Texas Instruments Corporation

Youn H Ting

Mitchell R Rowlette

Walter H Bailey

Werner Strasser

Ronald E Garnett

Leo Marcoux

Vicki V Ruszczyk

John Doherty, Jr

Richard H Carlson

John A Haug

John T Hancock

Tim H McMains

David Pierre Vieau

Bryan C Jansen

Stanley F Kummer

Ronald W Brown

Richard T Gordon

A gas fired furnace system (10) has a controller (14) controlling the supply of gas through a gas valve (12) and air for combustion by means of an induced air draft fan (28), ignition of the gas by means of ignitor (22), the delivery of heated air from a heat exchanger (20) by means of an air blower (34) in response to signals from a thermostat (42). A selected constant flow of air for combustion is provided by controlling the speed of the motor driving the induced motor fan (28) despite changes which may occur in back pressure. Induced draft fan motor parameters proportional to motor torque and motor speed are read on an ongoing basis and inputted to controller (14) which computes a desired voltage and compares that with referenced data stored in the controller memory and makes corrections to the speed of the induced draft fan motor to maintain the constant air flow. The motor speed and motor torque are also monitored to ensure that they are within selected limits indicative of safe operation and responsive to this input energization of a relay (KM1) is controlled to deenergize the gas valve and ignition.

Method for controlling an induced draft fan for use with gas furnaces

Induced draft fan control for use with gas furnaces

An electric switch is shown which is responsive separately to two different conditions, i.e. temperature and pressure. The switch includes a temperature sensing disc and a pressure sensing disc both coupled through several alternate motion transfer arrangements to the movable electrical contact of the switch. Several structures are shown for mounting a switch on a surface so that the pressure sensing disc is exposed to fluid pressure and the temperature sensing disc is thermally coupled to the surface.

Dual condition responsive switch apparatus

Differentially connected capacitive sensors are mechanically coupled with the flexible capacitor plate of one sensor coupled to the source of pressure to be measured, the flexible capacitor plate of the other sensor coupled to ambient pressure. In a second embodiment, inaccuracies due to forces on the flexible plate are minimized by providing a housing with a tapered inner wall, an O-ring and a support to apply a radial load to the sensor due to clamping action from the tapered housing against the O-ring to provide a seal for the pressure sensing chamber. In a further embodiment, the cost of fabrication of the pressure transducer is minimized by providing the housing as a one piece cup. The electronics are mounted on the exterior surface of the low pressure side of the ceramic capacitor pressure sensing element and sealed in thereat by potting with an epoxy. In addition, an electrical pin connector from the electronics and a vent to the low pressure surface of the movable plate are secured in the potting material and extend externally thereof. In a further embodiment, pressures applied to the movable diaphragm of the pressure sensing element by the gasket are eliminated by providing a ceramic capacitor having a movable diaphragm element having smaller length and width dimensions than the fixed capacitor substrate. The gasket is positioned around the movable diaphragm element and on the fixed capacitor plate with the housing being stepped to apply a force against the gasket but remain out of contact with the movable diaphragm element.

Low pressure sensor

A housing has a switch chamber in which an electric switch is placed and a recess in which is received a snap acting, thermally responsive disc which actuates and deactuates the switch upon snapping from one configuration to another. A thermal biasing assembly used to modify the operating temperature of the disc has a pair of cylindrical film type resistors electrically connected in parallel circuit relation and physically connected to a pair of rivets. Resistors of a rating chosen for a particular application are dropped into the recess with the leads of the resistors received in bores provided in the housing. A rivet is then inserted into each bore making good electrical connection with the leads without welding by deforming them a selected amount. The rivets are attached to suitable terminals and the disc is then placed over the thermal biasing assembly to provide a multiple temperature operating thermostat.

Thermostatic electric switch and thermal biasing assembly therefor

A housing has a switch chamber in which an electric switch is placed and a recess in which is received a snap acting, thermally responsive disc which actuates and deactuates the switch upon snapping from one configuration to another. A drop in thermal biasing assembly used to modify the operating temperature of the disc has a pair of cylindrical film type resistors electrically connected in parallel circuit relation and physically connected to a pair of connectors. An assembly having resistors of a rating chosen for a particular application is dropped into the recess before the disc is assembled, the connectors sliding into matching bores formed in the housing. The connectors are attached to suitable teminals and the disc is then placed over the thermal biasing assembly to provide a multiple temperature operating thermostat.

A housing has a switch chamber in which an electric switch is placed and a recess in which is received a snap acting, thermally responsive disc which actuates and deactuates the switch upon snapping from one configuration to another. A drop in thermal biasing assembly used to modify the operating temperature of the disc has a pair of cylindrical film type resistors electrically connected in parallel circuit relation and physically connected to a pair of connectors. An assembly having resistors of a rating chosen for a particular application is dropped into the recess before the disc is assembled, the connectors sliding into matching bores formed in the housing. The connectors are attached to suitable terminals and the disc is then placed over the thermal biasing assembly to provide a multiple temperature operating thermostat.

A heater system for a diesel fuel filter comprises a housing, a self-regulating electrical resistance heater element of positive temperature coefficient of resistivity arranged in heat-transfer relation to thermally conducting components to form a heater means, the heater means being mounted within the housing so that diesel fuel passes directly over and around the various thermally conducting components of the heater means to elevate the temperature of the fuel as it passes to the filter to deter clogging of the filter by paraffin or other fuel components which may solidify in the fuel at lower temperatures, and electrically conducting means which extend from the housing in sealed relation to the housing for electrically connecting the heater means to a source of electrical power.

Diesel fuel filter system

A sealed pressure-responsive switch is manually resettable and trip-free. The switch has a separate snap-acting, bistable, dished metal disc or disc element disposed between a sealed snap-acting pressure-responsive diaphragm and a spring-biased switch arm. The disc moves to an inverted dished configuration with snap action to move the switch arm to a trip position against the arm bias when the diaphragm moves in response to application of a selected fluid pressure. The disc remains in its inverted shape to releasably hold the arm in tripped position until the switch is manually reset even when the diaphragm returns to its original position after removal of the selected fluid pressure from the diaphragm. A push button or push button means is selectively movable to apply a force to the disc sufficient to restore the disc to its original disc configuration after the fluid pressure is removed from the diaphragm, thereby to permit the switch arm to reset in response to its spring bias and provide trip-free manual reset switch operation.

Pressure responsive switch

A control for modulating the duty cycle of diesel engine glow plugs has two heat sensitive, normally closed switches each thermally coupled to a respective positive temperature coefficient (PTC) of resistivity heater in turn thermally coupled to a common heat sink. The heat sensitive switches are serially connected to each other, to an ignition switch and to a glow plug relay. The PTC heaters are connected to a point between the heat sensitive switches and the relay and to ground. A third PTC heater is disposed on the heat sink intermediate the first and second heaters and thermally coupled to the heat sink. The third heater is connected to an alternator and serves to cut off power to the glow plugs after a selected after glow stage. The two heat sensitive switches can be selected to open at approximately the same temperature for a random operating mode or at slightly different temperatures for a sequential operating mode. The random operating mode is a redundant high reliability operating mode whereas the sequential operating mode, using slightly different temperatures allows one switch to control the cycling and the second to be a back up safety control. In one preferred embodiment a 'wait' lamp is connected between the ignition switch a double pole relay used to latch the lamp in the deenergized state when the first 'off' time of the heat sensitive switches occurs. In a second embodiment the 'wait' lamp is connected between the alternator and the coil of the glow plug relay with a diode serially connected to the lamp to preclude alternator current from energizing the lamp.

Glow plug duty cycle modulating apparatus

A fuel filter system for a diesel engine has filter means mounted in a housing so that diesel fuel flows through the filter as it passes to the engine and has self-regulating electrical resistance heater means mounted in the housing so that, particularly when the engine is started at low ambient temperatures, the fuel flows directly over the contacts, terminals and heater elements of the heater means for elevating the temperature of the fuel as it passes through the filter without risk of over heating the fuel, thereby to safely deter clogging of the filter by paraffin or other fuel components which may solidify in the fuel at relatively low engine starting temperatures.

A thermally actuated valve assembly comprising a housing having a passage extending therethrough with the passage having an inlet, an outlet and a valve seat therebetween. A thermostatic dish-shaped bimetallic disk constituting a valve member is positioned in the passage and is abruptly movable over center from a first curvature position in which the outer periphery of the disk is in engagement with the valve seat thereby to block communication through the passage and a second curvature position in which the disk is clear of the valve seat to permit the flow of fluid therepast. The disk is movable from its first to its second curvature position upon being subjected to a first temperature and is returnable from its second to its first curvature position upon being subjected to a second temperature. A spring member biases the disk toward the valve seat and holds the disk in sealing engagement therewith when the disk is in its first curvature position. The housing includes an abutment engageable by the center portion of the disk as the disk moves over center from its first to its second curvature position thereby to insure that the periphery of the disk moves clear of the valve seat.

Thermally actuated valve

A food warmer comprising a heat transfer plate with a flat portion and a flange of thermally and electrically conductive material to which at least one pill of positive temperature coefficient of resistance material is conductively secured and an electrically insulative base with a trough for receiving the rolled edge of the heat transfer plate. The pill is provided with an electrically conductive coating on its two opposite faces. An electrically conductive spring is mounted in the base adapted to make contact with one surface of the electrically conductive coating of the pill. Electrical connection is made to the heat transfer plate and to the spring to provide a current path through the pill upon positioning and sealing the rolled edge with a silicon rubber sealing compound thereby providing proper contact force and alignment between the spring and the conductive coating of the pill along with a water tight seal.

Food warming device

A valve assembly with a water dispersing and spreading system preferrable for use in drip-type beverage maker comprising a housing having a passage extending therethrough with the passage having an inlet, an outlet, and a valve seat therebetween. A thermostatic dish-shaped snap-acting bimetallic disk constitutes the valve member and is positioned in the passage in engagement with the valve seat thereby to block communication through the passage while in the first curvature position and while in the second curvature position to move clear of the valve seat to permit the flow of fluid therepast. The disk is movable from the first curvature position to the second and back again upon changes in temperature of the disk. A spring member biases the disk toward the valve seat in sealing engagement when the disk is in its first curvature position. An abutment in the housing engageable by the center portion of the disk as the disk moves to its second position insures that the periphery of the disk moves clear of the valve seat. In communication with the outlet passage, a plurality of outwardly curved channels are formed in the housing with a dispersing disk centrally blocking the outlet and thereby forcing the flow of fluid through the channels in a radially outward direction.

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Lexington, KY, United States of America

Youn H Ting