Trapped volume vent means for meshing lobes of roots-type supercharger

• US 5,131,829 A
• Filed: 06/19/1991
• Issued: 07/21/1992
• Est. Priority Date: 06/19/1991
• Status: Expired due to Term

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Hampton, Keith
• Primary Examiner(s): Bertsch, Richard A.
• Assistant Examiner(s): CAVANAUGH, DAVID
• Application Number:
  US07/717,742
• Time in Patent Office: 398 Days
• Field of Search: 418/75, 418/78, 418/189, 418/201.1, 418/206
• US Class Current: 418/189
• CPC Class Codes: F04C 18/088 Elements in the toothed wheels or the carter for relieving the pressure of fluid imprisoned in the zones of engagement
• CPC Class Codes: F04C 29/0035 Equalization of pressure pulses silencing F04C29/06

Abstract

A rotary positive displacement blower (10) of the Roots-type having inlet and outlet vents recess (60,62) for reducing fluid pressure build up in spaces between meshing, helical lobes (34a, 36a) on rotating rotors of the blower.

Claims

1. A rotary pump including a housing defining an inlet and an outlet, and first and second parallel, transversely overlapping cylindrical chambers having cylindrical and end wall surfaces;

first and second meshed lobed rotors respectively disposed in the first and second chambers for transferring volumes of substantially gaseous fluid from the inlet to the outlet via spaces between front and rear adjacent and unmeshed lobes of each rotor in response to rotation of the rotors about their respective axes, the rotors and lobes having end surfaces disposed for sealing relation with the end wall surfaces, the lobes having an end-to-end helical twist such that each lobe has a lead end and a trailing end in the direction of rotor rotation, the lobes of each rotor having a radially outer surface disposed for sealing relation with the cylindrical wall surface of the associated chamber and fore-and-aft surfaces in the direction of rotor rotation and a root surface extending between radially inner extents of the fore-and-aft surfaces of adjacent lobes;

rotation of the rotors effecting meshes of the lobes wherein one lobe of one rotor moves into and out of the spaces between front and rear adjacent lobes of the other rotor, each mesh forming first and second pockets extending along the meshed lobes, the pockets sealingly separated by a sealing relation of the one lobe outer surface extending diagonally across the root surface, the pockets initially formed at the lead ends of the meshing lobes and progressing toward the trailing ends in response to continued rotation of the rotors, the first and second pockets respectively open to the housing outlet and inlet when opposite ends of the diagonal sealing relations are spaced from the lead and trailing ends of the meshing lobes, the first pocket becoming a trapped volume contracting in cross-section and sealed from direct communication with the housing outlet in response to the diagonal sealing relation of the one lobe outer surface initially reaching the trailing ends of the meshing lobes and due to the sealing relation with the associated end wall surface, each trapped volume containing outlet fluid and the volume decreasing from a maximum to a minimum size in response to continued rotation of the rotors, and the second pockets expanding in cross-section in response to the diagonal sealing relation of the one lobe outer surface initially reaching the trailing ends of the meshing lobes;

vent means for relieving pressure build-up in the trapped volumes;

characterized by;

the vent means including outlet and inlet recess means formed in the end wall surface sealingly related with the rotor and lobe end surfaces at the lobe trailing ends, the outlet and inlet recess means respectively disposed on opposite sides of a plane defined by the rotor axes, the outlet recess means for communicating the fluid in the trapped volumes to the housing outlet, the inlet recess means for communicating the fluid in the trapped volumes to the housing inlet, the outlet recess means including first and second recess fingers in continuous communication with the outlet fluid in the housing outlet, the first and second recess fingers disposed such that the trapped volumes of the first pockets move from positions communicating with the associated recess finger to positions sealed from such communication while the expanding second pockets are sealed from communication with the associated recess finger and, the trapped volumes move from positions sealed from communication with the inlet recess means to positions communicating therewith as the trapped volumes move to positions sealed from communication with the associated recess fingers.

2. A rotary pump including a housing defining an inlet and an outlet, and first and second parallel, transversely overlapping cylindrical chambers having cylindrical and end wall surfaces;

first and second meshed lobed rotors respectively disposed in the first and second chambers for transferring volumes of substantially gaseous fluid from the inlet to the outlet via spaces between front and rear adjacent and unmeshed lobes of each rotor in response to rotation of the rotors about their respective axes, the rotors and lobes having end surfaces disposed for sealing relation with the end wall surfaces, the lobes having an end-to-end helical twist such that each lobe has a lead end and a trailing end in the direction of rotor rotation, the lobes of each rotor having a radially outer surface disposed for sealing relation with the cylindrical wall surface of the associated chamber and fore-and-aft surfaces in the direction of rotor rotation and a root surface extending between radially inner extents of the fore-and-aft surfaces of adjacent lobes;

rotation of the rotors effecting alternate meshes of the lobes wherein one lobe of one rotor moves into and out of the space between front and rear adjacent lobes of the other rotor, each mesh including an arc-of-action having a beginning axially and circumferentially spaced ahead of an ending thereof, the beginning arc-of-action for each mesh starting at the lobe lead ends and progressing to the lobe trailing ends in response to the rotation moving successive increments of the outer surface of the one lobe into a sealing relation with successive incremental portions of the root surface juxtaposed the radially inner extent of the fore surface of the rear adjacent lobe, the beginning arc-of-action occurring while a sealing relation exists between the fore surface of one lobe and the aft surface of the front adjacent lobe, the ending arc-of-action subsequently starting at the lobe lead ends and progressing to the lobe trailing ends in response to the rotor rotation moving the outer surface of the one lobe out of a sealing relation with a portion of the root surface juxtaposed the radially inner extent of the aft surface of the front adjacent lobe, the ending arc-of-action occurring while a sealing relation exists between the aft surface of the one lobe and the fore surface of the rear adjacent lobe, the outer surface of the one lobe defining a sealing relation extending diagonally across the full extent of the root surface while the beginning and ending of each arc-of-action is respectively spaced from the lobe trailing and leading ends;

each arc-of-action defining first and second pockets extending along the meshed lobes and sealingly separated by the sealing relation between the outer surface of the one lobe and the root surface, the first pocket formed between the fore surface of the one lobe and the root surface and the second pocket formed between the aft surface of the one lobe and the root surface, the first and second pockets each having cross-sectional spacing between the root surface and the respective for-and-aft surfaces of the one lobe, the cross-sectional spacing of adjacent incremental portions of the first and second pockets separated by the outer surface of the one lobe and progressively changing respectively from maximum and minimum amounts to minimum and maximum amounts as the arc-of-action goes from the beginning to the ending, the first and second pockets respectively open to the outlet and inlet while the beginning and ending arc-of-action of each is spaced from the lobe trailing and leading ends, each first pocket becoming a contracting trapped volume sealed from direct communication with the outlet in response to the beginning arc-of-action at the lobe trailing ends and the sealing relation with the associated end wall surface, each trapped volume containing outlet fluid and the volume decreasing from a maximum to a minimum as the cross-sectional spacing of the second pocket expands from the minimum to the maximum;

vent means for relieving pressure build-up in the trapped volumes;

characterized by;

the vent means including outlet and inlet recess means formed in the end wall surface sealingly related with the rotor and lobe end surfaces at the lobe trailing ends, the outlet and inlet recess means respectively disposed on opposite sides of a plane defined by the rotor axes, the outlet recess means for communicating the fluid in the trapped volumes to the housing outlet, the inlet recess means for communicating the fluids in the trapped volumes to the housing inlet, the outlet recess means including first and second recess fingers in continuous communication with the outlet fluid in the housing outlet, the first and second recess fingers disposed such that the trapped volumes of the first pockets respectively disposed between the root surfaces of the first and second rotors and the fore surfaces of the one lobe move from positions communicating with the associated recess finger to positions sealed from such communication while the expanding second pocket disposed between the root surfaces and the aft surfaces of the one lobe are sealed from communication with the associated recess finger and, the trapped volumes move from positions sealed from communication with the inlet recess means to positions communicating therewith as the trapped volumes move to positions sealed from communication with the associated recess fingers.