A METHOD IN THE OPERATION OF A REFRIGERATED DISPLAY UNIT

Abstract: In a refrigerated display unit, e.g. a refrigerator or freezer shelf assembly or counter, the air circulation fan is controlled so that when the unit is closed off in the non-business hours of the shop the fan is started and stopped at intervals according to a specific timetable which can be varied. This partly results in energy savings and also protects the goods stored in the refigerated display unit against damage caused by excessive cooling. Variation of the timetable may optionally lake place under control of a temperature sensor fitted in the refrigerated display unit.

Description: A method in the operation of a refrigerated display unit The invention relates to a method of the type defined in the introductory portion of claim 1. The refrigerated display unit may e.g. be a refrigerated or freezer display counter or shelf assembly of the type used in provision shops for storing and displaying provisions. During the periods when the goods in the display unit are not to be accessible to the public, i.e. in the non- business hours of the shop, the cold zone of the re¬ frigerated display unit is normally closed off from the warm zone of the shop, e.g. by means of insulating plates, foil or pull-down curtains. This cover reduces incident radiation and infiltration of air from the surroundings so much that the temperature of the goods in the refrigerated display unit falls, even if the air temperature in the refrigerated display unit is kept constant. As far as refrigerated goods .are con¬ cerned this may involve a risk of freeze damage. A thermostat and/or a pressostat is used for controlling the temperature in the refrigerated display unit. These means ensure that the compressor connected to the re¬ frigerated display unit only operates as long as the thermostat and/or the pressostat applies a signal that cooling is needed in the refrigerated display unit. If a thermostat is used, which is normally the case, the sensor of the thermostat is placed in the flow of circulating air in the refrigerated display unit. If the temperature in the refrigerated display unit is above the value set on the thermostat, the thermostat applies a cooling signal, and this signal may either directly start the compressor or open a magnet valve in the liquid line of the cooling system, which causes the pressostat to start the compressor. It is conceivable that the compressor thermostat might also be used for controlling the circulation fan so that both the compressor and the fan would operate when cooling was needed, and both members would be in¬ operative when no cooling was needed. However, this is not feasible in practice since for reasons of refri¬ geration the sensor of the thermostat is fitted ad¬ jacent the evaporator, usually in the inlet air of the. evaporator. If the thermostat stops the compressor and the fan, a cold zone will be formed around the evapo¬ rator and the thermostat sensor, which means that it will take too long before the thermostat again applies a start signal to the compressor. Another possibility of controlling the air temperature consists in fitting an additional thermostat in the flow of circulating air for the control of the fan. The sensor of this thermostat would then have to be placed at the point where the highest temperature would occur when the fan was inoperative. Thus, such a system comprises two thermostats to be set when the temperature level in the refrigerated display unit is to be changed. If the fan control thermostat is inadvertently not set, the danger exists that the fan either operates all the time or, at worst, is inoperative all the time. The object of the invention is to provide a method of the type described which permits energy savings for the operation of the circulation fan in the non-business hours while preventing detrimental supercooling of the goods in the refrigerated display unit. This object is achieved by carrying cut the method as stated in the characterizing portion of claim 1, it being possible to adapt, without difficulty, the time¬ table to the actual operating conditions so that the air temperature everywhere in the refrigerated display unit is kept within determined limits. Even if the air temperature is changed by adjustment of the compressor thermostat, it is not necessary to change the time¬ table according to which the fan is controlled. The regulation of the operating period of fan thus • established also reduces the consumption of energy for the operation of the compressor, because the heat supplied by the fan in the refrigerated display unit decreases so that the operating period of the compres¬ sor is reduced. It normally applies to all the open type refrigerator and freezer furniture that one or more heater wires are provided to counteract condensation where the cold and the warm air meet. When such a refrigerated display unit is constructed as stated in claim 2, additional savings in the energy spent on the operation of the heater wire or wires and a corresponding additional reduction in the energy consumption of the compressor will be ob¬ tained. To provide for the possibility of adapting the on/off periods of the circulation fan to varying conditions, the timetable should be variable as stated in claim 3- In practice, the simplest regulation is obtained when start and stop take place at intervals, as stated in claim 4, and when the on and off periods are independent- ly adjustable, as stated in claim 5. ■ i .J * '- ** The on and off periods can be set manually on an em¬ pirical basis, but when they are controlled by their respective temperature sensors or the same temperature sensor, as stated in claim 6, the temperature at one or more control points will with certainty never exceed a predetermined value. Switching of the refrigerated display unit from constant to intermittent operation of the circulation fan and vice versa can take place manually? but it is also possible to effect it automatically by establishing and removing, respectively, the cover, as stated in claim 7. Mounting and dismounting of the cover can be recorded in many ways, e.g. mechanically, capacitively or inductively or by means of a photocell. The same recording means can aJ.so be employed to control the defrosting of the re¬ frigerated display unit, if desired. An embodiment of a refrigerated display unit according to the invention having control circuitry is shown schematically in the drawing and will be described more fully below with reference to the drawing. The drawing shows the use of the invention in connection with a refrigerated shelf assembly which is shown in a vertical cross-section and is generally designated by 10. The shelf assemblyforms a box which is closed at all sides except at the front side, from which the goods stored on the shelves are accessible through an opening defined by the lower " edge of an upper front wall member 11 and the upper edge of a lower front wall member 12. A flange 13 is placed on the top wall of the shelf assembly at some distance from and parallel with the front wall member 11, and fittings for fluorescent tubes 14 are placed between this flange and the front wall. As shown in the drawing a removable cover plate 15 is mounted, extending from the lower edge of the flange 13 to the upper edge of the lower front wall member 12. This cover plate is mounted after business hours to reduce reception of heat from the sur¬ roundings and is removed again before the shop opens. In a bottom chamber 16 defined between the bottom wall of the shelf assembly and a base plate 17 is fitted an evaporator 18 which forms part of a cooling system of an ordinary known type. A fan 19 likewise mounted,in the bottom chamber 16 draws air across the evaporator to cool the air and presses it up through a channel 20, which is defined between a rear plate 21 and the rear wall of the shelf assembly and from which the cold air is guided towards the front side of the shelf assembly through another channel 22, defined between the top wall of the shelf assembly and an upper plate 23, and is then guided down to the bottom and finally through a gap 24 between the front wall of the shelf assembly and the front edge of the base plate 13- The path of the circulating air is indicated by arrows. The rear plate 21 may optionally be perforated so that air sub-flows can pass from the channel 16 across goods on shelves 25 attached to the rear plate. On the lower edge of the flange 13 where the cold air from the evaporator meets warm air from the outside, may be arranged a heater wire 34 in conventional manner which serves to prevent condensation of moisture in the warm air. The liquid line of the cooling " system has inserted in it a magnet valve 26 in whose electric supply circuit a switch 27 is inserted which is controlled by a ther o- / Z Pl stat 28 whose sensor 29 is placed in the bottom chamber 16 in front of the evaporator 18. Thus, the magnet valve 26 controls in conventional manner the start and stop of the not shown compressor of the cooling system in dependence upon the air temperature in the refrigerated shelf assembly. The electric supply circuit of the fan 19 and the heater wire 34 has inserted therein a switch 30 which serves to switch from continuous operation of the fan and the heater wire in the business hours of the shop when the cover plate 15 is removed, to intermittent fan and heater wire operation in the non-business hours when the cover plate 15 is mounted as shown. The switch 30 is shown in an open position corresponding to intermit- tent operation. In this state the supply of power to the fan is controlled by another switch 31 which is con¬ nected in parallel with the switch 30 and is actuated by a timer 32. The timer is in conventional manner adapted to close the switeh 31 and keep it closed for a specific period of time and then to open the switch and keep it open for another specific period of time, etc., and both periods of time can be varied indepen¬ dently of each other. The timer can thus be set manually on an empirical basis to connect and disconnect the supply of power to the fan and the heater wire at inter¬ vals with such on and off periods as will keep the air temperature in the refrigerated shelf assembly at the desired level. It is also possible to control the . timer 32 automatical- ly in dependence upon the air temperature at a control point in the refrigerated shelf assembly by means of a temperature sensor 33 which is arranged at this point and is connected to the timer as shown by a dashed line. The temperature sensor may e.g. be a temperature dependent resistor whose resistance is determined by the on and/or off period of the timer. There may also be provided a special temperature sensor for the control of each of these periods. The details of the shown and described refrigerated shelf assembly may moreover be modified in other ways. Thus, e.g. the switch 30 may be adapted to be actuated automatically on mounting and dismounting of the cover plate.

Claims: P a t e n t C l a i m s : 1. A method in the operation of a refrigerated display unit comprising a cooling element and at least one fan for circulating air past the cooling element in the unit and having cover means for closing off the interior of the unit from the surroundings in the non-business hours where no access is required to the goods stored in the unit, c h a r a c t e r i z e d in that in the non-business hours the fan is started and stopped auto¬ matically according to a predetermined timetable. 2. A method according to claim 1 i the operation of a refrigerated display unit having one or more heater wires for counteracting condensation, c h a r a c ¬ t e r i z e d in that also the supply of power to the heater wire or wires is connected and disconnected automatically according to the predetermined " time¬ table. 3- A method according to claim 1 or 2, c h a r a c ¬ t e r i z e d in that the time table is variable. 4. A method according to claim 1, 2 or 3, c h a r a c - t e r i z e d in that start and stop take place at intervals. 5. A method according to claim 4, c h a r a c t e r ¬ i z e d in that the operative and inoperative periods are independently adjustable. 6. A method according to claim 5, c h a r a c t e r ¬ i z e d in that the operative and/or inoperative periods are controlled by their respective temperature sensors or by the same temperature sensor. 7. A method according to any of the preceding claims, c h a r a c t e r i z e d in that switching from constant to intermittent operation of the fan and vice versa is effected automatically by respectively estab¬ lishing and removing the cover.

Inventors: CHRISTENSEN FINN G, OVERGAARD BENT
Applicants: CHRISTENSEN FINN G, KNUDSEN KOLING AS, OVERGAARD BENT
Application year: 1981
Main classification: A47F3
IPC codes: A47F3