Abstract: An immersible heater for an aquarium includes a waterproof, heat-resisting, flat plastic case which is tripartitioned in its interior, one chamber holding a flat coil carrier bonded or welded to the case; an upper chamber contains a leaf spring actuated by a bimetallic element; these chambers are separated by a thermally isolating chamber. The bias of the bimetallic actuator is adjusted by a sealed feedthrough screw. Current flow through the heating coil is indicated by a lamp covered with a thinner wall portion of the case. The front of the case carries heat-dissipating and -stiffening ribs; the rear of the case carries suction cups.

Abstract: An aquarium heater includes a tubular glass housing provided with a temperature control circuit in the upper part thereof for switching on and off a heating element disposed in the lower part of the housing and comprising an elongated non-metallic support tube on which a helical resistance heating wire is wound. A temperature responsive bimetallic breaker switch enclosed in a metallic housing is coupled within a feed line to the heating wire and is located in the interior of the support tube slightly below the upper end thereof and extends within a number of turns of the heating wire, with length of the breaker switch representing a small fraction of the length of the support tube.

Abstract: A temperature control device for use with an aquarium heater, including a control housing, a first contact fastened to the control housing, a second contact responsive to the temperature responsive movement of a bimetallic strip maintained at the control housing and movable between a closed position wherein the second contact abuts the first contact and an open position wherein the second contact is separated from the first contact, a plate spring, the second contact fastened at the free end of the plate spring and with the plate spring mounted on the control housing and movable through an unstable intermediate position between a first stable position wherein the contacts lie abuting one another and a second stable position wherein the contacts are separated from one another, and the plate spring abuting a stop on the control housing and with the bimetallic strip abuting the plate spring and moving the plate spring in response to temperature changes between the first and second positions.