Aerosol generator for an inhalation device

Abstract

The present invention provides an aerosol generator (21) for an inhalation device, comprising a vibratable membrane (25), a support member (22), a flexible connector (40), and an annular piezoelectric element (30) having a first conductive region (33) and a second conductive region (34) on its first surface (31) and second surface (32). The second conductive region (34) extends onto the first surface of the piezoelectric element to form a contact region (38), such that there are two electrical contacts on the first surface (31). The flexible connector (40) has a surface (42) that is an electrical insulator and has a first conductive region (47) and a second conductive region (48) respectively corresponding to the first conductive region (34) and the contact region (38) on the piezoelectric element. The flexible connector has two "S"-shaped legs (43, 44) for electrical connection to a controller that supplies drive current to the piezoelectric element.

Description

Field of the Invention

[0001] The present invention relates to an aerosol generator for an inhalation device, in particular a vibrating mesh nebulizer. Background Art

[0002] Aerosols for medical inhalation treatment typically contain an active ingredient dissolved or suspended in an aerosol liquid (usually water). For deep lung penetration, a uniform distribution of aerosol droplets with a droplet size of about 5 μm is required. A vibrating mesh nebulizer is a type of device for generating such aerosols. These devices include a vibrator, such as a piezoelectric element, which is excited at ultrasonic frequencies to induce vibrations; a membrane (sometimes called a mesh), having a large number of micropores (i.e., through-holes) with diameters typically ranging from 1 μm to 10 μm; and a reservoir that supplies the liquid drug formulation to the membrane. Such nebulizers typically have a piezoelectric element (a "piezoelectric plate") in the form of an annular ring, with one electrical contact (e.g., a positive electrode) on its upper surface and another electrical contact (e.g., a negative electrode) on its lower surface.

[0003] Many vibrating mesh nebulizers have a membrane disposed on an annular piezoelectric plate with a central hole. Either the membrane is directly attached to the piezoelectric plate, or both the mesh and the piezoelectric plate are attached to a support substrate, such as a planar metal ring. The piezoelectric plate expands and contracts radially in response to the applied voltage, thereby bending the membrane directly or through the substrate. Such nebulizers are disclosed, for example, in US2003 / 047620, US9027548, WO2012 / 046220, and WO2015 / 193432. US2010 / 0044460 discloses a vibrating mesh nebulizer that operates in a different manner. The piezoelectric plate is attached to a flange at one end of a transducer, and the membrane is attached to the other end. The piezoelectric plate causes the transducer to vibrate longitudinally, which in turn transfers the vibrations to the membrane. Thus, the membrane vibrates in a longitudinal "piston" mode, rather than being bent by the radial vibration of the piezoelectric plate. In each type of vibrating mesh nebulizer, the voltage is applied to the piezoelectric plate through two electrical contacts, one on each side. For example, a metal substrate can form a contact on one side, while a pin can contact a conductive layer applied to the other side. Each contact has a wire or other connector (such as a flexible strip connector) for connecting to a power source. This type of arrangement requires many different components. US2019 / 329281 discloses a first type of nebulizer in which the two electrical contacts to the piezoelectric plate are located on the same surface. Summary of the Invention

[0004] The inventors of the present invention have determined an improved way of arranging electrical contacts to a piezoelectric plate in an aerosol generator. In a first aspect, the present invention provides an aerosol generator comprising a vibratable membrane, a support member, and an annular piezoelectric element having a first surface with a first conductive region, a second surface with a second conductive region, an inner edge, and an outer edge. The second conductive region extends across at least part of the inner edge or the outer edge onto the first surface of the piezoelectric element to form a contact region. The first conductive region and the contact region are spaced apart on the first surface. The aerosol generator further comprises a flexible connector having a surface that is an electrical insulator and having a first conductive region and a second conductive region that respectively correspond to the first conductive region and the contact region on the piezoelectric element. The flexible connector has two "S"-shaped legs for making electrical connection to a controller that supplies drive current to the piezoelectric element.

[0005] The term "S-shaped" means that the legs have two reverse bends, curves, or corners. The bends / curves / corners can be such that the legs lie in the plane of the flexible connector. Alternatively, the bends / curves / corners can be such that the legs are arranged outside the plane of the flexible connector.

[0006] The second conductive region on the piezoelectric element can extend across part of the outer edge or across part of the inner edge to form a contact region on the first surface. The second conductive region on the piezoelectric element can extend across the entire outer edge or across the entire inner edge to form a contact region.

[0007] The first and second conductive regions can respectively cover most of the first and second surfaces of the piezoelectric element.

[0008] The piezoelectric element can be connected to the flexible connector by a layer of anisotropic conductive paste or anisotropic conductive tape.

[0009] The conductive regions on the piezoelectric element can be molded silver layers.

[0010] The support member of the aerosol generator can comprise a hollow tubular body having a flange and a second end, the flange being located at or near the first end to which the piezoelectric element is attached, and the membrane being mounted on or in the second end. Alternatively, the support member can comprise a substantially planar annular portion or disc, and the membrane can be in contact with the piezoelectric element, or the membrane and the piezoelectric element can be mounted on the support member, for example on opposite sides of the support member.

[0011] In a second aspect, the present invention provides an inhalation device comprising an aerosol generator according to the first aspect of the present invention. The inhalation device may comprise: an aerosol head comprising the aerosol generator; a base unit having one or more air inlets, an air outlet and a recess; and a mouthpiece member which can be inserted into the recess and has an air inlet attachable to the air outlet of the base unit, a lateral opening for receiving the aerosol generator, and an aerosol outlet; wherein the base unit, the mouthpiece member and the aerosol head are detachably connected to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 An exploded view of a known aerosol generator is shown.

[0013] Figure 2A and Figure 2B shows Figure 1 the piezoelectric plate used in the aerosol generator of

[0014] Figure 3 An exploded view of an aerosol generator according to the present invention is shown.

[0015] Figure 4A and 4B shows Figure 3 the electrical contacts on the piezoelectric plate for the aerosol generator of

[0016] Figure 5 shows the flexible connector used with the piezoelectric plate of FIG. 4.

[0017] Figure 6 shows Figure 3 a cross-section of the interface between the piezoelectric plate and the flexible connector in the aerosol generator of

[0018] Figure 7A and 7B shows other flexible connectors used with the piezoelectric plate of FIG. 4.

[0019] Figure 8A and 8B shows a second configuration of the electrical contacts on the piezoelectric plate.

[0020] Figure 9 shows the flexible connector used with the piezoelectric plate of FIG. 8.

[0021] Figure 10A and 10B shows a third configuration of the electrical contacts on the piezoelectric plate.

[0022] Figure 11A and 11B shows a fourth configuration of the electrical contacts on the piezoelectric plate.

[0023] Figure 12 Shows an exploded view of a vibrating membrane atomizer device using an aerosol generator according to the present invention. Detailed Description

[0024] Figure 1 Shows an exploded view of a known aerosol generator of the type disclosed in US2010 / 0044460. The aerosol generator 1 has a transducer 2 formed by a hollow tubular stainless steel body 4 with a flange 3 having a relatively large wall thickness, and the flange 3 serves as a stress concentration zone at one end. A membrane 5 having a large number of holes with an opening range of about 1 μm to about 10 μm is mounted on or within the other end of the tubular body. The internal volume of the tubular body forms a reservoir into which the liquid to be atomized is filled.

[0025] The transducer 2 is designed such that the minute vibrations of the piezoelectric plate 6 are amplified into larger vibrations of the membrane 5. The piezoelectric plate 6 is an annular single-layer or multi-layer ceramic and is thicker than the piezoelectric plates typically used in aerosol generators where the membrane is in direct contact with the piezoelectric plate (or is only separated by a substantially planar substrate). The stress concentration zone 3 has a relatively large mass. When the piezoelectric plate 6 is driven, it vibrates longitudinally (i.e., in a direction parallel to the axis of symmetry of the transducer 2), causing a displacement of the flange at the micron level. These micron-level displacements are amplified by the tubular body 4 of the transducer and cause the membrane 5 to vibrate in a longitudinal mode, typically at a frequency in the range of 50 to 200 kHz. The vibration of the membrane causes the formation and emission of aerosol droplets through the holes. The membrane can be made of plastic, silicon, ceramic, or more preferably metal, and can be adhered to the end or near the end of the transducer by various methods such as bonding, brazing, crimping, or laser welding.

[0026] Figure 2A and Figure 2B Show the upper surface 8 and the lower surface 7 of the piezoelectric plate 6, respectively. Except for the uncoated areas 19a at the inner edge 17 and the uncoated areas 19b at the outer edge 18, the conductive silver template layer 15 covers the lower surface 7. Similarly, except for the uncoated areas 19a, 19b, the second conductive silver template layer 16 covers the upper surface 8. The silver template layers 15, 16 form two electrical contacts, and the uncoated areas 19a, 19b prevent short circuits between the contacts.

[0027] The first flexible electrical connector 9 and the second flexible electrical connector 10 are respectively adjacent to the lower surface 7 and the upper surface 8 of the piezoelectric plate. Each connector has legs 11, 12 through which it is electrically connected to a printed circuit board (PCB). The connectors are bonded to the piezoelectric plate with a conductive adhesive (such as an anisotropic conductive film (ACF)); the second connector 10 (and thus the piezoelectric plate) is also bonded to the lower side of the flange 3, for example by an epoxy adhesive 13. The connectors form an electrical connection with the silver layer through the conductive adhesive, so that an electric field can be applied to the piezoelectric plate.

[0028] In Figure 1 the configuration shown, the second flexible connector 10 is located between the piezoelectric plate 6 and the flange 3. Thus, the second flexible connector 10 can absorb some of the mechanical energy from the piezoelectric plate, thereby reducing vibration. This can be avoided by an alternative configuration in which the second flexible connector 10 is located on the other side of the flange 3 such that the piezoelectric plate 6 is directly attached to the flange. In this alternative configuration, the electrical connection from the second flexible connector 10 to the upper side 8 of the piezoelectric plate is achieved through the flange 3 (which is metallic). However, it is necessary to form a good electrical and mechanical connection between the flange 3 and the upper surface 8 of the piezoelectric plate, which may be difficult to achieve.

[0029] Figure 3 An exploded view of an aerosol generator 21 according to the present invention is shown, similar to Figure 1 the aerosol generator. The transducer 22 has a flange 23 and a tubular body 24, and the piezoelectric plate 30 is attached to the flange 23, for example, by an epoxy adhesive 27. The tubular body 24 has a membrane 25 at its end, as Figure 1 . However, in Figure 3 there is only one flexible connector 40 which is adjacent to the lower surface 31 of the piezoelectric plate 30. The upper surface 32 of the piezoelectric plate 30 is directly bonded to the lower side of the flange 23. The flexible connector 40 has an annular contact portion 41 which has an upper surface 42 and two legs 43, 44 through which it forms an electrical connection with the PCB at the feet 45, 46. The flexible connector 40 is bonded to the piezoelectric plate by a layer of anisotropic conductive paste 50 (ACP).

[0030] Figure 4A and Figure 4B show the upper surface 32 and the lower surface 31 of the piezoelectric plate respectively. First and second conductive silver template layers 33, 34 cover most of the lower (first) surface 31 and the upper (second) surface 32 respectively. As Figure 2A and 2B shown, there are uncoated areas 35a at the inner edge 36 of the piezoelectric plate. Another uncoated area 35b occupies most of the outer edge 37. However, compared with Figure 2A and 2BIn contrast, the lower surface 31 has a detour portion 35c in the uncoated area 35b away from the outer edge 37, such that the first conductive layer 33 has a narrow portion 39. The second conductive layer 34 accordingly extends across a portion of the outer edge 37a and extends to the lower surface to form a small contact area 38 defined by the detour portion 35c. The uncoated detour portion 35c separates the contact area 38 from the first conductive layer 33, such that current cannot flow directly between the first and second conductive layers.

[0031] Figure 5 The upper surface 42 of the flexible connector 40 is shown, which faces the lower surface of the piezoelectric plate when assembled in an aerosol generator. The surface layer of the connector 40 is an electrical insulator (such as polyimide), except for two conductive areas 47, 48 formed of, for example, gold-plated copper. These areas correspond respectively to the positions of the first conductive layer 33 and the small contact area 38 of the second conductive layer on the piezoelectric plate. The conductive areas 47, 48 are connected to the PCB through tracks within each leg 43, 44, and each leg 43, 44 terminates at a contact point on each foot 45, 46. The legs are in the same plane as the annular contact portion 41 and are S-shaped (when viewed from above), which makes the legs more flexible. This separates the piezoelectric plate from the fixed connection between the feet 45, 46 of the flexible connector and the PCB. This minimizes the damping of the transducer vibration by the flexible connector, which would otherwise reduce the aerosol output rate from the membrane.

[0032] Figure 6 A cross-section of the interface between the small contact area 38 on the lower surface 31 of the piezoelectric plate and the conductive area 48 on the upper surface 42 of the flexible connector is shown. There is an anisotropic conductive paste 50 between these two areas. The ACP contains conductive particles in a non-conductive binder. When heat and pressure are applied, a thin layer 51 of the ACP is formed between the contact area 38 and the conductive area 48; a thicker layer 52 is formed where there is no conductive area on the flexible connector. The thin layer 51 is thin enough such that the conductive particles in the ACP span the gap between the contact area 38 and the conductive area 48, thus forming an electrical connection. (A similar thin layer is formed between the other conductive areas 33, 47). However, the thicker layer 52 is wider than the size of the conductive particles, so the particles remain isolated from each other within the non-conductive binder. Therefore, there is no electrical connection through the thicker layer 52, which prevents short circuits. The flexible connector can alternatively be attached to the piezoelectric plate by other means of preventing short circuits, such as using a non-conductive glue and an appropriate mask.

[0033] Figure 7A and 7B shows Figure 4A and 4B a second embodiment of a flexible connector 60 for use with a piezoelectric plate. Figure 7Ashows the upper surface 62 of the flexible connector 60 which, when assembled in the aerosol generator, faces the lower surface of the piezoelectric plate. The surface layer of the connector 60 is an electrical insulator (such as polyimide) except for two conductive regions 67, 68 formed of, for example, gold-plated copper. These regions correspond respectively to the positions of the first conductive layer 33 and the small contact regions 38 of the second conductive layer on the piezoelectric plate, but are arranged in a manner different from Figure 5 that of the flexible connector. The first conductive region 67 is in the form of a complete ring disposed at the inner edge of the annular contact portion 61 such that the first conductive region 67 contacts the first conductive layer 33 and does not contact the small contact regions 38. The first conductive region 67 is connected to a first track 69 disposed along the first leg 63. The second conductive region 68 is in the form of a small circle (similar to Figure 5 the second conductive region 48 in Figure 7B shows a perspective view of the flexible connector as viewed from below (so its upper surface is not visible). The legs 63, 64 curve out of the plane of the annular contact portion 61 and are S-shaped when viewed from the side. Thus, compared with the flexible connector in Figure 5 , the S-shape is in a different plane but still increases the flexibility of the legs in a similar manner. This separates the piezoelectric plate from the fixed connection between the feet 65, 66 of the flexible connector and the PCB, minimizing the damping of the transducer vibrations by the flexible connector.

[0034] Figure 8A and 8B shows an alternative configuration of the conductive silver template layers 133, 134 on the piezoelectric plate. This is similar to the embodiments in Figure 4A and 4B except that the detour portion 135c is formed in the uncoated region 135a of the inner edge 136 (instead of the outer edge 137). The second conductive layer 134 covers most of the upper surface 132 and also extends across a portion of the inner edge 136a and extends to the lower surface to form the small contact region 138. As shown in Figure 9 , two conductive regions 147, 148 on the upper surface 142 of the flexible connector 140 are shaped to correspond to the first conductive layer 133 and the small contact region 138 on the piezoelectric.

[0035] Figure 10A and 10B shows Figure 4A and 4BVariant of the embodiment, where there is an uncoated area 235a at the inner edge 236 of the piezoelectric plate as described above, but the uncoated area 235b is at a shorter distance on the lower surface 231 around the entire outer edge 237. The second conductive layer 234 extends over the entire outer edge 237 and extends to the lower surface 231 to form an annular contact area 238. Figure 11A and 11B shows Figure 8A and 8B Variant of the embodiment, where there is an uncoated area 335a at the outer edge 337 of the piezoelectric plate as described above, but the uncoated area 335b is at a short distance on the lower surface 331 around the entire inner edge 336. The second conductive layer 334 extends over the entire inner edge 336 and extends to the lower surface 331 to form an annular contact area 338. In each case, the shapes of the two conductive areas (not shown) on the upper surface of the flexible connector correspond to the conductive layers 233, 238 and 333, 338 on the piezoelectric plate respectively.

[0036] Placing the two contacts on the same side of the piezoelectric plate has the advantage that a single connector with positive and negative connections can be used instead of two connectors as in known aerosol generators. Therefore, fewer components are required, reducing costs and simplifying the assembly process. Fewer components also improve the reliability and lifespan of the aerosol generator as it eliminates potential failure points.

[0037] It is possible to simply have two connections on one side of the piezoelectric plate and no conductive area on the other side. However, this would result in reduced membrane vibration and thus poorer performance as the electric field applied between the contacts does not properly activate the entire piezoelectric plate. In the present invention, the conductive layer covers almost all the surfaces, such that the electric field is applied uniformly across the entire piezoelectric plate. This results in uniform deformation of the piezoelectric plate and thus good membrane vibration, while still having the benefit of fewer components. Additionally, maximizing the contact area on the piezoelectric plate minimizes the resistance generated by the contact.

[0038] Although Figure 4A and 4B the contact configurations shown in 8A and 8B, 10A and 10B, 11A and 11B all work well, the configuration of Figure 4A and 4B is preferred. This is because it is simpler to produce a conductive layer that wraps around a small area at the outer edge of the piezoelectric plate than to produce a conductive layer that wraps around part or all of the inner edge (as shown in Figure 8A and 8B compared to 11A and 11B) or around the entire or most of the outer edge (as shown in Figure 10A and 10B ).

[0039] Although the present invention is described with reference to an aerosol generator of the type described in US2010 / 0044460, in which the membrane is spaced from the piezoelectric plate by a tubular transducer body, the present invention can also be used in aerosol generators of the type described in US2003 / 047620, US9027548, WO2012 / 046220 and WO2015 / 193432, in which the membrane is in direct contact with the piezoelectric plate or is spaced only by a substantially planar support member.

[0040] Nevertheless, the present invention is particularly advantageous in aerosol generators of the type described in US2010 / 0044460 because the damping caused by the connector in these aerosol generators is of particular concern. Since the transducer amplifies the small vibrations of the piezoelectric plate into large vibrations of the membrane, any damping of the small vibrations is also amplified. This will result in reduced membrane vibrations and thus a reduced aerosol output rate. Replacing two flexible connectors with a single flexible connector avoids inserting a flexible connector (which causes damping) between the piezoelectric plate and the flange and also avoids forming electrical and mechanical connections between the piezoelectric plate and the flange, which can be difficult to achieve.

[0041] Figure 12Shows an exploded view of a vibrating membrane nebulizer device as described in detail in EP2724741 and WO2013 / 098334, which uses an aerosol generator of the type described in US2010 / 0044460. The device includes three parts: a base unit 60, a mouthpiece member 70, and an aerosol head 80. The base unit 60 has one or more air inlets, an air outlet 62, a groove 63 for receiving the mouthpiece member 70, and one or more key-lock members 64. The base unit contains an electronic controller that controls the operation of the nebulizer. The mouthpiece member 70 has an air inlet 71 that can be attached to the air outlet 62 of the base unit 60, a lateral opening 72 for receiving the aerosol generator 21, and an aerosol outlet 73. A mixing channel 75 extends from the air inlet 71 to the aerosol outlet 73. The mouthpiece 70 can be inserted into the groove 63 of the base unit 60. The aerosol head 80 has an aerosol generator 21, a filling chamber 82 for the liquid drug formulation to be nebulized that is in fluid contact with the upper end of the aerosol generator 21, and one or more key-lock members 83 that are complementary to the key-lock members 64 of the base unit 60. A lid 84 closes the upper end of the filling chamber 82 and prevents contamination or spillage of the liquid during use. The base unit 60, the mouthpiece 70, and the aerosol head 80 are detachably connected to each other. The device is assembled by inserting the mouthpiece member 70 into the groove 63 of the base unit 60, then placing the aerosol head 80 on the mouthpiece member 70, and engaging the key-lock member(s) 83 of the aerosol head 80 with the complementary member(s) 64 of the base unit 60 by applying a slight pressure to the aerosol head and the base unit. The aerosol generator 21 is positioned within the aerosol head 80 such that when the key-lock member(s) are engaged, the aerosol generator 21 is inserted into the lateral opening 72 of the mouthpiece 70. This forms an airtight connection between the aerosol generator 21 and the lateral opening 72 in the mouthpiece and between the air outlet 62 of the base unit 60 and the air inlet 71 of the mouthpiece 70. The base unit 60, the mouthpiece 70, and the aerosol head 80 can be separated by reversing these steps.

[0042] Example

[0043] Figure 3 The aerosol generator shown uses Figure 4A and 4B piezoelectric plates assembled. When tested with a saline solution, it was found to produce a good aerosol output rate, similar to that produced by the aerosol generator shown in Figure 1 Therefore, the aerosol generator of the present invention produces performance comparable to that of known aerosol generators, but with fewer components and is easier to manufacture.

Claims

1. An aerosol generator (21) for an atomizer, comprising: · a vibratable membrane (25), · a support member (22), · an annular piezoelectric element (30) having a first surface (31), a second surface (32), an inner edge (36), and an outer edge (37), · a first conductive region (33) and a second conductive region (34) on the first surface (31) and the second surface (32) respectively, wherein the second conductive region (34) extends across at least part of the inner edge (36) or the outer edge (37) to the first surface (31) of the piezoelectric element to form a contact region (38), and · a flexible connector (40) having a surface (42) and two "S"-shaped legs (43, 44), the surface (42) being an electrical insulator and having a first conductive region (47) and a second conductive region (48) corresponding respectively to the first conductive region (34) and the contact region (38) on the piezoelectric element, the legs (43, 44) being for electrical connection to a controller that supplies a drive current to the piezoelectric element.

2. The aerosol generator according to claim 1, wherein the second conductive region (34) extends across part of the outer edge (37a).

3. The aerosol generator according to claim 1, wherein the second conductive region (134) extends across part of the inner edge (136a).

4. The aerosol generator according to claim 1, wherein the second conductive region (234) extends across the entire outer edge (237).

5. The aerosol generator according to claim 1, wherein the second conductive region (334) extends across the entire inner edge (336).

6. The aerosol generator according to any one of claims 1 to 5, wherein the first conductive region (33) and the second conductive region (34) respectively cover most of the first surface (31) and the second surface (32).

7. The aerosol generator according to any one of claims 1 to 6, wherein the legs are in the plane of the flexible connector.

8. The aerosol generator according to any one of claims 1 to 6, wherein the legs are arranged outside the plane of the flexible connector.

9. The aerosol generator according to any one of claims 1 to 8, wherein the piezoelectric element is connected to the flexible connector (40) by a layer of anisotropic conductive paste (50) or anisotropic conductive tape.

10. The aerosol generator according to any one of claims 1 to 9, wherein the conductive regions (33, 34) on the piezoelectric element (30) are silver layers formed by molding.

11. The aerosol generator according to any one of claims 1 to 10, wherein the support member includes a hollow tubular body having a flange and a second end, the flange being located at or near the first end to which the piezoelectric element is attached, and the membrane being mounted on or in the second end.

12. The aerosol generator according to any one of claims 1 to 10, wherein the support member includes a substantially planar annular portion or disc, wherein the membrane contacts the piezoelectric element, or the membrane and the piezoelectric element are mounted on the support member.

13. An inhalation device comprising the aerosol generator (21) according to any one of claims 1 to 12.

14. The inhalation device according to claim 13, wherein the aerosol generator is the aerosol generator according to claim 11.

15. The inhalation device according to claim 14, comprising: An aerosol head (80) including the aerosol generator (21); a base unit (60) having one or more air inlets, an air outlet (62), and a groove (63); and a mouthpiece member (70) that can be inserted into the groove (63) and has an air inlet (71) attachable to the air outlet (62) of the base unit (60), a lateral opening (72) for receiving the aerosol generator (21), and an aerosol outlet (73); wherein the base unit (60), the mouthpiece member (70), and the aerosol head (80) are detachably connected to each other.

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