US2950725A - Ultrasonic cleaning apparatus - Google Patents

Description

3 Sheets-Sheet 1 S. E. JACKE ET AL FIG':1

ULTRASONC CLEAN ING APPARATUS Aug. 30, 1960 Filed March 26, 1958 Aug. 30, 1960 s. E. JACKE ETAL ULTRASONIC CLEANING APPARATUS 3 Sheets-Shea?, 2

Filed March 26, 1958 INVENTORS. /Wsw/we.

AT ORNEYS.

Aug, 30, 1960 s. E. .JACKE x-:TAL

uLTRAsoNIc CLEANING APPARATUS 3 Sheets-Sheet 3 Filed March 26, 1958 L@ /r mW/IJ ifa/m kiwi By ma@ ATTORNEYS.

United States Patent Oliice 2,950,725 Patented Aug. 30, 1960 ULTRASONIC CLEANiN G APPARATUS Stanley Emil Jacke, Milford, Lowell C. Newsome, Inkster,

and John W. Collison, Bloomeld Hills, Mich., assignors to Detrex Chemical industries, Inc., Detroit, Mlch., a corporation of Michigan Filed Mar. 26, 1958, Ser. No. 724,138

Claims. (Cl. 134-184) This invention relates to improvements in ultrasonic cleaning apparatus, and more particularly concerns such apparatus which includes a piezoelectric transducer contained within a hermetically sealed housing which is submerged in a cleaning liquid. It has long been desired to submerge piezoelectric transducers in a cleaning liquid and -to protect the piezoelectric ultrasonic transducers, and the cleaning apparatus of which they form a part, from electrical disturbances caused by submerging the tranducers in a cleaning liquid that is electrically conductive. It has also been desired to protect the transducers and cleaning apparatus from contamination, and 'orn physical and chemical attack by cleaning liquids. Electrically non-conductive cleaning liquids, such as trichlorethylene, may not cause electrical disturbances but may otherwise attack the transducers.

Heretofore to provide this protection it has been suggested to enclose the piezoelectric transducers in a housing which has an emitting membrane with a thickness that is very small, a few percent of the wave length of the ultrasonic waves emitted. A membrane of this thickness has a negligible etect on the acoustic coupling between the transducer and the cleaning liquid. At 400 kilocycles the thickness of such a membrane is .005 inch or less.

However, problems arise in the sealing of this thin membrane to the remainder of the housing containing the transducers. This sealing is dcult to accomplish and the housing is therefore prone to leaks which permit the cleaning fluid to enter the housing to attack the transducers. Another disadvantage of the thin membrane is that it does not aiord much protection to the transducers if an object should accidentally be dropped onto it.

It is accordingly an object of this invention to overcome the hereinbefore mentioned disadvantages, and to provide ultrasonic cleaning apparatus which has increased protection, increased eiciency, and increased intensity of the ultrasonic waves. lt is another object of this invention to provide ultrasonic cleaning apparatus which includes an emitting platewhich is strongly constructed to aiord protection to the transducers. It is another object to substantially reduce the frequency and impedance matching problems in such apparatus. It is another object to reduce the frequency drift caused by change in tank temperature, and thereby substantially reduce adjustment to the electrical generator when the tank temperature varies. It is another yobject of the invention to protect the transducers or electrical connections from being shorted out by the soils in the cleaning uid; It is another object of the invention to prevent electrical arcs and shorts. It is another object to eliminate the use of liquid seals and their associated gaskets, clamps, or bolts. It is another object to eliminate rubbing contacts between the electrical leads and the transducers. It is another object to provide a transducer assembly which is a separate entity, which is not necessarily attached to the well containing the cleaning uid, and which therefore can be submerged at any desired angle in any shape or size tank large enough to contain it.

Other objects and advantages of this invention will further become apparent hereinafter and in the drawings, in which:

Fig. l is a view in elevation of ultrasonic cleaning apparatus constructed in accordance with this invention with parts being broken away in order to illustrate important details;

Fig. 2 is a view in elevation and with parts broken away taken as indicated by the lines and arrows II--II which appear in Fig. 1;

Fig. 3 is a view in top plan of the apparatus shown in Fig. 2;

'Fig 4 is a view on an enlarged scale and partly in section of 'one of the ultrasonic -transducer elements;

Fig. 5 is a view of the cleaning liquid and a portion of the ultrasonic cleaning apparatus of Fig. 1, `and shows the apparatus operating and generating beams of ultrasonic waves which are focused at a focal zone;

Fig. 6 is a view similar to Fig. 5 and illustrates the operation of two ultrasonic generating units; and

Fig. 7 is a diagrammatic View of the electrical circuit of the transducers.

In describing the preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended to be limited to the specilic terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish `a similar purpose.

Turning now to the specific embodiments of the invention selected for illustration in the drawings, the number 11 designates generally an ultrasonic cleaning apparatus including a well or tank 12 containing a cleaning liquid 13 such `as trichlorethylene, and a hermetically sealed housing 14 which has a focused emitting plate 15 and a plurality of 4transducers 16 connected in an electrical circuit with a high frequency electrical generator (not shown). Positioned above the level of the cleaning liquid 13 is a conveyor 17 from which is suspended a basket 18 which contains a work object 21 submerged in cleaning liquid 13 to be cleaned or degreased.

Housing 14 is provided with a bottom plate 22, side walls 23 and 24, and end walls 25, 26. These elements welded together so that housing 14 is hermetically sealed. An aluminum half-coupling 27 is welded in end wall 26 and through this coupling pass the electrical wires or coaxial cable which extend from the 400 kilocycle electrical generator ,to supply transducers 16 with power. These electrical wires or cable are encased within an outer conduit which is sealed to coupling 27.

Aluminum ground brackets 28 are welded to the interior l ' fof end walls 25, 26 and the brackets 28 support ground connectors 31.

Focused emitting plate 15 is constructed of aluminum and in 400 kilocycle apparatus is 0.325 inch, plus or minus 0.002 inch, thick. Plate 15 is formed into iive segments 32, 33, 34, 35, and 36 with an angle of 221/2 degrees between the planes of each adjoining segment. understood that the invention is not limited to five segments or an angle of 221/2 degrees.

As shown in Fig. 4, transducers 16 include barium titanate discs 41 which have an upper silver electrode 42 and a lower silver electrode 43. These discs are attached to the underside of focused emitting plate 15 by a layer of glue 44 which may be epoxy resin. Transducers 16 form rows along the underside of segments 32-36. The lower silver electrodes 43 of all transducers 16 are electrically connected to the electrical generator and the upper silver electrodes 42 are all connected to ground.

It is to bed [intense ultrasonic energy.

Any desired electrical circuit may be used to effect these connections and one such circuit is shown in Fig. 7. ln Fig. 7 the electrical connectors are soldered' directly to electrodesAZ, t3-before the transducers 16 are. potted in the glue layers V44 and attached to lthe vunderside of Seg-v ments 3`2-,36. .Y

. YReferring to Fig. 5, thereis shown a focused emitting since such soils do not penetrate the hermetically sealed housing 14. Electrical arcs and shorts are prevented and the welded construction eliminates the use of liquid seals and their associated gaskets, lclamps or bolts. The electrical leads are soldered directly to the transducer electrodes, which eliminates the rubbing contacts between and which have been heretofore proposed. The ultravplate 15a which is formed by segments 32m-36a- At.

tachedto the underside of the 'segments are/transducers 16a-16e. ,These transducers, which form rows along Y the segments, generate ultrasonic waves which are emitted ing liquid is indicated by numeral 54 and the workobjrect Y kto be .cleaned Vis, indicated by the numeral .55.

Referring to Fig. V6, there is shown the emitting platesY i 15b and icfo'f two` transducer housings andthese'emitting plates are formedl of segmentsrS-di and 625-767 which have attached to thelr undersurfaceV the transducers Y713-74 Varid/'S 179'., YThese transducers generate ultrasonicrwaves which form beamsrd-SS and Sii-'93 of ultrasonic waves'which converge on a focal zone 94.Y The polygonal focal zones generated by plates V15b and 15C may be positioned so they overlap or not, as desired. The surface ofthe 'beam liquid is indicated by the 11umeral 95 and the work object to be cleaned isindicated bythe numeral 96.

Incineration, the work object is submerged' in cleaning liquid YT13, the electrical generator is turned on, andthe transducers. i generate ultrasonic waves which 'are emitted through the focused emitting platesr in the form of beams. `which converge on the focalV Zdne Yof YThe work `object is passed through this focal zonewhere it is thoroughlyV cleaned and degreased. v Y Y it is to be noted that the focusingl of the ultrasonic beams is of considerable advantage and that it provides for striking the work object with ultrasonic waves from various angles. Work objects may be passed below the Vfocal zone as wellas atrthe focal zoneror above it.

With Work objects having large recesses or cavities,v there is adistinct Yadvantage 1n passing the work objectA through cleaning liquid in Vsuch Va manner that the recess or cavityv passes through the focal zione of ultra-Y Y sonic energywhere this intensified energy can do the mos-t i Since the transducers are contained within a hermetically sealed housing 14, such electrical disturbances cannot sonic waveV emitting-apparatus comprises a separate package contained l,within housing 14, and it is easily inserted into any tank and positioned therein so as to emit its ultrasonic energy at any desired angle. Y

It is to be understood that theform ofthe invention herein shown and described is to be taken as a preferred embodiment. Various-"changes may Vbe made in the shape, size, andarrangement of parts. Equivalent elements may be substituted for those described herein, parts may be reversed, and certain features of the invention may beutilized independentlyl of the use of other features, all'withou't departing from the spirit of the invention or the scope of the subio-ined claims. i

Having thus described our inventionywe claim:V Y

1. Ultrasonic cleaningapparatus for cleaning a work object in a well containing a cleaning liquid, said apparatus comprising a hermetically sealed housing submerged in said liquid; a focused emitting plate for emitting'ultrasonic waves, said emitting plate forming part of said housing and being spaced away from said work object, said Yemitting plate being formed of dat segments with the exterior surface of the emitting plate being of generally concave conformation; and a plurality of flat Vtransducers attached to the'interior'surface of each of said segments with the interior surface of the emitting plate being of generally convex conformation, s'aidftransducers and said plate operating to emit a plurality of beams of ultrasonic waves, Veach of said beams being normal to the surface of the dat segment to which it is at- V-tached, whereby the VVbeams of ultrasonic Waves are focusedand converge at a focal zone outside of the housins- Y Y V2. The ultrasonic cleaning apparatus defined in claim Y1, wherein said hermeticallysealed housing is of welded aluminum construction. Y Y

3. Ultrasonic cleaning apparatus forcleanugV ka work i object yin a well containing a cleaning liquid, said apparatus comprising aY hermetically. sealed housing submerged in said liquid; a focused emitting plate for emitting ultrasonic waves of desired wave length, said emitting plate formingpart Yo f saidA housing andY being spaced away plate VbeingyofY generally concave conformation, Ysaid is emitting plate being oneV half of said wave length in thickness;.a plurality of flat transducers attached to the intcrior surface of'each of saidsegments with the'interiorV surface of the'emitting plate being of generallyl convexY conformation; and a high frequency electrical generator connected in circuit with saidVY transducers; said'transaffect them. 'Furthen'hermetically sealed housing 14 pr'o- Y tectsrthe transducers from contamination and fromrphysical and chemical attack`V by the cleaning liquids, and the thickness of focused emitting plate 15 protects theapparatus fromy damage caused by falling objects.

. 'Another advantage ofthe apparatus is Ythat a high g intensity focused ,zoneV ofY ultrasonic Yenergy has been and it reduces the impedance drift caused by change ofV Ytemperature of the cleaning liquid yin the tankQthereb'y ducers and plate operatingto emita plurality ofV beams of ultrasonic waves, each ofY said beams being normal to the surface 'of the flatrsegment to which it isY attached,

whereby the bearns ofl ultrasonic Waves are focused andconverge at a focal one outside of the housing.

4. The Vultrasonic cleaning apparatus deined in claimk 3,Y wherein'psaid titanate. i 5. Ultrasonic cleaning flat transducers are'hdiscs of barium object fin a well containing la 'cleaning liquid, comprissubstantially reducing the number of adjustments to the. Y

i electricalV generator ydue to variation in cleaning 'liquid' Ying'a hermeticallyrsealed', Welded aluminum housing submerged in the cleaning liquid; aY focused emitting plate for emitting ultrasonic waves of desired Vwave length, saidV emittingplate forming part of said housing and being spaced away from said work-object; saidV emitting plate being formed of flat-segments with'theexteriorsurface of the emitting plate being of generally concave Vconformation,.said emitting'plate being one-half of said apparatus'forcleaning a YworkV Wave length in thickness; a plurality of barium titanate discs glued to the interior surface of each of said segments with the interior surface of the emitting plate being of generally convex conformation; and a high frequency electrical generator connected in circuit With said discs; said discs and plate operating to emit a plurality of beams of ultrasonic waves, each of said beams being normal to the surface of its at segment, whereby the beams of ultrasonic Waves are focused and converge at a focal zone outside of the housing.

References Cited in the le of this patent UNITED STATES PATENTS Carlin Dec. 11, 1951 Fitzgerald Feb. 12, 1952 Rafuse Mar. 11, 1952 Williams Mar. 24, 1953 Kearney Apr. 22, 1958 FGREIGN PATENTS Italy Oct. 18, 1956

Images