An elongate tubular structure is disclosed. The elongate tubular structure has a first and second tubular structure wherein a first end of the first tubular structure is matingly and fasteningly engaged to a first end of the second tubular structure. The first and second tubular structures each have a first sheet metal having a machine direction being convolutely wound about a first longitudinal axis. The first sheet metal has a tail portion that is disposed upon and bonded to an immediately subjacent convolution of the first sheet metal to form the respective first and second tubular structures.

A fin-assembled tube includes a helical fin arranged in an interior of a tube, wherein the tube has: a straight tube portion the center line of which extends in a substantially straight line; and a bent portion the center line of which is curved, and the helical fin is formed such that a helical pitch in an axial direction is longer in a portion positioned in the bent portion relative to the helical pitch in a portion positioned in the straight tube portion, the helical pitch being a pitch of a plate-shaped fin material twisted by a certain angle about the center line.

A manufacturing method for a bent member of the present invention includes a holding step of holding one end portion of a long steel material having an opening end in a longitudinal direction by a chuck, a feeding step of feeding the steel material in the longitudinal direction with the one end portion as a head after the holding step, a heating step of performing high-frequency induction heating on a portion of the steel material in the longitudinal direction to form a heated portion, a bending step of moving the chuck in a three-dimensional direction to apply a bending moment to the heated portion, and a cooling step of injecting a cooling medium to the heated portion to cool the heated portion after the bending step. When the heating step is started, the chuck is cooled by the cooling medium in a state where a heating amount applied to the one end portion when the heated portion is formed on the one end portion is greater than that of an upstream side adjacent portion adjacent to the upstream side of the one end portion as seen along a feeding direction of the steel material.

A manufacturing method for a bent member of the present invention includes a holding step of holding one end portion of a long steel material having an opening end in a longitudinal direction by a chuck, a feeding step of feeding the steel material in the longitudinal direction with the one end portion as a head after the holding step, a heating step of performing high-frequency induction heating on a portion of the steel material in the longitudinal direction to form a heated portion, a bending step of moving the chuck in a three-dimensional direction to apply a bending moment to the heated portion, and a cooling step of injecting a cooling medium to the heated portion to cool the heated portion after the bending step. When the heating step is started, the chuck is cooled by the cooling medium in a state where a heating amount applied to the one end portion when the heated portion is formed on the one end portion is greater than that of an upstream side adjacent portion adjacent to the upstream side of the one end portion as seen along a feeding direction of the steel material.

An apparatus for manufacturing a heat exchanger including a refrigerant tube, the apparatus including a moving rod movable along a first direction; and a tube expansion body connected to the moving rod to be linearly movable along the first direction, the tube expansion body insertable into a tube base material of the refrigerant tub such that the tube base material is expanded outward when the tube expansion body is inserted into the tube base material of the refrigerant tube, wherein the tube expansion body includes a plurality of groove forming protrusions formed on an outer surface of the tube expansion body so as to extend along a direction inclined with respect to the first direction, the groove forming protrusions form a plurality of grooves on an inner surface of the tube base material, when the tube expansion body is moved to be inserted into the tube base material.

An apparatus for manufacturing a heat exchanger including a refrigerant tube, the apparatus including a moving rod movable along a first direction; and a tube expansion body connected to the moving rod to be linearly movable along the first direction, the tube expansion body insertable into a tube base material of the refrigerant tub such that the tube base material is expanded outward when the tube expansion body is inserted into the tube base material of the refrigerant tube, wherein the tube expansion body includes a plurality of groove forming protrusions formed on an outer surface of the tube expansion body so as to extend along a direction inclined with respect to the first direction, the groove forming protrusions form a plurality of grooves on an inner surface of the tube base material, when the tube expansion body is moved to be inserted into the tube base material.

A shaping method for a double pipe includes: bending the double pipe with a specified curvature to form a bent portion in the double pipe; and arranging the bent portion on a first shaping die having a first shaping surface at a position biased inward or outward in a curvature radius direction of the bent portion relative to the first shaping surface, wherein the first shaping surface is configured to shape a first outer surface of both outer surfaces of the bent portion that are located on both sides of a plane including a central axis of the bent portion, and pressing the bent portion arranged on the first shaping die by a second shaping die having a second shaping surface configured to shape a second outer surface of the both outer surfaces of the bent portion.

A shaping method for a double pipe includes: bending the double pipe with a specified curvature to form a bent portion in the double pipe; and arranging the bent portion on a first shaping die having a first shaping surface at a position biased inward or outward in a curvature radius direction of the bent portion relative to the first shaping surface, wherein the first shaping surface is configured to shape a first outer surface of both outer surfaces of the bent portion that are located on both sides of a plane including a central axis of the bent portion, and pressing the bent portion arranged on the first shaping die by a second shaping die having a second shaping surface configured to shape a second outer surface of the both outer surfaces of the bent portion.

An apparatus for bending a composite tube that includes an induction coil. Induction coil includes multiple turns and the turn-to-turn spacing changes at least once along the length of the induction coil. There is a heating element positioned near the induction coil and the induction coil is configured to cause the heating element to increase in temperature.

The present invention provides a new bending apparatus and bending method of a tube material which makes it possible to achieve all of bending by a large bending radius not requiring large scale equipment or die, bending resistant to wrinkling and buckling at an inner side of the bending, and bending with a high productivity, that is, a ram bending apparatus using a punch 12 and a set of rolls 13, 13 for three-point bending of a tube material wherein the punch 12 has a groove 12a of a width of the width of a circular tube 11 or more and wherein the set of rolls 13, 13 are supported by a frame 14. The rolls 13, 13 can freely move on the frame 14 in directions away from each other in a state contacting the punch 12. The frame 14 has a hollow space 14a enabling free movement of the descending punch 12 and the circular tube 11 bent along with this during the bending of the circular tube 11.