Alternating pump gaps

Information

  • Patent Grant
  • 11015605
  • Patent Number
    11,015,605
  • Date Filed
    Monday, June 17, 2019
    5 years ago
  • Date Issued
    Tuesday, May 25, 2021
    3 years ago
Abstract
A blood pump system includes a pump housing and an impeller for rotating in a pump chamber within the housing. The impeller has a first side and a second side opposite the first side. The system includes a stator having drive coils for applying a torque to the impeller and at least one bearing mechanism for suspending the impeller within the pump chamber. The system includes a position control mechanism for moving the impeller in an axial direction within the pump chamber to adjust a size of a first gap and a size of a second gap, thereby controlling a washout rate at each of the first gap and the second gap. The first gap is defined by a distance between the first side and the housing and the second gap is defined by a distance between the second side and the pump housing.
Description
BACKGROUND OF THE INVENTION

The present invention relates in general to pumping devices, and more specifically, to improved blood pumps with levitated impellers and methods for their control.


Mechanical circulatory support (MCS) devices are commonly used for treating patients with heart failure. One exemplary type of MCS device is a centrifugal flow blood pump. Many types of circulatory support devices are available for either short term or long term support for patients having cardiovascular disease. For example, a heart pump system known as a left ventricular assist device (LVAD) can provide long term patient support with an implantable pump associated with an externally-worn pump control unit and batteries. The LVAD improves circulation throughout the body by assisting the left side of the heart in pumping blood. Examples of LVAD systems are the DuraHeart® LVAS system made by Terumo Heart, Inc. of Ann Arbor, Mich. and the HeartMate II™ and HeartMate III™ systems made by Thoratec Corporation of Pleasanton, Calif. These systems typically employ a centrifugal pump with a magnetically levitated impeller to pump blood from the left ventricle to the aorta. The impeller is formed as the rotor of the electric motor and rotated by the rotating magnetic field from a multiphase stator such as a brushless DC motor (BLDC). The impeller is rotated to provide sufficient blood flow through the pump to the patient's systemic circulation.


Early LVAD systems utilized mechanical bearings such as ball-and-cup bearings. More recent LVADs employ non-contact bearings which levitate the impeller using hydrodynamic and/or magnetic forces. In one example, the impeller is levitated by the combination of hydrodynamic and passive magnetic forces.


There is a trend for making blood pumps more miniaturized to treat a broader patient population, more reliable, and with improved outcomes. To follow this trend, contactless impeller suspension technology has been developed in several pump designs. The principle of this technology is to levitate the pump impeller using one or a combination of forces from electromagnets, hydrodynamics, and permanent magnets. In the meanwhile, the pump should be hemocompatible to minimize the blood cell damage and blood clot formation. To that end, the bearing gap between the levitated impeller and the pump housing becomes an important factor. A small gap may lead to the high probability of the thrombus formation in the bearing or to elevated hemolysis due to excessive shear stress. Likewise, a large gap can compromise the hydrodynamic bearing performance and the pump efficiency.


One pump design utilizing active magnetic bearings achieves the desired bearing gap by levitating the impeller using magnetic fields generated by electromagnetic coils. However, in such a design there is the need for a separate bearing control system that includes the position sensors and electromagnetic coils to control the impeller position.


Another pump design levitates the impeller using hydrodynamic thrust bearings alone or combined with passive magnetic bearings. However, such a design usually requires a small bearing gap to provide sufficient hydrodynamic bearing stiffness to maintain impeller levitation and prevent contacts between impeller and the pump housing. Such a small gap may result in an insufficient washout and vulnerability to blood clotting thus compromising hemocompatibility.


Pumps utilizing hydrodynamic bearings to suspend the impeller are generally designed to maintain a generally constant gap through all operating conditions. A drawback of such designs is that the impeller starts to tilt when the pump flow rate increases. This impeller position shift under low pressure conditions across the narrow gap creates blood flow stasis, which in turn leads to thrombus formation on the bearing surfaces. One solution to solve the problem is to add a passive magnetic bearing to try to maintain a stable gap. However, the magnetic bearing solution increases the size of the pump and complexity of the system.


What is needed is a pump that addresses these and other problems of known designs. What is needed is a pump with a relatively small form factor and improved outcomes. What is needed is a pump that employs a simple bearing system and enhances blood flow gaps to reduce the risk of thrombus. What is needed is a solution to enhance the bearing gap to achieve adequate washout without increasing the complexity of the pump mechanical design or reducing the pump efficiency.


BRIEF SUMMARY OF THE INVENTION

In summary, various aspects of the present invention are directed to a blood pump system including a pump housing; an impeller for rotating in a pump chamber within the housing; a stator comprising drive coils for applying a torque to the impeller; a bearing mechanism for suspending the impeller within the pump chamber; and a position control mechanism.


Various aspects of the invention are directed to a blood pump system including a pump housing; an impeller for rotating in a pump chamber within the housing; a stator comprising drive coils for applying a torque to the impeller; a first bearing for fixing the impeller relative to a first end of the pump chamber, a first blood gap defined between the impeller and a first bearing surface; a second bearing for fixing the impeller relative to a second end of the pump chamber, a second blood gap defined between the impeller and a second bearing surface; and a position control mechanism.


In various embodiments, the position control mechanism is configured to alternate the pump secondary flow gaps. In various embodiments, the position control mechanism is configured to move the impeller in an axial direction within the pump chamber to adjust a blood gap distance between the impeller and an opposing wall of the housing. In various embodiments, the position control mechanism is configured to move the impeller in an axial direction within the pump chamber to increase the first blood gap thereby increasing a washout rate.


In various embodiments, the washout rate is the average washout rate during a respective period of time. In various embodiments, the washout rate is the peak washout rate during a respective period of time. For example, the respective period of time may be the period during which the impeller is moved to a target position to increase the washout rate.


In various embodiments, the position control mechanism is configured to move the impeller periodically and intermittently. The position control mechanism may be configured to move the impeller for at least several seconds every minute. The position control mechanism may be configured to move the impeller based on a triggering event. The position control mechanism may be configured to move the impeller based on the impeller crossing a speed threshold. The speed threshold may be a low speed threshold. The triggering event may be based on a low speed threshold and time threshold.


In various embodiments, the pump is configured with at least a first balanced position with a narrow first gap and a second balanced position with a narrow second gap. The impeller may be controlled such that the impeller spends substantially equal amounts of time in the first and second balanced positions. In various embodiments, the amount of time the impeller spends in each balanced position is inversely proportional to the gap size. In various embodiments, one of the gaps is identified as being prone to stasis and the impeller spends more time in a position away from the identified gap.


In various embodiments, the movement of the impeller is asynchronous with the native heartbeat. In various embodiments, the movement of the impeller is synchronous with the native heartbeat.


In various embodiments, a total blood gap under normal operating conditions is 50 micrometers. In various embodiments, a total blood gap under normal operating conditions is 100 micrometers. In various embodiments, a total blood gap under normal operating conditions is 200 micrometers. In various embodiments, a total blood gap under normal operating conditions is 1000 micrometers. In various embodiments, a total blood gap under normal operating conditions is 2000 micrometers. In various embodiments, the impeller is moved to a position to decrease a respective blood gap by about 20%, by about 30%, by about 40%, by about 50%, by about 60%, by about 70%, by about 75%, by about 80%, or by about 90%.


Various aspects of the invention are directed to a method of operating a pump as described in any of the preceding paragraphs.


Various aspects of the invention are directed to a method of operating a blood pump including a housing and an impeller for rotating within a pump chamber within the housing including rotating the impeller within the pump chamber, the impeller being suspended within the pump chamber by a first bearing at a first end of the pump chamber and a second bearing at a second end of the pump chamber; and moving the impeller in an axial direction within the pump chamber to increase a first blood gap defined by the first bearing and to decrease a second blood gap defined by the second bearing.


Various aspects of the invention are directed to at least one system, method, or computer-program product as described in the specification and/or shown in any of the drawings.


In one aspect, a blood pump system is provided. The pump system may include a pump housing and an impeller for rotating in a pump chamber within the housing. The impeller may have a first side and a second side opposite the first side. The pump system may also include a stator having drive coils for applying a torque to the impeller and at least one bearing mechanism for suspending the impeller within the pump chamber. The pump system may further include a position control mechanism for moving the impeller in an axial direction within the pump chamber to adjust a size of a first gap and a size of a second gap, thereby controlling a washout rate at each of the first gap and the second gap. The first gap may be defined by a distance between the first side and the housing and the second gap is defined by a distance between the second side and the pump housing.


In another aspect, a blood pump system may include a pump housing, an impeller for rotating in a pump chamber within the housing, and a stator having drive coils for applying a torque to the impeller. The pump system may also include a first bearing for fixing the impeller relative to a first end of the pump chamber. A first blood gap may be defined between the impeller and a first bearing surface. The pump system may further include a second bearing for fixing the impeller relative to a second end of the pump chamber. A second blood gap may be defined between the impeller and a second bearing surface. The pump system may include a position control mechanism for moving the impeller in an axial direction within the pump chamber to increase the first blood gap thereby increasing a washout rate at the first blood gap.


In another aspect, a method is provided of operating a blood pump including a housing and an impeller for rotating within a pump chamber within the housing. The method may include rotating the impeller within the pump chamber. The impeller may be suspended within the pump chamber by a first bearing at a first end of the pump chamber and a second bearing at a second end of the pump chamber. The method may also include moving the impeller in an axial direction within the pump chamber to increase a first blood gap defined by the first bearing and to decrease a second blood gap defined by the second bearing.


The structures and methods of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated in and form a part of this specification, and the following Detailed Description of the Invention, which together serve to explain the principles of the present invention.





BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1 is a diagram of an implantable pump as one example of a rotary machine employing the present invention.



FIG. 2 is an exploded, perspective view of the exemplary centrifugal pump of FIG. 1.



FIG. 3 is a cross-sectional view of the exemplary pump of FIG. 1, illustrating the impeller levitated at a first balanced position generally centered within the pumping chamber in accordance with aspects of the invention.



FIG. 4a is a schematic view of the exemplary pump of FIG. 1, illustrating the impeller levitated eccentrically in the pump chamber by the main bearing components.



FIG. 4b is a schematic view of the pump of FIG. 1, illustrating the impeller moved to another eccentric position at the bottom of the pump chamber.



FIG. 4c is a schematic view of the pump of FIG. 1, illustrating the impeller moved to yet another eccentric position at the top of the pump chamber.



FIG. 5 is a flowchart showing a method of controlling impeller position in accordance with the invention.



FIG. 6 is a block diagram of a pump control system in accordance with the invention.



FIG. 7 is a line chart depicting the method of controlling the impeller position in accordance with the invention.



FIG. 8 is a flowchart showing a method of controlling impeller position in accordance with the invention.



FIG. 9 is a flowchart showing a method of moving the impeller in accordance with the invention.



FIG. 10 is a flowchart showing a method of starting up a pump in accordance with the invention.



FIG. 11 is a cross-sectional view of a centrifugal flow pump in accordance with aspects of the invention, illustrating a supplemental electromagnetic bearing.



FIG. 12 is a cross-sectional view of an axial flow pump in accordance with aspects of the invention, the axial flow pump including mechanical bearings.



FIG. 13 is a perspective view of the impeller of FIG. 12, with arrows depicting the direction of translation in accordance with the invention.



FIG. 14 is a cross-sectional view of an axial flow pump in accordance with aspects of the invention.



FIG. 15 is a cross-sectional view of an axial flow pump in accordance with aspects of the invention, the axial flow pump including hydrodynamic and magnetic bearings.





DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.


For convenience in explanation and accurate definition in the appended claims, the terms “up” or “upper”, “down” or “lower”, “inside” and “outside” are used to describe features of the present invention with reference to the positions of such features as displayed in the figures.


In many respects the modifications of the various figures resemble those of preceding modifications and the same reference numerals followed by subscripts “a”, “b”, “c”, and “d” designate corresponding parts.


As used herein, “gap” generally refers to the secondary flow gaps around the impeller as would be understood by one of skill in the art. The primary flow is through the impeller blade regions. The secondary flow gaps are the other areas of fluid, generally around the impeller. In some respects, the secondary flow gaps are between the impeller and the housing wall and define the hydrodynamic bearing.


The term “machine-readable medium” includes, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instructions and/or data. A code segment or machine-executable instructions may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.


Furthermore, embodiments of the invention may be implemented, at least in part, either manually or automatically. Manual or automatic implementations may be executed, or at least assisted, through the use of machines, hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine readable medium. One or more processors may perform the necessary tasks.


Although aspects of the invention will be described with reference to a blood pump, one will appreciate that the invention can be applied to other types of pumps. The mechanisms and methods of the invention will be described in relation to blood pumps and in particular the ability to adjust the impeller operating position to address performance, such as the attendant risks for thrombus and hemolysis when pumping blood. One will appreciate from the description herein that the invention can be applied broadly to other pumps, rotary machines, and induction motors.


Turning to the drawings, aspects of the invention enable to the ability to enhance or control the bearing gaps. One might wish to increase the bearing gap to adjust the washout rate, lubricate the bearing surfaces, or remove materials (particulates, thrombus, etc.) from the bearing gap. Another use of the invention may be to increase pump efficiency. As is known in the art, the motor efficiency increases as the impeller magnet moves closer to the motor drive coils. Another use of the invention may be to correct impeller malpositioning due to bulk forces or external forces (e.g. bumps or movements of the patient's body). These and other advantages can be achieved without the need for complex control systems in accordance with the invention.


Various aspects of the invention are directed to improving the washout in a respective pump bearing gap by moving the impeller to a position to increase the respective gap size. The impeller may be moved periodically (e.g. by time) or triggered by an event. When the impeller moves up, the larger gap on the bottom of the pump leads to a higher flow rate, which in turn leads to a higher washout rate. The upward movement of the impeller may also “squeeze” the blood above the impeller in a sort of pumping action, which also increases the washout rate. The fluid above is squeezed as the impeller moves, but once the impeller is in the new position the pumping effect is lost whereas the higher washout rate still remains below at the larger gap. In other words, the pumping effect on washout rate occurs at a specific point in time whereas the larger gap effect is temporal in nature. The basic concept makes use of the fact that the gap size is correlated to the washout rate. The washout rate relates to an average time for a full exchange of fluid. Accordingly, if the gap size divided by the washout rate is equal to a few seconds that doesn't necessarily mean the impeller should move for only a few seconds. Oftentimes, the impeller is moved for between about 100%, 120%, 150%, 200%, or other percentage of the average time for full exchange calculated by the gap size divided by the washout rate to have higher confidence. The washout flow rate is generally proportional to the cube of the gap width. Therefore, theoretically the total washout flow rate will be 8 times greater when the gap becomes 2 times wider. See W. K. Chan et al., Analytical Investigation of Leakage Flow I Disk Clearance of Magnetic Suspended Centrifugal Impeller, Artificial Organ (2000). Washout rate is vital, as a failure to get full washout may result in thrombosis formation in areas of stasis or where fluid isn't exchanged. This creates two risks: 1) the thrombus may dislodge and flow into the body, thus causing an embolism (or a stroke depending on where it goes), and 2) the thrombus may continue unabated, causing the activated site to form more platelets, which in turn provide a site for thrombin to adhere.


Accordingly, alternating the gaps has been found to improve the hydrodynamic bearing washout while maintaining a small total gap (good pump efficiency, proper HD bearing operations, etc.). In other words, alternating the gaps improves the washout without increasing the total gap.


The above technique can be implemented in a pump with a hydrodynamic and/or electromagnetic bearing. With a hydrodynamic bearing design, it is expected that there will be power loss associated with movement of the impeller. In one embodiment using electromagnets and hydrodynamic pressure grooves, the power loss can be minimized by designing the bearing stiffness curve to have at least two stable (eccentric) positions and facilitating movement of the impeller between these at least two positions. In one example, the electromagnets need additional force only to move the impeller from one side to another, and no such force is required to keep the impeller on one side.


In one embodiment, an electromagnetic force control method is used to change the impeller position and enhance the effective gap between the impeller and the blood chamber. The technique uses the same pump motor stator coils adjust the impeller position as is used to apply a torque to the impeller. No additional control subsystems and components are necessary.


Turning now to the drawings, wherein like components are designated by like reference numerals throughout the various figures, attention is directed to FIG. 1 which depicts an exemplary pump implanted in a heart failure patient.


A typical cardiac assist system includes a pumping unit, drive electronics, microprocessor control unit, and an energy source such as rechargeable batteries and/or an AC power conditioning circuit. The system is implanted during a surgical procedure in which a centrifugal pump is placed in the patient's chest. An inflow conduit is pierced into the left ventricle to supply blood to the pump. One end of an outflow conduit is mechanically fitted to the pump outlet and the other end is surgically attached to the patient's aorta by anastomosis. A percutaneous cable connects to the pump, exits the patient through an incision, and connects to the external control unit.


Various aspects of the implantable pump are similar to those shown and described in U.S. Pat. Nos. 4,528,485; 4,857,781; 5,229,693; 5,588,812; 5,708,346; 5,917,297; 6,100,618; 6,222,290; 6,249,067; 6,268,675; 6,355,998; 6,351,048; 6,365,996; 6,522,093; 7,972,122; and 8,686,674; and U.S. Pub. No. 2014/0205467 and 2012/0095281, the entire contents of which patents and publications are incorporated herein by this reference for all purposes.


The exemplary system utilizes an implantable pump with contactless bearings for supporting the impeller. Contactless bearings (i.e., levitation) provide a number of potential benefits. Because they reduce rotational friction, theoretically they improve motor efficiency and reduce the risk of introducing particulates into the fluid. In one example, the impeller employs upper and lower plates having magnetic materials (the terminology of upper and lower being arbitrary since the pump can be operated in any orientation). A stationary magnetic field from the upper side of the pump housing attracts the upper plate and a rotating magnetic field from the lower side of the pump housing attracts the lower plate. The forces cooperate so that the impeller rotates at a levitated position within the pumping chamber. Features (not shown) may also be formed in the walls of the pumping chamber to produce a hydrodynamic bearing wherein forces from the circulating fluid also tend to center the impeller. Hydrodynamic pressure grooves adapted to provide such a hydrodynamic bearing are shown in U.S. Pat. No. 7,470,246, issued Dec. 30, 2008, titled “Centrifugal Blood Pump Apparatus,” which is incorporated herein for all purposes by reference.


The exemplary impeller has an optimal location within the pumping chamber with a predetermined spacing from the chamber walls on each side. Maintaining a proper spacing limits the shear stress and the flow stasis of the pump. A high shear stress can cause hemolysis of the blood (i.e., damage to cells). Flow stasis can cause thrombosis (i.e., blood clotting).


With continued reference to FIG. 1, a patient is shown in fragmentary front elevational view. Surgically implanted either into the patient's abdominal cavity or pericardium 11 is the pumping unit 12 of a ventricular assist device. An inflow conduit (on the hidden side of unit 12) pierces the apex of the heart to convey blood from the patient's left ventricle into pumping unit 12. An outflow conduit 13 conveys blood from pumping unit 12 to the patient's ascending aorta. A percutaneous power cable 14 extends from pumping unit 12 outwardly of the patient's body via an incision to a compact control unit 15 worn by patient 10. Control unit 15 is powered by a main battery pack 16 and/or an external AC power supply, and an internal backup battery. Control unit 15 includes a commutator circuit for driving a motor within pumping unit 12.


In various embodiments, the commutator circuit and/or various electronics may be on the implanted side of the system. For example, various electronics may be positioned on-board the pump or in a separate hermetically sealed housing. Among the potential advantages of implanting electronics is the ability to control the pump even when communication is lost with the control unit 15 outside the body.



FIGS. 2 and 3 show exemplary centrifugal pumping devices in accordance with various aspects of the invention. The exemplary pumping device includes an impeller position controller to modify or select a position for the impeller. As will be described in further detail below, the impeller is positioned with a fixed pump chamber such that movement causing one pump gap to decrease generally causes the other pump gap to increase, and vice versa.



FIG. 2 shows exemplary centrifugal pump unit 20 used in the system of FIG. 1. The pump unit 20 includes an impeller 21 and a pump housing having upper and lower halves 22a and 22b. Impeller 21 is disposed within a pumping chamber 23 over a hub 24. Impeller 21 includes a first plate or disc 25 and a second plate or disc 27 sandwiched over a plurality of vanes 26. Second disc 27 includes a plurality of embedded magnet segments 44 for interacting with a levitating magnetic field created by levitation magnet structure 34 disposed against housing 22a. For achieving a small size, magnet structure 34 may comprise one or more permanent magnet segments providing a symmetrical, static levitation magnetic field around a 360° circumference. First disc 25 also contains embedded magnet segments 45 for magnetically coupling with a magnetic field from a stator assembly 35 disposed against housing 22b. Housing 22a includes an inlet 28 for receiving blood from a patient's ventricle and distributing it to vanes 26. Impeller 21 is preferably circular and has an outer circumferential edge 30. By rotatably driving impeller 21 in a pumping direction 31, the blood received at an inner edge of impeller 21 is carried to outer circumferential 30 and enters a volute region 32 within pumping chamber 23 at an increased pressure. The pressurized blood flows out from an outlet 33 formed by housing features 33a and 33b. A flow-dividing guide wall 36 may be provided within volute region 32 to help stabilize the overall flow and the forces acting on impeller 21.



FIG. 3 shows impeller 21 located in a balanced position. In the exemplary embodiment, the balanced position is at or near the center of the pump chamber. In the balanced position, the forces acting on the impeller are generally balanced to stabilize the impeller. The balanced position sometimes refers to the position the impeller naturally stabilizes or finds equilibrium during operation.


As one will understand from the description above, however, the balanced position is not necessarily a specific, static location. The hydrodynamic forces on the impeller will change as the rotational speed of the impeller changes. In turn, the magnetic attractive forces on the impeller will change as the impeller moves closer to or away from the magnet structure 34 and stator assembly 35. Accordingly, the impeller generally finds a new balanced position as the rotational speed changes. As will be described below, however, aspects of the invention are directed to moving the impeller or changing the balanced position for each given rotational speed. For example, the impeller position control mechanisms to be described facilitate moving the impeller axially (up or down) without changing the rotational speed and all other. This has the effect of enabling movement of the impeller independent of rotor speed. An advantage of this technique is that rotor speed can be determined in normal course (e.g. by a physician based on the patient's physiological needs) without concern for changing the impeller position. Conversely, the impeller position can be changed without affecting pumping throughput.



FIG. 3 shows impeller 21 located at or near a centered position wherein disc 27 is spaced from housing 22A by a gap 42 and impeller disc 25 is spaced from housing 22B by a gap 43. In the exemplary embodiment, the center position is chosen as the balanced or eccentric point to ensure substantially uniform flow through gap 42 and gap 43. During pump operation, the balanced position is maintained by the interaction of (a) attractive magnetic forces between permanent magnets 40 and 41 in levitation magnet structure 34 with imbedded magnetic material 44 within impeller disc 27, (b) attractive magnetic forces between stator assembly 35 and embedded magnet material 45 in impeller disc 25, and (c) hydrodynamic bearing forces exerted by the circulating fluid which may be increased by forming hydrodynamic pressure grooves in housing 22 (not shown). By using permanent magnets in structure 34 a compact shape is realized and potential failures associated with the complexities of implementing active levitation magnet control are avoided. To properly balance impeller 21 at the centered position, however, and because other forces acting on impeller 21 are not constant, an active positioning control is still needed. In particular, the hydrodynamic forces acting on impeller 21 vary according to the rotational speed of impeller 21. Furthermore, the attractive force applied to impeller 21 by stator assembly 35 depends on the magnitude of the magnetic field and the angle by which the magnetic field leads the impellers magnetic field position. In one embodiment, the attractive force is created by a direct current (Id) as will be described in more detail below.


In one embodiment, the impeller position is controlled using vector motor control. Several structures and techniques for modifying impeller position using vector motor control will now be described with reference to FIGS. 3 to 7.



FIG. 4a shows the main structure of an exemplary centrifugal pump 50 similar to that shown in FIG. 3. It is understood that other pump configurations may be employed, including various combinations of permanent magnets, motor stator windings, and hydrodynamic bearings. In the exemplary embodiment, the rotor is formed as an impeller and driven by a motor. The impeller is also levitated by the combined force F, which can be expressed as the following equation:

F=Fhdb+Fpm+Fem


Where,


F is the combined force to levitate the impeller


Fhdb is the combination of hydrodynamic forces from the inlet side bearing, the motor side bearing, or both


Fpm is the combination of permanent magnet attraction forces


Fem is the magnetic attraction force generated from the motor.


When the impeller is stabilized, F should be equal to zero. Usually Fem can be controlled through the electronic system to adjust the impeller position since all the others are the fixed configurations as the passive mode. Therefore, the basic design concept of this invention is to apply the motor vector control (FOC) to control the force Fem so that the impeller position can be adjusted while rotating only using one set of motor coil and drive system. In such way, there is no additional cost in the pump structure.



FIGS. 4a, 4b, and 4c illustrate a pump in accordance with various aspects of the invention. FIG. 4a illustrates an exemplary pump 50 with an impeller 52 in a pump chamber. Pump 50 is configured similar to pump 10 in FIG. 3. FIGS. 4b and 4c illustrate the same pump 50 in FIG. 4a except with the impeller moved down and up, respectively, in accordance with the invention. In FIG. 4b, the impeller 52 is in a lowered position such that Gap 2 is smaller and Gap 1 is commensurately wider. In this position the washout rate across Gap 1 is exponentially higher relative to FIG. 4a. In FIG. 4c, the impeller 52 is in a raised position such that Gap 2 is wider and Gap 1 is commensurately narrower. In this position, the washout rate in Gap 2 is exponentially higher relative to FIG. 4a.


In various respects, the washout rate refers to the average washout rate during a respective period of time. In various respects, the washout rate refers to the peak washout rate. The respective period of time may be any designated period of time, for example, the period during which the impeller is moved to a target position to increase the washout rate.



FIG. 5 illustrates an exemplary simplified method for controlling the pump. In step S1, the pump is operated with the impeller at a first balanced position. In step S2, a trigger is identified. In response, the impeller is moved to a second position in step S3. Thereafter the impeller eventually moves back to the first position.


The trigger may be temporal-based or event-based. In various embodiments, the position control mechanism is configured to move the impeller periodically and intermittently. In other words, the trigger can be the passage of a predetermined amount of time and/or based on a set frequency and cycle. In one example, the position control mechanism is configured to move the impeller for at least several seconds every minute. In various embodiments, the position control mechanism is configured to move the impeller based on the impeller crossing a speed threshold. The speed threshold may be a low speed threshold. The trigger may be based on a low speed threshold and time threshold. For example, the impeller may be moved after it spends more than a set amount of time at a low speed. This may be beneficial because low speeds can lead to touchdown events, stasis, and other issues. Thus, the impeller may be moved to ensure any particulates or thrombus are cleared from the gap.


In various embodiments, the pump is configured with at least a first balanced position with a narrow first gap and a second balanced position with a narrow second gap. As compared to FIG. 4a, FIG. 4b shows the impeller defining a narrow Gap 2 and FIG. 4c shows the impeller defining a narrow Gap 1. Because the pump chamber dimensions are fixed and the total gap is likewise fixed, Gap 1 increases by the same distance that Gap 2 decreases. In FIG. 4c, the impeller has moved upward to a third balanced position such that Gap 1 has decreased and Gap 2 has increased by a commensurate amount.


The impeller may be controlled such that the impeller spends substantially equal amounts of time in the first and second balanced positions. This may be useful where the pump is otherwise designed for the impeller to normally be in a centered position, such as shown in FIG. 4a. In various embodiments, the amount of time the impeller spends in each balanced position is inversely proportional to the gap size. This may be useful where the pump is otherwise designed to have uneven gaps. In various embodiments, one of the gaps is identified as being prone to stasis and the impeller spends more time in a position away from the identified gap.


In various embodiments, the movement of the impeller is asynchronous with the native heartbeat. In various embodiments, the movement of the impeller is synchronous with the native heartbeat.


In various embodiments, a total blood gap under normal operating conditions is 50 micrometers. In various embodiments, a total blood gap under normal operating conditions is 100 micrometers. In various embodiments, a total blood gap under normal operating conditions is 200 micrometers. In various embodiments, a total blood gap under normal operating conditions is 1000 micrometers. In various embodiments, a total blood gap under normal operating conditions is 2000 micrometers. In various embodiments, the impeller is moved to a position to decrease a respective blood gap by about 20%, by about 30%, by about 40%, by about 50%, by about 60%, by about 70%, by about 75%, by about 80%, or by about 90%.


One will appreciate that FIGS. 4a, 4b, and 4c are illustrative only. In practice the impeller is freely suspended and not perfectly fixed in a position. Because the exemplary pump suspends the impeller by balancing a combination of passive forces, the impeller actually exhibits a moderate amount of movement in practice. Indeed, the impeller will move up and down depending on the rotational speed at least because of the relationship of rpms to hydrodynamic force. However, for a set rotational speed, the impeller is typically constrained with a defined envelope of space which is referred to her as a “position” for simplicity of explanation.


Mechanical or contact bearings exhibit little to no movement regardless of the rotational speed and other factors. Nonetheless, contact bearings demonstrate some operational movement even if such movement requires precise instruments to be measured. Many types of blood pumps, for example, utilize bearings which are washed and lubricated by an external source. Examples of a pump with a blood-immersed bearing are described in U.S. Pub. No. 2012/0095281 and U.S. Pat. No. 5,588,812, incorporated herein for all purposes by reference. In one example, a pump includes blood immersed contact bearings such as a ball-and-cup. In one example, the bearings are washed and/or lubricated by saline or infusate. The use of saline is a common scenario for percutaneous pumps because they have a fluidic connection to sources outside the body. Examples of percutaneous pumps with contact bearings are disclosed in U.S. Pat. Nos. 7,393,181 and 8,535,211, incorporated herein by reference for all purposes. As will be appreciated by one of skill in the art, contact bearings which are designed to have a fluid at least periodically washing between the contact surface will have some movement. Although this movement is small relative to non-contact bearings (e.g. on the order of 5, 10, 20, 100 or more times smaller), they are subject to some degree of movement.


Conventional thinking is that a blood pump (e.g. left ventricular assist device) should be designed to maintain a stable impeller position and consistent blood gaps across the device lifetime. In blood pumps, in particular, movement of the impeller is often associated with hemolysis and other undesirable risks. There is a belief that decreasing a pump gap creates a region of stasis which leads to thrombus and other adverse events.


However, it has been found that adjusting the pump gap in a controlled and designed manner can actually improve performance and outcomes. Various aspects of the invention are directed to pumps configured to actively and purposefully modify the impeller position. In one embodiment, the balanced position of the impeller is changed during operation.


There are several potential benefits to the technique described above for moving the impeller and alternating the pump gaps. One of these potential benefits is the ability to increase the peak washout flow velocity. Another potential benefit is the ability to prevent or reduce the collection of ingested thrombus in narrow gaps without increasing the total gap size. In turn, pump efficiency and performance are not compromised. Existing solutions (e.g. stable-gap hydrodynamic bearing designs) rely on the native heart to change the blood flow pattern in the narrow gap areas (such as systole/diastole). The inventive technique is advantageous because it actively changes the flow pattern independently of the native heart function, impeller speed, etc. Also, many heart failure patients have weakened native hearts with insufficient pulsatility to actually wash out the bearing gaps. With the inventive technique, the combination of the external pressure change and internal geometry change (rotor position change) will minimize the blood flow stasis which causes pump thrombosis.



FIGS. 6 and 7 illustrate an exemplary method for controlling voltages applied to a stator in order to provide a desired rotation for a permanent magnet rotor (e.g. the impeller) 52 using a field oriented control (FOC) algorithm, which is also known as vector control. It is known in FOC that the stator magnetic field should generally lead the impeller position by 90° for maximum torque efficiency. The magnitude of the attractive force on the impeller is proportional to the magnitude of the phase currents in the stator. Phase current is adjusted by the FOC algorithm according to torque demands for the pump.


At any particular combination of the (1) magnitude of the phase current and (2) the speed of the impeller, modifying the Id current for generating the phase voltages can change the attractive force generated by the stator thereby affecting the impeller balance. In turn, the impeller moves until it settles at a new balanced position where the hydrodynamic forces and magnetic forces are balanced. In this manner, the impeller can be moved simply by adjustments to the motor control signal.



FIGS. 4b, 4c, 5, 6, and 7 illustrate an exemplary system in accordance with aspects of the invention. FIG. 6 is a schematic diagram of pump control system with the proposed impeller position control. Based on the principle of motor vector control, the torque current that is usually called quadrature current (Iq current) and stator coil flux current that is called direct current (Id current) can be decoupled and controlled independently. The quadrature current Iq current is used to control the impeller rotational speed. The direct Id current controls the magnetic flux of electromagnetic coils which creates a resulting attractive force on the impeller.


In accordance with the invention, Id current is utilized to control the impeller position by enhancing or weakening the magnetic flux between impeller (rotor) and motor stator coils to adjust the attraction force Fem. This in turn changes the impeller position (shown in FIG. 7). In various embodiments, the attractive force is created by adjusting the phase angle using FOC.


In one embodiment, the impeller position control technique is implemented as an open loop control without impeller position sensors. In one embodiment, impeller position control technique is implemented as a closed loop control with impeller position sensors.


In order to ensure proper positioning, active monitoring and control of the impeller position has been employed in the exemplary embodiment by adjusting the stationary magnetic field. However, position sensors and an adjustable magnetic source occupy a significant amount of space and add to the complexity of a system. Accordingly, the use of sensors may depend on the design requirements. Suitable sensors may include, but are not limited to, Hall-effect sensors, variable reluctance sensors, and accelerometers.


In one embodiment using the open loop control, the impeller is controlled by periodically alternating the position from one side to another (e.g. from inlet side to motor side) by modulating the Id current as shown in FIG. 7. In this manner, the side gaps (Gap 1 and Gap 2) as shown in FIGS. 4b and 4c can be increased or decreased.


With continued reference to FIGS. 6 and 7, the position control technique can be implemented into the hardware and/or software of the system. By example, the controller may employ FOC to supply a multiphase voltage signal to the stator assembly 53. The exemplary stator assembly is a three-phase stator. Individual phases a, b, and c and currents Ia, Ib, and Ic may be driven by an H-bridge inverter functioning as a commutation circuit driven by a pulse width modulator (PWM) circuit. An optional current sensing circuit associated with the inverter measure instantaneous phase current in at least two phases providing current signals designated Ia and Ib. A current calculating block receives the two measured currents and calculates a current Ic corresponding to the third phase. The measured currents are input to Vector Control (FOC) block 54 and to a current observer block (not shown) which estimates the position and speed of the impeller. The impeller position and speed are input to the FOC block from speed control block 55 and position control block 56. A target speed or revolutions per minute (rpm) for operating the pump is provided by a conventional physiological monitor to FOC block 54. The target rpm may be set by a medical caregiver or determined according to an algorithm based on various patient parameters such heartbeat, physiological needs, suction detection, and the like. FOC block 54 and drive electronics 57 generate commanded voltage output values Va, Vb, and Vc. The Va, Vb, and Vc commands may also be coupled to the observer block for use in detecting speed and position.


The exemplary system differs from conventional configurations inasmuch as the FOC block and electronics are configured to alter the field oriented control algorithm so that the Id current can be varied independently to generated the required attractive force. The exemplary system potentially sacrifices such efficiency in return for other benefits. Among the benefits of the exemplary system is the ability to independently control the impeller position.



FIG. 8 illustrates a method of moving the impeller using a FOC algorithm. In one embodiment, the invention proceeds according to a method as shown in FIG. 8 which highlights a portion of the impeller position control with the field oriented control algorithm. Thus, in step 65 the phase currents are measured. Based on the measured phase currents, the current speed and rotor angle are estimated in step 66 based on the rotor angle determined in step 66. The phase currents are transformed into a two-axis coordinate system to generate quadrature current (called Iq current) and direct current (called Id current) values in a rotating reference frame in step 67. Quadrature current is used to control the torque to rotate the impeller and direct current is used to control the attraction force between rotor and stator to control the impeller position. In step 68, the next quadrature voltage is determined by the quadrature current error between the quadrature current transformed from step 67 and the required current for impeller rotation. In step 69, the next direct voltage is determined by the direct current error between the direct current transformed from step 67 and the required current for the attraction force alternation to control the impeller position. In step 70, the quadrature and direct voltage are transformed back to the stationary reference frame in order to provide the multiphase voltage commands which are output to the PWM circuit.



FIG. 9 is a flowchart showing another method of operating a rotary machine in accordance with the invention. The method includes operating the pump to rotate the impeller by applying a rotating magnetic field in step S10. During operation the impeller is levitated and positioned at a balanced position (P1) by a balancing of forces. As described above, in an exemplary embodiment the impeller is levitated by the combination of hydrodynamic forces F1 and other bearing forces F2 (e.g. stator attractive force, passive magnetic forces, and/or bulk forces like gravity) in steps S11 and S12. Next, at least one of the forces, F2, is modified to place the impeller out of balance in step S14. The impeller moves to a new position, P2, where the forces are once again balanced in step S15.


Turning to FIG. 10, in one embodiment, the impeller position control technique is used to facilitate start-up of the pump. In step S20, the exemplary pump is configured so the impeller rests against the inlet side (top of the housing) when the impeller is not rotating. In a typical pump with hydrodynamic forces alone, or in combination with magnetic forces, the impeller is levitated away from the wall as it rotates. The blood entrained in the gap between the impeller and the housing creates hydrodynamic pressure; however, the impeller must be rotating at a sufficient speed to create the hydrodynamic pressure. Until the minimum speed is met, the impeller rubs against the housing wall. In the exemplary pump, by contrast, the impeller is pulled away from the wall prior to, or just after, rotation begins thereby eliminating the deleterious effects of friction. The impeller is pulled away from the wall by applying a force, F, as described above in step S21. For example, the commutation angle may be modified to exert an attractive force. Referring to FIG. 7b, by example, the pump can be configured so the impeller rests at the inlet side. By applying an attractive force to the motor side the impeller moves down from the top wall. In step S22, the regular start-up sequence is initiated after the impeller is removed from the wall.



FIG. 11 shows a rotary machine in accordance with another embodiment making use of electromagnets. Pump 100 in FIG. 11 is similar in various respects to pump 10 in FIG. 3. In the exemplary embodiment, however, pump 100 includes an active electromagnetic (EM) system 101. The EM force generated by electromagnets is used primarily or adjunctively to move the impeller. Exemplary electromagnets 101 comprise iron cores and windings. The EM force is modified in a conventional manner by changing the current applied to the windings. The application of the EM force causes the impeller to move to position PE2. One will appreciate that the EM force can overpower hydrodynamic and passive magnetic forces present in the system. Accordingly, the EM structure must dimensioned and configured to apply a relatively balanced force. An advantage of using electromagnets over the existing stator assembly is that there is relatively greater positional control over the impeller. By contrast, as described above, the phase currents typically cannot be used as the primary variable to adjust the axial attractive force on the impeller. A disadvantage of this embodiment is the need to provide an entirely separate EM system. This may not be an issue with large industrial rotary machines, but many types of motors have restrictive form factors. For example, implanted pumps must be relatively small in order to address a wider patient population.



FIGS. 12 and 13 illustrate another implantable pump in accordance with the invention. Pump 200 is similar in various respects to pumps 10 and 100 described above except pump 200 is an axial flow pump. Blood flows from in through inlet 201 and out through outlet 202 in a generally linear, axial direction. Pump 200 includes an impeller 210 having blades for moving blood through the pump housing and imparting kinetic energy in the fluid.


Impeller 210 is fixed within the housing by ball-and-cup bearings 212 and 214. The ball-and-cup bearings are closely toleranced and generally fix the impeller in a specific position. However, the exemplary bearings are lubricated and washed by the blood flow around the impeller. Accordingly, there is some fluid between the ball and cup surfaces.


Torque is applied to the impeller by a stator assembly 205. The stator assembly 205 includes windings and is driven using a FOC algorithm in a similar manner to the stator assemblies described above. In practice, the impeller position is adjusted proceeding according to the method shown in FIGS. 5 and/or 9. Using the FOC technique described above the impeller is rotated in the pump housing. At a desired time the Id current is modulated to adjust the attractive force on the impeller in the axial direction. As long as the attractive force is sufficient to squeeze blood out from a respective bearing gap, the impeller will move axially towards inlet 201 or outlet 202. The bearing gaps of pump 200 are relatively small compared to Gap 1 and Gap 2 of pump 50 in FIG. 4. However, even relatively small impeller movement may be beneficial to enable control of the bearing gaps.


The method of adjusting the pump gaps to increase the washout rate may be particularly beneficial in pump designs with mechanical bearings. The relatively small gaps in the bearings mean that there is very little fluid flow and thus a higher risk of thrombus. The greater friction also can contribute to greater thrombus risk. Accordingly, the ability to increase the gap between the ball and the cup, even on a small scale, can lead to significant improvements in outcomes.



FIG. 14 illustrates another pump 300 similar to pump 200. Pump 300 includes an impeller fixed between two mechanical bearings 212 and 214. Pump 300 is slightly different than pump 200 because the outlet extends at an angle from the inlet. Pump 300 is configured in a relatively compact design compared to pump 200 including a relatively smaller stator assembly; however, the same general principles can be applied to control the motor and adjust the impeller position.



FIG. 15 is a cross-sectional view of another pump 400 similar to pumps 200 and 300, except pump 400 is an axial flow pump with non-contact bearings. Pump 400 includes a pump housing having an inlet 401 and outlet 402. An impeller 411 is positioned within a pump chamber for imparting flow to the blood fluid within the housing. The impeller is entirely formed of a magnetic material which is driven by interaction with a stator assembly 405.


Impeller 411 is stabilized in the pump chamber by a combination of hydrodynamic and passive magnetic forces. Impeller 411, which is a magnetic material, interacts with the magnetic material in stator assembly 405 to provide an axial centering force. A pump ring 452 with a chamfer surface is positioned at the leading end of the impeller to create hydrodynamic stabilization forces in the axial direction (left to right) and radial direction (up and down on page). A permanent magnet ring 450 is provided at the trailing edge of the impeller is oriented with a north pole facing a north pole of the impeller. This arrangement creates an axial bias force to push the impeller against the pump ring 452. The magnet ring 450 also provides a radially centering force. Finally, the impeller includes deep hydrodynamic grooves to generate a hydrodynamic pressure force against the inner walls of the pump chamber for radial stabilization.


In operation, the impeller remains stable in the axial and radial directions. There may be some axial movement as the rotational speed of the impeller changes or as a result of other forces (e.g. the native pulse), but generally the impeller remains centered below the stator assembly.


Using the FOC control technique described above, the attractive force of the stator assembly 405 on impeller 411 can be modified. In one embodiment, pump 400 is configured so impeller is eccentric when centered below the stator assembly 405. In this example, increasing the attractive force amounts to an increase in the axial stiffness to resist axial movement. In one embodiment, the attractive force is modified to actually move impeller 411 axially. For example, the impeller can be moved closer to pump ring 452 to squeeze blood out of the gap between impeller 411 and a surface of ring 452. The impeller may also be moved away from ring 452 to increase the blood gap therebetween. In this manner, the impeller position control technique adds an element of active position control otherwise not possible with the passive bearing configuration of pump 400.


The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.

Claims
  • 1. A blood pump comprising: a stator for applying force to an impeller;a sensing circuit for determining an axial position of the impeller; anda position control mechanism for moving the impeller in an axial direction independent of a rotational speed of the impeller by controlling, based on the axial position of the impeller, a field oriented control device which provides current to the stator.
  • 2. The blood pump of claim 1, wherein: the pump is an centrifugal pump.
  • 3. The blood pump of claim 1, wherein: the pump is an axial flow pump.
  • 4. The blood pump of claim 1, wherein: the position control mechanism is further for moving the impeller in the axial direction between a first eccentric position and a second eccentric position.
  • 5. The blood pump of claim 1, wherein: the position control mechanism is further for moving the impeller in the axial direction upon a trigger event occurring.
  • 6. The blood pump of claim 5, wherein: the trigger event comprises the impeller rotating below a predefined speed for a predefined length of time.
  • 7. The blood pump of claim 1, wherein: the position control mechanism is further for moving the impeller in the axial direction between a first position and a second position; andthe position control mechanism is configured to maintain the impeller in the first position and the second position for substantially equal lengths of time.
  • 8. The blood pump of claim 1, wherein: the position control mechanism is further for moving the impeller in the axial direction between a first position and a second position, wherein: in the first position there is a first gap between the impeller and a first wall of a pump chamber of the pump;in the second position there is a second gap between the impeller and a second wall of the pump chamber of the pump; andthe first gap is smaller than the second gap; andthe position control mechanism is configured to maintain the impeller in the first position for longer than in the second position.
  • 9. The blood pump of claim 1, wherein the sensing circuit comprises: a position sensor configured to determine the axial position of the impeller.
  • 10. The blood pump of claim 1, wherein: the sensing circuit is configured to determine the axial position of the impeller based on at least one measured current associated with the stator.
  • 11. A method for controlling a pump comprising: causing a stator to apply a rotational force to an impeller;determining an axial position of the impeller; andcausing, with a field oriented control device, the impeller to be moved in an axial direction based on the axial position of the impeller and independent of a rotational speed of the impeller.
  • 12. The method for controlling a pump of claim 11, wherein causing the impeller to be moved comprises: causing the impeller to be moved between a first eccentric position and a second eccentric position.
  • 13. The method for controlling a pump of claim 11, wherein causing the impeller to be moved comprises: causing the impeller to be moved upon a trigger condition occurring.
  • 14. The method for controlling a pump of claim 11, wherein causing the impeller to be moved comprises: causing the impeller to be moved in the axial direction between a first position and a second position; andmaintaining the impeller in the first position and the second position for substantially equal lengths of time.
  • 15. The method for controlling a pump of claim 11, wherein causing the impeller to be moved comprises: causing the impeller to be moved in the axial direction between a first position and a second position, wherein: in the first position there is a first gap between the impeller and a first wall of a pump chamber of the pump;in the second position there is a second gap between the impeller and a second wall of the pump chamber of the pump; andthe first gap is smaller than the second gap; andmaintaining the impeller in the first position for longer than in the second position.
  • 16. A non-transitory machine readable medium having instructions thereon for controlling a pump, wherein the instructions, when executed by at least one processor, cause steps to be performed comprising: causing a stator to apply a rotational force to an impeller;determining an axial position of the impeller; andcausing a field oriented control device to move the impeller axially based on the axial position of the impeller and independent of a rotational speed of the impeller.
  • 17. The non-transitory machine readable medium of claim 16, wherein moving the impeller axially comprises: moving the impeller between a first eccentric position and a second eccentric position.
  • 18. The non-transitory machine readable medium of claim 16, wherein causing the field oriented control device to move the impeller comprises: causing the field oriented control device to move the impeller upon a trigger condition occurring.
  • 19. The non-transitory machine readable medium of claim 16, wherein determining the axial position of the impeller comprises: determining at least one measured current associated with the stator; anddetermining the axial position of the impeller based on the at least one measured current.
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patent application Ser. No. 15/041,987, filed Feb. 11, 2016 and entitled “ALTERNATING PUMP GAPS,” which claims priority to U.S. Provisional Application No. 62/115,318, filed Feb. 12, 2015 and entitled “ALTERNATING PUMP GAPS,” which is hereby incorporated by reference in its entirety.

US Referenced Citations (437)
Number Name Date Kind
1093868 Leighty Apr 1914 A
2684035 Kemp Jul 1954 A
3023334 Burr et al. Feb 1962 A
3510229 Smith May 1970 A
3620638 Kaye et al. Nov 1971 A
3870382 Reinhoudt Mar 1975 A
3932069 Giardini et al. Jan 1976 A
3960468 Boorse et al. Jun 1976 A
4149535 Voider Apr 1979 A
4382199 Isaacson May 1983 A
4392836 Sugawara Jun 1983 A
4434389 Langley et al. Feb 1984 A
4507048 Belenger et al. Mar 1985 A
4528485 Boyd, Jr. Jul 1985 A
4540402 Aigner Sep 1985 A
4549860 Yakich Oct 1985 A
4645961 Maisky Feb 1987 A
4686982 Nash Aug 1987 A
4688998 Olsen et al. Aug 1987 A
4753221 Kensey et al. Jun 1988 A
4763032 Bramm Aug 1988 A
4769006 Papatonakos Sep 1988 A
4779614 Moise Oct 1988 A
4790843 Carpentier et al. Dec 1988 A
4806080 Mizobuchi et al. Feb 1989 A
4814677 Plunkett Mar 1989 A
4817586 Wampler Apr 1989 A
4846152 Wampler et al. Jul 1989 A
4857781 Shih Aug 1989 A
4888011 Kung et al. Dec 1989 A
4895557 Moise et al. Jan 1990 A
4900227 Troup lin Feb 1990 A
4902272 Milder et al. Feb 1990 A
4906229 Wampler Mar 1990 A
4908012 Moise et al. Mar 1990 A
4919647 Nash Apr 1990 A
4930997 Bennett Jun 1990 A
4944722 Carriker et al. Jul 1990 A
4957504 Chardack Sep 1990 A
4964864 Summers et al. Oct 1990 A
4969865 Hwang et al. Nov 1990 A
4985014 Orejola Jan 1991 A
4995857 Arnold Feb 1991 A
5021048 Buckholtz Jun 1991 A
5078741 Bramm et al. Jan 1992 A
5092844 Schwartz et al. Mar 1992 A
5092879 Jarvik Mar 1992 A
5100374 Kageyama Mar 1992 A
5106263 Irie Apr 1992 A
5106273 Lemarquand et al. Apr 1992 A
5106372 Ranford Apr 1992 A
5112202 Ozaki et al. May 1992 A
5129883 Black Jul 1992 A
5145333 Smith Sep 1992 A
5147186 Buckholtz Sep 1992 A
5112349 Summers et al. Dec 1992 A
5190528 Fonger et al. Feb 1993 A
5201679 Velte et al. Apr 1993 A
5211546 Isaacson et al. May 1993 A
5229693 Futami et al. Jul 1993 A
5275580 Yamazaki Jan 1994 A
5290227 Pasque Jan 1994 A
5360445 Goldowsky Jan 1994 A
5290236 Mathewson Mar 1994 A
5300112 Barr Apr 1994 A
5306295 Kolff et al. Apr 1994 A
5312341 Turi May 1994 A
5313128 Robinson et al. May 1994 A
5332374 Kricker et al. Jul 1994 A
5346458 Afield Sep 1994 A
5350283 Nakazeki et al. Sep 1994 A
5354331 Schachar Nov 1994 A
5370509 Golding et al. Dec 1994 A
5376114 Jarvik Dec 1994 A
5385581 Bramm et al. Jan 1995 A
5405383 Barr Nov 1995 A
5449342 Hirose et al. Dec 1995 A
5478222 Heidelberg et al. Dec 1995 A
5504978 Meyer, III Apr 1996 A
5507629 Jarvik Apr 1996 A
5519270 Yamada et al. May 1996 A
5533957 Aldea Sep 1996 A
5569111 Cho et al. Oct 1996 A
5575630 Nakazawa et al. Nov 1996 A
5588812 Taylor et al. Dec 1996 A
5595762 Derrieu et al. Jan 1997 A
5643226 Cosgrove et al. Jan 1997 A
5611679 Ghosh et al. Mar 1997 A
5613935 Jarvik Mar 1997 A
5678306 Bozeman, Jr. et al. Oct 1997 A
5692882 Bozeman, Jr. et al. Dec 1997 A
5695471 Wampler Dec 1997 A
5708346 Schob Jan 1998 A
5725357 Nakazeki et al. Mar 1998 A
5738649 Macoviak Apr 1998 A
5746575 Westphal et al. May 1998 A
5746709 Rom et al. May 1998 A
5755784 Jarvik May 1998 A
5776111 Tesio Jul 1998 A
5795074 Rahman et al. Aug 1998 A
5800559 Higham et al. Sep 1998 A
5807311 Palestrant Sep 1998 A
5814011 Corace Sep 1998 A
5824069 Lemole Oct 1998 A
5749855 Reitan Dec 1998 A
5843129 Larson et al. Dec 1998 A
5851174 Jarvik et al. Dec 1998 A
5853394 Tolkoff et al. Dec 1998 A
5890883 Golding et al. Apr 1999 A
5911685 Siess et al. Jun 1999 A
5917295 Mongeau Jun 1999 A
5917297 Gerster et al. Jun 1999 A
5921913 Siess Jul 1999 A
5924848 Izraelev Jul 1999 A
5924975 Goldowsky Jul 1999 A
5928131 Prem Jul 1999 A
5938412 Israelev Aug 1999 A
5941813 Sievers et al. Aug 1999 A
5945753 Maegawa et al. Aug 1999 A
5868702 Stevens et al. Sep 1999 A
5868703 Bertolero et al. Sep 1999 A
5947703 Nojiri et al. Sep 1999 A
5951263 Taylor et al. Sep 1999 A
5984892 Bedingham Nov 1999 A
5964694 Siess et al. Dec 1999 A
6004269 Crowley et al. Dec 1999 A
6007479 Rottenberg et al. Dec 1999 A
6030188 Nojiri et al. Feb 2000 A
6042347 Scholl et al. Mar 2000 A
6053705 Schob et al. Apr 2000 A
6066086 Antaki et al. May 2000 A
6071093 Hart Jun 2000 A
6074180 Khanwilkar et al. Jun 2000 A
6080133 Wampler Jun 2000 A
6082900 Takeuchi et al. Jul 2000 A
6083260 Aboul-Hosn et al. Jul 2000 A
6100618 Schoeb et al. Aug 2000 A
6058593 Siess Sep 2000 A
6123659 leBlanc et al. Sep 2000 A
6123726 Mori et al. Sep 2000 A
6139487 Siess Oct 2000 A
6086527 Talpade Nov 2000 A
6142752 Akamatsu et al. Nov 2000 A
6143025 Stobie et al. Nov 2000 A
6146325 Lewis et al. Nov 2000 A
6149683 Lancisi et al. Nov 2000 A
6158984 Cao et al. Dec 2000 A
6171078 Schob Jan 2001 B1
6176822 Nix et al. Jan 2001 B1
6176848 Rau et al. Jan 2001 B1
6179773 Prem et al. Jan 2001 B1
6190304 Downey et al. Feb 2001 B1
6200260 Bolling Mar 2001 B1
6206659 Izraelev Mar 2001 B1
6254359 Aber Mar 2001 B1
6222290 Schob et al. Apr 2001 B1
6227797 Watterson et al. May 2001 B1
6227820 Jarvik May 2001 B1
6234772 Wampler et al. May 2001 B1
6234998 Wampler May 2001 B1
6247892 Kazatchkov et al. Jun 2001 B1
6249067 Schob et al. Jun 2001 B1
6264635 Wampler et al. Jul 2001 B1
6268675 Amrhein Jul 2001 B1
6276831 Takahashi et al. Aug 2001 B1
6293901 Prem Sep 2001 B1
6295877 Aboul-Hosn et al. Oct 2001 B1
6319231 Andrulitis Nov 2001 B1
6320731 Eeaves et al. Nov 2001 B1
6245007 Bedingham et al. Dec 2001 B1
6458163 Slemker et al. Jan 2002 B1
6351048 Schob et al. Feb 2002 B1
6355998 Schob et al. Mar 2002 B1
6365996 Schob Apr 2002 B2
6375607 Prem Apr 2002 B1
6387037 Bolling et al. May 2002 B1
6394769 Bearnson et al. May 2002 B1
6422990 Prem Jul 2002 B1
6425007 Messinger Jul 2002 B1
6428464 Bolling Aug 2002 B1
6439845 Veres Aug 2002 B1
6447266 Antaki et al. Sep 2002 B2
6447441 Yu et al. Sep 2002 B1
6508777 Macoviak et al. Jan 2003 B1
6508787 Erbel et al. Jan 2003 B2
6517315 Belady Feb 2003 B2
6522093 Hsu et al. Feb 2003 B1
6532964 Aboul-Hosn et al. Mar 2003 B2
6533716 Schmitz-Rode et al. Mar 2003 B1
6544216 Sammler et al. Apr 2003 B1
6547519 deBlanc et al. Apr 2003 B2
6547530 Ozaki et al. Apr 2003 B2
6575717 Ozaki et al. Jun 2003 B2
6589030 Ozaki Jul 2003 B2
6595762 Khanwilkar et al. Jul 2003 B2
6605032 Benkowski et al. Aug 2003 B2
6609883 Woodard et al. Aug 2003 B2
6610004 Viole et al. Aug 2003 B2
6623420 Reich et al. Sep 2003 B2
6641378 Davis et al. Nov 2003 B2
6641558 Aboul-Hosn et al. Nov 2003 B1
6688861 Wampler Feb 2004 B2
6692318 McBride Feb 2004 B2
6698097 Miura et al. Mar 2004 B1
6709418 Aboul-Hosn et al. Mar 2004 B1
6716157 Goldowsky Apr 2004 B2
6716189 Jarvik et al. Apr 2004 B1
6732501 Yu et al. May 2004 B2
6749598 Keren et al. Jun 2004 B1
6776578 Belady Aug 2004 B2
6790171 Griindeman et al. Sep 2004 B1
6794789 Siess et al. Sep 2004 B2
6808371 Niwatsukino et al. Oct 2004 B2
6817836 Nose et al. Nov 2004 B2
6846168 Davis et al. Jan 2005 B2
6860713 Hoover Jan 2005 B2
6884210 Nose et al. Apr 2005 B2
6935344 Aboul-Hosn et al. Aug 2005 B1
6926662 Aboul-Hosn et al. Sep 2005 B1
6942672 Heilman et al. Sep 2005 B2
6949066 Beamson et al. Sep 2005 B2
6966748 Woodard et al. Nov 2005 B2
6974436 Aboul-Hosn et al. Dec 2005 B1
6991595 Burke et al. Jan 2006 B2
7010954 Siess et al. Mar 2006 B2
7011620 Siess Mar 2006 B1
7022100 Aboul-Hosn et al. Apr 2006 B1
7048681 Tsubouchi et al. May 2006 B2
7089059 Pless Aug 2006 B1
7090401 Rahman et al. Aug 2006 B2
7112903 Schob Sep 2006 B1
7122019 Kesten et al. Oct 2006 B1
7128538 Tsubouchi et al. Oct 2006 B2
7027875 Siess et al. Nov 2006 B2
7156802 Woodard et al. Jan 2007 B2
7160243 Medvedev Jan 2007 B2
7175588 Morello Feb 2007 B2
7202582 Eckert et al. Apr 2007 B2
7172551 Leasure Jun 2007 B2
7241257 Ainsworth et al. Oct 2007 B1
7284956 Nose et al. Oct 2007 B2
7331921 Viole et al. Feb 2008 B2
7335192 Keren et al. Feb 2008 B2
7393181 McBride et al. Jul 2008 B2
7431688 Wampler et al. Oct 2008 B2
7329236 Kesten et al. Dec 2008 B2
7462019 Allarie et al. Dec 2008 B1
7467930 Ozaki et al. Dec 2008 B2
7470246 Mori et al. Dec 2008 B2
7476077 Woodard et al. Jan 2009 B2
7491163 Viole et al. Feb 2009 B2
7575423 Wampler Aug 2009 B2
7645225 Medvedev et al. Jan 2010 B2
7660635 Verness et al. Feb 2010 B1
7699586 LaRose et al. Apr 2010 B2
7748964 Yaegashi et al. Jul 2010 B2
7731675 Aboul-Hosn et al. Aug 2010 B2
7802966 Wampler et al. Sep 2010 B2
7841976 McBride et al. Nov 2010 B2
7862501 Woodard Jan 2011 B2
7888242 Tanaka et al. Feb 2011 B2
7934909 Nuesser et al. May 2011 B2
7972122 LaRose et al. Jul 2011 B2
7976271 LaRose et al. Jul 2011 B2
7997854 LaRose et al. Aug 2011 B2
8007254 LaRose et al. Aug 2011 B2
8096935 Sutton et al. Jan 2012 B2
8123669 Siess et al. Feb 2012 B2
8152493 LaRose et al. Apr 2012 B2
8177703 Smith et al. May 2012 B2
8226373 Yaehashi Jul 2012 B2
8282359 Ayre et al. Oct 2012 B2
8283829 Yamamoto et al. Oct 2012 B2
8366381 Woodard et al. Feb 2013 B2
8403823 Yu et al. Mar 2013 B2
8512012 Mustafa et al. Aug 2013 B2
8535211 Campbell et al. Sep 2013 B2
8585290 Bauer Nov 2013 B2
8686674 Bi et al. Apr 2014 B2
8770945 Ozaki et al. Jul 2014 B2
8821365 Ozaki et al. Sep 2014 B2
8827661 Mori Sep 2014 B2
8652024 Yanai et al. Oct 2014 B1
8864644 Yomtov Oct 2014 B2
8870552 Ayre et al. Oct 2014 B2
8968174 Yanai et al. Mar 2015 B2
9039595 Ayre et al. May 2015 B2
9067005 Ozaki et al. Jun 2015 B2
9068572 Ozaki et al. Jun 2015 B2
9109601 Mori Aug 2015 B2
9132215 Ozaki et al. Sep 2015 B2
9133854 Okawa et al. Sep 2015 B2
9371826 Yanai et al. Jun 2016 B2
9381285 Ozaki et al. Jul 2016 B2
9382908 Ozaki et al. Jul 2016 B2
9410549 Ozaki et al. Aug 2016 B2
9556873 Yanai et al. Jan 2017 B2
20010039369 Terentiev Nov 2001 A1
20020051711 Ozaki May 2002 A1
20020058994 Hill et al. May 2002 A1
20020094281 Khanwilkar et al. Jul 2002 A1
20020095210 Finnegan et al. Jul 2002 A1
20030023302 Moe et al. Jan 2003 A1
20030045772 Reich et al. Mar 2003 A1
20030072656 Niwatsukino et al. Apr 2003 A1
20030144574 Heilman et al. Jul 2003 A1
20030163019 Goldowsky Aug 2003 A1
20030199727 Burke Oct 2003 A1
20030236488 Novak Dec 2003 A1
20030236490 Novak Dec 2003 A1
20040007515 Geyer Jan 2004 A1
20040015232 Shu et al. Jan 2004 A1
20040024285 Muckter Feb 2004 A1
20040030381 Shu Feb 2004 A1
20040064012 Yanai Apr 2004 A1
20040143151 Mori et al. Jul 2004 A1
20040145337 Morishita Jul 2004 A1
20040152944 Medvedev et al. Aug 2004 A1
20040171905 Yu et al. Sep 2004 A1
20040210305 Shu et al. Oct 2004 A1
20040215050 Morello Oct 2004 A1
20040263341 Enzinna Dec 2004 A1
20050004418 Morello Jan 2005 A1
20050008496 Tsubouchi et al. Jan 2005 A1
20050025630 Ayre et al. Feb 2005 A1
20050043665 Vinci et al. Feb 2005 A1
20050073273 Maslov et al. Apr 2005 A1
20050089422 Ozaki et al. Apr 2005 A1
20050131271 Benkowski et al. Jun 2005 A1
20050141887 Lelkes Jun 2005 A1
20050194851 Eckert et al. Sep 2005 A1
20050261542 Abe et al. Nov 2005 A1
20050287022 Yaegashi et al. Dec 2005 A1
20060024182 Akdis et al. Feb 2006 A1
20060055274 Kim Mar 2006 A1
20060127227 Mehlhorn et al. Jun 2006 A1
20070073393 Kung et al. Mar 2007 A1
20070078293 Shambaugh, Jr. Apr 2007 A1
20070095648 Wampler et al. Apr 2007 A1
20070114961 Schwarzkopf May 2007 A1
20070134993 Tamez et al. Jun 2007 A1
20070189648 Kita et al. Aug 2007 A1
20070213690 Phillips et al. Sep 2007 A1
20070231135 Wampler et al. Oct 2007 A1
20070253842 Horvath et al. Nov 2007 A1
20070282298 Mason Dec 2007 A1
20070297923 Tada Dec 2007 A1
20080007196 Tan et al. Jan 2008 A1
20080021394 LaRose et al. Jan 2008 A1
20080030895 Obara et al. Feb 2008 A1
20080119777 Vinci et al. May 2008 A1
20080124231 Yaegashi May 2008 A1
20080183287 Ayre Jul 2008 A1
20080211439 Yokota et al. Sep 2008 A1
20080281146 Morello Nov 2008 A1
20090041595 Garzaniti et al. Feb 2009 A1
20090060743 McBride et al. Mar 2009 A1
20090074336 Engesser et al. Mar 2009 A1
20090099406 Salmonsen et al. Apr 2009 A1
20090171136 Shambaugh, Jr. Jul 2009 A1
20090257693 Aiello Oct 2009 A1
20090318834 Fujiwara et al. Dec 2009 A1
20100185280 Ayre et al. Jun 2010 A1
20100168534 Matsumoto et al. Jul 2010 A1
20100222634 Poirier Sep 2010 A1
20100234835 Horikawa et al. Sep 2010 A1
20100256440 Maher et al. Oct 2010 A1
20100262039 Fujiwara et al. Oct 2010 A1
20100266423 Gohean et al. Oct 2010 A1
20100305692 Thomas et al. Dec 2010 A1
20100324465 Vinci et al. Dec 2010 A1
20110015732 Kanebako Jan 2011 A1
20110112354 Nishimura et al. May 2011 A1
20110118766 Reichenbach et al. May 2011 A1
20110118829 Hoarau et al. May 2011 A1
20110118833 Reichenbach et al. May 2011 A1
20110129373 Mori Jun 2011 A1
20110160519 Arndt et al. Jun 2011 A1
20110218383 Broen et al. Sep 2011 A1
20110218384 Bachman et al. Sep 2011 A1
20110218385 Bolyard et al. Sep 2011 A1
20110237978 Fujiwara et al. Sep 2011 A1
20110243759 Ozaki Oct 2011 A1
20110318203 Ozaki et al. Dec 2011 A1
20120003108 Ozaki et al. Jan 2012 A1
20120016178 Woodard et al. Jan 2012 A1
20120022645 Burke Jan 2012 A1
20120035411 LaRose et al. Feb 2012 A1
20120078030 Bourque Mar 2012 A1
20120078031 Burke et al. Mar 2012 A1
20120095280 Timms Apr 2012 A1
20120095281 Reichenbach et al. Apr 2012 A1
20120130152 Ozaki et al. May 2012 A1
20120226350 Ruder et al. Sep 2012 A1
20120243759 Fujisawa Sep 2012 A1
20120245681 Casas et al. Sep 2012 A1
20120253103 Jarvik Oct 2012 A1
20120308363 Ozaki et al. Dec 2012 A1
20130030240 Schima et al. Jan 2013 A1
20130121821 Ozaki et al. May 2013 A1
20130158521 Sobue Jun 2013 A1
20130170970 Ozaki et al. Jul 2013 A1
20130178694 Jeffery et al. Jul 2013 A1
20130225909 Dormanen et al. Aug 2013 A1
20130243623 Okawa et al. Sep 2013 A1
20130289334 Badstibner et al. Oct 2013 A1
20130331711 Mathur et al. Dec 2013 A1
20140030122 Ozaki et al. Jan 2014 A1
20140066690 Siebenhaar et al. Mar 2014 A1
20140066691 Siebenhaar Mar 2014 A1
20140100413 Casas et al. Apr 2014 A1
20140107399 Spence Apr 2014 A1
20140142367 Ayre et al. May 2014 A1
20140155682 Jeffery et al. Jun 2014 A1
20140200389 Yanai et al. Jul 2014 A1
20140205467 Yanai et al. Jul 2014 A1
20140241904 Yanai et al. Aug 2014 A1
20140275721 Yanai et al. Sep 2014 A1
20140275727 Bonde et al. Sep 2014 A1
20140296615 Franano Oct 2014 A1
20140309481 Medvedev et al. Oct 2014 A1
20140314597 Allaire et al. Oct 2014 A1
20140323796 Medvedev et al. Oct 2014 A1
20140343352 Arndt et al. Nov 2014 A1
20150017030 Ozaki et al. Jan 2015 A1
20150023803 Fritz et al. Jan 2015 A1
20150078936 Mori Mar 2015 A1
20150306290 Rosenberg et al. Oct 2015 A1
20150367048 Brown et al. Dec 2015 A1
20150374892 Yanai et al. Dec 2015 A1
20160058929 Medvedev et al. Mar 2016 A1
20160058930 Medvedev et al. Mar 2016 A1
20160228628 Medvedev et al. Aug 2016 A1
20160235899 Yu et al. Aug 2016 A1
20160235900 Yanai et al. Aug 2016 A1
20160281720 Yanai et al. Sep 2016 A1
20160281728 Ozaki et al. Sep 2016 A1
Foreign Referenced Citations (111)
Number Date Country
1347585 May 2002 CN
1462344 Dec 2003 CN
102239334 Nov 2011 CN
102341600 Feb 2012 CN
2945662 Sep 1999 EP
971212 Jan 2000 EP
1113117 Jul 2001 EP
1327455 Jul 2003 EP
1430919 Jun 2004 EP
1598087 Mar 2005 EP
1526286 Apr 2005 EP
1495773 Nov 2006 EP
2292282 Mar 2011 EP
2298375 Mar 2011 EP
2372160 Oct 2011 EP
2405140 Jan 2012 EP
2405141 Jan 2012 EP
2461465 Jun 2012 EP
2538086 Dec 2012 EP
2554191 Feb 2013 EP
2594799 May 2013 EP
2618001 Jul 2013 EP
2693609 Feb 2014 EP
2948202 Dec 2015 EP
2961987 Jan 2016 EP
3013385 May 2016 EP
58-9535 Jan 1983 JP
61-293146 Dec 1986 JP
H02-007780 Jan 1990 JP
H02-033590 Mar 1990 JP
04-091396 Mar 1992 JP
04-148094 May 1992 JP
05-021197 Mar 1993 JP
06-014538 Feb 1994 JP
06-053790 Jul 1994 JP
2006-070476 Sep 1994 JP
2006-245455 Sep 1994 JP
07-014220 Mar 1995 JP
07-042869 Aug 1995 JP
07-509156 Oct 1995 JP
09-122228 May 1997 JP
10-331841 Dec 1998 JP
11-244377 Sep 1999 JP
H11-241695 Sep 1999 JP
2001-309628 Nov 2001 JP
2003-501155 Jan 2003 JP
2003-135592 May 2003 JP
2004-166401 Jun 2004 JP
2004-209240 Jul 2004 JP
2004-332566 Nov 2004 JP
2004-346925 Dec 2004 JP
2005-094955 Apr 2005 JP
2005-127222 May 2005 JP
2005-245138 Sep 2005 JP
2005-270345 Oct 2005 JP
2005-270415 Oct 2005 JP
2005-287599 Oct 2005 JP
2006-167173 Jun 2006 JP
2007-002885 Jan 2007 JP
2007-043821 Feb 2007 JP
2007-089972 Apr 2007 JP
2007-089974 Apr 2007 JP
2007-215292 Aug 2007 JP
2007-247489 Sep 2007 JP
2008-011611 Jan 2008 JP
2008-104278 May 2008 JP
2008-132131 Jun 2008 JP
2008-99453 Aug 2008 JP
2008-193838 Aug 2008 JP
2008-297997 Dec 2008 JP
2008-301634 Dec 2008 JP
2006-254619 Sep 2009 JP
2010-133381 Jun 2010 JP
2010-136863 Jun 2010 JP
2010-203398 Sep 2010 JP
2010-209691 Sep 2010 JP
2010-261394 Nov 2010 JP
2011-169166 Sep 2011 JP
2012-021413 Feb 2012 JP
2012-062790 Mar 2012 JP
5171953 Mar 2013 JP
5572832 Aug 2014 JP
5656835 Jan 2015 JP
1993-07388 Apr 1993 WO
94-14226 Jun 1994 WO
1996-31934 Oct 1996 WO
1997-42413 Nov 1997 WO
2000-64509 Nov 2000 WO
2004-098677 Nov 2004 WO
2005-011087 Feb 2005 WO
2005-028000 Mar 2005 WO
2005-034312 Apr 2005 WO
2006-053384 May 2006 WO
2009-157408 Dec 2009 WO
2010-067682 Jun 2010 WO
2010-101082 Sep 2010 WO
2010-101107 Sep 2010 WO
2011-013483 Feb 2011 WO
2012-036059 Mar 2012 WO
2012-040544 Mar 2012 WO
2012-047550 Apr 2012 WO
2012-132850 Oct 2012 WO
2014-113533 Jul 2014 WO
2014-116676 Jul 2014 WO
2014-133942 Sep 2014 WO
2014-179271 Nov 2014 WO
2016-033131 Mar 2016 WO
2016-033133 Mar 2016 WO
2016-130846 Aug 2016 WO
2016-130944 Aug 2016 WO
2016-130989 Aug 2016 WO
Non-Patent Literature Citations (49)
Entry
Asama, J., et al., “A Compact Highly Efficient and Low Hemolytic Centrifugal Blood Pump With a Magnetically Levitated Impeller”, Artificial Organs, vol. 30, No. 3, Mar. 1, 2006 (Mar. 1, 2006), pp. 160-167.
Asama, J., et al.,“A New Design for a Compact Centrifugal Blood Pump with a Magnetically Levitated Rotor”, Asaio Jopurnal, vol. 50, No. 6, Nov. 1, 2004 (Nov. 1, 2004), pp. 550-556.
Asama, et al., “Suspension Performance of a Two-Axis Actively Regulated Consequent-Pole Bearingless Motor,” IEEE Transactions on Energy Conversion, vol. 28, No. 4, Dec. 2013, 8 pages.
European Search report Issued in European Patent Application No. 10748702.7, dated Apr. 2, 2013, all pages.
Extended European Search Report issued in European Patent Application No. EP 10748677.1, dated Nov. 19, 2012, all pages.
Extended European Search Report dated Jun. 18, 2015 in in European Patent Application No. 11825062.0, all pages.
Extended European Search Report issued in European Patent Application No. EP 11806627.3, dated Oct. 8, 2014, all pages.
Extended European Search Report dated Apr. 2, 2015 in European Patent Application No. EP 09770118.9 filed Jun. 22, 2009, all pages.
International Search Report (PCT-ISA-210) dated Jul. 14, 2009, by Japanese Patent Office as the International Searching Authority for International Application No. PCT-JP2009-061318, all pages.
International Search Report and Written Opinion issued in PCT-JP2011-050925, dated Apr. 12, 2011, all pages.
International Search Report and Written Opinion issued in PCT-JP2011-054134, dated Apr. 12, 2011, all pages.
International Search Report and Written Opinion issued in PCT-JP2011-064768, dated Sep. 13, 2011, all pages.
International Search Report and Written Opinion issued in PCT-JP2011-070450, dated Dec. 13, 2011, all pages.
International Search Report and Written Opinion of PCT-US2014-012448 dated Feb. 19, 2014, all pages.
International Search Report and Written Opinion of PCT-US2014-011786 dated May 5, 2014, all pages.
International Search Report and Written Opinion of PCT-US2014-012502 dated May 9, 2014, all pages.
International Search Report and Written Opinion of PCT-US2014-012511 dated May 14, 2014, all pages.
International Preliminary Report on Patentability dated Aug. 6, 2015 for International Patent Application No. PCT-US2014-012511 filed on Jan. 22, 2014, all pages.
International Preliminary Report on Patentability dated Aug. 6, 2015 for International Patent Application No. PCT-US2014-012502 filed on Jan. 22, 2014, all pages.
International Preliminary Report on Patentability dated Feb. 25, 2016 for International Patent Application No. PCT-US2014-035798 filed on Apr. 29, 2014, all pages.
Kosaka, et al., “Operating Point Control Systemt for a Continuous Flow Artificial Heart: In Vitro Study,” ASAIO Journal 2003, all pages.
Neethu, S., et al., “Novel design, optimization and realization of axial flux motor for implantable blood pump”, Power Electronics, Drives and Energy Systems (PEDES) & 2010 Power Indian, 2010 Joint International Conference on, IEEE, Dec. 20, 2010 (Dec. 20, 2010), pp. 1-6.
Sandtner, J., et al., “Electrodynamic Passive Magnetic Bearing with Planar Halbach Arrays”, Aug. 6, 2004 (Aug. 6, 2004), retrieved from the internet: <http:--www.silphenix.ch-lexington.pdf>, all pages.
Supplementary European Search Report issued in European Application No. 09831788.6, dated Jan. 7, 2013, 7 pages.
Terumo Heart, Inc., “Handled With Care—Significantly Reduce the Risk of Cell Damage,” Terumo brochure, Apr. 2010, 2 pages.
Yamazaki, et al., “Development of a Miniature Intraventricular Axial Flow Blood Pump,” ASAIO Journal, 1993, 7 pages.
European office action dated Jan. 27, 2016 for EP 10804230.0, all pages.
Extended European Search Report dated Feb. 4, 2016 in European Patent Application No. EP 12764433.4, filed Mar. 12, 2012, all pages.
International Preliminary Report on Patentability dated Jul. 30, 2015 for International Patent Application No. PCT/US2014/011786, filed on Jan. 16, 2014, all pages.
International Search Report and Written Opinion of PCT/US2014/017932, dated Jun. 16, 2014, all pages.
International Preliminary Report on Patentability dated Sep. 11, 2015 for International Patent Application No. PCT/US2014/017932, filed on Feb. 24, 2014, all pages.
International Search Report and Written Opinion of PCT/US2014/035798, dated Feb. 11, 2016, all pages.
International Search Report and Written Opinion of PCT/US2016/017611, dated May 16, 2016, all pages.
International Search Report and Written Opinion of PCT/US2016/017791, dated May 16, 2016, all pages.
Japanese office action dated Dec. 11, 2015 JP 2013-507344, all pages.
International Search Report and Written Opinion of PCT/US2016/017812, dated Jun. 7, 2016, all pages.
International Search Report and Written Opinion of PCT/US2016/017864, dated Jun. 8, 2016, all pages.
Decision to Grant for JP 2013-507344 dated Jun. 14, 2016, all pages.
International Search Report and Written Opinion of PCT/US2015/046844, dated Oct. 27, 2015, all pages.
International Search Report and Written Opinion of PCT/US2015/046846, dated Oct. 27, 2015, all pages.
European office action dated Jul. 22, 2016 for European Patent Application No. EP 09770118.9, all pages.
European office action dated Sep. 8, 2016 for EP 14741174, all pages.
Extended European Search Report for EP 14743371 dated Sep. 29, 2016, all pages.
European office action dated Oct. 31, 2016 for EP 10804230.0, all pages.
European Office Action issued in Application No. EP 11825062 dated Jul. 19, 2016, all pages.
Gieras, et al., “Advancements in Electric Machines”, Nov. 14, 2008, pp. 43-48.
International Search Report and Written Opinion of PCT/US2016/062284, dated Feb. 24, 2017, all pages.
Extended European Search Report dated Jul. 30, 2018 in European Patent Application No. 16749989.6, all pages.
Notice of Reasons for Refusal dated Jul. 14, 2020 in Japanese Patent Application No. 2017-542484, 8 pages.
Related Publications (1)
Number Date Country
20190301467 A1 Oct 2019 US
Provisional Applications (1)
Number Date Country
62115318 Feb 2015 US
Continuations (1)
Number Date Country
Parent 15041987 Feb 2016 US
Child 16443471 US