MICROFICHE REFERENCE LIBFUUW - Cd3wd.com

61materials evaluated for performance and wear--see Fannon and Frink (1979) .No costs were available on this “AID pUmp”, however, the above reportlists many agencies and businesses which are cooperating in its manufacture.3.2.4 Diaphragm RumpsDiaphragm pumps are often considered another form of the piston pumpsince many designs utilize a piston as an operational component. However,because bellows pumps are also a diaphragm device, this subclass isappropriately considered apart from piston pumps. The major feature ofdiaphragm pumps is that the reciprocating piston has been replaced by apulsating, flexible membrane which operates in basically one of three ways.In bellows devices, the diaphragm comprises a portion of a chamberwhich can thus expand and contract. The expanding bellows draws water inpast an inlet check-valve just as the retracting piston or plunger does.Then, as the bellows in contacted, the water is forced through an outletcheck-valve.This principle, combined with foot-operation (an idea originally usedby ancient blacksmiths for venting forges-- Rouse and Ince, 1963) has beendeveloped into a low-cost, low-lift pump by the International Rice ResearchInstitute (I>RI) under a contract with AID. As see-i; in Figure 3.15, thebellows in this “foot pump” are made of canvas with metal reinforcinginserts and a wooden frame. The operator stands on the two foot restsabove the bellows and shifts his weight from one foot to the other. Thisalternately expands and contracts each bellows and thus lifts water.