Abstract: A fuel inlet comprises an inlet pipe, a breather tube, a retainer, a spiral groove, and the like. The inlet pipe is formed by processing a metal pipe and has an expanded portion, a taper portion, and a main body in the order from the fuel port. The expanded portion is formed by increasing the diameter by bulging. In order to prevent defects in the pipe such as cracks from being caused during bulging, SUS304, SUS304L, or SUS436 according to JIS is used as the material of the pipe. The diameter of the main body is 25.4 mm and the diameter of the expanded portion is 50 mm. A spiral groove on which a screw-type fuel port cap can be screwed is formed in the vicinity of the open end of the expanded portion, by crimping the inlet pipe and the retainer together. On the outer surface of the expanded portion in the vicinity of the open end is provided an outer-cylinder-like flange formed integrally with the inlet pipe.

Abstract: In forming a fuel inlet pipe FP, (1) a portion of a base pipe is expanded by use of an expander punch to form a processed pipe comprising a neck portion, of which the diameter is the same as that of the base pipe, a tapering portion, and an expanded portion, all of these portions being connected in coaxial relation to one another (coaxially expanding process); and (2) a central axis of the neck portion and a central axis of the expanded portion are decentered relative to each other, and the expanded portion of the processed pipe is further expanded by use of an expander punch having a diameter larger than that of the expander punch used in the coaxially expanding process, thereby forming the fuel inlet pipe FP (eccentrically expanding process). The coaxially expanding process is performed one time or a plurality of times, while the eccentrically expanding process is performed only one time.

Abstract: A fuel inlet comprises an inlet pipe, a breather tube, a retainer, a spiral groove, and the like. The inlet pipe is formed by processing a metal pipe and has an expanded portion, a taper portion, and a main body in the order from the fuel port. The expanded portion is formed by increasing the diameter by bulging. In order to prevent defects in the pipe such as cracks from being caused during bulging, SUS304, SUS304L, or SUS436 according to JIS is used as the material of the pipe. The diameter of the main body is 25.4 mm and the diameter of the expanded portion is 5O mm. A spiral groove on which a screw-type fuel port cap can be screwed is formed in the vicinity of the open end of the expanded portion, by crimping the inlet pipe and the retainer together. On the outer surface of the expanded portion in the vicinity of the open end is provided an outer-cylinder-like flange formed integrally with the inlet pipe.

Abstract: A fuel inlet comprises an inlet pipe, a breather tube, a retainer, a spiral groove, and the like. The inlet pipe is formed by processing a metal pipe and has an expanded portion, a taper portion, and a main body in the order from the fuel port. The expanded portion is formed by increasing the diameter by bulging. In order to prevent defects in the pipe such as cracks from being caused during bulging, SUS304, SUS304L, or SUS436 according to JIS is used as the material of the pipe. The diameter of the main body is 25.4 mm and the diameter of the expanded portion is 50 mm. A spiral groove on which a screw-type fuel port cap can be screwed is formed in the vicinity of the open end of the expanded portion, by crimping the inlet pipe and the retainer together. On the outer surface of the expanded portion in the vicinity of the open end is provided an outer-cylinder-like flange formed integrally with the inlet pipe.

Abstract: In forming a fuel inlet pipe FP, (1) a portion of a base pipe is expanded by use of an expander punch to form a processed pipe comprising a neck portion, of which the diameter is the same as that of the base pipe, a tapering portion, and an expanded portion, all of these portions being connected in coaxial relation to one another (coaxially expanding process); and (2) a central axis of the neck portion and a central axis of the expanded portion are decentered relative to each other, and the expanded portion of the processed pipe is further expanded by use of an expander punch having a diameter larger than that of the expander punch used in the coaxially expanding process, thereby forming the fuel inlet pipe FP (eccentrically expanding process). The coaxially expanding process is performed one time or a plurality of times, while the eccentrically expanding process is performed only one time.