WO2005077445A1

WO2005077445A1 - Medicament dispenser

Info

Publication number: WO2005077445A1
Application number: PCT/EP2004/001322
Authority: WO
Inventors: Geir Jansen
Original assignee: Geir Jansen
Priority date: 2004-02-12
Filing date: 2004-02-12
Publication date: 2005-08-25
Also published as: EP1727579A1

Abstract

A dispenser serves for ejecting a substance (26) like a fluid or a powder when being used. The dispenser comprises a housing (2), which accommodates a cartridge (12) which contains the substance and which is provided with an ejection nozzle (24) directed against an outlet of the housing and a dosing piston (25) in sliding engagement with the cartridge. The housing also accommodates an actuator (22) which is in cooperation with the cartridge and which is provided with a drive spring (30) loaded drive piston (31) slidably mounted in the actuator between a retracted position, in which the drive spring (30) is compressed, and an advanced position, in which the drive piston has been released and the dosing piston of the cartridge has been impacted by the drive piston in the ejection mode of the dispenser. By means of the dispenser according to the invention it is possible to eject e.g. a medicine into an extremely fine mist and force the mist into the mouth and lungs of a user without using a propellant gas. Moreover it is possible to adjust the quantity of medicine per dose in strict agreement with the user's often very varying requirement for medicine. The dispenser is especially useful for a diabetic person, which now advantageously can inhale the required insulin instead of, as conventionally, intramuscularly injecting the insulin.

Description

MEDICAMENT DISPENSER

Field of the invention

The invention relates to a dispenser for ejecting a substance like a fluid or a powder.

Background to the invention

Dispensers are to a large extent employed in personal applications for delivering portions of wide range of different products, e.g. medicines of different kinds. One example of a dispenser is a syringe used for. intramuscularly injecting insulin into a diabetic person in need.

A dispenser for self-injecting insulin is known from the European patent EP 0 829 268. The dispenser comprises an insulin cartridge holder for accommodating an insulin-filled cartridge. By manually actuating a drive piston of the dispenser a portion of insulin is injected into the body of the user via a hypodermic needle. By varying the stroke of the piston the size of the doses can be regulated. However, this known dispenser suffers from the draw back that the loading force, at least partly, risks being transmitted to the user's body thereby disturbing the injection process which then cannot be carried out with the required care and accuracy.

US patent No. 6,35,442 discloses a dispenser of the kind, which is used by asthmatic persons - or other persons suffering from pulmonary problems. The dispenser comprises a cartridge, which contains medicaments and a pressurized propellant gas. The cartridge can be displaced in a housing of the dispenser by releasing a stretched power spring whereby a valve of the cartridge is opened and a mist of medicament is driven by the pressurized propellant gas into the mouth of the user via the valve's opening. It is however a problem that the quantity of medicament delivered to the user depends on both the instantaneous mix of medicament and propellant gas and the instantaneous pressure of the mix. Since both the mix and its pressure are inclined to vary as the inhalator is used, the user unfortunately risks getting too much - or too little medicament, thus the user does not does not receive a uniform dose of medicament through the lifetime of the cartridge. Another drawback, which this known inhalator suffers of, is that the pressurized propellant gas in time has a tendency to leak out of the cartridge resulting in that the dosages delivered are reduced such that the user unfortunately doesn't receive the needed quantity of medicine.

From US patent No. 5,320,714 is further known a dispenser for dispensing a powdery medicine to e.g. an asthmatic person. The dispenser comprises a housing with a reservoir of the powdery drug and a flow duct extending to a mouthpiece of the housing. The user can, via the mouthpiece and the flow duct, inhale doses of powder from the reservoir into his or her mouth and lungs. However, the dosing of powder depends, more or less, on the user's lung capacity and is therefore not very accurate.

Summary of the invention

In one aspect according to the invention is provided a dispenser of the type mentioned in the opening paragraph arranged in such a way that the loading of the dispenser and the discharging of the substance occur in two timely separated mechanical operations.

In a second aspect according to the invention is provided a dispenser of the type mentioned in the opening paragraph, which is arranged such that the body of a user is not affected during a dosing operation. In a third aspect according to the invention is provided a dispenser of the type mentioned in the opening paragraph, by which it is possible to dose the substance more accurately than hitherto known.

In a fourth aspect according to the invention is provided a dispenser of the type mentioned in the opening paragraph, by which it is possible to regulate the quantity of medicine in a dose more accurately than hitherto known.

In a fifth aspect according to the invention is provided a dispenser of the type mentioned in the opening paragraph, which is able to eject the substance as a finer mist than hitherto known.

In a sixth aspect according to the invention is provided a dispenser of the type mentioned in the opening paragraph functioning without using a propellant gas.

In a seventh aspect according to the invention is provided a dispenser of the type mentioned in the opening paragraph, which has a dosing mechanism actuated by inhaling the substance.

In an eighth aspect according to the invention is provided a dispenser of the type mentioned in the opening paragraph arranged for keeping the user informed of the consumption of the substance.

The dispenser comprises, according to the invention, a housing, a cartridge which contains the substance and which is provided with both an ejection nozzle directed against an outlet of the housing and a dosing piston in sliding engagement with the cartridge, and also an actuator which is in cooperation with the cartridge and which is provided with a drive spring loaded drive piston slidably mounted in the actuator between a retracted position, in which the drive spring is compressed, and an advanced position, in which the drive piston has been released and the dosing piston of the cartridge has been impacted by the drive piston in the ejection mode of the dispenser.

By means of this construction it is advantageously obtained that a loading step for manually loading the dispenser and a subsequent dosing step for mechanically discharging the substance are carried out for each dosing operation. Since the pressure for ejecting the substance in this way is not transmitted to the user's body via the dispenser, as is the case with conventional dispensers, such pressure when using the dispenser according to the invention does not uncomfortably affect the user.

The ejecting of the substance is carried out without using a propellant gas or a fluid mixture which is inclined to reduce the desired effect of medicine expelled into the mouth and lungs of a patient, and also without using a manually actuated pump for expelling the medicine.

The dispenser according to the invention works with a drive piston which transforms the stored energy in the compressed drive spring into an impact strength, which is effectively able to atomise the substance to a much finer mist than that which is possible when using a propellant gas or a manually activated pump for expelling the substance. By using the dispenser according to the invention an optimal efficiency of the used medicine is therefore obtained.

It is therefore very appropriate to use the dispenser for e.g. asthmatic persons. The dispenser according to the invention can also advantageously be used to expel a diabetic medicine into the mouth and lungs of diabetic person owing to the extremely fine mist, which is obtainable. The dispenser according to the present invention provides the possibility of adjusting the medicament doses exactly to the immediate requirement of e.g. an asthmatic or a diabetic person in need.

However, it is also very appropriate to use the dispenser to deliver a wide range of other products and medicines .

The person using the dispenser will normally try to inhale simultaneously with the expelling of the substance.

For that purpose the housing can have an air inlet for allowing airflow into the housing in response to air being sucked out of the housing at the outlet of the housing, a meter for measuring the velocity of the airflow, and a releasing arrangement for releasing a trigger from a retaining position when the airflow has reached a predetermined velocity, thereby expelling a dose of the substance. In this way the dispenser can, according to the invention, be used somewhat like a conventional inhalator but with a much better effect since the ejected mist of droplets or particles is extremely fine and is also forced into the mouth and lungs of the user by its own momentum. Additionally, the ejected droplets or particles are of substantially uniform size. Consequently, they will be ejected with substantially the same velocity so that the efficiency of the medication is optimised.

In a preferred embodiment of the invention the actuator can comprise a holder and a cylinder which by means of a screw connection is displaceably mounted in the holder, whereby the drive piston is slidably mounted in the cylinder between the retracted position and the advanced position, and the distance between said positions is constant.

In service, the drive piston will therefore always travel the same distance in the cylinder thereby supplying the same quantity of energy to the dose piston for each dosing operation. In this way it is secured that the dose piston discharges the substance with the same power each time. The ejection process is therefore carried out in exactly the same way each time. But the precise amount of the doses can of course be carefully adjusted to the immediate requirement of the user.

By simply screwing the cylinder forwards in the holder by means of the screw connection the user can furthermore accurately regulate the size of each dose in order to cover the immediate requirement of the user. In this way the very important advantage is thereby imparted that he or she can exactly harmonize the consumption of the substance as necessary.

The sizes of the substance doses can according to the invention easily and accurately be regulated by means of a dial drive having a stub shaft rotatably mounted in a bearing liner of the holder and a turn wheel extending out of the housing opposite the outlet of the housing, whereby the cylinder is firmly connected with the dial drive in the rotation direction and displaceably connected with the dial drive in the direction of the rotation axis.

Turning the dial drive in the housing results in the cylinder being displaced axially forwards in the housing by means of the screw connection for regulating the sizes of the substance doses while the dial drive itself is kept in the same axial position in relation to the housing.

The distance, which the cylinder is displaced in the housing by turning the dial drive, can in one embodiment according to the invention be visually seen on a dial of the dial drive. In another embodiment according to the invention a number of equally spaced depressions are distributed along the circumference of the bearing liner of the holder and at least one spring-loaded ball is mounted in a bore in the stub shaft of the dial drive for engaging a depression, thereby temporary locking the dial drive at a wanted angle in relation to the housing. The user can by means of this construction hear a click each time the ball engages with a depression and use this information to turn the dial drive an angle corresponding to the desired dose.

The dispenser can, according to the invention, in co-operation with the dial drive, furthermore comprise a dosing control arrangement for registering the angle the dial drive is turned for each desired dosage, counting the number of doses ejected, calculating the residual volume of substance in the cartridge and temporary locking the trigger in a retaining position when the cartridge is empty or at least close to being empty.

The user can thereby advantageously follow the progress of the dosage operations and be urged to change an empty cartridge with a filled one when experiencing that the dispenser is locked and can not be operated anymore. This has important safety benefits to the user.

The dispenser can moreover have an unlocking arrangement for being reset into its operational state. The unlocking arrangement functions by opening a cover for the cartridge compartment whereby the trigger, which is locked in the retaining position, is unlocked.

The actuator can comprise a row of retainer teeth, which are distributed, equally spaced, along the drive piston and a trigger on the holder for co-operating with the retainer teeth. Thereby is obtained the advantage that it easily and safety is possible to keep the drive piston in its retracted position in the cylinder when the dispenser has been loaded and to release the piston when requiring a dose of the substance.

The actuator can, according to the invention, moreover have a loader for retracting the drive piston to its retracted position.

Said loader can advantageously comprise a tension spring having a fixation end connected to the drive piston in an elongated cavity in the drive piston and a free end extending out of the housing via an opening in the dial drive for making it possible to manually pull the tension spring, e.g. by means of a grip attached to the tension spring.

The spring power of the tension spring in expanded state can furthermore be larger than the spring power of the compression spring in compressed state and the spring power of the tension spring in contracted state being lesser than the spring power of the compression spring in both compressed and expanded state. The tension spring is thereby able to retract the drive piston to its retracted position and subsequently to allow the displacement of the drive piston when a dose of the substance is required.

The dosing piston is for each dosing operation displaced a further distance into the cartridge until the dosing piston is abutting the bottom of the cartridge. The cartridge is in this state empty and must to be replaced by a new one while the drive piston is reset to its start position for making this operation possible.

For that purpose the actuator is equipped with a reset mechanism, which comprises a slide provided with an internal thread which matches the external thread of the screw connection and which is slidably mounted in a guideway of the holder between a first position, in which the internal thread engages the external thread of the screw connection, and a second position, in which the internal thread has disengaged the external thread.

By setting the slide in its second position it is now possible easily and quickly to retract the cylinder to the start position and at the same time loading the drive piston by simply pulling the tension spring into its expanded state.

Opening and closing a pivotable cover for a cartridge compartment in the housing preferably operate the reset mechanism. For that purpose the cover is connected with a rod, which is displaceably mounted in a slit in the slide and has a cam which engages the slit upon opening the cover and which disengages the slit upon closing the cover.

Thereby it is advantageously secured that the dispenser can be operated only when the cartridge has been replaced, the drive piston has been retracted and the cover has been closed.

For temporarily keeping the cover in its open position and the cam of the rod in engagement with the slit of the slide while replacing an empty cartridge with a new one the dispenser can moreover comprise at least one spring acting between the rod and the cover .

Brief description of the drawings

The invention will be explained in greater detail below where further advantageous properties and example embodiments are described with reference to the drawings, in which

Fig. 1 shows a dispenser according to the invention seen from above, Fig. 2 shows the dispenser seen from below,

Fig. 3 shows a sectional view of the dispenser,

Fig. 4 shows in perspective, partly in section an actuator for the dispenser shown in fig. 1 - 3 being loaded in an initial position,

Fig. 5 shows the actuator in the initial position after having been loaded,

Fig. 6 shows the actuator after having been discharged from the initial position,

Fig. 7 shows the actuator loaded in an intervening position,

Fig. 8 shows the actuator after having been discharged from the intervening position, and

Fig. 9 shows the actuator discharged to a final position.

Description of a preferred embodiment

Only as an illustrative example the dispenser according to the invention is described below based on the assumption that the substance is insulin for being ejected into the mouth and lungs of a diabetic person in need.

The dispenser is especially advantageous for being used to that very purpose owing to the fact that the ejected mist is extremely fine and thereby made easily absorbable in the lungs of the user. Also the mist is forced into the mouth and further into the lungs of the user without using a propellant gas and it is moreover possible to adjust the quantity of insulin per dose in strict agreement with a diabetic person's often very varying requirement for insulin. Within the scope of the invention the skilled person would be aware that the dispenser can be used for ejecting doses of medicament or many other ejectable substances e.g. terbutaline, theophylline, salmeterole, budesonide, beta- blockers and steroid hormones.

Fig. 1, 2 and 3 show the dispenser, which comprises a housing 2, which is equipped with a detachable mouthpiece 3 with an outlet 4.

On the topside 5 of the housing (fig. 1) an LCD screen 6, a start button 7, an ON/OFF button 8 and a lid 9 for covering a battery 10 in the housing are shown.

Fig. 3 shows that the housing 2 has a compartment 11 for accommodating an insulin cartridge 12, and fig. 2 shows that the dispenser 1 on the underside 10 has a cover 13 for said cartridge compartment 11. The cover has a window 15 through which parts of the interior of the housing can be observed. A button 16 serves for opening the cover, which is pivotably mounted on the housing by means of a crankshaft 17 (fig. 3) . Springs 18 serve for temporarily keeping the cover in the open position.

In addition the housing has an air inlet 19 for allowing air to flow into the housing in response to air evacuated from the housing via the outlet 4 in the mouthpiece 3. In the air inlet a non-return valve is placed in the shape of e.g. a membrane (not shown) .

The dispenser also has a pull ring 20 and a dial drive 21 the functions of which will be explained in detail later.

In the housing is furthermore placed an actuator 22, which in fig. 4 - 9 is shown in use in positions where it is cooperating with the insulin cartridge 12. These mutual positions are the same as the ones, which the actuator and cartridge take up in the housing, which for clarity purposes is left out in fig. 4 - 9.

The cartridge 12 has a top 23 with an ejection nozzle 24. In the cartridge a dosing piston 25 is slidably mounted. The insulin 26 is enclosed in -the cartridge 12 between the dosing piston 25 and the top 23 with the nozzle 24.

The actuator comprises a holder 27, a cylinder 28 which is displaceably mounted in the holder by means of a screw connection 29. A drive spring 30 loads a drive piston 31, which is slidably mounted in the cylinder 28.

The drive piston can travel in the cylinder between a retracted position, in which the drive spring has been compressed, and an advanced position, in which the drive spring has been at least partly decompressed. The distance, which the drive piston is allowed to travel, is defined by cooperating stop faces 32 and 33 on the drive piston 31 and the cylinder 28, respectively.

The distance, which the drive piston is allowed to travel, is defined by cooperating stop faces 32 and 33 on the drive piston 31 and the cylinder 28, respectively.

In the drive piston 31 an elongated slot 34 is shaped cooperating with a key 35 in the holder 27 in such a way that the drive piston is allowed to slide axially in the cylinder but not to rotate relative to the holder.

On the drive piston a row of retainer teeth 36 is furthermore shaped, cooperating with a trigger 37 pivotably mounted on the holder 27. The trigger serves to keep the drive piston in the retracted position in the cylinder by engaging one of the retainer teeth and serves to release the drive piston upon disengaging said retainer tooth.

The row of retainer teeth 36 will always be in the correct position opposite the trigger owing to the fact that the drive piston is not able to rotate relative to the holder.

In the drive piston 31 an elongated cavity 38 is shaped in which a loader 39 is fixed to the drive piston at one end while the other end freely extends out of the cavity via an opening in the dial drive 21.

The loader 39 comprises a tension spring 40 fixed to the drive piston with a cross pin 41 and mounted in a tube 42 with elongated slits 43 allowing the tube to slide in relation to the drive piston between a position where the tension spring is in a contracted state and a stretched state where the tension spring is in an expanded state. The free end of the tension spring is firmly connected with the free end of the tube, which again is connected with the pull ring 20.

The loader 39 serves, by manually pulling the pull ring 20, to retract the drive piston 31 to its retracted position while at the same time compressing the drive spring 30.

The spring power of the tension spring in an expanded state needs to be larger than the spring power of the compression spring in its compressed state in order to be able to perform the above named operation while the spring power of the tension spring in contracted state on the other hand needs to be lower than the spring power of the drive spring in both compressed and expanded state for allowing the drive spring to press the drive piston against the dosing piston during a dosing operation. The screw connection 29 between the holder 27 and the cylinder 28 consists of an internal thread 44 on a slide 45 slidably mounted in a guideway 46 of the holder 27 and an external thread 47 on the cylinder 28.

The cover 13 for the cartridge compartment 11 is, as mentioned above, pivotably mounted on the housing 2 by means of the crankshaft 17. The crankshaft has a crank 48 (fig. 3) connected with a rod 49 via a link 50 in such a way that the rod is displaced through a slit 51 in the slide 45 to an advanced position when opening the cover and to a retracted position when closing the cover. On the rod is furthermore shaped a cam 52, which engages the slit in the advanced position of the rod and disengages the slit in the retracted position of the rod.

By opening the cover 13 the slide 45 is therefore displaced in the guideway 46 in the direction away from the cylinder 28 resulting in that the internal thread 44 on the slide 45 disengages the external thread 47 on the cylinder 28.

By closing the cover 13 the slide 45 is displaced in the guideway 46 in the direction against the cylinder 28 resulting in that the internal thread 44 on the slide 45 is engaging the external thread 47 on the cylinder 28.

The dial drive 21 comprises a turn wheel 53 and a stub shaft 54 rotatably mounted in a bearing liner 55 of the holder 27. A key and slot connection between the stub shaft 54 and the cylinder 28 causes the cylinder to be rotated simultaneously with rotatation of the dial drive while the cylinder on the other hand is allowed to be displaced axially in a cylindrical cavity 56 of the stub shaft 54.

In the bearing liner 55 of the holder 27 a number of equally spaced depressions 57 are distributed along the circumference, and at least one spring-loaded ball 58 is mounted in a bore in the stub shaft for engaging one of the depressions.

The end part of the rod is slidable mounted in a first groove 59 shaped in the housing 2 while a corresponding second groove 60 is shaped in the dial drive 21, which is in its zero position when the two grooves 59 and 60 are aligned. In this position and only in this position is said end part of the rod 49 allowed to move into the second groove 60 when opening the cover 13.

Thereby is obtained that the cover 13 can be opened in the zero position of the dial drive 21 only to ensure that the internal thread 44 on the slide 45 will meet the external thread 47 on the cylinder 28 in the same start position every time a used cartridge 12 is to be replaced with a new one.

The function of the dispenser according to the invention will now be explained in more definite details with reference to fig. 4 - 9.

In fig. 4 it is supposed that the dial drive 21 has been set in its zero position and that the cover 13 then has been opened for replacing an empty cartridge with a filled one. As mentioned above this implies that the slide 45 is displaced away from the cylinder 28 and that the internal thread 44 thereby disengages the external thread 47 of the screw connection 29 whereby the cylinder 28 and the drive piston 31 can be displaced axially to their shown start positions in relation to the holder 27 when extracting the loader 39, thereby simultaneously compressing the drive spring 30.

Finally the trigger 37 engages one of the retainer teeth 36 keeping in this way the drive piston in its retracted state whereupon the cartridge is replaced. By relaxing the loader 39 and closing the cover 13 such that the internal thread 44 on the slide 45 again engages the external thread on the cylinder is the dispenser now ready for firing the first shot of insulin. This situation is seen in fig. 5.

This operation takes place by bringing the trigger 37 to disengage the retainer tooth 36 whereby the drive piston 31 is forced into the direction of the dosing piston influenced by the spring power of the drive spring 30.

This situation is illustrated in fig. 6, where the drive piston has pushed the dosing piston some distance into the cartridge whereby a dose of insulin has been ejected via the nozzle 24 of the cartridge 12.

Alternatively the dispenser can be arranged for displacing the drive piston only relatively close to the dosing piston in the first shot.

The stop faces 32 and 33 on the drive piston 31 and the cylinder 28 define the piston stroke, which therefore is exactly the same for each stroke thereby securing a uniform expelling of the insulin each time.

The stop faces 32 and 33 are shaped as e.g. toothed couplings (not shown) arranged for engaging each other at the end of a stroke. Such engagement locks the angle position of the cylinder 28 and the dial drive 21. The user is now not able to rotate the cylinder whereby it effectively is prevented that some of the substance from the cartridge is squeezed out into the housing by manipulating the turn wheel 53.

In fig. 7 has the cylinder been screwed a distance into the holder 27 by turning the turn wheel 53 of the dial drive 21 an angle which corresponds to the desired quantity of insulin in the dose to be ejected. The drive piston 31 has been retracted in the cylinder 28 and is kept in the retracted position by the engagement of the trigger 37 with another one of the retainer teeth 36.

It is necessary to screw the cylinder an appropriate distance into the holder for each shot for being able to drive a new dose of insulin out of the cartridge via the nozzle of this.

The dispenser is calibrated to dose a predetermined quantity of insulin when turning the dial drive a corresponding angle whereby the size of the doses becomes proportional with the angle, which the dial drive is turned. Said in other words, the user can turn the dial drive exactly the angle that corresponds to the desired size of the insulin dose, which he or she actually needs.

The cooperation between the depressions 57 in the holder 27 and the spring-loaded ball 58 in the bore of the stub shaft 54 of the dial drive 21 helps the user to adjust said angle correctly since each time the user hears a click he knows that the dial drive has now been turned a predetermined angle. By counting the clicks he knows the resulting angle, which the dial drive 21 has been turned, and thereby also the size of the dose of insulin, which he will receive.

The engagement between one of the depressions and the ball also keeps the dial drive and thereby the cylinder in the chosen angle during a dosing operation.

For making it easier and safer to dose the insulin correctly the dispenser also comprises a dosing control arrangement (not shown) for registering the angle the dial drive is turned for each desired dosage, counting the number of dosages ejected and thereby calculating the residual volume of substance in the cartridge. The dispenser has in fig. 8 now discharged a new shot and thereby a new dose of insulin by disengaging the trigger 37 from the retainer tooths 36. Such operations are carried out until the dosing piston has reached the top of the cartridge, which then is empty.

This situation is seen in fig. 9. The dosing control arrangement now temporary locks the trigger in a retaining position when the cartridge is at least close to be empty whereby is obtained advantageously that the diabetic person does not risk being injured by erroneously believing that he has in fact received the insulin necessary for his health.

The user now needs to open the cover for replacing the empty cartridge with a new one whereby the above explained operation cycle start over again from the situation shown in fig. 1.

It is very useful if the diabetic person is actively participating in the insulin dosing process by inhaling air via the air inlet 19 and the air outlet 4 of the housing until the air flow has reached a predetermined velocity in the respiratory passages of the diabetic person whereby a releasing arrangement (not shown) having an air velocity meter (not shown) transmits a signal to the trigger for bringing this to release the driye piston such that a dose of insulin is expelled and in an extremely fine mist flows into the respiratory passages of the diabetic person along with the inhaled air.

The dispenser can be provided with electronic intelligence making the dose setting of the dispenser electronically adjustable. For this purpose the dispenser may further comprise an USB connection (not shown) for downloading data regarding dosages, times etc. and for uploading data regarding release of insulin in correlation to the person's lung-data- volume of air. The invention is described above as a dispenser for insulin. There are, however, many other potential medications e.g. the ones stated above, that could be dispensed in this manner for various medical purposes. The dispenser is especially useful in conditions where the possibility of being able to vary the dosages is required. This is to be understood only as example embodiments since the dispenser according to the invention can advantageously be used for many other purposes within the scope of the invention.

Claims

1. A dispenser for ejecting a substance (26) like a fluid or a powder, comprising a housing (2) accommodating: a cartridge (12) which contains the substance and which is provided with an ejection nozzle (24) directed against an outlet of the housing and a dosing piston (25) in sliding engagement with the cartridge, and - an actuator (22) which is in cooperation with the cartridge and which is provided with a drive spring loaded drive piston (31) slidably mounted in the actuator between a retracted position, in which the drive spring (30) is compressed, and an advanced position, in which the drive piston has been released and the dosing piston of the cartridge has been impacted by the drive piston in the ejection mode of the dispenser.

2. A dispenser according to claim 1, characterised in that the actuator (22) comprises a holder (27) and a cylinder (28) which by means of a screw connection (29) is displaceably mounted in the holder, whereby the drive piston is slidably mounted in the cylinder between the retracted position and the advanced position, and the distance between said positions is constant.

3. A dispenser according to claim 1 or 2 , characterised in that the actuator comprises - a row of retainer teeth (36) , which with equal spaces are distributed along the drive piston (31) , and a trigger (37) on the holder (27) for retaining the drive piston in the loaded position when engaging one of the retainer teeth and for releasing the drive piston upon disengaging said retainer tooth, and - a loader (39) for retracting the drive piston into the loaded position.

4. A dispenser according to claim 1, 2, or 3 , characterised in that the loader (39) comprises a tension spring (40) having a fixation end connected to the drive piston (31) in a cavity in the drive piston and a free end extending out of the housing (2), whereby the spring power of the tension spring in expanded state is larger than the spring power of the drive spring (30) in compressed state and the spring power of the tension spring in contracted state is lesser than the spring power of the drive spring in both compressed and expanded state.

5. A dispenser according to any of the preceding claims, characterised in that the actuator (22) comprises a slide (45) which is provided with an internal thread (44) which matches the external thread (47) of the screw connection (29) and which is slidably mounted in a guideway (46) of the holder (27) between a first position, in which the internal thread engages the external thread (47) of the screw connection, and a second position, in which the internal thread has disengaged the external thread.

6. A dispenser according to claim 5, characterised in that the dispenser comprises - a cover (13) for a cartridge compartment (11) pivotably mounted to the housing between a closed and an open position, a rod (49) connected with the cover and displaceably mounted in a slit (51) in the slide (45) , and - a cam (52) of the rod for engaging the slit upon closing the cover and disengaging the slit upon opening the cover .

7. A dispenser according to any of the preceding claims, characterised in that the dispenser (1) comprises a dial drive (21) having a stub shaft (54) rotatably mounted in a bearing liner (55) of the holder (27) and a turn wheel (53) extending out of the housing (2) opposite the outlet of the housing, whereby the cylinder (28) is firmly connected with the dial drive in the rotation direction and displaceably connected with the dial drive in the direction of the rotation axis.

8. A dispenser according to claim 7, characterised in that the dispenser (1) comprises a number of depressions (57) equally spaced along the circumference of the bearing liner (55) of the holder (27) and at least one spring- loaded ball (58) mounted in a bore in the stub shaft (54) of the dial drive (21) for engaging one of the depressions .

9. A dispenser according to claim 7 or 8 , characterised in that the dispenser (1) comprises a dosing control arrangement for registering the angle the dial drive (21) is turned for each desired dosage, counting the number of dosages ejected, calculating the residual volume of substance in the cartridge (12) and temporary locking the trigger (37) in a retaining position when the cartridge is at least close to being empty.

10. A dispenser according to any of the preceding claims, characterised in that the dispenser (1) comprises - an air inlet (19) in the housing (2) for allowing airflow into the housing in response to air being sucked out of the housing via the outlet (4) of the housing, - a meter for measuring the velocity of the airflow, and - a releasing arrangement for releasing the trigger (37) from the retaining position when the velocity has obtained a predetermined size.