Noise and shock reduction in rotary positive displacement blowers

Abstract

A roots-style blower (210) has a housing (214), rotors (230) and manifolds (212) for the housing (214). The housing (214) forms an inlet plenum (220), a rotor chamber (224) and a discharge plenum (228). The rotors (230) have straight lobes (232) spaced by pockets (240). The pocket (240X) that traps gas between a leading and following lobe (232) and an inside wall of the rotor chamber (224) is a temporary closed cell (240X). The manifolds (212) and the housing (214) form a pair of back-pass loops (250-251), one for each rotor (230). Each back-pass loop (250-252) comprises a back-pass chamber (250), outer channels (252) from the discharge plenum (228) to the back-pass chamber (250), and inner channels (251) to the rotor chamber (224). Wherein, the back-pass chamber (250) volume as a percentage of closed cell (240X) volume ranges between about fifty-six percent (56%) and one-hundred-seventeen percent (117%).

Description

CROSS-REFERENCE TO PROVISIONAL APPLICATION(S)

[0001] This application claims the benefit of U.S. Provisional Application No. 61 / 336,495, filed Jan. 22, 2010, the disclosure of which is incorporated herein by this reference thereto.BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The invention relates to rotary positive displacement blowers (of the Roots type) and, more particularly, to a back-pass loop for gradually pressurizing the working cell to outlet pressure in order to weaken the strength of the pulsations that would otherwise happen without such a back-pass loop, and thereby reduce noise and shock (and perhaps better efficiency as well).

[0003] Briefly, the performance of such blowers is typically measured (or specified) in terms of the following factors:—flow, pressure, efficiency, noise, and reliability.

[0004] It is an object of the invention to provide improvements in particular for at least two or three of those factors, namely, noise and reliability, plus perhaps efficiency.[000...

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