Abstract: A hydraulic tensioning device for maintaining a predetermined amount of tensioning force on an endless drive belt of a vehicle accessories drive system. A housing is mounted in a fixed position on the engine in close proximity to the drive belt. A shaft is movably mounted within the housing by an elastomer block which biases the shaft in a belt tensioning rotational direction. A lever extends outwardly from the housing and is integrally connected to the shaft for pivotal movement upon rotation of the shaft. An expandable bladder or actuator is mounted in the housing and is engageable with the shaft and pivots the rotor and lever toward a belt tensioning direction when the bladder is expanded by hydraulic fluid. A hydraulic fluid supply and pump assembly supplies fluid under pressure to inflate the bladder. An idler pulley drivingly engages the fluid pump and is driven by the endless drive belt for actuating the pump.

Abstract: A belt tensioner for an endless drive belt for vehicle accessories has a shaft which is mounted in a fixed position adjacent the belt. A lever is pivotally mounted on the shaft and has an idler pulley rotatably mounted on an extended end of the lever. The pulley is movable into tensioning engagement with the belt by rotation of the lever. A first cam plate is slidably mounted on the shaft and is engaged with a second cam plate which is attached to the lever for rotation with the lever. The cam plates each have a plurality of a series of camming surfaces which are mutually engageable with the opposite cam plate surfaces. A plurality of spring discs are telescopically mounted on the shaft and bias the first camming block into engagement with the second block applying a rotational force on the lever to move the pulley into tensioning engagement with the drive belt.