Integrated fluid sensing device

[0002] 1. Field of the Invention

[0003] This invention relates generally to pneumatic and hydraulic equipment, and more particularly to the measurement of physical characteristics, such as flow rate, pressure, and temperature of a fluid used to control these devices.

[0004] 2. Description of the Prior Art

[0005] A fluid flow device, such as a valve manifold 10 and its corresponding base plate 12 shown in FIG. 1, is used to accurately direct fluids used to control pneumatic and/or hydraulic equipment. Fluid flow devices and other control devices are disclosed in U.S. Pat. No. 5,348,047 to Stoll, et al. and U.S. Pat. No. 5,458,048 to Hohner, which are incorporated herein by reference. The term “fluid” is generically used herein to refer to any gas, liquid, suspension, and/or slurry used as a control medium in such equipment.

[0006] The base plate 12 is mounted to a bottom surface of the valve manifold 10, as shown by dashed lines in FIG. 1. The base plate 12 includes channels 16, which pass through the base plate 12 and coincide with apertures on the underside of the fluid flow device 10. A fitting 14 is fitted to one end of each of the channels 16. The fittings 14 can readily be connected to tubes that direct the fluid to and/or from the valve manifold 10. The channels 16 then direct the fluid through the base plate 12 to the appropriate aperture in the valve manifold 10. The valve manifold 10 can then redirect or modify the flow of fluid in response to electronic control.

[0007] In addition to directing the flow of fluid, another function that may be performed is the measurement of fluid characteristics, such as flow rate, pressure, and temperature. One type of sensor 18, which is used to measure the flow of liquid, is shown in FIGS. 2a,2b,and 2c.The flow sensor 18 includes an orifice 20, a cantilever paddle structure 22, and an implanted piezo-resistive Wheatstone bridge 24. FIG. 2ashows the paddle structure 22 in an undeflected state, and FIG. 2bshows the paddle structure 22 in a deflected state.

[0008] The fluid to be measured is directed through the orifice 20 in the flow sensor 18. The dynamic pressure built up by the fluid deflects the paddle structure 22. The mechanical stress of the paddle structure 22 changes the resistance of the piezo-resistive Wheatstone bridge 24 at the base of the paddle structure 22, and this change in resistance creates a corresponding change in voltage. The change in voltage is detected on a set of contacts 26 electrically connected to the Wheatstone bridge 24, as shown in FIG. 2c.For temperature compensation, a second Wheatstone bridge is preferably positioned on the flow sensor 18 surrounding the orifice 20. A support member preferably positions the paddle structure 22. The size of the support member is preferably minimized to concentrate the mechanical stress of deflection, and thus increase the sensitivity of the flow sensor 18. Furthermore, the overall size of the flow sensor is determined by the paddle size, which can be adjusted to the specific needs of the control task.

[0009] The output voltage of the Wheatstone bridge 24 is proportional to the square of the volumetric flow rate. The sensitivity of the flow sensor 18 is dependent upon the size of the orifice 20, and is adjustable over a broad range. Thus, since the paddle structure 22 is perpendicularly oriented to the direction of flow of liquid, as liquid passes through the orifice 20 in the flow sensor 18, the kinetic pressure of the liquid induces a mechanical stress that is detected by the piezo-resistors in the Wheatstone bridge 24.

[0010] To incorporate the flow sensor shown in FIGS. 2a,2b,and 2cin conventional fluid flow devices, additional tubing, fittings, and connectors must be spliced into the network of tubes coupling the base plate 12 to and from the source of the fluid and portions of the equipment to be controlled. The additional tubes, fittings, and connectors increase measurement error, space requirements, and the cost of installing and maintaining the equipment. In addition, the electronics that monitor the sensors require a substantial amount of additional wiring, which adds to the clutter of the resulting system and severely degrades its reliability. Further, the sensors and associated electronics, by being externally located to the fluid flow device, are inherently unprotected from environmental hazards, such as shock, dust, and pollutants, which are common in and around hydraulic and/or pneumatic equipment.

[0011] It is an object of the present invention to provide an integrated fluid sensing device, which significantly reduces measurement errors, space requirements, and the cost of installing and maintaining sensors that measure the physical characteristics of a fluid used to control hydraulic or pneumatic equipment.

[0012] It is a further object of the present invention to provide an integrated fluid sensing device, which includes sensors mounted on a single circuit board having common signal processing, communication, error control, and connecting circuitry.

[0013] It is still a further object of the present invention to provide an integrated fluid lo sensing device, which can readily be adapted to various physical characteristics of a fluid used to control hydraulic or pneumatic equipment by changing a single circuit board.

[0014] It is yet a further object of the present invention to provide an integrated fluid sensing device, which can readily display and transmit sensed data, via wired or wireless means, which represents physical characteristics of a fluid used to control hydraulic or pneumatic equipment.

[0015] It is still another object of the present invention to provide an integrated fluid sensing device that significantly reduces the amount of external tubing, connectors, and fittings required to sense the physical characteristics of a fluid used in the control of hydraulic or pneumatic equipment.

[0016] It is yet another object of the present invention to provide an integrated fluid sensing device, which substantially encloses sensors that measure the physical characteristics of a fluid and protects these sensors against environmental hazards.

[0017] In accordance with the present invention, an integrated fluid sensing device is provided, which includes a fluid flow device and a circuit board. The fluid flow device includes a first mating portion and a second mating portion. The first mating portion includes a first aperture, and the second mating portion includes a second aperture. The first aperture and the second aperture are at least partially aligned such that the first aperture and the second aperture define a first channel through the first and second mating portions when the first and second mating portions are joined together. The first channel is able to communicate fluid therethrough. The circuit board is disposed between the first mating portion and the second mating portion and includes at least one sensor. The sensor is at least partially aligned with the first channel and is able to detect a physical characteristic of the fluid flowing through the first channel.

[0018] In further accordance with the present invention, a method of integrating a sensor in a fluid flow device is provided, which includes the steps of dividing the fluid flow device into a first mating portion and a second mating portion, and positioning a circuit board between the first mating portion and the second mating portion. The first mating portion including a first aperture, and the second mating portion including a second aperture. The first aperture and the second aperture are at least partially aligned such that the first aperture and the second aperture define a first channel through the first and second portions when the first and second mating portions are joined together. The first channel is able to communicate a fluid therethrough. The circuit board includes at least one sensor, which is at least partially aligned with the first channel. The sensor is able to detect a physical characteristic of the fluid flowing through the first channel.

[0019] In still further accordance with the present invention an integrated fluid sensing device is provided, which includes at least one valve, a base plate, and a circuit board. The base plate is removably coupled to the valve and includes a first mating portion and a second mating portion. The base plate includes a first channel through the first and second mating portions when the first and second mating portions are joined together. The circuit board is disposed between the first mating portion and the second mating portion The circuit board includes at least one sensor and an electrical contact. The electrical contact is coupled to the sensor and is accessible to an exterior of the fluid flow device when the first and second portions are joined together. The sensor is at least partially aligned with the first channel and is able to detect a physical characteristic of the fluid flowing through the first channel.

[0020] These and other objects, features, and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

[0021] FIG. 1 is an isometric view of a conventional fluid control device including a valve manifold and a base plate.

[0022] FIGS. 2aand 2bare side views of a conventional flow sensor.

[0023] FIG. 2cis an isometric view of the conventional flow sensor shown in FIGS. 2aand 2b.

[0024] FIG. 2dis an isometric view of a conventional hot-wire anemometer.

[0025] FIGS. 3aand 3bare bottom and top views, respectively, of the conventional base plate shown in FIG. 1.

[0026] FIG. 3cis a side, cross-sectional view of the base plate shown in FIG. 3btaken along the line A-A′.

[0027] FIG. 4ais a side, cross-sectional view of the base plate in which a circuit board has been inserted between an upper portion and a lower portion of a base plate in accordance with the present invention.

[0028] FIG. 4bis a side, cross-sectional view of one channel in the base plate shown in FIG. 4a.

[0029] FIG. 4cis a top, cross-sectional view of the base plate shown in FIG. 4btaken along the line Y-Y′.

[0030] FIG. 4dis a side, cross-sectional view of one channel in an alternative embodiment of the base plate formed in Accordance with the present invention.

[0031] FIGS. 4eand 4fare top, cross-sectional views of two embodiments of the base plate shown in FIG. 4dtaken along the line X-X′.

[0032] FIG. 4gis a side, cross-sectional view of one channel in an alternative embodiment of the base plate formed in accordance with the present invention without a bypass channel directing flow around the sensor.

[0033] FIGS. 5aand 5bare partially-exploded, side, cross-sectional views of two embodiments of the base plate formed in accordance with the present invention.

[0034] FIG. 6ais a top view of a circuit board.

[0035] FIG. 6bis a side, cross-sectional view of the circuit board shown in FIG. 6ataken along the line B-B′.

[0036] FIG. 6cis an alternative embodiment of the circuit board shown in FIG. 6a,which includes an application-specific integrated circuit (ASIC).

[0037] FIG. 6dis an alternative embodiment of the circuit board shown in FIG. 6c,which includes a telemetric unit for wireless transmission of sensor data.

[0038] FIG. 7ais a top view of a spacing layer.

[0039] FIG. 7bis a side, cross-sectional view of the spacing layer shown in FIG. 7ataken along the line C-C′.

[0040] FIG. 8ais a top view of a sealing layer.

[0041] FIG. 8bis a side, cross-sectional view of the sealing layer shown in FIG. 8ataken along the line D-D′.

[0042] FIG. 9 is a side, cross-sectional view of the integrated fluid sensing device formed in accordance with the present invention.

[0043] FIG. 3ashows a bottom view of a multipole or base plate 12. Threaded holes 28 are provided in the base plate 12 to accommodate fittings 14 as shown in FIG. 1. The fittings 14 enable tubes (not shown) to be connected to the base plate 12. The base plate 12 is preferably manufactured as a separate unit from the valve 10 shown in FIG. 1 so that the valve manifold 10 can be removed from the base plate 12 without disturbing the tubes connected to the base plate 12.

[0044] FIG. 3bshows a top view of the conventional base plate 12 including a line A-A′. FIG. 3cshows a side, cross-sectional view of the base plate 12 taken across the line A-A′. The arrows K in FIG. 3cindicate the flow of fluid through the channel in the base plate 12. As is best seen from FIG. 3C, the apertures in the top of the base plate 12 are preferably offset from the corresponding apertures in the bottom of the base plate 12. This offset diverts the flow of fluid through the channel, which limits the pressure of the fluid as it comes in contact with components in the valve manifold 10.

[0045] FIG. 4ashows a side, cross-sectional view of the base plate 12 after it has been separated into an upper portion 12A and a lower portion 12B along a line X-X′ shown in FIG. 3c.A circuit board 30, which includes at least one sensor 18, is inserted between the upper and lower portions of the base plate. An arrow L indicates the flow of fluid through the channel and through the sensor 18. A bypass path L′ is preferably provided to divert the majority of flow around die sensor 18. The bypass path L′ reduces the flow through the sensor 18, which protects sensitive components in the sensor 18 that are subject to wear and breakage. About 10-15% of the total flow of fluid is preferably allowed to pass through the sensor 18. The remaining flow is diverted around the sensor 18 and through the bypass path L′.

[0046] FIG. 4bshows a side, cross-sectional view of the base plate portions 12A, 12B and the circuit board 30 in which the bypass path L′ has been implemented around the sensor 18. FIG. 4cis a top, cross-sectional view of the circuit board taken along cross-section line Y-Y′ showing an orifice 32 for the bypass path L′ and an orifice 34, which allows the flow of fluid through the sensor 18.

[0047] FIG. 4dshows an alternative geometry for the channel in the base plate 12 having at least two (2) bypass paths L′. FIGS. 4fand 4eshow top, cross-sectional views of the circuit board 30 taken along cross-section line X-X′ shown in FIG. 4d.The circuit board 30 in FIG. 4eaccommodates six (6) bypass paths L′, and the circuit board 30 in FIG. 4faccommodates eight (8) bypass paths L′.

[0048] By appropriate dimensioning of the sensor 18, the channel may be constructed without a bypass channel directing flow around the sensor 18. FIG. 4gshows a side, cross-sectional view of the base plate portions 12A, 12B and the circuit board 30 in which a bypass path has not been implemented around the sensor 18. Thus, in the embodiment shown in FIG. 4g,about 100% of the flow is directed through the sensor 18.

[0049] FIG. 5A shows an alternative embodiment of the base plate, which incorporates four (4) layers between the upper portion 12A and the lower portion 12B of the base plate 12. Sealing layers 32 are preferably inserted above and below the circuit board 30, respectively. The sealing layers are preferably manufactured from a pliable and/or deformable material, such as rubber, which substantially prevents leakage of the fluid from the channel. Leakage is particularly prevalent between the hard surfaces of the circuit board 30 and the base plate 12A. In addition, a spacing layer 34 is preferably inserted above or below the circuit board 30 to protect the sensitive components and contacts on the circuit board 30. The spacing layer 34 may be separate from or integrated with the circuit board 30.

[0050] In addition, one or more alignment holes 36 are preferably provided through each of the layers 30, 32, and 34 and partially through the upper portion 12A and the lower portion 12B of the base plate. A guide pin (not shown) is preferably placed in each of the alignment holes, which ensures a preferably unique orientation of the layers 30, 32, and 34 with the portions of the base plate 12A, 12B as they are joined together.

[0051] One or more screw holes 38 are provided through the bottom portion 12B of the base plate, each of the layers 30, 32, 34, and partially through the upper portion 12A of the base plate to accommodate a screw, which joins the portions of the base plate together and sandwiches the layers. The screw maintains compression between the portions of the base plate, which aids in preventing leakage of fluid from the channel. FIG. 5bshows an alternative embodiment of the base plate 12 shown in FIG. 5a,in which the screw hole 38 has been relocated nearer an external surface of the base plate.

[0052] FIG. 6ashows the circuit board 30 with eight (8) sensors 18. Each of the sensors 18 is preferably positioned within a depression on the circuit board 30 and affixed to the circuit board 30 by an adhesive, surface mount technology (SMD), wire bond technology, flip-chip technology, or the like. The sensor 18 is preferably connected to bond pads 40, which are coupled to electrically conductive traces 42 on the circuit board 30. The traces 42 are brought to the edge of the board, which is preferably accessible from the outside of the base plate 12 when the upper portion 12A and the lower portion 12B of the base plate 12 are joined together.

[0053] The sensors 18 are advantageously encapsulated within and electrically accessible outside the integrated fluid sensing device formed in accordance with the present invention Thus, the fragile components of the sensor 18 are inherently protected from shock, humidity, dust, corrosive chemicals, and other environmental hazards.

[0054] FIG. 6bis a side, cross-sectional view of the circuit board 30 taken along the line B-B′, which shows the alignment holes 36, screw hole 38 and sensor 18. FIG. 6cshows an alternative embodiment of the circuit board 30 shown in FIG. 6a,which includes a microprocessor, a microcontroller, or an application-specific integrated circuit (ASIC) 44. The ASIC 44 monitors and processes signals from each of the sensors 18 and outputs the processed information externally to the base plate 12. The ASIC 44 may include circuitry that enables it to interface to Fieldbus compatible components and controllers.

[0055] Fieldbus is a commercial standard describing a digital, serial, multi-drop, two-way communication link, which interconnects measurement and control equipment such as sensors, actuators, and controllers. It serves as a Local Area Network (LAN) for instruments used in process control and manufacturing automation applications and has a built-in capability to distribute the control application across the network.

[0056] FIG. 6dshows an alternative embodiment of the circuit board 30 shown in FIG. 6C, in which, in addition to the ASIC 44, a telemetric unit 46 is provided for the wireless transmission of information processed by the ASIC 44. The telemetric unit 46 preferably inputs a signal from each of the sensors 18, which is representative of the sensed physical characteristic and outputs a wireless signal, such as a radio frequency or infrared signal.

[0057] FIG. 7ashows a top view of the spacing layer 34, which is also shown in FIGS. 5aand 5b.The spacing layer 34 is preferably used to protect the sensitive components of the sensor 18 and the bond pads 40, which electrically connect the sensor 18 to the edge of the circuit board 30. The spacing layer 34 is preferably sealed by an appropriate choice of pliable material deposited on the spacing layer 34 or by inserting an additional sealing layer between the spacing layer 34 and the circuit board 30. Bumps and/or recesses may be integrated onto the spacing layer 34 to further protect corresponding sensors 18 and bond pads 40 on the circuit board 30. The bumps or recesses may alternatively be incorporated on the circuit board 30 without requiring a separate spacing layer 34. FIG. 7bis a side, cross-sectional view of the spacing layer 34 taken along line C-C′, which shows the alignment holes 36, the screw hole 38, and an aperture 48 for the sensor 18.

[0058] FIG. 8ashows the sealing layer 32, which prevents leakage from the channel to the exterior of the base plate 12, The functionality of the sealing layer 32 could alternatively be incorporated into the circuit board 30 by applying, for instance, independent seals around each of the orifices in the circuit board 30. FIG. 8bis a side, cross-sectional view of the sealing layer 32 taken across the line D-D′, which shows the alignment holes 36, the screw hole 38, and the aperture 38 for the sensor 18.

[0059] FIG. 9 shows the integrated fluid flow device formed in accordance with the present invention. The circuit board 30, which includes one or more sensors 18 is sandwiched between the upper portion 12A and the lower portion 12B of the base plate. The primary flow of fluid within the channel is indicated by arrow L, which is preferably diverted around the sensor 18 through the bypass path L′. A small portion L″ of the primary flow L flows through the sensor 18 and continues through the channel into the upper portion 12A of the base plate. Once the fluid exits the upper portion 12A, it is preferably outputted to pneumatic components, such as pneumatically actuated cylinders or valves.

[0060] It is anticipated that the integrated fluid sensing device of the present invention can be implemented with any quantity of valves or manifolds used to control hydraulic and/or pneumatic equipment. It is also anticipated that the sensor can measure any conceivable physical characteristic of the fluid, such as temperature, flow rate, pressure, and the like. It is further anticipated that the sensor can be implemented as alternative types of transducers, such as a magnetic flowmeter, hot-wire anemometer, bimetallic strip, thermocouple, pressure cell, or pressure transducer. Additional details concerning transducers can be found in S. Wolf, “Guide to Electronic Measurements and Laboratory Practice”, Prentice-Hall, Inc., pp. 414-451, (1973), which is incorporated herein by reference.

[0061] The hot-wire anemometer 19 is shown in FIG. 2dand includes a fine resistive wire 21, which is heated by a current passing through it. If a cooler fluid flows past the wire 21, the fluid removes heat from the wire 21. The rate of heat transfer varies with the type of fluid, but it also tends to vary as the square root of the velocity at which the fluid flows past the wire 21. If the current in the wire 21 is kept constant, the change in resistance due to the cooling will yield a voltage signal, which can be monitored to indicate flow rate. Since the diameter of the wire 21 can be made very small, the anemometer 19 can be made very sensitive and responsive to high-frequency changes in the flow rate.

[0062] From the foregoing description, it will be appreciated that the integrated fluid sensing device formed in accordance with the present invention significantly reduces measurement errors, space requirements, external tubing, connectors, fittings, and the cost of installation and maintenance of sensors that measure the physical characteristics of a fluid used to control hydraulic or pneumatic equipment. It will also be appreciated that the integrated fluid sensing device of the present invention enables sensors to be mounted on a single circuit board having common signal processing, communication, error control, and connective circuitry.

[0063] Further, it will be appreciated that the integrated fluid sensing device formed in accordance with the present invention can readily display and transmit data, which represents physical characteristics of the fluid used to control hydraulic or pneumatic equipment. It will also be appreciated that the integrated fluid sensing device formed in accordance with the present invention substantially encloses sensors that measure the physical characteristics of the fluid and protects these sensors from environmental hazards.

[0064] Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.