Patent ID: 8480299
Filing Date: 2013-07-09
Classification: G01K

Abstract:
1. A multi-stage temperature indicating device comprising: an elongate housing having a longitudinally extending bore formed therein having a closed end and an open end, said housing having a first neck region spaced from said closed end of said bore, a first internal cavity between said first neck region and said closed end of said bore, a second internal cavity between said first neck region and said open end; an indicator rod comprising a first stem stretch and a second stem stretch; an extension segment comprising a first extension stretch and a second extension stretch, the second extension stretch slidably cooperating with the first stem stretch; the indicator rod and the extension segment slidably positioned in said bore, the second stem stretch extending at least partially out of the housing; a spring urging said indicator rod upwardly through said open end of said bore; and a fusible material retaining said indicator rod and said extension segment in said housing, said fusible material being in solid form under normal conditions to retain said indicator rod in said housing and softening at an elevated temperature to release said indicator rod for upward movement relative to said housing, wherein a first portion of said fusible material retains said indicator rod in said housing and a second portion of said fusible material retains said extension segment in said housing, whereby the softening of the first portion of the fusible material allows the spring to urge the indicator rod a first distance out of the housing indicating that a first temperature has been reached and the softening of the second portion of the fusible material allows the spring to urge the indicator rod a second distance out of the housing indicating that a second temperature has been reached.