Temperature monitoring device containing at least one element of an alloy which memorizes its shape

Claim 1

A temperature monitoring device, comprising: a casing of a generally rectangular shape provided with two elongate chambers at right angels to one another and leading one into the other; a motor element in said casing and comprising a spring received in a first of said chambers and composed of a shape-memorizing alloy, an end of said spring bearing against a bottom of said first chamber; a movement transmission element operatively coupled with said motor element and including a piston against which another end of said spring bears, and a rod projecting from said piston and having an end closing an end of a second of said chambers when said spring is in a relaxed position; and indicator means acted upon by said transmission element for irreversibly recording each overstepping of a predetermined temperature, said indicator means including balls received in said second chamber under a pressure urging said balls resiliently toward an opening of said second chamber communicating with said first chamber, said balls being adapted to be transferred to a part of said first chamber not containing said spring upon movement of said rod, said casing being formed with a transparent window over a portion thereof corresponding to said part of said first chamber to enable the presence of balls in said part to be ascertained.