Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
  • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
  • G01L9/0072—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance

Definitions

• the present invention relates in general to pressure sensor technology and, more particularly, to low cost pressure sensors for either disposable o.r high volume applications of pressure sensors for gas and liquid based pressure sensing with increased sensitivity, improved linearity, and even lower cost.
• Another advantage would be if a pressure sensors using mesopump construction would have increased linearization.
• the present invention provides improvements in low cost, effective meso-pressure sensors that are capable of measuring both positive and negative pressure, depending upon how the device is configured. It is made from inexpensive, injection molded plastics and plastic films that are readily available from many commercial sources.
• the sensors include a sealed chamber defining part, a first flexible diaphragm mounted on one side in communication with the sealed chamber and a second flexible diaphragm separated from the first diaphragm by an insulator.
• a sensor chamber defining part is mounted on the other side of the second diaphragm for communication with a sensing atmosphere.
• the first and second flexible diaphragms are mounted in a non-parallel alignment with each other, deflection of one flexible diaphragm will roll with respect to the other io provide increased linear capacitive response.
• a non-conductive spacer element is positioned between the diaphragms to separate them while permitting rolling contact upon displacement of at least one of the diaphragms.
• the spacer whether in the middle or at the periphery, causes the contact between the diaphragms to roll with respect to each other to provide a linear response.
• a cantilever hinge and tab of a rigid polymer disc is mounted in the chamber between the first flexible diaphragm and the chamber to thereby convert the first flexible diaphragm into a linearly deflecting diaphragm.
• FIGURE 1 is a side elevational view, in section, of an embodiment of the present invention as non-parallel diaphragms sensor;
• FIGURE 2 is an exploded plan view of the embodiment shown in FIGURE 1 ;
• FIGURE 3 is a side elevational view, in section, of another embodiment of the present invention as a dual diaphragm sensor; and
• FIGURE 4 is bottom view of the embodiment shown in FIGURE 3 ;
• FIGURE 5 is a side elevational view, in section, of one embodiment of the present invention as a cantilever style sensor
• FIGURE 6 is an exploded plan view of the embodiment shown in FIGURE 5.
• like reference characters designate identical or corresponding components and units throughout the several views.
• the sensor includes a sealed chamber defining part and a first flexible diaphragm having two sides and mounted on one side in communication with the chamber in the sealed chamber defining part.
• a first flexible diaphragm has a conductive surface and an insulator is mounted on the other side of the first flexible diaphragm.
• a second flexible diaphragm having two sides is mounted on one side in communication with the insulator.
• the second flexible diaphragm also has a conductive surface and is in communication with a sensor chamber defining part mounted on the other side of the second flexible diaphragm, which chamber has an opening for communication with a sensing atmosphere.
• Measurement of the capacitance between the diaphragms is a function of the pressure in the sensor chamber introduced through the opening and causing the one flexible diaphragms to move with respect to the other of the flexible diaphragms.
• Fig.. 1 illustrates a pressure sensor 10 generally that has an upper chamber forming element 11 defining closed chamber 13 and a lower chamber forming element 15, to define an open chamber 17, having port 19.
• the chamber defining elements U and 17 may be made from plastic or other nonconductive materials and may be molded or fabricated. Neither part 11 or 17 has any metallization or other patterning.
• An upper diaphragm 21 is mounted on the closed chamber forming element 13 and is spaced at an angle with respect to a vertical axis 23 by spacer 25.
• Diaphragm 21 may be a plastic film with metallization or a dielectric film. Diaphragm 21 may be perforated and remains rigid curing operation.
• a lower diaphragm 27 is mounted on the lower chamber forming element 15 and on the other side of spacer 25. Diaphragm 27 may be a plastic film, either with metallization or formed from, dielectric film and forms sealed cavity or closed chamber 13.
• Spacer 25 is also preferably made from plastic and contains no metallization. Spacer 25 separates diaphragms 21 and 27 at an angle with respect to axis 25. Since diaphragm 27 is flexible, pressure in open, chamber 17 will cause it to have increased contact with diaphragm 21, thus providing a linear pressure sensor.
• Fig. 2 is an exploded view of the parts of Fig. 1, shown in plan view.
• Upper chamber forming element 11 includes a cavity or backstop 31 and holes 33 which are open for electrical contact elements 36.
• Diaphragm 21 includes hole 33 for electrical contact, and may have holes 35 and does include a contact point 37.
• Spacer 25, which is pie shaped as shown in section in Fig. 1 and in plan view in Fig. 2, also has a hole 33 for electrical contact.
• Diaphragm 27 is not perforated and has contact point 37 for contact with elements 36.
• lower chamber defining element 15 provides pressure access via port 19 and includes cavity 39.
• chamber 15 may be replaced by a ring or other mounting means for mounting diaphragm 27 to spacer 25.
• the device of Figs. 1 and 2 provides for linear diaphragm deflection by initially setting one diaphragm at an angle to the other. When the deforming diaphragm deflects, it will roll along the other diaphragm, creating a more linear capacitive response than prior designs.
• FIG. 3 additional elements of the present invention are shown.
• a spacer element 45 is mounted between diaphragms 21 and 27 which are mounted on their respective peripheral edges by mounting elements 47 and include electrical contacts 49.
• Upper chamber element 11 and lower chamber element 15 are not shown in this view for simplicity of explanation.
• Spacer 45 is a nonconductive element of any shape, such as spherical or cubical, and may be a patterned SU8 pillar. Spacer 45 is molded or otherwise formed. Operation is the same as in Fig. 1, however, as pressure from pressure source 51 causes lower diaphragm 27 to deflect, once again causing a more linear capacitive response than prior designs.
• Spacer 45 initially keeps diaphragms 21 and 27 separated and allows rolling capacitive contact as the films 21 and 27 come into contact. Rolling contact actuation provides very high capacitive change relative to displacement and very high force for electro-static actuation.
• Diaphragm 21 in any embodiment has holes 33 to allow readout 53 if desired.
• the device of this invention serves as an absolute pressure sensor.
• pressure can be sensed on both sides of the device and may have increased sensitivity when compared to a device with only one deflecting diaphragm, such as in Figs. 1 and 2.
• the device shown in Figs. 3 and 4 also has the capability of differential sensing because diaphragms 21 and 27 will move asymmetrically if the pressures from the two sides are different
• FIGs. 5 and 6 a similar embodiment is shown with an upper chamber forming element 11 defining closed chamber 13 and a lower chamber forming element 15, to define an open chamber J 7, having port 19.
• An. upper diaphragm 21 is mounted on die closed chamber forming element 13 and lower diaphragm 27 is mounted on the lower chamber forming element 15.
• Spacer 55 separates diaphragms 21 and 27 as in the patent application from which this application depends. Spacer 55 is also preferably made from plastic and contains no metallization.
• cantilever 57 which supports a rigid part 59 such that cantilever 57 and rigid part 59 are located behind the deflecting diaphragm 27. Rigid element 59 converts the normal ballooning movement of a conventional deflecting diaphragm 27 into a linearly deflecting behavior.
• the sensing atmosphere may be any fluid, including gases such as the atmosphere, gas pumps, chemical and electrolytic reactions, and the like or including liquids such as reactors, test devices, pumps and the like. While particular embodiments of the present invention have been illustrated and described, they are merely exemplary and a person skilled in the art may make variations and modifications to the embodiments described herein without departing from the spirit and scope of the present invention. AU such equivalent variations and modifications are intended to be included within the scope of this invention, and it is not intended to limit the invention, except as defined by the following claims.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Fluid Pressure (AREA)
• Fluid-Driven Valves (AREA)

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• 2004
  • 2004-08-09 US US10/915,868 patent/US6991213B2/en not_active Expired - Fee Related
• 2005
  • 2005-08-09 EP EP05784436A patent/EP1778978A1/en not_active Withdrawn
  • 2005-08-09 JP JP2007525729A patent/JP5073493B2/ja not_active Expired - Fee Related
  • 2005-08-09 WO PCT/US2005/028235 patent/WO2006020620A1/en not_active Ceased

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