JPH02240497A - Electrifying time control method for electric fusing type pipe joint - Google Patents

Abstract

PURPOSE:To intend stable fusion in a fusion-connection method for a pipe and a pipe joint with electrical electrification-heating by measuring temperature at a recessed portion of the pipe joint and comparing the velocity of temperature rise with a preset value to continue or stop electrification. CONSTITUTION:For a method, when a plastic-made pipe 2A and a plastic-made pipe joint 1 are fusion-connected by electrical electrification-heating, the thermocouple 321 of a fusion plug 3 is inserted into a recessed hole 15 which is installed in the outer surface of the pipe joint 1 to measure temperature at the bottom portion of the recessed hole 15 and to control electrifying time in accordance with this temperature. The electrification is started to measure the velocity of temperature rise after the lapse of a preset time and to compare it with a preset value, and if the velocity of the temperature rise is larger than a preset value the electrification is continued and if it is smaller than a preset value the electrification is stopped. As a result, it is possible to obtain stable fusion which brings good measurement precision and no dispersion of electrifying time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for electrically welding and connecting a pipe made of a thermoplastic material and a pipe joint, and in particular to a method for stably obtaining the optimum current-carrying time. This relates to a control method.

[Conventional technology]

A method of electrically welding and connecting a pipe made of a general thermoplastic material, for example, a plastic pipe, to a pipe joint will be described with reference to FIG.

Heating wires 12 are embedded in a linear shape near the inner peripheral surface of the joint body 1 in the drawing, and both ends of the heating wires 12 are connected to the left and right connector bins 16.
are connected to each. When connecting the polyethylene pipe 2, first insert the polyethylene pipe 2 from both ends until it hits the stopper 14, and then insert a connector bushing leading to a power supply and control box (not shown) into the connector bin 16 to make an electrical connection. After that, the connection starts, and as the heating wire generates heat, the joint between the plastic pipe and the plastic pipe joint is melted and spliced. What is important in the above connection process is control of the current application time. This is because if the energization time is too long, an excessive amount of # may be added to the molten part, causing the material to melt too much and cause deformation.On the other hand, if the energization time is too short, the fusion may be incomplete. The problem remains that the strength is lacking. Therefore, there was a need for a method of setting and controlling the optimum energization time for proper fusion.

Conventionally, methods for controlling this energization time include, for example, measuring the temperature at the connecting station and selecting and setting the 1at time based on this temperature, and methods that vary depending on the temperature and dimensions of the connected pipes and pipe fittings themselves. We will discuss how to set the distance between F#f by taking both of these factors into account. Another method involves providing a concave PIT on the outer surface of the joint body and mechanically detecting changes in the characteristics of the material expanded by heating within the concave area to control the stop of energization. (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, those that set the energization time based on outside air temperature, joint temperature, dimensions, etc. collect a lot of data under various conditions.
The optimal time setting must be based on this. Therefore, it is difficult to set the optimal time when the amount of data is insufficient overall, when work is performed in a special atmosphere, or when the joint dimensions or material are special. In such cases, it is necessary to rely on the skill and intuition of the operator, and quantitative control has not been carried out.

Next, the method of mechanically detecting changes in the properties of the expanded material was thought to be able to obtain relatively quantitative and stable results, but according to the experiments conducted by the present inventors, for example, changes in properties In the case of a change in the amount, it was found that there were many variations in the expanded shape of the material due to external influences such as the mounting method of the joint, the dimensions, and the degree of fruitiness, and as a result, the state of the fusion also varied.

In addition, if the characteristic change is a temperature change, it may also be affected by the outside temperature or the condition inside the recess, specifically the insertion failure of the temperature measuring device, for example the presence or absence of a gap between the bottom of the recess and the temperature measuring device. It turned out that it would be done. For example, if the gap above is 1
Even if there is a gap, it takes a long time to apply electricity to reach the optimum welding temperature, resulting in a difference of several tens of seconds compared to one without a gap (
(See Figure 3). 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, in the above-mentioned method, especially in the method of detecting the melting temperature of the material and controlling the current supply, it is necessary to accurately measure the temperature change in the melting part. 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 is a control method that detects temperature changes in the molten part and sets the energization time t.The present invention provides easy and stable energization time control for electric fusion type pipe fittings, which incorporates measures to eliminate variations in energization time. method.

[Means for solving problems]

A pipe made of a thermoplastic material and a pipe joint are fused and connected by electrical current heating, a recessed hole is provided on the outer surface of the pipe joint, and the temperature at the bottom of the recessed hole is measured, In devices that control the energization time based on this temperature, the rate of temperature rise (°C/5ee) or temperature rise acceleration (°C/Be(!) at the bottom of the recessed hole after a certain period of time after the start of energization)
), and compares the temperature increase rate or acceleration with a preset value. As a result, if the temperature increase rate or acceleration is greater than the set value, the current is continued; The method is characterized in that the means for stopping the energization is included in the process of the total energization control method.

Therefore, the connection control method of the present invention can control the temperature change of the material.
Since the measurement is made at the bottom of the concave hole closest to the molten part, the molten state can be accurately determined, and there is no variation in the time required to reach the optimum set temperature for stopping the flow. Moreover, normally, when the thermocouple used in the temperature measuring device does not reach the bottom of the recessed hole (that is, when there is a gap), it is determined that there is an abnormality and the current is turned off. With safety measures in place, there is even less variation in time. Moreover, this control is provided relatively early after the start of the process. Specifically, it is desirable that this determination be made within 10 seconds after the start of energization. By the way, it is possible to determine the target value by simply looking at the difference in the temperature rise immediately after energization, but a simple temperature difference will cause errors due to fluctuations in outside temperature, and during continuous work, it is especially important to check the thermocouple for the previous work. The effect remains and the degree of welding varies.

Therefore, this method uses the rate of temperature increase (°C/5ec) or the acceleration of temperature rise (°C/sec''), which allows for stable changes over time. Furthermore, it is convenient because the device for these purposes can be easily constructed by providing a differentiating circuit in the control circuit.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a plastic (polyethylene) pipe joint, FIG. 1(A) is a longitudinal sectional view thereof, and FIG. 1(B) is a top view. A heating wire 12 is embedded in the inner circumference of the pipe joint body 1 and connected to connector bins 13 at both ends. A recessed hole 15 for inserting a thermocouple is provided near both connector bins, and its depth is approximately one snow level up to the heating wire. Reference numeral 8 indicates an indicator hole for visually confirming the state of the melt layer, and as melting progresses, the material rises and can be confirmed. Further, 14 is a stopper when the plastic tube 2 is inserted.

FIG. 2 is an enlarged sectional view of the main part of FIG. 1, and shows a state in which the fusion plug 6 is attached, and as shown, a connector bush 611 is connected to the connector bin 16 and the control box is connected to the connector bush 611. (not shown). The fusion layer plug is also provided with a thermocouple 621 that is fitted in parallel and integrally with the connector portion 31 described above. At the tip of the thermocouple body, there is a contact point of a different wire, so that temperature changes are caught at this tip.Furthermore, the thermocouple case 622 is made of ceramic. It is important to insert the thermocouple fully into the recessed hole 15 for thermocouple insertion, and to mount it so that there is no gap between the two. Then, electricity is started to heat the heating wire and melt the plastic material. In this example, the temperature at which both the pipe and the pipe joint appropriately melt is about 120° C., and it has been experimentally determined that this temperature is reached in about 100 seconds after the start of energization. However, if the thermocouple is inserted incorrectly or there is a foreign object on the bottom, a gap will occur between the concave bottom and the tip of the thermocouple. As mentioned above, if the gap is as large as 14, it will take a long time to reach 120° C., and too much thermal energy will be applied, causing the problem that the material will melt too much.

Therefore, in this embodiment, a control method with the following safety measures was adopted. In other words, the rate of temperature increase after the start of passage (°C/see
), and based on this, it is possible to determine whether or not there is the above-mentioned gap. Specifically, the rate of temperature rise is measured 7.5 seconds after the start of energization, and if it is greater than 0.5° C./sec, it is determined that there is no gap, and energization is continued. On the other hand, when it is less than 0.5° C./sec, it is determined that there is an abnormality and the current supply is stopped. FIG. 3 shows an example of the experiment, and compares the case where there is no gap and the case where there is a gap of 1 m. As shown in the figure, even with only a small IM gap, the temperature increase rate line i\1 shows a clear difference, and it can be seen that the determination can be easily made. Note that here, the rate of temperature rise was measured and used as the criterion, but the acceleration of temperature rise may also be used as the criterion.

If the power is turned off, an abnormality lamp or buzzer will sound9, which prompts the operator to reinsert the thermocouple and turn it on again. It will start. In this case, since the time is within several seconds from the start of energization, there is no thermal effect on the material, and there is no problem even if the process is repeated again.

As described above, according to the energization time control method of this embodiment, by controlling a relatively easy and inexpensive differentiation circuit and providing it in one box,
It is possible to take advantage of poor attachment of thermoelectric pairs and eliminate variations in energization time.

〔Effect of the invention〕

According to the energization time control method of the present invention, measures are taken to prevent the temperature measurement contact from being inserted into the recessed hole, so the measurement accuracy is good, and there is no variation in the energization time.
Stable fusion results can be obtained.

[Brief explanation of drawings]

FIG. 1 shows an electric fusion type pipe joint according to the present invention.
A) is a partial vertical sectional view, FIG. 1(B) is a top view, FIG. 2 is a partial enlarged sectional view showing the state in which the fusion plug is installed, and FIG. FIG. 4, which is a diagram illustrating the difference between the presence or absence of pigs and the temperature increase rate, is a longitudinal cross-sectional view showing a conventional electrically bonded pipe joint. 1 Fitting a Niblastik socket 2 Niblastik tube 3 : Fusion plug 12 : T hot wire 16 : Connector bin 14 : Stocher 15 : Recessed hole for thermocouple insertion 61 : Connector
66: Holder 621: Thermocouple body 622:
Thermocouple case pier diagram (B) Diagram (A>

Claims (1)

[Claims] A pipe made of a thermoplastic material and a pipe joint are fused and connected by electrical current heating, a recessed hole is provided on the outer surface of the pipe joint, and the temperature at the bottom of the recessed hole is measured, In the device that controls the energization time based on this temperature,
The rate of temperature rise (°C/sec) or the acceleration of temperature rise (°C
/sec^2) and compares the temperature increase rate or temperature increase acceleration with a preset value, and as a result, if the temperature increase rate or temperature increase acceleration is greater than the set value, the current is continued, and the same temperature increase rate or temperature increase acceleration is measured. A method for controlling energization time of an electric fusion type pipe joint, characterized in that energization is stopped when the value is smaller than a set value.