Patent ID: 8027772

Claim:
A power transmission gearbox for rotorcraft for transmitting rotary movement from at least two engine members (MG, MD) to a main shaft ( 1 ) with determined reduction ratios, wherein the gearbox presents at least two transmission systems (G, D) for imparting rotary movement to the main shaft ( 1 ), each of the transmission systems comprising: an inlet shaft ( 3 ) designed to be driven in rotation by an engine member (MG, MD); at least two reduction stages ( 4 , 5 ) presenting different reduction ratios (k 2 , k 1 ); a first gearwheel ( 6 ) connected to the inlet shaft ( 3 ) via a declutchable freewheel ( 7 ), said gearwheel ( 6 ) meshing with a first toothed wheel ( 8 ) secured to an intermediate shaft ( 9 ), thereby defining at least a first reduction stage ( 4 ); a second gearwheel ( 10 ) connected to the inlet shaft ( 3 ) via a simple freewheel ( 11 ), said second gearwheel ( 10 ) meshing with a second toothed wheel ( 12 ) secured to the intermediate shaft ( 9 ), thereby defining the second reduction stage ( 5 ); a main freewheel ( 13 ) mounted on the intermediate shaft ( 9 ) to rotate a complementary toothed wheel ( 14 ) secured to the main shaft ( 1 ); and a clutch mechanism for the declutchable freewheel ( 7 ) for the purpose, depending on circumstances, of putting the inlet shaft ( 3 ) into engagement with said declutchable freewheel ( 7 ) or for drivingly isolating the inlet shaft ( 3 ) from said declutchable freewheel ( 7 ).