Pen Tip Attachment Structure With Deformable Barb Locking
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Solution Overview
Problem
Existing pen-core locking structures require significant force for insertion and may lead to scratches and inadequate locking, causing the pen tip to easily come off.
Innovation Solution
A writing instrument attachment structure with a deformable barb portion in the fitting hole that allows easy insertion of the pen tip and secure locking, featuring a small-diameter and large-diameter portion with a deformable barb that locks into place after fitting, and a stopper for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pen core is press-fitted into the shaft tube with protrusions biting into the pen core, then the locking performance is improved, but the insertion force required becomes too great
Solution Approach 1:
The barb portion is designed to be deformable, allowing it to dynamically change its shape during insertion. When the pen tip is inserted, the barb portion deforms to allow passage, and after insertion, it recovers its original shape to bite into the pen tip and provide locking force. This dynamic behavior resolves the contradiction between requiring high locking force and low insertion force.
Solution Approach 2:
The barb portion changes its physical state from a deformed state during insertion to a recovered state after insertion. This parameter change allows the structure to provide different mechanical properties at different stages: flexible during insertion and rigid for locking, thereby resolving the force contradiction.
2Reliability
If the protrusions bite into the outer surface of the pen core, then the locking force is increased, but scratches are formed on the pen core surface
Solution Approach 1:
The barb portion is designed with a specific local geometry where the tip has a rounded shape rather than a sharp edge. This local quality change allows the barb to bite into the pen tip material without creating scratches on the outer surface, as the rounded tip distributes the contact pressure and prevents surface damage while still providing adequate locking force.
3Ease of operation
If the pen tip is easily inserted into the shaft tube, then the ease of operation is improved, but the locking reliability may be compromised
Solution Approach 1:
The barb portion's dynamic deformability allows it to accommodate the pen tip during easy insertion, then recover to provide reliable locking. This dynamic behavior enables the system to achieve both ease of operation and locking reliability through the same structural feature.
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
Facilitates easy fitting of the pen tip without resistance and ensures secure attachment, preventing it from coming off even under excessive force, while maintaining smooth ink supply.
Implementation Method 1
the barb portion is deformable by contact with the small-diameter portion when the second component is fitted
Implementation Method 2
when an axially forward force (that is, a force in the direction in which the second component comes off) is applied to the second component after the fitting of the second component, the barb portion tends to recover a state before the fitting (deformation) of the second component, and accordingly, the barb portion bites into the outer surface of the small-diameter portion of the second component to securely lock the second component
Data Source
AI summary
An attachment structure in a writing instrument, includes: a first component; and a second component configured to be fitted into a fitting hole provided at an end of the first component, the second component including: a small-diameter portion; and a large-diameter portion disposed in front of the small-diameter portion; and a first outer step portion disposed between the small-diameter portion and the large-diameter portion, the fitting hole including: a small-diameter hole portion; and an inner step portion disposed in front of the small-diameter hole portion, the small-diameter portion being fitted into or loosely fitted into the small-diameter hole portion, the first outer step portion coming into contact with the inner step portion, the small-diameter hole portion includes a barb portion protruding from the inner face of the small-diameter hole portion, the barb portion being deformable by contact with the small-diameter portion when the second component is fitted.