To fix a frame and a front panel together through thermal caulking by facilitating the registration thererbetween by providing projecting or recessed portions on the surface of the frame, fitting a part of the front panel into the recessed portion, heating, softening and collapsing the projecting portion so as to cover a part of the fitted front panel for fixation.

A frame 3 comprises a frame portion 4 and a partition plate 5 extended thereover. A projecting portion 14 and a projection 15 extending the projecting portion 14 are provided at a suitable interval on the upper surface of the partition plate 5. A hole 16 corresponding to the projection 15 is provided on the front panel 9, and an extruded portion 17 around the hole 16 is provided. In addition, the extruded portion 17 is constructed so as to be fitted into the convex portion 14 when the projection 15 on the upper surface of the partition plate 5 extend through the hoe 16 of the front panel. After the projection 15 has been penetrated through the hole 16, the projection 15 is heated, softened and collapse so that the opening of the extruded portion 17 of the front panel 9 are flat embeded.