US2828231A

US2828231A - Method and apparatus for ultrasonic cleansing

Info

Publication number: US2828231A
Application number: US420017A
Authority: US
Inventors: George E Henry
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1954-03-31
Filing date: 1954-03-31
Publication date: 1958-03-25
Anticipated expiration: 1975-03-25

Description

March 25,1958 Y G. E. HENRY METHOD AND APPARATUS FOR ULTRASONIC CLEANSING 2 Sheets-Sheet 1 Filed March 31, 1954 ULTRASONIC CLEANSER RECOVERY PROCESSING STATION 7 7 STATION 1 --5 Inventori George E. Henry, V by 22px;: 2) Wu- His Attorney- March 25, 1958 G. HENRY 2,828,231

METHOD AND APPARATUS FOR ULTRASONIC CLEANSING Filed March 31, 1954 2 Sheets-Sheet 2 Inventor": George E. Henry His Attorney.

United st fi P efi METHQD AND APPARATUS'FOR ULTRASONIC CLEANSING- Y G r e Hex y, c dy,IN -..Y,-, as i n fi a Electric Company, a corporation of New York 7 Application March 31, 1954, Serial No. 420,017

, Claims. (01. 134-4 This invention relates to the cleansing of objects, and;

more particularly to an" improved method, and apparatus,

ing mechanism. 1 I

The primary object of the present invention is to provide an improved method and apparatus for cleansing objects, wherein ultrasonic compressional waves are which utilize ultrasonic compressional Waves as a cleansy utilized as a cleansing agent, and :which perform thesubjecting the object to be cleansed to ultrasonic corn- 3 pressional waves, While the object is immersed in a liquid which has dissolved gas maintained therein, and whose temperature may also be controlled. The liquid in which the object, or at least that part of the object which'it is desired to cleanse, is immersed, may be a solvent to aid 1 in the cleansing'process, or'it may be any liquid suitable for the cleansing'prooess and for the transmission therethrough' ofyultrasonic compressional waves. However,

in eith er case, a substantial'amount of dissolved gas is maintained in the liquid.

"Apparatus-by means of whichthe method of the invention'conveniently maybe practiced, comprisesan outer containeiffor an ultrasonic transducer. The transducer may oe-energrzed byconventional generator means. to

prod'iie'ultrasonic compressional waves, which are trans; 50

or: objects to becleansed are immersed. Means miffed iri'tdaninner containerfor a liquid in which the ovided to maintain a substantial amount of dissolve g ashin the liquid, and means may also be provided: to {In ntain the temperature of the liquid within a certain range to'tend to'idecrease the amount of gas that isdriven oil the: liquid in'the cleansing process. Controlling the temperature offthe liquid may also be effective to obtain,

maximum cleansing action from the liquid itself.

- Fora better understanding of the invention, reference is made-to the following specification, taken in conjunction with the accompanying drawing, in which ,Ei gfl is. a vertical cross-sectional view of one form of apparatus. for carrying out the method of the inven-' tiony I EigiZ is a view similar to that of Fig. 1, showing another. form of the apparatus; and

Fig, 3 is 'a flow diagram useful in understanding the methodiof operation of the form of apparatus shown in Fig. 2. H a I v Fig.1 illustrates an apparatus constructed in accordance with the invention, which is particularly well.

" be used in the cleansing of large objects, or portions of large-objects. However, the size of the object cleansed must be such that at least "that part of the'objectwhichf it is desired to cleanse, may beimmersed in a liquid which has: ultrasonic;compressional waves transmitted there-, 'th'r'ough. f The apparatus illustrated in Fig; 1, which is adapted to'rest upon a bas e (not shown), comprises an outer container 10,;whichmay be conveniently constructed of; glasls,plastic, or other insulating material; The outeri container 10 contains a'transducer assembly, designated,

generally by the numeral 11, and is filled with a suitable dielectrici'fiuid 12, such'as oil, to a level above the transducer assembly'11; The transducer assembly i'nclud'es' a piezoelectric 'or electrostrictive element 13, and'fis" mounted with the piezoelectric element aligned with an opening 144 in thebottom surface of an inner container 14. a The transducer assembly may be energized by a conventional electronic generator (not shown) through, electrical connections, :which will be described hereafter,

to produce ultrasonic compressional waves and trans;

mit them upwardly into the inner container 14. v

The'inner container 14 may be constructed of any suitable conducting material, and is filled with an electro- It is necessary that the liquid in the inner container be an electrolyte because;

lytic liquid 15 such as water.

it must provide electrical contact with one face of the piezoelectric element 13 to completethe electrical cir cuit for energizing the element.

In the form of the invention shownin Fig. 1, it is do;

sired to immerse the part being cleansed in a solvent -16,.' in order toaid the cleansing action. Because the major-1 ity of desirable solvents are not good conductors of electricity, the solventv 16 and the object beingcleansed have been shown as being enclosed within a third. container 17 made of a metal such as stainless steel, aluminum, or nickel-plated brass. The container 17 is provided. with a bottom 18 that may be slanted somewhat to improve; its acoustic transmission (as, illustrated), and may be constructed of thin stainlesssteel, aluminum, or other material through which ultrasonic compressional waves, will easily pass. The ultrasonic compressional. waves. produced by the piezoelectric element 13 are transmittedupwardly through the liquid 15 and through. the bottom, 18 of the third container 17. Because such a beam of. ultrasonic waves normally will not be focused, a heavy metal reflector 20 may be placed inside the container 17 toreflect any ultrasonic waves striking it toward the object being cleansed i h It has been discovered that the ultrasonic cleansing process is greatly improved over that previously known if the condition of the liquid which is in contact with the object to be cleansed, in this case the solvent 16, is controlled in: certain ways so as to maintain a substantial amount of dissolved gas in the liquid. Various gases are suitable for this purpose, but, of course, the most easily obtainable is air. In the embodiment of the invention shown in Fig. 1, air is continuously bubbled through the liquid 16 from a supply pipe 21, to which it may be supplied from a conventional compressor or other means (not shown). It has been found that the quantity of gas that must be dissolved in the liquid 16, in order to obtain optimum cleansing, is not important so long as it tends to keep the liquid near saturation; and it is,

.r i duaa25.19 5,

waves, the liquid is alternately. rarefied and compressed b'ylthe waves. If, at apoint offlo-w pressure of rarefica-.-

tion, the pressure within the liquid. equals the. vapor pressure characteristic of the particular:temperaturenohthe liquid, this portion of .the liquid tends to boil. 1 When there are dissolved. gases in the liquid, they furnish nu- -clei from'which a vapor bubble can grow, andthus the tendency of the liquid to. boil during alternate. half-cycles of the ultrasonic wave is increased. This action, which has a beneficialleffect on the cleansing'process, tends to driveofithe gases in the liquid, and.thus reduce the likelihood'o'f formation of'vapor bubbles at pressurevaluesnear the value of the .vapor pressure It is to replace these driven-elf gases that air or .gasis continuouslybubbled through the liquid. Ithas been found that if a 'substantialamount of dissolved gas is main tained in the liquid, the cleansing. process is greatly. improved. a

I have'also discovered thatthe cleansing action is greatly improved if the liquid 16 is retained in a relatively cool state. The transmission. of ultrasonic compressional wavesof' high power through a liquid generally raises the temperature of that liquid, and permits the gas dissolved in the liquid to be, driven off more easily than-when theliquid is cool; As previously mentioned', thisiactio'n has a deleterious effect on the cleans-.

ing action of the apparatus. .The exact temperature of the liquid necessary to'obtain the most effective cleansing action varies from one applicationto another, but it has been discovered that the temperature generally should lie in the range from approximately 50 F. to 75 F.

In order to maintain the temperature. of the liquid'withinthis range, cooling 'coils22 are provided, in-thecontainer 17. In the present case, the coolingcoils22 are located on the inner'surfacesof the reflector 20, but their exact location within the container is relatively, unimportant so long as the. liquid16.ma"y be cooled"thereby.' A coolant may be supplied to the coils 22'from. any suitablesource, such as a conventional refrigerating mechanism or a cold water supply (not shown),.and the cooling system may beyclosedso that the' coolantmay ,be continuously. reused and'there'will be, no need to replenish the supply. i

If the liquidin' which. the object to .be :cleansed, is immersed is a solvent, itmay not benecessary to. provideseparate means for cooling the liquid,-.,but only. means to mam'taln a substantialjarnount of. gas. dissolved therein. Solvents are generally volatile, and, as,-.the solvent. evaporates, it tend'sto cool the remainder of the liquid; .Thus, the temperature ofthe liquid may, remain within the; optimum range of'5075 without cooling means being provided. It has also been found that certain solventsicleanse most effectively when they are maintained within certain temperature ranges. However, the rangevaries fromone solvent to another, and, must be determined for the particular solvent'b eing used.

.The transducer assembly 11 for generating the ultrasonic compressional waves comprises a supporting plate 23 made of a ceramic insulator such as that known commercially asMycalex, to which is attached-a'conductingflplate 24 which maybe :made of brass'or some other suitable 'metal. 'The. supporting plate 23 andconducting plate 241 aresecured togetherby a screw 25 thattalso serves as part of the electrical circuit of the apparatus aswill be-later described, Supported above the conducting plate 24, and in spaced relation-thereto is; the piezoelectric or..electrostrictive'element13, which may be--a-,..quartz. crystal, aslab. of barium titanate ceramic, orsother. suitableadevice. The.piezoelectricelement 13 is separated from the brass. conductingHplate 24 by a rubber or plastic ring 26, thatserves as a gasket, and

a"pad2'7 of time copper" wire is interposed betweenthc,

conducting plate 24 and the piezoelectric element 13 to provide good electrical contact with both these elements; The piezoelectric element 13 is also separated from the bottom surface of the inner container 14 by a second rubber or plastic 0 ring 28 which operates to prevent the dielectric fluid 12 from reaching the upper surface of the piezoelectric element l3i- The transducer assembly 11 is secured in: position withkthe piezoelectric element 13 aligned with the openinggl ia'in the bottom surface of the inner container by means of bolts 30, which extend through the--bottom surfaceoftheinnercontainer and through the supporting plate 23 By tightening'down 1 nuts 31.:ontheibolts-30, -the 0 rings 26' and- 28=may be compressed to maintain a seal between the electrolytic liquid 15 and the dielectric-'liquid 12; and also to maintain the transducer assembly securely mounted.

Electrical connections for the transducer assembly are made through studs v.32.- and 1a3, which extend...thr9flgh the bottom surface ofthe outercontai'ner .10, ;and may be provided with suitable .packing to prevent the escape of dielectric oil 12 from the container.

assembly to the inner container 14, and the other. leaf; spring .35 is in contact with the head of thescrew 25' that securesthesupporting plate 23 to the brass plate 24. Thus, it is seen that thepath of current flow between the

studs

33 and 32..includes leaf spring 35, screw, 25,

brass .plate24, copperwire pad 27,'piezoelectric'element: Y; 13, electrolytic liquid 15,..one of the bolts 30, and leaf spring 34.

...The.studs 32 and. 33 may be connected to theoutput the potential of. the stud. 32, it is normally desirable, to

have-the stud 32 connected tov the grounded side of the generator. Electronic generators which are suitable for this purpose are conventional and well-known in the art, and are available commercially from a number of sources. The particular frequency at which the piezoelectric ele mentoperates may vary for different applications, and, of course, the piezoelectric element must be selected, for the particular. operating frequency desired. However, it

has been found with the method, and apparatusv of thepresent, invention. that an "operating frequency, lying. bebetween..250.kc. and 1200 kc. isusually suitable.

Fig, 1.. illustratesthe cleansing. of a ballbearing 36, asan example of a typical-small-object which might convenientlybe. ,cleansediby. the method, and apparatus of the invention. ;The. bearing.36 is-Inountedpn an arbor 37, which mayv be. rotated-and .reciprocated; axially by, con-.

ventionahmeans (notishown). It.has-. been found, that a bearing vsuchas is..illustrated..mayhe quickly and, ef-

ficieutly cleansedof, grease, .dusty and 7 other particles by rotatingthe arbor-first inxone direction and then in the other, and, simultaneously reciprocating the arbor axially. The drag, ofjthe' liquid 16. on .the outer race of the bearing causes ..-relative movement.,between..theinnerand outer...races,,which is. desirable inItheEcIeansing, process.

Ina ddiition, it..has beeniound-that avery. beneficial, 1'e-- sult may beobtained it :the .ohjectbeing cleansed is moved upandsdown through. the agitatedfree, surface of..;the liquids. ,tsimultancously, of course,. the bearing is subjected to high power ultrasonic compressional waves thrpugh, Ithe:,liquid; .16, whose physical characteristics are controlled in the manner previously described. It has been .foundthatthe cleansing'power of the agitated liquid islfar greater, at or, near thesurface andthat by, moving the article repeatedly through said surface this increased cleansing action isapplied over the surface, of, the article with the result" of greatly increased rapidity of the cleansing peration.

The. .studs, and..33., have .a. pair of .small. leaf springs .34 -.and. 35',

Fig". 2; illustrates a modification of the apparatus of the thanbeing immersed in a liquid a separated container.

This form of the invention, which is generallysimilar" tor-that previously described with reference to Fig. 1,.

comprises the outer container :10, 'which is filled 'with a dielectricliquid 12 to a level' above the transducer assembly 11. The transducer assembly 11 is like that previously described,'bu t' the means by. which it is, secured 1 to the'bottom surfaceof the inner container 14 is -some--' what different from that previously described; In this case, such means" comprise a plurality of bolts 42, which are reversed in position from the bolts shown in Fig. 1. Each bolt 42' is surrounded by a coil spring 43, which bears against theflower surface of the supporting plate .23 and:

against the head 42a of each bolt. In,,this mannerythe transducer assembly maybe firmly pressed against the bottom of the inner container 14, and, if the O rings"2 6. and lose their resiliency with age,'the springs will continue to cause pressure to be exerted on them in order to maintain a liquid-tight seal between the inner and outer.

containers. The remainder of the transducer assembly 11'is like that previously described.

The electrical connections to the-transducer assembly are similar to those described in connection with Fig. 1, except that the

springs

34 and 35 of Fig. 1 are replaced by springs 45and 46, secured to the

studs

32 and 33, respectively. The small spring 45 contacts the head of onezfof the bolts 42, and the largespring 46 contacts the head ofuthe screw 25, that secures the conductingplate 24510 the supporting plate 23. If the liquid 15 in which the objefcts tobe cleansed are immersed is a conductor of electricity, since it is in contact with the upper surface of lthe piezoelectric element 13, it-may provide a part of the electrical circuit. In this case, the current path between the

studs

33 and 32 is similar to that described in connectionwith the arrangement shown in Fig. 1,; and; includes spring 46,"screw 25, conducting plate 24, wire pad27;pieioelectricelement 13, liquid 15, bolt 42, and spring 45. Thus, it is apparent that the production of ultrasonic compressional waves by the transducer assembl}:1 121 is the same in the apparatus shown in Figs. 1 an Alternatively, if the liquid 15 is not a good conductor of electricity, electrical contact to the upper surface of the piezoelectric element 13 may be made through the O ring 28. In this case, the O ring must be made of a conductive material, or, if made of a non-conductive material, it may be wrapped with a conducting metal foil. Of course, the top surface of the piezoelectric element 13 must be well silvered if the electrical contact with the surface is limited to a peripheral area.

The form of apparatus shown in Fig. 2 may be preferred for permanent or semi-permanent installations, in which the cleansing process is one of a sequence of operations and the cleansing apparatus will be in more-orless continuous use. In this case, the liquid 15 in which the parts to be cleansed are immersed may be continuously circulated through the container 14. An inlet pipe 47 provides means for admitting fresh liquid, which has been properly cooled and provided with dissolved gas or air, and an outlet pipe 48, which may be located near the top of container 14 to act as an overflow pipe, conducts used or exhausted liquid away from the tank to a reprocessing station.

Fig. 3 shows in diagrammatic form a typical installation for reprocessing the liquid 15 on a continuous basis. This assembly comprises the ultrasonic cleanser described with reference to Fig. 2, which is designated by the numeral 50, a recovery station 51, and a processing tion equipment such as isavailable commer'cially from several sources.

serve as overflow ,E'dischargeumeans, but both-the inlet pipe 47 and the outlet pipe 48 may-belo'cated at thebottom of the inner container, 17 of, the ;ultrasonic, cleanser. In this case, it maybedesirable to completely;

change the liquid 15 periodically as the 1needs1ofqthe particular processfmay.dictate;j If. the apparatus op-;;v

erates in this fashion, the-purifying and reprocessing functions would be performed periodically rather than continuously, as wouldbe the casewere the device constructed exactly as shown ingFig.'-2-.-

In thecleansing system shown and described with reference to Figs. 2 and 3, the basket .41 containing the v small parts 40 may be either held stationary in the liquid: 23,-..or may be moved about by conventionalmeans (not: shown), if desired. For example, it may be found that when cleansing parts of certain ,shapes" and sizes, .itis desirable to provide the basket; with certain types of beefiiciently accomplished even, though not moved during the operation. I

;It is now apparent thatthe present invention provides? a novel method and apparatus for efliciently cleansingvobjects by means of ultrasonic. compressional waves;

The outstanding feature of the inventionis that the cleansing process may be made more efficient and accomplished in a shorter time by controlling the amount of gas or air dissolved in the liquid, and by controlling the temperature of the liquid in which the parts are immersed.

Although several forms of the apparatus of the invention have been shown and described, it is apparent that many changes and modifications may be made therein by one skilled in the art. Therefore, it is intended to be limited only by the scope of the appended claims and not by the particular embodiments described herein.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A method of cleansing an object, which comprises immersing the object in a liquid, transmitting ultrasonic compressional waves through said liquid to said object in such a manner that the surface of said liquid is agitated thereby, repeatedly moving said object in and out of said liquid through the agitated free surface thereof, maintaining dissolved gas in said liquid, and controlling the temperature of said liquid to tend to prevent driving off of gas therefrom.

2. A method of cleansing an object, which comprises Unrecoverable or waste liquid may be removed from the recovery-station 51 and; discarded through discharge means 53. The 'purified liquid is then; transferred to the processingstation 52, which may-com: prise equipment.having'lcooling, means} and; means for; bubbling gas or. air; through the. liquid, f From the. processing station vthereprocessed liquid is transferred through ,inlet.pipe 47.,to;theultrasonic cleanser. F It is, 1 of course, apparent that the outlet pipe 48 neednot;

7 sembly relative to: each-other-,'=moving said l assembly in and out of said liquidthrough the-agitated free surface thereof; maintaining dissolved gas in a said. liquid, and controlling the temperature-of said liquid to tend -10 prevent driving offof gas therefrom.

4. A method -of cleansing a ball bearing assembly,

sembly-relative to each,other; moving said a-ssembly im andoutof said liquid through the 'agitated free surface thereof, and maintaining dissolved gas in saidliquid;

6. A method of cleansing-a ball bearing-assembly, which comprises immersing the asse'rnblyin: a liquid,

transmitting ultrasonic compressional wavesthrough-said liquidto s-aidlassernbly, rotating -th'e-= races o-f said as sembly relative to each-other, moving said} assembly in and outiof said liquid through the agitatedfree surfacethereof,. and maintaining said liquid-substantially saturated with dissolved gas.

7.. Apparatus for cleansing a :ballbearingassembly comprising means for immersing said assemblyin a liquid, means for transmitting ultrasonic compressional Waves through saidliquid to said assembly :whereby'the; surface of said: liquid is agitated,- means-forrotating-one ofthe: -racesof said assembly, means for movingsaid' assembly in and outof saidliquid through theagitated free surface thereof, means for main'taininga substantial amount: of. dissolved gas in. said liquid; and meansfor controlling the temperature of said li quid to tend toprevent driving off'ofgas: therefrom. a Y

8'. Apparatus for cleansinga ballbearing assembly comprising- .means-for immersing. said. assembly in' a liquid, means for transmitting ultrasonic. compressionalwaves-through said liquid toisaidassembly whereby the surface of. said liquid is agitated,- means for rotating one ofthe races of said assembly, means for moving: said assembly in :and out of said liquid t through the, agitated 7 free surface thereof, means for maintainingsaidliquid substantially saturated with dissolved gas, and means-for controlling-the temperature of said liquidto tend to-pre-' vent driving off of gas. therefrom. V

I 9. Apparatus for cleansing a ball bearing assembly comprising mCdIlslfOl' immersing said assembly in--' a liquid, ameansafor transmitting ultrasonic compressional waves -through sai'd liquid to saidassembly whereby: the

surface of said liquid is agitated,- means for-rotatirrg one of: the racesof said,assembly,-means for -movingsaid assern-blyx in -and out ofsaid liquid -=thr0ughthe agitated freesurface thereof, Land nieans for maintaining a sub stantial-.amount.: of 1 dissolved gas 'in said liquid;

I10.Apparatus for cleansing a ball bearingassembly comprising meansfor-'irnmersing -said-assembly in a liquid, emeans for transmitting ultrasonic compressional waves through said liquid to saidassembly whereby the surface ofisai-d liquid is agitated, means for rotating-one of the races of said: assembly, meansfor; moving said assembly in vand out i of said liquid 1 throughthe agitated free surface -thereof,-and"meansfor maintaining said liquid substantially" saturated withdissolved gasI r References'Cited in the file of this patent UNI E STATES PATENTS 101,129 yI-Iobson .r r Mar. 22,1870 574, 606 ,H ei de,man, ..Ian: 5}"1897' 71,? 66,208; 1 'Anstiss --Iune' 24,119 30 2,468,538 ;B,e,nioff; Apr. 26,194? 2,468,550 Frllthli. Apr'...26,1949 2,549,837 'j -Merritt Apr,' 24,l1951 FOR GN AT N 1592/31 7 Australia ',j; Apr; 13', 1931 Great Britain }foct .g 30,1942

Claims

1. A METHOD OF CLEANSING AN OBJECT, WHICH COMPRISES IMMERSING THE OBJECT IN A LIQUID, TRANSMITTING ULTRASONIC COMPRESSIONAL WAVES THROUGH SAID LIQUID TO SAID OBJECT IN SUCH A MANNER THAT THE SURFACE OF SAID LIQUID IS AGITATED THEREBY, REPEATEDLY MOVING SAID OBJECT IN AND OUT OF SAID LIQUID THROUGH THE AGITATED FREE SURFACE THEREOF, MAINTAINING DISSOLVED GAS IN SAID LIQUID, AND CONTROLLING THE TEMPERATURE OF SAID LIQUID TO TEND TO PREVENT DRIVING OFF OF GAS THEREFROM.

7. APPARATUS FOR CLEANSING A BALL BEARING ASSEMBLY COMPRISING MEANS FOR IMMERSING SAID ASSEMBLY IN A LIQUID, MEANS FOR TRANSMITTING ULTRASONIC COMPRESSIONAL WAVES THROUGH SAID LIQUID TO SAID ASSEMBLY WHEREBY THE SURFACE OF SAID LIQUID IS AGITATED, MEANS FOR ROTATING ONE OF THE RACES OF SAID ASSEMBLY, MEANS FOR MOVING SAID ASSEMBLY IN AND OUT OF SAID LIQUID THROUGH THE AGITATED FREE SURFACE THEREOF, MEANS FOR MAINTAINING A SUBSTANTIAL AMOUNT OF DISSOLVED GAS IN SAID LIQUID, AND MEANS FOR CONTROLLING THE TEMPERATURE OF SAID LIQUID TO TEND TO PREVENT DRIVING OFF OF GAS THEREFROM.