Ultrasonic dishwasher

Claim 2

In combination with a load device, apparatus for producing ultrasonic vibrations in said load device at continuously varying frequencies, comprising a plurality of transducers coupled to said load device, said transducers being in parallel electrical connection and operative to convert electrical energy to mechanical vibrations, an output transformer having a secondary winding connected to said transducers and a primary winding adapted for energization, a first pair of switching elements connected to said primary winding for controlling current flow therein, a second pair of switching elements operatively connected in parallel with said first pair of switching elements, a saturable core transformer operatively connected with said switching elements for alternate energization thereof, the primary winding of said saturable core transformer being operatively connected with the primary winding of said output transformer, the frequency of alternation being dependent upon the magnitude of voltage applied to said switching elements, means for supplying DC voltage to said switching elements for energizing same at a nominal frequency of alternation, and means for effecting cyclical variations in the DC voltage to cause variations in the frequency of alternations.

Claim 3

The combination set forth in claim 1 wherein said switching elements comprise transistors having collector electrodes connected to the primary winding of said transformer and adapted for energization from said saturable core transformer.

Claim 4

An ultrasonic dishwasher, comprising a housing forming an enclosure for receipt of dishware and the like and a fluid medium, a plurality of piezoelectric transducers mounted on the exterior of said housing for generating ultrasonic vibrations in the fluid medium contained therein, an inverter circuit for energizing said transducers, said circuit having a nominal frequency of operation in the ultrasonic frequency range and comprising an output transformer having a secondary winding connected to said transducers, a first pair of transistors having collector electrodes connected to the primary winding of said transformer, a second pair of transistors operatively connected in parallel with said first pair of transistors for energizing the primary winding of said transformer, and a saturable core transformer having a primary winding operatively connected to said collector electrodes and a secondary winding operatively connected in the base-emitter paths of said transistors, and means for energizing said inverter circuit with a DC voltage having a high ripple voltage, comprising an AC power source, a rectifier, and filter capacitor combination, said filter capacitor having a capacitance value to provide approximately 10 percent ripple voltage, whereby said transducers will provide ultrasonic vibrations in the fluid medium at frequencies continually varying about such nominal frequency.

Claim 5

An ultrasonic dishwasher, comprising a housing forming an enclosure for receipt of dishware and the like and a fluid medium, a plurality of piezoelectric transducers mounted on the exterior of said housing for generating ultrasonic vibrations in the fluid medium contained therein, an inverter circuit for energizing said transducers, said circuit having a nominal frequency of operation in the ultrasonic frequency range and comprising an output transformer having a secondary winding connected to said transducers, a first pair of transistors having collector electrodes connected to the primary winding of said transformer, a second pair of transistors operatively connected in parallel with said first pair of transistors for energizing the primary winding of said transformer, and a saturable core transformer having a primary winding operatively connected to said collector electrodes and a secondary winding operatively connected in the base-emitter paths of said transistors, and means for energizing said inverter circuit with a DC voltage having a high ripple voltage, comprising an AC power source, a rectifier, and filter capacitor combination, said filter capacitor having a capacitance value to provide approximately 10 percent ripple voltage, whereby said transducers will provide ultrasonic vibrations in the fluid medium at frequencies continually varying about such nominal frequency.

Claim 6

A dishwasher as set forth in claim 3 wherein said rectifier is a bridge rectifier, said power source is 60 cycle alternating current and the frequency of the ripple voltage is 120 cycles per second.