US5349844A
Expired / Lapsed
US
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System and method for resonant filter mass monitoring
Assignee: Thermo Environmental Instruments Inc
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Filing: 1992-09-11
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Granted: 1994-09-27
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Expires: 2012-09-11
Abstract
Abstract A system and method for measuring particulate concentrations. The system includes a substantially planar, peripherally supported filter for capturing the particulates, an oscillator for oscillating the filter substantially perpendicular to its planar surface, and a sensor for measuring the frequency of oscillation.
Inventors
- 👤 Pedro Lilienfeld
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:21
CPC Classifications
G; G01; G01N; G01N5/00; G01G; G01G3/00; G01G3/12; G01G3/16; G01N15/00; G01N15/06; G01N15/0606; G01N15/0618
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
75 words
A system for detecting airborne particulate concentration, comprising: (a) a substantially planar filter; (b) an air sampler for obtaining an ambient air sample and causing said air sample to flow through said filter whereby airborne particulates in said air sample are deposited on said filter; (c) an oscillator for causing oscillatory movement of said filter substantially perpendicular to the plane of said filter; and (d) a detector for detecting said oscillatory movement of said filter.
Claim 2
Independent Claim
75 words
A system for detecting airborne particulate concentration, comprising: (a) a substantially planar filter; (b) an air sampler for obtaining an ambient air sample and causing said air sample to flow through said filter whereby airborne particulates in said air sample are deposited on said filter; (c) an oscillator for causing oscillatory movement of said filter substantially perpendicular to the plane of said filter; and (d) a detector for detecting said oscillatory movement of said filter.
Claim 3
Dependent Claim
21 words
A system for detecting airborne particulate concentration according to claim 1, wherein said filter comprises a portion of a filter tape.
Claim 4
Dependent Claim
17 words
A system for detecting airborne particulate concentration according to claim 1, wherein said filter comprises a membrane.
Claim 5
Dependent Claim
18 words
A system for detecting airborne particulate concentration according to claim 1, wherein said filter comprises a circular membrane.
Claim 6
Dependent Claim
20 words
A system for detecting airborne particulate concentration according to claim 1, wherein said filter includes at least one diametric node.
Claim 7
Dependent Claim
20 words
A system for detecting airborne particulate concentration according to claim 1, wherein said filter includes a plurality of circular nodes.
Claim 8
Dependent Claim
23 words
A system for detecting airborne particulate concentration according to claim 1, wherein the periphery of said filter is attached to a fixed support.
Claim 9
Dependent Claim
34 words
A system for detecting airborne particulate concentration according to claim 1, wherein said filter is a membrane selected from the group consisting essentially of Teflon, polyester, polypropylene, and an acrylic copolymer with nylon substrate.
Claim 10
Dependent Claim
19 words
A system for detecting airborne particulate concentration according to claim 1, wherein said oscillator means comprises an acoustical drive.
Claim 11
Dependent Claim
20 words
A system for detecting airborne particulate concentration according to claim 9, wherein said acoustical drive comprises a piezo-electric harmonic drive.
Claim 12
Dependent Claim
19 words
A system for detecting airborne particulate concentration according to claim 1, wherein said oscillator means comprises a capacitive drive.
Claim 13
Dependent Claim
17 words
A system for detecting airborne particulate concentration according to claim 1, wherein said detector comprises a microphone.
Claim 14
Dependent Claim
20 words
A system for detecting airborne particulate concentration according to claim 1, wherein said detector comprises an optical motion pick-up device.
Claim 15
Dependent Claim
19 words
A system for detecting airborne particulate concentration according to claim 1, wherein said detector comprises a capacitive charge device.
Claim 16
Independent Claim
122 words
A system for determining airborne particulate concentration, comprising: (a) a substantially planar filter; (b) an air sampler for obtaining an ambient air sample and causing said air sample to flow through said filter at a flow rate (Q) whereby airborne particulates in said air sample are deposited on said filter; (c) an oscillator for causing said filter to oscillate substantially perpendicular to the plane of said filter at a natural resonant frequency (f); (d) a detector for detecting said oscillatory movement of said filter; and (e) particulate concentration determining means for determining the airborne particulate concentration (C m ) of said sample based on the ratio between the initial (f 0 ) and final (f 1 ) resonant frequencies of said filter.
Claim 17
Independent Claim
122 words
A system for determining airborne particulate concentration, comprising: (a) a substantially planar filter; (b) an air sampler for obtaining an ambient air sample and causing said air sample to flow through said filter at a flow rate (Q) whereby airborne particulates in said air sample are deposited on said filter; (c) an oscillator for causing said filter to oscillate substantially perpendicular to the plane of said filter at a natural resonant frequency (f); (d) a detector for detecting said oscillatory movement of said filter; and (e) particulate concentration determining means for determining the airborne particulate concentration (C m ) of said sample based on the ratio between the initial (f 0 ) and final (f 1 ) resonant frequencies of said filter.
Claim 18
Dependent Claim
27 words
A system for determining airborne particulate concentration according to claim 15, wherein said concentration is obtained from said initial and final resonant frequencies of said filtration means.
Claim 19
Dependent Claim
58 words
A system for determining airborne particulate concentration according to claim 15, wherein said concentration of said sample is determined by equation: ##EQU9## where s is the filter stiffness, Q is the volumetric sampling flow rate, t is the elapsed sampling time period, and f 0 and f 1 are the initial and final resonant frequencies of said filter.
Claim 20
Dependent Claim
21 words
A system for determining airborne particulate concentration according to claim 15, wherein said elapsed sampling time period (t) is user selectable.
Claim 21
Dependent Claim
65 words
A system for determining airborne particulate concentration according to claim 15, wherein said airborne particulate concentration (C m ) is determined by equation: ##EQU10## where m 0 is the initial mass of the clean filter, Q is the volumetric sampling flow rate, t is the elapsed sampling time period, and f 0 , f 1 are the initial and final resonant frequencies of said filter.
Claim 22
Dependent Claim
17 words
The system of claim 15 including a fixed support engaging and supporting the periphery of said filter.
Claim 23
Independent Claim
91 words
A method for determining airborne particulate concentration, comprising the steps of: (a) obtaining an ambient air sample and providing said sample at a flow rate (Q); (b) collecting airborne particulates in said sample on a substantially planar filter; (c) oscillating said filter in a direction substantially perpendicular to the plane thereof; (d) detecting a natural resonant frequency (f) of said oscillating filter; and, (e) determining the airborne particulate concentration of said sample based on the ratio between initial (f 0 ) and final (f 1 ) resonant frequencies of said filter.
Claim 24
Independent Claim
91 words
A method for determining airborne particulate concentration, comprising the steps of: (a) obtaining an ambient air sample and providing said sample at a flow rate (Q); (b) collecting airborne particulates in said sample on a substantially planar filter; (c) oscillating said filter in a direction substantially perpendicular to the plane thereof; (d) detecting a natural resonant frequency (f) of said oscillating filter; and, (e) determining the airborne particulate concentration of said sample based on the ratio between initial (f 0 ) and final (f 1 ) resonant frequencies of said filter.
Claim 25
Dependent Claim
30 words
A method for determining airborne particulate concentration, according to claim 21, wherein said airborne particulate concentration of said sample is obtained from said initial and final resonant frequencies of said.
Claim 26
Dependent Claim
58 words
A method for determining airborne particulate concentration, according to claim 21, wherein said concentration of said sample is determined by equation: ##EQU11## where s is the filter stiffness, Q is the volumetric sampling flow rate, t is the elapsed sampling time period, and f 0 and f 1 are the initial and final resonant frequencies of said filter.
Claim 27
Dependent Claim
65 words
A method for determining airborne particulate concentration according to claim 20, wherein said airborne particulate concentration (C m ) is determined by equation: ##EQU12## where m 0 is the initial mass of the clean filter, Q is the volumetric sampling flow rate, t is the elapsed sampling time period, and f 0 and f 1 are the initial and final resonant frequencies of said filter.
Claim 28
Dependent Claim
15 words
The method of claim 21 wherein said filter is supported by a fixed peripheral support.
Claim 29
Independent Claim
97 words
A system for determining airborne particulate concentration comprising a sampling chamber, a filter mounted within said chamber such that an air sample obtained by said chamber is passed through said filter and airborne particles in said sample are collected by said filter, an oscillator for oscillating said filter, and a detector for determining the concentration of particles collected by said filter, said system being characterized in that said filter includes a collection area on which said particles are collected, and said oscillator is arranged to oscillate substantially only the portion of said filter comprising said collection area.
Claim 30
Independent Claim
97 words
A system for determining airborne particulate concentration comprising a sampling chamber, a filter mounted within said chamber such that an air sample obtained by said chamber is passed through said filter and airborne particles in said sample are collected by said filter, an oscillator for oscillating said filter, and a detector for determining the concentration of particles collected by said filter, said system being characterized in that said filter includes a collection area on which said particles are collected, and said oscillator is arranged to oscillate substantially only the portion of said filter comprising said collection area.
Claim 31
Dependent Claim
15 words
The system of claim 26 further characterized in that said collection area is substantially planar.
Claim 32
Dependent Claim
27 words
The system of claim 27 further characterized in that said oscillator is arranged to oscillate said collection area in a direction substantially perpendicular to the plane thereof.
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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) | 1997-09-26 | 1998-03-28 | 1998-09-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-09-26 | 2002-03-28 | 2002-09-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-09-26 | 2006-03-28 | 2006-09-27 | $7700.00 | Window Closed / Lapsed |