Abstract:
A tracked vehicle has a frame, a straddle seat connected to the frame, an engine, a pair of slide rails, at least two idler wheels, at least one drive sprocket, and a drive track The drive track has an endless belt, a plurality of external and internal lug, at least a number of the plurality of internal lugs forming two outer longitudinal rows, the belt having at least two contact surfaces, each contact surface being a surface where a corresponding one of the at least two idler wheels is in contact with the belt, a plurality of apertures and a plurality of alignment cleats disposed between the two outer longitudinal rows, and a plurality of lateral rods embedded within the belt and extending in the lateral direction. Both ends of at least a number of the plurality of lateral rods being disposed inwardly of the contact surfaces.

Description:
CROSS-REFERENCE 
     The present application is a divisional application of U.S. patent application Ser. No. 14/125,250, filed Dec. 10, 2013, which is a national stage application of International Patent Application No. PCT/US2011/042316, filed Jun. 29, 2011, the entirety of both of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to drive tracks for tracked vehicles. 
     BACKGROUND 
     Tracked vehicles conventionally have a drive track that includes an endless belt and a plurality of idler wheels. 
     A portion of a prior art drive track  128 ′ is shown in  FIG. 1 . The drive track  128 ′ has an endless flexible belt  129 ′ which has an inner side  129   a ′ and an outer side  129   b ′. The endless track  128 ′ includes a plurality of external lugs (or ribs)  123 ′ that project from the outer side  129   b ′ to give the endless track  128 ′ traction against the snow as the endless track  128 ′ propels the vehicle, and a plurality of internal lugs  126 ′ that project from the inner side  129   a ′. The plurality of internal lugs  126 ′ defines four longitudinal rows of inner lugs  125 ′ and two longitudinal rows of outer lugs  127 ′. The two longitudinal rows of outer lugs  127 ′ are disposed outwardly of the four longitudinal rows of inner lugs  125 ′. 
     A slide frame assembly  44 ′ primarily includes a pair of spaced apart slide rails  46 ′ that engage the inner side of the drive track  128 ′. Two inner idler wheels  50 ′ and two outer idler wheels  51 ′ are rotatably connected to an axle  61 ′ which extends laterally between the slide rails  46 ′. The outer idler wheels  51 ′ are disposed outwardly adjacent to the outer rows of lugs  127 ′. A plurality of longitudinally spaced apertures (or windows) (not shown) are connected to the inner side  129   a ′ of the endless belt  129 ′. The slide rails  46 ′ are covered with slide shoes  41 ′ and slide over the alignments cleats  130 ′. 
     A plurality of lateral rods  200 ′ (only one being shown) extend laterally through the endless belt  129 ′ at regular intervals along a length of the belt  129 ′. The lateral rods  200 ′ provide reinforcement to the belt  129 ′. The rods  200 ′ extend from one lateral side  129   c ′ of the belt  129 ′ to the other. The rods  200 ′ are typically made of metal or fiber filled resin and the belt  129 ′ is typically made of rubber. 
     When in operation, as the endless belt  129 ′ is driven by sprocket wheels (not shown) that engage at least some of the lugs  125 ′,  127 ′ and windows and rotates around the idler wheels  50 ′,  51 ′. As the belt  129 ′ rotates, the rods  200 ′ are successively disposed vertically between the idler wheels  50 ′,  51 ′ and the ground. These rods  200 ′, which are vertically between the idler wheels  50 ′,  51 ′ and the ground, support the slide rails  46 ′ and the idler wheels  50 ′,  51 ′. 
     While the rods  200 ′ provide reinforcement to the belt  129 ′, they also increase a weight of the drive track  128 ′. Furthermore, the rods  200 ′ limit a motion of the snowmobile when side hilling (i.e. moving at an angle with respect to the slope of the hill). Also, noise is generated when the idler wheels  50 ′,  51 ′ run over the rods  200 ′. 
     Therefore, there is a need for a drive track having a reduced weight while providing adequate structural resistance. There is also a need for a drive track that reduces noise generation. Finally there is also a need for a drive track that is suited for side hilling. 
     SUMMARY 
     It is an object of the present invention to ameliorate at least some inconveniences of the prior art. 
     In one aspect, a drive track for a tracked vehicle is provided. The drive track comprises a belt having an inner side and an outer side. The belt has a longitudinal direction and a lateral direction. The belt has two lateral sides. A plurality of external lugs is distributed on the outer side of the belt. The plurality of external lugs is adapted to be in contact with a ground. A plurality of internal lugs is distributed on the inner side of the belt. The plurality of internal lugs is adapted to be at least partially in contact with at least one drive sprocket of the tracked vehicle. At least some of the plurality of internal lugs is forming two outer longitudinal rows. Each of the two outer longitudinal rows is disposed next to a corresponding one of the two lateral sides of the belt. Regions of the belt disposed outwardly of the two outer longitudinal rows are deprived of internal lugs. A plurality of apertures is disposed laterally between the at least two outer longitudinal rows. A plurality of alignment cleats is disposed laterally between the at least two outer longitudinal rows. The plurality of alignment cleats forms two cleat longitudinal rows. A plurality of lateral rods is embedded within the belt. The plurality of lateral rods is extending in the lateral direction. Both ends of at least some of the plurality of lateral rods is disposed laterally inwardly of the regions of the belt disposed laterally outwardly of the two outer longitudinal rows. 
     In a further aspect, the regions of the belt disposed laterally outwardly of the two outer longitudinal rows are adapted to each receive a corresponding idler wheel of the tracked vehicle. 
     In an additional aspect, each end of the at least some of the plurality of lateral rods is laterally aligned with a corresponding one of the two cleat longitudinal rows. 
     In a further aspect, the plurality of the lateral rods is embedded in the belt between the inner side and the outer side of the belt. 
     In an additional aspect, each end of at least some of the plurality of lateral rods is laterally aligned with a corresponding one of the two outer longitudinal rows. 
     In a further aspect, the two outer longitudinal rows of internal lugs each have an outer edge. Each end of at least some of the plurality of lateral rods is laterally aligned with a corresponding one of the outer edges. 
     In an additional aspect, the plurality of alignment cleats is adapted to be contacting sliding rails of the tracked vehicle. 
     In a further aspect, the plurality of alignment cleats is disposed over every other portion extending longitudinally between two apertures. 
     In an additional aspect, the regions of the belt disposed outwardly of the two outer longitudinal rows are adapted to contact idler wheels of the tracked vehicle. 
     In yet another aspect, a tracked vehicle is provided. The tracked vehicle comprises a frame. A straddle seat is connected to the frame. An engine is mounted on an engine cradle portion of the frame. A pair of slide rails is connected to a bottom of the frame. The vehicle comprises at least two idler wheels. At least one drive sprocket is operatively connected to the engine. A drive track is operatively connected to the at least one drive sprocket for propelling the snowmobile. The drive track comprises an endless belt having an inner side and an outer side. The belt has a longitudinal direction and a lateral direction. The belt has two lateral sides. A plurality of external lugs is distributed on the outer side of the belt. The plurality of external lugs is adapted to be in contact with a ground. A plurality of internal lugs is distributed on the inner side of the belt. The plurality of internal lugs is at least partially in contact with the at least one drive sprocket. At least some of the plurality of internal lugs is forming two outer longitudinal rows. The two outer longitudinal rows are disposed near to a corresponding one of the two lateral sides of the belt. The belt has at least two contact surfaces. Each contact surface is a surface where a corresponding one of the at least two idler wheels is in contact with the belt. A plurality of apertures is disposed between the at least two outer longitudinal rows. A plurality of alignment cleats is disposed between the at least two outer longitudinal rows. The plurality of alignment cleats is forming two cleat longitudinal rows. The slide rails are contacting the plurality of alignment cleats. A plurality of lateral rods is embedded within the belt. Each of the plurality of lateral rods is extending in the lateral direction. Both ends of at least some of the plurality of lateral rods are disposed inwardly of the contact surfaces. 
     In a further aspect, regions of the belt outwardly of the contact surfaces are deprived of internal lugs. 
     In an additional aspect, each end of each of the plurality of lateral rods is laterally aligned with a corresponding one of the two cleat longitudinal rows. 
     In a further aspect, the plurality of lateral rods is embedded in the belt between the inner side and the outer side of the belt. 
     In an additional aspect, each end of each the plurality of lateral rods is laterally aligned with a corresponding one of the outer longitudinal rows. 
     In a further aspect, the outer longitudinal rows of internal lugs each have an outer edge. Each end of the at least some of the plurality of lateral rods is laterally aligned with a corresponding one of the outer edges. 
     In an additional aspect, each of the at least two idler wheels is connected to a rear of a corresponding one of the slide rails. 
     In a further aspect, the plurality of alignment cleats is disposed over every other portion extending longitudinally between two apertures. 
     In an additional aspect, the vehicle is a snowmobile. The snowmobile has at least one ski connected to the frame. The at least one ski being is disposed forward of the drive track. 
     For purposes of this application, terms related to spatial orientation such as forwardly, rearwardly, upwardly, downwardly, left, and right, are as they would normally be understood by a driver of the vehicle sitting thereon in a normal riding position. 
     Embodiments of the present invention each have at least one of the above-mentioned objects and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present invention that have resulted from attempting to attain the above-mentioned objects may not satisfy these objects and/or may satisfy other objects not specifically recited herein. 
     Additional and/or alternative features, aspects, and advantages of embodiments of the present invention will become apparent from the following description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention as well as other objects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where: 
         FIG. 1  is a cross-sectional view taken along a laterally extending vertical plane of a portion of a prior art drive track shown with idler wheels mounted on an axle; 
         FIG. 2  is a left side elevation view of a snowmobile; 
         FIG. 3  is a perspective view taken from a rear, left side of a portion of a drive track and a suspension assembly of the snowmobile of  FIG. 2 ; 
         FIG. 4  is a perspective view taken from a rear, left side of a portion of the drive track of  FIG. 3  shown with sprocket wheels; and 
         FIG. 5  is a cross-sectional view taken along a laterally extending vertical plane of a portion of the drive track of  FIG. 3  shown with idler wheels mounted on an axle. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 2 , a snowmobile  10  includes a front end  2  and a rear end  4 , which are defined consistently with the forward travel direction of the vehicle. The snowmobile  10  includes a chassis  6  which normally includes a tunnel  8 , an engine cradle portion  11  and a front suspension assembly portion  12 . The snowmobile  10  has a longitudinal axis  111 , about which the snowmobile  10  may slightly rotate when side hilling. 
     An engine  14  which is schematically illustrated, is carried by the engine cradle portion  11  of the chassis  6 . A ski and steering assembly is provided, in which two skis  16  (only one of which is shown) are positioned at the front end  2  of the snowmobile  10 , and are attached to the front suspension assembly portion  12  of the chassis  6  through a front suspension assembly  18 . The front suspension assembly  18  includes ski legs  21 , supporting arms  22  and ball joints (not shown) for operatively joining the respective ski legs  21 , supporting arms  22  and a steering column  24 . The steering column  24  at its upper end is attached to a steering device such as a handlebar  26  which is positioned forward of a rider and behind the engine  14  to rotate the ski legs  21  and thus the skis  16 , in order to steer the vehicle. 
     A seat  38  extends from the rear end  4  of the snowmobile  10 . Two foot rests  40  (only one of which is shown) are positioned on opposed sides of the snowmobile  10  below the seat  38  to accommodate the rider&#39;s feet. 
     An endless drive track  128  is positioned at the rear end  4  of the snowmobile  10  and is disposed under the tunnel  8 . The endless drive track  128  is operatively connected to the engine  14  through a belt transmission system  30  which is schematically illustrated in broken lines. Thus, the endless drive track  128  is driven to run about a rear suspension assembly  32  for propulsion of the snowmobile  10 . The endless drive track  128  is engaged with and driven by two drive sprockets  80  (shown in  FIG. 4 ) which are journaled by the tunnel  8  and is driven by the engine  14  through the belt transmission system  30 . The drive sprockets  80  are mounted on a drive axle  70  (shown in  FIG. 4 ) which is driven in rotation by the engine  14 . 
     The endless drive track  128  is suspended for movement relative to the chassis  6 , by the rear suspension assembly  32 . The rear suspension assembly  32  includes a slide frame assembly  44  which primarily includes a pair of spaced apart slide rails  46  that engage the inner side of the endless drive track  128 . The rear suspension assembly  32  will be described below. A pair of slide shoes  41  (shown in  FIG. 5 ) is disposed around each slide rail  46 . The slide shoes  41  are made of UHWM PE (Ultra High Molecular Weight Polyethylene). The slide shoes  41  reduce the friction between the metal slide rails  46  and the metal alignment cleats  130 . It is contemplated that the slide shoes  41  could be made of a hard plastic other than UHWM PE. The lateral rods  200  will be described in greater detail below. 
     The slide frame assembly  44  journals a plurality of rollers including two rollers  52 ,  55  and idler wheels  50 ,  51 . The rollers  55  are carried by the rear suspension arm  64 , in order to define the path over which the endless drive track  128  travels. The idler wheels  50 ,  51 , which are sometimes called rear idler wheels, are rotatably connected to an axle  61  which extends laterally between the slide rails  46  at a rear of the slide rails  46 . It is contemplated that the snowmobile  10  could have more or less rollers and idler wheels than the ones shown in the Figures. 
     The snowmobile  10  includes other elements, which will not be described herein. 
     Referring to  FIG. 3 , the rear suspension assembly  32  comprises left and right front suspension arms  54  and a single rear suspension arm  64 . It is contemplated that the single rear suspension arm  64  could comprise left and right rear suspension arms. The front suspension arms  54  extend downwardly and rearwardly from a front portion of the tunnel  8 . Upper ends of the front suspension arms  54  are pivotally attached to the tunnel  8 , and lower ends of the front suspension arms  54  are each pivotally attached to their respective slide rails  46  of the slide frame assembly  44 . 
     The rear suspension arm  64  extends downwardly and rearwardly from a rear portion of the tunnel  8 , and are disposed rearward of the front suspension arms  54 . The rear suspension arm  64  is pivotally attached to the tunnel  8  of the chassis  6  by means of a tube and shaft assembly. The tube and shaft assembly includes a tube  66  rotatably supported by a shaft (not shown) which is mounted at the opposite ends thereof to the tunnel  8 . The shaft supports rollers  55 , which support an upper portion of the endless drive track  128 . An upper end of the rear suspension arm  64  is affixed to the tube  66 , and a lower end of the rear suspension arm  64  is pivotally connected to the slide rails  46 . 
     The rear suspension assembly  32  includes other elements, which will not be described herein. 
     Turning to  FIGS. 4 and 5 , the endless track  128  will now be described. The endless track  128  has an endless flexible belt  129 . The flexible belt  129  has the inner side  129   a , an outer side  129   b  and two lateral sides  129   c . The endless track  128  includes a plurality of external lugs (or ribs)  123  that project from the outer side  129   b  to give the endless track  128  traction against the snow as the endless track  128  propels the snowmobile  10 , and a plurality of internal lugs  126  that project from the inner side  129   a . The endless track  128  has a longitudinal direction  112  and a lateral direction  114 . A vertical direction  113  is perpendicular to both the longitudinal direction  112  and the lateral direction  114 . The belt  129  has a width  132  in the lateral direction  114 . 
     The endless track  128  is made of rubber. It is contemplated that the endless track  128  could be made of another strong, flexible material such as rubber reinforced with fabric and metal. The endless belt  129 , the external lugs  123  and the internal lugs  126  are integrally formed with each other. 
     The plurality of internal lugs  126  includes two left and two right longitudinal rows of inner track lugs  125  and a left and a right longitudinal row of outer track lugs  127 . The inner track lugs  125  are aligned with the outer track lugs  127  in the longitudinal direction  112 . The outer track lugs  127  and the inner track lugs  125  are spaced with a same pitch. It is contemplated that the inner track lugs  125  could be offset from the outer track lugs  127  in the longitudinal direction  112 . It is also contemplated that the outer track lugs  127  and the internal lugs  125  could have a different pitch. It is contemplated that a layout of the outer track lugs  127  and internal lugs  125  on the endless belt  129  could be different from shown in the Figures. 
     The outer track lugs  127  define three regions of the belt  129 . Regions  141  are defined laterally between the outer track lugs  127  and the lateral sides  129   c  of the belt  129  they are next to, and a region  142  is defined laterally between the two rows of outer track lugs  127 . The regions  141  are deprived of internal lugs  126 . As best seen in  FIG. 5 , the regions  141  include contact surfaces  143  which are surfaces where the idler wheels  51  contact the belt  129 . 
     As best seen in  FIG. 4 , the inner track lugs  125  come in contact with the two sprockets  80  for providing traction to the snowmobile  10 . As best seen in  FIG. 4 , the outer track lugs  127  contact the slide rails  46  to ensure that the endless belt  129  stays in alignment. The slide rails  46  are sliding in a space defined between the outer track lugs  127  and inner track lugs  125  on the left side, and between the outer track lugs  127  and inner track lugs  125  on the right side. It is contemplated that that the internal lugs  126  could be in contact with sprockets other than the sprockets  80  mounted onto the drive axle  70 . 
     A plurality of longitudinally spaced apertures (or windows)  124  are defined in the endless belt  129 . The plurality of spaced apertures  124  is disposed into two longitudinal rows disposed laterally between the outer track lugs  127  and outer most of the inner track lugs  125 . It is also contemplated that the plurality of longitudinally spaced apertures  124  could form only one or more than two rows. 
     The endless track  128  also comprises a plurality of alignment cleats  130  that are mounted adjacent onto the outer track lugs  127  and extend across every second one of portions longitudinally between two apertures  124  to the inner track lugs  125 . The alignment cleats  130  include each a base portion  131  and a cleat portion  133 . It is contemplated that the cleat portion  133  could be omitted. The cleat portions  133  of the alignment cleats  130  extend upwardly against sides of the corresponding outer track lugs  127 . The base portions  131  of the alignment cleats  130  receive the pair of slide shoe  41  (left and right) thereon. The alignment cleats  130  comprise a strong, light, stamped sheet of steel. It is contemplated that other suitable material such as aluminum could be used to make the alignment cleats  130 . It is also contemplated that the alignment cleats  130  could not be stamped but cast or molded into the desired shape. 
     Referring more specifically to  FIG. 5 , the lateral rods  200  will be described. 
     The lateral rods  200  are embedded in the belt  129  between the inner side  129   a  and the outer side  129   b . The plurality of lateral rods  200  is incorporated to the belt  129  during molding of the belt  129 . The rods  200  are made of fiber filled resin. It is contemplated that the rods  200  could be made of another material. For example, the rods  200  could be made of carbon fiber or steel. It is also contemplated that the rods  200  could be made of an other composite material. It is contemplated that the rods  200  could be different from each other. For example, they could have a different length  201  in the lateral direction  114  from each other, or a different material. The lateral rods  200  are disposed parallel to each other in the lateral direction  114  at a constant pitch and are laterally aligned. It is contemplated that the rods  200  could be offset from each other. 
     To allow edges  129   c  of the belt  129  to flex, the length  201  of the rods  200  is smaller than the width  132  of the belt  129 , and the ends  203  of the rods  200  are positioned inwardly of the contact surfaces  143  of the idler wheels  51 . As shown in  FIG. 5 , the ends  203  are laterally aligned with outer edges of the outer track lugs  127 . As a consequence, the regions  141  can bend more than if the belt  129  had the prior art rods  200 ′. It is desirable that the regions  141  bend during side hilling, for example. Since, the regions  141  are deprived of internal lugs  126  and the ends  203  are laterally aligned with outer edges of the outer track lugs  127 , the rods  200  do not directly support the outer idler wheels  51 . It is contemplated that the ends  203  of the rods  200  could be positioned laterally inwardly from the outer edges of the outer track lugs  127 . For example, as shown in dotted lines in  FIG. 5 , the ends  203  are laterally aligned with a center of the outer track lugs  127 . In another example, the ends  203  are laterally aligned with the slide rails  46 . In another example, the ends  203  are laterally aligned with outer edges of the slide rails  26 . In yet another example, the ends  203  are laterally aligned with outer edges of the slide shoes  41 . In another example, the ends  203  are laterally aligned with the alignment cleats  130 . 
     Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present invention is therefore intended to be limited solely by the scope of the appended claims.