Retractable Pen Spring Integrating Actuation and Cushioning
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Solution Overview
Problem
The complexity and cost of manufacturing retractable writing instruments with a cushioning device are increased due to the need for multiple parts and limited space within the barrel for the ink cartridge, and there is a risk of torque transmission when using a spring member with a helical shape.
Innovation Solution
A spring member elastically deformable along the central axis is integrated with the actuating mechanism, featuring a wavy shape to prevent torque transmission and a through hole for connecting the actuation member, allowing for a reduced number of parts and space-saving design, along with an additional metallic helical spring for adjustable cushioning force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cushioning device is added to a retractable writing instrument, then writing comfort and protection are improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The spring member is integrally formed with the actuating mechanism, merging two separate components (cushioning spring and actuator) into a single integrated part. This reduces the total number of parts, simplifies assembly, and lowers manufacturing cost while maintaining the cushioning function that protects the writing tip and improves writing comfort.
2Reliability
If a cushioning device is added to a retractable writing instrument, then writing comfort and protection are improved, but the remaining space for the ink cartridge is reduced
Solution Approach 1:
By integrating the spring member with the actuating mechanism, the patent eliminates the need for separate cushioning device space. The combined structure utilizes the existing actuator volume, thereby preserving maximum space within the barrel for the ink cartridge while still providing effective cushioning protection.
Solution Approach 2:
The spring member is positioned within the actuating mechanism structure, with its through hole allowing the stem to pass through. This nested arrangement allows the cushioning element to be contained within the existing mechanical structure without adding external volume, thus preserving ink cartridge space.
3Reliability
If a helical spring member is used for cushioning, then cushioning function is provided, but torque transmission occurs around the central axis
Solution Approach 1:
The spring member is designed with a specific asymmetric geometry featuring a through hole along the central axis. This asymmetric design allows the spring to compress axially without rotating, as the through hole configuration and its interaction with the stem constrain rotational movement, thereby preventing torque transmission while maintaining the cushioning function.
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 reduces manufacturing costs, simplifies assembly, and prevents torque transmission, while providing effective cushioning and space for the ink cartridge, enhancing the usability and durability of the writing instrument.
Implementation Method 1
a spring member elastically deformable in said central axis direction
Implementation Method 2
said spring member has a free end abutting said barrel toward its rear end
Data Source
AI summary
A retractable writing instrument that includes a barrel, a writing tip, an actuating mechanism that includes a plurality of parts for extending and retracting the writing tip upon actuation of the actuation member, and a cushioning device enabling a retraction of the writing tip when an excessive pressure is exerted by a user. The cushioning device includes a spring member elastically deformable, which is integrally formed with a movable part of the actuating mechanism, the part being movable relative to the barrel. The spring member has a free end abutting the barrel toward its rear end and has a through hole. A stem extends within the spring member's hole and connects the actuating member to the actuating mechanism.