Abstract:
A disc harrow composed of one or more disc gangs has a subframe coupled to the disc gangs to move the disc gangs in response to variations in farmland terrain to limit the impact of ground variation when encountered during the harrowing process. When the obstruction is cleared, the subframe automatically returns the disc gangs to their pre-obstruction position. In addition to reducing the potentially-damaging impact of obstructions, the subframe also maintains a more consistent reel depth during undulations or changes in the farmland terrain, such as during harrowing of slopes or unleveled fields such as valleys, near waterways, and along fence rows.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to agricultural implements, and in particular, to an implement having a spring and damper assembly to which a disc gang is mounted that maintains the disc gang at a relatively constant height yet absorbs the impact imparted by the disc gang when the disc gang encounters variations in terrain contours. 
   BACKGROUND OF THE INVENTION 
   Once a crop has been harvested, residual crop materials frequently remain on the farmland surface. Typically, these residual crop materials are incorporated within the soil profile of the farmland in an effort to maintain soil nutrient integrity. For example, management of corn cropped fields commonly includes the incorporation of the residual corn stalks with field soil once the corn, and occasionally a portion of the stalk, has been harvested. Whereas some growers harvest a majority of the kernel, cob, and stalk material, others harvest only the kernel and discharge a majority of the chaff or cob and stalk materials onto the farmland. Regardless of the quantity of stalk material that is harvested, the subsequent preparation of the farmland requires incorporation of the stalk or crop residue with the field soil. It is generally understood that the size of the crop residue particles as well as the surface area of the crop residue exposed to the soil affects crop residue decomposition. Specifically, reduced crop residue particle size and increased surface contact of the crop residue with adjoining soil improves crop residue decomposition. 
   Frequently, a crop residue conditioner, such as a stalk chopper, is pulled across the harvested field during autumn. The stalk chopper cuts the remaining stalks into smaller, more easily workable and degradable sized pieces. Thereafter, a disc harrow is used to smooth and level the farmland or seedbed and till a portion of the crop residue with the soil. The disc harrow not only mixes the crop residue with the underlying soil to return nutrients to the soil, but also can be used to establish a residue layer over the farmland to protect against erosion and provide moisture control during the winter months before replanting in the spring. 
   Disc harrows include one or more disc gangs, each including a series of steel discs or reels with tapered or beveled peripheral edges. The discs, although tending to roll or rotate as they are pulled forward, penetrate into and break up the soil and stalks and other crop residue. The soil and crop residue then ride along and across the concave surfaces so as to be turned or inverted. A portion of the residue is buried with this turning, with the percentage of buried residue increasing with the amount of soil turning. The amount of crop residue that is retained on the seedbed surface may also be controlled by setting the angle of attack or “gang angle”, such as described in U.S. Pat. No. 6,612,381, the disclosure of which is incorporated herein by reference. 
   During harrowing of the farmland the disc harrow may encounter various obstructions, such as rocks, stumps, and roots. To reduce the impact of such obstructions and thereby potential damage to the disc harrow, the disc gangs are often resiliently supported on the harrow mainframe so that each gang can independently yield to the obstructions. Conventionally, the reels are mounted to a shaft or axle which is then mounted to the harrow mainframe via U-shaped or C-shaped spring members, also referred to as shanks or cushions. These spring members are designed to maintain a uniform depth of the reels and flex when the reels meet with an obstruction. Exemplary spring members are illustrated in U.S. Pat. No. 4,066,132 to Rehn, U.S. Pat. No. 4,407,372 to Rozeboom, and U.S. Pat. No. 7,131,501 to Svendsen et al. While such cushions are generally effective at maintaining a uniform depth of the disc gangs and flexing in response to any obstruction, their effectiveness is limited at reducing the impact of the obstruction on the harrow mainframe. 
   Thus, there remains a need for a farm implement having a shock absorbing assembly that not only maintains the disc gangs at a uniform depth, but also absorbs the impact of the natural ground variation and larger obstructions during the harrowing process in a manner that places less stress on the farm implement when such ground conditions are encountered. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a disc harrow having a disc frame carrying one or more disc gangs and coupled to a mainframe. The disc frame is designed to allow the disc gangs to respond to variations in the farmland terrain to limit the impact of ground variations when encountered during the harrowing process. Specifically, the disc frame is coupled to the mainframe by a series of struts that hold the disc frame at a relatively constant height yet absorb the impact that results when the disc gangs encounter ground variation. Each strut includes a spring component that is biased to maintain a constant depth of the disc gangs. Each strut also has a damper component that absorbs the movement associated with the disc gang as it follows the ground contours and variations. As a result, the force of the impact is absorbed by the strut and the amount of force that is transferred to the mainframe is reduced. 
   Therefore, in accordance with one aspect, the present invention is directed to a disc harrow having a mainframe and a disc frame coupled to the main frame. The disc harrow further has a disc gang assembly coupled to the disc frame and composed of a plurality of crop residue and soil tilling reels. A strut is interconnected between the disc frame and the mainframe, and is configured to hold the disc gang assembly at a relatively constant depth and absorb the impact associated with the disc gang assembly encountering ground variation during harrowing of a farmland. 
   According to another aspect, the present invention includes a farm implement for tilling farmland. The farm implement has a mainframe defined by a pair of rails and a harrow. The farm implement further has a strut interconnected to the main frame and the harrow. The strut is adapted to support the harrow yet allow limited movement of the disc frame along only a single axis relative to the mainframe when the harrow encounters ground variation. 
   In accordance with another aspect of the present invention, an apparatus for tilling crop residue and soil is presented. The apparatus has a disc harrow including a first disc gang and a second disc gang connected to the first disc gang by a floating frame. A mainframe is defined by a pair of rails and a plurality of transverse supports, and carries the disc harrow and is coupled to the floating frame by at least one strut. The at least one strut is adapted to maintain the disc harrow at a defined depth during normal working operation and automatically dampening any force presented when the disc harrow encounters ground variation during harrowing of a field. 
   Other objects, features, 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 DRAWINGS 
     Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout. 
     In the drawings: 
       FIG. 1  is an isometric view of a disc harrow according to one aspect of the invention; 
       FIG. 2  is a section view of the disc harrow taken along line  1 - 1  of  FIG. 1 ; and 
       FIG. 3  is a section view similar to  FIG. 2  showing movement of a disc gang from a normal working position to a clear-an-obstruction position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to  FIG. 1 , a disc harrow  10  has a mainframe  12  defined by a pair of rails  14  connected to one another by a series of transverse supports  16  spaced from one another along the length of the rails  14 . The disc harrow  10  is designed to be towed by a tractor or other powered device. In this regard, the disc harrow  10  includes a hitch  18  for connecting the mainframe  12  to the tractor. In the illustrated embodiment, the disc harrow  10  includes a pair of disc gangs  20 ,  21  mounted to the mainframe  12  using a subframe or disc frame  22 , which will be described in greater detail below. The pair of disc gangs includes a forward disc gang, designated by numeral  20 , and a rearward disc gang, designated by numeral  21 . 
   The disc gangs  20 ,  21  are connected to one another by an I-beam  24  and a pair of gang braces  26 , only one of which is visible in the figure. Each disc gang  20 ,  21  has a series of reels or discs  28  each of which is mounted to a disc support beam  30 ,  31 , respectively, by a clamping device  32 . In the illustrated example, each disc support beam  30 ,  31  has a pair of support arms  30   a ,  30   b  and  31   a ,  31   b , respectively. The support arms are angled relative to one another in such a manner that disc support beam  30  is generally V-shaped whereas disc support beam  31  has a generally inverted V shape. The support arms  30   a ,  30   b ,  31   a ,  31   b , and I-beam  24  collectively form an A-frame. Each clamping device  32  includes a clamp  34  fastened to a clamp plate  36  having a downwardly extending arm  38  that connects to the hub  40  of each reel  28 . 
   The subframe  22  has a forward rockshaft  42  and a rearward rockshaft  43  spaced from one another and coupled to respective transverse supports  16  using suitable connectors. The rearward rockshaft  43  has a strut  60  attached permanently to both ends of the rockshaft. The strut  60  is attached to support arm  31   a  on one side and  31   b  on the other side. The disc support arm  31  is raised and lowered by rotating the rockshaft thereby changing the operating depth of the disc unit. The forward rockshaft  42  is of similar construction having a strut  60  attached to both ends which are attached to support arm  30   a  and  30   b . More particularly, rearward rockshaft  43  mechanically communicates with forward rockshaft  42  via piston  48  that is coupled to forward rockshaft  42 . The piston  48  is also connected to an actuator  52  via a lever  54  that is rotatable about forward rockshaft  42 . In this regard, the actuator  52  may be energized to pull lever  54  forward to lower the forward disc gang  20  and the rearward disc gang  21  or push lever  54  rearward to raise the forward disc gang  20  and the rearward disc gang  21 . When lowering the disc gangs  20 ,  21 , the actuator  52  is activated so that lever  54  pushes piston  48  rearward, which causes rockshaft  43  and attached strut  60  to rotate downward thereby resulting in the rearward disc gang  21  being lowered in concert with the forward disc gang  20 . When raising the disc gangs  20 ,  21 , the actuator  52  is activated so that lever  54  pulls piston  48  forward, which causes rockshaft  43  and strut  60  at each end to rotate upward, thereby resulting in the disc gangs  20 ,  21  being raised. This construction allows the disc gangs  20 ,  21  to be positioned at an infinite number of heights defined between the rotational limits of levers  54 ,  56 . The subframe  22  also includes a pair of lateral supports  58  interconnected between braces  26  and gang arms  30   a ,  30   b.    
   As further shown in  FIG. 2 , each strut  60  includes a bracket  62  which is attached to the end of a rockshaft, such as rockshaft  42 . For purposes of description, only one strut  60  will be described, but it is understood that the other struts are similarly constructed. The bracket  62  includes a vertically oriented slot  66  that defines a range of motion for pin  68  that is connected to or otherwise a part of a mounting lug  70 . The mounting lug  70  is coupled to a disc arm, thereby coupling the disc gang to bracket  62 . Bracket  62  has an arm  72  with a shock absorber  74  extending downwardly thereon and into engagement with mounting lug  70 . The shock absorber  74  extends concentrically through spring  76 . 
   The spring  76  presents a spring load on the disc gang, such as disc gang  21 . During unobstructed passage of the disc gang  21 , the spring load maintains the depth of the disc gang  21  at a relatively constant level. When an ground variation is encountered, spring  76  will deflect slightly compensating for the ground variation. Shock absorber  74  is operative to absorb or otherwise damper the energy transferred from the disc gang  21  to the bracket  62  when the ground variation is encountered. As such, when ground variation is encountered, the spring  76  will deflect and the disc gang will rise relative to the mainframe  12 , as shown in  FIG. 3  without the mainframe  12  also experiencing the shock of the ground variation. In this regard, the shock absorber  74  and spring  76  effectively support the weight of the disc gang  21  but also provide dampening of the forces transferred thereto by the disc gang  21  when ground variation is encountered. 
   Pin  68  is snuggly received when slot  66  so that the pin  68  is only allowed to move vertically within the slot  66 . Thus, the disc gang  21  is only permitted to float, in response to an encountered ground variation, along only a single axis. More particularly, the pin  68  and slot  66  arrangement does not allow the disc gang  21  to oscillate fore and aft when ground variation is encountered. 
   In one preferred embodiment, there is a pair of struts  60  associated with each disc gang  20 ,  21 ; however, it is understood that fewer than two or more than two struts may be used. For example, in one alternate embodiment, a single strut  60  is used for each disc gang  20 ,  21 . In this alternate embodiment, the struts  60  are connected to the disc gangs  20 ,  21  at opposing rails  14  of the mainframe  12 . 
   The present invention has been described with respect to a disc harrow, but is understood that the present invention is equivalently applicable with other soil tilling implements. Moreover, the invention may be applicable for a stand-alone disc harrow or a farm implement carrying multiple types of soil tillage tools. For example, cultivating tines may be coupled to the transverse supports  16 . Additionally, it is contemplated that the reels  28  of the disc gangs  20 ,  21  may be of similar size or of dissimilar size. For example, the forward disc gang  20  may have large reels for primary tillage whereas the rearward disc gang  21  may have smaller reels for secondary tillage. 
   Many changes and will 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.