Patent Application
20220347408
The present invention relates to dose counting mechanisms for medicament inhaler devices, for example metered-dose inhaler (MDI) devices. In particular, the invention relates to an improvement of the indexing of a rotating wheel forming at least a part of the mechanical dose counting mechanism.
Accurate and reliable counting of doses is an important consideration for inhaler devices of all types, so that a user can be confident of the number of doses remaining for delivery. Counters can be broadly categorised into electronic dose counters and mechanical dose counters. Electronic counters are typically used where large numbers of doses need to be counted, but mechanical counters have the benefit of needing no power supply to register or display a dose count, so are generally preferred wherever possible.
Where a mechanical counter is required to count a large number of doses, multiple linked count wheels or drums are often employed to display the count. This avoids having to provide a physically large display surface on a single element of the counter, because each wheel need only display digits 0-9, and maybe end-of-life indicators/positions. A problem can arise, however, in ensuring that the first wheel, displaying the units value of the count, is sufficiently advanced/indexed during use of the device.
For a press-and-breathe pressurised metered-dose inhaler (pMDI) device, the indexing mechanism should be operated as part of the normal use-sequence. This generally means that the counter will be actuated by the movement of the medicament canister between its rest position and its fire point. This movement occurs over a relatively short distance, typically between 2 mm and 3 mm. For a counter where individual doses are registered by movement of a units wheel in a multi-wheel counter, the small movement must effect a relatively large rotation of 36° of the units wheel (i.e. a tenth of a rotation).
The timing, appearance, and accuracy of this indexing has potential implications for the user experience. Slowly indexing the counter throughout the act of depressing the canister can be slightly confusing to the user, especially if the counter is front-mounted and thus potentially visible during use. The partial indexing that may result can also be confusing, particularly if the counter remains in that state once the user has (even if just temporarily) stopped interacting with the device.
To avoid these problems, most dose counters only start to index at a defined commitment-point during the depression of the canister. There will also be a fire-point, i.e. a distance of canister depression at which the canister fires. Known inhaler devices are typically unable to tie these two points to the same depression distance unless some form of firing sensor is provided, but it is important that they are situated as close to each other as possible. However, care must be taken to ensure that, in all tolerance conditions, the counting commitment-point does not occur after the fire-point. After the commitment-point the dose counter will tend to complete an index, either during depression or on return to the rest position of the canister, regardless of whether the user continues depressing the canister or just releases it. Counting of a dose when there has been no delivery is undesirable, but delivery of a dose without indexing the counter should be minimised as far as is reasonably possible.
A counter indexing system will require energy-input, which can come directly from the user (in the form of increased canister-depression-force) and/or be harvested from unused force applied by the canister spring as the canister returns to its rest position. The lack of information surrounding the force-requirements for the canister spring may present reliability risks for the latter option, rendering it undesirable. However, care must be taken to ensure that the peak force experienced by the user during operation, if user force is directly harvested on the downward stroke, does not exceed a specified maximum force.
According to a first aspect of the invention there is provided an indexing mechanism as defined in the appended claim 1. Further optional features are recited in the associated dependent claims.
The mechanism comprises a counting component, a locking element for resisting movement of the counting component and a distinct driving element for driving movement of the counting component. The locking and driving elements have an initial position in which the locking element is engaged with the counting component, and the locking and driving elements are actuated by movement of a common element to move the locking element out of engagement with the counting component and to move the driving element, wherein the driving element applies a motive force to the counting component before the locking element fully disengages from the counting component. Engagement of the first element with the counting component may prevent movement of the counting component.
WO 2012/150427 discloses a dose counter mechanism where an actuator 2,102, 202 drives an index wheel 18,118,218 to advance a count wheel 26,126,226 once for every ten doses released. A hook 10,210 on the actuator drives the index wheel, and an engagement feature 17,217 on the actuator holds the count wheel in position between actuations. Both the hook and the engagement feature are moved simultaneously as the actuator is moved, so that engagement feature disengages from the count wheel as the hook moves towards engagement with the index wheel.
The count wheel is free to advance when the hook engages and drives the index wheel.
AU 2016204147 relates to a dose counter for a metered dose inhaler. As a canister is initially depressed, an actuator 240 moves anticlockwise to the position shown in
The driving element of the present invention may move into contact with the counting component from the first position to apply the motive force, or may be pre-engaged and apply a force in the first position prior to movement of the common element. Movement of the counting element may be driven by movement of the driving element from the first position.
The mechanism may incorporate some means of storing or charging energy behind or within the driving element. For example, the driving element may be provided on a resilient arm. The resilient arm may be deformed on/during engagement of the driving element with the counting component, or with a chassis or some other feature of a device housing the mechanism, such as an inhaler device, to store potential energy in the resilient arm.
The resilient arm may comprise a hinged or bent section. The hinged or bent section may be deformable or collapsible to adjust the spring rate of the resilient arm, or to provide a specific region with a different spring rate.
The resilient arm may comprise an abutment feature, for example a slot, loop, slot or similar, to resist deformation of the hinged or bent section in a first direction. This may provide a higher spring rate/resistance to deformation in said first direction than in one or more other directions.
The driving component may be out of engagement with the counting component in the initial position, and actuation of the driving element by the common element may then move the driving element into engagement with the counting component to apply a motive force to the counting component.
The driving element may engage with a slot in the counting component.
The slot in the counting component may comprise a cam surface for engagement with the driving element. The slot in the counting component may comprise first and second cam surfaces for engagement with the driving element. The first and second cam surfaces may be engaged in opposite movement directions of the of the driving element, so as to deform the resilient arm in opposite directions during use. Different spring rates/resistances to deformation may be provided, for example by an abutment feature as previously described.
The indexing mechanism may further comprise a restoring element providing a biasing force to urge the locking and/or driving element back to the initial position. Providing different spring rates as discussed may reduce the biasing force needed to urge the locking and/or driving element back to the initial position. The restoring element may comprise a spring, for example a metal or polymer spring.
The spring may be a leaf spring and may be part of an integrally formed component which also comprises the locking and/or driving element.
The locking element may engage with a recess in the counting component.
The locking and driving elements may be provided on separate components such that the indexing mechanism may comprise an indexing actuator and a locking actuator, or the locking and driving elements may provided on a common component such that the mechanism comprises a single indexer component.
The counting component may be a rotatable component and movement of the counting element may comprise rotation. The rotatable component may be a count wheel of a dose counter.
Movement of the common element may comprise depression of the common element, for example by a user. The common element may be an MDI canister.
The invention also provides a method of indexing a counter as defined in the appended claim 22. Further optional features are recited in the associated dependent claims.
The method comprises sequential steps of:
The locking and driving elements are moved in steps B and C by movement of a common element, the driving element applies the motive force to the counting component before the locking element fully moves out of engagement with the counting component and the driving element drives movement of the counting component once the locking element is fully out of engagement with the counting component.
The locking and driving elements may be moved simultaneously in steps B and C. Step B may comprise storing energy to drive movement of the counting component.
The counting component may be rotatable and the driving element may drive rotation of the counting component. The driving element may further hold the counting component in a rotated position after driving rotation.
The method may comprise the further step of:
Movement of the locking and/or driving element may comprise rotation around a pivot.
Movement of the common element may comprise depression of the common element.
The method may be implemented using an indexing mechanism as previously described.
Practicable embodiments of the invention are described in further detail below with reference to the accompanying drawings, of which:
An exploded view of a press-and-breathe pressurised metered-dose inhaler (pMDI) device 2 is shown in
The front housing 8 further comprises a window 12 through which a portion of the counter wheel 20 can be viewed, and a mouthpiece 14 providing fluid connection to the medicament canister 6 when the pMDI is assembled. The precise internal geometry of the rear housing 4 to provide the fluid communication and facilitate release of a dose from the canister 6 is unimportant to the present invention, and various suitable configurations will be familiar to a skilled reader. A mouthpiece cover 18 for closing and protecting the mouthpiece 14 is also provided, as is conventional.
A rear perspective view of the counter wheel 20 is shown in
The charging feature 24 comprises ten evenly spaced curved fingers 28 defining ten slots 30 therebetween. Each curved finger 28 provides a first camming surface 32 and a second camming surface 34, with each slot 30 provided between the first camming surface 32 of one curved finger 28, and the second camming surface 34 of an adjacent curved finger 28. The curved fingers 28 are shaped so that each slot 30 is wider at an end that is nearest the outer circumference of the counter wheel 20.
The outer circumference of the disc portion 22 of the counter wheel 20 is provided with ten evenly spaced locking recesses 36, each of which comprises one chamfered edge 38, angled to the radius of the counter wheel 20.
The various features on the rear of the counter wheel 20, specifically the first and second camming surfaces 32,34 and locking recesses, cooperate with parts of the locking actuator 40 and indexing actuator 60 to provide an indexing system in accordance with the present invention.
As shown in
The indexing actuator 60 is shown in
The indexing arm 68 comprises a hairpin bend 74, hereafter referred to as a hairpin 74, part way along its length, and is thicker at a lower end, adjacent the mounting pin 62, than at the upper end, adjacent the indexing peg 70. A diagonal brace 76 is also provided between the substantially rigid arm 66 and the indexing arm 68, at a position between the mounting pin 62 and the hairpin 74. A first part of the indexing arm 68 therefore has a relatively high rigidity, and a second part is more easily deformable.
Each of the locking actuator 40 and indexing actuator 60 is pivotally mounted to the rear housing 4 at its respective mounting pin 42,62, and the free ends of the spring arms 57,72 are bearing against an inner surface of the rear housing 4. The counter wheel 20 is mounted via its central mounting hole 26 so at to be rotatable relative to the rear housing 4.
The lower end 16 of a canister 6 can be seen just above the bearing surfaces 50,66 of the locking actuator 40 and indexing actuator 60. In this position, the indexing peg 70 of the indexing actuator 60 is adjacent but spaced from the end on one of the curved fingers 28, and the locking peg 46 of the locking actuator 40 is engaged with one of the locking recesses 36 provided around the edge of the counter wheel 20. The chamfered edge 38 at one side of each of the locking recesses 36 can also be seen clearly in
Operation of the dose counter will now be described with reference to
In
Further downward movement of the lower end 16 of the canister 6 further rotates the indexing actuator 60, causing the indexing peg 70 to move along the first camming surface 32 towards the centre of the counter wheel 20. The locking actuator 40 also continues to rotate, but the locking peg 46 remains in engagement with a locking recess 36. Accordingly, the counter wheel 20 is prevented from rotation, and the indexing arm 68 resiliently deforms as the indexing peg 70 moves along the first camming surface 32. As shown in
The length of the indexing arm 68 locates the drive peg 70 relatively far from the mounting pin 62 of the of the indexing actuator 60, which serves to amplify movement of the drive peg 70 during operation.
The point at which the locking peg 46 clears the locking recess 36 to unlock the counter wheel 20 represents a commitment point before which depression of the canister 6 will not result in a dose being counted. The location of the locking peg 46 relatively close to the mounting pin 42 of the locking actuator 40 helps to minimise variation of this commitment point due to manufacturing tolerances.
The rotation of the counter wheel 20 continues until, as shown in
When pressure on the canister 6 is released, its lower end 16 begins to move vertically upwards clear of the bearing surfaces 50,66 of the locking actuator 40 and indexing actuator 60, as shown in
It will be appreciated that the operation described in
It will be understood that the indexing arm 68 can be resiliently deformed and stressed during operation by the camming surface 32,34 via compression or extension of the hairpin 74 or simply by bending in the arm 68. Although primarily designed to rely on deformation at the hairpin 74, it is likely that some bending of the arm 68 will also occur. Indeed, it is possible to design an alternative indexing arm that will store elastic potential energy by deforming more equally in both of these modes simultaneously.
The applicant has also investigated the possibility of using different deformation modes and/or directions to achieve differential spring forces in an indexing arm during its two stages of being stressed. This would allow, for example, a higher spring force to be provided when an indexing arm is deformed during engagement with the first camming surface 32, and a lower spring force to be provided by the same arm during engagement with the second camming surface 34. The energy input for the indexing of the counter wheel 20 needs to be relatively high, to ensure that the indexing operation is reliably completed. In contrast, the spring force during reset of the arm should ideally be as low as possible, since it directly impacts the size and strength of the spring arm required to return the indexing arm under all environmental and/or tolerance conditions, and thus the force that the user must put into depressing the canister 6 and stressing the spring arm during use.
Some possible alternative indexing actuators for the present invention are illustrated in
This indexing actuators 160,260 of
A perspective view of the same indexing actuator 360 in its primed condition is shown in the perspective view of
In the primed condition the stop peg 482 is engaged with the loop 478 by bending the hairpin 474. The engagement of the stop peg 482 with the loop 478 essentially performs a similar function to the end-stop 378 in the third alternative indexing actuator 360, providing a cam track to limit the movement of the indexing peg 70. During depression of the canister 6 the indexing peg 70 cannot move away from the mounting pin 62 through expanding the hairpin 474, because this movement is prevented by the stop peg 482 and loop 478. Movement during the indexing can therefore only be achieved through bending of the indexing arm 468 as the indexing actuator 460 rotates. In contrast, the stop peg 482 can move within the loop 478, towards the mounting pin 62, during reset. The hairpin 474 is therefore free to compress in this mode of operation, which provides a relatively lower spring force. As above, this provides a desirable balance of a larger spring force during indexing, and a lower spring force for reset.
A final example showing a fifth alternative indexing actuator 560 in moulded and primed configurations is provided with reference to
In use, radial movement of the indexing peg 70 away from the mounting pin 62, while storing up energy for indexing, quickly causes the end-stops 592 in the second hinge 588 to engage and ‘lock out’ the hinge 588 preventing further opening/expansion. Further movement of the pin is possible only by bending the two limbs of the first branch 568a to open out the ‘V’. This results in a relatively high spring force, sufficient for the indexing operation.
Radial movement of the indexing pin 70 towards the mounting pin 62, during reset, can be achieved with a relatively lower force, because the end-stops 592 move apart allowing the two hinges 586,588 to collapse the V with minimal bending of either limb of the first branch 568a so that the indexing pin 70 can move down the cam slot 578 under minimal resistance. The necessary restoring force to be provided by the spring arm 72 is therefore minimised.
It will be understood that the movement of the indexing pin 70 in the fifth alternative indexing actuator 560 regulated by the first branch 568a of the indexing arm 568 and the cam slot 578. The remainder of the indexing arm 568, including the second branch 568b, can be made relatively stiff to minimise bending in the arm 568, so that the behaviour of the indexing actuator 560 under load, and in particular the precise position of the indexing pin 70, is as predictable as possible.
All of the indexing actuators 60,160,260,360,460,560 described above are intended to be used with a locking actuator 40 substantially as shown and described in
An alternative embodiment 602 of the invention is shown in an exploded perspective view in
In a similar manner to the counter wheel 20 of
As shown in the assembled view of
In use, a downward pressure is applied to the lever 666 to cause anticlockwise rotation of the indexer 650. The anticlockwise rotation causes a locating peg 682 on the indexing arm 668 to move over a small camming surface 694 on the front plate 608, flexing the end of the indexing arm 668 towards the pivot 626 in the direction indicated by arrow 696. Continued rotation of the indexer 650 brings the indexing tooth 570 into contact with an angled surface of one of the slots 630 which acts as a first camming surface 632 on the counter wheel 620. The locking hook 646 remains engaged with a locking recess 636 at this stage, so that continued anticlockwise rotation of the indexer 650 results in the indexing arm 668 flexing further in the direction of arrow 696.
When the lever 666 has been depressed sufficiently to rotate the locking hook 646 clear of the locking recess 636 in the counter wheel, the spring force stored in the indexing arm 668 will then be transferred to the counter wheel 620 via the indexing tooth 670, rotating the counter wheel 620 anticlockwise. The disengagement of the locking hook 646 defines a commitment point that would, in practice, be coordinated with the release of a dose from a pMDI canister 6.
Anticlockwise rotation of the counter wheel 620 is limited by engagement of the indexing tooth 670 with a second camming surface 634 on the opposite side of the slot 630 from the first camming surface 632. Continued downward pressure on the lever 666, indicative of further downward movement of a pMDI canister 6, results in continued rotation of the indexer 650 and moves the indexing tooth within the slot 630. This maintains a rotational position of the counter wheel 620 and provides some dwell time at the end of an indexing operation.
During subsequent rotation of the indexer 650 in a clockwise direction, the engagement of the indexing tooth 670 in the slot 630 initially maintains the rotational position of the counter wheel 620 until the locking hook 646 engages with the next locking recess 636′. A chamfered edge 638 is provided so that the engagement can to help account for any slight misalignment of the counter wheel 620 if necessary.
With the counter wheel 620 again locked against rotation, continued movement of the indexing tooth 670 along the second camming surface 634 as the indexer rotates clockwise serves to flex the indexing arm 668 in the opposite direction to arrow 696. This stores energy in the indexing arm 668 so that is springs past the end of the slot 630 once disengaged, ready for a subsequent indexing operation. A coil spring may be provided at the pivot 626 to store energy during the anticlockwise rotation and drive the clockwise rotation of the indexer 650. In a fully realised system, other resilient/spring biasing means, such as a torsion spring or integrated leaf spring(s), may be provided to provide a restorative force to the indexer 650.
It should be understood that the embodiments described above comprise a single counter wheel for simplicity. The principles described would be scalable for a larger number of doses by using larger wheels with a greater number of slots 30,630 and locking recesses 46,646, or by employing multiple linked count wheels with the described counter wheel 20,620 providing the unit count.
As noted above, the distance of translation of the canister during depression is relatively small compared to the required movement of the dose-counter wheel. Therefore, it may be beneficial for the distance of movement of the feature that interacts with the counter-wheel, and enables the component to store the required energy for rotation of the counter wheel, to be ‘geared up’ or otherwise amplified. This will help to provide enough movement to effect the necessary index, but may also increase the tolerances on the position of that feature at any given moment. To counteract the poor positional tolerances on this indexing feature, the locking feature of the mechanism—which sets the trigger-point for the indexing of the counter wheel relative to the position of the canister—can be kept as a separate feature, and situated close to its axis of rotation (or other point joining it to the chassis) to ensure good tolerances and good positional control of the trigger-point.
Once the trigger-point has been reached, and the indexing feature has indexed the counter wheel, there are a variety of possible ways in which the counter wheel can be stopped in the desired angular position:
Various other modifications would also be apparent to a skilled reader. As such, it is emphasised that the forgoing description is provided by way of example only, and is not intended to limit the scope of protection as defined with reference to the appended claims.
Examples of alternative configurations include reversing the direction of rotation of the counter wheel, reversing the direction of radial movement of the indexing peg/tooth (i.e. from towards the centre of the counter wheel toward its outer edge) and/or providing a similar dual charge/release system in a non cam-driven system, for example using a more direct, tangential driving of the counter wheel.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1911576.5 | Aug 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2020/051939 | 8/13/2020 | WO |
