Pulsator

A pulsator comprising:

• a valve element;
• a first chamber;
• a second chamber;
• a first circuit having a first outlet and a second outlet which, by displacement of the valve element, are arranged to be connected alternately to a first source of a first pressure level and a second source of a second pressure level, respectively, the valve element being displaceable by means of a pressure difference between the first and second chambers;
• and
• a second circuit which is arranged to provide said displacement of the valve element and which comprises a first inlet connected to the first source and a second inlet connected to the second source, the second circuit being designed to take one of a first stable position at which the first inlet is connected to the first chamber at the same time as the second inlet is connected to the second chamber or a second stable position at which the first inlet is connected to the second chamber at the same time as the second inlet is connected to the first chamber,
• wherein the second circuit comprises two valve members having respective first and second control inlets each comprising a closing member that at a rest position closes the control inlet and which are arranged to enable change-over of the second circuit from one of said stable positions to the other of these positions by means of a connection of short duration to the second pressure source by an opening of the closing member of the respective control inlet.