DE9116973U1 - Arc welding machine with remote control - Google Patents

Description

FRONIUS Schweißmaschinen KG. Austria Gewerbestraße 15-17, A-4600 Wels

Arc welding machine with remote control

The invention relates to an arc welding machine with an idle circuit and a power unit that can be switched on and controlled via a control device for generating welding current, which is connected to an electrode holder and the workpiece via a welding current cable and is connected to a control device associated with the control device and can be set manually or via a remote control.

Welding current setting device in which the remote adjuster with a control device is arranged between the workpiece and the electrode holder and comprises a manually operable welding current setpoint transmitter to which an evaluation element is assigned in the control device.

An arc welding machine is already known - according to DE-OS 2904 458 - in which an adjustable power section for generating welding current can be controlled via a control device. For this purpose, the power section is connected to an electrode holder and the workpiece via a welding current cable and is equipped with a welding current setting device assigned to the control device, which can be set manually or via a remote control. The remote control is arranged between the workpiece and the electrode holder and comprises a manually operated welding current setpoint transmitter. An evaluation element is assigned to this in the control device. The current consumption of the remote control is changed via the remote control, thereby increasing the power consumption. The change in the current flow in the remote control is detected by the evaluation element in the control device and the welding current setting device is adjusted accordingly. The disadvantage is that external influences can trigger resistance changes in the control circuit, which lead to an increase in the no-load current and thus to an incorrect setting on the welding current setting device.

Furthermore, an arc welding machine with a welding current adjustment device is already known - according to DE-OS 33 29 216 - in which a remote adjuster is inserted between the conductive surfaces of a workpiece and a welding electrode. Depending on the order of the conductive surface and the polarity of the workpiece and welding electrode, a higher or lower frequency of the welding voltage is superimposed on the welding voltage. The evaluation unit increases or decreases the welding current by adjusting the welding current adjustment device, as long as the control loop is closed. The disadvantage here is that the adjustment process has to be repeated several times in order to determine through welding tests carried out in the meantime whether the set actual current value already corresponds to the desired value or not. In the case of delicate workpieces, this means that additional material parts have to be kept ready in order to be able to carry out these welding tests.

The present invention is based on the object of creating an arc welding machine with which an exact remote setting of the desired welding

current values is easily possible.

This object of the invention is achieved in that the remote adjuster is designed as a consumer with a predetermined power consumption and is connected to the workpiece and the electrode holder via an input each, and in that the control device has a vibration generator which is connected to a frequency adjustment controller forming the welding current setpoint generator and whose output is connected to a control input of an interrupter or frequency generator which is connected in a line connection arranged between the workpiece and the electrode holder. The advantage of this embodiment is that the adjustment process can be carried out completely unaffected by external influences such as scaling of the electrode and the like. In addition, accidental ignition of an arc is reliably prevented by the constant, uniform power output of the power unit during the control process. In addition, it is surprisingly easy to adjust to an exactly predefined value even without an external energy source. In addition, this remote adjuster does not require an additional controller cable.

According to another embodiment, a rectifier is interposed in the cable connection between the workpiece and the electrode holder, whereby the polarity of the workpiece or electrode holder does not have to be taken into account when switching on the remote control between the workpiece and the electrode holder, i.e. any contact surface can be contacted either with the electrode holder or with the workpiece and the welding current can be regulated. At the same time, this ensures a polarity-independent power supply for the control device if this is carried out via the cable connection.

According to a further embodiment of the invention, a frequency detection element forms the evaluation element in the control device, the output of which is connected to a control input for the welding current setting device. By directly converting the frequency signal received in the evaluation unit into an adjustment value, it is possible to immediately adjust the welding current setting device to a desired target value.

In another design variant, in which the vibration generator has an empty

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By reducing the running voltage to a value that is greater than the supply voltage of the control device, the advantage is that the power supply of the control device is secured in any case.

It is also advantageous if the reference voltage is lower than the ignition voltage for an arc between the electrode and the workpiece, as this reliably prevents damage to the remote adjuster or the formation of an arc between the electrode holder and the contact surface of the remote adjuster.

According to another embodiment, it is provided that a power source for the control device is arranged between the rectifier and the interrupter, whereby the current flow required to generate a control signal can simultaneously be used to supply the control device in the remote adjuster.

It is also advantageous if the frequency adjustment controller of the control device is formed by a control resistor, as this enables continuous adjustment with known robust components.

However, it is also possible for the control element of the regulating resistor to interact with a scale, as this makes it easy to see the respective position of the remote adjuster over the entire control range.

It is also advantageous if the individual markings on the scale correspond to the desired current values of the welding current, as this allows precisely predeterminable current values to be set on the remote control.

According to another possible development, it is provided that the evaluation element changes the welding current setting device in the arc welding machine by a value corresponding to the frequency setting controller depending on the change in the frequency of the vibration generator, whereby a direct dependency is given between the current values set in the remote adjuster and the settings made by the welding current setting device in the arc welding machine.

It is also advantageous if the control range of the remote control can be changed

and preferably extends between 1 and 3 KHz, as this allows sufficient fine gradation between the individual setting values and also simple evaluation.

However, it is also advantageous if the control device is assigned a power source that is independent of the rectifier, as this allows the no-load voltage to be kept very low even when using a remote adjuster.

However, a further development is also possible, according to which the interrupter is arranged in a line connection leading from the positive to the negative potential of the rectifier, in which at least one protective resistor is arranged in series with the interrupter, whereby no undefined voltage increase can occur and thus accidental ignition of an arc is reliably eliminated.

It is also advantageous if the remote control has a display element that emits a signal when the welding current setting on the welding current setting device and the remote control match, as this makes it easy to show the operator that the control process is complete and that the desired current value has actually been set.

According to another development, it is provided that if the setting values on the remote adjuster and the welding current setting device match, an additional consumer is connected between the evaluation element and the workpiece, whereby the match between the desired target value and the current value set with the welding current setting device can be easily transmitted to the remote adjuster just by sending the supply voltage.

According to a further advantageous embodiment, the frequency adjustment controller is infinitely adjustable, whereby the current value can be adapted as precisely as possible to the respective specified welding conditions.

Finally, it is also advantageous if a control lamp is arranged on the remote adjuster to indicate the contact between the electrode holder and the contact surface and the contact surface with the workpiece, as this allows the operator to immediately see whether the desired adjustment process is running smoothly.

The invention is explained in more detail below with reference to the embodiments shown in the drawings.

Show it:

Fig. 1 is a schematic diagram of an arc welding machine with the remote adjuster arranged according to the invention;

Fig. 2 a block diagram of the control circuit between the remote control and the welding current setting device;

Fig. 3 is a block diagram of another embodiment of a remote adjuster designed according to the invention;

Fig. 4 is a circuit diagram of the remote control;

Fig. 5 is a schematic diagram of the evaluation unit in the control device of the power section.

Fig.l shows an arc welding machine 1 with a control device 2 and a power section 3 that can be controlled with it for generating welding current. This power section 3 can be connected to an idle circuit 4 via the control device 2. This connection of the power section 3 only takes place when the current value exceeds a certain preset threshold value. If the current falls below this threshold value, the power section 3 is switched off by the control device 2 and the machine is in its idle position, in which only the idle circuit 4 is activated. This is sufficient to switch the power section 3 back on when the electrode touches the workpiece due to the increased current flow in the event of a short circuit by monitoring the current increase when the threshold value is exceeded. The arc welding machine 1 is connected to a power supply network, e.g. with 380 V, via connections.

The power unit 3 is connected to an electrode holder 7 and a workpiece 8 via welding current cables 5, 6. A remote control 9 can be inserted between the electrode holder 7 and the workpiece 8. This has a contact surface

before 10, which is placed on the workpiece 8 and a contact surface 11, onto which the electrode 12 of the electrode holder can be placed. A control lamp 13 is provided to monitor the perfect contact between the electrode holder 7 and the workpiece 8.

In addition to the remote adjuster 9, the control device 14 integrated in it is shown schematically. This control device 14 comprises a vibration generator 15, the output of which is connected to a control input 16 of a breaker 17. Between the contact surfaces 10 and 11, in addition to a breaker contact 18 of the breaker 17, a protective resistor 19 is arranged, which prevents a short circuit when the breaker contact 18 is closed. The control device 14 is designed as a consumer with a predeterminable power consumption. As a result, depending on the different switching states in the control device 14 or in the remote adjuster 9, a different current flows in the welding current cables 5, 6 or through the electrode holder 7 and the remote adjuster 9 or the workpiece 8, which is, however, designed or limited in such a way that an undesirable build-up of an arc between the electrode 12 and the contact surface 11 is reliably prevented in every case. Above all, the power consumption of the control device 14 or the protective resistor 19 is designed such that the current flowing in the welding current cables 5, 6 in the various switching states of the control device 14 does not exceed the current value preset as a threshold value in the control device 2, which leads to a fully automatic switching on of the power unit 3.

In Fig.2, the arc welding machine 1 and the remote control 9 are shown again in the block diagram. The design of the remote control 9 corresponds to the principle diagram in Fig.1. This diagram also shows in detail that the idle circuit 4 is arranged in the arc welding machine 1 in parallel with the power section 3. A relatively high total resistance 20 is arranged in the idle circuit 4, which has a value of 560 Ω, for example. This total resistance in the idle circuit 4 always comes into effect when the current in the welding current cables 5, 6 is below a preset value required for welding. This is done by monitoring the current flow in the welding circuit with a shunt or other measuring device. If the current value in the welding circuit falls below a preset value, the power section 3 is switched off from the welding circuit via a switch 21. In this case, the total resistance 20 therefore determines the idle

current that flows through the welding current cables 5, 6, the interrupter 17 and the protective resistor 19. If the electrode holder 7 is now contacted with the workpiece 8 with the remote adjuster 9 interposed, the structure of the remote adjuster 9 prevents the formation of a short circuit, so that the current value in the welding current cables 5, 6 cannot rise above the predefined threshold value for switching on the power unit 3. If, on the other hand, the electrode is contacted directly with the workpiece 8, a short circuit occurs and thus a strong current increase in the welding current cables 5 and 6, which causes the control device 2 to switch on the power unit 3 and thus to supply the welding current. The remote setting or the remote setting process using the remote adjuster 9 therefore only takes place when the arc welding machine 1 is idle.

As can also be seen from the illustration in Fig.2, the voltage supply to the control device 14 is also provided by means of the open circuit voltage supplied via the welding current cables 5,6.

Fig.3 shows a variant that essentially corresponds to the variant according to Fig.2. The differences from the variant shown in Fig.2 are that the control device 14 has a vibration generator as the vibration generator 15, which is supplied with energy via its own independent power source 22, e.g. a battery, arranged in the remote control 9. This frequency generator imposes a superimposed frequency on the voltage, which can be evaluated in the control device 2 of the arc welding machine 1. In this case too, the protective resistor 19 is provided in order to prevent a short circuit in the welding power cables 5 and 6.

Of course, it is also possible in the embodiment shown in Fig. 2 that the energy supply of the vibration generator 15 or the entire control device 14 is provided by an additional independent power source 22.

The control device 14 and the control unit 2 are shown in more detail in Figs. 4 and 5.

In Fig.4 it is shown that the two contact surfaces 10, 11 are connected to the two inputs of a rectifier 23. A line 24 is connected to the positive potential of the rectifier 23, while a line 25 is connected to the negative potential.

Connected in parallel to the rectifier is the control lamp 13, which in this case is formed by an LED. Voltage regulators 26 with corresponding capacitors 27 assigned to them are arranged in series with this control lamp 13. The interrupter contact 18 is arranged between the line 24 and the line 25, and the protective resistor 19 formed by two resistors is arranged in front of it in the line 24. This prevents a short circuit in the circuit formed by the lines 24 and 25 when the interrupter contact 18 is closed. The interrupter contact 18 of the interrupter 17 is formed by a transistor, e.g. a field effect transistor (MOSFET), which is controlled by the oscillation generator 15, which can be formed by an integrated circuit.

The minimum and maximum frequencies of the vibration generator 15 that limit the control range can then be set using setting controls 28, 29. Furthermore, a frequency setting controller 30 is assigned to the vibration generator 15, with which a frequency signal located between the minimum and maximum frequencies set with the setting controls 28 and 29 and corresponding to the respective preselected current value of the arc welding machine 1 can be produced at the output of the vibration generator 15.

The circuit shown in Fig.4 reduces the value Ui when the interrupter contact 18 closes, as shown schematically in Fig.2 in the area of the welding current cable 6 by a diagram, depending on the size of the protective resistor 19, whereby a square-wave pulse is superimposed on the voltage signal. Depending on the frequency or the number of pulses per unit of time, a specific current value in the arc welding machine 1 is assigned to each frequency or each number of pulses per unit of time in accordance with the preselected definition of the minimum and maximum value using the setting controls 28 and 29.

If, however, a frequency generator is used as the vibration generator 15, as shown in Fig. 3, the signal applied to the circuit between the welding current cables 5 and 6 increases the voltage value Ui when the contact is closed, and the rectangular signal obtained in this way can be used to transmit the welding current values desired by the operator to the arc welding machine 1 via the frequency or the number of pulses per unit of time.

To evaluate the signals fed into the welding current cables 5, 6 by the remote adjuster 9, the control device 2 is connected via inputs 31 into the supply circuit consisting of the welding current cables 5 and 6. The incoming signals from the remote adjuster 9 are freed of the DC voltage component via a filter element 32, with the remaining square wave signal being prepared for further processing by subsequent amplifiers 33 and filters 34. The signal prepared in this way is then expanded to an evaluation element 35, which can be formed by a frequency detection element 36.

A detection element 37, which is arranged downstream of the evaluation element 35, determines whether the current value of the arc welding machine 1 set with the welding current setting device 38 should be increased or decreased. Depending on the output signal of the detection element 37, counters 40 are controlled via a line 39 to increase or decrease the numerical values set on the counters 40. This control is carried out via a comparator 41, to whose input an output of the evaluation element 35 is connected via a line 42, while at another input an actual signal corresponding to the current value currently set with the welding current setting device 38 is connected via a line 43.

The numerical value determined by the counters 40 is converted in a digital-analog converter 44 into an analog control signal, which is applied to a control input 45 of the welding current setting device 38. For this purpose, an output 46 of the digital-analog converter 44 is connected to the control input 45 of the welding current setting device 38 by a line 47.

The welding current setting device 38 is then adjusted until the control signals present at the output 46 of the digital-analog converter 44 match the signals present at the welding current setting device 38 or, depending on the type of circuit, the output 46 of the digital-analog converter 44 is zero.

The operator therefore has the option of using the remote control 9 to set the required welding current strength. After waiting for the adjustment time normally required, e.g. 1 to 2 seconds, the remote control 9 can be removed by the operator and the welding process can then be continued with the newly set welding current.

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If the welding current needs to be adjusted again due to unsatisfactory welding or a change in the material thickness, the operator of the arc welding machine 1 only needs to switch it to the idle state by interrupting the power and gas supply or, if applicable, the welding wire supply. The operator then places the remote adjuster 9 with the contact surface 10 on the workpiece 8 and then contacts the welding wire or the welding electrode with the contact surface 11 of the remote adjuster 9. He then sets the desired current value according to a scale division specified on the remote adjuster 9, and the adjustment process in the arc welding machine 1 is then carried out again in the manner described above.

As further shown schematically in Fig. 4, the frequency setting controller 30 or the actuator of a control resistor formed by it is assigned a setting scale 48, which is provided with a scale 49 on which the current values required for the arc welding machine 1 are indicated in amperes. The individual markings on the scale 49 therefore correspond to a precisely predefined current value for the arc welding machine 1.

In order to increase the certainty that the current value desired by the user is actually set on the arc welding machine 1, it is possible to provide an additional display element 50 - Fig. 1 - on the remote adjuster 9, which is activated, for example, by a frequency additionally transmitted by the evaluation element 35 via the welding current cables 5, 6. This ensures that the user does not end the adjustment process before the desired current value has been set using the welding current adjustment device 38.

Preferably, however, it is also possible that, if the current value on the welding current setting device 38 and the remote adjuster 9 match, an additional consumer is interposed between the evaluation element 35 and the remote adjuster 9 in order to be able to display the match between the desired current values and those actually set on the arc welding machine 1 via the display element 50.

Of course, it is possible for the remote control 9 to be equipped with either a continuously or stepwise switchable frequency setting controller 30.

However, it is also possible to enable a step-by-step adjustment between the individual current values.

Individual combinations of features described above can also form independent inventive solutions.

Reference symbol list

1 arc welding machine

2 Control device

3 Power unit

4 Idle circuit

5 welding power cables

6 welding power cables

7 Electrode holder

8 Workpiece

9 Remote adjuster

10 Contact surface

11 Contact surface

12 Electrode

13 Indicator light

14 Control device

15 Vibration generators

16 Control input

17 breakers

18 Breaker contact

19 Protective resistor

20 Total resistance

21 switches

22 Power source

23 Rectifier

24 Line

25 Line

26 Voltage regulator

27 Capacitor

28 Adjustment controls

29 Adjustment controls

30 Frequency adjustment controls

31 Entrance

32 sieve element

33 Amplifiers

34 filters

35 Evaluation element

36 Frequency detection element

37 Recognition element

38 Welding current adjustment device

39 Management -

40 counters

41 Comparator

42 Line

43 Management

44 Digital-to-analog converters

45 Control input

46 Output

47 Management

48 Setting scale

49 scale

50 Display element

Claims (17)

Protection claims 1. Arc welding machine with an idle circuit and a power unit for generating welding current that can be switched on and regulated via a control device, which is connected to an electrode holder and the workpiece via a welding current cable and with a welding current setting device assigned to the control device, adjustable manually or via a remote adjuster, in which the remote adjuster is arranged with a control device between the workpiece and the electrode holder and comprises a manually operable welding current setpoint transmitter, to which an evaluation element is assigned in the control device, characterized in that the remote adjuster (9) is designed as a consumer with a predetermined power consumption and is contacted via an input each with the workpiece (8) and the electrode holder (7) and that the control device (14) has a vibration generator (15) that is connected to a frequency setting controller (30) forming the welding current setpoint transmitter and whose output is connected to a control input (16) of an interrupter (17) or frequency generator which is interposed in a line connection arranged between the workpiece (8) and the electrode holder (7). 2. Arc welding machine according to claim 1, characterized in that a rectifier (23) is interposed in the line connection between the workpiece (8) and the electrode holder (7). 3. Arc welding machine according to claim 1 or 2, characterized in that a frequency detection element (36) forms the evaluation element (35) in the control device (2), the output of which is connected to a control input (45) for the welding current setting device (38). 4. Arc welding machine according to one or more of claims! to 3, characterized in that the vibration generator (15) reduces an open circuit voltage to a value which is greater than the supply voltage of the control device (14). 5. Arc welding machine according to one or more of claims 1 to 4, characterized in that the reference voltage is lower than the ignition voltage for an arc between the electrode (12) and the workpiece (8). 6. Arc welding machine according to one or more of claims 1 to 5, characterized in that a power source (22) for the control device (14) is arranged between the rectifier (23) and the interrupter (17). 7. Arc welding machine according to one or more of claims 1 to 6, characterized in that the frequency adjustment controller (30) of the control device (14) is formed by a control resistor. 8. Arc welding machine according to one or more of claims 1 to 7, characterized in that the actuator of the control resistor interacts with a scale (49). 9. Arc welding machine according to one or more of claims 1 to 8, characterized in that the individual markings of the scale (49) correspond to desired current values of the welding current. 10. Arc welding machine according to one or more of claims 1 to 9, characterized in that the evaluation element (35) changes the welding current setting device (38) in the arc welding machine (1) by a value corresponding to the frequency setting controller (30) depending on the change in the frequency of the vibration generator (15). 11. Arc welding machine according to one or more of claims 1 to 10, characterized in that the control range of the remote adjuster (9) is variable and preferably extends between 1 and 3 KHz. 12. Arc welding machine according to one or more of claims 1 to 11, characterized in that the control device (14) is assigned a power source (22) which is independent of the rectifier (23). 13. Arc welding machine according to one or more of claims 1 to 12, characterized in that the interrupter (17) is arranged in a line connection leading from the positive to the negative potential of the rectifier (23), in which at least one protective resistor (19) is connected in series with the interrupter (17) is arranged. 14. Arc welding machine according to one or more of claims 1 to 13, characterized in that a display element (50) is present on the remote adjuster (9), which emits a signal after the welding current setting on the welding current setting device (38) and the remote adjuster (9) match. 15. Arc welding machine according to one or more of claims 1 to 14, characterized in that if the setting values on the remote adjuster (9) and those on the welding current setting device (38) match, an additional consumer is interposed between the evaluation element (35) and the workpiece (8). 16. Arc welding machine according to one or more of claims 1 to 15, characterized in that the frequency adjustment controller (30) is continuously adjustable. 17. Arc welding machine according to one or more of claims 1 to 16, characterized in that a control lamp (13) indicating the contacting of the electrode holder (7) with the contact surface (11) and the contact surface (10) with the workpiece (8) is arranged on the remote adjuster (9).