Patent Application
20080265056
This invention relates to an ultrasonic spray apparatus used to apply a fluid to a substrate.
A wide variety of operations, especially food processing, involve the application of a fluid coating material. Conventionally, the fluid coating solution or slurry is applied to the food substrate with conventional spray nozzles that dispense the slurry in a spray pattern using only the hydrostatic pressure of the slurry supply to form the spray. While useful and effective, the ease of conventional hydrostatic slurry restrictive orifice discharge nozzles has numerous disadvantages.
One disadvantage involves the difficulty of applying low flow rates, especially below 500 ml/min. The conventional hydrostatic pressurized nozzle is known to have difficulty maintaining a good spray pattern at an accurate flow rate. These low flow rates are often required for fluid additives to the food substrate, especially when applying expensive or highly functional materials.
Another disadvantage involves the difficulty of spraying slurry of large particle sizes. This is because the orifice size for the conventional hydrostatic pressurized nozzle is typically below 500 μm in diameter. Nozzle clogging is known to be one of the major drawbacks of slurry applications.
Yet another disadvantage involves the gradual build-up of the slurry upon the interior of the nozzle. After this build-up, the nozzle must be thoroughly cleaned. Depending upon a variety of factors, the cleaning operation must be conducted at least once per day and perhaps as frequently as once per operating shift. Cleaning the nozzle is thus a standard element of operating hygiene that usually takes up to an hour to perform. Thus, slurry build-up requires the direct cost of maintenance servicing. More importantly, since most processing lines are generally continuous, slurry build-up can cause more significant cost of downtime of the entire processing line.
Still another problem resides in the momentum of spray from the conventional hydrostatic pressurized nozzle, which can reach a speed over fifty meters per second. Such a momentum of the spray, if closely coupled with the food product, can be destructive to the shape and texture of the product. It may also disorientate the packing arrangement of the product on the process line. These limitations place restrictions on the potential location of the nozzle relative to the product stream.
Still another problem resides in the large amount of expensive ingredients lost due to overspray. The conventional nozzle is known to have large droplet size distribution which makes it difficult to contain the spray in a small targeted area. The large droplet size distribution means a significant amount of extremely fine droplets may be generated. These fines droplets do not have sufficient mass and are often lost to the surrounding environment. Further, these fines droplets can pose potential health risks due to inhalation.
Surprisingly, use of an ultrasonic apparatus provides dramatic improvements in the fluid coating of food substrates.
The present invention is an apparatus which ejects fluid from a surface. The apparatus comprises a.) a power supply operating at a frequency; b.) a transducer, which upon being applied the power is made to vibrate with a first amplitude; c.) a vibrating nozzle, comprising the surface, which is acoustically coupled to the transducer, to transmit the transducer vibration to the surface with a second amplitude; and, d.) a control unit to control the power supply applied to the transducer. The fluid is delivered to the surface of the nozzle. During this time the control unit cycles the power applied to the transducer at the frequency between a low power level and a high power level. Meanwhile, the fluid is ejected from the surface when the high power level (i.e., first power level) is applied to the transducer but not when the low power level (i.e., second power level) is applied to the transducer.
The transducer and the vibrating nozzle can be one unit. The cycling of the power supplied to the transducer follows a function which can be a sinusoidal function, a step function, and a linear function, or a combination thereof. In one alternative embodiment when the fluid is ejected upon a substrate the substrate can move relative to the apparatus; and the cycling of the power applied to the transducer from a low power level to a high power level is linked to a time event related to when the moving substrate will be in position to receive the fluid. The high power level is sustained for a predetermined length of time, after which the control unit will adjust the power supply applied to the transducer back to the low power level. The moving substrate can be edible. The vibrating nozzle can be acoustically coupled to the transducer directly or indirectly. The first amplitude and second amplitude can be different. The second amplitude can be greater than 10 microns. The fluid can have a critical power level requirement associated with the apparatus above which the fluid can be ejected from the surface and the low power level is below the critical power level, and the high power level is above the critical power level.
The magnitude of the second amplitude at the high power level is greater than about 5% compared to a magnitude of second amplitude at the lower power level. The fluid can have a viscosity of from about 1 to about 500 cps. The fluid can have a solids content of from about 0 to about 70%. The fluid can comprise a flavorant. The power supply can operate at a frequency of from about 10 to about 500 kHz. In one alternative embodiment, the power supply can operate at a frequency of from about 15 to about 120 kHz. In another alternative embodiment, the power supply can operate at a frequency of from about 18 to about 50 kHz. The cycling from a low power level to a high power level can be produced at a rate of at least 60 times per minute.
In another alternative embodiment, the apparatus has a.) a power supply operating at a frequency; b.) a transducer, which upon being applied the power is made to vibrate with a first amplitude; c.) a vibrating nozzle, comprising the surface, which is acoustically coupled to the transducer, to transmit the transducer vibration to the surface with a second amplitude; d.) a dampening unit; and e.) a control unit to adjust the activity of the dampening unit. The fluid is delivered to the surface. The control unit cycles the level of activation of the dampening unit between a first condition and a second condition. The fluid is ejected from the surface when the level of activation of the dampening unit is adjusted to the first condition and not when the level of activation is adjusted to the second condition. The level of activation of the first condition can create a resonant wave in the vibrating nozzle. The level of activation of the first condition can correspond to the dampening unit being inactive. The level of activation of the first condition can correspond to the dampening unit being active.
While the specification concludes with claims particularly pointing out and distinctly claiming the invention, it is believed that the invention will be better understood from the following description of the accompanying figures in which like reference numerals identify like elements, and wherein:
The figures herein are not necessarily drawn to scale.
Section I. will provide terms which will assist the reader in best understanding the features of the invention, but not to introduce limitations in the terms inconsistent with the context in which they are used in this specification. These definitions are not intended to be limiting. Section II. will discuss the present invention.
As used herein, “amplitude” is referred to as the vibration displacement of the nozzle tip. The displacement is measured from peak-to-peak.
As used herein, “edible substrate” or “substrate” includes any material suitable for consumption that is capable of having a fluid disposed thereon. Any suitable edible substrate can be used with the invention herein. Examples of suitable edible substrates can include, but are not limited to, snack chips (e.g., sliced potato chips), fabricated snacks (e.g., fabricated chips such as tortilla chips, potato chips, potato crisps), extruded snacks, cookies, cakes, chewing gum, candy, bread, fruit, dried fruit, beef jerky, crackers, pasta, hot dogs, sliced meats, cheese, pancakes, waffles, dried fruit film, breakfast cereals, toaster pastries, ice cream cones, ice cream, gelatin, ice cream sandwiches, ice pops, yogurt, desserts, cheese cake, pies, cup cakes, English muffins, pizza, pies, meat patties, and fish sticks.
The edible substrate can be in any suitable form. For example, the substrate can be a finished food product ready for consumption, a food product that requires further preparation before consumption (e.g., snack chip dough, dried pasta), or combinations thereof. Furthermore, the substrate can be rigid (e.g., fabricated snack chip) or non-rigid (e.g., gelatin, yogurt).
In addition, the edible substrate can include pet foods such as, but not limited to, dog biscuits and dog treats.
In a preferred embodiment, the substrate is a fried fabricated snack chip. The fluid can be disposed upon the snack chip by any suitable means. For instance, the fluid can be disposed on the chip dough before the dough is fried to make the fried fabricated snack chip, or the fluid can be disposed on the chip after it has been fried.
In one embodiment, the fabricated snack chip is a fabricated potato crisp, such as that described by Lodge in U.S. Pat. No. 5,464,643, and Villagran et al. in U.S. Pat. No. 6,066,353 and U.S. Pat. No. 5,464,642.
As used herein, the term “coating” refers to a thin film.
As used herein, the term “critical power” refers to the minimum power level sufficient to eject the liquid from the nozzle.
As used herein, the term “fluid” refers to a homogeneous liquid; slurry and flowable paste; and powder.
As used herein, the term “piezoelectric effect” is the ability of crystals and certain ceramic materials to generate a voltage in response to applied mechanical stress. The piezoelectric effect is reversible in that piezoelectric crystals, when subjected to an externally applied voltage, can change shape by a small amount. The effect finds useful applications such as the production and detection of sound. As used herein, the term “piezoelectric transducer” refers to the actuators and sensors built with the piezoelectric materials.
As used herein, the term “magnetostriction” is a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field. Magnetostrictive materials can convert magnetic energy into kinetic energy, or the reverse. The actuators sensors built with the magnetostrictive materials are magnetostrictive transducers. As used herein, the term “magnetostrictive transducer” refers to the actuators and sensors built with the magnetostrictive materials.
As used herein, the term “registered pulse” refers to modulating the power level of the converter to pulse the spray coming out of the vibrating nozzle to coincide with an event in time.
As used herein, the term “solids” refers to particles that are not in dissolved in the fluid.
As used herein, the term “viscosity modifiers” refers to materials that change the viscosity of the fluid or enhance the ability of the fluid to suspend other materials.
As used herein, the term “structurants” refers to materials that change the viscosity of the fluid or enhance the ability of the fluid to suspend other materials by imparting a shear thinning viscosity.
The ultrasonic apparatus of the present invention offers multiple benefits based on the accurate delivery of materials (e.g., salt, seasoning, flavors, vitamins, nutrients, or other particulates) to substrates such as chips, including the ability to accurately control the flavor intensity and/or flavor type from one substrate to the next in an arrangement of these substrates. Furthermore, the ultrasonic apparatus provides accurate delivery of a given amount and accurate targeting of a substrate such that only a precise area of the substrate receives the additive materials. This can be helpful in the application of salt, where, for example, a more precise application can enable lower sodium level declarations in an ingredient label. In addition, the ultrasonic apparatus provides the additional advantages of cost reduction by avoidance of application of expensive additive materials outside of the substrate that would otherwise be lost, having, in turn, the added advantage of minimizing or eliminating the need to create a recycle stream of the material being applied.
Moreover, the ultrasonic apparatus of the present invention offers multiple process benefits such as
Referring to
As shown in
Second, the control 31 is set to have
As shown in
The optical sensor 27 senses the substrate 1 (not shown) and signals to the control 31. The control 31 is programmed to determine the pulse amplitude, pulse width, and delay time. The liquid 19 is fed into the ultrasonic nozzle 14 whereby the liquid is atomized by the ultrasonic process.
In one embodiment, a plurality of vibrating nozzles 14 may be used to spray a baked snack product with an atomized mist while it is being conveyed on a continuous belt in a hooded, cooling conveyor.
In another embodiment, the fluid 19 may be applied via a set of vibrating nozzles 14 located in series and/or in parallel. Vibrating nozzles 14 in series deliver the capability to add variety of coating benefits in the direction of the machine or the capability to deliver increased levels of the fluid 19. Vibrating nozzles 14 in parallel allow for multiple lanes of product coating, or for potentially even coating of an entire substrate, like for example, coating of the dough sheet with a coating to modify how the behavior of the dough sheet upon cooking, to modify texture, fat absorption, or to flavor the product.
In another embodiment, the spray may be applied in a continuous mode where the high and low voltage settings in the control are set to be the same value.
Referring to
Below will detail each component of the ultrasonic apparatus 10.
i. Power Supply
Referring to
The power supplied to the ultrasonic apparatus 10 may be varied during the process of the present invention.
For ultrasonic atomization, power levels are generally under 15 watts. Power is controlled by adjusting the output level on the power supply 12.
The exact magnitude of power required depends on several factors. These include nozzle type; operating frequency; fluid characteristics (e.g., viscosity, solids content); and flow rate.
Nozzle Type and Operating Frequency
Each nozzle type, because of its specific geometry and other factors, will generally have a different critical power level for the same fluid. For example, the critical power level of a 48 kHz nozzle, designed with a conical atomizing surface to deliver a wide spray pattern at substantial flow rates, will generally be in the neighborhood of from about 3.5 to about 4 watts of input power when atomizing water. Another nozzle, operating at the same frequency, but designed for microflow operation (a very small atomizing surface), may require only about 2 watts to atomize water.
The type of fluid being atomized strongly influences the minimum power level. More viscous fluids or fluids with high solids content generally increase the minimum power requirement. For example, the 48 kHz nozzle with a conical atomizing surface mentioned in the last paragraph, might require at least 8 watts of input power if the fluid being atomized were a 20% solids-content, isopropanol based material.
Fluid Characteristics
Section iv. titled Fluid (see below) provides further information on fluids which are good candidates for ultrasonic atomization.
Flow Rate
The flow rate also plays a role in determining minimum power level. For a given nozzle, the higher the flow rate, the higher will be the power required, since the nozzle is working harder at higher flow rates. The vibrating nozzle 14 can cover a wide range of flow rates, from a few microliters/min to as much as over about 350 ml/min. As a result of our observations, the maximum flow velocity that still allows for proper atomization or critical flow velocity is on the order of from about 30 cm/sec. As an example, for a vibrating nozzle 14 with an orifice diameter of 2.5 mm this translates into a maximum flow rate of from about 88 ml/min, assuming continuous spray. The flow rate range of a specific nozzle is governed by the following factors: power supply, operating frequency, orifice size, atomizing surface area, and fluid characteristics.
Referring to
In theory, there is no lower flow rate limit for any orifice 37 size since the process is independent of pressure. However, in practical terms, lower limits do exist. As the flow is reduced, a point is reached where the velocity becomes so low that the fluid emerges onto the atomizing surface in a non-uniform circumferential manner, causing the atomization pattern to become distorted. In some applications, where stable spray patterns are unimportant (e.g., some chemical reaction chambers), this distortion may be tolerable. In other applications, where the integrity of the pattern is vital (e.g., surface coatings), the low-velocity stream distortions are unacceptable. As a practical matter in such cases, the minimum velocity of the stream from an orifice 37 of a given size is about 20% that of the maximum velocity. For our example above, where the maximum flow rate is 88 ml/min, the minimum flow rate is approximately 18 ml/min.
The amount of atomizing surface area available is the final factor influencing the maximum flow rate available from a given nozzle. An atomizing surface of a given size obviously has a limitation as to how much fluid it can support and still create the film that is required to create capillary waves. If the quantity “dumped” onto the surface becomes too great, it overwhelms the capability of the surface to sustain the fluid film.
The last factor, fluid characteristics, has been covered in the section under Fluids. The more difficult a fluid is to atomize, the lower will be its maximum flow rate for a given nozzle.
Maximum sustainable flow rate not only depends on the surface area of the tip of the nozzle but also on the vibrating nozzle's 14 operating frequency. Lower frequency nozzles can support greater flow rates than higher frequency nozzles having the same atomizing surface area.
In summary, there are a number of factors that can determine maximum flow rate for a given nozzle. However, in every instance, only one of these factors will set the limit. If we are dealing with a hard-to-atomize material, for example, it is likely that the maximum flow rate will not depend on orifice 37 size nor available surface area, but solely upon the atomizability of the fluid. Similarly, if we have a vibrating nozzle 14 with an orifice 37 whose capacity exceeds that of the available atomizing surface area, the surface area becomes the limiting factor. This interplay among the limiting factors is important in specifying a vibrating nozzle 14 for a given application.
ii. Converter
Referring to
iii. Vibrating Nozzle
Referring now to
Disc-shaped ceramic piezoelectric converters 13 convert electrical energy into mechanical energy. The converters 13 receive electrical input in the form of a high frequency signal from a power supply 12 and convert that into vibratory motion at the same frequency.
Vibrating nozzles 14 are configured such that excitation of the piezoelectric crystals (not shown) creates a transverse standing wave along the length of the vibrating nozzle 14. The ultrasonic energy originating from the crystals (not shown) located in the large diameter of the vibrating nozzle 14 undergoes a step transition and amplification as the standing wave as it traverses the length of the vibrating nozzle 14.
Referring to
Referring to
In coating applications, the unpressurized, low-velocity spray significantly reduces the amount of overspray since the drops tend to settle on the substrate 11, rather than bouncing off it. This translates into substantial material savings and reduction in emissions into the environment. In addition, the spray can be controlled and shaped precisely by entraining the slow-moving spray in an ancillary air stream.
Spray patterns from as small as about 2 mm wide to as much as 30-60 cm wide can be generated. Referring to
The vibrating nozzle 14 can be fabricated from titanium because of its good acoustical properties, high tensile strength, and excellent corrosion resistance.
Specifically, in the preferred embodiment, the vibrating nozzle 14 can be of any shape. In one embodiment, the vibrating nozzle is cylindrical.
The vibrating nozzle of this invention can be made of any material known by one of ordinary skill in the art capable of holding compositions in place for an indefinite period of time. While soft or nonrigid materials can be used; materials rigid enough to sit in a substantially upright position are preferred. Such materials include, but are not limited to, metals such as aluminum, stainless steel, and titanium; diamonds; and combinations thereof.
iv. Fluid
Referring to
Snack food-flavoring fluid of any suitable viscosity which is capable of dispersion into fine droplets can be used with the present invention. As nonlimiting examples, fluid 19 having viscosities at 110 degree F. of from about 1 centipoise to over 560 centipoise have been used with this invention.
The desired flow rate of the fluid 19 for a single vibrating nozzle 14 may vary depending upon the concentration of flavoring ingredients in the fluid, the throughput of the product being flavored, the desired flavor intensity of the final product, and the like. As non-limiting examples, for a single vibrating nozzle 14 flow rates of up to 300 ml/min have been used with this invention.
The physical nature of a fluid 19 plays a central role in the ultimate success of any atomization process. Factors such as viscosity, solids content, miscibility of components, and the specific rheological behavior of a fluid affect the outcome.
The present invention can be used with a fluid containing a carrier or mixture of carriers (e.g., oil, propylene glycol, and water) and functional compounds comprising flavors, sugar, spices, and mouthfeel agents (e.g., lecithin, glycerin) as well as a fluid modifier (e.g., maltodextrin, carboxylmethyl cellulose) to the desired taste purpose and processability. The fluid characteristic is defined as a free flowable liquid, or slurry or paste with viscosity range of from about 1 to about 500 cps, solid content less than about 45% and particle size smaller than about 185 um, more preferably to less than about 100 um, most preferably to smaller than about 50 um.
v. Process Mode
Referring to
a. Pulsed Spray
Pulsed ultrasonic atomization can be achieved by operating the ultrasonic power on and off at a low repetition rate, e.g., one pulse every few seconds. In order to deliver a coating to each substrate in a sequence of fast moving substrates, and not the gap in between substrates, the spray needs to be pulsed, and the pulse needs to be accurately controlled with a start timing and a duration.
Referring to
Another embodiment to achieve pulsed spray is to pulse the fluid by for example using a pump which moves the fluid in a pulsed motion. The rate of the pulse may be adjusted by pump RPM.
In yet another embodiment, pressurized air can be injected into the fluid pipe intermittently, which segments the fluid periodically with a small volume of air pockets. The pulsed spray is then achieved by the discontinuity created by the air pockets.
In yet another embodiment, a mechanical deflection can be employed to periodically deflect/catch/recycle the stream to avoid deposition of the material in unwanted regions.
b. Registered Spray
The combination of pulsed ultrasonic spray with choice of control logic can provide new processing flexibility that enables new product offerings. In one non-limiting example, two vibrating nozzles 14 are on the same row, each dispensing a different seasoning, e.g., the following are some of the possible product variations where x represents a chip and y represents a chip.
The combination could be expanded to include registering a flavor to a visual effect of choice, such as color, image and text information. One of the immediate possibilities is to integrate the registered pulsed spray with digital printing technology, enabling the connection of printed information with a registered flavor. The digital printing technology is disclosed in currently pending, commonly assigned, U.S. patent application Ser. No. 10/887,032, filed Jul. 8, 2004, entitled “Image Variety on Edible Substrates” to LuFang Wen, et al.; U.S. patent application Ser. No. 11/201,552, filed Aug. 11, 2005, entitled “Ink Jetting Inks for Food Application” to LuFang Wen, et al.; U.S. patent application Ser. No. 11/410,676, filed Apr. 25, 2006, entitled “Ink Jet Printing of Snacks with High Reliability and Image Quality” to Dechert, et al.; and U.S. patent application Ser. No. 11/398,294, filed Apr. 5, 2006, entitled “Image Registration on Edible Substrates” to Jeffrey W. Martin.
vi. Atomization Process
Referring to
Any suitable fluid flow rate sufficient to reduce the fluid 19 to fine droplets which rain downward in a substrate 11 in a tumbling drum 23 (
In general, the drops produced by ultrasonic atomization have a relatively narrow size distribution. Median drop sizes range from about 18 to about 68 microns, depending on the operating frequency of the specific type of vibrating nozzle 14. As an example, for a vibrating nozzle 14 at 20 kHz with a median drop size diameter of approximately 40 microns, 99.9% of the drops can fall in from about 5 to about 200 micron diameter range.
vii. Materials
While a variety of materials and equipment are known and acceptable for these purposes, a power supply and transducer are available from Sonics and Materials, VibroCell 750.
Referring to
In another alternative embodiment, an amplitude booster could be used to achieve the required amplitude. The amplitude booster can be inserted between the converter 13 and the vibrating nozzle 14. In a non-limiting example, the converter 13 can have a maximum amplitude of 20 μm. To achieve the 180 μm amplitude required, three different designs for converters 13 were used to increase the amplitude from about 20 μm to about 180 μm. In another non-limiting example, the converter 13 serves both as the atomizer and as the amplitude booster to increase the amplitude from about −20 μm to about 180 μm.
Referring to
As is known in the art, snack food to be seasoned or flavored is fed into an upper end of the drum 23 and as the tumbling drum 23 rotates, the snack food tumbles and moves by gravity down to the lower end where it exits the drum over the lip 42. This is as well known and conventionally practiced in the art.
In accordance with the present invention, the fluid 19 can be connected to a pipe 41 which extends into the drum a predetermined distance. The pipe 41 has positioned along its length a plurality of connectors 43 (all T-connectors except the end L-connector) for connecting a plurality of vibrating nozzles 14. Each nozzle tube 14 has an exit opening 36.
The following are a listing of examples illustrating various embodiments of the present invention. It would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention.
With this setting, the liquid slurry is atomized in a pulsed mode, and into a corn shaped spray pattern, containing fine droplets.
With this setting, the liquid slurry is ejected in a pulsed mode but contained in a single large droplet.
With this setting, the liquid slurry is atomized into a corn shape with fine droplets and is a continuous mode.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
All documents cited in the Detailed Description of the Invention are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to the term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
This application claims priority to and the benefit of U.S. Provisional application 60/926,892, filed on Apr. 30, 2007, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60926892 | Apr 2007 | US |
