Hollow cylindrical filter and manufacturing apparatus

A hollow cylindrical filter formed by winding a metal wire rod in a spiral and multilayered manner, and is configured to filter a fluid by passing it in a diameter direction to an inner diameter side or an outer diameter side, wherein:

• the metal wire rod has repeated recesses and projections along the longitudinal direction throughout an entire length of the metal wire rod,
• the metal wire rod is wound so that one side thereof faces the inner diameter side or the outer diameter side in the diameter direction, while another side faces the outer diameter side or the inner diameter side in the diameter direction, and extends in a direction inclined with respect to an axial direction of the hollow cylindrical filter,
• the metal wire rod of the adjacent wire rod layers extends in a direction intersecting with each other with a fixed inclined angle with respect to the axial direction, to form a plurality of communication paths communicating in a direction into which the wire rod layers overlap with each other, and
• an intersection portion space that allows the plurality of communication paths to communicate with each other is formed by overlapping the recesses formed in the metal wire rod of one of the wire rod layers, with the metal wire rod of a wire rod layer adjacent to the one wire rod layer at an intersection portion of the metal wire rod of the one wire rod layer and the metal wire rod of the other wire rod layer adjacent to the one wire rod layer;
• wherein the metal wire rod further includes thick narrow portions and thin wide portions repeated along the longitudinal direction;
• and
• wherein a back side of the metal wire rod is a flat surface with no recess and a recess is formed in the thin wide portions.