Multi-piece canister assembly for magnetically coupled fluid handling devices

The present disclosure provides a multi-piece containment canister assembly for use in magnetically coupled fluid handling devices such as rotary pumps, mixers, flowmeters or valves. The canister assembly includes a generally tubular single-piece body and an end cap that are sealingly fastened together to form a generally cup-shaped canister. The canister body may be made of strong, non-conductive or low conductive materials, such that it greatly reduces eddy currents. The generally tubular shape of the canister body is easier, and therefore less costly to manufacture than typical cup-shaped canisters.

BACKGROUND

Field of the Invention

The present invention generally relates to containment canisters used in magnetically coupled fluid handling devices such as rotary pumps, mixers, flowmeters or valves.

Description of the Related Art

In rotary fluid handling devices, magnetic couplings are commonly used to prevent fluid from leaking around the rotating drive shaft. These magnetic couplings typically consist of three main components; a larger, outer rotating coupling component with multiple magnets on its inner surface, a smaller, inner rotating coupling component with multiple magnets on its outer surface, and a stationary containment canister, generally cup-shaped, separating the inner and outer components and forming a stationary fluid chamber barrier.

The magnets on the inner and outer components are axially aligned and a magnetic field synchronizes the rotation of the two components, such that as one component is rotated, the other component is forced to rotate. But neither component physically touches the other, and they rotate in separate environments, separated by the canister. These magnetic couplings generally fall into one of two arrangements.

The first and most common arrangement is commonly called an outer drive arrangement, where; the outer coupling component is outside of the device's fluid chamber, and is driven by an external power source, such as a motor; the inner coupling component is inside the device's fluid chamber and is connected to the equipment's rotor; the containment canister is a boundary of the device's fluid chamber, and the fluid chamber is inside the canister.

Although less common, some devices have a second arrangement commonly called an inner drive arrangement, which utilizes the same three main components, except the roles are reversed. The inner coupling component is outside of the device's fluid chamber, and is driven by an external power source, such as a motor; the outer coupling component is inside the device's fluid chamber and is connected to the equipment's rotor; the containment canister is a boundary of the device's fluid chamber, and the fluid chamber is outside the canister.

Typically, the canister is of a one-piece design generally shaped like a cup, including a thin tubular portion disposed within a radial gap between the inner and outer magnets and having an end cap portion closing off one end of the tubular portion. Generally the other end of the tubular portion is open to receive the inner coupling component and is sealingly connected to the device's casing to form and define a portion of the fluid chamber. The canister must be designed to withstand the maximum anticipated pressure of the device's fluid chamber.

The amount of torque that a radial magnetic coupling can generate is related to the radial gap or distance between the inner and outer magnets, where the torque increases as the gap decreases. Therefore it is advantageous to minimize the gap, so that one can obtain the greatest torque possible. In most cases, the canister is made of metal, since metal allows for a strong yet thin design. But this has a disadvantage; most metals are good electrical conductors. For instance, common metal materials for a canister may include 316 stainless steel or 304 stainless steel, which have an electrically conductivity level of roughly 1,300,000 Siemens per meter (S/m) and 1,400,000 S/m, respectively. When using such common metal materials for a canister, electrical eddy currents are created in the metal canister by the rotating magnetic field when the coupling is rotating. The eddy currents convert some of the transmitted power into heat, which wastes power and often has detrimental effects on the device and/or the fluid within the device, which may be referred to as the pumped fluid. With some pump designs, additional measures must be taken to deal with the detrimental eddy currents, such as adding cooling systems.

Some one-piece canister designs use non-conductive or low conductive materials, such as ceramics or structural composites, instead of metal. They have an advantage in that they greatly reduce eddy currents. But they have a disadvantage in that they often are difficult and costly to manufacture, due to the necessary generally cup-like shape of the canister.

Some canisters, particularly in outer-drive arrangements, incorporate a multi-layered design to increase the canister strength. An inner layer generally is made of a material that is chemically resistant to the intended pumped fluid, but may have relatively low strength. The outer layer is not in contact with the pumped fluid, so it can be made from a wider choice of materials, such as a much stronger material to reinforce the inner layer. But these designs are inherently more expensive due to their complexity, and may be thicker, reducing the torque.

Generally the only function of the canister end cap is to close off one end of the canister, but in some cases, the end cap additionally may be used to provide support for the rotor. This may provide an advantage of a simpler and smaller overall design, however, such support adds additional complexity to the canister, further increasing the manufacturing difficulty and cost of the canister when using non-conductive materials.

Thus, there is a need in the industry for a canister design that includes a tubular portion that is thin, strong and generates zero or very low eddy currents, yet is easier and less costly to manufacture.

SUMMARY

The present disclosure provides a multi-piece containment canister for use in magnetically coupled fluid handling devices such as rotary pumps, mixers, flowmeters or valves. The canister includes two main components; a generally tubular single-piece body and an end cap that together form a generally cup-shaped canister.

The canister body can be made of strong, non-conductive or low conductive materials, such that it generates zero or greatly reduced eddy currents in the presence of a rotating magnetic field. The generally tubular shape of the canister body is easier, and therefore less costly to manufacture than typical one-piece cup-shaped canisters or multi-layered canisters.

The canister end cap is sealingly connected to a flange at one end of the canister body, closing off that end. The canister end cap may be made of any suitable material, including metals that have high electrical conductivity, because the canister end cap is not in proximity to the rotating magnetic field of the magnetic coupling, and therefore, will not generate eddy currents.

In a first aspect, the disclosure provides a magnetically driven fluid handling device comprising: a stationary casing having a front portion, a rear portion, a discharge port, and an inlet port; a rotatable rotor assembly having a plurality of magnet segments; a rotatable drive magnet assembly having a plurality of magnet segments in axial alignment with the magnet segments of the rotor assembly; a stationary canister assembly of multi-piece construction further comprising an end cap and a body that is generally tubular, with the body being disposed within a radial gap between the magnet segments of the rotor assembly and the magnet segments of the drive magnet assembly; wherein the body has a central axis and further comprises a central cavity that is open at opposed first and second ends, with a dimension RMAX defined by a radial distance from the central axis to a point on the body farthest away from the central axis, and a dimension RMIN defined by a radial distance from the central axis to a point on the body nearest to the central axis, wherein the dimensions RMIN and RMAX have a ratio of RMIN to RMAX that is at least 0.5, and the body is constructed of a single piece of material; and wherein the body further comprises a flange at the first end, and the end cap is fastened to and sealingly closes the central cavity at the flange at the first end of the body, and wherein the canister assembly is sealingly attached to the casing at the second end of the body, and the canister assembly separates a fluid chamber within the casing from the drive magnet assembly.

In a second aspect, the disclosure provides a canister assembly for a magnetically driven fluid handling device, said canister assembly being of multi-piece construction and comprising: an end cap and a body that is generally tubular; the body having a central axis and a central cavity that is open at opposed first and second ends, with a dimension RMAX defined by a radial distance from the central axis to a point on the body farthest away from the central axis, and a dimension RMIN defined by a radial distance from the central axis to a point on the body nearest to the central axis, wherein the dimensions RMIN and RMAX have a ratio of RMIN to RMAX that is at least 0.5, and the body is constructed of a single piece of material; and wherein the body further comprises a flange at the first end, and the end cap is fastened to and sealingly closes the central cavity at the flange at the first end of the body.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and provided for purposes of explanation only, and are not restrictive of the subject matter claimed. Further features and objects of the present disclosure will become more fully apparent in the following description of the preferred embodiments and from the appended claims.

It should be understood that the drawings are not to scale. While some mechanical details of the example fluid handling devices, including details of fastening means and other plan and section views of the particular components, have not been shown, such details are considered to be within the comprehension of those skilled in the art in light of the present disclosure. It also should be understood that the present disclosure and claims are not limited to the preferred embodiments illustrated.

DETAILED DESCRIPTION

Referring generally toFIGS. 1-14, it will be appreciated that canisters of the present disclosure generally may be embodied within numerous configurations. Indeed, the teachings within this disclosure may pertain to canisters used in magnetically coupled pumps, mixers, flowmeters or valves. The magnetic couplings may be of an inner drive or outer drive arrangement, and the canister end cap may or may not provide support for the rotor.

Referring to a preferred first example embodiment, inFIGS. 1-6, an example magnetically coupled fluid handling device10is shown in the form of a pump12connected to a standard C-face electric motor14. The configuration of pump12happens to be a gear pump with a magnetic coupling of an outer drive arrangement, and where a canister end cap does not provide support for a rotor. Pump12includes a motor adapter16having a first or rear flange18that extends outward and is connected to the motor14by use of a plurality of fasteners20, such as threaded screws or other suitable means of connection.

The pump12includes a casing22that is intended to be mounted in place, so as to be stationary. The casing22includes a front portion24and a rear portion26. The casing rear portion26also has an outlet or discharge port28and an inlet port30. The casing front portion24and casing rear portion26are connected together by use of a plurality of fasteners32that pass through apertures in the casing front portion24and engage threaded holes in a front surface34of the casing front portion24. Sealing is provided between the casing front portion24and the casing rear portion26by an o-ring36, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like.

The motor adapter16has a second or front flange38that extends outward. The casing rear portion26and motor adapter16are connected together by use of a plurality of fasteners40that pass through apertures in the motor adapter front flange38and engage threaded holes in a rear surface42of the casing rear portion26. The casing front portion24, casing rear portion26and motor adapter16may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like.

The pump12further includes a rotatable drive magnet assembly, such as an outer magnet assembly44that includes an outer ring46connected directly to a shaft48of the motor14. Outer ring46includes an inner opening50that slidably receives the motor shaft48. The outer ring46also includes a keyway52and one or more threaded apertures54. A key56is positioned in the outer ring keyway52and engages with a keyway58of the motor shaft48, to provide a positive rotational connection between the outer ring46and the motor shaft48. One or more setscrews60are positioned in the outer ring threaded apertures54and are tightened against the motor shaft48, to provide a positive axial connection between the outer ring46and the motor shaft48. The outer ring46may be constructed of rigid materials, but is preferably constructed of a material with high magnetic permeability, such as iron, carbon steel or the like.

The outer ring46of the drive magnet assembly, such as outer magnet assembly44includes an inner surface62to which are connected eight magnet segments64, although it will be appreciated that one may construct an embodiment with a different quantity of magnet segments. The magnet segments64are radially charged and are positioned with alternating polarity. The magnet segments64are rigidly connected to the outer ring46using an adhesive, although alternative suitable means of connection may be used, such as use of fasteners or the like.

The pump12also includes a rotatable rotor assembly66that includes an inner magnet assembly68having an inner ring70. The inner ring70includes an outer surface72, to which are connected eight magnet segments74, which corresponds to the number of outer magnet segments64connected to the outer ring46, although it will be appreciated that one may construct an embodiment with a greater or lesser quantity of magnet segments. The magnet segments74are radially charged and are positioned with alternating polarity. The magnet segments74are rigidly connected to the inner ring70using an adhesive, although alternative suitable means of connection may be used, such as use of fasteners or the like. An inner magnet sleeve76is included having a thin cylindrical portion78that closely fits along the outer surfaces of the magnet segments74. The inner magnet sleeve76also includes a rear flange80that extends inward. The inner magnet sleeve76is sealingly connected to the inner ring70by continuous weld joints located at an inner end of the rear flange80and at a front end of the cylindrical portion78. It will be appreciated by one of skill in the art that other methods of connection may be used, such as liquid adhesive, gaskets, o-rings or the like. The inner ring70may be constructed of rigid materials, but preferably is constructed of a material with high magnetic permeability, such as iron, carbon steel or the like.

The pump12also includes a generally cup-shaped canister assembly82of multi-piece construction, shown in more detail inFIG. 4, which includes a generally tubular single-piece canister body84having a first or rear end86, a second or front end88and a central cavity90that is open at both ends. Central cavity90has a flange92that extends inward at the first end86; the flange92includes inward facing threads94and a groove96in a rearward facing first surface98.

Canister body84may be constructed of any material having electrical conductivity in the range of zero to low, such as from zero to around 800,000 Siemens per meter (S/m). This may include materials having around zero S/m, such as thermoplastic, polymer, silicon carbide, ceramic or other structural composite materials, or the like. Alternatively, it may include certain metals with low electrical conductivity, such as alloy C-22, alloy C-276 or titanium, which may be roughly 590,000 S/m, 590,000 S/m, and 770,000 S/m, respectively, so as to be in a range from zero to about 800,000 S/m. In one preferred embodiment, the canister may be constructed of a structural composite comprising PEEK (Polyetheretherketone) thermoplastic and elongated carbon fibers in the form of several layers of a thin tape wound over a mandrel and having the layers melted together.

As shown inFIG. 5, canister body84is of a generally tubular shape having a central axis A. The shape of canister body84includes a dimension RMAX defined by a distance from the central axis A to a point on the canister body84farthest away from the central axis A, and a dimension RMIN defined by a distance from the central axis A to a point on the canister body84nearest to the central axis A. A ratio of dimension RMIN to RMAX is 0.5 or greater, so that canister body84may be machined from a tubular piece of raw material100having an outer radius R3slightly greater than dimension RMAX and an inner radius R4slightly less than dimension RMIN. With respect to any of the examples provided herein, the ability to machine the material of the body is preferable.

Referring toFIG. 4, canister assembly82also includes an end cap102. End cap102has an outward extending flange104and a raised portion106having outward facing threads108that cooperate with the inward facing threads94of the canister body flange92. Canister end cap102is removably fastened to canister body flange92via engagement of threads108and94. Sealing is provided between canister end cap102and canister body flange92by an o-ring110positioned in canister body flange groove96and opposite end cap flange104, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like. Thus, canister end cap102sealingly closes canister body central cavity90at the body flange92. The end cap102is spaced apart from the casing22. The end cap102may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like. The canister end cap102is not in proximity to any strong magnetic fields, so the electrical conductivity of the material used is unimportant. Thus, in this first example, the drive magnet assembly44is sized to fit inside the canister body84, the rotor assembly66is sized to fit outside the canister body84, and the first end86of the canister body84is located at the front end of the canister body84.

The canister body84also includes a flange112that extends outward at second end88. The canister body flange112and the casing rear portion26are connected together by use of a plurality of fasteners114that pass through apertures in the canister body flange112and engage threaded holes in a rear surface116of the casing rear portion26. Sealing is provided between casing rear portion26and the canister assembly82by an o-ring118, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like. Thus, canister assembly82is sealingly attached to the casing rear portion26and separates a fluid chamber120from the outer magnet assembly44.

The rotor assembly66also includes a rotor122. Rotor122includes a rotor shaft portion124that further includes a rear portion126containing a keyway128. The inner ring70further includes a central opening130containing a keyway132. Inner ring central opening130receives rotor shaft rear portion126. Inner ring70and rotor122are rotationally locked together by means of a key134that is located in keyways128and132.

Casing rear portion26includes a central opening136that receives a rotor bushing138. Rotor bushing138is attached to casing rear portion central opening136via interference fit, although it will be appreciated that the components may be connected in outer suitable ways. Rotor shaft portion124includes a front portion140having an outer surface142. Rotor bushing138includes an inner surface144that is slightly larger than rotor shaft front portion outer surface142. Rotor bushing inner surface144receives and provides a bearing surface for the rotor shaft front portion outer surface142.

Casing front portion24further includes an opening146that receives a front portion148of an idler pin150. Idler pin front portion148is attached to casing front portion opening146via interference fit, although it will be appreciated that the components may be connected in outer suitable ways. Idler pin150further includes a rear portion152having an outer surface154.

Pump12further includes an idler gear assembly156. Idler gear assembly156includes an idler gear158having a central opening160and an idler bushing162having an outer surface164. Idler bushing162is attached to idler gear central opening160via interference fit, although it will be appreciated that the components may be connected in outer suitable ways. Idler bushing162further includes an inner surface166that is slightly larger than idler pin rear portion outer surface154. Idler pin rear portion outer surface154receives and provides a bearing surface for the idler bushing inner surface166.

The magnet segments64of the outer magnet assembly44are in axial alignment with the magnet segments74of the inner ring70. The stationary canister body84of the canister assembly82is located in a radial gap between the magnet segments64of the outer magnet assembly44and the magnet segments74of the inner ring70. The alternating polarity of the magnet segments64creates an outer magnetic field, and the alternating polarity of the magnet segments74creates an inner magnetic field. These two magnetic fields synchronize together to provide a strong magnetic coupling torque between the outer magnet assembly44and the rotor assembly66, such that when the motor14is energized, it rotates the motor shaft48, which rotates the outer magnet assembly44, which in turn, rotates the rotor assembly66.

Rotor122further includes a rotor head170having a plurality of rotor teeth172. Idler gear156further includes a plurality of idler teeth174sized to mesh smoothly with the rotor teeth172. Rotation of the rotor assembly66causes rotation of the idler gear assembly156through the meshing of rotor teeth172and idler gear teeth174. Rotation of the rotor assembly66and idler gear assembly156causes a pumping action that moves liquid, the pumping fluid, into the pump through the casing rear portion inlet port28and out of the pump through the casing rear portion outlet port30via the common internal gear pumping principle that is well known in the industry.

FIG. 7shows a second example canister assembly200of multi-piece construction that includes a generally tubular single-piece canister body202having a first or rear end204, a second or front end206and a central cavity208that is open at both ends. Canister body202has a flange210that extends inward at the first end204; the flange210includes outward facing threads212at the first end204. Similar to the first example, canister body202also includes a flange that extends outward at the second end206for connection to a casing. Canister body202may be constructed of similar materials to those discussed in reference to the foregoing first example, having zero to low electrical conductivity.

Canister body202is of a generally tubular shape similar to canister body84previously discussed and shown inFIG. 5, having a central axis A. Similar to the first example, the shape of canister body202can be considered to include a dimension RMAX defined by a distance from the central axis A to a point on the canister body202farthest away from the central axis A, and a dimension RMIN defined by a distance from the central axis A to the point on the canister body202nearest to the central axis A. The ratio of dimension RMIN to RMAX is 0.5 or greater, so as with the first example, the canister body202may be machined from a tubular piece of raw material100having an outer radius R3slightly greater than dimension RMAX and an inner radius R4slightly less than dimension RMIN.

Canister assembly200also includes an end cap214. End cap214has inward facing threads216that cooperate with the outward facing threads212of the canister body flange210. Canister end cap214is fastened to canister body flange210via engagement of threads212and216. Sealing is provided between canister end cap214and canister body202by a gasket218, although other methods of sealing may be employed, such as use of an o-ring, liquid sealant or the like. Thus, canister end cap214sealingly closes canister body central cavity208at the first end204of the canister body202at the body flange210. The end cap214may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like. The canister end cap214is not in proximity to any strong magnetic fields, so the electrical conductivity of the material used is unimportant.

FIG. 8shows a third example canister assembly300of multi-piece construction that includes a generally tubular single-piece canister body302having a first or rear end304, a second or front end306and a central cavity308open at both ends. Canister body302has a flange310that extends inward at the first end304and includes a plurality of threaded apertures312and a groove313. Similar to the first example, canister body302also includes a flange that extends outward at the second end306for connection to a casing. Canister body302may be constructed of similar materials to those discussed in reference to the foregoing first example, having zero to low electrical conductivity.

Canister body302is of a generally tubular shape similar to canister body84previously discussed and shown inFIG. 5, having a central axis A. Similar to the first example, the shape of canister body302can be considered to include a dimension RMAX defined by a distance from the central axis A to a point on the canister body302farthest away from the central axis A, and a dimension RMIN defined by a distance from the central axis A to the point on the canister body302nearest to the central axis A. The ratio of dimension RMIN to RMAX is 0.5 or greater, so as with the first example, the canister body302may be machined from a tubular piece of raw material100having an outer radius R3slightly greater than dimension RMAX and an inner radius R4slightly less than dimension RMIN.

Canister assembly300also includes an end cap314. End cap314has a flange316that extends outward and includes a plurality of apertures318that cooperate with the threaded apertures312of the canister body302. Canister end cap314is fastened to canister body302via engagement of a plurality of threaded fasteners320that pass through the end cap flange apertures318and engage the canister flange threaded apertures312. Sealing is provided between canister end cap314and canister body302by an o-ring322positioned in canister body groove313, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like. Thus, canister end cap314sealingly closes canister body central cavity308at the body flange310. The end cap314may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like. The canister end cap314is not in proximity to any strong magnetic fields, so the electrical conductivity of the material used is unimportant.

FIG. 9shows a fourth example canister assembly400of multi-piece construction that includes a generally tubular single-piece canister body402having a first or rear end404, a second or front end406and a central cavity408open at both ends. Canister body402has a groove410in a flange412that extends inward at the first end404. Similar to the first example, canister body402also includes a flange that extends outward at the second end406for connection to a casing. Canister body402may be constructed of similar materials to those discussed in reference to the foregoing first example, having zero to low electrical conductivity.

Canister body402is of a generally tubular shape similar to canister body84previously discussed and shown inFIG. 5, having a central axis A. Similar to the first example, the shape of canister body402can be considered to include a dimension RMAX defined by a distance from the central axis A to a point on the canister body402farthest away from the central axis A, and a dimension RMIN defined by a distance from the central axis A to the point on the canister body402nearest to the central axis A. The ratio of dimension RMIN to RMAX is 0.5 or greater, so as with the first example, the canister body402may be machined from a tubular piece of raw material100having an outer radius R3slightly greater than dimension RMAX and an inner radius R4slightly less than dimension RMIN.

Canister assembly400also includes an end cap414having a flange416that extends outward and includes a plurality of threaded apertures418and a clamp ring420having a plurality of apertures422that cooperate with the threaded apertures418of the end cap414. End cap414is positioned adjacent the rear side of canister body flange412and clamp ring420is positioned adjacent the front side of canister body flange412, although the positions of the end cap414and clamp ring420may be reversed.

End cap414, clamp ring420and canister body402are fastened together via engagement of a plurality of threaded fasteners424that pass through the clamp ring apertures422and engage the end cap threaded apertures418, which clamp the canister body flange412between the end cap414and the clamp ring420. Sealing is provided between canister end cap414and canister body402by an o-ring426positioned in canister body groove410, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like. Thus, canister end cap414sealingly closes canister body central cavity408at the canister body flange412. The end cap414and clamp ring420may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like. The canister end cap414and clamp ring420are not in proximity to any strong magnetic fields, so the electrical conductivity of the material used is unimportant.

FIG. 10shows a fifth example canister assembly500of multi-piece construction that includes a generally tubular single-piece canister body502having a first or rear end504, a second or front end506and a central cavity508open at both ends. Canister body502further includes a flange510that extends inward at the first end504. Similar to the first example, canister body502also includes a flange that extends outward at the second end506for connection to a casing. Canister body502may be constructed of similar materials to those discussed in reference to the foregoing first example, having zero to low electrical conductivity.

Canister body502is of a generally tubular shape similar to canister body84previously discussed and shown inFIG. 5, having a central axis A. Similar to the first example, the shape of canister body502can be considered to include a dimension RMAX defined by a distance from the central axis A to a point on the canister body502farthest away from the central axis A, and a dimension RMIN defined by a distance from the central axis A to the point on the canister body502nearest to the central axis A. The ratio of dimension RMIN to RMAX is 0.5 or greater, so as with the first example, the canister body502may be machined from a tubular piece of raw material100having an outer radius R3slightly greater than dimension RMAX and an inner radius R4slightly less than dimension RMIN.

Canister assembly500also includes an end cap514. Canister end cap514has a flange516that extends outward and at which end cap514is fastened and sealed to canister body flange510via an adhesive. Thus, canister end cap514sealingly closes canister body central cavity508at the canister body flange510. Locating the end cap514within the central cavity508and to be stopped and sealed against the canister body flange510ensures that pressures within the central cavity508do not try to unseal the canister assembly500. The end cap514may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like. The canister end cap514is not in proximity to any strong magnetic fields, so the electrical conductivity of the material used is unimportant.

Referring to a further example embodiment, inFIGS. 11-14, an example magnetically coupled fluid handling device610is shown in the form of a pump612connected to a standard C-face electric motor614. The configuration of magnetically coupled fluid handling device610happens to be in the form of a centrifugal pump with a magnetic coupling of an inner drive arrangement, and where a canister end cap provides support for a rotor. Pump612includes a motor adapter616having a first flange618that extends outward and is connected to the motor614by use of a plurality of fasteners, such as threaded screws or other suitable means of connection.

The pump612includes a casing622that is intended to be mounted in place, so as to be stationary. The casing622includes a front portion624and a rear portion626. The casing front portion624also has an outlet or discharge port628and an inlet port630. In this further example, the discharge port628is radially facing, while the inlet port630is axially facing, although alternative configurations may be utilized. The casing front portion624includes a rear face632that is connected to a second flange634of the motor adapter616by use of a plurality of fasteners that pass through apertures in the second flange634and engage threaded holes in the casing front portion rear face632. The casing622may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like.

Casing rear portion626has a flange638that extends outward. The casing rear portion flange638is clamped between the casing front portion624and the motor adapter616when connecting the pump612to the motor adapter616by installing the fasteners632. Sealing is provided between the casing front portion624and the casing rear portion638by an o-ring640, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like. The pump612also includes a rear cover642that has a flange644that extends outward. The rear cover642is connected to the casing rear portion626by use of a plurality of fasteners, such as threaded screws that pass through apertures in the rear cover642and engage threaded holes in a rear face of the casing rear portion626.

The pump612further includes a rotatable drive magnet assembly, such as an inner magnet assembly646that includes an inner ring648connected directly to a shaft650of the motor614. Inner ring648includes an inner opening652that slidably receives the motor shaft650. The inner ring648also includes a keyway654and may include one or more threaded apertures to receive set screws to provide a positive axial connection between the inner ring648and the motor shaft650. A key656is positioned in the inner ring keyway654and engages with a keyway658of the motor shaft650to provide a positive rotational connection between the inner ring648and the motor shaft650. The inner ring648may be constructed of rigid materials, but is preferably constructed of a material with high magnetic permeability, such as iron, carbon steel or the like.

The inner ring648of the drive magnet assembly, such as inner magnet assembly646includes an outer surface660to which are connected twenty-four magnet segments662, although it will be appreciated that one may construct an embodiment with a different quantity of magnet segments. The magnet segments662are radially charged and are positioned with alternating polarity. The magnet segments662are rigidly connected to the inner ring648using an adhesive, although alternative suitable means of connection may be used, such as use of fasteners or the like. Although not required, this example embodiment includes an inner magnet sleeve664having a thin cylindrical portion666that closely fits over the outer surfaces of the magnet segments662.

The pump612also includes a rotatable rotor assembly, such as a rotatable rotor or impeller assembly668that includes a rotor, such as an impeller670. The impeller670includes a rear opening672, which receives an outer ring674having an inner wall surface676to which are connected twenty-four magnet segments678, which corresponds to the number connected to the inner ring648, although it will be appreciated that one may construct an embodiment with a greater or lesser quantity of magnet segments. The magnet segments678are radially charged and are positioned with alternating polarity. The magnet segments678are rigidly connected to the outer ring674using an adhesive, although alternative suitable means of connection may be used, such as use of fasteners or the like. An impeller magnet sleeve680is included having a thin cylindrical portion682that closely fits along the inner surfaces of the magnet segments678. The impeller magnet sleeve680also includes a rear flange684that extends outward. The impeller magnet sleeve680is sealingly connected to the impeller670by continuous weld joints located at an outer end of the rear flange684and at a front end of the cylindrical portion682. It will be appreciated by one of skill in the art that other methods of connection may be used, such as liquid adhesive, gaskets, o-rings or the like. The rotor or impeller670may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like. The outer ring674may be constructed of rigid materials, but preferably is constructed of a material with high magnetic permeability, such as iron, carbon steel or the like.

Referring toFIGS. 13-14, the impeller670has a central opening686. A bushing688is received in the central opening686of the rotor or impeller670. The bushing688is held in a forward direction against a step690in the central opening686proximate an end of the central opening686of the impeller670, where there is a transition from a first inner surface692to a second inner surface694having a smaller diameter. The rotor or impeller670further includes a rear surface696that includes one or more threaded holes698. An impeller rear cap, such as rotor ring700having a central opening702is connected to the impeller rear surface696by at least one fastener704, such as by a plurality of screws that pass through apertures in the rotor ring700and engage the threaded holes in the impeller670. The bushing688includes a rear portion706with a shape that is not cylindrical, and it corresponds to a non-cylindrical shape of the central opening702in the rotor ring700to prevent relative rotation between the bushing688, rotor ring700and impeller670, although as previously noted, alternative ways of preventing relative rotation may be utilized. Thus, the bushing688fits inside the central opening686extending axially through the rotor or impeller670and is held in place between the rotor ring700and the step690in the central opening686of the impeller670.

The pump612also includes a generally cup-shaped canister assembly708of multi-piece construction that includes a generally tubular single-piece canister body710having a first or front end712, a second or rear end714and a central cavity716open at both ends. Canister body710has a flange718that extends inward and inward facing threads720at the first end712and a groove722at a first surface724. Canister body710may be constructed of similar materials to those discussed in reference to the foregoing first example, having zero to low electrical conductivity.

As shown inFIG. 14, canister body710is of a generally tubular shape having a central axis A. Similar to the first example, the shape of canister body710can be considered to include a dimension RMAX defined by a distance from the central axis A to a point on the canister body710farthest away from the central axis A, and a dimension RMIN defined by a distance from the central axis A to a point on the canister body710nearest to the central axis A. A ratio of dimension RMIN to RMAX is 0.5 or greater, so as with the first example, the canister body710may be machined from a tubular piece of raw material100having an outer radius R3slightly greater than dimension RMAX and an inner radius R4slightly less than dimension RMIN.

Canister assembly708also includes an end cap assembly726having an end plate728. End plate728has a flange730that extends outward and outward facing threads732that cooperate with the inward facing threads720of the canister body flange718. Canister end cap assembly726is fastened to canister body710via engagement of threads720and732. Sealing is provided between canister end cap assembly726and canister body flange718by an o-ring734, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like. Thus, canister end cap assembly726sealingly closes canister body central cavity716at the canister body flange718. The end cap assembly726is spaced apart from the casing622.

The canister body710also includes a flange736that extends outward at second end714. The canister body flange736is clamped between the casing rear portion726and the rear cover642when connecting the rear cover642to the casing rear portion726by installing the fasteners632. Sealing is provided between casing rear portion726and the canister assembly708by an o-ring738, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like. Thus, canister assembly708is sealingly attached to the casing rear portion726and separates a fluid chamber740from the inner magnet assembly646.

Canister end cap assembly726also includes a nose cap742, which has a threaded aperture744, a rear face746and a rear extended portion748. The nose cap742is attached to the canister end plate728by a fastener748, such as a threaded screw that passes through an aperture750in the end plate728and engages the threaded aperture744in the rear of the nose cap742. In this further example embodiment, there is just one fastener748securing the nose cap742, but it will be appreciated by one of skill in the art that a plurality of fasteners or other suitable fastening means may be employed in assembling the components of the canister end cap assembly726. Also, in this further example pump612, the canister end cap assembly726is spaced from the casing front portion624, such that it does not receive support from and is not compressed by the casing front portion624. The end plate728and nose cap742may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like. The canister end cap assembly726is not in proximity to any strong magnetic fields, so the electrical conductivity of the material used is unimportant. Thus, in this further example, the drive magnet assembly646is sized to fit outside the canister body710, the rotor assembly668is sized to fit inside the canister body710, and the first end712is located at the rear end of the canister body710.

Within this further example pump612, the bushing688provides the rotatable rotor assembly or impeller assembly668a radial bearing surface752, a first or front axial bearing surface754, and a second or rear axial bearing surface756. In this further example, these bearing surfaces engage respective bearing surfaces of the canister end cap assembly726, which include a radial bearing surface758provided by a bearing sleeve760, a first or front axial bearing surface762provided by a front thrust washer764, and a second or rear axial bearing surface766provided by a rear thrust washer768. It should be appreciated that alternatively, bearing surfaces766and758could be integral with canister end plate728, and/or bearing surface762could be integral with nose cap742. As such, canister end cap assembly726provides support for the rotor assembly668.

The magnet segments662of the inner magnet assembly646are in axial alignment with the magnet segments678impeller assembly668. The stationary canister body710of the canister assembly708is located in a radial gap between the magnet segments662of the inner magnet assembly646and the magnet segments678of the rotor assembly668. The alternating polarity of the magnet segments662creates an inner magnetic field, and the alternating polarity of the magnet segments678creates an outer magnetic field. These two magnetic fields synchronize together to provide a strong magnetic coupling torque between the inner magnet assembly646and the impeller assembly668, such that when the motor614is energized, it rotates the motor shaft650, which rotates the inner magnet assembly646, which in turn, rotates the impeller assembly668.

Referring toFIGS. 12-13, the impeller670includes a plurality of vanes770. The casing front portion624includes a discharge collector cavity772that is fluidly connected to the casing discharge port628. The rotation of the impeller vanes770causes a pumping action that moves liquid, the pumping fluid, into the pump through the casing inlet port730, radially outward to the discharge collector cavity772, and out of the pump through the discharge port728.