Centrifugal pump for liquids, in particular for blood in extracorporeal circulation

Abstract: In a centrifugal pump for liquids, in particular for blood in extracorporeal circulation, characterized in that it comprises a containment body (1) for an impeller (2) having the shape of a disk and comprising magnets inside it and having, on both faces, blades (2b) adapted for making contact with the liquid; the containment body (1) has at least one liquid inflow connection (3), which is connected to ducts for conveying the liquid proximate to the center of the impeller (2) on both sides thereof, and at least one liquid outflow connection (4); the containment body (1) is shaped so that it can be removably inserted in a seat defined in a fixed base within which there is at least one magnet arranged so as to face the seat and being connected to means adapted for rotating it so as to rotationally entrain the impeller (2).

Description: The invention relates to centrifugal pump for liquids, in particular for blood in extracorporeal circulation as defined in the preamble of the appended claim 1 and as seen in DE-B-1 063 035. It is known that in extracorporeal blood circuits shunted from a patient, particularly during certain operations, circulation is ensured by a pump which is inserted in the circuit, and the known art essentially provides two types of pump: peristaltic pumps and centrifugal pumps. Centrifugal pumps essentially comprise a body for the containment of an impeller whereto a magnet is rigidly associated; said magnet is adapted for being rotated, thus rotationally entraining said impeller, by a second rotating magnet contained in a fixed base provided with a seat for the accommodation of said impeller containment body; said centrifugal pumps have considerable functional advantages with respect to peristaltic pumps, in particular as regards safety against high increases in pressure at the outlet end and as regards the possibility of sending air to the patient. The constructive forms of centrifugal pumps present in the known art, however, are not devoid from disadvantageous characteristics, the first whereof is related to fluid mechanics: the presence of regions in which the blood is stagnant occurs in known pumps, with negative consequences from the point of view of the flow conveyed by the pump and from a strictly medical point of view. A second disadvantageous characteristic in known centrifugal pumps is furthermore constituted by the presence of sealing gaskets which are adapted for preventing the access of blood to a chamber in which the magnet rigidly associated with the impeller is present; said sealing gaskets, which notoriously constitute a delicate element which is often the source of malfunctions, are arranged in a region in which the flow of liquid is not particularly active, and are therefore in bad functional conditions due to the overheating to which they are subjected. In known centrifugal pumps, the sterilization operation also has problems, since it is necessary to resort to the adoption of sophisticated sealing gaskets in the method which uses a sterilization gas when one wishes to avoid resorting to the method which uses gamma rays, which compels to select special materials. The aim of the present invention is, therefore, to provide a centrifugal pump for liquids, in particular for blood in extracorporeal circulation, having optimum characteristics from the fluid mechanics point of view and wherein all problems related to liquid tightness are eliminated. Within the scope of the above described aim, an object of the invention is to provide a centrifugal pump suitable for any sterilization treatment without having to resort to particular contrivances. The aim is achieved by a centrifugal pump for liquids, in particular for blood in extracorporeal circulation, according to the invention, as defined in the appended claim 1. The body for containment of the impeller of the pump may be shaped so that it can be removably inserted in a seat defined in a fixed base within which there is at least one magnet, facing said seat and being connected to means adapted for rotating it, so as to rotationally entrain said impeller. Further characteristics and advantages will become apparent from the description of two preferred, but not exclusive, embodiments of the invention, illustrated only by way of non-limitative example in the accompanying drawings. Figure 1 is a view of the impeller containment body; figure 2 is a sectional view taken along the plane II-II of figure 1; figure 3 is a sectional view taken along the plane III-III of figure 1; figure 4 is an enlarged-scale view of the cross-section shown in figure 3; figure 5 is an exploded view of the elements which compose the pump; figure 6 is a view of the pump with an indication of the flow of the liquid inside it; figure 7 is a sectional view of the pump inserted in the fixed base; and figure 8 is a sectional view of the pump according to a further embodiment. With reference to figures 1 to 7, the reference numeral 1 generally indicates the containment body for the impeller 2, said body has a substantially cylindrical shape with substantially planar bases, a liquid inflow connection 3 and a liquid outflow connection 4 arranged substantially tangent to the lateral surface. According to an important characteristic of the invention, the impeller 2 has the shape of a disk which comprises magnets 2a within itself and is provided, on both faces, with blades 2b intended to make contact with the liquid which is conveyed proximate to the center of said impeller 2 on both sides thereof by means of ducts connected to the inflow connection 3 and defined by virtue of the particular configuration of the body 1, which is now described in detail. First, however, for completing the description of the impeller 2, it is to be noted that it has, at its axis of rotation, the pivot 2c which is monolithically associated therewith and is supported, at its ends, by the bushes 5a and 5b inserted within the body 1. Returning to the detailed description of the body 1, which comprises the two cambered (curved baffels) elements 6 and 7, open at the center at 6a and 7a, have mating perimetric edges 6b and 7b and being rigidly associated for example by ultrasonic welding in the illustrated embodiment, which uses polycarbonate material; said elements 6 and 7 delimit a portion of space in which the impeller 2 is accommodated. The body 1 furthermore comprises the covers 8 and 9 which are rigidly associated with the cambered elements 6 and 7 at the edge and are shaped so as to delimit, together with said elements, two lenticular portions (convex on both sides) of space 10 and 11 which are open toward the portion of space (at the center of the inside of the body) containing the impeller 2 at 6a and 7a and are suitable, as will shortly become apparent, for constituting ducts for the conveyance of the liquid to the impeller. The reference numeral 12 furthermore indicates a first opening located at a portion of the mating edges 6b, 7b of the cambered elements 6 and 7 without interrupting, as is evident from figure 4, the continuity of the mating of said edges; said opening 12 is thus adapted for connecting the lenticular portions of space 10 and 11 to the inflow connection 2, arranged so as to face said opening 12. The reference numeral 13 furthermore indicates a second opening also located at a portion of the mating edges 6b, 7b but, unlike the first opening, interrupts the continuity of the mating between said edges, and thus the portion of space which accommodates the impeller 2 is connected to the outflow connection 4 arranged so as to face said opening 13. The circulation of the liquid produced inside the pump is clearly shown in figure 6. After entering from the connection 3 as indicated by the arrow A, the liquid flows through the first opening 12 where it is divided as indicated by the arrows labelled B and enters the lenticular portions of space 10 and 11 adjacent to the portion of space containing the impeller 2; the arrow C indicates the flow of liquid entering the lenticular portion of space 10. The entry of the portion of lenticular space 11 would be identical but cannot be seen in figure 6 as it is below the impeller 2. Flowing through the lenticular portions of space 10 and 11, the liquid arrives above and below the impeller 2 at and passes through the openings 6a and 7a respectively, as indicated by the arrows D and E, respectively. The flow makes contact with the blades 2b of impeller 2 and then is driven by centrifugal force to enter, as indicated by the arrow F, the opening 13 leading to the outflow connection 4, wherefrom outflow occurs as indicated by the arrow G. The described type of circulation is optimum to resist the formation of blood thrombin because there are no regions in which an even minimal stagnation of liquid occurs and also because the contacts of the pivot 2c of the impeller with the respective bushes 5a and 5b are included in an active flow of liquid which ensures their constant cooling and their operation in particularly advantageous conditions. The body 1, according to what is illustrated in figure 7, is shaped so that it can be removably inserted in a seat defined in a fixed base 14 within which the two magnets 15 and 16 are present; said magnets are inserted in the magnet-holder disks 15a and 16a which rotate synchronously and are arranged so as to face on opposite sides the seat of the body 1 for the containment of the impeller 2 and are therefore such as to rotationally entrain said impeller in an axially balanced manner by acting on the magnets 2a comprised within said impeller. The magnet-holder disk 16a is rotated by being keyed directly on the output shaft 17a of the motor 17 supported by the base 14 by means of the bearing 17b, and motion is transmitted synchronously from said disk to the magnet-holder disk 15a by means of a kinematic train which comprises toothed belts 18 and 19 operating in combination with the wheels 20 and 21 and keyed on the transmission shaft 22 supported by the bearings 22a and 22b. The reference numeral 15b finally indicates the bearings supporting the magnet-holder disk 15a. In the described embodiment of the invention there are no sealing gaskets, and therefore problems cannot arise from gasket failures or leaks. Operating conditions are also optimum in the embodiment shown in figure 8, which provides the presence of gaskets. In figure 8, there are containment body 1 and impeller 2 which has magnets 2a and blades 2b. Inflow connection 3, cambered elements 6 and 7 function with the openings 12 and 13 and are a part of covers 8 and 9. In this embodiment the impeller 2 rotates upon and about a rolling bearing 23 about a fixed axis, one half of which is formed by the tab 24a extending as part of cover 8, the other half being formed by the tab 24b extending as part of cover 9. Sealing gaskets 25 and 26 are arranged so as to protect the bearing 23. The sealing gaskets are in a region in which the flow of the liquid is active and therefore are, as previously mentioned, in the best locations to function and thereby prevent stagnated flow. The described invention provides a pump with excellent flow characteristics to eliminate seizure due to blood clotting and thrombin problems which occur in known pumps. It is important to note that the inside of the pump of this invention is easily accessible for sterilization by gas or by gamma rays. The pump operates simply. The described invention is susceptible to numerous modifications and variations, all of which are within the scope of the independent claim 1. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: A centrifugal pump for liquids such as blood for the extracorporeal circulation thereof comprising: a body (1) for the centrifugal pump to contain parts thereof for the operation therein and the passage therethrough of liquids in an inside thereof; an impeller (2) carried within the inside of the body (1) and movable therein about a center of the impeller (2), the impeller (2) having a pair of opposed sides and carrying magnets (2a) therein; inflow connection means (3) on the body (1) to receive liquid and permit flow into the inside of the body (1); outflow connection means (4) on the body (1) to receive liquid from the impeller (2) and permit flow out of the inside of the body (1); and baffel means (6,7) within the inside of the body (1) located for directing the flow of liquid to pass through the inflow connection means (3), the baffel means (6,7) shaped to direct the flow toward the centers of the opposed sides of the impeller, the baffel means internally configured to thereafter maintain the centrifugal flow of liquid radial from each center, and into the outflow connection means (4); characterized in that said impeller has a disk shape in which the major surfaces of the disk are said pair of opposed sides; the pump further comprising a plurality of blades (2b) on the impeller and extending from the surfaces of the disk in opposite directions, the blades (2b) set to make contact with the liquid for directing the passage of the liquid radially along the impeller (2) from its center and through the inside of the body (1); said plurality of blades (2b) extending on the impeller substantially below the extension of the baffel means (6,7), thereby to define an open center (6a,7a) in the pump through which the blood flows. Centrifugal pump according to claim 1, characterized in that a nonmovable base (14) has seating means shaped to removably receive and hold the body (1) in position therewithin, and rotating magnet means (15,15a; 16,16a) in the seating means, the rotating magnet means (15,15a;16,16a) facing the body (1) to rotationally drive the impeller (2). Centrifugal pump according to claim 1, characterized in that the impeller (2) has a pivot shaft (23) affixed thereto through the center thereof and along an axis of rotation, the pivot shaft (2c) having opposite ends supported by bushings (5a,5b) carried by and inserted within the inside body (1), the bushings (5a,5b) being aligned along the axis for receiving the opposite ends of the pivot shaft (2c). Centrifugal pump according to claim 1, characterized in that the impeller (2) is supported upon a bearing (23) located in the center thereof, the impeller (2) rotatable about a pivot shaft (24a,24b) having opposite ends fixed and rigidly associated within the inside of the body (1), the impeller (2) being carried to rotate about an axis of rotation estabilished by the pivot shaft (24a,24b) within the inside of the body (1). Centrifugal pump according to claim 4, characterized in that the impeller bearing (23) includes rollers protected from contact with liquid flow through the inside of the body (1) by a pair of sealing gasket (25,26) positioned at the center of the impeller (2) on each side thereof. Centrifugal pump according to claim 1, characterized in that the impeller body (1) has opposed covers (8,9), each of substantially cylindrical and generally planar shape and a lateral surface thereabout and in that the inflow and outflow connections means (3,4) are arranged substantially tangent to the lateral surface. Centrifugal pump according to claim 6, characterized in that lenticular spaces are formed between the baffel means (6,7) and the covers (8,9), the lenticular spaces are in fluid communication with the centers on the opposite sides of the impeller (2), the lenticular spaces connect to the liquid connection inflow means to allow flow of liquid to the centers of the impeller (2), the centers of the impeller (2) are in fluid communication with the liquid outflow connection means (3,4). Centrifugal pump according to claim 1, characterized in that the body (1) has two covers (8,9) including cambered elements (6,7) extending radially inwardly and open at the center, each cover (8,9) having rigid edges about its perimeter and the perimeter of its cambered element, the edges are shaped to mate with each other, the cambered elements (6,7) being shaped for minimizing the space available inside the body (1) to accommodate the impeller (2); a first opening (12) located at a portion of the mating edges of the cambered elements (6,7), the first opening (12) shaped not to interrupt the continuity of the mating edges of the cambered elements (6,7), the first opening (12) connecting the lenticular spaces to the inflow connection means (3); a second opening (13) at another portion of the mating edges of the cambered elements (6,7), the second opening (13) shaped so as not to interrupt the continuity of the mating edges, the second opening (13) connecting space available inside the body (1) to accommodate the impeller (2) to the outflow connection means (4). Centrifugal pump according to claim 1, characterized in that the nonmovable base (14) includes two magnets (15,15a;16,16a) which rotate synchronously and are positioned in opposed facing relation; a seat adapted for accommodating the impeller body (1) so that it is removably received therewithin. Centrifugal pump according to claim 9, characterized in that the magnets (15,16) held within magnet-holder disks (15a,16a) are connected for ensuring synchronous motion to a drive (18,19,20,21) and a motor (17). Centrifugal pump according to claim 10, characterized in that the drive (18,19,20,21) for the magnet-holder disks (15a,16a) are kinematically connected with an identical transmission ratio by a transmission shaft (22) by means of toothed belts (18,19).

Inventors: GHELLI NICOLA, PANZANI IVO, VESCOVINI PIETRO, GHELLI, NICOLA, PANZANI, IVO, VESCOVINI, PIETRO
Applicants: DIDECO SPA, DIDECO S.P.A.
Application year: 1991
Main classification: A61M1
IPC codes: A61M1, F04D29, F04D13