Captive Screw Sleeve With Spring Tongues for Tolerance Compensation
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Solution Overview
Problem
Existing captive devices for screws lack a simple structure that is tolerant to manufacturing variations and assembly tolerances, leading to screws falling out of through-holes during assembly.
Innovation Solution
A captive device with an annular sleeve featuring leaf-shaped spring tongues that allow radial displacement within a through-hole, compensating for tolerances and securely holding the screw in place while allowing radial adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional captive device with rigid structure is used, then the screw is held securely, but the device cannot accommodate manufacturing tolerances and assembly variations, causing screws to fall out
Solution Approach 1:
The patent applies parameter changes by transforming the rigid structure into a flexible one through the leaf-shaped spring tongue. This spring tongue can deflect and adapt its position, allowing the captive device to accommodate variations in through-hole dimensions and screw positions while maintaining secure retention. The spring tongue's elasticity enables it to compensate for tolerance deviations without compromising the screw-holding function.
2Reliability
If a complex captive device structure is used to ensure secure screw retention, then reliability improves, but manufacturing complexity and cost increase
Solution Approach 1:
The captive device is segmented into distinct functional elements: the annular sleeve and the leaf-shaped spring tongue. This segmentation allows each component to be manufactured separately using simple processes, then assembled together. The spring tongue can be formed by cutting and bending a simple metal strip, avoiding complex machining or molding operations, thus maintaining ease of manufacture while achieving reliable screw retention.
Solution Approach 2:
The patent employs a flexible spring tongue made from a thin metal strip that is cut and bent into the leaf shape. This flexible element provides the necessary compliance and retention force without requiring complex structural features. The simplicity of forming a bent metal strip makes the device easy to manufacture cost-effectively while ensuring reliable screw capture and retention.
3Strength
If the annular sleeve is made rigid to maintain structural integrity, then strength is improved, but the device cannot allow radial displacement for tolerance compensation
Solution Approach 1:
The annular sleeve exhibits local quality by having different mechanical properties in different regions. The main body of the sleeve maintains rigidity for structural integrity and positioning, while the leaf-shaped spring tongue introduces local flexibility. This localized flexibility allows radial displacement and tolerance compensation without compromising the overall structural strength and stability of the captive device.
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 device provides secure screw retention with tolerance compensation, enabling easy assembly and preventing screws from falling out, even in thin sheet metal or plastic components, while being cost-effective and easy to manufacture.
Implementation Method 1
the annular sleeve is provided with at least one leaf-shaped spring tongue which extends from the annular sleeve and projects in the direction of a central longitudinal axis of the sleeve
Data Source
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AI summary
The invention relates to a securing means for a screw, comprising an annular sleeve for insertion into a through-hole in a workpiece, characterized in that the annular sleeve is provided with at least one leaf-type flexible tongue which extends from the annular sleeve and protrudes in the direction of a central longitudinal axis of the sleeve.