Abstract:
A hub assembly for a seed disk has a conical surface that mates with a cylindrical edge on a hub portion of a seed disk to establish the concentricity of the two components. A pair of paddles on the hub are received in, and inter-fit with corresponding recesses on the seed disk to provide torque transmission. A retention element holds the two components together.

Description:
FIELD OF THE INVENTION 
   The present invention relates to agricultural seeding machines, and, more particularly, to hubs for seed disks used to meter seeds for placement in a seed trench. 
   BACKGROUND OF THE INVENTION 
   An agricultural seeding machine such as a row crop planter or grain drill places seeds at a desired depth within a plurality of parallel seed trenches formed in soil. In the case of a row crop planter, a plurality of row crop units are typically ground driven using wheels, shafts, sprockets, transfer cases, chains and the like. Each row crop unit has a frame which is moveably coupled with a tool bar. The frame may carry a main seed hopper, herbicide hopper and insecticide hopper. If a granular herbicide and insecticide are used, the metering mechanisms associated with dispensing the granular product into the seed trench are relatively simple. On the other hand, the mechanisms necessary to properly meter the seeds, dispense the seeds at a predetermined rate and place the seeds at predetermined relative locations within the seed trench are relatively complicated. 
   The mechanisms associated with metering and placing the seeds generally can be divided into a seed metering system and a seed placement system which are in communication with each other. The seed metering system receives the seeds in a bulk manner from the seed hopper carried by the frame. Different types of seed metering systems may be used such as seed plates, finger plates, and seed disks. In the case of a seed disk metering system, a seed disk is formed with a plurality of seed cells spaced about the periphery thereof. Seeds are moved into the seed cells, with one or more seeds in each seed cell depending upon the size and configuration of the seed cell. A vacuum or positive pressure air may be used in conjunction with the seed disk to assist in movement of the seeds into the seed cells. The seeds are singulated and discharged at a predetermined rate to the seed placement system. 
   The seed placement system may be categorized as a gravity drop system or a power drop system. In the case of a gravity drop system, a seed tube has an inlet end which is positioned below the seed metering system. The singulated seeds from the seed metering system merely drop into the seed tube and fall via gravitational force from a discharge end thereof into the seed trench. The seed tube may be curved in a rearward manner to assist in directing seed into the seed trench. The rearward curvature also assists in reducing bouncing of the seeds back and forth within the tube as it falls into the seed trench. Further, the rearward curvature reduces bouncing of the seed as it strikes the bottom of the seed trench. 
   A seed placement system of the power drop variety generally can be classified as a seed conveyor belt drop, rotary valve drop, chain drop or air drop. These types of seed placement systems provide more consistent placement of the seeds along a predetermined path at a desired spacing. 
   Certain seed types, notably flat corn seed with insecticide or other treatments, are difficult for vacuum meters to singulate. Poor singulation of difficult seed types is characterized by doubles, skips, and bunches of seed carried by the disk. Doubles and skips refer to multiple seeds and no seed respectively in each seed cell. Bunches are multiple seeds carried up by the seed pool accelerators which protrude from the surface of the seed disk. These seed types generally are best planted with a flat seed disk in combination with double eliminator. Compared to a celled disk, a flat disk has less favorable seed trajectory into the seed tube, generally requires more vacuum, and a production “double eliminator” adjustment is difficult. 
   The seed disk is an integral and key part of the seeding machine in that it performs the function of separating seeds into individual elements. It is therefore important that the seed disk be concentric with its drive mechanism that is journaled within the seeding machine. Manufacturing of the seed disk entails the establishment of tolerances for a multiplicity of surfaces which increases the cost of manufacturing and increases the probability of missed tolerances. 
   What is needed in the art is an effective hub for a seed metering disk that enables simplified and precise positioning. 
   SUMMARY OF THE INVENTION 
   The invention includes a drive hub for connecting a drive spindle to a seed disk. The drive hub includes a cylindrical element connected to one of the seed disk and drive spindle, the cylindrical element having a circular edge at one end thereof. A conical element is connected to the other of the seed disk and drive spindle. The conical element is received in the one end of the cylindrical element to pilot the conical element and cylindrical element relative to each other. The conical element and the cylindrical element inter-fit to transmit torque therebetween. 
   In another form the invention includes a seed metering assembly having a seed metering disk substantially circular and rotating about a central axis. A drive spindle is provided for the metering disk and is rotatable about the same axis. A drive hub connects the drive spindle to the seed disk and comprises a cylindrical element connected to one of the seed disk and drive spindle. The cylindrical element has a circular edge on one end thereof and a conical element connected to the other of the seed disk and drive element is received in the one end of the cylindrical element to pilot the conical element and cylindrical element relative to each other. The conical element and the cylindrical element inter-fit to transmit torque therebetween. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a seed metering machine; 
       FIG. 2  is a perspective view of a drive hub used in the seed metering machine of  FIG. 1 ; 
       FIG. 3  is a perspective view of the drive hub of  FIG. 2  in with a drive spindle and retention device; 
       FIG. 4  is a perspective view of  FIG. 2  and the seek disk of  FIG. 1  showing a relative position for assembly; 
       FIG. 5  is a perspective view of the hub of  FIG. 2  and the seed disk of  FIG. 1  in the installed position; 
       FIG. 6  is a perspective view of the assembled hub of  FIG. 2  and disk of  FIG. 1  without the spindle and associated elements taken on lines  6 - 6  of  FIG. 5 ; and 
       FIG. 7  is a partial perspective view of the hub of  FIG. 2  and the disk of  FIG. 1  showing a portion of the drive spindle assembly and associated elements. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a seed meter, generally indicated by reference character  10 , is incorporated in a seeding machine (not shown). The seeding machine has many additional features such as a main hopper or seed air pump to deliver seed to individual seed meters of which unit  10  is one of multiple units. Details of such an overall system may be found in U.S. Pat. No. 6,758,153, of common assignment with this invention, the disclosure of which is hereby incorporated in its entirety. The seed meter  10  includes a housing  12  and a seed hopper  14  which receives an appropriate supply of seeds from a main hopper (not shown). Seed hopper  14  delivers seeds to a chamber in a housing  16  at the lower portion of housing  12 . A seed disk  18  is journaled in housing  12  and has a seed side  22  exposed to chamber  16  and a lower pressure side  24  exposed to a vacuum source for maintaining a pressure differential across seed disk  18 . Seed disk  18  has a plurality of seed cells  20  positioned in a circular fashion around seed disk  18 . Seed cells  20  may take many different forms, but in the illustrated form they are apertures extending through seed disk  18  to connect the seed side  22  to the lower pressure side  24 . It should be understood by those skilled in the art that the pressure levels of sides  22  and  24  may be reversed. 
   Seed disk  18  is journaled on drive spindle  26  which is driven by an appropriate motor  28  through a gear mechanism (not shown) to turn the seed disk  18  in the direction of arrows A. The seeds that have accumulated against the bottom of seed disk  18  then find their way to the seed cells by virtue of the pressure differential across the seed disk. As the disk turns in a counterclockwise fashion, as shown in  FIG. 1 , the seeds that are in the seed cells are retained one at a time. The rotation of the disk takes the individual seeds to a segment (not shown) where the pressure differential is locally interrupted so that the seed may be discharged into an appropriate planting mechanism. 
   Seed disk  18  is connected to spindle  26  by a hub system generally indicated by reference character  30 . It is necessary for the seed disk to be accurately positioned relative to the rotational axis of spindle  26 , both from the standpoint of concentricity and an axial position relative to housing  12 . In the past, the axial position and concentricity of such drive hubs have been established through a complex series of surfaces in which the run out has to be controlled within limits. Furthermore, since the drive hub transmits torque between the spindle  26  and the seed disk  18  provisions must be made for adequate torque transmittal. 
   As shown particularly in  FIG. 2 , the hub  30  has a flange  32  with an outer circumferential portion  34  that retains and supports a flexible annular sleeve, to be later described. Inboard of the outer circumferential section is a conical section  36  manufactured to be concentric with a rotational axis A of the hub  30 . The hub  30  has a center through hole  38  which is threaded to receive the end of the drive spindle  26 . The threaded hole  38  is retained within an annular section  40  having a plurality of notches  42  for an adjustment purpose, to be described later. Integral with the element  40 , are a pair of radially extending paddles  44 . Although a pair of paddles  44  is illustrated, it should be apparent to those skilled in the art that any number of paddles may be utilized. 
     FIG. 3  shows the hub  30  threaded onto the threaded end  46  of the spindle  26 . A retaining collar  48  is threaded to the end  50  of spindle  26 . End collar  48  is appropriately affixed to spindle  26  and acts as a stop for a spring  52 , herein shown as a coil spring. The other end of spring  52  acts on a base wall (not shown) of a retention element  54  having a central hub  56  and a pair of radially extending tabs  58  which approximate in dimension the paddles  44 . The spring  52  is retained within a recess  60  of hub  56 . The resulting combination causes the retention element  54  to be yieldably urged towards the flange  32 . The axial position of flange  32  and therefore the conical surface  36 , relative to spindle  26 , is set by the degree to which hub  40  is threaded over the threaded section  46 . The threaded section  46  has a radial through passage (not shown) which receives a spring loaded key element  62  extending through recesses  42  to fix the relative threaded position of hub  40  on drive spindle  26 . 
     FIG. 4  shows the interaction between the hub system  30  and the seed disk  18 . Seed disk  18  has an inner cylindrical hub section  64  extending from the seed disk  18  towards the hub  30 . Cylindrical section  64  has an inner end diameter  66  controlled to a given tolerance level with respect to the rotational axis A of the assembly. The circular edge of the end of diameter  66  is adapted to abut the conical surface  36  of hub  30  so that the two elements are concentric with respect to one another. Seed disk  18  also has a central opening  68  for accommodating the hub system  30  and a pair of radial slots  70  adapted to receive paddles  44 . 
     FIGS. 4 ,  5  and  6  show the hub assembly  30  without the spindle  26  and associated elements in order to more fully describe the invention. As shown in  FIG. 5 , the hub  30  is seated against seed disk  18  and  FIG. 6  shows the opposite side  24  of seed disk  18 . To further facilitate the explanation of the invention, the retaining element  54  is omitted. It can be seen that the paddles  44  extend through the recesses  70  to the side  24  of seed disk  18 . In order to ensure that the retention assembly  54  holds or retains seed disk against the hub  30  a pair of ramps  72  extend through approximately little more than 90° arc. Ramps  72  each start out at a level at an end  74  that is approximately at the axial height of paddles  44  and extend upward to detents  76  at an elevated level to ensure that the retention element  54  remains in place. 
     FIG. 7  shows a partial view of  FIG. 6  but with the spindle  26  and retention element  54  in place. It can be seen that after the hub  30  is inserted through seed disk  18  the tabs  58  clear the entry point of ramps  72  so that the tabs  58  can be rotated clockwise as shown by arrow B in  FIG. 7  so that the tabs  58  are received and retained in detents  76 . In this position the bottoms of tabs  58  act against the seed disk  18  to urge it against hub  30  by virtue of the spring element  52 . Thus, the concentricity of the seed disk relative to the spindle is defined by the conical surface  36  and the cylindrical edge  66 . Torque is transmitted between the hub  30  and the seed disk  18  through paddles  44  which interact with the walls of slots  70 . Thus, the torque transmission is provided in a parallel path to the concentricity position of the assembly relative to the spindle  26 . 
   The axial position of the seed disk of the hub  30 , and therefore seed disk  18  relative to spindle  26  and housing  12 , is adjusted by pulling out the pin  62  and threading the hub  40  in a clockwise or counterclockwise direction as needed to obtain the axial position. Once this established the pin  62  is inserted through the nearest slot  42  through the radial passage in the threaded section  46  of spindle  26 . 
   In order to provide a seal between the hub  30  and seed disk  18 , a conical, resilient, seal element  80  (shown partially cut away) is affixed to flange  34  of hub  30 . Seal  80  ensures that an adequate pressure differential is maintained across the seed disk  18  and that no significant leakage passes through the interconnected hub and seed disk. 
   Thus it is seen that the concentricity of the hub relative to the spindle is determined by several key dimensions rather than a multiplicity of dimensions as done in the past 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.