Abstract: A pressure measuring device is provided with a change-over valve connecting the pressure sensor either with the pressure to be measured or with a reference pressure. The change-over valve is actuated by a separate control pressure and will protect the pressure sensor from the influence of the pressure medium to be measured in the spring-loaded idle position of the valve.

Abstract: A combined fluid pressure gage and safety pressure relief device for interconnection with systems wherein excess fluid pressure will cause explosions likely to result in injury to personnel and damage to surrounding equipment. The device accurately measures fluid pressure within the system to which it is connected so long as the system pressure remains within the working range of the pressure gage. However, should the system pressure exceed the normal full scale pressure reading on the gage, the device will instantly and automatically safely vent the system to atmosphere. Once the device is vented the pressure relief mechanism must be manually reset by skilled technicians using special tools before the apparatus can be reused.

Abstract: A method and apparatus for testing pressure applied to a smoking article is provided and is particularly useful in testing lip pressure applied to cigarettes. The system includes a pressure sensor adapted to be positioned on a predetermined portion of the smoking article that is to be subjected to external pressure. A pressure transducer is connected to the sensor. The output of the transducer responsive to the pressure applied to the smoking article and sensed by the sensor is displayed. Additionally, a method and apparatus for calibrating the pressure sensor is included. The calibration system includes a rigid enclosure and an elastomeric tube positioned in a recess in the enclosure and connected to a pressure regulator.

Abstract: The disclosure is drawn to a statc pressure unit having a circular dividing fitting with two silicon strain gauges glass bonded thereto. The strain gauges are located to place one strain gauge in tension and one in compression when the fitting is pressurized. One of two embodiments may be employed. In either case, one strain gauge is positioned in tension symmetrically across the center of the fitting. The other strain gauge is placed so that it is in compression.

Abstract: An atmospheric differential pressure sensor is disclosed comprising a pressure transducer, having a diaphram, mounted within a two piece protective transducer housing. An ambient atmospheric pressure receiving cavity is formed by the housing and coupled to the transducer diaphragm by a pressure transmitting tube that has a isolating oil drop within the tube to keep atmospheric contaminants away from the diaphram. The atmospheric pressure receiving cavity has external openings extending peripherally over more than 180.degree. of rotation about a central axis of said housing, and the ambient cavity provides a non-linear directional path between the end of the tube connected to the cavity and the exterior of the housing.

Abstract: A hermetically sealed pressure transducer suitable for implantation in a human body. A pressure sensitive circuit is fabricated using contemporary silicon technology. The pressure sensitive circuit is sealed in an oil-filled chamber formed within a titanium cylinder having a glass substrate bottom and a thin titanium top. According to one embodiment, the pressure sensitive circuit contains a sealed inner chamber at a known pressure, thereby measuring pressure relative to a known value. A second embodiment vents the pressure sensitive circuit to produce a relative pressure measurement. A grill protects the assembly and aids insertion into the desired area. A lead connects the transducer to an implantable sensing circuit.

Abstract: A capacitive differential pressure transducer for sensing the difference in pressure between at least two fluids includes first and second halves of a housing separated by a diaphragm which acts as a common capacitive plate to the capacitive differential pressure transducer with each housing half being identical and containing an interior chamber which is filled with a force transmitting fluid, a sensing capacitive plate located within the chamber and cooperating with the common capacitive plate, a fastening mechanism for holding the sensing capacitive plate tight against its housing half, sealing devices for sealing in the force transmitting fluid and terminals for connecting the common capacitive plate and the sensing capacitive plate to a sensing circuit.

Abstract: This invention provides a pressure transmitting and sealing apparatus between a high or low pressure fluid line and a gauge monitoring the pressure of the fluid in the line. This apparatus transmits pressure fluctuations between the measured fluid and a dissimilar fluid in the standline line connected to the measuring gauge. The invention is particularly applicable in instances where the ambient temperature is below the freezing point of the measured fluid and a non-freezing fluid is required in the standing line and gauge. The apparatus comprises an in-line piston and cylinder unit which transmits variations in the pressure in the measured line to the fluid in the standing line to the gauge, while maintaining separation of the two fluids and at the same time allowing the non-freezing fluid in the standing line to lubricate the piston and cylinder. In the event of a break in the standing line, the piston will prevent leakage from the measured fluid line.

Abstract: In a pressure indicator for measurement of hot pressure mediums, comprising an indicator housing adjustable to an opening in an enclosure for the medium to be measured, a measuring element, and a power train comprising a diaphragm connected to the housing and a power transmission element for connecting the diaphragm to the measuring element, a narrow gap is provided for between at least one of the parts of the power train on the one side and the housing on the other side, and that part of the housing being adjacent the gap is substantially in direct heat conducting connection with the enclosure for the medium when the indicator is adjusted to the opening therein.

Abstract: An apparatus which utilizes solid state piezoresistive strain sensing means to measure the static pressure as well as the differential pressure across a primary element, such as an orifice plate, venturi tube, nozzle or wedge.

Abstract: A pressure sensor for an internal combustion engine has a piezoceramic transducer in an operating connection, by way of a plunger, with a membrane, the sensor being secured in a cylinder head of an internal combustion engine with the membrane located within a cylinder. The pressure sensor serves for detecting knock and ping.

Abstract: A capacitance transducer has a central chamber with a conductive diaphragm disposed therein to separate the chamber into at least two portions, at least one portion having an electrical conductor disposed thereon to form in combination with the diaphragm at least one variable sensor capacitor, and wherein at least one portion of the chamber is coupled by a passageway to communicate with an isolator having an isolator chamber and an isolator diaphragm which in combination with the conductive diaphragm enclose a substantially incompressible fluid such that when pressure is applied to an exposed side of the isolation diaphragm, the conductive diaphragm is urged to deflect and thus change the sensor capacitance. Configuration of the isolators, spaced from the sensor capacitors, and other factors disclosed herein, eliminate unwanted mechanical and thermal stresses thereby improving the capacitive sensors' response to pressure.

Abstract: The melt pressure transducer is preferably for use in pressure measurements associated with an injection molding machine, and is designed to be mounted inside a mold to measure cavity pressure directly. In addition to being small in size, the transducer is also adapted for high cycle life. The transducer utilizes an internal filler rod for temperature compensation and, also, to reduce liquid volume rather than a capillary. The strain gauges are secured to opposing flats of the housing to provide a pressure-ranged section. The housing is in the form of a thick-walled cylinder with the flats forming the sensitive areas. Further, a unique fill and seal technique is described for charging the transducer and, at the same time, pre-stressing the coupling diaphragm.

Abstract: A pressure transducer body is described which has a bore running its length and contains (a) a means for receiving a pressure transducer, (b) a fluid reservoir, (c) a stationary elastic plug member having embedded therein a T-shaped rigid pin member, and (d) a chamber for receiving a fluid under pressure. The elements of the transducer body are combined in such a way that pressures of fluids flowing into chamber (d) are accurately measured using conventional pressure transducers even at very high pressures (e.g. 20,000 psi). More importantly, perhaps, the configuration of the transducer body permits accurate pressure measurements on pressurized fluids which are corrosive and/or abrasive. This makes the pressure transducer bodies particularly useful in the oilfield service industries for measuring the pressure of acidizing or hydraulic fracturing fluids used in stimulation.

Abstract: A differential pressure measuring transducer assembly including a measuring diaphragm formed of semiconductor material having gauge resistance elements on one surface thereof and a central boss area of large thickness and a peripheral support flange on the other surface thereof defining therebetween an annular portion of small thickness. The measuring diaphragm is attached at the peripheral support flange to a glass support member and a metallic support member formed with pressure conducting bores respectively communicating with each other. The metallic support member is formed of material having a Young's modulus substantially equal to that of the measuring diaphragm.

Abstract: A displacement converter useful for pressure gauges and similar instruments, the converter including a displacement detector provided with a variable capacitor responsive to the displacement to be metered and a fixed capacitor insensitive thereto. Also included is an amplitude-controllable oscillator whose AC output is applied to both capacitors, means being coupled to the capacitors to derive therefrom electrical signals which are a function of their capacitance values. These electrical signals are fed to a control circuit to produce a control signal corresponding to the difference therebetween, the control signal being applied to the oscillator to govern the output amplitude thereof in a manner maintaining the control signal at a constant value.

Abstract: An apparatus which utilizes solid state piezoresistive strain sensing means to measure the static pressure as well as the differential pressure across a primary element, such as an orifice plate, venturi tube, nozzle or wedge.

Abstract: Fluid pressure indicating apparatus which may comprise: a body assembly adapted for connection to a source of fluid pressure; an indicator assembly attached to the body assembly for indicating magnitude of the fluid pressure; a transducer assembly carried by the body assembly for translating pressure applied to one side thereof to linear motion at the opposite side thereof; and an amplification assembly carried by the body assembly between the transducer assembly and the indicator assembly for amplifying the linear motion of the transducer assembly to increased motion at the indicator assembly in predetermined relationship with the pressure magnitude of the source of fluid pressure.

Abstract: A differential pressure transmitter has a pressure receiving portion and a sensor portion which are constituted from separate parts separably jointed with each other. The sensor portion includes a semiconductor sensor having one side formed with a resistance pattern and the other side which has a thick-walled peripheral portion and a thick-walled central portion. The semiconductor sensor is incorporated in the sensor portion as being supported at the thick-walled peripheral portion thereof. The pressure receiving portion includes seal diaphragms disposed on both sides of the pressure receiving portion and a central diaphragm disposed therein. The semiconductor sensor is arranged such that the side thereof carrying the resistance pattern faces the pressure receiving portion.

Abstract: An adjustable overload mechanism for a differential fluid pressure transmitter includes a first and a second overload control diaphragm and an adjustable spring pressure means for applying an adjustable preload pressure to the control diaphragms. The spring pressure means for each diaphragm includes a spring such as a Belleville washer spring located between a diaphragm back-up plate in contact with a side of the control diaphragm and a wedge shaped support for the Belleville washer spring. A wedge shaped drive means is arranged to be selectively movable with respect to the wedge shaped spring support while maintaining the sloping wedge surfaces in contact. An adjustable drive screw is connected to the drive wedge to provide a means for changing the relative position of the support wedge and drive wedge.

Abstract: Apparatus for protecting a pressure-sensitive transducer in an extracorporeal blood system and for providing a sterile barrier while the apparatus transmits the blood pressure to the pressure-sensitive transducer. The apparatus (34) comprises a housing (40, 42) having first (40) and second (42) generally hemispherical members which symmetrically enclose a generally planar silicone membrane diaphragm (44). The membrane diaphragm (44) has a thickness that is less than 0.040 inch and a diameter that is at least twice as great as the intended total deflection distance. The membrane (44) is centered within the housing (40, 42) and greater pressure on either side of the membrane (44) will cause the membrane (44) to deflect to the other side by stretching.

Abstract: A liquid filled pressure pick-up or transducer comprises a housing, as strain gage sensor is supported in a liquid filled cavity in the housing and a membrane extends across an opening in the housing. A force transmitting rod connects the membrane to the strain gage sensor. In order to avoid damage especially to the membrane by extreme excess pressures, a plastically deformable support member acting as a stop is operatively held in the housing substantially in parallel to the membrane whereby the rod extends with play through the support member. An elastic seal extends around the rod hole in the support member toward the membrane. A substantially mirror symmetrical arrangement of two membranes and two support members results in a differential pressure transducer.

Abstract: A system for protecting a transducer connected thereto by damping, through a pressurized fluid, a signal to be converted by the transducer is disclosed. The system includes a transducer protector apparatus having a housing and an element for damping the signal to be converted by the transducer. The housing includes a first connector for coupling with the transducible signal source and a second connector for joining the transducer. The housing also has a fluid-containing cavity and a member for transferring to the fluid in the cavity the transducible signal received through the first connector. The damping element includes a bore defined in the housing to directly communicate the cavity with an aperture in the second connector and a pin, having a predetermined diameter less than the diameter of the bore, disposed within the bore.

Abstract: A differential pressure to electrical signal transmitter has a pair of barrier diaphragms and a central control diaphragm located between the barrier diaphragms. Input fluids are applied to respective chambers on the outside of the barrier diaphragms while the chambers between the control diaphragm and the barrier diaphragm are filled by corresponding substantially incompressible fill liquids. The fluid pressure of the two fill fluids are conducted by corresponding fluid channels to respective sides of a displacement sensing element to produce an electrical signal representative of differential pressure. The control diaphragm is biased by spring loaded spacers located on corresponding sides of the control diaphragm. The spacers have fluid passages to permit the respective fill fluids to reach the control diaphragm.

Abstract: A high temperature pressure gauge comprising a pressure gauge positioned in fluid communication with one end of a conduit which has a diaphragm mounted in its other end. The conduit is filled with a low melting metal alloy above the diaphragm for a portion of its length with a high temperature fluid being positioned in the remaining length of the conduit and in the pressure gauge.

Abstract: A pressure measuring apparatus using process transmission media and comprising measuring and compensation systems. These systems have the substantially same construction which comprises a pressure receiving portion, a pressure transmitting portion and a pressure detecting portion. The pressure transmitting portion is divided into two sections, each of them contains a liquid NaK and a heat-resisting inert liquid, respectively, as pressure transmission media. A pressure of a fluid to be measured which is introduced into the pressure receiving portion of the measuring system is transmitted through the transmitting portion to the pressure detecting portion where the pressure is detected. A pressure of a gas introduced into the pressure receiving portion of the compensation system is detected in the pressure detecting portion of the compensation system in a same manner. The temperature compensation is conducted by subtracting a detected pressure in the compensation system from that in the measuring system.

Abstract: A transducer dome for isolating a transducer from the liquid which actuates it. The transducer dome has a hemispherical or conical portion containing a single inlet and a threaded portion for connection to a transducer. The inlet is isolated from the transducer by a diaphragm formed from a hydrophobic bacterial filter, which allows venting of air during priming.

Abstract: A catheter is disclosed for measuring the intrauterine pressure of a woman in labor. It comprises an elongated flexible tube filled with liquid and having one end apertured to permit the liquid therein to communicate with bodily fluids in the uterus; the other end is sealed by a relaxed diaphragm. The catheter tube is inserted into a curved guide tube which is scored at the end adjacent the apertured end of the catheter to permit the catheter to be extended from the guide tube. The guide tube is also scored along its length to permit a portion of the wall of the guide tube to be peeled away leaving a longitudinal slot through which the catheter can be passed after insertion into the uterus. The catheter and guide tube are disposed in a liquid-tight envelope, the open end of which is sealed about the catheter to prevent escape of the liquid within the catheter.

Abstract: This invention provides a pressure transmitting and sealing apparatus between a high or low pressure fluid line and a gauge monitoring the pressure of the fluid in the line. This apparatus transmits pressure fluctuations between the measured fluid and a dissimilar fluid in the standing line connected to the measuring gauge. The invention is particularly applicable in instances where the ambient temperature is below the freezing point of the measured fluid and a non-freezing fluid is required in the standing line and gauge. The apparatus comprises an in-line piston and cylinder unit which transmits variations in the pressure in the measured line to the fluid in the standing line to the gauge, while maintaining separation of the two fluids and at the same time allowing the non-freezing fluid in the standing line to lubricate the piston and cylinder. In the event of a break in the standing line, the piston will prevent leakage from the measured fluid line.

Abstract: A capacitive pressure transducer constituted by a pressure sensor whose capacitance is caused to vary as a function of an applied pressure and a coupling assembly adapted to hydraulically convey the variable pressure of the fluid to be metered to the pressure sensor while isolating the structure of the sensor from the fluid. The sensor is formed by a cylinder, one end of which is enclosed by a deformable diaphragm that serves as one plate of a capacitor, deformation of the diaphragm in response to pressure acting to vary the dielectric spacing between the diaphragm plate and a second plate to produce a corresponding change in the value of the capacitance.

Abstract: The pressure monitoring assembly monitors changes in pressure of a fluid passing through the assembly. This is accomplished by passing a liquid through a pressure transfer device having first and second chambers therein separated by a flexible diaphragm. The first chamber has air therein and pressure changes are transmitted across the diaphragm from the second chamber through which the liquid flows. The assembly further includes a pressure transducer and a pressure coupling mechanism for coupling the pressure transfer device to the pressure transducer. The pressure coupling mechanism includes a body having a cylindrical chamber and a piston positioned for movement therein with a piston shaft protruding from a coupling end of the body. The shaft is biased outward from the coupling end of the body by a spring.

Abstract: Apparatus for protecting a pressure sensitive transducer in an extracorporeal blood system and for providing a sterile barrier while the apparatus transmits the blood pressure to the pressure sensitive transducer. The apparatus includes a pressure chamber having a lateral inlet and a lateral outlet, to enable convenient packaging, and having a membrane disposed transverse the chamber and surrounded by the chamber to segregate an inlet side of the chamber from the outlet side of the chamber. The membrane has a generally planar, circular center portion which lies in a plane between the outer peripheral portion of the membrane and the outlet side of the chamber. The membrane has an intermediate portion contiguous with and between the central portion and the outer peripheral portion, with the intermediate portion having a generally U-shaped cross-sectional configuration.

Abstract: A differential pressure to electrical signal transmitter has a pair of barrier diaphragms and a pair of nested internal control bellows located between the barrier diaphragms. A first internal volume defined between one barrier diaphragm and a corresponding mating support plate in the transmitter body is pressurized with a first fluid, and a second internal volume defined by the other barrier diaphragm and a respective mating support plate in the transmitter body is pressurized with a second fluid. The first volume is connected by a first fluid of conduit to a first chamber of a differential pressure sensor and is filled with a first incompressible fill fluid. The second volume is connected by a second fluid conduit to a second chamber of the sensor and is filled with a second incompressible fill fluid. The pressures of the two fill fluids act on opposite sides of the differential pressure sensor whereby an electrical output signal is produced dependent on the difference between the fill fluid pressures.

Abstract: A pressure responsive sensing device includes a housing defining a chamber. The chamber is filled with a non-compressible fluid and is closed at one end by a diaphragm. The diaphragm is retained in position by a cover plate. A stem connected to the outside of the cover plate projects through a bearing passage and has an outer end exposed to receive a force. A force on the end of the stem is transmitted via the plate and diaphragm against the fluid in the chamber. The pressure in the chamber, in turn, is transmitted ,o an electronic transducer sensing device through a constricted passage in the wall of the housing.

Abstract: An improved isolation diaphragm assembly for use in pressure transducers includes an open plenum containing an inert transmission fluid such as silicone oil. The plenum opening is bridged by a corrugated, circular diaphragm which has been tack welded at spaced locations on its periphery and then deformed into an underlying circular groove in the transducer housing, thereby providing a smooth sealing surface between the tack welds and the deformed portion. A domed cover having an O-ring seal contacting the smooth sealing surface is attached to the transducer housing so that a fluid whose pressure is to be measured may be introduced on the other side of the diaphragm from the inert transmission fluid. A method of manufacture is also disclosed.

Abstract: A diaphragm seal assembly for use with a fluid pressure responsive instrument includes an upper housing member having a first inner side. This inner side has a recessed surface defining a cavity and includes a passageway extending through the upper member for connection with the fluid pressure responsive instrument. A lower housing member has a second inner side and a passageway extending through the lower housing member. A diaphragm is received in the cavity and is clamped between the upper and lower housing members. A clamping device is provided for securing the upper and lower housing members together. The improvement comprises a deformable lip structure extending from the first inner side for bending over the periphery of the diaphragm to sealingly secure the diaphragm to the upper housing member.

Abstract: Disclosed is a device for sensing and indicating the pressure within a food extruder. Preferably, means are provided to supply a controlled flow of fluid to the interior of the food extruder at a pressure just above that needed to balance the process pressure and sufficient to provide a low positive flow of fluid into the extruder. Means are provided to sense the pressure of the supplied fluid and to indicate its value. By proper calibration of the fluid pressure indicator, the internal extruder pressure can be measured indirectly.

Abstract: A compensating bladder (30) for use in a pressure measuring device (10) for sensing pressure generated at a source. Pressure measuring device (10) includes a pressure responsive element (14) and pressure responsive structure (16) mounted within housing (12) for providing indications of pressures encountered at the source. The pressure responsive element (14) is connected by means of a socket (18), having an access opening (20), to the fluid source and for permitting pressure change to be sensed by the pressure responsive element (14). Compensating bladder (30) is disposed within the socket 18 to isolate pressure responsive element (14) from the fluid or gas entering the socket (18) and for forming a pressure transmitting chamber (66) that may be filled with a fluid. Compensating bladder (30) includes a generally longitudinal portion (44) and an integrally connected generally cylindrical portion (32).

Abstract: A pressure sensing device having a separator diaphragm through which pressure is transmitted from a working fluid to a liquid within a first part of the device and a transducer for measuring the pressure of the liquid or the difference between the pressure of the liquid and the pressure of an external fluid. A pressure overload diaphragm comprises a dished plate which forms part of a side wall of the first part of the device and has an inner section of the plate extending inwardly of that part. The overload diaphragm is inflexible or substantially inflexible over a working range of differential pressures applied thereto but the inner section thereof moves outwardly of the first part of the device if the differential pressure exceeds a predetermined value.

Abstract: A differential pressure sensor comprises a pressure-to-displacement transducer resiliently coupled to a cantilever beam strain gauge arrangement. The pressure-to-displacement transducer is provided with overrange protection permitting substantial displacement in the range of measurable pressure differentials and the more fragile cantilever beam is provided with separate overrange protection more narrowly constraining its displacement. The resilient coupling between the transducer and the beam absorbs the displacement differential. As a consequence of this structure, the device can provide high sensitivity readings in the measurable range of pressure differentials and is protected against pressure differentials greatly in excess of the measurable range.

Abstract: A self-contained pressure sensing cell responsive to an applied input pressure to produce a force for deflecting the pivoted force beam in the transducer section of a transmitter for converting the pressure into a corresponding signal. The cell includes a housing that is seatable within a well formed in the meter body of the transmitter and communicating with a chamber therein into which the lower end of the beam is extended. The cell housing is divided into a rear section, a mid section and a front section. Disposed within the rear section and integral with the wall thereof at its junction with the mid section is a wafer functioning as a flat sensing diaphragm. The flat diaphragm is provided with a connector pin that projects into the body chamber and is joinable to the beam whereby deflection of the flat diaphragm results in a corresponding beam deflection.

Abstract: A pressure indicating device according to the present invention includes a diaphragm assembly engaging one extremity of an indicator actuating means whereby flexing of the diaphragm caused by fluid pressure or other force will induce movement of the indicator actuating means. Movement of an indicator in relation to a fixed delineated face caused by movement of the indicator actuating mechanism results in a visual representation of reading bearing some predetermined relationship to the pressure causing the flexing of the diaphragm.

Abstract: The specification discloses a system and process for producing discrete chilled products having preselected weights from a semi-fluid mixture. The semi-fluid mixture is pumped along a distribution path to an extruding manifold which extrudes a plurality of parallel continuous lengths of the mixture. The continuous lengths are directed through a chilling station in a parallel relationship in order to chill and firm the lengths such that the lengths maintain their extruded cross-sectional configuration. A cutter periodically severs the continuous lengths at predetermined intervals to provide a plurality of discrete products having predetermined weights. The pumping rate, rate of travel through the freezer and periodic severing of the continuous lengths may be selectively varied in order to maintain any desired weight of the discrete products.

Abstract: A differential pressure transducer utilizing fluid-filled chambers as pressure transfer linkage to an isolated, fluid-filled aneroid sensing system. Isolation diaphragms are spread by means of internal fluid pressure fill of transfer chambers, thus providing elevated line pressure mode and pressure-biased operation. Construction offers media isolation from sensitive interior elements of the transducer. Material to come into physical contact with a pressure medium may thus be chosen for specific application. Dual, nested aneroid sensors cooperated to produce a linear displacement in response to an applied pressure differential. A cantilever beam assembly responds to the linear displacement so caused by flexing in a degree proportional to the applied pressure differential. The fluid-filled sensing system may comprise nested, aneroid capsule diaphragms, carrying a sufficient amount of incompressible fluid to support the capsule diaphragm for high line pressure use.

Abstract: A differential pressure transducer assembly which indicates pressure differences while remaining insensitive to variations in line pressure and overload pressure. The assembly has a transducer consisting of a semi-conductor sensor isolated from the medium being measured by mounting it on a resilient diaphragm between two small hydraulic chambers. The chambers are closed with a pair of diaphragms which isolate the two chambers from the external environment. The transducer sensor is comprised of a silicon chip having a large center boss area which is supported by a silicon back plate of similar material fused to the silicon chip at the periphery. The back plate is mounted by a hollow support stud to a threaded hub at the center of the resilient diaphragm separating the chambers. A space between the silicon chip and back plate communicates with the hydraulic fluid of one chamber through an inlet in the support stud. The opposite side of the silicon chip is immersed in the hydraulic fluid of the other chamber.

Abstract: A method and apparatus for protecting the transducer in a liquid-filled differential pressure transmitter having stroke limited, isolation diaphragms from exposure to overrange pressure are disclosed. Bidirectional overrange pressure protection is provided through the use of a single, preloaded bellows that is restrained by a preloaded stop means preferably including a preloaded mechanical spring. The bellows remains stationary when the differential pressure transmitter is exposed to a normal, operational differential pressure. When an overrange pressure is applied to the transmitter, the bellows expands or contracts to accommodate the liquid displaced by either of the isolation diaphragms thereby protecting the transducer from the overrange pressure. Upon removal of the overrange pressure condition, the protection apparatus automatically resets itself.

Abstract: Disclosed is a control device for use in fluid systems. In one embodiment the fluid is a liquid. A substantially cylindrical housing has therein a symmetrical cavity. The cavity is divided in upper and lower chambers by a circular and planar diaphragm. The upper chamber housing wall has protruding therefrom a cylindrical boss having a port for admitting a liquid. The boss forms a valve seat. The diaphragm has a plurality of concentric corrugations surrounding a central planar integral valve member. A media port in the lower chamber housing admits media for putting pressure on the diaphragm. When the pressure exceeds a predetermined value, the valve member closes upon the seat and entraps liquid between the diaphragm and upper chamber housing. The liquid acts to cushion, conforming to the shape of the diaphragm, thereby preventing damage to the diaphragm.

Abstract: A pressure responsive diaphragm has on its periphery axially spaced annular projections to define a peripheral annular groove therebetween which receives an annular projection at the coupling surface of a coupling flange. The diaphragm is thus releasably retained on the coupling flange and encloses a recess formed in the flange which recess communicates with the instrument. A compressible sealing ring for the recess within the flange is positioned on the peripheral surface of an annular projection of the diaphragm. The diaphragm may also be provided with an axially extending annular projection which is received in a corresponding axially opening groove formed in the coupling flange. A compressible sealing O-ring may be positioned within this axially opening groove radially outwardly of the diaphragm projection or may be positioned on the peripheral edge of the second annular projection of the diaphragm and arranged so that the O-ring contacts two or three metal walls of the coupling flange.

Abstract: A pair of vertically spaced rubber diaphragm covered bellows are employed with output means to produce a DC voltage directly proportional to the movement of the free end of one bellows. The upper bellows and diaphragm are inverted from their conventional positions. A conduit connects the two bellows together. The conduit, both bellows and both diaphragms are filled with an incompressible fluid. The fixed ends of both bellows are fixed relative to each other. This arrangement may be employed with a DC voltmeter calibrated in linear measure to indicate the level of a liquid in a storage tank. In this case, one bellows is located inside of and fixed relative to the tank at the top. The other bellows is located inside the tank at the bottom and fixed relative thereto thereat. A two bellows densitometer is also provided which may be employed with or without the liquid level system.

Abstract: A pressure sensor for use in measuring pressures in liquid at high temperatures, especially such as liquid sodium or liquid potassium, comprises a soft diaphragm in contact with the liquid. The soft diaphragm is coupled mechanically to a stiff diaphragm. Pressure is measured by measuring the displacment of both diaphragms, typically by measuring the capacitance between the stiff diaphragm and a fixed plate when the stiff diaphragm is deflected in response to the measured pressure through mechanical coupling from the soft diaphragm. Absolute calibration is achieved by admitting gas under pressure to the region between diaphragms and to the region between the stiff diaphragm and the fixed plate, breaking the coupling between the soft and stiff diaphragms. The apparatus can be calibrated rapidly and absolutely.