blood pump

Abstract

To provide a blood pump having a small outer diameter.SOLUTION: An intravascular blood pump 1 comprises a pump casing 2 having a blood flow inlet 21 and a blood flow outlet 22, and an impeller 3 arranged in the pump casing 2 so as to be rotatable about an axis of rotation, where the impeller 3 has blades 31 sized and shaped for conveying blood from the blood flow inlet 21 to the blood flow outlet 22. The blood pump 1 further comprises a drive unit 4 for rotating the impeller 3, the drive unit 4 comprising a plurality of posts 40 arranged about the axis of rotation 10, where each of the posts 40 includes a shaft portion 41 and a head portion 42. Coil windings 47 around the posts are sequentially controllable to create a rotating magnetic field. The drive unit 4 further comprises a back plate 50 which engages ends 44 of the shaft portions 41 of the posts 40 opposite the head portions 42.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a blood pump, and more particularly to an intravascular blood pump that is percutaneously inserted into a patient's blood vessel to assist blood flow within the patient's blood vessel. The blood pump has an improved drive unit that allows for a reduction in the outer diameter of the blood pump. [Background technology]

[0002] Various types of blood pumps are known, such as axial blood pumps, centrifugal blood pumps, or mixed-flow blood pumps in which blood flow is achieved by both axial and radial forces. Intravascular blood pumps are inserted into a patient's blood vessel, such as the aorta, by a catheter. Blood pumps typically include a pump casing having a blood inlet and a blood outlet connected by a passageway. An impeller or rotor is rotatably supported within the pump casing to induce blood flow along the passageway from the blood inlet to the blood outlet, and the impeller includes blades for transporting the blood.

[0003] Blood pumps are typically driven by a drive unit, which may be an electric motor. For example, U.S. Patent Application Publication No. 2011 / 0238172A1 discloses an extracorporeal blood pump having an impeller that can be magnetically coupled to an electric motor. The impeller includes a magnet positioned adjacent to a magnet in the electric motor. Rotation of the motor is transmitted to the impeller through attractive forces between the magnets in the impeller and the motor. To reduce the number of rotating parts, U.S. Patent Application Publication No. 2011 / 0238172A1 also discloses the use of a rotating magnetic field. The drive unit includes multiple static struts arranged around a rotation axis, each strut carrying a wire coil winding and acting as a magnetic core. To generate the rotating magnetic field, a control unit continuously supplies a voltage to the coil winding. To provide a sufficiently strong magnetic coupling, the magnetic force must be strong enough, which can be achieved by supplying a sufficiently strong current to the drive unit or by providing a large magnet, which increases the overall diameter of the blood pump. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention therefore aims to provide a blood pump, preferably an intravascular or transvalvular blood pump, with magnetic coupling between the drive unit and the impeller, which has a compact design, in particular an outer diameter that is small enough to allow the blood pump to be inserted transvascularly, transvenously, transarterially or transvalvularly. [Means for solving the problem]

[0005] This object is achieved according to the invention by a blood pump having the features of independent claim 1. Preferred embodiments and further developments of the invention are specified in the claims dependent on independent claim 1.

[0006] According to the present invention, a blood pump, preferably an intravascular blood pump and which may be one of an axial flow blood pump, a centrifugal blood pump, and a mixed-type blood pump, includes a drive unit for rotating an impeller. The drive unit includes a plurality of struts arranged around a rotation axis, such as at least two, at least three, at least four, at least five, or preferably six struts. A greater number, such as eight, ten, or twelve, may also be possible. The number of struts is preferably an even number for balanced impeller control, but may be an odd number, such as three or five. Each strut includes a shaft portion and a head portion, with the head portion facing the impeller. To generate a rotating magnetic field, a coil winding is arranged around the shaft portion of each of the struts, and the coil winding is continuously controllable to generate the rotating magnetic field. The impeller includes at least one magnet arranged to magnetically couple the impeller to the drive unit, i.e., to interact with the rotating magnetic field to cause rotation of the impeller.

[0007] The drive unit, which generates a rotating electromagnetic field, reduces the number of moving parts compared to a typical electric motor, thereby simplifying the blood pump's mechanism. This also reduces wear because contact bearings for the electric motor are not required. The magnetic coupling between the drive unit and the impeller not only causes the impeller to rotate, but also allows for precise alignment of the impeller. Specifically, the magnetic coupling can provide bearings in both the axial and radial directions.

[0008] To increase the density of the magnetic coupling between the drive unit and the impeller magnets, it may be advantageous to activate several struts simultaneously, where "activating" means supplying power to each coil winding to generate a respective magnetic pole. For example, depending on the number of struts and the number of impeller magnets, more than half the struts may be activated simultaneously, such as four out of six struts. The arrangement of activated and deactivated struts is preferably rotationally symmetric, and the struts are preferably controlled in pairs.

[0009] The drive unit further includes a backplate that engages with the ends of the shaft portions of the plurality of struts opposite the head portions. In one embodiment, the backplate may include a plurality of openings, preferably spaced at regular angular intervals around the axis of rotation, for receiving the ends of the shaft portions. However, it will be understood that the struts may be permanently or releasably attached, connected, or secured to the backplate by other means. The backplate specifically serves to close the magnetic flux circuit to facilitate and enhance magnetic flux generation and improve coupling performance. Because the backplate enhances magnetic flux, the overall diameter of the blood pump can be reduced, which is particularly advantageous for intravascular blood pumps. The configuration including the struts with the backplate further enables higher frequencies for the blood pump, i.e., the blood pump can operate at higher speeds. Furthermore, because the backplate engages the struts, it provides structural stability to the strut assembly.

[0010] The backplate may be made of magnetic steel or other material suitable for closing a magnetic flux circuit, preferably cobalt steel. The diameter of the backplate may be about 3 mm to 9 mm, such as 5 mm or 6 mm to 7 mm. The thickness of the backplate may be about 0.5 mm to about 2.5 mm, such as 1.5 mm. The outer diameter of the blood pump may be about 4 mm to about 10 mm, preferably about 6 mm. The outer diameter of the multiple strut arrangement, specifically the maximum outer diameter of the multiple strut arrangement measured at the head portion of the struts, may be about 3 mm to 8 mm, such as 4 mm to 6 mm, preferably 5 mm.

[0011] The dimensions of the struts, specifically their length and cross-sectional area, may vary and depend on various factors. Unlike the dimensions of the blood pump, such as its outer diameter, which depend on the application of the blood pump, the dimensions of the struts are determined by the electromagnetic properties of the drive unit, which are adjusted to achieve the desired performance. One of these factors is the magnetic flux density achieved by the minimum cross-sectional area of ​​the struts. The smaller the cross-sectional area, the higher the current required to achieve the desired magnetic flux. However, a higher current generates more heat in the coil wire due to electrical resistance. That is, "thin" struts are preferred to reduce the overall size, but this requires a large current, resulting in undesirable heat. The heat generated in the wire also depends on the length and diameter of the wire used for the coil winding. To minimize winding losses (called "copper loss" or "copper power loss" when copper wire is used, and copper wire is typically used), a short wire length and a large wire diameter are preferred. In other words, a smaller wire diameter generates more heat for the same current compared to a thicker wire, and a preferred wire diameter is, for example, 0.05 mm to 0.2 mm, such as 0.1 mm. Additional factors affecting the dimensions of the support and the performance of the drive unit are the number of coil turns and the outer diameter of the turns, i.e., the outer diameter of the support including the turns. Multiple turns may be arranged in two or more layers around each support, for example, two or three layers. However, the greater the number of layers, the more heat will be generated due to the increased length of the wire in the outer layers, which have a larger turn diameter. The increased wire length may generate more heat due to the greater resistance of a longer wire compared to a shorter wire. Therefore, a single layer of turns with a small turn diameter should be preferred.

[0012] A typical number of turns may be from about 50 to about 150, for example 56 or 132, depending on the length of the strut.

[0013] In one embodiment, the impeller may also include a yoke or backplate attached to at least one magnet of the impeller, for example, between the magnet and the blades, preferably on the side of the impeller facing away from the drive unit. Similar to the backplate attached to the end of the shaft of the support, the impeller yoke or backplate serves to close the magnetic flux circuit to enhance magnetic flux generation and improve coupling performance. The impeller yoke or backplate may be made of magnetic steel, preferably cobalt steel.

[0014] The support pole may also be made of magnetic steel. The drive unit, including the support pole and back plate, is preferably made of cobalt steel. The use of cobalt steel contributes to reducing the size of the pump, particularly its diameter. Of all magnetic steels, cobalt steel has the highest magnetic permeability and the highest saturation magnetic flux density, generating the most magnetic flux for the same amount of material.

[0015] It may be further advantageous to the efficiency and performance of the drive unit if the posts are magnetically isolated from one another. Thus, magnetically insulating material may be disposed between the head portions of adjacent posts to separate the posts from one another and keep their respective magnetic fields within their respective posts. The magnetically insulating material may be a magnetic material whose magnetic field keeps the electromagnetic field generated by the coil windings within their respective posts. To avoid short circuits between the posts, at least an air gap or other insulating, i.e., electrically non-conductive, material may be provided between the head portions of the posts.

[0016] In one embodiment, the head portion of at least one of the struts, preferably each strut, has an upper surface inclined at an angle relative to a plane perpendicular to the rotation axis. The distance between the rotation axis and the radial center of the inclined surface can be equal to or less than the distance between the rotation axis and the radial center of the cross-sectional area of ​​the shaft portion of each strut. The radial center of a surface or area is the center between the radially innermost point and the radially outermost point of that surface or area. In other words, the inclined upper surface of the head portion, which is the surface facing the impeller, can extend obliquely or be inclined at an angle relative to the rotation axis, and more than half of the inclined surface can be located radially inward relative to the center of the shaft portion. This allows the outer diameter of the drive unit, and therefore the blood pump, to be kept to the minimum required to magnetically couple the drive unit to the impeller. This reduced-diameter design is particularly advantageous for intravascular blood pumps that are placed within a patient's blood vessels during operation and can be deployed via a catheter. Furthermore, the inclined coupling surface provides radial centering of the impeller. The aforementioned angle is preferably 45° relative to a plane perpendicular to the axis of rotation, but may be between about 0° and about 90°, preferably between about 30° and about 60°, and more preferably between about 40° and about 50°. The inclined surfaces of the struts preferably face radially outward, i.e., they form a convex shape. Alternatively, the inclined surfaces may face radially inward, forming a concave shape.

[0017] Preferably, all of the struts are identical so that the drive unit is symmetrical about the axis of rotation. However, it will be understood that the struts do not have to be strictly identical, provided they are compatible with forming a drive unit according to the invention. However, it is preferred that the shaft portions have the same length and that the inclined surfaces of the head portions have the same inclination angle. The different struts may be arranged irregularly or regularly, such as in an alternating pattern, to form the drive unit.

[0018] The inclined surface of the head portion of the at least one strut, preferably each of the head portions, may be radially aligned with the radially outermost surface of the coil winding of the respective strut, or may be positioned radially inward or outward relative to that surface. The inclined surface preferably extends radially inward toward the rotation axis beyond the respective shaft portion to maximize the surface area of ​​the magnetic bearing while minimizing the outer diameter of the drive unit. For example, in an axial projection, i.e., as seen in a top view in the axial direction, the inclined surface of the head portion may be positioned within the coil winding or at least aligned with the shaft or coil winding in the axial direction. In another embodiment, the head portion may extend radially and / or circumferentially beyond the outer periphery of the coil winding. The head portion may have a cross-sectional dimension in a plane perpendicular to the rotation axis that is larger than that of the respective shaft portion, and each coil winding preferably does not extend beyond the head portion, at least radially. In other words, the head portion may form a shoulder that can act not only as an axial stop but also as a radial limit for the coil winding.

[0019] At least one of the head portions, and preferably all of the head portions, may be substantially triangular or trapezoidal in cross section along a plane containing the axis of rotation. When assembled, the angled or sloping surfaces of the head portions may together form a conical or substantially conical surface, e.g., a surface with facets but roughly forming a conical surface. Generally, the shape of the formed surface may be convex. Illustratively, the head portions may be brought together like pie slices to form a circular configuration with a conical upper surface. At least one magnet of the impeller may have or form a conical or substantially conical recess that substantially matches the size and shape of the conical surface formed by the head portion of the support. Generally, the magnet may form a concave surface facing the convex surface formed by the support to improve magnetic coupling. In another embodiment, the arrangement of the concave and convex surfaces may be reversed, i.e., the head portion of the support may form a conical recess, while the magnet forms a convex conical surface.

[0020] The convex and concave surfaces of the drive unit and impeller, respectively, may form a gap such that the distance between the surfaces is constant. However, the gap spacing is preferably not constant, but is selected so that the cross-sectional area of ​​the gap is constant in the radial direction when viewed circumferentially. In the latter case, the distance between the surfaces increases toward the axis of rotation. Combinations are also possible. The shape and size of the gap between the impeller and drive unit can contribute to the performance of the hydrodynamic bearing.

[0021] The magnets of the impeller may be formed as a single unit with a conical or substantially conical recess that matches the shape of the head portion of the support post, including the variable gap spacing, as described above. However, it will be understood that there may be more than one magnet, such as four, preferably six, or even eight, ten, or twelve magnets, positioned in the impeller around the axis of rotation to form the conical recess. Providing a plurality of magnets, preferably an even number, more preferably a number matching the number of support posts, is advantageous because the magnets can be positioned in alternating north / south orientations of the magnetic field without blind spots. If the magnets are formed as a single unit, blind spots may be created at the transitions between magnetic fields of different orientations.

[0022] When the impeller includes multiple magnets, the magnets can be arranged with substantially no gaps between them to increase the amount of magnetic material. However, it has been found that the efficiency of magnetic coupling is not reduced when the magnets are separated by gaps, particularly radial gaps. This is due to the properties of the magnetic field and the gap between the drive unit and the impeller. When the magnets in the impeller are close to each other, the innermost magnetic field lines arching from one magnet (north) to the adjacent magnet (south) do not extend beyond the gap between the drive unit and the impeller and therefore do not reach the drive unit. In other words, the innermost magnetic field lines do not contribute to driving the impeller. Therefore, there is no loss of efficiency if gaps are provided between the magnets in the impeller. The size of the gaps between the magnets in the impeller that can be provided without loss of drive efficiency depends on the size of the gap between the impeller and the drive unit, as can be calculated by one skilled in the art. The gaps between the magnets in the impeller can be used, for example, as washout channels.

[0023] Generally speaking, and whether the head portion forms a conical surface or not, the impeller magnets can have a surface facing the head portion of the support and can be inclined at an angle that substantially matches the angle of the inclined surface of the head portion. By way of example, the configuration can be the opposite of the above configuration, i.e., the head portion of the support can form a concave surface, such as a conical recess, and the impeller magnets can form a convex surface, such as a conical surface.

[0024] Regardless of the inclination of their respective surfaces, the impeller magnet(s) may be radially aligned with the head portion of the support post. However, in some embodiments, the impeller magnet(s) may be radially offset, e.g., radially inward or radially outward, relative to the head portion of the support post. This radial offset may improve stabilization and radial centering of the impeller because the magnetic force between the impeller and drive unit has a radial component, as opposed to when the magnets are radially aligned with the head portion of the support post, where the magnetic force is substantially only axially directed.

[0025] In one embodiment, the impeller can at least partially extend around the drive unit, specifically the head portion of the support. In other words, the impeller can have an extension that overlaps the drive unit in the circumferential direction. This means that magnetic coupling occurs not only in the area of ​​the inclined surface of the head portion of the support, but also on its radially outer side. The impeller can have an increased diameter, specifically a diameter larger than that of the drive unit, so that it can extend around the area of ​​the head portion of the support. Thus, the impeller can have a recess with a conical portion as described above and a cylindrical portion. This impeller design can improve magnetic coupling because the impeller and the drive unit are also radially coupled where the magnetic field lines extend radially. Due to the largest diameter in this area, a high torque can be generated to drive the impeller.

[0026] In one embodiment, the intravascular blood pump may further include a housing enclosing the drive unit. The housing preferably has a size and shape that matches the outer contour of the struts. Specifically, the housing may have a conical axial end surface that matches the shape of the surface formed by the inclined surfaces of the strut heads. The opposite end may be open and may engage a back plate to close the housing. The housing serves as a protector for the strut assembly, particularly against blood contact, which is particularly useful for the coil windings. The housing is preferably disposed inside the pump casing. Regardless of the presence of such a housing, the drive unit is preferably disposed inside the pump casing. The housing is preferably made of a non-magnetic and non-conductive (i.e., electrically insulating) material and provides good heat transfer. The housing material may be, for example, aluminum.

[0027] The coil windings may be embedded in an electrically non-conductive (i.e., electrically insulating) thermally conductive matrix. The matrix protects the coil windings and conducts heat generated by the coil windings. The thermally conductive matrix material may be a plastic material that includes an additive to enhance its heat transfer properties. By way of example, the matrix may include an epoxy resin with an aluminum additive. The matrix may be formed by shaping the material around and between the coil windings and subsequently curing the material.

[0028] The drive unit preferably has a central opening extending along the axis of rotation. The central opening may be formed by the head portions of the struts and may be configured to receive an elongated pin, the axial end surface of the pin being sized and dimensioned to form a bearing surface for the impeller. This configuration allows for a compact design of the blood pump, as the space between the struts is used for the pin. The other end of the pin may be supported by the pump casing. The central opening may also be provided for the insertion of a guide wire or the like, or may form a fluid path.

[0029] To enhance the washout flow through the gap between the impeller and the drive unit, a secondary set of vanes may be provided on the impeller. Specifically, the secondary vanes may be provided on the side of the magnet or magnets facing the drive unit, i.e., in the gap between the impeller and the drive unit. The washout flow may additionally or alternatively be increased by channels recessed into the surface of the magnet facing the drive unit. The channels may extend, for example, radially or helically.

[0030] In one embodiment, one or more hydrodynamic bearings may be provided to support the impeller. For example, the aforementioned secondary vanes and channels may form a hydrodynamic bearing or at least support the hydrodynamic bearing performance described above with respect to the size and shape of the gap between the impeller and the drive unit. Conversely, the surface of the drive unit facing the impeller, specifically the end surface of the housing surrounding the drive unit, may be adapted to form a hydrodynamic bearing. The hydrodynamic bearing may be axial or radial, or both axial and radial. Specifically, the conical shape of the common area between the impeller and the drive unit may form a hydrodynamic bearing in both the radial and axial directions. A radial hydrodynamic bearing may also be formed between the outer surface of the impeller and the inner surface of the pump casing. Specifically, a gap may be formed between the impeller and the pump casing, allowing a sufficient amount of blood to flow through the gap and exit the pump casing through an additional blood outlet. The primary blood flow leaves the pump casing through the blood outlet and does not flow through the gap. Hydrodynamic bearings, which are non-contact bearings, can assist the function of the drive unit by reducing frictional forces.

[0031] The foregoing summary, as well as the following detailed description of the preferred embodiments, will be better understood when read in conjunction with the accompanying drawings. For purposes of illustrating the present disclosure, reference is made to the drawings. However, the scope of the present disclosure is not limited to the specific embodiments disclosed in the drawings. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a cross-sectional view of a blood pump according to the present invention. [Figure 2] FIG. 2 is an enlarged detailed view of the blood pump of FIG. 1. [Figure 3] FIG. 10 is a perspective view of a support column of the drive unit. [Figure 4] 10(a), (b), (c), and (d) show various views of another embodiment of the support pillar. [Figure 5]A diagram of a configuration including six struts. [Figure 6] FIG. 6 is a diagram of the configuration of FIG. 5 with a back plate added. [Figure 7] FIG. 7 is a diagram of the configuration of FIG. 6, with the addition of coil windings. [Figure 8] FIG. 8 is a diagram of the configuration of FIG. 7, plus a housing. [Figure 9] (a), (b), and (c) are various views of the back plate. [Figure 10] (a), (b), and (c) are various views of the impeller magnet. [Figure 11] FIG. 10 is a diagram of another embodiment of a drive unit. [Figure 12] FIG. 10 is a diagram of another embodiment of a blood pump. [Figure 13a] 10A-10C are various views of a drive unit and impeller magnet according to another embodiment. [Figure 13b] 10A-10C are various views of a drive unit and impeller magnet according to another embodiment. [Figure 14a] FIG. 2 is a diagram illustrating the magnetic field lines between the magnets of the impeller. [Figure 14b] FIG. 2 is a diagram illustrating the magnetic field lines between the magnets of the impeller. [Figure 15] FIG. 10 is a cross-sectional view of a drive unit and impeller magnet according to another embodiment. [Figure 16] 3A-3C are diagrams illustrating the operating modes of the drive unit; DETAILED DESCRIPTION OF THE INVENTION

[0033] Referring to FIG. 1, a cross-sectional view of blood pump 1 is shown. FIG. 2 shows an enlarged view of the interior of blood pump 1. Blood pump 1 comprises pump casing 2 having blood inlet 21 and blood outlet 22. Blood pump 1 is designed as an intravascular pump, also known as a catheter pump, and is deployed within a patient's blood vessels via catheter 25. Blood inlet 21 is located at the end of a flexible cannula 23, which in use may be placed through a heart valve, such as the aortic valve. Blood outlet 22 is located on the side of pump casing 2 and may be positioned within a heart vessel, such as the aorta. Blood pump 1 is connected to catheter 25, with power lines 26 extending through catheter 25 to provide power to blood pump 1 for driving pump 1 via drive unit 4, as described in more detail below.

[0034] Blood is conveyed along a passage 24 connecting the blood inlet 21 and the blood outlet 22 (the blood flow is indicated by an arrow). An impeller 3 is provided to convey blood along the passage 24 and is rotatably mounted within the pump casing 2 around a rotation axis 10 by a first bearing 11 and a second bearing 12. The rotation axis 10 is preferably the longitudinal axis of the impeller 3. In this embodiment, both bearings 11 and 12 are contact bearings. However, at least one of the bearings 11 and 12 may be a non-contact bearing, such as a magnetic bearing or a hydrodynamic bearing. The first bearing 11 is a pivot bearing with a spherical bearing surface that allows not only rotational movement but also some pivotal movement. A pin 15 is provided and forms one of the bearing surfaces. The second bearing 12 is disposed within a support member 13 to stabilize the rotation of the impeller 3, and the support member 13 has at least one opening 14 for blood flow. Blades 31 are provided on the impeller 3 and transport blood as the impeller 3 rotates. Rotation of the impeller 3 is provided by a drive unit 4 that is magnetically coupled to magnets 32 at the end of the impeller 3. The blood pump 1 shown is a mixed type blood pump, in which the main direction of flow is axial. It will be understood that the blood pump 1 may also be a purely axial blood pump, depending on the configuration of the impeller 3, and in particular the configuration of the blades 31.

[0035] FIG. 2 shows the interior of the blood pump 1 in more detail, particularly the impeller 3 and drive unit 4. The drive unit 4 includes a plurality of struts 40, such as six struts 40, only two of which are visible in the cross-sectional view of FIG. 2. The struts 40 have a shaft portion 41 and a head portion 42. The head portion 42 is disposed adjacent to the impeller 3 to magnetically couple the drive unit 4 to the impeller 3. To this end, the impeller 3 includes a magnet 32, which in this embodiment is formed as a multi-piece magnet, as will be described in more detail with reference to FIGS. 10a-c. The magnet 32 ​​is disposed at the end of the impeller 3 facing the drive unit 4. The struts 40 are continuously controlled by a control unit (not shown) to create a rotating magnetic field for driving the blood pump 1. The magnet 32 ​​is disposed to interact with the rotating magnetic field to cause rotation of the impeller 3 about the rotation axis 10. As will be explained in more detail below with reference to FIG. 7, a coil winding is disposed around the shaft portion 41 of the post 40 .

[0036] To close the magnetic flux path, a back plate 50 is disposed at the end of the shaft portion 41 opposite the head portion 42. The strut 40 acts as a magnetic core and is made of a suitable material, such as steel or a suitable alloy, particularly cobalt steel. Similarly, the back plate 50 is made of a suitable magnetic material, such as cobalt steel. The back plate 50 strengthens the magnetic flux, thereby enabling a reduction in the overall diameter of the blood pump 1, which is important for intravascular blood pumps. For the same purpose, a yoke 37, i.e., an additional back plate, is provided on the impeller 3 on the side of the magnet 32 ​​facing away from the drive unit 4. The yoke 37 in this embodiment has a conical shape to guide blood flow along the impeller 3. The yoke 37 may also be made of cobalt steel. One or more washout channels extending toward the central bearing may be formed in the yoke 37 or the magnet 32.

[0037] Details of the drive unit 4 are shown in Figures 3 through 9, while Figure 10 shows the magnet 32 ​​of the impeller 3. Referring to Figure 3, one of the posts 40 is shown in perspective view. In this embodiment, all of the posts 40 in the assembly (i.e., six posts 40) are identical. The post 40 includes a shaft portion 41 and a head portion 42. The head portion 42 has an inclined surface 43 that, in this embodiment, is angled at 60° relative to the longitudinal axis (i.e., 30° relative to a plane perpendicular to the longitudinal axis). The shaft portion 41 includes an end portion 44 opposite the head portion 42, which has a reduced diameter for engaging the backplate 50. The head portion 42 has a larger cross-sectional dimension in a plane perpendicular to the longitudinal axis than the shaft portion 41. The head portion 42 has a side 47 that abuts the side of an adjacent post when assembled to form the drive unit 4. To avoid short-circuiting of magnetic flux between the posts 40, a slight air gap or other type of insulation is provided between the head portions 42. To further avoid short-circuiting, it may be advantageous to provide insulating material between the head portions 42 of the posts 40 that maintains the magnetic field within each of the posts 40. In other words, the head portions 42 may be separated by a magnetically insulating material. By way of example, magnets, e.g., plates of magnetic material, may be disposed between the head portions 42 to isolate the head portions 42 and their respective magnetic fields from one another. The radially inner surface 48 of the post head portion 42 forms a central opening 54. It will be understood that the transition between surfaces 43 and 48 need not be rounded.

[0038] Various views of another embodiment of the support post 40 are shown in FIG. 4, which corresponds to the previous embodiment except for slight changes in the shape of the shaft portion 41 and head portion 42. FIG. 4a shows a cross-sectional view along line AA shown in FIG. 4d, which shows a top view of the support post 40 (i.e., looking toward the head portion 42). FIG. 4b shows a perspective view of the support post 40, and FIG. 4c shows a bottom view (i.e., looking toward the end portion 44 of the shaft portion 41). The support post 40 may have an overall length of approximately 9 to 10 mm, and the head portion 42 may have a length of approximately 2 mm. In this embodiment, the head portion 42 has a surface 43 that is inclined at a 45° angle relative to the rotational or longitudinal axis. Thus, the angle 45 between the surface 43 and the lug 49 shown in FIG. 4a is 135°. The lug 49 may function as a stop when the support post 40 is assembled within a housing. Additionally, a shoulder 46 that may serve as a stop for the coil winding is formed by head portion 42. As described in connection with Figure 3, head portion 42 includes a side surface 47 and a radially inner surface 48.

[0039] FIG. 5 shows an assembly including six struts 40, as described in connection with FIG. 3. All struts 40 are identically shaped so that each head portion 42 forms a 60° arc of a circle, i.e., a 60° "pie slice." It will be understood that the assembly can include fewer or more struts, such as two, three, four, or five, or even more than six, with the angle depending on the number of struts, e.g., four struts each forming a 90° arc, or eight struts each forming a 45° arc. As already mentioned above, the number of struts 40 is preferably even, in which case diametrically opposed struts 40 can form pairs, e.g., with respect to magnetic field control, i.e., each pair of struts can be controlled as a unit to simultaneously activate the struts of each pair. The head portions 42 form a cone with a conical surface formed by the inclined surface 43. This can be seen more clearly in FIG. 6. In FIG. 6, the reduced diameter end portion 44 of the shaft portion 41 is attached to a back plate 50 .

[0040] In FIG. 7, the same configuration is shown including a coil winding 47 around the post 40. The coil winding 47 does not extend radially beyond the head portion 42, thereby providing a compact outer diameter. It will be appreciated that the maximum cross-sectional area defined by the head portion 42 is preferably used for the coil winding 47 to optimize use of the available space and minimize air gaps that act as insulators and affect the magnetic flux. Furthermore, the diameter of the shaft portion 41 of the post 40 is selected to optimize the number of turns of the coil winding 47. FIG. 8 shows a housing 60 that fits over the post configuration. The housing 60 conforms to the shape of the post configuration and includes a substantially cylindrical portion 62 and a conical end portion 61. The conical end portion 61 tapers at the same angle as the conical surface formed by the inclined surface 43 of the post head portion 42, i.e., the angle is preferably about 30° to 60°, preferably 30° or 45°, relative to a plane perpendicular to the longitudinal axis. The housing 60 is closed at an open end 63 opposite the conical end portion 61 by the back plate 50. The conical end portion 61 has a central opening 64 that aligns with the central opening 54 formed by the post 40 and the central opening 53 in the back plate 50.

[0041] The back plate 50 is shown in more detail in various views in FIG. 9 (a top view in FIG. 9a, a cross-sectional view along line AA in FIG. 9b, and a cross-sectional view along line BB in FIG. 9c). The back plate 50 has openings 51 for receiving the reduced-diameter end portions 44 of the shaft portions 41 of the posts 40. The number of openings 51 in the back plate 50 preferably matches the number of posts 40 in the drive unit 4. In the illustrated embodiment, six openings 51 are spaced at regular intervals of 60° around the rotation axis 10, with each opening 51 located the same distance from the rotation axis 10. The openings 51 are shown in the cross-sectional view of FIG. 9c as extending completely through the back plate 50. However, the openings 51 may instead extend into the back plate 50 to a certain depth rather than completely through the back plate 50. As noted above, a central opening 53 is formed to receive the bearing pin 15. The backplate 50 is made of a magnetic material, preferably cobalt steel, to close the magnetic flux path. The diameter of the backplate 50 may be approximately 5 to 7 mm. Additionally, notches 52 are provided around the periphery of the backplate 50 to receive wires 56 for connecting the coil windings 47 to a control unit 55, such as a printed circuit board (PCB), located on the backside of the backplate 50, as shown schematically by dashed lines in FIG. 9b.

[0042] Referring to FIG. 10, the magnets 32 of the impeller 3 (see FIG. 2) are shown in a top view ( FIG. 10a ), a cross-sectional view ( FIG. 10b ), and a perspective view ( FIG. 10c ). In this embodiment, six magnets 32 are provided, evenly spaced around the axis of rotation 10, with their respective magnetic field orientations alternating. Fewer or more magnets, such as four, eight, ten, or twelve magnets, may be provided. The magnets 32 form a recess 35 having a surface 33. The recess 35 matches the size and shape of the conical surface formed by the surface 43 of the head portion 42 of the post 40, as best shown in FIG. 6 , taking into account the housing 60 surrounding the drive unit 4, and in particular the conical end portion 61 ( FIG. 8 ). It will be understood that this includes the fact that the distance between the impeller 3 and the drive unit 4 may not be constant but may increase toward the axis of rotation 10, as discussed above. The recess 35 in this embodiment has a conical shape with an angle 34 of 45° relative to the rotation axis 10 or longitudinal axis. Other angles, such as 60°, are also possible depending on the shape of the drive unit 4, in particular the end surface formed by the head portion 42 of the support post 40. Furthermore, the magnet 32 ​​forms a central opening 36 for receiving the bearing pin 15, as shown in FIG. 2. The central opening 36 is aligned with the central opening 54 of the drive unit 4. As shown in FIG. 10b, the magnetic flux of the magnet 32 ​​is closed by a yoke 37. The yoke 37 may have any suitable shape depending on the shape of the impeller 3, such as a cone shape as shown in FIG. 2 or a disk shape as shown in FIG. 10b. Optionally, an encapsulation 38 is provided that encases the magnet 32 ​​and, if applicable, the yoke 37, to protect the magnet 32 ​​and the yoke 37 from corrosion.

[0043] FIG. 11 shows another embodiment of a drive unit substantially similar to the previous embodiment. This configuration includes six struts 40′ each having a respective coil winding 47 on a shaft portion 41′. As in the previous embodiment, there may be fewer or more struts 40′. The struts 40′ are preferably attached to a back plate (not shown), as in the previous embodiment. Each strut 40′ has a head portion 42′ having a different shape than the head portion 42 described above. The angle may be similar to that described above, but the inclined surface 43′ faces radially inward rather than radially outward. That is, the head portion 42′ forms a substantially conical recess. It will be understood that the impeller magnets are shaped accordingly, i.e., the magnets have a corresponding conical shape rather than the conical recess of the previous embodiment. As in the previous embodiment, the drive unit has a central opening 54′. While the head portions 42 of the posts 40 in the previous embodiments are shown either directly adjacent to one another or separated by only a small gap, the posts 40' in the embodiment of Figure 11 are separated by gaps 57' which prevent bypass or short circuits between the posts 40'. However, it will be understood that short circuits between posts should be avoided in all embodiments.

[0044] Referring to Figure 12, another embodiment of a blood pump 1 similar to the embodiment of Figures 1 and 2 is shown. Unlike the above-described embodiments, the blood pump 1 of Figure 12 has an additional radial hydrodynamic bearing. A circumferential portion 28 of the pump casing 2 or sleeve is provided to form a gap 27 between the impeller 3 and the circumferential portion 28. In addition to the blood outlet 22, a further blood outlet 29 allows blood to exit the pump casing 2 through the gap 27. The size of the gap 27 is selected to form a radial hydrodynamic bearing.

[0045] FIGS. 13a and 13b schematically illustrate the magnets 32 of the impeller and their arrangement relative to the drive unit 4. In this embodiment, four magnets 32 are provided, separated by respective gaps 66. The gaps 66, which may be formed as channels between the surfaces 33 of the magnets 32, extend radially from the central opening 36 toward the outer periphery of the magnets 32. As will be explained in more detail below with reference to FIGS. 15a and 15b, reducing the size of the magnets 32 does not result in a loss of magnetic coupling efficiency. FIG. 13b illustrates the relative arrangement of the magnets 32 and the drive unit 4, where a gap 65 is provided between the drive unit 4 (i.e., the stator) and the magnets 32 of the impeller (i.e., the rotor). The channel or gap 66 provides a centrifugal pumping effect on the blood, thereby improving cleaning of the gap 65.

[0046] 14a and 14b, the principle of magnetic coupling between the rotor, specifically the magnets 32, and the stator, i.e., the drive unit 4, is shown schematically. In FIG. 14a, the magnets 32 are not separated, or are not substantially separated, by a gap. Several exemplary magnetic field lines are shown running from north N to south S. Due to the gap 65 between the drive unit 4 and the magnets 32, the innermost magnetic field lines do not interact with the drive unit 4. This means that this portion of the magnetic field does not contribute to driving the impeller. Therefore, the efficiency of the magnetic coupling is not lost if a gap 66 is provided between the magnets 32. In FIG. 14b, the same amount of magnetic field lines reach the drive unit 4 as in FIG. 14a. As those skilled in the art know, the direction of the magnetic field lines can be calculated, and the size of the gap 66 directly depends on the size of the gap 65.

[0047] Referring to FIG. 15, another embodiment of a drive mechanism for a blood pump is shown. The drive unit 4, including a strut 40 with a coil winding 47, is substantially identical to that described above. Like reference numerals refer to like parts. As in the previous embodiment, the drive unit 4 includes a back plate 50. However, the impeller design is different. In FIG. 15, only the impeller magnet 32 ​​and yoke 37 are shown. The impeller has an enlarged diameter, specifically a larger diameter than the drive unit 4, and an axial extension 39, which extends circumferentially around the drive unit 4, specifically in the region of the head portion 42 of the strut 40. This configuration allows for improved magnetic coupling, as will be explained below.

[0048] As shown by some exemplary schematic magnetic field lines, extension 39 creates magnetic coupling between magnet 32 ​​and drive unit 4 not only in the region of inclined surface 43, but also in the region of the outer side of head portion 42 of strut 40. In this region, the magnetic field lines extend substantially radially between the rotor and stator of the blood pump, and high torque can be generated to drive the impeller. As also shown in FIG. 15 , as in all other embodiments, the magnetic field lines form a closed loop that extends through strut 40, including head portion 42 and shaft portion 41, through magnet 32, and through both end plates or yokes 50 and 37.

[0049] Referring to FIG. 16, the operating mode of the drive unit is shown schematically in an example having six struts 40a, 40b, 40c, 40d, 40e, and 40f. The struts are controlled sequentially to create a rotating magnetic field. The struts are controlled in pairs to ensure balanced impeller rotation, with diametrically opposed struts 40a and 40d, 40b and 40e, and 40c and 40f forming pairs, respectively. Magnetic density can be increased by simultaneously activating four of the six struts. FIG. 16 shows a three-step sequence, with the activated struts highlighted in each step. In the first step, struts 40a, 40c, 40d, and 40f are activated, i.e., current is supplied to their respective coil windings to create a magnetic field. In the second step, pillars 40a, 40b, 40d, and 40e are activated, while in the third step, pillars 40b, 40c, 40e, and 40f are activated. This sequence is repeated to create a rotating magnetic field.

Claims

1. A transvalve blood pump (1) configured to be placed through a heart valve, comprising: a pump casing (2) with a blood inlet (21) and a blood outlet (22); an impeller (3) arranged within said pump casing (2) so as to be rotatable about an axis of rotation (10), said impeller (3) having blades (31) sized and shaped to convey blood from said blood inlet (21) to said blood outlet (22); a drive unit (4) for rotating said impeller (3), said drive unit (4) comprising a plurality of struts (40) arranged around said axis of rotation (10); Equipped with each of the struts (40) includes a shaft portion (41) parallel to the rotation axis (10) and a head portion (42), the head portion (42) facing the impeller (3), a coil winding (47) disposed around the shaft portion (41) of each of the struts (40), the coil winding (47) being continuously controllable to generate a rotating magnetic field, the impeller (3) including at least one magnet (32) disposed to interact with the rotating magnetic field to cause rotation of the impeller (3), and the drive unit (4) further includes a back plate (50) engaging an end (44) of the shaft portion (41) opposite the head portion (42) of each of the struts (40).

2. 2. The transvalve blood pump according to claim 1, wherein the head portion (42) of at least one of the struts (40) has an upper surface (43) that is inclined at an angle with respect to a plane perpendicular to the rotation axis (10).

3. 3. The transvalve blood pump according to claim 2, wherein the distance between the rotation axis (10) and the center of the inclined upper surface (43) in the radial direction is equal to or less than the distance between the rotation axis (10) and the center of the cross-sectional area of ​​the shaft portion (41) of each of the support columns (40) in the radial direction.

4. 4. A transvalve blood pump according to claim 2 or 3, characterized in that the head portion (42) of the support (40) having the inclined upper surface (43) is substantially triangular in cross section along a plane including the rotation axis (10).

5. 5. A transvalve blood pump according to claim 2, wherein the inclined upper surfaces (43) of the head portions (42) of all the struts (40) having the inclined upper surfaces (43) together form a conical surface.

6. 6. The transvalve blood pump of claim 5, wherein the at least one magnet (32) of the impeller (3) defines a conical recess (35) that matches the size and shape of the conical surface.

7. 7. A transvalve blood pump according to claim 2, wherein the at least one magnet (32) of the impeller (3) has a surface (33) that faces the head portion (42) of one of the struts (40) having the inclined upper surface (43) and is inclined at an angle (34) that matches the angle of the inclined upper surface (43).

8. 8. The transvalve blood pump according to claim 2, wherein the angle is greater than 0° and less than 90°.

9. A transvalvular blood pump as described in any one of claims 2 to 8, characterized in that the head portion (42) of the support (40) having the inclined upper surface (43) has a cross-sectional dimension larger than that of each of the shaft portions (41) in a plane perpendicular to the rotation axis (10).

10. 10. A transvalve blood pump according to any one of claims 1 to 9, characterized in that the impeller (3) comprises at least two of the magnets (32).

11. 11. A transvalve blood pump according to any one of claims 1 to 10, characterized in that the drive unit (4) comprises at least two of the struts (40).

12. 12. The transvalve blood pump according to claim 1, wherein the back plate (50) is provided with a plurality of openings (51) arranged around the rotation axis (10) and receiving the end (44) of the shaft portion (41).

13. 13. The transvalve blood pump according to claim 1, further comprising a housing (60) surrounding the drive unit (4), wherein the housing (60) is made of a non-magnetic and electrically non-conductive material.

14. 14. A transvalve blood pump according to any one of claims 1 to 13, characterized in that the drive unit (4) has a central opening (54) extending along the rotation axis (10).

15. 15. Transvalve blood pump according to any one of claims 1 to 14, characterized in that the drive unit (4) is arranged inside the pump casing (2).

16. 16. A transvalve blood pump according to any one of claims 1 to 15, characterized in that a magnetically insulating material is disposed between the head portions (42) of adjacent struts (40).

17. 9. The transvalve blood pump of claim 8, wherein the angle is between 30° and 60°.

18. 9. The transvalve blood pump according to claim 8, wherein the angle is 45 degrees.

19. 9. The transvalve blood pump according to claim 8, wherein the inclined upper surface (43) faces radially outward.

20. 10. The transvalve blood pump according to claim 9, wherein the impeller (3) comprises at least four of the magnets (32).

21. 21. A transvalve blood pump according to claim 20, characterized in that the impeller (3) comprises six or eight of the magnets (32).

22. 22. The transvalve blood pump of any one of claims 9, 20 or 21, wherein the magnets (32) are separated by radially extending gaps (66).

23. 11. Transvalvular blood pump according to claim 10, characterized in that the drive unit (4) comprises at least four of the struts (40).

24. 24. Transvalvular blood pump according to claim 23, characterized in that the drive unit (4) comprises six or eight of the struts (40).

25. 12. The transvalve blood pump of claim 11, wherein each of the coil windings (47) does not extend beyond the head portion (42) at least radially.

26. 14. The transvalve blood pump according to claim 13, wherein the non-magnetic and electrically non-conductive material is aluminum.

27. 15. The transvalve blood pump according to claim 14, wherein the central opening (54) is adapted to receive an elongated pin (15), the axial end surface of which forms a bearing surface for the impeller (3).

28. 28. A transvalve blood pump according to any one of claims 1 to 27, characterized in that the coil winding (47) is embedded in an electrically non-conductive, thermally conductive matrix.

Images