EP2188527B1 - Linear peristaltic pump with fingers and membrane and finger for such a pump - Google Patents

Description

The invention relates to a linear peristaltic finger pump comprising a membrane placed between the pumping fingers and the tubing, and a membrane and fingers for such a pump.

Peristaltic pumps consist of a series of parallel fingers moved by a vertical back and forth motion. The movement of each finger is offset from the previous one so that the ends of the fingers form a sinusoidal which moves in the direction of pumping. The end of fingers is pressed on a flexible tubing placed between them and a support plate. The lowest finger causes an occlusion that migrates downstream from the finger pump to the last finger. When the last finger is in the occlusion position, the at least one first finger is again in the occlusion position thus causing the fluid contained in the tubing to move.

To protect the pump unit from external aggressions, such as the penetration of liquids or foreign bodies, it is usual to place between the fingertips and the tubing a flexible membrane fixed to the pump housing.

These membranes have two main disadvantages: their wear due to the friction of the fingers and the effect of their elasticity on the return of the tubing to its normal shape.

The membrane is compressed between the pumping fingers and the backing surface (usually the door covered with a hard plastic material), as is the tubing. It can often be observed that the membranes, after several years of operation, are damaged in the zone of contact of the fingers. This is due to the fatigue of the material which is subjected to repeated cycles of compressive stresses and friction (micro displacements). On the counter-support surface, on the contrary, no damage is observed. This shows that hard plastics resist compression stresses much better than soft plastics. During the life of the device, it is common to change the membrane at least once. Obviously, the main problem is the cost of the part, but also the cost of labor (This may be relatively large depending on how the membrane is assembled and whether it is necessary to recalibrate the pump after such replacement). With the wear of the membrane, there is a decrease in the accuracy of the pump which can be a major drawback for peristaltic pumps for medical purposes.

In addition, the tubing is successively compressed and released during pumping. During the phase where the tubing is not compressed, it must return to its initial cylindrical shape so as to circulate the liquid. To resume its original shape, the tubing is generally aided by its own elasticity and by the pressure of the fluid upstream of the pump (which corresponds to the height of the liquid). However, the flexible membrane, which is normally flat, itself opposes the reshaping of the tube. Indeed, to return to its original form, the tube must push and deform the membrane. This phenomenon can be observed after long periods of pumping: the elasticity of the tube is degraded and a decrease in its elastic properties is observed.

In the document pump DE 32 02 251 A1 which discloses the features of the preamble of claim 1, the free ends of peristaltic fingers are enclosed by a common cover membrane to protect the tubing. This membrane is attached to the pump housing at both ends of the pumping stroke.

The document US 4,909,710 A discloses a pump provided with a membrane interposed between the finger and the tubing and for separating the fingers from the pumping zone and isolating the tubing and the pumping area of the peristaltic mechanism. It can be seen in the figures that this membrane is stretched by its lateral edges on the end of the fingers.

The objective of the invention is therefore to develop a membrane which on the one hand is more resistant to wear due to the friction of the fingers on one of its faces and which on the other hand does not support by itself. even on the tubing so as not to disturb it when it resumes its normal cylindrical shape.

This object is achieved according to the invention in that means are provided for maintaining the part of the membrane on which the fingers, called the chenille part, are in permanent contact with the fingertips for the duration of the cycle. pumping, even in the absence of tubing. Thus, it is possible to choose a more resistant material for the part called chenille. This material will be stiffer than the rubber usually used, but thanks to the holding means in contact, the caterpillar will not remain in support against the tubing, but instead will be raised by the finger. Thus, we can choose a stronger material that will not wear out. The accuracy of the pump will be guaranteed longer and we will avoid membrane changes that are tedious and costly in terms of time and personnel.

It is preferable that the means for permanently contacting the caterpillar with the fingertips are constituted by means for mechanically coupling the caterpillar and the end of at least one finger. It is of course possible to mechanically couple the caterpillar and the end of at least one finger. It is of course possible to mechanically couple the track to the end of all the fingers. However, it may be sufficient to couple it only to the end of some fingers, in particular at the end of a single finger, for example one of the middle fingers.

To allow the use of a non-elastic material, it is preferable that at least the means for permanently contacting the caterpillar with the ends of fingers having two neighbors have a degree of freedom parallel to the pumping direction to allow the crawler has a reciprocating motion substantially parallel to the pumping direction with respect to the end of said fingers during a pumping cycle.

In order to prevent the track from migrating at the same time as the liquid under the effect of pumping fingers, it is preferable to provide in the pump means for blocking the general movement of the track in the direction of flow.

In practice, the membrane may be provided in the part on which the fingers support during use, part called chenille, means for mechanically coupling the latter to the end of at least one finger, which coupling means constitute part of the means for maintaining in permanent contact the ends of the fingers with the caterpillar.

It is preferred that at least the means for mechanically coupling the crawler to the fingertips having two neighbors have a degree of freedom parallel to the pumping direction to allow the crawler to have a reciprocating translational motion. substantially parallel to the pumping direction with respect to the end of said fingers during a pumping cycle. By playing on its geometry and / or its material, we can choose a caterpillar that is flexible without being elastic. Thus, the track can be made of a flexible but inelastic material.

The membrane is preferably constituted by a rigid frame provided with means for fixing the membrane in the pump, the caterpillar and a flexible intermediate membrane connecting the caterpillar to the frame so that the membrane forms a sealed continuous surface, said intermediate membrane being preferably overmolded on the frame and the caterpillar. Thanks to the flexible intermediate membrane, the caterpillar can move not only to follow the movements of back and forth fingers, but also in the direction of flow in relative motion relative to the ends of the fingers. The choice of a more resistant material for the track is compensated by the flexibility of the intermediate membrane.

In order to ensure a sufficient clearance to allow the displacement of the track in the three directions of the space while preventing the intermediate membrane from being stretched, it is intended to dimension the latter so as to push the track in the opposite direction to coupling means in the absence of stress, in particular on the part of the pumping fingers.

In a first embodiment, the coupling means are constituted by mushroom-shaped elements engageable in grooves extending in the pumping direction and placed at the end of one or more pumping fingers.

In a second embodiment, the coupling means are constituted by rings placed on the crawler parallel to the pumping direction and in which can penetrate tenons placed at the end of one or more pumping fingers, the rings in front of interacting with fingers having two adjacent fingers preferably being oblong with their major axis parallel to the pumping direction and / or the rings to cooperate with the upstream and downstream fingers being preferably circular.

In both cases, the caterpillar, although attached to the ends of the fingers, may have a relative movement with respect thereto, movement substantially parallel to the direction of flow. This makes it possible to compensate for the difference in distance between the ends of two successive fingers as a function of the progress of the pumping cycle. According to the embodiment, it is possible to distinguish the upstream and downstream fingers and the intermediate fingers that are characterized by the presence of two adjacent fingers.

In order to prevent the track from migrating at the same time as the liquid under the effect of pumping fingers, it is preferable to provide on the track means for blocking the general movement of the track in the direction of the flow.

In the second embodiment, this is achieved by choosing circular rings for the upstream and downstream fingers. Thus, the crawler is locked in longitudinal translation with respect to the upstream and downstream fingers. Another solution is to place a central tongue between two successive coupling means, perpendicular to the pumping direction, preferably in the middle of the caterpillar.

In order to increase the resistance of the membrane, it is preferable to extend the track on either side of the coupling means by two end tabs.

The invention also relates to pumping fingers for the peristaltic pump according to the invention. Such a finger can be provided with means for cooperating with the coupling means of the membrane, the cooperation means constituting part of the means for maintaining in permanent contact the ends of the fingers and the caterpillar.

In a first embodiment, the cooperation means are constituted by a groove extending in the direction of pumping. In a second embodiment, the cooperation means consist of a tenon extending perpendicularly to the pumping plane.

Figure 1 :

une vue en perspective d'un premier mode de réalisation de la membrane conforme à l'invention, vue du côté des moyens de couplage ;

Figure 2 :

vue en perspective de la membrane de la figure 1, vue du côté opposé aux moyens de couplage ;

Figure 3 :

vue en perspective de la chenille de la membrane de la figure 1 montée sur les doigts de la pompe ;

Figure 4 :

vue en perspective d'un second mode de réalisation de la membrane conforme à l'invention, vue du côté des moyens de couplage ;

Figure 5 :

vue en perspective de la membrane de la figure 4, vue du côté opposé aux moyens de couplage ;

Figure 6 :

vue agrandie des moyens de couplage de la membrane de la figure 4 ;

Figure 7 :

vue en perspective d'un doigt muni de moyens pour coopérer avec les moyens de couplage de la membrane de la figure 4 ;

Figure 8 :

vue en coupe du doigt de la figure 7 et de la membrane de la figure 4 clipsée dessus ;

Figure 9 :

vue éclatée de la membrane de la figure 4 ;

Figure 10 :

vue en coupe du bloc de pompage d'une pompe péristaltique mettant en évidence les différentes distances entre deux doigts successifs.

The invention is described below with the aid of two exemplary embodiments presented in the figures which show:

Figure 1 :

a perspective view of a first embodiment of the membrane according to the invention, seen from the side of the coupling means;

Figure 2:

perspective view of the membrane of the figure 1 , seen from the opposite side to the coupling means;

Figure 3:

perspective view of the caterpillar of the membrane of the figure 1 mounted on the fingers of the pump;

Figure 4:

perspective view of a second embodiment of the membrane according to the invention, seen from the side of the coupling means;

Figure 5:

perspective view of the membrane of the figure 4 , seen from the opposite side to the coupling means;

Figure 6:

enlarged view of the coupling means of the membrane of the figure 4 ;

Figure 7:

perspective view of a finger provided with means for cooperating with the coupling means of the membrane of the figure 4 ;

Figure 8:

sectional view of the finger of the figure 7 and the membrane of the figure 4 clipped on it;

Figure 9:

exploded view of the membrane of the figure 4 ;

Figure 10:

sectional view of the pump block of a peristaltic pump highlighting the different distances between two successive fingers.

The object of the invention comprises on the one hand a membrane (110, 210) for separating the pump unit from the outside, and in particular of the tubing in which the liquid to be pumped is located, and secondly the fingers (151, 152, 155, 250) to cooperate with the membrane (110, 210). To ensure that the membrane remains in constant contact with the fingers and therefore follows their reciprocating movement, there are provided holding means in contact which consist on the one hand of coupling means located on the face of the membrane directed towards the fingers and secondly means for cooperating with these coupling means and placed at the end of the fingers directed towards the membrane.

To simplify the description, refer to the "flow direction" or "flow plan". This is the direction taken by the tubing during use and the plane parallel to this direction and the pumping fingers. "Transverse directions" or "transverse planes" are directions or planes perpendicular to the "flow direction" or "flow plane". When describing the membrane or the fingers, the reference to these marks relates to their mounted state.

The membrane of the invention (110, 210) consists of a rigid frame (111, 211), a caterpillar (112, 212) and an intermediate membrane (113, 213). The membrane is liquid-tight and serves to protect the pumping unit against the intrusion of foreign objects and dust. It is placed between the pumping fingers and the tubing containing the liquid to be pumped.

The frame (111, 211) is preferably made of a relatively rigid material, for example polyamide 6. It is provided with fixing means (114, 214) for fixing it to the pump. It may be holes (114) for the passage of fastening screws as in the first embodiment, or of tabs (214) latching as in the second embodiment. On the face intended to be in contact with the tubing, the frame (111, 211) may also be provided with means (215) for fixing said tubing.

The intermediate membrane (113, 213) is made of a very flexible material, for example TPE (thermoplastic elastomer). It is preferably overmolded on the frame (111, 211) and on the track (112, 212). The shape of the intermediate membrane (113, 213) is chosen such that, in the absence of external stress, the caterpillar (112, 212) is in a plane offset from the tubing side with respect to the plane of the frame (111, 211), as shown for example the cut of the figure 8 . The flexibility of the intermediate membrane (113, 213) must be such that it offers practically no resistance to the vertical and horizontal translation movement of the track (112, 212).

The track (112, 212) is made of a material sufficiently flexible to accompany the movements of the fingers (151, 152, 155, 250), while being strong enough not to wear under the effect of finger friction. The flexibility of the piece can be obtained by two means: either a very fine piece with a material of high stiffness (for example a 0.1 mm thick steel sheet could be suitable) or a thick piece with a soft material or low modulus of elasticity. For example, we can choose for the caterpillar a compound of the family of high density polyethylenes or polyamides. The polyamide 12 Grilamid® L 20 W 20 from the company EMS-Chemie works very well. It is characterized in particular by the following mechanical characteristics: Elasticity modulus at tensile test (1 mm / min): 500 MPa Tensile strength at creep threshold (50 mm / min): 30 MPa Tensile extension at the creep threshold (50 mm / min): 20% Breaking load (50 mm / min): 40 MPa Elongation at break (50 mm / min): > 50% Resistance on notched specimen (Charpy, 23 ° C): 40 kJ / m ² (Charpy, -30 ° C): 3 kJ / m ² Shore D hardness: 65

The membrane of the invention is provided on the track (112, 212) with coupling means for coupling to each of the fingers (151, 152, 155, 250) of the pump unit. The objective of the invention is indeed that the caterpillar follows the movements of the fingers. In other words, the caterpillar must not only be resting on the tubing when a finger is in the occlusion position, but it must also follow the withdrawal movement of the finger so as not to exert pressure on the tubing when finger is in the up position.

The curve defined by the fingertips corresponds to a sinusoidal figures 3 and 10 . Whatever the state of progress of the curve, its total length measured between the two outer fingers (351, 355) remains constant. It is therefore not necessary that the caterpillar (112, 212) is elastic, it is sufficient that it is flexible enough to follow the sinusoidal movement of the fingers (151, 152, 155, 250). However, the distance between two successive fingers (351, 352/353, 354) varies as a function of the progress of the cycle back and forth. It is smaller when the fingers (351, 352) are near the ends of their race and more important when the two fingers (353, 354) are close to the center of their race. In the example of the figure 10 the distance between the first two fingers (351, 352) is about 4.2 mm, while between the third and fourth fingers (353, 354) is about 4.4 mm. It is therefore necessary, if the caterpillar is not elastic that it can follow the movement of the fingers (151, 152, 155, 250) with the possibility of translating in a slight movement back and forth by compared to the fingers (151, 152, 155, 250). The coupling means must not be too rigid and thus have a degree of freedom in the flow direction of the fluid.

In the first embodiment shown in Figures 1 to 3 , the coupling means (120) are constituted by a series of rings (121, 122) in which can penetrate pins (161) placed at the ends of the fingers (151, 152, 155). The rings (121, 122) are placed on the face of the track which in the mounted state is on the side of the pump block. In the example presented, they are divided into two groups, the first group being placed on one longitudinal side of the track, the other being arranged on the other side. This facilitates the mounting of the rings (121, 122) on the pins (161). The pins (161) are placed substantially at the end of the fingers (151, 152, 155), perpendicular to the flow plane. These rings are clearly visible on the figure 3 which shows a caterpillar (112) of which all the rings (121, 122) are oblong. As shown in figure 1 however, it is preferred that the end rings (122) be substantially circular, while the intermediate rings (121) retain an oblong elongated shape in the direction of flow. This keeps the upstream and downstream ends of the track substantially fixed relative to their respective fingers (151, 155) while allowing the track (112) to slide back and forth over the fingers. intermediates (152). We thus observe on the figure 3 the rings of the ^3rd finger and the 9 ^th finger (counting from the left), finger lying in end position are almost centered on their respective tenon, while observed for example that the ^5th finger ring is shifted to the left with respect to its tenon. The crawler therefore has a translational movement relative to the ends of intermediate fingers (152).

In a second embodiment of the invention presented to the Figures 4 to 9 , the coupling means consist of mushroom-shaped detent elements (220). These mushrooms (220) consist of a rod (221) surmounted by a plate (222). This plate (222) is dimensioned and placed on the rod (221) so that it is formed in the transverse plane ( Fig. 6b ) shoulders (223).

The fingers (250) intended to cooperate with these mushrooms (220) are provided at their end with a groove (260). This groove (260) is arranged such that in the mounted state, the groove (260) is parallel to the flow plane. At its opening, the groove is provided with two shoulders (261). The width of the groove (260) is at least equal to the width (transverse) of the plate (222) of the mushroom, and the opening between the two shoulders (261) is at least equal to the width (transverse) of the stem (221) of the mushroom. In the assembled state shown at figure 8 , the mushroom penetrates into the groove (260), the shoulders (223) of the mushrooms (220) being in abutment against the shoulders (261) of the groove (260).

To facilitate the engagement of the mushrooms (220) in the grooves (260), it is preferable that the plate (222) is pointed or rounded on the face opposite the rod (221) and that at least one of the walls the groove (260) is made by an elastic plate that can yield when the mushroom (220) is introduced.

Thanks to the shoulders (223, 261), the mushrooms (220) can move in the grooves (260) in a movement parallel to the direction of flow perpendicular to the plane of the groove. figure 8 . To prevent the caterpillar (212) from migrating under the effect of the general movement of the fingers, as does the fluid in the tubing, it is preferable to provide a retaining tab (217) which will be placed between two successive fingers. It is better to place it in the center as in the figure 9 .

Similarly, to prevent the intermediate membrane (213) from tearing at the upstream and downstream ends of the track (212), it is possible to extend the latter in the direction of flow by two end tongues (216). ) so that the rigid part of the caterpillar receives solicitations and makes a smoother transition with the flexible part.

Thanks to the holding means in contact with the invention, it is possible to choose for the part of the membrane on which the fingers support a relatively hard material that will not wear under the effect of finger friction. The relative stiffness of this caterpillar does not interfere with the tubing when it returns to its open cylindrical state, because the holding means in contact force the caterpillar to follow the withdrawal movement of the fingers away from the tubing.

Thanks to the stronger material of the track, it is no longer necessary to replace the diaphragm during the life of the pump. This avoids tedious recalibrations.

List of references:

110 210 Membrane 111 211 Membrane frame 112 212 Chenille of the membrane 113 213 Membrane intermediate membrane 114 214 Means for fixing the membrane 215 Means for securing the tubing 216 End tabs 217 Restraints 120 220 Means of coupling 121 Intermediate coupling ring 122 Outer coupling ring 221 Mushroom stem 222 Mushroom plate 223 Shoulder of the mushroom 250 Finger 151 351 Outdoor finger 152 352, 353, 354 Intermediate fingers 155 355 Outdoor finger 160 260 Means cooperating with the means of coupling 161 Coupling tenon 261 shoulder

Claims (14)

1. Linear peristaltic pump with fingers, comprising a membrane (110, 210) placed between the pumping fingers (151, 152, 155, 250) and the tubing, means (120, 160, 220, 260) being provided to keep the part of the membrane on which the fingers press, called the track (112, 212), in permanent contact with the ends of the fingers (151, 152, 155, 250) during the entire pumping cycle, even in the absence of any tubing, characterised in that the means for putting the track (112, 212) in permanent contact with the ends of the fingers (152, 250) consist on one hand side of coupling means (120, 121, 122, 220) located on the track (112, 212) and on the other hand side of cooperating means (160, 260) for mechanically cooperating with the coupling means (120, 121, 122, 220) of the track and placed on the ends of the fingers facing the membrane of at least one finger (151, 152, 155, 250).
2. Peristaltic pump according to claim 1, characterised in that at least the means for putting the track in permanent contact with the ends of the fingers (152, 250) that have two neighbors have a degree of freedom parallel to the pumping direction, so that during a pumping cycle, the track (112, 212) can have reciprocating translational movement, substantially parallel to the pumping direction, with respect to the ends of said fingers (152, 250).
3. Peristaltic pump according to one of the preceding claims, characterised in that it is provided with means (122, 217) for blocking the overall movement of the track (112, 212) in the direction of flow.
4. Membrane (110, 210) for a peristaltic pump according to one of the preceding claims, characterised in that in the part where the fingers press during operation, called the track (112, 212), the membrane is equipped with coupling means (120, 220) for mechanically coupling the track (112, 212) to cooperating means (160, 260) located on the end of at least one finger (151, 152, 155, 250), which coupling means (120, 220) constitute part of the means for keeping the ends of the fingers (151, 152, 155, 250) in permanent contact with the track (112, 212).
5. Membrane (110, 210) according to the preceding claim, characterised in that it is provided with means (122, 217) for blocking the overall movement of the track (112, 212) in the direction of flow.
6. Membrane (110, 210) according to one of the claims 4 or 5, characterised in that at least the means (120, 220) for mechanically coupling the track (112, 212) to the ends of fingers (152, 250) that have two neighbors have a degree of freedom parallel to the pumping direction, so that during a pumping cycle, the track (112, 212) can have reciprocating translational movement, substantially parallel to the pumping direction, with respect to the ends of said fingers.
7. Membrane (110, 210) according to one of the claims 4 to 6, characterised in that the track (112, 212) is flexible, but not elastic, due to the combination of its geometry and its material.
8. Membrane (110, 210) according to the preceding claim, characterised in that the membrane is made of a rigid frame (111, 211) equipped with means (114, 214) for fixing the membrane (110, 210) inside the pump, of the track (112, 212) and of an intermediate flexible membrane (113, 213) connecting the track (112, 212) to the frame (111, 211) in such a way that the membrane forms a continuous, impermeable surface, with said intermediate membrane (113, 213) being preferably overmolded on the frame (111, 211) and the track (112, 212).
9. Membrane (110, 210) according to the preceding claim, characterised in that the intermediate membrane (113, 213) is proportioned so as to push the track (112, 212) in the opposite direction from the coupling means (120, 220) in the absence of any external stress, particularly from the pumping fingers.
10. Membrane (210) according one of the claims 4 to 9, characterised in that the coupling means consist of mushroom-shaped elements (220) engageable in slots (260) extending in the direction of pumping and placed in the end of one or more pumping fingers (250).
11. Membrane (110) according to one of the claims 4 to 9, characterised in that the coupling means consist of rings (120) placed on the track (112) parallel to the direction of pumping, into which pins (161) placed on the end of one or more pumping fingers (151, 152, 155) can fit, the rings (121) that must cooperate with fingers (152) that have two neighboring fingers being preferably oblong, with their long axis parallel to the direction of pumping, and/or the rings (122) that must cooperate with the upstream and downstream fingers (151, 155) being preferably circular and forming blocking means of the track (112).
12. Membrane (210) according to one of the claims 4 to 11, characterised in that the means for blocking the track (212) consist of a retaining tab (217) placed between two successive coupling means (220), perpendicular to the direction of pumping, preferably in the middle of the track (212).
13. Membrane (210) according to one of the claims 4 to 12, characterised in that the track (212) is extended on both sides of the coupling means (220) by two end tabs (216).
14. Pumping finger (151, 152, 155, 250) for a peristaltic pump according to one of the claims 1 to 3, characterised in that it is equipped with cooperating means (160, 260) for mechanically cooperating with the coupling means (120, 220) of the part of the membrane (110, 210) where the fingers press during operation, called the track (112, 212), the cooperating means (160, 260) constituting part of the means for maintaining permanent contact between the ends of the fingers and the track, these cooperating means (160, 260) consisting of a slot (260) extending in the direction of pumping or of a pin (161) extending perpendicular to the pumping plane.

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