Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1998-12-03
2001-07-24
Yasko, John D. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S131000, C417S423100, C417S423700
Reexamination Certificate
active
06264635
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns blood pumps. More specifically, the invention pertains to continuous flow pumps of rotary design, which may be suitable for installation in humans, for use as chronic ventricular assist devices.
BACKGROUND OF THE INVENTION
In Wampler U.S. Pat. No. 5,695,471, a continuous flow pump of rotary design is disclosed, suitable for permanent implantation in humans, for use as a chronic ventricular assist device. The disclosed device uses passive, magnetic radial bearings to maintain an impeller and its support shaft for rotation about an axis, thus eliminating the necessity for a drive shaft seal.
Typically prior art blood pumps use mechanical bearings to support the rotor with respect to the stator. The use of hydrodynamic thrust bearings has been disclosed for aiding in preventing thrombosis. However, blood cell damage and various other problems may be created by the use of hydrodynamic thrust bearings and mechanical bearings and it is desirable for a blood pump to use a magnetically suspended rotor if possible. However, a problem associated with magnetically suspending the rotor is that movement of the pump may result in movement of the rotor in the axial direction, causing the rotor or the impeller to contact a part of the pump casing. It is highly undesirable in a blood pump construction to have any continuing contact between the impeller and a part of the blood pump casing.
In Wampler U.S. Pat. No. 5,695,471, there is disclosed the shuttling back and forth of the rotor assembly with each cardiac cycle of the user, in order to prevent thrombosis. If this axial shuttling would not happen naturally, it would be desirable to have a system in which it could be induced electromagnetically.
In Wampler U.S. application Ser. No. 08/910,375, filed Aug. 13, 1997, now U.S. Pat. No. 5,840,070, the use of hydrodynamic bearings in an implantable blood pump is disclosed. With the hydrodynamic bearings, there is a frictional engagement which has to be overcome before the hydrodynamic bearings can be fully effective. The frictional engagement is a result of a preload that is applied by the front loading of the magnetic bearing. Thus an initial starting force is required that will enable the initial frictional engagement to be overcome. This initial starting force can create difficulties, and it would be advantageous to avoid its necessity.
Due to the preload of the negative axial spring rate of the passive radial magnetic bearings of the rotor, there is an axial magnetic force urging the impeller rearward against the casing. In view of the foregoing, it would be advantageous to be able to manipulate the axial force on the impeller during the starting of the pump.
There have been attempts to alleviate the starting axial force problem by having suspended systems using electromagnets. Typically in such systems, a dedicated electromagnetic control system is used to control the position of the impeller. There would be separate dedicated electronic controls and electromagnets for controlling the position of the rotor and the impeller. However, these separate dedicated electronic controls and electromagnets add to the weight, volume and complexity of the system.
It is, therefore, an object of the present invention to provide a rotary blood pump in which the rotor is magnetically suspended.
Another object of the present invention is to provide a rotary blood pump in which contact between the impeller and the blood pump housing is avoided.
A still further object of the present invention is to provide a novel rotary blood pump in which the axial forces on the impeller may be controlled.
An additional object of the present invention is to provide a novel rotary blood pump in which the axial position of the impeller may be controlled in an efficient manner.
Another object of the present invention is to provide a novel rotary blood pump that is small, light, simple in construction, and relatively easy to manufacture.
Other objects and advantages of the present invention will become apparent as the description proceeds.
SUMMARY OF THE INVENTION
In accordance with the present invention, a rotary blood pump is provided. The pump comprises a pump housing and a rotor mounted for rotation within the housing. The rotor has a shaft portion and an impeller carried by the shaft portion. A rotor motor is provided. The motor includes a plurality of permanent magnets carried by the impeller and a motor stator including electrically conductive coils and pole pieces located within the housing. The motor is operable to transmit torque and also to provide an axial magnetic force that acts as an axial bearing.
In the illustrative embodiment, the rotary blood pump includes passive radial magnetic bearings carried by the shaft portion and radial magnetic bearings carried by the housing. A sensor is provided for detecting axial deflection of the impeller and a circuit is provided for energizing the stator in response to the detector.
In the illustrative embodiment, there is a first motor stator positioned on one side of the impeller and a second motor stator positioned on an opposite side of the impeller. The motor stators each include electrically conductive coils and pole pieces located within the housing. A detector senses the axial position of the impeller. If the axial position is neutral, then current to the stators is not varied. However, if the axial position is other than neutral the relative currents to the first and second stators are varied to provide an axial force to return the impeller to neutral.
A more detailed explanation of the invention is provided in the following description and claims, and is illustrated in the accompanying drawings.
REFERENCES:
patent: 3572982 (1971-03-01), Kozdonsohn
patent: 4876492 (1989-10-01), Lester et al.
patent: 4880362 (1989-11-01), Laing et al.
patent: 5049134 (1991-09-01), Golding et al.
patent: 5197865 (1993-03-01), Sevrain et al.
patent: 5350283 (1994-09-01), Nakazeki et al.
patent: 5591017 (1997-01-01), Dwyer
patent: 5692882 (1997-12-01), Bozeman, Jr. et al.
patent: 5695471 (1997-12-01), Wampler
patent: 5725357 (1998-03-01), Nakazeki et al.
patent: 5728154 (1998-03-01), Crossett et al.
patent: 5738503 (1998-04-01), Schmidt-Marloh et al.
patent: 5840070 (1998-11-01), Wampler et al.
patent: 41 02 707 (1991-08-01), None
patent: WO8807842 (1988-10-01), None
patent: WO 98 11650 (1998-03-01), None
C. Peter Cho et al.; Eddy Current Loss Calculation in the Permanent Magnet of a Large Horse Power Axial-Field Motor; Jun. 14, 1994; Proceedings, Twenty-third Annual Symposium, Incremental Motion Control Systems & Devices, pp. 245-253.
C. Peter Cho et al.; Cogging Torque Reduction, Axial Force Variation, and Output Torque Effect of a High-Power-Density, Axial Field, Brushless, Permanent Magnet Motor; Jun. 6, 1995; Proceedings, Twenty-fourth Annual Symposium, Incremental Motion Control Systems & Devices, pp. 297-307.
C. Peter Cho et al.; Feasibiltiy Study of a Novel Integrated Electric Motor/Pump for Underwater Applications; Jun. 6, 1995; Proceedings, Twenty-sixth Annual Symposium, Incremental Motion Control Systems & Devices, pp. 309-316.
C. Peter Cho et al.; Ongoing Feasibility Study of a Novel Integrated Electric Motor/Pump Concept; Jun. 11, 1996; Proceedings, Twenty-fifth Annual Symposium, Incremental Motion Control Systems & Devices, pp. 51-62.
C. Peter Cho et al.; Energy Losses in Magnetic Lamination Materials of a Novel Integrated Motor/Pump System; Jul. 22, 1997; Proceedings, Twenty-sixth Annaul Symposium, Incremental Motion Control Systems & Devices, pp. 325-333.
Lancisi David M.
Wampler Richard K.
Gerstman George H.
Kriton Medical, Inc.
Shaw Seyfarth
Yasko John D.
LandOfFree
Active magnetic bearing system for blood pump does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Active magnetic bearing system for blood pump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Active magnetic bearing system for blood pump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2459764