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N. PETERS, PHOTO-LITHOGRAPHER, WASHINGTON. 0. C.

UNITED STATES PATENT OFFICE.

THOS. STEWART, OF PHILADELPHIA, PENNSYLVANIA.

ROTARY VALVE FOR STEAM-ENGINES.

Specification of Letters Patent No. 21,579, dated September 21, 1858.

To all whom it may concern:

Be it known that I, Thomas Stewart, of the city of Philadelphia, in the State of Pennsylvania, have invented a new and Im5 proved Rotary Cut-Off Valve for SteamEngines; and I do hereby declare that the following is a full, clear, and exact description of the construction and operation of the same, reference being had to the accom10 panying drawings, making a part of this specification, in which—

Figure 1 is a plan view of the cut-off and valve as applied to the middle of the cylinder of an engine, the cap of the steam chest 15 being removed; Fig. 2, a vertical transverse section through the middle of the same; Fig. 3, a plan view of the under side of the valve disk; and Figs. 4, 5, and 6, sectional representations of actuating parts of the cut-off— 20 like letters in the different figures indicating the same objects.

The nature of my invention consists in making the disk of a rotary valve, with two or more sets of ports or steam ways therein, 25 for the induction and eduction of the steam, in such a manner as to allow of the said steam being cut off at any required position of the piston in the cylinder without producing any connection with the opposite 30 side of the said piston when the steam is cut “ short ” off; and in so constructing and operating the cut-off as to cause it to work independently of the said valve.

Referring to the drawings, A, is the ro35 tary valve; B, the cut-off; and C, the valveseat, or bottom of the steam chest. The valve-seat is cast with the cylinder, D, and has its ports leading therefrom into the respective ends of the cylinder, as shown by 40 the red lines in Fig. 1, and also with a boss or mass of metal, C', projecting down from the middle of the under side of the same which, being bored, receives the stem A', of the valve (A) ,and also affords the exhaust way 45 g~ as shown by the red lines in Fig. 2. The stem A', of the valve (A) is also bored and receives the stem B', of the cut-off. The two ports through the valve-seat which open into the cylinder (D) are indicated by the 50 red lines e and e' in Fig. 1; and in the same figure, the supply ports f /-, /³, of the valve (A) are indicated in blue lines; but these ports, as also the exhaust ports or ways, g', g², g³, are more fully shown in Figs. 55 2 and 3.

h', and h², are the ports in the cut-off, and, h³, the entrance opening in the cap of the steam chest.

I, is a bevel wheel which is fast on the lower end of the valve stem (A'), and into go which gears a bevel pinion, K, which is fixed on the inner end of a shaft, L, which connects, by a pair of bevel wheels with the crank shaft M. The stem (B') of the cut off projects through the stem of the valve 65 (A) and has an equal-armed lever, N, fixed thereon. Parallel with the steam cylinder (D), a shaft, O, having two cylinders, P and P', and a spur wheel, Q, fixed thereon, is connected by the pinions, R³ and S³, with 70 the shaft (L) so as to be rotated thereby. These cylinders are each surrounded with a thin, metallic, spring-band, R and R', which has its two ends jointed to a lever, S', so that when the said lever is operated, the 75 band can be made to clutch upon the cylinder so as to be carried thereby. The lower or inner ends of these bands (R and R') are connected by a chain or wire rope T and Τ', respectively with the arms of the hori- 80 zontal lever (N), while the power-ends of each of the levers, S and S', are connected by a like chain or wire rope, respectively to the ends of an equal-armed lever, U, which is placed above and so as to be vibrated 85 upon its fulcrum, by means of a lever connecting it at, W, with the usual governor of the steam engine. The cut-off (B) is adjustable vertically by means of the two set screws V and V'. The gear wheels for giv- 90 ing motion to the valve (A) are made so as to cause the latter to make one third of a rotation for every full rotation of the crank ₍shaft (M), and are arranged relatively so as to cause the valve to commence opening 95 the ports to the cylinder as the crank passes the dead point.

Operation: When steam is admitted into the valve chest and sufficient rotation given to the crank shaft to open either port, the 100 steam would afterward continue to be admitted and exhausted alternately to and from each side of the piston; but the cutoff (B) being previously arranged in connection with the usual governor so as to cut 105 off the steam at any required position of the piston, it is obvious that any irregularity in the speed of the engine will instantly be communicated to the said governor through the media of the lever (U) and either the 110 one or the other of the cylinders (R, R') connected therewith so as to cause the cyl21,579

St inder carrying the friction clutch to draw | on the lever (N) and thus partially to rotate the cut-off and so regulate the size of the opening for the steam, to suit the re5 quirements of the engine, because the cylinders (P and P') being always rotating in the direction of the arrow it is manifest that when one of the friction clutches is caused by the governor to grasp its cylinder, the 10 other, by the same motion · of the governor, is caused to release the other cylinder until the cut-off is sufficiently turned by the cylinder to produce the equalization required in the speed of the engine; while at the same 15 time, the cut-off being adjustable vertically upon the valve (A) by means, of the set screws (V and V') the valve can thereby be packed or balanced so as to diminish the friction very materially, and thus save 20 power without allowing steam to pass between their faces.

The arrangement of the openings or ports of the valve (A) as described, allows of the steam being cut off at any required position 25 of the piston without producing any connection with the opposite side of the said piston; and hence the action of the cut-off upon the valve may be termed universal— j the two being adapted together so as to ad³⁰ mit, cut off, and work the steam expansively . and exclusively on either side of the piston at any position Of the same in the cylinder^ Besides, the construction and arrangement of the several parts are simple, inexpensive, and not liable to get out of order from use. 35