Peristaltic pump powered by piezoelectric transducers

Abstract

Peristaltic pump, intended to pump a liquid along a capillary (2), the pumping resulting from a stress exerted on the capillary, successively along a pumping direction, the pump comprising: K annular piezoelectric transducers (11k), extending around a central axis (Δ), K resonators (10k), formed of a deformable solid material, each resonator being connected to a piezoelectric transducer, and extending around the central axis, thinning towards the central axis, each resonator being configured to deform under the effect of a polarization of the piezoelectric transducer to which it is connected; a control unit (20), configured to bias each piezoelectric transducer the pump being characterized in that: each resonator is connected to a sleeve (3k), extending around the central axis; each resonator is arranged so that the sleeves of each resonator are aligned along a central axis.

Description

Title of the invention: Peristaltic pump powered by piezoelectric transducers technical field

[0001] The technical field of the invention is a peristaltic pump configured to be actuated by a piezoelectric transducer. EARLIER ART

[0002] Most pumps use moving parts, which can lead to problems with reliability, wear, and limited compactness. In the healthcare field, peristaltic pumps are commonly used. However, repeated compression of a tube, which causes the liquid to move, can lead to premature wear of the tube.

[0003] Patent application WO2013 / 41700 describes a non-peristaltic, piezoelectrically actuated, implantable pump. A sleeve, positioned at the center of a resonator, undergoes bending under the effect of a rotational deformation of the resonator, generated by piezoelectric transducers activated at an ultrasonic frequency. The bending of the sleeve generates a pumping effect, which causes the fluid to be expelled. Reducing the cross-sectional area of ​​the resonator, in the vicinity of or along the sleeve, amplifies the vibrations propagating to the sleeve. Such a pump is efficient. However, it has been observed that the sleeve undergoes repeated bending, which can lead to wear. Furthermore, the pump is intended to be coupled to a fluid circuit. Flow control depends on the vibration amplitude of the sleeve, which must be controlled according to the mechanical load of the fluid circuit, which is not easy.

[0004] In particular, we seek to ensure that the pumping principle, the frequency and amplitude of the ultrasonic pumping vibration are less dependent on the mechanical coupling of the pump with the fluidic circuit.

[0005] Another objective is to design a peristaltic pump, enabling pumping to be carried out, according to a controlled flow rate, with optimized energy expenditure, and which can be particularly compact. Description of the invention

[0006] An object of the invention is a peristaltic pump, intended to pump a liquid along a capillary, by means of a pressure exerted on the capillary, successively along a pumping direction, the pump comprising: - K annular piezoelectric transducers, extending around a central axis, each piezoelectric transducer configured to be polarized by a polarization electrode, K being an integer greater than or equal to 2 - K resonators, formed of a deformable solid material, each resonator being connected to a piezoelectric transducer, and extending around the central axis, thinning towards the central axis, each resonator being configured to deform under the effect of a polarization of the piezoelectric transducer to which it is connected; - a control unit, configured to bias each biasing electrode according to a biasing voltage, modulated according to a modulation frequency;

[0007] The pump being characterized in that: - each resonator is connected to a sleeve, extending around the central axis; - each resonator is arranged so that the sleeves of each resonator are aligned along a central axis; - the control unit is configured to successively polarize each resonator, according to their respective ranks, so that under the effect of the polarization, a successive deformation of each resonator occurs, the deformation propagating to the sleeve, and causing a successive deformation of the capillary (2) arranged between the sleeves, around the central axis.

[0008] The constraint may in particular be a compression and / or a displacement along the central axis.

[0009] The modulation frequency may in particular be greater than 20 kHz.

[0010] According to one possibility: - each resonator comprises a peripheral portion, delimited by two flat faces, and a central portion, extending between the peripheral portion and the sleeve, the central portion thinning towards the sleeve; - each piezoelectric transducer extends along a flat face.

[0011] According to one possibility, the flat face along which each peripheral transducer extends is delimited by a shoulder, the piezoelectric transducer being inserted by force against the shoulder, so that the shoulder goes around the piezoelectric transducer.

[0012] According to one possibility, each resonator is coupled to at least one ring piezoelectric transducer, the ring piezoelectric transducer extending around the resonator, so as to generate a radial compression of the resonator, in the direction of the central axis.

[0013] Each piezoelectric transducer can be force-inserted around the resonator to which it is connected.

[0014] According to one possibility, each resonator is coupled to two piezo- transducers

[0015]

[0016]

[0017]

[0018]

[0019] annular electrics, extending around the resonator, and offset in a direction parallel to the central axis, the central unit being configured to power the piezoelectric transducers in such a way as to generate a displacement of the sleeve, along the central axis and / or a compression of the sleeve perpendicular to the central axis. According to one possibility, each piezoelectric transducer exhibiting a dipole moment: - the dipole moments of the piezoelectric transducers coupled to the same resonator are oriented in the same direction, in which case the control unit is configured to supply said piezoelectric transducers in phase; - the dipole moments of the piezoelectric transducers coupled to the same resonator are oriented in two opposite directions, in which case the control unit is configured to supply said piezoelectric transducers in opposite phase; - so as to generate a radial compression of the sleeve that predominates over a displacement of the sleeve along the central axis. According to one possibility, each piezoelectric transducer exhibiting a dipole moment: - the dipole moments of the piezoelectric transducers coupled to the same resonator are oriented in the same direction, in which case the control unit is configured to supply said piezoelectric transducers in opposite phase; - the dipole moments of the piezoelectric transducers coupled to the same resonator are oriented in two opposite directions, in which case the control unit is configured to supply said piezoelectric transducers in phase; - so as to generate a displacement of the sleeve, along the central axis, which predominates over a compression of the sleeve. According to one possibility, the control unit is configured to supply said piezoelectric transducers with a predetermined phase shift, between 0° and 180°, so as to obtain a predetermined ratio between the displacement of the sleeve around the central axis and the compression of the sleeve. The pump may include the capillary tube, which may, for example, be press-fitted between each sleeve. The capillary tube may be rigid. The invention will be better understood by reading the explanation of the examples of embodiment presented, in the continuation of the description, in connection with the figures listed below. FIGURES

[0020] Figures IA and IB show an embodiment of a peristaltic pump.

[0021] Figure 2 represents a variant of the configuration described in relation to the figures AI and IB

[0022] Fig. 3A shows another embodiment of a peristaltic pump.

[0023] Fig. 3B shows an example of an annular piezoelectric transducer.

[0024] Fig. 4 shows another embodiment of a peristaltic pump. PRESENTATION OF SPECIFIC IMPLEMENTATION METHODS

[0025] Figure 1A describes a peristaltic pump, in which a pumping effect is obtained by applying progressive compression along a capillary 2. The capillary 2 is coaxial with a central axis

[0026] The pump comprises K resonators 10k, where k is a rank assigned to each resonator. The minimum number of resonators is 2, and the optimal number is between 3 and 5. In the example shown, K = 4. Thus, there are 4 identical resonators 10i, 102, 103, 104, aligned along the central axis. Each resonator extends in an annular shape, between a peripheral portion, comprising flat sections of constant thickness, and a portion tapering towards the central axis. Each resonator tapers, preferably gradually, to a cylindrical sleeve 3k extending around the central axis. This gradual tapering increases the strain forces transferred to the sleeve.

[0027] The capillary 2 is arranged along the central axis, between each sleeve. Preferably, the capillary 2 is rigid so that it can be forced into the sleeves. Forced insertion minimizes losses at the interfaces in the form of parasitic reflection of mechanical energy or dissipation due to friction. Furthermore, forceful insertion does not require any clamping means. The capillary can be made of the same material as the resonator.

[0028] Each resonator has a 15k shoulder, allowing it to clamp the transducer to which it is coupled, thereby applying a preload. Each shoulder thus wraps around the piezoelectric transducer it clamps. Each piezoelectric transducer can therefore be held in place without glue, by simple mechanical stress. This prevents the bond from deteriorating over time due to aging.

[0029] Each 10k resonator is coupled to a 11k ring piezoelectric transducer. Fig. 1B shows a detail of the mechanical coupling of a 11k ring piezoelectric transducer connected to a 10k resonator. The 11k piezoelectric transducer comprises a layer of a 13k piezoelectric material extending between at least one 12k electrode and a 14k counter electrode. When the 10k resonator is made of an electrically conductive material, the 12k electrode preferably has a slightly smaller outer diameter, for example, from 0.2 mm to 0.5 mm, than the 14k counter electrode. This design prevents an electrical short circuit between the 12k and 14k electrodes via the 15k shoulder. The 10k resonator is symmetrical about the central axis A. The 10k resonator is annular around the central axis A, tapering towards it. Thus, its thickness, defined parallel to the central axis A, decreases with distance from the central axis A. This tapering increases the amplitude of the vibrations propagating through the resonator towards the sleeve.

[0030] In this configuration, the piezoelectric transducers have a small thickness, typically between 0.05 mm and 5 mm, preferably 0.5 mm for a radius r of 25 mm and 0.2 mm for a radius r less than 10 mm, which maximizes the electric field, the latter being on the order of 300 V / mm. This makes it possible to increase the mechanical stress, which is directly proportional to the electric field.

[0031] Each layer of 13k piezoelectric material can be formed from a PZT (lead zirconate titanate) type material, in particular Ferroperm references PZ26, PZ27, PZ46 and PZ29. Preferably, the coefficients d33 and d31, which account for the coefficient of the observed deformation for an applied electric field (also perceived as a charge density collected for an applied stress), are respectively: - of at least 200 pC / N and preferably beyond 570 pC / N for the coefficient d33 quantifying the response of the piezoelectric material in a direction parallel to the direction of the applied electric field. - and at least 50 pC / N and preferably on the order of -240 pC / N. for d31, which quantifies the response of the piezoelectric material in a direction perpendicular to the direction of the applied electric field.

[0032] The outer radius R of each 10k resonator, defined around the central axis A, can extend up to 50 mm, or more. The planar portion of each resonator extends beyond a first radius smaller than the previously defined outer radius R. Below the first radius RB, each resonator has a portion that tapers towards the central axis A. The first radius Ri is, for example, equal to 50% of the outer radius R of the resonator.

[0033] Each resonator can extend to a thickness preferably less than 5 mm, for example 1 or 2 mm. The thickness is defined parallel to the longitudinal axis.

[0034] The 10k resonator extends to a first cylindrical 3k sleeve, coaxial with the central axis A. The diameter D of the 3k sleeve is, for example, between approximately 0.2 mm and 2 mm, and preferably close to 1 mm. The 3k sleeve is preferably formed by an extension of the 10k resonator, the resonator and the sleeve forming a monolithic piece. The radius of the sleeve forms an internal radius of the The first resonator is 10kΩ. The height of each 3kΩ sleeve is preferably less than one wavelength of the waves propagating within the sleeve. The height of each 3kΩ sleeve is preferably equal to half a wavelength. The wavelength depends on the sleeve thickness and the resonant frequency. In practice, the sleeve height is less than 1 mm and preferably less than or equal to the resonator thickness in the portion applied against the piezoelectric transducer.

[0035] This allows the sleeve of each resonator to be as close as possible to the sleeve of another resonator, without being in direct contact. The gap between two adjacent sleeves can be at least 0.05 mm.

[0036] Each resonator is made of a deformable solid material, which may be of the type metal (titanium, stainless steel, aluminum or aluminum alloy, brass, or other copper-based alloy, or nickel-based alloy), inorganic material (glass), organic material (PEEK), alumina.

[0037] The pump includes a control unit 20, connected to each first electrode 12k so as to apply a frequency-modulated bias voltage to them. The modulation frequency depends on the size and material of each resonator. The frequency is the same for each piezoelectric transducer. When the radius of each resonator is 25 mm, the modulation frequency can be approximately 25 kHz. When the radius of each resonator is 12.5 mm, the modulation frequency can be approximately 50 kHz. When the radius of each resonator is 6.5 mm, the modulation frequency can be approximately 100 kHz. In all cases, the modulation frequency is preferably ultrasonic, so as to avoid the generation of an audible sound.

[0038] Each counter electrode 14k is connected to a fixed potential, which may be common to all counter electrodes (for example a ground), or independent of the potential to which another electrode is connected, each independent potential being for example a floating ground.

[0039] Each 10k resonator is configured to be deformed by a compression wave acting on each sleeve, so as to radially compress the capillary. Under the effect of compression, the internal diameter of each sleeve oscillates at a radial compression resonance frequency. According to one possibility, each sleeve can move parallel to the axis of the capillary at a radial bending resonance frequency.

[0040] More precisely, since the dimensions of the resonator are finite, a surface element located on the inner wall delimiting each sleeve oscillates in an ellipse at each resonance period. The major axis sz of the ellipse is parallel to the central axis A at a radial bending resonance frequency. There is therefore a slight effect of The bearing is imprinted on the capillary. The 10k resonator can vibrate at its fundamental frequency or at a harmonic frequency. In the latter case, the ratio between the major axis sz and the minor axis sr of the traversed ellipse becomes closer to 1. The motion becomes more circular for a higher harmonic frequency.

[0041] The resonators can be separated from each other by spacers 4. This allows the stack to be made more rigid.

[0042] The stacking thickness can be between 5 mm and 10 mm.

[0043]

[0044]

[0045] The transducers are phase-shifted along the longitudinal axis A, so that the communication Pressure moves along the central axis. The time phase shift is 7, where T This corresponds to the period during which each transducer was activated. The resonant frequency is estimated to be at a maximum of 150 kHz for a fundamental frequency. Figure 2 illustrates a variant of the embodiment described in connection with Figures IA and IB, in which the stack is housed in a casing. Each end of the capillary is conical, which facilitates connection with a flexible capillary 5, for example, made of silicone. In this example, the assembly formed by the resonators is held on a base 6a onto which a cover 6b is clipped. Figures 3A and 3B illustrate an embodiment similar to that of Figures IA and IB, in which each piezoelectric transducer is a ring arranged around the resonator to which it is coupled. Such a configuration is conducive to the generation of symmetrical Lamb waves propagating radially, converging towards the central axis. This allows the compression forces to be concentrated at the sleeve. In this case, the ellipse traced by the displacement of a surface element of the sleeve at the interface with the capillary has its major axis oriented perpendicular to the central axis A of the capillary. The transducers are phase-shifted (or activated according to a time shift) about the central axis A, so that the compression associated with the major axis of the ellipse moves along the central axis. The phase shift or time shift is T, where T corresponds to the period during which each The transducer has been activated.

[0046] The use of piezoelectric transducers arranged at the periphery of resonators makes it possible to increase the frequency, as the latter can resonate in thickness resonance at a high frequency, in practice above one megahertz, or at a lower frequency if a radial compression resonance of the thinned disc is exploited. This makes it possible to use a finer capillary, close to one-tenth to a few tenths of a millimeter. Such a configuration is suitable for delivering small doses of active ingredient, or for an implanted pump, or for dispensing small volumes of fluids such as catalysts or expensive products, or for supplying slow and well controlled release of powders or various products (gas, lubricant, etc.) required for a particular production or maintenance.

[0047] Figure 3B shows an annular piezoelectric transducer: the 12kΩ electrode and the 14kΩ counter electrode are annular, as is the 13kΩ piezoelectric layer. In this example, the thickness of the 13kΩ piezoelectric layer is 1 mm, and the diameter of the 12kΩ electrode is, for example, 22 mm. To ensure electrical isolation between the 12kΩ electrode and the 10kΩ resonator to which it is attached, the 13kΩ piezoelectric layer can be beveled (bevel not shown) to a depth of at least 0.1 mm at the edges of the outer 12kΩ electrode. In the radial direction, the width of the piezoelectric layer can be between 0.5 mm and 1 mm. The resonant frequency for a thickness of 1 mm is approximately 2 MHz.

[0048]

[0049] Figure 4 shows a configuration similar to that described in connection with Figures 3A and 3B. In this configuration, each resonator is coupled to two ring-shaped piezoelectric transducers, 1 lb 21 b, activated in opposite phase and arranged around the resonator. Such a configuration is conducive to the generation of antisymmetric Lamb waves propagating radially, converging in the thinned region and causing shearing of the capillary 2. This shear propagates along a predetermined direction. In this case, the ellipse traced by a surface element at the interface between the sleeve and the capillary has a major axis sz parallel to the central axis D of the capillary. As in the previous embodiment, the transducers coupled to two adjacent resonators are phase-shifted along the longitudinal axis A, so as to propagate the shear stress step by step along the capillary. The time phase shift is 2% T, where T corresponds to the period over K from which each transducer was activated. During the same phase, the first transducer 1kΩ of a 10kΩ resonator is activated, so as to induce buckling in one direction of the resonator in its central region, while the second transducer 21kΩ of a 10kΩ resonator is activated, so as to induce buckling in the same direction of the resonator and must therefore be phase-shifted by ji at the central axis. This is achieved if the external electrodes 12kΩ of the 1kΩ and 21kΩ transducers are subjected to the same electrical excitation voltage and if the electrical dipole moments of the piezoelectric materials 1k and 23k are in opposite directions as indicated by the arrows passing through the transducers shown in [Fig. 4]. This results in pumping by peristaltic shear effect, due to the progressive shear of capillary 2, which generates fluid displacement by viscosity and incompressibility of the fluid along the central axis. The pumping efficiency is reinforced by a displacement component sr in the plane of each resonator, corresponding to the minor axis of the displacement ellipse and inducing compression of the capillary tube. The symmetric SO and antisymmetric AO acoustic modes initiated at the periphery of the resonators in Figures 3A and 4 both include compressional displacement components sr and shear components sz of the capillary corresponding to the major and minor axes of the ellipse traversed by a displacement vector, but with a dominant compressional component in sr for the symmetrical mode and a dominant shear component in sz for the antisymmetrical mode. These two vibrational modes are considered peristaltic.

[0050] The configuration shown in [Fig.4] also allows the formation of symmetrical SO acoustic modes, as shown schematically in [Fig.3A], when the external electrodes 12k of the two piezoelectric transducers 1lk, 21k connected to each resonator 10k are in opposite phase and if the electric dipole moments of the piezoelectric transducers 1lk and 21k are in opposite directions as shown in [Fig.4],

[0051] When the dipole moments of the transducers 1k and 21k are oriented in the same direction, and the excitation voltages are out of phase, an antisymmetric vibration mode A0 is obtained as previously described. When the excitation voltages are in phase, a symmetric vibration mode S0 is obtained.

[0052] A symmetrical vibration mode has the effect of compressing the capillary and producing a displacement of the capillary / sleeve interface following an ellipse with a major axis orthogonal to the axis D. This vibration is transmitted in the wall of the capillary in the form of a bending wave with axial symmetry with respect to the axis D.

[0053] An antisymmetric vibration mode has the effect of producing a displacement of the capillary / sleeve interface whose major axis of the ellipse is parallel to the axis D, which results in a shearing of the capillary while respecting the axial symmetry with respect to the axis A.

[0054] It follows that if the electrical phase shift between the two transducers 1k and 21k is varied from 0 to 180°, there is a continuous transition from a predominant generation of a symmetrical deformation mode to a predominant generation of an antisymmetrical mode with respect to the median plane of the resonator 10k. The two vibration modes, symmetrical and antisymmetrical, are created simultaneously but in different proportions depending on the phase shift and with distinct phase velocities, the latter being greater for the symmetrical mode than for the antisymmetrical mode. Given that these vibration modes can coexist simultaneously and elastically within the resonator, it suffices to impose a specific electrical excitation phase shift between 0 and 180° to obtain a vibration of the capillary wall such that each surface element of the capillary moves along an ellipse, the major axis of which is susceptible to vary from an orientation perpendicular to the D axis to an orientation parallel to the D axis depending on the phase shift that will be chosen between the two transducers 1k and 21k.

[0055] Regardless of the configuration, the peak-to-peak bias voltage can vary, for example, from a few volts to several hundred volts, the voltage affecting the amplitude of the out-of-plane deformation component of the resonator. The amplitude of this deformation component affects the volume of fluid at the internal interface of the capillary undergoing the elliptical rolling effect, which generates its entrainment and therefore the pumping pressure.

Claims

Demands

1. Peristaltic pump, intended to pump a liquid along a capillary (2), the pumping resulting from a stress exerted on the capillary, successively along a pumping direction, the pump comprising: - K ring piezoelectric transducers (1k), extending around a central axis (A), each piezoelectric transducer and configured to be polarized by a polarizing electrode (12k), K being an integer greater than or equal to 2 - K resonators (10k), formed of a deformable solid material, each resonator being connected to a piezoelectric transducer, and extending around the central axis, thinning towards the central axis, each resonator being configured to deform under the effect of a polarization of the piezoelectric transducer to which it is connected; - a control unit (20), configured to bias each biasing electrode according to a biasing voltage, modulated according to a modulation frequency;the pump being characterized in that: - each resonator is connected to a sleeve (3k), extending around the central axis; - each resonator is arranged so that the sleeves of each resonator are aligned along a central axis; - the control unit (20) is configured to successively polarize each resonator, according to their respective ranks, so that under the effect of the polarization, a successive deformation of each resonator occurs, the deformation propagating to the sleeve, and causing a successive deformation of the capillary (2) arranged between the sleeves, around the central axis.

2. Pump according to claim 1, wherein the constraint is a compression and / or a displacement about the central axis.

3. Pump according to claim 1, wherein the modulation frequency is greater than 20 kHz.

4. Pump according to any one of the preceding claims, in which: - each resonator has a peripheral portion, delimited by two flat faces, and a central portion, extending between the peripheral portion and the sleeve, the central portion thinning towards the sleeve; - each piezoelectric transducer extends along a flat face.

5. Pump according to any one of the preceding claims, wherein the flat face along which each peripheral transducer extends is delimited by a shoulder (15k), the piezoelectric transducer being inserted forcibly against the shoulder, so that the shoulder bypasses the piezoelectric transducer.

6. Pump according to any one of the preceding claims, wherein each resonator is coupled to at least one ring piezoelectric transducer, the ring piezoelectric transducer extending around the resonator, so as to generate a radial compression of the resonator, in the direction of the central axis.

7. Pump according to claim 6, in which each piezoelectric transducer is force-inserted around the resonator to which it is connected.

8. Pump according to any one of the preceding claims wherein each resonator is coupled to two annular piezoelectric transducers, extending around the resonator, and offset in a direction parallel to the central axis, the central unit being configured to power the piezoelectric transducers so as to generate a displacement of the sleeve, along the central axis and / or a compression of the sleeve perpendicular to the central axis.

9. Pump according to claim 8, wherein each piezoelectric transducer having a dipole moment: - the dipole moments of the piezoelectric transducers coupled to the same resonator are oriented in the same direction, in which case the control unit is configured to supply said piezoelectric transducers in phase; - the dipole moments of the piezoelectric transducers coupled to the same resonator are oriented in two opposite directions, in which case the control unit is configured to supply said piezoelectric transducers electrical in opposite phase; - so as to generate a radial compression of the sleeve predominating over a displacement of the sleeve along the central axis.

10. Pump according to claim 8 in which each piezoelectric transducer having a dipole moment: - the dipole moments of the piezoelectric transducers coupled to the same resonator are oriented in the same direction, in which case the control unit is configured to supply said piezoelectric transducers in opposite phase; - the dipole moments of the piezoelectric transducers coupled to the same resonator are oriented in two opposite directions, in which case the control unit is configured to supply said piezoelectric transducers in phase; - so as to generate a displacement of the sleeve, along the central axis, predominating over a compression of the sleeve.

11. Pump according to claim 8, wherein the control unit is configured to supply said piezoelectric transducers with a predetermined phase shift, between 0° and 180°, so as to obtain a predetermined ratio between the displacement of the sleeve around the central axis and the compression of the sleeve.

12. Pump according to any one of the preceding claims, comprising the capillary (2), the capillary being press-fitted between each sleeve.

13. Pump according to claim 12, wherein the capillary is rigid.

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