Belt tensioner

In the combination of a tensioner and an endless power transmission belt which is employed in driving a sheave comprising at least one accessory which upon being driven creates a slack side and a tight side in said belt on opposite sides of said sheave, said belt having an outside surface and an inside surface, said tensioner comprising, a first support arm having pivot means, a first idler pulley rotatably carried by said arm, and a pivot pin extending through said pivot means for pivotally supporting said first arm adjacent said sheave with said first pulley engaging said slack side of said belt on said outside surface thereof to enable tensioning thereof, a second support arm integrally formed with said first support arm, and supported by said pivot pin, a second idler pulley rotatably carried by said second arm and engaging said tight side of said belt on said outside surface thereof, and means connecting said second arm to said first arm to thereby move said first arm and its pulley into belt tensioning and dampening engagement against said slack side once said tight side of said belt moves said second pulley and second arm, said first arm being of extended length and having an inner end provided with said pivot means and said first pulley rotatably carried adjacent the outer end of said first arm, said second arm having an inner end and said second pulley rotatably carried adjacent the outer end of said second arm, said connecting means comprising means fixing said inner end of said second arm to said inner end of said first arm to define a substantially V-shaped unitary structure, the improvement wherein said first arm is longer than said second arm and said first pulley engages said slack side of said belt at a distance from said sheave greater than the distance said second pulley engages said tight side of said belt from said sheave whereby a greater amount of slack side tensioning than tight side tensioning is provided through the mechanical advantage of said first arm being longer than said second arm.