Locking structure for cover covering handle seat

A locking structure for a cover covering a handle seat, the cover being placed to cover a front surface and a circumferential surface of a disk-shaped handle seat mounted opposite an inner side surface and an outer side surface of a door for supporting a square core equipped with a handle for actuating a latch mechanism arranged within the door, the locking structure comprising:

• a cover locking mechanism including a plurality of protrusion-shaped cover-side locking portions protruding inward at circumferential intervals at an opening end edge of the cover, and a handle seat-side locking portion formed of a groove portion extending from a front surface to a rear surface through which the cover-side locking portion formed on the cover can be inserted when the cover is placed and a hooking groove portion formed from a front surface to a rear surface of the handle seat continuously in a rotation direction of the groove portion, to which the cover is hooked when the cover-side locking portion formed on the cover is inserted when the cover placed is rotated;
• and
• a rotation prevention mechanism including a latch arranged to be movable back and forth and biased in a direction of an end along an axis from a center to an outer circumferential surface of the handle seat at a position of the groove portion forming the handle seat-side locking portion and having, at an end, an engagement portion projecting and retracting with respect to a bottom surface of the groove portion such that, when the locking mechanism is in a hooked state, the engagement portion is protruded to the groove portion and contacts the cover-side locking portion erected on the cover.