Fenestration Sash Retention via Segmented Counterbalance

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Solution Overview

Problem

Fenestration units, such as windows, often face the challenge of upper sashes moving unintentionally when the lower sash is operated, leading to a lack of independent movement control between the two sashes.

Innovation Solution

A fenestration unit design featuring separate counterbalance mechanisms and resilient detents within tracks allows for independent vertical movement of both the upper and lower sashes, with detents preventing unintended movement of the upper sash when the lower sash is operated.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single counterbalance mechanism is used for both sashes, then device complexity is reduced, but the upper sash cannot be restrained from moving when the lower sash is operated

Engineering Contradiction:

Improvesash position stabilityVSAvoidcounterbalance mechanism structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The single counterbalance mechanism is divided into two separate mechanisms: a first counterbalance mechanism for the lower sash and a second counterbalance mechanism for the upper sash. This segmentation allows independent control and restraint of each sash, enabling the upper sash to be held in place while the lower sash operates, thereby resolving the contradiction between position stability and mechanism complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Resilient detents are introduced as intermediary elements between the slide members and the tracks. These detents act as mediators that provide temporary holding positions for the slide members, preventing unintended movement of the upper sash while allowing controlled operation of the lower sash, thus achieving position stability without requiring a completely separate restraint system.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If resilient detents are added to restrain the upper sash, then sash position stability is improved, but device complexity increases

Engineering Contradiction:

Improveupper sash position controlVSAvoidtrack and slide member structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The resilient detents are designed to automatically engage and disengage based on the operational state of the slide member. When the lower sash is operated, the detents self-adjust to maintain the upper sash in its position without requiring additional actuators or complex control mechanisms. This self-service capability improves position control while minimizing the increase in device complexity.

Inventive Principle:

Principle #25Self-service

3Ease of operation

If separate counterbalance mechanisms are used for each sash, then independent movement control is achieved, but manufacturing cost and assembly complexity increase

Engineering Contradiction:

Improveindependent sash movementVSAvoidassembly process

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

Each counterbalance mechanism is customized to the specific requirements of its associated sash, with the first counterbalance mechanism optimized for the lower sash and the second for the upper sash. This local quality approach enables independent movement control while allowing each mechanism to be manufactured and assembled using standardized procedures, thereby managing the complexity of separate mechanisms.

Inventive Principle:

Principle #3Local quality

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

Enables separate and independent movement of upper and lower sashes while maintaining the upper sash in place during lower sash operation, enhancing user control and reducing accidental movement.

Implementation Method 1

A first resilient detent is secured to either the first track or the second track such that the first resilient detent interacts with either the first slide member or the second slide member when the sash is in a closed position

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

A first counterbalance mechanism is disposed proximate the first side member and a second counterbalance mechanism is disposed proximate the second side member

Methodology Applied

Scientific EffectCounterbalance: Balance

Data Source

PatentUS9650822B2Fenestration unit with sash retention

Publication Date: 2017.05.16 PELLA CORP

AI summary

A fenestration unit, such as a window, having an upper sash and a lower sash can be configured to permit separate and independent movement of the upper sash and the lower sash when desired, while restraining the upper sash from movement caused by movement of the lower sash. A fenestration unit having a single movable sash can also be configured to provide securement of the single movable sash against undesired vertical movement.