Abstract:
A device for cutting the tops of crops in a crop bed includes a separator having an inlet, an outlet and an interior space defined between the two. A fan is in fluid communication with the separator and creates an air stream that flows into the separator inlet, through the interior space of the separator, and out the separator outlet. The air stream has an upstream end at or near the separator inlet, where air is pulled into the separator, and a downstream end at or near the fan and continuing beyond. A cutter is positioned upstream of the separator inlet. When the device is in operative position over a crop bed, the air stream lifts the tops of the crops into position to be cut by the cutter. The air stream carries the cut tops away from the crop bed.

Description:
RELATED APPLICATIONS 
     This application claims priority of U.S. Provisional Patent Application No. 61/666,699, filed Jun. 29, 2012 and entitled “Device and System for Harvesting Onions and Other Bulb Crops,” and which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a device for agricultural harvesting, and more specifically to a harvester for onions and other bulb crops. 
     2. Background 
     Devices for harvesting bulb crops are known in the art. Known devices suffer from a variety of drawbacks, however, including inadequate cutting of the tops and roots of the bulb crops, as well as damaging the bulb crops during harvesting. It is desirable to cut the onion tops cleanly, and to relatively uniform specifications, a practice traditionally performed by hand. What is needed is a device for efficient cutting of bulb crop tops that is capable of cutting across an entire row of crops in a single pass. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a device for cutting the tops of crops in a crop bed. The device includes a separator having an inlet, an outlet and an interior space defined between the two. A fan is in fluid communication with the separator and creates an air stream that flows into the separator inlet, through the interior space of the separator, and out the separator outlet. The air stream has an upstream end at or near the separator inlet, where air is pulled into the separator, and a downstream end at or near the fan and continuing beyond. A cutter is positioned upstream of the separator inlet. When the device is in operative position over a crop bed, the air stream lifts the tops of the crops into position to be cut by the cutter. The air stream carries the cut tops away from the crop bed. 
     In one embodiment of the invention, the separator has an intake hood attached to the inlet of the separator. The intake hood has an intake hood inlet and defines an interior space within the intake hood. The air stream created by the fan enters the intake hood inlet and travels through the interior space of the intake hood to the separator. The intake hood is adjustable such that the size and shape of the intake hood inlet can be altered. 
     In another embodiment of the invention, the separator includes a screen positioned in the interior space of the separator. The air stream traveling through the separator passes through the screen, preventing tops within the air stream from reaching the fan. 
     In another embodiment of the invention, the separator outlet leading to the fan is a fan outlet. The separator also includes a chopper outlet at a rear portion of the separator. The interior space of the separator is shaped such that the air stream propels the cut tops toward the rear portion of the separator. A chopper is attached to the chopper outlet of the separator and is positioned below the chopper outlet so that tops propelled to the rear of the separator fall into the chopper. 
     In another embodiment of the invention, the device includes an air lock attached to the bottom of the chopper and in fluid communication with the chopper. Tops passing through the chopper fall into the air lock. The air lock includes an air lock inlet, an air lock outlet, and an interior wall extending between the two and defining an air lock interior. A rotor is rotatably positioned within the air lock interior. The rotor includes a number of fins in sealing engagement with the interior wall of the air lock when the rotor rotates such that any given fin is adjacent to the interior wall. The tops are passed through the air lock by rotation of the rotor, without breaking the air tight seal between the air lock inlet and the air lock outlet. 
     In another embodiment of the invention, the device includes a screw conveyor attached to the air lock and in fluid communication therewith. Tops passing through the air lock fall into the screw conveyor. The screw conveyor includes at least one side outlet positioned to extend over the furrow of the crop bed when the device is in operative position over a crop bed. A rotatable screw extends horizontally along the width of the screw conveyor and is rotatably attached to the screw conveyor. When the rotatable screw rotates, it conveys the tops to the at least one side outlet such that they fall into the crop bed furrow. 
     In another embodiment of the invention, the cutter includes a first rotatable wheel attached to a first end of the cutter, and a second rotatable wheel attached to a second end of the cutter. A band saw blade engages the first and second rotatable wheel and extends between the two. Rotation of the rotatable wheels results in a corresponding rotation of the band saw blade. 
     In another embodiment of the invention, the cutter includes a blade scraper fixedly attached to the cutter and positioned in sufficient proximity to either the upper surface of the band saw blade, the lower surface of the band saw blade, or both, to remove debris from the surface of the band saw blade. 
     In another embodiment of the invention, the cutter includes at least one adjustable, rotatable guide. The guide is in contact with the band saw blade and can be adjusted from side to side, or up and down to raise or lower the height of the band saw blade with respect to the crop bed, or to otherwise adjust the positioning of the blade. 
     In another embodiment of the invention, the cutter includes a blade tensioner for adjusting the tension of the band saw blade. 
     In another embodiment of the invention, the height of the device with respect to a crop bed is independently adjustable from side to side. The device can be adjusted so that the first side of the cutter can be set at a different height with respect to the crop bed than the second side of the cutter. 
     In another embodiment of the invention, the device includes at least one flipper rotatably attached to the device. The flipper is positioned so that it extends partially into the furrow of the crop bed when the device is in operable position over a crop bed. The flipper engages tops that extend into the furrow, and the rotation of the flipper lifts the tops from the furrow and positions them properly for the cutter. 
     In another embodiment of the invention, the at least one flipper is a conical flipper. 
     In another embodiment of the invention, the device includes at least one camera. The camera is positioned in view of the interaction between the cutter and the tops. The at least one camera is in communication with a display in view of an operator of the device so that the operator can make adjustments to the device based on what is seen on the display. 
     In another embodiment of the invention, the separator includes a constriction between the inlet and outlet of the separator. The separator is shaped so that the air stream changes direction between the inlet and the outlet. The rear portion of the interior space of the separator includes an area of reduced air stream velocity. Tops traveling into the separator are accelerated after entering the inlet, and this acceleration propels the tops to the area of reduces air stream velocity as the air stream changes direction to leave the separator. 
     In another embodiment of the invention, the device includes two gauge wheels attached to the underside of the device so that the device can travel along the length of a crop bed. A steering mechanism is provided for rotating the first and second gauge wheels to allow steering of the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of a rough topper of the present invention. 
         FIG. 2  is a bottom perspective view of one embodiment of a rough topper of the present invention. 
         FIG. 3  provides various views of one embodiment of a rough topper of the present invention. 
         FIG. 4  is a perspective view of one alternative embodiment of a rough topper of the present invention. 
         FIG. 5  is a perspective view of one embodiment of a finish topper of the present invention. 
         FIG. 6  is a bottom perspective view of one embodiment of a finish topper of the present invention. 
         FIG. 7  is a perspective view of one embodiment of an onion topper of the present invention. 
         FIG. 8  is a section view of one embodiment of an onion topper of the present invention. 
         FIG. 9  is an exploded view of one embodiment of a chopper-extractor assembly of the present invention. 
         FIG. 10  is an exploded view of one embodiment of an air lock rotor assembly of the present invention. 
         FIG. 11  is an exploded view of one embodiment of a screw conveyor assembly of the present invention. 
         FIG. 12  is an exploded view of one embodiment of a bandsaw assembly of the present invention. 
         FIG. 13  is a perspective view of one embodiment of a guide roller of the present invention. 
         FIG. 14  is an exploded view of one embodiment of a center guide assembly of the present invention. 
         FIG. 15  is a perspective view of exemplary placement of cameras in one embodiment of the present invention. 
         FIG. 16  is a perspective view of one embodiment of rotating flippers of the present invention. 
         FIG. 17  is a top view of one embodiment of a cutter assembly of the present invention. 
         FIG. 18  is a perspective view of one embodiment of a blade scraper of the present invention. 
         FIG. 19  is an exploded view of one embodiment of a conical flipper of the present invention. 
         FIG. 20  shows exemplary operator controls for use in one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the drawings, wherein like numerals indicate like parts,  FIG. 1  shows one embodiment of a ‘rough topper’  10  of the present invention. The device functions to provide a rough cut of the “top” of an onion plant, or other plant. This portion of the plant may be referred to as a stalk or stem, but is generally referred to herein as the “top” of the plant. Further, although the terms “onion” and “onion plant” are used predominantly throughout this writing, it is to be understood that the present invention may be adapted for use with any bulb plants. 
     Rough topper  10  travels along a field (for example, behind a tractor or other device), cutting the tops of the onion plants as it travels the length of the field. As rough topper  10  travels, gauge wheels  22  ensure that the other components of rough topper  10  remain at the proper height with respect to the field. Fan  18  of rough topper  10  pulls air through adjustable inlet  14  and along elbow  16  before expelling the air into the surrounding environment. The action of fan  18  causes the tops of the onion plants to stand more straight as the device moves over them. Maintaining the tops in this more straight orientation allows sickle bar cutter  20  to more effectively cut the tops of the onion plant, preferably pruning them to four or five inches in height. The material cut from the tops of the onion plants is then pulled through inlet  14 , along elbow  16 , and expelled through fan  18 . The various components of rough topper  10  are affixed to a rigid frame  12  with attachments for attaching rough topper  10  to a tractor or other vehicle. 
       FIG. 2  provides another view of rough topper  10 , with the underside of the device visible. Rough topper  10  preferably includes a diesel engine  24  to power fan  18 , though any suitable power source may be employed. 
       FIG. 3  depicts various other views of rough topper  10 , including a view showing a three-point hitch used to attach rough topper  10  to a tractor or other vehicle. 
       FIG. 4  depicts one alternative embodiment of a rough topper of the present invention. The embodiment shown in  FIG. 4  includes a gearbox  26 . In any of the embodiments of the rough topper of the present invention, any suitable fan or other mechanism to create suction at the inlet may be used. 
       FIG. 5  illustrates one embodiment of a finish topper  100  of the present invention. Finish topper  100  includes a frame  112  on which the other components of finish topper  100  are mounted. As finish topper  100  travels along a field, preferably attached to a tractor or other vehicle. Gauge wheels  122  of the finish topper preferably travel along the furrows flanking the bed in which the onions are planted. Controls are provided so that the operator can adjust the cut height of the finish topper, ensuring that the cutting mechanism of finish topper  100  is at the proper height in relation to the onions or other plants in the field. 
     As finish topper  100  moves along a field, fan  118  is engaged, creating suction at inlets  114 . Due to this suction, the remaining tops of the onion plants (i.e. that portion not cut by the rough topper, described above) are made to stand more straight. Reel cutters  120  pass over the plants, cutting the remaining tops of the onions. The remaining tops cut by reel cutters  120  are pulled into inlets  114 , and through an air passage connecting inlets  114  with wye duct  116 . The cut tops are then pulled through fan  118 , where they are chopped into smaller pieces and expelled into the environment. As with rough topper  10 , finish topper  100  includes a diesel engine  124  or other suitable power source for powering fan  118 . Also included in some embodiments of finish topper  100  is chair  128 , for use by an operator of finish topper  100 . A tongue  126  is affixed to or part of frame  112  for attaching finish topper  100  to a tractor or other vehicle. The underside of the embodiment of the finish topper shown in  FIG. 5  is depicted in  FIG. 6 . 
     It is further contemplated that in some embodiments of finish topper  100 , reel cutters  120  may be adjustable to match the shape of the bed containing the crop to be harvested. For example, if the bed is crowned, the reel cutters  120  may be disposed at angles to match the crown of the bed. The general structure of reel cutters such as reel cutters  120  is known in the art. Reel cutters generally include a stationary cutter bar or, as referred to herein, a bed knife. It is contemplated that the angle of the reel cutters may also be adjusted in relation to the bed knife according to the needs or desire of a user of the present device. Further, the bed knife itself may be adjustable and may, for example, be tilted forward for a more aggressive cut, or tilted backward for a less aggressive cut. 
       FIG. 7  shows an embodiment of an onion topper  200  of the present invention not requiring the two-step process of employing a rough topper followed by a finish topper. Although referred to herein as an “onion” topper, it should be noted that the present device and the principles associated therewith may be applied to cutting the tops of any suitable bulb plant. Onion topper  200  is pulled behind a tractor or other vehicle, to which onion topper  200  is attached via hitch  228 . 
     Onion topper  200  includes fan assembly  218 , containing fan  310 , powered by the power take off (PTO) of the tractor or other vehicle used to pull onion topper  200 . The vehicle PTO drives fan drive  216  via a CV driveshaft (not shown). Fan assembly  218  draws air through intake nozzle assembly  214 , the force of the air being drawn therethrough causing the tops of the onions to stand more straight, and also causing the tops to be angled slightly to position the tops for more effective cutting. Intake nozzle assembly  214  includes an intake hood  235  having an adjustable front deflector  232 , the position of which can be adjusted in two directions. 
     The size of the opening in intake hood  235  through which air is drawn can be narrowed or widened by use of a screw, bolt, pin, or the like, positioned at various points along the plurality of openings  233 . Though not visible in the drawings, a complementary set of openings are provided on the other side of intake nozzle assembly  214 . Front deflector  232  can also be adjusted along the length of intake nozzle assembly  214 , extending forward so that front deflector  232  is in closer relation to a bed of onions or related crops, or may be retracted along the length of intake hood assembly  214 , such that front deflector  232  is further removed from the crop bed. It may be desirable to position front deflector  232  close to the crop bed when the tops of the crops are relatively short, while relatively long tops may be best cut when front deflector  232  is retracted along the length of intake nozzle assembly  214 . 
     Intake nozzle assembly  214  further includes adjustable side members  230  on either side of air intake hood  235 . Adjustable side members  230  are adjustable to better fit with the physical characteristics of the crop bed, to help ensure proper air flow into intake nozzle assembly  214  across a variety of crop beds. By adjusting intake nozzle assembly  214  using the various mechanisms described above, a user of onion topper  200  can adjust the air flow therethrough while maintaining operation fan  310  at a constant speed. The shape of intake nozzle assembly  214  may be adjusted according to characteristics of the crops being cut, the “mattress” of plant material atop the plant bed, characteristics of the soil, and the like, such that the tops will be held in optimal position for cutting and as little other debris as possible enters material separator  212 . 
     The tops of the onions or other crops, having been made to stand more straight by the action of air flowing into intake nozzle assembly  214 , are cut by cutter assembly  220 . Cutter assembly  220  includes a hydraulically-powered band saw, and is described in more detail below. The severed tops are pulled into material separator  212  The details of the internal structure of material separator  212  are provided, below. Air flow from intake nozzle assembly  214  is accelerated as it moves into material separator  212 , and thus the tops and other solid components in the air steam are likewise accelerated. The air stream bends within material separator  212 , curving toward fan assembly  218 , where the air stream will exit the system. The momentum of the onion tops carries them toward the rear of material separator  212 , into a dead space where the air stream is unable to support the tops any further. A continuously-moving screen  238  is provided within material separator  212  to intercept any material that remains in the air steam and attempts to move toward fan assembly  218 . 
     While the air stream bends toward fan assembly  218  and exits onion topper  200 , the onion tops that have been carried toward the rear of material separator  212  drop into chopper  226  through the separator&#39;s chopper outlet  372  (the chopper outlet being the outlet from the separator and into the chopper). Chopper  226  includes a plurality of rotating blades  244  that chop the tops into smaller pieces. These smaller pieces fall through air lock inlet  374  into airlock  240 , which includes a rotor that moves the pieces to the bottom of airlock  240 , allowing them to fall through air lock outlet  376  into screw conveyor  242  while maintaining an air tight seal between screw conveyor  242  and material separator  212  by maintaining the seal between the inlet and outlet of the air lock. Screw conveyor  242  uses a rotating action to move the chopped tops to either side of onion topper  200  (depending on the direction of rotation of screw conveyor  242 ), and allows the tops to fall from either or both of first and second side outlets  378  and  380  of onion topper  200  into the furrow between onion beds. Material separator  212  preferably includes at least one window to allow an operator to view the interior thereof. 
     In the embodiment of onion topper  200  shown in the figures, fan  310  is located downstream of the material separator outlet  320 . The fan  310  pulls air through intake hood  235 , through the interior space of material separator  212 , and out the fan outlet  320  of material separator  212 . It is contemplated that in some embodiments of the invention, however, the fan may be located within the material separator, positioned so as to move air in substantially the same manner as that shown. Any suitable placement of the fan may be used. 
       FIG. 8  is a cross-sectional view of onion topper  200 , providing a view of the internal structural thereof. The figure shows front deflector  232 , and provides a good view of the plurality of openings  233  that allow for up and down adjustment of front deflector  232  in order to make the opening of the intake nozzle assembly larger or smaller, according to the needs or desires of the user. As the airstream and any accompanying matter such as onion tops moves into intake hood  235 , the air stream reaches a first constriction  246 , where the intake hood attaches to material separator  212 . The airway continues to constrict slightly, reaching its narrowest point at second constriction  248  before opening into the larger portion of material separator  212 . The effect of these constrictions is to accelerate the air stream, and thus also to accelerate the material traveling within the air stream. By the time the air stream reaches the larger internal space of material separator  212 , the onion tops and other solid matter traveling in the air stream has sufficient velocity to be propelled toward the rear of onion topper  200  even though the air stream begins immediately to bend toward fan assembly  218 . The opening of material separator  212  into a larger internal space decreases the air velocity so that it is insufficient to stop the momentum of the cut tops toward the back of the device. 
     When the air steam begins to bend toward fan assembly  218  immediately following second constriction  248 , it is possible that a small percentage of the onion tops will be pulled upward by the motion of the air, instead of traveling toward the rear of onion topper  200 . A continuously moving screen  238  is provided within material separator  212  to trap those portions of the onion tops that are not carried directly to the rear of onion topper  200 . Screen  238  moves in the direction of the rear of onion topper  200 , so that onion tops impacting screen  238  are pressed against screen  238  and moved toward the back of the device. As the onion tops reach the rear-most portion of screen  238 , they enter the dead zone within material separator  212  and drop from the screen, being carried into chopper  226  along with the bulk of the onion tops. 
       FIG. 9  is an exploded view of one embodiment of a chopper-extractor assembly  226  of the present invention. As can be seen in the figure, chopper  254  makes up the upper portion of chopper-extractor assembly  226 , while air lock  240  makes up the lower portion. Chopper-extractor assembly  226  includes a housing  252  with an upper compartment for receiving chopper  254  therein. Chopper  254  includes a first shaft  256  and a second shaft  258 , each of which has a plurality of blades  244  disposed thereon. During operation of onion topper  200 , first shaft  256  and second shaft  258  rotate in opposing directions, each toward the center of chopper-extractor assembly  226 . Onion tops falling into chopper-extractor assembly  226  are chopped into smaller pieces by the action of chopper  254 . These smaller pieces have an easier time passing through air lock  240 , and also decrease the volume of material deposited into the furrow. The smaller pieces will also dry faster in the furrow as compared to full-size onion tops. 
     As the chopped portions of the onion tops leave chopper  254  they fall into air lock  240 . Air lock  240  includes a rotor  260  having a plurality of fins  250 , the edge of each of the fins  250  being in air tight relationship to the interior walls of air lock  240 . The rotation of rotor  260  allows the chopped pieces of the onion tops to be passed to screw conveyor  242  without disrupting the air flow in material separator  212  and without providing an opening through which fan assembly  218  can pull air. A shear blade  322  present within air lock  240  severs onion tops that rest on or around fins  250  as rotor  260  rotates. 
       FIG. 10  provides a more detailed view of rotor  260 . As can be seen, fins  250  have seals  262  associated therewith, the seals providing the air tight connection with the interior wall of air lock  240 . A seal backing plate  264  is provided to allow seal  262  to be firmly attached to a fin  250 . It is contemplated, however, that any suitable structure for sealing rotor  260  may be used. Rotor shaft  266  provides for rotation of rotor  260 , thereby moving cut onion top material away from chopper  254  and toward screw conveyor  242 . 
       FIG. 11  provides an exploded view of screw conveyor  242  showing the details thereof. Screw conveyor  242  includes a conveyor housing  268 , which is open at the top to receive the pieces of chopped onion tops exiting air lock  240 . Within conveyor housing  268  are first screw  270  and second screw  272 . During operation of the device, one or both of the screws  270  and  272  may be in operation. The rotational movement of screws  270  and  272  causes movement of the chopped onion top material along the length of screw conveyor  240 . Depending on the direction of rotation, onion top material can be directed to one side of onion topper  200  or the other. Alternatively, if each of screws  270  and  272  is rotated in an opposite direction, onion top material may be deposited on both sides of onion topper  200  simultaneously. 
       FIG. 12  shows an exploded view of cutter assembly  220 . Cutter assembly includes a first cutter wheel  274  and a second cutter wheel  276  on which a flexible band saw blade  314  (shown in other drawings and described in greater detail, below) is mounted. When onion topper  200  is in use, the rotational movement of first cutter wheel  274  and second cutter wheel  276 , which may be driven by a single hydraulic motor  290 , for example, causes a corresponding movement of the band saw blade, which cuts through onion tops when the blade encounters them as onion topper  200  moves across an onion bed. A blade tensioner  278  is provided, along with an adjustment knob  288 , so that a user of the device can adjust the tension of the band saw blade. First and second saw guards  280  and  282  are provided at opposing ends of cutter assembly  220  to protect against injury when onion topper  200  is in use. First cutter wheel  274  and second cutter wheel  276  are preferably offset at an angle with respect to the horizontal plane of band saw blade  314 . In the embodiment shown in the figures, first cutter wheel  274  and second cutter wheel  276  are offset at a twenty-five degree angle. 
     Cutter assembly  220  further includes two guide rollers  286  and two center guides  284  to ensure a proper path of travel for the band saw blade.  FIG. 13  depicts one embodiment of a guide roller  286  for use with the present invention. The guide roller  286  shown is positioned on the left side of cutter assembly  220  (the term ‘left’ being based on the perspective of an operator traveling in the direction of onion topper  200 ). As shown in  FIG. 13 , guide roller  286  includes a top roller  294  and a bottom roller  292 , each of which includes a plurality of bearings  296  that rotate with the motion of the band saw blade. 
       FIG. 14  shows an exploded view of a center guide  284 . Center guide  284  includes a rail  298  that is attached to the cutter assembly  220 . The rail has a slot that receives a portion of bar  300 . Bar  300  can be moved along the length of slot  308  of rail  298  to allow for variable positioning of center guide  284 . As with the guide rollers  286  positioned toward the left and right ends of cutter assembly  220 , center guides  284  also include a plurality of bearings  302 . Bearings  302  are attached to bar  300  using a shoulder bolt  304 . Bar  300  is held in place at the desired location within slot  308  by adjustment screw  306 . 
     As best shown in  FIG. 17 , guide rollers  286  and center guide  284  define the shape of the blade path for band saw blade  314 . Guide rollers  286 , positioned toward the outer sides of cutter assembly  220 , may be placed slightly lower than the more centrally-positioned center guides  284 . This is because the crop bed is crowned, with crops at the edges of the bed positioned slightly lower in the soil than those nearer the center of the bed, and the slight angling of band saw blade  314  allows onion topper  200  to maintain a more consistent cut profile across the width of the device. It should be noted that the relative height of guide rollers  286  and center guides  284  are easily adjusted with respect to one another and also with respect to the crop bed. The side to side position of guide rollers  286  and center guides  284  may also be adjusted. Further, the tension in band saw blade  314  is easily adjusted using adjustment knob  288 . Finally, an operator can easily adjust the tracking of band saw blade  314  along the various cutter wheels and guides when necessary. 
     Some embodiments of cutter assembly  220  may also include blade scrapers to keep dirt and other debris from building up on band saw blade  314  and interfering with the normal operation of onion topper  200 . In one embodiment of onion topper  200 , the band saw blade scraper includes two spring-steel blades held by adjustable blocks located at the top and bottom sides of band saw blade  314 . The adjustable blocks may hold the scraper blades at a forty-five degree angle to band saw blade  314 , for example. The adjustable blocks can be loosened, pushed inward toward one another, and then tightened in order to hold the scrapers tight against band saw blade  314 . When onion topper  200  is in operation, the tight positioning of the scrapers with respect to band saw blade  314  allows the scrapers to keep both the upper and lower surfaces of band saw blade  314  free of debris. 
     In another embodiment of onion topper  200 , a blade scraper such as that shown in  FIG. 18  may be utilized. As shown in the figure, blade scraper  324  includes a first arm  326  and a second arm  328 , which mirror one another. The end of each of arms  326  and  328  has a carbide insert  330  rotatably attached thereto. The rotation of carbide insert  330  is such that it can match the angle of band saw blade  314 . First and second arms  326  and  328  are attached to a pivot  332 , and also attached to each other by spring  334 . Spring  334  applies even pressure to both of arms  326  and  328  and ensures that the carbide inserts  330  are in constant contact with band saw blade  314 . The arms  326  and  328  and the carbide insert  330  attached to each are angled to aid in scraping band saw blade  314  and to direct debris away from the wheels. 
     Onion topper  200  provides for both steering of the device, and for side to side lateral adjustment, so that the height of cutter assembly  220  can be adjusted as necessary according to the physical conditions of the crop bed. The steering and side to side adjustments can be accomplished by hydraulic or mechanical action, or by a combination of the two. In the embodiment of onion topper  200  shown in the figures, the turning of gauge wheels  222  for purposes of steering is accomplished by hydraulic cylinder  234 . In  FIG. 7 , a hydraulic cylinder  234  is shown in the drawings. It should be noted that a corresponding steering rod (not shown) controls a second gauge wheel  222 , which is located on the opposite side of the device from the gauge wheel  222  shown in the figure. The action of hydraulic cylinders  234  is controlled via an operator within the cab of a tractor pulling onion topper  200 . The operator can control the steering of gauge wheels  222  independently of the steering of the tractor itself, allowing the operator to make adjustments to the position of onion topper  200  along a crop bed without adjusting the direction of the tractor. 
     In addition to steering onion topper  200  by adjusting the position of gauge wheels  222 , an operator of onion topper  200  can also make side to side, lateral adjustments of onion topper  200 , thereby adjusting the position of cutter assembly  220 . It should be noted that differential side to side adjustment, such that one side of the device can be raised or lowered independently of the other, allows cutter assembly  220  to be positioned such that it is higher or lower, with respect to onion topper  200  as a whole, on one side versus the other. As shown in  FIG. 7 , onion topper  200  includes a vertical adjustment cylinder  236 . Vertical adjustment cylinder  236  can be actuated by mechanical or hydraulic means, or by a combination of the two. An operator in the cab of a tractor or other vehicle pulling onion topper  200  can raise or lower vertical adjustment cylinder  236  along the length of vertical shaft  237 . It will be appreciated from the drawings that when vertical adjustment cylinder  236  is adjusted along the length of vertical shaft  237 , the corresponding side of onion topper  200 , including cutter assembly  220 , is also raised or lowered. Although  FIG. 7  only shows one side of onion topper  200 , it is to be understood that a corresponding structure is present on the opposite side of onion topper  200  for raising or lowering the opposite side of onion topper  200  in the same manner. 
     As can be seen from the drawings, an operator in the cab of a tractor pulling onion topper  200  will not have a good line of sight to gauge wheels  222 , and will not be able to see the height of cutter assembly  220  in relation to the crop bed. In order to provide the operator with the information necessary to make adjustments to the steering or height of onion topper  200 , cameras  308  are provided at various points along the structure of onion topper  200 . As shown in  FIG. 15 , for example, a camera  308  is provided near the bottom of the chopper-extractor housing  252 . Also as shown in the figure, additional cameras  308  are mounted from the underside of material separator  212 . Cameras  308  are pointed toward the interior of onion topper  200 , thereby being positioned to record the activity of onion topper  200  at the point of cutter assembly  220 , and also to provide a view of the position of gauge wheels  222  as onion topper  200  moves along a crop bed. The operator of the device has access to video monitors within the cab of the tractor pulling onion topper  200 . The video monitors display in real time the video recorded by cameras  308 . It is contemplated that cameras  308  transmit the video image to the monitors in the cab via a wired connection, though in some embodiments of the invention a wireless connection may be provided. Further, in some embodiments of the invention, the operator may be able to make adjustments to the field of view of cameras  308  by pivoting the cameras  308  up and down or side to side using controls within the cab of the tractor. Fewer or more cameras  308  may be provided, and they may be provided in locations other than those shown in the drawings. 
       FIG. 16  shows the position of rotating flippers  312 , which may be used in some embodiments of onion topper  200 . Rotating flippers  312  are positioned on either side of onion topper  200  such that they contact the tops of onions or other crops nearest the furrows flanking the crop bed. These tops are, in some cases, less likely to be made to stand up appropriately by the action of air flow through intake nozzle assembly  214  alone. The action of rotating flippers  312  pushes the tops of the plant up sufficiently for the tops to be caught and held in place by the air flowing into intake nozzle assembly  214 . It is contemplated that a variety of shapes and sizes of rotating flippers  312  may be utilized, depending on the conditions of the crop bed, the characteristics of the plants being cut, and the like. 
       FIG. 19  depicts and exploded view of another embodiment of a flipper suitable for use with the present onion topper  200 . Conical flipper  336  rotates to lift onion tops from the furrow so that they can be properly positioned for cutting by band saw blade  314 . Conical flipper  336  may be constructed from rubber or other suitable material that will grab the onion tops as it rotates. As shown in the figure, an outer cone  338  is provided for lifting the onion tops. Within outer cone  338 , an inner cone  340  is provided, the exterior surface of inner cone  340  engaging the inner surface of outer cone  338  such that when inner cone  340  rotates, there is a corresponding rotation of outer cone  338 . A plate  342  is attached to a rear surface of inner cone  340 , and the plate  342  includes an opening to receive the shaft  346  of a hydraulic motor  344 . The entire assembly is mounted to onion topper  200  via mount  348 . In operation, a conical flipper  336  is located on each side of onion topper  200 , at roughly the same location as the flippers shown in  FIG. 16 . The two conical flippers  336  rotate in opposite directions, actuated by separate hydraulic motors, and lift onion tops out of the furrow, positioning them to be grabbed by the air flow into onion topper  200  so they will be available for cutting by band saw blade  314 . 
     Example 1 
     Certain dimensions and other characteristics of an exemplary embodiment of onion topper  200  are now described. It should be noted that the information provided here, as well as above with respect to the embodiments of the invention shown in the figures, are intended to be exemplary and are not meant to limit the invention. 
     In the embodiment of onion topper  200  depicted in  FIG. 8 , second constriction  248  has a width of approximately six inches, providing a choke point for acceleration of the air stream entering material separator  212 . The rearward portion of material separator  212  disposed above chopper-extractor housing  252  has a width of approximately 16.2 inches, and constitutes a dead space in which tops cut by the device are not significantly impacted by the air stream flowing through material separator  212 . The height of the opening between this rearward portion of material separator  212  and the larger interior space of material separator  212  is approximately 9.7 inches. The curvature of the top of material separator  212  has a first radius at point  316  of approximately thirty inches, the curvature then inverting to a second radius at point  318 , also of approximately thirty inches. The height of material separator  212  at exit  320  is approximately 21.4 inches. Band saw blade  314  in the exemplary embodiment is one inch wide and approximately 0.035 inches thick. 
     The exemplary device described above may be operated at a fan speed of from 1500 to 2000 rpm, and the device itself may travel along the crop bed at a speed of from about 0.5 to about 1.0 mph. It should be noted that any of these speeds may be varied as necessary or desirable depending on characteristics of a specific crop bed and crop. 
       FIG. 20  depicts the operator controls for the exemplary device. The controls are provided within a tractor pulling onion topper  200 . As can be seen in the figure, a display  350  is provided so that the operator can see the views recorded by various cameras  308 . Control switches are provided for operating various components of the system, including a master switch  352 , a switch  354  for controlling the band saw blade, a switch  356  for controlling the continuously-moving screen, a switch  358  for controlling the flipper, a switch  360  for controlling the chopper, a switch  362  for controlling the air lock, and a switch  364  for left and right control of the screw conveyor. Steering control  366  is also provided, as is a control  368  for adjusting the height of the left side of onion topper  200 , and a control  370  for adjusting the right side of onion topper  200 . 
     Various modifications to the disclosed invention will be readily apparent to those of skill in the art upon reading this disclosure. These are considered within the spirit and scope of the present invention.