Angled Stem Block Actuation for Low-Force Inhalers
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Solution Overview
Problem
Existing metered dose inhalers are difficult for individuals with weakness or stiffness in the fingers and hands, particularly those with arthritis or small hands, to operate effectively due to the requirement of manual force to activate the spray.
Innovation Solution
A stem block mechanism that allows for the inhaler to be activated at a predefined angle relative to the longitudinal axis, facilitating easier operation by reducing the need for manual thumb pressure, and includes a ledge to prevent upward movement of the valve stem, coupled with an actuation mechanism for controlled aerosol release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional manual metered dose inhaler is used, then the device structure is simple and easy to manufacture, but it requires significant manual force from the user's hand or thumb to activate the spray
Solution Approach 1:
A stem block is introduced as an intermediary component between the canister and the actuation mechanism. The stem block includes a hollow valve stem that receives the canister valve stem, and a ledge portion that contacts an upper end of the hollow valve stem to prevent upward axial movement. This intermediary structure transforms the actuation force application and enables angled actuation while maintaining structural simplicity
Solution Approach 2:
The actuation mechanism is configured to apply force to the stem block at a predefined angle (e.g., 45 degrees) relative to the longitudinal axis of the elongated passage, rather than requiring purely axial compression. This dimensional change in force application allows users with hand weakness to activate the inhaler more easily by leveraging angled pressing motion
2Ease of operation
If the inhaler requires axial compression force to activate, then the valve stem can be simply pushed down, but individuals with arthritis or small hands cannot generate sufficient force
Solution Approach 1:
The stem block acts as a mechanical intermediary that redistributes and redirects the actuation force. By engaging the stem block at an angled position and utilizing the ledge portion constraint, the system reduces the direct axial force requirement on the canister valve stem, making activation feasible for users with limited hand strength
Solution Approach 2:
The valve actuation system is segmented into distinct functional components: the canister valve stem, the hollow valve stem within the stem block, the ledge portion constraint mechanism, and the angled actuation interface. This segmentation allows each component to perform its specific function efficiently, with the stem block serving as a force transformation element
3Device complexity
If the dispensing passage has the same width as the elongated passage, then the flow path is simple, but the valve stem can move upward into the dispensing passage causing malfunction
Solution Approach 1:
The dispensing passage is designed with a localized width reduction at its upper end, creating a ledge portion. This local geometric modification serves the specific function of preventing upward movement of the hollow valve stem while maintaining adequate flow capacity for aerosol delivery. The ledge portion acts as a mechanical stop without significantly impeding the dispensing function
Data Source
AI summary
An inhaler including a housing having a chamber to receive a valved canister and a stem block, and a mouthpiece in fluid communication with a passage of the stem block; and an actuation mechanism including configured to engage an outer surface of the stem block at a predefined angle relative to the longitudinal axis of the stem block to cause the downward movement of the stem block to activate the valve and release the aerosolizable liquid as the dose of the aerosolized spray out of the mouthpiece of the mechanical inhaler.