Abstract:
An adjustable track tractor formed by a control and slave drive unit connected together at their front and rear ends with respective front and rear cross beams pivoted at each end thereto. Each drive unit is converted from a conventional tractor to have only a single front and rear wheel. When the cross beams are pivoted by rotary hydraulic actuators, the drive units are moved together or apart to change the wheel track.

Description:
CROSS REFERNCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. provisional application Ser. No. 60/904,907 filed on Mar. 5, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention concerns wide track tractors which are adjustable in width. Since the early 80&#39;s in Australia 5 million acres of grain crops are under production where the high powered tractors, large combines and heavy trucks all have the same track settings of either 2 or 3 m so that they operate on controlled pathways centered 2 or 3 m apart. This is called “Controlled Traffic Farming” [CTF]. The 3 m setting is becoming the standard. In the field the 3 m tracks are centrally spaced 9 m apart and the combine and planters are 9 m wide with the chemical booms 27 m wide. The advantages are that the tractor can be less powerful because the wheels run on packed soil, minimum or no tilling of the soil is needed, neither is there any need to subsoil every few years, water penetration is better, there are no ruts or ridges left over from previous operations, the fuel saved is substantial and the crops are much larger because of the zero compaction. Further explanation, in detail with the cost savings, can be obtained on the internet sit [www.controlledtrafficfarming.com] and the ASABE papers noted in the references. 
         [0003]    The small farmer could benefit from CTF in the small scale production of vegetables, fruit, nuts, flowers, seeds and bulbs, etc. but existing equipment is too large and expensive. 
         [0004]    A tractor for small scale CTF should be low powered, no higher than 40 kW and should use as many production parts as possible from current conventional tractors to keep the price low. It should be easily adjusted from the tractor seat for road use between the plots and vice versa. It should not be too wide in order to enable the Cat.11 3 point hitch to handle many mounted implements already in use. A maximum width of the soil between the tracks of 3.66 m should be satisfactory with a wheel track setting of 4.27 m. 
         [0005]    The object of the present invention is to provide a low cost efficient tractor for small scale controlled traffic forming. 
       SUMMARY OF THE INVENTION 
       [0006]    The above recited object of the invention and other objects which will become apparent upon a reading of the following specification and claims are achieved by a tractor comprised of two separated but interconnected units, a master or control unit and a slave unit each unit driving its own single main rear wheel. 
         [0007]    The control unit is basically the same as a typical production tractor consisting of an engine, transmission, rear axle assembly and sheet metal etc. It has one front wheel and one rear driving wheel removed including the fender, axle shaft, bell housing, planetary driving gear set, differential gears, differential lock and brake. A means is provided to connect the remaining planetary gear set to the differential housing in order to drive the remaining rear wheel and a cast plate replaces the bell housing and holds the bearing cup which supports the differential housing. The hydraulic lift housing is also removed. Both the PTO and the drawbar are retained. 
         [0008]    The slave unit consists of a transmission and a rear axle assembly which drives only one rear wheel of the opposite hand of the one in the control unit. The PTO and the hydraulic lift are not required. The drawbar is retained. It also only has one front wheel, of the opposite hand to the one on the control tractor and it is rigidly supported by side channels extending forward from the transmission housing, which also carry ballast weights to make the slave drive unit equal in weight with the control unit. 
         [0009]    Single front wheels can be used because they run on packed soil making front wheel assist drives unnecessary. They also are easier to turn through greater angles when Helac™ hydraulic rotary actuators [www.helac.com] are used controlled with a steering wheel. Freely mounted caster wheels can be used if the transmissions are used for steering with control levers similar to that of a zero-turn lawn tractor. 
         [0010]    The transmission in the control unit is either a hydraulic unit with one or more pumps and motors or an electric transmission with one or more generators and motors. The transmissions must be able to share the engine power equally between the control unit and the slave unit. The transmission in the slave unit has either hydraulic or electrical motors driven from the control unit through hydraulic hoses or electric cables depending on the nature of the transmissions. 
         [0011]    The control unit and the slave unit are joined together with a cross beam at their rear ends and a smaller cross beam at their front ends. The rear beam has horizontal pivots at both ends to allow the two units to articulate with each other on uneven ground and vertical pivots to enable the beam to turn through 90 degrees, in the plan view, when changing the track from the field position to the road position and vice versa. The vertical pivots are integrated with Helac™ hydraulic rotary actuators [www.helac.com] which assist when the track is changed and which locks the beam rigidly in position in both the field and road positions. 
         [0012]    The horizontal pivots can be connected to the control unit and the slave unit with sleeves which allow the beam to be lowered into position onto two half bearing blocks attached to a plate which is bolted to the opening on top of each rear axle housing, formally covered by the hydraulic lifts, and then held in place with two half bearing caps. The horizontal pivots are spring loaded against the outer ends of the sleeves longitudinally in order to keep the lower plate, which has a circular end attached to the rear cross beam, firmly in contact with the mating circular cut-out attached to each rear axle housing. This arrangement keeps the two driving units in an upright position, with each other, when the track is being changed and also allows the two units to articulate with each other in the road position. 
         [0013]    The front cross beam is attached to each driving unit with vertical and horizontal pivots to allow for articulation and to maintain them parallel to each other when the beam is rotated 90 degrees to change the track. The front beam also reacts to vertical loads at its center from a torque arm attached to the rear cross beam which transmits the torque from an implement attached to the 3 pt. hitch evenly between each drive unit. The 3 pt. hitch and drawbar are mounted on a steel plate bolted to the rear of the cross beam so that, in the field position, its front face makes contact with the rear end of the torque arm in order to make the torque arm and the rear cross beam revolve as one unit in the field position and to be no longer effective when rotated through 90 degrees in the road position allowing the arm to oscillate at its horizontal pivot on uneven ground. 
         [0014]    To comply with the road regulations in different countries the control unit with the cab and the slave drive unit can be interchanged during manufacture. When the tractor is shipped from the place of manufacture to the dealer or farmer the two cross beams and the torque arm can be shipped separately and the control unit and the slave drive unit are connected together with a short round slave shaft allowing it to be driven onto a truck etc. 
         [0015]    When the front wheels are steered with hydraulic actuators only the control tractor is used to drive and steer the tractor on the road. The rear axle on the slave unit is disconnected from the transmission and is free to turn, because there is no differential, and the front wheel on the slave drive unit is fixed in the straight ahead position. The track is a maximum of 2.69 m legally suitable for most roads. 
         [0016]    Should the tractor be used permanently in the fields and never driven on a road the vertical pivots on the rear and front cross beams are not required as well as the hydraulic rotary cylinders which operate the rear cross beam. Should this situation arise the tractor would most likely use the transmissions for steering in the field with caster front wheels. 
         [0017]    PTO driven implements are powered from the PTO drive on the control unit. 
         [0018]    The method of construction of the tractor makes it easy to adapt existing designs of high clearance tractors should there be the need for such a vehicle. 
         [0019]    Australians are making increasing use of satellite steering systems to set out the controlled tracks in the first place and to find the tracks when they are grown over each new seasons and to steer the machines automatically in work. While expensive this can pay off on the larger plots [www.controlledtrafficfarming.com]. 
         [0020]    When an implement is too heavy or large to be operated on the 3 pt. hitch, such as a harvesting wagon, it can be pulled by the tractor by attaching it to both drawbars of the two drive units and using caster wheels at each of its four corners to run on the controlled tracks. This makes the implement revolve with the tractor during turns in almost the same space as mounted equipment. For road use the trailer can be pulled from a hitch attached to one of its narrow sides. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1   a  is a plan view of an adjustable width wide track tractor according to the present invention running in tracks depicted with broken lines. 
           [0022]      FIG. 1   b  is a rear view of the tractor shown in  FIG. 1   a  depicting packed soil tracks and intervening untilled soil areas. 
           [0023]      FIG. 1   c  is a left side elevational view of the tractor shown in  FIGS. 1   a  and  1   b.    
           [0024]      FIG. 1   d  is a plan view of the tractor shown in  FIG. 1   a  with the track adjusted to be of reduced width for road transport. 
           [0025]      FIG. 1   e  is a side elevational view of the adjusted width track tractor shown in  FIG. 1   d.    
           [0026]      FIG. 2   a  is an enlarged side elevational view of the tractor control with rear axle housing. 
           [0027]      FIG. 2   b  is a rear view of the rear axle housing shown in  FIG. 2   a.    
           [0028]      FIG. 2   c  is a top view of the rear axle housing shown in  FIG. 2   a  and  2 B. 
           [0029]      FIG. 3   a  is a plan view of the rear cross beam horizontal pivots and rear axle housing slave included in the tractor according to the invention. 
           [0030]      FIG. 3   b  is a front view of the components shown in  FIG. 3   a.    
           [0031]      FIG. 3   c  is an end view of the rear cross beam and pivots shown in  FIG. 3   a.    
           [0032]      FIG. 4   a  is a side elevational view of the rear portion of the tractor of  FIG. 1   a,  showing a connector to the rear beam  16  with a point linkage and diameter. 
           [0033]      FIG. 4   b  is a fragmentary rear view of the rear cross beam with components connecting the three point linkage and drawbar thereto. 
           [0034]      FIG. 5   a  is a rear view of the front cross beam and fragmentary views of the front wheel supports and connecting clevis and clevis connection to the torque arm. 
           [0035]      FIG. 5   b  is a plan view of the front cross arm and torque arm shown in  FIG. 5   a.    
           [0036]      FIG. 5   c  is a side view of the torque arm clevis connection to the cross arm and pivot clevis on the plate connection to a rear cross beam. 
           [0037]      FIG. 6  is a plan view of the tractor shown in  FIG. 1   a  assembled for shipment. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. 
         [0039]      FIGS. 1   a, b,  and  c  show how a tractor according to the invention is configured for field work with rear drive wheels running on controlled tracks  50 - 51  and adjusted together ( FIGS. 1   d, e ) for road travel between the fields. 
         [0040]    It consists of a control unit  1  which has an engine  2  driving a hydrostatic or electric transmission  3  including a pump and motor (not shown) or a motor and generator (not shown) connected to a conventional double reduction rear axle assembly  4  which has several components removed including the inner driving wheel, axle, trumpet housing, differential gears, differential lock, planetary reduction gears, and disc brake. Also removed is the inner fender (leaving outer fender F), the 3 Pt. linkage components and the drawbar. The PTO is retained. A cast iron plate  7  replaces the trumpet housing and houses the bearing cup which supports the difference housing. A means is also provided to connect the remaining planetary gear set to the differential housing in order to drive the rear wheel. A cab  58  is attached to the control drive unit  1  in the conventional manner. 
         [0041]    The inner front wheel is also discarded and the remaining front wheel  6  is rigidly attached to the front end of the control unit  1  and controlled for steering with a rotary actuator  6 A (see www.helac.com for a description of a suitable rotary actuator). 
         [0042]    A slave driving unit  8  is combined with the control drive unit  1  and does not have an engine. The hydrostatic or electrical transmission  9  is driven remotely from the control tractor  1  transmission  3  via fluid or electrical connections  60  depicted diagrammatically, and drives the rear axle  5  which has similar components removed as in the control unit  1  except that they are of the opposite hand. Also removed is the seat, steering wheel, platform, instrument panel, sheet metal, grille, pedals, controls, battery, radiator, fuel tank, etc. 
         [0043]    Side channels  53  and  54  extend from the transmission housing  9  to support the front wheel  55  and ballast weights  57  are added to compensate for the absence of the engine and the other parts. 
         [0044]      FIGS. 2   a, b,  &amp; C are rear views of the control unit rear axle housing  4  and show the details as to how the control unit  1  is connected to the slave unit  8 . The opening left vacant with the removal of the hydraulic power lift housing is covered with a steel plate or casting  10 . Welded or cast to the new cover plate  10  are two half bearing blocks  11  and  12  which holds a hollow sleeve  13 . It is also prevented from moving sideways. A similar arrangement of the sleeve  13  is also carried out on the slave unit  8 . 
         [0045]    Also bolted to the underside of the plate  10  is a steel plate  14  containing a half circular cut-out  15  which connects with the rear cross beam  16  as shown in  FIGS. 3   a, b,  and  c.    
         [0046]      FIGS. 3   a, b  &amp;  c.  These show how the rear cross beam  16  is connected with horizontal pivots  17  and  18  to the rear axle housing sleeve  13 . 
         [0047]    The cross beam  16  is fabricated in a hollow rectangular form with two steel plates  19  and  20  bolted to it at each end which attach with splined vertical pivots  28  and  29  to rotary hydraulic actuators  21  and  22  similar to the rotary actuator  6 A which are required to help in changing the tracks. The actuators  21  and  22  are attached to horizontal pivots  17  and  18  which run in the sleeves  13  and are spring loaded  23  to keep the round shaped plate  20  in contact with the half circle cut-out  15  in the steel plate  14  when the tractor is changing tracks. This keeps the control unit  1  and the slave unit  8  in vertical alignment with each other in the road position. 
         [0048]    If the tractor is never to be operated on a road then the vertical pivots  28  and  29 , the rotary actuators  21  and  22 , and the springs  23  are not required as are the vertical pivots  35  and  36  attached to the front cross beam  34 . 
         [0049]      FIGS. 4   a, b,  &amp; C show how the 3 point linkage  30  and drawbar  31  are attached to the rear cross beam  16  with a steel plate  32  and how the rear end of a torque arm  33 , which is needed to resist the turning moments caused by an implement  56  about the horizontal pivots  17  and  18  on the rear cross beam  16 , is connected to the cross beam  16 . It is arranged so that, in the field position as shown, a steel plate  39  welded to the hollow square torque arm  33  makes contact with the plate  32  so that the loads on the front cross beam from the torque arm are always vertical (see  FIG. 5 ). When the torque arm  33  is rotated 90 degrees when changing to the road position it is then free to oscillate on uneven ground. 
         [0050]    FIGS.  5 , a, b,  &amp;  c  show how the front cross beam  34  is attached with devises  36  and  37  to each drive units  1  an  8  and how the front end of the torque arm  33  is connected to it at its middle point by clevis  30  in order to balance out the loads equally between the two drive units  1  and  8  in the field position. 
         [0051]      FIG. 6  shows how the tractor can be configured for shipping from the place of manufacture to the field. The long rear beam  16  and the long front beam  34  and the torque arm  33  are shipped separately. The two drive units  1  and  8  are connected with a short one-piece hollow shaft  68 .