JPH04220524A - Method and apparatus for forming lining in pipe - Google Patents

Abstract

PURPOSE:To remove bubbles generated on an inner face of a lining, improve accuracy in an inner diameter size and eliminate need of subsequent processing of an inner peripheral face. CONSTITUTION:A circular empty chamber 16 is formed between a core 13 and an outer cylinder 14, and also bubble reservoirs 19 connected to the circular empty chamber 16 are formed on both sides of the core 13, while the circular empty chamber 16 is filled with a lining material 17, which is to be heated and melted, and the core 13 is rotated together with a rotation axis 11. When rotation speed reaches a predetermined region, a Weissenberg effect works to discharge bubbling gas to the bubble reservoirs 19.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe lining forming method and apparatus suitable for application to insulating linings applied to the inner surface of measuring pipes of electromagnetic flowmeters.

0002

[Prior Art] An electromagnetic flowmeter (such as Japanese Utility Model Application Publication No. 2-28411) uses the principle of electromagnetic induction to convert the flow rate of a conductive fluid flowing in a measurement pipe into an electrical signal and measure it.
Usually, as shown in FIG. 2, the measuring tube 1 is lined with an insulating lining 2 to reinforce the inner wall surface and to provide insulation between the electrodes 3 and 4. A pair of excitation coils (not shown) that form a magnetic field in a direction perpendicular to the flow direction of the fluid to be measured in the tube are provided on the outer periphery of the measurement tube 1, facing each other, and flanges 1a and 1b are provided at the openings at both ends. are each provided integrally. The insulating lining 2 is made of an insulating material such as fluororesin or PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), and is usually lined by a centrifugal method for measuring tubes with small diameters, and The material is lined by a coating method. In the centrifugal method, powder (lining material) is sealed in the measuring tube 1, heated, and rotated around the axis to sequentially melt the powder starting from the surface closest to the outer cylinder jig 1, thereby uniformly melting the powder. It is something to be molded. On the other hand, the coating method involves heating and melting the powder and applying it to the inner wall surface. The pair of electrodes 3 and 4 are provided in the measurement tube 1 so as to face each other via a magnetic field in a direction perpendicular to the flow direction of the fluid to be measured, and their inner ends are exposed in the flow path. 5 is a connection terminal board, and this terminal board 5 and the electrodes 3 and 4 are connected by lead wires 6 and 7.

By the way, in an electromagnetic flowmeter, the surface roughness and accuracy of the inner cylinder surface directly affect the performance of the flowmeter. That is, as described above, the electromagnetic flowmeter is based on the principle of measuring the potential difference excited between a pair of electrodes 3 and 4 provided facing each other in an internal flow path to which a magnetic field is applied. Therefore, it is necessary to insulate between the electrodes 3 and 4, but if bubbles are present in the insulating lining 2, the insulation will be broken, and if the flow path surface is not well finished, the streamlines of the fluid to be measured will be disturbed. This results in a decrease in measurement accuracy. Therefore, lining 2
After molding, the inner diameter was finished by machining.

0004

As mentioned above, in products such as electromagnetic flowmeters that require high inner diameter dimensional tolerances and surface roughness, finishing is performed by machining after lining the lining. It also served to remove air bubbles that formed on the surface. However, since the lining requires post-processing, there are problems in that the number of work steps increases and the manufacturing cost increases.

[0005] Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to obtain a high inner diameter dimension, to have a large degassing effect during molding, and to provide a lining. An object of the present invention is to provide a method for forming a pipe lining and an apparatus therefor that eliminates the need for post-processing after forming.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and a first aspect of the present invention is to provide a rotating shaft disposed within a heating furnace, and a rotating shaft fitted to the rotating shaft. It comprises a core and an outer cylinder that are given a relative shaft rotation difference, and forms a slight annular gap filled with a lining material that solidifies at room temperature between the outer circumferential surface of the core and the inner circumferential surface of the outer cylinder, Bubble reservoirs communicating with the annular gap are provided on both sides of the core. A second invention is that in the first invention, the outer cylinder is a measurement tube of an electromagnetic flowmeter. The third invention is a lining material that forms an annular cavity between the core and the outer cylinder and bubble reservoirs located on both sides of this cavity and communicating with the cavity, and solidifies at room temperature within the annular cavity. is injected and filled in a heated molten state, giving angular velocities in relatively different directions to the inner and outer wall surfaces of this annular cavity, and after cooling and solidifying the lining material, the outer cylinder and core are separated and the bubbles are collected in the bubble reservoir. The lining material is removed.

[0007]

[Operation] In the present invention, a non-Newtonian fluid with a large elastic modulus, such as a heated polymer solution, is injected into the annular gap formed between the core and the outer cylinder. When a relative angular velocity is applied between and, a Weissenberg effect occurs in which the material wraps around the core side. In addition, the solution extends well in the direction of the axis of rotation, and as a result, bubbles move and are collected in bubble reservoirs provided on both sides of the annular gap. When the core is removed from the outer cylinder as the solution solidifies, a lining is formed on the inner surface of the outer cylinder.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on embodiments shown in the drawings. FIG. 1 is a sectional view showing an embodiment of a pipe lining forming apparatus according to the present invention. In the same figure,
10 is a housing that forms a heating furnace; 11 is a rotating shaft that is supported at both ends by bearings 12 and is disposed within the housing 10; 13 is a core that is fitted and fixed to the rotating shaft 11; and 14 is a rotating shaft that is fixed to the rotating shaft 11. An outer cylinder is rotatably disposed via a bearing 15, and the outer cylinder 14 is an outer cylinder main body fitted coaxially to the outer periphery of the core 13 to form an annular cavity 16 with a small gap. 14A, and a pair of left and right side plates 14B and 14C that hold the outer cylinder body 14A. The outer peripheral surface of the core 13 is mirror finished. An injection port 18 is formed in the outer cylinder main body 14A for injecting and filling the annular cavity 16 with a powder 17 of fluororesin, PFA, etc., which is a lining material. Both sides of the core 13 and side plates 14B, 14
Bubble reservoirs 19 communicating with the annular cavity 16 are formed between the inner surfaces of C and the inner surfaces of C, respectively. In addition, the outer cylinder body 14
When this device is used to form the insulating lining of an electromagnetic flowmeter, A is used as a measuring tube.

Reference numeral 20 denotes a motor for rotating the rotary shaft 11 at a constant speed (for example, 400 to 500 rpm), and is installed outside the housing. 21 is a heating means such as a burner that is provided at the lower part of the housing 10 and heats the outer cylinder 14; 22 is a thermometer that measures the internal temperature of the housing 10; 23 is a heating means 2 based on a signal from the thermometer 22;
1, a temperature regulator that controls 24, a heat-resistant O-ring, 25,
26 is a nut, 27 is a presser, 28 is a seal ring, 2
9 is a stopper.

Next, lining forming by the pipe lining forming apparatus 30 having such a structure will be explained. First, a predetermined amount of powder 17 is poured into the annular cavity 1 through the injection port 18.
The core 13 is rotated together with the rotary shaft 11 by the motor 20, and at the same time, the outer cylinder 14 is heated by the heating means 21 to raise the temperature to the melting point of the powder 17. The powder 17 that has reached its melting point changes into a viscous fluid (particularly a non-Newtonian fluid) and receives the rotational energy of the core 13. For example, if PFA is used as the lining material,
Foaming occurs at 325°C, and above that temperature it becomes molten. Generally, a viscous fluid is placed between two coaxial cylinders,
When the inner cylinder is fixed and the outer cylinder is rotated at a constant angular velocity,
It is known that the Weissenberg effect (an effect in which the part of the free surface close to the inner cylinder swells up, causing the liquid to wrap around the inner cylinder) causes the molten fluid to move along the inner cylinder. By utilizing such a phenomenon, air bubbles when changing from powder 17 to molten fluid are stored in bubble pool 1.
Collected at 9. After the whole is melted without bubbles,
Gradually slow down the rotation and begin the annealing process while lowering the temperature. After the molten fluid has solidified, the outer cylinder 14 is disassembled, the core 13 is extracted from the outer cylinder main body 14A, and the resin containing air bubbles accumulated in the bubble reservoir 19 is cut and removed. The cylinder body 14A, that is, the measurement tube of the electromagnetic flowmeter is obtained, and then the electrodes, excitation coil, etc. are assembled at predetermined positions. When pulling out the core 13,
Resin materials such as fluororesin have weak surface adhesion after solidification,
It is easy because it does not adhere to mirror-finished metal surfaces. Moreover, the surface condition of the resin after drawing is extremely good.

[0011] Thus, in the lining formed by such a pipe lining forming apparatus 30, the inner diameter accuracy of the lining can be obtained by the outer diameter of the core 13, and degassing can be achieved by the Weissenberg effect, so that molding is possible. It does not require subsequent machining and can be manufactured at low cost, and since heat is generated by the shear force generated between the core 13 and the outer cylinder body 14A, the time required to heat up the powder 17 can be shortened. In addition, although the above-mentioned embodiment explained the case where the core 13 was rotated by the motor 20, the present invention is not limited to this.
Of course, the outer cylinder 14 may be rotated.

0012

Effects of the Invention As described above, according to the pipe lining molding method and apparatus according to the present invention, an annular cavity is formed between the core and the outer cylinder and filled with powder. By applying a high angular velocity and heating the powder, the bubbles generated as the powder melts are defoamed using the Weissenberg effect, resulting in high inner diameter accuracy.
In addition, no air bubbles are generated on the surface, thus eliminating the need for post-processing after lining molding, and reducing manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a pipe lining forming apparatus according to the present invention.

FIG. 2 is an external perspective view of an electromagnetic flowmeter with insulating lining.

[Explanation of symbols]

1 Measurement tube 2　Insulating lining 10 Housing 11 Rotation axis 13 Core 14 Outer cylinder 16 Annular vacant room 17 Powder 19 Foam pool

Claims (3)

[Claims] Claim 1: Comprising a rotating shaft disposed in a heating furnace, a core and an outer cylinder that are fitted onto the rotating shaft to provide a relative shaft rotation difference, the outer circumferential surface of the core and the inside of the outer cylinder A pipe lining forming apparatus characterized in that a slight annular gap is formed between the core and the surrounding surface and filled with a lining material that solidifies at room temperature, and bubble reservoirs are provided on both sides of the core that communicate with the annular gap. . 2. The pipe lining forming apparatus according to claim 1, wherein the outer cylinder is a measuring pipe of an electromagnetic flowmeter. 3. Forming an annular cavity between the core and the outer cylinder, and bubble reservoirs located on both sides of this cavity and communicating with the cavity,
A lining material that solidifies at room temperature is injected into the annular cavity in a heated molten state, and angular velocities in relatively different directions are applied to the inner and outer wall surfaces of the annular cavity, and after the lining material is cooled and solidified, the outer cylinder and core are A method for forming a pipe lining, characterized in that the lining material separated and accumulated in the bubble reservoir is removed.