Single flare tube and joint structure of single flare tube

摘要

A single flare tube (13), and a joint structure of the single flare tube makes a flare (14) of the single flare tube (13) hardly deformed plastically. Additionally, a tensile stress remains lower and is lower when the single flare tube (13) is fastened. A joint structure of the single flare tube coupled with a union (11) includes a single flare tube (13) having a tube (15) and a flare (14), a flare nut (12) having a thread (12b) and a through-hole (12a) that receives the tube of the single flare tube, and a union (11) having a thread (11b) for coupling with the thread (12b) of the flare nut (12). A width of a narrow inner circumferential groove (14a) of a radially outward extending part of the flare (14) is substantially zero and stays substantially zero when the single flare tube (13) is pushed against and coupled with the union (11) by fastening the threads (12b) of the flare nut (12) and the union (11) together. Additionally, an internal diameter (r1) of the inner circumferential groove (14a) preferably is smaller than an external diameter (r2) of the tube (13). Furthermore, a curvature at a radially outer side of an outer corner (13a) of the single flare tube (13) (where the tube is connected with the flare) is larger than a curvature at a radially inner side of the outer corner (13a) of the single flare tube (13) along a longitudinal cut section of the single flare tube (13). IMAGE