Abstract:
A knife assembly includes a unique finned point with angled soil-engaging surfaces defining several fracture areas and preventing slabbing to avoid excessive soil disturbance and knife wear. The knife has an extended length between the point and upper mounting brackets to facilitate operation of the point over a substantial range of depths, and the mounting brackets operate above ground level even at maximum point depth operation.

Description:
FIELD OF THE INVENTION 
   The present invention relates to agricultural implements and, more specifically, to knife and point structure for applying fertilizer below the ground surface. 
   BACKGROUND OF THE INVENTION 
   Many growers in the United States are currently switching from conventional tillage methods or minimum tillage methods to zone or strip tillage methods to reduce input costs and increase crop yields. The strip tillage machines currently on the market are designed to perform zone tillage, apply fertilizer, and make a mellow, friable seedbed for the upcoming crop. Residue levels for strip tillage range from light soybean stubble to heavy standing corn stubble. 
   An implement for zone or strip tillage typically includes a cutting coulter, a row cleaner, and fertilizer injection knife system mounted on a shank assembly and covering disks. The cutting coulter is design to cut residue, and the row cleaner removes crop residue from the formed strip. The shank-mounted fertilizer injection knife system fractures the soil in the strip and applies fertilizer. The covering disks are designed to catch the dirt spray off of the fertilizer knife and move the dirt back over the row to seal the fertilized area and make a berm. 
   Many of the currently available strip tillage implements have problems with residue flow between the fertilizer knife and closing disks. The residue flow problems result from the operation of attaching brackets for a tall knife at ground level or in the ground when the strip-till bar works at depths from approximately six to ten inches. Residue catches on the brackets and impedes the flow of residue and soil clods between the knife and closing disks. Once there is sufficient residue build up, clearance between the knife and closing disks disappears. With no clearance, the closing disks stop turning and a ball of residue and clods starts to drag. The operator then has to stop the machine to dislodge the plug. 
   Providing an economical knife point that is long-wearing and has good soil operation characteristics has also been a continuing source of difficulty. Welded knife points have worked well but are expensive to manufacture and usually require replacement of the entire long knife when the point is worn out. Providing good subsurface soil shattering action without soil slabbing, excessive knife side wear, and excessive soil surface inversion and disturbance also continues to be a source of difficulty, especially on fertilizer knives working in strip tillage applications. 
   SUMMARY OF THE INVENTION 
   A knife assembly constructed in accordance with the teaching of the present invention includes a unique point defining several fracture areas and preventing slabbing and similar soil action that causes wear on the knife and excessive soil disturbance. The knife has an extended length between the point and upper mounting brackets to facilitate operation of the point over a substantial range of depths, and the mounting brackets operate well above ground level even at the deepest operation. The smooth knife shank sheds residue easily and eliminates the plugging typical in conventional knife assemblies with the bulkier mounting brackets having transversely extending bolts. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a portion of a strip tillage implement. 
       FIG. 2  is an enlarged view of the fertilizer knife and point assembly for the implement of  FIG. 1 . 
       FIG. 3  is an enlarged side view of the point for the assembly of  FIG. 2 . 
       FIG. 4  is a top view of the point of  FIG. 3 . 
       FIG. 5  is a rear view of the point. 
       FIG. 6  is a sectional side view of the point taken generally along the lines  6 - 6  of  FIG. 4 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1  therein is shown a portion of an implement  10  including a main frame  12  supported for forward movement over the ground. As shown, the implement  10  is a strip tillage machine having a plurality of strip tillage units  16  extending downwardly and rearwardly from the frame  12 . Each unit  16  includes a forward cutting coulter for cutting a slit in the row area, a clearing disk assembly  20  for clearing trash from the row area adjacent the slit, and a fertilizer injection knife assembly  22  for penetrating the soil in the area of the slit and depositing fertilizer. A covering disk assembly  26  is located adjacent the knife assembly  22  for moving soil over the penetrated area after the fertilizer is deposited beneath the surface. 
   The knife assembly  22  includes a spring trip shank assembly  30  connected at a forward end to the frame  12  extending rearwardly to a connection  32  with a long, upright knife  34 . A replaceable point  40  is attached to the lower forward portion of the knife  34 , and an NH 3  tube  44  is attached to rear edge  46  to deliver fertilizer behind the point  40 . The area of the connection  32  is offset a substantial distance above the lowermost portion of the point  40  so that the connection  32  is located above the surface of the ground when the point  40  is operating at maximum depth. By way of example for the strip tillage units  16  shown in  FIG. 1 , the connection  32  is located above the forward tip or edge  40   a  of the point  40  at least twenty inches. The point  40  can operate over a large range of depths with the connection  32  located above the surface of the soil to help prevent trash build-up and improve soil and trash flow around the knife and the rear of the spring trip standard assembly  30 . Typically, the point  40  operates over a depth range that extends from about six inches to approximately ten inches or more. 
   The knife  34  includes an upright shank portion  34   a  terminating at the area of the connection  32 , which as shown in  FIG. 2 , is a pair of offset bolt holes spaced a distance of approximately 2 ¾ inches apart. Two shear bolts  32   b  connect the upper end of the shank portion  34   a  to the lower aft end of an arm of the spring trip shank assembly  30 . 
   The knife  34  terminates in a lower, forwardly projecting point receiving portion  34   b . The point  40  is matingly received on the portion  34   b  and includes an upper apertured area  48  pinned to a corresponding apertured area on the knife  34  by a roll pin  50 . The point  40  can be easily removed and replaced by driving the roll pin  50  from the apertures, sliding a new point  40  in place on the lower portion  34   b  and then driving a new roll pin  50  through the apertures. 
   At the juncture of the upright shank portion  34   a  and lower portion  34   b , segmented shank protectors  54  are welded to front edge  56  of the knife  34 . The shank protectors  54  extend upwardly from the top of the point  40  to cover the area of the exposed shank subject to the highest wear. 
   As best seen in  FIGS. 2-6 , the forward point or edge  40   a  of the point  40  extends substantially transversely to the forward direction F with a slight rearward taper from the centerline C L  of the point to initially penetrate the soil. As shown, the edge  40   a  has a width W 1  which, as shown in the example, is approximately two inches. A first lift surface  61  extends rearwardly and upwardly from the leading edge  40   a . As best seen in  FIG. 3 , the lift surface  61  is upwardly convex between the edge  40   a  and locations  61   a . The angle of a line tangent to the midpoint of the surface (near the lead line for  61  in  FIG. 3 ) is approximately 31 degrees. The convex lift surface  61  lies generally on a radius of approximately 5 inches centered below the point and initiates gentle lifting action and fracturing of the soil behind the leading edge  40   a . Sides  62  of the first surface  61  extend generally parallel to each other and are also spaced a distance W 1  apart. The first surface  61  decreases slightly in an upward slope at the locations  61   a  and terminates in a rearwardly facing upright surface or heel  66 . A centrally located small tapered fin  68  projects slightly downwardly from the bottom of the point  40  adjacent the rear surface  66 . 
   Opposed rearwardly diverging soil shattering surfaces  70  project upwardly from the lift surface  61  adjacent the leading edge  40   a  and extend rearwardly from a forward nose or edge  71  which terminates at a location  72  a substantial distance above the locations  61   a.  The soil penetrated at the forward area of the surface  61  is lifted to intersect the forward edge  71 . The soil is forced outwardly by the diverging surfaces  70  which define a first soil shatter zone. The surfaces  70  terminate generally along a line extending between the locations  61   a  and  72 , and upwardly and outwardly facing surfaces  76  extend rearwardly from that line. The surfaces  76  converge at an upper rearwardly directed edge  78  which extends from the location  72  to the uppermost extremity of the point  40 . Soil is forced upwardly and outwardly at the surfaces  76  where the collision of the soil flow from the surfaces  61  and  70  provides another soil shatter zone. At the rear of the surface  61  behind the location  61   a  where the slope of the surface decreases, soil drops behind the surface  66  to define another shatter zone behind the point heel. 
   Generally parallel side surfaces  80  extend upwardly and rearwardly from the aft portion of the surface  61  along joint lines  82 . The distance between the surfaces is less than the distance W 1 . Protrusions or fins  90  extend outwardly and downwardly from vertically offset locations on the surfaces  80 . As best seen in  FIGS. 4 and 5 , the outermost extremities of the fins  90  are spaced a distance approximately equal to the distance W 1 . The soil flow off of the surfaces  70  and  76  is lifted by the fins  90  and  92  at locations behind the surfaces adjacent the joint lines  82  and dropped over the aft edges  90   a  and  92   a  of the fins  90  and  92  to complete the shattering effect behind the knife  34 . 
   The multiple shatter zones provided by the unique surface configuration and fin structure described above shatters the soil to avoid slabbing effect for reduced draft and reduced wear on the sides of the knife. The point design with multiple shatter zones also reduces soil disturbance and soil inversion on the surface of the ground. 
   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.