US2694981A - Centrifugal pump - Google Patents

Description

N 3, 1954 R. H. DAUGHERTY ETAL ,6

CENTRIFUGAL PUMP 3 Sheets-Sheet 3 Filed Aug. 27, 1949 United States Patent CENTRIFUGAL PUMP Roland Henry Daugherty, Minneapolis, Hans A. Stadem, Columbia Heights, and Edward H. Rouse, St. Louis Park, Minn.

Application August 27, 1949, Serial No. 112,812 4 Claims. (Cl. 103111) This invention relates to centrifugal pumps, and particularly to a pump, in which features have been incorporated, which increased efficiency, lower maintenance costs and prolong life.

Much has been done in the field but there is still room pump, that has greater with less expense, and

of centrifugal pumps,

for improvement in providing a efficiency, that can be maintained that will have a longer life. This is particularly true in meeting present day needs with a small pump for farm, factory and industrial use. Such a pump should have good delivery, be light in weight, so it can be easily transported, set up and handled, and it should be available at a reasonable cost. To provide a small light pump with increased delivery, means ability to operate under higher pressures and elimination of disturbing influences. To provide this in a pump, that will render long lasting trouble free service, and which may be disconnected for maintenance with minimum work, requires special consideration of structure.

An important object of our invention is to provide a centrifugal pump, with an arrangement of ports respectively through the front and rear shrouds of the impeller, directing secondary flowage of fluid, eliminating disturbing influences and turbulence, so that maximum unhindered delivery results.

Another important object is to also provide such arrangement of ports, so there is a scavenging of grit and foreign matter from the seal areas, eliminating wear on seal surfaces and bearings, resulting in longer life, and also minimizing leakage to better sustain higher pressures.

Another important object is to provide a pump with such construction, that all Working parts may readily be removed for inspection, without detaching casing from piping or its setting, saving maintenance expense directly and also resulting in keeping a closer check on condition of the pump.

Another important object is to provide a pump with i such construction, that a housing to support impeller shaft bearings is integral with and bracketed from pump casing, eliminating a separate standard to support the shaft.

Another object is to provide a pump, which although possessing these desirable features, can be economically manufactured.

Other objects will be apparent from the description and appended claims.

For a full disclosure of our invention, reference is mlade to the description following and to the drawings, in w ich- Fig. 1 is a side elevational view showing the drive side of our pump.

Fig. 2 is a sectional view thereof, taken on the line 22 of Fig. l, but drawn on a larger scale.

Fig. 3 consists of diagrams of arrangements of ports in front and rear shrouds of impeller.

Fig. 4 is an end elevation view of the seal assembly, as viewed from the left side in Fig. 2, but drawn on a still larger scale.

Referring now to the figures of the drawing, the ref erence characters and 11 indicate respectively the two alloy cast iron castings, which comprise the entire casing for the pump. The casting 10, which is the volute casing, includes integral therewith, flanged inlet and outlet con nections 12 and 13 and a base 14. The casting 11, serving as a cover, includes integral therewith, a tubular housing 15, which provides support for bearings 16 for impeller shaft 17. This shaft is preferably made of Monel steel, so it will have long lasting qualities without corroaction of pressure existing component force toward the shaft.

sion. It will be noted, that the construction of the housing 15 is such, that a sealing edge 18 is provided to cooperate with a shaft seal assembly. This seal assembly is denoted generally by the numeral 19. It rotates with the shaft and is positioned by a spring disk member, having a plurality of fingers. There is free flow of fluid through spaces between the fingers.

Referring to Fig. 2 and Fig. 4, this seal assembly consists specifically of a sealing member 19a, a resilient ring 19b between the sealing member and the shaft 17, and a spring member having a plurality of fingers 19d. This seal assembly acts against the sealing edge 18 of the housing 15. The sealing member 19a is axially movable and is preferably made of bronze. It has a bore of a diameter to freely encompass the driving shaft 17 of the pump, without contact. A finished sealing face of the sealing member, coincides when rotated, with the finished sealing edge 18 of the housing. The drawing discloses plane surfaces coinciding under relative rotation, but such surface might in cross section be on the arc of a circle or of other shape, so long as there is an annular arrangement and the surfaces register under rotation. It will be observed, that the housing sealing edge is substantially narrower than the sealing face of the sealing member. It is also finished circumferentially on the inside and outside, concentric with the axis of the shaft 17. By reason of this, the wearing of the edge 18 on the sealing member is recessed truly into the bronze sealing member face. This in fact increases with wear the effectiveness of the sealing surface, since the area is somewhat increased, and also by reason of the re-entrant angles, the path of pressure escape is more tortuous. The resilient ring 19b between the sealing member and the shaft 17 is of circular cross-section and 1S commonly called an O ring. It encompasses the shaft 17 and is seated in an internal recess of the sealing member 19a. This ring is preferably made of a synthetic rubber, to withstand damage from heat, oil and substances that may be in the fluid. The internal recess has an inward sloping incline and fillet. This incline and fillet favors a tighter seating of the 0 ring, by in the pump, resulting in a The ring of course rolls or slides with substantially a line contact on the shaft, as shown, so as to take care of any end movement of the seal on the shaft. It will be noted, that the hub construction of the impeller is of such diameter, that clearance is provided and permits the hub to rotate within the internal recess of the sealing member 19a, permitting substantial end movement, in case the wear on the face of the sealing member 19a requires it. It will also be noted, that clearance between the housing and balance of the seal assembly permits of an equivalent end movement. The sealing member 19a has symmetrically spaced recesses provided in that side of it, which is opposite to the sealing face. The spring member 19c has fingers 19d fitting into each of the recesses, and it has a convex shape thrusting against the sealing member. The spring member has two diametrically opposed lugs 192, extending into oval shaped recesses, formed in the impeller. The relative spacing of parts is such as to develop the tension in the spring, and the width of the oval shaped recesses allows for slight lateral movement of the ends of the lugs 192, when the spring member 190 is flexed. The spring member compensates for any permanent wear on the face of the sealing member 19a, and absorbs any variations of thrust imparted by the impeller, so that the sealing member rotates with its sealing face coinciding with the finished sealing edge 18 of the housing, resulting in uniform wear and a tight sealing surface. It will be noted, that the section of the impeller adjoining its hub, has a slight negative angle, to provide clearance for the sealing member, if the spring member is flexed in extreme reverse.

Referring more particularly to the casing, it will be noted, that the cover casting 11 is secured to the main casing casting 10 by a series of stud bolts 20. By removing these stud bolts, the cover 11 can be removed from the pump, and included therewith are all the moving parts of the pump, which have hearings in and are supported by the housing 15. It is apparent, that the moving parts can quickly be removed for inspection and attention, since there is no need to disconnect piping at inlet or outlet or disturb the base in its setting. This saves much direct maintenance expense, and since inspection is not burdened with a heavy job of dismantling pump and pipe connections, a closer check on condition of pump is kept, so matters needing attention are taken care of in time. Our construction requires a minimum length of shaft, centered and supported by the housing 15, with no overhanging brackets or separate standards. integral with the cover casting 11 and shaft housing 15, are full length ribs 21, and interspersed between these are bracket ribs 22, which combined with a cantilever beam protrusion 23, provide very ample structural support of housing for impeller shaft and bearings, withoutv any separate end support of the shaft. The closely coupled up pump construction is made possible by this structural'support, which combined with the demountability above described, gives the novel feature of easily removing all moving parts, without disturbing setting or piping.

included in our construction are quite conventional elements, consisting of a lubricator 24, a water fiinger 25, a drain hole '26 for leakage water, locking snap rings 27 for ball bearing assembly, a spacing sleeve 28 between bearings, a gasket 29 between casing and cover castings, a keyway 30 in the shaft for securing a driving pulley, casing and bearing housing, to serve variously for inspecting, draining, venting, priming, testing and greasing.

The impeller, which is preferably of integrally cast bronze, is secured to the shaft 17 by a key 32 and an acorn cap nut 33, with a lock washer 34. It consists of a rear shroud 35 and a front shroud 36, with a series of vanes 37, formed between the shrouds and extending to the edge shroud has a collar construction 38 extending forwardly, machine fitted externally and bearing in a machined bore 39 in the casing casting 10. It will be noted, that the collar 38 and bore 39 are cut with corresponding steps in same. This facilitates insertion of the impeller assembly, which when also in assembly with the shaft housing and easing cover 11, needs piloting in directing it to a fit in the bore, and likewise the flanged cover simultaneously into the casing casting. The collar 38 and bore 39 form a front end bearing, with a close fit forming a seal to reduce leakage flow. The step cut, referred to, is of even greater importance, in creating a tortuous passage to reduce leakage flow. In Fig. 2, full line arrows indicate leakage flow, as it would affect front and rear seal areas, if no special provision were made. To direct this secondary flowage of fluid, which may take place around the entire perimeter of the seals, we provide a port 40 in the front shroud and a port 41 at a point diametrically opposed in the rear shroud. The ports are preferably provided with slightly chamfered edges on both sides. This leakage flow then takes place almost entirely only through these ports, as indicated by the dotted arrows in Fig. 2. This is because the high speed of the water through the vane chambers, produces a diminution in pressure in the ports, to cause leakage flow from communicating spaces to be picked up by the impact of the high speed stream. instead of leakage fizzing around the entire perimeter of the seal, which causes turbulence hindering delivery. This detrimental effect of turbulence would occur principally at the front seal edge at the intake of the pump. At the rear seal, this leakage flow is not detrimental to delivery, unless leakage becomes excessive, resulting in drop in pressure, as this leakage is discharged through the drain hole 26. At the rear seal, however, by the" same action, grit and foreign matters are scavenged from the seal area through the port 41. This is important with respect to the rear seal, as the vital parts 'of the seal and the bearings, which it protects, will have a longer life, and at the same time minimize leakage to better sustain higher pressures. There is of course also helpful scavenging through the port 40, but the detrimental effect at the front seal is turbulence. Tests made with a one inch discharge pump, handling water containing a considerable amount of grit, develop that operating at deliveries ranging from to 40 gallons per rn inut With /8 inch diameter ports in diametrically opposed position,

as above desenbed, the delivery on the average was It is self supporting and self contained.

and threaded pipe plugs 31, tapped into pump of the rear shroud. The front This takes place naturally and quietlyu ens;

4 10% greater with the same R. P. M., compared with the same pump with the ports plugged. The reduction of the leakage flow across the'front seal, by the shunting provided for by our construction, definitely stills turbulence and substantially increases the delivery.

Experiments with ports of different diameters develop, that there is a definite relation of hole diameter to the size of the impeller for the best results. This is again subject to variation, due to type and condition of fluid.

tects the shaft bearings. L body, turbulence may be of lesser consideration. The

a single port.

This variation also calls for different arrangements of holes. With' a water like fluid, without much grit, the matter of turbulence is of primary consideration. As this prevails in the front seal area, it may require a Series o ro ts hrough h fr nt sh ud i stead f If the same fluid be well loaded with grit, it may also require a series of ports through the rear shroud, instead of a single port, as the damage from grit predominates in the rear seal area, which proifthe fluid be of a heavier requirements may vary, from a port in each of the shrouds diametrically opposed to each other, to a series of ports inboth of the shruds and also with a series in either one with one port in the other. The size of the pump is also a factor, as well as the fluid conditions above stated. So that impeller balance is not affected, all ports must be on a circumference about the center of rotation, and all ports of the front and rear shroud combined should be equi-spaeed on this circumference.

Certain symmetrical arrangements would not destroy balance, but the combined equi-spaced arrangement would be infallible. Dilferent arrangements are illustrated by diagrams A, B, C and D of Fig. 3 In this diagram, the ports through the rear shroud are indicated by full line circles and the ports through the front shroud by dotted squares, since same are through the collar and at right angles relative to ports through the rear shroud. The ports through the front shroud determine radial distance from center of rotation. The simplest arrangements with a minimum number of ports are used for illustration. Any requirement of a greater number of ports would be handled accordingly.

In providing an improved centrifugal pump of superior performance, longer life and easier maintenance, it is apparent that ourpump has many advantages. It is of simple construction, with a minimum number of parts, so that it can be produced at a low cost. By increasing speed, it will work against a high head and produce pressures up to lbs. per sq. in. This, together with its light weight, makes it valuable for booster service, fire fighting and many different uses on the farm, on estates, and around the factory. For these purposes, we provide a portable wheeled unit on which we mount the pump, a priming tank and a gas engine or electric motor. By reason of the materials from which the pump is made and the scavenging effect of its construction, it is particularly adapted to pumping of chemicals and liquids containing grit and deleterious substances as well as water, oils, gasoline, kerosene, alcohol and the like. Instead of the pump materials described, it may be desirable in special cases to substitute other materials to resist attack of the fluid pumped. All in all, our pump well meets present day needs.

While we have shown and described a preferred form of our invention, it is obvious that many changes, which are within the scope of our invention, will be apparent to those skilled in'the art. We therefore desire to be limited only by the scope of the appended claims.

What we claim is:

l. A centrifugal pump impeller of the class described rotatably mounted in a casing, said casing having a fluid inlet at its center and a tangential discharge outlet and fiuid seals respectively at front and rear of said'irnpeller, and the interior contour of said casing providing a sealiugedge for and a space surrounding said rear seal, said front seal consisting of an externally machine fitted collar extension bearing in a machined bore, said rear seal rotating with the impeller shaft and consisting of a sealing member with a sealing face and a resilient ring between said member and said shaft, and a spring disk member arranged to thrust said sealing member against said sealing edge of said casing, said spring disk member having a plurality of fingers with open spaces between said fingers allowing for free flow of fluid, said impeller comprising a front'shroud having a clearance space between it and said casing except for a forward collar extension toward inlet forming a bearing and a part of said front seal, a rear shroud concentric with said front shroud, a plurality of vanes shaped and spaced to provide fluid passages between said shrouds, ports of pre-determined diameter at diametrically opposed positions, respectively, through said shrouds, the port through said front shroud extending through said collar at a location giving direct access to said clearance space between said front shroud and said casing, said ports located at the same radial distance from axis of impeller as determined by port through said collar of front shroud, the port extending through said rear shroud having access to said space surrounding said rear seal through spaces between fingers of said spring disk member, said ports by reason of their location with respect to course of water of high speed through said vane chambers and also with respect to leakage flow areas bring about a diminution in pressure within same, resulting in a flow from said areas and which is picked up by the impact of the course of water of high speed, whereby leakage flow fizzing around entire perimeter of seals is eliminated, thus reducing turbulence in front seal with increased delivery and increasing scavenging at rear seal with less wear on seal and bearings and consequently less pressure loss.

2. An impeller as claimed in claim 1, characterized by a plurality of ports of pre-determined number instead of a single port through the front shroud, whereby turbulence of particularly effervescent fluids pumped is reduced resulting in increased delivery, said ports in combination with the port in the rear shroud being spaced for balance about axis of said impeller.

3. An impeller as claimed in claim 1, characterized by a plurality of ports of pre-determined number instead of a single port through the rear shroud, whereby scavenging is increased for fluids well loaded with grit but which have a relatively heavy body with little turbulence, resulting in longer life of shaft seal and bearings and reduced pressure loss from leakage, said ports in combination with port in the front shroud being spaced for balance about axis of said impeller.

4. An impeller as claimed in claim 1, characterized by a plurality of ports of pre-determined number through each shroud instead of a single port through each of the front and rear shrouds, whereby a fluid which is particularly effervescent and also at the same time loaded with grit may be handled so that turbulence at front seal is reduced resulting in increased delivery and scavenging at rear seal is increased resulting in longer life of shaft seal and bearings and reduced pressure loss from leakage, said ports in combination with each other being spaced for balance about axis of said impeller.

References Cited in the file of this patent UNITED STATES PATENTS

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