US2684033A - Centrifugal pump - Google Patents

Description

July 20, 1954 H. M. MONTGOMERY ETAL 2,684,033

CENTRIFUGAL PUMP Fild Dec. 50, 1949 INVENTORJ. Velma-E m: Mammal-115mm fammz'w W7. fiM/FH AHTTQWMEYW Patented July 20, 1954 2,684,033 swar s UMR Hog-ace M. Montgomery and Edward M. Smith,

Mansfield; Ohio," assignor's *td'Barn"es Mannfaotu'ring00.;Mansfield, Qhim-a corporation of Ohio 1 This invention elates to improvements in a centrifugal puihp and 'more particiilaily' to a pump adapted to be driven by a motor of very 's'iiiall hoijs epoyver such as one-fiftieth"'horsepower. It has long been desirable to provide centrifngal u ps for very light duty; Such as dishivashingand adapted to'be driven by such small motors as those of say one fiftiethhorsepower. One of the difficulties heretofore encountered in providing such alpiirn j; is the reduction of 'ii'iction load both at starting and at'full load, and one of the objects of the present'invention is to so reduce the friction of such a'centriingal p in lp both b vane lea a qes an im ev n en fi in he seal around the shaft which extends into the b imp ham e t- Another object of the present invention is to provide a centrifugal pump of the type'de'scribe-cl with critical clearances hetween the'blades and the housing which contribute to high e ciency in pump nd a 'it e Sa tim lm t ou pump to handle efie'ctively small solids in the stream, such as garltioles of food in dish washing ap ara u 1 Another object of the present invention is to provide a seal about a' shaft entering 'a punip chamher so constructed and aijr ed thatfthe pump chamber is" well sealed. aga nst {l kage wh n the p imp s dlje d the embraci a of the seal 'onthe shaft is antoniatioally reduee'd as the pump loagl'inier eases. 1

Another object ofthje'fpi esent invention is to provide a pum 11 ng vanes of resilientfibiit iai 'lystifi rhbberlilge ateri'a'l so constructed and ai i'anged th t' thevanes extend "substantially" in lia'dial dii'ecti'on' undei 'low'loads but Whieh "tend {totake a reverse irivo lu'te bend. when the pump is under heavy d therebyautomatically main- Itaiziingthe efiicie cylof the l'piiiniiunder various .s. V. ,4 1 V t Another object of the present invention is to provide a ,novei'cqm ation of an electric motor having a beating h'ess'conoentric with" the drive shaft 'theietanii "s'hell' neans rigid 'ivith the pump housing and conelentfic with the eylinldr'ical pump" chainbeiiflthese parts so' coasting when assemble'dithat the motor 'beafing' boss centiersia n d alines the pump'snnmna the pnnip ,housingor'pnm ing'chamheil Aifn 'ther object ofthe present invention to provide, in oonibina'tion with the b'enefits of "the breeeding pai a'giif aphljan end I-fa'ce on the motor leiiteri orly 'Q f the boss lying in Plane noi inal to the m q fiif ii' e h {w h an e 'O 2 Elaims. (c1. 103 103) the shell means also lying in a plane normal to the shaft Wherebyengag'ementof the shell means against therhotorefidface accurately positions the pnmp'im'p'eller in the'pu'mp' housing." 5 Still another object iofthe present invenmonis to"15rovide"an"end plate'ioi" the pump housing'vvhich is""a "bolting Bracket for securing the pump housing totli'e' motoianol at the same time provides a seal 'for'closing the outer end of the'bunip'hous'ing, this'end-plate alsocarrW iflg thesiiction flange. Other objectsandadvantages of our invention will" be' apparent "from the-accompanying drawin'gs 'anddesriptio'rr and the essential features thereofwilrbe setfforthin the'appended claims. lnthe'drawings', Fig.1 is a sideelevational View of our novel pump assembled to its driving-motor; Fig. '2 Ban end"'ielei/"ation'of' thesanie'taken at'the iight-hahdend' of Fig. '1; Fig; 3 isanenlargedvieivsimilar to Fig. 1 with the right-hand po'i't'ion' "thereof in" central sectional' VieWtci more" clearly" Show "the "construcr w 1W n i- Fig. 4 is an enlarged fragmental sectional view through'the 'searp'drtionbf Fig. 3;" Fig."5i 'n -agpiental" sectional view similar to Flgf bfit showing''the'*'position Of the'eal, sornewhateiiag'geiated, at'toiimotor speed; while Fig. 6'is anen d 'l'vational' view of the vanes of the pumgi'teken he the linea -6 6i Fig." 3

and slightly i'e'ducedfi izethe'iefroin.

Thedrawmesiniewtui mpfoved pinup secured k meme J31 whichi'ii the pi esntfiiistance is abrie-fifti e'thh"isepbwef motor 35 'havingtwo bolifi ai'ld 'ppemt ng at volts 1 close "b the assist enters the pump chamber. A seal 20 is provided between the shaft i4 and the pump housing for the purpose of closing the opening 190 against egress of fluid from the pump or ingress of air to the pump. A retaining washer 2i secures the seal in position and the washer is held in place by peening a portion of the pump housing end wall over on the outer face of the washer as by means of a center punch as indicated at H.

Shell means [Ed is provided at the motor end of the housing 9 for positioning the housing [9 relative to the motor. This consists of upper and lower arcuate shells, each of about 135 in extent, rigid with the housing i9 and extending toward the motor iii and having an end at [96 terminating in a plane at right angles to the shaft H. The inside diameter of the portions i911 is adapted to snugly embrace the boss 2. The shell portions Hid are concentric with the inside diameter of the housing portion i911 and, since the boss I2 is concentric about the shaft I i, when the parts are assembled as shown in Figs. 1 and 3 the parts [2 and 19d serve to hold the pump chamber properly alined in both horizontal and vertical planes with respect to the motor E and its shaft H. Since the impeller i8 is fixed on the shaft M, which in turn is fixed to the shaft ii, the abutment of the end [9e of the pump housing against the motor face [3 properly positions the impeller with respect to the face i9 of the pump chamber.

An end plate 22 serves to close the open outer end of the pump housing and at the same time serves as a clamping bracket to secure the housing to the motor it. The walls 59a terminate at the open end of the pump housing in a plane at right angles to the axis of the pump housing. An annular recess 22a in the end plate 22 snugly receives the outer ends of the walls i911. A sealing gasket 23 is provided between the parts to make a liquid tight seal. On the outer face of the end plate there is provided a stiffening rib 22b extending across the end plate and providing outstanding ears 220 through which pass bolts 24 which are threaded into the motor I0. Nuts 25 and lock washers 26 clampingly secure the end plate in the positions shown in Figs. 1 and 3 so as to close the open outer end of the pump housing and to secure the housing to the motor H in proper position. Centrally of the end plate there is provided a suction flange 2'! which carries the fluid inlet 28 communicating with the pump chamber l6 centrally thereof. A

fluid outlet 29 is provided tangentially of the chamber it and communicating therewith.

The pump impeller 18, as clearly seen in Fig. 6, comprises a hub portion [8a having an internal diameter of about /4 inch and an external diameter of about inch. This hub portion is bonded to the finely knurled portions ll of the shaft [4. The impeller also comprises two radially extending vanes i821 extending diametrically opposite each other away from the hub portion i8a. In this form of our invention, where the pump chamber it has an internal diameter of 1% inches, the vanes [to extend 1% inches from tip to tip, leaving a clearance all around between the vanes and the pump housing walls Hie of about inch. In this form of our invention, each vane has a thickness A near the hub of about inch and a thickness B at the outer end of about inch. The vane thickness tapers gradually from the base to the outer tip. In this form of our invention, the dimension from the root to the tip of each vane is about 1% of an inch. Our invention comprises the use of rubberlike material which is resilient but fairly stiff. We find that a hardness of 75 to 30 durometer is about right in the present instance to give maximum efiiciency. It results from this construction that as the pump is turning in the direction of the arrow of Fig. 2, the vanes I82) at low loads hold a substantial radial position as shown in Fig. 6 and is indicated in dotted lines in Fig. 2. However, as the load increases, the vanes bend backwardly at the tip and the graduated thickness of the vanes tends to cause them to take the form of an involute curve bending backwardly with respect to the direction of rotation as indicated in dot-dash lines in Fig. 2. The greater the speed of the pump and the greater the load on the pump, the greater the curvature of the vanes so that the efficiency is automatically increased as the load increases. The pump here shown is designed to pump about eight gallons per minute of water at the top capacity of the one-fiftieth horsepower motor.

As previously mentioned, one of the purposes of the present invention is to reduce the frictional drag of the pump on the motor while at the same time retaining pumping efficiency. We have found that in a pump of the size described, the dimension C as shown in Fig. 3 between the side edge of the vane nearest the motor end of the pump housing should be about inch. We have also found that the dimension D as shown in Fig. 3 between the other side of the vane and the end plate 22 should be about inch for best eiiiciency. It has previously been taught by many that centrifugal pumps should have the minimum clearance between the vanes and the housing. In the present instance, we have obtained very high efficiencies with the construction as clearly shown in Fig. 3 where there are clearances on all sides of the vanes.

Another advantage of the clearance D and the clearance between vane tips and the housing, coupled with the resilient quality of the vanes, is that we are enabled to pump liquids containing a considerable proportion of solids such as particles of food, toothpicks, etc. found in dish washing applications.

We have found that the seal 26 between the shaft and the pump housing is one of the very critical spots in this design and therefore it will be shown and described in great detail. The seal is of cup-shape and comprises uninterrupted annular ring of resilient rubber-like material of 45 to 50 durometer hardness. The seal is U-shape in section as clearly shown in Figs. 4 and 5. The radially inner lip of the U-shape section is adjacent shaft i4 and has a free edge 26 which sealingly engages shaft i i. In dot-dash lines in Fig. 4, there is shown the unstressed condition of the seal. The thickness at the base of the U-shape section as indicated at E in Fig. 4 is about .040 inch. The thickness at F and G is approximately .025 to .030 inch. In unstressed condition, as shown in dot dash lines in Fig. 4, the inner and outer leg of the U-shape section flare outwardly at about 8% from an axial position. The outside diameter between the lips as indicated at K in Fig. 4 in the unstressed condition is approximately .716 inch. This is compressed inwardly to the full line position of Fig. 4 to a dimension of about .670 inch. The inside dimension L as indicated in Fig. 4 in unstressed condition is approximately .226 inch. This is extended outwardly by engagement with the shaft portion I4 to a dimension of .250 inch.

To show how critical this seal is, it may be mentioned that when the dimension L in unstressed condition was .236 inch, the seal was unsatisfactory because it was too loose. When the dimension L was .220 inch, the seal was unsatisfactory because it was too tight. In Fig. 4, the seal 2i: is shown in its approximately correct position in full lines when the pump is idle. In Fig. 5, the position of the seal at top speed of the pump is shown slightly exaggerated. It will have been noted that the vanes of the pump impeller have no shrouding and therefore there is free access of the pump suction near the shaft E4 on both sides of the vane. In other words, the suction at the hollow side of the cup-shape seal 20 is approximately the same as the suction at the suction flange 21. This suction inside the seal combined with the fact that the outer portion of the seal as indicated at 30 in Fig. 5 is open to atmosphere causes a differential pressure on opposite sides of the zone 3| as indicated in Fig. 5. With greater speed of rotation, the vacuum inside the housing is greater, thus causing a greater differential relative to atmospheric pressure outside. The tendency is to bend the resilient lips very slightly where the inner leg of the U-shape joins the base so that less of the lip is in engagement with the shaft portion is at top speed as indicated in Fig. 5 than at idle or lower speed as indicated in Fig. 4. When the dimension L (unstressed) changed to .226 inch, the lips at F hug the shaft sufficiently at the zone 3| at top speed of this model to prevent the intake of air at this point. The U-shape form of the seal also takes care of slight misalinements of the shaft portion with respect to the housing. It results from this construction, that the seal contact area on the shaft is decreased as the suction increases, thus reducing the load on the motor. As a matter of fact, at the very start of pump operation, which is the critical period as regards load on the low starting torque motor, the friction load due to the seal 20 drops off as the fluid pumping load begins to build up at the impellers or vanes.

While the embodiment shows the pump close coupled to an electric motor, other drive means may be used and the pump characteristics remain the same.

What we claim is:

1. A pump comprising a housing having a generally cylindrical chamber and end closure members therefor, there being a fluid outlet positioned near the periphery of said chamber, one of said closure members having a fluid inlet centrally of said chamber, the other of said closure members having a central through opening, a driven shaft extending through said opening axially of said cylindrical chamber, an impeller fixed on said shaft and having radially extending vanes free of shrouding, said vanes being free of engagement with the walls of said housing by reason of a clear space provided between the sides and ends of said vanes and said housingsealing means closing said opening between said shaft and said housing, said sealing means comprising an uninterrupted resilient annular lip extending about said shaft and generally parallel thereto and having a free edge extending toward the pump chamber, the interior of said annular ring communicating with the central interior portion of said chamber, said free edge sealingly engaging said shaft, the resiliency of said lip normally urging said free edge against said shaft and providing the sole bias for said edge, and the face of said lip toward said shaft and spaced from said free edge being spaced slightly from said shaft, there being an opening communicating between said face and atmosphere, whereby the greater the speed of rotation of said impeller, the greater is the differential pressure outside and inside of the housing and the less friction said lip exerts against said shaft.

2. A pump comprising a housing having a generally cylindrical chamber and end closure members therefor, there being a fluid outlet positioned near the periphery of said chamber, one of said closure members having a fluid inlet centrally of said chamber, the other of said closure members having a central through opening, a driven shaft extending through said opening axially of said cylindrical chamber, an impeller fixed on said shaft and having radially extending vanes free of shrouding, said vanes being free of engagement with the walls of said housing by reason of a clear space provided between the sides and :ends of said vanes and said housing, sealing means closing said opening between said shaft and said housing, said sealing means comprising a resilient annular cup of U-shape section surrounding said shaft with the open side thereof toward said chamber and in communication with the central portion of said chamber, the radially innermost wall of said cup surrounding said shaft and having its free edge sealingly engaging said shaft, said innermost wall away from said free edge being slightly spaced from said shaft, there being an opening communicating between the outer face of said wall and atmosphere, whereby the greater the speed of rotation of said impeller, the greater is the differential pressure outside and inside of the housing and the less friction said lip exerts against said shaft.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,328,061 Smith Jan. 13, 1920 1,621,272 Raymond Mar. 15, 1927 2,047,329 Petersen July 14, 1936 2,292,125 Ifield Aug. 4, 1942 2,382,839 Wuensch Aug. 14, 1945 2,464,936 McConaghy Mar. 2, 1949 2,508,678 MacDougall May 23, 1950 2,509,436 Isenbarger May 30, 1950 2,517,233 Peters Aug. 1, 1950 2,570,862 Rosenkrans Oct. 9, 1951

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