Abstract:
An agricultural plough ( 1 ) including a longitudinally extending support member ( 2 ) having a forward portion to be attached to a vehicle to thereby enable the apparatus ( 1 ) to be towed by the vehicle; a generally “n” shaped frame ( 500 ) fixed to the support member ( 2 ) and including a pair of ends ( 505, 510 ) located on opposite longitudinal sides and spaced normal to the support member ( 2 ); a pair of axles ( 13, 14 ) attached to and extending laterally from the ends and providing a pair of laterally extending rotational axes, the axes being located on opposite sides of the member ( 2 ) and in a plane extending transversely normal to the member ( 2 ) and at an acute angle longitudinally so as to extend rearwardly down, the axes each being inclined by an acute angle of 6 to 12 degrees to a plane extending normal to the member ( 2 ) to diverge rearwardly; a plough disc ( 18, 20 ) supported on each axle to rotate about the rotational axes, with the discs ( 18, 20 ) and axles being configured so that the discs ( 18, 20 ) converge rearwardly and downwardly, the discs ( 18, 20 ) being displaced rearwardly from the forward portion; a wheel attached to the support member ( 2 ) and rotatable about an axis generally transverse of the support member ( 2 ), the wheel ( 12 ) being located rearwardly of the axles ( 13, 14 ); and structure connected to the support member ( 2 ) and to be attached to the vehicle, to urge the member downwardly so that the discs ( 18, 20 ) are urged into soil and the wheel ( 12 ) is urged into contact with a soil surface rearwardly of the discs ( 18, 20 ) so that upon forward movement of the vehicle with the discs ( 18, 20 ) engaged in the soil, each disc ( 18, 20 ) forms a separate groove and a corresponding ridge in the soil between the grooves, with the ridge being engaged by the wheel ( 12 ) to urge the soil to cover seeds located in the grooves.

Description:
This application is a continuation-in-part of application Ser. No. 10/220,673 filed on Oct. 23, 2002 now U.S. Pat. No. 7104206, claims the benefit thereof and incorporates the same by reference. 

   The present invention relates to an agricultural apparatus for use in the sowing of seeds. In particular, the invention relates to an agricultural plough having a disc planter. 
   BACKGROUND OF THE INVENTION 
   Conventional disc planters typically have a frame attachable to a towing vehicle. The frame usually comprises a pair of parallel support arms spaced vertically, one above the other. The arms are hingedly attached to a support plate or beam which is attached to the towing vehicle. A support fame is attached to the other ends of the arms to support the seed planting apparatus. A pair of discs are mounted on the support frame in addition to two press wheels which are spaced from and located behind the two discs. The discs are mounted on an axle to which is attached a disc lever to alter the lateral spacing of the discs relative to one another on the axle. Each pair of discs are arranged to cut a single furrow or groove in the soil into which the seed is deposited. Typically, a plurality of disc planters of the type described above are attached in parallel to the towing vehicle, the disc planters being spaced laterally from one another, to enable a number of rows of seeds to be sown simultaneously. 
   In operation, the plurality of disc planters are attached to the towing vehicle and the lateral spacing of the discs on the axles on which they are mounted is adjusted to suit the type of seed to be planted. The discs rotate about the axles to cut grooves in the soil as the towing vehicle is driven over the ground on which the seed is to be sown. The soil cut by the discs is typically thrown out in a sideways direction by the discs as it is cut, there being no actual control over the amount or direction of soil thrown. The seeds are dropped into the grooves made by the discs via grain tubes, the outlets of which are typically located between the discs and the press wheels. Once the seed has been dropped into the grooves, the press wheels push the soil into the grooves to cover the seeds. In some conventional embodiments a further wheel or wheels are located between the discs and the press wheels to cover the sown seeds before the soil is compacted further by the press wheels. 
   OBJECTS OF THE INVENTION 
   It is an object of the present invention to overcome or ameliorate some of the disadvantages of the prior art, or at least to provide a useful alternative. 
   SUMMARY OF THE INVENTION 
   According to the present invention there is preferably provided a plough including: 
   a longitudinally extending support member having a forward portion to be attached to a vehicle to thereby enable the apparatus to be towed by the vehicle; 
   a generally “n” shaped frame fixed to said support member and including a pair of ends located on opposite longitudinal sides and spaced normal to, said support member; 
   a pair of axles attached to and extending laterally from said ends and providing a pair of laterally extending rotational axes, the axes being located on opposite sides of the member and in a plane extending transversely normal to said member and at an acute angle longitudinally so as to extend rearwardly down, the axes each being inclined by an acute angle of 6 to 12 degrees to a plane extending normal to the member to diverge rearwardly; 
   a plough disc supported on each axle to rotate about said rotational axes, with the discs and axles being configured so that the discs converge rearwardly and downwardly, the discs being displaced rearwardly from said forward portion; 
   a wheel attached to said support member and rotatable about an axis generally transverse of the support member, the wheel being located rearwardly of said axles; and 
   means connected to the support member and to be attached to the vehicle, to urge said member downwardly so that said discs are urged into soil and said wheel is urged into contact with a soil surface rearwardly of the discs so that upon forward movement of the vehicle with the discs engaged in the soil, each disc forms a separate groove and a corresponding ridge in the soil between said grooves, with the ridge being engaged by the wheel to urge the soil to cover seeds located in the grooves. 
   Preferably, the axes are inclined by an acute angle of 8 to 10 degrees. 
   Preferably, said support member may be comprised of a first member and a second member, said second member being attached to said first member, for example said second member being welded to said first member. 
   Preferably, said axles extend through said second member. 
   Preferably, said second member includes said frame. 
   Preferably, said wheel for pressing soil into the grooves may be mountable on said second member. 
   Preferably, said axles are rotatable with respect to said support member. 
   Preferably, the means for urging the discs into the soil is operable to enable adjustment of the depth of the grooves to be formed. 
   Preferably, means for urging the discs into the soil may comprise a hydraulic cylinder connectable between said vehicle and the support member. 
   Preferably, including locking means for locking said adjustment assembly in a preselected position thereby inhibiting movement of the axles relative to the support member. 
   Preferably, further comprising an adjustable assembly operatively associated with said axles to adjust the position of the axles relative to said support member and soil. 
   Preferably, the discs are outwardly inclined by an acute angle to a plane extending normal to the member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various embodiments of the agricultural apparatus according to the invention will now be more fully described, by way of example only, with reference to the drawings in which: 
       FIG. 1  is a schematic plan view of a disc planter; 
       FIG. 2  is a schematic side elevation of the disc planter of  FIG. 2 ; 
       FIG. 3  is a schematic third angle projection of the disc planter of  FIG. 1 ; 
       FIG. 4  is a schematic plan view of an alternative disc planter; 
       FIG. 5  is a schematic plan view of a further alternative disc planter; 
       FIG. 6  is a schematic cross-sectional side elevation along the line A—A of the disc planter of  FIG. 5 ; 
       FIG. 7  is a schematic cross-sectional side elevation along the line B—B of the disc planter of  FIG. 5 ; 
       FIG. 8  is a schematic third angle projection of the disc planter of  FIG. 5 ; 
       FIG. 9  is a schematic plan view of a further alternative disc planter; 
       FIG. 10  is a schematic side elevation of a further alternative disc planter; 
       FIG. 11  is a schematic end elevation of two disc planters of  FIGS. 1 to 3  connected together; 
       FIG. 12  is a schematic end elevation of an alternate embodiment of the disc planter; and 
       FIG. 13  is a schematic end elevation of two disc planters of  FIG. 12  connected together. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The disc planter  1  shown in  FIGS. 1 to 3  has a longitudinally extending support member comprising a main beam or bar  2  which is pivotally attachable, by means of a hinge  4  located towards one free end  6  of the main beam  2 , to a bar  3  attached to the seed dispensing apparatus or towing vehicle (not shown). Pivotally attached to the other end  7  of the main beam  2  is a U-shaped bracket  8 . The base portion  9  of the U-shaped bracket  8  is adjacent the end  7  of the main beam  2  and the arms  5  of the U-shaped bracket  8  extend in a direction away from the main beam  2 . A first axle  10  extends through an aperture in each of the arms  5  of the U-shaped bracket  8  towards the free ends thereof in a plane parallel to the base portion  9  of the U-shaped bracket. A press wheel  12  is rotatably located on the first axle  10 . The first axle  10  extends through a central aperture in the press wheel  12  such that the press wheel  12  is partially located in the cavity defined by the base and arm portions of the U-shaped bracket  8 , as shown in  FIG. 1 . 
   A second axle  13  extends through an aperture in the main beam  2  at a position adjacent the base section  9  of the U-shaped bracket  8 . The second axle  13  is comprised of a central portion  16  and two arm portions  14 . The arm portions  14  forming a pair of axles and being angled with respect to the central portion  16  and extending one from each end of the central portion  16 . As shown in  FIG. 1 , the axes being located on opposite sides of the member and in a plane extending transversely normal to said member and at an acute angle longitudinally so as to extend rearwardly down, the axes each being inclined by an acute angle X of 6 to 12 degrees to a plane extending normal to the member and preferably, 8 to 10 degrees. The central longitudinal axes of the arm portions  14  and the central portion  16  lie in a common plane so that the arm portions  14  are angled in the same plane. 
   The second axles  13  may be rotatable in the aperture in the main beam  2  through which they extend. Two plough discs  18  and  20  are rotatably mounted to the angled portions  14  of the second axles  13 , the angled portions  14  of the second axles  13  extending through a central aperture in each of the discs  18  and  20 . The discs  18  and  20  are arranged in planes which converge rearwardly in relation to the direction of travel Z and downwardly in relation to the main beam  2 . The discs being displaced rearwardly from said vehicle. This has the advantage that little or no soil is thrown around during the cutting of the grooves/furrows. Also, any soil which is thrown up during the formation of the grooves in the soil is thrown by each disc  18  and  20  towards the central longitudinal plane Y of the main beam  2  rather than outwardly away from the outer surfaces  19  of the discs. This is particularly advantageous as the soil surface ends up reasonably flat and the seeds are able to be placed accurately in the desired location in the soil. Also, it enables the apparatus to be used at higher driving speeds, for example at 25 to 30 kilometres per hour. The press wheel  12  presses the soil into place shortly after the grooves/furrows have been cut and the seeds sown, which also enables the apparatus to be used at higher speeds. As shown in  FIG. 11 , two or more disc planters  1  can be connected together and towed by a vehicle. 
   As shown in  FIG. 2 , an adjustment assembly in the form of a lever  22  is attached to the second axles  13 , for example by welding. The lever  22  is adjustable by location of a lever pin  25  in one of a number of apertures  26  in an arcuate plane  27  attached to the main beam  2 , to permit alteration of the rotational position of the second axles  13  and therefore the position of the angled arm portions  14  relative to the ground. This enables selection and variation of the angle of the discs  18  and  20  attached to the arm portions  14  relative to the ground, to suit the type of seed to be sown. The lever  22  is also used to lock the second axles  13  in the desired position. A pair of seed tubes  23  are each attached at one end to a seed container (not shown) and have a seed dispensing outlet end  21  located adjacent the outer face of each disc  18  and  20  at a position between the second axles  13  and the periphery of the discs  18  and  20  adjacent the press wheel  12 . The angle of the seed tubes  23  in the vicinity of the outlet end  21  relative to the ground is adjustable, as is the position of the seed tubes  23  relative to the main beam  2 . The closer back they are to the press wheel  12 , the shallower the seeds may be sown, and the further away the seed tubes  23  are from the press wheel  12 , the deeper the seeds may be sown. 
   Urging means in the form of a hydraulic cylinder  24  is fixed to the main body of the seed dispensing apparatus or towing vehicle (not shown), the hydraulic cylinder  24  being positioned such that it acts on the main beam  2  to exert a downward force on the main beam  2  to push the discs  18  and  20  into the ground during use. 
   In operation, a plurality of disc planters  1  are attached to the seed sowing apparatus/towing vehicle (not shown), the disc planters being spaced laterally from and parallel to one another across the rear of the towing vehicle. The adjustment means  22  is adjusted to select and set the position of the angled arm portions  14  relative to the ground which sets the spacing of the discs  18  and  20  fixed thereto to the ground and thus the width of the grooves to be made in the ground by the discs  18  and  20  to suit the type of seed to be sown. As the discs  18  and  20  are dragged through the soil by the seed sowing vehicle, the discs  18  and  20  rotate and leave grooves in the soil, the width and spacing of which will be set by the angle between the discs  18  and  20 . Each disc  18  and  20  cuts a separate groove or furrow in the soil so that for each pair of discs  18 ,  20 , two grooves or furrows are formed in the soil. The depth of the grooves made by the discs  18  and  20  is set by the pressure exerted on the main beam  2  by the hydraulic cylinder  24 . 
   As the seed sowing vehicle moves over the ground and the discs  18  and  20  cause grooves to be made in the soil, the soil is pushed to form a ridge between the discs  18  and  20 , the seed contained in the hopper (not shown) attached to the seed dispensing apparatus and towing vehicle is dropped into the grooves through seed tubes  23 , and the soil is then pushed back by the press wheel  12  to press the soil firmly around the sown seeds to improve germination. As little or no soil is thrown around during the aforementioned process, the soil surface ends up reasonably flat and the seeds are able to be placed accurately in the desired location in the soil. 
   The disc planters shown in  FIGS. 4 to 10  are modified versions of the disc planter  1  shown in  FIGS. 1 to 3 . Like reference numerals are used for the corresponding parts in the various embodiments. 
   The disc planter  100  shown in  FIG. 4  differs from that shown in  FIGS. 1 to 3  in that the press wheel  12  is no longer mounted to a U-shaped bracket  8  attached to the main beam  2  but rather is attached by means of a U-shaped bracket  80  attached to a secondary beam  82  which is spaced vertically from and above the main beam  2 . The U-shaped bracket  80  is attached to the underside of the secondary beam  82  adjacent a first end  83  thereof. The secondary beam  82  is attached, towards the second end  85  thereof, to the main beam  2 , by a bar or flat section  84  welded to the main beam  2  at a position between the point of attachment to the main beam  2  of the hydraulic cylinder  24  and the discs  18 ,  20 . 
   The disc planter  100  of  FIG. 4  also differs from that shown in  FIGS. 1 to 3  in the means of adjusting the position of the angled arm portions  14  of the second axles  13  supporting the discs  18  and  20  relative to the ground. The disc planter  100  of  FIG. 4  comprises a first bar  86  attached to the main beam  2  by means of a pivot pin  87  extending through one of a plurality of apertures  99  in a side face  88  of the main beam  2  at a location between the point of attachment of the secondary beam  82  and the free end  88  of the main beam  2  opposite to the end  6  which is adjacent the bar  3  attached to the seed dispensing apparatus or towing vehicle (not shown). The provision of a plurality of apertures  99  through which the pivot pin  87  may be located enables the position of the discs  18 ,  20  to be adjusted relative to the main beam  2 . A second flat bar  89  is attachable to the first bar  86  adjacent the free end  90  thereof opposite the free end  97  adjacent which the pivot pin  87  is located. A pin  91  is locatable in one of a number of apertures  92  spaced vertically along the second bar  89  and the pin  91  extends through a correspondingly aligned aperture through the first bar  86  to retain the second bar in position relative to and attached to the first bar. This arrangement enables further alteration of the position of the discs  18 ,  20  relative to the main beam  2 . 
   The disc planter  200  shown in  FIGS. 5 to 8  is a further modification of the disc planter  1  shown in  FIGS. 1 to 3 . It differs therefrom in that there is a single main beam  2  to which the discs  18 ,  20  and press wheel  12  are attached, thereby reducing the number of constituent components of the disc planter. 
   The discs  18 ,  20  of the disc planter  200  of  FIGS. 5 to 8  are attached to the main beam  2  by means of an axle  160  comprising a vertically extending portion  161  which depends from and is secured by means of, for example, a U-bolt to the main beam  2 . Two arm portions  164  extend outwardly from the vertically extending portion  161  towards the free end  162  thereof. The arm portions  164  are angled downwardly at an angle “B” to the horizontal plane of about 6 to 12 degrees and preferably 8 to 10 degrees. The angled portions  164  of the axle  160  extend through a central aperture in each of the discs  18  and  20 . 
   In contrast to the embodiments shown in  FIGS. 1 to 4 , the disc angle in the embodiment shown in  FIGS. 5 to 8  is fixed and not adjustable. 
   The disc planter  200  of  FIGS. 5 to 8  further differs from those shown in  FIGS. 1 to 4  in the manner in which the press wheel is attached to the main beam  2 . In this embodiment, an L-shaped section  155  is bolted to the underside  165  of the main beam  2  adjacent the free end  7  thereof which is opposite that attached to the towing vehicle. An axle  156  extends through a central aperture in the press wheel  12  and through a corresponding aperture in the L-shaped section  155  to hold the press wheel  12  in position relative to the main beam  2 . The axle  156  may be welded to the L-shaped section  155 . 
   In the embodiment shown in  FIGS. 5 to 8 , the seed sowing tubes  23  are attached to a plate  201  bolted onto the underside  165  of the main beam  2 . The sowing tubes  23  have a spring section  202  along their length to allow for movement. 
   The additional advantages of the configuration of disc planter  200  shown in  FIGS. 5 to 8  are that the sowing tubes  23 , press wheel  12  and discs  18 ,  20  may be placed anywhere along the main beam  2  allowing for a sowing row spacing of down to around 5 inches (13 cm), which is considerably less than is achievable with conventional disc planters, and advantages also lie in its simplicity of construction and use. Also, the disc planter  200  is fully adjustable and can be easily dismantled for transport. Alternate arrangements are shown in  FIGS. 12 and 13  which will be discussed later. 
   The operation of the disc planters shown in  FIGS. 4 to 8  is essentially as described above with respect to the disc planter shown in  FIGS. 1 to 3 , with the exception of the differences outlined above. 
   The disc planters  300  and  400  shown in  FIGS. 9 and 10  respectively are further modifications of the disc planter  1  shown in  FIGS. 1 to 3 . 
   The disc planter  300  shown in  FIG. 9  differs from that shown in  FIGS. 1 to 3  in that there is a support member or main beam  2  comprising a first member  302  and a second member  303  welded to the first member  302  adjacent one fee end  304  thereof, the discs  18 ,  20  and press wheel  12  being attached to the second member  303 . In a preferred embodiment, the first member  302  comprises a 3 inch (7.5 cm) beam and the second member  303  comprises a 1 inch (2.5 cm) beam. The second member  303  comprises an integrally formed first section  305 , second section  306  and third section  307 . The first section  305  is welded to and is substantially parallel to the main beam  2 , the second section  306  is angled with respect to the first section  305  and extends between the first section  305  and the third section  207 , and the third section  207  is substantially parallel to the first section  305  but is spaced laterally therefrom by the second section  306 . 
   In the embodiment of  FIG. 9 , the axle  160  on which the discs  18  and  20  are retained is identical to that described above in relation to  FIGS. 5 to 8 . Furthermore, the press wheel  12  is attached to the third section  307  of the secondary beam  303  in the same manner as the press wheel  12  is attached to the main beam  2  in the embodiment of  FIG. 8  as described above. 
   The disc planter  300  of  FIG. 9  further differs from those shown in  FIGS. 1 to 4  in the manner in which the seed tubes  23  are attached. In the embodiment of  FIG. 9 , the seed tubes  23  are attached to the secondary beam  303  around the point of intersection of the first section  305  and the second section  306  by means of a first member  308  to which a second member  309  is attached, for example, by welding, such that the first and second members  308 ,  309  form a T-shaped section, the first member  308  forming the stem portion and the second member  309  forming the arm portion. The first and second members  308 ,  309  may formed of flat pieces of metal and the first member  308  may be welded or U-bolted to the secondary beam  303 . Each seed tube  23  is welded or secured by means of a U-bolt to respective ends of the second member  309  and extends in a plane substantially perpendicular to the plane of the upper face of the second member  309 . 
   In the disc planter  300  shown in  FIG. 9 , the secondary beam  303  could be attached to the main beam  2  by being welded to it or it could slot into a channel in the main beam  2 , The secondary beam  303  is preferably formed of a 6 inch (15 cm) by one inch (2.5 cm) bar which is bent to form the Z-shaped section illustrated. 
   The disc planter  400  shown in  FIG. 10  differs from that shown in  FIGS. 1 to 3  in that the support member  2  comprises a first beam portion  401  and a second beam portion  402  attached thereto, for example by welding. In a preferred embodiment, the first beam portion  401  is a 3 inch (7.5 cm) square beam and the second beam portion  402  is a 1 inch (2.5 cm) square beam. The discs  18  (shown) and  20  (not shown) are attached to the main beam  2  by means of axle  160  of the type and in the manner described above with regard to  FIGS. 5 to 8 . The press wheel  12  in the embodiment of  FIG. 10  is attached to the main beam  2  by means of an axle  10  which extends through and aperture in the main beam  2  adjacent the end of the main beam  2  opposite to that which is attachable to the towing vehicle. The seed tubes  23  in the embodiment of  FIG. 10  are attached to the main beam  2  in the same way as the seed tubes  23  described above in relation to the embodiment of  FIG. 9 , the first member  308  of the T-shaped section being attached to the main beam  2  by means of welding or a U-bolt. The second member  309  of the T-shaped section is not shown in  FIG. 10 . 
   The hydraulic cylinder  24  shown in  FIGS. 1 to 3  is also to be used in connection with the disc planters  300  and  400  shown in  FIGS. 9 and 10  although it is not shown in those figures. 
   Further embodiments are shown in  FIGS. 12 and 13 , where the support member or main beam  2  is attached to the discs  18 ,  20  by way of a frame  500 . The frame  500  being generally “n” shaped and having a pair of ends  505 ,  510  located on opposite longitudinal sides and spaced normal from the main beam  2 . The axles  10 ,  13  extend laterally from the ends  505 ,  510  and when viewed from the discs  18 ,  20  converge rearwardly and downwardly. 
   The operation of the disc planters shown in  FIGS. 9 ,  10 ,  12  and  13  is essentially as described above with respect to the disc planter shown in  FIGS. 1 to 3  and  11 , with the exception of the differences outlined above. 
   Various modifications to the apparatus described will be apparent to those skilled in the art, for example, the hydraulic cylinder  24  described above as being hingedly attached to the towing vehicle may be attached to the bar  3  which is itself attached to the towing vehicle. Also, the hydraulic cylinder  24  used to provide an adjustable downward pressure on the main beam  2  may be replaced by another means of exerting pressure such as pneumatically, or using a spring or a weight. In another preferred embodiment, the second axles  13  may be V-shaped. Also, the U-shaped bracket  8  could be replaced by an L-shaped bracket, the single arm of which could extend adjacent either outer face of the press wheel  12 . Whilst the preferred angle of orientation X of the arm portions  14  of the second axles  13  has been described as being between 6° and 12° and preferably 8 to 10°, it is possible that an angle outside this range could be used, 
   In a preferred embodiment, the length of the disc planters  1 ,  200 ,  300  and  400  including the main beams  2 , frame  500 , any first and second members thereof, and the press wheels  12  maybe around 8 feet (2.5 m) from front to back to enable them to fit onto a truck for transportation in the assembled state. 
   As mentioned above, in use a plurality of disc planters  1 ,  200 ,  300  or  400  are attached to the towing vehicle (such as shown in  FIGS. 11 and 13 ) each being spaced laterally from and parallel to one another. In a preferred embodiment (not shown), the plurality of disc planters  1 ,  200 ,  300  or  400  may be arranged such that the discs  18 ,  20  and/or press wheels  12  are laterally staggered with respect to one another in a zig-zag pattern. This may be achieved, for example, by altering the length of adjacent main beams  2  and/or any members of which the main beams  2  may be comprised. As an example, the lengths of adjacent main beams may vary by 3 inches (7.5 cm). This has the advantage that heavier axles may be used to support the discs  18 ,  20  which are tougher and more durable. 
   The disc planters  1 ,  100 ,  200 ,  300  and  400  described herein have a number of advantages, in particular, they are very simple mechanisms with a minimum number of moving parts. The provision of one press wheel  12  per two discs  18  and  20 , each disc cutting a separate groove in the soil, is in contrast to conventional disc planters which typically have one disc cutting a groove in the soil or a pair of discs cutting a single groove in the soil, and typically one or more press wheels per disc. Furthermore, the disc planter  1  described herein has an easily and fully adjustable disc angle. 
   Due to the structural configuration of the disc planters  1 ,  100 ,  200 ,  300 , and  400  it is possible to achieve a closer spacing between adjacent grooves than is possible with conventional disc planters which leads to improved germination of the seeds sown. The disc planters  1 ,  100 ,  200 ,  300  and  400  are capable of handling large amounts of trash on the ground and it is anticipated that they will be able to operate at speeds of up to around 30 km/hour. As the discs  18  and  20  of disc planter  1  are located one on either side of the central portion  16  of the second axles  13 , there is an equal pull exerted on the main beam  2  from opposite sides thereof and the disc planters  1 ,  100 ,  200  are therefore able to be towed in a substantially straight line with little or no sideways drift. 
   It will be appreciated that the variations shown in  FIGS. 4 to 10  for example, the means of attaching various components to the main beam  2 , or the seed sowing tubes  23  may be incorporated into one or more of the embodiments described.