at the gap 23 between the upper elastic element 21 and the lower elastic element 22 toward the sliding groove 24 of the joint member 2 when the joint member 2 completely enters the sliding groove 24 the gap 23 between the upper elastic element 21 and the lower elastic element 22 becomes void so that users can press and thus deflect the upper elastic element 21 and the lower elastic element 22 toward the gap 23 then the pivot 211 221 respectively provided on the upper face of the upper elastic element 21 and the bottom face of the lower elastic element 22 can be retracted from the upper and the lower pivot holes 13 14 respectively provided on the upper and lower walls of the assembly slot 12 so as to release the pivotal connection between the joint member 2 and the assembly slot 12 of the frame 1 in this manner the disassembly between the joint members 2 with the temples 4 integrally formed thereon and the frame 1 is thus accomplished referring to fig6 after the two joint members 2 with the temples 4 integrally formed thereon are detached from the frame 1 users can assemble the two joint members 2 with a strap 5 tied thereon to the frame 1 each joint member 2 with the strap 5 tied thereon has a strap perforation.