Counterweighted Backdraft Damper Blade for Airflow and Sealing Balance
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Solution Overview
Problem
Backdraft dampers in HVAC systems face challenges in maintaining airflow efficiency while preventing backdrafts, as the bias towards the closed position under gravity reduces airflow in the outflow direction and can lead to leakage or inadequate thermal protection.
Innovation Solution
A heavy-duty backdraft damper with counterweighted blades and a bull-nosed profile, featuring a crank arm linkage and static heads to balance airflow, allowing easy opening with low force and ensuring closure under gravity, thereby maintaining airflow efficiency and preventing backdrafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blades are biased to the closed position by gravity, then the backdraft prevention is improved, but the airflow in the outflow direction is reduced
Solution Approach 1:
The patent applies a counterweight mechanism to balance the gravitational force on the damper blades. The counterweight is positioned to create a moment that opposes the gravitational moment, allowing the blades to remain balanced or slightly biased toward the closed position without requiring excessive force to open. This resolves the contradiction by maintaining backdraft prevention while minimizing airflow resistance.
2Ease of operation
If the blades are balanced about their pivot rods, then the force required to open them is reduced, but inadvertent leakage in the backdraft direction occurs
Solution Approach 1:
The patent implements different quality characteristics at different locations of the blade system. The blades are designed with specific geometric profiles and surface characteristics at the sealing edges to maintain tight closure, while the pivot mechanism incorporates friction elements or detents that provide sufficient resistance to prevent inadvertent opening. This local differentiation allows easy intentional opening while maintaining reliable sealing.
3Reliability
If the blades are biased strongly to the closed position, then the thermal protection is improved, but the pressure loss in the outflow direction increases
Solution Approach 1:
The patent employs a dynamic biasing mechanism where the force acting on the blades changes with their position. Spring elements or counterweights are configured to provide stronger restoring force when the blades are partially open, ensuring thermal protection, but this force decreases as the blades approach the fully open position, minimizing pressure loss during normal operation. The system dynamically adjusts the biasing force based on the blade angle.
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 solution ensures minimal pressure loss during airflow while effectively preventing backdrafts, maintaining thermal protection and safety by balancing blade movement and reducing friction, thus optimizing airflow distribution and safety.
Implementation Method 1
The blade is counterweighted, balancing the blade so that it readily pivots to the open position under the influence of an airflow in the output direction, and pivots to the closed position under the influence of gravity when the airflow ceases.
Implementation Method 2
the leading edge of the blade has a bull nosed profile, which helps to un-restrict air flow across the blade profile
Implementation Method 3
the downstream portion of the blade has a trough-like feature designed to capture the air flow by creating a static head in the trough, which enables the blade to smooth out the air flow
Data Source
AI summary
A backdraft damper for permitting a flow of air in an outflow direction and preventing the flow of air in a backdraft direction has a frame provided with a transverse opening allowing the passage of air through the frame. One or more blades extend across the frame and are mounted to the frame about a central portion by pivot members, for rotation between open and closed positions. Each blade comprises a blade body having a leading portion upstream of the central portion, the leading portion of the blade body comprising a channel, a trailing portion downstream of the central portion, the trailing portion of the blade having a larger surface area than the leading portion and comprising a seal disposed adjacent to a distal edge of the trailing portion, for sealing against either the leading portion of an adjacent blade or a blade stop projecting from the frame, and a counterweight disposed in the channel, whereby the counterweight balances the blade such that the blade is biased to the closed position by gravity and movable to the open position by the force of air flowing through the frame in the outflow direction.