US3496732A - Control system for refrigerated enclosures - Google Patents

Description

Feb. 24, 1970 R. EfvoGEL ET AL CONTROL SYSTEM FOR REFRIGERATED ENCLOSURES 4 sheets-sheet 1 Original Filed Nov. 18. 1968 t o ....v.. .0..

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Feb. 24, 1970 R. E. VOGEL ET AL.

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Neural 6 V Relays 584 Sttcs Unite 7 Claims ABSTRACT OF THE DISCLOSURE A control system for refrigerated enclosures of the type defining an access opening for viewing goods within the enclosure and permitting one to reach into the enclosure for loading or withdrawing of goods. The control system includes switch means which are operated to place various protective means in operation so that in the event of a power failure or loss of refrigeration, damage to the goods will not result. Specifically, the control system cuts off circulating fans, prevents the operation of antifrost heaters, and eliminates the possibility of a defrost cycle in the event of refrigeration failure. Warning light and an alarm system can also be included in the circuitry.

This application is a division of applicants copending application Ser. No. 776,449, filed Nov, 18, 1968.

This invention is directed to an improved system for the operation of refrigerated enclosures. The invention is particularly concerned with refrigerated constructions of the type employing moving air streams which create and maintain refrigerated conditions in areas of the construction located within or adjacent to the air stream paths.

In describing the instant invention, reference will be made to refrigerated cabinet constructions of the type normally employed in super markets for storing food products which must be maintained at reduced temperatures. In one particular type of contruction, air curtains are moved across an access opening for the cabinets and the character of the curtains is controlled to provide efficient operation of the construction.

In Hagen et al. Patent No. 3,134,243 and in Simons Patent No. 2,862,369, there are described refrigerated display cabinets which are provided with access openings exposed to the atmosphere while still being capable of maintaining the contents in a refrigerated state. Loss of refrigeration from the enclosed space through the access opening is reduced in a highly effective manner in these constructions by the use of a gaseous, preferably air, curtain which is continuously advanced across the open side from one edge of the opening to the opposite edge.

The air curtain in these constructions is adapted to be formed of adjacent panels of air, with the innermost panel comprising a refrigerated cold air panel, and with one or more outer panels having temperatures more closely approaching the ambient temperature. It has been found that it is desirable to recirculate the inner cold air panel and to provide means for circulating the adjacent guard panels, to conserve the refrigeration and to maintain the enclosed space in a satisfactory refrigerated state.

The eicient operation of systems of the type referred to can be satisfactorily maintained during normal business hours, Thus, the refrigerating and defrosting mechanisms are adapted to operate in a desired sequence so 3,496,732 Patented Feb. 24, 1970 that the product will be maintained at desired temperatures while the front of the cabinet is open for access by customers.

Obviously, this operation could be maintained during off business hours, for example throughout the night. It is clear, however, that the expense of maintaining the same level of refrigeration and defrosting operations during such off hours is high and, therefore, means should be provided for economizing during such periods.

It is a general object of this invention to provide an impro-ved control system for refrigerated enclosures which permits economical operation of the enclosures, particularly during off hours, and which provides an alarm system usable both during and after business hours.

It is a more specilic object of this invention to provide a control system which may be used in conjunction with a night cover construction so that economies in operation can be achieved during off hours While the control system will prevent damage to the product in the event of mechanism failures during the off hours.

These and other objects of this invention will appear hereinafter, and for purposes of illustration, but not of limitation, specic embodiments of the invention are shown in the accompanying drawings in which:

FIGURE l is a front elevation of a night cover of a type suitable for use in the system;

FIGURE 2 is a vertical sectional view of a refrigerated enclosure of the type suitable for use in conjunction with the system of this invention;

FIGURE 3 is an enlarged fragmentary sectional view taken about the line 3 3 of FIGURE 1 illustrating the means employed for attaching the night cover to a refrigerated enclosure;

FIGURE 4 is an enlarged horizontal fragmentary sectional view of the night cover;

FIGURE 5 is a graphic illustration of the operating temperatures of a refrigerated enclosure;

FIGURE 6 is a circuit diagram illustrating the control means of the invention; and,

FIGURE 7 is a detailed illustration of the time delay control means employed in the system.

As noted, the instant invention will be described with reference to constructions which employ air curtains moving in side-by-side relationship across an access opening of the refrigerated cabinet construction. Such air curtains are commonly employed for the purpose of forming bariers to prevent or minimize refrigeration loss.

The invention will be specifically described with respect to refrigerated enclosures of the type defining an opening in one wall to provide access to the space within the enclosure. The enclosures or cabinets are provided with a plurality of 'nozzles arranged in side-by-side relationship across one edge of an access opening and corresponding inlets are located across the opposite edge of the access opening. The inner nozzles and inlets are provided for the passage of a refrigerated stream across the access opening while the adjacent outer nozzles and inlets circulate progressively warmer air panels. The inner refrigerated stream is circulated through a passage having refrigeration coils located therein and one or more of the outer adjacent streams may also be refrigerated.

One aspect of the instant invention relates to the use of a night cover which is put in place during off business hours. The night cover comprises an insulated board which is intended to confine the cold within the construction to a greater degree than is possible when the access opening is uncovered or is covered with an uninsulated panel. With this arrangement, the product in the enclosure can be maintained at safe temperatures while reduced power can be employed for supplying refrigeration.

The night cover construction may be used in conjunction with circuit control elements designed to minimize the possibility of loss of product in the event that a refrigeration failure, or other disruption of the operation should occur. On the other hand, the control system may be used independently of a night cover.

The circuitry of this invention includes means which will prevent operation of circulating fans and antifrost heaters. In addition, the circuitry is designed to eliminate the possibility of a defrost cycle starting when a failure has occurred. Finally, warning lights and an alarm systern can be incorporated in the circuitry so that efforts to correct the failures can be initiated as quickly as possible.

FIGURES 1 through 4 illustrate a refrigerated cabinet construction and an associated night cover 12. The refrigerated construction includes a top wall 14, bottom wall 16, back wall 18 and front wall 20. The front wall denes opening 22 which provides access to the interior 24 of the construction. Shelves 26-32 and the oor 34 are provided for holding product to be stored within the construction.

In accordance with the constructions described in the aforementioned patents, the illustrated arrangement includes a partition 36 which divides the outer wall into inner passage 38 and outer passage 40. Refrigerating means 42 are located in the inner passage, and circulating fans 44 are provided foi both passages.

Inlets 46 are provided for each passage, and air streams are adapted to move from the outlet nozzles 48 across the access opening and into inlets 46.

During normal operation of the construction, air is circulating through the inner passage 38 whereby the refrigeration means 42 will provide a refrigerated stream of air crossing the access opening. The second circulating stream which moves in the passage 40 and across the access opening serves as a guard stream. An additional stream may be provided by drawing ambient air into duct 47 by means of fan 49 and by discharging the ambient air through the outermost nozzle 48.

The night cover 12 consists of an insulating material which may be formed from a plurality of individually sealed sections 50. A wood or extruded plastic frame 51 may be formed around the sections 50, and a protective aluminum or plastic skin 53 may be provided over each face of the construction. Urethane comprises a particularly useful material for construction of the board. The panels can be advantageously produced by employing a oamed in place system wherein the skin 53 is assembled with the frame 51 to provide mold walls and then foaming material is introduced.

The frame 51 comprises a U-shaped member with the legs being divided into outer strips 102 and inner strips 104. These strips deiine a slot 106 for receiving the facing sheets 53. The ends 108 of the strips 104 are turned in to provide locking means for the insulating material 50. This locking arrangement is particularly desirable when the material 50 is foamed in place.

The base 110 of the U-shaped frame members defines inwardly facing grooves 112. These grooves are adapted to receive the base portion 114 of flexible magnetic re-v taining elements 116. These elements include elongated pockets 118 which receive magnets 120.

The design of the frame members 51 greatly facilitates the construction of individual sections of the night cover 12. When the cover is located in position relative to the cabinet access opening, magnets 120 on the outermost sections are attracted to a magnetic strip 122 which may be adhesively secured around the periphery of the access opening. Use of magnetic tape or some other material which will attract the magnet 120 is required where the structural members of the cabinet are formed of nonmagnetic materials.

The sections 50 are dimensioned so that the combined sections have a width slightly less than the width of the the access opening. This provides gaps between the sections when they are in place as shown in FIGURES 1 4 and 4. These gaps are lled due to the exibility of the magnet retaining means. This iiexibility insures the formation of a seal between the frame members and the peripheral wall of the access opening and between the individual sections.

The top and bottom frame members are of a slightly different design. As shown in FIGURE 3, the top frame member 124 includes a recessed portion for receiving the magnet retaining means 116. The magnetic material in the retaining means is attracted to magnetic strip 126 which is applied over the front face of the innermost nozzle 48.

The lower frame member 128 denes downwardly extending portions 130` having shoulders which rest on the U-shaped bar 132. Magnetic material 134 is located on the under surface of this bar to provide the desired sealing relationship. It has been found that the use of magnetic sealing all around the cover is particularly important from the standpoint of achieving a virtually complete seal. Any leaks present will cause frost build up and this could be substantial even with only a few leaks.

The graph shown in FIGURE 5 illustrates the conditions within a refrigerated enclosure of the type shown in FIGURE 2 when refrigeration is lost. The temperature measurements obtained were initiated after the heat of defrost was removed from the cabinet. From this point, temperature measurements were made every -hour up to 7 hours, and, iinally, after 71/2 hours. Throughout this time, the night cover 12 was in place, and the refrigerating means did not operate so that the test simulated a situation where refrigeration failure had occurred.

During the test, ice cream was in place in the cabinet, and thermocouples were embedded in the ice cream for measuring the temperature of the product at various locations within the construction. `Gallon and pint containers were employed; however, all of the thermocouples were associated with pint containers except one thermocouple which was associated with a half gallon container at the front of the third shelf 30.

The ice cream started at temperatures from -7 to -10 F. After 71/2 hours, the pint of ice cream at the front of the rst shelf 26 had risen to 15 F.; while each of the remaining products tested maintained temperatures between 2 and 10 F. Since the temperatures are well within a safe range for preservation of the ice cream, the use of the night cover, in conjunction with the control circuitry to be described, provides a completely adequate arrangement.

The control circuitry utilized for the cabinet 10 is shown in FIGURES 6 and 7 and comprises a temperature measuring bulb 60 which is preferably fastened to one of the Crossovers 61 between the evaporator coils (see FIGURE 2) and which is associated with control element `62. This element is designed so that the switch 64 will close when the temperature measured exceeds a certain level. In a typical embodiment of the invention, the element 62 is set so that the switch `64 will close when the temperature exceeds 0 F.

The switch 64 is connected through line 66, and terminal block 67 to switch 68. The switch 68 comprises the enabling switch for the control circuit. This switch may comprise a manual switch which when opened cornpletely removes the control circuit from the standard electrical circuits. This is required, for example, during servicing of the freezer.

The switch `64 through lines 66 and 70 and terminal blocks 67 and 71 provides 115 volt power for the time delay relay 72. This circuit includes clock motor 74 (see FIG- URE 7) which will energize on the closing of switch 64, as well as a switch 76 which will be closed mechanically at the end of the selected time delay. In a typical embodiment of the invention, the time delay relay 72 is set to close switch 76, 25 minutes after the switch 64 closes. The temperature control unit 62 is designed so that the switch 64 will open again and reset time delay relay 72 when the temperature detected by the element 60 drops to -10. Accordingly, during a defrost period `when the temperature of the evaporator coil reaches 0, switch 64 will close energizing the clock mechanism 74 in the time delay relay 72. If the temperature of the coil reaches before the end of the 25 minute time delay switch 64 opens, and the time delay relay 72 resets itself. Under such circumstances, the switch 76 will never be closed.

If, however, the refrigeration means is not functioning properly, the switch 76 will be mechanically closed after the expiration of 25 minutes. This will energize the relay 78 thereby opening normally closed switches 80 and 82. These switches are located, respectively, in the power lines leading to the antisweat heaters and to the fan motors so that these mechanisms will not operate when the switches are open. Beckwith Patent No. 3,243,- 971 provides an example of heaters of the type employed for preventing frost build-up. Heaters 92 of the type shown in Beckwith et al. Patent No. 3,403,525 may also be included for preventing moisture build-up, and the control circuit may also be employed for cutting off power to such heaters.

Closing of the switch 76 also energizes relay 84 whereby switches `86 and 88 are closed. The switch 86 shorts out the defrost mechanisms 87 for the system so that a defrosting operation cannot take place after there is a loss of refrigeration. The switch 88 may be connected to an alarm system which will serve to warn the store operator. The light 90 is turned on when the switch 76 is closed so that a visible indication of trouble will be provided.

The system can, of course, be used to equal advantage `with different temeprature controls, for example, where the cabinet operates at higher temperatures.

As shown at FIGURE 4, a spring loaded switch 89 can be installed so that when the night covers are in place the switch will be closed and perform the same function as switch `86 shown in FIGURE `6. With this switch connected to the defrost termination control, defrost cannot occur when the night covers are in use. This is very desirable, since in most freezer cabinets, the defrosting occurs at regular intervals, for example every four hours, six times per day. Thus, with the night covers in use, three defrosts could be eliminated without diiculty since almost no frost is added to the coil with the night cover in place. Additional power saving is achieved because the heat put into the cabinet during the defrost period does not have to be removed. Alternatively, the switch 89 may be used as an enabling means for the control means, for example, by placing the switch in line with the switch 68.

The night cover and control means may be used in conjunction with a variety of cabinet constructions. When employed with the construction shown `in FIGURE 2, however, the night cover is preferably located in the area between the rst guard stream and the refrigerated'stream. During night operation, the circulating fans for the guard streams can be turned ol so that only the circulating fans for the refrigerated stream will be in operation. This can be done automatically by locating a suitable button switch at some point around the periphery of the access opening so that the switch will be operated when the night cover is put into place.

During extremely high ambient conditions, it is possible that after a defrost period, the compressor may have trouble pulling back down to temperature, or may cut off because of high head pressure or because of inherent temperature protection in the motor windings. With the control system of this invention, if the temperature of the coil does not reach the preset temperature in the preset time allotted, the heat load is automatically removed from the condensing unit by shutting off the fans and antisweat heaters. This allows the condensing unit to pull down the suction pressure and lower the head pressure allowing the condensing unit to recover and get over the peak load period, eliminating a possible service call.

It is also contemplated that the means for refrigerating the cabinet can be modied where night covers are regularly used. The compressors employed may be of smaller capacity, and may be included in a circuit which will have them operating continuously. When the night cover is in place, the continuous operation will cause the product to become much colder than necessary. During the period when the covers are off, the product will warm up due to the inability of the compressors to maintain lower temperatures; however, the rise in temperature can be controlled so that the product temperature will never rise to undesirable levels.

In this alternative arrangement, the evaporator coil will operate at a higher temperature so that frost problems will be greatly reduced. This will permit operation of the cabinet at higher humidities which also provides more desirable operating conditions.

It will be understood that various changes and modications may be made in the above described construction which provide the characteristics of this invention without departing from the spirit thereof particularly as defined in the following claims.

That which is claimed is:

1. In a construction comprising a refrigerated enclosure including refrigerating means, circulating means for driving air into contact with said refrigerating means, defrosting means, and means for normally operating the defrosting means at intervals, the improvement comprising control means including temperature detecting means, time delay means adapted to operate when said temperature detecting means indicate a rise in temperature to a rst predetermined level, and adapted to be reset if the temperature detected drops below a second predetermined level before expiration of the time set on said time delay means, said time delay means, if not reset, operating to cut off the operation of said circulating means and to prevent operation of said defrosting means until the temperature is restored to a safe level.

2. A construction in accordance with claim 1 including passage means defined by said enclosure for carrying said air, and heater means located in said passage means for preventing frost and moisture build-up, and wherein said time delay means, if not reset, also operates to cut off power to said heater means.

3. A construction in accordance with claim 1 including alarm means, and wherein said time delay means, if not reset, also operates to power said alarm means.

4. A construction in accordance with claim 1 including a light connected to said time delay means to provide a visible indication of difliculty, and wherein said time delay means, if not reset, also operates to power said light means.

5. A construction in accordance with claim 1 wherein said temperature detecting means operate when the temperature rises to a certain level, a switch connected between said time delay means and a source of power, said switch being closed by said temperature detecting means when said temperature reaches said level to thereby initiate operation of said time delay means, and wherein said switch is opened by said temperature detecting means when the temperature falls t0 a level below said rst mentioned level, said time delay means being reset if the temperature falls to the lower level within a set period time.

6. In a method for operating a refrigerated enclosure wherein evaporator means are operated in association with circulating means for moving air, and wherein defrost means are provided for operation at desired intervals, the improved method comprising the steps of providing a control means including temperature detecting means associated with said evaporator means, said control means operating when the temperature detected by said detecting means rises above a predetermined level, providing time delay means, energizing said time delay means in response to detection of temperature at said predetermined level, said time delay means being set to disable said defrost means and said circulating means if the time delay means is not reset Within a specific time period, resetting of the time delay means to avoid disabling of the defrost means and circulating means occurring in response to detection of a lower predetermined temperature by said temperature detecting means before the expiration of said time period.

7. A method in acordance with claim 6 wherein antisweat heaters are operated in association with said evaporator means, and including the step of disabling said heaters along with said defrost means and circulating means.

References Cited UNITED STATES PATENTS 5/1950 Jones 62-155 1 1/1962 Dickson 62-155 10/1963 Gould 62126 3/1965 Kuhn 62-155 11/1965 Crotser 62-155 WILLIAM J. WYE, Primary Examiner U.S. Cl. X.R.

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