[Illustration: FIGS. 298, 299.]
The accompanying sectional view of steam end of the “Smith-Vaile”
exhibits some very novel features. So far as the piston and cylinder
in this pump are concerned they are not unlike the average first class
pump, but with this difference. It has only one set of cored ports, B,
B. The supplemental ports, C, C, are drilled.
The main valve, A, is a slide and is moved by a valve piston, D. Almost
all the valve pistons as now made are simply plugs turned accurately
to fit the holes in the chest and without any means of adjustment to
compensate for wear. After these valve pistons become worn they have to
be replaced with new ones, but there is a period between the time when
the valve piston becomes so leaky as to render the action of the pump
uncertain and the time when the worn valve is replaced by a new one
that the pump is very wasteful of steam.
The valve piston in this pump is provided with packing rings, E, E,
which compensate for wear of these parts so that this valve is expected
to do efficient service long after a slow valve. The supplemental
valve, F, has a reciprocating rotary motion which is communicated to
it by the rock arm, G, and pitman, H, connecting with the crosshead,
I, secured to the piston rod. It will be observed that the piston
rod, J, and the rod, K, of the water end are separated so that should
either one give out through wear or accident it can be replaced without
sacrificing both, as would be the case if they were solid in one
piece. This supplemental valve, F, in general appearance very closely
resembles the “Corliss” valve, and its action is somewhat similar, in
controlling the action of the valve piston, which will be understood
from the engraving without further description. These pumps all have
removable water ends and can be rebored or otherwise manipulated
without disturbing the steam end of pump. The cylinder can be separated
from the foot by removing the bolt, M.
The duplex pump is also shown in the accompanying engraving, where, A,
A, represents the steam cylinders, secured to the foot, B, by bolts, as
previously described.
The usual slide valves have been replaced by piston valves, C, in this
instance and are provided with removable seats, D, D.
These piston valves have packing rings, E, E, also to compensate for
wear and the valves are cast hollow to reduce their weight as much as
possible consistent with good workmanship, also to serve as ports for
steam admission. When these valve seats become worn they may be easily
removed and rebored or replaced by new ones, as desired. It will be
observed that these ports are very short to reduce the clearance as
much as possible, and to secure a more satisfactory cushion. Each valve
is operated by the rock arm connected with the opposite engine in the
usual way.
THE DUPLEX
PUMP
[Illustration: FIG. 300.]