JPH0571835B2 - - Google Patents

Abstract

PURPOSE:To eliminate difficulty in setting an energizing time by measuring the temperature of a plastic pipe joint so as to stop the energization when the temperature reaches a predetermined temperature. CONSTITUTION:A connecter 3 is provided with a connecter bushing 33, electrical wires 34 and a thermocouple 31 by which the temperature of a plastic pipe joint 1 is measured. The plastic pipe joint 1 is energized through the electrical wires 34 and a connector bushing 33, and a increased temperature of the pipe joint 1 is measured after several seconds elapsing. If an increased temperature is lower than a set increased temperature, the energization is stopped, but it is higher, the energization is continued. Further, when the temperature of the plastic pipe joint 1 comes to the set temperature, the energization is stopped. With this arrangement, it is possible to eliminate the control of energizing time, and therefore, it is possible to eliminate a difficulty in setting an energizing time. Further, it is possible to prevent inferior fusing since an abnormality during insertion of the connector 3 may be detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for electrically welding and connecting a pipe made of a thermoplastic resin material and a pipe joint (hereinafter referred to as a plastic pipe and a plastic pipe joint). .

[Prior Art] A general method for connecting plastic pipes by electric fusion will be described with reference to FIG.

Figure 6 shows the state in which two plastic pipes 2 to be connected are inserted from both ends of the plastic pipe joint 1, and this plastic pipe joint 1 is of a socket type and connects the plastic pipes in a straight line. .

As shown in FIG. 6, insert the plastic pipe 2 into the plastic pipe joint 1 until it contacts the pipe stopper 14 formed on the inner peripheral surface of the plastic pipe joint 1, and connect the control box (not shown) and the plastic pipe joint 1. Wiring connection is made between each connector pin 13 of No. 1 and each connector pin 13 of No. 1.

Electricity is then applied to the plastic pipe joint 1 via the control box, and the heat generated by the heating wire 12 due to this current supply fuses and connects the plastic pipe joint 1 and the plastic pipe 2.

What is important in the above connection process is control of the energization time. This is because if the energization time is too long, an excessive amount of heat will be applied to the welded part, causing the material to melt too much and cause deformation.On the other hand, if the energization time is too short, the fusion will be incomplete and the strength will increase. Problems remain due to lack of capacity. Therefore, there was a need for a method of setting and controlling the optimum energization time for proper fusion.

Conventionally, methods for controlling the energization time include, for example, measuring the temperature at the connection site and selecting and setting the energization time based on this temperature, and methods that take into consideration differences due to the temperature and size of the pipes and pipe fittings themselves to be connected. There is a method of setting the current value and time by taking this into account. (For example, see Japanese Patent Application Laid-Open No. 61-274920.) In addition, a recess is provided on the outer surface of the pipe joint body, and changes in the characteristics of the material expanded by heating within the recess are mechanically detected and the energization is stopped. There are ways to control it. (Refer to Japanese Patent Publication No. 63-24820) [Problems to be Solved by the Invention] However, each of the above-mentioned methods has the following problems.

First, in order to set the energization time based on outside air temperature, pipe joint temperature, size, etc., a large amount of data must be collected under various conditions, and the optimum time setting must be based on this data. Therefore, it has been difficult to set the optimal time when the amount of data is insufficient overall, when work is performed in a special atmosphere, or when a special joint size or material is used. In cases like this, it is necessary to rely on the skill level and intuition of the operator, and quantitative control has not been performed.

Next, the method of mechanically detecting changes in the properties of the expanded material provides relatively quantitative and stable results, but according to the experiments of the present inventors, for example, when the changes in properties are quantitative changes, It has been found that the expanded shape of the material may vary depending on the mounting direction and dimensional accuracy of the joint, and as a result, the state of fusion may also vary. In addition, in the case of temperature changes due to characteristic changes, it is also affected by the outside air temperature and the condition inside the recess, specifically the insertion failure of the temperature measuring device, that is, the presence or absence of a gap between the bottom of the recess and the temperature measuring device. I found out that it would happen. For example, even if the gap is a few tenths of a millimeter, it takes a long time to apply electricity to reach the optimum fusion temperature, resulting in a difference of several tens of seconds compared to a case with no gap. Therefore, an excessive amount of heat for several tens of seconds is applied to the material, causing the problem that the material melts too much. Therefore, it is necessary to accurately measure the temperature change in the melting zone in a method that detects the temperature of the material and controls the current flow. Furthermore, it is necessary to take safety measures such as determining whether there is a gap between the temperature measuring device and the bottom of the recess during the energization process.

The present invention provides an easy and stable electric fusion type connection method that incorporates measures to eliminate variations in energization time in a method of connecting by detecting temperature changes in a molten part.

[Means for Solving the Problems] The present invention includes a tube made of a thermoplastic resin material, a heating wire embedded in the inner circumference of the tube, and a concave hole extending close to the heating wire. A method of fusion splicing a pipe joint provided from the surface by electrical current heating, and after starting current flow,
The process of measuring the temperature at the bottom of the recessed hole with a temperature sensor, and counting the rate of temperature rise at the bottom of the recessed hole after a certain period of time after starting electricity supply, and comparing this rate of increase with a preset value. However, if the rising speed is lower than the set value, the energization is stopped, and if it is higher than the set value, the energization is continued.When the energization is continued after that, the temperature at the bottom of the recessed hole is continued to be measured, and the temperature is set in advance. This is an electric fusion type connection method for plastic pipe joints, which is characterized by the step of stopping current supply when the temperature reaches a certain temperature.

[Function] Since the connection method of the present invention measures the temperature change of the material at the bottom of the recessed hole closest to the molten part, the molten state can be accurately determined and the optimum set temperature at which the current is stopped can be reached. There is no variation in the time. Moreover, the temperature sensor used is usually a safety measure that determines that there is an abnormality when the thermocouple does not reach the bottom of the recessed hole (if there is a gap) and stops energizing, which makes the time variation even more. There is no. Further, this control is provided relatively early after the start of energization. Specifically, it is desirable to make this determination within 10 seconds after the start of energization. by the way,
It is possible to determine the target value by looking at the difference in the temperature rise after the start of energization, but a mere temperature difference will cause errors due to fluctuations in outside temperature, and during continuous work, the thermocouple will be affected by the previous work. remains, causing variations in fusion. Therefore, since it is possible to stably change the rate of temperature increase over time, this method was used. In some cases, rising acceleration may also be used. A device for these purposes is advantageous because it can be easily constructed by providing a differentiating circuit in the control circuit.

Embodiment FIG. 1 shows an embodiment of the method of electrically fusion connecting a plastic pipe joint and a plastic pipe according to the present invention. FIG. 1 is a longitudinal cross-sectional view showing a connecting portion between one end of a plastic pipe joint 1 and a plastic pipe 2. As shown in FIG. Plastic pipe joint 1 in this figure 1
The entire structure is shown in a vertical cross-sectional view in FIG.

This plastic pipe joint 1 is almost the same as the plastic pipe joint 1 described in the [Prior Art] section, and has a substantially cylindrical plastic joint main body 11.
and two connector pins 13, which are connected to both ends of the heating wire 12 embedded in the inner peripheral surface of the plastic joint body 11 and wound, and whose lower part is embedded in the plastic joint body 11 and whose upper part protrudes from the outer peripheral surface. It's summery.

However, unlike conventional plastic pipe joints, the plastic pipe joint 1 of this embodiment has a thermocouple hole 15.
It has a thermocouple 31 on its bottom.
The temperature of the plastic pipe fitting 1 is measured by bringing the plastic pipe fitting 1 into contact with the plastic pipe fitting 1.

Next, the connection method of this embodiment will be explained using FIG.

First, the plastic pipe 2 to be connected to one end of the plastic pipe joint 1 is inserted until it contacts the pipe stopper 14 (not shown in FIG. 1). This is also the same as inserting the plastic tube into the plastic fitting 1 for a conventional connection.

Second, insert the connector 3 into the connector pin 13 of the plastic pipe joint 1 and connect it. The connector 3 includes a connector bush 33 having a hole that fits into the connector pin 13, an electric wire 34 connected to the connector bush 33, and a thermocouple 31 positioned almost parallel to the connector bush 33. , these connector bushes 3
3, an electric wire 34, and a holder 32 that holds the thermocouple 31 together. Inserting and connecting the connector 3 to the connector pin 13 of the plastic pipe joint 1 means fitting the connector bush 33 of the connector 3 onto the connector pin 13. When the connector 3 is connected to the plastic pipe joint 1, the lower end of the thermocouple 31 held in the connector 3 is inserted into the thermocouple hole 15 of the plastic pipe joint 1, and the lower end of the thermocouple 31 is inserted into the thermocouple hole 15 of the plastic pipe joint 1. It is in light contact with the bottom of the hole 15.
The length from the bottom of the thermocouple hole 15 to the heating wire is somewhat larger than the length from the heating wire to the inner peripheral surface of the plastic pipe joint body 11.

Third, electricity is applied to the plastic pipe joint 1 through the connector 3 from a control box (not shown). Figure 3 shows the temperature of the fused portion at the boundary between the plastic pipe fitting 1 and the plastic pipe 2 (more precisely, the temperature at the bottom of the thermocouple hole 15 of the plastic pipe fitting 1) over time at this time. be. Figure 3 shows the ambient temperature when a gas polyethylene pipe joint with a nominal diameter size of 50A and a polyethylene pipe are connected by electric fusion, that is, when the outside air temperature is -7℃, 22℃, and 38℃. 3
The relationship between the elapsed time and the temperature of the plastic pipe joint 1 is shown for the following cases.

In this embodiment, the temperature at the bottom of the thermocouple hole 15 of the plastic pipe fitting 1 is measured using the thermocouple 31, and the temperature is determined as the temperature of the plastic pipe fitting 1. Therefore, the temperature at the boundary between the plastic pipe fitting 1 and the plastic pipe 2 is almost the same.

Further, the temperature at the boundary between the plastic pipe joint 1 and the plastic pipe 2 is a temperature at a location where the molten state when they are fused and bonded can be clearly indicated.

Fourth, the electricity supply to the plastic pipe joint 1 is stopped, and the timing is determined depending on the temperature indicated by the thermocouple 31. That is, the temperature of the bottom surface of the thermocouple hole 15 is set appropriately depending on the type of plastic, and when this temperature is reached, the current supply is stopped.

Fig. 3 shows the case where the set temperature for stopping the energization is 135°C, and the energization time is 31 seconds when the outside temperature is 38°C, and 40 seconds when the outside temperature is -7°C.

Fifth, remove the connector 3 from the plastic pipe fitting 1 to complete the connection.

Next, a connection failure or connection abnormality of the connector 3 to the plastic pipe joint 1 will be explained. In the case of these abnormal connections, the rate of temperature rise of the plastic pipe joint 1 during energization is lower than in the case of normal connections, as shown in FIG. Figure 4 shows, as in Figure 3, a gas polyethylene pipe joint with a nominal diameter of 50A and a polyethylene pipe are electrically fused together at an outside temperature of 22°C, and the thermocouple 31 shown in Figure 1 is
The distance between the tip of the thermocouple hole 15 and the bottom of the thermocouple hole 15 is 0 mm.
The relationship between the energization time and the measured joint temperature is shown for three cases: (normal connection), 0.3 mm (abnormal connection), and 0.5 mm (abnormal connection). From FIG. 5, it can be seen that when the connection is abnormal, the rate of temperature rise is lower immediately after the start of energization than when the connection is normal, and it takes a longer time to reach the set temperature. The energization control method in the case of a connection failure in this embodiment utilizes the speed of temperature rise several seconds after the start of energization.

First, the connector 3 is connected to the plastic pipe joint 1, and a control box (not shown) starts energizing the plastic pipe joint 1 through the connector 3.

A few seconds after the second power supply starts (approximately 10 seconds)
If the temperature does not reach the set temperature rise rate, it is determined that there is a poor connection and the power is turned off. In other words, if the temperature at the start of energization is different, measure the temperature at the start of energization and a few seconds after this, count the rate of temperature rise from these, and stop energization if this rate of increase does not reach the set value. do.

FIG. 5 shows the rate of temperature rise, which is calculated by dividing the temperature difference between the time at the start of energization and a certain period of time after that period, that is, the energization time. It is also possible to judge the connection status of the connector 3 to the plastic pipe joint 1 based on this temperature rise rate curve.

According to the electric fusion connection method of the plastic pipe joint 1 and the plastic pipe 2 according to the present embodiment described above, the energization time is determined by temperature measurement by the thermocouple 31, so the difficulty in setting the energization time is solved. In addition, variations in energization time due to poor connector connection are eliminated, and the accuracy of energization control is improved.

[Effects of the Invention] As explained above, the method of electrically fusion connecting a plastic pipe joint and a plastic pipe according to the present invention has the effect of resolving the difficulty in setting the energization time.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a plastic pipe joint, etc., showing an embodiment of the present invention, Fig. 2 is a longitudinal cross-sectional view of the plastic pipe joint shown in Fig. 1, and Fig. 3 is a longitudinal cross-sectional view of a plastic pipe joint and a plastic pipe. A diagram showing the relationship between the energization time and the temperature of the welded part during connection,
Figure 4 shows the measured temperature of a plastic pipe joint when energizing is applied when the connector is connected normally and when it is abnormal. Figure 5 is the measured temperature rise of the plastic pipe joint a few seconds after the start of energization when the connector is inserted normally and when it is abnormal. FIG. 6, which is a diagram showing the rate of temperature, is a longitudinal cross-sectional view showing a conventional example. DESCRIPTION OF SYMBOLS 1...Plastic pipe fitting, 2...Plastic pipe, 3...Connector, 11...Plastic pipe fitting body, 12...Heating wire, 13...Connector pin, 1
5... Thermocouple hole, 31... Thermocouple, 32... Holder, 33... Connector bush.

Claims (1)

[Scope of Claims] 1. A pipe made of a thermoplastic resin material, and a pipe joint made of a thermoplastic resin material, in which a heating wire is buried in the inner periphery and a recessed hole extending close to the heating wire is provided from the outer surface. A method of fusion splicing and splicing by electrical current heating, which includes the steps of: measuring the temperature at the bottom of the recessed hole with a temperature sensor after the start of current flow; A process of counting the rate of temperature rise at the bottom of the recessed hole, comparing this rate of increase with a preset value, and stopping energization if the rate of increase is lower than the set value, and continuing energization if it is also higher. and, when the current is continued, the temperature at the bottom of the recessed hole is continuously measured, and the current is stopped when the temperature reaches a preset temperature. Wearing connection method.