. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . th noother change than cutting away the valveseat so that steam can enter the valvewhen it overtravels the seat. A piston valve with the .Allen ports hasbeen • designed for the standard locomo-tives, and is illustrated in the accompany- ways open to the exhaust through thehollow central portion of the valve exhaust passages from the steamchest, it being understood, lead off fromends of the valve. The cylinder has a double-ported con-nection with the steam chest, as shownin the engraving
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . th noother change than cutting away the valveseat so that steam can enter the valvewhen it overtravels the seat. A piston valve with the .Allen ports hasbeen • designed for the standard locomo-tives, and is illustrated in the accompany- ways open to the exhaust through thehollow central portion of the valve exhaust passages from the steamchest, it being understood, lead off fromends of the valve. The cylinder has a double-ported con-nection with the steam chest, as shownin the engraving. Here the valve is shownmoved from its central position, so thatsteam is being admitted through the portH from the steam space at the centre ofthe valve. .At the same time the steamis admitted to the connecting port I fromthe auxiliary space D to the port I, whichunites with H and enters the cylinderat K. At the same time the valve, at the op-posite end of the cylinder, has uncoveredthe ports I and H, and the steam isescaping, as indicated by the arrow, outand into the exhaust spaces at the end. A DOUBLE-PORTED PISTON VALVE ing engraving. The simplest form of pis-ton valve is a spool with a set of packingrings at each end which correspond tothe lips of a plain slide valve. With this,as with the plain slide valve, there is butone port opening in the valve seat foreach end of the cylinder and the doubleopening is obtained with the Allen valveby carrying the steam from one end ofthe steam chest to the steam port at theother through the valve itself. The double-ported piston valve is morecomplicated and requires a special ar-rangement of the cylinder ports for itsuse. In the first place it carries three sets ofpacking rings at each end, or six sets inall, and there is a double port in thesteam chest leading to the cylinder. Thesets designated A are the main packingrings, and serve to open and close theports as they travel over them. The setsmarked B are to separate the steam fro
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Keywords: ., bookcentury1900, bookdecade1900, bookidrailwaylocom, bookyear1901
