With reference to FIG. 1, a conventional pipe coupler 9 for interconnecting joining regions 81 of two pipes 8 is shown to include a first jaw member 91, a second jaw member 92, a screw member 93, and a tightening member 94. Each of the first and second jaw member 91, 92 has a hinged end 901 and a locked end 902, and has an inner peripheral surface 903. The hinged ends 901 of the first and second jaw members 91, 92 are hinged to each other. The screw member 93 has a pivot end 931 mounted pivotably to the locked end 902 of the first jaw member 91, and a threaded body 933 which extends from the pivot end 931 through the locked end 902 of the second jaw member 92, and which has a male threaded region 934. The tightening member 94 includes an abutment segment 940 which is disposed to abut against the locked end 902 of the second jaw member 92, and which has a through hole 941 and a female threaded region (not shown) in the through hole 941. The female threaded region is configured to threadably engage the male threaded region 934 to permit the abutment segment 940 to rotatably sleeve on the threaded body 933. When the tightening member 94 is driven to rotate to move toward the locked end 902 of the first jaw member 91, the locked ends 902 of the first and second jaw members 91, 92 are forced by the abutment segment 940 to move toward each other and the inner peripheral surfaces 903 of the first and second jaw members 91, 92 are tightened against the joining regions 81 of the two pipes 8 to thereby provide a fluid-tightness between the joining regions 81 of the two pipes 8.
However, for providing a sufficient fluid-tightness between the joining regions 81 of the two pipes 8, a tool is used to apply on the tightening member 94 a relatively large force, which may cause wearing of the male threaded region 934 or the female threaded region.