Abstract:
A liquid ring pump includes a planar port plate having first and second planar walls, a sidewall which defines a shaft receiving aperture, an inlet, and an outlet. An opening is formed in the port plate and includes an open end that extends through the sidewall and an open face that extends through the first planar wall. A rotor shaft is rotatable about a central axis and is positioned such that a portion of the rotor shaft extends into the shaft receiving aperture. An aperture is formed in the port plate and positioned substantially opposite the opening. The opening, a space defined between the rotor shaft and the sidewall, and the aperture, cooperate to define a channel that extends between a first side of the shaft receiving aperture and a second side of the shaft receiving aperture, wherein the channel is formed entirely coplanar with the port plate.

Description:
PRIOR APPLICATION DATA 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/674,736 filed Nov. 12, 2012, now U.S. Pat. No. 9,689,387, which claims priority to U.S. Provisional Application No. 61/720,175 filed Oct. 30, 2012, the contents of both are fully incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention concerns a liquid ring pump that has a passage which scavenges gas trapped in a rotor bucket of a liquid ring pump after the bucket has swept past a closing edge of an outlet in a port plate and before the bucket opens into an inlet of the port plate. The passage is in the port plate angularly between the closing edge of the port plate outlet and the leading edge of the port plate inlet. 
         [0003]    Liquid ring pumps are well known. Generally a liquid ring pump includes a housing; a rotor within the housing; a shaft extending into the housing on which the rotor is fixedly mounted; and a motor coupled to the shaft. During operation, the housing is partially filled with operating liquid so that when the rotor is rotating, the rotor blades engage the operating or pumping liquid and cause it to form an eccentric ring that diverges and converges in the radial direction relative to the shaft. Where the liquid is diverging from the shaft, the resulting reduced pressure in the spaces between adjacent rotor blades of the rotor assembly (buckets) constitutes a gas intake zone, low pressure zone. Where the liquid is converging towards the shaft, the resulting increased pressure in the spaces between adjacent rotor blades (buckets) constitutes a gas compression zone 
         [0004]    U.S. Pat. No. 4,850,808, Schultze, recites that in a conically or cylindrically ported liquid ring pump, compressed gas that would otherwise be carried over from the compression zone to the intake zone of the pump is made to bypass the intake zone by passing through a first aperture in the port member into a clearance between the rotor shaft and the port member and then through a second aperture in the port member from the clearance to an initial portion of the compression on zone. 
         [0005]    U.S. Pat. No. 5,769,609, Plescher, recites that in a liquid-ring compressor having a rotor mounted in a compressor housing, the rotor is mounted eccentrically relative to the center axis of the compressor housing. At least one control disk is arranged on one of the end faces of the rotor. The control disk is provided with a suction slot and a pressure slot for the feed and discharge of the medium to be compressed, respectively. The control disk also has an encircling distribution groove in the area covered radially by the hub of the rotor. Operating liquid is introduced into a feed opening, which leads to the distribution groove, to seal an axial gap between the control disk and the rotor hub. A blocking element projects radially into the distribution groove and is provided on the side of the feed opening that has the greater pressure differential between the pressure of the operating liquid entering the feed opening and the pressure in the rotor cells. The blocking element improves the sealing of the axial gap. 
         [0006]    U.S. Pat. No. 6,354,808, Shenoi, recites that liquid ring pumps, of the type having a port structure that extends into an annular recess in an end of the rotor, have several parts that are designed so that they can be used to make pumps having either relatively demanding service requirements or substantially less demanding service requirements. Some of these parts can be substantially exactly the same in both final pump configurations. Others of these parts may be castings that differ substantially only in some subsequent machining in order to adapt them for each final pump configuration. Some of the final pump configurations have more compact mechanical seal structures and/or improved structures for supplying liquid to the seal structures. 
         [0007]    International publication WO 2010 071651 is directed to a liquid ring pump that has a channel in a portion of a liquid ring pump. The channel has a first opening which opens into a first bucket formed by rotor blades. The first opening is located along an arcuate path between a closing edge of an inlet port and a leading edge of a discharge port. The inlet port and discharge port are in a port plate of the liquid ring pump. The channel has a second opening which opens into a second bucket formed by rotor blades. The second opening is on an arcuate path between a closing edge of the discharge port and a leading edge of the inlet port. A fluid pathway interconnects the first and second openings. At least a portion of the liquid ring pump forming the channel is disposed in a circumferential cylindrical cavity, wherein the cavity is formed from a plurality of axially extending rotor blade ends. The portion of the liquid ring pump providing the channel can be a removable cylinder. The channel is isolated and sealed off from the discharge port and the inlet port of the port plate when the pump is in the running mode. 
       SUMMARY 
       [0008]    In one aspect the invention is embodied in a partial assembly of a liquid ring pump. The pump has a pump head. A port plate is coupled to the pump head. The port plate has a side wall which defines a shaft receiving aperture. A rotor shaft is disposed in said shaft receiving aperture. A space is between the sidewall and a portion of the shaft radially opposite the sidewall. A rotor is fixedly coupled to the shaft. The rotor has a plurality of blades which are arranged about a central axis of the rotor. Each blade of the plurality of blades is adjacent at least two other blades. The plurality of blades forms a plurality of pairs of adjacent blades. Between each pair of adjacent blades is a bucket. The adjacent blades form a plurality of buckets. Rotation of the shaft in the shaft receiving aperture rotates the rotor and plurality of buckets about the central axis. 
         [0009]    The port plate defines an inlet and an outlet. The inlet has a closing edge and a leading edge. The outlet has a closing and a leading edge. The port plate has an opening with a first end at a first section of the opening and a second end at a second section of the opening. The first section opens through a portion of a surface forming a first face of the port plate. The second section opens at the second end into the shaft receiving aperture. The first and second sections are continuous. The first section is angularly between the closing edge of the outlet and leading edge of the inlet. A length measured from the first section to the inlet&#39;s leading edge is less than a length measured from the first section to the outlet&#39;s leading edge. The length is measured along a straight line. The first section does not open into the outlet or inlet; 
         [0010]    Rotation of the buckets will rotate a first one of the buckets, in a direction of rotation to a position between the leading edge of the inlet and closing edge of the outlet. When said first one of said buckets has rotated to the position between the leading edge of the inlet and the closing edge of said outlet, said bucket overlaps said first section of said opening and said first section of said opening opens into said bucket, said buckets at said position are between said leading and closing edge without overlapping said inlet and outlet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a simplified stripped down sectional view of a liquid ring pump embodying the present invention; the sectional view is taken along the length of the shaft&#39;s central axis. 
           [0012]      FIG. 2  is a stripped down and simplified exploded isometric view of a partial assembly of the liquid ring pump shown in  FIG. 1 ; the rotor and shaft have been sectioned along view line  4   a - 4   a;  the view looks into a first face of a head of a liquid ring pump. 
           [0013]      FIG. 3  is an isometric view of the rotor shown in  FIG. 2 ; the view is looking into a face of the rotor; the face of the rotor, when the rotor is assembled, faces the valve port plate and first face of the head. 
           [0014]      FIG. 4 a    is a simplified sectional view of the liquid ring pump of  FIG. 1 ; the section is perpendicular the pump shaft&#39;s axis looking into the rotor, port plate and first face of the head and taken along view line  4   a - 4   a;  a portion of the rotor has been cut-away to show a portion of the port plate normally hidden by the hub and also show a space between the shaft and a sidewall of the of the port plate normally hidden by the hub. 
           [0015]      FIG. 4 b    is the close-up detail indicated at  4   b  of  FIG. 4   a.    
           [0016]      FIG. 4C  is a close-up of the detail indicated at  4   c  in  FIG. 4 a   , phantom lines have been omitted. 
           [0017]      FIG. 5  is same as  FIG. 4  except arrows have been drawn to show the flow of air as it passes through the gas scavenge channel and except the rotor has not been cut away. 
           [0018]      FIG. 6 a    is an irregular sectional view of the assembly shown in  FIG. 5 ; the section is taken to extend through the radial length of the passage in the port plate which scavenges air and to extend through and be parallel with the central axis of the shaft and rotor. 
           [0019]      FIG. 6 b    is the close-up detail indicated at  6   b  of  FIG. 6   a.    
           [0020]      FIG. 7 a    is an isometric view of the port plate shown in  FIG. 2  looking into a first face of the port plate; the first face faces the rotor. 
           [0021]      FIG. 7 b    is a close up of the detail shown in  FIG. 7 a    at  7   b , the detail isometricaly looks into the first face. 
           [0022]      FIG. 7 c    is a close up of the detail shown in  FIG. 7 a    at  7   c , the detail looks into the first face. 
           [0023]      FIG. 8  is an isometric view of the port plate of  FIG. 7  looking into a second face of the port plate; the second face faces the pump head. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    While embodiments of this invention can take many different forms, an embodiment thereof is shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention, and is not intended to limit the invention to the specific embodiment illustrated. 
         [0025]    The below description uses the term air when describing the invention. The term air includes ambient air and air made suitable for the application in which the liquid ring pump embodying the invention is used. The invention can also be used in connection with gases and mixtures of air and gases. It can be used in connection with any compressible fluid suitable for being conveyed through the inlet  47  and outlet  46  of a flat sided liquid ring pump. 
         [0026]    Now referring more particularly to the Figures, a flat sided liquid ring pump  20  is shown. The pump  20  has a rotor  22 . The rotor  22  has a plurality of  19  blades  24  which are arranged around a central area of the rotor. More particularly they are arranged circumferentially about the rotors central axis  26 . The blades are equidistantly spaced from each other. The blades extend from surface  88  of hub  86 . The rotors central axis, the rotor hubs central axis, the shafts central axis, and the central axis of the shaft receiving aperture in the port plate  40  are coextensive and shown as axis  26 . The blades  24  are arranged so that each blade  24  is adjacent at least two other blades of said plurality of blades  24 . Between each pair of adjacent blades is a space which can be called a bucket  28 . There are a total of  19  buckets  28 . Each bucket, when the liquid ring pump is operating at its running speed, forms a separate chamber which has a volume which expands and contracts depending on the angular orientation of the bucket  28  relative to a surface  30  forming an inner ring of the rotating liquid ring. The surface  30  delimits a radial inner boundary of the liquid ring. The liquid ring surface  30  forms a radial outer boundary of a respective chamber  34  formed in each bucket  28 . The radial inward boundary of each chamber  34  and bucket is formed by hub&#39;s  86  radially outward surface  88 . Each chamber  34  can be called a compressible fluid receiving chamber  34 . There are  19  chambers. A bucket  328  and its chamber  334  of the  19  buckets  28  and  19  chambers is at starting point A. The bucket  328  rotates in direction of rotation  36  an amount to overlap and sweep by an air inlet  38  of the port plate  40 . As the bucket  328  rotates to overlap the inlet  38 , the surface  30  forming the inner diameter of the rotating liquid ring diverges radially away, in a first radial direction  42 , from central axis  26  of the rotor  22 . As the surface  30  diverges, the volume of the chamber  334 , formed by the bucket  328  rotating to overlap the inlet, expands. As the bucket is rotating by the inlet its chamber  334  opens into the inlet  38  and overlaps the inlet and thus air is drawn into the expanding volume of the chamber formed by the bucket. Bucket  328 ′ and its expanded chamber  334 ′ exemplify bucket  328  and its chamber  334  overlapping with the inlet  38  as it rotates by the inlet  38 . Bucket  328 ′ and chamber  334 ′ are part of the  19  buckets  28  and  19  chambers  34 . As bucket  328  which rotates and sweeps by the inlet  38  continues to rotate in the direction  36 , the surface  30  continues to diverge in the first radial direction  42  away from the rotor&#39;s central axis  26 . As the surface  30  diverges, the volume of the chamber formed in the bucket continues to increase. Bucket  328 ″ and its chamber  334 ″ exemplify bucket  328  swept past the inlet  38  as its chamber increases in volume. Bucket  328 ″ and chamber  334 ″ are part of the  19  buckets  28  and  19  chambers  34 . As the bucket rotates in direction  36  it overlaps the port plate outlet  44 . The surface  30  of the liquid ring converges towards rotor central axis  26  in a second radial direction  43 . The volume of the chamber decreases. The chamber also opens into and overlaps the port plate outlet  44 . Therefore air trapped in the chamber of the bucket exits the bucket&#39;s chamber through the port plate outlet  44  and through the liquid ring pump outlet  46 . Bucket  328 ″′ and its chamber  334 ″′ exemplify bucket  328  and its chamber  334  as the chamber opens into and overlaps the port plate outlet  44 . 
         [0027]    During rotation of the bucket  328  past the outlet  44 , the surface  30  does not typically converge radially inward enough to completely collapse the volume of the bucket&#39;s chamber  334 . Bucket  428  exemplifies bucket  328  at this position. The non- collapsed chamber  334  at this position is shown as  434 . As can be seen, at an angular and circumferential point  48  between the closing edge  44   a  of the outlet port  44  and opening edge  38   a  of the inlet port  38 , the surface  30  does not contact the surface  50  delimiting a radial inward boundary of bucket  428 . The bucket  328 , shown as bucket  428 , has rotated to overlap the point  48 . The bucket  328  as it overlaps point  48  is shown as bucket  428 . Thus at the point  48  there is an open space shown as  434  that exists between the surface  30  and surface  50 . The open space  434  is angularly and circumferentially between a leading blade  52  and a trailing blade  54  delimiting bucket  428 . The open space  434  is also between inward bucket surface  50  and surface  30 . The open space thus forms a volume of a chamber  434  of the bucket  428 . The volume of chamber  434 , is the volume of chamber  334  of bucket  328  after bucket  328  has rotated past outlet  44  and before it has rotated to overlap the inlet  38 . As stated the bucket  328  in this position is shown as bucket  428 . Bucket  428 , in the above orientation, does not overlap either the inlet  38  or outlet  44 . Bucket  428  does not open into the outlet or inlet. The bucket is between the inlet  38  and outlet  44 . More particularly the bucket is between closing edge  44   a  of the outlet  44  and the leading edge  38   a  of the inlet  38 . The tip  54   a  of the trailing blade  54  of the bucket  428  in the above orientation is at the landline. The landline position is when the tip of a rotor blade, during the blade&#39;s 360 degree rotation about axis  26 , becomes closest to the internal surface  56   a  of the housing  56 . Also in the above described position of bucket  428 , the leading blade  52  and trailing blade  54  of the bucket  428  will each next rotate and sweep past, in the direction of rotation  36 , the leading edge  38   a  of the inlet  38  and the inlet  38  before they rotate and sweep past the outlet  44 . Accordingly the length between the tip  54   a  of the trailing blade  54  and the closing edge  44   a  of the outlet  44  is less than the length between the tip  54   a  of the trailing blade  54  to the leading edge  44   b  of the outlet  44 . The length between the tip  52   a  of the leading blade  52  and the leading edge  38   a  of the inlet  38  is less than between the tip  52   a  of the leading blade  52  to closing edge  38   b  of the inlet  38 . The lengths being measured are in a straight line. Also in the above described position, the bucket  428  trailing blade  54  has a leading surface  54   b  defining a trailing end of the bucket  428 . The leading surface  54   b  has rotated and swept past, in direction  36 , of the closing edge  44   a  of the outlet  44 . The leading surface  54   b  is thus between the closing edge  44   a  of the outlet  44  and the leading edge  38   a  of the inlet. The bucket  428  leading blade  52  has not yet rotated in direction  36  to overlap the inlet  38 . The leading blade  52  is between the closing edge  44   a  of the outlet  44  and the leading edge  38   a  of the inlet  38 . 
         [0028]    A channel or passage has a first  58 , second  66  and third  76  channel portion or passage. The first channel portion  58  is formed in the port plate  40 . The first channel portion has an opening which opens through a portion of a surface  78   a  forming a first face  78  of the port plate  40 . The opening  59  does not open through the port plate. The opening forms an open portion of the first channel portion. The opening is an open side which extends an entire length of the first channel portion as measured from a first end  60  to a second end  62  of the first channel portion. The second end  62  is radially inward of the first end  60 . At least a portion of the opening  59  that opens through a portion of the first face surface  78   a  overlaps the bucket  428 . The overlapping portion, which can be called the first section  59   a  of the first channel portion  58 , opens into the chamber  434  of the bucket  428 . The first section  59   a  overlaps the chamber  434 . The first section  59   a  thus opens through a portion of the surface  78   a  forming the first face of the port plate. The bucket  428  is in a high pressure zone of the working chamber  80  of the liquid ring pump  20 . Compressible fluid, which in this example is air, trapped in the chamber  434  exits the chamber  434  and enters the first channel  58  at the opening  59  and more particularly at the first section  59   a.  The air enters the first section  59   a  and travels through the first section  59   a.  The air travels through the channel made of portions  58 ,  66  and  76 . The air exits the channel into a chamber  534  of a bucket  528  that is between the closing edge  38   b  of the inlet  38  and leading edge  44   b  of the outlet  44 . The bucket  528  is in a low pressure zone of the liquid ring pump&#39;s working chamber  80  relative to bucket  428 . There is more pressure in bucket chamber  434  than in bucket chamber  534 . Bucket  528  and chamber  534  are one of the  19  buckets  28  and chambers  34 . The channel thus allows for air trapped in bucket  428  to escape bucket  428  before it is carried by bucket  428 , during rotation in direction  36 , to overlap the inlet  38 . By allowing air trapped in the chamber  434  to avoid being carried over to the inlet  38 , the chamber, when its volume expands as it sweeps by the inlet, as shown by bucket  328 ′ and chamber  334 ′, will have and exert a greater vacuum and thus be able to take in more air. Arrows  110  show the compressible fluid as is travels through channel portions  58 ,  66  and  76 . On some occasions the surface  30  may contact boundary surface  50  and close chamber  434  such that it has no volume. It may also contact the boundary surface of bucket  328  such that chamber  434  has no volume and is completely collapsed. In these cases the ring will not collapse. 
         [0029]    In more detail bucket  528 , in the low pressure zone, has a trailing blade  528   b  that has a leading surface  528   b ′ that has moved in the direction of rotation  36  past the closing edge  38   b  of the inlet  38  and the leading blade  528   a  of the bucket has yet to rotate in direction  36  enough to overlap the outlet  44 . The bucket  528  is between the inlet  38  and outlet  44 . It does not open up into or overlap the inlet  38  or outlet  44 . The trailing  528   b  and leading  528   a  blades are between the inlet and outlet. The leading blade  528   a  and trailing blade  528   b  of the bucket  528  and the bucket  528  will each next rotate and sweep past, in the direction of rotation  36 , the outlet  44  before they rotate and sweep past the inlet  38 . The length between the tip  528   b ″ of the trailing blade  528   b  and the leading edge  44   b  of the outlet  44  is less than the length from the tip  528   b ″ of the trailing blade  528   b  to the closing edge  44   a  of the outlet  44 . The length between the tip  528   a ′ of the leading blade  528   a  and the closing edge  38   b  of the inlet  38  is less than from the tip  528   a , of the leading blade  528   a  to the leading edge  38   a  of the inlet  38 . The lengths are measured along a straight line. 
         [0030]    Now referring back to the channel, the air travels through the first channel portion  58  into and through the second channel portion  66 . The air next travels from the second channel portion  66  into and through the third channel portion  76 . The air exits the third channel portion  76  and enters the bucket  528  through an aperture. The aperture is divided into a first  82   a  and second  82   b  aperture by portions of the port plate  40 . The aperture, made of apertures  82   a,    82   b , forms the end part of the third channel portion  76 . Thus the channel  58 ,  66  and  76  opens into bucket  528  through aperture  82   a,    82   b.  The aperture  82   a,    82   b  opens through the port plate. The aperture  82   a,    82   b  is angularly between and circumferentially spaced between the closing edge  38   b  of the inlet  38  and leading edge  44   b  of the outlet  44 . A length measured from the any part of the aperture  82   a,    82   b  to the inlet&#39;s closing edge  38   b  is less than a length measured from any part of the aperture  82   a,    82   b  to the outlet&#39;s  44  closing edge  44   a.  A length measured from any part of the aperture  82   a,    82   b  to the outlet&#39;s  44  leading edge  44   b  is less than a length from any part of the aperture  82   a,    82   b  to the inlet&#39;s  38  leading edge  38   a.  The lengths are measured along a straight line. The aperture  82   a,    82   b  does not overlap or open into the inlet  38  or outlet  44 . The aperture is radially outward of radially inward boundary surface  84  delimiting the radially inward surface of bucket  528 . The inward boundary surface  84  is formed by a portion of the hub&#39;s radially outward surface  88 . The aperture  82   a,    82   b  opens into bucket  528  and is between the buckets trailing  528   b  and leading  528   a  blade. The aperture overlaps bucket  528 . The aperture  82   a    82   b  also provides an opening for liquid used to form the liquid ring to enter the working chamber  80  in which the liquid ring rotates during operation of the pump  20  at running speed. 
         [0031]    The first section  59   a  and indeed the entire opening  59  is angularly between and circumferentially spaced between the closing edge  44   a  of outlet  44  and leading edge  38   a  of inlet  38 . A length measured from the first section  59   a  and indeed any part of the opening  59  to the inlet&#39;s leading edge  38   a  is less than a length measured from any part of the opening  59  to the outlet&#39;s leading edge  44   b.  A length measured from the first section  59   a  and indeed any part of the opening  59  to the outlet&#39;s closing edge  44   a  is less than a length measured from any part of the opening  59  to the inlet&#39;s closing edge  38   a.  The lengths are measured along a straight line. The first section  59   a  and indeed the entirety of the opening  59  do not open into the outlet  44  or inlet  38 . A portion of the opening  59  is axially across from and adjacent an axial delimiting end  90  of the surface  50  which delimits the radial inward boundary of bucket  428 . The surface  50  which delimits the inward boundary of bucket  428  is as stated a portion of the rotor hub&#39;s radially outer surface  88 . The surface  50  and the hub&#39;s radially outer surface  88  are circumferential. The first section  59   a  extends outward in the radial direction  42 . It is radially outward of the axial end  90  and the portion of the boundary surface  50  delimited by the end. It is radially outward of the entire boundary surface  50  and the hub&#39;s radially outer surface  88 . The opening  59  is bounded and closed at the first end  60  by an end wall  61  which is rounded, has a u shape, and has a peak at  60 . The end wall  61  delimits a closed end of the opening  59  and a closed end of the first section  59   a.  The first end  60  and at least a portion of the end wall  61  are radially outward of the boundary surface  50 . No portion of the port plate  40  delimiting the opening  59  of the first channel portion is more radially outward from the boundary portion  50  than the portion of the end wall  61  which delimits the first end  60 . 
         [0032]    A length measured from the portion  60  of the first section most radially outward from the boundary surface  50  to the internal surface  56   a  of the housing  56  enclosing the rotor  22  is X. The length is measured along a radius extending from the rotor&#39;s central axis  26 . A length measured from the portion of the boundary surface  50  delimited by the axial end  90  to the internal surface  56   a  of the housing  56  is Y. The length is measured along a radius extending from the rotor&#39;s central axis Y is greater than X. A length measured from the rotor&#39;s central axis  26  to the portion of the boundary surface  50  delimited by the axial end  90  is Q. The portion delimited is shown at  50   a.  The distance is measured along a radius extending from the rotor&#39;s axis  26 . A length measured from the rotor&#39;s central axis  26  to the most radially outward portion  60  of the first section is R. The distance is measured along a radius extending from the rotor&#39;s axis  26 . R is greater than Q. A length measured from the rotor&#39;s central axis  26  to the inner surface  30  of the liquid ring is Z. The length is measured along the radius that the distance R was measured. Z is greater than R. As shown no part of the first section  59   a  or any part of the opening  59  opens into the liquid ring. As the liquid ring surface can converge and contact surface  50 , opening  59  may open into the liquid ring. Also a portion of the opening  59   a  may open into the liquid ring from time to time without collapsing the ring. 
         [0033]    P is the length measured from a portion  60  of the first section most radially outward to the boundary surface  50 . The length is measured along a radius extending from the rotor&#39;s central axis  26 . The length is no greater than the length of a shortest radius from the central axis to the curve path  114  fit along a radial outer sidewall  44   c  of the outlet  44 . 
         [0034]    The radial outer sidewall is a portion of the port plate that delimits a boundary of the outlet in the radial outward direction  42 . A radial inner sidewall  44   d  delimits a boundary of the outlet in the radial inward direction  43 . 
         [0035]    The first channel portion  58  has a portion which extends radially inward from the first section  59   a  to the second end  62 . The first  60  and second ends  62  of the opening  59  and the first channel portion  58  are aligned along a straight line. The portion extending radially inward of the first section  59   a  has an opening which can be called a second section  59   b.  The second section  59   b  is continuous with the first section  59   a.  The second section  59   b  is continuous with the second end  62 . The second section  59   b  is radially inward of the boundary surface  50  and the hub&#39;s radially outward facing surface  88 . The second section  59   b  is overlapped by a portion of an axial facing surface  92  of the hub  86 . The axial facing surface  92  faces the first surface  78   a  of the port plate  40 . In the present construction the entire second section  59   b,  except any portion that opens through a portion of the port plate  20  extending radially inward of hub inner circumferential surface  94 , is overlapped by the portion of the axially facing surface  92 . The entire second section  59   b  opens through a portion of the first facing surface  78   a  of port plate  40 . The entire second section  59   b  forms a portion of opening  59 . The portion of the axial facing surface  92  is bounded, in the radial outward direction by boundary surface  50  and the radial inward direction by radially inward facing circumferential hub surface  94 . The portion of the axial facing surface  92  faces a surface  96   a  of the port plate  40  forming a base of the second section  59   b.  The surface  96   a  can be called a base surface  96   a.  The base surface  96   a  delimits the second section in an axial direction going away from the port plate first face surface  78   a  and towards the port plate second face surface  79 . A base surface  96   b  formed by a surface of the port plate also delimits the first section  59   a  in an axial direction going away from the port plate first face surface  78   a  and towards the port plate second face surface  79 . The base surface  96   b  of the first section and the base surface  96   a  of the second section are continuous. The bases can be formed by a portion of the pump head as opposed to the port plate. 
         [0036]    The bases form a single base surface of the first channel portion  58 . The single base surface  96   a,    96   b  is spaced in the axial direction from the first face surface  78   a  and delimits the opening  59  in the axial direction going away from the port plate first face surface  78   a  and towards the port plate second surface  79 . The opening  59  has a width, measured from a first side wall  63  to a second sidewall  64  of the first channel portion  58 . The width is about ′X to % the width of the bucket  428 . The width of the opening  59  is the arc length between the sidewalls. The arc length has a radius extending from the rotors central axis  26 . The arc length is taken along the arc drawn between the sidewalls at a point on each sidewall; the point is radially inward of the first end  60 ; and the point is midway between, in the radial direction  43 , the bounding surface  50  of the hub  86  and the hub&#39;s inner circumferential surface  94 . The width of the bucket is the arc length between the trailing blade  54  and leading blade  52  of the bucket  428 . The arc length is drawn between the bases of each blade. The base is the point where the blade first extends radially outward from the boundary surface  50  formed by the hub. The arc length has a radius extending from the rotors central axis. The arc length can be formed between the trailing blade  54  and leading blade  52  along surface  50 . Put another way the angular distance between the sidewall  63  and sidewall  64  of aperture  59 , measured from the central axis  26 , is ′X to % the angular distance between the base of a trailing blade and leading blade of a bucket measured from the central axis. 
         [0037]    The shortest angular distance from the centerline of opening  59 , when the centerline is drawn along a radius from the central axis, to the closing edge is % the angular distance between a trailing blade and leading blade of a bucket measured at the base of each blade. The vertex of the angle is a point on the central axis. 
         [0038]    The opening  59  has a length measured as a straight line from the first end  60  to the second end  62 . The bucket  428  has a length measured as a straight line from a rotor tip  52   a  of the leading blade  52  to the boundary surface  50 . The length of the opening is % to % the length of the bucket. 
         [0039]    The first sidewall  63  of the opening is continuous and integral with a first portion of the end wall  61 . The second sidewall  64  is continuous and integral with a second portion of the end wall  61 . The first and second sidewalls  63 ,  64  are spaced apart and opposite each other. The first sidewall  63  delimits the opening in the first circumferential direction  36  and the second sidewall  64  delimits the opening in the second circumferential direction  37 . The first and second sidewalls extend radially inward to the second end  62 . 
         [0040]    The second section  59   b,  at the second end  62 , opens into an aperture  100 . The aperture is radially inward of and does not open into the outlet  44 , inlet  38 , buckets  34 , and third channel portion aperture  82   a,    82   b.  The aperture  100  is circumscribed by sidewall  102  formed in and from the port plate  40 . The second section  59   b  opens into the aperture  100  through side wall  102 . The air thus travels from the first section  59   a  into and through the second section  59   b.  In the second section  59   b,  the air travels between the second section base  96   a  and the hub&#39;s axial face surface  92  and into the aperture  100 . The first  59   a  and second  59   b  sections form a single continuous opening which extends from the first end  60  to the second end  62  and directs air from the bucket  428  into the aperture  100 . The aperture receives a portion of the rotor shaft  106 . 
         [0041]    There is an open space  100   a  between the sidewall  102  and the portion of the shaft  106  outer surface radially opposite the sidewall  102 . The space  100   a  is continuous and extends 360 degrees around the portion of the shaft  106  opposite the sidewall. The open space  100   a  receives air from the second section  59   b  opening at second end  62  at and into aperture  100 . The open space  100   a  forms the second channel portion  66 . 
         [0042]    The sidewall  102  has a portion which defines an opening  100   b  through the port plate  40  which extends radially outward in direction  42  from aperture&#39;s  100  central axis. It also extends radially outward from portions of the side wall  102  defining an open end  100   b ′ of the opening  100   b.  The opening  100   b  can be called a notch or slot. Air received in the open space  100   a,  second channel portion  66 , from the first channel portion  58  exits the open space  100   a  through the notch  100   b.  The air travels through the notch  100   b  in the axial direction away from the hub axial facing surface  92  and towards the pump head  108 . The air, after it passes through the notch  100   b,  loops around a portion of the port plate second facing surface  79  and travels through aperture  82   a,    82   b  in an axial direction away from the pump head and towards the rotor hub  86  and into bucket  528 . The passage from the space  100   a,  and more particularly notch  100   b , through the aperture  82   a,    82   b  is the third channel portion  76 . 
         [0043]    The hub&#39;s circumferential inner surface  94  forms an opening which receives the rotor shaft  106 . The rotor  22  is fixedly mounted to the shaft  106 . The port plate  40  is between the rotor  22  and the pump head  108  and in particular the plurality of blades  24  and the head  108 . Rotation of the shaft  106  rotates the rotor  22 . The buckets  28  formed by the rotor  22  all rotate as the bucket  328  described above. 
         [0044]    In more detail, the rotor  22  is a flat sided rotor. The flat side  22   a  of the rotor is adjacent and faces the port plate  40 . Each blade  24  of the plurality of blades, at the flat side  22   a  of the rotor  22 , has a radially extending surface  24   a.  The surface extends from the tip end  24   b  of the blade to the end of the blade  24   c  at the hub  86 . The surface  24   a  is unbent and un-curved. The surface  24   a  of each blade is flush with the axial facing surface  92  which faces in the axial direction towards the pump head. The surface  24   a  is at a right angle to the hub&#39;s circumferential outer surface  88 . The end of each blade  24   c  at the hub is at a right angle relative to each blade&#39;s surface  24   a.  The end  24   c  of the blade  24  is integral with the hub  86  and more particularly hub surface  92 . 
         [0045]    Compressible fluid, which in this example is air, enters pump head  108  through head inlet  47 . It enters working chamber  80  though inlet  38 . It exits working chamber  80  through outlet  44 . It exits the head through outlet  46 . 
         [0046]    The head  108  has an auxiliary inlet  47 ′ and auxiliary outlet  46 ′ which in this case are sealed off. The port plate is substantially planar. When the liquid ring pump is operating at running speed the channel portions  58 ,  66 ,  76  are each substantially sealed-off from the inlet and outlet; the inlet and outlet are sealed-off from each other; the buckets, but for channel  58 ,  66  and  76 , are sealed-off from each other; and all the buckets accept when in the position of buckets  528  and  428  are sealed- off from each other. 
         [0047]    The outlet  44  is formed by a plurality of outlet sections. The plurality of outlet sections is separated from each other by portions of the port plate  40 . The closing edge  44   a  of the outlet and leading edge  44   b  of the outlet delimit the plurality of sections in radial directions  42  and  43 . The inlet  38  is formed by a plurality of inlet sections. The plurality of inlet sections is separated from each other by portions of the port plate  40 . The closing edge  38   b  of the inlet and leading edge  38   a  of the inlet delimit the plurality of inlet sections in radial directions  42  and  43 . 
         [0048]    The hub&#39;s outer surface  88  delimits the radial inward boundary and forms the inward boundary surface of all buckets  28 . The surface  88  is circumferential. The buckets are all the same. 
         [0049]    The phrases “radially outward” and “radially inward” are relative phrases and in relation to the rotor&#39;s central axis and the central axis of the shaft receiving aperture of the port plate. A point or construction of the liquid ring pump radially outward of another point or construction is further from the central axis than the other point as measured in the radial direction. The term “leading” and “trailing” are relative terms in relation to the direction of rotation of the rotor. Thus a leading blade of a bucket is a blade that passes a point as the rotor is rotated in a direction of rotation  42  before the trailing blade. A “closing edge” and a “leading edge” are relative terms and also in relation to the direction of rotation of the rotor. A closing edge is an edge passed by a rotor blade, rotating in the direction of rotation, after the blade has passed the leading edge. 
         [0050]    All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
         [0051]    The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.