A VISCOUS DAMPING DEVICE FOR REDUCING THE ROTATION SPEED OF A WINDING ROLLER

The present invention concerns a viscous damping device for reducing the rotation speed of the winding roller (3) of a screen once the screen has been previously unrolled from the roller (3) against an energy storing device, which causes the rotation of the roller (3) as the screen is being rewound. According to the invention, the device has a shaft (8), with a first end (9) having means (10) for axial coupling thereof to the screen winding roller (3), a rotor (15), coaxially placed on said shaft (8), a box-like element (16) enclosing said rotor (15), as well as means for connecting said shaft (8) to said rotor (15) as the roller (3) rotates and the screen is rewound and for disconnecting said shaft (8) from said rotor (15) as the screen is unwound from the roller (3). It is characterized in that the means for connecting and disconnecting said shaft (8) to and from said rotor (15) comprise a wheel (12) placed on the shaft (8) at its second end (11) axially opposite to the first end, said wheel (12) having a plurality of peripheral teeth (13) which define notches (14) therebetween, that said rotor (15) comprises a radial portion (15a) having at least one pair of seats (18, 19), each seat defining a first opening (20, 23) and a second opening (21, 24) at the outer peripheral surface (22) of said rotor (15), each of said first opening (20, 23) being axially opposed to its respective second opening (21, 24) and opening toward the teeth (13) and the notches (14) of said wheel (12), a magnet (27) being inserted in one of said first (20, 23) or said second (21, 24) openings, and freely sliding therein, said shaft (8) having an axial cavity (28) and a magnet (29) housed in said cavity (28).