Refrigeration – Automatic control – Refrigeration producer
Patent
1992-07-20
1994-06-07
Tapolcai, William E.
Refrigeration
Automatic control
Refrigeration producer
62256, A47F 304
Patent
active
053178815
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to apparatus for displaying food or other material under refrigerated conditions.
The installations currently used for the refrigerated display of food, for example in a self-service display, tend to suffer from uneven temperature distribution in the display compartment, leading to food in some areas of the display compartment being at undesirably high temperatures and food in other areas being at undesirably low temperatures.
An aim of the present invention is to minimize this drawback.
SUMMARY OF THE INVENTION
According to the present invention, there is provided apparatus for displaying material under refrigerated conditions, comprising a display compartment, means for generating a stream of cooled air which passes through the display compartment, an air inlet sensor for sensing the temperature of the air at the inlet to the display compartment, an air outlet sensor for sensing the temperature of the air at the outlet from the display compartment, and control means responsive to the sensors for controlling the operation of the refrigeration means, thereby maintaining the air temperature in the display compartment within a narrow predetermined range.
Desirably the control means is responsive to the computed mean of the inlet and outlet temperatures, the computed mean temperature corresponding approximately to the actual temperature approximately at the mid-point between the inlet and outlet.
Preferably the refrigeration means includes a condenser, an evaporator and a fan. In that case preferably the fan is a centrifugal fan and is located upstream of the evaporator so that the air stream in the vicinity of the evaporator is slightly pressurized. The fan may then be located near the outlet from the display compartment and in communication with it so that the air follows a closed circuit. Preferably again the fan and the configuration of the display compartment are such that an evenly distributed laminar air flow is achieved. If desired, a further fan may be located downstream of the evaporator to drive a branch airstream to a refrigerated storage compartment.
Conventional refrigerated display installations have typically been run with an average temperature in the display compartment of +10.degree. C. With the current concern over the bacterial contamination of food, such a temperature is not now regarded as sufficiently low, and it is desirable, and may in the future even be necessary, to operate refrigerated display installations at a temperature as low as +5.degree. C. However, such relatively low temperature operation will exacerbate the disadvantage suffered by conventional installations which tend to deposit moisture on the evaporator, thus dehumidifying the air passing over the displayed food which consequently becomes dehydrated. Moreover, the consequent accumulation of ice on the evaporator leads to inefficient refrigeration and the need for more frequent de-frosting.
Preferably, in an apparatus in accordance with the present invention in which the refrigeration means includes a condenser, an evaporator and a fan, the evaporator has a large surface area, for example at least twice that of a conventional area in the case of a gravity fed unit, allowing it to be operated at a temperature such that moisture is retained in the air stream. The humidity of the air stream in the display compartment may thereby be increased by from 10 to 20%, typically about 15%, with respect to ambient relative humidity (RH). The evaporator may comprise a conventional coil, in which case the air flow over the evaporator may be so widely distributed that the coil never becomes blocked. The higher operating temperature reduces the amount of defrosting necessary. The fan speed may be so controlled as to permit automatic air flow defrosting without the need for heaters, thus allowing the temperature of the air flow to be kept at a low level during the de-frosting cycle.
There may be, downstream of the refrigeration means, continuous humidification means, for example a h
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patent: 4117698 (1978-10-01), Vogel
patent: 4738806 (1988-04-01), Noma et al.
Colbrook Equipment Limited
Reynolds Florence U.
Tapolcai William E.
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