Importance

Loading Importance Indicators...

Abstract

An improved rotory positive displacement blower (10) of the Roots-type with reduced airborne noise and superior efficiency. The blower includes a housing (12) defining generally cylindrical chambers (32, 34) having cylindrical wall surfaces (20a, 20b) and containing meshed lobed rotors (14, 16) having the lobes (14a, 14b, 14c, 16a, 16b, 16c) thereon formed with an end-to-end helical twist according to the relation 360.degree./2n, where n equals the number of lobes per rotor. Preferably, n equals three. The blower housing (12) also defines inlet and outlet ports (36, 38) and the intersections of wall surfaces (20a, 20b) define a cusp (20d) associated with the inlet port (36) and a cusp (20e) associated with outlet port (38). The inlet and outlet port openings are skewed in opposite directions to increase the time the top lands of the lobes are in sealing relation with cylindrical walls (20a, 20b) of chambers ( 32, 34). Transverse boundaries (20g, 20i) of the inlet port are traversed by the lobes prior to traversal of the inlet port cusp (20d) by trailing ends (14h, 16h) of the lobes. In a similar manner, the transverse boundaries (20n, 20r) of the outlet port are traversed by the lobes subsequent to traversal of the outlet port cusp (20e) by leading ends (14g, 16g) of the lobes. Elongated backflow slots (40, 42) having a length/width ratio of at least four are disposed on opposite sides of the outlet port cusp and substantially parallel to the traversing lobes of the associated rotor. The backflow slots are traversed by the lobes prior to traversal of cusp (20e) and outlet port boundaries (20n, 20r) by the lobes.

Loading the Abstract Image...

First Claim