Method of manufacturing driving drum

A method of manufacturing a driving drum disposed on a rotational axis in a rotatable manner, the driving drum having a cylindrical shape, and including a first cam groove formed on an inner circumferential surface in a circumferential direction thereof and a second cam groove formed on an outer circumferential surface in a circumferential direction thereof, the method comprising:

• forming a first cylindrical member including a plurality of protrusions on an end face thereof, each of the plurality of the protrusions protruding in an axial direction thereof, the end face having projections and recesses in the axial direction thereof so as to correspond to cam profiles of the first and the second cam grooves;
• forming a second cylindrical member having an end face having projections and recesses in an axial direction thereof so as to correspond to the projections and the recesses of the end face of the first cylindrical member;
• and
• at a position where the projections and the recesses of the end face of the first cylindrical member correspond to the projections and the recesses of the end face of the second cylindrical member, joining each of the protrusions of the first cylindrical member to the end face of the second cylindrical member, thereby forming the first cam groove on an inner side of each of the protrusions in the circumferential direction thereof and forming the second cam groove on an outer side of each of the protrusions in the circumferential direction thereof by means of the end faces of the first and the second cylindrical members.