Seat belt locking buckle and seat belt apparatus including seat belt locking buckle

A seat belt locking buckle directly or indirectly mounted on one of a seat belt and a vehicle body, the seat belt locking buckle securing a top end of the seat belt to the vehicle body by latching a seat belt locking tongue mounted directly or indirectly on the other of the seat belt and the vehicle body, the seat belt locking buckle comprising:

• a seat belt locking tongue insertion port that allows a tongue latch member of the seat belt locking tongue to be inserted into the seat belt locking buckle;
• a buckle latch member having a substantially solid cylindrical shape, the buckle latch member being disposed so as to be rotatable about an axis extending in a direction perpendicular or substantially perpendicular to a plane of the motion of the tongue latch member inserted into the seat belt locking buckle through the seat belt locking tongue insertion port at least between a non-latch position at which the tongue latch member is not latchable by the buckle latch member and a latch position at which the tongue latch member is latchable by the buckle latch member;
• a latch member rotation control member that disables rotation of the buckle latch member and holds the buckle latch member at the non-latch position when the tongue latch member is not inserted into the seat belt locking buckle and that enables rotation of the buckle latch member when moved by the tongue latch member inserted into the seat belt locking buckle along a plane parallel or substantially parallel to the plane of the motion of the tongue latch member;
• and
• a latch-member operating member that moves along a plane parallel or substantially parallel to the plane of the motion of the tongue latch member when the buckle latch member is rotatable and pushes the buckle latch member to rotate the buckle latch member from the non-latch position to the latch position.