Asymmetric Slip Coupling for Injection Device Dosage Control
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Solution Overview
Problem
Existing injection devices require significant force to set and correct dosages, making them cumbersome for users, particularly in administering substances like insulin or growth hormones.
Innovation Solution
An injection device with a slip coupling mechanism featuring asymmetrical latching elements that provide lower resistance for dosage increase and higher resistance for dosage correction, allowing for easier setting and correction of dosages with reduced applied force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-way slip coupling with toothed rings is used to prevent inadvertent slippage, then the coupling reliability is improved, but the force required to set the dosage increases significantly
Solution Approach 1:
The patent applies asymmetry by providing latching elements with different geometries for different movement directions. The first latching element has a first geometry that engages with a second latching element to provide high resistance in the first direction (preventing inadvertent slippage), while the same latching elements provide lower resistance in the second direction (easier dosage correction). This asymmetric design resolves the contradiction by directionally differentiating the coupling characteristics.
Solution Approach 2:
The patent implements local quality by making the resistance characteristics location-dependent within the coupling mechanism. Different regions of the latching elements are designed with different geometries to provide locally optimized resistance: high resistance in the engagement region for one direction and lower resistance for the opposite direction. This allows the coupling to exhibit different mechanical properties at different operational stages.
2Reliability
If the latching elements are designed to withstand spring tension to prevent inadvertent slippage, then the holding force is improved, but the ease of operation deteriorates
Solution Approach 1:
The patent uses asymmetry in the latching element geometries to create different engagement characteristics for different directions. The first latching element's first geometry is designed to engage the second latching element with high holding force to prevent inadvertent slippage, while the same configuration allows easier engagement in the opposite direction for dosage correction, thus improving ease of operation without sacrificing holding force.
Solution Approach 2:
The patent applies dynamics by making the coupling characteristics adaptable based on the direction of movement. The latching elements dynamically transition between high-resistance engagement (for preventing slippage) and lower-resistance engagement (for intentional dosage adjustment). This dynamic behavior allows the system to optimize both holding force and ease of operation depending on the operational context.
3Power
If a spring member is used to charge the coupling member with elasticity force, then the delivery function is improved, but the force required to overcome spring tension increases
Solution Approach 1:
The patent applies asymmetry by designing the latching elements to provide directionally different resistance to spring tension. When moving in the first direction (dosage setting), the asymmetric geometry of the latching elements allows the spring tension to be overcome more easily. When moving in the second direction (delivery), the same asymmetric design provides higher resistance, allowing the spring to build up sufficient tension for effective delivery. This resolves the contradiction between delivery power and the force required to operate the mechanism.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device enables reliable dosage administration with reduced user effort, enhancing usability and safety by minimizing the force required for setting and correcting dosages while maintaining a secure holding mechanism.
Implementation Method 1
a spring member which charges the coupling member with an elasticity force and thus holds it in a coupling engagement with the dosing member
Implementation Method 2
co-operating latching elements engageable with each other and coupling the operating button to the casing in discrete latching positions
Data Source
AI summary
An injection device including casing with a reservoir for an injectable product, an operating button which can be moved relative to the casing in a dosing direction which increases the dosage and in a correcting direction to set a product dosage, a conveying member for delivering the dosage set, a slip coupling comprising a latching element and a co-operating latching element which latch to each other in a latching engagement and couple the operating button to the casing in a positive and non-positive fit in discrete latching positions during a movement in the dosing direction or the correcting direction, and a spring member which opposes the movement of the operating button in at least one of the directions with a spring force, wherein the latching element or co-operating latching element are shaped such that in the latching engagement they offer a lower resistance to the movement in the at least one of the directions than to the movement in the other direction.