US3374747A

US3374747A - Self-priming device and method for pumps

Info

Publication number: US3374747A
Application number: US573659A
Authority: US
Inventors: William L King; John F King
Original assignee: Loyal W James; Leonard James
Current assignee: Baker Hughes Oilfield Operations LLC
Priority date: 1966-08-19
Filing date: 1966-08-19
Publication date: 1968-03-26
Anticipated expiration: 1985-03-26

Description

March 26, 1968 w. L. KING EITAL SELF-PRIMING DEVICE AND METHOD FOR PUMPS 2 Sheets-Sheet 1 Filed Aug. 19, 1966 L mm whom wh m OE WILLIAM L. K! JOHN F Kl lNVE/VTOR BUG/(HORN, BLORE, KL/JROU/ST 8 SPAR/(MAN ATTORNEYS March 26, 1968 w; L. KING ETAL SELF-PRIMING DEVICE AND METHOD FOR PUMPS Filed Aug. 19, 1966 2 Sheets-Sheet B BUCKHOR/V, BLORE, KLAROU/ST a SPAR/(MAN ATTORNEYS United States Patent 0 3,374,747 SELF-PRIMING DEVICE AND METHOD FOR PUMPS William L. King and John F. King, Eugene, Oreg., as-

signors to Loyal W. James and Leonard James, both of Eugene, Oreg.

Filed Aug. 19, 1966, Ser. No. 573,659 14 Claims. (Cl. 103-101) ABSTRACT OF THE DISCLOSURE This application discloses several different pump embodiments all of which utilize the aspirator or jet pump principle to withdraw air from the suction line of the pump either directly or indirectly, and significantly, use air or other ambient gas as the aspirating or pumping medium rather than requiring an auxiliary supply of Water, steam or the like as in prior art self-priming pumps. The aspirating means in each instance includes an aspirator head, or velocity tube, incorporating a venturi, reverse pitot nozzle, orifice or equivalent means to create a zone of low pressure within the tube as air at high velocity generated by rotation of the pumps impeller passes axially therethrough. The aspirating means also includes a suction tube which opens into the zone of low pressure within the velocity tube and extends into communication With the pumps suction line so that the air Within the line will be drawn through the suction tube toward the velocity tube, thereby evacuating the suction line to permit the fluid to be pumped to enter such line and the impeller.

In one illustrated embodiment, the velocity tube is mounted on the outside of a rotatable pump casing and the suction passage extends through a wall of the casing and opens into the main pump chamber, which is in communication with the suction line, so that upon rotation of the casing, air exterior to the casing passes through the velocity tube to reduce pressure within the casing and suction line.

In a second embodiment the velocity tube is stationarily mounted within the main chamber of a rotatable pump casing which incorporates radial impeller passages Within its walls, and the suction tube passes from the chamber into the suction line of the pump. The high velocity airstream created within the chamber by rotation of the pumps impeller means passes through the velocity tube to draw air from, and thereby reduces pressure in, the suction line.

In a third illustrated embodiment the self-priming device is incorporated in a conventional centrifugal pump having a stationary casing and rotatable impeller within the main chamber of the casing. In this embodiment the velocity tube of the self-priming device is mounted on an interior wall of the pump casing on the discharge side of the impeller, and the suction tube passes from the velocity tube exteriorly of the casing to the suction side of the impeller so that the airstream created by rotation of the impeller passes through the velocity tube to suck air from the suction line of the pump.

The present invention relates to self-priming pumps, and more particularly to a method of automatically priming pumps and to self-priming devices for fluid pumps.

The self-priming device of the present invention is adapted for use with any rotary fluid pumping means having a suction line from which air or other ambient gas must be evacuated so as to enable the fluid to be pumped to enter the suction line and flood the impeller means. The device is useful, for example, both with conventional centrifugal pumps having a stationary casing and an impeller rotatably mounted within the casing and also with centrifugal pumps of the type having a casing which rotates as the impeller means to force fluid into a stationary pickup and discharge tube stationarily mounted within the casing.

Self-priming pumps of the prior art have the disadvantage of being extremly complex and therefore very costly. Most such prior pumps require an auxiliary source of priming fluid, some with means for pressurizing the priming fluid. Self-priming pumps of the prior art also have the disadvantage of being considerably less sufilcient than comparable pumps without the self-priming feature.

It is therefore a primary object of the present invention to provide a self-priming device for pumps which is greatly simplified and therefore considerably less expensive than prior art self-priming devices.

Another primary object is to provide a self-priming device which does not require an auxiliary source of priming fluid.

Still another primary object is to provide a self-priming device which can be adapted for use on nearly all types of rotary pumps.

A further primary object is to provide a self-priming device which will not reduce appreciably the efliciency of the pump incorporating such device.

Another important object is to provide a self-priming device which can be installed on existing pumps,

A more specific object is to provide a self-priming device utilizing an aspirator or jet pump principle capable of using ambient air as the aspirating medium.

Another specific object is to provide a self-priming device which can be used with a centrifugal pump having either a rotatable casing or a stationary casing.

A further object is to provide a self-priming device which can be adapted for use with a pump having a rotary casing either by mounting the device itself on the rotating casing or by mounting the device stationarily within the casing.

Another object is to provide a centrifugal pump which does not require a fluid seal between the rotary and stationary elements of the pump.

Another primary object is to provide a method of priming a pump automatically using the ambient air or other gas as the priming medium.

The foregoing objects, advantages and applications of the invention will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings wherein:

FIG. 1 is an axial sectional view through a pump having a rotatable casing and a self-priming device in accordance with the invention mounted on the exterior of the casing;

FIG. 2 is an enlarged sectional view taken along the line 2-2 of FIG. 1 showing the details of the head portion of the self-priming device;

FIG. 3 is an axial sectional view through a pump similar to that of FIG. 1 having a modified self-priming device mounted within the main chamber of the pump casing;

FIG. 4 is a somewhat schematic elevational view, partly in section, of a conventional centrifugal pump incorporating a self-priming device in accordance with the present invention; and

FIG. 5 is a vertical sectional view through the pump of FIG. 4 taken along the line 55 of FIG. 4.

Detailed description With reference to the drawings, FIG. 1 illustrates a type of centrifugal pump which is the subject of a copending application Ser. No. 447,133, filed Apr. 12, 1965, now abandoned, in the name of William L. King, entitled Centrifugal Pump. This particular type of pump, of itself, is not the subject of the present invention, and only 3 illustrates one of several applications of theself-priming device which is the subject of the present invention. The illustrated pump is characterized by a generally cylindrical, rotatable casing 19 which is keyed at a hub portion 12 to the outer end of a motor shaft 14 and mounted in bearings 15 for rotation about its axis. The casing defines a main pump chamber 16 within which there are no moving parts. The impeller means for the pump is provided by a series of small radial passages 18 within one side wall 20 of the pump, such passages radiating from a central intake opening 22 in such side wall to outer discharge ports 24 opening into the pump chamber at its outer periphery.

A stationary suction line 26 extends from an intake (not shown) at a source of fluid to be pumped and includes a straight extension 28 thereof which extends through a central hub portion 39 of a stationary outer cylindrical casing 32. The stationary casing partly envelopes the rotatable casing to serve as a mount for the stationary elements of the pump. The suction line extension continues through a central opening 34 in a side Wall 36 of the rotatable casing and through the pump chamber to an outlet opening 38 adjacent and aligned with the central intake opening 22 in the rotatable casing. Thus fluid flowing through the suction line will pass directly into the impeller passages of the rotatable casing as it is rotated, from which the fluid will be discharged at high velocity, due to centrifugal force, into the main pump chamber.

Within the main chamber a fluid pickup and discharge tube 40 is stationarily mounted to form a part of the pressure or discharge line of the pump, such tube being illustrated and described in greater detail in the aforementioned co-pending application. In general, however, such tube includes a generally circumferentially extending outer tube portion 42 positioned adjacent the outer periphery of the pump chamber and having an intake opening 44 positioned at the level of ports 24 for receiving fluid discharged into the pump chamber by the impeller means through such ports. The pick tube also includes a generally radially extending stem portion 46 which is stationarily' mounted within a base sleeve member 48 which encircles extension 28 of the suction line within the chamber and is held in place by set screw 50. A continuation of stem 46 extends through sleeve 48 and an opening in suction line 28, and is connected at 51 to a discharge pipe 52 within the suction line, which pipe passes through the suction line portion at 54 outside the pump casing and leads to a desired point of use or storage of the fluid being pumped.

A suitable fluid seal 56 prevents the escape of fluid from the pump chamber through central opening 34 between the rotatable casing and the suction line, although sealing at this point presentsrno particular problem because a minimal fluid pressure is developed at such point in the illustrated type of pump.

The foregoing describes the essential portions of a centrifugal pump which is the subject of the aforementioned patent application without regard to the self-priming device which is the subject of the present invention and which will now be described.

The self-priming device in general operates on the aspirator or jet pump principle and therefore includes aspirator means including an aspirator head, or what will be referred to hereinafter as a velocity passage means, and a suction passage means connected to the velocity passage means. The velocity passage. means is a tubeshaped element formed to provide along its passage a pressure differential, and specifically a zone of low pressure below the ambient air pressure and below the pressure in the suction line so that upon creation of the zone.

of low pressure within the velocity tube air within the pumps suction line will be drawn from the same through the suction passage of the aspirator and into the velocity tube, thereby reducing pressure with the suction line to a degree sufficient to draw fluid to be pumped into the same. 7 It is to be understood that the term velocity tube is intended to include any form of aspirating head adapted to create a zone of low pressure by the passage of fluid therethrough, whether it be by means of a venturi'construction, orifice, nozzle or other well-known means or any combination of the same within the tube.

One example of a velocity passage means suitable for use as part of the self-priming device of the present invention is the velocity tube 60 shown mounted on the outside of the rotatable casing of FIG. 1 and illustrated in FIG. '2. Such tube includes a main tube portion 62 having an axial passage 64 with an intake opening 66 at the of the axial passage which defines the zone of low pressure created behind the high velocity jet of fluid from the nozzle. A tubular stem 76 extending laterally from the main tube defines the outlet end of the suction passage 78 of the aspirator which enters the enlarged cavity 74 at right angles to the main passage. Thus, the velocity tube incorporates the so-called jet pump principle to draw air or other fluid from a remote source through the suction passage into the main axial passage 64 from which it is discharged at =68 with the high velocity air stream passing axially through the velocity tube.

In the embodiment of FIG. 1 the stem 76 of the velocity tube is threaded into an opening 80 in an outside wall of the rotatable casing, such opening forming the outer end of suction passages 78 which passes through side wall 36 of the easing into communication with the main pump chamber at a port 82. Passage 78 is formed in side wall 36 by a pair of parallel radial bores 83, 84 which are plugged at their outer ends by plugs 85 and jointed at their inner ends by a lateral bore 86. Such lateral bore is plugged at '87 at the inner surface of the wall so that such bores from a generally U-shaped suction passage that will prevent water or other fluid being pumped from being aspirated upon rotation of the casing should any such fluid accidentally enter the passage through port 82.

Port 82 of the suction passage is preferably positioned nearer the radially outer periphery of the chamber than to the center thereof, but radially inwardly of ports 24 of the impeller passages and radially inwardly of intake opening 44 of the pickup tube so that as the casing rotates air will continue to be drawn from the chamber and suction line, even though a certain amount of residual water from the chamber or suction line may enter the pickup tube. In other words, it is preferable that the aspirating effect of the priming device not be cut off until after there is a positive and continuous flow of water through the impeller passages into the pickup tube.

With the foregoing arrangement rotation of the casing causes a stream of ambient air adjacent the outside of the casing to pass through the velocity tube, thereby reducing pressure in cavity 74 of the tube below that initially within the pump chamber and suction line to effect withdrawal of air through the suction passage from the chamber. This results in a lowering of the pressure-within the chamber and suction line below that of the ambient air so thatrthe fluid to be pumped will be drawn (in reality forced by the ambient air) into the suction line and impeller passages to flood the same, whereafter the fluid will be pumped continuously into the chamber and out through discharge line 52.

FIG. 3 form With reference now to FIG. 3, there is illustrated a pump of the same general type as that shown in FIG. 1,

including a rotatable casing a with impeller passages 18a in one side wall thereof. Suction line 26a and its extension 28a lead into a main chamber 16a defined by the casing and into communication with the impeller passages through a central opening 34a in the opposite side wall of the casing. A fluid pickup tube 40a mounted as in FIG. 1 receives fluid ejected into the chamber at high velocity through impeller ports 24a and conveys such fluid into discharge line 52a as before.

However, the pump of FIG. 3 incorporates a modified self-priming device in the form of a stationary aspirator means 100 stationarily mounted within the pump chamber and including a velocity tube 102 adjacent the outer periphery of the chamber at the outer end of a hollow stem I104 forming a part of the aspirators suction passage. The suction passage has an extension 106 passing into the suction line and an intake opening 108 well upstream in the suction line, although such opening could be provided at any point in the suction line if desired. Stem 104 terminates at an annular base 110 which surrounds the inner end of the suction line extension wtihin the pump chamber and has an opening 112 therethrough by which the interior of the stem is placed in communication with extension 106 of the suction passage.

With the foregoing arrangement, rotation of the casing with air in the suction line will cause the impeller passages 18a to discharge air circumferentially at high velocity into the pump chamber through ports 24a. Velocity tube 102, which may have the same configuration as that of FIG. 2, is positioned with its intake upstream so that the airstream will pass therethrough, creating a zone of low pressure within the tube to draw air from the suction line of the pump through suction tubes 106 and 104 thereby enabling the liquid to be pumped to enter the suction line and eventually the impeller passages. Velocity tube 102 is preferably positioned at least slightly radially inwardly toward the center of the pump chamber from the intake opening of pickup tube 40a so that the velocity tube will not be blocked by either residual liquid within the chamber or liquid first drawn into the chamber through the impeller passages. This assures that the aspirating efiect of the velocity tube will continue for a period of time after liquid initially enters the pump chamber and fluid pickup tube to provide a continuous flow of liquid to be pumped into the suction line and impeller passages.

The pump of FIG. 3 incorporates another significant feature which eliminates the need for a fluid seal, such as fluid seal 56 provided in the pump of FIG. 1, at the central opening 340 through which the stationary suction line extends into the rotatable casing. This feature includes partition means in the form of a pair of discs 112, 114 spaced apart laterally within the pump chamber and extending radially from annular base member 10. The discs terminate at marginal edges spaced inwardly of the outer periphery of the chamber so that fluid impelled into the chamber through the impeller ports are not blocked from entering the intake opening of the fluid pickup tube. However, the discs are positioned on opposite sides of the pickup tube and the aspirator tube so as to block the passage of a liquid from the chamber through central opening 34a regardless of the absence of a seal at such opening, both when the casing is rotating and, more importantly, when the casing comes to rest. This features enables the inexpensive manufacture of a centrifugal pump without close tolerances and without a fluid-tight seal between the stationary and rotatable pump elements without affecting appreciably the operating efliciency of the pump.

FIG. 4 form FIGS. 4 and 5 illustrate the application of the selfpriming device of the invention in conjunction with a conventional centrifugal pump having a stationary casing 120 forming a main pump chamber 122 within which an impeller P4 is mounted for rotation by a motor (not shown) transmitting power to the impeller through a shaft 126 extending into the casing. The illustrated pump includes a suction line 128 extending from a source of liquid 130 to be pumped to a central opening 132 in the casing. A discharge line 134 extends tangentially from a peripheral portion of the casing.

A velocity tube [136 of an aspirator-type self-priming device is mounted on an interior wall of the casing or discharge line 134, but in any event on the dicharge side of the impeller so that upon rotation of the impeller the airstream created thereby will pass axially through the velocity tube. The aspirator means also includes a suction tube 138 which extends through the wall of the casing from the velocity tube into communication with the interior of the suction line so that a low pressure zone in the airstream passing through the velocity tube will draw air from the suction line, whereby liquid from source 130 will rise into the line, eventually to a point where it will enter the casing to be acted upon by the impellers.

Method Having illustrated several modifications and applications of the self-priming device of the invention, it will be apparent that all such modifications utilize a novel method of priming rotary pumps in general which permits revolutionary simplification in the construction of self-priming pumps and which can be adapted for use with existing pumps. Essentially, the method comprises the creation of a zone of low pressure remote from the suction line through rotation of the pumps impeller means and constriction of the resultant high velocity airstream to draw air or other gas from such line toward the low pressure zone. The use of ambient air surrounding the impeller means as the priming fluid medium eliminates the need for an auxiliary source of priming fluid, and in this respect is a novel concept revolutionizing the field of selfpriming pumps. It is to be understood that the term fluid as used herein is intended to include both liquids and gases.

Having illustrated and described several preferred embodiments of the invention, it should be apparent to those skilled in the art that the same permit of modification in arrangement and detail, and of application to pumps not illustrated. We claim as our invention all such modifications and applications as come within the true spirit and scope of the following claims.

We claim:

1. A pump comprising:

a rotatable casing defining a main pump chamber,

impeller means comprising radial impeller passages within the walls of said casing for impelling fluid centrifugally into said main chamber adjacent the outer periphery thereof,

a stationary suction line passing through a central opening in said casing and into communication with said impeller passages for directing fluid into said passages,

a fluid pickup tube stationarily mounted within said chamber and including an intake opening adjacent the outer periphery of said chamber in a position for receiving fluid impelled into said chamber by said impeller passages,

a stationary discharge line connected to said pickup tube means and passing outwardly of said casing through said central opening,

means mounting said casing for rotation about the axis of said central opening and relative to said suction and discharge lines,

partition means within said chamber extending continuously circumferentially and radially from said suction line to an outer marginal edge spaced radially inwardly of the outer periphery of said chamber,

said partition means being positioned within said chamber so as to block the flow of any substantial amount of fluid from said chamber through said central opening,

whereby the need for a fluid seal between said casing and the stationary elements of the pump at said central opening is eliminated.

2. Apparatus according to claim 1 wherein said partition means includes a pair of laterally spaced'apart stationary discs in said chamber one on each of the opposite sides of said pickup tube means.

3. Apparatus according to claim 2 wherein the outer marginal, edges of said discs are positioned radially inwardly of the intake opening of said pickup means so that fluid discharged into said chamber by said impeller means can pass unobstructed into said intake opening.

4. A self-priming device for a pump having a rotary casing defining a pump chamber, impeller means carried by said casing and rotatable therewith, a suction line leading to said impeller means and being in communication with said chamber, a stationary fluid pickup means in said chamber, and a discharge line extending from said fluid pickup for leading fluid under pressure from said casing,

said self-priming device comprising:

aspirator means including a velocity passage means and a suction passage means,

said velocity passage means being mounted on the outside of said casing for rotation therewith in a position so that rotation of said casing causes ambient air to pass through said velocity passage means, suction passage means extending from said velocity passage means through said casing and into communication with said chamber so that air passing through said velocity passage means upon rotation of said casing will eflect withdrawal of air from said chamber and from said suction line.

5. Apparatus according to claim 4 wherein said fluid pickup means includes an intake opening adjacent the radially outer periphery of said chamber and said suction passage means includes an intake port opening into said chamber at a position radially inwardly of said intake opening.

6. Apparatus according to claim 4 wherein said suction passage means extends into a sidewall of said casing from an intake port at an interior surface of said wall in a position closer to the outer periphery of said chamber than to the center of said chamber, then radially inwardly toward the center of said casing within said wall, then radially outwardly within said Wall to a discharge opening in an' exterior surface of said wall nearer the outer periphery of said casing than the center thereof and at said velocity passage means so that any liquid within said chamber entering said suction passage will be prevented from being discharged from said discharge opening.

7. A centrifugal pump comprising in combination:

a rotatable pump casing defining a main pump chamber,

impeller means comprising radial passages within an end wall of said casing and extending from a central portion thereof and opening into a peripheral portion of said main chamber,

a fluid pickup tube stationarily mounted in said main chamber and having an intake opening adjacent the radially outer periphery of said chamber for receiving fluid impelled into said chamber from said radial passages,

a suction line in communication with the radially inner ends of said radial passages,

a discharge line in communication with an outlet end of said pickup tube,

aspirator means within said chamber including a stationary suction tube portion extending from an intake opening within said suction line radially to an outer peripheral portion of said main chamber,

and a venturi tube portion extending in the direction of fluid flow within said chamber at the radially outer end of said suction tube portion so that upon the initial rotation of said casing, air entering said main chamber from said radial passages passes through said venturi tube and thereby draws air from said suction line through said suction tube and into said venturi tube,

said venturi tube discharging air from said suction line into said chamber so as to be inhaled and subsequently expelled from said chamber by said pickup tube.

8. Apparatus according to claim 7 wherein said velocity passage means is positioned radially inwardly of the intake opening of said fluid pickup tube.

9. A self-priming device for a pump having a rotatable casing, impeller means carried by said casing and rotatable therewith, a main chamber defined by said casing, a fluid pickup tube'stationarily mounted in said chamber and having an intake opening adjacent the radially outer periphery of said chamber for receiving fluid from said impeller means, a suction line in communication with said impeller means and a discharge line in communication with said pickup tube.

said self-priming device comprising:

an aspirator means including a velocity passage means and a suction passage means,

said velocity passage means :being stationarily mounted in said chamber and positioned so that fluid impelled through said chamber by said impeller means at high velocity will pass through said velocity passage means,

said suction passage means extending from said velocity passage means into said suction line and being in communication with both, whereby upon rotation of said casing fluid passes through said velocity passage means to eflect a reduction of fluid pressure within said suction line,

partition means extending radially and circumferentially within said chamber and terminating at a marginal edge spaced inwardly of the radially outer periphery of said chamber,

said partition means being positioned within said chamher so as to block the passage of any substantial amount of fluid from said chamber other than through said pickup tube both when said casing is rotating and when said casing is at rest, thereby enabling the elimination of fluid seals in connection with the mounting of said casing for rotation relative to the stationary elements of said pump. 7

10. A pump comprising:

a rotatable casing defining a main pump chamber and impeller means,

a suction line leading into communication impeller means, 7

a discharge line extending from communication with said impeller means,

aspirator means, including a velocity passage means and a suction passage means,

said velocity passage means being mounted on the outside of saidcasing and being rotatable therewith and extending generally in a direction of ambient fluid movement relative to said impeller means upon rotation of said impeller means so that ambient fluid is caused to pass through said velocity tube upon rotation of said impeller means,

said suction passage means passing through a wall of said casing and extending from communication with a low pressure zone within said velocity passage means into communication with said suction line so that fluid passing through said velocity passage means draws air from said suction line to reduce pressure thereinand thereby draw fluid to be pumped into said suction line and impeller means.

11. A pump comprising:

a rotatable impeller means,

a s c i n line le ding into communication with said impeller means,

with said a discharge line extending from communication with said impeller means, aspirator means including a velocity passage means and a suction passage means,

said velocity passage means being positioned adjacent said impeller means and extending generally in a direction of ambient fluid flow relative to said impeller means upon rotation of said impeller means so that ambient fluid is caused to pass through said velocity tube upon rotation of said impeller means,

said suction passage means extending from communication with a low pressure zone within said velocity passage means into communication with the interior of said suction line so that fluid passing through said velocity passage means draws air from said suction line to reduce pressure therein and thereby draw fluid to be pumped into said suction line and impeller means,

said velocity passage means being rotatable with said impeller means.

12. The method of priming with air a centrifugal pump for fluids heavier than air having a rotatable impeller means for impelling said fluids, a suction passage leading to said impeller means on a suction side of said impeller means from a source of fluid to be pumped, and a discharge passage leading from said impeller means on a pressure side of said impeller means, with air normally surrounding said impeller means and occupying space on the suction side thereof when said impeller means is at rest,

said method comprising the steps:

creating relative movement between a venturi restriction and air ambient to said restriction at a position remote from the suction side of said impeller means by rotating said impeller means,

creating a zone of low air pressure below the pressure in said suction passage by placing said venturi restriction in said air stream so that a portion of said air stream passes through said restriction,

and connecting said zone of low air pressure to the suction side of said impeller means so that upon rotation of said impeller means with high pressure air on said suction side, such air will flow toward said zone of low air pressure to reduce the air pressure on said suction side to a level suflicient to draw fluid to be pumped into said impeller means.

13. A self-priming device for a pump having a rotary casing defining a pump chamber, impeller means carried by said casing and rotatable therewith, a suction line leading to said impeller means and being in communication with said chamber, a stationary fluid pickup means in said chamber, and a discharge line extending from said fluid pickup for leading fluid under pressure from said casing,

said self-priming device comprising:

aspirator means including a velocity passage means and a suction passage means,

said velocity passage means being mounted for rotation therewith in a position so that rotation of said casing causes ambient air to pass through said velocity passage means,

suction passage means extending from said velocity passage means into communication with said suction line so that air passing through said velocity passage means upon rotation of said casing will eflect withdrawal of air from said chamber and from said suction line.

14. A pump comprising:

a rotatable casing defining a main pump chamber,

impeller means comprising radial impeller passages within an end wall of said casing for impelling fluid centrifugally into said main chamber adjacent the outer periphery thereof,

a stationary suction line passing through a central opening in said casing and into communication with said radial impeller passages for directing fluid into said passages,

a fluid pickup tube stationarily mounted within said chamber and including an intake opening adjacent the outer periphery of said chamber in a position for receiving fluid impelled into said chamber by said radial impeller passages,

a stationary discharge line connected to said pickup tube and passing outwardly of said casing through said central opening,

aspirator means including a venturi tube and a suction passage means,

said venturi tube being positioned adjacent said rotating casing in a position so that rotation of said casing imparts a flow of air at high velocity through said venturi tube to create a zone of low air pressure within said venturi tube and remote from said suction line,

said suction passage means having an intake opening in communication with the interior of said suction line and a discharge opening in communication with the low pressure zone of said venturi tube so that upon initial rotation of said casing air passes through said venturi tube and draws air from said suction line through said suction passage means into said venturi tube,

whereby said venturi tube and said pickup tube act collectively during initial rotation of said casing to expel air from said suction line and chamber so that continued rotation of said casing will flood said impeller passages with fluid to be pumped.

References Cited UNITED STATES PATENTS 790,702 5/ 1905 Nash 1031l3 2,690,130 9/1954 Boeckeler 103113 2,733,725 2/ 1956 Zachariassen 103--101 3,004,495 10/ 1961 Macklis 103-413 3,307,485 3/1967 Loque.

FOREIGN PATENTS 72,081 6/ 1866 France. 671,703 5/ 1952 Great Britain. 727,906 11/ 1942 Germany.

HENRY F. RADUAZO, Primary Examiner.