US3270678A - Self-priming centrifugal pump - Google Patents

Description

P 1966 J. A. LA MONICA 3,270,678

SELF-PRIMING CENTRIFUGAL PUMP Filed June 50, 1964 2 Sheets-Sheet 1 INVENTOR.

JAMES A. LA MONICA BY Z2647 qr 5 z ATTOR YS Sept. 6, 1966 J. A. LA MONICA 3,270,678

SELF-PRIMING CENTRIFUGAL PUMP Filed June 30, 1964 2 Sheets-Sheet 3 FIG. 7

INVENTOR. JAMES A. LA MONICA f G I 2 ATTOREZYS United States Patent 3,270,678 SELF-PRIMING CENTRIFUGAL PUMP James A. La Monica, Salem, Ohio, assignor to Crane C0., New York, N.Y., a corporation of Illinois Filed June 30, 1964, Ser. No. 379,121 2 Claims. (Cl. 103-113) This invention pertains to the art of self-priming centrifugal pumps and more particularly to improvements in the self-priming capabilities of such pumps.

The present invention is particularly applicable to a centrifugal self-priming pump of the axial feed type having an impeller rotatably mounted within a single vane diiluser employing volute recirculation priming and it will be discussed in reference thereto. However, it is to be appreciated that the invention has much broader applications and may be utilized wherever recirculation of a priming liquid is the means for establishing an initial vacuum.

Self-priming centrifugal pumps customarily employ within a pump casing, a diffuser which forms a volute shaped pumping chamber around a rotatably mounted impeller having an inlet eye at its axis. A priming liquid, which may be a residual amount of liquid retained in the casing after a pumping operation, or a quantity of liquid initially poured in prior to pump operation, partially fills the casing immersing the impeller. A normally submerged priming passage formed in the lower regions of the pump casing permits recirculation of the priming liquid into the pumping chamber during the priming cycle. During priming, air and priming liquid are hurled by the centrifugal force of the impeller from the pumping chamber into an air space in the casing where the air is separated and escapes while the substantially air-free priming liquid is returned or recirculated to the impeller via the priming passage. The priming time depends largely upon the speed at which the impeller can take air out of the intake line and pump casing and exhaust it to the atmosphere. For example, the faster the impeller is rotated the faster the priming. However, another factor which bears on the priming capabilities is the efiiciency of recirculation of the priming liquid. The inlet of the priming passage is normally within the deepest part of the pump casing so as to be submerged at all times while the outlet opens into the pumping chamber adjacent the impeller periphery. Rotation of the impeller within the pumping chamber creates a pressure differential between the inlet and outlet of. the priming passage causing priming liquid to be drawn into the pumping chamber during the priming cycle. The more rapid the rate of recirculation of the priming liquid, the more efficient the pump is at volnte priming. Also, the more air-free the priming liquid is, the faster the prime.

A common priming passage is merely a port at the lowest point in the pumping chamber which opens into the bottom of the pump casing. Experience has shown that ditficulties arise with such a construction. For example, while the lowest part of the pumping chamber may be advantageous from the standpoint of obtaining more priming suction due to the closer proximity of the port with the impeller, it is not necessarily the best location to obtain substantially air-free priming liquid. Due to turbulence and the tendency for the impeller to beat air into the priming liquid, it often happens that in the lowest part of the casing a considerable volume of air is entrained in the priming liquid. When this is the case, the impeller will receive gulps of air from the priming passage precisely at the moment when it is trying to evacuate air from the pumping chamber and intake lines, thus decreasing the priming efficiency of the pump.

Various expedients have been tried to improve the priming time. For example, different types of louvers situated in the lower portion of the pump casing have been used to slow down the priming liquid and decrease the turbulence so that a uniform fee dinto the priming passage could be obtained. However, only limited gains have been achieved with structures of this type.

Still another problem with present-day centrifugal pumps and to which this invention pertains has been that the diffuser is normally formed or cast as a part of the pump casing. This requires complicated coring to form the volute shape of the vanes. In addition, cast metal vanes in a self-priming pump are subject to corrosive attack almost continuously because of their submerged location in the priming liquid and when integral with the casing, replacement costs are excessive.

In accordance with a principal aspect of the invention these and other difficulties are overcome by providing a self priming centrifugal pump adapted to contain a priming liquid and comprising a casing having a pump intake and outlet; a rotatable impeller in the casing having an intake eye at its axis communicating with the pump intake and being immersed in the priming liquid; a vane member defining a pumping chamber around the impeller having a discharge opening adjacent the outlet and having a wall portion remote from its discharge opening submerged in the priming liquid, the vane member and casing defining a flow space extending from adjacent the discharge opening to a region of reduced turbulence in the casing adjacent the wall portion; and a priming passage formed with the wall portion opening from the pumping chamber into the region of reduced turbulence.

Also in accordance with the invention, the priming passage extends parallel to the axis of the pumping chamber and has an inlet mouth in the region of reduced turbulence and an outlet port in the pumping chamber, the inlet mouth being circumferentially offset with respect to the outlet port in the direction of impeller rotation.

Further, in accordance with the invention, and particularly where the vane member has a single volute diffusion surface and the discharge opening is in a vertical plane through the impeller axis, the priming passage is located at least from such discharge opening.

It is also contemplated by the invention that the wall portion project radially outwardly from the vane memher in defining the priming passage and that the priming passage inlet mouth is enlarged with respect to the outlet port.

Further, in accordance with the invention, and particularly where the pump casing is in two sections, the vane member is a separate unit adapted to be removably mounted in one of the sections.

The principal object of the invention is to provide a new and improved centrifugal self priming pump which is simple in construction, economical to manufacture, and which has an improved priming capability.

Another object is the provision of a centrifugal self priming pump employing a single volute diffusion vane member having a priming passage therein which is so shaped and positioned in the pump casing as to provide optimum recirculation priming.

Another object of the invention is the provision of a self priming centrifugal pump having a diffusion vane member which is separable from the casing and may be replaced if repairs are necessary or interchanged with a vane member of different size or type with a minimum of labor and pump down time.

The invention may take physical form in certain parts and arrangements of parts the preferred embodiments of which will be described in detail in this specification and illustrated in the accompanying drawings which are a part hereof and wherein:

FIGURE 1 is a vertical cross-sectional view of an axial feed centrifugal pump incorporating the invention;

FIGURE 2 is a transverse cross-sectional view taken along line 22 of FIGURE 1 with portions of the im peller broken away;

FIGURE 3 is a fragmentary view taken along line 33 of FIGURE 2;

FIGURE 4 is a perspective view of the diffuser only, shown in FIGURES 1-3;

FIGURE 5 is a fragmentary view of the recirculation area of a modified diffuser;

FIGURE 6 is another fragmentary view similar to FIGURE 5 showing another modification of the invention; and

FIGURE 7 is still another fragmentary view of a further modification of the invention.

Referring generally to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, the figures show an axial feed, selfpriming, centrifugal pump and motor unit 10. A motor 12 is mounted on a pump casing 14 having an intake opening 16 and outlet opening 17. The intake opening 16 communicates with a volute shaped pumping chamber 18 defined by a diffuser 20. A rotatable impeller 22 in the pumping chamber 18 is adapted to be driven by motor 12 and has an intake eye 23 at its axis. Those acquainted with pumps of this type will recognize that the normal operation is such that the pump casing 14 retains a residual amount of the liquid being pumped at the end of a pumping operation. This liquid immerses the impeller 22 and serves as a priming liquid for developing an initial vacuum when the pump is again started.

In more detail, the pump casing 14 is divided into two sections and includes a support head 27 and a bowl 28 which provides an air separation and discharge chamber 29. The support head 27 is adapted to be removed from the bowl 28 and mounts the motor 12 on one side and has an axially facing surface 30 engageable with the diffuser 20 on the other. An inwardly extending collar 32 joining with the surface 30 defines a seal chamber 34 behind the impeller 22 and has a central opening 37 through which projects a drive shaft 38 driven by the motor 12. An axial mechanical seal, generally indicated by the numeral 40, sealably closes the opening 37 preventing the leakage of air into or escape of liquid from the seal chamber 34. The drive shaft 38 supports the impeller 22 which has a plurality of spiral passages 45 defined by volute-shaped vanes 46 curving radially outwardly from the eye 23 between side plates 47 and 49. A sleeve 50 projecting from the side plate 49 rotatably engages a wear ring 52 carried by the diffuser 20. The impeller 22 forms no part of the invention and may be a metal casting, but is preferably molded from a thermosetting plastic material suitably selected to resist the corrosive environments of the pump.

The diffuser 20 has a sleeve 54 adapted to carry the wear ring 52 and is removably fitted within an annular wall 56 projecting inwardly from the side wall of bowl section 28. An O-ring 58 is squeezed between the end of annular wall 56 and the diffuser 20 to seal the pump intake from the air separation and discharge chamber 29. The annular wall 56 provides a straight open, direct intake passage into the eye 23 of the impeller 22 from the intake opening 16. A one way hinge valve 59 prevents the residual liquid in the chamber 29 from being syphoned off through the intake 16 when the pump stops. This liquid normally serves as the priming liquid when the pump is started. After standing idle for a long period, the pump may require manual priming. For this purpose, an opening 60, closed by a stopper 62, in the upper wall of the bowl section 28 provides an access where priming liquid may be poured in.

The motor 12. support head 27 and impeller 22 form a subassembly which may be removed from the bowl section 28 thus exposing the diffuser 20 which may be easily withdrawn from its sleeved mounting in wall 56 and replaced with a new unit if repair is needed without having to replace any part of the pump casing. In contrast, prior art pumps usually have the diffuser cast integrally with the pump casing resulting in a costly replacement if it fails. The diffuser 20 may be a metal casting but is preferably formed of a suitable thermosetting plastic material similar of the type used for the impeller 22.

In the present invention, the diffuser 20 is marked by a single volute vane 70 having a cutwater 72 and a dis charge opening 74 which is located in a vertical plane through the impeller axis. At the cutwater 72, the vane 70 is closely adjacent the periphery of the impeller vanes 46. From that point, moving in the direction of rotation of the impeller 22, clockwise as viewed in FIGURE 2, the inner surface 76 of the vane 70 increasingly diverges radially outwardly from the periphery of the impeller 22 to a maximum radial sweep discharging into the chamber 29.

In accordance with the invention and in the preferred embodiment shown in FIGURES l-4, a portion of the vane 70 projects radially outwardly to form a hooded enclosure or generally rectangular Wall 78 which defines a priming passage 80 extending parallel to the axis of the pumping chamber 18. The passage 80 has a mouth 82 at one end opening into a recirculation chamber 90 and a port 84 at the other end opening into the pumping chamber 18. A second cutwater 85 is provided in the vane 70 adjacent the port 84. An important aspect of the invention is the circumferential location of the priming passage 80 with respect to the pumping chamber discharge opening 74. The priming passage 80 is on the side of the diffuser 20 approximately 260 from the discharge opening 74 in the direction of impeller rotation. This is contrasted to the prevailing practice of locating the priming passage in the lowest part of the pump casing which would normally be at the bottom of the diffuser.

In the modifications of the invention shown in FIG- URES 5-6, like parts will be identified with like numerals and similar part by like numerals with the addition of a prime mark. In the modification shown in FIG- URE 5, the hood 78 of the preferred embodiment is removed and the port 84 is allowed to open directly into the flow space of the air separation and discharge chamber 29.

A further variation is shown in FIGURE 6 where a partial hood is used. In this arrangement, the wall 92 is connected with the vane 70 on only one side of the port 84 and opens downwardly into the recirculation chamber 90.

In FIGURE 7, a further modification is shown where a crescent shaped hood 78' is used which is otherwise similar to the hood 78 of the preferred embodiment. In each of these embodiments, the priming liquid is recirculated to the impeller at a location approximately 260 from the diffuser discharge opening. However, it should be understood that while this is the preferred location for the priming passage, satisfactory results may be obtained with a circumferential spacing ranging from approximately 180 to 270 from the diffuser discharge opening.

To increase the priming suction, an important consideration is the radial spacing between the periphery of the impeller 22 and the port 84 and in this connection it is noted, for example, in the preferred embodiment, that the port 84 is circumferentially offset with respect to the axis of the priming passage 80 in a direction opposite to that of impeller rotation. This places the port 84 closer to the periphery of the impeller 22 to obtain increased suction while permitting the passage 80 to be retained in the preferred location. It should also be noted that the priming passage inlet mouth 82 is elongated in a circumferential direction and enlarged with respect to the port 84. The significance of these features will be brought out in more detail hereinafter.

The basic operation of the self priming centrifugal pump as described above involves the initial creation of a vacuum that draws liquid into the pump and then discharges it under pressure. When the pump is started, a partial vacuum is developed as the impeller 22 centrifugally evacuates the pumping chamber 18 of air and priming liquid. For eflicient operation, a substantial portion of this vacuum is created adjacent the impeller eye 23 so that maximum efficiency is attained in drawing liquid into the pump inlet 16. Any atmospheric leaks decrease the vacuum and correspondingly hinder the priming of the pump.

During priming, as the impeller is rotated, the air and priming liquid within the pumping chamber 18 are forced radially outwardly along the impeller passages 45 discharging from the pumping chamber 18 through diffuser opening 74 into the air space in the upper part of the air separation and discharge chamber 29. Here the air is separated and escapes through the pump outlet 17 while the substantially air-free priming liquid is propelled into the recirculation chamber 90 formed generally between the outer boundaries of the diffuser 20 and the casing 14. Due to the rotation of the impeller 22, a turbulent condition exists in the recirculation chamber 90 which progressively diminishes in the direction of impeller rotation the farther the liquid is from the diffuser opening 74. As a result, an area may be located within the recirculation chamber 90 which will be at near minimum turbulence and consequently will have .a maximum concentration of air-free priming liquid. The location of a definite area of reduced turbulence is possible primarily because a single vane diffuser is used, e.g., a diffuser having plural vanes would have a plurality of discharge openings with the result that it would be nearly impossible to locate a substantially nonturbulent region within the chamber 29. Not only is the priming fluid less turbulent at such a location and has less entrained air but with a pump having a single vane diffuser, it is moving at a lower velocity. Under these conditions the fluid is less likely to by-pass the intake opening of a priming passage.

For these reasons, recirculation of the priming liquid in the invention occurs approximately 260 from the diffuser discharge opening 74 in the direction of impeller rotation. This region is sulliciently remote from the discharge opening 74 so that the priming liquid is relatively nonturbulent and a uniform feed of priming liquid to the impeller 22 is thus achieved. This circumferential spacing may vary depending on the speed of the impeller, the shape of the pump casing, and the size or shape of the vane member, but in any case should not be less than about 180, or diametrically opposite to the discharge opening 74, nor greater than approximately 270 from it and still achieve good results. For normal impeller speeds of around 3500 rpm, the preferred location is approximately that shown.

In addition to the circumferential location of the priming passage in a nonturbulent region of the pump, the location of the port 84 is an important aspect of the invention. Due to the rotation of the impeller 22, a pressure differential is created during priming across the port 84 which causes priming liquid to be drawn into the pumping chamber 18. The closer the port 84 is to the periphery of the impeller, the greater the suction and the more rapid the recirculation of the priming liquid. For this reason, in the preferred embodiment for example, the port 84 is circumferentially offset with respect to the axis of the priming passage in a direction opposite to that of impeller rotation. The offset condition may be less than an inch in certain cases, but the prime consideration is to achieve an optimum balance between suction power at the port 84 and maximum air-free liquid concentration at the entrance of the priming passage.

It should also be noted that the inlet mouth 82 is enlarged with respect to the port 84 to provide a full opening for the ingress of priming fluid under the influence of the suction created by the impeller. This also compensates for the tendency of the priming liquid to surge past the inlet of the priming passage.

With the invention, only enough priming liquid is needed to provide a Working fluid and maintain sufficient airfree liquid concentration in the recirculation chamber for recirculation to the impeller 22. When the pump begins normal operation the chamber 29 is completely filled with the liquid being pumped which is discharged under pressure through outlet 17 and the priming passage ceases to function as such.

While this invention has been described with reference to the prefererd embodiment or embodiments of the invention, obviously modifications and alterations will occur to others upon reading and understanding of this specification and it is my intention to include such modifications and alterations insofar as they come within the scope of the appended claims except where limited by the prior art.

Having thus described my invention, I claim:

1. A self-priming, axial feed, centrifugal pump comprising a casing having an axially extending fluid inlet opening and an outlet opening in the upper portion thereof,

a rotatable impeller within the casing having an intake eye at its axis connected to the inlet opening,

a single volute vane member surrounding the impeller so as to define a continuously expanding volute passageway outwardly of the periphery of the impeller which diverges increasingly radially outwardly in the direction of impeller rotation,

a cutwatcr at the narrowest part of said passageway and a discharge opening approximately 360 therefrom each located substantially in a vertical plane through the impeller axis,

a recirculation chamber between the vane member and casing outwardly of the volute passageway extending from the discharge opening and to about 270 in the direction of impeller rotation,

an elongated closure projecting outwardly from and integral with the vane member considerably wider circumferentially than it is radially and defining a priming passage having an inlet mouth opening axially into the recirculation chamber between 180 and 270 from said discharge opening and having,

a discharge port at the end of said priming passage opening into the volute passageway at a location closely adjacent one side of said enclosure so as to be circumferentially offset in a direction of continuously decreasing area of said volute passageway whereby an optimum relationship is achieved between suction power at the port and air-free recirculated fluid at the mouth of the priming passage.

2. A self-priming, axial feed, centrifugal pump as set forth in claim 1 wherein said elongated enclosure is of generally rectangular configuration having an outer wall closely adjacent the interior wall of said casing joined at each end by a side wall projecting substantially perpendicularly from said vane member.

References Cited by the Examiner UNITED STATES PATENTS 2,292,529 8/1942 La Bour 1031 13 2,627,817 2/1953 Mann et a1 lO3-ll3 2,642,004 6/1953 Bergh 103-1 13 2,755,743 7/1956 Rupp 1031l3 3,045,603 7/1962 Hunter l03l 13 MARK NEWMAN, Primary Examiner.

75 HENRY F. RADUAZO, SAMUEL LEVINE, Examiners.

Claims (1)

1. A SELF-PRIMING, AXIAL FEED, CENTRIFUGAL PUMP COMPRISING A CASING HAVING AN AXIALLY EXTENDING FLUID INLET OPENING AND AN OUTLET OPENING IN THE UPPER PORTION THEREOF, A ROTATABLE IMPELLER WITHIN THE CASING HAVING AN INTAKE EYE AT ITS AXIS CONNECTED TO THE INLET OPENING, A SINGLE VOLUTE VANE MEMBER SURROUNDING THE IMPELLER SO AS TO DEFINE A CONTINUOUSLY EXPANDING VOLUTE PASSAGEWAY OUTWARDLY OF THE PERIPHERY OF THE IMPELLER WHICH DIVERGES INCREASINGLY RADIALLY OUTWARDLY IN THE DIRECTION OF IMPELLER ROTATION, A CUTWATER AT THE NARROWEST PART OF SAID PASSAGEWAY AND A DISCHARGE OPENING APPROXIMATELY 360* THEREFROM EACH LOCATED SUBSTANTIALLY IN A VERTICAL PLANE THROUGH THE IMPELLER AXIS, A RECIRCULATION CHAMBER BETWEEN THE VANE MEMBER AND CASING OUTWARDLY OF THE VOLUTE PASSAGEWAY EXTENDING FROM THE DISCHARGE OPENING AND TO ABOUT 270* IN THE DIRECTION OF IMPELLER ROTATION,

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