Latching means for sensing apparatus

Claim 1

A sensing apparatus comprising: a sensor device including a housing member defining a chamber, an electrically conductive tip member for being exposed to a fluid, said tip member secured to said housing and forming a closure for said chamber to prevent fluid entrance into said chamber, an electrical and heat conductive member within said chamber having a greater heat transfer capability than said tip member, an electrically resistive heater means within said chamber having first and second spaced apart electrically conductive portions, said first portion in heat conductive relationship to said electrical and heat conductive member, said second portion in heat conductive relationship to said electrically conductive tip member, and first and second electrically conductive heat responsive means having substantially similar characteristics of thermal deflection and in heat conductive relationship to said first and second spaced apart portions, respectively, and each having a free end for mutual engagement only when the temperature difference between said first and second spaced apart portions exceeds a predetermined level, said difference resulting from a difference in rates of heat transfer of said heat conductive member and said tip member; and means for sensing when said heat responsive means are engaged including an electrical circuit having a source of electrical potential operatively connected to said heat responsive means and a current indicating means for indicating electrical current in the circuit when said heat responsive means are engaged, said electrical circuit further including a latching means for providing a steady electrical signal from said sensor device to said current indicating means.