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Positive displacement pump system and methodRelated Patent Categories: Pumps, Motor Driven, Electric Or Magnetic Motor, Reciprocating Rigid Pumping MemberPositive displacement pump system and method description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080008609, Positive displacement pump system and method. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application No. 60/806,667 filed on Jul. 6, 2006, the disclosure of which is herein incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] Embodiments of the present invention generally relate to pumps. More specifically, and not by way of limitation, embodiments of the present invention relate to positive displacement pumps for the circulation of fluids. [0004] 2. Description of Related Art [0005] Many natural and manmade fluids contain molecules that can be damaged or destroyed by excessive shearing strains or stagnation that can occur in devices that attempt to pump these fluids. Fluids containing molecules with high molecular weights such as proteins, long stranded synthetic polymers, DNA, RNA, or fluids such as blood, which contain concentrations of delicate cells, are especially susceptible to being compromised by many conventional pumping techniques. [0006] Typical axial flow and centrifugal pumps operate by rotating an impeller at very high speeds, often exceeding 12,000 RPM. The shearing stresses that can arise at these velocities can strain larger fluid molecules until they break, leading to destruction or undesirable alteration of the pumping medium. For instance, it is well documented that the pumping of blood using centrifugal and axial flow pumps shears the phospholipid bilayer of erythrocytes and platelets to the point of lysing the cells and releasing their cytosolic proteins and organelles into the blood stream. This phenomenon, known as hemolysis, is an issue in the field of artificial blood circulation because the releasing of hemoglobin into the blood stream can cause kidney failure in patients who receive this blood. Thus, there is useful need for pump designs that can provide fluid circulation without damaging a delicate pumping medium such as blood. [0007] Further objects and advantages of this system and method will become apparent from a consideration of the drawings and ensuing description. SUMMARY OF THE INVENTION [0008] Embodiments of the present disclosure provide systems and methods for pumping fluids. While certain embodiments may be particularly suited for pumping delicate fluids with low shearing strains, it is understood that embodiments of the present disclosure are not limited to pumping such fluids. Other embodiments may be used to pump fluids that are not delicate or do not have low shearing strains. [0009] Certain embodiments comprise: a pumping chamber forming a loop; a pump inlet in fluid communication with the pumping chamber; a pump outlet in fluid communication with the pumping chamber; a first piston disposed within the pumping chamber; a second piston disposed within the pumping chamber; an electric motor; and an electromagnet, wherein the system is configured such that during operation: the electromagnet is initially coupled to the first piston; the electric motor is initially coupled to the second piston; the electromagnet is subsequently coupled to the second piston; and the electric motor is subsequently coupled to the first piston. In certain embodiments, the electromagnet is coupled to either the first or second piston when the electromagnet is energized and the electromagnet is not coupled to either the first or second piston when the electromagnet is de-energized. Certain embodiments further comprise a magnetic ring, and are configured such that during operation: the electric motor exerts a first magnetic force on the first piston; the magnetic ring exerts a second magnetic force on the first piston; and the first magnetic force opposes the second magnetic force. In certain embodiments, the magnetic ring and/or the pistons comprise a permanent magnet or Halbach array. In certain embodiments, the system is configured such that during operation: the motor comprises a rotor with a magnetic link (which may comprise a permanent magnet or Halbach array) and the magnetic link is initially coupled to the second piston and subsequently coupled to the first piston. [0010] Certain embodiments are configured such that during operation a portion of the magnetic link extends beyond a leading face of the piston. In certain embodiments, the system is configured such that during operation the pump inlet is inserted into a ventricle and the pump outlet is in fluid communication with the ascending aorta, the descending aorta, or a pulmonary artery. In certain embodiments, the system is configured such that: the motor comprises a rotor coupled to a linking arm; the linking arm is coupled to a first magnet, wherein the first magnet is located on a first side of the piston during operation; the linking arm is coupled to a second magnet, wherein the second magnet is located on a second side of the piston during operation; and the first side is opposed to the second side. In certain embodiments, the first piston or the second piston comprise a hydrodynamic bearing surface. [0011] Other embodiments comprise a method of pumping a fluid, the method comprising: providing a pumping chamber, wherein the pumping chamber contains the fluid; providing a pump inlet in fluid communication with the pumping chamber; providing a pump outlet in fluid communication with the pumping chamber; providing a first piston disposed within the pumping chamber; providing a second piston disposed within the pumping chamber; providing an electric motor comprising a rotor; providing an electromagnet; coupling the electromagnet to the first piston; coupling the rotor to the second piston; holding the first piston in a first location with the electromagnet; rotating the rotor and moving the second piston closer to the first piston so that a portion of the fluid is forced out of the pump outlet; de-energizing the electromagnet and uncoupling the electromagnet from the first piston; energizing the electromagnet so that it couples to the second piston; and coupling the rotor to the first piston. Certain embodiments further comprise rotating the rotor and moving the first piston closer to the second piston so that a portion of the fluid is forced out of the pump outlet. In certain embodiments, the first location is between the pump inlet and the pump outlet. [0012] Still other embodiments comprise: a pumping chamber comprising an inner surface forming a loop; a pump inlet in fluid communication with the pumping chamber; a pump outlet in fluid communication with the pumping chamber; a piston disposed within the pumping chamber; and a first electric motor magnetically coupled to the piston, wherein: the piston comprises a hydrodynamic bearing surface configured to repel the piston away from the inner surface as the piston moves within the pumping chamber. In certain embodiments, the loop is centered about a central axis; the piston comprises an upper surface, a lower surface, an inner surface, an outer surface, a leading face, and a trailing face; and the inner surface comprises an upper wall, a lower wall, an inner wall and an outer wall. [0013] In certain embodiments, during operation: a first lower gap exists between the lower surface and the lower wall proximal to the leading face; a second lower gap exists between the lower surface and the lower wall proximal to the trailing face; the first lower gap is larger than the second lower gap; a first upper gap exists between the upper surface and the upper wall proximal to the leading face; a second upper gap exists between the upper surface and the upper wall proximal to the trailing face; and the first upper gap is larger than the second upper gap. In certain embodiments, a portion of the lower surface is not perpendicular to the central axis and a portion of the upper surface is not perpendicular to the central axis. [0014] In certain embodiments, a first outer gap exists between the outer surface and the outer wall proximal to the leading face; a second outer gap exists between the outer surface and the outer wall proximal to the trailing face; and the first outer gap is larger than the second outer gap. Certain embodiments comprise a pinch valve between the pump inlet and the pump outlet. Certain embodiments also comprise a second piston disposed within the pumping chamber, and a second electric motor coupled to the second piston, wherein the second piston comprises a hydrodynamic bearing surface configured to repel the second piston away from the inner surface as the second piston moves within the pumping chamber. [0015] Certain embodiments comprise: a power supply; a driver circuit electrically coupled to the electric motor and the power supply; a microprocessor electrically coupled to the driver circuit; and a sensor for sensing a position of the piston within the pumping chamber, wherein: the driver circuit is configured to selectively couple the power supply to the electric motor upon receiving a control signal; the sensor is electrically connected to the microprocessor; the microprocessor is configured to interpret the position from the sensor; the microprocessor is configured to output the control signal to the driver circuit. In certain embodiments, a position and a velocity of the piston are controlled to produce a predetermined waveform in an outlet flow from the pump outlet. Certain embodiments comprise a fluid within the pumping chamber and a sensor configured to measure a property of the fluid. In certain embodiments, the piston or inner surface comprise one or more of the following: a nanoparticulate surface, a microporous coating, or a fibrous flocking. In certain embodiments the nanoparticulate surface, microporous coating, or fibrous flocking are configured to facilitate endothelial or pseudoneointimal protein or cell aggregation. [0016] Certain embodiments comprise a pacemaker and a microprocessor, wherein: the pacemaker comprises one or more electrodes electrically coupled to a heart; the pacemaker is electrically coupled to the microprocessor; the pacemaker provides a depolarization output to the one or more electrodes; and the heart is controlled to contract at a predetermined time relative to an actuation stroke of the pump. Certain embodiments comprise a sensor, wherein the sensor is configured to sense a physiological parameter and the system is configured to increase or decrease a volumetric flow rate from the pumping chamber based on the physiological parameter. In certain embodiments the sensor comprises one or more electrodes for measuring thoracic impedance, p-wave activity, renal sympathetic nerve activity, or aortic nerve activity. In other embodiments, the sensor comprises an accelerometer for sensing heart contraction, diaphragm motion, bodily inclination, or walking pace. [0017] Certain embodiments comprise a pump for circulating fluid comprising: a pumping chamber; a pump inlet in fluid communication with the pumping chamber; a pump outlet in fluid communication with the pumping chamber; a drive piston disposed within the pumping chamber; and a hollow valve sleeve configured to recess into the pump outlet. [0018] Other embodiments comprise: a pumping chamber forming a loop; a pump inlet in fluid communication with the pumping chamber; a pump outlet in fluid communication with the pumping chamber; a piston disposed within the pumping chamber; an electric motor comprising a rotor coupled to a shaft; a magnet coupled to an end of the shaft; a sensor proximal to the magnet; and a control system, wherein: the electric motor is magnetically coupled to the piston; the magnet produces a magnetic vector that rotates with the rotor; the sensor is configured sense the magnetic vector; and the control system is configured to determine the angular position of the rotor. In certain embodiments, the sensor is a 2-axis Hall effect sensor and the electric motor is an axial flux motor. In certain embodiments, the control system is configured to access a lookup table. [0019] Certain embodiments comprise a pumping chamber comprising an inner surface forming a loop; a pump inlet in fluid communication with the pumping chamber; a pump outlet in fluid communication with the pumping chamber; a first piston disposed within the pumping chamber; and a series of electromagnets disposed around the pumping chamber, wherein: the series of electromagnets are configured to move the first piston around the pumping chamber; and the first piston comprises a hydrodynamic bearing surface configured to repel the first piston away from the inner surface as the first piston moves within the pumping chamber. Certain embodiments further comprise a second piston disposed within the pumping chamber, wherein: the series of electromagnets are configured to move the second piston around the pumping chamber; and the second piston comprises a hydrodynamic bearing surface configured to repel the second piston away from the inner surface as the second piston moves within the pumping chamber. Certain embodiments further comprise a pinch valve between the pump inlet and pump outlet. [0020] As used herein, the terms "a" and "an" are defined as one or more unless this disclosure explicitly requires otherwise. [0021] The term "substantially" and its variations are defined as being largely but not necessarily wholly what is specified as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term "substantially" refers to ranges within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5% of what is specified. 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