Duct and method of manufacturing the same
A duct of the present invention includes a pair of groove-shaped members which are formed of sound absorbing sheets and a pair of flange portions which are formed of parts of the pair of groove-shaped members that are extended outward from groove opening edges and which are joined in an overlaid state on each other when the pair of groove-shaped members are arranged such that groove openings are opposed to each other. The pair of flange portions includes a seal portion which is formed by crimping the sound absorbing sheets in parts of the flange portions along the groove opening edges and an outer thick portion which is extended outward from the seal portion and which is formed of the sound absorbing sheet thicker than the sound absorbing sheet of the seal portion.
1. A duct comprising:
a pair of groove-shaped members formed of sound absorbing sheets; and
a pair of flange portions formed of parts of the pair of groove-shaped members extending outward from groove opening edges and joined in an overlaid state on each other when the pair of groove-shaped members are arranged such that groove openings are opposed to each other,
the pair of flange portions including:
a seal portion formed by crimping the sound absorbing sheets in parts of the flange portions along the groove opening edges;
an outer thick portion extending outward from the seal portion and formed of the sound absorbing sheet thicker than the sound absorbing sheet of the seal portion; and
an outer crimped portion extending outward from the outer thick portion, the outer crimped portion formed by crimping the sound absorbing sheets along an outer edge of the outer thick portion.
2. The duct according to claim 1 , wherein:
at least one of the sound absorbing sheets located on a duct wall of the duct is compressed in a thickness direction, and
the sound absorbing sheets on the outer thick portion is thicker than the sound absorbing sheets on the duct wall.
3. The duct according to claim 2 ,
wherein the outer thick portion is sandwiched between the outer crimped portion and the seal portion.
4. The duct according to claim 1 ,
wherein the outer thick portion is sandwiched between the outer crimped portion and the seal portion.
5. The duct according to claim 1 , wherein:
in the duct, a corner portion which is curved within a surface parallel to a junction surface of the pair of groove-shaped members is provided, and
the outer thick portion is arranged inside the corner portion.
6. The duct according to claim 1 ,
wherein the sound absorbing sheets are laminated sheets, each including a closed-cell layer which is formed of a closed-cell member and a non-woven fabric layer which is formed of a non-woven fabric, and the sound absorbing sheets are arranged such that the closed-cell layer faces inward of the duct.
7. A method of manufacturing a duct comprising:
forming a pair of sound absorbing sheets obtained by overlaying the pair of sound absorbing sheets, with at least one of molding methods of vacuum molding and pressure molding, into a shape of a groove so as to form a pair of groove-shaped members; and
joining a pair of flange portions which are extended outward from groove opening edges of the pair of groove-shaped members, the joining of the pair of flange portions including:
crimping the pair of sound absorbing sheets in parts of the pair of flange portions along the groove opening edges so as to form a seal portion as a junction of the pair of flange portions;
forming an outer thick portion which is extended outward from the seal portion and which is formed of the pair of sound absorbing sheets, the pair of sound absorbing sheets being thicker at the outer thick portion than at the seal portion; and
crimping the pair of sound absorbing sheets along an outer edge of the outer thick portion, the crimping of the pair of sound absorbing sheets forming an outer crimped portion extending outward from the outer thick portion; and
trimming the pair of flange portions such that at least a part of the outer thick portion remains.
8. The method according to claim 7 , wherein:
the crimping of the pair of sound absorbing sheets sandwiches the outer thick portion with the seal portion, and
joining the pair of flange portions includes trimming the pair of flange portions along the outer crimped portion.
9. The method according to claim 8 further comprising:
forming the pair of groove-shaped members into a shape to include a corner portion curved within a surface parallel to a junction surface of the pair of groove-shaped members; and
forming the outer thick portion in parts of the pair of flange portions located inward of the corner portion.
10. The method according to claim 7 further comprising:
forming the pair of groove-shaped members into a shape to include a corner portion curved within a surface parallel to a junction surface of the pair of groove-shaped members; and
forming the outer thick portion in parts of the pair of flange portions located inward of the corner portion.