Peristaltic pump and pumping method, in particular for use as implant

Abstract

A pump having at least a fluid pump chamber (11) and a first driver chamber (12) separated from the fluid pump chamber (11) by an elastic wall (13, 13-1, 13-2) is described with the first driver chamber (12) expanding after a chemical reaction between fuel and oxidant and driving through deformation of the elastic wall fluid out of the fluid pump chamber (11), with the main parts of the pump being made of an elastic material to be used for example as a body implant.

Claims

1. Peristaltic pump driven by a chemical reaction between a fuel and an oxidant comprising at least one fluid pump chamber and a first driver chamber separated from the fluid pump chamber by a first elastic wall, wherein the first driver chamber comprises one or more ports for fuel or oxidant containing fluids to enter and for exhaust fluids to leave the first driver chamber, and wherein the first driver chamber expands after a first chemical reaction between fuel and oxidant in said first driver chamber.

2. The pump of claim 1 comprising at least two pairs of chambers each comprising a fluid pump chamber and a first driver chamber separated from the fluid pump chamber by a first at least partly elastic wall.

3. The pump of claim 2 wherein the fluid pump chamber of each pair is located closer to the geometrical center of the pump than its associated first driver chamber.

4. The pump of claim 1 comprising a second driver chamber separated from the fluid pump chamber or the first driver chamber by a second at least partly elastic wall wherein the second driver chamber expands after a chemical reaction between fuel and oxidant different from the first chemical reaction expanding the first driver chamber.

5. The pump of claim 1, further comprising several driver chambers and an ignition controller adapted and structured to initiate the chemical reactions expanding said driver chambers at different times within the duration of one period of a cyclic process.

6. The pump of claim 1, wherein said first driver chamber comprises catalytic material to promote the reaction.

7. The pump of claim 1, wherein one or more interior walls comprise an elastomeric material.

8. The pump of claim 1, comprising of at least 80% of an elastomeric material.

9. The pump of claim 1 made essentially of a homogeneous elastomeric material.

10. The pump of claim 7, wherein the elastomeric material is selected from a group of nitrile (NBR), Hypalon, Viton, silicone, PVC, EPDM, EPDM with polypropylene, polyurethane and natural rubber and mixtures and blends thereof.

11. The pump of claim 1, comprising at least one wall section having a base material and fibrous material embedded in the base material.

12. The pump of claim 1 wherein at least said fluid pump chamber, said driver chamber(s) and said ports are of a single material.

13. Use of the pump in accordance with claim 1, in farming, hazardous fluids or fluids loaded with solid particles.

14. Body implant, particularly artificial heart, comprising a pump in accordance with claim 1.

15. The pump of claim 1 wherein the first driver chamber comprises an ignition device integrated into an exterior wall and at least partly exposed to the interior of the first driver chamber.

16. The pump of claim 1 wherein said one or more ports are in an exterior wall of the first driver chamber for fuel or oxidant containing fluids to enter and for exhaust fluids to leave the chamber.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic cross-section of a two chamber pump in accordance with an example of the invention;

(2) FIGS. 2A-2C are schematic cross-sections of a three chamber pump in accordance with an example of the invention during three different stages of a pump cycle;

(3) FIG. 3 is a schematic cross-section of another three chamber pump in accordance with an example of the invention; and

(4) FIGS. 4A-4C are schematic cross-sections of pump designs shaped as heart replacement in accordance with further examples of the invention.

DETAILED DESCRIPTION

(5) A first schematic representation of a basic device in accordance with an example of the invention is shown in FIG. 1.

(6) The device of FIG. 1 is a two chamber pump 10 having a fluid pump chamber 11 and a driver chamber 12. The walls of the chambers are made of a silicone based material. The inter-chamber wall 13 is made of a reduced thickness compared to the exterior walls. Ports 121, 122 in the exterior walls of the driver chamber provide a supply path to a fuel and oxidant reservoir (not shown) and an exhaust path for reaction products. Ports 111, 112 in the exterior wall of the fluid pump chamber provide inlet and outlet, respectively, for fluid to be pumped.

(7) An ignition device 14 is integrated into one exterior wall and at least partly exposed to the interior of the driver chamber 12. The device can include for example two electrodes connected to two poles of a voltage source in a manner similar to a spark plug.

(8) Elements of a three chamber pump in accordance with an example of the invention are shown in FIGS. 2A to 2C. The pump differs from the pump of FIG. 1 by addition of a second drive chamber 12. Hence the pump has two inter-chamber walls 13-1 13-2. As the elements of the second driver chamber 12 are identical to those of the first driver chamber already described above, the same numerals have been used to denote the same elements.

(9) In a preferred geometry of a three chamber pump, one chamber serves as a driver chamber, one as a liquid pumping chamber and one chamber assists the aspiration of air as oxidant, for example for use in a later stage of a pump operation cycle.

(10) This intake of air can be used advantageously in an embodiment where the two driver chambers 12 that are each used in a pump cycle as described in further detail below alternating as exhaust/intake chamber, i.e., first as expansion chamber and in the following pump cycle as exhaust/intake chamber, and so forth. The chambers 12 may either be arranged in a linear way, with the fluid pumping chamber 11 in the middle, or, the two driver chambers may be next to one another, sharing a common wall (driver 1/driver 2) and both a common wall with the pumping chamber. The wall thickness of (driver 1/driver 2) will be different from the wall (driver 1 or 2/pumping). Chambers may include sensors to measure fluid concentration levels etc.

(11) A pump as shown in FIG. 2 can be operated according to the following cyclic steps:

(12) Step 1: The first driver chamber 12 is filled with a ready-to-react fuel mixture whilst the pump chamber 11 and second driver chamber 12 are in a relaxed state. This state is illustrated in FIG. 2A.

(13) Step 2: The fuel mixture in the first driver chamber 12 is ignited and its volume is growing. At its maximum expansion, the volume of the gas contained in this first driver chamber is between 1.3 to 3 times the volume before ignition. In this expansion step both the pumping chamber is pumping fluid and the second driver chamber 12 exhausts reaction products of a previous cycle. This is a result of a deformable, soft design, where the pumping chamber can be significantly deformed, hence also changing the volume of its adjacent second driver chamber. This state is illustrated in FIG. 2B showing the deformation of the inter-chamber walls 13-1 and 13-2. The liquid displacement (pump volume) is (the pump chamber volume displacement due to deformation of the wall between first driver chamber 12 and the fluid pump chamber 13) minus (the volume displacement due to expansion of the pumping chambers wall to the second driver chamber) minus (the volume displaced at walls facing the outside of the pump). Typical liquid displacements as a result of a single pumping event (i.e. one ignition in a driver chamber) are between 0.2 to 0.8 times the volume of the liquid pumping chamber when relaxed.

(14) Valves at the entry and exit points of the individual chambers direct the flow of gas or liquids typically in a unidirectional way and avoid backflow of liquids or gases. Suitable valves are known in this field and can consist of ball valves or flap-based valves, amongst others.

(15) Step 3: System relaxes to its initial state as the elastic material restores all chambers of the pump back to their most relaxed form. The first driver chamber 12 cools down whilst the fluid pumping chamber 11 sucks in fluid up to its relaxed position (usually straight walls) and the second driver chamber 12 refills by taking in the fuel mixture. The fuel mixture can be injected or sucked in into second driver chamber 12. This state is illustrated in FIG. 2C which is identical to FIG. 2A with the role of fuel-filled and exhaust filled driver chamber 12 reversed.

(16) In the following steps the function of the first and second driver chamber 12 is reversed and hence:

(17) Step 4: The first driver chamber 12 is compacted and exhausts the burned fuel mixture whilst the pumping chamber 11 is pumping out the fluid and the second driver chamber 12 is expanding after an ignition and reaction of the fuel mixture

(18) Step 5: The first driver chamber 12 relaxes again and takes in the fuel mixture and the pumping chamber refills and the second driver chamber 12 cools down and exhausts the reaction products.

(19) Step 6: The system at this step is now equal to the system at the start of Step 1 thus terminating one pumping cycle.

(20) In the cycle fuel and oxidants are provided and exhaust exits the driver chamber through the ports 121, 122. It is preferred to use at least one first port 121 solely for fuel supply and at least one second port 122 solely as exit for the exhaust of the reaction products. The flow through the port can be controlled by valves, particularly one-way valves (not shown) as mentioned above.

(21) In addition to such valves or alternatively, the deformation used for the pumping can also be used to provide a valve-like action on supply and/or exhaust tubes. For example deformable sections of tubular connectors to the ports can be used, which are closed and opened through the expansion or compression of driver chambers. The soft design of the pump hence permits to have deformable sections of tubing at inlet or exit of gas/liquid ports. Deformation due to use of a driver chamber then alters the opening in such deformable sections, hence permitting some control on the flow through that section.

(22) The ports can optionally be open or covered by a permeable membrane, for example a hydrophilic, semipermeable membrane. Due to its hydrophilicity, the membrane can permit slow transfer of water out of the liquid pump. In such a design, water as a waste product is slowly released out of the driver chamber similar to a drain. This exploits an effect similar to wetted fabric (e.g. woven cotton), which is known to be nearly impermeable for air, while water can flow almost freely through it. This effect is best known when cotton cloth get soaked with water and held under water with air trapped inside. Driving air through wetted cotton requires significant pressure. Since the pressure depends on the mesh width of the cloth, finer fabrics withstand higher pressure. This allows the adaptation of the membrane to a given design or purpose.

(23) The fuel can include for example a volatile organic, combustible liquid and hydrogen peroxide or of a gas mixture such as hydrogen gas and air.

(24) The fuel can be ignited electrically using sparks as generated by the ignition controller 14. Alternatively or in addition, the ignition controller can include a catalyst, such as a noble metal or metal composition including a noble metal, igniting the fuel mixture at defined concentration levels of fuel and oxidant.

(25) In a specific form of the invention, a self-igniting effect is used, well known from the ignition of hydrogen containing gas mixtures on fine powdered noble metals, particularly platinum, as platinum sponge. This effect is known from the so called Dbereiner' Fire lighter. The control on the pumping cycle is then possible through timing the inflow of reactants (e.g. hydrogen and air): If fuel (e.g. hydrogen) is being fed very slowly into the driver chamber, it takes more time to reach critical hydrogen concentration for ignition then when the hydrogen flow is higher. Hence, the frequency of the ignition and hence pumping can be controlled to a certain extent by the hydrogen feed rate.

(26) For certain applications, particularly in artificial hearts, a four chamber design can be advantageous, as it resembles the biological design of the human heart. However, an even higher number of chambers may be used.

(27) In FIG. 4 there is shown an example of a pump with an aspect ratio of 1:1 between height and diameter. Such an aspect ratio leading to a relatively shallow volume of the chamber and long inter-chamber walls is preferred to increase the efficiency of the pump.

(28) Depending on the pressure and volume of the liquid to be conveyed, other designs are preferred, e.g. concentric arrangement of the chambers. Here, the geometry of the natural, human heart chamber can be better matched. The pumping chamber is then an asymmetric chamber as in a biological heart chamber, and at least partly surrounded by a driver chamber in a geometry similar to the natural heart muscle. This arrangement is very efficient to transform the expansion of the driver chamber into pushing/compaction of the liquid chamber. Ignition and feed ports are then preferably located at the outside of this concentric arrangement.

(29) For a complete heart replacement, two pumping chambers similar to the natural human heart are needed. There, the arrangement of the natural human heart can be used as a guiding principle. The two pumping chambers are dissimilar in size (the left and right heart chambers are of different strength as the lung branch of the blood circulation has less flow resistance and hence a lower pressure than the larger main branch of the heart, with higher liquid pressure). Both chambers are each surrounded at least to a large extent by a driver chamber. As a result of these constraints, the driver chamber takes the volume between an approximately cylindrical pump chamber in the center, and the outer envelope or wall of the pump itself. Typical chambers will be 2-5 times longer (if the pump is located in a similar fashion as a human heart in a standing human being) then wide. The aspect ratio of 2:1-5:1 and design is similar to the human heart muscle. As stated above, the outside wall of the pump are more resistant to expansion than the wall separating a driver chamber from a pumping chamber.

(30) Examples of four chamber pumps with these aspect ratios are shown in FIG. 4A-4C. In the example of FIG. 4A, the pump 10 has two inner driver chambers 12 and two outer fluid pump chambers 11. Each of the fluid pump chambers 11 have two fluid intake ports 111 and one exit port 112. The material is a room temperature vulcanizing silicone Neukasil RTV23 (Vulcanizer VN A 7, vulcanized at 50 C.) as provided by Altropol Kunststoffe GmbH, Stockelsdorf, Germany. The material is extremely flexible having breaking elongation of about 1000%.

(31) The shape as shown can be manufactured using for example investment casting with the cast from ABS generated through a 3D printing process and later dissolved in an acetone solution.

(32) The pump has a material volume of 485 cm{circumflex over ()}3 of silicone (weight: 530 g) with the volume of a driver chamber 11 95 cm{circumflex over ()}3 and the volume of a pumping chamber 12 60 cm{circumflex over ()}3. The inter-chamber walls 13-1, 13-2 have a thickness of 3 mm while the exterior walls have a thickness of 8 mm.

(33) For pumping, the inner driver chambers 12 are alternatingly filled with a methane/air mixture and ignited at (4.8 Volt, 3 A) using a commercially available electronic igniter. The driver chambers are filled with a gas flow 0.22 L/min of CH4 (at 0.25 Hz pumping frequency) and 2.2 L/min Air (at 0.25 Hz pumping frequency). The replacement of burned gas volume in a driver chamber is approximately 85% at the flow rate as stated. If the pump is operated at higher frequency (e.g. 1 Hz), the gas flow rates and ignition are increased to 0.9 L/min of CH4 (at 1.0 Hz pumping frequency) and 9 L/min Air.

(34) In the example of FIGS. 4B and 4C the relative arrangement of pumping chambers and driver chambers is reversed compared to the 4 chamber pump of FIG. 4A. Hence, the pumping chambers 11 occupy an essentially cylindrical core volume in the center of the pump 10, whilst the driver chambers 12 are located between the core volume and the outer walls of the pump.

(35) The cross-section of FIG. 4B shows a layer of the pump 10 at about mid-height. One of the driver chambers 12 is larger than the other, thus rendering the design asymmetric. The second cross-sectional view (FIG. 4C) is taken from above the pump. Here the locations of the interior pump chambers 11 are indicated as dashed line. A dotted line shows the location of the vertical central plane of the pump thus emphasizing the asymmetric design of the pump. Each pump chamber 11 has an inlet port 111 and an outlet port 112 to provide pumping fluid transport into and out of the pump.

(36) While there are shown and described presently preferred embodiments of the invention, it is to be understood that the invention is not limited thereto but may be otherwise variously embodied and practised within the scope of the following claims.