US4596150A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Contact-free, magnetic, stress and temperature sensor
Assignee: Boeing North American Inc
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Filing: 1985-03-21
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Granted: 1986-06-24
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Expires: 2005-03-21
Abstract
Abstract A method and apparatus for contact-free measurements of stress, temperature, torque, or other physical conditions which affect the magnetic properties of a non-ferromagnetic test object 10. The non-contacting magnetic sensor detects the large Barkhausen effect. Magnetic layers 12,14 of thin magnetic material are formed on surface 16 of test object 10. An easy axis of magnetization is formed on the magnetic layers 12,14 making them susceptible to the large Barkhausen effect. A physical condition, such as stress 17,17', is applied to test object 10 and magnetic field 18 is generated by source 19. Magnetic field 18 causes large Barkhausen effects to be generated in magnetic layers 12,14 which are detected by detector 20. The level of the physical condition is a function of the time required for the large Barkhausen effect to occur in the different magnetic layers 12,14. The level of the physical condition is calculated by comparing the time difference required for the large Barkhausen effect to take place in magnetic layers 12,14 with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of the physical condition.
Inventors
- 👤 George A. Kuhr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 18:42
CPC Classifications
G; G01; G01B; G01B7/00; G01B7/16; G01B7/24; G01K; G01K7/00; G01K7/36; G01L; G01L1/00; G01L1/12; G01L1/125; G01L3/00; G01L3/02; G01L3/04; G01L3/10; G01L3/101; G01L3/102
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
145 words
A contact-free method of determining the physical condition on a non-ferromagnetic object which comprises the steps of: subjecting the object having at least two magnetic layers, wherein each magnetic layer is a different ferromagnetic material each having an easy axis of magnetization, to a physical condition which influences the time reponse of each magnetic layer to a magnetic field; subjecting said magnetic layers to a magnetic field whereby a large Barkhausen effect is generated in each of said magnetic layers; detecting the large Barkhausen effect within each of said magnetic layers; measuring the difference in the times, Δt, at which said large Barkhausen effects take place in said magnetic layers; and determining the physical condition of the object by comparing said time difference with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of said physical condition.
Claim 2
Dependent Claim
145 words
A contact-free method of determining the physical condition on a non-ferromagnetic object which comprises the steps of: subjecting the object having at least two magnetic layers, wherein each magnetic layer is a different ferromagnetic material each having an easy axis of magnetization, to a physical condition which influences the time reponse of each magnetic layer to a magnetic field; subjecting said magnetic layers to a magnetic field whereby a large Barkhausen effect is generated in each of said magnetic layers; detecting the large Barkhausen effect within each of said magnetic layers; measuring the difference in the times, Δt, at which said large Barkhausen effects take place in said magnetic layers; and determining the physical condition of the object by comparing said time difference with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of said physical condition.
Claim 3
Dependent Claim
15 words
The method as described in claim 1 wherein the physical condition being determined is stress.
Claim 4
Dependent Claim
15 words
The method as described in claim 1 wherein the physical condition being determined is temperature.
Claim 5
Dependent Claim
29 words
The method as described in claim 1 wherein said easy axis is formed by prestressing the object, depositing the magnetic materials onto the object, and then releasing the object.
Claim 6
Dependent Claim
33 words
The method as described in claim 1 wherein the easy axis and magnetic layers are formed by depositing the magnetic material onto the object in the presence of a static, biasing magnetic field.
Claim 7
Dependent Claim
17 words
The method of claim 1 wherein two magnetic layers of magnetic material are formed on the object.
Claim 8
Dependent Claim
16 words
The method of claim 1 wherein the large Barkhausen effect is detected by a pickup coil.
Claim 9
Dependent Claim
24 words
The method of claim 1 wherein said magnetic layers are formed by attaching them to the object via a film gage which contains them.
Claim 10
Dependent Claim
26 words
The method as described in claim 1 wherein the object is stationary and said magnetic field is an alternating, time-varying magnetic field having a period, T.
Claim 11
Dependent Claim
60 words
The method as described in claim 9 wherein the determination of physical condition is made by taking the ratio of the time difference, Δt, to the period, T, of the time-varying magnetic field, i.e., Δt/T, and comparing this ratio to ratios determined while using magnetic layers similarly formed on a calibration object subjected to known levels of said physical condition.
Claim 12
Dependent Claim
75 words
The method of claim 1 wherein the object is a rotatable shaft with period T s , and wherein the method of subjecting said magnetic layers to a magnetic field comprises the steps of: rotating said magnetic layers through a first magnetic field for aligning the magnetic domains of the magnetic layers in a first direction along the easy axis; and rotating said magnetic layers through a second magnetic field for reversing said magnetic domains.
Claim 13
Dependent Claim
13 words
The method of claim 11 wherein the physical condition being determined is torque.
Claim 14
Dependent Claim
18 words
The method of claim 11 wherein said magnetic fields are generated by two permanent magnets with oppositely-oriented poles.
Claim 15
Dependent Claim
17 words
The method of claim 11 wherein said magnetic fields are generated by two electromagnets with oppositely-oriented poles.
Claim 16
Dependent Claim
61 words
The method of claim 11 wherein the determination of physical condition is made by taking the ratio of the time difference, Δt, to the period, T s , of rotation of the shaft, i.e., Δt/T s , and comparing this ratio to ratios determined while using layers similarly formed on a calibration object subjected to known levels of said physical condition.
Claim 17
Dependent Claim
126 words
A contact-free method of determining the stress on a non-ferromagnetic stationary object comprising the steps of: stressing the object having at least two magnetic layers, wherein each magnetic layer is a different ferromagnetic material each having an easy axis of magnetization; subjecting said magnetic layers to an alternating, time-varying magnetic field whereby a large Barkhausen effect takes place within each of said magnetic layers; detecting the large Barkhausen effect within each of said magnetic layers; measuring the difference in the times at which said large Barkhausen effects take place in said magnetic layers; and determining the physical condition of the object by comparing said time difference with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of stress.
Claim 18
Dependent Claim
126 words
A contact-free method of determining the stress on a non-ferromagnetic stationary object comprising the steps of: stressing the object having at least two magnetic layers, wherein each magnetic layer is a different ferromagnetic material each having an easy axis of magnetization; subjecting said magnetic layers to an alternating, time-varying magnetic field whereby a large Barkhausen effect takes place within each of said magnetic layers; detecting the large Barkhausen effect within each of said magnetic layers; measuring the difference in the times at which said large Barkhausen effects take place in said magnetic layers; and determining the physical condition of the object by comparing said time difference with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of stress.
Claim 19
Dependent Claim
154 words
A contact-free method of determining the torque on a non-ferromagnetic rotatable shaft which comprises the steps of: subjecting the object having at least two magnetic layers, wherein each magnetic layer is a different ferromagnetic material each having an easy axis of magnetization, to a torque; rotating said magnetic layers through a first magnetic field for aligning the magnetic domains of the magnetic layers in a first direction on the easy axis; rotating said magnetic layers through a second magnetic field whereby a large Barkhausen effect takes place within each of said magnetic layers; detecting the large Barkhausen effect within each of said magnetic layers; measuring the difference in the times at which said large Barkhausen effects take place in said magnetic layers; and determining the torque on the shaft by comparing said time difference with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of torque.
Claim 20
Dependent Claim
154 words
A contact-free method of determining the torque on a non-ferromagnetic rotatable shaft which comprises the steps of: subjecting the object having at least two magnetic layers, wherein each magnetic layer is a different ferromagnetic material each having an easy axis of magnetization, to a torque; rotating said magnetic layers through a first magnetic field for aligning the magnetic domains of the magnetic layers in a first direction on the easy axis; rotating said magnetic layers through a second magnetic field whereby a large Barkhausen effect takes place within each of said magnetic layers; detecting the large Barkhausen effect within each of said magnetic layers; measuring the difference in the times at which said large Barkhausen effects take place in said magnetic layers; and determining the torque on the shaft by comparing said time difference with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of torque.
Claim 21
Dependent Claim
132 words
A contact-free sensor for determining physical conditions comprising: a non-ferromagnetic object; at least two magnetic layers formed on said object, wherein each of said magnetic layers is a different ferromagnetic material such having an easy axis of magnetization; means for subjecting said magnetic layers to a magnetic field for generating a large Barkhausen effect in each of said magnetic layers; detection means for detecting the large Barkhausen effect within each of said layers; means associated with said detector for measuring the difference in the times at which said Barkhausen effects take place in said magnetic layers and for determining the physical condition of the object by comparing said time difference with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of said physical condition.
Claim 22
Dependent Claim
132 words
A contact-free sensor for determining physical conditions comprising: a non-ferromagnetic object; at least two magnetic layers formed on said object, wherein each of said magnetic layers is a different ferromagnetic material such having an easy axis of magnetization; means for subjecting said magnetic layers to a magnetic field for generating a large Barkhausen effect in each of said magnetic layers; detection means for detecting the large Barkhausen effect within each of said layers; means associated with said detector for measuring the difference in the times at which said Barkhausen effects take place in said magnetic layers and for determining the physical condition of the object by comparing said time difference with time differences measured while using magnetic layers similarly formed on a calibration object subjected to known levels of said physical condition.
Claim 23
Dependent Claim
14 words
The contact-free sensor of claim 18 wherein the physical condition being determined is stress.
Claim 24
Dependent Claim
14 words
The contact-free sensor of claim 18 wherein the physical condition being determined is temperature.
Claim 25
Dependent Claim
23 words
The sensor of claim 18 wherein the object is stationary and wherein said magnetic field is produced by an alternating, time-varying, magnetic source.
Claim 26
Dependent Claim
87 words
The contact-free sensor of claim 18 wherein the object is a rotatable shaft and said means for subjecting said magnetic layers to a magnetic field comprise: a first magnet in the vicinity of the shaft for generating a magnetic field to align the magnetic domains of said magnetic layers in a first direction on the easy axis; and a second magnet in the vicinity of the shaft, with poles oriented in opposite directions from said first magnet for generating a large Barkhausen effect in said magnetic layers.
Claim 27
Dependent Claim
14 words
The contact-free sensor of claim 22 wherein the physical condition being determined is torque.
Claim 28
Dependent Claim
14 words
The contact-free sensor of claim 22 wherein the physical condition being determined is temperature.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-06-23 | 1989-12-23 | 1990-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-23 | 1993-12-23 | 1994-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-06-23 | 1997-12-23 | 1998-06-24 | $7700.00 | Window Closed / Lapsed |