Elution pump for chromatographic sample analysis - has circuit controlling speed of piston drive motor to control output

摘要

An elutriation pump for analysis of chromatographic samples, in which the sample is pumped through a vertical column by a block (1) with a vertical channel (2) by a horizontal piston (9), employs an electric motor to drive the piston. The drive arrangement includes an eccentrically mounted ring (10) rotating inside an elongated groove (15) in a slider (13) with an extension (16) to which the piston is attached by a threaded connection (18b). The output of the pump is controlled by varying the motor speed, by means of an automatic control circuit with a set of resistors at the input which can switch in as required, followed by an operational amplifier and a comparator stage. The proportions of the size and the travel of the piston are specified.