Four-Loop Window Balance Cord Configuration
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Solution Overview
Problem
Conventional block and tackle window balances with five-loop configurations require stronger springs and higher operating forces, leading to increased stress on components and manufacturing costs, while also limiting the range of window travel and balance performance.
Innovation Solution
A four-loop cable configuration with a fused pulley set in the movable pulley block, which reduces the number of loops and introduces additional friction to improve balance performance and reduce the required spring force, allowing for lighter and potentially lower-cost components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a five-loop cord configuration is used in conventional block and tackle window balances, then the balance can support the window sash weight, but stronger springs and higher operating forces are required, leading to increased stress on components and higher manufacturing costs
Solution Approach 1:
The invention segments the cord configuration into four distinct loops instead of five, redistributing the mechanical load across fewer, more efficiently arranged segments. This segmentation reduces the cumulative stress on each component while maintaining the overall balancing function.
Solution Approach 2:
The invention changes the fundamental parameter of loop count from five to four, which fundamentally alters the mechanical advantage ratio and force distribution. This parameter change enables the use of lighter springs and reduces operating forces while maintaining adequate component strength through optimized force distribution.
2Stability of the object's composition
If a five-loop cord configuration is used, then the window balance can maintain stability, but the range of window travel is limited and balance performance is restricted
Solution Approach 1:
The four-loop configuration creates a more dynamic system where the cord and pulleys can accommodate greater displacement ranges. The reduced loop count allows for larger angular movements of the pulleys and greater linear travel of the cord, enabling extended window travel ranges while maintaining balance stability through the optimized mechanical geometry.
3Force
If stronger springs are used in five-loop configurations to maintain balance, then the window sash can be supported, but manufacturing costs increase
Solution Approach 1:
By changing the loop count parameter from five to four, the invention fundamentally alters the force multiplication ratio. This parameter change enables the use of lighter, less expensive springs that produce lower forces while still achieving adequate balancing performance, thereby reducing manufacturing costs.
Solution Approach 2:
The invention creates a simplified version of the traditional five-loop system by copying only the essential four loops needed for effective balancing. This simplified configuration eliminates the need for over-engineered components, allowing for cost-effective manufacturing while maintaining functional performance.
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 four-loop configuration reduces the spring force needed by 20% and improves balance performance by reducing stress on components and manufacturing costs, while enabling increased window travel and smoother operation.
Implementation Method 1
a spring having a first spring end fixed within the channel and a second spring end
Implementation Method 2
a plurality of rollers rotatably mounted in the movable block; a single roller rotatably mounted in the fixed block
Data Source
AI summary
A window balance has a channel with two ends. A top guide is disposed at one end of the channel and a bottom guide is disposed at the other end of the channel. One end of a spring is fixed within the channel. A movable block is secured to the other end of the spring. Rollers are rotatably mounted in the movable block. A single roller is rotatably mounted to a fixed block which is secured to the channel. A cord exit roller is disposed proximate the bottom guide. The first end of a cord is fixed relative to the channel. The middle portion of the cord is routed about the rollers mounted in the movable block and mounted to the fixed block. A second end of the cord is routed around the cord exit roller and is attachable to a window jamb.