Self-priming centrifugal pump

Abstract

A self-priming centrifugal pump has enhanced efficiency and performance characteristics and/or features which facilitate installation, inspection and maintenance of the pump. For efficiency and performance, the pump may include a smooth fluid flow path which enhances pump output for a given input power, including one or more of a specially shaped and directed volute discharge, a lack of internal stiffening ribs on the pump casing walls, a necked inlet and a rounded, flow-channeling outlet aperture. For maintenance and serviceability, the pump may include one or more of a coarse-threaded drive shaft and impeller with a concentricity feature, a combination port for both filling the casing and accessing the inlet flapper valve, and a drive disassembly system which facilitates attachment or removal of the drive system from the pump.

What is claimed is: 
     
         1 . A centrifugal pump comprising:
 a drive mechanism;   an impeller drivingly connected to the drive mechanism;   a casing having an inlet and an outlet, the casing comprising:
 an inlet-side wall having an inlet aperture formed therein; 
 an outlet-side wall joined to the inlet-side wall to form a cavity within the casing, the outlet-side wall having an outlet aperture; 
 a volute disposed in the casing and in fluid communication with the inlet aperture and the outlet aperture, the volute having a central opening sized to receive the impeller and a spiral-shaped fluid channel such that the fluid channel progresses radially outwardly toward a volute discharge opening, the volute discharge opening defining a longitudinal discharge axis which extends through the outlet aperture, 
   whereby the volute is adapted to receive fluid accelerated outwardly by the impeller, direct the fluid radially outwardly through the spiral-shaped fluid channel, and discharge the fluid along the longitudinal discharge axis toward the outlet aperture.   
     
     
         2 . The centrifugal pump of  claim 1 , wherein the casing defines a vertical center plane containing an axis of rotation of the impeller, and the longitudinal discharge axis is oriented to cross the vertical center plane. 
     
     
         3 . The centrifugal pump of  claim 1 , wherein the impeller defines a spin plane perpendicular to the axis of impeller rotation, the discharge axis is angled with respect to the spin plane. 
     
     
         4 . The centrifugal pump of  claim 3 , wherein the casing further comprises a partition wall interposed between the inlet-side wall and the outlet-side wall to form an inlet pump chamber and an outlet pump chamber, the partition wall having an inner drive aperture positioned to allow fluid communication between the inlet pump chamber and the outlet pump chamber via the inner drive aperture. 
     
     
         5 . The centrifugal pump of  claim 4 , wherein the discharge axis is angled away from the partition wall. 
     
     
         6 . The centrifugal pump of  claim 4 , wherein the casing further comprises a plurality of fastener bosses disposed within the outlet pump chamber and adjacent the outlet aperture, the fastener bosses each having a smooth, rounded outer surface. 
     
     
         7 . The centrifugal pump of  claim 6 , wherein the fastener bosses each have a convex distal surface and a concave surface at the junction between the convex distal surface and the adjacent inner surface of the outlet pump chamber. 
     
     
         8 . The centrifugal pump of  claim 6 , wherein the fastener bosses define a tear drop shape with a pointed end of the tear drop shape pointing toward the outlet aperture, whereby the fastener bosses promote laminar flow of fluid discharged from the volute and advanced toward the outlet aperture. 
     
     
         9 . The centrifugal pump of  claim 4 , wherein the casing of the pump comprises a sump region formed in a lower region of the outlet pump chamber, the sump region including a central portion in direct fluid communication with the impeller and a peripheral portion in indirect fluid communication with the impeller,
 the casing further comprising at least one drain channel in direct fluid communication with the peripheral portion of the sump region and in indirect fluid communication with the central portion of the sump region, whereby the at least one drain channel does not form any part of the volute.   
     
     
         10 . The centrifugal pump of  claim 9 , wherein the casing comprises a first drain channel and a second drain channel, the first and second drain channels positioned on opposite side of the volute. 
     
     
         11 . The centrifugal pump of  claim 1 , wherein the pump further comprises an inlet adapter connected to the inlet aperture, the inlet adapter including a necked portion in which a flow area through the inlet adapter gradually increases along a flow direction toward the inlet aperture. 
     
     
         12 . The centrifugal pump of  claim 11 , wherein:
 the pump further comprises an outlet adapter connected to the outlet aperture, the outlet adapter having a substantially cylindrical fluid passage, and   the inlet and outlet adapters configured to receive a common nominal size of fluid conduit and the necked portion of the inlet adapter leading to the inlet aperture having larger area than the outlet aperture.   
     
     
         13 . The centrifugal pump of  claim 1 , wherein the outlet aperture comprises an outlet transition area having a radiused internal edge operable to facilitate smooth flow therethrough, the outlet transition area defining a nominal radius at least equal to a minimum thickness of the outlet-side wall. 
     
     
         14 . The centrifugal pump of  claim 13 , wherein the nominal radius of the outlet transition area is at least 131% of the minimum thickness of the outlet-side wall. 
     
     
         15 . The centrifugal pump of  claim 1 , further comprising a plurality of stiffening ribs extending along and integrally formed with the inlet-side wall and the outlet-side wall of the casing, the stiffening ribs disposed only on an exterior surface of the casing. 
     
     
         16 . The centrifugal pump of  claim 15 , wherein a plurality of ribs on the outlet-side wall extend along a substantially vertical face of the outlet-side wall, round a corner at the junction between the vertical face a side face of the outlet-side wall, and extend along a front-to-back direction on the side face. 
     
     
         17 . The centrifugal pump of  claim 16 , wherein the plurality of extend radially outwardly along the vertical face from a central area of the vertical face. 
     
     
         18 . The centrifugal pump of  claim 1 , wherein the outlet-side wall of the casing comprises an outer drive aperture sized to receive the drive mechanism. 
     
     
         19 . A centrifugal pump comprising:
 a drive mechanism;   an impeller drivingly connected to the drive mechanism;   a flapper valve;   a casing having an inlet and an outlet, the casing comprising:
 an inlet-side wall having an inlet aperture formed therein, the flapper valve positioned at the inlet aperture to admit a flow of fluid into the casing via the inlet aperture while preventing a flow of fluid out of the casing via the inlet aperture; 
 an outlet-side wall joined to the inlet-side wall to form a cavity within the casing, the outlet-side wall having an outlet aperture; 
 a partition wall interposed between the inlet-side wall and the outlet-side wall to form an inlet pump chamber and an outlet pump chamber, the partition wall having an inner drive aperture positioned to allow fluid communication between the inlet pump chamber and the outlet pump chamber via the inner drive aperture; 
 a combination port formed in the casing near the flapper valve, the combination port sized and positioned to allow access to the flapper valve by a maintenance person, and to allow fluid to be added to the inlet pump chamber; and 
 a fill vent formed through the casing on an opposite side of the partition wall as the combination port, such that the fill vent allows fluid communication between the outlet pump chamber and the ambient environment, whereby liquid added to the inlet pump chamber is allowed to flow to the outlet pump chamber via the inner drive aperture while air contained in the outlet pump chamber vents to atmosphere via the fill vent. 
   
     
     
         20 . The centrifugal pump of  claim 19 , further comprising a combination port cover comprising:
 a fill port cover portion sized to be received over the combination port to fluidly isolate the combination port from the ambient environment; and   a fill vent cover portion sized to be received over the fill vent to fluidly isolate the fill vent from the ambient environment.   
     
     
         21 . The centrifugal pump of  claim 20 , wherein the fill vent cover portion is formed as a forward extension of the fill port cover portion in order to pass over the partition wall onto the fill vent. 
     
     
         22 . The centrifugal pump of  claim 20 , wherein the fill port cover portion and the fill vent cover portion are integrally, monolithically formed as a single component. 
     
     
         23 . The centrifugal pump of  claim 19 , wherein the outlet-side wall of the casing comprises an outer drive aperture formed therein, the outer drive aperture sized to receive the drive mechanism. 
     
     
         24 . A centrifugal pump comprising:
 a drive shaft having a first coarse thread and a first centering feature;   an impeller drivingly connected to the drive shaft, the impeller having a second coarse thread and a second centering feature, the second coarse thread engageable with the first coarse thread of the drive shaft to selectively rotatably fix the drive shaft to the impeller, and the second centering feature engageable with the first centering feature to concentrically align the impeller with the drive shaft.   
     
     
         25 . The centrifugal pump of  claim 24 , wherein the first coarse thread of the impeller is a female thread and the second coarse thread of the drive shaft is a male thread. 
     
     
         26 . The centrifugal pump of  claim 24 , wherein the first and second coarse threads are trapezoidal threads. 
     
     
         27 . The centrifugal pump of  claim 24 , wherein the first centering feature is a bore formed in the impeller and the second centering feature is a nubbin formed at a distal end of the drive shaft. 
     
     
         28 . The centrifugal pump of  claim 27 , wherein the nubbin and the bore fit together with a radial clearance of less than 0.004 inches. 
     
     
         29 . The centrifugal pump of  claim 24 , wherein the drive shaft is part of a drive mechanism further comprising:
 a casing having an inlet and an outlet, the casing comprising:
 an inlet-side wall having an inlet aperture formed therein; 
 an outlet-side wall joined to the inlet-side wall to form a cavity within the casing, the outlet-side wall having an outlet aperture; 
   a drive shaft housing affixed to the casing, the drive shaft rotatably received in the drive shaft housing;   at least one bearing supported by the drive shaft housing and rotatably supporting the drive shaft;   a drive side wear plate connected to the drive shaft; and   a biasing element between the drive side wear plate and the impeller which biases the drive side wear plate toward the drive shaft housing and away from the impeller.   
     
     
         30 . The centrifugal pump of  claim 29 , wherein:
 the first centering feature of the drive shaft comprises a locating nubbin at a distal end thereof;   the second centering feature of the impeller includes a locating bore sized to receive the locating nubbin;   the drive shaft is operably connected to the impeller by engagement of the first coarse thread with the second coarse thread, thereby allowing for a radial play in the drive shaft, and   the drive shaft is concentrically located with respect to the impeller by a close-tolerance interaction between the locating nubbin and the locating bore such that the radial play is eliminated.   
     
     
         31 . The centrifugal pump of  claim 30 , wherein the radial play is less than 0.004 inches. 
     
     
         32 . The centrifugal pump of  claim 29 , wherein the outlet-side wall includes an outer drive aperture formed therein, the outer drive aperture sized to receive the impeller, the casing further comprising:
 a partition wall interposed between the inlet-side wall and the outlet-side wall to form an inlet pump chamber and an outlet pump chamber, the partition wall having an inner drive aperture positioned to allow fluid communication between the inlet pump chamber and the outlet pump chamber via the inner drive aperture.   
     
     
         33 . A centrifugal pump comprising:
 a drive mechanism;   an impeller drivingly connected to the drive mechanism;   a casing having an inlet and an outlet, the casing comprising:
 an inlet-side wall having an inlet aperture formed therein; 
 an outlet-side wall joined to the inlet-side wall to form a cavity within the casing, the outlet-side wall having an outlet aperture; 
 a bore extending inwardly from the exterior of the outlet-side wall whereby the bore is accessible to a user of the pump; 
   a drive disassembly system comprising:
 a guide rail sized to be snugly received within the bore; and 
 a rail guide having a bearing and a flange fixed to the bearing, the bearing sized to be slidingly received on the guide rail while the flange is fixed to the drive mechanism, such that the drive mechanism can be assembled into or removed from the casing while being supported by the guide rail. 
   
     
     
         34 . The centrifugal pump of  claim 33 , wherein the casing further comprises:
 a partition wall interposed between the inlet-side wall and the outlet-side wall to form an inlet pump chamber and an outlet pump chamber, the partition wall having an inner drive aperture positioned to allow fluid communication between the inlet pump chamber and the outlet pump chamber via the inner drive aperture; and   a stiffener extending through the outlet pump chamber from the outlet-side wall to the partition wall, the stiffener having the bore formed therein as a blind bore.   
     
     
         35 . The centrifugal pump of  claim 33 , wherein:
 the drive mechanism includes a housing secured to the casing by a plurality of first fasteners passing through a corresponding plurality of annularly arranged apertures formed in the housing, the first fasteners threadably received in the casing; and   the flange of the rail guide is secured to the casing by a plurality of second fasteners threadably received in a plurality of annularly arranged apertures formed in the flange,   the plurality of annularly arranged apertures formed in the flange of the rail guide oversized relative to the size of the plurality of second fasteners, whereby alignment of the drive disassembly system relative to the casing is a function of interaction between the guide rail and the bearing rather than between the flange and the casing.   
     
     
         36 . The centrifugal pump of  claim 33 , wherein an outer surface of the guide rail includes a notch positioned to be adjacent the exterior of the outlet-side wall when the guide rail is fully received in the bore, the drive disassembly system further comprises a rail keeper shaped to engage the notch and thereafter be secured to the casing such that the rail keeper and the casing cooperate to axially fix the guide rail with respect to the casing. 
     
     
         37 . The centrifugal pump of  claim 36 , wherein the drive disassembly system further comprises a caster selectively fixed to the drive mechanism, the caster positioned to cooperate with the guide rail to support the drive mechanism while the drive mechanism is assembled into or removed from the casing. 
     
     
         38 . A method of disassembling a drive mechanism from a centrifugal pump, the method comprising:
 inserting a rail into a bore formed in a casing of the pump, such that the rail fits snugly within the bore;   sliding a rail guide over the rail and into engagement with the pump;   affixing the rail guide to the drive mechanism while maintaining the rail guide in sliding engagement with the rail; and   disconnecting the drive mechanism from the casing and sliding the drive mechanism away from the casing using the support of the rail.   
     
     
         39 . The method of  claim 38 , further comprising affixing a caster to a lower portion of the drive mechanism, the step of disconnecting including rolling the caster on a support surface. 
     
     
         40 . The method of  claim 38 , further comprising reconnecting the drive mechanism to the casing using the support of the rail. 
     
     
         41 . The method of  claim 38 , further comprising, after the step of inserting the rail into the bore, of connecting a rail keeper to the casing, the rail keeper engaging a notch formed in the rail to axially fix the rail relative to the casing.