CONTAINING SUSPENDED SOLIDS

RELATED APPLICATION

[0001] This application claims priority to US Provisional Application serial number 61/372,716, filed August 11, 2010, entitled TARGETED SPRAYING OF VISCOUS SOLUTION CONTAINING SUSPENDED SOLIDS, which is hereby incorporated by reference in its entirety for all that it teaches.

BACKGROUND OF THE INVENTION

[0002] Certain food products are still prepared by hand today, and for these products, the application of various required coatings, while time-consuming, can generally be executed in a satisfactory manner. For example, applications of oil coatings, egg coatings, and so on, whether suspended mixtures or otherwise, are easily accomplished by hand in small batches. However, for certain volume operations, hand coatings are simply not practical. For example, it would be prohibitively expensive and time-consuming to use a hand-coating process in a plant that must produce hundreds of thousands of product pieces each day.

[0003] For these operations, any required coating must be applied automatically.

However, it is difficult to apply a unifonn concentration of a suspended solid over the course of many applications, due to settling of the suspension, changes in concentration due to reclamation processes, and application difficulties. For example, some producers use a spinning disc system to apply such coatings, wherein the suspended solution is directed at a sequence of spinning discs which then centrifugally disperse the material. Part of the dispersed spray impacts the product of interest, forming a coating. A good portion of the spray, however, does not hit the product, and is either wasted or collected and reused. If the overspray is wasted, the cost of materials for using the system will be higher, whereas if the overspray is recycled, this may change the concentration of the suspension, leading to nonuniform product quality.

BRIEF SUMMARY OF THE INVENTION

[0004] The invention provides a method for detecting the product to be sprayed, monitoring the flow and spraying a viscous solution with suspended solids onto the product in a targeted manner. Used in conjunction with a system to heat the solution, the system includes a means to detect the product on a flat conveyor, e.g., a level change detector or a color change detector. In one embodiment of the invention, the product is relatively thin, such as a tortilla, and the system uses a special detector to determine when the product is in the spray zone. In an embodiment, flow may be monitored, even when the spray nozzle is being pulsed on-off, i.e., during pulse width modulation or single shot application, to control flow as the line speed varies. The spray nozzle is configured to eliminate the suspended solids from settling out as the solution flows through (recirculated) the nozzle. The nozzle is heated to provide viscosity control to provide uniform spray of the solution. The fluid supply system includes recirculation and other features to maintain the material in suspension.

[0005] Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0006] FIG. 1 is a schematic view of a system as described herein for spraying a product with a material suspended in solution, e.g., salt suspended in oil;

[0007] FIG. 2 is a cross-sectional side view of a valve used in application of the suspended solution in keeping with the described principles;

[0008] FIG. 3 is a cross-sectional side view of a more preferred valve used in application of the suspended solution in keeping with the described principles;

[0009] FIG. 4 is a cross-sectional side view and exterior view of a valve nozzle used in an implementation of the described principles; and

[0010] FIG. 5 is a collection of cross-sectional views of a valve nozzle used in an implementation of the described principles.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Before discussing the details of the invention and the environment wherein the invention may be used, a brief overview is given to guide the reader. In general terms, not intended to limit the claims, the invention is directed to a system and method for

automatically spraying a food product with a suspended material without overspray and/or reclamation and without significant variation in coating properties for different product instances. The system works by detecting the product to be sprayed, monitoring a fluid flow and spraying a viscous solution with suspended solids onto the product in a targeted manner. The system includes a sensor to detect the product on a flat conveyor to determine when the product is in the spray zone. In an embodiment of the invention, the spray nozzle is configured to prevent the suspended solids from settling out of solution as the solution flows through the nozzle. The nozzle may be heated to provide viscosity control to provide uniform spray of the solution.

[0012] FIG, 1 is a schematic view of a system for spraying a product with a material suspended in solution, e.g., salt suspended in oil. The system 100 includes a heated system and liquid supply 101. The heated system and liquid supply 101 includes a controller for taking prescribed actions as well as the means, e.g., pumps, heaters, and conduits, for executing the necessary actions. Before further describing the operation of the heated system and liquid supply 101 , the other components of the overall system 100 will be described top lend context,

[0013] As illustrated, the exemplary system 100 further includes a flow meter 102, one or more spray nozzles 103, and a product sensor 104. Each of the one or more spray nozzles 103 and product sensor 104 may positioned and supported by an appropriate support bracket 105, 106 respectively. The system 100 further includes a conveyor 107 for conveying food items 108 through a target zone 108 within which the spray from the spray nozzle impinges.

[0014] The one or more nozzles 103 receive a fluid supply input 109 as well as a control input 1 10 from the heated system and liquid supply 101. The fluid supply input 109 provides heated fluid to the head which is recirculated back to the heated system and liquid supply 101 via recirculation output 1 1 1. The incoming fluid flow is measured by the flow meter 102, which provides a flow rate output back to the heated system and liquid supply 101.

[0015] The control input 1 10 from the heated system and liquid supply 101 to the one or more nozzles 103 is adapted to control the flow there from, e.g., via a pulse width modulated (PWM) signal configuration. Thus, for example, if the flow rate output indicates a lower than desirable flow to the one or more nozzles 103, the heated system and liquid supply 101 may increase the flow by increasing the duty cycle or on-time of the control input 110 to each nozzle 103.

[0016] In an example embodiment, the system provides an application of 1.5g+/-5% per product of the suspended material at conveyor speeds of 100-150ft/min. In this embodiment, the suspended material is salt and the suspending fluid is food grade oil, resulting in, e.g., a 10-15% % salt concentration. Though only a single line of product is shown in the side view of FIG. 1 , the system may treat multiple lines of product in parallel at a single time in an embodiment of the invention. [0017] The system may be implemented with a wide range of product sizes, but in one implementation, the product is a tortilla with dimensions of 5.5" diameter uncooked dough. As noted above, heating may be used to ensure proper flow. In an embodiment, the fluid is maintained at a temperature of 125F +/- 5F in the heated system and liquid supply 101. Thus, the operation of the heated system and liquid supply 101 contributes to the proper operation of the overall system.

[0018] The one or more nozzles are also adapted for the illustrated operation. In an embodiment of the invention, each nozzle is a heated SPRAYING SYSTEMS PULSAJET® nozzle using high speed operation to spray moving targets. In an implementation, solenoid actuation is used for the nozzle valve (the solenoid being activated via the control input 110 from the heated system and liquid supply 101). In an embodiment of the invention, the spray nozzle is designed with the valve mechanism and orifice directly in the recirculation flow path to eliminate stagnant areas where fluid velocity is reduced allowing suspended solids to drop out. This design provides the benefit that any solids which do fall from suspension will immediately be flushed away from the seal face when the valve is opened.

[0019] In an embodiment, the solenoid coil is placed vertically above the valve to prevent solids suspended in the liquid from collecting in the coil area, since they will naturally drop back into the re-circulating fluid flow. An extended length valve pin with guide bushing maintains alignment to prevent jamming and ensures a positive seal.

[0020] FIG. 2 shown an embodiment of the invention embodiment of the invention wherein the orifice of the nozzle 200 is located directly in the recirculation flow path. In particular, the illustrated nozzle 200 includes a pin 201 covering an orifice 202. The pin 201 passes across a tubular flow path 203 to cover the orifice 202. The pressurized liquid supplied to the one or more nozzles continues to circulate in the flow path under pressure, and escapes the orifice 202 whenever the pin 201 is drawn back via a solenoid (not shown). The viscous media with solids (e.g., olive oil with 13.5% salt) circulates through the nozzle to maintain solids in suspension.

[0021] In an embodiment of the invention, an offset valve pin is used to allow a higher flow through the valve body. Moreover, removal of the valve pin from the main fluid stream reduces the moment on the moving pin to allow faster actuation, reduced wear and eliminate potential binding.

[0022] Such an arrangement 300 is shown in FIG. 3. In the illustrated embodiment of the invention, the offset valve pin chamber 301 creates turbulence when the valve pin 302 is opened, thus flushing out solids which may have dropped from suspension near the sealing area 303.

[0023] In an embodiment of the invention, the use of a core configured for full cone round spray creates consistent well-developed full cone patterns within short spray times such as 0.100 seconds or less. Such a nozzle is shown in the multiple views of FIG. 4. In particular, the nozzle 400 includes an orifice insert 401 inserted in the nozzle body 402 to influence the spray pattern of the nozzle 400. Core subassemblies 403 included in the valve body 402 further control the flow rate and pattern of the resultant spray from the nozzle 400. These subassemblies will be further discussed below with reference to FIG. 5.

[0024] FIG. 5 illustrates a set 500 of core subassemblies usable in an embodiment of the invention. The core subassemblies include a core tip 501 and a core body 502. The core tip 501 has a cylindrical cross-section, a portion of which fittingly mates with a cylindrical opening in the core body 502. However, the configuration of the nozzle and its component parts is not critical, and those of skill in the art will be familiar with the selection of various nozzle parts to yield the spray pattern most fitting for their particular application. For example, a tighter spray pattern would be desired for smaller items and a broader, wider pattern would be desired for larger items.

[0025] A heating jacket (not shown) for the nozzles provides consistent temperature for the suspension, which allows for consistent fluid viscosity and shot size. With respect to fluid delivery, a pressure vessel (see FIG. 1) supplies fluid to a pump, where the pump increases the head pressure delivered to the nozzles. The use of a pressure vessel feed to the pump reduces energy consumption requirements of the pump (compared to the differential pumping from ambient pressure) to maintain pressure and flow requirements for the system. In an implementation, the pump provides re-circulated flow through all nozzles, with fluid returning to the original pressure vessel to eliminate fall-out of suspended solids within the system.

[0026] The pressure vessel may be heated and insulated to maintain consistent temperature of the suspension. The return port into the pressure vessel may include an element to entrain nearby fluid to create agitation within the tank and means for mixing, e.g., props or paddles, to maintain a homogeneous mixture. In an embodiment of the invention, the return port into the pressure vessel (see FIG. 1) includes a check valve outside the tank. The tank can be pressurized to obtain proper pressure at the nozzle header, and in a further embodiment of the invention a pressure transmitter located at the nozzle header allows proper pressure measurement at the spray location.

[0027] With regard to conveying and detecting the product, the detection of individual product pieces, e.g., tortillas, is used to fire nozzles independently, avoiding overspray. In an implementation, the system operates by sensing a height change due to the height of a tortilla on the conveyor belt. Such a sensor, e.g., product sensor 104, accommodates gradual height changes, but reacts to sharp changes in height. A shaft encoder, not shown, or other conveyor position mechanism, determines conveyor speed for accurate spray with respect to detection point, since the spray point and detection point will be offset by some small distance.

[0028] With respect to fluid supply, in an embodiment, the supplied suspension is at a minimum of 15psi above tank operating pressure. A flow meter in the fluid circulation loop (flow meter 102) measures density to 0.0005g/cc to ensure appropriate concentration of the suspended material, via reference density measurements of the appropriate suspension at the appropriate temperature, as stored in memory associated with the system processor. For example, in the case of salt suspended in oil, the reference densities can be used in combination with the measured density to obtain salt concentration by weight.

[0029] In operation, the system circulates fluid via a centrifugal pump and adjusts tank pressure to achieve the appropriate fluid pressure at the spray header. The density of suspension is monitored as described above, and if a specified range is exceeded, an alarm is sounded so that remedial action may be taken.

[0030] As the product detection sensors monitor and signal the presence of product on the conveyor, the specific distance to the spray point is counted via the shaft encoder, and at a set distance the nozzle fires for a set length of time. The system monitors the fluid level in the feeder tank and signals to a refill valve upon detection of a low level. The valve then turns on to accept solution at a pressure greater than the spray system.

[0100] It will be appreciated that the described system allows for the efficient and uniform application of a sprayed suspension to multiple food product pieces automatically. It will also be appreciated, however, that the foregoing methods and implementations are merely examples of the inventive principles, and that these illustrate only preferred techniques.

[0101] It is thus contemplated that other implementations of the invention may differ in detail from foregoing examples. As such, all references to the invention are intended to reference the particular example of the invention being discussed at that point in the description and are not intended to imply any limitation as to the scope of the invention more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the invention entirely unless otherwise indicated.

[0102] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0103] Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law.

Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.