Medication Dose Knob Ratchet Mechanism for Overset Correction
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Solution Overview
Problem
Existing medication delivery systems, such as those described in US5,104,380 and WO02/053214, do not allow for easy reduction of an overset dose without expelling the medication, requiring users to activate a trigger and re-dial the correct dose, which is inconvenient and inefficient.
Innovation Solution
The proposed system includes a dose setting mechanism with a torsion spring, ratchet drive shaft, and drive gear that allows the dose knob to be rotated clockwise for setting and anti-clockwise for reducing doses, utilizing a button to temporarily decouple the dose knob from the drive shaft and spring, enabling dose reduction without medication ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the dose knob is rotated clockwise to set a dose, then the dose is set correctly, but the user cannot reduce the setting by rotating in reverse direction
Solution Approach 1:
The ratchet mechanism allows the dose knob to rotate freely in the counter-clockwise direction (for dose reduction) while preventing rotation in the clockwise direction (for dose setting). This dynamic one-way locking system enables flexible dose adjustment by allowing users to overshoot and then correct by rotating back, while maintaining precise dose setting capability when rotating forward.
Solution Approach 2:
The ratchet teeth act as an intermediary mechanism between the dose knob and the drive gear. They transmit rotational motion in one direction (counter-clockwise for dose reduction) while blocking motion in the opposite direction, enabling the dose knob to be decoupled from the medication ejection mechanism during dose reduction operations.
2Ease of operation
If the user activates the trigger to expel the set dose, then the dose can be reset, but medication is wasted and time is lost
Solution Approach 1:
The ratchet mechanism extracts the unwanted restriction of bidirectional rotation from the dose setting system. By removing the constraint that prevented counter-clockwise rotation, users can now reduce doses by rotating the knob backward without needing to expel medication through the trigger, thereby eliminating medication waste and time loss.
3Ease of operation
If the ratchet mechanism allows free rotation for dose reduction, then dose adjustment flexibility is improved, but the drive gear may rotate unintentionally
Solution Approach 1:
The ratchet teeth and drive gear are designed with asymmetric tooth profiles that create directional engagement. The teeth are shaped to engage firmly when the dose knob rotates counter-clockwise (allowing dose reduction) while automatically disengaging or locking when rotation attempts occur in the clockwise direction, thus preventing unintentional drive gear rotation while maintaining operational flexibility.
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
This design allows for precise and efficient dose adjustment, enabling users to easily reduce set doses without expelling medication, improving user convenience and reducing the need for redundant dosing procedures.
Implementation Method 1
a torsion spring arranged to provide the drive force for ejecting medication from a loaded cartridge
Implementation Method 2
a ratchet plunger body component comprising: three arms, each arm comprising a moulded spring body and an end tooth comprising sloped surfaces
Implementation Method 3
a leadscrew located within the ratchet drive shaft, the leadscrew comprising a screw thread formed along the length of its outer surface
Data Source
Figure 1
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Figure 4
AI summary
Medication delivery apparatus for receiving a medication containing member. The apparatus comprises spring means 4 for storing a force which when released causes ejection of the medication from a received medication containing member, a dose knob 2 which when rotated in a first direction moves the spring 4 to a force storing position, the dose setting knob 2 providing a plurality of discrete setting positions corresponding to respective doses, a user actuable trigger 12 for releasing said stored force to eject medication from said medication containing member, and a user actuable button 6 arranged to reduce a stored force in the spring 4 with each press of the button without causing ejection of medication from said medication containing member.