EP0026704A1 - Peristaltic pump - Google Patents

Abstract

1. Peristaltic pump comprising a casing (1) constructed in two sections with a detachable cover (2) ; a rotor (11) providing a support for rollers (15) and rotatably mounted on the shaft (12) of the casing (1) which is perpendicular to the cover, rollers (15) which have a conical surface centered on the shaft (12) of the casing ; resilient means for applying said rollers (15) against one wall of the cover (2) when this latter is in the closed position, a tube (24) being flattened against a stationary supporting track at least to a partial extent by said rollers (15), said pump being characterized in that the rollers (15) are applied against the edges of a channel (27) for receiving the tube (24), the channel being of variable depth and having a bottom wall which constitutes said supporting track ; that this channel (27) for receiving the tube (24) is formed in the detachable cover (2) and that said channel has a first upstream segment (E-A) in which its depth decreases progressively, an intermediate delivery segment in which its depth remains constant and sufficiently small to ensure that the tube (24) is completely closed locally by flattening when a roller (15) passes, at all points over a length of this channel which corresponds at least to the distance between two successive rollers, the depth of said channel (27) being such as to increase progressively and continuously along a downstream segment (B-C) until it attains the thickness of the tube when no roller pressure is applied.

Description

The invention relates to positive displacement pumps, and more precisely to liquid pumps which are said to be peristaltic, such as those used in medicine, for conveying blood or other liquids administered by infusion.

The peculiarity of peristaltic pumps lies in the use of a deformable tube leading the liquid between the inlet and the outlet of the pump and in that of rollers or other organs which make it possible to locally clamp the tube from the outside, in points that are made to move repeatedly, always in the same direction along the tube, from the inlet to the outlet.

The invention aims to increase the qualities and performances of these pumps, and especially those which are used to advantage in their use as infusion pumps. It aims in particular to facilitate the positioning of the tube in the pump housing to allow a rapid change of this tube between two infusions, to avoid subjecting the transported liquid to forces such that they could for example cause hemolysis in the case of blood, to improve the operating conditions and to extend the possibilities of application.

The pump according to the invention comprises a housing made in two parts, with a removable cover, a roller support rotor mounted to rotate on an axis of the housing perpendicular to the cover, rollers with conical surface centered on the axis of the housing mounted to rotate on their respective axes radially in said rotor, and elastic means for pressing said rollers against a wall of the cover, when the latter is in the closed position, said wall offering, opposite the surface of the rollers, a support track in a circuit substantially circular defined for an elastically deformable tube, tightened locally against said track when the rollers pass. This track has a conical surface with the same inclination on the axis of the housing as that of the rollers. Preferably, the cover has a conical surface with the same inclination and has a flat bottom groove constituting said support track, in an arc around the axis of the housing, between an inlet and an outlet of the housing intended for the passage of a deformable tube partially housed in section in said throat. The edges of this groove can form bearing surfaces for said rollers, possibly arranged to encourage the drive of the latter, by friction or by gear.

The invention is not limited to the number of rollers. It is preferable to provide an antireflux effect and also to ensure the balance of the rotary assembly in connection with the pressure necessary to locally tighten the deformable tube, but, to do this, two diametrically opposite rollers on their rotary support are generally sufficient.

The invention also aims to prevent the appearance of a flow-back movement each time one of the rollers or other pressing members, driven in pressure rotation on the deformable tube, releases the tube on the side of the pump outlet. Indeed, the abrupt opening of the section of the tube causes a suction effect which recalls part of the liquid in the retrograde direction and, in the case of blood, this phenomenon is particularly annoying, because, on the one hand it causes by moments aspiration of the patient's blood, on the other hand it may promote hemolysis of the blood by mechanical effect.

To avoid these drawbacks, provision is made to impose, at the outlet of the pump, by the shape of the support track in connection with the path of the rollers, a gradual release of the pressure from the rollers, on a downstream section of the circuit, where the difference between the track of the rollers and the support track gradually increases.

The tube circuit can then remain circular between the inlet to the pump and the outlet, and the construction of the rollers and their support also need not be modified. It suffices, in accordance with a preferred embodiment of the invention, to constitute the support track of the tube by the bottom of a groove whose depth increases gradually on a last downstream section of the tube circuit, before it leaves the pump, until the thickness of the tube is reached, normally, in the absence of any roller pressure. The last downstream section of the circuit preferably covers a length corresponding at least to the distance separating two successive rollers, and the gap between the roller and the fixed support track increases continuously there. The pressure can be complete over the rest of the circuit, the pressure of a roller then completely closing the tube locally in its passage. The number of rollers can be chosen at will, as long as the tube always remains subjected to at least the action of two rollers on the entire circuit in the pump. That is to say that at all times there is always at least one roller on the progressive release zone which constitutes the last section of the circuit, and at least one other on the discharge zone where the tube is closed by the roller is complete. This leads to using at least three rollers in the most frequent case where the circuit does not cover an entire circumference.

The support track of the tube, in particular the bottom of the guide groove, can have a constant slope, for the sake of simplification, but it can also advantageously have a longitudinal profile defined so as to ensure along the developed profile a even more regular variation of the internal volume of the tube, during the progression of a roller, by compensating by this profile the variation in volume as a function of the crushing by the pressure roller which does not follow a linear law. It has been found that particularly good results can be obtained if the profile developed describes a curve with a relatively steep slope in the vicinity of the ends of the section and a relatively slight slope in the middle part of the section, and whose point of preference is preferably inflection constitutes a center of symmetry. All these means make it possible to provide the pump with a regular constant flow, free of any retrograde flow at the rate of passage of the rollers.

The pump according to the present invention makes it possible to vary transfusion rates over a very wide range, practically without risk of blood hemolysis. To take even better advantage of it, it is possible to use to conduct the transported liquid a deformable tube made practically inextensible in its longitudinal direction, but compressible in section, at least over a section capable of forming a loop in an arc of a circle on the path of rollers pressers in a peristaltic pump according to the invention.

In accordance with a preferred embodiment of the invention, there are in fact provided on the above section two coaxial flexible tubes. The inner tube is the one that carries the physiological fluid. It is generally made of a deformable material based on synthetic resin, silicone resin or synthetic elastomer for example. This internal tube is placed inside an external tube which ensures non-extensibility. The outer tube can advantageously be fixed to the inner tube at its two ends, for example by means of heat-shrink rings and / or by gluing. The outer tube is preferably made of a material capable of also providing mechanical resistance properties to the assembly. One can use a metal braided tube, or a tube comprising a reinforcement of longitudinal fibers, glass fibers or synthetic fibers, or any other tube of equivalent properties. In most cases, it is not necessary for this outer tube to be waterproof.

• La figure 1 représente la pompe en coupe partielle suivant un plan passant par son axe, dans un premier mode de réalisation ;
• la figure 2 représente schématiquement la même pompe dans une vue de dessous supposant enlevé le boîtier de la figure 1 ;
• la figure 3 illustre une variante de réalisation de la figure 1 ;
• la figure 4 représente schématiquement, en coupe longitudinale, un conduit de sang constituant le tube déformable pour la pompe ci-dessus ;
• la figure 5 représente schématiquement la pompe, vue en coupe partielle suivant un plan passant par son axe, dans un second mode de réalisation ;
• la figure 6 représente la même pompe dans une vue de dessous supposant enlevé le boîtier de la figure 1 ;
• la figure 7 illustre le fonctionnement de la pompe sur une représentation du profil développé de la piste d'appui du tube déformable ;
• la figure 8 est l'homologue de la figure 3 pour une position différente du rotor.

Other characteristics and advantages of the invention may appear in the course of the description below of particular embodiments chosen by way of examples. These embodiments, in no way limiting, are illustrated by FIGS. 1 to 8 of the appended drawings, in which:

• Figure 1 shows the pump in partial section along a plane passing through its axis, in a first embodiment;
• Figure 2 shows schematically the same pump in a bottom view assuming removed the housing of Figure 1;
• Figure 3 illustrates an alternative embodiment of Figure 1;
• FIG. 4 schematically represents, in longitudinal section, a blood conduit constituting the deformable tube for the above pump;
• FIG. 5 schematically represents the pump, seen in partial section along a plane passing through its axis, in a second embodiment;
• Figure 6 shows the same pump in a bottom view assuming removed the housing of Figure 1;
• FIG. 7 illustrates the operation of the pump on a representation of the developed profile of the support track of the deformable tube;
• Figure 8 is the counterpart of Figure 3 for a different position of the rotor.

As seen in particular in Figure 1, the housing 1 of a pump according to the invention is made in two parts, with a removable cover 2, the bottom 3 being integral with the cylindrical side wall 4. The upper edge of this side wall 4 forms a collar 5 on which an outer ring 6 of the cover 2 comes to bear when the latter is in the closed position on the housing. At at least two points, which are then diametrically opposite, the crown 6 carries lever members 7 which allow manual locking of the cover on the flange 5 of the housing.

The outer faces of the bottom 3 and of the cover 2 are generally flat and parallel to each other, perpendicular to the general axis of the housing, the assembly thus being produced in the form of a flat disc. In Figure 1, the housing thus produced is shown pressed against a casing 8 which contains the control apparatus of the pump and the drive motor. Several similar pumps can be stacked on top of each other.

Inside the housing 1, a roller support rotor 11 is constituted by a disc secured to a shaft 12 by which it is mounted in the housing so as to be able to rotate on its axis. The shaft 12 is essentially mounted at the center of the bottom 3 of the housing, and it is provided on the outside thereof with a coupling system 13 with the motor output axis contained in the casing 8. In addition , in the particular case considered here, the shaft 12 also passes through the cover 2 when the latter is in the closed position on the housing. The cover 2 therefore has in its center a bore for the passage of the shaft 12 and when it is in place on the housing 1 it participates in maintaining the shaft 12 in the axis of the pump. A coupling system is also provided at the upper end of the shaft 12 to allow the rotor of another similar pump stacked on the housing 1 to be driven by the same motor.

As it appears not only in FIG. 1 but also in FIG. 2, two rollers 15 and 16 are arranged at diametrically opposite points in the space left free in the housing between the periphery of the support 11 and the side wall 4. It these are rollers with a conical outer surface, the axis of which is arranged radially relative to the axis of the pump. Each is mounted by its axis in the support 11 so as to be able to rotate around this axis 17. Each roller in fact occupies the volume of a truncated cone and its conical outer surface 18 is centered on the axis of the pump, which corresponds to the axis of the shaft 12 or of the support 11.

On the edge of the support 11, and therefore close to the rollers that it carries, the support 11 is supported by means of an annular rolling track on a ring 21 held in an annular housing 22 of the bottom of the housing 3. Springs 23 arranged in this housing tend to elastically push the crown 21 upwards, as well as the roller support 11 and the rollers themselves.

The role of the rollers 15 and 16, when the pump is in operation, is to clamp against the cover 2 a deformable tube which conducts the liquid to be conveyed. This tube 24 is arranged in the pump to form an arc of a circle, or rather an almost complete circle, on the path of the rollers. When the pump is mounted, it is placed under the cover 2 according to a circuit which enters and leaves the pump respectively through inlet and outlet orifices 25 and 26, formed for this purpose through the housing, at the edge of the side wall 4 and of the cover 2. The recesses in these two elements together form circular orifices where the tube 4 can take its natural shape, offering the maximum cross-section for the passage of the liquid.

On the path of the rollers, all around the housing, the cover 2 forms on its internal face a wall of generally frustoconical shape, centered on the axis of the housing, with the same inclination on this axis as the conical surface of the rollers 15 and 16 But, more precisely, this wall has a groove 27 with a flat bottom oriented at this inclination, with projecting annular edges, constituting for the rollers annular bearing surfaces 28 and 29, also with the same inclination. The groove 27 follows the circle described by the rollers 15 and 16 in operation. It is intended to guide the deformable tube 24, which is housed there partially in section as shown on the right-hand side of FIG. 1. The outer annular bearing 29 is interrupted at the level of the orifices 25 and 26 to allow the passage of the tube. The width of the groove 27 is naturally less than that of the rollers so that they can come to bear on the bearing surfaces 28 and 29 on either side of the groove. It is however clearly wider than the diameter of the tube 24 and it is shallow, so that when the tube is crushed inside the groove, it no longer allows any passage of the liquid. There is shown the tube 24 not crushed on the right part of FIG. 1 and on the left part of this same figure, it has been shown locally crushed, where a roller 15 presses it on the conical surface of the bottom of the groove 27.

When the pump is thus in operation, the cover in the closed position on the housing 1, the ring 21, urged by the springs 23, pushes the rollers in abutment on the bearings 28 and 29. The rollers are thus driven in rotation, either simply by friction, or possibly by means of cooperating gears provided for this purpose on the bearing surfaces and on the rollers.

Thanks to the design which has been described, the deformable tube is easy to mount in the pump, especially as its position is defined by the groove 27. In addition, tilting collars, which have not been shown in the figures , keep it in place at the holes 25 and 26.

In the pump, the deformable tube is arranged in a plane along an arc of a circle concentric with the axis of rotation of the roller support in a plane generally parallel to the plane of rotation. This makes it possible in particular to avoid distending the tube with respect to its mean line under the action of the rollers as in conventional pumps where the tube is crushed by radial rollers on a cylindrical wall. The tube housing groove also has the advantage of avoiding crushing the tube too strongly, which could lead to hemolysis of the transported blood, this while ensuring effective and regular pressure thanks to the bearing surfaces of the rollers on the edges of the throat. The frustoconical shape of the rollers is such that the peripheral linear speed of these rollers corresponds to the radius of curvature of the trajectory of the contact point on the tube and on the surfaces of the housing cover. The regular drive of the rollers is also ensured thanks to the degree of freedom presented by the rotor supporting the rollers sliding along its axis of rotation and thanks to the system of springs which push elastically the assembly towards the cover. In general, the freedom inherent in the construction of electric motors is sufficient, without the need for special provisions at the axis of the rotor.

According to a variant, the elastic thrust produced by means of the springs 23 in the embodiment of FIGS. 1 and 2 in order to apply the rollers both to the deformable tube and to the surfaces of the cover which ensure their drive, can no longer be exerted on the roller support 11 itself, but even closer to these rollers, on the axes 17 by which they are mounted in the support. These axes are then provided with ball bearings 19 at the level of the rolling track constituted by the ring 21, as shown in FIG. 3.

According to another variant, the roller support rotor can carry several series of rollers distributed on different concentric circles, so as to cooperate with grooves formed at different distances from the axis of rotation, on the same cover or on covers different.

The deformable tube 24 inserted in the pump is in fact constituted by two coaxial tubes, on a section of a longer conduit conveying the blood from the reservoir to the transfusion syringe. FIG. 4 shows such a conduit, with on the section being placed in the pump, an external tube 32 around an internal tube 31.

The section formed by the two tubes 31 and 32 is flexible enough to be able to take the curvature imposed by the mechanical housing of the pump. The assembly of the two tubes is also elastically deformable therein in section so as to allow operation under the action of the rollers. The internal tube 31 is in fact entirely made of an elastically deformable material, for example of synthetic elastomer. This material is also chosen to facilitate sterilization and to be inert with respect to the liquid. transported. The outer tube 32 is not in contact with the blood. It is made of a material chosen to have good mechanical strengths and to be almost inextensible in the longitudinal direction of the tube. In the particular case shown, this tube is made of a braid of plastic fibers.

At the two ends of the external tube 32, the latter is fixed to the tube 31 by high frequency bonding or welding and by shrinking by means of heat-shrinkable rings 33 and 34. At the end intended to be placed in operation upstream of the pump, the tube 31 is connected by the same ring 33 to a cone 35 which is here of the female type and which allows the connection, by a cooperating male cone, to another conduit ensuring the supply of blood, in series on the same circuit. It will be noted that at this same end the ring 33 constitutes a rigid part projecting slightly from the tube 32 in section. Therefore, it is capable of forming a stop cooperating with the pump housing to avoid entrainment of the tube by the rollers in the longitudinal direction. During assembly the rings 33 and 34 are placed outside the pump housing. At the other end of the section, therefore downstream of the pump, the blood circuit is extended as much as is desirable by a conduit 37 formed for example from polyvinyl chloride, with standardized dimensions. As the tube 31 of the section corresponding to the pump is of larger section than the section of conduit 37 and the cone 35, intermediate rings 36 are interposed between the latter and the ends of the tube 31.

In the second embodiment, the subject of Figures 5 and 6, the same essential elements bear the same reference numbers as above. The number of conical rollers 15, rotating on their aces 17 radially in the rotor 11, has been increased to three, distributed at 120 degrees from one another around the axis 12. The main modification relates to the shape of the groove 27. In FIG. 1, it can be seen that the groove 27 is deeper on the right, on the downstream portion of the circuit, towards the outlet 26, than on the upstream portion, to the left of the figure, and it follows that if upstream the tube 24 is completely crushed locally when the rollers pass, it remains largely open downstream.

In fact, the bottom of the groove has a particular longitudinal profile, which is shown developed in Figures 7 and 8. In these figures, as in Figure 5, we distinguished several sections on the circuit of the tube engaged in the groove guide. The sections AB and BC, each with an angle at the center of 120 degrees, are arranged symmetrically with respect to the vertical axis of FIG. 2, passing between the inlet 25 and the outlet 26. The first represents the discharge zone, the second the progressive clearance zone. They each cover a length of circuit corresponding substantially to the angular distance separating two successive rollers. The AC sector surrounds the blind spot between D and E, occupied by the inlet and outlet of the pump, where the rollers have no action on the tube.

Along the discharge AB section, the bottom of the groove remains flat, the gap between this bottom and the rollers as they pass is constant and small enough that the tube is completely crushed by the roller and closes locally to circulation. . On the section BC, defining the progressive clearance zone, the difference between the bottom of the groove and the plane of rotation of the rollers increases continuously, until reaching in C the thickness of the tube returned to its circular section. Figures 7 and 8 illustrate the deformation of the tube by the roller Gl in the discharge zone (from A to B), by the roller G2 in the progressive release zone (from B to C).

The roller G3 is him, without action until the entry E. Indeed, the depth of the groove remains constant from C and until, at least, the exit D. The roller there is therefore without action on the tube. From E, the depth gradually decreases to A. On the upstream section EA, the tube therefore gradually closes when the roller passes be completely overwritten at A.

The precise profile of the bottom of the groove is that which is shown in FIGS. 7 and 8. At the ends of the progressive clearance zone, at B and at C, the curve presents a significant slope whereas in its median part the slope is low compared to the flat profile of the area AB where the bottom is parallel to the flat path of the rollers. The increase in the gap from B to C is exactly equal to the internal diameter of the uncrushed tube. In fact, the increase ends a little before C, by the value of a fraction of the radius of the rollers. In the middle of the slope is the center of symmetry. In practice, this curve can be replaced by a straight line from B to slightly before C.

Naturally, the invention is in no way limited to the embodiments previously described and represented by the drawings. Any variant that a person skilled in the art could imagine is of course part of the present invention.

Claims (12)

1. Peristaltic pump, characterized in that it comprises a housing made in two parts, with a removable cover, a roller support rotatably mounted on an axis of the housing perpendicular to the cover, rollers with conical surface centered on the axis of the housing rotatably mounted on their axis radially in said support, and elastic means for pressing said rollers against a wall of the cover, when the latter is in the closed position, said wall offering, opposite the surface of the rollers, a conical surface likewise inclination on the axis of the housing, forming a support track for a deformable tube clamped locally between said surfaces when the rollers pass. 2. Pump according to claim 1, characterized in that in the cover is formed a flat bottom groove having said inclination on the axis of the housing, in an arc around said axis, between an inlet and an outlet of the housing intended the passage of a deformable tube partially housed in section in said groove. 3. Pump according to claim 2, characterized in that the edges of said groove form bearing surfaces for said rollers to ensure the drive of the latter. 4. Pump according to any one of claims 1 to 3, characterized in that the axis of the roller support is rotatably mounted both in the bottom of the housing and in the cover. 5. Pump according to any one of claims 1 to 4, characterized in that, on a downstream section (B-C) of the circuit, the difference between the path of the rollers and the support track gradually increases. 6. Pump according to claim 5, characterized in that it comprises a groove (27) for guiding the tube along said circuit, the bottom of which constitutes said support track. 7. Pump according to claim 6, characterized in that the depth of said groove increases progressively continuously on said last section of the circuit, until reaching the thickness of the tube in the absence of any roller pressure . 8. Pump according to claim 7, characterized in that the developed longitudinal profile of said track follows along said downstream section a curve with a relatively steep slope in the vicinity of the ends of the section and relatively small in its middle part, and in that said downstream section covers a circuit length corresponding at least to the distance separating two successive rollers. 9. Pump according to any one of claims 1 to 8, characterized in that it comprises three pressure rollers, distributed at equal angular distances around the rotor. 10. Pump according to any one of claims 5 to 9, characterized in that said circuit further comprises a first upstream section (EA) where the difference between the path of the rollers and the support track gradually decreases and an intermediate delivery section where this difference remains constant and sufficiently small for the tube to be completely closed locally by crushing when a roller passes, at all points along a length of circuit corresponding at least to the distance separating two successive rollers. 11. Pump according to any one of claims 1 to 10, characterized in that it comprises an elastically deformable tube, made meaningly-inextensible in its longitudinal direction, but compressible in section, at least on a section capable of forming a circular arc loop in the pump, and comprising on said section two coaxial tubes (31, 32), said elastically deformable tube (31) being disposed inside an inextensible external tube (32) to which it is linked to less at an upstream end. 12. Pump according to claim 11, characterized in that said tube comprises at least at said upstream end a stop (33) adapted to cooperate with the pump housing outside of the latter.

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