CA1093850A - Reverse flow medium temperature display - Google Patents

Abstract

REVERSE FLOW MEDIUM TEMPERATURE DISPLAY

ABSTRACT OF THE DISCLOSURE
An upright, open front, single curtain refrig-erated display case having reverse flow air defrost com-bined with openings in the rear panel between the display zone and the recirculatory conduit to create a negative pressure in the display zone during defrost to cause initial cold air from the defrosting coil to cascade into the storage zone for minimizing product warming and shock.

Description

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1 BACK~ROUNI) OF T~IE INVENTION
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This invention relates to single curtain upright, open front, re-frigerated display cases~
~:. In recent years, reverse flow air defrost l-as been adapted to multi.ple curtain, upright, open front, ~` display cases, and also to chest type display cases. In :. the former, air is shortcircuited directly between the inner conduit and the adjacen-t conduit at the nozzles ~ and intakes as shown in Ij. S. Patent ~,026,121. The cold 10 air in the product display zone remains relatively quiescent and undisturbed so that ~arming of the product .j . is minimal. ~ncl, in the chest type o:E case, wherein the access openi.ng :is a~ the top, the cold air pool in tl~e product storage zone is retained intact by gravity, for .15 protection of the product agdinst warming.
llowever, reversal of the air flow in a single curtain, open front dlsplay case results in the air that ~: is flowing from the lower opening which normally forms an inlet Eor the refrigerated air curtain, being propelled up and out of the cabinet, which causes cold air in the ` product zone to be entra:ined and drawn out. I~arm ambient ' air replaces it and this can cause thermal shock and damage to tlle food products.
, SU~ IARY OF TI-I~ INVENTION
;~ 25 l~he novel, single curtain, open front, upri~]~t, ; refrigerated display cabinet of this invention employs reverse flo~ air defrost in combination with a negative pressure condition in the display cabinet, causing the initial cold defrost air ejected from the lower opening to cascade into tlle storage area and maintain lower : temperatures about the product. Specifically, a series : -2- j ~ ~ 3 8 ~ ~

l of air flow openings provided in the back panel at the rear of the case, between the storage area and the air flow conduit, creates this negative pressure during reverse air flow, witn the result that thc initial cold air flow from the defrosting coil is drawn into the display zone. As defrost continues and warmer air emerges from the conduit, thermal and volumetric differences in this warmer~ lighter air overcome the negative pressure effect to cause the warmer air to basically depar-t from the display area rather than flowing in arowld the product.
~s a consequence, the encr~y saving concept of reverse flow air de~rost can bc safely adapted to single curtai.n, upright, open frollt display cases without jeopar-dizing the qual:ity of the food being stored and displayed.
Ihese and other objects, advantages and features of the invention will be readily apparent from the detailed disclosure including the drawing.
BRI~E DESCRIPTION OF T~IE DRAWING
The figure is a sectional, side elevational view of the refrigerated display case of this invention.
BRIEF DESCRIPTION OF 'l'l-IE PREFERRED F~1130DI~IENT
Referring IIOW specifically to the drawings, the display case assembly 10 constitutes an open front, upright refrigerated display cabinet employing a single recircula-tory air curtain. The cabinet has a housing 12 supported on a base 14, the housing having a top wall 16, a rear wall 1~, a pair o[ end walls 2(), a bottom 22, a lower front wall 24, and an open front 26 between lower front wall 24 and the frontal portion of the top wall 16. These elements collec-tively define a product storage area or space 2~3 which includes a lower storage bin 30 at the bottom thereof, i.e.

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1 between the back wall and the lower front wall. The open front 26 serves as an access opening to tl~e storage and display area or zone.
Spaced inwardly from the top wall, back wall 9 bottom wall and lower front wall is an interconnected pancl assembly W]liC]I defi.nes a recirculatory air flow conduit around the storage area. More specifically, top panel 32 is spaced from top wall 16 and interconnects with back panel 34, which is spaced from the rear wall 18 and interconnects with bottom panel 36, which is spaced from bottom 22 and interconnects with lower front panel 38, which is spaced from lower front wall 24. Tllere is thus -formed a passage or conduit 40 extending laterally the lengtil of the di.s~lay case. ~t tlle top front portion of t~le clisplay case and of this conduit 40 is an elongated, upper opening 42 oriented basically downwardly and serving as an outlet for refrig- :
erated air during normal refrigeration operation of the display case. Preferably aLr flow directi.onal control means such as honeycomb is employed in conventional fashion. Tliis upper opening is along the upper edge of the open front access opening. Adjacent the upper edge portion o-f lower front wall 24 is an elongated lower opening 4~ which, in normal operation of the case, serves as tlle intake for the refrigerated curtain o air passed across the open front of the display zone, to be recooled as it is recirculated again around the d]splay zone. This :Lower opening 44 preferably includes an orificed grid which serves to prevent articles from falling into the front vertical portion of the duct 40.
ri`he grid preferably has upwardly facing orifices at the top and inwardly facing orifices on the inner upper surface, so arrarlged as to encourage the cascading effect previously r~ ., .~
~ ~ 3 1 described, A series of vertically spaced shelves 50 are mounted to -the back of the display case in -the display and storage zone, typically in canti.lever fashion from vertical uprights (not shown) or the like in the slanted or level positions depi.cted in solid and doubled lines~ as is conven-tional.
Positioned within the duct 40, as at the lower rear of the duct, is a refrigeration coil 54 for heat exchange between ai.r flowing through the coil and re-frig-erant in tubes of the coil in conventional fashion. This coil is preferably associ.ated with a compressor mechanism (not S}IOWII) and a control system for regulating the tempera-ture withill the case. These single curtain cases are typically used for meat and/or produce, maintaini.ng tempera-. tures in the display area just below the freezing point of : water, e.g. about 28 F. or so.
Also in duct 40 is a series of air propelling units such as-fans 56 spaced at intervals along the length

2~ of the display case. The air propelling means in this apparatus is operable to propel air in either direction, the air movement in the refrigeration mode of the cycle being in the direction indicated by the broken arrows, and the air movement or flow in the defrost mode of the cycle being in the direction indicated by solid arrows. The fans or blowers are arranged, e.g. by shape of blades or otherwise, to cause the refrigeration air -flow to be considerably less than the air fIow in the reverse direction -for defrost.
This reversal of air movement may be achieved by employing two-way motors on the fans or by llavillg one set of fans for forward flow and another set for reverse flow, or some other ~3~

l suitable equivalent. /~n electrical control interconnected with the de-frost mechanism can be used to cause the air flow to be reversed.
In the vertical rear panel 34 of the display case is a ser:ies of air flol~ openings 34' preferably at least at the upper rear of the panel, i.e. abo-ve and below the top shelf, provicling communication between the display zone and the duct 40.
~uring operation of the apparatus, when the display is in the refrigeration mode, the refrigeration coil is operative to cool air flowing therethrough, the air being propelled by fans which draw air into the lower opening 44 at the lower front of the case, through duct ~0 past thé
Eans and through the coil where the air is cooled, up tl1e back wall portion of the duct in contact with the rear panel 34 to cool the storage zone, across the top of the display zone, and out the elongated nozzle ~2. The downwardly directed air then flows as a s~ingle curtain in a somewhat S
shaped pattern across the open -front of the display in front of the shelves to the return opening ~ small amount of the refrigerated air flows out openings 3~' and tumbles down across the product shelves. TlliS does not significantly interfere with the curtain, and in fact usually assists in maintaining -the product cool, and a positive pressure refrigerated chamber.
During refrigeration, the coil components accumulate frost and/or ice because of condensation onto the coils o-f moisture entrained in the air being recirculated. Therefore, the coil MUst be periodicallY defrosted. When the defrost mode is activatedi, as by a conventional timer switch or temperature sensing mechanism, the refrigeration equipment ' i ~ ~ ' ! , , 1 to the coil is inactivated and the air propulsion means is operated to propel the air in reverse. Wllen this happens, substanti.al amowlts of air are drawn into the upper opening or nozzle 42, into the top of duct 40 from whence it flows downwardly behind the display zone and through the coil.
Since this ambient air is at a substantially higher tempera-ture, and the coil has been inactivated, the ice and frost are melted from the coil. A small amount is entralned by the a~r and the majority of moisture flows down the drain 60 of the display. The air flow proceeds from the coil through the fans and out the lower opening 44. The openings 34' ln the upper rear of the display serve an important function in ~,.. . .
tllls deLrost operation. Specifically since they allow communication between duct 40 and the display zone, and 1~5 ~becaus~e the duct 40 is under a negative pressure from the fans, a negative pressure is also created in the display zone. This negative pressure and the relative heaviness of th~e cold air off the coil biases the initial cold air flow from lower opening 44 in toward the storage zone. It tumbles .
into tlie lower bin 30,`and tends to cascade upwardly over the shelves and products tllereon (see solid arrows A) to maintain the products cool during the initial stages of the ~ ~ defrost. soDle of it passes through openings 34' and much ; discharges to the ambient air. This minimizes thermal shock and product damage. As defrosting continues and co]l tem~p-~ -eratures rise, the defrost air flowing through the coil and out opening 4~ increases in temperature and thus becomes ; ~ lighter in wélgiht. The thermal and volumetric dlfferences - -in this warmer air cause it to rise more rapidly and more vertically (see solid arrows A') than the initial colder heavier air dischargecl from opening 44. Preferably, the :'~

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1 lower part of the cabinet and the lower opening are offset forwardly relative to the upper opening. The rising warmer defrost air then can readily depart the cabinet without significant tendency to enter the display zone. This effect counteracts the negative pressure effect in the display zone rather than complementing this effect as did the thermal and volumetric characteristics of the initial colder heavier air. Consequently, the warmer air tends to rise upwardly and outwardly from the display zone rather than tumbling into the display zone. This is advantageous to prevent undue warming of the product which now is in a rather stagnant air zone of a cooler temperature than the defrost-ing air discharge. When the defrost mode :is terminated, the re~rigeration system is reactivated, ancl the cycle is repeated.
Once the concept is understood~ the simplicity of the operation and the apparatus is appreciated. This very simplicity is a distinct aclvantage to enable energy savings without sacrifice of food quality, at little added expense for the equipment.
Conceivably, millor variations can be made in the specific structure oE tlle invent:ion to suit a particular heig]lt displ~y) a particular product, an~/or a particular refrigeration system, as examples. Thus, the invention, which is illustrated by one particular and preferred embodi-ment, is defined by the appended claims and the reasonable equivalents thereof . . . :.. - -... ~ .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

An open front, upright, single curtain refrig-erated display cabinet comprising:
a housing defining a product display space with an open front, a conduit around said display space, with upper and lower openings at the top and bottom of said open front; cooling means and air propelling means in said conduit for recirculating a curtain of refrigerated air through said conduit, out of said upper opening, and down across said open front to said lower opening;
the improvement comprising, said air propelling means being operable to propel air through said conduit in one direction during refrigeration mode and through said conduit in the reverse direction during defrost mode so that defrost air is ejected from said lower opening, and openings between said storage space and said conduit for creating a negative pressure in said storage space during said reverse flow such that initial cold defrost air from said lower opening flows into said storage space.

An open front, upright, refrigerated display cabinet comprising:
a housing defining a product display space with an open front, a conduit around said display space, with upper and lower openings at the top and bottom of said open front; cooling means and air propelling means in said conduit for recirculating a curtain of refrigerated air through said conduit, out said upper openings, and down across said open front to said lower opening;
the improvement comprising, said air propelling means being operable to propel air through said conduit in one direction during refrigeration mode and through said conduit in the reverse direction during defrost mode so that defrost air is ejected from said lower opening, and means for creating a negative pressure in said storage space during said reverse flow such that initial cold defrost air from said lower opening flows into said storage space.

The cabinet in claim 2 wherein said lower opening is offset forwardly of said upper opening.

An open front, upright, single curtain refrig-erated display cabinet comprising:
a housing having a top, a bottom, a rear wall, end walls, and a lower front wall, collectively defining a product display space with a lower bin; an open front between said lower front wall and said top; product display shelves supported on said rear wall in said display space; a lower front panel, a bottom panel, a back panel, and a top panel cooperative with said lower front, bottom, rear wall, and top to form a conduit around said display space, with upper and lower openings at the top and bottom of said open front, cooling means and air propelling means in said conduit for recirculating a curtain of refrigerated air through said conduit, out said upper opening, and down across said open front to said lower opening.
the improvement comprising, said air propelling means being operable to propel air through said conduit in one direction for refrigeration and through said conduit in the reverse direction during defrost of said coil so that the defrost air is ejected from said lower opening, and said back panel having openings in the upper portions thereof between said storage space and said conduit for creating a negative pressure in said storage space during said reverse flow such that initial cold defrost air from said lower opening flows into said storage space.