Abstract:
Improvements in the sealing area and dynamic operation of liquid ring pumps. The sealing improvement involves providing aspirating means between the cone inlet and the fluid adjacent the shaft on the inboard or high pressure side of the sealing area. In operation, the high pressure fluid that would tend to leak past the seal in prior art to contaminate the bearings or create a potentially dangerous gas explosion is harmlessly aspirated off into the gas being drawn into the pump. Further, in doing so, the sealing properties of the pump seal are enhanced. The dynamic improvement is directed particularly to duplex liquid ring pumps and calls for the rotor blades on one side of the central partition to be offset or out of phase from the mirror-image rotor blades on the other side of the partition. In this manner, the offset rotor blades in the adjacent pump chambers have a counter balancing effect to improve the operation of the pump by reducing the amplitude of the dynamic pulsations resulting in a pump with smoother operation and longer life.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to the field of liquid ring pumps. 
     2. Background Discussion 
     Liquid ring pumps are widely used in industrial and other applications to pump air or other gases. In a typical application, water or other liquid is introduced into the pump and centrifugally flung outwardly by a rotating rotor to form an annular ring of liquid within the stationary pump housing. The liquid ring rotates with the rotor and is centered about the longitudinal axis of the housing. The rotational axis of the rotor, however, is offset from the axis of the housing. Consequently, as the liquid ring rotates with the rotor, an air core or pocket is formed at the center of the annular liquid ring wherein the air core like the liquid ring is also centered relative to the housing axis but offset from and eccentrically positioned relative to the shaft axis. 
     The liquid volume in the housing is maintained to provide a seal at the outer portions of the rotor blades isolating individual chambers between adjacent blades. In one complete rotation of the rotor, liquid will first fill a chamber and then recede as the chamber advances about the housing until the chamber is almost empty of liquid wherein the chamber again fills with liquid to complete a cycle. As the liquid recedes from the chamber, it is replaced by air or other gas entering the inlet of the pump. Then, as the liquid is forced back into the rotor chamber, the air is compressed and exits through the outlet of the pump. 
     Two problems that presently occur in liquid ring pumps are outward leakage of fluid past the shaft seals and dynamic imbalance of the operating pump. In regard to the first problem, the liquid introduced into the liquid ring pump to form the annular ring commonly enters the pump and fills the space adjacent the shaft between the pump cone and the shaft. It then flows outwardly through passages in the cone or between the cone and the base of the rotor. The problem subsequently arises that liquid and/or gas under the pressure generated by the pump tends to leak past the shaft seal from the inboard or high pressure side of the seal to the outboard or low pressure side of the seal. Such leakage can contaminate the bearings and if the bearings are contaminated, it becomes a very expensive and time consuming ordeal to disassemble the pump and repair or repack the sealing area. Also, if the gas being pumped is combustible such as methane or gasoline fumes, exterior leakage of the fumes past the seal area can result in a potentially dangerous explosion. 
     Attempts to control outboard leakage after it has occurred and fluid has passed through the sealing area are known as in U.S. Pat. Nos. 4,273,343 to Visser; 2,312,837 to Jennings; and 722,219 to Fielden. However, these prior art approaches are essentially trying to clean up and contain the problem (i.e., leakage past the sealing area) after it has occurred while the present invention attempts to prevent the problem (i.e., leakage past the seal area) before it happens. In doing so, the present invention aspirates away fluid adjacent the rotating shaft and fixed cone on the inboard or high pressure side of the seal and harmlessly draws it into the pump itself. In this manner, the sealing properties of the pump seal are enhanced and the leakage problem virtually eliminated to the extent that simple lip seals can be used if desired in applications that previously called for much more expensive and harder to maintain and install sealing arrangements. 
     In regard to the second problem of dynamic imbalance particularly in duplex liquid ring pumps which essentially have two mirror-image pumping chambers on either side of a central partition, several U.S. patents have addressed the problem but in rather complex terms. For example, in U.S. Pat. No. 3,209,987, Jennings addressed the problem of balancing the bending moments on the pump shaft by offsetting the inlets and outlets and housing structure of the adjacent pumping chambers by 180 degrees. In his earlier U.S. Pat. No. 1,766,751, Jennings also attempted to improve dynamic balance by facing the curved blades of each rotor section in different directions, staggering the lobes, and crossing or laterally displacing the water and fluid being pumped from one side of the rotor to the other. Similarly, Nelson in his U.S. Pat. No. 2,416,538 continues along the crossover theme of Jennings by articulating only the outer portions of each blade combined with the crossing or laterally displacing of the water and fluid being pumped from one side of the rotor as in Jennings. 
     In contrast, the present invention addresses and improves the dynamic operation of a duplex liquid ring pump by simply offsetting the blades in each rotor section. In doing so, the rotor blades on one side of the central partition are then staggered or out of phase from the mirror-image rotor blades on the other side of the partition in the adjacent pumping chamber. 
     SUMMARY OF THE INVENTION 
     This invention relates to improvements in the sealing area and dynamic operation of liquid ring pumps. In regard to the sealing improvement, the invention involves providing aspirating means between the cone inlet and the fluid adjacent the shaft on the inboard or high pressure side of the sealing area. In operation, the high pressure fluid that would tend to leak past the seal in prior art to contaminate the bearings or create a potentially dangerous gas explosion is harmlessly aspirated off into the gas being drawn into the pump. Further, in doing so, the sealing properties of the pump seal are enhanced to the extent that simple lip seals can be used if desired in pumps that previously required more elaborate and expensive and harder to maintain sealing arrangements. 
     In reference to the dynamic improvement, it is directed particularly to duplex liquid ring pumps and calls for the rotor blades on one side of the central partition to be offset or out of phase from the mirror-image rotor blades on the other side of the partition. In this manner, the offset rotor blades in the adjacent pump chambers have a counter balancing effect to improve the operation of the pump by reducing the amplitude of the dynamic pulsations resulting in a pump with smoother operation and longer life. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a duplex liquid ring pump. 
     FIG. 2 is an end view of the pump taken along lines 2--2 of FIG. 1. 
     FIG. 3 is a partial cross-sectional view of the pump of the present invention. 
     FIG. 4 is a partial cross-sectional view taken generally along line 4--4 of FIG. 3 schematically illustrating the overall operation of the pump. 
     FIG. 5 is an enlarged view of the sealing area depicted in FIG. 3 illustrating the aspirating feature of the present invention. 
     FIG. 6 is a view taken along line 6--6 of FIG. 5 further illustrating portions of the aspirating feature of the present invention. 
     FIG. 7 is an enlarged view taken along line 7--7 of FIG. 6. 
     FIG. 8 illustrates an alternate adaptation of the aspirating feature of the present invention. 
     FIG. 9 illustrates another alternate adaptation of the aspirating feature of the present invention. 
     FIG. 10 is an exploded view of the pump housing and duplex rotor illustrating the offset or out of phase nature of the blades on each side of the central partition of the rotor. 
     FIG. 11 is a schematic view taken generally along line 11--11 of FIG. 10 and line 11--11 of FIG. 12 illustrating the offset or staggered relationship of the rotor blades in the adjacent pumping chambers. 
     FIG. 12 is a schematic view taken generally along line 12--12 of FIG. 10 further illustrating the offset relationship between the blades on each side of the central partition of the rotor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As best seen in FIGS. 1-3, the liquid ring pump 1 of the preferred embodiment is a duplex one with mirror-image inlets 3 and outlets 5 on either side of the central plane A--A. In operation, any one of the multiple outlets 5 on each side can be used (see FIG. 2) depending upon the desired delivery orientation with the unused outlets 5 being closed by cover plates 7. The shaft 9 of the pump 1 can be driven by any desired arrangement including a simple drive motor such as 11 of FIG. 1. 
     Referring to FIG. 3, the shaft 9 of the pump 1 extends along a longitudinal axis S--S substantially perpendicular to the central plane A--A and central partition 13 of the rotor 15. The rotor 15 includes a plurality of blades 17 and 17&#39; mounted on either side of the central partition 13. The rotor 15 with its blades 17 and 17&#39; and central partition 13 is fixedly mounted to the shaft 9 and rotates with it relative to the annular pump housing 19 and the head members 21 and the cone members 23 on each side of the central plane A--A. 
     In operation as best seen in FIG. 3, water or other liquid is first introduced through the line 25 into the pump 1 to the space at 27 between the cone 23 and shaft 9. From there it flows outwardly along path 29 between the fixed cone 23 and rotating rotor 15 into the pump housing 19 where the rotating rotor causes it to form a liquid ring 31 (see FIG. 4). The annular ring 31 formed by the rotating rotor 15 is symetrically centered about the longitudinal axis H (see FIG. 4) of the housing 19. As shown, the longitudinal axis S--S of the shaft 9 is substantially parallel to but eccentrically offset from the longitudinal axis H of the housing 19. In this manner, an air core or pocket 33 is formed which like the liquid ring 31 is centered about the housing axis H and offset and eccentrically positioned relative to the shaft axis S. 
     Consequently, as the rotor 15 makes a complete clockwise revolution from location P at about seven o&#39;clock in FIG. 4, the liquid first fills a chamber 35 between adjacent blades 17. Then, as the chamber 35 advances clockwise in FIG. 4 about the shaft axis S, the liquid in the chamber 35 recedes (see the liquid-gas interface 37 at about one o&#39;clock in FIG. 4). Thereafter, the chamber 35 again fills with liquid as it approaches location P to complete a cycle. As the liquid recedes from the chamber 35 as it moves clockwise from location P to about one o&#39;clock in FIG. 4, the liquid 31 is replaced by air or other gas 33 entering the pump through the inlet 39 in the cone member 23. Then as the liquid 31 is forced back into the chamber 35, the air 33 is compressed and exits through the outlet 41 in the cone member 23 (just before location P at about five-seven o&#39;clock in FIG. 4). The air or other gas from inlet 3 is thus drawn through inlet passage 38 and 39 (see FIG. 3) in the port means of head member 21 and cone member 23 into the rotor 15 where it is compressed and then discharged through the outlet passages 41 and 42. The liquid 31 to form the annular ring enters the pump 1 as discussed above through inlet 25 (see FIG. 3). It then fills the space or chamber 27 between the cone 23 and shaft 9 and flows outwardly through make-up passage 29 between the cone 23 and rotor 15. As also discussed above, the problem subsequently arises that liquid 31 and/or gas 33 in the space or chamber 27 is subjected to the pressure generated by the pump 1. Without the aspirating feature of the present invention, this fluid would tend to leak past the shaft seal 45 (i.e., from right to left in FIGS. 3 and 5). In doing so in prior art devices without the aspirating feature of the present invention, the fluid of liquid 31 and/or gas 33 is driven by the pressure differential between chamber 27 (which is substantially under the full, discharge pressure of the pump 1) and the outboard area 47 (which is substantially at ambient, atmospheric pressure). If allowed to leak past the shaft seal 45 in FIG. 5 from the inboard or high pressure side HP (on the right of plane B--B in FIG. 5) to the outboard or low pressure side LP of the seal 45 (on the left of plane B--B in FIG. 5), the escaping fluid can contaminate the main bearings 49 (see FIG. 3). Further, if the fluid contains combustible fumes, it may well result in a potentially dangerous explosion. 
     To prevent this leakage problem and enhance the sealing operation of the lip seal 45, the sealing area of the pump 1 on the inboard or high pressure side HP of the seal 45 is provided with an aspirating means. The aspirating means places the high pressure fluid adjacent the shaft 9 in space 27 in fluid communication with the low pressure generated in the pump 1 itself. In this manner, the leakage problem of prior art devices caused by the large pressure differential across the sealing area is defused and the high pressure fluid in chamber 27 is harmlessly drawn into the inlet flow of the pump 1. In the preferred embodiment as shown in FIG. 5, the aspirating means includes a flow passage comprising channel portion 51 in the cone 23 and the channel portions 53, 54, and 55 in the secondary bearing 43. The secondary bearing 43 (see FIG. 7) is actually spaced at 57 from the shaft 9 in a non-sealing relationship by tolerances substantially twice that of the main bearing 49. The secondary bearing 43 in operation is intended to limit damage to the pump 1 should the main bearings 49 break down. 
     As shown, the liquid is introduced at 25 in FIG. 3 and subsequently admitted into the chamber 27 and thereafter into the housing 19 through the make-up passage way 29. The chamber 27 is defined by parts of the cone 23 and head 21 which are fixedly mounted relative to the housing 19. These parts form a portion that extends about and along the shaft 9 and is radially spaced from the shaft 9 to define or form the chamber 27. As illustrated in FIGS. 3, 5, and 7-9, the chamber 27 extends longitudinally (from left to right in the figures) along the shaft 9 from a first location (on the left in the figures) at the seal line B to a longitudinally spaced second location (on the right) at rotor 13. The make-up passage 29 then adds liquid to the housing 19 from the right side of the chamber 27 and the aspirating means then draws fluid from the left side of the chamber 27 at the high pump pressure (from next to the shaft 9 substantially adjacent the seal line B on the left side of chamber 27). As shown, the make-up passage 29 and aspirating means including channel portions 53-55 are essentially at opposite sides or ends of the chamber 27. That is, the make-up passage 29 is positioned at or at least substantially closer to the second location or right side of the chamber 27 near the rotor 13 than to the first location at the seal line B on the left side of chamber 27 in the figures. Conversely, the aspirating means is located substantially closer to the first location or the left side of the chamber 27 than to the make-up passage 29 or the right side of the chamber 27. 
     Referring again to FIGS. 5-7, the channel portion 51 in the cone 23 extends radially through the cone 23 relative to the longitudinal axis S--S of the shaft 9. Similarly, the channel portion 53 and part of 54 also extend radially. The connecting channel 55 (see FIGS. 5 and 7) then extends at a right angle thereto along the shaft 9 substantially parallel to the shaft axis S. In the preferred embodiment, the aspirating means has a plurality of such passages with the respective channel portions 55 (see FIG. 6) extending parallel to each other and being radially and evenly spaced from each other about the shaft axis S. Interconnecting all of the channel portions 53 and 55 is the circumferential channel portion 54 that extends about the shaft axis S. In this manner, all of the aspirating passages of channel portions 53-55 are in fluid communication with each other as well as in fluid communication with the high pressure fluid adjacent shaft 9. Additionally, the channel portions 53-55 are all in fluid communication with the channel portion 51 and consequently, they are also all in fluid communication with the low pressure gas in the inlet passage 38, 39 of the pump 1. 
     FIGS. 8 and 9 illustrate adaptations of the aspirating feature to other sealing arrangements. However, in each case as in the preferred embodiment, the aspirating means is positioned on the inboard or high pressure side HP of the packing seal 45&#39; in FIG. 8 and the lip seal 45&#34; in FIG. 9. Additionally, the secondary bearings 43&#39; and 43&#34; are also in a non-sealing relationship to the shaft 9 at tolerances substantially twice those of the main bearings 49. However, in the embodiments of FIGS. 8 and 9, the aspirating channel portions 53&#39; and 54&#39; and 53&#34; and 54&#34; and portions of channels 55&#39; and 55&#34; are in separate ring members 61&#39; and 61&#34; which are preferably in a non-sealing relationship to the shaft 9 like the secondary bearings 43&#39; and 43&#34;. Further, the channel portions 51&#39; and 51&#34; in the adaptations of FIGS. 8 and 9 lead to the inlet passage 38, 39 of the pump 1 through the head member 21&#39; and 21&#34;. This is in contrast to the channel portion 51 in the preferred embodiment which passes through the cone 23 rather than the head member 21. 
     The second feature of the present invention is illustrated in FIGS. 10-12 and is directed to improving the dynamic balance of the duplex liquid ring pump 1. More specifically and as illustrated in the exploded view of FIG. 10, the rotor 15 of the duplex liquid ring pump has two rotor sections on either side of the central partition 13. The central partition 13 as best seen in FIG. 3 separates the pump 1 into two pumping chambers on either side of the central plane A--A of the pump 1. Each pumping chamber has its own inlet 3 and outlets 5 and the central partition 13 cooperates with the central rib 59 of the housing 19 to essentially separate the operations of the two pumping chambers. The rotor blades 17 in one pumping chamber extend about the rotor in a manner corresponding to the blades 17&#39; in the other pumping chamber; but, unlike prior art devices, the first set of blades 17 are offset from the second set of blades 17&#39;. This improves the operation of the pump by reducing the amplitude of the dynamic pulsations resulting in smoother operation and longer life. 
     In the preferred embodiment as shown in FIGS. 11 and 12, the blades 17 and 17&#39; are evenly offset relative to each other. That is, if there were n blades 17 and n blades 17&#39;, adjacent blades 17 in one rotor section would be spaced angle a (see FIG. 12) or 360/n degrees from each other. Similarly, adjacent blades 17&#39; would be spaced angle a or 360/n degrees from each other about the shaft axis S. Additionally, the offset or out of phase amount would be 1/2 a or 360/2n degrees. For example, if each set of rotor blades has 20 blades, adjacent blades in each set would be evenly spaced 360/20 or 18 degrees from each other about the axis S. Additionally, each rotor set would be one-half that or 9 degrees out of phase with the mirror-image set of blades on the other side of the central partition 13. As shown, each blade 17 and 17&#39; respectively extends along and substantially radially outwardly of the shaft axis S. Further, as shown in FIGS. 4 and 12, the blades 17 and 17&#39; also preferably curve slightly in a continuous and uniform manner in the direction of rotation for enhanced operation of the pump. 
     While several embodiments of the present invention have been shown and described in detail, it is understood that various changes and modifications could be made thereto without departing from the scope of the invention.