A ceiling light fixture, for projecting light downward, conventionally has a light body mounting base to be embedded in a ceiling board (a fitting surface) and a light body to be mounted in the light body mounting base. These are generally supplied as separate items.
In a ceiling fixture like this, the light body mounting base is previously embedded in the ceiling board. An electric power cable passes through the rear of an inside of the light body mounting base. The cable is connected to a terminal block of the light body. The light body is then inserted inside the light body mounting base. A stopper mechanism of the light body side is hooked mechanically to a stopper mechanism of the light body mounting base side.
However, there is a problem that, when mounting the light body to the light body mounting base, it takes time and labor to assemble the light body because electrical connection and mechanical connection are made in separate operations. Further, since the light body mounting base and the light body are generally made of metal, an insulation structure is required to provide electric insulation. These factors complicate the installation process.
What is more, when mounting the light body to the light body mounting base, since the stopper mechanism of the light body side must be hooked mechanically to the stopper mechanism of the light body mounting base side while the light body is inserted inside the light body mounting base, alignment of the two stopper mechanisms is complicated by the inability of the installer to visually confirm the alignment from the outside. This increases the time and labor to install the light body.
Also, when installing an ordinary ceiling fixture to a ceiling board, a frame part of the ceiling fixture is inserted into a fitting hole formed in the ceiling board. A stopper metal arranged in a side face of the frame part is pushed sideways and pulled down by inserting a hand inside the frame part (an inside space where a lamp and a reflection plate are mounted). Thus the frame part is installed in the ceiling board by holding the ceiling board with a flange part of the frame which is hidden behind the front surface of the ceiling board and the stopper metal which is hidden by the rear face of the ceiling board.
However, according to a configuration like this, there is a problem that, since the stopper metal must be handled by inserting the hand inside the frame part, operation is awkward.
To cope with these problems, U.S. Pat. No. 5,331,531 discloses a configuration in which a feed screw is provided in a side face of a frame part so as to freely rotate along a vertical direction. A nut is threaded onto the feed screw. A stopper metal is attached to the nut so as to freely rotate. Rotation of the feed screw causes the stopper metal to advance and retreat with regard to the frame part. The stopper metal, when the nut moves to its upper end by rotational of the feed screw, is allowed to lay down by rotating the same toward an inside of the frame part so as not to engage the ceiling board. When the nut moves to its lower end, the stopper metal is forcibly rotated to protrude toward a side of the frame part where it can engage a rear face of the ceiling board. When the frame part is embedded into the ceiling board, it is embedded into the ceiling board under a condition the stopper metal lays inside of the frame part. The feed screw is operated by way of an end part of the feed screw facing a lower face of the frame part when the nut is moved toward the lower end side, and thus the frame part contacts the rear face of the ceiling by forcibly moving the stopper metal outside the frame part. Thereby, the stopper metal can be operated without inserting a hand inside the frame part.
However, according to the configuration shown in U.S. Pat. No. 5,331,531, when the nut is moved to the upper end side, since it is possible to lay down the stopper metal by rotating it toward the inside of the frame part and oppositely it is also possible to protrude the stopper metal from the frame part by rotating the same in an outside direction, the stopper metal may protrude from the frame part during the process of embedding the frame part into the ceiling board. Thus, there is a problem in work such that the protruded stopper metal is caught by the ceiling board and interferes with the installation.