Abstract: A fire door release mechanism includes a pair of levers engaging a bearing disc to hold a toothed clutch in engagement between a shaft of the fire door and a shaft of its operator. One of the levers has, at its end remote from the bearing disc, a pin on which a holding block is pivotally mounted. The other lever also has a pin at its remote end which is retained within a pocket on the holding block so long as tension is applied to the block, which tension is normally provided by a fuse link chain. When the tension is released, the levers, which are lightly spring biased, pivot out of engagement with the bearing disc to allow the clutch to disengage and separate the operator shaft from the fire door shaft.

Abstract: A hold and release mechanism for a fire door spring tension adjusting wheel includes a finger which is retractable when the adjusting wheel is rotated in a direction to increase the tension of the door spring but remains in engagement with a notch on the periphery of the adjusting wheel to prevent rotation of the adjusting wheel in the other direction as urged by the spring tension. The finger is held within a bore in a block which is pivotably mounted to the plate supporting the adjusting wheel. A toggle arrangement coupled to the holding chain and the block keeps the finger engaged in the notch. When tension on the holding chain is released, the block is allowed to pivot so that the finger disengages from the adjusting wheel, which is then allowed to rotate under the urging of the fire door spring. This arrangement permits an operator to adjust the spring tension without requiring that the tension applied by the holding chain be relieved.