| 摘要 |
A belt tensioner for a vacuum cleaner includes a roller and a torsion spring to bias the roller against an endless, non-stretch, flat vacuum cleaner belt to exert an increasing force thereon as the belt lengthens with wear and the torsion spring unwinds, thereby maintaining the tension in the belt substantially constant as the belt lengthens with wear. The tensioner includes a pair of connecting arms each having a first end coupled to opposite ends of the roller and each having a second end pivotal about a pivot axis, the torsion spring being disposed adjacent to the second ends of the connecting arms. The spring rate of the torsion spring is relatively low so that the moment about a pivot axis through the center of the torsion spring of the force applied to the connecting arms by the free end of the torsion spring decreases only slightly as the belt lengthens with wear.
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