Timing belt tensioner with damped constant spring tensioning and belt tooth disegagement prevention

Claim 1

A timing belt tensioning device comprising a fixed structure, a pivoted structure mounted with respect to said fixed struture for pivotal movement about a first axis between first and second limiting positions, a timing belt engaging pulley rotatably carried by said pivoted structure for rotational movement about a second axis parallel with said first axis, spring means mounted between said fixed and pivoted structures for resiliently biasing the pivoted structure to move in a direction away from said first limiting position toward said second limiting position with a spring force that decreases as the pivoted structure is moved in a direction away from said first position toward said second position, one-way clutch means for permitting pivotal movement of said pivoted structure in a direction toward said second limiting position and for limiting the pivotal movement of said pivoted structure in an opposite direction toward said first limiting position beyond a predetermined distance measured from the nearest position of said pivoted structure to said second limiting position, the predetermined distance having a maximum dimension such as to prevent loosening of the timing belt engaged by said pulley sufficient to allow disengagement of a tooth thereof with a tooth of a timing pulley and a minimum dimension such as to accommodate normal operating low amplitude movements and thermal expansion during operation, and damping means for damping the operating movements of said pivoted structure permitted by said one-way clutch means.