Coil Spring Anchor Configuration for Window Sash Counterbalance
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Solution Overview
Problem
Existing counterbalance systems for windows, particularly those using coil springs, face challenges with reliable anchoring methods that can loosen over time or obstruct the window frame, leading to inefficient operation and increased labor and costs during manufacturing and maintenance.
Innovation Solution
A novel anchoring system for coil springs in window counterbalance systems, where the spring is bent into an anchor configuration with a barb flap and offset tab that engages a mounting slot in the window frame without the need for mechanical fasteners, ensuring secure attachment and easy installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coil spring is attached to the window frame directly with a screw, then the coil spring can be anchored to the window frame, but the coil spring must be partially unwound to provide an accessible segment for attachment, which adds significantly to the labor and costs associated with the manufacture of the window
Solution Approach 1:
The anchor is divided into a head portion and a shaft portion that can be inserted separately through the mounting slot. The shaft portion is segmented to form engagement bars that can be inserted into recesses in the mounting slot, allowing attachment without unwinding the spring and reducing manual manipulation labor
Solution Approach 2:
The anchor is pre-formed with the shaft portion bent at specific angles to create engagement bars before installation. This preliminary shaping allows the anchor to be inserted through the mounting slot and engage the recesses automatically, eliminating the need for on-site manual bending or unwinding operations
2Reliability
If a screw anchor is used to attach the coil spring to the window frame, then the coil spring can be anchored, but the screw anchor tends to loosen over time and may interfere with the movement of the window sashes
Solution Approach 1:
The anchor design extracts the threaded screw portion entirely, replacing it with a smooth shaft portion that has engagement bars. This eliminates the loosening problem inherent in threaded connections while maintaining secure attachment through the engagement bars fitting into recesses in the mounting slot
Solution Approach 2:
Instead of using a threaded connection that screws into the mounting slot, the anchor uses a reverse approach where the shaft portion is inserted through the slot and the engagement bars engage recesses from the opposite side. This inversion of the attachment mechanism prevents loosening and avoids interference with sash movement
3Reliability
If an anchor block is used to attach the coil spring to the window frame, then the anchor is more reliable than a screw, but the anchor block protrudes into the guide track of the window frame and presents an obstruction that may inhibit a window sash from fully opening
Solution Approach 1:
The anchor transitions from a three-dimensional block protruding into the guide track to a two-dimensional flat structure that lies substantially within the plane of the mounting slot. The engagement bars extend laterally into recesses, providing secure attachment without protruding into the guide track and obstructing sash movement
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
This solution provides a reliable, cost-effective, and labor-efficient anchoring method that prevents accidental disengagement of the coil spring, allowing for smooth operation and reduced manufacturing complexity, while eliminating the need for mechanical fasteners and obstructions in the window frame.
Implementation Method 1
a coil spring that is selectively wound into a coil and that has a free end... the coil spring winds and unwinds as a window sash is opened and closed
Implementation Method 2
The end of the coil spring is bent into an anchor configuration that is received within a mounting slot formed in the window frame
Data Source
AI summary
An anchoring system used to anchor a ribbon spring to a guide track. A mounting slot is formed in the guide track that provides access to the internal gap space. A counterbalance spring is provided having an offset tab section proximate a free end. A barb flap is formed by bending a segment of the counterbalance spring from the offset tab section. The offset tab section with barb flap are extended into the gap space through the mounting slot. As the counterbalance spring is unwound, a bias is created that engages both the offset tab section and the barb flap within the gap space. This locks the free end of the counterbalance spring in place without the need of any mechanical fastener.