Abstract: A float switch for sensing a liquid level and switching between "on" and "off" states in response to the same. Overall, the device is carried within a hollow housing, with its movement restrained by the tethering action of a power cord. "Snap action" switching is achieved by the interaction between an actuator having camming surfaces formed on its exterior, and a spring-loaded switch mechanism. The switch mechanism includes a thin, flexible E-shaped snap member, having two legs bowed to form a leaf spring and having a bearing point located on the central leg. The actuator is carried in a tube within the housing and the switch mechanism is positioned adjacent the actuator's path of travel, so that a camming surface of the actuator can make contact with the bearing point. As the water level rises, an increasing proportion of the actuator's weight is carried by the bearing point, until the vertical component of the actuator weight exceeds the spring resistance of the snap member.

Abstract: A timer manager for use in a network control system of one node of a connectionless communication network provides message receipt reliability. The network control system includes a buffer pool for storing messages to be transmitted from the one node and a data link stage for receiving the buffer pool storage address of a message to be transmitted and causing the message to be accessed and transmitted onto the bus. The timer manager is coupled to the buffer pool and to the data link stage and includes a table including a plurality of entry slots for storing the buffer pool storage address of a message to be transmitted with an associated timer entry index.

Abstract: An output torque sensing and limiting mechanism, for preventing the continued application of torque to a load when the torque exceeds a selected value. The mechanism is positioned at the end of a gear train, meshed with the final gear and adapted to transmit the output torque to the load, through an output adapter. An input gear assembly includes a sector gear, meshed with the gear train, for receiving the input torque. A housing assembly is rotationally carried on the input gear assembly, with wing members extending to define a wing angle. The sector gear lies in the wing angle, with vertical gear ends adjacent each wing member. A torque sensor subassembly is carried in each wing member, consisting of a bearing button positioned in registration with the sector gear end, biased into position by a wave spring and adjustable by means of a retainer button. Microswitches are carried on the sector gear, located with the switch elements extending into the gap between the sector gear and each wing member.

Abstract: A network control system controls the receipt and transmission of messages at one node of a communication network which includes a plurality of nodes coupled together on a bi-directional bus. Both short messages having a length less than a predetermined number of bytes and long messages having a length greater than the predetermined number of bytes may be conveyed between nodes. The network control system incudes a connectionless network control portion for controlling the receipt and transmission of the short messages and a connection-oriented network control portion for controlling the receipt and transmission of the long messages including establishing a connection between its node and another node before a long message is transmitted.

Abstract: A network control system of one node of a communication network includes a data link stage and a session stage which provide a priority protocol. The network control system includes a storage and the data link stage stores received messages in the storage. When the number of stored messages reaches a predetermined limit, the data link stage limits the receipt of messages to priority messages. The session stage is arranged such that if it and a session stage of another node simultaneously initiate a session service, a connection is established, the session stage having a higher priority completes its session first, and the connection is maintained to permit the lower priority session stage to complete its session.

Abstract: The present invention provides a cable extension linear position transducer which according to one aspect of the invention, has an integrated support structure including a base and a housing. A potentiometer is attached to the housing and includes a shaft which extends into the housing. A drum is affixed to the shaft and to a spring which is connected to the housing. As the drum is turned, the spring is wound tighter to provide the retraction torgue necessary to return the drum to its initial position.

Abstract: The present invention relates to hollow elements prepared from alloys having shape memory characteristics and techniques for heating the elements to effect the martensite (or R-phase) to austenite transformation. In its most preferred embodiment, the invention relates to the use of shape memory alloys to prepare hollow springs or tubular beams, bending and torsional, and the preferred methods of heating the elements include passing an insulated resistance heating wire through the core thereof and applying a current, or applying two layers of coating to the inside or outside of the tube, one of which is insulating and the other of which is electrically conductive. In the latter example, application of current to the conductive coating will heat the element. It is also envisioned that hot fluid may be passed through the element as the heating technique.

Abstract: A network control system for use in a communication network controls the receipt and transmission of messages between at least a pair of nodes of the network. Messages conveyed within the network include short messages having a length less than a predetermined number of bytes and long messages having a length greater than the predetermined number of bytes. The network control system is located at least at one of the nodes and includes a connectionless network control portion for controlling the transmission and receipt of the short messages and a connection-oriented network control portion coupled to the connectionless network control portion for establishing a connection with the other node for controlling the transmission and receipt of the long messages between the pair of nodes.

Abstract: A fume hood controller utilizing feed forward and closed loop control to maintain a constant average face velocity of air entering the fume hood. A sash position sensor provides the controller with a signal indicative of the area of the fume hood opening. An air flow sensor provides the controller with a signal indicative of flow rate. Fast response to a change in sash position is provided by feed forward control which adjusts an air valve or fan to provide a constant face velocity. After initial adjustment by the feed forward control, closed loop control is operable to fine tune the air valve or fan to provide highly accurate control of face velocity. Emergency control is also provided to drive the air flow to a maximum rate when an emergency exhaust button located on the fume hood is pressed.

Abstract: A temperature control system and method for maintaining the temperature of air within an air pressure controlled enclosure at a desired temperature. The system uses an energy flow model to determine the temperature to which the air supplied to the enclosure must be heated to attain the desired temperature within the enclosure. The energy flow model determines the desired supply air temperature based on the temperature and flow rate of the supply air, the current temperature of the air in the enclosure, the heat transfer rate within the enclosure, and the temperature and flow rate of make-up air entering the enclosure.

Abstract: There is disclosed a control system for use, for example, in facility management which controls an environmental parameter to maintain the parameter at a given set point. A PID Controller is coupled to a remote sensor for generating a feedback signal responsive to the parameter level sensed by the remote sensor. The PID Controller is responsive to being coupled to a field device for providing the field device with an automatic control signal having a level derived from the sum of integral, derivative, and proportional actions to the feedback or error signal to place the field device under automatic control, and is responsive to being decoupled from the field device when the field device is under manual control for either terminating the generation of the automatic control signal or providing an estimate of a manual control signal.

Abstract: A positioner for use in pneumatic systems moves a pneumatic operator. The positioner is an electronic pilot positioner or electronic to pneumatic interface which provides accurate positioning of linear actuators in response to an electronic control signal. The actuator is moved as pneumatic fluid is exhausted or supplied through the exhaust valve and supply valve. The positioner utilizes two solenoids for controlling a supply valve and an exhaust valve. The positioner includes a control circuit which receives a signal from a central controller and a signal from a feedback circuit. The control circuit compares the feedback signal and the controller signal and generates a signal for positioning the actuator.

Abstract: A capacitance humidity sensor according to the invention has a film core which is in contact with a pair of polymeric conductive layers bonded to opposite faces of the core. The core is made of a polymeric material having a dielectric constant which varies substantially linearly with humidity, such as a polyimide or polyparabanic acid. The conductive layers are made of a polymeric material, at least a portion of which includes sulfur atoms in the backbone chain and having conductive particles, such as carbon particles, dispersed therein. Such conductive layers provide superior performance and corrosion resistance in comparison to the metal films employed in the prior art and in comparison to cellulosic polymers containing conductive particles.

Abstract: A pivotal electrical connector for connecting a shape memory alloy element in the form of a coil spring to a fixed member, the connector including a strip of electrically conductive material having a clip or a pair of legs for securing the connector to one of the coils of the element. A pair of holes may be provided in the strip through which the coil is threaded. A rotational connector is provided in the strip for engaging the fixed member.

Abstract: The sensor according to the present invention provides a device for measuring the magnitude of an applied load as a shift in resonant frequency of a mechanical resonator caused by load-induced strains on the resonator. The sensor includes a substrate, generally constructed of a semiconductor material, e.g. silicon, a diaphragm substantially supported along its outer periphery by the substrate, a boss abutting a region of the diaphragm remote from the outer periphery of the diaphragm, at least one resonator in the form of a beam having one end integral to the diaphragm proximate the region of the boss and the other end integral to the diaphragm remote from the boss, a hermetic seal for enclosing the resonator, and an exciter/detector for measuring changes in the natural frequency of the resonator due to an applied load. Preferably, the sensor includes a differential resonator configuration in which the resonators are positioned rectilinearly with respect to each other and are covered by the same hermetic seal.

Abstract: Pressure vessel components of a sensing element are formed from liquid crystal polymers. Individual LCP components may be ultrasonically adhered to one another to form a hermetic seal. In the preferred embodiment, a metal tube is hermetically sealed to a pressure vessel cup by molding an LCP resin around a cleaned and heated tube to form a hermetic seal. Also in the preferred embodiment, the sensing element includes a single convolution diaphragm formed under heat and pressure using a polyimide film.

Abstract: A network control unit for monitoring and controlling all of the operational components of a facility management system, the unit including a modular base frame having a wiring board assembly mounted on the back, a number of termination board assemblies mounted on the front of the frame and being operably connected to the wiring board assembly, one or more function modules, digital control modules, expansion modules, and a network control module are mounted on the front of the frame and operably connected to the wiring board assembly.

Abstract: An improved control system utilizing infrared communication channels for remote station control is provided. A central base controller communicates with one or more channels of sub-networks through one or more field interface controllers. Each field interface controller utilizes a dedicated base infrared transceiver for transmitting envelopes of definable duration at a preselected infrared oscillation frequency. At least one remote station receives said transmitted infrared signals at an infrared transceiver tuned to said oscillation frequency. Associated devices at the remote station decode the information from said infrared transmission or issue instructions and information to an associated input/output device. Communication over the infrared channel between the base and the remote stations utilizes a unique pulse position protocol. An initiating clear pulse begins all communications. The remote station responds to the time-location of ensuing pulses following the initiating pulse.

Abstract: A pressure switch according to the invention combines a pressure chamber with diaphragm, plunger, spring-loaded switch mechanism and electrical contacts in a single compact assembly. According to one aspect of the invention, the terminal board of the pump motor is incorporated into the control switch housing, eliminating the need for wiring from the switch to the terminal board and enabling the switch to be mounted inside the wiring compartment of the motor. According to another aspect of the invention, a pair of opposing blades are used in the switch mechanism to eliminate side forces and decrease friction, improving accuracy and life of the switch. A simple set screw may be used with one of the switch blades, in cooperation with a stop associated with the other blade, to adjust the spring force and thereby control the pressure control differential.

Abstract: This invention relates to a pneumatic control device having an operating mode selecting means for operating in either the manual or automatic modes. Pneumatic pressure is regulated in the manual mode by a hand operated leakport, and in the automatic mode by a voice coil or other pressure regulating device. The pneumatic input supply, manual pressure regulating means and voice coil all communicate at a common surface. The mode selecting means slides across this common surface to connect together the pneumatic input supply with one of the selected pressure regulating means.