Pumps – Processes
Patent
1981-09-25
1984-03-20
Freeh, William L.
Pumps
Processes
417442, 2101982, 222 1, 221129, F04B 4900, B67D 546
Patent
active
044378122
ABSTRACT:
In a high-performance, high-pressure liquid chromatography system, gradient elution of solvent components from a plurality of component reservoirs can be accomplished according to a programmed temporally variable ratio by a single reciprocating pump. The pumping cycle comprises a plurality of fill strokes with intervening pumping strokes. During one of the fill strokes of the cycle, a proportioned mixture of solvent components is admitted to the pump chamber from the respective reservoirs by means of proportioning valves. During each of the other fill strokes of the cycle, only a single solvent component is admitted to the pump chamber. Consequently, a relatively low concentration of a particular component can be delivered by the pump with precision over a complete pumping cycle, although a comparatively higher and therefore more accurately measurable concentration of that component is admitted to the pump chamber during any given fill stroke. The opening and closing of the proportioning valves during the component proportioning fill stroke is sequenced to minimize deviations of the relative concentrations from the programmed concentration ratio. Proper sequencing of the proportioning valves reduces inaccuracies that would otherwise tend to occur, especially at the upper and lower concentration limits, due to effects related to the compressibility of residual solvent remaining in the pump chamber at the end of each pumping stroke.
REFERENCES:
patent: 3136616 (1964-06-01), Thompson
patent: 3771490 (1973-11-01), Kinney et al.
patent: 3893591 (1975-07-01), Hocksmith
patent: 3985019 (1976-10-01), Boehme et al.
patent: 3990610 (1976-11-01), Boer
patent: 4045343 (1977-08-01), Achener
patent: 4060178 (1977-11-01), Miller
Abu-Shumays Ahmad
Helmer John C.
Luchetti Stephen J.
Cole Stanley Z.
Fisher Gerald M.
Freeh William L.
Varian Associates Inc.
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