Note: Descriptions are shown in the official language in which they were submitted.
21237~
33i4-001-30
TIT~E OF THE INVENTION
AUTOMATIC FOOD PREPARATION DEVICE
BACKG~OUND OF T~E INVENTION
Field of the Invention
The invention relates to a kitchen appliance for
automated preparation of food products, especially, but not
limited to, chilled desserts. This appliance can cycle
through heating, refrigeration, freezing and mixing functions
without having to remove a detachable container from the
machine. All appliance functions are controlled by a powerful
programmable computer circuit located internally in the
device. Food products that can be prepared and stored in the
automatic food preparation device include: ice creams,
sherbets, soft yogurts, jellos, puddings, custards, milk
shakes, sorbets, frappes, frozen juices, mousses, souffles,
jams and jellies, soft baby foods, poached fruits, chilled
soups, cranberry and blueberry salads, gelatin salads, pasta
sauces, seafood sauces, poultry sauces, hollandaise sauce,
~ernaise sauce, gravy, chili, stews, scrambled eggs, wild rice
salads, waldorf salads, potato salad, crab and shrimp salad,
hot cereals, deep fried foods, popcorn, pie crust, bread
dough, doughnut dough, pizza dough, chocolate candy, fudge,
cake frostings, pie fillings, and food products requiring
-pasteurization.
21237~8
BAC}~GROUND OF THE RELATED ART
In the past, kitchen appliances have been designed to
perform one or more of the functions of heating, cooling, and
mixing. For example, several companies produce automatic
breadmakers which ~oth knead and bake bread. The American Gas
Associatlon is developing a gas tabletop oven that is capable
of both heating and cooling. However, a single appliance has
not been developed which permits automated preparation of food
products involving heating, cooling, and mixing according to a
programmed recipe wherein human intervention during food
preparation is unnecessary or significantly minimized.
Since the early 1980's, some Italian companies such as
Simac have designed ice cream makers with built-in chilling
systems. Patents 4,535,604, 4,538,427, 4,573,329, and
4,681,458, all to Cavalli, disclose ice cream making machines
that perform chilling and mixing. However, none of these ice
cream makers include means for heating. Appliances are
generally not constructed which perform heating and cooling
functions ~ecause refrigeration systems cannot withstand high
temperatures. For example, low-level chemical decomposition
of R-12 refrigerant begins to take place at approximately
250F. Raising the temperature of R-12 refrigerant from 70~F
to 200F will result in a 500% increase in the pressure of the
refrigerant. These high pressure levels in the refrigeration
-system can result in the failure of solder joints. High heat
also increases the chance of compressor failure. Furthermore,
212375~
R-12 refrigerant reaches its "critical point" at a temperature
between 220F and 233~F. Above the "critical point", the
refrigeration system ceases to function. Additionally, the
efficiency of the refrigerant decreases as the "critical
point" temperature is neared. Non-CFC refrigerant
replacements for R-12 such as R-134A have even less chemical
stability than R-12, thus producing even more of a problem
with loss of refrigerant at high temperatures.
For several years, combined heating and chilling baths
have been available as laboratory apparatus. The major
application for these laboratory refrigerated baths is to
provide direct temperature measurement and control in an
external closed-loop system. Pressure and/or suction pumps
located in the refrigerated bath housing circulate liquid
around external laboratory apparatus, such as electrophoresis
setups. One such apparatus is the Cole-Parmer~ miniature
refrigerated bath available from Cole-Parmer~ Instrument
Company of Chicago, Illinois. The bath has a built in
refrigeration compressor and further includes an immersion
heating and cooling coil that extends into a stainless steel
bath tank designed to hold water or a silicone bath oil. The
Cole-Parmer~ miniature refrigerated bath has an operating
temperature range of -20 to 100C. Cole-Parmer~ Instrument
Company also makes the Cole-Parmer~ Polystat~ refrigerated
bath, which has an operating temperature range of -20 to
200OC.
2123~8
Another type of laboratory temperature control bath is
the circulator bath. This type of bath has an automatic
heater and an immersion coolant circulating coil protruding
into the cavity that forms the bath tank for holding water,
silicone oil or another heat transfer fluid. An external
chiller system can--be connected to the coolant coil allowing
the liquid in the bath to be chilled. A pump circulates the
liquid within the bath tank and externally, if desired. The
Cole-Parmer~ Polystat~ Circulator Baths are examples of this
type of laboratory apparatus. These baths refrigerate
indirectly throush the use of an intermediate single phase
fluid such as methanol or glycol. The single-phase fluid
flows by pump from a refrigerated holding tank located in the
external chiller through cooling coils in contact with the
bath tank. This indirect chilling method is thermally
inefficient since the refrigerant does not directly cool the
bath. Furthermore, single-phase intermediate fluids have heat
transfer coefficients that are low in comparison to two phase
refrigerants such as R-12 or R-134A. The methanol or other
intermediate heat transfer fluid must be chilled separately in
a heat exchanger before it can cool the bath. Several thermal
resistance points are created by this process. Another
disadvantage of the Cole-Parmer~ circulating baths is that an
external intermediate fluid holding tank, refrigeration
-system, heat exchanger, and pump are required for system
operation. The size, weight, mechanical complexity, and
2123~58
manufacturing cost of the refrigeration system are increased
by the added refrigeration system components. Furthermore,
the Cole-Parmer~ refrigerated or circulating baths disclose no
means by which recipe ingredients could be mixed within the
refrigerating or heating bath. The different types of
laboratory liquid temperature control baths are neither
designed nor used for food processing applications. Also, the
baths are not constructed so they can easily be removed from
the refrigeration unit. A~detachable foodstuff container is
necessary for convenience and sanitation reasons.
Furthermore, immersion type coils that cannot be easily
removed are not suitable for use with foodstuffs. Immersion
coils protruding into a container would make effective mixing
of recipe ingredients difficult. Cleaning the container and
coil assembly after food preparation would also be a difficult
task.
Several detachable container designs for use in ice cream
machines have been advanced by the Italians and Japanese.
Patents 4,775,233 (Kawasumi et al) and 4,827,732 (Suyama et
al) each freeze the detachable container in place, creating an
ice gap between the wall of the cylindrical shaped evaporator
and the container. Ice is a poor thermal conductor, thus
resulting in inefficient cooling of the detachable container.
To remove the detachable container from the evaporator
assembly, hot gas must be channeled from the compressor bac~
through the evaporator to melt the ice holding the container
2123758
-
--6--
in place. This design is poor in thermal performance,
expensive to manufacture, and inconvenient to the consumer.
Furthermore, as in the case of all prior art ice cream
machines, any heating of recipe ingredients must be done on a
stove before the ingredients can be transferred to the ice
cream making machine for freezing.
Evaporator designs used in prior art refrigeration
devices also leave room for substantial improvements.
Existing evaporator designs use thin metal construction
wherein an evaporator coil is fastened to the outer wall of
the evaporator assembly. The evaporator assembly is a
cylindrical shaped well that accepts a detachable container.
Such construction provides inferior thermal performance in
comparison to the present design because only about 25% of the
round coil surface actually contacts the thin metal.
Additionally, prior designs could not be manufactured with
precise uniformity from piece to piece because metal
distortion occurred when the evaporator coil was soldered or
brazed to the outer metal skin. Even a minute amount of metal
distortion in these prior art devices increased thermal
resistance by creating air or ice gaps. Additionally, the
distortion prevented the detachable container from coupling
properly with the evaporator assembly, making insertion and
removal difficult.
A few prior art designs, of which Cavalli 4,573,329 is a
typical example, made use of elastically formable evaporator
- 2123758
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assemblies to improve contact with the detachable container.
With this design, a mechanical system allows the evaporator
assembly to be loosened or tightened around a detachable
container. Cavalli 4,573,329 used a series type manifold
refrigerant flow tube pattern that re~uired several connection
joints using low-temperature sealant. The attachment of the
complex manifold related tube network onto the outer metal
wall surface of a cylindrical shaped metal surface to create
an evaporator is a difficult and tlme consuming assembly
procedure. The only practical method of attaching the tube
network to the metal skin is by using thermal conductive
epoxy. This creates a very large thermal resistance point,
lowering potential performance. To achieve the elastically
formable design, a complex mechanical system consisting of
flanges, seats, pistons, pins and cams is used to loosen and
tighten the evaporator around the detachable container.
Springs are employed to maintain tension. Because of this
design, over time and heavy usage, the contact junction with
the removable container can be expected to loosen as the
mechanical system weakens. Second, in conjunction with the
movement related stress placed on the refrigerant flow coil
connection joints as a result of the mechanical system's
operation, the chance of refrigerant leaking at the
connections from stress cracks is increased.
Prior art evaporator designs were also incapable of
maintaining uniform temperatures throughout their evaporator
21~3~8
coils. These designs, of which Cavalli 4,681,458 is a typical
example, lnclude a single coil into which cold refrigerant
enters at the top. The refrigerant flowing through the coil
takes on heat and leaves the base of the evaporator at a
higher temperature. Since the refrigerant at the base has
less capacity to carry away heat, the area being cooled will
be kept colder at the top than at the bottom in the prior art
devices.
As mentioned earlier, Cavalli 4,573,329 suggested the use
of a manifold refrigerant flow network for application with
elastically formable designs. This design consists of a
plurality of lengths of tubing connected together in series by
means of two manifold bodies spaced apart in a circumferential
direction. The lengths of tubing connected to the manifold
are arranged above one another in contact. This design
creates an uneven flow of refrigerant through the tube network
as the refrigerant pressure drops along the length of the
manifold network.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a
kitchen appliance which can accomplish the tasks of chilling,
heating, and mixing recipe ingredients for food products
according to programmable sequences of preparation steps.
It is another object of the invention to provide a
heating and cooling appliance wherein the integrity of a
- 2123758
refrigerant or the refrigeration syste~ components used for
cooling are not adversely affected when the appliance is used
for heating.
It is yet another object of the invention to provide a
kitchen appliance which performs heating, refrigeration,
and/or mixing operations in response to either manual or pre-
programmed preparations steps.
It is a further objecl of the invention to provide a
refrigerating appliance with an evaporator having improved
heat transfer characteristics so a food product can be
uniformly and efficiently cooled.
The present invention provides an automated food
preparation device which can chill, heat, and mix or blend
food products within a container according to sequences of
programmed preparation steps. The device includes a container
adapted to contain a food product, and means for cooling,
heating, and mixing the contents within the container.
Additionally, the device includes means for automatically
actuating at least one of the cooling, heating, and m; X; ng
means, whereby the food products may be automatically
processed within the container.
According to one embodiment of the device, the container
is of a truncated conical shape which follows the shape of an
evaporator plate cooled by a refrigeration circuit. The
evaporator plate serves as the means for cooling the
container, and includes a refrigerant flow channel through
- 21237~
--10--
which a refrigerant such as R-12 or R-134A flows to remove
heat from the container. The means for heating the container
includes a heating plate or heating element beneath the
detachable container. The means for mixing the food product
within the detachable container includes a rotatable shaft
carrying at least one blade.
The evaporator assembly can be made shorter in length
than the detachable container, reducing the amount of metal
used in the evaporator's construction. The shorter length
version of the evaporator is positioned around the upper
length of the detachable container. This design minimizes the
potential for the detachable container to stick in the
evaporator assembly after insertion. Furthermore, use of this
design variation lowers the cost of scaling up the volume
capacity of the food processing appliance. This design wor~s
since the chilling effect of the evaporator extends below the
actual evaporator due to a buoyancy effect and the mi ~; ng
capabilities of the appliance.
In the preferred embodiment of the invention, mechanical
means are provided for moving the detachable container between
a first and second position. In the first position, the
detachable container is in contact with the evaporator plate
for removing heat from the detachable container. In the
second position, the detachable container is elevated out of
contact with the evaporator plate, such that the contents of
the container can be heated without heating the refrigerant
--- 21237~8
within the evaporator plate. This second position also allows
the contents of the detachable container to precool by natural
convection before switching to the first position. Precooling a
hot foodstuff for a short period reduces the load on the
refrigeration system.
In a second embodiment of the invention, a secondary
refrigerant such as methanol is used. Since methanol is a single
phase refrigerant, its use avoids the pressure and temperature
decomposition problems associated with refrigerants such as R-12
and R-134A discussed previously. Thus, in this second embodiment
of the invention, a mechanical means is not required for moving
the detachable container out of contact with the evaporator
plate. This second embodiment of the invention, however,
nonetheless includes a ventilating fan and an air channel around
the detachable container for pre-cooling the container before
refrigeration begins. This pre-cooling step is important to
lessen the load on the refrigeration system, which otherwise
would have to remove all of the heat trapped in the food product
during a preceding heating step.
It should also be appreciated that alternative means for
chilling, heating, and mixing could be used by the present
invention. Rather than a vapor compression cycle, for example,
alternative refrigeration means such as thermoelectric, Stirling
Cycle, Absorbtion, Propane or thermoacoustic refrigeration could
-- 21231 58
-12-
be used. Likewise, rather than a conductive heating plate, a
microwave, magnetic induction or halogen heat source could be
employed.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings; wherein:
Figure 1 is an overall orthogonal view showing the external
appearance of a preferred embodiment of the food preparation
device of the present invention.
Figure 2 is a top view of the food preparation device shown
in Figure 1.
Figure 3 is a side view of a slightly different embodiment
of an automatic food preparation device according to the present
invention.
Figure 4 is a schematic side view of the automatic food
preparation device of Figure 1 shown in its heating position.
Figure 5 is a schematic side view of the food preparation
device of Figure 1 shown in its cooling position.
Figure 6 is a cross-section of an evaporator plate which may
be used with the present invention.
Figure 7 is a schematic drawing showing one possible
refrigerant flow path through the evaporator plate.
212~758
Figures 8 and 9 show possible arrangements of a
temperature sensor placed within the automatic food
preparation device.
Figure 10 is a schematic side view of the invention
wherein a shortened evaporator assembly is used.
Figure ll is an alternate embodiment of the present
invention wherein a secondary coolant is used.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In Figures 1 and 2, an automated food preparation device
1 includes a housing 3, an evaporation plate 5 having a
refrigerant flow channel 54 (see Fig. 7), and a ventilation
opening 7 through which heat is expelled from a condenser
(Figs. 4-5). A container of food to be processed is placed
within a receiving space 9 in contact with evaporator plate 5.
A refrigerant such.as R-12, or alternatively 134A, is passed
in a liquid state through evaporator plate 5, extracting heat
from the food product causing the refrigerant to vaporize.
The details of the construction of the evaporator will be
discussed in detail later. Refrigerant in its gaseous state
flows from the evaporator to the condenser (Figures 4 and 5),
wherein heat is expelled from the refrigerant. Such a
condenser would typically consist of finned tubing that is
available from several manufacturers including Heatron, Energy
Transfer, Inc., and Heat Exchange Applied Technology. A fan
(Figs. 4-5) is used to blow air over the condenser coil to
21231~8
.
-14-
enhance heat transfer to the environment through forced
conduction. A thin brushless DC motor fan such as the
Micronel F-80 equipped with a bridge rectifier and capacitor
for AC current operation could be used. Alternatively, a
miniature AC fan such as the V-72 from Micronel could be
employed.
After refrigerant leaves the condenser, a compressor is
used to compress the refrigerant gas back into liquid state.
Suitable compressors are available from several manufacturers
including Necchi and Matsushita (Panasonic). Necchi makes the
Mini-ES series and Matsushita makes a similar line of small
compressors.
Capillary tubing is used to control the mass flow rate of
refrigerant into the compressor. Capillary tubing is readily
available from many sources, including Wolverine Tube, Inc. of
Decatur, Alabama. For connections between the compressor,
condenser, evaporator, and capillary tubing, basic copper
tubing such as that available from Wolverine Tube, Inc. could
be used.
As can also be seen in Figure 1, the device includes a
motor drive tower 11 having a motor 13 (Figure 4). Motor 13
is connected via a drive arm 15 to a mixing shaft 17. An
operator provides instructions to the device by way of buttons
on control panels 19 and 21. A display screen 22, which can
be either a Liquid Crystal Display (LCD), or Plasma Gas or
another technology, flashes information regarding appliance
-- 2123758
-15-
s.atus, entered data, or information communicated to the
device by telephone link. Messages from the device's memory
can also be displayed on the display screen for an operator to
read.
Figure 3 shows a side view of an automatic food
preparation device wherein the motor 13 is not provided within
the motor drive tower 11. Instead, motor 13 is provided
between power drive arm 15, and the detachable food container
25. This arrangement reduces stress on the power drive arm.
It can be appreciated from Figure 3 that the detacha~le food
container 2S and its lid 27 would be received in a similar
fashion within the embodiment shown in Figures 1 and 2.
Figure 4 shows the embodiment of Figures 1 and 2 in a
schematic cross-section. Motor 13 turns a pulley 30 carrying
a belt 32 within power drive arm 15. The belt 32 transfers
rotary motion to drive shaft 17 by way of pulley 34. Drive
shaft 17, in turn, can rotate a mixing blade 36 mounted
thereon. Mounting means 38 secure the mixing blade 36 to
drive shaft 17.
Figure 4 depicts detachable container 25 in its heating
position, out of contact with evaporator plate S to prevent
the adverse effects of heating the refrigerant contained
therein. The container 2S is mounted on a heating plate 40,
which carries heating elements 42. The heating elements 42
can, for example, be tubular heating elements or high-watt
density etched foil heating elements. Attached to heating
21237~
-16-
plate 40 is a sensor 43 for controlling the surface
temperature of the heater. Detachable contairler 25 is secured
to heating plate 40 by loc~ing means such as .ating grooves
and ridges. Thus, container 25 is twist-locked into place on
heating plate 40 for added stability.
Mechanical means is provided for raising container 25 to
the heating position shown in Figure 4. In a preferred
embodiment of the invention, the mechanical means comprises a
motor 44, a rac~ 46, and a pinion 4~. Rack ~6 is carried on a
column or shaft which supports heating plate ~o. When the
motor 44 is activated, pinion 48 rotates and engages rack 46
to move the column up or down and thereby shi^t container 25
between its heating (Fig. 4) and cooling (Fig. 5) positions.
As the container is raised or lowered, power drive arm 15
serves to transfer the upward or downward motion to motor 13
and motor-drive tower 11. Thus, as container 25 is lifted,
motor drive tower 11 is lifted, and as container 25 is
lowered, motor drive tower 11 is lowered as well. This
permits operation of mixing blade 36 when the container is in
either position. Mixing blade 36 can also be operated while
the container is in transit from one position to another.
Figure 5 shows the container 25 in its cooling position.
In this position, the exterior walls of the container are in
contact with evaporator plate 5. Accordingly, motor drive
tower 11 is shown in its lowered position. It should ~e noted
~that the truncated conical shape of detachable container 25
21237~8
-17-
insures an improved contact area between the container and the
evaporator plate in this position. Air gaps and ice formation
inherent in the prior art are minimized by this design.
Figure 5 also shows (dotted lines) a dispensing pump 50.
The dispensing pump permits single serving size supplies of
soft ice cream, yogurt, or the like to be dispensed from
container 25 without necessitating removal of lid 27. Hot
syrups, gravies, and the like could likewise be dispensed from
the pump when the container is in its heating position.
Figures 6 and 7 show the details of evaporator plate 5.
In all previous known detachable container designs, the
evaporator coil has been attached to the outer surface of the
metal skin of a female cooling well assembly. Only around 25
of the round coil surface actually contacts the metal wall in
such an arrangement. Thermal transfer is therefore
inefficient. Furthermore, and since the temperature of the
flowing refrigerant increases after it evaporates as it flows
downstream, it is difficult to achieve a uniform temperature
at the top and bottom of the coil in the prior art
evaporators.
As shown in Figure 6, the evaporator plate of the present
invention includes two main segments located within an
insulating layer 51. The first segment is a machined metal
piece 52. Piece 52 is an extruded or cast metal composition
having a cylindrical truncated conical shape. The piece 52
may be constructed for example of 6061 aluminum, which is
212~758
.
-18-
machined or cast with a refrigerant flow groove pattern 54 on
its outer wall 55, and bored or cast so that its interior
surface 56 is smooth. The second main segment of evaporator
plate 5 is a metal sleeve 60 which is placed over the groove
pattern 54 of the metal piece 52 to cc~plete flow channels
formed by the grooves 54.
Metal sleeve 60 may also be of aluminum construction.
When both segments 52 and 60 are of aluminum, attachment of
the pieces may be made, for example, by tinning with a
fluxless aluminum solder such as Ney 380 by use of an
ultrasonic solder bath for later joining in an oven. The
piece 52 can be tinned before the machining operations take
place. As a means of obtaining a tight fit, the piece 52 is
cooled down to cause shrinkage and the sleeve 60 is placed
over the grooved pattern. Additionally, tinned tube
connectors 66 and 68 (Fig. 7) are connected to the inlet and
outlet openings. Heating the evaporator assembly in an oven
to the melting point of the solder joins the parts together
and creates a bond stronger than the aluminum metal itself.
If sufficient ungrooved space is left at the top and bottom,
the solder joint will be strong and leak-tight. Tube
connectors 66 and 68 can be reinforced with epoxy compounds if
desired.
If copper, copper based alloys, or steel alloys are used
for the segments 52 and 60, solder paste can be applied to the
metal surfaces before joining in an oven. Brazing metals can
2123~8
--19--
also be used in the metal joining process. Other methods are
availa~le for assem~ly of the evaporator including vacuum
brazing a metal sleeve clad with brazing metal onto the
extruded part containing the refrigerant flow channels. For
example, automobile air conditioning evaporators and
condensers have ~een assembled for several years using a 4004
aluminum, silicon and magnesium bearing brazing alloy clad to
a pure 3003 aluminum core metal. The silicon lowers the
melting point of the clad below that of 6061 aluminum and the
magnesium flashes at 900F and combines with leftover oxygen,
stopping oxidation during the furnace vacuum brazing process.
Additionally, seam welding the top and bottom of the sleeve 60
onto extruded part 52 is feasible.
Forging the metal piece 52 provides certain advantages
over extruding this part. Sharper angles and larger sizes
than what is practical using an extrusion fabrication
technique is possible. If forging is used, a truncated
conical piece of metal is precision forged to the desired
angle and wall thickness. After the forging step has been
completed, the surface of the metal is smoothed. The flow
channel network is then machined into the outer wall. During
the machining step, the conical forged part can be tilted at
an angle so that the milling bit works along a horizontal
surface. With this method of construction, metal sleeve 60 is
of the same material as the forged metal, and is manufactured
to an identical angle as the forged part. This metal sleeve
212375~
-20-
is bonded over flow channels 54 using the same surface tinning
and oven soldering procedure described above for the aluminum
extrusion assembly technique. Shrink freezing of the forged part
is not required. If the sleeve is slightly shorter than the
forged part, or if the forged part is placed on a mandrel,
gravity or simple even pressure during the oven heating process
will result in a strong solder bond between the sleeve and the
forging containing the machine refrigerant flow network 54. A
copper or steel weight can be used to apply the pressure during
the oven soldering operation. Investment casting, vacuum
casting, and die casting and machining methods allow the depth
and width of the refrigerant flow-grooves 54 to be adjusted. The
thickness of the metal can be reduced by using this process.
As can be seen in Figures 4-6, the metal plate 40 can be
provided with one or more recessed grooves 41 for receiving
locking ridges 141 which are provided on the base of container
25.
Figure 7 shows one possible arrangement of the flow-channel
groove 54. Refrigerant entering the evaporation plate is devided
into two different flow sub-circuits 62 and 64 so that more
uniform cooling is achieved. Coolant entering through inlet tube
66 flows upward and is devided into the paths 62 and 64. The
flow from these sub-circuits then again merges before exiting
through exit tube 68. With this structure, the temperature along
path 62 are essentially equal to those along path 64.
Furthermore, this design avoids superheating of the refrigerant.
2123758
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-21-
Figures 8 and 9 show the details of rotating shaft 17, the
mounting structure for blade 36, and a temperature sensor 70.
In Figure 8, temperature sensor 70 is mounted on a
stationary hollow outer shaft 72. The hollow outer shaft 72
receives a rotating inner shaft 74 with adequate clearance so
that there is no frictional resistance between the shafts.
Wiring 76 leads from temperature sensor 70 to the micro-
controller of the device (not shown), and is isolated from
rotating shaft 74. The rotating shaft 74 carries locking
members 38 for securing mixing blade 36 (see Figures 4 and 5) in
place.
Figure 9 shows an alternative embodiment of the shaft 17
wherein the inner portion of the shaft 74 is stationary and the
outer portion of the shaft 72 rotates and carries locking means
38. The temperature sensor 70 is mounted at the base of the
stationary inner shaft 74 and its wires 76 lead through
stationary inner shaft 74. A sealing means 80 is provided to
prevent any food product from coming between inner shaft 74 and
outer shaft 72.
Figure 10 shows the automatic food preparation device
wherein a short evaporator assembly 105 is used in place of the
evaporator assembly 5 shown in Figures 4-6. By utilizing a
refrigeration system evaporator assembly that is shorter in
length than detachable container 25, the amount of metal used
in the evaporator construction can be reduced. Furthermore,
2123758
-22-
the use of the short evaporator design provides an additional
advantage in that it lowers the cost of scaling up the volume
capacity of the food processing appliance. The design
nonetheless provides adequate cooling because the chilling
effect of the evaporator extends below the actual evaporator
due to a buoyancy effect. Additionally, the mixing
capabilities of the appliance asslst in transferring heat from
the entire contents of the detachable container 25 to
evaporator plate lOS.
In the embodiment shown in Figure 10, evaporator 105 is
supported around the upper part of detachable container 25 by
a protruding ridge 107. This design minimizes the potential
of detachable container 25 to stick in the evaporator assembly
after insertion because an air space 109 is provided adjacent
a substantial portion of the external surface of detachable
container 25. Air space 109 also provides adequate space to
receive inlet and outlet tubes conducting refrigerant to and
from evaporator assembly 105. A layer of insulation 111 is
provided around evaporator assembly 105 and the air space 109,
and the insulation also extends beneath heating plate 40. The
insulation may be of any suitable variety, although a plastic
insulation material is preferred.
Figure 11 shows an alternative embodiment of the
invention wherein an intermediate coolant (single phase) is
used for the refrigeration function. Coolants that can be
used for this purpose include propylene glycol, ethylene
2123~58
-23-
glycol, methanol, sodium chloride, calcium chloride,
trichloroethylene, and methylene chloride. These coolants do
not vaporize within the refrigeration cycle, and therefore
excessive pressures do not build up within an evaporator
assembly 205 when the refrigerant is heated. Nonetheless,
after heating takes place using a heating plate 240, a
precoolant step is desirable to remove heat from container 225
before refrigeration begins. For this purpose, a fan 204 is
provided along with an air channel 209 through which
ventilating air is forced by the fan. A layer of insulation
211 is provided around evaporator assembly 205 and the air
space 209 in a manner similar to that shown in Figure 10. The
precooling step releases heat trapped in the food product
mixture that other~ise would have to be removed from the
container by the refrigeration system alone. This allows the
present invention to make use of smaller, less expensive
components, reduces compressor running times and increases
refrigeration efficiency. Mixing blade 236 in Figure 11
operates in much the same way as mixing blade 36 in Figure 4
and 5. It should be noted that an intermediate coolant such
as methanol or the like could also be used in the embodiment
of the invention shown in Figures 4 and 5. Likewise, a fan
such as fan 204 of Figure 11 could be provided near the motor
44 in Figure 4 and 5 for cooling the removable container 25
before it is lowered into its cooling position.
21237~
-24-
Additionally, it should be appreciated that apparatus for
automatic addition of recipe ingredients could be provided
above removable container 2S. Detachable container top 27,
for example, could have holes located on its surface for
accepting matching sized ingredient containers. These
ingredient containers could contain either liquids, powders,
or solid pieces. Pressure exerted on the ingredient
containers could cause trap doors on the containers to open,
spilling the contents. Liquid containers could utilize a
syringe type design which empties a measured amount of
contents when pressure is exerted on the contents of the
container by a plunger. The actuator system for the
ingredient containers can be located internally in the
detachable container top or be external.
A powerful micro-controller consisting of computer chips
controls the functlons of the automatic food preparation
device. These chips can be located, for example in or behind
control panels 19 and 21 shown in Figure 1. A manual mode
allows an operator to enter timing, mixing, heating, and
chilling instructions by push button. As an additional
convenience, a bar-code device can be included which allows an
operator the flexibility of entering automatic food
preparation instructions from a recipe book or from a premixed
product package, bypassing a need to press any buttons. By
using a bar-code system, the recipe could be customized beyond
the preset or manual entry buttons located on the control
2123~ 58
-25-
panels 19 and 21. Other automatic recipe entry options
include storing a recipe book on a memory card or disk and
allowing the operator to call up and select a recipe for use
with the appliance. Furthermore, the capability can be
designed into the appliance to accept recipes down-line from a
telephone hookup with an information service. The telephone
can also be used as a means for entering operational
instructions into the appliance from a remote location.
The following is an explanation of the operating
procedure of the food preparation device of the present
invention with reference to the embodiment of Figures 4 and 5.
Typically, the removable container 25 and its lid 27
would be removed for adding ingredients to the container. The
container would then be placed within the receiving space 9
and the power arm 15, rotating shaft 17, mixing blade 36, and
container lid 27 would be assembled in place as shown in
Figure 4. The capability of adding recipe ingredients to the
detachable container after assembly can be accommodated by
using a container lid with a removable section (not shown~.
Using the control panels l9 and 21, an operator would then
program a sequence of chilling, mixing, and heating
instructions. Alternatively, the user could select a button
corresponding to a preprogrammed set of instructions or load a
recipe program into memory by some other means. Preprogrammed
buttons on control panel l9 may include recipes for commonly
prepared items such as ice cream, pudding, and yogurt. If the
21237~8
-26-
user desires storing the ingredlents in a heated, refrigerated
or frozen state before or after food preparatlon, this can be
programmed as well. The actual sequence of cooling, mixing,
and heating is controlled by the micro-processor within the
device according to the instructions given by the user.
Functions that are controllable include heating and cooling
times, temperature, mixing speed and mixing direction. Other
functions such as automatic recipe ingredient addition and
foodstuff dispensing are also software controllable. The
micro-controller would have adequate memory space to store
complicated recipe instructions. When cooling is to be
performed, detachable container 25 is maintained in its lower
position as shown in Figure 5. The compressor, condenser, and
evaporator are actuated to remove heat from the container by
circulating refrigerant through the refrigeration cycle. If
desired, mixing can take place using blade 36 while
refrigeration is being performed. Temperature sensor 70
provides feedbac~ to the micro-controller so that either a
mild chilling or hard freezing can be achieved as desired.
When heating to a temperature above room temperature is
desired, heating elements 42 are activated, and the container
25 is raised to the heating position shown in Figure 4. To
prevent a large amount of moisture from freezing on evaporator
plate 5 once heating has begun, it may be desirable to program
the micro-controller to warm the evaporator plate to room
temperature or slightly warmer before the container is raised.
~ 2123758
-27-
Once in the heating mode, temperature sensor 70 again provides
feedbac~ to the micro-controller so that a desired temperature
can be maintained. Mixing blade 36 may also be activated
during the heating mode. Once food preparation is complete,
the device is capable of holding the prepared dish at any
desired temperature, and it will do so automatically if such a
step was programmed with the preparation instructions. For
soft, frozen desserts such as ice cream, custard, or yogurt,
the optional dispensing pump 50 can be installed for
dispensing the food product directly from food container 25.
Hot syrups, gravies, and the like could be dispensed in a
similar manner from the device when it is in its heating
position.
Obviously, numerous modifications and variations of the
present invention are possible in light of the above
teachings. It is therefore to be understood that within the
scope of the appended claims, the invention may be practiced
otherwise than as specifically described herein.
