Abstract:
A vertical turbine pump which operates with its inlet sub-merged in a body of liquid to be pumped employs an impeller provided with two or three equiangularly spaced vanes and a diffuser section provided with three equiangularly spaced stationary vanes. A vertical turbine pump incorporating such a combination of impeller and diffuser vanes exhibits favorable hydraulic efficiency and smooth operation and can effectively handle liquids with entrained solids. The pump bowl bearings are part of a cartridge which is readily removed and installed through the upstream end of the pump to facilitate servicing in the field.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a vertical turbine pump and more particularly to such a pump which is resistant to clogging when handling fluids with entrained stringy materials and other solids. 
     Vertical turbine pumps are well known which operate in an upright position and employ a bowl assembly including a rotary impeller submerged in a body of liquid to be pumped. In these pumps, the impeller develops a diverging tangential flow of the liquid which passes through a bulbous diffusion zone and then through a discharge conduit and elbow. 
     When a vertical turbine pump is employed for pumping sewage and other liquids having considerable amounts of entrained stringy materials and other solids, clogging of the pump can be a problem. To avoid clogging, careful attention must be given to the size and shape of the passages in the impeller and in the downstream components of the pump. Generally, clog-resistant performance is realized by making the passages as large and as streamlined as possible. 
     A vertical turbine pump which can effectively handle liquids with entrained stringy materials and other solids is disclosed in U.S. Pat. No. 4,063,849 which issued to Modianos. The Modianos pump incorporates a bowl assembly having a fully shrouded two-vane impeller, a diffusion zone provided with two symmetrically disposed stationary vanes and a discharge column and elbow provided with an axially extending “splitter” vane. 
     When compared to vertical turbine pumps employing greater numbers of impeller and diffuser vanes, a vertical turbine pump having just two impeller vanes and two diffuser vanes exhibits limited hydraulic efficiency and generates significant pressure pulses which are manifested by relatively rough operation. 
     Vertical turbine pumps constructed according to known designs employ a pump bowl assembly having bowl bearings which are only accessible after completely disassembling the pump. Because of their location in the lower region of the pump, the bowl bearings are particularly vulnerable to wear and degradation when handling sewage and other corrosive and grit-laden liquids. Of the drive shaft bearings employed in a vertical turbine pump, the bowl bearings are usually the first to require servicing. In known vertical turbine pumps, the disassembly of the pump which is required in order to access the bowl bearings makes servicing of the bearings in the field a difficult prospect. 
     SUMMARY OF THE INVENTION 
     Accordingly, a primary object of the present invention is to provide a vertical turbine pump which can effectively handle solids-laden liquids and also exhibit favorable hydraulic efficiency. 
     Another object of the present invention is to provide a vertical turbine pump which can handle solids-laden liquids without the pressure pulsations and accompanying rough operation exhibited by vertical turbine pumps employing fewer numbers of impeller and diffuser vanes. 
     Still another object of the present invention is to provide a solids-handling vertical turbine pump having bowl bearings which can be readily serviced in the field. 
     The foregoing and other objects of the present invention are realized by a vertical turbine pump comprising: a pump bowl assembly including a casing having a bulbous diffuser section between relatively narrow axially opposed upstream and downstream sections: a rotary impeller disposed in said casing upstream section adjacent a fluid inlet, said impeller incorporating flared shrouds which are axially spaced from each other and spirally oriented impeller vanes disposed between said shrouds and spaced from each other equiangularly about the axis of impeller rotation; a bulbous diffuser core disposed centrally in said casing diffuser section; and three stationary diffuser vanes spaced equiangularly about said diffuser core, said diffuser vanes extending laterally between said diffuser core and said casing and having upstream ends which curve about said diffuser core and downstream ends which extend generally axially through said casing downstream section. 
     The objects of the invention are also realized by a vertical turbine pump incorporating a pump bowl assembly including a casing having a bulbous diffuser section between relatively narrow axially opposed upstream and downstream sections, a bulbous diffuser core disposed centrally in said casing diffuser section, a drive shaft extending centrally and axially through said diffuser core and a rotary impeller fastened to an end of said drive shaft and disposed in said casing upstream section adjacent a fluid inlet, a bearing cartridge separably fastened within said diffuser core and said bearing cartridge carrying axially spaced bearings which surround and rotatably support said drive shaft. 
     The detailed description which follows will reveal the further scope of the present invention. However, it should be understood that the detailed description and specific examples are illustrative only, and various changes and modifications within the spirit and scope of the invention may become apparent to persons skilled in the art who have had the benefit of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are provided by way of illustration only and should not be regarded as limiting the scope of the present invention. 
         FIG. 1  is an exploded view showing the assembly of the components employed in the vertical turbine pump of the present invention. 
         FIG. 2  is a cross-section in elevation of the assembled pump illustrated in FIG.  1 . 
         FIG. 3  is a cross-section showing details of the diffuser core, bearing cartridge, tubular adapter and drive shaft of the assembled pump illustrated in FIG.  1 . 
         FIG. 4  is a cross-section in elevation of the impeller of the pump illustrated in FIG.  1 . 
         FIG. 5  is a cross-section in plan of the impeller of the pump illustrated in FIG.  1 . 
         FIG. 6  is a graph illustrating the performance of a vertical turbine pump constructed according to the teachings of the present invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 and 2 , the illustrated vertical turbine pump, shown in its upright working position, comprises a bowl assembly  10  including a casing having a bulbous diffuser section  12  located between axially opposed relatively narrow upstream and downstream sections  14  and  16 , respectively. Located centrally within the casing diffuser section is a bulbous, acorn-shaped, diffuser core  18 . Three stationary diffuser vanes  20  extend laterally between the diffuser core and the inner wall of the casing diffuser section. The diffuser vanes are spaced equiangularly about the diffuser core and have upstream ends which curve about the diffuser core and generally axially extending downstream ends. A suction bell  22  is fastened to the casing upstream section. 
     A discharge conduit  24  fasten to the casing, forming a continuation of the casing upstream section, and incorporates a vane  26  which projects radially into the discharge conduit and extends axially along the direction of flow. This vane is aligned with the downstream end of one of the diffuser vanes and is joined to an interior surface of the discharge conduit. The vane  26  has an interior edge  28  disposed along a central region of the discharge conduit. The discharge conduit may comprise a single conduit or conduit sections which are fastened together. The length of the discharge conduit is chosen to accommodate the particular installation of the pump. 
     Fastened to the discharge conduit is a discharge elbow  30  incorporating a vane  32  which is aligned with the vane  26  in the discharge conduit. The vane  32  is joined to the interior surface within the outer bend of the discharge elbow and has an interior edge  34  aligned with the interior edge  28  of vane  26  in the discharge conduit. 
     Incorporated into the discharge elbow are a support for the pump drive motor and a bearing and seal assembly (not shown) for the upper end of the pump drive shaft. 
     The pump drive shaft  36  extends centrally and axially through the discharge elbow, the discharge conduit and the diffuser core. The lower end of the drive shaft carries an impeller  38  which is disposed beneath the diffuser core within the casing upstream section  14 . As shown in  FIGS. 4 and 5 , the impeller incorporates three spirally oriented vanes  40  arranged equiangularly about its axis of rotation and between inner and outer upwardly and outwardly flared shrouds  42 ,  44 . 
     As best shown in  FIG. 2 , a tubular shroud  46  extends centrally and axially through the discharge elbow  30  and discharge conduit  24  and encloses the drive shaft. At its upper end the tubular shroud is supported in the discharge elbow. At its lower end, the tubular shroud abuts the upper end of a tubular adapter  48  which engages a surface formed at the top of the diffuser core. An externally threaded connector bearing  50  joins the adjacent interiorly threaded ends of the tubular shroud and the tubular adapter. Within the discharge elbow and discharge conduit, the tubular shroud extends closely adjacent to the interior edges  28 ,  34  of the vanes  26 ,  32 , respectively. Intermediate bearings (not shown) may be provided within the tubular shroud to afford added support to the drive shaft if needed. If a tubular shroud made up of sections is used, these bearings may be externally threaded like lower connector bearing  50  in order to serve as couplings for the internally threaded ends of adjacent tubular shroud sections. 
     As illustrated in  FIG. 3 , a pair of axially spaced bearings  52 ,  54  within the diffuser core surround and rotatably support the drive shaft. These bearings are part of a bearing cartridge  56  which comprises a tubular housing  58  surrounding the drive shaft. The bearings, which may be metal or elastomeric sleeves, are fixed within the tubular housing by pressing, for example. The tubular housing fits closely within upper and lower formations  60 ,  62  provided within the diffuser core. Threads  64  formed on the upper end of the tubular housing engage with threads  66  formed within the tubular adapter to secure the tubular housing within the diffuser core. To effect axial alignment and prevent relative rotation between the tubular adapter and the diffuser core during installation or removal of the bearing cartridge, mating formations such as circumferentially spaced lugs  68 ,  70  may be provided on the abuting end surfaces of the tubular adapter and the diffuser core. Other means may be employed for securing the bearing cartridge within the diffuser core. For example, the tubular housing might carry threads which directly engage threads tapped into the upper or lower formations  60 ,  62  within the diffuser core. Or, the tubular housing might be threaded within an adapter pressed into the upper formation  60  within the diffuser core; this adapter could also secure the lower end of the tubular shroud. A retaining ring  70  may be employed in the lower formation of the diffuser core to prevent dislodgement of the tubular housing downwardly through the diffuser core. 
     To lubricate the bearings in the cartridge, water may be introduced through the bearing and seal assembly at the upper end of the pump drive shaft and into the tubular shroud. Alternatively, oil or grease may be introduced through a bore (or bones) in one or more of the diffuser vanes into the interior of the diffuser core and through a passage (or passages) extending through the sidewall of the tubular housing of the bearing cartridge. To accommodate flow of a viscous lubricant, radial passages may be formed through the bearings in alignment with passages in the tubular housing. 
     A formation, of circumferentially spaced lugs  59 , for example, may be provided at the lowermost end of tubular housing  58  for engagement with a mating formation on the end of a special tool to facilitate turning of the tubular housing during removal or installation of the bearing cartridge. 
     As best shown in  FIG. 4 , the lower end of the drive shaft is joined to the impeller by means of a split tapered bushing  72 . The taper of a bore within impeller hub  74  matches the externally tapered surface of the bushing. A key  76  fits within the slot in the bushing and keyways formed in the drive shaft and the impeller hub. Bolts (not shown) extend through openings in a flange of the bushing and into the impeller hub. Other openings in the flange may be tapped to accommodate jacking screws which van be used to forcibly separate the bushing and impeller hub. To reduce exposure of the joint between the drive shaft and the impeller hub to the pumped liquid and inhibit corrosion which might impede disassembly of the joint, an elastomeric sealing washer  78  is tightly fitted into the annular space between the end of drive shaft  36  and the counterbore  80  in the impeller hub  74 . Preferably, grease is applied to the joint prior to installing the sealing washer to provide an additional barrier between the joint and the pumped liquid. 
     In a typical installation, the vertical turbine pump of the present invention would be positioned upright with the suction bell disposed below the surface of a body of liquid to be pumped. The rotation of the impeller generates a flow of the liquid upwardly through the passage between diffuser section  12  of the casing and the diffuser core  18 , through the discharge conduit and discharge elbow. The diffuser vanes convert the diverging tangential flow from the impeller to an axial flow entering the discharge conduit. By virtue of the three diffuser vanes employed, there is little impediment to flow of solids through the diffuser section. The close spacing of the tubular shroud to the interior edges of the vanes  26 ,  34  within the discharge conduit and elbow effectively presents a unitary guide vane which prevents stringy materials from wrapping about the tubular shroud and impeding flow through the pump. 
     The vertical turbine pump of the present invention having three impeller vanes and three diffuser vanes achieves very favorable hydraulic performance, as shown in  FIG. 6  by the head versus flow curves which slope downwardly from left to right and the iso-efficiency curves which are labelled with percentages. (The curves were obtained from testing of a pump having a twelve inch diffuser exit). This performance is not achieved by a similarly configured vertical turbine pump having two impeller vanes and two diffuser vanes. In addition, the vertical turbine pump of the present invention, configured with two or three impeller vanes and three diffuser vanes, generates less pronounced pressure pulsations and achieves noticeably smoother operation than a vertical turbine pump having two impeller vanes and two diffuser vanes. 
     Servicing the pump bowl bearings in the field is simple and straight forward. After removing the pump from its working location and supporting the pump horizontally, the suction bell is separated from the pump bowl casing, the impeller is removed from the end of the drive shaft, the retaining ring  70  within the lower formation  62  in the diffuser core is removed and the bearing cartridge is turned to disengage the threads  64  at the upper end of the tubular housing from the threads  66  in the tubular adapter; the bearing cartridge can then be removed through the lower end of the pump bowl casing and replaced with another bearing cartridge having new or reconditioned bearings. The use of a special tool having an end formation which mates with the formation at the lower end of the bearing cartridge facilitates turning of the bearing cartridge during removal and installation. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.