JPH01266393A - Defect indicating method for electro-fusion joint - Google Patents

Abstract

PURPOSE:To prevent the quantity of electric power from being given too much or too little, by checking in comparison a resistance value sought by running an inspection electric current to an electric heat line and a resistance value read from the indicating means of a joint, and detecting abnormality, and indicating it. CONSTITUTION:A weak inspection direct current is run to an electric heat line 2 through a connector as a sensor 6 reads the data for electrification, and the resistance value of an electric heat line 3 inclusive of the contact resistance of the connector is measured by means of a resistance sensor 8, and is inputted into a computer 5. And the resistance value read by the sensor 6 and the resistance value measured by the resistance sensor 8 are checked in comparison, and if a resistance value detected surpasses an allowable extent, defect is indicated at an indication 9, and if within the allowable extent, O.K. is indicated.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is used to connect plastic pipes, and detects defects or fusion failures in electrofusion joints in which heating wires are embedded in the contact surface with the pipes. Concerning how to display.

BACKGROUND OF THE INVENTION Electrofusion joints have been developed in recent years as pipe joints and saddle joints for plastic pipes used for water and sewage pipes, gas pipes, etc. This joint is made of a molded product with heating wires embedded in the contact surface with the pipe.In the case of a pipe joint, the pipe is inserted from both sides of the joint, and in the case of a saddle joint, it is fused to the pipe. This is done by pressing the tube from the side and applying electricity to heat and melt the contact surface.

The amount of electricity applied to these fittings will affect the quality of the plastic tube connections; too much electricity may cause overheating and deformation of the fitting or vibrator, while too little may result in insufficient heating. As a result, the fusion strength decreases. Conventionally, devices that energize joints have been manually operated, and the amount of electricity to be energized has been determined by the operator on site, based on the appearance of the joint during welding. In recent years, a method has begun to be adopted in which the amount of power to be provided is set in advance according to the size and type of the joint, and the operator identifies the type from the appearance of the joint and determines the corresponding amount of power. . Recently, regarding pipe joints, there has been a method of detecting the resistance value by embedding a resistor with different resistance values depending on the type of joint separately from the heating wire and passing a test current through it, and a method of detecting the resistance value of the heating wire itself. A method of detecting the type of pipe joint to identify the type of pipe joint and applying the corresponding amount of electric power, and a method of determining the energization time by reading the pattern of the coding tab provided integrally with the joint (Japanese Patent Application Laid-Open No. 61-17
No. 5022) have also been proposed.

Problems to be Solved by the Invention According to the method of detecting the resistance value of the resistor or heating wire embedded in the joint, or the method of reading the pattern of the coding tab provided on the joint, the plug or jack attached to the end of the cord can be detected. Alternatively, by simply inserting a connector, etc. (hereinafter simply referred to as a connector, etc.) into a socket or tab, data regarding the type of joint and energization time can be obtained, and a predetermined amount of power can be automatically provided based on that data. It is possible, but
However, there are the following problems. In other words, if the socket, tab, connector, etc. of the joint into which the connector etc. is inserted is dirty, the resistance value detected by the contact resistance of the connector etc. will be different from that of the resistor or heating wire itself, and therefore the resistance value will be too high or too low. This means that a large amount of electricity will be provided.

The first invention detects an abnormality in the resistance value to prevent the above-mentioned problem, that is, the application of too much or too little electric power.

The solution to the problem, that is, the first invention, is used to connect plastic pipes, a heating wire is buried in the contact surface with the pipe, and the fusion with the pipe imparts a predetermined amount of electric power to the heating wire. In electrofusion joints, which are performed by heating and melting the contact surfaces, the joint is provided with a display means that records data regarding resistance values, and a sensor that reads the display means is provided on the connector etc., and the connector etc. is connected to the insertion port of the joint. When inserting into the socket or into the tab provided separately from the socket, the sensor compares the resistance value read from the display means with the resistance value including the contact resistance of the connector etc. measured from the heating wire, and the difference between the two is within the allowable range. An abnormality is displayed when the value exceeds the limit.

The display means here includes, for example, a bar code, a magnetic tape, a magnetic piece, a hole, a protrusion, etc. In the case of a magnetic piece, hole, protrusion, etc., the display means includes the number or size such as height, depth, length, etc. The resistance value is displayed by the method, but among these, it is preferable to use holes or protrusions.

This is because it can be formed at the same time as the joint is formed, so there is no need to newly provide parts for the display means, and there is no need for post-processing, which is economical.

When a working connector or the like is inserted, the resistance value is determined from the data read by the sensor from the display means. Then, a test current is applied and the resistance value including the contact resistance of the connector etc. is measured from the heating wire. If the difference exceeds the allowable range, an abnormality is displayed, and if it is within the range, the energization switch is turned on. and a predetermined amount of electric power is applied.

Problems to be Solved by the Invention When welding with electrofusion joints, it is desirable to heat the entire joint uniformly in order to perform proper welding, but when the resin is in a molten state during welding, it is often The heating wires may come into contact with each other and cause a short circuit, resulting in local overheating or insufficient heating, and proper fusion bonding may not be achieved.

A short circuit in the heating wire will appear as an increase in the current value, and overheating will appear as a decrease, so it is thought that short circuits and overheating in the heating wire can be discovered by measuring the current value while the current is flowing. For example, in the case of a heating wire wound several dozen times into a coil, even if two or three of them are shorted, the increase in current value will be small enough to fall within the allowable range.
It is virtually difficult to detect a short circuit. Regarding overheating, it is difficult to detect until the decrease in current value exceeds the allowable range, and by the time it is detected, overheating has progressed.
This often results in resin deterioration.

A second object of the present invention is to quickly and accurately detect when the heating wire is not being properly fused due to short circuits or overheating, and to display the defective fusion.

Therefore, the second invention is used to connect plastic pipes, and a heating wire is embedded in the contact surface with the pipe, and the fusion with the pipe imparts a predetermined amount of electric power to the heating wire. In electrofusion joints, which are made by heating and melting the contact surfaces, one or more of the electrical properties such as current, voltage, and electrical resistance are sensed during the energization period to measure the speed of change or acceleration. This calculation is made, and when the rate of change or acceleration exceeds an allowable range, a defective fusion is displayed.

Poor fusion is indicated by an alarm sound, lighting of an alarm lamp, etc. Note that when a fusion failure occurs, it may be sufficient to simply display the indication, but preferably, the switch of the energizing circuit is automatically turned off at the same time as the indication, and the energization is stopped.

The resistance value of the working heating wire increases as the temperature rises,
Generally, there is the following relationship with temperature.

R=R, +(1+αt) where R: resistance Ro at t'C: resistance α at 0° C.: resistance temperature coefficient energization is started, and as heating progresses, the temperature rises. As a result, as shown in the above equation, the resistance of the heating wire gradually increases over time, and conversely, the current flowing through the heating wire gradually decreases.

FIG. 2A shows a current curve during energization, and as shown by the solid line, the current value initially drops suddenly, but the drop gradually becomes smaller and the slope of each tangent line gradually becomes gentler. θ, which indicates the difference in the slope of the tangent lines, indicates the difference in the rate of current change per time, that is, the acceleration of the current change. For example, θ in the figure
, is the rate of current decrease (change) at time t0 and 1. The difference in current decreasing speed at 1. -1. Similarly, θo is the difference in current drop rate between time t2 and time t1, which is 1. -1. It is divided by time.

Assume that an abnormality occurs due to a short circuit in the heating wire after t1 time has elapsed since the current was turned on. At that time, the current begins to rise as shown by the dotted line. Even if the amount of increase in current is small, the slope of the tangent line at the time the abnormality occurs reverses from the downward direction and suddenly becomes upward, and the difference in the slope of the tangent line, in the figure, is θ1.
In other words, the acceleration obtained by dividing the speed difference between time t8 and time t0 by the time t, ~to increases rapidly as it exceeds the set tolerance range, so abnormalities due to short circuits can be easily detected ( (Displayed when an abnormality is detected), even when the current starts to drop rapidly (overheating may be the cause), the difference θ4 between the slope of the tangent line and the slope of the tangent line at time t4 exceeds the allowable range. When it becomes large, an abnormality is detected and displayed.

Figure 2B shows the change in θ, or acceleration, per time.When an abnormality occurs and θ changes rapidly, a pulse-like waveform that exceeds the allowable range is generated. Detection becomes easier.

Embodiment A heating wire 2 wound into a coil is buried inside the pipe joint 1, and each terminal 3 protrudes from both sides of the pipe joint 1. The connector on the controller 4 side can be detachably connected. The controller 4 is equipped with a computer 5, and when the connector on the controller side is connected to the terminal on the joint side, the sensor 6 detects the heating wire from the record Vi7 provided on the joint side. 2
The resistance value, the voltage at the time of energization, and other data necessary for energization are read and input into the computer 5, and the computer 5 determines the energization time and voltage based on the data. In parallel with the sensor 6 reading data for energization, a weak direct current for testing is applied to the heating wire 2 through the connector.
(at this time, switch B is closed), the resistance value of the heating wire 3 including the contact resistance of the connector is measured by the resistance sensor 8, and input into the computer 5.

The resistance value read by the sensor 6 and the resistance value measured by the resistance sensor 8 are then compared and verified. If the detected resistance value exceeds the tolerance range, the display 9 will display a defective value, and if it is within the tolerance range, it will display a suitable value. is done. At the same time that the proper indication is displayed, switch B is turned off and switch A is turned on, the voltage is adjusted by the voltage regulator 11, and the voltage is turned on for a predetermined time.
While the current is being applied, the current sensor 12 continues to measure the current and inputs it to the computer 5. From this, the computer 5 calculates the speed or acceleration of the change in current value, and if these exceed the allowable range due to a short circuit or abnormal heating of the heating wire 2, an abnormality is displayed and the switch A is turned off to stop the current supply.

Although the example of a pipe joint has been described above, in the case of a saddle joint, failure of the joint or failure of fusion can be similarly displayed.

In the above embodiment, the data such as the energization time and voltage required when energizing the joint is taken in, and the sensor reads this data. Identification mechanism that displays embedded resistor or joint size, type, resistance value, energization time, etc.
For example, the same applies to systems that use sensors to obtain data about the joint from holes, protrusions, magnetic strips, bar codes, magnetic tape, etc. of different sizes and numbers, and then determine the energization time and current or voltage based on that data. Can be applied.

Further, in the above embodiment, an abnormality during energization is detected by current, but it can also be detected by other electrical characteristics such as resistance.

Effects of the Invention As described above, the first invention detects an abnormality by comparing and comparing the resistance value obtained by passing a testing current through the heating wire with the resistance value read from the display means of the joint, and displays it. With this configuration, it is possible to eliminate excessive or insufficient amount of electric power from being applied based on an abnormal value, and it is possible to prevent quality deterioration of the connected portion.

According to the second invention, defective fusion due to short circuit or overheating of the heating wire during energization can be detected reliably at an early stage.

[Brief explanation of the drawing]

Fig. 1 is a mechanical diagram of the controller, and Figs. 2A and 2B are explanatory diagrams of the operation when energized. 1... Pipe joint 2... Electric heating vA 3... Terminal 4...
Controller 5...Computer Applicant Mitsui Petrochemical Industries Co., Ltd. Agent Patent Attorney Akira Sasai - Ken 11i1 Procedure (Method) 1. Indication of the case 1985 Patent Application No. 334885 2. Name of the invention Electro How to indicate defective fusion fittings 3.
Relationship with the case of the person making the amendment Patent applicant address: 3-2-5 Kasumigaseki, Chiyoda-ku, Tokyo Name: Shogo Takebayashi 4, representative of Mitsui Petrochemical Industries, Ltd. Address of agent: 7-3 Okiichi Chuo, 737 Japan No. 12 (
6. Subject of amendment: Drawing t3j 5:01 Town

Claims (4)

[Claims] (1) Used to connect plastic pipes; a heating wire is buried in the contact surface with the pipe, and the fusion with the pipe is achieved by applying a predetermined amount of electricity to the heating wire and heating and melting the contact surface. In electrofusion joints that are performed, a display means that records data regarding resistance values is provided on the joint, and a sensor that reads the display means is provided on the plug, jack, connector, etc., and when the plug, jack, connector, etc. is inserted, the sensor The resistance value read from the display means is compared with the resistance value including the contact resistance of the plug, jack, connector, etc. measured from the heating wire, and when the difference between the two exceeds an allowable range, an abnormality is displayed. How to indicate defects in electrofusion fittings (2) A method for indicating a defect in an electrofusion joint according to claim 1, wherein the indicating means is a hole or a protrusion that can be formed at the same time as the joint is molded. (3) Used to connect plastic pipes; a heating wire is buried in the contact surface with the pipe, and the fusion with the pipe is achieved by applying a predetermined amount of electricity to the heating wire and overheating and melting the contact surface. In electrofusion joints that are performed, one or more of the electrical characteristics such as current, voltage, and electrical resistance during energization is sensed during the energization period, and the speed of change or acceleration is calculated, and the speed of change or acceleration is calculated. A method for displaying fusion failure of an electrofusion joint, characterized in that the fusion failure is displayed when the tolerance exceeds the tolerance range. (4) A method for displaying fusion failure in an electrofusion joint according to claim 3, wherein switch A of the current-carrying circuit is turned off together with the indication of fusion failure.