Drug Delivery Drive Spring Pre-Charging Assembly
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Solution Overview
Problem
The assembly of pre-charging a torsion spring in drug delivery devices is complicated, especially when attaching it to components in threaded engagement, which can lead to inefficiencies in providing sufficient torque for dispensing small doses.
Innovation Solution
A method involving attaching a torsion spring to a rotationally fixed component and a rotatable component in threaded engagement, allowing the spring to be pre-charged during assembly by disengaging and re-engaging the threads, with end stops to prevent disengagement, facilitating easy charging and ensuring the spring is pre-strained for operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a torsion spring is attached to components in threaded engagement, then the spring can be pre-charged during assembly, but the assembly process becomes complicated
Solution Approach 1:
The device is divided into modular components: a cartridge section, a dosing section, and a needle assembly. The dosing section further includes separate elements like the rotatable component, rotationally fixed component, and end stop. This segmentation allows the torsion spring to be pre-charged during assembly of the dosing section without complicating the entire device assembly, as each module can be prepared independently.
Solution Approach 2:
The torsion spring is pre-charged (pre-strained) during the assembly process itself, before the device is put into service. This preliminary action is achieved by rotating the rotatable component relative to the rotationally fixed component while they are in threaded engagement, storing energy in the spring. The end stop prevents over-rotation and maintains the pre-charged state. This eliminates the need for separate spring charging operations later.
2Power
If the spring is pre-charged during assembly, then sufficient torque is provided for dispensing small doses, but the assembly process requires additional steps
Solution Approach 1:
The spring pre-charging operation is merged with the assembly process. As the rotatable component is threaded onto the rotationally fixed component during normal assembly, the torsion spring is simultaneously charged. The end stop is integrated into the dosing section to automatically limit rotation and maintain spring tension. This combining of operations ensures sufficient torque for small dose dispensing without requiring separate spring charging steps that would reduce productivity.
3Manufacturing precision
If end stops are provided to prevent rotation beyond a certain point, then the spring charging is controlled, but the device structure becomes more complex
Solution Approach 1:
The end stop structure enables the dosing mechanism to self-regulate the spring charging process. During assembly, when the rotatable component is rotated to charge the spring, the end stop automatically prevents over-rotation by providing a mechanical stop. This self-service feature ensures precise control of spring charge without requiring external monitoring or control systems, and the simple mechanical stop adds minimal complexity to the dosing section.
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 method simplifies the assembly process and ensures the drive spring is pre-charged, providing sufficient torque for dispensing variable doses with minimal additional effort, enhancing the usability and efficiency of the drug delivery device.
Implementation Method 1
A torsion spring (90) is attached with one end to the housing (10) and with the other end to a rotatable component part (60)... the rotatable component part (60) is in threaded engagement with a second rotationally fixed component part (110)... preventing rotation of the rotatable component part (60) relative to the second rotationally fixed component part (110) in a first spring releasing direction
Data Source
AI summary
A method for assembling a drive spring, especially into a drug delivery device includes rotating a component part to which the drive spring is attached in a first direction, followed by a rotation of the component part in the opposite direction and followed by attachment of a rotational stop. Further, the disclosure includes a drug delivery device for selecting and dispensing a number of user variable doses of a medicament, which device comprises a pre-charged drive spring.