Drive Sleeve Clutch Interface Segmentation for Torque Transmission
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Solution Overview
Problem
Existing drug delivery devices, particularly pen-type devices, face challenges in allowing users to select and dispense variable doses of medicament effectively, with limitations in resettable and disposable designs, and lack of efficient torque transmission mechanisms that prevent underdosage and malfunction.
Innovation Solution
A drive sleeve with a clutch interface featuring a ring of crown teeth and cavities allows for easy assembly with a full nut, maximizing torque transmission while minimizing wear, and includes a last dose protection mechanism to prevent excessive dose setting based on remaining medicament in the cartridge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a clutch interface with crown teeth is used for torque transmission, then torque transmission efficiency is improved, but the outer diameter of the clutch interface increases, making assembly with a full nut difficult
Solution Approach 1:
The clutch interface is segmented into multiple crown teeth distributed around the circumference, allowing the nut to be assembled incrementally between the teeth rather than requiring the entire interface to be clear at once. This segmentation enables both full nut assembly and effective torque transmission.
Solution Approach 2:
The crown teeth are positioned only in specific circumferential regions rather than forming a continuous ring, creating local transmission zones. This allows the nut to pass through non-tooth regions during assembly while still achieving adequate torque transmission through the distributed tooth regions.
2Ease of operation
If the clutch interface outer diameter is reduced to facilitate nut assembly, then assembly ease is improved, but torque transmission capability and wear resistance deteriorate
Solution Approach 1:
The clutch interface transitions from a static continuous ring to a dynamic segmented structure where the nut can move freely during assembly but engages with the crown teeth during torque transmission. This dynamic behavior allows the interface to adapt to different operational phases.
Solution Approach 2:
The solution moves from considering only the radial dimension (outer diameter) to incorporating the circumferential dimension. By distributing crown teeth around the circumference rather than forming a continuous ring, the interface achieves adequate torque transmission with reduced material and improved assembly characteristics.
3Reliability
If a last dose protection mechanism is added to prevent underdosage, then reliability is improved, but device complexity increases
Solution Approach 1:
The drive sleeve's own structural features (crown teeth, cavities, threading) are utilized to provide the last dose protection function. The mechanism uses the existing components in a dual capacity, where the same structural elements that enable assembly also provide dose verification, eliminating the need for separate protection components.
Solution Approach 2:
The drive sleeve is designed with multi-functionality, serving both as the torque transmission interface (through crown teeth) and as the last dose protection mechanism (through cavity-nut interaction). This universal design consolidates multiple functions into a single component, improving reliability without proportionally increasing complexity.
Data Source
AI summary
The present disclosure is directed to a drive sleeve with a hollow body having a ring of crown teeth with a first outer diameter forming a clutch interface at a first end and a thread extending on an outer surface of the body. The thread has a major diameter and a minor diameter, wherein the ring of crown teeth has at least two cavities. The at least two cavities extend on the outer surface of the body from the first end to the thread and defining a second outer diameter which is smaller than the major diameter of the thread. Further, some embodiments are directed to a drug delivery device with such a drive sleeve and a method for assembling a drug delivery device.