Medicament Delivery Device Locking Assembly
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Solution Overview
Problem
Medicament delivery devices face challenges in setting larger doses, as the dose knob must be moved a significant distance, making it difficult for users to push it in the proximal direction during injection, and there is a risk of failing to unlock the dose button for subsequent doses.
Innovation Solution
A medicament delivery device with a locking assembly that reliably transitions from a non-activated to an activated state, allowing the lead screw to move a predetermined distance independently of the dose size, featuring a primary and secondary dosing member that can be rotated for dose setting or cancellation, and a spring force mechanism to facilitate easy dose delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the dose knob is moved a long distance in the distal direction to set larger doses, then the dose quantity to be delivered is increased, but it becomes difficult for the user to push the dose knob in the proximal direction during injection
Solution Approach 1:
The device separates the dose setting function (rotational movement of dosing member) from the dose delivery function (linear movement of lead screw and plunger rod). This segmentation allows the user to set large doses by rotating the dosing member without needing to push it the full injection distance, making operation easier while maintaining the ability to deliver large quantities.
Solution Approach 2:
The invention introduces rotational movement as a new dimension for dose setting, replacing the conventional linear pushing motion. By converting the dose setting action from linear (distal-proximal) to rotational, the user can set larger doses through rotation while the actual injection still occurs through linear movement of the lead screw, resolving the contradiction between dose quantity and ease of operation.
2Quantity of substance
If the dose knob is moved a long distance to set larger doses, then the dose quantity is increased, but the risk of failing to unlock the dose button for subsequent doses increases
Solution Approach 1:
The locking assembly is automatically engaged when the dosing member is rotated to the zero position, preliminarily preparing the device for the next dose. This preliminary locking action ensures that the dose button and lead screw are reliably locked after each injection, preventing accidental movement and ensuring they are ready for the next dose setting cycle.
Solution Approach 2:
The device provides mechanical feedback through the locking assembly that confirms when the dose button is properly locked and when the lead screw is in the correct position. This feedback mechanism ensures reliable operation by giving the user confirmation that the device is ready for the next dose, reducing the risk of failure to unlock.
3Productivity
If a threaded plunger rod is used to act on the stopper, then the dose can be delivered through linear movement, but the device complexity increases with multiple locking mechanisms
Solution Approach 1:
The invention merges the locking function with the existing structural components. The locking assembly utilizes the housing, dose button, and lead screw structure itself, rather than adding completely separate locking mechanisms. This merging approach maintains productivity while minimizing the increase in device complexity.
Solution Approach 2:
The locking assembly is designed to be self-actuating through the rotation of the dosing member. The mechanical interaction between the dosing member, lead screw, and locking lever automatically engages or disengages the locking function without requiring additional actuators or complex control systems, maintaining simplicity while ensuring reliable operation.
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
Enables intuitive and simple dose setting, reduces user effort, and ensures reliable unlocking of the dose button for subsequent doses, improving usability and safety by maintaining the lead screw's consistent position regardless of the set dose quantity.
Implementation Method 1
a first spring force means arranged between the first inner wall of the housing and the nut, wherein the first spring force means is in a pre-tensioned state when said locking means are engaged
Implementation Method 2
a nut coaxially connected to the threaded plunger rod by a treaded engagement between them
Data Source
AI summary
A dose setting mechanism for a medicament delivery device is presented having a locking assembly that reliably and consistently unlocks a dose injection button and concurrently a lead screw when the dose setting mechanism is transitioned from a non-activated state to an activated state. This locking assembly uses a rotating plate having a locking protrusion that engages a radial projecting tab on a rotationally fixed plunger rod nut. An alignment member is also presented that prevents rotational drift of a dosing member.