Welding system provided with wire feed and arc control

Claim 2

A short-circuit arc welding system comprising, a source of welding energy, a device for feeding a consumable electrode wire towards a workpiece to provide regular alternate short-circuit and arcing relationship between the electrode wire and workpiece, an electrode wire holder having a terminal connected to a terminal of said welding energy source, means connecting said workpiece to a second terminal of said welding energy source, a measuring device including means for producing a measuring quantity representative only of the mean arc power P b of the welding system, a comparison device having a first input for receiving a preset reference quantity indicative of a desired value of mean arc power and a second input for receiving said measuring quantity and means for comparing said reference and measuring quantities to generate a control quantity in the event of a deviation between the reference and measuring quantities, and regulating means responsive to said control quantity for adjusting a welding control parameter of the welding system in a compensating sense to maintain the mean arc power substantially constant.

Claim 3

A welding system as claimed in claim 1 wherein the comparison device comprises an integrating amplifier having an output terminal connected via an integrating capacitor to a first input terminal and a second input terminal connected to ground whereby the output terminal delivers the control quantity, the first input terminal also being a summation point for receiving the measuring quantity and the reference quantity, said reference quantity being determined by the position of a slider of a potentiometer which is connected to a reference potential and the value of a resistor which is connected between the slider and the first input terminal.

Claim 4

A welding system as claimed in claim 1 wherein said regulating means includes a first regulating device controlled by said control quantity and a motor regulating device coupled to the output of the first regulating device to control said wire feeding device to adjust the electrode wire feed rate as a function of said control quantity.

Claim 5

A welding system as claimed in claim 1 wherein said regulating means includes a first regulating device controlled by said control quantity, and the source of welding energy includes a controllable current switch and a control unit responsive to the output of the first regulating device to control the operation of said controlled current switch so as to adjust the open-circuit voltage E o of the welding system in a sense to reduce the value of said control quantity.

Claim 6

A welding system as claimed in claim 1 wherein said welding energy source, said wire feeding device, said wire holder and the means connecting the energy source to the wire holder and the workpiece together comprise a welding current circuit, said measuring device comprising a current measuring device having an input connected to the welding current circuit so as to measure the flow of arc current during the arc time of a welding cycle and having an output at which it delivers a measuring quantity control signal proportional to said arc current so that the measuring quantity is proportional to the mean arc current flowing during the welding cycle arc time.

Claim 7

A welding system as claimed in claim 1 wherein the measuring device comprises means responsive to the flow of welding current for deriving a control signal proportional thereto, means responsive to the welding voltage for generating a rectangular waveform signal which is a measure of the arc time T b , and means for combining said control signal and said rectangular arc time signal for producing a measuring quantity signal proportional to the product of the mean arc current and the arc time.

Claim 8

A welding system as claimed in claim 1 wherein the comparison device comprises an integrating amplifier having an input terminal for receiving the measuring quantity and the reference quantity and an output terminal and with an integrating capacitor connected between said input and output terminals, and the measuring device comprises means responsive to the welding voltage for generating a rectangular waveform signal which is a measure of the arc time T b , a timing circuit comprising first and second monostable multivibrators the first of which is triggered by an edge of the rectangular waveform signal which corresponds to the end of the short-circuit welding condition to deliver a sampling pulse, said second multivibrator being triggered by the trailing edge of the sampling pulse to produce a reset pulse, a first controlled switch connecting the output of the integrating amplifier to a storage capacitor which develops a voltage corresponding to the control quantity, means coupling the storage capacitor to said regulating means, a second controlled switch connected to selectively short-circuit the integrating capacitor, means for applying the sampling pulse to a control input of the first switch to cause said first switch to pass current, and means for applying the reset pulse to a control input of the second switch to cause the second switch to pass current during the receipt of said reset pulse.

Claim 9

A welding system as claimed in claim 1 wherein said measuring device includes a current measuring device having input means responsive to the flow of arc current to supply at its output a measuring quantity control signal proportional to the mean arc current flowing during the arc time of a welding cycle that also includes a short-circuit time period.

Claim 10

A welding system as claimed in claim 8 wherein the measuring device comprises a pulse shaper having an input responsive to the welding voltage during a welding cycle, short-circuit/arc/short-circuit, for generating a corresponding rectangular signal, and a time keeper circuit connected to the output of the pulse shaper for supplying to the current measuring device a first time signal which is a measure of the arc time T b .

Claim 11

A welding system as claimed in claim 9 wherein the time keeper circuit supplies a second time signal which is a measure of the welding cycle time T and includes a divider circuit by means of which the second time signal is divided by the first time signal to deliver at its output a third time signal proportional to the relative arc time A b defined as T b /T.

Claim 12

A welding system as claimed in claim 10 wherein the measuring device includes means responsive to the arc current for deriving a control signal proportional thereto and a multiplying circuit to which the said control signal and the said third time signal are applied and which produces at its output the product of said signals so that the measuring quantity is proportional to the product of the relative arc time and the mean arc current.

Claim 13

A welding system as claimed in claim 1 having a welding cycle composed of regular alternate arc time periods and short-circuit time periods and wherein the measuring device comprises, means responsive to the welding energy source output voltage for deriving a time control signal determined by the arc time only, and current measuring means responsive to said time control signal and to the flow of welding current for deriving at its output an electric control signal proportional only to the mean arc current that flows during the arc time of a welding cycle.