US3855847A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Acoustic emission transducer and monitoring system
Assignee: Westinghouse Electric Corp
•
Filing: 1972-06-20
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Granted: 1974-12-24
•
Expires: 1992-06-20
Abstract
Abstract An improved acoustic emission transducer and transmission system for the on-line monitoring of acoustic signals generated by a metal when under mechanical stress. The transducer structure includes a tubular housing having a continuous side wall, a bottom wall and an open top. A piezoceramic element is fastened to the bottom of the housing by means of a conductive high temperature adhesive. A positive electrode is fixed to the piezoceramic element by the adhesive and both the piezoceramic element and the positive electrode are cushioned and insulated from the side wall of the housing by means of an inner tubular housing of high temperature insulating material. The inner housing assembly is sealed to enclose the piezoceramic element, adhesive and electrode - the sealant preventing moisture from penetrating the assembly and shorting the crystal. The upper end of the positive electrode passes through the sealant and is connected to an electrical cable which transmits any signal picked up by the transducer to a remote location. The cable is attached directly to a transformer which is used to couple maximum power from the transducer to an output transmission line. The transformer is selected to match the impedance of the transducer to the transmission line.
Inventors
- 👤 W Leschek
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:14
CPC Classifications
G; G01; G01N; G01N29/00; G01N29/22; G01N29/24; G01N29/2437; G01N2291/00; G01N2291/02; G01N2291/028; G01N2291/02872; G01N2291/26; G01N2291/269; G01N2291/2695
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
230 words
An improved acoustic emission transducer system for monitoring acoustic signals generated by a metal specimen when subject to mechanical stress comprising: a tubular housing having a side wall; a thin metallic window enclosing one end of said housing to form the bottom wall thereof; a piezoelectric element acoustically coupled to the interior of said bottom wall of said housing; a positive electrode electrically coupled to said piezoelectric element; means for electrically insulating said electrode and said piezoelectric element from the side wall of said housing; means for sealing said piezoelectric element against moisture so as to prevent moisture from shorting said element, access being provided to said electrode through said sealing means; means for mechanically damping both piezoelectric element resonances and spurious housing resonances; an electrically conductive connecting cable having two leads, one grounded at one end to said housing and the other electrically coupled at one end to said positive electrode; an electRically conductive transmission cable circuit having two leads, one positive and one ground; a transformer, having primary and secondary windings, designed to match the transducer impedance coupled to said primary winding through said connecting cable to the characteristic impedance of said transmission cable coupled to said secondary winding, one end of said primary and secondary windings, respectively, is grounded at separate electrically isolated points; and means for insulating said primary winding ground from said secondary winding ground.
Claim 2
Dependent Claim
230 words
An improved acoustic emission transducer system for monitoring acoustic signals generated by a metal specimen when subject to mechanical stress comprising: a tubular housing having a side wall; a thin metallic window enclosing one end of said housing to form the bottom wall thereof; a piezoelectric element acoustically coupled to the interior of said bottom wall of said housing; a positive electrode electrically coupled to said piezoelectric element; means for electrically insulating said electrode and said piezoelectric element from the side wall of said housing; means for sealing said piezoelectric element against moisture so as to prevent moisture from shorting said element, access being provided to said electrode through said sealing means; means for mechanically damping both piezoelectric element resonances and spurious housing resonances; an electrically conductive connecting cable having two leads, one grounded at one end to said housing and the other electrically coupled at one end to said positive electrode; an electRically conductive transmission cable circuit having two leads, one positive and one ground; a transformer, having primary and secondary windings, designed to match the transducer impedance coupled to said primary winding through said connecting cable to the characteristic impedance of said transmission cable coupled to said secondary winding, one end of said primary and secondary windings, respectively, is grounded at separate electrically isolated points; and means for insulating said primary winding ground from said secondary winding ground.
Claim 3
Dependent Claim
15 words
The acoustic transducer of claim 1 wherein said transmission cable circuit comprises a coaxial cable.
Claim 4
Dependent Claim
73 words
The acoustic transducer of claim 1 including a preamplifier circuit; a termination transmission line coupled at one end to said preamplifier; and a second transformer having a primary and secondary winding designed to match the impedance of said transmission cable circuit coupled to said primary winding of said second transformer to the minimum noise impedance of said preamplifier circuit coupled through said termination transmission line to said secondary winding of said second transformer.
Claim 5
Dependent Claim
28 words
The acoustic transducer of claim 3 including a termination resistor shunting the primary winding of said second transformer so as to form part of said transmission cable circuit.
Claim 6
Dependent Claim
16 words
The acoustic transducer of claim 3 including means for processing and displaying the preamplifier output signal.
Claim 7
Dependent Claim
16 words
The acoustic emission transducer of claim 1 including electrostatic shielding around said transducer and transmission means.
Claim 8
Dependent Claim
21 words
The acoustic emission transducer of claim 6 wherein an aluminum oxide layer is interposed between said window and the metal specimen.
Claim 9
Dependent Claim
173 words
An improved acoustic emission monitoring system for monitoring acoustic signals generated by a metal specimen when subjected to mechanical stress comprising: an acoustic emission transducer having an electrical output responsive to and representative of acoustic input signals received by said transducer, said electrical output having a characteristic impedance associated therewith; an electrically conductive cable for transporting said electrical output to a remote location; a first means for electrically coupling said electrical output to said conducting cable and matching the characteristic impedance of said electrical output to the impedance of said conducting cable at the transducer/cable coupling interface; means for procesing said electrical output at the remote location having an input from said electrically conductive cable; and a second means for electrically coupling said conductive cable at the remote location to said signal processing input and matching the characteristic impedance of said conducting cable to the minimum noise impedance of said signal processing input at the cable/processor coupling interface in a manner to terminate said conductive cable in its characteristic impedance at both ends.
Claim 10
Dependent Claim
173 words
An improved acoustic emission monitoring system for monitoring acoustic signals generated by a metal specimen when subjected to mechanical stress comprising: an acoustic emission transducer having an electrical output responsive to and representative of acoustic input signals received by said transducer, said electrical output having a characteristic impedance associated therewith; an electrically conductive cable for transporting said electrical output to a remote location; a first means for electrically coupling said electrical output to said conducting cable and matching the characteristic impedance of said electrical output to the impedance of said conducting cable at the transducer/cable coupling interface; means for procesing said electrical output at the remote location having an input from said electrically conductive cable; and a second means for electrically coupling said conductive cable at the remote location to said signal processing input and matching the characteristic impedance of said conducting cable to the minimum noise impedance of said signal processing input at the cable/processor coupling interface in a manner to terminate said conductive cable in its characteristic impedance at both ends.
Claim 11
Dependent Claim
23 words
The acoustic emission monitoring system of claim 8 wherein said transducer and said conducting cable are respectively grounded at separate electrically isolated points.
Claim 12
Dependent Claim
20 words
The acoustic emission monitoring system of claim 8 wherein said first and second coupling means respectively comprise impedance matching transformers.
Claim 13
Dependent Claim
52 words
The acoustic emission monitoring system of claim 10 wherein the corresponding secondary winding of said first coupling means and primary winding of said second coupling means have a grounded center tap so as to provide a symmetrical output signal with respect to ground across the secondary winding of said second coupling means.
Claim 14
Dependent Claim
139 words
An improved acoustic emission transducer system for monitoring acoustic signals generated by a metal specimen when subject to mechanical stress comprising: a tubular housing having a side wall; a thin metallic window enclosing one end of said housing to form the bottom wall thereof; a piezoelectric element forMed in the shape of a disc having approximately equal thickness and radial resonance frequencies coupled to the interior of said bottom wall of said housing; a positive electrode electrically coupled to said piezoelectric element; means for electrically insulating said electrode and said piezoelectric element from the side wall of said housing; means for sealing said piezoelectric element against moisture so as to prevent moisture from shorting said element, access being provided to said electrode through said sealing means; and means for mechanically damping both piezoelectric element resonances and spurious housing resonances.
Claim 15
Dependent Claim
139 words
An improved acoustic emission transducer system for monitoring acoustic signals generated by a metal specimen when subject to mechanical stress comprising: a tubular housing having a side wall; a thin metallic window enclosing one end of said housing to form the bottom wall thereof; a piezoelectric element forMed in the shape of a disc having approximately equal thickness and radial resonance frequencies coupled to the interior of said bottom wall of said housing; a positive electrode electrically coupled to said piezoelectric element; means for electrically insulating said electrode and said piezoelectric element from the side wall of said housing; means for sealing said piezoelectric element against moisture so as to prevent moisture from shorting said element, access being provided to said electrode through said sealing means; and means for mechanically damping both piezoelectric element resonances and spurious housing resonances.
Claim 16
Dependent Claim
18 words
The acoustic emission transducer of claim 12 wherein said positive electrode is constructed from oxygen-free high conductivity copper.
Claim 17
Dependent Claim
24 words
The acoustic emission transducer of claim 12 wherein said housing and said window are constructed from materials having substantially equivalent coefficients of thermal expansion.
Claim 18
Dependent Claim
28 words
The acoustic emission transducer of claim 12 wherein said housing and said window are constructed from a material having a radioactive half-life in the order of 1 month.
Claim 19
Dependent Claim
33 words
The acoustic emission transducer of claim 12 wherein said piezoelectric element is fastened to the interior of said bottom wall of said housing by means of a thin electrically conductive high temperature adhesive.
Claim 20
Dependent Claim
19 words
The acoustic emission transducer of claim 12 wherein said insulating means and said damping means comprises a ceramic material.
Claim 21
Dependent Claim
15 words
The acoustic emission transducer of claim 12 wherein said sealing means comprises a silicone sealant.
Claim 22
Dependent Claim
92 words
The acoustic emission transducer of claim 12 wherein said means for insulating said electrode and said piezoelectric element from the side wall of said housing, said means for sealing said piezoelectric element against moisture and said means for mechanically damping said piezoelectric element comprises an inner tubular housing of high temperature insulating material characteristically resistant to moisture which is closely received within said tubular housing, said inner housing having an inner formed channel which closely surrounds said piezoelectric element and said positive electrode around the perimeter thereof excluding the piezoelectric element/window interface.
Claim 23
Dependent Claim
18 words
The acoustic emission transducer of claim 19 wherein said high temperature insulating material comprises a high temperature plastic.
Claim 24
Dependent Claim
38 words
The acoustic emission transducer of claim 12 including an end cover hermetically sealed to and enclosing the other end of said housing opposite said window, said end cover having an access port to said electrode for terminal connection.
Claim 25
Dependent Claim
169 words
An improved acoustic emission transducer for monitoring acoustic signals generated by a metal specimen when subject to mechanical stress comprising: a tubular housing having a side wall; a thin metallic window enclosing one end of said housing to form the bottom wall thereof; a piezoelectric element acoustically coupled to the interior of said bottom wall of said housing wherein said bottom wall is constructed to have an effective area in acoustic contact with the specimen at least equal to and juxtaposed the surface area of said piezoelectric element in contact with said window; and a thermal standoff acoustically coupling and separating the effective area of said window and specimen, shaped in the form of a truncated cone having the area of the plane replacing the cone''s apex substantially equal to the effective area of said window and acoustically coupled to the specimen, the base of said cone is acoustically coupled to said window so as to provide a thermally insulated acoustic path from the specimen to said piezoelectric element.
Claim 26
Dependent Claim
169 words
An improved acoustic emission transducer for monitoring acoustic signals generated by a metal specimen when subject to mechanical stress comprising: a tubular housing having a side wall; a thin metallic window enclosing one end of said housing to form the bottom wall thereof; a piezoelectric element acoustically coupled to the interior of said bottom wall of said housing wherein said bottom wall is constructed to have an effective area in acoustic contact with the specimen at least equal to and juxtaposed the surface area of said piezoelectric element in contact with said window; and a thermal standoff acoustically coupling and separating the effective area of said window and specimen, shaped in the form of a truncated cone having the area of the plane replacing the cone''s apex substantially equal to the effective area of said window and acoustically coupled to the specimen, the base of said cone is acoustically coupled to said window so as to provide a thermally insulated acoustic path from the specimen to said piezoelectric element.
Claim 27
Dependent Claim
25 words
The acoustic emission transducer of claim 22 wherein the height of said cone is sized to substantially equal one half wavelength of the acoustic signal.
Claim 28
Dependent Claim
15 words
The acoustic emission transducer of claim 22 wherein said thermal standoff is construCted from quartz.
Claim 29
Dependent Claim
178 words
An improved acoustic emission transducer system for monitoring acoustic signals generated by a metal specimen when subject to mechanical stress and transmitting such signals generated over relatively long distances comprising: a tubular housing having a side wall; a thin metallic window enclosing one end of said housing to form the bottom wall thereof; a piezoelectric element acoustically coupled to the intereior of said bottom wall of said housing; a positive electrode electrically coupled to said piezoelectric element; means for electrically insulating said electrode and said piezoelectric element from the side wall of said housing; an electrically conductive connecting cable having two leads, one grounded at one end to the transducer housing and the other electrically coupled at one end to said positive electrode; an electrically conductive transmission cable circuit having two leads; and a transformer, having primary and secondary windings, designed to match the transducer impedance coupled to said primary winding through said connecting cable to the characteristic impedance of said transmission cable coupled to said secondary winding and wherein said secondary winding has a grounded center tap.
Claim 30
Dependent Claim
178 words
An improved acoustic emission transducer system for monitoring acoustic signals generated by a metal specimen when subject to mechanical stress and transmitting such signals generated over relatively long distances comprising: a tubular housing having a side wall; a thin metallic window enclosing one end of said housing to form the bottom wall thereof; a piezoelectric element acoustically coupled to the intereior of said bottom wall of said housing; a positive electrode electrically coupled to said piezoelectric element; means for electrically insulating said electrode and said piezoelectric element from the side wall of said housing; an electrically conductive connecting cable having two leads, one grounded at one end to the transducer housing and the other electrically coupled at one end to said positive electrode; an electrically conductive transmission cable circuit having two leads; and a transformer, having primary and secondary windings, designed to match the transducer impedance coupled to said primary winding through said connecting cable to the characteristic impedance of said transmission cable coupled to said secondary winding and wherein said secondary winding has a grounded center tap.
Claim 31
Dependent Claim
18 words
The acoustic emission transducer of claim 25 wherein said connecting cable and said transmission cable have twisted leads.
Claim 32
Dependent Claim
74 words
The acoustic emission transducer of claim 25 including: a preamplifier circuit; a termination transmission line coupled at one end to said preamplifier; and a second transformer having a primary and secondary winding designed to match the impedance of said transmission cable circuit coupled to said primary winding of said second transformer to the minimum noise impedance of said preamplifier circuit coupled through said termination transmission line to said secondary winding of said second transformer.
Claim 33
Dependent Claim
29 words
The acoustic emission transducer of claim 27 including a termination resistor shunting the primary winding of said second transformer so as to form part of said transmission cable circuit.
Claim 34
Dependent Claim
17 words
The acoustic emission transducer of claim 27 including means for processing and displaying the preamplifier output signal.
Claim 35
Dependent Claim
20 words
The acoustic emission transducer of claim 27 wherein the primary winding of said second transformer has a grounded center tap.
Claim 36
Dependent Claim
24 words
The acoustic emission transducer system of claim 25 including electrostatic shielding around said housing, said connecting cable, said transformer and said transmission cable circuit.
Claim 37
Dependent Claim
21 words
The acoustic emission transducer of claim 31 wherein an aluminum oxide layer is interposed between said window and the metal specimen.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-23 | 1978-06-24 | 1978-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-23 | 1982-06-24 | 1982-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-23 | 1986-06-24 | 1986-12-24 | $7700.00 | Window Closed / Lapsed |