Patent ID: 8245868

Claim:
A case locking mechanism located between a first case part and a second case part, which are made of synthetic resin and are openable and closable, wherein the locking mechanism holds the case parts in a closed state, the mechanism comprising: a projection formed on an outer side surface of the first case part; a deformable piece that is integrally formed with an outer side surface of the second case part, and has a folded back curved portion at a midpoint in a longitudinal direction, wherein the deformable piece is elastically deformable in a first direction perpendicular to the outer side surface of the second case part; a hook portion formed at a distal portion of the deformable piece, the hook portion being engageable with the projection; a guide portion formed on the projection, wherein, when the case parts are closed, the guide portion guides a claw portion formed in the hook portion in such a direction that the claw portion engages with the projection; and a holding portion that is formed on the projection to maintain the engaged state between the claw portion and the projection, wherein the projection includes an elongated stopper hole extending in a circumferential direction of the outer side surface of the first case part, wherein the stopper hole includes a wide portion and a narrow portion, the narrow portion being formed in a center portion of the projection adjacent to the wide portion, a width of the narrow portion being less than a width of the wide portion, wherein a width of the hook portion is greater than the width of the narrow portion and less than the width of the wide portion, and wherein, when the case parts are closed, the deformable piece is elastically deformed in the first direction so that the hook portion is moved to a position that corresponds to the wide portion and inserted into the wide portion, thereafter the deformable piece is restored from being elastically deformed so that the hook portion is moved in a direction opposite to the first direction and engages with an upper surface of the projection outside of the wide portion of the stopper hole.