Coupling structure for a casing

A coupling structure for coupling first and second casing halves into a casing, comprising:

• a detachment tool storable in a tool retention bore formed in said casing;
• an opening formed at an overlapping position of said first and second casing halves of said coupled casing;
• a first coupling element projecting inward from an inner surface of the first casing half and formed with a detachment hole, said detachment hole in open communication with said opening to permit extension of said detachment tool therein;
• and
• a second coupling element projecting inward from an inner surface of the second casing half for engaging the first coupling element;
• wherein said casing is matingly engaged by aligning said first and second casing halves to engage said first and second coupling elements, and disengaged by inserting said detachment tool into said detachment hole through said opening to abut said second coupling element resulting in inward bending of said second coupling element with respect to said first coupling element, thereby disengaging said second coupling element from said first coupling element.