Screw Cage Nut Structure for High Torque Without Coating Damage
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Solution Overview
Problem
Existing screw cages made of metal sheet struggle to provide high holding forces and torque transmission while minimizing scratch and chip formation during assembly, which can lead to corrosion risks, especially when used with coated screws.
Innovation Solution
A screw cage design featuring metal sheet lugs and additional positive locking elements that provide axial fixation and torque anchoring, with a gap for movement to reduce assembly stress and a fork-like configuration to prevent notch effects, allowing for high torque transmission without precise fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the screw nut is secured with precise fit in the opening of the screw cage, then high holding forces and torque transmission are achieved, but scratch and chip formation increases during assembly
Solution Approach 1:
The holding section is segmented into multiple lugs (at least three, preferably four or six) that are distributed around the opening. These lugs make localized contact with the screw nut at specific torque transmission surfaces, distributing the clamping force and reducing concentrated stress that causes scratching and chipping during assembly.
Solution Approach 2:
The lugs are designed to contact the screw nut only at specific locations (torque transmission surfaces) rather than across the entire circumference. This localized contact approach maintains high holding forces where needed while minimizing contact area that could cause damage during insertion.
2Object-affected harmful factors
If the opening is configured larger than the screw nut to reduce scratch formation, then assembly stress is reduced, but holding force decreases
Solution Approach 1:
Instead of relying on a tight circumferential fit, the holding section uses segmented lugs that contact the screw nut at discrete points. This allows the opening to be slightly larger than the screw nut while still achieving high holding forces through concentrated contact at the lug-nut interface.
Solution Approach 2:
The lugs extend in the axial direction (erect lugs) rather than only radially, creating a three-dimensional contact structure. This axial extension allows the lugs to engage the screw nut's torque transmission surfaces effectively even when there is a radial gap between the opening and the nut.
3Object-affected harmful factors
If multiple lugs are used to distribute force, then scratch formation is reduced and holding force is maintained, but device complexity increases
Solution Approach 1:
The multiple lugs are integrated into a single holding section that is formed as one piece with the clamping section. This merging approach allows the screw cage to be manufactured as a single component (e.g., from a folded metal sheet), reducing assembly complexity while maintaining the force-distributing benefits of multiple lugs.
Solution Approach 2:
The lugs serve multiple functions simultaneously: they provide clamping force to prevent rotation, distribute contact pressure to reduce scratching, and engage with the torque transmission surfaces for effective torque transmission. This multi-functionality reduces the need for additional components.
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 achieves high holding forces and reduced risk of corrosion by distributing force through lugs and positive locking elements, facilitating easy assembly and supporting high tightening and loosening torques while minimizing damage to coatings.
Implementation Method 1
Due to a clamping effect, the lugs bring about very high holding forces, for the axial fixation of the screw nut in the screw cage and also facilitate the exertion of counter-torques (for torque anchoring) onto the screw nut
Data Source
AI summary
A screw nut with a screw cage made of metal sheet, which includes a holding section securing the screw nut and a clamping section supporting the holding section. The holding section is configured with a circumferentially closed opening in which the screw nut is arranged in a rotationally fixed manner. The opening comprises multiple lugs configured as metal sheet passages which are in contact with the lateral torque transmissions surfaces of the screw nut.