| 摘要 |
An automatic belt tensioner has a vacuum motor which is stroked by a variable vacuum source such as a gasoline engine intake to drive a one-way device which is operatively connected to rotate a nut in one direction. A nut is threadably engaged with a nonrotatable screw member and is connected to a pivotal support member. When the nut is rotated in one direction by the vacuum motor and the one-way device, the screw member is moved longitudinally to pivot the pulley support in a direction to increase belt tension. The reaction force between the nut and screw member which is proportional to belt tension is applied to a vacuum cut-off mechanism which disconnects the vacuum source from the vacuum motor so that a predetermined belt tension is maintained.
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