MICROFICHE REFERENCE LIBFUUW - Cd3wd.com

52flow in through a check-valve (e.g. flap, bakl, etc.). On the*reverse stroke (downward), the plunger forces water out throughanother,but outward opening, check-valve.(b) The piston-pump operates the same as the plunger pump exceptthat is utilizes a solid piston which fits tightly against thecylinder walls.(c) The bucket-pump uses a piston having check-valve(s) which openon the downward stroke. On the upward stroke, the piston suckswater in through the bottom inlet and simultaneously pushes waterout through the upper outlet. Then, on the downward motion, thepiston’s check-valves open, allowing the water to flow frombeneath the piston to above it --ready to be pushed out on thenext upward stroke.All three of these pump types, but particularly the bucket-pump, areoften referred to as lift or force pumps since they can both lift the waterto the piston (or plunger) level and force it out of the cylinder. However,as shown in Table 2.2, the next subdivisionof these pumps is into direct-acting and power categories, depending on the method used to motivate thepiston or plunger.3.2.3.1 Direct-Acting PumpsDirect-acting piston or plunger pumps are so named because theyutilize a driving piston mounted on a common rod(s) with the water-endpiston or plunger. As illustrated in Figure 3.11, steam (or compressedair) alternately enters both sides of the driving piston, causing it tomove back and forth,along with the connecting rod which in turn recipro-cates the water-end piston or plunger, In most modern designs, thereciprocating connecting rod also automatically moves the inlet and