Thermal Cut-Out Arrangement For An Electric Water Heater
Patent No. US4358665 (titled "Thermal Cut-Out Arrangement For An Electric Water Heater") was filed by IMI Santon on Jun 9, 1980. The application was issued on Nov 9, 1982.
What is this patent about?
'665 is related to the field of instantaneous electrical water heaters, specifically addressing safety and efficiency concerns. These heaters rapidly heat water as it flows through a small container, but can overheat dangerously if the water flow stops while the heating element remains energized. Prior solutions using thermal cut-outs to prevent overheating suffered from nuisance tripping or insufficient responsiveness.
The underlying idea behind '665 is to improve heat transfer from the heating element to the water and to the thermal cut-out, thereby preventing both overheating and nuisance tripping. This is achieved by a specific heating element geometry that includes a helical portion for efficient water heating and a U-shaped portion positioned close to the container's end face for direct thermal contact.
The claims of '665 focus on an electrical heating element for a water heating container that includes a helical portion and a U-shaped portion extending in a plane parallel to the principal axis of the helix. The closed part of the U-shaped portion is arranged to lie closely adjacent to or in contact with a face of the container extending in a plane perpendicular to the principal axis of the helix.
In practice, the helical portion of the element heats the water as it flows through the container. The U-shaped portion, with its linear segment brazed to the container's end face, provides a direct thermal path to a thermal cut-out mounted on the outside of the container. This arrangement ensures rapid heat transfer to the cut-out, enabling it to quickly disconnect the power supply if overheating occurs. Furthermore, directing the cold water inlet flow towards the U-shaped portion helps to prevent localized hot spots and nuisance tripping.
This design differentiates itself from prior approaches by optimizing the element's geometry for both heating efficiency and safety. The close proximity of the U-shaped portion to the container wall and the thermal cut-out ensures rapid response to temperature increases. The directed water flow further stabilizes the temperature distribution within the container, reducing the likelihood of false triggers. This combination of features provides a more reliable and safer instantaneous water heater.
How does this patent fit in bigger picture?
Technical Landscape
In the late 1970s when '665 was filed, instantaneous water heaters were gaining popularity for domestic applications at a time when safety and efficiency were primary concerns. At that time, thermal cut-out devices were commonly used to prevent overheating, but their implementation could lead to operational issues such as nuisance tripping, especially with high-wattage heating elements. The challenge was to balance rapid response to prevent container rupture with reliable operation under normal usage conditions.
Prosecution Position
The disclosed invention addresses the problem of balancing safety and reliability in instantaneous water heaters. It achieves this by integrating a heating element with a specific geometry (a helical portion with a U-shaped extension) and a container designed to position the U-shaped portion in close proximity to the container's end face. This architectural shift enables more efficient heat transfer to the container wall, allowing for more effective temperature sensing and control, and reducing the risk of both overheating and nuisance tripping.
Claims
This patent contains zero claims, so there are no independent or dependent claims to analyze.
Patent Family
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Date
Description
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US4358665
- Application Number
- US15784080
- Filing Date
- Jun 9, 1980
- Publication Date
- Nov 9, 1982
- External Links
- Slate, USPTO, Google Patents