Writing Tool Front Shaft Slit Design for Fitting Force
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Solution Overview
Problem
The existing writing tool design, where the main cylinder and detachable cylinder are connected by pressure contact, faces issues with inconsistent fitting force due to creeping or sticking of resin parts, leading to undesired detachment or difficulty in separating the components.
Innovation Solution
The design incorporates a front shaft with a smaller-diameter base featuring a slit that deforms to facilitate insertion into a larger-diameter base, providing a resilient pressure contact that ensures a consistent and easy detachment mechanism, along with additional features like outward-facing and inward-facing pressure contact parts for enhanced stability and engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the main cylinder and detachable cylinder are connected by pressure contact between projections and surface, then the structure is simple and easy to manufacture, but the fitting force becomes inconsistent due to creeping or sticking of resin parts
Solution Approach 1:
The patent changes the physical state of the smaller-diameter base from rigid to flexible by incorporating a slit, allowing it to deform elastically during insertion and then maintain consistent pressure contact. This parameter change (from rigid to flexible) resolves the contradiction by enabling reliable fitting force while remaining manufacturable through standard molding processes
Solution Approach 2:
The smaller-diameter base is segmented by introducing a slit that divides the base structure, allowing it to flex and deform during insertion. This segmentation enables the base to adapt to the larger-diameter base while maintaining consistent pressure contact, solving the reliability issue without complicating manufacturing
2Reliability
If the fitting force is increased to prevent detachment, then the connection stability is improved, but the detachable cylinder becomes difficult to remove by operational force
Solution Approach 1:
The smaller-diameter base transitions from a static rigid structure to a dynamic flexible structure that deforms during insertion and then maintains elastic pressure contact. This dynamic behavior allows the base to provide strong holding force while still permitting easy removal when force is applied, resolving the contradiction between connection stability and ease of detachment
3Force
If the resin parts are made tighter to prevent creeping, then the fitting force increases, but the resin parts stick and become difficult to separate
Solution Approach 1:
The smaller-diameter base is designed as a flexible structure with a slit that allows elastic deformation. This flexibility enables the base to create strong pressure contact force while maintaining the ability to be separated when needed, resolving the contradiction between fitting force and ease of separation that plagues rigid resin connections
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 allows for easy setting and maintenance of the fitting force, providing a stable connection that enhances writing performance and user experience by ensuring proper engagement and air-tightness, while also simplifying the replacement of the ink absorbent body.
Implementation Method 1
the smaller-diameter base can deform in such a manner that a width of the slit can be narrowed, which can make the inserting operation smoother
Implementation Method 2
after the smaller-diameter base has been inserted (press-fitted) into the larger-diameter base, a resilient force is exerted to return the width of the slit, so that the outward-facing pressure contact part and the inward-facing pressure contact part are brought into a pressure contact radially with each other
Data Source
AI summary
In a writing tool 1, a front shaft 5 is detachably provided on a rear shaft 6 containing an ink absorbent body 7. A filling part 51 is provided on an outside surface of a rear part of the front shaft 5. The filling part 51 detachably fits to a fitted part 61 formed on an inside surface of an opening part of the rear shaft 6. The filling part 51 has an outward-facing pressure contact part 53 and a radially penetrating slit 54. The fitted part 61 has an inward-facing pressure contact part 63. The front shaft 5 and the rear shaft 6 are brought into a pressure contact with each other when the front shaft 5 and the rear shaft 6 are fitted to each other.