Abstract:
A dose counter system, and a dispensing apparatus having such a dose counter system, for counting activations of a pressurised dispensing container including: a hydraulic system; and a counter; the hydraulic system having a hydraulic cylinder with a primary piston, a secondary piston and a working fluid, wherein the secondary piston is coupled to, or otherwise operates the counter and the primary piston is engaged by, fixed to, coupled to, or otherwise moved by, a pressurised dispensing container.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a dispensing apparatus having a hydraulic system for activating a dose counter based on movement of a received pressurised dispensing container. In particular, the invention relates to improvements in apparatus and dose counters for use in dispensing metered doses of pharmaceutical formulations or products from metered dose inhalers. 
     BACKGROUND 
     Dispensing apparatus such as metered dose inhalers are well known in the art for use in dispensing products such as pharmaceutical formulations for the treatment of respiratory conditions including asthma. A metered dose inhaler typically comprises an actuator housing in which is received a pressurised dispensing container which itself comprises a dispensing canister and a metering valve which are assembled together by means of a ferrule. The pressurised dispensing container contains a product to be dispensed and a propellant which is volatile at atmospheric conditions. An example of a metered dose inhaler of this type is described in the applicant&#39;s European patent application EP1088567. It is desirable to provide such a dispensing apparatus with a dose counter to provide an indication to a user of how many doses of product either remain in the pressurised dispensing container or have been dispensed from the pressurised dispensing container. In the past, a number of mechanical dose counters for such apparatus have been proposed. Examples are described in the applicant&#39;s patent applications GB2348928 and GB2438396. For mechanical dose counters for use with metered dose inhalers it is typical to use the linear movement of the pressurised dispensing container within the actuator housing for triggering or activating the mechanical dose counter mechanism. The metering valve of the pressurised dispensing container comprises a valve stem which protrudes and engages with a valve stem receiving block of the actuator housing. For a typical metering valve which is used in such applications the degree to which the valve stem travels in use relative to the remainder of the metering valve is relatively small and in the order of 3.5 mm. In addition, the travel of the valve stem before actuation of the valve is typically only in the order of 1.5 to 2.0 mm. This has been found to lead to problems in designing efficient and reliable mechanical dose counter mechanisms in that the relatively small physical travel of the valve stem, and hence the remainder of the pressurised dispensing container on actuation provides only limited physical movement of the pressurised dispensing container for triggering a mechanical dose counter mechanism. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a mechanism which provides more reliable triggering of dose counters for dispensing apparatus and in particular mechanical dose counter mechanisms which are to be activated by movement of a device that has relatively limited travel. 
     Accordingly, the present invention provides a dispensing apparatus comprising:
         a housing suitable to receive in use a pressurised dispensing container capable of dispensing metered doses of a product; and   a dose counter;       

     wherein the dispensing apparatus further comprises a hydraulic system for activating the dose counter based on movement of the received pressurised dispensing container. 
     Advantageously, the use of the hydraulic system allows the relatively limited movement of the pressurised dispensing container to be converted into a sufficient movement for triggering the dose counter. 
     Preferably, the hydraulic system comprises a hydraulic cylinder comprising a primary piston, a secondary piston and a working fluid. 
     In use, the primary piston may be engaged by, fixed to, coupled to, or otherwise moved by, the received pressurised dispensing container. 
     The secondary piston may comprise, or be coupled to, or otherwise move, a trigger, wherein the trigger is operative to activate the dose counter. 
     Preferably a working cross-sectional area of the secondary piston is less than a working cross-sectional area of the primary piston such that movement of the primary piston by a unit distance produces a movement of the secondary piston that is greater than unit distance. 
     The dose counter may be a mechanical dose counter. 
     The mechanical dose counter may comprise a counter wheel. 
     The hydraulic system may be located within the housing beneath the received pressurised dispensing apparatus. 
     Preferably the received pressurised dispensing container comprises a dispensing canister, a metering valve and a ferrule and the hydraulic system is engaged by, fixed to, or coupled to, the ferrule of the received pressurised dispensing container. 
     The present invention also provides a combination of a dispensing apparatus as claimed in any preceding claim and a pressurised dispensing container comprising a dispensing canister, a metering valve and a ferrule. 
     The present invention further provides a dose counter for counting activations of a pressurised dispensing container comprising:
         a hydraulic system; and   a counter;       

     the hydraulic system comprising a hydraulic cylinder with a primary piston, a secondary piston and a working fluid, wherein the secondary piston is coupled to, or otherwise operates the counter and the primary piston is engaged by, fixed to, coupled to, or otherwise moved by, a pressurised dispensing container. 
     Preferably a working cross-sectional area of the secondary piston is less than a working cross-sectional area of the primary piston such that movement of the primary piston by a unit distance produces a movement of the secondary piston that is greater than unit distance. 
     The dose counter may form an integral part of a dispensing apparatus. 
     The dose counter may further comprise a dose counter housing at least partially enclosing the hydraulic system and the counter to form a hydraulic dose counter unit. 
     The dose counter may be adapted to be removeably, semi-permanently or permanently attached to a pressurised dispensing container. 
     The dispensing apparatus may be, for example, a pulmonary, nasal, or sub-lingual delivery device. A preferred use of the dispensing apparatus is in a pharmaceutical metered dose aerosol inhaler device. The term pharmaceutical as used herein is intended to encompass any pharmaceutical, compound, composition, medicament, agent or product which can be delivered or administered to a human being or animal, for example pharmaceuticals, drugs, biological and medicinal products. Examples include antiallergics, analgesics, bronchodilators, antihistamines, therapeutic proteins and peptides, antitussives, anginal preparations, antibiotics, anti-inflammatory preparations, hormones, or sulfonamides, such as, for example, a vasoconstrictive amine, an enzyme, an alkaloid, or a steroid, including combinations of two or more thereof. In particular, examples include isoproterenol [alpha-(isopropylaminomethyl) protocatechuyl alcohol], phenylephrine, phenylpropanolamine, glucagon, adrenochrome, trypsin, epinephrine, ephedrine, narcotine, codeine, atropine, heparin, morphine, dihydromorphinone, ergotamine, scopolamine, methapyrilene, cyanocobalamin, terbutaline, rimiterol, salbutamol, flunisolide, colchicine, pirbuterol, beclomethasone, orciprenaline, fentanyl, and diamorphine, streptomycin, penicillin, procaine penicillin, tetracycline, chlorotetracycline and hydroxytetracycline, adrenocorticotropic hormone and adrenocortical hormones, such as cortisone, hydrocortisone, hydrocortisone acetate and prednisolone, insulin, cromolyn sodium, and mometasone, including combinations of two or more thereof. 
     The pharmaceutical may be used as either the free base or as one or more salts conventional in the art, such as, for example, acetate, benzenesulphonate, benzoate, bircarbonate, bitartrate, bromide, calcium edetate, camsylate, carbonate, chloride, citrate, dihydrochloride, edetate, edisylate, estolate, esylate, fumarate, fluceptate, gluconate, glutamate, glycollylarsanilate, hexylresorcinate, hydrobromide, hydrochloride, hydroxynaphthoate, iodide, isethionate, lactate, lactobionate, malate, maleate, mandelate, mesylate, methylbromide, methylnitrate, methylsulphate, mucate, napsylate, nitrate, pamoate, (embonate), pantothenate, phosphate, diphosphate, polygalacturonate, salicylate, stearate, subacetate, succinate, sulphate, tannate, tartrate, and triethiodide, including combinations of two or more thereof. Cationic salts may also be used, for example the alkali metals, e.g. Na and K, and ammonium salts and salts of amines known in the art to be pharmaceutically acceptable, for example glycine, ethylene diamine, choline, diethanolamine, triethanolamine, octadecylamine, diethylamine, triethylamine, 1-amino-2-propanol-amino-2-(hydroxymethyl)propane-1,3-diol, and 1-(3,4-dihydroxyphenyl)-2 isopropylaminoethanol. 
     The pharmaceutical will typically be one which is suitable for inhalation and may be provided in any suitable form for this purpose, for example as a solution or powder suspension in a solvent or carrier liquid, for example ethanol, or isopropyl alcohol. Typical propellants are HFA134a, HFA227 and di-methyl ether. 
     The pharmaceutical may, for example, be one which is suitable for the treatment of asthma. Examples include salbutamol, beclomethasone, salmeterol, fluticasone, formoterol, terbutaline, sodium chromoglycate, budesonide and flunisolide, and physiologically acceptable salts (for example salbutamol sulphate, salmeterol xinafoate, fluticasone propionate, beclomethasone dipropionate, and terbutaline sulphate), solvates and esters, including combinations of two or more thereof. Individual isomers such as, for example, R-salbutamol, may also be used. As will be appreciated, the pharmaceutical may comprise of one or more active ingredients, an example of which is flutiform, and may optionally be provided together with a suitable carrier, for example a liquid carrier. One or more surfactants may be included if desired. 
     The seals and gaskets of the pressurised dispensing container may be formed from any suitable material having acceptable performance characteristics. Preferred examples include nitrile, EPDM and other thermoplastic elastomers, butyl and neoprene. 
     Other rigid components of the pressurised dispensing container, such as the valve body, valve member and valve stem may be formed, for example, from polyester, nylon, acetal or similar. Alternative materials for the rigid components of the pressurised dispensing container include stainless steel, ceramics and glass. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings and which: 
         FIG. 1  is a schematic cross sectional representation of a dispensing apparatus according to the present invention together with a pressurised dispensing container; and 
         FIG. 2  is an enlarged schematic cross sectional representation of a portion of the apparatus of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 1 , the dispensing apparatus of the present invention comprises a housing  2  in which is received in use a pressurised dispensing container  3  in the form of a dispensing canister  10  and a metering valve  12  secured to the canister  10  by means of a ferrule  11 . 
     The housing  2  comprises a cylindrical section  4  which is open at its upper end and houses in use the pressurised dispensing container  3 . At a lower end of the cylindrical section  4  there is provided a mouthpiece section  5  which terminates in an outlet though which a product is dispensed in use. At a base of the cylindrical section  4  is provided a valve stem receiving block  7  which engagingly receives an outlet end of the valve stem of the metering valve  12  as shown in  FIG. 1 . The valve stem receiving block  7  is provided with an outlet orifice  8  for directing product dispense from the metering valve towards the outlet of the mouthpiece  5 . 
     In accordance with the present invention, the housing  2  is further provided with a counter housing section  6  in which is located a counter mechanism  20  which is shown in more detail in  FIG. 2 . Whilst in the illustrated embodiment the housing  2  is shown with an enlarged section  6  for receiving the counter mechanism  20 , this is not essential and the counter mechanism  20  may be provided within the cylindrical section of a standard shaped housing. 
     The counter mechanism  20  is shown schematically in  FIG. 2 . The counter mechanism  20  comprises a means for counting the number of doses dispensed from or remaining within the pressurised dispensing container  3 . In the illustrated example, a counter wheel  21  is provided rotatable mounted within the housing  2 . The counter wheel  21  has marked on it periphery a series of numbers indicating the dose count which are viewable through a dose counter window  23  formed in the counter housing section  6 . The counter wheel  21  is further provided with a series of teeth  22  which are disposed around the circumference of the counter wheel  21 . The counter mechanism  20  further comprises a hydraulic activation mechanism  24 . The hydraulic activation mechanism  24  comprises a hydraulic cylinder  27 , a primary piston  25 , a secondary piston  26  a trigger  29  and a support  30 . The primary piston  25  is received in an upper end of the hydraulic cylinder  27  and the secondary piston  26  is received in a lower end of the hydraulic cylinder  27 . Both pistons  25 ,  26  form fluid tight sliding seals with the hydraulic cylinder  27  in a known manner by use of components such as o-ring seals. The primary piston  25  is provided with an upper elongate extension  31 . The secondary piston  26  is formed unitarily with the trigger  29  which is provided in the form of a laterally extending arm which terminates in a pawl  34  which engages the counter wheel  21  as will be described below. The hydraulic cylinder  27  is filled with a working fluid  28  such as oil. 
     The support  30  comprises an elongated tube having an open upper end which receives a lower end of the secondary piston  26  as shown in  FIG. 2 . The support  30  is further provided with a slot  39  in one side to accommodate the lateral extension of the trigger arm  29 . A biasing spring  32  is provided within support  30  which extends from a base of the housing upwardly into contact with an under face of the secondary piston  26  in order to bias the secondary piston  26  upwards when viewed in the orientation shown in  FIG. 2 . 
     The figures show the dose counter  20  and hydraulic mechanism  24  schematically. In practice, supports for the dose counter wheel and hydraulic cylinder  27  would be necessary can could be provided as part of the moulded housing  2 . 
     The working cross sectional area of the primary piston  25  is greater than the working cross sectional area of the secondary piston  26 . By “working cross sectional area” is meant the area of the internal end face of a piston which is exposed to, and acted on by, the hydraulic fluid  28  of the hydraulic cylinder  27 . For example, the working cross sectional area of the primary piston  25  may be 7.07 mm 2  (piston diameter of 3 mm) and the working cross sectional area of the secondary piston  26  may be 1.77 mm 2  (diameter of piston of 1.5 mm2). 
     The configuration of the hydraulic cylinder  27  in this way causes the secondary piston  26  to move a greater than unit distance on movement of the primary piston  25  through a unit distance. For example, for the working cross sectional areas given above, the ‘distance multiplication factor’ of the secondary piston  26  relative to the primary piston  25  is 7.07÷1.77=4. Thus, for each unit movement of the primary piston  25 , the secondary piston  26  will move 4 units. 
     In use, activation of the pressurised dispensing container  3  by depressing the dispenser canister  10  manually will move the ferrule  11  downwards when viewed in the orientation shown in  FIG. 2 . The leading face of the ferrule  11  will engage the elongate extension  31  of the primary piston  25  and will depress the primary piston  25  within hydraulic cylinder  27 . As noted above, this movement of the primary piston  25  within the hydraulic cylinder  27  will produce a larger movement of the secondary piston  26  which correspondingly moves the trigger arm  29  downwards relative to the counter wheel  21 . Downward movement of the trigger arm  29  engages pawl  34  with one of the series of teeth  22  on the counter wheel  21  which causes the wheel  21  to rotate through an incremental amount to advance the dose count. Release of the pressurised dispensing container  3  allows the ferrule  11  to move upwardly under the internal spring biased of the metering valve  12 . This disengages the ferrule  11  from the upper elongate extension  31  of the primary piston  25  which allows the hydraulic mechanism  24  to reset by virtue of the biasing effect of the spring  32 . Resetting occurs because the biasing force of spring  32  acts upwardly on the secondary piston  26  to move the secondary piston  26  upwardly relative to the hydraulic cylinder barrel  27  and this upward force is transmitted to the primary piston  25  through the hydraulic working fluid  28 . Upward movement of the trigger arm  29  causes the pawl  34  to move upwardly and ride over the neighbouring tooth  22  on the counter wheel  21 . Counter-rotation of the counter wheel is prevented by standard means such as a ratchet (not shown). 
     Various modifications may be made to the inventive apparatus. The primary piston  25  may be fixed or coupled to the ferrule  11  rather than merely being engaged by the ferrule  11 . For example, the upper elongate extension  31  may be welded to the ferrule  11 . In such a case, resetting of the hydraulic mechanism  24  could be achieved without the requirement to provide a separate biasing means such as spring  32 . 
     In a separate modification, the biasing means for resetting the hydraulic mechanism  24  may be provided by means of a spring located within the hydraulic cylinder  27  rather than in a separate support  30 . 
     In the illustrated embodiment, the hydraulic mechanism  24  is illustrated as being provided in a section of the housing  2  underneath the received pressurised dispensing container  3 . However, the hydraulic mechanism  24  may be located elsewhere in the dispensing apparatus  1 . For example, the hydraulic mechanism  24  may be provided higher up within the cylindrical section  4  of the housing  2  alongside the canister  10  and engaged by a portion of the canister  10  (or a structure depending from the canister  10 ) rather than from the ferrule  11 . Alternatively, the hydraulic mechanism  24  may be provided above the pressurised dispensing container  3 . In a further alternative, the hydraulic mechanism  24  may be provided together with the counter mechanism as part of a separate housing which is coupled to a fixed or engaged with a housing containing the pressurised dispensing container  3 .