Abstract:
A device is disclosed for dispensing a fluid supplied from an external fluid source. The device comprises a transducer adapted to receive a fluid from the fluid source, and a collapsible linkage coupling the transducer and the fluid source. The linkage has a collapsible joint inhibiting discharge of the fluid source when in a locked orientation. The device further comprises a movable member coupled to the linkage such that inhalation forces on the device cause the linkage to collapse thereby discharging the fluid from the fluid source. The device may further include a dose counter coupled to the fluid source for registering the amount of doses administered from the fluid source.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of copending application Ser. No. 10/888,445, filed on Jul. 9, 2004, incorporated herin by reference in its entirety, which claims priority from U.S. provisional application Ser. No. 60/487,493, filed on Jul. 14, 2003, incorporated herein by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable  
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC  
       [0003]     Not Applicable  
       NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION  
       [0004]     A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C.F.R. § 1.14.  
       BACKGROUND OF THE INVENTION  
       [0005]     1. Field of the Invention  
         [0006]     This invention pertains generally to metered dose inhalers and more specifically, to a metered dose inhaler with a breath actuated delivery mechanism and dose counter.  
         [0007]     2. Description of Related Art  
         [0008]     Inhalers are commonly used to deliver a wide range of medicaments to the bronchial passages, lungs and bloodstream of the user. Typical inhalers hold a container of pressurized medicament and propellant that is actuatable, generally by compression, to deliver a dose of medicament through a mouthpiece to the patient.  
         [0009]     It is generally desirable for the dose of medication to be dispensed at the same time that the patient inhales air to permit the majority of medication to enter the lung rather than the mouth or esophagus. A number of inhalers have been developed that use breath actuated devices to automatically initiate the discharge of the medicament from the container when the patient inhales. Many of these devices, such as U.S. Pat. No. 5,069,204 to Smith et al., use latching mechanisms that require a considerable amount of air pressure to release the medicament. These higher release pressures lead to difficulty of use, and discharge at non-optimal points in the patient&#39;s breath cycle.  
         [0010]     It is therefore an object of the present invention to provide a breath-actuated inhaler having a controllable release mechanism that is sensitive to the inhalation forces of the user to provide synchronous air entrainment and medicament delivery. It is further an object of the present invention to provide a simple and reliable dose counter responsive to discharge of the medicament container.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     According to a first aspect of the invention, an apparatus is provided for dispensing a first fluid supplied from an external fluid source comprising a transducer adapted for receiving the first fluid from the fluid source, wherein translation of a portion of the fluid source along a first axis releases the first fluid into the transducer. The apparatus will generally have a loading member coupled to the fluid source to impose a biasing force to the fluid source along the first axis.  
         [0012]     In all cases, the apparatus has a linkage coupling the transducer and the fluid source, the linkage having a collapsible joint inhibiting translation of the fluid source in the first axis when the collapsible joint is oriented in a first position, and allowing translation of the fluid source in the first axis when the collapsible joint is oriented in a second position. The apparatus further comprises a movable member coupled to the linkage, the moveable member responsive to an inhalation force exerted on the moveable member, the inhalation force causing the movable member to shift the collapsible joint from the first position to the second position, thereby allowing translation of a portion of the fluid source in the first axis from a stowed position to a discharge position to discharge the first fluid into the transducer.  
         [0013]     In preferred embodiments, the transducer further comprises one or more vents to entrain the first fluid with a second fluid. Additionally, there may be a plug coupled to the transducer. Ideally, the plug is retained in a first chamber of the transducer and has a bluff surface such that the axis of the bluff surface is perpendicular to the first axis.  
         [0014]     The apparatus of the present invention has an inhalation horn coupled to the transducer. The inhalation horn has a second chamber positioned along a second axis, wherein the second chamber is in communication with the first chamber via an outlet positioned at a first end of the second chamber. Suction on the inhalation horn by the user causes an inhalation force on the moveable member. In many embodiments, the second axis is perpendicular to the first axis. Generally, the second chamber has an internal cross section that increases from the first end to a second end forming an opening in the horn. In some embodiments, the internal cross section of the second chamber is parabolic.  
         [0015]     Typically, the moveable member comprises a flap rotatably mounted to the transducer, wherein the flap rotates in response to the inhalation force. The flap is generally configured to rotate from a first orientation retaining the collapsible joint in the first position, to a second orientation allowing the collapsible joint to move to the second position as a result of the force applied in the first axis. Usually the device includes a flap spring coupled to the flap and the transducer to return the flap from the second orientation to the first orientation after the inhalation force has subsided.  
         [0016]     In a preferred embodiment, the linkage comprises an upper link and a lower link, the upper link and the lower link rotatably attached to form the collapsible joint, a first end of the lower link rotatably housed in the transducer. A second end of the lower link is coupled to the flap and the mating surfaces of the lower link and the flap are configured so that the lower link contacts the flap to retain the collapsible joint in the first position when the flap is in the first orientation. When the flap is in the second orientation, the lower link is free to advance past the flap to allow the collapsible joint to move to the second position. In a preferred embodiment, a reset spring is coupled to the lower link to return the collapsible joint from the second position to the first position.  
         [0017]     In some embodiments, a container holder is configured to receive a first end of the fluid source, wherein the container holder is coupled to the upper link. The container holder further comprises one or more protrusions.  
         [0018]     Preferably, a dust cover is pivotably coupled to the transducer. The dust cover covers the horn opening in a first orientation, and allows access to the horn opening in a second orientation. In a preferred embodiment, the dust cover comprises one or more cams that are configured to contact the one or more protrusions on the container holder upon rotation of the dust cover from the second orientation to the first orientation, thereby advancing the container holder and fluid source from the discharge position to the stowed position.  
         [0019]     In an alternative embodiment, the moveable member comprises a diaphragm mounted to the transducer, wherein a central portion of the diaphragm moves in response to the inhalation force. In this configuration, the collapsible joint is coupled to the central portion of the diaphragm, so that the inhalation force deflects the central portion of the diaphragm to orient the collapsible joint from the first position to the second position.  
         [0020]     In another aspect of the invention, the apparatus comprises a dose counter coupled to the fluid source. Ideally, the dose counter is responsive to motion of the fluid source in the first axis to count each dose of fluid released from the fluid source.  
         [0021]     In one embodiment, the dose counter further comprises a first wheel having a plurality of teeth along its perimeter, the plurality of teeth positioned to rotationally advance the first wheel in response to movement of the fluid source along the first axis. A second wheel positioned adjacent the first wheel, the second wheel having markings for indicating the number of doses discharged from the fluid source. The first wheel is preferably configured to engage the second wheel such that the second wheel rotates at a scaled movement in relation to the first wheel.  
         [0022]     The apparatus may further comprise a sleeve configured to house a portion of the fluid source, wherein the sleeve has a protrusion that contacts the teeth of the first wheel to rotationally advance the first wheel as the fluid source is advanced in the first axis. The loading member may also have a spring coupled to the sleeve, wherein the spring provides a compressive force to the fluid source to bias the fluid source to move in the first axis.  
         [0023]     In some embodiments, the apparatus may further have a manual release button. The button is coupled to the collapsible joint to manually shift the collapsible joint from the first position to the second position, thereby releasing the first fluid into the transducer.  
         [0024]     In another aspect of the invention, an inhaler for dispensing metered doses of a medicament comprises a fluid source containing the medicament, wherein the fluid source has a cylindrical container having a nozzle located in line with a discharge axis of the container. The nozzle discharges the medicament when the container is advanced relative to the nozzle from a stowed position to a discharge position along the discharge axis. The inhaler further includes a transducer having a surface configured to engage the nozzle of the fluid source. The inhaler preferably has a loading member coupled to the container, the loading member imposing a biasing force to the container to discharge the container along the first axis. A linkage couples the transducer and the container, wherein the linkage has a collapsible joint inhibiting translation of the container in the first axis when the collapsible joint is oriented in a first position, and allowing translation of the container in the first axis when the collapsible joint is oriented in a second position. The inhaler also has a movable member coupled to the linkage, the moveable member responsive to an inhalation force, the inhalation force causing the movable member to shift the collapsible joint from the first position to the second position, thereby allowing translation of the container in the first axis from the stowed position to the discharge position to discharge the fluid into the transducer.  
         [0025]     The moveable member comprises a flap rotatably mounted to the transducer, wherein the flap rotates in response to the inhalation force. The flap is configured to rotate from a first orientation retaining the collapsible joint in the first position, to a second orientation allowing the collapsible joint to move to the second position as a result of the force applied in the first axis.  
         [0026]     The linkage preferably has an upper link and a lower link, the upper link and the lower link rotatably attached to form the collapsible joint, a first end of the lower link rotatably housed in the transducer. A container holder is configured to receive a first end of the container, wherein the container holder is coupled to the upper link. In some embodiments, the container holder further comprises one or more protrusions. A dust cover is pivotably coupled to the transducer, wherein the dust cover covers a horn opening in a first orientation, and allowing access to the horn opening in a second orientation. The dust cover may also have one or more cams configured to contact the one or more protrusions on the container holder. Upon rotation of the dust cover from the first orientation to the second orientation, the container holder and container are advanced from the stowed position to the discharge position.  
         [0027]     In another aspect of the invention, a dose counter is coupled to the container, wherein the dose counter is responsive to motion of the container in the first axis to count each dose of fluid discharged from the fluid source. In one embodiment, the dose counter comprises a first wheel having a plurality of teeth along its perimeter, the plurality of teeth positioned to rotationally advance the first wheel in response to movement of the fluid source along the first axis, and a second wheel positioned adjacent the first wheel, the second wheel having markings for indicating the number of doses discharged from the fluid source. Preferably, the first wheel is configured to engage the second wheel such that the second wheel rotates at a scaled movement in relation to the first wheel.  
         [0028]     In yet another aspect of the invention an inhaler for dispensing metered doses of a medicament comprises a fluid source containing the medicament. The fluid source has a nozzle and a container, wherein the nozzle discharges the medicament when the container is advanced relative to the nozzle from a stowed position to a discharge position along a first axis. The inhaler has a transducer having a surface configured to engage the nozzle of the fluid source and a loading member coupled to the container, the loading member imposing a force to the container to bias the container to discharge along the first axis.  
         [0029]     The inhaler further has a means for collapsibly retaining the fluid source from translating along the first axis a means for releasably supporting the collapsible retaining means, wherein the releasable support means releases support of the collapsible retaining means in response to an inhalation force.  
         [0030]     In many embodiments, the releasable support means has a first orientation retaining the collapsible retainer means in a first, locked position, and a second orientation allowing the retainer means to collapse to a second unlocked position, and wherein the inhalation force causes the releasable support means to shift from the first orientation to the second orientation, thereby allowing translation of the container in the first axis from the stowed position to the discharge position to discharge the fluid.  
         [0031]     In another aspect of the invention, the inhaler also includes a means for counting the number of doses of dispensed medicament, wherein the counting means is responsive to the axial motion of the container. Preferably, the counting means is responsive to both the motion of the container from the stowed position to the discharged position, and the motion of the container from the discharged position back to the stowed position.  
         [0032]     In many embodiments, the counting means comprises a gear means for translating the axial motion of the container into a corresponding radial motion, and a display means for displaying the number of doses based on the radial motion of the gear means. In preferred embodiments, the display means may be scaled with respect to the gear means to match the total dose count of the fluid source.  
         [0033]     In yet another aspect of the invention, an inhaler for dispensing metered doses of a medicament comprises a fluid source comprising a cylindrical container having a nozzle located in line with a discharge axis of the container, wherein the nozzle discharges the medicament when the container is advanced relative to the nozzle along the discharge axis. A container sleeve is configured to house a portion of the container, the container sleeve having a protrusion extending outward radially from the container. The inhaler further comprises a first wheel having a plurality of teeth along its perimeter, the plurality of teeth positioned to rotationally advance the first wheel in response to contact from the protrusion on the container sleeve as the container sleeve and container advance in the discharge axis, wherein the rotation motion of the first wheel indicates the number of metered doses dispensed from the fluid source.  
         [0034]     In a preferred embodiment, a second wheel is positioned adjacent the first wheel, the second wheel having markings for indicating the number of doses discharged from the fluid source, wherein the first wheel is configured to engage the second wheel such that the second wheel rotates at a scaled movement in relation to the first wheel. The first wheel has a plurality of engagement surfaces for engaging the second wheel, wherein the number of engagement surfaces varies the rate of the movement of the second wheel with respect to the first wheel.  
         [0035]     In yet another aspect, an inhaler for dispensing metered doses of a medicament is disclosed. The inhaler has, or is designed to be used with a fluid source containing medicament. The fluid source has a container having a nozzle located in line with a discharge axis of the container, wherein the nozzle discharges the medicament when the container is advanced relative to the nozzle from a stowed position to a discharge position along the discharge axis.  
         [0036]     The inhaler further comprises a housing having a surface configured to engage the nozzle of the fluid source, the surface adapted for receiving the fluid from the fluid source. A loading member is coupled to the container, wherein the loading member imposes a biasing force to the container in the stowed position to discharge the container along the first axis. A linkage couples the housing and the container, wherein the linkage has a collapsible joint connecting first and second links configured to restrain translation of the container in the first axis. The collapsible joint is restrained from moving by a restraining surface on a movable member.  
         [0037]     The moveable member is responsive to an inhalation force causing the movable member to shift the restraining surface to release the collapsible joint, thereby allowing translation of the container in the first axis from the stowed position to the discharge position to discharge the fluid into the housing.  
         [0038]     In one embodiment of the current aspect, the first link and second link each have first ends rotationally mounted with respect to the housing to form a loading path parallel to the first axis. The collapsible joint is located off-center from the loading path in the stowed position such that the collapsible joint is predisposed to collapse in absence of restraint from the moveable member.  
         [0039]     In several embodiments, the moveable member comprises a flap rotatably mounted to the housing, wherein the flap rotates in response to the inhalation force to shift the restraining surface.  
         [0040]     In one embodiment, the second member has a second end restrained by the restraining surface of the flap, and the flap is configured to rotate from a first orientation retaining the second end of the second member, to a second orientation releasing the second member from the restraining surface, thereby collapsing the collapsible joint as a result of the force applied in the first axis.  
         [0041]     In an alternative embodiment, the second member has a second end restrained by a trip link rotationally coupled to the flap. The trip link having a catch restraining motion of the second end of the second link in the stowed position.  
         [0042]     Preferably, the trip link has a contact surface mating with the restraining surface of the flap. The restraining surface is configured to inhibit rotation of the trip link with respect to the flap (when the flap is in a first orientation) to retain the second end of the second link in the catch. The flap is configured to rotate from the first orientation to a second orientation to allow the contact surface of the trip link to advance past the restraining surface of the flap, thereby allowing the trip link to rotate to release the second end of the second link from the catch.  
         [0043]     In one embodiment, the inhaler further comprises a container holder configured to receive a first end of the container, wherein the container holder allows translation of the first end of the first link along the loading path to allow collapse of the collapsible knee when not restrained by the moveable member. The container holder may further comprises one or more protrusions, such that one or more cams of a dust cover pivotably coupled to the housing contact the one or more protrusions on the container holder upon rotation of the dust cover, thereby advancing the container holder and linkage from the discharge position to the stowed position. Preferably, the trip link is configured to engage the second end of the second link upon advancement of the container holder from the discharge position to the stowed position.  
         [0044]     Another aspect is an apparatus for dispensing a fluid supplied from an external fluid source. The apparatus has a housing adapted for receiving the fluid from the fluid source, wherein translation of a portion of the fluid source from a stowed position to a discharge position along a first axis releases the first fluid into the housing. A loading member imposes a biasing force on the fluid source in the stowed position to discharge the fluid source along the first axis.  
         [0045]     The apparatus further comprises a linkage coupling the housing and the fluid source, the linkage having a collapsible joint connecting first and second links configured to restrain translation of the fluid source in the first axis. The second link has a first end rotationally mounted with respect to the housing and a second end coupled to a restraining surface on a movable member. The moveable member may be a flap that is responsive to an inhalation force, the inhalation force causing the movable member to shift the restraining surface to release the collapsible joint, thereby allowing translation of the fluid source in the first axis from the stowed position to the discharge position to discharge the fluid into the housing.  
         [0046]     In one embodiment, the second end of the second member is restrained by a trip link rotationally coupled to the flap, wherein the trip link has a catch restraining motion of the second end of the second link in the stowed position.  
         [0047]     The trip link has a contact surface mating with the restraining surface of the flap, wherein the restraining surface is configured to inhibit rotation of the trip link with respect to the flap when the flap is in a first orientation to retain the second end of the second link in the catch. The flap is configured to rotate from a first orientation to a second orientation to allow the contact surface of the trip link to advance past the restraining surface of the flap, thereby allowing the trip link to rotate to release the second end of the second link from the catch.  
         [0048]     The first link preferably has a first end rotationally mounted with respect to the housing such that the first ends of the first and second links form a loading path parallel to the first axis. In the stowed position, the collapsible joint is located off-center from the loading path to predispose collapse of the collapsible joint in absence of restraint from the moveable member.  
         [0049]     A further aspect is an inhaler for dispensing metered doses of a medicament. The inhaler comprises a housing configured to house the translating portion of a fluid source. There are first and second angled contact surfaces coupled to the housing along with a rotational member that translates in the direction of the housing in the discharge axis. The first angled surface is disposed on the rotational member in opposition to the second angled surface such that motion of the housing upon discharge engages the first and second opposing angled surfaces to rotationally advance the rotation member with respect to the housing. A display wheel advances in response to motion from the rotation member to indicate the number of metered doses dispensed from the fluid source.  
         [0050]     Preferably, the display wheel is scaled with respect to the motion of the rotation member. A planetary gear mechanism may be coupled to the rotational member to scale the motion of the display wheel to be a fraction of the motion of the rotational member.  
         [0051]     In one embodiment, the first angled surface comprises one or more keys disposed on a perimeter of the rotating member. The second angled surface may comprise a plurality of tines disposed on the inside of a cover disposed around the housing such that the keys engage successive tines upon each discharge of the fluid source.  
         [0052]     In addition, third and fourth angled contact surfaces may also be included. The third angled surface may be disposed on the rotational member in opposition to the fourth angled surface. The fourth angled surface is fixed from rotational motion so that motion of the housing upon recharge engages the third and fourth opposing angled surfaces, thereby further rotating the rotation member with respect to the housing.  
         [0053]     Another aspect is a method for counting metered doses of medicament dispensed from a fluid source. The method includes the steps of advancing the fluid source in a first direction to dispense medicament, advancing a rotational member incrementally in response to motion from the fluid source, scaling the motion of the rotational member, and advancing a display wheel in response to the scaled motion of the rotational member to indicate the number of metered doses dispensed from the fluid source.  
         [0054]     The method may further include the steps of advancing the fluid source in a second direction opposite said first direction to recharge the medicament, and advancing a rotational member incrementally in response to motion from the fluid source in the second direction.  
         [0055]     A first angled surface on said rotational member may be engaged with a second angled surface that is fixed with respect to rotation to advance the rotational member in response to motion from the fluid source in the first direction. Furthermore, a third angled surface on said rotational member may be engaged with a fourth angled surface that is fixed with respect to rotation to advance the rotational member in response to motion from the fluid source in the second direction.  
         [0056]     Further aspects of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)  
       [0057]     The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:  
         [0058]      FIG. 1A  is an exploded view of the upper portion and dose counter of an embodiment of the present invention  
         [0059]      FIG. 1B  is an exploded view of the lower portion of the embodiment of  FIG. 1A , including the release mechanism.  
         [0060]     FIGS.  2 A-C are perspective views of the exterior housing of the embodiment of the inhaler of FIGS.  1 A-B in a fully assembled configuration.  
         [0061]      FIG. 3A  is a cross-sectional view detailing the release mechanism of the present invention in a stowed configuration.  
         [0062]      FIG. 3B  illustrates the device of  FIG. 3A  with the flap rotated as a result of inhalation forces.  
         [0063]      FIG. 3C  illustrates the device of  FIG. 3A  with the collapsible knee in a collapsed configuration and the fluid source discharged.  
         [0064]      FIG. 3D  illustrates the device of  FIG. 3A  with the flap returned to the stowed position and the collapsible knee still in a collapsed configuration.  
         [0065]      FIG. 3E  illustrates the device of  FIG. 3A  with the release mechanism returned to its stowed configuration.  
         [0066]      FIG. 4A  is a perspective view of an embodiment of the flap of the present invention.  
         [0067]      FIG. 4B  illustrates a cross-sectional schematic view the flap of  FIG. 3A  with the lower linkage retained by the flap in the stored configuration.  
         [0068]     FIGS.  5 A-B show schematic views of the flap and transducer of the present invention.  
         [0069]      FIG. 6A  is a perspective view of an embodiment of the transducer of the present invention.  
         [0070]      FIG. 6B  illustrates a cross-sectional schematic view the transducer of  FIG. 6A  with the fluid source in a stowed configuration.  
         [0071]      FIG. 7A  is a cross-sectional view detailing the release mechanism of the present invention in a stowed configuration and the dust cover cut out to show the release mechanism.  
         [0072]      FIG. 7B  illustrates the device of  FIG. 7A  with the dust cover rotated away from the horn and the release mechanism in the stowed configuration prior to breath actuation.  
         [0073]      FIG. 7C  illustrates the device of  FIG. 7B  with the release mechanism in the discharged configuration after breath actuation.  
         [0074]      FIG. 7D  illustrates the device of  FIG. 7B  with the cam of the dust cover driving the release mechanism back to the stowed configuration.  
         [0075]      FIG. 8A  is a cross-sectional view of the outer cover of the device to illustrate the dose counting mechanism of an embodiment of the present invention in a stowed configuration.  
         [0076]      FIG. 8B  illustrates the device of  FIG. 8A  with the container sleeve traveling part way through the discharge of the fluid source.  
         [0077]      FIG. 8C  illustrates the device of  FIG. 8A  with the container sleeve at the fully discharged configuration.  
         [0078]      FIG. 8D  illustrates the device of  FIG. 8A  with the container sleeve returning to the stowed position.  
         [0079]      FIG. 9  is a schematic view of the container sleeve and biasing spring of the present invention.  
         [0080]      FIG. 10  illustrates an embodiment of the dose counter wheel of the present invention.  
         [0081]     FIGS.  11 A-C illustrate an embodiment of the display wheel of the present invention.  
         [0082]     FIGS.  12 A-E are schematic views of the dose counter wheel and display wheel through various counting configurations.  
         [0083]      FIG. 13  is a cross-sectional view of an alternative embodiment of the present invention having a release mechanism using a diaphragm.  
         [0084]      FIG. 14  is a perspective view of an alternative embodiment of the present invention having a release mechanism above the fluid source.  
         [0085]      FIG. 15  is an exploded view of the device of  FIG. 14 .  
         [0086]     FIGS.  16 A-D are schematic views of the device of  FIG. 14  traveling trough its range of motion from the stowed position, to discharge position, back to the stowed position.  
         [0087]      FIG. 17  illustrates the device of  FIG. 14  having an electronic dose counter.  
         [0088]      FIG. 18  is an alternative embodiment of the present invention with a portion of the outer cover removed to show the release mechanism and a mechanical dose counter with a vertically mounted display wheel.  
         [0089]     FIGS.  19 A-B illustrate the release mechanism of the device of  FIG. 18 .  
         [0090]     FIGS.  20 A-B illustrate the dose counter of the device of  FIG. 18 .  
         [0091]     FIGS.  21 A-F illustrate a further embodiment of the dose counter through one breath actuation cycle.  
         [0092]      FIGS. 22A  and B illustrate perspective views of the dose counter of FIGS.  21 A-F.  
         [0093]      FIG. 23  shows a top view of the dose counter of FIGS.  21 A-F.  
         [0094]      FIG. 24  A-D illustrates motion of a breath actuation mechanism using a trip link. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0095]     Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus generally shown in  FIG. 1A  through  FIG. 24D . It will be appreciated that the apparatus may vary as to configuration and as to details of the parts, and that the method may vary as to the specific steps and sequence, without departing from the basic concepts as disclosed herein.  
         [0096]     Referring first to  FIGS. 1A and 1B , an inhaler  20  of the present invention is shown in an exploded view with a breath actuation assembly  100  and a dose counter assembly  130 . The breath actuation assembly  100  and the dose counter assembly  130  are housed along with medicament fluid source  22  inside front cover  42 , back cover  44 , and top cap  54 , all preferably comprising medical grade plastic or other suitable materials known in the art. Fluid source  22  may comprise a conventional Metered Dose Inhaler (MDI) container or other propellant based medicament readily available in the art. Fluid source  22  generally comprises container  108  holding a mixture of medicament and propellant, and nozzle  110 , which is in line with the discharge axis  86  of the container  108 , as shown in  FIG. 6B . When the container  108  is advanced relative to the nozzle  110  in the direction of the discharge axis  86  (i.e. the nozzle  110  is pushed into the container  108 ), the medicament is discharged out the nozzle  110  in the direction of the discharge axis  86 .  
         [0097]     Turning now to  FIGS. 2A through 2C , inhaler  20  is shown in an assembled configuration with dust cover  40  pivotally mounted to cover inhalation horn  58 . The dust cover  40  may be rotated away from horn  58  to expose opening  60 , as shown in  FIG. 2B . A manual release button  62 , as shown in  FIG. 2C , may also be incorporated into the back cover  44 . Top cap  54  has an opening  56  to give visual access to display wheel  52 .  
         [0098]     Referring also to  FIGS. 1B and 3A  through  3 E, the breath actuation assembly  100  comprises a housing or transducer  32  that rotatably houses lower link  28  at pivot  78 . Lower link  28  is connected to upper link  26  at collapsible joint  66 . Reference may also be made to  FIGS. 5A-6B , wherein the transducer is illustrated in greater detail. Container holder  24  is shaped to receive the nozzle end of container  108  such that the nozzle  110  passes through to contact surface  112  of the transducer  32 . Container holder  24  also has a pair of guides  122  having slots  90  sized to house a pair of bosses  92  as shown in  FIG. 7A  at the upper end of upper link  26 .  
         [0099]     As shown in  FIGS. 3A through 4B , flap  34  is rotatably mounted to the transducer  32  via peg  98 , which extends across the top surface of flap  34 , and holes  114  in the sidewalls of transducer  32 . The bottom and side extremities of flap  34  are sized to fit within the internal surface of transducer  32  to form gap  76 . The flap  34  has an upper restraining surface  72  configured to retain arm  74  of lower link  28  when the flap is in its nominal position shown in  FIG. 4B .  
         [0100]     As illustrated in  FIGS. 6A and 6B , the transducer  32  is configured to receive nozzle  110  of fluid source  22  at surface  112 . The transducer also comprises an inlet  106  that spans from surface  112  to a first chamber  102 . The inlet  106  is configured to be in line with the nozzle  110  and discharge axis  86  such that medicament discharged from the fluid source  22  is received through the inlet  106  and downstream into first chamber  102 .  
         [0101]     The transducer  32  is also configured to receive plug  38  having bluff surface  104 . Fluid entering chamber  102  through inlet  106  is dispersed and redirected by plug  38  and into outlet  124  that terminates downstream at section  68  of second chamber  64 . The fluid dispersion characteristics of transducer  32  can be seen in greater detail with reference to U.S. Pat. No. 4,972,830 and EP308524B, which are expressly incorporated by reference herein.  
         [0102]     The fluid source  22  is biased to discharge along axis  86  by compressing a loading member, such as biasing spring  48 , between the top cap  54  and container sleeve  46 , which is adapted to receive the other end of the container  108  opposite the nozzle  110 . Biasing spring  48  preloads the container  108  to move in the direction of surface  112  of transducer  32  along the discharge axis  86 .  
         [0103]     In the stowed configuration shown in  FIG. 3A , the fluid source container  108  is retained from translating along axis  86  by a collapsible linkage comprising upper link  26  and lower link  28 . Upper link  26  and lower link  28  are rotatably coupled at a collapsible knee-type joint  66 . The upper end of upper link  26  has a pair of bosses  92  that are retained by a pair of guides  122  in the container holder  24  having slots  90 . The guides are generally in-line, or at least parallel with the discharge axis  86 , and allow motion of the bosses  92  (see  FIG. 7A ) of the upper link to slideably translate upward and downward in the discharge axis  86 , as well as allow the boss to rotate as necessary. The lower link  28  has one end fixed to the transducer  32  at pivot  78 . As illustrated in  FIG. 3A , the boss  92  of the upper link  26  and pivot  78  of the lower link are essentially in-line with discharge axis  86 , i.e. they form a loading path that is parallel to, or aligned with the discharge axis  86 . Because collapsible joint  66  is off-center, i.e. positioned away from the loading path formed by the boss  92  of the upper link  26  and pivot  78 , the downward force imposed by biasing spring  48  on the container  108  in the stowed position predisposes the knee joint  66  to collapse. Such collapse is restrained in the stowed position by imposition of arm  74  of lower link  28  on flap  34 .  
         [0104]      FIG. 3B  illustrates the initiation of the breath actuation mechanism  100  caused by inhalation by a patient through the opening  60  of horn  58 . As shown in  FIGS. 3B-3C  and  4 A, an outward airflow  80  is created in the second chamber  64 , which pulls through a plurality of slots  70  in the transducer. Suction of air through slots  70  creates a small pressure differential  82  across the inner surface of flap  34 , causing the flap to rotate about peg  98  and into the cavity of the transducer  32 , as illustrated in  FIGS. 3A and 3B . The gap  76  between the flap  34  and the transducer  32  provides enough clearance to allow the flap to rotate into the cavity of the transducer, while also being small enough to allow a pressure differential with minimal suction on the horn. As the flap  34  rotates, arm  74  of the lower link  28  is no longer retained by the upper surface  72  of the flap, and the arm  74  clears the flap  34  through recess  88  as the lower link  28  is allowed to rotate about pivot  78 .  
         [0105]     With rotation of the lower link  28  as shown in  FIG. 3C , the collapsible joint  66  moves over center, allowing the container holder  24  and container  108  to translate downward along axis  86 , forcing a portion of the nozzle  110  into the container  108  to stimulate discharge of the medicament from the container  108 . The medicament travels through the first chamber  102  and into the second chamber  64  where it is entrained with air flowing through slots  70 , as described in further detail in U.S. Pat. No. 4,972,830, previously incorporated by reference. In the embodiment shown, the second chamber  64  has an internal cross section that is shaped like a parabola. The entrained medicament flows through the second chamber  64  and out of the opening  60  of horn  58  to be inhaled by the patient. Therefore, the release of the metered dose of medicament is timed to be inhaled by the patient at an optimal moment during the inhalation phase of the patient&#39;s breath cycle.  
         [0106]     After the inhalation of the dose by the patient, the flap is returned to its nominal position shown in  FIG. 3D  by a return force exerted by flap spring  36 . Flap spring  36  is a metallic rod or wire assembled between retention arms  96  of the transducer  32  and flange  94  on the flap  34 . Rotation of the flap bends the spring to create a return force to return the flap  94  to its nominal position after the inhalation forces have subsided.  
         [0107]     The upper and lower links  26 ,  28 , container holder  24 , and container  108  remain in the collapsed discharge position as seen in  FIG. 3D  due to the force imposed by the biasing spring  48 . The return of the dust cover  40  (described in greater detail with reference to  FIGS. 7A-7E  below) to cover the horn  58  manually forces the container holder  24  and container  108  to return to the stowed position under compression from biasing spring  48 . Return torsion spring  30  is mounted on lower link  28  to engage the transducer  32  such that a torsional force is exerted on the collapsible linkage to return to the locked configuration. The collapsible joint  66  is thus retained from collapsing once the dust cover  40  is again opened.  
         [0108]     Turning to  FIGS. 7A-7E , the operation of the dust cover  40  will now be described. In the present embodiment, the dust cover  40  not only serves as a shield to cover horn entrance  60 , but it also serves to reset the container to the stowed position after discharge of the medicament.  FIG. 7A  illustrates inhaler  20  in a stowed configuration with the dust cover  40  shielding the entrance  60  to horn  58 . The dust cover  40  is pivotably connected to the transducer  32  such that it can be rotated out of place to allow access to the horn opening  60 . In alternative embodiments, the dust cover may be pivotably connected to either the front or back covers  42 ,  44 . The dust cover  40  has two cams  120 , which are configured to engage the bottom surface of guides  122  of container holder  24  through its entire range of motion along axis  86 . When the dust cover  40  is rotated about pivot  118  (shown in  FIG. 7B ), the cams disengage guides  122 . The container holder  24  and container  108  remain in the stowed position from the over-center orientation of the collapsible linkage.  
         [0109]      FIG. 7C  illustrates the breath actuation assembly  100  in the collapsed configuration with the container holder  24  and container  108  in the discharge position. The breath actuation assembly  100  is biased to remain in this configuration due to the compressive force of the biasing spring  48 . When the dust cover is rotated back toward the horn opening  60 , as shown in  FIG. 7D , the cams  120  engage the bottom surface of guide  122 , pushing the container holder  24  and container  108  upward along axis  86 . When the dust cover  40  is in its final stowed position covering the horn entrance  60 , the cams  120  have pushed the container holder  24  to the stowed position, as shown in  FIG. 7A . In this configuration, the return spring  30  has reset the breath actuation assembly  100  to the locked position, and movement of the container  108  will be retained by the dust cover cams independent of the collapsible linkage.  
         [0110]     The inhaler  20  preferably includes a dose counter for automatically counting the remaining doses left in the container after each discharge of the medicament. The inhaler may be configured with a dose counter having a number of different configurations, including mechanical or electrical counters. The operation of a preferred embodiment utilizing a mechanical dose counter assembly  130  will be described with respect to  FIGS. 8A  to  12 E.  
         [0111]      FIG. 8A  illustrates inhaler  20  with dose counter assembly  130  configured above the container sleeve  46 . The container sleeve  46  is sized to receive the non-dispensing end of the container  108 . The container sleeve preferably has one or more tabs  132  having a boss  136  configured to engage the teeth of first wheel  50  disposed just above the container sleeve  46 . The embodiment shown in  FIG. 9  has two tabs  132  and bosses  136 . However, it will be appreciated that any number of tabs and bosses may be employed.  
         [0112]     Referring back to  FIG. 8A , first wheel  50  is a gear rotatably mounted in a horizontal orientation to top cap  54 . Wheel  50  has a plurality of lower teeth  140  and upper teeth  138  disposed along the outer perimeter of wheel  50 .  
         [0113]     In a preferred embodiment, display wheel  52  is also rotatably mounted to top cap  54  in a horizontal orientation between first wheel  50  and the top cap. Display wheel  52  has an opening  154  to allow clearance for column  142  of first wheel  50  that is vertically disposed to mount to top cap  54 . Display wheel  52  has markings  150  to indicate the number of doses left in the container  108  based on the position of the display wheel  52 . As seen in  FIGS. 2A and 2B , the markings  150  that are showing through opening  56  in top cap  54  indicate the number of remaining doses.  
         [0114]      FIGS. 8A-8D  illustrate the interaction between the container sleeve  46  and the first wheel  50  upon discharge of the fluid source  22 . When the container  108  is in the stowed position, boss  136  lines up on the perimeter of wheel  50  between two of the upper teeth  138 . As the container  108  and container sleeve  46  moves downward along the discharge axis as a result of the breath actuation mechanism, boss  136  contacts the upper incline of one of the lower teeth  140 , as shown in  FIG. 8B . The boss  136  continues its translation along axis  86 , forcing the first wheel  50  to turn clockwise (looking down from the top) until the container  108  reaches the discharge position, as shown in  FIG. 8C . When the dust cover  40  is closed to return the container  108  to the stowed position, boss  136  translates upward until contacting the lower incline of upper tooth  138 , as shown in  FIG. 8D . The boss  136  continues its upward translation, forcing the wheel  50  to further turn clockwise until the container  108  reaches the stowed position, shown in  FIG. 8A . When another dose is dispensed, the cycle repeats.  
         [0115]     The lower wheel  50  may be configured to vary the number of doses required to turn the lower wheel 360 degrees by varying the number of teeth. In the above embodiment, a 40-tooth index was used. However, this number may be varied depending on the number of doses included in the container.  
         [0116]      FIGS. 12A-12C  illustrate the interaction between the display wheel  52  and the lower wheel  50 . As shown in  FIG. 10  and in hidden line in  FIGS. 12A-12C , the lower wheel  50  has a drive peg  144  disposed on the upper surface of the lower wheel. Display wheel  52  has a plurality of semi-circular receiving pegs  152  disposed on the lower surface of the display wheel. As first wheel rotates about column mount  142 , drive peg  144  engages a first of the receiving pegs  152  and causes the display wheel  52  to rotate about mount  156  a specified distance along mark  150 , the specified distance indicating the range of doses left (e.g. “full 200 to 160”) (see  FIG. 12A ). At a portion of first wheel&#39;s rotation, the drive peg  144  slips past the first of the receiving pegs  152  (see  FIG. 12B ) and continues to complete one full rotation (40 doses) until contacting the second of the receiving pegs  152  ( FIG. 12C ). The cycle repeats itself until all the receiving pegs  152  are driven such that the “empty” indicator is displayed at window  56  when the specified number of doses has been dispensed.  
         [0117]     The effect of the gearing as shown in FIGS.  12 A-C is to scale the motion of the display wheel  52  with respect to the first wheel  50 . To change the scale of the motion, one or more additional driving pegs  144  may be disposed on the upper surface of the first wheel  50 . For example, a second driving peg (not shown) may be disposed 180 degrees from the first such that the display wheel would advances twice as fast relative to the first wheel for a container having 100 total doses.  
         [0118]      FIG. 13  illustrates an alternative embodiment showing an inhaler having a breath actuated release mechanism  200  using a diaphragm  202  rather than the flap  34  shown in  FIGS. 1-7E . The diaphragm  202  is configured to mount to transducer  204  and be sized so that a portion of the diaphragm deflects in response to inhalation forces from the patient. Release mechanism  200  further includes a catch  204  coupled to the diaphragm and the lower link  208  to retain the collapsible linkage comprised of the lower link  208  and the upper link  210 .  
         [0119]     During use, inhalation forces from the patient deflect the portion of the diaphragm in communication with catch  204 . Motion of the catch  204  allows lower link  208  to rotate past the catch, thereby allowing the  208 / 210  linkage to collapse and discharge fluid source  22 .  
         [0120]      FIGS. 14-17  illustrate another alternative embodiment of inhaler  300  having a load lever  302  and a breath actuated release mechanism  350  on top of fluid source  22 . By placing the release mechanism above the MDI container, the mechanism can be applied to any MDI actuator with minimal mold modification. Inhaler  300  has a lower portion  304  housing fluid source  22  and a transducer (not shown) for dispersing the medicament. Middle body  308  interfaces with lower portion  304  and slideably houses plunger  318  to selectively advance fluid source  22  downward to discharge the medicament.  
         [0121]     Plunger  318  is retained from moving relative to middle body  308  by a collapsible linkage comprising lower link  320  and upper link  322 . Plunger  308  is also configured to receive biasing spring  312  at its up extremity. The biasing spring  312  is shaped to receive spring cap  310  which may be depressed to compress spring  312  against plunger  318  in a downward discharge direction, as shown in  FIG. 16A . To depress spring cap  310 , load lever  302  is rotatably attached to top shell  306  such that rotation of load lever  302  to a vertical orientation forces the spring cap  310  down to bias the plunger to discharge fluid source  22 .  
         [0122]     Motion of the collapsible link  320 , and linkage  320 / 322 , is restrained by flap  316 . Flap  16  is pivotably mounted such that inhalation forces cause it to rotate as illustrated in  FIG. 16B , thereby allowing the lower link  320  to rotate downward such that linkage  320 / 322  collapses. The biasing force from spring  312  forces the plunger downward as illustrated in  FIG. 16C . The load lever  302  is then reset to the first position, allowing the fluid source  22  to translate back to the stowed position illustrated in  FIG. 16D .  
         [0123]      FIG. 17  illustrates an embodiment of the inhaler  300  incorporating an electronic dose counter  324 . In such a configuration, flap  316  is coupled to trigger  326 , which depresses a sensor in dose counter  324  each time the flap is tripped to dispense a dose of medicament. Dose counter  324  generally comprises a printed circuit board (PCB) and other electronic components such as an LCD to digitally display the dose count. Alternatively, a mechanical dose counter may instead be incorporated into inhaler  300  in much the same way as the inhaler disclosed in  FIGS. 9-12 , or  FIGS. 21A-23 .  
         [0124]      FIGS. 18 through 20 B illustrate another alternative embodiment of the present invention with inhaler  400  having a mechanical dose counter  420  that has a vertically mounted display wheel  422 . Inhaler  400  has a load lever  402  that manually biases the fluid source  22  discharge upon downward motion.  
         [0125]     As illustrated in  FIG. 19A , fluid source  22  is retained from discharging by collapsible joint  416 , which is formed by the junction of upper link  406  and lower link  408 . Lower link is coupled to horizontally oriented flap  410 . Inhalation forces on horn  404  cause air flow through port  412  into negative pressure chamber  414  such that a negative pressure is exerted on flap  410  to force flap  410  to rotate downward, as shown in  FIG. 19B . With collapsible joint  416  away from the locked position, the fluid source is free to translate downward and discharge the medicament.  
         [0126]      FIGS. 20A and 20B  illustrate an alternative embodiment of using a dose counter  420  with a vertically oriented display wheel  422 . Container sleeve  426 , adapted to receive the non-dispending end of container  22 , has a plurality of protrusions  434 . When the container cycles downward upon discharge, translation of the container sleeve  426  causes protrusions  434  to strike the teeth  432  of gear  424 , forcing the gear  424  to rotate clockwise. The clockwise rotation of gear  424  engages vertically oriented sprocket  430  of display wheel  422 , causing the display wheel  422  to turn. Sprocket  430  may be configured to engage gear  424  at specified intervals to vary the rate of rotation of the display wheel  422  with respect to the rate of rotation of the gear  424 .  
         [0127]     Referring now to  FIG. 21A -F, another preferred embodiment is shown as dose counter mechanism  450 . In  FIG. 21A , the mechanism  450  is in ready state (prior to breath actuation) with the canister sleeve  46  in the upward-most position in its travel. The canister sleeve  46  has a plurality of teeth  456  that are shaped to mate with and lock with the teeth  454  of a rotational member, or top link  452 . I.e., both teeth  456  and  454  have opposing angled surfaces that shift the angular position of the top link  452  with the canister sleeve  46  when engaged. When MDI canister  22  (shown in  FIG. 1B ) is actuated, the canister sleeve  46  and top link  452  move downward.  
         [0128]     A compression load is generated on the top link  452  from count spring  462 , which is disposed between the display wheel  464  and top link  452 . The top link has a plurality of radial protrusions, or keys  460  which are positioned and sized to mate with the columnar tines  458  of cap bottom  466 . Cap bottom  466  may be bonded to or integral with top cap  470  (shown in  FIG. 22 ), such that the cap bottom  58  remains fixed during motion of the canister sleeve  46 . Because of the compression force applied by the count spring  462 , the opposing inclined surfaces of the key  460  and cap bottom  466  cause the top link  452  to lift from the canister sleeve  46  and rotate 4.5°, sliding on the opposing angled surfaces as seen in  FIG. 21B . The top link is coupled to gear column  468  a such that gear column  468  rotates incrementally with rotation of the top link  452   
         [0129]     Referring now to  FIG. 21C , the canister sleeve  46  continues to travel downward, following the keys  460  of the top link to push in between the columnar tines  458  of the cap bottom  466 . When the canister sleeve  46  has bottomed out, as shown in  FIG. 21D , it will then rebound and then start moving up toward its original ready state position, pushing the top link  460  up with it. As the canister sleeve  46  moves up, the key  460  clears the tines  458  of the cap bottom  466  as shown in  FIG. 21E . The teeth  456  of the canister sleeve  46  then re-engage the teeth  454  of the top link  452 , causing the top link  452  to rotate another 4.5° clockwise, as shown in  FIG. 21 F . This completes the full cycle of MDI canister actuation and the indexing mechanism rotated a total of 9°. The indexing mechanism top link  452  has advanced 1/40th of a full revolution per actuation.  
         [0130]     Referring now to  FIG. 22A , the dose counter mechanism  450  is mounted on top of the breath actuation assembly  100  (see  FIG. 1B ). Top cap  470  surrounds canister sleeve  46 , shown in  FIG. 22B  with a section of the top cap  470  removed for clarity. The top cap has a window  472  for showing the dose count as provided by the display wheel  464 . Display wheel  464  has a display label  474  showing remaining dose counts from 0 to 200 in ten dose increments (e.g. markings of 200, 190, 180, etc.)  
         [0131]      FIG. 23  illustrates a top portion of the top cap  470  cut out and display label  474  removed to show planetary gear mechanism  478 . The display wheel  464  is rotationally coupled to gear column  468  via three intermediary gears  476 . The three intermediary gears  476  of the planetary gear mechanism  478  are driven by the rotation of center gear column  468 . The teeth of the three intermediary gears  476  mate with the internal geared surface of the top cap  470  such that the display wheel  464  rotates clockwise. When the center gear column  468  rotates 9° due to motion of the indexing mechanism, the planetary gear will rotate the display wheel 1/10 of a graduation. The label is set to a resolution of 10 shots per indication, however may be altered to reflect different increments. After 200 actuations, the label will have advanced total of 260°—going from “200” to “0” or “Empty”.  
         [0132]     The planetary gear mechanism  478  has the effect of scaling down the rotational motion of the top link  452  and gear column so that the display wheel may rotate through 200 actuations in less than one full rotation. For smaller dose counts (e.g. 120 or 60 count canisters), the display wheel may simply be positioned so that the correct count is initially viewed through window  472 . Alternatively, a different tooth count for the planetary gear mechanism  478  may be implemented along with changing the display label  474  to accommodate different total dose counts.  
         [0133]     Referring to  FIG. 24A -D, the breath actuation mechanism  500  is another preferred embodiment that incorporates a trip link  502  to increase the operational range of previously described breath actuation mechanism  100  shown in  FIGS. 3A through 4E .  
         [0134]      FIG. 24  illustrates the breath actuation mechanism in ready (non actuated, and loaded) state. Instead of interfacing directly with flap  34 , lower link  504  interfaces indirectly with flap  34  via trip link  502 . The upper link  506  and lower link  504  retain motion of the fluid source  22  and load F from biasing spring via locking knee joint  66 . Knee joint  66  is located off-center from load F in discharge axis  86  (i.e. the discharge axis  86  passes through pivot  78  and the boss  516  of upper link  506  throughout FIGS.  24 A-D), thus the downward force imposed by biasing spring  48  on the container  108  in the ready position predisposes the knee joint  66  to collapse.  
         [0135]     The upper link  506  and lower link  504  are restrained from rotating or collapsing because the lower link  504  is locked from rotation from a catch, or trip edge  510  in trip link  502 . Trip link  502  is locked from rotating because of impingement of upper surface (contact surface)  512  of the trip link  502  with a restraining surface, or circular cutout  514 , in flap  508 .  
         [0136]     Referring now to  FIG. 24B , when flap  508  rotates due to the force created by patent inhalation (vacuum), upper edge  512  if the trip link clears the cutout  514 , allowing the trip link  502  to rotate to rotate clockwise. Trip edge  510  correspondingly rotates to release the contacting surface of the lower link  504 .  
         [0137]     With lower link  504  now unrestrained, as shown in  FIG. 24C , knee joint  66  collapses and shifts to the left. Because of constraints on the top edges of upper link  506  with container holder  24 , the upper link can only travel in line with the force load path F, and trip link  502  further rotates clockwise, causing lower link  504  to further rotate counter clockwise.  
         [0138]     Referring now to  FIG. 24D , the mechanism further collapses as lower link  504  continues to rotate counter-clockwise on joint  78 ,  26  travels down allowing the MDI canister  22  to travel downward causing the valve stem to activate.  
         [0139]     After the activation, the canister travels upward such that the knee joint moves back toward its stowed orientation with lower link rotating clockwise toward trip link  502 . The trip link  502  is able to catch lower link  504  in trip edge  510  for retention of the knee joint  66  until subsequent breath actuation of flap  508 .  
         [0140]     The addition of trip link  502  over previously described embodiments expands the operational margin of the lower  504  with the flap  508 , improving overlap on trip edges to ease manufacturing tolerances while maintaining breath actuation sensitivity.  
         [0141]     Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”