Method of assembling piston ring and method of assembling set oil ring and apparatus for assembling set oil ring

An apparatus for assembling a set oil ring into a piston ring groove of a piston, the set oil ring comprising a spacer ring and a pair of side rail rings to be placed on both sides of the spacer ring, said apparatus comprising:

• a guide member which is larger in diameter than an outside diameter of the piston, a front end of said guide member being able to be positioned relative to the piston into a predetermined positional relationship with the piston ring groove, said guide member being able to mount on an outside thereof the spacer ring and the pair of side rail rings such that the spacer ring is positioned in a foremost side towards the front end of said guide member, followed by the pair of side rail rings;
• pushing means for pushing, in sequence out of the front end of said guide member, the spacer ring and the pair of side rail rings;
• and
• a restricting member which is movable back and forth in a radial direction relative to said guide member and which can be placed, relative to the front end of said guide member, with a clearance to be formed to open into that groove portion which is formed between that groove surface of the piston ring groove which is closer to said guide member and the spacer ring assembled into the piston ring groove.