Tensioner for track of tracked vehicle

In combination with

• a frame;
• an idler wheel displaceable relative to the frame;
• and
• a flexible endless element spanned over the idler wheel, a tensioning device comprising:
• an inner end plate mounted on the frame;
• a sleeve having inner and outer ends and fixed at its inner end to the inner end plate and extending along an axis toward the idler wheel;
• a cover plate at the outer sleeve end;
• an axially compressible stack of inner and outer spring rings closely surrounded by the sleeve, wholly received between the inner and outer sleeve ends, forming an annular friction spring, and having an inner end and an outer end;
• an outer end plate bearing axially toward the inner end plate directly on the outer end of the annular friction spring;
• an inner stem extending axially through the spring and having an outer end fixed to the outer end plate and an inner end adjacent the inner end plate;
• a guide on the inner end of the inner stem, the inner end of the spring bearing axially directly on the guide;
• means including a nut threaded on the inner stem and axially outwardly engageable with the guide for effectively shorting the inner stem and thereby prestressing the spring;
• means including a plurality of axially extending bolts securing the cover plate to the outer sleeve end and precompressing the annular friction spring axially between the end plates;
• and
• a hydraulic unit braced axially between the outer end plate and the idler wheel.