WO2000035514A1

WO2000035514A1 - A pumping arrangement

Info

Publication number: WO2000035514A1
Application number: PCT/SE1999/002363
Authority: WO
Inventors: Gunnar Anders BJÖRK
Original assignee: Bjoerk Gunnar Anders
Priority date: 1998-12-15
Filing date: 1999-12-15
Publication date: 2000-06-22
Also published as: SE9804317D0; AU3090700A

Abstract

The invention comprises a pumping arrangement (1) consisting of a housing or casing (2) with a cavity (2C) whose inner surface (2a) has a circular cross section, one vane or a plurality of vanes (3) arranged inside the casing's cavity to pump by means of a rotary movement a liquid from an inlet (22) in the casing to an outlet (21) in the casing, said inlet and said outlet being separated from one another, and at least one end panel section (7) for the casing. A centre of rotation (4') for said vane (3) is eccentric in relation to an assigned centre (2') of said inner surface (2a), and said vane (3) is capable of reciprocal movement in relation to a shaft (4) at said centre of rotation.

Description

A PUMPING ARRANGEMENT

Technical field

The present invention relates generally to a pumping arrangement and, more particularly, to a pumping arrangement consisting of an housing or casing with an interval cavity, such as one whose interior surface is cylindrical, preferably with a circular or, in any case, essentially circular cross-section, one or a plurality of co-ordinated vane(s) inside the casing, said vane(s) devised to pump by a rotary movement a liquid from a casing inlet to a casing outlet, said inlet and outlet being positioned at a distance from each other and, in any case, one casing end panel devised to seal the casing and enclose said internal cavity.

Even if the present pumping arrangement is devised for pumping fluids, such as a liquid, of all kinds and for all kinds of applications, it should be noted that the pumping arrangement is primarily designed to support blood circulation for a person or patient with an impaired cardiac function, such as a patient waiting for a donor.

The present pumping arrangement will accordingly be useful in thorax surgery as a complementary pumping arrangement connected to the human body's circulatory system or can also be an alternative to heart replacement. However, the pumping arrangement was primarily designed to provide relief and assistance for heart failure patients and is therefore capable for operating with a weak, defective and/or weakened, although still basically functional, heart, even if the patient's condition therefore requires access to an arrangement for myocardial stimulation, such as a pacemaker. In this kind of application, treatment usually consists of medical therapy,

ACE inhibitors to dilate the venous system, diuretics and beta-adrenergic block- ers.

Utilisation of the present invention as a supplementary pumping arrangement operating in parallel with the heart will therefore greatly reduce the need for diuretics and also improve oxygenation of the bodies of disabled patients, thereby improving patient mobility.

A pumping arrangement of this kind, connected in parallel with the heart, requires some co-ordination of the pumping arrangement's strokes or activation periods and the heart's beats or activation periods.

Prior art Pumping arrangements of the aforesaid kind are previously known from a plurality of different embodiments.

Different pumping arrangements, devised for use as a supplementary pumping arrangement or pumping station for the purpose of improving the condition and well-being of patients with heart failure and/or impaired cardiac function, are also previously known.

Thus, a pumping arrangement, operating on the centrifugal pump principle, for pumping biological fluids, primarily blood, is known from the US patent US-A-5, 458,459 and comprises a casing, defined as a pumping chamber. The pumping chamber contains an impeller consisting of a rotating spindle on whose shaft a plurality of vanes or wings, devised so the inner end section of each vane is located close to the spindle, are located.

An arrangement and a method utilising a centrifugal pump unit 10 for pumping sensitive biological fluids or liquids and containing an impeller and a rotor 21 which is fully supported by and rotated by magnetic force produced by electri- cally actuated magnets, i.e. electromagnets 52, 54, are previously known from WO 97/42414 with the international application number PCT/US 97/07567. A pump casing and a passage 32, 34, 36 are employed for the flow. A brushless drive motor 40 is enclosed in and integrated with the pump casing. There is also a power supply and specific electronics sensitively driven by a control algorithm.

All of these units interact with one another in achieving an efficient, sustainable pumping sequence with modest maintenance costs.

A specially devised elastic impeller and an appropriate pump casing result in a mechanism for transporting and passing a liquid through the pump to a pump outlet devised to reduce liquid turbulence.

The international publication WO 94/03731 , with the international applica- 0

tion number PCT/US 93/071 10, also depicts a centrifugal pump arrangement 10 for pumping biological fluids, such as blood, and consists of an housing or casing 12 which encloses a pumping chamber 36.

The pumping chamber 36 contains an impeller 14 mounted on a spindle 16. The impeller 14 carries connector mechanisms devised for connecting an external source for driving the impeller 14 via a rotary movement. The spindle 16 allows the impeller 14 to rotate freely, but both ends of the spindle 16 are devised in an axial and lateral direction. The casing 16 has an inlet 24 and outlet 26.

The publication EP-B1-0 467 234 also depicts and describes a centrifugal pump arrangement for liquids, blood in particular, when extracorporal circulation is required.

An implantabie rotating blood pump with no need for axial seals is previously known from US-A-5,695,741. This pump contains a rotating means with pump impellers mounted at one end. The impellers are specially devised with large, thick vanes and high, narrow blood channels in order to minimise haemolysis.

The rotating means and the impeller are retained in their radial position by passive or permanently magnet bearings.

The rotating means are driven by an integrated, brushless electric motor. A plurality of permanent magnets is arranged in a circle around the impeller, which forms the motor's rotor.

The motor's stator consists of circular windings, made from electrically conductive wire, inside the pump casing and concentrically arranged with the motor. When electromagnetic force is applied to the stator, magnetic conditions allowing the rotating means and the impeller to rotate are created between the stator and the rotor.

During operation the rotating means moves back and forth along the shaft between surfaces depending on the heart's pulsation. This bi-stable operation of the pump allows fresh blood to pass through the bearing in a continuous fashion, thereby minimising the probability of thrombosis which could develop through the pump's operation. As regards pumping arrangements of the kind hitherto known, it can be noted that the pumping arrangement in the aforementioned application primarily has a design enabling outflow to be pulsed with an adjustable duration for each pulse and synchronised with the heart's generation of pulses.

Description of the present invention

Technical problems

If the circumstance that the technical considerations anyone well-versed in the prior art must make in order to offer a solution to one or a plurality of technical problems is taken into account, an initial insight into the measures and/or sequence of measures required and a choice of one or more means accordingly needed, the following technical problems should be relevant in achieving the present invention.

Taking the prior art, as described above, into account, being able to real- ise the importance and advantages of devising a pumping arrangement which can easily be adapted to the aforementioned special application and which can be made from a few simple parts, such as only two moving simple parts, can be viewed as a technical problem.

A technical problem is then involved in being able to realise the impor- tance and advantages of having such a pumping arrangement consist of a casing or housing with an internal cavity or a pumping chamber and a rotating shaft on which at least one vane is mounted inside the cavity, the vane guided by vane- related and/or casing-related means to run along a cylindrical internal surface, thereby creating a pumping sequence co-ordinated with a heart beat. A technical problem is then involved in being able to realise the importance and advantages of changing, in some simple fashion, the distribution of the pumping sequence's pressure and/or volume distribution over time merely by changing the shape of the inner surface against which the vane runs or by other simple measures. A technical problem is also involved in being able to realise the importance and advantages of creating such conditions for a pumping arrangement of the aforementioned kind that the vane's/vanes' centre of rotation is eccentric in relation to an assigned centre for the inner surface of the said cylindrical internal surface.

A technical problem is also involved in being able to realise the importance and advantages involved when the length of the said vane is less than a selected minimum diameter for the said inner cylindrical surface, and the vane, while rotating, is constantly retained by or in conjoined interaction with the rotating shaft.

A technical problem is also involved in being able to realise the importance of the vane having reciprocating movement within and through the shaft's centre of rotation.

A technical problem is also involved in being able to realise the importance and advantages of having two parallel, or essentially parallel, vanes oriented through the said shaft in order to create conditions for a complete stroke or activation period in only a 180° rotary movement inside the pumping arrangement. Moreover, devising a simple vane-related or casing-related means using simple measures and design steps, devised to control the said vane (or vanes) so it/they is/are in requisite contact with the said inner surface throughout the shaft's entire rotary movement and, if deemed desirable, to provide facilities for stirring the fluid and/or during its passage from the negative pressure side to the positive pressure side, should also be viewed as a technical problem.

A technical problem is also involved in being able to realise the importance and advantages of having the ratio between a first diameter, of the cylindrical inner surface, and a second diameter, i.e. of a shaft driven by the rotary movement of a vane, be a value between 3.0 and 1.5, e.g. 2.0 to 1.75. A technical problem is also involved in being able to realise the importance of having the said means consist of one or a plurality of guide tabs, e.g. two, attached to vanes and devised to run in peripheral grooves on the end panels and/or floor, said grooves being arranged close to the inner surface.

A technical problem is also involved in being able to realise the impor- tance and advantages of selecting a stroke volume which can be assigned a value of 40 to 250 ml, e.g. 100-150 ml.

A technical problem is also involved in being able to realise the impor- tance and advantages of equipping the said vane (or vanes) with one or a plurality of permanent magnets oriented towards the part or parts of the vane (or vanes) facing and brushing against the said inner surface.

A technical problem is also involved in being able to realise the impor- tance and advantages of arranging, inside the casing, although somewhat outside the said internal surface, a number of electromagnets devised for sequential activation in terms of time and output by a control unit and powerful enough to rotate the vane inside the cavity.

A technical problem is also involved in being able to realise the impor- tance of arranging said control unit so it increases or decreases the vane's and shaft's rotational speed on the basis of the level of oxygen measured in the patient's bloodstream and/or on the basis of control signals from a myocardial stimulation means so as to synchronise pulses emitted by the pumping arrangement and heart's pulsed beats. A technical problem is also involved in being able to realise the importance and advantages of having the said vane's and shaft's rotary movement activated and controlled by a driving arrangement, powered from a control unit by a battery, at least the latter being separate from the casing.

A technical problem is also involved in being able to realise the impor- tance and advantages of having glossy and durable surfaces on all parts in contact with liquid in the pumping arrangement, such as plated or coated with titanium nitrite or the equivalent.

A technical problem is also involved in being able to realise the importance and advantages of having the design of each of the parts and the shape of the cavity be devised, with few and simple moving parts in the cavity, with small passive areas in relation to one another and to the cavity.

A technical problem is also involved in being able to realise the importance and advantages of arranging an outlet from the cavity for interaction with one or a plurality of nipples, in which a turbulent stream of liquid produced by the pump can be transformed into a linear flow of liquid.

A technical problem is also involved in being able to realise the importance of adapting the distance between the inlet and outlet and make it somewhat adjustable, mainly by selecting a special casing from a plurality of available casings) so as to tailor the morphology of the curve of the liquid's pressure variation over time.

A technical problem is also involved in being able to realise the impor- tance of assigning said inlet a larger cross-section or area than the cross-section or area of the outlet, the difference in area amounting to about 20%.

Realising the importance and advantages of having the casing and its cavity in this application enclose a shaft with at least one vane should especially be viewed as a technical problem, and the simplicity of the design allows a single panel to be attached to the casing, the rotary movement of the vane, and said shaft being activated by external means so the cavity is hermetically sealed by the panel.

A technical problem is also involved in being able to realise the importance of equipping the housing or casing with a number of electrically controlled magnets arranged for sequential activation in order to impart a rotary movement to the vane.

A technical problem is also involved in being able to realise the importance of equipping the outer section of the vane facing the inner surface with one or more permanent magnets or having the entire vane consist of a magnetically active material such as magnetic steel.

It is especially demonstrated that the surface section of the vane shall be able to serve as a support surface and sliding surface against the inner surface. Creating with simple means conditions enabling the vane's straight surfaces to sweep, with a very small gap, e.g. about 0.1 mm, across the flat bottom section of the cavity and the flat, inward-facing upper part of the panel section and inner surface should also be viewed as a technical problem.

A technical problem is also involved in being able to realise the importance and advantages of letting the away-facing flange parts of the shaft run in circular notches in the bottom section and end panel with no need to use circular through holes. o

Solution

Thus, the present invention is based on a pumping arrangement consisting of a housing or casing with an inner cavity with a cylindrical inner surface and a circular or, in any case, an essentially circular, cross-section, one vane or a plu- rality of vanes whose rotary movement is devised to pump fluid from a casing inlet to a casing outlet inside the casing and cavity, said inlet and outlet being located at distance from one another, and a casing end panel.

In such a pumping arrangement, the present invention states that said vane shall be eccentric in relation to an assigned centre for the said cylindrical in- ner surface, said vane shall have a length less than a minimum diameter for said inner surface, and said vane is arranged for reciprocal movement in a shaft in said rotation centre in order to solve one or more of the aforementioned problems.

As proposed embodiments within the field of the invention concept, the use of two vanes which are parallel or, in any case, essentially parallel vanes, ori- ented through said shaft for interaction with opposing surface areas on the cylindrical inner surface, thereby creating conditions for a complete stroke or activation period when a vane only makes a 180° rotary movement inside the pumping arrangement's cavity.

The invention also proposes a vane-related or casing-related means ar- ranged to guide the vane (or vanes) against and along the said inner surface during the vane's and shaft's rotary movement.

The selection of a ratio between a first diameter for the inner surface of the cylindrical cavity and a second diameter for the shaft of the said vane between 3.0 and 1.5, e.g. between 2.0-1.75, is especially cited. Said means can be devised without one or more guide tabs attached to vanes, such as two guide tabs, designed to run in a peripheral groove on the end panel and in a groove on the floor of the casing.

The invention also proposes the possibility of varying and changing the pumping arrangement's stroke volume. This stroke volume is particularly stipu- lated as having a value from 40 to 250 ml, e.g. 100-150 ml.

As an alternative to the said means, said vane (or vanes) can be equipped with one or a plurality of permanent magnets, oriented towards the part, or parts, facing said inner surface, on its/their edges, or all or parts of the vane can be made of magnetic steel.

The invention further cites that a number of electromagnets, devised for sequential activation in time and output by a control unit in order to rotate the vane with a rotary movement, are arranged in the casing material, slightly outside the inner surface.

Said control unit is arranged to allow the rotational speed of the vane and shaft to increase or decrease on the basis of the oxygen level measured in a bloodstream or on the basis of control signals from a myocardial stimulator. The invention also stipulates that the rotary movement shall be activated by a driving arrangement powered by an external battery.

All inner surfaces in contact with blood in the pumping arrangement shall advantageously be glossy and plated with a metal, such as titanium nitrite, titanium carbonate or the equivalent. The pumping arrangement's design is further devised to display small passive areas.

Moreover, the invention stipulates that the outlet shall be arranged to interact with one or more nipples in which a turbulent stream of fluid generated by a pump can be converted into a linear stream of fluid. The invention further offers the opportunity to vary the distance between the inlet and outlet in order to modify the morphology of the curve for the liquid's pressure variation as a function of time.

The said inlet has been assigned a larger diameter or cross-section than the diameter or cross-section of the outlet. The invention further shows that the only moving parts in the casing's cavity are a shaft and at least one vane mounted on the shaft, and an end panel is attached to the casing to form said internal cavity, rotation of said vane and its shaft being capable of activation by external means.

Said housing or casing is further equipped with a number of closely spaced electrically controlled magnets, arranged for sequential activation in order to impart a rotary motion to the vane.

In particular the invention stipulates that the outer section of the vane fac- ing the interior surface is equipped with one or a plurality of permanent magnets, and only the edge surface area serves as a support surface and a sliding surface against the inner surface.

The vane can also consist of a magnetic material such as blade steel. The vane can further run along the interior surface and sweep across bottom and end panel surfaces with a gap devised to prevent the crushing blood corpuscles.

Advantages The advantages mainly deemed to be significant to a pumping arrangement have the distinguishing features of the present invention, hereby creating conditions for the creation of a pumping arrangement made from simple parts with a few moving parts and offering very reliable operation.

Further, the invention provides a pumping arrangement, which can be well adapted to serve as a blood circulation support for a patient with an impaired inherent cardiac function.

The features mainly regarded as significant to a pumping arrangement, according to the present invention, are set forth in the characterizing part of claim 1 below.

Brief description of the figures

Several proposed embodiments displaying the significant features of the invention will now be described in greater detail, referring to the enclosed drawing in which Figure 1 is a schematic depiction of a selected application in which a pumping arrangement according to the invention is connected in parallel to the patient's cardiac function; Figure 2 shows a perspective view of a first embodiment of the invention, but with an upper end panel removed and utilisation of a single vane in- side an internal cavity;

Figure 3 shows a perspective view of a pumping arrangement according to

Fig. 2, supplemented with an additional vane, the two adjacent vanes forming two internal cavity sections;

Figure 4 shows a section through the casing according to Fig. 2 with an applied end panel;

Figure 5 shows an additional embodiment of the present invention, which can have two vanes, only the casing and inner cavity being shown;

Figure 6 shows a perspective view of an end panel adapted to the embodiment according to Fig. 5;

Figure 7 shows a perspective view of a shaft, to which a single vane is attached, which can be inserted into the casing's inner cavity accord- ing to Fig. 5;

Figure 8 shows a perspective view of a single vane, arranged for reciprocal movement in a shaft, according to Fig. 7, in a fashion illustrated in Fig. 1 ;

Figure 9 shows a volume-time diagram for a heart with a somewhat defective function and a volume-time diagram for a pumping arrangement with one vane and

Figure 10 shows a schematic circuit arrangement for acting on cardiac function with a myocardial stimulator and on the function of the pumping arrangement in synchrony.

Description of the proposed embodiment

An application of the present invention is illustrated referring to Fig. 1.

Here, a pumping arrangement 1 is connected in parallel to the heart H of a living creature B and controlled by a extracorporal control unit and powered by a set of extracorporal batteries D.

Fig. 2 is a perspective view of housing or casing 2 utilised for a complete pumping arrangement 1 . The casing 2 consists of a circular wall section 2A integrated with a bottom section 2B. However, the bottom section 2B can be in the form of a separate end panel section T. The bottom section 2B, wall section 2A and an end panel section 7 can be arrayed to form an inner, hermetically sealed cavity 2C as illustrated in Fig. 4.

The casing 2 is shown with a shape in which it has a cylindrical inner sur- face 2a and a circular cross-section. This inner surface 2a serves as guide surface for the end section 3a of a vane 3, so the end section 3a is displaced along the inner surface or guide surface 2a when the vane rotates in the cavity 2C, thereby forcing any fluid in the cavity 2C out through an outlet 21. The term "circular cross-section" should not be interpreted in a purely mathematical sense. The cross-section can advantageously depart from the stipulated circular cross-section in order to alter the pumping arrangement's pressure/volume-time characteristics and the stroke volume.

A somewhat elliptical guide surface 2a in the cavity 2C can be used for changing features, such as changing the stroke volume somewhat and changing volume-time characteristics according to Fig. 9B by reducing the peak value somewhat.

Other changes also become possible when the shape of the cylindrical inner surface 2a is altered. Fig. 2 shows that a vane 3 arranged in the casing 2 is intended to display an externally generated and assigned rotary movement, and a shaft 4 rotates when the vane 3 rotates.

The vane 3 and shaft 4 shall be driven from outside the casing 2, and liquid is pumped from a casing inlet 22 to a casing outlet 21 when the edge section 3a of the vane 3 runs along the inner surface 2a in the rotary movement.

Said outlet 21 and said inlet 22 are separated by a small selected distance.

An end panel section 7, not shown in Fig. 2, must be attached to the casing to achieve a complete pumping arrangement 1. A centre of rotation 4' for the said shaft 4, as well as for the said vane 3, is eccentric in relation to an assigned centre 2' for said cylindrical inner surface 2a or the cavity 2C.

Said vane 3 is arranged to move back and forth in the associated shaft 4 at the centre of rotation 4' through a slot 4a in the shaft 4. Fig. 3 illustrates an embodiment with two parallel, or at least essentially parallel, vanes 3, 3' arranged through said shaft 4 in separate slots 4a, 4a'.

This embodiment is essentially the same as the one shown in Fig. 2, a!- though with the difference that a vane 3 or 3' only needs to rotate 180° to perform one stroke or activation phase, according to Fig. 9B.

Fig. 4 shows that one and the same means 5 is arranged for both the embodiments according to Figs. 2 and 3 in order to guide the said vane 3 (vanes 3 and 3' respectively) against the said inner surface 2a during the rotation of the shaft 4 and vane 3.

Here, the said means 5 can consist of guide tabs 3b, 3c devised to run in a peripheral groove 6b in the end panel and in a groove 6c in the bottom section 2B (7'). The groove 6b in the end panel section 7 is devised to follow the curvature of the surface 2a, and the groove 6c in the opposite end panel section 7' section, or the bottom section 2B, is devised to follow the curvature of the surface 2a in a similar fashion.

The invention shows that the ratio between a first diameter D1 for the cy- lindrical inner surface 2a and a second diameter D2 for the shaft 4 was selected to be 3.0 to 1.5, e.g. 2.0 to 1.75.

The invention also shows that a stroke volume shall be assigned a value from 40 to 250 ml, e.g. 100-150 ml.

Here, 'stroke volume' refers to the volume pumped out with one vane 3 and in a single rotation of the vane 3.

Figs. 5 and 8 show perspective views of the various parts of an alternative embodiment.

Fig. 8 is a perspective view showing that the said vane 3, in another embodiment, is equipped with a means 5 in the form of one or more permanent mag- nets 30, 31 in the edge area 3e or edge areas 30, 31 facing the said inner surface 2a.

Fig. 5 shows that the wall of the casing 2 is equipped with a plurality of electromagnets, some of which assigned the reference designations 40a, 40b, ... 40m devised for sequential activation by a control unit (see Fig. 10) in order to im- part a desired rotary movement to the vane 3.

Said control unit can be arranged to increase or decrease the shaft's 4 speed of rotation according to the level of oxygen measured in a bloodstream or according to control signals from a myocardial stimulation arrangement.

The rotary movement is activated by a driving arrangement whose energy is obtained from a battery C.

All surfaces and all parts in the pumping arrangement's cavity 2C are also stipulated as being glossy, e.g. plated with a metal such as a titanium nitrite, and the rest of the design also displays small passive areas.

Passive areas refer to areas in which stagnant blood could accumulate in the cavity 2C and thereupon coagulate into a blood clot.

The outlet 21 is designed to interact with one or more nipples 23 in which a turbulent flow of liquid can be transformed into a linear flow of liquid.

The distance between the inlet and the outlet can be varied when different shapes are selected for the casing 2 according to Figs. 2 and 3 and Fig. 5 respectively, making it possible to modify the morphology of the curve for the liquid's volume/pressure variation over time. It is also evident that the inlet 22 must be given a larger diameter and area than the diameter and area of the outlet 21. 20% larger is proposed here.

The housing 2 according to Fig. 5 contains a shaft 4 (not shown) in the cavity 2C, according to Fig. 7, and at least one vane 3, according to Fig. 8, and an end panel 7, according to Fig. 6, is attached to the housing in the known fashion. Rotation of the said shaft 4 via the vane 3 can be activated by external means 8 attached to or a part of the end panel 7.

The said external means 8 can be in the form of a control unit 8a which delivers DC pulses to one or a plurality of electrically activated casing magnets 40a-40m. In order to rotate the vane 3 from one position, e.g. at magnet 40b, to another position, e.g. magnet 40a, the control unit can generate a current pulse to the magnet 40a so an attractive magnetic force is exerted on the magnets 30, 31.

As Fig. 5 shows, the casing 2 is equipped with a closely spaced, electrically controlled magnets located in a circle around and outside the entire inner surface 2a, and these magnets are arranged for sequential activation in order to impart a circular movement to the vane 3.

The side 3a of the vane facing the inner surface is equipped with a num- ber of permanent magnets 30, 31 , whereas the edge surface areas 3f, 3g serve as support surfaces against the inner surface 2a.

A distinguishing feature of the pumping arrangement according to the invention is that it is capable, thanks to the shape selected for the cavity 2C, the choice of one or two vanes 3, 3' and the speed selected for vane rotation, of operating within a wide range, i.e. from light support to a life-saving function when cardiac collapse is imminent.

Moreover, the pumping arrangement does not require any valves, thereby reducing maintenance. In the event of a motor failure, much less blood is lost than is the case with pulsators of other designs.

As a result of the design, all surfaces are either in motion or in the bloodstream. No pocket of stagnant blood can form, so the presence of any passive areas will therefore be very rare. The value selected for the distance between the inlet and the outlet is decisive to volume/time characteristics, and having two or three different casings available and selecting the best one for current use with a particular patient may be appropriate.

The pressure exerted by magnetic forces against the surface 2a can be relieved by the surface sections 3f, 3g or the tabs 3b, 3c. The distance to the surface 2a should be large enough to preclude any risk of crushing blood cells, e.g. about 0.10 mm.

This reduces the risk of individual blood cells being mangled and crushed during the pump's operation and accordingly subjected to haemolytic changes. The pumping arrangement shall be driven at a slow speed, thereby ensuring minor wear and tear of moving parts.

Fig. 9 illustrates the co-ordination of cardiac function A and operation of the pumping arrangement B

It is assumed a heartbeat commences at time tO and has completed con- eluded at time t2.

By time t1 , the heartbeat has virtually subsided.

The pumping arrangement starts its synchronised pumping stroke at time tO and concludes the stroke at time t1.

A myocardial stimulation arrangement 10, according to Fig. 10, is arranged to transmit a pulse to the myocardium over a line 10a at tO, and the same pulse triggers the control unit 8a to trigger the pumping arrangement 1 via a pulse on line 10b.

This synchronises cardiac function and the pumping arrangement.

With a shaft design according to Figs. 2 and 3 and/or Fig. 7, it may be appropriate to have circular grooves 71', 72' in the end panel section 7 and the bottom section 2B for projecting flanges 71 , 72 enabling the longitudinal edges 3k and 31 of the vane 3 to run at a short distance from the flat surface 7' of the end panel section 7 and the flat surface 2B' of the bottom section 2B.

Here the distance can be about 0.1 mm.

The cavity 2C should not have any through holes for the shaft projection 73, 74; they shall be incorporated into the thickness of the material of the end panel section 7 and the bottom section 2B.

None of the parts 2a, 3, 4 has any joints.

The entire vane 3 can advantageously be made of magnetic steel, such as blade steel plated with titanium nitrite, to which no sediment should stick.

The rotational speed selected for the vane 3 can be from 70-140 revolu- tions/minute or pulses/minute.

When cardiac output is 1.5 litres/minute, the pumping arrangement can deliver 3.2 litres/minute or some other value through selection of the free volume and shape of the cavity 2C.

Arranging a suitable connection or choke between the positive pressure side and negative pressure side, such as shaping the shaft 4 in the manner shown in Fig. 7, may also be appropriate.

The moving parts should have a gap between them of 0.08-0.12 mm, e.g. 0.10 mm. This also applies to the shaft's 4 positioning in relation to the surface 2a.

The invention is, of course, not limited to the aforementioned exemplifying embodiment but can be modified within the scope of the invention as illustrated in the following patent claims.

Claims

1. A pumping arrangement consisting of an housing or casing with a cavity whose inner surface has a circular cross-section, one vane, or a plurality of vanes, arranged inside the cavity, devised so a rotary movement pumps a liquid from an inlet in the casing to an outlet in the casing, said inlet and said outlet being separated from one another, and at least one end panel section, characterized in that the said vane's centre of rotation is eccentric in relation to an assigned centre of said inner surface, and said vane can produce reciprocal movement in relation to a shaft at the centre of rotation.

2. The pumping arrangement according to claim 1 , characterized in that two vanes are arranged parallel, or essentially parallel, through the said shaft.

3. The pumping arrangement according to claim 1 or 2, characterized in that a means is provided for guiding said vane, or vanes, against said inner surface during the shaft's rotation.

4. The pumping arrangement according to claim 1 , characterized in that a ratio between an assigned diameter for the shape of the inner surface and an assigned diameter for the shaft is from 3.0 and 1.5, e.g. 2.0-1.75.

5. The pumping arrangement according to claim 3, characterized in that said means consists of one or a plurality of guide tabs or studs, e.g. two, devised to run in peripheral grooves on the end panel section or bottom section.

6. The pumping arrangement according to claim 1 , characterized in that a stroke volume is assigned a value from 40 to 250 ml, e.g. 100-150 ml.

7. The pumping arrangement according to claim 1 , characterized in that said vane, or vanes, is/are equipped with one or more permanent magnets on the part, or parts, facing the said inner surface.

8. The pumping arrangement according to claim 1 or 7, characterized in that a number of electromagnets, whose activation in time and output is controlled by a control unit, are arranged outside the casing cavity.

9. The pumping arrangement according to claim 1 or 8, characterized in that said control unit is arranged to increase or decrease the shaft's speed of rotation, depending on the level of oxygen measured in a bloodstream.

10. The pumping arrangement according to claim 1 , characterized in that the speed of rotation is activated by a driving arrangement whose energy is derived from an external battery.

11. The pumping arrangement according to claim 1 , characterized in that all surfaces are glossy , e.g. plated with titanium nitrite or the equivalent.

12. The pumping arrangement according to claim 1 , characterized in that the design is devised so the cavity has small passive areas.

13. The pumping arrangement according to claim 1 , characterized in that the outlet is arranged to interact with one or more nipples in which a turbulent flow of liquid in the pump can be transformed into a linear flow of liquid.

14. The pumping arrangement according to claim 1 , characterized in that the distance between the inlet and the outlet can be varied so as to modify the morphology of the liquid's pressure or volume variation over time.

15. The pumping arrangement according to claim 1 , characterized in that said inlet is assigned a larger diameter or area than the diameter or the area of the outlet.

16. The pumping arrangement according to claim 1 , characterized in that the casing has a shaft and at least one vane inside a cavity, and an end panel section is attached to the casing, rotation of the said shaft being activatable by external means.

17. The pumping arrangement according to claim 1 , characterized in that said housing or casing is equipped with a number of electrically controlled magnets, near the cavity, arranged for sequential activation in order to impart a circular movement to the vane.

18. The pumping arrangement according to claim 17, characterized in that the part of the vane facing the inner surface is equipped with a permanent magnet.

19. The pumping arrangement according to claim 1 or 18, characterized in that a surface area on the edge is devised to serve as a support surface against at least the inner surface.