Abstract: To provide positive on-off switching when a pneumatic pressure threshold is passed, a movable switching element is magnetically attracted by a moving magnet, movable under force of a pressure diaphragm subjected to the pneumatic pressure. The movable switch element itself is biassed away from the magnet by a spring which is weaker than the restoring spring counteracting the pneumatic pressure. The non-linear displacement-force characteristics of the magnet cause snap action of the movable switch element, thus providing positive switching at accurately predeterminable pressure positions.

Abstract: A latch mechanism for an apparatus having a rotatable member, a cabinet enclosing the rotatable member and an access door on the cabinet. The latch mechanism includes a first portion on the access door and a second portion on the cabinet which cooperate to lock the access door in the closed position at predetermined times in a cycle of operations. The second portion of the latch mechanism is controlled through a bimetal actuator which is heated by a low voltage current inductively generated in an auxiliary winding associated with a pump motor.

Abstract: An overflow control unit for a washing machine which interconnects the drain hose of the washing machine to a stand-pipe is provided which comprises a cylindrical plug device having a central axially extending passageway therethrough and a by-pass valve interconnecting the passageway of the cylindrical plug with the atmosphere, the by-pass valve having an open and a closed position. In one embodiment the overflow control unit is operatively connected to a pressure switch so that upon a build-up of water pressure within the stand-pipe due to the drain being obstructed the switch is activated to break the electrical circuit to the washing machine.

Abstract: A dishwasher control circuit including a single-pole, double-throw door interlock switch and a water level sensing means, which sensing means includes a single-pole, double-throw switch. The sensing means switch connects the water inlet valve control solenoid and the drain valve control under normal operating conditions, and connects in series a direct power line and the pump motor and drain solenoid during flooding conditions. The control provides continuous protection against flooding in the dishwasher.

Abstract: This invention relates to a liquid flow monitoring device which uses a probe comprising an energy transmitter spaced apart from an energy receiver such that the bridging of the gap between the transmitter and receiver by flowing liquid emits a signal.

Abstract: In apparatus for monitoring the liquid level in a tank which includes a resistance bridge supplied with d-c current having two bridge arms arranged inside the tank, one of which is electrically heated, with the output of the resistance bridge followed by a signal stage with a binary indication and by a current regulator for the heating current, and a testing arrangement for simulating a given filling level, the resistance bridge is supplied from a constant current source whose current is switched from one current value to another upon the operation of the testing device in order to preclude operating disturbances during the testing.

Abstract: A master cylinder assembly has a stamped steel reservoir and a cover in which a switch, appropriate electrical conduits, and a connector are integrally molded. A fluid level sensor float and rod are arranged to open and close the switch depending upon the level of fluid in the reservoir. A diaphragm seal is assembled to the underside of the cover and has a rod guide provided for the sensor rod. The guide also provides a suitable vent between the fluid chamber of the reservoir and the otherwise sealed space between the diaphragm and the cover. The cover has a peripheral channel receiving a peripheral mounting edge of the diaphragm so that the diaphragm also acts as a seal between the cover and the reservoir housing. The sealing action is primarily radial, between a channel wall and the reservoir housing wall, therefore not requiring the cover to be tightly clamped in place in order to compress a seal. The cover assembly is snapped into place on the reservoir housing.

Abstract: Liquid rheostat system especially a water rheostat, employing the principle wherein electrical energy may be dissipated in the form of heat, by passing the electrical current through a liquid resistor or electrolyte, and wherein the apparatus is reasonably portable, inexpensive, and economical to operate and maintain. The invention readily compensates in use for variations in respective resistivity of fresh and/or brackish waters in a test mixture whereby to provide sufficient initial resistance as well as an adequate range of control of resistance, while maintaining current density within the desired limits. In use the heat energy developed is absorbed and removed by the controllable water mixture which in operation of the rheostat system continuously flows out of the rheostat.

Abstract: A resistive fluid detecting means utilizes a probe means having three electrically conductive areas that are interconnected between a power source and an amplifier. The detecting means is particularly useful in detecting the presence or absence of water in a boiler used in a heating plant. The presence of water between two of the electrically conductive areas reduces the resistance of that path so that the amplifier responds and operates an output switch, which in turn can be used to energize a fuel burner for the boiler. If boiler scale builds up on the probe means or if the water or fluid rises too high, the electrically conductive areas shunt current away from the amplifier and allow the output switch to open.

Abstract: An electric system normally responsive to radiation over a path traversed by a body of material. An auxiliary radiation source generates a continuous signal through the portion of the circuit monitored for failure. The continuous signal opposes deenergization of the system relay during the period the material blocks normal radiation to the system and while the monitored circuit is operative.

Abstract: A liquid level control system is disclosed. The system includes at least one level sensing electrode which is fixedly mounted to a vessel and projects therein. The probe is adapted to contact a fluid within the vessel to utilize the electrical conductivity of the fluid to complete a circuit when the fluid contacts the probe. The probe is coupled between a point of reference potential and the control electrode of a single silicon controlled rectifier (SCR). The main electrodes of the SCR are serially coupled with the coil of a low-voltage A.C. relay and the secondary winding of a step-down transformer. Accordingly, the use of a relatively low secondary voltage avoids shock hazards; and, the sensitivity of the system is increased by the effective gain provided by the SCR. The use of an A.C. current in the probe avoids the galvanic corrosion which otherwise follows from D.C. current operation.

Abstract: Fluid flow control systems for lawn sprinkling flow control systems which include rain override means and continuously available rain alarm signals during rainfall. Provisions are provided to prevent valve flutter during light or intermittent rainfall by means of conventional time delay relays. A novel, simple, and economic hermetically sealed outdoor casing is provided. Use of unique remote transformer plug and cord insures consumer product safety compliance against electrical shock hazzard.

Abstract: The arrangement includes at least one upper and one lower cooperating sensor element, each comprised of a naked electrically conductive portion adjoining the corresponding portion of the other and together defining an interelectrode gap. The naked portions are exposed to precipitation. The naked conductive portion of the lower sensor element is comprised of upwardly projecting teeth having pointed ends closely adjoining the naked conductive portion of the upper sensor element. Water droplets occupying the interelectrode gap will tend not to cling to the electrically conductive portion of the lower sensor element because of the pointed configuration of the ends of the upwardly projecting teeth.

Abstract: A control circuit for a motor has an electronic RC timing circuit with a fluid pressure switch for shunting the timing circuit if the fluid pressure reaches and maintains a predetermined magnitude. The timing circuit terminates the energization of the motor when not shunted for a predetermined duration.

Abstract: The apparatus includes two temperature sensitive switching devices having substantially identical electrical characteristics and exhibiting regenerative switching at a power level which is dependent on the temperature sensed by the switching devices. Both switching devices are exposed to the same ambient temperature in a surrounding medium but only one of them is exposed to variations in the heat exchange properties of the surrounding medium. Means are provided for applying D.C. power to both switching devices at a level such as to maintain them below their switching point under preset conditions of the medium. A coupling device is interconnected between the two switching devices for inducing regenerative switching in one of the switching devices in response to unbalance in the heat dissipated by the switching devices due to variations in the heat exchange properties of the surrounding medium from the preset conditions.

Abstract: In a fuel injection controlled internal combustion engine, a magnetic trigger device provides the source of electrical timing signals for operating the injectors. A single rotating magnet has its magnetic field extended to an effective angular radiation area substantially greater than the angular radiation area of the magnet alone. A pair of magnetizable members are positioned on either side of the path of a rotating magnet for developing an enlarged magnetic field for actuating a single reed switch. The reed switch connects a source of power to a pair of signal lines wherein one line contains an inverter, whereby, the signal on one line is the complement of the signal on the other line.

Abstract: A miniature electric fluid immersion heater adapted for instantaneously heating relatively small bodies or flow increments of fluid to a predetermined temperature. The heater is particularly adaptable to be mounted immediately in advance of a hot water faucet in a home or building so as to provide a continuous flow of instantaneously heated water and thereby eliminate the standard hot water heater and the entire hot water piping system in the building. The heater comprises a small, cylindrical, thermally insulated pressure vessel having a fluid inlet and outlet as opposite ends. A series of individually actuated electrical heating elements are positioned within the vessel so as to be in intimate physical contact with the flowing fluid. The heating elements are constructed of a heavy gauge resistance element which is thinly coated with a glass or ceramic frit fused into an impervious, chemically resistant, electrically non-conductive coating having negligible thermal insulation and heat storage capabilities.

Abstract: A liquid level shutoff control for minimum level control of conductive fluids. A pair of electrodes are disposed in the liquid at the minimum level desired for the fluid. The electrodes provide a conductive path for a high frequency electrical signal and circuits energize a controlled load such as a liquid heating or mixing apparatus whenever the electrodes are in contact with the fluid. Failure of the control circuit results in shut off of the controlled load thereby providing fail-safe minimum level control.

Abstract: Apparatus for determining in-situ the moisture content of potting soil in a plant receptacle. A pair of metallic electrodes are positioned on opposite sides of a plant receptacle adjacent the interior wall thereof and at a distance from the top of the receptacle which corresponds to the normal root depth of a plant to be contained therein. Each electrode extends externally of the receptacle for electrical connection to one probe lead or terminal of a resistance meter. When a plant is potted with soil in the receptacle, the resistance measured between the terminals is related to the moisture content of the potting soil.

Abstract: A system for detecting the fluid level in an intravenous bottle wherein a disposable electrode assembly, consisting of a piece of tape having upper, middle and lower electrode strips, is adhered to the bottle and connected to sensing equipment. The upper strip is longer than the middle strip and the middle strip is longer than the lower strip, so that the capacity between the upper and middle strips (C.sub.1) is normally greater than that between the middle and lower strips (C.sub.2). The sensing equipment includes a bias capacity (C.sub.3) connected between the middle and lower strips so that C.sub.1 is less than C.sub.2 plus C.sub.3 except when the tape is on a bottle with the fluid level in the bottle above the top strip. Pulses having a gradually sloped leading edge and a steep trailing edge are fed to the centre strip.

Abstract: A capacitance type material level detector for a hopper for particulate solid materials has a support that extends through an opening in a hopper sidewall to carry a detector unit for which it provides a hood. An electrically conductive sensor member of the detector unit is protected from contact with material in the hopper by a dielectric shield, and is sealed in a chamber defined by the shield and a mounting plate. A manually slidable and rotatable paddle hangs alongside the shield where it may be swung in front of the shield to check operativeness of the detector unit; and by moving the paddle rearwardly it may be used to break accumulated material off the face of the shield.

Abstract: A control system for a motor having a required oil pressure for the safe operation thereof, the system having a time delay switch for interconnecting an electrical source to the motor to operate the same each time the time delay switch is initially activated by being placed across the power source. The time delay switch has a time delay bimetal means that is adapted to move and open the switch if the oil pressure of the motor does not reach the required value within a predetermined time period from the initial activation of the time delay switch. An oil pressure responsive switch is operatively interconnected to the time delay bimetal means and to the motor to terminate the switch opening movement of the time delay bimetal means if the oil pressure reaches the predetermined value thereof during the predetermined time period so that the motor will be continuously operated as long as the system is not manually or automatically turned off or the oil pressure does not fall below the predetermined value thereof.