Venturi for boiler

A venturi comprising:

• a housing, in which an air passage opened along a reference direction, a first gas passage extending from the air passage, a second gas passage extending from one side of the first gas passage, and a third gas passage extending from an opposite side of the first gas passage are formed;
• a first opening/closing part configured to open and close the second gas passage in an interior of the housing;
• a second opening/closing part configured to open and close the third gas passage in the interior of the housing;
• and
• a flow rate adjuster, at least a portion of which is disposed in the interior of the housing and configured to adjust a flow rate of air flowing through the air passage and supply of gas through the second gas passage or the third gas passage,
• wherein the flow rate adjuster includes:
• a shaft rotatably coupled to the housing and passing through the air passage in an upward/downward direction perpendicular to the reference direction;
• a cam integrally and rotatably coupled to the shaft and configured to apply or release an external force to the first opening/closing part and the second opening/closing part to control opening and closing of the second gas passage and the third gas passage;
• and
• a blade integrally and rotatably coupled to the shaft and provided with a plurality of wings configured to adjust a degree, to which a portion in an interior of the air passage is opened.