the top tube 4 (down tube 5) airtightly while the top tube 4 (down tube 5) is in close contact with the annular seal members. The annular seal members 18 are made of material having a resilience such as plastic, and the space 10 filled with the bonding agent 13 is formed between the annular seal members 18. An air exhaust outlet 19 formed of a cavity is formed in the periphery of the end of the lug 1a (1b) to communicate with the space 10. In the embodiment, a tolerance of fitting the lug 1a (1b) into the top tube 4 (down tube 5) can be made large and accordingly the lug and the tube can be both manufactured easily. Figs. 4(A), (B) and (C) show modifications of Fig. 3, respectively. The modification of Fig. 4(A) includes a tapered opening end of the top tube 4 (down tube 5) and an annular seal member 18' is disposed between the opening end and the outer periphery of the lug 1a (1b). The bonding agent pouring inlet 11 and the air exhaust outlet 12 are formed in the top tube 4 (down tube 5) in opposing relationship with each other. The modification of Fig. 4(B) includes an annular groove 17' formed in an end of the top tube 4 (down tube 5) and an annular seal member 21 fitted into the annular groove 17'. The annular seal member 21 abuts against a step of the lug 1a (1b). An end of the lug 1a (1b) is covered with an annular seal member 20 formed into an L-letter in section and the annular seal member 20 abuts against the inner periphery of the top tube 4 (down tube 5). In the modification of Fig. 4(C), the lug 1a (1b) includes a large-diameter portion 16A and a small-diameter portion 16B and the annular seal member 18 is fitted into the annular groove 17 formed in the periphery near the end of the small-diameter portion 16B. The space 10 filled with the agent is formed between the annular seal member 18 and the large-diameter portion 16A. With the tube fixing structure as constructed above, a nozzle of a bonding agent injection device not shown is pushed against the inlett 11 to pour the bonding agent 13 made of an epoxy thermosetting resin through the inlet 11 into the space 10 so that the space 10 is filed with the agent 13. In this case, since the agent 13 is poured into the space 10 with a fixed pressure, the agent is poured into the space 10 so that the space is filled with the agent while air in the space 10 is exhausted through the outlet 12 or 19. Thus, when the space 10 is completely filled with the agent 13, the agent 13 is to be exhausted through the outlet 12 or 19 having a large fluid resistance. Accordingly, if a fixed amount of bonding agent 13 corresponding to a capacity of the space 10 is poured into the space 10, unnecessary use of the agent 13 can be prevented and also no wiping-off operation is required in the cases of Figs. 4(A) and 4(B). Further, since only the pouring operation of the agent 13 is required, the filling operation is finished in about five seconds and hence the operation efficiency is extremely improved. In addition, since the fixed amount of agent is poured with the fixed pressure, the air bubbles are not almost produced in the bonding agent. Accordingly, the tube and the lug are fixedly joined to each other strongly and the joining strength is stable, so that a length of the fitted portions of the lug into the tube can be made shorter. In the embodiment, the lugs and the tubes of the seat bracket 2 and the bottom bracket 3 may be fixedly joined to each other by pouring the bonding agent 13 through the inlet 11 into the space 10 while exhausting air in the space through the outlet 12 or 19. It is a matter of course that the present invention can also be applied to the case where a handle tube is fixed to a handle lug or other tubes are fixed to portions to be fitted therein. Further, the space 10 can be filled with agent 13 even if air in the space 10 is sucked from the outlet 12 or 19 without pouring the agent 13 with the fixed pressure or even if the pouring operation of the agent 13 from the inlet 11 and the suction of air from the outlet 12 or 19 are made simultaneously.

Claims: A tube fixing structure of a bicycle including a tube (4, 5) constituting the bicycle and a portion (1a, 1b) to be fitted in the tube (4, 5), said tube (4, 5) and said portion (1a, 1b) are to be assembled together by a bonding agent (13) which is to be poured into a space (10) formed between said tube (4, 5) and said portion (1a, 1b) so that said space (10) is filled with said bonding agent (13), said fixing structure further comprises a bonding agent inlet (11) communicating with said space (10) and an air exhaust outlet (12, 19) also communicating with said space (10), characterized in that said space (10) is further formed by at least one annular seal member (18, 18', 20) disposed between said tube (4, 5) and said portion (1a, 1b) to keep said space (10) airtight. A tube fixing structure of a bicycle according to claim 1, characterized in that said inlet (11) and said outlet (12) are provided in said tube (4, 5) or said portion (1a, 1b). A tube fixing structure of a bicycle according to claim 1, characterized in that said outlet (19) includes a cavity formed in the periphery of the end of said portion (1a, 1b) to communicate with said space (10). A tube fixing structure of a bicycle according to claim 1, characterized in that said outlet includes a gap formed between an inner periphery of said tube (4, 5) and an end of said portion (1a, 1b) having a diameter which is slightly smaller than that of said inner periphery. A tube fixing structure of a bicycle according to any one of claims 1 to 4, characterized in that bonding agent (13) fills said space (10). A method for manufacturing a tube fixing structure of a bicycle including a tube (4, 5) constituting the bicycle and a portion (1a, 1b) to be fitted in the tube (4, 5) for assembling said tube (4, 5) and said portion (1a, 1b) together by a bonding agent, said method comprising the steps of (a) forming a space (10) between said tube (4, 5) and said portion (1a, 1b), (b) forming a bonding agent inlet (11) which communicates with said space (10), (c) forming an air exhaust outlet (12, 19) which communicates with said space (10), and (d) pouring the bonding agent (13) into said space (10) so that said space (10) is filled with said bonding agent (13), characterized by further forming said space (10) by at least one annular seal member (18, 18', 20) by disposing said annular seal member (18, 18', 20) between said tube (4, 5) and said portion (1a, 1b) to keep said space (10) airtight.

Inventors: NAKAMURA, FUJIO
Applicants: SAKAE RINGYO CO.,LTD.
Application year: 1988
Main classification: B62K19
IPC codes: C09J5, B62K19