BLOOD PUMP

Abstract

This invention concerns an intravascular blood pump for percutaneous insertion into a patient's blood vessel. The blood pump comprises a pump casing having a blood flow inlet and a blood flow outlet, an impeller arranged in said pump casing so as to be rotatable about an axis of rotation. The impeller has blades sized and shaped for conveying blood from the blood flow inlet to the blood flow outlet. The blood pump comprises a drive unit for rotating the impeller, the drive unit comprising a magnetic core including a plurality of posts arranged about the axis of rotation and a back plate connecting the posts and extending between the posts in an intermediate area. A coil winding is disposed around each of the posts. The coil windings are controllable so as to create a rotating magnetic field, wherein the impeller comprises a magnetic structure arranged to interact with the rotating magnetic field so as to cause rotation of the impeller. A material of at least a portion of at least one of the posts is integral with a material of the intermediate area of the back plate. Further, the invention concerns a method of manufacturing a magnetic core and a method of manufacturing an intravascular blood pump.

Claims

1. An intravascular blood pump for percutaneous insertion into a patient's blood vessel, comprising: a pump casing having a blood flow inlet and a blood flow outlet, an impeller arranged in said pump casing so as to be rotatable about an axis of rotation, the impeller having blades sized and shaped for conveying blood from the blood flow inlet to the blood flow outlet, a drive unit for rotating the impeller, the drive unit comprising a magnetic core including a plurality of posts arranged about the axis of rotation and a back plate connecting the posts and extending between the posts in an intermediate area, and a coil winding disposed around each of the posts, the coil windings being controllable so as to create a rotating magnetic field, wherein the impeller comprises a magnetic structure arranged to interact with the rotating magnetic field so as to cause rotation of the impeller, wherein a material of at least a portion of at least one of the posts is integral with a material of the intermediate area of the back plate.

2. Intravascular blood pump according to claim 1, wherein the magnetic core comprises or consists of a soft magnetic material which is discontinuous regarding electric conductivity in a cross-section transverse to the rotational axis.

3. Intravascular blood pump according to claim 2, wherein the soft magnetic material comprises laminated sheets of soft magnetic material.

4. Intravascular blood pump according to claim 2, wherein the sheets of soft magnetic material are oriented parallel to the axis of rotation.

5. Intravascular blood pump according to claim 2, comprising at least one weld bridging a discontinuity regarding electric conductivity in the soft magnetic material.

6. Intravascular blood pump according to claim 5, wherein at least one of the at least one weld is arranged on a surface of the back plate opposite to the posts.

7. Intravascular blood pump according to claim 5, wherein at least one of the at least one weld is arranged on an end surface of a post opposite to the back plate.

8. Method of manufacturing a magnetic core for a drive unit of an intravascular blood pump, the magnetic core having an axis of rotation and including a plurality of posts arranged about the axis of rotation and aback plate connecting the posts, said method comprising the steps of providing a monoblock of magnetically conductive material and cutting slots into the monoblock so as to create the posts, so that the posts are arranged about the axis of rotation, and the back plate, so that the back plate forms one integral piece with the posts.

9. Method according to claim 8, wherein at least one of the slots is cut through the axis of rotation.

10. Method according to claim 8, wherein the slots are cut so that the posts all have an identical length.

11. Method according to claim 8, wherein the slots are cut such that the back plate has a thickness which is smaller than a maximum cross-sectional dimension of the posts transverse to a longitudinal axis thereof.

12. Method according to claim 8, wherein the slots are cut using electric discharge machining.

13. Method according to claim 12, wherein the slots are cut using wire cutting by electric discharge machining.

14. Method according to claim 8, wherein the slots are cut using electrochemical machining.

15. Method of manufacturing an intravascular blood pump having a drive unit with a magnetic core, wherein the magnetic core (400) is manufactured according to claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The foregoing summary, as well as the following detailed description of preferred embodiments, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, reference is made to the drawings. The scope of the disclosure is not limited, however, to the specific embodiments disclosed in the drawings. In the drawings:

[0028] FIG. 1 shows a cross-sectional view of a blood pump;

[0029] FIG. 2 shows a cross-sectional view of a preferred embodiment of a drive unit-impeller-arrangement;

[0030] FIGS. 3A to 3C show steps of manufacturing an integrated magnetic core for the drive unit according to FIG. 2;

[0031] FIGS. 4A to 4C show welds on the integrated magnetic core as manufactured according to FIGS. 3A to 3C; and

[0032] FIGS. 5A to 5J show cross-sections through posts according to various embodiments.

DETAILED DESCRIPTION

[0033] Referring to FIG. 1, a cross-sectional view of a blood pump 1 is illustrated. The blood pump 1 comprises a pump casing 2 with a blood flow inlet 21 and a blood flow outlet 22. The blood pump 1 is designed as an intravascular pump, also called a catheter pump, and is deployed into a patient's blood vessel by means of a catheter 25. The blood flow inlet 21 is at the end of a flexible cannula 23 which may be placed through a heart valve, such as the aortic valve, during use. The blood flow outlet 22 is located in a side surface of the pump casing 2 and may be placed in a heart vessel, such as the aorta. The blood pump 1 is electrically connected with an electric line 26 extending through the catheter 25 for supplying the blood pump 1 with electric power in order to drive the pump 1 by means of a drive unit 4, as explained in more detail below.

[0034] If the blood pump 1 is intended to be used in long term applications, i.e. in situations in which the blood pump 1 is implanted into the patient for several weeks or even months, electric power is preferably supplied by means of a battery. This allows a patient to be mobile because the patient is not connected to a base station by means of cables. The battery can be carried by the patient and may supply electric energy to the blood pump 1, e.g. wirelessly.

[0035] The blood is conveyed along a passage 24 connecting the blood flow inlet 21 and the blood flow outlet 22 (blood flow indicated by arrows). An impeller 3 is provided for conveying blood along the passage 24 and is mounted to be rotatable about an axis of rotation 10 within the pump casing 2 by means of a first bearing 11 and a second bearing 12. The axis of rotation 10 is preferably the longitudinal axis of the impeller 3. Both bearings 11, 12 are contact-type bearings in this embodiment. At least one of the bearings 11, 12 could be a non-contact-type bearing, however, such as a magnetic or hydrodynamic bearing. The first bearing 11 is a pivot bearing having spherical bearing surfaces that allow for rotational movement as well as pivoting movement to some degree. A pin 15 is provided, forming one of the bearing surfaces. The second bearing 12 is disposed in a supporting member 13 to stabilize the rotation of the impeller 3, the supporting member 13 having at least one opening 14 for the blood flow. Blades 31 are provided on the impeller 3 for conveying blood once the impeller 3 rotates. Rotation of the impeller 3 is caused by the drive unit 4 which is magnetically coupled to a magnet 32 at an end portion of the impeller 3. The illustrated blood pump 1 is a mixed-type blood pump, with the major direction of flow being axial. It will be appreciated that the blood pump 1 could also be a purely axial blood pump, depending on the arrangement of the impeller 3, in particular the blades 31.

[0036] The blood pump 1 comprises the impeller 3 and the drive unit 4. The drive unit 4 comprises a plurality of posts 40, such as six posts 40, only two of which are visible in the cross-sectional view of FIG. 1. The posts 40 are arranged parallel to the axis of rotation 10, more specifically, a longitudinal axis of each of the posts 40 is parallel to the axis of rotation 10. One end of the posts 42 is disposed adjacent to the impeller. Coil windings 44 are arranged about the posts 40. The coil windings 44 are sequentially controlled by a control to create a rotating magnetic field. A part of the control unit is the printed circuit board 6 which is connected to the electric line 26. The impeller has a magnet 32, which is formed as a multiple piece magnet in this embodiment. The magnet 32 is disposed at the end of the impeller 3 facing the drive unit 4. The magnet 32 is arranged to interact with the rotating magnetic field so as to cause rotation of the impeller 3 about the axis of rotation 10.

[0037] In order to close the magnetic flux path, a back plate 50 is located at the end of the posts 40 opposite the impeller-side of the posts. The posts 40 act as a magnetic core and are made of a suitable material, in particular a soft magnetic material, such as steel or a suitable alloy, in particular cobalt steel. Likewise, the back plate 50 is made of a suitable soft magnetic material, such as cobalt steel. The back plate 50 enhances the magnetic flux, which allows for reduction of 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 impeller back plate, is provided in the impeller 3 at a side of the magnet 32 facing away from the drive unit 4. The yoke 37 in this embodiment has a conical shape in order to guide the blood flow along the impeller 3. The yoke 37 may be made of cobalt steel, too. One or more wash-out channels that extend towards the central bearing 11 may be formed in the yoke 37 or the magnet 32.

[0038] FIG. 2 shows a cross-sectional view of a preferred embodiment of a drive unit-impeller-arrangement for the blood pump according to FIG. 1. As can be seen in FIG. 2, the impeller-side ends 420 of the posts 40 do not extend radially over the windings 44. Rather, the cross section of the posts 40 is constant in the direction of a longitudinal axis LA of the posts 40. It is thus avoided that the posts 40 come close to each other, as this could cause a partial magnetic short-circuit with the result of a reduced power of the electric motor of the blood pump.

[0039] The drive unit according to FIG. 2 may comprise at least two, at least three, at least four, at least five or preferably six posts 40. Higher numbers of posts 40, such as nine or twelve, may be possible. Due to the cross-sectional view, only two posts 40 are visible. The posts 40 and the back plate 50 form a magnetic core 400 of the drive unit 4 which may have a diameter of less than 10 mm.

[0040] The magnetic core 400 comprises the magnetic components of the drive unit 4, which are the posts 40 and the back plate 50, as one single piece or monoblock. The monoblock consists of discontinuous soft magnetic material that is discontinuous in regard of electric conductivity. The discontinuous soft magnetic material comprises a plurality of sheets 85 which are made of a ferromagnetic material and which are laminated to each other. A direction of lamination is arranged in direction of the longitudinal axis LA of the posts 40 and marked by an arrow DL. As shown, the posts 40 are arranged in parallel to the axis of rotation 10.

[0041] The coil windings 44 extend up to the impeller-side end 420 of the posts 40. This has the advantage that a magneto-motive force can be generated along the complete post 40. The magnetic core 400 comprises a protrusion 401 at the rear end 450 of the posts 40 protruding radially in respect to the posts 40. This protrusion 401 can be a stop for the coil windings 44 towards the back plate 50. As the integral magnetic core 400 has a high rigidity between the back plate 50 and the posts 40, a spacer between the posts 40 at the impeller-side end 420 of the posts may be omitted. The integral magnetic core 400 provides the advantage that an optimum magnetic connection between the posts 40 and the back plate 50 can be achieved. The magnetic core 400 may have a diameter of less than 10 mm.

[0042] FIGS. 3A to 3C show steps of manufacturing the magnetic core 400 for the drive unit 4 of the drive unit-impeller-arrangement as shown in FIG. 2. FIG. 3A shows in a perspective view a monoblock 9 in cubical shape which forms a work piece for manufacturing the magnetic core 400. The monoblock 9 consists of a discontinuous soft magnetic material which is discontinuous regarding electrical conductivity. It comprises sheets 85 which are oriented in a direction of lamination DL which runs along the main plane of the sheets 85. The sheets 85 are each bonded to their respective neighbouring sheet by a bonding layer of an electrical non-conductive material, which is not explicitly shown in FIGS. 3A to 3C.

[0043] FIG. 3B shows the magnetic core 400 in a semi-manufactured state in which it has been machined, e.g. turned, from the cubical monoblock 9 into a substantially cylindrical body 94. In this machining step, the protrusion 401 is manufactured. A section 404 of reduced diameter of the body 94, which forms a peripheral surface of the posts 40 of the magnetic core 400, is manufactured with a diameter that corresponds to an outer radius of the outermost convex side surfaces 842 of the posts 40.

[0044] Then, the body 94 can be further manufactured to produce the magnetic core 400 as shown in FIG. 3C. For this production step, electric discharge machining can be used. Especially electric discharge machining by wire cutting can be applied to produce the slots 49 which separate the posts 40 from each other. Inside the slots, space for the coil windings 44 is provided. At the ground of the slots 49, an intermediate area 59 of the integral back plate 50 extends between the rear ends of the posts 40. The intermediate area is integral with the posts 40 and with the back plate 50. Thus, the whole magnetic core is formed by the monoblock 9.

[0045] The direction of lamination DL in the magnetic core 400 is such that it is parallel to the axis of rotation 10. It may be tolerated that the direction of lamination DL in the base plate 50 is not parallel with respect to the magnetic flow between the posts 40 in the base plate 50. It is also possible to manufacture the magnetic core 400 from coiled soft magnetic sheet material which is separated by electrically non-conducting layers. Then, the direction of lamination DL in the base plate 50 is always in the circumferential direction which is advantageous to avoid eddy currents in the magnetic flux in the base plate 50.

[0046] FIGS. 4A to 4C show how one or more welds may be provided on surfaces of the integrated magnetic core as manufactured according to FIGS. 3A to 3C. Accordingly, in the embodiment shown, three weld seams 82, 83 are provided on one side face of the cubical monoblock 9. The weld seams 82, 83 are welded at a distance to each other and across the cross section of the body 94 to be cut out of the monoblock 9. The weld seams 82, 83 run perpendicular to the direction of lamination DL of the sheets 85. In this way, the sheets of the discontinuous soft magnetic material are connected to each other. Instead of three weld seams, more weld seams or a single wide weld may be provided. In addition, similar weld seams may be provided on the opposite side of the monoblock 9 (not shown). Alternatively or in addition to the welds on the opposite side faces, one or more weld seams may be provided on a side surface of the monoblock 9 at the level of the back plate 50 so as to surround the back plate 50 completely or at least partially. The sheets 85 have a better mechanical connection to each other due to the weld seams 82, 83 and are also electrically connected. The latter has the advantage that electrical current can flow from any position of the discontinuous soft magnetic material to each position of electrical connection of the body 94 which may be required e.g. for electric discharge machining. This way, electrical discharge machining is facilitated significantly. Furthermore, higher process reliability is achieved as the back plate-post unit to be cut-out of the body 94 cannot fall apart by delamination. Preferably, laser welding is applied. It may be advantageous to apply welding power to the same weld twice or even more often.

[0047] FIGS. 5A to 5J illustrate various embodiments of posts seen in cross section. FIGS. 5A to 5D show embodiments in which the post is slotted, i.e. is formed of a plurality of sheets 171 insulated from each other by insulating layers 172. The insulating layers 172 can comprise adhesive, lacquer, baking enamel or the like. FIGS. 5A and 58 show embodiments in which the thickness of the sheets 171 is uniform. The thickness may be in the range from 25 μm to 450 μm. The sheets 171 shown in FIG. 5A have a greater thickness than the sheets 171 shown in FIG. 5B. The sheets in FIG. 5C have varying thicknesses, with the central sheet having the greatest thickness and the outermost sheets having the smallest thickness. This may be advantageous because eddy currents in the side regions of the posts are more critical and can be reduced by the thin sheets. Eddy currents in the central area are less critical, and the relatively thick central sheet may help in improving the magnetic flux. The orientation of the sheets 171 may be different as exemplarily shown in FIG. 5D as long as the soft magnetic material in the shown cross-section, i.e. the soft magnetic material in cross-section transverse to the direction of the magnetic flux, is discontinuous or interrupted.

[0048] FIGS. 5E and 5F show embodiments in which the posts 141 are formed by a bundle of wires 181 which are insulated from each other by an insulating material 182. The insulating material 182 may be present as a coating of each of the wires 181 or may be a matrix in which the wires 181 are embedded. In the embodiment of FIG. 5E all wires have the same diameter, whereas in the embodiment of FIG. 5F a central wire has a largest diameter and outer wires have smaller diameters, similar to the embodiment shown in FIG. 5C having sheets with varying thicknesses. As shown in FIG. 5G, wires 181 of different diameters may be mixed, which may increase the total cross-sectional area of soft magnetic material compared to embodiments in which all wires have the same diameter. Still alternatively, in order to further minimize insulating layers 184 between the wires 183, the wires 183 may have a polygonal cross-sectional area, such as rectangular, square etc.

[0049] Alternatively, the discontinuous cross-section of the posts 141 may be created by metal particles 185 embedded in a polymer matrix 186 as shown in FIG. 5I, or by steel wool or other porous structures impregnated with an insulating matrix. A porous and, thus, discontinuous structure of soft magnetic material may also be produced by a sintering process or high-pressure molding process, in which an insulating matrix may be omitted because insulating layers are formed automatically by oxidation of the soft magnetic material by exposure to air. Still alternatively, the post 141 may be formed of a rolled-up sheet 187 of a soft magnetic material in which the layers of the rolled-up sheet 187 are separated by insulating layers 188 as shown in FIG. 5J. This also provides a discontinuous cross-section in the sense of the present invention which reduces eddy currents in the posts 141 or the posts 40.