Medicament Dose Setting Mechanism with Spring Unlocking
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Solution Overview
Problem
Medicament delivery devices face challenges in setting larger doses, as the dose knob needs to be moved a long distance, making it difficult for users to push it in the proximal direction during injection, and there is a risk of the dose button not unlocking reliably for subsequent doses.
Innovation Solution
A medicament delivery device with a housing, medicament container holder, threaded plunger rod, lead screw member, nut, and locking mechanism, where the device is designed to unlock the lead screw and dose button reliably by a spring force mechanism, allowing the lead screw to move a predetermined distance independently of the dose size, facilitating easier dose setting and administration.
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 desired dose quantity can be achieved, but it becomes difficult for the user to push the dose knob in the proximal direction during injection
Solution Approach 1:
The dose setting mechanism is divided into two independent functional segments: a ratchet mechanism for dose setting (distal movement) and a trigger mechanism for dose delivery (proximal movement). This segmentation allows the dose knob to be pushed in for delivery regardless of how far it was turned for setting, resolving the contradiction between achieving large doses and ease of pushing during injection
Solution Approach 2:
A trigger member acts as an intermediary between the user's pushing action and the plunger rod. When the user pushes the dose knob proximal, the trigger member engages with the plunger rod to deliver the dose, decoupling the delivery action from the dose setting position and making it easier to administer any set dose
2Stability of the object's composition
If the dose button locking feature is designed to securely lock during dose setting, then dose setting stability is improved, but reliable unlocking for subsequent doses may fail
Solution Approach 1:
The spring member automatically performs the unlocking function when the dose knob is rotated to the initial position. The spring's stored energy self-activates to move the dose button distally and disengage the locking member, ensuring reliable unlocking without requiring additional user actions or complex control systems
Solution Approach 2:
The spring member is pre-loaded during dose setting to store potential energy. This preliminary action ensures that when unlocking is needed (after dose administration), the stored energy is immediately available to reliably disengage the locking mechanism and prepare for the next dose, preventing failure to unlock
3Reliability
If the lead screw member moves a predetermined distance independent of dose size, then unlocking reliability is improved, but the relationship between knob movement and dose quantity is reduced
Solution Approach 1:
The mechanism separates the dose setting function (ratchet mechanism with dose indications) from the delivery function (trigger mechanism with spring-loaded lead screw). The lead screw's predetermined movement ensures reliable unlocking, while the ratchet mechanism independently provides precise dose setting through controlled distal movements with visual feedback
Solution Approach 2:
The ratchet mechanism acts as an intermediary that translates rotational knob movement into precise incremental distal movement of the plunger rod for dose setting. Meanwhile, the trigger mechanism handles the proximal delivery movement independently, allowing both precise dose setting and reliable unlocking to coexist
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 solution allows for simple and intuitive dose setting, reduces user effort, especially for larger doses, and ensures reliable unlocking of the dose button and lead screw after each administration, enabling easy setting of subsequent doses.
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
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
The present invention relates to a dose setting mechanism (201) for a medicament delivery device comprising, a housing (12) having a longitudinal axis; a lead screw (58) positioned with the housing (12); a locking member (96) rotationally and slidably fixed to the housing (12), the locking member (96) comprising a locking slot (430); a dose member assembly (66a) comprising a biasing element (420), an inner sleeve (410) and an outer sleeve (400), where the dose member assembly (66a) is arranged coaxially around the locking member (96) and the lead screw (58), the biasing element (420) is operatively engaged with the locking member (96) and the inner sleeve (410), and where the inner sleeve (410) has a radially projecting key (412) configured to travel in the locking slot (430) to engage the lead screw (58) to prevent axial movement of the lead screw (58) when the dose setting mechanism (201) is in a non-activated state.