Fire Extinguisher Nozzle Thread Geometry for Low-Temperature Impact Resistance
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Solution Overview
Problem
Handheld fire extinguishers face performance compromise due to nozzle brittleness at low temperatures, leading to potential damage from impacts, as existing designs fail to maintain functionality across a wide range of temperatures.
Innovation Solution
A valve body and nozzle assembly featuring a metallic valve body and a non-metallic nozzle with a unique threaded connection and interference fit, utilizing a root portion with radii and projections to enhance durability and prevent damage from impacts, where the nozzle is made of high-strength nylon and the valve body is metallic, ensuring a secure and strong connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the nozzle is made of polymeric material to reduce weight and simplify manufacturing, then ease of manufacture is improved, but the nozzle becomes brittle at low temperatures resulting in reduced reliability
Solution Approach 1:
The patent modifies the geometric parameters of the threaded connection by adding a root portion with specific radii of curvature between adjacent thread rows. This parameter change reduces stress concentrations in the polymeric nozzle material, preventing brittle failure at low temperatures while maintaining the ease of manufacturing polymer components.
Solution Approach 2:
The patent introduces curved radii at the root portion of the threads instead of sharp corners. This curvature distributes stress more evenly throughout the polymeric material, eliminating stress concentration points that would cause brittleness at low temperatures, while still allowing the nozzle to be manufactured as a single polymer component.
2Ease of manufacture
If the threaded connection is made with standard sharp-cornered threads to simplify manufacturing, then ease of manufacture is improved, but stress concentrations occur resulting in reduced strength
Solution Approach 1:
The patent replaces sharp corners at the thread root with curved radii, which eliminates stress concentration points. This curvature allows the threaded connection to be manufactured with standard processes while significantly improving the strength and resistance to brittle failure of the polymeric nozzle, particularly at low temperatures.
3Ease of operation
If the connection between valve body and nozzle is made loose to facilitate assembly, then ease of operation is improved, but the connection becomes insufficient to withstand impacts resulting in reduced reliability
Solution Approach 1:
The patent incorporates a root portion with radii of curvature that acts as a stress-absorbing feature before impacts occur. This design cushions the polymeric nozzle against impact forces by distributing and reducing stress concentrations, allowing the connection to remain relatively loose for easy assembly while still withstanding impacts reliably.
Data Source
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AI summary
A valve body and nozzle assembly for a fire extinguisher includes a valve body (32) that includes a nozzle connection (58) that has a valve body threaded portion (60). A non-metallic nozzle (30) includes a proximal end (30a) that has a valve body connection (34) with a nozzle threaded portion (38) in engagement with the valve body threaded portion (60). The nozzle threaded portion (38) includes a root portion (72) that has at least one radius of curvature (R) extending between adjacent rows of a thread (70) of the nozzle threaded portion (38).