Abstract: A fail safe redundancy circuit for controlling a gas valve relay in a gas fired furnace or similar burner is disclosed. The status of the relay contacts is monitored and if those contacts are in the position for enabling the gas valve prior to an ignition attempt, a gate is enabled to shunt the control side of a circuit breaking device such as a fuse to overload that device causing it to kick out or open and interrupt power to the circuit thus disabling the burner. The burner combustion chamber is purged of any accumulated gas after the circuit breaker has been opened.

Abstract: A sealed enclosure is provided for electrical circuitry to be located in a moist environment, as near a spa. The enclosure includes a housing of electrical insulating material, a display overlay adhesively bonded to the housing and covering certain openings in the housing for switches and displays, and a retaining bezel over the graphic overlay. Relief porting is provided in the bezel, and preferably also through a flange in a contiguous portion of the housing for assuring that water deposited on the display overlay will be drained away and thus not degrade the seal between the overlay and the housing.

Abstract: A blower control circuit for a furnace includes a blower relay having normally-open contacts connected in the power circuit to the blower. Energization of the relay via a drive circuit serves to close the contacts and thereby operate the blower. Control of the drive circuit resulting in relay energization is effected by either a time-delay circuit which responds to a space thermostat or a safety sense circuit which responds to a high temperature limit thermostat.

Abstract: A compact linear operator is provided for a gas valve. The operator may be of modular form for operative combination with combination gas controls of existing design, as by threaded engagement with an existing threaded bore in the control. The operator is suited for directly controlling displacement of a valve or more typically, for controlling displacement of the seat for the regulating spring associated with a servo pressure regulating diaphragm/valve arrangement. The operator includes a controllably heated bimetallic actuator, and a plunger directly or indirectly driven linearly by deflection of the actuator. To enhance compactness of the operator, a displacement-amplifying lever is interposed between the actuator and the plunger. Stops are included for establishing "high fire" and "low fire" limits for the regulated gas pressure.

Abstract: A bistable electrical contactor employs a one-piece permanent magnet plunger operating in conjunction with an aligned pole piece and a pair of oppositely-wound coils to afford pulse-operated bistable operation of the associated contacts. The coils are wound in opposition to provide respective opposite electromagnetic fields, one "aiding" and one "opposing" the inherent magnetic flux of the plunger. The plunger may be spring-biased toward one of its two bistable positions, typically the one in which the plunger is most remote from the pole piece. When an appropriate coil is briefly energized, the respective "aiding" or "opposing" force is respectively added to or subtracted from the inherent magnetic force of the plunger to cause the appropriate change of state. The pole piece is structured and positioned to facilitate interaction with the plunger. An adjustable stop arrangement minimizes bounce of resiliently-mounted contacts.

Abstract: A control system for a heating appliance, such as a microwave oven, includes a display and electronic circuitry for controlling operation of the appliance and the display. One of the control operations involves the timing of an interval, such as a cooking interval. Another such operation involves the selection of a power level. The display and a memory associated with the circuitry include predetermined dedicated time intervals and/or power level values depicted thereon and stored therein, respectively. Appropriate data-entry keys allow for the selection of these time and/or power values by slewing the display and thus the memory through the dedicated values. Separate keys may be provided for respectively incrementing and decrementing time and power.

Abstract: A bistable solenoid switch has a plunger and associated movable contact adapted for controlled reciprocation by a coil and bobbin assembly to either of two stable states not requiring sustained energization of the coil. The movable contact is biased toward one of the stable states, for example, "Contacts Closed" in which a pair of stationary contacts are engged by the movable contact. The bobbin is provided with one or more radial projections extending into its core for serving a detenting function with respect to a land formed on an end face of the plunger. When the bobbin projection is engaged by the plunger land, it is prevented from displacing the movable contact into engagement with the stationary contact, and the second, or "Contacts Open", state exists. Means are also provided for translating axial displacement of the plunger into angular displacement for moving it into and out of the detented engagement with the bobbin projection.

Abstract: An electrical equipment controller is provided with a delayed turn-off capability. A thermostat is in series with a control relay. The thermostat is further in parallel with the series combination of a relay latch contact and a first positive temperature coefficient (PTC) device. A second PTC device is connected in parallel with the control relay. The arrangement of first and second PTC devices provides a predeterminable drop-out relay including compensation for ambient temperature changes.

Abstract: A display element mounting arrangement provides a pair of display holders for frictionally-engaging and supporting an elongated display element at its opposite ends. The display holders are adapted to be mounted on and frictionally secured to a support member, such as a circuit board. Each display holder includes a display-engaging portion and a support member-engaging portion. The display-engaging portion includes four walls which define a chamber into which an end of the display is inserted. Friction tabs in the chamber aid in retainedly engaging the display. The support member-engaging portion includes a leg adapted to extend through and move in a slot which extends inward from an edge of the circuit board. A foot formed on the end of the leg is so spaced from the display-engaging portion as to provide frictional engagement between it and the circuit board.

Abstract: A compact and inexpensive current sensor includes a planar coil assembly mounted, as by printing, on a substrate such as a circuit board. A closed-loop flux concentrator extends through the coil and also through the board. A conductor carrying the AC current to be sensed is positioned in proximity with the flux concentrator. The flux concentrator is of one-piece construction, having a pair of opposed leg portions in overlapping relation and fastened to the circuit board. A current-summing amplifier amplifies the low-amplitude emf provided by the coil assembly and, with further circuitry, provides an indication and/or control commensurate with the sensed current being above or below some value.

Abstract: A solenoid contactor arrangement facilitates soft contact between the movable and stationary contacts and provides for overtravel of an armature in a manner which ensures that good and consistent electrical contact is maintained between the movable and the stationary contacts. The movable contacts are carried on an axially reciprocable armature assembly and are afforded limited axial displacement relative thereto. The movable contacts are biased by a coil spring to a first position on the armature assembly in preparation for engagement with the stationary contacts. When that engagement occurs, the movable contacts stop, the spring yields, and further displacement of the armature assembly occurs until a stop on it firmly contacts and is stopped by a corresponding stop on the movable contacts. The spring is formed and positioned such that it does not dimensionally interfere with the firm contact between the movable contacts and the armature assembly.

Abstract: A thermostat mounting arrangement includes a thermostat fixedly retained by a mounting member, and the mounting member then being mounted in a panel using a "twist-in" motion. The mounting member is of one-piece metal construction having a tubular housing portion, a pair of rigid arcuate flanges at its base and, intermediate the arcuate flanges, a pair of separate resilient flange tabs. The flange tabs are spaced above the rigid arcuate flanges and include downwardly-extending detent knobs. The panel includes a notched aperture for passing the mounting member housing and the flange tabs in a certain rotative position. The flange tabs are inclined to facilitate both the rotation of the mounting member relative to the panel and its retention in the panel. The mounting member is rotated until the detent knobs on the flange tabs detentingly snap into detent holes in the panel.