Firestop Collar Locking Strip for Intumescent Expansion Loads
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Solution Overview
Problem
Existing firestop collars with thin sheet metal casings are not suitable for larger diameter applications as they cannot withstand radial expansion forces when intumescent material swells during a fire, leading to a weak connection between the end portions.
Innovation Solution
A firestop collar design with a sheet metal strip connected on one end to the casing, allowing it to flex and interlock securely, using a hook member to catch behind the strip, providing a sturdy connection even with thicker sheet metal casings, and incorporating resilient or spring steel for flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin sheet metal is used for the casing to allow bending of detent tabs, then the casing can be formed with resilient connections, but the casing cannot withstand radial expansion forces when intumescent material swells
Solution Approach 1:
The connection mechanism is segmented into a strip portion and a detent tab portion, where the strip is connected to the casing at one end only. This segmentation allows the strip to flex independently to accommodate the locking member while the detent tab provides the resilient connection. The strip can be made of thicker material for strength without compromising the flexibility needed for assembly.
Solution Approach 2:
The resilient function is extracted from the main casing body and concentrated in the detent tab portion, while the strip portion focuses on providing a stable anchoring surface for the locking member. This separation allows the detent tab to be made of thinner resilient material while the strip can be made of thicker, stronger material.
2Strength
If thick sheet metal is used for the casing to withstand radial expansion forces, then the connection strength is improved, but the sheet metal cannot be bent to form resilient detent tabs
Solution Approach 1:
The connection structure is divided into functional segments: the strip portion (connected at one end) handles the mechanical anchoring function with thicker material for strength, while the detent tab portion handles the resilient connection function with thinner material that can be bent. This segmentation resolves the contradiction between needing thick material for strength and thin material for flexibility.
Solution Approach 2:
Different parts of the connection mechanism have different local qualities: the strip portion has higher thickness and stiffness for providing a stable engagement surface, while the detent tab has lower thickness and higher flexibility for resilient connection. This local differentiation allows each part to be optimized for its specific function.
3Ease of operation
If thin walled casing is used to allow detent tab deflection, then the casing can be assembled with flexible connections, but the connection is not sturdy enough for larger diameter applications
Solution Approach 1:
The connection system is segmented into a flexible detent tab portion for ease of assembly and a sturdy strip portion for reliable engagement. The strip is connected to the casing at one end only, creating a lever arm that provides mechanical advantage and sturdiness without requiring the entire casing to be thick-walled.
Solution Approach 2:
The connection mechanism transitions from a two-dimensional planar connection to a three-dimensional structure where the strip extends perpendicular to the casing surface. This dimensional change creates a lever arm effect that amplifies the connection strength without increasing the casing wall thickness.
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 design ensures a strong and flexible connection that maintains the intumescent material within the collar, effectively preventing fire and smoke spread by focusing radial pressure on the pipe, even during swelling, and can be made from thicker sheet metal for enhanced durability.
Implementation Method 1
the sheet metal strip has one free end and one end integrally connected to the casing by a flexible connection portion, wherein the locking member comprises a hook member adapted to hook behind a rear end edge of the sheet metal strip
Implementation Method 2
the intumescent material swells in case of a fire
Implementation Method 3
when the intumescent material swells in case of a fire
Data Source
AI summary
A firestop collar is arranged around a duct at a passage through a partition. The firestop collar includes an outer casing of sheet metal and an inner lining of intumescent material. The outer casing has a first end portion and a second end portion adapted to be mutually connected so as to maintain the firestop collar in a closed position around a duct. A locking member is formed integrally with the casing at the first end portion and a catch member is integrally formed with the casing at the second end portion. The catch member includes a sheet metal strip extending spaced apart from the outer surface of the casing to define a slot between the catch member and the outer surface of the casing.