Reciprocating diaphragm pump with packless piston-cylinder unit

Pumps – Expansible chamber type – Pumping member position controlled port

Reexamination Certificate

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Details

C417S489000, C417S199100, C092S09800R, C092S099000

Reexamination Certificate

active

06299419

ABSTRACT:

BACKGROUND
1.0 Field Of The Invention
This invention relates generally to reciprocating diaphragm pumps, and more particularly to the sealing of the dosing piston/cylinder unit of a reciprocating diaphragm pump.
2.0 Discussion Of Related Art
The dosing precision of reciprocating diaphragm pumps depends on the exactness with which the dosing piston is sealed in the associated cylinder unit. The use of mechanical sealing elements, for example O-rings, has the disadvantage that when the sealing elements wear, dosing accuracy is reduced. In addition, it is often very difficult and expensive to maintain the narrow tolerances essential for adequate precision at the assembly stage.
European patent EP-B-0 129 187 describes a reciprocating diaphragm pump with pre-delivery. In this pump, the dosing piston is actuated via a slidably mounted drive piston. The product to be delivered or dosed is fed to the dosing piston by means of a membrane. The dosing piston/cylinder unit sealed by O-rings as the sealing element. The system of dosing piston, sealing elements and stroke adjustment screw is subject to wear and limits the useful life. The more stringent the requirements which dosing precision has to satisfy, the shorter the time a system such as this can be used without readjustment or replacement of the sealing elements.
SUMMARY OF THE INVENTION
An object of the present invention is to ensure simple assembly and guarantee exact sealing of the dosing piston/cylinder unit of a reciprocating diaphragm pump.
In a one embodiment of the invention, a sealing system of the pump includes a dosing piston/cylinder unit that is substantially free from play in the micrometer range and is sealed by a hydrodynamic gap seal.
In another embodiment of the invention, a reciprocating diaphragm pump includes a dosing piston guided with minimized play, i.e. with a tolerance in the &mgr;m range, in that both part of the cylinder which forms the compression zone, and the gap remaining between the dosing piston and the cylinder are sealed by a hydrodynamic gap seal which seals by means of the product taken in by the pump. The hydrodynamic gap seal works without wearing and, accordingly, provides for virtually unlimited useful life in regard to the sealing of the system.
In a preferred embodiment of the invention, the dosing piston and the cylinder are made of oxide ceramic. The fact that the dosing piston/cylinder is made of oxide ceramic has the particular advantage that these elements can readily be manufactured to the narrowest tolerances.
In another embodiment of the sealing system and the reciprocating diaphragm pump, the dosing piston is floatingly actuated via a coupling and, in the reciprocating diaphragm pump, the dosing piston is floatingly connected by a coupling to a drive piston. The floating actuation of the dosing piston via a coupling provides for simple assembly and enables the dosing piston/cylinder unit to operate with high reliability.


REFERENCES:
patent: 3495544 (1970-02-01), Enssle
patent: 3602613 (1971-08-01), Guenther et al.
patent: 4516479 (1985-05-01), Vadasz
patent: 4572056 (1986-02-01), Funke
patent: 4883467 (1989-11-01), Franetzki et al.
patent: 5492449 (1996-02-01), Hunklinger et al.
patent: 25 49 008 (1977-05-01), None
patent: 3629742 A (1988-03-01), None
patent: 0 129 187 (1984-12-01), None
patent: 2 370 877 (1978-06-01), None

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