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TECHNICAL FIELD OF THE INVENTION 
     The present invention generally relates to farm implements, and more particularly, to an apparatus for folding over corn stalk stubble and the like. 
     BACKGROUND OF THE INVENTION 
     It is widely recognized that farming is a capital-intensive business. It is not unusual for farm tractors to cost more than $100,000 and for tires for such tractors to cost $3,000 a piece. In the past, tractor tires would generally be run at an inflation of 18-20 pounds per square inch. Modern tractor tires are designed to run on a lower air pressure (approximately 7-10 pounds per square inch), thereby allowing the tires to flatten out and minimize soil compaction as the tractor traverses the field. Lower compaction reduces damage to plant roots and facilitates water drainage by the soil. Manufacturers rate such tires to have a normal life of approximately 3,000 hours of operation. 
     In recent years, no-till farming has become common practice in the United States. No-till farming practices seek to control soil erosion by not plowing fields after the crop has been harvested. The U.S. Government mandates no-till on some lands, and most other farmers have adopted the practice, realizing that it is beneficial to reducing soil erosion and that it minimizes the number of times that the farmer is required to run over his fields during a growing season. 
     Prior to no-till farming practices, a corn crop (for example) would be harvested and the corn stalk stubble left in the field would be plowed under in the fall. The field would then be replanted again the following spring. Under the no-till methodology, the corn stalk stubble is not plowed under in the fall and the new crops are planted directly over the stubble-laden field the following spring. This means that the corn stalk stubble cures in the field all winter, allowing its water content to be purged, resulting in an extremely stiff stalk. Measurements have shown that the hardness of such cured stalks ranges between 75-95 on the Rockwell scale, whereas the newer low-pressure tires exhibit a hardness of 68-72 Rockwell. The result is that the corn stalk stubble can produce significant wear when the tractor is driven over it in the spring to plant a new crop. In tests performed by the present inventors, cords were visible through the tire tread after just 60 hours of operation under such conditions. Although corn is the principle crop in the United States that causes such accelerated wear, it will be appreciated that the same problem is exhibited to a greater or lesser degree with any crop that leaves a plant-stem stubble after harvesting. 
     There is therefore a need for a device that will minimize tire wear resulting from driving over corn stalks and the like. The present invention is directed toward meeting this need. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a device which may be mounted to the front of a tractor and which is operative to fold over corn stalk stubble and the like before they engage the front tires of the tractor. The device positions dragging units in front of each of the front tires of the tractor, whereby the dragging units are dragged over the ground in front of the tires when the tractor is moving. The weight of each of the dragging units is sufficient to cause it to substantially fold over .corn stalk stubble and the like prior to their engagement with the front tires of the tractor, thereby greatly minimizing wear to the tires caused by engagement with the corn stalk stubble and the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a preferred embodiment of the present invention, attached to the front of a tractor. 
     FIG. 2 is a partial top plan view of the preferred embodiment of the present invention attached to a tractor. 
     FIG. 3 is a side-elevational view of the preferred embodiment of the present invention attached to a tractor, and shown in the raised position. 
     FIG. 4 is a side-elevational view of the preferred embodiment of the present invention attached to a tractor and shown in the lowered position with the tractor moving forward. 
     FIG. 5 is a side-elevational view of the preferred embodiment of the present invention attached to a tractor and shown in the lowered position with the tractor moving rearward. 
     FIG. 6 is a front-end elevational view of the preferred embodiment of the present invention attached to a tractor. 
     FIG. 7 is a top plan view of a preferred embodiment dragging unit of the present invention. 
     FIG. 8 is an end elevational view of the preferred embodiment dragging unit of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and alterations and modifications in the illustrated device, and further applications of the principles of the invention as illustrated therein are herein contemplated as would normally occur to one skilled in the art to which the invention relates. 
     FIG. 1 illustrates a preferred embodiment of the present invention, indicated generally at  10 . The apparatus  10  is shown coupled to a tractor  12 . Preferably, a mounting panel  14  is bolted to either side of the front end of tractor  12  using bolts  16  extending through a portion of the tractor  12  frame. A support member  18 , preferably comprising C-channel iron, is welded to each of the mounting panels  14  and extends approximately 18 inches in front of the tractor  12 . Preferably, a C-channel cross brace  19  is coupled between the support members  18  (see FIG.  2 ). 
     Extending across the front of the tractor  12  and above the support members  18  is a crossbar  20 . Crossbar  20  is attached to the support members  18  by means of pairs of semi-cylindrical brackets  22  bolted together via pieces of angle-iron welded to the exterior of each of the brackets  22 . In certain embodiments, the lower portions of the brackets  22  are welded directly to the support members  18 . In certain other embodiments, the brackets  22  are affixed to the support members  18  by welding the exterior pieces of angle-iron to the support member. The brackets  22  define a cylindrical hole which contains a portion of the crossbar  20 , thereby preventing the crossbar  20  from translating with respect to the brackets  22 , but permitting the crossbar  20  to rotate. In certain preferred embodiments the brackets  22  are formed from section of iron pipe split along its axis of symmetry. The brackets  22  preferably include grease ports to permit the injection of grease, both to lubricate the crossbar  20 , and to protect the crossbar  20  and brackets  22  from oxidation or corrosion. 
     As more clearly seen in FIG. 2, the crossbar  20  includes a flange  24  extending therefrom. The flange  24  has a hole (not shown) formed therethrough. The flange  24  forms a rotatable coupling with a coupler  26  mounted to the end of a hydraulic cylinder  28 . A proximal end of the hydraulic cylinder  28  is mounted to the front of the cross brace  19 , while a distal end of the hydraulic cylinder  28  is mounted to the coupler  26 . The coupler  26  is mounted to the flange  24  by means of a rod, bolt, or the like extending through the hole in the flange  24 . As will be appreciated by those having ordinary skill in the art, extension of the hydraulic cylinder  28  acts upon the flange  24  to cause the crossbar  20  to rotate within the pipe sections held by the brackets  22 . 
     Returning now to FIG. 1, the crossbar  20  includes four lead arms  30  extending therefrom (although the present invention comprehends a lesser or greater number of lead arms). Lead arms  30  preferably extend downwardly toward the ground. Lead arms  30  are further preferably formed from C-channel iron and are welded to the crossbar  20 . Four trailing arms  32  are also preferably formed from C-channel iron and welded to the crossbar  20 . Trailing arms  32  preferably extend back toward the tractor  12  and only slightly downwardly. 
     A pair of drag units  36  are suspended from the lead arms  30  and trailing arms  32  by means of a plurality of connecting members  38  connected therebetween. Although the preferred embodiment of the present invention utilizes chains as the connecting members  38 , it will be appreciated by those having ordinary skill in the art that any resilient connecting member that is substantially perfectly compressible may be used. A perfectly compressible connecting member is one which exerts no force in opposition to compression along the axis defined by the points at which it connects to the elements being connected. Therefore, the drag units  36  exert a downward force upon the ground which is substantially proportional only to the weight of the drag unit  36 . In a preferred embodiment of the present invention, each of the drag units  36  is coupled to two of the lead arms  30  by means of two chains  38 , while each of the drag units  36  is coupled to two of the trailing arms  32  by means of six chains  38 . 
     A stop bar  40  is mounted above and slightly behind the crossbar  20  upon a pair of stop bar elevating brackets  42 , each welded to a respective support member  18 . A gauge  44  extends downwardly from either end of the stop bar  40 . Preferably, each gauge  44  is positioned just inside each of the outside trailing arms  32 . 
     In operation, the apparatus  10  is positioned in the down position (as illustrated in FIG. 1) and the tractor  12  is moved forward across the field. In the down position, each of the drag units  36  lays upon the ground solely by virtue of its own weight. In the preferred embodiment of the present invention, each drag unit  36  weighs approximately 60 pounds. The connecting members  38  limit the range of motion of the drag unit  36  with respect to the crossbar  20 , however they do not exert any downward or upward force upon the drag unit  36  when the apparatus  10  is in the down position. As the tractor  12  moves forward across the field, the connecting members  38  extending between the lead arms  30  and the drag unit  36  limit the rearward (i.e. toward the tractor  12 ) movement of the drag unit  36 , so that it does not interfere with the tires of the tractor  12 . In order to assure that the drag unit does not interfere with the wheels of the tractor, the connecting members  38  are preferably anchored to the lead arms  30  or trailing arm  32  at a point further away from any point where the wheels contact the ground than the sum of the length of the connecting members  38  plus the length of the drag unit  36 . This way, even if the trailing edge of the drag unit  36  is pulled as far back towards the Wheels as possible, such that the entire length of the connecting member  38  and the drag unit  36  form a straight line, causing the drag unit to be lifted off the ground along most or all of it&#39;s length, the drag unit still cannot get between the tires and the ground. 
     During forward movement, the leading edge of each drag unit  36  is the leading edge of the tractor  12 / 10  and is therefore the first part of the device to come into contact with the corn stalk stubble sticking up in the field. Because of the substantial weight of the drag unit  36 , interaction between the drag unit  36  and the corn stalk stubble results in the corn stalk stubble being folded over in a direction facing away from the tractor  12 . When the wheels of the tractor  12  eventually reach the folded over corn stalk stubble, the stubble does not poke into the surface of the tires and therefore wear to the tires is substantially eliminated. 
     As will be familiar to those skilled in the art, tractors are generally constructed to be able to move in at least two directions—forward and in reverse—in order to improve their mobility. Typically, the wheel arrangement, driver position, and the positioning of other elements all define a forward direction of motion. Thus, although the apparatus  10  is preferably coupled to the tractor  12  so as to place the mounting panels  14 , and the drag units (shown as  36  in FIG. 3) forward of the tires, in certain alternative embodiments the apparatus  10  is coupled to the tractor  12  so as to place the drag units  36  behind the tires. In these embodiments, the apparatus  10  would clear corn stubble and the like when the tractor was moved in reverse, so that the preferred direction of motion would be towards the rear of the tractor. 
     With reference now to FIGS. 2 and 3, the apparatus  10  may be lifted off of the ground by extension of the hydraulic cylinder  28  (preferably controlled from inside the tractor  12 ). Extending the hydraulic cylinder  28  causes the flange  24  on the upper surface of crossbar  20  to be rotated away from the tractor  12 . This causes rotation of the crossbar  20 , which in turn causes rotation of the trailing arms  32  away from the ground. Because the distance between the drag unit  36  and the trailing arms  32  is limited by the connecting members  38 , sufficient rotation of the crossbar  20  causes the drag unit  36  to be lifted off of the ground. In the case of tractors  12  having large front wheels (such as that illustrated in the drawings), it is generally not possible for the operator of the tractor  12  to directly view the drag units  36 . The gauge bar  44  is therefore provided at a location that is visible to the operator of the tractor  12 . By viewing the location of the outboard trailing arm  32  with respect to the gauge bar  44 , the operator of the tractor  12  is able to easily determine the extent of raising or lowering of the drag unit  36 . Preferably, the gauge  44  includes an upper marking indicating the proper raised position, and a lower marking indicating the proper lowered position of the apparatus  10 . It is preferable that the upper marking be chosen at a position which will prevent excessive pressure being placed on the hydraulic cylinder  28  in order to prevent bending of the hydraulic cylinder  28  components. The apparatus  10  is illustrated in raised position in FIG. 3, and the lowered position in FIG.  4 . 
     Referring now to FIG. 4, the apparatus  10  is illustrated in the lowered position (drag unit  36  resting upon the ground) with the tractor  12  moving in the forward direction. It can be seen that the connecting member  38  extending between the lead arm  30  and the drag unit  36  limits rearward travel of the drag unit  36 . This limitation on the rearward travel of the drag unit  36  while the vehicle is in forward motion prevents any possible interference between the drag unit  36  and the tires of the tractor  12 . FIG. 5 illustrates the apparatus  10  position when the tractor  12  is moving in a rearward direction. In this position, the connecting member  38  between the lead arm  30  aid the drag unit  36  is slack, however, the connecting members  38  between the trailing arm  32  and the drag unit  36  are taut. This limits forward movement of the drag unit  36  while the tractor  12  is traveling in a rearward direction. FIG. 6 illustrates the apparatus  10  from the front of the tractor  12 . As can be seen, it is preferred that each of the drag units  36  are at least as wide as the tire(s) positioned behind the drag unit  36 . This ensures that any stubble in the field is folded over by the drag unit  36  prior to contact therewith by the tire of the tractor  12 . 
     Referring now to FIGS. 7 and 8, a preferred embodiment of the drag unit  36  of the present invention is illustrated in greater detail. Each drag unit  36  is preferably composed of three pieces of two-inch by three-inch by one-quarter-inch angle iron  50 . Each piece of angle iron  50  includes several brackets  52  welded thereto which allow connection to the connecting members  38 , preferably by means of a nut and bolt combination. Each piece of angle iron  50  includes further brackets  54 , which allow for coupling of a drag unit joint bar  56  therebetween. There are preferably two joint bars  56  coupling each piece of angle iron  50  to each of its immediate neighbors. Rotatable couplings are preferably utilized between the brackets  54  and the joint bars  56  in order to allow vertical movement of the angle irons  50  with respect to one another as the drag bar  36  moves across uneven terrain. This minimizes the tendency of the drag bar  36  to be lifted off the ground as the leading edge of the drag bar  36  moves over an obstacle. By providing rotatable couplings between the joint bars  56  and the brackets  54 , the drag bar  36  deforms itself in order to maintain close contact with the ground as it moves over obstacles. Although the jointed drag bar  36  illustrated in FIGS. 7 and 8 is preferred, the present invention does comprehend the use of a non-jointed drag bar  36 . 
     It will be appreciated from the above description that the apparatus  10  of the present invention is effective in folding over field stubble, such as corn stalks and the like, prior to their interaction with the tractor tires. By folding the stubble over prior to such interaction, abrasion of the tires is greatly reduced or substantially eliminated. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. For example, specific materials are disclosed for each of the components of the preferred embodiment, however those having ordinary skill in the art will recognize that the materials used are not critical, so long as the materials chosen are adequate in view of the required performance of the component.

Summary:
The present invention relates to a device which may be mounted to the front of a tractor and which is operative to fold over corn stalks and the like before they engage the front tires of the tractor. The device positions dragging units in front of each of the front tires of the tractor, whereby the dragging units are dragged over the ground in front of the tires when the tractor is moving. The weight of each of the dragging units is sufficient to cause it to substantially fold over corn stalks and the like prior to their engagement with the front tires of the tractor, thereby greatly minimizing wear to the tires caused by engagement with the corn stalks and the like.