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Publication numberUSRE18826 E
Publication typeGrant
Publication dateMay 9, 1933
Filing dateJul 28, 1923
Publication numberUS RE18826 E, US RE18826E, US-E-RE18826, USRE18826 E, USRE18826E
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
And one-third to james e
US RE18826 E
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Description  (OCR text may contain errors)




.llllaiiiiiiiliii. i.- w

'mummmmamuummun "Reissued May 9, v1933- UNITED STATES PATENT or-'rice annif "roMsou, or4 sWAMPsco'rrQMassAcHusmTS, AssIGNoB or ONE-THIRD 'ro' JOHN A. MCMANUS, 0F LYNN, MASSACHUSETTS; .AND ONE-THIRD 'I0 JAMES E.

i GRAHAM, or NEWTON-VILLE, MASSACHUSETTS mareujnarme rumeurs Original No. 1,568,102 dated January. 5, 1 926, -Serial No. 654,377, filed July 28, 1923. Application for reissue mea october 17, 1932. 'seriar No. 638,265.

The present invention relates specifically to refrigerating apparatus, suitable for domestic needs, and which is of the type where in Aa liquid of large latent heat of vaporlza- 6 tion such for example as sulphur dioxide and its vapor. fill :the spaces of the refrigerating apparatus, the said liquid being used in very -limited amount to secure advantages to be afterwardjpointed out. The systemincludes' l0 the usual elements of condensing pump and condenser with a lcooler or evaporator for vaporizing a liquid gas in attaining refrigeration; The objects of the invention may be stated to be to provide an apparatus of low cost, and relatively'low power consumption for' a given output of practical cooling, providing means for regulating in vdesirable .ways the application of the4 cooling to useful ends and at a rate depending on the call of the apparatus for such cooling; to improve the construction and details of the various elements of the apparatus rendering it more reliable in practice, an'd .to provide further an eiec- 25 tive means for'conse'rvingthe cooling effect by the provision of what I term :ineffective cooling barrier between the evaporator or cooler and the outside air, automatically regu. lating the access of heat to the evaporator in accordance with the needs. This last mentioned feature constitutes, in fac'i a negative heat storage or 'storage of cold, as it may be termed, which, at the same time, becomes an automatically adjusted conductor for car l ing heat tothe evaporator or cooler.' e particular function of thispa'rt of my invention' is that it secures a considerable latitude as to times of .operation ofthe motor, which I nay belc'ut out, ysay for several'hours, as' during the-night or at any other time, and operated during the-remaining parts of the day, 4depending on the cooling needed, the interval ojE non-operation being covered by the erlod f the stored or negative heat or cool- 45 lng provided for in the operation of the apparatus. It will be evident that since the consumption of energy is generally that of an electric motor` such power may be drawn ."from the mains ata time when its cost is the 9 least, or when it is desired to lill in load at the station, and the "apparatus can be removed from the s stem or shut down during the period of light load or the period of overload. In'accordance with this idea, it is desirable that the cooling effect of the motor and condensing pump, together with the oth:

.er appliances, besuiliciently great to only require operation during, say, daytime, with the shut-down during sleeping hours, so that in domestic service lit Will not be necessary to have the apparatus running during the night,

.which is a time at which even a slight amount of noise would be disturbing. -Whilst automatic regulation to permit predetermined rest periods of compression follows effectively from my ice barrier, any conventional automatic regulation (as by means of a thermostat .or such like) ma beadditionall employed if desired. 'With the system o -cold storage herein provided by means of the ice barrier, the pump, while Working continuously during periods of light or no demand for cooling, would be doing substantially no work, as the amount of SO2 in the apparatus I is so small in proportion to the spaces therein that there is practically no pressure When, however, the ice barrier melts sulficientlv and there 'is a real demand for coolingatlie refrigerant in the evaporator vaporizes, the pressure in the'spaces be s to rise and the pump has work to do an performs this work automatically of building up the pressure again to working value.

Instead of using a large lot of liquefied gas, it is possible with the apparatus of my invention to make use of a smallest quantity of liquid, according tothe interior capacity of the whole apparatus, and so arrange. the cycle that this 'same liquid can beevaporatd and condensed over and over again, without.

:sel l the necessity forproviding a reservoir or a considerable storage of liquid SO2, which is the case in sulphur dioxide refrigerating machines heretofore used. This is im rtant because in case of a leak of SO2 a minimum of this refrigerant is' available for leakage. The advantage of using this minimum amount df liquid is that when the appara- 'tus is unused or standing idle, no considerable pressure much'above atmosphere willv 'ever accumulate and strain the joints. This avoids leakage and difficulty of keeping the apparatus tight.

A further description andy figures of my apparatus will deal with the various-features of construction to secure the abovementioned results. y

My invention further provides in the conldensingqpump piston, means' for automati-A cally adjusting the clearance of the piston' in accordance with the load on the pump, whereby when the load is heavy the clearance of the piston from its head is greater than when the load is at a minimum, passstructed with as high efficiency-as possible,

and this for the reason that economy of power in such 'a device will amply pay for the' increased cost of obtaining better efiiciency 1n the motor. lConnections to f such motor are, as is,.,usual in such cases, carried through the casing by insulated bushings in the latter, and there will usually be two wires and sometimes a third, either let in through separate bushings in the motor casing, or combined in a cable,4this, however, beingr unimportant and a well known arrangement. To

discharge heat from the motor and its? cas# ing, it can have fins al1. over it or wherever it maybe found best for conveying heat therefrom. These are constructions so well known `that it is not necessary to elaborate them-here. Referring to the drawing, Fig. 1 represents a side elevation, mostly in section, of the apparatus of iny invention; F ig.

'2 represents a modification o'f the lso-called,

cooling barrier or low pressure cooling circuit for increasing the-voverall `efficiency nofthe apparatus; Fig. 3 represents an enlarged section of the mechanism for automatically limiting the movement of the compression piston in accordance with the. variations inpressu're of therefrigerating vapor; Fig. L 're'presents a plan View of the valve seat Ibetween the compression pump and compression cham-ber above the compression pump. It is preferred that the shaft' 1 on which the rotor-'is carried shall 'i have a single bearing 2 because of its greater simplicityfor lubrication instead ofthe usual two bearings. The otherend of the shaft from that carrying the rotor 3 bears a crank and crank pin* 6, the eccentric of which is proper for the traverse of the piston` actuated by the connecting 4'rod 7. An air' cooled casing 4, to which is secured a stator 5 encloses the rot-or 3, shaft 1 and oiling arrangements therefor.

In Fig. '3, will be foundthe preferred con# struction, in general terms, 'ofthe connection between the piston 8 and the connecting rod 7. This is accomplished`not by the usual wrist pin arraxlgnment.but by providing two strongly opposed springs a: and D of well tempered steel, the excursion of which iis always Well within the limit of elasticity. These springs are opposed and bear uponA a flange or extension cof the connecting rodl laterally, as shown, While they are secured firmly into the interior space of the piston body. In this Way the connecting rod can swing from side to side, as is needed in making the stroke, and at the same time, under spring pressure the piston can move slightly longitudinally to the connecting rod. This means'that if-the piston is opposed by a high pressure in passing up tothe head d ofthe cylinder,the clearance space e in the cylinder will be adjusted to a little larger amount than if the backpressure on the piston f is small. In the head d of the cylinder are perforations y' upon which,` rest 'an unperforated disk or valve g havingsufficient clearance between its circumferential edge and the inner. wall of the chamber 9 to allor:7 gas to pass by said -disk or valve into said vchamber whenA thev pressure is sufiicient'to cause the valve ff to rise and to lift said disk onvalve against the compressive force of the 'spring S. It will be seen that by this arrangement the pumping is not by a constant traverse of the piston, but one Whichis shortened somewhat, though to' a small-degree,'by the loaden the apparatus .being grsaterthat' is',.if the piston has to .compress -a dense gas it canyield somewhat,

especially when the back pressure into the v condenser, into which it is feeding the gas is higher.` 4. 0n the other hand, if the gas is comparatively'rare and of 'low pressure or density, the clearance space e is not so increased bythe pressure, but the pistonmakes substantially its full stroke without any dimi inuation wh atever. It is contemplated in the use of the invention that there shall be consid.- j erable variation in the density ofthegas Which is .being pumped, and also in the back pressure of the condensing chamber, especially at 'the start. The .intake openings which feed the gas into the space above the piston are. indicated as a set'of openings h and h' in the sleeve which are uncovered at the lowest part ofthe stroke of the piston. lA ll'these openfings are fed from the 4intake pipe or conduit I-I leading thereto.

v This'may be. modified considerably without affecting the nature of the invention; and, in fact, the arrangement.y chosen is adapted because of `its great simplicity. To be more specific, the advantage of the yielding spring maybe described 'furf ther.' When the'pressure in this condensing chamber becomes very excessive, th at is, more than a predetermined amount, the valve is maintained nearly, or quite, closed until the pressure falls off to a value below that which the pressure .of the spring in the piston can exert'whenthe valve isagain opened and the pressure again builds up to the desired value. In this way avery desirable automaticregu- 4lating mechanism for the pressure in :the

. system is, obtained, and iu addition fa very effective regulator providing against injury to the apparatus by blowing up dueto "an abnormal increase of pressure which might occur in case of an air leak inwards.

. traversed space so thatit is small when the pressures are low,and much larger when the pressures are high.

The piston, when drawn down, leaves a .i partial vacuum back of it which fillsv at once "which can be dissipated at this part of the" on the uncovering ofthe openings or 4passages and h inthe walls of the c ylinder when the end, of. the piston passes them'in its outward stroke.v These are covered at' apparatus, the better will be the economy. A duct or conduit pipeP leads fromj he passage' 9 over to the interior of what may be called. a' condenser o'r liquefying chamber within the shell l0, Thisvconsists preferably of .a more' or less cylindrical body lor shell capped at'each end, and in the interior of'which have been slipped a number of hol- .low tubes say four T and T', etc.- or sheei metal fines, so as to increase gradually the lnteriork' surface exposed lt6`thel gas. These tubes may be 1n a group which bear upon the outer sides and bear uponea-ch other, so that good heat' conduction may take' place between the outer wallsand the inner parts of the structure, and both the shell l() and inner structures may be made of -a good conducting metal, such as copper, Surrounding the shell 10 and extending from it is a series of fins or Wings W made in good conductive relation thereto, as by tinning or soldering, and these wings or extensions are staggered circum` ferentially with relation to Vone another whereby the air will successively flow over the multiple metallic fins and absorb heat there.- from thus cooli'ngthe condensed SO2 in the multiple tubes and spaced-in such a way that they give great freedomto the passage of air upwards and between and through and about them for the removal of heat or convection currents. They are very numerous, and while they might be exposed to a current of air This arrangement automatically regulatesthe unvcomplete closure of (he valve.

without further attention, they are` preferably ja'cketed vby an outer drum lin contact with theprojections, so to speak, this outer drum being of thin sheet metal of only such strength as isnecessary to provide air currents. as need be, or to allow` handling without destruction or deforn'iation. This outer f drum furnishes oracts as a chimney in itsvertical relation, whereby fair is drawn in at ,the basev betweenl the projections or wings ofthe shell 10 and delivered above in consequence of the fact that the air is solnewhat i taining itsI tightness' and making'it act still more effectively as an upecast draft chimney,

- increasing greatly'the flow `of heat from'the wingsor fills into the' bodyvof air which is .thus actively'passingthem. It is, of course, presumable that such chimney may, if it is convenient to do so, be extended at still greater length in any ready way, such, for example,

as turning the ,chimney extension directly into Hue whereby a chimney draft of the ordinary type is added to the effect before described. This is very desirable, and decidedly leffective. -As there is no damaging heat concerned 1n the appliance, the extension of the chimney may be made even of wood extending up towards the-roof of a building. These devices effectively obviate all necessity for Water cooling, which has been a decided bugbear in many types of refrigeraiing apparatus. T lie shell or receptacle 10 or condenser, as itm'a-y be termed, receives from the pump tsulphur dioxide gas only, but at such a pressure that when it losesheat from the wings, it condenses ino liquid sulphur dioxide7 which trickles down in the interior, and fina-lly is discharged into a small float chamber, which has much the structure or appearance of a carbureter float valve arrangement employed in gasolene feed for automobiles. There is a hollow float 11 connec'led by a system .of levers to a small conical or needlevalve 12 tightly fitted to its seat in the valve box 13.' -The leverage connection between the ioat and the valve is made so that the float moves, say, twelve times as far as the valve will move. This means that a slight amountv of fiuid vsurrounding the float l1, namely, sulphurdioxide liquid, lifts the fioat on a cer'ain accumulation having taken place, and opens the needle valve 12, 'allowing this accumulation to runthrough the needle valve, thus lowering the level of' the liquid in which the fioat exists,` and immediately causing' These intermittent feeds of sulphur dioxide liquid pass down into the evaporating chamber or cooler through the pipe 14 which is a tube of small bora-entering into the base of a cooling coil 15. Therefore, -in general the arrangemen;

consists of a hollow vessel shown as a sphere of light metal and empty, or a solid body of very light material may take itsplace. The stem of a valve 12 passes throughan opening in the center of this float body downward, which stem actuates the valve to open and close it. The valve is of small dimensions e andfits closely to its seat in the ordina-rywvay.`

The float body in rising will, as is seen, lift the long i'ns of two levers A-A provided with stationary fulcrums,lthe short arm outwardly extending being linked byfa pair of links B-B to the long arm of a second set of levers C--C fulcrumed in fixed position' from the upper cover while the short arm is an extension wlnch engages between two discs centering on the valve stem itself at 1ts lpper end. Thus an upward movementof g the float lifts the valve Vbut at a slower rate than the float itself moves. The oat body fits closely the chamber in 'which it rests, but

.. it is free to rise when liquid coming down valve., the' pressure differenceu is, in part neu-I tralized and the floatovershoots o r rises beyond mere equilibrium, thus permitting' a rapid emptying 'of the space around the float ofthe liquid accumulated therein. The sulphur dioxide refrigerant being of very low viscosity, escapes rapidly as a liquid into the evaporator and the iloat, alittle behind time,

'.comes down and recloses the valve, butnot until practically all of the condensed liquid -has been discharged; This loperation is repeated at intervals. This coil 15 corresponds to. the ordinary cooler in the refrigerating system exposed by its surface tothe cooling of air or the cooling of water in a refrigeratingvbox. l' i 5..--

- My invention, however, .contemplates a further step', in .that in normal operation the coil is submerged in a freezable liquid, 'such as' water, whereby the space surrounding the;

coil becomes an ice box` or ice block more or less extended. As' the box is sealed it is not .filled with water, but an expansion'space is'v allowed above it, so 'that on freezing there will be no overflow nor rupture 'of the boxl The box containing the water as an example is .of sheet metal,'such as copper, though any suitable metal for the purpose may be ployed, and conducts the heatinwardly from the outside, as in the cooling operation. lIn operation, .under these circumstances,- there will form af coating Aof ice 18' aroundthecoil' vliquid .ma

and the water interior-thereto will gradually freeze, as wellas the water 19 exterlor thereto, and a coating. will gradually thicken as the cooling advances, provided that there is not a large excess of heat from the outside tending to keep the ice melted as fast or faster than it forms. Should the demand for coole ing be continually lessened, then theA ice layer 18i will gradually extend, and it may' be conceived at the last as leaving no water unfrozen 1n the space or box 16. Thls'is the `extreme case, for during the process of freezing of the ice layer all over the coil 15, there comes into play another function; that is the ice being fair non-conductor of heat, the ilowrof h eat as the layer thickensis grad-l automatic adjustment of theheatflow to the qoil, or a stoppage of the heat flow to the coil whent'he demand is sma1l and the .storage of the negative heat, or, as one may say, of the cold around the coil. There are at least two results of this happening. In the first place, the temperature of the coil itself falls yso that the sulphur dioxide in the apparatus vsill accumulatethere and. not b e rapidly evaporated, at the Vsame time that the pressure on ually niore and more cut off, resul ing in .an

the working'pump will fall, since the gas which' it gets from the evaporator or cooler Y becomes more and more rare, or approaches more and more a partial vacuum, while at the same time -the effect, of the cooling of the condenser 1() goes on a pace and reduces its temperature,` fand consequently the back pressureon the pump, thus saving'p'ower when crease economy. By means f the above -inentloned process also super-cooling is prevented lwithout theuse of 'thermostatic orpressure controlV necessarily, because theY temperature 1n the refrigerator box can never fall below the tempeature'of the freezing liquid. Such pose of such mixture simply -beingfto lower tlie temperature in the ice boxfa slight amount below 32 F. when such is desire' Now, if, at this time,the pump 'be shut down by shutting off the driving power of the motor,there willbe an accumulation in the condenser of substantially `all the' free sulphuiadioxide liquid possible to exist there-7 in; and there w1ll alsobe a mass of ice around the cooler or"`evaporator coils.v In this Way,

We have secured -a storage which may con- 'be plain' waterwith amixture of' a' slight amount f other' substance, the purv10o .the'load is light,- and at thesametime savi ing wearand tear on the apparatus, everyi Jthing working, as it lwere, favorably to intinue the refrigeriatng action of the appara# .tus for a considerable time while it/is shut As the apparatus rests and` heatdown. reaches the tank 16,- .there, wi.l1 be,.of course, ya reduction offthel-famont of ice which is supplanted by water, and later an evapora- 'tion of the sulphur 'dioxide contained in the condenser coilsowith -a fair equalization ofl pressure throughout the whole apparatus.

If now the, starting current 'is put on the motor, it carries the piston over center .and starts to run with verylittle load and an entirely favorablecondition, and gradually accumulates in the pumping process i the former difference of pressure betweenpthat 1n 'the condenser 1Q andthe space below the .pump piston and in the evaporatorcr cooler. 'Ihis seriesof actions just detailed is pointed out as constituting a regulating feature of the layer of ice, which Iv call the ice barrier around the cooling coil or receptacle.

-In Fig. 2, the evaporator coil 15 is modied to be a chamber 15 with an inlet tube 14 for allowing the liquid spray from the valve l2 to enter, anda pipe 17 returns to the pump of F ig. 1, the sulphur dioxide'vapor. It may be here mentioned that in Fig. l, the cooling coil or evaporating coil 15 will have attached to its outer surfaces extensions of the metal in the form of wings' or vanes 18 for the l more extended surface and lessen the intensity ofthe diiference between the outer layers of the surroundingv liquid and the in` ner layers of ice When frozen. They, in other Words, modify the acuteness of the barrier which forms aroun by the-freezing-of the su rounding Water in the vessel 16, and are capable of being adjusted or regulated by cdnstruction to" any circumstances which may be4 found most fai .vorable to be met, and this may vary under different applications.

The shaft 1 Fig. 1 is, as it Will'be seen, oiled by a. set of wick oilers coming up from oil spaces below, as is marked 20. There is little lubrication needed as a single bearing is used, and it is ofsuch a nature as not to demand agreat amount of lubrication. It is desirable to arrange the lubrication drip to be taken up again and be reconveyed to the,Y

bearing after it has passed through a piece of felt forfiltering.

While many formsv of valve may be suit-il able, even automatic valves, for the exit valvesover the pump cylinder above the piston, a simple valve g, Fig. 4 may be illustrated as effective for the purpose, which .con-

sists of a flat sheet of substance, such as hard rubber, of small thickness and preferably internally reenforced by metal bars or Wire pressed down by Ia spring S (shown in Figs.

`1-` 'and 3) over a `series of holes .7'- Thlg van has been used with success.

The operation of the device is as follows:

the inner chamber The machine is first charged with the requisite amount ,of liquid, the pump is started into operation, the liquid evaporating nair compressed over and over again, which' lwould resultin doing work on air, from which there would be no benefit and it 'would `act as a clog. The object is to compress pure sulphur dioxide gasv The gas Ais then pumped to the condensing f' chamber, where.4v

the heat of compression is lost externally by, means of lthe condenser. The gas then liquefies and runs down into the float'valve chamber. Vhen a sufficient amount of liquid has accumulated in this chamber, i the needle -v'alve opens and' emits a small quantity of liquid to the evaporatory chamber -or expansion vessel, which is in the ice box. Or, this evaporator or .expansion coilv may be a conventional coil of copper pipe, or it may take the form'or structure shown in Fig. 2 of the drawing. When the liquid reaches the evaporating coil in turning into'fa gaseous state, it takes up the necessary heat to accomplish this transformation from vthe surrounding medium. The gas isthenreturned to the com-pression pump and the cycle repeated.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now lconsider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means.

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

1. In a refrigerator the combination of a compressor having a spring supported piston yielding increasingly compression pressure increases to reduce supply of a volatile sof refrigerant and reduce the compressed charge under increasing back pressure, a condenser having multiple metallic lins a chimney carry,-` iiw air for condensation in amount correspending to increase condenser temperature, controlling means at the outlet of said condenser comprising an automatic intermittent .valve, an evaporator receiving 'refrigerant' periodically in small increments, and a Water tank of such capacity as to permit a graduated thickness of ice as a thermal barrier in amount to cover rest periods from compres- Ision, said tank surrounding and closely adjacent to the evaporator. ,v

- 2. In a refrigerator a storage tank for frozen liquid, an evaporator containing liqueicd volatile refrigerant in close thermal relation to said tank, said evaporator having` radiating heat conducting extensions proportioned relatively to the tank capacity to permit a thickness of ice due to evaporation of l-liquefied refrigerant to form and to retard fevaporationof refrigerant at predetermined low pressure during a desired period of rest from compression.

3. In a refrigerator a tank for containing a reezable liquid, an `evaporator Within the tank for evaporating a volatile refrigerant, a compressor in operative relation with said evaporator, fins of large superficial area around the ,evaporator in close heatconducting relation thereto and Vwithin the tank; a condenser, and a valve operated automatically under a differential condenser and evaporator pressure to permit feeding of regulable quantities of liquefied refrigerant frigerant tothe evaporating chamber wherep by a definite low temperature may. be held substantially constant during service. 5. A refrigerator containing the following elements asembled; a chamber having/volatile refrigerant, a pump' or compressor supplied from said chamber and delivering such volatile refrigerant under pressure to a condenser chamber surrounded by extended fins consti' A tuting draught spaces for cooling air passing over them, an evaporator arranged with an i i outlet in connection with the intake ofthe compressor, a .tank outside the evaporator, a body 'freezable liquid in said tank, extensions'o' fins. of heat conducting metalon the 'outside o f the evaporator-itself, a controller valve, and means to close' and 'open said valve automatically and .intermittently in passing condensed liquid from the condenser chamber or space to the evaporator.

6. A method 'of refrigeration consisting in compressing in variable volume ldependent on back ressure of compression a condensible l gas o large latentheat such as sulphur dioxide, coohng the same to liquefaction, releasing the liquid as needed at suitable pressure for cooling, conveying the cooling e'ect to a second liquid to form an ice block allowing a free space for-expansion of suchliquid by freezing,y and lay-passinglheat through or -arou`nd the accumulating body `of frozen liqui'dfto store coldto cover rest periods of functioning and enhance the overall eiciency, and also to reduce the temperature. dropin regulating supply of gas and liquefaction..

7. In arefrigerator a compressor for compressing liquid refrigerant, a closed storage tank for frozen liquid, an evaporator containing liquefied volatile refrigerant in close thermal relation to said tank, said evaporator having radiating heat conducting extensions proportioned relatively to the tank capacity to permit a thickness of ice due to evaporation of liquefied refrigerant to .form and to retard evaporation of refrigerant at predetermined lowpressure during a desired period of rest from compression while the compressor is stopped.

: 8. In a refrigerator a sealed storage tank for frozen liquid having an expansion space, a compressor for compressing liquid refrigerant, an evaporator containing liquefied volatile'refrigerant in close thermal relation to said tank and. in substantially non-convective relation therewi'th'surrounded by the frozen liquid, s6 thatl practically the Whole cooling 'effect of the evaporator is conveyed only to and through said liquid, radiating heat con.

ducting extensions on the evaporator' proportioned relatively to the tank capacity to permit a thickness of' ice due to evaporation of llqueiiedfrefrigerant to fprm -and `to retard evaporation of refrigerant at predetermined low pressure during the desired period of rest -195' from compression, while the compressor is stopped.


Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2867129 *Oct 28, 1953Jan 6, 1959Gen Motors CorpFluid power steering valve
US5474717 *Apr 19, 1995Dec 12, 1995The Coca-Cola CompanyApparatus including means for controlling the formation of an ice bank in a carbonator tank
U.S. Classification62/59, 62/439
International ClassificationF25B31/00
Cooperative ClassificationF25B31/00
European ClassificationF25B31/00