Abstract:
A suspension system for a row crop planter unit which includes a shock absorber extending between the planter unit mounting bracket and the parallel arm linkage which vertically mounts the planter unit to a toolbar. The shock absorber permits the planter unit to move more quickly in the rebound cycle than in the compression cycle to reduce row unit bounce.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Application Ser. No. 60/964,920 entitled “SUSPENSION SYSTEM FOR A ROW CROP PLANTER UNIT” filed Aug. 16, 2007, the disclosure of which is hereby incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a suspension system for a row crop planter unit and more particularly to a suspension system preferably in the form of a coil-over shock absorber which is operatively connected to the supporting frame of the planter unit and to the parallel arm linkage of the row crop planter unit to reduce row unit bounce (R.U.B.). 
   2. Description of the Related Art 
   Many types of suspension systems or mounting systems for row crop planter units have been previously provided. In most instances, the row crop planter units are connected to a transversely extending toolbar in a horizontally spaced-apart manner for single row planting or in a horizontally spaced-apart and staggered or offset manner for twin row planting. The toolbar is normally wheel supported or three-point hitch supported and is pulled through a field by a prime mover such as a tractor or the like. Each of the planter units is normally connected to the toolbar by means of a parallel arm linkage so that the planter units may vertically move with respect to the toolbar. As the planter is pulled through the field, the planter units tend to bounce upwardly and downwardly due to encountering uneven terrain. If the planter unit does objectionably bounce, the seed spacing and seed depth of the planter unit will not be proper. Seed spacing is extremely important in planting operations wherein single rows are planted, and is even more important when the row crops are being planted in twin rows. 
   One prior art method of attempting to reduce the row unit bounce is to utilize coil springs which interconnect the upper and lower parallel arms of each of the parallel arm linkages. See, for example, U.S. Pat. No. 5,709,271 and published application No. 2006/0213407 A1. The coil springs of the prior art do exert a certain amount of down pressure on the planter unit and do reduce row unit bounce to some degree. However, it has been found that the coil spring arrangements commonly found in the prior art do not satisfactorily reduce row unit bounce thereby resulting in improper seed spacing and seed depth. 
   SUMMARY OF THE INVENTION 
   A suspension system is provided for a row crop planter unit wherein a plurality of the row crop planting units are positioned rearwardly of a transversely extending frame member or toolbar. Each of the planter units is pivotally connected to the toolbar by a parallel arm linkage including a pair of upper parallel arms and a pair of lower parallel arms. The parallel arm linkage enables the planter unit to move vertically with respect to the toolbar. The forward ends of the upper and lower pairs of parallel arms for each planter unit are pivotally connected to a mounting bracket secured to the toolbar. In some cases, the mounting brackets permit the planter units to be staggered to enable the row crop to be planted in twin rows. The rearward ends of the upper and lower pairs of parallel arms are pivotally connected to the planter unit. 
   A fluid-filled shock absorber, preferably of the coil-over shock type, is associated with each of the parallel arm linkages. The upper end of the shock absorber is pivotally secured to the upper end of the associated mounting bracket and extends downwardly and rearwardly therefrom. The lower end of the shock absorber is pivotally connected to the lower pair of parallel arms of the parallel arm linkage. The shock absorber is available for purchase and includes a rebound chamber and a compression chamber separated by a piston which includes valving. The fluid in the compression chamber is compressed as the planter unit moves upwardly with respect to the toolbar and the fluid in the rebound chamber of the shock absorber is compressed as the row unit moves downwardly with respect to the toolbar. The shock absorber is designed so that the damping force in the compression cycle is greater than the damping force in the rebound cycle. In other words, the fluid in the compression chamber will flow through the valving in the piston during the compression cycle at a slower rate (velocity) than the fluid in the rebound chamber will flow through the piston during the rebound cycle. The lower compression damping in the rebound cycle allows the row unit to move down quickly and the greater compression damping in the compression cycle reduces the rate of upward bounce of the row unit, thereby maintaining better seed depth and seed spacing. The shock absorber, by way of the coil-over construction, maintains down pressure throughout the entire travel range. The coil-over spring of the shock absorber may be preloaded to increase down pressure. 
   It is therefore a principal object of the invention to provide an improved suspension system for a row crop planter unit. 
   A further object of the invention is to provide a suspension system for a row crop planter unit which includes a shock absorber operatively connected to the parallel arm linkage of each planter unit to reduce row unit bounce. 
   Yet another object of the invention is to provide a suspension system of the type described above wherein the shock absorber is a coil-over shock absorber wherein the spring may be preloaded to increase down pressure. 
   Yet another object of the invention is to provide a suspension system of the type described above wherein the shock absorber has a higher compression damping force than rebound damping force which allows the row unit to go down quickly but will not bounce up quickly, maintaining better seed depth and seed spacing. 
   Still another object of the invention is to provide a suspension system for a row crop planter unit which employs a fluid-filled shock absorber. 
   Still another object of the invention is to provide a suspension system for a row crop planter unit including a gas pressurized shock absorber. 
   Yet another object of the invention is to provide a suspension system for a row crop planter unit which maintains pressure throughout the entire travel range of the row crop planter unit. 
   Still another object of the invention is to provide a suspension system for a row crop planter unit which is economical of manufacture and durable in use. 
   These and other objects will be obvious to those skilled in the art. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a row crop planter unit having the suspension system of this invention mounted thereon; 
       FIG. 2  is a rear view of the mounting bracket for the suspension system; 
       FIG. 3  is a side view of one of the plates of the mounting bracket; 
       FIG. 4  is a side view of the other plate of the mounting bracket; 
       FIG. 5  is a top view of the mounting bracket; 
       FIG. 6  is a side view of one of the arms of the upper pair of parallel arms; 
       FIG. 7  is a top view of the upper pair of parallel arms; 
       FIG. 8  is a side view of one of the arms of the lower pair of parallel arms; 
       FIG. 9  is a top view of the lower pair of parallel arms; 
       FIG. 10  is a top view of the suspension system and planter unit; and 
       FIG. 11  is an exploded perspective view of the suspension system of this invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The numeral  10  refers generally to a row planter which may be either a single row planter or a twin row planter. A twin row planter is disclosed in U.S. Pat. No. 6,520,100. Planter  10  generally includes a toolbar or frame  12  and planter units  14  which include conventional furrow opening discs, depth gauge wheels, furrow closing discs, compaction wheel, etc. 
   A plurality of horizontally spaced-apart mounting brackets  16  are secured to the toolbar  12  in conventional fashion such as by U-bolts  18  or the like. Mounting bracket  16  includes an upper end  20  and a lower end  22 . Mounting bracket  16  includes spaced-apart side plates  24  and  26  which have a rearwardly extending arm assembly  28  at their upper ends. Arm assembly  28  may have a plurality of adjustment openings  30  formed therein. 
   Each of the planter units  14  is pivotally secured to a mounting bracket  16  by a parallel arm linkage  32  which includes an upper pair  34  of parallel arms and a lower pair  36  of parallel arms. The upper pair  34  of parallel arms is comprised of arms  34 A and  34 B while the lower pair  36  of parallel arms is comprised of arms  36 A and  36 B. The forward ends of the upper pair  34  of parallel arms are pivotally secured to the mounting bracket  16  at  38  in conventional fashion. The forward ends of the lower pair  36  of parallel arms are pivotally secured to the mounting bracket  16  at  40  in conventional fashion. 
   The rearward ends of upper pair  34  of parallel arms are pivotally secured to the associated planter unit at  42 . The rearward ends of the lower pair  36  of parallel arms are pivotally secured to the associated planter unit  14  at  44  in conventional fashion. 
   The numeral  46  refers generally to a fluid-filled shock absorber which is preferably of the coil-over shock type. Coil  48  is adjustable in conventional fashion to vary the down pressure on the planter unit. The upper end of shock absorber  48  is connected to arm  28  of mounting bracket  16  at  50  and extends downwardly and rearwardly therefrom. The lower end of shock absorber  48  is connected to a bracket  52  at  54  which is secured to the lower pair  36  of parallel arms. Although it is preferred that a coil-over shock absorber be utilized, the coil  48  may be omitted if a separate coil is secured to and extended between the upper pair  34  of parallel arms and the lower pair  36  of parallel arms. A suitable shock absorber  46  is readily available from either QA1, 21730 Hanover Avenue, Lakeville, Minn. 55044, or from Bilstein through Speedway. The shock absorber, if purchased from QA1, is identified as Item Number 2179-1B, Shock Mono LRG Steel 13-20 Eye-B/Eye-B, V9-1 Axle Damp. The shock absorber, if purchased from Speedway, is identified as a Bilstein 2″ Steel Shock, Part No. 213-S7Z1090. In both shock absorbers, a compression chamber and a rebound chamber are separated by a movable piston having valving incorporated therein which controls the compression damping and the rebound damping. Each of the available shock absorbers is designed so that the damping force in the compression cycle is greater than the damping force in the rebound cycle. In other words, the fluid in the compression chamber will flow through the valving in the piston during the compression cycle at a slower rate (velocity) than the fluid in the rebound chamber will flow through the piston during the rebound cycle. The velocity or damping force is preferably approximately 9-1 and is set at the factory although adjustable shock absorbers are also available. 
   Shock absorber  46  is positioned on the planter unit so that the fluid in the compression chamber thereof is compressed as the planter unit moves upwardly and so that the fluid in the rebound chamber is compressed as the planter unit moves downwardly. The damping force in the compression cycle is greater than the damping force in the rebound cycle which allows the row unit to go down quickly but move upwardly more slowly, thereby reducing row unit bounce to achieve more uniform seed depth and seed spacing. The shock absorber maintains down pressure throughout the entire travel range by way of the coil spring. The coil spring of the shock absorber may be pre-loaded to increase down pressure on the row unit. 
   Thus it can be seen that the invention accomplishes at least all of its stated objectives.