Patent ID: 7997885
Filing Date: 2011-08-16
Classification: F04C

Abstract:
1. A Roots-type blower exhibiting reduced noise, comprising: a pair of rotors, configured to counter-rotate about parallel axes in an axis plane, wherein the respective rotors each comprise a plurality of cycloidal-profile lobes having tips that are located at the maximum radial extent thereof, and advancing with axial position as opposite-handed helices, and wherein rotation of the tips of the respective rotor lobes defines a negative body in the form of a pair of overlapping cylindrical sections truncated at axial extents of the rotors; a blower housing with walls that define a chamber to enclose the rotor pair, wherein the negative body establishes a physical extent of the chamber, and wherein the chamber wall is further positioned away from the negative body by a substantially uniform clearance distance; an inlet port penetrating the chamber wall, wherein an inlet port perimeter wall is symmetric about an interface plane substantially equidistant between the rotor axes; an outlet port penetrating the chamber wall, wherein an outlet port perimeter wall is symmetric about the interface plane at a location substantially opposed to that of the inlet port; and a pair of relief recesses in the chamber wall, positioned and shaped with substantial bilateral symmetry to one another with reference to the interface plane, wherein the relief recesses are bounded on their respective perimeters by continuous cylindrically curved portions of the chamber wall.