Abstract:
A counter containing: a first ring member having first indicia and a second ring member having second indicia, each of the first and second ring members being rotatable in increments about a common axis, one or both of the first and second indicia indicating a count; a drive mechanism for rotating the first ring member; and a coupling mechanism for releasably coupling the first ring member to the second ring member, to allow the first and second ring members to rotate cooperatively when coupled and to allow independent rotating of the first ring member when not coupled; wherein the coupling mechanism contains first and second engagement structures, the first engagement structures being movable radially outwardly and radially inwardly relative to the axis.

Description:
This application is the U.S. national phase of International Application No. PCT/GB2010/050404, filed 10 Mar. 2010, which designated the U.S. and claims priority to GB Application No. 0904040.3, filed 10 Mar. 2009, the entire contents of each of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention generally relates to counters and in particular to counters for use with dispensers and to dispensers comprising said counters. More particularly the present invention relates to counters for use with metered-dose dispensers, such as metered-dose inhalers (MDIs). 
     BACKGROUND OF THE INVENTION 
     Counters are useful in a wide variety of applications, and are especially important in the field of medical dispensers where an accurate determination of the number of doses of medicament remaining in a medicament container might otherwise be difficult to obtain. An example of such a medical dispenser is a metered-dose inhaler. 
     Metered-dose inhalers (MDIs) are devices for dispensing medicaments, e.g. in aerosol form, to the lungs. Broadly speaking dispensers such as MDIs are comprised of two components: a container and a delivery device. The container holds the medication, e.g. dissolved or suspended in a propellant under high pressure to maintain a liquid phase. Additionally the container often comprises an internal metering valve, which is designed to release a precisely measured, reproducible dose of medicament when the valve is actuated. The delivery device typically includes an actuator and a mouthpiece. The actuator, which can be triggered by the user, for example by inhalation or manual operation, typically interacts with the metering valve of the container to induce release of a dose. The mouthpiece serves to direct the medication towards the user.  FIG. 1  provides a view of a breath actuated dispenser and will be discussed in more detail below. 
     As medicament containers are typically made of an opaque material such as aluminium, and may be housed entirely within a delivery device, it is generally not possible for a user to gauge effectively how many doses of medicament remain therein. This may result in a user prematurely discarding a MDI still containing doses of medicament or worse using the MDI beyond its recommended lifetime. Neither situation is desirable—the former is wasteful while the latter is potentially dangerous. Users sometimes shake MDIs to try to obtain a measure of whether any medicament is present therein, but this only provides a very crude qualitative measure of the container contents. It would not, for example, enable a user to distinguish between a container comprising enough medicament and propellant to form a dose and one comprising a quantity of medicament and propellant that is less than that needed to fill the metering valve. In other words, there is a risk that users overestimate the amount of medicament present in a container and mistakenly conclude that there is sufficient medicament remaining for another dose when in fact there is not. Additionally a user may not be provided with sufficient warning to obtain a replacement medicament container prior to the one in use running out. 
     It is therefore desirable to provide dispensers, e.g. inhalers, with a counter mechanism that enables a user to track how many doses have been dispensed therefrom and, complementarily, how many doses remain. Indeed, regulatory bodies such as the Food and Drug Administration (FDA) of the United States and the European Medicines Agency (EMEA) have issued guidelines encouraging the implementation of dose-counters (Food and Drug Administration, “Guidance for industry: integration of dose counting mechanisms into MDI drug products”, 2003; European Agency for Evaluation of Medicinal Products, “Final guideline on the quality of inhalation and nasal products”, 2005). 
     Dose counters can generally be classified according to the manner by which a ‘count’ is registered, these being mechanical counters comprised of a series of moving parts that respond to a movement or mechanical force resulting, for example, in a displacement of the container/housing; electronic counters having electrical circuitry to sense an event associated with an actuation such as sound, temperature or pressure change; and electro-mechanical counters which combine electrical and mechanical parts. 
     Some background prior art relating to dose counters includes: EP1169245 Dispensing Apparatus Comprising a Dosage Counting Device; PCT/GB97/03480 Inhaler Dose Counter; PCT/US1996/008418 Indicator Device Responsive to Axial Force; PCT/FR2004/001844 Improved Dose Indicator for Fluid Product Dispensing Device; GB2372542 Dosage Counting Device; PCT/CA04/001884 Indicating Device with Warning Dosage Indicator; PCT/US04/039926 Dose Counter for Dispensers; and U.S. Pat. No. 7,047,964 Dispenser for Medicament. 
     Other developments in the field of dose counters include Bang &amp; Olufsen Medicom&#39;s ‘Insulair’ (Trade Mark) device, and the disclosures of: WO 98/056444 Dispenser with Doses Counter; WO 04/001664 Actuation Indicator for a Dispensing Device; WO 07/012,854 Canister-Supported Rotating Ring Count Readout Assembly for a Metered Dose Inhaler; and DE 10061723 Zählwerk zum Zählen dosierter Abgaben flüssiger oder fester Produkte sowie Einrichtung zum dosierten Abgeben solcher Produkte. 
     Although such devices have provided the advantage of being able to provide some measure of the number of doses of medicament dispensed from a container and/or the number of doses remaining therein, there remains room for improvement. In particular it has proven difficult to provide dose counters that reliably “count” the release of medicament doses from containers. The difficulty encountered is that a relatively small movement, typically of the metering valve stem, needs to be detected and translated into a count. This difficulty is exacerbated by the fact that manufacturing tolerances in the length of medicament containers means they do not have a consistent length. At the same time, it is highly undesirable for any movements to not be counted since this will lead to the counter indicating a higher number of doses remaining than is actually the case. Moreover there is also regulatory pressure to minimise the number of false counts. 
     Additionally it is desirable that a counter, especially a medicament dose counter, display the count information in an easy to read form so it may be used by children and the elderly as well as adults. Naturally there is also a need that the counter can be manufactured at low cost. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention there is therefore provided a counter comprising: 
     a first ring member having first indicia and a second ring member having second indicia, each of said first and second ring members being rotatable in increments about a common axis, one or both of said first and second indicia indicating a count; and 
     a drive mechanism for rotating said first ring member and for rotating the second ring member after one or more predetermined degrees of rotation of the first ring member. Preferably the rotations serve to provide a predetermined alignment of said first and second indicia. 
     In a preferred embodiment the counter further comprises a coupling mechanism for releasably coupling said first ring member to said second ring member, to allow said first and second ring members to rotate cooperatively when coupled and to allow independent rotating of said first ring member when not coupled. 
     In a particularly preferred embodiment the coupling mechanism comprises first and second engagement means, said first engagement means being movable radially outwardly and radially inwardly relative to said axis. 
     Thus in a further aspect the present invention provides a counter comprising: 
     a first ring member having first indicia and a second ring member having second indicia, each of said first and second ring members being rotatable in increments about a common axis, one or both of said first and second indicia indicating a count; 
     a drive mechanism for rotating said first ring member; and 
     a coupling mechanism for releasably coupling said first ring member to said second ring member, to allow said first and second ring members to rotate cooperatively when coupled and to allow independent rotating of said first ring member when not coupled; 
     wherein said coupling mechanism comprises first and second engagement means, said first engagement means being movable radially outwardly and radially inwardly relative to said axis. 
     A skilled person will understand that in this context “movable” is to be interpreted broadly as including any suitable movement/displacement such as a bending, flexing, tilting, pivoting and/or shifting movement. However, in preferred embodiments the first engagement means is deflectable radially outwardly to engage with said second engagement means. Thus, the coupling mechanism preferably includes a deflector to deflect the first engagement means radially outwardly. The deflector may be in a fixed position relative to the rotating first and second ring members. Preferably the deflector is attached to a medicament container or a housing surrounding said container. 
     In preferred embodiments the first engagement means is deflected radially outwardly after a predetermined degree or amount of rotation of the first ring member. The predetermined amount of rotation of the first ring member is associated with less than a full rotation of the first ring member about the common axis, for example a quarter rotation of the first ring member about the common axis. However, other arrangements may equally be implemented such as a half rotation of the first ring member about the common axis. 
     In preferred embodiments the first engagement means is connected to, or integral with, the first ring member. This allows for a reduction in the number of components that are movable relative to one another. For practical purposes, however, the first engagement means and first ring member could be manufactured separately and then assembled. Preferably the first engagement means comprises an arm. Particularly preferably the first engagement means comprises an arm having a slot and a contact end member, and in especially preferred embodiments two, three or four arms (e.g. four arms) each having a slot and a contact end member are provided. The contact end is preferably an upwardly extending component that contacts (e.g. rides over) the deflector. 
     Preferably the second engagement means is connected to, or integral with, the second ring member. In preferred embodiments the second engagement means comprises a plurality of protrusions. The protrusions are preferably equally spaced apart. Preferably the protrusions extend in an arc approximately between a quarter way and half way around the common axis. 
     In preferred embodiments, when the arm is moved radially outwardly the slot (e.g. the end of the slot) of the arm engages with one of the plurality of protrusions. In such an arrangement the rotation of the first ring therefore pulls the second ring member along (i.e. causes it also to rotate). However, by using an alternative (but equally suitable) coupling mechanism it is also possible for the first ring member to push the second ring member along. 
     In preferred embodiments, the counter also comprises a third ring member being coaxially arranged about the common axis of the first and second ring members. Also, the deflector is preferably connected to, or integral with the third ring member. Preferably the third ring member is fixed in use to prevent rotation of the third ring member. Preferably, the third ring member also comprises a limiting mechanism to limit free rotation of the second ring member relative to the third ring member about the common axis. This prevents over-rotation of the second ring member, which would indicate an incorrect number of remaining doses. 
     Preferably, the limiting mechanism comprises a resiliently deformable portion for applying pressure on the second ring member for limiting the free rotation of the second ring member. 
     In this embodiment, the second ring member preferably comprises a plurality of substantially equally-spaced protrusions protruding from an upper circumferential edge of the second ring member, and the limiting mechanism engages with the protrusions for limiting the free rotation of the second ring member. 
     Furthermore, the third ring member preferably comprises one or more locating recesses disposed in an upper circumferential surface for engaging with correspondingly-shaped protrusions in a housing or container for preventing free rotation of the third ring member. 
     The first and second indicia can comprise one or more of: numbers, colours, letters and symbols. In preferred embodiments the first indicia comprise a first row of numbers, and said second indicia comprise a second and a third row of numbers. For example, the first row of numbers can represent units digits, the second row can represent tens digits, and the third row can represent hundreds digits. 
     Preferably the first row of numbers comprises repeated sets of integers, for example four sets of the numbers ‘0’ to ‘9’ (one set per quarter of the first ring member). Preferably the second row of numbers also comprises repeated sets of integers, for example two sets of the numbers ‘0’ to ‘9’ (the two sets filling half the second ring member). Preferably the third row of numbers comprises a set of integers (e.g. ten ‘1’s and one ‘2’ or ten ‘1’s). Optionally the third row additionally includes blanks. This allows counting from ‘200’ or ‘199’ down to ‘0’ respectively. 
     The first and second indicia can be printed, cut out from, embossed, moulded, adhered, incorporated, painted and/or otherwise marked (e.g. laser marked) on the first and second ring members. 
     In preferred embodiments, the second ring member comprises a display cover element for obscuring a view of the first indicia. This enables the counter to indicate that the number of doses has reached zero and requires replacing. 
     In preferred embodiments at least part of the drive mechanism is integral with the first ring member. Preferably the drive mechanism comprises a pawl-and-teeth mechanism comprising two pawls. Broadly speaking the drive mechanism translates vertical movements, e.g. of a junction member or medicament container, into rotational movements, e.g. of the first ring member. 
     Preferably the counter is attached to a dispenser having a body for receiving a medicament container and a dispensing mechanism for dispensing a dose of medicament from the container. For example, the rotating of the first ring member can be performed in response to the dispenser being actuated. Thus, the count can be indicative of doses of medicament dispensed from, or remaining in, the container. 
     In preferred embodiments the dispenser includes a housing having a window to allow only a portion of the first and second indicia to be displayed. The window may be a hole in the housing or may be a transparent area of the housing. This allows a precise reading of the quantity of unit product, such as metered doses of medicament, remaining in the container or dispensed therefrom. 
     In a related aspect of the invention there is provided a dispenser comprising the counter as hereinbefore described. 
     In another related aspect of the invention there is provided a dispenser comprising: a body for receiving a medicament container; a medicament container; a dispensing mechanism for dispensing a dose of medicament from said container; and a counter as hereinbefore described. Preferably the dispenser is a pressurised metered-dose inhaler (pMDI). 
     In yet another related aspect of the invention there is provided a counter strip comprising a row of numbers, said numbers comprising repeated sets of integers. 
     In yet another related aspect of the invention there is provided a counter strip comprising a first and second row of numbers, wherein said first row comprises repeated sets of integers and said second row comprises a set of integers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects of the invention will now be further described, by way of example only, with reference to the accompanying figures in which: 
         FIG. 1  is a cross-sectional view of a dispenser to which a counter according to the present invention may be attached; 
         FIG. 2  is a perspective view of a dispenser including a counter according to the present invention; 
         FIG. 3  is a perspective view of a dispenser including a counter according to the present invention; 
         FIGS. 4   a  and  4   b  show a drive mechanism for a counter according to the present invention; 
         FIGS. 5   a  to  5   d  are schematic diagrams showing a part of the principle of operation of the drive mechanism of a counter according to the present invention; 
         FIGS. 6   a  to  6   d  are schematic diagrams showing another part of the principle of operation of the drive mechanism of a counter according to the present invention; 
         FIGS. 7   a  and  7   b  show a preferred drive mechanism for a counter according to the present invention; 
         FIGS. 8   a  to  8   d  are schematic diagrams showing a part of the principle of operation of the preferred drive mechanism of a counter according to the present invention; 
         FIGS. 9   a  to  9   d  are schematic diagrams showing a part of the principle of operation of the preferred drive mechanism of a counter according to the present invention; 
         FIG. 10  is a perspective view of a counter according to the present invention; 
         FIG. 11  is a perspective view of a first ring member of the counter of  FIG. 10 ; 
         FIG. 12  is a top view of the counter of  FIG. 10 ; 
         FIGS. 13   a  to  13   d  schematically show in perspective view the operating principle of a counter according to the present invention; 
         FIGS. 14   a  to  14   d  schematically show from a top view the operating principle of a counter according to the present invention; 
         FIGS. 15   a  to  15   c  are schematic diagrams showing the principle of operation of a counter according to the present; 
         FIG. 16  is a perspective view of a dispenser including a counter according to the present invention; 
         FIG. 17  is a perspective view of a dispenser including a counter according to the present invention. 
         FIGS. 18   a  to  18   c  are perspective views of portions of a counter according to the present invention. 
         FIGS. 19   a  to  19   b  are perspective views of a third ring member of  FIG. 18 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Dispenser 
     To explain the invention, a brief overview of some features and operating principles of exemplary dispensers is initially provided. As used herein the term “dispenser” is intended to mean any device having a body suitable to receive a container holding a product and which has a mechanism to dispense the product from the container upon actuation. 
       FIG. 1  shows in partial cross section an example of a breath-actuated, kink valve dispenser. The dispenser  100  comprises a body  102  with a mouthpiece  104  and a pivotable mouthpiece cover  106 . The mouthpiece cover is pivotable about an axis, A, low in the body and carried on a cam arrangement comprising two cam lobes (only one cam lobe  108  is shown), together with a central finger  110 . The body has an opening  112  for receiving a medicament container  114 . The container may be held fixedly in place at the upper end of the body, at a location where the body extends completely around a metering valve assembly of the container (not shown). The metering valve assembly comprises a metering chamber  116  and an outlet stem  118 . Alternatively, or additionally, if the container is housed entirely within the dispenser, the container may be held at an end distal of its metering valve assembly, for example by a cap portion of an outer housing. 
     Moulded inside the body, inwards of the opening  112  are internal grooves (not shown). A junction member  120  is slidably accommodated in the body with the grooves engaged by ribs in its periphery. The junction member has a pair of pivot clips (not shown) for pivotally locating the flap  122  in the junction member  120 . Centrally, the junction member has a socket  124  for the outlet stem  118  of the metering valve assembly. The socket is continued by a passage  126 , which has a thin wall, kinkable portion and a nozzle end. The nozzle end is in a movable part of the junction member. The main part and the movable part of the junction member are connected by a living hinge. 
     The moving part of the junction member  120  also carries a pair of sears (not shown) that are arranged to engage with latches on the underside of flap  122  as described below. The movable part of the junction member also carries a finger for engagement with the cam arrangement. 
     Initially when the dispenser is closed the flap is unlatched and the movable part of the junction member is in its lower position. The kinkable portion, sometimes called a kinkable valve, is open. On opening of the mouthpiece cover  106 , the central finger of the cam arrangement acts on the movable part of the junction member to close the kink valve. The movement of the movable part of the junction member also serves to engage the sears of the movable member with the latches of the flap, thereby fixing the flap in an upper position. The junction member  120  is also lifted by the main cam lobes  108  against an internal spring (not shown) of the metering valve assembly, with displacement of the stem  118  inwards of the container. Further lifting of the mouthpiece cover  106  opens the container valve and a metered dose is released into the upper part of the tube, the dose being retained by the closed kink valve acting as a closed valve. 
     Breathing in through the mouthpiece causes an air flow through the dispenser and impinges on flap  122 . This causes release of the sears and the kink tube tends to straighten under the action of its own resilience and the pressure of the retained dose. The dose is thus released through the nozzle into the mouthpiece for inhalation. The flap may also carry a finger (not shown) that can act on the moveable part of the junction member to ensure that the kink valve is opened when the flap is breath actuated. 
     These and other features of exemplary dispensers are described in more detail in Clinical Designs Limited&#39;s prior PCT applications WO 1998/41254 (U.S. Pat. No. 6,422,234); WO 2002/11802 (U.S. Pat. No. 7,036,505); WO 2002/058772 (U.S. Pat. No. 6,866,038) and especially WO 2004/073776 (US 2007 062522), the disclosures of all of which are fully incorporated herein by reference. 
     Tolerance Adjustment Mechanism 
     Due to the build up of manufacturing tolerances in the manufacture of the dispenser and medicament container, the medicament container may be insufficiently accurately located longitudinally with respect to the dispenser body and the cam mechanism. This may result in an insufficient dose being metered from the container. 
     In preferred dispensers for use with the counter of the present invention, the dispenser comprises a tolerance adjustment mechanism such as the can fixture mechanism described in WO 03/080161 (also U.S. application Ser. No. 10/508,688). 
     In the preferred dispenser, the correct relative locations of the container and the body  102  are achieved during assembly of the dispenser. A pre-assembled body  102 , mouthpiece cover  106 , junction member  120  and release member, or flap  122  are set to their mouthpiece cover ‘open’ position (i.e. with the cover pivoted down from the  FIG. 1  position). In this position, the junction member  120  is lifted, which would ordinarily displace the stem  118  of an installed container when installed. With the components set to their ‘open’ position, a container  114  is introduced into the tubular section of the body  112 . With the container  114  and body  112  properly aligned, the stem  118  engages in the socket  124  in the junction member  120 . A predetermined force F is applied to ensure that the spout is fully depressed. This causes the container to release a dose of medicament into the kinkable valve. With the force still applied, the relative positions of the body  102  and container  114  are fixed (examples given below). 
     Once the relative positions of the container and body are fixed, the release mechanism may be triggered to release the dose of medicament metered during the above process and the mouthpiece cover moved to the closed position (as shown in  FIG. 1 ), after which the dispenser is ready for shipment. 
     For fixing the relative positions of the container and body, a printed label coated with self-adhesive may be wrapped around the joint between the body and the container (either all of the way around the joint, or partially). 
     Alternatively, instead of a self-adhesive label, a shrink-wrap label all of the way around the joint may be used. This is particularly advantageous where the body stands slightly proud of the container. 
     Alternatively, instead of labels, the container and body may be welded together to fix their positions relative to one another. For example, when the container is an aluminium or glass extrusion with a coating of polypropylene of sufficient thickness, a ultrasonic welding process may be used to weld the coated portion to the body. 
     Alternatively, the container and body may be glued together in the correct relative positions using a low temperature hot melt adhesive or fast curing two-part adhesive. 
     Of course, the skilled reader would appreciate that there are a many number of alternative fixing means available for the purpose of fixing the relative positions of the container and body. 
     In an alternative tolerance adjustment mechanism, an abutment feature is used as described in WO2007/029019 (also U.S. application Ser. No. 11/991,680). 
     In this alternative mechanism, the dispenser is provided with a closed sleeve or housing, much like the housing  1402  shown in  FIG. 14 . This housing provides abutment for the exposed end of the container  114 . An adjustable abutment is provided between the container  114  and the housing. The required size of the adjustable abutment is calculated by measuring the distance between the exposed end of the container  114  and the opening  112  of the body  102  to give the measured ‘source’ length. With knowledge of the effective length of the source, and knowledge of the distance below the opening  112  at which the outlet stem  118  should be located, one can calculate the required size of adjustable abutment taking into account the length of the housing. 
     After sizing the abutment, the housing is assembled to the body  102  and the housing is laser welded to the body. The result is that the source is supported firmly for displacement of the outlet stem  118  inwards on operations of the cam mechanism by opening of the mouthpiece cover. 
     The abutment is made, for example, of an aluminium honeycomb of a wall thickness that can be readily compressed to the required dimension, yet can resist the force exerted on it in operation, i.e. when the container is urged against it. It should be noted that the compression is plastic and permanent. The abutment may be fixed to the housing, for example by welding. 
     Alternatively, the abutment may form part of the housing, and the abutment may comprise many thin, radial ribs protruding from the closed end of the housing and arranged around the radially outer part of that closed end. The ribs are plastically deformable. They can be compressed and form an abutment. 
     Drive Mechanism 
     The term “drive mechanism” is to be interpreted broadly as any means by which the dispensing of a dose from the medicament container is linked to a count being made by the counter. In described embodiments the dispensing of a dose will involve a vertical movement, e.g. of junction member  120 , as described earlier with reference to  FIG. 1 . In the described preferred embodiment, this vertical movement is translated into an incremental rotation that is counted. In other embodiments the vertical movement that is translated into an incremental rotation may be the movement of a medicament container. 
       FIGS. 2 and 3  schematically show a dispenser  200  having a counter  203  and a drive mechanism  205 . The counter comprises a first ring member  201  and a second ring member  202 . The drive mechanism  205  is a pawl-and-teeth mechanism having a pawl-bearing member  204  (not shown in  FIG. 3 ) and a teeth-bearing member  206  (partially hidden from view in  FIG. 2 ). In this particular embodiment, the teeth-bearing member  206  is a hollow cylinder integral with the first ring member  201 . The pawl-bearing member extends fully around the teeth-bearing member  206 . The reverse configuration may also be used, i.e. the pawl bearing member  206  may be integral with the first ring member  201 . This arrangement is shown in  FIG. 7 . 
     Two pawls  208  are defined by a cutaway portion of pawl-bearing member  204 . The pawls operatively engage with a ring of teeth  210  moulded on an outwardly facing surface of the teeth-bearing member  206  by means of inwardly extending protrusions on the tips of the pawls, as will be described in more detail later. A pair of arms  212   a ,  212   b  extend downwardly from the pawl-bearing member on either side of the metering valve assembly. The arms can be spring-loaded against, or affixed to, an upper portion of a junction member (hidden from view). The junction member moves vertically when a dose is dispensed. Alternatively the arms can be spring-loaded against, or affixed to, a moving container, e.g. a moving medicament container. 
     The action of lifting the junction member  120  (which causes the release of a dose from a pressurised medicament container  114 ) imparts an upward force on the pawl-bearing member  204  in a direction parallel to the vertical axis  214  of the dispenser  200 . This results in frictional engagement between the pawl(s) and the teeth. In turn, the teeth-bearing member  206  and first ring member  201  are rotated (clockwise in this particular case) about the vertical axis  214  by an increment. 
     Once a dose is released and the mouthpiece cover is being closed or is closed, the junction and pawl-bearing members are able to move downwards to their original positions by, for example, an internal spring (not shown) of the medicament container  114 . This downward movement also results in frictional engagement between the pawl-bearing and teeth-bearing members, resulting in a further clockwise rotation of members  206 ,  201  about the vertical axis  214  by an increment. 
     Taken together, these two increments of rotation define a “complete” incremental rotation of the first ring-like member  201  from a first to a second position. 
       FIG. 4   a  illustrates an exemplary drive mechanism  205  in which the ring of teeth  210  is disposed on an inwardly facing surface of the teeth-bearing member  206 , with the pawl-bearing member  204  being disposed within its bore. It will be recognised that the pawl- and teeth-bearing members are in a reverse configuration compared to the configuration shown in  FIGS. 2 and 3 , though the operating principle of the drive mechanism remains substantially the same. 
     Two pawls  402   a ,  402   b , are integrally defined in the pawl-bearing member  204 , by a cutaway portion of its body. Viewed from this perspective, each pawl extends toward the ring of teeth  210  in an annular plane of the pawl-bearing member  204 , at about the same (but opposite) angle α, β. The second (lower) pawl  402   b  is offset in a circumferential direction relative to the first (upper) pawl  402   a . The pawls each have a root end and a free end. A lip  408   a ,  408   b , protrudes radially outwardly from each of the free ends, to operatively engage with the teeth. 
     The valve stem  118  of the metering valve assembly inserts down through the clearance hole in the base of the pawl-bearing member  204  to rest on a shelf  410  in a stem block  412 . This differs from the preferred configuration shown in  FIGS. 2 and 3 . It will be appreciated that this difference, in itself, is not of particular significance in the context of the drive mechanism. 
     In operation, and viewed from this perspective, the pawl-bearing member  204  moves up and down, and rotates, relative to the teeth-bearing member  206 . For convenience, the upward and downward movements of the pawl-bearing member  204  will be referred to as the ‘count stroke’ and ‘return stroke’, respectively. These terms are only used for convenience and are not to be construed as meaning that a count only occurs during the count stroke. It will be apparent to those skilled in the art (and from the following description) that a count may occur during the count stroke, return stroke or a combination of both strokes. 
       FIGS. 5   a  to  5   d  show a sequence of cross-sectional views of the drive mechanism during the count stroke. In  FIG. 5   a , the pawl-bearing member is at rest on the teeth by means of a protruding block  510 . An upwardly directed force on the pawl-bearing member initially results in frictional engagement between the lip  408   a  of the first (upper) pawl  402   a  and a vertical face  512  of tooth  502 . This action guides the pawl-bearing member substantially vertically upwards, until such a time as the lip  408   b  of the second (lower) pawl  402   b  engages with a lower, sloped face  514  of tooth  506  ( FIG. 5   b ). This effects an upward diagonal movement, which proceeds until lip  408   b  reaches, and then surpasses, the apex  516  of tooth  506  ( FIGS. 5   c  and  5   d , respectively). At the same time, the first (upper) pawl  402   a  flexes slightly inwardly to allow lip  408   a  to pass over tooth  502  ( FIG. 5   c ). Dashed arrows indicate the direction of movement. 
       FIGS. 6   a  to  6   d  show a sequence of cross-sectional views of the drive mechanism during the return stroke. Like elements to those of  FIG. 5  are indicated by like reference numerals. 
     In  FIG. 6   a , which corresponds substantially to  FIG. 5   d , the lip  408   a  of the first (upper) pawl  402   a  moves vertically downwards until it frictionally engages with an upper, sloped face  518  of tooth  502 , resulting in a downward diagonal movement. In  FIG. 6   b , the lip  408   a  has proceeded further down face  518 , and block  510  now engages an upper, sloped face  520  of tooth  504 . This time the second (lower) pawl  402   b  flexes slightly inwardly to allow lip  408   b  to pass over tooth  504 . This proceeds until the pawl-bearing member again comes to rest on the teeth ( FIGS. 6   c  and  6   d ).  FIG. 6   d  corresponds substantially to  FIG. 5   a , but rotated by one tooth, i.e. from tooth  506  to tooth  504 . 
     Referring to  FIG. 4   b , this shows a side profile of the pawls  402   a  and  402   b  and the lips  408   a  and  408   b . Each lip comprises a driving engagement face  440 , which contacts a tooth during a driving engagement of that lip  408 . Each lip also comprises a sliding engagement face  430 , which enables a lip  408  to contact and lift over a tooth without engaging the tooth. The large arrows denote the faces of the pawl lips that contact teeth during one of the strokes. The opposite faces (shown without arrows) contact teeth during the other stroke. The angle γ (that is the angle of the slope of the sliding engagement face  430  of the lip with respect to a vertical axis in the figure) must be sufficiently large enough to enable the lip  408   b  lift away and ride over the teeth when lip  408   a  is engaged with a tooth (i.e. driving engagement face  440   a  is in contact with, and drivingly engaged with a tooth). An angle greater than 15° is preferred. If the angle is less than 15°, the pawl may not lift above the tooth. 
       FIG. 7   a  illustrates a preferred embodiment of the drive mechanism  205  in which the ring of teeth  210  is disposed on an outwardly facing surface of a teeth-bearing member  206 , which is placed within the bore of the pawl-bearing member  204 . 
     Two pawls  402   a ,  402   b , are integrally defined in the pawl-bearing member  204 , by a cutaway portion of its body. Viewed from this perspective, each pawl comprises two arms extending toward the ring of teeth  210  in an annular plane of the pawl-bearing member  204 . The second pawl  402   b  is offset in a circumferential direction relative to the first pawl  402   a . A lip  408   a ,  408   b , protrudes radially outwardly from the point at which the two arms meet, to operatively engage with the teeth. 
       FIG. 7   b  shows a side profile of the pawls  402   a ,  402   b . The numerals of  FIG. 4   b  refer to like features of  FIG. 7   b . As with  FIG. 4   b , the angle γ (i.e. the angle of the sliding engagement face  430  from the vertical of the drawing) must be sufficiently large enough to enable the sliding engaging face  430  to lift up and ride over the tooth (not shown). For example, the angle is preferably larger than 15°. More preferably, the angle is approximately 45°. It will also be noted that the orientation of the first pawl  402   a  is reversed to that shown in  FIG. 4   b . It will be appreciated that the engaged pawl (i.e. the pawl in driving engagement with the tooth) experiences a compression force that forces the pawl towards the toothed surface during engagement. 
     In operation, and viewed from this perspective, the teeth-bearing member  206  moves up and down (driven by the actuation of the junction member as described above), causing the pawl-bearing member  204  to rotate relative to the teeth-bearing member  206 . For convenience, the upward and downward movements of the teeth-bearing member  206  will be referred to as the ‘count stroke’ and ‘return stroke’, respectively. 
       FIGS. 8   a  to  8   d  show a sequence of cross-sectional views of the preferred drive mechanism during the count stroke. In  FIG. 8   a , the teeth- and pawl-bearing members are at rest. An anti-slip bar  450 , comprising a protrusion extending from the inner surface of the pawl-bearing member, is in an engaged position that is in line with the teeth to prevent non-count rotation of the pawl-bearing member (i.e. rotation of the pawl-bearing member in an opposite direction to that of the pawl-bearing member during a count). The anti-slip bar  450  is configured to prevent relative rotation between the teeth-bearing member and pawl-bearing member in a non-count direction by blocking motion of the pawl-bearing member. The bar extends sufficiently from the inner surface of the pawl-bearing to hit one of the teeth, but not the outer surface of the teeth-bearing member. 
     An upwardly directed force on the teeth-bearing member initially results in an edge of the lip  408   a  coming into frictional engagement with a sloped face  512  of tooth  502  and moves the anti-slip bar  450  out of the path of the teeth to permit rotation. Further upward movement of the teeth-bearing member causes rotational movement of the pawl-bearing member (towards the left of the figure). At the same time, the inner non-vertical surface of lip  408   b  (shown as the arrowed surface in  FIG. 7   b ) contacts a vertical non-leading edge  522  of tooth  520 , which causes the pawl  402   b  to lift away from the plane of the teeth, and permits the pawl  402   b  to ride over the tooth without engagement. 
     Rotational movement of the pawl-bearing member continues until lip  408   a  and surface  512  no longer contact. At this point, lip  408   b  has cleared tooth  520 , and falls back to the plane of the teeth by virtue of the pawl arms being resiliently deformable. Further upward motion of the teeth-bearing member has no further effect on rotation of the pawl-bearing member. However, a second anti-slip bar  452  (configured similarly to anti-slip bar  450 ) is brought into the path of the teeth to prevent backward (i.e. non-count) rotation of the pawl-bearing member. 
       FIGS. 9   a  to  9   d  show a sequence of cross-sectional views of the drive mechanism during the return stroke. Like elements to those of  FIG. 8  are indicated by like reference numerals. 
     In  FIG. 9   a , which substantially follows  FIG. 8   d , the teeth-bearing member is lowered until lip  408   b  of the first pawl  402   b  frictionally engages with a lower, sloped face  518  of tooth  502  (simultaneously, the second anti-slip bar  452  is moved from the path of the teeth). Further downward movement of the teeth-bearing member causes rotational movement of the pawl-bearing member by virtue of the face  518  and lip  408   a  being frictionally engaged. 
     Face  518  proceeds further down lip  408   b . At the same time, the inner non-vertical surface of lip  408   a  contacts a vertical non-leading edge of a tooth, which causes the pawl  402   a  to lift away from the plane of the teeth, and permits the pawl  402   a  to ride over the tooth without engagement. 
     Rotational movement of the pawl-bearing member continues until lip  408   b  and surface  518  no longer contact. At this point, lip  408   a  has cleared the tooth over which it was riding, and falls back to the plane of the teeth by virtue of the pawl arms being resiliently deformable. Further downward motion of the teeth-bearing member has no further effect on rotation of the pawl-bearing member. However, the first anti-slip bar  450  is brought back into the path of the teeth to prevent backward rotation of the pawl-bearing member. 
     Although the foregoing discussion describes the case where the pawl-bearing member rotates about an axis (i.e. rotates relative to the dispenser as a whole), it is equally possible that the teeth-bearing member rotates. Naturally it is also possible that the teeth could point in either direction around the circumference of the teeth bearing member. 
     It will be appreciated that a rotational displacement need not be performed by way of two engagements (though this may be beneficial), nor need it comprise vertical and rotational movement. For example, a drive mechanism providing purely rotational motion, in other words without vertical movement, could also be used. 
     Counter 
       FIGS. 10 to 19  provide various depictions of the counter in more detail. 
     Turning first to  FIG. 10 , the counter  203  is comprised of first ring member  201  and second ring member  202 . The ring members are rotatably and coaxially arranged about the central axis  214 , encircling the container of the dispenser. The second ring member is arranged substantially flush on top of the first ring member, with their outer circumferential surfaces being aligned so as to form a substantially continuous surface interrupted only by a hairline  720  where the two ring members meet. A pawl-bearing member  205  of a drive mechanism is integral with the first ring member  201 . 
     A first row of numbers  701  (‘8’, ‘9’, ‘0’, ‘1’) is displayed on the first ring member  201 , with a second row of numbers  702  (‘0’, ‘1’, ‘2’, ‘3’, ‘4’) and a third row of numbers  703  (‘1’, ‘1’, ‘1’) displayed on the second ring member  202 . For clarity, only some of the numbers are depicted. A coupling mechanism  700  comprising an arm  704 , a series of equally spaced protrusions  705 , and a deflector  1002  can also be seen. The coupling mechanism allows the first ring member  201  to be coupled to the second ring member  202 , so that they can be rotated in tandem by the drive mechanism when coupled, as detailed below. The spaced apart protrusions  705  are formed on an inner surface of the second ring member  202 , and in this particular case extend only half way around the axis. 
     It will become clear in due course that, depending on the counting scheme used, multiple arms and/or deflectors may be provided. However, for purposes of clarity only, only one arm and/or deflector is depicted in these figures. 
     Referring now to  FIG. 11 , the arm  704  is integrally formed with an annular band  802  that fixedly sits in a recess of an upper radial surface  804  of the first ring member  201 . Alternatively, the arm  704  can be directly mounted on, or integral with, upper radial surface  804 . The arm  704  has a slotted body  712  which extends arcuately with approximately the same curvature of first ring member  201 , and an upwardly extending contact end  710 . 
     With reference to  FIG. 12 , being a view of  FIG. 10  from above, the second ring member  202  (shown as a shaded ring) is slidably mounted on an outer portion of the upper radial surface  804  of the first ring member (shown as a blank ring, part of which is hidden from view underneath the shaded ring). From this perspective, it is apparent that the thickness of the second ring member  202 , designated ‘t 2 ’, is about a third of the thickness of the first ring member  201 , designated ‘t 1 ’. The thickness of the first ring member  201  may be consistent along its height or it may be tapered, it being thickest at its upper radial surface  804 . The dashed line represents an imaginary boundary line between the arm  704  and the spaced apart protrusions  705  formed on the inner surface  902  of the second ring member  202 . 
       FIGS. 13 and 14  show, in a series of corresponding perspective and downward views respectively, the operation of the coupling mechanism. 
       FIGS. 13   a  and  14   a  show the arm  704  at a distance from the deflector  1002 . In  FIGS. 13   b  and  14   b , the first ring member  201  and arm  704  are rotated in an anticlockwise direction, so that the upwardly extending contact end  710  of the arm  704  approaches the deflector  1002 . The deflector  1002  is fixed to the container, or alternatively to an upper portion of a housing of the dispenser and/or to a sleeve surrounding the container. The deflector extends downwardly only to such an extent that the body  712  of the arm is allowed to pass underneath unimpeded. 
     As the contact end  710  reaches an inclined face  1004  of the deflector  1002 , the arm  704  is deflected outwards ( FIGS. 13   c  and  14   c ). At this point a trailing end  718  of the slot  714  catches one of the teeth  1102 , thereby causing the second ring member  202  to be pulled along. When the contact end descends down face  1006  of the deflector, the tooth  1102  is released by the trailing end of the slot and the arm returns to its non-flexed position ( FIGS. 13   d  and  14   d ). As seen in  FIG. 14   b , the upwardly extending contact end  710  of the arm  704  may have a face  720  complementing the inclined face  1004  of the deflector  1002 , to allow for a smooth deflection. Preferably the contact end  710  is pointed so that when it reaches the apex of deflector  1002 , the arm can immediately begin to return to its non-flexed position. 
     As shown herein, the slot  714  forms an engaging portion of the arm  704 , but it is recognized that any suitable engaging means could be used such as a hook. Accordingly, recesses could be formed in the second ring instead of protrusions. 
     The arm  704  is sufficiently flexible to permit a radially outward deflection (that is, towards the protrusions) when encouraged to do so, but also resilient enough to return to its original position. The counter may additionally comprise a second deflector that functions to move or deflect the engagement means (e.g. arm  704 ) back to its non-flexed position. This second deflector may, for example, be fixed to, or integral with, an inner surface of the second ring member  202 . Additionally the second ring member is preferably slidably mounted on the first ring member so as to resist rotation when there is no engagement between the arm and the teeth. 
     An exemplary counting scheme for a counter configured for 200 doses is now described with reference to  FIGS. 15   a  to  15   c , which show the first and second ring members in three different display positions. For convenience, the ring members  201 ,  202  are shown as flat rings. Also shown are the protrusions  705 , the deflector  1002 , a window  1202  through which the counter can viewed, and a display cover element  1204 . 
     In this particular scheme, the first ring member  201  has a first row of numbers comprising four repeated sets of consecutive integers ‘0’ to ‘9’, i.e.: 
     0123456789012345678901234567890123456789. 
     Each set of integers covers a quarter turn of the first ring member  201 , and here represents the ‘units’ digits of a count. 
     The second ring member  202  has second and a third rows of numbers. The second row comprises two repeated sets of consecutive integers ‘1’ to ‘9’ separated by a ‘0’, while the third row comprises ten ‘l’s optionally followed by a ‘2’, e.g.: 
     
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                      11111111112 
               
               
                   
                 12345678901234567890 
               
               
                   
                   
               
             
          
         
       
     
     Similarly, each set of integers of the second and third rows covers a quarter turn of the second ring member  202 . Here, the second row represents ‘tens’ digits, and the third row represent ‘hundreds’ digits of a count. Also shown on the second ring is a warning symbol in the form of an exclamation mark ‘!’. 
     In practice it may be more convenient to start a count at say ‘199’ rather than ‘200’, to avoid having to rotate the second ring member  202  initially. The integers forming the number ‘200’ seen to the right of the window  1202  in  FIG. 15   a  may therefore be omitted. Thus, when the first and second ring members are initially aligned in a housing of the dispenser, the first, second and third rows cooperatively display the number ‘199’ (when read from top to bottom): 
                                             ------------------------------1111111111           --------------------01234567890123456789           0123456789012345678901234567890123456789                        
where ‘-’ indicates a blank space.
 
     For each of the first nine dispensed doses, the first ring member is rotated anticlockwise by an increment, i.e. counting down from ‘9’ to ‘0’, until the number ‘190’ is displayed. Then for the tenth dispensed dose, the first and second ring members are coupled by means of the coupling mechanism so that the ring members are rotated in tandem by an increment. This results in the number ‘189’ being displayed through window  1202 . For the subsequent nine dispensed doses, the first ring member is again rotated anticlockwise by increments until the number ‘180’ is displayed. For the twentieth dispensed dose, the coupling mechanism is again engaged, so that the first and second ring members are rotated in tandem by an increment and the number ‘179’ is displayed through the window  1202 . 
       FIG. 15   b  shows an intermediate count position, in which the number ‘72’ is displayed. In this position, the third row has run out and a blank space appears instead. Alternatively, the blank space may be filled with indicia other than numbers, such as colours. 
     As the container becomes exhausted, e.g. below ten doses remaining, the second row of numbers can be replaced by an exclamation marks ‘!’ or other warning indicators. Preferred warning indicators for this purpose are colours (e.g. red). Once the final dose has been dispensed ( FIG. 15   c ), a cover element  1204  that is preferably attached to the second ring member and has therefore rotated at the same rate, is aligned with the window  1202 . This occludes from view any indicia. The cover may have the word ‘EMTPY’ written on it for example. 
     Further actuations of the dispenser may still result in the first ring member  201  being rotated. However, since the teeth are disposed only half way around the second ring member  202 , the coupling mechanism can no longer be engaged, i.e. there are no teeth for the slot of the arm to engage with. Thus, no further rotations of the second ring member  202  can be effected, so that the display cover element  1204  remains in place even if the first ring is still rotated by further actuations of the dispenser. 
     Thus viewed from a still further aspect the present invention provides a ring member for use in a counter having indicia and carrying protrusions that are disposed only partially around said ring member. Preferably the protrusions are disposed on the inner surface of the ring member. 
     In preferred embodiments the protrusions (e.g. teeth) are equally spaced apart. Particularly preferably the protrusions only extend three quarters of the way (e.g. about 270°) around the ring member, still more preferably the protrusions only extend between a quarter and half way (e.g. about 90°, 108° or 180°, or any angle therebetween) around the ring member. 
     It will be apparent that the number of deflectors and/or arms (not shown in  FIG. 15 ) will depend on the implemented counting scheme. In  FIG. 15  for example, where the first ring member  201  has a first row of numbers comprising four repeated sets of consecutive integers ‘0’ to ‘9’ such that each set covers a quarter turn of the first ring member  201 , and where one deflector  1002  is provided, the counter will have four arms spaced at 90 degree intervals. Of course, other configurations will also be possible. For example, where the first ring member  201  has a first row of numbers comprising two repeated sets of consecutive integers ‘0’ to ‘9’ such that each set covers half a turn of the first ring member  201 , and where one deflector  1002  is provided, the counter will have two arms spaced at 180 degree intervals. Alternatively, it may be possible to have a single arm and multiple deflectors  1002  spaced at intervals, or multiple arms and deflectors. 
       FIGS. 16 and 17  are perspective views of a dispenser including the counter. In contrast to  FIGS. 2 and 3 , the pawl-bearing member rather than the teeth-bearing member is integral with the first ring member  201 . Also visible in  FIG. 16  is a strip of colour following the third row of numbers  703 .  FIG. 17  shows how a count (‘ 119 ’) can be viewed through a window  1202  of a housing  1402  of the dispenser. 
       FIGS. 18   a  to  18   c  show part of a preferred embodiment of the counter. In this preferred embodiment, the second ring member  1510  is rotatably and coaxially arranged with a first ring member  201  about a central axis  214  as described above (and as shown in  FIGS. 10 and 11 ). For clarity, the first ring member  201  is not shown in these drawings. 
     As with the embodiments described above, the second ring member is arranged substantially flush on top of the first ring member, with their outer circumferential surfaces being aligned so as to form a substantially continuous surface interrupted only by a hairline where the two ring members meet. A pawl-bearing member  205  of a drive mechanism is integral with the first ring member  201 . 
     In this preferred embodiment, the counter further comprises a third ring member  1502  that is coaxially arranged with the second ring member  1510 . In use, the third ring member does not rotate. The third ring member comprises a deflector  1504  to deflect arm  704  on the first ring member  201  to engage with protrusions  1516  on the inside surface of the second ring member  1510  in the manner as described above with reference to  FIGS. 13 and 14 . As can be seen, the third ring member has a gap  1518  in its outer wall to enable the arm  704  to deflect outwards. A sloped edge on the trailing boundary of the window  1518  engages with an edge of the arm  704  to push the arm  704  away from the teeth  1516  after the arm has engaged with the teeth  1516 . This ensures that unwanted further engagement of the tens (second) ring (which would lead to an incorrect dosage value being displayed) does not happen. 
     The third ring member  1502  further comprises a limiting mechanism  1506  which comprises a flexible and resiliently deformable portion that applies pressure to an upper circumferential surface of the second ring member  1510 . The limiting mechanism limits the amount of rotation of the second ring member relative to the third ring member. More specifically, the limiting mechanism prevents the second ring member incorrectly rotating by two protrusions (or counts) in the event that the arm fails to decouple properly. In this embodiment, the second ring member  1510  also comprises a plurality of protrusions  1512  on an upper circumferential surface to engage with the limiting mechanism  1506  of the third ring member  1502 . Preferably, protrusions  1512  are substantially equally-spaced. More preferably, the protrusions  1512  have substantially the same spacing as protrusions  1516  on the inside surface of the second ring member. 
     As described above with reference to  FIGS. 13 and 14 , when the first and second ring members are coupled, the second ring member rotates at the same rate as the first ring member (until the first and second ring members become uncoupled). By spacing the protrusions  1512  at substantially the same distance as protrusions  1516  (which form part of the coupling mechanism between the first and second ring members), this prevents the second ring member rotating further than is desired even if the arm does not properly decouple, which would indicate an incorrect count. 
     Furthermore, the third ring member also comprises a plurality of locating recesses  1508   a ,  1508   b  and  1508   c  in the upper circumferential surface. In preferred embodiments, correspondingly-shaped protrusions locate within these recesses to hold the third ring member in place and therefore to prevent rotation of the third ring member. The protrusions may be located in a container or a dispenser (e.g. in a dispenser cap). By preventing the third ring member from rotation, this ensures that the deflector  1504  remains in a consistent position relative to the first and second ring members. 
     A plurality of corresponding-shaped protrusions located in a container or dispenser may be designed with an asymmetrical pattern to provide a keying function. That is, the third ring member will only locate in one rotational position relative to the container and dispenser, and therefore also the first and second ring members. This ensures that the third ring member is always located correctly with respect to the first and second ring members to allow the count to correctly register. 
     The second ring member  1510  further comprises a display cover element  1514  for obscuring a view of the first indicia (as described above with reference to  FIG. 15 ) to indicate that the counter has reached zero, indicating an empty dispenser. 
       FIGS. 19   a  and  19   b  show the third ring member without the second ring member. The reference numerals correspond with those in  FIG. 18 . 
     It will be apparent that the third ring member does not comprise indicia, and it is not intended to carry indicia, as this embodiment requires the third ring member to remain in a fixed rotational position relative to the first and second ring members for the count to indicate the correct remaining doses. 
     While the invention has been exemplified by the above description of specific embodiments, and uses thereof, the foregoing should not be considered by the reader as a limitation on the scope of the invention, which is defined in the appended claims.