Wax thermostatic elements
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The wax thermostatic element was invented by Sergius Vernet (USA) in 1936.[1]
The principal application of the wax element technology is for the production of automotive thermostats. The first applications of this technology in the plumbing and heating industries were in Sweden (1970) and in Switzerland (1971).
Wax thermostatic elements permit the transforming of thermal energy into mechanical energy. Their working principle is based on the large increase in the thermal expansion of waxes when they pass from the solid to the liquid state. The range of application includes but is not limited to the automotive industry, military and civil aviation, domestic heating, plumbing, industrial, fire, and agriculture.
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[edit] Types of elements
[edit] Flat diaphragm element
The temperature sensing material contained in the cup transfers pressure to the piston by means of the diaphragm and the plug, held tightly in position by the guide. On cooling, the initial position of the piston is obtained by means of a return spring. Flat diaphragm elements are particularly noted for their high level of accuracy, and therefore mainly used in sanitary installations and heating.
[edit] Squeeze-push elements
Squeeze-Push elements contain a synthetic rubber sleeve-like component shaped like the 'finger of a glove' which surrounds the piston. As the temperature increases, pressure from the expansion of the thermostatic material moves the piston with a lateral squeeze and a vertical push. As with the flat diaphragm element, the piston returns to its initial position by means of a return spring. These elements are slightly less accurate but provide a more powerful stroke.
[edit] Piston stroke
The strokes is the movement of the piston in relation to its starting point. The ideal stroke corresponds to the temperature range of the elements. According to the type of element, it can vary from 1.5 mm to 16 mm.
[edit] Temperature range
The temperature range lies between the minimum and maximum operating temperature of the element. Elements can cover temperatures ranging from -15°C to +120°C.
The temperature curve represents the movement of the piston in relation to the temperature. It can be a continuous or broken line. The angle varies according to the composition of the waxes.
[edit] Hysteresis
Hysteresis is the difference noted between the upstroke and down stroke curve (i.e. heating and cooling of the element). Hysteresis is caused by the thermal inertia of the element and by the friction between the parts in motion.
[edit] References
- ^ Refer to patent US2115501 US patent office
[edit] External links
- Vernet.fr - Themostatic Elements Cartridges Thermostats Electrothermic Actuator
- Raymot.com - Wax thermostatic elements page
- Ysnews.com - Vernet founded leading Yellow Springs company
