1. 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.
2. Related Background
Many edible items (xe2x80x9cpiecesxe2x80x9d) 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 item. Candy shells also give an identified xe2x80x9ccrunchxe2x80x9d when eaten.
Many devices are known for applying a coating to edible pieces. For example, U.S. Pat. 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. Pat. 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. Pat. 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.
Still other prior art devices fluidize objects for coating. For example, in U.S. Pat. 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.
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.
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 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 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 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 4-12xc2x0 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.
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.