US 3403245 A
Description (OCR text may contain errors)
p 24, 68 T. EATON I 3,403,245
ULTRASONIC CLEANER CONTROLS Filed Aug. 15, 1966 5 2a 220 2 13 POWER 4 SUPPLY OSCILLATOR INVENTOR. THO/I44 5 EA ro/v ATTORNEY United States Patent 3,403,245 ULTRASONIC CLEANER CONTROLS Thomas Eaton, Hawthorne, Calif., assignor to Vernitron Corporation, Farmingdale, N.Y. Filed Aug. 15, 1966, Ser. No. 572,380 2 Claims. (Cl. 219494) This invention is concerned with ultrasonic cleaners and more particularly with a control system for operating an ultrasonic cleaner, and more specifically with a control system for minimizing the power requirements of an ultrasonic cleaner.
In general an ultrasonic cleaner is comprised of a tank having a suitable solvent liquid and a transducer secured to the tank for converting high frequency electrical oscillations produced by an electrical generator into mechanical vibrations which are propagated through the liquid to form alternate regions of compression and rarefaction. In the rarefaction region a negative pressure exists to create cavitation bubbles, the walls of which are then forced inward by the compression regions. Thus when the bubbles collapse, extremely powerful shock waves occur which impinge on any solid surface present in the liquid and very effectively scour and cleanse the surface. The effect is similar to mechanical scrubbing but acts much more efiiciently, rapidly penetrating to every hole, crevice, and corner of an assembly immersed in the liquid. This type of ultrasonic cleaner normally operates in a frequency spectrum ranging from 50 to 75 kilocycles and is extremely effective in removing dirt, oil, grease, etc., from articles immersed in the fluid. Recent developments, however, including the vast increased power density capabilities of transducers, have permitted ultrasonic cleaners to operate as sterilizers to kill bacteria and micro organisms by operating at frequencies of several hundred kilocycles, whereby cavitation may only be induced by providing heat to the solvent liquid. Thus in an ultrasonic cleaner utilized as a sterilizer, electric heaters raise the temperature of the solvent liquid to elevated temperatures, where cavitation is most efficiently produced. Unfortunately, the increased power for driving the transducer, and the power required for heating the solvent liquid, have necessitated special wiring for operating this type of ultrasonic cleaner in hospitals and other facilities and it would be extremely desirable if this requirement could be eliminated.
In accordance with the invention, a switch control permits rapid heating of the solvent liquid in an ultrasonic cleaner, and upon approaching a liquid temperature where cavitation will be most eificiently produced, a portion of the power used for heating is diverted by the switch control to drive an electronic generator which produces electronic pulses for transmission to a transducer and thereby permit initiation of the cleaning process. This power sharing by the switch control substantially reduces the overall power requirements of the ultrasonic cleaner, thereby eliminating any need for special wiring.
Accordingly, one object of the invention is in the provision of a control switching means for providing power sharing operation of the heaters and the transducer of an ultrasonic cleaner.
Another object of the invention is in the provisions of a control switching means which minimizes the power required to operate an ultrasonic cleaner.
Still another object of the invention is to provide -a control switching means which functions as a safety device to prevent exposure of personnel to any detrimental effects of ultrasonic waves.
()ther objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with 3,403,245 Patented Sept. 24, 1968 the accompanying drawing. The features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.
FIGURE 1 is a front elevational schematic view of an ultrasonic cleaner embodying the invention.
Referring now to the drawing, wherein like reference characters designate like or corresponding parts throughout, there is shown in FIGURE 1 an ultrasonic cleaner generally designated as reference numeral 12 for sterilizing and killing bacteria on articles immersed therein. Cleaner 12 is comprised of a tank 13 to which is mounted a transducer 14 powered by an electrical generator or oscillator 15 whose input power is obtained from a power supply 16 via a switch control generally designated as reference numeral 17. The oscillator 15 is tuned to produce high frequency electrical oscillations in the multihundred kilocycle range. Switch control 17, in addition to transmitting the power to oscillator 15 also provides the power to energize a first and second heating coil 18 and 19 and thereby raise the temperature of a solvent fluid 20 in a manner now to be described.
As shown in FIGURE 1, the switch control 17 is comprised of two thermostatic switches 22 and 23, which are respectively coupled via leads 24 and 25 from terminals 22a and 23a to the heating coils 18 and 19. A second terminal 23b, from thermostat 23, is coupled via lead 26 to the electric oscillator 15. As illustrated in FIG- URE 1, thermostatic switches 22 and 23 are conventional bimetallic switches which are connected to their respective a terminals below their respective operating temperatures. Thus, for example, in the embodiment illustrated in FIGURE 1, switch 23 is coupled to terminal 23a below F. and then coupled to terminal 23b for any increasing temperature. On the other hand, switch 22 is coupled to terminal 22a at temperatures below F., and is opened for all temperatures above this value. Although a bimetallic thermostat has been illustrated in FIGURE 1, other heat sensitive switches, e.g., thermistor switches, may be used.
In operation, the articles to be sterilized are placed via access door 31 in the tank 13 which is filled with the solvent liquid 20 to an operating level indicated by an arrow 27. A power switch 30 is closed whereby AC. power flows through leads 28 and 29 from the power supply 16 to thermostatic switches 22 and 23 respectively. Since the solvent liquid 20 is well below the respective operating temperatures of switches 22 and 23 they are coupled to their respective terminals 22a and 23a whereby power is supplied to the heaters 18 and 19. When the solvent liquid temperature is elevated to approximately 170 F. the thermostatic switch 23 decouples from terminal 23a and couples to terminal 2312 thereby providing power via lead 26 to oscillator 15 which generates pulses to transducer 14 for producing ultrasonic waves. After the solvent liquid temperature reaches approximately 190 F. thermostatic switch 22 decouples from terminal 22a thereby terminating heat input to the solvent liquid. As conventional in the switching art, if the liquid temperature drops below 190 F. thermostatic switch 22 will again couple to terminal 22a to supply power to heat the liquid and thereby maintain the liquid at this most eflicient cavitation temperature. Thus by operating the transducer only at elevated liquid temperatures not only are the overall power requirements of the ultrasonic cleaner reduced but personnel cannot maintain physical contact with the solvent liquid at these temperatures and therefore this switch control acts as a safety device to prevent exposure to any harmful effects of ultrasonic waves. Moreover, since the oscillator 15 operates only within water temperatures ranging from 170 F. and 190 F., it may be tuned to a very fine degree.
It will now appear that I have provided a switching control that attains the several objects set forth above in a thoroughly practical and eflicient manner.
As other embodiments of the invention are possible and as changes may be made in the one disclosed without departing from the scope of the invention, it is to be understood that the foregoing should be interpreted as illustrative and not in a limiting sense.
1. Apparatus for controlling an ultrasonic cleaner comprising:
an AC. power supply,
a tank having a liquid solvent solution,
an ultrasonic transducer mounted to the tank,
heating means supported in said tank and immersed in said solution,
an electric generator for producing high frequency electrical oscillations coupled to said transducer,
and switch control means adapted to connect said power supply to said heating means and responsive to the temperature of said liquid solution to disconnect a portion of said heating means from said power supply and couple said power supply to said electric generator.
2. Apparatus in accordance with claim 1 wherein said heating means is comprised of two heating coils and said switching means is comprised of a first thermostat coupled to one of said heating coils and a second thermostat coupled to the second of said heating coils and wherein said second thermostat is responsive to one elevated temperature of said liquid solution to decouple said second heater from said power supply and couple said power supply to said electric generator and said first thermostat is responsive to another elevated temperature of said liquid solution to decouple said first heater from said power supply.
References Cited UNITED STATES PATENTS 2,368,869 2/1945 Osterheld 219-330 3,085,185 4/1963 Jacke et al. l34-l 3,318,578 5/1967 Branson 134-l BERNARD A. GILHEANY, Primary Examiner.
F. E. BELL, Assistant Examiner.