As the plunger nears the end of its stroke and before it starts on the return stroke, the valve fork closes the valve, and thus prevents slip and avoids pounding, so common in pumps having valves that close by their own weight. In case of any obstruction between the valve and its seat the rubber buffer spring will be compressed thus preventing all injury to mechanism.
The lost work expended in closing the valves is hardly worth any consideration as it is practically the friction only of the eccentric and the members of the valve gearing, the bearings of which are all small.
The motion for these valve gears is usually taken from an eccentric on the main shaft.
The standard speed of the Riedler pumps is about 150 revolutions per minute. Smaller pumps run even faster than this.
It may be desired to connect a pump directly to a high speed electric motor or water wheel already installed. To meet these conditions, a special design known as the Riedler Express pump, is built.
The chief feature of this pump, is its suction valve. This valve is concentric with, and outside of the plunger, and lifts in the opposite direction to that of the plunger when on its suction stroke. At the end of the suction stroke, the plunger presses the valve to its seat, thus making it certain that the valve is seated when the plunger starts on its delivery stroke, allowing practically no slip. A high air suction chamber containing a column of water is placed immediately before the suction valve, so it is certain that the pump will fill as the plunger moves. Ordinarily the pump would not completely fill, owing to the high speed of the plunger.
These pumps are also built with steam cylinders both of the plain slide valve and Corliss designs.
THE ELECTRIC
PUMP
Compass Needle—[See Page 266].