Abstract:
U-shaped cushions, also known as shanks or spring members, resiliently support a gang of disks on the frame of a disk harrow. The agricultural disk cushion is manufactured from a round section of raw material which is lighter and more resistant to torsion related failure than traditional rectangular section shanks. Two leg portions are each tapered to have flat surfaces on opposite sides for flush fitting with mounting elements, while a central portion connecting them remains circular in cross section. The round cross section in this critical area can withstand severe omni-directional loading, as its resistance is equal in all directions The spring rate the leg portions of the disk cushion can be tailored individually to meet the requirements of the application.

Description:
This invention relates generally to agricultural implements, and more particularly to a structure for resiliently supporting a gang of earth working tools on the frame of an agricultural implement. 
   BACKGROUND OF THE INVENTION 
   Disk gangs of harrows are often resiliently supported on the harrow frame so that each gang can independently yield to obstructions met by the disks in the farmland being harrowed. This reduces the impact forces transmitted to the frame and the potential damage to the disk gang caused by engagement with obstructions such as rocks, stumps or roots. 
   Existing resilient mounting arrangements often include U-shaped spring members mounted between a cross member on the frame and the shaft on which the disks are mounted. These U-shanks or disk cushions are typically manufactured from square or rectangular cross-section material, formed to shape and heat-treated. U.S. Pat. Nos. 4,066,132 and 4,407,372 disclose U-shaped spring members having rectangular cross sections. In some cases these disk cushions may have one or two tapered legs, where the thickness of the leg is variable along its length. This is done to provide exactly the right spring rate to meet the application requirements. 
   Disk cushions undergo loading in many planes, often resulting in a torsional load being applied to the part, concentrated at the central portion of the U-shaped member between the leg portions. This applied torsion tends to be a repeated and cyclic load that often leads to failure of the part. The square shape of the part is not the optimum shape to resist this form of torsional fatigue. Therefore, there is a desire for a cushion with an improved resistance to torsional loads applied during use of the disk harrow. 
   SUMMARY OF THE INVENTION 
   According to an aspect of the invention there is provided a disk harrow comprising: 
   a frame adapted for motion along a ground surface; 
   an upper cross member supported generally horizontally on the frame; 
   a lower cross member supported below the first cross member and extending generally parallel to said first cross member; 
   U-shaped spring members resiliently supporting the lower cross member on the upper cross member, said spring members being spaced apart along said cross members, each U-shaped spring member comprising a curved central portion extending between parallel first and second leg portions; 
   upper mounting elements each connecting the first leg portion of a respective one of the spring members to the upper cross member; 
   lower mounting elements each connecting the second leg portion of a respective one of the spring members to the lower cross member; and 
   a plurality of disk members supported on and spaced along the lower cross member, each disk member being arranged to engage the ground surface; 
   the central portion of each U-shaped spring member having a circular cross section; 
   the first leg portion of each U-shaped spring member having a first generally flat surface facing the second leg portion of said U-shaped spring member and a second generally flat surface opposite said first generally flat surface; 
   the second leg portion of each U-shaped spring member having a first generally flat surface facing the first leg portion of said U-shaped spring member and a second generally flat surface opposite said first generally flat surface; and 
   the U-shaped spring members being arranged such that the central portions of each spring member extend generally vertically and are disposed forward of the upper and lower cross members and the first and second leg portions of said spring member extend generally horizontally rearward from said central portion. 
   Preferably the first and second generally flat surfaces of each leg portion of each spring member are spaced apart by a respective distance, said respective distance being less than a diameter of the circular cross section of the central portion of said spring member. 
   The U-shaped spring member, or disk cushion, is created from a round section of raw material. The raw material is sheared to length and each end is hot rolled to the required tapered thickness in order to achieve the proper spring rate. The part is then heat-treated, formed and receives a final surface preparation. With a diameter equal to the thickness of a typical cushion having a rectangular cross section, the round cross section of the central portion of the U-shaped spring member provides the same torsional resistance using less material, resulting in a lighter product. Aside from being lighter and stronger, these cushions are also easily customized to achieve a unique spring rate for specific applications. 
   Preferably the U-shaped spring members are arranged such that the first and second leg portions of each spring member extend generally perpendicular to the upper and lower cross members. 
   Preferably each upper mounting element comprises a first mounting member disposed above the upper cross member and a second mounting member disposed below said upper cross member, said first and second mounting members being attached so as to clamp said upper cross member therebetween. 
   Preferably there are provided pairs of aligned holes in the first and second mounting members of each upper mounting element for attachment of said mounting members by bolting. 
   Preferably the pairs of aligned holes in the first and second mounting members of each upper mounting element are disposed on opposite sides of the upper cross member. 
   Preferably there is provided at least one hole in the first leg portion of each U-shaped spring member, at least one of the pairs of aligned holes in the first and second mounting members of each upper mounting element aligning with the at least one hole in the first leg portion of the respective spring member for attachment of said upper mounting element and said respective spring member by bolting. 
   Preferably the first mounting member of each upper mounting element comprises a generally flat plate. 
   Preferably the second mounting member of each upper mounting element comprises a block having at least one recessed portion arranged to receive a portion of at least one of the upper cross member and the first leg portion of the respective spring member. 
   Preferably each lower mounting element comprises a first mounting member supported on the lower cross member and a second mounting member disposed above said first mounting member, said first and second mounting members of the lower mounting element being attached so as to clamp the second leg portion of the respective spring member therebetween. 
   Preferably the first mounting member of each lower mounting element is supported above the lower cross member such that the second leg portion of the respective spring member is immediately adjacent each of the first and second mounting members of said lower mounting element above said lower cross member. 
   Preferably the second mounting member of each lower mounting element comprises a generally flat plate. 
   Preferably the first mounting member of each lower mounting element comprises an angled member having a generally vertical portion extending upward from the lower cross member and a generally horizontal portion supported on said generally vertical portion upward of said lower cross member, the second leg portion of the respective spring member being clamped between said generally horizontal portion of said first mounting member and the second mounting member of said lower mounting element. 
   Preferably there are provided pairs of aligned holes in the first and second mounting members of each lower mounting element for attachment of said mounting members by bolting. 
   Preferably the pairs of aligned holes in the first and second mounting members of each lower mounting element are disposed on opposite sides of the lower cross member. 
   Preferably there is provided at least one hole in the second leg portion of each U-shaped spring member, at least one of the pairs of aligned holes in the first and second mounting members of each lower mounting element aligning with the at least one hole in the second leg portion of the respective spring member for attachment of said lower mounting element and said respective spring member by bolting. 
   Preferably the lower cross member comprises a shaft adapted for rotation about an axis thereof, said shaft being supported by the lower mounting elements connected to the second leg portions of the spring members, the disk members being mounted on said shaft for rotation therewith. 
   Preferably the lower cross member further comprises at least one hollow housing member extending between adjacent disk members, the shaft being supported for rotation within said at least one housing member, said at least one housing member having the lower mounting elements attached thereto. 
   According to a second aspect of the invention there is provided a disk harrow comprising: 
   a frame adapted for motion along a ground surface; 
   an upper cross member supported generally horizontally on the frame; 
   a shaft supported below the first cross member, said shaft adapted for rotation about a longitudinal axis thereof and extending generally parallel to said first cross member; 
   a plurality of disk members supported on and spaced along the shaft, each disk member being arranged to engage the ground surface and rotate with said shaft; 
   U-shaped spring members resiliently supporting the shaft on the upper cross member, said spring members being spaced apart along said cross members, each U-shaped spring member comprising a curved central portion extending between parallel first and second leg portions; 
   upper mounting elements each connecting the first leg portion of a respective one of the spring members to the upper cross member; and 
   lower mounting elements each connecting the second leg portion of a respective one of the spring members to the shaft; 
   the central portion of each U-shaped spring member having a circular cross section; 
   the first leg portion of each U-shaped spring member having a first generally flat surface facing the second leg portion of said U-shaped spring member and a second generally flat surface opposite said first generally flat surface; 
   the second leg portion of each U-shaped spring member having a first generally flat surface facing the first leg portion of said U-shaped spring member and a second generally flat surface opposite said first generally flat surface; and 
   the U-shaped spring members being arranged such that the central portions of each spring member extend generally vertically and are disposed forward of the upper and lower cross members and the first and second leg portions of said spring member extend generally horizontally rearward from said central portion. 
   Preferably the first and second generally flat surfaces of each leg portion of each spring member are spaced apart by a distance, said distance being less than a diameter of the circular cross section of the central portion of said spring member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings, which illustrate exemplary embodiments of the present invention: 
       FIG. 1  is an isometric view of a U-shaped spring member having a rectangular cross section as described in prior art. 
       FIG. 2  is an isometric view of a U-shaped spring member according to the present invention. 
       FIG. 3  is a side view of the U-shaped spring member according to the present invention. 
       FIG. 4  is a cross sectional view of the U-shaped spring member according to the present invention as taken from line  4 – 4  of  FIG. 3 . 
       FIG. 5  is a cross sectional view of the U-shaped spring member according to the present invention as taken from line  5 – 5  of  FIG. 3 . 
       FIG. 6  is a cross sectional view of the U-shaped spring member according to the present invention as taken from line  6 — 6  of  FIG. 3 . 
       FIG. 7  is an exploded isometric view of a single support assembly of a disk harrow according to the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a typical U-shaped spring member, or disk cushion, described in prior art for use as a resilient supporting member in a disk harrow. The disk cushion  2  features a first leg portion  3  having a first flat surface  4  and a second flat surface  5 . Similarly, a second leg portion  6  has a first flat surface  7  and a second flat surface  8 . These flat surfaces are defined by the rectangular cross section of the cushion. The two leg portions  3  and  6  are connected at one end by a curved central portion  9 . 
     FIG. 2  illustrates a disk cushion  20  according to the present invention. Similar to the prior art in the arrangement of it components, the disk cushion  20  features a first leg portion  22  having a first fiat surface  24  and a second flat surface  26 , a second leg portion  28  having a first flat surface  30  and a second flat surface  32  and a curved central portion  9  connecting the two leg portions  22  and  28  at one end. The two leg portions  22  and  28  are parallel and extend in the same direction from the central portion  9 , thereby defining the U-shape of the cushion  20 . The first flat surfaces  24  and  30  of the two leg portions  22  and  28  face each other inside the U-shape. The second flat surfaces  26  and  32  are each opposite their respective first surfaces  24  and  30 , such that the second surface  26  of the first leg portion  22  faces away from the second leg portion  28  and the second surface  32  of the second leg portion  28  faces away from the first leg portion  22 . 
   The disk cushion  20  is manufactured from round bar stock which results in the round cross section of the central portion  34 . The diameter of the round bar stock is selected based upon the application of the part, specifically the required strength and required spring rate. In the prior art shown in  FIG. 1 , the flat surfaces  4 ,  5 ,  7  and  8  were automatically provided by the rectangular cross section of the disk cushion  2 . Since the disk cushion  20  of the present invention is made from a round section, the flat surfaces must be produced during the manufacturing process. Each of the legs  22  and  28  of the disk cushion  20  is tapered in a hot roll machine to the desired finished thickness, resulting in the tapered shape best shown in  FIG. 3 . The part is then heat-treated, formed and receives a final surface preparation. As can be seen, the leg portions  22  and  28  have a resulting thickness that is less than the diameter of the cross section of the central portion  34 , which remains circular (as shown in  FIG. 4 ). As shown by the cross sections  25  and  33  of the first and second leg portions  22  and  28  respectively in  FIGS. 5 and 6 , the leg portions  22  and  28  can have different thicknesses chosen based on the spring rate required by the specific application of the final product. 
     FIG. 7  illustrates the arrangement of a single support assembly for a disk harrow featuring the disk cushion  20  as the resilient supporting means. A frame adapted for motion along the ground by means well known to those of skill in the art includes an upper cross member  40  from which a gang of disks  90  is resiliently suspended by disk cushions  20 . The drawing shows a single support assembly  200  disposed between an adjacent pair of disks  90 . Two or more support assemblies  200  featuring the cushion  20  are provided spaced along the upper cross member  40  depending on the length of the gang of disks. An upper mounting element consisting of a first mounting member  50  and a second mounting member  30  supports the disk cushion  20  on the upper cross member  40  by means of the first leg portion  22 . At the second leg portion  28  of the disk cushion  20 , a lower mounting element consisting of a first mounting member  70  and a second mounting member  60  for connecting the disk cushion  20  to a lower cross member  80 . The lower cross member  80  consists of a hollow housing member  82  having a rotatable shaft  84  supported within. The disks  90  are mounted on the shaft  84  for rotation with the shaft. The housing  82  serves to provide a means of connecting the shaft  84  and the lower mounting element without transferring the rotational motion of the shaft  84  to the mounting element and connected disk cushion  20 . Means of mounting a rotating shaft within a non-rotating housing are well known to those of skill in the art. 
   As seen in  FIG. 7 , the purpose of the flat surfaces of each leg portion of the disk cushion is to provide suitable surfaces for flush mounting against other components of the disk harrow. The second mounting member  30  of the upper mounting element is a block featuring recesses  32  and  34  in its lower surface  31  and upper surface  33  respectively. The lower recess  32  is shaped to receive a portion of the second flat surface  24  of the first leg portion  22  of the cushion  20  such that the two parts fit flush together. Similarly, the upper recess  34  receives the lower surface  42  of the upper cross member  40  in a flush engagement. 
   The first mounting member  50  of the upper mounting element is a flat plate that is placed atop the upper cross member  40 , which as described above, is received within the upper recess  34  of the second mounting member  30 . Holes  100  are provided in the first and second mounting members  50  and  30  of the upper mounting element, the holes in the first mounting member  50  being axially aligned with those in the second mounting member  30 . The holes  100  of each mounting member of the upper mounting element are arranged two on a first side of the upper cross member  40  nearest the central portion  34  of the cushion  20  and one on a second side opposite the first side. The holes on the first side of the upper cross member  40  allow the attachment of the mounting members  30  and  50  by bolting means known to those of skill in the art. A mounting hole  23  provided in the first leg portion  22  of the disk cushion  20  is axially aligned with the holes  100  on the second side of the upper cross member  40  such that the first mounting element  50 , second mounting element  30  and cushion  20  can all be attached by means of bolting. This results in a layered arrangement consisting of, from top to bottom, the first mounting element  50 , the upper cross member  40 , the second mounting element  30  and the disk cushion  20 . 
   The first mounting member  70  of the lower mounting element consists of a right angle plate member having a vertical portion  72  supported on the housing member  82  and a horizontal portion  74  supported on the vertical portion  72 . The vertical portion  72  extends upward from the lower cross member  80  to support the horizontal portion  74  above it. The second leg portion  28  is supported upon the first mounting member  70  such that the second flat surface  32  sits flush on the horizontal portion  74 . The second mounting member  60  of the lower mounting element is a flat plate  60  that is disposed above the second leg portion  28  of the cushion  20  so as to sit flush on the first flat surface  30 . Axially aligned holes  101  are provided in the two mounting members  60  and  70  of the lower mounting element. Mounting holes  31  in the second leg portion  28  of the cushion  20  are axially aligned with the holes  101  in the mounting members  70  and  60  such that the three components can be attached by means of bolting. This arrangement results in the clamping of the second leg portion  28  between the first  70  and second  60  mounting members of the lower mounting element. 
   When the disks  90  engage the soil during harrowing, loads are imparted onto the disk cushion  20 . These loads result from the weight of the disks  90  and lower cross member  80 , the force required to pull the disks through the soil, impact between the disks and rocks or other obstructions and forces exerted on the disks during cornering of the harrow. These multiple loads act in a variety of planes, resulting in an offset or torsional load being applied to the central portion  34  of the disk cushion  20 . Sharp corners, like those found in the square or rectangular cross sections of prior art cushions  2 , act as stress risers to this type of torsional loading. Stress risers lead to premature failure of the component in areas of close proximity. The round cross section  35  of the central section of the disk cushion  20  of the present invention, as seen in  FIG. 4 , does not have corners and therefore is not weakened by the presence of stress risers. As a result, the cushion  20  as described above is better suited to deal with these torsional loads and thus has a greater fatigue life. 
   The cushion  20  according to the present invention is lighter than a cushion made from square or rectangular cross sectional material designed to have similar properties. When used for this application, square or rectangular stock has essentially unused or wasted material in the corners that does little to add to the strength of the final product. Selecting the proper diameter of material sets the spring rate of the disk cushion. A round section with a diameter equivalent to the thickness of a rectangular section provides similar strength with less material. With the elimination of the wasted corner material the part will be significantly lighter. This reduces the overall weight of the disk harrow, thereby reducing the amount of power needed to move the implement over the ground. 
   The above discussion describes a single embodiment of the present invention. It should be noted that the disk cushion  20  having a central portion  34  of circular cross section can be used to resiliently support gangs of disks in disk harrows having different mounting arrangements. The rotating shaft can be supported by means other than the longitudinal cylindrical housing shown. Similarly, alternate mounting elements and methods of attaching the various components of a disk harrow are well known to those of skill in the art. 
   Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.