Abstract:
A suspension system for a tractor-drawn mower used for crops for agricultural purposes is made up of parallel links, connected at a first end to a frame and to a mowing unit at a second end. A torsion spring assembly, similar to that used for torsion axles, is used to bear a portion of the weight of the mowing unit when the mowing unit is in a lower, mowing position. All torsional stress is removed from the torsion spring when the mowing unit is in a transport position. During mowing, the weight of the mowing unit is divided up between the torsion spring and the surface of the ground. The ratio of the weight supported by the ground to that supported by the torsion spring is adjustable by an operator.

Description:
TECHNICAL FIELD 
   The principles disclosed relate to the suspension for an agricultural mower. More particularly, this disclosure relates to the construction of a mower in a manner that provides a simple and cost effective product that provides adequate suspension. 
   BACKGROUND 
   Towed agricultural mowers typically comprise a mowing unit that is supported by a frame, typically in a manner that there are two basic positions. The first is a transport position wherein the mowing unit is in fixed position with the frame supporting its full weight. The second is the lowered operating position wherein it is able to float, move relative to the frame, with a portion of its weight carried by a suspension system to the frame (ultimately through the wheels to the ground). The remaining portion of the weight is transferred directly to the ground via a skid or sliding member. The weight, or force transferred directly to the ground via the skid is hereinafter referred to as ground pressure. The amount of ground pressure will affect the performance of the mower. Many designs provide an operator-adjustable suspension system. Suspension systems are designed to suspend a specific range of weight. The weight range corresponds to a large percentage of the weight of the mowing unit. In this way, the desired ground pressure is provided in order to minimize damage that the skid on the mowing unit may cause to the ground in comparison to allowing the full weight to act against the ground (that is, with no weight being carried on the frame and wheels). 
   The most common mowing units include a cutting apparatus, a crop conditioning apparatus and the drive train necessary to transfer power to both; the total weight can be significant. Thus, the suspension systems require the use of elements with correspondingly significant load bearing capacity, typically relatively large extension springs. Other suspension systems utilize other types of springs, including rubber torsion springs as disclosed in U.S. Patent Applications publication number 2003/0140610 to Boyko wherein a towed rotary mower uses rubber torsion elements mounted onto the frame, the rubber torsion elements supporting crank arms to support wheels and suspend the frame and mowing unit. U.S. Pat. No. 5,960,614 to Jones discloses a suspension for a mower that is mounted to a tractor with a frame that moves up and down to control the height of the mower, and a suspension element comprising a rubber torsion axle, used to urge one of two parallel linkages in a direction to support a mower unit attached to the frame with a four bar linkage. Neither of these configurations provides an operator control of the ground pressure. 
   A need thus exists for an improved suspension system for a mower that provides operator adjustment of ground pressure and that is adapted to optimize the mounting onto a trailed frame. 
   SUMMARY 
   The mower unit of an agricultural crop mowing machine may be suspended from a frame. The frame is supported by wheels engaging the ground. An object of the present invention is to provide a linkage assembly that permits the mowing machine to be raised into a transport position and lowered into an operating position. 
   A set of parallel links may be used to attach the mowing machine to the frame. The parallel links, along with a housing on the mowing machine to which the links are attached, and the frame, comprise a parallelogram regardless of the position of the mowing machine. Therefore, the mowing machine does not rotate relative to its frame when its position is altered relative to the frame. 
   Usually, the mowing machine is partially supported by skids, wheels or the like when it is in its operating position. Another object of the present invention is to provide for varying the fraction of the mowing machine&#39;s weight that is supported on these supports. To accomplish this object, two link arms making up a portion of the linkage assembly mentioned above comprise torsion springs such as torsion axles used on trailers. One end of the axle of such a torsion spring is pivotally attached to the mowing machine. The other end of the torsion spring is rigidly attached to a link arm that is, in turn, flexibly attached to the frame. When the mowing machine is in its upper, transport position, no torque is transferred to the torsion spring as the axle is free to pivot relative to the mowing machine. As the mowing machine is lowered to its operating position, the rotation of the axle is stopped relative to the mowing machine by a torque arm and torque is applied to the torsion spring such that some of the mowing machine&#39;s weight is supported by the torsion spring. By adjusting the location at which the axle&#39;s rotation is stopped relative to the mowing machine, the amount of weight supported by the torsion spring is adjustable. 
   The torque arm has an aperture shaped to engage an end of the axle of the torsion spring. It may be turned and/or reversed by an operator relative to the axle and reengaged on the end of the axle to adjust the weight borne by the torsion spring when the mowing machine is in its operating position. 
   The torque arm engages a stop pin that is affixed to the mowing machine. Further adjustment to the weight borne by the torsion spring when the mowing machine is in its operating position may be effected by relocating the stop pin in angular position relative to the axis of rotation of the torsion spring. 
   In another embodiment of the present invention, the torsion spring may be pivotally attached to the frame and the link arm attached to the mowing machine. 
   Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view of a trailed frame supporting a mowing unit of the present invention with the mowing unit in the raised transport position; 
       FIG. 2  is a side elevation view of a trailed frame supporting a mowing unit of the present invention with the mowing unit in a partially lowered position; 
       FIG. 2   a  is a detail of a portion of the side view indicated in circle  2   a  of  FIG. 2 ; 
       FIG. 3  is a cross-sectional view taken along line  3 — 3  as illustrated in  FIG. 2 ; 
       FIG. 4  is an exploded isometric view of one lower link with the torsion spring from a first side; 
       FIG. 4   a  is an isometric view of the lower link assembled from a second, or opposite side; 
       FIG. 5  is a side elevation view of a trailed frame supporting a mowing unit of the present invention with the mowing unit in a lowered operating position; 
       FIG. 6  is a free body diagram of the mowing unit raised in a transport position; 
       FIG. 7  is a free body diagram of the upper suspension link of the present invention raised in a transport position; 
       FIG. 8  is a free body diagram of the lower suspension link of the present invention raised in a transport position; 
       FIG. 9  is a free body diagram of the rubber torsion spring axle of the present invention raised in a transport position; 
       FIG. 10  is a free body diagram of the mowing unit lowered to an operating position; 
       FIG. 11  is a free body diagram of the upper suspension link of the present invention lowered to an operating position; 
       FIG. 12  is a free body diagram of the lower suspension link of the present invention lowered to an operating position; 
       FIG. 13  is a free body diagram of the rubber torsion spring axle of the present invention lowered to an operating position; and 
       FIG. 14  is an isometric view of the overall machine from the rear right side with the right side wheel removed. 
   

   DETAILED DESCRIPTION 
   With reference now to the various figures in which identical elements are numbered identically throughout, a description of various exemplary aspects of the present invention will now be provided. The preferred embodiments are shown in the drawings and described with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the embodiments disclosed. 
     FIG. 1  illustrates a trailed mower  100  that is comprised of a frame  110  supported at the rear on two tires  120 , only one is illustrated as this is a side view, and at the front by a hitch  102  of a tractor  104 . The position of the wheels  120  is fixed in relation to the frame  110  such that the height of the frame  110  from the ground is fixed. In this figure, a mowing unit  200  is in a raised transport position, with a front side, closest to the front of the frame, configured to accept crop material, and a rear side configured to eject crop material. The mowing unit  200  is mounted to the frame  110  by a linkage including parallel links. The parallel links include two bottom links  140   a ,  140   b . The left link  140   a  is shown, while the right link  140   b  is not shown. Further, the parallel links include a single top link  130 , located between the two bottom links  140   a ,  140   b.    
   In  FIG. 2  this linkage is illustrated in a partially lowered position wherein the top link  130  is connecting the mowing unit  200  to the frame  110 . The single top link  130  is attached to the frame  110  at a top link frame pivot support  133 , which is illustrated as approximately concentric with the center of the wheels  120 . This pivot support  133  can be located in other positions, its position relative to the wheels is not critical, and the present invention is not limited to any particular location for the pivot support  133 . The single top link  130  is attached to the mowing unit  200  at a top link pivot  134  by a top link ear  135 . 
     FIG. 14  illustrates the linkage, showing both bottom links  140   a ,  140   b  attached to the frame  110  at two frame pivots  142   a ,  142   b , configured with pivot supports  143 , on each end of the frame  110 . The pivot supports  143  of frame  110  include apertures that align to define a pivot axis. 
   The bottom links  140   a ,  140   b  both attach on the opposite end to the mowing unit  200  at two mower pivots  144   a ,  144   b . The mower pivots  144   a ,  144   b  are configured with bearings  202 ,  204 , as will be described below, as components of the mowing unit  200 . The mowing unit  200  further includes stops  206  that can be positioned in a variety of positions, as illustrated in  FIGS. 2   a  and  3 . 
   The pivot joints at pivots  132 ,  134 ,  142  are basic pivots. Any known type of bearing or bushing could be employed in these pivots, preferably comprising spherical ball joints to provide two degrees of freedom, similar to pivot  142  which includes spherical ball joint  143 , illustrated in  FIG. 3 . The present invention incorporates a novel mower pivot  144  including a rubber torsion axle assembly  301  (see  FIG. 4 ). 
     FIGS. 4 and 4   a  illustrate the arrangement of the components of the mower pivot  144 . The outer square tube portion  308  of a traditional rubber torsion axle assembly  301  is fixedly connected to, and a component of, the lower link  140 , in this embodiment configured as a bolted joint. The mower pivot  144  is configured when the axle  300  is installed through the square tube  308 , rubber springs  306  are installed in the spaces between the inside surfaces of the square tube  308  and the outer surface of the square shape of the center section of the axle  300 . This rubber torsion axle assembly  301  is secured in position as the shaft portion  304  is mounted in the bearing  204 , a torque arm  310  is attached to the axle portion  300  of the rubber torsion axle assembly  301  and shaft portion  302  is mounted to bearing  202 . The torque arm  310  is rotationally secured to the square portion of the axle portion  300  of the rubber torsion axle assembly  301 , by the configuration of aperture  311  which mates with the square tube portion of the rubber torsion axle assembly  301 . An aperture  311  is constructed such that the torque arm  310  is reversible, and the same component is used on both sides of the mower. 
     FIG. 3  illustrates the torque arm  310 , positioned as shown in  FIG. 2   a , to come into contact with the stop pin  206  which is supported in the frame  200  and the support plate  208 . After the torque arm  310  contacts the stop pin  206 , the axle  300  will be restrained from further rotation relative to the frame  200 . The mowing unit  200  can be lowered, from the position shown in  FIGS. 2 and 2   a , towards an operational position illustrated in  FIG. 5 , by further extending two cylinders  150 , only one cylinder  150  shown in  FIG. 5 . As the mowing unit  200  is thus lowered, the outer tube  308  will rotate counterclockwise, as shown in  FIG. 2   a , while the axle  300  is held from rotating, causing relative rotation between the outer tube  308  and the axle  300 , resulting in a compression load in the rubber springs  306 , generating a moment load at the mower pivot  144 . 
   In  FIG. 1  the mowing unit  200  is illustrated raised into and held in the transport position by the cylinder  150  that connects to the frame  110  and to the lower link  140 .  FIG. 8  illustrates a cylinder force  152  acting on one lower link  140 , with a resultant force  148   a  acting at the mower pivot  144 . A force  141  acting generally at the pivot  142  is the sum of the two other forces  148   a ,  152  acting on the lower link  140 . This force will result in combined distributed loading on the rubber springs  306 . The resulting equal and opposite force  148   b  is applied to the axle  300  as illustrated in  FIG. 9  where an equal and opposite force  248   a  is applied from the mowing unit  200  through the bearings  202  and  204 . The free-body-diagram of  FIG. 6  shows force  248   b  applied to the mowing unit  200 . In this way, the lower links  140  transfer force from the cylinder to lift the mowing unit  200  with the rubber torsion axle assembly  301 , while the upper link  130  holds the mowing unit  200  from freely rotating, via the force  136   b  applied at pivot  134 . The upper link  130  will be subjected to a tensile load, as illustrated in the free body diagram of  FIG. 7 . 
   The cylinders  150  are extended to lower the mowing unit  200  into the operating position illustrated in  FIG. 5 . As the cylinders  150  extend, and the mowing unit  200  lowers, there will be rotation between both the top link  130  and the bottom links  140   a ,  140   b  and their mating components on both the frame  110  and the mowing unit  200 . As a result of this rotation the torque arm  310  will move relative to the mowing unit  200  from the position as illustrated in  FIG. 1 , to the position as illustrated in  FIG. 2   a  with the mowing unit  200  in a partially lowered position. In this position the torque arm  310  will come to a position where it first contacts the stop pin  206 . As the cylinders  150  continue to extend, lowering the mowing unit to the position as illustrated in  FIG. 5  until there is no load on the bottom links  140   a ,  140   b , as provided by a slot  152  of the cylinder  150 . In addition, the lowering action causes rotation of the bottom link  140  relative to the mowing unit  200  which will generate a torque  146  within the axle  300  resulting from the contact of the torque arm  310  with the stop pin  206 , and a reaction force  312   a . The moment  146  is the result of compression of the rubber springs  306 . The equal and opposite force  312   b  on the mowing machine associated with the reaction force  312   a  on the torsion axle is shown in  FIG. 10 . 
   As illustrated in the free body diagram of  FIG. 12 , with the cylinders  150  completely extended, there will be no cylinder force, and the moment  146  will be applied to the end of the link  140  by the axle  300 , which will simultaneously transmit a force  148   a . The force  148   a  is the result of unequal loading within the rubber springs  306 . A force  145  acting generally at the pivot  142  is the resultant due to the force  148   a , and the moment  146  acting on the lower link  140 .  FIG. 13  illustrates the equal and opposite force  148   b  applied to the rubber torsion axle assembly  301  and torque arm  310 , along with the reaction force  312   a  as applied to the torque arm. The force  248   a  is applied from the mowing unit. The moment  146  is generated by a reaction force  312   a  as a function of the relative rotation at the mower pivot  144 , which causes compression of the rubber springs  306 .  FIG. 10  illustrates a force  136   a  acting at a pivot point  134 , to effectively hold the mowing unit  200  from rotation. The upper link  130  will be subjected to an equal and opposite tensile load, as illustrated in the free body diagram of  FIG. 11 . The net effect of the forces applied to the mowing unit  200  is that the ground contact force  250  will be reduced, as a function of the torque  146 . 
   The torque generated within the rubber torsion axle assembly  301  is a function of the relative rotation between the outer tube  308  and the axle  300 . This relative rotation is determined by the position at which the torque arm  310  first contacts the stop pin  206 , and the position at which the mowing unit  200  contacts the ground. The pin  206  can be inserted into one of several holes as illustrated. By changing the location of the stop pin  206 , the orientation at which the torque arm  310  initially contacts the stop pin  206  is modified. This modification affects the relative rotation the axle  300  is subjected to. Thus, by adjusting the position of the stop pin  206 , while the mowing unit  200  is in its raised position, as illustrated in  FIG. 1 , the amount of torque generated by the axle  300  when the mowing unit  200  is lowered to the operating position, as illustrated in  FIG. 5 , is controlled. This adjustment allows the operator to adjust the lift force and thus the resulting ground pressure. 
   The above embodiment is the preferred embodiment, but this invention is not limited thereto. It is, therefore, apparent that many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.