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WO2011072214A2 - Système et procédé pour détecter la présence de liquide à l'aide de modes acoustiques hors du plan confinés - Google Patents

Système et procédé pour détecter la présence de liquide à l'aide de modes acoustiques hors du plan confinés Download PDF

Info

Publication number
WO2011072214A2
WO2011072214A2 PCT/US2010/059873 US2010059873W WO2011072214A2 WO 2011072214 A2 WO2011072214 A2 WO 2011072214A2 US 2010059873 W US2010059873 W US 2010059873W WO 2011072214 A2 WO2011072214 A2 WO 2011072214A2
Authority
WO
WIPO (PCT)
Prior art keywords
acoustic wave
mesa
transducer
substrate
moat
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2010/059873
Other languages
English (en)
Other versions
WO2011072214A3 (fr
Inventor
Terence J. Knowles
Kenneth A. Albrecht
Charles F. Bremigan Iii
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Illinois Tool Works Inc
Original Assignee
Illinois Tool Works Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Illinois Tool Works Inc filed Critical Illinois Tool Works Inc
Publication of WO2011072214A2 publication Critical patent/WO2011072214A2/fr
Publication of WO2011072214A3 publication Critical patent/WO2011072214A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/96—Touch switches
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2239/00—Miscellaneous
    • H01H2239/054—Acoustic pick-up, e.g. ultrasonic
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K2217/00—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
    • H03K2217/94—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00 characterised by the way in which the control signal is generated
    • H03K2217/96—Touch switches
    • H03K2217/96003—Touch switches using acoustic waves, e.g. ultrasound
    • H03K2217/96011—Touch switches using acoustic waves, e.g. ultrasound with propagation, SAW or BAW

Definitions

  • Embodiments of the present invention generally relate to acoustic wave switches, and, more particularly, to a system and method for detecting the presence of liquid through an acoustic wave switch.
  • an acoustic wave switch includes a substrate having an acoustic wave/resonant cavity and a transducer that is configured to generate a trapped acoustic wave within the acoustic wave cavity.
  • United States Patent No. 7,027,943 entitled “Acoustic Wave Ice and Water Detector” (the “'943 patent”), which is also hereby incorporated by reference in its entirety, discloses an acoustic wave sensor that utilizes one or more acoustic waves trapped in an acoustic wave cavity to detect the presence of one or more substances on a surface of the acoustic wave cavity. To detect the presence of liquid, a trapped torsional acoustic wave is used.
  • the sensor includes a number of transducers adjacent the acoustic wave cavity where a controller drives different sets of the transducers to generate different acoustic waves.
  • Certain embodiments of the present invention provide an acoustic wave switch assembly that includes a substrate, a mesa, and a transducer.
  • the substrate has contact and mounting surfaces.
  • the contact surface is opposite the mounting surface.
  • the mesa defines an acoustic wave cavity formed in the substrate.
  • the mesa gradually thins radially outward from a center to a thinned moat that surrounds the mesa.
  • the transducer is secured to the mounting surface of the substrate.
  • the transducer is configured to generate a trapped acoustic wave within the acoustic wave cavity.
  • the transducer may be a compressional wave transducer configured to generate the trapped acoustic wave as a compressional out-of-plane wave.
  • the transducer may be secured to an acoustic mass that is secured to a mounting surface of the substrate.
  • the acoustic mass is of sufficient size and material to ensure that the transducer is configured to generate a trapped acoustic wave within the acoustic wave cavity.
  • the transducer may be a compressional wave transducer configured to generate the trapped acoustic wave as a compressional out-of- plane wave.
  • the transducer may be positioned between the substrate and the acoustic mass.
  • the acoustic mass may be secured to the exposed top of the transducer such that it is securely positioned between the substrate and the transducer.
  • the assembly may also include a raised ridge surrounding the thinned moat.
  • the raised ridge may be thicker than the mesa, which is, in turn, thicker than the moat.
  • Certain embodiments of the present invention provide an acoustic wave switch assembly that includes a substrate, a mesa defining an acoustic wave cavity formed in the substrate, a thinned moat that surrounds the mesa, and a raised ridge that surrounds the thinned moat.
  • the mesa gradually thins radially away from a center toward the thinned moat.
  • an acoustic wave switch assembly that includes a substrate, a mesa defining an acoustic wave cavity formed in said substrate, wherein the mesa gradually thins radially away from a center toward a thinned moat that surrounds the mesa, a raised ridge that surrounds the thinned moat, wherein the raised ridge is thicker than the mesa, which is thicker than the thinned moat, and a compressional wave transducer secured to a mounting surface of the substrate.
  • the transducer is configured to generate a trapped compressional acoustic wave within the acoustic wave cavity.
  • Figure 1 illustrates an isometric, partial cross-sectional view of an acoustic wave switch.
  • Figure 2 illustrates a front view of an acoustic wave switch, according to an embodiment of the present invention.
  • Figure 3 illustrates a simplified cross-sectional view of an acoustic wave switch through line 3-3 of Figure 2, according to an embodiment of the present invention.
  • Figure 4 illustrates a cross-sectional view of an acoustic wave switch through line 3-3 of Figure 2, according to an embodiment of the present invention.
  • Figure 5 illustrates a cross-sectional view of an acoustic wave switch, according to an embodiment of the present invention.
  • Figure 6 illustrates a cross-sectional view of an acoustic wave switch, according to an embodiment of the present invention.
  • Figure 1 illustrates an isometric, partial cross-sectional view of an acoustic wave switch 10.
  • the acoustic wave switch 10 includes an associated acoustic wave/resonant cavity 12 that extends through the thickness b s of a substrate 14.
  • the substrate 14 may be formed of metal, plastic, glass, ceramic, or the like that is capable of supporting a resonant acoustic wave.
  • the resonant cavity 12 is formed in the substrate 14 such that the mass per unit surface area of the resonant cavity 12 is greater than the mass per unit surface area of the substrate 14 adjacent the resonant cavity 12.
  • the mass per unit area of the substrate 14 in the switch region is increased to form the resonant cavity 12 by forming a thin plateau or mesa 16 on a surface of the substrate 14 that is parallel to the plane of the substrate 14 and/or a contact surface 18.
  • the mesa 16 may be formed on a back surface 20 of the substrate 14 opposite the contact surface 18 of the resonant cavity 12. Alternatively, the mesa 16 may be formed on the contact surface 18.
  • a transducer 22 such as a piezoelectric transducer, is mounted on a surface 24 of the resonant cavity 12 to generate an acoustic wave that is substantially trapped or localized within the resonant cavity 12.
  • the transducer 22 is shown as being mounted on the mesa 16, if the mesa 16 is formed on the contact surface 18 of the substrate 14, the transducer 22 may be mounted directly on the substrate surface of the resonant cavity 12 opposite the mesa 16.
  • the transducer 22 is electrically connected to a sensing circuit 26 or separate processing unit.
  • the acoustic wave switch 10 may use any type of acoustic wave capable of being substantially trapped in the resonant cavity 12.
  • the acoustic wave switch 10 is described using a shear wave in a direction that is in the plane of the substrate 14, wherein the shear wave energy extends in a direction perpendicular to the plane of the substrate 14, that is, through the thickness of the substrate 14.
  • the fundamental or zeroth order mode of a horizontally polarized shear wave may not be substantially trapped, higher order shear wave modes are used in accordance with embodiments of the present invention.
  • the wave is a standing wave.
  • a standing wave has a number of advantages over an acoustic wave that propagates or travels along a path in a substrate. For example, propagating waves are not confined to the main path of propagation but can diffract off of the main path complicating touch detection. This is opposed to a standing wave that, by its nature, is confined to the area of a particular resonant cavity 12. Because the acoustic wave is confined, touch detection is easily accomplished.
  • the wave energy of a propagating wave is not stored at any location along the path. Once a propagating wave passes a point along the path, the wave is gone, thereby making timing and control critical for touch detection with propagating waves. There are no timing or control issues with a standing wave because the wave energy is stored in the resonant cavity 12. Moreover, a propagating wave is not a resonating wave. As such, the wave energy decays as it travels. A standing wave is resonant so that the wave is reinforced and prolonged. As a result, the standing wave has a much greater amplitude than a wave that is not confined.
  • the operation of the acoustic wave switch 10 is further described in United States Patent No. 7,106,310, entitled “Acoustic Wave Touch Actuated Switch" (the "'310 patent”).
  • the acoustic wave switch 10 provides a system and method of detecting pressure and movement with respect to the contact surface 18 of the acoustic wave switch 10, using acoustic wave energy that employs trapped energy concepts to create a localized mechanical resonator, or resonant cavity 12.
  • the '310 patent discloses an acoustic wave switch that includes a substrate with an acoustic wave/resonant cavity formed therein such that the mass per unit area of the acoustic cavity is greater than the mass per unit area of the substrate adjacent the acoustic cavity.
  • a transducer is mounted on the acoustic cavity for generating an acoustic wave that is substantially trapped in the cavity.
  • the acoustic wave switch 10 has a high Q (the ratio of the stored energy to lost or dissipated energy over a complete cycle) so as to enable contact to be detected by extremely simple, low-cost circuitry.
  • the acoustic wave switch 10 is rugged, explosion proof, operates in the presence of liquids and other contaminants, and has a low power consumption.
  • the acoustic wave switch 10 may be connected to an extremely simple touch detection or sensing circuit, such as shown and described in the '310 patent.
  • the transducer 22 may be coupled to a multiplexer that sequentially couples the transducer 22 and its associated acoustic wave switch 10 to an oscillator, as discussed in the '310 patent.
  • a touch on the contact surface 18 may be detected through a detected change in impedance, as described in the '310 patent.
  • a change in impedance is detected as soon as contact is made with the contact surface 18.
  • contact on the contact surface 18 may be detected by measuring the decay time of the acoustic wave within the resonant cavity 12.
  • United States Patent No. 7,265,746, entitled “Acoustic Wave Touch Detection Circuit and Method” (the “'746 patent"), describes a controller that detects a sensed event such as a touch on an acoustic wave switch/sensor based on the decay time.
  • the trapped acoustic wave within the acoustic wave/resonant cavity acts to "ring" the acoustic wave/resonant cavity. That is, as a voltage is applied to the transducer, the transducer operates to resonate the resonant cavity.
  • the sensing circuit 26 is operatively connected to the acoustic wave switch 10 may include a controller that drives the transducer 22 to generate a resonant acoustic wave in the resonant cavity 12 during a first portion of a sampling cycle.
  • the controller monitors the time that it takes for the acoustic wave signal from the transducer 22 to decay to a predetermined level. Based on the decay time, the controller detects a sensed event, such as contact on the contact surface 18.
  • United States Patent No. 7,027,943 entitled “Acoustic Wave Ice and Water Detector” discloses an acoustic wave sensor that utilizes one or more acoustic waves trapped in an acoustic wave cavity to detect the presence of one or more substances on a surface of the acoustic wave cavity. To detect the presence of liquid, a trapped torsional acoustic wave is used.
  • Out-of-plane acoustic mode displacements are desirable for detecting the presence of liquid, because the amplitudes of the out-of-plane acoustic modes are generally more sensitive to the presence of liquids than shear modes.
  • out-of- plane acoustic modes generally do not exhibit waveguide cut-off phenomena, and therefore may not be trapped by way of a cut-off. That is, before development of embodiments of the acoustic wave switch described below, out-of-plane acoustic waves were difficult to trap within a resonant cavity.
  • Embodiments of the present invention have been developed to provide an acoustic wave switch that uses out-of-plane acoustic modes to detect the presence of liquid. It has been found that an acoustic wave switch having a mesa that is creased or clamped around its periphery to form a thinned area is capable of trapping out-of-plane acoustic waves within the mesa.
  • FIG. 2 illustrates a front view of an acoustic wave switch 30, according to an embodiment of the present invention.
  • the acoustic wave switch 30 includes a contact surface 32 connected to a support post 34, which may be threaded.
  • the support post 34 is configured to be secured into a reciprocal opening of a panel (not shown), or the like, onto or into which the acoustic wave switch 30 is positioned.
  • Figure 3 illustrates a simplified cross-sectional view of the acoustic wave switch 30 through line 3-3 of Figure 2, according to an embodiment of the present invention.
  • the contact surface 32 of the acoustic wave switch 30 is formed from a substrate 36 having a mesa 38, which defines an acoustic wave cavity.
  • a thinned periphery or moat 40 is formed around the mesa 38.
  • the moat 40 may be formed through creasing or clamping, for example.
  • the moat 40 is, in turn, surrounded by a raised circumferential ridge 42, which may be thicker than the mesa 38, as shown in Figure 3.
  • the substrate 36 may be formed of metal, such as stainless steel, plastic, or any other material that is capable of trapping an acoustic wave within the mesa 38.
  • a compressional transducer 44 is secured underneath the mesa 38 and is configured to excite the acoustic wave cavity defined by the mesa 38, thereby resulting in out-of-plane acoustic mode displacement, which is confined to the face 46 of the mesa 38.
  • the acoustic wave switch 30 includes a mesa 38 surrounded by the thinned circumferential moat 40, which is, in turn, surrounded by the raised circumferential ridge 42. As shown in Figure 3, the mesa 38 gradually thins from the center X of the switch 30 radially outward. Thus, the center of the mesa 38 is the thickest portion of the mesa 38, while the thickness gradually decreases radially outward toward the moat 40.
  • the moat 40 is the thinnest portion of the contact surface 32.
  • the thickness of the contact surface 32 increases from the moat 40 radially outward to the circumferential ridge 42.
  • the circumferential ridge 42 may be thicker than the mesa 38.
  • the ridge 42 may be an upright wall that surrounds the moat 40.
  • the thinned moat 40 provides out-of-plane acoustic mode displacements when the transducer 44 is excited to produce acoustic waves within the mesa 38.
  • the out-of-plane acoustic mode displacements are particularly useful in detecting the presence of liquid because the amplitudes of the modes are generally more sensitive to the presence of liquids, as compared to shear modes.
  • the thinned moat 40 causes the contact face 46 to act as a diaphragm. Excitation of the acoustic wave cavity defined by the mesa 38 with the compressional mode transducer 44 creates displacement modes that do not extend beyond the moat 40 into the circumferential ridge 42. That is, the waves do not pass into the circumferential ridge 42. Instead, the thinned moat 40 acts to trap the out-of-plane acoustic waves to the face 46 of the mesa 38.
  • This configuration may operate as a membrane with radial symmetry, similar to drumstick contact surfaces of a steel drum.
  • the moat 40 may be a creased area that causes the out-of-plane acoustic waves to be trapped within the mesa 38.
  • the contact face 46 acts as a clamped plate or diaphragm. It has also been found that the gradual thinning toward the moat 40 is not overly sensitive to bubble formation, which could otherwise lead to liquid detection errors.
  • Figure 4 illustrates a cross-sectional view of the acoustic wave switch 30 through line 3-3 of Figure 2, according to an embodiment of the present invention.
  • the switch 30 may also include a printed circuit board 48, which may control operation of the acoustic wave switch 30.
  • a connection pin 50 connects the compressional transducer 44 to the printed circuit board 48.
  • a ground pin 52 may abut into an underside of the substrate 36 and connect to the printed circuit board 48.
  • FIG. 5 illustrates a cross-sectional view of the acoustic wave switch 30, according to an embodiment of the present invention.
  • a mass 60 such as a stud, post, block, or the like, is secured to an underside of the transducer 44 (on the side of the transducer 44 that is not contacting the substrate 36).
  • the mass 60 may be formed from a melted hemisphere of solder that is positioned on the underside of the transducer 44.
  • the mass 60 may be formed of ferrous and/or non-ferrous materials. It has been found that the mass 60, which may weigh approximately 0.065 - 0.8 grams, for example, dramatically improves resonance within the mesa 38.
  • Figure 6 illustrates a cross-sectional view of the acoustic wave switch 30, according to an embodiment of the present invention.
  • the mass 60 such as a stud, post, block, or the like, is secured between the transducer 44 and the substrate 36.
  • the mass 60 is positioned on top of the transducer 44 and to an underside of the substrate 36.
  • the embodiment shown in Figure 6 is similar to the embodiment shown in Figure 5, except that the mass 60 is positioned between the transducer 44 and the substrate 36 in Figure 6, as opposed to the transducer 44 being positioned between the mass 60 and the substrate 36, as shown in Figure 5.
  • the inertia of the mass 60 may cause the out-of-plane displacement on the face 46 to increase, and to increase the tensile and compressional attributes of the transducer 44.
  • embodiments of the present invention provide an acoustic wave switch that is configured to efficiently detect the presence of liquid.
  • Embodiments of the present invention provide an acoustic wave switch that uses out-of-plane acoustic modes to detect the presence of liquid.
  • the thinned periphery or moat that surrounds the mesa acts to trap the out-of-plane acoustic mode waves within the mesa 38.
  • out-of-plane acoustic mode waves are more sensitive to the presence of liquid than shear modes.

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  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

L'invention porte sur un ensemble commutateur d'onde acoustique, ledit ensemble comprenant un substrat comportant des surfaces de contact et de montage, la surface de contact étant opposée à la surface de montage, une mesa définissant une cavité d'onde acoustique formée dans le substrat, la mesa s'amincissant graduellement radialement vers l'extérieur vers un fossé aminci qui entoure la mesa, et un transducteur fixé à la surface de montage du substrat. Le transducteur est configuré de façon à générer une onde acoustique piégée à l'intérieur de la cavité d'onde acoustique.
PCT/US2010/059873 2009-12-11 2010-12-10 Système et procédé pour détecter la présence de liquide à l'aide de modes acoustiques hors du plan confinés Ceased WO2011072214A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US28587709P 2009-12-11 2009-12-11
US61/285,877 2009-12-11

Publications (2)

Publication Number Publication Date
WO2011072214A2 true WO2011072214A2 (fr) 2011-06-16
WO2011072214A3 WO2011072214A3 (fr) 2011-08-04

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PCT/US2010/059873 Ceased WO2011072214A2 (fr) 2009-12-11 2010-12-10 Système et procédé pour détecter la présence de liquide à l'aide de modes acoustiques hors du plan confinés

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7027943B2 (en) 2002-11-12 2006-04-11 Infineon Technologies Ag Method, device, computer-readable storage medium and computer program element for the computer-aided monitoring of a process parameter of a manufacturing process of a physical object
US7106310B2 (en) 2001-01-18 2006-09-12 Texzec, Inc. Acoustic wave touch actuated switch
US7265746B2 (en) 2003-06-04 2007-09-04 Illinois Tool Works Inc. Acoustic wave touch detection circuit and method

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7307627B2 (en) * 2003-05-12 2007-12-11 Illinois Tool Works, Inc. Individual acoustic wave switch

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7106310B2 (en) 2001-01-18 2006-09-12 Texzec, Inc. Acoustic wave touch actuated switch
US7027943B2 (en) 2002-11-12 2006-04-11 Infineon Technologies Ag Method, device, computer-readable storage medium and computer program element for the computer-aided monitoring of a process parameter of a manufacturing process of a physical object
US7265746B2 (en) 2003-06-04 2007-09-04 Illinois Tool Works Inc. Acoustic wave touch detection circuit and method

Also Published As

Publication number Publication date
WO2011072214A3 (fr) 2011-08-04

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