EP0453226A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Fiber optic liquid leak detector
Assignee: Raytheon Co
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Filing: 1991-04-16
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Granted: —
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Expires: 2011-04-16
Abstract
Abstract A precision liquid leak detector 10 free of mechanical moving parts is disclosed herein. The liquid leak detector 10 of the present invention is disposed to measure the rate of change of the volume of a liquid within a container 14. The leak detector 10 includes a light guide 16, implemented as an optical fiber, which is disposed within the container 14 and at least partially immersed in the liquid. The optical fiber 16 includes a fiber core circumscribed by a fiber cladding selected such that evanescent wave loss occurs as a result of immersion of the cladding within the liquid. The optical fiber 16 is positioned in optical alignment with a laser source 26, which injects optical energy therein. The leak detector 10 of the present invention further includes an arrangement 24 for measuring the decrease in the intensity of the injected optical energy occurring over a length of the fiber 16 immersed in the liquid. The measuring arrangement 24 then generates an intensity loss signal indicative of this intensity decrease. The inventive leak detector 10 also includes a network 36 and 38 for measuring the rate of change of the intensity loss signal and for calculating the rate of change of the liquid volume on the basis of the change in the intensity loss signal.
Inventors
- 👤 Victor Vali
- 👤 David B. Chang
- 👤 Patrick C. Brownrigg
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 12:14
CPC Classifications
G; G01; G01F; G01F23/00; G01M; G01M3/00; G01M3/02; G01M3/26; G01M3/32; G01M3/3236; G01M3/3245
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
107 words
A liquid leak detector for measuring a rate of change of volume of a first liquid within a container comprising: a light guide in which evanescent wave loss occurs as a result of immersion thereof in said liquid, said light guide at least partially immersed in said liquid; light source means for injecting optical energy into said light guide; means for measuring evanescent wave loss in said guide and providing an intensity loss signal indicative thereof; and leak detector means for measuring a rate of change of said intensity loss signal and calculating the rate of change of the volume of said first liquid in response thereto.
Claim 2
Dependent Claim
14 words
The leak detector of Claim 1 wherein said light guide includes an optical fiber.
Claim 3
Dependent Claim
59 words
The leak detector of Claim 2 wherein said optical fiber includes first and second ends, said light source means includes means for injecting said optical energy into said first end, and said leak detector further includes a fiber reflector disposed at said second end for reflecting said injected optical energy back into said fiber toward said light source means.
Claim 4
Dependent Claim
61 words
The leak detector of Claim 3 wherein said measuring means includes means for providing an input intensity signal indicative of the intensity of said optical energy injected into said first end and means for providing a return intensity signal indicative of the intensity of said injected optical energy which has traversed the optical fiber and has been reflected by said reflector.
Claim 5
Dependent Claim
39 words
The leak detector of Claim 4 wherein said measuring means further includes means for providing a ratio signal proportional to said intensity loss signal in response to the ratio of said return intensity signal and said input intensity signal.
Claim 6
Dependent Claim
74 words
The leak detector of Claim 4 wherein said measuring means includes first and second photodetectors and a fiber optic beamsplitter for directing a portion of the optical energy injected into said fiber to the first photodetector thereby providing said input intensity signal, and for directing a portion of the optical energy, which has traversed the optical fiber and reflected by said reflector, to the second photodetector in order to provide said return intensity signal.
Claim 7
Dependent Claim
74 words
The leak detector of Claim 2 further including a flexible membrane circumscribing at least the portion of said optical fiber within said container and a second liquid disposed within said flexible membrane wherein said leak detector measures the rate of change of the level of said second liquid and the rate of change of the level of said second liquid is indicative of the rate of change of the level of said first liquid.
Claim 8
Dependent Claim
77 words
The leak detector of Claim 2 further including an open rigid "J" shaped tube positioned within the tank and circumscribing at least a portion of said optical fiber, and a second liquid disposed within said tube, said second liquid having a density greater than the density of said first liquid and wherein the rate of change of the level of said second liquid is indicative of the rate of change of the level of said first liquid.
Claim 9
Dependent Claim
53 words
The leak detector of Claim 2 wherein said fiber cladding is characterized by an index of refraction n₁, said fiber core is characterized by an index of refraction n₂ where n₂ is greater than n₁, and wherein the liquid is characterized by an index of refraction n₃, where n₃ is greater than n₁.
Claim 10
Dependent Claim
181 words
A liquid leak detector for measuring the rate of change of the volume of a first liquid within a container, comprising: an optical fiber having a first end and a second end, said fiber being disposed within said container and at least partially immersed in said liquid wherein said fiber includes a fiber core circumscribed by a fiber cladding selected such that evanescent wave loss occurs as a result of immersion of said cladding in said liquid; a fiber end reflector attached to said first end of said optical fiber; light source means for injecting light into said second end of said optical fiber; beamsplitter means for coupling off a first portion of said injected light and for coupling off a second portion of the light which has traversed said fiber and been reflected by said reflector; and comparator means for comparing the intensity of said first portion of light with the rate of change of the intensity of said second portion of light and for determining the rate of change of the volume of said first liquid in response thereto.
Claim 11
Dependent Claim
63 words
The leak detector of Claim 10 further including a first photodetector responsive to the intensity of said first portion of light to provide an input intensity signal and a second photodetector responsive to the intensity of said second portion of light to provide an output intensity signal, wherein said comparator means is responsive to said input intensity signal and said output intensity signal.
Claim 12
Dependent Claim
27 words
The leak detector of Claim 1 wherein said leak detector means includes memory means for storing the value of said intensity loss signal at predetermined time intervals.
Claim 13
Dependent Claim
38 words
The leak detector of Claim 12 wherein said leak detector means further includes processor means for computing the rate of change of the volume of said first liquid by utilizing said stored values of said intensity loss signal.
Claim 14
Independent Claim
137 words
A method of measuring the rate of change of the volume of a liquid within a container, comprising the steps of: a) at least partially immersing a light guide within said liquid, said light guide including a core circumscribed by a cladding selected such that evanescent wave loss occurs as a result of immersion of said cladding in said liquid; b) injecting optical energy into said light guide; c) measuring any decrease in the intensity of said injected optical energy over a length of said fiber due to said evanescent wave loss; d) providing an intensity loss signal indicative of said decrease in the intensity of said injected optical energy; and e) calculating a rate of change of said intensity loss signal in order to determine the rate of change of the volume of said first liquid.
Claim 15
Dependent Claim
179 words
A liquid leak detector for detecting the presence of a contaminating liquid of refractive index n₄ in a container disposed to hold a first liquid of refractive index n₃ therein, comprising: an optical fiber disposed within said container and at least partially immersed in said first liquid, said fiber including a fiber core of refractive index n₂ circumscribed by a fiber cladding of refractive index n₁ selected such that evanescent wave loss occurs as a result of immersion of said cladding in said liquid, wherein n₂ > n₁, n₁ < n₃ and n₁ > n₄; light source means for injecting optical energy into said optical fiber; means for measuring any decrease in the intensity of said injected optical energy over a length of said fiber due to said evanescent wave loss, said measuring means including means for providing an intensity loss signal indicative of said intensity decrease; and leak detector means for generating a detection signal indicative of the presence of said contaminating liquid within said container in response to changes in the magnitude of said intensity loss signal.
References Cited (Backward Citations)
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