US3438329A - Multistage hydraulic pump having improved diffuser means - Google Patents

Description

A ril ls, 19 9 3,438,329

MULTISTAGE HYDRAULIC PUMP: HAVING IMPROVED DIFFUSER MEANS Filed June 13 1967 'r. WJFULLER Sheet 4 ATTORNEY v "r. w. FULLER 3,438,329 VMUL'I'ISTAGE HYDRAULICPUMP HAVING IMPROVED DIFFUSER MEANS April 15, 1969 z of 3 Sheet Filed June 13, 1967 INVENTOR izzpiwlmq/aae ATTORNEY April 15, 1969 T. w. FULLER vMULTISTAGE HYDRAULIC PUMP HAVING IMPROVED DIFFUSER MEANS Sheet Filed June 13. 1967 BYE; %MS

ATTORNEY United States Patent 3,438,329 MULTISTAGE HYDRAULIC PUMP HAVING IMPROVED DIFFUSER MEANS Thaddeus W. Fuller, Overland Park, Kans., assignor to Fairbanks Morse Inc., New York, N.Y., a corporation of Delaware Filed June 13, 1967, Ser. No. 645,653 Int. Cl. F04d 1/06, 13/02 U.S. Cl. 103-102 Claims ABSTRACT OF THE DISCLOSURE A diffuser for a multistage submersible pump utilizing in particular, stage impellers of turbine or mixed flow type, wherein the diffuser has improved guide vanes defining passages for efficient and smooth fluid transfer from the output of one impeller to the intake of the next succeeding impeller; is formed as an integral, one-piece member of suitable material such as a plastic, and is adapted to be cast or molded by a two-part, straight-draw mold.

This invention relates to improvements in hydraulic pumps, and more particularly to the provision of a multistage submersible pump embodying stage impellers of turbine or mixed flow type, and having improved diffuser means for the pump stages.

In conventional multistage submersible pumps as for example the known submersibles of four inch diameter and larger which are employed generally in domestic water systems, desirable high hydraulic efficiency is sacrificed to a more or less considerable degree in the interest of axial stage compactness and economy in manufacturing construction of such pumps. Usually, therefore, these pumps employ stage impellers of straight centrifugal form, and intervening plate type diffusers. Such diffusers generally provide peripheral apertures to receive the impeller discharge, and radial or curved vanes upstanding on the upstream side of the plate for directing the flow to the inlet of the next stage impeller. As a consequence, turbulence and frictional losses are present which preclude desirable smooth flow transfer from the outlet of one impeller to the inlet of the next stage impeller.

Accordingly, an object of this invention is to provide a multistage submersible pump of improved character and construction which overcomes the above indicated and other disadvantages of conventional submersibles, and which is particularly suitable for economical manufacture.

Another object is to afford an improved submersible pump characterized by stage impellers of the mixed flow or turbine type, and diffusers of presently improved form and construction affording efficient and smooth flow transfer between impellers.

Another object is to provide a diffuser for pumps of the character indicated in the foregoing object, which is of unitary or one-piece construction having smoothy curved guide vanes each extending angularly in the axial direction from an inlet end positioned for close proximity to the discharge periphery of an impeller, to its outlet end adjacent the intake of the impeller in the next succeeding stage.

Another objectis to provide an improved diffuser of the character aforesaid, which may be formed of suitable plastic material and which is of such form and design as to enable ready and economical production thereof by die-casting or injection molding in a two-part, straight draw mold.

The foregoing as well as other objects and advantages of the present invention will appear from the following description of a preferred embodiment as illustrated in the accompanying drawings, wherein:

3,438,329 Patented Apr. 15, 1969 FIG. 1 is a view in longitudinal section of a submersible pump unit embodying the present improvements, the view including a portion of the pump drive motor shown in elevation;

FIG. 2 is an enlarged top plan view of the presently improved diffuser for such pump;

FIG. 3 is a transverse sectional view through the diffuser as taken along line 3--3 in FIG. 2, this view also showing in section related pump impeller and diffuser cap elements;

FIG. 4 is a bottom plan view of the diffuser of FIG. 2;

FIG. 5 is an enlarged perspective view of the diffuser, shown with portions broken away to better illustrate details of the vanes; and

FIGS. 6 through 9 are sectional views in certain regions of the diffuser as taken respectively along lines 6-6; 7-7; 8-8 and 9-9 in FIG. 2, illustrating the cooperating relation of portions of upper and lower mold halves of a straight draw mold utilized in forming the diffuser.

Referring first to FIG. 1, illustrated is a submersible pump comprising multistage pump unit 10 and pump drive motor unit 11 (shown in part only). The pump unit provides an outer casing or shell 12 in threaded assembly at its upper end to a discharge head member 14, and in threaded connection at its lower end with a bracket 15. Bracket 15 affords a bottom flange 16 for attachment to the motor unit 11, and is laterally open to provide the fluid supply inlet to the bottom or first stage of the pump. The open portion of the inlet bracket may be covered by an inlet screen 18, as is usual practice in submersible pumps. Further, discharge head 14 is in connection to a discharge pipe 19 which serves also to support the pump in the well or other place of pumping installation (as in a tank, for example). Included in head 14 is a check valve 20 of any suitable form, provided for preventing return flow from pipe 19 through the pump unit.

Within the pump shell 12 in stacked relation therein, are a plurality of pump stages having the stationary elements thereof in stacked engagement and clamped in assembly between the bracket 15 and discharge head 14. Each stage includes a rotary impeller 22 which in accordance with present improvements is of a turbine or mixedflow form, the impellers of all stages being suitably keyed or otherwise fixed as by the splined connection shown, to a common pump shaft 23. The upper end of the shaft is rotatably journalled by suitable bearing means 24 in a bearing support 26 carried by the discharge head 14, while its lower end is in driven connection with motor shaft 27 through a coupling 28 within bracket 15.

Continuing in reference to FIG. 1, the bottom or first pump stage comprises a diffuser member 30, a bottom diffuser cap 31 forming with the diffuser an impeller chamber for its impeller 22a, and a top diffuser cap 32 which cooperates with the diffuser in directing fluid from the first stage to the inlet of the impeller 22b in the next or second stage. Similarly the second stage comprises diffuser 3011, top diffuser cap 32b, and bottom diffuser cap which is here provided by the top cap 32 of the first stage. Cap 32 and diffuser 30b form the pumping chamber for impeller 22b. The third stage is identical with the second stage, having diffuser 300, top cap 32c, and bottom cap provided by cap 32b of the second stage, the latter with the diffuser forming a chamber for third stage impeller 22c. All succeeding impeller stages are formed in like manner, except that as to the last or topmost stage the top cap may be omitted. The diffuser members of all stages are identical in form and construction, one such diffuser (for example, diffuser 30b of the second stage) being more particularly illustrated in FIGS. 2, 3, 4 and 5 to which reference will be now made.

Each diffuser, as 3012, is a unitary, one-piece member which while it may be formed of desired metallic material,

is especially suitable to be formed of a desired plastic material by die-casting or injection molding in a two-part straight draw mold, in a manner hereafter appearing. As will appear from FIGS. 2 through 5, the diffuser comprises an annular wall having an outer diameter for slide fit in the pump shell 12 (FIG. 1), a disc-form hub element 41, and a plurality of diffuser vanes 42 integrally joining the hub element 41 and wall 40. Element 41 provides a disc-form body portion 44 having its peripheral margin 45 spaced from the internal surface 46 of wall 40, and a central upstanding hub portion 48 apertured to accommodate the impeller shaft and the extended hub portion 49 of the associated impeller, as impeller 22b in the present example. The diffuser vanes are equally spaced about the hub element, and are identical in form and curvature.

Eachdiffuser vane 42 includes an outlet end portion 50 upstanding on the upper surface 52 of disc hub 41, and having-a terminal edge 53 preferably slanted upwardly and outwardly from disc surface 52, as shown. The vane extends in smoothly curving trend, to and in overlapping relation with the peripheral margin 45 of disc 41, and thence downwardly across the space between disc margin 45 and wall 40 forming an inlet or intake end portion 54 integrally joining with the internal surface 46 of wall 40. As appears in FIG. 3, the vane intake end 54 is beyond or below the plane of the undersurface 56 of disc 41, and terminates at 57 in mergence with the internal surface 46 of wall 40. In pump assembled position of the diffuser, the vane intake end portion 54 is relatively close to the discharge periphery 58 of the associated impeller (FIG. 3), for receiving the fluid in discharge by the impeller and smoothly guiding the fluid along the forward generally concave vane surface 59 (fluid flow direction being indicated by arrow A in FIG. 2) from the vane intake end 54 to its outlet end 50. Fluid is confined to such vane guided flow by the upper or top cap, as 3212 in this example, which provides a circular flange 60b internally of the annular wall portion 62b, the flange being formed such that its undersurface 63b corresponds to the curvature of the vane margins 64. In assembly with cap wall 62b engaging the diffuser wall 40, the cap flange seats on the vane margins 64, as shown in FIG. 3. Further, the cap flange presents a central aperture 66b to accommodate the hub portion of the impeller in the next succeeding pump stage (as impeller 220, FIG. 1).

In accordance with present improvements, the diffuser vanes are given a predetermined curvature such that in respect of each vane, the inlet end portion 54 and its margin 70 each occupy a particular position relative to the back side or rear surface 71 of the next preceding vane. Referring to FIGS. 2 and 4 and considering the adjacent vanes 72 and 74 for example, vane 72 which has its forward generally concave guide surface 59 facing or 0pposed to the rear surface 71 of vane 74, is disposed such that no part of its inlet end portion 54 and the margin 70 thereof underlaps the adjacent portions of vane 74. As appears in the top plan view of FIG. 2, there is an appreciable open area 75 (viewed in the axial direction of the diffuser) between vane margin 70 of vane 72 and the opposed back side of vane 74, such area extending as at 76 beyond the terminal end 57 of the vane portion 54 t0 the junction zone of the back side 71 of vane 74 with the diffuser wall 40. This area or clearance between the indicated vane portions is of particular significance to successful casting or molding of the diffuser in integral, one-piece form, by a two-part straight draw mold.

Further facilitating two-part, straight draw mold formation of the diffusgi' is the particular trend given to each diffuser vane. Each vane in its outlet end portion 50 projects substantially normal to the to side 52 of disc hub 41, this portion having a molding draft taper converging from the vane base on hub 41 to the vane top margin 64. From outlet end portion 50 to the inlet terminal 57, the vane turns smoothly and increasingly from the normal or substantially right-angle relationship of vane portion 50 relative to side 52 of disc hub 41, toward and to a slanted position of the vane inlet end portion 54. Such portion 54 slants downwardly and inwardly from diffuser wall 40 to its margin 70, as this clearly appears in the views of FIGS. 1 and 5. Vane slanting relative to the vane outlet portion begins along the line T shown in FIG. 3, this line representing the zone of transition in the described vane directioning, being substantially parallel (in the presently preferred embodiment) to the longitudinal axis of the pump shaft 23 and extending from the peripheral margin 45 of disc hub 41. Such transitional zone of vane curvature facilitates vane formation in a two-part, straight draw mold, permitting vane-forming juncture of the upper and lower mold halves along the line T at the back side 71 of the vane for ready straight draw separation after casting or molding is complete. While it is presently preferred to effect vane curvature transition in the zone of line T parallel to the pump shaft axis, the line of transition in vane directioning may be somewhat angled outwardly from line T, as for example along a line T (FIG. 3) extending from disc hub margin 45 outwardly at a preselected acute angle to the shaft axis. In the latter case, one junction of the mold halves may be along line T Considering formation of the now described diffuser as a one-piece structure, preferably of suitable plastic material and formed by injection molding for example, a two-part straight draw mold is provided such that each mold half affords molding surfaces for specific portions of the diffuser. For the now described diffuser, the upper mold half has molding surfaces to define: (1) the entire upper face 52 of the disc hub body 44 and hub portion 48, and the adjacent surface of the disc periphery 45; (2) the entire fluid guide side or face 59 of each vane between the vane edges 53 and 7f), the vane edge 53, and the back side 71 of the vane between edge 53 and transition line T; and (3) the entire upper edge 64 of the vane and the top margin M of diffuser wall 40, and a portion of the inner surface 46 of wall 40 adjacent the front face side of the vane and between the wall margin M and entrance tip 57 of the vane.

The lower mold half affords molding surfaces to define: (a) the entire bottom face 56 of disc hub body 44 and hub portion 48, and the remainder of disc hub periphery 45; (b) the remainder of the back side face of each vane, as between line T and the vane tip 57, and the edge 70 of the vane; and (c) the outer side of wall 40 and its bottom annular margin M and the remainder of the inner surface of wall 40.

In mold assembly, portions of both mold halves cooperate in over-lapping fitted engagement to define the space 75 (FIG. 2) between each adjacent pair of vanes, one juncture of such portions being (according to the present example) in a plane containing the transition line T. FIGS. 6 to 9 illustrate the relation of cooperating mold portions at several points in the region of each diffuser space 75, these views being taken along the respective lines 66; 7-7; 8-8 and 9-9 in FIG. 2 and in each view the upper mold half portions are shown in crossed hatch lines, as at 100, while the lower mold half portions are shown by straight hatching as at 101. It will be apparent from these views, wherein FIGS. 7 and 8 in particular show the fitted engagement of upper and lower mold portions in the area defining the diffuser space 75 (FIG. 2), that the cooperating relation of these mold portions is such as to permit ready straight draw separation of the mold halves after casting or molding of the diffuser.

Having now illustrated and described the improved diffuser according to a presently preferred embodiment thereof adapted for formation as a one-piece member by casting or molding in a two-part, straight draw mold, it is to be understood that various modifications may be made thereto without departing from the spirit and scope of the invention as hereinafter claimed.

I claim:

1. In a plural stage turbine pump having at least two turbine impellers on a common drive shaft, and a sectionalized pump casing providing input sections one associated with each impeller and a diffuser section between the input sections, the diffuser section comprising a one-piece integral member having an annular casing wall portion, a disc-form hub element having its peripheral edge spaced from said wall portion and including a central opening for said drive shaft and a plurality of diffuser vanes integrally joining said hub element and wall portion, each of said vanes providing on one side a smooth continuously curving fluid guide surface extending from a vane end portion upstanding on one face of the hub element to and along the opposite vane end portion, and said opposite vane end portion projecting beyond the plane of the opposite face of the hub element and terminating in a margin in close proximity to the discharge periphery of the associated turbine impeller.

2. A diffuser section for a plural stage turbine pump having at least two turbine impellers on a common drive shaft and a sectionalized pump casing including input sections one associated with each impeller, with the diffuser section between the input sections; said diffuser section comprising an annular casing wall portion, a disc-form hub element therein having its peripheral edge spaced from the internal surface of the wall portion and including a central opening to accommodate said drive shaft therethrough, and diffuser vanes between the hub element and wall portion, each of said vanes providing on one side a smooth continuously curving fluid guide surface extending from a vane end portion upstanding on one face of the hub element, to and along the opposite vane end portion, and said opposite vane end portion extending along and at a slant angle inwardly from the internal surface of the wall portion beyond the plane of the opposite face of the hub element, and terminating in an end margin located for close proximity to the discharge periphery of the associated turbine impeller.

3. A diffuser section in accordance with claim 2 wherein the said one end portion of the diffuser vane is integral with the said hub element and the said opposite end portion of the vane is integral with the said wall portion.

4. A diffuser of the character described, provided for a pump having impellers of turbine type, the diffuser comprising a unitary member having an annular casing wall portion, a disc-form hub element therein with its peripheral edge spaced from the wall portion, and a plurality of equally spaced diffuser vanes between the hub element and wall portion, each diffuser vane providing on one side a smooth continuously curving fluid guide surface extending from a vane end portion upstanding on one face of the hub element, through overlapping relation with the peripheral edge of the hub element and thence in an op posite vane end portion extending to said wall portion beyond the plane of the opposite face of said hub element, and said opposite vane end portion being at a slant angle inwardly from the inner surface of the wall portion and providing a terminal margin extending from the peripheral edge of the hub element to the inner surface of the .wall portion said terminal margin being in position for close proximity to the discharge periphery of the associated turbine impeller.

5. A pump diffuser according to claim 4 wherein each said diffuser vane provides a generally concave front face for fluid flow guidance and a generally convex back face, and wherein the said terminal margin of each vane occupies a position removed from underlapping relation to the back face of the next preceding diffuser vane.

References Cited HENRY F. RADUAZO, Primary Examiner.

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