Cap Inner Grooves for Pressure Equalization in Writing Instruments
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Solution Overview
Problem
Conventional writing instruments experience ink loss due to pressure changes when the cap is alternately attached and detached, leading to ink displacement and waste, particularly when using liquid ink systems.
Innovation Solution
The cap features grooves on its inner surface that extend to the axial opening, acting as an air passage to balance pressure during cap engagement and disengagement, preventing ink loss and allowing easy air escape, while maintaining effective retention through reliefs and a sealing member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cap is used to cover the writing tip, then the tip is protected from drying, but ink loss occurs due to pressure changes during cap attachment and detachment
Solution Approach 1:
The cap is segmented into functional zones: a sealing portion for tip protection, a retention portion with reliefs for secure attachment, and pressure equalization grooves that allow air to escape in controlled segments during attachment, preventing ink displacement
Solution Approach 2:
Air passages (grooves) are introduced as intermediary elements between the sealed cap interior and exterior, allowing pressure equalization without compromising the sealing function. These grooves act as mediators that enable controlled air flow to prevent ink loss while maintaining tip protection
2Ease of manufacture
If the cap has a simple design without air passages, then manufacturing is easier, but ink displacement and waste occur during cap operations
Solution Approach 1:
The cap structure is segmented with integrated grooves formed directly during molding, creating pressure equalization pathways without requiring separate components or complex assembly steps, thus maintaining manufacturing simplicity while preventing ink displacement
Solution Approach 2:
The grooves are self-formed integral features of the cap structure that automatically provide pressure equalization functionality during normal cap attachment and detachment operations, eliminating the need for additional mechanisms or components
3Reliability
If reliefs are added to the cap for retention, then cap retention is improved, but the cap structure becomes more complex
Solution Approach 1:
The retention reliefs and pressure equalization grooves are merged into a single integrated cap structure, where both features are formed simultaneously during molding, reducing overall complexity compared to separate components while achieving both retention and pressure equalization functions
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 effectively prevents ink loss and pressure-related issues during cap operations, ensuring efficient ink usage and maintaining the cap's simplicity and ease of assembly.
Implementation Method 1
a flow of the air accumulated at the bottom of the cap towards the opening of the cap during a closing operation. The groove is used as an intervening air passage between the cap and the writing body. This prevents pressurization of the cap when it is put in place or depression when it is removed
Data Source
Figure 1~2
Figure 3A~5
Figure 6~8
AI summary
The writing implement of the invention comprises a writing body and a removable cap (C) for covering the writing tip (11) in a position coupled with the writing body. The cap has a bottom (35), a tubular wall (32) extending longitudinally between a first end (20a) making contact with the wall (35) and a second end (20b) defining an opening (24). The tubular wall (32) advantageously has an inner surface on which raised contours (31) capable of making contact with the writing body (10) in the contact position protrude, the inner surface of the cap (C) having at least one groove tread (33) arranged between two of said contours (31) and extending to the second end (20b) of the tubular wall. The groove tread thus prevents pressure from being applied to the cap (C) during fitting and prevents the cap from being applied with negative pressure during removal, without impeding the removal of the cap and maintaining a specific simplicity of design.