Abstract:
Dispensers, in particular dispensers for dispensing a dose of a gaseous, gas borne or droplet substance from a substance source and dispensers containing dosage counters are described herein.

Description:
FIELD OF THE INVENTION 
     The present invention relates to dispensers, in particular to dispensers for dispensing a dose of a gaseous, gas borne or droplet substance from a substance source and dispensers comprising dosage counters. 
     BACKGROUND OF THE INVENTION 
     In general, 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. 
     We have previously described a number of dispensers, see for example U.S. Pat. No. 7,721,731. We have also disclosed dosage counters for use with such dispensers, see for example WO 2010/103315. Further examples of dose counters and dispensers may be found in WO2005/060535, GB2372542 and US2011/259324. 
     It has been found that, during use of the dispenser and counter, manufacturing tolerances may in some instances affect the performance. As such, we have appreciated the need for an improved dispenser and an improved counter. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a dispenser for dispensing a dose of a gaseous, gas borne or droplet substance from a substance source, the dispenser comprising: a body for receiving a substance source, the body having a mouthpiece; a junction member slideably arranged in the body for movement in a longitudinal axis of the body to release a dose of a substance from a substance source, the junction member comprising a socket for receiving a spout of a substance source; a dispenser driver for moving the junction member in the longitudinal axis of the body to release a dose of a substance from a substance source, the dispenser driver comprising a pivot shaft and a cam arranged on the shaft, the dispenser driver being arranged within the body such that rotation of the pivot shaft causes the cam to rotate and apply a force to the junction member so as to move the junction member in the longitudinal axis; and a cam follower slideably arranged within the body, the cam follower comprising a base and a substantially rigid protrusion extending from the base, the protrusion being arranged between the dispenser driver and the junction member such that a force applied by the cam of the dispenser driver to the protrusion causes the cam follower to slideably move in the longitudinal axis of the body and apply a force to the junction member so as to release a dose of a substance from a substance source. 
     The provision of a cam follower between the junction member and the cam provides more reliable longitudinal movement of the junction member within the body to effect release of a dose of a medicament from a medicament container. Since the protrusions are substantially rigid, the whole cam follower moves longitudinally up and down as the cam arrangement imparts an upward force on the protrusion. In prior versions (where tongues were anchored at one end to the main body part), the tongues would flex at the fixed end, and the tongues had tendencies to bend and buckle under the force. In the preferred embodiment, the protrusions remain rigidly in place and instead the cam follower slideably moves within the guide of the main body part. As such, this enables a more reliable longitudinal action of the junction member  41 . 
     In embodiments, the body comprises a guide for guiding the slideable motion of the cam follower base in the longitudinal axis, the guide being shaped to receive the base of the cam follower in a slideable engagement. Preferably, the guide comprises one or more guide rails arranged and adapted to co-operate with one or more guide rails on the cam follower base such that the cam follower is slideable within the body. 
     In some embodiments, the cam follower further comprises a resiliently deformable clip disposed on a lower edge of the base for engaging with a correspondingly shaped protrusion in the body, and wherein, when the clip is engaged with the protrusion, the cam follower is retained in the longitudinal position in the body until a force is exerted on the cam follower by the cam. Such a clip aids assembly during manufacture of the dispenser, since the clip will maintain the cam follower in the correct position whilst other components are assembled around the cam follower. 
     In embodiments, the dispenser further comprises a pivotally mounted closure for the mouthpiece, the closure being coupled to the dispenser driver such that pivoting of the cover causes rotation of the pivot shaft of the dispenser driver. 
     In further embodiments, the dispenser further comprises: a breath actuatable valve incorporated with the junction member, for controlling the release of a gas and/or liquid comprising a substance, the valve comprising: a flexible tube for receiving a dose of a substance, the tube extending from an inlet end connected to the junction member socket, having a location which is kinkable for closure of the valve in a ready position and moveable to a release position in which the tube is un-kinked for opening of the valve, and having an outlet end moveable for kinking/un-kinking of the tube; and an outlet member carrying the outlet end of the flexible tube and pivotally connected to the junction member for control of kinking/un-kinking movement of the flexible tube; the tube being kinked to an obturating extent when the pivotal outlet member is in a ready position and un-kinked when the pivoted outlet member is moved to a release position. Preferably, the dispenser further comprises: a sear on the outlet member to hold the outlet member in the ready position prior to inhalation; a breath actuatable flap carried on the junction member and arranged for action of inhalation breath on it, the flap having: a latch complementary to the sear; the flap being arranged: to releasably receive the pivotal outlet member for kinked closure of the flexible tube by cooperation of the latch and the sear and to release the pivotal outlet member for un-kinking of the tube, and substance release, on inhalation, by release of the sear from the latch and movement to the release position of the outlet member. 
     In these further embodiments, the pivotal outlet member is arranged to move by the force arising from pressure in the kinked location and/or under the resilience of the kinked location itself. Furthermore, the junction member, the kink tube and the pivotal outlet member may be of an integral plastics material injection moulding, the pivotal outlet member being pivoted to the junction member by one or more living hinges and having an outlet nozzle held by the outlet member. 
     In embodiments, the flap has an integral spring acting on the junction member to bias it normally to an upward position in which the flap rests on an upper crown portion of the junction member. Furthermore, the flap may include a finger arranged to act on the pivoted outlet member to urge it towards its open position as the flap moves under the action of inhalation breath. 
     In embodiments, the dispenser may further comprise a dose counter for indicating a number of actuations of the dispenser corresponding to a number of doses dispensed from a substance source, or a number of doses remaining in a substance source. 
     Preferably, the dose counter comprises: a counter having indicia, the counter being rotatable within the body in increments about the longitudinal axis of the body; a counter driver for driving the counter, the counter driver being coupleable to the junction member and arranged to be reciprocatably moveable within the body in the longitudinal axis with the junction member; and a drive mechanism for rotating the counter, the drive mechanism being coupled to the counter driver and configured to rotate the counter in response to longitudinal movement of the counter driver. 
     Preferably, the body comprises a counter driver guide configured to guide the counter driver in the body so as to prevent rotation of the counter driver in the longitudinal axis. Preferably, the counter driver guide comprises a protrusion extending from the body, the protrusion being configured and shaped so as to co-operate with a correspondingly shaped notch in the counter driver. 
     The counter driver guide prevents the counter driver from rotating about the longitudinal axis. Since rotation of the counter driver about the longitudinal axis would cause the counter to mis-count (i.e. actuate when it should not, or not actuate when it should), the counter driver guide provides for a more reliable count action. 
     In embodiments, the junction member comprises one or more slots, and the counter driver comprises one or more protrusions for engaging with the junction member so as to couple the junction member and counter driver. 
     In preferred embodiments of the dispenser comprising the counter, the counter comprises 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 the longitudinal axis, one or both of said first and second indicia indicating a count, and the dosage 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. Preferably, the dispenser further comprises a third ring member being coaxially arranged about said longitudinal axis. 
     In embodiments having the third ring member, the third ring member comprises a limiting mechanism to limit free rotation of said second ring member relative to said third ring member about said common axis. Preferably, the limiting mechanism comprises a resiliently deformable portion for applying pressure on said second ring member for said limiting. 
     In embodiments, the second ring member comprises a plurality of substantially equally-spaced protrusions and wherein said limiting mechanism engages with said protrusions for limiting said free rotation of said second ring member. 
     In embodiments having the third ring member, the third ring member comprises one or more locating recesses disposed in an upper circumferential surface for engaging with correspondingly-shaped protrusions in a counter housing for preventing free rotation of said third ring member. 
     In some embodiments, the first and second indicia each comprise one or more of: numbers, colours, letters and symbols. Preferably, the first indicia comprise a first row of numbers, and said second indicia comprise a second and a third row of numbers. Preferably, the first row of numbers represents units digits, said second row represents tens digits, and said third row represents hundreds digits. In some embodiments, the first row of numbers comprises repeated sets of integers. Furthermore, in some embodiments, the second row of numbers comprises repeated sets of integers and said third row of numbers comprises a set of integers. 
     In embodiments, the second ring member comprises a display cover element for obscuring a view of said first indicia. 
     Furthermore, in some embodiments of the dispenser comprising the counter, at least part of said drive mechanism is integral with said first ring member. 
     Preferably, the drive mechanism of the counter comprises a pawl-and-teeth mechanism. And preferably, the pawl-and-teeth mechanism comprises: a first and second pawl engageable with a plurality of teeth, and wherein each of said first and second pawls comprise a driving engagement face for engaging in a driving engagement with one of said plurality of teeth, and a sliding engagement face for siding over one of said plurality of teeth. 
     In some embodiments having a pawl-and-teeth mechanism, each of said first and second pawls is arranged such that: said first pawl engages in a driving engagement with one of said plurality of teeth during a count stroke of said teeth, and said second pawl engages in a driving engagement with one of said plurality of teeth during a return stroke of said teeth. 
     Furthermore, each of said first and second pawls may be arranged such that: said second pawl rides over one of said plurality of teeth during said count stroke, and said first pawl rides over one of said plurality of teeth during said return stroke. 
     In further embodiments, said first and second pawls are integral with said first ring member, and said plurality of teeth are disposed on a teeth-bearing member arranged to be reciprocally moveable within the bore of said first ring member, and wherein said pawl-and-teeth mechanism is configured such that reciprocal movement of the teeth-bearing member within the bore of the first ring member causes rotational movement of the first ring member. 
     In some embodiments, the drive mechanism comprises third and fourth pawls engageable with the plurality of teeth, the third and fourth pawls being integral with the first ring member on a surface radially opposing the first and second pawls. 
     The present invention also provides a dispenser as described above in its various embodiments, further comprising a substance source. Preferably, the substance source is a pressurised metered-dose inhaler (pMDI). 
     The present invention also provides a dispenser for dispensing a dose of a gaseous, gas borne or droplet substance from a substance source, the dispenser comprising: a body for receiving a substance source, the body having a mouthpiece; and a dose counter for indicating a number of actuations of the dispenser corresponding to a number of doses dispensed from a substance source, or a number of doses remaining in a substance source, the dose counter comprising: a counter having indicia, the counter being rotatable within the body in increments about the longitudinal axis of the body; a counter driver for driving the counter, the counter driver being arranged to be reciprocatably moveable within the body in the longitudinal axis in response to an actuation of the dispenser; and a drive mechanism for rotating the counter, the drive mechanism being coupled to the counter driver and configured to rotate the counter in response to longitudinal movement of the counter driver, wherein the body comprises a counter driver guide configured to guide the counter driver in the body so as to prevent rotation of the counter driver in the longitudinal axis. 
     The counter driver guide prevents the counter driver from rotating about the longitudinal axis. Since rotation of the counter driver about the longitudinal axis would cause the counter to mis-count (i.e. actuate when it should not, or not actuate when it should), the counter driver guide provides for a more reliable count action. 
     In some embodiments of the dispenser, the counter driver guide comprises a protrusion extending from the body, the protrusion being configured and shaped so as to co-operate with a correspondingly shaped notch in the counter driver. 
     Furthermore, the dispenser may comprise a junction member slideably arranged in the body for movement in a longitudinal axis of the body to release a dose of a substance from a substance source, the junction member comprising a socket for receiving a spout of a substance source. In an embodiment comprising the junction member, the junction member may comprise one or more slots, and the counter driver comprises one or more protrusions for engaging with the junction member so as to couple the junction member and counter driver. 
     The present invention also provides a dispenser for dispensing a dose of a gaseous, gas borne or droplet substance from a substance source, the dispenser comprising: a body for receiving a substance source, the body having a mouthpiece; a junction member slideably arranged in the body for movement in a longitudinal axis of the body to release a dose of a substance from a substance source, the junction member comprising a socket for receiving a spout of a substance source; a dispenser driver for moving the junction member in the longitudinal axis of the body to release a dose of a substance from a substance source, the dispenser driver comprising a pivot shaft and a cam arranged on the shaft, the dispenser driver being arranged within the body such that rotation of the pivot shaft causes the cam to rotate and apply a force to the junction member so as to move the junction member in the longitudinal axis; a cam follower slideably arranged within the body, the cam follower comprising a base and a substantially rigid protrusion extending from the base, the protrusion being arranged between the dispenser driver and the junction member such that a force applied by the cam of the dispenser driver to the protrusion causes the cam follower to slideably move in the longitudinal axis of the body and apply a force to the junction member so as to release a dose of a substance from a substance source; and a dose counter for indicating a number of actuations of the dispenser corresponding to a number of doses dispensed from a substance source, or a number of doses remaining in a substance source, the dose counter comprising: a counter having indicia, the counter being rotatable within the body in increments about the longitudinal axis of the body; a counter driver for driving the counter, the counter driver being arranged to be reciprocatably moveable within the body in the longitudinal axis in response to an actuation of the dispenser; and a drive mechanism for rotating the counter, the drive mechanism being coupled to the counter driver and configured to rotate the counter in response to longitudinal movement of the counter driver, wherein the body comprises a counter driver guide configured to guide the counter driver in the body so as to prevent rotation of the counter driver in the longitudinal axis. 
    
    
     
       We shall now describe embodiments of the present invention, by way of example only, and with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a dispenser according to the invention in closed position; 
         FIG. 2  is a similar view of the dispenser in open position; 
         FIG. 3  is a central cross-sectional view of the dispenser closed; 
         FIG. 4  is an exploded view of a prior version of the dispenser; 
         FIG. 5 a    is an inside, front view of a main body part of a prior version of the dispenser; 
         FIG. 5 b    is an inside, front view of a main body part of a preferred embodiment of the dispenser; 
         FIG. 5 c    is an inside, front view of a portion of the main body part shown in  FIG. 5   b;    
         FIG. 5 d    is a cross-sectional view along line X-X of the main body part of  FIG. 5   b;    
         FIG. 5 e    is a cam follower component of a preferred embodiment of the dispenser; 
         FIG. 5 f    is a rear view of the cam follower of  FIG. 5   e;    
         FIG. 6  is an inside, rear, view of a cover of the dispenser; 
         FIG. 7  is an oblique view from the front and below of a front body part of the dispenser; 
         FIG. 8  is a view from the opposite direction of the front body part; 
         FIG. 9  is an oblique view from the front and below of a junction member of the dispenser (shown in a form after moulding, but prior to insertion into the main body part); 
         FIG. 10  a rear view of the junction member; 
         FIG. 11  is a cross-sectional side view of the junction member on the line A-A in  FIG. 10 ; 
         FIG. 12  is a cross-sectional side view of the cover on line C-C in  FIG. 6 ; 
         FIG. 13  is a central, cross-sectional side view of the cover on line B-B in  FIG. 6 ; 
         FIG. 14  is a perspective view from behind of a flap of the dispenser; 
         FIG. 15  is a plan view of the flap; 
         FIG. 16  is a side view of the flap; 
         FIG. 17  is a series of scrap views of the flap and kink valve in the junction member illustrating operation of the valve; 
         FIG. 18 a    is a perspective view of a dispenser including a counter; 
         FIG. 18 b    is a perspective view of a dispenser including the counter; 
         FIGS. 19 a  and 19 b    show a drive mechanism for the counter; 
         FIGS. 20 a  to 20 d    are schematic diagrams showing a part of the principle of operation of the drive mechanism of the counter; 
         FIGS. 21 a  to 21 d    are schematic diagrams showing another part of the principle of operation of the drive mechanism of the counter; 
         FIGS. 22 a  and 22 b    show a preferred drive mechanism for the counter; 
         FIG. 22 c    shows a yoke (also known as a counter driver or teeth-bearing member) of a preferred embodiment of the counter; 
         FIG. 22 d    shows a junction member of a preferred embodiment of the dispenser; 
         FIG. 22 e    shows a top perspective view of a main body part for use with the yoke of  FIG. 22   c;    
         FIGS. 23 a  to 23 d    are schematic diagrams showing a part of the principle of operation of the preferred drive mechanism of the counter; 
         FIGS. 24 a  to 24 d    are schematic diagrams showing a part of the principle of operation of the preferred drive mechanism of the counter; 
         FIG. 25  is a perspective view of the counter; 
         FIG. 26  is a perspective view of a first ring member of the counter of  FIG. 25 ; 
         FIG. 27  is a top view of the counter of  FIG. 25 ; 
         FIGS. 28 a  to 28 d    schematically show in perspective view the operating principle of the counter; 
         FIGS. 29 a  to 29 d    schematically show from a top view the operating principle of the counter; 
         FIGS. 30 a  to 30 c    are schematic diagrams showing the principle of operation of the counter; 
         FIG. 31  is a perspective view of a dispenser including the counter; 
         FIG. 32  is a perspective view of a dispenser including the counter; 
         FIGS. 33 a  to 33 c    are perspective views of portions of the counter; 
         FIGS. 34 a  to 34 b    are perspective views of a third ring member of  FIG. 33 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Dispenser 
     Referring first to  FIGS. 1 to 4  of the drawings, the dispenser has a body  1  with a mouthpiece  2  and a pivoted mouthpiece cover  3 . The mouthpiece is formed as an aperture  4  in a separate body part  5  clipped to a main body part  6  (although the skilled reader would appreciate that this formation could be made using a single-moulded piece). The main part  6  has upper and lower formations  7 , 8  (see  FIG. 5 a   ) and the mouthpiece part has upper and lower complementary formations  9 , 10  (see  FIG. 8 ) which engage when the mouthpiece part is slid from below to engage with the main part. The separate body part  5  has cutaway  11  with respect to the main body part  6 , to define an air inlet  12  exposed by the cover  3  when this is opened. A medicament can C is fitted to the body part  6 . Immediately within the air inlet  12  is a guard  13  against fingers. It is backed up by strengthening flanges  14 , which additionally guard the cam mechanism to be described in the next paragraph. 
     Above the guard  13 , a series of four ribs  151 ,  152  (in  FIG. 7 ) extend and provide rigidity to the structure. The end ones  151  are longer and provide eventual stops for the flap of the actuation mechanism described below in the case of malfunction. The inner ones  152  act as flow restrictors to cause a pressure drop between the inlet  12  and the aperture  4  when the mechanism has been actuated, primarily to control the air flow rate through the device. 
     The cover  3 —see  FIGS. 6,12 &amp; 13 —is pivoted about an axis A low in the body  6  at the joint between the two body parts. Integrally moulded with the cover  3  is a C section shaft  21 , via webs  22 . The shaft carries a cam arrangement  23  (see  FIG. 4 ), comprising two cam lobes  231  and  232 , together with two fingers, a central one  24  and a outer one  25 . The latter is integral with one of a pair of discs  26 , between which are the cam lobes, the shaft is bearingly supported by part circular journals  27  in flanges  28  integrally moulded within the main body part  6  (see  FIG. 5 a   ). At the joint line between the two body parts  5  and  6  further coaxial scallops  29  are provided in the main body part  6  for the shaft  21 . 
     The body parts  5 , 6 , and the cover  3  (with the shaft and cam arrangement) in the described embodiments are of moulded polypropylene material, whereby they can be fitted together with a modicum of flexure. 
     The can C is held in an opening  31  at the upper end of the main body part  6 , where the body part extends completely around a valve crimp portion CP of the can C. 
     Moulded inside the main body part, inwards of the opening are internal grooves  32  ( FIG. 5 a   ). A junction member  41 —see  FIGS. 9,10 &amp; 11 —is slidably accommodated in the body with the grooves  32  engaged by ribs  42  at its periphery. The junction member in this embodiment also is of moulded polypropylene. Centrally, the junction member has a socket  43  for accommodating a spout or an outlet stem S of the can C. The socket is continued by a flexible tube  44 , which has a thin wall, kinkable location  45  and a nozzle end  46 . This is in a movable outlet member  48  of the junction member. The main part  411  of the junction member  41  and the outlet member  48  are connected by a living hinge  49 , in the form of two membranes  491 , 492  at respective sides of the junction member between lugs  561 , 562  and tabs  563 , 564 . The tabs are interconnected by a bar  52  having the nozzle aperture  53 . Between the lugs  561 , 562  and on either side of the kinkable location  45  extend two followers  541 , 542 , which are integral with the respective lugs  561 , 562  and are acted on by the cam lobes  231 , 232  (see  FIG. 6 ), with the interposition of tongues  551 , 552  extending from the inside of the main body part  6  to react lateral action on the junction member from the cam arrangement. The followers  541 , 542  have radiused portions  56 , centred on the hinge axis, with upper and lower valve travel stops  571 , 572 . 
     The lugs  561 , 562  carry on their sides facing the same direction as the radiused portions  56 , pairs of pivot clips  581 , 582  for pivotally locating the flap to be described below. One the same side of moulding a pair of sears  591 , 592  are provided on the tabs  563 , 564 . 
     It was found that the tongues  551 ,  552  extending from the inside of the main body part  6  did not always provide a reliable longitudinal action on the junction member (i.e. motion along the longitudinal axis of the main body part  6 , that is along the long axis of the main body part), as the tongues often bent or buckled under the forces being applied by the cam. As such, the force from the cam on the tongues did not always translate into a sufficient longitudinal movement of the junction member, which affected the dispensing of the medicament from a medicament source, or the action of the counter (described below—the counter is driven by the motion of the junction member). 
     In order to overcome this problem, we propose the features shown in  FIGS. 5 b  to 5 f   , which show a preferred embodiment of the main body part  6  comprising a guide  15  along a back wall of the main body part. Two guide rails  20  are provided in the guide, and a protrusion  34  is provided at a lower portion of the base (extending from the back wall of the main body part). 
     Into the guide sits a cam follower  16 , having a base  17 . Two substantially rigid protrusions  18   a  and  18   b  extend from the base  17 . Two guide rails  19   a ,  19   b  are disposed on the rear of the base  17 . The cam follower  16  slides longitudinally within the guide  15  of the main body part  6 , with the guide rails  20  and  19   a ,  19   b  interacting to retain the cam follower  16  in the guide  15 . The cam lobes  231 ,  232  contact the underside surface of the protrusions  18 ,  18   b  and the junction member sits atop the upper surface of the protrusions  18   a ,  18   b . As such, the cam lobes indirectly can apply a force to the junction member via the cam follower. 
     Since the protrusions  18   a ,  18   b  are substantially rigid, the whole cam follower moves longitudinally up and down as the cam arrangement imparts an upward force on the protrusion. In the prior version (where tongues  551 ,  552  were anchored at one end to the main body part at anchor point  553 ), the tongues would flex at the fixed end, and the tongues had tendencies to bend and buckle under the force. In the preferred embodiment, the protrusions  18   a ,  18   b  remain rigidly in place and instead the cam follower slideably moves within the guide of the main body part. As such, this enables a more reliable longitudinal action of the junction member  41 . 
     To aid with the manufacturing and assembling process, resiliently deformable clips  35  are disposed along the lower edge of the base of the cam follower. The clips are arranged to cooperate with the protrusion  34  in the main body part  6 . During assembly, the cam follower is placed in the guide, and the resiliently deformable clips engage with the protrusion  34  in order to retain the cam follower in place (i.e. along the lower edge of the main body part). The clips and protrusion are configured such that the force generated by the cam as the mouthpiece is opened is much greater than the force which can be resisted by the clips. As such, the clips do not affect the operation of the cam follower during use. 
     The flap  61 —see  FIGS. 14,15 &amp; 16 —has a pivot axis B. At opposite ends of the axis, the flap has small thrust flanges  62 , with pivot pins  60  set in from them. Inboard of the pins, two swellings  63  are formed. Each has a finger  64 , 65  extending obliquely down from it. One of the swellings has a spring loop  66  extending backwards, inwards and forwards again with its distal end  67  adjacent the swelling to which its proximal end  68  is attached. Set into the swellings  63  from the pins are apertures  69  formed from above and latches  70  extending below the apertures. These have latch surfaces  71  formed during moulding by projections through the apertures. The latches have cam surfaces  72 . These are positioned so as to abut the sears  591 , 592  as the device is in the ready position. The sears then pass over the end of the cam surfaces and come to engage on the latch surfaces. The final feature of the flap is a tongue  73 , which extends between the followers  541 , 542  to control air leakage as might otherwise occur. 
     The operation of the device will now be described. 
     Initially, the device is closed and the flexible members are relaxed. In others words the flap is in its upper, upstream position, as shown in  FIGS. 3, 9 &amp; 17  ( 1 ), and the outlet member  48  of the junction member is in its lower position. The flap is held in this position by its spring  66 , bearing with it distal end  67  on an abutment  81  set in from the lug  562  and the flap  61  resting on crown  41   a  of the junction member. The outlet member  48  of the junction member is pivoted down, due to the tendency of the kinked location to straighten to its as moulded state. Its position is controlled by two fingers  82  projecting laterally from the bar  52  to abut with the cam lobes  231 , 232 . 
     On opening of the cover, the cam lobes act via substantially rigid protrusions  18   a ,  18   b  of the cam follower  16  on the followers  541 , 542  of the junction member  41 . The cam follower  16  slides within the guide  15  of the main body part  6 , which lifts the junction member  41  against the internal spring (not shown) of the metering valve in the can, with displacement of stem S inwards of the can. As the cover  3  is rotated, the central finger  24  between the cam lobes engages with a notched projection  83  between the fingers  82  on the outlet member of the junction member. This action lifts the outlet member and closes the kinked location. Further lifting of the junction member opens the can&#39;s valve and a dose metered by the can&#39;s valve is released into the inlet end of the flexible tube. It is retained there by the kinked location acting as a closed valve. 
     Naturally, the dose is retained only whilst the outlet member  48  of the junction member is retained in the upper ready position to which it has been moved. This is achieved by the sears  591 , 592  running along the cam surfaces  72  and engaging with the latch surfaces  71 . As the sears move into engagement, the latches  70  are moved back, rotating the flap down against the action of the spring  66 . Once the sears clear the end of the cam surfaces, the spring urges the latches fully under the sears. There is clearance for the outlet member  48  to continue to pivot further, until the central finger  24  passes on out of engagement with the projection  83 . The device is now ready for inhalation. 
     Breathing in through the mouthpiece causes an air flow down through the air inlet  12 , exposed on opening of the cover, and impinging on the flap  61 . The flap is forced down against the action of the spring  66 , releasing the sears  591 ,  592 . The kink tube tends to straighten under the action of its own resilience and the pressure of the retained dose; thus the outlet member straightens through flexing of the hinges  491 ,  492  and the dose is released through the nozzle into the mouthpiece for inhalation, the nozzle traversing the mouthpiece aperture  4  as the dose is released. 
     The geometrical arrangement of the flap and the outlet member  48  can be seen in  FIG. 17 . The pivot axis B of the flap is spaced from the pivot axis D of the hingeable part, with the point of engagement of the sears  591 ,  592  and latches  70  lying between parallel planes B′ and D′ passing through the axes B and D. The actual points of engagement lie to the flap side of a common plane P passing through the axes. 
     After use, the mouthpiece cover is closed. The rotation of the cam arrangement allows the junction member  41  to return down and the finger  24  passes the notched projection  83  as a result of cam surfaces on its reverse faces. 
     Should the kink tube have lost its resilience and be slow in opening, the finger  64 , at the spring side of the flap pivot acts on a lug  85  moulded integrally with the outlet member&#39;s lug  563  and extending back past the hinge axis H. Thus the hingeable part is moved to its open position. 
     A further eventuality is closure of the mouthpiece cover without inhalation. In this event, the finger  65  is engaged by the finger  25  to deflect the flap to its position in which the outlet member releases the dose. The spring  66  returns the flap after this movement of it (which of course occurs on closure even if the dose has been released by inhalation). Thus the device is returned to its initial position in which the plastics material resilient features are relaxed. 
     All the components of the device (excluding the can) are moulded of polypropylene, with the exception of the flap, whose spring dictates use of acetal copolymer. 
     Counter 
     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. 
     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 07/012854 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 not to 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. 
     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  41 , as described earlier. 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 of a counter may be the movement of a medicament container. 
       FIGS. 18 a  and 18 b    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. 18 b   ) and a teeth-bearing member  206  (partially hidden from view in  FIG. 18 b   ). In this particular embodiment, the teeth-bearing member  206  is a hollow cylinder integral with the first ring member  201 . The pawl-bearing member  204  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. 22 . 
     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 (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. 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. 19 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. 18 a  and 18 b   , 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 . 
     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. 20 a  to 20 d    show a sequence of cross-sectional views of the drive mechanism during the count stroke. In  FIG. 20 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. 20 b   ). This effects an upward diagonal movement, which proceeds until lip  408   b  reaches, and then surpasses, the apex  516  of tooth  506  ( FIGS. 20 c  and 20 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. 20 c   ). Dashed arrows indicate the direction of movement. 
       FIGS. 21 a  to 21 d    show a sequence of cross-sectional views of the drive mechanism during the return stroke. Like elements to those of  FIG. 20  are indicated by like reference numerals. 
     In  FIG. 21 a   , which corresponds substantially to  FIG. 20 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. 21 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. 21 c  and 21 d   ).  FIG. 21 d    corresponds substantially to  FIG. 20 a   , but rotated by one tooth, i.e. from tooth  506  to tooth  504 . 
     Referring to  FIG. 19 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. 22 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 . In this embodiment, the teeth-bearing member is a yoke (also known as a counter driver), and the pawl-bearing member is the first ring (or units ring) of the counter. 
     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. 22 b    shows a side profile of the pawls  402   a ,  402   b . The numerals of  FIG. 19 b    refer to like features of  FIG. 22 b   . As with  FIG. 19 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. 19 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. 
     In preferred embodiment of the counter, the pawl-bearing member (i.e. the first ring member, or units ring of the counter) is provided with two sets of pawls, located substantially 180° apart around the pawl-bearing member. The second set of pawls is not shown in  FIG. 22   a.    
       FIG. 22 c    shows a yoke  206  (or teeth-bearing member or counter driver) according to preferred embodiments of the counter. In this preferred embodiment, the yoke comprises a notched portion  220 , which is shaped and dimensioned to slideably engage with correspondingly shaped protrusions ( 230 ) on the inside of the main body part  6  (see  FIG. 22 e   ). Only one protrusion  230  is shown in the figure. In preferred embodiments, a second protrusion is positioned on the inside surface opposite protrusion or rail  230 , which corresponds with an appropriately positioned notch on the yoke  206 . These notches and protrusions allow the yoke to longitudinally move within the main body and prevents the yoke from rotating in the same axis of the counter rings. As such, this provides a more reliable count, as there is no rotational movement of the yoke (which would cause the counter mechanism to over count or under count). Whilst we describe feature  230  as a protrusion, the feature may also be considered a rail.  FIG. 22 e    also shows a recess  240 , into which the arms of the yoke  206  are slideably arranged to allow movement in the longitudinal axis of the main body part  6 . 
     The preferred yoke  206  is also provided with protrusions  222   a  and  222   b , which are shaped to engage with correspondingly shaped holes  450   a  and  450   b  in the junction member  41  (see  FIG. 22 d   ). In such embodiment, the yoke is coupled to the junction member via the protrusions and holes such that longitudinal motion of the junction member produces longitudinal motion of the yoke (which in turn drives the counter mechanism). 
       FIGS. 23 a  to 23 d    show a sequence of cross-sectional views of the preferred drive mechanism during the count stroke. In  FIG. 23 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 sufficiently 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 ant-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. 22 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. 24 a  to 24 d    show a sequence of cross-sectional views of the drive mechanism during the return stroke. Like elements to those of  FIG. 23  are indicated by like reference numerals. 
     In  FIG. 24 a   , which substantially follows  FIG. 23 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. 25 to 34  provide various depictions of the counter in more detail. 
     Turning first to  FIG. 25 , the counter  205  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. 26 , the arm  704  is integrally formed with an annular band  802  that 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. 27 , being a view of  FIG. 25  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. 28 and 29  show, in a series of corresponding perspective and downward views respectively, the operation of the coupling mechanism. 
       FIGS. 28 a  and 29 a    show the arm  704  at a distance from the deflector  1002 . In  FIGS. 28 b  and 29 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. 28 c  and 29 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. 29 d  and 29 d   ). As seen in  FIG. 29 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 chamfered 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 . Whilst the second ring member is preferably slidably mounted on the first ring member, the second ring member is configured to resist rotation when there is no engagement between the arm and the teeth. For example, the second ring member comprises engagement features that engage with corresponding features on a dispenser cap, or a third ring member (described below) is employed. 
     An exemplary counting scheme for a counter configured for  200  doses is now described with reference to  FIGS. 30 a  to 30 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 in stylised form 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 ‘1’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. 30 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. 30 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. 30 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 ‘EMPTY’ 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. 30 ) will depend on the implemented counting scheme. In  FIG. 30  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 and multiple sets of teeth. 
       FIGS. 31 and 32  are perspective views of a dispenser including the counter. In contrast to  FIGS. 18 a  and 18 b   , the pawl-bearing member rather than the teeth-bearing member is integral with the first ring member  201 . This is for illustration purposes only. As discussed above, the preferred embodiment of the drive mechanism is shown in  FIG. 22 . Also visible in  FIG. 31  is a strip of colour following the third row of numbers  703 .  FIG. 32  shows how a count (‘ 119 ’) can be viewed through a window  1202  of a housing  1402  of the dispenser. 
       FIGS. 33 a  to 33 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. 25 and 26 ). 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. 28 and 29 . 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. 28 and 29 , 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. 30 ) to indicate that the counter has reached zero, indicating an empty dispenser. 
       FIGS. 34 a  and 34 b    show the third ring member without the second ring member. The reference numerals correspond with those in  FIG. 33 . 
     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. 
     In all embodiments, the components are preferably made from polypropylene, except for the flap and cam follower, which are preferably made from acetal copolymer. 
     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. 
     Whilst the cam follower, counter driver guide and counter have been disclosed in combination in a single dispenser, it will be appreciated by the skilled reader that each of the cam follower, counter driver guide and counter need not all be present in the same dispenser and could be used in a dispenser without the other features being present. For example, the cam follower can be used in a dispenser without the counter driver guide and counter, and likewise with the counter driver guide and counter.