Abstract:
A dispensing device for dispensing a powdered product includes a housing having a first end and a second end defining a first outlet; a plunger slidably received in the first end of the housing, the housing and plunger together defining an interior of the dispensing device which is open to atmosphere; a chamber located within the plunger for housing a powdered product; a sheathing member slidably mounted on an end of the plunger proximate the second end of the housing, and having an inlet and a second outlet closed by a frangible membrane. Additionally, the plunger includes a perforating element for puncturing the frangible membrane when the plunger is moved towards the second end of the housing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present patent application claims priority under 35 U.S.C. to patent application GB 0201409.0 filed Jan. 22, 2002, which is incorporated herein by reference. 
   BACKGROUND OF INVENTION 
   The present invention relates to a disposable dispensing apparatus for delivering a powdered product nasally or orally. More specifically, but not exclusively, there is provided a single use dry powder medicament inhaler which can be used by persons who have not had medical training. 
   Such dispensing devices are well known in the art and are of particular use for the dispensing of drugs which can easily be absorbed through the nasal or pulmonary passages, especially for drugs which only need to be dispensed occasionally. 
   A dispensing device is known from U.S. Pat. No. 5,683,361 (incorporated herein by reference) which dispenses a single dosage of a powdery drug which is stored in a cylindrical storage chamber within the sealed main body of the device until dispensation of the drug is required. The chamber is located in an axially displaceable piston, which is mounted in the main body of the device between an end wall of the main body and a plunger for releasing the drug. The chamber is sealed with breakable membranes at either end of the cylinder which are, upon activation of the dispensing device, punctured by one or more perforating elements. An outlet duct is provided at the end of the main body remote from the plunger for dispensation of the drug to the user. The perforating element is provided at the end of the outlet duct nearest to the piston to puncture at least the outermost membrane of the drug chamber. 
   Both embodiments of the device described in U.S. Pat. No. 5,683,361 involve pressurization of the air inside the device prior to dispensation of the powdered medicament. When the plunger is pressed by the user into the main body of the device a pocket of air, which is trapped inside the main body of the device between the piston and the plunger, is compressed and the pressure inside the device increases. This increase in pressure causes the piston to move towards the outlet duct of the dispensing device, thereby causing the outermost membrane to be punctured by the perforating element. The remaining intact membrane is then punctured in one of two possible ways: by the penetrating element provided at the inner end of the outlet duct as the plunger, and therefore also the piston, is pushed further into the main body of the device, or by a second perforating element which is optionally provided at the inner end of the plunger. 
   A disadvantage with the devices described in U.S. Pat. No. 5,683,361 is that they do not always dispense the whole drug dose to the patient. As the outermost membrane is punctured, pieces of the perforated membrane are pushed into the chamber in the opposite direction to movement of the plunger and the desired drug flow path. This results in some of the powdered drug particles being trapped between pieces of the perforated membrane and the wall of the chamber as the drug is forced out of the dispensing device via the outlet duct. Furthermore, as the patient inhales, the pieces of the perforated membrane are drawn in the direction of the outlet duct and thereby interfere with the dispensing of the drug as the powder can no longer flow freely out of the drug chamber. In this way, the dose dispensed by the device is often incomplete, which can mean that the drug is not wholly effective. 
   Another single-use dispensing device is described in patent application GB 0025027.4 (incorporated herein by reference) which device comprises a bellows unit for pressurizing the interior of the device and for propelling the powdered drug out of the dispensing apparatus. 
   A single-use dispensing device needs to be simple and cheap to manufacture. The known devices described above require a sealed main body to enable the device to be pressurized. 
   SUMMARY OF INVENTION 
   According to the present invention there is provided a dispensing device for dispensing a powdered product comprising a housing, having a first end and a second end defining a first outlet, a plunger slidably received in the first end of the housing, the housing and plunger together defining an interior of the dispensing device which is open to atmosphere, a chamber located within said plunger for housing a powdered product, a sheathing member slidably mounted on an end of the plunger proximate the second end of the housing, and having an inlet and a second outlet closed by a frangible membrane, and the plunger comprising a perforating element for puncturing the frangible membrane when the plunger is moved towards the second end of the housing. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a cross-sectional view of a first embodiment of a dispensing apparatus according to the present invention in a storage condition; 
       FIG. 2  is a cross-sectional of the apparatus of  FIG. 1  in a dispensing condition; 
       FIGS. 3   a ,  3   b  and  3   c  show plan views of three variants of frangible membranes for use in the dispensing device of the present invention; 
       FIG. 4  is a cross-sectional of a part of the dispensing device of the present invention showing a variant storage chamber inlet aperture; and 
       FIG. 5  is a cross-sectional of a second embodiment of a dispensing apparatus according to the present invention in a storage condition. 
   

   DETAILED DESCRIPTION 
   A preferred embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings. 
   As shown in  FIGS. 1 and 2 , the apparatus of the present invention comprises a housing  1 , a plunger  3  and a sheath  19 . The housing  1  comprises a generally tubular body  2  of varying diameter having an open second end forming a first outlet  31  in a tip  4  and an open first end in which the plunger  3  is slidably received. The housing  1  is provided with an external shoulder  5  for use as a finger rest. Alternatively, the housing  1  may be provided with a protruding lip to act as a finger rest. 
   The tip  4  comprises an outer wall  16  which defines an outlet duct  17  through which medicament may be dispensed. An innermost end of the outlet duct  17  is provided with an enlarged duct  27  which has a larger cross-sectional diameter than the outlet duct  17 . The innermost end of the enlarged duct  27  is provided with a shoulder  26 . 
   The tip  4  is frusto-conically shaped so as to form a nozzle which is inserted, in use, into a patient&#39;s nostril. However, the tip  4  may also be shaped into a substantially cylindrical shape or similar, suitable for insertion, in use, into a patient&#39;s mouth. 
   The plunger  3  comprises a substantially cylindrical body  8  and a probe  6 . The body  8  is closed at one end to form an end face  12 . The opposite end is left open. The probe  6  is coupled or joined to an inner surface of the end face  12  and projects there from. The probe  6  is coupled to the end face  12  by means of a retaining lip  7 , although in an alternative embodiment the probe  6  and plunger  3  may be moulded as one piece, therefore avoiding the need for a retaining lip  7 . With the plunger  3  received in the housing  1 , the probe  3  projects towards the first outlet  31  of the tip  4 . Together, the plunger  3  and housing  1  define an interior  32  of the apparatus. 
   The probe  6  is substantially cylindrical in shape and is provided with an inwardly directed shoulder  28 . Alternatively, the inwardly directed shoulder  28  could be replaced by a flange. An end  33  of the probe  6  remote from the end face  12  is provided with a piercing tip  14 . The piercing tip  14  is provided with a sharpened cutting edge  15 . 
   A portion of the probe  6 , at the end  33  of the probe  6 , is provided with a hollow bore forming a storage chamber  24 . The storage chamber extends upwardly to the piercing tip  14 . A radially directed aperture  23  is provided through the thickness of the wall of the probe  6  communicating with a lower end of the storage chamber  24 . 
   The storage chamber  24  is substantially cylindrical in shape and is large enough to contain a single dose of powdered medicament which is to be dispensed. The powdered medicament is located in an end of the storage chamber  24  remote from the tip  4 . Likewise, the aperture  23  is located at the end of the storage chamber  24  remote from the tip  4 . 
   An external surface of the body  8  of the plunger  3  is provided with at least one axially oriented channel  9 . Each channel  9  receives a lug  10  which is located on an inner surface  11  of the housing  1 . The lug  10  and channel  9  arrangement prevents the plunger  3  from being withdrawn fully from the housing  1 . The channel  9  also allows for air from atmosphere to pass between the plunger  3  and the housing  1 , since the interference fit is not air tight. 
   The end face  12  of the plunger  3  is provided with an indentation  13  which is suitable for use as a thumb rest. 
   A sheath  19 , which is substantially cylindrical in shape, is slidably received over the end  33  of the probe  6  remote from the end face  12 . The sheath  19  comprises an open end  20  for receiving the probe  6  and an opposite closed end  21 , which is closed by a frangible membrane  18 . An aperture  22  is provided in the sheath  19 . The aperture  22  is in the form of a radially directed inlet which passes through the wall thickness of the sheath  19 . An outwardly directed shoulder  25  is provided on the sheath  19  in the vicinity of the closed end  21 . 
   Typically, the thickness of the frangible membrane  18  is between 0.03 and 0.20 mm. Furthermore, as shown in  FIGS. 3   a  and  3   b , the membrane  18  is provided with one or more pre-formed lines of weakness  29  to aid the rupturing of the membrane by the piercing tip  14 .  FIG. 3   a  depicts a star pattern of weaknesses and  FIG. 3   b  depicts a half-moon pattern of weaknesses. Alternatively, the frangible membrane  18  may comprise a plurality of castellations  30  which are of a reduced thickness compared to the rest of the frangible membrane  18  as shown in  FIG. 3   c.    
   In a storage position, as shown in  FIG. 1 , the sheath  19  is mounted on the probe  6  with the piercing tip  14  in close proximity but not quite abutting against the frangible membrane  18 . In this position, the radial apertures  22  and  23  are out of alignment and there is consequently no open flow path between the interior  32  of the housing  1  and the storage chamber  24 . Thus, the apertures  22  and  23 , which together form an inlet valve are in a closed position. However, there is an open flow path from the interior  32  of the housing  1  to the outlet duct  17 , via the duct  27 . 
   In use, a user holds the apparatus typically by means of two or more fingers positioned on the external shoulder  5  and a thumb positioned on the end face  12 . The tip  4  is then inserted into the nose (or mouth if the apparatus is for pulmonary use). Inhalation at this stage is possible freely but is ineffective since air is drawn from the interior  32  of the housing  1  through the enlarged duct  27  and out via the outlet duct  17 . Pressure in the interior  32  is equalized by air flow into the interior  32  between the plunger  3  and the housing  1 . 
   The user depresses the end face  12  of the plunger  3  relative to the housing  1  so as to move the probe  6  and sheath  19  axially in the direction of the tip  4 . Initially, the probe  6  and the sheath  19  are free to move unhindered into the enlarged duct  27 . 
   Further movement of the probe  6  and sheath  19  brings the outwardly directed shoulder  25  of the sheath  19  into contact with the internal shoulder  26  of the enlarged duct  27 . At this point, further movement of the sheath  19  towards the tip  4  is prevented. The abutment of the outwardly directed shoulder  25  of the sheath  19  against the internal shoulder  26  also closes the flow path from the interior  32  of the housing  1  to the outlet duct  17 . Continued movement of the probe  6  towards the tip  4  causes the probe  6  to slide relative to the sheath  19  and the piercing tip  14  of the probe  6  to pierce and break the frangible membrane  18 . 
   Advantageously, the frangible membrane  18  is ruptured from below with the piercing tip  14  moving relative to the membrane  18  in the direction of tip  4 . As a result the flap of the membrane  18  which is left after rupture is positioned above the membrane periphery such that as powdered medicament particles pass the membrane  18  the flap tends to be moved away from the hole formed in the membrane so as not to block the flow path. 
   Subsequent inward movement of the probe  6  causes the storage chamber  24  to be moved into the outlet duct  17 . During this stage of actuation, air within the housing  1  can escape between the plunger  3  and the housing  1 . Further relative axial movement of the sheath  19  and probe  6  causes the apertures  22  and  23  to come into alignment, opening the inlet valve of the storage chamber  24 . The apparatus is now in the dispensing position, as shown in FIG.  2 . 
   In the dispensing position the inlet valve is open and the frangible membrane  18  is ruptured. Thus a continuous flow path is established between the interior  32  of the housing  1 , and the outlet duct  17  via the storage chamber  24 . As a result, upon inhalation air is displaced from the interior  32  of the housing  1 , through the inlet valve formed by the apertures  22  and  23  and into the storage chamber  24  where it entrains the powdered product. The air and entrained product is then displaced through the piercing tip  14 , and outlet duct  17  where it exits the apparatus and is inhaled. 
   Movement of the probe  6  is finally limited by abutment of the inwardly directed shoulder  28 , against the open end  20  of the sheath  19 . 
   In an alternative embodiment of the invention, shown in  FIG. 5 , a second porous membrane  34  is provided in the storage chamber  24 , between the aperture  23  and the piercing tip  14 , on which a single dose of powdered medicament  35  is located. During use of this alternative embodiment, the tip  4  is placed into the nose or mouth and the end face  12  is depressed relative to the housing  1  so that the apparatus is in a dispensing position. During subsequent inhalation by the user, air is displaced from the interior  32  of the housing  1  through the apertures  22 ,  23  into the storage chamber  24 . Due to the porosity of the second membrane  34 , the air travels through the membrane  34 , thus entraining the powdered medicament  35  such that air and powdered medicament  35  exit the apparatus via the first outlet  31  and are inhaled. The second membrane  34  may be made of a porous paper, sintered plastic or similar material, provided that the pore size of the material is large enough to allow air through but small enough not to allow the powdered medicament  35  through. 
   The dispensing device is described above as being placed in the nose, or mouth as the case may be, before the device is actuated. However, the dispensing device may also be actuated prior to insertion of the tip  4  into the nose or mouth, as long as the device is maintained in an upright position to avoid spillage of the powdered medicament prior to insertion of the device in the nose or mouth. 
   The dispensing apparatus may be provided in a sterile package such as a foil packet in order to prevent moisture from affecting the apparatus, and also for reasons of hygiene. The apparatus will not function adequately if the powdered drug becomes damp. Alternatively, a cover may be provided to encase and close tip  4  before use. 
     FIG. 4  shows a variant of the aperture  23  wherein the aperture is directed so as to have a component in the axial direction as well as the radial direction. In this way the air entering the storage chamber  24  is directed towards the closed lower end of the chamber  24  so as to more efficiently entrain the powdered product. Alternatively, the inlet aperture  23  may be angled so as to have components in the radial, axial and circumferential directions such that air entering the storage chamber  24  is directed towards the lower end of the chamber  24  with a spiraling motion. In any of these arrangements the inlet aperture  23  may be positioned so as to be covered or uncovered by the powdered product in the storage condition. More than one aperture  23  may be provided. 
   Alternatively, the inlet aperture  23  may be positioned in the lower end of the storage chamber  24  such that air entering the chamber enters underneath the powdered product and is directed axially along the chamber  24  towards the piercing tip  14 . In a yet further alternative, the powdered product may be suspended on a mesh within the storage chamber  24  such that air entering the storage chamber  24  enters below the mesh and entrains the powdered product as it passes through the mesh. 
   Optionally, the storage chamber  24  may be provided with rifling grooves or similar along its length to impart a spiraling motion to the air and entrained product as it passes along the chamber towards the piercing tip  14 . 
   In the above description, item  19  is described as a “sheath”. This item may be in the form of a cap, case or similar. 
   The housing  1 , plunger  3 , probe  6  and sheath  19  are manufactured from polyethylene, polypropylene, polyester, any engineering plastic or a similar material. Similarly, the frangible membrane  18  is manufactured from polyethylene or polypropylene or a similar material. Alternatively, the probe  6  may be manufactured from a metal such as stainless steel. 
   The variants described above may be combined with the described embodiments in any combination as will be obvious to the skilled person. 
   Advantageously, the materials of the dispensing apparatus lend themselves to easy and ready recycling. In the preferred embodiment, the absence of any metallic or ceramic components reduces the cost of processing the recycled material. 
   Advantageously, the components of the dispensing apparatus are moulded. This leads to low levels of material waste. The current design allows for a low number of individual parts which reduce the assembly time and cost. In a preferred embodiment of the invention, the whole apparatus may be formed from only three components, the first component being the housing  1  including the tip  4 , the second component being the plunger  8  and probe  6  and the third component being the sheath  19  including the frangible membrane  18 .