Slurry-pumping means

Claim 1

A slurry-pumping means comprising driving pump means and two diaphragm pump means said diaphragm pump means comprising an inlet, a check valve, an intake diaphragm pump, another check valve, an exhaust diaphragm pump, and an outlet, connected together and in series, said diaphragm pump means being adapted to be driven by said driving pump, by using a fluid medium in such a manner that intake strokes and exhaust strokes of the two diaphragm pumps are alternate with each other so that two unit volumes of slurry are taken in by the intake diaphragm pump during an intake stroke thereof, of which one unit volume is exhausted from said exhaust diaphragm pump during the subsequent exhaust stroke of said intake diaphragm pump and the other one unit volume is exhausted out of said exhaust diaphragm pump during the subsequent intake stroke of said intake diaphragm pump, so that output of said diaphragm pump means is substantially continuous with a uniform pressure, said driving pump being pneumatically driven and comprising a cylinder, a piston and a controlling valve, said controlling valve including a housing and a spool, said housing being arranged coaxially on and fixed to said cylinder, and formed with an upper air-connecting hole connected to a space above said piston, a lower air-connecting hole connected to another space under said piston, and an air inlet in the center of the axial distance between the said two air-connecting holes, said spool being arranged coaxially inside and freely slidable relatively to said housing, and formed with a central coaxial bore, an air intake land adapted to cut off said air inlet when said piston is brought to its neutral position, four guiding lands arranged symmetrically above and below said air intake land and having the same diameter as said air intake land and a number of axial external flutes, respectively, two exhausting lands arranged symmetrically above and below said air intake land and having the same diameter as said air intake land and a number of axial external flutes, respectively, two exhausting lands arranged symmetrically above and below said guiding lands and having a diameter shorter than said guiding lands'' diameter, respectively, and two radially internally and externally flanged stoppers formed on the endmost surfaces of said exhausting lands, said piston having a piston rod extended into said bore and having two washers axially freely mounted on the upper end of said piston rod and a coil spring axially freely mounted on said upper end and arranged between said two washers, said spool being adapted to be axially slid by said piston when said washers are brought into engagement with said stoppers.