US2641112A - Refrigerator-cabinet defrosting - Google Patents

Description

June 9, 1953 G. Mur-FLY REFRIGERAToR-CABINET DEFRosTING Filed Aug. 9, 1947 2 Sheets-Sheet 2 1N V EN TOR.

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pearance 'stacked up to too high a level so that the upper Patented June 9, 1953 UNITED STATES PATENT OFFICE REFRIGERATOR-CABINET DEFROSTING Glenn Muiiy, Springfield, Ohio Application August 9, 1947, Serial No. 767,731

' (c1. see-.1.16)

23 Claims- 1 This invention has to do with refrigerated dis.- play cases, particularly of the type designed for packaged frozen foods.

The recent growth of the frozen food industry and particularly in the sale of packaged frozen `foods through retail stores hascreated a demand for an improved type of frozen food cabinet. There is a preference for the open type of cabinet` which allows the customer to see the product and to remove the desired packages without having to open a door. This is particularly im.- portant in the self-service type of store but `certain disadvantages have been encountered in the use of such cabinets.

One serious difficulty is in properly defrosting the evaporators without damaging the frozen food stored in the cabinet either by allowing it to partially thaw or by allowing defrost water to contact the packages and freeze on them or freeze packages together. One-defrosting method commonly employed is to scrape the frost from the cooling surfaces, but this is difcult todo without removing the frozen food packages from the cabinet and hence the defrosting operation is often neglected or improperly done. When Ian attempt is made to do a more thorough defrosting job, there is a serious problem in caring for the packages of frozen food which are tem.-

vporarily removed from the cabinet during the defrosting operation.

Another difficulty of the open display type of frozen food cabinet is that customers are inclined to disarrange the packages in an attempt to select one which has been stored at a lower level and presents a cleaner, harder-frozen ap.-

This often results in packages being ones start to thaw. Even after an attendant rearranges the stock these packages which have lstarted to thaw are less salable and must often be disposed of at a loss.

One object of this invention is to provide a :cabinet in which one package of each variety iS "visible to the customer and when removed is automatically replaced by a similar package.

An additional object is to insure that packages which have been in the .Cabinet for the longest `period of time will be delivered first.

A still further object is to provide means for .defrosting the evaporator which cools the cabinet without defrosting the product stored in the l,cabinet and without allowing drip Water to fall upon the packages of frozen product.

A further object is to provide a pair of mirrors arranged for double reflection of the images of the packages visible in the delivery space. such images being visible to the customer with the labels directly readable because of the double reflection.

`Sltll another object is to provide a door for closing the access opening during hours when the store is not open to customers.

A further object is to provide step and running board means for convenience in filling the-cabi,- net from the top and to assure that the access opening is closed at the time the upper door through which new packages are inserted ,is Open.

Still another object is to provide for rapid de frosting of the evaporator by means of a secondary circuit which causesrefrigerant vapor to oon.- dense in the evaporator.

A still further object is to provide for auto.- matic actuation of the defrosting means during each period when the cabinet is beingrestocked.

An addtional object is to provide for catching the drip water during the defrosting period and vconveying it to a receptacle from which it is later evaporated by means of heat dissipated by the condensing unit of the refrigerating System.

In the drawings:

Figure 1 is a vertical sectional View of the cabinet from its rightfhand end.

Figure 2 is a somewhat enlarged sectional View of a portion of the top door and evaporator in the position assumed when the door is open, showing the method of draining drip water from the evaporator while it is being defrosted.

Figure 3 is a diagram of the electrical circuits for operation of the condensing unit and for ellergizing the defrosting means.

Figure 4 is a sectional view of the top door in its open position on the Order of Figure 2 but taken in a different plane `to show the refrigerant circuit and one type 4of heating means employed during the defrosting period.

Figures 4A and 4B are fragmentary enlarged views of certain of the elements shown in Figs. l and 4.

Figure 5 is a detail fractional view .of the .cabinet showing the top of the front wall and a por.- tion of the top door to illustrate details of the door liner, breaker strip and door gaskets,

Figure 6 is a diagrammatic illustration of ra modification in which the direction of compressor rotation is reversed for the purpose of defrost-ing the evaporator.

Figure 7 is a diagrammatic representation of another modicationusing solenoid valves.

'in-the cabinet. holder is shown at 42 and may be either a permanent sign or a frame designed to support Figure 8 is an enlarged detail of a spring stop seen in Figure 1.

The cabinet seen in the sectional view, Fig. 1, is ordinarily of a length considerably greater than the front to back horizontal dimension seen in this gure. The total height of the cabinet may be 6 or 8 feet, its depth from front to back 2 or 3 feet and its length varied according to the storage ycapacity desired. Various models might be from 4 to 10 feet long. These typical dimensions are mentioned as an aid to the explanation of the usage of the cabinet. The dimensions and proportions may vary considerably to fit special products or locations.

The cabinet I is designed to be placed with its back (right side of Figure 1) against a wall|` or a pair of cabinets may be placed back to back. In any event the front opening I2 is next to the aisle so that customers can reach through this opening into the refrigerated space I4 to remove a package I6, I8, or 20 as desired. When one of these packages is removed, a similar package is pushed into view by the action of gravity upon packages stored in the corresponding vertical chute or magazine 26, 28 or 30.

The mirrors 34 and 36 are mounted at suitable angles for reflection of the images of the packages which are visible in the space I4 so that customers at some distance from the cabinet can see true reflections in the mirror 34 and, assuming the packages to be properly placed in the cabinet, can read the labels on the packages in the mirror 34 whereas images seen in a single mirror, not using this double reection principle,

'are reversed. As the customer walks toward the cabinet the changing angles of reflection will cause a shifting of the images until she can look directly into the space I4 at the visible packages I6, I8 and 20. There will, of course, be a large number of packages visible within the space I4 due to the length of the cabinet. In a cabinet having an overall length of 8 feet, there may be or more sets of chutes 2B, 28 and 3D Iproviding for the display of 30 or more packages in the space I4.

At a higher level on the front of the cabinet, there is a frame and sign-supporting device 40 for display of advertising signs, price cards, etc., preferably of a removable nature so that they can' be changed to match the products displayed i Another sign and price card changeable signs as desired. This lower sign `holder 42 is primarily a door hinged at 44 to the cabinet I0 so that it may be swung through an arc of 270 to the position 42 indicated by dotted lines. In this position the door 42 closes the opening I2 in a substantially airtight manner by making contact with the rubber gaskets 46 and 48. In this position the door 42 serves as a running board or platform upon which merchandise can be stacked and the attendant can stand when refilling thecabnet.

The side of the door 42 which is hidden dur- -ing the day and is uppermost when the door is yclosed during the night may be provided with a .tread 50 (50 in the dotted position).

.cation of air and retard its circulation in the spacel4, thus it is n ot necessarythat the vdoor 42 be as heavily insulated as the main walls of the cabinet.

Below the door 42 in its open position is a rail or ledge 52 which may be used as a step to aid in mounting the running board. The hinge 54 of the door 56 is also designed to serve as a step for the attendant who rells the cabinet.

The proportions of these parts and of the cabinet itself are preferably such that the attendant will be virtually forced to close the door 42 before opening the top door 6U of the cabinet. Very little of the rail 52 should extend beyond the door 42 when the door is in its open position. The door 56 is opened only occasionally for access to the condensing unit and when thus opened rests in the position 56 shown by dotted lines.

The feature of discouraging 'the improper opening of the door 60 while the door 42 remains open is to prevent the excess spillage of cold air which would result from this practice. The door 60 is tted around its outer edge with a gasket 62 which seals the outer metal covering of the door to the liner 63 which is preferably made of non-conducting material. The cabinet is fitted with an additional gasket 64 which makes contact with the door 6D. This gasket seals the lining of the cabinet to the insulating breaker strip or frame 65. The use of two gaskets is to minimize and substantially eliminate air leakage into the cabinet when the door 60 is closed.

The flap 58 is a curtain of flexible material designed to contact the packages I6 and retard air ow between the chute 26 and the space I4. Additional flaps of this material may be employed at the sides of packages and at the delivery ends of the other chutes, but the one shown at 58 is the most important since it is nearest to the opening I2 and acts to retard the rlowlgf cold air from the chutes 26 to the openmg The finned evaporator 66 is supported by hangers 61 from the door 60 and extends substantially the full length of the upper space 6B above the chutes which hold the frozen food packages. This evaporator may be formed of tubes passing through sheet metal fins or it may be of the sheet metal or plate type and may be provided with headers in any preferredmanner, but it is desirable that the evaporator be arranged to drain liquid downwardly and toward the door 60 when in the position 66' which it assumes when the door 60 is opened to the position 60.

During business hours of normal usage of the cabinet, the door 6D remains closed and the door 42 remains open. The evaporator 66 is operated at a temperature considerably below freezing and preferably well below 0 F. This cools the a1r in the space 68 and this cold air drops into the several chutes 26, 28 and 30. There will be some thermal circulation of air Within the chutes and a more pronounced thermal circulation of air in the space 68 but it is preferred that this circulation be quite slow.

Due to the height from the opening I2 to the upper door 60, there will be a tendency for the air in the chutes 2:6, 28 and 30 to flow through the space I4 and spill out of the opening I2, but this gravitational movement of cold air is minimized by the use of the double gaskets 62 and 64.

The result will be a slight reduction of atmosphericpressure in the space 68 and substantially no upward fiow of cold air through the `ammira space "I4, but air currents within the room will cause some circulation of air through the opening l2. In order to minimize this loss of refrigeration due to circulation of room air the end Walls of the cabinet I are provided with wings 1U which need notk be heavily insulated and may omit insulation entirely. These wings may be continuations ofthe outer metal sheathing of the two ends of the cabinet and their inner faces may be mirrors so that a person approaching the cabinet from one end will see the food display mirrored in the opposite Wing 10.

The condensing unit 72 comprises a motorcompressor unit 14, a condensery 16 and a fan 'I8 mounted on a common base, the whole being removable through the front of the cabinet by opening the door 56 and disconnecting the tubes and wires at vpoints which are accessible through its opening. The motor-compressor unit 14 is indicated as a sealed unit `of horizontal type because it is desirable to keep the overall height of the condensing unit 'l2 as low as possible, but any suitable types of motor and compressor may be used. The liquid tube 80 and the suction tube 82 are preferably in heat exchange with each other within the conduit 84 which extends up the back of the cabinet. The upper end of the liquid tube 89, above the heat exchange section, is connected with the restrictor tube 86 or with an equivalent liquid control device, but in any eventthere is a section of liquid tube 86 of `suillcient length and ilexibility to permit opening of the door'n without undue bending stress which might in time cause this tube to break.

When the door 60 isin its normal closed position (seen in Fig. 1) thev liquid refrigerant ilow from the restrictor tube 88 is directly to the inlet tube 88 of the evaporator 65. Refrigerant vapor leaves the evaporator through the tube 90 which normally leads directlyto the coiled tube 92. Since the suction tube must be of larger diameter than the liquid tube 86 and must also be'flexible, it is coiled in several turns around the hinge pin 94. The tubes 82 and 8U are preferably connected with the ilexible tubes 92 and 86 by means of unions so that the door 60 and parts mounted thereon can be vcompletely assembled as a unit and then mounted on a cabinet; Thisalso provides for removal of the door assembly for servicing. In order to provide for this coil 92 surrounding the hinge pin, the pin is located farther from the body of the door Gllthan would otherwise be required, but to `minimize the requirement for clearance back of the cabinet when the door 69 is open, the hinge' pin 94 is located somewhat above'the plane of contact between the door 69 and the cabinet I0.

Thel coiled suction tube 92 connects withthe suction tube 82 extending downwardly within the conduit 84 to the compressor 14 which discharges compressed refrigerant through the tube Bl'to the condenser 16, thus completing the norinal circuit of the system as employed in cooling the-cabinet.

Since this cabinet is to be held at temperatures considerably below freezing, the controls of the system will necessarily be set to prevent any defrosting of the evaporator or of the product stored within the cabinet during normal operation, thus frost must necessarily build up on the evaporator 6B. The amount of frost collected is minimized by the fact that infiltration of airis substantially prevented while the ydoor 6, B0 is closed. Therewill, however, be some slight leakage of air past the double gasketsBZ and vGII. The air thus leaking into the cabinet will be lighter than the air already within the space 68 kbecause it is warmer and because it will carry a much higher water vapor contentv than the lcold air'within the cabinet. The location of the evaporator 66, its shape, the shape, of the baille 98 and this fact of. the incoming air being lighter will insure that the air leaking into the cabinet makesY contact with the evaporator G6 before it can make contactwith the walls'of the chutes 29, 28 and 30 or withany of the packages i6, I8 and 28.

The'temperature of the evaporator 86 is to be maintained lower than the temperature of the packages and therate of air flow over the evaporator and its extended surfaces is slow enough to insure that the absolute humidity of air in the vspace 98 is maintained at avalue low enough to prevent condensation of moisture from this air inthe form of Afrost upon the packagesor upon the walls of the chutes containing them when this air falls from the spacev 6B into the chutes.

As seen in Figures 1 and 2, the baille 98 is formed to provide a trough which will hold a small amount of water of condensation which will collect from the evaporator 6'6 during the brief pull-down period whenthesystem isilrst started up or after the evaporator has been defrosted. The evaporator 65 may have ilns rounded at the lower front corners and inclined on their bottom edges for the purpose of directing drip into this trough, but such drip collection is limited to a very short period while the evaporator is being pulledv down to its operating temperature.

Idle periods of the system will not be long enough to allow any defrosting of the evaporator 6E while the door 99 is closed, hence there will be no accumulation of condensate in the trough of baille 98 and the small amount of water in it will be in the form of ice.

This baille is designed specifically for performing a drainage function whenthe door Bil/is open, as seen in Figure 2. While the baille is perforated with numerous openings I Bil for ilow oi air to the evaporator when the lid 60 is closed, these openings are so located relative to tubes and ns of evaporator 9S and so surrounded by up-turned edges that water dripping from the evaporator 66 while the door is open, as seen in Figure 2, will be conveyed to one or niore'pockets or troughs |82 from which water will drain through the tube or tubes |84 into the funnel Mill from which water drains through the tube |88 into container l l0 which is mounted adjacent to or actually upon the vcondenser 16.

This drip trough or container will be designed to hold more water than is normally obtained from completely defrosting the evaporator after the maximum permissible collection of frost thereon. Between derostings, the drip lwater will be'evaporated from the container H0 by means of heat from the condenser 'I6 and air moved by the fan 58. To facilitate lthis action, 'a piece of fabric H2 extends downwardly inside of the trough H0 to near its bottom and downthe outside of the trough where air circulated .by the fan will flow over it. This will easily provide `for evaporating all of the water which can be collected from a single deirosting in less timethan thatfof a normal period between defrostings.`

in order tolexpedite defrostingof. the :evaporator 66 when the door 60 is open provisions are made for insuring that the condensing unit stops operation with respect to the cooling of evaporator 66 and means is provided for supplying heat to the evaporator 66 while the door is open. One method of doing this is illustrated by Figures 3 and 4, 4A and 4B. In Figure 3 the thermostatic switch is connected in series with the motor of the motor-compressor unit T4 as usual but there is also in series with switch |20 a gravityoperated switch |24, which is here shown as being of the mercury type. In the position shown in Figure 3, the switch |24 closes the connection between the line wire |26 and the wire |28 which leads to a terminal of the thermostatic switch |20, the circuit through the motor being completed by the wire |30 and wire |32 which leads back to the line, assuming the switch |20 to be closed.

A suitable bulb connected with switch |20 is located in contact with 90 or at some suitable point within the refrigerated space and the mercury switch |24 is mounted on or within the door 60 so that it is tilted thereby when the door is opened. Assuming now that the mercury switch |24 as seen in Figure 3 is tilted 90 to the right, as would be caused by opening the door 60, it will be seen that the mercury will flow to the opposite end of the tube, breaking contact between |26 and |28 which will stop the motor in the event that it is running or prevent its starting in the event it is idle. The mercury in ilowing to the opposite end of the tube makes Contact between the line |26 and the wire |36 which leads to a resistance heating element |38 having its opposite end connected with the wire |40 which connects with the opposite side of the line, thus putting the heating element directly across the line while the motor of the condensing unit is definitely cut oi.

The heating element |38 is protected by insulation |42, which may be of material on. the order of mica, but is thermally associated with the coil of tubing |44 which acts as the evaporator of a secondary refrigerant circuit while the door 60 is open. Referring to Figure 4 in which the evaporator 66 is represented diagrammatically to show drainage of liquid therefrom into the tube 88 which was the inlet for liquid flow to the evaporator while the lid was closed, the tube 88 leads into a fitting which includes a ball check valve |52. This ball closes the connection with the capillary tube 86 so that liquid flowing from the evaporator 66' will be diverted to flow downwardly through the tube |54 to the coil |44 which has an outlet end |56 leading to the tting |58 within which there is a ball check valve |60 normally closing the now open port |62 which connects with the tube |64 leading to a tting |66 within which there is a third ball check valve |68 now closing the end of tube 92 while allowing vapor to flow from tube |64 into the tube 90 which leads to the upper portion of the evaporator 66 which is no longer serving as an evaporator in this position. This completes a secondary refrigerant circuit which operates as follow:

When the door 60 is opened the circuit to the compressor motor is broken and the circuit to the heating element |38 is closed and in addition to this the check Valve |52 has closed the port through which liquid refrigerant normally enters the evaporator and check valve |68 has closed the port through which refrigerant vapor normally leaves the evaporator. This isolates the evaporator from the high pressure side of the system and at the same time the lball check valve |60 opens the port |62 so that the evaporator 66 is in 8. open communication with the coil |44 which is now located at a lower 1eve1 than evaporator 66, indicated by 66' in Figure 4.

The result is a reversal of function of the evaporator 66 which now serves as a condenser for refrigerant vapor produced by the electrical heating of the coil |44 and the drainage of liquid from 66 which now serves as a condenser. Since heat is applied to the coil |44 rapidly enough to cause defrosting of 66 within a short period of time. the pressure within the secondary refrigerant circuit which includes 66 may be higher than the pressure in the tube or tube 92. If at the start of the defrosting operation someliquid ows from tube 86 into the fitting |50, it will not flow into the evaporator 66 but will flow through the tube |54 into the secondary evaporator |44. l

'I'he cover plate |14 is removably gasketed to the outer wall of the door 60 to provide access to the connections seen in Figure 4 and to the switches |20 and |24 for the purpose of servicing. This cover also provides gasketed outlets for the tubes 86 and 92 as well as for electrical leads connected with the heating element |38 and the switches which are located within the door.

It will be seen by reference to Figure 1 or by reference to Figure 4 rotated 90 to the left that during normal operation with the door closed the ports closed by check valves |52 and |68 will be open while the port |62 is closed by the check valve |60.

Refrigerant liquid entering the fitting |50 through the capillary tube 86 is prevented from flowing upwardly through the tube |54 -by the fact that this tube has its outlet closed and because the coil |44 will be lled with warmer vapor. There is, therefore, no circulation of refrigerant through the tubes |54, |44, |56 and |64 when the door 60 is closed. Likewise there is no heat applied to the coil |38 while the door is closed as the circuit is broken at mercury switch |24.

Figure 5 is an enlarged detail of the top forward portion of the cabinet showing how the liner 63 of the top door and the breaker strip or frame 65 at the top opening of the cabinet are attached to the outer metal pan of the door and the liner of the cabinet respectively using the gaskets 62 and 64 which are designed both for sealing the door opening when the door is closed and for sealing the joint between the door liner and the outer metal covering of the door and for sealing the breaker frame to the cabinet liner.

Figure 6 shows the wiring diagram used in the event that it is desired to defrost the evaporator by reversing the pumping action of the compressor instead of by isolating the evaporator and using the electrical heating element |38. This method eliminates the need for the valves |50, |58 and |66. With this arrangement the mercury switch |24 shorts out the thermostat and closes a circuit through the wire |80 to cause the motor-compressor unit 14 to rotate in the reverse direction. This assumes the use of a rotary compressor of a type which reverses the direction of its pumping action when its direction of rotation is reversed. The result is that refrigerant vapor is discharged under high pressure into the evaporator 66' which now acts as a condenser and refrigerant liquid flows in the reverse direction through the capillary tube downward to the condenser 16 which now acts as an evaporator.

Figure 7 illustrates a further modification in which the defrosting is accomplished by opemt ing the motor-compressor unit in its normal direction of' rotation, but-reversing the flow of refrigerant to produce the same result as that obtained in Figure 6. llhe wire |82 connects with mercury switch |24 so that current flows in series through a pair of solenoids and the wire |84 to the motor of unit i4. The solenoid |86 acts to lift the suction valve |81 iand the solenoid |88 acts to lift the discharge valve |89. When these two valves are lifted as a result of the top door 60 being opened the compressor discharges high pressure refrigerant vapor to the evaporator 66 which now acts as the condenser and refrigerant of these three systems, it may be considered advisable to provide automatic means for limiting the defrosting period in the event that the door is left open for a longer period than is required to melt all of the frost from the evaporator. Such means is easily provided by a thermostatic or pressure operated switch connected in the heating circuit or in the reverse motor circuit and arranged to open in response to the rise of pressure in the evaporator EG or of temperature of the evaporator 56' to a point high enough to insure that all frost has been melted from the evaporator, any extended surface thereof and from the baffle 98.

The check valves |52, |50 and |68, Figure 4, may be dispensed with by connecting the tubes 86 and 92 so that liquid does not flow downwardly in either of them by gravity when the door 69 is yopen.V It is only necessary that liquid owing from the evaporator Et flows into the coil IM and not'into the tube 8B and that vapor leaving the coil |44 flows to the evaporator 65. Normally there will be some now of vapor through the tube S2 during a defrosting period as, shown by Figure 4 if the check valve 58 is omitted, thus building up some vapor pressure in the compressor housing. Likewise there will be some flow of vapor through the tubes 35i and v8d into the condenser 1E. Such transfer of refrigerant vapor will reduce the charge of refrigerant available for defrosting the evaporator G5 of Figure 4 but not-to the extent of preventing the defrosting. Since the compressor and condenser will always be well above 32 F., there will be no condensation of refrigerant vapor except in the colder portions of theevaporator 56. After all of the frost has been melted from the evaporator 65', there will be more transfer of refrigerant to the compressor housing and to the condenser but this occurs after the defrosting operation is completed.

The door Eil or its hinges will be provided with suitable balancing or latching means to hold the door in its open position without requiring that the door be tilted too far beyond its vertical position. Itis desirable that hardware of this type be used so that it is not necessary to open the door more than 90 as such wider opening to reach a balancing point would require additional space back of the cabinet which will often be placed with its back against a wall of the room.

The coiled portion of tube 92 which provides flexibility for door movement will normally be wound so that when not stressed in either direction it will represent the position it assumes when the door is 45 open; thus the amount of nexibility required is 45 of movement in each direction from this half-way point. There are various types of flexible tubing made of metals and plastics which could be used in place of the plain coiled tube shown. It is also possible to make the connection through a movable joint associated with a hinge and this joint may also serve as a valve to isolate the evaporator 66 and the coil |44 from the balance of the system when the door is opened. Another use for such a hinge type valve would be to utilize it to perform the functions of the valves E87 and l 89 shown in Figure 7.

The drain tube |04 seen in Figure 2 is preferably formed so that when the lid Sii is closed it forms a trap for water at a point far enough from the inside of door Si) and from cold parts of the refrigerating system so that water does not freeze in this trap but serves only as a seal to prevent air circulation. This trap is formed so that it also retains enough water at the end of each defrosting period while the lid is in its open position 60 to provide a water seal of sufiicient depth to prevent ambient air from entering the refrigerated space through the tube |04 when the li'd 'Eil is closed. As previously explained, the air pressure at the top of space 68 will be less than that of room air due to the Weight of the column of cold air in this space and in the chutes above the level of the opening I2. Trapped water seals the tube 0d against this slight pressure difference.

A number of diagonal broken lines leading from i572 at the left of Figure 1 indicate angles ofreection as seen by a human eye at position |92. It will be noted that when the customers eye is in this position packages Iii and I3 are directly visible, package 2|) is visible by reflection in mirror 34 and package I3 is visible by double reiiection in mirrors 34 and 36. The reflected images which the customer sees in mirror 34 first as the cabinet is approached thus provide a moving effect. The lettering on packages seen by double reflection is directly readable and when the customer approaches the cabinet closely the lowermost package in each chute is directly visible.

While I have shown the evaporator 66 and the baile Sil movably mounted as a unit with the door (iii and the evaporator moving to a position entirely outside of the refrigerated space, it will be understood that some of the objects of my invention may be attained by moving only the evaporator or by moving only the baiiie or drip pan. rPhe evaporator may lift or slide instead of being hinged or the exaporator may remain stationary while the baffle or pan isolates it from the stored product so that the defrosting can occur without undue rise of temperature of the frozen foods.

Packages stored in this refrigerator will collect much less frost than usual because of the fact that all inward leakage is at the top and incoming air has its dew point lowered by the evaporator 56 before it contacts the packages in the chutes. In addition defrost water is prevented from touching the packages so that ice does not .form on them. Any tendency of the packages to freeze together will be the result of frost collected on them prior to placing them in the cabinet. This frost will not form an ice bond between the packages if the cabinet temperature is properly maintained, but in the event that there is a tendency for the packages to freeze together in the chutes.

For inventory purposes the number of packages in each chute can be calculated by measuring the distance from the uppermost package to the top of the cabinet. An approximate indication of the number of packages in each chute is provided by means of the spring stop |94 which is indicated in Figure 1 and shown enlarged in Figure 8. This spring stop provides a cushion effect when packages are dropped into an empty chute and the amount of spring deflection is an approximate measure of the Weight of the packages in the chute. During business hours an attendant may observe the positions of these spring stops to determine whether or not any of the chutes are nearly empty, thus avoiding the necessity for opening the top door 60 unnecessarily. It may sometimes be desirable to open the door 160 for a short period to reiill one or more chutes withut defrosting the evaporator. This is easily provided for by placing a manual switch in the line |40 of Figure 3, |82 of Figure 5 or |30 of Figure 6 according to the type of defrosting arrangement employed.

As will be seen in Figure 1, the width of the opening I2 may be considerably less than the Width of the display represented by the packages I6, I8 and 20. This opening need only be wide enough for the convenience of the customer in reaching the packages and may be even narrower than indicated in the drawing. The gasket 46 or the reflector above the lamp 49 may narrow the opening further. Mirrors 34 and 35 may be fiat as shown or curved to enhance or modify the display by reection. This double reflection which makes labels readable before the observer comes close enough to the cabinet to actually look down into the space |4 makes it practical to reduce the Width of the opening |2 and thus reduce loss of refrigeration due to air flow and radiant heat transfer.

The use of the curved chutes allows the outer wall of the cabinet to be curved at the bottom above the condenser 'I6 as seen in Figure 1. This curvature greatly facilitates air flow over the condenser, making it possible to omit the fan 18 and depend upon thermal circulation of air if the designer prefers such an arrangement.

The drain tube |04 is shown in Figure 2 only, but it Will be understood that the section seen in Figure 2 is very close to the section seen in Figure 4 and the tube |04 may be in heat exchange With the tube 86 and the tube |56. The object of such heat exchange is to insure against freezing of water in the tube |04 during either the operating period with the door 60 closed or the defrosting Vperiod with the door in the position of 60.

During operation of the system to cool the cabinet the tube |04 is heated by liquid refrigerant owing through the tube 86. During the defrosting operation the tube |04 is heated by the hot vapor flowing through the tube |56.

The thermostatic control indicated at |20 in Avarious drawings may have a bulb associated with the suction tube 90 or it may be responsive to the temperature of the evaporator 66 or to the temperature of air adjacent to this evaporator. It may be a switch of the so-called low pressure type which is actuated directly by the pressure of refrigerant vapor leaving the evaporator. In any of these cases the switch |20 Will close during the defrosting operation if it was open at the time defrosting started. This insures that when the 12 lid 60 is closed at the end of the defrosting period the evaporator 66 Will immediately start cooling the cabinet.

I claim:

1. In a refrigerator, a food storage space, 'a refrigerating system including an evaporator for cooling said space, a door for access to said space, and means activated by the opening of said door for causing said evaporator to act as the condenser of said system for the purpose of defrosting it.

2. A refrigerator including a storage space, a refrigeration system including an evaporator operated at below 32 F. to cool said space, means for defrosting said evaporator, and means for collecting the defrost Water which drips from said evaporator, said collecting means serving during normal operation of said system as a baffle to'direct air ow within the refrigerator.

3. In a refrigerator, a food storage space, an upper door providing access to said space for loading it, a hinged lower door providing access to said space for removal of articles inserted through the upper door, means facilitating the opening of said upper door, said means being effective only when said lower door is swung to its closed position, and a refrigerating system including a cooling element located adjacent to said upper door.

4. In a refrigerator cabinet, a refrigerating system, a door, a cooling element of said system mounted on the inner side of said door, heating means for defrosting said cooling element, drip collecting means, and means actuated by the opening of said door to energize said heating means to initiate a defrosting period of said cooling element and to move said drip collecting means into position to receive the drip from said cooling element.

5. In a refrigerator cabinet, an evaporator of a refrigerating system arranged to cool said cabinet, means for stopping said cooling, and means for causing said evaporator to act as the condenser of a one pressure evaporative heat transfer system for the purpose of defrosting said evaporator.

6. In a refrigerator cabinet, an evaporator for cooling said cabinet, a door for said cabinet, and valve means actuated by movement of said door, said valve means serving to control the defrosting of said evaporator.

7. A refrigerator cabinet, a refrigerating system including an evaporator arranged to cool a space Within said cabinet by the evaporation of a volatile refrigerant, means for isolating said evaporator from said space, and means actuated simultaneously with the first said means for causing said evaporator to operate temporarily as a condenser for the purpose of defrosting it by condensing said volatile refrigerant therein While the vtemperature of said space remains substantially constant.

8. A refrigerator, a storage space within said refrigerator, a refrigerating system, an evaporator of said system located within said space,said system including a compressor of a type adapted to reverse its direction of pumping action when its direction of rotation is reversed, means for reversing the direction of rotation of said compressor to cause said evaporator to be defrosted by functioning temporarily as a condenser, and means for modifying the normal relationship of said evaporator to said space during its period of operation as a condenser so that it dissipates heat to animent air and drains defrost water outside of said space during -its defrcsting period.

9. In a refrigerator, a space for the storage of products to be cooledpan evaporator for cooling said space, a movable baie element within said space, said element being movable to a second position in which it serves as a drip collecting means adapted to receive defrost water as it drips from said evaporator, and means made effective upon movement of said element to its drip collecting position for causing said evaporator to defrost.

10. In a refrigerator, a space for storage of products to be maintained at a low temperature, an evaporator for cooling said space, means for cooling said evaporator by supplying a volatile refrigerant to it and removing vaporized refrigerant therefrom, a normally by-passed heat exchanger, means for heatingv said evaporator by evaporating a volatile refrigerant in said heat exchanger and causing it to condense in said evaporator for the purpose of defrosting it, and switch means operable to connect either of the rst two means with a source of electrical energy, said switch means operating to cutoff the electrical energy supply to either of the rst two means before closing the circuit which energizes the other.

11. In a refrigerated cabinet, a chamber for storage'of frozen foods, a plurality of chutes in said chamber adapted to hold said foods, an evaporator located within said chamber for cooling air therein, an upper door for said chamber adjacent said evaporator, a second door vopening into said chamber at a lower level, said evaporator being adapted to operate at a temperature far enough below the freezing point of water and so located with relation to said upper door that any air leaking into the cabinet around said `door will be cooled by said evaporator to the extent of having its dew point reduced to a temperature below that of the food in storage in said cabinet before said air comes in contact with said food or with packages containing the food.

12. A refrigerator having a door and enclosing a storage space for frozen foods, a refrigerating system for cooling said space to a sub-freezing temperature, a cooling element forming a part of said system, and means for applying heat to Vsaid cooling element to defrost it, Asaid means being energized by the opening of said door, means for collecting drip water from said cooling element while it is being defrostedy the last said means including a drip trough normally located within said storage space and moved to its `defrosting position by said door, and means for conducting said drip water to a disposal point, said collecting means, conducting means and disposal point being located entirely outside of said storage space during the defrosting operation.

13. In a refrigerator, a space for storage of foods, a refrigerant evaporator for cooling said space, a door for closing said space, means responsive to the opening of said door to applv articial heat to said refrigerant evaporator, a drip water evaporator, and means actuated by said door as it is moved to its open position to provide for catching defrost water from said refrigerant evaporator and draining it to said drip water evaporator.

14. In a refrigerator cabinet, a space within said cabinet for storage of a product to be refrigerated, a door opening for access to said space. a door for closing said opening, a refrigeratinar system including an evaporator arranged to cool said space by the evaporation of a volatile refrigerant therein, valve means .for 'changing the direction of flow of said refrigerant through a part of said system and thereby causing said evaporator to function temporarily as a condenser for the purpose of defrosting it, and means actuated by a movement of said door for operating said valve means.

15. The method of defrosting an evaporator of a refrigerating system by a single movement which shuts it off from other parts of the system and causes it to operate temporarily as the condenser of a single pressure volatile fluid heat transfer system with condensed fluid draining to a lower level, being reevaporated by the application of heat and returning as vapor to heat the evaporator which is temporarily actingas a condenser.

16. In a refrigerating l system employing a volatile refrigerant, a high side section including a condenser, a low side section including an evaporator, and a normally inactive heat exchange section, means for causing liquid refrigerant to drain from said evaporator intoV said heat exchange section, means becoming effective simultaneously with said draining means for applying heat to said heat exchange section to cause said liquid to evaporate therein, and means for conveying vapor from said section directly to said evaporator with no change of pressure for the purpose of causing the evaporator to operate temporarily as a condenser and thereby be defrosted.

17. In a refrigerator cabinet, a space for storage of a product to be cooled, a refrigerating system including an evaporator arranged to cool said space, means for defrosting said evaporator by applying artificial heat thereto, a door on said cabinet, and control means actuated by a movement of said door, said control means being connected with said system and with said defrosting means so that one movement of said door stops the cooling operation of said evaporator and starts its defrosting while an opposite movement of said door stops the defrosting and causes the cooling to start again.

18. In a refrigerator cabinet, a space for the storage of products to be cooled, closure means for said space, a refrigerating system including an evaporator for cooling said space by the evaporation of a volatile refrigerant, means for reversing the action of said evaporator so that refrigerant condenses therein to defrost it, and a drip evaporator, said reversing means being actuated in response to a relative movement between said evaporator and space, said movement also acting to provide a non-refrigerated path Vfoicarrying drip water from the first said evaporator to the drip evaporator.

19. In a refrigerating system, an evaporator section including an evaporator and a normally by-passed heat exchanger, a refrigerant condensing section including a condenser, a volatile refrigerant enclosed within said system and normally circulating therein to vaporize in said evaporator and liquefy in said condenser, means for stopping the circulation of said refrigerant between said sections, and electrical means for heating a portion of said refrigerant which is in its liouid phase in said heat exchanger to evaporate it and thereby cause it to condense in said evaporator for the purpose of defrosting the evaporator.

20. In a refrigerator cabinet of the type adapted for cooling a product in its original containers, a delivery opening for said containers. multiple chute means for guiding the movement containers remaining in that chute, ci

pf said containers toward said 'delivery opening, `and means responsive to changes in vthe total Weight of the containers in one .of-said chutes for indicating at least approximately then being rellable at .one end and adapted to rdeliver containers at the 'other end so that a rcontainer which has `been in a Agiven one of said 'chutes for the longest time will be the next vone delivered therefrom.

'21. A refrigerated rcabinet adapted for the storage of frozen foods, a compartment for the storage of frozen foods having Ya pair of access openings, one of said openings being at a higher level for the introduction of packages to 'said compartment, another of said openings being at a lower level for the removal of paclragesfrom said compartment, a tightly vfitting operable `closure for said higher opening, an evaporator carried ,by said closure and positioned within said compartment for cooling the air therein,.said evaporator being closely adjacent said `upper opening whereby any air leaking into said compartment will be cooled by said evaporator to a tempera- `ture below that of saidpackages 'whereby its vdew point is reduced below said package temperature before said air comes in `contact with said pack-- ages, an openable closure for lsaid lower opening, and means dependent upon the placing vof said second-named closure ina position to close said lower opening for facilitating the opening of first-named closure whereby the user is impelled to close said lower opening before opening said upper opening.

22. A refrigerated cabinet adapted fA r the. storage of Afrozen foods, a compartment for the storage 'of frozen foods having a `pair access openings, one of said openings being vat a high level for the introduction of 'packages to said compartment, another of said openings being at a lower level for the removal of packages from said compartment, a tightly fitting hinged closure for said higher opening, an evaporator adapted to be cooled below the freezing point of `water carried by said closure and positioned within said compartment for cooling the air therein, said evaporator being closely adjacent said upper opening whereby any air leaking into said com- `partment will be cooled by said evaporator to 'a temperature below that o'f said packages whereby its dew point is reduced below said package teinperature and the excess moisture condensed out in a frozen form on said evaporator before said air comes in contact with said packages, means for causing said condensed nioistureto melt from said evaporator as a consequence of *the opening of said closure, means rendered effective'uponthe opening of said closure for `collecting the moisture melting from said evaporator whereby it is prevented from coming in contact with said packages, a hinged closure for said lower opening, and means dependent upon the placing 'of said secondnamed closure in closed position for facilitating the opening of said first-named closure whereby the user is :impelled to :close fsaid lower opening before opening saidupper opening.

23. In a refrigerator, faicompartment adapted for the storage yof lfrozen foods, a refrigerating system including an evaporator arranged to cool said compartment, means for isolating `said evaporator from ,said compartment, means for shutting said evaporator oli from kconnection withother parts ofsaid system, means for heating said evaporator to defrost it, and control means for substantially simultaneosuly'actuating two of the aforesaid means.

GLENN MUF-FLY.

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