Abstract:
A sprocket and hub assembly for use with a mechanical drive assembly of an agricultural implement includes a generally flat disc having an outer edge and a generally center mount portion. A series of teeth are radially defined around the outer edge of the disc. The assembly further includes a hub removably mounted to the generally center mount portion of the disc. The hub has a shaft engagement portion for removably coupling the hub to a driven shaft of the mechanical drive assembly. In one embodiment, the agricultural implement includes a retainer designed to hold a set of differently sized sprockets that can be interchangeably coupled to the driven shaft by the hub.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to agricultural implements and, more particularly, to a detachable hub and sprocket for use with the mechanical drive transmission of an agricultural implement. 
         [0002]    Some agricultural implements, such as planters and seeders, have various systems or devices that are powered by power that is derived from rotation of a ground engaging wheel of the implement. For example, a planter will typically deposit seed as a function of the rotational speed of the ground engaging wheel. However, most planters will also include a mechanical drive system or transmission to provide some control in the seed deposition rate as a function of the rotational speed of the ground engaging wheel. In other words, the mechanical drive system will include an output shaft that interfaces with the seed metering or seed deposition system and a set of gears will be used to control the rotational speed of the output shaft relative to the speed of the ground engaging wheel. 
         [0003]    In a typical arrangement, a chain or belt drive is used to rotate a driven shaft with rotation of the axle (drive shaft) of the ground engaging wheel. A sprocket (also referred to as a cog or gear ring) is mounted to each end of the driven shaft and the sprockets will typically have different diameters (gear ratios) so that the output shaft, which is connected to one of the sprockets by a chain drive, will rotate at a different rotational speed than the drive shaft. As known in the art, the gear ratios of the sprockets will dictate the relative differences in the rotational speed of the output shaft and the drive shaft. And, since the rotational speed of the output shaft dictates the rate by which seed or other particulate matter is deposited onto the planting surface, the gear ratios will also dictate the seed deposition rate. 
         [0004]    Different types of seed and field conditions will often require different seed deposition rates. Therefore, a planter will often require a large number of gear ratios to achieve a large range of desired seed populations to accommodate variations in seed types and field conditions. Typically, a change in the drive ratio of the mechanical drive system is accomplished by swapping sprockets of different sizes from a collection or set of available and differently sized sprockets. Each sprocket has a disc portion, with a series of teeth formed on an outer edge thereof, and a hub for coupling the sprocket to the driven shaft. The hub, which is integrally formed with the disc portion, will typically have a hex shaped bore, a square shaped bore, or a keyway that allows the hub to interface with the driven shaft so that the shaft will rotate with rotation of the sprocket. As noted above, to accommodate variations in seed types and field conditions, several sprockets are required and are typically stored on the agricultural implement itself. While reasonably effective, the collective size of the sprockets can be substantial, especially on an agricultural implement with limited space for storage of unused equipment. 
         [0005]    Therefore, there is a need in the art to reduce the size of the sprockets to reduce storage loads on the agricultural implement without sacrificing the variability afforded by having multiple sprockets for accommodating variations in seed types and field conditions. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is directed to a sprocket (or similar rotatable member, such as a pulley disc) and hub combination that allows the hub to be decoupled from the sprocket and, when desired, used with another sprocket of different size to change the drive ratio of a mechanical drive system of an agricultural implement. The invention therefore allows a set of hub-less sprockets to be stored flat against one another in a relatively compact and space saving manner on the agricultural implement. Additionally, the invention provides a manufacturing cost savings since only one hub is needed for a set of sprockets of various sizes (gear ratios). 
         [0007]    It is therefore an object of the present invention to provide a set of hub-less sprockets that can be interchangeably mounted to a hub used to interconnect the sprocket to a shaft of the mechanical drive system of an agricultural implement. 
         [0008]    It is another object of the present invention to provide a quick-change sprocket and hub combination that allows a user, such as a farmer, to make quick adjustments to the drive ratio of the mechanical drive system. 
         [0009]    It is another object of the invention to provide a set of sprockets that can be stored flat against one another as a sprocket set on an agricultural implement. 
         [0010]    Other objects, features, aspects, and advantages of the invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0011]    Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout. 
           [0012]    In the drawings: 
           [0013]      FIG. 1  is a pictorial view of a planter having a mechanical drive system incorporating a sprocket and hub according to one aspect of the present invention; 
           [0014]      FIG. 2A  is an isometric right side view of a mechanical drive system of the planter shown in  FIG. 1 ; 
           [0015]      FIG. 2B  is an isometric left side view of the mechanical drive system; 
           [0016]      FIG. 3  is an exploded view of the interconnection of a sprocket and hub to a driven shaft of the mechanical drive system; 
           [0017]      FIG. 4  is a front elevation view of the sprocket of  FIG. 3 ; 
           [0018]      FIG. 5  is an isometric view of the hub of  FIG. 3 ; 
           [0019]      FIG. 6  is a side elevation view of the hub of  FIG. 3 ; 
           [0020]      FIG. 7  is a front elevation view of the sprocket and hub with pins of the hub inserted into keyways formed in the sprocket; and 
           [0021]      FIG. 8  is a front elevation view similar to that of  FIG. 7  illustrating locking of the pins of the hub in the keyways of the sprocket upon rotation of the hub. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown an agricultural work system  10  that includes an agricultural work vehicle, such as tractor  12  that tows an agricultural implement  14 , which is depicted as a multi-row front fold transport planter. Planter  14  can include a toolbar  16  with left and right marker assemblies  18 ,  20  that are attached to left and right ends  22 ,  24  of toolbar  16 , respectively. Supports  25  can support marker assemblies  18 ,  20  when in a folded position. 
         [0023]    Planter  14  can include other elements such as drawbar  26  for connection to tractor  12 , large seed hoppers  28 ,  29  which provide seeds to row or seed units  30 , and platform and gate assembly  32  for accessing and filling large seed hoppers  28 ,  29 . Row or planting units  30  can include a variety of elements for dispensing seed, fertilizer, pesticide, herbicide and other agricultural materials. Such elements can include, but are not limited to, a furrow opening apparatus, gage wheels, a pair of lateral spaced, or staggered, furrow opener discs, or alternatively, and without detracting or departing from the spirit and scope of the present invention, a runner opener type for providing a furrow in the ground, a pair of furrow closer discs, a seed meter, a press wheel arranged in fore-and-aft relationship relative to each other, and a agricultural chemical hopper. Additionally, planter  14  can have planting units  30  with individual seed boxes in addition to the large seed hoppers  28 ,  29 . Bulk fill hopper  28  holds seed for the seed units  30  mounted to the left wing of frame  16  and bulk fill hopper  29  holds seed for the seed units  30  mounted to the right wing of frame  16 . Seed is metered from the bulk fill hoppers  28 ,  29  to the individual seed units by a seed metering system, generally designated by reference number  34 , in a manner generally known in the art. The planter  14  is designed such that seed (or other particulate matter) is metered as a function of the rotational speed of ground engaging wheels  36 . 
         [0024]    A mechanical drive system  38 , shown in  FIGS. 2A and 2B , is designed to deliver mechanized power to the seed meting system  34  as a function of the rotational speed of ground engaging wheel  36  that rotates around an axle  40 , which has a sprocket  42  coupled to an end thereof. The mechanical drive system  38  includes sprockets  44  and  46  which are rotated by chain  48  that is entrained around sprocket  44  and  46  and the sprocket  42  coupled to the drive shaft  40 . Preferably, the chain  48  is also entrained around a tensioner  50 . It will thus be appreciated that when the ground engaging wheel  36  is rotating, sprocket  42  will follow that rotation and cause translation of chain  48 , which will in turn cause rotation of sprockets  44  and  46 . Sprocket  44  is coupled to an inner end of shaft  52  and sprocket  54  is mounted to an opposite end of the shaft  52 . Since sprocket  44  and sprocket  54  are mounted to a common shaft  50 , shaft  54  will rotate with rotation of the ground engaging wheel  36 . A drive chain  56  is entrained around sprocket  54  as well as tensioning sprockets  57 ,  58  and a removable drive sprocket  60 . The construction of the removable drive sprocket  60  will be described in greater detail below. 
         [0025]    As shown in  FIG. 2B , the removable drive sprocket  60  is coupled to an end of a driven shaft  62  and thereby causes rotation of the driven shaft  62  when rotated by translation of drive chain  56 . Coupled to the opposite end of the driven shaft  62  is removable driven sprocket  64 . As will be described more fully below, sprockets  60  and  64  are designed to be quick-change sprockets that allow a user to replace the sprockets in a relatively quick manner with differently sized sprockets to vary the drive ratio of the drive assembly  38 . 
         [0026]    A driven chain  66  is entrained around the driven sprocket  64  and tension sprockets  68 ,  70  and an output shaft sprocket  72 . The output shaft sprocket  72  is coupled to an output shaft  74  such that rotation of the sprocket  72  via translation of chain  62  causes rotation of the output shaft  74 . The output shaft  74  also carries an output sprocket  76  that is designed to interface with a chain of the seed metering system  34  or other system. It will thus be appreciated that rotation of mechanical drive assembly  38  translates mechanized power derived from rotation of the ground engaging wheel  36  to the seed metering system  34  or other system of the agricultural implement. Moreover, it will be appreciated that the rotational speed of the output sprocket  76  can be varied by replacing the drive sprocket  60  and/or driven sprocket  64  with a differently sized sprocket, e.g., a sprocket with a different gear ratio. As noted above, conventionally, replacing the sprockets has required decoupling of the sprocket and its hub from respective ends of the driven shaft. However, as will be described below, the present invention simplifies such replacement. 
         [0027]    Referring now to  FIG. 3 , the present invention provides a sprocket and hub design that allows the sprocket to be removed from the hub, or vice-versa. It will be understood that that the drive sprocket and the driven sprocket described above can each have a similar construction and, as such, the description of the sprocket  78  shown in  FIG. 3  will be understood to cover the construction and design of both the drive and driven sprockets. Sprocket  78  has a generally planar disc shaped body  80  with a peripheral edge  82  around which a series of teeth  84  are extend. A hub mounting portion  86  is formed in the center of the body  80  and includes a central bore  88  and a set of spaced keyways  90 . In a preferred embodiment, the bore  88  includes a chamfer wall  91 , the significance of which will be described below. 
         [0028]    A hub  92  has a generally cylindrical body  94  from which a set of pins  96  outwardly extend. A bore  98  ( FIG. 5 ) extends centrally through the hub body  94  which allows the hub  92  to be fit over an end of a shaft  100 , such as driven shaft  62 . In a preferred embodiment, an opening  102 , generally transverse to bore  98  is formed in the hub body  94 , as shown in  FIGS. 5 and 6 , and is adapted to receive a set screw  104  for retaining the hub  92  around the end of the shaft  100 . The bore  98  shown in the figures has a hexagonal profile and is thus shaped to receive a shaft  100  having a similar hexagonal profile, but it is understood that the bore could be shaped to mate with shafts having differently shaped profiles. Additionally, it is understood that other types of retention mechanisms other than, or in addition to, a set screw could be used to couple the hub  92  to the shaft  100 . Furthermore, it is contemplated that more than one opening could be formed in the hub body so that more than one set screw could be used to secure the hub  92  to the shaft  100 . 
         [0029]    When assembled, the pins  96  of the hub  92  are retained within the keyways  90  of the sprocket  78  and an alignment boss  106  formed at the end of the shaft  100  extends past the hub body  94  and into the central bore  88  of the sprocket  78 . In a preferred embodiment, the alignment boss  106  has a chamfer feature  101  that fits against the chamfer wall  91  of the sprocket  78 . The chamfer feature  101  thus prevents the sprocket  78  from being mounted onto the shaft  100  incorrectly. It is understood that other types of features, such as a counter-bore in the bore  88  and a shoulder on the alignment boss  106  could be used, to prevent incorrect connection of the sprocket  78  to the shaft  100 . 
         [0030]    Referring now to  FIG. 4 , each of the keyways  90  of the sprocket  78  has a wide diameter portion  108  and a narrow diameter portion  110  that communicate with one another. The keyways  90  are thus formed so that the wide diameter portions  110  of the sprocket  78  are fit over the pins  96  of the hub, as shown in  FIG. 7 , and once the pins  96  pass through the wide diameter portions  110 , the sprocket  78  (or hub  92  and shaft  100 ) is rotated so that the pins move from the wide diameter portions  110  to the narrow diameter portions  112 , as shown in  FIG. 8 . To facilitate this movement of the pins  96  within the keyways  90 , each pin  96  is comprised of two general portions: a post  114  and a head  116 , which is illustrated in  FIG. 6 . 
         [0031]    As shown in  FIG. 6 , the posts  114  extend outwardly from the hub body  94  and the heads  116  are formed on the distal ends of the posts  114 . The posts  114  have a diameter generally less than that of the heads  116 . As such, a channel or groove (not numbered) is effectively defined between the heads  116  and the hub body  94  along the posts  114 . The width of this channel, or in other words, the length of the posts  114 , is slightly greater than the width of the sprocket body  80 . The excess length of the posts  114  allows the heads  116  to be clear of the sprocket body  80  when the sprocket  78  is fit onto the hub  92 ; however, the excess length is sufficiently small to maintain a snug fit of the sprocket  78  against the body  94  of the hub  92 . 
         [0032]    The detachability of the hub  92  from the sprocket  78  provides advantages over conventional integrated sprocket and hub designs. Firstly, the present invention allows a single hub to be used interchangeably with sprockets of different diameters, or gear ratios. Thus, when a user wishes to change the drive ratio of the mechanical drive system, slack can be introduced to the chain entrained around the sprocket, the sprocket detached from the hub with counter-rotation of the sprocket to move the pins  96  from the narrow diameter portions  110  to the wide diameter portions  108 , and a new sprocket mounted to the hub  92 . Secondly, the hub-less sprockets allows a set of sprockets to be stored on the agricultural implement as a single sprocket set  112 , as shown in  FIG. 2B . That is, the sprockets of the set can be placed relatively flat against one another and held on a retention arm  114  as a single unit. 
         [0033]    While the present invention has been described with respect to a sprocket and detachable hub assembly for use with a mechanical drive system of an agricultural planter, it is understood that the invention could be used with other systems of the planter or with other types of agricultural implements in which it would be advantageous to reduce the storage of multiple sprockets and provide a sprocket and hub design that allows a single hub to be used interchangeably with multiple sprockets. Additionally, while the invention has been described with respect to roller chains and sprockets, it is understood that belts and pulleys could also be used. 
         [0034]    Many changes and modifications could be made to the invention without departing from the spirit thereof. The scope of these changes will become apparent from the appended claims.