Abstract:
A cutter carriage for moving a rotary cutter between a front side of the back roller and a back side of the back roller. The preferred system has a pair of guide rods located on the left and right side plates of the sheeting head. The rotary cutter is held at either end by pivot arms. Each arm, in turn is attached to a carriage side piece that slidingly engages one of the guide rods. The two side pieces are joined into a single cutter carriage by an elongate member parallel to the rotary cutter. Each carriage is equipped with a cutter engagement system that moves the pivot arms and attached rotary cutter into an operational position in relation to the sheeting head. When the rotary cutter is serviced, the engagement system is released allowing the pivot arm to move the rotary cutter away from the sheeting head roller, and the cutter carriage is slid along the guide rods making the rotary cutter readily accessible from the rear side of the sheeting head.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to machinery for processing foods and, more particularly, to a sheeting head or “sheeter” for processing dough into relatively thin sheets out of which corn tortillas, tortilla chips, sheeted corn chips, sheeted potato chips, and similar food products are cut and to an improved system for handing the rotary cutter which cuts the dough sheet. 
     2. Description of Related Art 
     Maize (corn) is the chief cereal grain of the Americas, but dried maize cannot be readily steamed into a palatable staple like rice. Consequently, the native American peoples developed a technique in which they cooked dried maize with calcium carbonate or other alkali and then ground the resulting cooked kernels to produce a sticky dough known as masa. 
     Traditionally masa dough was shaped by hand and baked on a stone griddle to make tortillas. The popularity of tortillas and other comestibles made from masa has continued to increase. Today special machines called sheeting heads form the masa into relatively thin sheets from which tortillas and other food products such as chips or tortillas are cut. As shown in cross-section in FIG. 1 a,  a typical sheeting head comprises a pair of parallel counterrotating rollers, a front-roller  12  and a rear roller  14 , rotating on horizontal axes between a spaced pair of side plates  17 . Masa dough  16  is loaded into the sheeting head, where it is drawn between the rollers and formed into a thin sheet  18  in a pinch point or extrusion zone. 
     The dough is sticky and tends to cling to both rollers. However, differential roller motion or a physical stripping device like a wire or a “doctor blade” transfers the dough sheet to the front roller  12 . As the rollers rotate, the sheet of dough is carried away from the extrusion zone by the front roller  12 . 
     A rotary cutter,  24  sometimes called a cutter roller, counterrotates on a shaft  25  and is in contact with the front roller  12 . The surface of the rotary cutter  24  bears a series of raised ridges that define the shapes of the tortillas, chips, or other products to be cut from the masa dough sheet  18 . When the rotary cutter  24  rotates into contact with the dough sheet  18 , carried by the front roller  12 , the ridges cut the dough sheet  18  into pieces  26 . The cut dough pieces  26  still stick to the front roller  12 , but as the cut dough pieces  26  are moved along by the rotation of the front roller  12 , they come into contact with a stripper wire  22  which scrapes the dough pieces from the front roller  12 . 
     The dough pieces  26  fall onto a moving conveyor belt  28  which carries them into an oven or fryer for final cooking. In some sheeting heads an ingenious system of grooves and bands on the front roller retains edge remnants of the dough sheet on the roller. Thus, only the desired cut dough pieces  26  are removed by the stripper wire  22 . The front roller  12  carries the dough remnants or “rework” back into the top of the sheeting head to be added back in to the main mass of dough for recycling. 
     The rotary cutter  24  requires rather frequent attention. It is not unusual to replace the rotary cutter  24  during a shift either because chips or tortillas of a different size or shape are desired or because the rotary cutter  24  has become worn or damaged. 
     Some sheeters include a mechanism that alternately engages or disengages the rotary cutter  24  from interaction with the dough sheet  18 . FIGS. 1 a  to  1   c,  for example, show an air cylinder  32  including a piston  37  attached to a pivoting lever arm  34  which terminates in a yoke  38  that carries the rotary cutter  24 . When the cylinder  32  is energized as in FIG. 1 a,  the lever arm  34  pivots upward to bring the rotary cutter  24  into contact with the dough sheet  18 . When the cylinder  32  is not energized as in FIG. 1 b,  the weight of the rotary cutter  24  causes the lever arm  34  and the attached rotary cutter  24  to swing away from the dough sheet  18 . An advantage of this arrangement is that whenever the sheeting head power is turned off, the rotary cutter  24  is automatically moved out of contact with the dough sheet  18  into a removal position where the rotary cutter can be removed from the lever arm  34 . 
     Nonetheless, severe removal problems still exist because, as shown in FIGS. 1 a - 1   c,  the rotary cutter  24  is inaccessibly located between the side plates  17  and beneath the front roller  12 , making it difficult to reach the cutter from the back of the sheeting head or from the side. The conveyor belt  28  and other mechanisms generally make it impossible to access the rotary cutter from the front side as well. Accordingly, the side plates  17  in a conventional sheeting head are provided with access ports or lower cut outs  19 , as shown, so that the rotary cutter  24  can be inserted and removed from the side. 
     The rotary cutter  24  is typically removed through the access port  19 , as shown in FIG. 1C, by laboriously lifting it out of the yokes  38  of the pivoting lever arms  34  and then carefully guiding it through the access port  19  in one of the side plates  17 . Cutter replacement is accomplished by reversing this process. In either case, it is troublesome, time-consuming, and may result in injury to the operator or damage to the rotary cutter. 
     There remains a considerable need, therefore, for a system that makes cutter replacement simple and avoids the need to work through the side plates and under the rollers of the sheeting head to service or replace the rotary cutter. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a simple system to improve the ease of cutter replacement; and 
     It is a further objective of the present invention to permit simple cutter replacement from the rear of the sheeting head without having to reach under the rollers and then guide the rotary cutter laterally through a side plate. 
     These and other objectives are met by a cutter replacement system that consists of a pair of guide rods located on the inner surfaces of the left and right hand side plates of the sheeting head. These rods are parallel and are oriented horizontally at right angles to the longitudinal axes of the rollers. The rotary cutter is held at either end by a cutter carriage that slidingly engages the guide rods. The cutter carriage is preferably equipped with a rotary cutter engagement system that moves a pivot arm and attached rotary cutter into an operational position in relation to the sheeting head. When the rotary cutter is to be serviced or replaced, the engagement system is released allowing the pivot arm to move the rotary cutter away from the front sheeting head roller, and cutter carriage holding the rotary cutter is slid rearward along the guide rods under the back roller so that it is readily accessible from a back side of the sheeting head. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objectives and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objectives and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings. 
     FIG. 1 a  shows a diagrammatic cross-section of a prior art sheeting head where a rotary cutter pivots on lever arms fixed to the side plates of the sheeting head; 
     FIG. 1 b  shows a close up diagrammatic cross-section of the prior art sheeting head of FIG. 1 a  to illustrate the rotary cutter in a lowered position; 
     FIG. 1 c  shows the prior art rotary cutter of FIG. 1 b  being removed from the sheeting head through an access port in the side plate; 
     FIGS. 2A to  2 D are schematic side views showing the function and general operation of a sheeting head equipped with a rotary cutter handling system according to the present invention; 
     FIG. 3 is a perspective view of the back side of an overall sheeting head equipped with a rotary cutter handling system according to the present invention; 
     FIG. 4 is a schematic, cut-away, perspective view front a front side of the sheeting head of FIG. 3, with the discharge conveyor belt removed for clarity; 
     FIG. 5 is a perspective view of the preferred rotary cutter handling system; and 
     FIG. 6 is an exploded perspective view of one side of the preferred rotary cutter handling system of FIG. 5; and 
     FIG. 7 is a side view of a preferred latch mechanism used to retain the cutter carriage in the operating position shown schematically in FIG.  2 D and in more detail in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventor of carrying out his invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide a rotary cutter handling system  10  for a sheeting head, wherein the rotary cutter is operationally mounted on a carriage which slidingly moves the rotary cutter between an operating position for sheeting dough and an accessible position for ease of replacement. 
     FIGS. 2A to  2 D are schematic side views of a sheeting head equipped with a rotary cutter handling system  10  of the present invention. FIGS. 2A to  2 D illustrate the operation of the rotary cutter handling system  10  as it moves a rotary cutter  24  between a replacement position (FIG. 2A) and an operating position (FIG.  2 D). 
     As discussed above and specifically shown in FIG. 2D, the rotary cutter  24  must rotate in contact with a front roller  12  so that the rotary cutter  24  contacts and cuts a dough sheet  18  that is carried on the front roller  12 . The rotary cutter  24  is a cylindrical roller that has actual cutter patterns machined as raised ridges into its surface. The rotary cutter  24  is frequently machined from UHMW (ultra-high molecular weight plastic, a food grade plastic manufactured by Du Pont) or brass. The rotary cutter  24  rotates on a shaft  25  that is carried by a yoke of a pivoting lever arm  34 . Unlike the prior art (FIG. 1) where the lever arm  34  pivots from a fixed position relative to the side plates or frame of the sheeting head, the present invention provides a cutter carriage  36  which carries the lever arm  34  and a means for moving the carriage  36  beneath the rollers between a “cutting” position below the front roller  12  to a “replacement” position near the back of the sheeter  100  adjacent to the back roller  14 . 
     FIGS. 2A to  2 D illustrate the insertion of a rotary cutter  24 . In FIG. 2A, the cutter carriage  36  is in the “replacement” position so that, as shown, the shaft  25  of the rotary cutter  24  may easily be inserted into the yoke  38  of the lever arm  34  residing in a lowered position. In FIG. 2B, the cutter carriage  36  is being slid toward the front roller  12  below the back roller  14 , the lever arm  34  being sufficiently low that the rotary cutter  24  clears the bottom of the back roller  14 . In FIG. 2C, the cutter carriage  36  has brought the rotary cutter  24  to its operating position below the front roller. Finally, in FIG. 2D, the lever arm  34  has been raised to bring the rotary cutter  24  against the surface of the front roller  12  so that cut dough pieces  26  may be produced. 
     The removal of the rotary cutter  24 , of course, simply requires a reversal of the process just described with reference to FIGS. 2A to  2 D. In other words, the rotary cutter  24  would be lowered on the pivot arm  34  away from the front roller  12 , slid on the cutter carriage  36  beneath the back roller  14 , and then removed from the yoke  38  of the lever arm  34  from a back side of the sheeting head  100  where the rotary cutter  24  is easily accessible. 
     The preferred moving means  40 , as suggested by FIGS. 2A-2D, comprises a sliding means  42  that is attached to the sheeting head  100  and cooperative bearing means  44  that is attached to the cutter carriage  36 . The preferred sliding means comprises rods  42  that are attached to the side plates  17  of the sheeting head  100  and the preferred bearing means comprises bearing blocks  44  that are attached to side plates  39  of the cutter carriage  36 . The preferred rods  42  comprise stainless steel and the preferred bearing blocks  44 , as best shown in FIG. 6 discussed below, comprise internal guide shoes  58  made of sintered, oil impregnated bronze which allow the carriage  36  to slide easily along the rods  42 . It is possible, of course, to use any variety of drawer-like mechanisms, other than a sliding bearing, such as rollers and rails such as a V-rail and a wheel with a matching periphery. 
     FIG. 3 is a perspective view of a rotary cutter handling system  10  of the present invention in the context of the overall sheeting head supported on a frame  20 . This particular frame  20  is provided with an incline  22  sloping downward below a front side of the sheeting head and directs loose particles to a disposal bin. This incline  22  provides clearance for the preferred rotary cutter handling system  10  disclosed herein, but other configurations could be made in the absence of such incline  22 . 
     In FIG. 3, the rotary cutter  24  is in an operating position below the front roller  12 . As shown, the rods  42  are preferably attached to the side plates  17  of the sheeting head by spacers  46  and, where the rods  42  extend beyond the side plates  17 , to the top of the frame  20  by L-brackets  47 . The bearing blocks  44  that slide along the rods  42 , one pair of blocks  44  for each rod  42 , have a slotted C-shaped design discussed in more detail below so that they can pass unimpeded over the spacers  46 . 
     When the rotary cutter  24  is in contact with the dough sheet  18  on the front roller  12 , as shown, the rotary cutter  24  must be driven so that it rotates at substantially the same surface speed as the front roller  12 . There are a number of ways of driving the rotary cutter  24  which permits the rotary cutter  24  to be pivoted on the lever arm  34  and carried by the cutter carriage  36  of the present invention. The inventor&#39;s preferred means  60  for driving the rotary cutter  24 , however, comprises a motor  61  that is driven by an inverter (not shown) and mounted on the frame  20  below the sheeting head, a flexible shaft  62  that rises through and moves within a slot  24  in the top of the frame  20 , and a right angle gear box  63  with a rigid, splined drive shaft  65  that releasably engages corresponding splines (not explicitly shown) on the shaft  25  of the rotary cutter  24  via the access port  19  in one of the side plates  17 . The flexible shaft  62  permits the rotary cutter to be raised and lowered on the pivot arms  34  and can be easily disengaged from the rotary cutter shaft  25  so that the rotary cutter  24  may be moved to the replacement position. 
     Other varieties of drive means, however, are certainly possible besides that shown in FIG.  3 . One alternative would be a gear fixed concentrically on the cutter shaft  25  that engages a complementary gear connected to the front roller  12 , both gears being located inside of the side plates  17 . In such case, the two gears would mesh with one another whenever the lever arm  34  brought the rotary cutter  24  into contact with the front roller  12 . The cutter shaft  25  could also extend beyond the side plate  17  having the access opening  19  and the gears be located on the outside of the side plate  17 , provided of course that the side plate was modified to include a notch to permit the lengthened shaft to move rearward. 
     FIG. 4 is a schematic, cut-away, perspective view front a front side of the sheeting head of FIG. 3, with the discharge conveyor belt removed, to more clearly illustrate the construction of the cutter carriage  36  used to implement a preferred rotary cutter handling system  10 . As shown, the cutter carriage  36  comprises a pair of side plates  39  that are rigidly connected to one another by a pair of elongated cross-members  41 . Each side plate  39  supports a lever arm  34  that carries the rotary cutter  24 , a mounting bracket  31  that pivotally supports an air cylinder  32  that operates the lever arm  34 , and a pair of bearing blocks  44  which permit the overall cutter carriage  36  to be slid back and forth on the rods  42 . The preferred side plate  39  further comprises a cutter notch  33  to receive the cutter  24  and its shaft  25  when the lever arm  34  holds them in a lowered position, but the cutter notch  33  may be unnecessary given different component dimensions. As shown, the preferred bearing blocks  44  have a C-shaped design so that they can pass over the spacers  46  which connect the rods  42  to the side plates  17 . Although an air cylinder  32  is shown, it should be readily apparent that other cylinders and solenoids. 
     FIGS. 5 and 6 best illustrate the detailed construction of the preferred cutter carriage  36 , FIG. 5 being an overall perspective view thereof and FIG. 6 being an exploded view of the left side of FIG.  5 . As shown, the cutter carriage  36  is slidably supported on the rods  42  by a pair of bearing blocks  44  respectively connected to left and right side plates  39  via hollow spacers  49  and bolts  43 . A pair of elongate cross-members  41  span the two side plates  39  and are connected to L-brackets  35  which are connected to the bearing blocks  44  via the same bolts  43  and hollow spacers  49 . An air cylinder  32  is pivotally suspended on a pin  59  via a bracket  31  connected to the underside of the L-bracket  35  at the front of each side plate  39 . Each air cylinder  32  has a shaft  37  which terminates in a yoke  53  that operates the lever arm  34  via a lever drive arm  54  and a pin  56 . The lever drive arm  54  and lever arm  34  are, as best shown in FIG. 6, connected to a common shaft  55 , but are offset from one another so that the linear motion of the air cylinder&#39;s drive shaft  37  is converted into rotary motion about the shaft  55 . The lever arm shaft  55  is rotatably held between a bearing hole  85  in an appendage  83  on the front bearing block  44  and a bearing hole  86  in the side plate  39 . 
     FIG. 7 shows a preferred latch mechanism  90  which is designed to be included on the bearing blocks  44  located at a front side of the cutter carriage. The operation of the latch mechanism  90  is best understood with reference to FIG. 5 which could be modified to include such mechanism. Once the cutter carriage  36  has been fully inserted into sheeting head  100  where the rotary cutter  24  will be raised and held against the front roller  12 , it is, of course, necessary to maintain the cutter carriage  36  in that position. Although FIG. 5 does not show any latching mechanism for purposes of clarity, FIG. 7 illustrates the preferred latch mechanism  90  which comprises a striker plate  96  and a cooperating pawl  92 . The striker plate  96  is simply a rectangular plate secured to the front end of each rod  42  by any appropriate means, such as, a machine screw threaded into the rod  42 . The pawl  92  is arranged to pivot upon an upstanding support block  91  secured to the bearing block  44 . As suggested by FIG. 7, the pawl  92  pivots about a central point so that an end portion  95  thereof may selectively engage or disengage the striker plate  96 . A spring  93  preferably connects an opposite end of the pawl  92  with a spring retention member  94  in order to bias the end portion  95  of the pawl  92  downward. A direct mechanical or power assisted linkage of any variety well known in the art may be used to operate the pawl  92  to selectively engage or to selectively disengage its end portion  95  to the striker plate  96  so that the cutter carriage  36  may be retracted for removal or replacement of the cutter  24 . As shown in FIG. 7, the end portion  95  of the pawl  92  is beveled so that the pawl  92  will automatically engage the striker plate when the cutter carriage is inserted forward into the sheeting head  100 . Numerous other locking mechanisms are possible, of course, for retaining the cutter carriage  36  in the operating position. 
     Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.