US2110883A - Self-priming centrifugal pump - Google Patents

Description

H E. LA BOUR SELF PRIMING CENTRIFUGAL PUMPv March-15, 1938.

Filed May 294, 1933 6 Sheets-Sheet 1 ILP. UNH. HIIIIH y In venon- 562W Zcmf? H. E. LA BOUR SELF 4 PRIMNG CENTR IFUGAL PUMP 6 Sheets-Sheet 2 Filed May 29, 1.953

March 15, 1938. H. E. LA BOUR SELF PRIMING CENTRIFUGAL PUMP Filed May 29. 1933 6 sheets-sheet 5 wm @u afffy il; f

March Vl5,` 1938. H, E, LA BQUR .2,110,883

SELF PRIMING CENTRIFUGAL PUMP Filed May 29. i953 6 Sheets-Sheet 4 H. E. LA BOUR SELF PRIMING CENTRIFUGAL PUMP Filed May 29. 1953 6 Sheets--Sheet` 5 March 15, 1938. H; E. LA BOUR 2,110,833

SELF PRIMING CENTRIFUGAL PUMP Filed May 29, 1933 6 Sheets-Sheet 6 l mi l uhmm /////////////////77 l nl Patented 15, 1938 z,11u,ss3 SELF-ramo cEN'rmFUGAr. PUMP Harry EfLa Bour, Elkhart, Ina. Application May 29, 1933, Seal No. 673,469

-i 'sa claims.. (cl. ros-11s) f My invention relates to pumps, and more particularly to self-priming centrifugal pumps of the type disclosed in my United States Patent No. 1,518,236. 'I'his type of pump employs the principle of hydraulic balance in the auxiliary or4 priming throat. By the employment of this principle, the rate andV direction of ilow of liquid in the auxiliary or priming passageway may be` automatically determined by the iluid which is being drawn through the suction pipe into the v pump casing. When the pump 'casing is being evacuated by the withdrawal of air from the pump casing and the suction pipe, the direction of flow of liquid in the auxiliary or priming passageway is inwardly, and when the pump is pumping liquid the direction of flow is outwardly.

This application is a continuation in part oi' `my application, Serial No. 629,617, iiled August 20, 1932.

Pumps of the aforesaid class employ a charge of liquid operating in a closed cyclebetween pump runner and separator forv evacuating the pump and suction line of air or other gas, and upon attaining a full complement of liquid the pressureA developed in the auxiliary, or primingthroat,is great enough to oppose return flow of liquid and 'preferably to serve as an additional discharge throat. f Y

In passing through this cycle of operations, i. e., evacuation, of the pumpcasing by pumping gas to a point where the suction pipe will be lled with liquid and pumping'of liquid begins, two important phases of operation are exhibited. Therst is the automatic compensation or control of rate of liquid reentry for changes in head or pressure difference available upon the auxiliary or priming passageway,` causing return iiow of priming liquid during gas pumping. The second is the automatic stopping or reversal ,of ow in the auxiliary or priming passageway. In this phase of operation not only may the return ow or recirculation be reduced or stopped, but in the full use of the principle the ow is actually reversed, thereby constituting the auxiliary or priming passageway an additional discharge passageway which increases both the capacity and the efliciency of the pump.

It is the chief object of the present invention to provide in a self-priming pump a structure and mode voi' operation which will employ the aforesaid principle to greater advantage than has heretoiore'becn possible. Y

More specically, it is an object of the invention, to increase the gas pumping capacity of a given size of pump.

It is a further object of the invention to increase the gas pumping efficiency of self-priming pumps.

It is ay further obJect to increase the vacuum Y attained by pumps of this general class. 5

It is a further object to produce' a given rate of gas evacuation with a smaller amount of priming water than has heretofore been possible. This permits reduction in the voiumeof the inlet trap. l0

It is a further object to enhance the inherent stability of operation onprming and of equalizing the work upon the throats, particularly during priming. f

It is a further object to shorten the time re- 1.5

' quired to evacuate thepump`casing and suction pipe.

The increases ingas pumping capacity and efficiency, with resulting reduction in time required forpriming, andl ability to vdraw higher vacua, are secured, as will `be set forth in detail later, b?Y improvement in the structure'and mode of operation whereby the circulating liquid is employed in a more advantageous manner for entraining and discharging gas and by a novel utilization oi the principleiof compensation.

A further object of the 1nvention is to increase the liquid Dumping capacity of a given size of pump of thisgeneral class.

Y Another object of the invention is to improve 30 the pumping efficiency of hydraulic pumps, particularly pumps of the self-priming class.

The increases in capacity and efliciency during liquid pumping are secured, as will be set forth in detail later, by improvement in structure and mode of operation, whereby the liquid is carried' through a small angular travel and discharged through a plurality of throats operating in parallel about the periphery of the pump, and whereby an improved' utilization of the action of reverse 40 flow in the lauxiliary or priming passageways is secured.

A further object of the invention is to improve the efliciency and increase the capacity for gas disentrainment or separation in pumps oi this character.

This object is attained, as will oe described more in detail hereafter: partly by the discharge of the mixture of gas and liquid in parallel from a number of throats disposed about the periph- -ery of the impeller and partly by the gradual deceleration of the streams discharged from said throats in the curved tapered manifold. Thereby the gas bubbles are permitted to agglomerate through a relatively long, slow travel. An unsize.

`less load upon the bearings,

usually small discharge or separator chamber may be employed. Kinetic separation may be largely or wholly avoided with the consequent f avoidance in loss of head and consumption of en particularly in the liquid and facilitate the construction of pumps of thel'self-priming type and reduce the cost` of a pump of a/given capacity..

A feature of the preferred form of the pump of the present invention is an improvement of the balance ofthe impeller which tends to impose and vsubstantially eliminate or reduce noiseancl vibration. 'I'hereby the wear upon the lpump shaft packing is greatly reduced and substantial tightnessis more easily maintained, and with less friction.

A further improvement of the preferred form of pressure attainable from an "impeller of a given n A further object of the inventionis to provide a more compact pumping unit.

According to the preferred form herein-,disclosed, a separate bearing for the impeller shaft need not be provided, as the impeliershaft forms merely an' extensionof the motor shaft and the bearings of the motor are. when the impelleris thus adequately balanced, amply suficient to guide and 'suDDQrt the impeller and its shaft. The pump unit may thus be made much shorter .in an axial direction and the cost of the unit materially decreased.

Other and additional objects will appear from the following detailed description and claims.

In the drawings:

v Figure 1 is Aa. vertical longitudinal section' through a pump embodying my invention, showlng certain of the parts in elevation;

Figure 2 is a plan viewl of the pump end of the unit shown in Figure 1; i

. `Fig-ure 3 is a vertical cross section taken on the line 3 3 of Figure 2;

. Figure 4 is a developed diagrammatic` view lllustrating the iiow during the priming phase;

Figure 5 is a similar developed view illustratingl the flow during liquid pumping; Figures 6 and 7 are line diagrams illustrating the flow of the liquid .during primingand during liquid pumping, respectively;

Figure 8 is a sectional view, largely diagrammatic, `illustrating a self-priming pump having two pairs of throats;

Figures 9 and 10 are line diagrams illustrating the ow occurring in the pump of Figure 8 dur-` ing primingand liquid pumping, respectively;

Figure 11 is a side 12 is a plan View of pair of throats placed so as to secure a balanced operation during liquid pumping;

Figure 13 is a top plan view and Figure 14 a front elevational view of a modified form of pump, largely diagrammatic, illustrating an alternative method 'of securing the required unbalance between two sets oi throats to initiate and maintainthe priming action; n

Figure l is a diagram of a pump employing two pairs of throa illustrating a condition of iiow unbalance when just the iight amount of elevational view and Figure the present invention is an increase in delivery a pump employing a single and in suitable driving relation.

priming liquid enters both bypasses or auxiliary passageways;

Figure 16 is a similar diagram, illustrating the action` of the pump when one bypass or auxiliary passageway supplies more liquid than is necessary, with compensation upon the other bypass or auxiliary passageway; and

Figure 17 is a similar diagram, illustrating the action when the pressure difference is great enough to compel compensation on or `auxiliary throats.

Referring ilrst to Figures 1, 2 and 3, the unit herein shown comprises a common base I, the pump unit 2 and the motor unit 3.

The -base I may be a continuous castingJ for 15 supporting both the pump 2 and the motor 3 or' it may be built up, as herein shown, of a, pair of channel bars 4 4 with transverse barsf5 5 con'- necting the channel bars 4 4 to provide a sultable attachment forthe pump, similar cross'bars 6 6 upon the channel bars 4 4 for providing a suitable mounting foruthe mounting legs or lugs 1 1 of the motor.

'I'he pump unit comprises a main annular holbcth bypasses 1o Y and a pair of 20 low casting 8 which has an inwardly extending 25 annular projection or nange 9. 'I'his ring or iiange 9 forms the inner periphery of the im-v peller chamber, in which the impeller I6A is mounted to rotate.

The inner periphery ofthe ring 9 is machined 30 to provide a cylindrical surface embracing fairly closely the impeller Ill. The ring has tapered shoulders I3 I3 at the sides of the cylindrical bore I2 and it has radial faces I4 I4 against which are adapted to rest the Y the front and back plates I6 and I1, respectively. 'I'hese plates have osets I8 of similar` contigui-af tion with their outer -sloping surfaces machined to fit the sloping surfaces I3 I3 on the ring 9.

The plates I6 and I1 are machined to provide .40

parallel* annular surfaces adjacent the cylindrical surface I2 to provide a raceway in which the.

outer ends of the blades`of the impeller I6 are"A confined. A clearance at I9 between -the back face of the impeller and the adjacent face of the 45 back plate I1 is provided. The impeller' I0 is an openimpeller having arms such as 26, the outer ends of which are-curved backward with respect to the direction of rotation, as indicated at 22 center, axially projecting vanes 23 to assist the entering liquid in taking up the motion of the blades or arms 20, so that the liquid, in entering the impeller chamber, is accelerated rotarlally in Figure 3. These arms have, adjacent the 50 and radially with as little shock, or sharp change 55 in direction as it is feasible to secure.

The back plate I1 has a boss or hub 24 which is counterbored to receive the packing 26 i'orv packing the impeller shaft 26. 'I'he impeller thereupon, the shaft 26 in this case being pro' vided with an axial bore to receive a tie rod 21 for holding the end of the impeller shaft 26 and shaft is here shown as having the impeller cast the end of the motor shaft 28 in axial alignment 'I'he motor shaft 28may be providedwith a central bore and the tie rod 21 extended completely therethrough. Due to the balanced load upon the impeller I6,

separate bearings for the impeller shaft are not required, the bearings of the cient to support run true.

'I'he packing 25 `is motor I being sumthe impeller and to' cause it to held in place and is com the peripheries 2,110,883 annular recess 32 with which the grease cup 33 communicates. opening 32 is closed by packing received' in the inner recess in the outer end of the follower 3l! and in turn compressed by the second follower Il. The follower 3l is urged to the left by a pair of compressiony springs 35, one on each side of the" shaft, these springs resting against a stirrup formed integral with the follower 3l at their left hand end and at the right hand end against a movable abutment which in this case is a hand wheel 33 threaded on the stud 31 abutting against the bearing of the motor 3.

The motor 3 3l having an integral bracket 33Vwhich terminates in a suitable clamping flange l0 and which is clamped against the flange I5 of the rear plate Y I1, as will be later described.

The packing sageways 42 formed in the hub 2l, and water circulating pipes |3443 connect to said passageways through the medium of the plate 44,.. which is clamped to the end of the hub 2l.

The top of the bracket 39 is provided with aslot through which extends the connection for the grease cup 33 to the pump connection from the grease cup l5 extending to `the motor bearings I6 passes through the said of the bracket member 39 are to the packing gland for tending into recesses in the back and front plates `l1 and I6, respectively,-and said flanges are engaged by clamps 52--52 mounted upon the bolts -53, these bolts being suitably spaced about of the clamping through the ring 9 in such posiinterfere with the said ring 9, as will ,be de-V tending axially tions as not to extending through scribed later. V"I'he clamps 52-52 rest in an axial direction against the outer edges of the clamping flanges l0 and 5l, and in a radial direction with respect to the. axis of the pump rest against the adjacent cylindrical shoulders SI--Sl of the hollow casting l. d

The intake trap l! is provided with a pipe flange 55 for connecting to `a suction pipe;v An

. opening through this flange extends to the top of the trap l! which, is separated from the bottom by a wall 66, through` an opening in which extendsthe inlet strainer 51. cover 5l, held in place by the clamping yoke 59, permits access to be had to the interior of the strainer 51.

The vcasting! contains the separating charnber 30 (see Figure 3) and provides also two circ'umferentially extending passageways 62 and 63, disposed side by side, separated by a central wall Il. -This central wall il terminates at 65, short of the separating chamber GII.

Referring now to Figure 3, there are shown three pairs of' discharge passageways distributed about the inner peripheryof the impeller chamber, these discharge passageways comprising the The outer end of the annular throats $6,

is provided with a special end bell gland is cooled by suitable pasthird main discharge throat, 6B.

vor manifold 63. It

. cated therein,

the same.

flanges and exf A removable cap or v or' main discharge passageways or B1 and 6B, disposed at 120 with respect to each other, and auxiliary, or posterior passageways or throats $9, 10 -and 1I, respectively.

These throats are all substantially tangential withrespect to the movement of the impeller. The throat 86 is continued as a passageway 66a which opens into the circumferentially extending duct or manifold sideof the dividing wall 6l as viewed in Figure 1. 0n the plan view v shown in dotted lines, and similarly the continuaanterior tion or passageway 66a which is shown in dotted lines turns to the right as viewedin Figure l and discharges into the manifold or .duct Likewise, the throat 61 is continued way 61a, bending the duct or manifold 62.

as passage- The same is true of the v It extends as a passageway over into the duct or manifold 62. The manifold or duct 62 then, in turn, opens into the separating chamber 60. The chamber 60 has a discharge opening 12 provided with a surroundin'g bolting flange 13.

The posterior, or auxiliary throats 69, `'Illand 1| `likewise have continuations comprising passageways 69a, 10a and lia, opening into ,the duct is to be observed that the that is, occupy full axial length of the impeller channel,.and since'the wall 6l is disposed substantially in the median plane of the impeller, the wall 6l is bulged to provide throats and passageways. suitable for leading liquid out or in, as the case may of the impeller blades. l

Referring now to Figures 4 and 5, I have indimore or development of the circumferentially extending ducts or manifolds 62 and 63, and the way in which the discharge VOnlyl two pairs of throats, namely, the pair Sli- 1I and the pair 61-10 'are herein shown. The ends of' the passageways and the 4manner in which they direct flow into the ducts or'manifolds 62-63 is indicated in Figure 4, which shows the flow of liquid during the priming phase of operation. f v j Figure 5 shows the ow of liquid duringthe pumping phase their connected passageways discharge in paralrignt hand over into communication with I full width of the impeller,v

be, across the full width" less diagrammatically, a'

throats communicate with when Aboth sets of throats and lel into the ducts 62-63 and these in turn discharge in parallel intol the chamber 6D and out through the flanged outlet opening 12.

A comprehensive understanding of the the fluid during the two stages of operation may be obtained from Figures 6 and 7, and later by reference to Figures 15, 16 and 17 for the compensating action.

, Assume that the suction flange is connected to a'suction pipe and the discharge flange 13 to an open discharge pipe, the pump being provided with a suitable priming rcharge, which maybe the amount trapped in the intake trap, pump casing and passageways after a. period of operation of the pump and the flowing back of liquid from the open discharge pipe back through the pump, intake trap, and into the suction pipe to break the vacuum therein. It will be observed that permits air to pass chamber passageways s through the discharge ducts and as much liquid as can be drawn from the intake trap 48 enters the pump casing and is discharged through the various throats of the pump. If suiiicient liquid were immediately available to ll the runner, all six of the throats would continue to operate as discharge throats, discharging the liquid in two parallel groups of three into the manifolds 6 2 and 63, and they, in turn, discharging in parallel into the separating chamber 60. However, such action cannot continue, since insuiicient liquid is provided for continued operation of the pump as a liquid pump. The discharge of a part ofthe priming liquid into the discharge passageways and separator immediately causes a deficiency of liquid in'the impeller chamber, with the'result that the pressure upon the vthroats rapidly dropsA and liquid tends to rethrough the throats-into the Immediately upon the rethe impeller chamber it is enter, by gravity, impeller chamber. entry of liquid into met by the rapidly ture of air an'd 'liquid -is formed and, by the centrifugal eil'ect oi the impeller, the mixture is driven out through the throats. However, since there is insuiiicient entering liquid to develop a full hydraulic pressure, and since the anterior throats are of suiiicient capacity to carry out substantially allrof the mixture which is formed. they rob the posterior throats and insufficient prevent the reentry of orderly recirculation is established, as indicated in Figure 6.

The amount of return flow depends upon the size of the-auxiliary or priming passageways and the difference in pressure or head between the separator and the inner ends of the passageways where they enter the channel.

of liquid in the impeller chamber, which, under the action of the impeller, entrains air and acquires centrifugal force to secure discharge at the main discharge ports. The second body or pool is that in the separating space of the separator and adjacent parts of the ducts. It also is a transient body being constantlyreplenished by liquid with entrained gas.- 'I'he gas is liberated, and the liquid substantially free of gas .pinges 'upon the next succeeding auxiliary or replenishes the liquid pool or body in the impeller chamber. By this continuous interchange or circulation, the gas in the-impeller chamber and the connected suction pipe is evacuated.

I f the return of liquid through one of the auxilia'ry or priming ports isin excess of that which when mixed with air can be discharged out of v the nearest discharge port, the excess is carried through a greater angular distance than `that in which normal pressure is developed, and it iml normal for priming,

ffold ,B2 into, the separator chamber 6|). 4manifold 62 is of the stream moving blades and a mix- As the lsuction 'A is increased there is a tendency to increase the priming port, thereby tending to Areduce or stop the return of vliquid port. This provides 'an inherent stability of action, maintaining proper distribution of the liquid charge in the two Afunctionally separate bodies. Evacuation thereupon proceedsy in a stable efficient manner'.

When liquid is drawn into the impeller chamber through the suction pipe, the amount of liquid inthe transient working body or pool in the impeller is-increased above and, asa result, the entraining action is reduced, and the pressure upon all the throats is increased with resultant discharge of liquid at all the original entraining pool or body is present inthe impeller chamber. If at any time the iniiow of liquid from the suction pipe fails, the pump reestablishes the priming action above described.

Liquid is discharged through the duct or mani- The preferably of a volute coniiguration for the dual purpose of reducing the velocity and also of stratifying the same to assist ,in agglomerating the air into Alarger bubbles. The stream is turned back in the opposite direction in the chamber 60, with the result that satisfactoryseparation is secured in unusually small space. The proportioning of the volute discharge passageway 62 may be such as to effect sufficient reduction of velocity to provide the major air separating action. The most difcult part of separation is to agglomerate the minute bubbles into bubbles of sufficient size to make a marked difference in specific gravity or density. For ltwo bubbles to agglomerate when adjacent to each other there must be allowed a certain amount of time for the nlm of liquid between them to thin out and break. Turbulence ports, both main and auxiliary. The pump strives as it were to reduce the` through said second auxiliary Y that which is l of the mixture tends to separate such bubbles before the skin or film between them breaks', which latter-action is a necessary action before they oin. Agglomeration of fine. air bubbles is fostered by concentration of the entrained air in a part of the mixture. For'example, if a uniform mixtureof air bubbles and water be treated to cause all the vair bubbles to gather in one part vofthe liquid, they tend to agglomerate by the greater tendency to 'contact/ each other, and longer period of contact. Concentration of the air bubbles in one part of the mixture may be secured by a number of diierent actions. mode employed in the present case is to reduce the velocity and turbulence of the mixture stream.

This permits, rst, of gravity concentration, and second, of longer engagement or contact between adjacent bubbles, with consequent agglomeration of air bubbles, even if no free surface is present. Another mode also employed, preferably in minor degree, is concentration by inertia effect as, for example, by causing the liquid to follow a curved path. The denser fluid, i. e., the water with less entrained air, seeks the outer side of the path and the less dense fluid, i. e., the water with more entrained air, seeks theinner part of the 1path, and even if no free surface is presented `in the path, agglomeration occurs. 'I'he removal of the agglomerated air is then readily eiected by providing a free liquid surface. This surface need not be quiet, like a pool, butmay be moving, as in y* the case of a stream, a whirlpool, or the like.

One-

operate as a liquid pump, and does so for the major part of its operating life, it is highly im- `In the construction shown in Figures 1 to 5 the agglomeration occurs by reduction in velocity and reduction in turbulence, and also by the inertia effect, i. e., change in direction of flow. A highly developed inertia effect, or whirlpool, requires relatively high velocity of whirl and sufcient diameter and confinement to allow a free whirl to be established. While it is quite effective, and desirable in some cases.A I find it to be undesirable where high efficiencies are to besecured, because of the loss of energy and interference with delivery when the .pump is operaton a vertical' axis, or it may be secured by providing suillcient space to permit the air in the liquid to be separated by gravity or in any other preferred manner. While I have shown the liquid as being whirled in the chamber G during the priming phase (see Figures 4 and 6) it is not essential that the whirling action be employed, as gravity separation may be suflicient. Obviously, the chamber 6|) may be made larger and the mixture introduced at high velocity to secure pure centrifugal separation.

The shape of the ducts 62 and B3 is, in general,

thatl of a volute, that is, a constantly increasing passageway extending circumferentially of the pump chamber and in the design herein shown there is a tendency for the liquid to stratify' upon the outer wall of the duct or manifold 63. This may be so controlled as to assist in the-final separating of gas from liquid, or it may perform substantially the entire function of separating gas from liquid during priming. j

As soon as liquid enters the intake connection l1 in suiilcient volume to fill the impeller, the quantity to be discharged increases beyond the capacity of the throats 66, B1 and 68 to carry the same, .with the result that pressure is developed in the throats 69, 1li and 1I, and outward flow in said throats and passageways intothe duct or manifold 63 occurs. Thereupon, both the main throats 65, 61 and 68, and the auxiliary throats $9, 10 and 'Il become discharge throats, and

both ducts or manifolds 62 and 63 become discharge passageways, discharging liquid in paral.

lel to the chamber 6U and out through the discharge pipe connection.

I have found that by this construction a great increase in capacity for a given size of impeller is secured, and surprisingly high efficiencies are attainable. At the .same time, the air handling capacity of the pump is greatly increased over known 'forms of pumps and the device operates,

' quietly and smoothly to a degree not heretofore attained in any self-priming pump with which I am familiar.

While I have described above the preferred em bodiment of the invention it is to be understood that certain advantages of my invention may be secured without embodying all of the features thereof. f

Since a pump of this character must-essentially portant that the efficiency of the 'pump and' its balance, when running as a liquid pump, be made as good as possible. v

In Figures 15, 16 and 17 I have indicated the novel mode of compensation involved in the operation of the pump of the present invention'. While these diagramsishow only two pairs of throats it is to be understood that the mode of operation and the same principles are involved in three pairs of throats or more. During the priming stage, the impeller performs two chief functions, the first of whichis to form a mixture of gas and liquid, and the second of which is to discharge the same from the pump casing through the discharge throat or throats. The two actions are in large degree antagonistic, in that the development of centrifugal force tends to disentrain the gas from the liquid, that is to say, therel is a tendency for the air to be' squeezed radially inwardly as the same is' carried about,

due to the development of centrifugal force. It

is therefore apparent that the denser fluid is radially outermost and the lighter fluid, that is, the mixture of air and liquid containing the greatest amount of air, lies radially inward. Itis desirable to carry the liquid no further angular- 1y than is necessary to develop the desirable pressure. My 'present form of pump greatly reduces the angular carry of the mixture, as compared with previous forms of self-priming pumps, and

thereby less disentrainment ofA the air occurs. Also, in the liquid pumping phase, it is undesirable to carry the liquid any furtherthan is necessary to develop discharge pressure, and by reducing the angular carry, as I have done in the pump of the present invention, I have reduced v the eddy current losses within the casing and I find, as a matter 'of fact, that the discharge pressure attainable with the same diameter of impeller is actually greater with the short angular carry.

Since -the mixture tends to stratify, due to the centrifugal force developed by rotary motion, any greater. depth of liquid in the pump channel than can be discharged through the discharge throat results in a discharge ofthe liquid containing ythe least air, whereas it is desirable to carry out of the casing the liquid containing the most air.

Hence, it will be apparent that if the return flow of liquid is greater than that required to fill the discharge throat or throats, the excess of liquid is not only undesirable, but actually hinders the rapid evacuation of the casing andsuction pipe.

V'Ihe rate of return ow of liquid from the separa- `tor to the pump casing through the by-pass or auxiliary passageway lis controlled by the difference in pressure or head prevailing on the bypass or auxiliary passageway. As the vacuum in the pump casing increases, `greater difference between the pressurein'the separator and the pressure Vin the pump casing arises, with consequent increase in the rate of returnY flow. This same difference in pressure tends to oppose the outflow of liquid' at the discharge or main throats, but such difference in pressure is relatively minor compared with the discharge pressure developed by operationV of the rotor, and hence no appreciable difference' in rate lof outflow occurs. But both of these tendencies work in the direction of returning fthe circulating water from the separator to the pump casing more rapidly. This may v result, if not counteracted, in an excessive amount of liquid being present in the pump casing. It is here that the automatic compensation which is illustrated in Figures 15,' 16 and 17 assists in controlling the return of liquid in a manner which is highly benecial to secure more rapid evacuation and greater eiciency of evacuation than has heretoforebeenpossible in pumps of this class. In the diagrams of Figures 15, 16 and 17 the primary throats or discharge throats are indicated at A 'and A'. The auxiliary throats or by-pass throats are indicated at B and B'. The arrows indicatethe direction of flow, and this flow within the casing is maintained by rotation of the impeller.

Figure. 15 illustrates a condition of ow balance when just the right amount of water enters both by-passes. Hence the incoming stream from B meets the impeller, which mixes it with air, and the mixture is carried around and all of it is discharged through the throat A' into the ,separator, it being understood that all of the throats are connected to the separator. Similarlmliquid from the separator entering the throat B" meets the impeller, is mixed with air, and all discharges through the throat A. This is the ideal condition, and vassuming that the pump starts with no difference in pressure between the separator and' the pump casing, the design may be such as to secure initially such condition of operation. As soon, however, as a greater pressure difference occurs by carrying out a part of the air from the pump casing, the condition shown in Figure 16 begins to prevail. IIn that case, one of the auxiliary or by-pass throats, for example B, assumes the controlling action. More liquid ows through the throat B than heretofore because of thegreater difference in pressure on theends of the throat, and a larger quantity of liquid is carried on the left hand side of the diagram, as indicated. Since the throat A' cannot discharge all of the liquid carried by the impeller, a part of the mixture as indicated in Figure 16 is carried past th'e main throat A', and creates a pressure condition upon the throat B'," tending to retard the flow of liquid from the separator through the bypass B' intothe pump casing. The same difference in pressure which operates on the throat B operates on B', but because of the opposition of the excess liquid carried by the throat A', throat B' is not able to supply the same amount of liquid that is supplied by the throat B. The excess which has been introduced at B thereby prevents excessoccurring at the throat B', and conditions may be so selected as to permit the mixture, consisting of the liquid carried by the throat A and introduced by the throat B and mixed with air, to be fully discharged at the throat A. Thus it will be seen that although the left hand part of the pump is working at some disadvantage for the evacuation of air, the right hand half in Figure 16 is still working at a high eiilciency for the evacuation of air, because not only the heavier iluid, but also the lighter :duid containing more air, is being carried out the main discharge throat A If the diierence in pressure between the separator and the pump casing is further increased, then conditions such as shown in Figure 17 may prevail.

In this case there is illustrated the action when the vacuum is suilcient to make both by-passes tryto feed too' much water. B still supplies more than B'. Both discharge throats are properly filled, and the excess from B tends to compensate or balance the action of B', the tendency of which is to supply an increased amount, 1314i' the tendency is not completely overcome, and some oi.' the excess liquid by-passing A' together with the liquid entering at B' is carried past the main discharge throat A, and begins to compensate on the flrst main throat B. The mutual control of the by-passes upon each other may.

be interchangeable, that is, either one may initially sieze control or preponderance.

The result of the above described mode of op-l eration is that evacuation ofA air is more rapid. There is less disentrainment oi air due to the shorter travel, and a higher degree of vacuum can be reached than has heretofore beenpossible in pumps of this type. It is generally custom-` ary to make each of the by-passes with an area of about of the main throats. It is desirable to make the capacity o f the by-pass` throats'i'airly large, since they become discharge passageways upon filling of the suction pipe and the pump with liquid. By the scheme of automatic and progressive compensation, the throats may be made so large that they would supply far more priming Water than is required if compenf sation were not effected.

Obviously, while I have illustrated two pairs o1.'

throats, this invention is not conncd to twol pairs, nor is the action any different if more than two pairs of throats are utilized. Either one of the by-pass or priming vthroats may assume kpreponderance to dominate the return flow. of liq'- uid, lt being a matter of indifference in the operation ofthe pump. Obviously, by suitable def sign, a particular throat may be given the dominating action. In experiments which I have conducted, the self-compensation, that is, the

carrying of liquid from the throat B clear back to itself, as illustrated in Figure 17, does not occur until vacua around twenty-tive inches or bet.`

ter are reached.

By the provision of a common separator connected to all of the discharge throats and the return throats in parallel, the action of the pump during priming, particularly as to the exterior path of the priming liquid, is stabilized, and the eiciency of the pump improved. This common separator equalizes the Work of the various pairs of throats during priming. The separation of gas from liquid is also improved, particularly bythe employment o f the two manifolds between the discharge throats and the separator.

The discharges of all the anterior throats, such as 6E, 61 and E8, enter the manifold and are mixed and equalized both in the manifold and in the separator 60, and the agglomeration of gas bubbles is promoted. The posterior or auxiliary` adjacent anterior throat, the tendency to cause :fluctuations inI pressure or surging is greatly reduced or prevented. f

The external part of the priming circuit is stabilized and equalized through the usev of the common separating chamber. 'Stability andl eficiency of priming is promoted in the internal part of the priming circuit by a hydraulic com pensation as between liquid entering one -inlet l pump in Figure 1,

the auxiliary, -or

- in illustration. When the pump is axiomas 4a capacity about 80% throat and liquid entering another inlet throat as heretofore described. The pump as a whole has a pronounced inherent stability. 'Ihis is particularly important because of the relatively small amount of priming water which the pump employs for the amount of gas which is handled.

In the pump herein shown, particularly the the discharge' manifold 52 blends together the discharge streams of mixture and provides a preliminary separation of the gas fromthe liquid before the stream enters the separator 58. Here the gas rises out through the outlet 12 and the liquid passes through the priming manifold 53 towards the priming throats. In this manifold during this action, the liquid is further equalized, particularly as to gas content, so that substantially a uniform quality is supplied ,lat each of the priming'throats. Thus these manifolds, by the perfomance of new functions, secure new results orY results which were performed less advantageously in the separator of previous self-priming pumps.

` The efliciencies attainable are comparable with those of the best closed impellertype pumps, with allI the simplicity of construction and clearances of the open type impeller.

It is not essential in the construction of the p pump that the circular arrangement of manifold here shown be employed. The throats may communicate directly with the separator. chamber, or two chambers might be employed.

While I have shown three pairs of throats in the pump of Figures 1 to 'l it is to be understood that any number of pairs which is found suitable maybe employed, but I also wish to point out that it is not essential that the throats be arranged in closely grouped pairs. For example, in the structure illustrated in Figures 11 and 12, there are provided onlytwo throats, and 18, placed diametrically opposite each other with respect to the axis of the impeller. 'I5 and 16 communicate with the raceway f or the impeller blades within the pump casing and communicate through separately formed ducts, or passageways 18 and 19, respectively, with a vor.- tex separating chamber 88. Obviously, anyother form of separating chamber may The two conduits `|8 and 18 open substantially tangentially into the cylindrical separator chamber 81|. An inlet trap is` provided for the inlet 28, this being omitted for the sake of simplicity started 4up it is provided with a suitable priming charge, and assuming that the impeller chamber stands filled with water, the difference in the hydrostatic head upon the throats 15 and 18 is suflicient to start an unbalanced action. At the same time, the

friction of the passageways 18 and 18 also assists in establishing a proper direction of flow. Since the hydrostatic head on the throat 15 is less than the hydrostatic head on the throat 16, assuming substantially equal pressures to be caused by the motion of the impeller Il), there is a tendency to drive the liquid out of the throat 15 'more easily than out of the throat 1G, and hence circulation in the direction causing the throat 15 to be the main discharge throat and the throat 16 to be priming throat, is usually instituted. If the throats are of the same capacity it is immaterial which one assumes the discharge function and which one the priming function during priming. I have found it generally desirable where the' throats arey arranged in pairs, to

make the posterior throat of the pair, which throat becomes the by-pass or priming throat, of

, arator sure to occur at said throats,

These two .throats be employedi 7 of that of the anterior or discharge throat. served inthe present pump when one throat is Vdesigned to assume the priming function.

It will be observed that where only a single pair of throats such as 15 and 1B are disposed diametrically with respect to each other', during priming one half of the impeller periphery is all that is doing active work. This unbalances the thrust radially on the impeller shaft during priming', but as soon as liquid pumping -begins the effect is balanced, or substantially so, since liquid enters axially through the inlet opening and moves radially in all directions to fill the impeller lll and to be thrown out on two sides of the same. whereby the radial forces are substantially balanced. I

In Figure 8 I have shown how two pairs of throats may be employed in a pump of this char- 1 acter to secure a balanced effect during both priming and liquid pumping. j

In this case the main or anterior throats 15 and 1B are connected to a manifold or duct 82 which, in turn, leads tangentlally into the sepchamber 88 for providing centrifugal separation. The posterior throats 83 and 8l are connected to the separator 80 by a duct or manifold 85. The form of separator and its mode of operation is optional.

'I'he operation of apparent Vfrom the diagrams of Figures 9 and y10 and from the foregoingdes'cription. The'anterior throats 15 and 15 rob the posterior throats This proportion may be obthis form of device willbey and 84 of liquid, causing regions of reduced preswith the result that while liquid, or liquid mixed with gas, is discharged out of the anterior throats into the separating chamber, liquid from which gas has been separated in the chamber 80 is returned through the throats 83 and 8l into the impeller I8. each half of the impeller l0 is used equally during both priming and liquid pumping, the balanced effect which it is desired to secure is thereby attained during both phases of operatori.

In the diagrams of Figures -7 and 10 the axial iniiow'of liquid and its movement by theimpeller is indicated by the lines 815-85.

In Figures 13 and 14 I have illustrated a modifled form of construction. In this lcase the primary throats, or throats which are invariably discharge throats, are indicated at 81,- 88 and 88. They are connected by passageways 81a, 88a and 89a with the duct or manifold 8D which discharges into the separator 88. Equally spaced angularly with respect to the primary discharge throats are the auxiliary discharge throats 82, 83 and 94.

All of these throats, instead of discharging tangentially with respect to the inner cylindrical wall 95 of the casing 85, discharge laterally therefrom. The throats 92, 93'and 94 are connected by short passageways 82a, 93a and 94a with the duct Since` or manifold 91 which also leads to the centrifugal discharge the mixture of air and liquid -during the priming phase out of the throats 81, 88 and 88 and to secure reentryithrough the throats 82, 93

widening the outer, or

Obviously, instead of having the throats all equally spaced angularly about the periphery oi the casing, these throats may be grouped in pairs if desired.

Also, while I have shown lboth groups of throats as opening axially instead of tangentially, the group of primary throats 81, 88 and 89 may be disposed tangentially and the auxiliary throats arranged to open axially. Also, if desired, tangential throats for the primar'y'discharge may be provided and axially disposed throats registering with each other from opposite sides of the casing may be provided. In this case three ducts, or manifolds would be employed, the primary duct opening tangentially into the separator 80 and the return duct, preferablywith a common opening from a lower point in the separator 8D, if desired.

From the foregoing it will be seen that various methods of producing the desired unbalance in pressure inthe two sets of throats may be employed. The preferable embodiments are those in which `the reaction of the various throats is balanced substantially radially and axially uponthe impeller, soy that it may run substantially without the necessity for guiding bearings. In the construction shown in Figures l to 3, inclusive, the impeller shaft is short and forms merely a rigid extension of the motor shaft Without requiring any bearings in addition to the /motor shaft bearings. Where the impeller tends to run true by balancing the stresses thereupon it is much simpler to maintain the packing tight and far less wear upon the bearings occurs.V

-While I have shownxa'form of impeller-which ishighly advantageous, it is to be understood 'that the invention is not limited to this specio form. The impeller is substantially self-balancing in an axial direction duringboth the priming phase and during the liquid pumping phase. The forwardly extending vanes 23 of the` impeller Ill assist in directing the liquid and giving it the proper motion to enter the actual working space or channel in which the blades or arms of the runner move, so as to secure a gradual acceleration,A both axially and radially, as well as circumferentially.

I do not intend to be limited to the details shown and described, except as they are recited in the appended claims. It will be apparent to those skilled infthe art that various modifications and refinements will at once occur'to'those skilled in the art, all of which are contemplated vas coming within the spirit and scope of my invention.

I claim:

1. In -a self-priming pump,'the combination ofa casing having a centralA inlet and containing a channel for an impeller, an impeller lying in a vertical plane and being mounted on a hori-` zontal axis to run in said channel, vthere being an even number of substantially tangential discharge outlets from said channel, the maximum angular distance between adjacent outlets which are connected to different ing its longitudinal axis disposed substantially vertically, a first passageway serving always as a discharge passageway connecting half of said discharge outlets to said separator at one side of the axis thereof, and a second passageway serving on the priming phase'as a priming passageway and on the liquid pumping phase as a discharge passageway connecting the other half oi' said outlets to the separator at the other side passageways being notl ,a separator havof the axis thereof, said passageways opening -into said separator substantially horizontally and atl -substantially the same level, said separator having an outlet opening at the top of the same.

2. In a pump of the class described, the combination of a casing providing an impeller chamber and an axial inlet, said chamber having a pluralityof pairs "of throats disposed about its periphery, a separator, said pairs of throats beingfspaced angularly about said periphery by greater angular distances than are the throats of each pair, said angular spacing between adjacent pairs of throats being not substantially Agreater than that within `which the mixture of gas and liquid receives its full discharge velocity from the motion of the impeller, each pair of .throats comprising a main discharge throat serving always for discharge of liquid, and an auxiliary or priming throat, serving during priming for the return of liquid from the separator to the impeller chamber, a duct connecting all of the main 'throats to the separator, and a duct connecting all of the auxiliary throats to the separator, said ductsy and separator serving to stabilize the action of the pump during priming.

3. In a pump of the class described, the combination of the casing providing an impeller chamber and an axial inlet, said chamber having a plurality oi pairs oiL throats disposed about its periphery, each pair comprising a main throat and an auxiliary throat, as'eparatorchamberhav-- lng a cylindrical wall, a manifold duct connecting the main throats and leading the discharge there` of into the separator chamber substantially tangentially of said cylindrical Wall, said duct producing agglomeration of air bubbles of the mixture of air and liquid discharged thereinto, a second manifold,A duct connecting the auxiliary throats with the separator chamber, said ducts extending peripherally of said impeller chamber, said ducts and separator serving to stabilize the action of the pump during priming.

4. ,In a pump of the`class described, the combination of a casing providing an impeller'chamber and an axial inlet, said chamber having a plurality of pairs of throats disposed about its periphery, each pair comprising a main throat 'and' an auxiliary throat, a separator disposed at the upper end of the pump icasing. said casing vcomprisingv a\hol1ow annular portion encircling 'the impeller chamber, a dividing wall extend'- ing around the, major part of thenpehiphery and dividing said hollow annular portion into two passageways which terminate in said separator,

-said main throats being connected to one pasvsageway and the auxiliary throats being con-w nected to said other passageway.

5. In apump of the class described, a hollow annular casing having two peripherally extending passageways constituting manifolds and hav' ing an enlargement with which said passageways lconnect, constituting a separator chamber with an outlet for gas during priming and for liquid during liquid pumping, a plurality of pairs of throats,v said lpairs of throats being equally spaced about the inner periphery of said casing, each pair comprising a main discharge throat and an auxiliarythroa't, the main throats communicating with one passageway and the auxiliary throats communicating with said lother passageway, a pair -of side plates cooperating with said annular casing to define an impeller chamber, and an impeller in said impeller chamber, said impeller having a shaft mounted in one ofsaid plates, the other' plate having an inl opening substantially centrally thereof.

6. VIn a pump of the class described, an annular casing having a centrally disposed radially inwardly extending annular ring and a hollow casing extending about the ring, said casing having an enlargement forming' a separator chamber and having a dividing wall extending throughout the major part of the periphery and terminating i short of the separator chamber, substantially tangential main discharge passageways extending through said ring and leading to one side of said dividing wall, substantially tangential auxiliary discharge passageways extending through said ring and leading to the other side oi' said dividing wall, inwardly dished side plates having margins resting against the sides of said rln'g, said ring .and side plates defining an impeller chamber, an

impeller mounted for rotation in said impeller chamber, and bolts extending through said ring outside the margins of said side platesfor clamping said side plates against the ring.

'1.4 In a pump of the class described, an annular Y,

casing having a centrally disposed inwardly extending annular `ring and a hollow casing extending about the ring, saidl casing having an enlargement forming a separator chamber and having a dividing wall extending throughout the major part of the periphery and terminating short of the separator chamber, substantially tangential main discharge passageways extending through said ring and leading to one side of said d ividing wall, substantially tangential auxiliary discharge I peller, an inlet trap having a flange resting against the flange of said inlet plate, a motor bracket member having a flange resting against the flange of the other side plate, and bolts extending through said-'ring radially outside of said flanges and clamping said flanges against said ring.

8. In a self-priming pump, a pump casing comy,

prising an impeller chamber, an impeller mounted for rotation therein, said chamber having an inlet i'or liquid leading into that part of the impeller lying radially inward of the periphery thereof, a separator chamber-having an outlet for the iluid discharged by the pump, two manifolds, and a plurality of pairs of adjacent discharge passageways, said pairs being equally spaced about the peripheryof the impeller chamber and like ones of said pairs being connected by said two manifolds respectively to said separator, said manifolds and separator serving to stabilize the action of the pump during priming by pooling the incoming and outgoing streams.

9. In a self-priming pump, a pump casing providing an impeller chamber, an impeller mounted torun insaid impeller chamber, a. plurality of substantially tangential discharge throats spaced substantially equally aboutrtheinner periphery of the impeller chamber to provide a multiple throat discharge, the angular spacing between throats being not substantially greater than that in which the liquid receives the necessary discharge velocity i'rom the motion of the impeller, a separator towhich said discharge throats are. connected, and a passageway between the sepa-l rator and a part of the impeller chamber wherein pressure is developed by operation of the impeller when it is supplied with water ior returning liquid from the separator to the impeller chamber during the priming phase whereby return of liquid through said passageway during the liquid pumping phase. is prevented, said separator having an outlet through which the pumped uid is dis'- charged, said separator acting to equalize the effect o! saiddischarge throats upon said return passageway during priming. s

10. In a seli'epriming pump, a pump casing providing an impeller chamber, an impeller mounted for rotation in said-v chamber,` a separator chamber having an outlet for fluid discharged by the pump, there being a plurality of discharge throats spaced substantially equally about the periphery of the impeller chamber and all leading to the separator and servingy at allv times to discharge liquid from the impeller chamber, the angular spacing between `throats being not substantially greater than that'in which the liquid receives the necessary discharge pressure from. the motion of the impeller, and means for conducting liquid from the separator to the interior of the impeller chamber during the priming operation, said means comprising an auxiliary throat which is subjected to lower hydraulic pressure during the priming operation than are the discharge throats, saidauxiliary throat being subjected to sufiicient hydraulic pressure during liquid pumping that recirculation is substantially prevented, said separator serving to equalize the gas content of the liquid returned through said auxiliary throat.

`11. In a self-priming pump,Y an impeller chamber, an open impeller mounted for rotation therel in, a separator, said chamber having multiple discharge throats spaced about the periphery thereof to provide a'balanced discharge from said impeller, and a plurality of ducts connecting said discharge throats to said separator, sad pump being organized to compel outflow invariably from the impeller chamber through all of the throats and through both of the ducts when the pump `is pumping liquid, and to compel return iiow from the separator through 'one of said ducts and at leastv one of said discharge throats when the pump is operating on the priming phase", said ducts being .disposed laterally of each other and on oppositey sides ofthe median plane of the impeller chamber, and having walls formed integral with the Walls of the impeller chamber.

12. In a self-priming pump, a casing comprising an impeller chamber having an inlet opening and having a pluralityof pairs of substantially tangential throats, an impeller mounted to rotate in\ said chamber, a separator chamber disposed substantially at the top of the impeller chamber,

` liquid is discharged during liquid pumping serving to ualize the return ilow of priming liquid to the throats which are connected to said other manifold, both as to Y amount and as to Vgas content, and serving to-stabiiize the action ofthe 13. In a self-primingpump, a casing compris- 7ing an impeller-,chamber vhaving an inlet opening and having a plurality of pairs of substantially tangential throats.- an impeller mounted' to rotate in said chamber, .a separator chamber, a pair of volute shaped manifolds leading into vsaid separator chamber, the throats of each pair anterior in respect to the Adirection of rotation of the impeller'being connected to one manifold and the throats of eachfpair posterior in respect to the direction of rotation of the impeller being connected to the other manifold, said manifolds lying in planes substantially parallel with the plane of the impeller, lsaid separator cham- ,ber being approximately' circular and having its circular axis substantially parallel to the plane of the-impeller.

14. In a self-.priming centrifugal pump, a

f pump casing comprising a central inlet, an internal channel, a runner operating ln said channel, there being a plurality of pairs of outlets from the channel. a separator chamber into which all of said outlets open, each pair oi outlets comprising amain outlet and an auxiliary or .priming outlet, said main outlet of each pair being with respect to the direction of rotation of the impeller anterior to theauxiliary or priming outlet whereby during priming of the pump the auxiliary or priming outlet of one pair supplies from the separator chamber liquid which is introduced into the peripheral part of the impeller to be mixed with gas in the casing, some of said introduced liquid being discharged-at the main outlet of another pair and some being carriedbeyond said main outlet of the other pair,

and the liquid which is carried beyond said main outlet of said other pair retards the inow of liquid from the separatorA through the auxiliary or priming throat of said other pair into the pump casing whereby to increaseA the efiiciency and stability of the priming action.-

15. In a pump, the combination of an annu- -lar frame casting havingv a substantially cylindrical interior peripheral wall forming the bottom. wall of a channel, there being openings at a plurality ofv substantially equidistant pointsv in said cylindrical wall forming throats, the annular casting having a peripheral manifold passageway formed therein extending partially around the outer periphery of 'the pump and there being tangential passageways for conducting fluid discharged through said openings into the manifold passageway, said manifold passage- .way conducting -the liquid from said throats in the same peripheral direction throughout, a pair of side plates clamped against said annular- -frame casting, said plates having planar surfaces cooperating with said circular-wall to deline a channel, and a runner having blades traveling in said channel.

16. In a pump, the combination of an annular frame casting` having a substantially cylindrical interior peripheral wall forming-the bottom wall of av channel, there being openings at a plurality of substantially equidstant points in said cylindricalwall forming throats, the annular casting having 'a peripheral manifold passageway Kformed therein extending partially around the outer periphery of the pump and there being tangential passageways for conducting uid discharged through said openings into the manifold passageway, said manifold passageway conducting the liquid from said throats in thesame peripheral direction throughout, a pair of side plates `clamped against said annular frame casting, said .plates having planar surfaces cooperating with said circular'wall to denne .a channel, a runner having blades traveling in said channel, and bolts disposed parallel-to the-longitudinalaxis of the annular casting, saidbolts extending through the annular'casting radially within said mani.- fold passageway and being spaced angularly between the tangential passageways, said bolts clamping the side plates against the annular casting'.

17. A self-priming pump having a casing pro- 'vided with an inlet, an open runner, a single separator and a plurality of pairs of passageways providing communication between the casing and the separator, each pair of passageways comprising a discharge passageway and a return passageway during priming, said separator serving to equalize the. work of said throats and to stabilize the operation of the pump during ,priming and having a common outlet for the fluid being pumped.

18. A self-priming pump comprising a casing having a central inlet for liquid, an open runner therein, a single separator, a pluralityof pairs of tangential throats all leading .to the separator and all serving as discharge passages in parallel when the pump is 'pumping liquid, the anterior throat, in the direction of rotation of the runner, of each pair serving as a discharge passagewayfor discharging a mixture of gas and liquid from the casing to the separator, and the posterior throat, in the direction of rotation of the runner, of each pair serving to receive liquid freed of gas from'the separator into the casing while liquid is'being circulated during the priming operation, said separator serving to equalize the work of said throats and to stabilize the operation of the pump during priming and having a discharge outlet for the uid being pumped.

19, A self-priming pump comprising a casing having a central inlet for liquid, an open run'- .ner therein, a single separator disposed substantially at the top of the casing, a plurality of pairs of tangential throats disposed at substantially equal distances about the inner periphery of the casing and all leading to the separator and lall serving as discharge passages in parallel when thepump is pumping liquid, the anterior throat,

in the direction of rotation`of the runner, of each pair serving as a discharge passageway for discharging a mixture of gas and liquid from the casing to the separator, and the posterior throat,

in the direction of rotation of the runner, of

each pair serving to receive liquid freed of gas from` the separator into the casing while liquid is being circulated during the priming operation,

said separator comprising a chamber with a wall curved in a horizontal plane to cause horizontal circular travel of the circulating liquid during priming, said separator serving to equahze the work of said throats and to stabilize the operation of the pump during priming and having a discharge outlet for the fluid being pumped.

- 20. A self-priming pump comprising a casing,

an open runner therein, a single separator, a plu-` rality of pairs of tangential throatsalleading to the separator and all serving as discharge passages in parallel when the pump is pumping liquid, the anterlor'throat, in the direction .of rotation of the runner, of each pair serving as a .discharge passageway for discharging a mixture of gas and liquid from the casing to the separator, and the posterior throat, in mennen-.ion of rotation of the runner, of each pair serving to receive liquid freed of gas from the separator into the casing while liquid is being circulated during the priming operation, said separator th thev W Sets channel vanchas comprising a substantially cylindrical chamber axis substantially vertical an'd a pair f substantially parallel volute manifolds for the of discharge throats, said manifolds opening substantially tangentially into said separator at. opposite sides thereof. 21. A self-priming centrifugal having a central inlet of uniform depth, an open runner having pump, a casing and comprising a circular substantially uniform clearance with the periphery of the channel, a-- plurality of pairs o'f adiacent throats tangential tothe periphery of the channel, said pairs about the periphery of the channel.'

uniformly and a. common being spaced substantially separator connected to all of said throats, anterior ones ,of each pair being connected by by a seco a common manifold to said separator -and posterior ones of each pair being connected nd common manifold, said manifolds comprising volutes having their outlet ends extending substantially horizontally into a common separator chamber and providing additional space within which gas separation may take place, said separator having an outlet for the fluid being pumped,

with sai`d and serving in combination manifolds during priming to equalize the work upon the throats.

22. In a self-priming pump,

an impeller, a

casing therefor provided with a central inlet and having a plurality of substantially equally spaced tangential 'discharge rator for returning ripheral part of the through outlet for throats, a common sepasaid discharge throats, and means for liquid from the separator to the peis driven out of the casing throats in parallel during said separator having an fluid being pumped, said separator the fluids discharged throats and equalizing the the gas content of said liquid returned to the impeller during priming.

23. In a self-priming pump, the combination of a runner casing and runner, said casing having a single central inlet and a peripheral throats which all separator plurality of pairs of and a common separator to throats are connected, said an outlet for the fluid being of the having pumped, the throats of each pair being so close to each other that the runner does not have suillient pressure betweenV them,

angular travel to build up discharge the by only sufficient angular distance to allow discharge pressure to be built up between them, whereby during the priming operation *the mixture of gas and liquid is not subjected to unnecessary of liquid centrifugal separation, the discharge throats during pumping of the axis of the separator to provide parallel discharge flow through the outlet. the fluidstreams discharged duringl priming from corresponding throats of each pair being all blended in said common separator and the other throats 4 of -each pair being supplied with liquid from said common separator, whereby to upon said pairs equalize the work of. throats and to stabilize the action of the pump during priming.

combination of claim 23,' wherein the pairs yoi! throats are substantially equally spaced aboutthe nectcd periphery of the casing and are conby two manifolds tothe separator, one

connecting those throats of each pair anterior in the direction of motion of the throats `of each pair impeller Ifor circulation the impeller and formation of a gas and liquid mixture which through the discharge priming -of the pump,

pairs being separated l 1 l the runner and the other manifold connecting which are posterior in the direction of motion of the runner, the throats of the first half. discharging in parallel through the first manifold to provide a single stream entering the separator.

25. In a self-priming pump, the combination yof a casing comprising a peripheral portion for cooperation with animpeller and having a central inlet, an impeller having vanes for driving liquid from the central inlet intothe peripheral portion during liquid pumping, said casing having a series of ports disposed about and opening out of said peripheral portion, a first manifold connecting alternate ones of said ports, a second manifold connecting the other ones of said ports, and a discharge and separating chamber in which gas is liberated from the liquid entering the same and through which one manifold discharges into the other in series during the priming operation of the pump, said chamber having an outlet through which gas alonevis discharged during priming and through which both manifolds discharge liquid in parallel during liquid pumping, said ports connectedY to the first manifold being spaced apart by an angular distance not substantially greater than that within which the fluid being moved acquires full discharge pressure by normal motion of the impeller.

26. The combination of claim 25 wherein the impeller is an open impeller having blades curved backwardly with respect to the direction of rotation, and wherein the peripheral portion of the casing provides a channel which is substantially 1cylindrical at its periphery, and wherein the separator chamber having a cylindrical inner wall with a vertical axis and an outlet at the top, means defining two tapering volute manifolds extending circumferentially of said ringlike member and having their larger ends opening substantially horizontally into the sides of the separator, alternate ones of said passageways leading into one manifold and the other passageways leading into the other manifold. 1

I28. In a self-priming centrifugal pump, the combination of a casing providing a pumping chamber having a peripheral portion for cooperation with an impeller and providing a central inlet for liquid to the impeller, an impeller having vanes for driving the liquid from the central inlet to the channel during liquid pumping, a separating and discharge chamber having an outlet, said peripheral portionhaving a series of throats all of which discharge liquid in parallel into the second named chamber and through the outlet when liquid is supplied to the inlet, and when liquid supply at thek inlet fails, discharge of liquid in -parallel ceases and liquid from said second, chamber reenters the pumping chamber through a plurality -of said throats to be mixed with air by rotation of-the impeller and gagain discharged into said second chamber, said second at an adjacent point of reentry tending to limit reentry of liquid at said second point.

29. In a self-priming pump, a pump casing having a single continuous channel open toward the center of the casing and having an inlet opening communicating with the central part of the casing, a single open type impellerA running in said channel, a, plurality of priming and ldischarge openings disposed at angularly spaced points about said channel, the angular distance between a priming opening and its nearest cooperating discharge opening being not substantially greater than that within which the impeller forms and builds up discharge pressure of a mixture of air and liquid during priming, a separator and discharge .chamber having an outlet through which gas is" discharged during priming andl through which liquid is discharged during 'liquid pumping, a passageway of substantially greater cross section than that of the sum oi' the discharge openings for conducting all the mixture discharged by said discharge openings to said separator and permitting agglomeration of gas bubbles as the mixture is being conducted,

and a passageway -leading from the separator to said priming openings for the return of priming liquid substantially freel of entralned gas, said separator and said passageways servingto equalize the circulation of liquid in both amount and gas content duringvpriming, all of said openings serving as parallel discharge openings when liquid is supplied to the inlet of the pump.

30. A pump of the class described, comprising y an impeller adapted to receive liquid axially and to discharge the same substantially tangentially, a casing having a peripheral portion embracing the peripheral portion of the impeller and having a central inlet for fluid tobe pumped, said casing having pairs of throats spaced about-saidperipheral portion by angular distances substantially great enough only to permit the impeller to build up the desired liquid discharge'pressure between the posterior throat of one pair and the anterior throat of another pair, whereby the mixture of gas and liquid formed during priming is subjected to minimum centrifugal separation, a chamber having inlet means through which the liquid from all the anterior throats enters in a posterior throats serving as discharge throatsv common stream in the same direction during either priming on liquid pumping, whereby during priming the gas contents of said common stream is equalized, said chamber having a discharge outlet through which gas is discharged during priming and through which liquid is dis- -charged during liquid pumping, and conduit means-through which liquid freed from gas flows from the chamber `to said posterior throats and into the peripheral part of the impeller during priming,- excessive re-entry at one priming throat` being caused to hinder re-entry of priming liquid at the next adjacent primingthroat, whereby `the eflciency of entrainment of gas is enhanced, said .during liquid pumping.

31. In a self-priming pump, a pumping chamber 'with a, central inlet having an even number peripheral-ly disposed throats, an impeller in the chamber serving when liquidis supplied at the inlet to discharge liquid at all of said throats in parallel, a manifold of relatively great cross sec`- tion at its central part and having an outlet at said central part for the fluid being pumped, said manifold lbeing progressively reduced in crosssection fromsaid cent part to yboth ends, one half of said manifold being connected to alter through the other half of vthe through the other half of said throats into thenate ones'of said throats and the other half of said manifold being connected to the others of said throats, said two halves of the manifold being curved peripherally about the pumping chamber, and-when liquid at said inlet fails said impeller forming a mixture of air and liquid in the chamber and driving the same through said alternate throats inparallel into the one-half. of the manifold wherein the gas separates from themixture and passes out said outlet, the liquid from which gas has been liberated passing periphery of the; impeller, the maximum angular distance between coperating adjacent throats connected to different halves of the manifold being Aonly substantially the distance within which the mixture attains discharge velocity,

the travel of the priming-liquid in said manifold being at a relatively lowyelocity and in a. long path as compared with its travel in the casing, said manifold equalizing the supply and gas content of the. priming liquid and serving to stabilize the actionof the pump.

32. A self-priming'centrifugal pump comprising an impeller casing in which an impeller is mounted to run for entraining gas and liquid during priming and for 'imparting centrifugal force to the mixture to discharge the same, said vcasing having an axial inlet to which a suction pipe for water is adapted to be connected, a separator having an outlet at its upper end for the discharge of y gas during priming and liquid 'dure ing liquid pumping, the impeller casingh'aving a plurality of angularly spaced discharge ports manifold and which communicate withthe separator, the angular spacing between discharge ports being not substantiallygreater than that required to develop full discharge pressure when the pump is supplied with liquid, means to trap suiilcient liquid to establish a working charge for evacuating gas from the impeller chamber during priming, rotation of the imponer causing the trapped liquid during priming to be distributed partly inthe impeller casing as a transientmoving pool of liquid entraining gas and passing out of theA discharge ports simultaneously at a plurality of angularly spaced points to -the separator and partly as a transient moving pool of liquid in the separatorwhich latter pool gives up vthe en-` trained gas and permits its escape at the said outlet ofthe separator, there being a plurality of auxiliary ports lin the impeller chamber communieating with the separator and through which liquid from the pool in the separator is returned to replenish the pool in the impeller chamber, said fauxiliary ports being so disposed with respect to the discharge ports that an excess of returning liquid at 'one auxiliary port iscarried through a greater angular distance than that in which normal pressure is developed and lmpinges upon another auxiliary port with the eifect of reducing lthereturn ilow whereby the circulation -between said ports is stabilized and maintained in' emcient operation, said pump beingv organized to discharge liquid throughboth the discharge ports and the auxiliary ports when the inflow of liquid at the inlet increases the amount Vof liquid in the transient pool in the impeller chamber.

33. In a centrifugal pump, an impeller cham-v ber having an impellerlchannel and an impeller.y

therein adapted during-priming to form a mixture of gas andliqiiid and to impart centrifugal force to the mixture to discharge the same, a separator having an outlet for gas during priming,

a pair of auxiliary throats leading to the impeller channel for returning liquid from the separator to the impeller channel during priming, said Patent No. 2,110,885.

throats being separated angular-1y by'a distance greater than that required to build up normal y CERTIFICATE OE CORRECTION..

stantially greater than that required for building up normal discharge pressure of mixture during priming, whereby the entry of excessive priming liquid from the auxiliary throat anterior to the discharge throat in direction of rotation o1' the `impeller will cause liquid to be carried past the discharge throat and exert a retarding eilect upon the return flow of the auxiliary throat which is posterior to the discharge throat. in the direction of rotation of the impeller.

. HARRY E. LA BoUR.

March 15, 1958.

HARRY E. LAy BOUR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as foilows: Page 8,second column, .line 2'?, claim 5, for the article "the" read a; page 10A, first Ico1- urnn`-1ine 55, clairn lLL, after. "the" insert said; 'page 12, first column,

I line 50, claim 3Q, for "on" read or; and 'that the -said LettersPatent should be read with these correct-ions therein that the samemay conform to the record of the case in the Patent Office. I

Signed and sealed this'fsd day of May, A.D. 19758.

(Seal)` Henry Van Arsdale, 'Acting Commissioner of Patents a pair of auxiliary throats leading to the impeller channel for returning liquid from the separator to the impeller channel during priming, said Patent No. 2,110,885.

throats being separated angular-1y by'a distance greater than that required to build up normal y CERTIFICATE OE CORRECTION..

stantially greater than that required for building up normal discharge pressure of mixture during priming, whereby the entry of excessive priming liquid from the auxiliary throat anterior to the discharge throat in direction of rotation o1' the `impeller will cause liquid to be carried past the discharge throat and exert a retarding eilect upon the return flow of the auxiliary throat which is posterior to the discharge throat. in the direction of rotation of the impeller.

. HARRY E. LA BoUR.

March 15, 1958.

HARRY E. LAy BOUR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as foilows: Page 8,second column, .line 2'?, claim 5, for the article "the" read a; page 10A, first Ico1- urnn`-1ine 55, clairn lLL, after. "the" insert said; 'page 12, first column,

I line 50, claim 3Q, for "on" read or; and 'that the -said LettersPatent should be read with these correct-ions therein that the samemay conform to the record of the case in the Patent Office. I

Signed and sealed this'fsd day of May, A.D. 19758.

(Seal)` Henry Van Arsdale, 'Acting Commissioner of Patents

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