Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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
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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
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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
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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
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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
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