US Patent 10113359 Steady-state gear structure for roller shade

A gear structure includes at least one return wheel unit (1) and a power transmission unit (2). The at least one return wheel unit includes a first wheel (12) having a first gear (123), a second wheel (13) having a second gear (133), and a spring (14) mounted between the first wheel and the second wheel. The power transmission unit includes a first driven gear set (22), a second driven gear set (23) and a transmission member (24). The first driven gear set has a third gear (222) and a first bevel gear (223). The third gear meshes with the second gear. The second driven gear set has a second bevel gear (232) meshing with the first bevel gear. The transmission member is connected between the driving member and the second driven gear set.