Griboiedoff, ALEXANDER

1792-1829. Ru ian dramatist. Gridiron Valve. Form of valve for admi ion of steam to an engine cylinder, in which a number of ports or openings are separated by bars or bridges of the same thickne , and where a similar arrangement of ports and bars exists on the valve seat. Then for a given length of port and port area required, the valve need only be moved over a distance which bears to the motion nece ary to give that area with one port the relation which unity bears to the number of ports in the gridiron valve; e.g., if there are three ports, the valve need be moved only of the distance nece ary with a one-ported valve opening the same area. Its advantages are the diminished work on the valve gear, and large port areas rapidly opened.