LOUDSPEAKER WITH INERTIAL EXCITER COMPRISING A MAGNET ASSEMBLY SUSPENDED FROM A MOUNTING FRAME

Abstract

A loudspeaker comprising: a mounting frame; an acoustic radiator; a drive unit. The drive unit includes: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the inertial exciter; a coil assembly, and a drive unit suspension. The coil assembly includes: an attachment portion which provides an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap, wherein the voice coil is mounted to the voice coil former so the voice coil sits in the air gap when the drive unit is at rest; a tubular member, which is positioned radially outwardly of the voice coil former with respect to the movement axis, and which overlaps the voice coil former along a portion of the movement axis.

Claims

1-35 (canceled)

36. A loudspeaker comprising: a mounting frame; an acoustic radiator; a drive unit, including: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the inertial exciter; and a coil assembly including: an attachment portion which provides an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap, wherein the voice coil is mounted to the voice coil former so that the voice coil sits in the air gap when the drive unit is at rest; and a tubular member, which is positioned radially outwardly of the voice coil former with respect to the movement axis, and which overlaps the voice coil former along at least a portion of the movement axis; and at least one drive unit suspension attached to the tubular member and a part of the magnet assembly positioned radially outwardly of the tubular member so that the acoustic radiator is suspended from the magnet assembly via the coil assembly by the at least one drive unit suspension; wherein the magnet unit assembly is suspended from the mounting frame by at least one mounting frame suspension.

37. A loudspeaker according to claim 36, wherein the drive unit comprises: a first suspension attached to the tubular member and the part of the magnet assembly positioned radially outwardly of the tubular member; and a second suspension, separated from the first suspension in a direction extending parallel to the movement axis, wherein the second suspension is either: attached to the tubular member and the part of the magnet assembly positioned radially outwardly of the tubular member or is attached to the voice coil former and a part of the magnet assembly positioned radially inwardly of the voice coil former.

38. A loudspeaker according to claim 37, wherein: the first suspension is attached to a distal portion of the tubular member and a distal portion of the part of the magnet assembly positioned radially outwardly of the tubular member.

39. A loudspeaker according to claim 38, wherein: the second suspension is attached to a proximal portion of the tubular member and a proximal portion of the part of the magnet assembly positioned radially outwardly of the tubular member.

40. A loudspeaker according to claim 36, wherein the magnet assembly includes a magnet assembly frame to which the magnet unit is attached, wherein the part of the magnet assembly positioned radially outwardly of the tubular member is a part of the magnet assembly frame.

41. A loudspeaker according to claim 36, wherein: the tubular member is shaped to include the attachment portion, and optionally the voice coil former; and/or the tubular member has one or more extensions in a radial direction with respect to the movement axis to provide a respective attachment surface for the/each suspension attached to the tubular member, thereby facilitating attachment of the/each suspension to the tubular member.

42. A loudspeaker according to claim 36, wherein: the attachment portion is a coupling element which is separately attached to the voice coil former and/or tubular member; and/or the attachment portion is configured to provide an attachment between the coil assembly and the acoustic radiator by including bayonet features configured to engage with corresponding bayonet features on the acoustic radiator to provide a bayonet attachment between the attachment portion and the acoustic radiator.

43. A loudspeaker according to claim 36, wherein the drive unit includes one or more wires configured to provide an electrical path for supplying an electrical current carrying an audio signal to the voice coil, wherein: the electrical path provided by the one or more wires extends from a connector formed on the magnet assembly to the voice coil; and/or the one or more wires include a wire that passes through or around the tubular member, wherein optionally a coupling element is configured to guide said wire through or around the tubular member; and/or the one or more wires includes a wire that passes through a frame included in the magnet assembly.

44. A loudspeaker according to claim 36, wherein the at least one mounting frame suspension is tuned to have a resonance frequency in the range 10 Hz to 20 Hz.

45. A loudspeaker according to claim 36, wherein the loudspeaker includes: a first mounting frame suspension and a first drive unit suspension that are both part of a first piece of material; and, optionally a second mounting frame suspension and a second drive unit suspension that are both part of a second piece of material.

46. A loudspeaker according to claim 36, wherein the acoustic radiator has a width in at least one direction perpendicular to the movement axis that is larger than a width of the drive unit in the same direction.

47. A loudspeaker according to claim 36, wherein: the acoustic radiator has a laminate structure formed of at least two layers, wherein the at least two layers include a first layer of a first material having a first density, and a second layer of a second material having a second density, wherein the first density is lower than the second density; and/or the acoustic radiator has a laminate structure formed of at least three layers, wherein the at least three layers include a first layer of a first material having a first density, wherein the first layer is sandwiched between a second layer of a second material having a second density, and a third layer of a third material having a third density, wherein the first density is lower than both the second density and third density.

48. A loudspeaker according to claim 47, wherein the second layer covers 75% or less of the surface area of the face of the first layer to which the second layer is attached and, optionally, the third layer covers 75% or less of the surface area of the face of the first layer to which the third layer is attached.

49. A loudspeaker according to claim 36, wherein: the acoustic radiator has: a first radiating surface which faces in a forward direction, away from the drive unit; and a second radiating surface which faces in a backward direction, toward the drive unit; the coil assembly of the drive unit is attached to the second radiating surface of the acoustic radiator; the acoustic radiator is curved so that the first radiating surface is concave and so that the second radiating surface is convex.

50. A loudspeaker according to claim 36, wherein the loudspeaker is a subwoofer configured as a dipole loudspeaker.

51. A loudspeaker according to claim 36, wherein a frame of the magnet assembly and the mounting frame overlap at one or more locations as viewed in a plane perpendicular to the movement axis.

52. A loudspeaker comprising: a mounting frame; an acoustic radiator; a drive unit, including: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the exciter; and a coil assembly including: an attachment portion which provides an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap, wherein the voice coil is mounted to the voice coil former so that the voice coil sits in the air gap when the drive unit is at rest; and a tubular member, which is positioned radially inwardly of the voice coil former with respect to the movement axis, and which overlaps the voice coil former along at least a portion of the movement axis; and at least one drive unit suspension attached to the tubular member and a part of the magnet assembly positioned radially inwardly of the tubular member so that the acoustic radiator is suspended from the magnet assembly via the coil assembly by the at least one drive unit suspension; wherein the magnet unit assembly is suspended from the mounting frame by at least one mounting frame suspension.

53. A loudspeaker according to claim 52, wherein the drive unit comprises: a first suspension attached to the tubular member and the part of the magnet assembly positioned radially inwardly of the tubular member; and a second suspension, separated from the first suspension in a direction extending parallel to the movement axis, wherein the second suspension is either: attached to the tubular member and the part of the magnet assembly positioned radially inwardly of the tubular member or is attached to the voice coil former and a part of the magnet assembly positioned radially outwardly of the voice coil former; wherein the first suspension is attached to a distal portion of the tubular member and a distal portion of the part of the magnet assembly positioned radially inwardly of the tubular member; wherein the second suspension is attached to a proximal portion of the tubular member and a proximal portion of the part of the magnet assembly positioned radially inwardly of the tubular member; wherein the magnet assembly includes a magnet assembly frame to which the magnet unit is attached, wherein the part of the magnet assembly positioned radially inwardly of the tubular member is a part of the magnet assembly frame.

54. A seat assembly including: a seat; and a loudspeaker; wherein the loudspeaker comprises: a mounting frame; an acoustic radiator; a drive unit, including: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the inertial exciter; and a coil assembly including: an attachment portion which provides an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap, wherein the voice coil is mounted to the voice coil former so that the voice coil sits in the air gap when the drive unit is at rest; and a tubular member, which is positioned radially outwardly of the voice coil former with respect to the movement axis, and which overlaps the voice coil former along at least a portion of the movement axis; and at least one drive unit suspension attached to the tubular member and a part of the magnet assembly positioned radially outwardly of the tubular member so that the acoustic radiator is suspended from the magnet assembly via the coil assembly by the at least one drive unit suspension; wherein the magnet unit assembly is suspended from the mounting frame by at least one mounting frame suspension; wherein the seat is configured to position a user who is sat down in the seat such that each ear of a user is located at a respective listening position that is 25 cm or less, more preferably 20 cm or less from a first radiating surface of the loudspeaker, wherein the loudspeaker may be mounted within a headrest of the seat.

55. A seat assembly according to claim 54, wherein the seat includes a waveguide which at least partially surrounds the acoustic radiator and is configured to guide sound produced by the first and/or second radiating surface of the acoustic radiator, wherein a gap between the waveguide and a periphery of the acoustic radiator is less than 5 mm at one or more locations at the periphery of the acoustic radiator.

Description

SUMMARY OF THE FIGURES

[0287] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0288] FIG. 1(a) shows an example traditional loudspeaker.

[0289] FIG. 1(b) shows an example inertial exciter.

[0290] FIG. 2(a) shows a loudspeaker incorporating a wide bandwidth inertial exciter implementing principles derived from the prior art.

[0291] FIG. 2(b) is a graph showing force level vs frequency for the loudspeaker shown in FIG. 2(a).

[0292] FIG. 2(c) illustrates a problem with the inertial exciter shown in FIG. 2(a).

[0293] FIG. 3(a)(i) and (ii) illustrate “Solution A” as taught by the prior art.

[0294] FIG. 3(b)(i) and (ii) illustrate “Solution B” as taught by the prior art.

[0295] FIG. 3(c)(i) and (ii) illustrate “Solution C” as taught by the prior art.

[0296] FIG. 3(d)(i) and (ii) illustrate “Solution D” as taught by the prior art.

[0297] FIG. 3(e)(i) and (ii) illustrate “Solution E” as taught by the prior art.

[0298] FIG. 3(f)(i) and (ii) illustrate “Solution F” as taught by the prior art.

[0299] FIG. 4(a)(i)-(v) show a first drive unit 101a that exemplifies a drive unit of the inner magnet type, and a loudspeaker 180a incorporating the first drive unit 101a.

[0300] FIG. 4(b)(i)-(iv) show a second drive unit 101b that exemplifies an inertial exciter of the inner magnet type, and a loudspeaker 180b incorporating the first drive unit 101b.

[0301] FIG. 4(c) shows a third drive unit 101c that exemplifies a drive unit of the inner magnet type.

[0302] FIG. 4(d) shows a fourth drive unit 101d that exemplifies a drive unit of the inner magnet type.

[0303] FIG. 4(e) shows a fifth drive unit 101e that exemplifies a drive unit of the inner magnet type.

[0304] FIG. 4(f) shows a sixth drive unit 101f that exemplifies a drive unit of the inner magnet type.

[0305] FIG. 4(g) shows a seventh drive unit 101g that exemplifies a drive unit of the inner magnet type.

[0306] FIG. 4(h) shows an eighth drive unit 101h that exemplifies a drive unit of the inner magnet type.

[0307] FIG. 4(i)(i)-(viii) shows a ninth drive unit 101i that exemplifies a drive unit of the inner magnet type.

[0308] FIG. 4(j)(i)-(ii) show a tenth drive unit 101j that exemplifies a drive unit of the inner magnet type.

[0309] FIG. 4(k) shows an eleventh drive unit 101k that exemplifies a drive unit of the inner magnet type.

[0310] FIG. 4(l) shows a twelfth drive unit 101l that exemplifies a drive unit of the inner magnet type.

[0311] FIG. 5(a) shows a first drive unit 201a that exemplifies a drive unit of the outer magnet type.

[0312] FIG. 5(b) shows a second drive unit 201b that exemplifies a drive unit of the outer magnet type.

[0313] FIG. 5(c) shows a third drive unit 201c that exemplifies a drive unit of the outer magnet type.

[0314] FIG. 5(d) shows a fourth drive unit 201d that exemplifies a drive unit of the outer magnet type.

[0315] FIG. 6(a) shows a first example loudspeaker.

[0316] FIG. 6(b) shows a second example loudspeaker.

[0317] FIG. 6(c) shows a third example loudspeaker.

[0318] FIGS. 6(d)(i)-(iii) shows a fourth example loudspeaker.

[0319] FIGS. 6(e)(i)-(ii) shows a fifth example loudspeaker.

[0320] FIG. 6(f) shows a sixth example loudspeaker.

[0321] FIG. 6(g) shows a seventh example loudspeaker.

[0322] FIG. 6(h) shows an eighth example loudspeaker.

[0323] FIG. 6(i) shows a seat headrest incorporating ninth and tenth example loudspeakers.

DETAILED DESCRIPTION OF THE INVENTION

[0324] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0325] For the purpose of this description, example drive units are divided into two types, referred to as “inner magnet” type according to the first aspect of the invention and “outer magnet” type according to the second aspect of the invention.

Drive Unit—Inner Magnet Type Examples

[0326] A first drive unit 101a that exemplifies an drive unit of the inner magnet type is shown in FIG. 4(a)(i).

[0327] Here, we note for completeness that the drive unit 101a is referred to as a drive unit because it is intended for use in a loudspeaker where an acoustic radiator is suspended from a magnet assembly of the drive unit.

[0328] Were the drive unit 101a intended for use in a loudspeaker where a magnet assembly of the drive unit is suspended from an acoustic radiator, then the drive unit 101a might instead be referred to as an “inertial exciter”. The terms “drive unit” and “inertial exciter” can thus be used interchangeably in relation to the drive unit 101a, until the drive unit 101a is incorporated into a loudspeaker, at which point the drive unit 101a should be referred to as an “inertial exciter” only if the loudspeaker has a magnet assembly of the drive unit suspended from an acoustic radiator.

[0329] The drive unit 101a of FIG. 4(a) comprises a magnet assembly 102a and a coil assembly 104a.

[0330] The magnet assembly 102a includes a magnet unit 110a and a frame 120a to which the magnet unit 110a is attached.

[0331] In this example, the magnet unit 110a includes a main magnet 112a, a washer 113a an extra magnet 114a and a U-yoke 115a. The magnet unit 110a is configured to provide a magnetic field in an air gap 116a. The air gap 116a extends around a movement axis 106a of the drive unit 101a.

[0332] The frame 120a includes a base portion 122a which extends radially outwardly with respect to the movement axis 106a (in this example from a base of the U-yoke 115a), and a rim 124a which extends axially with respect to the movement axis 106a, that is at least partly along the movement axis 106a. The rim 124a of the frame 120a is positioned at the periphery of the base portion 122a, and is positioned radially outwardly of the magnet unit 110a.

[0333] The rim 124a of the frame 120a is positioned radially outwardly of a tubular member 140a, and thus serves as the “part of the magnet assembly positioned radially outwardly of the tubular member” referenced in the “Summary of the invention” section of this document, above.

[0334] In this example, the main magnet 112a, washer 113a, extra magnet 114a, U-yoke 115a, and air gap 116a are circular, though other forms are possible.

[0335] In this example, the washer 114a and U-yoke 116a may be made of steel, though other materials are possible.

[0336] In this example, the coil assembly 104a includes a voice coil 130a, a voice coil former 132a, a tubular member 140a and an attachment portion 150a.

[0337] In this example, the attachment portion 150a is a coupling element which is separately attached to the voice coil former and tubular member, e.g. by glue. The coupling element 150a is configured to provide an attachment between the coil assembly 104a and an acoustic radiator (not shown) by including a gluing surface 151a configured to be glued to the acoustic radiator. The coupling element 150a could for example be a plastic or cardboard ring-shaped element.

[0338] The voice coil former 132a extends axially with respect to the movement axis 106a from the coupling element 150a into the air gap 116a. The voice coil 130a is mounted to the voice coil former 132a so that the voice coil 130a sits in the air gap 116a when the drive unit 101a is at rest.

[0339] The tubular member 140a is positioned radially outwardly of the voice coil former 132a with respect to the movement axis 106a. The tubular member 140a also overlaps the voice coil former 132a along a portion of the movement axis (this portion corresponding to the full length of the voice coil former 132a).

[0340] In this example, the voice coil former 132a and tubular member 140a are cylindrical, though other shapes are possible.

[0341] Two planes are depicted in FIG. 4(a)(i).

[0342] A first plane 108a is perpendicular to the movement axis 106a and extends through the attachment portion which as noted above is the coupling element 150a.

[0343] A second plane 109a is perpendicular to the movement axis 106a and extends through the air gap 116a.

[0344] The rim 124a of the frame 120a includes: [0345] a proximal portion, wherein the proximal portion of the rim 124a is located between the first plane 108a and the second plane 109a; and [0346] a distal portion, wherein the distal portion of the rim 124a is located is on an opposite side of the second plane 109a from the proximal portion of the rim 124a.

[0347] The tubular member 140a similarly includes: [0348] a proximal portion, wherein the proximal portion of the tubular member 140a is located between the first plane 108a and the second plane 109a; and [0349] a distal portion, wherein the distal portion of the tubular member 140a is located is on an opposite side of the second plane 109a from the proximal portion of the of the tubular member 140a.

[0350] The drive unit 101a includes: [0351] a first drive unit suspension 160a that is attached to the distal portion of the tubular member 140a and the distal portion of the rim 124a; and [0352] a second drive unit suspension 165a that is attached to the proximal portion of the tubular member 140a and the proximal portion of the rim 124a.

[0353] Each drive unit suspension 160a, 165a in this example is a spider including multiple corrugations. Such drive unit suspensions are well known in the art.

[0354] Thus, when the coil assembly 104a is attached to the acoustic radiator via the attachment portion/coupling element 150a, the acoustic radiator is suspended from the magnet assembly 102a via the coil assembly 104a by the first and second drive unit suspensions 160a, 165a.

[0355] As can be seen from FIG. 4(a)(i), the rim 124a of the frame 120a includes a first ledge 125a to which the first drive unit suspension 160a is attached, and a second ledge 126a to which the second drive unit suspension 165a is attached.

[0356] In this example, the first and second drive unit suspensions 160a, 165a are each shown as a respective spider having multiple corrugations.

[0357] The drive unit 101a includes wires 134a, 135a configured to provide an electrical path for supplying an electrical current carrying an audio signal (representative of sound) to the voice coil 130a.

[0358] The electrical path provided by the wires 134a, 135a extend from a connector 138a formed on an outwardly facing surface of the rim 124a of the frame 120a to the voice coil 130a.

[0359] In this example, the wires include part of the voice coil winding 134a as well as a lead wire 135a. In this example, the voice coil winding 134a extends around the tubular member 140a as guided by the coupling element 150a.

[0360] The voice coil winding 134a and lead wire 135a meet at an electrical junction formed at a solderpad or glue dot 136a on an outwardly facing surface of the tubular member 140a.

[0361] FIG. 4(a)(ii) shows a loudspeaker 180a including the drive unit 101a of FIG. 4(a)(i) and an acoustic radiator 190a suspended from the magnet assembly 102a, wherein the coil assembly 104a of the drive unit 101a is attached to the acoustic radiator 190a via the attachment portion/coupling element 150a so that the acoustic radiator 190a is suspended from the magnet assembly 102a via the coil assembly by the first and second drive unit suspensions 160a, 165a.

[0362] Preferably, the magnet assembly 102a is itself suspended from a mounting frame via at least one mounting frame suspension (not shown here, but shown in the examples discussed below under the heading “Loudspeakers in which the magnet assembly is suspended from a mounting frame”).

[0363] In use, electrical current carrying an audio signal is supplied to the voice coil 130a via the connector 138a and wires 134a, 135a. This energises the voice coil 130a and causes a magnetic field to be produced by the current in the voice coil 130a, which interacts with the magnetic field produced in the air gap 116a by the magnet unit 110a, and causes the voice coil assembly 104a to move relative to the magnet assembly 102a. This relative movement is accommodated by the first and second drive unit suspensions 160a, 165a.

[0364] Because the acoustic radiator 190a is suspended from the magnet assembly 102a via the coil assembly 104a by the first and second drive unit suspensions 160a, 165a, the loudspeaker is able to be moved by MC and MM excitation.

[0365] Because the voice coil former 132a and tubular member 140a are tubular, they provide good stiffness even when made of a lightweight material such as paper, cardboard, Kapton, aluminium, kevlar etc. Thus, the voice coil assembly 104a can have low weight and good stiffness, as is needed for good wide bandwidth performance from MC excitation.

[0366] Moreover, because the tubular member 140a has a distal portion which overlaps the voice coil former 132a so as to extend beyond the air gap 116a, i.e. to the opposite side of the second plane 109a from the proximal portion of the tubular member 140a, it is possible to have a large distance between the first and second drive unit suspensions 160a, 165a, which helps inhibit rotation of the voice coil assembly 104a relative to the magnet assembly 102a when the loudspeaker is vertically mounted.

[0367] Note that this is achieved whilst providing one interface (the glue surface of the coupling element 150a) with the acoustic radiator 190a, and also whilst permitting MC excitation. The low mass of the voice coil assembly (see above) help to achieve acoustic sensitivity and balance in the upper frequency band, as depicted in FIG. 4(a)(iii).

[0368] FIG. 4(a)(iv) shows a method step involved in assembling the drive unit 101a which makes use of a conventional centering jig 195a to align the voice coil former 132a in the air gap 116a before the components of the voice coil assembly 104a are glued together. The coupling element 150a may be flush with an inwardly facing surface of the voice coil former 132a to facilitate use of the centering jig 195a.

[0369] FIG. 4(a)(v) shows an alternative or additional method step involved in assembling the drive unit 101a in which apertures are incorporated into the frame 120a to allow a centering jig 196a to be inserted into the apertures during assembly, e.g. to help with aligning the voice coil former 132a in the air gap 116a.

[0370] Preferably the voice coil assembly (including the coupling element 150am the voice coil 130a, voice coil former 132a and the tubular member 140a) could be pre-assembled on a separate jig (not shown) before being assembled in the magnet assembly 102a.

[0371] Various alternative inner magnet examples will now be described. Alike features have been given alike reference numerals where appropriate and are not described in further detail, except where necessary.

[0372] A second drive unit 101b that exemplifies an drive unit of the inner magnet type is shown in FIG. 4(b)(i).

[0373] The coupling element 150b of the drive unit 101b is shown in FIG. 4(b)(ii) and includes bayonet features in the form of radial extensions 151 b configured to engage with corresponding bayonet features 191b on the acoustic radiator 190b shown in FIG. 4(b)(iii) to provide a bayonet attachment between the coupling element 150b and the acoustic radiator 190b. The bayonet features 191b on the acoustic radiator preferably form slots for accommodating the radial extensions 151b. The resulting loudspeaker 180b is shown in FIG. 4(b)(iv).

[0374] The above-described bayonet feature could facilitate assembly and replacement of the drive unit 101b to the acoustic radiator 190b.

[0375] The above-described bayonet features could be combined with adhesives or filler (e.g. grease) to avoid rattling during operation. The adhesive or filler could have temperature dependent properties so that by applying heat the drive unit 101b can be replaced.

[0376] A third drive unit 101c that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(c).

[0377] In this example, the tubular member 140c includes a collar 141c that provides a flat face to facilitate gluing of the first drive unit suspension 160c, which in this example could be a fabric damper, a metal or plastic spiral spring, a rubber element, etc.

[0378] A fourth drive unit 101d that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(d).

[0379] In this example, the a ring 141d, e.g. made of cardboard or plastic, is attached to the distal portion of the tubular member 140d to provide a flat surface 141d to facilitate gluing of the first drive unit suspension 160d.

[0380] A fifth drive unit 101e that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(e).

[0381] In this example, the tubular member 140e is integrally formed with the attachment portion 150e by appropriately shaping the tubular member 140e to include the attachment portion 150e. This allows the tubular member 140e to be glued directly to the voice coil former 132e, and avoids the use of a coupling element as described in previous examples. In this example, the attachment portion 150e is a flat face of the tubular member 140e that is configured to be glued to the acoustic radiator (not shown).

[0382] The tubular member 140e could be made of paper, cardboard, Kapton, aluminium, kevlar, PE, ABS etc.

[0383] A sixth drive unit 101f that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(f).

[0384] The drive unit 101f is the same as the fifth drive unit 101e shown in FIG. 4(e), except that holes are formed in the attachment portion 150f to enhance the glue attachment to the acoustic radiator (not shown).

[0385] A seventh drive unit 101g that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(g).

[0386] In this example, the coupling element 150g is attached only to the voice coil former 132g, with the tubular member 140g being attached to the voice coil former 132g.

[0387] An eighth drive unit 101h that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(h).

[0388] In this example, the tubular member 140h forms an angle with respect to the movement axis, thereby forming a frusto-conical tubular member 140h. In this case, the angle is preferably no more than 15°.

[0389] A tubular member 140h shaped in this way could facilitate the making of the tubular member 140h from paper or from plastic in a deep draw process.

[0390] In this example, the tubular member 140h is again integrally formed with the attachment portion 150h by appropriately shaping the tubular member 140h to include the attachment portion 150h.

[0391] A ninth drive unit 101i that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(i)(i).

[0392] This example is essentially the same as the first drive unit 101a shown in FIG. 4(a)(i), except that in this case the first and second drive unit suspensions 160i, 165i include only a single corrugation, and the single corrugations mirror each other (in a plane 108i perpendicular to the movement axis 106i) to help cancel asymmetries in stiffness between the two drive unit suspensions 160i, 165i. The first and second drive unit suspensions 160i, 165i may in this case be roll drive unit suspensions, e.g. made of rubber, textile or foam.

[0393] FIG. 4(i)(ii) show the attachment between the frame 120i and the drive unit suspensions 160i, 165i. In this particular example, the rim of the frame 120i is provided in two parts, 124i(i) and 124i(ii).

[0394] Example dimensions are drawn on FIG. 4(i)(i) and FIG. 4(i)(ii), noting that the distance between locations at which the two drive unit suspensions 160i, 165i attach to the rim of the magnet assembly is 6.3 mm in this example, which is large given the overall size of the drive unit 101i.

[0395] FIGS. 4(i)(iii)-(viii) are 3D views showing the drive unit 101i from various angles.

[0396] A tenth drive unit 101j that exemplifies an drive unit of the inner magnet type is shown in FIG. 4(j)(i).

[0397] The drive unit 101j shown in FIG. 4(j)(i) is the same as the drive unit 101a shown in FIG. 4(a)(i) except that the drive unit includes an alternative form of first and second drive unit suspensions 160j, 165j.

[0398] The alternative form of drive unit suspension used for the first and second drive unit suspensions 160j, 165j is shown in more detail in FIG. 4(j)(ii).

[0399] As can be seen most clearly from FIG. 4(j)(ii), the alternative form of first and second drive unit suspensions 160j, 165j is a piece of sheet material having a geometry configured to allow deflection in a direction parallel to the movement axis 106j, whilst inhibiting movement in a direction perpendicular to the movement axis 106j.

[0400] A suitable material for the alternative form of first and second drive unit suspensions 160j, 165j could be a fiber-reinforced plastic, e.g. a polymer matrix reinforced with glass fibres or carbon fibres, or a metal, e.g. steel spring material.

[0401] An eleventh drive unit 101k that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(k).

[0402] The drive unit 101k shown in FIG. 4(k) is the same as the drive unit 101a shown in FIG. 4(a)(i) except that in this example the second drive unit suspension 165k is attached to a proximal portion of the voice coil former 132k and a proximal portion of a part of the magnet assembly positioned radially inwardly of the voice coil former (in this case the extra magnet 114k).

[0403] Note, that in this case the drive unit 101k has: [0404] a first drive unit suspension 160k that is attached to a distal portion of the tubular member 140k and the distal portion of the rim 124k; and [0405] a second drive unit suspension 165k that is attached to a proximal portion of the voice coil former 132k and a proximal portion of a part of the magnet assembly positioned radially inwardly of the voice coil former 132k (in this case the extra magnet 114k).

[0406] Thus, this arrangement still allows for a wide separation between the first and second drive unit suspensions 160k, 165k, thereby helping to inhibit rotation of the magnet assembly 102k relative to the voice coil assembly 104k.

[0407] Besides providing drive unit suspension, the second drive unit suspension 165k can also serve as a dust cover to prevent dust in the airgap 116k prior to mounting the drive unit 101k to an acoustic radiator.

[0408] In this example, the first drive unit suspension 165k is a roll drive unit suspension including only one corrugation.

[0409] A twelfth drive unit 101l that exemplifies a drive unit of the inner magnet type is shown in FIG. 4(l).

[0410] The drive unit 101l shown in FIG. 4(l) is the same as the drive unit 101a shown in FIG. 4(a)(i) except that a third drive unit suspension 168l is attached to a proximal portion of the voice coil former 132l and a proximal portion of a part of the magnet assembly positioned radially inwardly of the voice coil former (in this case the extra magnet 114l).

[0411] Besides providing drive unit suspension, the third drive unit suspension 168l can also serve as a dust cover to prevent dust in the airgap 116l prior to mounting the acoustic radiator to the drive unit 101l.

Drive Unit—Outer Magnet Type Examples

[0412] A first drive unit 201a that exemplifies a drive unit of the outer magnet type is shown in FIG. 5(a).

[0413] The drive unit 201a shown in FIG. 5(a) includes many features which are common to the drive unit 101a shown in FIG. 4(a)(i). Alike features have been given alike reference numerals where appropriate and are not described in further detail, except where necessary.

[0414] The magnet assembly 202a includes a magnet unit 210a and a frame 220a to which the magnet unit 210a is attached.

[0415] In this example, the magnet unit 210a includes a (ring-shaped) main magnet 212a, a (ring-shaped) washer 213a and a T-yoke 215a (which looks like an upside down “T” as drawn). The magnet unit 210a is configured to provide a magnetic field in an air gap 216a. The air gap 216a extends around a movement axis 206a of the drive unit 201a.

[0416] The outer magnet type examples can be useful as they allow more magnet material to be used compared with the inner magnet type examples, and therefore enable more powerful exciters, as may be desirable in some cases.

[0417] In this example, the frame 220a includes a base portion 222a which extends radially inwardly with respect to the movement axis 206a (in this example from a base of the T-yoke 215a).

[0418] In this example, the frame 220a also include a hub 224a which extends axially with respect to the movement axis 206a, that is at least partly along the movement axis 206a. The hub 224a of the frame 220a is positioned at the centre of the base portion 222a, and is positioned radially inwardly of the tubular member 240a.

[0419] In this example, the tubular member 240a is positioned radially inwardly of the voice coil former 232a with respect to the movement axis 206a, and overlaps the voice coil former 232a along at least a portion of the movement axis 206a.

[0420] The drive unit 201a includes: [0421] a first drive unit suspension 260a that is attached to a distal portion of the tubular member 240a and the distal portion of the hub 224a; and [0422] a second drive unit suspension 265a that is attached to the proximal portion of the tubular member 240a and the proximal portion of the hub 224a.

[0423] The proximal portions of the tubular member 240a and hub 224a are located between the first plane 208a and the second plane 209a as defined above. The proximal portions of the tubular member 240a and hub 224a are located on an opposite side of the second plane 209a from the proximal portions.

[0424] As can be seen from FIG. 5(a), the hub 224a of the frame 220a includes a first ledge 225a to which the first drive unit suspension 260a is attached, and a second ledge 226a to which the second drive unit suspension 265a is attached.

[0425] In this example, the drive unit 201a includes a lead wire 234a configured to provide an electrical path for supplying an electrical current carrying an audio signal (representative of sound) to the voice coil 130a.

[0426] In this example, the electrical path provided by the lead wire 234a extend from a connector 238a formed on an outwardly facing surface of the base portion 222 of the frame 220a (outward in the sense of facing away from the hub 224a) to the voice coil 230a.

[0427] In this example, the lead wire 234a extends through the frame 220a.

[0428] In this example, the coupling element 250a is similar to that shown in FIG. 4(a)(i).

[0429] In use, electrical current carrying an audio signal is supplied to the voice coil 230a via the connector 238a and lead wire 234a. This energises the voice coil 230a and causes a magnetic field to be produced by the current in the voice coil 230a, which interacts with the magnetic field produced in the air gap 216a by the magnet unit 210a, and causes the voice coil assembly 204a to move relative to the magnet assembly 202a. This relative movement is accommodated by the first and second drive unit suspensions 260a, 265a.

[0430] Various alternative inner magnet examples will now be described. Alike features have been given alike reference numerals where appropriate and are not described in further detail, except where necessary.

[0431] A second drive unit 201b that exemplifies a drive unit of the outer magnet type is shown in FIG. 5(b).

[0432] This example is that same as that shown in FIG. 5(a), except that a third drive unit suspension 268b is attached to the voice coil former 232b and to a part of the magnet assembly 202b (in this case the washer 213b) positioned radially outwardly of the voice coil former 232a.

[0433] Besides providing drive unit suspension, the third drive unit suspension 268b can also serve as a dust cover to prevent dust in the airgap 216b when the drive unit 201b is in use.

[0434] A third drive unit 201c that exemplifies a drive unit of the outer magnet type is shown in FIG. 5(c).

[0435] This example is that same as that shown in FIG. 5(a), except that in this example the second drive unit suspension 265c is attached to the voice coil former 232b and to a part of the magnet assembly 202b (in this case the washer 213b) positioned radially outwardly of the voice coil former 232a.

[0436] Note, that in this case the drive unit 201c has: [0437] a first drive unit suspension 260c that is attached to a distal portion of the tubular member 240c and the distal portion of the hub 224c; and [0438] an second drive unit suspension 265c that is attached to a proximal portion of the tubular member 240c and a proximal portion of a part of the magnet assembly positioned radially outwardly of the tubular member 240c (in this case the washer 213b).

[0439] Thus, this arrangement still allows for a wide separation between the first and second drive unit suspensions 160k, 165k, thereby helping to inhibit rotation of the magnet assembly 202c relative to the voice coil assembly 204c.

[0440] Besides providing suspension, the second drive unit suspension 265c can also serve as a dust cover to prevent dust in the airgap 216c when the drive unit 201b is in use.

[0441] A fourth drive unit 201d that exemplifies a drive unit of the outer magnet type is shown in FIG. 5(d).

[0442] This example is that same as that shown in FIG. 5(b), except that: [0443] the tubular member 240d is integrally formed with the attachment portion 250d by appropriately shaping the tubular member 240d to include the attachment portion 250d. [0444] holes are formed in the attachment portion 250d to enhance the glue attachment to the acoustic radiator (not shown)

Loudspeakers in which the Magnet Assembly is Suspended from a Mounting Frame

[0445] In all the examples that follow, an acoustic radiator is suspended from the magnet assembly by at least one drive unit suspension, and the magnet assembly is suspended from a mounting frame by at least one mounting frame suspension. Although such an arrangement is only explicitly shown in the examples that follow, a skilled person would appreciate that such an arrangement could equally be adopted with all of the drive units previously discussed.

[0446] In the examples loudspeakers that follow, the drive units includes many features which are common to the drive unit 101a shown in FIG. 4(a)(i). Alike features have been given alike reference numerals where appropriate and such features are not described in further detail, except where necessary. In some examples, the acoustic radiator is omitted for clarity, but it would be appreciated in all cases that the loudspeaker would have an acoustic radiator attached to the coil assembly, wherein the attachment portion provides the attachment between the coil assembly and the acoustic radiator.

[0447] In all the examples that follow, the loudspeakers incorporate drive unit of the outer magnet type, but a skilled person would readily appreciate that drive units of the inner magnet type could equally be used.

[0448] In all the examples that follow, the loudspeaker is preferably configured to move the diaphragm at bass frequencies and is configured to be used as a dipole loudspeaker, e.g. as described in [14].

[0449] FIG. 6(a) shows a first example loudspeaker 300a, in which there is an acoustic radiator 390a attached to the coil assembly 304a, wherein the attachment portion 350a provides the attachment between the coil assembly 304a and the acoustic radiator 390a.

[0450] As shown in FIG. 6(a), the loudspeaker 300a additionally includes a mounting frame 380a, wherein the magnet unit assembly 302a is suspended from the mounting frame 380a by at least one mounting frame suspension 370a, 375a. In this example, the magnet unit assembly is suspended from the mounting frame by two mounting frame suspensions 370a, 375a, which are in this example both roll suspensions, wherein the single corrugations mirror each other (in a plane perpendicular to the movement axis) to help cancel asymmetries in stiffness between the two mounting frame suspensions 370a, 375a.

[0451] In this example, the mounting frame 380a is configured to fixedly (i.e. rigidly) attach to a rigid supporting structure, such as a car seat frame, by including one or more mounting formations. In this example, the mounting formations are holes 392a, through which bolts can pass in order to bolt the mounting frame 380a to the rigid supporting structure.

[0452] To facilitate the use of the bolt, the acoustic radiator 390a may include one or more access holes 392a to configured to provide access to the one or more mounting formations. The one or more access holes 392a may be closed with tape 393a after access is no longer needed, so as to reduce/avoid loss of acoustic performance due to the presence of the one or more access holes. Other acoustic radiator constructions are of course possible.

[0453] As shown in FIG. 6(a), the acoustic radiator 390a has a width in a direction d perpendicular to the movement axis 306a that is larger than a width of the drive unit 301a in the same direction. In other words, the acoustic radiator 390a extends beyond the sides of the drive unit 301a in at least one direction (d) perpendicular to the movement axis.

[0454] The acoustic radiator 390a has: a first radiating surface 394a which faces in a forward direction F, away from the drive unit 301a; and a second radiating surface 394a′ which faces in a backward direction B, toward the drive unit; wherein the coil assembly 304a of the drive unit 301a is attached to the second radiating surface 394a′ of the acoustic radiator (via the attachment portion 350a).

[0455] FIG. 6(b) shows a second example loudspeaker 300b, wherein the acoustic radiator has been omitted, for clarity.

[0456] In this example, the loudspeaker 300b includes: [0457] a first mounting frame suspension 360b and a first drive unit suspension 370b that are both part of a first piece of material (which may be an elastic material, in some examples); and [0458] a second mounting frame suspension 365b and a second drive unit suspension 375b that are both part of a second piece of material (which may be an elastic material, in some examples).

[0459] The magnet unit 310b in this case includes a two-pole piece with a recession 317b at the voice coil location. This recession 317b can be filled, e.g. with copper.

[0460] The first and/or second drive unit suspension 360b, 365b may include one or more holes/interruptions to help silence its operation. In this particular example, the first drive unit suspension 360b is perforated to achieve this effect.

[0461] FIG. 6(c) shows a third example loudspeaker 300c.

[0462] In this example, the acoustic radiator is curved 390c so that the first radiating surface 394c is concave and so that the second radiating surface 394c′ is convex.

[0463] The first and/or second drive unit suspension may include one or more interruptions to help facilitate the attachment of a lead wire 334c. In this particular example, the second drive unit suspension 365c include an interruption through which the lead wire 334c passes.

[0464] Again, the acoustic radiator 390c has a width in a direction d perpendicular to the movement axis that is larger than a width of the drive unit 301c in the same direction.

[0465] FIGS. 6(d)(i)-(iii) show a fourth example loudspeaker 300d.

[0466] In this example, the acoustic radiator 390d is curved so that the first radiating surface 394d is concave and so that its second radiating surface 394d′ is convex.

[0467] Again, the acoustic radiator 390d has a width in a direction d perpendicular to the movement axis that is larger than a width of the drive unit 301d in the same direction.

[0468] The attachment portion 350d is attached to the acoustic radiator 390d at multiple locations on the acoustic radiator 390d, wherein a centre of mass of the acoustic radiator 390d is located between two of the locations at which the attachment portion 350d is attached to the acoustic radiator, preferably such that the acoustic radiator is driven (substantially) at its centre of mass. In this example, the centre of mass is located on the movement axis 306d, and is therefore between the two locations at which the attachment portion 350d is attached to the acoustic radiator 390d in the plane of cross-section depicted in FIG. 6(d)(iii) (these two locations correspond to the two points labelled by reference numeral 350d in FIG. 6(d)(iii)).

[0469] In this example, the drive unit suspensions 360d, 365d each extend in a linear direction in a plane perpendicular to the movement axis, e.g. for increased linearity of movement, for silent operation and/or for avoiding trapped air that can make blowing noises. Interruptions in the drive unit suspensions 360d, 365d are provided by gaps between the linear suspensions.

[0470] FIGS. 6(e)(i)-(ii) show a fifth example loudspeaker 300e, wherein FIG. 6(e)(i) is a view of the front (forward-facing) surface of the loudspeaker 300e, and FIG. 6(e)(ii) is a view of the back (backward-facing) surface of the loudspeaker 300e.

[0471] In this example, the loudspeaker 300e shares many of the features of the example loudspeaker shown in FIG. 6(b), but in this case the acoustic radiator 390e has a laminate structure formed of three layers: a layer of polystyrene 395e sandwiched between two layers of balsa 395e′, 395″, wherein a first layer of balsa 395e′ is attached to a first (forward-facing) face of the layer of polystyrene 395e, and a second (backward-facing) layer of balsa 395e′ is attached to a second face of the layer of polystyrene 395e.

[0472] The first layer of balsa 395e′ covers less than 75% or less of the surface area of the face of the layer of polystyrene 395e to which the first layer of balsa 395e′ is attached, The first layer of balsa 395e′ and the part of the face of the layer of polystyrene 395e exposed behind the first layer of balsa 395e′ provides a first radiating surface 394e of the acoustic radiator 390e.

[0473] The second layer of balsa 395e″ covers less than 75% or less of the surface area of the face of the layer of polystyrene 395e to which the second layer of balsa 395e″ is attached, The second layer of balsa 395e″ and the part of the face of the layer of polystyrene 395e exposed behind the second layer of balsa 395e″ provides a second radiating surface 394e′ of the acoustic radiator 390e.

[0474] The first and second layers of balsa 395e′, 395e″ help to stiffen the acoustic radiator 390e.

[0475] The polystyrene in the layer of polystyrene 395e is preferably expanded, but could be extruded instead. Example parameters for the layer of polystyrene 395e may be: [0476] Density: as low as possible e.g. 15 kg/m.sup.3 up to 60 kg/m.sup.3 [0477] E modulus (which is related to density) may be in the range 1.4 MPa-4.0 MPa [0478] Thickness may be up to 10 mm, preferably 3 mm to 5 mm.

[0479] The balsa in the layers of balsa 395e′, 395e″ may be a sheet of balsa wood, or a balsa veneer. If a sheet of balsa is used, then a grain direction of the balsa preferably extends in a direction in which the balsa is longest. Example parameters for each layer of balsa 395e′, 395e″ may be: [0480] Density: 100 kg/m.sup.3 to 150 kg/.sup.3 [0481] Bending modulus along the grain may be 3.5 GPa-5 GPa (note that bending modulus rises with frequency) [0482] Thickness may be 0.5 mm-1.5 mm

[0483] Note that each layer of balsa 395e′, 395e″ covers only part of a surface formed from the layer of polystyrene 395e, e.g. so that only the minimum amount of balsa is used to achieve a desired stiffness.

[0484] FIG. 6(f) shows a sixth example loudspeaker 300f.

[0485] In this example, the acoustic radiator 390f has a laminate structure formed of at least two layers wherein the at least two layers include a first layer of a first material having a first density, and a second layer of a second material having a second density, wherein the first density is lower than the second density. In some examples, there may be an additional third layer of the second material, wherein the first layer is sandwiched between the second layer of the second material and the third layer of the second material having the second density. The at first and second materials may be, for example: [0486] balsa-foam [0487] paper-foam [0488] paper-honeycomb [0489] carbon fibre-foam [0490] glass fibre-paper

[0491] A laminate structure including two layers of the same material are also possible, e.g. balsa-balsa.

[0492] In this example, the attachment portion 350f of the drive unit 301f includes alignment features configured to engage with corresponding alignment features 391f (here drawn as shoes) on the acoustic radiator 390f to facilitate alignment and easy attachment of the attachment portion 350f and acoustic radiator 390f. This attachment may be mechanical (e.g. screw, bayonet or heat weld) or chemical (adhesive).

[0493] This example shows two alternative forms of crash protection (circled with dotted lines), i.e. two locations at which a frame of the magnet assembly 302f and the mounting frame 380f overlap as viewed in a plane (e.g. plane 308f) perpendicular to the movement axis 306f. These crash protection features help to prevent the magnet assembly 302f from protruding out from a headrest during a crash of a vehicle in which the loudspeaker 300f is mounted within the headrest.

[0494] Of course, it would be possible to have just one of the crash protection features as shown in FIG. 6(f), rather than both. It would equally be possible for either/both of these crash protection features to be present continuously (or discontinuously) along a path extending around the movement axis.

[0495] FIG. 6(g) shows a seventh example loudspeaker 300g.

[0496] In this example, the acoustic radiator 390g has, at its periphery (outer edge), an extension which extends along the movement axis in the backward direction B.

[0497] For the purposes of demonstrating different solutions, FIG. 6(g) shows two possible forms of the extension.

[0498] In a first form, the extension 397g is an integral part of the acoustic radiator which is folded to extend along the movement axis in the backward direction.

[0499] In a second form, the extension is provided by a foam strip 397g′ attached (e.g. by adhesive) to the remainder of the acoustic radiator 390g at the periphery of the acoustic radiator 390g.

[0500] A seat (e.g. part of a seat headrest in which the loudspeaker is mounted) may include a waveguide 378g which at least partially (preferably entirely) surrounds the acoustic radiator 390g and is configured to guide sound produced by the first and/or second radiating surface of the acoustic radiator 390g.

[0501] Preferably, a gap between the waveguide and a periphery of the acoustic radiator 390g less than 5 mm, more preferably less than 2 mm (e.g. in the range 1 mm to 2 mm), at one or more (preferably all) locations at the periphery of the acoustic radiator.

[0502] FIG. 6(h) shows an eighth example loudspeaker 300h.

[0503] In this example, there is only one mounting frame suspension 370h, wherein this mounting frame suspension 370h is formed of elastic foam, preferably a single piece of elastic foam, e.g. which may have properties as described in [15], though other forms of elastic foam are of course possible.

[0504] FIG. 6(i) shows a seat headrest 1000i incorporating ninth and tenth loudspeakers 300i, 300i′, and additionally incorporating two mid-high frequency loudspeakers 1010i, 1010i′.

[0505] The two mid-high frequency loudspeakers 1010i, 1010i′ may be of a cardioid type, e.g. as described in [16], though other forms of mid-high frequency loudspeakers are of course possible.

[0506] Also shown in FIG. 6(i) are: [0507] an electronic unit 1015i [0508] headrest chassis 1030i to which the mounting frame 380i of the loudspeaker 300i is attached (the headrest chassis 1030i is part of a rigid seat frame) [0509] acoustic transparent finishing material 1020i, e.g. perforated leather, textile, etc (noting that parts can be left non transparent for aesthetic reasons) [0510] Open cell elastic foam 1025i, preferably acoustic transparent in front of the acoustic radiators 300i, 300i′ (this can be combined with areas of non-transparent foam to increase support comfort)

[0511] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0512] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0513] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventor does not wish to be bound by any of these theoretical explanations.

[0514] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0515] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0516] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/−10%.

REFERENCES

[0517] A number of publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below. The entirety of each of these references is incorporated herein. [0518] [1] U.S. Pat. No. 6,618,487B1 [0519] [2] U.S. Pat. No. 4,506,117A [0520] [3] U.S. Pat. No. 8,247,930B2 [0521] [4] U.S. Pat. No. 7,372,968B2 [0522] [5] U.S. Pat. No. 4,550,428A [0523] [6] U.S. Pat. No. 6,965,679B1 [0524] [7] U.S. 2005/180587A1 [0525] [8] U.S. Pat No. 4,675,907A [0526] [9] U.S. Pat. No. 4,354,067A [0527] [10] U.S. Pat. No. 4,750,208A [0528] [11] DE102004009902A1 [0529] [12] U.S. Pat. No. 9,621,994B1 [0530] [13] U.S. Pat. No. 5,734,132 [0531] [14] WO2019/121266 [0532] [15] GB2008724.3 [0533] [16] GB2004076.2