blood pump

Abstract

To provide a blood pump.SOLUTION: A blood pump 1 comprises a pump casing 2 having a blood flow inlet 5 and a blood flow outlet 6 connected by a passage 7, and an impeller 3 arranged in the pump casing 2 so as to be rotatable on an axis of rotation 9. The impeller 3 is provided with blades 4 sized and shaped for conveying blood along the passage 7 from the blood flow inlet 5 to the blood flow outlet 6, the impeller 3 being rotatably supported in the pump casing 2 by a contact-type bearing 20 comprising a bearing surface of the impeller 3 facing a bearing surface of the pump casing 2. A wash out channel 30 extends through the impeller 3 and is in fluid connection with the passage 7 via a first opening 34 and with the bearing 20 via a second opening 35. The wash out channel 30 is operatively associated with a secondary pump, and the secondary pump is formed at least partially by the wash out channel 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to blood pumps that are implanted in a patient to provide cardiac support. In particular, blood pumps may be used as "bridge-to-recovery" devices, where the blood pump provides temporary support until the patient's heart has fully recovered.

[0002] Various types of blood pumps are known, such as axial flow blood pumps, centrifugal blood pumps, or mixed flow blood pumps, which generate blood flow through both axial and radial forces. Blood pumps may be inserted into a patient's blood vessels, such as the aorta, using a catheter, or may be placed intrathoracic. Blood pumps generally include a pump casing having a blood inlet and a blood outlet connected by a passageway. An impeller with blades that transport blood is rotatably supported within the pump casing to generate blood flow along the passageway from the blood inlet to the blood outlet.

[0003] The impeller is supported within the pump casing by at least one bearing, which may be of different types depending on the intended use of the blood pump, e.g., whether the blood pump is intended for short-term use (hours or days) or long-term use (weeks or years). Different types of bearings are known, such as contact and non-contact bearings. In non-contact bearings, the bearing surfaces do not contact each other, for example, in the case of magnetic bearings, where the bearing surfaces are "levitated" by repulsive magnetic forces. Generally, contact bearings may include all types of bearings, such as plain bearings, pivot bearings, hydrodynamic bearings, hydrostatic bearings, ball bearings, or any combination thereof, in which the bearing surfaces may be in at least partial contact at any time during pump operation (i.e., constantly or intermittently). In particular, contact bearings may be "blood-immersed bearings," in which the bearing surfaces are in blood contact. Contact bearings may heat up during use and are prone to mechanical wear due to contact between the rotating and stationary bearing surfaces during pump operation. It may be desirable to provide a cooling fluid, such as the blood itself, to the bearings. In non-contact bearings, the bearing surfaces are not in physical contact but are separated by gaps that are in fluid communication with passages or other fluid supplies. Similarly, other gaps between the impeller and the pump casing should be flushed to avoid blood clotting and clogging, for example at the downstream front face of the impeller.

[0004] An arrangement for rinsing gaps or bearing surfaces within a blood pump is disclosed, for example, in U.S. Patent Application Publication No. 2011 / 0238172 A1. A flushing channel extends through the impeller and is in fluid communication with the passageway and gap via first and second openings. Pressure distribution within the pump casing induces blood flow through the gap and flushing channel when pressure increases downstream along the impeller. Blood enters the gap at the downstream end of the impeller and flows through the flushing channel toward the area of ​​the passageway at low pressure. This flushing flow has the disadvantage of being dependent on the rotational speed of the impeller, due to the pressure differential that must be created to induce blood flow. Other forces, such as centrifugal force and counterforces due to the reverse direction of the flushing flow, must also be overcome. In another embodiment disclosed in U.S. Patent Application Publication No. 2011 / 0238172 A1, in which the impeller is supported within the pump casing by hydrodynamic bearings, the inlet opening of the wash channel is disposed at the upstream end of the impeller, and auxiliary vanes at the downstream end of the impeller are provided to induce wash flow through the wash channel and gap in a direction from the low-pressure area to the high-pressure area. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, a main object of the present invention is to provide a blood pump in which stagnation of blood flow and blood coagulation and clogging in gaps between rotating and stationary parts of the blood pump, particularly between the bearings or impeller and the stationary and rotating parts of the pump casing, are effectively avoided regardless of the rotational speed or operating conditions of the pump.A further object of the present invention is to provide a blood pump capable of effective cooling of contact-type bearings.A still further object of the present invention is to provide a blood pump capable of effective flushing of gaps. [Means for solving the problem]

[0006] The main object is achieved according to the invention by a blood pump with the features of independent claim 1. Preferred embodiments and further developments of the invention are specified in the claims dependent on the independent claim.

[0007] Like known blood pumps, the blood pump according to the present invention comprises a pump casing having a blood inlet and a blood outlet connected by a passageway. The pump casing may be understood as comprising all stationary parts of the blood pump. An impeller or rotor is disposed within the pump casing so as to be rotatable about an axis of rotation, which may be the longitudinal axis of the impeller, and the impeller comprises blades sized and shaped to transport blood along the passageway from the blood inlet to the blood outlet. The impeller is rotatably supported within the pump casing by at least one contact bearing, preferably a pivot bearing, with a bearing surface of the impeller facing a bearing surface of the pump casing.

[0008] At least one flush channel extends through the impeller and is fluidly connected to the passageway through a first opening and to the bearing through a second opening. To generate a flush flow, sometimes referred to as a dynamic flush flow, the flush channel is operatively associated with an auxiliary pump that pumps blood through the flush channel toward the bearing. According to the present invention, the auxiliary pump is at least partially formed by the at least one flush channel that extends through the impeller along a direction having at least one tangential component. In other words, the second pump is at least partially formed by the at least one flush channel itself, which is specifically sized, shaped, and positioned to pump blood through the flush channel toward the bearing. By providing an auxiliary pump that generates a dynamic flush flow, rinsing of the contact bearing, and thus cooling of the bearing, can be improved compared to configurations that do not include means for dynamically pumping blood toward the bearing. The auxiliary pump may be supported by a suitable pressure distribution within the pump, as described in more detail below. However, it will be appreciated that the backing pump operates independently of the pressure distribution within the pump.

[0009] Dynamic flush flow is particularly useful for contact-type bearings or "blood-immersed bearings" because it increases the amount of blood delivered to the bearing for flushing and cooling it compared to pumps without an auxiliary pump. Bearing cooling can be further improved by effectively dissipating heat from the bearing surface. To this end, the bearing may comprise a highly conductive material, such as stainless steel, which can dissipate heat better than ceramics or titanium. It may be advantageous to provide a bearing with at least two components, particularly where the bearing surface is made of a smooth, resistant material, such as ceramic, provided, for example, in the form of a ceramic cap, and the portion of the bearing facing away from the bearing surface may be made of a highly conductive material, such as stainless steel.

[0010] In one embodiment, the rinse channel may extend straight through the impeller and be offset relative to the axis of rotation. In particular, the rinse channel may extend in a plane parallel to the axis of rotation. By providing an arrangement with a straight rinse channel that is oblique to, i.e., does not intersect, the axis of rotation, a dynamic rinse flow can be directed through the rinse channel.

[0011] In another embodiment, the flushing channel may be curved and extend from the first opening in a direction around the axis of rotation, in particular along a helical shape. A helical shape is to be understood as any curved, spiral, helical or other curved shape in a direction around the axis of rotation of any length. Such a shape may be advantageous as it can support a dynamic flushing flow towards the bearing.

[0012] Preferably, the flushing channel extends from the first opening in a circumferential direction opposite the direction of rotation at an angle relative to the surface of the impeller. In particular, in contrast to flushing channels extending perpendicular to the surface of the impeller, the angled inlet opening facilitates blood entry into the flushing channel and increases the flow rate through the flushing channel. This effect can be further improved by selecting an appropriate angle. For example, the angle may be less than 20°, preferably less than 15°, and more preferably less than 10°. The flushing channel may extend from the first opening in a direction substantially tangential to the surface of the impeller, i.e., at a very small angle relative to the surface of the impeller. However, it is important that the angle be in a circumferential direction opposite the direction of rotation, i.e., that the first opening be open in the direction of rotation, in order to increase the amount of blood flowing through the flushing channel compared to an arrangement in which the flushing channel extends perpendicular to the surface of the impeller.

[0013] In one embodiment, the distance between the second opening and the rotation axis may be equal to or less than the distance between the first opening and the rotation axis. In other words, the flush channel extends downstream toward the rotation axis. Preferably, the distance between the first opening and the rotation axis is as short as possible to reduce the centrifugal force that the flush flow in the flush channel must overcome. In other words, the distance between the first opening and the second opening in the radially inward direction should be as short as possible. Furthermore, it is preferred that the distance between the rotation axis and the first opening is significantly shorter, for example, less than half (50%), less than 40%, or even less than 30%, of the distance between the rotation axis and the point where the flush flow exits the passage. This configuration can improve centrifugal blood pumps over axial or mixed-flow blood pumps, i.e., it can increase the distance between the first opening and the point where the flush flow exits the passage.

[0014] The impeller may have a central opening extending along the axis of rotation and receiving the bearing, and the second opening may be fluidly connected to the central opening. Further, the rinse channels may be oriented substantially radially at the second opening and toward the axis of rotation, which may improve rinsing of the bearing and thereby cooling of the bearing.

[0015] Preferably, the first opening of the wash channel is disposed adjacent to one of the impeller vanes on the vane's forward side (commonly referred to as the vane's pressure side) relative to the direction of rotation. In this area, the pressure is higher than in the area on the vane's reverse side (commonly referred to as the vane's suction side), thereby improving the dynamic wash flow through the wash channel toward the bearing. In one embodiment, the first opening may be disposed on the vane's forward side and the second opening may be disposed on the vane's reverse side, i.e., both openings are disposed on the vane's radially outer surface, and the wash channel extends downward and across the vane. In another embodiment, the wash channel may extend within the vane, whereby the first opening is disposed on the vane's forward side and the second opening is disposed on the vane, particularly at the vane's radially outer edge. It should be understood that the wash channel is in fluid communication with the area to be washed.

[0016] As described, the performance or output of the auxiliary pump can be improved by a particular configuration of the wash channel through the impeller, e.g., a straight or curved wash channel, which may extend at an angle relative to the surface of the impeller. The performance of the auxiliary pump can be further improved by the cross-section of the first opening of the wash channel. The cross-section of the first opening can be circular or non-circular. If the wash channel has a circular cross-section and extends at an angle relative to the surface of the impeller, this results in a non-circular cross-section, such as an elliptical cross-section. In one embodiment, the first opening can be formed by an end portion of the wash channel that is at least partially exposed due to the wash channel being angled relative to the surface of the impeller. In other words, the first opening can be elongated at the surface of the impeller, which can further increase the amount of blood entering the wash channel during operation of the blood pump.

[0017] In another embodiment, the protrusions extend into the first opening of the flush channel and are sized and shaped to increase blood flow through the first opening into the flush channel, particularly compared to the cross-section of the first opening without the protrusions. The shape of the first opening without the protrusions may be either circular or non-circular. The protrusions are disposed on the opposite side of the first opening relative to the direction of rotation, thereby acting as an "airfoil" to promote blood flow into the first opening and thereby improve the performance of the auxiliary pump. Alternatively, or in addition, the impeller may include wings extending radially therefrom and disposed adjacent to the first opening of the flush channel and rearward of the first opening relative to the direction of rotation. Preferably, the wings extend over the first opening of the flush channel and are open in the direction of rotation to allow blood to enter the first opening. The wings form pockets that collect blood during impeller rotation and direct the collected blood into the first opening. To achieve a similar effect, the impeller may include a nose or protrusion with the first opening such that the cross section of the first opening extends at an angle relative to the surface of the impeller, preferably greater than 45°, more preferably 90°, and opens in the direction of rotation, thereby significantly increasing the amount of blood entering the flushing channel.

[0018] Preferably, the blood pump comprises two or more of the above-mentioned flushing channels, which may be arranged symmetrically with respect to the axis of rotation. In particular, the blood pump may comprise two, three, four, five or six flushing channels.

[0019] In addition to the size, shape, and placement of the flush channel forming at least a portion of the auxiliary pump, the auxiliary pump may further include grooves or vanes formed in the surface of the impeller, which may be disposed on the downstream front face of the impeller to assist blood flow through the flush channel toward the bearing.

[0020] In one embodiment, the impeller may have a portion extending radially outward in the downstream direction, and the first opening of the wash channel is disposed in the portion. In particular, the portion has a conical tapering shape extending radially outward in the downstream direction. The portion may be formed integrally with the impeller or separately. The performance of the auxiliary pump may be further improved by locating the first opening in the radially extending portion of the impeller so that it is oriented in a direction opposite to the main direction of blood flow through the passage. This allows the first opening to capture more blood, improving the performance of the auxiliary pump. The impeller vanes may extend over the portion.

[0021] In a preferred embodiment, the first opening of the washout channel is positioned in a region of the impeller that is under higher pressure than the second opening during pump operation, forcing blood flow from the first opening through the washout channel to the bearing. In other words, the first opening of the washout channel, i.e., the inlet opening of the washout channel, is in a high-pressure region of the impeller, but because pressure is lower downstream of the impeller, the washout flow is directed in a "forward" direction, i.e., toward the blood outlet of the pump casing. Therefore, by utilizing this pressure difference that arises during blood pump operation, particularly the local pressure gradient within the washout channel, forward flow washout is created. This has the advantage that the required pressure difference is present at all times during pump operation, independent of rotational speed and operating conditions (e.g., preload, afterload, magnitude of initial forward flow), especially at the beginning of operation when the impeller starts to rotate and rotational speed is slow, especially below the design speed of the blood pump. In contrast, in known blood pumps in which the wash flow is directed in the "reverse" direction, a pressure difference must be built up, which takes some time, during which the wash flow may be slow or stagnant. This can lead to blood clotting and clogging in the gap or the wash channel, or both. Furthermore, the reverse flow must overcome forces generated by the main direction of flow, which can also lead to stagnation of the wash flow and consequently to blood clotting and clogging. According to the present invention, the wash flow is in the "forward" direction throughout the operation time of the blood pump, and in particular takes advantage of the pressure distribution within the pump casing during operation of the pump.

[0022] The first opening of the wash channel may be located in the downstream half of the impeller. During pump operation, pressure increases along the length of the impeller, particularly in the region where the impeller blades are located. Therefore, higher pressure exists in the downstream half of the impeller than in the upstream half of the impeller. Because higher pressure is preferred at the first opening of the wash channel, it is preferred to locate the first opening in the downstream half of the impeller. More preferably, the first opening may be located in the downstream third, downstream quarter, or downstream fifth of the impeller. It is particularly advantageous to locate the first opening as close as possible to the downstream end of the impeller, for example, within the last 10% of the impeller's length in the downstream direction.

[0023] With respect to the pressure distribution, the first opening of the flushing channel is preferably disposed in a region of the impeller where, during operation of the pump, the pressure is higher than the intermediate pressure, more preferably substantially the maximum pressure, relative to the pressure distribution along the length of the passage in which the impeller is located. A high pressure difference between the first and second openings of the flushing channel improves the flushing flow from the first opening of the flushing channel to the bearing. In particular, a high pressure difference is advantageous for supporting the auxiliary pump.

[0024] The foregoing summary, as well as the following detailed description of the preferred embodiments, will be better understood when read in conjunction with the appended drawings. For purposes of illustrating the present disclosure, reference is made to the drawings. However, the scope of the present disclosure is not limited to the specific embodiments disclosed in the drawings. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view of a blood pump according to the present invention for extracardiac applications; [Figure 1A] 1 is a cross-sectional view of a blood pump according to the present invention for extracardiac applications; [Figure 2] 1 is a cross-sectional view of a blood pump according to the invention designed as a catheter pump; [Figure 3] FIG. [Figure 4a] 1A-1C show various views of a portion of an impeller; [Figure 4b] 1A-1C show various views of a portion of an impeller; [Figure 4c] 1A-1C show various views of a portion of an impeller; [Figure 4d] 1A-1C show various views of a portion of an impeller; [Figure 5a] 10A and 10B show other embodiments of the impeller. [Figure 5b] 10A and 10B show other embodiments of the impeller. [Figure 6a] FIG. 10 illustrates another embodiment of a portion of an impeller. [Figure 6b] FIG. 10 illustrates another embodiment of a portion of an impeller. [Figure 7] FIG. 10 is a cross-sectional view of a portion of a blood pump according to another embodiment. [Figure 8] FIG. 10 is a cross-sectional view of a portion of an impeller according to another embodiment. [Figure 9] FIG. 10 is a cross-sectional view of a portion of an impeller according to another embodiment. [Figure 10] FIG. 10 is a cross-sectional view of a portion of an impeller according to yet another embodiment. [Figure 11] FIG. 10 is a cross-sectional view of a portion of a blood pump according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] Referring to FIG. 1, a cross-sectional view of a blood pump 1 is shown. The blood pump 1 is designed for extracorporeal, extracardiac, or extraluminal use and includes a pump casing 2 having a blood inlet 5 and a blood outlet 6. During operation, the pump casing 2 is located outside the patient's body, and the blood inlet 5 and the blood outlet 6 are connected to respective connectors (specifically, the inflow from the heart and the outflow to the aorta). FIG. 2 shows an embodiment similar to FIG. 1, except that it is designed as a catheter pump 1′. The blood inlet 5′ is at the end of a flexible catheter 50 placed through a heart valve, such as the aortic valve. During use, the blood outlet 6′ is located on the side of the pump casing 2′ and within a cardiac vessel, such as the aorta. The blood pump 1′ is connected to a catheter 51, through which electrical wires 52 extend to drive the pump 1′. Both blood pumps 1 and 1′ function in the same way. It will be understood that all features described below are applicable to both embodiments.

[0027] Blood is transported along a passageway 7 connecting the blood inlet 5 and the blood outlet 6. The impeller 3 is provided to transport blood along the passageway 7 and is rotatably mounted within the pump casing 2 by a first bearing 10 and a second bearing 20 about a rotation axis 9. The rotation axis is preferably the longitudinal axis of the impeller 3. Both bearings 10 and 20 are contact-type bearings. However, at least one of the bearings 10 and 20 can be a non-contact bearing, such as a magnetic or hydrodynamic bearing. The second bearing 20 is a pivot bearing with a spherical bearing surface that allows some rotational and pivotal movement. The first bearing 10 is disposed within a support member 15 to stabilize the rotation of the impeller 3, and the support member 15 has at least one opening 16 for blood flow. Blades 4 are provided on the impeller 3 to transport blood as the impeller 3 rotates. Rotation of the impeller 3 is caused by an electric motor stator 8 that is magnetically coupled to an end portion 37 of the impeller 3. As will be appreciated by those skilled in the art, other suitable drive mechanisms are possible. The illustrated blood pump 1 is a mixed-type blood pump, with the primary flow direction being axial. It will be appreciated that depending on the arrangement of the impeller 3, particularly the blades 4, the blood pump 1 may also be a purely axial-flow blood pump.

[0028] The impeller 3 includes a portion 33 disposed at a downstream portion of the impeller 3 and extending radially outward. The portion 33 may be referred to as a yoke, a flange portion, or an end portion. In this embodiment, the portion 33 includes an outer surface extending at an angle of 45° relative to the rotation axis 9. Other suitable angles, such as angles between 30° and 60°, may be selected, or the surface may be curved. The portion 33 may be formed integrally with the impeller 3 or separately, as shown in this embodiment. At least one flush channel 30, preferably two or more, such as three, four, five, or six, flush channels 30, only one of which is shown in FIG. 1 , extends through the impeller 3, particularly through the portion 33, to allow flushing or rinsing of the pivot bearing 20 and the gap 31 between the impeller 3 and the stationary portion of the blood pump 1, particularly the pump casing 2 or the motor 8, which may be considered associated with the pump casing 2. At least one rinse channel 30 may also extend at least partially beyond portion 33 into the main portion of the impeller 3 .

[0029] The flush channel 30 has a first opening 34 or inlet opening and a second opening 35 or outlet opening. The first opening 34 forms a fluid connection between the passage 7 and the flush channel 30, and the second opening 35 is fluidly connected to the gap 31. In particular, the second opening 35 is fluidly connected to a central bore or central opening 32 of the portion 33, which receives the second bearing 20. The gap 31 is fluidly connected to the passage 7 through a gap transition point 36, i.e., the location where the gap 31 opens to the passage 7.

[0030] The first opening 34 of the wash channel 30 is disposed in the downstream half of the impeller 3. In particular, the first opening 34 is disposed in a region of the impeller 3 that is under high pressure due to the rotation of the impeller 3 during operation of the blood pump 1. In particular, the first opening 34 may be located in a region close to or at the maximum pressure within the pump casing 2. The pressure increases due to the vanes 4 and the deflection of the fluid from the axial direction to the radial direction, and decreases downstream of the vanes 4. Therefore, by appropriately selecting the location of the first opening 34 near the downstream end of the impeller 3, the pressure at the gap transition point 36 is lower than at the first opening 34 of the wash channel 30. This pressure distribution can be appropriately improved by selecting the shape of the vanes 4, resulting in a flow direction from the first opening 34 through the wash channel 30 and the gap 31 to the gap transition point 36. Alternatively, a further pressure drop at point 36 can be achieved by creating a local pressure drop by the Venturi effect in the vicinity of point 36, for example by providing a constriction 53 in passage 7 (see FIG. 1A). In other words, blood flows in a forward direction through wash channel 30 towards blood outlet 6 of pump casing 2. During operation of blood pump 1, particularly during phases of low rotational speeds below the design speed of blood pump 1, the forward flow wash occurs at all rotational speeds, thereby effectively avoiding blood coagulation.

[0031] Apart from flushing the pivot bearing 20 and gap 31, the blood flow through the flush channel 30 also results in cooling of the pivot bearing 20. The pivot bearing 20 is located in the central opening 32 of the portion 33. Thus, blood is transported through the flush channel 30 towards the bearing 20. The pivot bearing 20 can be effectively cooled and rinsed. As will be described in more detail below, the effect can be further improved by providing an auxiliary pump that actively pumps blood through the flush channel 30 towards the bearing 20. Although the "forward" direction of the flush flow through the flush channel 30 as described is advantageous, the flush flow may be directed in any direction.

[0032] Referring now to FIG. 3, one embodiment of an impeller 3 is shown. The impeller has blades 4 arranged around the body of the impeller 3. The blades 4 are sized and shaped to transport blood as the impeller 3 rotates in a direction of rotation (indicated by the arrow in FIG. 3). The impeller 3 has a downstream end 33 that has at least one washout channel 30 with an inlet opening 34. As mentioned above, the inlet opening 34 is located within the area of ​​the impeller 3. The impeller 3 ensures that under high pressure, blood flow through the washout channel 30 is directed from the first opening 34 or the inlet opening to the second opening 35. In this embodiment, the inlet opening 34 is disposed on the forward side of one of the blades 4 relative to the direction of rotation (also referred to as the pressure side of the blade). In particular, the pressure is higher on the forward side compared to the reverse side of the vane 4 (also called the suction side of the vane), thereby favoring the direction of inflow to the inlet opening 34 of the wash channel 30. In any case, the opening 34 is disposed on the reverse side of the vane 4. The reverse side of the vane 4 is the side where the pressure may be high enough for the opening 34 to be disposed in the portion 33 at the downstream end of the impeller 3.

[0033] 4a-4b show various views of one embodiment of portion 33. In this embodiment, flush channels 30 form an auxiliary pump that pumps blood from the flush channels 30 through their respective first openings 34 to the second openings 35, and thus to the central opening 32 and bearing 20, and further to the clearance transition point 36 (see FIG. 1). In this embodiment, the flush channels 30 extend linearly through the impeller 3 and are offset from the axis of rotation 9 (indicated by the dashed line in FIG. 4b, a bottom view of portion 33). Because the flush channels 30 extend in a plane parallel to the axis of rotation 9, the flush channels 30 extend along a direction that has a tangential component. This arrangement directs blood flow from the first openings 34 to the second openings 35. Two flush channels 30 are shown in this embodiment. However, it will be understood that three, four, or more flush channels could similarly be provided and may be symmetrically arranged around the axis of rotation 9. As can be seen in particular in Figure 4d, which is a cross-sectional view along line BB in Figure 4b, the rinse channel 30 is inclined in the downstream direction. The second opening 35, which is downstream relative to the first opening 34, is closer to the axis of rotation 9 than the first opening 34. The rinse channel 30 opens into a central opening 32, which at least partially receives the second bearing 20, as shown in Figure 1.

[0034] Further embodiments of the impeller 3 having a flush channel 30 forming an auxiliary pump are shown in Figures 5a and 5b. According to the embodiment of Figure 5a, the first opening 34 is not circular. More precisely, a protrusion 38 extends into the first opening 34 to increase the amount of blood flowing through the first opening 34 into the flush channel. The protrusion 38 is located on the opposite side of the first opening 34 relative to the direction of rotation. The resulting shape of the first opening 34 may be called kidney-shaped. This acts like an "airfoil," since as the impeller 3 rotates, a pull or suction is created, increasing the amount of blood entering the first opening 34, especially compared to embodiments without the protrusion 38 (such as the embodiment of Figure 3). The shape of the protrusion 38 can be selected according to the desired amount of blood to flow through the flush channel 30. The cross section of the first opening 34 may be symmetrical or asymmetrical.

[0035] Instead of or in addition to the protrusions 38, wings 39 may be provided as shown in FIG. 5b. The wings 39 are positioned behind the first openings 34 relative to the direction of rotation and form pockets that capture more blood as the impeller 3 rotates in the direction of rotation. The wings 39 may have any size and shape suitable for increasing the amount of blood entering the first openings 34 compared to embodiments without wings 39 (such as the embodiment of FIG. 3). The same effect can be achieved by positioning the first openings 34 on a nose or protrusion extending radially from the impeller 3, with the first openings 34 pointing in the direction of rotation.

[0036] 6a and 6b, one embodiment of a portion 33' having a flush channel 30' is shown. The direction of rotation is indicated by the arrows. As in the previously described embodiment, the flush channel 30' has a first opening 34' and a second opening 35' facing a central opening 32'. The flush channel 30' forms part of an auxiliary pump, as described in connection with other embodiments, to drive blood flow from the first opening 34' to the second opening 35' toward the second bearing 20. In this embodiment, the flush channel 30' is curved and extends around the axis of rotation 9 in a helical shape. It will be understood that the term "helical shape" includes any curved shape, whether forming a regular spiral or any other curved shape having at least one tangential component. The flush channel 30' enters the impeller 3 at a first opening at a small angle, whereby the first opening 34', formed by the exposed portion of the flush channel 30', has an elongated shape. This promotes blood capture and helps increase the amount of blood entering the first opening 34', particularly compared to configurations in which the flush channel 30' extends to the surface of the impeller 3 at a larger angle, such as perpendicular or substantially perpendicular. The flush channel 30' extends in a curved shape toward the central opening 32' and exits the second opening 35' in a substantially radial direction. Blood is effectively pumped into the central opening 32' and thus to the second bearing 20, rinsing and cooling the second bearing 20. As described in connection with FIG. 1 , blood flow through the flush channel 30' effectively flushes the gap 31 between the rotating impeller 3 and the stationary pump casing 2. To further improve the performance of the backing pump, the backing pump may further comprise grooves or vanes formed on the surface of the impeller 3, particularly in the gap 31.

[0037] It should be understood that the auxiliary pump described above cannot overcome the centrifugal effect of a rotating channel of any shape extending from a large diameter to a small diameter without assistance from the centrifugal pumping action in the gap 31.

[0038] The performance of the backing pump can be further improved by the position of at least one of the first opening 34 and the clearance transition point 36 relative to the rotation axis 9, and in particular relative to each other. As shown in FIG. 7 , the first opening has a first distance d1 to the rotation axis 9, and the clearance transition point 36 has a second distance d2 to the rotation axis 9. The performance of the backing pump can be improved if the first opening 34 is as close as possible to the rotation axis 9, i.e., if the distance d1 is as small as possible and the wash channel 30 extends only a short distance toward the rotation axis 9. This reduces the centrifugal force that the wash flow must overcome in the direction toward the rotation axis. In particular, it is advantageous if the first distance d1 is small compared to the second distance d2, and preferably d1 may be less than half of d2.

[0039] In another embodiment, shown in cross section perpendicular to the axis of rotation 9 in FIG. 8 , the impeller 3 includes a wash channel 40 having a first opening 41 and a second opening 42 disposed on the radially outer surface of the impeller 3. The first opening 41 is disposed on the forward side of one of the vanes 4 relative to the direction of rotation (indicated by the arrows in FIG. 8 ), and the second opening 42 is disposed on the reverse side of the vane 4. This results in blood flow from the first opening 41 to the second opening 42. The wash channel 40 is in fluid communication with the central opening 32 to wash and cool the bearing 20. In the embodiment of FIG. 9 , a wash channel 43 is provided, similar to the embodiment of FIG. 8 , having a first opening 44 disposed on the forward side of one of the vanes 4. However, the wash channel 43 extends through the vane 4 and exits through a second opening 45 located at the edge of the vane 4. This arrangement makes it possible to use centrifugal force to direct the wash flow from the first opening 44 to the second opening 45. Figure 10 shows another embodiment similar to Figure 9, except that the first opening 44' of the wash channel 43' is disposed on the diagonally opposite side of the vane 4 through which the channel 43' extends, where it exits at a second opening 45'. Thus, in this embodiment, the wash channel 43' runs diagonally or radially, rather than tangentially as in the embodiment of Figure 9, and therefore touches all sides of the bearing 20.

[0040] An embodiment similar to FIG. 8 is shown in FIG. 11. A wash channel 40′ has a first opening 41′ disposed on a forward side of one of the vanes 4 relative to the direction of rotation, and a second opening 42′ disposed on a reverse side of the vane 4. (Note that the wash channel 40′ is shown in cross section in FIG. 11, but does not extend in the plane of the cross section, similar to the cross section shown in FIG. 8.) The wash channel 40′ extends below the vane 4. However, in the embodiment of FIG. 11, the wash channel 40′ does not extend in a plane perpendicular to the longitudinal axis 9, and the second opening 42′ is disposed downstream of the first opening 41′. Thus, the second opening 42′ is also disposed radially outward from the first opening 41′. This arrangement allows the flushing flow to be increased by centrifugal forces at the outlet section of the flushing channel 40' leading to the second opening 42'. Also, the pressure difference between the first opening 41' and the second opening 42' in the passage 7 enhances the flushing flow.

[0041] It will be appreciated that at least one of the flushing channels 40, 40', 43, 43' described in connection with Figures 8-11 may be provided in place of or in addition to the flushing channels 30, 30' described above. It will also be appreciated that the channels 40, 40', 43, 43' are in fluid communication with the central opening 32 and the gap 31, thereby enabling overall flushing flow in the same manner as described above.

[0042] Preferred embodiments are described in the following paragraphs.

[0043] 1. A pump casing 2 having a blood inlet 5 and a blood outlet 6 connected by a passage 7; an impeller (3) disposed within said pump casing (2) so as to be rotatable about a rotation axis (9), said impeller (3) having blades (4) sized and shaped to transport blood along a passage (7) from a blood inlet (5) to a blood outlet (6), said impeller (3) being rotatably supported within said pump casing (2) by at least one contact bearing (20) having a bearing surface of said impeller (3) facing a bearing surface of said pump casing (2); at least one flush channel (30) extending through the impeller (3) and fluidly connected to the passage (7) via a first opening (34) and to the bearing (20) via a second opening (35), the flush channel (30) being operatively associated with an auxiliary pump that pumps blood through the flush channel (30) and toward the bearing (20); A blood pump (1) wherein the auxiliary pump is at least partially formed by said at least one flush channel (30) extending through the impeller (3) along a direction having at least one tangential component.

[0044] 2. The blood pump of paragraph 1, wherein the flush channel 30 extends in a straight line through the impeller 3 and is offset relative to the axis of rotation 9.

[0045] 3. The blood pump of paragraph 2, wherein the flushing channel 30 extends in a plane parallel to the axis of rotation 9.

[0046] 4. The blood pump of paragraph 1, wherein the flush channel 30 is curved and extends from the first opening 34 in a direction circumferential about the axis of rotation 9.

[0047] 5. The blood pump of any one of paragraphs 1 to 4, wherein the flush channel 30 extends from the first opening 34 in a circumferential direction opposite the direction of rotation and at an angle to the surface of the impeller 3.

[0048] 6. The blood pump of paragraph 5, wherein the angle is less than 20°, preferably less than 15°, and more preferably less than 10°.

[0049] 7. The blood pump of paragraph 5 or 6, wherein the flush channel 30 extends from the first opening 34 substantially tangentially to the surface of the impeller 3.

[0050] 8. The blood pump of any one of paragraphs 1 to 7, wherein the distance between the second opening 35 and the rotation axis 9 is less than or equal to the distance between the first opening 34 and the rotation axis 9.

[0051] 9. The blood pump of any one of paragraphs 1 to 8, wherein the distance between the rotation axis 9 and the first opening 34 is less than 50%, preferably less than 40%, and more preferably less than 30% of the distance between the rotation axis 9 and the point 36 where the flush flow exits the passage 7.

[0052] 10. The blood pump of any one of paragraphs 1 to 9, wherein the impeller 3 extends along the rotation axis 9 and has a central opening 32 that receives the bearing 20, and the second opening 35 is fluidly connected to the central opening 32.

[0053] 11. The blood pump of any one of paragraphs 1 to 10, wherein the flush channel 30 in the second opening 35 is oriented substantially radially toward the axis of rotation 9.

[0054] 12. The blood pump of any one of paragraphs 1 to 11, wherein the first opening 34 of the flushing channel 30 is disposed adjacent to one of the blades 4 of the impeller 3, on the forward side of the blade 4 relative to the direction of rotation.

[0055] 13. The blood pump of any one of paragraphs 1 to 12, wherein the cross section of the first opening 34 is circular.

[0056] 14. The blood pump of any one of paragraphs 1 to 12, wherein the cross section of the first opening 34 is non-circular.

[0057] 15. The blood pump of any one of paragraphs 1 to 13, wherein the first opening 34 is formed by an end portion of the flushing channel 30 that is at least partially exposed by the flushing channel 30 being inclined relative to the surface of the impeller 3.

[0058] 16. The blood pump of any one of paragraphs 1 to 15, wherein the protrusions 38 extend into the first openings 34 of the flushing channel 30 and are sized and shaped to increase blood flow through the first openings 34 and into the flushing channel 30.

[0059] 17. The blood pump of any one of paragraphs 1 to 16, wherein the impeller 3 has at least one wing 39 extending radially therefrom and disposed adjacent to and aft of the first opening 34 of the flushing channel 30 in the direction of rotation.

[0060] 18. The blood pump of paragraph 17, wherein the wings 39 extend over the first opening 34 of the flush channel 30 and are rotationally open to allow blood to enter the first opening 34.

[0061] 19. The blood pump of any one of paragraphs 1 to 16, wherein the impeller 3 has protrusions extending radially therefrom, the protrusions having first openings 34 such that a cross section of the first openings 34 extends at an angle to the surface of the impeller 3 and is open in the direction of rotation, the angle preferably being greater than 45°, more preferably 90°.

[0062] 20. The blood pump of any one of paragraphs 1 to 19, comprising two or more flush channels 30 arranged symmetrically with respect to the axis of rotation 9.

[0063] 21. The blood pump of any one of paragraphs 1 to 20, wherein the auxiliary pump has grooves or vanes formed on the surface of the impeller 3.

[0064] 22. The blood pump of any one of paragraphs 1 to 21, wherein the impeller 3 has a portion 33 in the downstream direction extending radially outward, and the first opening 34 of the flushing channel 30 is arranged in said portion 33.

[0065] 23. The blood pump of paragraph 22, wherein the portion 33 is conically tapered radially outward in the downstream direction.

[0066] 24. The blood pump of paragraph 22 or 23, wherein the blades 4 of the impeller 3 extend over the portion 33.

[0067] 25. The blood pump of any one of paragraphs 22 to 24, wherein part 33 is formed integrally with or separately from impeller 3.

[0068] 26. The blood pump of any one of paragraphs 1 to 25, wherein the first opening 34 of the flush channel 30 is disposed in the downstream half of the impeller 3.

[0069] 27. A blood pump according to any one of paragraphs 1 to 26, wherein the first opening 34 of the flushing channel 30 is disposed in an area of ​​the impeller 3 that is under a higher pressure than an area of ​​the impeller 3 in which the bearing 20 is disposed so as to direct blood flow from the first opening 34 through the flushing channel 30 to the bearing 20 during operation of the blood pump 1.

[0070] 28. The blood pump of any one of paragraphs 1 to 27, wherein the blood flow from the first opening 34 to the flush channel 30 is in a direction toward the blood flow outlet 6 of the pump casing 2.

[0071] 29. The blood pump of any one of paragraphs 1 to 28, wherein the first opening 41 is disposed on the forward side of the blade 4, the second opening 42 is disposed on the reverse side of the blade 4, and the flush channel 40 extends below the blade 4.

[0072] 30. A blood pump according to any one of paragraphs 1 to 29, wherein the flushing channel 43 extends within the vane 4, the first opening 44 is disposed on the forward side of the vane 4, and the second opening 45 is disposed in the vane 4, particularly at the radially outer edge of the vane 4.

[0073] 31. The blood pump of any one of paragraphs 1 to 30, wherein the contact bearing 20 is a pivot bearing.

[0074] 32. The blood pump of any one of paragraphs 1 to 31, wherein blood pump 1 is an axial blood pump, a centrifugal blood pump, or a mixed-type blood pump.

Claims

1. a pump casing (2) having a blood inlet (5) and a blood outlet (6) connected by a passage (7); an impeller (3) disposed within the pump casing (2) so as to be rotatable about a rotation axis (9), the impeller (3) having blades (4) sized and shaped to transport blood along the passage (7) from the blood inlet (5) to the blood outlet (6), the impeller (3) being rotatably supported within the pump casing (2) by at least one contact bearing (20) having a bearing surface of the impeller (3) facing a bearing surface of the pump casing (2); at least one flush channel (40, 43) extending through the impeller (3) and fluidly connected to the passage (7) through a first opening (41, 44) and to the bearing (20) through a second opening, the flush channel (40, 43) being operatively associated with an auxiliary pump that pumps blood through the flush channel (40, 43) toward the bearing (20); the auxiliary pump is at least partially formed by the at least one wash channel (40, 43) extending through the impeller (3) along a direction having at least one tangential component relative to the axis of rotation (9); In the circumferential direction of the rotation axis, the first opening (41) is on the forward side of one of the vanes (4), the outlet opening (42) of the wash-off channel (40) is on the backward side of the vane (4), and the wash-off channel (40) extends below the vane (4), or The blood pump (1) is characterized in that, in the circumferential direction of the rotation axis, the first opening (44) is on the forward side of one of the vanes (4), and the flushing channel (43) extends through the vane (4) and exits at an outlet opening (45) arranged at the radially outer end of the vane (4).

2. 2. The blood pump according to claim 1, wherein the distance between the axis of rotation (9) and the first opening (41, 44) is less than 50% of the distance between the axis of rotation (9) and the point (36) where the flush flow exits the passage (7).

3. 3. The blood pump according to claim 1, wherein the impeller (3) has a central opening (32) extending along the rotation axis (9) and receiving the bearing (20), and the second opening is fluidly connected to the central opening (32).

4. 4. The blood pump according to claim 1, wherein the first opening (41, 44) of the flushing channel (40) is arranged adjacent to one of the vanes (4) of the impeller (3) on the forward side of the vane (4) relative to the direction of rotation of the impeller (3).

5. 5. A blood pump according to any one of claims 1 to 4, characterized in that the cross section of the first opening (41, 44) is circular or non-circular.

6. 6. Blood pump according to any one of claims 1 to 5, characterized in that it comprises two or more flushing channels (40, 43) arranged symmetrically with respect to the axis of rotation (9).

7. 7. A blood pump according to claim 1, wherein the impeller (3) has a portion (33) in the downstream direction extending radially outward, and the first openings (41, 44) of the flushing channels (40, 43) are arranged in the portion (33).

8. 8. A blood pump according to any one of claims 1 to 7, characterized in that the first openings (41, 44) of the washout channels (40, 43) are arranged in the downstream half of the impeller (3).

9. 9. A blood pump according to claim 1, wherein the first openings (41, 44) of the flushing channels (40, 43) are arranged in an area of ​​the impeller (3) that is under a higher pressure than an area of ​​the impeller (3) in which the bearing (20) is arranged, so as to cause blood flow from the first openings (41, 44) through the flushing channels (40, 43) to the bearing (20) during operation of the blood pump (1).

10. 10. The blood pump according to claim 1, wherein the blood flow from the first opening (41, 44) to the washout channel (40, 43) is in a direction towards the blood outlet (6) of the pump casing (2).

11. 3. The blood pump according to claim 2, wherein the distance between the axis of rotation (9) and the first opening (41, 44) is less than 40% of the distance between the axis of rotation (9) and the point (36) where the flush flow exits the passage (7).

12. 12. The blood pump according to claim 11, wherein the distance between the axis of rotation (9) and the first opening (41, 44) is less than 30% of the distance between the axis of rotation (9) and the point (36) where the flush flow exits the passage (7).

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