Abstract:
A sheeter device capable of producing a full-width continuous sheet of masa. A series of ultrasonic horns are placed in close proximity to a sheeter roller, thereby scraping the sheeted dough from the roller. The ultrasonic vibration precludes the buildup of dough on the horns. The invention eliminates the need for sheeter wires and their accompanying plastic bands while increasing the dough throughput of the sheeter.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an apparatus for sheeting dough products and, in particular, to a series of ultrasonic horns or blades used to strip a sheeter roller. The use of ultrasonic horns eliminates the need for a stripper wire and allows for the production of full-width dough sheets. 
     2. Description of Related Art 
     A sheeter is a device commonly used in the food industry for making flattened food products, such as tortilla chips, in a continuous processing operation. Typically, a dough product is compressed between a pair of counter rotating sheeter rollers that are located closely together, thereby providing a pinch point through which the dough is formed into sheets. The dough can then be cut by, for example, a cutting roller to form the shape of the product desired. 
     Many dough products, particularly those that are corn based (“masa”), have a tendency to stick to the sheeter rollers rather than dropping onto a conveyer for transportation to the next processing step, such as a baking oven. This is because masa is relatively sticky and has very little cohesive strength. The masa will not support its weight as it falls from the sheeter and cannot be pulled off the sheeter. The use of a stationary scraper blade, as is commonly used with flour dough applications, is not practical because the masa tends to build on and stick to the scraper blade. One common approach to this problem is to string a stripper wire across the face of the sheeter roller so that the stripper wire can scrap away the dough product off of the surface of the roller. 
     An example of a prior art sheeter wire design in this regard is illustrated by FIGS. 1 and  2 . FIG. 1 is a perspective view of the output of a dough sheeter device  110 . The cut dough product, in this case uncooked tortilla chips  120  made from masa, can be seen on a conveyer  130  after being deposited on the conveyer  130  by a sheeter roller  140 . The sheeter roller  140  will typically have a plurality of plastic bands  150  about the circumference of the sheeter roller  140 . These bands  150  ride in groves (now shown) in the sheeter roller  140  and hold the sheeter wire  160  close to the surface of the sheeter roller  140 . The bands  150  also provide a surface for returning ribbons of unused masa to the sheeter  110 . 
     A sheeter wire  160  is shown strung across the face of the sheeter roller  140 . This sheeter wire  160  is attached to two fixed points  170 ,  180  and is threaded across the face of the sheeter roller  140  underneath each of the bands  150 . This provides a flush contact between the sheeter wire  160  and the surface of the sheeter roller  140 . The second fixed point  180  could also comprise a tension device such as a hydraulic or pneumatic device that provides a constant tension on the wire  160 . Such a tension device is typically connected to a warning device to provide an indication of wire breakage. 
     FIG. 2 is a schematic side view of a prior art sheeter wire design installed on a sheeter device. Masa  205  is fed between a press roller  207  and the sheeter roller  240 . The press roller  207  turns at a slower rotational speed than the sheeter roller  240 . This results in the masa  205  adhering to the sheeter roller  240 . The masa  205  is next cut by a cutter roller  209 . The cut masa is then stripped from the sheeter roller  240 , by the sheeter wire  260 . The cut product  220  then drops onto a conveyor  230  to be transported for further processing. As will be described below, sheeters using a sheeter wire arrangement such as illustrated in FIGS. 1 and 2 have three primary drawbacks—wire  160  breakage, band  150  breakage, and an inability to produce full-width sheets. 
     Returning to FIG. 1, the sheeter wire  160  is typically commercial piano wire. A typical tension on the wire during operation is 100 to 125 pounds. Contact with hardened masa, particularly during start-up, can subject the sheeter wire  160  to higher tension for short time periods. During operation the wire  160  is also subject to friction from the moving face of the sheeter roller  140 . This wire  160  must be replaced periodically or the wire  160  is prone to breakage after time. In fact, in a continuous use operation for a typical sheeter device producing tortilla chips, it has been observed that such fixed sheeter wire  160  will break, if not replaced, nearly daily. 
     In order to replace a broken sheeter wire the entire sheeter device  110  and, consequently, the entire chip processing assembly, must be stopped. The broken sheeter wire  160  is removed. A new sheeter wire  160  is attached to the first attaching point  170 , strung across the face of the sheeter roller  140  under the bands  150 , and attached to a second attaching point  180 . Then the tension device  190  must be reactivated. Raw material is lost because the dough that was on the sheeter must be thrown away and additional product downstream may need to be discarded. Start-up procedures must next be followed, which result in further lost product. A wire breakage event, therefore, results in a substantial amount of unscheduled downtime and lost product. The alternative is to schedule, on a daily basis, the replacement of the sheeter wire  160 . A scheduled replacement of the sheeter wire  160 , however, results in even more frequent, although scheduled, downtime. 
     One attempt at addressing the wire breakage problem is reflected in U.S. Pat. No. 5,720,990 (“Lawrence”) issued on Feb. 24, 1998. The Lawrence patent discloses a wire separator system for a sheeter device comprising a motor that drives a feed spool and a motor that drives a take-up spool. Tension is maintained on the sheeter wire by use of a tension sensing pulley providing input to a controller which modulates the torque on the take-up reel. Provided that the wire does not unexpectedly break, the Lawrence patent discloses a device that will allow the sheeter to run for long periods of time without the necessity of stopping the sheeter to replace the sheeter wire, because new wire is constantly drawn across the contact surface. 
     The invention disclosed by Lawrence has several drawbacks, however. First, the design assumes that the wire will not break during operation. Unfortunately, this is not a safe assumption. In fact, it is not an infrequent occurrence that wire breakage occurs on the prior art model illustrated by FIG. 1 shortly after a new wire has been installed. This could occur due to a sudden contact with a dried piece of dough that has become affixed to the sheeter while the sheeter is stationary. Further, an initial steady-state friction between the sheeter wire and the sheeter must be overcome at the instant the sheeter begins to rotate. Since the Lawrence device provides that one motor feeds wire while another motor takes-up wire, a breakage between the two motors can result in the continued feeding of wire into the sheeter until the feed motor comes to a stop. A breakage also results in a loss of tension on the feed spool and can lead to unraveling or the “weed eater” effect, whereby the spool becomes unwound. Further, the Lawrence device is designed to maintain constant tension of the wire by using a variable speed pulling motor connected to the take-up reel. Since the Lawrence feed spool is connected to a fixed speed motor, the tension will necessarily fluctuate at the point that the wire is leaving the feed spool when, for example, the wire encounters a piece of dried dough product on the sheeter during operation. These torque fluctuations could effect the consistency of the feed spool&#39;s wound tension, thereby leading to further torque fluctuations and potential feed problems. 
     Minor breakage issues aside, the prior art sheeter device illustrated in FIG.  1  and the Lawrence device have other shortcomings and problems. For example, the bands  150  that hold the sheeter wire  160  in place are also subject to frequent breakage. Band breakage will probably occur with even greater frequency when a continuously drawn sheeter wire  160 , such as disclosed in Lawrence, is used. Again, as with a wire  160  breakage event, band  150  breakage results in stopping the entire sheeter device and assembly line, thereby resulting in down time, loss of downstream product, and loss of product due to start-up procedure requirements. These bands can be periodically replaced; however, replacement also requires shutting down the sheeter device. 
     The use of bands  150  also precludes the possibility of sheeting a fall-width sheet of dough product. This is because masa adheres to the exterior of the bands  150  and is returned in ribbons to the sheeter  110 . It may be desirable in certain applications to sheet an uncut, full-width continuous sheet of masa. For example, it may be desirable to cook or partially cook the sheet of dough downstream from the sheeter and then later apply a die cutter to the sheet. Such an arrangement would allow for a higher volume of product to be dispensed from a single sheeter since little to no dough is returned to the sheeter. 
     Consequently, a need exists for a dough sheeting device capable of sheeting masa and other sticky dough products without the use of stripper wire and the attending bands. Such apparatus should be capable of producing a full-width and continuous sheet of masa without a buildup of masa on the stripping mechanism. 
     SUMMARY OF THE INVENTION 
     The proposed invention comprises a sheeter device that utilizes a series of vibrating horns in close proximity to the sheeter roller for stripping the sheeted product off the roller, thereby forming a fall-width continuous sheet of dough. The horns vibrate in the ultrasonic range, thereby precluding masa buildup on the surface of the horns. 
     Use of the ultrasonic horns as a scraping device eliminates the need for a sheer wire and the attending bands. Consequently, the invention can be operated continuously without concern for replacing worn or broken sheeter wire or bands. Further, since the need for bands is eliminated, the device can produce fall-width, continuous sheets of dough product. These full-width sheets result in a higher volume of dough product being produced by a single sheeter device. This is evident by the fact that dough does not return to the sheeter as ribbons attached to the bands. 
     The above as well as additional features and advantages of the present invention will become apparent in the following written detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective representation of a prior art sheeter device with a fixed sheeter wire; 
     FIG. 2 is a schematic side view representation of a prior art sheeter device with a fixed sheeter wire; 
     FIG. 3 is a perspective view of a single horn of the invention; 
     FIGS. 4 a  and  4   b  are schematic side view representations of a horn of the invention in operational proximity to a sheeter roller; 
     FIG. 5 is a side view of a single scraper device of the invention; 
     FIG. 6 is an overhead view of the scraper assembly of one embodiment of the invention; and 
     FIG. 7 is a perspective representation of one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 3 is a perspective view of a horn or blade of the scraper device of the invention. The horn  332  is typically constructed of a single piece of titanium and is shaped to provide a specific resonant frequency. The horn  332  comprises a pointed edge or tip  334  that, as will be explained in farther detail below, is placed in close proximity to a sheeter roller. The horn  332  is attached at a butt end  336  to a device for producing ultrasonic vibration. A suitable horn  332  is a ten inch, Half Wave Titanium Guillotine Horn manufactured to increased precision dimensional tolerances by Dukane Corporation of St. Charles, Ill. 
     FIGS. 4 a  and  4   b  are schematic side views of the horn  442  in a relative position to the sheeter roller  440 . FIG. 4 b  is a magnified view of the portion of FIG. 4 a  identified by a dashed circle. The long axis of the horn  432  must be placed at an optimal angle  443  to the horizontal plane in order to insure an optimal scraping angle near the surface of the sheeter roller  440 . In one embodiment, it has been determined that an angle  443  of approximately 12° to 16° results in the best scraping angle for the apparatus. It should also be noted that the blade tip  434  is placed in close proximity, but not in contact with, the sheeter roller  440 . This placement is critical, as allowing the blade tip  434  to contact the sheeter roller  440  dampens the horn vibration. With the horn  432  vibration dampened, masa can quickly build-up on the underside  438  of the horn  432 . Conversely, if the blade tip  434  is placed too far away from the sheeter roller  440 , the device will not efficiently strip the dough product from the surface of the sheeter roller  440 . It has been determined in one embodiment of the invention that an ideal distance  445  (not shown to scale) between the blade tip  434  and the surface of the sheeter roller  440  is approximately 0.004 to 0.011 inches. 
     FIG. 5 is a side view of a single scraper device  552  in close proximity to a sheeter roller  540 . The sheeter scraper device  552  comprises the horn or blade  532  which is attached to a booster  554 . The booster tunes vibrations produced by a probe  556 . The probe  556  and booster  554  are in turn connected to a bracket assembly  558 . The probe  556  is electrically connected to a power supply by a cord  590 . A suitable probe  556  and booster  554  assembly is a 41530 Sealed Probe Stack manufactured by Dukane Corporation of St. Charles, Ill. 
     FIG. 6 is an overhead view of several of the single scraper devices  652  mounted in series to a stationery bar  667 , thereby forming a scraper assembly  663 . The assembly  663  requires a small separation  646  (not shown to scale) between each individual horn  632 . The individual horns  632  cannot be allowed to contact each other, as such contact would result in dampening the beneficial vibration of the horns  632 . However, the gap  646  between adjacent horns  632  should be as small as possible to accomplish this separation in order to avoid any noticeable effect, such as a seam, on the sheeted dough. An acceptable distance  646  between adjacent horns  632  has been found to be approximately 0.004 to 0.011 inches. This separation issue is eliminated in an alternative embodiment that comprises a single horn that is sufficiently wide to span the sheeting length required. Also, gap  646  tolerances might be less crucial and could be widened if full width sheeting is not required. 
     FIG. 7 is a perspective view of an embodiment of the invention showing a scraper assembly  763  producing a fall-width, continuous sheet of masa  721 . It should be noted that the sheeter  710  does not require bands or a sheeter wire. Consequently, practically all of the dough fed into the sheeter  710  is actually sheeted and placed on the conveyor  730 . It is preferable, however, to leave a thin circulating ribbon of masa  765  on either end of the sheeter roller  740  such that the edges of the sheeted masa  721  are clean and uniform. This is accomplished by keeping the aggregate blade content width of the scraper assembly slightly narrower than the width of the sheeter roller  740 . Clean and uniform edges on the masa sheet  721  allow for the use of a die cutting device that can take advantage of the linear geometry of the edge of the sheeted masa  721  in cutting shapes out of said sheet  721 . 
     The full-width sheeting capability of the invention can be used to produce a full-width sheet  721  of dough. This may be preferable when it is desired to cook or partially cook the dough in its sheeted form prior to cutting or further processing. Alternatively, the invention can also be utilized to scrape cut dough off of the sheeter roller  740 , using a cutter roller such as the one shown in FIG.  2 . As previously noted, the scraper assembly  763  comprises a series of scraper devices  752 , all attached from their respective brackets  758  to a stationary bar  767 . This bar  767  is mounted to two side brackets  791 ,  792  in order to precisely hold the entire assembly  763  in relative position to the sheeter roller  760  such that the angles  443  illustrated in FIG. 4 a  and distance  445  illustrated in FIG. 4 b  can be precisely maintained. 
     The key to the invention is the use of scrapers or horns that are allowed to constantly vibrate in the ultrasonic or other suitable range. In one embodiment of the invention, the ultrasonic vibration produced was in the frequency range of 10 kHz to 40 kHz and amplitude of 0.001 inches to 0.004 inches. The preferred frequency range for the ultrasonic vibration is from 20 kHz to 40 kHz. One preferred embodiment of the invention operates at 20 kHz. The amplitude of the ultrasonic vibration embodiment is preferably at least 0.001 inches. The preferred embodiment that operates at a frequency of 20 kHz operates at an amplitude of 0.003 inches. With the distances and angles previously described, this frequency and amplitude promotes the clean and uniform stripping of the dough product  721  off of the sheeter roller  740  without any residual buildup of the dough on the horns  732 . In one preferred embodiment, the sheeter roller  740  is sandblasted. A sandblasted surface promotes the desired scrapping of the invention. 
     Since the sheeter device  710  of the invention requires no bands or sheeter wire, the sheeter  710  can be operated continuously. This continuous operation in combination with the fact that little masa is returned to the sheeter results in an individual sheeter device  710  producing a substantially higher amount of sheeted product  721  over a given time period. Further, component wear is minimal, since the horns are never in contact with the sheeter roller  740 . 
     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.