Vacuum pulsator valves

A relay valve control means for transmitting pulses of vacuum alternately with non-vacuum pulses between a pair of pulsators, each said pulsator comprising a body including means for connecting a first zone of said body to a permanent vacuum source and a diaphragm valve comprising a first valve element cooperating with a first valve seat adapted to connect a second zone of said body to a non-vacuum source of air, said body further including a second valve seat adapted to be opened or closed to establish or prevent communication between said first and second zones, said body further housing a first deformable diaphragm having first and second opposed surfaces with said first surface arranged for exposure to said permanent vacuum source and cooperating with said first valve element whereby said first valve element is movable such that said first valve seat is open for at least a major portion of the time during which said second valve seat is closed thereby applying non-vacuum air to said second zone, and when said second valve seat is open, said first valve seat is closed thereby applying vacuum to said second zone, said relay valve control means enabling communication of the second zone of one of said pulsators with the second surface of the first deformable diaphragm of the other of said pulsators, said communication occurring via a non return valve and an adjustable valve means arranged in parallel flow relation.