Expandable Washer With Cam Expansion for Fastener Tension Retention
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Solution Overview
Problem
Conventional washers fail to maintain a tight connection over time due to shifting or moving components, leading to loss of compressive force and compromised structural integrity in applications like wood frame buildings, where wood shrinkage or movement can cause screws to lose contact with wall plates.
Innovation Solution
An expandable washer design featuring a first and second expander member that cooperatively define a channel for the fastener, with a cam or coil spring mechanism to maintain tension by driving the expander members apart, ensuring the fastener remains in contact with the component despite dimensional changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional washers are used to distribute compressive force, then the connection is initially tight, but the connection becomes loose over time due to component shifting
Solution Approach 1:
The washer transitions from a static conventional design to a dynamic expandable design. The expander members can move relative to each other along the expansion axis, allowing the washer to adapt its internal dimensions as components shift over time, thereby maintaining connection tightness throughout the service life
Solution Approach 2:
The washer changes its physical parameters (internal channel dimensions) in response to component movement. As the fastener moves away from the component, the expander members expand to increase the channel dimension, maintaining the compressive force on the fastener head and preventing connection loosening
2Object-generated harmful factors
If a long floor screw is used instead of a strap, then strap buckling is resolved, but the tightness of the connection is compromised due to screw head movement
Solution Approach 1:
The expandable washer acts as an intermediary mechanism between the fastener and the component. It transfers and maintains the compressive force from the fastener head to the component, ensuring that the connection remains tight even when the fastener moves, thereby resolving the reliability issue without requiring straps
3Adaptability or versatility
If the fastener moves away from the component over time, then component shifting is accommodated, but the compressive force is lost
Solution Approach 1:
The washer employs dynamic expander members that can adjust their position along the expansion axis. As the fastener moves away from the component, the expander members expand to maintain contact and continue applying compressive force, accommodating shifting while preserving the necessary force
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 expandable washer effectively maintains the compressive force and prevents loss of contact between components, ensuring a snug and secure connection even as the components shift or shrink over time, thereby maintaining the structural integrity and resisting uplift forces.
Implementation Method 1
A coil spring is located radially outward from the expansion axis. The coil spring is biased for movement toward the expansion axis in the channel between the first and second expander members. This movement drives the first and second expander members apart to maintain the application of force to maintain the fastener in tension
Implementation Method 2
A cam located radially outward from the expansion axis is biased for movement toward the expansion axis and between the first and second expander members to drive the first and second expander members apart to maintain the application of force to place the fastener in tension
Data Source
AI summary
An expandable washer for use with a fastener to maintain tension in the fastener after connection to a component comprises first and second disks. The first and second disks cooperatively define a channel having a dimension parallel to the expansion axis which decreases from a location remote from to a location closer to the expansion axis. The first and second disks are configured to pass the fastener through them and to the component. The fastener operatively engages the first disk for moving with the first disk and to place the fastener in tension when the fastener is connected to the component. The expandable washer further includes a cam located radially outward from the expansion axis and biased for movement toward the expansion axis to drive the first and second disks apart to maintain the application of force against the fastener.