Pen-Type Drug Injection Dose Setting Limiter Mechanism
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Solution Overview
Problem
Existing pen-type drug delivery devices often require users to exert significant force during dose dispensing, which can be challenging for manually impaired users, and may require the dose setting member to protrude from the housing, increasing device size and complexity.
Innovation Solution
A limiter mechanism with a dose setting member that rotates relative to the housing during dose setting and reversely during dispensing, utilizing a limiting element that moves on both axial and helical paths with end stops to define zero and maximum dose positions, decoupling the limiting element from the dose setting member to reduce required force and maintain the dose setting member within the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the limiting element is coupled to the dose setting member to prevent over-rotation, then the maximum dose position is accurately limited, but the force required for dose dispensing increases significantly
Solution Approach 1:
The limiting element is separated into two independent functional components: a ratchet mechanism that limits dose setting rotation in one direction, and a pawl mechanism that limits dose dispensing rotation in the opposite direction. This segmentation allows each component to perform its limiting function independently without creating excessive friction or resistance, thereby maintaining accurate dose position limitation while reducing the force required for dispensing.
Solution Approach 2:
A spring-loaded pawl acts as an intermediary between the dose setting member and the housing, providing controlled engagement and disengagement. The spring mechanism allows the pawl to flexibly engage with the ratchet teeth during both dose setting and dispensing, reducing friction and resistance while maintaining precise rotational limits. This intermediary mechanism resolves the contradiction by enabling accurate positioning without requiring excessive force.
2Adaptability or versatility
If the dose setting member protrudes from the housing to allow sufficient rotation range, then the full dose range can be set, but the device size and complexity increase
Solution Approach 1:
The limiting element is designed to move along a helical path combined with axial displacement rather than simple radial protrusion. This dimensional transformation allows the dose setting member to achieve the necessary rotation range through a combination of rotational and axial movements within the housing, eliminating the need for the member to protrude externally while maintaining full dose range capability.
Solution Approach 2:
The limiting element is nested within the housing structure, with its helical movement path contained entirely within the device boundaries. The ratchet and pawl mechanisms are integrated into the housing walls, allowing the dose setting member to rotate and displace axially without requiring external protrusion. This nesting approach maintains compact device geometry while achieving the required adaptability for full dose range setting.
3Device complexity
If the limiting element moves only on an axial path, then the structure is simpler, but the rotational movement control between zero and maximum dose positions is insufficient
Solution Approach 1:
The limiting element's movement path is transformed from a simple one-dimensional axial line to a two-dimensional helical trajectory combined with axial displacement. This dimensional enhancement allows the element to simultaneously control rotational position and axial location, providing precise rotational movement control between zero and maximum dose positions while maintaining relatively simple structural implementation through the helical geometry.
Data Source
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AI summary
The present invention relates to a pen type drug delivery device having a dose setting limiter mechanism. The mechanism comprises a housing (10, 30, 40; 40'), a dose setting member (50), which during dose setting rotates relative to the housing (10, 30, 40; 40') in a first direction and which during dose dispensing rotates relative to the housing (10, 30, 40; 40') in a second opposite direction, and a limiting element (60) limiting the rotational movement of the dose setting member between a zero dose position and a maximum dose position. The limiting element (60) is rotationally constrained but axially displaceable relative to one of the housing (10, 30, 40; 40') or the dose setting member (50) and is movable helically (53) relative to the other of the housing (10, 30, 40; 40') or the dose setting member (50). These movements have end stops (54, 55) limiting the relative movement of the limiting element (60) and thus the dose setting member.