RU2629054C1 - Axial pump of auxiliary circulation - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: pump consists of a tubular hollow body. A pressure element with blades, oriented along the axis is rotatably mounted Inside the body. The pressure element forms a gap between the pressure element and the hollow body. The pump contains guide blocks with blades installed along the flow path. Blocks with blades are rigidly fixed to the inner wall of the body and are located in front and behind the discharge element. The motor is located in one of the guide blocks. A labyrinth seal is installed between the guide blocks and the impeller. The discharge element is mounted on the rotor shaft and is made in the form of an impeller.

EFFECT: simplified design of the axial pump and reduced power consumption by eliminating magnetic bearings.

7 cl, 3 dwg

Description

Technical field

The invention relates to medical equipment and can be used for pumping single-phase or multiphase liquids, for example, for pumping blood without significant impact on it (temperature, shear), i.e. moving parts in contact with blood do not cause high shear stress gradients.

State of the art

Blood is a polydisperse system (a suspension of uniform elements (red blood cells, platelets, white blood cells) in plasma). The circulatory system in the human body is closed, which prevents the interaction of blood with the environment and, consequently, a change in its properties. According to the results of studies, it is known that blood is sensitive to contact with foreign materials or force (shear) effects. With such contacts in the blood, hemolysis occurs (the destruction of red blood cells, followed by the release of excess hemoglobin) and the formation of blood clots. The formation of blood clots can lead to blockage of small vessels and affect the mechatronic devices of the auxiliary blood circulation, which, in turn, can lead to death. With hemolysis, an increased release of hemoglobin into the blood occurs, which leads to organ damage.

Over the past 20 years, tremendous progress has been made in the development of auxiliary circulatory systems. Auxiliary circulatory devices can partially replace or completely replace the pumping function of the heart. According to the latest INTERMACS data, the number of installed implantable assisted circulatory systems in the USA is growing every year. In 2013, this figure in the United States reached the level of 1052 implantations. In Russia, the number of implantations of the domestic AVK-N pump over three years is 19 (in 2013 - 3 implants, in 2014 - 7 implants, in 2015 - 9 implants). For comparison, over the past 20 years in the United States conducted from 2300 to 2500 heart transplants per year. In Russia, this figure over the past 2-3 years is at the level of about 160 operations per year.

In the prior art there are several areas for the development of auxiliary circulation pumps: pulsating pumps and constant flow pumps. In turn, constant flow pumps are divided into axial, centrifugal and diagonal. The design is based on the criteria of physiological pressure drop (compared to a healthy heart), flow rate, minimization of stagnation and recirculation zones, and maximization of efficiency.

The prior art axial circulation pump (US Pat. US 4,779,614), which consists of two fixed parts (guide blocks) and one impeller, is known. To ensure rotation and holding the impeller in a predetermined position, active magnetic supports are provided in the design. The rotation is provided by means of magnets mounted in the body of the impeller (rotor part) and on the outer tube (stator part). It is worth noting that the installation of external magnets outside the flow part requires an increase in the size of the entire product, also such an installation scheme imposes significant requirements on the distance between the magnets: on the one hand, torque transmission will be more efficient with a small distance between the rotor and stator magnets, but with a decrease in distance a decrease in the flow cross-sectional area, which leads to an increase in the particle velocity gradient. In addition, a small gap between the impeller vanes and the casing leads to an increase in shear stresses, which can lead to an increase in hemolysis in the flow part of the pump. The impeller presented in the application, due to its shape, is unreliably fixed in the axial direction. It is also worth noting the bulkiness of the circuit with two electric motors.

A different implementation of the axial pump of auxiliary circulation is known (Patent No. US 5951263, USA). The flowing part consists of an impeller on sliding bearings and two guide blocks. In the axial direction, the rotor is fixed in sliding bearings. The rotation of the impeller is carried out by means of magnets built into the body of the impeller (rotor part), and external magnets brought to the outer tube (stator). The efficiency of such an engine substantially depends on the gap between the magnets; when the rotor is located in the stator with a large gap, the external dimension (diameter) of the stator should be large enough. To reduce the gap between the rotor and the stator in this scheme is not possible without significant damage to the formed elements of the blood.

The RF patent No. 2430748 proposes the design of an axial auxiliary circulation pump according to the previous layout of the flow part, but with a slightly modified geometry of the straightener and diffuser, as well as a rotor with blades, interfaced with segments of a logarithmic spiral. Axial holding of the impeller is carried out by bearings. Permanent magnets are located in the body of the impeller, which are driven by a stator winding that is removed from the flow part of the pump to prevent contact of the windings with blood. The removal of the stator part also leads to an increase in the overall size of the entire product, which imposes significant restrictions on the size of the cavity in the human body for long-term implantation of the pump.

A device for auxiliary circulation (Patent No. 2266141, Russia), adopted as a prototype. The axial pump of auxiliary circulation consists of a tubular hollow body, inside of which is installed a rotary discharge element with vanes, oriented along the axis and forming a gap between the discharge element and the hollow body, and guide blocks with vanes, rigidly fixed to the inner wall of the body and located in front and behind the discharge element The flow part of the pump consists of fixed guide blocks equipped with blades. Permanent magnets are located in the guide blocks and impeller. Magnets provide axial retention of the rotor and are located opposite each other with magnetization of opposite polarity. This embodiment of the pump with a protruding central part is not optimal in terms of product dimensions, the placement of a large number of magnetic supports requires more control system complexity and greater energy consumption of the entire product.

Disclosure of invention

The task to be solved by the claimed invention is directed is to reduce the size of the pump, reduce blood trauma in the process of passing the stream through the flow part of the device, and reduce energy consumption.

The technical result of the claimed invention is achieved by the fact that the axial auxiliary circulation pump consists of a tubular hollow body, inside of which is installed a rotary discharge element with vanes, oriented along the axis and forming a gap between the discharge element and the hollow body, and guide blocks with vanes, rigidly fixed on the inner wall of the housing and located in front and behind the discharge element, while the motor is placed in one of the guides forge, and the discharge element is mounted on the rotor shaft and is made in the form of an impeller

Besides:

- the guide blocks are made with detachable covers having a spherical, conical or ellipsoidal shape;

- the impeller is made thin-walled with the implementation between it and the guide blocks of the labyrinth seal;

- the motor wires are led out through the blades of the guide elements;

- the number of impeller vanes is not equal to and not a multiple of the number of guide vanes;

- the gap between the blades of the impeller and the inner surface of the pump housing is in the range of 0.1-1 mm;

- the gap between the end surfaces of the impeller and the guide blocks is in the range of 0.2-1 mm;

- the pump housing is detachable.

The technical result of the invention is achieved by the fact that the internal cavity of the stationary elements of the flow part is used to accommodate the motor, thus, the design is simplified by eliminating the magnetic bearings to keep the rotor in axial position. The motor windings can be located relative to each other with a minimum clearance and be compact enough.

The combination of the above essential features leads to the fact that the pump cross section increases to reduce the impeller rotation speed, which leads to a decrease in blood trauma during the passage of the flow through the flow part of the device while maintaining the small size of the entire device in comparison with analogues, and the rejection of axial Stabilization due to magnetic supports reduces energy consumption.

Brief Description of the Drawings

In FIG. 1 shows the installation of the pump during the operation to bypass the left ventricle, where

1 - output knee

2 - cover of the guide block

3 - guide block

4 - impeller

5 - guide block

6 - cover of the guide block

7 - input knee

8 - direction of blood flow from the heart

9 - output power and control wires

10 - electric motor

In FIG. 2 shows the design of the auxiliary pump, where

2 - cover of the guide block

3 - guide block

4 - impeller

5 - guide block

6 - cover of the guide block

8 - direction of blood flow from the heart

10 - electric motor

11 - clamping nut

12 - fitting

13 - pump housing

14 - bearing support

15 - seal

16 - motor shaft

In FIG. 3 shows the design of the auxiliary circulation pump with a thin-walled impeller, where

2 - cover of the guide block

3 - guide block

4 - impeller

5 - guide block

6 - cover of the guide block

8 - direction of blood flow from the heart

10 - electric motor

11 - clamping nut

12 - fitting

13 - pump housing

14 - bearing support

15 - seal

16 - motor shaft

The implementation of the invention

In FIG. 1 shows an embodiment of the device. An electric motor 10, located in one of the guide blocks 5 or 3 with blades, transmits torque to the shaft 16 passing through at least one bearing support 14 with a seal 15. A seal 15 or a seal system isolates the electric motor 10 from the ingress of blood into the motor chamber. At the exit of the guide block 5 or 3, an impeller 4 with blades is mounted on the shaft 16. The second support of the motor shaft 16 is the opposite guide block 3 or 5 with the bearing 14 and the seal 15, or a sealing system for better insulation of the inner cavity of the guide block 3 or 5. Both guide blocks 3 and 5 are rigidly fastened to the pump casing 13 through the blades. The impeller 4 is mounted only on the shaft of the electric motor 16.

The proposed axial pump operates as follows.

The pumped blood flows from the ventricular chamber through the knee 7 to the impeller 4. Passing through the vanes of the guide block 3 or 5, the flow is captured by the vanes on the impeller 4, while the vanes are designed on the guide block at the inlet of the flow for reasons of shock-free running of the flow to increase pump efficiency . Impeller 4 gives energy to the flow and accelerates it. Once on the blades of the guide block at the outlet, the flow is inhibited, actively interacting with the blades, thereby achieving the necessary pressure difference between the inlet to the pump and the outlet from it. To minimize eddies between the ends of the guide blocks and the impeller, the smallest possible gap is set from 0.2 to 1 mm, which is especially important for the second experimental version of the device, where a thin-walled impeller 4 is used, because the minimum gap between the ends allows you to implement an effective labyrinth seal and better isolate the cavity with the electric motor 10. Thin-walled impeller 4 is a cylinder with a variable diameter, while in one embodiment, the configuration of the thin-walled impeller is made in the form of a thin-walled cylinder (at least 10 times thick less than the diameter) that goes into a thick-walled cylinder for landing on the shaft (the landing length is selected from the conditions of reliable fixation of the impeller on the shaft). The thick-walled part, in turn, passes into the thin-walled part.

To eliminate additional flow disturbances, the number of impeller vanes 4 is not equal to and not a multiple of the number of guide vanes. The gap width between the blades of the impeller 4 and the inner part of the housing 13 can be selected in the range of 0.1-1 mm The gap is selected from the condition of minimizing shear stresses in relation to the critical value while maintaining a sufficient hydraulic pump efficiency, since The main damage to the blood occurs precisely in the gaps. At the exit of the guide block 5, blood enters the outlet knee 1, which is connected to one of the large vessels of the circulatory system.

Power and signals to the electric motor 10 are transmitted through the supply and control wires 9 in the insulating winding and the shielding. The covers of the guide blocks 6 and 2, mounted on the guide blocks by means of a threaded connection, fit or glued in, allow mounting the electric motor, bearings and seals and ensure assembly of the entire product. Elbow 1 and 7, which in one embodiment is a flexible or rigid tube worn on the fitting. When assembling the nozzle 12 is inserted into the pump housing 13 and tightly fixed with a clamping nut 11, after inserting the nozzle 12 into the inner part of the housing, a guide block with an electric motor, bearing, seal is inserted and fixed in a certain axial position by means of a measuring device in the form of a rod mounted on the nozzle in build time. After fixing the guide block 3 or 5 with the electric motor, the impeller 4 is put on the motor shaft 4. After that, another guide block 5 or 3 is started on the motor shaft 16 and fixed in a certain position. Fixation takes place with the measuring device described above. For convenience, as one of the options, you can use not a one-piece pump housing, but a detachable one.

This device provides implantation into the human body during the ventricular bypass operation, when the pump takes blood from the top of the ventricle and pumps it directly to bypass the heart valve into the ascending aorta. The flow through the cannula (flexible or rigid tube) enters the flow part of the pump: first, the flow passes through the area of the guide apparatus with straight or turned vanes to regulate the flow, i.e. to reduce the peripheral component of the velocity of the input stream, shock-free (or close to shock-free) run-up of the flow on the blades of the impeller. Further, the flow enters the region of the impeller, where the rotational energy of the rotor is transmitted to the incoming flow. After this, the accelerated flow enters the region of another guide block, the curved blades of which, by changing the flow area, convert the kinetic energy of the flow into pressure energy. The blades of the impeller, diffuser and flow straightener are designed by mathematical modeling of the pump under physiological flow conditions (pressure drop depending on the operating mode 80-180 mm Hg, flow depending on the operating mode from 2 to 6 l / min), minimize stagnation and recirculation zones, maximize the hydraulic efficiency, minimize the impeller rotation speed, because this is the main factor initiating the hemolysis process. The electric motor may be located in one of the guide blocks. The guide blocks are stationary parts of the pump, their fastening is carried out by spot welding to the body or by drilling holes and fastening to the body with screws or gluing. Before installing the stationary part (guide block) with an electric motor, a bearing support (rolling or sliding bearing) and a seal are put on the motor shaft to isolate the cavity driven by contact with the working fluid, several levels of seals (one after the other) can also be installed for more reliable insulation of the engine cavity. After installing the engine mount and mounting the seals and bearing on the motor shaft, the impeller is mounted to fit or using heat. After installing the impeller, another guide block is mounted, which also provides seats for the seal and bearing or under the tandem of seals. A feature of the manufacture of guide blocks is that they are made of two elements: the sleeve directly with the blades and the cover, which can be glued, welded or screwed to the sleeve.

This design of the bearings allows for easy installation of the motor, seals and bearing during assembly of the pump.

To achieve the specified result (reducing the dimensions of the final product, reducing energy consumption and simplifying installation), the impeller electric motor is located inside one of the guide blocks. The rejection of axial stabilization due to magnetic supports allows to reduce power consumption, reduce the number of output wires for the control board, simplify the control board itself due to the reduction of control signals (it is only necessary to control the motor, and axial stabilization is ensured by the coaxial execution of the impeller and motor shaft) .

EFFECT: invention makes it possible to reduce the size of the auxiliary circulation pump in comparison with analogs while maintaining the physiological parameters of the flow (flow rate, differential pressure) for a more convenient long-term placement of the pump in the patient's body. The simplicity of the design is achieved through the use of a scheme with sliding / rolling bearings and integral guide blocks with covers.

Thus, the claimed invention solves the problem of mechanical support of blood circulation for patients who are either unable to implant a living heart from a donor, or donor organs are insufficient to meet demand. In some cases, the device allows you to refuse transplantation of a donor organ, and in some cases, restore healthy heart function. There are cases when the unloaded myocardium (main cardiac muscle) was restored over time, which allowed to remove the auxiliary circulation pump.

The proposed device is a miniature circulatory support pump, which due to its size can be conveniently placed in small cavities of the human body, thereby providing mobility and a better quality of life for the patient.

Claims (7)

1. An axial auxiliary circulation pump, consisting of a tubular hollow body, inside of which a discharge element with blades is mounted for rotation, oriented along the axis and forming a gap between the discharge element and the hollow body, and guide blocks with vanes installed along the flow, rigidly fixed to the inner wall of the housing and located in front and behind the discharge element, characterized in that the electric motor is placed in one of the guide blocks, between the guide with blocks and impeller, a labyrinth seal is installed, and the discharge element is mounted on the rotor shaft and is made in the form of an impeller. 2. The device according to p. 1, characterized in that the guide blocks are made with detachable covers having a spherical, conical or ellipsoidal shape. 3. The device according to claim 1, characterized in that the electric motor wires pass through the blades of stationary elements. 4. The device according to claim 1, characterized in that the number of impeller vanes is not equal to and not a multiple of the number of guide vanes. 5. The device according to claim 1, characterized in that the gap between the blades of the impeller and the inner surface of the pump housing is in the range of 0.1-1 mm. 6. The device according to claim 1, characterized in that the gap between the end surfaces of the impeller and the guide blocks is in the range of 0.2-1 mm. 7. The device according to p. 1, characterized in that the bearings of the shaft of the electric motor mounted bearings or rolling bearings.

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