Composite-type heat-system fire sensing device

A composite heat-system fire sensing device including differential and constant temperature sensing elements comprising in combination:

• an open-mouthed generally bowl-shaped heat-receiving member having a bottom wall;
• a diaphragm positioned across the open mouth of said heat-receiving member and forming a heat-receiving chamber therewith, venting means being provided for venting said chamber to the atmosphere;
• a reversible bimetallic element positioned within said chamber adjacent the bottom wall thereof and adapted to reverse shape at a predetermined temperature from a normally concave configuration to a convex configuration;
• a pair of electrical contact members mounted in predetermined adjustably spaced relation on one side of said diaphragm remote from said reversible bimetallic element and adapted to be connected to an electrical circuit of an alarm device;
• a push rod member mounted within said chamber having one end thereof adjacent said reversible bimetallic element in the normally concave configuration thereof, said push rod member being shiftable by said reversible bimetal element upon reversal of the shape thereof so as to engage with one side of said diaphragm to displace said diaphragm a distance sufficient to engage with one of said electrical contact members to thereby urge said one electrical contact member into engagement with the other of said electrical contact members;
• a gaseous medium being provided within said chamber adapted, upon expansion thereof due to a rise in temperature in excess of a predetermined rate, to displace said diaphragm a distance sufficient to engage with said one of said electrical contact members to thereby urge said one electrical contact member into engagement with the other of said electrical contact members;
• said reversible bimetallic element being so dimensioned that the maximum displacement distant thereof from the concave to the convex configurations is greater than the displacement distance of said diaphragm during a predetermined standard period of time;
• and means for adjusting the spacing between said electrical contact members to thereby regulate the sensitivity of the device.