Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Nachine Dishwashina Process
FIELD_OF THE INVENTION
This invention relates to a machine dishwashing
process; more particularly, it relates to an
improvement in continuous or non-continuous machine
dishwashing, whether conducted using a single tank,
multitank or conveyor type machine.
BACKGROUND OF THE INVENTION
In a typical machine dishwashing process,
tableware or cookware, such as dishes soiled with food
remains, trays, cutlery and lipstick-smeared glasses, is
in~ensively sprayed with water in a prewash zone or
prewash cycle. The water used for the prewash may be
cold or preheated fresh water or cooling water from a
vapor condensation process, but is generally overflow
water of a wash liquor, which is generally sprayed onto
the articles under relatively low pressure and in
relatively large amounts using suitably located spray
nozzles. After this prewash zone or prewash cycle, the
articles enter the actual wa~h zone or wash cycle, where
they are again vigorously sprayed this time with a wash
liquor.
The wash liquor is generally water at a
temperature of from 50 to 60C to which a liquid or
powder-form detergent is added. In order to remove
grease, starch, stains and protein with sufficient
reliability, for example powder detergent or liquid
detergent is added to water to provide from 0.1 to 0.3
weight percent of active ~leaning agent in solution.~
This resulting wash liquor is sprayed onto the articles
by pump means through lower and upper nozzles and, in
soma cases, through additional lateral noz~les. The
soil present on the articles is removed or at least
cwollen or ssftened and partially dissolved by the wash
liquor. In following rinse zones or cycles, the swollen
or softened food remains are removed and, at the same
time, the wash liquor is rinsed off by water. In a
final rinse zone or final rinse cycle, any residues of
the wash liquor are re~oved by water at a temperature
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up to about 85C. The final-rin~e water consists of
fresh water with an added rinse aid, which ensures that
only an ultra~hin film of water rPmains on the articles,
which can evaporate in a following drying zone.
Even the use of relatively large amounts o~
detergent in regular conventional cleaning will not
always avoid the need for periodic heavy-duty cleaning.
The object of this extra cleaning is to remove coatings
of, for example water-insoluble stains or starch which
have gradually built up, but which are not immediately
discernible. For this heavy-duty cleaning, the articles
are treated occasionally with a wash liquor containing
several times the normal quantity of detergent.
Optionally, a manual pre-soak may be employed to the
same end. Both of these methods also mean additional
pollution of the wastewater.
SUMMARY OF THE INVENTION
According to the present invention a surprisingly
advantageous dishwashing is provided. The improved
efficiency of cleaning obtainable may reduce labor,
water and chemical consumption, hence lower pollution
and rejects, while ensuring satisfactory cleaning even
in adverse conditions.
~he present invention provides a machine
dishwashing process characterized in that a highly
concentrated aqueous cleaning formulation is sprayed
onto at least partially soiled articles and, after a
contact time, the cleaning ~ormulation and soil are
removed in one or more subsequent stages.
The present invention also provides a dishwashing
machine adapted to effect such a process, for example by
addition of extra spray noæzles and associated systems
and/or by modifications to the control systems of the
machine.
According to an aspect of the invention, a machine
dishwashing process which comprises spraying onto at
least partially soiled articles at low volume and low
intensity a highly concentrated aqueous cleaning
formulation comprising at least 0.5 weight percent of
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one or more active cleaning agents and, after an
uninterrupted time of at least 2 seconds, removing the
cleaning formulation and soil in one or more subsequent
stages.
According to another aspect of the invention, in a
machine dishwashing process for removing soil from an
article of ware of the type wherein the soiled article
is washed in at least one washing stage and rinsed in at
least one rinsing stage, the improvement which comprises
an additional step for softening soil on the article,
said additional step being applied before any final
rinse and the additional step comprises:
a) applying at a low volume, low intensity and
low temperature, during a wash cycle, a highly
concentrated, aqueous, alkaline detergent formulation
having from at least 0.5 weight percent to about 30
weight percent of at least one active alkaline cleaning
agent onto at least partially soiled articles, the
formulation being in substantially complete contact and
substantially even distribution on the soiled articles
after application;
b) allowing the alkaline detergent formulation to
: stay in contact uninterruptedly with the articles for a
period of between 2 to 100 seconds after application to
chemically soften the soil and during which time no
additional cleaning formula is applied;
c) subsequently, during a rinse cycle, removing
the detergent formulation and soil from the articles,
and
wherein the soil is not removed from the
article during the wash cycle.
According to another aspect of the invention, in a
machine dishwashing process for removing soil from an
article of ware of the type wherein the soiled article
iæ washed in at least one washing stage and rinsed in at
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least one rinsing stage, the improvement comprises:
a) at least intermittently complementing the at
least one washing stage by softening soil on the article
of ware by the additional step of:
misting onto the article at low volume, low
intensity and low temperature, a sprayable, aqueous,
highly alkaline detergent formulation having at least
0.5% to about 30~, by weight, of at least one alkaline
active cleaning ingredient, the formulation being
substantially evenly distributed and in substantially
complete contact with the article after misting;
b) maintaining contact between the formulation
and the article for an uninterrupted contact period of
between 2 to about 100 seconds, during which time no
further operation is performed on the article, any soil
on the article being softened during the contact period;
c) rinsing the article to remove the softened
soil and the detergent formulation therefrom; and
wherein the soil is not removed from the
article during the misting or the contact period.
According to a further aspect of the invention, in
a machine dishwasher process for removing soil from an
at least partially soiled article of ware wherein the at
least partially soiled article is washed and rinsed
during a washing cycle which includes at least one wash
stage and at least one rinse stage, the at least one
rinse ~tage including at lea~t a final rinse, the
: improvement comprises:
: complementing said at least one wash stage by
softening soil for its removal before any final rinse of
said at least one rinse stage, said softening of said
soil during said washing cycle comprises the step6 of:
a) applying at a low volume, low intensity and
low temperature, a highly concentrated, aqueous,
alkaline detergent formulation having from at least 0.5
weight percent to about 30 weight percent of at least
one active alkaline cleaning agent onto at least
partially soiled articles, the formulation being in
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substantially complete contact and substantially even
distribution on the soiled articles after application;
b) allowing the alkaline detergent formulation to
stay in contact uninterruptedly with the articles for a
period of between 2 and 100 seconds after application to
chemically soften soil during which time no additional
cleaning formula is applied; and
c) subsequently removing the detergent
formulation and soil from the articles.
The aqueous cleaning formulation may be derived
from powder-form or liquid materials. Generally, the
sprayed cleaning formulation comprises at least 0.5
weight percent of one or more active cleaning agents.
While, say, 30 weight percent might be regarded as an
upper limit/ the critical factor is that the ~ormulation
must remain sprayable. Preferably, the sprayed cleaning
formulation comprises from 0.8 to 10 weight percent,
more preferably from 0.9 to 3 weight percent, of one or
more active cleaning agents.
Generally, a contact time of at least two seconds
will be sufficient for the desired chemical, as opposed
to mechanical, action. In preferred embodiments, this
may be from 5 to 100 seconds, in particular from 8 to 25
seconds. So as to provide the desired prolonged
intimate contact or "saturation", the "mechanical
effect" of spraying is at least minimized, if not
avoided. During this contact time, the articles being
washed are not deliberately sprayed.
In order to optimize results, it is important that
substantially the whole surface of a soiled article
should be contacted by the sprayed cleaning formulation
and the amount of formulation sprayed and the manner in
which it is sprayed may be adapted bearing this aim in
mind. A fine, gentle mist-like spray is particularly
desirable. In a conveyor-type machine, the belt speed
will also be a fac~or. More particularly, the volume
sprayed and/or the number and/or arrangement of spray
nozzles is/are selected so that low volume sprayin~ will
ensure the desired type of complete coverage and even
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distribution. The nature, volume and concentration of
the sprayed formulation may be varied, as may the spray
means, depending, for example, on the load and, where
appropriate, the motion and/or speed of the conveyor.
The present low volume/low intensity mist-like
application of concentrated cleaning formulation is in
contrast to the vigorous high volume spraying used in
conventional dishwashing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Generally, a machine dishwashing process may
comprise one or more prewash cycles or zones, which may
be optional, for example to remove heavy soil, one or
more wash zones and one or more rinse zones. In
accordance with the present invention, the unusually
high concentration cleaning solution is sprayed
somewhere prior to the final rinse, com~tonly as at least
part of a wash cycle or in a wash zone.
While all of the cleaning agents required may be
included in the sprayed concentrate, it may be
advantageous to introduce additional cleaning
formulation in a conventional manner at some stage of
the process. This further material is generally not the
same as the sprayed concentrate, but may merely be the
same composition further diluted. The use of a
complementary formulation particularly commends itself.
The balance of the complementary products may also be
adjusted. For example, a high alkalinity spray might be
balanced by a lower alkalinity wash to follow. The
present system also enables chemicals which would
normally be incompatible when mixed in a single product
to be used in conjunction, for example oxidizing agents,
such as hypochlorite, may be used in the spray with, for
example, water conditioning agents, such as NTA
; ~nitrilotriacetate) being introduced later.
While the concentrated cleaning formulation is
generally sprayed more or less throughout the
appropriate part of the dishwashing process, it may b~
used inter~ittently or occasionally, for example during
the wash cycle in a non-conveyor type machine.
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The aqueous cleaning formulation sprayed must be
flowable, but may be in the form of a solution, emulsion
or slurry, for example. Various materials are known
which will cause or facilitate at least some penetration
and/or swelling and/or loosening and/or dissolution of
soil. Typically, a basic cleaning formulation will
comprise a source of alkalinity and a source of
sequestering activity. Such formulations may be adapted
to combat particular problems. For example, tea-stain
lo removal might suggest the inclusion of bleaching agents,
while products based on amylase may be useful for starch
removal without alkalinity.
For purposes of illustration, a machine for
carrying out the present process may be a conveyor
transport machine and may comprise a prewash zone, a
wash zone, a rinse zone, a final rinse zone and a drying
zone. Fresh water is only supplied to the final-rinse
zone, subsequently passing cascade-fashion towards the
prewash zone in countercurrent to the direction of
transport of the dishes.
A simple product fairly efficient in removing
built-up starch residues and stains may be formulated
from the following :
Potassium hydroxide20 - 30 wt ~
Chelating agent(s)15 - 25 wt %
Threshold agent(s~2 - 4 wt ~
Dispersing polymer(s) 2 - 4 wt %
Wetting agent(s) 1 - ~ wt %
Balance water
Optimization of such a product is possible and
desira~le. Such a product may be blended with water in-
line before being sprayed at a dilution of about 2.5 %
through suitable spray nozzles situated within the wash
zone immediately before or after the conventional wash
zone. Sprayed ware may then pass through part of the
wash zone with the pumps turned off (unless there is
already sufficient separation batween zones) so as to
allow a contact time of about 15 seconds, before
reaching a further wash or rinse zone. Further
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detergent may be added by conventional means at other
stages to provide additional destaining and prevention
of incrustation of machine parts. Thereafter, the ware
passes to a final rinse stage where rinse aid may be
introduced.
After soiled dishes have been loaded onto the
conveyor belt, in the prewash zone it is deluged in
overflow water from the wash zone, which has a
temperature of about 40C. All coarse or relatively
large quantities of food remains are thus removed from
the dishes. The dishes then enter the actual wash zone.
In the wash zone, the dishes are sprayed with the highly
concentrated detergent solution, each nozzle may be
delivering in a fine spray or mist form as little as 6
l/hour and typically there will be from 3 to 10 nozzles.
The system is arranged or adapted to ensure that nothing
disturbs the desired prolonged intimate contact.
; The speed of the conveyor belt is advantageously
selected so that the contact time of the detergent
solution, depending on its concentration, is from 5 to
100 seconds, generally about 10 seconds. Such a contact
time and the high concentration of the detergent
solution ensure that all food remains on the dishes,
especially grease (fats), starch, stains and protein,
- 25 are completely removed and bacteria destroyed.
After this contact time, the detached food remains,
together with the detergent solution sprayed on, are
washed off by the subsequent stages using conventional
spray nozzles, the wash liquor consisting of overflow
water from the rinse zone and of rinsed-off,
concentrated detergent solution and any additional dosed
complementary cleaning formulation. With the process
according to the present invention, there is no longer
any need for the inter~ittent heavy-duty cleaning or the
manu~l pre-soak hitherto necessary.
In the s~bsequent rinse zone, any loosened food and
soil remains still present on the dishes and residues of
the wash li~uox are rinsed off with clear water at a
temperature of about 70-C. In the final- rinse zone,
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fresh water at a temperature of about 85C with rinse
aid added ensures that only a thin film of water remains
on the dishes, which dries rapidly in the following
drying zone either through the heat of the dishes or by
introduction of hot air.
By virtue of the present process, dishes are
reliably maintained to a consistent high standard of
cleanliness.
Although preferred embodiments of the invention
have been described herein in detail, it will be
understood by those skilled in the art that variations
may be made thereto without departing from the spirit of
the invention or the scope of the appended claims.
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