Abstract:
A tractor having a front end and a rear end adaptable for a variety of different environments. Methods related to the conversion of the tractor are also disclosed. In one embodiment, the invention includes a front wheel assembly that is removably attached to the front end of the tractor to facilitate adaptation of the tractor a various environments. Also, a steering actuator is removably attached to the front wheel assembly and fixedly attached to the chassis of the tractor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of and priority to U.S. Provisional Patent Application No. 60/388,356, filed on Jun. 13, 2002, the entire disclosure of which is hereby incorporated by reference. 

   FIELD OF THE INVENTION 
   The invention relates generally to a tractor and more specifically to a tractor with an interchangeable front wheel assembly and variable rear wheel track width. 
   BACKGROUND OF THE INVENTION 
   Generally, tractors are designed with the large landowner and corporate farms in mind. For example, the components of the tractor (i.e., the engine, electrical system, and transmission) are highly integrated. Therefore, in the event of a mechanical or electrical problems the tractor requires service by highly specialized technicians and transportation of the tractor to the repair shop for even the most minor of malfunctions. In many developing nations, the farmer must often be the service technician, and thus be able to locate and repair any failures that may happen without requiring the entire tractor be taken into the repair shop. 
   Furthermore, the turning radius of most tractors is tailored to the large empty spaces that exist in most fields of the large land owner or corporate farmer. Most often, the front end of the tractor includes a fixedly attached two wheel assembly and a fixed rear wheel track width. The farmers of many developing nations typically have land tracts that are a fraction of the size of those for which most tractors are designed, and cannot afford empty spaces at the ends thereof dedicated only to the turning of the tractor. 
   Therefore, there exists a need for a service friendly tractor having a variable rear wheel track width and an adaptable front end to vary the turning radius as needed. 
   SUMMARY OF THE INVENTION 
   The invention is directed to a tractor having an interchangeable front wheel assembly and an adjustable rear wheel track width. The removable front wheel assembly allows for easy conversion between a single wheel and a two wheel front wheel assembly. In combination with the interchangeable front wheel assembly, the adjustable rear wheel track width allows for the manipulation of the turning radius of the tractor. Additionally, the modular design of the components of the tractor facilitate repair of individual components without the need for bringing the entire tractor in for repair. 
   In one aspect, the invention is directed to a tractor. The tractor has a front end and rear end. The tractor includes a front wheel assembly, an attachment mechanism, and a steering actuator. The attachment mechanism is at the front end of the tractor and is configured to removably attach the front wheel assembly to the tractor. The steering actuator is fixedly attached to a steering mechanism on the tractor. Also, the steering actuator is removably attached to the front wheel assembly. The front wheel assembly may include one wheel or two wheels. 
   In one embodiment, the attachment mechanism may include a mounting mechanism that receives a corresponding mounting mechanism, which is part of the front wheel assembly. The mounting mechanisms can include bores that receive fasteners to attach the front wheel assembly to the front end of the tractor. 
   In another embodiment, the rear end of the tractor includes at least one rear axle, two rear wheels, and a spacer placed between each of the wheels and the axle. The spacer allows the width between the rear wheels to be adjusted. For example, the width of the rear wheels may be greater than or equal to the width of the front wheel assembly having two wheels. 
   In another embodiment, the tractor includes a power transmission unit having a clutch assembly, a gear box and a rear end differential box. The clutch assembly is in communication with the gear box and engine. 
   The gear box includes an input shaft, a first output shaft, a lay shaft, and a second output shaft. The first output shaft includes two gears. A first gear for providing a low range speed and a second gear for providing a high range speed. The lay shaft includes a first gear, a second gear, and a reverse gear, and is in communication with the first output shaft and the second output shaft. The second output shaft includes a first shifter gear and a second shifter gear. The first shifter gear is in communication with the first gear of the lay shaft and the reverse gear. The second shifter gear is in communication with the second gear of the lay shaft and also is in communication with the first output shaft via a set of splines. 
   The rear end differential box is in communication with the gear box. A set of final gears that deliver power to the rear end of the tractor is disposed within the rear end differential box. The gears of the rear end differential box and the gear box are viewable when a top cover of each box is removed. 
   In another aspect, the invention is directed to a method of facilitating the conversion of tractor for use in a variety of environments. The tractor includes a front end and a rear end. The method includes the steps of removing a first front wheel assembly from the front end of the tractor, and a steering actuator from the front wheel assembly. In turn, a second front wheel assembly is attached to the front end of the tractor and the steering actuator is attached to the second front wheel assembly. 
   In one embodiment, the method includes the steps of removing a rear wheel from a rear axle of the rear end of the tractor, attaching a spacer to the rear axle to control the width of the rear end of the tractor, and reattaching the rear wheel. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is pointed out with particularity in the appended claims. The advantages of the invention may be better understood by referring to the following description taken in conjunction with the accompanying drawing in which: 
       FIGS. 1A-1C  are various views of an embodiment of a tractor of the invention with a front wheel assembly having two wheels; 
       FIGS. 2A-2E  are various views of an embodiment of a tractor off the invention with a front wheel assembly having one wheel; 
       FIGS. 3A-3C  are plan views of various embodiments of a tractor having a variable track width; 
       FIG. 4A  is a top view of an embodiment of a transmission of the tractor of the present invention; and 
       FIG. 4B  is a side view of an embodiment of the transmission of FIG.  4 A. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIGS. 1A-1C , in one-embodiment a tractor  10  includes a front wheel assembly  20  attached to a chassis  30 , which includes a rear wheel assembly  40 . The front wheel assembly  20  includes, in one embodiment, a pair of front wheels  22 A and  22 B attached to a front axle  24 . The front axle  24  can be a solid front axle or a split front axle to provide independent suspension of the two front wheels  22 A and  22 B. A pair of steering joints  28 A and  28 B are attached to a stabilizer bar  28 C to facilitate turning of the front wheels  22 A and  22 B. Additionally, a steering actuator  50  is removably attached to a steering actuator attachment mechanism  29 . The steering actuator  50  is removably attached to a steering mechanism  54  (e.g., a steering wheel) on the chassis  30  of the tractor  10 . 
   As an operator turns the steering wheel  52 , the steering mechanism  54  of the chassis  30 , the steering actuator  50 , the steering actuator attachment mechanism  29 , the steering joints  28 A and  28 B, and the stabilizer bar  28 C cooperate to facilitate the turning of the front wheels  22 A and  22 B. For example, if the steering wheel  52  is turned to the right, the steering actuator  50  is pulled back (i.e., towards the rear wheel assembly  40 ). In turn, the steering actuator attachment mechanism  29  is pulled back (i.e., moves toward the rear wheel assembly) and thus the steering joints  28 A and  28 B and stabilizer bar  28 C cooperate to turn the front wheels  22 A and  22 B to the right. In order to facilitate a left turn, the steering wheel  52  forces the steering actuator  50  forward (i.e., toward the front wheels  22 A and  22 B). Similar to the above, the steering actuator attachment mechanism  29  is pushed forward (i.e., moves toward the front wheels  22 A and  22 B) and thus the steering joints  28 A and  28 B and stabilizer bar  28 C cooperate to turn the front wheels  22 A and  22 B to the left. 
   The front axle  24  is attached to a front wheel assembly attachment bar  26 , which is removably attached to the chassis  30 . The chassis  30  includes, at the front end, an attachment mechanism  32  configured to receive the front wheel assembly attachment bar  26 . In more detail, the attachment mechanism  32  includes a mounting mechanism configured to a receive a corresponding mounting mechanism of the front wheel assembly  20 . In one embodiment, the mounting mechanisms are shaped to facilitate proper alignment and retention of the front wheel assembly  20  to the chassis  30 . The mounting mechanisms include bores  34  adapted to a receive fasteners  36 . The fasteners  36  can include, but are not limited to bolts, rivets, pins and the like. 
   With reference to  FIGS. 2A-2E , in one embodiment the tractor  10  includes a front wheel assembly  20 ′ attached to the chassis  30 , which includes a rear wheel assembly  40 . In one embodiment, the front wheel assembly  20 ′ includes a single front wheel  22 A′. The front wheel assembly  20 ′ includes a pair of front forks  25 A and  25 B. The front forks  25 A and  25 B are attached to a front axle  24 ′ to hold the front wheel  22 A′ in place. Additionally, the front forks  25 A and  25 B are attached to a suspension mechanism  27  (e.g., a coil, leaf spring, shock, strut, hydraulic mechanism, or gas mechanism), which provides suspension of the front wheel assembly  20 ′ during operation. The steering actuator  50  is removably attached to a steering actuator bar  99  at a pivot point  96 . The steering actuator bar  99  is fixed to a fabricated extension  97  of the front axle  24 ′ through a pivot pin  98 . The steering actuator bar  99  is attached to a steering actuator mechanism  94  at a pivot point  95 . The steering actuator mechanism  94  is attached to at least one of the front forks  25 A and  25 B. 
   The steering actuator mechanism  94  is removably attached at a pivot point  52  to the steering actuator attachment mechanism  29 ′. The steering actuator attachment mechanism  29 ′ includes an attachment point  58 , which attaches the steering actuator mechanism  94  to the forks  25 B. In one embodiment, the attachment point  58  is a bore configured to a receive a pin. 
   As an operator turns the steering mechanism of the chassis the steering actuator  50  facilitates turning of the front wheel  22 A′. For example, if the steering wheel  52  is turned to the right, the steering actuator  50  is pulled back (i.e., towards the rear wheel assembly  40 ). In turn, the pivot point  96  is pulled back towards the rear wheel assembly  40 . This causes the actuator bar  99  to rotate counterclockwise about pivot pin  98 . In turn, the steering actuator mechanism  94 ′ is pushed forward (i.e., moves away from the rear wheel assembly), and the front wheel  22 A′ moves to the right. In order to facilitate a left turn, the steering wheel  52  forces the steering actuator  50  forward (i.e., away from the rear wheel assembly  40 ). In turn, the pivot point  96  is pushed forward away from the rear wheel assembly  40 . This causes the actuator bar  99  to rotate clockwise about pivot pin  98 . In turn, the steering actuator mechanism  94 ′ is pulled backward (i.e., moves toward the rear wheel assembly), and the front wheel  22 A′ moves to the left. 
   The suspension mechanism  27  is attached to a front wheel assembly attachment bar  26 ′, which is removably attached to the chassis  30 . The front wheel attachment bar  26 ′ is shaped to provide attachment of the single front wheel assembly to the chassis at the same point as the two wheel configuration. The chassis  30  includes, at the front end, an attachment mechanism  32  to receive the front wheel assembly attachment bar  26 ′. In more detail as described above, the attachment mechanism includes a mounting mechanism configured to a receive a corresponding mounting mechanism of the front wheel assembly  20 . In one embodiment, the mounting mechanisms are shaped to facilitate proper alignment and retention of the front wheel assembly  20 ′. The mounting mechanisms include bores  34  adapted to a receive fasteners  36 . The fasteners  36  can include, but are not limited to bolts, rivets, pins and the like. 
   It is often desirable to change between a front wheel assembly having one wheel and a front wheel assembly having two wheels. To accomplish this end, a block, jack, or other height adjusting mechanism is placed under the chassis  30  to maintain the height of the chassis. The fasteners  36  are removed from the mounting mechanisms. Also, the steering actuator  50  is detached. Thereafter, the front wheel assembly is removed and replaced with the other front wheel assembly. The fasteners  36  are reattached to secure the front wheel assembly in place. In turn, the steering actuator of the front wheel assembly having two wheels is attached. 
   With reference to  FIGS. 3A-3C , the track width of the rear wheel assembly  40  of the tractor  10  is adjustable to accommodate various crop spacings and farm implementations. As shown in  FIG. 3A , the rear wheel assembly  40  includes a rear axle  42 , which transfers power to a rear axle flange  44 . A pair of rear wheels  46 A and  46 B is attached to each rear axle flange  44 . The rear axle  42  receives power from a rear differential, as described below in  FIGS. 4A and 4B . As shown, the track width of the rear wheels is substantially equal to the width of the front wheel assembly  20  having two wheels. 
   With reference to  FIG. 33 , the track width of the rear wheels can be increased by the attaching a spacer  60  to the rear axle flange  44 . The spacer  60  includes a spacer body  62 , a rear axle attachment flange  64 , a spacer axle  66 , and a wheel attachment flange  68 . In one embodiment, the spacer body is composed of cast iron, although other materials are possible. The rear axle attachment flange  64  is disposed at one end of the spacer body  62 . The spacer axle  66  is disposed within the spacer body  62  and attached to the rear axle attachment flange  64  at one end of the spacer axle  66 . The other end of the spacer axle  66  is attached to the wheel attachment flange  68 . The wheel attachment flange is substantially similar to the rear axle flange  44 . The rear wheel is attached to the wheel attachment flange  68 . 
   To change the track width of the rear wheels, a block, jack, or other height adjustment mechanism is placed in communication with the chassis to hold the rear wheel assembly  40  at a height necessary to facilitate the removal of the rear wheels  46 A and  46 B. The rear wheels  46 A and  46 B are removed from the rear axle flange  44 . The spacer body  62  is attached to the rear axle flange  44 . More specifically, the rear axle attachment flange  64  is attached to the rear axle flange  44  by fasteners, such as, bolts. In turn, the rear wheels are attached to the wheel attachment flange  68 . The spacer  60  thereby increases the track width of the rear wheel assembly  40  such that it is greater than the width of the front wheel assembly  20  having two wheels. 
   The turning radius of the tractor is a direct function of the track width of the rear wheel assembly and the front wheel assembly configuration. For example, as shown in  FIG. 3C , when a front wheel assembly  20 ′ having only a single wheel is used, the turning radius of the tractor  10  is less than the turning radius of a tractor  10  having a front wheel assembly  20  with two wheels. Additionally, if the track width of the rear wheels is increased using the spacer  60 , as in  FIG. 3B , the turning radius of the tractor is affected. As such, the turning radius of the tractor  10  is a function of the front wheel assemblies and the track width of the rear wheels. 
   With reference to  FIGS. 4A and 4B , the tractor  10  includes a transmission  100  having gear box  110  and a rear differential  114 . An input shaft  118  transfers power from the engine of the tractor to the gear box  110 . Power is transferred from the gear box  110  the rear differential  114 , which, in turn, rotates the rear axle  42  and turns the rear wheels  46 A and  46 B. The gear box  110  and rear differential  114  each include a top cover (not shown). Removing the top covers of each of the gear box  110  and rear differential  114  exposes the gears within. As such, the gears are easily accessible for trouble shooting and repair. 
   In more detail, the gear box  110  includes a portion of the input shaft  118 , a first output shaft  122 , a lay shaft  126 , and a final output shaft  130 . The input shaft  118  includes a first gear  134 A that engages a low range gear  124 , a second gear  134 B that engages a high range gear  125  on the first output shaft  122 . The low range gear  124  and high range gear  125  allow two different speeds of rotation for each gear on the lay shaft  126 . Power is transferred from the input shaft  110  to the lay shaft  126  via the first output shaft  122 , through gear pinion  135  and gear  136  of the lay shaft. 
   The lay shaft  126  includes a reverse gear  138 , a first forward gear  142 , and a second forward gear  146 . A third forward gear is provided by transferring power directly from the first output shaft  122  to the final output shaft  130  through a spline drive (not shown), as described in more detail below. 
   The final output shaft  130  includes a first shifter gear  150 , which engages the reverse gear  138  and the first forward gear  142 . Also, the final output shaft includes a second shifter gear  154 , which engages the second forward gear  146  and the internal spline drive, which provides the third forward gear. The internal splines (not shown) of gear  154  engage a set of external splines (not shown) on first output shaft  122 . The final output shaft  130  is in communication with the rear differential  114 . 
   A set of final gears  158 , a high power gear assembly  166 , and a high power gear  170  are located in the rear differential  114 . The final gears  158  receive power from the final output shaft  122  and deliver it to the rear axle  42  via the high power gear  170  and high power gear assembly  166 . 
   A power take-off (PTO) shaft  162  can provide two speeds, one is directly proportional to the engine speed, and the other is proportional to the rotational speed of the rear wheels. To provide a PTO shaft speed proportional to the engine speed, a PTO gear  174 A, which is on the lay shaft  126 , is selected by a PTO shifter (not shown) to engage a PTO shifter gear  174 . When selected, power is transferred from the lay shaft  126  to the PTO shaft  162 . Alternatively, the PTO shaft can receive power from a gear  174 B fixed on a hypoid pinion  170 A. As such, the speed of the PTO shaft  162  is directly proportional to the rotational speed of the rear wheels  46 A and  46 B. 
   In operation, the operator of the tractor  10  uses a gear selector (not shown) to select either one of the three forward gears or the reverse gear. More specifically, the gear selector may cause either of the shifter gears  150  or  154  to engage one of the forward gears  142  or  146 , the splines of the gear  154 , or the reverse gear  138 . Additionally, the operator uses a high/low range selector (e.g., a hand clutch or the like) to select an operating range of the gears. More specifically, by selecting the high range, high range gear  125  engages the second spindle  134 B. Alternatively, if the low range is desired, the low range gear  124  engages the first gear  134 A. 
   As the engine runs, power from the input shaft  118  is transferred to the first output shaft  122  via the first gear  134 A or the second gear  134 B. The gear ratio between the first gear  134 A and the high range gear  125  or the second gear  134 B and the low range gear  124  determines the rotational speed of the first output shaft  122 . In turn, power maybe transferred either directly to the final output shaft  130 , by engaging the splines of gear  154  with the first output shaft  122 . Alternatively, power is transferred to the lay shaft  126 , and in turn, to the final output shaft  130 , if one of the first forward gear  142 , second forward gear  146 , or reverse gear  138  is selected. Depending on the gear selected, the rotational speed of the final output shaft  130  is determined by the gear ratio between the chosen shifter gear and the gear on the lay shaft that the shifter gear engages. Power from the final output shaft  130  is transferred to the final gear  158 , and, in turn, to the high power pinion  170 . The high power gear assembly  166  receives the power from the high power pinion  170  and rotates the rear axle  42 . Although describes as having six forward speeds and two reverse speeds (i.e., a high and low range for each of the forward and reverse gears), the transmission is not limited to any particular number of gears. 
   Having shown the preferred embodiments, one skilled in the art will realize that many variations are possible within the scope and spirit of the claimed invention. It is therefore the intention to limit the invention only by the scope of the claims.