Patent ID: 6031610
Filing Date: 2000-02-29
Classification: F04C,G01N

Abstract:
In a particle counter of the type having a gas flow path extending through a volumetric space illuminated by a beam of light that is obscured or scattered by particles in a flowing stream of gas in the flow path wherein the obscured or scattered light is indicative of a particle count, the improvement comprising:a multi-lobe type pump including a pump housing of efficient compact size and having inner walls within which are set a plurality of rotatable shafts, each shaft having at least one lobe interleaving with a lobe on another shaft in a noncontacting manner in gas flow communication with the volumetric space, the rotatable shafts being set in the pump housing to provide clearance between the lobes and the inner walls to prevent spurious introduction of particles into the flowing stream of gas, and the pump housing having a height not exceeding a few inches and along which the lobes substantially entirely extend.