Patent ID: 7588423
Filing Date: 2009-09-15
Classification: B01D,F04B,G01N

Abstract:
1. A liquid chromatograph pump comprising: an upstream-side plunger pump as a first pump and a downstream-side plunger pump as a second pump, said first and second pumps being connected fluidly in series; a first motor for driving a plunger of the first pump and a second motor for driving a plunger of the second pump whereby the plunger of the first pump and the plunger of the second pump may be driven at different speeds from each other; a first check valve arranged at an upstream side with respect to the first pump to prevent a liquid from flowing from the first pump to the upstream side with respect to the first pump when the plunger of the first pump moves forward to pressurize the liquid in the first pump, and to allow the liquid to flow toward the first pump from the upstream side with respect to the first pump when the plunger of the first pump moves backward to take the liquid into the first pump; a second check valve arranged between the first and second pumps to prevent the liquid from flowing from the second pump toward the first pump when the plunger of the first pump moves backward to take the liquid into the first pump and the plunger of the second pump moves forward to pressurize the liquid in the second pump, and to allow the liquid to flow from the first pump toward the second pump when the plunger of the second pump moves backward to take the liquid into the second pump and the plunger of the first pump moves forward to pressurize the liquid in the first pump to make a flow rate of the liquid discharged from the first pump greater than a flow rate of the liquid taken into the second pump; and first and second cylinders and said first and second plungers to form said first and second pumps, and a stepped part being formed at least on an outer peripheral surface of the second plunger in the second pump, along a driving direction of the second plunger so as to define a working chamber between the stepped part and an inner wall surface of the second cylinder, wherein one end part of the second plunger on a side remote from a drive side is exposed to a gas atmosphere.