U.S. patent application number 11/745321 was filed with the patent office on 2007-09-06 for steam system for continuous cleaning of hood fans.
Invention is credited to Jason Cheng, Kok Ki Tam.
Application Number | 20070204855 11/745321 |
Document ID | / |
Family ID | 46327849 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070204855 |
Kind Code |
A1 |
Cheng; Jason ; et
al. |
September 6, 2007 |
Steam system for continuous cleaning of hood fans
Abstract
A device and method for cleaning fans in range or stove hoods by
spraying steam onto the fan impeller area on which soot and cooking
fumes condense to clean the impeller and wash the accumulated
condensates down a drain. By using steam above atmospheric pressure
as the cleaning fluid, the device uses significantly less water
that other devices that spray water or an aqueous solution to clean
the fan blades.
Inventors: |
Cheng; Jason; (Brooklyn,
NY) ; Tam; Kok Ki; (Brooklyn, NY) |
Correspondence
Address: |
BRADLEY N. RUBEN, PC
463 FIRST ST, SUITE 5A
HOBOKEN
NJ
07030
US
|
Family ID: |
46327849 |
Appl. No.: |
11/745321 |
Filed: |
May 7, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11600469 |
Nov 16, 2006 |
|
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11745321 |
May 7, 2007 |
|
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60772182 |
Feb 10, 2006 |
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Current U.S.
Class: |
126/299D |
Current CPC
Class: |
F24C 15/2057 20130101;
F24C 15/20 20130101 |
Class at
Publication: |
126/299.00D |
International
Class: |
F24C 15/20 20060101
F24C015/20 |
Claims
1. A hood for ventilating a home cooking area, comprising: a hood
enclosure; a fan disposed in the enclosure for exhausting cooking
fumes, the fan having an impeller and a fan housing; and a steam
generator within the hood enclosure for generating pressurized
steam from a water supply, the steam generator having an outlet,
and the outlet being fluidly connected to the fan housing effective
to direct pressurized steam onto the impeller, the pressure of the
steam generated being above atmospheric pressure.
2. The hood of claim 1, further comprising a steam generator
housing having a mating base and cover enclosing the steam
generator, and a pump mounted on the steam generator housing and
fluidly connected between the water supply and the steam
generator.
3. The hood of claim 1, wherein the steam generator further
comprises a heating coil, at least one temperature regulator
controlling the temperature at which the heating coil shuts off,
and at least one second temperature regulator controlling the
temperature at which the heating coil is turned on.
4. The hood of claim 1, wherein the steam generator has a low
profile.
5. The hood of claim 3, further comprising a temperature-sensitive
fuse controlling power to the induction heating coil by sensing the
temperature of the steam generator.
6. The hood of claim 3, wherein the steam generator comprises a
base and a cover, said heating coil is disposed in the base, and a
plate having a plurality of small holes and disposed immovably
between the base and the cover.
7. The hood of claim 1, further comprising a user-accessible
controller for initiating a cleaning cycle, the controller
including a timer, and the controller energizing the pump and the
heating coil during the cleaning cycle.
8. The hood of claim 7, further comprising a water reservoir
attached to the hood and fluidly connected to the steam generator,
and a low level sensor connected to the controller, the controller
adapted to de-energize the heating coil on a low level sensed.
9. A method for degreasing the impeller of a fan mounted in a
cooking exhaust hood installation in a home, comprising: A.
providing a hood installation including said fan; B. providing
water and heating the water to steam in a low profile vessel wholly
within the hood installation to generate steam above atmospheric
pressure; and C. directing said steam from said vessel against the
impeller of said fan in an amount effective to degrease the
impeller.
10. The method of claim 9, wherein the pressurized steam is
generated at a temperature of at least about 140.degree. C.
11. The method of claim 10, wherein the pressurized steam is
generated at a temperature of at least about 175.degree. C.
12. The method of claim 11, wherein the pressurized steam is
generated up to a temperature of about 200.degree. C.
13. The method of claim 9, further comprising the step of stopping
the heating when the temperature of the steam generated exceeds
about 215.degree. C.
14. The method of claim 9, further comprising pumping water to said
vessel.
15. The method of claim 9, further comprising restricting the flow
of steam from said vessel onto said impeller with a nozzle.
16. The method of claim 9, further comprising providing a
refillable reservoir of water, and providing the water by pumping
the water from the reservoir, and further comprising automatically
shutting off the steam generator if water in the reservoir falls
below a predetermined level.
17. The method of claim 9, further comprising cycling the heating
between two predetermined temperatures for a predetermined period
of time.
18. The method of claim 17, further comprising a user-accessible
control for starting the cycling.
19. The hood of claim 1, wherein the steam generator has a low
profile.
Description
RELATED APPLICATIONS
[0001] This application is based on U.S. patent application Ser.
No. 11/600,469, filed 16 Nov. 2006, which application is based on
provisional application 60/772,182, filed Feb. 10, 2006, the
disclosures of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a system for continuously cleaning
fans operating in a ventilation hood for a stove or other cooking
device.
[0003] Kitchen vent or exhaust systems are commonly used to remove
steam, odors, and other airborne vapors resulting from cooking on
stoves. The exhaust systems often include grease filters to capture
grease carried by the airborne vapors. For homes and smaller
establishments, the most common is an up draft system utilizing a
hood covering a portion or all of the stove burners to capture the
rising air. The hood is attached to the wall, or in the case of a
kitchen island, is suspended from the ceiling. Conventional vent
hoods typically are cone shaped and include a centrally positioned
fan which provides a centralized suction to draw air into the hood.
Stove hoods are well-known in the cooking appliance arts for
exhausting steam and smoke from the cooking area. Such devices
generally include a hood and at least one fan in the hood area
blowing from the hood to an exhaust duct. Over time, smoke
particles, aerosols, and volatiles from the cooked food adhere
and/or condense onto the surfaces of the hood, including the fan
blades. The fans used are typically axial fans, although radial
fans can also be used.
[0004] There are various disclosures of systems for cleaning the
fan blades of hoods over stoves. Some systems utilize a reservoir
adjacent the fan, where the fan motor causes reservoir fluid to be
sprayed onto the fan blades; the liquid can be recycled to the
reservoir, and replaced when desired. Other systems rely on tap
water or hot water, optionally including a detergent or surfactant,
sprayed onto the fan blades, and then collected and discharged, or
retained for later removal. Still other systems ignore the fan
blades but have a pipe running into the exhaust conduit or duct,
and the pipe including nozzles for spraying against the inner
conduit surface to remove cooking residue therefrom. Some systems
combine cleaning of the duct and the fan blades. These systems are
analogous to systems for cleaning turbine blades. Other systems
treat the exhaust gas stream with a spray prior to its entry to the
hood to wash the volatiles and smoke particles from the exhaust gas
so that less has to be cleaned from the hood, fan, and exhaust
conduit surfaces. Various systems include a filter disposed
downstream or upstream of the exhaust fan for removing smoke and
aerosols, and further include a spray that occasionally or
continuously washes the filter.
[0005] These systems are described in the following U.S. patents
and published applications, the disclosures of which are
incorporated herein by reference: U.S. Pat. Nos. 3,616,744;
3,805,685; 3,854,388; 4,085,735; 5,158,429; 5,860,412; 6,047,694;
6,503,334; 6,662,800; 6,712,068; 6,732,729; 6,880,551.
[0006] For devices that fit under a hood, or within a hood
enclosure, a source of water can be roughed in to the wall behind
the stove area. Accordingly, all that is needed for such devices is
a valve, which may be essentially controlled by a pump (e.g., the
cost of an electronic control valve using the existing water system
pressure can be more expensive than a small electric pump connected
to a valve at the fan housing). For those devices that provide
heated water, electricity is taken from the local source used for
the fan to power a heating coil immersed in a reservoir for the
water. The prior art devices show a fluid being provided to the fan
housing by a pump, so the fluid must be liquid.
SUMMARY OF THE INVENTION
[0007] In light of the foregoing, an object of this invention is to
provide a better cleaning system for hood fans. In particular, by
using steam, the condensed aerosols and volatiles and smoke
particles are more easily removed from the fan blades. Also, by
using steam there is no need to add a detergent or surfactant to an
existing source of water.
[0008] In general, this invention provides an exhaust hood with at
least one fan and a pressurized steam source supplying steam to
impinge on the fan blades. That is, this invention provides device
and method for cleaning fans in range or stove hoods by spraying
steam onto the fan impeller area on which soot and cooking fumes
condense to clean the impeller and wash the accumulated condensates
down a drain. By using steam as the cleaning fluid, the device uses
significantly less water that other devices that spray an aqueous
solution.
[0009] One embodiment of the invention comprises an exhaust hood
defining an enclosure and having an orifice adapted for attachment
to exhaust duct, a fan disposed in the enclosure and having an
output in fluid communication with the orifice, a steam generating
for producing steam above atmospheric pressure from a water supply,
and a conduit for channeling the high pressure steam to blades of
the fan. In preferred embodiments, there is a gutter to collect
condensed steam from the fan blades, the flow of water into the
steam generator is controlled by a pump, the steam generator has
emergency safeties, and/or the conduit has a nozzle.
[0010] In another embodiment, this invention provides a method for
degreasing the impeller of a fan mounted in a cooking exhaust hood,
comprising providing a hood installation including said fan,
heating water to steam in a vessel pressurized above atmospheric
pressure, and directing pressurized steam from said vessel against
the impeller of said fan in an amount effective to degrease the
impeller.
[0011] Viewed another way, this invention provides a device for
cleaning the impeller of a fan installed in a hood ventilating a
cooking area, said device directing a fluid onto the impeller and
draining water from the impeller, the improvement comprising a
steam generator for generating steam as said fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 depicts an exploded view of the steam generator and
pump.
[0013] FIG. 2 depicts a range hood installation including a
cut-away perspective showing two fans, a steam generator, and a
user-accessible controller on the outer surface.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0014] The invention is for a device and method for continuously
cleaning, or degreasing, fan impellers in hoods used for exhausting
stovetops or cooktops (the former being used in an exemplary manner
herein). The hood is typically mounted on a wall against which the
stovetop is installed, or suspended over a stovetop installed on an
island. The hood can be a simple canopy, or it can include a
housing in which the fans are supported. Water is fed to a steam
generator, preferably disposed within the housing of a hood. Steam
is generated at a pressure above atmospheric pressure, and the
pressurized steam is directed by a conduit to the fan impeller,
preferably so that the hub, the blades, and any other part of the
impeller that normally comes into contact with the cooking fumes
being exhausted is impinged by the steam. Because there is no
superheater for the steam generated, the pressurized steam is
essentially saturated steam at elevated pressure and
temperature.
[0015] As shown in FIG. 1, the steam generator 101 preferably
comprises an outer housing 103 having a base 105 and a cover 107.
Disposed within the outer housing is the inner steam generating
housing 109, comprising a generator base 111 (preferably about 1300
W) and a generator cover 113. When the base and cover are attached,
a steam generating volume is defined. Heat can be provided to the
generator by any means, including gas burners, but preferably the
base includes an resistive/inductive heating coil 115. The
generator base and cover are joined by a high pressure (and
temperature) seal 117 at the periphery where they mate. Disposed
within the steam generating volume can be a plate 119. The plate
can have a high surface area (e.g., with hills or upstanding
flanges as shown, and optionally openings), the bulk which adds to
the thermal inertia of the steam generating volume and the hills
and holes providing increased surface area for generating steam
when the plate is at temperature. The plate can be attached to the
base or it can be dimensioned to fit immovably between the base and
cover, in which case preferably a spring 116 is disposed between
the plate and the cover. The plate can be provided with small holes
to act like a separator, whereby inlet water is maintained near the
base and heated to steam that escapes through the holes into the
cover region on the other side of the plate.
[0016] Water is supplied preferably to the center 121 of the steam
generator base. In a preferred embodiment, water from lines roughed
into the wall behind the stovetop is supplied to a pump 123 (shown
with electrical contacts on the top for connecting to a power
supply and control); the pump is designed, like a check valve, to
prevent water from moving from the steam generator back through the
pump. The pump increases the water pressure and forces the water
through a tube 125 connected to the steam generator base center.
The pump is preferably mounted to the base of the housing as part
of a sold unit, but can be mounted elsewhere, preferably on the
unit.
[0017] At the top of the steam generator is an orifice 127 disposed
accessible or within an opening 129 in the cover. A conduit 301
connects the orifice to a second orifice 305a/b in a housing 307
surrounding the exhaust fan 309 disposed in the range hood. As
shown in FIG. 2, a cut-away perspective of a hood installation, the
fan is centered in a housing disposed around the periphery of the
fan. The fan housing includes at least one if not two or more
orifices where steam can be introduced. As shown in the drawing,
one orifice directs the steam supplied from the steam generator
radially inwardly against the blades and hub. Alternatively, one or
more orifices can be provided on just the top portion (e.g., at or
above the blades) or just the bottom portion (e.g., below or at the
blades). As shown, the housing can include a pair of gutters 311a/b
or a single gutter (that is, without the center wall) to collect
steam condensate and degreased debris flung centrifugally by the
fan onto the inner portion of the housing. A single gutter is
preferred because there is less surface area on which debris can
accumulate. The collected condensate is removed by the drainage
tubes 313 to a waste water pipe also roughed in to the wall, or to
a container for collection at a later time. The second orifice is
shown penetrating the gutters (and thus is actually a plurality of
orifices) to direct the steam supplied by the steam generator
axially in the direction of the incoming cooking fumes.
[0018] The steam generator is designed to generate steam at a
pressure above atmospheric, preferably significantly above
atmospheric. Thus, the steam generator is pressurized. The water
supply pump must be able to supply water at the designed operating
pressure, overcoming the pressure in the steam generator. Disposed
in the outlet in the steam generator cover, and/or attached to the
orifice(s) in the fan housing, most preferably on the inside wall
of the housing proximate to the fan blades and hub, is a nozzle 315
creating a backpressure and creating a spray of steam directed at
the fan blades and housing where there cooking fumes first contact
the fan. Alternatively, the conduit connecting the steam generator
cover to the orifices in the fan housing can be sized to provide
the backpressure needed for the desired operating pressure without
a separate valve.
[0019] The steam generator parts are preferably made of aluminum,
stainless steel, or any other suitable material, preferably metal.
The steam outer housing cover is preferably plastic or metal, and
the outer housing base is preferably metal. The water tube from the
pump to the steam generator base can be plastic or metal.
[0020] The steam generator and pump are preferably controlled by
simple means to provide the pressurized steam as well as safe
operation. A temperature regulator 141 senses the temperature of
the steam generator base and/or the temperature within the steam
generating volume. Such devices (and all of the other parts
required for this invention) are commercially available or can be
easily manufactured. Preferably there are two temperature
regulators, 141 and 143. A single temperature regulator is
preferably set (and fixed at the factory) to a temperature of
between about 175.degree. C. and about 200.degree. C. At that
temperature, saturated steam has a pressure of about 225 psia, or
about 15.5 times atmospheric pressure; it can be considered as
pressurized steam with respect to that generated at ambient
pressure. A temperature, voltage, and/or current activated fuse 145
is used to provide a safety if there is insufficient water on the
heating surface; preferably a temperature based fuse to shut off at
about 220.degree. C. (about 340 psia), more preferably about
216.degree. C., is used. In the embodiment shown with two
temperature regulators, preferably one is set to about 130.degree.
C. (equivalent to about 35 psia) and the other is set to about
175.degree.-200.degree. C. It is preferable to have a temperature
of at least about 120.degree. C., and more preferably at least
about 140.degree. C., and most preferably at least about
175.degree. C. to generate sufficient pressure for an adequate
supply of steam. A pressure relief valve is preferably included in
the cover. The temperature regulator can toggle the resistance
heater on and off to maintain the desired temperature in the steam
generating volume. When two temperature regulators are used, the
system will heat until the higher set point temperature is reached,
and then the heater is turned off; if there is time remaining in
the cleaning cycle, if the temperature falls below the lower set
point temperature (i.e., 130.degree.), the resistance heater will
start heating again to maintain steam generation. In operation, the
device cycles between from about 140.degree. C. (52 psi for
saturated steam) up to about 215.degree. C. (311 psi for saturated
steam), shuts off the heater, and then restarts when the low set
point is reached. The spring (which instead can be one or more leaf
springs, although a helical spring is shown) prevents the plate
from contacting and blocking the orifice, and also prevents
chattering of the plate within the generator. The spring also acts
to force the plate in contact with the generator so that it heats
and can be used as a thermal mass to heat the water.
[0021] Supply water can be held in a small reservoir 280 from which
the pump feeds, and a low reservoir level sensor (not shown) can be
used to shut off the pump and/or the heating coil if the reservoir
level is too low. As mentioned, the reservoir can be fed by
plumbing roughed-in behind the stove and hood, or the reservoir can
be attached to a wall or the top of the hood with a door accessible
by the user for manually filling the reservoir. A preferred
reservoir size is about 1.6 L (about 0.4 gallons), and a low
shut-off sensor is preferably provided set to about 0.3 L. The
reservoir preferably includes a water level sensor (preferably
electrical) that will shut off the system, or prevent the system
from being started, if sufficient water is not present in the
reservoir.
[0022] As pressure builds in the steam generating volume, steam
exits the outlet and impinges on the fan after passing through at
least one nozzle. While not desirous of being constrained to a
particular theory, it is believed that the significantly enhanced
enthalpy of the fluid impinging the fan acts to degrease the fan
without the need for the addition of a detergent or surfactant to
the water supply. For example, even with expansion of the steam
through a valve, the steam has an enthalpy significantly higher
than hot water, and about four times boiling water at atmospheric
pressure. Accordingly, the operator is not burdened with having to
buy detergent and refill the reservoir of the prior art devices on
a regular basis, else the degreasing efficiency is decreased. In
areas of hard water, it may be desirable for the present device to
have a small reservoir feeding the pump to allow for the addition
of vinegar or another additive to clean scale from inside the steam
generator. Although geometry of the volume defined by the steam
generator, tubing, and nozzle, in combination with the vapor flow
rate, heat input, water pump pressure, and pressure drops may
likely affect whether the spray includes some water droplets (i.e.,
a mixed vapor-liquid phase is produced), the intent is to impinge
as much steam (vapor phase) as possible on the impeller because
there is significantly more energy available for degreasing in
steam than in water, and because a lower ratio of liquid to vapor
generated (at the nozzle outlet) means less water will be used. It
is critical that pressurized steam, saturated steam above ambient
pressure (optionally superheated), be produced from the steam
generator so that effluent from the generator exits the nozzle
stays and impinges the impeller blades as steam and not a finely
divided liquid spray.
[0023] Of course, the size and length of the conduit (including any
cooling therein), and any decrease in the amount or heat value of
steam after expansion through the valve, will have an effect the
efficiency if not compensated in the design. What is important is
the generation of steam above atmospheric pressure at a pressure
and rate sufficient to provide an adequate flow of steam against
the fan impeller. Unlike a commercial installation where there is
significant ductwork upstream of the exhaust fan, and the exhaust
fan is located at the duct exit, at the building exterior, a home
kitchen typically has a cooking ventilation system with the exhaust
fan at the duct intake. Home cooking ventilation ducts are rarely
cleaned because there is a relatively short distance between the
fan and the exterior exhaust, and the fan can exhaust the air by
pushing it out before vapors condense and particles settle. A
commercial installation ventilates higher and smokier volumes,
through longer distances, and so the fan is positioned at the exit.
In a home hood installation, the fan (and any filter that might be
positioned in front of the fan) is a prime location for the
accumulation of grease and vapor condensation because the that
surface is the first contacted by the cooking vapors and smoke.
Thus, while there are systems for cleaning the exhaust stream and
associated ducts in commercial settings, the present invention is
especially adapted for cleaning the fan in a home ventilation
installation. The figures presented herein are drawn to scale to
the extent that the pressurized steam generator has a low profile,
or a high aspect ratio, enabling it to be placed within the
enclosure of the hood installation in a typical home setting, thus
utilizing available space within the enclosure. As shown, the parts
of the steam generator are plate-like or pan-like, creating a low
profile (span to height ratio) that does not require significant
space for placement entirely within the hood enclosure, and with
relatively simple connections to readily available power and water
supplies adjacent the stove area of a typical home kitchen (or just
electricity if a reservoir is used).
[0024] For home installations, the hood preferably houses two fans,
as shown. A single steam generation unit can be used for more than
one fan: as shown in FIG. 2, the reservoir 280 is connected by a
conduit 282 to the pump of the steam generator, and an outlet
conduit 284 joins from the steam outlet 127 through opening 129 to
a manifold 288 from where the steam is directed to the fan housings
and ultimately the fans. Although shown as rigid piping, flexible
tubes and a simple "Y"-connection can be used to transfer the steam
from the generator to the bottom portions of the fan housings. The
fan blades can be metal or any plastic that will withstand the
design temperature of the superheated steam exiting from the nozzle
and impinging the fan blades. The plastic should not soften during
the cleaning cycle (described below).
[0025] In another embodiment, a spray of water, as in the prior
art, can be used in combination with the present device to treat
the exhaust before it contacts the fan. Such a spray can be used to
entrain smoke particles with the condensate contacting the impeller
being flung into the gutter. Because of the additional water
content of the exhaust stream, it is desirable to increase the flow
of steam and/or its enthalpy content to account for the cooling
effect of the additional water present.
[0026] An advantage of the present invention is that it uses less
liquid water than the prior art devices because the water is used
in the form of steam (perhaps unless an additional non-steam water
spray is added). Thus, although less preferred because more water
will be used, the steam generator can produce a mixed phase (liquid
and vapor) at an elevated pressure sufficient to force a quantity
of the mixture onto the impeller effective for degreasing, by
varying the water pressure from the pump and the heat supplied.
[0027] As with prior art devices, the present device is preferably
actuated through the use of a control panel 211 (including one or
more buttons, switches, toggles, control knobs, etc., and
optionally a simple computer or chip controller) on the hood
accessible to the user, as shown in FIG. 2 (control wires to pump
and heater not shown). The user actuates a cleaning cycle using the
control panel, by which the controller starts a timer and actuates
the heater for a set period of time (cycling on and off), for
generally between 15 seconds and five minutes, with about one to
two minutes being preferred. The controller can start the timer
immediately or wait for a signal from the lower set point
temperature regulator before the time is counted down. Shown in
FIG. 2 is an input device on the control panel for the user to
adjust the preset time and a display 213 indicating the duration of
the cleaning cycle (e.g., a countdown until completed, and
otherwise, optionally, the time of day). The electrical connections
to the controller, the heating coil, the pump, and the fans are not
shown in the drawings, and neither are the control lines from the
temperature regulator(s) and the water level sensor.
[0028] In a more preferred embodiment, when the user actuates a
cleaning cycle the generator starts to heat and once the
temperature reaches the set point of the low temperature sensor
(e.g., above about 130.degree. C.) the pump is started for a fixed
time, preferably about one minute. The generator will continue to
heat until the temperature reaches the set point of the upper set
point regulator, at which point the heating will be stopped. The
pump may continue if the upper set point temperature is reached
before the pump times out. Once the heating is stopped and the pump
is shut off, the active portion of the cycle is ended. However,
steam may continue to be generated and impinge on the blades so
long as the residual heat and any water left in the generator is
sufficient to generate steam.
[0029] In the prior art devices using water and detergent,
actuating the device typically results in a water/detergent spray
for three 15-second intervals over the period of about one minute.
During that time (the 45 seconds of spraying), the prior art
devices use about one liter of water. In the present invention, it
is preferred that the preset time be about one to two minutes.
During that time, the instant device has been tested and found to
use approximately 0.1 to 0.2 liters of water. Thus, for each
actuation of the cleaning device, the present invention uses about
one-tenth to one-fifth the amount of water the prior art devices
use, and without the presence of detergent in the water
run-off.
[0030] The cooking fume load, the amount of material already
adhered to the impeller, how often the steam cleaner is operated,
and under what conditions it is operated are among the variables
that will effect how quickly the impeller will be degreased; by
"degreased" is meant removal of the grime from the impeller. For
extending cooking, the controller can be provided with a timer to
initiate cleaning at given intervals; for example, every 15
minutes.
[0031] The foregoing description is meant to be illustrative and
not limiting. Various changes, modifications, and additions may
become apparent to the skilled artisan upon a perusal of this
specification, and such are meant to be within the scope and spirit
of the invention as defined by the claims.
* * * * *