Patent Publication Number: US-2011057508-A1

Title: Endless track for an off-road work vehicle to produce a net non-null lateral force

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application No. 61/032,247 filed on Feb. 28, 2008 and hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to endless tracks for off-road work vehicles, such as construction vehicles, agricultural vehicles, forestry vehicles, and other vehicles designed for other types of industrial work in off-road conditions. 
     BACKGROUND 
     Off-road work vehicles, such as construction vehicles (e.g., bulldozers, loaders, backhoe loaders, excavators, etc.), agricultural vehicles (e.g., harvesters, combines, tractors, etc.) and forestry vehicles (e.g., feller-bunchers, tree chippers, knuckleboom loaders, etc.), are often equipped with endless tracks which enhance their traction and reduce pressure they apply on soft, low friction and/or uneven grounds (e.g., soil, mud, sand, ice, snow, etc.) on which they operate. 
     In some situations, an endless track of an off-road work vehicle may experience undesirable side loads and/or lateral movements that can have adverse effects on the endless track, such as accelerate its wear (e.g., accelerate wear of inner drive/guide lugs of the endless track) or promote its detracking. For example, in some cases, such undesirable side loads and/or lateral movements may be due to intrinsic mechanical imbalances which may arise in the vehicle (e.g., “toe-in”, negative camber, etc.), motion of the vehicle on the ground (e.g., if the vehicle moves on an inclined ground area, or turns almost exclusively or significantly more often on one side), and/or use of a working implement (e.g., a dozer blade, a bucket, a grapple, a combine head, etc.) with which the vehicle may be equipped (e.g., if the working implement causes the vehicle to be subjected to a higher loading on one of its sides). 
     For these and other reasons, there is a need for solutions directed to opposing undesirable side loads and/or tendencies for lateral movements that may be experienced by endless tracks of off-road work vehicles. 
     SUMMARY OF THE INVENTION 
     According to a first broad aspect, the invention provides an endless track for providing traction to an off-road work vehicle. The endless track has a longitudinal axis and comprises an inner side for engaging a drive wheel of the off-road work vehicle to move the endless track and a ground-engaging outer side for engaging the ground. The ground-engaging outer side comprises a tread pattern characterized in that, when the off-road work vehicle moves on the ground, the tread pattern produces lateral traction force components acting laterally on the endless track such that a resultant of the lateral traction force components is a net non-null lateral force acting on the endless track in a lateral direction generally perpendicular to the longitudinal axis. 
     According to a second broad aspect, the invention provides a method for opposing a tendency for an endless track of an off-road work vehicle to move in a first lateral direction as the off-road work vehicle moves on the ground. The method comprises: providing the endless track with a tread pattern that generates, as the off-road work vehicle moves on the ground, a net non-null lateral force acting on the endless track in a second lateral direction generally opposite the first lateral direction; and driving the off-road work vehicle to give rise to the net non-null lateral force. 
     According to a third broad aspect, the invention provides a method for reducing wear in an endless track of an off-road work vehicle carrying a working implement that creates a non-uniform lateral load distribution whereby the vehicle is subjected to a higher loading on one of its sides which tends to steer the vehicle in a first direction. The method comprises: providing the endless track with a tread pattern that generates, as the vehicle moves on the ground, a net force acting laterally on the endless track and tending to steer the vehicle in a second direction that is generally opposite the first direction; and driving the vehicle on the ground to give rise to the net force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A detailed description of embodiments of the invention is provided below, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  shows an off-road work vehicle in accordance with an embodiment of the invention; 
         FIG. 2  shows a top view of a portion of an endless track of the off-road work vehicle shown in  FIG. 1  in accordance with an embodiment of the invention; 
         FIG. 3  shows a side view of the portion of the endless track shown in  FIG. 2 ; 
         FIG. 4  shows a cross-sectional view of the portion of the endless track shown in  FIG. 2 ; 
         FIG. 5  shows an example of traction force components produced by a tread pattern of the endless track when the off-road work vehicle moves on the ground; 
         FIGS. 6 and 7  show top views of endless tracks having different tread patterns in accordance with other embodiments of the invention; and 
         FIGS. 8 to 12  illustrate examples of situations in which a net non-null lateral force produced by the tread pattern of the endless track can be useful. 
     
    
    
     It is to be expressly understood that the description and drawings are only for the purpose of illustrating certain embodiments of the invention and are an aid for understanding. They are not intended to be a definition of the limits of the invention. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows an off-road work vehicle  10  in accordance with an embodiment of the invention. In this embodiment, the off-road work vehicle  10  is a construction vehicle designed to perform construction work. More specifically, in this example, the construction vehicle  10  is a bulldozer. In other examples, the construction vehicle  10  may be a loader, a backhoe loader, an excavator, or any other type of construction vehicle. 
     In this embodiment, the construction vehicle  10  comprises a frame  12  supporting a prime mover  14 , a pair of track assemblies  16   1 ,  16   2 , a working implement  18 , and an operator cabin  20 , which cooperate to enable an operator to move the construction vehicle  10  on the ground and perform construction work. 
     The prime mover  14  provides motive power to move the construction vehicle  10 . For example, the prime mover  14  may comprise an internal combustion engine and/or one or more other types of motors (e.g., electric motors, etc.) for generating motive power to move the construction vehicle  10 . The prime mover  14  is in a driving relationship with each of the track assemblies  16   1 ,  16   2  that is connected to the prime mover  14  via a power train or other power transmission mechanism of the construction vehicle  10 . 
     The operator cabin  20  is where the operator sits and controls the construction vehicle  10 . More particularly, the operator cabin  20  comprises a set of controls that allow the operator to steer the construction vehicle  10  on the ground and perform construction work using the working implement  18 . 
     The working implement  18  is used to perform construction work. In this embodiment where the construction vehicle  10  is a bulldozer, the working implement  18  is a dozer blade that can be used to push objects and shove soil, debris or other material. In other embodiments, depending on the type of construction vehicle, the working implement  18  may take on various other forms, such as a backhoe, a bucket, a fork, a grapple, a scraper pan, an auger, a saw, a ripper, a material handling arm, or any other type of construction working implement. 
     The track assemblies  16   1 ,  16   2  are drivable by the prime mover  14  to propel the construction vehicle  10  on the ground. In this embodiment, each track assembly  16   i  (i=1 or 2) comprises an endless track  22  disposed around a drive wheel  24 , an idler wheel  26 , and a plurality of bogie wheels  28   1 - 28   4 . 
     The drive wheel  24  is operative for driving the endless track  22  to propel the construction vehicle  10  on the ground. When driven by the drive wheel  24 , the endless track  22  moves along an endless path around the wheels  24 ,  26 ,  28   1 - 28   4 . The idler wheel  26  and the bogie wheels  28   1 - 28   4  do not convert power supplied by the prime mover  14  to motive force, but rather support and distribute part of the weight of the construction vehicle  10  on the ground as well as guide the endless track  22  and maintain it under tension as it is driven by the drive wheel  24 . 
     The track assembly  16   i  may be configured in various other ways in other embodiments. For example, in some embodiments, the track assembly  16   i  may comprise an additional drive wheel (e.g., the idler wheel  26  may be replaced by a drive wheel) and/or may comprise more or less bogie wheels. Also, in some embodiments, the track assembly  16   i  may be provided on the construction vehicle  10  during manufacturing of the construction vehicle  10 , while, in other embodiments, it may be installed at a later time (e.g., the construction vehicle  10  may initially be designed and manufactured to move on wheels and the track assembly  16   i  may be retrofitted to the construction vehicle  10  to replace one or more of its wheels). 
     The endless track  22  provides traction to the construction vehicle  10  on the ground. With additional reference to  FIGS. 2 to 4 , the endless track  22  comprises an inner side  25  engaging the wheels  24 ,  26 ,  28   1 - 28   4  and defining an inner area of the endless track  22  in which these wheels are located. The endless track  22  also comprises a ground-engaging outer side  27  engaging the ground on which the construction vehicle  10  travels. 
     In this embodiment, the endless track  22  comprises an elastomeric body  29  containing rubber or other suitable elastomeric material. The elastomeric body  29  is reinforced with reinforcements, including a layer of longitudinal cables  31  (e.g., steel cords) and one or more layers of fabric  35 . In other embodiments, the endless track  22  may be constructed in various other ways using various other materials and components (e.g., transverse metallic core members). 
     The inner side  25  of the endless track  22  engages the drive wheel  24  in order to cause the endless track  22  to be driven. More particularly, in this embodiment, the inner side  25  of the endless track  22  comprises a plurality of drive lugs  33   1 - 33   N  that interact with the drive wheel  24  in order to cause the endless track  22  to be driven. In this example, the drive wheel  24  comprise a drive sprocket having teeth or bars that engage respective ones of the drive lugs  33   1 - 33   N  of the endless track  22  in order to drive the endless track  22 . The drive lugs  33   1 - 33   N  may also serve to guide the endless track  22  as it is driven and in that sense can also be viewed as guide lugs. In other embodiments, the inner side  25  of the endless track  22  may be configured in other ways depending on a configuration of the drive wheel  24 . For instance, in some embodiments, the inner side  25  of the endless track  22  may comprise recesses or holes in which can enter teeth of the drive wheel  24  in order to drive the endless track  22 . In other embodiments, the inner side  25  of the endless track  22  may be frictionally driven by the drive wheel  24 . 
     The ground-engaging outer side  27  comprises a tread pattern  40  producing traction force components when the construction vehicle  10  moves on the ground. More specifically, as the endless track  22  is driven by the drive wheel  24 , the tread pattern  40  produces longitudinal traction force components acting on the endless track  22  in a longitudinal direction generally parallel to a longitudinal axis  45  of the endless track  22  such that a resultant of the longitudinal traction force components is a longitudinal force acting on the endless track  22  in the longitudinal direction. This longitudinal force can be used to move the construction vehicle  10  forward or backward on the ground. 
     In addition, as further discussed below, the tread pattern  40  is characterized in that, when the construction vehicle  10  moves on the ground, the tread pattern  40  produces lateral traction force components acting laterally on the endless track  22  such that a resultant of the lateral traction force components is a net non-null lateral force acting on the endless track  22  in a lateral direction generally perpendicular to the longitudinal axis  45  (i.e., in a left-to-right or right-to-left direction). This net non-null lateral force (which may also be referred to as a net positive lateral force) can be used for various purposes. For example, in some cases, the net non-null lateral force produced by the endless track  22  can be used to oppose undesirable side loads and/or tendencies for lateral movements that may be experienced by the endless track  22  due to intrinsic mechanical imbalances which may arise in the construction vehicle  10  (e.g., “toe-in”, negative camber, etc.), motion of the construction vehicle  10  on the ground (e.g., if the vehicle  10  moves on an inclined ground area, or turns almost exclusively or significantly more often on one side), and/or use of the working implement  18  (e.g., if the working implement  18  creates a non-uniform lateral load distribution whereby the vehicle  10  is subjected to a higher loading on one of its sides). By opposing such undesirable side loads and/or tendencies for lateral movements, the net non-null lateral force may in some cases help to, for instance, reduce wear of the endless track  22  (e.g., reduce wear of the drive lugs  33   1 - 33   N ), reduce a tendency for detracking of the endless track  22 , and/or provide additional centering of the construction vehicle  10  along its intended path of travel (e.g., on an inclined ground area). 
     The tread pattern  40  may be designed in various ways to produce a net non-null lateral force. For example, in this embodiment, the tread pattern  40  is asymmetrical relative to the longitudinal axis  45  of the endless track  22 . That is, in this case, the longitudinal axis  45  is a central longitudinal axis relative to which the tread pattern  40  is asymmetrical. This asymmetry results in the tread pattern  40  producing opposite lateral traction force components having different magnitudes such that a resultant of these opposite lateral traction force components is a net non-null lateral force acting on the endless track in a lateral direction generally perpendicular to the central longitudinal axis  45 . 
     More particularly, in this embodiment, the tread pattern  40  comprises a plurality of tread projections  42   1 - 42   P  that project outwardly. In this example, each of the tread projections  42   1 - 42   P  has an elongated shape. The tread projections  42   1 - 42   P  may have various other shapes in other examples (e.g., curved shapes, shapes with straight parts at different angles, etc.). Also, in this example, each of the tread projections  42   1 - 42   P  is angled relative to the central longitudinal axis  45 , i.e., it defines an acute angle θ relative to the central longitudinal axis  45 . In this case, the acute angle θ is about 60°. The acute angle θ may have various other values in other examples (e.g., between 50° and)70°. 
     In this embodiment, the tread projections  42   1 - 42   P  are arranged in two (2) rows  43   1 ,  43   2  running longitudinally along the endless track  22 , with the tread projections  42   1 - 42   k  being part of the row  43   1  and the tread projections  42   k+1 - 42   P  being part of the row  43   2 . The tread projections  42   1 - 42   k  of the row  43   1  are longer than the tread projections  42   k+1 - 42   P  of the row  43   2 . Thus, in this case, the tread projections  42   1 - 42   k  of the row  43   1  cross the central longitudinal axis  45  while the tread projections  42   k+1 - 42   P  of the row  43   2  do not. In this example, the tread projections  42   1 - 42   k  of the row  43   1  are about twice as long as the tread projections  42   k+1 - 42   P  of the row  43   2 . There may be a greater or smaller difference in length between the tread projections  42   1 - 42   k  of the row  43   1  and the tread projections  42   k+1 - 42   P  of the row  43   2  in other examples. 
       FIG. 5  illustrates an example of traction force components produced by the tread pattern  40  when the construction vehicle  10  moves on the ground (as viewed from the ground). In this example, the traction force components produced by a pair of projections of the tread projections  42   1 - 42   P  that are located on a bottom ground-engaging run of the endless track  22 , namely the tread projection  42   i  in the row  43   1  and the tread projection  42   m  in the row  43   2 , will be considered. Similar considerations apply to other ones of the tread projections  42   1 - 42   P  that are located on the bottom ground-engaging run of the endless track  22 . 
     Without wishing to be bound by theory, it is believed that, as the tread projection  42   i  engages the ground due to movement of the endless track  22 , there is a normal force component F x′,i  acting on its vertical face along a normal x′-axis. There may also be a shear force component F y′,i  acting on the vertical face of tread projection  42   i  along a tangential y′-axis due to sliding of ground material along that face towards a side edge of the endless track  22 . Thus, there is a longitudinal traction force component F x,i  acting along a longitudinal x-axis generally parallel to the central longitudinal axis  45  of the endless track  22 , as well as a lateral traction force component F y,i  acting along a lateral y-axis generally perpendicular to the central longitudinal axis  45  of the endless track  22 . In this example, these force components can be viewed as: F x,i =F x′,i  sin θ+F y′,i  cos θ and F y,i =F x′,i  cos θ−F y′,i  sin θ. 
     The normal force component F x′,i  acting on the vertical face of the tread projection  42   i  can be viewed as being proportional to an area of this face, and thus a length L i  of this face, such that F x′,i =f(γ s , h b , C, φ)L i  where f(γ s , h b , C, φ) is a function of various parameters, such as ground parameters (e.g., a weight density γ s  and a cohesion C of the ground, an internal shearing resistance φ of the ground), a sinkage level h b  of the tread projection  42   i  in the ground, or other parameters. The shear force component F y′,i  acting on the vertical face of tread projection  42   i  can be also be viewed as being proportional to an area of this face, and thus a length L i  of this face, such that F y′i =g(γ s , h b , C, φ, δ, B)L i  where g(γ s , H b , C, φ, δ, B) is a function of various parameters, such as those mentioned above, an angle of friction δ between the ground and the vertical face of the tread projection  42   i , an adhesion B between the ground and the vertical face of the tread projection  42   i , or other parameters. Therefore, the longitudinal traction force component F x,i  can be viewed as F x,i =[f(γ s , h b , C, φ)sin θ+g(γ s , h b , C, φ, δ, B)cos θ]L i , while the lateral traction force component F y,i  can be viewed as F y,i =[f(γ s , h b , C, φ)cos θ−g(γ s , h b , C, φ, δ, B)sin θ]L i . 
     Similarly, as the tread projection  42   m  engages the ground due to movement of the endless track  22 , there is a longitudinal traction force component F x,m  and a lateral traction force component F y,m  that can be viewed as F x,m =[f(γ s , h b , C, φ)sin θ+g(γ s , h b , C, φ, δ, B)cos θ]L m  and F y,m =[−f(γ s , h b , C, φ)cos θ+g(γ s , h b , C, φ, δ, B)sin θ]L m , where L m  is a length of the vertical face of the tread projection  42   m . 
     By adding the longitudinal traction force components and lateral traction force components produced by the tread projections  42   i ,  42   m , it can be seen that, in this example, a total longitudinal traction force component produced by this pair of projections is F x,i+m =[f(γ s , h b , C, φ)sin θ+g(γ s , h b , C, φ, δ, B)cos θ](L i +L m ), while a total lateral traction force component produced by this pair of projections is F y,i+m =[f(γ s , h b , C, φ)cos θ−g(γ s , h b , C, φ, γ, B)sin θ](L i −L m ). Since in this example the tread projection  42   i  is longer than the tread projection  42   m , the length L i  of the vertical face of the tread projection  42   i  is greater than the length L m  of the vertical face of the tread projection  42   m  and thus the total lateral traction force component F y,i+m  produced by this pair of projections is positive (i.e., non-null) and acts in the lateral direction along which extends the lateral y-axis. In other words, the lateral traction force components F y,i  and F y,m , which are opposite to one another, have different magnitudes such that they result in the total lateral traction force component F y,i+m  being non-null and acting in the lateral direction of the largest one of these lateral traction force components (in this case, F y,i ). 
     When summing all the longitudinal traction force components and lateral traction force components produced by the tread pattern  40  when the construction vehicle  10  moves on the ground, it can be seen that a resultant of the longitudinal traction force components (such as F x,i  and F x,m ) is a longitudinal force F longitudinal  acting on the endless track  22  in the longitudinal direction. This longitudinal force can be used to move the construction vehicle  10  forward or backward on the ground. 
     It can also be seen that a resultant of the lateral traction force components (such as F y,i  and F y,m ) is a net non-null lateral force F lateral  acting on the endless track  22  in a lateral direction (in this example, a left-to-right direction). The magnitude of the lateral force F lateral  depends on various factors, such as, for example, the number of tread projections  42   1 - 42   P  in contact with the ground, the shape of the tread projections  42   1 - 42   P , the torque with which the endless track  22  is driven, and/or other factors. The lateral force F lateral  produced by the endless track  22  can be used for various purposes. 
     For example, consider a situation in which the construction vehicle  10  exhibits intrinsic mechanical imbalances such as mechanical misalignments that cause the endless tracks  22  to tend to move laterally with respect to the vehicle  10 . For instance, the weight of the construction vehicle  10  and/or other loads acting on the vehicle  10  may sometimes cause portions of the frame  12  and/or certain axles which connect the prime mover  14  to the track assemblies  16   1 ,  16   2  to deflect. In some cases, as shown (in dotted lines) in  FIG. 9 , this may cause negative camber for the vehicle  10 , tending to move the endless track  22  laterally outwardly. In other cases, as shown (in dotted lines) in  FIG. 8 , this may cause a tendency for “toe-in” of the endless track  22 , whereby the front of the track  22  tends to move laterally inwardly. In these and other cases, the lateral force F lateral  produced by the tread pattern  40  may oppose a tendency for lateral movement of the endless track  22 , and may thus help to reduce wear of the endless track  22 . 
     As another example, consider a situation in which the construction vehicle  10  turns almost exclusively or significantly more often on one side than the other.  FIG. 11  shows an example of such a situation, where the construction vehicle  10  with the working implement  18  is being used to level a ground surface (e.g., a surface for an airport runway) by following a path  90 . As it follows the path  90 , the vehicle  10  makes a series of right-hand turns such that the working implement  18  may pass repeatedly over the ground surface in order to apply a certain amount of leveling to it. In this situation, the lateral force F lateral  produced by the tread pattern  40  of the endless track  22  may help to counter the effect of the repeated right-hand turns on the endless track  22 . For instance, this may help to reduce wear of the endless track  22 , in particular the drive lugs  33   1 - 33   N  along its inner side  25 , and thus help extend the operational lifespan of the endless track  22 . 
     As yet another example, consider a situation in which the construction vehicle  10  often travels on inclined terrain defining a side slope  80 , as shown in  FIG. 10 . The effect of the slope  80  on the vehicle  10  may cause the vehicle  10  to become somewhat imbalanced. As a result, the actual path that the vehicle  10  follows may parallel the direction of the slope  80  somewhat, resulting in a difference from its intended path as set by the operator (also known as a “drift angle” or “crab angle”). In this situation, the lateral force F lateral  produced by the tread pattern  40  of the endless track  22  may help to counter the effect of the side slope  80 . For instance, the lateral force F lateral  may be generated in an opposite direction of the slope  80 . As a result, the lateral force F lateral  may counter somewhat the imbalance caused by the slope  80  on the vehicle  10  and may reduce wear of the endless track  22  and extend its operational lifespan, especially in cases where the construction vehicle  10  is used for extended periods of time along inclined terrain. 
     As yet another example, consider a situation in which the working implement  18  of the construction vehicle  10  creates a non-uniform lateral load distribution whereby the vehicle  10  is subjected to a higher loading on one of its sides which tends to steer the vehicle  10  in a particular direction. For instance, with reference to  FIG. 12 , consider a case where the working implement  18 , which in this example is a dozer blade, is angled relative to a longitudinal axis  70  of the construction vehicle  10  (i.e., is oriented at an acute angle relative to the longitudinal axis  70 ) in order to push objects or shove soil, debris or other material towards a left side of the vehicle  10 . This causes the construction vehicle  10  to be subjected to a lateral load P lateral  acting on the working implement  18  in a left-to-right direction, which tends to generally steer the vehicle  10  in the left-to-right direction. In this situation, the lateral force F lateral  produced by the tread pattern  40  of the endless track  22  may be used to oppose the effect of the lateral load P lateral  acting on the working implement  18 , which may help reduce wear on the endless track  22 . 
     In other embodiments where the working implement  18  is another type of working implement, other situations may arise in which the working implement  18  creates a non-uniform lateral load distribution whereby the vehicle  10  is subjected to a higher loading on one of its sides which tends to steer the vehicle  10  in a given direction. For example, in some embodiments, the working implement  18  may be an elongated moveable device (e.g., a grapple or extendible crane) that is located on one side of the construction vehicle  10  and is likely to be deployed during use at an angle such that it extends transversally to the longitudinal axis  70  of the vehicle  10 . This may result in a lateral load on vehicle  10  which causes a tendency for the vehicle  10  to steer in a particular direction and thus cause a drift angle to develop between its intended direction and its actual path. In such situations, the lateral force F lateral  produced by the tread pattern  40  of the endless track  22  may be used to oppose the effect of the lateral load caused by the working implement  18 . 
     As yet another example, the lateral force F lateral  produced by the endless track  22  may help to counter a tendency for detracking of the endless track  22  that may otherwise arise in some cases. 
     The examples considered above illustrate some situations in which the lateral force F lateral  produced by the endless track  22  may be useful. It will be appreciated that this lateral force may be useful in various other situations, depending on the type of construction vehicle  10  and its working environment. 
     While in the embodiment considered above the tread pattern  40  is configured in a particular manner to produce the lateral force F lateral , the tread pattern  40  may be configured in various manners to produce such a lateral force in other embodiments. 
     For example, in some embodiments, as shown in  FIG. 6 , the tread projections  42   k+1 - 42   P  of the row  43   2  may be longer than the tread projections  42   1 - 42   k  of the row  43   1 . In such embodiments, the lateral force F lateral  produced by the endless track  22  is directed in a lateral direction opposite to that produced in the embodiment considered above in connection with  FIG. 2 . 
     As another example, in some embodiments, different ones of the tread projections  42   1 - 42   k  of the row  43   1  may have different shapes, and/or different ones of the tread projections  42   k+1 - 42   P  of the row  43   2  may have different shapes. For instance, in some cases, different ones of the tread projections  42   1 - 42   k  of the row  43   1  may have different lengths, and/or different ones of the tread projections  42   k+1 - 42   P  of the row  43   2  may have different lengths. In a similar manner, in some embodiments, different ones of the tread projections  42   1 - 42   P  may define respective acute angles θ having different values. 
     As yet another example, in some embodiments, the tread projections  42   1 - 42   P  of the tread pattern  40  may be arranged in any number of rows running longitudinally along the endless track  22 . For instance, in some cases, as shown in  FIG. 7 , the tread projections  42   1 - 42   p  of the tread pattern  40  may be arranged in a single row. In other cases, the tread projections  42   1 - 42   P  of the tread pattern  40  may be arranged in three (3) or more rows. Also, in some embodiments, the tread projections  42   1 - 42   P  of the tread pattern  40  may be arranged in various configurations that do not form any row. 
     While in the embodiment considered above the off-road work vehicle  10  is a construction vehicle designed to perform construction work, in other embodiments, the off-road work vehicle  10  may be an agricultural vehicle (e.g., a harvester, a combine, a tractor, etc.) designed to perform agricultural work, a forestry vehicle (e.g., a feller-buncher, a tree chipper, a knuckleboom loader, etc.) designed to perform forestry work, or any other work vehicle designed to perform another type of industrial work (e.g., mining, geophysical surveying, etc.) in off-road conditions. In such embodiments, the off-road work vehicle  10  may be equipped with various types of working implements depending on the nature of the work to be performed (e.g., a combine head for an agricultural vehicle, a mulching head for a forestry vehicle, etc.). 
     Although various embodiments and examples have been presented, this was for the purpose of describing, but not limiting, the invention. Various modifications and enhancements will become apparent to those of ordinary skill in the art and are within the scope of the invention, which is defined by the appended claims.