U.S. patent number RE30,478 [Application Number 06/067,866] was granted by the patent office on 1981-01-13 for apparatus for rinsing and chemically sanitizing food ware items.
This patent grant is currently assigned to Hobart Corporation. Invention is credited to Stuart E. Athey, Louis F. Fraula.
United States Patent |
RE30,478 |
Fraula , et al. |
January 13, 1981 |
Apparatus for rinsing and chemically sanitizing food ware items
Abstract
A low wash and rinse temperature (120.degree.-140.degree. F.)
warewasher accomplishes the same general washing and rinsing
effectiveness as a conventional high temperature (150.degree. F.
minimum wash, 180.degree. F. minimum rinse) warewasher without loss
of productivity resulting from time lost between completion of
washing and commencement of rinsing a given load of ware, through
use of independent, dedicated wash and rinse systems, the latter of
which includes a holding tank which enables independent batching of
a predetermined volume of rinse solution from properly-proportioned
fresh water and sanitizing agent while washing a given load of
ware. The sanitizing agent is introduced independently into the
holding tank and independently of the fresh water line, and is
therefore unaffected by a great range of water line pressures and
the mineral conditions of the water.
Inventors: |
Fraula; Louis F. (Troy, OH),
Athey; Stuart E. (Troy, OH) |
Assignee: |
Hobart Corporation (Troy,
OH)
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Family
ID: |
22078943 |
Appl.
No.: |
06/067,866 |
Filed: |
August 20, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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835197 |
Sep 21, 1977 |
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Reissue of: |
875868 |
Feb 7, 1978 |
04147559 |
Apr 3, 1979 |
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Current U.S.
Class: |
134/57D;
134/103.1; 134/99.2 |
Current CPC
Class: |
A47L
15/4236 (20130101); A47L 15/0081 (20130101) |
Current International
Class: |
A47L
15/44 (20060101); B08B 003/02 () |
Field of
Search: |
;134/56D,57D,58D,95-96,100-101,176,186 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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223053 |
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Mar 1959 |
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AU |
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426994 |
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Oct 1970 |
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AU |
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1098492 |
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Feb 1961 |
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DE |
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1072346 |
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Sep 1954 |
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FR |
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1272981 |
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May 1972 |
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GB |
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Primary Examiner: Bleutge; Robert L.
Attorney, Agent or Firm: Biebel, French & Nauman
Parent Case Text
This is a division of application Ser. No. 835,197, filed Sept. 21,
1977.
Claims
What is claimed is:
1. A sanitizing rinse system for use in a warewasher such as a
dishwashing machine for supplying a predetermined quantity of rinse
solution comprising fresh water and a chemical sanitizing agent
uniformly distributed therein at a predetermined concentration, and
for spraying the solution onto food ware items such as dishes
within a chamber in the warewasher, the warewasher having a sump
for retaining a quantity of wash water for spraying successive
loads of food ware items during successive wash cycles,
comprising:
(a) rinse nozzles for spraying the rinse solution onto the items
within the chamber, the nozzles being connected and dedicated for
spraying only the rinse solution,
(b) a holding tank for accumulating a predetermined quantity of the
rinse solution prior to spraying through said rinse nozzles,
(c) a rinse pump connecting said holding tank to said rinse nozzles
and controllable for pumping substantially all the rinse solution
from the tank and onto the food ware items at a predetermined
pressure and at a predetermined time during operation of the
warewasher,
(d) a source of fresh water at a temperature below effective
bacteria killing temperatures and connected for introducing and
circulating such fresh water into said holding tank, said source
being openable and closeable for introducing fresh water when open
and terminating the introduction thereof when closed,
(e) a source of the chemical sanitizing agent connected and
constructed for introducing a predetermined quantity thereof into
said holding tank when actuated,
(f) control means for controlling at least said fresh water and
sanitizing agent sources for initiating filling of the
predetermined quantity of rinse solution into said holding tank by
opening said fresh water source and actuating said sanitizing agent
source at predetermined times and closing said sanitizing agent
source after a predetermined quantity of the agent has been
supplied into said holding tank,
(g) quantity sensing means for sensing the quantity of solution in
said holding tank and closing said fresh water source when said
holding tank contains the predetermined quantity of solution, and
.[.(i).]. .Iadd.(h) .Iaddend.said control means also controlling
said rinse pump during operation of the warewasher to pump and
spray substantially all of the predetermined quantity of rinse
solution from said holding tank onto the food ware items at a
predetermined time during operation of the warewasher.
2. The system of claim 1 wherein said control means comprises means
for opening said fresh water source and actuating said sanitizing
agent source while the warewasher is in the process of washing
items therein.
3. The system of claim 1 wherein said control means comprises means
for opening said fresh water source and actuating said sanitizing
agent source as substantially the same time.
4. The system of claim 1 wherein said fresh water source and said
sanitizing agent source comprise means positioning them for
introducing the fresh water and sanitizing agent into said holding
tank at substantially the same place, above the highest level of
fluid in the tank, and for entraining the sanitizing agent in the
water to minimize the escape thereof into the surrounding
atmosphere.
5. The system of claim 1 including actuatable fill cycle means for
the warewasher, comprising:
(a) means mounting said holding tank above the height of the
warewasher sump,
(b) an overflow drain connecting said holding tank and the sump for
draining fluid in excess of said predetermined holding tank
quantity from said holding tank into the warewasher sump, and
(c) means for overriding said quantity sensing means and holding
said fresh water source open when said fill cycle means is actuated
for overflowing a predetermined quantity of water from said holding
tank into the sump, to provide for filling the warewasher from the
same, single fresh water source which supplies the water for the
rinse solution.
6. The system of claim 5 wherein said overriding means is part of
said control means and overrides said quantity sensing means for a
predetermined time interval.
7. The system of claim 6 wherein said fill cycle means further
comprises means for operating said rinse pump to drain the contents
of said holding tank and spray the same into the warewasher chamber
after the predetermined time interval of said overriding means has
expired.
8. The system of claim 1 wherein the warewasher chamber is a single
chamber for holding, washing, and rinsing the food ware items.
9. The system of claim 1 further comprising freely rotating rinse
arms connected to said rinse pump and supported and located at both
the bottom and top of the warewasher chamber for spraying food ware
items therein from both above and below, said rinse nozzles being
located on said rinse arms, and said rinse means including means
for rotating said arms in response to the pressure of the rinse
solution supplied thereto by said rinse pump. .[.10. In a
sanitizing rinse system for a warewasher which includes a
spray-type washing system for removing soil from articles to be
washed prior to being rinsed, the improvement comprising:
a chamber in which articles to be rinsed are supported for washing
and rinsing,
a rinsing spraying system having spray nozzles within said
chamber,
a source of fresh water under facility line pressure associated
with a main water supply,
a holding tank for receiving a predetermined volume of water from
said source,
valve means for connecting and disconnecting said source with said
tank for filling said tank,
a sanitizing material supply,
means for dispensing a predetermined quantity of sanitizing
material into said tank for dispersion with water to produce a
batch of sanitizing solution capable of destroying bacteria when
sprayed onto said articles,
pump means interconnecting said tank and spray nozzles to pump said
batch of solution under pressure onto said articles to rinse said
articles,
first control means for operating said valve means to commence
introduction of fresh water into said tank,
second control means for operating said dispensing means to
introduce said predetermined quantity of sanitizing material into
said tank, and
third control means independent of said first control means for
operating said valve means to discontinue water introduction into
said tank in
response to achieving a predetermined batch of solution therein..].
11. A sanitizing rinse system for use in a warewasher such as a
dishwashing machine for supplying a predetermined quantity of rinse
solution comprising fresh water and a chemical sanitizing agent
uniformly distributed therein at a predetermined concentration, and
for spraying the solution onto food ware items such as dishes
within the warewasher during a washing cycle, the warewasher having
a single chamber for holding the food ware items during both the
washing and rinsing thereof and a sump for retaining a quantity of
wash water for spraying onto the food ware items during successive
wash cycles, comprising:
(a) rinse nozzles for spraying the rinse solution onto the items
within the chamber, the nozzles being connected and dedicated for
spraying only the rinse solution,
(b) a holding tank mounted above the height of the warewasher sump
for accumulating a predetermined quantity of the rinse solution
prior to spraying through said rinse nozzles,
(c) a rinse pump connecting said holding tank to said rinse nozzles
and controllable for pumping substantially all the rinse solution
from the tank and onto the food ware items at a predetermined
pressure and at a predetermined time during operation of the
warewasher,
(d) freely rotating rinse arms connected to said rinse pump and
supported and located at both the bottom and top of the warewasher
chamber for spraying food ware items therein from both above and
below, said rinse nozzles being located on said rinse arms, and
said rinse arms including means for rotating said arms in response
to the pressure of the rinse solution supplied thereto by said
rinse pump,
(e) a source of fresh water at a temperature below the effective
bacteria killing temperatures and connected for introducing and
circulating such fresh water into said holding tank, said source
being openable and closeable for introducing fresh water when open
and terminating the introduction thereof when closed,
(f) a source of the chemical sanitizing agent connected and
constructed for introducing a predetermined quantity thereof into
said holding tank when actuated,
(g) means positioning said fresh water source and said sanitizing
agent source for introducing the fresh water and sanitizing agent
into said holding tank at substantially the same place, above the
highest level of fluid in the tank, for mixing and for entraining
the sanitizing agent in the water to minimize the escape thereof
into the surrounding atmosphere,
(h) control means for controlling at least said fresh water and
sanitizing agent sources for initiating filling of the
predetermined quantity of rinse solution into said holding tank by
opening said fresh water source and simultaneously actuating said
sanitizing agent source as the washing machine begins a washing
cycle and closing said sanitizing agent source after a
predetermined quantity of the agent has been supplied into said
holding tank,
(i) quantity sensing means for sensing the quantity of solution in
said holding tank and closing said fresh water source when said
holding tank contains the predetermined quantity of solution,
(j) said control means also controlling said rinse pump during
operation of the warewasher to pump and spray substantially all of
the predetermined quantity of rinse solution from said holding tank
into the food ware items at a predetermined time during operation
of the warewasher, and
(k) actuatable fill cycle means for the warewasher, including:
(i) an overflow drain connecting said holding tank and the sump for
draining fluid in excess of said predetermined holding tank
quantity from said holding tank into the warewasher sump,
(ii) overriding means incorporated in said control means for
overriding said quantity sensing means and holding said fresh water
source open for a predetermined time interval when said fill cycle
means is actuated for overflowing a predetermined quantity of water
from said holding tank into the sump, to provide for filling the
warewasher from the same, single fresh water source which supplies
the water for the rinse solution, and
(iii) means for operating said rinse pump to drain the contents of
said holding tank and spray the same into the warewasher chamber
after the
predetermined time interval of said overriding means has expired.
12. A sanitizing rinse system for use in a warewasher such as a
dishwashing machine for supplying a predetermined quantity of rinse
solution comprising fresh water and a chemical sanitizing agent
uniformly distributed therein at a predetermined concentration, and
for spraying the solution onto food ware items such as dishes
within a chamber in the warewasher, the warewasher having a sump
for retaining a predetermined quantity of wash water and for
collecting the wash and rinse solutions after spraying onto the
food ware items for spraying successive loads of food ware items
during successive wash cycles, the sump including a sump overflow
drain for automatically controlling the level of wash water within
the sump, and the rinse solution refreshing the wash water within
the sump as the rinse solution is collected therein,
comprising:
(a) rinse nozzles for spraying the rinse solution onto the items
within the chamber, the nozzles being connected and dedicated for
spraying only the rinse solution,
(b) a holding tank for accumulating a predetermined quantity of the
rinse solution prior to spraying through said rinse nozzles,
(c) a rinse pump connecting said holding tank to said rinse nozzles
and controllable for pumping substantially all the rinse solution
from the tank and onto the food ware items at a predetermined
pressure and at a predetermined time during operation of the
warewasher,
(d) a source of fresh water at a temperature below effective
bacteria killing temperatures and connected for introducing and
circulating such fresh water into said holding tank, said source
being openable and closeable for introducing fresh water when open
and terminating the introduction thereof when closed,
(e) a source of the chemical sanitizing agent connected and
constructed for introducing a predetermined quantity thereof into
said holding tank when actuated,
(f) control means for controlling at least said fresh water and
sanitizing agent sources for initiating filling of the
predetermined quantity of rinse solution into said holding tank by
opening said fresh water source and actuating said sanitizing agent
source at predetermined times and closing said sanitizing agent
source after a predetermined quantity of the agent has been
supplied into said holding tank,
(g) quantity sensing means for sensing the quantity of solution in
said holding tank and closing said fresh water source when said
holding tank contains the predetermined quantity of solution,
and
(h) said control means also controlling said rinse pump during
operation of the warewasher to pump and spray substantially all of
the predetermined quantity of rinse solution from said holding tank
onto the food ware items
at a predetermined time during operation of the warewasher. .Iadd.
13. In a sanitizing rinse system for a warewasher which includes a
spray-type washing system for recirculating wash liquid over
articles to be washed at a temperature below effective bacteria
killing temperatures during each wash cycle of the washing
system,
a chamber in which articles are supported for washing and
rinsing,
a rinsing spraying system separate from said washing system and
having rinse spray nozzles within said chamber dedicated to
spraying only fresh rinse solution,
a source of fresh water under facility line pressure associated
with a main water supply and at a temperature below effective
bacteria killing temperature,
a holding tank for receiving water from said source,
valve means for connecting and disconnecting said source with said
tank for filling said tank,
a sanitizing material supply,
means for dispensing a predetermined quantity of sanitizing
material from said supply into said tank for dispersion with water
to produce a batch for sanitizing solution capable of destroying
bacteria when sprayed onto said articles,
pump means interconnecting said tank and said rinse spray nozzles
to pump said batch of solution under a predetermined pressure onto
said articles to rinse said articles;
the improvement comprising a cycle controller including:
timed means for opening said valve means to commence introduction
of fresh water into said tank during each wash cycle,
timed means for operating said dispensing means to introduce a
predetermined quantity of sanitizing material into said tank with
each operation thereof for mixing with the fresh water,
means independent of said timed valve opening means and responsive
to filling said tank with a predetermined fresh batch of solution
for closing said valve means to discontinue water introduction into
said tank, and
timed means for operating said pump means to discharge the fresh
batch of sanitizing solution from said tank through said rinse
spray nozzles after the completion of each wash cycle.
Description
BACKGROUND OF THE INVENTION
This invention relates to equipment for economically and
effectively cleaning and chemically sanitizing food-handling
articles at a high rate of productivity. An example of such
equipment is a dishwasher for use in commercial applications like
restaurants, cafeterias, hospitals and other institutions where
dishes are frequently reused during a meal period, although the
sanitizing principle is applicable to any kind of ware with which
food comes into contact.
It is necessary in the use of such equipment to destroy bacteria
during a rinsing operation to meet minimum sanitation standards.
That is generally done by providing high temperature rinse water,
e.g., 180.degree.-195.degree. F., or, where such temperatures are
not achievable, by adding a chemical sanitizing agent to low
temperature water (approximately 120.degree.-140.degree. F.) to
produce the bacteria-killing effect. Use of the terms "high" and
"low" herein relate approximately to the above temperature ranges.
The present invention is concerned with the latter approach of
cleaning and sanitizing food-handling articles with low temperature
water and a chemical additive, such as is illustrated in U.S. Pat.
Nos. 2,592,884, 2,592,885, 2,592,886, 3,044,092, 3,146,718, and
3,370,597, all of which are assigned to the assignee of the present
invention.
Although several different types of chemical sanitizing agents are
available on the market, the one most commonly used today is liquid
sodium hypochlorite (NaOCl), because of its high degree of
effectiveness, relatively low cost, and general availability. This
particular chemical, however, is not without its disadvantages, the
most common being its chemical reaction with hard water minerals
like iron, calcium, and magnesium, the latter two causing liming or
mineral deposits onto the machine parts with which they come in
contact. These deposits also tend to build upon orifices when a
water powered venturi is used to draw the agent from a supply
thereof into the water line en route to the rinse nozzles of the
washing machine. The deposits continue to change the proportion of
NaOCl to a given volume of water as they build up on the venturi.
Eventually the volume of NaOCl becomes insufficient for santizing.
Deposits also tend to clog the rinse nozzles themselves, often
requiring frequent removal and cleaning to maintain their
efficiency. For these reasons, devices such as disclosed in the
aforementioned patents have limited reliability and have found
limited application, both where the agent is injected into a rinse
line or directly into a wash chamber. High temperature sanitizing
equipment has achieved much greater use, even though the higher
temperature requires considerable energy usage as well as higher
initial cost for electric or gas-fired booster heater units.
In recent years, due to increasing prices and decreasing
availability of energy, increased emphasis has been placed on
chemical sanitizing warewashers to reduce energy consumption, and
manufacturers are again introducing specialized equipment of this
type to meet this need. However, to minimize the pressure variation
and liming problems inherent in water introduction of sodium
hypochlorite, and to maintain the efficiency and proper operation
of their systems, users of systems which introduce the chemical
sanitizing agent directly into a fresh water line have had to
accept the need for frequency service calls from their chemical
suppliers.
Possibly because of the flow pressure, mineral deposit, and
frequent service problems associated with introducing a chemical
sanitizing agent directly into a fresh water line of a dedicated
rinse system, several U.S. manufacturers have also introduced
chemical low temperature sanitizing dishwashers which operate
essentially on the recirculating rinse principles described in U.S.
Pat. No. 3,903,909. (However, not all of them interconnect the
fresh water line and recirculating system as does the design of the
'909 patent). The '909 device still uses a water driven venturi,
but since the rinse fluids are mixed in the sump and recirculated,
it is not necessary to maintain precise metering of the sanitizing
solution into the water line, so long as the proper total amount is
eventually injected.
Typically, such machines provide a wash chamber having a sump for
containing wash water and a pump which draws water from the sump
and recirculates it under pressure through nozzles in one or more
rotating wash arms to spray the dishes. The wash water is drained
from the sump after washing a load of dishes and is replaced by
fresh rinse water. The rinse water, into which the sanitizing
chemical is injected, is then sprayed and recirculated onto the
dishes through the same pump and wash arms to provide a single,
recirculated rinse. The rack containing the washed and rinsed
dishes is then removed from the machine and replaced by a rack of
dirty dishes. The rinse water is retained in the sump after
rinsing, detergent is added thereto, and it is then used as the
wash water for the next rack of dirty dishes. Ordinarily, these
dirty dishes will have been scraped only, and thus contain gravies,
residue of mashed potatoes, bread crumbs, small bits of food,
etc.
Because the wash water must be drained after each wash in this type
of machine, the sump, pump, and spray nozzles of the combined wash
and rinse system are designed to operate with a minimum quantity of
water, for example, as little as two gallons for each rack. This
places an operational restriction on the pump, limiting its ability
to deliver large volumes of water to the dishes in a short period
of time, and forcing restrictions on the size of the openings in
the wash and rinse nozzles, thus increasing their chances of
clogging with food particles, Additionally, since large food
particles frequently accidentally remain on the tops and bottoms of
dishes when placed in the wash chamber, a strainer system is
required to capture these larger particles and prevent their
passing through the pump and clogging the nozzles. The strainers
are generally provided with very closely spaced holes of 1/8 inch
diameter or less, and are said to be 1/32 inch in the
aforementioned '909 patent. What happens when using systems of this
type, therefore, is that the smaller food particles and other tiny
suspended granular objects pass through the strainer, and the pump
continually redeposits them on the ware and on the inside surfaces
of the wash chamber, the pump, the wash arms, and so on. Compromise
is therefore necessary in designing the size of the strainer holes
in order to satisfy conflicting conditions. On the one hand, the
holes should be as small as possible to prevent passage of soil
particles; on the other, they must be large enough to prevent
strainer clogging and pump starvation with accompanying loss of
water circulation. For this reason, redeposition of small soil
particles in such machines is an unavoidable condition during
washing.
The aforementioned '909 patent proposes to rinse out the spray arms
and drain some of the rinse water before closing the drain by
connecting the wash arms to both the fresh water line and the
recirculating pump (with a check valve therebetween). Before the
drain closes, approximately 20% of the water consumed in each cycle
is immediately drained in an attempt to flush debris from the wash
system and chamber. This water is lost, passing down the drain with
the soiled wash water. Effective cleaning with such a system is
still believed difficult, however, because of other operational
compromises inherent in such a machine. For example, the commercial
machines of a U.S. manufacturer believed to be the owner of the
aforementioned '909 patent also have the drain maintained open
while introducing approximately two quarts of fresh water for
flushing purposes, but the water is introduced directly into the
sump rather than into the wash arms. The structural design appears
such that the pump probably cannot pick up much, if any at all, of
this small quantity of water while the drain is open, and therefore
cannot recirculate it for flushing the arms or the wash chamber.
Some soil will therefore inevitably remain in the system.
On general principles as well, such retained soil is all but
impossible to remove in the single rinsing action with the limited
water volume which is commonly provided in commercial dishwashers
of this particular design. The strainers conventionally found in
these machines are designed in the form of baskets or trays which
capture the larger food particles, to enable their easy lifting
from the machine and dumping into a disposer or garbage pail. In
order for the strainer to be effective, the recirculating water
must pass continually through the strainer on the way to the pump
intake, and therefore through the garbage in the strainer as well.
The manufacturers therefore recommend frequent cleaning of these
trays, to reduce the amount of soil which the recirculating rinse
water must necessarily pass through. However, machine operators
cannot be relied on to perform such tasks, particularly where more
than one individual may use or be responsible for the machine
during the same meal period. The end result in such machines is
that, while the bacteria on the dishes may be properly killed,
there is nevertheless a continual redeposition of fine soil even
during rinsing. These effects--fine soil remaining in the
recirculating system for the rinse, and soil remaining in the
strainer--sometimes result in an unappetizing appearance or feel of
the dishes, giving the user of the dishes the impression that they
are unsanitary, even though the bacteria may have been
destroyed.
As suggested above, the design direction in recent years for
equipment for cleaning and chemically sanitizing dishes (as
exemplified by the aforementioned U.S. Pat. No. 3,903,909), has
also created a substantial reduction in productivity as compared to
standard dishwashing machines utilizing high temperature water for
sanitizing the dishes. In standard, high temperature dishwashers,
the rinse water is normally introduced through a "dedicated" rinse
system, i.e., one which is separate from the wash system and
carries only fresh, very hot rinse water. Generally, the wash water
in the wash system is saved in the wash system sump and reused for
washing successive racks of dishes. Used rinse water from the
independent rinse water system is conducted to the wash system,
causing overflow of some of the used wash water through a standpipe
connected to the drain, and continually replenishing the wash water
supply with hot clean water. The rinse may use about two gallons
(of which some will overflow through the standpipe before mixing
with the wash water, so that only a part of the rinse water will
dilute the wash water). Detergent is then added (usually
automatically) to the wash water periodically because of this
partial dilution.
Since the wash water is maintained in the sump rather than being
drained each cycle, the volume thereof may be relatively large.
This provides considerable flexibility in the design of the water
pump and the size of the nozzle orifices in the wash arms, simply
because the large volume of water in the sump permits usage of a
high capacity pump for delivering water in large volumes through
the spray system to the dishes.
Minimum total spray volumes are specified by the organizations that
create industry standards. For example, Standard No. 3, Section
6.05 of the National Sanitation Foundation of the U.S. (N.S.F.),
pertaining to Single Tank, Stationary-Rack, Door-Type Chemical
Sanitizing Machines, requires not less than 80 gallons of water to
be delivered for each 20 inch.times.20 inch rack for the combined
washing and rinsing of a rack of dishes. The minimum pump delivery
capacity is required to be at least 40 gallons per minute (g.p.m.).
This is easy to achieve if the sump is large and plenty of water is
available. However, if the sump is small and a minimum-capacity
pump is used to deliver 80 gallons of water, the pump time during
the cycle will be a full two minutes. This sets a theoretical
production maximum of 30 racks of dishes per hour for a minimum
capacity pump, but is achievable only if absolutely no time is
required for water fill, drain, loading and unloading the racks, an
impossibility even in an automated machine. Even if a high capacity
pump is used, wash volumes and delivery rates will still be
restricted far more in a machine of the '909 type than in one with
a dedicated rinse system.
More particularly, these restrictions and this reduction in
productivity are a result of several things. First, since the same
sump and same spraying system are used for both washing and
rinsing, it becomes essential to drain the sump for each machine
cycle, i.e., for each rack of dishes washed, and this results in a
loss of productive time. The machine must stop in the middle of
each cycle and drain the sump almost completely, and sometimes
flush as well, before the actual dish rinsing can commence. This
waiting period is a minimum of 10 seconds, and may be as much as 30
seconds, before the rinse spray becomes effective, depending on how
rapidly the sump fills. This seemingly small time actually
constitutes a minimum of 8%, and as much as 25%, of a total two
minute cycle time. When multiplied over a large volume of dishes,
this could be a very serious cost disadvantage in labor alone.
Secondly, because of the cost of heating water even to the "low"
temperature of 140.degree. F., the machines are constructed (as
indicated above) to use as small a quantity of water as possible,
approximately two gallons, plus a few extra quarts where a "flush"
period is used. The amount of water thus consumed each cycle is
only slightly greater than that used for rinsing in high
temperature machines which sanitize by means of heat. However,
since this rinse water (which is dumped during the next cycle) is
the only water available in the sump for recirculation, the sump
and pump capacities must be kept small. Obviously, the higher the
pump capacity, the greater the supply of water that is required to
feed the pump is order to prevent cavitation and attendant loss of
pressure, which result in reduced effectiveness of the water spray
contacting the dishes. Compensation is therefore made for the
smaller quantity of water in the sump by reducing the pump capacity
and restricting the orifice size of the nozzles of the spraying
system. This in turn reduces the flow of water through the nozzles
and reduces the volume of water which, in a given time period,
contacts the dishes which are being washed. It also increases the
chances that a nozzle will clog with particles of food and other
materials. The reduced flow is then compensated for by extending
the washing time, but this further reduces productivity.
The low temperature chemical sanitizing dishwashers such as
illustrated in U.S. Pat. No. 3,903,909 and its commercial
couterparts ordinarily lack a tank heater. They rely solely on the
rinse water temperature to maintain adequate wash water
temperature. The N.S.F. minimum temperature for washing is
120.degree. F. This requires the inlet fresh rinse water
temperature to be about 140.degree. F., because the water cools as
it is circulated by the pump and contacts the dishes and the walls
of the dishwasher. Under some circumstances, such as in nursing
homes, the water heater temperature may be around 120.degree. F. to
begin with, requiring a separate booster heater for the fresh water
line connected to the dishwasher. If after the rinse is completed,
the next washing cycle is not started within a short time, the wash
water will cool below the 120.degree. F. washing temperature. Under
these operating conditions the machine must be cycled to bring in
hot wash water to meet code requirements and to control foam and
pump cavitation.
Thus, when considering the total costs of detergent, sanitizing
chemical, rinse agent, heat energy for the water, machine
depreciation and maintenance, and increased manual labor for each
rack of dishes (due to reduced machine capacity), it is likely that
the total cost to the user is greater when using a single rack
machine such as illustrated in the '909 patent, than when using a
comparable machine in which high-temperature sanitizing is
employed. Labor alone is one of the major cost factors in washing
dishes, and this is considerably reduced with the present apparatus
and method as compared to that of '909 patent.
In addition to the standard high temperature dishwashers previously
described, there are known to exist in other countries,
particularly where hot water heaters are not readily available or
are available only at low temperatures (perhaps 120.degree. F.),
prior art dishwashers in which a low temperature fresh water supply
line introduces water into a holding tank mounted on the
dishwasher. The holding tank includes an air gap for physically
separating the fresh water line and the water system of the
dishwasher. The level of the water in the holding tank is
controlled by a float which opens a valve in the fresh water supply
line upon descent of the float, and closes the valve when the float
reaches its upper level. Between the holding tank and rinse
nozzles, which are dedicated solely to the rinse system, there is
an auxiliary booster heater tank having heating coils for raising
the low temperature water to the high temperature necessary to
destory bacteria when rinsing. When rinsing is to take place, the
recirculating pump for the wash water stops and an auxiliary pump
in a water line between the holding tank and the auxiliary booster
heater tank is operated to pump rinse water through the rinse
nozzles. Fresh water is introduced into the holding tank as soon as
the float begins to descend, functioning merely to maintain a
supply of rinse water available for the rinse system. Control of
the quantity of water utilized for rinsing is a function of the
time the rinse pump operates.
Thus recently introduced machines for achieving chemical
sanitization of dishes, while solving one problem, namely a
reduction in consumption of energy by eliminating the need to heat
water to 180.degree. F. or more, have thus introduced new problems
in productivity, cost of operation, and poorer washing results, as
compared with existing high temperature machines. The present
invention proposes to solve the washability, productivity, and cost
problems inherent in these prior art designs.
SUMMARY OF THE INVENTION
Briefly, the present invention solves the washability,
productivity, and cost problems of prior art chemical sanitizing
designs through the use of separate, dedicated wash and rinse
systems. That is, the present invention combines the advantages of
standard dishwashing machines which use high temperature water for
sanitizing the dishes with the economies possible with lower
temperature chemical sanitization. Thus the present invention saves
the wash water for reuse in the wash system sump, and the rinse
carries only fresh, chemically sanitizing rinse water which is
sprayed directly onto the dishes and then collected in the sump for
replenishing and refreshing the wash water. In contrast, therefore,
with those prior art chemical sanitizing machines which dump the
wash water after each cycle, and thus limit the wash water in the
sump to approximately 2-21/2 gallons, the preferred embodiment of
the present invention retains 16 gallons of wash water in the sump
and recirculates this water during the wash cycle at a rate of 160
gallons per minute. This reduces the required wash time to as
little as 1/2 that of prior art machines, while also improving the
washability. A single rack machine according to the present
invention, for example, has a capacity of 53 racks per hour,
whereas a typical, comparable, prior art machine is limited to 28
racks per hour.
These advantages are possible because the present invention
provides a fresh water chemical sanitizing rinse which is
consistently and reliably properly proportioned, properly mixed,
properly pressured, and properly distributed. As indicated in the
prior art discussion above, such a rinse has heretofore been
unavailable. That is, considerable prior art effort has gone into
direct sanitizer injection into the fresh water line as it is
supplied directly to rinse arms. However, and as indicated,
maintaining and assuring the proper ratio of sanitizing agent to
wash water is extremely difficult, due to variations and
fluctuations in line pressure, resultant changes in flow rates, and
interference with proper operation of the system caused by hard
water deposits. The alternative and more recent approach provides a
more consistent ratio by using the sump for mixing the sanitizer
with the rinse water, and recirculating the rinse water onto the
dishes. This may be done either by injecting the sanitizer into the
rinse water as it is carried into the system, or adding the
sanitizer to the wash tank separately, where it is entrained,
mixed, and recirculated. Either way the system is less sensitive to
the rate at which the sanitizer is injected, as long as the net
quantity is correct.
In the present invention, however, the sanitizing agent is neither
injected into a directly fed rinse line nor mixed in the wash
chamber sump. Instead, a separate holding tank is provided which
accumulates a predetermined quantity of the chemically sanitizing
rinse solution prior to spraying through the rinse nozzles. The
fresh water supply line is connected to supply water to the holding
tank, as needed, and preferably is open only during the wash cycle
for the dishes, so that fresh, hot rinse solution is prepared only
as needed. A float within the holding tank assures that the proper
amount of fresh, hot water (approximately 120.degree.-140.degree.
F.) will be accumulated regardless of the available supply pressure
or fluctuations therein. (It should be noted, however, that N.S.F.
standards call for available supply pressures of 15-25 psi). At the
same time, a precisely controlled quantity of sanitizing agent,
such as a 5.2% solution of sodium hypochlorite, is separately added
to the holding tank. In the preferred embodiment, the holding tank
has a capacity of 1.8 gallons, and 10 cc of the 5.2% NaOCl solution
is added to provide a rinse solution having approximately 75 ppm of
NaOCl. (N.S.F. standards call for a minimum of 50 ppm). As the
water enters the holding tank it circulates for thorough mixing of
the water and sanitizer, thus assuring that the entire quantity of
rinse solution will be properly proportioned and properly mixed.
Normal fluctuations in line pressure are automatically accommodated
and do not alter the quality or quantity of the rinse solution.
Following the wash cycle and a dwell period, the rinse solution is
sprayed onto the dishes by a rinse pump which forces the rinse
solution at a reliable and consistent pressure (20 psi in the
preferred embodiment) from the holding tank to a pair of dedicated,
rotating rinse arms which spray the solution onto the dishes,
sanitize, and removes redeposited soil. Because a pump is used,
thus assuring a reliable rinse pressure, it is possible with the
present invention to use rotating rinse arms both above and below
the dishes for better distribution of the sanitizing rinse
solution. Many prior art machines which use line pressure for the
rinse spray (whether chemically or thermally sanitizing) do not use
rotating upper arms since they cannot be sure that the spray
pressure will be sufficient to assure proper rotation of such arms.
With the present invention, the dedicated mixing and holding tank,
rinse pump, and rotating spray arms assure that the rinse spray
will be properly proportioned, properly mixed, properly pressured,
and properly distributed.
It should also be noted that the present invention is much more
tolerant of liming or hard water deposits. In the preferred
embodiment, the sanitizer is supplied to the holding tank
independently of the fresh water supply so that hard water deposits
will not impair the sanitizing agent supply system, or injector. In
the preferred embodiment, the sanitizer is injected by means of an
air transport injector such as described in U.S. application Ser.
No. 788,039, filed Apr. 15, 1977. Preferably, and as shown in the
preferred embodiment herein, the sanitizer is introduced into the
rinse solution holding tank at the same place the stream of fresh
water is added to the tank, above the surface of the water therein.
This helps capture or entrain the sanitizer in the water and
minimizes the escape of sanitizer vapor into the surrounding
atmosphere, while assuring that the proper quantity of sanitizer
will be consistently added to the tank without the formation of
hard water deposits on the sanitizer injection system.
Similarly, the formation of deposits on the rinse spray arms will
not alter the strength of the rinse solution, since the rinse
solution is already premixed in the holding tank. Such deposits, at
most, will merely change the flow rate as the solution is pumped by
the rinse pump. However, since the holding tank is filled with
exactly the proper quantity of rinse solution at the proper
strength, it follows that the proper concentration will be sprayed
onto the dishes.
Thus, the preferred embodiment incorporates a holding tank, a rinse
pump, dedicated rinse nozzles, sources of fresh rinse water and
chemical sanitizing agent, and suitable control means which are
actuated by the washing machine at predetermined times in its cycle
for simultaneously introducing the fresh rinse water and the
sanitizing agent into the holding tank, and for separately
terminating the introduction thereof after the proper quantities of
each have been introduced therein. In the preferred embodiment, the
sanitizing solution is prepared in discrete, properly proportioned
batches, each of which is then pumped from the holding tank through
the dedicated rinse nozzles, followed at the appropriate time by
the preparation of another batch.
It is therefore an object of the present invention to provide a
method and an apparatus for rinsing and chemically sanitizing food
ware items in a warewashing machine; a method and apparatus which
have substantially higher productivity and substantially lower
service needs than prior art machines; which provide the
substantially improved productivity by means of a separate,
dedicated rinse system having a holding tank, a rinse pump for
pumping the solution from the tank to dedicated rinse nozzles, and
means for supplying precise quantities of rinse water and
sanitizing agent to the holding tank substantially independently of
supply line pressures; which thereby permit the wash water to be
saved and recirculated for washing successive racks of dishes;
which are substantially unaffected by the formation of hard water
deposits; and which assure a properly proportioned, properly mixed,
properly pressured and properly distributed sanitizing rinse spray
in an economical, highly reliable configuration readily suited and
adapted for widespread use.
Other objects and advantages of the invention will be apparent from
the following description, the accompanying drawings and the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially broken away front view of a dishwashing
machine incorporating a rinse system according to the present
invention;
FIG. 2 is a top view of the machine;
FIG. 3 is a partially broken away side view of the rinse holding
tank, rinse pump, and associated assemblies at the top of the
dishwashing machine;
FIG. 4 is a cross-sectioned view of the chlorine injector
venturi;
FIG. 5 is a timing chart showing both a normal wash cycle and an
initial fill cycle;
FIGS. 6A and 6B are the circuit diagrams for the dishwasher
controller; and
FIGS. 7A and 7B are the circuit diagrams for the timer in FIG.
6B.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 illustrates a single tank dishwashing machine 10 for washing
food ware items such as dishes, utensils and so on. Typical prior
art machines of this type, but which use high temperature rinse
water for sanitizing the food ware items, are illustrated in U.S.
Pat. Nos. 2,286,203 and 3,911,943, assigned to the assignee of the
present invention. Such machines are well-known, and the general
operation will therefore be described only briefly.
Machine 10 is a batch type machine, in which a rack of soiled
dishes is loaded into a single, enclosable wash chamber 12. There
the rack of dishes is first washed with a high pressure spray of
recirculated wash water, and then rinsed with a sanitizing rinse
spray. Machine 10 thus includes a sump 13 which holds about 16
gallons of wash water. The wash water is reusable and is
recirculated under pressure by a pump and motor assembly 14 through
suitable conduits 16 to upper and lower rotating wash arms 17 and
18. Due to the large quantity of water available in the sump, the
pump and motor assembly 14 and wash arms 17 and 18 recirculate the
wash water at a rate of about 160 gallons per minute, thus
providing excellent washability and rapid performance.
After the dishes have been washed for a suitable period of time
(minimum times and flow standards are specified by the National
Sanitation Foundation), the motor and pump assembly 14 are turned
off and the dishes are rinsed and sanitized by supplying a fresh
rinse solution to the upper and lower rinse arms 20 and 21. The
rinse system is dedicated. That is, only fresh rinse solution
passes through it, and it is not recirculated. The rinse arms are
thus provided with conduits separate from those of the wash system,
and in prior art machines, were connected directly to the external
fresh water supply for the dishwashing machine. The rinse water
which is sprayed onto the dishes then flows to the sump 13 where it
refreshes the wash water therein. The sump includes an overflow
drain (not shown) which automatically controls the level of water
in the sump.
Unlike such prior art machines, however, the present invention
provides a sanitizing, low temperature fresh water rinse which is
fully compatible with this type of dishwashing machine. In the
present invention, a holding tank 25 is mounted on top of machine
10, and connected through a rinse control valve 26 operated by a
solenoid 26a (FIG. 6B) to a fresh water line 27. Line 27 provides
fresh rinse water of at least 120.degree. F. and above, but
ordinarily well below the thermal sanitizing range of 180.degree.
F. When valve 26 is open, a conduit 28 then introduces the rinse
water into tank 25 through its outlet end 29 (FIG. 3).
As the fresh water flows into tank 25, the chemical sanitizing
agent is also introduced into the tank. In the preferred
embodiment, the sanitizing agent is 5.2% NaOCl which is aspirated
from a bottle 31 thereof into holding tank 25 by an air driven
venturi aspirator 32 (FIGS. 3 and 4) similar to that shown in U.S.
application Ser. No. 788,039, filed Apr. 15, 1977. This includes an
air compressor 33 which is energized at a suitable time to provide
compressed air through an air conduit 34 to the aspirator. This, in
turn, draws the chemical sanitizing agent through a conduit 36 from
the bottle 31 and injects it by means of air transport into holding
tank 35. In the preferred embodiment, the venturi aspirator 32 is
designed to discharge the chemical sanitizing agent substantially
at atmospheric pressure, in order to minimize vapor formation.
Further, the distance between the venturi outlet and the water
within the holding tank 25 is very short (see FIG. 3) and the
aspirator outlet 37 is positioned adjacent the outlet 29 of the
fresh water line conduit 28 (FIGS. 3 and 4) so that the fresh water
and sodium hypochlorite are introduced into holding tank 25 at
substantially the same place, and such that the NaOCl is entrained
therein to minimize the escape of NaOCl vapor into the surrounding
atmosphere.
Preparation of the sanitizing rinse solution in holding tank 25 is
preferably inhibited until the wash cycle is engaged, so that the
rinse solution will be fresh and warm. When the wash cycle is
started, air compressor 33 is operated for 17 seconds and injects
approximately 10 ml of the 5.2% NaOCl into holding tank 25. The
rinse water supply valve 26 is simultaneously opened and held open
a somewhat longer time until tank 25 has been filled with 1.8
gallons, yielding a concentration of approximately 75 ppm of
chlorine. As the fresh water is introduced into tank 25 through the
conduit outlet 29, it creates sufficient turbulence within tank 25
to circulate and mix the fresh water and sanitizing agent to assure
proper and uniform mixing thereof. They are thus properly mixed
within the tank, and certainly by the time they exit from the rinse
arms. When the 1.8 gallons have been drawn, valve 26 is closed by a
float control 38 which operates independently of the air compressor
33. Details of such a float control 38 are known in the prior art,
as described in U.S. Pat. Nos. 3,844,299 and 3,911,943 assigned to
the assignee of the present invention.
After the wash cycle has been completed, a rinse pump 40 is
energized. Pump 40 pumps substantially all of the rinse solution
under pressure from tank 25 through rinse solution supply conduits
41 into the dedicated rinse arms 20 and 21. Rinse pump 40 provides
a uniform, reliable pressure which is independent of the pressure
available from the fresh water line 27. As a result, both the upper
and lower rinse arms 20 and 21 are freely rotatable and are
propelled by the pressure of the rinse solution supplied by rinse
pump 40, as the solution is sprayed through the rinse nozzles 42
located on the rinse arms.
Holding tank 25 is also connected directly to the wash chamber 12
through a standpipe or overflow drain 43. Ordinarily float 38
determines the level of solution in tank 25, but if valve 26 should
fail to close for any reason, pipe 43 protects against an overflow.
Tank 25 also includes a weir 44 at its rear (FIGS. 2 and 3) which
provides additional overflow protection, by dropping excess water
into the vent pipe 46 for chamber 12. The aspirator outlet 37 and
the fresh water conduit outlet 29 are both located above the level
of the weir 44 (FIG. 3) to provide an air gap for protection
against inadvertent siphoning of the solution back into these
lines.
Overflow pipe 43 is also used in the present invention for
initially filling the dishwashing machine 10. For the initial fill
cycle, the float control 38 is bypassed, and valve 26 is held open
until sump 13 has been filled with a sufficient quantity of water.
This provides for filling machine 10 through a single valve 26 and
a single fresh water line 27. In the preferred embodiment, the sump
actually receives approximately 12 of its 16 gallons through the
overflow pipe 43. Rinse pump 40 is then actuated to drain the 1.8
gallons in tank 25 into the wash chamber 12. In this manner tank 25
is returned to its empty standby condition, so that when a rinse
solution is required it may be prepared fresh. Otherwise, it might
cool during an extended dwell period.
Operation of machine 10 is preferably under the control of a
suitable automatic control means such as a controller 50. Such
controllers are well-known in the art, and any suitable controller
may be selected. The preferred embodiment is shown in FIGS. 6A, 6B,
7A, and 7B. FIGS. 6A and 6B illustrate the control circuit within
controller 50, and FIGS. 7A and B are the circuit for timer 52 in
FIG. 6B. The circuits are similar to those shown and described in
the aforementioned U.S. Pat. Nos. 3,844,299 and 3,911,943, and the
operating principles thereof are thus known to practitioners in the
art. Reference is accordingly made to these patents for further
details of the several control boards in controller 50.
FIG. 5 is a timing chart for operation of machine 10 under the
control of controller 50. Thus, during a typical wash cycle the
wash chamber 12 is first loaded with a rack of soiled utensils and
then closed. The wash cycle is commenced (either automatically by
closing the wash chamber, or manually) and the wash water is
recirculated onto the dishes for 43 seconds. Pump 14 is then
stopped and machine 10 has a five second dwell period. During the
first 17 seconds of the wash cycle the air compressor 33 is
operated to inject the sanitizing agent into the holding tank. The
fresh water valve 26 is simultaneously opened as the wash cycle and
air compressor start, for also introducing fresh water into holding
tank 25. However, while the air compressor 33 is exclusively under
the control of controller 50, valve 26 is also under the control of
float 38, and during normal operation it is float 38 which closes
valve 26. (If the water line pressure is extremely low, valve 26
will eventually be closed at the end of the wash cycle). Thus the
controller 50 initiates the filling of the predetermined quantity
of rinse solution (i.e. 1.8 gallons) into the holding tank 25 by
opening the fresh water rinse supply valve 26 and "opening" the
supply of NaOCl by actuating the air compressor 33 at the beginning
of the wash cycle. The controller 50 also "closes" the supply of
NaOCl after the predetermined quantity has been supplied to holding
tank 25 by terminating operation of compressor 33. However, valve
26 is separately closed by the float control 38 which senses the
quantity of solution in tank 25 and closes the valve when the
predetermined quantity thereof has been supplied.
After the five second dwell period (FIG. 5), rinse pump 40 is
energized by controller 50 for a period of 14 seconds. This is
sufficient to pump substantially all of the rinse solution from
holding tank 25 and to spray it onto the food ware items within the
wash chamber 12 of the dishwashing machine 10.
The initial fill cycle, as described above, is also illustrated in
FIG. 5 and is under control of controller 50. When the initial fill
cycle is engaged, controller 50 bypasses float control 38 and holds
the fresh rinse water valve 36 open for 171 seconds. Controller 50
then jumps to the rinse portion of a regular wash cycle, actuating
rinse pump 40 for 14 seconds. The controller 50 then stops
operation of machine 10, and resets to the beginning of a wash
cycle, standing by to wash a load of dishes.
Although not illustrated, an electrical or other heater is provided
below or within the sump 13. The heater is thermostatically
controlled similarly to the shown in U.S. Pat. No. 3,911,943,
issued to the assignee of this application. Use of the heater is
necessitated, as a practical matter, by the fact that a large
quantity of water is contained in the sump to provide the pump and
washing efficiencies of the standard high-temperature machines.
There are times when the machine may be idle from a few minutes up
to several hours in a normal wash period. During such times, the
large volume contents of the sump must be maintained ready and at
the proper operating temperature designed to provide most efficient
washing. Present-day detergents used for washing dishes drastically
begin to lose effectiveness below water temperatures of 120.degree.
F. Thus, the thermostat is designed to control the heater to
maintain the sump water at or above that temperature. Obviously, if
detergents which can operate at lower temperatures are formulated,
the thermostat can be adjusted accordingly and additional energy
savings obtained.
What has been described herein as the preferred embodiment of the
invention is the practical version of timing the filling of the
holding tank 25 to start when the door of the wash chamber 12 is
closed. With this embodiment, one is assured that the holding tank
will not be filled and the water therein allowed to cool, should
there by any time delay between two successive racks of dishes to
be washed. For example, when a rack of washed dishes has also been
completely rinsed, the wash chamber 12 will be opened and the rack
of cleaned and rinsed sanitized dishes removed. The holding tank 25
remains empty during this time, the only water in the machine being
that contained in the sump 13, which of course, is being maintained
at the proper wash temperature. It twenty-five minutes elapses
before the next rack of dishes is placed in the wash chamber, the
holding tank remains empty for that entire period. Then, when the
rack is placed in the machine and the chamber closed by lowering
the door, not only is the washing cycle for that rack of dishes
started, but the fill cycle for introducing fresh water and
sanitizing agent into the holding tank commences. Since the wash
cycle takes 43 seconds as shown in FIG. 5, obviously the
introduction of water and sanitizing agent into the holding tank
should take less than 43 seconds. The actual water fill time
depends primarily on the flow rate of fresh water from the outlet
29. Ideally then, to conserve water and also to avoid having to
reheat water that has been standing and cooling in the holding
tank, it is ideal to fill the holding tank while the washing
portion of a total cycle takes place.
However, it would also be possible (though less practical) for some
or all of the time period for filling the holding tank to occur
prior to commencement of the washing cycle. For example, the
holding tank might be refilled as soon as the rinse pump 40 shuts
off after draining the tank. If consecutive racks are being washed
in rapid succession, little heat would be lost in the short time
that the sanitizing rinse solution would stand in the holding tank.
The main difficulty would be in those instances where the rinse
solution stands for such a length of time that it cools below the
washing temperature, particularly if no sump heater is provided to
bring that rinse solution back up to washing temperature when it
enters the sump. This obvious variation is believed to be within
the scope of this invention.
As may be seen, therefore, the present invention provides numerous
advantages. It makes possible a compact, single tank, low
temperature machine which does not require the wash water to be
dumped for each load. The rinse water is therefore never
recirculated through the debris in the strainer, but is always
fresh and clean. The invention is also applicable to multiple tank
configurations, according to the particular needs and applications
at hand. It is free from the prior art problems of uniform mixing
and distribution, and always supplies the same quantity at the same
mix ratio amd the same rinse pressure, regardless of line pressure
or fluctuations therein. In the preferred form of the invention,
the rinse solution is always fresh and above the minimum
temperature, since preparation is inhibited until just before it is
needed. The invention operates at high speed, is inexpensive,
uncomplicated (using, for example, but a single water supply line
and valve), compact, and reliable. Thus the present invention
provides a properly proportioned, properly mixed, properly
pressured, properly distributed, separately fed and sprayed,
chemically sanitizing, low temperature fresh water rinse in which
the sanitizing mixture is uniform from beginning to end.
While the method herein described, and the form of apparatus for
carrying this method into effect, constitute preferred embodiments
of this invention, it is to be understood that the invention is not
limited to this precise method and form of apparatus, and that
changes may be made in either without departing from the scope of
the invention.
* * * * *