Abstract: An electric radiant heater unit of the kind used in glass ceramic top cookers comprises first and second heater elements disposed adjacent to each other on a base layer of thermal and electrical insulating material, the arrangement being such that, in use, the heat emitted by the second heater element augments the heat emitted by the first heater element. A peripheral wall of thermal insulating material surrounds the heater elements and a thermal cut-out device extends over both of the heater elements. There is also provided means such as a block of thermal insulating material or a heat sink for shielding the thermal cut-out device in the regions thereof which pass over the second heater element from heat emitted by both the first and second heater elements.

Abstract: An electric radiant heater unit for a glass ceramic top cooker comprises two independently energizable heater elements supported on a base of electrical and thermal insulation material. A thermal cut-out device, which may be of the differential expansion type, extends from a peripheral wall of the unit across one element and across a zone normally occupied by at least a part of the other element. However, that zone of the heater unit heated by said one element is extended to influence substantially the entire effective length of the cut-out device, that is including that portion of the cut-out device which extends across the zone normally occupied by at least a part of the other element.

Abstract: A snap acting switch structure for thermostats or the like is disclosed in which the switch's movable contact is supported on a pair of arms the first of which is placed in compression and the second of which is placed in tension by a bistable spring system. The first arm is formed of relatively thin metal providing deep flanges to cause the arm to act as a rigid beam pivoted at one end. The two arms are welded together in face-to-face adjacency and the actuating force applied to the switch is applied substantially at the joint between the arms. Therefore, there are no substantial bending forces applied to the first arm, and the switch efficiently produces good wiping between the contacts and sufficient shear forces to break welds which may occur therebetween.

Abstract: A glass ceramic hob electric cooker is provided on each of the radiant heaters thereof with a temperature responsive element such as a bi-metallic switch or a thermistor, which element is arranged adjacent to or within an opening which communicates with an enclosed chamber formed between the heater and the underside of the glass ceramic cooking surface. When the heating element of the heater is energized, hot air issues from the opening and impinges on the temperature responsive element thus heating said element. A warning lamp is connected with the temperature responsive element to indicate when said element and thus the glass ceramic cooking surface is at or above a safe touching temperature of 50.degree. to 60.degree. C.

Abstract: The invention relates to electric heater units for "smooth top" cookers which employ two or more heater elements in the same unit. It is directed particularly at the problem of monitoring the temperature of the unit and/or the "smooth top" thereover to protect against overheating. It is known to use a thermal cut-out device extending over the heater unit where a single element is used, but design problems develop when two or more elements are employed in the same unit, of which at least one element is independently energizable. According to the invention an elongate thermal cut-out device (10) extends across said one element (10) but is thermally isolated from the other element or elements. Thus, the device operates only in response to the one element.

Abstract: A glass ceramic cooking appliance having at least two separately switchable or combined switchable heating elements has a thermal cutout preventing overheating of the glass ceramic surface. A single temperature sensor acts on the thermal cutout and the sensor is subject to the influence of all the heating means elements. To ensure that the operating temperature of the glass ceramic hotplate is as close as possible to the permitted permanent operating temperature, the cutout operating temperature is detuned as a function of the nature and number of heating elements switched on in order to compensate for different thermal influences.The temperature sensor can be an expansion sensor acting on a plurality of switches with different operating temperatures. Upon operating the heating elements a different switch is connected in series in each case to the individual heating elements.

Abstract: A reusable thermally actuated linkage arrangement includes a first link member having a longitudinal bore therein adapted to receive at least a portion of a second link member therein, the first and second members being sized to effect an interference fit preventing relative movement therebetween at a temperature below a predetermined temperature. The link members have different coefficients of thermal expansion so that when the linkage is selectively heated to a temperature above the predetermined temperature, relative longitudinal and/or rotational movement between the first and second link members is enabled. Two embodiments of a thermally activated linkage are disclosed which find particular application as actuators for a grapple head positioning arm in a nuclear reactor fuel handling mechanism to facilitate back-up safety retraction of the grapple head independently from the primary fuel handling mechanism drive system.

Abstract: A thermal cut-out for gas-heated glass ceramic cooking surfaces has a temperature sensor extending from a switch housing which contains a snap switch. The sensor consists of a tube with a rod therein, the tube and at least one portion of the length of the rod having differing coefficients of thermal expansion. The temperature sensor is surrounded by an enveloping tube which is at a distance from the temperature sensor.

Abstract: A thermal element having a tubular casing with an open end, a volume of heat-responsive, expandable wax positioned in said casing at a distance from the open end thereof, a spherical resilient seal member compressively positioned in the casing adjacent said wax, a motion-transmitting pin extended between the seal member and the open end of the casing and having a relatively soft washer affixed thereto for engagement against the seal member and with at least one peripheral notch in the washer permitting flow of liquid thereacross.

Abstract: A probe-type thermostat is disclosed in which the probe is mounted for swiveling movement in a manner in which the thermostat calibration is not adversely affected. The probe includes a tube mounted on the thermostat base for swiveling movement about a first center and a rod connected to the thermostat operator or movable member for swiveling movement about a second center. The base and the movable member are each formed with spherical seats which are opened through lateral openings to an edge so that the probe assembly can be moved along the lateral openings to the assembled position.

Abstract: There is disclosed a thermally responsive actuator useful for solenoids of electromagnetic valves and the like that includes a thermally responsive assembly of first and second metallic members that function as a thermocouple to generate an electrical voltage and also as a bimetallic operator for a switch carried within a housing of the device and operative to make and break the thermocouple circuit.

Abstract: A sensor which utilizes the difference in thermal characteristic between two fluids to detect the presence of one fluid or the other. A continuously heated thermal expansion element activates a switch. When the element is brought in thermally conductive contact with a liquid, the heated element drops in temperature, shortening the length of the expansion element and activating the switch.

Abstract: A differential expansion rod and tube thermostat wherein the material of the inner rod has a much lower coefficient of thermal expansion than does the material of the outer tube. The thermostat is adapted to be mounted through an opening in the wall of an oven cooking cavity. A certain amount of the tube remains outside the oven cooking cavity. The inner rod is adapted to lie within the oven cooking cavity. Joined to the inner rod is an extension strap of a material having a high linear coefficient of thermal expansion substantially the same as that of the outer tube. The longitudinal motion created by the difference in the rates of expansion between the outer tube and the combined inner rod and extension strap is transferred by a hinged amplifier lever to a switch mechanism which is calibrated to operate at a predetermined oven temperature.

Abstract: A rod and tube thermosensing device adapted for high temperature use has a first rod member comprising a rod of refractory metal having a metal cladding thereon which protects the refractory metal against excessive oxidation and which cooperates with the rod of refractory metal in providing the first member with a relatively low effective coefficient of thermal expansion. This first rod member is coaxially disposed in a tube of a metal of relatively higher coefficient of thermal expansion and has one end of the rod member secured to a corresponding end of the tube, whereby the opposite ends of the first rod member and tube are free to move relative to each as an indication of the temperature to which the device is subjected.