Abstract:
A method and apparatus for pressing tortilla dough into a tortilla product in a continuous operation including: an extruder for compressing tortilla dough through a nozzle; a knife for slicing the extruded dough into a series of dough pucks; a conveyor press assembly which sandwiches the dough puck between a pair of belts to carry the puck between a pairs of platens to gradually press the puck into its final tortilla form; and a conveyor oven which sandwiches the tortilla between a pair of belts to carry the tortilla between pairs of heated platens to cook the tortilla. The system is particularly well suited to automation and, in one embodiment, includes measuring equipment which provides feedback to produce tortillas of consistent size, shape, and quality.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority from copending U.S. provisional patent application Serial No. 60/365,409, filed Mar. 19, 2002, the disclosure of which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates generally to methods and apparatuses for extruding, cutting, and automatically pressing tortilla dough.  
           [0004]    2. Background  
           [0005]    Flour tortillas are typically produced in a series of steps which involves: mixing the ingredients into dough; extruding and cutting the dough to form dough pucks, pressing each dough puck into a round, flat tortilla, and cooking the tortilla.  
           [0006]    Current systems for pressing flour tortillas typically utilize heavy platen presses and require at least three distinct indexing steps. In the first step, the product dough is indexed into the press assembly. In the second step, the assembly indexes the dough to a press position wherein the heavy platens move toward the dough to press the dough into its final shape. In the third step, the pressed product is indexed to a product removal position. The requirement that such prior art devices be operated in a sequence of distinct indexing steps significantly limits the available speed and production capacity of the prior art system.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention satisfies the needs and alleviates the problems and shortcomings indicated above. In one aspect, the present invention provides a method and apparatus for extruding ant cutting tortilla dough to provide dough pucks of controlled size, weight, shape, and quality. In contrast to previous extruding systems and methods, the inventive system and method does not significantly “work” (i.e., impart energy into) the dough during the extrusion process. Thus, there is no need for a proofing and resting step following extrusion to allow the gluten structures of the dough to reform.  
           [0008]    The inventive extruding apparatus also includes interchangeable nozzles which allow the operator to quickly and conveniently change the diameter of the product. The inventive extrusion apparatus is also computer controlled to allow the operator to essentially dial in any product weight and speed desired. In contrast, the extrusion devices used heretofore are typically labor intensive and require highly skilled operators who are capable of selecting and exchanging the appropriate system components and of making the appropriate fine tuning adjustments to obtain the product weights, size, and speeds desired.  
           [0009]    In another aspect, the present invention provides an apparatus and method for pressing the tortilla dough in a continuous manner without requiring a series of discrete indexing steps. The inventive press thus provides much higher production speeds than the existing technology. The inventive press is highly adaptable to and can quickly be adjusted for variations in dough rheology.  
           [0010]    In yet another aspect, the present invention provides a combined apparatus and method for extruding and pressing tortilla dough. In this system, the inventive extruder is preferably coupled and fully integrated with the inventive press to provide quick, automated synchronization of the extrusion and pressing operations. The inventive integrated system produces high quality round tortilla products at speeds of 4 times, or more, that of existing systems.  
           [0011]    In still another aspect, the present invention provides a combined apparatus and method for extruding, pressing, and cooking tortilla dough. In this system, the inventive extruder is coupled to and fully integrated with the inventive press, which is further coupled to and integrated with an oven to provide synchronization of the extrusion, pressing, and cooking operations.  
           [0012]    Further objects, features and advantages of the present invention will be apparent to those skilled in the art upon examining the accompanying drawings and upon reading the following detailed description of the preferred embodiments.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 provides a flow diagram describing the steps and processes of the inventive method for making a tortilla product.  
         [0014]    [0014]FIG. 2 provides a perspective view of a preferred extruder used in conjunction with the present invention showing the output end of the extruder.  
         [0015]    [0015]FIG. 3 provides a perspective view of the extruder of FIG. 2 as viewed from the motor end of the extruder.  
         [0016]    FIGS.  4 A- 4 C provide a perspective view of preferred embodiments of the combined extruder, press, and oven.  
         [0017]    FIGS.  5 A- 5 B provide a perspective view of the inventive tortilla press.  
         [0018]    [0018]FIG. 6 depicts a pressure plate assembly particularly preferred for use in the inventive pressing system.  
         [0019]    [0019]FIG. 7 depicts a heated pressure plate assembly particularly preferred for use in the inventive pressing apparatus.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    Before explaining the present invention in detail, it is important to understand that the invention is not limited in its application to the details of the construction illustrated and the steps described herein. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.  
         [0021]    Referring now to the drawings, wherein like reference numerals indicate the same parts throughout the several views, a preferred embodiment of the inventive tortilla press  20  is shown in FIGS.  4 A- 4 C. Preferably tortilla press  20  comprises three major assemblies: extruder  22 ; press assembly  24 ; and oven assembly  26 . In the preferred embodiment, tortilla dough is fed into the system  20  through hopper  28  and, in a continuous process, extruded and sliced into dough pucks  30  by extruder  22 . In turn, dough pucks  30  are pressed into flat tortillas by press  24 , and cooked in oven  26 .  
         [0022]    Generally speaking, screw extruders are well known in the art. Such devices typically include: a hopper through which an extrudable food product is fed; a motor driven auger, or screw, positioned below the hopper which compresses and drives the product towards the output of the extruder; and an extrusion die at the output of the extruder which imparts a desired cross-sectional shape to the product stream. Referring to FIGS. 2 and 3, extruder  22  is fairly typical of such screw extruders. Preferably, extruder  22  includes: funnel-shaped hopper  28 ; a motor  32  and gearbox  34  for rotationally driven a pair of augers (not shown); a pair of extruder tubes  36  through which the dough is driven by the augers; an extrusion die  38  which extrudes the flow of dough into a desired form; and knife subassembly  40 , preferably a guillotine-type cutter, slices the flow of compressed dough into individual dough pucks  30  (FIG. 4A) as the dough exits the extrusion die. In the preferred embodiment, the interior surfaces of extrusion tubes  36  are polished to reduce dough friction.  
         [0023]    Preferably motor  32  is driven by a servo controller, or similar closed-loop controller such that the speed of motor  32  can be controlled to maintain dough pucks of consistent thickness or consistent weight. As will become apparent to those skilled in the art from the discussion hereinbelow, knife  40  is typically operated at a rate which achieves a desired spacing between dough pucks in light of the conveyor speed of downstream assemblies. Motor  32  may then be controlled to maintain consistent size or weight between individual dough pucks  30 . Alternatively, motor  32  could be set to operate at a consistent speed and knife  40  controlled to produce consistent pucks. Unfortunately, in such an arrangement the throughput of the system would suffer somewhat.  
         [0024]    Turning again to FIG. 4A, as dough pucks  30  are produced by extruder  22 , pucks  30  are deposited onto weight check conveyor  42 . Weight check conveyor  42  measures either the weight or height of pucks  30  as they are produced and provides feedback to the controller of motor  32  to increase or decrease the speed of the augers as necessary to ensure pucks of consistent weight or size. The weight check conveyor  42  delivers dough pucks  30  to the infeed portion  44  of the continuous pressing apparatus  24 .  
         [0025]    Referring to FIGS. 5A and 5B, preferably pressing apparatus  24  comprises: a frame  50  having a plurality of supporting legs  52 ; a lower conveyor belt  54 ; a counter-rotating upper conveyor belt  56  which moves at the same speed as lower belt  54 ; a pair of motors and gearboxes  58  and  60  for driving the lower conveyor belt  54  and upper conveyor belt  56 , respectively; a plurality of pressure plate assemblies  62   a - c;  a plurality of pressure plate covers  64  (only one shown) each cover  64  sandwiched between the top of its corresponding pressure plate assembly and the upper run of upper belt  56 ; and conveyor cover  66 .  
         [0026]    As dough pucks  30  reach the infeed portion  44  of lower belt  54 , the pucks are drawn into pressing apparatus  24  where pucks  30  become sandwiched between the upper run of lower belt  54  and the lower run of upper belt  56  as they are conveyed through press  24 . As pucks  30  progress through the system, sandwiched between belts  54  and  56 , they are carried successively through the series of pressure plate assemblies  62   a - c  which gradually press and move the dough outward to provide the desired size and shape of the finished tortilla product. In a particularly preferred embodiment, each conveyor belt is a Teflon® coated, stainless steel belt.  
         [0027]    With further reference to FIG. 6, wherein is shown a section view of pressure plate assembly  62   a.  Assembly  62   a  is typical of the other pressure plate assemblies  62   b - c.  Preferably pressure plate assembly  62   a  includes: a lower platen  70  supported by a pair of axially extending rods  72 ; an upper platen  75 , likewise supported by a pair of axles  74 ; a lower slide  78  secured to the upper surface of lower platen  70  for contact with belt  54 ; and a top slide  80  secured to the lower surface of upper platen  78  for contact with belt  56 . Preferably upper platen  75  and lower platen  70  are held in a fixed relationship such that a gap  82  of ever decreasing thickness is created therebetween. As will be apparent to those skilled in the art, since conveyor belts  54  and  56  are counter-rotating, both belts are moving in the same linear direction, preferably at the same linear speed, as they pass through gap  82 . Thus, as a dough puck  30  is drawn through pressure plate assembly  62   a  by upper belt  56  and lower belt  54  (shown moving left to right in FIG. 6), dough puck  30  will be pressed into an ever thinner form. Platens  70  and  75  may optionally be heated.  
         [0028]    Continuing with FIGS. 5A and 5B, the upper platens  75  of pressure plate assemblies  62   a - c  are attached to frame  50  through a series of eccentric lobes  100  connected to axles  74 . Each eccentric lobe  100  includes a control arm  102  and link  104  which is, in turn, connected to a servo  106 . Servos  106  may be controlled to adjust the size and taper of gap  82  (FIG. 6) to control the amount of “press” applied to the dough puck during each pressing stage and to control the thickness of the final product. In fact, if a vision system, or other measuring system, is used at outfeed  48 , pressure plate assemblies  62   a - c  may be continuously adjusted to produce tortillas of a consistent, precise diameter at outfeed  48 .  
         [0029]    As will be apparent to those skilled in the art, the ultimate shape of the tortilla will be dependent on both the shape of the dough puck, as determined by extrusion die  38  (FIG. 2) and the motion of the conveyors  54  and  56  which tend to move dough more in a longitudinal direction than across the conveyors. By controlling the aspect ratio of the dough pucks through the selection of die  38 , tortillas of virtually any shape may be produced by the inventive apparatus. To obtain round tortillas, dough puck  30  would be given a generally elliptical shape.  
         [0030]    Referring again to FIGS.  4 A- 4 C, as individual tortillas exit press  24  at outfeed portion  48 , they are delivered to the infeed portion of oven  26 . Construction of oven  26  is very similar to that of press  24 . Oven  26  preferably includes: a frame  110  supported by a plurality of legs  112 ; a lower conveyor belt  114 ; a counter-rotating upper conveyor belt  116  which moves at the same speed as lower belt  114 ; a pair of motors and gearboxes  118  and  120  for driving the lower conveyor belt  114  and upper conveyor belt  116 , respectively; a plurality of heated platen assemblies  122   a - c;  a plurality of platen covers  124 , each cover  124  sandwiched between the top of its corresponding platen assembly and the upper run of upper belt  116 .  
         [0031]    Referring to FIG. 7, heater platen subassembly  122   a  is typical of its sister heater platen assemblies  122   b  and  122   c.  Platen assembly  122   a  comprises: a lower heater platen  126  supported by axles  128 ; an upper heater platen  130  supported by axles  132 ; a bottom slide  134  secured to lower platen  126  for contact with lower belt  114 ; heating medium  136  sandwiched between slide  134  and platen  126 ; a top slide  138  secured to upper platen  130  for contact with upper belt  116 ; and heating medium  140  sandwiched between top slide  138  and upper platen  130 . Heating elements  142  are used to heat platens  126  and  130 . Formed tortilla from press  24  are carried through gap  144  formed between platens  126  and  130  while sandwiched between the upper belt  116  and lower belt  114 .  
         [0032]    With further reference to FIG. 4C, after successively passing through the series of heated platens  122   a - c,  cooked tortillas are delivered to outfeed area  108  of oven  26 . In a manner similar to that employed in press  24 , upper heater platens  130  can be adjusted vertically through eccentric lobes  146  and servos  148  to control gap  144 . As will be apparent to those skilled in the art, gap  144  could be controlled in a tapered fashion, as in press  24 , to perform some measure of pressing during one or more cooking steps.  
         [0033]    The process of making a tortilla using the inventive system of described in the flow diagram of FIG. 1. While not a performed within the apparatus of the present invention, tortilla dough must be prepared at step  200  according to a recipe or process as indicated at  202 . Once made, at step  204  tortilla dough is fed into the extruder, for example through a hopper, where it is compressed and forced through an extrusion nozzle at  206 . As dough exits the nozzle at step  208 , the extrusion is sliced into a series of dough pucks. At  210 , pucks are transferred to the pressing apparatus and, in a continuous operation, gradually compressed into a final tortilla shape at step  212 . As tortillas pass from the press, they move to the oven wherein cooking takes place at  214 . The pressing apparatus may be heated, as indicated at step  213  to impart sufficient heat to the tortillas to improve their ability to transfer from the pressing operation to the cooking operation.  
         [0034]    Optionally, as dough pucks are created pucks can be weighed, or measured through a machine vision system, to determine the weight or thickness of the pucks at step  216 . Puck-to-puck variations can be virtually eliminated by using this information to control the speed of the extruder at step  206 . In another optional step at  218 , a machine vision system, or video system, can be used to measure the size of the pressed tortilla just prior to cooking. This information can be used to adjust the press platens so that the pressing operations at  212  produce tortillas of precise dimensions. The information gathered at  218  can likewise be used to control the speed of the extruder to obtain consistent product.  
         [0035]    As will be apparent to those skilled in the art, numerous modifications could be made to the preferred embodiment without deviating from the scope or spirit of the present invention. For example, while a screw extruder has been employed in conjunction with the preferred embodiment, virtually any type of extruder will suffice, the important feature simply being the production of consistent dough pucks. Similarly, in the preferred embodiment, vertical adjustment of the various platen assemblies is achieved using eccentric lobes. While such vertical adjustment plays an important role in the versatility of the present invention, the means of achieving such vertical adjustment is unimportant. Thus, linear actuators, hydraulic or pneumatic cylinders, or various cam arrangements could be employed to adjust the platens up or down without deviating from the scope or spirit of the present invention.  
         [0036]    Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those skilled in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims.