Abstract:
A seed sensor for an agricultural planter adapted to be disposed proximate an egress end of a seed tube through which seeds pass during planting operations. The seed sensor capable of generating an output signal corresponding to the passage of seed therethrough.

Description:
BACKGROUND 
     In conventional planters, seed sensors are employed to detect the passage of seed through the seed tube. There are various types of sensors suitable for detecting seeds passing through a seed tube, but the most common sensor is a photoelectric or optical sensor, such as the type distributed by Dickey-John Corporation of Auburn, Ill. As disclosed in U.S. Pat. No. 7,152,540 (“the &#39;540 patent”), incorporated herein by reference, photoelectric seed sensors generally include a light source element and a light receiving element or detector disposed over apertures in the forward and rearward walls of the seed tube. When a seed passes between the light source and the detector, the seed interrupts the light beam. When the light beam is interrupted a signal pulse is generated indicating the passage of a seed. The generated signal pulse is communicated to the planter monitor (not shown). The planter monitor counts the signal pulses for purposes of determining seed count or population as well as monitoring the time between signal pulses for purposes of determining seed spacing. In addition to determining seed count and seed spacing, if the time interval between generated signal pulses exceeds a predefined time period, the monitor is typically configured to provide an audible and/or visual alarm to indicate to the operator that there is a problem with the particular row unit, such as the seed hopper running empty or a malfunction of the seed meter or the sensor. 
     In conventional planters the seed sensors are mounted near the midpoint of the seed tube to protect the sensor from damage during planting operations as well as to minimize ambient light, dust and particulate matter interfering with the light beam. However, it is well known that by the time the seeds pass through the seed tube before being deposited into the seed furrow, the actual in-furrow seed-to-seed spacing can vary dramatically from the seed-to-seed spacing detected by the seed sensor at the midpoint of the seed tube. This is due to the fact that no matter how uniformly spaced the seed meter may dispense sequential seeds into the seed tube, seed ricochet within the seed tube as the seed passes through the tube can significantly affect the velocities of the seeds as they exit the tube. 
     Seed ricochet off the sidewalls of the seed tube may be caused by the seed not entering the seed tube at the proper location, or due to irregularities or obstructions along the path of travel of the seed within the seed tube, or due to changes in vertical accelerations caused by the row unit encountering dirt clods, crop residue, rocks or changes in terrain as the planter traverses the field. If one seed ricochets more or less than an adjacent seed as it passes through the seed tube, it can result in significant irregularities or differences in the spatial placement between adjacent seeds within the furrow. For example, if one seed ricochets off the sidewalls of the seed tube three times before exiting the seed tube versus a seed that does not ricochet at all, or a seed that only ricochets once or twice, seeds experiencing more ricochet will exit the seed tube at a slower velocity than those experiencing fewer ricochets. This difference in seed velocity upon exiting the seed tube results in inconsistent seed-to-seed spacing in the furrow. 
     Thus, to more accurately reflect the actual in-furrow seed-to-seed placement, ideally the seed sensor should be placed at or near the bottom of the seed tube. However, for the reasons identified above, an optical sensor would be rendered non-functional if it was positioned at or near the end of the seed tube because the ambient light, dust and particulate matter would interfere with the light beam. Accordingly, there is a need for a seed sensor that can be mounted at or near the bottom or egress end of the seed tube and which can withstand the environmental conditions at such a location while still accurately detecting the passage of seeds as they exit or are about to exit the seed tube. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a conventional row unit with a conventional seed sensor mounted in a conventional manner at about the midpoint of the seed tube. 
         FIG. 2  is a partial rear elevation view of the row unit of  FIG. 1  as viewed along lines  2 - 2  showing the furrow opening discs in relation to the seed tube. 
         FIG. 3  illustrates a conventional row unit with an embodiment of an electromagnetic seed sensor mounted to a conventional seed tube at or near the bottom end of the seed tube. 
         FIGS. 4A-4C  illustrate various views of the electromagnetic seed sensor of  FIG. 3  mounted at or near the bottom end of a conventional seed tube. 
         FIG. 5  is a partial rear elevation view of the row unit of  FIG. 3  as viewed along lines  5 - 5  showing the furrow opening discs in relation to the seed tube and electromagnetic seed sensor mounted thereon. 
         FIG. 6  is a side-by-side comparison of a conventional seed tube and the same conventional seed tube as modified with the electromagnetic seed sensor mounted at the end thereof. 
         FIG. 7  is an exploded perspective view of the embodiment of the electromagnetic energy sensor of  FIG. 3 . 
         FIG. 8A  is a perspective view of the liner of the electromagnetic sensor of  FIG. 3 . 
         FIG. 8B  is a side elevation view of the liner of  FIG. 8A . 
         FIG. 8C  is a top plan view of the liner of  FIG. 8B . 
         FIG. 8D  is a left side elevation view of the liner of  FIG. 8B . 
         FIG. 9A  is a perspective view of the housing of the electromagnetic sensor of  FIG. 3 . 
         FIG. 9B  is a side elevation view of the housing of the electromagnetic sensor of  FIG. 9A . 
     
    
    
     DESCRIPTION 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1  illustrates a single row unit  10  of a conventional row crop planter. As is well known in the art, the row units  10  are mounted in spaced relation along the length of a transverse toolbar  12  by a parallel linkage  14  which permits each row unit  10  to move vertically independently of the toolbar and the other spaced row units in order to accommodate changes in terrain or upon the row unit encountering a rock or other obstruction as the planter is drawn through the field. Each row unit  10  includes a frame  16  which operably supports a seed hopper  18 , a furrow opening assembly  20 , a seed meter  44 , a seed tube  46  and a furrow closing assembly  50 . 
     The furrow opening assembly  20  comprises a pair of furrow opening discs  22 ,  24  which are rotatably mounted on shafts  26 ,  28  secured to a shank  30  comprising a part of the row unit frame  16 . The furrow opening assembly  20  further comprises a pair of gauge wheels  32 ,  34  rotatably supported by gauge wheel arms  35 ,  37  also secured to the frame  16 . As best illustrated in  FIG. 2 , which shows the furrow opening assembly  20  as viewed along lines  2 - 2  of  FIG. 1 , the discs  22 ,  24  are canted at an angle such that their outer peripheries come in close contact at the point of entry into the soil  36  and diverge outwardly and upwardly away from the direction of travel of the planter as indicated by arrow  38 . Thus as the planter is drawn through the field, the rotating discs  22 ,  24  cut a V-shaped furrow  40  through the soil surface. The egress end of the seed tube  46  is disposed between the rearwardly diverging furrow opening discs  22 ,  24 . 
     In operation, as the planter is drawn through the field, the seed hopper  18  communicates a constant supply of seeds  42  to the seed meter  44 . The seed meter  44  meters or dispenses individual seeds  42  at regularly spaced intervals into the seed tube  46 . The seed tube  46  directs the seeds downwardly and rearwardly between the diverging furrow opening discs  22 ,  24  before depositing the seeds into the V-shaped furrow  40 . The seeds are then covered with soil by the furrow closing assembly  50 . A conventional optical seed sensor  60 , comprising a light source  62  and a light detector  64  is shown mounted at the conventional location at about the midpoint of the seed tube  46 . 
       FIG. 3  illustrates the same row unit  10  as in  FIG. 1 , but with the conventional optical seed sensor  60  replaced with an embodiment of an electromagnetic energy sensor  100  for detecting the passage of seeds (hereinafter “the sensor  100 ”). The sensor  100  preferably operates under the principals as described in U.S. Pat. Nos. 6,208,255 and 6,346,888 (hereinafter “the &#39;255 and &#39;888 patents”), both of which are incorporated herein in their entireties by reference, and is preferably substantially in accordance with the sensors disclosed therein. 
     As best shown in  FIGS. 4A-4C  and  5 - 6  the sensor  100  is preferably mounted at or near the bottom end of the seed tube  46  and is preferably sized and configured so that when mounted to the end of the seed on the planter it will fit between the furrow opening discs  22 ,  24  and will ride just above the soil surface during planting operations. 
     The preferred configuration of the sensor  100  in relation to the seed tube  46  is best illustrated in  FIGS. 4A-4C  and  6 . It should be appreciated that the seed tube  46  may be any conventional or later developed seed tube and that the present invention is not limited to any particular shape or configuration of a seed tube. As illustrated, the seed tube  46  includes a rearwardly curving front wall  45  and rear wall  47  and opposing side walls  49  which together define a rearwardly curving passageway. Seeds dispensed by the seed meter  44  enter the open top end  41  of the seed tube  46  and are guided or directed downwardly and rearwardly through the passageway before exiting the seed tube  46  at the lower egress end  43 . The seed tube  46  may include hooks or mounting ears as is conventional for mounting to the shank  30  and/or other mounting points of the row unit frame  16 . 
     Although the sensor  100  is preferably positioned at the egress end  43  of seed tube  46  to better reflect the in-furrow seed-to-seed placement as described above, the sensor  100  may be located anywhere along the passageway of the seed tube  46 . It should also be appreciated that the configuration of the sensor  100  may also vary depending on the configuration of the seed tube and the position and spacing between the furrow opening discs (or disc depending on the make and model of planter), as well as other factors associated with the planter. 
       FIG. 7  shows an exploded perspective view of the sensor  100 . The sensor  100  preferably includes an access cover  110 , a lead  120 , a connector  130 , circuitry  150 , a liner  160 , and a housing  170  within which is received the liner  160  and circuitry  150 . 
     The circuitry  150  includes a transmitter  152 , a detector  154  and a circuit board  156 . The transmitter  152  and detector  154  preferably comprising copper electrodes mounted to the substrate of the circuit board  156 . U.S. Pat. Nos. 6,208,255 and 6,346,888, previously incorporated herein by reference, disclose the circuitry incorporated into the circuit board  156 . As will become apparent, when the sensor  100  is assembled, the transmitter  152  and detector  154  are disposed on either side of the liner  160  and within housing  170  so as to detect the seeds passing therebetween. 
     As best illustrated in  FIGS. 8A-8D , the liner  160  is preferably formed of plastic or other suitable material and includes sidewalls  161 ,  162  and front and rear walls  163 ,  164  which together define a through opening  166  through which the seeds will pass upon exiting the end of the seed tube  46 . The through opening  166  of the liner  160  is preferably configured and sized so as not to obstruct or interfere with the trajectory of the seeds exiting the egress end  43  of the seed tube  46 . The exterior of the sidewalls  162  preferably include guides  168  which slideably receive the transmitter  152  and detector  154 . The liner  160  further includes a boss  167  for receiving a threaded connector for securing the circuit board  156  thereto. The exterior of the sidewalls  162  also preferably include spacers  169  the purpose of which will be described later. 
     As shown in  FIGS. 9A and 9B , the housing  170  includes a top opening  172  and a bottom opening  174 . As best illustrated in  FIG. 6 , the top opening  172  is sized and configured to receive the bottom end of the seed tube  46  without obstructing the opening of the seed tube so as not to interfere with the trajectory of the seed as it exits the seed tube. The bottom opening  174  is also configured so as not to interfere with the trajectory of the seed as it exits the seed tube. The housing  170  further preferably includes an upper leg  176  configured to receive the upper portion of the circuit board  156  and to align with the rearward wall  47  of the seed tube  46 . Ears  178  are preferably formed in the upper leg  176  for receiving a threaded fasteners for securing the access cover  110  thereto. The housing  170  further includes side walls  180 ,  181  and a front wall  182  which define a cavity  184  sized and configured to received the liner  160  and circuitry  150 . A boss  186  is preferably formed within the upper leg  176  for securing the circuit board  156  thereto with a threaded fastener. The sidewalls  180  of the housing  170  preferably include sockets  188  for receiving wear inserts  190  positioned where the furrow opening discs  22 ,  24  are likely to contact or rub against the housing  170  during planting operations. The wear inserts are preferably made of a relatively hard wear-resistant material such as tungsten carbide or other suitable wear resistant material. 
     The cover  110  includes ears  112  which mate with the ears  178  in the housing  170  for securing by threaded fasteners thereby enclosing the circuitry  150 . Preferably, before the cover  110  is secured to the housing  170 , a non-conducting gel (not shown), such as epoxy or other potting compounds as are known in the art, is poured over the circuitry  150  filling the interior volume between the cover  110  and circuit board  156  and between the housing  170  and liner  160  to protect the sensor circuitry from moisture and impact. 
     In operation, the sensor  100  generates electromagnetic energy at the transmitter  152  which is received by the detector  154  disposed on the opposite wall of the liner  160  between which is the through opening  166  through which the seed passes as it exits the seed tube  46 . The transmitter  152  is preferably a sine wave generator, the design of which is familiar to those skilled in the art, such as an oscillator as disclosed in the &#39;255 and &#39;888 patents. The electromagnetic energy generated by the transmitter  152  is detected at the detector  154  using an element incorporated in the circuit board  156 , such as a mixer model ADEX-10L+ also available from Mini-Circuits Fort Wayne LLC. The circuit board  156  generates an output signal related to the magnitude and phase of electromagnetic energy detected at the detector  154 . The output signal is communicated through lead  120  and connector  130  to a planter monitor (not shown) having a processing module. The circuit board  156  preferably draws power through lead  120  and connector  130  from a power supply, such that lead  120  preferably comprises a harness containing electrical connections for transmitting signals from the sensor  100  and for transmitting power to the sensor  100 . 
     When seeds pass through the through opening  166  and between the transmitter  152  and the detector  154 , the output signal generated by circuit board  156  is modified because the seed perturbs the electromagnetic energy detected by the detector  154 . This variation may be used by a planter monitor or similar systems to record the time at which each seed has been released as is well known in the art and therefore does not warrant further description here. 
     The perturbation in the electromagnetic energy caused by a seed passing between the transmitter  152  and detector  154  is distinguishable from the perturbation caused by dust or other particles because the variation in signal caused by a dust will be smaller than that of a seed which has a much larger dielectric mass. Thus, the sensor  100  can clearly and accurately distinguish between seeds, dust and other particulate matter and is therefore capable of being used in environments such as at the egress end of the seed tube, where an optical sensor would not be capable of functioning accurately. For example, with an optical sensor, a plume of dust may cause a comparable light obstruction to a seed and cause erroneous readings by an optical sensor. Additionally, the sensor  100  has no sensitivity to increased ambient light near the bottom of the seed tube as does an optical sensor. 
     While the sensor  100  has advantages over an optical sensor as described above and therefore may be placed at or near the egress end of the seed tube between the furrow opening discs  22 ,  24 , certain factors must be taken into consideration when placing an electromagnetic generator near or between electrically conductive opening discs  22 ,  24 . Because each opening disc  22 ,  24  constitutes a moving conductor, the presence of the magnetic field causes eddy currents to form in the opening discs. Each such eddy current induces a magnetic field tending to oppose the field that created it. Thus the rotation of nearby furrow opening discs  22 ,  24  will cause secondary magnetic fields that are received by the detector  154 , resulting in significant interference in the signal produced by the sensor  100 . Experimental data have shown that when the detector  154  is located near the bottom of the seed tube  46  and within approximately one centimeter of either of the inner surfaces of opening discs  22 ,  24 , eddy currents interfere with sensor operation. 
     Thus, the transmitter  152  and detector  154  are preferably magnetically shielded by a structure having a relative permeability preferably between the ranges of about 100 to 10,000, but preferably the relative permeability is around 600. Such relative permeability may be achieved by making the housing  170  out of ferromagnetic materials such as iron, cobalt or nickel, or from an alloy such as mu-metal, permendur, permalloy, steel, alfenol or rhometal. The high effective permeability is particularly important in the lateral sidewalls  180 ,  181  of the housing because the lateral sidewalls are disposed between the opening discs  22 ,  24  and the transmitter and receiver  152 ,  154 . With such external shielding in place, the magnetic field generated by transmitter  152  is prevented from reaching the opening discs  22 ,  24  (and thus prevented from forming eddy currents in the opening discs), and any external magnetic fields are prevented from reaching the detector  154 . 
     Experimental data have shown that the sensitivity of the detector  154  is reduced near the distal and proximal ends of the detector furthest from the circuit board  156 . Thus, as best seen in  FIG. 8B , the lower surface of the liner  160  is preferably separated by a distance D from the interior surface of housing  170 , while the detector  154  and transmitter  152  continue past the lower surface of the liner  160  toward the inner surface of housing  170 . Thus, as may be observed in  FIG. 8B , seeds do not pass by the less sensitive distal or proximal send of detector  154 . Because the lower surface of liner  160  does not contact the housing  170 , the spacers  169  serve to contact the housing and hold the liner in place. 
     An additional advantageous function of the liner  160  is that the guides  168  prevent substantial deflection of the transmitter  152  and detector  154 , as best illustrated in  FIG. 8B . Experimental data have shown that deflection of either the transmitter or detector can interfere with the signal produced by the sensor  100 . The gel (not shown) filling the interior volume between the housing  170  and liner  160  also limits deflection of the transmitter  152  and detector  154 . It will be appreciated that the same function may be accomplished by any suitable means preventing deflection of the transmitter  152  or the detector  154 . 
     The foregoing description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment of the apparatus, and the general principles and features of the system and methods described herein will be readily apparent to those of skill in the art. Thus, the present invention is not to be limited to the embodiments of the apparatus, system and methods described above and illustrated in the drawing figures, but is to be accorded the widest scope consistent with the spirit and scope of the appended claims.