JPH07346B2 - Method and apparatus for electric welding of thermoplastic pipe hand joints - Google Patents

Description

Description: INDUSTRIAL APPLICABILITY The present invention welds a thermoplastic pipe joint and a thermoplastic connected pipe by applying a heating current to the thermoplastic pipe joint in which an electric resistance heating element is embedded. The present invention relates to an electric welding method and apparatus.

2. Description of the Related Art Japanese Patent Laid-Open No. 58-131025 and Japanese Patent Laid-Open No. 61-274920 disclose methods and devices for welding and joining a thermoplastic pipe joint and a thermoplastic connected pipe by applying a heating current to the thermoplastic pipe joint. JP-A-62-116128 and the like.

In such an electric welding method and apparatus, it is general that the same kind or different kinds of thermoplastic pipe joints are energized and welded one by one. Further, it is general that the heating current is also continuously applied to one thermoplastic pipe joint.

On the other hand, recently, in order to improve work efficiency, it has been desired to develop an electric welding method and apparatus capable of simultaneously and continuously welding a plurality of thermoplastic pipe joints.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, if a plurality of thermoplastic pipe joints are to be efficiently and continuously welded, there is a problem that the welding apparatus becomes large and the cost is significantly increased.

Another problem in such continuous welding of a plurality is the problem of welding quality. One of the important keys to ensure the welding quality is to not touch, apply force, or move the object to be welded after the heating is completed and until the temperature of the thermoplastic pipe joint decreases to the curing temperature. . However, it is difficult to visually judge that the object to be welded is being cooled, and it is often touched carelessly. This is considered to be a problem that tends to occur especially when a plurality of consecutive welds are to be performed.

Further, since welding conditions differ depending on the type of thermoplastic pipe joint, there is a problem that setting mistakes are likely to occur when the type is manually set. In particular, it is considered that an error is likely to occur when attempting continuous welding of a plurality of pieces, and it is difficult to find the error only by visually confirming the welding result.

Furthermore, when attempting to weld a plurality of pieces simultaneously at the same time, since there are multiple connecting cords that connect the thermoplastic pipe joint to the welding device, it is conceivable that the connecting cords will be mixed up and mistaken for connection. To be In such cases,
Under some circumstances, the welding device may be destroyed. Therefore, the correct connection of the connecting cord is an important issue in terms of welding quality and device security.

The present invention has been made to solve the above problems, and an object thereof is an electric welding method and apparatus for a thermoplastic pipe joint capable of quickly and continuously welding a plurality of pieces at a low cost without increasing the size of the apparatus. To provide.

Another object of the present invention is to provide the above-mentioned electric welding method and apparatus which can surely and continuously weld a plurality of types of thermoplastic pipe joints at once in a short time.

Still another object of the present invention is, for each thermoplastic pipe joint, the above-mentioned electrical connection capable of performing reliable and high-quality welding by detecting a circuit abnormality such as a connection failure with the main body device, a disconnection, or a short circuit. It is to provide a welding method and apparatus.

Still another object of the present invention is to provide the above-mentioned electric welding method with good operability and convenience by displaying, for each thermoplastic pipe joint, that cooling is being performed after heating, and the remaining time until the end of cooling is displayed. And to provide a device.

Means for Solving the Problems The present invention, in order to achieve the above object, a plurality of thermoplastic pipe joints are connected in parallel to a common heating current power source, and a heating current power source is connected to each thermoplastic pipe joint. It is configured such that energization is continuously switched by sequentially switching energization.

The present invention also connects a plurality of thermoplastic pipe joints in parallel to a common heating current power source capable of intermittent energization, and energizes each of the thermoplastic pipe joints to other thermoplastic pipe joints during a pause time of intermittent energization. In order to perform the above, the heating current power supply is sequentially switched over so as to be continuously energized.

The present invention also, by measuring the resistance value of each electric resistance heating element of a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source before heating current conduction, by each thermoplastic pipe joint. It is configured to detect a connection state with the electric welding device and a circuit abnormality such as a disconnection or a short circuit.

The present invention also determines the type of a plurality of thermoplastic pipe joints connected in parallel to a common heating current power supply by detecting their identification parameters, and sets the heating current conditions and heating preset according to each type. It is configured to energize based on time.

The present invention is further configured to indicate that heating is completed and cooling is being performed for each of the plurality of thermoplastic pipe joints connected in parallel to the common heating current power source.

The present invention is further configured to display the remaining time until the end of cooling in the welding time for a plurality of thermoplastic pipe joints connected in parallel to a common heating current power supply.

Further, the present invention detects whether or not the connection cords of a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source by connection cords respectively are connected to an electric welding device, Is configured so that energization and various controls are performed only for the thermoplastic pipe joint to which is connected.

Action According to the present invention, a plurality of thermoplastic pipe joints are connected in parallel to a common heating current power source, and the current from the heating current power source is sequentially switched to continuously energize each thermoplastic pipe joint. A plurality of thermoplastic pipe joints can be continuously and quickly welded in a short time. Also, the heating current power supply to be used may be the one that supplies the minimum resistance, that is, the maximum current among the types of thermoplastic pipe joints, so that the heating current power supply has the same capacity as the conventional single welding. The same device as that used in the above apparatus may be used, and although a plurality of devices can be continuously welded, a small-sized and low-cost apparatus can be realized.

Further, according to the present invention, a plurality of thermoplastic pipe joints are connected in parallel to a common heating current power source that can be intermittently energized, and for each thermoplastic pipe joint, another thermoplastic pipe is connected during a pause time of intermittent energization. Since the energization from the heating current power source is sequentially switched to energize the joint to energize continuously, the entire welding time can be shortened.

The intermittent application of a heating current is suitable for controlling the temperature rise characteristics with respect to the welding time of the electric resistance heating element according to the type of thermoplastic pipe joint. That is, it is possible to arbitrarily and easily control the energization of the current supplied to and to the down time with high accuracy.

Furthermore, according to this intermittent energization, a welding current can be supplied to other thermoplastic pipe joints by utilizing the energization pause time, and if there is a margin in the pause time, still another thermoplastic pipe joint Can be supplied with current. Therefore, a plurality of thermoplastic pipe joints can be continuously and almost simultaneously welded, and the overall welding time can be greatly shortened.

Further, according to the present invention, the resistance value of each electric resistance heating element of the plurality of thermoplastic pipe joints connected in parallel to the common heating current power source is measured before the heating current is applied, and each thermoplastic pipe joint is measured. Since the abnormal state of the circuit such as the connection state and the electric welding device and the disconnection or the short circuit is detected, highly reliable and high quality welding can be performed.

Connecting a plurality of thermoplastic pipe joints in parallel means connecting a plurality of similar-shaped connecting cords at the same place, and it is easy to make a mistake in attaching the connecting cords. There is also a risk of damage.
In addition, the method in which a connection failure or a contact failure of the connection cord may occur even at one place brings importance to the visual inspection after welding. Furthermore, the actual situation of the welding site may be a narrow place or a dark place, and it is difficult to ensure the reliability of connection of the connection cord to the apparatus body. Therefore, according to the present invention, in order to eliminate the above-mentioned problems in the welding work before the welding and ensure the quality of the welding, the resistance of the electric resistance heating element of each thermoplastic pipe joint connected to the main unit is secured. By measuring the value before welding and judging the result, circuit failure such as connection failure of the connecting cord and disconnection or short circuit is detected.

According to the present invention, the type of a plurality of thermoplastic pipe joints connected in parallel to the common heating current power source is determined by detecting the identification parameter, and the heating current condition and preset according to each type and Since electricity is supplied based on the heating time, different types of thermoplastic pipe fittings can be continuously and reliably welded automatically at one time.

When multiple thermoplastic pipe joints are connected in parallel and continuously welded, another important factor is to automatically identify each type of multiple thermoplastic pipe joints and to apply the heating current according to each type. It is to automatically set the conditions and the heating time so that the operator's judgment cannot be entered during that time. Therefore, the type discrimination means contributes to ensuring quality and improving work efficiency.

Further according to the invention, for each of the plurality of thermoplastic pipe joints connected in parallel to a common heating current power supply,
Since the fact that the heating is completed and the cooling is being performed is displayed, it is possible to prevent deterioration in quality due to contact with the object to be welded during welding.

The welding time in the electric welding method is divided into a heating time for supplying a heating current to the thermoplastic pipe joint for welding and a subsequent cooling time. What affects the welding quality is:
The heating time remains important, but another important condition is that the thermoplastic fittings are not moved or exerted during cooling, so that the operator does not touch them carelessly during this time. As described above, the welding quality is ensured by displaying the status of the work process with a lamp.

Further, according to the present invention, for a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source, in order to display the remaining time until the end of cooling in the welding time, the welding of the next thermoplastic pipe joint is performed. Can be prepared, the operability is improved, and the welding tact can be shortened.

As described above, the welding time is divided into the heating welding time and the cooling time, and the welding of the next thermoplastic pipe joint is started after the cooling time ends. Further, in the present invention, since a plurality of thermoplastic pipe joints are continuously and sequentially welded, the ones that have been cooled are sequentially replaced with new ones, or the number set at one time in the device is used as a unit. Each unit is replaced with a new one and welding is performed sequentially. Therefore, by displaying the cooling end time, it is possible to prepare to set the next thermoplastic pipe joint, which reduces the waiting time to improve the operability and shorten the overall working time. Is.

Further, according to the present invention, it is detected whether or not the connection cords of the plurality of thermoplastic pipe joints connected in parallel to the common heating current power source by the connection cords are connected to the electric welding device, and the connection is made. Since the energization and various controls are performed only for the thermoplastic pipe joint to which the cord is connected, the control accuracy and the convenience of the device can be improved.

Although the present invention is configured so that a plurality of continuous welding can be performed, all the connecting cords are always used, and the same number of thermoplastic pipe joints are not always the welding target, and depending on the content of the work, a smaller number may be used. It may be a target of welding. In such a case, a terminal to which the connection cord is not connected appears on the device body side, but the abnormality detection circuit should judge whether this state is because the connection cord is not connected or it is broken. Since it is not possible to perform this, it is designed such that energization and various controls are performed only on the thermoplastic pipe joint to which the connecting cord is connected.

Embodiment FIG. 1 is a schematic block diagram showing an embodiment of the present invention. In FIG. 1, 1 (1a to 1x) is a plurality of thermoplastic pipe joints, each of which has an electric resistance heating element 2 (2a to 2x) according to a type such as a shape and a size. Further, each thermoplastic pipe joint 1 is provided with resistors 3 (3a to 3x) having different resistance values which are identification parameters for type discrimination. Four
Is a reading unit for automatically reading the value of the resistor 3 representing the type of the thermoplastic pipe joint 1 described above, and the reading result is output to the control unit 5. The control unit 5 is composed of one integrated device such as a semiconductor integrated circuit or a microprocessor unit, and has control of each unit in the welding apparatus and various data necessary for the control.

6 is a common heating current power source, and is a power source section 6a and this power source section.
And a switching unit 6b connected to 6a. Each thermoplastic pipe fitting
Each of 1a to 1x is connected in parallel to the common heating current power source 6, thereby forming a plurality of parallel circuits corresponding to the respective thermoplastic pipe joints. Here, the circuit number No. 1 is assigned to the thermoplastic pipe joint 1a, the circuit number No. 2 to the thermoplastic pipe joint 1b, the circuit number No. X to the thermoplastic pipe joint 1x, respectively. It is assigned. The switching unit 6b sequentially switches and outputs the power supply unit 6a to each thermoplastic pipe joint 1 under output conditions such as energizing current and energizing time according to the type. This switching is performed based on a command from the control unit 5. Reference numeral 7 denotes a resistance-side constant portion for measuring the resistance value of the electric resistance heating element 2 of each thermoplastic pipe joint 1, and the result is output to the control portion 5.

Reference numeral 8 (8a to 8x) is a display lamp for notifying that the heating is being conducted to each thermoplastic pipe joint 1 according to each circuit No. Lights up. Here, the No. 1 circuit thermoplastic fitting 1a is shown on the indicator lamp 8a, and the No. 2 circuit thermoplastic fitting is
1b is connected to the indicator lamp 8b, and the thermoplastic pipe joint 1x of the No. X circuit is connected so as to correspond to the indicator lamp 8x.

Reference numerals 9 (9a to 9x) are indicator lamps indicating that the thermoplastic pipe joint 1 that has been heat-welded in accordance with the circuit No. is being cooled for a specified time, and is similarly turned on by a command from the control unit 5. Similarly, the indicator lamp 9 has the indicator lamp 9a for the No. 1 circuit, and the indicator lamp 9b for the No. 2 circuit.
The oX circuit is connected to the indicator light 9x.

10 (10a to 10x) is a connection code for type identification 11 (11a to 11x)
And a storage portion for storing and placing the electric resistance heating element connection cord 12 (12a to 12x) when not in use. The actual connection code is, as shown in FIG.
11 and the connection cord 12 for electric resistance heating element are combined into one cord, and clips 17 and 18 are attached to each terminal.
Is equipped with.

Reference numeral 13 (13a to 13x) is a storage sensor that detects whether or not the connection cords 11 and 12 are stored in the storage portion 10. 14
Is a storage reading unit that notifies the control unit 5 which connection cord is connected to the apparatus main body by a signal from the storage unit sensor 13.

The reference numeral 15 (15a to 15x) is an abnormality alarm unit for notifying, for each thermoplastic pipe joint 1, disconnection or short circuit of the electric resistance heating element 2 or connection failure of the connection cords 11 and 12 based on the measurement result of the resistance measurement unit 7. Is. Reference numeral 16 (16a to 16x) is a remaining time display portion for counting the remaining time from the start of energization to the end of cooling in the total welding time for each thermoplastic pipe joint 1.

Next, the operation of the above embodiment will be described. In the above embodiment, the types of the respective thermoplastic pipe joints 1a to 1x forming the plurality of parallel circuits are the type determination resistors 3a to 3x provided in the respective thermoplastic pipe joints 1a to 1x and read by the welding device. Part 4
The reading is discriminated by connecting to. In addition, the resistance values of the electric resistance heating elements 2a to 2x of the thermoplastic pipe joints 1a to 1x are also measured by the resistance measuring unit 7. This result is given to the control unit 5, and the resistance measurement data of the electric resistance heating elements 2a to 2x is determined by confirming that the electric resistance heating elements 2a to 2x are correctly connected, or the electric resistance heating elements 2a to 2x or the connection cord.
It is determined whether or not there is a disconnection or short circuit abnormality in 11a to 11b, 12a to 12x, and when abnormality occurs, the abnormality alarm units 15a to 15x are activated, and energization to the electric resistance heating elements 2a to 2x is prohibited.
It should be noted that the fact that the electric resistance heating elements 2a to 2x are not properly connected means that the connection cords 11 and 12 have two electric resistance heating element connection cords for each circuit as shown in FIG. This is a case where one type identification connection cord is combined into one cord, and therefore these cords are connected in a plurality of circuits. Then, the type determination data output from the reading unit 4 is input to the control unit 5, and the control unit 5 controls the common heating current power supply 6 based on the output condition preset according to each type, Department
The output of 6a is switched and output by the switching unit 6b according to each circuit number and each type.

In this control, for example, as shown in the time chart of FIG. 3, in the circuits from No. 1 to No. X, the heating current is mainly applied during the heating time of T ₁ , T ₂ ... T _x . In addition, at the time of these outputs, the display lamps 8a to 8x indicating that heating is being performed are turned on in response to a command from the control unit 5 in synchronization with T ₁ , T _2, ... T _x . Further, from the time when the output of the time T ₁ of the No. 1 circuit is completed, the cooling indicator lamp 9a is turned on for the required cooling time T. Similarly, for Nos. ₂ to No. _X , the in-cooling display lamps 9b and 9x are lit up after the end of the time T2 and during the time T after the end of the time Tx. Then, the remaining time from the start of heating to the end of cooling of each circuit is displayed by counting down the remaining time display unit 16 in response to a command from the control unit 5. No.1
Since the total welding time ST from the start of heating the circuit to the end of cooling the No. X circuit is ST = T ₁ + T ₂ + ... + T _x + T, the remaining time of this total welding time ST is displayed on the remaining time display section 16. Let me display
The remaining time until the welding of the entire number of the thermoplastic pipe joints 1 set in the apparatus at one time for welding may be displayed may be displayed.

The connection cord storage unit 10 is a connection cord 1 that is not used.
1 and 12 are stored in the storage portions 10a to 10x corresponding to the circuit number. Accordingly, the corresponding storage unit sensors 13a to 13x are actuated by the stored connection cords 11 and 12, the output thereof is input to the storage reading unit 14, and which connection cord 11, 12 is sent from the storage reading unit 14 to the control unit 5. For each circuit, it is notified whether or not it is not connected to the welding device, that is, which connection cord 11, 12 is connected to the welding device. As a result, the control unit 5 performs energization and various controls only on the circuit to which the connection cords 11 and 12 are connected.

Next, another embodiment of the present invention will be described with reference to FIG. The welding device used is the same as that shown in FIG. In this embodiment, the heating and energizing of the thermoplastic pipe joints 1 are intermittently performed, and the other thermoplastic pipe joints 1 are energized during the non-energization time, so that the plurality of thermoplastic pipe joints 1 are
The heating, cooling, replacement, etc. are performed at once.

In this example, the heating time T ₁ of the No. 1 circuit is the energization time.
It is a repetition of t ₁ and energization pause time t ₁ ′, and the condition is
It is determined by the type of the thermoplastic pipe joint 1. The energization pause times t _{1 to} t _x are set to be longer than t ₁ + t ₂ + ... T _x , and when energization to the No. X circuit is completed, the next heating of the No. 1 circuit is performed. I am trying to move to. The same applies to the No. 2 circuit to No. X circuit. The feature of such intermittent energization is that the heating temperature gradient of the thermoplastic pipe joint 1 can be conditioned by setting the energization time and the rest time. Further, here, the welding to the thermoplastic pipe joint 1 of a plurality of circuits is performed automatically. In order to reduce the working time of all the processes, the other thermoplastic fitting
Electricity is applied to 1b to 1x to heat and cool the thermoplastic pipe joints 1a to 1x set at one time in the welding device at substantially the same time. Therefore, all thermoplastic pipe fittings 1a
Total welding time ST from the start of energization to the end of cooling for ~ 1x ST
Becomes ST = T ₁ + t ₂ + ... + t _x + T, which is shorter than the total welding time ST in the above-mentioned embodiment. Further, the time display on the remaining time display portion 16 is the remaining time in this total welding time ST.

In this embodiment, during the energization pause time t ₁ ′ of the thermoplastic pipe joint 1a of the No. 1 circuit, the thermoplastic pipe joints 1b to 1x of the other circuits No. 2 to No. X are sequentially energized. Although the control unit 5 controls the heating current power source 6, the No. 2 circuit is energized during the No. 1 circuit energization off time t ₁ ′ depending on the energization time or the energization off time. .2 Various combinations are conceivable, such as energizing the No. 3 circuit during the circuit de-energization time t ₂ ′. In this embodiment as well, the control other than the energization control described above is the same as that in the above embodiment.

EFFECTS OF THE INVENTION The present invention has the following effects, as is clear from the above-described embodiments.

(1) Since the common heating current power source is sequentially switched and a plurality of thermoplastic pipe joints are continuously welded, the efficiency and speed of the welding work can be improved, and the common heating current power source is the power source. Since the capacity can be set to the maximum capacity among the types of thermoplastic pipe fittings, it can be the same as that used in the conventional single-piece welding device, realizing downsizing and cost reduction of the device. can do.

(2) Since the heating current is intermittently applied and the other thermoplastic pipe joints are energized during the energization stop time, the welding work can be performed more efficiently, and the working time can be greatly shortened. You can

(3) Since it is possible to confirm the connection state of a plurality of connection cords and connection circuits and circuit abnormalities such as disconnection and short circuit before heating and energizing, continuous welding of a plurality of thermoplastic pipe joints can be performed efficiently and reliably. Can be done with high quality.

(4) Further, since the type of each of the thermoplastic pipe joints connected to the plurality of connection circuits can be automatically determined, different types of thermoplastic pipe joints can be continuously and automatically welded without error.

(5) In addition, the work status, especially the fact that cooling is being performed after welding, the remaining time until the end of cooling, and circuit abnormalities such as connection failure, disconnection, short circuit, etc., are displayed, so wasteful time is saved and work time is saved. It can be shortened and the operability and convenience can be improved.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an electric welding apparatus for thermoplastic pipe joints showing an embodiment of the present invention, FIG. 2 is a partial perspective view of a connecting cord in the same embodiment, and FIG. 3 is welding in the same embodiment. Process time chart, FIG. 4 is a time chart of the welding process in another embodiment of the present invention. 1 ... Thermoplastic pipe joint, 2 ... Electric resistance heating element, 3 ...
Type discrimination resistor, 4 ... Type reading unit, 5 ... Control unit, 6 ... Heating current power source, 6a ... Power source unit, 6b ... Switching unit, 7 ... Resistance measuring unit, 8 ... Heating Indicator lamp, 9
…… Cooling indicator lamp, 10 …… Connection cord storage, 11…
… Connection cord for type identification, 12 …… Connection cord for electric resistance heating element, 13 …… Storage unit sensor, 14… Storage reading unit, 15
…… Alarm display, 16 …… Remaining time display, 17, 18 …… Clip.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Isamu Tanabe 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yuichiro Goto 64, Ishizukita-machi, Sakai City, Osaka Prefecture Inside the factory (72) Hideki Baitou 64, Ishizukita-cho, Sakai City, Osaka Prefecture Inside the vinyl pipe factory of Kubota Iron Works Co., Ltd. (56) Reference JP-A-58-131025 (JP, A)

Claims (17)

[Claims] Claim: What is claimed is: 1. A plurality of thermoplastic pipe joints are connected in parallel to a common heating current power source, and the resistance value of each electric resistance heating element of each of the plurality of thermoplastic pipe joints is measured to measure the respective thermoplasticity. An electric welding method for a thermoplastic pipe joint, which detects a connection state between the pipe joint and the electric welding device, and then sequentially energizes the thermoplastic pipe joints by sequentially switching energization from the heating current power source. 2. A type of a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source is discriminated by detecting its discriminating parameter, and heating current conditions and heating preset according to each type. The electric welding method according to claim 1, wherein electricity is applied based on time. 3. The method according to claim 1, wherein each of the plurality of thermoplastic pipe joints connected in parallel to the common heating current power source indicates that heating is completed and cooling is being performed. Method of electric welding. 4. The remaining time until the end of cooling in the welding time of a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source is displayed. The electric welding method according to. 5. A connecting cord is detected by detecting whether or not the connecting cords of a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source by connecting cords are connected to an electric welding device. The electric welding method according to any one of claims (1) to (4), wherein energization and various controls are performed only on the connected thermoplastic pipe joint. 6. A plurality of thermoplastic pipe joints are connected in parallel to a common heating current power source capable of intermittent energization, and the resistance value of the electric resistance heating element of each of the plurality of thermoplastic pipe joints is measured. By detecting the connection state of each thermoplastic pipe joint and the electric welding device by, after that, to each of the thermoplastic pipe joint, to energize all other thermoplastic pipe joints during the pause time of the intermittent energization And a method for electrically welding a thermoplastic pipe joint in which energization from the heating current power source is sequentially switched to energize continuously. 7. A type of a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source is discriminated by detecting its discriminating parameter, and heating current conditions and heating preset according to each type. The electric welding method according to claim 6, wherein electricity is applied based on time. 8. The method according to claim 6, wherein it is indicated that heating has been completed and cooling is being performed for each of the plurality of thermoplastic pipe joints connected in parallel to a common heating current power source. Electric welding method. 9. A method according to any one of claims 6 to 8, wherein a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source indicate the remaining time until the end of cooling in the welding time. The electric welding method according to. 10. A connection cord is detected by detecting whether or not the connection cords of a plurality of thermoplastic pipe joints connected in parallel to a common heating current power source by the connection cords are connected to an electric welding device. The electric welding method according to any one of claims (6) to (9), wherein energization and various controls are performed only for the connected thermoplastic pipe joint. 11. A common heating current power source, a plurality of connecting cords for connecting a plurality of thermoplastic pipe joints to the heating current power source in parallel, and electric resistance heat generation of each of the plurality of thermoplastic pipe joints. A resistance measuring unit that measures the resistance value of the body, and a control unit that compares the measured resistance value with a preset standard resistance value to detect a circuit abnormality between the thermoplastic pipe joint and the device body. And a switching unit for sequentially energizing each of the thermoplastic pipe joints by sequentially switching the heating current power source, and an electric welding apparatus for the thermoplastic pipe joints. 12. A reading unit for detecting an identification parameter that defines types of a plurality of thermoplastic pipe joints, and each thermoplastic pipe joint based on a heating condition and a heating time preset according to each detected type. The electric welding device according to claim 11, further comprising: a control unit that energizes the device. 13. The electric welding device according to claim 11, further comprising a display lamp that indicates that heating is completed and cooling is being performed for each of the plurality of thermoplastic pipe joints. 14. The electric welding according to any one of claims 11 to 13, further comprising a display unit for displaying a remaining time until the end of cooling of the plurality of thermoplastic pipe joints. apparatus. 15. A storage unit for storing connection cords of a plurality of thermoplastic pipe joints, and detecting which connection cord is stored in the storage unit by detecting which connection cord is connected to the apparatus main body. And a control section for performing energization and various controls only on the thermoplastic pipe joint to which the connecting cord is connected based on the output from the detecting means. The electric welding device according to any one of claims. 16. A common heating current power source is capable of intermittent energization, and each thermoplastic pipe joint is provided with a control unit for energizing other thermoplastic pipe joints during a pause time of intermittent energization. The electric welding device as described in any one of 11) to 15). 17. The electric welding device according to claim 11, wherein the control unit is one integrated device.