Track roller for tracked vehicles
BACKGROUND OF THE INVENTION 
     The present invention relates to a track roller for tracked vehicles. 
     Track rollers are known which are composed of a shaft on which the actual roller turns with lubricated bearings interposed therebetween. 
     The opposite ends of the shaft are inserted in bushes which are externally provided with expansions in which bolts engage in order to fix the bushes to a supporting frame. The shaft is prevented from rotating by diametrical pins inserted in it through the bushes. 
     In order to provide a tight seal in the regions between the bushes and the opposite ends of the roller, sliding-ring gaskets, i.e. gaskets each composed of a pair of metallic rings which are pressed against one another, are provided. The axial force with which the rings of each pair are pushed toward one another is determined by the elastic deformation of respective rubber rings which are accommodated in seats defined in flanges of the bushes and in the roller. 
     Known rollers have the disadvantage that they are rather complicated from the point of view of construction and assembly; this complication is to be ascribed to the need to provide diametrical holes in the bushes and in the shaft for the passage of the pins and to provide seals between the shaft and the bushes in order to avoid the outward leakage of the lubricating oil of the bearings. 
     SUMMARY OF THE INVENTION 
     The technical aim of the present invention is therefore to provide a roller wherein the above described problems are substantially eliminated. 
     This aim is achieved, according to the present invention, with a track roller for tracked vehicles which is characterized in that the roller supporting shaft is inserted with a tight fit in respective blind bushes preset for fixing to a supporting structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further peculiarities of the present invention will become apparent from the following description of a preferred embodiment, illustrated only by way of non-limitative example in the accompanying drawing, wherein: 
     FIG. 1 is a side view of the track roller according to the present invention; 
     FIG. 2 is an axial view of said track roller; and 
     FIG. 3 is a sectional view, taken along the plane III--III of FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the above figures, the track roller is generally designated by the reference numeral 1 and comprises a roller body 2, which is composed of two halves 3 and 4 which are exactly specular and are welded by friction along the median plane 5. 
     The roller 2 is supported so as to be able to rotate about a perfectly cylindrical shaft 8 by means of a pair of bushings 6 and 7. 
     Two annular seats 9 and 10 are defined at the opposite ends of the roller and, by means of axial channels 11, are connected to a central cavity 12 of the roller 2 in which lubricating oil for the bearings 6 and 7 is introduced through a hole which is closed by a plug 13. 
     The opposite ends of the shaft 8 extend on both sides beyond the heads of the roller and are inserted with a tight fit in blind bushes 14 and 15, i.e. bushes which in practice have the shape of cups closed by bottoms 16 and 17. 
     The edges 18 and 19 of the bushes 14 and 15 which are directed toward the median plane 5 are flared and make sliding contact with shoulders 20 and 21 of the opposite heads of the roller 2 which protrude from the bottom of the seats 9 and 10. 
     The bushes are furthermore externally provided with flange 22 and 23 which define annular lips 24 and 25 which partially enter the seats 9 and 10 and close them with respect to the outside. 
     Two gaskets 26 and 27 are accommodated inside the seats 9 and 10 and prevent the outward leakage of the lubricating oil and at the same time prevent the penetration of dirt or other matter between the rotating parts. 
     Each gasket is composed of a pair of metallic rings 28 and 29 which have a substantially triangular cross-section and are arranged symmetrically with respect to a common plane of contact. 
     Respective rubber rings 30 and 31 are arranged peripherally with respect to said metallic rings 28 and 29 and rest externally on inclined surfaces 32 and 33 which are located inside the lips 24 and 25 and respectively circumscribe the seats 9 and 10. 
     The surfaces 32 and 33 converge and have such a diameter that when the bushes 14 and 15 are inserted on the shaft 8 the rings 28 and 29 are compressed. In this manner axial force components are produced which push the rings 28 and 29 toward each other, providing an oil-tight seal at the surface of contact, whereas tightness outside the rings 28 and 29 is provided by the rubber rings. 
     As can be seen, the described invention allows to achieve considerable structural simplification. In particular, the tight fit of the blind bushes 14 and 15 on the shaft 8 providing a sealing fixed coupling avoids the application of keying pins through said bushes and said shaft as well as the forming of annular grooves on the shaft in order to accommodate the sealing rings required to prevent axial leakages of lubricating oil. 
     The shaft 8 furthermore becomes significantly shorter, since it is no longer crossed by diametrical pins. 
     It should be noted that the bushes 14 and 15 are force-fitted until their bottoms 16 and 17 abut against the opposite ends of the shaft 8. In this manner the tight fit of the bushes 14 and 15 on the shaft 8 is sealed with respect to the environment and furthermore it is possible to determine exactly the axial plays between the edges 18 and 19 and the shoulders 20 and 21 and the thrusts by which the rings 28 and 29 are pushed toward one another. 
     The bushes can be conventionally provided with lateral expansions 34 and 35 which are rigidly associated with the bottoms 16 and 17 and are provided with holes 36 and 37 for the passage of bolts for mounting the roller onto a supporting structure.