Compression-Limiting Sleeve Retainer Without Secondary Staking
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Solution Overview
Problem
Conventional fastener systems that limit compression require a secondary staking operation, result in significant scrap due to stamping, and have uncontrolled tolerances, and cannot easily adjust column strength by altering sleeve wall thickness or hardness.
Innovation Solution
A fastener system comprising a threaded bolt or screw with a compression-limiting sleeve that is not staked, using a retainer to retain the sleeve, allowing for cold heading to minimize scrap and achieve tight tolerances, and varying the sleeve's column strength by adjusting its wall thickness or hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stamped sleeve or bushing is staked to a threaded fastener to limit compression, then compressive forces are absorbed by the sleeve, but a secondary staking operation is required and manufacturing complexity increases
Solution Approach 1:
The compression limiting member is integrated directly into the fastener body as a unified component, eliminating the need for separate staking operations. The fastener is formed with a head portion and a body portion that together create the compression limiting structure, merging two previously separate components (fastener and compression limiting member) into one.
Solution Approach 2:
The fastener body is designed to perform multiple functions: it provides the threading for fastening while simultaneously incorporating the compression limiting structure through its head and body geometry. This multi-functional design allows the single fastener component to both secure workpieces and limit compression forces.
2Strength
If a stamped sleeve or bushing is used to limit compression, then compressive forces are absorbed, but significant scrap is generated and material loss increases
Solution Approach 1:
The compression limiting function is achieved through the geometry of the fastener's head and body portions rather than through a separate stamped component. This eliminates the need to discard stamped sleeves or bushings, as the compression limiting capability is built into the fastener itself using the same material and forming process.
Solution Approach 2:
The fastener is formed as a unified composite structure where the head portion and body portion work together to provide both fastening and compression limiting functions. The integration of these portions creates a composite functional unit that eliminates material waste associated with separate stamped components.
3Strength
If a stamped sleeve or bushing is used to limit compression, then compressive forces are absorbed, but tolerances cannot be closely controlled
Solution Approach 1:
The fastener is divided into distinct head and body portions with defined geometric relationships. This segmentation allows for precise control of the compression limiting characteristics through the head geometry while maintaining standard fastener body tolerances. The head portion acts as a separate functional element within the unified fastener.
Solution Approach 2:
The compression limiting capability is controlled by varying geometric parameters of the head portion, such as its diameter, height, and profile. By changing these parameters, the compression limiting characteristics can be precisely adjusted without affecting the fastener body tolerances, allowing independent optimization of both functions.
4Strength
If the column strength of a sleeve or bushing is to be changed, then wall thickness or hardness must be altered, but the system does not readily provide this adjustment
Solution Approach 1:
The column strength of the compression limiting structure is adjusted by changing the geometric parameters of the head portion, such as its diameter, height, and wall thickness. These parameter changes can be easily implemented during the fastener forming process without requiring separate operations to modify wall thickness or hardness of a stamped component.
Solution Approach 2:
The compression limiting geometry is built into the fastener during the initial forming process, with the head portion configured to provide the desired column strength. This preliminary configuration of the compression limiting structure eliminates the need for subsequent operations to adjust wall thickness or hardness.
Data Source
AI summary
A fastener system that includes a fastener, a compression-limiting sleeve, and a retainer which generally retains the compression-limiting sleeve on the fastener. By providing that the compression-limiting sleeve is not staked to the fastener, existing technology can be used, and no extra staking processing step needs to be performed. The fastener may comprise a conventional metal threaded screw or bolt, possibly having a recess in its head for receiving a driver. Preferably, the compression-limiting sleeve is cold headed as opposed to being stamped, and preferably includes a counter bore which assures that an end of the retainer is below an end surface of the compression-limiting sleeve. Preferably, the retainer is formed of a thermoplastic elastomer or another suitable material.