Programmed control system

Claim 2

A pulse width modulator for providing a train of output pulses at a selected repetition rate and with a selected duty cycle, comprising: a control signal; means for generating a repetitive ramp signal; a comparator responsive to the control signal and to the ramp signal for producing an output pulse that is initiated when said ramp signal attains a magnitude having a predetermined relation to the control signal and that terminates upon termination of the ramp signal; a source of welding current; a plurality of switches arranged to connect and disconnect the current source to and from a weld head; and means responsive to the output of said comparator for repetitively operating said switches at a duty cycle represented by said control signal.

Claim 3

A programable control system including means to regulate the Current supplied to a welding torch, said apparatus comprising: a welding torch, a source of welding supply current, a source of program voltage, a plurality of signal circuits for generating output signals for application in controlling functions of said welding torch including current command generating circuits and timing circuits operable to generate current command output signals and first and second timing output signals respectively, each of said current command generating and timing circuits having therein a resistor which provides electrical communication between said current command generating and timing circuits and said source of program voltage, each of said timing circuits controlling a time interval having a value dependent upon the value of its said resistor; a logic circuit in electrical communication with said signal circuits including a first output signal operable to control the operation of said timing circuits and a second output signal responsive to said first output signal of said timing circuits operable to control said current command generating circuits; an error comparator for generating an output signal; means responsive to the second output signal of said timing circuits and to said second output signal of said logic circuits for generating a signal for input to said error comparator; a group of modulator transistor switches for providing electrical communication between said source of welding supply current and said welding torch; a pulse width modulator responsive to the output signal of said error comparator and operable to control the operation of said switches and thereby control the current supplied to the welding torch; means for providing as a second input to said error comparator, a signal representing welding current.

Claim 4

A programable control system including means to regulate the Current supplied to a welding torch, said apparatus comprising: a welding torch, a source of welding supply current, a source of program voltage, a plurality of signal circuits for generating output signals for application in controlling functions of said welding torch including current command generating circuits and timing circuits operable to generate current command output signals and first and second timing output signals respectively, each of said current command generating and timing circuits having therein a resistor which provides electrical communication between said current command generating and timing circuits and said source of program voltage, each of said timing circuits controlling a time interval having a value dependent upon the value of its said resistor; a logic circuit in electrical communication with said signal circuits including a first output signal operable to control the operation of said timing circuits and a second output signal responsive to said first output signal of said timing circuits operable to control said current command generating circuits; an error comparator for generating an output signal; means responsive to the second output signal of said timing circuits and to said second output signal of said logic circuits for generating a signal for input to said error comparator; a group of modulator transistor switches for providing electrical communication between said source of welding supply current and said welding torch; a pulse width modulator responsive to the output signal of said error comparator and operable to control the operation of said switches and thereby control the current supplied to the welding torch; means for providing as a second input to said error comparator, a signal representing welding current.

Claim 5

The control system of claim 2 wherein one of said signal circuits includes a motor speed control circuit and further including: a motor for driving a workpiece relative to the welding torch; a pulse width modulator for energizing the motor with a series of motor driving pulses; means for deriving a motor speed feedback signal during intervals between said motor driving pulses; means for sampling the feedback signal and the signal generated by the motor speed command signal circuit; means for comparing said sampled signals and storing the comparison; means for disabling the last mentioned pulse width modulator during the sampling time; and means for controlling the last mentioned pulse width modulator in accordance with the stored comparison signals.

Claim 6

A program control system according to claim 3 including means for starting a welding arc, said starting means comprising: a high frequency starter for ionizing inert welding gas and a high frequency impulse starter responsive to ionization of said gas for providing a high current pulse through the ionized gas and through the welding arc.

Claim 7

A variable signal generating circuit comprising: a level control circuit for generating level signals having predetermined values; a capacitor for generating a varying signal; first constant current means in electrical communication with said capacitor and operable to charge said capacitor to the level of one of said level signals in electrical communication with said capacitor; means for rapidly charging said capacitor to the level of a second one of said level signals; second constant current means in electrical communication with said capacitor for discharging said capacitor; an output terminal; logic means for selectively coupling the first and second constant current generating means to the level control circuit and to the means for rapidly charging, said logic means including means for selectively coupling to said output terminal selected ones of said level signals and said varying signal; a plurality of groups of circuit elements; a program control means for selecting one of said groups; switch means for selectively connecting different ones of the elements of the selected group into said level control circuit to determine the value of the signal generated thereby; a welding torch; a current supply for the torch; a power switch for selectively connecting the torch with the current supply; a pulse width modulator responsive to signals on said output terminal for operating said power switch.

Claim 8

A variable signal generating circuit comprising: a level control circuit for generating level signals having predetermined values; a capacitor for generating a varying signal; first constant current means in electrical communication with said capacitor and operable to charge said capacitor to the level of one of said level signals in electrical communication with said capacitor; means for rapidly charging said capacitor to the level of a second one of said level signals; second constant current means in electrical communication with said capacitor for discharging said capacitor; an output terminal; logic means for selectively coupling the first and second constant current generating means to the level control circuit and to the means for rapidly charging, said logic means including means for selectively coupling to said output terminal selected ones of said level signals and said varying signal; a plurality of groups of circuit elements; a program control means for selecting one of said groups; switch means for selectively connecting different ones of the elements of the selected group into said level control circuit to determine the value of the signal generated thereby; a welding torch; a current supply for the torch; a power switch for selectively connecting the torch with the current supply; a pulse width modulator responsive to signals on said output terminal for operating said power switch.

Claim 9

A welding power supply comprising: a source of welding current; a plurality of transistors each detachably connected in series between the current source and a welding electrode, said transistors being connected in parallel with each other; and means for repetitively switching at least some of said transistors together between a first state of substantially full conduction and a second state of substantially no conduction, whereby the current to the welding electrode may be varied in increments by connecting a selective combination consisting of at least one of said transistors, and said transistors, when connected, operate only in a low voltage-high current state or high voltage-low current state to minimize power dissipation.

Claim 10

A welding power supply comprising: a source of welding current; a plurality of transistors each detachably connected in series between the current source and a welding electrode, said transistors being connected in parallel with each other; and means for repetitively switching at least some of said transistors together between a first state of substantially full conduction and a second state of substantially no conduction, whereby the current to the welding electrode may be varied in increments by connecting a selective combination consisting of at least one of said transistors, and said transistors, when connected, operate only in a low voltage-high current state or high voltage-low current state to minimize power dissipation.

Claim 11

The power supply of claim 6 including means for varying the time in which said transistors are maintained in said first state, whereby the current to the welding electrode may be varied in addition to or in lieu of said incremental variation.

Claim 12

The power supply of claim 6 including: closed loop control means for generating an error signal indicative of the difference between a commanded current and current drawn by said welding electrode; and said means for repetitively switching comprising means responsive to the closed loop control means for operating the transistors in accordance with said error signal.

Claim 13

The power supply of claim 6 wherein said means for repetitively switching comprises: a pulse width modulator connected to control the duty cycle of said transistors; and closed loop control means for selectively controlling the duration of pulses produced by the pulse width modulator.

Claim 14

The welding supply of claim 6 including: an inductor in series with said transistors to minimize fluctuation of the repetitively switched current fed to the electrode; means to provide a feedback signal representative of weld current; a command signal; a comparator for generating an error signal indicative of the difference between said command and feedback signals; and a pulse width modulator responsive to said error signal for controlling the time during which said transistors are maintained in said first state.

Claim 15

A welding power supply comprising: a current supply; a welding torch; and means for varying current from the supply to the torch in predetermined discrete increments and linearly with respect to a commanded level within said increments, said varying means comprising: a plurality of bi-state devices detachably connected between said supply and torch, and a pulse width modulator connected to operate all of said devices with a duty cycle in accordance with said commanded level.

Claim 16

A welding power supply comprising: a current supply; a welding torch; and means for varying current from the supply to the torch in predetermined discrete increments and linearly with respect to a commanded level within said increments, said varying means comprising: a plurality of bi-state devices detachably connected between said supply and torch, and a pulse width modulator connected to operate all of said devices with a duty cycle in accordance with said commanded level.

Claim 17

The power supply of claim 11 wherein the pulse width modulator comprises: an oscillator; a capacitor; a constant current generator connected to linearly charge the capacitor; means responsive to the oscillator for repetitively discharging the capacitor; a source of command signal; a modulator comparator having first and second inputs thereof connected to receive a signal from said capacitor and an error signal; a weld current circuit providing a feedback signal representative of welding current, said circuit having included therein a resistor; an error comparator responsive to said feedback and command signals for generating said error signal; whereby the modulator comparator provides an output pulse that is initiated upon attainment of a predetermined relation between the inputs to the modulator compaRator and that is terminated upon discharge of the capacitor by said oscillator; and means for driving all of said devices in accordance with the output pulses from said modulator comparator.

Claim 18

A modular power supply comprising: a plurality of power supply units; a welding torch; and means for detachably connecting a combination consisting of at least one of said power supply units in parallel to said torch; each said unit comprising: a power switch, an inductor connected between the switch and the unit output, and a switch driving circuit for operating the switch in response to a current command signal; and command means for applying a common current command signal to all of said driving circuits in unison.

Claim 19

A modular power supply comprising: a plurality of power supply units; a welding torch; and means for detachably connecting a combination consisting of at least one of said power supply units in parallel to said torch; each said unit comprising: a power switch, an inductor connected between the switch and the unit output, and a switch driving circuit for operating the switch in response to a current command signal; and command means for applying a common current command signal to all of said driving circuits in unison.

Claim 20

The power supply of claim 13 wherein said command means comprises: an oscillator; a capacitor in electrical communication with said oscillator; a constant current generator connected to linearly charge the capacitor; a source of command signal; a modulator comparator having first and second inputs thereof connected to receive a signal from said capacitor and an error signal; a resistor in electrical communication with the current supplied to said welding torch for generating a feedback signal indicative of welding current; an error comparator responsive to said feedback and command signals for generating said error signal; whereby the modulator comparator provides an output pulse that is initiated upon attainment of a predetermined relation between the inputs to the modulator comparator and that is terminated upon discharge of the capacitor by said oscillator; and means for controlling said driving circuits in accordance with the output pulses from said modulator comparator.

Claim 21

A closed loop welding power supply comprising: a source of welding current; a welding torch; a switch electrically interposed between the source of welding current and the torch; means for generating a feedback signal indicative of current through the torch; a source of current command signal; and means responsive to said feedback and current command signals for repetitively operating said switch between states of conduction and nonconduction at a controlled duty cycle.

Claim 22

A closed loop welding power supply comprising: a source of welding current; a welding torch; a switch electrically interposed between the source of welding current and the torch; means for generating a feedback signal indicative of current through the torch; a source of current command signal; and means responsive to said feedback and current command signals for repetitively operating said switch between states of conduction and nonconduction at a controlled duty cycle.

Claim 23

The power supply of claim 15 wherein said source provides direct current, said last mentioned means comprises a comparator for generating an error signal indicative of the difference between the current command and feedback signals, a pulse width modulator responsive to the comparator for producing a train of pulses, each having a duration in accordance with said error signal, and means for operating the switch in accordance with the pulses of said train of pulses.