US 2706894 A
Description (OCR text may contain errors)
April 26, 1955 M. G. sHoEMAKER 2,706,894
Two TEMPERATURE REFRIGERATOR Filed July s, 1952 2 sheets-sheer 1 April 26, 1955 M. G. sHoEMAKER 2,706,894
Two TEMPERATURE REFRIGERATOR Filed July 3, 1952 2 Sheets-Sheet 2 V" j /G' *3' l(5a* d@ J7 'h 4,0 x
JZ J j @law/n, sf- M United States Patent O TWO TEMPERATURE REFRIGERATOR Malcolm G. Shoemaker, Doylestown, Pa., assignor t Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application July 3, 1952, Serial No. 296,995
Claims. (Cl. 624) The invention hereinafter disclosed and claimed relates to refrigeration apparatus, being particularly concerned with household refrigerators of the kind which include separate freezing and food storage compartments each provided with evaporator means adapted to maintain the associated compartment within a predetermined temperature range.
Heretofore there have been two fundamental types of household refrigerators commercially available, the older type, which was long regarded as standard in the industry, being so constructed that both the freezing and the food storage areas are cooled by a single evaporator formed to dene the freezing area. It is now well recognized that it is impossible to obtain stable and independent control of the temperatures prevailing in both the freezer section and in the general food storage area of a refrigerator, when a single cooling element is utilized to refrigerate the entire cabinet. At best, each design of this kind represents a compromise between the desired frozen food temperature and an acceptacle temperature within the food storage zone. Also, rapid accumulation of frost upon the evaporator has constituted a serious problem.
Recently automatic defrosting of this single evaporator has been resorted to, but it has been realized that for a number of important reasons such defrosting is not very satisfactory. It results in warming of the contents of the freezing compartment, creates an icing problem within the compartment, and causes stored packages lto become cemented together, theseshortcomings being common to all systems which involve automatic defrosting of the freezer section.
The second of the above-mentioned fundamental types of refrigerators is of more recent origin, and it is with improvements in this latter class of machines that the present invention is concerned. In this second type the freezing compartment is isolated from the rest of the refrigerator in order that frost accumulation therein may be minimized and, since this arrangement precludes use of the freezing evaporator in refrigerating the food storage area, the latter compartment is cooled by an auxiliary evaporator.
Prominent among currently available refrigerators of this kind is the type in which the lower or food storage compartment is refrigerated through the agency of tubing secured in convoluted arrangement about the exterior surfaces of the inner liner which denes the food storage compartment. This tubing and the liner surfaces which it refrigerates are operated at a temperature value above the freezing point of water, but since they are necessarily maintained at a temperature lower than the temperature of the air within the food storage compartment, condensation upon the liner walls has constituted a very serious problem. Attempts have been made to meet this problem by utilizing, in addition to the evaporator which cools the walls of the inner liner, a small subfreezing evaporator disposed within the food storage compartment and upon which latter evaporator the deposition of moisture is substantially localized. By effecting periodic defrosting of this auxiliary evaporator it has been possible, to Some extent, to ameliorate the condensation problem.
While it might at iirst appear that constructions of the kind last-mentioned would be eminently satisfactory, such has not proven to be the case. Refrigerators of this kind frequently rely upon relatively complicated temperature control devices and valving arrangements and, because of the expense inherent in refrigerating a cabinet through the walls thereof, are too costly to meet the requirements rrice of a wide market. Further, and perhaps more importantly, it has been difficult to maintain stable temperatures within the freezing and food storage compartments under the widely varying ambient temperature and usage conditions encountered in practice.
With the foregoing in mind, and in the broader aspect, it is an object of my invention to provide a truly automatic refrigerator of the multi-compartment type, in which the freezing compartment will be held at a uniform zero-zone temperature and the food storage cornpartment will be capable of maintaining desired stabilized water load temperatures, for example in the region of 38 to 40 F., regardless of changes in ambient temperature and almost independent of the usage demands made upon the refrigerator. Importantly this improved refrigerator is characterized by virtually complete elimination of the aforesaid condensation problem which has been one of the primary diificulties encountered with previous multi-compartment machines.
It is a further object of my invention to provide a refrigerator of the mentioned type which includes control means of such a kind that refrigeration is continued, and temperatures positively maintained, within the freezing compartment throughout the entire defrosting cycle of the evaporator portion which cools the food storage compartment and controls its humidity.
Additionally this invention has as an object the provision of such a refrigerator in which factory pre-set control devices, requiring no adjustment by the user, may be employed, and in which a super-freeze adjustmcntto enable quick freezing of desserts and the likeis possible without sacrice of other features of the apparatus and without interfering with defrosting of the evaporator which cools the food storage compartment.
The apparatus of my invention is featured by the fact that defrosting is accomplished automatically without the use of clocks, timers, electric heaters, or the like, and it is noteworthy that, as fully set forth hereinafter. the particular mode of defrosting utilized in practicing the invention is in itself a factor serving to maintain the desired temperature within the food storage compartment throughout a wide range of ambient temperatures.
In the achievement of the foregoing general objectives, and rst briefly described, this invention utilizes, in addition to a freezing evaporator, a relatively large evaporator preferably of plate-like form disposed vertically within the food storage compartment, in combination with novel refrigerant circuitry, flow through which is controlled primarily from the freezing compartment and including auxiliary control means responsive to temperatures at Said plate-like evaporator to establish and terminate, cyclically, the ow of refrigerant to the latter evaporator and thereby to cause it to cycle between a predetermined minimum temperature value well below the freezing point of water and a predetermined maximum temperature value slightly above freezing. This plate-like evaporator can constitute the sole means providing refrigeration within the food storage compartment, cooling of the walls of the inner liner which defines that compartment being unnecessary. It is to be emphasized that the particular refrigeration circuitry and the control apparatus utilized therewith results in automatic maintenance of unusually stable temperature conditions within both compartments, and with no continuously variable temperature control means being required,
In this improved refrigerator the pair of evaporator portions which cool the two compartments and one of which limits the humidity of the food storage compartment, areutilized in combination with extremely simple and inexpensive means making it possible to continue refrigeration within the freezing compartment while yet positively preventing flow of liquid refrigerant to the food storage evaporator during defrosting of the latter.
The manner in which the foregoing and other obiects and advantages of my invention may best be achieved will be fully understood from a consideration of the following detailed description taken together with the accompanying drawings, in which there is illustrated a preferred embodiment of the invention.
In the drawings:
Figure 1 is a face, perspective, view of a multi-compartment refrigerator incorporating apparatus of the present invention;
Figure 2 is a sectional view, on an enlarged scale, of the refrigerator shown in Figure 1, the view being taken through the vertical midplane of the cabinet;
Figure 3 is a perspective view (diagrammatic in certain respects) illustrating the refrigerant circulating system of the invention and the thermally responsive control apparatus employed thercwith; and,
Figure 4 is a graphical presentation of certain performance characteristics of my improved apparatus, as compared with refrigeration equipment of known type.
Now making more detailed reference to the drawings, and initially to Figures l and 2 thereof, it will be seen that the invention is therein illustrated as embodied in a household or domestic refrigerator comprising an outer cabinet shell and an inner shell or liner member 11, spaced and insulated from the outer shell 10 by means of any suitable insulation, shown at 12. As is customary, breaker strip means 13 of low thermal conductivity extends about the forward face, or throat area, of the cabinet and bridges the gap between the said outer shell 10 and inner liner 11. It will be understood that the cabinet also includes a compartment housing a com presser-condenser unit of any desired type. The condensing apparatus is shown somewhat diagrammatically in Figure 3, but illustration of those portions of the cabinet which house the same is not necessary herein, since the present invention is not concerned therewith.
As clearly appears in both Figures 1 and 2, the space within the inner liner 11 is sub-divided into an upper freezing compartment 14 and a lower food storage compartment 15, by means of a thermally non-conductive partition or vapor barrier 16 which thermally isolates the freezing compartment from the food storage compartment and prevents migration of moisture from the lower compartment to the freezer. Upper and lower insulated doors 17 and 18, of known type, provide access to the two compartments, being adapted to seal the cabinet by seating against the aforesaid breaker strip means 13.
The upper surface of the partition or vapor barrier 16 is dished as shown at 19, in order that the partition may serve to collect frost and moisture during cleaning and occasional defrosting of the freezing compartment. The partition is removable to facilitate cleaning operations and, to this end, the access panel 20 which closes the upper rear portion of inner liner 11 is provided with a horizontally extending indented area 21 within which is received a mounting flange or extension 22 provided along the rear edge of partition 16. The forward part of the partition is supported through the agency of a pair of releasable latch members 23 which engage portions of the side wall structure of the cabinet. Gasket means 24, carried by the cabinet, cooperates with the partition to assist in sealing the same. A central drain opening 25 may be used during the above-mentioned cleaning operations.
The two compartments 14 and 15 are each provided with individual cooling means (see particularly Figures 2 and 3), the cooling means for the freezing compartment taking the form of a rectangular evaporator 26 of known type, whereas the lower compartment is cooled solely through the agency of a plate-like evaporator member 27 supported, in any convenient manner, upon the rear wall of inner liner 11. As will be fully described hereinafter, the lower, plate-like evaporator 27 is periodically defrosted by automatic means and to collect the moisture which drops therefrom during the defrosting operation there is provided a trough 28 and an associated drain receptacle 29.
As mentioned above, the two evaporator portions 26 and 27, in combination with a novel circulating and control circuit, serve to maintain both compartments of the refrigerator at stable, predetermined temperatures regardless of changes in ambient temperature, and accomplish this purpose in such a way as completely to eliminate the condensation of moisture within the food storage compartment. The circuitry used to achieve the objects of the invention, and the manner in which it operates, is described in detail in what follows, with particular reference to the showings of Figure 3.
The system shown in Figure 3 includes, in addition to the aforesaid evaporators 26 and 27, a compressor 30 and a condenser 31 connected in refrigerant flow rcliOIlship with said two evaporators through suitable conduits including a restrictor 32 of the capillary tube type and a suction conduit 33. Liquid refrigerant derived from the condenser 31 ilows through the capillary restrictor 32 and is delivered to a liquid and gas separator 34, passing through a suitable drier 35 just prior to entry into the separator. As indicated above, the food compartment evaporator 27 is caused, cyclically, to pull down to a predetermined minimum temperature, for example 0 F., and thereafter to rise to a predetermined maximum temperature slightly in excess of the freezing point of water, for example 36 F. The manner in which this cyclic operation, under the influence of the control means provided, serves to maintain stable temperature conditions Within the two compartments 14 and 15 will be mentioned in greater detail hereinafter. The operation of the refrigerant circulating system of Figure 3 will first be described under the condition in which both evaporators are in series circuit and are fed with liquid refrigerant. Under the above-mentioned condition, liquid refrigerant accumulates in the separator 34 and passes to the evaporator 27 through a conduit 36 which includes a short auxiliary restrictor 37. Liquid so delivered passes through the convolutions 38 secured to the plate of evaporator 27 and thereafter ows into the upper freezing evaporator 26 through a conduit 39 and a connection 40. The latter connection leads to the convolutions 41 provided upon the upper surface of said evaporator 26. As indicated above the evaporator 26 is of known type, being of the kind in which refrigerant supplied to the upper convolutions 41 flows into parallel passages 42 (through tubing not shown) and the gaseous refrigerant which results from the normal refrigeration process is collected in a pair of headers, one of which appears at 43. From these headers the gaseous refrigerants returned to the compressor through the suction ine During this phase of the operation of the apparatus the switching devices presently to be described cause the upper evaporator 26 to cycle between predetermined upper and lower temperature limits, for example between +1 and 10 F., whereas the temperature of the lower evaporator is reduced to the mentioned zero-zone value. In order to achieve the aforesaid cyclic operation of the lower evaporator 27 the refrigerant circulating system is provided with a solenoid valve 44 of known type, which valve is disposed in a by-pass passage provided by two conduits 45 and 46. Conduit 45 connects the valve with the lower portion of separator 34 and conduit 46 leads to the entry point 40 of the upper evaporator 26. As will later appear, this valve-controlled passage, in conjunction with the separator 34 and the auxiliary restrictor 37, makes it possible completely to terminate flow of liquid refrigerant to the lower evaporator 27, in order that said lower evaporator may be defrosted without interfering with normal operation and cycling of the upper evaporator 26.
A pair of temperature-responsive control devices 47 and 48 are provided, the device 47 having associated therewith a feeler bulb 47a so disposed as to render the device 47 responsive to temperatures at the lower platelike evaporator 27. It is to be understood that the bulb 47a may be associated with the plate as shown, or it may be disposed in contact with the tubing 38, or spaced somewhat from the plate assembly, depending upon the requirements of the particular system. Any of these alternative locations of the bulb 47a is contemplated by description of the device 47 as being responsive to temperatures at the evaporator 27. The second switch device 48 is provided with a similar bulb 48a and while, in the embodiment illustrated, this latter bulb is directly associated with the tubing 41 disposed upon the upper surface of evaporator 26, variation in location of the bulb is feasible.
As will be apparent from a consideration of Figure 3. the compressor 30 is directly under control of the switch device 48 which, in response to a predetermined increase in the temperature of the freezer evaporator 26, places the compressor 30 across the line L. The second switch device 47, in response to the temperature condition prevailing at evaporator 2'7, is adapted to energize the solcnoid valve 44 and thereby to move said valve to open position and to provide for ow through the 'oy-pass passage 46. Since the valve 44 can be energized through switch device 47 only when the contacts of switch device 48 are closed, it will be apparent that control of refrigeration at the evaporator 27 is exercised when the compressor 30 is in operation, which, in turn, is under control of device 48. Because the compressor is controlled solely from the switch device 48 it might at first appear that maintenance of proper temperatures within the food storage compartment 15 would be adversely affected by unusual conditions prevailing at the freezer. However this problem is met in very simple manner by proper adjustment of the calibration of switch device 48 and, specifically, by narrowing the differential between cut-in and cut-off of said device 48, to a value such that sufficient cycles of the compressor occur under any conditions encountered in practice to assure adequate opportunity for operation of the lower evaporator 27.
The solenoid valve 44 is of the normally closed type and for this reason closing of the contacts of switch device 47, in response to attainment of the predetermined minimum temperature at evaporator plate 27, results in opening of said valve 44. When the valve has been opened the liquid refrigerant within the separator 34 ows directly to the evaporator 26 through the by-pass conduit, since the auxiliary restrictor 37 causes the circuit through evaporator 27 to present appreciably more restriction to the flow of liquid refrigerant than is presented by the alternative circuit through upper evaporator 26. Thus, when the valve is open, liquid refrigerant bypasses the evaporator 27 completely, the auxiliary restrictor 37 passing only a very small quantity of gaseous refrigerant. As will be understood, complete termination of flow of liquid refrigerant through the plate 27 enables heat which flows from the lower compartment 15 to said plate-like evaporator 27, to melt the frost which has accumulated upon the plate during the preceding period when the plate was supplied with liquid refrigerant. In this way moisture which would otherwise be deposited upon the walls and other surfaces of the food compartment 15 is removed. The melted frost is, of course, delivered to the above-mentioned receptacle 29 through the agency of trough 28. The switch device 47 is so calibrated that the contacts thereof are not again opened (with resultant closing of the by-pass valve 44) until the plate 27 has attained a temperature somewhat above freezing, for example in the region of 36 F. This ternperature corresponds to a temperature within the food storage compartment, under stabilized conditions, of about 40 F.
It will be observed that both the inflow and the outflow passages 36 and 39 of plate 27, and a portion 32a of the main capillary tube restrictor, are disposed in heat exchange relation. This disposition of the aforesaid passages provides for transfer of sufiicient heat from the relatively warm liquid in capillary passage 32a to the colder refrigerant in the inlet tube 36, to elevate the said inlet tube to a temperature above 32 F. In addition, since the heat exchange relationship includes the plate outlet tube or passage 39, the heat of liquid available in the refrigerant flowing in the main restrictor warms the said outlet passage and prevents the cooling of plate 27 which would otherwise occur as a result of the thermal conductivity of said passage.
The mentioned heat exchanger does not form a part of the present invention, being fully disclosed and claimed in the copending application of Elmer W. Zearfoss bearing Serial No. 304,272, filed August 14, 1952. Further description of said heat exchanger is therefore not necessary herein. In brief, the described heat exchanger, while not essential to operation of the apparatus of my invention, is preferably employed therein, since it makes it possible for the evaporator plate 27 to rise to its predetermined maximum value rapidly and uniformly.
The following brief description of the entire operating cycle is given in summary and in the interest of a thorough understanding of the advantages of the invention. In this description it is assumed that operation is started with a warm cabinet.
(a) Under the assumed condition the contacts of the freezer control device 48 are closed with the result that operation of the compressor is immediately initiated. Due to the elevated temperature within the food storage compartment 15 the contacts of the control device 47 re main open, with the result that the solenoid valve is closed and liquid refrigerant is delivered to the plate 27 as described above.
(b) As operation of the compressor continues, both evaporator portions 26 and 27 are reduced in temperature, the plate switch 47 first exercising control and terminating refrigeration within the plate by by-passing the same when the predetermined minimum temperature value at the plate has been achieved. This of course permits the plate to start its warmup, defrosting cycle.
(c) As soon as the aforesaid termination of flow of liquid refrigerant to the plate has been achieved, the entire capacity of the condensing system is concentrated in the freezer evaporator 26, the temperature of which continues to be reduced until the control device 48 ter-l minates operation of the compressor. The compressor now remains inactive until the device 48 again demands refrigeration.
(d) Warming of the plate 27 continues until said plate reaches its predetermined upper temperature limit (for example 36 F.) and, when this temperature is reached, the control device 47 is so actuated as to permit the solenoid valve 44 to close. If the compressor is at that time in operation, as will be determined by the refrigeration demand required of the freezer evaporator 26, liquid refrigerant is again caused to flow through the plate. If, however, the freezer evaporator has not yet risen to its cut-in point, refrigeration of the plate 27 is not resumed until the freezer control device 48 again calls for refrigeration and places the compressor back in operation. Occasionally there may result a slight delay in restoring refrigeration within the food storage compartment l5, but this delay is never of sufiicient duration to interfere appreciably with maintenance of proper temperatures within the food storage compartment.
By virtue of the described arrangement, socalled short-cycling of the compressor is prevented and there is no possibility of unnecessary tripping of the overload device which protects the compressor motor. Under conditions of high thermal load, plate 27 will be refrigerated during at least a portion of each operating period of the compressor, whereas at lower room temperatures, when the thermal load is correspondingly less, refrigeration at the plate 27 will occur less frequently and several cycles of the compressor may occur between successive operations of the plate.
(e) The temperature of the freezer is independent of both the temperature within the food compartment and the room temperature, and it can be set at any desired value. In practice it is preferred that the control devices be pre-set at the factory, the calibration being such as to result in the desired optimum temperatures within both portions of the refrigerator and with no adjustments required by the user.
It is evident, as has been stated above, that in order to insure complete defrosting of the plate the cut-in of the plate control device 47 should be set at a value a few degrees above the freezing point of water. lf the calibration is such that the plate reaches 36 F., the ternperature within the food storage compartment 15 must necessarily be a few degrees above this value. Experience shows that temperatures lying in a region between 38 and 40 F. are achieved. The optimum cut-out temperature of the plate cold control is determind by a number of design factors including plate size, compressor running time, and cabinet heat load. ln a representative embodiment of the invention which has functioned in a highly satisfactory manner, the cutout temperature has been in the neighborhood of 0 F.
The fact that the desired temperature within the food storage compartment is very closely maintained, although the temperature of the evaporator 27 varies over a rather wide range, is in large measure a result of the fact that the defrosting function is utilized as a factor stabilizing the cabinet temperature, and this without loss of temperature control within the freezing compartment. This aspect of the invention is now described further, with reference to the graphical showings of Figure 4.
In Figure 4 stabilized, average, water load temperatures for a given control setting are plotted, as ordinates, against ambient temperature, as abscissae. Since access to a refrigerator immediately affects the temperature within the cabinet, particularly the air temperature, it is common to judge the levelness or steadiness of operation under setabilized conditions when the cabinet has been closed for a considerable period of time, and to utilize water load temperatures rather than air temperatures. Thelower horizontal line 49 of the grap represents the median temperature of frozen food (there would of course be a relatively slight control spread to either side of this median temperature) and it will be seen from this line that the temperature within the freezing compartment is maintained at a substantially stable value throughout all room temperatures normally encountered.
The 32 F. cabinet temperature line is also shown on the graph, and the upper horizontal line 50 represents the food compartment temperature maintained by the apparatus of the present invention under the stabilized conditions mentioned. Again it is to be understood that an average temperature is designated, there being a fluctuation of about il" from the indicated temperature as a center line. The fact that both of the lines 49 and 50 are horizontal throughout the entire spread of room temperatures, and particularly considering the lack of complication of apparatus constructed in accordance with my invention, is an achievement.
Cabinet Water load temperatures which would normally be encountered within a conventional refrigerator, that is within a refrigerator in which a single evaporator cools the entire cabinet, are represented by the upwardly inclined line 51. The temperature at the intersection point of the lines 50 and 51 may be regarded as optimum desired performance. As shown by the inclined line 51, in lower room temperatures and particularly during over-night periods, the temperature within the conventional refrigerator may drop to freezing, or even below, this being a difficulty encountered in greater or less degree in all such refrigerators, if the evaporator is operated at a temperature sufficiently low to preserve ice cream and other frozen foods. 1t is particularly to be noted that the left-hand end of the line 5t), representing the performance of apparatus constructed in accordance with my invention, remains at the desired 40 value, and it is in this connection that the defrosting cycle assists in stabilization of cabinet temperatures.
Since the evaporator 27 which cools the food storage compartment must pass above freezing and complete its defrosting operation, before refrigeration at the evaporator 27 is re-initiated, it is evident that the temperature of the cabinet must periodically rise toward and above the` upper control point of switch device 47. Because of this fact it is impossible for the temperature within compartment 15 to drop below freezing, even under conditions of low ambient temperature. It will be noted that that portion of line 51, representing conventional performance, which lies above the above-mentioned intersection point, continues to rise. Thus, when the ambient temperature is high it is impossible to maintain a desired temperature in the food storage area of such a refrigerator when the freezer compartment is being satistied, and steadily maintained at a given preselected temperature. Control of the compressor is effected solely from the surface temperature of the evaporator and, ob-
viously, greatly increased heat leakage under high ambient temperature conditions makes it impossible to maintain level cabinet temperatures. This is in sharp contrast with the fact, as indicated by the right-hand end of line 50, that the cabinet temperature achieved by a refrigerator embodying my invention continues to remain level. Although the room temperature may increase, this very increase results in a corresponding increase in the on time of the evaporator and in a corresponding decrease in the time required for defrosting, that is, in the period of time required to reach 36 F. For this reason the evaporator 27 increases in effectiveness as the need for increased refrigeration arises. Therefore, and as discussed above, the mode of operation which results in periodic automatic defrosting of evaporator 2'7 also serves to stabilize the food compartment temperature at F both ends of the range of ambient temperatures.
Certain multi-compartment refrigerators recently introduced to the market achieve satisfactory temperatures within the food compartment, particularly if resort is had to the use of electric lights or other heaters, but since in such refrigerators the circulating system is controlled solely in accordance with the temperature of the evaporator which cools the food compartment, constructions of this kind do not result in maintaining the desired optimum temperature of stored frozen foods during defrosting of the food compartment evaporator. ln addition, the cost of the refrigerators referred to has been excessive.
From the foregoing description it will now be recognized that by the present invention there is provided a relatively inexpensive, truly automatic refrigerator of the multi-compartment type, in which the freezing compartment is maintained at a uniform zero-zone temperature and the food storage compartment is very closely held within an optimum temperature range, regardless of changes in ambient temperature and almost independently of the usage demands placed upon the refrigerator. In addition, the defrosting problem has been solved in the simplest possible manner without the use of timers, heaters, or the like, and without any interference with proper refrigeration of stored frozen foods. importantly, the aforesaid improvements are realized by a construction in which there is complete elimination of objectionable condensation within the food storage compartment.
l. In a refrigerating system of the type including refrigerant circulating means, a restrictor and first and second evaporator portions, and in which system flow of refrigerant is normally from said restrictor through said first and second evaporator portions in series and thence back to said circulating means, means, including a conduit, effective to cause refrigerant to by-pass said first evaporator portion and to flow directly to said second evaporator portion under a modified condition of operation, and means preventing liow of any liquid refrigerant to said first evaporator portion under the said modified condition of operation, said last means comprising a liquid and gas separator to which is delivered the refrigerant flowing from said restrictor prior to entry within said evaporator portions, said separator having a liquidcollecting portion connected to said by-pass conduit, a gas-collecting portion connected to said first evaporator portion, and an auxiliary restrictor connected between said gas-collecting portion and said first evaporator portion.
2. A system in accordance with claim l, and further characterized in that said separator comprises a vertically elongated receptacle having exit ports at either end thereof and an inlet port intermediate the length thereof, said inlet port being in communication with said restrictor, the upper of said exit ports leading to said auxiliary restrictor and being in communication with said first evaporator portion, and the lower of said exit ports being in communication with said by-pass conduit.
3. ln a refrigerator of the type including individual freezing and food storage compartments, a refrigerant circulating and control system, comprising: an evaporator associated with said freezing compartment; an evaporator disposed to present a sub-freezing surface within said food storage compartment, said evaporators normally being connected in series circuit; and means for cyclically operating said food compartment evaporator between a minimum temperature well below freezing and a maximum temperature in excess of freezing without interfering with the temperature desired within said freezing cornpartrnent, said means including; a conduit adapted to bypass said food compartment evaporator, a valve controlling flow of refrigerant through said conduit, means, including a gas and liquid separator and a refrigerant iiow restrictor disposed between said separator and said food compartment evaporator, insuring that no liquid refrigerant enters said food compartment evaporator when said valve is open, and a pair of temperature-responsive devices, one of said devices being responsive to temperatures at said freezing compartment evaporator to initiate circulation of refrigerant within the system and the other of said devices being responsive to temperatures at said food compartment evaporator to control said valve.
4. A refrigerator, comprising: separate freezing and food storage compartments; a closed refrigerant circulating system including condensing means, a main restrictor and first and second evaporator portions normally connected to form a series liow circuit leading from the exit of said main restrictor through said first and second tvaporator portions, sequentially, and back to said condensing means, said first evaporator portion being disposed in heat exchange relation with said food storage compartment and said second evaporator portion being disposed in heat exchange relation with said freezing compartment; and apparatus for periodically defrosting said rst evaporator portion and for making said rst portion effective to provide controlled removal of moisture from the air within said food storage compartment, said apparatus comprising; a by-pass conduit including valve means and having one end thereof disposed in the circuit at a location to receive refrigerant from said main restrictor prior to passage through said first evaporator portion and having the other end thereof disposed in the circuit between said two evaporator portions, means including an auxiliary restrictor of the capillary tube type disposed in the circuit between said location and the inlet of said first evaporator portion, said last means serving to prevent flow of liquid refrigerant to the said first evaporator portion when said valve means is open, and means responsive to temperatures in the vicinity of said first evaporator portion to control said valve means.
5. A refrigerator, comprising: separate freezing and food storage compartments, a closed refrigerant circulating system including condensing means, a main restrictor, first and second evaporator portions normally connected to form a series ow circuit leading from the exit of said main restrictor through said first and second evaporator portions, sequentially, and back to said condensing means, said first evaporator portion being disposed within said food storage compartment and said second evaporator portion being disposed in heat exchange relation with said freezing compartment; and apparatus for defrosting said first evaporator portion and for making said first portion effective to provide controlled removal of moisture from the air Within said food storage compartment, said apparatus comprising; a by-pass conduit including impedance varying means and having one end thereof disposed in the circuit at a location to receive refrigerant from said main restrictor prior to passage through said first evaporator portion and having the other end thereof disposed in the circuit between said two evaporator portions, said impedance varying means being adjustable to vary the flow impedance of said by-pass circuit between a relatively high value and a relatively low value, and means including an auxiliary restrictor disposed in the circuit between said location and the inlet of said first evaporator portion, said last means imparting to the path through said first evaporator portion a flow irnpedance of a value intermediate the impedance Values aforementioned, said last means serving to prevent flow of liquid refrigerant to said first evaporator portion when said impedance varying means is so adjusted as to cause said by-pass conduit to present the relatively low impedance value mentioned,
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