Medicament Delivery Locking Assembly for Reliable Dose Unlocking
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Solution Overview
Problem
Existing medicament delivery devices face challenges in setting larger doses, as the dose knob needs to 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 from the injection actuation function. The dose setting is achieved by rotating the dose setting member, which moves the plunger rod independently, while the injection is triggered by pushing the dose button. This segmentation allows the dose knob travel distance to be decoupled from the injection stroke, resolving the contradiction between setting large doses and easily actuating injection.
Solution Approach 2:
The mechanism transitions from linear motion for both dose setting and injection to rotational motion for dose setting and linear motion for injection. The dose setting member rotates to set the dose by moving the plunger rod, while the dose button moves linearly to trigger injection. This dimensional change allows independent optimization of each function's operational characteristics.
2Reliability
If the locking assembly fails to reliably unlock the dose button for subsequent doses, then the device remains in a non-activated state, but the user needs to administer additional doses
Solution Approach 1:
The locking assembly incorporates a spring mechanism that provides tactile feedback and ensures reliable engagement and disengagement. The spring-loaded locking member automatically returns to the unlocked position when the dose setting member is rotated, providing consistent and reliable unlocking for subsequent doses without requiring additional user actions.
Solution Approach 2:
The locking assembly is designed to automatically unlock when the dose setting member is rotated to the initial position. The spring mechanism self-actuates to release the locking member, eliminating the need for separate unlocking actions and ensuring the device is ready for the next dose without user intervention beyond the normal dosing rotation.
3Ease of operation
If the lead screw member moves a predetermined distance independent of dose size, then the injection stroke is consistent, but the dose setting complexity increases
Solution Approach 1:
The dose setting member is rotated during the dosing phase to pre-position the plunger rod at the correct location corresponding to the desired dose. This preliminary positioning action separates the dose setting from the injection actuation, allowing the lead screw to always move the same predetermined distance during injection while the variable dose is set by the rotation amount before injection.
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 and the device is in the non-activated state
Implementation Method 2
a threaded plunger rod arranged to pass through a first inner wall of the housing and arranged to act on a stopper in the medicament container; a lead screw member coaxially connected to the threaded plunger rod by co-acting first slidably-and-rotatably-locked means
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.