Wax-Motor Fire Sprinkler Layout to Prevent Unintended Valve Closure
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Solution Overview
Problem
Conventional fire sprinklers with wax motor actuators require complex and expensive designs to prevent water from cooling the wax motor, leading to unintended valve closure during water sprinkling.
Innovation Solution
A fire sprinkler design that positions the wax motor orthogonally to the water flow, using a sealing actuator and a shroud to direct water away from the wax motor, allowing the wax motor to be actuated by ambient temperature, and utilizing water supply pressure to seal the actuator when temperature falls below a threshold, eliminating the need for return springs and mechanical linkages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the wax motor is positioned orthogonally to water flow, then the design complexity is reduced, but water may cool the wax motor causing unintended valve closure
Solution Approach 1:
The patent extracts the wax motor from the water flow path by positioning it orthogonally, separating the actuation function from the water flow to eliminate the need for complex return springs and linkages
Solution Approach 2:
The patent introduces a shroud as an intermediary component that directs water away from the wax motor, preventing thermal interference while maintaining the simplified orthogonal configuration
2Reliability
If the wax motor is positioned parallel to water flow, then water cooling effect is minimized, but complex mechanisms such as return springs and mechanical linkages are required
Solution Approach 1:
The patent transitions from a parallel (one-dimensional) arrangement to an orthogonal (two-dimensional) arrangement, positioning the wax motor perpendicular to the water flow to eliminate the need for complex return mechanisms
3Reliability
If the actuator is sealed against the passage, then water-tight sealing is achieved, but water pressure must overcome sealing force to actuate the valve
Solution Approach 1:
The patent replaces complex mechanical sealing and actuation mechanisms with a thermally-actuated system where the wax motor's thermal expansion directly overcomes the sealing force, simplifying the force transmission mechanism
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
Simplifies the design and reduces costs by ensuring reliable actuation and sealing of the sprinkler without complex mechanisms, maintaining water flow efficiency and preventing unintended cooling of the wax motor.
Implementation Method 1
A wax motor is a linear actuator device that converts thermal energy into mechanical energy by exploiting the phase-change behavior of waxes and other inorganic materials
Implementation Method 2
During melting, wax typically expands in volume by 5% to 20%
Implementation Method 3
the pressure from the water supply tends to move the actuator in a second direction opposite to the first direction to seal the first end of the actuator and the first end of the passage
Data Source
AI summary
A fire sprinkler including: a body connected to a water supply and having a passage, the passage having a sealing material or a sealing surface at a first end; an actuator disposed in the passage, the actuator and passage configuring a water-tight seal; a water spreader configured to direct water radially outward; and a wax motor actuated by an ambient temperature greater than a predetermined threshold temperature such that actuation of the wax motor exerts an actuation force on the second end of the actuator to move the actuator to a seal between the water supply and the water spreader; wherein the actuator is arranged such that the pressure from the water supply tends to move the actuator to stop water flow when the ambient temperature falls below the predetermined threshold temperature.