US20130209292A1

US20130209292A1 - Axial flow blood pump with hollow rotor

Info

Publication number: US20130209292A1
Application number: US13/740,832
Authority: US
Inventors: Doan Baykut; Goekhan Baykut
Original assignee: Individual
Current assignee: Beijing Research Institute of Precise Mechatronic Controls
Priority date: 2005-07-01
Filing date: 2013-01-14
Publication date: 2013-08-15

Abstract

An axial flow blood pump includes a housing and a hollow rotor in the housing. The housing has an entrance end, an exit end, and a pump axis. The rotor has at least one spiral conveying rotor blade arranged on an inner surface of the rotor. The spiral conveying rotor blade extends toward a center of the rotor while leaving the center of the rotor open to define a central axial passage for a blood flow. The spiral conveying rotor blade has a pitch and a height that vary along the pump axis.

Description

RELATED APPLICATIONS

This application is a continuation in part (CIP) of U.S. patent application Ser. No. 11/994,480, which is the U.S. national stage of International Application No. PCT/EP2006/006344, filed Jun. 30, 2006, designating the United States and claiming the benefit of European application 05405423.4, filed Jul, 1, 2005. The entire contents of all of the above-referenced applications are incorporated by reference herein.

BACKGROUND

The disclosure relates to an axial flow blood pump with a hollow rotor.
A device to be used for pumping blood has different specifications than pumps designed for transporting water, organic solvents, or diluted solutions etc., as blood additionally contains cells. The behavior of the blood flow is different compared to a Newtonian fluid. Furthermore, blood cells are potentially seriously damaged by drag and shear stress generated on contact surfaces. Axial flow rotary blood pumps known to the inventor(s) of the instant application comprise rotor blades wound around a solid central cylinder of a rotor body. This configuration tends to damage blood cells during the blood transport through the pump. The relatively large total contact area of flowing blood with various components of the pump tends to promote the creation of deposits and thrombotic debris generated by the pump surface. A potential solution is using an axial flow blood pump with a transport element that has no central cylinder, i.e., no solid rotor body that produces destructive effects by impact. U.S. Pat. No. 6,527,521 B2 discloses a blood pump with a pipe-shaped housing in which a hollow cylindrical rotor is arranged provided with permanent magnets at the periphery. This pump has a hollow spiral vane with a constant pitch.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout. The drawings are not to scale, unless otherwise disclosed.

FIG. 1 a is an axial cross-sectional view of an axial flow blood pump in accordance with some embodiments.

FIG. 1 b is an axial cross-sectional view of an axial flow blood pump similar to the pump of FIG. 1 a and having rifling on an outside of a rotor body, in accordance with some embodiments.

FIG. 2 a is an axial cross-sectional view of an axial flow blood pump with magnetic bearings for axial stabilization, in accordance with some embodiments.

FIG. 2 b is an axial cross-sectional view of an axial flow blood pump similar to the pump of FIG. 2 a and having rifling on an outside of a rotor body, in accordance with some embodiments.

FIG. 2 c is an axial cross-sectional view of an axial flow blood pump similar to the pump of FIG. 2 a but having larger magnetic bearings for axial stabilization, in accordance with some embodiments.

FIG. 3 a is a perspective view of a hollow rotor in accordance with some embodiments.

FIG. 3 b is a perspective view of a hollow rotor similar to the rotor of FIG. 3 a and having a flat (rather than hydro-dynamically formed) front of a rotor barrel, in accordance with some embodiments.

FIG. 4 is a schematic, axial cross-sectional view of a hollow rotor with a flow straightener and a diffuser, in accordance with some embodiments.

FIG. 5 a is a schematic, axial cross-sectional view of a hollow rotor with one spiral conveying rotor blade, in accordance with some embodiments.

FIG. 5 b is a schematic, axial cross-sectional view of a hollow rotor with two conveying rotor blades angularly displaced at an angle of 180° relative to each other, in accordance with some embodiments.

FIGS. 5 c-5 e are schematic, axial cross-sectional views of various hollow rotors with spiral conveying rotor blades having a decreasing blade height and/or a decreasing blade pitch, in accordance with some embodiments.

FIGS. 5 f-5 h are schematic, axial cross-sectional views of various hollow rotors with two conveying rotor blades axially displaced relative to each other, in accordance with some embodiments.

FIG. 6 a is a perspective, partially cross-sectional view of a bent rotor blade in accordance with some embodiments.

FIG. 6 b is a perspective, partially cross-sectional view of a rotor blade with a notched free edge, in accordance with some embodiments.

FIG. 6 c is a perspective, partially cross-sectional view of a rotor blade with a textured surface, in accordance with some embodiments.

FIG. 6 d is a perspective, partially cross-sectional view of a rotor blade having a cross section that changes along a spiral length of the rotor blade, in accordance with some embodiments.

FIG. 6 e is a perspective, partially cross-sectional view of a rotor blade which has a torsion therealong, in accordance with some embodiments.

FIG. 6 f is a perspective, partially cross-sectional view of a rotor blade with surface geometry features, in accordance with some embodiments.

FIG. 6 g is a perspective, partially cross-sectional view of a rotor blade with one or more openings or slits, in accordance with some embodiments.

FIGS. 7 a-7 b are schematic, axial cross-sectional views of various hollow rotors with spiral conveying rotor blades having a constant angle of attack and a varying angle of attack, respectively, in accordance with some embodiments.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. The inventive concept may; however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. It will be apparent, however, that one or more embodiments may be practiced without these specific details. Like reference numerals in the drawings denote like elements.
In some embodiments, an axial flow blood pump includes a hollow rotor with a spiral conveying rotor blade that has both a pitch and a height varying along a pump axis. In one or more embodiments, the variation of the pitch of the rotor blade along the pump axis contributes to the minimization of backflow effects. In one or more embodiments, the variation of the height of the rotor blade along the pump axis permits the pump to operate at high speeds which is less likely obtainable if only the pitch of the rotor blade varies along the pump axis. The variation of the height of the rotor blade along the pump axis contributes, in one or more embodiments, to the minimization of backflow effects.
FIG. 1 a is an axial cross-sectional view of an axial flow blood pump (10) in accordance with some embodiments. The axial flow blood pump (10) has a hollow rotor (5) in a housing (1) with an inlet or entrance end (2), an outlet or exit end (3), and a pump axis (X). In one or more embodiments, the hollow rotor (5) is a magnetically active hollow rotor. The hollow rotor (5) contains a central axial passage (6) and a transport element in the form of a conveying spiral rotor blade (7). The blade pitch (7 c) and the blade height (7 a) of the conveying spiral rotor blade (7) vary along the pump axis (X).
The blade pitch (7 c) is the distance between adjacent turns of the rotor blade (7) as measured along the pump axis (X). The blade height (7 a) is measured, in a radial direction perpendicular to the pump axis (X), between a root 71 and a free end 72 of the rotor blade (7).
In the embodiment(s) specifically disclosed in FIG. 1 a, the blade height (7 a) increases along the pump axis (X), so that the central axial passage (6), which is the cross section left open within the rotor blade (7) at the center of the hollow rotor (5), decreases in a flow direction along the pump axis (X). At the inlet (2) where the blood enters the rotor (5), the central axial passage (6) starts wide but ends narrow at the outlet (3) where the blood exits the rotor (5). In the embodiment(s) specifically disclosed in FIG. 1 a, the blade pitch (7 c) also increases along the pump axis (X), i.e., the blade pitch (7 c) is shorter at the inlet (2) than at the outlet (3). By increasing the blade pitch (7 c) in the flow direction, it is possible to significantly reduce a backflow of the blood flow. However, in certain situations, where the axial flow blood pump (10) with a hollow rotor (5) is to be operating at high speeds, such as between 1000 and 30,000 rotations per minute, an increasing blade pitch (7 c) alone is potentially insufficient to reduce the backflow in the pump axis (X) to an acceptable level. By additionally increasing the blade height (7 a) along the pump axis (X), thereby decreasing the diameter of the central axial passage (6), it would be possible to efficiently diminish or minimize the backflow in the pump axis (X). Other configurations where the blade pitch (7 c) and/or the blade height (7 a) decrease(s) along the pump axis (X) from the inlet (2) to the outlet (3) are within the scope of various embodiments. For example, if the blade pitch (7 c) of the rotor (5) is decreased and the blade height (7 a) of the rotor (5) is narrowed towards the outlet (3), the volume flow at the center of the rotor (5) is decelerated. This effect is compensated for by other hydrodynamic features in accordance with some embodiments.
The rotor blade (7) in the particular embodiment(s) of FIG. 1 a has a pointed profile (7 b). The axial flow blood pump (10) in FIG. 1 a also has a magnetic bearing, defined by a stator magnetic part (4) at the pump housing (1) and a rotor magnetic part (8) at the hollow rotor (5), for rotatably supporting, while carrying and radially stabilizing, the hollow rotor (5). The magnetic transmission to spin the rotor (5) acts through an interaction of the stator magnetic part (4) with the rotor magnetic part (8) as indicated by the arrow (Y). The arrow (9) shows the flow direction of the blood. The rotor (5) in the embodiment(s) specifically disclosed in FIG. 1 a is a hollow cylinder. However, other rotor configurations adapted to the flow are within the scope of various embodiments. The pump (10) includes a flow straightener (11) at the inlet (2), and a diffuser (12) at the outlet (3).
The axial flow pump (10) in the particular embodiment(s) depicted in FIG. 1 a includes an electromagnetic drive to drive the rotor (5) in a contact-free manner across a gap (51), with the stator magnetic part (4) in the pump housing (1) and the rotor (5) or a magnetic part (8) thereof being magnetically active. The rotor magnetic part (8) contains, in at least one embodiment, a permanently magnetic material or a ferromagnetic material, or a coil with at least one closed (i.e., short circuit) turn of a conductive wire. The stator magnetic part (4) contains, in at least one embodiment, one or more windings which are arranged on a soft magnetic core to generate a rotary magnetic field in operation.
FIG. 1 b is an axial cross-sectional view of an axial flow blood pump (10′) with rifling in accordance with some embodiments. The axial flow blood pump (10′) is similar to the axial flow blood pump (10) of FIG. 1 a, and additionally includes rifling (50) on an outer surface of a rotor body of the hollow rotor (5). The rifling (50) enhances a smooth blood flow in the gap (51) between the spinning hollow rotor (5) and the static housing (1) and induces blood washout from the gap (51).
Rifling (50) is one of the possible ways of changing the outer surface of the hollow rotor (5) to enhance a smooth blood flow in the gap (51) between the spinning hollow rotor (5) and the static housing (1) and for inducing blood washout from the gap (51). In accordance with some embodiments, various other modifications, such as selective corrugation, trenching or denting of the outer surface of the hollow rotor (5), achieve similar effects for a direction-controlled, fast bypass flow through the gap (51) around the hollow rotor (5) without stagnation areas.
FIG. 2 a is an axial cross-sectional view of an axial flow blood pump (20 a) with magnetic bearings for axial stabilization, in accordance with some embodiments. The axial flow blood pump (20 a) is similar to the axial flow blood pump (10) of FIG. 1 a, and additionally includes magnetic bearings for radial as well as for axial stabilization of a hollow rotor (16). The magnetic bearing includes, at the entrance end (2) of the pump (20 a), a stator axial stabilization bearing (14) and a rotor side entrance bearing (15) at the entrance end of the hollow rotor (16) which, in one or more embodiments, contain permanent magnets, electromagnets or a combination of both. The magnetic bearing further includes, at the exit end (3) of the pump (20 a), a stator axial stabilization bearing (18) and a rotor side exit bearing (19) which, in one or more embodiments, also contain permanent magnets, electromagnets or a combination of both.
In at least one embodiment, the rotor side entrance bearing (15) and the rotor side exit bearing (19) are each in the form of a ring magnet, and the stator axial stabilization magnets (14), (18) at the entrance and at the exit of the pump (20 a) are each in the form of a set of individual magnets (for example, 3 magnets disposed at 120° from each other or 4 magnets disposed at 90° from each other, etc.). In one or more embodiments, the magnets (14 and 18) are hidden in covers or caps (13 and 17) from the blood flow in order to reduce the hydrodynamic resistance and minimize the adverse effects at the inlet (2) as well as at the outlet (3) of the pump (20 a). In some embodiments the magnets are bar magnets.
FIG. 2 b is an axial cross-sectional view of an axial flow blood pump (20 b) with rifling in accordance with some embodiments. The axial flow blood pump (20 b) is similar to the axial flow blood pump (20 a) of FIG. 2 a, and additionally includes rifling (50) on an outer surface of a rotor body of the hollow rotor (16). The rifling (50) enhances a smooth blood flow in the gap (51) between the spinning hollow rotor (5) and the static housing (1) and induces blood washout from the gap (51).
FIG. 2 c is an axial cross-sectional view of an axial flow blood pump (20 c) similar to the pump (20 a) of FIG. 2 a but having larger magnetic bearings for axial stabilization, in accordance with some embodiments. The axial flow blood pump (20 c) has rotor caps (33 and 37) which have a ring shape and arranged before (upstream) and after (downstream) the rotor (16) in the direction of flow. The axial flow blood pump (20 c) includes magnets (34, 35, 38, 39) corresponding to magnets (14, 15, 18, 19) of the pump (20). However, the magnets (34 and 35) disposed at the inlet (2) of the axial flow blood pump (20 c) are larger, in the radial direction, than the magnets (38 and 39) disposed at the outlet (3). The larger magnets are arranged in the rotor cap (33), for example, a ring-shaped permanent magnet (34) is arranged in the rotor cap (33) at the inlet side to absorb axial forces. Since the axial force resulting due to the pressure differential between the inlet (2) and the outlet (3) is to be completely absorbed by the magnetic bearings with a contact-free support of the rotor (16), it is possible to generate a greater pressure differential using the axial flow pump (20 c). In some embodiments, instead of permanent magnets, electromagnets are provided in the rotor caps (33, 37) with which the axial position of the rotor (16) is actively stabilizable.
FIG. 3 a is a perspective view of a hollow rotor (41 a) in accordance with some embodiments. The hollow rotor (41 a) has similar general characteristics to the hollow rotor (5) in the pump (10) shown in FIG. 1 b. On the outside, this rotor (41 a) also has a helical rifling (50), as depicted in the pump (10′) in FIG. 1 b, in order to support a smooth blood flow between the rotor (41 a) and the housing (not shown) when the rotor (41 a) is spinning. The rotor blade (40) is partially visible at the entrance end of the rotor (41 a). The rotor blade (40) is a spiral that has about one turn between the entrance end and the exit end of the rotor (41 a). A rotor side radial stabilization and transmission bearing (60) is schematically depicted on the outer surface of the rotor (41 a). The half-cut cross-section view of the front part of the rotor (41 a) is to show the hydrodynamic form of the rotor nose entrance that faces the entrance end (2) of the housing (1). The first cross-section (48) is taken perpendicular to the pump axis (X). The second cross-section (49) is taken along the pump axis (X) and shows the rotor nose entrance having a curved profile that faces the entrance end (2) of the housing (1).
FIG. 3 b is a perspective view of a hollow rotor (41 b) similar to the rotor (41 a) of FIG. 3 a and having a flat (rather than hydro-dynamically formed) front (43), in accordance with some embodiments. The hollow rotor (41 b) has similar general characteristics to the rotor (16) in the pump (20 a) shown in FIG. 2 a. Similar to the rotor (41 a) shown in FIG. 3 a, the rotor blade (40) of the rotor (41 b) is a spiral that has about one turn between the entrance end and the exit end of the rotor (41 b). On the outside the rotor (41 b) has helical rifling (50) in order to support a smooth blood flow between the rotor (41 b) and the housing (not shown) when the rotor (41 b) is spinning. Front and/or back ends of this rotor (41 b) have flat faces (42) where ring magnets are integrated for the axial stabilization of the rotor (41 b). The counterparts of these magnetic rings are either a set of separate static magnets (in some embodiments, bar magnets) or a single static ring magnet in the housing, as described with respect to FIGS. 2 a-2 c.
FIG. 4 is a schematic, axial cross-sectional view of a hollow rotor (90) with a flow straightener (70) and a diffuser (80), in accordance with some embodiments. The hollow rotor (90) has a rotor body (91) and a spiral rotor blade (92) of which the pitch increases in the axial direction. The rotor blade height also increases in the axial direction, and consequently, the cross section (95) left open within the spiral rotor blade (92) becomes smaller toward the exit. In one or more embodiments, the hollow rotor (41 a or 41 b) in FIG. 3 a or 3 b has the cross-sectional configuration of the hollow rotor (90) of FIG. 4. The pump using the hollow rotor (90) also includes the flow straightener (70) for the blood to pass through before entering the hollow rotor (90). The flow straightener (70) includes at least one vane (71). Two flow straightener vanes (71) are shown in FIG. 4 as an example. The diffuser (80) includes at least one vane for re-laminarization of the flow exiting the hollow rotor (90). In one or more embodiments, the diffuser (80) includes at least one spiral vane. Four spiral vanes (81-84) are shown in FIG. 4 as an example. The vanes of the flow straightener (70) and the diffuser (80) are stationary relative to the pump housing (not shown).
FIG. 5 a is a schematic, axial cross-sectional view of a hollow rotor (90 a) with one spiral conveying rotor blade (92), in accordance with some embodiments. FIG. 5 b is a schematic, axial cross-sectional view of a hollow rotor (90 b) with two conveying rotor blades (92, 93) angularly displaced at an angle of 180° relative to each other, in accordance with some embodiments. Other phase differences between the conveying rotor blades (92, 93) are within the scope of various embodiments. The height of the conveying rotor blades (92, 93) increase axially toward the exit so that the cross section (95) left open within each of the spiral rotor blades (92, 93) decreases toward the exit.
FIG. 5 c is a schematic, axial cross-sectional view of a hollow rotor (90 c), in accordance with some embodiments. Unlike the hollow rotor (90 a) in FIG. 5 a with a spiral conveying rotor blade (92) having an increasing blade height and an increasing blade pitch, the hollow rotor (90 c) in FIG. 5 c has a spiral conveying rotor blade (92′) with a decreasing blade height and an increasing blade pitch. The blade height of the conveying rotor blade (92′) decreases axially toward the exit so that the cross section (95′) left open within the spiral rotor blade (92′) increases toward the exit.
FIG. 5 d is a schematic, axial cross-sectional view of a hollow rotor (90 d) with a spiral conveying rotor blade (92″) having an increasing blade height and a decreasing blade pitch, in accordance with some embodiments. The blade height of the conveying rotor blade (92″) increases axially toward the exit so that the cross section (95″) left open within the spiral rotor blade (92″) decreases toward the exit.
FIG. 5 e is a schematic, axial cross-sectional view of a hollow rotor (90 e) with a spiral conveying rotor blade (92″′) having a decreasing blade height and a decreasing blade pitch, in accordance with some embodiments. The blade height of the conveying rotor blade (92″′) decreases axially toward the exit so that the cross section (95″′) left open within the spiral rotor blade (92″′) increases toward the exit.
FIG. 5 f is a schematic, axial cross-sectional views of a hollow rotor (90 f) with two conveying rotor blades (92, 92 a) axially displaced relative to each other, in accordance with some embodiments. The conveying rotor blades (92, 92 a) extend in parallel, i.e., the conveying rotor blade (92 a) is obtained by axially displacing the conveying rotor blade (92) toward the exit. Both conveying rotor blades (92, 92 a) start from the entrance of the hollow rotor (90 f).
FIG. 5 g is a schematic, axial cross-sectional views of a hollow rotor (90 g) with two conveying rotor blades (92, 92 b) axially displaced relative to each other, in accordance with some embodiments. The conveying rotor blade (92, 92 b) extend in parallel. Unlike the hollow rotor (90 f) in FIG. 5 f with both spiral conveying rotor blades (92, 92 a) starting from the entrance of the hollow rotor (90 f), at least one of the spiral conveying rotor blades (92, 92 b) of the hollow rotor (90 g), e.g., the spiral conveying rotor blade (92 b) starts from a position within the hollow rotor (90 g).
FIG. 5 h is a schematic, axial cross-sectional views of a hollow rotor (90 h) with two conveying rotor blades (92, 92 c) axially displaced relative to each other, in accordance with some embodiments. The conveying rotor blade (92 c) is obtained by axially displacing the conveying rotor blade (93) in FIG. 5 b toward the exit. Similar to the spiral conveying rotor blade (92 b), the spiral conveying rotor blade (92 c) starts from a position within the hollow rotor (90 h).
To increase the pumping efficiency of the hollow rotor, one or more additional features on the rotor blade is/are applied. One of the major differences between the hollow rotor in accordance with some embodiments and the known axial flow pumps with a solid central cylinder is that the free edge of the conveying spiral rotor blade in the known axial flow pumps is the “trailing” edge where the fluid stream leaves the surface of the rotor blade. Due to the hollow center of the rotor in accordance with some embodiments, however, the free edge of the rotor blade, located at a low speed area, becomes the “leading” edge which takes over the blood flow. Furthermore, there is a boundary layer of the blood flow at the free edge where the front and back surfaces of the rotor blade merge. Additional turbulences or cavitation possibly occur in the blood flow at the free edge of the rotor blade.
Another consideration is the “wash-off” effect on the rotor surface(s) by centrifugal forces. In known axial flow pumps with a solid central cylinder, blood moves radially to a stagnant surface (i.e., the inner surface of the housing) with a high speed which additionally leads to shear forces. In contrast, the surrounding inner surface of the hollow rotor in accordance with some embodiments is moving together with the rotor blade, i.e., the relative axial speed of the rotor blade to the rotor's inner surface (where the root of the rotor blade is) is virtually zero. A better wash-off effect is achievable in accordance with some embodiments by using one or more surface modifications, such as rifling, as described above.
FIG. 6 a is a perspective, partially cross-sectional view of a bent rotor blade (101 a) in accordance with some embodiments. The rotor blade (101 a) has a root (130) where the rotor blade (101 a) is connected to a rotor body (100) on an inner surface (133) of the rotor body (100). The rotor blade (101 a) has opposite front surface (139) and back surface (not numbered) which merge at a free edge (143). The front surface (139) is upstream of the back surface (141) in the flow direction. A line (137) is a boundary between the front surface (139) of the rotor blade (101 a) with the inner surface (133) of the rotor body (100) at the root (130). A line (139 a) is an interface of the front surface (139) with a plane of the cross-section in FIG. 6 a. A line (141 a) is an interface of the back surface with the plane of the cross-section in FIG. 6 a. The lines (139 a, 141 a) meet at a point (143 a) which is an intersection of the free edge (143) with the plane of the cross-section in FIG. 6 a. The root (130) is present in the plane of the cross-section in FIG. 6 a as a root section (131). A line (135) is an imaginary center line in the plane of the cross-section of the rotor blade (101 a). The imaginary center line (135) is perpendicular to the inner surface (133) of the rotor body (100) and extends through a midpoint of the root section (131) of the rotor blade (101 a). In other words, the imaginary center line (135) extends in the radial direction perpendicular to the pump axis (X).
The free (leading) edge (143 a) of the rotor blade (101 a) is bent to better handle the boundary layer to reduce backflow at the center of the hollow rotor and/or to avoid turbulences. As shown in FIG. 6 a, the rotor blade (101 a) has a bent free edge or leading edge (143) which is best seen at the plane of the cross-section in FIG. 6 a where a bending angle (102) indicates the deviation between the imaginary center line (135) and the actual bent position (143 a) of the free edge (143) of the rotor blade (101 a). In this particular embodiment, the free edge (143) is bent toward the exit of the hollow rotor. The frontal surface of the rotor blade (101 a) with such a bent free edge (143) is larger than the rear surface of the rotor blade (101 a). The bent free edge (143) directs the central flow into the main flow direction, thereby reducing the backflow. As a result, the pumping efficiency is improved. Other configurations are within the scope of various embodiments. For example, in some embodiments, the bent free edge (143) is bent toward the entrance, which, depending on the rotational speed of the blood pump, potentially increases the backflow. This effect is compensated for by other hydrodynamic features in accordance with some embodiments.
FIG. 6 b is a perspective, partially cross-sectional view of a rotor blade (101 b) with a notched free edge, in accordance with some embodiments. FIG. 6 b shows a first cross-section similar to the cross-section of FIG. 6 a, and also shows a second cross-section. A line (139 b) is an interface of the front surface (139) of the rotor blade (101 b) with a plane of the second cross-section in FIG. 6 b. A line (141 b) is an interface of the back surface of the rotor blade (101 b) with the plane of the second cross-section in FIG. 6 b. The lines (139 b, 141 b) meet at a point (143 b) which is an intersection of the free edge (143) of the rotor blade (101 b) with the plane of the second cross-section in FIG. 6 a. A line (138) is a boundary between the back surface of the rotor blade (101 b) with the inner surface (133) of the rotor body (100) at the root (130).
As an option to enhance one or more of the effects described above, the leading edge (143) of the rotor blade (101 b) has a notched shape (103) in some embodiments instead of being straight.
FIG. 6 c is a perspective, partially cross-sectional view of a rotor blade (101 c) with a textured surface, in accordance with some embodiments. The front surface (139) has a region (139 c) adjacent to the free edge (143) and having an increased roughness compared to a region (139 d) adjacent the inner surface (133) of the rotor body (100). Thus, a “controlled roughness effect” is added in predetermined areas, i.e., the region (139 c) of the rotor blade (101 c), by implementing a textured rotor surface (104) in the region (139 c). This leads to a better attachment of the blood flow on the surface of the rotor blade (101 c) and increases the efficiency of the pump without increasing the shear stress significantly in some embodiments. Specifically, the textured surface of the front surface (139) in the flow direction operates similarly to a set of vortex generators on the wing of an aircraft to prevent the airflow separation from the wing surface. Vortex generators keep the flow at the wing surface by producing mini vortices. The textured surface of the front surface (139) on the rotor blade (101 c) provides a similar effect where the blood remains better attached on the surface of the rotor blade (101 c). In one or more embodiments, the back surface of the rotor blade (101 c) is provided with the textured rotor surface (104) in lieu of or in addition to the front surface (139). Although the embodiment disclosed in FIG. 6 c includes the textured surface in the region (139 c) adjacent the free edge (143), other embodiments are not limited to such an arrangement. Specifically, various embodiments include the textured surface at one or more regions on the rotor surface to optimize the flow. For example, in some embodiments, the textured surface is provided in the region (139 d) adjacent the inner surface (133) of the rotor body (100), while leaving the region (139 c) adjacent the free edge (143) as a smooth surface. In some embodiments, the textured surface is provided in a middle part of the rotor surface, while leaving both regions adjacent the inner surface (133) of the rotor body (100) and adjacent the free edge (143) as smooth surfaces. In some embodiments, multiple, discrete regions of the textured surface are scattered on the rotor surface.
FIG. 6 d is a perspective, partially cross-sectional view of a rotor blade (101 d) having a cross section or profile that changes along a spiral length of the rotor blade (101 d), in accordance with some embodiments. For example, the rotor blade (101 d) has a cross-section that increases along the length of the spiral from the inlet side, e.g., a profile (105), to the outlet side, e.g., a profile (106). This leads to a better management of the blood flow and in dependence of the flow characteristics within the hollow-rotor, in accordance with some embodiments. Specifically, by changing the profile (105), the space between adjacent turns of the spiral rotor blade (101 d) is manipulated and an additional radial component of the blood is established on the surface of the rotor blade (101 d). This leads to an accelerated volume transport in the axial direction towards the pump outlet. In one or more embodiments, not only the size, but also the shape and/or other characteristics of the cross-section (profile) of the rotor blade (101 d) varies along the spiral length.
FIG. 6 e is a perspective, partially cross-sectional view of a rotor blade (101 e) which has a torsion therealong, in accordance with some embodiments. The root (130) is present in the plane of the second cross-section in FIG. 62 as a second root section (132). A line (136) is a second imaginary center line in the plane of the second cross-section of the rotor blade (101 e). The second imaginary center line (136) is perpendicular to the inner surface (133) of the rotor body (100) and extends through a midpoint of the second root section (132) of the rotor blade (101 e). A line (140) is a center line of the root (130) on the inner surface (133) of the rotor body (100). A plane (107) defined by the lines (135, 136 and 140) is a radial plane perpendicular to the pump axis (X). A rotor blade center line (136′) in the plane of the second cross-section of the rotor blade (101 e) extends from the midpoint of the second root section (132) and remains equidistant from the lines (139 b, 141 b) (which are the interfaces of the front and back surfaces of the rotor blade (101 e) with the plane of the second cross-section in FIG. 6 e) at least in the vicinity of the second root section (132). An angle of attack of the rotor blade (101 e) in the plane of the second cross-section is defined by an angle between the rotor blade center line (136′) and the flow direction (9) of the blood, and is smaller than 90 degrees. In the specifically illustrated embodiment, the angle of attack of the rotor blade (101 e) in the plane of the first cross-section corresponding to the imaginary center line (135) is 90 degrees. In other words, the imaginary center line (135) is also the rotor blade center line in the plane of the first cross-section of the rotor blade (101 e) and extends from the midpoint of the root section (131) while remaining equidistant from the lines (139 a, 141 a) (which are the interfaces of the front and back surfaces of the rotor blade (101 e) with the plane of the first cross-section in FIG. 6 e) at least in the vicinity of the root section (131). An angle (108) between the rotor blade center line (136′) and the second imaginary center line (136) defines a difference in angle of attack between the second and first cross-sections in FIG. 6 e. As can be seen in FIG. 6 e, the free edge (143 b) is bent, relative to the plane (107), at a greater angle at the second cross-section corresponding to the line (136) than the free edge (143 a) at the cross-section corresponding to the line (135). The difference in bending angle of the free edge (143) along the spiral length defines a twist or torsion in the rotor blade (101 e).
This configuration leads to a better management of the blood flow and in dependence of the flow characteristics within the hollow-rotor, i.e., the rotor blade has a varying angle of attack of the leading edge (143) that is adapted to the flow generated by the hollow rotor, which resulting in torsion along the rotor blade surface in some embodiments. In some embodiments, as exemplarily shown in FIG. 7 b, the rotor blade (101 e) is provided with an adapted angle of attack of the leading edge (143) along the entire rotor blade. Specifically, FIG. 7 a is schematic, axial cross-sectional view similar to FIG. 5, showing the hollow rotor (90) with a spiral conveying rotor blade (92) having a constant angle of attack (210), e.g., 90 degrees, at various points along the rotor blade (92), whereas FIG. 7 b is schematic, axial cross-sectional view of a hollow rotor (190) with a spiral conveying rotor blade (192) having a varying angle of attack at various points along the rotor blade (192), in accordance with some embodiments. The rotor blade (192) has an angle of attack (210) of 90 degrees near the entrance, an angle of attack (211) smaller than 90 degrees at an intermediate point inside the hollow rotor (190), and an even smaller angle of attack (212) near the exit. In other words, the angle of attack of the rotor blade (192) decreases toward the exit. As a result, an increased flow speed is obtained. Other angle of attack variations are within the scope of various embodiments
FIG. 6 f is a perspective, partially cross-sectional view of a rotor blade (101 g) with surface geometry features, in accordance with some embodiments. As shown in FIG. 6 g, to increase the hydrodynamic efficiency, the front surface (139) of the rotor blade (101 g) includes ripples (111) for coordinating the flow in dependence of the rotor blade surface in some embodiments. In one or more embodiments, the back surface of the rotor blade (101 g) is provided with ripples in lieu of or in addition to the front surface (139).
FIG. 6 g is a perspective, partially cross-sectional view of a rotor blade (101 h) with one or more openings or slits (112), in accordance with some embodiments. The opening or slit (112) extends through the rotor blade's thickness in some embodiments, or terminate inside the rotor blade (101 h) in further embodiments. A shape, size, depth and other characteristics of the opening or slit (112) are variable in accordance with some embodiments. By providing one or more openings and/or slits in the rotor blade, it is possible to eliminate flow disturbances between the front and back surfaces of the rotor blade (101 h) which, in turn, leads to a more effective flow pattern in some embodiments.
Embodiments described with respect to FIGS. 2 a, 2 b, and 2 c include transversal and longitudinal magnetic bearings in the axial flow pump to support the hollow rotor (16) in a contact-free manner. The electromagnetic drive including the magnetic parts (4) and (8) define the magnetic bearing. The axial flow blood pump is provided with one or more axially offset magnetic bearings. In embodiments described with respect to FIGS. 2 a to 2 c, permanent magnets (14 and 15, 18 and 19) define passive magnetic bearings in the end regions of the rotor (16) at the inlet side and at the outlet side, respectively. The guide vanes (13, 17), also referred to herein as flow straightener and diffuser, respectively, are used for carrying the permanent magnets (14 and 19) in the parts adjacent the rotor (16), whereas the rotor (16) is fitted with one or more respective permanent magnets (15 and 18) in the end regions at the inlet side and at the outlet side. The magnets (14 and 19) carried by the guide vanes of the flow straightener (13) or the diffuser (17) are encapsulated into a hydro-dynamically adapted cover to reduce the hydrodynamic resistance. Instead using a plurality of permanent magnets at different angles, a ring-shaped permanent magnets is used in each rotor end region in accordance with some embodiments.
In some embodiments, a pressure differential of 150 hPa and more is generated with the axial flow pump described herein. Thanks to the contact-free drive and the contact-free support of the hollow rotor, the axial flow pump is useable as a blood pump. It is advantageous in this connection that the axial flow pump in accordance with some embodiments has a comparatively low contact area with the main volume blood flow and that a better washing around of the rotor is possible by the described rifling in the gap between the housing and the rotor.
The transport element (i.e., the spiral conveying rotor blade) and/or a free edge thereof has a rounded or pointed profile in accordance with some embodiments. The transport element includes one or more vanes and/or holes and/or slits and/or local elevated portions and/or local recesses in accordance with some embodiments.
In some embodiments, at least one part of the rotor contains a permanently magnetic or a soft magnetic material, or the rotor includes a solenoid or at least one short-circuit (closed) turn to define a coil to which energy is transferrable by electromagnetic induction from the stator part (4). The electromagnetic drive simultaneously functions as a magnetic bearing in at least one embodiment. At least two magnetic bearings, which are arranged axially offset, are provided in the pump in accordance with some embodiments, with at least one of the magnetic bearings being arranged, for example, in the inlet side end region of the rotor and/or in the outlet side end region of the rotor.
In some embodiments, the axial flow pump includes one or two ring-shaped rotor caps (13, 17) which are, for example, fastened to the housing. The rotor caps include one or more vanes and are arranged before and/or after the rotor in the direction of flow.
In some embodiments, at least one coupling part is provided at the housing for the connection of the axial flow pump to an inlet cannula and/or outlet cannula.
In some embodiments, an axial flow blood pump with at least one spiral conveying rotor blade, the pitch and the height of the rotor blade vary along the rotor axis. In one or more embodiments, the height of the rotor blade extending toward the center of the hollow rotor varies in the flow direction from the entrance end to the exit end of the hollow rotor. Thus, the free edge of the rotor blade follows a geometric function with a linear or non-linear increase or decrease of the blade height, or a superposition of more than one increasing or decreasing functions.
In some embodiments, the blade height of the rotor blade is described, along the flow direction, by a sequence of an increasing function followed by a decreasing function, or by a sequence of a decreasing function followed by an increasing function. The height of the rotor blade in one or more embodiments shows periodic variations at the rotor blade's free edge, such as a sine function. In at least one embodiment, a notched-edge rotor blade is formed by varying the blade height in the flow direction with an superposition of, e.g., a slowly decreasing linear function with a relatively fast oscillating periodic function, for example, a sine function.
In some embodiments, more than one spiral rotor blades is placed in a single rotor body to increase the pumping efficiency. One example way to implement this configuration is to arrange the spiral rotor blades symmetrically around the pump axis so that the rotor is balanced at every point along the pump axis. With two spiral rotor blades, the second rotor blade has an angular phase difference of 180° from the first rotor blade. With n rotor blades, in a symmetric rotor configuration, the angular phase difference between adjacent rotor blades is (360° /n). However, in one or more embodiments, the rotor blades are arranged in an asymmetric way around the pump axis. In this case, for example, the rotor blades start at the same point but the angular phase is not restricted to (360°/n). The spiral rotor blades are alternatively or additionally axially displaced relative to each other, in at least one embodiment.
The hollow rotor of the pump has an entrance and an exit. For achieving a laminar blood flow at the entrance of the hollow rotor, a hollow flow straightener is placed, in at least one embodiment, before the entrance. After exiting the hollow rotor, the blood flows through a hollow re-laminarization device, i.e., a diffuser, in at least one embodiment. The flow straightener and/or the diffuser includes one or more vanes Like the rotor blades, multiple vanes of each of the flow straightener and the diffuser are symmetrically distributed around the pump axis in some embodiments. However, in some embodiments, the vanes are placed in an asymmetric arrangement. Individual diffuser vanes are axially displaced relative to each other in accordance with some embodiments.
Axially, the rotor blade ends at the both ends of the rotor in accordance with some embodiments. However, in at least one embodiment, the rotor blade partially extends over the ends of the rotor, such as an adequately shortened rotor body, to enter into a range of the flow straightener and/or the diffuser, without touching blades of the flow straightener and/or the diffuser.
In some embodiments, the hollow axial flow blood pump has one or more bearings such as mechanical, magnetic, electromagnetic bearings or hybrid type bearings being a combination of two or more of the listed bearing types. The hollow rotor contains permanent magnets or a solenoid or at least one closed coil of a wire (or a conducting material) to be able to be magnetically activated by electromagnetic induction. The stator parts of the bearing also contain permanent magnets or a solenoid or at least one closed coil of wire (or a conducting material) to be able to be magnetically activated by electromagnetic induction.
The profiles of the rotor blades and/or the hollow diffuser vane are variable along the pump axis in accordance with some embodiments. The profile of the rotor blade and/or the hollow diffuser vane in at least one embodiment has a straight rectangular cross section, a straight trapezoid-shaped cross-section, or a triangular cross section having a pointed tip. In some embodiments, instead of being straight rectangular or straight triangular, the cross sections of the rotor blade and/or the hollow diffuser vane is curved or has a bent geometric form. Consequently, the free edge of the rotor blade and/or the diffuser vane is produced as plain, or curved, or cylindrical, or pointed, depending on various optimized flow conditions at selected rotation speed ranges during operation. One or more surfaces of the rotor blade and/or the hollow diffuser vane are flat in some embodiments, or manufactured in some embodiments with textures, again depending on various optimized flow conditions at selected rotation speed ranges, to achieve minimum damage to blood cells. The surface textures vary along the pump axis in some embodiments.
The rotor blade and/or the hollow diffuser vane, in at least one embodiment, is provided with a notched free edge for better tailoring the blood flow dynamics through the hollow rotor and/or for minimizing damage to blood cells during operation.
The axial flow hollow rotor blood pump is usable in extracorporeal operations in accordance with some embodiments. The axial flow blood pump is also made for implantation purposes in order to be used, e.g., as a ventricular assist device in accordance with some embodiments. The surface of the pump, at least of the components that come in contact with blood, are made of blood compatible material or have blood compatible coatings in accordance with some embodiments. When used as implantable device, the entire pump is made of implantable, blood compatible material.
According to some embodiments, an axial flow blood pump comprises a housing and a hollow rotor in the housing. The housing has an entrance end, an exit end, and a pump axis. The rotor has at least one spiral conveying rotor blade arranged on an inner surface of the rotor. The spiral conveying rotor blade extends toward a center of the rotor while leaving the center of the rotor open to define a central axial passage for a blood flow. The spiral conveying rotor blade has a pitch and a height that vary along the pump axis.
According to some embodiments, an axial flow blood pump comprises a housing, a hollow rotor in the housing, and a diffuser. The housing has an entrance end, an exit end, and a pump axis. The diffuser is disposed downstream of the hollow rotor in a flow direction from the entrance end to the exit end. The diffuser comprises at least one spiral vane stationary relative to the housing. The rotor has at least one spiral conveying rotor blade arranged on an inner surface of the rotor. The spiral conveying rotor blade extends toward a center of the rotor while leaving the center of the rotor open to define a central axial passage for a blood flow. The spiral conveying rotor blade has at least one of a pitch or a height that varies along the pump axis.
According to some embodiments, an axial flow blood pump comprises a housing, a hollow rotor in the housing, a diffuser, a flow straightener, at least one bearing and an electric motor. The housing has an entrance end, an exit end, and a pump axis. The diffuser is disposed downstream of the hollow rotor in a flow direction from the entrance end to the exit end. The flow straightener is disposed upstream of the hollow rotor in the flow direction. The at least one bearing rotatably supports the hollow rotor inside the housing. The electric motor is configured to drive the hollow rotor. Each of the flow straightener and the diffuser comprises at least one vane stationary relative to the housing. The rotor has at least one spiral conveying rotor blade arranged on an inner surface of the rotor. The spiral conveying rotor blade extends toward a center of the rotor while leaving the center of the rotor open to define a central axial passage for a blood flow. The spiral conveying rotor blade has a pitch and a height that vary along the pump axis.
It will be readily seen by one of ordinary skill in the art that one or more of the disclosed embodiments fulfill one or more of the advantages set forth above. After reading the foregoing specification, one of ordinary skill will be able to affect various changes, substitutions of equivalents and various other embodiments as broadly disclosed herein. It is therefore intended that the protection granted hereon be limited only by the definition contained in the appended claims and equivalents thereof.

Claims

What is claimed is:

1. An axial flow blood pump, comprising:

a housing having an entrance end, an exit end, and a pump axis; and

a hollow rotor in the housing;

wherein

the rotor has at least one spiral conveying rotor blade arranged on an inner surface of the rotor, the spiral conveying rotor blade extending toward a center of the rotor while leaving the center of the rotor open to define a central axial passage for a blood flow; and

the spiral conveying rotor blade has a pitch and a height that vary along the pump axis.

2. An axial flow blood pump according to claim 1, wherein the pitch of the spiral conveying rotor blade increases along the pump axis from the entrance end to the exit end.

3. An axial flow blood pump according to claim 1, wherein the pitch of the spiral conveying rotor blade decreases along the pump axis from the entrance end to the exit end.

4. An axial flow blood pump according to claim 1, wherein the height of the spiral conveying rotor blade increases along the pump axis from the entrance end to the exit end, so as to decrease a diameter of the central axial passage within the spiral conveying rotor blade in a flow direction from the entrance end to the exit end.

5. An axial flow blood pump according to claim 1, wherein the height of the spiral conveying rotor blade decreases along the pump axis from the entrance end to the exit end, so as to increase a diameter of the central axial passage within the spiral conveying rotor blade in a flow direction from the entrance end to the exit end.

6. An axial flow blood pump according to claim 1, wherein the hollow rotor has rifling on an outer surface thereof that faces the housing across a gap between the hollow rotor and the housing.

7. An axial flow blood pump according to claim 1, wherein the at least one spiral conveying rotor blade includes a plurality of spiral conveying rotor blades which are axially displaced relative to each other.

8. An axial flow blood pump according to claim 1, wherein the at least one spiral conveying rotor blade includes a plurality of spiral conveying rotor blades which are angularly displaced relative to each other.

9. An axial flow blood pump according to claim 1, further comprising:

a flow straightener comprising at least one vane which is shaped to straighten a blood flow entering the hollow rotor.

10. An axial flow blood pump according to claim 1, further comprising:

a diffuser which is shaped for re-laminarization of a blood flow exiting the hollow rotor.

11. An axial flow blood pump according to claim 10, wherein the diffuser comprises at least one spiral vane.

12. An axial flow blood pump according to claim 1, wherein a profile of the spiral conveying rotor blade varies along a spiral length of the rotor blade.

13. An axial flow blood pump according to claim 1, wherein a free edge of the spiral conveying rotor blade is bent.

14. An axial flow blood pump according to claim 1, wherein a free edge of the spiral conveying rotor blade has a notch.

15. An axial flow blood pump according to claim 1, wherein the spiral conveying rotor blade has a torsion along the rotor blade.

16. An axial flow blood pump according to claim 1, wherein a chord width of the spiral conveying rotor blade varies along the rotor blade.

17. An axial flow blood pump according to claim 1, wherein the spiral conveying rotor blade contains at least one hole or slit.

18. An axial flow blood pump according to claim 1, wherein a surface of the spiral conveying rotor blade includes ripples.

19. An axial flow blood pump, comprising:

a housing having an entrance end, an exit end, and a pump axis;

a hollow rotor in the housing; and

a diffuser disposed downstream of the hollow rotor in a flow direction from the entrance end to the exit end;

wherein

the diffuser comprises at least one spiral vane stationary relative to the housing;

the spiral conveying rotor blade has at least one of a pitch or a height that varies along the pump axis.

20. An axial flow blood pump, comprising:

a housing having an entrance end, an exit end, and a pump axis;

a hollow rotor in the housing;

a flow straightener disposed upstream of the hollow rotor in the flow direction;

at least one bearing rotatably supporting the hollow rotor inside the housing; and

an electric motor configured to drive the hollow rotor;

wherein

each of the flow straightener and the diffuser comprises at least one vane stationary relative to the housing;

21. An axial flow blood pump according to claim 20, wherein the at least one bearing comprises a magnetic bearing or an electromagnetic bearing.