Gearing Mechanism for Dose Delivery Device
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Solution Overview
Problem
Geared dose delivery devices face challenges in balancing mechanical advantage with additional friction, particularly in ensuring precise dose setting and controlled drug delivery without overwhelming the user with excessive force requirements.
Innovation Solution
The design incorporates a gearing mechanism with differential axial and rotational movements, utilizing a piston rod and nut system with specific thread pitches and engagements to allow for a larger distance movement of the dose dial sleeve compared to the piston rod, facilitating precise dose setting and controlled delivery while minimizing friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gearing mechanism is used to increase the movement distance of the dose selector, then measurement precision and ease of operation are improved, but friction increases
Solution Approach 1:
The patent extracts the harmful friction-generating components (gears) from the dose delivery path. The dose selector connects directly to the piston rod without intermediate gears, eliminating gear mesh friction while preserving the mechanical advantage benefit of the original geared design through optimized direct coupling.
Solution Approach 2:
The patent introduces a friction-reducing intermediary mechanism (such as a cam or lever system) that transfers motion from the dose selector to the piston rod with minimal friction. This intermediary allows the dose selector to move through a larger distance while the piston rod moves the required smaller distance, maintaining measurement precision without the friction penalty of direct gearing.
2Ease of operation
If the dose selector moves through a larger distance, then ease of operation and measurement precision are improved, but the mechanism complexity increases
Solution Approach 1:
The patent resolves the contradiction by changing the dimensional relationship between the dose selector movement and piston rod movement. Through a geometric transformation (such as a cam profile or lever arm configuration), the larger linear movement of the dose selector in one dimension is converted to the precise smaller movement of the piston rod in another dimension, achieving ease of operation without proportionally increasing mechanism complexity.
3Ease of operation
If mechanical advantage is improved to reduce user force, then ease of operation is improved, but friction increases
Solution Approach 1:
The patent removes the gear train that provided mechanical advantage but also generated friction. Instead, it employs a direct mechanical coupling between the dose selector and piston rod with optimized leverage geometry, achieving sufficient mechanical advantage through geometric multiplication of force without the friction losses inherent in geared systems.
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 solution enables precise and controlled drug delivery with reduced user effort, maintaining the benefits of gearing while minimizing frictional resistance, thus improving the usability and accuracy of the dose delivery device.
Implementation Method 1
a piston rod and nut system with specific thread pitches and engagements to allow for a larger distance movement of the dose dial sleeve compared to the piston rod
Data Source
AI summary
In a dose setting mode of a dose delivery device, a dose selector is rotated to turn a nut, which thereby moves backward along a thread of a piston rod through a first axial distance. A gearing mechanism transmits the axial movement of the nut to a connector that moves backward, without rotation, through a second axial distance. In a dose delivery mode of the device, the dose selector is pushed forward and drives the connector to move forward through the second axial distance. The gearing mechanism transmits the axial movement of the connector to the nut, which pushes the piston rod forward, without rotation, through the first axial distance. The gearing mechanism includes a first gear that rotates without axial movement relative to the housing, and a second gear that rotates without axial movement relative to the nut.