US Patent 7886805 Roll-up closure

A spring tensioning unit for a roll-up closure, the closure having a pair of end plates and an axle rotatably mounted on the endplates. A drum for carrying a closure is rotatably mounted on the axle, and a tensioning coil spring is mounted on the axle and connected between the axle and the drum. The tensioning unit has a ratchet wheel fixedly mounted on the axle adjacent one end plate, the wheel having spaced apart teeth. A stop member is slidably mounted on the one end plate with a stop tab cooperating with the teeth on the wheel to stop rotation of the wheel in a direction reducing tension on the spring. A lever is mounted between the wheel and the end plate, the lever having a lever tab for cooperating with the wheel, the lever movable on the axle to position the lever tab against a tooth and to then rotate the tooth, and the axle, in a direction to increase tension on the spring.