Dial-down Mechanism for Wind-up Pen Using Ratchet Arm
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Solution Overview
Problem
Existing wind-up pens with torsion spring mechanisms lack a robust dial-down mechanism, making it difficult to decrease set doses without expelling the entire dose, and small dimensioned cam and key parts are prone to breakage.
Innovation Solution
A dial-down mechanism featuring a ratchet arm with a radially extending knob, engaged by a reset element, allows for relative rotation to move out of engagement with a fixation element, enabling dose reduction without breaking small parts, and a torsion spring's stored force is delivered through a drive element for precise dose adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If small dimensioned cam and key parts are used in the dial-up/dial-down mechanism, then the device complexity is reduced, but the reliability deteriorates due to tendency to break during manufacture or use
Solution Approach 1:
The patent replaces the traditional cam and key mechanical engagement system with a ratchet and pawl mechanism. The ratchet arm with radially extending knob engages with teeth on the fixation element, providing a more robust mechanical interaction that is less prone to breakage during manufacture and use, while still enabling the dial-up/dial-down functionality.
2Ease of manufacture
If the dose setting member is located at the proximal end with a simple rotation mechanism, then the ease of manufacture is improved, but the adaptability deteriorates as it cannot decrease the set dose
Solution Approach 1:
The patent implements a dynamic dose adjustment mechanism where the ratchet arm can engage with different teeth on the fixation element depending on the rotation direction. By rotating the dose setting member clockwise, the ratchet arm engages subsequent teeth to increase dose (dial-up). By rotating counter-clockwise, the ratchet arm disengages and can engage previous teeth to decrease dose (dial-down), providing bidirectional adjustment capability.
Solution Approach 2:
The ratchet arm acts as an intermediary element between the dose setting member and the fixation element. It mediates the rotational motion to achieve both dose increase and decrease functions, allowing the user to adjust the dose in both directions while maintaining a simple proximal end location for the dose setting member.
3Measurement precision
If the ratchet arm engages multiple teeth on the fixation element, then the measurement precision is improved for dose setting, but the device complexity increases
Solution Approach 1:
The fixation element is segmented into multiple discrete teeth, each representing a specific dose increment. The ratchet arm engages with these segmented teeth to provide precise dose setting. Each tooth engagement corresponds to a predetermined dose amount, allowing the user to set the dose with precision by the number of teeth engaged while keeping the overall mechanism relatively simple.
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 mechanism provides a robust and reliable way to decrease set doses in wind-up pens, avoiding breakage and allowing for precise control of the torsion spring's force delivery, enhancing user convenience and device reliability.
Implementation Method 1
based on a torsion spring, the user usually strains the torsion spring by rotating a rotatable dose setting member of the injection device. The force thereby applied by the user is stored in the torsion spring for later release.
Implementation Method 2
The ratchet arm provided on the dose setting tube engages one or more teeth on the fixation element.
Data Source
AI summary
The present invention relates to a dial-down mechanism for an injection device comprising a torsion spring for assisting injection of a dose of medicament from the injection device, the dial-down mechanism comprising a ratchet arm (21) engaging a ring element (10) and a reset element (30) which acts on a knob located on the periphery of the ratchet arm (21) to move the ratchet arm (21) out of engagement with the ring element (10) in order to allow the set dose to be reduced.