FIG. 4 is a view similar to FIG. 3. but showing the valving element in valve closing position; H0. 5 is an enlarged central sectional view of the control means provided to actuate the plurality of individual valves such as the one shown in FIG. 2. this FlG. showing the structure in such condition as to cause opening of all the individual valves; FIG. 6 is a fragmentary sectional view generally sim