US3136138A - Refrigeration system having serially arranged evaporators - Google Patents

Description

June 9, 1964 G. MUFFLY 3,136,138

REFRIGERATION SYSTEM HAVING SERIALLY ARRANGED EVAPORATORS Original Filed June 4. 195'? 3 Sheets-Sheet 1 INVENTOR. 'lzrm Mllfilj June 9, 1964 G. MUFFLY 3,136,138

REFRIGERATION SYSTEM HAVING SERIALLY ARRANGED EVAPORATORS Original Filed June 4. 1957 3 Sheets-Sheet 2 IN VEN TOR.

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G. MUFFLY June 9, 1964 REFRIGERATION SYSTEM HAVING SERIALLY ARRANGED EVAPORATORS 3 Sheets-Sheet 3 Original Filed June 4. 1957 /5 INVENTOR.

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Z/IVE United States Patent 3,136,138 REFRIGETIQN SYSTEM HAVING SERIALLY ARRANGED EVAPORATOR This is a division of application Serial Number 31,205 filed May 23, 1960, now Patent No. 3,043,113 issued July 10, 1962, which is a division of my application Serial Number 663,526 filed June 4, 1957, now Patent No. 2,993,347 issued July 25, 1961. The invention relates to refrigerators, ice makers, and air conditioning systems, referring particularly to the latter. Various earlier patents and patent applications of mine are referred to herein as explanatory and to call attention to them as representing prior art in this field.

One object of this invention is to control a system having multiple evaporators in a manner which provides for heating a first evaporator while cooling one or more other evaporators.

Another object is to utilize the warming of one evaporrator to reheat air after it has been cooled to a lower-thandesired temperature in an air conditioning system for the purpose of reducing its humidity.

An additional object is to do the reheating, defrosting or ice releasing with specific heat of liquid refrigerant instead of with latent heat, thereby efiecting a considerable economy of operation.

Another object is to provide van improved type of refrigerant flow control which not only regulates normal flow of liquid refrigerant to an evaporator while it is actively cooling, but also opens wide to cause the evaporator to be heated by high pressure refrigerant.

Another additional object is to provide an improved method for defrosting one evaporator with warm liquid refrigerant which then expands in a second evaporator at higher efiiciency because the liquid has been cooled nearer to the evaporating temperature, thereby reducing the loss due to flash gas forming as the liquid enters the second evaporator.

With these and other objects in view, I describe the system and the refrigerator with reference to the following figures of the drawings:

FIGURE 1 is a partial front view of the left side of a refrigerator, showing the ice storage bin, water tank and pump as seen with the refrigerator door open.

FIGURE 2 is a side view of the parts seen in FIGURE 1, partly in section.

FIGURE 3 is a top view of FIGURE 2 on the line 3-3 thereof, partly in section and showing 'a top view of the ice maker and the ice storage bin.

FIGURE 4 is a diagram of the refrigerating system and of electrical connections to the various controls.

FIGURE 5 is a view of an evaporator suitable for use as a part of the ice maker, showing the two ice maker evaporators of FIGURE 6 as made in one piece prior to forming into the necessary U-shape.

FIGURE 6 is a section of FIGURE 5.

FIGURE 7 is a plan view showing how the triangular water tank fits into a refrigerator with revolving shelves to utilize space otherwise wasted.

FIGURE 8 is -a vertical sectional view of a household refrigerator of two-zone type showing parts of the system enlarged and in section.

FIGURE 9 is an alternative control and wiring diagram showing thermal instead of clock control of defrosting.

FIGURE 10 is a diagrammatic view of a refrigerating Glenn Mufiy, Application May 23, 1960,

Patented June 9, 1964 air conditioning system, illusimproved control method to system and a portion of an trating the application of my air conditioning.

FIGURES 1, 2 and 3 are arranged relative to each other in the common (3rd angle or American) relationship to aid in identification of parts, which are each indicated by the same numeral throughout the various figures. Referring to the three figures of sheet 1, it will be seen that the numeral 10 is located in the main food space of the. refrigerator cabinet which has portions of its outer insulated walls shown in section. 12 is the door of this cabinet closing the main food space, and 14 is the usual door gasket.

Within the main food space, which is to be held at a non-freezing temperature, are the ice maker and associated parts now to be described. The tank 16, of fiat rectangular form, is placed vertically in a rear corner of the food space, the two longer outer sides being contacted by the embossed portions of evaporators 18 and 19 on spaced round areas, preferably about one inch in diameter and arranged directly opposite each other. These evaporators may be combined in one, as shown later, and may be provided with fins 20 to aid in cooling the air in space 10 and by transfer of heat from the air to aid in releasing ice disks 22. These parts are best seen in FIG- URE 3, but an edge of evaporator 18 and portions of tank 16 are seen in FIGURE 1, indicating that the tank 16 extends upward beyond the evaporator 18 and is closed at its top to prevent air circulation from the food compartment 10 contacting the ice and water within the tank.

Water is circulated through the tank 16, entering from tube 24 at, or near, the bottom of the tank, under force of the centrifugal pump 26 driven by the motor 28. The pump is supplied from the tank 30 through pipe 32 and water overflows near the top of the tank 16 into the ice delivery chute 34 which guides the ice into the ice bin 36, the ice disks rolling or sliding on the wire 38, which serves as a track, while the water falls into the return tube 40 leading back into the water tank 30. A grid, or screen, 42 prevents any ice except very small pieces from falling into the water tank.

The tank 16 and evaporator 18 are here shown with the ice-making areas staggered in two vertical rows and set at an angle, but in some cabinets it may be preferred to place these areas in one verical row, making tank 16 narrower. Also the tank 16 may be parallel with a rear or side wall of the cabinet where that fits in with location of the ice bin 36. Another modification would to use two single-row tanks in parallel where space may be thus conserved.

The operation of the ice maker, which employs the principle disclosed in my US. Patent No. 2,774,223, is briefly as follows: Water flowing Upwardly through the ice maker tank 16 is cooled by the tank walls, particularly by inner areas where the outer wall of 16 is contacted by the raised evaporator areas. As the water is cooled a portion of it freezes upon these several small, directly opposed, areas in the form of thin disks which grow in thickness and diameter until the two disks of each pair join to form a thicker disk of the general shape shown at 22 in FIGURES 2 and 3.

After formation of ice disks to the desired size and shape, the cooling is cut off and the ice released by thawing free from the walls of tank 16, whereupon the flow of water causes the released disks of ice to fioat or roll out of the tank 16 (over the edge not sectioned in FIGURE 3) into the chute 34 and thence to bin 36, as above described. This cyclic operation continues, with pump 26 operating during ice release as well as during ice freezing periods until the ice accumulated in bin 36 has partially covered. the control bulb 44, which may be merely a part of the tube leading to it. Bulb 44 is connected with a switch to stop the motor 28, as will be described in more detail later herein. Bulb 44, shown broken in FIGURE 4, may be longer than shown in FIGURE 2 and is vapor-charged, thus. response is to any short coldest portion of the bulb.

When the water flow stops, the water in tank 16 drains back through tube 24, pump 26 and tube 32, into storage tank 30, thus no more ice is produced, even though evaporators 18-19 continue to be cooled.

The ice bin 36 is fitted with a door 46, hinged at 43 just above the top edge of wall and is formedwith two wings 52 fitting as tightly against the side walls of 36 as is practical for free movement of door 46. Thesewings are to prevent the ice from falling out when the door is opened, as provided for by the handle or lip 54.

Within the door, and preferably supported on it, is. the scoop 56 for use in removing ice from the bin and transferring it to drinking glasses or other dishes.

A drain 58 is provided in the bottom of bin'36 for returning meltage water to the tank 30. The edge forms a pan-like bottom for bin and drain 58 insures that meltage water does not overflow at 59. An opening in the pan or shelf supporting bin 36 serves to anchor drain tube or collar 58 to hold the bin in place, but it can be removed by lifting, say a half inch, which also releases 36 from 40. v

Water is supplied to tank 30 through tube 6%, which leads from a suitable valved connection with the water supply system of the house. The tube 60 is preferably connected within tank 30 to a float valve (not shown) which opens whenever the water level falls below a desired minimum level such as 62. When pump 2-6 sto s and water drains back into tank 39, the water therein will rise to some slightly higher level as indicated at 64. This higher level is preferably a considerable distance below the top of tank 30 to allow a capacity for storage of meltage water from bin 36 in the event of failure of the refrigerating system or of its current supply. In the event that tank 30 has inadvertently been filled too full, this meltage water will overflow tank 3b at a notch orhole 66 to the drain regularly provided for drip water in refrigerators. See my US. Patent No. 2,765,633 for such a drain to a pan (84) in the base of the cabinet with provision for evaporating the drip water to room air and ample storage capacity to hold the water until it is evaporated.

As in previous patents of mine, I have provided a faucet 68, here connected by means of tubes 70 and 32 with tank 30, for drawing cold drinking water. Since the amount of cold water which a normal family will use is many times the amount of blow-down water required to be removed from an ice maker (say of a normal daily production of 2 or 3 pounds of ice) in order to make clear ice, it is not considerednecessary to provide 'the blow-down feature in a household refrigerator; but

where this feature is desired, I propose to use the trap 72 which collects a denser portion of the water circulated by pump 26. This trap may be drained to the base of the cabinet for evaporation, as from the pan 84 of my US. Patent 2,765,633 above mentioned. The trap feature is shown as applied to a commercial ice maker in my US. Patent No. 2,672,017.

As seen in FIGURE 3, ice disks 22 roll from chute 34 in a direction which causes them to strike one wall of bin 36 and rebound to aid in filling the bin more uniformly than if allowed to drop at one point in the bin each time. Another arrangement would be to deliver the ice in a direction to pile up at thefront next to the door. This piling of the ice is preferably so related to the position of bulb 44 that the bin is nearly filled before ice begins to cover a part of the bulb, thus insuring the maximum supply of ice before stopping pump 26.

FIGURE. 4 illustrates the refrigerant and electrical circuits of a system. as used in a refrigerator such as the one shown in FIGUURES 1, 2 and 3, including the freezer evaporator which is designed to cool a drawertype freezer such as shown in my US. Patents Nos. 2,709,343 and 2,765,633. This freezer drawer is in the lower portion of the cabinet 18 which is broken off in FEGURES l and 2. Further details of it are shown in the above patents and pending divisions of them, including SN. 444,422 filed July 20, 1954, now Patent No. 2,866,322 issued December 20, 1958, SN. 464,041, filed October 22, 1954, now patent No. 2,894,374 issued July 14, 1959, and SN. 552,530, filed December 12, 1955, now patent No. 2,942,432 issued June 28, 1950.

The normal path of refrigerant while making ice and cooling the main food space is indicated in FIGURE 4 by the solid arrows leading from motor-compressor unit 33 to condenser 32, receiver 84 through valve 86, tube and expansion valve 913, to the ice maker evaporator Mixed vapor and liquid refrigerant leaving the ice maker evaporator flows through open valve 92 to the evaporator which cools the air in the main food space, returning as vapor through tube 96 to the unit 8 2. This circuit is modified in either of two ways:

First: When switch N2 is closed in response to the cooling of bulb M4 by ice forming within tank 116, the current actuates valve 1% to open it and valve 92 to close it, causing high pressure refrigerant to follow the dotted arrows, entering evaporator 18 to release the ice and then flowing through the expansion valve or other pressure-reducing device 108 to cool evaporator 94 while the ice is being released. This warms bulb 164 to reopen switch 1&2 causing normal flow through 9% and 92 to resume, cooling both 18 and 94.

Second: When bulb Ill-i located near the freezer evaporator, rises to the cut-in temperature of switch 112, the solenoid 114- is energized to actuate valve 86 and cause a change in the path of refrigerant flow. Liquid leaving receiver 34 now flows through the expansion valve or other pressure-reducing device 116 to the freezer evaporator 113 where it evaporates under a lower pressure than is required in the evaporators just mentioned, returning in vapor form to the unit 8h. e

The receiver 84 may be eliminated and vapor-lock restrictors (such as capillary tubes) used in place of expansion valves if the internal volumes and heat transfer capacities of thethree evaporators are so proportioned as to operate with valve 86 in either position. On the other hand, thermostatic expansion valves or float valves may be used at and 116 if desired.

The evaporators 18 and 94 are operated in series at substantially the same pressure while ice is being frozen, expansion device 108 being bypassed through the open valve 92. When valve 106 is. opened and valve 92 closed by the closing of switch 102 upon completion of the freezing of a batch of ice,'the evaporating pressure in evaporator 94- is controlled by expansion device 108. This pressure may be approximately the same as that previously maintained in the two evaporators by 90, but is preferably higher than that maintained in evaporator 11.8 by the expansion device 116. The evaporator 94 is intended to defrost during idle periods under the effect of heat picked up from the air in the main food space 10, whereas evaporator 18 is cyclically defrosted by warm liquid refrigerant and evaporator 118 is defrosted by hot gas or by the heating coil 129, as will be described.

It will be noted that the solenoid valves 1196 and 92 are energized simultaneously and only for the very short periods when ice is being released. This means that expansion device 1% is used only during ice releasing periods which may last for two to six minutes and occur only a few times in twenty-four hours, thus 108 may be a simple orifice or restrictor combined in the body of valve 92. This orifice for either 1% or 92 may be a simple hole, a tube or a groove in the valve orits seat, as shown by FIGURES 4, ll, l3, 16, 17 or 18 of my US. Patent No. 2,145,774, but in the present case free flow is in the same direction as the restricted flow, hence solenoids or other power means are provided to actuate the valves instead of opening them by reversal of flow. Valve 1116 differs from 92 in being designed to open instead of to close when current is supplied to its solenoid.

The switch 122 is of the usual thermostatic type which closes to operate the motor-compressor unit 80 when bulb 124 rises to the cut-in temperature of air in the main food space. This bulb 124 is also warmed to the cut-in point by either of the two resistance heaters 125 or 126; by 126 when switch 128 is closed and 112 is not. In this condition motor 28 drives the water pump 26 for the purpose of making ice. The long bulb 44 located in the ice bin 36, as seen in FIGURE 2, warms up when not contacted by ice to close switch 128 and start ice production, which continues in cycles controlled by switch 102 until a short section of bulb 44 is again contacted by enough ice to cool it to the cut-out point of switch 128 or the operation is interrupted by starting of freezer cooling or freezer defrost.

During operation of the ice maker the heater 126 insures that switch 122 remains closed to operate the compressor. If switch 122 remains closed, due to high air temperature in space 10, after the ice supply has been replenished, and switch 128 has opened, the compressor continues to operate, cooling the two evaporators 18 and 94 both of which now cool the air of the main food space 10, but no ice is made since the water pump 26 is now idle. This continues until bulb 124 is cooled to the cutout point of switch 122. p

The above description assumes that switch 112 has remained open, but in the event that the bulb 111), which is affected by changes of temperature in the frozen food compartment of the refrigerator, rises to the cut-in point of switch 112, the solenoid 130 is energized to open switch 132 and stop the water pump. This prevents unnecessary operation of pump 26 during cooling of evaporator 118.

Since closing of switch 112 heats coil 125, warming bulb 124 to close switch 122, the compressor is operated. At the same time solenoid 114 is energized tolift valve 86 and direct the flow of liquid refrigerant to expansion device 116 and freezer evaporator 118 while flow to evaporators 18 and 94 is stopped. Such flow is indicated by dot-dash arrows, only the freezer evaporator 118 being cooled.

Elements 114, 125 and 1311 are shown connected in series as none of them requires much current and they are always actuated together. They may, of course, be connected in parallel to employ the full line voltage if such design is preferred. Likewise it is optional whether 1116 and 92 be connected in parallel as shown or designed for lower voltage and connected in series.

The evaporating pressure in evaporator 11% may be (and preferably is) much lower than that in either of the other evaporators. By operating 18 and 94 separately from the freezer evaporator 118, a considerable gain of efficiency is obtained since the compresser is not required to operate at a low suction pressure except when low temperature cooling is required.

The clock motor 134 runs continuously and is mechanically connected to shift switch 136 to its dotted position during short periods, which may be one to seven days apart. Normally switch 136 remains in the position shown, and when actuated by the clock it moves to the dotted position, in which it remains for a very short period of say five minutes to energize the motor 138, which is connected as shown in my previous U.S. patent applications, to move drawer 14% in its opening direction away from 142, thus allowing the spring-actuated switch 142 to close so that heater coil 12th is energized to defrost the freezer evaporator 118. The drawer 140 is held open by the stalled motor 138 and 120 remains hot until the clock-actuated switch 136 snaps back to its solid-line position, thus cutting off the current from motor 138 and heater 120 so that the defrosting is terminated and the drawer 140 allowed to reclose under the force of gravity net, or optionally the tube 70 or a yieldable element as explained in the earlier applications above mentioned. It will be seen that switch 136 cuts off unit and all controls in the upper portion of FIGURE 4 during the freezer defrost. My preferred method for reclosing the drawer is by utilizing its own weight and the fact that it rolls closed on slightly inclined tracks.

The switch 144 may be manually moved to its dotted position by means of a pedal or push button 145 to energize motor 138 when it is desired to open the freezer drawer without energizing the defrost heater 120. This switch is designed to remain in the dotted position for a short period, during which the stalled motor 138 holds the drawer open. While the switch is in its dotted position the small heater coil 146 is energized, thus causing the bellows or diaphragm 148 to expand slowly. At the end of a preselected length of time the switch 144 assumes its normal solid line position, allowing the drawer to reclose, thus providing against the chance that the user may forget to reclose the drawer.

The lamp 150, located in the main food space, lights when door-actuated switch 152 is closed, in accordance with standard practice. Lamp 154 likewise lights when switch 156 is closed by the opening of the freezer drawer, whether the drawer opens for defrost, is pulled open by hand, or is opened by the manual operation of switch 144. The door or doors of the main food space may be opened at any time by closing switch 158 to energize the door motor 160, as disclosed in my earlier patents and applications above mentioned.

The door switch 152 (FIGURE 4) may have another contact to stop motor 266 as it lights lamp 150.

FIGURE 5 shows details of the ice maker evaporator or evaporators 18, here shown as one sheet metal evaporator in the flat to illustrate the refrigerant passages.

This flat evaporator is then bent into U-shape with contact areas 162 in alignment on opposite sides of the tank 16. The small sectional view in FIGURE 6 shows one of the passages leading to the outlet tube 164. This evaporator may also be formed by bending into U-shape and then opening the passages by means of hydraulic pressure, particularly in case the two sheets are welded together by the roll-bond method.

.FlGURE 7 shows a small plan view of a corner of the main food space and relationship of the water tank 30 to a swingable shelf, this being the next shelf below the tube 71) and faucet 68. The shelf 166, which can be rotated on vertical post 168, is fitted with a stop engaging stop 172 on vertical post 168 to prevent rotation in the wrong direction. This shelf can be rotated clockwise with no danger of interference between tube 70 and articles on the shelf. Also, the cut-away corner of the shelf next below the faucet makes room for a pitcher while filling it with ice water. Other shelves may be rotatable in either direction if desired.

An alternative arrangement, allowing all of the rotatable shelves to be alike, is to curve the tube 70 so that it clears the maximum radius of shelf 166. Such curvature may call for a clearance pocket in the liner of the cabimay be embedded in the walland the faucet 68 made accessible from outside of the refrigerator without opening a door of the cabinet, but it is preferred to keep the tank 30 and its connections more easily removable for service or cleaning. Another alternative is to make the tank 30 flat with one small horizontal dimension and locate it at one side of the shelf.

It will be seen that either the flat or tn'angular tank 30 may also be used in connection with sliding shelves, though in that case the designer may prefer to use a fiat vertical tank across the back of the space at the rear of the shelf, placing the ice maker tank parallel with the rear wall, as shown in FIGURE 5 of my U.S.. Patent No.

2,695,502, but including features of the present application.-

Certain modifications will be obvious to a designer familiar with my previous US patents and pending applications. For example the switch 102, its bulb 104 and in some cases the solenoid valves 106 and 92 can be replaced by elements from various of my earlier U.S. patents such as 2,145,777; 2,349,367; 2,359,780; 2,497,- 903; 2,774,223 or 2,795,112, to provide a preselected length for the ice-freezing period and a rninimuurn length of time for the release of ice. Another optional design would be to use a timer switch on the order of 52 in FIG- URE 2 of my Patent 2,709,343 in place of the thermallyactnated device illustrated by 144-148 in this application to end the freezer defrost operation and reclose the freezer drawer.

FIGURE 8 shows an application of this defrost method to a system having only two evaporators, of which the first one in series (18') cools the freezer compartment 180 of a two-temperature refrigerator which has an upper compartment 182 cooled by the second evaporator 94'. In this case the defrosting is to keep the freezer evaporator clear of frost rather than for the purpose of releasing ice. The evaporator 94' may be operated on a defrosting cycle, as 94 is in FIGURE 4. It may be used in part for making ice or ice may be frozen in the freezer 180, but the ice-making feature is omitted in FIGURE 8 to allow a simpler showing of the defrosting method.

The receiver and valve assembly 84 replaces 84, 90 and 106 of FIGURE 4 while elements 92' and 108' replace 92 and 100, no equivalent of 86 and 114 being required since no third evaporator is shown. Within the assembly 84' is the float 186, which is free to move on the stem 188 of valve 90 except as limited by collar 190. Armature 192, also movable on stem 188, lifts valve 90' when solenoid coil 194 is energized, causing 192 to strike the top head of 188 and lift valve 90 so that liquid refrigerant in 84' flows freely into evaporator 18' to defrost it, valve 92' being closed by the resulting rush of refrigerant to prevent defrosting of 94'.

Normally valve 90' is lifted slightly by float 186 after the liquid level in 84 rises to the height at which the float strikes collar 190 plus enough more to lift the added weight and overcome the pressure difference at 90'. At this time assembly 84 acts as a high side float valve assembly and as a receiver holding a definite volume of liquid refrigerant in the high side of the system, the liquid level being higher than shown.

Liquid and vapor flowing from evaporator 18 through tube 164 during such normal operation passes valve 92.

without lifting it, hence flows freely into evaporator 94 where the remaining liquid evaporates at substantially the same pressure as prevails in evaporator 18, while vapor flows to the motor-compressor unit 80. As shown, the stem of valve 92 is deeply fluted to allow fairly free flow of refrigerant and is heavy enough to keep itfrom lifting when refrigerant flow is normal, but the'valve is light enough to be lifted by a sudden increase of flow to close its port, leaving only the restrictor 108' open for flow from tube 164 to evaporator 94'.

Such normal cooling of the two evaporators in series occurs whenever unit 80 operates, except while evaporator 18 is being defrosted, as will now be described. When switch 196 is closed, preferably by a clock mechanism which closes it for a period of say ten minutes at intervals of say one week, the solenoid 194 is energized to lift its armature 192, opening valve 90' fully, the warm' liquid refrigerant stored in 84' rushes at high pressure into evaporator 18', driving before it much of the vapor already in 18. This excessive flow of vapor mixed with some liquid lifts valve 92 to prevent the warm liquid from flowing on into evaporator 94' under high pressure. The result is that the warm liquid at too high a pressure to evaporate defrosts evaporator 18' and flows slowly therefrom through the restrictor 108' into evaporator 94', which thus continues to be cooled while 18' is heated. At the end of the desired defrost period, predetermined by the clock-driven switch or by a thermostat, the switch opens the circuit of coil 194, allowing armature 192 to drop and valve to reclose. Valve 92 will, however, remain closed and liquid continue to flow through 108' into evaporator 94' until the pressure in 18' drops to a point which allows evaporation to resume in 18'. Meantime liquid collects in 84' until float 186 again lifts valve 90' slightly to resume normal operation.

The liquid volume normally held back in 84' by valve 90 is such that it will fill evaporator 18' with liquid during the defrost period. This volume is also such that the time required to refill 84' with liquid is ample to allow the pressure in 18' to drop to an operating level and valve 92' to reopen under its own weight before valve 90 is again opened by the float.

Whenever the air temperature in main food space 182 rises to the desired cut-in point the bulb 202 (located near but preferably isolated and shielded from direct cooling by 54') is warmed, closing switch 204 which starts both the motor-compressor unit 30 and motor 2% to drive the centrifugal fan drawing air through evaporator 94. Likewise when bulb 208 adjacent evaporator 13 rises to the desired cut-in point for cooling freezer it causes switch 210 to close, starting the motor compressor 80, but not the fan motor 206. Thus refrigeration starts whenever space 1182 rises to say 40 F. and also whenever space 180 rises to say 10 F., continuing until both switches 204 and 210 reopen at say 35 F. in space 182 and 20 F. in space 180. However, should switch 204 reopen before switch 210 the motor 206 will stop so that its fan no longer circulates air over evaporator 94, thus stopping most of the cooling of space 1182 while evaporator 13 continues to cool freezer space 130. Under this condition there is no danger of freezing foods on shelves above evaporator 94.

When the defrost switch 196 closes it energizes solenoid 194 to open valve $0 full, as before described. If motor-compressor 80 is not running at that time it will be started promptly by the rise of temperature of evaporator 18, thus insuring that the compressor operates during the defrost period and until evaporator 18' is again cooled down to the normal cut-out temperature of switch 210 as controlled by bulb 208.

The insulated drawer containing freezer space opens during the defrost operation, as disclosed in my US. Patent 2,765,633 issued October 6, 1956 and in my copending application S.N. 444,422, filed -luly 20, 1954, issued December 30, 1958, as Patent No. 2,866,- 322. The details of drawer operation are not shown in the present application as they are disclosed and claimed in the earlier applications, along with automatic and manual controls forinitiating the defrost. As in these earlier applications, the refrigerator cabinet is supported on the pan 212 which catches the defrost water from both evaporators and provides for its re-evaporation to ambient air. Theclock motor of switch 196 is here shown as running continuously, but it may alternatively be wired to run only while unit 80 operates, thus regulating the frequency of defrost periods on accumulated running time instead of upon elapsed time. Parts such as 84' and cold tubes, shown outside of the cabinet for convenience, will naturally be located inside or insulated.

FIGURE 9 shows another method of controlling defrost periods. Substituted for 196 is a thermostatic switch 214 with a bulb 216 located much as is 208, but preferably closer to a tube of 18'. The switch closes one drop of temperature instead of on a rise. Thus when the bulb 216 is embedded by frost and hence cooled to more nearly the temperature of evaporator 18' thermostatic switch 214 closes to initiate the defrosting period and reopens at a temperature which insures that all of the frost has been melted from evaporator 18'.

FIGURE 10 illustrates another use of the features of this invention, showing an application to air conditioning systems instead of to'household refrigerators. The

refrigerating system and the controls for defrosting can be identical except for size, but some modifications are included in FIGURE to shown optional designs which are also usable in the systems of FIGURE 4 and FIG- URE 4 and FIGURE 8.

When operating the evaporators 18" and 94" in air duct 218, with solenoids 220 and 222 not energized, both evaporators are cooled, just as are the corresponding evaporators 18 and 94 of FIGURE 4 or 18' and 94 of FIGURE 8. Expansion device 90" regulates the flow of liquid refrigerant to the two evaporators in series with valve 106" closed and valve 92" open. Now, if we energize the two solenoids 220 and 222 by moving switch 224 upwardly the valve 106" opens and valve 92" closes so that warm high pressure refrigerant liquid stored in receiver 84" below the outlet to 90" now flows into evaporator 18" and through it to expansion valve 108 which now controls flow into evaporator 94" since valve 92" is closed. The result is to warm evaporator 18" while cooling evaporator 94", just as in FIGURE 4 or 8, but for a different purpose.

In air conditioning systems it is often advisable to cool air to a lower temperature than is desired in the space cooled in order to condense out more of the water vapor contained in the air. After thus removing excess moisture the air is reheated prior to mixing with room air. Such reheating is wasteful of energy when done with steam or by passing the air over a portion of the condenser, but in the present case the heat is supplied by the specific heat of warm liquid refrigerant, which heat would otherwise cancel a portion of the refrigerating effect by causing flash gas to form in the evaporator. This economy of employing specific heat of liquid is important in both air conditioning and in the defrosting of an ice maker or a freezer evaporator, and for the same reason that the added heat is subtracted from the heat which otherwise offsets a portion of the refrigerating efiect.

The switch 224 energizes motor-compressor unit 80 when closed in either direction, but only when moved upwardly are the two solenoids 220 and 222 also energized to operate valves so that 18" reheats the air after it has been cooled by evaporator 94" and before delivery to the air-conditioned space. Since the refrigerants in common use today have rather high specific heats in their liquid phase there is a lot of heat available in 18 at no cost and the resultant cooling of liquid before it enters the expansion valve 108 represents an actual increase in the available latent heat capacity of evaporator 94".

Since operation .by the reheat method may be considered normal in certain air conditioning applications, the designer may prefer to arrange 220 and 222 to act in reverse, solenoids moving the valves to the positions shown instead of to their reheat positions. There are times and locations where both 18" and 94" will be operated as evaporators to obtain the maximum cooling effect on dry air, just as 18 and 94 of FIGURE 4 or 18' and 94 of FIGURE 8 are most of the time. The valves of FIGURE 10 may be controlled by a humidistat connected as thermostat 102 is in FIGURE 4 to switch between the full cooling and the reheat method of operation as the humidity varies. In other installations it may be the exception to operate both 18 and 94" as evaporators, but this does not change the basic similarity of the three systems shown. It is apparent that the valves of FIGURE 4 or 8 might be used in FIGURE 10.

The duct 218 is shown as provided with a drain for moisture removed from air by either evaporator. The drain from 94 to 212 is not shown in FIGURE 8, this being shown in my earlier patent applications mentioned herein. The armature of solenoid 22.0 in FIGURE 10 may have the lost-motion feature of solenoid 192 in FIGURE 8 if required to lift the valve against the high side pressure, or a valve such as 92' may replace 92" 10 in FIGURE 10, eliminating the solenoid 222. These are optional features of design which it does not seem necessary to show in drawings as they will be readily understood by those skilled in the art of refrigeration.

FIGURES 4, 8 and 11 show self-contained systems and FIGURE 10 shows a remote system, illustrating the fact that the principles of this invention are general in application. They may be employed in many types of systems, of which only three are illustrated. The condenser 82 may be either air or water cooled, with or without a separate fan. While no specific defrosting means is shown for evaporator 94, 94 or 94" they are normally located in air above 32 F. and may be assumed to defrost at each cycle. In FIGURE 8, for instance, the fan motor 206 may be operated while the system is idle to defrost evaporator 94.

Thermostatic switches are shown diagrammatically, but are assumed to have the usual readily accessible adjustments. During defrost of evaporator 18' in FIGURE 8 the drawer 140 is automatically opened, but the manual opening of the drawer by means of its handle (FIGURE 8) or by switch 144 of FIGURE 4 does not cause defrosting.

Where the term compressor is used herein it is understood that this refers to any pressure imposing element such as a jet-type pump, an absorber-generator or other device for delivering refrigerant vapor to a condenser. The terms restrictor, expansion valve," pressure reducing device, capillary tube, float valve," etc. as used herein are in the main equivalents, but attention is called to the fact that valve (FIGURE 8) serves both as a high side float valve and as a solenoid-actuated valve which allows free flow, thus by-passing the restricting device although flow is through the same valve port. This might also be done by using concentric valves with the expansion valve port in the larger valve which allows free flow when open. Valve 90 stops or arrests the free flow at the end of a defrost period, yet it continues after the float rises again to regulate the flow of liquid as a float-type expansion valve, which is one form of pressure reducing device.

The choice between various controls shown will depend to a great extent upon the purpose for which the system is designed and the internal volumes of the evaporators and the pressures employed. If desired to insure that defrost does not start while the system is idle the use of a running-time clock may be preferred for switch 196, but there is no object in using such a clock on switch 224 of the air conditioning system, which may be actuated manually or in response to humidity changes.

I claim:

1. In an air conditioning system, a duct through which air flows on its way to the conditioned space, a refrigerating system including a pressure imposing means, a condenser, two evaporators connected in series and operable simultaneously the first of said evaporators in series being the second in direction of air flow over them, a pressure reducing device for regulating flow of liquid refrigerant into the first of said evaporators which is located downstream in said duct, bypass means for said device whereby high pressure liquid refrigerant many he allowed to enter said first evaporator to reheat said air after it has been cooled by the second evaporator, a second pressure reducing device connected in series between said evaporators, a bypass for said second device, valve means for each said bypass whereby either may be substantially closed, and power actuated means for causing the opening of one and the closing of the other of said valve means.

2. In a refrigerating system charged with a volatile refrigerant, a pressure imposing means, a condensor, two evaporators through which said refrigerant flows in se quence while cooling both, means for directing a flow of air over said evaporators in the opposite sequence of refrigerant flow, a condenser for said refrigerant, a receiver for liquid refrigerant flowing from said condenser,

enemas 1 1 an expansion device for feeding liquid refrigerant to a first one of said evaporators whilea quantity of liquid is trapped in said receiver, conduit means normally allow ing free flow of refrigerant from said first evaporator to the second evaporator, means for heating said first evaporator by substantially filling it with liquid refrigerant from said receiver and means for imposing restriction on the flow of liquid between said evaporators, whereby refrigeration continues in the second evaporator while the first is being heated. I V

3. In a refrigerating system arranged to cool air, a pressure imposing means, a condenser, two evaporators connected in series with means forming a normally open passage between them, an expansion device for normally controlling flow of liquid refrigerant to the first in series of said evaporators, liquid storage means located after the condenser in flow relationship for accumulating a predetermined quantity of liquid under its condensing pressure while some liquid flows through said device, normally inactive means for restricting flow from the first to the second of said evaporators, and means operable simultaneously to allow said quantity of liquid to flow freely into the first in series of said evaporators and to restrict flow therefrom into the second evaporator, whereby specific heat of the liquid raises the temperature of the first evaporator while the second evaporator continues to be cooled by evaporation of refrigerant liquid flowing to it from said first evaporator.

References (Iited in the file of this patent UNITED STATES PATENTS 2,068,249 Terry Jan. 19, 193? 2,107,243 Gay Feb. 1, 1938 2,195,781 Newton Apr. 2, 1940 2,407,794 Mufiiy Sept. 17, 1946 2,667,757 Shoemaker Feb. 2, 1954 2,888,808 Jacobs June 2, 1959

Claims (1)

1. IN AN AIR CONDITIONING SYSTEM, A DUCT THROUGH WHICH AIR FLOWS ON ITS WAY TO THE CONDITIONED SPACE, A REFRIGERATING SYSTEM INCLUDING A PRESSURE IMPOSING MEANS, A CONDENSER, TWO EVAPORATORS CONNECTED IN SERIES AND OPERABLE SIMULTANEOUSLY THE FIRST OF SAID EVAPORATORS IN SERIES BEING THE SECOND IN DIRECTION OF AIR FLOW OVER THEM, A PRESSURE REDUCING DEVICE FOR REGULATING FLOW OF LIQUID REFRIGERANT INTO THE FIRST OF SAID EVAPORATORS WHICH IS LOCATED DOWNSTREAM IN SAID DUCT, BYPASS MEANS FOR SAID DEVICE WHEREBY HIGH PRESSURE LIQUID REFRIGERANT MANY BE ALLOWED TO ENTER SAID FIRST EVAPORATOR TO REHEAT SAID AIR AFTER IT HAS BEEN COOLED BY THE SECOND EVAPORATOR, A SECOND PRESSURE REDUCING DEVICE CONNECTED IN SERIES BETWEEN SAID EVAPORATORS, A BYPASS FOR SAID SECOND DEVICE, VALVE MEANS FOR EACH SAID BYPASS WHEREBY EITHER MAY BE SUBSTANTIALLY CLOSED, AND POWER ACTUATED MEANS FOR CAUSING THE OPENING OF ONE AND THE CLOSING OF THE OTHER OF SAID VALVE MEANS.

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