Sheet Metal Screw Cage for High-Torque Nut Retention
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Solution Overview
Problem
Existing screw cages made of sheet metal struggle to provide high holding forces and counter-torques while minimizing scratching and chip formation during assembly, especially on coated nuts, and are prone to corrosion.
Innovation Solution
A screw cage design with sheet metal through-holes as tabs and additional positive locking elements, allowing for axial fixation and torque support, featuring a gap for movement and rounded edges to reduce scratching and corrosion, and a one-piece spring steel construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the screw cage opening is designed to tightly fit the nut, then rotational fixation is improved, but scratching and chip formation increases during assembly
Solution Approach 1:
The opening is segmented into multiple tabs (at least three tabs arranged circumferentially) that can independently deform and flex. This segmentation allows the tabs to elastically deform during nut insertion, reducing scratching on coated nuts, while still providing sufficient rotational fixation when engaged
Solution Approach 2:
The tabs are designed with specific geometric parameters including a free end portion that can elastically deform, and a contact surface area that is optimized to distribute contact pressure. The tab geometry allows controlled flexibility to reduce scratching while maintaining holding capability
2Strength
If the sheet metal thickness is increased, then holding forces and counter-torque capacity are improved, but manufacturing complexity and material usage increase
Solution Approach 1:
The tabs are designed to be elastically deformable rather than rigid, allowing them to flex during nut insertion and engagement. This dynamic behavior enables thin sheet metal to provide sufficient holding forces while maintaining ease of assembly and reducing manufacturing complexity
Solution Approach 2:
The screw cage is constructed from thin sheet metal with flexible tabs that provide the necessary mechanical properties through elastic deformation rather than through thick rigid material. This approach reduces material usage and manufacturing complexity while maintaining strength
3Strength
If tabs are added to bear against the nut surfaces, then holding forces are improved, but the risk of scratching coated nuts increases
Solution Approach 1:
The contact interface is segmented into multiple discrete tabs rather than a continuous rigid surface. Each tab can independently deform to accommodate the nut surface, distributing contact pressure and reducing localized scratching while maintaining overall holding force
Solution Approach 2:
The tabs are designed with inherent elastic compliance that acts as a cushion during the pre-assembly insertion process. This beforehand cushioning protects the coated nut surface from scratching while the tabs engage, allowing smooth insertion before full load bearing
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
Enables high holding forces and counter-torques with reduced scratching and chip formation, while preventing corrosion and facilitating assembly, by distributing load through tabs and positive locking elements.
Implementation Method 1
The tabs, through a clamping effect, generate very high holding forces for the axial fixation of the nut in the screw cage
Implementation Method 2
The screw cage (120) comprises a retaining section (122) that holds the screw nut (110) and a clamping section (121) that supports the retaining section (122) (e.g., against a body panel)
Data Source
Figure 1a~1b
Figure 2
AI summary
The invention relates to a screw nut (110) having a screw cage (120) manufactured from sheet metal which has a holding portion (122) holding the screw nut (110) and a clamping portion (121) supporting the holding portion (122), the holding portion (122) being formed having a peripherally closed opening in which the screw nut (110) is rotationally fixed. The opening (123) has a plurality of tabs (124) formed as sheet metal extrusions which contact the the lateral torque transfer surfaces (114) of the screw nut (110).