| 摘要 |
PROBLEM TO BE SOLVED: To improve the locking force of a cover closing the opened bottom surface of a cartridge chamber at a closing position. SOLUTION: The periphery of the cover 31 covering the opened bottom surface of the cartridge chamber is coupled with the inner wall of a front cover 22 by three locking parts 33, 34 and 35, and is locked at the closing position. The engaging directions of catches 33a and 34a and engaging protrusions 33b and 34b are set to be the back-and-forth direction of a unit main body at the locking parts 33 and 34, and the engaging direction of the catches 35a and the engaging protrusion 35b is set to be in a right-and-left direction at the locking part 35. At least one of three locking parts 33-35 is held in an engaged state even though the front cover 22 is distorted in any direction by impact.
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