US3192863A - Blood pump - Google Patents

Description

July 6, 1965 v VADOT 3, 92,8 3

, BLOOD PUMP Filed March 14, 1962 '2 Sheets-Sheet 1 I '1 l. BLOOD OUT 1 '1 t nh 9 INVENTOR. LOU/3 VADOT ATTORNEY-S July 6, 1965 Filed March 14, 1962 L. VADOT BLOOD PUMP Tia-5b.

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INVENTOR. A 00/5 VADOT HTTOEA/EKS United States Patent 3,192,863 BLGUD PUMP Louis Vadot, Grenoble, Isere, France, assiguor to Societe Grenohloise dEtudes et dApplicafions Hydrauliques, Grenoble, France, a corporation of France Filed M 14, E62, Ser. No. 'l7,628 Claims prioifit application France, Mar. 17, 1961, 45%, Patent 1,291,725 5 Claims. (Cl. 103-149) This invention relates to a pump for use astan artificial heart or blood pump in certain branches of surgery, such as hypothermia.

The type of pump usually employed for the indicated purposes are known as roller-and-flexible tube pumps because the blood is advanced through an arc-shaped flexible tube by means of one or more rollers rotating about an axis common to that of the arcuate tube. An advantage of'this type of pump is its simple design which does not include any valves. Furthermore, its operation is almost entirely volumetric, so that the rate of flow of the blood can readily be determined by measuring the rotational speed of the rollers thereof. This pump however, as conventionally constructed, is not strictly volumetric because the tube thereof is not completely sealed when flattened by the rotating roller or rollers. In the conventional pump, the flexible tube has a circular crosssection and when flattened by a roller passing therealong tends to assume a shape which in cross-section approxi mates a flattened out figure eight. Thus, while the major parts of the inner walls of the flattened out portion of the tube are in contact, there are left openings at the ends of such portion through which leakage can occur. produces the further disadvantage that the blood spurting through these leakage openings causes an undesirable turbulence which can ive rise to hemolysis of the blood.

It has been found that while such a pump could be This made to seal oif completely-by increasing the bearing pressure of the roller on the flexible tube, the degree of would likely be such as to cause hemolysis of the blood.

Further, any roller bearing pressure capable of accom-.

plishing such sealing action would also produce fairly high stresses in the sides of the tube during the flattening process and as such stresses are alternating stresses they may eventually cause the tube to crack and then burst. Furthermore, the rollers of such conventional pumps are usually attached to a rotating central portion and no means are provided for adjusting the bearing pressure thereof. Therefore, While the rollers may be mounted in the pump to provide a given bearing pressure on the flexible tube, because of the rigidity of such mounting any variations in the thickness of the walls of the tube would cause variations in the pressure applied by such rollers to the blood through such tube. It has been found that considerable pressure variations likely to cause hemolysis of the blood, may result in this fashion from unavoidable small variations in the thickness of the tube.

It is the purpose of the instant invention to provide a roller-and-flexible tube pump for use as an artificial heart or blood pump in certain surgical operations, and of such improved construction that it will be freefof the aforesaid disadvantages of conventional pumps of the indicated type. j

In accordance with the invention there is provided in the improved pump a flexible tube of such a form that in cross-section it has a flattish shape which is approximately defined by two opposite and intersecting circular arcs, the common chord of which is parallel tothe pump roller center line. With a tube of this particular shape, all symmetrically opposite points on the inside surfaces of the two walls threof whose sides are defined by the junc occlusive so that its rate of flowcan be calculated ac curately from the rotational'speed of the rollers thereof. Further, such tube. design enables the tube to be completely flattened at a substantially lower. bearing pressure than is possible with the conventional tubing and without any risk of blood hemolysis. As such lower pressures the sides of the tube are subjected to very low strains so that risks of failureof the tube by cracking and bursting are practically eliminated.

. A furtheradvantage resulting from the improved shapeof the tube is that such shape gives the tube a certain amount of elasticity during the. pressure buildup and delivery. This elasticity shows up as pulsations bearing a a certain similarity to the systolic action ofthe human heart (one systole for each roller passage) and facilitating the stimulation of normal physiological conditions.

' The tubehas projecting outwardly. from the central portion of 'one of such waHs, a fin or projection configured to fit a correspondingly shaped groove in the pump body, and cooperating with the latter tomaintain the tube correctly positioned hard against the rolling face.

of the pump body for the entire length of the loop formed by such tube, and to prevent the tube from creeping in the direction of rotationof the rol-lerassembly.

In accordance with the invention also, the rollers and roller spindles are fitted with a self aligning bearing system, and the roller spindles are mounted on a variable tension system, to ensure that the rollers will exert a predetermined, practically constant, bearing pressure on the tube irrespective of any longitudinal or lateral variation in the thickness of the tube. There is thus eliminated the danger of blood hemol sis which mi ht otherwise occur n1 1 a a .11 the bearing pressure were to exceed a certain value as m the use of rigidly mounted rollers suchas are provided with conventional pumps of the indicated type. In the operation of thisimproved system, the self aligning roller bearing mounting ensures that any transverse tube thickness variations are absorbed Without undesirable effects, while the variable tension spring carriers absorb any minor longitudinal variations in the tube thickness witl1- FIGS. 2a, 2b "and 2c are detailed cross-sections, on an enlarged scale, of the type of circular flexible tube which is used in conventional pumps, and illustrating, respectively, its normal shape, the shape it assumes as it is being flattened, and its fully flattened shape;

FIGS. 3a, 3b and 3c are detailed cross-sections, on an enlarged scale, of a tube embodying this invention, and illustrating, respectively, its normal shape, the shape it assumes as it is being flattened, and its fully flattened shape; and

FIG. 4 is a detailed cross-sectional view, on an enlarged scale, of one of the rollers in the pump shown in FIG. 1.

Referring to FIG. 1 of the drawings, the reference numeral 1 generally indicates the body of the roller-andflexible tube pump on which is provided a combined mounting and guide 2 for the flexible tube 3. The guide 2 is configured to hold the tube 3 in a substantially U- shaped form with the two legs 3, 3' thereof in substantially vertical parallelism. The upper ends of the tube legs 3', 3' are provided with suitable unions 12, 13 supported by a cross bar 30 mounted on the body 1 of the pump. In the operation of the pump, blood enters the same at the tube end provided with the union 12 and is discharged through the union 13 at the other end of the tube. The tube 3 is provided on the convex side of the central arcuate section thereof with a longitudinal fin or projection 9 that extends throughout the length of such arcuate section and is seated in a corresponding groove 2 provided in the guide 2. The fin 9 is wholly received within the groove 2 so that the outer wall 8 of the tube 3 is positioned in tight engagement with the inner concave edge or rolling face of the guide 2. The fin 9 may be positively secured in position in the groove 2' against any possibility of creepage therein by means of lock bolts 31.

The inner wall 8 of the tube 3 is engaged by two rollers 4, 4' mounted for rotational movement about an axis located at the center of the arc defined by the central arcuate section of the tube. The rollers 4, 4' rotate in the direction of the arrow f and as they travel along such inner wall 8' they progressively compress and flatten the walls 8, 8' one against the other to cause the blood to flow in the direction of the arrows f1.

As has been indicated, the tube usually employed in the conventional roller-and-flexible tube blood pump has a circular wall, in cross-section, as is illustrated by the circular tubing 5 shown in FIG. 2a of the drawings. When such a tube is compressed by a roller 4 passing over it, each transverse portion thereof as the roller approaches the same tends to assume the shape of a figure 8 as is shown in FIG. 2b of the drawings. When the roller comes into contact with such transverse hose por tion, the opposite sides of the latter are flattened one against the other to close the body of the 8, but the folds in the lateral ends thereof maintain the ends of the 8 open to some extent and there remain two lateral leakage openings 6, 6 through which the blood may leak, as is shown in FIG.2c.

By way of contrast, the corresponding FIGS. 3a, 3b and 3c illustrate the normal form and manner of operation of the tube of this invention. It will be noted in FIG. 3a, that in the normal condition of the tube 3, it has in cross-section, a flattish shape resembling the section of a fruit pit. The outer wall 8 and the inner wall 8' of the tube generally have a somewhat similar shape whose sectional configuration may be approximately defined by two opposite and intersecting circular arcs having a common chord 10 which is parallel to the centerline 10' in FIGS-1 and 4 of the pump roller. The longitudinal edge portions of the walls 8, 8' adjacent to their junctures thereof are disposed at an acute angle to each other and said junctures thereof form the longitudinal side edges 7, 7 of the tube 3. It will be further observed in FIG. 3a, that except for the area provided with the fin 9, thetube 3 has substantially the same thickness through- 4 out its circumference and therefore possesses the advantages inherent with a tube wall of uniform thickness.

FIGS. 3b and 30 show how the cross-sectional area of a transverse portion of the tube 3 will be varied by a roller. As the roller approaches such transverse portion, the walls of the latter become flattened in such manner that all points symmetrically opposite in substantially the entire areas of the inner surfaces of such walls, such as the points designated d, e on the inner surfaces of walls 8, 8', respectively, will move toward each other as indicated in FIG. 312. When the roller engages such. transverse portion and entirely flattens the same against the inner rolling face of the guide 2, all of such symmetrically opposite points across the transverse Width of such inner wall surfaces will meet and the tube will be completely closed throughout the entire extent 11-11 thereof and no lateral leakage openings will remain. As in such flattening of the tube very little strain occurs in the vicinity of the side edges 7, 7 thereof, due to the uniform thickness of the tube, its configuration and the reduced pressure needed to obtain a complete closing thereof, there is little risk of failure of the tube due to cracking or bursting along its side edges 7, 7.

The rollers 4, 4' are mounted on a self-aligning bearing and adjustable tension spring lever assembly comprising two arms 16, 16 forming part of the pump drive shaft 17 whose rotational axis is located at the center of the arc defined by the central arcuate section of the tube 3. Fixed to the outer ends of the arms 16, 16 are spindles 15, 15', respectively, on which are mounted for free pivotal movement the arms 14, 14', respectively, on the outer ends of the latter of which are provided the rollers 4, 4', respectively. The inner ends 19, 19' of the arms 14, 14', respectively, are connected together by an elastic link located between the spindles 15, 15' and comprising a spring 18 connected at one end to the inner arm end 19 by an enclosing thrust collar 20 forming part of arm 14 and a securing member 21 screwed into such spring end. The other end of spring 18 is enclosed by a movable collar 20' adjustably mounted on an adjusting screw 21 extending through the inner arm end 19' and into such other end of the spring. By manually turning the head of the adjusting screw 21', the position of collar 20' can be adjusted relative to the roller arm 14' to adjust the tension of spring 18.and thereby to adjust the bearing pressure exerted by the rollers 4, 4' on the flexible tube 3 to any given value. The screw 21' can be locked in its adjusted position by means of a set screw 22 threaded into the inner arm end 19' and engaging such adjusting screw. With the parts so set, the bearing pressure of the rollers 4, 4 on the tube 3 will remain practically constant, as the spring 18 will absorb any minor variations in the tube thickness as the rollers move longitudinally thereover.

To avoid any possibility of an interruption in a surgical operation due to a failure of spring 18 to perform its functions in the pump, the roller assembly includes adjustable stops 23, 23'.mounted in diametrically opposed and spaced relation on the drive shaft 17 and engaging in coactive relation with the inner ends 19 and 19', respectivcly, of the roller arms 14, 14, respectively. The construction of the steps 23, 23 is such that normally it permits the spring assembly to absorb any minor variations in the tube thickness within a given range without interference with the functioning of such spring assembly. However, should there occur a failure of the spring, the stops 23, 23' Will coact directly with the arms 14, 14, respectively, to enable the pump to still run, though under less satisfactory conditions, for then the rollers will function in the manner of rigidly mounted rollers and without the flexibleness imparted by the spring assembly,

It will be noted also that this coaction of the stops 23, 23 and the arms 14, 14, respectively, will also function to prevent major variations of the spring assembly beyond said given range andin this respect the former will control the operation of the latter.

Each of the rollers 4, 4' is mounted on its associated spindle 24 by means of a known type of self-aligning bearing 25 constructed to enable the roller to absorb transverse variations in the tube thickness without undesirable effects on the blood in the tube 3. As is shown in FIG. 4 of the drawings, the bearing 25 of each roller is en closed within the roller by means of bearing seals 26, 26 of known construction.

While there has been hereinabove described and illustrated in the drawings, a preferred embodiment of the invention, it will be understood that changes therein may be made without departing from the spirit of the invention. Thus, for example, the flexible tube may be constructed so that the outer and inner walls may be given any suitable form of convexity to provide, in section, any desired fiattish shape with acute angles defined by the side edge portions of such walls. It is accordingly understood that it is intended to cover all forms of the invention coming within the scope of the appended claims.

What is claimed is:

1. A blood pump comprising a pump body having a 7 horizontal central axis, a U-shaped guide seat mounted on said body with the arc-shaped central portion thereof disposed below and centered about said central axis, a flexible'resilient U-shaped tube seated on said, guide seat and having its ends extending upwardly on opposite sides of said central axis, means on the upper portion of said pump body for supporting the ends of said tube, a plurality of pressure rollers mounted on said body with their axes in spaced parallel relation to said central axis for rotational movement about the latter and in engagement with the arc-shaped central portion of said tube, means supporting said pressure rollers for movement as a whole about pivotal points offset from lines connecting said roller axes with said central axis, and means for resiliently biasing each pressure roller into contact with said tube with a given, substantially constant bearing pressure, said tube having a flattish, convexo-convex shape and including an outer wall seated on said guide seat and an inner wall engaged by said pressure rollers, said flattish walls being substantially uniform in thickness throughout their widths, being oppositely convex and meeting at their side edges in acute angles, said tube along the longitudinal lines of juncture of the walls thereof being of substantially the same thickness as in the walls thereof and having in cross-section a transverse axis parallel to said central am's and substantially greater in length than its conjugate axis and such that all symmetrically opposite portions of the walls thereof come into contact when the tube is flattened by a roller to completely close the tube without leaving any lateral openings, the outer wall of said tube having a central longitudinally extending integral fin of substantial cross-sectional area for securing said tube to said guide seat, and the inner wall of said tube being smooth to enable the rollers to uniformly contact the same throughout its width.

2. A blood pump comprising a pump body having a horizontal central axis, a U-shaped guide seat mounted on said body with the arc-shaped central portion thereof disposed below and centered about said central axis, a flexible resilient U-shaped tube seated on said guide seat and having its ends extending upwardly on opposite sides of said central axis, means on the upper portion of said pump body for supporting the ends of said tube, a plurality of pressure rollers mounted on said body with their axes in spaced parallel relation to said central axis for rotational movement about the latter and in engagement with the arc-shaped central portion of said tube, said tube having an outer wall seated on said guide seat and an inner Wall engaged by said pressure rollers, said walls being oppositely convex and meeting at their side edges in acute angles, said tube along the longitudinal'lines of juncture of the walls thereof being of substantially the same thickness as in the walls thereof and having in crosssection a transverse axis parallel to said central axis and substantially greater in length than its conjugate axis and 1 such that all symmetrically opposite portions of the walls thereof come into contact when the tube is flattened by a roller to completely close the tube without leaving any lateral openings, the outer wall of said tube having, a central longitudinally extending integral fin of substantial cross-sectional area for securing said tube to said guide seat, and the inner wall of said tube being smooth to enable the rollers to uniformly contact the same throughout its width, and means for causing said rollers to exert a predetermined, practically constant, bearing pressure on said tube irrespective of any variation in thethickness of the walls thereof, said last mentioned means comprising a spindle rotatably supporting each roller, and a self-' aligning bearing between said roller and said spindle, and enabling said roller to vary its inclination relative to said spindle as it travels over said tube due to transverse'tuoe thickness variations without substantial variation in the pressure of the roller on the blood.

3. A blood pump comprising a pump body having a horizontal central axis, a U-shaped guide seat mounted on said body with the arc-shaped central portion thereof disposed below and centered about said central axis, a flexible resilient U-shaped tube seated on said guide seat and having its ends extending upwardly on opposite sides of said central axis, means on the upper portion of said pump body for supporting the ends of said tube, a plurality of pressure rollers mounted on said body with their axes in spaced parallel relation to said central axis for rotational movement about the latter and in engagement with the arc-shaped central portion of said tube, said tube having an outer wall seated on said guide seat and an inner wall engaged by said pressure rollers,said walls being oppositely convex and meeting at their side edges in acute angles, said tube along the longitudinal lines of juncture of the walls thereof being of substantially the same thickness as in the walls thereof and having in crosssection a transverse axis parallel to said central axis and substantially greater in length than its conjugate axis and such that all symmetrically opposite portions of the walls thereof come into contact when the tube is flattened by a roller to completely close the tube without leaving any lateral openings, the outer wall of said tube having 'a central longitudinally extending integral fin of substantial cross-sectional area for securing said tube to said guide a movable supporting member for each roller, variable tension spring means connecting said movable supporting members so as to cause all of said rollers to bear against said tube with the same yieldable pressure and to enable said spring means to absorb variations in the tube thickness as the rollers travel along said tube, and means for selectively varying the tension in said spring means to cause said rollers to bear on the tube with a given substantially constant pressure such as will prevent hemolysis' other end of said spring to the other of said supporting members and operable to vary the positionof said other spring end relative to said other supporting member.

5. A blood pump such as defined in claim 4,'includ 314,851 3/85 Kelly 103--149- ing stop means carried by said shaft and connected to 2,249,806 7/41 BOgOSIOWSKY 1 -1 said supporting members so as to limit pivotal movement 2,406,485 8/46 Arnold 103-149 of said supporting members to a given range and to pro- 2,693,766 11/54 Seyler 103-149 vide an auxiliary means for fixing the position of said 5 2,898,864 8/59 Japolsky 103-149 rollers relative to said flexible tube. 2,917,002 12/59 Mascaro 1O3149 References Cited by the Examiner LAURENCE V. EFNER, Primary Examiner.

UNITED STATES PATENTS WARREN E. COLEMAN, Examiner.

87,837 3/69 Gilmore 103-149X

Claims (1)

1. A BLOOD PUMP COMPRISING A PUMP BODY HAVING A HORIZONTAL CENTRAL AXIS, A U-SHAPED GUIDE SEAT MOUNTED ON SAID BAODY WITH THE ARC-SHAPED CENTRAL PORTION THEREOF DISPOSED BELOW AND CENTERED ABOUT SAID CENTRAL AXIS, A FLEXIBLE RESILIENT U-SHAPED TUBE SEATED ON SAID GUIDE SEAT AND HAVING ITS ENDS EXTENDING UPWARDLY ON OPPOSITE SIDES OF SAID CENTRAL AXIS, MEANS ON THE UPPER PORTION OF SAID PUMP BODY FOR SUPPORTING THE ENDS OF SAID TUBE, A PLURALITY OF PRESSURE ROLLERS MOUNTED ON SAID BODY WITH THEIR AXES IN SPACED PARALLEL RELATION TO SAID TUBE, MEANS ROTATIONAL MOVEMENT ABOUT THE LATTER AND IN ENGAGEMENT WITH THE ARC-SHAPED CENTRAL PORTION OF SAID TUBE, MEANS SUPPORTING SAID PRESSURE ROLLERS FOR MOVEMENT AS A WHOLE ABOUT PIVOTAL POINTS OFFSET FROM LINES CONNECTING SAID ROLLERS AXES WITH SAID CENTRAL AXIS, AND MEANS SAID TUBE BIASING EACH PRESSURE ROLLER INTO CONTACT WITH SAID TUBE WITH A GIVEN, SUBSTANTIALLY CONSTANT BEARING PRESSURE, SAID TUBE HAVING A FLATTISH, CONVEXO-CONVEX SHAPE AND INCLUDING AN OUTER WALL SEATED ON SAID GUIDE SEAT AND AN INNER WALL ENGAGED BY SAID PRESSURE ROLLERS, SAID FLATTISH WALLS BEING SUBSTANTIALLY UNIFORM IN THICKNESS THROUGHOUT THEIR WIDTHS, BEING OPPOSITELY CONVEX AND MEETING AT THEIR SIDE EDGES IN ACUTE ANGLES, SAID TUBE ALONG THE LONGITUDINAL LINES OF JUNCTURE OF THE WALLS THEREOF BEING OF SUBSTANTIALLY THE SAME THICKNESS AS IN THE WALLS THEREOF AND HAVING IN CROSS-SECTION A TRANSVERSE AXIS PARALLEL TO SAID CENTRAL AXIS AND SUBSTANTIALLY GREATER IN LENGTH THAN ITS CONJUGATE AXIS AND SUCH THAT ALL SYMMETRICALLY OPPOSITE PORTIONS OF THE WALLS THEREOF COME INTO CONTACT WHEN THE TUBE IS FLATTENED BY A ROLLER TO COMPLETELY CLOSE THE TUBE WITHOUT LEAVING ANY LATERAL OPENINGS, THE OUTER WALL OF SAID TUBE HAVING A CENTRAL LONGITUDINALLY EXTENDING INTEGRAL FIN OF SUBSTANTIAL CORSS-SECTIONAL AREA FOR SECURING SAID TUBE TO SAID GUIDE SEAT, AND THE INNER WALL OF SAID TUBE BEING SMOOTH TO ENABLE THE ROLLERS TO UNIFORMLY CONTACT THE SAME THROUGHOUT ITS WIDTH.

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