Injection Pen Dose Limiter With Gear-Nut Dose Tracking
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Solution Overview
Problem
Existing injection devices, particularly syringe pens, face challenges in manufacturing complexity and cost due to complex shapes and designs of dose-setting mechanisms, leading to increased rejection rates and costs, and require a reliable mechanism to prevent setting doses exceeding the available drug amount in the cartridge.
Innovation Solution
The injection device incorporates a cylindrical dose-setting mechanism with a gear wheel and nut system, where the nut is rotatably mounted parallel to the cylindrical driving portion, using a longitudinal groove and protrusion for translational motion, simplifying manufacturing and assembly, and ensuring the dose limiter prevents excessive dose setting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex dose-setting mechanism with threaded connections is used to prevent excessive dosing, then dose limitation reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The dose-setting mechanism is divided into separate functional components: a drive member with an internally threaded cavity, a dose-setting member with an externally threaded portion, and a limiting member with a gear wheel. This segmentation allows each component to be manufactured independently using standard threading processes, reducing overall manufacturing complexity while maintaining reliable dose limitation through the coordinated interaction of these simpler parts.
Solution Approach 2:
The limiting member with the gear wheel is positioned within the drive member's cavity, and the dose-setting member threads into the drive member. This nested arrangement allows the dose-limitation functionality to be integrated within the existing dose-setting structure without adding external complexity, enabling reliable dose control while keeping the overall device design compact and manufacturable.
2Measurement precision
If a mechanical summation mechanism with translational motion of the limiting member is implemented, then dose tracking accuracy is improved, but device complexity increases
Solution Approach 1:
The complex mechanical summation mechanism is replaced with a simpler gear-driven rotational system. The gear wheel on the limiting member engages with the threaded portion of the dose-setting member, converting rotational motion during dose setting into precise angular displacement of the limiting member. This substitution maintains accurate dose tracking while eliminating the need for complex translational motion mechanisms.
Solution Approach 2:
The dose-tracking mechanism transitions from linear translational motion to rotational angular motion. The limiting member's gear wheel rotates in response to the threaded engagement during dose setting, providing accurate dose measurement through angular displacement rather than linear movement. This dimensional change simplifies the mechanical requirements while maintaining measurement precision.
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 design enhances reliability, stability, and reduces manufacturing costs while ensuring accurate dose limitation, with simplified assembly and reduced rejection rates.
Implementation Method 1
The injection device incorporates a cylindrical dose-setting mechanism with a gear wheel and nut system
Implementation Method 2
the threaded shaft is rotatably mounted parallel to the axis of the cylindrical driving portion, wherein an inner surface of the cylindrical driving portion is provided with a longitudinal groove
Data Source
Figure 1
Figure 2
AI summary
A device for injection comprising a housing, a cylindrical dose setting mechanism, a cylindrical driving portion, and a rod, the cylindrical dose setting mechanism being mounted inside the housing, and the cylindrical driving portion being mounted inside the cylindrical dose setting mechanism coaxially therewith, wherein the cylindrical driving portion is provided with a cavity in which a dose limiter is arranged longitudinally with respect to the axis of said portion, said dose limiter comprising a threaded shaft, a gear, and a nut, the threaded shaft being rotatably mounted parallel to the axis of the cylindrical driving portion but offset therefrom, the gear is rigidly fastened to the shaft axis, the nut is mounted on the shaft such as to be capable of limited translational motion and limited rotation, and the inner surface of the cylindrical dose setting mechanism is provided with longitudinal grooves for engagement with the gear of the dose limiter.