Belt tensioner with frustoconical pivot bearing

In a belt tensioning device comprising a fixed structure, a pivoted structure, first bearing means mounting said pivoted structure on said fixed structure for pivotal movement about a first axis between first and second limiting positions, spring means acting between said fixed and pivoted structures for resiliently biasing said pivoted structure to move in a direction away from said first limiting position toward said second position, a belt engaging pulley, second bearing means mounting said pulley on said pivoted structure for rotational movement about a second axis parallel with said first axis in such a way that a belt tension load applied to said pulley will be transmitted to said pivoted structure with a tangential force component acting in a direction to be resisted by an opposed spring load force component and a radially inward force component acting in a direction to be resisted by said fixed structure through said first bearing means, and damping means for damping by friction surface sliding movements of said pivoted structure with a damping load which decreases as said pivoted structure is moved in a direction away from said first position toward said second position, said damping means including means for transmitting to said pivoted structure a damping load (1) which decreases as said pivoted structure is moved in a direction away from said first position toward said second position and (2) which includes a damping radially inward force component acting in a position parallel with said first mentioned radially inward force component so as to establish a combined radially inward force component acting in a position between the two inward force components which is proportional to the relative magnitudes thereof, the improvement which comprises

• said first bearing means comprising a frustoconical sleeve bearing having frustoconical exterior surface and a frustoconical interior surface,
• said pivoted structure including an annular portion having a frustoconical surface engaging one of said bearing frustoconical surfaces for applying the combined radially inward force component transmitted to said pivoted structure to said sleeve bearing,
• said fixed structure including an annular portion having a frustoconical surface engaging the other of said bearing frustoconical surfaces for resisting the combined radially inward force component applied to said sleeve bearing by said pivoted structure,
• the frustoconical surface of one of said annular portions being (1) formed on the exterior periphery thereof and (2) disposed in engagement with said interior bearing frustoconical surface,
• the pivotal movements of said pivoted structure with respect to said fixed structure being defined about said first axis by relative pivotal sliding friction contact between at least one of said bearing frustoconical surfaces with the frustoconical surface of the associated annular portion engaged thereby,
• said one annular portion having a load center point disposed on said first axis,
• the other of said annular portions having a load center point disposed on a line disposed within a plane passing through said first and second axes corresponding to the one line of the two lines of intersection of said bearing frustoconical surface with said plane through which the combined radially inward force component transmitted by said pivoted structure is applied to said sleeve bearing,
• said load center points being positioned such that in at least one position of said pivoted structure between said first and second limiting positions the combined radially inward force componenet transmitted by said pivoted structure and resisted by said fixed structure is transmitted generally from one load center point to the other along a line extending between said points which is perpendicular to and bisects said one line so that the combined radially inward force component transmitted by said pivoted structure to said sleeve bearing is distributed evenly through the axial extent of said sleeve bearing.