Abstract:
A metered dose inhaler pump for delivering a metered dose of an active compound from an active compound inlet through a spray outlet without the need of a pressurized active compound container. Reciprocating action of an inlet valve, an outlet valve and a plunger alternately draw a metered dose of the active compound from an active compound container into an active compound chamber and pressurize the drawn metered dose of the active compound to eject the metered dose through the spray outlet. The plunger substantially fills and evacuates the metered dose chamber, leaving no void head space therein.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to metered dose inhalers, and, more particularly, to a pump for a metered dose inhaler which does not require the use of a pressurized container of medicine. 
     2. Brief Description of Related Art 
     Metered dose inhalers have been commercially available for use in the treatment of a variety of respiratory ailments, such as asthma. Such metered dose inhalers typically require a pressurized cylinder or canister of medicine to deliver a metered dose of such medicine to a person&#39;s respiratory tract. These pressurized cylinders or canisters have employed a halogenated hydrocarbon as a propellant, with the active compound dissolved in the propellant or suspended in the propellant in solid, micronized form. 
     For example, U.S. Pat. No. 4,955,371 describes a disposable inhalation device wherein an aerosol measured dose canister provides a short spray for releasing a fixed dose of medicine. However, environmental concerns have disfavored the use of halogenated hydrocarbons in aerosol containers. U.S. Pat. No. 4,534,345 describes a dosage inhaler employing a dosing unit for dosing a pharmacologically active compound separate from a pressurized propellant container. The pressurized container contains liquified, pressurized carbon dioxide. In either case, the propellant is delivered into a person&#39;s respiratory tract with the medicine dose. 
     Thus, there is a need for a metered dose inhaler capable of delivering a metered dose of an active compound without the use of a pressurized propellant. Therefore, in order to alleviate these and other problems, an objective of the present invention is to provide a metered dose inhaler pump for pressurizing and delivering a metered dose of an active compound to a person&#39;s respiratory tract. 
     SUMMARY OF THE INVENTION 
     The above and other beneficial objects are obtained in accordance with the present invention by providing a metered dose inhaler pump having an active compound inlet for drawing a metered dose of a pharmacologically active compound from an unpressurized container into a metered dose chamber and a spray outlet for delivering the active compound from the metered dose chamber into a person&#39;s respiratory tract. A first valve is provided at the inlet, and a second valve is provided at the outlet. The metered dose chamber is provided between and in fluid communication with the first valve and the second valve. A spring-loaded trigger urges a plunger into the metered dose chamber, closing the first valve, opening the second valve and filling and evacuating the metered dose chamber, thereby delivering the metered does of the active compound from the metered dose chamber to a person&#39;s respiratory tract through the outlet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a front perspective view of a metered dose inhaler pump according to the present invention; 
     FIG. 2 is a front sectional view of the metered dose inhaler pump; 
     FIG. 3 is a front sectional view of a valve block of the metered dose inhaler pump; 
     FIG. 4 is a top plan view of a trigger of the metered dose inhaler pump; 
     FIG. 5 is a front elevational view of a cocking arm of the metered dose inhaler pump; 
     FIG. 6 is a perspective view of an inlet valve of the metered dose inhaler pump; and 
     FIG. 7 is a perspective view of an outlet valve of the metered dose inhaler pump. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Those skilled in the art will gain an appreciation of the invention when viewed with the accompanying drawings of FIGS. 1-7, inclusive. The individual reference characters designate the same or similar elements throughout the several drawings. 
     FIG. 1 is a front perspective view of a metered dose inhaler pump  10 . Metered dose inhaler pump  10  includes a housing  12  having an active compound inlet  14 , a spray nozzle  16 , a trigger  18  and a cocking trigger  32 . Housing  12  is in the form of a shell having a first shell half  22  and a second shell half  24 . First shell half  22  and second shell half  24  have mirror-image internal structures, which will be described in detail below. First shell half  22  and second shell half  24  are joined by ultrasonic bonding. First shell half  22  and second shell half  24  may be made of any suitable material. However, a plastic material is preferred because of its light weight and manufacturing characteristics. 
     Cover  124  is mounted onto housing  12  rotatably about pin  132 . Cover  124  can be opened and closed by the user of metered dose inhaler  10  to selectively expose active compound inlet  14  for receiving the canister of active compound, not shown. Cover  124  may be formed of a clear plastic material or may include a clear window for allowing a user to visually determine the number of metered doses remaining in the active compound container. Mouthpiece  126  is mounted in housing  12  rotatably about pin  134 . Mouthpiece  126  is adapted by size and configuration for insertion into the oral cavity of a person and to couple or sealingly engage with the oral lips for inspiration and expiration of the breath of the person. Alternatively, mouthpiece  126  can be adapted to engage with the person&#39;s nasal passages. Serrations  128  are provided on the body of mouthpiece  126  to facilitate the rotation of mouthpiece  126  about pin  134 . A pocket  130  is formed in housing  12  so that mouthpiece  126  can be rotated to a closed position, wherein the top surface of mouthpiece  126  as shown in FIG. 2 becomes flush with housing  12 . When both cover  124  and mouthpiece  126  are in their closed positions, metered dose inhaler  10  forms a compact and easily carried and stored device, and mouthpiece  126  and active compound inlet  14  are protected from contaminants and physical damage. 
     Now referring to FIG. 2, the internal structure of first shell half  22  disclosing structure of pump  23  is described in detail. It will be understood that the description of the internal structure of first shell half  22  necessarily describes the internal structure of second shell half  24  by virtue of second shell half  24  being a mirror image of first shell half  22 . First shell half  22  has wall members defining a trigger channel  56 , a linkage channel  60 , a valve channel  62 , an inlet channel  64 , and an outlet channel  66  for respectively receiving trigger  18 , linkage  26 , valve block  38 , active compound inlet  14  and spray outlet  16 . 
     Trigger  18  is received in housing  12  by trigger channel  56 . Trigger  18  has a shaft portion  88 , a button portion  86  at a proximal end of shaft portion  88  and a spring guide  76  at a distal end of shaft portion  88 . A helical spring  68  is provided to bias trigger  18  outwardly from housing  12 , and, more specifically, to bias button portion  86  outwardly from opening  74 . One end of spring  68  is urged against the blind end of trigger channel  56 , the other end is received by spring guide  76  protruding from distal end of trigger  18 . Spring guide  76  is provided for maintaining proper orientation of spring  68 . A lip  80  is provided generally near the distal end of shaft portion  88  for engaging with a detent  90  of trigger channel  56  to counteract the action of spring  68  and to maintain trigger  18  within housing  12 . 
     Now referring to FIG. 4 the further structure of trigger  18  will be described in detail. FIG. 4 is a top view of trigger  18 , which illustrates that shaft portion  88  includes a step portion  92  of decreased width where shaft portion  88  extends from button portion  86 . Button portion  86  is shown with a generally square shape. It will be appreciated that button portion  86  may have any shape. A channel  50  is provided in shaft portion  88  generally located centrally along the length of shaft  88  between step portion  92  and lip  80 . Channel  50  is provided to receive cocking arm  30  as will be described below. Trigger  18  may be made of any suitable material. However, trigger  18  is preferably made of a plastic material, which is preferred because of the relatively light weight and ease of manufacturing plastic materials. 
     Now referring to FIG. 5 the structure of cocking arm  30  will be described in detail. Cocking arm  30  is disposed within cocking arm channel  58  and has a block portion  94  and a shank portion  96  extending from block portion  94  and terminating at a head portion  98 . Head portion  98  includes an internally threaded hole  100  for receiving screw  36  and protrudes through housing  12  through channel  58 . The diameter of head portion  98  is larger than that of shank portion  96  so that head portion  98  prevents cocking arm  30  from completely entering housing  12 . Head portion  98  may be integrally formed with cocking arm  30  or head portion  98  may be separately manufactured and screwed onto the end of shank portion  96 . Block portion  94  has a width that will permit block portion  94  to be slippingly fitted into channel  50  of trigger  18  and has a generally U-shaped channel  102  for allowing trigger  18  to slide perpendicularly to cocking arm  30  as will be described below. Cocking arm  30  may be made of any suitable material. However, cocking arm  30  is preferably made of aluminum or an alloy thereof because of its material and manufacturing characteristics. 
     Now referring to FIG. 2, a helical spring  34  is disposed along the length of shank portion  96  so that one end of spring  34  is urged against block portion  94 , illustrated in FIG. 5, and the other end of spring  34  is urged against the end of cocking channel  58 . Spring  34  acts to bias cocking arm  30  inwardly into housing  12 , as illustrated in FIG.  1 . The proximal end of shank  96  has an internally threaded hole  100  for receiving screw  36  for attaching cocking trigger  32  thereto. 
     Linkage  26  is disposed within housing  12  in linkage channel  60 . First shell half  22  has a hole, not shown, and linkage has a hole  104  for receiving pin  28  about which linkage  26  is rotatable. Linkage  26  is generally L-shaped having a first leg  52  and a second leg  54 . Each leg  52 ,  54  has a U-shaped channel for respectively receiving seat  78  of plunger  20  and step  92  of trigger  18 . Linkage may be made of any suitable material but is preferably made of aluminum or an alloy thereof for its material and manufacturing characteristics. 
     Plunger  20  is a generally cylindrical member having seat  78  disposed along the length thereof. A distal end of plunger  20  defines a shank  106 , and a proximal end of plunger  20  defines a head  108 , shank  106  and head  108  being separated by seat  78 . Plunger may be integrally formed. Alternatively, seat  78  may be formed as a distinct portion thereof and mounted on shank  106 . Plunger  20  may be made of any suitable material but is preferably made of stainless steel or an alloy thereof for its material and manufacturing characteristics. Shank channel  114  should have a surface finish in accordance with the surface finish requirements of seal  46 . 
     Now referring to FIG. 3, the internal structure of valve block  38  is described in detail. Valve block  38  is disposed within valve channel  62  of housing  12  and its position is fixed thereby. Valve block  38  has a shank channel  114  for receiving shank portion  106  of plunger  20 , an inlet valve channel  110 , an outlet valve channel  112  and a metered dose chamber  44 . A seal  46  is provided in a seat along the length of shank  106  to form a fluid-tight seal between shank  106  and metered dose chamber  44 . An inlet valve  40  is provided within inlet valve channel  110 , and an outlet valve  42  is provided within outlet valve channel  112 . Inlet valve has a generally cylindrical body  120  of substantially the same diameter as inlet valve channel  110  and a conical tip  122 . FIG. 6 illustrates the preferred configuration of inlet valve  40 . Fins  48  are provided along the length of the body  120  of inlet valve  40 . Inlet valve  40  may be made of any suitable material but is preferably made of a resilient material to ensure fluid-tight sealing. More specifically, inlet valve  40  is made of a silicone elastomer. The resiliency of inlet valve  40  permits inlet valve  40  to act both as a sealing member and as a spring. Inlet valve  40  is provided with a plurality of fins  48  to maintain inlet valve  40  centrally positioned within inlet valve channel  110 , while permitting fluid flow between fins  48  at a low resistance. 
     FIG. 7 illustrates the preferred configuration of outlet valve  42 . Outlet valve  42  has a generally cylindrical body  136  having substantially the same diameter as outlet valve channel  122  and a conical tip  138 . Outlet valve  42  has a cylindrical portion  140  of larger diameter than cylindrical body  136 . Portion  140  has a single channel  142  to minimize the volume of active compound retained in the area of spray nozzle  16 . The single channel  140  further prevents air bubbles in and evaporation of the active compound. 
     Metered dose chamber  44  is in fluid communication with inlet valve channel  110 , outlet valve channel  112  and shank channel  114 ; outlet valve channel  112  is in fluid communication with spray outlet  16 ; and inlet valve channel  110  is in fluid communication with active compound inlet  14 . An inlet adapter  116  is provided between valve block  38  and active compound inlet  14  to permit fluid communication therebetween. Valve block  38  connects directly with spray nozzle  16 . Inlet adapter  116  may be of any design that will permit fluid communication with medicament reservoir. Threads  146  are provided in inlet adapter  116  for receiving the container of active compound, not shown. A needle  144  is provided to puncture the collar of the container when the container is threaded into inlet adapter  116 . 
     The operation of metered dose inhaler pump  10  is now described in detail. Active compound inlet  14  may be of any design that will permit an active compound container, not shown, to be connected thereto for delivering the active compound to metered dose chamber  44 . In a normal condition of metered dose inhaler pump  10 , trigger  18  is in a fully depressed position and held in such position by block portion  94  of cocking arm  30 . In the normal condition, shank portion  106  of plunger  20  is urged into valve block  38  by block portion  94  of cocking arm  30  so that seat  78  is urged against valvetered dose inhaler pump  10  for usage, cocking arm  30  is pulled outwardly from housing  12  by pulling outwardly on cocking trigger  32  against the action of spring  34 . When U-shaped channel  102  of cocking arm  30  is in vertical alignment with shaft portion  88  of trigger  18 , spring  68  urges trigger  18  outwardly from housing  12  and perpendicularly to the movement of cocking arm  30 . When trigger  18  is in its fully extended position, the interaction of U-shaped channel  102  and channel  50  of shaft portion  88  prevents further outward movement of trigger  18  and cocking arm  30 . As trigger  18  is urged outwardly by spring  68 , linkage  26  is rotated about pin  28  in a counter-clockwise direction, as viewed from the perspective of FIG. 2, by step portion  92  of trigger  18  acting upon leg  54 . In turn, the foregoing rotation of linkage  26  urges plunger  20  outwardly from valve block  38  by the action of leg  52  against seat  78 . The outward movement of plunger  20  creates a vacuum condition in metered dose chamber  44 , inlet valve channel  110  and outlet nozzle  16 . This vacuum condition causes both inlet valve  40  and outlet valve  42  to be urged inwardly toward metered dose chamber  44 . The conical tip of outlet valve  42  is urged against the opening of the wall defined between metered dose chamber  44  and outlet valve channel  112 , thereby fluidly sealing outlet valve channel  112  with respect to metered dose chamber  44  and preventing air or other gas or fluid from entering metered dose chamber  44  through spray outlet  16 . 
     The vacuum condition further draws an amount of active compound from the active compound container, not shown, through inlet  14 , inlet adapter  116  and inlet valve channel  110  and into metered dose chamber  44 . Fins  48  of inlet valve  38  permit the active compound to be drawn past inlet valve  38 . The amount of active compound drawn into metered dose chamber  44  is equal to the volume displacement of shank  106  of plunger  20 . Thus, such volume displacement designed into metered dose inhaler pump  10  should be equal to the volume of the desired metered dose. 
     Once metered dose inhaler pump  10  is charged as described above, metered dose inhaler pump  10  is prepared to deliver a metered dose of the active compound to a person&#39;s respiratory tract. By depressing trigger  18 , channel  50  is aligned with block portion  94 , allowing cocking arm  30  to slide inwardly toward valve block  38 . At such time, block portion  94  is urged against head  108  of plunger  20  by spring  34 , and linkage  26  is rotated about pin  28  in a clockwise direction as viewed from the perspective of FIG.  2 . Block portion  94  urging against head  108  of plunger  20  urges shank  106  of plunger  20  thereby pressurizing metered dose chamber  44 , inlet valve channel  110  and outlet nozzle  16 . Such pressurization urges inlet valve  40  and outlet valve  42  outwardly with respect to metered dose chamber  44 . Conical tip of inlet valve  40  is urged against outlet nozzle  16  forming a fluid-tight seal, thereby preventing active compound from being ejected from active compound inlet  14 . 
     Plunger  20  is urged into metered dose chamber  44  forcing active compound from metered dose chamber  44  through outlet nozzle  16  and delivering active compound to a person&#39;s respiratory tract. It will be appreciated that the dimensions of outlet nozzle  16  are such that outlet nozzle may deliver particle sizes suitable for inhalation treatment, which may be, for example, in a size range of 3 to 6 microns. Channel  142  of outlet valve  42  permit active compound to be delivered past outlet valve  42 . The volume of active compound delivered to an operator&#39;s respiratory tract is equal to the volume displacement of metered dose chamber  44  by the action of shank  106 . Metered dose chamber  44  has a diameter substantially equal to the diameter of shank  106  of plunger  20 , so that the inward movement of shank  106  substantially fills and evacuates metered dose chamber  44 , leaving substantially no void head space in metered dose chamber  44 , inlet valve channel  110  or outlet nozzle  16 . 
     Thus the several aforementioned objects and advantages are most effectively attained. Although a single preferred embodiment of the invention has been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.