Can and Actuator Assembly

Abstract

An apparatus for inserting a canister (3) into an inhaler actuator device (20), wherein the apparatus comprises a force sensor (25) adapted to measure a reaction force between the canister and actuator device as the canister moves relative to the actuator device, and a corresponding method.

Claims

1. An apparatus for inserting a canister into an inhaler actuator device, said apparatus comprising an inhaler actuator device support member at a first end of said apparatus and an insertion device at a second end adapted to cause a canister to move relative to the actuator device and to enter an open end of said actuator device, wherein the apparatus further comprises a force sensor adapted to measure a reaction force between the canister and actuator device as the canister moves relative to the actuator device.

2. An apparatus as claimed in claim 1, further comprising a controller adapted to receive an input from said force sensor and to compare the measured reaction force against a predetermined reaction force limit for the canister/actuator device combination.

3. An apparatus as claimed in claim 2, wherein the controller is adapted to output a signal and/or record or output data indicating that a predetermined reaction force has been met or exceeded.

4. An apparatus as claimed in claim 2, wherein the controller is provided with a plurality of predetermined reaction force limits and is provided with a selector permitting a user to select from the plurality of predetermined reaction force limits.

5. An apparatus as claimed in claim 4, wherein a first of said plurality of reaction force limits is approximately 20 Newtons and a second of said plurality of reaction forces is approximately 30 Newtons.

6. An apparatus as claimed in claim 2, wherein the controller is arranged to output a signal to prevent movement of the insertion device if a predetermined reaction force is reached or exceeded.

7. An apparatus as claimed in claim 1, wherein the insertion device is controlled such that the canister is moved into the canister by a predetermined distance.

8. An apparatus as claimed in claim 7, wherein the predetermined distance is such that a distal end of a stem of a metered dose valve of the canister is located within a stem receiving channel in the stem block of the actuator device.

9. An apparatus as claimed in claim 1, wherein the force sensor in located between the insertion device and a portion of the apparatus arranged to apply a moving force to the canister.

10. An apparatus as claimed in claim 9, wherein the force sensor is a piezoelectric force sensor.

11. An apparatus as claimed in claim 2, wherein the controller is arranged to continuously process the measured reaction force with respect to the predetermined reaction force limit and to control the movement of the insertion device to maintain the measured reaction force below the predetermined reaction force limit.

12. An apparatus as claimed in claim 1, wherein the insertion device is a pneumatically driven cylinder.

13. An apparatus as claimed in claim 1, wherein the insertion device is operable to move the canister at different speeds with respect to the actuator device.

14. An apparatus as claimed in claim 13, wherein the insertion device operates at a first speed to bring the canister towards the actuator device and a second speed as a stem of the canister moves into a stem receiving channel of the actuator device.

15. An apparatus as claimed in claim 1, wherein the canister is a metered dose inhaler canister and the actuator device is a metered dose inhaler actuator device.

16. An aerosol inhaler assembly apparatus comprising a first portion arranged to support an inhaler actuation device and a second portion arranged to support an aerosol canister, said apparatus being arranged to move the aerosol canister into an assembled position within the inhaler actuation device and wherein as the aerosol canister is moved a reaction force between the actuation device and the canister is measured.

17. A method of inserting a canister into a canister actuation device comprising: causing a canister to move into an open end of a canister actuation device; and simultaneously measuring a reaction force between said canister and said canister actuation device.

18. A method as claimed in claim 17, further comprising: comparing the measured reaction force against a predetermined reaction force limit for the canister/canister actuation device combination.

19. A method as claimed in claim 18, further comprising: a controller, wherein the controller at least one of outputs a signal and/or records or outputs data indicating that the predetermined reaction force has been met or exceeded.

20. A method as claimed in claim 19, wherein the controller is arranged to output a signal to prevent movement of the canister if the predetermined reaction force is reached or exceeded.

21. A method as claimed in claim 18 wherein the canister is automatically rejected if the predetermined reaction force is reached or exceeded.

22. A method as claimed in claim 18, wherein the canister actuation device is automatically rejected if the reaction force reaches or exceeds an actuation force of the canister and/or the predetermined reaction force limit for the canister/canister actuation device combination.

23. A method as claimed in claim 18, wherein the controller is arranged to continuously process the measured reaction force with respect to the predetermined reaction force limit and to control the movement of the canister to maintain the measured reaction force below a reaction force limit.

24-25. (canceled)

Description

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

[0036] Specific embodiments of the present invention will be described by way of example only and with reference to the accompanying figures in which:—

[0037] FIG. 1 shows two sub-components of a simple metered dose inhaler;

[0038] FIG. 2 shows a cross-section of an actuator;

[0039] FIG. 3 shows an end view of an actuator;

[0040] FIG. 4 shows a valve stem and stem block in detail;

[0041] FIG. 5 shows an illustrative ‘damaged’ valve stem;

[0042] FIG. 6 is a schematic of the assembly machine; and

[0043] FIG. 7 is a displacement force diagram.

[0044] While the invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description of the specific embodiments are not intended to limit the invention to the particular forms disclosed. On the contrary, the invention covers all modifications, equivalents and alternatives falling within the spirit and the scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION

[0045] FIG. 1 shows two sub-components of a metered dose inhaler in partial cross-section.

[0046] The metered dose inhaler 1 is made up of 2 fundamental subcomponents, an actuator device 2 and an aerosol canister 3.

[0047] The actuator 2 has a cylindrical opening 4 to receive the stem of a cylindrical canister 3 at one end and an output nozzle mouthpiece 5 at the other which is placed into the mouth of a user to inhale the medicament. The actuator is configured to activate the canister by means of a channel 6 formed in a stem block 7. The channel 6 is aligned such that an opening 8 can receive a stem of a canister (described in more detail below).

[0048] The channel 6 is also in fluid communication with a medicament dispersing diffuser 9 which receives medicament from the channel and diffuses it into the nozzle 5.

[0049] The canister 3 comprises a cylindrical body containing a propellant and medicament and metered dose valve with a projecting valve stem 10. Aerosol containers or canisters of this type are very well known in the art and will not be described in detail save as to say that axial movement or depression of the valve stem 10 causes a metered dose of medicament entrained in the propellant to be expelled from an end of the valve stem.

[0050] FIG. 2 shows a cross-section of another actuator 2 with like reference numerals referring to like features. As shown in FIG. 2 (and shown in more detail in FIG. 4) the stem block 7 is provided with a projection 11 on an inner surface of the channel 6 against which a valve stem engages. The projection 11 provides an abutment preventing downward movement of the valve stem and causing the relative movement of the canister body and valve stem to cause the actuation to occur.

[0051] FIG. 3 is an end view of the actuator viewed into the generally cylindrical end which receives the canister. The stem block 7 and projection 11 can be seen in the end view of FIG. 3. FIG. 3 also shows optional support ribs 12a, 12b . . . which circumferentially support the canister once in-situ.

[0052] The inhaler assembly is achieved before delivery to a patient by inserting a full canister into the actuator body such that the valve stem is located within the channel 6. The valve stem may extend all the way into the channel in abutment with the projection 11 such that it is ready to operate i.e. a user pressing the end of the canister (the upper part as seen in FIG. 1) causes the valve stem to be compressed against the projection and medicament is released.

[0053] The canister valve stem is secured within the actuator stem block by a light press fit between the inner surface of the channel 6 and the outer surface of the valve stem 10. The ribs provide radial support for the canister and additionally assist with aligning the canister coaxially with respect to the actuator during assembly. Importantly the valve stem has to be aligned with the stem block channel as the canister is inserted into the actuator as will be discussed below.

[0054] Turning to FIG. 4 there is shown an expanded view of the stem block 7 and valve stem 10. As shown the channel 6 has a projection 11 arranged to abut with the distal end 13 of the valve stem 10 on insertion of the stem into the stem block.

[0055] As described above, one of the problems that the inventors have identified (and solved) is that assembly of the canister into the actuator can result in accidental activation of the canister valve. This may be caused by a number of reasons.

[0056] One reason for accidental activation of the canister is damage to the valve stem. FIG. 5 illustrates an example of a splayed (expanded) end of the valve stem 10 where the outer diameter d1 is greater than the normal diameter d2. Because the valve stem channel 6 is adapted to closely match the diameter of the given valve stem (so as to provide the necessary interference fit to secure the canister in the actuator) any damage such as that shown in FIG. 5 will cause the end of the valve stem 13 to abut the upper surface 14 of the stem block. This creates a reaction force which quickly exceeds the activation force for the canister causing the stem to depress and medicament to be accidentally released during the assembly process.

[0057] It will be recognised that corresponding damage to the stem block in the actuator might equally cause accidental activation of the canister.

[0058] Returning to FIG. 4 the canister is assembled by causing the canister to first move along distance A such that the distal end 13 of the valve stem 10 aligns with the stem block. Next the canister is moved along distance B to slide the valve stem into the stem block. It is here where further accidental activation can occur.

[0059] As the stem moves into the block the outer surfaces 15 of the valve stem engage with the inner surfaces 16 of the stem block. A reaction force is generated by virtue of the friction (both dynamic and static) against the force which is being applied to cause the movement of the canister.

[0060] As one example accidental activation can occur if this reaction force is permitted to exceed the actuation force of the given canister. As an example the metered dose valve of a canister manufactured by the 3M Company has an actuation force of 30 Newtons.

[0061] If accidental actuation occurs, a dose of medicament 17 will be discharged into the channel. In the absence of inhalation by a user it will remain in the channel causing the channel to become blocked.

[0062] In any of these circumstances the actuator or canister in question must be discarded automatically by the control system on the line.

[0063] Thus, measurement of the reaction forces being generated as the canister and actuator are assembled can not only be used to identify defective canisters or defective actuators but also to determine if an accidental actuation has occurred that could cause a blockage of the actuator as described above.

[0064] The assembly apparatus and method will now be described with reference to FIG. 6 which is a schematic showing the general arrangement and sub-components of the assembly machine.

[0065] The assembly machine comprises an actuator support portion 18 and an opposing canister support portion 19. The actuator support portion is arranged to support an actuator 20 such that a stem block 21 is aligned with a longitudinal axis 22 of the machine. It will be recognised that the actuator may be supported in a range of different ways. The important feature of the actuator support being that it aligns the stem block with the axis 22.

[0066] The canister support portion 19 is adapted to support and hold the canister and further to be coupled to a linear actuator 23. The canister support portion 19 is also arranged such that the valve stem 10 of the canister is aligned with the axis 22 such that movement of the canister with respect to the actuator maintains alignment of the stem block 21 and valve stem 10.

[0067] The canister support portion 19 is connected on an opposing side to a pneumatically driven linear actuator 23 which, when operated, causes the canister support portion 19 to move along the axis of the machine 22 in the direction 24. Thus, the canister can be inserted into the actuator.

[0068] A force sensor in the form of a Kistler load cell 25 is located between the pneumatic linear actuator 23 and the canister support portion 19. Any reaction force generated along the axis of the machine (for example by abutment of a damaged valve stem against the stem block 21) which causes a load to be applied to the sensor 25. The load sensor is provided with a control arrangement 26 which received output signals from the sensor along control lines 27.

[0069] The control arrangement 26 is provided with a plurality of predetermined reaction force limits matching the activation forces of various canister and actuator combinations. An operator is able to interface with the controller via interface 28 to select the correct reaction force limit for the current canister and actuator combination.

[0070] The controller may be optionally provided with feedback control lines 29 which communicate with the control arrangement 30 for the pneumatic linear actuator 23. The control arrangement 30 is arranged to cause the canister supporting portion to reciprocate between a loading position where a new canister and actuator can be laid onto the machine and an assembled position where the canister is moved into the actuator and the valve stem at least part way into a channel in the stem block 21.

[0071] The control line 29 allows the controller 26 to optionally control the movement of the linear actuator so as to ensure that the reaction force remains below a predetermined limit, for example the activation force for the given canister less a tolerance.

[0072] The operation of the machine will now be described with reference to FIG. 6 and FIG. 7 which is a displacement force diagram.

[0073] First, a canister and actuator pair is inserted into their respective support portions of the machine. The control arrangement is activated and the pneumatic linear actuator causes the canister to move along the axis 22 and through the distances d.sub.1, d.sub.2 and d.sub.3 shown in both FIG. 6 and FIG. 7.

[0074] FIG. 7 is a graph showing force (N) versus distances d.sub.1, d.sub.2 and d.sub.3 along the machine. [0075] d.sub.1 corresponds to the distance between the linear actuator's loading position [0076] d.sub.2 corresponds to the distance of movement of canister into the actuator; and [0077] d.sub.3 corresponds to the distance of movement into the stem block.

[0078] During the movement of the canister the control arrangement continuously receives signals from the load cell 25 which are converted into reaction force data which is continuously compared against the activation force setting which has been selected by the user via the interface 28.

[0079] FIG. 7 shows how the forces measured by the load cell change as the canister is moved into an assembled position in the actuator.

[0080] As the canister moves through a first distance d.sub.1 after a small initial rise caused by overcoming static friction the reaction force is low because there is no resistance to movement of the canister.

[0081] At distance d.sub.2 the canister shoulder 31 engages with the ribs shown in FIG. 3 and a small increase in force is seen owing to the slight resistance to movement as the canister outer wall slides along the ribs.

[0082] The three examples below represent three different scenarios illustrated by lines N1, N2 and N3 in FIG. 7.

Line N1 is a Non-Defective Canister i.e. a Canister with an Undamaged Valve Stem.

[0083] As the valve stem enters the stem block the outer surface engages tightly with the inner surface of the block to cause the interference fit. An initial increase in force is seen which then reduces slightly and finally falls to zero when movement of the canister support portion stops. In this example the canister has been accurately inserted into the actuator. The canister support portion can be retracted and the assembled canister and actuator removed for packaging. The reaction for limit has not been exceeded.

Line N2 Illustrates the Same Graph for a Damaged Valve Stem.

[0084] As the valve stem approaches the stem block the damaged end surface (reference 13 in FIG. 4) abuts with the end face 14 of the stem block. This causes an immediate and large increase in reaction force as shown by line N2 at distance d2. Here the reaction force exceeds the reaction force limit shown in FIG. 7 which is detected by the force sensor 25 and control arrangement 26. Here the operator is alerted that the force has been exceeded indicating that the canister is likely to have been activated accidentally. This may be by any suitable signal such as an audible or visual alarm. The controller may additionally be arranged to cause the canister support portion to retract in combination with an alert of a defective canister.

Line N3 Illustrates an Alternative Feedback Control Arrangement.

[0085] Line N3 represents a situation where the valve stem has a minor defect in the geometry of the valve stem. Here, at distance d3 a damaged outer portion of the valve stem engages and abuts partially with the end of the stem block. In this feedback arrangement the force sensors detects the increase in reaction force which approaches the activation force limit. The controller is arranged to slow down the movement of the pneumatic actuator to reduce the reaction force generated (as shown by line N3 over distance d3). The valve stem slowly slides into the stem body as the defect is deflected by the slower movement of the canister support portion.

[0086] Thus, the continuous monitoring of the reaction force allows the controller to proactively control the reaction force being generated preventing accidental activation of the valve and furthermore preventing a defective canister being identified which might actually pass the quality test if it is inserted into the assembly with greater care i.e. at a lower speed and resulting lower force.

[0087] The location of the sensor head (such as a sensor head manufactured by Kistler) is generally arranged such that it experiences the direct load as imparted on the canister during the insertion step, typically mounted in line on the drive arm. A Kistler load cell may be advantageously used as it is a recognised robust measurement device, but any load cell from equivalent quality instrumentation suppliers would be interchangeable on the design.