Uniform flow displacement pump

Abstract

A displacement pump comprising a pump assembly and a cassette assembly. The pump assembly includes upper and lower housing portions that define a cavity, an arm disposed in the cavity, a roller attached to the distal end of the arm, and a motor attached to the proximal end of the arm for rotating the arm. The cassette assembly is removably disposed in the cavity and comprises upper and lower cassette housing portions that form an annular compression surface with a channel therein. A hollow compression tube having a flange extending along a length thereof is secured to the compression surface by the flange being engaged with the channel. As the motor rotates the roller arm, the roller presses the compression tube against the compression surface to create a moving occlusion of the compression tube for pushing fluid through the compression tube.

Description

[0001] This application is a continuation of U.S. Pat. No. 7,150,607, filed on Oct. 29, 2003, which claims the benefit of U.S. Provisional Application No. 60 / 427,468, filed Nov. 18, 2002.FIELD OF THE INVENTION [0002] The present invention relates to methods and systems for analyzing particles in a dilute fluid sample, and more particularly to pumps utilized by such systems to manipulate the fluid samples. BACKGROUND OF THE INVENTION [0003] Methods and systems for analyzing particles and particularly sediments are well known in the art, as disclosed in U.S. Pat. Nos. 4,338,024 and 4,393,466, which are incorporated herein by reference. Such systems utilize a flow cell though which fluid samples are passed, and a particle analyzer for capturing still frame images of the fluid passing through the flow cell. Thus, the flow cell positions and presents the sample fluid containing particles of interest for analysis. The more accurately that the sample fluid is positioned by flow cell, the b...

AI Technical Summary

Benefits of technology

The pump provides uniform and repeatable fluid flow without pulsations or tube deformation, ensuring consistent performance and preventing 'flat spotting, thereby enhancing the accuracy and reliability of particle analysis systems.

Problems solved by technology

For example, multiple rollers engaging with and disengaging from the flexible tube cause pulsations in the fluid flow through the pump, which can be problematic for proper operation of flow cells.

Thus, the tube can stretch and contract as the rollers move across its length, which again can cause varying flow and uncertainty in the volume moved by rollers.

Lastly, when the pump is shut down, rollers are left in contact with the tube, causing compression setting (flat spotting) of the tube, which adversely affects the uniform flow of the fluid after the pump is activated again.

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