PURPOSE: To couple plural members without forming an unnecessary backlash space and to firmly couple them without deforming them when the plural member are coupled by constituting a cartridge frame body of the plural member and coupling them with a shape memory member.

CONSTITUTION: The joining part of upper and lower frame bodies 12 and 13 is provided with a through-hole 15. Then, the bodies 12 and 13 are coupled by fitting a coupling member 16 to the hole 15. As the coupling member 16, the shape memory member whose shape is restored by heating, for example, the member made of the alloy of titanium and nickel is used. When the coupling member 16 is inserted in the hole 15, it is linear pin shape as shown in a figure (b). When it is heated to prescribed temperature, it is bent and restored (d). Besides, projections 16a are formed in the inside of both ends of the coupling member 16. Then, when the coupling member 16 is restored, the projections 16a are engaged with a recessed part 18 and the frame bodies 12 and 13 are more firmly coupled.