Patent Description:
A shaft coupling is utilized in various applications to transmit power (in particular, to transfer torque) from one shaft (the drive shaft) to another shaft (the driven shaft). As a general example, a shaft coupling may couple a prime mover (e.g., an electric motor) to the rotating component (rotor) of a device or machine, whereby the power supplied or generated by the prime mover is utilized to drive the rotation of the rotor. Various types of pumps (e.g., scroll pump, rotary vane pump, gear pump, screw pump, Roots-type pump, claw pump, etc.) have one or more pump rotors that require such power.

Many pumping applications require the pump components to be hermetically sealed (i.e., isolated in a fluid-tight or leak-free manner) from the ambient environment outside of the pump. In particular, the driven side of the shaft coupling may need to reside within the confines of the hermetic sealing envelope, as well as the pumping components that act on the working fluid (the liquid or gas being pumped). Helium recirculation is one example where a hermetic vacuum pump is required. It is recognized by persons skilled in the art that hermeticity has two components, which are defined by <NUM>) a leakage rate and <NUM>) a permeation rate. In systems that use helium or other light gases, the hermeticity of the system is usually dominated by the permeation rate of the light gas through the sealing o-rings and any polymer barriers in the system. Typically, the permeation rate can be several orders of magnitude larger than the leakage rate in light gas applications, requiring the selection of special sealing and barrier materials with a low permeation rate. Hermetic pumps may be required to control fluid pressure inside the pump, such as a desired vacuum level in the case of a vacuum pump, and/or to prevent contamination such as by leakage of lubricants, solid particles, and/or the working fluid from the pump. Known components for realizing a hermetic pump add significant cost. Examples include a magnetic (shaft) coupling, an orbiting bellows in the case of a scroll compressor or vacuum pump, a canned motor, and a ferrofluidic seal. It would be desirable to provide a lower cost solution for a hermetic pump than those currently known, and further which has the potential for both a low leakage rate and low permeation rate for both the system gases and ambient gases (i.e. air).

In addition, many types of shaft couplings are mechanical shaft couplings. That is, they require a direct physical connection between the coupling component(s) on the drive (e.g., motor) side and the coupling component(s) on the driven (e.g., pump head) side. Such a shaft coupling is problematic when utilized with a hermetic pump, as a portion of the shaft coupling must physically cross or pass through the hermetic barrier of the pump. Such an arrangement requires special shaft seals (particularly on the driven side) to maintain the integrity of the hermetic barrier. However, the performance of such shaft seals can be unreliable, they require maintenance, and they can have limited service life.

As an alternative to intrusive mechanical shaft couplings, a magnetic coupling may be utilized. A magnetic coupling includes one or more drive magnets and one or more driven magnets separated by an air gap, thereby establishing magnetic fields in the air gap between the drive magnet(s) and driven magnet(s). The associated magnetic forces are utilized in a known manner to transfer the torque from the drive shaft to the driven shaft without any contact between the drive side and the driven side of the magnetic coupling. This configuration enables a separating wall to be positioned in the air gap between the drive side and the driven side. The separating wall can form a part of a hermetic barrier for a hermetic pump, provided it is made from a material with a low permeation rate for both the working fluid in the system and the ambient gases (e.g., nitrogen, oxygen, water). A metallic material might seem to be an obvious choice for the barrier material except for the fact that an electrically conductive material is disadvantageous in the context of a magnetic coupling. In particular, an electrically conductive material would result in excessive power loss and heat buildup in the hermetic barrier material in the air gap region caused by eddy currents generated by the time-varying magnetic fields in the conductive barrier material. It is therefore critical that the hermetic barrier material in the air gap region of the magnetic coupling be an electrically nonconductive, low-cost material that is also resistant to permeation, especially for light gases such as helium and hydrogen. The hermetic barrier material would also need to resist permeation of water, nitrogen, and oxygen to avoid contamination of the system from atmospheric gases permeating into the system, (e.g., a helium recirculation system). A further requirement of the barrier material is that it have a sufficient structural modulus, yield strength, and low creep rate to prevent excessive deflection or structural failure caused by the pressure differential across the barrier material. It would therefore be desirable to provide a special barrier material that meets one or more, and preferably all, of these potentially conflicting requirements (e.g., low permeation, low cost, non-conductive, high modulus of elasticity, high yield strength, and low creep rate). As other advantages, a magnetic coupling may eliminate the need for the shaft seals noted above. Also, a magnetic coupling is intrinsically torque-limiting in that it will not transfer torque greater than a certain maximum value ("pull-out" torque), and thus provides self-protection against an overload condition. Further, a magnetic coupling allows for an appreciable amount of tolerance for misalignment between the drive shaft and driven shaft. Magnetic couplings having radial configurations have been utilized. A radial magnetic coupling includes a ring-shaped outer magnet coaxially surrounding a ring-shaped inner magnet. Both magnets rotate about the central axis of the magnetic coupling, with one driving the rotation of the other. Accordingly, the air gap between the magnets is cylindrical and parallel with the central axis. Radial couplings have been provided with gear pumps and rotary vane pumps. Examples of these configurations are respectively disclosed in <CIT> and <CIT>. However, the radial configuration can add complexity and cost to the pump along with a larger hermetic barrier in comparison to an axial configuration (described below). The larger hermetic barrier typically requires additional surface area in the radial air gap region that increases the permeation rate compared to an axial air gap coupling, as well as creating assembly difficulties that arise from one coupling component tending to attract the other coupling component with a large attractive force during the assembly process.

Magnetic couplings having axial configurations also have been utilized. In axial magnetic coupling, a set of drive magnets and a set of driven magnets are arranged about a common axis of rotation, and are separated by an axial air gap. Examples of these configurations are disclosed in <NPL>; <NPL>; <NPL>; and <NPL>. An axial air gap magnetic coupling could potentially offer a simpler and lower cost solution in comparison to a radial magnetic coupling. However, axial magnetic couplings of known designs produce a significant axial force. In a typical application such as a pump, this axial force must be reacted by the bearings of the system associated with the transfer of motorized power to the load (e.g., the pump head), such as motor bearings and pump shaft bearings. However, the bearings typically provided are not designed to bear the large axial forces generated by an axial magnetic coupling. Consequently, the incorporation of an axial magnetic coupling into the typical application would require non-standard components to accommodate such axial forces, and thereby offset any cost reduction that might be realized with the utilization of the axial magnetic coupling.

<CIT> discloses an electrorheological fluid torque transmission and conversion system for clutch and brake applications which is provided with a magnetic coupling. Permanent magnets are associated respectively with each of a drive member and a driven member which are magnetically coupled through a surface with low magnetic permeability so that the drive member and the driven member rotate in unison. The strong attraction associated with the magnetic coupling between the permanent magnets of the drive member and driven member, respectively, may be counteracted by providing the drive member and the driven member with respective repulsive magnets.

<CIT> discloses a magnetic clutch system including a first magnet rotor coupled to a drive shaft and having a first sequence of magnets and a second magnet rotor coupled to a driven shaft and having a second sequence of magnets, the first and second sequence of magnets are arranged such that rotation of the first magnet rotor causes rotation of the second magnet rotor to drive the driven shaft. In order to prevent the first and second magnet rotors from collapsing against each other and/or to facilitate separation of the first and second magnet rotors from each other, the first and second magnet rotors are provided with respective repulsive magnets.

<CIT> discloses a refrigeration compressor provided with a magnetic coupling. The refrigeration compressor comprises a stator, a rotor orbiting in engagement with the stator to cyclically open, fill with refrigerant gas from at least one inlet port, compress and discharge compressed refrigerant gas through at least one discharge port, a rotary drive for orbiting the rotor, a driven element of a magnetic coupling in driving connection with the rotary drive, a casing sealed save for the ports and enclosing all of the foregoing components, a driving element of the magnetic coupling outside of the casing in close proximity to the driven element, and means to rotate the driving element.

In view of the foregoing, there is an ongoing need for improved magnetic couplings and the implementation of magnetic couplings to pumping applications.

To address the foregoing problems, in whole or in part, and/or other problems that may have been observed by persons skilled in the art, the present disclosure provides methods, processes, systems, apparatus, instruments, and/or devices, as described by way of example in implementations set forth below.

A magnetic coupling assembly includes: a drive shaft rotatable on a drive axis; a driven shaft rotatable on the drive axis; a drive magnet assembly coupled to the drive shaft and rotatable therewith, the drive magnet assembly comprising a first balancing magnet positioned on the drive axis, and a drive magnet coaxially positioned with the first balancing magnet; and a driven magnet assembly coupled to the driven shaft and rotatable therewith, the driven magnet assembly comprising a second balancing magnet disposed on the drive axis, and a driven magnet coaxially positioned with the second balancing magnet, wherein: the drive magnet assembly is spaced from the driven magnet assembly by an axial gap, with the first balancing magnet facing the second balancing magnet across the axial gap, and the drive magnet facing the driven magnet across the axial gap; the drive magnet and the driven magnet are configured to drive rotation of the driven magnet in response to rotation of the drive magnet, and to generate a tangential drive force and an axial attractive force between the drive magnet and the driven magnet; and the first balancing magnet and the second balancing magnet are configured to generate an axial.

repulsive force between the first balancing magnet and the second balancing magnet that counterbalances the axial attractive force.

A magnetic coupling assembly includes: a drive shaft rotatable on a drive axis; a drive shaft rotatable on a drive axis; a driven shaft rotatable on the drive axis; a drive magnet assembly coupled to the drive shaft and rotatable therewith; a driven magnet assembly coupled to the driven shaft and rotatable therewith, wherein: the drive magnet assembly is spaced from the driven magnet assembly by a gap; and the drive magnet assembly and the driven magnet assembly are configured to drive rotation of the driven magnet assembly in response to rotation of the drive magnet assembly; and according to the invention a structural boundary disposed in the gap between the drive magnet assembly and the driven magnet assembly, wherein the structural boundary is preferably composed of a liquid crystal polymer.

In an embodiment, the structural boundary at least partially encloses the driven magnet assembly.

In an embodiment, the drive magnet assembly comprises a first balancing magnet, the driven magnet assembly comprises a second balancing magnet, and the first balancing magnet and the second balancing magnet are configured to generate a repulsive force between the first balancing magnet and the second balancing magnet that balances the attractive force. In a further embodiment, the drive magnet assembly comprises a plurality of drive magnets circumferentially spaced from each other about the drive axis and surrounding the first balancing magnet, and the driven magnet assembly comprises a plurality of driven magnets circumferentially spaced from each other about the drive axis and surrounding the second balancing magnet.

In an embodiment, the gap is an axial gap, and the drive magnet assembly and the driven magnet assembly are configured to generate the attractive force as an axial attractive force. In another embodiment, the gap is a radial gap relative to the drive axis, and the drive magnet assembly and the driven magnet assembly are configured to generate the attractive force as a radial attractive force.

In an embodiment, the drive magnet assembly comprises a plurality of drive magnets circumferentially spaced from each other about the drive axis, and the driven magnet assembly comprises a plurality of driven magnets circumferentially spaced from each other about the drive axis.

According to another embodiment, a pump assembly includes: a magnetic coupling assembly according to any of the embodiments described herein; a pump head comprising a fluid inlet and a fluid outlet; and a pumping stage disposed in the pump head and communicating with the fluid inlet and the fluid outlet, the pumping stage comprising a pump rotor communicating with the driven shaft and rotatable therewith, wherein rotation of the drive shaft drives rotation of the pump rotor via the magnetic coupling assembly, and the pumping stage is configured to pump fluid from the fluid inlet to the fluid outlet in response to the rotation of the pump rotor.

According to another embodiment, a method for operating a magnetic coupling assembly includes: providing the magnetic coupling assembly with a drive magnet assembly and a driven magnet assembly spaced from each other by an axial gap along a drive axis, wherein the drive magnet assembly and the driven magnet assembly are coupled by a magnetic coupling and generate a tangential drive force and an axial attractive force across the axial gap; rotating the drive magnet assembly about the drive axis to drive rotation of the driven magnet assembly about the drive axis via the magnetic coupling; and rotating the drive magnet assembly about the drive axis to drive rotation of the driven magnet assembly about the drive axis via the magnetic coupling; and balancing the axial attractive force by generating an axial repulsive force between the drive magnet assembly and the driven magnet assembly.

According to another embodiment, a method for pumping fluid includes: operating a magnetic coupling assembly according to any of the embodiments described herein, wherein: a pump rotor of a pumping stage communicates with the driven shaft; and the operating of the magnetic coupling assembly drives rotation of the pump rotor such that fluid flows from a fluid inlet, through the pumping stage, and to a fluid outlet.

According to any of the foregoing embodiments, a structural boundary may be disposed in the axial gap between the drive magnet assembly and the driven magnet assembly, wherein the structural boundary is composed of an electrically insulating material. In an embodiment, the electrically insulating material is a polymer, such as a liquid crystal polymer, or a ceramic such as a suitable glass composition.

According to any of the foregoing embodiments, a casing may enclose the driven magnet assembly. In an embodiment, the casing is configured to fluidly isolate the driven magnet assembly from an ambient outside of the casing. In an embodiment, the casing includes or is attached to a structural boundary as disclosed herein. In an embodiment, the casing is part of or is attached to a pump head.

According to any of the foregoing embodiments, the first balancing magnet may include a first inside face and have a first polarity (e.g., north or south) at the first inside face, the second balancing magnet may include a second inside face facing the first inside face across the axial gap and have a second polarity (e.g., north or south) at the second inside face, and the first polarity and the second polarity are the same.

According to any of the foregoing embodiments, the drive magnet comprises a plurality of drive magnets circumferentially spaced from each other about the drive axis and surrounding the first balancing magnet, and the driven magnet comprises a plurality of driven magnets circumferentially spaced from each other about the drive axis and surrounding the second balancing magnet.

According to any of the foregoing embodiments, the drive magnet comprises a plurality of drive magnets circumferentially arranged with alternating polarities about the drive axis, and the driven magnet comprises a plurality of driven magnets circumferentially arranged with alternating polarities about the drive axis.

Alternatively in any of the foregoing embodiments, the drive magnet comprises an annular structure magnetized with a plurality of dipole circumferentially arranged with alternating polarities about the drive axis, and the driven magnet comprises an annular structure magnetized with a plurality of dipole circumferentially arranged with alternating polarities about the drive axis.

Alternatively in any of the foregoing embodiments, the drive magnet is configured as a Halbach array, and the driven magnet is configured as a Halbach array.

According to any of the foregoing embodiments, a pump rotor may communicate with the driven shaft and be rotatable therewith. In various embodiments, the pump rotor may be an orbiting scroll, a rotary vane component, a crank, a cam, a gear, a screw, a Roots lobe, or a claw.

According to any of the foregoing embodiments, the pumping stage may be a scroll pumping stage, a rotary vane pumping stage, a gear pumping stage, a screw compressor stage, a Roots pumping stage, or a claw pumping stage.

According to any of the foregoing embodiments, the pump rotor is part of a scroll pumping stage and comprises an orbiting scroll blade. The pumping stage further comprises a stationary scroll blade nested with the orbiting scroll blade. The orbiting scroll blade is configured to move in an orbiting manner relative to the stationary scroll blade in response to rotation of the driven shaft, to create a moving pocket between the orbiting scroll blade and the stationary scroll blade effective to pump fluid.

In an embodiment, the pumping stage further comprises a crank positioned in eccentric relation to the driven shaft and configured to move in an orbiting manner in response to rotation of the driven shaft, and the orbiting scroll blade is coupled to the crank.

According to any of the foregoing embodiments, a motor is configured to drive rotation of the drive shaft.

In an embodiment of the method for operating a magnetic coupling assembly, generating the axial repulsive force comprises providing the drive magnet assembly with a first balancing magnet, and providing the driven magnet assembly with a second balancing magnet facing the first balancing magnet across the axial gap. In an embodiment, the first balancing magnet and the second balancing magnet are positioned on the drive axis.

In an embodiment of the method for operating a magnetic coupling assembly, the drive magnet assembly and the driven magnet assembly comprise any the configurations disclosed herein.

In an embodiment of the method for operating a magnetic coupling assembly, generating the axial repulsive force comprises providing the drive magnet assembly with a first balancing magnet surrounded by the drive magnet or magnets, and providing the driven magnet assembly with a second balancing magnet surrounded by the driven magnet or magnets and facing the first balancing magnet across the axial gap.

In an embodiment of the method for operating a magnetic coupling assembly, the method includes inserting a structural boundary in the axial gap between the drive magnet assembly and the driven magnet assembly, wherein the structural boundary is composed of an electrically insulating material according to any of the embodiments disclosed herein.

In an embodiment of the method for pumping fluid, the operating of the magnetic coupling assembly comprises operating a motor to drive rotation of the drive shaft.

Other devices, apparatus, systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.

The invention can be better understood by referring to the following figures. In the figures, like reference numerals designate corresponding parts throughout the different views.

<FIG> is a schematic cross-sectional view of an example of a ("balanced" or "counterbalanced" as defined herein) axial magnetic coupling assembly <NUM> according to an embodiment of the present disclosure. For reference purposes, the axial magnetic coupling assembly <NUM> may be considered as being arranged along a drive axis L, which corresponds to the axis of rotation of the axial magnetic coupling assembly <NUM>, and may further correspond to the central, longitudinal axis of the axial magnetic coupling assembly <NUM>. Also, for reference purposes, <FIG> includes an arbitrarily positioned Cartesian (x-y-z) frame of reference. In this example, the drive axis L corresponds to the z-axis, and the transverse plane orthogonal to the drive axis L corresponds to the x-y plane. In the context of the present disclosure, the term "axial" relates to the drive axis L or a direction generally parallel to the drive axis L.

The axial magnetic coupling assembly <NUM> generally includes a drive (driving) shaft <NUM> and a driven shaft <NUM>, both of which are rotatable on the drive axis L. The axial magnetic coupling assembly <NUM> also generally includes a drive (driving) magnet assembly <NUM> coupled to the drive shaft <NUM> and thereby rotatable with the drive shaft <NUM>, and a driven magnet assembly <NUM> coupled to the driven shaft <NUM> and thereby rotatable with the driven shaft <NUM>. The drive magnet assembly <NUM> includes a drive magnet <NUM>, and the driven magnet assembly <NUM> includes a driven magnet <NUM>. The drive magnet <NUM> and the driven magnet <NUM> each may include one or more distinct magnets. That is, the drive magnet <NUM> may include a single drive magnet or a plurality of drive magnets, and the driven magnet <NUM> may include a single driven magnet or a plurality of driven magnets. In the present embodiment, the drive magnet assembly <NUM> includes a plurality of peripheral drive (driving) magnets <NUM> arranged in an array or pattern in the transverse plane. Similarly, the driven magnet assembly <NUM> includes a plurality of peripheral driven magnets <NUM> arranged in an array or pattern in the transverse plane. Only one diametrically opposite pair of drive magnets <NUM>, and only one diametrically opposite pair of driven magnets <NUM>, are shown in <FIG>.

According to an aspect of the present disclosure, the drive magnet assembly <NUM> further includes a first (drive-side) balancing magnet <NUM> and the driven magnet assembly <NUM> further includes a second (driven-side) balancing magnet <NUM>, both of which are centrally positioned on the drive axis L. The drive magnets <NUM> coaxially surround the first balancing magnet <NUM>, and the driven magnets <NUM> coaxially surround the second balancing magnet <NUM>. The first balancing magnet <NUM> and the second balancing magnet <NUM> are described further below.

In an embodiment, the drive magnet(s) <NUM>, driven magnet(s) <NUM>, first balancing magnet <NUM>, and second balancing magnet <NUM> are permanent magnets. Thus, these magnets may be composed of, for example, a suitable alloy such as (permanently magnetized) neodymium (i.e., neodymium alloyed primarily with iron and boron), alnico (i.e., iron alloyed primarily with aluminum, nickel, and cobalt), a hard ferrite (i.e., an iron oxide-containing ceramic), etc..

The drive magnet assembly <NUM> may further include a drive magnet support structure <NUM>. The drive magnet support structure <NUM> is configured to couple the drive magnet assembly <NUM> to the drive shaft <NUM>, and to support and fix the positions of the drive magnets <NUM> and the first balancing magnet <NUM> relative to each other and to the drive axis L. Thus, the drive magnets <NUM> are mounted to (e.g., attached to, secured to, or otherwise retained or held by) the drive magnet support structure <NUM>, and are thereby coupled to and rotatable about the drive shaft <NUM>. Similarly, the driven magnet assembly <NUM> may further include a driven magnet support structure <NUM>. The driven magnet support structure <NUM> is configured to couple the driven magnet assembly <NUM> to the driven shaft <NUM>, and to support and fix the positions of the driven magnets <NUM> and the second balancing magnet <NUM> relative to each other and to the drive axis L. Thus, the driven magnets <NUM> are mounted to (e.g., attached to, secured to, or otherwise retained or held by) the driven magnet support structure <NUM>, and are thereby coupled to and rotatable about the driven shaft <NUM>. For all such purposes, the drive magnet support structure <NUM> and the driven magnet support structure <NUM> each may include one or more structural components as needed. Moreover, depending on the configuration of the various magnets, all or part of the drive magnet support structure <NUM> and the driven magnet support structure <NUM> may serve as a magnetic or magnetizable yoke to complete the circuit for the magnetic flux of corresponding magnets. For example, all or part of the drive magnet support structure <NUM> and the driven magnet support structure <NUM> may be composed of a ferromagnetic material such as soft iron, nickel, cobalt, etc., and certain alloys thereof.

The drive magnet assembly <NUM> and the driven magnet assembly <NUM> are spaced from each other (along the drive axis L) by an axial gap <NUM>, for example an air gap. The array of drive magnets <NUM> and the array of driven magnets <NUM> face each other across the axial gap <NUM>. Likewise, the first balancing magnet <NUM> and the second balancing magnet <NUM> face each other across the axial gap <NUM>. Specifically, the drive magnets <NUM> have (first) inside faces <NUM> facing the axial gap <NUM>, the driven magnets <NUM> have (second) inside faces <NUM> facing the axial gap <NUM> and facing the drive magnets <NUM>, the first balancing magnet <NUM> has a (first) inside face <NUM> facing the axial gap <NUM>, and the second balancing magnet <NUM> has a (second) inside face <NUM> facing the axial gap <NUM> and facing the first balancing magnet <NUM>. <FIG> is a schematic plan view of an example of a magnet assembly <NUM> according to an embodiment. The magnet assembly <NUM> includes a balancing magnet <NUM> positioned on the drive (central) axis, and a plurality of peripheral magnets <NUM> circumferentially spaced from each other about the drive axis (at a radial distance from the drive axis) and coaxially surrounding the balancing magnet <NUM>. The balancing magnet <NUM> and peripheral magnets <NUM> are mounted to and supported by an appropriately configured magnet support structure <NUM> that can be coupled to a shaft for rotation with the shaft. To provide balanced and uniform (and rotationally symmetric) magnetic fields and axial forces, the peripheral magnets <NUM> all have the same size, shape, and position relative to each other. As to the latter, the peripheral magnets <NUM> are circumferentially spaced at equal distances from each other and with the same angular orientation relative to the drive axis, and are radially spaced at equal distances from the drive axis and thus from the centrally located balancing magnet <NUM>. Generally, the peripheral magnets <NUM> may have any (preferably symmetrical) shape, which may be rounded, polygonal, or have a combination of rounded and polygonal (e.g., straight-edged features). In the illustrated embodiment, by way of example only, the peripheral magnets <NUM> have racetrack shapes.

<FIG> in particular is a plan view of the inner side, or gap side, of the magnet assembly <NUM> (namely, the side facing the axial gap when assembled as part of an axial magnetic coupling), thus showing inside faces <NUM> of the peripheral magnets <NUM> and an inside face <NUM> of the balancing magnet <NUM>. In an embodiment, the peripheral magnets <NUM> and the balancing magnet <NUM> are configured (e.g., magnetized) as north-south (N-S) magnetic dipoles. The peripheral magnets <NUM> and the balancing magnet <NUM> are oriented such that the north and south poles are located on the inside faces <NUM> and <NUM> and on the axially opposite outside faces. By this configuration, the magnetic flux is directed axially through the thickness of the peripheral magnets <NUM> and the balancing magnet <NUM> (namely, in the z-direction through the drawing sheet). As illustrated, the peripheral magnets <NUM> are circumferentially arranged with alternating polarities about the drive axis. Thus, for each peripheral magnet <NUM>, the polarity (e.g., N) at the inside face <NUM> is opposite to the polarity (e.g., S) at the inside faces <NUM> of the peripheral magnets <NUM> adjacent to that peripheral magnet <NUM>.

As an alternative, <FIG> is a schematic plan view of an example of a magnet assembly <NUM> according to another embodiment. The magnet assembly <NUM> includes a balancing magnet <NUM> positioned on the drive (central) axis, and a peripheral magnet <NUM>. The balancing magnet <NUM> and peripheral magnet <NUM> may be mounted to and supported by an appropriately configured magnet support structure <NUM> that can be coupled to a shaft for rotation with the shaft. In this embodiment, instead of being an array of individual magnets, the peripheral magnet <NUM> (as the drive magnet or the driven magnet) may be realized as a single (continuous, contiguous, unitary, monolithic, etc.) annular (i.e., ring-shaped or donut-shaped) magnet positioned at a radial distance from the drive axis and coaxially surrounding the balancing magnet <NUM>. Such an annular structure may be magnetized with a plurality of circumferentially arranged magnetic (north-south) dipoles with alternating polarities parallel to the drive axis, as appreciated by persons skilled in the art. In this embodiment, the support structure <NUM> and the peripheral magnet <NUM> may be combined into a single component. Likewise, the balancing magnet <NUM> could be combined into this single component as well.

In an embodiment, the magnet assembly <NUM> or <NUM> is representative of both the drive magnet assembly <NUM> and the driven magnet assembly <NUM> illustrated in <FIG>. That is, the drive magnet assembly <NUM> and the driven magnet assembly <NUM> may have the same configuration, or may be mirror images of each other. In such embodiment, the peripheral magnet(s) <NUM> or <NUM> is/are representative of both the drive magnets <NUM> and the driven magnets <NUM>. Additionally, the balancing magnet <NUM> is representative of both the first balancing magnet <NUM> and the second balancing magnet <NUM>. Alternatively, one of the drive magnet assembly <NUM> or the driven magnet assembly <NUM> may have a multi-magnet configuration such as illustrated in <FIG>, while the other has a single magnet configuration such as illustrated in <FIG>.

The drive magnet assembly <NUM> and the driven magnet assembly <NUM>, particularly the array of drive magnets <NUM> and the array of driven magnets <NUM>, are configured to drive rotation of the driven magnet assembly <NUM> (and thus the driven magnets <NUM>) in response to rotation of the drive magnet assembly <NUM> (and thus the drive magnets <NUM>). An example of such configuration is described above in conjunction with <FIG> and <FIG>. In practice, the axial magnetic coupling assembly <NUM> is installed (coupled) between a prime mover or source or rotational power such as a (for example electric) motor and a load that consumes the rotational power such as a rotor (for example as part of a pumping mechanism). In this case, the drive shaft <NUM> is (or is coupled to) the motor shaft, and the driven shaft <NUM> is (or is coupled to) the rotor. Upon rotation of the drive shaft <NUM> (e.g., as powered by a motor), the drive magnet assembly <NUM> rotates with the drive shaft <NUM>. Due to the contactless magnetic coupling established between the drive magnets <NUM> and the driven magnets <NUM> across the axial gap <NUM>, the rotation of the drive magnet assembly <NUM> drives (or induces) rotation of the driven magnet assembly <NUM>. The rotation of the driven magnet assembly <NUM> thereby rotates the driven shaft <NUM> couple thereto, and consequently drives rotation of a rotor or other load coupled to the driven shaft <NUM>.

The rotation caused by the magnetic coupling is due to a relative angular displacement, d, about the drive axis L of the driven coupling <NUM> relative to the drive coupling <NUM>. This relative angular displacement, d, results in a tangential drive force, Ft, about the drive axis L from the drive coupling's drive magnets <NUM> to the driven coupling's driven magnets <NUM> (as depicted in <FIG>) resulting in a drive torque, T. Consequently, as the drive magnets <NUM> rotate (in the transverse or xy plane) in a certain (clockwise or counterclockwise) direction, the drive magnets <NUM> pull on or drag the driven magnets <NUM> to rotate in the same direction. As this relative angular displacement, d, increases there is an increase in drive torque, T, but only up to a point where the drive torque reaches a maximum value, Tmax, (i.e. "pull-out torque") dictated by the magnetic coupling's design parameters (i.e. diameter, air gap, number of pole pairs, magnetic strength, etc.). If the "pull-out torque" of the magnetic coupling <NUM> is exceeded, the magnetic coupling <NUM> will slip into an asynchronous mode and may require the pump to which the magnetic coupling <NUM> is coupled to be stopped and restarted for proper engagement and synchronous operation of the magnetic coupling <NUM>. Along with the beneficial drive torque, T, there is an axial attractive force, FA, across the axial gap <NUM> between the drive magnets <NUM> and driven magnets <NUM> which decreases as the relative angular displacement, d, increases. For example, <FIG> depicts by arrows <NUM> the axial attractive force between the north poles at the inside faces <NUM> of two drive magnets <NUM> and, respectively, the south poles at the inside faces <NUM> of two corresponding driven magnets <NUM>. Likewise, an axial attractive force in the direction of arrows <NUM> is generated between the south poles at the inside faces <NUM> of other drive magnets <NUM> and the north poles at the inside faces <NUM> of other driven magnets <NUM>. Typically, this undesirable axial attractive force, FA, at full load operation up to the "pull-out torque" is still a relatively large fraction of the maximum axial attractive force, FAmax, (i.e., the axial force when the relative angular displacement, d, is zero). <FIG> shows a relationship between the beneficial drive torque, T, and the undesirable axial force, FA, as experimentally determined by the inventor. As appreciated by persons skilled in the art, the drive torque T and axial attractive force FA can also be calculated theoretically (as a function of the relative angular displacement, d,) from the magnetic B field and an integration of the resulting Maxwell Stress Tensor over a closed surface containing either the drive or driven coupling. The theory shows that there needs to be a helical twisting of the magnetic B field in the air gap about the drive axis L caused by the relative angular displacement, d, in order to generate a drive torque between the drive and driven coupling. The hatched area in <FIG> corresponds to a typical operating range for a scroll vacuum pump. It is evident that the counterbalancing achieved by the present teachings is able to drastically reduce the axial force. The force reduction is to a point where the relevant bearings of the pumping system can react the axial force without a significant loss of life. Bearing life is typically inversely proportional to roughly the cube of the load. Hence, even a reduction in bearing load by a factor of <NUM> (such as shown in <FIG>) may result in an increase in bearing life by a factor of <NUM>.

As noted in the Background section, depending on the physical size and magnetic strength (or flux density) of the drive magnets <NUM> and driven magnets <NUM> in a given axial magnetic coupling assembly <NUM>, the axial attractive forces generated between the drive magnet assembly <NUM> and the driven magnet assembly <NUM> can be large. The system in which the axial magnetic coupling assembly <NUM> operates must be able to support these large axial attractive forces by deploying suitable loadbearing components such as bearings (e.g., axial thrust bearings, roller bearings designed to react axial forces, bushings, etc.). According to an aspect of the present disclosure, the first balancing magnet <NUM> and the second balancing magnet <NUM> are provided to counteract the axial attractive forces by generating an on-axis, counterbalancing axial repulsive force, as depicted by an arrow <NUM> in <FIG>. That is, the first balancing magnet <NUM> and the second balancing magnet <NUM> are configured to generate an axial repulsive force between the first balancing magnet <NUM> and the second balancing magnet <NUM>. The axial repulsive force is effective to counterbalance the axial attractive force(s) existing in and/or developed by the axial magnetic coupling assembly <NUM>. Depending on the embodiment, the axial repulsive force may be large enough to completely balance the axial attractive forces and thereby effectively zero out the net axial force produced by the axial magnetic coupling assembly <NUM> in operation, or to at least partially balance the axial attractive forces and thereby effectively reduce the net axial force produced by the axial magnetic coupling assembly <NUM> in operation. In either case, the counterbalancing axial repulsive force provided by the first balancing magnet <NUM> and the second balancing magnet <NUM> is advantageous because it reduces the axial load required to be borne by the system associated with the axial magnetic coupling assembly <NUM>, thereby avoiding any requirement for costly and/or complex load-bearing components.

Accordingly, in the context of the present disclosure, the term "counterbalance" (or even the term "balance") encompasses providing an offset or opposing force or forces to the axial attractive forces effective to either partially balance (and significantly partially balance if desired) or fully balance the axial attractive forces, and thereby either reduce (and significantly reduce if desired) or eliminate the net axial force produced by the axial magnetic coupling assembly <NUM> in operation. Thus, depending on the embodiment, the counterbalancing axial repulsive force may be less than, equal to, or greater than the axial attractive force(s) being offset or opposed by the first balancing magnet <NUM> and second balancing magnet <NUM>. <FIG> (discussed above) shows a typical reduction in axial load with and without a central balancing magnet as a percentage of the maximum drive torque of the coupling (i.e. "pull-out torque").

As noted above, in the embodiment illustrated in <FIG> and <FIG>, the first balancing magnet <NUM> and the second balancing magnet <NUM> have magnetic dipole configurations, with the magnetic field lines running through the axial thicknesses of the first balancing magnet <NUM> and the second balancing magnet <NUM>. In this case, the first balancing magnet <NUM> and the second balancing magnet <NUM> are oriented such that the polarity of the first balancing magnet <NUM> at its inside face <NUM> is the same as the polarity of the second balancing magnet <NUM> at its inside face <NUM>, thereby generating the axial repulsive force across the axial gap <NUM> between the first balancing magnet <NUM> and the second balancing magnet <NUM>. Thus, in the illustrated example, the respective north poles of the first balancing magnet <NUM> and the second balancing magnet <NUM> face each other across the axial gap <NUM>. As an alternative, the orientation of the first balancing magnet <NUM> and the second balancing magnet <NUM> could be reversed such that their respective south poles faced each other to generate the same or similar axial repulsive force.

<FIG> is a schematic plan view of an example of an array of peripheral magnets <NUM> according to another embodiment. Here, the peripheral magnets <NUM> are wedge-shaped, or shaped as truncated pie slices. In an embodiment, the peripheral magnets <NUM> are representative of both the drive magnets <NUM> and the driven magnets <NUM>. Alternatively, as described above, the magnetic field generated by the array of peripheral magnets <NUM> could be achieved by a single annular (e.g., donut shaped) magnet that is magnetized with a similar number of peripherally spaced alternating north south dipoles.

<FIG> is a schematic plan view of an example of an array of peripheral magnets <NUM> according to another embodiment. This embodiment differs from those illustrated in <FIG> in that the peripheral magnets <NUM> are configured as a Halbach array. Halbach arrays are known to persons skilled in the art, and thus need not be described in detail herein. Briefly, in a Halbach array, the peripheral magnets <NUM> are permanent magnets exhibiting, from one magnet to the next, a spatially rotating pattern of magnetization (or magnetic flux distribution). Thus, in the simplified schematic view of <FIG>, the magnetization (and orientation of the magnetic field) is directed out of the transverse plane (the plane of the drawing sheet) in magnet 420A, as depicted by the dot-in-circle symbol. The magnetization has components directed or tilted in one angular direction (e.g., counterclockwise) in magnet 420B, as depicted by the arrow. The magnetization is directed into the transverse plane in magnet 420C, as depicted by the cross-in-circle symbol. The magnetization has components directed or tilted in the other angular direction (e.g., clockwise) in magnet 420D, as depicted by the arrow. This pattern repeats around the remainder of the array. The pattern results in one side of the array having a significantly strengthened magnetic field (relative to the other side) while the opposite side of the array has a near-zero strength (or nearly canceled) magnetic field. In an embodiment, the peripheral magnets <NUM> may be utilized as both the drive magnets <NUM> and the driven magnets <NUM>, with the strong sides facing each other across the axial gap <NUM>. The Halbach array may be preferable to the more common alternating polarity array shown in <FIG> in certain cases, such as where for a given magnet size the Halbach array provides a stronger magnetic field (and a stronger magnetic field is desired), or where the weaker side of the Halbach array enables a simpler design of the supporting or backing structure of the drive/driven magnet assembly <NUM>/<NUM>.

<FIG> illustrates one non-limiting example of a system-level or apparatus-level implementation of the subject matter disclosed herein. Specifically, <FIG> is a schematic view of an example of a pump (or pumping) assembly <NUM> according to an embodiment. The pump assembly <NUM> includes a (balanced) axial magnetic coupling assembly according to any of the embodiments disclosed herein, such as the axial magnetic coupling assembly <NUM> described above in conjunction with <FIG>.

The pump assembly <NUM> generally may include a suitable motor <NUM> disposed on the drive side of the axial magnetic coupling assembly <NUM>, and a pump head (assembly) <NUM> disposed on the driven side of the axial magnetic coupling assembly <NUM>. As described above, the axial magnetic coupling assembly <NUM> intercouples the motor <NUM> and the pump head <NUM> in a contactless manner. The motor <NUM> is configured to generate rotational power and transfer it to the drive shaft <NUM>, which is or is coupled to a motor shaft of the motor <NUM>. The axial magnetic coupling assembly <NUM> is configured to transfer the rotational power from the drive shaft <NUM> to the driven shaft <NUM>, which is or is coupled to a pump shaft of the pump head <NUM>, via the drive magnet assembly <NUM> and the driven magnet assembly <NUM> as described above. The driven shaft <NUM> rotates or orbits one or more rotatable or orbital components of the pump head <NUM>, which depend on the type or configuration of the pump head <NUM>.

The motor <NUM> generally may be any suitable motor such as an electric motor. Accordingly, the motor <NUM> is connected to a suitable power input <NUM> such as an electrical power input. The pump head <NUM> generally may include one or more pumping stages <NUM> communicating with a pump inlet <NUM> and a pump outlet <NUM>. The pump inlet <NUM> schematically represents one or more fluid conducting components (pipes, passages, chambers, valves, etc.) utilized to supply fluid to the pumping stage <NUM>, i.e., the working fluid to be pumped, which may be a gas or a liquid depending on the embodiment. The pump outlet <NUM> schematically represents one or more fluid conducting components (pipes, passages, chambers, valves, etc.) utilized to conduct outputted fluid away from the pumping stage <NUM>. Generally, the pump inlet <NUM> is associated with the low pressure side of the pumping stage <NUM>, and the pump outlet <NUM> is associated with the high-pressure side of the pumping stage <NUM>. Generally, no limitation is placed on the type or configuration of the pump head <NUM>. The pump head <NUM> may represent a vacuum pump utilized to evacuate (or pump down) a chamber communicating with the pump inlet <NUM>, or a compression pump utilized pressurize and/or transport a fluid at a desired pressure and/or flow rate. For all such purposes, the pumping stage <NUM> generally may include one or more pump rotors <NUM> and one or more pump stators (or housings) <NUM>. The pump rotor <NUM> is coupled to, and therefore rotates or orbits with, the driven shaft <NUM>. The pump rotor <NUM> rotates or orbits relative to the pump stator (or housing) <NUM>, which is a stationary component. Generally, the pump rotor <NUM> and the pump stator (or housing) <NUM> cooperatively define one or more fluid flow paths through which the working fluid is conducted (pumped) through the pumping stage <NUM>, as appreciated by persons skilled in the art. The pump head <NUM> further generally includes a pump housing <NUM>. As appreciated by persons skilled in the art, the pump stator <NUM> and the pump housing <NUM> are often combined or integrated (i.e., as a single structure or component) to perform both the functions of a stator and a housing instead of being two or more separate components.

The type or configuration of the pump rotor <NUM> (and corresponding pump stator <NUM>) depends on the embodiment. Examples of pump rotors <NUM> include, but are not limited to, an orbiting scroll, a rotary vane component, a crank, a cam, a gear, a screw, a Roots rotor (e.g., lobe), and a claw, all of which are generally understood by persons skilled in the art. Accordingly, examples of the pumping stage <NUM> include, but are not limited to, a scroll pumping stage, a rotary vane pumping stage, a gear pumping stage, a screw compressor stage, a Roots pumping stage, and a claw pumping stage, again all of which are generally understood by persons skilled in the art.

The pump assembly <NUM> generally may have any type and number of bearings <NUM> on the drive side and bearings <NUM> on the driven side of the axial magnetic coupling assembly <NUM>, as appreciated by persons skilled in the art. At least some of these bearings <NUM> and <NUM> are configured (e.g., designed and positioned) to bear the axial forces generated during operation of the pump assembly <NUM>. As described herein, the axial magnetic coupling assembly <NUM> balances the additional axial forces it generates. Therefore, the use of the axial magnetic coupling assembly <NUM> may allow for the same bearings <NUM> and <NUM> to be utilized in the pump assembly <NUM> (as would be utilized in a case where a more conventional mechanical coupling is provided between the motor <NUM> and the pump head <NUM>). In other words, the pump assembly <NUM> may not require larger, special or nonstandard designed, or additional bearings to accommodate the use of the axial magnetic coupling assembly <NUM>. The pump housing <NUM> may be configured in a manner appreciated by persons skilled in the art. The pump housing <NUM> may represent one or more components (e.g., cover, cowling, wall, etc.) that enclose the pumping stage <NUM>, at least portions of the pump inlet <NUM> and pump outlet <NUM>, pump-side bearings <NUM>, and other internal components of the pump head <NUM>. The pump housing <NUM> may include a frame that supports the pumping stage <NUM>. As noted above, all or a portion of the pump stator <NUM> may be integral with, or attached to or supported by, the frame or other part of the pump housing <NUM>. The pump housing <NUM> may further define one or more fluid passages of the pump inlet <NUM> and/or pump outlet <NUM>. The pump housing <NUM> may also enclose and/or define a pump cooling system, such as a fan and associated air passages.

The contactless configuration of the axial magnetic coupling assembly <NUM> allows a structural boundary <NUM>, such as a wall, plate, or the like, to be positioned in the axial gap <NUM> between the drive magnet assembly <NUM> and the driven magnet assembly <NUM>. Preferably, to avoid eddy current losses (which may be significant), the structural boundary <NUM> is composed of an electrically insulating (non-electrically conductive) material. Examples of suitable electrically insulating materials for the structural boundary <NUM> include various organic polymers (plastics) and ceramics (e.g. glass). In an embodiment, the structural boundary <NUM> is composed of a liquid-crystal polymer (LCP) or an LCP-containing composite (for example, a combination of an LCP and a filler such as glass fiber). As appreciated by persons skilled in the art, LCPs are a class of aromatic polymers (e.g., aramids) processed to form a liquid crystalline phase. A structural boundary <NUM> constructed of an LCP is found to be advantageous for applications of the axial magnetic coupling assembly <NUM>. The LCP material does not conduct electrical current and therefore avoids eddy current losses. The LCP material also exhibits high structural strength (high modulus) and therefore can withstand significant pressure differentials as may be encountered in a pumping application. Additionally, the LCP material exhibits a very low gas permeation rate compared to other polymers.

The role of the structural boundary <NUM> in conjunction with the axial magnetic coupling assembly <NUM> depends on the embodiment. In the embodiment illustrated in <FIG>, the pump assembly <NUM> includes a casing <NUM> that encloses the driven side (e.g., driven magnet assembly <NUM>) of the axial magnetic coupling assembly <NUM>. The casing <NUM> may be integral with or attached to pump housing <NUM>. The casing <NUM> may be, or be part of, a hermetic barrier of the pump head <NUM> configured to fluidly isolate all or part of the pump head <NUM> from the ambient (environment outside of the pump head <NUM>). The structural boundary <NUM> described above may be, or be part of, the casing <NUM>.

<FIG> is an exploded perspective view of an example of a (balanced) axial magnetic coupling assembly <NUM> according to another embodiment of the present disclosure. <FIG> is another exploded perspective view of the axial magnetic coupling assembly <NUM>.

<FIG> is a view from the load side (e.g., pump side) and <FIG> is a view from the motor side of the axial magnetic coupling assembly <NUM>. The axial magnetic coupling assembly <NUM> in assembled form is best shown in <FIG>.

The axial magnetic coupling assembly <NUM> generally includes a drive magnet assembly <NUM> configured to be coupled to a drive shaft (not shown), and a driven magnet assembly <NUM> configured to be coupled to a driven shaft (not shown). When assembled, the drive magnet assembly <NUM> and the driven magnet assembly <NUM> are separated by an axial gap as described herein. The axial magnetic coupling assembly <NUM> further includes a structural boundary <NUM> interposed in the axial gap between the drive magnet assembly <NUM> and the driven magnet assembly <NUM>. The structural boundary <NUM> is composed of an electrically insulating material as described herein. In the present embodiment, the structural boundary <NUM> is provided in the form of a plate, disk, dish, or cap.

As in other embodiments, the drive magnet assembly <NUM> includes a first (drive-side) balancing magnet <NUM> (<FIG>) positioned on the drive axis and a plurality of peripheral drive magnets <NUM> coaxially surrounding the first balancing magnet <NUM>. Similarly, the driven magnet assembly <NUM> includes a second (driven-side) balancing magnet <NUM> and a plurality of peripheral driven magnets <NUM> coaxially surrounding the second balancing magnet <NUM>. The first balancing magnet <NUM> and second balancing magnet <NUM> face each other, and the drive magnets <NUM> and driven magnets <NUM> face each other, across the axial gap as described herein. The first balancing magnet <NUM>, second balancing magnet <NUM>, drive magnets <NUM>, and driven magnets <NUM> may be configured according to any of the embodiments disclosed herein, such as any of those illustrated in <FIG>.

The drive magnet assembly <NUM> includes a drive magnet support structure <NUM>. In the present embodiment, the drive magnet support structure <NUM> includes an annular drive (or first) magnet holder or retainer <NUM> and an annular drive-side (or first) hub <NUM>. The drive magnet holder <NUM> is configured to hold (retain, fix, etc.) the drive magnets <NUM> in their arrayed position and support their rotation about the drive axis. For this purpose, in the present embodiment, the drive magnet holder <NUM> includes a plurality of drive magnet receptacles <NUM> in which the drive magnets <NUM> are respectively mounted. The drive magnet holder <NUM> also has a central bore <NUM> to accommodate the first balancing magnet <NUM>. The drive-side hub <NUM> is configured to securely couple the drive magnet holder <NUM> with the drive magnets <NUM> to the drive shaft. For this purpose, the drive-side hub <NUM> has a central bore <NUM> through which the drive shaft passes. By way of illustrated example, the central bore <NUM> of the drive-side hub <NUM> includes a keyway <NUM> configured to engage a key on the drive shaft. The drive-side hub <NUM> may further include a central recess <NUM> for receiving the first balancing magnet <NUM>.

Similarly, the driven magnet assembly <NUM> includes a driven magnet support structure <NUM>. In the present embodiment, the driven magnet support structure <NUM> includes a driven (or second) magnet holder or retainer <NUM> and a driven-side (or second) hub <NUM> (<FIG> and <FIG>). The driven magnet holder <NUM> is configured to hold (retain, fix, etc.) the driven magnets <NUM> in their arrayed position and support their rotation about the drive axis. For this purpose, in the present embodiment, the driven magnet holder <NUM> includes a plurality of driven magnet receptacles <NUM> in which the driven magnets <NUM> are respectively mounted. The driven magnet holder <NUM> also has a central bore <NUM> to accommodate the second balancing magnet <NUM>. The driven-side hub <NUM> is configured to securely couple the driven magnet holder <NUM> with the driven magnets <NUM> to the driven shaft, as best shown in <FIG>. The driven-side hub <NUM> may further include a central recess (see <FIG> and <FIG>) for receiving the second balancing magnet <NUM>.

The respective sets of components of the drive magnet assembly <NUM> and the driven magnet assembly <NUM> may be secured together by any suitable means such as, for example bolts and corresponding threaded holes that clamp the components together in the axial direction(s). If desired, additional means may be taken to secure the various magnets in their respective receptacles or recesses, such as press-fitting, adhesive, etc. In a further embodiment and as illustrated, the structural boundary <NUM> may include central recesses at its drive side and driven to at least partially accommodate the first balancing magnet <NUM> and the second balancing magnet <NUM>, respectively.

<FIG> is a schematic view of an example of a vacuum scroll pump (or pumping) assembly <NUM> according to another embodiment, as another non-limiting example of a system-level or apparatus-level implementation of the subject matter disclosed herein. The pump assembly <NUM> includes a (balanced) axial magnetic coupling assembly according to any of the embodiments disclosed herein. In the illustrated example, the pump assembly <NUM> includes the axial magnetic coupling assembly <NUM> described above in conjunction with <FIG> and <FIG>. <FIG> is a closeup view of the axial magnetic coupling assembly <NUM> and surrounding portions of the pump assembly <NUM>. The structure and operation of vacuum scroll pumps are generally understood by persons skilled in the art, and thus the pump assembly <NUM> and certain components thereof are descried only briefly herein to provide a context for the presently disclosed subject matter.

The pump assembly <NUM> generally includes a motor <NUM> disposed on the drive side of the axial magnetic coupling assembly <NUM>, and a pump head (assembly) <NUM> disposed on the driven side of the axial magnetic coupling assembly <NUM>. As described above, the axial magnetic coupling assembly <NUM> intercouples the motor <NUM> and the pump head <NUM> in a contactless manner via a drive shaft <NUM> and a driven shaft <NUM>, respectively.

The pump head <NUM> generally may include one or more pumping stages communicating with a pump inlet <NUM> and a pump outlet <NUM>. In the present embodiment, the pump head <NUM> includes a first (or upstream) pumping stage 718A fluidly communicating in series (with respect to the fluid flow path) with a second (or downstream) pumping stage 718B. The first pumping stage 718A receives the (lower-pressure) working fluid from the pump inlet <NUM>, compresses the fluid, and outputs the compressed fluid to the second pumping stage 718B. The second (or downstream) pumping stage 718B further compresses the fluid, and discharges the (now even higher-pressure) fluid to the pump outlet <NUM>. In this example, the multi-stage compression mechanism of the pump head <NUM> is defined by a pump rotor <NUM> in the form of an orbiting plate scroll, a first pump stator 736A in the form of a first stationary plate scroll, and a second pump stator 736B in the form of a second stationary plate scroll. The pump rotor <NUM> (orbiting plate scroll) is interposed between, and orbits relative to, the first pump stator 736A (first stationary plate scroll) and the second pump stator 736B (second stationary plate scroll). The pump rotor <NUM> (on one axial side thereof) and the first pump stator 736A cooperatively define the first pumping stage 718A, and the pump rotor <NUM> (on the opposite axial side thereof) and the second pump stator 736B cooperatively define the second pumping stage 718B.

The pump rotor <NUM> includes an orbiting plate <NUM> that orbits in the transverse plane (the plane orthogonal to the drive axis of the axial magnetic coupling assembly <NUM>, as described above). The pump rotor <NUM> further includes a first orbiting scroll blade 766A that extends (or projects) axially from the orbiting plate <NUM> toward the first pump stator 736A, and a second orbiting scroll blade 766B that extends (or projects) axially in the opposite direction from the orbiting plate <NUM> toward the second pump stator 736B. The first pump stator 736A includes a first stationary plate 770A, and a first stationary scroll blade 774A that extends (or projects) axially from the first stationary plate 770A toward the pump rotor <NUM>. The second pump stator 736B includes a second stationary plate 770B, and a second stationary scroll blade 774B that extends (or projects) axially in the opposite direction from the second stationary plate 770B toward the pump rotor <NUM>.

The first orbiting scroll blade 766A, second orbiting scroll blade 766B, first stationary scroll blade 774A, and second stationary scroll blade 774B are shaped as spirals (i.e., run along a spiral path) in the transverse plane, as appreciated by persons skilled in the art. The cross-sectional view of <FIG> shows the several turns or wraps of the spiral-shaped blades. As illustrated, the first orbiting scroll blade 766A is juxtaposed with the first stationary scroll blade 774A in the radial direction (relative to the longitudinal axis of the pump assembly <NUM>), such that the first orbiting scroll blade 766A and the first stationary scroll blade 774A are nested together with a clearance and a predetermined relative angular positioning. By this configuration, one or more pockets are defined in the first pumping stage 718A by (and between) the nested first orbiting scroll blade 766A and first stationary scroll blade 774A. Likewise, the second orbiting scroll blade 766B is juxtaposed with the second stationary scroll blade 774B in the radial direction, such that the second orbiting scroll blade 766B and the second stationary scroll blade 774B are nested together with a clearance and a predetermined relative angular positioning. By this configuration, one or more pockets are defined in the second pumping stage 718B by (and between) the nested second orbiting scroll blade 766B and second stationary scroll blade 774B.

In the present embodiment, the driven shaft <NUM> is a crank shaft that is part of an eccentric drive mechanism. The main portion of the driven shaft <NUM> rotates on the drive axis as described above, and is attached to the driven-side (or second) hub <NUM> of the axial magnetic coupling assembly <NUM>. At the end axially opposite to the axial magnetic coupling assembly <NUM>, the driven shaft <NUM> includes (is integral with or coupled to) an eccentric member or crank <NUM>. The crank <NUM> is coupled to the pump rotor <NUM>. Various bearings <NUM> support the rotation of the driven shaft <NUM>, the coupling of the crank <NUM> with the pump rotor <NUM>, and the axial loads associated with the operation of the pump head <NUM>. As in other embodiments, the use of the axial magnetic coupling assembly <NUM> allows for the bearings <NUM> to be the same type of standard bearings that would be utilized in a case where a more conventional mechanical coupling is provided between the motor <NUM> and the pump head <NUM>.

As illustrated, the central longitudinal axis of the crank <NUM> is radially offset from the central longitudinal axis of (the main portion of) the driven shaft <NUM> (which is coincident with the drive axis of the axial magnetic coupling assembly <NUM>). Consequently, rotation of the driven shaft <NUM> causes the crank <NUM>, and in turn the pump rotor <NUM>, to orbit (rotate in an orbiting manner) around the drive axis. Accordingly, rotation of the driven shaft <NUM> causes the first orbiting scroll blade 766A to orbit relative to the first stationary scroll blade 774A, and the second orbiting scroll blade 766B to orbit relative to the second stationary scroll blade 774B. These motions cause the pockets between the nested pairs of blades to vary in volume and to move within the first pumping stage 718A and second pumping stage 718B in a manner whereby the pockets are selectively placed in open communication with the pump inlet <NUM> (or preceding pumping stage) and the pump outlet <NUM> (or succeeding pumping stage). As a result, the working fluid is conducted from the pump inlet <NUM>, through the first pumping stage 718A, through the second pumping stage 718B, and to the pump outlet <NUM>, and is compressed in each of the first pumping stage 718A and second pumping stage 718B.

The pump assembly <NUM> further includes a casing <NUM> that encloses the driven side of the axial magnetic coupling assembly <NUM>. The casing <NUM> may be attached (in a fluid-sealed manner, if desired) to a stationary part of the pump head <NUM>, such as a frame, the back of the second pump stator 736B, etc. The above-described structural boundary <NUM> positioned in the axial gap of the axial magnetic coupling assembly <NUM> may be an integral part of, or attached to, the casing <NUM>. The casing <NUM> and structural boundary <NUM> may be, or be part of, a hermetic barrier of the pump head <NUM>.

It will be understood that the multi-stage scroll pump configuration described above and illustrated in <FIG> and <FIG> is but one example of a scroll pump in which the presently disclosed subject matter may be implemented. In another embodiment, the pump assembly <NUM> may include a single scroll pump stage, i.e., a single nested pair of an orbiting scroll blade and a stationary scroll blade. Scroll pumps are further described in, for example, <CIT> and <CIT>.

The structural boundary <NUM> or <NUM> described above is useful in any configuration of the magnetic coupling. Accordingly, in addition to axial magnetic couplings, other embodiments of the present disclosure encompass any magnetic couplings incorporating the structural boundary <NUM> or <NUM>, including radial magnetic couplings as described herein.

It will be understood that terms such as "communicate with" and "in. communication with" (for example, a first component "communicates with" or "is in communication with" a second component), as well as "coupled to" or "coupled with," are used herein to indicate a structural, functional, mechanical, electrical, signal, optical, magnetic, electromagnetic, ionic or fluidic relationship between two or more components or elements. As such, the fact that one component is said to communicate with or be coupled to/with a second component is not intended to exclude the possibility that additional components may be present between, and/or operatively associated or engaged with, the first and second components.

Claim 1:
Magnetic coupling assembly (<NUM>), comprising:
a drive shaft (<NUM>) rotatable on a drive axis;
a driven shaft (<NUM>) rotatable on the drive axis;
a drive magnet assembly (<NUM>) coupled to the drive shaft and rotatable therewith, the drive magnet assembly comprising a first balancing magnet (<NUM>) positioned on the drive axis, and a drive magnet (<NUM>) coaxially positioned with the first balancing magnet; and
a driven magnet assembly (<NUM>) coupled to the driven shaft and rotatable therewith, the driven magnet assembly comprising a second balancing magnet (<NUM>) disposed on the drive axis, and a driven magnet (<NUM>) coaxially positioned with the second balancing magnet, wherein:
the drive magnet assembly (<NUM>) is spaced from the driven magnet assembly (<NUM>) by an axial gap (<NUM>), with the first balancing magnet (<NUM>) facing the second balancing magnet (<NUM>) across the axial gap (<NUM>), and the drive magnet (<NUM>) facing the driven magnet (<NUM>) across the axial gap (<NUM>);
the drive magnet (<NUM>) and the driven magnet (<NUM>) are configured to drive rotation of the driven magnet (<NUM>) in response to rotation of the drive magnet (<NUM>), and to generate a tangential drive force and an axial attractive force between the drive magnet (<NUM>) and the driven magnet (<NUM>); and
the first balancing magnet (<NUM>) and the second balancing magnet (<NUM>) are configured to generate an axial repulsive force between the first balancing magnet (<NUM>) and the second balancing magnet (<NUM>) that counterbalances the axial attractive force,
wherein the magnetic coupling assembly (<NUM>) further comprises a structural boundary (<NUM>) disposed in the axial gap (<NUM>) between the drive magnet assembly (<NUM>) and the driven magnet assembly (<NUM>), characterized in that the structural boundary (<NUM>) is composed of an electrically insulating material.