Tortilla pressing apparatus and method

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]FIG. 1 provides a flow diagram describing the steps and processes of the inventive method for making a tortilla product.

[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]FIG. 3 provides a perspective view of the extruder of FIG. 2 as viewed from the motor end of the extruder.

[0016] FIGS. <b>4</b>A-<b>4</b>C provide a perspective view of preferred embodiments of the combined extruder, press, and oven.

[0017] FIGS. <b>5</b>A-<b>5</b>B provide a perspective view of the inventive tortilla press.

[0018]FIG. 6 depicts a pressure plate assembly particularly preferred for use in the inventive pressing system.

[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 <b>20</b> is shown in FIGS. <b>4</b>A-<b>4</b>C. Preferably tortilla press <b>20</b> comprises three major assemblies: extruder <b>22</b>; press assembly <b>24</b>; and oven assembly <b>26</b>. In the preferred embodiment, tortilla dough is fed into the system <b>20</b> through hopper <b>28</b> and, in a continuous process, extruded and sliced into dough pucks <b>30</b> by extruder <b>22</b>. In turn, dough pucks <b>30</b> are pressed into flat tortillas by press <b>24</b>, and cooked in oven <b>26</b>.

[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 <b>22</b> is fairly typical of such screw extruders. Preferably, extruder <b>22</b> includes: funnel-shaped hopper <b>28</b>; a motor <b>32</b> and gearbox <b>34</b> for rotationally driven a pair of augers (not shown); a pair of extruder tubes <b>36</b> through which the dough is driven by the augers; an extrusion die <b>38</b> which extrudes the flow of dough into a desired form; and knife subassembly <b>40</b>, preferably a guillotine-type cutter, slices the flow of compressed dough into individual dough pucks <b>30</b> (FIG. 4A) as the dough exits the extrusion die. In the preferred embodiment, the interior surfaces of extrusion tubes <b>36</b> are polished to reduce dough friction.

[0023] Preferably motor <b>32</b> is driven by a servo controller, or similar closed-loop controller such that the speed of motor <b>32</b> 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 <b>40</b> is typically operated at a rate which achieves a desired spacing between dough pucks in light of the conveyor speed of downstream assemblies. Motor <b>32</b> may then be controlled to maintain consistent size or weight between individual dough pucks <b>30</b>. Alternatively, motor <b>32</b> could be set to operate at a consistent speed and knife <b>40</b> 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 <b>30</b> are produced by extruder <b>22</b>, pucks <b>30</b> are deposited onto weight check conveyor <b>42</b>. Weight check conveyor <b>42</b> measures either the weight or height of pucks <b>30</b> as they are produced and provides feedback to the controller of motor <b>32</b> to increase or decrease the speed of the augers as necessary to ensure pucks of consistent weight or size. The weight check conveyor <b>42</b> delivers dough pucks <b>30</b> to the infeed portion <b>44</b> of the continuous pressing apparatus <b>24</b>.

[0025] Referring to FIGS. 5A and 5B, preferably pressing apparatus <b>24</b> comprises: a frame <b>50</b> having a plurality of supporting legs <b>52</b>; a lower conveyor belt <b>54</b>; a counter-rotating upper conveyor belt <b>56</b> which moves at the same speed as lower belt <b>54</b>; a pair of motors and gearboxes <b>58</b> and <b>60</b> for driving the lower conveyor belt <b>54</b> and upper conveyor belt <b>56</b>, respectively; a plurality of pressure plate assemblies <b>62</b><i>a</i>-<i>c; </i>a plurality of pressure plate covers <b>64</b> (only one shown) each cover <b>64</b> sandwiched between the top of its corresponding pressure plate assembly and the upper run of upper belt <b>56</b>; and conveyor cover <b>66</b>.

[0026] As dough pucks <b>30</b> reach the infeed portion <b>44</b> of lower belt <b>54</b>, the pucks are drawn into pressing apparatus <b>24</b> where pucks <b>30</b> become sandwiched between the upper run of lower belt <b>54</b> and the lower run of upper belt <b>56</b> as they are conveyed through press <b>24</b>. As pucks <b>30</b> progress through the system, sandwiched between belts <b>54</b> and <b>56</b>, they are carried successively through the series of pressure plate assemblies <b>62</b><i>a</i>-<i>c </i>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 <b>62</b><i>a. </i>Assembly <b>62</b><i>a </i>is typical of the other pressure plate assemblies <b>62</b><i>b</i>-<i>c. </i>Preferably pressure plate assembly <b>62</b><i>a </i>includes: a lower platen <b>70</b> supported by a pair of axially extending rods <b>72</b>; an upper platen <b>75</b>, likewise supported by a pair of axles <b>74</b>; a lower slide <b>78</b> secured to the upper surface of lower platen <b>70</b> for contact with belt <b>54</b>; and a top slide <b>80</b> secured to the lower surface of upper platen <b>78</b> for contact with belt <b>56</b>. Preferably upper platen <b>75</b> and lower platen <b>70</b> are held in a fixed relationship such that a gap <b>82</b> of ever decreasing thickness is created therebetween. As will be apparent to those skilled in the art, since conveyor belts <b>54</b> and <b>56</b> are counter-rotating, both belts are moving in the same linear direction, preferably at the same linear speed, as they pass through gap <b>82</b>. Thus, as a dough puck <b>30</b> is drawn through pressure plate assembly <b>62</b><i>a </i>by upper belt <b>56</b> and lower belt <b>54</b> (shown moving left to right in FIG. 6), dough puck <b>30</b> will be pressed into an ever thinner form. Platens <b>70</b> and <b>75</b> may optionally be heated.

[0028] Continuing with FIGS. 5A and 5B, the upper platens <b>75</b> of pressure plate assemblies <b>62</b><i>a</i>-<i>c </i>are attached to frame <b>50</b> through a series of eccentric lobes <b>100</b> connected to axles <b>74</b>. Each eccentric lobe <b>100</b> includes a control arm <b>102</b> and link <b>104</b> which is, in turn, connected to a servo <b>106</b>. Servos <b>106</b> may be controlled to adjust the size and taper of gap <b>82</b> (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 <b>48</b>, pressure plate assemblies <b>62</b><i>a</i>-<i>c </i>may be continuously adjusted to produce tortillas of a consistent, precise diameter at outfeed <b>48</b>.

[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 <b>38</b> (FIG. 2) and the motion of the conveyors <b>54</b> and <b>56</b> 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 <b>38</b>, tortillas of virtually any shape may be produced by the inventive apparatus. To obtain round tortillas, dough puck <b>30</b> would be given a generally elliptical shape.

[0030] Referring again to FIGS. <b>4</b>A-<b>4</b>C, as individual tortillas exit press <b>24</b> at outfeed portion <b>48</b>, they are delivered to the infeed portion of oven <b>26</b>. Construction of oven <b>26</b> is very similar to that of press <b>24</b>. Oven <b>26</b> preferably includes: a frame <b>110</b> supported by a plurality of legs <b>112</b>; a lower conveyor belt <b>114</b>; a counter-rotating upper conveyor belt <b>116</b> which moves at the same speed as lower belt <b>114</b>; a pair of motors and gearboxes <b>118</b> and <b>120</b> for driving the lower conveyor belt <b>114</b> and upper conveyor belt <b>116</b>, respectively; a plurality of heated platen assemblies <b>122</b><i>a</i>-<i>c; </i>a plurality of platen covers <b>124</b>, each cover <b>124</b> sandwiched between the top of its corresponding platen assembly and the upper run of upper belt <b>116</b>.

[0031] Referring to FIG. 7, heater platen subassembly <b>122</b><i>a </i>is typical of its sister heater platen assemblies <b>122</b><i>b </i>and <b>122</b><i>c. </i>Platen assembly <b>122</b><i>a </i>comprises: a lower heater platen <b>126</b> supported by axles <b>128</b>; an upper heater platen <b>130</b> supported by axles <b>132</b>; a bottom slide <b>134</b> secured to lower platen <b>126</b> for contact with lower belt <b>114</b>; heating medium <b>136</b> sandwiched between slide <b>134</b> and platen <b>126</b>; a top slide <b>138</b> secured to upper platen <b>130</b> for contact with upper belt <b>116</b>; and heating medium <b>140</b> sandwiched between top slide <b>138</b> and upper platen <b>130</b>. Heating elements <b>142</b> are used to heat platens <b>126</b> and <b>130</b>. Formed tortilla from press <b>24</b> are carried through gap <b>144</b> formed between platens <b>126</b> and <b>130</b> while sandwiched between the upper belt <b>116</b> and lower belt <b>114</b>.

[0032] With further reference to FIG. 4C, after successively passing through the series of heated platens <b>122</b><i>a</i>-<i>c, </i>cooked tortillas are delivered to outfeed area <b>108</b> of oven <b>26</b>. In a manner similar to that employed in press <b>24</b>, upper heater platens <b>130</b> can be adjusted vertically through eccentric lobes <b>146</b> and servos <b>148</b> to control gap <b>144</b>. As will be apparent to those skilled in the art, gap <b>144</b> could be controlled in a tapered fashion, as in press <b>24</b>, 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 <b>200</b> according to a recipe or process as indicated at <b>202</b>. Once made, at step <b>204</b> tortilla dough is fed into the extruder, for example through a hopper, where it is compressed and forced through an extrusion nozzle at <b>206</b>. As dough exits the nozzle at step <b>208</b>, the extrusion is sliced into a series of dough pucks. At <b>210</b>, pucks are transferred to the pressing apparatus and, in a continuous operation, gradually compressed into a final tortilla shape at step <b>212</b>. As tortillas pass from the press, they move to the oven wherein cooking takes place at <b>214</b>. The pressing apparatus may be heated, as indicated at step <b>213</b> 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 <b>216</b>. Puck-to-puck variations can be virtually eliminated by using this information to control the speed of the extruder at step <b>206</b>. In another optional step at <b>218</b>, 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 <b>212</b> produce tortillas of precise dimensions. The information gathered at <b>218</b> 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.