BLOOD PUMP

Description

Technical field

[0001] The invention relates to a blood pump with a pump housing comprising a bottleneck-shaped flow inlet region in which a blade assembly is arranged and fixed to a rotatably mounted rotating shaft. This blade assembly encloses a main flow channel with the pump housing and has a number n of blades, each with a flat surface, oriented radially to the rotating shaft and arranged equidistantly to one another around the rotating shaft. Downstream of the bottleneck-shaped flow inlet region is a hollow cylindrical pump housing section, along which is a flow outlet oriented substantially orthogonally to the flow inlet. Within an inner housing, a rotary motor is arranged, which is operatively connected to the blade assembly via a magnetic coupling to drive its rotation.The inner casing, together with the pump casing, encloses a flow channel extending the main flow channel, and, together with the impeller assembly, a secondary channel that communicates fluidically with the main flow channel and is fluidically connected to at least one flushing channel that penetrates the impeller assembly and opens into the bottleneck-shaped flow inlet region. The inner casing also provides a lower bearing facing the impeller assembly for the rotatable mounting of a lower end of the rotating shaft, the upper end of which is supported in a bearing sleeve located in the bottleneck-shaped flow inlet region. State of the art

[0002] German patent application DE 196 26 224 A1 describes a blood pump in whose pump housing a vane assembly is arranged. This vane assembly, together with a rotary shaft, is rotatably mounted about an axis of rotation that passes centrally through the pump housing. The rotary shaft is rotatably mounted at its ends on upper and lower bearings. The lower bearing sits on the upper side of an inner housing located downstream of the vane assembly within the pump housing and encloses an electric motor drive. This drive is operatively connected to the vane assembly, which is fixed to the rotary shaft, via a magnetic coupling.

[0003] The helically shaped impellers of the impeller assembly enclose an axial main flow channel with the inner wall of the pump housing. Pressure drives this channel, creating a blood flow through the blood pump. The impeller assembly also features a secondary or flushing channel that hydraulically connects the suction side of the assembly to its rear side. This allows blood to enter and flush a gap at the rear of the impeller assembly between the assembly and the inner housing. This effectively prevents dead zones at the rear of the impeller assembly.

[0004] Document US 2018 / 0050140 A1 discloses a blood pump with an impeller that provides snail-shaped blades and is interspersed with six so-called washing channels that have at least one tangential directional component and essentially have a circular channel cross-section.

[0005] A blood pump is described in publication EP 1727 987 B1, featuring a blade assembly rotatably mounted within the pump housing via a magnetic bearing. The blades of this assembly can be flat, helical, or otherwise curved. The magnetic bearing of the blade assembly allows for the realization of a cost-effective and low-wear pump, which, in particular, provides for a bearing arrangement that is contactless with the pump housing. The absence of bearing struts connected to the pump housing reduces the problem of blood clot formation in the blood flow area of ​​the pump. The known blade assembly is supported solely by a ball bearing mounted on an inner housing that contains the rotary motor.

[0006] A comparable blood pump with magnetic bearing of the impeller assembly can be found in the publication EP 2 566 533 B1, which has a metallic, conical pin connected to the inner housing inside the pump housing for the purpose of dissipating frictional heat generated during operation, on which the impeller assembly is rotatably mounted via a spherical contour.

[0007] All known blood pumps based on the rotational principle of a blade assembly utilize the centrifugal effect of the rotating blade assembly to generate flow and pressure within the pump. This effect, in addition to a main flow along the main flow channel radially bounded by the blade assembly, the inner casing, and the pump housing, generates a series of secondary flows. These secondary flows branch off from the main flow and flow through further spaces within the pump. To prevent the design-related gap between the blade assembly and the inner casing surrounding the rotary motor from creating a dead space and the associated risk of thrombus formation, the blade assembly incorporates a so-called flushing channel. Due to the prevailing pressure conditions, a secondary blood flow passes through this channel, through the gap, and into the flushing channel to which it is fluidically connected.Without special precautions, a secondary flow retrograde to the main flow direction is formed through the flushing channel penetrating the blade arrangement.

[0008] US patent 2017 / 0361001 A1 discloses a centrifugal blood pump in which the flow inlet and outlet are located in the same hemisphere relative to the rotating impeller assembly. Due to the design, the blood is deflected radially outward by the impeller assembly immediately upon entering the known pump housing and exits radially outward through an outlet located above the plane of the impeller assembly. In one embodiment, the impeller assembly has sectorally shaped openings around the axis of rotation, through which blood can also reach the underside of the impeller assembly.Flow channels, essentially radially oriented and groove-shaped, are provided on the underside of the impeller assembly. These channels create a pressure differential, causing the blood that reaches the underside of the impeller assembly to flow radially outwards and back through openings in the impeller assembly to the upper part of the assembly, finally exiting the blood pump radially outwards. The openings, which are sectorally shaped around the axis of rotation, do not constitute flushing channels in the aforementioned sense and are not subject to any retrograde secondary flow.

[0009] German patent application DE 10 2006 036948 A1 discloses a blood pump with a vane assembly and a cover plate, which incorporates magnetic bearings such that an upper bearing for the vane assembly is unnecessary. The vane assembly is rotatably mounted on a central bearing axis, which, together with the vane assembly, defines an annular flushing channel. Description of the invention

[0010] The invention is based on the objective of providing a blood pump with a pump housing comprising a bottleneck-shaped flow inlet region in which a blade assembly is arranged in a rotationally fixed manner on a rotatably mounted rotating shaft, which encloses a main flow channel with the pump housing and has a number n of blades radially oriented to the rotating shaft, each with a flat surface, which are arranged equidistant from one another around the rotating shaft, as well as a hollow cylindrical pump housing section adjoining the bottleneck-shaped flow inlet region downstream, along which a flow outlet is oriented substantially orthogonally to the flow inlet and in which a rotary motor is arranged within an inner housing, which is operatively connected to the blade assembly for its rotary drive via a magnetic coupling.and the inner housing, together with the pump housing, includes a flow channel extending the main flow channel, and together with the impeller assembly, a secondary channel fluidly communicating with the main flow channel, which is fluidly connected to at least one flushing channel penetrating the impeller assembly and opening into the bottleneck-shaped flow inlet region, and the inner housing also provides a lower bearing facing the impeller assembly for the rotatable mounting of a lower end of the rotating shaft, the upper end of which is supported in a bearing sleeve arranged in the bottleneck-shaped flow inlet region, to be further developed in such a way as to improve the efficiency of the blood pump, i.e., the blood volume pumped with the aid of the blood pump should be achieved with less energy expenditure. In particular, it is important to significantly reduce the operating speed of the rotatably driven impeller assembly.without reducing the pumped blood volume compared to conventional blood pumps. Furthermore, the proposed measure, aimed at more economical operation of the blood pump and a corresponding, desirable reduction in operating speed, is intended to ensure gentler blood transport.

[0011] The solution to the problem underlying the invention is specified in claim 1. Advantageous features of the blood pump according to the solution are the subject of the dependent claims and can be found in the further description, in particular with reference to the illustrated embodiment.

[0012] The blood pump according to the solution with the features specified in the preamble of claim 1 is characterized in that three separate flushing channels, each with a flushing channel longitudinal axis oriented parallel to the rotating shaft, are arranged equally distributed around the rotating shaft and the three flushing channels each have a flushing channel cross-section oriented orthogonally to the rotating shaft, which is each kidney-shaped and encompasses the rotating shaft sectorally.

[0013] Through a large number of flow tests with differently configured blood pumps, the aforementioned blood pump design with optimized fluid dynamic properties was developed. These properties are particularly evident in the fact that the maximum flow rate can be achieved at a given rotational speed through the specific selection of the shape and number of flushing channels oriented parallel to the longitudinal axis of the flushing channel, in conjunction with flat impeller blades extending radially to the rotating shaft and equidistant from each other around the shaft. In other words, compared to known blood pumps of the same size, this design can handle a given flow rate at a lower rotational speed, thereby reducing the mechanical stress on the blood flowing through the pump.

[0014] Preferably, the kidney-shaped irrigation channel cross-sections are each enclosed by a circumferential rim that has a radially outer convex circumferential contour facing away from the rotating shaft and a radially inner concave circumferential contour facing the rotating shaft. The concave circumferential contours of the three irrigation channel cross-sections each lie on a first virtual circle arranged centrally to the rotating shaft. The convex circumferential contours of the three irrigation channel cross-sections, on the other hand, lie on a second virtual circle arranged centrally to the rotating shaft, the radius of which is larger than the radius of the first circle.

[0015] It has proven particularly advantageous to arrange six blades evenly spaced around the rotating shaft.

[0016] In a particularly preferred embodiment, each of the six impeller blades has a radial extension that, in axial projection onto the impeller assembly along the rotating shaft, extends from the aforementioned second virtual circle, which defines the concave circumferential contours of the flushing channel cross-sections, to a third virtual circle arranged centrally to the rotating shaft, wherein the radius of the second virtual circle is smaller than the radius of the third virtual circle. Preferably, the radius of the third circle corresponds at most to the radius of the circular circumferential edge of the impeller assembly in axial projection to the rotating shaft.

[0017] In an alternative embodiment of the blood pump, the six impeller blades are each divided into two groups, a first and a second group, with respect to their shape, size, and arrangement on the impeller assembly. Three of the six impeller blades, belonging to the first group and hereinafter referred to as primary blades, each have a radial extension that, in axial projection onto the impeller assembly along the rotating shaft, extends from the first virtual circle, which defines the aforementioned concave circumferential contours of the kidney-shaped flushing cross-sections, to a third virtual circle arranged centrally to the rotating shaft, which, as in the above case, corresponds at most to the radius of the circular circumferential edge of the impeller assembly.

[0018] The three blades belonging to the second group, the so-called secondary blades, each have a radial extension that, in axial projection onto the blade assembly along the rotating shaft, stretches from the second virtual circle to the third virtual circle, which is arranged centrally to the rotating shaft. The primary and secondary blades are arranged around the rotating shaft in alternating sequences. Further design features and details can be found in the subsequent description with reference to the figures.

[0019] Preferably, the upper and lower bearings, in which the upper and lower ends of the rotating shaft are rotatably but axially fixed, respectively, are made of a ceramic or abrasion-resistant plastic material, preferably UHM plastic. The lower bearing attached to the inner housing preferably comprises a cup-shaped inlay element fixed to the inner housing, into which the lower end of the rotating shaft rotatably and axially fixedly opens, and which is made of a different material than that of the inner housing itself. Brief description of the invention

[0020] The invention is described below by way of example, without limiting the general concept of the invention, with reference to preferred embodiments and the drawings. The drawings show: Fig. 1a, b Side and top view of the pump housing, Fig. 2 Longitudinal section through the pump housing in the area of ​​the flow inlet, Fig. 3 Upper bearing element, Fig. 4 Longitudinal section through the pump housing, Fig. 5 Top view of the blade assembly according to a first embodiment, Fig. 6 Perspective view of the blade assembly according to a second embodiment, Fig. 7 Top view of the blade assembly according to the second embodiment, and Fig. 8a-c Multi-views of a blade assembly with cover plate. Ways to implement the invention, industrial applicability

[0021] The Figures 1a and bFigure 1 shows a side and top view of the pump housing 1 of the blood pump. The pump housing 1, which is essentially bottleneck-shaped in its upper section, has a flow inlet 1' through which blood enters the blood pump along the longitudinal extension of the pump housing 1. The pump housing 1 can be subdivided into a bottleneck-shaped flow inlet region 2 and a hollow cylindrical pump housing section 7 that is flush with it. A flow outlet 1" is provided in the region of the hollow cylindrical pump housing section 7, oriented essentially orthogonally to the flow inlet.

[0022] In order to keep the wall thickness of the pump housing 1 of the blood pump as low as possible, among other reasons for cost and weight, four stabilizing struts 1‴ are attached to the outside of the pump housing 1 in the area of ​​the bottleneck-shaped flow inlet area 2.

[0023] Immediately downstream of the flow inlet 1', four support struts 1st are connected on one side to the inner wall of the pump housing 1. These struts converge orthogonally to form a star-shaped inlet and together provide the spatial support for the upper pivot bearing, which will be discussed later. The support struts 1st are designed with optimized flow dynamics to minimize flow resistance for the blood flow entering through the flow inlet 1'.

[0024] The blood pump shown is a diagonal pump, i.e. the blood flow entering through the flow inlet 1' along the longitudinal extension of the pump housing 1 is redirected orthogonally to the direction of inflow into a blood flow exiting the pump housing 1 tangentially through the flow outlet 1".

[0025] Figure 2Figure 1 shows a partial longitudinal section through the upper part of the pump housing 1 in the region of the bottleneck-shaped flow inlet area 2. Downstream of the flow inlet 1' are the flow-optimized support struts 1st, which are integrally connected to the pump housing 1 and converge to form a star-shaped inlet and terminate centrally at a flow-optimized, capsule-shaped bearing structure 1L. Preferably, the pump housing 1, together with the support struts 1st and the bearing structure 1L, is manufactured in one piece from plastic, preferably by injection molding. A bearing sleeve 15, preferably made of ceramic or largely wear-free plastic material, is flush-mounted (i.e., edgeless) within the bearing structure 1L, into which the upper end of the rotating shaft 3 is axially fixed and rotatably joined (see also). Figure 3 .

[0026] Figure 4shows another partial longitudinal section through the pump housing 1, which represents the bottleneck-shaped flow inlet area 2 and part of the adjoining hollow cylindrical pump housing section 7.

[0027] The pump housing 1 comprises a rotary shaft 3, the upper end of which 30 is axially fixed and rotatable in the bearing sleeve 15, a blade assembly 4 connected to the rotary shaft 3 in a rotationally fixed manner, and an inner housing 8, on the upper side of which is a lower bearing 14 with an inlay element 21, in which the lower end of which 3u is axially fixed and rotatable.

[0028] The blade assembly 4, which is non-rotatably connected to the rotating shaft 3, has six flat blades 5, which are arranged in the Figure 4The illustrated embodiment is identical in shape and size. The six impeller blades 5 are arranged equidistant from each other around the rotating shaft 3. Their radially outer impeller contours enclose a main flow channel 6 with the inner wall of the pump housing 1, through which the blood flow passes in the main flow direction HR when the blood pump is in operation.

[0029] Additionally, we would like to draw your attention to the following: Figure 5 Reference is made to the figure, which shows the blade assembly 4 in an axial plan view in the direction of flow. The blade assembly 4 connects three flushing channels 13, which are arranged equally distributed around the rotating shaft 3. Each of the flushing channels 13 has a kidney-shaped flushing channel cross-section 17, which has a convex circumferential contour 17' facing away from the rotating shaft 3 and a radially inner concave circumferential contour 17" facing the rotating shaft 3.

[0030] The concave circumferential contours 17" of the three flushing channel cross-sections 17 lie on a first virtual circle 18 arranged centrally to the rotating shaft 3. The convex circumferential contours 17' of the three flushing channel cross-sections 17, on the other hand, lie on a second virtual circle 19 arranged centrally to the rotating shaft.

[0031] In the illustrated embodiment, all blades 5 have radial extensions, the radially extending blade ends 5' of which, facing the rotating shaft 3, all lie on the virtual second circle 19 in axial projection onto the blade assembly 4. The radially outer ends 5" of the blades 5, on the other hand, lie on a third virtual circle 20, which corresponds to the circumferential edge of the blade assembly 4 or is spaced from it by a small distance Δx of 0.1 mm ≤ Δx ≤ 2 mm.

[0032] The three flushing channels 13 extend parallel to the axis of rotation 3 and each has a flow-dynamically optimized lower flushing channel opening 13u and an upper flushing channel opening 13o.

[0033] The upper flushing channel opening 13o opens into two flow regions S1 and S2, each of which is bounded by two airfoil blades 5. The orchid-shaped upper flushing channel openings 13o offer minimal flow resistance in the case of a flushing channel flow SR oriented retrogradely to the main flow HR flowing along the main flow channel 6. This allows the retrograde flushing flow SR to enter the main flow HR in the bottleneck-shaped flow inlet region 2 with minimal, or at least virtually no, turbulence.

[0034] The lower flushing channel opening 13u of each flushing channel 13 is also designed for optimal flow to minimize flow resistance. For this purpose, the lower bearing 14 attached to the inner housing 8 provides a flow-dynamically oriented flow profile towards the lower flushing channel opening 13u, which creates the lowest possible entry resistance into the respective flushing channels 13 for a retrograde flushing channel flow SR.

[0035] The blade assembly 4 also features a magnetic coupling 10, which is magnetically coupled to a rotary motor 9 located within the inner housing 8. The permanent magnets or magnetic units required for the magnetic coupling 10 are completely embedded within the blade assembly 4, which is preferably made of a wear-resistant plastic material. The magnetic units can be fully encapsulated either during a casting process or an additive manufacturing process to produce the blade assembly 4.

[0036] In the Figures 6 and 7 An alternative embodiment for a blade arrangement 4 is shown in a perspective oblique view and an axial top view. In contrast to the one shown in the Figures 4 and 5 The blade arrangement shown indicates that blade arrangement 4 is located in the Figures 6 and 7Three primary blades 5P, identical in shape and size, are arranged axially around the rotating shaft 3, alternating with radially shorter secondary blades 5S. All blades 5P and 5S are planar. The primary blades 5P extend radially from the first virtual circle 18 to the third circle 20 at the outer edge. The secondary blades 5S, on the other hand, extend only from the second virtual circle 19 to the third circle 20.

[0037] Out of Figure 6 It can be seen that the upper flushing channel opening 13o opens in an orchid-like manner between two primary blades 5P, with a secondary blade 5S dividing the upper opening area into two flow areas S1 and S2.

[0038] The three primary blades 5P each terminate directly or indirectly at the rotating shaft 3 at their radially directed ends. The secondary blades 5S, with the exception of their shortened radial extent, otherwise have a uniform and identically dimensioned flat surface area like the primary blades 5P.

[0039] In the Figures 8 a, b , c and d Each alternative design form for the configuration of the blade arrangement 4 with a cover plate 22 is illustrated in different views or representation forms. Fig. 8a shows the blade arrangement 4 in a perspective view from a slanted top view, Fig. 8b as a longitudinal section Fig. 8c from the side and Fig. 8d from above. The blade arrangement 4 is similar to the blade arrangement already shown in the Figures 4 and 5As shown, the individual blades 5 are all identically designed and their radially inner blade edges 5' each border the convex circumferential contours of the kidney-shaped flushing channel cross-sections 17. In addition, the flow-facing side edges 5k are shown, see Figure 4 The impeller blades 5 are connected to a cover plate 22, which, together with the inner wall of the pump housing 1, defines the main flow channel 6. The cover plate 22 is conical and has an otherwise straight frustoconical surface, which, together with the inner wall of the pump housing 1, defines a main flow channel 6 that remains constant regardless of the rotational speed of the impeller assembly 4. The cover plate 22 helps to reduce the shear forces and mechanical stresses acting on the blood flow as it passes through the blood pump, thus allowing the blood to pass through the pump more gently.

[0040] Of course, it is also possible to attach the cover plate 22 to the blade assembly 4 according to the instructions in the Figures 6 and 7 to be provided accordingly as illustrated in the exemplary embodiments. Reference symbol list

[0041] 1 Pump housing 1' Flow inlet 1" Flow outlet 1‴ Stability struts 1st Support struts 1LL Bearing structure 2 Bottle-necked flow inlet area 3 Rotating shaft 3o Upper rotating shaft end 3u Lower rotating shaft end 4 Blade assembly 5 Blades 5P Primary blades 5S Secondary blades 5' Radial inner blade edge 5" Radial outer blade edge 5K Side edge 6 Main flow channel 7 Hollow cylindrical pump housing section 8 Inner housing 9 Rotary motor 10 Magnetic coupling 11 Continuing flow channel 12 Secondary channel 13 Flushing channel 13u Lower flushing channel opening 13o Upper flushing channel opening 14 Lower bearing 15 Bearing sleeve 16 Flushing channel longitudinal axis 17 Flushing channel cross-section 17' Convex circumferential contour 17" Concave Circumferential contour 18 First circle 19 Second circle 20 Third circle 21 Inlay element 22 Cover plate SR Secondary flow, flushing flow HR Main flow S1, S2 Flow areas R1, R2, R3 Radii

Claims

1. A blood pump with a pump housing (1) comprising a bottleneck-shaped flow inlet region (2), in which there is arranged a blade assembly (4) that is mounted for conjoint rotation on a rotatably mounted rotary shaft (3), encloses a main flow channel (6) together with the pump housing (1), through which a blood flow passes in the main flow direction (HR) when the blood pump is in operation, and has a number n of blades (5), which are oriented radially to the rotary shaft, each have a flat shape, and are arranged about the rotary shaft (3) equidistantly to one another, and a hollow-cylindrical pump housing portion (7) which adjoins the bottleneck-shaped flow inlet region (2) downstream thereof along a flow outlet (1") oriented essentially orthogonally to the flow inlet, and in which a rotary motor (9) is arranged within an inner housing (8), said rotary motor (9) being operatively connected to the blade assembly (4) in order to rotate same via a magnetic coupling (10), and the inner housing (8) together with the pump housing (1) encloses a flow channel (11), which continues the main flow channel (6), and together with the blade assembly (4) encloses a secondary channel (12), which fluidically communicates with the main flow channel (6), said secondary channel being fluidically connected to at least one flushing channel (13) which passes through the blade assembly (4) and opens into the bottleneck-shaped flow inlet region (2), and the inner housing (8) additionally provides a lower bearing (14) facing the blade assembly (4) for receiving a lower end (3u) of the rotary shaft (3) in a rotatable manner, the upper end (3o) of the rotary shaft being mounted in a bearing sleeve (15) which is arranged in the bottleneck-shaped flow inlet region and which is indirectly secured to the pump housing (1), characterised in that three flushing channels (13), each of which has a flushing channel longitudinal axis (16) oriented parallel to the rotary shaft (3), are distributed evenly around the rotary shaft (3), by which, during operation of the blood pump, a flushing channel flow (SR) oriented retrograde to a main flow direction (HR) flowing along the main flow channel (6) is formed in each case, and in that each of the three flushing channels (13) has a flushing channel cross-section (17) oriented orthogonally to the rotary shaft (3), said cross-sections (17) each being kidney-shaped and surrounding the rotary shaft (3) in sectors.

2. The blood pump according to claim 1, characterised in that the kidney-shaped flushing channel cross-sections (17) are each enclosed by a peripheral edge which has a radially outer convex peripheral edge contour facing away from the rotary shaft and a radially inner concave peripheral edge contour facing towards the rotary shaft, and in that the concave peripheral edge contours of the three flushing channel cross-sections (17) lie on a first virtual circular line (18) arranged centrically to the rotary shaft (3), and in that the convex peripheral edge contours of the three flushing channel cross-sections (17) lie on a second virtual circular line (19) arranged centrically to the rotary shaft (3).

3. The blood pump according to claim 1 or 2, characterised in that the number n of blades is 6.

4. The blood pump according to claim 2 or 3, characterised in that the blades (5) each have a radial extent which, in axial projection onto the blade assembly (4), extends along the rotary shaft (3) from the second virtual circular line (19) to a third virtual circular line (20) arranged centrically to the rotary shaft (3), and in that the radius (R2) of the second virtual circular line (19) is smaller than the radius (R3) of the third virtual circular line (20).

5. The blood pump according to claim 2 or 3, characterised in that a first group (G1) of n / 2 of the blades (5) each have a radial extent which, in axial projection onto the blade assembly (4), extends along the rotary shaft (3) from the second virtual circular line (19) to a third virtual circular line (20) arranged centrically to the rotary shaft (3), the radius (R3) of the third circular line (19) being greater than the radius (R2) of the second circular line (19), in that a second group (G2) of n / 2 of the blades (5) each have a radial extent which, in axial projection onto the blade assembly (4), extends along the rotary shaft (3) from the first virtual circular line (19) to the third virtual circular line (20) arranged centrically to the rotary shaft (3), and in that the blades of the first and second groups (G1, G2) are each arranged in alternating order around the rotary shaft (3).

6. The blood pump according to one of claims 1 to 5, characterised in that the lower bearing (14) attached to the inner housing (8) provides a pot-shaped inlay element (21) which is fixedly joined to the inner housing (8) and into which the lower end (3u) of the rotary shaft (3) opens in a rotatable and axially fixed manner and is made of a different material than that of the inner housing (8).

7. The blood pump according to claim 6, characterised in that the material of the inlay element (21) consists of a ceramic or of a UHM plastic.

8. The blood pump according to claim 7, characterised in that the bearing sleeve (15) is made of the same material as the inlay element (21).

9. The blood pump according to one of claims 1 to 8, characterised in that the blade assembly (4) provides a cover disc (22) which delimits the main flow channel (6) with the pump housing (1).

10. The blood pump according to claim 9, characterised in that the cover disc (22) has a straight frustoconical surface oriented facing towards the pump housing.