Sealed pump

Abstract

A liquid pump has an annular stator having wire windings that extend around a generally tubular central opening. An inner housing made of a non-ferrous material has an inner opening, an input end, and an output end such that liquid can enter the input end, pass through the inner opening and exit through the output end. A portion of the housing extends through the central opening of the stator and a brushless rotor mounted on a shaft is positioned entirely within the housing to thereby seal the shaft from leakage. A drive attached to the shaft urges the liquid from the input end of the housing to the output.

Description

The present application relates to liquid pumps and in particular to one having the moving parts thereof sealed against leakage.

BACKGROUND OF THE INVENTION

Certain industries, such as nuclear energy, require purified liquids or gases to be pumped through tubing that is totally sealed against leakage. To create such a sealed system, the pump itself must be totally sealed. Pumps have moving parts, and where the parts are moved by a shaft extending through the wall of a pump housing, leakage can occur around the portion of the shaft extending through the aperture. As a practical matter, such apertures cannot be totally sealed against leakage and therefore where it is desirable to have a totally enclosed system, the pump must have moving parts that are driven without requiring an aperture through which a shaft extends.

Presently, pumps driven without an aperture in the pump wall have ferrous portions connected to the pump drive that are magnetically conductive. The magnetically conductive portions of the pump rotate within a non-ferrous housing, and surrounding the housing is a drive consisting of one or more magnets that are rotated around the circumference of the non-magnetic housing. The magnets of the drive attract the ferrous portions of the pump and cause the blades of the pump to be rotated with the rotating magnets of the drive, thereby transferring the energy from exterior of the enclosed system to the rotating portions therein. Such drive assemblies can be large and bulky, and it would be desirable to provide an alternative drive which can be constructed so as to be more compact.

SUMMARY OF THE INVENTION

Briefly, the present invention is embodied in a pump for pumping a liquid or a gas in a sealed environment. For the purposes of this discussion, the pump will be described as pumping a “liquid” where the term “liquid” is intended to include any substance in either a liquid or gaseous state. The key to the invention is that the pump is driven by a brushless rotor mounted on a shaft on which is also mounted a drive for urging liquid within the pump from an input end to an output end. The rotor, the drive, and the two ends of the shaft are all enclosed within a sealed chamber having only an input opening through which liquid enters the chamber and an output opening toward which liquid is urged by the drive.

The pump is surrounded by a housing, a portion of which may include a cylindrical outer shell of a stator for driving the rotor. The stator has a plurality of wire windings in the form of lobes that extend radially inward from the inner surface of the shell, with a central opening extending axially through the inner ends of the lobes through which the rotor extends.

In one embodiment, a channel extends along the outer surface of the rotor and through the central opening of the stator such that liquid is forced by the drive through the central opening of the stator as it moves from the input end to the output end. In this embodiment, the channel may be positioned between the spaced apart lobes of the windings of the stator.

In a second embodiment, an inner enclosure is configured to have a cylindrical portion extend through the central opening of the stator with the interior of the cylindrical portion occupied solely by the rotor. In this embodiment, the inner enclosure has an input opening and an output opening and the drive moves liquid from the input opening to the output opening without requiring the liquid to pass through the central opening of the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the invention will be had by a reading of the following detailed description taken in conjunction with the drawings wherein:

FIG. 1 is a schematic cross-sectional drawing of a first embodiment of a pump in accordance with the invention;

FIG. 2 is a cross-sectional view of the pump shown in FIG. 1 taken through lines 2-2 thereof;

FIG. 3 is a cross-sectional view of a pump in accordance with the second embodiment of the invention; and

FIG. 4 is a circuit for operating the pump shown in FIGS. 1 through 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIG. 1, a sealed pump 10 in accordance with the invention has a sealed housing 12 that includes as a central portion the outer surface of a tubular shell 15 for a stator 16 for rotating a brushless rotor as is further described below.

Sealed against one annular surface of the stator 16 is a generally tubular input end cap 18 having an outer end 20 and sealed against the opposing annular surface of the shell 15 of the stator 16 is a generally tubular output end cap 22 having an outer end 24. The input end cap 18 has an input orifice 26 entering into a cavity 28 which in turn communicates with the central opening of the stator 16. In similar fashion, the output end cap 22 has an output orifice 30 that communicates with a cavity 32 within the output end cap 22 that also communicates with the central opening of the stator 16.

Extending axially through the housing 12 is an elongate shaft 34 one end of which is fitted into a bearing 36 centrally located in the outer end plate 20 of the input end cap 18 and the other end of which is rotatably mounted and a bearing 38 in the outer end plate 24 of the output end plate 22. Mounted to the shaft 34 within the cavity 28 of the input end cap 18 is a mechanical liquid drive 40 for urging liquid within the input cap cavity 28 through the opening in the stator 16 and into the cavity 32 of the output end cap 22. It should be appreciated that while the drive 40 is depicted in FIG. 1 as being an impeller, that the drive can be in any suitable form for applying pressure for urging liquid entering the cavity from the input orifice 26 toward the output orifice 30. For example, the drive 40 may be in the form of a centrifugal pump having a plurality of blades that urge the liquid radially outward, or it may be a positive displacement piston operated pump having the advantage of a fixed displacement with each stroke.

Referring to FIGS. 1 and 2, also mounted in the shaft 34, and positioned within the stator 16 is a brushless rotor 42 of the type having one or more permanent magnets oriented with the axis between poles positioned perpendicular to the axis of rotation as best shown in FIG. 2. Although the rotor 42 is depicted as being formed of two permanent magnets adjacent to one another, it should be appreciated that the rotor 42 may be formed with any number of permanent magnets.

An important feature of the invention is that the brushless rotor 42 and the drive 40 are entirely sealed within the housing 12 such that the housing is sealed except for the input orifice 26 and the output orifice 30. To ensure that the parts are totally sealed against leakage, the entire housing 12, including the input end cap 18, the stator 16, and output end cap 22 may be enclosed within a tubular plastic outer housing 44 thereby ensuring that liquid can only enter the pump 10 through the input orifice 26 and exit through the output orifice 30.

Referring to FIGS. 1, 2, and 4, the stator 16 has a plurality of projections 46-46 that extend radially inward of the shell 15 with each of the projections made of laminated ferrous material surrounded by wire windings 48-48 (shown only in FIG. 4). Applied to the outer surfaces of the projections 46-46 and along the inner surface of the stator housing 16 is a protective coating 50 made of a suitable plastic or other material which will not interfere with the magnetic field created by the windings 48-48 but will protect the wires of the winding 48-48 from damage caused by the liquid being pumped by the pump 10.

As best shown in FIG. 2, the radially inwardly extending projections 46-46 are separated from each other by a spacing, only a small portion of which is consumed by the protective coating 50 such that a cavity 52, 53, 54, 55 exists between each adjacent pair of projections 46-46 with each cavity extending axially through the length of the stator 16 and connecting at one end to the cavity 28 of the input end cap 18 and the cavity 32 of the output end cap 22.

Referring further to FIG. 1, within the output end cap 22 adjacent the annular end surface of the stator 16 is a generally planar annular circuit board 56 having a plurality of Hall effect sensors 58, 59, 60, 61 thereon which are integral parts of a resolver 64 (shown in FIG. 4) built on to the circuit board 56 for detecting the angular orientation of the rotor 42. Also within the output end cap 22 is a second annular circuit board 66 having an electronic control unit (ECU) built thereon that includes a microprocessor 68 which controls a driver 70 for directing power to an external power source 72 to the various windings 48-48 of the stator 16. Accordingly, within the housing 12 is both a resolver and a ECU for controlling the application of power to the stator 16 such that only two connectors 74, 76 (shown only in FIG. 4) are needed to extend through the outer wall of the housing 12 for applying power to the stator 16. The connectors 74, 76 can be sealed against leakage around the circumference thereof by any suitable means known in the art.

Referring to FIG. 3, a second embodiment of a sealed pump 80 in accordance with the invention has an irregularly shaped sealed housing 81 that includes an input opening 82, an output opening 83, and a generally tubular protrusion 84 that extends axially through the cylindrical inner opening of an annular stator 86. Extending axially through the central opening within the protrusion 84 is a brushless rotor 88 mounted on a shaft 89 having a first end 90 mounted on a bearing 91 in the end of the protrusion 84 and the second end 92 that extends through a drive 94. Since the ends of the shaft 89 do not pierce the walls of the sealed housing 81, there is no leakage from the interior of the sealed housing 81. In this embodiment, the drive 94 is depicted as being a centrifugal pump having vanes that drive liquid radially outward and into a channel 96 that leads towards the output opening 83. The second end 92 of the shaft is rotatably mounted in a second bearing 100. The rotor 88 and drive 94 are entirely enclosed within the walls of the sealed inner housing 81 such that liquid can only enter the inner housing through the input opening 82 and can only exit through the output opening 83.

The sealed pump 80 also includes a resolver and an ECU configured in a circuit substantially identical to that shown In FIG. 4; however, in this embodiment it is not necessary that the resolver and ECU be within the sealed inner housing 81.

While the present invention has been described with respect to two embodiments, it will be appreciated that many modifications and variations may be made without departing from the spirit and scope of the invention. It is therefore the intent of the appended claims to cover all modifications and variations that fall within the spirit and scope of the invention.

Claims

1. A liquid pump comprising

an annular stator having wire windings and a central opening,

a non-ferrous sealed housing having an inner opening that is accessible only through an input opening and an output opening,

a portion of said housing extending through said central opening of said stator,

a brushless rotor mounted on a shaft,

said brushless rotor and said shaft being entirely within said housing, and

a drive attached to said shaft wherein liquid from said input opening is urged by said drive toward said output opening.

2. A pump comprising

a sealed outer housing,

said sealed outer housing having a central opening accessible only through an input opening and an output opening,

a stator having a plurality of windings surrounding a central opening,

said central opening of said stator forming a portion of said central opening of said housing wherein liquid entering said central opening of said pump through said input opening will pass through said central opening of said stator to reach said output opening,

a rotor within said central opening of said stator, and

a drive connected to said rotor and within said central opening of said housing for urging said liquid or gas from said input opening to said output opening.

3. The pump of claim 21 wherein

said windings are configured as a plurality of lobes around a portion of said central opening of said housing, and

a spacing between two of said lobes wherein a portion of said liquid moving from said input opening passes between said spacing to reach said output opening.

4. The pump of claim 3 wherein said stator comprises at least four of said lobes and a spacing exists between adjacent pairs of said lobes wherein a portion of said liquid will pass between said adjacent pairs of lobes.

5. The pump of claim 2 and further comprising a sealing material applied to an outer surface of said windings to protect said windings from said liquid.