Patent ID: 6059008
Filing Date: 2000-05-09
Classification: E05F,E05Y,E06B

Abstract:
In a rollup shutter comprising a shutter curtain which descends due to its own weight, a winding drum for winding said shutter curtain including a rotatable winding wheel for winding said shutter curtain thereon, said winding wheel being supported on a shaft, said shaft being supported by at least one support member;a braking mechanism for retarding but not arresting rotation of said winding wheel to allow descent of said shutter curtain due to its own weight by unwinding of said shutter curtain from said winding wheel, said braking mechanism including a viscous clutch comprising a generally cylindrical housing of a diameter at least slightly less than the diameter of said winding wheel on which said shutter curtain is wound so as to allow said braking mechanism to be stored at least partially within a wound shutter curtain when said shutter curtain is wound on said winding wheel, said viscous clutch further comprising a hub and a plurality of clutch plates arranged such that a first predetermined number of clutch plates are connected to said housing and are nonrotatable with respect to said housing and are interleaved between a second predetermined number of clutch plates which are connected to said hub for rotation therewith relative to said first predetermined number of clutch plates, said hub is supported on said shaft by way of a directional clutch to provide for free rotation of said winding wheel with respect to said one support member in a direction of rotation to wind said shutter curtain on said winding wheel, and said viscous clutch includes a high viscosity oil disposed in spaces between said plates, respectively, for retarding rotation of said winding wheel to allow descent of said shutter curtain due to its own weight.