Abstract: An actuating drive with a spring return feature for valves in heating, ventilation and air-conditioning systems includes an electric drive (1), a reduction gearing (2) having a return spring tensionable by the actuating movement and serving for the spring return movement, a clutch (3) between the electric drive (1) and the reduction gearing (2) and a brake device (4) actuated during the spring return movement. The brake device (4) takes the form of a centrifugal brake having a fixed brake drum (7) and a rotatably mounted brake shoe carrier (6) on which brake shoes (8) movable radially by centrifugal force are disposed. The brake shoe carrier (6) serves as the clutch member on the gearing side and has a journal (9) having an end pinion (10) engaging in the reduction gearing. The clutch member (5, 11) on the drive side is rotatably mounted on the journal (9) of the brake shoe carrier (6).

Abstract: A transmission for an actuating drive having a spring return feature includes a drive pinion (2) associated with the actuating drive; an intermediate pinion (5) meshing with the drive pinion (2); an output shaft (3) having a clutch (4 for a final control element, and two gears (6, 7) rotatably mounted within the transmission housing (1). Each gear (6, 7) has an external toothing (8, 9) and a rotatably mounted hub (10, 11) so extending around the output shaft (3) as to leave an annular gap between the same and the hub. The drive gear (2) meshes with the external toothing (8) of one of the two gears. The intermediate pinion (5) meshes with the external toothing (9) of the other gear. A coupling sleeve (14) is disposed in the annular gap between the output shaft (3) and the gears (6, 7), is releasably connected to the output shaft (3) and is coupled positively with the hub (10, 11) of one of the gears. The direction of rotation of the output shaft (3) is variable by changing the coupling sleeve (14).