1. Field of the Invention
This invention relates to an elastic crawler.
2. Description of the Prior Art
An elastic crawler used for a civil engineering machine as well as a construction machine, an agricultural machine and a snowmobile is generally formed by providing an outer circumferential surface of an endless belt-like crawler body of an elastic material, such as rubber with lugs with a predetermined pitch which are adapted to eat into the ground and generate a tractive force. This elastic crawler is passed around a driving wheel, a driven wheel and rolling wheels in a track frame to form an endless track vehicle.
Such an elastic crawler is driven and travels by a so-called meshed transmission system and a so-called friction transmission system. Out of these systems, the meshed transmission systems include a system having a sprocket as a driving wheel provided on an outer circumferential portion thereof with a multiplicity of projecting driving pins with a predetermined pitch in the circumferential direction thereof, and on an inner circumferential surface thereof with driving projections with a predetermined pitch. The elastic crawler is turned and travels by engaging the driving pins with these driving projections.
Since the driving projections are engaged with the driving wheel, the projections are provided on the crawler body with the same pitch, of course, as the driving pins.
On the other hand, the lugs are provided in most cases with the same pitch and in the same circumferential positions as the driving projections.
Namely, the related art elastic crawler is formed on the basis of a designing concept that the pitch of the driving projections is set in accordance with that of the driving pins with the pitch of the lugs set in accordance with that of the driving projections.
In order to reliably effect the transmission of power of the driving wheel, setting the pitch of the driving pins and driving projections smaller is desirable. However, when the pitch of the lugs is set small as well in accordance with that of the driving projections, the possibility that the tractive force is lost due to the mud collected in recesses between the lugs becomes high. In addition, the bending characteristics of a driving wheel-wrapping portion of the crawler become inferior, so that there was the possibility that the dislocation of the wheel occurs.
Moreover, since the weight of the elastic crawler increases, the crawler was not suitably used for a vehicle traveling at a comparatively high speed, such as a vehicle which can travel on a public road and a snowmobile.