FLUID PUMP HAVING AT LEAST ONE IMPELLER BLADE AND A SUPPORT DEVICE

[0001] The invention is in the field of mechanical engineering, in particular micromechanics, and addresses fluid pumps which work with rotating impeller blades and are particularly configured for use in areas which are difficult to access.

[0002] Pumps of this type can be used, for example, in the medical field and can also have particularly small construction shapes for this purpose.

[0003] A special application of micropumps is, for example, the assistance for the pump force of the human heart. Pumps used in this area are usually introduced into the body through blood vessels and are optionally operated in a chamber of the heart.

[0004] A plurality of such pumps have already become known which have different constructional shapes. An axial flow pump has become known, from WO 98/53864, and equally from EP 1 738 783 A1, which in each case has a rotor in the form of a rigid shaft, said rotor being provided with impeller blades and said shaft being outwardly journalled in a stator. The drive can be directly integrated into the stator and the rotor as an electromagnetic drive.

[0005] Pumps of this type have the disadvantage that they have a large diameter in relation to the pumping capacity and can hardly be introduced through a blood vessel.

[0006] In contrast to this, a rotor is known from WO 03/013745 A2 which has a smaller diameter in a compressed state than in an expanded state and which has an expandable rotor blade which expands in operation by the fluid counterpressure of the blood.

[0007] Other rotors which have become known likewise have impeller blades which are expandable for operation, for example by joints or by elastic deformability of the impeller blades.

[0008] A particular problem in this respect is that the impeller blades are usually fastened to a central neck and are rotationally drivable and also movably pivotable from this; that the impeller blades thus have to be flexible, but have a certain stiffness or a restriction in its movability, on the other hand, to exert the required pressure onto the fluid for conveying.

[0009] This object has previously not been ideally achieved in the prior art. It is therefore the underlying object of the present invention to further develop a pump of the described type to achieve a good pumping capacity in operation despite a small pump diameter in the compressed state. The design should in this respect be as uncomplicated and as inexpensive as possible.

[0010] The object is achieved in accordance with the invention by the features of claim 1.

[0011] In this respect, at least one impeller blade is provided which is rotatable about an axis of rotation to convey the fluid as well as support device which supports the at least one impeller blade in a support region. The support device is moreover changeable between a compressed rotor state and an expanded rotor state and at least one part of at least one impeller blade extends at least partly, viewed from the support region, radially inwardly toward the rotor axis in the expanded rotor state. Since the support region is not disposed at the radially inner end of the impeller blade, but is rather offset to the impeller blade exterior, viewed radially, the impeller blade/impeller blades is/are supported in a region in which the relative speed to the fluid is greater than in the region of the axis of rotation and, where applicable, the mechanical load of the impeller blade is correspondingly higher. The support region and the support device can be the only region in which the impeller blade/impeller blades is/are journalled or is/are connected to another component. The impeller blade/impeller blades can, for example, be connected to other components in a force-transmitting manner only by means of the support device. In this respect, the region of the impeller blade/impeller blades conveying the fluid can lie wholly or only partly radially within the support region. A lower mechanical demand is in any case made here on the support device and on its connection to the respective impeller blade than if the support device were to support the impeller blades in the region of the axis of rotation. The impeller blades can moreover be made weaker since they are supported in a region of higher load and the mean spacing of the regions of the impeller blade/impeller blades conveying the fluid, viewed in the radial direction, is smaller than if it/they were supported in the region of a neck on the axis of rotation.

[0012] The support device can have a strand-like body which extends transversely to the impeller blade surface with respect to its longitudinal direction and/or, in the region in which it supports the impeller blade, passes through said impeller blade or a tangential surface of said impeller blade. The angle between the longitudinal direction of the strand-like body and of the surface normal of the impeller blade surface/of the tangential surface at the impeller blade surface should be less than 89°, preferably less than 85°.

[0013] Provision can also be made that the predominant part of the region of the impeller blade/impeller blades conveying the fluid extends radially within the support region/support regions. The support region is thus closer to the parts of the impeller blade/impeller blades which move the fastest and can support them efficiently, for example transmit a torque to them.

[0014] Provision can advantageously also be made that the support region is arranged radially outwardly at the periphery of the fluid-conducting region of the impeller blade/impeller blades. In this respect, the support region can completely radially outwardly surround the impeller blades.

[0015] The impeller blade can generally be fixedly connected to the support device so that it rotates with the impeller blade.

[0016] This is a construction shape which can be manufactured particularly simply and which is mechanically stable. The support device can, for example, comprise the same material as the impeller blade and can be manufactured in one piece therewith.

[0017] Provision can, however, also be made that the support device is manufactured from a material different from that of the impeller blade, for example from a superelastic compound or from a shape memory material, in particular nitinol, so that the support device can actively change into an operating shape in order thus to erect the rotor with the impeller blades so that no further demands are made on the impeller blades with respect to an automatic deformation. They can then be manufactured as thin, pliable films which are not self-supporting.

[0018] The at least one impeller blade can, however, also be guided and journalled movably with respect to the support device. The support device can then be stationary with respect to the impeller blades as a stator. A guidance, for example in the form of a mechanical or magnetic journaling of the impeller blades with respect to the support device is then necessary.

[0019] The support device can, for example, be formed by at least one ring positioned concentrically and optionally journaled with respect to the axis of rotation. This ring can have an axial length which is smaller than the axial length of the impeller blades.

[0020] Two or more such rings can also respectively be connected, axially spaced apart, to the impeller blade/impeller blades. The rings can be designed in meandering form in the peripheral direction, for example, to be able to implement a corresponding deformability, for example as a consequence of superelasticity or shape memory properties in a particularly simple manner. A plurality of rings are preferably arranged coaxially to one another.

[0021] A helical body can also be provided coaxial to the axis of rotation as a support body instead of one or more rings. It can, for example, have a round or flat cross-section. The helix can extend in the same direction or in the opposite direction to a helical outer margin of an impeller blade.

[0022] The support device can, however, also be formed by a flexible tube surrounding the impeller blade/impeller blades. Such a tube can itself comprise a shape memory material, for example, also a wire meshwork of nitinol wire or it can comprise a flexible organic material impermeable for the fluid and have support elements such as support rings, for example. The tube can be inflatable in pumping operation by overpressure as a result of the fluid pressure which has built up.

[0023] The tube can be connected at points or in parts to the outer ends of the impeller blade/impeller blades.

[0024] In accordance with the present invention, the rotor does not need a neck in the region of the impeller blades so that the impeller blade/impeller blades, with all its/their parts, can be spaced apart from the axis of rotation. In this case, the cross-section of the rotor, which is otherwise taken up by a neck, is additionally available for conveying fluid.

[0025] When the support device rotates with the impeller blade/impeller blades, it can be journalled in at least one rotary bearing which is axially arranged outside the region over which the impeller blade/impeller blades extends/extend.

[0026] This design allows a simple journalling in a commercial rotary bearing, for example a roller bearing or a magnetic bearing. Such a journalling is less complicated and lower in friction than a journalling at the periphery of the support device in the region of the impeller blades.

[0027] However, a hydrodynamic journalling can, for example, also be provided at the periphery of the support device when a rotor of the described kind runs in a housing and when a gap is provided between the housing and the support device in which a fluid is located. In a particularly simple embodiment, this fluid could be identical with the conveyed fluid.

[0061] FIG. 1 shows, in a three-dimensional view, a rotor of a fluid pump, in particular of a micropump, for the axial conveying of blood, such as is typically used in medicine to assist the human heart. Such a pump is, for example, mounted at the end of a hollow catheter and conducts blood under pressure from a chamber of the heart into a blood vessel when it is introduced into a heart ventricle through a blood vessel. For this purpose, a rotor rotates at some thousand revolutions per minute to achieve the required conveying capacity. The impeller blade 1 is helical in form, is connected to a neck 2 in the region of the axis of rotation 3 and is supported outwardly by a support device 4 in the form of a tubular sleeve, to which the impeller blade 1 is connected at its outer margin.

[0062] The neck 2 is typically connected to a drivable shaft which extends through the hollow catheter and blood vessel to a motor drive which can typically be arranged outside the body. A sluice is provided between the motor drive and the hollow catheter.

[0063] FIG. 2 shows a plan view in which the upper margin of the impeller blade 1 and the tubular sleeve 4 can easily be recognized.

[0064] The impeller blade 1 can also be understood as two partial impeller blades which extend respectively radially from the neck 2 to the tubular support device 4 and axially extend helically.

[0065] FIG. 3 shows the rotor from FIG. 1 in a side view, with the closed pipe-like or tubular sleeve 4 being easy to recognize and the ends of the neck 2 projecting beyond it.

[0066] FIG. 4 shows a broken away representation of the rotor of FIG. 3, with the marginal regions of the impeller blade 1 being shown in dashed form where it is connected to the sleeve/support device 4.

[0067] FIG. 5 shows a longitudinal section through the rotor of FIG. 1, with the impeller blade 1 intersecting the plane of the drawing at the upper end of the rotor.

[0068] The impeller blade can, as shown in FIG. 5 and also in the following FIG. 6, be manufactured in one piece with the support device 4 made as a collapsible tube or as a collapsible pipe. Said support device can, for example, comprise a plastic as a flexible hose and can be held in an expanded and shape-stable manner by the pump action as a result of the overpressure built up in its interior. The shape stability can, however, also be established by the elastic restoring forces of the material. At the same time, the impeller blades are expanded and brought into the shape ready for operation by the expansion movement. The impeller blade 1, for example, is strained by tension and thus properly stabilized between the support device 4 and the neck 2 in the expanded state.

[0069] An embodiment can be seen from FIG. 7 with two rings 6, 7 which together form the support device and support the impeller blade 1. The support regions of the impeller blade 1 in this respect lie radially of its furthermost margin.

[0070] The rings 6, 7 can comprise a shape memory alloy, nitinol, for example, and can be directly expanded after introduction into a body to adopt the shown circular shape. At the same time, they pull the support regions of the impeller blade 1 radially outwardly and tension it.

[0071] FIG. 8 shows a longitudinal section through the rotor in accordance with FIG. 7 and FIG. 9 shows the extent of the margin of the impeller blade in a side view.

[0072] FIG. 10 shows a three-dimensional side view which illustrates the helical structure of the impeller blade 1.

[0073] In addition to the elements shown, spacers can be provided between the rings 6, 7 which do not have to be shape-changeable and which can maintain their form on the transition between the compressed shape and the expanded shape of the rotor. They can be made as bars or braces extending parallel to the neck 2.

[0074] The rings 6, 7 can generally also comprise an elastic material, for example rubber-like material, which has small restoring forces on the transport to the point of use in compressed form and which stabilizes itself after adopting the circular ring shape.

[0075] FIG. 11 shows an axial plan view of the rotor in accordance with FIG. 7 and FIG. 12 shows a section in which the impeller blade 1 intersects the plane of the drawing at the upper and lower ends of the rotor. The impeller blade passes through 180 degrees of a helix between the upper end and the lower end of the rotor.

[0076] A rotor of a fluid pump is shown in FIG. 13 which has a support device with three rings 6, 7, 8 which are each, viewed radially in the marginal region of the impeller blade 1, connected to it and can be spaced apart from one another by means of braces, not shown.

[0077] FIG. 14 shows a side view of the rotor of FIG. 13.

[0078] In FIG. 15, a rotor having four rings 6, 7, 8, 9 is shown perspectively, said rings together forming the major part of a support device. In another respect, what was already said with regard to the embodiments described above applies to the rings 6, 7, 8, 9.

[0079] Instead of individual rings, a helical body 7a can also be provided circumferentially at the periphery which is shown in dashed form in FIG. 15 and which is fastened spot-wise to the periphery of the impeller blade.

[0080] The torque can generally be introduced into the rotor via the support device. For this purpose, a part of the support device must, for example, be connected to a drive device or to a drive shaft via braces. This coupling will be looked at in more detail further below.

[0081] Alternatively, the torque can also be introduced via the neck 2 provided such a neck is present. In this case, the effect of the support device is restricted to the radial support and shape of the impeller blade/impeller blades.

[0082] FIG. 16 shows an embodiment in a three-dimensional representation in which an impeller blade 1 is stabilized at its periphery by a pipe section 10 or a tubular section. FIG. 17 shows the same arrangement in a longitudinal section.

[0083] The pipe section 10 can comprise a plastic, for example, and can be made in one piece with the impeller blade, but can also comprise a material different from the material of the impeller blade, for example a shape memory alloy. A tubular section or pipe section of this type has the disadvantage with respect to a ring of possibly being more difficult to compress, but has the advantage of being easy to stabilize in the expanded shape.

[0084] FIG. 18 shows, in a three-dimensional view, a rotor of a fluid pump having a rotor blade 1 which is supported by a support device 11 in the form of a throughgoing tube element. The tube element 11 extends across the complete axial length of the impeller blade. The tube element can, however, also be axially shorter than the impeller blade 1.

[0085] FIG. 19 shows a longitudinal section through the embodiment of FIG. 18, with in particular three ring-like reinforcement elements 12, 13, 14 being able to be recognized which are fastened radially outwardly to the tube element 11 or are manufactured in piece therewith in a contiguous manner.

[0086] The reinforcement elements 12, 13, 14 can comprise the same material as the tube element 11, but can also comprise another material tending to be stiffer, for example a shape memory alloy of a rubber which may tend to be stiffer than the flexible material which the tube element 11 comprises.

[0087] In this respect, the tube element 11 can be at least partly co-expanded on the unfolding by expansion of the ring-shaped reinforcement elements 12, 13, 14. This expansion movement can moreover be reinforced by an overpressure built up in the rotor as soon as the rotor is set into rotation.

[0088] FIG. 20 shows a side view of the rotor of FIGS. 18, 19 in a closed form.

[0089] A variant is shown in FIG. 21 in which the ring-shaped reinforcement elements 12′, 13′, 14′ are made in meandering form in the peripheral direction. These reinforcement elements can comprise a shape memory material and are particularly easily collapsible by the meander-like design. In addition to the rectangular meander-like structure shown, these reinforcement elements can also have a saw-tooth structure or a wavy-line structure.

[0090] Such reinforcement elements can be adhered to the tube element, for example.

[0091] FIG. 22 shows, in a three-dimensional representation, a tube element 15 which forms a support device for the vane wheel 1 and is reinforced by wire meshwork 16 on its outer side. The wire meshwork 16 can be adhered, in particular also only spot-wise, to the tube element 15, for example. The wire meshwork can, as usual with stents, be made so that a radial compression does not result in a change in the length of the wire meshwork. The wire meshwork can comprise a shape memory alloy as a metal wire or also as a grid structure, in particular in one piece; however, a manufacture from a plastic is also conceivable.

[0092] FIG. 23 shows an embodiment of a rotor having two impeller blades 1′, 1″ which are each helically fastened, for example adhesively bonded, at their outer sides in a tubular element 15, with the two helical shapes being matched to one another such that the two impeller blades 1′, 1″ being able to slide past one another radially with respect to the axis of rotation on compression of the support device 15 so that an extensive compression of the rotor is possible overall.

[0093] Both impeller blades 1′, 1″ end radially spaced apart from the axis of rotation, with a neck not being present. Only small forces act on the impeller blades at the margin of the rotor blades close to the axis of rotation due by the fluid to be conveyed since the relative movement is small in this region close to the axis. The space saved by omitting the neck can additionally be utilized for the transport of the fluid and the lack of the neck and the ability to push the impeller blades together makes an extensive compression of the rotor possible in the radial direction.

[0094] FIG. 24 shows the arrangement of FIG. 23 in a longitudinal section.

[0095] In a similar manner to the design of FIG. 22, the tubular sleeve which forms the support device for the impeller blades comprises an inner flexible sleeve and an outer wire meshwork.

[0096] FIGS. 25-29 in particular show the coupling of the support device to two shaft journals which are provided at both sides of the rotor and can serve both a journalling and the introduction of a torque.

[0097] FIG. 25 shows, in a longitudinal sectional representation, a tubular support device 17 which is connected via braces 18, 19, 20, 21 to two shaft journals 22, 23. Since the impeller blade 1 is supported by the support device 17, the total rotor is rotatably journalled and driven via the shaft journals 22, 23.

[0098] FIG. 26 shows a representation rotated by 90° about the axis of rotation 24 in a side view.

[0099] FIG. 27 shows a view from the same direction as FIG. 26 in a sectional representation.

[0100] FIGS. 28, 29 show respective three-dimensional representations of the subject of FIGS. 25, 26, 27, with FIG. 28 showing an outer view while FIG. 29 shows a partially broken away representation in which the impeller blade 1 becomes visible within the support device 17.

[0101] FIGS. 28, 39, unlike FIGS. 25, 26, 27, do not show fork-like braces 18, 19 as the connection between the support device 17 and the shaft journals 22, 23, but rather a triangular plate 25. It has the advantage with respect to two fork-like braces of being more stable, but the disadvantage that the fluid has to be displaced through the plate 25 on a rotational movement at high rotational frequency.

[0102] It becomes visible from FIG. 29 that a single helical impeller blade 1 is provided which has no neck.

[0103] FIG. 30 shows a support device in which the torque is transmitted from the tubular element 17 into the shaft journal 22 by means of a triangular plate 25. FIG. 31 shows the same constellation in a partly broken away representation.

[0104] In contrast to this, FIG. 32 shows the connection of the shaft journal 22 directly to a prolongation 26 of the impeller blade 1.

[0105] FIG. 33 shows the same constellation as FIG. 32 in a longitudinal section. FIGS. 32 and 33 make clear that the torque is introduced directly into the impeller blade 1 there and that the support device 17 only serves the stabilization of the impeller blade/impeller blades radially in the outer region or the expansion of the impeller blade and the subsequent shape stabilization. The prolongation of the helical structure 26 up to the shaft journal 22 moreover has the advantage that this also causes less resistance in the surrounding fluid on rotation since it represents a prolongation of the helical structure of the impeller blade.

[0106] It was made clear by the above-described examples that a high stabilization of the impeller blades is achieved with a small effort with the means of the invention by the support of one or several impeller blades radially in their outer region. The connection of impeller blades to a neck is thereby either not particularly taken up or it becomes unnecessary in total, which can also result in the omission of the neck. The support device can moreover co-expand the rotor blade/rotor blades on the expansion of the rotor so that they can be manufactured from commercial, flexible materials without any particularly high mechanical demands.