Friction Wheel Assembly for Pen-Type Injector Jamming
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Solution Overview
Problem
Existing pen-type injectors face issues with jamming due to foreign substances in gear wheel and pinion systems, leading to mechanical damage and dosage inaccuracies.
Innovation Solution
The use of a friction wheel assembly that transforms rotational movement into linear movement, eliminating the need for gear wheels and racks, providing a sliding coupling that is insensitive to tolerances and reducing the risk of jamming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gear wheels and racks are used to transmit motion, then mechanical advantage and precise dosage control are achieved, but the mechanism is susceptible to jamming by foreign substances and mechanical damage
Solution Approach 1:
The patent replaces the gear wheel and rack mechanical transmission system with a friction wheel system that uses friction-based force transmission. The friction wheel engages with the piston rod through friction contact rather than toothed engagement, eliminating the risk of jamming by foreign substances in gear teeth while still providing mechanical advantage for dose delivery
Solution Approach 2:
The patent changes the fundamental transmission parameter from mechanical interlocking (gear teeth) to friction-based force transmission. By controlling the coefficient of friction and contact pressure between the friction wheel and piston rod, the system achieves reliable force transmission without the complexity and vulnerability of gear mechanisms
2Force
If form-locking connections are used to ensure secure engagement, then mechanical advantage is achieved, but the mechanism can warp under excessive force and prevent dosage selection
Solution Approach 1:
The patent transitions from a static form-locking connection to a dynamic friction-based connection. The friction wheel maintains engagement with the piston rod through controlled friction pressure that can accommodate force variations during operation, allowing the mechanism to absorb excessive force without warping while maintaining secure engagement for accurate dosage delivery
3Productivity
If gear transmission is used to move the injection button axially, then dose delivery is achieved, but noise is generated from gear meshing
Solution Approach 1:
The patent eliminates the noise-generating gear meshing by replacing it with a friction-based force transmission system. The friction wheel transmits force to the piston rod through continuous friction contact, which operates silently compared to the periodic impact and meshing noise of gear teeth, while still achieving effective dose delivery
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
The friction wheel assembly ensures reliable and accurate dose delivery with reduced noise and no potential for mechanical damage, allowing for adjustable friction force and improved manufacturing tolerances.
Implementation Method 1
a friction wheel or friction wheel assembly... The friction wheel or friction wheel assembly can transform rotational movement to linear movement... Mechanical advantage is supplied by the use of the friction wheels engaging the linear bearing surfaces
Data Source
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AI summary
An injection device for injection of set doses of medicine from a cartridge, in which one or more friction wheels engage linear bearing surfaces during dose setting and dose delivery.