Torch height control for flame cutting machines

Claim 1

A system for maintaining at least one cutting torch in a flame cutting machine at a predetermined distance from a workpiece comprising: motor means for advancing said torch toward said workpiece and for retracting said torch away therefrom in response to control signals, an electrical power supply having first and second output terminals, conductive means connecting said torch to said first power supply terminal and connecting said workpiece to said second power supply terminal whereby an electrical current passes through the flame of said torch and said flame becomes a variable electrical resistor, the resistance of which is a function of the spacing of said torch from said workpiece, wherein said conductive means comprises a voltage divider resistor and a circuit junction connected between one of said power supply terminals and one of said torch and said workpiece to form a voltage divider in conjunction with said flame whereby the electrical voltage at said circuit junction varies in accordance with said variations of said electrical resistance of said flame, means for producing a reference voltage, control signal means for actuating said motor means in response to variations of said resistance of said flame, detector means for sensingg changes of said electrical resistance of said flame, wherein said detector means is connected between said control signal means and said circuit junction and has means for actuating said control signal means in response to variations of said voltage at said circuit junction, and wherein said detector means includes means for comparing said voltage at said circuit junction with said reference voltage and for actuating said control signal means when said circuit junction voltage departs from a predetermined relationship to said reference voltage, and safety shutdown means for blocking actuation of said motor means in response to said detector means when said circuit junction voltage departs from predetermined relationship to said reference voltage by a predetermined amount.

Claim 2

A system for maintaining at least one cutting torch in a flame cutting machine at a predetermined distance from a workpiece comprising: motor means for advancing said torch toward said workpiece and for retracting said torch away therefrom in response to control signals, an electrical power supply having first and second output terminals, conductive means connecting said torch to said first power supply terminal and connecting said workpiece to said second power supply terminal whereby an electrical current passes through the flame of said torch and said flame becomes a variable electrical resistor, the resistance of which is a function of the spacing of said torch from said workpiece, wherein said conductive means comprises a voltage divider resistor and a circuit junction connected between one of said power supply terminals and one of said torch and said workpiece to form a voltage divider in conjunction with said flame whereby the electrical voltage at said circuit junction varies in accordance with said variations of said electrical resistance of said flame, means for producing a reference voltage, control signal means for actuating said motor means in response to variations of said resistance of said flame, detector means for sensingg changes of said electrical resistance of said flame, wherein said detector means is connected between said control signal means and said circuit junction and has means for actuating said control signal means in response to variations of said voltage at said circuit junction, and wherein said detector means includes means for comparing said voltage at said circuit junction with said reference voltage and for actuating said control signal means when said circuit junction voltage departs from a predetermined relationship to said reference voltage, and safety shutdown means for blocking actuation of said motor means in response to said detector means when said circuit junction voltage departs from predetermined relationship to said reference voltage by a predetermined amount.

Claim 4

A system for maintaining at least one cutting torch in a flame cutting machine at a predetermined distance from a workpiece wherein said flame cutting machine has a switch which is operated following preheating of said workpiece in order to initiate cutting thereof, comprising: motor means for advancing said torch toward said workpiece and for retracting said torch away therefrom in response to control signals, an electrical power supply having first and second output terminals, conductive means connecting said torch to said first power supply terminal and connecting said workpiece to said second power supply terminal whereby an electrical current passes through the flame of said torch and said flame becomes a variable electrical resistor, the resistance of which is a function of the spacing of said torch from said workpiece, wherein said conductive means comprises a voltage divider resistor and a circuit junction connected between one of said power supply terminals and one of said torch and said workpiece to form a voltage divider in conjunction with said flame whereby the electrical voltage at said circuit junction varies in accordance with said variations of said electrical resistance of said flame, means for producing a reference voltage wherein said means providing a reference voltage includes a first voltage source providing a first reference voltage for preheating operations of said flame cutting machine and a second voltage source providing a second reference voltage for cutting operations of said flame cutting machine, cotrol signal means for actuating said motor means in response to variations of said resistance of said flame, detector means for sensing changes of said electrical resistance of said flame, wherein said detector means is connected between said control signal means and said circuit junction and has means For actuating said control signal means in response to variations of said voltage at said circuit junction, and wherein said detector means includes means for comparing said voltage at said circuit junction with said reference voltage and for actuating said control signal means when said circuit junction voltage departs from a predetermined relationship to said reference voltage, and means for transmitting said first reference voltage to said detector means when said switch is unoperated and for transmitting said second reference voltage to said detector means in response to operation of said switch.

Claim 5

A system for maintaining at least one cutting torch in a flame cutting machine at a predetermined distance from a workpiece wherein said flame cutting machine has a switch which is operated following preheating of said workpiece in order to initiate cutting thereof, comprising: motor means for advancing said torch toward said workpiece and for retracting said torch away therefrom in response to control signals, an electrical power supply having first and second output terminals, conductive means connecting said torch to said first power supply terminal and connecting said workpiece to said second power supply terminal whereby an electrical current passes through the flame of said torch and said flame becomes a variable electrical resistor, the resistance of which is a function of the spacing of said torch from said workpiece, wherein said conductive means comprises a voltage divider resistor and a circuit junction connected between one of said power supply terminals and one of said torch and said workpiece to form a voltage divider in conjunction with said flame whereby the electrical voltage at said circuit junction varies in accordance with said variations of said electrical resistance of said flame, means for producing a reference voltage wherein said means providing a reference voltage includes a first voltage source providing a first reference voltage for preheating operations of said flame cutting machine and a second voltage source providing a second reference voltage for cutting operations of said flame cutting machine, cotrol signal means for actuating said motor means in response to variations of said resistance of said flame, detector means for sensing changes of said electrical resistance of said flame, wherein said detector means is connected between said control signal means and said circuit junction and has means For actuating said control signal means in response to variations of said voltage at said circuit junction, and wherein said detector means includes means for comparing said voltage at said circuit junction with said reference voltage and for actuating said control signal means when said circuit junction voltage departs from a predetermined relationship to said reference voltage, and means for transmitting said first reference voltage to said detector means when said switch is unoperated and for transmitting said second reference voltage to said detector means in response to operation of said switch.

Claim 6

A system for maintaining at least one cutting torch in a flame cutting machine at a predetermined distance from a workpiece comprising: motor means for advancing said torch toward said workpiece and for retracting said torch away therefrom in response to control signals, an electrical power supply having first and second output terminals, conductive means connecting said torch to said first power supply terminal and connecting said workpiece to said second power supply terminal whereby an electrical current passes through the flame of said torch and said flame becomes a variable electrical resistor, the resistance of which is a function of the spacing of said torch from said workpiece, wherein said conductive means comprises a voltage divider resistor and a circuit junction connected between one of said power supply terminals and one of said torch and said workpiece to form a voltage divider in conjunction with said flame whereby the electrical voltage at said circuit junction varies in accordance with said variations of said electrical resistance of said flame, means for producing a reference voltage, control signal means for actuating said motor means in response to variations of said resistance of said flame, detector means for sensing changes of said electrical resistance of said flame, wherein said detector means is connected between said control signal means and said circuit junction and has means for actuating said control signal means in response to variations of said voltage at said circuit junction, and wherein said detector means includes means for comparing said voltage at said circuit junction with said reference voltage and for actuating said control signal means when said circuit junction voltage departs from a predetermined relationship to said reference voltage, and wherein said flame cutting machine has a plurality of said torches each having separate ones of said conductive means and detector means connected therewith, and wherein said means providing a reference voltage provides a basic reference voltage to each of said detector means and wherein each of said detector means has a fine control means for selectively modifying said basic reference voltage at that detector means only.

Claim 7

A system for maintaining at least one cutting torch in a flame cutting machine at a predetermined distance from a workpiece comprising: motor means for advancing said torch toward said workpiece and for retracting said torch away therefrom in response to control signals, an electrical power supply having first and second output terminals, conductive means connecting said torch to said first power supply terminal and connecting said workpiece to said second power supply terminal whereby an electrical current passes through the flame of said torch and said flame becomes a variable electrical resistor, the resistance of which is a function of the spacing of said torch from said workpiece, wherein said conductive means comprises a voltage divider resistor and a circuit junction connected between one of said power supply terminals and one of said torch and said workpiece to form a voltage divider in conjunction with said flame whereby the electrical voltage at said circuit junction varies in accordance with said variations of said electrical resistance of said flame, means for producing a reference voltage, control signal means for actuating said motor means in response to variations of said resistance of said flame, detector means for sensing changes of said electrical resistance of said flame, wherein said detector means is connected between said control signal means and said circuit junction and has means for actuating said control signal means in response to variations of said voltage at said circuit junction, and wherein said detector means includes means for comparing said voltage at said circuit junction with said reference voltage and for actuating said control signal means when said circuit junction voltage departs from a predetermined relationship to said reference voltage, and wherein said flame cutting machine has a plurality of said torches each having separate ones of said conductive means and detector means connected therewith, and wherein said means providing a reference voltage provides a basic reference voltage to each of said detector means and wherein each of said detector means has a fine control means for selectively modifying said basic reference voltage at that detector means only.

Claim 8

A system for controlling the spacing of a plurality of torches from a plurality of workpieces in a flame cutting machine comprising: a plurality of servomotors for advancing and retracting individual ones of said torches relative to the associated individual ones of said workpieces, each of said servomotors having a terminal which may be energized to retract the associated torch and a second terminal which may be energized to advance the associated torch, a plurality of normally open relay means each connected between a power source and an individual one of said servomotor terminals, a DC power supply having positive and negative output terminals relative to a circuit ground, a plurality of flame height control circuits each controlling an individual pair of said relay contacts which control an individual one of said servomotors, each said flame height control circuit having a circuit junction and having a voltage divider resistor connected between said circuit junction and one of said power supply terminals and having first conductive means connecting said circuit junction with one of said torch and said workpiece aNd having second conductive means connecting the other of said power supply terminals with the other of said torch and said workpiece whereby said voltage divider resistor and the flame of said torch act as a voltage divider to cause the voltage at said circuit junction to vary in accordance with variations in the spacing of the associated ones of said torches and workpieces, each said flame height control circuit further having a summing junction and means transmitting said voltage at said circuit junction to said summing junction and means transmitting a predetermined reference voltage to said summing junction and having a first relay driver for operating the first of said pair of relay contacts and a second relay driver for operating the second of said relay contacts, each said flame height control circuit still further having an amplifier with an input connected to said summing junction and an output connected to each of said relay drivers through separate unidirectional circuit elements wherein one such element is inverted relative to the other such element whereby a positive output from said amplifier closes a first of said pair of relay contacts and a negative output from said amplifier closes the other of said pair of relay contacts.

Claim 9

A system for controlling the spacing of a plurality of torches from a plurality of workpieces in a flame cutting machine comprising: a plurality of servomotors for advancing and retracting individual ones of said torches relative to the associated individual ones of said workpieces, each of said servomotors having a terminal which may be energized to retract the associated torch and a second terminal which may be energized to advance the associated torch, a plurality of normally open relay means each connected between a power source and an individual one of said servomotor terminals, a DC power supply having positive and negative output terminals relative to a circuit ground, a plurality of flame height control circuits each controlling an individual pair of said relay contacts which control an individual one of said servomotors, each said flame height control circuit having a circuit junction and having a voltage divider resistor connected between said circuit junction and one of said power supply terminals and having first conductive means connecting said circuit junction with one of said torch and said workpiece aNd having second conductive means connecting the other of said power supply terminals with the other of said torch and said workpiece whereby said voltage divider resistor and the flame of said torch act as a voltage divider to cause the voltage at said circuit junction to vary in accordance with variations in the spacing of the associated ones of said torches and workpieces, each said flame height control circuit further having a summing junction and means transmitting said voltage at said circuit junction to said summing junction and means transmitting a predetermined reference voltage to said summing junction and having a first relay driver for operating the first of said pair of relay contacts and a second relay driver for operating the second of said relay contacts, each said flame height control circuit still further having an amplifier with an input connected to said summing junction and an output connected to each of said relay drivers through separate unidirectional circuit elements wherein one such element is inverted relative to the other such element whereby a positive output from said amplifier closes a first of said pair of relay contacts and a negative output from said amplifier closes the other of said pair of relay contacts.