Abstract:
A thickness control system for a high speed tortilla sheeting machine can adjust a pinch point gap between a pair of sheeting rollers to maintain a generally uniform thickness of the produced “masa” (i.e., corn dough) sheet. The sheeting machine can include a pinch point gap adjustment device which guides at least one of the rollers through an arcuate path to thereby adjust a magnitude of the pinch point gap. The controller can direct one or more actuators to change the position of the roller along the archive path to thereby change the distance between the two sheeting rollers as desired to produce a masa sheet at the desired preset thickness.

Description:
PRIORITY INFORMATION 
     The present application is a continuation application of U.S. patent application Ser. No. 13/247,932, which is now a U.S. Pat. No. 8,740,602, filed Sep. 28, 2011, which claims priority under 35 U.S.C. §120 to U.S. Provisional Patent Application No. 61/387,388, filed Sep. 28, 2010, the entire contents of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTIONS 
     1. Field of the Inventions and 
     The present inventions relate to improvements in high speed production sheeting devices for comestible products (e.g., tortillas and tortilla chips). More specifically, the present inventions relate to sheeting devices which control the spacing of rollers used to roll a comestible product to a desired thickness. 
     2. Description of the Related Art 
     Corn tortillas and tortilla chips are cut from a sheet of corn dough, called “masa,” and then baked and/or fried. In mass production, the sheeting and cutting stages are accomplished by a tortilla sheeter. 
     High production tortilla sheeters feed masa from a hopper between a pair of large, stainless steel rollers which roll the masa into a sheet of substantially uniform thickness. The rollers are spaced apart in production to form a gap, known as a “pinch point gap,” through which the masa passes. The masa adheres to the surface of one of the rollers, known as the exit roller, after passing through the pinch point gap. A third roller then cuts the masa into either tortillas or tortilla chips. The third roller, known as the cutting roller, commonly has either circular shaped (for tortillas) or triangular-shaped (for tortilla chips) cutting guides positioned on the cylindrical external surface of the cutting roller. The cut tortillas or chips then are stripped from the exit roller by a wire and/or a blower, or by a similar device. 
     High production tortilla sheeters automate virtually every step of the sheeting and cutting process. One challenge that remains, however, is to accurately control the thickness of the masa sheet before cutting. 
     The consistency of corn masa commonly varies over time depending upon humidity, temperatures, granularity, and other known factors, and occasionally will contain hard kernels of corn. If the distance between the sheeting rollers is rigidly fixed, the thickness of the exiting masa sheet will change depending on the masa consistency. The consistency of the masa can also vary within the hopper, and, thus, vary across the length of the sheeting rollers. As a result, the thickness of produced tortillas or chips undesirably varies. 
     Prior sheeting devices included computer controlled motors driving jack screws to guide one of the rollers along a linear path to thereby control the size of the pinch point gap. For example,  FIGS. 1 and 2  illustrate such a known sheeting device. 
     With reference to  FIG. 1 , the known sheeting device  10  includes a roller component  14  and a drive component  16 . A lower housing  18  houses the drive component  16 . The drive component  16  includes a conventional electric motor (not shown) which drives the roller component  14  via a series of common gears and chains or belts (not shown), as known in the art. A conventional pneumatic control system controls the pneumatic devices of the sheeting device  10  (e.g., a stripping wire  44  and a cutting roller  38 ). 
     The roller component  14  rests on, or is attached to, the top of the lower housing  18  and includes a hopper  22  positioned above a pair of counter rotating rollers  24 ,  26 . The front roller  24  and the rear roller  26  are generally cylindrical. The rollers can also have a roughened surface (obtained, for example, with sandblasting). The rollers  24 ,  26  desirably rotate at the same speed; however, it is understood that the rollers  24 ,  26  can rotate at different speeds if required by specific application. 
     The rollers  24 ,  26  are positioned parallel to each other and, as shown in  FIG. 2 , define a pinch point  28 , i.e., the point at which the rollers  24 ,  26  contact or nearly contact each other. In operation, the rollers  24 ,  26  are spaced slightly apart to form a gap between the surfaces of the rollers  24 ,  26  at the pinch point  28 . 
     With continued reference to  FIG. 2 , the hopper  22  is positioned above the rollers  24 ,  26  so as to contain masa  30  between the rollers  24 ,  26 . As noted above, the term “masa” is used to denote a corn dough which is commonly used to form tortillas and tortilla chips. However, this type of sheeting device  10  can be used with other types of comestible products, such as, for example, grain-based doughs or doughy-like food mixtures. 
     The rear roller can be adjusted relative to the front roller to thereby vary the spacing between the rollers  24 ,  26 , i.e., to vary the spacing of the size of the pinch point gap  28 . Thus, as is known in the art, this type of sheeting device  10  includes an electric motor-driven jack screw arrangement  38  which allows the roller  26  to be slid along the axis  32  toward and away from the roller  24 . 
     More specifically, as shown in  FIG. 2 , the rear roller  26  rotates about an axis defined by the axle  34 . A movable bearing plate  36  supports one end of the axle  34  and another bearing plate (not shown) supports the opposite end of the axle  34 . Each of the bearing plates  36  rides in a track (not shown) supported by the frame  39 . A jack screw  38  is connected to each bearing plate  36  to move the corresponding bearing plate within the track. 
     The axis of the track, which defines the slide axis  32 , is aligned with the longitudinal axes of both rollers  24 ,  26  and through the pinch point  28 . Thus, movement of the bearing plates  36  within their tracks moves the rear roller  26  relative to the front roller  28  to vary the size of the pinch point gap  28 . 
     This type of sheeting device  10  also includes a controller  54  which, through the use of various sensors, controls the jack screw drive to maintain the desired thickness of the masa  42  exiting the sheeting device  10 . 
     SUMMARY OF THE INVENTIONS 
     An aspect of at least one of the embodiments disclosed herein includes the realization that the type of sheeting device described above with reference to  FIGS. 1 and 2  can suffer from excessive movements of the various components forming the jack screw drive assembly. For example, elastic deformations of the screw itself, due to its length, can cause significant displacements of the roller as the forces produced by the masa changes. Additionally, the other bearings and joints requiring lubrication clearances can also contribute to unintended movements of the rollers during operation. These movements can be as great as 2/10,000 ths  of an inch (0.0002 inches) every 20 seconds, or more. Although the system described above is actively controlled to adjust the thickness in response to these changes, the adjustments do not eliminate waste or unacceptable product discharged from the sheeter. Rather, even with the computer controlled thickness adjustment system included in the above-described sheeter  10  (as described in U.S. Pat. No. 5,470,599) there is a continuous stream of unacceptable product discharge from the sheeter due to unintended movement of the rear roller  26 . 
     An aspect of at least one of the embodiments disclosed herein includes the realization that an eccentric pinch point adjustment system can eliminate several of the mechanical joints necessary for a jack screw drive and thereby reduce unintended movements of a roller of a sheeting device. 
     Thus, in accordance with at least one embodiment disclosed herein, a rolling device can include a support housing, a first roller having a first outer surface and supported by the first housing to rotate about a first axis, and a second roller having a second outer surface and supported by the housing to rotate about a second axis spaced from the first axis such that juxtaposed portions of the first and second outer surfaces define a pinch point gap. The roller device can also include at least a first pinch point gap adjustment mechanism comprising a rotatable roller mounting plate supported by the housing so as to be rotatable about a third axis and a mount supporting the first roller such that the first axis is offset from the third axis, thereby causing the first axis to revolve about the third axis when the roller mounting plate is rotated about the third axis and thereby changing a magnitude of the pinch point gap. 
     In accordance with another embodiment, a rolling device can comprise a support housing, a first roller having a first outer surface and supported by the first housing to rotate about a first axis, and a second roller having a second outer surface and supported by the housing to rotate about a second axis spaced from the first axis such that juxtaposed portions of the first and second outer surfaces define a pinch point gap. Additionally, the rolling device can include a first pinch point gap adjustment means for revolving the first axis about a third axis spaced from the first axis and changing a magnitude of the pinch point gap. 
     In accordance with yet another embodiment, a method of adjusting a spacing of two rollers can comprise supporting a first roller so as to rotate about a first axis, supporting a second roller so as to rotate about a second axis spaced from the first axis such that juxtaposed portions of outer surfaces of the first and second rollers define a pinch point gap, and revolving the first roller such that the first axis revolves about a third axis spaced from the first and second axes thereby changing a magnitude of the pinch point gap. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features of the inventions disclosed herein are described below with reference to the following drawings. The illustrated embodiments of the sheeter are intended to illustrate, but not to limit, the inventions. 
         FIG. 1  is a top, front, and right side perspective view of a prior art sheeting device; 
         FIG. 2  is an enlarged and partial right side elevational view of the prior art sheeting device of  FIG. 1 ; 
         FIG. 3  is a schematic representation of an eccentric adjustment device which can be used with any of the embodiments disclosed herein; 
         FIG. 4  is a schematic diagram of two rollers of a sheeting device in which one of the rollers is adjustable with the eccentric adjustment device of  FIG. 3 . 
         FIG. 5  is a top, front, and right side perspective view of a sheeting device in accordance with an embodiment; 
         FIG. 6  is a left side elevational view of the sheeting device of  FIG. 5 ; 
         FIG. 7  is an enlarged, front, top, and left side perspective view of a roller drive of the sheeter illustrated in  FIG. 6 ; 
         FIG. 8  is a bottom, front, left side perspective, exploded view of the roller drive of  FIG. 7 ; 
         FIG. 9  is an enlarged and partial right side elevational view of the sheeter device of  FIG. 5 ; 
         FIG. 10  is a right side elevational view of the sheeter device illustrated in  FIG. 9 , with an eccentric drive cover removed; 
         FIG. 11  is a rear, top, and right side perspective view of the eccentric drive mechanism illustrated in  FIG. 10 ; 
         FIG. 12  is an exploded view of some of the components of the eccentric adjustment mechanism illustrated in  FIG. 12 ; 
         FIG. 13  is a further exploded view of a portion of the eccentric adjustment mechanism illustrated in  FIG. 12 ; 
         FIG. 14  is a sectional view of a portion of the eccentric drive mechanism of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The inventions disclosed herein have applicability to sheeters used in conjunction with continuously moving conveyor systems. However, an understanding of the inventions disclosed herein is facilitated with the following description of the application of the principles of the present inventions to dough rolling, and in particular, rolling dough into tortillas and tortilla chips. In some embodiments, the inventions disclosed herein can be used in conjunction with sheeters that have a sheet thickness control system, such as that disclosed in U.S. Pat. No. 5,470,599, the entire contests of which is hereby incorporated by reference. In particular, in some embodiments, the eccentric pinch point adjustment devices and the associated methods of operation disclosed herein can be used in place of the jack-screw type thickness adjustment hardware disclosed in U.S. Pat. No. 5,470,599, while using the same control system electronics, including the controllers, sensors, etc. as that disclosed in U.S. Pat. No. 5,470,599, or other similar control systems. 
     With reference to  FIG. 3 , an eccentric mechanism  100  which can be configured to adjust a pinch point gap between rollers, can include a shaft mount  102  rotatably mounted within a frame  104 . The shaft mount  102  can be in the form of a circular and rotatable member having a shaft aperture  106 . 
     In the illustrated embodiment, the shaft mount  102  is rotatable about its center axis  108  relative to the support frame  104 . In an initial position of the shaft mount  102 , a center  110  of the aperture  106  is in an initial position. However, as the mount  102  is rotated clockwise relative to the frame  104 , the center  110  of the aperture  106  also moves clockwise. Similarly, when the mount  102  is rotated counter-clockwise, the center  110  of the aperture  106  also moves counter-clockwise. 
     With reference to  FIG. 4 , the eccentric adjustment device  100  is illustrated as adjusting a magnitude of a pinch point gap between two rollers of a comestible product sheeter. For example,  FIG. 4  schematically illustrates the rollers  124 ,  126  of a comestible product sheeter. In the illustrated embodiment, the roller  124  rotates about an axis  128 . The axis  128  can be defined by fixed bearings and an axle (not shown), or it can be mounted so as to be movable. Such bearings can serve as a support configured to allow the roller  124  to rotate about the axis  128 . 
     The roller  126  can be mounted with bearings and an axle so as to rotate about axis  130 . Additionally, in the illustrated embodiment, the axle of the roller  126  can be mounted to an eccentric adjustment device, such as the eccentric adjustment device  100  illustrated in  FIG. 3 . 
     When the adjustment device  100  is adjusted such that the axles  128  and  130  are closest to each other, the pinch point gap  132  between the rollers  124 ,  126  is at its smallest magnitude, i.e., the rollers  124 ,  126  are at their closest possible position. 
     When the mount  102  is rotated counter-clockwise over an angle θ, the axis of rotation  130  of the roller  126  also moves counter-clockwise over an angle θ about axis  108 . In this position, the pinch point gap grows to a larger pinch point gap  134 , based on the radius R and the angle θ. Thus, by controlling the rotation of mount  102 , the size of the pinch point gap  132  can be controlled. 
       FIG. 5  illustrates an embodiment of a comestible product sheeter  200  including an eccentric pinch point adjustment mechanism. The illustrated comestible product sheeter  200  includes a roller assembly  202  supported above a housing  204 . The housing  204  can house electronics, power connections, components of a control system, etc. In the illustrated embodiment, the housing  204  is wheeled for convenient placement and servicing. 
     The roller system  202  can include a hopper  206  positioned above a pair of counter-rotating rollers  208 ,  210 . The rollers  208 ,  210  can be generally cylindrical. In some embodiments, the rollers  208 ,  210  have a slightly roughened surface (obtained, for example, by sandblasting). The rollers  208 ,  210  can be driven at the same speed; however, the rollers  208 ,  210  can also be rotated at different speeds depending on the desired effect and application. 
     The rollers  208 ,  210  are generally positioned parallel to each other so as to define a pinch point therebetween, as described above with reference to  FIG. 4 . In some embodiments, the rollers  208 ,  210  can be mounted and sized such that, in their original or “brand new” state, the outer surface of the rollers  208 ,  210  would contact each other and/or interfere with each other if the adjustment mechanism used to adjust the position of the rotational axis of the roller  210  were set at its minimum pinch point gap position. This can be particularly advantageous because, over time, the outer surfaces of the rollers  208 ,  210  will become deformed and/or wear away. As such, the rollers  208 ,  210  may be removed from the sheet device  200  to be resurfaced. When the rollers  208 ,  210  are resurfaced, the diameters of the rollers  208 ,  210  are reduced. Thus, by mounting the rollers  208 ,  210  such that they would interfere with each other were they positioned in the minimum pinch point gap position, the pinch point gap adjustment mechanism can accommodate the smaller size of the rollers  208 ,  210  after resurfacing yet still achieve the desired magnitude of the pinch point gap. 
     With reference to  FIG. 6 , the hopper  206  can be configured to contain masa (corn-based dough) between the rollers  208 ,  210 . As noted above, the term “masa” is used to refer to a corn dough which is commonly used to form tortillas or tortilla chips. However, it is understood that the present sheeter device  200  can be used with other types of comestible products, such as, for example, grain-based doughs, doughy food mixtures, or other substances. 
     A drive system for the roller  208  can be disposed in the housing  204 .  FIG. 6  illustrates a drive cover  210  which covers the drive system for the roller  208 . Such a drive system can be configured in any known manner. 
     In the illustrated embodiment, the roller  210  is mounted to as to be movable relative to the roller  208 . More specifically, the rotational axis of the roller  210  can be moved relative to the rotational axis of the roller  208 , described in greater detail below. 
     The drive system  212  for the roller  210  can be constructed using any known motor, such as stepper motors or server motors, and gear reduction drives. With reference to  FIGS. 7 and 8 , the drive system  212  can include an electric motor  214  and a gear reduction drive  216 . The gear reduction drive  216  can be mounted directly to an axle  218  of the roller  210 . In this arrangement, the drive system  212  thus moves as the position of the axle  218  is moved, described in greater detail below. Thus, in the illustrated embodiment, the drive  212  is connected to a portion of the housing  204  with a linkage assembly  220 . The linkage assembly  220  prevents the drive system  212  from rotating relative to the housing  204 , and thus ensures proper transference of rotational energy from the motor  214  to the axle  218   
     With reference to  FIG. 9 , the sheeter  200  can also include two support plates  242 ,  244  located at opposite sides of the housing  204 .  FIG. 9  includes a right side elevational view of the plate  242 . The plates  242 ,  244  support both of the rollers  208 ,  210 , as well as other devices. 
     The plate  242  can be made from any desired material. It is most common in the food industry to use stainless steel for all components that will come into contact with any food product. Additionally, the illustrated embodiment is designed to roll masa. As such, the plates  242 ,  244  should be designed to withstand approximately 10,000 pounds of force each. In practice, during operation, a sheet such as the sheeter  200  can experience loads of about 15,000 pounds between the rollers, i.e., the masa being squeezed between the rollers  208 ,  210  experts about 15,000 pounds of pushing force pushing the rollers  208 ,  210  away from each other. Thus, the plates  242 ,  244 , in some embodiments, can be made from stainless steel of a thickness of about 1″ or greater. 
     The adjustment drive system  240  can include an electric motor  242  and a gear reduction device  243 . The gear reduction device can be used to drive a chain drive mechanism covered by a chain drive cover  246 . In some embodiments, the sheeter  200  can include to adjustment drive systems located at opposite ends of the roller  210 . However, in the description set forth below, only one adjustment drive system  240  is described. It is to be understood that in some embodiments, an identical adjustment drive system  240  can be disposed at the opposite end of the roller  210 . 
     With reference to  FIGS. 10 and 11 , the chain drive cover  246  has been removed exposing the chain drive assembly  248 . The chain drive assembly  248  can include a drive spur  250 , a drive chain  252 , and a driven spur  254 . In the illustrated embodiment, the drive  248  is a double chain arrangement. Thus, the drive spur  250  has two sets of teeth in the form of a double spur, there are two chains  252 , and the driven spur  254  has two sets of teeth just as the drive spur  250 . As shown in  FIG. 10 , the rotational axis  260  of the driven spur  254  is offset from the rotational axis  262  of the roller  210 . 
     In some embodiments, a position tab  264  can be mounted on the driven spurs  254  to aid in sensing a rotational position of the driven spurs  254 . For example, in some embodiments, proximity sensors or other types of sensor can be mounted to a sensor bracket  266  so as to detect the presence of the position tab  264  and thus provide a means for an associated control system to determine the rotational position of the drive spur  255 . Other sensors can also be used, such as any of those disclosed in U.S. Pat. No. 5,470,599, or any other sensors. 
       FIGS. 12 and 13  illustrate exploded views of the eccentric drive assembly for changing the spacing of the rotational axis  262  of the roller  210  relative to the rotational axis  269  and of the roller  208 .  FIG. 14  illustrates a cross-sectional view of the eccentric drive assembly in an assembled state and. 
     With continued reference to  FIGS. 12, 13, and 14 , the roller  210  includes an axle  270 . The axle  270  is supported by a bearing  272 , which can be in the form of a roller bearing unit. The outer surface of the bearing  272  is designed to rest within an eccentric adjustment plate  274 . As illustrated in  FIG. 13 , the inner bore of eccentric adjustment plate  274  has an axis that is offset from the axis of the outer surface of the eccentric adjustment plate  274 . 
     The outer surface of the eccentric plate  274  is designed to fit within the bearing sleeve  276 . Retaining plates  278 ,  280  secure the bearing  272 , eccentric plate  274 , and the sleeve  276  within a u-shaped recess  282  formed in the plate  242 . 
     With reference to  FIG. 12 , the plate  242  also includes a removable journal  290 . With the journal  290  inserted into the u-shaped recess  282 , the retaining plates  280  and  278  can be bolted to each other, through a series of bolt holes provided around the u-shaped recess  282  and the journal member  290 . As such, as shown in  FIG. 14 , the retaining plates  278 ,  280  and the journal  290  are all fixed relative to the plate  242 . 
     An additional eccentric drive plate  294  can also be partially journaled within the inner bore  296  of the eccentric plate  274 . Additional bolts can be extended through the bolt hole patterns in the driven spurs  254 , retaining ring  298 , the eccentric drive plate  294  and the eccentric plate  274 . As such, the driven spurs  254  are rotationally coupled with the eccentric plate  274 . Thus, as the drive spurs  254  are rotated, the bearing  272  and thus the axle  270  of the roller  210  revolve along a circular path about the axis  260 , thereby changing the spacing between the rotational axis  262  relative to the rotational axis  269  of the roller  208 , and thereby change the spacing between the outer surfaces of the rollers, i.e., the “pinch point gap”. 
     As noted above, the sheeter device  200  can include a control system configured to control the speed of the rollers  208 ,  210 , as well as the roller spacing drive system  248 . Such a control system can include various sensors, feedback control system components, actuators, and user interface devices. Such a control system is disclosed in U.S. Pat. No. 5,470,599 which is hereby expressly incorporated by reference. For example, such a control system can include a controller device and at least one sensor configured to detect a magnitude for the pinch point gap. The controller device, can be configured to drive the adjustment drive system  240  so as to adjust the detected size of the pinch point gap, as detected by the sensor, to a desired magnitude, which can be input into the controller device by a user. Such a configuration and programming of the controller device is within the skill of one of ordinary skill in the art, in light of the disclosure above and that set forth in U.S. Pat. No. 5,470,599. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.