US2693944A - Sonic generator for the agitastion of fluids - Google Patents

Description

NOV- 1954 A. A. FowLE SONIC GENERATOR FOR THE AGITATION OF FLUIDS 2 Sheels-Sheet. l

Filed May 5, 1951 IN VEN TOR.

Nov. 9, 1954 A A- FOWLE; 2,693,944

SONIC GENERATOR FOR THE AGITTION OF' FLUIDS Filed May 5, 1951 2 Sheets-Sheet 2 O ID Fig. 3

ATTORNEYS United States Patent SONIC GENERATOR, FOR

AGITATION ,OE FLUIDS Arthur A. Fowle, Waltham, Mass.assignor toUltra'sonic Corporation, Cambridge,` Mass., 'corporationlo'fMassachusetts Application May 5, 1951,-Srerial N0.22'4694 s. Claims. (CL259--D My invention relates to devices for generatingsound waves in bulkliquids.

lt has been observed by others that sound waves acting upon various liquids exhibit phenomenawhich ,maybe applied to achieve many valuable results. Forjexample, sonic energy is vuseful for pasteurizing milk, for accelerating the chemical processes'involved in the ageing of spirits, for making emulsions, and for many other purposes. These phenomena have been observed largelyupon-Ia laboratory scale vinthe past, generally' in conjunction `with electronically generated sonic venergy involving theuse' 'of piezo-electric crystals or magnetostriction' rods. However, `the Apower losses and large cst of equipment Iinvolved in the generation of sound waves by"such means are so large as to render it unfeasible from the economic standpoint to utilize them on'a' commercial scale.

The primary object of my invention yisfto''reduce."thfe cost and improve `the eiliciency in the operation of generating sound waves in bulk liquids.

An important feature ofA the invention resides lin vthe combinationfof a valve supported on a llexible diaphragm and'arrangcd to operate as a water hammer to s et'up pressure waves in a liquid caused `to travelbetween thev valve and its seat.

Another feature of the invention resides in the combination lofta duplex conduit havingr a water hammer at one end and a treating tank at the other, `the two parts ofthe conduit being separated'by a-plug'of solid'mater'ial hav-y ing an acoustic impedance comparable to that of the liquids involved. By means of this arrangement one liquid may be employed to 'operate the water hammerthrough a closed system including a pumpand the water hammer, while the other portion `of theconduit maybe employed for the passage of the liquid to be treated. v

These and other objects and featuresof'myinvention will more readily be yunderstood and appreciated from thefollowing detailed description Ofapreferredembodiment thereof selected Vfor purposes of',ill'ustrationfand shownin the accompanying drawings in which:

Fig. lis a diagrammatic view'of'anentiresonic treating system constructed in accordance with `the invention,

Fig. 2 is a plan view of ythe waterhammer,

Fig. 3 is a view in cross section lalong 'the linef-'rof Fig. 2, and n Fig. 4 is a viewlin cross section through the valve and its-seat.

.With reference lirst to Fig. l, it will be seenthatjthere is provided a heavy hollow housing'10 having 'acentral hollow boss y12 forming a chamber 1444 into 'the outer `end of which apipe 16 is inserted. Withinthe chamber 14 there extends avalve stem 22 terminated' by afvalvell and supported by andextending'through the center ofga resilient steel diaphragm`20 held attitsv periphery bythe housingv 10. Across the rear of the housing 10 'there is secured a` heavy strap 18 provided with a'threaded 'central aperturefor a rod 26 heldin fixedpositionby a'lolzkV nut 28 and carrying at its innerfendlaf rubber stop `or bumper 24 disposed in axial alignment with the end of thevalve steml 22. Aconduit 32 connects thepipe 16 to a high pressure tank served bya variable drive pump connected to a low pressure tank which in turn is connected to the interior or the housing by aA drain condnitsBS. A pressure gauge 34 is inserted in the-,line from thepump to indicate the pressure beingmaintainedin the` system.

When the pump is operated liquidzunder pressureows from the high pressure tank through theconduit 32 and into the pipe` 16. `It surgesagainstjthervalvehead 30 and ICC causes the valve stem and valve head to reciprocatqthus alternately increasing and decreasing the space-.between the 'valve headt) and its seat in the boss 12. Thevalve stem 22 is so adjusted with respect to the-diaphragm-2tl that the valve head does not actually touch the boss r12` at any time'during its cycle or' movement. The rod 26 is adjusted axially in the strap l18 so that the bumper 24 will be struck bythe end of thevalve stem 22 when thevalve 30 is not quite in contact with the boss 12. The surge of pressurized liquid first causes a closing movementor thevalve 30 and the resiliency of the diaphragm 20 then causes reverse movement of the valve to open the passage. While a diaphragm is an efficient form of resilient member for the purpose, a heavy compression spring or other suitable spring may be employed in place of 4 the diaphragm. ln consequence of the movement of the `valve`3il and the alternate decrease and increase in the flow of fluid through'the valve, there is generatedin the pipel pressure waves which travel through the liquid at a frequency within the sonic range. The frequency is the natural frequency of the system.

Liquid which has passed through thevalve 30 and into the interior of the housing ltl'drains through the conduit 36- into the low pressure tank from which it is again pumped into the high pressure tank. I provide arelief valvev 40 in a by-pass conduit 38 connecting the high and low pressure tanks. Thepressure relief valve 40 may be set to control the now rate of the liquid. Thus the speed of the pump may be Varied to vary the pressure in the system while therelief valve 40 may be adjusted to attain a desired flow rate.

The operation of the Water hammer is based upon the principle of a self-growing water hammer wherein the ilow through the valve is reduced when the pressure upon the valvev rises and wherein the ow through the valve is increased 'when the pressure upon the valve falls. In constructing a Water hammer sound wave generator of the type disclosed herein, it should be borne in mind that under one set of conditions the operation is stable; that is to say, the tluid is pumped through the circuit in a steadyflow, but under another set of conditions the valve mechanism is set in self-excited vibration which causes an interruption of `the tluid flow at the valve with the consequent generationof pressure pulses proceeding away from the valve. Ordinarily a small pressure pulse generated at the valve end of the pipe will make multiple rellections at both ends of the pipe until it is damped out.

However, if the valve is so constructed that it operates in the manner described above, the pressure wave being reflected from the valve is actually increased in amplitude due to the motion or' the valve; this amplitude of the Ipressure wave increases until it is limited by damping or by cavitation. The natural frequency of the sound waves in such a system is that corresponding to the natural vibration frequency of the water column in the pipe, the period being the time the pressure Wave requires' to ltraverse the length of the pipe four times. From an inspection of Fig. l it will be evident that as pressure is applied upon thevalve 30 by the liquid in thepipe 16, the valvey moves to the left and thereby decreases the flow, since rthe valve passage is decreased in volume. Then as the'pressure upon thevalve 30 is decreased, the valve moves to the right (due tothe force of the spring diaphragm 24)) and the iiow past the valve increases. It should be noted that the chamber into which the fluid ows from the valve is sufficiently large and is also drained adequately so as to permit the diaphragm to oscillate in air undamped by the presence of a significant volume of liquid.

In the pipe I6 above the liquid inlet conduit 32 there isfdisposed asolid yplug 42 of a material having an acoustic impedance comparable to that of the liquid employed to loperate the water hammer. This liquid may conveniently comprise oil of the type commonly used irr hydraulic systems, and theplug 42 may be constituted of.rubber or similar material having a compressibility similar toV that of the oil.

lAbove theplug 42 thepipe 16 isprovided with an inletconduit through which the liquid to be treated may kbe 'introduced' into the system. The end ofthepipe 16 leads into a large surge tank provided with an outlet so that the liquid undergoing treatment may be passed continuously through the system. Apressure gauge 44 is provided upon the tank so that the pressure of the system may be observed. If the intensity of the waves generated in the water hammer are sufficiently high, cavitation may be experienced. However, pressure may be applied to the surge tank so that the liquid undergoing treatment is subject to a pressure high enough to eliminate cavitation. On the other hand, in certain processes cavitation may prove ellicacious in promoting the desired result, in which case the liquid to be treated will be circulated with minimum pressure.

In Figs. 2, 3 and 4 an embodiment of the water hammer is shown in more detail than in Fig. 1. There'is provided astout metal plate 50 into which is threaded the end of a pipe 52, this pipe being similar in function to thepipe 16 shown in Fig. 1. A secondflat plate 54 is secured to theplate 50 by a series ofbolts 58 and,

contains ahollow block 56 provided with a passage for a valve stem 70 carrying an integral head 60 disposed opposite a seat formed in the interior of ahollow block 56. Incidentally a portion of the block immediately surrounding the valve seat is provided with a concaveannular recess 62 in order to minimize turbulence above the valve.

Welded or otherwise suitably secured to the face of theplate 54 is acylindrical metal housing 64 whichis threaded internally to receive a pair ofclamping rings 66 between which is held the margin of aresilient diaphragm 68, of low alloy tool steel or similar tough resilient metal. Thering 66 and the margin of thediaphragm 68 are secured by a circumferential series ofbolts 67. Astout strap 72 disposed across thehousing 64 and bolted thereto is provided with a threaded aperture at the center to receive a threaded rod 76 carrying on its inner end arubber bumper 74 and secured in position upon thestrap 72 by alock nut 80. Thebumper 74 serves as a damping pad for limiting the travel of the valve; this eliminates mutilation of the valve due to pounding as well as failure of the diaphragm due to overstress.

Therings 66 are held in fixed position by fourbolts 82 which pass throughlugs 84 bolted to the rear end of thecylindrical housing 64. It will be appreciated that therings 66 may be adjusted in and out with respect to thehousing 64 and thereby vary the clearance of the valve 60 with respect to its seat. In this way the pressure at the valve may be adjusted, the pressure decreasing as the valve clearance is increased.

It will be evident that a water hammer generator of the type herein disclosed will be more effective at relatively low frequencies, say from 100 to 1,000 cycles per second. However, at such frequencies considerable sonic energy may be developed; for example, sound waves in the order of ten kilowatts may easily be obtained.

While the device as shown herein utilizes the back generated pressure waves traveling from thevalve 30 through thepipe 16, it is equally possible to couple the diaphragm 20 to a suitable treating or radiating system wherein the diaphragm serves as a source of useful sound waves. Alternatively a drill bit may be mounted upon the diaphragm to form an impact drilling rig.

The nature of the work to be done and the frequency desired for operation will, of course, affect the design adapted for any particular application but itis believed that the foregoing description is adequate to provide those skilled in the art with suflicient information to permit successful commercial embodiments of the invention to be constructed. y,

Having thus disclosed my invention and described in detail specific embodiments thereof I claim asnew and desire to secure by Letters Patent:

l. Sonic treating apparatus comprising an elongated conduit, a plug intermediate the ends of said conduit dividing said conduit into first and second compartments, means for supplying an operative fluid under pressure to the first compartment, means adjacent the first compartment end of said conduit responsive to the operative fluid in said first compartment to produce b ack pressure sonic waves in said lrst compartment,`.and means for supplying a liquid to be treated to the second compartment, said first compartment and said plug providing an acoustical connection for the sonic wavesffrom:

the sonic wave producing means to said second compartment.

" -2". "Sonic 4treating"apparatus4 as `defined in claim l, wherein ,themeans for producing back pressureA sonic waves comprises a chamber in fluid communication with said rst compartment, a yalve means mounted in said chamber in the path of fluid leaving said first compartment, resilient means coupled to said valve means to oppose movement of said valve means and a stop operatively associated With said resilient means to prevent closing of said valve means.

3. Sonic treatingA4 apparatus comprising an elongated conduit, a solid plug in said conduit dividing said con duit into two'c'ompartments, means for introducing a liquidto'b'e treated into'one compartment, means for introducing an operative fluid into the other compartment, andmeans including a resilient diaphragm controlledvalve mounted externally of said other compartment restricting the passage of operative fluid out of said other compartment for producing back pressure sonic Waves in said other compartment, said plug having an acoustic impedancecomparable to the operative fluid, whereby saidplug and operative fluid provide a transmitting medium for said pressure waves between said valve and said fluid to be treated.

4. Sonic treating apparatus comprising a conduit, a

y plug dividing said conduit into two compartments, means for supplying an operative liquid to one of said compartments, means for circulating a liquid to be treated through the'oth'er of said compartments, and means adjacent the first-named compartment end of said conduit responsive I to the 'saidf operative liquid to produce back pressure sonic'waves in' said first-named compartment, the length of theV conduit being such that the liquid filled conduit is reson'antA at said sonic frequency.

5. Sonic treating apparatus comprising an elongated conduit, a plug dividing said conduit into two compartments, means for introducing a lluid under pressure to one' of said compartments, means responsive to said fluid for generating pressure waves at a sonic frequency,

and means for circulating a fluid to be treated through the other of said compartments, the combined length of thetwo compartments being such that the fluid filled conduit is resonant at said frequency. v

6. Sonic treating apparatus as defined in claim 5 wherein said4 plug is madeof material having an acoustic impedance comparable to that of the fluid to which the means forproducing pressure waves responds.

7.` A'sonicwave generator comprising walls forming a Yhollow housing, a hollow member projecting through a,:wall of said housing, a valve opening formed in said member communicating with said housing, means for supplying an operative fluid under pressure to said member, a'valve mounted for axial movement in said member operatively associated with said valve opening movable in response" to the flow of operative iluid to restrict said opening fromthe member to the housing, a resilient diaphragm mounted in said housing and coupled to said valve urging said valve to a non-restricting position after said opening has been partially restricted, a stop member cooperating with said diaphragm for preventing said valve from closing said opening and means for draining lluidzfrom said housing.

8. Sound wave producing means comprising a chamber, an inlet and anoutlet for said chamber, a conduit l coupled to said inlet adapted to pass fluid to said chamber, a valve operatively associated with said inlet movable in response to fluid flow in said conduit to partially restrict said inlet, a spring loading said valve to a non-restricting position for moving said valve to said non-restricting position upon a reduction of fluid flow in said conduit, means supplying liquidunder pressure to said conduit, valve andchamber; the load of said spring, the diameter and length of said conduit, and the mass of said valve being such that upon the application of pressure to said liquid, said valve opens and closes at a frequency equal 5' to the resonant frequency of said conduit.

References Cited in the f'lle of this patent UNITED STATES PATENTS I Number- Name Date 1,178,528' Loepsinger Apr. l1, 1916 1,210,9134 Dougherty et al. Ian. 2, 1917 1,454,353 Thrush May 8, 1923 Y (Other references on following page)-l 2,138,839 Chambers Dec. 6, 1938

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