The thermo-bimetal is a composite material, made of 2 layers of (Fe+Ni) metal, having different expansion coefficients, and bonded together by lamination process. The obtained strip has the property to change its curvature, under temperature variation.

Interactive demonstration : here

The proper choice of bimetal type and dimensions allows to ensure, upon specific request, through an adapted forming, as well as a particular fabrication process:

• a gradual (slow deflexion) or switch (snap) movement
• a specific mechanical force
• a movement amplitude, functions of a temperature range (for slow deflexion applications)
• a snap temperature and a reset temperature (for switch applications)

• a manual or automatic reset
• important accuracy, reliability and durability

Thermal and mechanical properties of a bimetal allow it, once it’s cut and formed, to ensure on its own the function of regulation or security, or even to actuate:

• an electrical contact,
• an air or liquid intake valve,
• any mechanical system.

In order to operate, the bimetal uses:

• The natural heat, coming from the environment which this one is supposed to measure,
• Or an electrically-heated component (as thermistor) .  Such a system can replace an electromagnet, with significant advantages.

Advantages of bimetal technology:

• Simple and low cost (a simple piece of metal is used as both thermal detector and actuator or valve)
• Self-working, ecological, the bimetal generally needs no energy supply to operate
• Reliable and durable, it can operate thousands of cycles, with a very small drift of its characteristics
• Reliability test is possible at any time, without destruction (i.e electrical or thermal fuse)

The industrial applications are various – as examples:

• Domestic appliance (iron anti-drip system, door locking security system for oven or washing machine, heating device cover, fireplace insert, fridge compressor switch-off  if too long door opening …)
• Automotive (circuit breakers and thermocontacts …)
• Electromechanics (micro circuit breakers, overheating motor protection …)
• Electronics (bad component overheating detection)
• Aeronautics (Shock absorber for humanitarian supplies dropping parachutes)
• Food and Drug (Refrigerating chain control)