Abstract: An apparatus for remote inspection of fire extinguishers at one or a system of fire extinguisher stations includes, e.g., at each fire extinguisher station: a detector for lack of presence of a fire extinguisher in its installed position at the fire extinguisher station; a detector for out-of-range pressure of contents of the fire extinguisher at the fire extinguisher station; a detector for an obstruction to viewing of or access to the fire extinguisher at the fire extinguisher station; and a device for communication of inspection report information by wireless signal between the fire extinguisher station and a remote central station.

Abstract: An apparatus for use in a multi-purpose piping system that provides water to both domestic uses and to fire sprinklers, the apparatus comprising: piping having an inlet and an outlet; a detector, located between the inlet and outlet, that distinguishes between a fire sprinkler water flow and a domestic use water flow; and a drain connection located between the inlet and the outlet. A multipurpose piping system using the apparatus in a system incorporating at least one fire sprinkler, the piping system also supplying at least one other use in the structure.

Abstract: A system for verifying fuel cap engagement utilizes a transducer coupled to a purge line of a fuel vapor recovery system to generate an electrical signal corresponding to one of the vapor pressure and the vapor flow rate in the purge line. A monitor receives the electrical signal and estimates the vapor pressure when the electrical signal corresponds to the vapor flow rate. The monitor likewise estimates the vapor flow rate when the electrical signal corresponds to the vapor pressure. The monitor also correlates the electrical signal and the estimate to generate a dataset relating vapor pressures to corresponding vapor flow rates at predetermined time intervals, computes a linear approximation of pressure versus flow rate, and computes a curve approximation of pressure versus flow rate. An indicator is actuated by the monitor when the difference between the computed linear and curve approximations is less than a predetermined threshold value.

Abstract: A pressure sensing device, such as a tire pressure monitoring unit comprises a pressure sensor for measuring pressure of a fluid, such as air or an inert gas, in an environment external to the device, such as within the cavity of a tire. A hollow resonator, or standing wave tube, is coupled to the pressure sensor. The resonator has a free end exposed to the external environment to the extent that pressure variations in the fluid are propagated through the hollow resonator to the pressure sensor via the free end. The hollow resonator has a resonant frequency substantially matching a target frequency such that resonance is established in the tube at the resonant frequency in response to the presence of an audio signal in the fluid having a frequency that substantially matches the target frequency.

Abstract: A warning device for a gas cylinder, it is provided on a gas pressure gauge at least with a dial, a needle pointer and a pointer switch; the pressure gauge is connected to an electric power supply and a warning unit; when the amount of the combustion gas is reduced, the needle pointer activates the pointer switch to turn on the warning unit, thus the warning unit emits a warning to remind a user to change the gas cylinder because of exhaustion of combustion gas, thus the bothersome work of inspecting the remaining gas amount by looking at a gas pressure gauge time after time can be saved, and an effect of convenience of using can be provided.

Abstract: A system for distinguishing between a fire sprinkler water flow and a domestic use water flow by supplying water to a dwelling through a multipurpose piping system to at least one domestic use and at least one fire sprinkler and providing a means for distinguishing between the fire sprinkler and domestic flow.

Abstract: A digital signal representative of a difference in pressure is received from a differential pressure transmitter. A noise signal is obtained by processing the signal through a band pass filter or otherwise to provide a filtered noise signal. Absolute values of the filtered noise signal are calculated and compared to one or more predetermined threshold values to determine if one or more impulse lines are plugged. A training mode is used to determine the thresholds, which may be a function of flow rate and other flow conditions.

Abstract: A method for estimating actuator position includes the steps of receiving fluid pressure data signals from a plurality of fluid pressure sensors (31), receiving spool position signals from at least one spool position sensor (33), and receiving actuator position data signals from at least one actuator position sensor (35). Corrected flow rates to and from an actuator (21) are determined with each corrected flow rate being based on fluid pressure data signals, the spool position signals, and an error-correction factor, wherein the error-correction factor is a function of the fluid pressure data signals and the spool position signals. An estimated actuator position is determined wherein the estimated position includes a kinematic component and a dynamic component. Adaptive gain factors are applied to calibrate the estimated actuator position to the actuator position data signals from the actuator position sensor.

Abstract: A gear pump for the dosed conveyance of pigmented lacquers or paints and which is adapted for use with a painting robot. The gear pump comprises two toothed wheels meshing with one another and which are mounted within a pump housing in such a manner that they can be rotated by a driven drive shaft and a fixed bearing shaft. For this, the drive shaft is mounted by a bearing section at multiple points in a pump housing and a coupling section of the drive shaft projects out of the pump drive to connect to a drive. In order, on the one hand, to avoid wear due to high pressure forces and, on the other hand, to absorb a pronounced load from the outside, a supporting bearing for the radial and axial support of the drive shaft is formed on the drive shaft's coupling section projecting outside of the pump housing.

Abstract: An internal pressure explosion-proof system is provided that is capable of detecting high-pressure abnormality of an internal pressure explosion-proof mechanism, urging a check of gas/air apparatus by providing a means for notifying a user of abnormality, and decreasing excessive pressure of an internal pressure chamber. A high-pressure abnormality detector and a pressure regulating valve are provided in an air discharging portion for releasing the gas/air discharged from the internal pressure explosion-proof mechanism. The working pressure of the high-pressure abnormality detector is set to be lower than the working pressure of the pressure regulating valve. The high-pressure abnormality detector sends a signal when the pressure becomes higher than the set pressure to make the alarm give a warning and makes the open valves open to decrease the pressure of the internal pressure chamber of the internal pressure explosion-proof mechanism which became excessive.

Abstract: It is known that determination of bleed valve activation in a gas turbine engine can be difficult unless the engine is maintained at a steady idle state for comparison between that state and effects of activation of the bleed valve. Furthermore, specific test activation of bleed valves increases wear and tear on those valves. By sensing a flow pressure response signal and then through appropriate averaging and processing through a non-linear filter, it is possible to identify bleed valve activation by a target signal response exceeding a threshold indicative of such bleed valve activation.

Abstract: A bottoming indication system indicates contact between an inner wall of a fluid conducting conduit and a tip of a differential pressure measuring probe. The system includes a piezoelectric device and an indicator. The piezoelectric device is affixed to the tip of the differential pressure measuring probe so that pressure exerted on the piezoelectric device by contact between the piezoelectric device and the inner wall of the conduit produces a voltage difference across the piezoelectric device. The indicator is in electrical communication with the piezoelectric device so that a voltage difference across the piezoelectric device activates the indicator to indicate contact between the inner wall of the conduit and the tip of the differential pressure measuring probe.

Abstract: An information transmission system comprising a conductor operable to carry a desired information signal. A first tube substantially surrounds the conductor and a second tube substantially surrounds the first tube to define a substantially fluid-tight chamber therebetween. In another aspect, the invention provides an information transmission system suited to transmit information between a first electronic device and a second electronic device located a distance from the first electronic device. The system includes an information transmission line that connects to the first electronic device and the second electronic device. A conduit surrounds at least a portion of the information transmission line. The conduit defines a substantially fluid-tight chamber. A quantity of fluid is disposed within the chamber and a sensor is positioned to measure a parameter of the quantity of fluid. An indicator is operable to signal a breach condition in response to the measured parameter.

Abstract: A pressure detector for detecting a high side pressure from a high pressure side impulse line and a low side pressure from a low pressure side impulse line includes a high side pressure variance calculating section for calculating a high side pressure variance from a high side pressure fluctuation calculated from a high side pressure signal, a low side pressure variance calculating section for calculating a low side pressure variance from a low side pressure fluctuation calculated from a low side pressure signal, a rate calculating section for calculating a variable according to a ratio of the high side pressure variance to the low side pressure variance, and a determining section for determining blockage of the high pressure side impulse line or blockage of the low pressure side impulse line based on a value of the variable.

Abstract: An apparatus for measuring at least one parameter associated with a fluid flowing within a pipe includes a spatial array of pressure sensors disposed at different axial locations x1. . . xN along the pipe. Each of the pressure sensors provides a pressure signal P(t) indicative of unsteady pressure within the pipe at a corresponding axial location of the pipe. A signal processor receives the pressure signals from each of the pressure sensors and determines the parameter of the fluid using pressure signals from selected ones of the pressure sensors. By selecting different pressure sensors, the signal processor can configure the array to meet different criteria. In one embodiment, the array of pressure sensors may be formed on a single sheet of polyvinylidene fluoride (PVDF) that is wrapped around at least a portion of an outer surface of the pipe. This arrangement allows a large number of pressure sensors to be quickly and economically installed.

Abstract: A vehicle steering wheel lock with a burglar-proof alarm device comprises a burglar-proof alarm circuit, A wireless signal detecting unit, an air pressure detecting unit; supersonic detecting unit for detecting movements of objects; an infrared receiver for receiving infrared signals from the portable alarm device. The wireless wave emitting unit includes a receiving antennal circuit, a high frequency amplifier, a band pass filter, a local oscillating circuit, a mixing circuit, a middle frequency circuit, and a second middle frequency IC; the receiving antenna circuit being for adjusting the harmonic receiving frequency for receiving high frequency signal, which is then passed through the high frequency amplifier, band pass filter, local oscillating circuit, and the mixing circuit; the local oscillator circuit having a baseband oscillating circuit, a nine-time amplifier circuit, a nine-time frequency modulating circuit for generating an oscillating frequency signal to the mixing circuit.

Abstract: A flow sensor having an inlet and an outlet comprising: a plate moving in response to fluid flow therethrough, being displaced further as flow increases; a sensor for determining moving plate's position and creating an electronic signal related thereto; a biasing device for biasing the plate towards the sensor's inlet end. The sensor may include a sealing device for preventing flow therethrough until a specified differential pressure is reached allowing the device to be used as a bypass mechanism. The sealing device may also constitute a check valve device to prevent flow in an undesired direction. The method using the sensor in multipurpose piping systems includes use of the apparatus in a system incorporating at least one fire sprinkler, the piping system also preferably providing at least one other use in the structure. The other use in the structure may be supplying domestic needs, or supplying heating/cooling water for a heating/air conditioning system.

Abstract: An apparatus for remote inspection of fire extinguishers at one or a system of fire extinguisher stations includes, e.g., at each fire extinguisher station: a detector for lack of presence of a fire extinguisher in its installed position at the fire extinguisher station; a detector for out-of-range pressure of contents of the fire extinguisher at the fire extinguisher station; a detector for an obstruction to viewing of or access to the fire extinguisher at the fire extinguisher station; and a device for communication of inspection report information by wireless signal between the fire extinguisher station and a remote central station.

Abstract: Respiration monitoring equipment comprises, in one embodiment, a medical face mask (2), adapted to be located adjacent, or to cover a patient's nostrils and/or mouth; a transducer (7) adapted to be impinged by the patient's inspired and/or expired breaths, being sensitive to the presence and/or absence of a respiratory air flow, and being capable of emitting electrical signals in accordance with the presence and/or absence of a respiratory air flow; and a monitoring unit (9) electrically connected to the transducer (7) and responsive to the presence and/or absence of signals emitted by the transducer (7), and including means of triggering at least an alarm signal in the circumstances of non-detection of respiratory air flow within one or more predetermined parameters. Another embodiment provides for “cordless” monitoring, with a transmitter unit (11) at the face mask (2) and a receiver (12) at the monitoring unit (9).

Abstract: An alarm for a hydraulic system, a hydraulic system incorporating an alarm, a vehicle having a hydraulic system which incorporates an alarm, and a method of giving an alarm in a hydraulic system, where the hydraulic system comprises hydraulic fluid which is put in contact with a pressure detector, the pressure detector being for giving a signal in response to a condition of the hydraulic fluid in the hydraulic system. An alarm generator integral with said pressure detector is provided for giving an audible alarm in response to a said signal.

Abstract: A method of providing an indication of the position of a valve member of a valve in a fluid path where the valve member is moveable between a fully open position in which a maximum flow of fluid past the valve member is permitted and a closed position in which fluid flow past the valve member is at least substantially prevented, the method including sensing the fluid pressure in the fluid path upstream of the valve member to provide a first signal to a controller, sensing fluid pressure in the fluid path downstream of the valve member to provide a second signal to the controller, and sensing fluid flow downstream of the valve member to provide a third signal to the controller, the controller comparing the first and second signals and applying the third signal, and depending on the comparison of the first and second signals and the third signal, the controller signalling an alerting device which indicates whether the valve member is in at least one of an open and closed position.

Abstract: A system that includes a container containing a fluid, a fluid line coupled with the container, and a pump configured to pump the fluid out of the container through the fluid line. The system further includes a sensor that includes a wireless transmitter. The sensor is configured to sense the pressure in the fluid line and to periodically transmit, using the wireless transmitter, an alarm message when the pressure reaches an alarm threshold.

Abstract: A medical gas alarm system for use in a healthcare facility having a medical gas system and having a network of computer devices is provided. The alarm system includes at least one area alarm controller adapted to receive a first signal indicative of a condition of a first portion of the medical gas system. The area alarm controller is adapted to communicate with the network. The alarm system also includes at least one master alarm controller adapted to receive a second signal indicative of a condition of a second portion of the medical gas system. The master alarm controller is adapted to communicate with the network. The area alarm controller is adapted to communicate with the master alarm controller through the network.

Abstract: A system for monitoring air pressure in a telecommunications network comprises a plurality of monitoring units, at least one device server, a computer network, and a terminal. Each monitoring unit is connected to a device server. A user at the terminal receives air pressure data from the monitoring units over the computer network.

Abstract: A flow sensor having an inlet and an outlet comprising: a plate moving in response to fluid flow therethrough, being displaced further as flow increases; a sensor for determining moving plate's position and creating an electronic signal related thereto; a biasing means for biasing the plate towards the sensor's inlet end. The sensor may include a sealing means for preventing flow therethrough until a specified differential pressure is reached allowing the device to be used as a bypass mechanism. The sealing means may also constitute a check valve means to prevent flow in an undesired direction.

Abstract: A system and method are provided for detecting leaks between a door and a primary seal of a vehicle. The system includes a mist generator that generates a mist and an illuminating device for illuminating any condensed mist on at least one of the primary seal or the door. The generator includes an output nozzle that is inserted at a predetermined distance from the door and the primary seal.

Abstract: A system and method for monitoring a pressure relief device are provided. The system includes a release sensor that provides an indication when the pressure relief device activates. A wireless transmitter is connected to the release sensor and sends a wireless transmission having an activation signal when the indication is provided by the release sensor. A receiver receives the wireless transmission from the transmitter and generates a warning when the activation signal is identified.

Abstract: An apparatus for dosing lubricant into a compressed air flow includes a lubricant container, a pneumatically operated lubricant pump, an injection channel, a non-return valve interposed between the outlet of the pump and the injection channel, and an electronic sensor cooperating with or coupled to the non-return valve so that the sensor emits an electrical signal responsive and corresponding to the stroke travel of the non-return valve. When the pump carries out a lubricant injection cycle, the pressurized lubricant pushes open the non-return valve, flows into the injection channel and from there into a main channel through which compressed air flows. The travel of the valve is sensed by the sensor, and the sensor signal indicates whether the lubricant injection was proper or faulty, e.g. if the proper amount of lubricant was injected.

Abstract: A system for monitoring air pressure in a telecommunications network comprises a plurality of monitoring units, at least one device server, a computer network, and a terminal. Each monitoring unit is connected to a device server. A user at the terminal receives air pressure data from the monitoring units over the computer network.

Abstract: Child safety seats with alarms notify the driver of a vehicle that an infant is in its carrier inside of the vehicle when a door is opened. Forgetting a child inside of the vehicle can result in severe injury to or the death of the child from extreme temperature conditions and/or dehydration. Child safety seats with alarms not only protect the child in the event of accident, but also detect the opening of a vehicle door and remind the driver of the presence of the child through visual and audio alerts. The detector and alarm system are automatically engaged when the buckle of the child safety seat is closed. The condition of the batteries powering the detector and alarm system are also monitored so that the user can be confident that the detector and alarm system have adequate power to function. A pressure transducer is employed as a detector to sense the changing air pressure caused by the opening or closure of a vehicle door.

Abstract: There is provided a failure diagnostic system for an atmospheric pressure detecting device, which is capable of rationally determining whether that device has failed or not and is capable of improving the diagnostic accuracy. The failure diagnostic system is comprised of an atmospheric pressure sensor for detecting an atmospheric pressure of the air taken into an engine; a condition determination section for determining that conditions required for determining that the atmospheric pressure sensor has failed are satisfied if the number of operations, in each of which the engine continuously operates for a predetermined period of time, has exceeded a predetermined number; and a failure diagnosis section for determining that the atmospheric pressure sensor has failed if a variation in the atmospheric pressure over a period of time equivalent to that predetermined number is equal to or less than a predetermined value and the required conditions have been satisfied.

Abstract: A system for monitoring air pressure in a telecommunications network comprises a plurality of monitoring units, at least one device server, a computer network, and a terminal. Each monitoring unit is connected to a device server. A user at the terminal receives air pressure data from the monitoring units over the computer network.

Abstract: The present invention is directed to an apparatus, system and method for detecting a user's oral health habits and providing the oral health data over a network for access by a remote user. For example, the user may utilize an oral health apparatus to brush his teeth. During brushing, oral health data may be obtained relating to the user's oral health habits and usage of the oral health apparatus. The oral health data may then be provided over a network to a remote user, such as the user's dental health professional or parent in the case of a young child.

Abstract: A system for monitoring a structure includes cavities on an outer surface and a fluid source at substantially constant pressure coupled to the cavities through high fluid impedances to create pressure differentials therebetween. A telemetry system has pressure differential switches across each of the high impedances for monitoring differential pressure changes across the impedances and providing a signal indicative of the location of the cavity associated with the high impedance across which the change is monitored. A fluid capacitance is associated with each cavity and the corresponding impedances to facilitate a transient fluid flow through the impedances.

Abstract: A high-diagnostic, dual sensor pressure switch having a one-out-of-two voting architecture useful in commercial and industrial fluid transport systems is provided for determining whether process connections and isolation valves are plugged or closed, and whether pressure sensors are deformed, corroded or otherwise compromised. The dual pressure sensors functionally employ similar electronic technology, and are each disposed to provide variable electrical outputs to one of a plurality of discrete A/D converters. The dual pressure sensors' electrical outputs are compared prior to the A/D conversion process in order to immediately identify large pressure deviations between the sensors. Each of the A/D converters' digital signals are routed to one of a plurality of independent CPUs or data processors; the CPUs then generate digital output signals representing either a logical 0 (Low) or 1 (High).

Abstract: A system for monitoring air pressure in a telecommunications network comprises a plurality of monitoring units, at least one device server, a computer network, and a terminal. Each monitoring unit is connected to a device server. A user at the terminal receives air pressure data from the monitoring units over the computer network.

Abstract: A controller controls a physical variable such as temperature of a controlled system. A variable calculator calculates and output a manipulated variable on the controlled system based on of a target value such as a target temperature and a feedback value such as the measured temperature of the controlled system. A dead-time compensator provides a dead-time compensated output using a model simulating the controlled system having a dead time and an idealized model having no dead time, based on the manipulated variable outputted from the variable calculator to carry out an ordinary control and a dead-time compensated control. A switch functions to select the dead-time compensated control by providing a dead-time compensated output to the variable calculator or an ordinary control providing no dead-time compensated output to the variable calculator. The dead-time compensated control is carried out at least during set point response of the controller.

Abstract: A tubing installation checking device is provided for determining proper installation of a tubing along a tube receiving channel in a peristaltic pump of the type having a tube receiving channel and a door for holding a tubing therein. The tubing installation checking device includes a pressure sensor held in the peristaltic pump positioned along the tube receiving channel downstream from the pumping mechanism for sensing pressure in the tubing and for providing a signal representing the sensed pressure. A valve is provided held in the peristaltic pump along the tube receiving channel downstream from the pressure sensor for closing the tubing when it is installed in the tube receiving channel.

Abstract: A mechanical gauge having a mechanism for setting multiple alarms within tolerance values. When such tolerance values defined by the mechanism are reached, the same mechanism activates an alarm.

Abstract: This invention relates to a monitoring, alarm and automatic adjustment system for oxygen and/or compressed air, specifically to warn users of oxygen and/or compressed air of low pressure and/or no supply and automatically adjust the flow of oxygen and/or compressed air to the optimum rate according to the actual real time monitored condition and physiological needs of the user.

Abstract: Systems and methods for remotely starting a cable pressure monitoring unit operable for monitoring the air pressure within a pressurized cable route, such as a telecommunications cable route, including a remote computer operable for generating and transmitting a command signal directing the cable pressure monitoring unit to start, an automated transfer system operable for receiving the command signal directing the cable pressure monitoring unit to start, and a computer network operable for communicating the command signal from the remote computer to the automated transfer system.

Abstract: A system and method for monitoring a pressure relief device are provided. The system includes a release sensor that provides an indication when the pressure relief device activates. A wireless transmitter is connected to the release sensor and sends a wireless transmission having an activation signal when the indication is provided by the release sensor. A receiver receives the wireless transmission from the transmitter and generates a warning when the activation signal is identified.

Abstract: A control system for use in connection with control systems on construction equipment includes an electronic control module that records pressure sensor signals of a hydraulic pressure sensor and responsively determines whether the pressure sensor has failed.

Abstract: A medical gas alarm system for use in a healthcare facility having a medical gas system and having a network of computer devices is provided. The alarm system includes at least one area alarm controller adapted to receive a first signal indicative of a condition of a first portion of the medical gas system. The area alarm controller is adapted to communicate with the network. The alarm system also includes at least one master alarm controller adapted to receive a second signal indicative of a condition of a second portion of the medical gas system. The master alarm controller is adapted to communicate with the network. The area alarm controller is adapted to communicate with the master alarm controller through the network.

Abstract: A leakage detection device is provided for a fluid supply system. The detection device includes control means which can be selectively operated to close a valve and hence prevent further supply. The device includes at least one sensor which senses the flow of fluid through the supply system. Thus the device allows detection of fluid leakage and flow rates and can prevent or limit damage caused by fluid leakage.

Abstract: A vacuum chamber (22) of a pneumatically operated servo unit (30) of a motor vehicle is subjected to vacuum by an electric suction pump (28). In order to monitor the vacuum chamber (22) and the electric suction pump (28), the invention proposes that a starting pressure in the vacuum chamber (22) be determined. In addition, after a certain time interval, an ending pressure in the vacuum chamber (22) is determined. Furthermore, the difference between the ending pressure and the starting pressure is calculated and compared to a limit value. If this difference falls below the limit value, a signal is generated, in particular a warning and/or alarm signal.

Abstract: A pressure sensor 10 has a sensor chip 14 attached in a package 13 formed with a stem 11 and a cap 12 bonded at open surface sides thereof On both sides of a diaphragm 14a of the sensor chip, pressures are applied via a measurement pressure introducing tube 11a formed in the stem and a reference pressure introducing tube 12a formed in the cap. Here, a filter 15 is arranged in the reference pressure introducing tube and response to pressure at the reference pressure side is made slow. When the sensor is arranged in a room with a door and a pressure in the room is applied via two introducing tubes, if there is an abrupt change caused by the opening/closing of the door, the pressure change is immediately introduced only at the side of measurement pressure introducing tube with fast response and the differential pressure corresponding to the pressure change is applied on the diaphragm. As the differential pressure is employed, it can be determined whether the door is opened or closed.

Abstract: The invention relates to a heavy goods vehicle, specially for the transportation of slag, comprising a loading platform for vessels containing slag, fitted with a gripper device for receiving and moving a standardized load-bearing implement which can be actuated by a hydraulic cylinder (11) and an anti-tilt device (15) for the vehicle which operates during movement of the load-bearing implement. The vehicle is also fitted with at least one hydraulic cylinder (11) with switches. Upon a given stroke of the piston, at least one switch engages a device detecting hydraulic pressure inside the cylinder on one or both sides of the piston. The pressure detection device triggers a security device, e.g. a display for the driver or an operation blocking device.

Abstract: A meteorological information system useable by aircraft pilots and others. A receiver-calculator unit receives raw meteorological data and site-specific physical data from a ground-based weather station having a signal transmitter for broadcasting signals conveying data about weather conditions at the station. The transmitted raw data signals are received by the receiver-calculator unit in the aircraft. The receiver-calculator unit may feature an input with which the operator inputs information about the physical character, such as the heading, of the runway of interest. The receiver-calculator unit processes both received raw weather data and received site-specific physical data, and/or operator-input data, to derive additional meteorological information. The raw and derived weather conditions information is displayed by the unit to be available to the aircraft pilot during landing or take-off maneuvers.

Abstract: A flow sensor having an inlet and an outlet comprising: a plate moving in response to fluid flow therethrough, being displaced further as flow increases; a sensor for determining moving plate's position and creating an electronic signal related thereto; a biasing means for biasing the plate towards the sensor's inlet end. The sensor may include a sealing means for preventing flow therethrough until a specified differential pressure is reached allowing the device to be used as a bypass mechanism. The sealing means may also constitute a check valve means to prevent flow in an undesired direction.