Drive sprocket for a tracked vehicle

Abstract

A snowmobile is propelled by an endless track that is operatively connected to the snowmobile's engine by two drive sprockets. Each drive sprocket includes one set of external teeth and two sets of internal teeth that engage three corresponding sets of track teeth formed on the track. Alignment cleats are mounted on the inside of each of one of the sets of track teeth. During low-load operation, contact between the cleats (and the track teeth on which the cleats are mounted) is minimized or eliminated, which reduces or eliminates noise caused by collisions between the metal sprocket and the metal cleats. During higher load operation, the track deforms such that the set of external sprocket teeth engage the cleats and associated set of track teeth.

1 . A vehicle comprising: 
 a frame;    a power plant supported by the frame;    a sprocket operatively connected to the power plant, the sprocket comprising: 
 a sprocket wheel rotationally supported by the frame and operatively connected to the power plant, the sprocket wheel having a rotational axis, a perimetrical surface, and first and second axial surfaces,  
 a first plurality of sprocket teeth extending radially outwardly from the perimetrical surface in spaced-apart relation,  
 a second plurality of sprocket teeth extending axially outwardly from the first axial surface in spaced-apart relation, and  
 a third plurality of sprocket teeth extending axially outwardly from the second axial surface in spaced-apart relation;  
   an endless track supported by the frame passing around and engaging the sprocket comprising: 
 an outer side and an inner side, the track defining a plurality of holes therethrough, the portions of the track between the plurality of holes being a first plurality of track teeth adapted to engage the first plurality of sprocket teeth;  
 a second plurality of track teeth projecting from the inner side of the endless track adapted to engage the second plurality of sprocket teeth; and  
 a plurality of ground-engaging lugs projecting from the outer side of the endless track,  
   wherein, only when the second plurality of track teeth deform under load exerted thereon by the second plurality of sprocket teeth, does the first plurality of sprocket teeth engage the first plurality of track teeth to supplement traction between the sprocket and the endless track.    
     
     
         2 . The vehicle according to  claim 1 , wherein the endless track further comprises a third plurality of track teeth projecting from the inner side of the endless track adapted to engage the third plurality of sprocket teeth.  
     
     
         3 . The vehicle according to  claim 1 , wherein each of the second and third pluralities of track teeth are disposed laterally adjacent to each of the first plurality of track teeth, on opposite sides thereof.  
     
     
         4 . The vehicle according to  claim 1 , wherein each of the first plurality of sprocket teeth, each of the second plurality of sprocket teeth, and each of third plurality of sprocket teeth are axially aligned.  
     
     
         5 . The vehicle according to  claim 1 , wherein the endless track further comprises a plurality of cleats, each cleat including a base portion secured to one of the first plurality of track teeth and at least one cleat portion projecting from the base portion away from the inner side of the endless track.  
     
     
         6 . The vehicle according to  claim 5 , wherein when the second plurality of track teeth do not deform under load exerted thereon by the second plurality of sprocket teeth, the base portions of the cleats do not contact the first plurality of sprocket teeth.  
     
     
         7 . The vehicle according to  claim 5 , wherein only when the second plurality of track teeth deform under load exerted thereon by the second plurality of sprocket teeth, does the first plurality of sprocket teeth engage the cleats to enhance traction between the sprocket and the endless track.  
     
     
         8 . The vehicle according to  claim 5 , wherein each of the second plurality of sprocket teeth has at least one notch formed therein.  
     
     
         9 . The vehicle according to  claim 8 , wherein each of the second plurality of sprocket teeth has a base portion and a tip portion, wherein the at least one notch is formed on one side of the base portion of the second plurality of sprocket teeth such that the cleat portion projecting from the base portion of the cleat enters therein.