Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
1997-07-01
2001-03-27
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Electric or magnetic motor
C417S356000, C417S423140, C415S900000, C416S18600A
Reexamination Certificate
active
06206659
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an improved rotor structure for implementation as a pump for transferring fragile or aggressive fluids. Examples of fragile fluids include human or animal blood, neither of which can tolerate exposure to unusual impact and/or sheer forces. Aggressive fluids include corrosive or poisonous fluids, as well as fluids which cannot tolerate contamination, or which otherwise may destroy seals and/or bearings to reduce the lifetime and/or longevity of the pump structure. Poisonous fluids, for example, are extremely dangerous if a leak develops. More particularly, the present invention relates to a rotor for a pump which is bearing and seal-free and wherein the rotor has a core body with one or more shrouds coupled to the outer surface of the core and arranged in parallelly disposed relationship with the outer surface of the core. In addition, the rotor is dynamically balanced by a combination of hydrodynamic and buoyant forces. In this configuration, the design of the rotor provides a plurality of parallelly arranged flow channels through which a fluid contacting area is provided for enhancing flow. In the other configuration, the vanes are presented between the core and the shroud, or between the shrouds for enhancing flow. In the configuration utilizing multiple shrouds, a primary flow channel will be created between the shroud and the core, with a secondary flow channel being arranged outside of the shroud. The primary channel provides meridional channels, while the secondary flow channel provides communication for flow between the inlet and the outlet.
The pump of the present invention is particularly adapted for transferring human blood and is capable of creating a flow of such liquids without damaging and/or otherwise adversely affecting the quality of the material being pumped. The rotor employed in the pump of the present invention including its multiple flow channels is rotated electromagnetically by means of an electromagnetic drive system operating in conjunction with one or more arrays of permanent magnets disposed on the rotor in a brushless motor configuration. Alternatively, a permanent magnet-to-permanent magnet coupling may be employed. As such, the arrangement of the present invention is capable of achieving relative rotation while at the same time being bearing and seal-free.
In the past, pumps and pumping systems have been designed which have been characterized as being bearing and seal-free. Such systems typically employ magnetic levitation means which is in effect an actual form of bearing, much the same as sleeve bearings, ball bearings, or other friction-inducing bearings. Such arrangements using magnetic bearings, while being operational and functional, may be rendered complex and accordingly require significant number of additional components including magnetic devices, position sensors, and rapid-response magnetic drive means. A number of such patents have been granted in the past, including those to Olsen et al. U.S. Pat. Nos. 4,688,998 and 5,195,877. The apparatus of the present invention, by contrast, is fully bearing and seal-free, with dynamic balance being achieved through a combination of hydrodynamic and buoyant forces.
Among the disadvantages inherent in pumps utilizing friction-reducing bearings include local heat generation such as may occur from the use of ball bearings, friction bearings, sleeve bearings, and the like. Low flow and high pressure may result in local areas due to the use of such structures. In addition, with all such bearing-equipped pumps, a high spring constant is provided wherein a small displacement of the rotor (or impeller) introduces very high forces which can damage or effectively destroy bearings. In addition, different forces are introduced in the structure whenever variations in axial positions occur.
In the present structure, the pump is bearing and seal-free, with the effective low compliance of the rotor allowing for relatively high displacement without the creation of large forces otherwise required to hold the rotor in its predetermined position. In addition, the rotor seeks and finds an equilibrium position which in certain situations can be off-set from the housing axis (in either the rotational or transverse axes) which typically occurs when the rotational axis of the pump is altered. Rotational movement of the pump housing will be manifested in displacement of the rotational or vertical axis of the rotor. The present arrangement has been found to eliminate the need for a highly precise axis in design, fabrication and operation. The lack of a positionally fixed rotational axis reduces the introduction of large forces which otherwise would be created when the axis of the rotor is shifted away from its normal centrally disposed position. In addition to the outer surface of the rotor core, one or more shrouds are arranged concentrically with the outer surface of the rotor core, with the configuration providing one or more annular channels for flow. In addition to this, introduction of the vanes acting as paddles between the core and the shroud or in the case of multiple shrouds, then between the shrouds, with this arrangement providing even more channels for flow through the rotor.
In the arrangement of the present invention, the pump includes a pumping chamber with a central axis, and with a rotor body being disposed within the chamber for bearing and seal-free rotation therewithin. The rotor has a double or dual-conical configuration which converges toward opposed polar regions, and with the axis of rotation extending between these polar regions. In addition to the rotor core, one or more concentric shrouds are provided to increase the area of contact between the fluid being pumped and the surface of the rotor, and to provide annular channels through which fluid flow may occur. Fluid inlet ports are arranged in the pumping chamber in oppositely disposed relationship within the chamber, with the fluid being transported or transferred to the inlet port area either externally or internally of the chamber. Except for those occasions when the rotor is displaced, it is normally arranged in coaxial relationship with both the pumping chamber and the fluid inlet ports. The outlet port or ports are arranged generally medially of the chamber, midway between the inlet ports and typically are positioned tangentially of the medial portion of the pumping chamber. In those situations where the axis of rotation of the rotor is arranged vertically, the dual-conical configuration is such that flow on the outside surface of the rotor core and in the annular channels proceeds downwardly on the upper portion, and upwardly on the lower portion of the dual-cone.
An example of an external transfer of fluids between the oppositely disposed fluid inlet ports is a fluid transfer line which introduces the fluids at opposite ends of the housing. As an example of an internal transfer, an internal bore may be provided which extends along the rotational axis of the rotor between opposite ends thereof, so as to permit transfer of fluids internally.
The term “oppositely disposed inlet ports” is intended to reflect the utilization of fluid introduction at opposite ends of the rotor, and is intended to include those arrangements wherein all of the fluid being pumped is initially introduced into one polar region of the housing, the fluid nevertheless is transferred either internally or externally to the oppositely disposed polar region.
The pump shown in the drawings is in operational mode with the rotor spinning about its axis of rotation and with all forces acting on the rotor balanced. In the stationary
on-operational mode with the fluid in the housing, only the buoyant forces are acting on the rotor, and the rotor floats up in the random position. In the stationary
on-operational mode with no fluid in the housing, the rotor is resting on the interior of the housing under gravitational forces.
Levitation of the rotor, as indicated, is achieved by a combination of hydrodynami
Advanced Bionics, Inc.
Freay Charles G.
Haugen Law Firm PLLP
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