WO1996018817A1

WO1996018817A1 - Impeller

Info

Publication number: WO1996018817A1
Application number: PCT/US1995/016076
Authority: WO
Inventors: Donald P. Sloteman
Original assignee: The Ingersoll-Dresser Pump Company
Priority date: 1994-12-14
Filing date: 1995-12-12
Publication date: 1996-06-20

Abstract

An integral pump motor (97) or sealless magnetically coupled pump having a shrouded impeller (10) with a removable magnet carrier ring (30) attached to one side of the impeller shroud. Permanent magnets (38) are embedded in the magnet carrier ring and encapsulated to prevent contact with potentially agressive pumped fluids. The magnet carrier ring is mounted to the impeller shroud using an interlocking (or multiple keys) (32, 34) to transmit torque. The magnet carrier ring is fastened axially to prevent separation from the impeller shroud. Damage or breaking of the blading of the impeller and its being rendered inoperable will not necessarily dictate the accompanied loss of the high value magnet ring.

Description

IMPELLER

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This invention relates generally to impellers and more particularly to impellers for sealless pumps. A sealless pump is a type of centrifugal pump that has at least its impeller and bearing system isolated from the impeller driving mechanism by an isolating wall or shell that seals the pumping mechanism from the surrounding environment and eliminates the necessity to use rotary seals to seal the pumped fluid against leaking along the shaft. This type of pump is particularly desirable when pumping environmentally sensitive fluids such as hydrocarbons. In one type of sealless pump, the driving mechanism is coupled to the pump impeller by an arrangement of magnets located on the opposite sides of the isolating wall which magnetically connects the torque of the driving mechanism to the impeller. In another type of sealless pump, a rotating electric field is provided by a stator. The rotating field then drives the magnets imbedded in the pump impeller. The stator can either be located outside of the pumped fluid environment by using an isolating wall to separate the stator from the pumped fluid or can be immersed in the pumped fluid.

The operation of an integral pump motor, such as the pump described in U. S. Patent No. 5, 158,440, depends upon the torque delivered to the pumped fluid from a centrifugal pump impeller. The impeller is typically driven by a permanent magnet rotor integral to the impeller. The permanent magnets embedded in the impeller rotor complete an electromagnetic circuit and when exposed to a rotating electric field, generated by field winding (the stator) in close proximity to this rotor, supply the drive torque required to rotate the impeller. Often during the operation of a pump, the impeller can become damaged, either from corrosion, erosion, cavitation damage or damage from contact with foreign objects in the flow stream. Destruction of the impeller pumping blades usually means the scraping of the impeller along with the embedded magnets. The loss would be not only the impeller shell, and the magnetic material, but also the value of the embedding process and the related sealing of the magnets from the pumped fluid.

The foregoing illustrates limitations known to exist in present integral permanent magnet rotor impellers. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.

SUMMARY OF THE INNENTTON

In one aspect of the present invention, this is accomplished by providing an impeller comprising a disk shaped shroud member; a plurality of pumping vanes attached to a first side of the shroud member; and a magnet carrier removably attached to the shroud member.

The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a cross-sectional side view of an impeller with a removable magnet carrier ring; FIG. 2 is a partial cross-sectional view showing the details of one embodiment of the removable magnet carrier ring;

FIG. 3 is a partial plan view of an alternate embodiment of the removable magnet carrier ring; FIG. 4 is a cross-sectional view of an integral pump motor incorporating the impeller and the removable magnet carrier ring shown in FIG. i;

FIG. 5 is a cross-sectional view of an alternate impeller with a removable magnet carrier ring; and FIG. 6 is a cross-sectional view of a magnetically coupled sealless pump incorporating the impeller and removable magnet carrier ring shown in FIG. 5.

DETAILED DESCRIPTION

FIG. 4 shows an integral motor pump with an impeller 10 having a removable magnet carrier ring 30. The impeller 10 rotates about a horizontal axis. The pumped fluid flows from an inlet 14 through the impeller 10 to the discharge 16. The impeller 10 is comprised of two disk-shaped shrouds 12 connected by a plurality of pumping vanes 20. The center of each shroud opens into an axially extending collar which forms the inlet 14 of the impeller 10. A removable magnet carrier ring 30 with a plurality of permanent magnets 38 is attached to the back side of each shroud 12. The impeller 10 is driven by a rotating magnetic field generated by stator coils 50 within the pump housing adjacent the permanent magnets 38. A cover plate 40 is bolted over the removable magnet carrier ring 30 to hold the magnet carrier ring 30 in place. In one embodiment shown in FIG. 1, a plurality of bolts 42 attach the cover plate 40 and the removable magnet carrier ring 30 to the impeller shroud 12. These bolts 42 also transmit torque from the magnets 38 and magnet carrier ring 30 to the impeller shroud 12 and impeller 10.

FIG. 2 shows the details of an alternate embodiment of the removable magnet carrier ring 30. The base or conductive back iron 36 of the magnet carrier ring 30 is formed from a conductive metal such as low carbon steel or cast iron. A plurality of axially extending drive keys 32 are formed in one surface of the conductive back iron 36. A plurality of corresponding drive key holes 34 are formed in the shroud 12. The drive keys 32 engage the drive key holes 34 to transmit torque from the magnets 38 to the shroud 12 and impeller 10. As shown in FIG. 2, the removable magnet carrier ring 30 and conductive back iron 36 are a unitary structure. The magnet carrier ring 30 can be a separate piece from the conductive back iron 36. The cover plate 40 and the magnet carrier ring 30 may be assembled as an integral unit which is removably attached to the shroud 12. Preferably, the magnet carrier ring 30 and magnets 38 are encapsulated to protect the magnets 38 from exposure to the pumped fluid. As an alterative, the cover plate 40 can act as an enclosure barrier to protect the magnets 38 from exposure to the pumped fluid.

A further embodiment of the removable magnet carrier ring 30 is shown in FIG. 3. Instead of axially extending drive keys 32 and axially extending drive key holes 34, a plurality of radially extending drive keys 32' and radially extending key slots 34' are used to transmit torque from the magnets 38 to the shroud 12 and impeller 10.

FIGS. 5 and 6 show a sealless magnetically coupled pump using a removable magnet carrier ring 30. The pump shown includes a pump housing

71 containing an axial inlet 14, a pumping chamber and an outlet 16, all of which are interconnected by passages extending through the pump housing 71. The pump housing 71 also contains an annular flange 76 surrounding the pumping chamber. The annular flange 76 is adapted to receive a sealing diaphragm 77 and support ring 78. The sealing diaphragm 77 prevents liquid from leaking to the atmosphere, thus making the pump "sealless".

An axially extending stationary shaft 81 carrying a pump impeller 10 rotating in the pump chamber during pump operation is attached to a threaded hole 80 formed in the sealing diaphragm 77. Although impeller 10 is a fully enclosed impeller having front and back shrouds, a semi-open impeller having a single back shroud can also be used. The impeller 10 has a disk-shaped shroud 12 with a plurality of pumping vanes 20 attached thereto. A removable magnet carrier ring 30 and cover plate 40 are attached to the shroud 12 by a plurality of bolts 42. The magnet carrier ring 30 consists of a conductive back iron 36 with a plurality of permanent magnets 38 attached thereto. Similar to the removable magnet carrier ring 30 shown in FIGS. 1 through 4, a plurality of drive keys 32 and drive key holes 34 transmit torque from the magnets 38 to the shroud 12 and impeller 10.

An electric motor 97 provides the driving force for the magnetically coupled centrifugal pump shown in FIG. 6. A motor support frame 86 attaches the motor 97 to the pump by a plurality of bolts which are screwed into threaded holes in the support ring 78. The motor support frame 86 attaches to the pump separately from the sealing diaphragm 77. Since the sealing diaphragm 77 is bolted separately to the pump housing 71, the sealing diaphragm 77 remains sealing attached to the pump housing 71 wherever the motor support frame 86 and the motor 97 are removed from the pump housing 71. Thus, the motor can be removed without draining the pump or leaking any of the pumped fluid.

An outer magnet carrier 95 is attached to the motor shaft 90. High strength magnets 84 are attached to the face of the outer magnet carrier 95 adjacent the sealing diaphragm 77. These driving magnets 84 are magnetically coupled to the driven magnets 38.

Claims

Having riftsr.rihfiri the invention what is daimed is-

1. An impeller comprising: a first disk shaped shroud member; a plurality of pumping vanes attached to a first side of the first shroud member; a first magnet carrier member removably attached to a second side of the first shroud member; and a torque transmitting means for transmitting torque from the first magnet carrier member to the first shroud member.

2. The impeller according to claim 1, further comprising: a second disk shaped shroud member, the plurality of pumping vanes being attached to a first side of the second shroud member; a second magnet carrier member removably attached to a second side of the second shroud member; and a torque transmitting means for transmitting torque from the second magnet carrier member to the second shroud member.

3. The impeller according to claim 1, further comprising: a cover plate removably attached to the first shroud member, the cover plate securing the first magnet cattier member to the first shroud member.

4. The impeller according to claim 3, wherein the torque transmitting means comprises a plurality of bolts extending through the cover plate and the first magnet carrier member into the first shroud member.

5. The impeller according to claim 3, wherein the cover plate and the first magnet carrier ring member form an integral member.

6. The impeller according to claim 1, wherein the first magnet carrier member is encapsulated within a protective coating.

7. The impeller according to claim 1, wherein the first magnet carrier member comprises a conductive back iron member and a plurality of magnets circumferentially spaced in the conductive back iron member.

8. The impeller according to claim 7, further comprising. a cover plate integral with the back iron member, the integral cover plate and the back iron member forming a protective barrier around the plurality of magnets, the cover plate being removably attached to the first shroud member.

9. The impeller according to claim 1, wherein the torque transmitting means comprises a plurality of magnet carrier member torque transmissions members formed in the first magnet carrier member; and a plurality of shroud torque transmission members formed in the first shroud member, the magnet carrier member torque transmission members and the shroud torque transmissions members interengaging one another.

10. The impeller according to claim 9, wherein each shroud torque transmission member is an axially extending aperture and each magnet carrier member torque transmission member is an axially extending projection.

11. The impeller according to claim 9, each shroud torque transmission member is a radially extending aperture and each magnet carrier member torque transmission member is a radially extending projection.

12. The impeller according to claim 1, wherein the first shroud has a centrally located inlet aperture.

13. An impeller comprising: two disk shaped shroud members, each shroud member having an inlet aperture, a first side and a second, a plurality of first torque transmission member being formed in each shroud member second side; a plurality of pumping vanes attached to each shroud member first side thereby connecting the shroud members; two magnet carrier rings, a magnet carrier ring being removably attached to a shroud member second side, a plurality of second torque transmission members being formed in each magnet carrier ring, the second torque transmission member engaging the first torque transmission members on an adjacent shroud member.

14. The impeller according to claim 13, wherein each shroud torque transmission member is an axially extending aperture and each magnet carrier ring torque transmission member is an axially extending projection.

15. The impeller according to claim 13, wherein each shroud torque transmission member is a radially extending aperture and each magnet carrier ring torque transmission member is a radially extending projection.

16. The impeller according to claim 13, further comprising: a cover plate removably attached to a shroud member, the cover plate securing the magnet carrier ring to the shroud member.

17. The impeller according to claim 13, wherein the magnet carrier ring it encapsulated in a protective coating.

18. The impeller according to claim 13, wherein the magnet carrier ring comprises a conductive back iron member proximate the shroud member second side and a plurality of magnets circumferentially spaced in the conductive back iron member, distal the shroud member second side.

19. An impeller comprising: a disk shaped shroud member having an axis of rotation; a plurality of pumping vanes attached to a first side of the shroud member; a magnet carrier removably attached to a second side of the shroud member; and a plurality of magnets circumferentially spaced about the magnet carrier.