Forced air supply type of combustion apparatus

A forced air supply type of combustion apparatus comprising:

• an exterior case having contained therein, a burner, a combustion box for enclosing a combustion space of air-fuel mixture ejected from the burner, and a combustion fan;
• an air-supply-port-formed plate having formed therein an air supply port through which outside air is introduced into an internal space of the exterior case, such that the air required for combustion is sucked by the combustion fan from the air supply port into the internal space of the exterior case;
• and an air filter mounted on the air-supply-port-formed plate in a manner to cover the air supply port in an insertable and drawable manner, thereby collecting foreign matters in the air,
• wherein the air filter comprises:
• a filter main body;
• a filter frame to enclose the filter main body, supposing that:
• a direction of inserting and drawing the air filter into, and out of, the air-supply-port-formed plate is defined as an X-axis direction;
• the direction of drawing the air filter is defined as an X-axis plus direction;
• the direction of thickness of the air filter is defined as a Z-axis direction;
• and the direction perpendicular to the X-axis direction and the Z-axis direction is defined as a Y-axis direction;
• retaining pieces which are provided at side edge parts and which are elastically deformable by deflection in the Z-axis direction so as to support side frame parts on side edge parts by retaining the side frame parts in the Z-axis direction relative to the side edge parts while allowing the side frame parts insertable and drawable in the X-axis direction,
• said side edge parts being elongated in the X-axis direction on both sides, in the Y-axis direction, of the air supply port in the air-supply-port-formed plate;
• said side frame parts extending in the X-axis direction on both sides, in the Y-axis direction, of the filter frame;
• projections in the Z-axis direction, partly formed in those surfaces of the side frame part which lie opposite to the retaining pieces,
• wherein a distance in the Z-axis direction between the side edge parts of the air-supply-port-formed plate and the retaining pieces is set to be larger than a dimension, in the Z-axis direction, of the side frame parts, and is set to be smaller than a sum of the dimensions to be obtained by adding the projection height of the projections to the dimension in the Z-axis direction of the side frame parts;
• and
• guide piece parts disposed at a front end, in the X-axis plus direction, of the retaining pieces in an inclined manner such that the distance in the Z-axis direction to the side edge parts of the air-supply-port-formed plate gradually increases toward the X-axis plus direction.