Abstract:
A sectored disc assembly, removable disc sector, and method of replacing a disc sector are disclosed for use with a soil opener that uses a disc assembly to open the soil prior to injection of a fertilizer or seed into the ground. The sectored disc assembly includes a rotatable hub and a plurality of disc sectors cooperatively forming a substantially continuous disc around the hub. Connectors, such as bolts, secure each of the disc sectors to the hub. The disc sector includes a body with radially inner and outer margins and side margins that are configured for continuous abutment with adjacent side margins of other disc sectors. The method of replacing a disc sector includes removing the connector securing the disc sector to the hub, moving the disc sector radially outwardly away from the hub, placing a replacement disc sector into contact with the hub, and inserting the connector.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to soil openers that use a disc assembly to open the soil prior to injection of a fertilizer or seed into the ground. More specifically, the present invention concerns a sectored disc assembly for use in such a soil opener, a removable disc sector of a sectored disc assembly, as well as a method of replacing a disc sector of a sectored disc assembly. 
     2. Discussion of the Prior Art 
     Those of ordinary skill in the art will appreciate that farmers often use no-till planting techniques to produce all types of agricultural crops. Such no-till techniques minimize the disturbance to the soil and leaves the stubble, or organic matter from the previous crop, standing in the field. This, in turn, reduces water runoff in the field, thereby greatly reducing erosion of the top soil. 
     Typically, no-till planting involves using a rotatable disc soil opener to cut a furrow in the soil as it is pulled across a field, creating a small disturbed soil zone. Fertilizer, seeds, or both, are then injected into this disturbed soil zone, after which the furrow is closed. The closing of the furrow can be accomplished by naturally allowing the disturbed soil to flow back into the furrow, or by following the rotatable disc soil opener with a closing wheel designed to push soil into the disturbed soil zone and close the furrow. Often, the opening of the furrow, formation of the seed bed, injection of fertilizer, seed, or both, and closing of the furrow are accomplished in a single pass with a soil opener that includes a rotatable disc, an injector foot, and a closing wheel. 
     Conventional rotatable discs used in soil openers have been formed, most typically out of carbon steel, as single, annular bodies for rotation about a spindle on the soil opener. While this unitary construction has been satisfactory in some respects, such solid discs are very heavy components that can be difficult to handle and are often expensive to produce. As the rotatable disc component of a soil opener directly contacts the soil as the implement moves through a field, the disc is subject to considerable stress and is exposed to damage. Damage to a rotatable disc, often the result of transport, inexperienced or poor operators, or hitting a railroad track or rocks in the soil, requires replacement of the entire disc. Such disc replacement is expensive and time consuming, as the entire heavy disc must be removed from the soil opener, typically involving tedious disassembly of the entire supporting frame, and only then can an entire new disc be installed. 
     The cost associated with whole disc replacement can be disproportional to the amount of damage to the disc, such as when a single portion of the edge of the disc is damaged from hitting a rock. Additionally, the replacement of the whole disc results in considerable down time of the implement, as heavy components must be elevated out of the soil to facilitate removal of the disc to be replaced and installation of a new disc. The time requirement associated with such replacement adds to the cost and inconvenience of the periodic and necessary change out of rotatable discs. 
     SUMMARY 
     The present invention provides a unique sectored disc assembly, removable disc sector, and method of replacing a disc sector for use with a soil opener that uses a disc assembly to open the soil prior to injection of a fertilizer or seed into the ground. The sectored disc includes multiple disc sectors that can be removed and replaced individually, requiring a fraction of the cost and time of whole disc replacement. The quick and simple change out of disc sectors also allows an operator to match the disc material to the soil type for improved performance of the soil opener. 
     According to one aspect of the present invention, a sectored disc assembly for use in a soil opener of an agricultural implement is provided, wherein the disc assembly serves as a blade to open the soil prior to injection of a fertilizer or seed into the ground. The sectored disc assembly includes a rotatable hub, wherein the hub presents a central rotational axis and a radial outer periphery. The sectored disc assembly also includes a plurality of disc sectors, wherein each disc sector is disposed around the periphery of the hub and extends radially outwardly therefrom. The disc sectors cooperatively form a substantially continuous disc disposed radially around and coaxial with the hub. The disc sectors cooperate with the hub to define a substantially continuous interface therebetween around the periphery of the hub. Each disc sector cooperates with the hub to present a tongue-and-groove connection along the interface, wherein one of the disc sector and hub includes a radially extending internal groove and the other of the disc sector and hub includes a radially extending tongue, with the tongue being snugly received in the groove to restrict axial movement of the disc sector relative to the hub. 
     Another aspect of the present invention concerns a disc sector that is removably and individually connectable to a rotatable hub of a sectored disc assembly serving as a blade of a soil opener to open the soil prior to injection of a fertilizer or seed into the ground, wherein the hub presents a central rotational axis and a pair of circumferentially extending opposed faces along the outer periphery thereof, and wherein the disc sector cooperates with other disc sectors to form a substantially continuous disc disposed radially around the hub. The disc sector includes a sector body that presents a radially inner margin, a radially outwardly spaced generally arcuate outer margin, and generally radially extending side margins each defined between the inner and outer margins. The body includes a pair of opposed engagement surfaces configured for flush contact with the opposed faces of the hub so that axial movement of the disc sector relative to the hub is thereby restricted. The body presents an axial thickness that tapers in a radially outer direction adjacent the outer margin. The side margins cooperatively form an acute angle therebetween and are configured for continuous abutment with adjacent ones of the other disc sectors. 
     Yet another aspect of the present invention concerns a method of replacing a disc sector of a sectored disc assembly serving as a blade of a soil opener to open the soil prior to injection of a fertilizer or seed into the ground. The method includes the steps of removing the connector that secures the disc sector to the rotatable hub of the sectored disc assembly, moving the disc sector radially outwardly and away from the hub, placing a replacement disc sector into contact with the hub so that the replacement disc sector and hub cooperatively form a tongue-and-groove connection extending along the periphery of the hub, and inserting the connector to secure the replacement disc sector to the hub. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description of the preferred embodiments. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
     Various other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       A preferred embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein: 
         FIG. 1  is a side elevational view of a portion of a towable agricultural implement with a soil opener including a rotatable sectored disc assembly constructed in accordance with the principles of a preferred embodiment of the present invention; 
         FIG. 2  is an enlarged, fragmentary top-down plan view of a portion of the soil opener shown in  FIG. 1 , with an optional closing wheel shown in phantom lines, particularly illustrating the coupling of the soil opener to the toolbar and the rotatable sectored disc assembly; 
         FIG. 3  is a fragmentary top-down plan view on a reduced scale of a towable agricultural implement having a toolbar and a plurality of soil openers including rotatable sectored disc assemblies constructed in accordance with the principles of a preferred embodiment of the present invention; 
         FIG. 4  is an enlarged, side elevational view of the soil opener shown in  FIG. 2 , presented from the opposite vantage point of that in  FIG. 1 , with the optional closing wheel shown in solid lines, particularly illustrating the rotatable sectored disc assembly coupled to a draw bar assembly and an adjacently disposed injector foot; 
         FIG. 5  is a an enlarged, side elevational view of the soil opener shown in  FIG. 4 , presented from the opposite vantage point, with the optional closing wheel shown in phantom lines, particularly illustrating the rotatable sectored disc assembly coupled to the draw bar assembly and the adjacently disposed injector foot; 
         FIG. 6  is an enlarged, top-down sectional view of the rotatable sectored disc assembly and associated portion of the draw bar assembly, the view taken along the line  6 - 6  of  FIG. 5 , particularly illustrating in detail a plurality of disc sectors disposed about a rotatable hub with a tongue-and-groove connection and secured thereto with connecting bolts; 
         FIG. 7  is an exploded perspective view of the sectored disc assembly shown in  FIG. 6 , particularly illustrating the separate components thereof, including the rotatable hub, the plurality of disc sectors, and the connecting bolts; and 
         FIG. 8  is a perspective assembly view of the sectored disc assembly shown in  FIG. 7 , particularly illustrating the plurality of disc sectors cooperatively forming a substantially continuous disc disposed about the rotatable hub, with one disc sector shown in phantom lines to depict removal of a single disc sector from the sectored disc assembly and the associated disposition of the connecting bolt through a portion of the rotatable hub. 
     
    
    
     The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiment. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is susceptible of embodiment in many different forms. While the drawings illustrate, and the specification describes, certain preferred embodiments of the invention, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present invention to the particular disclosed embodiments. 
     With initial reference to  FIG. 1 , a towable agricultural implement  10  selected for purposes of illustration includes a floating hitch section  12  and a framework  14 . The floating hitch section  12  includes a hitch connector  16  at a terminal end thereof. It will be appreciated by one of ordinary skill in the art that the hitch connector  16  is configured for coupling the implement  10  to a corresponding towing hitch on a driving power source (not shown) for pulling the implement  10  across a field. It is also noted that such a driving power source could take the form of a tractor, or any other suitable power source known in the art, without departing from the teachings of the present invention. 
     The framework  14  is supported above the ground  18  by wheels  20 , rotatably connected to the framework  14  by bolts  22 , in a manner known in the art and not shown in detail here. With reference to  FIG. 3 , the implement  10  is pulled through a field in the direction indicated by the large arrow. Thus, the wheels  20  support the rear portion of the framework  14 . The front portion of the framework  14  is supported by the connection of the floating hitch section  12  to a driving power source and an additional section  15  of the framework  14  is supported in the front by a supplemental swiveling support wheel  24 . 
     As shown in  FIG. 1 , the swiveling support wheel  24  is journaled to a wheel arm  44  for rotation therebetween. The wheel arm  44  is pivotally coupled to a forward extension  46  in a manner known in the art and not shown in detail here. The forward extension  46  brackets to the toolbar  28  to space the swiveling support wheel  24  ahead of the toolbar  28  as the implement  10  moves across a field. It is noted that the swiveling support wheel  24  is disposed on the section  15  of the framework  14  that is not otherwise supported in the front by the connection of the floating hitch section  12  to a driving power source. Additionally, this section  15  of the framework  14  may pivot upwards relative to the central section of the framework  15  to facilitate transport of the implement  10  across the ground other than in a field, as will be readily appreciated by one of ordinary skill in the art. It is noted, however, that such arrangement of the framework  14  is not critical to the principals of the present invention. 
     Returning now to  FIG. 1 , the framework  14  also includes a vertically extending support member  26 , extending downwardly from the framework  14 . The support member  26  connects the framework  14  to a toolbar  28 , through a spacing element  30 , in a manner known in the art. As shown particularly in  FIG. 3 , the toolbar  28  extends transverse to the direction of travel of the implement  10 . A plurality of soil opener assemblies  32  are coupled to the toolbar  28 , as described in more detail below. 
     It is noted that  FIG. 3  depicts a plurality of soil opener assemblies  32  linearly coupled to the toolbar  28  in a single gang. However, it will be appreciated that the layout of the plurality of soil opener assemblies  32  could take other forms, such as a two gang configuration, or be variously configured in any manner known in the art, including any alternative suitable number or spacing of soil opener assemblies  32 . It is further noted that each soil opener assembly  32  is virtually identically configured to each other soil opener assembly  32 . Thus, in each of the drawing figures other than  FIG. 3 , only a single soil opener assembly  32  is depicted, with the understanding that other soil opener assemblies  32  are similarly constructed. 
     With continued reference to  FIG. 1 , the exemplary soil opener assembly  32  depicted broadly includes a drawbar assembly  36 , a sectored disc assembly  38 , an injector boot assembly  40 , and a closing wheel  42 . The drawbar assembly  36  is bracketed to the toolbar  28  to thereby pull the other components of the soil opener assembly  32  behind the toolbar  28  while yieldably biasing the components downwardly into engagement with the ground  18  as the implement  10  moves through a field. With particular reference to  FIGS. 2 and 5 , a swiveling assembly  48  is attached to the toolbar  28  with a plurality of bolts  50 . The swiveling assembly includes an inner member  52  and a coaxial outer member  54  that are configured for relative rotation therebetween. A mounting bracket  56  extends outwardly from the outer member  54 . The bolts  50  pass through a plate  58 , around the toolbar  28 , and are secured to the mounting bracket  56  to thereby clamp the swiveling assembly  48  to the toolbar  28 . 
     A drawbar bracket  60  connects the drawbar assembly  36  to the inner member  52  so that the drawbar assembly  36  can swivel relative to the toolbar  28 . A locking pin  62  selectively locks the inner member  52  and the outer member  54  together to prevent relative rotation therebetween, thereby permitting an operator to “lock out” the swiveling movement of the drawbar assembly  36 . Such locking out of the swiveling assembly  48  is often used, for example, to prevent drift of the soil opener assemblies  32  as the implement  10  is towed along steep inclines, as will be readily appreciated by one of ordinary skill in the art upon review of this disclosure. 
     Turning now to  FIGS. 4 and 5 , the drawbar assembly  36  includes a disc opener arm  64  pivotally coupled to the drawbar bracket  60  with a pin  66 . The pivotal movement of the drawbar assembly  36  allows the components thereof to be vertically adjusted relative to the ground  18 . The vertical position of the drawbar assembly  36  is controlled by an adjustable-length strut  68 . The strut  68  includes an outer cylinder  70  and a telescopingly interfitted inner rod  72 , wherein the inner rod  72  is coaxial with and configured for relative sliding within the outer cylinder  70 . A strut pin  74  passes through the outer cylinder  70  and into at least a portion of the inner rod  72  in a manner known in the art to lock the strut  68  at a particular length. 
     A strut support  76  is fixed to and extends vertically upwardly from the drawbar bracket  60 . The ends of the adjustable-length strut  68  extends between a fixed position on the strut support  76  and a fixed position on the disc opener arm  64 . In the illustrated embodiment, an end of the outer cylinder  70  is coupled to the top of the strut support  76  with a bolt-and-nut assembly  78  in a manner known in the art. Similarly, an end of the inner rod  72  is coupled to the disc opener arm  64  with a bolt-and-nut assembly  80  in a manner known in the art. It is noted that the depicted orientation of the strut  68  could be reversed, or an alternative device for adjusting the vertical height of the drawbar assembly  36  relative to the ground  18  could be used, without departing from the teachings of the present invention. 
     The sectored disc assembly  38  is rotatably coupled with and vertically fixed to the disc opener arm  64 , as is discussed in greater detail below, for relative rotation therewith. Thus, it is noted that as the drawbar assembly  36 , including the disc opener arm  64 , is vertically adjusted relative to the ground  18  as described above, the sectored disc assembly  38  is correspondingly vertically adjusted relative to the ground  18 . It is further noted that the principles of the present invention are not limited to the production of any particular crop and can readily be adapted to virtually all crops generated by placement of seed and/or fertilizer in the ground, as will be understood by one of ordinary skill in the art. 
     A closing wheel arm  82  is adjustably mounted to the disc opener arm  64 , wherein the closing wheel arm  82  rotatably supports the closing wheel  42  at the end thereof. The closing wheel arm  82  is fixed to a closing wheel arm mounting bracket  84  that attaches to the disc opener arm  64  with a pair of bolt-and-nut assemblies  86 . The bolt-and-nut assemblies  86  attach the mounting bracket  84  to the disc opener arm  64  by extending through a selected pair of a plurality of holes  88  in the disc opener arm  64 . Extending the bolt-and-nut assemblies  86  through distinct pairs of holes  88  allows the closing wheel arm  82  to be adjustably mounted to the disc opener arm  64 . By extension, this relative adjustability affects the relative position of the components mounted to the end of each of these arms, namely the sectored disc assembly  38  and the closing wheel  42 , respectively. As shown in the difference between  FIGS. 4 and 5 , it is noted that the closing wheel  42 , and its associated closing wheel arm  82 , are depicted in  FIG. 4  by way of example only and that the principals of the present invention do not depend on the selective inclusion of these elements, as will be readily appreciated by one of ordinary skill in the art upon review of this disclosure. 
     With continued reference to  FIG. 5 , an injector boot support element  90  is fixed to the end of the disc opener arm  64  with a pair of bolt-and-nut assemblies  92 . The bolt-and-nut assemblies  92  attach the boot support element  90  to the disc opener arm  64  by extending through a selected pair of a plurality of holes  94  in the disc opener arm  64 . Extending the bolt-and-nut assemblies  92  through distinct pairs of holes  94  allows the boot support element  90  to be adjustably mounted to the disc opener arm  64 . The injector boot assembly  40  is fixed to the distal end of the boot support element  90  relative to the disc opener arm  64  by a bolt-and-nut assembly  96 . Thus, adjustment of the boot support element  90  relative to the disc opener arm  64  as described above changes the disposition of the injector boot assembly  40  relative to the sectored disc assembly  38 . 
     The injector boot assembly  40  broadly includes a pair of conduits  98  and  100  for carrying and controllably inserting seed, fertilizer, or both, into the ground in a manner generally known in the art and not described in detail here. Additionally, as shown in  FIG. 6 , a threaded extension  102  controls the lateral disposition of a distribution end  104  of the injector boot assembly  40  relative to the sectored disc assembly  38 . The threaded extension  102  is coupled to the boot support element  90  and secured thereto with a nut  106 . In the depicted embodiment, the distribution end  104  of the injector boot assembly  40  is adjacent an end of the sectored disc assembly  38 , although this placement could be changed without departing from the teachings of the present invention. 
     As discussed briefly above, the sectored disc assembly  38  is rotatably coupled to the disc opener arm  64  for relative rotation therewith. The sectored disc assembly  38  broadly includes a rotatable hub  108  and a plurality of disc sectors  110  disposed around the hub  108  to cooperatively form a substantially continuous disc  111 . In the illustrated embodiment, the hub  108  has considerable mass, weighing slightly more than one hundred pounds, substantially contributing to the total weight of each soil opener assembly  32  of approximately five hundred pounds. 
     The disc sectors  110  cooperate with the hub  108  to present a tongue-and-groove connection therebetween along the interface between the disc sectors  110  and the hub  108 . As will be readily appreciated by one of ordinary skill in the art, as the agricultural implement  10  moves across a field, the soil opener assemblies  32  are often disposed at a slight angular offset relative to the direction of travel of the implement  10 . It is particularly noted that while  FIG. 3  depicts the soil opener assemblies  32  generally aligned with the direction of travel, the soil opener assemblies  32  may move about the swiveling assembly  48  during operation and often do not precisely follow the direction of travel. It is additionally noted that sometimes the soil opener assemblies  32  are intentionally offset from the direction of travel to facilitate the opening of the soil. This angular offset can lead to the introduction of considerable lateral forces to the components of the soil opener assemblies  32 , including the substantially continuous disc  111 . The tongue-and-groove connection between the disc sectors  110  and the hub  108  of the unique sectored disc assembly  38  described herein directs these lateral forces inward to the central hub  108  such that axial movement of the disc sectors  110  is restricted. 
     As shown particularly in  FIG. 6 , a spindle  112  is fixed to the disc opener arm  64  with a pair of bolts  114 , wherein the spindle  112  extends generally transverse to the direction of travel of the implement  10  across a field. The hub  108  includes a generally central hole  116  therethrough about which the hub  108  is disposed about the spindle  112  for relative rotation therewith in a manner generally known in the art. A cap  118  is attached to the hub  108  with a plurality of screws  120  to cover the hole  116  when the hub  108  is disposed on the spindle  112 . The cap  118  prevents dirt or other debris from entering the hole  116  in the hub  108 , as will be appreciated by one of ordinary skill in the art. 
     With continued reference to  FIG. 6  and turning also to  FIGS. 7 and 8 , the component parts of the sectored disc assembly  38  will be discussed in greater detail. The hub  108  is generally circular and presents a continuous outer periphery  122 , although it is noted that it is within the ambit of the present invention to incorporate alternative hubs of other general shapes (e.g., polygonal), so long as such a hub is rotatable about the spindle  112  or the like. The hub  108  also includes a radially inwardly extending circumferential groove  124  that extends continuously about the outer periphery of the hub  108 . 
     In the illustrated embodiment, the hub  108  includes an additional groove  126 , substantially identical to the groove  124 , but disposed axially away from the groove  124 . The second groove  126  can provide an alternative location for the disposition of the plurality of disc sectors  110 . The second groove  126  can also provide a location for the disposition of a depth band for controlling the depth to which the soil is opened, as will be appreciated by one of ordinary skill in the art. Although it is not necessary to provide multiple grooves in the hub  108 , it is further noted that more than the two depicted grooves could be provided in the hub  108 , so long as there is at least one groove to cooperate with the plurality of disc sectors  110  to form the substantially continuous disc  111  of the sectored disc assembly  38 . It is further noted that an alternative hub (not shown) could present a noncontinuous groove without departing from the teachings of the present invention, as will be readily appreciated by one of ordinary skill in the art upon review of this disclosure. 
     The plurality of disc sectors  110 , depicted individually in detail in  FIG. 7 , each includes a radially inner margin  128  and a radially outer margin  130 . Each disc sector  110  further includes radially extending side surfaces  132  and  134  that extend generally flatly between the inner margin  128  and the outer margin  130 . The disc sectors  110  are each partially received within the groove  124  to restrict axial movement of each disc sector  110  relative to the hub  108 . The disc sectors  110  and the hub  108  interfit in a tongue-and-groove connection along the outer periphery  122  of the hub  108  to form the substantially continuous disc  111  about the hub  108 , as will be described in more detail below. 
     The radially outer margins  130  of the plurality of disc sectors  110  are generally arcuate and cooperate to form a substantially continuous disc edge  136 . The disc edge  136  is generally circular and serves as the end of a blade to open the soil as the implement  10  moves across a field, as will be readily appreciated by one of ordinary skill in the art. It is noted that it is clearly within the ambit of the present invention to provide alternative disc sectors that cooperate to form a disc edge that is noncontinuous and presents, for example, an edge that is fluted, serrated, or spoked. 
     The axial width of the disc sectors  110  taper inwardly from the radially inner margins  128  to the radial outer margins  130  such that the tongue-and-groove connection is sufficiently strong to take the lateral forces and the disc edge  136  is sufficiently narrow to penetrate into the soil to form the furrow. In the illustrated embodiment, the radially inner margins  128  of the disc sectors  110  are also generally arcuate and correspond with the shape of the groove  124  in the hub  108  to interfit therein. It is noted, however, that with an alternately shaped hub, such as described above, it is clearly within the ambit of the present invention for the corresponding radially inner margins of cooperating alternative disc sectors to have a shape that is nonarcuate to flushly engage a corresponding surface on the outer periphery of such an alternative hub. 
     With continued reference to the embodiment depicted in  FIGS. 7 and 8 , it is noted that the illustrated groove  124  of the hub  108  presents a generally U-shaped channel with opposed faces  138  and  140 . Similarly, the groove  126  of the hub  108  presents a generally U-shaped channel with opposed faces  142  and  144 . Also in the illustrated embodiment, the each disc sector  110  includes a tongue section  146  that presents opposed engagement surfaces  148  and  150 . In the tongue-and-groove connection between the disc sectors  110  and the hub  108 , the opposed faces  138  and  140  of the groove flushly contact the engagement surfaces  148  and  150  of the tongue section  146 . 
     It is clearly within the ambit of the present invention to provide an alternative groove that is not U-shaped, so long as the tongue and groove sections correspond for a snug connection therebetween. It is additionally specifically noted that in an alternative embodiment (not shown) that the components of the tongue-and-groove connection could be switched, such that a central hub presents a tongue section and a plurality of disc sectors present a corresponding groove. In such an alternative embodiment, similar flush contact would result between opposed faces and engagement surfaces such that a substantially continuous disc would be formed about the hub, wherein axial movement of the disc sectors relative to the hub was restricted. 
     Regarding additional specifics of the depicted central hub  108 , it is noted that the hub  108  includes a pair of axially opposed, generally planar side portions  152  and  154 . The grooves  124  and  126  in the central hub  108  define radially extending flange sections  156 ,  158 , and  160  along the outer periphery  122  of the hub  108 , wherein the grooves  124  and  126  extend between the flange sections  156 ,  158 , and  160 . The flange section  156  extends axially between the hub side portion  152  and the opposed face  138  of the groove  124 . Similarly, the flange section  158  extends axially between the opposed face  140  of the groove  124  and the opposed face  142  of the second groove  126 . Also, the flange section  160  extends axially between the opposed face  144  of the second groove  126  and the hub side portion  154 . 
     Regarding additional specifics of the depicted individual disc sectors  110 , it is noted that each disc sector includes a pair of axially extending flared shoulder sections  162  that each extend axially outward beyond the dimension of the tongue section  146 . Each of the shoulder sections  162  present a radially inner shoulder surface  164 . In the sectored disc assembly  38 , the shoulder surfaces  164  flushly contact the outer periphery  122  of the hub  110 . 
     As described briefly above, the radially extending side surfaces  132  and  134  of each disc sector  110  extend generally flatly between the inner margin  128  and the outer margin  130 . A surface  132  of an individual disc sector  110  bears against the corresponding surface  134  of an adjacent disc sector  110  to restrict circumferential movement of any individual disc sector  110  of the substantially continuous disc  111 . In addition, as shown in  FIG. 8 , the generally flat shape of the side surfaces  132  and  134  allow a single disc sector  110  to be removed from or inserted into the hub  108  without disturbance to the other disc sectors  110 . 
     With continued reference to the embodiment depicted in  FIGS. 7 and 8 , a plurality of bolt connectors  166  are included to secure each of the disc sectors  110  to the central hub  108 . The hub  108  includes a plurality of holes  168  that extend axially therethrough, spanning all of the flange sections  156 ,  158 , and  160 . Each of the disc sectors  110  similarly includes a hole  170  that is axially aligned with the corresponding hole  168  in the hub  108  when the disc sector  110  is disposed therein. A bolt  166  extends through a washer  172 , through one of the holes  168  in the flange section  156 , through one of the holes  170  in the disc section  110 , and through the remainder of the hole  168  in the hub  108 . Each of the disc sectors  110  are secured to the hub  108  in like manner, as will be readily appreciated by one of ordinary skill in the art. 
     The front side  152  of the hub  108  also includes a recess  174  around each of the holes  168 . The recess  174  is axially larger than the diameter of the hole  168  and extends radially inwardly through the flange  156  toward the groove  124 . Each of these recesses  174  allow the head of the bolt  166  to countersink below the surface of the front side  152  of the hub  108  as shown in  FIG. 8 . The countersinking of the bolts  166  into the hub  108  provides the sectored disc assembly  38  with a clean design without exposed hub nuts or bolts to disturb material as the blade cuts into the soil. 
     Finally, it is noted that in the illustrated embodiment, the sectored disc assembly  38  includes four substantially identical disc sectors  110  that each define a quadrant of the substantially continuous disc  111 . It is clearly within the ambit of the present invention to provide alternative disc sectors that are not substantially identical or require more or fewer than the depicted four sectors to make up a substantially continuous disc. Such variations will be readily appreciated by one of ordinary skill in the art upon review of this disclosure. 
     The disc sectors  110  are preferably, although not necessarily, formed by casting the sectors from a metal alloy. Examples of preferred alloys for the material of the disc sectors  110  include steel 8630, ASTM 897 heat treated, and YC chrome, as will be understood by one or ordinary skill in the art. The efficient and simple ability to change out individual disc sectors  110  allows an operator to replace damaged or worn disc sectors  110  without the cost of replacing an entire unitary disc. In addition, an operator can easily change the material of the disc sectors  110 , and thus the entire disc  111 , as desired to match the material of the disc to the particular characteristics of the soil to be worked by the implement  10 . 
     The method of replacing a given disc sector  110  of the sectored disc assembly  38  should be apparent from the foregoing and, therefore, will be described here only briefly. With particular reference to  FIGS. 7 and 8 , the connecting bolt  166  is accessed through the recess  174  and removed from the sectored disc assembly  38  in the axial direction. After the removal of this single connecting bolt  166 , the disc sector  110  to be removed is simply moved radially outwardly and away from the hub  108 . As the disc sector  110  is moved away from the hub  108 , the opposed faces  138  and  140  of the groove  124  and the corresponding engagement surfaces  148  and  150  of the tongue section  146  slide radially past each other so that the disc sector  110  moves smoothly out of the hub  108 . 
     In substantially the reverse of the above-described removal procedure, a replacement disc sector  110  is placed into contact with the hub  108  so that the replacement disc sector  110  and the hub  108  cooperatively form a tongue-and-groove connection extending along the periphery of the hub  108 . In making such tongue-and-groove connection, the engagement surfaces  148  and  150  of the tongue section  146  of the replacement disc sector  110  contact and slide into a snug connection with the corresponding opposed faces  138  and  140  of the groove  124 . As the replacement disc sector  110  is inserted into the groove  124  of the hub  108 , the generally flat radially extending side surfaces  132  and  134  of the replacement disc sector  110  slidingly engage the corresponding side surfaces  132  and  134  of the adjacent disc sectors  110  already secured to the hub  108 . As is shown particularly in  FIG. 8 , this sliding engagement of the side surfaces  132  and  134  allows removal and insertion of a single disc sector  110  relative to the hub  108  without removing other disc sectors  110 . 
     Finally, the connecting bolt  166  is inserted into the hole  168  in the hub  108  and extended axially through the hole  170  in the replacement disc sector  110  to secure the disc sector  110  to the hub  108 . As will be readily appreciated by one of ordinary skill in the art, the ability to replace a disc sector  110  with manipulation of only a single connecting bolt  166  and without disturbance of the other disc sectors  110  in the sectored disc assembly  38  allows for replacement in an efficient and simple manner as described above. 
     The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
     The inventor hereby states his intent to rely on the Doctrine of Equivalents to determine and access the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention set forth in the following claims.