Transmission assembly, especially for engines in walk-behind equipment and engines equipped with such a transmission assembly

Transmission assembly, particularly for an engine preferably of the walk-behind type, said assembly comprising an input shaft (1) such as an endless screw, driven in rotation and in engagement with a toothed wheel (2A), this wheel being mounted freely in rotation on a shaft (3A) called a drive shaft of the engine and coupleable to said shaft by means of a clutch device (4A) adapted to pass from a clutched position to an unclutched position and vice versa, by means of a suitable control device, the movement of the shaft (3A) carrying the clutch device (4A) being transmitted directly or by means of an intermediate device to an output shaft (6), such as the wheel carrying shaft of the engine, characterized in that said transmission assembly comprises at least two toothed wheels (2A, 2B) tangent to the input shaft (1), counter-rotating, respectively in engagement with the input shaft (1), each wheel (2A, 2B) being coupleable to a shaft (3A, 3B) called a drive shaft for forward movement or respectively for rearward movement of the engine by means of a clutch device (4A, 4B) adapted to pass from a clutched position to an unclutched position and vice versa, the clutch devices (4A, 4B) being selectively actuable as a function of the position taken by at least one angularly displaceable member (5, 7) of the clutch control device, the movement of each shaft (3A, 3B) carrying a clutch device (4A, 4B) being, in the active condition of its clutch device, transmitted directly or by means of an intermediate device to an output shaft (6) such as the wheel carrying shaft of the engine.