JPS6213218A - Pipe bending device by high frequency heating - Google Patents

Abstract

PURPOSE:To execute bending for generating no buckling nor flattening by attaching an electrode to a pipe to be worked and its bending fittings, and supplying locally a high frequency current. CONSTITUTION:An electrode 7 is attached to a bending start side of a pipe A, an electrode 6 is attached to bending fittings 1, and both of them are con nected to a high frequency power source, rspectively. When executing the work ing, the pipe A is fixed to a pipe bending curved surface 3 by a clamp 4, a high frequency current is made to flow between the electrodes 6, 7, the pipe A is pressed and slide-moved by slide metallic fittings 5, and bending is execut ed. Accordingly, the high frequency current flows concentrically to a contact starting point of the fittings 1 and the pipe A, therefore, the minimum local heating is executed. Therefore, even in case of bending in which ratios of a bend radius R and a wall thickness T to an outside diameter D, namely, values of R/D and T/D are small, pipe bending can be executed without generating the buckling and flattening.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a tube bending device using high frequency heating for bending tubes such as heating tubes and cooling tubes of boilers, heat exchangers, etc.

<Conventional technology> Conventionally, for pipe bending, a method has been adopted in which a bending fitting having a pipe bending surface on the outer periphery is used, and the pipe is forcibly aligned to cause permanent deformation. , pipe bending devices such as pipe benders are used.

In conventional pipe bending equipment, the bending radius R relative to the outside diameter of the pipe is
When the ratio f'7D becomes 1.5 or less, the appearance of the tube at this time is shown in Fig. 4.

Even in the case of hot bending, the upper bent portion of the tube A had an extremely flat shape where wrinkles a were generated due to buckling on the bent abdomen. In addition, the ratio T/D of the wall thickness T of the tube to the outer diameter of the tube
A similar phenomenon occurred even when 0.08 or less.

For this reason, in the past, a swing pend method was adopted in which the bending radius was gradually reduced while forming.
/I) When bending a small radius thin-walled tube, the tube is heated using a gas burner or high-frequency induction heating.

<Problem that the invention seeks to solve> In the heating method in conventional tube bending equipment.

・Since the heating area for g is wide, the tube thickness T
The ratio Δt/T of the width Δt of the heating region to the width Δt of the heating region increases.

Generally, the larger Δt/T is, the more likely buckling is to occur, and in order to prevent buckling, it is necessary to perform extremely localized heating to suppress Δt/'I' to 1 to 2. power that cannot satisfy the conditions).

The present invention provides such a pipe bending device (in view of these three problems, it is possible to perform extremely small local heating) and to perform pipe bending work with a small value of T without causing buckling. To provide a pipe bending device capable of quickly bending a pipe without making the processed part flat.

〈Means for solving problems〉 The pipe bending device using high frequency heating of the present invention is as follows.

A bending fitting that has a deep bending curved surface formed on its outer peripheral surface and rotates the tube along the tube bending curved surface, a clamp that presses and fixes the tube to the tube bending curved surface of the bending fitting, and a rotation of the bending fitting. a slide fitting that moves in the tangential direction of the bending fitting according to the motion and sequentially presses the tube along the bending curved surface, and one electrode is electrically connected to the bending fitting and bends the tube. High frequency 'F! with the other electrode connected near the bending fitting on the starting side. L flow supply means.

<Function> When an electrode is connected to the bending fitting and the bending start point of the pipe and a high frequency current is conducted between the bending fitting and the pipe, the contact point between the bending fitting and the pipe is caused by the characteristics of the high frequency current. ? ! As a result of the concentrated flow, heat is generated due to contact resistance at the bending start portion, resulting in localized heating. Moreover, due to this heating, the neutral axis of bending of the tube shifts to the back side, and the rate of decrease in tube thickness due to bending decreases.

<Embodiment> As shown in FIG. 1 showing the external appearance of an embodiment of the pipe bending device according to the present invention and FIG. It is forcibly rotated around the center by a drive means (not shown).

A semicircular pipe bending curved surface 3 having a curvature corresponding to the radius of the pipe A to be bent is formed in the circumferential direction, and a clamp 4 for holding one end of the bent part of the pipe A is provided on the side thereof. It is being In addition, the slide fitting 51 that reciprocates in the tangential direction of the bending fitting l sequentially presses the back surface of the tube A, whose one end is fixed to the tube bending curved surface 3 of the bending fitting L, to bend the tube A into the tube bending curved surface 3. I try to press in the direction of overflowing. An electrode 6 for supplying high-frequency current is slidably connected to the pipe bending curved surface 3 of the bending fitting l, and the other electrode 7 is connected to the bending fitting at the rear end extension of the bending part of the pipe A. It is slidably connected to the vicinity of l.

On the other hand, as shown in FIG. 3 showing the cross-sectional structure of the first bending fitting 1, the first bending fitting 1 has a cooling water introduction passage 8 formed along the pipe bending curved surface 3 on the center side thereof. A cooling water injection nozzle (not shown) for spraying cooling water onto the outer surface of the pipe A is attached.

Therefore, by fixing the tube A with the clamp 4 within the tube bending curved surface 3 of the bending fitting 1, pressing the back side of the tube A with the slide fitting 5, and passing a high frequency current between the two electrodes 6 and 7, the electric current can be set to a high frequency. Due to the characteristics of , the electric current flows along the surface of the bending fitting l and the pipe A, concentrates at the bending starting point where the contact between the pipe A and the pipe bending curved surface 3 begins, and the contact electrical resistance between the pipe bending curved surface 3 and the core pipe A at this bending starting point increases. This generates heat, and the bending starting point of the tube A is locally heated. Further, this local heating is performed over a substantially semicircular portion where the outer circumferential surface of the tube and the tube bending curved surface 3 are in contact. In this way, the bending fitting 1 is rotated together with the clamp 4 while being locally heated, and the sliding fitting 5 is sequentially moved in accordance with this, and the bending process is performed by making the tube A follow the tube bending curved surface 3. . Note that, due to the supply of high-frequency current l, the bending fitting l itself also generates heat due to electrical resistance.

Cool water by flowing it through the 8-circle cooling water introduction channel.

Similarly, the back side of the tube A is also heated, but is cooled by jetting cooling water.

<Effect of the invention> The high frequency heating device of the present invention is a tube bending device.

Pipe bending with small values of R/D and D can be performed quickly without buckling or flattening. In addition, uniform heating in an extremely small range is possible during pipe bending, and the neutral axis of one bend moves to the back side of the bent pipe, reducing the rate of wall thinning at the back and increasing the degree of freedom in design. It is possible to expect a significant reduction in material due to the expanded processing tolerance.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of an embodiment according to the present invention, Fig. 2 is a right side view thereof, Fig. 3 is a sectional view of the bending fitting, and Fig. 4 is a perspective view of a pipe bent by a conventional device. be. In the drawings, A is a tube, l is a bending fitting, 3 is a tube bending surface, 4 is a clamp, 5 is a slide fitting, and 6° and 7 are electrodes. Turtle 1 Figure 2 Figure 3 Figure 1F-4

Claims (1)

[Claims] A bending fitting having a pipe bending curved surface formed on an outer peripheral surface and rotating the pipe along the pipe bending curved surface, a clamp that presses and fixes the pipe to the pipe bending curved surface of the bending fitting, and a rotation of the bending fitting. a slide fitting that moves in the tangential direction of the bending fitting according to the motion and sequentially presses the tube along the bending curved surface; and one electrode is electrically connected to the bending fitting and the bending of the tube starts. A tube bending device using high frequency heating, comprising a high frequency current supply means with the other electrode connected near the side bending fitting.