The valve-seat is so constructed that it can be taken up to compensate for its own wear and that of the valve. This seat consists of a ring, or rather two rings, made in one piece and connected by several bridges across the port-opening which the space between them forms. The seat is crescent-shaped, split and adjustable to fit the valve, by the stem which extends to the upper side of the steam-chest, where it can be turned by a box-wrench, as shown in the cut, after removing the cap which covers its end. By disconnecting the eccentric-roil from the valve-rod slide or rocker and moving the valve to and fro by hand while turning the stems, a very close adjnstment of the scats to the valve can be made without any danger of making them too tight for the valve to work freely. Each adjustable seat is held steam-tight between two permanent seats, but is free to move in the plane of the port and tnny be said to ride on the valve. This arrangement makes the valve less liable to stick than with a rigid seat, if the engine is started without warming it up thoroughly. The steam does not enter the port-openings from the steam-chest over the inside edge of each valve-end. as is usually the case, but through port-shaped openings in the rim of the valve, leaving a detached por tion on the inner edge of each valve-rim, which greatly increases the bearing-surface of the valve. This engine has proved exceedingly efficient as a motor for dynamos.
Thr Coln pound Automatic Engine is shown in Fig. 33. It is built by the Sioux City Engine Works, Simi!: City, Iowa. The special fealiire of this engine is a novel device for packing the piston-rod between the two cylinders. The space between the cylinders is jacketed and provided with a means for opening, to test for leakage around the piston-rod and to adjust or renew the packing. The intermediate receiver has been discarded in these en gines.
The Giddings ralve.—Fig. 34 shows the Giddings equilibrium slide-valve, used in the Giddings high-speed automatic engines. This slide-valve consists of one piece ; takes steam from underneath. supplies the cylinder through double ports, giving twice the original port area, and close approximation to boiler-pressure. It is self-adjusting to wear and. position, and is free to lift from its scat a sufficient. amount to relieve the cylinder from water. Equilibrium is obtained by two needle ports in brass plugs in the top edge of the valve, one supplying live steam to the back of the valve to avoid lifting, another connecting with the exhaust-passage, thereby preventing accumu lation of pressure, and still maintaining about 2 lbs. of surplus pressure per sq. in. on the back of the valve, which insures a positive and per manent tight joint.. The connection is made by a hinge-joint, whereby the valve can be opened outward like a door, without disconnecting.
The Valley Engine.—Fig. 35 shows the balanced valve used by the Valley Iron Works, Williamsport, Pa., on their automatic high-speed engine. It consists of but one piece, and
has no rings or sleeves. The shape is clearly shown in the illustration. It is set in the valve seat, with the corner pointing to the center. Between the cover and cover-seat are placed strips of copper in. in thickness. which are for the purpose of removal and taking up wear as the valve may require it. The objection to wear existing in the piston-valve is over come by this construction. Live steam is admitted inside the cover around the valve, and exhaust let out at the ends. This con struction admits of the engine being run under full boiler-pressure with the cover removed, and an inspection of valve for leakage made under full steam-pressure. The construction of the valve-bracket and slide is shown in Fig. 36. The bracket is bolted to the bed and carries the slide, between the bracket and stuffing-box. On the valve-stem is a clamp-wrist, split in the back and pinched on the slide by a +-in. bolt, as shown. In case of accident or of the valve striking the end of chest, this wrist will slip, preventing all damage. Fig. 37 is a perspective view of the en gine.
The Armington & Sims Engine.—Two recent styles of the Armington C Sims engine are shown in Figs. 38 and 39. The first is a double compound engine, with cranks at 180°, and the second is known as a special double engine, especially designed for electric-lighting on board of steamships, where saying of space is a prime requirement. Numerous other forms of engine are }Milt by the & Sims ('o., of Providence. it. such as vertical double acting compound engines, etc., all of which are developments from the original engine built by this company with a single cylinder. A section of the cylinder and valve of the Arming ton & Sims engine is shown in Fig. 40. The steam-chest, with val•e-seat, is in one casting with the cylinder; the valve-chest is inclosed by a cover in the usual manner. It will be seen that the steam-chest is filled with live steam, which surrounds the valve, and that by tak ing steam in the center of the valve and exhausting at each end, the steam-ports from the cylinder can be very direct, and the waste-room kept small. In the engraving the valve is shown as just taking steam into the cylinder-port at the pis ton-end; the port in the valve at the other end is also just taking steam from the steam-chest into a port which passes through the valve into the sante cylinder-port ; this enables steam to be taken very quickly at the commencement of the stroke. The steam is exhausted at each end of the valve by direct passages which quickly free the cylinder. The piston is hollow, fastened by a taper fit to the rod, and furnished with two snap-rings. The valve is a hollow piston-valve, with cast iron ends, made very light, with a body of steel tubing. It i8 ground, and perfectly balanced.