Patent ID: 7669501

Claim:
A contrivance for automatic rope length correction of a traction mechanism ( 5 ) in a rope pull drive, said contrivance comprising: a housing ( 1 ) including a tooth system ( 15 ); a threaded bushing ( 4 ) coupled to said housing ( 1 ) allowing axial movement between said threaded bushing ( 4 ) and said housing ( 1 ) and rotational movement between said threaded bushing ( 4 ) and said housing ( 1 ) in a first direction, said threaded bushing ( 4 ) including flexible flaps ( 43 ) and a nut thread ( 421 ), said flexible flaps ( 43 ) engaging said tooth system ( 15 ) of said housing ( 1 ) to block any rotational movement between said threaded bushing ( 4 ) and said housing ( 1 ) in a second direction; a threaded spindle ( 3 ) adapted to be fixed to said housing ( 1 ), said threaded spindle ( 3 ) having threads ( 311 ) threadably coupled with said nut thread ( 421 ) of said threaded bushing ( 4 ); and a spring mechanism ( 2 ) extending between and directly engaging said housing ( 1 ) and said threaded bushing ( 4 ), said spring mechanism ( 2 ) urging said housing ( 1 ) and said threaded bushing ( 4 ) axially in opposite directions; wherein axial movement of said housing ( 1 ) away from said threaded bushing ( 4 ) is coupled with rotational movement of said threaded spindle ( 3 ) and therefore rotational movement of said housing ( 1 ) in said first direction relative to said threaded bushing ( 4 ) thereby lengthening said contrivance, and wherein axial movement of said housing ( 1 ) toward said threaded bushing ( 4 ) is prevented because rotational movement of said threaded spindle ( 3 ) and therefore said housing ( 1 ) in said second direction relative to said threaded bushing ( 4 ) is blocked by said flexible flaps ( 43 ) engaging said tooth system ( 15 ).