Carbide deposition structure and method

Claim 2

Structure as set forth in claim 1 wherein the low voltage, low frequency electric signal means comprises an oscillator including a pair of silicon controlled rectifiers driven by a unijunction transistor.

Claim 3

Structure as set forth in claim 1 wherein the high voltage, high frequency electric signal generating means is a direct current to alternating current square wave inverter.

Claim 4

Structure as set forth in claim 1 and further including means connected across the gap between the electrode and workpiece for isolating the switching means, and low voltage, low frequency electric signal generating means from the high voltage, high frequency electric signal generating means.

Claim 5

Structure as set forth in claim 1 wherein the workpiece is steel, and the positive terminal of the source of electric energy is connected to the electrode, and the negative terminal is connected to the workpiece.

Claim 7

The method as set forth in claim 7 and further including protecting the switching means and low voltage, low frequency electric signal generating means from the signals of the high voltage, high frequency electric signal generating means.

Claim 8

Apparatus for hardening a conducting workpiece by the deposition of carbide thereon comprising a carbide electrode, means for supporting said carbide electrode in spaced relation to the workpiece to be hardened, a source of electrical energy and switch means connected in series with each other and connected across the means for supporting said electrode and the workpiece, said source of electrical energy being sufficient to sustain an arc across said electrode carried by the means for supporting said electrode and the workpiece after the arc has been initiated therebetween, a low voltage, low frequency source of electrical energy connected to the switch means for opening and closing the switch means to provide spaced welding pulses and a high voltage, high frequency source of electrical energy connection means for connecting said high frequency source of energy across the means for supporting said electrode and the workpiece for providing a continuous high voltage, high frequency signal thereacross for initiating an arc between said electrode carried by the means for supporting an electrode and the workpiece on closing of the switch means.

Claim 9

Apparatus for hardening a steel workpiece by the deposition of carbide thereon comprising a carbide electrode, a variac source of variable voltage alternating electric energy, a full wave rectifier connected to the variac for rectifying the alternating output voltage thereof, an inductance capacitance filter circuit connected to the rectifier circuit for filtering the rectified output signal of the rectifier to provide direct current electrical energy sufficient to maintain an arc between said carbide electrode and a steel workpiece maintained in predetermined spaced apart relation after the arc has been established but insufficient to establish the arc, a switch, variable resistance means and the principal electrodes of a silicon controlled rectifier having two principal electrodes and a control electrode connected in series with the direct current electrical energy, the electrode and workpiece, a source of low frequency, low voltage oscillations connected between the control electrode and one of the principal electrodes of the silicon controlled rectifier for turning the silicon controlled recTifier on and off at the low frequency to provide spaced welding pulses, a high voltage, high frequency oscillator, connection means for connecting said oscillator across said carbide electrode and workpiece for continuously providing a high voltage, high frequency signal between the electrode and workpiece insufficient to maintain an arc therebetween but sufficient to initiate an arc on turning on of the silicon controlled rectifier to connect the source of direct current electric energy across the electrode and workpiece, a diode and resistor in parallel connected between the high voltage, high frequency oscillator and said carbide electrode and workpiece for isolating the high frequency, high voltage oscillator from the direct current electrical energy, and resistance and diode means connected in parallel between the silicon controlled rectifier and said carbide electrode and workpiece for isolating the silicon controlled rectifier and low frequency, low voltage oscillation source from the high voltage, high frequency oscillator whereby on occurrence of a low frequency, low voltage electrical signal the direct current electrical energy is applied across said carbide electrode and steel workpiece and an arc is initiated between said carbide electrode and workpiece by the high frequency, high voltage source of electrical energy, which arc is maintained by the direct current electrical energy until the silicon controlled rectifier is subsequently turned off to deposit a carbide nodule on the surface of the steel workpiece.

Claim 10

Structure as set forth in claim 10 wherein the source of low frequency, low voltage oscillations includes a separate source of direct current electrical energy, means for regulating the electrical energy from the separate direct current source, a unijunction transistor circuit connected to the power supply for providing an output pulse at a predetermined frequency and a first and second silicon controlled rectifier connected in a multivibrator circuit to receive the output pulses of the unijunction transistor circuit for producing output square wave electric signals in accordance with the frequency of the output pulses from the unijunction transistor and means for applying the output signals from the multivibrator across the control electrode and the one principal electrode of the silicon controlled rectifier at different turn-on and turn-off power levels including a parallel resistor and diode in the output circuit of the multivibrator.

Claim 11

Structure as set forth in claim 11 wherein the high voltage, high frequency oscillator comprises a pair of transistors having emitter, base and collector electrodes, a transformer having a secondary winding in series with the electrode and workpiece and a secondary winding, a voltage divider network connected across the secondary winding of the transformer, a first capacitor one side of which is connected centrally of the secondary winding of the transformer and the other side of which is connected centrally of the voltage divider network, the bases of the transistors being connected to the voltage divider between the capacitor and opposite ends of the voltage divider network, a separate capacitor connected between the base of the transistors and the respective ends of the voltage divider network, a separate diode connected between the base and emitter of each of the transistors, a pair of zener diodes connected in series with opposite polarities between the emitters of the transistors, and an alternating current power supply connected across the first capacitor.