Pen-shaped Torsion Spring Injection Device Helical Scale Drum
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Solution Overview
Problem
Conventional pen-shaped injection devices with helical movable scale drums are bulky due to multiple constructional layers, limiting the number of dose settings and increasing the outside diameter, which is a challenge for users requiring a high number of dose settings.
Innovation Solution
A pen-shaped torsion spring-driven injection device with a housing, piston rod, rotatable piston rod guide, torsion spring, and rotatable scale drum, where the scale drum helically rotates on the piston rod's external thread, allowing for multiple dose settings visible through a window, reducing the number of constructional layers and outside diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a helical movable scale drum is implemented to display a high number of different dose settings, then the number of dose settings is increased, but the device becomes thicker and bulkier
Solution Approach 1:
The patent combines the scale drum and piston rod into a single integrated component, where the scale drum is formed as a helical extension of the piston rod itself. This merging eliminates the need for separate constructional layers and reduces device thickness while maintaining the ability to display multiple dose settings through the helical structure.
Solution Approach 2:
The scale drum is nested within the housing structure, with the helical scale portions arranged concentrically around the piston rod. This nesting allows the scale indicators to be viewed through a window in the housing without requiring additional radial space, thereby reducing overall device bulk while displaying multiple dose settings.
2Adaptability or versatility
If multiple constructional layers are used in pen-shaped injection devices, then the device can accommodate various components, but the outside diameter increases making it bulky
Solution Approach 1:
The patent merges multiple functional components into fewer integrated structures. The scale drum serves both as a dosing indicator and as a mechanical element engaged with the piston rod thread. The housing integrates the window structure directly into the main body, eliminating separate layers and reducing outside diameter while maintaining component functionality.
Solution Approach 2:
The patent transitions from a multi-layer radial arrangement to a more compact axial arrangement. The helical scale drum utilizes the axial dimension along the piston rod, allowing multiple dose settings to be displayed along the length of the device rather than requiring radial expansion through multiple constructional layers.
3Adaptability or versatility
If the scale drum is helically guided in a thread on the inner surface of the housing, then high number of dose settings can be displayed, but the device becomes thicker
Solution Approach 1:
Instead of having the scale drum guided by a separate thread on the housing inner surface, the patent merges the guiding function directly into the piston rod by forming an external thread on the piston rod itself. The scale drum engages this external thread, eliminating the need for a separate housing thread and reducing device thickness.
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 a high number of dose settings while minimizing the device's thickness and bulk, improving user accessibility and usability, especially for users with impaired vision.
Implementation Method 1
a torsion spring for rotating the piston rod guide at least during dose expelling
Implementation Method 2
The torsion spring is torsional strained when a dose is set and released during dosing to drive the drive shaft
Implementation Method 3
the scale drum helically rotates on the piston rod's external thread
Implementation Method 4
A piston rod having an external thread
Data Source
AI summary
The invention relates to a pen-shaped torsion spring driven injection device for apportioning set dose of a liquid drug. A piston rod having an external thread is driven forward by a rotatable piston rod guide engaging the piston rod. The piston rod guide is rotated by a torsion spring encompassed between the housing and the piston rod guide. A scale drum having a thread engaging the external thread of the piston rod is provided, and the scale drum is rotated up and down the piston rod by a proximal located rotatable dose setting member cooperating with the scale drum. The scale drum thus move helically when rotated as the piston rod is held inrotatable during dose setting.