Method of manufacturing a vibratable head for an aerosol generator and vibratable head for an aerosol generator

Abstract

The invention relates to a method of manufacturing a vibratable head (1) for an aerosol generator (2), the vibratable head (1) comprising a support member (4), a vibratable membrane (6) supported by the support member (4) and a vibrator (8) configured to vibrate the vibratable membrane (6). The method comprises the steps of providing the support member (4), roughening a surface portion (10) of the support member (4) by laser structuring, applying an adhesive (9) to at least a part of the roughened surface portion (10) of the support member (4) and attaching at least one element to the support member (4) by at least a portion of the adhesive (9). Further, the invention relates to a vibratable head (1) manufactured by this method, an aerosol generator (2) comprising such a vibratable head (1) and a method of manufacturing such an aerosol generator (2).

Claims

1. A method of manufacturing a vibratable head for an aerosol generator, the vibratable head comprising a support member, a vibratable membrane supported by the support member, and a vibrator configured to vibrate the vibratable membrane, the method comprising the steps of providing the support member, roughening a surface portion of the support member by laser structuring, applying an adhesive to at least a part of the roughened surface portion of the support member, and attaching the vibrator and/or the vibratable membrane to the support member by at least a portion of the adhesive.

2. The method according to claim 1, wherein the adhesive is applied to the entire roughened surface portion of the support member.

3. The method according to claim 1, wherein the surface portion of the support member is roughened by laser structuring using a pulsed laser beam.

4. The method according to claim 1, wherein, in the laser structuring of the surface portion of the support member, the support member and a laser beam are moved relative to each other with a speed in the range from 500 mm/s to 10000 mm/s.

5. The method according to claim 1, wherein the support member is made of metal, preferably stainless steel.

6. The method according to claim 1, wherein a surface portion of the vibratable membrane is roughened by laser structuring.

7. The method according to claim 1, wherein the vibratable membrane is formed integrally with the support member.

8. A method of manufacturing an aerosol generator, the method comprising the steps of manufacturing a vibratable head using the method according to claim 1, and at least partially accommodating the vibratable head in a housing.

9. A vibratable head for an aerosol generator, the vibratable head comprising a support member, a vibratable membrane supported by the support member, and a vibrator configured to vibrate the vibratable membrane, wherein a surface portion of the support member is roughened by laser structuring, an adhesive is applied to at least a part of the roughened surface portion of the support member, and the vibrator and/or the vibratable membrane is attached to the support member by at least a portion of the adhesive.

10. The vibratable head according to claim 9, wherein the adhesive is applied to the entire roughened surface portion of the support member.

11. The vibratable head according to claim 9, wherein a surface portion of the vibratable membrane is roughened by laser structuring.

12. The vibratable head according to claim 9, wherein the vibratable membrane is formed integrally with the support member.

13. An aerosol generator comprising the vibratable head according to claim 10, and a housing, wherein the vibratable head is at least partially accommodated in the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Hereinafter, non-limiting examples of the invention are explained with reference to the drawings, in which:

(2) FIG. 1 shows a schematic longitudinally cut cross-sectional view of an aerosol delivery device comprising an aerosol generator according to an embodiment of the present invention;

(3) FIG. 2 shows schematic views of a part of a vibratable head according to an embodiment of the present invention, wherein FIG. 2(a) shows a schematic plan view of the part of the vibratable head and FIG. 2(b) shows a schematic cross-sectional view of the part of the vibratable head;

(4) FIG. 3 shows schematic views of a part of a vibratable head according to an embodiment of the present invention, wherein FIG. 3(a) shows a schematic plan view of the part of the vibratable head and FIG. 3(b) shows a schematic cross-sectional view of the part of the vibratable head;

(5) FIG. 4 shows schematic views of a part of a vibratable head according to an embodiment of the present invention, wherein FIG. 4(a) shows a schematic plan view of the part of the vibratable head and FIG. 4(b) shows a schematic cross-sectional view of the part of the vibratable head;

(6) FIG. 5 shows schematic views of a part of a vibratable head according to an embodiment of the present invention, wherein FIG. 5(a) shows a schematic plan view of the part of the vibratable head and FIG. 5(b) shows a schematic cross-sectional view of the part of the vibratable head;

(7) FIG. 6 shows schematic views of a part of a vibratable head according to an embodiment of the present invention, wherein FIG. 6(a) shows a schematic plan view of the part of the vibratable head and FIG. 6(b) shows a schematic cross-sectional view of the part of the vibratable head;

(8) FIG. 7 shows schematic views of a part of a vibratable head according to an embodiment of the present invention, wherein FIG. 7(a) shows a schematic plan view of the part of the vibratable head and FIG. 7(b) shows a schematic cross-sectional view of the part of the vibratable head;

(9) FIG. 8 shows schematic views of a part of a vibratable head according to an embodiment of the present invention, wherein FIG. 8(a) shows a schematic plan view of the part of the vibratable head and FIG. 8(b) shows a schematic cross-sectional view of the part of the vibratable head;

(10) FIG. 9 shows schematic views of a part of a vibratable head according to an embodiment of the present invention, wherein FIG. 9(a) shows a schematic plan view of the part of the vibratable head and FIG. 9(b) shows a schematic cross-sectional view of the part of the vibratable head;

(11) FIG. 10 shows measured surface profiles of three different roughened surface portions of support members of vibratable heads according to embodiments of the present invention.

(12) FIG. 11 shows SEM images of four different roughened surface portions of support members of vibratable heads according to embodiments of the present invention.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

(13) FIG. 1 shows a schematic longitudinally cut cross-sectional view of an aerosol delivery device 100 comprising an aerosol generator 2 according to a currently preferred embodiment of the present invention.

(14) The aerosol delivery device 100 comprises a first housing part 102 and a second housing part 108 which are joined to each other at a connection portion 118. The first housing part 102 has an aerosol chamber 104 and a mouthpiece 106. The second housing portion 108 forms a fluid chamber for receiving a fluid 110 to be aerosolised.

(15) An aerosol generator 2 is received in recesses 114, 116 formed in the second housing part 108 and the first housing part 102, respectively. The aerosol generator 2 comprises an annular housing 3 and a vibratable head 1 which is partially accommodated in the housing 3. The vibratable head 1 comprises an annular support member 4 and a circular vibratable membrane 6 supported by the support member 4. The vibratable membrane 6 is integrally formed with the support member 4. The vibratable membrane 6 and the support member 4 are made from a metal, such as stainless steel. The vibratable membrane 6 has a plurality of holes or openings (not shown).

(16) The vibratable head 1 further comprises a vibrator 8 which is configured to vibrate the vibratable membrane 6. The vibrator 8 is attached by an adhesive to a surface portion of the support member 4 which has been roughened by laser structuring. The details of the attachment of the vibrator 8 to the support member 4 will be described in more detail below with reference to FIG. 2. The vibrator 8 is an annular piezoelectric element made of ceramic.

(17) In the following, operation of the aerosol delivery device 100 for the generation and delivery of an aerosol will be described.

(18) A fluid 110 to be aerosolised, for example, a fluid comprising an active compound, such as a drug substance or a medicament, is filled into the fluid reservoir formed by the second housing part 108.

(19) The fluid 110 received in the fluid reservoir abuts the vibratable membrane 6 of the vibratable head 1.

(20) A control (not shown) is operated to supply an activation signal to the vibrator 8 via electrical contacts (not shown) of the vibrator 8, activating the vibrator 8 and thus causing the vibratable membrane 6 to vibrate. The electrical contacts of the vibrator 8 may be provided in the form of one or more conductors, e.g., one or more flexible strip conductors, for example, printed circuit board tracks or strip lines. The one or more conductors may be attached to one or more surface portions of the vibrator 8, e.g., by an adhesive.

(21) The fluid 110 abutting the membrane 6 is conveyed through the holes or openings (not shown) in the vibrating membrane 6 and thereby aerosolised into the aerosol chamber 104. The aerosol 112 thus provided in the aerosol chamber 104 is inhaled by a patient or user through the mouthpiece 106, which is arranged in fluid communication with the aerosol chamber 104.

(22) FIG. 2 shows schematic views of a part of the vibratable head 1 of the aerosol generator 2 of the aerosol delivery device 100 shown in FIG. 1. FIG. 2(a) shows a plan view of the part of the vibratable head 1. FIG. 2(b) shows a schematic cross-sectional view of the part of the vibratable head 1. In the upper parts of FIGS. 2(a) and (b), the vibrator 8 and the adhesive 9 have been omitted and, in the lower part of FIG. 2(b), a roughened surface portion 10 has been omitted for better presentability. The same form of presentation has also been used in FIGS. 3 to 9.

(23) As is indicated by a hatched area in the upper part of FIG. 2(a) and by a solid line in the upper part of FIG. 2(b), the support member 4 of the vibratable head 1 comprises an annular surface portion 10 which has been roughened by laser structuring. In the radially inward direction of the support member 4, the roughened surface portion 10 extends to the peripheral edge of the vibratable membrane 6. In the radially outward direction of the support member 4, the roughened surface portion 10 stops before the peripheral edge of the support member 4, leaving an annular non-roughened surface portion 12 at the circumference of the support member 4.

(24) The adhesive 9 is applied to the entire roughened surface portion 10 of the support member 4 (see the lower part of FIG. 2(a)), thus reliably preventing corrosion or oxidation of this surface portion 10. As is schematically shown in FIGS. 2(a) and (b), an area of an attachment surface of the vibrator 8, over which the vibrator 8 is attached to the roughened surface portion 10 by a portion of the adhesive 9, is smaller than the area of the roughened surface portion 10, thus providing the benefit of manufacturing tolerances.

(25) FIG. 3 shows schematic views of a part of a vibratable head according to another embodiment of the present invention. In FIG. 3, like elements are designated with like reference signs as in FIG. 2.

(26) The vibratable head according to the embodiment shown in FIG. 3 differs from the vibratable head 1 according to the embodiment shown in FIG. 2 in that the roughened surface portion 10 of the support member 4 extends in the radially outward direction of the support member 4 to the peripheral edge of the support member 4, as is schematically shown in FIG. 3(a) and the upper part of FIG. 3(b).

(27) FIG. 4 shows schematic views of a part of a vibratable head according to another embodiment of the present invention. In FIG. 4, like elements are designated with like reference signs as in FIGS. 2 and 3.

(28) The vibratable head according to the embodiment shown in FIG. 4 differs from the vibratable head 1 according to the embodiment shown in FIG. 2 in that, in the radially inward direction of the support member 4, the roughened surface portion 10 does not extend to the peripheral edge of the membrane 6, leaving an annular non-roughened surface portion 14 around the circumference of the membrane 6. In this way, it can be ensured in a particularly reliable manner that the roughening of the surface portion 10 does not affect the oscillatory behaviour or vibrating characteristics of the membrane 6. As is schematically shown in the lower parts of FIGS. 4(a) and (b), the adhesive 9 is applied over a surface area of the support member 4 which extends beyond the roughened surface portion 10 in the radially outward and radially inward directions of the support member 4.

(29) FIG. 5 shows schematic views of a part of a vibratable head according to another embodiment of the present invention. In FIG. 5, like elements are designated with like reference signs as in FIGS. 2 to 4.

(30) The vibratable head according to the embodiment shown in FIG. 5 differs from the vibratable head 1 according to the embodiment shown in FIG. 2 in that the vibratable membrane 6 is not formed integrally with the support member 4 but attached thereto at an annular connection portion 16. The vibratable membrane 6 may be attached to the support member 4 at the connection portion 16, for example, by welding, soldering or the like.

(31) Alternatively, the surface portion of the support member 4 at which the membrane 6 is attached thereto may be partially or entirely roughened by laser structuring and the membrane 6 may be attached to the support member 4 at the connection portion 16 by an adhesive, substantially in the same way as the vibrator 8 is attached to the roughened surface portion 10 of the support member 4.

(32) The membrane 6 has a convex portion 20 and an annular, flat peripheral portion 21 integrally formed with and surrounding the convex portion 20. The peripheral portion 21 of the membrane 6 is attached to the support member 4 at the connection portion 16.

(33) As is schematically shown in FIG. 5(a) and the upper part of FIG. 5(b), the roughened surface portion 10 extends to the peripheral edge of the peripheral portion 21 of the membrane 6 in the radially inward direction of the support member 4, but stops before the peripheral edge of the support member 4 in the radially outward direction of the support member 4, leaving the annular non-roughened surface portion 12 at the circumference of the support member 4.

(34) As is schematically shown in the lower parts of FIGS. 5(a) and (b), the adhesive 9 is applied over a surface area of the support member 4 which extends beyond the roughened surface portion 10 in the radially outward direction of the support member 4 but stops before the peripheral edge of the peripheral portion 21 of the membrane 6 in the radially inward direction of the support member 4.

(35) FIG. 6 shows schematic views of a part of a vibratable head according to another embodiment of the present invention. In FIG. 6, like elements are designated with like numerals as in FIGS. 2 to 5.

(36) The vibratable head according to the embodiment shown in FIG. 6 differs from the vibratable head according to the embodiment shown in FIG. 5 in that the roughened surface portion 10 of the support member 4 does not extend to the peripheral edge of the peripheral portion 21 of the vibratable membrane 6 in the radially inward direction of the support member 4, leaving the annular non-roughened surface portion 14 along the outer circumference of the membrane 6.

(37) In this way, it can be ensured in a particularly reliable manner that the oscillatory behaviour or vibration characteristics of the vibratable membrane 6 are not affected by the roughening of the surface portion 10.

(38) As is schematically shown in the lower parts of FIGS. 6(a) and (b), the adhesive 9 is applied over a surface area of the support member 4 which stops before the outer peripheral edge of the roughened surface portion 10 in the radially outward direction of the support member 4 and the inner peripheral edge of the roughened surface portion 10 in the radially inward direction of the support member 4.

(39) FIG. 7 shows schematic views of a part of a vibratable head according to another embodiment of the present invention. In FIG. 7, like elements are designated with like numerals as in FIGS. 2 to 6.

(40) The vibratable head according to the embodiment shown in FIG. 7 differs from the vibratable head according to the embodiment shown in FIG. 5 in that the roughened surface portion 10 of the support member 4 extends to the peripheral edge of the support member 4 in the radially outward direction of the support member 4.

(41) As is schematically shown in the lower parts of FIGS. 7(a) and (b), the adhesive 9 is applied over a surface area of the support member 4 which extends to the peripheral edge of the peripheral portion 21 of the membrane 6 in the radially inward direction of the support member 4 but stops before the peripheral edge of the support member 4 in the radially outward direction of the support member 4.

(42) FIG. 8 shows schematic views of a part of a vibratable head according to another embodiment of the present invention. In FIG. 8, like elements are designated with like reference signs as in FIGS. 2 to 7.

(43) The vibratable head according to the embodiment shown in FIG. 8 differs from the vibratable head according to the embodiment shown in FIG. 7 in that a peripheral surface portion 17 of the vibratable membrane 6, i.e., of the peripheral portion 21 thereof, is roughened by laser structuring.

(44) The roughened surface portion 17 extends in the radially inward direction of the membrane 6 to the peripheral edge of the convex portion 20 of the membrane 6 and in the radially outward direction of the membrane 6 to the peripheral edge of the peripheral portion 21 of the membrane 6.

(45) The adhesive 9 is applied to the roughened surface portion 17 of the vibratable membrane 6. The adhesive is applied to the roughened surface portions 10, 17 so as to extend over a step 18 formed between the membrane 6 and the support member 4, as is schematically shown in the lower part of FIG. 8(b). In the radially outward direction of the support member 4, the surface area of the support member 4 over which the adhesive 9 is applied stops before the peripheral edge of the support member 4.

(46) By applying the adhesive to the roughened surface portion 10 of the support member 4 and the roughened surface portion 17 of the vibratable membrane 6 in this way, the step 18 formed between membrane 6 and support member 4 is reliably sealed, thus particularly efficiently preventing corrosion or oxidation of the membrane 6 and/or the support member 4 at the connection portion 16.

(47) FIG. 9 shows schematic views of a part of a vibratable head according to another embodiment of the present invention. In FIG. 9, like elements are designated with like reference signs as in FIGS. 2 to 8.

(48) The vibratable head according to the embodiment shown in FIG. 9 differs from the vibratable head according to the embodiment shown in FIG. 8 in that the roughened surface portion 17 of the vibratable membrane 6 does not extend to the peripheral edge of the convex portion 20 of the membrane 6 in the radially inward direction of the membrane 6, leaving an annular non-roughened surface portion 22 along the circumference of the convex portion 20.

(49) The adhesive 9 is applied to the roughened surface portions 10, 17, thereby sealing the step 18 between the vibratable membrane 6 and the support member 4. By leaving the annular non-roughened surface portion 22 at the circumference of the convex portion 20, it can be particularly reliably ensured that the oscillatory behaviour or the vibrating characteristics of the vibratable membrane 6 are not affected by the roughening of the surface portion 17.

(50) As is schematically shown in the lower parts of FIGS. 9(a) and (b), the adhesive 9 is applied over a surface area of the support member 4 which extends to the peripheral edge of the convex portion 20 of the membrane 6 in the radially inward direction of the support member 4 but stops before the peripheral edge of the support member 4 in the radially outward direction of the support member 4.

(51) In the following, measurements performed on surface portions of different support members which had been roughened using different laser structuring processes will be discussed. In particular, in these laser structuring processes, the processing speed, i.e., the speed with which the support member and the laser beam were moved relative to each other, was varied, resulting in variations of the roughness of the roughened surface portion. Moreover, for the surface portions which had been roughened at the same processing speed, variations in the average surface roughness R.sub.z and the roughness average R.sub.a were achieved by varying further process parameters, namely the laser power, the laser focus position, the laser pulse frequency and the number of laser passes. The surface profiles of the roughened surface portions were measured using a Perthometer with a diamond tip and an inductive transducer. The Perthometer was moved over the surface portion to be measured, allowing the diamond tip to follow the surface roughness, and the resulting vertical displacement of the diamond tip was converted into an electrical signal.

(52) The average surface roughnesses R.sub.z and roughness averages R.sub.a in m and the processing speed modes for the different roughened surface portions are given in Table 1 below. The processing speeds of modes 1 to 3 are in the range from 500 mm/s to 10,000 mm/s. The processing speed of mode 1 is higher than the processing speed of mode 2 and the processing speed of mode 2 is higher than the processing speed of mode 3.

(53) TABLE-US-00001 TABLE 1 Processing Speed Average Surface Roughness Average [mode number] Roughness R.sub.Z [m] R.sub.a [m] 1 9.51 1.85 1 8.78 1.77 1 9.54 1.52 2 10.14 2.07 2 19.71 2.50 2 11.56 2.07 3 13.35 2.05 3 11.98 2.26 3 9.77 2.12

(54) Adhesive was applied to the above roughened surface portions and the durability of the joint formed between the adhesive and the roughened surface portion was determined.

(55) The solidity and durability of the adhesive on the laser structured substrate was tested by simulating a stress test. The stress test indicates the maximal reliability of the adhesive bonding.

(56) A simulated use test was performed, in which the use of the vibratable head by a patient was simulated under substantially realistic conditions. The test was carried out by performing a repeated sequence of nebulisation, cleaning and thermal disinfection in the same manner as in normal operation. The stress test also included using an autoclave for thermal disinfection/sterilisation up to 50 cycles. For example, an autoclave of the company Systec can be used for this purpose, e.g., Autoklav 3850 EL.

(57) As a further test, a frequency band analysis was performed to analyse the vibratable head of the aerosol generator. Especially, an impedance measurement of the vibratable head was performed. The analysis or measurement of the vibrational spectrum may show a shift in resonance pattern of the vibratable head that can indicate invisible changes of the quality of the adhesive bonding. In the normal case, the resonance frequency of the vibratable head is within the specified range.

(58) An additional test regarding the aerosol performance of the vibratable head, such as aerosol output rate, particle size distribution (MMD, GSD), was performed to ensure the correct and specified performance characteristics of the vibratable head in the aerosol generator.

(59) It was found that a particularly high durability of the adhesive joint was achieved for roughened surface portions having an average surface roughness R.sub.z in the range from 5.0 to 18.0 m and a roughness average R.sub.a in the range from 0.5 to 3.0 m. Particularly durable adhesive joints were obtained by laser structuring with an adequate processing speed, for example mode number 3 (Table 1).

(60) Measurement profiles for the roughened surface portions shown in Table 1 above which were provided with laser structuring at an adequate processing speed are shown in FIG. 10. As has been detailed above, these profiles were measured using a Perthometer with a diamond tip and an inductive transducer.

(61) As can be seen from the surface profiles shown in FIG. 10, roughened surfaces with an ordered roughness can be created by laser structuring.

(62) FIG. 11 shows SEM images of four different roughened surface portions of support members of vibratable heads according to embodiments of the present invention. The surface portions shown in FIG. 11 were roughened by laser structuring with an adequate processing speed, an adequate laser power and an adequate laser pulse frequency. For the surface portions shown in FIGS. 11(a), (c) and (d), the laser was applied in a first pattern, while for the surface portion shown in FIG. 11(b), the laser was applied in a second pattern. The laser structuring processes employed for roughening the surface portions shown in FIGS. 11(a), (c) and (d) differ in the number of laser pulses, which is medium for FIG. 11(a), high for FIG. 11(c) and low for FIG. 11(d). The number of laser pulses for the surface portion shown in FIG. 11(b) is medium. As is evident from FIG. 11, varying the number of laser pulses and/or the laser structuring pattern allows for the resulting surface profile to be varied in a controlled manner.

(63) Alternatively or additionally, the processing speed and/or the laser power and/or the laser pulse frequency may be varied to create different laser structuring patterns.

(64) The foregoing embodiments and their variants have been disclosed for illustrative purposes only, and further variation is wholly possible within the capabilities of the skilled reader. Accordingly, the appended claims are intended to cover all modifications, substitutions, alterations, omissions and additions which one skilled in the art could achieve from the foregoing disclosure, taking into account his own general and specialist knowledge and expertise.