Flow controlled piston valve

Piston valve (10) comprising a hollow housing (13) with a longitudinal axis (15), an inlet (11) provided in the housing (13), an outlet (12) communicating with the inlet only through the piston valve (10) and a pushbutton (27) that can be moved in and out direction compared to the housing (13) wherein the pushed in and pulled out states of the pushbutton (27) set the closed respectively open states of the piston valve (10), comprises furthermore a valve piston (17) with two opposite end faces and arranged in the hollow interior of the housing (13) and guided for displacement along said longitudinal axis (15), a valve seat (14) provided on an element extending normal to said longitudinal axis (15), wherein in an extreme position of the valve piston (17) when it is pressed to the valve seat (14) the piston valve (10) is in closed state, and the inlet (11) is led through a passage (16) into the inner cavity of the housing (13) so that in the closed state of the valve piston (17) a lower portion of the valve piston (17) closes said passage (16), characterized in that a control valve (30) is arranged in the inner cavity of the housing (13) in a predetermined axial distance from the valve seat (14) and the opening and closing of the control valve (30) is controlled by the position of the pushbutton (27), and in the interior of the housing (13) between the valve piston (17) and the control valve (30) and intermediate space (34) is formed and the size of the intermediate space (34) depends on the momentary position of the valve piston (17), and a shunt flow passage is provided between the two end faces of the valve piston (17) providing a small fluid flow, wherein the cross section of the shunt passage is smaller than the flow cross section of said control valve (30) when being in open state, and above the control valve (30) the inner cavity of the housing (13) defines an upper space (32) between the control valve (30) and the pushbutton (27), a spring (26) is arranged in the upper space (32) that presses the control valve (30) to its closing direction, and in said intermediate space (34) a further spring (25) is arranged that presses the valve piston (17) to take a closed position, and the housing (13) comprises a passage (31) that interconnects the interior space under the valve seat (14) with said upper space (32), and between the pushbutton (27) and the valve piston (17) there is no mechanical connection, and the pushbutton (27) controls the valve piston (17) only by utilizing the established fluid flow and the associated pressure patterns.