Abstract:
An inhaler for dispensing a plurality of doses of particulate material has means for receiving and retaining a container ( 20 ) having a plurality of compartments, each for holding a respective dose (or part thereof). The container is moved by an indexing mechanism so as to bring successive compartments into registry with an airway to enable the contents of each compartment to be dispensed through the airway ( 50 ). The indexing mechanism is operated by a control member ( 6 ) which is movable through a series of alternating advance and return strokes (preferably rotational movements), the inhaler including a non-return mechanism ( 112, 114, 116  and  104 ) for preventing movement of the member in the direction of each return stroke before the completion of the respective preceding advance stroke, thereby to help to ensure that the indexing mechanism is properly operated.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to devices for dispensing a plurality of doses of particulate material, and in particular to inhalers for use in the self administering of a pharmacologically active substance in powder form by inhalation.  
         BACKGROUND TO THE INVENTION  
         [0002]    Inhalers for dispensing a medicament in a dry powder form are becoming increasingly common, and in many cases are intended for use with containers having a number of compartments, each holding a respective dose of medicament, and sealing means, for example a laminated foil seal for hermetically sealing each dose in its compartment. Such inhalers include a mechanism for piercing the seal to enable the medicament to be released from a compartment, and an indexing mechanism which moves the container relative to the inhaler to bring each compartment in turn into registry with an airway, through which the user inhales.  
           [0003]    In order to operate such devices properly, the indexing mechanism must be operated correctly, otherwise (for example) it is possible that the compartment in registry with the airway has not had its seal broken when the user inhales, or has previously been emptied or that a compartment is indexed out of registry with the airway before its dose has been dispensed.  
         SUMMARY OF THE INVENTION  
         [0004]    According to the invention, there is provided a device for dispensing a plurality of doses of particulate material from a container having a plurality of compartments, each for holding a respective dose or part thereof, the device comprising an airway extending from the portion of the device for receiving the container to an outlet, indexing means for moving a container received by the device relative to the airway so as to bring successive compartments into registry with the latter, a control member movable through a series of alternating advance and return strokes to operate the indexing means, wherein the device includes a non-return mechanism for preventing movement of the control member in the direction of each return stroke before the completion of the respective preceding advance stroke.  
           [0005]    Thus, the invention ensures that the control member is moved to a sufficient extent properly to operate the indexing means. Thus, if a user inadvertently fails to move the control member through a full advance stroke, the non-return mechanism prevents the user from returning the control member to its original position, and thus from obtaining the incorrect impression that the indexing means has been properly operated.  
           [0006]    Preferably, the control member is so linked to the indexing means that, in use, said movement of the container is caused by the return strokes of the control member.  
           [0007]    The device may to advantage be adapted for use with a container in which each dose is sealed in its compartment, in which case the device preferably includes opening means for breaking or opening the seal on each compartment, wherein the opening means is also linked to the control member so that operation of the latter operates both the indexing means and opening means.  
           [0008]    In this case, the non-return mechanism not only ensures that the indexing means is properly operated, but also that the indexing means and opening means are operated in the correct sequence.  
           [0009]    The opening means may conveniently comprise a piercing member so linked to the control member that each advance stroke of the latter extends the piercing member from its retracted position, in which it is situated clear of a compartment into an extended position in which it has pierced that compartment&#39;s seal.  
           [0010]    Preferably, the device includes a holding member so linked to the control member as to be extended by each advance stroke of the latter to engage a container held in the device and thereby hold a compartment in registry with the airway.  
           [0011]    The holding member thus helps to ensure that the compartment does not move out of registry with the airway prematurely, as a result of (for example) sudden movement of the inhaler.  
           [0012]    Preferably, the non-return mechanism is also operable to prevent movement of the control member in the direction of each advance stroke until the end of the respective preceding return stroke has been reached. This ensures that the control member is in its proper starting position before each cycle of operation of the device.  
           [0013]    Preferably, the advance and return strokes of the control member are constituted by rotational movements of the latter relative to a body of the device, the non-return mechanism comprising a pawl means and a set of teeth, each mounted on a respective one of the control member and the body. Conveniently, the teeth are mounted on the body and the carrier on the control member.  
           [0014]    Preferably, the pawl means comprises a pair of opposed pawls mounted on a movable carrier, one pawl engaging the teeth on each advance stroke, the other on each return stroke, the mechanism including abutment means for moving one pawl into engagement with the teeth and disengaging the other pawl at the end of each stroke.  
           [0015]    The invention also lies in an inhaler comprising a device as herein above described.  
           [0016]    Preferably, the control member of the inhaler includes a cover for covering the outlet of the airway when the inhaler is not in use, wherein the cover is moved clear of the outlet by each advance stroke of the control member.  
           [0017]    The invention also lies in a housing for a device/inhaler as herein above described, the housing having receiving means for receiving a container of particulate material, means for receiving indexing means, an outlet for the airway of the container, the housing also carrying a control member for operating the indexing means and means for linking the control member to an indexing means contained, in use, within the housing, wherein the control member is movable through a series of alternating advance and return strokes, and there is provided a non-return mechanism for preventing the movement of the member in the direction of each return stroke before the completion of the respective preceding advance stroke. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:  
         [0019]    [0019]FIG. 1 is an exploded isometric view of an inhaler in accordance with the invention;  
         [0020]    [0020]FIG. 2 is a similarly exploded view of the inhaler when rotated through 180° relative to FIG. 1;  
         [0021]    [0021]FIG. 3 is a further exploded view of the inhaler, showing certain components in an assembled form;  
         [0022]    [0022]FIG. 4 is an exploded view of those components;  
         [0023]    [0023]FIG. 5 is a sectional side view of the inhaler;  
         [0024]    [0024]FIG. 6 is a sectional view taken along the line H-H of FIG. 5;  
         [0025]    [0025]FIG. 7 is a similar view (from a slightly different angle) to FIG. 3;  
         [0026]    FIGS.  8 A-D to FIGS.  14 A-D are cut-away end views of the inhaler during various stages in one cycle of its operation;  
         [0027]    [0027]FIG. 15 is a perspective view, from a different angle, of one of the components shown in FIG. 4;  
         [0028]    [0028]FIG. 16 is a further perspective view of another component of the inhaler;  
         [0029]    [0029]FIG. 17 is a perspective view of the inhaler, when assembled and with its mouthpiece uncovered; and  
         [0030]    [0030]FIG. 18 is a graph illustrating the relationship between pressure drop in the inhaler and the rate of airflow therethrough. 
     
    
     DETAILED DESCRIPTION  
       [0031]    With reference to FIGS. 1 and 2, an inhaler comprises an elongate shell  2 , at one side of which a mouthpiece  4  is attached. The inhaler includes a rotatable control member  6  which is situated at one end of the shell  2  and which incorporates a cover  8  for covering the mouthpiece  4  when the inhaler is not in use. The shell  2  is fitted with a window  3 , through which a container (of medicament) in the inhaler can be viewed.  
         [0032]    The shell accommodates an elongate hollow core  10  which is axially and radially fixed at one end to the end (denoted by reference numeral  12 ) of the shell  2 . The core  10  is rotationally and axially fixed to the shell  2 . As can be seen from FIG. 15, the bottom of the core  10  is provided with three equi-angularly spaced slots  11 ,  13  and  15 , each defined by a respective pair of opposed ribs which extend towards the core centre. As can be seen from FIG. 16, the end of the shell  2  is provided with three ribs  19 ,  21  and  23 . Each of the ribs  19 ,  21  and  23  extends a respective one of the slots  11 ,  13  and  15  in the core  10  (when the inhaler is assembled) and frictionally engaged the ribs defining that slot. The frictional engagement between the ribs on the core  10  and the shell  2  retains the core  10  in and axially and rotationally fixes the core  10  to the shell  2 . These formations leave clear an opening  25  in the bottom edge of the core to allow air to travel from an inlet (not shown) up through the core centre.  
         [0033]    The core  10  has a bottom portion  18  which is externally screw-threaded and on which a cylindrical dose carrier  20  is mounted. The dose carrier carries a helical array of radial through bores, each of which contains a respective dose of powdered medicament, and is sealed by means of inner and outer laminated foil seals. A more detailed description of this type of container can be found in PCT publication No. WO 95/31238. The present container differs from a container as described in the earlier publication only in that the present container includes indentations (not shown) on its inner cylindrical surface for receiving an end of a locator device  22  as described below.  
         [0034]    The container  20  has radial inward protuberances, for example  24 , which engage the screw-thread of the bottom portion  18  such that rotation of the container  20  about the axis defined by the core  10  causes the container also to move axially along the core  10  to bring successive compartments into registry with the central portion of an opening  26  (that defines part of an airway in the inhaler) in the core  10 . The opening  26  is an axial alignment with the locator  22  which is, in turn, slidably mounted in the core  10  so as to be movable in a direction perpendicular to the core axis. The locator  22  is hollow, has an end opening and slidably contains a pin holder  28  from which a U-section pin  30  extends. The locator  22  has four conical end projections, for example  32  and  34 , which, in use, engage corresponding indentations on the inside surface of the container  20 . One face of the locator  22  also carries a lug  36  positioned adjacent a generally C-shaped camming aperture  38  in a face of the locator  22 .  
         [0035]    The pin holder  28  is also provided with a key way  40  which is provided with a forward ramp  42  and is used in the extending and retracting of the pin  30  to rupture the seals on the compartments in the container  20 .  
         [0036]    The pin  30  is axially aligned with a central passage, referenced  44  of an airway insert  46  which fits over a corresponding boss  45  on the mouthpiece  4 . As can be seen from FIG. 5, the airway insert  46  has a central passage  48  which extends into a corresponding passage  50  in the boss  45  of the mouthpiece  4 , and which is in registry with a compartment (in this case the compartment  52 ) of the container  20 . The portion of the insert  46  defining the passage  48  is spaced from the walls of the passage  50  to define an annular air inlet  54  for air flowing in directions indicated by the arrows  56  and  58 . It will be seen from FIG. 5 that the inlet  54  also constitutes a throat as it is narrower than both the upstream portions of the airway that feed it and than the passage  50 .  
         [0037]    The opening  26  in the core  10  provides the second air inlet which is situated behind a dose in the compartment  52 . The insert  46  has four spacer lugs  60 ,  62 ,  64  and  66  which are equi-angularly arranged around the passage  50 , and which extend generally radially relative to the core  10  and maintain the spacing between the insert  46  and the mouthpiece  4 .  
         [0038]    The locator  22  is extended by the action of a camming surface  68  (visible in FIG. 2) which bears against the lug  36  and forms part of the end of the drive shaft  70 . A peg  72  projects from the same end of the drive shaft  70  and is operable to engage the slot  38  to retract the locator  22 . The peg also engages the key way  40  in the holder  28  to extend and retract the pin  30 .  
         [0039]    The core  10  has an upper portion  74  into which the drive shaft  70  is inserted. As can be seen from FIG. 2, one side of the upper portion  74  includes a slot  76  which allows a pawl  78  on the drive shaft  70  to extend radially beyond the upper portion  74  when the pawl is in registry with the slot  76 .  
         [0040]    As can be seen from FIG. 3, the upper portion  74  and shaft  70  both fit within a generally cylindrical index collar  80 . The collar  80  is fitted onto the upper portion  74  before the shaft  70  is inserted, and is rotatably retained on the upper portion, and axially located by the annular shoulder  82  defined by the top of the lower portion  18  of the core  70 .  
         [0041]    A further pawl  79  is situated on the outside of the upper portion  74  at a position generally opposite the slot  76 .  
         [0042]    The index collar  80  has a series of longitudinal external slots, for example,  84  and  86  which engage corresponding inwardly directed lugs, for example  88 , on the container  20 . The relative dimensions of the container  20  and index collar  80  are such that the container  20  can slide along the outside of the index collar  80 , but is rotationally fixed to the collar by the engagement of fixed lugs in the slots in the collar. Thus, rotation of the index collar  80  will cause a corresponding rotation of the container  20  which therefore also travels axially along the core  10  as a result of its engagement with the screw-threaded portion  18 .  
         [0043]    A ring gear  90  is provided at the end of the collar  80  opposite the end which rests on the shoulder  82 . The teeth of the gears  90  are inwardly directed, and are, in use, engaged by the pawls  78  and  79 . In the described embodiment, the shapes of the ends of the pawls and of the teeth are such that the pawls can be pulled over one tooth onto the next, but cannot readily be pushed in the opposite direction.  
         [0044]    A gear wheel  92  is provided at the end of the drive shaft  70  in such a position as to protrude from the end of the sub-assembly of the core  10 , container  20 , indexing collar  80  and drive shaft  70 .  
         [0045]    The mouthpiece  4  has latching components, for example  5 , which engage in corresponding recesses/apertures in the shell  2  so that the mouthpiece  4  can be snap-fitted into position on the shell  2 . With reference to FIG. 17, an end of the mouthpiece  4  is spaced from the shell  2  and control member  6  to define an air inlet  93 . When a user inhales through the mouthpiece  4 , air travels through the inhaler from the inlet  94  to the mouthpiece  4  generally along the path indicated by the arrows A in FIG. 5. As can be seen, air flows towards and through the opening  25 , up the hollow interior of the core  10 , and through the pin  30 , locator  22  and dose cavity  52 .  
         [0046]    The sub-assembly is radially located by means of an inner cap  94  which has latching components  96  for engaging corresponding apertures  98  in the shell  2  to retain the cap  94  in position thereon. The cap  94  has an end stop  98  which carries a boss which is in axial alignment with the circular aperture  93  in the gear wheel  92 . The end stop  98  also carries a second boss  102  the axis of which is spaced from that of the boss  100 , and which extends in the opposite direction from the other boss. The inner cap  94  also incorporates an annular component  104 , the outer surface of which carries a number of gear teeth. The component  104  also carries a pair of stops  106  and  108  which project axially from the end face of the component  104 .  
         [0047]    The member  6  is rotatably mounted on the boss  102  and incorporates a ring  110  (FIG. 2) of inwardly directed teeth for meshing with the teeth on the gear wheel  92  of the shaft  70 . A carrier device  112  is also mounted on the inside of the member  6 , and carries a pair of oppositely directed pawls  114  and  116 . The carrier  112  has an actuator  118  which projects radially inwards and (in use) engages either of the stops  106  or  108  (depending on the position of the member  6 ) to rock the carrier  12  so as to bring one or other of the pawls  114  and  116  into engagement with the teeth on the annular component  104 . An end piece  120  clips onto the member  6  to conceal tooling holes in the end of the latter.  
         [0048]    The member  6  is rotatable through approximately 180°, and one cycle of movement of the member comprises rotation in one direction about 180° and then rotation in the reverse direction through the same angle to return the member to its original position. This motion pierces the foil seal of a compartment  20  in registry with the pin  30  (and hence the airway defined by the insert  46  and mouthpiece  4 ), whilst uncovering the exit of the passage  50  to enable the user to inhale a dose through that exit, and then indexes the container  20  so that the next full compartment is in registry with the airway, and covers the mouthpiece. This cycle of operation will be described in more detail with reference to FIGS.  8 - 14 .  
         [0049]    FIGS. ( 8 - 14 )A illustrate the effect of the rotation of the cover member  6  on the locator  22 , FIGS. ( 8 - 14 )B the effect of the same rotation on the pin holder  28  (and hence the pin  30 ), FIGS. ( 8 - 14 )C the effect on the indexing mechanism, constituted by the indexing collar, the upper portion of the core  74  and the shaft  70 , and FIGS. ( 8 - 14 )D the effect on the non-return mechanism provided by the component  112  by the teeth  94  and the stops  106  and  108 .  
         [0050]    With the device in a start position shown in FIGS.  8 A-D, the sealed, full compartment of the container  20  is in registry with the pin  30  and the airway defined by the passages  48  and  50 . Thus, in order to make the contained dose available for inhalation, it is necessary to pierce the two sheets of foil which seal that compartment.  
         [0051]    To that end, the cap  6  is rotated relative to the shell  2  in a clockwise direction as indicated in FIG. 9D. This causes the ring of gear teeth  110  to rotate the gear wheel  92  and hence the shaft  70  in the same clockwise direction. The rotation of the shaft  70  brings the camming surface  68  on the base of that shaft into engagement with the lug  36  on the locator  22 , causing the locator to extend into the position shown in FIG. 9A, in which the cones (for example  32  and  34 ) on the end of the locator  22  extend into corresponding recesses in the container  20 , firmly to locate the compartment relative to the pin  30 . During this phase of movement, the peg  72  passes along a circumferential portion ( 122  in FIGS. 8B and 9B), which corresponds to the arc of movement of the peg  72 . As a result, the pin  30  remains retracted within the core  10  during this first phase of operation of the device.  
         [0052]    [0052]FIG. 9B shows the peg when it has reached a non-circumferential portion  124  of the key way  40 . Consequently, further rotation of the cover  8  in the same direction will then extend the pin  30  as shown in FIG. 10B. This movement of the pin  30  causes it to travel through the compartment, and thus to pierce both foil seals on either side of the compartment. The sectional shape of the pin  30  is such that this movement does not eject any significant amount of the material to be inhaled from the compartment. The initial rotation of the control member  6  causes the pawl  78  on the shaft  70  to be withdrawn into the upper portion  74  of the core  10  so that it cannot engage the teeth  90  on the indexing collar  80 . It can also be seen from FIGS. 8D, 9D and  10 D that the pawl  116  engages the ring of teeth  110  on the inner cap  94 . The pawl  116  thus allows the rotation of the control member  6  in an anti-clockwise direction, but prevents rotation in the opposite sense. The continuing anti-clockwise rotation of the control member  6  into the position shown in FIG. 11D causes the peg  72  to engage a further surface  126  of the key way  40 , and thus to withdraw the pin  30  from the compartment. Again, the shape of the pin  30  is such that its withdrawal does not remove any substantial amount of particulate material from the compartment. During this movement of the cover member  6 , the camming surface  68  continues to hold the locator  22  in engagement with the container  20 , and the upper portion  76  of the core  10  continues to keep the pawl  78  out of engagement with the teeth  90  of the indexing collar  80 . As the cover  8  has been rotated to the opposite side of the shell  2  from the mouthpiece  4 , the exit  50  is at this stage accessible to a user who can inhale the dose of material from the compartment. Inhalation by the user through the mouthpiece  4  creates a stream of air flowing into the passage  50  through the annular inlet  54 . The airway insert and passage  50  define between them a throat which accelerates this flow of air, thus creating an area of low pressure in front of the passage  48 , and hence the dose in the compartment  52 , and this helps to establish a stream of air flowing through the compartment  52  and into the passage  50 , in which stream of air the dose is entrained. As the dose leaves the ejection zone, (defined in this case by the compartment  52  and passage  48 ) the air flowing in through the inlet  54  forms a jacket which prevents the entrained dose from significantly impinging on the walls of the passage  50 .  
         [0053]    As can be seen from FIG. 11D, the actuator  118  of the carrier  112  has been rocked by the stop  108  so as to bring the pawl  114  into engagement with the teeth and to disengage the pawl  116 . Since the pawl  116  is now disengaged, the control member can be rotated in the opposite sense (i.e. clockwise), but the pawl  114  will prevent anti-clockwise rotation until the control member  6  has been returned to its start position.  
         [0054]    With reference to FIGS.  12 A-D, as the control member  6  returns to its start position, the shaft  70  rotates within the core  10  to move the pawl  78  towards the slot  76 . In addition, the peg  72  passes in front of the pin holder  28  and towards the inclined ramp  42 . Continued clockwise rotation of the control member  6  moves the camming surface  68  out of engagement with the lug  36  and the peg  72  into engagement with the camming aperture  38 , and thus causes the locator  22  to be withdrawn back into the core  10 . The movement also causes the pawl  78  to extend out of the slot  76  and into engagement with one of the teeth  90  in the indexing collar  80  (FIG. 13C). Continued rotation of the control member  6  then causes the pawl  76  to push the indexing collar  80  in an anti-clockwise direction as viewed from FIG. 13C, thus allowing the pawl  79  to ride over a tooth of the gear  90 . This rotation of the indexing collar  80  correspondingly rotates the container  20 , and moves the container in a small axial direction towards the inner cap  94  by virtue of the screw-threaded engagement with the portion  18 . Thus, the container  20  is indexed into the next position in which the next compartment is in registry with the pin  30  and the airway  48 . FIG. 14D shows the cover member when it is close to its original position, at which stage the actuator  118  engages the stop  106  to move the carrier  112  back to its original position (in which it is the pawl  116  that engages the teeth  94 ). It will be appreciated that the pawl  79  stops the collar  80  (and hence the container  20 ) rotating as the control member is moved in a clockwise direction, whilst allowing movement of the member in the other direction to index the container  20 .  
         [0055]    In addition, since the gear wheel  92  is of a smaller diameter than the ring of teeth  110 , a rotation of 180° of the control member  6  causes the shaft  70  to rotate through a larger angle, thus enabling the peg  76  both to extend and withdraw the pin  30  in response to the rotation of the cover member from the start position to the position shown in FIG. 11D. In this particular example, that movement of the cover member constitutes an advanced stroke, whilst the return, anti-clockwise movement position shown in FIG. 8D is a return stroke of the cover member  6 .  
         [0056]    [0056]FIG. 18 is a graph illustrating the relationship between the pressure drop along the passage  48  and the total rate of flow of air through the inhaler. The graph shows that even low flow rates provide a significant pressure drop. The inhaler design thus helps to ensure that a full dose of powder is inhaled even if the user is unable to inhale properly.