Method for mounting an elastic annular member

A method for fitting an elastic annular ring on an outer circumferential portion of a workpiece, said method comprising the steps of:

• partially inserting a hollow diameter-enlarging member into the elastic ring positioned at a supply position, the diameter-enlarging member holding the elastic ring on an outer circumferential portion in a partially enlarged diameter state;
• grasping the diameter-enlarging member and ring positioned thereon with a robotic mechanism having a guide shaft insertable into the diameter-enlarging member and a pair of jaws securing an exterior portion of the diameter-enlarging member;
• moving the diameter-enlarging member and ring positioned thereon grasped by the robotic mechanism to a fitting position to be received by a receptacle having a guide groove for receiving the elastic ring and a receiving guide for receiving the diameter-enlarging member;
• holding the ring at the fitting position and further inserting the diameter-enlarging member by axially displacing the robotic mechanism to further expand the ring to an enlarged diameter state;
• and
• inserting the workpiece, which has a flange portion, into the diameter-enlarging member such that the flange portion of the workpiece contacts an end surface of the diameter-enlarging member and axially displaces the diameter-enlarging member in the receiving guide past the position of the ring while keeping the elastic ring in the guide groove at the fitting position to transfer the elastic ring to the workpiece by a contraction of the elastic ring from the enlarged diameter state to a normal diameter state.