The valve gear of the Clapp & Jones village engine is simple yet controls the moving mechanism of the two pumps working in unison. Each pump is driven directly by its own steam cylinder, and the steam valves are actuated by the positive movement of the opposite piston rod. The principle is substantially the same as practiced in the “Duplex” pump construction, and may be readily understood by reference to the detailed views which are given of these parts in other portions of this work.
Fig. 423.
The steam cylinders and pump are self-contained, and aside from the distinctive difference in the reciprocating gear the design of the steam and water ends does not differ from the vertical engines of the Clapp & Jones type.
On these engines intended for use in cold climates a “thaw-pipe” is attached, at the engineer’s side, inside the frame, and is used in extremely cold weather to prevent the feed-pump, as well as the main pump and connecting pipes, from freezing. It is operated by means of a small globe valve. If it is desired to warm the main pump, the two-way cock used in feeding the boiler should be turned as when feeding directly from the main pump, when steam will have access both to the main pump and the feed-pump; but care must be observed not to heat the main pump too warm. When the two-way cock is closed, and also when it is open as when feeding from the tank, the steam goes only to the feed-pump.
After using it to warm the main pump, the two-way cock, should be closed; otherwise, if the check-valve should happen to stick fast, the water would pass out of the boiler through the main pump.
Fig. 424.
Always keep the globe valve closed when not in use. It will be observed that the vacuum chamber upon the suction pipe is located within the air chamber upon the discharge passage.