Design & Manufacturing Corporation

Roper Corporation

Karmen D Cox

Paul R Scheuer

Steven B Sample

An induction heating apparatus which includes an induction coil with an associated load and a resonant inverter circuit coupled to a DC power supply for energizing the heating coil. The inverter circuit includes a gate controlled thyristor which is cyclically gated to produce a conductive first period followed by an nonconductive second period in order to energize the heating coil. A diode of opposite polarity to the gate controlled thyristor is coupled in parallel therewith and has an impedance connected in series. The voltage across this series impedance is coupled to the gate of the gate controlled thyristor. The inverter circuit additionally includes an improper load check circuit for disabling the gating of the thyristor in the event of an improper load coupled to the heating coil, and a gate triggered timing generator for adjusting the timing of production of thyristor gate pulses to maintain substantially constant power to proper heating coil loads.

Induction heating apparatus

A cycle-select switching system for automatic appliances and the like of the type for selectively performing any one of a plurality of distinct operating cycles. The switching system comprises selection means having a plurality of outputs, each corresponding to one of the operating cycles, and a momentary contact switch for producing a control signal of variable time duration. The selection means is responsive to the control signal by sequentially advancing to the output defined by a selected time duration of the control signal and thereby initiating the operating cycle corresponding thereto.

Electronic cycle-select switching system

A circuit for the automatic starting of an induction motor of the type having a sensing means for producing a signal proportional to the main winding current and control means for allowing current flow through a start winding only when energized by a start winding control signal. The starting circuit includes means for continuously producing a variable threshold level which is proportional to a condition capable of affecting the current level in the main winding and which defines an adjustable threshold switching level. A comparison means continuously compares the adjustable threshold switching level to the signal proportional to the main winding current and, whenever the latter signal exceeds the former, the comparison means generates a start winding control signal which activates the start winding control means thereby establishing current flow through the start winding. When the main winding current decreases to a sufficient extent, the comparison means is characterized by the absence of a start winding control signal whereby the start winding control means will block the flow of current through the start winding.

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Lafayette, IN, United States of America

Karmen D Cox