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Bearingless blood pump and electronic drive system
| Details |
Inventors: Hart, Robert M.;
Assignee: Abiomed, Inc. (); Danvers, Inc. ()
Primary Examiner: Thorpe; Timothy S.
Assistant Examiner: Gartenberg; Ehud
Attorney, Agent or Firm: Engellenner; Thomas J., Lane, Jr.; David A.
A magnetically operated blood pump includes a rotor with an impeller that rotates within a housing, and the housing fastens to a driver that preferably electromagnetically controls the speed and disposition of the impeller in response to sensed conditions. The impeller and housing constitute a disposable assembly in which permanent magnets embedded in the impeller stabilize its position to maintain pumping tolerances in at least one dimension, and also couple to external fields to rotate the impeller. In one embodiment concentric arrangements of cylinder magnets passively maintain radial centering, while coils in the driver are actuated to simultaneously produce a rotational torque and to correct axial or tilt displacements. In a preferred embodiment of this type, sensors around the periphery detect axial displacement and/or tilt as the impeller turns, while the drive circuit responds to the sensor signal to produce compensating phase changes in the coil drive signals. The drive coils are disposed in a common plane and are symmetrically spaced about the central axis, and the phase changes in their drive signals result in a compensating axial force, which may be different in each of the coils to correct tilt. In another or further embodiment, the rotor is freely suspended such that blood washes over one or more surfaces of the rotor, and fluid pressure produces a net restoring force on the rotor to counteract changes in tilt or axial position within the housing. In this case, the driver need only drive rotation of the pump. The drive unit works with a variety of multipole impeller pumps, including ones with magnetic segmented rotors and conventional mechanical support bearings such as ones with a jewel or shaft bearing element. In other embodiments, plural sets of magnets provide passive constraint of radial disturbances and two tilt movements, while axial disturbances are corrected either passively by hydrodynamic surfaces or actively with the driver. The driver unit may include a hand crank assembly, enabling continued operation during power outages. |
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DETAILED DESCRIPTION The invention addresses these needs by providing a blood pumping and pump drive system wherein a housing defines inlet and outlet ports, and a rotor is suspended in the housing and stabilized to maintain gaps entirely around the rotor and thus prevent damage to pumped blood as the rotor turns.
A first set of permanent magnets carried partly in the rotor and partly in the housing passively maintain radial centricity about a central axis, and the rotor is driven by a magnetic coupling to rotate about the axis.
Other degrees of freedom are controlled to stably suspend the rotor without mechanical bearings.
In one embodiment a second set of magnets are adaptively driven by a set of coils to rotate the rotor and also maintain axial height alignment, and may correct wandering or motion in other degrees of freedom.
The coils are carried in a separate drive unit which fastens to the housing and interacts with the second set of magnets to produce both axial force and, independently, rotational torque.
In a preferred embodiment, a controller drive unit varies the axial force within a continuous range centered at a neutral position-maintaining force by shifting the phase of signals applied to the drive coils, while pump rotation speed is controlled by changes in frequency of a drive signal.
In another aspect of the invention, the rotor body is a cap-shaped body which rotates within a closely fitting housing, and a blood inlet provides blood to the center of the cap so that rotation of the rotor carries the blood over a pumping surface and imparts centrifugal energy to the blood.
The rotor is suspended in space, out of contact with the housing, and is positioned in the blood flow path such that blood contacts and flows along both sides of the rotor.
A gap defined between the rotor and housing is shaped so that the pressure differential between center and periphery of the rotor permits a counter-flow of blood over the non-pumping surface of the rotor, and results in a pressure distribution which varies as the rotor is shifted or displaced
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