JP2000107826A - Manufacture of fin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacturing method by which the fin tube with bent parts bent to the side formed on the periphery of the fin, can be efficiently produced continuously. SOLUTION: While rotating the tube 57 at a constant speed and feeding it in the axial direction, after winding the band steel shape fin 58 in helical form on the periphery of the tube 57, they are welded. And, after that, a jig 55 is made to come into contact with the fin 58, and the jig 55 is rotated in the reverse direction to the tube 57. Consequently, while notches are produced on the outer periphery of the fin by blades 56, the bent parts 59 which are in the reverse direction each other, are formed on both sides of the notch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a fin tube used in a heat exchanger, in which fins are spirally wound around a tube.

[0002]

2. Description of the Related Art Fin tubes are used to increase the heat transfer area.
As shown in FIG. 2, a band-shaped fin a is spirally wound around a tube b, and is called a solid fin tube as shown in FIG. 2 or a segment formed by cutting a fin as shown in FIG. Serrated fin tubes with fins are widely used, and among the serrated fin tubes, fins formed in a strip shape by cutting are twisted at a certain angle to further improve heat transfer to form an impeller shape. Eggplant is also known (June 55-42140)
issue).

In such a fin tube, the fin is generally attached to the tube by high-frequency resistance welding, that is, by passing a high-frequency current while one electrode is applied to the fin and the other electrode is applied to the tube.

[0004]

The prior applications of the present invention, Japanese Patent Application Nos. 9-7378 and 9-18569, include:
A fin tube shown in FIG. 5 is formed by making a cut in the outer peripheral edge of the fin and folding both sides of the cut as shown in FIG. 4 to form a bent portion in the opposite direction, and bending both sides of the cut in the same direction as shown in FIG. FIG. 8 in which the direction of the bent portion c formed in the spiral direction is alternately reversed, and FIG. 8 in which the direction of the bent portion c is the same direction.
Are proposed. According to such a fin tube, the bent portion suppresses separation of the external flow, reduces the wake area, improves the heat transfer coefficient on the outflow side of the external flow, and obtains an effect of enlarging the heat transfer area. The effect that the whole heat transfer effect can be improved is produced.

The present invention relates to a manufacturing method suitable for continuous production of fin tubes described in the above-mentioned prior application, and a first object of the present invention is to provide a fin tube having one or both bent portions as described above. The second object is to provide a method for manufacturing a fin tube in which continuous production is possible, and the third object is to provide a method for manufacturing a fin tube in which the number of steps is reduced. Things.

[0006]

The invention according to claim 1 is an invention for achieving the first object, in which a notch is formed at one side edge of a band-like fin at an appropriate interval using a press machine. A first step of forming a bent portion protruding laterally by pressing one side, preferably both sides of the fin, and a second step of helically winding the fin obtained in the first step around a tube and fixing the fin by welding means. It is characterized by consisting of.

Various methods can be considered as the processing method of the first step. 9 and 10 are preferred.
As shown in the figure, the die 2 is fixed to the fixed die 1a,
a, using a press machine in which a punch 4 is arranged in parallel with the other mold 1b which is supported so as to be able to ascend and descend along a vertically provided guide rod 3, and a fixed amount of band-shaped fins 5 are arranged between the molds. When the feed is stopped, the die 1b is lowered when the feed is
By being engaged with the die 2, cuts are formed at one side edge of the fin at appropriate intervals, and a bent portion is formed on one side, preferably both sides of each cut. Such a bent portion can be arbitrarily changed in shape and direction by replacing the mold or as shown in FIG. 9 by incorporating a punch or a die into the mold so as to be replaceable. For example, if a metal fitting as shown in FIG. 9 is used, a bent portion in the opposite direction as shown in FIG. 4 is formed, and if a tool having a die having a V groove and a punch having a V-shaped projection is used, A bent portion as shown in FIG. 6 is formed.

In the present invention, the fins bent in the first step are intermittently fed out by a fixed amount from the first step, whereas the fins are continuously wound on a tube in the second step. Therefore, it is conceivable that the fins obtained in the first step are once wound on a reel, for example, and then are unwound from the reel at any time in the second step. However, in this case, fin tube production lacks continuity.

The invention described in claim 2 is an invention for achieving the second object, and in the invention described in claim 1, the first invention is provided.
Between the step and the second step, for example, a slack absorbing means such as a tension roller is provided, and the fins sent out from the first step are temporarily fed in and stored, and the stored fins are fed out gradually and continuously to the second step. It is characterized by the following. The invention according to claim 3 is also an invention for achieving the second object, and comprises a pair of rotating rollers, and a die 2 shown in FIGS. Using a tool provided with a plurality of punches 4 on the peripheral surface of the roller, preferably at a certain interval in the circumferential direction, feeding the band-shaped fins between the rotating rollers while rotating the rotating roller, and adapting the punch to the die. A first step of forming a bent portion protruding laterally by pressing one side, preferably both sides of the notch, and fins sent out from the first step are spirally wound around a tube. And a second step of fixing by welding means.

In the first step of the present invention, since the rotating roller can be continuously rotated, the fin having the bent portion can be continuously sent to the second step. Therefore, in this case, the slack absorbing means according to the second aspect of the present invention is not required. Similarly to the above-described mold, the rotating roller of the present invention can change the shape and direction of the bent portion arbitrarily by replacing the rotating roller or replacing a punch or a die incorporated in the rotating roller. it can.

According to a fourth aspect of the present invention, there is provided another invention for achieving the first object, wherein a fin-shaped fin is spirally wound around a tube and fixed by welding means, and cutting means. A second step of making a slight cut in the outer peripheral edge of the fin fixed to the tube by the tube axis direction, and applying the jig to the cut using a bending jig, and pushing one or both sides of the cut into the side. A third step of forming a bent portion protruding laterally.

When the fin is wound around the tube and cuts to form a bent portion, the fin is guided or gripped from both sides during winding onto the tube, and the fin is wound around the tube. Since the fins can be pressed and welded with a constant force, the fins can be attached at a constant pitch without inclining or twisting, and the welded portion to the tube can be attached without waving.

In the case of the invention according to claim 4,
The bent portions can be aligned in the tube axis direction at the same position in the circumferential direction, and the bent portions can be formed only where necessary in the circumferential direction, for example, only on one side or in the circumferential direction.

As the cutting means of the present invention, a rotary blade is preferably used. The rotary blade can be advanced and retracted in the diametrical direction of the fin tube to make a cut in the fin, but is preferably moved in the axial direction of the fin tube parallel to the fin tube to make a cut in the fin. You. When the cutting means moves in the axial direction of the fin tube in comparison with the method in which the cutting means advances and retreats in the diametric direction and makes a cut, and after the cut, the movement of the cutting means is repeated in the tube axis direction by the pitch of the fins, the movement is reduced. Because of the simplicity, the structure and control of the cutting means are simple, the work efficiency is improved, and the cutting is completed in a short time.

FIGS. 15 and 1 show a folding jig.
6, a blade portion 13 inserted into the cut 12 of the fin 11, and an inverted triangular bent portion 14 protruding from the blade portion 13 at the same pitch as the fin 11,
A roller having a trapezoidal rotating roller 16 as shown in FIG. 17 is exemplified. In the former jig shown in FIGS. 15 and 16, after the blade portion 13 is inserted into the cut 12 of the fin 11, it can be bent at the bending portion 14 by pulling in the direction of the arrow in FIG. In the jig shown, by moving the rotary roller in the diametrical direction of the tube, preferably in the axial direction of the fin tube while driving the rotary roller, the bent portion can be formed by pushing in the portion corresponding to the rotary roller.

A fifth aspect of the present invention relates to a method of manufacturing the fin tube shown in FIG. 5. In the fourth aspect of the present invention, the bending jig used in the third step is placed on a circumference around the fin tube. A plurality of jigs are arranged at appropriate intervals in the circumferential direction, each jig has a trapezoidal cross section, and using a rotating roller with a large diameter portion directed toward the notch, reciprocating in the axial direction of the fin tube while rotating each rotating roller. It is characterized in that one side of the cut is pushed in one direction when going forward, and the other side is pushed in the opposite direction when going backward, so that bent portions opposite to each other are formed.

The bending jigs in the present invention are respectively
One rotating roller, one at the time of going and returning
The large-diameter portion may be turned to the cut by turning by 80 °, or may be constituted by a pair of rotating rollers facing the large-diameter portion. The roller may be switched to the operative position when returning to form the bent portion of the fin.

According to a sixth aspect of the present invention, in the first aspect of the invention, a plurality of bending jigs used in the third step are arranged on the circumference around the fin tube at appropriate intervals in the circumferential direction. A pair of cross-section rotating rollers whose large-diameter portions face each other and are close to each other are trapezoidal, and both sides of the cut are made by moving each roller in the diametrical direction of the fin tube or in the axial direction of the fin tube while rotating each roller in the opposite direction. A bent portion is formed by pushing in the opposite direction.

According to the present invention, the bending portion can be formed by a single operation of pushing the rotary roller in the diametrical direction or the axial direction of the fin tube, and particularly, the rotary roller is moved in the axial direction of the fin tube. In this case, the bent portion can be formed in all the cut portions in one step of the forward step. The invention according to claim 7 relates to a method for manufacturing the fin tube shown in FIG.
In the invention described above, a plurality of bending jigs used in the third step are arranged on the circumference of the fin tube at appropriate intervals in the circumferential direction, and a cross section in which the large-diameter portion faces and approaches each jig has a trapezoidal shape. By using a pair of rotating rollers and moving the pair of rotating rollers of each jig in the axial direction of the fin tube while rotating the pair of rotating rollers, both sides of the cut are pushed by the rotating rollers to form a bent portion in the same direction. I do.

In the present invention, the processing for forming the bent portions at all the cut portions can be performed in one step only by moving the jig in one direction along the tube. The invention according to claim 8 relates to a method of manufacturing the fin tube shown in FIG. 7. In the invention according to claim 4, a plurality of bending jigs used in the third step are formed on a circumference around the fin tube. Using a pair of rotating rollers whose cross section is trapezoidal with the large-diameter part facing each jig and approaching each other at appropriate intervals in the direction, and rotating the pair of rotating rollers of each jig, move the jig in the axial direction of the fin tube. Of the cuts formed in the spiral direction at the time of going forward by reciprocating, an appropriate location, for example, pressing both sides of every other cut from one side with a rotating roller to form a bent portion in the same direction, the remaining at the time of returning A feature is that both sides of the cut are pushed in from the opposite direction by a rotating roller to form a bent portion in the opposite direction.

In the present invention, it is necessary to reciprocate the jig in order to form a bent portion at all cut portions. The rotating rollers according to the present invention can be switched between an active position and an inactive position, and at the time of going forward, an appropriate position, for example, every other rotating roller is switched to the active position, and the other rotating rollers are switched to the inactive position. At the same time, each rotating roller may be switched in the reverse direction when returning, or the entire jig composed of rotating rollers can be rotated in the circumferential direction, and the jig is switched when switching forward and returning. You may make it rotate by a fixed angle.

According to a ninth aspect of the present invention, in order to achieve the third object, a band-shaped fin is spirally wound around a tube and welded, and then the outer peripheral edge is sharpened to form a blade. Using a cross-section trapezoidal or abacus cross-section rotary cutter,
While making a cut in the fin fixed to the tube, one side or both sides of the cut is pushed to the side to form a bent portion. According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the rotation axis of the rotary cutter is formed at an acute angle with respect to the axis of the tube. The invention according to claim 11 is another invention which achieves the third object, wherein a fin in the form of a metal band is spirally wound around a tube and welded, and then the cutting edge is formed on the peripheral surface of the wheel along the axis of the tube. On the other hand, using a jig with an approximately triangular blade protruding at an acute angle, the jig is brought into contact with a fin fixed to the tube, and one of the jig and the tube is moved in the axial direction of the fin tube while rotating. In this method, one side or both sides of the notch is pushed in while making a notch to form a bent portion. In each of the above inventions, the cutting means and the bending jig according to the fourth aspect of the invention are shared, and the second and third steps can be performed simultaneously.
In particular, in the tenth and eleventh aspects of the present invention, FIG.
As shown in FIG. 1, on one side of the cut 7 on one side,
On the other side, the bent portion 8 is pushed out to the other side so as to protrude, so that the amount of protrusion of the bent portion 8 to the side is increased.

In a preferred aspect of the present invention, the bent portion is formed only on one side of the fin, for example, only on the outflow side of the fluid passing outside the fin tube. In the case of the exhaust heat recovery heat exchanger connected to the gas turbine exhaust gas, the gas hits the fin tube at a high speed. If only the outlet side is formed, the pressure loss is reduced, and the output of the turbine is increased correspondingly, and the overall efficiency is improved. The bent portion of each of the above inventions includes not only a triangular bent portion as shown in FIGS. 4 and 6, but also a protruding portion that protrudes or protrudes to the side. The welding means for fixing the fins in the first or fourth aspect of the present invention includes, for example, arc welding, fillet welding, high frequency resistance welding or brazing.

[0024]

FIG. 12 shows an overall configuration of a fin tube manufacturing apparatus in which a bent portion is formed on a fin and then wound around a tube, and a reel 21 on which a band-shaped unfinished fin is wound. , A press 22, guide rollers 23 a, 23 b, 23 c, 23 d and a welding station 24.
Are formed on one side edge of the band-like fin 25 fed out from the reel 21 so as to form a bent portion composed of the bent portion shown in FIG. 4 or FIG. 6 or a combination thereof. Has become.

Guide rollers 23a, 23b, 23c, 2
One 23b of the 3d is a tension roller which is urged in the direction of the arrow by a spring (not shown) and absorbs the slack of the fin 25 up to the welding station 24, which is a welding means. At the welding station 24, although not shown, the tube 26 is fed forward while rotating, so that the fin 25 having the bent portion is spirally wound. And FIG.
As shown in FIG. 3, one of the pair of electrodes 27a and 27b of the high-frequency resistance welding used as the welding means is used.
“a” is applied to the tube 26 and the other electrode 27 b is applied to the fin 25, and the fin 25 is welded to the tube 26 by passing a high-frequency current.

The manufacture of the fin tube in this embodiment is performed as follows. In the first step, the fins 25 are fed out from the reel 21 by a predetermined amount due to intermittent feeding of the feed roller 28 provided on the feed side of the press machine 22. On one side edge, a bent portion made of a bent portion shown in FIG. 4 and / or FIG. 6 or a combination thereof is formed by a press machine 22.

The fins 24 obtained in the first step are sent out by the drive of the feed roller 28, and are temporarily fed and stored by the tension roller 23b before reaching the welding station 24 in the second step. Then, as the tube is spirally wound around the tube 26 at the welding station 24, it is gradually and continuously fed out. In the welding station 24 in the second step, the fins 25 are welded by high frequency resistance welding while being continuously wound around the tube 26.

FIG. 14 shows a configuration in which a pair of rotating rollers 31a and 31b are used instead of the press machine 22 in the apparatus shown in FIG.
The dies 2 shown in FIGS. 9 and 10 are provided on one roller peripheral surface of each of the rotating rollers 31a and 31b, and the tool 32 having the punch 4 attached to the other roller peripheral surface is provided. In the case of this embodiment, the fin 2 is
5 is continuously unwound, bent by a tool 32, and continuously fed to a welding station 24, where the tube 2 is fed.
6 is spirally wound and fused by high frequency resistance welding. In this embodiment, since the fins 25 are continuously moved to the welding station, the above-described tension roller 23 is used.
b is unnecessary, and thus the tension roller 23b and the guide roller 23c shown in FIG. 12 are omitted. FIG.
5 to 22 show an embodiment in which a bent portion is formed after spirally winding a band-shaped fin around a tube, or a first step of winding the band-shaped fin. Then, a known method is used, and fins are wound by high-frequency resistance welding as welding means while winding through a guide, that is, one of a pair of electrodes is applied to the tube, and the other is applied to the fin, and a high-frequency current is applied to the tube. Welded to.

FIGS. 18 and 19 show a bending jig used in the second and third steps. The rotary roller 4 having a trapezoidal cross section with a sharpened outer peripheral edge and a sharpened tip is used.
The rollers 41 are radially arranged on the circumference at equal intervals, and the diameter of the inscribed circle is smaller than the diameter of the fin tube 42 obtained in the first step. When cutting and bending the fin 43 of the fin tube 42, the fin tube 42 is made to travel along the fin tube 42 in the direction of the arrow in FIG. Then, the fin 43 is
One side of the cut is pushed in while the cut is made,
It is bent at the bending line crossing the cut. When reaching the end of the fin 43, the direction of the rotary roller 41 is reversed as shown in FIG. 20, and the other side of the cut is pushed in and bent in the same way while going backward. As described above, a fin tube as shown in FIG. 5 is obtained.

In the above embodiment, one rotating roller is used to reverse the direction of the bent portions on both sides of the cut, but in another embodiment, a pair of rotating rollers is used. , Each roller can be switched to a use position and a non-use position, and one of the rollers is
At the time of return, the other rotating roller is switched to the use position.

In still another embodiment, as shown in FIG. 21, a pair of rotating rollers 45a, 45b rotating in opposite directions to each other.
However, it is moved along the fin tube 46 with the large-diameter portion approaching. In this case, only the movement in one direction causes both sides of the cut to be bent in the opposite direction. FIG.
8 shows a method for manufacturing the fin tube shown in FIG. 8, in which a substantially abacus ball-shaped rotary roller 48 having a sharpened outer peripheral edge and a sharp tip made of a carbide blade is moved along the fin tube 49 and cut into the fin 50. In this embodiment, both sides of the cut are pushed in and bent in the same manner as described above. Although only one rotating roller 48 is shown in the drawing for simplicity, the rotating rollers 48 are actually arranged radially at equal intervals on the circumference, similarly to the one shown in FIG.
The bending process is performed simultaneously at a plurality of locations in the circumferential direction.

FIG. 23 shows a case in which the same rotating roller 51 as the rotating roller 48 shown in FIG. 22 is provided only on the half-circumferential side. According to this, as shown in FIG. A bending process is performed on a half circumference of the fin 52. FIG. 25 is a diagram showing an embodiment relating to a method of manufacturing a fin tube in which projections which are opposite to each other are formed on both sides thereof while making a cut with a jig 55,
The jig 55 has substantially triangular blades 56 formed on the peripheral surface of the wheel at equal intervals in the circumferential direction so as to protrude so that the blade edges thereof form an acute angle with the axis.

The manufacture of the fin tube according to the present embodiment is performed as follows. While rotating the tube 57 at a constant speed and in the axial direction, a band-like fin 58 is spirally wound therearound and welded. Thereafter, the jig 55 is brought into contact with the fins 58 and rotated in the opposite direction to the tube 57. As a result, the blade 56 cuts the outer periphery of the fin, and the projections 59 are formed on both sides thereof in opposite directions.

[0034]

According to the first aspect of the present invention, in the method of manufacturing a fin tube having a bent portion formed on the periphery of the fin, the notch and the bent portion can be formed in one step by a press machine. Can be arbitrarily changed by changing the mold of the press machine or by changing the die or punch incorporated in the mold.

According to the second aspect of the present invention, the fins having the bent portions formed in the first step can be continuously sent to the second step to efficiently produce the fin tubes.
Also in the invention according to the third aspect, the notch and the formation of the bent portion can be performed in one step, and furthermore, the fixing of the fin to the tube can be continuously performed, so that the fin tube having the bent portion formed on the periphery of the fin can be efficiently and continuously produced. In addition, the shape and direction of the bent portion can be arbitrarily changed by replacing the rotating roller or the die or punch incorporated in the rotating roller, and continuously changing from the first step to the second step. Therefore, there is no need to provide fin slack absorbing means between the first step and the second step, and the configuration is simplified.

According to the fourth aspect of the present invention, when the fins are spirally wound around the tube, the fins are wound into a tube while passing the fins through a guide to form a strip without processing. The fins can be welded, so that the fins can be welded by pressing the fins to the tube with a constant force at a constant pitch without tilting or twisting. Are aligned in the axial direction of the fin tube, which facilitates the formation of cuts and bends, and also has the advantage that bends can be formed only at required locations in the circumferential direction or at appropriate intervals in the circumferential direction. Play.

According to the fifth aspect of the present invention, it is possible to form bent portions that are opposite to each other by reciprocating the jig in the tube axis direction of the tube. According to the sixth aspect of the present invention, the formation of the oppositely bent portions on both sides of the cut can be performed by a single operation of merely pushing the rotary roller in the diameter direction or the axial direction of the fin tube.

According to the seventh aspect of the present invention, the formation of the bent portion in the same direction at each cut location is performed only by moving each pair of rotary rollers radially arranged in the circumferential direction in the axial direction of the fin tube. be able to. According to the eighth aspect of the present invention, by bending the jig back and forth, the bent portion can be formed in one direction at a required cut portion in the circumferential direction and in the opposite direction at the remaining cut portions.

According to the ninth to eleventh aspects of the present invention,
The notch and the formation of the bent portion can be performed in one step. In particular, in the inventions according to claims 10 and 11,
Since the bent portion can be formed so as to protrude only on one side, the protrusion amount of the bent portion can be increased.

[Brief description of the drawings]

FIG. 1 is a plan view of a fin tube.

FIG. 2 is a side view showing an example of a fin tube.

FIG. 3 is a side view showing another example of the fin tube.

FIG. 4 is a perspective view showing one mode of a bent portion.

FIG. 5 is a plan view of a fin tube having a bent portion shown in FIG.

FIG. 6 is a perspective view showing another mode of the bent portion.

FIG. 7 is a plan view of a fin tube in which bent portions in the mode shown in FIG. 6 are alternately formed in the circumferential direction.

FIG. 8 is a plan view of a fin tube in which all the bent portions have the shapes shown in FIG. 6;

FIG. 9 is a sectional view of a mold.

FIG. 10 is a perspective view of a main part showing one side of a mold.

FIG. 11 is a diagram illustrating one embodiment of a bent portion.

FIG. 12 is a schematic view of a manufacturing apparatus used in the present invention.

FIG. 13 is a front view showing details of the welding station shown in FIG. 12;

FIG. 14 is a schematic view of another manufacturing apparatus used in the present invention.

FIG. 15 is a plan view showing an example of a bending jig.

FIG. 16 is a side view of the bending jig shown in FIG. 9;

FIG. 17 is a plan view showing another example of the bending jig.

FIG. 18 is a plan view showing a mode in which a fin is bent in one direction using the bending jig shown in FIG. 17;

FIG. 19 is a side view in which bending jigs are radially arranged.

FIG. 20 is a plan view showing an aspect when bending is performed in the opposite direction.

FIG. 21 is a plan view showing a state in which the fin is bent in the opposite direction.

FIG. 22 is a plan view showing a mode in which fins are bent in the same direction.

FIG. 23 is a diagram showing one embodiment of a bending jig arrangement.

24 is a side view of a fin tube formed by the jig shown in FIG.

FIG. 25 is a perspective view showing an object when forming a fin tube having a projection.

[Explanation of symbols]

1a, 1b ·················································· Die ··················· Punch 5, 15 ····························· 13, blade part 14, bent part 16, 41, 45a, 45b, 48, 51, rotating roller 21, reel 22, press machine 23a, 23b, 23c, 23d, guide roller 24, welding Station 26 Tube 27a, 27b Electrode 28 Feed roller 31a, 31b Rotary roller 32 Tool 42, 46, 49 Fin tube 55 Jig 56 Blade 57 Tube 59 ·protrusion

Claims (11)

[Claims] 1. A first step of forming cuts at one side edge of a band-shaped fin at an appropriate interval using a press machine, and pressing one or both sides of the cut to form a bent portion projecting sideways. And a second step in which the fin obtained in the first step is spirally wound around a tube and fixed by welding means. 2. A slack-absorbing means for interposing a fin intermittently fed from the first step to absorb slack between the first step and the second step.
The method for producing the fin tube described above. 3. A band-shaped fin using a tool comprising a pair of rotating rollers, a die attached to the peripheral surface of one rotating roller, and a punch attached to the peripheral surface of the other rotating roller, while rotating the rotating roller. And a fin sent out from the first step of forming a bent portion by pressing one side or both sides of the notch to form a bent portion while feeding the punch between the rotating rollers, making the punch conform to the die, making a cut. A second step of spirally winding the helical tube around the tube and fixing it by welding means. 4. A first step of spirally winding a band-shaped fin around a tube and fixing it by welding means, and making a cut in the outer peripheral edge of the fin fixed to the tube by cutting means in the axial direction of the tube. A second step, and a third step of applying the jig to the cut using a bending jig and pressing one or both sides of the cut to the side to form a bent portion protruding sideways. Fin tube manufacturing method. 5. In a third step, a plurality of bending jigs are arranged on the circumference of the fin tube at appropriate intervals in the circumferential direction, each jig has a trapezoidal cross section, and the large-diameter portion faces the cut. While rotating each rotating roller, reciprocate in the axial direction of the fin tube while rotating each rotating roller, push one side of the cut in one direction when going forward, and push the other side of the cut in the opposite direction when going backward to reverse each other. The method for manufacturing a fin tube according to claim 4, wherein a bent portion is formed in a direction. 6. In the third step, a plurality of bending jigs are arranged on the circumference of the fin tube at appropriate intervals in the circumferential direction, and a pair of cross sections whose large diameter portions face and approach each jig are trapezoidal. By rotating the rollers in the direction opposite to each other and moving them in the diametrical direction of the fin tube or in the axial direction of the fin tube while rotating the rollers in the opposite direction, the opposite sides of the cut are pushed in opposite directions to form a bent portion. The method for producing a fin tube according to claim 4. 7. In the third step, a plurality of bending jigs are arranged on the circumference of the fin tube at appropriate intervals in the circumferential direction, and a cross section in which the large-diameter portion faces and approaches each jig has a trapezoidal shape. By using a pair of rotating rollers and moving the pair of rotating rollers of each jig in the axial direction of the fin tube while rotating, the both sides of the cut are pushed by the rotating rollers to form a bent portion in the same direction. A method for producing a fin tube according to claim 4. 8. In the third step, a plurality of bending jigs are arranged on the circumference of the fin tube at appropriate intervals in the circumferential direction, and a cross section in which a large-diameter portion faces and approaches each jig has a trapezoidal shape. Using a pair of rotating rollers, reciprocating in the axial direction of the fin tube while rotating a pair of rotating rollers of each jig, both sides of some of the cuts formed at appropriate intervals in the spiral direction when going forward 5. A bent portion having the same direction is formed by pushing in from one side with a rotating roller, and both sides of the remaining cut are pushed in from a reverse direction by a rotating roller to form a reversed bent portion when returning.
The method for producing the fin tube described above. 9. A band-shaped fin is spirally wound around a tube and welded, and then fixed to the tube using a rotary cutter having a trapezoidal cross section or an abacus cross section having a sharpened outer peripheral edge. A method for manufacturing a fin tube, wherein a bent portion is formed by pushing one side or both sides of the cut into the side while making a cut in the cut fin. 10. The method for manufacturing a fin tube according to claim 9, wherein the rotary shaft of the rotary cutter forms an acute angle with respect to the axis of the tube. 11. A jig in which a band-shaped fin is spirally wound around a tube and welded, and a jig having a substantially triangular blade having a cutting edge formed at an acute angle with respect to the axis of the tube is provided on a peripheral surface of the wheel. Use the jig in contact with the fin fixed to the tube, rotate and move one of the jig and the tube in the axial direction of the fin tube, make a cut with a blade, and push one or both sides of the cut to bend. Forming a fin tube.