Multiple piston pump with a constant discharge capacity

摘要

A multiple piston pump with a constant discharge capacity for liquid chromatographs comprises at least three piston-cylinder units (1,2,3), whereof the pistons (7) are driven through a non-linear drive by a motor (23) with a mutual phase displacement of 360 DEG /n, when n represents the number of piston-cylinder units. A regulating system varies the speed of the motor (23) during each period or cycle of the piston movement in such a manner as to compensate for the non-linear drive so that the pressure of the liquid conveyed during each period or cycle remains at least approximately constant. The motor (23) can be constructed as a stepping motor, which is supplied with current pulses whereof the frequency determines the speed of the motor.