Employing a shape memory alloy in a fire alarm temperature sensi

Details Employing a shape memory alloy in a fire alarm temperature sensi Employing a shape memory alloy in a fire alarm temperature sensi

1980-04-17

1982-10-26

Swann, III, Glen R.

Communications: electrical

Condition responsive indicating system

Specific condition

337140, G08B 1706, H01H 3760

Patent

active

043564780

ABSTRACT:
A fire alarm is provided with a temperature sensitive element formed of a shape memory alloy, which following cold working, upon heating to a critical temperature, typically for instance about 70.degree. C., returns to the original impressed shape and also retains this shape even after subsequent recooling. Due to the movement of the element there is triggered a self-holding alarm signal, either directly by closing contacts or indirectly. Resetting of the fire alarm can be accomplished by mechanically cold working the element, or by using two-way shape memory alloys through cooling to a lower temperature threshold which can be below room or ambient temperature. A further beneficial construction is realized by combining the arrangement with a different type of fire detection or sensing element, for instance by arranging a shape memory alloy element in a scattered radiation-smoke detector. Upon reaching a critical temperature, the shape memory alloy element moves into the radiation region, or when used in an ionization fire alarm, the shape memory alloy element screens the radioactive radiation source and reduces the ionic current. Suitable shape memory alloys are, by way of example, nickel 55/titanium 45, or nickel 45/titanium 45/copper 10.

REFERENCES:
patent: 2886804 (1959-05-01), Behrendt
patent: 2989738 (1961-06-01), Taylor
patent: 3516082 (1970-06-01), Cooper
patent: 4205293 (1980-05-01), Melton et al.

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