JPH08332578A - Device for manufacturing spiral fin tube - Google Patents

Abstract

PURPOSE: To prevent leakage or spark through spatter or metal powder by thermally spraying alumina, an insulating material, on two surfaces of a square electrode. CONSTITUTION: An electrically insulating film 7 is formed by thermally spraying alumina, an insulating material, on two surfaces, a surface oppositely facing the fin 6 immediately after being welded as shown in hatched part on the side face of a square electrode 3, and a surface behind one oppositely facing a flat electrode 4. Consequently, conductivity is eliminated from the square electrode 3 in the direction opposing the fin 6; hence, a high-frequency current does not flow between the electrode and the fin, in spite of the accumulation of a metal powder generated at the time of sliding of the electrode on a tube stock 1 or a spatter from a weld zone between the electrode 3 and the fin just after the welding; therefore, leakage or spark is completely prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency resistance welding type spiral fin tube manufacturing apparatus suitable for preventing leakage during welding.

[0002]

2. Description of the Related Art FIG. 2 is a perspective view showing a main part of a conventional spiral fin tube manufacturing apparatus. As shown in the figure, 1 is a plain tube, 2 is a fin material, 3 is a square electrode for welding current conduction, 4 is a flat electrode for welding current conduction, 5
Is a pressure roller, and 6 is a fin immediately after welding. In addition, there are an unillustrated feeding mechanism that feeds the element tube 1 in the axial direction while rotating it, and an unillustrated high frequency power source that supplies a high frequency current to the rectangular electrode 3 and the flat electrode 4. When the spiral fin is welded to the tube by high frequency resistance welding, the fin material 2 is spirally attached to the element tube 1 as shown in this figure.
Square electrode 3 for passing welding current in the process of winding
Is pressed against the base tube 1, the other flat electrode 4 is pressed against the fin material, and a high-frequency current is applied to the base tube 1 and the fin material 2 while the fin material 2 is pressed against the base tube 1 by the pressure roller 5. Welding is carried out continuously by utilizing the high-frequency local heat generated at the contact point. During high-frequency welding of fins, spatter is generated from the molten portion, and metal powder of the electrodes is generated due to abrasion when the rectangular electrode 3 slides on the raw tube 1. When the pitch of the spiral fin is small, these spatters and metal powders often accumulate between the square electrode 3 and the fin 6 immediately after welding to form a conductive bridge between the electrode and the fin. This bridge causes high frequency current leakage and sparking.

[0003]

The prior art described above does not take into consideration that the rectangular electrode 3 is in an uncovered state and is susceptible to leakage of electric current and spark due to adhesion of conductive foreign matter. There is a problem that the tip portion of the electrode 3 is damaged, and the electrode must be frequently replaced, so that the work is interrupted and the productivity is reduced. In addition, there is a problem that the raw tube 1 is damaged by sparks and the quality of the product is deteriorated. An object of the present invention is to provide a highly reliable spiral fin tube manufacturing apparatus.

[0004]

[Means for Solving the Problems] The above-mentioned object is to provide a feed mechanism that feeds an elementary tube in an axial direction while rotating it, a pressure roller that presses a fin material in a direction orthogonal to the axial direction of the elementary tube, and A spiral fin tube manufacturing apparatus having a first electrode that contacts an outer periphery, a second electrode that contacts a fin material, and a high-frequency power supply that supplies a high-frequency current to the first electrode and the second electrode. This is achieved by forming a ceramic electric insulation coating on the surface of the electrode. The purpose is to feed the axial direction of the element tube while rotating the element tube, a pressure roller that presses the fin material in a direction orthogonal to the axis direction of the element tube, and a first electrode that contacts the outer circumference of the element tube. In a spiral fin tube manufacturing apparatus having a second electrode in contact with a fin material and a high frequency power supply for supplying a high frequency current to the first electrode and the second electrode, an alumina coating film formed by thermal spraying on the surface of the first electrode It is achieved by forming.

[0005]

By forming an electrically insulating coating on the surface of the first electrode, it is possible to prevent electric leakage and sparks due to spatter and metal powder accumulated between the first electrode and the fin immediately after welding, Since the tip of the first electrode is not damaged, the reliability of the device is improved. By using a ceramic having high heat resistance as the material of the electric insulating coating of the first electrode, which is heated to a high temperature due to heat generated during welding, the electric insulating coating is not deteriorated.
The alumina coating formed by thermal spraying as an electrical insulating coating has a high insulating effect because alumina is excellent in insulating properties against high frequencies as a raw material and adheres without gaps due to thermal spraying and does not peel off.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing a main part of a spiral fin tube manufacturing apparatus according to an embodiment of the present invention. As shown in the figure, 1 is a plain tube, 2 is a fin material, 3 is a square electrode for welding current application, 4 is a flat electrode for welding current application, 5 is a pressure roller, 6 is a fin immediately after welding, 7 Is an electrically insulating coating.
This drawing basically operates in the same manner as in FIG. 2, and the feature of this embodiment is that the side surface of the rectangular electrode 3 faces the fins 6 immediately after welding, which faces immediately after welding, and the surface facing the flat electrode 4. That is, alumina, which is an electrical insulating material, was sprayed on the two back surfaces of the above to form the electrical insulating coating film 7. If the electric insulating coating 7 is formed on the entire circumference of the rectangular electrode 3, the insulating effect is complete.
The reason for limiting to only the surface is that as a result of various trials, almost no electric leakage was observed from the surface where the electrically insulating coating 7 shown by the diagonal lines in this figure is not formed. As a result, the conductivity of the surface of the rectangular electrode 3 opposite to the fin 6 is lost, and metal powder or welding generated when the electrode slides on the raw tube 1 between the rectangular electrode 3 and the fin 6 immediately after welding. Even if the spatter from the part accumulates, the high-frequency current does not flow between the electrode and the fin, and leakage and spark can be completely prevented.

Thermal spraying using alumina was performed under the following conditions. Thermal spray method Explosive thermal spray Thermal spray material Al ₂ O ₃ (particle size 1 to 10 μm) Thermal spray gas flow rate C ₂ H ₂ 29 liters / min O ₂ 45 liters / min Thermal spray cycle 3 Cycle / Sec Coating thickness 100 μm Ceramics other than alumina For example, Silica (Si
The same effect can be obtained by spraying O ₂ ).

Next, the material of the electrode will be described. Chromium copper is used as the electrode material in this embodiment. Conventionally, electrolytic copper or metallic carbon was used, but there were problems such as bending due to heat, rapid wear, and brittleness. However, most of these problems were solved by using chromium copper as the material of the electrodes. The comparison between the wear amounts of chrome copper and electrolytic copper is as follows. As described above, according to the present embodiment, (1) productivity is improved by reducing the interruption of welding, (2) unmanned operation of the welding device is possible, and the operator can set up the next work. (3) The reduction of sparks reduces repair work due to damage to tubes and fins, and improves quality.

[0009]

EFFECTS OF THE INVENTION According to the present invention, by forming an electrically insulating coating on the surface of a rectangular electrode, it is possible to prevent leakage of electric current or sparks due to spatter or metal powder accumulated between the rectangular electrode and the fin immediately after welding. Prevents and improves the reliability of the device. An alumina coating formed by thermal spraying as an electrically insulating coating has excellent heat resistance and adhesion, and has a high insulating effect.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of a spiral fin tube manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of a conventional spiral fin tube manufacturing apparatus.

[Explanation of symbols]

 1 Elementary tube 2 Fin material 3 Square electrode 4 Flat electrode 5 Pressure roller 6 Fin just after welding 7 Electrical insulation coating

Claims (2)

[Claims] 1. A feed mechanism that feeds an element tube in an axial direction while rotating the element tube, a pressure roller that presses a fin material in a direction orthogonal to the axis direction of the element tube, and a first contacting the outer circumference of the element tube. Spiral fin tube manufacturing apparatus having a second electrode in contact with the fin material, and a high frequency power source for supplying a high frequency current to the first electrode and the second electrode, wherein the first electrode An apparatus for manufacturing a spiral fin tube, characterized in that a ceramic electric insulation coating is formed on the surface of the. 2. A feed mechanism for axially feeding the raw tube while rotating the raw tube, a pressure roller for pressing the fin material in a direction orthogonal to the axial direction of the raw tube, and a first contacting the outer circumference of the raw tube. Spiral fin tube manufacturing apparatus having a second electrode in contact with the fin material, and a high frequency power source for supplying a high frequency current to the first electrode and the second electrode, wherein the first electrode An apparatus for manufacturing a spiral fin tube, characterized in that an alumina coating is formed on the surface of said by thermal spraying.