MECHANICAL COUNTER FOR A METERING APPARATUS

The invention concerns a mechanical counter for a metering apparatus for metering powder, liquid or gaseous substances, and metering apparatus comprising such a counter. The apparatus comprises inter alia two coaxially arranged housing portions which are rotated relative to each other upon actuation of the apparatus. The number of metering portions of the substance is counted and displayed by the counter.

An aim of the invention is to provide optimum adaptation of a counter of that kind to handling of the metering apparatus in an operationally reliable manner, and to simplify manufacture of the counter.

The invention has been particularly, though not exclusively, developed for application to metered dose inhalers (MDI's) such as are disclosed in US Patent 5497944 (derived from WO91/14468) the entire contents of both of which are incorporated herein by reference. Pressure (generally at least 50 bar) is generated in a metered amount of fluid which is discharged through a nozzle assembly having one or more very small openings e.g. in the range 25 to 500 square micrometres. Preferred nozzle assemblies are disclosed in US Patent 5472143 (and parallel WO94/07607), the entire contents of both of which are incorporated herein by reference. An energy storage means, such as a spring, is preferably manually loaded e.g. by a rotary sawtooth wedge arrangement as disclosed in US Patent 4260082 and GB Patent Application 2291135, the entire contents of both of which are incorporated herein by reference. A latching mechanism is generally provided to hold the spring in the loaded position and is manually releasable to pressurise the metered amount of fluid e.g. using a piston and cylinder arrangement. A reservoir and valve arrangement can be provided for recharging the cylinder. Further details are described in PCT/EP96/04351 and parallel USSN 08/726219, the entire contents of both of which are incorporated herein by reference.

Metering apparatuses are used for example in medical aerosol therapy for dealing with ailments of the respiratory tracts. In that situation a liquid or powder medicament is atomised to form an aerosol by means of an atomiser or entered into a stream of gas. The medicament is contained in a supply container which is inserted into the metering apparatus. The supply in a container may be sufficient for several days up to some months. It is therefore necessary to display the consumed amount of medicament or the amount of medicament which is still present in the container.

PCT Patent Publication WO-93/24167 provides a display device for a medical metering apparatus. That display device comprises a ring which is rotatable in coaxial relationship with respect to the apparatus and which, for each dose of a medicament under pressure which is taken from the metering apparatus, is automatically rotated through a predetermined angle by a wedge drive, a small portion of the ring being visible. The display device is pneumatically actuated when the medicament is inhaled.

US Patent No. 4 817 822 discloses a display device for a metering apparatus, the display device comprising a linear or a rotatable disk-like scale which is disposed beside the metering device and which is moved by means of a locked wheel and a locking pawl. Only a small portion of the scale is visible through a window.

PCT Patent Publication WO-86/05991 describes a display device for a metering apparatus, which device comprises a disk-like scale with teeth on the periphery of the disk, and is rotated by means of a helix member. Only a small portion of the scale is visible through a window.

PCT Patent Publication WO-92/09324 discloses a display device for a metering apparatus in which the axial movement of the supply container wichin the housing is transmitted by means of a locking pawl and a worm gear to a rotatable scale of which a small portion is visible through a window.

In accordance with PCT Patent Publication WO-86/02275 a display device for a medical spray apparatus comprises a digital mechanical counter which is advanced by the movement of the supply container within the housing as soon as a dose of the substance is taken from the supply container. That apparatus comprises a large number of individual parts.

A display device which is actuated pneumatically or mechanically upon displacement of the supply container, which is under pressure, in the housing of the metering apparatus, is unsuitable for a metering apparatus having two housing portions which are rotatable relative to each other and a supply container which is fixedly disposed in the metering apparatus.

WO-A-9 321 980 discloses an inhaler with a housing having two parts, one of them being a manoeuvring wheel (10). The two parts can be rotated relative to each other between two stop means. The inhaler has a mechanical counter comprising a rotatable spindle with a screwthread thereon wherein the upper flanks of the threads are at an oblique angle to the axis of the screw and the lower flanks of the screw are substantially perpendicular to the screw axis. One end of the screw has a tooth arrangement whereby it is rotated by the manoeuvring wheel via a transmission. The number of operations of the inhaler are indicated by a scale and a cursor, the latter comprising a tip with an underside parallel to the upper flanks of the screw threads and an upperside parallel to the lower flanks of the screw threads so that the cursor can slide along the screw in one direction only. When the cursor reaches its lowest position it blocks any further rotation of the manoeuvring wheel and thereby indicates that the inhaler should not be further used.

Ways were therefore sought of providing a suitable mechanical counter for a metering apparatus having two housing portions which are rotatable relative to each other and which can be reset.

The invention provides according to one aspect, a mechanical counter for a metering apparatus having two coaxially arranged housing portions which are rotated relative to each other when the metering apparatus is operated, the counter comprising

• at least one rotatable spindle with a screw thread thereon,
• whose axis extends substantially parallel to the axis of the metering apparatus and
• which is disposed in the region of the peripheral surface of the metering apparatus and
• which is mounted in the vicinity of the spindle ends with respective rotary mountings on the first housing portion,
• a tooth arrangement at the spindle end which is closest to the second housing portion,
• a cursor movable along the spindle by the screwthread when the spindle rotates,
• a scale which is disposed adjacent the cursor, characterised in that
• there is at least one projection at the edge of the second housing portion, for engaging the tooth arrangement and rotating the spindle, and
• the cursor has at least one resetting projection and at least one resilient limb with a screwthread engagement portion on the cursor, which screwthread engagement portion engages into the screwthread on the spindle.

In order to provide good running properties for the transmission assembly, the tooth arrangement at the spindle end and the projections are preferably in the form of an involute tooth configuration. Disposed on the spindle is a cursor with rotary securing (prevention of rotation), a scale being disposed opposite same.

According to another aspect, the invention provides a metering apparatus having the mechanical counter of the invention.

Preferred features of the counter and the metering apparatus will now be described.

The two housing portions are rotated relative to each other to actuate the metering apparatus. The angle of rotary movement may be a preferably integral fraction of 360 degrees; it is preferably 30 to 360 degrees. The relative movement of the two housing portions relative to each other is taken off and converted into a rotary movement of the spindle and a sliding movement of the cursor by means of the transmission assembly which comprises the tooth arrangement at the one end of the spindle and the at least one projection at the edge of the second housing portion. The rotary mountings for the spindle are preferably in the form of snap-action mountings. The transmission ratio of the projection-type transmission assembly is fixed by the number of projections and the number of teeth on the pinion; that also fixes the number of revolutions of the spindle, which corresponds to an actuation of the metering apparatus. For each actuation of the metering apparatus the number of revolutions of the spindle can be from 1/30th (one thirtieth) to 10. The pitch of the screwthread on the spindle is adapted to the number of metering portions which can be taken from the supply container in the metering apparatus, and to the travel of the cursor on the spindle. When the spindle is rotated the cursor on the spindle is displaced relative to the scale which is disposed for example on the first housing portion. The scale is preferably linearly divided. The position of the cursor indicates what proportion of the substance to be metered has already been taken from the supply container and what proportion is still present. The direction of rotation of the screwthread on the spindle is either in the same direction or in the opposite direction to the direction of rotation of the housing portions relative to each other.

The cursor substantially comprises a display ring, at least one limb having a screwthread portion and at least one further limb with a resetting projection. There are preferably a plurality of limbs and the limbs are preferably of a resilient nature. The screwthread portion positively lockingly engages into the screwthread on the spindle. The cursor can be displaced on the spindle for resetting thereof, by means of the resetting projection. When the cursor is displaced the screwthread portions on the resilient limbs slide resiliently over the spindle screwthread without damage. The contours of the cursor and the housing are so selected that the cursor is prevented from being rotated on the spindle, by positively locking engagement. For example at least one of the resetting projections may project beyond the screwthread to such a degree that it does not pass through the gap between the spindle and the peripheral surface of the first housing portion. That projection serves as a rotary securing means for the cursor.

A recess can be provided at the other end of the spindle which is in opposite relationship to the drive portion of the spindle. As soon as the screwthread portions on the resilient limbs have reached that recess the cursor ceases to be displaced. The recess serves as a free-motion means for the cursor so that damage to the cursor is avoided if the admissible travel distance of the cursor on the spindle is exceeded upon further actuation of the metering apparatus.

preferably a cover can be fitted over the first housing portion to protect the metering apparatus and the counter. The cover is connected to the first housing portion releasably in an axial direction in a predetermined position. The cover when in the condition of being fitted in position cannot rotate relative to the first housing portion. Accordingly the first housing portion can still be rotated with respect to the second housing portion although the first housing portion is covered by the cover.

The scale which is disposed opposite the cursor is provided either on the first housing portion or on the inside or the outside of the cover. The cover is transparent in a region-wise manner or it comprises transparent material.

At least one rigid entrainment means may be provided on the inside of the cover, which entrainment means pushes the cursor back into the starting position thereof at the one end of the spindle by means of the resetting projections when the cover is fitted into place.

Elastic entrainment means may be provided in place of the rigid entrainment means. In this case the resetting projections of the cursor can be provided with rigid limbs.

When the cursor is reset the cursor abuts against a step at the one end of the spindle before the cover reaches its end position. The cover is further moved to its end position, in which case the elastic portion, that is to say the resilient limb or the elastic entrainment means, springs back and the cursor and the entrainment means are uncoupled. Accordingly the cursor is in its starting position from which it is displaced when the spindle is rotated.

In a specific configuration of the counter the pinion at the one end of the spindle has four teeth of which two oppositely disposed teeth are wider than the other two teeth. Provided on the edge of the second housing portion are two projections, between which there is a recess in which the wider teeth of the pinion can roll. That transmission assembly preferably has a transmission ratio of half a spindle revolution to two actuations of the metering apparatus, for example half a revolution to a rotary movement of 360 degrees of the two housing portions relative to each other.

If a rotational movement of for example 120 degrees of the two housing portions relative to each other is required for actuation of the metering apparatus there may be three projections on the second housing portion, more specifically being displaced through 120 degrees relative to each other. Furthermore in this case also the projections on the second housing portion may be present only singly. Then the spindle is further rotated only in each third actuation of the metering apparatus, although each actuation is counted.

The flanks of the wider teeth lie on the inner or outer peripheral surface of the second housing portion. The spindle is therefore rotatable only when the wider teeth can engage into the opening between the projections. That rotary locking arrangement always holds the spindle in the starting position which is provided at the beginning of the rotary movement.

A plurality of supply containers containing the substance to be metered can possibly be successively fitted into the metering apparatus and used. If the substance to be metered is for example a medicament it may be necessary for reasons of hygiene to limit the permitted number of metering portions with the re-usable metering apparatus. Then it is additionally necessary to count and display the total number of metering portions which have already been discharged with the metering apparatus or the total number of metering portions which are still available. The above-described mechanical counter can be developed in various ways to cover that situation.

In a first embodiment of such a development a gear is provided on the other end of the spindle, which is opposite to the drive side. Provided at the corresponding end of the first housing portion is a coaxial ring gear, preferably with a flange, which is mounted rotatably with respect to the first housing portion and into which the gear engages. The ring gear is also rotated through a given angle for each revolution of the spindle.

Provided on the flange is at least one first mark which, after less than a 360 degree rotation of the ring gear relative to the first housing portion and after consumption of a supply container is disposed opposite a second mark which is in a fixed position relative to the first housing portion. The number of marks on the flange is equal to the number of supply containers which are permitted as a maximum for the metering apparatus (or for the substance to be metered). The second mark can be disposed on the first housing portion or it can be a window in the cover which is fitted onto the first housing portion.

The flange can be provided, instead of the marks, with a scale which quasi-continuously displays the total number of metering portions discharged with the metering apparatus or the total number of metering portions still available, for example in a window. The ring gear is rotated through at most 360 degrees to display the maximum permissible metering portions. For that purpose, a high step-up ratio is possibly required between the rotation of the spindle and the rotation of the ring gear, that ratio being structurally fixed by means of a suitable ratio between the numbers of teeth involved.

In a second embodiment of the development of the counter the counter includes a second spindle which may be similar to and arranged parallel to the first spindle and which carries a cursor which is possibly not resettable. Provided at one of the two ends of the first spindle is a gear which engages into a gear at the corresponding end of the second spindle. Disposed opposite the cursor on the spindle is a scale in a fixed position with respect to the first housing portion, which scale can be disposed either on the first housing portion or on the cover fitted thereon. In the case of this counter the total number of metering portions which have already been discharged or the total number of metering portions which are still available is represented on the displacement travel of the cursor on the second spindle.

In place of the second spindle with cursor, the arrangement may have a rotatably mounted roller, on the periphery of which a helical line is drawn with an entire revolution over the entire length of the roller. The surfaces on the two sides of the helical line are marked in different ways, preferably in two colours, for example red and white or red and green. In this construction the cover has a narrow window which is as long as the roller and through which a narrow strip of the peripheral surface of the roller is visible. A scale can be disposed beside the window and extends over the entire length of the roller. The scale can be divided in accordance with the maximum permitted number of metering portions or it can be divided into numbered sections according to the maximum permitted number of supply containers.

A third embodiment of the development of the counter has a second spindle which is of a similar design configuration to the first spindle but which is disposed at another location in the region of the peripheral surface of the metering apparatus. It is provided with a transmission arrangement, similarly to the first spindle, but the transmission ratio is matched to the total number of permissible metering portions. That spindle is driven by projections at the edge of the second housing portion, preferably by the projections which are already used for driving the first spindle.

In order to provide the high step-up ratio which is possibly required between the first and second spindles or between the first spindle and the ring gear, the arrangement may have, instead of the gear on the first spindle, a single-tooth transmission arrangement with which the gear on the second spindle or the ring gear is further rotated by one tooth for each revolution of the first spindle. The step-up ratio can be from 2 to 1 to 10 to 1.

The rotary locking means for the spindle or the ring gear (i.e. the means for inhibiting unwanted movement) may be a locking pawl or the rotary locking means lies in the friction between the spindle and the mounting or the ring gear and the mounting or in a specific configuration of the parts, for example a positively locking tooth configuration. The cursor is rotationally secured on the spindle by virtue of the positively locking contour of the cursor.

The components of the counter may consist of virtually any material. They are preferably made from plastics material, for example by an injection moulding process. For medical purposes, physiologically harmless materials are used such as for example polybutyleneterephthalate (PBT) or a compound of PBT and Teflon (polytetrafluoroethylene). The materials are preferably so selected that different materials run against each other, for example PBT with Teflon against PBT or PBT against acryl-butadiene-styrene.

The counter according to the invention can be used for example in a metering apparatus which serves as a high-pressure atomiser for a liquid medicament. The liquid to be atomised is disposed in a pressure-less supply container which communicates with a miniaturised high-pressure generating means with which an aerosol is generated; for details in this respect see German laid-open application (DE-OS) No. 195 36 902.5 (the entire contents of which are incorporated herein by reference). The device for producing the high pressure is operated by means of a spring-actuated locking stressing mechanism, the spring being stressed by rotation of two housing portions relative to each other; for details attention is directed to German laid-open application (DE-OS) No. 195 45 226.7 (the entire contents of which are incorporated herein by reference). The counter according to the invention is automatically advanced when the housing portions are rotated relative to each other.

A preferred embodiment of the invention will now be described in greater detail with reference to the drawing (Figure 1) which shows part of a metering apparatus having a counter. In this embodiment the first housing portion is rotated through 180 degrees relative to the second housing portion for actuation of the metering apparatus.

The first housing portion 1 is mounted coaxially rotatably relative to the second housing portion 2. The cover 3a which is mounted thereon encloses the first housing portion 1 and the counter. The cover is additionally shown in broken lines in the withdrawn position 3b. The number of metered portions taken from the supply container which is in use at the time is counted with the spindle (rotary shaft) 4. The spindle 4 is rotatably mounted on the first housing portion by the two snap-action mountings 5 and 6 which act as bearings. The groove 7 which accommodates mounting 5 serves for axially fixing the spindle. The cursor with display ring 9 is provided with two resilient limbs 10 each having a respective screwthread engagement portion 11 and two resetting projections 12 on two limbs 13. The recess 8 is the free-motion means for the portions 11 at the end of their travel. Provided on the inside of the cover are two entrainment means 14 which, when the cover is fitted in position, push the cursor 9 back into the starting position at the end of the spindle by means of the resetting projections 12. When that happens the cursor ring 9 bears against the abutment 15 and the cursor is released as described above.

Disposed at the one end of the spindle is a four-tooth pinion 16 having two (axially) narrow teeth 17 and two (axially) wide teeth 18. The edge of the second housing portion carries the two projections 19 and 20 between which there is the opening 21. As described aboave, the teeth and projections are preferably of involute shape. Disposed at the other end of the spindle is the gear 22 which engages into the ring gear 23. Provided on the flange 24 of the ring gear are a plurality of numbered marks 25, of which a respective mark appears in the window 26 in the cover 3a after a given rotary movement of the ring gear.

The position of the cursor 9 against marker means in the form of the labelled scale 27 shows the number of metering portions taken from the supply container or the number of metering portions which can still be taken therefrom. When the supply container is empty a respective one of the numbered marks 25 appears in the window 26.

The illustrated counter incorporates the preferred features of the invention discussed above (but not the second and third "developments" discussed above) and the description just given should be read in conjunction with earlier discussion of these preferred features.

The preferred counter according to the invention has the following advantages:

• it is automatically advanced when the metering apparatus is actuated;
• it is non-critical in terms of tolerances and is therefore reliable and sure in operation;
• the transmission can be designed to cover a wide range;
• it displays the number of discharged metering portions and/or the number of metering portions still available, quasi-continuously and with an adequate degree of accuracy;
• it is inaccessible and cannot be displaced by mistake when using the metering apparatus;
• it can be used for a plurality of supply containers in succession;
• it can be produced for a different number of metering portions from each supply container and for a different maximum number of supply containers which may be used with a metering apparatus;
• it is integrated into the metering apparatus and does not require any substantial modification thereof;
• it can be produced in miniaturised form and therefore takes up only a small amount of space;
• the individual parts of the counter are preferably made from plastics material which operate without lubricant at a low level of friction;
• no substances can get, into the substance to be metered, from the counter;
• it comprises a small number of individual parts which can be inexpensively produced by injection moulding;
• it is easy to assemble;
• the counter can be reset each time a supply container is emptied; as a result the starting position of the cursor on the spindle is clearly established whenever a fresh supply container is introduced;
• the combination of a spindle which counts the actuations of the metering apparatus during use of a supply container with a second spindle or with a ring gear means that the metering apparatus can be reliably used for a predetermined total number of metering portions or for a predetermined total number of supply containers in succession. The period of use of the metering apparatus can be reliably reviewed.