Patent ID: 7246648

Claim:
A friction device for rolling up curtains comprising: a tubular roller ( 1 ), for winding and unwinding a curtain ( 1 a ) between a rolled up configuration (A), in which the curtain ( 1 a ) is wound on the roller ( 1 ), and an unrolled configuration (B), in which the curtain ( 1 a ) is unwound from the roller ( 1 ); support means ( 10 ) for rotatably supporting said roller ( 1 ); a threaded stem ( 2 ) supported inside said roller ( 1 ) disposed for angularly displacing said roller with respect to said threaded stem during rotation of said roller; first stop means ( 40 ) fastened to a part of said stem ( 2 ) and second stop means ( 50 ) fastened to a second part of said stem ( 2 ); an operative body ( 3 ), slidingly movable inside the roller ( 1 ) and fitted onto said stem ( 2 ) between said first stop means and said second stop means, said operative body ( 3 ) being engaged to and driven by said roller ( 2 ) so as to move axially along said threaded stem ( 2 ) during rotation of the roller during the unrolling and rolling up of said curtain ( 1 a ); first elastic means ( 4 ) interposed between said first stop means ( 40 ) and a first surface ( 3 a ) of said operative body ( 3 ), and second elastic means ( 5 ) interposed between said second stop means ( 50 ) and a second surface ( 3 b ) of the operative body ( 3 ), wherein, in a rolled up configuration (A), the operative body ( 3 ) is positioned in respect to the stem ( 2 ) such that said first elastic means ( 4 ) are at least partially compressed and said second elastic means ( 5 ) are at least partially released, while in an unrolled configuration (B), the operative body ( 3 ) is positioned in respect to the stem ( 2 ) such that said first elastic means ( 4 ) are at least partially released and second elastic means ( 5 ) are at least partially compressed, said operative body ( 3 ), during rotation of the roller ( 1 ) for unrolling of the curtain ( 1 a ) from the rolled up configuration (A) to the unrolled configuration (B), being moved axially along the stem ( 2 ) close to said second stop means ( 50 ) so that second elastic means ( 51 ) are gradually compressed and said first elastic means ( 41 ) are gradually released and, during rotation of the roller ( 1 ) for rolling up of the curtain ( 1 a ) from the unrolled configuration (B) to the rolled up configuration (A), being moved axially along the stem ( 2 ) close to said first stop means ( 4 ) so that the first elastic means ( 41 ) are gradually compressed and second elastic means ( 51 ) are gradually released.