Electrical control circuits for flash welders

In a flash welder having relatively movable platens which carry the workpieces to be welded, said platens moving relatively through flashing and upset operations toward closed position, the improved method of initiating the start of upset operation of said platens at an operator-selectable value of flashing electrical energy, comprising:

• feeding an energy signal to one input of an operational amplifier, said energy signal derived from voltage and current input to said welder during flashing operation and progressively changing as said platens move toward closed position,
• feeding a voltage to the other input of said operational amplifier,
• feeding the output signal of said operational amplifier to a diode which controls energization of a relay having contacts,
• adjusting said voltage to an operator-selectable value to bias said diode to a condition to prevent energization of said relay until said energy signal reaches a value to counteract said adjusted voltage and bias said diode to a condition to energize said relay and operate relay contacts, and
• utilizing operation of said relay contacts to energize an electrical circuit which includes means for initiating the start of upset operation of said platens.

In a flash welder having relatively movable platens which carry the workpieces to be welded, said platens moving relatively through flashing and upset operations toward closed position, the improved method of initiating the start of upset operation of said platens at an operator-selectable value of flashing electrical energy, comprising:

• feeding an energy signal of negative polarity to the inverting input of a first operational amplifier, said energy signal derived from voltage and current input to said welder during flashing operation and progressively increasing as said platens move toward closed position,
• feeding a voltage of negative polarity to the noninverting input of said first operational amplifier,
• feeding the output signal from said first operational amplifier to a diode which controls energization of a relay having contacts,
• adjusting said voltage to an operator-selectable value to reverse bias said diode and prevent energization of said relay until said energy signal increases to exceed the value of the adjusted voltage and thereby forward bias said diode and energize said relay and operate the contacts of the latter,
• feeding a signal of positive polarity to the inverting input of a second operational amplifier, the output of the latter being connected to a second diode which is reverse biased by this signal, and
• utilizing the operation of said relay contacts to remove the positive polarity signal from said inverting input of said second operational amplifier and replace it with a signal of negative polarity to thereby forward bias said second diode and energize a circuit which includes means for initiating the start of upset operation of said platens.

In a flash welder having relatively movable platens which carry the work pieces to be welded, said platens moving relatively through flashing and upset operations toward closed position, the improved method of initiating the start of upset operation of said platens at an operator-selectable value of flashing electrical energy, comprising:

• applying a first voltage of negative polarity to the inverting input of an operational amplifier and increasing said first voltage in a negative direction as flashing progresses,
• applying a second voltage derived from a negative source to the noninverting input of said operational amplifier, said second voltage being operator-adjustable to a magnitude corresponding to the magnitude of said first voltage at any selected point in the movement of said platens toward closed position,
• applying the output of said operational amplifier to a diode which controls energization of a relay having contacts,
• wherein when said second voltage exceeds the magnitude of said first voltage, the output of said operational amplifier is of negative polarity to reverse bias said diode and prevent energization of said relay, and when said first voltage exceeds the magnitude of said second voltage, the output of said operational amplifier is of a positive polarity to forward bias said diode and effect energization of said relay and actuation of said relay contacts,
• applying a third voltage to the inverting input of a second operational amplifier,
• applying the output of said second operational amplifier to a second diode which is adapted to control conduction of a silicon-controlled rectifier, the latter controlling initiation of the start of upset motion, said third voltage being of positive polarity so that the output of said second operational amplifier reverse biases said second diode and prevents conduction of said silicon-controlled rectifier, and
• utilizing the actuation of said relay contacts to replace said third voltage with a fourth voltage applied from a source of negative polarity to said inverting input of said second operational amplifier whereby the output of said second operational amplifier forward biases said second diode to trigger said silicon-controlled rectifier into conduction and effect initiation of the start of upset motion of said platens.

In a flash welder having relatively movable platens which carry the work pieces to be welded, said platens moving relatively through flashing and upset operations toward closed position, an improved control circuit for initiating the start of upset operations of said platens at an operator-selectable value of flashing electrical energy, comprising:

• an energy monitor connected to said flash welder and providing an output signal which is derived from voltage and current input to said welder,
• an operational amplifier, having one input connected to said energy monitor output signal,
• a source of voltage independent of the voltage of said energy monitor,
• a potentiometer connected to said source so that the voltage therefrom is applied across the resistance of the potentiometer, the slider of the potentiometer being movable along said resistance to vary the voltage of said source to a magnitude selected by said operator, the variable voltage from said slider being connected to the other input of said operational amplifier, and
• means effected by the output of said operational amplifier to control initiation of the start of upset operation.

In a flash welder having fixed and moveable platens which carry the workpieces to be welded, said moveable platen being moveable toward closed position with respect to said fixed platen through flashing and upset operations, the improved method of controlling the amount of upset motion of said moveable platen to a machine operator selectable amount, comprising,

• applying a voltage from a first source across the resistance of a first potentiometer,
• moving the slider of said first potentiometer in unison with movement of said moveable platen so that the voltage on said slider varies in decreasing manner as the moveable platen moves toward closed position,
• feeding the variable voltage on said slider to a sample-hold conversion unit and feeding the output of said unit to one terminal of a summing junction,
• applying a voltage from a second source across the resistance of a second potentiometer, the slider of which is moveable by the machine operator so that voltage on said slider has an adjusted value in selected proportion to the amount of desired platen movement,
• feeding the adjusted voltage on said slider of said second potentiometer to the other terminal of said summing junction so that the output of the latter is the algebraic sum of said variable voltage and said adjusted voltage,
• interrupting conversion of said sample-hold unit at the time of initiation of upset motion of said moveable platen to fix the voltage at the output of said conversion unit to the value at the initiation of upset motion,
• feeding the voltage so fixed to one input of an operational amplifier, also feeding said variable voltage on the slider of said first potentiometer to the other input of said operational amplifier, the latter comparing the two voltages fed to its two inputs and causing its output to actuate controls for interruption of upset motion of said moveable platen when said two voltages reach a predetermined relative value.

In a flash welder having fixed and moveable platens which carry the workpieces to be welded, said moveable platen being moveable toward closed position with respect to said fixed platen through flashing and upset operations, the improved method of controlling the amount of upset motion of said moveable platen to a machine operator selectable amount, comprising,

• applying a voltage of positive polarity across the resistance of a first potentiometer,
• moving the slider of said first potentiometer in unison with movement of said moveable platen so that the voltage on said slider varies in positive polarity in a decreasing manner as the moveable platen moves toward closed position,
• feeding the variable voltage on said slider to a sample-hold conversion unit and feeding the output of said unit to one terminal of a summing junction,
• applying a voltage of negative polarity across the resistance of a second potentiometer, the slider of which is moveable by the machine operator so that the negative voltage on said slider has an adjusted numerical value in proportion to the amount of desired platen movement,
• feeding the adjusted voltage on said slider of said second potentiometer to the other terminal of said summing junction so that the output of the latter is the algebraic sum of the output of said conversion unit and said adjusted voltage,
• interrupting conversion of said sample-hold unit at the time of initiation of upset movement of said moveable platen to fix the output of said unit to said summing junction to the value established at the initiation of upset motion, and thereby fix the algebraic sum of the output of said conversion unit and the machine-operator-adjusted voltage from said second potentiometer to a predetermined value,
• feeding the algebraic sum so fixed to the noninverting input of an operational amplifier,
• also feeding said variable positive voltage on said slider of said first potentiometer to the inverting input of said amplifier,
• feeding the output of said amplifier to the input of a diode which is adapted to energize a relay when said diode is forward biased, said diode remaining reverse biased until said variable voltage applied to the inverting input of said amplifier becomes less than said fixed algebraic sum, whereupon said diode is forward biased to energize said relay and effect operation of a circuit to interrupt upset motion of said moveable platen.

In a flash welder having fixed and moveable platens which carry the workpieces to be welded, said moveable platen being moveable toward closed position with respect to said fixed platen through flashing and upset operations, an improved circuit for controlling the amount of upset motion of said moveable platen to a machine operator selectable amount, comprising,

• a first potentiometer having a voltage of positive polarity applied across its resistance, said potentiometer having a slider which is moveable in unison with movement of said moveable platen to vary said voltage in a progressively decreasing positive polarity as said moveable platen moves toward closed position,
• a meter having a binary coded decimal output and a print command signal, said output and said signal being electrically connected to the input of a digital to analog converter, the input of said meter being connected to receive the variable voltage signal from the slider of said first potentiometer, and the analog output of said converter tracking said variable signal,
• a summing junction having one of its inputs connected to said analog converter to receive its analog output,
• a second potentiometer having a voltage of negative polarity applied across its resistance, and having a slider connected to the other input of said summing junction, said slider being adjustable by the operator of the welding machine to a selected position along the resistance of said second potentiometer to provide a variable voltage signal,
• said summing junction having an output representing the algebraic difference between said analog output and the variable voltage signal from the slider of said second potentiometer,
• an operational amplifier, having a noninverting input receiving the output of said summing junction and an inverting input receiving the variable voltage signal from the slider of said first potentiometer, said amplifier also having an output,
• a diode having its input connected to receive the output of said amplifier, and having an output,
• a relay coil connected to the output of said diode and energized when said diode is forward biased,
• and a switch adapted to be operated at the time of initiation of the start of upset motion of said moveable platen to prevent further conversion of said digital analog converter and to clamp the output thereof at the value it had at the start of upset motion, whereby
• when the voltage on the slider of said first potentiometer decreases to a value less than the output of said summing junction, the output of said operational amplifier will forward bias said diode and energize said relay coil, and
• contacts affected by energization of said relay coil to halt movement of said moveable platen toward closed position, thereby to control upset movement of said moveable platen in accordance with the setting of the slider of said second potentiometer.

In a flash welder having fixed and moveable platens which carry the workpieces to be welded, said moveable platen being moveable toward closed position with respect to said fixed platen through flashing and upset operations, the improved method of providing a reading of the magnitude of upset motion, comprising,

• applying a voltage across the resistance of a potentiometer,
• moving the slider of said potentiometer in unison with movement of said moveable platen so that voltage on said slider varies in a progressive manner as the moveable platen moves toward closed position,
• feeding the variable voltage on said slider to the input of a sample-hold conversion unit and also to the inverting input of an operational amplifier,
• feeding the output of said conversion unit to one terminal of a summing junction,
• feeding the output of said amplifier to the other input of said summing junction, the output of said summing junction representing the algebraic difference between the output of said conversion unit and the voltage signal from the slider of said potentiometer,
• feeding the output of said summing junction to a voltage meter having a digital readout,
• the voltage signal from said conversion unit tracking and being equal to and of the same polarity with respect to the voltage signal from the slider of said first potentiometer during conversion operation of said sample-hold unit, whereby the output of said summing junction and the input to said meter are zero,
• interrupting conversion of said conversion unit at the time of initiation of upset movement of said moveable platen to clamp the output of said unit and to said summing junction to a value established at the initiation of upset motion, while the voltage signal from the slider of said potentiometer continued to progressively vary so that the output of said summing junction represents a progressively varying algebraic difference between the clamped output and the progressively varying voltage to effect progressive readout on said meter, and
• interrupting upset movement of said moveable platen at a predetermined time to thereby clamp the voltage from the slider of said potentiometer and halt further input to said meter.

In a flash welder having fixed and moveable platens which carry the workpieces to be welded, said moveable platen being moveable toward closed position with respect to said fixed platen through flashing and upset operations, the improvement for providing a readout of the magnitude of upset motion of said movable platen, comprising,

• a potentiometer having a voltage applied across its resistance, the slider of said potentiometer being moveable in unison with movement of said moveable platen to vary voltage on the slider in a progressive manner as said moveable platen moves toward closed position,
• a sample-hold conversion unit and an operational amplifier, and means connecting the voltage from said slider to the input of said sample-hold unit and to the inverting input of said amplifier,
• a summing junction, and means connecting the output of said sample-hold unit to one terminal of said summing junction and the output of said amplifier to the other terminal of said summing junction, the latter having an output representing the algebraic difference between the output of said sample-hold unit and the voltage from the slider of said potentiometer,
• a voltage meter having a digital readout, and means feeding said output of said summing junction to said meter, the output voltage of said sample-hold unit tracking but being of opposite polarity than the voltage from said slider of said potentiometer, whereby the output of said summing junction and the input to said meter are zero,
• means interrupting conversion of said sample-hold unit at the time of initiation of upset movement of said movable platen to clamp the output of said unit and to said summing junction at a value established at the initiation of upset motion, while the voltage from the slider of said potentiometer varies, so that the output of said summing junction progressively varies to effect a progressively varying reading on said meter,
• and means interrupting upset movement of said movable platen at a predetermined time to thereby clamp the voltage from said slider of said potentiometer and thereby halt further input to said meter.

In a flash welder having relatively movable platens which carry the workpieces to be welded, said platens moving relatively through flashing and upset operations toward closed position, the improved method of initiating the start of upset operation of said platens and thereafter controlling the amount of upset motion thereof to a machine operator selectable amount, comprising,

• adjusting the magnitude of a voltage from a first voltage source to an operator-selectable value to block operation of a switch-controlling device until an energy signal representing electrical energy input to said welder during flashing operation has reached a value to counteract said adjusted voltage and effect operation of said switch-controlling device,
• utilizing the operation of said switch-controlling device to energize a circuit which includes means for initiating the start of upset operation of said platens,
• applying a voltage from a second source across the resistance of a first potentiometer,
• moving the slider of said first potentiometer in unison with movement of said movable platen so that the voltage on said slider varies in decreasing manner as the movable platen moves toward closed position,
• feeding the variable voltage on said slider to a sample-hold conversion unit and feeding the output of said unit to one terminal of a summing junction,
• applying a voltage from a third source across the resistance of a second potentiometer, the slider of which is movable by the machine operator so that voltage on said slider has an adjusted value in selected proportion to the amount of desired platen movement,
• feeding the adjusted voltage on said slider of said second potentiometer to the other terminal of said summing junction so that the output of the latter is the algebraic sum of said variable voltage and said adjusted voltage,
• interrupting conversion of said sample-hold unit at the time of initiation of upset motion of said movable platen to fix the voltage at the output of said conversion unit to the value at the initiation of upset motion,
• feeding the voltage so fixed to one input of an operational amplifier, also feeding said variable voltage on the slider of said first potentiometer to the other input of said operational amplifier, the latter comparing the two voltages fed to its two inputs and causing its output to actuate controls for interruption of upset motion of said movable platen when said two voltages reach a predetermined relative value.