Reduced noise multi-ribbed power transmission belt
A multi-ribbed power transmission belt has transverse grooves in the compression section which are oriented at angles other than perpendicular. The combination of longitudinal grooves and transverse grooves form a plurality of cogs on the belt surface, with a row of cogs being defined between adjacent transverse grooves. Each cog has a pitch length P extending from a location on the cog to the identical location on the longitudinally adjacent cog. The pitch lengths of the rows of cogs are randomized over the entire length of the belt to reduce the noise of the belt as it travels about its associated pulleys.
1. A power transmission belt having an inner surface comprising longitudinally extending grooves and transverse grooves, the transverse grooves are inclined at an angle less than 90° relative to the longitudinal direction of the belt and all the transverse grooves have the same groove depth, the transverse and longitudinal grooves form transverse rows of cogs on the belt inner surface, wherein the rows of cogs have at least three different longitudinal lengths, and the rows of differing lengths are randomly arranged, in a non-sequential manner, along the entire length of the belt.
2. A belt in accordance with claim 1 wherein the belt is characterized by the rows of cogs having three different longitudinal lengths.
3. A belt in accordance with claim 1 wherein the belt is characterized by the rows of cogs having three to six different longitudinal lengths.
4. A belt in accordance with claim 1 wherein no more than four longitudinally adjacent rows of cogs have the same longitudinal length.
5. A belt in accordance with claim 1 wherein the belt has three different longitudinal lengths, the smallest length being designated as 1, the medium length being designated as 2, and the largest length being designated as 3, and the sequence around the entire belt is 3 3 3 2 1 2 3 2 3 2 1 1 2 1 1 2 1 2 3 1 3 3 1 2 2 2 1 3 1 2 1 3 1 1 1 2 3 3 2 2 2 3 2 1 1 3 3 3 2 1 2 3 2 3 3 2 1 2 2 1 1 3 2 1 2 3 1 1 3 1 2 3 2 1 1 3 1 2 2 3 3 3 1 1 3 3 2 3 1 1 1 2 2 3 2 1 1 2 1 3 3 2 3 3 3 2 2 3 3 1 1 3 2 1 2 2 1 1 3 2 2 3 3 3 1 2 2 1 1 1 2 3 2 3 1 1 1 2 1 2 2 3 3 1 1 3 2 1 3 3 2 3 1 3 3 2 3 2 1 2 3 1 3 1 1 2 1 2 1 2 3 2 3 3 3 1 1 2 1 2 3 2 2 2 2 3 3 2 1 1 3 2 3 2 3 1 2 2 1 2 1 3 1 1 1 1 3 2 1 2 1 3 3 2 3 2 1 2 1 2 3 2 1 2 2 3 1 1 1 3 1 3 1 3 2 3 3 2 1 1 2 3 1 2 2 3 2 3 3 3.