US 2667757 A
Description (OCR text may contain errors)
Feb. 2, 1954 M. G. SHOEMAKER PLURAL TEMPERATURE REFRIGERATION SYSTEM Filed Feb. 7, 1952 ifa,
Patented Feb. 2, A1954 .".PLUBALIIJEMBERATURE REFBIGERATLON n SYSTEM Malcolm G.1Shoemaker, Doylestown; Bayfassignr 'i ,:t0;Pfhi1c0,Corporativa Philadelphia Re a0rhporationzof, Pennsylvania fteAgpplicaton February 7, 1,952, Serial-Nor2-705325 :"The ftinvention Aa:hereinafter fi disclosed ,v and f; claimed' lrelatesfttorvrefrigerationpbeing .concerned withrefrigerationi systems having.'A provisionJ for 1; rapidiandzautomaticf :removal fof "frost from vthe evaporator.. means, .rendi .which :systems also4 con- -template' modulating yor controlling, the refrigerating temperaturezof' the. evaporator means.
Moreparticularlypmy. invention =has.to do with `,improvements in plural-,compartmentrefrigerators, of, thettype-:iwhichtnotonly include a vmain nestor-age.; compartmentnormally maintained at temperatures above the freezingzpoint of-water, "-.butlalso anompartment maintainedrat relatively 'lowfsharp-freezing. temperaturessuitable -or the preservation f of.y foods :oven-extended Aperiods of time.
- tors; i; inrorderntoLy defrost tthe-sameg4 while conistinuingthe normalfrefrigeratingffunction (rf-the Y... othenA evaporator.
@Inf cnet-aspect ot ther-invention itf is--an--ob-ject 'ltor-:provideedefrosting: :modulating-apparatus ..controlledbycircuitsiwhichf'areof 'sign-ple andin- -expensivez .typen bye-virtueel' of'-liaving-=eertairr4 con- :trol-1 elements inocommon.
Amongtthetmoresignieantf-advantagesfoftthe --'apparatusf'o-@thefinventiona isithethigh 4thermof; dynamice-ciency-thereof; this advantjage-v being f achieved, .ini they manner fully-#setf-fo'rth` irl-what Mfol1ovvs,,` by fvirtueofilthe :facts that refrigerant condensed in one evaporator, in orderto defrost -`-thefl.same, is. Ive-evaporated in the---other evaponatur, thereby.;being-*immediately-useful to -pro- Ivide refrigeration; inw said @then evaporator.
Theizapparatus is also advantageous in that it f utilizes; f simple Connell-elements of 1- known -and .-proved type.` i2 In .this connection the various 4.oon-V x trol functions 'are preferably-carried out through z'theivgagency of simple solenoid-*operated f :valves sog-,employeQ/in ,-the; fsysteln:,thata.'` lleakage atathe valves,l as lrflongfas; s': not.: excessive, does :not ,seriously impair :the-' foperability of4 theg equipment.
Additionallythe apparatus iszconsi-derablyless expensvethan, otheryknown types: of ,defrostng ,equinment, andl partcularly is.,.ths,the. oaser as compared with, devicesl ofthe type f which utilize resistance heating elements ,arranged in heatwex- 'changeirelationwith the evaporator.
`.In the achievement."ot-theabovesstated general -v objectives l. 'vprovidegeinz atrefrigerationi. system including a pair ofvseries-connected evaporators,
a -paiixof.ocestriorsors one .fofowhich isfdisposedsbeis Y olisposedk between/theotwo'sevaporators. is VYfur-thereincluded :apparatusaprovidingtnselectively, either-1 forxcondensationxof gaseous. nretween the .condensinglmeans and vthe evaporator which is= to be1y defroste-a-nd tthe; other-i'ofJ-.Which '-Ihere frigerant within ones ofetho .s ev ap oratorstlan d; :oonsequentLheatingeofetheifsame forgdefrostingfpurposes, or -frforf.modulationfi'of sthearef-rigerating temperature of'- thatoevaporator, the/` stated;L appara-tus taking:l thefform fotnaepair 50i-v: conduits each arranged :to :by-pass yan-=`associat'edu-.onez,of said restrictors; /utogether .wvvitlmv controlfnmeans erant is -zdesi-red,` tto..causeerefrigerant .sto'isflow l' through .one oflsaidrconduitsbyepassing onlyzzthe restrictor which is associated iwithtthe evaporator t0 be l defrostednThe control meansmfurther A serves,` When modulationI f of :tthefarefrigerating temperature of th'el latterfhevaporatOrl:is desi-red,
to t eausevnow ofsrefrigeranlthnouglr thefotherrof saidconduits thy-passing. onlyttheiotherf.restrioton I The concepts i oi= :the a.irvventions` areeapplicable,
generallyntoarefrigerationmaohine `in whichlitfis nested evaporators Without interferingnvzithwthe operation o-ffstherothena on: Aton"moda-1ate thet refrigerating-ftemperature?.ofoneonlgv of 'the evapofir .The manner inrwhich the-foregoingsoloects and advantagestrnaytbest be'. achieved:ltvillbesunder- .comprises as1diagrammeziolrepresentation--fof` a s preferred.` .embodiment oftmyoinvent-ion.
1 z N 0W makingnfzmore-l detailed; reference :Atogwthe drawing; it Willtbe seenuthat-theillustratediem- :zone to'g: ehe. ,-cooledn @that evaporator; al 25 being @,adapted; to v:loool e;the:fzLeompartmentitshowndiagrammaticallyf: at; i4; and theaevaporatoniloeing arranged-1.tovfirefrigeratetthef compartments I 5.o; A pair of restrictors H and.z I'evvh'ichiLprefenablyzare Of fthevapillarv tube type providelfonon on re- .rigelantf from-fthe@ fcandensert Lisanne-spannen o. the. same. .inthe evaporator@ I Zanglg l .3k-.the
resulta-nt Warm gaseous refrigerant being reto by-pass an associated one of the restrictorsA I6 and I1. Thus the conduit I9 is arranged to by-pass the restrictor I6 and the conduit 20 is similarly arranged as respects the restrictor l1.
Means is provided to control the flow of refrigerant through the by-pass conduits and, for the purposes of this disclosure, this means takes the form of a pair of solenoid-actuated valves of known type, shown diagrammatically at 2| and 22, the valve 2| controlling flow of refrigerant through the conduit |9 and the valve 22 controlling ow through the conduit 20.
The apparatus further includes three pressureresponsive temperature control devices which are preferably of the known Sylphon bellows type, these temperature control devices being shown at 23, 24 and 25. As will be more fully understood from what follows, the device 23, which is provided with a control bulb 23a, is responsive to the temperature of the evaporator i3 which refrigerates compartment l5, this compartment preferably comprising a low temperature compartment adapted for the storage of frozen foods. When normal refrigeration is required the compressor l is placed across the line L through conductors 26 and 21, under the control of a switch 28 associated with the device 23.
A main switch of the double-throw, doublepole type is shown at 29, this switch serving to control the defrosting operation and including a pair of switch blades or arms 30 and 3| cooperable with associated contacts which appear in the drawing. It is to be understood that this switch is moved between left and right-hand terminal positions, to initiate and to terminate the defrosting cycle, such movement of the switch being under the control of any suitable actuator (shown diagrammatically at 32), such for example as any one of a number of known timing devices. Alternatively the switch may be controlled manually.
It is contemplated that the valves 2| and 22 beof the normally closed type, that is, of the type which remains closed in the absence of supply of electrical current thereto. The operation of the equipment during defrosting is as follows:
Upon movement of the main switch 23 to the left-hand (dotted line) position as viewed in the drawing, valve 2 is placed across the line through the contacts of a switch 33 (this switch is associated with control device 25 and, as later described, is responsive to the temperature of the evaporator |2 to terminate the defrosting operation should it not first be terminated through movement of the main switch 32), through the right and left-hand blades 30 and 3| of the main switch, which then occupies the left-hand position shown in dotted lines, and thence through a conductor 34 and the aforesaid conductor 21. Energization of the solenoid associated with valve 2| results in opening the valve and consequent iiow of refrigerant through the conduit |9, bypassing the restrictor IB.
It is to be noted that this operation takes place independently of the control normally imposed by the device 23, since the switch contacts 4 of that device are shunted through the blades of the main switch and the conductor 34. It will also be observed that when defrosting is initiated in the manner above described, the compressor is energized, regardless of the position of the switch 28, since the compressor is also placed across the line through conductors 26 and 21 and through the left-hand blade of the main switch 29. Valve 22, which is under the control of pressure-responsive switch device 24 (through the right-hand` blade of the main switch 29) remains unenergized, and therefore closed, during the defrosting operation.
Immediately upon opening of the valve 2| gaseous refrigerant ows through the conduit I9 and is delivered directly to the cool, frost-laden evaporator |2 wherein it is condensed. Such condensation results in a transfer of latent heat which warms the evaporator and defrosts the: same, as will be understood without further description. It is particularly to be noted, how-- ever, that in accordance with` the invention the condensed refrigerant present in the evaporator |2, as a result of the defrosting operation, flows. through the restrictor I1 and is avaliable to produce refrigeration in the lower temperature evaporator I3. Thus refrigeration is continued at the second evaporator, it being apparent that the thermodynamic efficiency of the system is high since the condensed refrigerant is immediately available to produce useful refrigeration in'. the evaporator I3.
Preferably, although not necessarily, the defrosting operation is terminated by opening of the contacts of switch 33, under the control ofi feeler bulb 25a, which latter is directly associated with the evaporator being defrosted. As will be apparent from the drawing, opening of the: switch 33 de-energizes the solenoid associated with valve 2l and, consequently, refrigerant is, again liquied in condenser and flows through the restrictor I6 to be volatilized in evaporators. |2 and 3. Should the switch 33 not terminate the defrosting operation, the valve 2| will be de energized and closed, and the defrosting operation therefore terminated, upon right-hand movement of the main switch 29. As will be recognized by those skilled in the art to which the present invention pertains, a timer or other device can be utilized directly to return the main switch to the right-hand position, and thus reestablish the normal refrigeration cycle, without inclusion of control device 25 and switch 33. A number of alternative defrost control arrangements are now well known, and maybe utilized in practice of this invention, but the foregoing description is sufiicient for purposes of the present disclosure. Y
The apparatus has an additional important function which is the modulation or controlof the refrigerating Vtemperature of the compartment I4. Valve 22 and temperature-responsive switch device 24 perform this function in cooperation with the main switch 29. It will be noted that device 24 is also provided with a switch shown at 35, and further includes a control or feeler bulb 24a. whichis responsive to the temperature of the atmosphere within the compartment |4. Under conditions of normal refrigeration, when the main switch occupies the righthand position shown in full lines, the valve 22 serves asa means for controlling the temperature of evaporator l2, and thence of compartment I4, byeffectng controlled passage of refrigerant through the conduit 20 bil-passing the secondre- E3 strictor i1. When the temperature of the air within the compartment It reaches a predetermined upper limit switch 35 closes and the solenoid of valve 22 is placed across the line through the agency of the contacts of said switch 2li, and through the right-hand blade of main switch 29 which latter is, of course, arranged in series circuit with the device 23 which serves to energize the compressor under norznal conditions of operation. lEnergization of the solenoid `associated with valve 22 opens that valve and, since restrictor I'I is by-passed, the pressure in evaporator I2 becomes equalized with the pressure in evaporator I3 and the temperature within said evaporator I2 is therefore reduced and approaches the temperature or" the colder evaporator i3. When the temperature of compartment I4, as sensed by the feeler bulb 2da, is again reduced to a predetermined lower limit, switch 35 is opened by control device 24 and the solenoid associated with valve 22 is de-energized. `Such de-energization results in closure of the valve 22 and re-insertion of the restrictor II into the circuit. The pressure in evaporator I2 accordingly rises, as does its temperature. Under all normal operation, however, including the defrosting cycle, the temperature of evaporator I3 remains substantially unchanged since the pressure within the latter evaporator does not vary materially and since all of the refrigerant supplied to the evaporator i2 flows to the evaporator I3 prior to return to the compressor.
It is to be understood that the specific switching devices and the paticular flow control means shown and described may be varied without departing from the broader aspect of the invention. For example, although normally closed valves are described, the switching circuit could be modified in such manner as to make it possible to substitute a normally open valve for the valve shown at 22, with a resultant saving of power. Additionally, modified ow of refrigerant, to supply gaseous refrigerant to evaporator I2, may be accomplished without the use of a valve. In any case, however, the restrictors I6 and I'I are rendered active, or the action thereof is modified, in accordance with the foregoing description and in such manner as to achieve the several functions of the system.
From the foregoing specification it will be evident that this invention provides novel and unusually eicient apparatus making it possible to utilize gaseous refrigerant to defrost one of a pair of series-connected evaporators, without interfering with normal operation of the other of said evaporators, and `also to provide for ready and accurate control of the refrgerating temperature of both evaporators.
1. In a series-now refrigeration system, refrigerant circulating means, iirst and second series-connected evaporators, a pair of restrictors one of which is disposed between said circulating means and said rst evaporator and the other of which is disposed between said rst and second evaporators, and apparatus providing, selectively, either for condensation of gaseous refrigerant within said rst evaporator and consequent heating of the same with continuance of normal refrigeration Within said second evaporator, or for modulation of the refrigerating temperature of said first evaporator, said apparatus comprising: a pair of conduits through which refrigerant may iiow, one conduit being arranged to by-pass the restrictor which is disposed between said circulating means and said first evaporator, and the other conduit being arranged to by-pass the restrictor which is disposed between said first and second evaporators; and means including a rst valve device adapted to control flow of refrigerant through said one conduit, said rst valve device being effective, when opened, to cause gaseous refrigerant flowing from said circulating means to by-pass said rst restrictor only and to flow into said rst evaporator through said one conduit, whereby to effect condensation of gaseous refrigerant Within said first evaporator, said means further including a second valve device adapted to control ow of refrigerant through said other conduit, said second valve device being responsive to predetermined temperature conditions at said first evaporator to move to open position and to cause flow of refrigerant through the said other conduit by-passing said second restrictor only, whereby to modulate the temperature of said first evaporator.
2. A refrigeration system in accordance with claim l, and further characterized by the in clusion of a switching device adapted to control said second valve device to effect the recited modulation, said switching device including 'a temperature-sensitive element disposed in heat exchange relation with said first evaporator and being responsive to variations from predetermined temperature conditions at said first evaporator to control said second valve device and to initiate and terminate flow of refrigerant through the said other conduit.
3. A refrigeration system in accordance with claim 2, and further characterized by the inclusion of a second switching device having a temperature-sensitive element disposed in heat exchange relation with said first evaporator and being responsive to an elevated condensing temperature at said iirst evaporator to control said first valve device and to terminate ow of refrigerant through said one conduit.
MALCOLM G. iSHOEMAKER.
References Cited in the le of this patent UNITED STATES PATENTS Brandin Feb. 19, 1952