| 摘要 |
A viscous damper for influencing and retarding rotation of a shaft, particularly the reel shaft of a roll-down fire door. The viscous damper unit comprises a housing having radially extending lugs, a cover for mounting to a side face of the housing, and a rotor arranged to be trapped between the cover and the housing and rotatable with respect to the housing. The rotor provides a bore for receiving the roll-down shaft for the fire door. The housing lugs are positioned to be selectively locked with respect to the framework of the fire door to prevent rotation during down rolling of the fire door. A viscous material is applied between the housing, the cover, and the rotor which retards the rotation of the rotor with respect to the housing by, shear forces. The housing is arranged to be compatible with a plurality of damping units being axially stacked along the shaft and provides aligned apertures for pinning or bolting the plurality of the housings together. In this way, the damping influence of the assembly can be adjusted by adding or subtracting units.
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