Exhaust connection structure and combustion apparatus with exhaust connection structure

An exhaust connection structure constructed to connect a combustion apparatus and an exhaust tube having projections and recesses in an outer surface, the exhaust connection structure comprising:

• a sealing member arranged on an outer circumferential surface of the exhaust tube;
• and
• an exhaust joint which has an inner circumferential surface opposed to the outer circumferential surface of the exhaust tube and is arranged to sandwich the sealing member between the inner circumferential surface and the outer circumferential surface of the exhaust tube,
• the exhaust joint including:
• an engagement member having an annular portion and an engaging portion bent toward an inner circumference of the annular portion, and the engaging portion being constructed to be engaged with the projections and recesses in the exhaust tube in a state where the exhaust tube is inserted in the annular portion of the engaging portion;
• a joint body having a combustion apparatus connection portion for connection to the combustion apparatus and an exhaust tube connection portion for connection to the exhaust tube, to which the engagement member is attached;
• and
• a nut member having a screw portion screwed to the exhaust tube connection portion and a locking portion for preventing the engagement member from coming out of the joint body, wherein
• there is a gap in which the engagement member increases in diameter with insertion of the exhaust tube between the outer circumferential surface of the engagement member and the inner circumferential surface of the nut member,
• the screw portion has a first threaded portion and a second threaded portion, and
• the first threaded portion and the second threaded portion are separate from each other in a circumferential direction.

An exhaust connection structure constructed to connect a combustion apparatus and an exhaust tube having projections and recesses in an outer surface, the exhaust connection structure comprising:

• a sealing member arranged on an outer circumferential surface of the exhaust tube;
• and
• an exhaust joint which has an inner circumferential surface opposed to the outer circumferential surface of the exhaust tube and is arranged to sandwich the sealing member between the inner circumferential surface and the outer circumferential surface of the exhaust tube,
• the exhaust joint including:
• an engagement member having an annular portion and an engaging portion bent toward an inner circumference of the annular portion, and the engaging portion being constructed to be engaged with the projections and recesses in the exhaust tube in a state where the exhaust tube is inserted in the annular portion of the engaging portion;
• a joint body having a combustion apparatus connection portion for connection to the combustion apparatus and an exhaust tube connection portion for connection to the exhaust tube, to which the engagement member is attached;
• and
• a nut member having a screw portion screwed to the exhaust tube connection portion and a locking portion for preventing the engagement member from coming out of the joint body, wherein
• there is a gap in which the engagement member increases in diameter with insertion of the exhaust tube between the outer circumferential surface of the engagement member and the inner circumferential surface of the nut member,
• an inner surface of the exhaust tube connection portion has a first surface located on a side of an opening end and a second surface located closer to the combustion apparatus connection portion than the first surface, and
• in a cross-section in parallel to an axial line of the exhaust tube connection portion, each of the first surface and the second surface is inclined with respect to the axial line such that an inner diameter of the exhaust tube connection portion is smaller toward the combustion apparatus connection portion and an angle of inclination of the first surface with respect to the axial line is greater than an angle of inclination of the second surface with respect to the axial line.