Removable Shoulder Screw Assembly for Crack-Free Fan Mounting
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Solution Overview
Problem
Existing mechanical systems face challenges in reducing stresses and flexure due to the use of traditional screws and bolts, particularly in applications like cooling fans where flanges can bend or crack under torque.
Innovation Solution
The development of a removable shoulder screw assembly that includes a first screw shaft portion, a second screw shaft portion with a smaller diameter, a threaded portion, and a shaft edge, along with a removable shoulder that engages the shaft edge to apply a clamping force without bending the fan flanges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional screws and bolts are used to assemble mechanical systems, then the assembly is secure, but stresses and flexure increase causing flange bending or cracking
Solution Approach 1:
The screw is segmented into multiple portions with different diameters: a first screw shaft portion, a second screw shaft portion with smaller diameter, and a driver portion. This segmentation allows each portion to serve a specific function - the larger first portion provides structural strength, the smaller second portion reduces stress concentration, and the driver portion enables tool engagement without transmitting excessive torque to the flange.
Solution Approach 2:
Different portions of the screw have different local properties - the first screw shaft portion has a larger diameter for strength, the second screw shaft portion has a smaller diameter to reduce stress, and the driver portion has a specific diameter for tool engagement. This local quality variation allows the screw to provide secure assembly while minimizing harmful stresses and flange deformation.
2Strength
If a larger diameter screw is used to reduce stress, then assembly security improves, but the mounting real estate required increases
Solution Approach 1:
The screw is divided into portions with different diameters, allowing the mounting hole to be sized for the smaller second screw shaft portion while the first screw shaft portion provides the necessary structural strength. This segmentation enables reduced mounting real estate without compromising assembly security.
Solution Approach 2:
The screw concentrates its strength-providing geometry in the first screw shaft portion while the second screw shaft portion has a smaller diameter that fits through smaller mounting holes. This local quality differentiation allows the assembly to be secure while requiring less mounting real estate.
3Area of stationary object
If a smaller diameter screw is used to reduce mounting space, then mounting real estate decreases, but assembly security and stress resistance worsen
Solution Approach 1:
The screw is segmented so that the first screw shaft portion has a larger diameter to provide structural strength and assembly security, while the second screw shaft portion has a smaller diameter that fits through smaller mounting holes. This segmentation resolves the contradiction by providing both small mounting footprint and strong assembly security.
Solution Approach 2:
Different portions of the screw have different diameters optimized for different functions - the first portion for strength and the second portion for space efficiency. This local quality variation allows the screw to simultaneously achieve small mounting real estate requirements and high assembly security.
Data Source
AI summary
A screw assembly, including: a removable shoulder screw including: a first screw shaft portion; a second screw shaft portion; a first threaded portion; and a first shaft edge between the first screw shaft portion and the second screw shaft portion, wherein the second screw shaft portion is between the first screw shaft portion and the first threaded portion, and wherein a diameter of the second screw shaft portion is smaller than the diameter of the first screw shaft portion; and a first removable shoulder including a first removable shoulder opening and a first removable shoulder edge, wherein the first removable shoulder opening has a diameter less than the diameter of the first screw shaft portion and is configured to engage the second screw shaft portion, and wherein the first removable shoulder edge is configured to engage the first shaft edge.