Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
COATING AND DRYING APPARATUS
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to apparatuses and
processes for mixing, coating and drying a plurality of
objects. Most preferably, this invention relates to
apparatuses and processes for distributing and drying a
sugar coating to the surfaces of confectionery.
Related Background
Many edible items ("pieces") have an outer coating
comprised of sugar and other edible material. Such
outer coatings, or candy shells, serve many functions,
including preserving the center confectionery, as well
as supplying an appealing look and taste to the edible
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item. Candy shells also give an identified "crunch"
when eaten.
Many devices are known for applying a coating to edible
pieces. For example, U.S. Patent No. 5,507,868
discloses a typical prior art sugar coating apparatus.
The reference describes a device having a rotary drum
panner having a plurality of air holes and hollow shaft
portions. Drying gas is supplied through one of the
hollow shaft portions and directed downward toward an
accumulated layer of particles for drying.
U.S. Patent No. 4,050,406 discloses a sugar coating
apparatus which uses an annular mesh trough for
containing objects for coating. The apparatus is
mounted on springs and is vibrated to move the objects
around the annular container. Drying air is supplied
through the center of the apparatus directly to the
mesh. The airflow then flows straight through the mesh
to exit the top of the apparatus. The airflow is not a
tangential flow.
Another prior art device is disclosed in U.S. Patent No.
5,158,804. This patent discloses a coating apparatus
and process for coating small quantities of tablets
(drugs during the initial stages of formulation and
development). A spray coating is applied from above the
tablets on a mesh and drying air is supplied upwardly
from below the mesh. In addition, the mesh is vibrated
to make the tablets bounce up and down.
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Still other prior art devices fluidize objects for
coating. For example, in U.S. Patent Nos. 5,792,507 and
5,296,265, disclose coating apparatuses and processes
which use a rotating disc in conjunction with an air
flow at the periphery of the disc near the inner wall of
a cylindrical container to fluidize the particles to be
coated.
The above apparatuses and processes are insufficient for
economically coating a multitude of confectionery since
the costs associated with building, operating and
maintaining them are relatively high. In addition, the
prior art processes require a relatively long period of
time to coat confectionery, which results in the
expenditure of a greater amount of energy per unit mass
of coated material. Further longer coating times reduce
productivity of a piece of equipment resulting in higher
cost per unit mass of product.
Thus, there is a need for an efficient, compact, and
faster apparatus, which consumes less energy than
existing apparatuses, and which produces coated
confectionery in shorter period of time.
SUMMARY OF THE INVENTION
The present invention addresses the above concerns and
presents new and novel apparatuses and processes for
coating and drying a plurality of particles. Moreover,
the present invention lends itself to any process which
benefits from good mixing of particles within a deep bed
of product, especially for coating, mixing and drying a
hard-panned sugar shell applied to confectionery.
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The factory floor area required for the present
invention is greatly reduced over existing apparatuses,
yielding additional cost savings.
In one aspect of the present invention, an apparatus for
heating and/or cooling a plurality of particles includes
a generally circular bed for holding the particles, the
bed including a substantially centered annular inner bed
wall, an outer bed wall and an irregular bottom. The
irregular bottom is an uneven surface which may or may
not be perforated and most is preferably a screen. The
apparatus also includes a drive mechanism rotatably
affixed to the bed, where rotation of the drive
mechanism at a predetermined rate produces a
displacement of the bed horizontally and vertically
resulting in a particle flow in the x, y and z
directions. The particle flow in the x and y planes for
a majority of. the particles is in a dominant direction.
The apparatus also includes an air plant which provides
a heated and/or cooled airflow tangentially below the
screen. The airflow moves through the screen, and into
the bed of particles.
The air plant may include a pump for providing an
airflow into a duct, a dehumidifier in fluid
communication with the pump, a heater positioned
downstream from the dehumidifier and in-line with the
duct, and a generally circular intake manifold having an
outer manifold wall and an airflow inlet in fluid
communication with the duct and tangentially arranged on
the outer manifold wall. The intake manifold is
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positioned below the bed and includes an outer
circumference substantially corresponding to the bed.
An outlet may be included along the outer wall of the
bed and be removably covered by a tangentially
positioned cover provided around a portion of an inner
surface of the outer wall. The cover includes a first
end affixed to the inner circumference of the outer wall
downstream of the outlet in the dominant direction, and
a second movable end adjacent the inner surface of the
outer wall when the outlet is closed. The movable end
is be positioned upstream from the outlet in the
dominant direction and is opened when the movable end is
moved toward the center of the bed. The cover and outer
wall form a funnel having an entry for accepting
particles from the dominant direction.
In another aspect of the present invention, a process
for heating or cooling a plurality of particles in an
apparatus as described in the previous aspect includes
the step of displacing the bed at a predetermined
frequency vertically and horizontally to produce a
particle flow in the x, y and z directions. Particle
flow in the x and y planes for a majority of the
particles is in a dominant direction. The process also
includes the step of heating and/or cooling an airflow
to a predetermined temperature and directing the airflow
tangentially to the bed via a generally circular intake
manifold substantially corresponding in circumference to
the circular bed and positioned below the screen. The
airflow flows in a circumferential pattern around the
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interior of the intake manifold, through the screen and
into the bed.
In yet another aspect of the present invention a process
for coating and drying a plurality of particles in the
apparatus, as described in the first aspect, includes
the step of displacing the bed as described in the
previous aspect to produce a similar particle flow.
Other steps of the process include, in the case of
coating particles, applying a coating material from a
nozzle positioned above the bed, the application of the
coating occurring during a first predetermined period of
time, providing a temperature controlled airflow and
directing the temperature controlled airflow
tangentially to the bed via a generally circular intake
manifold which substantially corresponds in
circumference to the circular bed and is positioned
below the irregular bottom. The airflow being.provided
after a second period of time has passed after the
coating material has been applied. The airflow moves in
a circumferential pattern around the interior of the
intake manifold, through the irregular bottom and into
the bed.
While a preferred embodiment provides the airflow
tangentially to the bed in a direction opposite to the
dominant mixing direction, air flow in the direction of
the dominant mixing direction may also be used.
The high degree of mixing of the individual particles in
the x, y and z directions in the present invention
ensures consistent treatment of all particles with the
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desired process. This high mixing reduces piece to
piece variation which that results when individual
pieces remain in localized areas within the process
volume when drying, coating or other conditions differ
from the average.
Accordingly, it is a feature of the present invention
that a high degree of shear and contact is created
between individual pieces of the confectionery product
as a result of the particle flow created. This results
in faster coating and drying times since confectionery
are mixed more thoroughly and evenly and are more
uniformly coated, without damaging the confectionery or
causing rough surfaced candies.
The tangential air injection into the cylindrical area
creates a centrifugal pressure gradient which encourages
the majority of the air flow to occur through the outer
area of the bed where the majority of the particles are
present. This maximizes the desired transfers between
the air and the particles.
The present invention optimizes airflow and temperature
to maximize evaporation rate. This results in a cycle
time for some confectionery which is 20-40~ of the time
of traditional apparatuses and methods, even with
relatively high air humidity dew-points approximately
between 4-12°C. By carefully monitoring and controlling
the temperature of the product in the bed throughout the
coating cycle, a hotter supply of air on average can be
used, thereby increasing the amount of moisture that can
be removed per cfm.
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Thus, it is a further feature of the present invention
that the dehumidified and heated airflow provided
tangentially to the bed provides maximum evaporative
effect to the particles within the bed so that they may
be dried faster than other apparatuses and processes
disclosed in the prior art.
The speed of coating and drying occur so much faster
than in existing techniques, that lower-solids coating
solution may be used. High-solids coatings, used in
existing techniques, are generally used so that less
moisture will be required to be removed from the coated
particles after application. High-solids coatings,
however, must be kept at heated higher temperatures.
Thus, use of lower-solids coating solutions eliminates
the need for keeping coatings hot, thereby eliminating
the need to heat the coatings and also eliminates the
need for water jacketing of piping and containers for
ferrying and storing the hot coating. The elimination
of hot coating also contributes to significant energy
savings due to less heat loss to the environment air.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic elevational view of the fluid flow
system for the coating and drying apparatus according to
the present invention.
Fig. 2 is a schematic top plan view of the coating and
drying bed according to the present invention.
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Fig. 3 is a schematic side elevational view of the
coating and drying bed according to a first embodiment
of the present invention.
Fig. 4 is a schematic side elevational view of the
coating and drying bed according to a second embodiment
of the present invention.
Fig. 5 is a schematic top plan view of the coating and
drying bed according to the second embodiment of the
present invention.
Fig. 6 is a schematic isometric view of a coating
apparatus according to the present invention.
Fig. 7 is a schematic side elevational view of the
coating apparatus according to the present invention.
Fig. 8 is a schematic top plan view of the fluid flow
within the mixing and coating bed according to the
present invention.
Fig. 9 is a schematic side elevational view of the fluid
flow within the coating and drying bed according to the
present invention.
Fig. 10 is a schematic top plan view of the coating and
drying bed according to the present invention.
Fig. 11 schematically illustrates the forces applied to
confectionery.
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Fig. 12 is a side-sectional view of a coated
confectionery.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figures 1-11 illustrate preferred embodiments of the
coating and drying system 2 according to the present
invention. A cylindrical bed 4 includes a central
longitudinal axis 6, a side wall or outer bed wall 8, a
bottom 12 formed of an irregular uneven surface,
perforated or non-perforated, and a center cone 14. The
center cone provides a substantially centered inner bed
wall. The irregular bottom surface preferably comprises
a mesh screen.
The bed, side wall, cone and irregular bottom may be
coated with a non-stick material (e.g. Teflon) to
provide low friction so that confectionery particles 1
impacting thereon do not get damaged. Preferably, the
screen on the bottom of the bed is a stainless steel
market grade wire cloth. The mesh size would depend on
the size of particles 1 to be coated.
The bed may be a commercially available separator unit
(Sweco, Division of Emerson Electric Co.), which is
generally used to separate solids from liquids or
segregate dry materials into various particle sizes.
The screen comes pre-assembled with the round
separators, and is available in a number of mesh sizes.
The bed may be of any depth so that it can contain a
deep bed of product. The depth of the bed is between
approximately about 2.5cm - 60cm, and preferably between
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approximately about 5 cm - 30 cm, and most preferably
between approximately about l0cm-l5cm.
The bed, which may include an air intake manifold 16
below the screen 12, is mounted on a motor frame 18.
The bed and motor frame assembly, in turn, are mounted
on a base 20, via springs 22 secured to the bottom or
side of the air intake manifold. Although the apparatus
need not be secured to concrete or other structural
surface, it is preferred that the apparatus be fastened
to a concrete floor 24 by a one or more mechanical or
chemical anchors (not shown).
Located approximately at the center of the motor frame
18 is an opening 26 for housing an electric drive motor
28. The motor is substantially centrally aligned with
the center axis 6. The motor is provided with shafts 30
and 32 that project to the side from above and below the
motor, respectively. A first agitation weight assembly
34 and second agitation weight assembly 36 are mounted
on each shaft 30 and 32. When the motor rotates, the
assemblies 34 and 36 are spun around by the motor shafts
and 32, respectively, and are responsible for
vertical and horizontal displacement of the bed during
25 shaft rotation. Both weight assemblies are rotated in
the same direction in two different substantially
parallel horizontal planes which are also substantially
parallel with the bottom of the bed. Thus, the weight
assemblies provide an agitating motion horizontally and
30 vertically to the bed.
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The first weight assembly 34 includes adjustment bar 38
and horizontal displacement weight 40, and is positioned
above the motor to provide centrifugal forces that
impart processional motion around the bed in the x and y
planes. The second weight assembly 36, adjustment bar
42 and vertical displacement weight 44 impart a
spiraling mixing motion in the z plane.
The weight of each assembly may be positioned at
different locations along their respective adjustment
bar, to achieve a variety of different bed displacements
to yield a particular desired flora motion of the product
within the bed. Weight 44 is also split to form an
adjustable angle there between, and an angle between the
adjustment bars of the top weight assembly and the
bottom weight assembly, the lead angle, may also be
adjusted. Both adjustments yield additional refinements
to the bed displacement. Changing the weight positions
and angles changes the effective mass and center of
gravity of the particular weight assembly, thus changing
its associated driving force on the bed, ultimately
changing the magnitude and degree of agitation and flow
pattern of particles within the bed.
It would be appreciated by one skilled in the art that
the important feature of the process being discussed is
the motion induced by the motion generator rather than
the particular specifics of the mechanism of this
example. A wide selection of other mechanical devices
exist or could be conceived which can create this
required bed motion to produce the desired product
motion and, mixing in the bed.
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The openings in the screen and screen roughness assist
in transferring (i.e., coupling) the horizontal screen
vibration into product motion. The screen opening size
is preferably chosen to be slightly less than the size
of the piece being processed.
It will be appreciated by one of ordinary skill in the
art, that in the case of mixing product only, that any
irregular bottom surface may be used in place of the
screen to create the desired particle flow.
It has been observed that larger batch sizes can be
coated by using larger diameter beds with more powerful
motors driving greater eccentric weights. The
consistent factor in obtaining the desired motion of
particles is the accelerations in the x, y, and z
directions and phase angles previously described. The
exact motor size required is determined by a host of
factors previously described. Additional factors
include but are not limited to desired piece motion,
piece size, piece density, piece surface friction
properties, and machine size plus mechanical attributes.
The frequency employed will depend on a number of
factors including the size of the apparatus. Generally,
the larger the unit, the lower the frequency to get the
desired motion.
A preferred motion for coating and drying the product is
achieved by rotating the weight assemblies at a
frequency preferably between approximately 5-100Hz,
preferably at approximately 12-25 Hz, and most preferred
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at about 15-20 Hz. Since a product's characteristics
change during different stages of the process (i.e.,
coating, mixing and drying), adjustment of the frequency
may also be required during a particular stage so that
the preferred motion may be maintained.
Generally, the maximum forces of acceleration in the x,
y, and z directions will be in a range from about +/- 20
to about +/- 100 m/secz, although any accelerations that
provide appropriate movement of the particles for
coating will be acceptable. The accelerations may be
measured using an accelerometer fixed on the outside of
the apparatus approximately 15 cm vertically above the
screen surface and approximately 45 cm horizontally out
from the screen centerline. The maximum accelerations
chosen for use in the apparatus will vary depending on
the size of the apparatus, and operating conditions,
e.g., airflow, product load, particle size and the
particle surface friction properties. Generally, the x,
y and z direction accelerations are relatively close,
e.g., +/- about 10~.
In a preferred embodiment, for coating lentil shaped
confectionery, the following accelerations and phase
angle yield the preferred motion for the bed:
g Y Z Lead Anale
+/-43.3 m/s2 +/-44.2 m/s~ +/-43.3 m/sz 80°
The frequency of the vibration of the bed may also be
varied at any point during mixing, coating, drying,
discharge or any combination thereof, to deliver the
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optimal motion for a particular point in a particular
process. It will also be appreciated that the laws of
mechanics allow the vibratory bed to be balanced or
unbalanced around its perimeter so that the motion of
the bed wall can vary from elliptical to circular in the
x, y and z directions at different points around and
through the bed. Unbalancing may be controlled in order
to impart additional desired mixing and motion of the
product.
It will also be appreciated that generally, larger
diameter agitation beds require lower rotational
frequencies in order to obtain the desired product
motion.
During agitation, the walls 8 and screen 12 of the bed
impact on the particles causing the particles to impact
upon themselves thereby creating a circumferential
procession around the bed. The screen in the bottom of
the bed also introduces both a displacement torque and a
rotational torque around the axes of the individual
products, aiding in the flow procession from the bottom
of the bed to the top. As shown in Figure 11, the
forces acting on the confectionery particles decrease as
one moves up the side wall and toward the center of the
bed. Between both flow processions (around and through
the bed), confectionery particles are thoroughly
intermingled during bed agitation.
The combined flow processions through the x, y and z
planes yield the preferred motion forming a generally
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torus flow pattern of the particles in the bed. The
torus motion, as shown in Figures 2 and 3, illustrate a
procession of the product around the major axis of the
torus, a circulation around the minor axis, and thus a
migration around and through the bed. As previously
discussed, an additional random motion component is also
induced which causes a high rate of migration of
individual pieces near each other to move randomly away
from one another over time.
Depending upon the direction that the weights assemblies
are rotated, the majority of the confectionery particles
in the bed is caused to rotate in a dominant flow
direction 43 in the x and y planes. The motion is
either clockwise or counterclockwise direction depending
upon the spinning direction of the rotating weight
assemblies.
Preferably, the individual pieces within the bed
traverse around the major axis and the minor axis on
average approximately between 1-10 times/minute, and
more preferably between 3-10 times/minute. The higher
values are obtained when the particles are dry.
The induced motion causes the confectionery pieces
positioned at or near the top of the bed to flow in the
dominant flow direction, spiraling toward the center of
the bed. As the particles approach the edge of center
cone 14, they begin rotating in a direction opposite to
the dominant flow direction and are then dragged under
in the negative z direction. Once they are pulled down
in the center of the bed, the particles proceed up and
out from the bottom of the bed as they move toward the
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outer wall. The center cone is used to prevent
particles from entering the very center of the bed,
which is an area having little mixing flow. While a
center cone is preferred, the substantially centered
inner wall is not limited to a cone shape and may take
any form, e.g., a cylinder, that serves to prevent
particles from entering the center of the bed.
The size of the individual confectionery particles also
determines how fast the confectionery particles are
carried in the torus mixing procession. Specifically,
the smaller the confectionery, the faster the motion.
Thus, smaller confectionery pieces are more thoroughly
mixed for a given time period.
Airflow to dry the particles that have been freshly
coated is supplied from an airflow system 46 is provided
to the bed at tangential air induction inlets 17, which
preferably may be positioned on the intake manifold 16
located below the bed, or at the base of the wall 8 of
the bed. The inlets are positioned on either side of
the bed separated by approximately 180 degrees. The
airflow enters the bed preferably from below the
screened bottom, in the case that the airflow is
provided through the intake manifold, in a swirling
pattern around the circumference of the bed 4 to dry
confectionery that have been freshly coated. However,
the swirling airflow may also be directed tangentially
from the base of the walls of the bed.
The airflow system 46 provides air which can be
conditioned and delivered at a range of dew-points,
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temperatures and flow rates. The system is preferably
an open loop system which feeds air at predetermined
flow rates through the bed via the tangential air
intakes. The system includes a centrifuge blower 48
powered by a variable speed electric drive motor 50. An
air intake 52, provided with a filter 54, for removing
dust particles and the like, feeds fresh or recycled air
into the center of the blower, which compresses and
propels the air out tangentially at an adjustable
controlled flow rate.
The flowrate of the airflow system is controlled by a
dedicated single loop controller 55, which receives flow
rate information from a flow sensor 56, positioned
within the intake portion of the system. Based on the
flow sensor output, the controller adjusts the speed of
the variable drive motor powering the blower. Flowrate
in the present invention is controllable from 0 CFM to
400 CFM, and preferably between 180-350 CFM.
The airflow is initially sent to a diffuser element 58
to diffuse the air into a wider path for entry into a
humidity controlling unit 60. The humidity unit 60
dehumidifies the entrained airflow, and also lowers the
temperature of the airflow since compression of the air
by the blower causes the airflow to increase slightly in
temperature. A cooler or air-conditioner may also be
used in addition to or in place of the humidity
controlling unit.
Preferably, the humidity unit 60 is a multiple tube
chilled water cooler having chilled water at a
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temperature of approximately about 1-10°C; and preferably
between 4-6°C. As the airflow passes over the tubes,
moisture condenses on the tubes and the temperature of
the air is lowered. The dew point of the air flow is
reduced to approximately about 0-10°C, and preferably
reduced to approximately 5°C. It is preferred that the
humidity unit 60 include a large number of coils to
ensure that the air temperature becomes equilibrated
close to the water circuit temperature, and thus the
water temperature determines the air dew-point.
From the cooling unit, the airflow is directed to a
heater 62 which heats the air to a preferred temperature
for removing moisture from the coating bed 4 for the
particular type of confectionery and coating used. A
second controller unit 63 controls the temperature of
the airflow by controlling the amount of heat added to
the airflow by the heater 62. A temperature sensor 64,
positioned immediately after the heater, and a
temperature sensor 66 positioned within the bed adjacent
the particles provide input to the temperature
controlling unit. The temperature sensors may be
infrared sensors, or any other temperature sensor
familiar to one of ordinary skill in the art. Based on
the temperature at these two locations, the temperature
of the airflow is carefully adjusted so that evaporative
cooling is maximized. Airflow temperatures are
controllable from 5-60°C.
Preferably, the airflow is heated to a temperature
between approximately about 21-50°C, so that the bed
temperature is kept approximately between 20-26°C, and
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preferably at a temperature between 21-25°C, and most
preferably at a steady-state temperature of 22-24°C. The
present invention is capable of heating the airflow at a
rate of approximately about 1-2°C/second. To quickly dry
coated product, the temperature of the bed is maintained
as high as possible without damaging the particles in
order to maximize the difference in humidity between the
airflow and the coating surface to maximize the drying
rate. This temperature, however, is below a temperature
at which the coating or the confectionery itself are
harmed. Once the airflow is heated, it exits the heater
and enters a mixing element 68 which insures that the
airflow is even in temperature.
As one of ordinary skill in the art will appreciate, the
present invention may apply a wide range of temperatures
and dew-points to effectively, heat, cool, and dry
product in the bed.
The airflow is split into two streams after the heater -
one being an exhaust stream 70 and one being a bed
stream 72. Each includes a valve 71 and 73,
respectively, to control the amount of airflow each
stream receives. The exhaust stream 70 is used to
exhaust the airflow (bypass) from the bed once the
coated confectionery have dried, or when coating
material is being applied. The airflow is exhausted by
closing valve 73 on the bed stream 72, and opening the
valve 71 on the exhaust stream 70. The bed stream is
further split into two more streams, 74 and 76, each
directed to one each of the tangential air intakes 17 on
the intake manifold.
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In a preferred embodiment, as the airflow passes through
the screen and into the particles in the bed 4, the
airflow encounters a pressure drop of approximately
about 0.5 inches water column (125 Pa). However, it is
worth noting that the pressure drop through the bed of
particles is dependent upon the confectionery size. The
smaller the confectionery, the higher the pressure drop.
Moreover, pressure drop in the present invention is also
dependent upon bed agitation, with an agitated bed
having approximately about 330 less pressure drop than a
bed of stagnant product.
With the exception of the reduced pressure drop
resulting from bed agitation, the air pressure drop
through the bed of product can be closely modeled with
conventional accepted equations governing air flow
through beds of particles.
A shroud 78 which is part of the dust collection device
(DCD), covers the bed during operation and channels the
airflow blown through the bed into ambient air, via a
filtration element 80. The filtered air may be directed
to the air intake of the system. The shroud includes a
humidity probe 82 which is placed in the exhausted
airflow connected to a controller 83 for controlling the
airflow stream directions and coating systems.
It has been determined that the humidity level of the
air which has been passed through the product
corresponds substantially to that of the equilibrium
relative humidity of the product within the bed. Thus,
when the humidity of the air reaches a predetermined
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value, the coated product is dry. It will be
appreciated by one of ordinary skill in the art that to
obtain the most accurate humidity level of the product,
and thus, determine when a drying cycle is complete,
that substantially all the air which passes through the
product bed is preferably captured by the shroud.
Upon the exhaust airflow reaching a predetermined dew-
point, indicating that the product is dry, the drying
airflow bypasses the bed and another coating layer may
be added, or the confectionery may be removed from the
bed. Depending upon the particular confectionery, the
drying is completed when the air dew point has reached
approximately 10 to 15 C, depending on the particular
shot layer being applied.
A coating system 84 dispenses coating material into the
bed 4 and also monitors and controls the airflow to the
bed. The system includes one or more storage containers
86 which are connected to a pump 88 via a pipeline 92.
The pump 88 draws coating material from the containers
to spray onto the confectionery from above via two
nozzles 90 and 92 positioned on either side of bed 4.
Electrical or mechanical valves 94 control which
containers) material is used for dispensing, with one
or several of the containers being selected at a time
for dispensing material. The flow of the material from
the storage containers is monitored by a metering device
96, which determines the exact amount of material
sprayed onto the edible pieces.
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Any confectionery coating may be applied in the present
invention including liquid and powder materials, sugar
syrups, and flavored fats including cocoa butter and
oils. For the present invention, process speed is not
significantly slowed by lower concentration coating,
i.e., a higher moisture content solution. It has been
determined that for sucrose based solutions, the
preferred concentration is approximately about between
50 and 70 Brix, and more preferably between 60 and 70
Brix. It has been found that the most preferred
concentration is 65 Brix which maximizes drying rates
while avoiding sugar crystallization issues generally
associated with higher solids syrups.
Prior to applying the coating material and shortly
thereafter, however, the airflow is substantially
directed away from the bed by completely diverting the
airflow to the exhaust stream. This is preferred so
that a minimum amount of coating material is entrained
into the airflow and that the coating material applied
to the confectionery is maximized. Bypassing the drying
air flow away from the bed is also advantageous because
it gives time for the liquid to be evenly distributed
around the pieces.
After the coating has been applied, the coating pump is
shut off and the valves to the storage containers are
closed preventing any further coating material from
entering the bed. During coating operations, the bed is
continuously agitated to ensure even and equal
distribution of the coating material over all surfaces
of the product. Any coating particles which do not
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adhere to the product fall through the screen to be
collected at a later time.
It will be appreciated to one of ordinary skill in the
art, that as the airflow in the present invention passes
through the bed, it is of relatively low velocity, so
that coating material is not carried away in the airflow
stream. For a preferred embodiment, this velocity is
approximately between 0.10 - 2 m/s, and more preferred
at 0.25 - 0.5 m/s, and most preferred when the velocity
is approximately 0.35 m/s. This preferred airflow may
vary depending on the product being processed.
By directing the airflow away from the bed during the
application of the coating and shortly thereafter (while
the coating is distributed over the surfaces of the
particles) the system ensures that coating material does
not end up wasted and trapped in the filtering system.
This keeps costs down since the filters of the system
need not be replaced as often, and use of the coating
material is maximized.
The process of applying or varying the coatings may be
repeated as many times as required to build the desired
coat thickness with confectioneries receiving at least
one or more coats.
After the coating material has been distributed to the
surfaces of the particles, the control valves on the
airflow streams are adjusted to direct the majority of
the airflow to the bed to initiate the drying process.
It is preferred that during the drying operation, at
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least approximately 80-100% of the airflow be directed
to the bed, and more preferably 85-100%, and most
preferably 90-95%. The lost air represents undesirable
leakage which occurs in the system.
The airflow, as previously described above, is
preferably tangentially introduced under the bed in a
direction opposite to that of the dominant mixing
direction (see Figure 8) to better interact with the
confectionery. As shown in Figure 9, it is preferred
that the airflow enter the thickest portion of the bed
containing the confectionery to counter the general flow
of the confectionery to maximise the removal of humidity
from the bed. Preferably, a contoured center 15 is
placed in the intake manifold area, to assist in
directly the air flow to the regions of the bed
containing the thickest portion of particles, as well as
encouraging the airflow towards the outer wall by
designs which aid the centrifugal effect. The direction
of the airflow around (A) and through the bed (B) is
shown in Figures 8 and 9, respectively. One skilled in
the art will appreciate that for processing small pieces
it may be desirable to induce the air in the same
direction as the dominant mixing direction in order to
assist the motion around the bed and aid subsequent
product discharge from the pan at the end of the cycle.
For ellipsoid shaped coated product, the present
invention produces a dried coating thickness
substantially equal at the circumference of the major
axis to that at the apogee of the minor axis.
Specifically, as shown in Figure 12, it is preferred
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that the ratio of the thickness between the major axis
87 and minor axis 89 of a coating shell 91 applied after
a first coat 93 on a particle center 95 is approximately
between 0.9:1 - 1.1:1, and most preferably about 1:1.
Once the confectionery have been coated and completely
dried, the airflow is either shut down or directed away
from the agitation bed so that another coating may be
applied, or so that finished confectionery may leave the
bed. To remove the confectionery from the bed, a novel
discharge mechanism 98 having a discharge chute 100 has
been designed for the present invention and is described
as follows. Along the outer wall 8 of the bed, an
opening 101 is provided large enough to quickly remove a
stream of the confectionery from the dominant flow
direction in a short period of time. During coating and
drying operations, the outlet is covered by a tangential
cover 102 positioned along the inner surface 7 of the
bed wall 8. One end 104 of the tangential cover is
affixed to the inner surface 7 on one side of the
outlet, while the other end 106 of the tangential cover
may be moved. The movable end 106 is attached to a
solenoid 108 which, upon activation, moves the movable
end 106 from the inner surface 7 of the bed wall 8,
towards the center of the bed. This is shown in Figure
10 of the present invention.
The distance created between the tangential cover 102
and the inner surface 7 of the outer wall 8 creates a
funnel portion 110 having an inlet 112 for accepting
confectionery particles moving in the dominant flow
direction. In Figure 10, this is shown as the clockwise
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direction. The newly created funnel portion 110 quickly
allows the confectionery to be removed from the
agitation bed 4~ without the need to stop the agitation
mechanism, and without the need for worker intervention.
The discharge mechanism 98 may also be used as an
entrance for placing yet to be coated confectionery into
the bed. By reversing the dominant flow direction
(reversing the rotation of the weight assemblies), a
predetermined amount of confectionery may be added into
the bed via the outlet. As the confectionery enter the
bed, the pieces rotate in a direction opposite to the
funnel direction (opposite the dominant flow direction)
so that confectionery may be led away from the opening
and into the bed. Once the predetermined amount of
confectionery is received, the tangential cover is
returned to the position adjacent the outer wall. At
that time, the rotation of the weight assemblies is
reversed to allow the confectionery to flow in the
dominant flow direction once again for coating and
drying.
The above stated process for heating, cooling, coating,
and/or drying particles of confectionery is best
illustrated and summarised with the following examples.
The apparatus used for all examples includes the
following: Bed Diameter: 76 cm. Sweco, Inc., Florence,
KY 41022-1509, Model LS30 agitator driven by a ~ HP,
1150 RPM (19.2 Hz rotation frequency) motor @ 60 Hz
electrical supply frequency. Additional weight equal to
approximately 50o more than the maximum standard weight
setting was added to the bottom weight assembly in order
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td achieve the desired vertical mixing motion of the
bed.
Example 1
Product: M&M Plain Chocolate candies.
30kg of uncoated product were placed in the coating bed.
The density of the individual pieces were 1.28
grams/cubic centimeter. The uncoated M&M chocolate
centers were ellipsoidal in shape with dimensions 13 +/-
0.5 mm diameter and 6.2 +/- 0.5 mm in thickness. The
coating was applied to the particles using upwards of 50
individual syrup shots in the following process.
Particles were equilibrated to a start temperature of
approximately 23°C by passing controlled temperature and
humidity air up through the agitated particles.
When the product temperature set point was achieved, the
majority of the air was then diverted from the bed. A
small percentage of the air volume approximately 5~ is
allowed to continue to pass through the bed in order to
maintain instrumentation function, and maintain control
of certain variables, e.g., the temperature and humidity
of the airflow.
A sugar syrup shot of volume approximately 200 grams was
added to the candy over a time of approximately 20
seconds.
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The candy was mixed an additional 20 seconds
(approximately) to evenly distribute the syrup over all
the candy pieces prior to introducing the drying
airflow.
The drying air was then introduced into the product.
The temperature of the drying air was modulated to
maintain the bed at a preferred temperature of
approximately 23°C. When air was first introduced into
the bed, the air temperature was increased to nearly
60°C, in order to maintain the bed temperature of the set
point of 23°C. This was the result of the cooling effect
of the rapidly evaporating moisture. The temperature of
the air flow into the bed decreased to near 23°C during
the later part of the drying due to the much lower rate
of moisture evaporation (i.e., lower evaporative cooling
effect). When the particles were almost completely
dried.
When the dew point of the air emerging from the bed of
product reached the set point for that particular
application of syrup, e.g., between approximately 10-
15°C, the process was repeated by returning to step 2
until the required number of syrup shots was applied.
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Example 2
Product: Cocoa butter fat coated M&M Mini Plain
Chocolate candies. Approximately five percent cocoa
butter was applied using about 10 individual
applications of cocoa butter with the following process.
20 kg of pieces were equilibrated to the desired start
temperature of 18°C by passing controlled temperature and
4°C dew-point air up through the agitated pieces. The
vibration settings were substantially similar to that
for the sugar shell process previously described. The
air volumes were also substantially similar to that for
sugar coating.
When the product temperature set point was achieved, the
majority of the air was diverted from the bed.
A cocoa butter shot having a temperature of about 40°C
and a mass of approximately 100 grams was added to the
candy over a time of approximately 20 seconds.
The candy was mixed approximately 20 seconds after the
end of the cocoa butter shot to evenly distribute the
cocoa butter over all the candy pieces.
Cooling air was introduced into the product.
The temperature of the cooling air was modulated to
maintain the bed at the preferred temperature of about
18°C. When air was first introduced into the bed, the
air temperature approaches 6°C in order to keep the bed
from heating above the set point of 18°C due to the
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heating effect of the rapidly crystallizing cocoa
butter. The air temperature was increased to near 18°C
during the later part of the cooling due to the much
lower rate of fat crystallization heat evolution.
When the temperature of the air emerging from the bed of
product reached the set point for that particular shot,
and/or the set amount of crystallization time was
achieved, the process was repeated by returning to step
2 until the required number of shots were applied.
Example 3
Product: Skittles bite size candies
An edible adhesive was firstly applied followed by the
addition of an edible powder which adheres to the
adhesive. The formulation of the components was such
that no air addition was needed to heat, cool or dry the
product.
20 kg of pieces were added to the vibrating bed. The
vibration settings were very similar to that for the
sugar shell coating process previously described in
Example 1.
100 grams of glue material at a temperature of
approximately 50°C was added to the Skittles over a time
period lasting approximately 60 seconds. The
formulation of the edible glue was approximately ~ 250
edible dextrin starches, ~ 38% sucrose, and 37% water.
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The candy was mixed another 60 seconds to evenly
distribute the glue over all the candy pieces.
Approximately 1 kg of a substantially equal mixture of
180 micron granular sucrose and 300 micron citric acid
was added to the candy over a time period lasting about
90 seconds.
The candy was immediately discharged from the bed,
requiring approximately 60 seconds to empty the pan.
It will be appreciated by one of ordinary skill in the
art, that the above described processes, apparatuses,
and examples could be applied to: (i) using a chocolate
coating or other matrix to coat particles including
adhesives and powder and edible and non-edible coatings;
and (ii) heating, cooling, drying, coating or any
combination thereof, any material, edible and non-
edible.
Other variations and modifications of this invention
will be apparent to those skilled in this art after
careful study of this application. This invention is
not to be limited except as set forth in the following
claims.
