Mechanical Pencil Cam Mechanism for Low Lead Retraction
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Solution Overview
Problem
Mechanical pencils with rotation drive mechanisms often cause discomfort due to the retraction of the writing lead during writing, which is visually and tactilely noticeable, despite the necessity of the cushion operation for rotating the lead.
Innovation Solution
A mechanical pencil design with a rotation drive mechanism that reduces the amount of writing lead retraction by configuring the cam faces and fixed cam faces to be offset by half a phase in the axial direction, ensuring the writing lead rotates with minimal retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rotation drive mechanism is activated to rotate the writing lead during cushion operation, then the writing lead rotation is improved, but the retraction of the writing lead becomes noticeable and bothersome
Solution Approach 1:
The patent changes the geometric parameters of the cam mechanism, specifically setting the pitches of the first and second cam faces to be substantially the same, and configuring the cam faces to be offset by half a phase. This parameter optimization reduces the retraction amount during cushion operation while maintaining the lead rotation function, thereby reducing user discomfort without sacrificing the rotation benefit
Solution Approach 2:
The patent introduces a switching mechanism that allows dynamic control of the rotation drive mechanism between on and off states. This enables the system to adapt to different writing scenarios: when rotation is needed for even wear, the mechanism is activated; when minimal retraction is preferred, the mechanism can be deactivated, providing user-controlled optimization of the contradiction
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 design minimizes the retraction of the writing lead, enhancing the writing experience by reducing visual and tactile discomfort while maintaining the functionality of lead rotation.
Implementation Method 1
a first cam face (40a) formed at a rear end face of the rotor (40), a ring-shaped second cam face (40b) formed at a front end face of the rotor (40), a first fixed cam face (41a) formed at an end face of the upper cam forming member (41), and a second fixed cam face (42a) formed at an end face of the lower cam forming member (42), the first cam face (40a) and the first fixed cam face (41a) being offset in the axial direction by half a phase with respect to one tooth of the cam, while the second cam face (40b) and the second fixed cam face (42a) being offset in the axial direction by half a phase with respect to one tooth of the cam
Data Source
AI summary
A mechanical pencil 1 has a first cam surface 140a, a second cam surface 140b, a first fixed cam surface 141a that cooperates with the first cam surface to cause a rotating element to rotate, and a second fixed cam surface that cooperates with the second cam surface to cause a rotating element to rotate. The first cam surface is provided with first cam teeth 140aa, the second cam surface is provided with second cam teeth 140ba, the first fixed cam surface is provided with first fixed cam teeth 141aa that cooperate with the first cam teeth, and the second fixed cam surface is provided with second fixed cam teeth 142aa that cooperate with the second cam teeth. The first cam teeth are configured such that in each first cam tooth, the relationship 0<Y<X is achieved, where, with respect to a perpendicular line drawn from the apex, X is the length of the base on the rear side with respect to the rotating direction of the rotating element 140, and Y is the length of the base on the front side with respect to the rotating direction of the rotating element.