AU2284400A

AU2284400A - Pulsatile pump

Info

Publication number: AU2284400A
Application number: AU22844/00A
Authority: AU
Inventors: Ursula Bluschke; Manfred Gollner; Hendrik Heinze; Petra Killat; Johannes Muller; Werner Neumann; Peter Nusser
Original assignee: Berlin Heart GmbH
Current assignee: Berlin Heart GmbH
Priority date: 1998-12-18
Filing date: 1999-12-20
Publication date: 2000-07-12
Also published as: RU2211709C2; CA2355324A1; WO2000037126A1; CN1330561A; EP1140249A1; DE19963533A1; JP2002532204A

Description

P83799PC Pulsating pump Description The invention relates to a pulsating pump according to the prior art part of claim 1, as well as to a blood pump for supporting or substituting the human or animal heart. From DE-C1-196 09 281 an electromagnetic drive for a blood pump is known, in which two core halves relatively movable to each other, form together with excitating coils an iron circuit. The one core half is fixed to the housing of the blood pump, while the other core half is movable back and forward in dependency of the magnetic excitation between a discharge position and an inlet position. In the discharge position a blood chamber of the blood pump is compressed and the blood is discharged through the discharge valve. Because of the use of a magneto-fluid in the gaps of the electromagnetic circuit, the magnetic characteristics of the drive are improved, so that the size of the pump can be reduced. US-A-5,599,173 described a blood pump with a deformable blood chamber, which has a pair of opposed, essentially planar, circular walls. The walls are compressed by a pair of pressure plates of a solenoid-drive for emptying the blood chamber. The drives or blood pumps known from the aforementioned publications have the disadvantage, that they use relatively a lot of space. Because of this an implantation into the human or animal body is made difficult or is made impossible. The invention has the object to provide drives for a pump as well as pumps, which are distinguished by a small design size, especially a small design height and show no own movement during operation and have a small mass.

2 This object is solved by a pulsating pump with the features according to claim 1 and with the features of claim 22. Preferred and advantageous improvements of the invention are given in the sub-claims. Accordingly, the solution according to the invention provides a reduction in size of the drive system, insofar as the stator and actuator of the drive are formed in such a way, that they engage each other in the one or the other of the two possible end positions (engagement position) and provide, because of this, only a small design height. With this the design height of the engaging parts is smaller than the sum of the design heights of stator and actuator. In this way an extremely flat drive is provided, so that further a blood pump can advantageously be formed very flat with the solution according to the invention. Such a blood pump enables a better implantability. In a preferred embodiment of the invention the stator and the actuator form together a height in the inter-engaging position, which is only insignificantly larger than the height of the stator. Therefore compared to the known drives, nearly a bisection of the height of the drive or of a pump provided with the drive is possible. Advantageously, the stator as well as the actuator have magnetic core elements, circumferentially extending and having essentially a U-like cross-section, which inter engage in the engagement position. A U-like cross-sectional design of the magnetic core elements enables an inter-engagement of the core elements with a simple geometric structure. In this case, an annular magnet coil, serving for the magnetic excitation of the magnetic circuit formed by stator and actuator, is preferably inserted into the U-like cross-sectional recess of the stator. A compact geometric structure is provided by this. Furthermore, because of the integration of the magnet coil into the stator, energy is saved during the operation of the blood pump, as the magnet coil is stationary fixed and does not move. The to be moved mass is reduced therefore. A further advantage is the increase of the reliability, as the moving parts have no flow carrying areas.

3 It should be noted here, that the invention especially relates to electromagnetic drives. However, the invention is not limited to such drives, but comprises all the drives for pumps, which are provided with a stator and a movable actuator. The actuator can for example also be driven electro-mechanically, electro-hydraulically or electro pneumatically. The drive (stator-actuator-combination) according to the invention has preferably means, which exert a force in the direction of the other position onto the actuator in the engagement position. These are especially spring means, which, after the magnetic excitation has stopped, separate the actuator from the stator and press against the fluid chamber to discharge the to be transported fluid. The actuator forms at the same time preferably an essentially flat pressure plate on its side facing the fluid chamber, so that the fluid chamber is compressed uniformly. The fluid chamber is formed by membranes, which abut in a non fixed state the pressure plate of the actuator. In an embodiment of the invention the pressure plate has pressure compensation openings, which compensate under- and over pressures produced during the pumping process and prevent an adherence of the membrane. By profiling the face of the pressure plate the adherence of the membrane is additionally prevented. It is provided that actuator and stator in the engagement position only contact each other on the abutment faces, so that no tilting or jamming of the parts, frictional losses, material wear, noise pollution, etc. can appear. In a further embodiment of the invention according to claims 11 to 16 the stator actuator-combination has a guide, on which the actuator is supported and by which means the actuator is movable intermittently relative to the stator. The guide of the actuator causes a defined intermittent movement between the two end positions, so that the actuator and stator can both be formed flat, as a tilting and a jamming of actuator and stator, easily possible, is eliminated or reduced because of the flat design. The guide is advantageously centrically arranged, so that a symmetrical arrangement is given and a tipping can be prevented or reduced with only one guide. Because of 4 using of a centric guide the component number is kept low, whereby the compactness of the drive is further increased. The guide has in one embodiment variant a longitudinal guide, especially a central guide pin of the drive, on which the actuator is supported longitudinally displaceable. Alternatively, the guide is formed by using suitable leaf spring arrangements as a leaf guide. Here the necessity of a central guide element is eliminated, so that the compactness of the drive is further increased. Leaf spring arrangements also act in a centering manner, i.e. a force, acting non-centrally on the actuator, experiences a counterforce in the direction of a central arrangement, so that adjustment to the wanted orientation relative to the stator is achieved. Ideally the guide is formed as a linear guide, which has only one degree of freedom in the axial direction. For this however, it is necessary, because of the flat arrangement of stator and actuator and the small guide length connected therewith, to form the drive- and guide elements very accurately. This is cumbersome and expensive and it is often not reachable with the necessary accuracy. Therefore, to prevent, when using an axial guide, a jamming of the actuator on the guide and/or with the stator, the guide is alternatively formed as a wobble guide. This solution allows consciously the possibility of a small amount of tipping of the actuator. This tipping does not impede the functioning of the drive, as, because of the inter-engagement of stator and actuator according to the invention, a defined position of the elements is achieved in the inter-engaging position. A wobble guide can be realised for example by a leaf spring arrangement or by a wobble bearing connected to a central guide pin. Actuator and stator are preferably formed rotational-symmetrical, which additionally contributes to a simple and compact design of the drive. A blood pump according to the invention has preferably a housing essentially formed flat and surrounding the drive and the pump chamber and has the suction- and discharge openings for the fluid to be transported, which are connected to the pump 5 chamber. For this the stator is stationary fixed to the housing, while the actuator is movable relative to the stator and the housing. A pump according to the invention can have one or even several stator-actuator combinations. Of advantage is the use of two electromagnetic drives, which are arranged symmetrically opposed in the pump housing. The fluid chamber is hereby arranged between the respective actuators and is compressed from two sides by the actuators. The advantage of a symmetrical system with two symmetrically arranged drives is such, that in comparison with a single-sided system only a small impulse is transmitted during the pump process into the human and animal body, into which the pump is implanted. Because of the use of two stator-actuator-combinations a redundant system is further provided, which still can function when one combination breaks down. It is referred to the fact, that the pump according to the invention is not limited to the use of two drives. A higher number of drives, e.g. four drives, can be provided. The pump according to the invention with the extremely flat drive has preferably the size of a hand, so that it can be implanted into a to be treated person relatively without problems. It is especially used as a blood pump for supporting or substituting the human heart. The invention is described in detail in the following by reference to the figures by means of several embodiments. Fig. 1 a is a schematic view of a pump with attracted actuator; Fig. lb is a schematic view of a pump with pushed forward actuator; Fig. 2 is a schematic view of a pump with filled fluid chamber; Fig. 2b is a schematic view of a pump with emptied fluid chamber; Fig. 3 is a schematic view of a double leaf spring; 6 Fig. 4 is a schematic sectional view of a pump with a known wobble guide; Fig. 5 is a single leaf spring; Fig. 6 is a single leaf spring with helical compression springs; Fig. 7 is a double leaf spring arrangement with helical compression springs; Fig. 8a-d are schematic views of the effect of a wobble guide according to the invention; Fig. 9 is a schematic view of the connection between actuator and stator by means of catch spring and catch hook; Fig. 10a is a schematic sectional view of a blood pump formed flat (shallow); and Fig.1Ob is a schematic sectional view of the blood pump as a top view. Fig. la shows a pulsating pump, which is formed as a single-sided system, i.e. as an actuator-stator-combination. The pump is formed flat (shallow) and annular. A stator 12 and an actuator 15 are arranged in a housing 11. The actuator 15 is attracted in the view of Fig. la, which enables the filling of a fluid chamber 16. The fluid chamber 16 is limited by a membrane 161 towards the actuator 15. The attraction of the actuator 15 is carried out via magnet coils 19, which are formed as an annulus, here. Fig. lb shows a pulsating pump during the compression of the fluid chamber 16 after switching off the magnet coil 19 by the actuation of the helical compression springs 18. The fluid is discharged via the suction- or discharge opening 17 from the fluid chamber 16. Fig. 2a and 2b show the pump process of the pulsating pump when using two symmetrically opposed stator-actuator-combinations. Because of the attraction of the actuators 15 via the switched-on magnet coils 19 the chamber provided for the fluid 7 chamber 16 in the pump, is increased, whereby a filling of the fluid chamber 16 is enabled. After switching-off the magnet coil 19 a compression of the two actuators 15 via the helical compression springs 18 during the emptying of the fluid chamber 16 is carried out, wherein the discharge process of the fluid is ended by limiting the maximal distance between the actuator 15 and the stator 12 by means of an arrangement of catch hooks 4 and catch springs 3 (Fig. 9a to d). The electrical connection conducts for the magnet coil 19 are not represented separately. The control- and current supply unit for the operation of the pump can be carried outside, in case of a blood pump, for example, on the belt of a patient. Furthermore, the pump has several helical compression springs 18 arranged on a circle, exerting a force away from the stator 12 onto the actuator 15. For the support of the helical compression springs 18 in the stator 12 and in the actuator 15, small recesses are provided in these. The wobble bearing 14 provided for the axial guide of the actuator 15 is connected via connection elements and assigned pins to the base plate of the actuator 15. As it especially can be seen from Fig. 4, the use of a known wobble bearing 14 on the axially extending guide pin 13 for the tipping of the actuator 15 relative to the stator 12 provides two additional degrees of freedom. The tipping of the actuator 15 and the compensation effect can be seen from Figures 8a to 8d. While common axial guides especially act to prevent a tipping of an element on the axial guide, as a tipping is connected with an unwelcome clamping, the invention allows a tipping by means of the wobble bearing 14 and because of this prevents a jamming of the guide 13. As the outer diameter of the stator 12 and the corresponding recesses in the actuator 15, respectively, are adapted to each other in such a way, that even during a tipping of the actuator 15 a contact does not or only takes place on the support faces, no jamming can take place neither at this position. Therefore, it is possible, to carry out a safe guidance of the actuator 15 relative to the stator 12 with only one axial guide. The operation of the fluid pump is as following: 8 During the current supply of the magnet coil 19 a magnetic field is produced, which exerts a force onto the actuator 15 in the direction of the stator 12. The actuator 15 moves accordingly along the guide 13 towards the stator 12. At the same time the magnet coil 19 arranged there is received in the recess of the actuator 15. Corresponding forms and recesses and projecting parts of the stator 12 and 15 are provided. The actuator is now in the inter-engaging position. Together with the movement of the actuator 15 into the inter-engaging position, an enlargement of the chamber provided for the fluid chamber 16 takes place, which leads to the inflow of the to be transported fluid via the suction opening 17. During the filling phase a holding current is lead through the magnet coil 19, so that the magnetic excitation is maintained and the actuator 15 and the stator 12 remain for a while in the inter-engaging position, until the blood chamber 16 is filled with blood. For discharging the fluid the current supply of the magnet coil 19 is interrupted by the current supply- and control unit. Because of the clamping force of the helical compression springs 18, the actuator 15 now moves in the direction of the blood chamber 16 and compresses the blood chamber 16 with its side formed as a pressure plate 5, while the to be transported blood is discharged via the discharge opening 18 from the pump. Suitable valves (not represented) are provided in this case, which control the direction of the flow. The movement ends in a further end position of the actuator 15. In a further alternative the fluid chamber 16 has pressure compensation openings for the prevention of a high underpressure (vacuum), through which a pressure compensation can take place (Fig. 1 and 2). In Figures 8a to 8d the movement of the actuator 15 between the two end positions is represented. A tipping of the actuator 15 is hereby possible because of the wobble bearing 14 (Fig. 4), without a jamming of the actuator 15 to occur on the guide 13. Because of the mutual guidance of the stator 12 and the actuator 15, when inter engaging each other, it is secured, that a defined position is present in the inter engaging position.

9 In an embodiment the capacity necessary for the electro-magnetic drive is around 120W. At the same time the coil 16 is flown through by a current, per discharge process, for maximal lOms. Per discharge process around 70 ml fluid, e.g. blood, is transported by the pump. The used helical compression springs 18 have preferably a spring force between 80 and 120 N over a length of 6 mm. The height of the stator 12 lies especially between 5 and 15 mm, the height of the actuator 15 is also 5 to 15mm, the total height of the stator 12 and the rotor 15 is 6 to 20 mm in the inter-engaging position and the total height of the pump is preferably 1.5 to 4.5 cm. The diameter of the pump lies preferably between 5 and 11 cm. In figures 3, 5, 6 and 7 an alternative wobble guide is shown, which is realised by a leaf spring arrangement. This wobble guide substitutes the guide 13 and the wobble bearing 14 of Fig. 4. Furthermore, the pump is formed as described with reference to Fig. 1 and Fig. 2, respectively. The wobble guide, based on the leaf spring arrangement, has a leaf spring 2, which is formed star-like and has, starting from an actuator mounting 23, four legs bent by 1809 downwards. The stator 12 is connected via mounting points 32 of the bent leg areas to the leaf spring 2. This arrangement provides for a movement of the actuator 15 relative to the stator 12 three degrees of freedom, namely a degree of freedom in the axial direction and two degrees of freedom for a tipping. The leaf spring arrangement acts in a centering manner, as a non-centric force application on the actuator 15 experiences a counterforce in the direction of the longitudinal axis of the leaf spring 2. Furthermore, the wobble movement, similar as already described, secures, that the actuator 15 and the stator 12 cannot be jammed and that these elements for the further reduction of the design height can securely inter-engage despite of the small design height of actuator 15 and stator 12. The embodiments of the helical compression springs 18 , shown in Fig. 6 and 7, serve as described with reference to Fig. 1 and 2, for producing a force onto the actuator 15 10 away from the stator 12, so that the actuator 15 is moved in the direction of the fluid chamber 16 when the magnetic excitation is cancelled. Fig. 5 shows an alternativ embodiment of the wobble guide, wherein separate helical compression springs 18 have not been used and the leaf spring 2 serves for guiding the actuator 15, as well as for producing a force for moving the actuator 15 against the fluid chamber 16. In this solution the leaf spring 2 is preferably harder, so that the function of producing a force onto the actuator 15 is securely fulfilled, which enables, that a smaller value of tipping is possible. The wobble guide shown in Fig. 3 corresponds firstly to the wobble guide of Fig. 5. However a further leaf spring 2a, identical in design, but smaller, is additionally provided to the star-like leaf spring 2, which is arranged within the larger leaf spring 2. The respective mounting faces are connected to each other by a connection element 33. The bent leg ends of the leaf springs 2 and 2a are connected at mounting points to the stator 12. For fixing the actuator 15 a mounting point is provided on the upper face of the mounting face of the leaf spring 2. This leaf spring arrangement leads in the ideal case to a solemnly linear guidance of the actuator 15 relative to the stator 12, as a tipping of the outer leaf spring 2 is prevented or at least is strongly reduced by the inner leaf spring 2a. This variant realises therefore a centric linear guidance of the actuator 15 relative to the stator 12. When providing only one degree of freedom in the axial direction, the elements of stator 12 and actuator 15, adapted to each other, have to be accurately manufactured, so that a jamming can be securely eliminated. Fig. 7 shows a combination of a double leaf spring arrangement 2 and 2a, which has helical compression springs 18 in addition to the leaf springs 2 and 2a. In this embodiment the leaf springs 2 and 2a are formed smaller, as they only serve the function of guiding. Fig. 10 shows exemplarily an embodiment of a blood pump according to the invention, which is provided with a leaf spring arrangement according to Fig. 6 with a 11 single leaf spring 2 and helical compression spring 18 instead of the guide 13. A stroke limitation according to Fig. 9a is also realised here. The invention is not limited in its realisation of the above described embodiments. The invention is not especially limited to the use of forms, which have a U-like cross section and inter-engage. It is only essential for the invention, that in a drive for a fluid pump the stator 12 and the actuator 15 have corresponding forms, recesses and projections, respectively, on their sides, adjoining each other, in such a way, that stator 12 and actuator 15 inter-engage with each other in the inter-engaging position and the design height of the drive is reduced at the same time and/or that a guide of the actuator is provided.

12 List of reference numerals 1 2 Leaf spring 2a Leaf spring 3 Catch spring 4 Catch hook 5 Pressure plate 6 7 8 9 10 11 Housing 12 Stator 13 Guide 14 Wobble bearing 15 Actuator 16 Fluid chamber / Blood chamber 161 Membrane 17 Suction - or discharge opening 18 Helical compression spring (Coil spring) 19 Magnet coil 20 21 22 23 Actuator mounting 24 25 Opening to the environment 26 Pressure compensation opening 27 28 29 30 13 31 32 Mounting on the stator 33 Spacer block between stator and actuator 34 T Wobble point E Plane Ss Stator axis Sa Actuator axis

Claims

1. Pulsating pump, consisting of a stator arranged in a housing and an actuator, movable relative to the stator electro-magnetically and by spring force, which is movable intermittently between a first position and a second position, by this increasing or decreasing a fluid chamber having a suction- and discharging opening, characterised in that the actuator (15) has on the side adjoining the stator (12) referring to the design of the stator corresponding recesses (154) and projections (121), which are inter-engageable in the stator (12).

2. Pulsating pump according to claim 1, characterised in that in the inter-engaged position the stator (12) and the actuator (15) form together a height, which only exceeds insignificantly the height of the stator (12).

3. Drive according to claim 1 or 2, characterised in that the stator (12) as well as the actuator (15) have magnetic flow carrying areas, circumferentially extending and formed essentially U-like in cross-section, and inter-engaging in the inter-engaging position.

4. Pulsating pump according to one of claims 1 to 3, characterised in that a magnet coil (19) is integrated into the stator (12).

5. Pulsating pump according to claim 3 and 4, characterised in that the magnet coil (19) is annularly arranged on the stator (12).

6. Pulsating pump according to one of claims 1 to 5, characterised in that 15 a flexible membrane (161), which is limiting a fluid chamber (16) and which is not constantly in contact with the pressure plate of the actuator (15), is arranged on the actuator (15).

7. Pulsating pump according to one of claims 1 to 6, characterised in that the actuator (15) is movable away from the inter-engaged position by means of a helical compression spring (18).

8. Pulsating pump according to one of claims 1 to 7, characterised in that the actuator (15) is formed essentially as a planar pressure plate (5) on its side facing away from the stator (12).

9. Pulsating pump according to one of claims 1 to 8, characterised in that the actuator (15) and the stator (12) can contact each other only on the supporting faces.

10. Pulsating pump according to one of claims 1 to 9, characterised in that the actuator (15) is supported in a guide (13).

11. Pulsating pump according to one of claims 1 to 10, characterised in that the guide (13) is arranged centrically.

12. Pulsating pump according to one of claims 1 to 11, characterised in that the guide (13) is a longitudinal guide, on which the actuator (15) is supported longitudinally displaceable.

13. Pulsating pump according to claim 9 or 10, characterised in that 16 the guide (13) has a leaf spring (2, 2a).

14. Pulsating pump according to claim 11 or 12, characterised in that the guide (13) is formed centrically, linearly.

15. Pulsating pump according to one of claims 1 to 14, characterised in that the guide (13) is formed as a wobble guide (14, 2).

16. Pulsating pump according to one of claims 1 to 15, characterised in that the leaf spring (2, 2a) is formed star-like and has at least three legs bent by 180 downwards and extending from an upper face with an actuator mounting (23), wherein the actuator (15) is connected to the upper face of the leaf spring (2) and the stator (12) is connected to the legs of the leaf spring (2) bent downwards or vice versa.

17. Pulsating pump according to claim 15, characterised in that the leaf spring (2) has additionally a further leaf spring (2a) of smaller size, which is arranged within the larger leaf spring (2), wherein the legs and the upper faces of the two leaf springs (2, 2a) are rigidly connected to each other.

18. Pulsating pump according to claim 15 or 16, characterised in that the leaf spring (2, 2a) serves additionally as a spring element for producing a force, forcing the actuator (15) away from the stator (12).

19. Pulsating pump according to one of the aforementioned claims, characterised in that the actuator (15) and the stator (12) are formed rotational-symmetrical.

20. Pulsating pump according to one of claims 1 to 19, 17 characterised in that the stator (12) and the actuator (15) are limited via an arrangement of catch springs (3) and catch hooks (4).

21. Pulsating pump according to one of claims 1 to 20, characterised in that two opposed stator (12)- and actuator (15)-combinations are arranged, wherein the fluid chamber (16) is arranged between the two actuators (15) of the arrangement.

22. Blood pump for supporting or substituting the human or animal heart, characterised by a pulsating pump (1) according to the claims 1 to 21.

23. Pulsating pump according to claim 22, characterised by an essentially shallow formed housing (11), surrounding the stator-actuator combinations and a blood chamber (16), and has suction- and discharging openings (17), which are connected to the blood chamber (16).

24. Pulsating pump according to claim 22 or 23, characterised in that the housing (11) is formed circular.

25. Pulsating pump according to one of claims 1 to 22, characterised in that the actuator (15) has pressure compensation openings (26).

26. Pulsating pump according to one of claims 1 to 22 and 25, characterised in that the pressure plate (5) of the actuator (15) has a fairing (grooving).