US2368529A - Pump - Google Patents

Description

Jan. 30, 1945. L EDWARDS 2,368,529'

PUMP

Filed Sept. 8, 1942 2 Sheets-Sheet 1 v Hum MILES (Oh/ELL EDWARDS INVENTO Jan. 30, 1945, EDWARDS PUMP Filed Sept. 8, 1942 2 Sheets-Sheet 2 Patented Jan. 30, 1945 Nl'rEo STATES mm-mm" Miles Lowell Edwards, Lonlvlew. Wash.

This invention relates to pumps, and more particularly to centrifugal pumps designed to handle liquids at temperatures at the flashin point of the liquid. Such temperatures may be occasioned either by the application of heat to the liquid, or by a reduction 'of pressure of the liquid, or where the fluid is being reduced to a liquid state from a gaseous state by removal of heat, as in a distilling process.-

In a tank which contains liquid at the boiling,

pressure increases with thedepth of the liquid,

the boiling action is lessened and boiling is lessinclined to take place at-the bottom of the tank. However, in a tank containing boiling liquid, in the area adjacent the bottom where gas is not freely forming, a hydraulic disturbance, such as occurs when the liquid enters a centrifugal pump, will cause the formation of gas. For this reason, in pumpingliquids at boiling temperatures a pump of the centrifugal type willbecome gas bound due to the accumulation of gas from the flashing liquid. In order, therefore, to handle boiling liquids in a centrifugal pump, it has been necessary heretofore either to locate the centrifugal impeller closely adjacent the intake from the tank and in such position that the gas which forms in the impeller passages may free itself from the revolving impeller and flow in a coun-. ter-gravity direction back into the tank away pump intake in a side wall of the well. Obviously, the wellmust be of suflicient size to admit not only the pump but provide room also for the manipulation of tools for effecting replacement and repair. The primary disadvantages of such an installation reside in the weight and cost inherent in the construction of the well and in the structure of the tank made necessary by the relatively large arm hole opening to the well.

An example of a construction embodying the location of the pump by pipe connection at an appreciable distance below the surface of the liquid in a tank is to be found in the oil refining industry where distillate is collected in condensing tanks which are mounted at relatively high elevations in order that the'pump may be submerged a suflicient depth below the surface of from the pump, or to locate the pump by pipe located at any appreciable distance below the fuel tank. It has been found necessary to locate these pumps in'a horizontal position with the. in-

so that gas which forms at the entrance to the impeller passages may free itself therefrom and 7 return to the tank. In a construction heretofore in use, thepump is located within an'inverte'd well in the bottom of the tank with the pump mounted in a horizontal position and with the the liquid to utilize the pressure of the liquid for avoiding the excessive formation of gasby the hydraulic disturbance created by the impeller vanes.

In the present invention applicant has provided a centrifugal pump comprising the usual intake communicating with the eye of the impeller and a volute casing communicating with the discharge port, and in combination therewith a new and novel arrangement of elements comprising a radial flow or centrifugal pump'having a discharge therefrom to'the volute casing, and an axial flow pump having a discharge therefrom back to the liquid supply, i. e., the tank. In this pump there are two components of flow, one of which is radial due to the function of the centrifugal impeller and the other of which is axial due to the function. of the axial flow impeller. Applicant has found that a simple axial fiow pump, when working at very low differential pressures, will function to pass quantities of gas along with the pumped liquid without becoming gas bound. The centrifugal impeller is so constructed that the vanes extend to within the area of axial flow and the gases which collect in the inner ends of the passages of the centrifugal imtake flanged directly to a vertical wall of the tank 1 peller are withdrawn therefrom by the axialflow impeller and removed from the path of radial flow.

This combination of elements permits the location of the pump unit at a distance away from the tank for pipe connection to the tank or, if desired, the pump may be located'within the tank in a vertical position with the motor above the pump for withdrawal 'ofliquid from the tank into the bottom of the pump. Pumps embodying constructions heretofore in use have been. inoperative in vertical positions for bottom suction arrangement for the reason that when operated in (this vertical position gases which collect in the pump are trapped therein by the position of the pump with respect to gravity. Applicant's construction enables the installation of a centrifugal pump in a vertical position in the floor of a tank with the motor above the pump, the motor being immersed in and tightly sealed from the liquid in the tank. Suitable passages vent the motor chamber to the atmosphere.

It is a principal object of the invention to provide a pump of the centrifugal type for pumping liquids at temperatures at the flashing point of the liquid.

It is a further object of the invention to provide a pump wherein a centrifugal impeller functions to create a radial flow and a screw impeller functions to create an axial flow, and wherein gases which may collect in the centrifuga1 impeller are conducted to within the area of the axial flow and withdrawn thereby from the area of radial flow.

It is a further object of the invention to provide a pump which will operate under conditions of minimum submergence in a condensing liquid as when pumping the condensed liquid in a distilling process.

It is a further object of the invention to provide a pump which may be installed in a vertical position for bottom suction and which will operate in this position without becoming gas bound.

It is a further object of the invention to provide a pump for use as an aircraft fuel booster pump and which will maintain the delivery of fuel under conditions accompanying the ascent of the aircraft to substratosphere altitudes, and to enable such ascent within an absolute minimum period of time.

With these and other objects and advantages in mind, the invention resides in the novel construction and combination of parts hereinafter described, illustrated in the accompanying drawings, and set forth in the appended claims; it being understood that various changes in form, proportion, size and details of construction within the scope of the claims may be resorted to without departing from the spirit or sacrificing any of the advantages of the invention.

In 'the drawings: Figure 1 is a sectional elevation of a vertically positioned bottom suction pump embodying the principles of the invention; Figure 2 is a sectional View taken on the line 22 of Figure 1, showing the configuration of the impeller unit and volute casing; Figure 3 is a sectional view taken on the line 33 of Figure 1. showing the configuration of the axial impeller and disposition of the passages for venting the motor chamber and seal; Figure 4 is a fragmentary sectional elevation of the pump shown in Figur 1, showing the passages for venting the seal; Figure 5 is a sectional elevation of the impeller unit; Figure 6 is a perspective view of a detail showing the leading edge of an axial impeller blade; and Figure 7 is a, sectional elevation of a horizontally positioned side suction pump illustrating a modification of the invention.

The pump illustrated in Figure 1 of the drawings is shown 'as mounted in a vertical position within a tank, with the pump arranged for bottom suction and with the motor above the pump. In

opening 2 through the floor through which the pump unit may be inserted or withdrawn. The opening 2 is defined by a recessed flange 3 to which the plate 4 which supports the pump may be attached as by suitable fastening means 5. The construction just described provides a flush outer surface of the tank wall, which is of importance in installations where the outer surface of the tank wall is the wing surface of an aircraft. In the construction illustrated in the drawings the pump structure is supported upon four struts B. These struts support that portion of the pump casing I which forms the volute 8 and to which is bolted, at meeting flanges 9 and 9, the upper side plate ll.

Supported by means of struts I 2 in a vertical axial position above the pump is the motor chamher [3 within which is mounted the motor (not shown) for driving the pump. The housing ll which encloses the motor chamber I3 may be separable at meeting flanges (not shown) to per: mit access to the motor. The motor is directly connected to a vertical shaft l5 to the lower end of which is threaded an impeller unit It comprising a centrifugal impeller I1 and a screw impeller 18. The shaft 15 extends through a chamber l9 within the housing 2] and within which is contained the sealing means for sealing the motor chamber from the liquid which may follow up-' wardly along the shaft. The shaft is supported by bearing 22 mounted in the bottom wall of the motor housing l4.

-Air is admitted to the motor chamber l3 and to the chamber 1 9 in the housing 2| by way of passages 23 and 24 extending through selected ones of the struts 12, through the meeting flanges 9 and 9, through complementary ones of the struts 6 and through the plate 4. Surrounding the shaft 15 in the housing 2| is a seal comprising a steel washer 25 closely fitting the shaft, a carbon sealing washer 26 keyed to the wall, of the housing 2! and having seating engagement with the steel washer 25, and a bellows seal 21 the ends of which are compressed against a machined surface 28 of the housing 2| and against the lower surface of the sealing washer 28, respectively, by means of a helical spring 29. The upper surface of the steel washer 25 is recessed to receive a shouldered portion 3! of the shaft l5, a gasket 32 being inserted.

between the washer 25 and the shoulder 3| to prevent the leakage of fluid therepast. The sealing washer 26 is provided with ears 33 which engage in niches 34 provided in the wall of the housing 2| to prevent rotation of the washer relative to the bellows seal. By this construction, while fluid being acted upon by the pump may enter that portion of the chamber l9 within the bellows seal, entrance of such fluid into that portion of the chamber l9 surrounding the bellows seal and through the bearing 22 into the motor chamber I3 is precluded.

In the illustrated embodiment of the invention. the impeller unit, comprising both the radial or centrifugal impeller H and the axial or screw impeller I8, is machined from a. homogeneous solid block of metal. The impeller unit comprises a cylindrical element 31 open at both ends and receiving through one end thereof an internally threaded sleeve 38 by which the impeller unit is fastened to the shaft l5. Mounted within the cylindrical element 31 is the axial flow impeller l8 consisting of complementary screw-like flanges of approximately one-half turn. The inner edges of the screw-like flanges are secured to the sleeve 38, while the outer edges aresecured to the wall of the cylindrical element ".110 that-die blades of the impeller l6 furnish driving connection between the shaft l6 and the impeller unit. An annular flange 35 at the lower end of the cylindrical element 31 forms the shroud plate for a radial flow impeller of the centrifugal type having vanes 35 extending generally outwardly from the eye of the impeller. Adetail of the constructionof the axial impeller is illustrated in Figure 6 where'the. sharp leading edge 45 of each screw-like flange is shown as leading from the lower surface of the flange. Any tendency toward cavitation around the impeller will occur on the pressure side of the blade rather than on the vacuum side of the blade due to this leading edge 45, and, since the flow of liquid is approximately parallel to the surfaces of peller andyet of somewhat smaller diameter than the intake port as through the volute casing 1. It

is important that the intake port be large enough to P event excessive velocities of the liquid entering the pump. Fluid acted upon by the screw impeller is is discharged therefrom into the area surrounding the housing 2| and may flow from thence. between the struts l2 into the tank I.

The liquid pumped by the centrifugal impeller. I'l flows through the volute 6 and is delivered by suitable pipe connection as may be; desired. The drawings illustrate a thimble 4| to which-a flexible hose 42 may be fastened by couplings 43. By loosening the couplings 43 the hose 42 may be disconnected from the pump to permit withdrawal of the entire pump unit through the open-' ing 2 in the floor of the tank.

The struts 6 support the pump a short distance above the floor of the tank to provide for the flow of liquid from the tank to theintake port 39. A screen 44 is positioned peripherally of the v pump and extends between the floor of the tank and the volut'e casing I so as to screen li uid flowing from the tank to the intake port.

In the event the liquid being pumped is at the 'boiling point, the moment the liquid moves to within the area of rotation of the centrifugal impeller H the hydraulic disturbance created by rotation of the impeller causes the formation .of gas bubbles which, if permitted to accumulate in the inner ends of the impeller passages, would cause the pump to become gas bound. Gas bubbles from any source whatsoever appearing within the areaof rotative influence of the centrifugal impeller vanes are forced by the separating effect of centrifugal force to flow to the area of smallest diameter within rotative effect of the centrifugal vanes, i. e., to within the inner ends of the passages between the impeller vanes. The centrifugal impeller I1 is so constructed that the inner ends of the impeller vane 35 extend to within the radial area defined by the cylindrical element 31 and soto within the area of the axial pump mounted in a horizontal position exteriorly of thc with the intake through a vertical wall of the tank. While in this view the pump intake is flanged more or less directly to the wall of the tank, it is a feature of the invention that the pump ,may be positioned at some distance from the tank for pipe connection therewith. as may be necessitated in constructions where supporting girders and other similar framework would prevent the pump being mounted closely adjacent the tank inthe manner shown. Figure 7 shows a tank 46 havin an outlet opening 41 adjacent the bottom of the tank a sealed chamber as described in connection with 1 the device shown in Figure 1. The motor 53 is directly connected to the drive shaft 54 which extends through 'a sealing chamber 55 and into' the volute casing 5| for driving connection with the impeller unit 56. Impeller unit 56 comprises a cylindrical element 51 mounted upon the shaft 54 by means of an internally threaded sleeve 58 in the manner as described in connection with the disclosure of Figure 1. Within the cylindrical element 51 is mounted the screw vanes of an axial impeller 59, these vanes merging with both the sleeve 58 and the walls of the cylin drical element 51 to impart driving force to the impeller unit. The ,fianged portion v6| of the cylindrical element forms a shroud plate for a centrifugal impeller 62.

Thebracket 52 carries thereupon a housing 60 enclosing a sealing chamber 55 containing thereelements functions to prevent liquid fromfollowing along the'shaft 54 and leaking into the sealing chamber and from thence past the beari 68.

In operation, liquid is withdrawn from the tank 46 through the opening 41 and into the impeller unit 56 through the intake 69. Liquid is discharged from the centrifugal impeller by way of volute 5| through the discharge port H to suitable pipe connection. Fluid acted upon by the axial flow impeller 56 is discharged thereby into the passage 12 from whence it is conducted through pipe connection 13 back to the tank 46.

The impeller unit 55 produces both a radial and an axial flow, these being the normal functions, respectively of the centrifugal impeller 62 and the axial flow impeller 59. The inner ends of the vanes of the centrifugal impeller-extend to within the area of the cylindrical element 51 and-so to within the area of the axial now, and

- ases which collect in the inner ends of the centrifugal impeller passages are withdrawn therefrom by action of the axial impeller and discharged from the impeller unit back into the tank 46 by way of pipe connection I3.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

I. A pump for handling liquids at temperatures at the flashing point of the liquid, comprising P casing defining a volute chamber having a peripheral discharge, a shaft mounted in vertical position and extending axially of said casing. an

impeller unit mounted on said shaft, a motor for driving said haft mounted above said pump in vertical axial alignment with said impeller, an intake port in said casing below said impeller unit, a discharge port in said casing above said impeller unit, said impeller unit having vanes for discharging liquid from said inlet into said volute chamber, said impeller unit having varies for inducing a flow of liquid axially of said first mentioned vanes and for discharging said axial flow of liquid from said pump.

2. A pump for handling liquids at temperatures at the flashing point of the liquid, comprising a casing defining a volute chamber having a peripheral discharge, a shaft, means for driving said shaft, an impeller unit mounted on said shaft, said impeller unit having vanes for centrifugally discharging liquid into said volute chamber, said impeller unit having vanes for creating a flow of liquid axially of said casing, said first mentioned vanes extending to within the area of flow created by said last mentioned vanes whereby gases collecting between said first mentioned vanes are actedupon by said last mentioned vanes and discharged from the pump, and means for conducting the admixture of liquid and gases discharged by said axial flow vanes to the source of liquid supply.

3. A pump comprising a casing having means defining an inlet and means defining an outlet in opposite end portions of said casing and having a peripheral discharge, an impeller mounted in said casing having vanes for creating a flow of liquid axially through said casing, and a second impeller mounted in said casing and having radial vanes extending outwardly to a point beyond the area of influence of axial flow created by said first impeller for centrifugally discharging a portion of the liquid entering said casing through said peripheral discharge, said outlet for said axial flow pump communicating with the source of liquid supply.

4. A pump comprising a, shaft, an impeller unit mounted on said shaft, means for driving said shaft, said impeller unit comprising a centrifugal impeller having radially extending blades for creating a flow radially of said shaft, and an axial flow impeller having screw-like varies for creating a flow axially of said shaft and said centrifugal impeller, said radial vanes extending outwardly to a point beyond the influence of axial flow for centrifugally discharging a portion of the liquid entering said pump and extending inwardly to within the area of axial flow whereby gases collecting in the passages between said radial vanes are withdrawn therefrom by said axial flow, and means for conducting said axial flow away from said pump.

5. A pump comprising a shaft, an impeller unit mounted on said shaft, said impeller unit comprising a cylindrical element open at both ends and having an annular flange extending laterally from one end thereof, a shaft engag comprising a cylindrical element having an annular flange at one end thereof, a shaft engaging sleeve positioned axially of said cylindrical element, pump vanes secured to said sleeve and to said cy indrical element and providing driving connection between the shaft and the impeller unit, said pump vanes comprising an axial flow pump, and pump vanes secured to said flange and comprising a radial flow pump, the longitudinal axes of said pumps being in axial alignment whereby said axial flow pump induces an axial now through said radial flow pump for expelling gaseous fluids from said radial flow pump.

7. A pump assembly comprising a casing defining a volute chamber having a peripheral discharge, means in said casing defining a central opening extending through said casing and defining at one end thereof an inlet and at the other end thereof a discharge, an impeller unit mounted in said casing comprising a cylindrical element mounted in one end of said opening, an annular flange extending from one end thereof, a shaft engaging sleeve positioned axially of said cylindrical element, pumpvanes secured to said sleeve and to said cylindrical element and providing driving connection between the shaft and the impeller unit, said vanes being operable to create a flow of liquid axially through said casing, and pump vanes secured to said flange and extending to within the radial area of said cylindrical element for centrifugally discharging a portion of the liquid entering said casing into said volute chamber.

8. A device for pumping fully liquid material such as volatile fuel'froma supply of such material, comprising a casing defining a volute chamber having a central inlet and a peripheral discharge, a cylindrical portion of said casing extending axially of said pump from said volute chamber and defining an axial discharge, a pump impeller in said casing for centrifugally discharging liquid from said inlet into the volute chamber, a pump impeller in said cylindrical extension for inducing a flow of liquid axially of said first pump impeller and discharging it through said axial discharge, and means for returning liquid from said axial discharge to the source of liquid supply.

ing avolute chamber having a central inlet and a peripheral discharge, an impeller unit mounted in said casing comprising an axial flow pump and a radial flow pump, the longitudinal axes of said pumps being in axial alignment, means defining a discharge for saidaxial flow pump, and means for returning liquid from said discharge to the source of liquid supply.

10. A pump assembly comprising a tank, a pump-mounted within said tank comprising a, casing defining a volute chamber having a pcripheral discharge, means in said casing defining a central opening extending through said casing and defining at one end thereof a central inlet providing for the flow of liquid from said tank into said casing and providing at the other end thereof a central discharge from said casing into said tank, a pump impeller in said casing for centrifugally discharging liquid from said inlet into said volute chamber, and apump impeller mounted in one end of said opening for inducing a flow of liquid axially through said casing and into said tank.

11. A pump assembly comprising a casing defining a volute chamber having a central inlet and an outlet orifice in said casing for said axial flow disposedon the opposite side of said impeller unit with respect to said inlet.

12. A pump assembly comprising a casing de-' fining a volute chamber having acentral inlet and a peripheral discharge, means defining an axial discharge port in said casing on the opposite side of said volute chamber with respect to said inlet, a pump impeller in said casing for centrifugally discharging liquid into said volute chamber, and a pump impeller in said casing for inducing a flow of liquid axially of said first impeller and discharging it through said axial discharge.

13. A device for pressuring fully liquid material from a source of liquid which comprises a pump assembly having an open passage with an inlet and an outlet accommodating free fiow of liquid therethrough and a peripheral pumping chamber having an annular inlet communicating with said passage, pumping means in said pump assembly for pressuring material through the pumping chamber from said passage together with agitating means extending into said passage for releasing bubbles of gas and vapor from the liquid being pumped, and means for inducing a of said source and having a casing defining an annular pumping chamber with a central inlet and a'peripheral outlet, an impeller having pumping vanes for pressuring liquid through the pumping chamber to the outlet, said assembly having an open passage in communication with the liquid of said source on opposite sides of the pumping vanes accommodating flow of bubbles released by the impeller back to said source, and means inducing aflow of liquid through the passage .to sweep bubbles off of the inner edges of the pumping vanes and out of the passage.

15. A pump impeller construction comprising an open ended cylindrical member having an outturned flange at one end thereof, pumping vanes depending from said flange beyond the member, said vanes havinginner edges extending inwardly beyond the inner end of the flange to provide agitators disposed outwardly from the axis of the impeller, an axial hub, and screw vanes connecting the cylindrical member and hub flow of liquid through the passage for removal of bubbles liberated by said agitating means.

14. A device for pressuring fully liquid material from a source of liquid which comprises a pump assembly adapted to be submerged in the-liquid 35 gas bound.

arranged to impell fiuid axially of the agitators to sweep oil bubbles developed thereon.

16. A pump impeller comprising circumferentially spaced pumping vanes having open inner ends defining a ring, said vanes extending outwardly from the ring to define pumping channels therebetween arranged to receive fluids from the space inside. of the ring, said space inside of the ring providing a through axially extending channel, and means for inducin a substantial flow of fluids through said axially extending channel to circulate fluids along the inner open ends of said vanes to prevent the vanes from becoming MILES LOW LL EDWARDS.

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