Dose Indicator for Metered Dose Inhaler with Integrated Drive Pawl
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Solution Overview
Problem
Existing dose counters and indicators for pressurized metered dose inhaler (pMDI) devices are complex, costly, and prone to undercounting doses, which can be critical for patients relying on them for life-saving medication, and they require tight dimensional tolerances and many mechanical parts.
Innovation Solution
A dose indicator/counter with a simplified design featuring a chassis with a drive pawl and indexing teeth, where the drive pawl has jaws defining a socket to engage indexing teeth, ensuring reliable and consistent counting with a small number of components, capable of counting 200 doses and fitting within existing pMDI actuators, using a unitary chassis with springs and hinges for resetting and resistance management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex dose counters with multiple mechanical parts are used, then dose counting functionality is achieved, but device complexity increases and manufacturing cost increases
Solution Approach 1:
The drive pawl combines multiple functions into a single component: it has a socket for engaging indexing teeth to advance the display, an outer surface for engaging subsequent teeth during resetting, and integrates with the displacement portion. This merging of functions reduces the number of separate mechanical parts while maintaining reliable dose counting functionality.
Solution Approach 2:
The drive pawl serves multiple purposes: it indexes the display unit forward during actuation, prevents reverse rotation through its socket engagement, and enables resetting by engaging subsequent indexing teeth. This multi-functionality reduces overall device complexity while ensuring reliable operation.
2Measurement precision
If tight dimensional tolerances are applied to mechanical parts, then indexing precision is improved, but manufacturing difficulty increases
Solution Approach 1:
The indexing mechanism is segmented into discrete indexing teeth on the display unit and corresponding engagement features on the drive pawl. This segmentation allows each component to be manufactured independently with standard tolerances, avoiding the need for tight overall dimensional tolerances while maintaining precise indexing through the interlocking tooth design.
3Reliability
If many small mechanical parts are used, then dose counting functionality is achieved, but assembly difficulty increases
Solution Approach 1:
The drive pawl is integrated with the displacement portion as a single piece, eliminating the need for separate assembly of these components. The socket is formed directly in the pawl structure, and the resetting surface is part of the same component, significantly reducing assembly steps and potential assembly errors.
4Volume of moving object
If the dose counter is made compact, then it fits within existing pMDI actuators, but manufacturing precision requirements increase
Solution Approach 1:
The dose counter components are nested within the actuator housing, with the display unit rotating within the actuator body and the drive pawl positioned to engage teeth on the display unit. This nested arrangement maximizes space utilization, keeping the dose counter compact while allowing each component to be manufactured with standard tolerances.
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
The present disclosure relates to a dose indicator comprising, a chassis comprising a chassis frame and a displacement portion, an indexable first display unit, mountable on the chassis, the first display unit being indexable about a first display axis, the indexable first display unit comprising a plurality of indexing teeth, a first display non-return arm, and a drive pawl connected at its proximal part to the displacement portion, the drive pawl comprising a socket at its distal part, the socket being adapted to engage an indexing tooth of the first display unit during indexing. The disclosure further relates to an actuator for an inhaler, wherein the actuator comprises a dose indicator as described above. The present disclosure is also directed to an inhaler comprising such actuator.