Abstract: The present invention relates to a valve assembly (10) which is mounted on a part (piston unit 40) of an air motor (10) arranged for reciprocating movement in a housing (cylinder 12). The valve assembly includes a first valve unit (50), which is mounted on one side of the part (40), and a second valve unit (70), which is mounted on the other side of the part (40). The second valve unit is connected to the first valve unit (50) by means of the part (40) for common movement with the first valve unit relative to the part (40) when the valve assembly is switched as the part (40) reaches one of its two end turning-positions.