GB2443228A - Piezo-electric loudspeaker - Google Patents

Piezo-electric loudspeaker Download PDF

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Publication number
GB2443228A
GB2443228A GB0621218A GB0621218A GB2443228A GB 2443228 A GB2443228 A GB 2443228A GB 0621218 A GB0621218 A GB 0621218A GB 0621218 A GB0621218 A GB 0621218A GB 2443228 A GB2443228 A GB 2443228A
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GB
United Kingdom
Prior art keywords
diaphragm
loudspeaker according
sound
piezo
coupled
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB0621218A
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GB2443228B (en
GB0621218D0 (en
Inventor
Gary Paul Nicholson
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Individual
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Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to GB0621218A priority Critical patent/GB2443228B/en
Publication of GB0621218D0 publication Critical patent/GB0621218D0/en
Priority to PCT/GB2007/004067 priority patent/WO2008050123A1/en
Publication of GB2443228A publication Critical patent/GB2443228A/en
Application granted granted Critical
Publication of GB2443228B publication Critical patent/GB2443228B/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/34—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by using a single transducer with sound reflecting, diffracting, directing or guiding means
    • H04R1/345—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by using a single transducer with sound reflecting, diffracting, directing or guiding means for loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/40—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers
    • H04R1/403—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers loud-speakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
    • H04R7/12—Non-planar diaphragms or cones
    • H04R7/14—Non-planar diaphragms or cones corrugated, pleated or ribbed
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/30—Combinations of transducers with horns, e.g. with mechanical matching means, i.e. front-loaded horns

Abstract

A piezo-electric loudspeaker 1 includes at least one piezo-electric actuator 2, at least one corrugated diaphragm 4 with multiple sound-radiating zones 5,6,7 for different frequencies, and at least one sound-radiating front part 8, e.g. a phase plug or phase equalizer, with multiple compression regions 9,10,11, and multiple expansion regions 12,13,14, each adapted to operate with at least one of the multiple sound-radiating zones 5,6,7 of the diaphragm 4. A variety of embodiments are disclosed (figs 5-10) that involve multiple actuators and multiple diaphragms.

Description

Piezo-electric Loudspeaker This invention relates to a piezo-electric
loudspeaker with improved dispersion and frequency response characteristics.
Piezo-electric loudspeakers have traditionally been used in high sound pressure level applications such as horn-loaded loudspeaker assemblies for public address and live music. In typical applications, the range of frequencies reproduced by this kind of speaker is around 2kHz upwards. Often the quality of audio signal reproduction from such loudspeakers is limited, and the dispersion of the high-frequency sound is not as wide as would be desired.
The purpose of this invention is to overcome these undesirable characteristics of conventional piezo-electric loudspeakers, and to provide a useable audible frequency range from approximately 20kHz down to below approximately 100Hz.
In this description reference to a front or front-facing part means a part positioned generally on the part of a loudspeaker facing towards a listener, and reference to a rear or rear-facing part means a part positioned generally facing away from a listener.
One aspect of this invention is a piezo-electric loudspeaker characterized by having at least one piezo-electric actuator for audio frequency signals, coupled to at least one sound-radiating diaphragm with at least one corrugated zone, and at least one sound-directing front part with at least one compression region and at least one expansion region arranged to interact with the said corrugated zone(s) of the said diaphragm or diaphragms, wherein the totality of said compression and expansion region(s) is adapted to control sound pressure levels over several overlapping or discreet frequency ranges.
Another aspect of the invention is the provision of at least one sound-directing front part with multiple compression and expansion regions for the sound waves radiating from the front part of the said diaphragm or diaphragms, wherein each of said compression and expansion regions relates to at least one region of at least one said diaphragm. The said compression and expansion regions are preferably adapted to compensate for phase shifts at the different frequencies. The said compression and expansion regions are preferably adapted to minimize differences in sound pressure levels at the different frequencies. The said compression and expansion regions are preferably adapted to provide an effective driver size small enough to prevent beaming of the sound waves at the particular frequencies associated with each region or regions.
Another aspect of the invention is the provision of at least one sound-directing rear part with multiple compression and expansion regions for the sound waves radiating from the rear part of the said diaphragm or diaphragms. The said compression and expansion regions are preferably adapted to compensate for phase shifts at the different frequencies. The said compression and expansion regions are preferably adapted to minimize differences in sound pressure levels at the different frequencies. The said compression and expansion regions are preferably adapted to provide an effective driver size small enough to prevent beaming of the sound waves at the particular frequencies associated with each region or regions.
Another aspect of the invention is the provision of at least one sound-directing rear part with multiple compression and expansion regions for the sound waves radiating from the rear part of the said diaphragm or diaphragms, wherein each of said compression and expansion regions relates to at least one region of at least one said diaphragm. The said sound-directing rear part(s) is (are) adapted to provide a path for low frequency sound waves, preferably below 200Hz. The said sound-directing rear part(s) is (are) preferably adapted to provide a wave-guide, band-pass, transmission line, bass-reflex or similar arrangement. The said compression and expansion regions are preferably adapted to minimize sound pressure levels at frequencies above the required frequency. The said compression and expansion regions are preferably adapted to provide at least one exit for the said low frequency sound waves in or through at least one front part.
Another aspect of the invention is the provision of at least a second sound-radiating diaphragm, acting at an angle between 0 and 180 degrees to at least one first diaphragm(s).
The said at least second diaphragm(s) being preferably adapted to act in phase or out of phase with the said at least first diaphragm(s), and coupled to the same or different piezo-electric actuators as the said at least first diaphragm(s).
Another aspect of the invention is the provision of at least a second sound-radiating diaphragm, positioned to the rear of at least one first diaphragm(s). The said at least second diaphragm(s) being preferably adapted to enclose a volume between the rear of the said at least first diaphragm and the rear of the said at least second diaphragm, and acting in phase or out of phase with the said at least first diaphragm.
Another aspect of the invention is the provision of at least one sound-directing front part with multiple compression and expansion regions for the sound waves radiating from the front part of the said diaphragm or diaphragms, wherein each of said compression and expansion regions relates to at least one region of at least one said diaphragm, and said sound-directing front part is adapted to be coupled to said diaphragm or diaphragms in at least one location on at least one diaphragm. The said sound-directing front part may alternatively be coupled to at least one piezo-electric element, wherein said piezo-electric element may be coupled or not coupled to at least one said diaphragm or diaphragms. It is anticipated that said sound- directing front part(s) may be coupled to combinations of said diaphragm(s) and said piezo-electric actuator(s).
The said diaphragm or diaphragms may be manufactured from any suitable material, such as paper, plastics, cloth, etc., and may be formed as one continuous piece of material or assembled from several pieces of similar or dissimilar materials.
The said sound-directing front part may be manufactured as one continuous piece of material, for example by injection moulding, or assembled from several pieces of similar or dissimilar materials.
The said sound-directing rear part may be manufactured as one continuous piece of material, for example by injection moulding, or assembled from several pieces of similar or dissimilar materials.
The said coupling means for the said piezo-electric actuator(s) may include bonding, mechanical fixing, and partial or complete encapsulation within the said diaphragm.
Preferred embodiments of the invention are described with reference to the accompanying drawings in which: Figure 1 shows a typical cross-section of a loudspeaker according to the invention.
Figures 2a to 2d show the effect of the diaphragm movement at different frequencies.
Figure 3 shows a typical embodiment for circular and elliptical styles.
Figure 4 shows a typical embodiment for various polygonal styles.
Figure 5 shows an alternative embodiment wherein multiple piezo elements are coupled to a single diaphragm.
Figure 6 shows an alternative embodiment wherein multiple piezo elements are coupled to multiple diaphragms.
Figure 7 shows another alternative embodiment wherein multiple piezo elements are coupled to a single diaphragm.
Figure 8 shows an alternative embodiment wherein the piezo elements are coupled to inclined regions of a single diaphragm, and the sound-radiating front part is coupled to the diaphragm.
Figure 9 shows an alternative embodiment wherein the piezo elements are coupled to both inclined and non-inclined regions of a single diaphragm, and the sound-radiating front part is coupled to the diaphragm.
Figure 10 shows an alternative embodiment with compression and expansion regions formed in the front sound-directing part by an array of non-uniform cross-section holes, and the sound-radiating front part is coupled to the diaphragm.
Figure 11 shows a cut-away view of a typical assembly for one preferred embodiment, wherein multiple piezo-electric elements are coupled to a single diaphragm, a single sound-directing front part is coupled to the diaphragm, and a single rear enclosing part is provided.
Description
In figure 1 a piezo-electric loudspeaker I includes at least one piezo-electric element 2, coupled by coupling means 3 to a corrugated diaphragm 4 with multiple sound-radiating zones 5,6,7 for reproducing multiple frequency ranges, and at least one sound-directing front part 8 with multiple compression regions 9,10,11 and expansion regions 12,13,14 adapted to work with the multiple sound-radiating zones 5,6,7 of the diaphragm 4. The sound-directing front part 8, the compression regions 9,10,11 and expansion regions 12,13,14 are provided with means to position them relative to the diaphragm 4. Preferably, the sound-directing front part 8, the compression regions 9,10,11 and expansion regions 12,13,14 are formed as a single piece, for example by injection moulding. Preferably, the rear of the loudspeaker has a rear enclosing part 15, which may provide an acoustic path, and may have provision for electrical connections. Coupling means 3 may include encapsulation of the piezo-electric element(s) 2 within the diaphragm 4.
Electrical signals cause vibration of the piezo-electric element 2, which, through coupling means 3 causes the diaphragm 4 to vibrate. Different frequencies produce different nodal responses in the diaphragm 4, leading to greater displacement in certain regions than in others. Each of the sound-radiating zones 5,6,7 is arranged to generate acoustic pressure against each of the related compression regions 9,10,11 of the sound-directing front part 8.
The expansion regions 12,13,14 guide the resulting acoustic pressure waves, allowing controlled expansion and dispersion of these waves. As the optimum rates of compression and expansion differ for each frequency, the shapes of the compression regions 9,10,11 and expansion regions 12,13,14 are adapted to suit the range of frequencies they are each designed to handle. The effective working area of each of the sound-radiating zones 5,6,7 may be of different or similar size according to the desired acoustical characteristics.
In figures 2a and 2b, for one preferred embodiment, the effect of different frequencies on the amplitudes of the displacements 20 of the multiple sound-radiating zones 5,6,7 is compared to the amplitude 19 at the location of the said attachment means 3 of the said piezo-electric element 2. At lower frequencies (figure 2a) the parts 5 and 6 are more effective, and their pressure waves are emitted through aperture 16 in the sound-directing front part 8. At higher frequencies (figure 2b) part 7 is more effective and its pressure waves emit through aperture 17 in the sound-directing front part 8. In one preferred embodiment, the said diaphragm(s) 4 has (have) symmetry about at least one axis 18.
In figures 2c and 2d, for another preferred embodiment, the effect of different frequencies on the amplitudes of the displacements 20 of the multiple sound-radiating zones 5,6,7 is compared to the amplitude 19 at the location of the said attachment means 3 of the said piezo-electric element 2. At lower frequencies (figure 2c), the parts 5 and 6 are more effective, and their pressure waves are emitted through aperture 16 in the sound-directing front part 8. At higher frequencies (figure 2d) part 7 is more effective and its pressure waves emit through aperture 17 in the sound-directing front part 8. In one preferred embodiment, the said diaphragm(s) 4 has (have) symmetry about at least one axis 18.
In figure 3 alternative embodiments are shown where the shape of the diaphragm 4 when viewed along the primary loudspeaker axis 21 is generally circular, oval, or elliptical.
In figure 4 alternative embodiments are shown where the shape of the diaphragm 4 when viewed along the primary loudspeaker axis 21 is generally polygonal.
In figure 5 alternative embodiments provided with multiple piezo-electric elements 2 are used with a single diaphragm 4 and single or multiple sound-radiating front part(s) 8.
In figure 6 an alternative embodiment is provided with multiple piezo-electric elements 2, multiple diaphragms 4, and a single sound-directing front part(s) 8.
In figure 7 an alternative embodiment is provided with multiple piezo-electric elements 2, a single diaphragm 4, and single or multiple sound-directing front part(s) 8, wherein the piezo-electric elements are coupled at an angle to the diaphragm.
In figure 8 an alternative embodiment has multiple piezo-electric elements 2, with single or multiple diaphragm(s) 4, and single or multiple sound-directing front part(s) 8. In this embodiment, the piezo-electric elements 2 are coupled to the substantially inclined part(s) 21 of the diaphragm(s) 4, such that the bending of the diaphragm(s) 4 due to the action of the piezo-electric elements causes pressure waves to be generated between adjacent substantially inclined part(s) 21 of the diaphragm(s) 4, or between substantially inclined part(s) 21 of the diaphragm(s) 4 and the sound-directing front part(s) 8, or combinations of both.
In figure 9 an alternative embodiment has multiple piezo-electric elements 2, with single or multiple diaphragm(s) 4, and single or multiple sound-directing front part(s) 8. In this embodiment, the piezo-electric elements 2 are coupled to the substantially inclined part(s) 21 and substantially non-inclined part(s) 22 of the diaphragm(s) 4, such that the bending of the diaphragm(s) 4 due to the action of the piezo-electric elements causes pressure waves to be generated between adjacent substantially inclined and substantially non-inclined part(s) 21,22 of the diaphragm(s) 4, or between substantially inclined and substantially non-inclined part(s) 2 1,22 of the diaphragm(s) 4 and the sound-directing front part(s) 8, or combinations of both.
In figure 10 an alternative embodiment has multiple piezo-electric elements 2, with single or multiple diaphragm(s) 4, and single or multiple sound-directing front part(s) 8. In this embodiment, the said compression and expansion regions in the sound-directing front part(s) 8 are formed by a regular or irregular array of holes, each of uniform or non-uniform cross-section, and each of a length that preferably allows the array as a whole to follow the contours of the said diaphragm(s) 4.
In figure 11 a typical assembly for one preferred embodiment has one diaphragm 4, with multiple piezo-electric elements 2, a single sound-directing front part 8, and a single rear enclosing part 15.

Claims (27)

  1. Claims I. A loudspeaker comprising of at least one piezo-electric
    actuator, coupled to at least one diaphragm, said diaphragm or diaphragms being arranged with a plurality of sound-radiating zones, and at least one front-facing sound-directing part adapted to provide at least one compression and expansion region for at least one of the sound-radiating zones of said diaphragm or diaphragms, and at least one rear enclosing part.
  2. 2. A loudspeaker according to any other claim, wherein at least one said diaphragm is substantially corrugated.
  3. 3. A loudspeaker according to any other claim, wherein at least one said diaphragm has corrugations with parts substantially inclined to a plane or planes perpendicular to the primary axis or axes of the loudspeaker.
  4. 4. A loudspeaker according to any other claim, wherein at least one said diaphragm has corrugations with parts substantially not inclined to a plane or planes perpendicular to the primary axis or axes of the loudspeaker, and with parts substantially inclined to said plane or planes.
  5. 5. A loudspeaker according to any other claim, wherein at least one said piezo-electric actuator is coupled to at least one said inclined part of at least one said corrugation in at least one said diaphragm.
  6. 6. A loudspeaker according to any other claim, wherein at least said one piezo-electric actuator is coupled to at least one said not inclined part of at least one said corrugation in at least one said diaphragm.
  7. 7. A loudspeaker according to any other claim, wherein at least one said piezo-electric actuator is encapsulated in at least part of at least one said diaphragm.
  8. 8. A loudspeaker according to any other claim, wherein at least a second diaphragm provides a substantially enclosed volume with at least a first diaphragm, said at least first and second diaphragms being adapted to operate substantially in phase with each other.
  9. 9. A loudspeaker according to any other claim, wherein at least a second diaphragm provides a substantially enclosed volume with at least a first diaphragm, said at least first and second diaphragms being adapted to operate substantially out of phase with each other
  10. 10. A loudspeaker according to any other claim, wherein said at least second diaphragm is coupled to at least one said piezo-electric actuator which is also coupled to said at least first diaphragm.
  11. 11. A loudspeaker according to any other claim, wherein said at least second diaphragm is coupled to at least one said piezo-electric actuator which is not coupled to said at least first diaphragm.
  12. 12. A loudspeaker according to any other claim, wherein at least one said front-facing sound-directing part is coupled in at least one location to at least one said diaphragm.
  13. 13. A loudspeaker according to any other claim, wherein at least one said front-facing sound-directing part is coupled in at least one location to at least one said piezo-electric actuator.
  14. 14. A loudspeaker according to any other claim, wherein at least one said rear enclosing part is coupled in at least one location to at least one said diaphragm.
  15. 15. A loudspeaker according to any other claim, wherein at least one said rear enclosing part is coupled in at least one location to at least one said piezo-electric actuator.
  16. 16. A loudspeaker according to any other claim, wherein at least one said front-facing sound-directing part has compression and expansion regions formed by a regular or irregular array of holes of uniform or non-uniform cross-section.
  17. 17. A loudspeaker according to any other claim, wherein at least one said front-facing sound-directing part has compression and expansion regions formed by a regular or irregular array of holes of uniform or non-uniform cross-section, and each of a length that allows the array as a whole to follow the contours of the said diaphragm(s).
  18. 18. A loudspeaker according to any other claim, wherein at least one said rear enclosing part is adapted to provide an acoustic path for sound waves emanating from the rear of at least one said diaphragm.
  19. 19. A loudspeaker according to any other claim, wherein at least one said front-facing sound-directing part is adapted to provide an acoustic path for sound waves emanating from the rear of at least one said diaphragm.
  20. 20. A loudspeaker according to any other claim, wherein at least one said diaphragm(s) is (are) generally of circular, elliptical, or oval shape when viewed along the primary axis of the loudspeaker.
  21. 21. A loudspeaker according to any other claim, wherein at least one said diaphragm(s) is (are) generally of square, rectangular, hexagonal, triangular, or other polygonal shape when viewed along the primary axis of the loudspeaker, the sides of said polygonal shape being straight or curved.
  22. 22. A loudspeaker according to any other claim, wherein at least one of the said diaphragm(s) is (are) comprised of a single piece of material.
  23. 23. A loudspeaker according to any other claim, wherein at least one of the said diaphragm(s) is (are) comprised of multiple pieces of similar or dissimilar materials.
  24. 24. A loudspeaker according to any other claim, wherein the said front-facing sound-directing part(s) is (are) comprised of single pieces of material.
  25. 25. A loudspeaker according to any other claim, wherein the said front-facing sound-directing part(s) is (are) comprised of multiple pieces of similar or dissimilar materials.
  26. 26. A loudspeaker according to any other claim, wherein the said rear enclosing part(s) is (are) comprised of single pieces of material.
  27. 27. A loudspeaker according to any other claim, wherein the said rear enclosing part(s) is (are) comprised of multiple pieces of similar or dissimilar materials.
GB0621218A 2006-10-25 2006-10-25 Piezo-electric loudspeaker Expired - Fee Related GB2443228B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB0621218A GB2443228B (en) 2006-10-25 2006-10-25 Piezo-electric loudspeaker
PCT/GB2007/004067 WO2008050123A1 (en) 2006-10-25 2007-10-25 Loudspeakers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0621218A GB2443228B (en) 2006-10-25 2006-10-25 Piezo-electric loudspeaker

Publications (3)

Publication Number Publication Date
GB0621218D0 GB0621218D0 (en) 2006-12-06
GB2443228A true GB2443228A (en) 2008-04-30
GB2443228B GB2443228B (en) 2010-02-10

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Family Applications (1)

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GB0621218A Expired - Fee Related GB2443228B (en) 2006-10-25 2006-10-25 Piezo-electric loudspeaker

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GB (1) GB2443228B (en)
WO (1) WO2008050123A1 (en)

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CN102959992A (en) * 2010-07-23 2013-03-06 日本电气株式会社 Vibration device and electronic device

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CN113365192A (en) * 2020-03-06 2021-09-07 华为技术有限公司 Piezoelectric speaker and electronic apparatus
CN117857985A (en) * 2022-09-30 2024-04-09 华为技术有限公司 Speaker and electronic device

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JPS61158300A (en) * 1984-12-29 1986-07-17 Sony Corp Piezoelectric speaker
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JPS59117900A (en) * 1982-12-25 1984-07-07 Murata Mfg Co Ltd Piezoelectric speaker
JPS61158300A (en) * 1984-12-29 1986-07-17 Sony Corp Piezoelectric speaker
JP2000350279A (en) * 1999-06-01 2000-12-15 Shinsei Kk Horn speaker

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102959992A (en) * 2010-07-23 2013-03-06 日本电气株式会社 Vibration device and electronic device
EP2568720A1 (en) * 2010-07-23 2013-03-13 Nec Corporation Vibration device and electronic device
EP2568720A4 (en) * 2010-07-23 2013-11-06 Nec Corp Vibration device and electronic device
US8897096B2 (en) 2010-07-23 2014-11-25 Nec Corporation Oscillator and electronic device
CN102959992B (en) * 2010-07-23 2016-10-19 日本电气株式会社 Agitator and electronic equipment

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Publication number Publication date
GB2443228B (en) 2010-02-10
WO2008050123A1 (en) 2008-05-02
GB0621218D0 (en) 2006-12-06

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