| 摘要 |
PURPOSE:To contrive a uniform printed density irrespective of thermal expansion of a wiring board, by a construction wherein a clamping means for clamping a wiring board between a board holder and a heat-releasing plate is provided with a mechanism for absorbing the thermal expansion of the wiring board. CONSTITUTION:Springs 10 for supporting engaging balls 6 are disposed in lateral grooves 9 provided in inside walls of recesses 7 to constitute the mechanism 11 for absorbing the thermal expansion of the wiring board 2. When an engaging projected part 5 of the board holder 4 is fitted into the recess 7 on the heat- releasing plate 3 side, the balls 6 makes elastic engagement with necked parts on both sides of the projected part 5, whereby the board 2 is clamped between the holder 4 and the plate 3. In this clamping condition, when the board 2 undergoes thermal expansion due to the heat generated on passing an electric current to a heating resistor 1, the forces of thermal expansion are transmitted to the parts between the projected parts 5 and the balls 6, and are absorbed by the springs 10. Accordingly, even where the holder and the plate 3 are formed of different materials, warping will not occur, and uniform printed density can be maintained, thereby obviating a rise in cost. |
