US4710752A
Expired / Lapsed
US
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Apparatus and method for detecting a magnetic marker
Assignee: Pitney Bowes Inc
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Filing: 1986-08-08
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Granted: 1987-12-01
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Expires: 2006-08-08
Abstract
Abstract This invention relates to an apparatus and method for detecting the presence of a magnetic marker in an interrogation zone. A dual frequency magnetic field is generated causing a magnetic marker to produce amplitude modulated side band signals at harmonics of the higher frequency field. These side band signals are readily distinguishable from amplitude noise.
Inventors
- 👤 Robert A. Cordery
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 01:14
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2408; G08B13/2465; G08B13/2468; G08B13/2477; G08B13/2488
Claims Analysis
Total Claims: 40
Claim 1
Independent Claim
91 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: first generating means for generating a first magnetic field in the interrogation zone at a first frequency, second generating means for generating a second magnetic field in the interrogation zone at a second frequency, said second frequency having a value less than approximately one-fifth of said first frequency and means for detecting amplitude modulated signals produced by a magnetic marker present in the interrogation zone when said first and second magnetic field generating means are enabled.
Claim 2
Independent Claim
91 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: first generating means for generating a first magnetic field in the interrogation zone at a first frequency, second generating means for generating a second magnetic field in the interrogation zone at a second frequency, said second frequency having a value less than approximately one-fifth of said first frequency and means for detecting amplitude modulated signals produced by a magnetic marker present in the interrogation zone when said first and second magnetic field generating means are enabled.
Claim 3
Dependent Claim
23 words
The system of claim 1 wherein said first frequency is greater than 5 kHz and said second frequency is less than 2 kHz.
Claim 4
Dependent Claim
26 words
The system of claim 1 wherein the ratio of the frequency of said first magnetic field to said second magnetic field varies from 5:1 to 100:1.
Claim 5
Dependent Claim
24 words
The system of claim 1 wherein the ratio of the frequency of the first magnetic field to the second magnetic field is approximately 20:1.
Claim 6
Independent Claim
87 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: first generating means for generating a magnetic field in the interrogation zone at a first frequency and first amplitude, second generating means for generating a second magnetic field in the interrogation zone at a second frequency and a second amplitude, said second frequency having a value of less than one fifth of said first frequency, and means for detecting amplitude modulated signals produced by a magnetic marker present in the interrogation zone.
Claim 7
Independent Claim
87 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: first generating means for generating a magnetic field in the interrogation zone at a first frequency and first amplitude, second generating means for generating a second magnetic field in the interrogation zone at a second frequency and a second amplitude, said second frequency having a value of less than one fifth of said first frequency, and means for detecting amplitude modulated signals produced by a magnetic marker present in the interrogation zone.
Claim 8
Dependent Claim
29 words
The system of claim 5 wherein the ratio of the amplitude of said first magnetic field to the amplitude of the second magnetic field varies from 2:1 to 30:1.
Claim 9
Dependent Claim
27 words
The system of claim 5 where the ratio of the amplitude of said first magnetic field to the amplitude of the second magnetic field is approximately 5:1.
Claim 10
Dependent Claim
29 words
The system of claim 5 wherein the ratio of the frequency of the first magnetic field to the frequency of the second magnetic field varies from 5:1 to 100:1.
Claim 11
Dependent Claim
26 words
The system of claim 5 wherein the ratio of the frequency of the first magnetic field to the frequency of the second magnetic field is 20:1.
Claim 12
Dependent Claim
39 words
The system of claim 6 wherein said first frequency is greater than 5 kHz, said first amplitude is greater than 3 Oe, said second frequency is less than 2 kHz and said second amplitude is less than 0.5 Oe.
Claim 13
Independent Claim
100 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: first generating means for generating a first magnetic field in the interrogation zone at a first frequency, second generating means for generating a second magnetic field in the interrogation zone at a second frequency, said second frequency having a value less than approximately one-fifth of said first frequency and means for measuring amplitude variations of a predetermined harmonic frequency of said first magnetic field produced by a magnetic marker present in the interrogation zone when said first and second magnetic field generating means are enabled.
Claim 14
Independent Claim
100 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: first generating means for generating a first magnetic field in the interrogation zone at a first frequency, second generating means for generating a second magnetic field in the interrogation zone at a second frequency, said second frequency having a value less than approximately one-fifth of said first frequency and means for measuring amplitude variations of a predetermined harmonic frequency of said first magnetic field produced by a magnetic marker present in the interrogation zone when said first and second magnetic field generating means are enabled.
Claim 15
Dependent Claim
23 words
The system of claim 11 wherein said first frequency is greater than 5 kHz and said second frequency is less than 2 kHz.
Claim 16
Dependent Claim
29 words
The system of claim 11 wherein the ratio of the frequency of the first magnetic field to the frequency of trhe second magnetic field varies from 2:1 to 100:1.
Claim 17
Dependent Claim
26 words
The system of claim 11 wherein the ratio of the frequency of the first magnetic field to the frequency of the second magnetic field is 20:1.
Claim 18
Independent Claim
119 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: first generating means for generating a magnetic field in the interrogation zone at a first frequency and first amplitude, second generating means for generating a second magnetic field in the interrogation zone at a second frequency and a second amplitude, said second frequency having a value less than one-fifth of said first frequency and said second amplitude having a value of less than one-fourth of said first amplitude, and means for detecting amplitude variations about a predetermined multiple of said first magnetic field produced by a magnetic marker present in the interrogation zone when said first and second magnetic field generating means are enabled.
Claim 19
Independent Claim
119 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: first generating means for generating a magnetic field in the interrogation zone at a first frequency and first amplitude, second generating means for generating a second magnetic field in the interrogation zone at a second frequency and a second amplitude, said second frequency having a value less than one-fifth of said first frequency and said second amplitude having a value of less than one-fourth of said first amplitude, and means for detecting amplitude variations about a predetermined multiple of said first magnetic field produced by a magnetic marker present in the interrogation zone when said first and second magnetic field generating means are enabled.
Claim 20
Dependent Claim
39 words
The system of claim 15 wherein said first frequency is greater than 5 kHz, said first amplitude is greater than 3 Oe, said second frequency is less than 2 kHz and said second amplitude is less than 0.5 Oe.
Claim 21
Dependent Claim
29 words
The system of claim 15 wherein the ratios of the amplitude of said first magnetic field to the amplitude of the second magnetic field varies from 2:1 to 30:1.
Claim 22
Dependent Claim
27 words
The system of claim 15 wherein the ratio of the amplitude of said first magnetic field to the amplitude of the second magnetic field is approximately 5:1.
Claim 23
Dependent Claim
29 words
The system of claim 15 wherein the ratio of the frequency of the first magnetic field to the frequency of the second magnetic field varies from 5:1 to 100:1.
Claim 24
Dependent Claim
25 words
The system of claim 15 wherein the ratio of the frequency of the first magnetic field to the frequency of second magnetic field is 20:1.
Claim 25
Independent Claim
87 words
A method of detecting a magnetic marker in an interrogation zone, the steps comprising: (a) generating a first magnetic field in the interrogation zone at a first frequency, (b) generating a second magnetic field in the interrogation zone at a second frequency having a lower value than said first frequency, and (c) detecting the presence of a magnetic marker in the interrogation zone by detecting side band signals generated by the magnetic marker as a result of being exposed to the first and second magnetic fields simultaneously.
Claim 26
Independent Claim
87 words
A method of detecting a magnetic marker in an interrogation zone, the steps comprising: (a) generating a first magnetic field in the interrogation zone at a first frequency, (b) generating a second magnetic field in the interrogation zone at a second frequency having a lower value than said first frequency, and (c) detecting the presence of a magnetic marker in the interrogation zone by detecting side band signals generated by the magnetic marker as a result of being exposed to the first and second magnetic fields simultaneously.
Claim 27
Dependent Claim
36 words
The method of claim 21 including the step of generating a magnetic field with a first frequency of greater than 5 kHz and generating a second magnetic field with a frequency of less than 2 kHz.
Claim 28
Dependent Claim
51 words
The method of claim 21 wherein the step of generating the first and second magnetic fields includes generating said first and second fields in a manner such that the ratio of the frequency of the first magnetic field to the frequency of the second magnetic field varies from 2:1 to 100:1.
Claim 29
Dependent Claim
48 words
The method of claim 21 wherein the step of generating the first and second magnetic fields includes generating said first and second fields in a manner such that the ratio of the frequency of the first magnetic field to the frequency of the second magnetic field is 20:1.
Claim 30
Independent Claim
114 words
A method of detecting a magnetic marker in an interrogation zone, the steps comprising: (a) generating a first magnetic field in the interrogation zone at a first frequency and first amplitude, (b) generating a second magnetic field in the interrogation zone at a second frequency having a lower value than the first frequency and a second amplitude having a lower value than the first amplitude, and (c) detecting the presence of a magnetic marker in the interrogation zone by detecting side band signals about a predetermined multiple of the frequency of the first magnetic field generated by the magnetic marker as a result of being exposed to the first and second magnetic field simultaneously.
Claim 31
Independent Claim
114 words
A method of detecting a magnetic marker in an interrogation zone, the steps comprising: (a) generating a first magnetic field in the interrogation zone at a first frequency and first amplitude, (b) generating a second magnetic field in the interrogation zone at a second frequency having a lower value than the first frequency and a second amplitude having a lower value than the first amplitude, and (c) detecting the presence of a magnetic marker in the interrogation zone by detecting side band signals about a predetermined multiple of the frequency of the first magnetic field generated by the magnetic marker as a result of being exposed to the first and second magnetic field simultaneously.
Claim 32
Dependent Claim
57 words
The method of claim 25 wherein the step of generating the first and second magnetic fields includes generating the first field with a frequency greater than 5 kHz and an amplitude greater than 3 Oe, and generating the second magnetic field with a frequency of less than 2 kHz and an amplitude of less than 0.5 Oe.
Claim 33
Dependent Claim
38 words
The method of claim 25 wherein generating the first and second magnetic fields yields a ratio of the amplitude of said first magnetic field to the amplitude of the second magnetic field that varies from 2:1 to 30:1.
Claim 34
Dependent Claim
35 words
The method of claim 27 wherein generating the first and second magnetic fields yields a ratio of the amplitude of the first magnetic field to the amplitude of the second magnetic field of approximately 5:1.
Claim 35
Dependent Claim
38 words
The method of claim 25 wherein generating the first and second magnetic fields yields a ratio of the frequency of the first magnetic field to the frequency of the second magnetic field which varies from 5:1 to 100:1.
Claim 36
Dependent Claim
35 words
The method of claim 25 wherein generating the first and second magnetic fields yields a ratio of the frequency of the first magnetic field to the frequency of the second magnetic field of approximately 20:1.
Claim 37
Independent Claim
87 words
A method of detecting the presence of a magnetic marker in an interrogation zone, the steps comprising: (a) generating a dual frequency magnetic field of frequencies f 1 and f 2 in the interrogation zone, wherein f 1 is at least twice the value of f 2 , (b) passing a magnetic marker through the interrogation zone to generate sideband signals around the harmonics of the frequency f 1 and (c) determining the presence of the magnetic marker in the interrogation zone by detecting the sideband signals.
Claim 38
Independent Claim
87 words
A method of detecting the presence of a magnetic marker in an interrogation zone, the steps comprising: (a) generating a dual frequency magnetic field of frequencies f 1 and f 2 in the interrogation zone, wherein f 1 is at least twice the value of f 2 , (b) passing a magnetic marker through the interrogation zone to generate sideband signals around the harmonics of the frequency f 1 and (c) determining the presence of the magnetic marker in the interrogation zone by detecting the sideband signals.
Claim 39
Independent Claim
88 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: (a) means for generating a magnetic field of frequencies f 1 and f 2 in the interrogation zone, wherein f 1 is at least twice the value of f 2 , whereby sideband signals around the harmonics of the f 1 frequency are generated upon a magnetic marker's being passed through the interrogation zone and (b) means for determining the presence of a marker in the interrogation zone by detecting said sideband signals.
Claim 40
Independent Claim
88 words
A system for detecting the presence of a ferromagnetic marker in an interrogation zone, comprising: (a) means for generating a magnetic field of frequencies f 1 and f 2 in the interrogation zone, wherein f 1 is at least twice the value of f 2 , whereby sideband signals around the harmonics of the f 1 frequency are generated upon a magnetic marker's being passed through the interrogation zone and (b) means for determining the presence of a marker in the interrogation zone by detecting said sideband signals.
References Cited (Backward Citations)
US3747086A
Cited
US4139844A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-11-30 | 1991-06-01 | 1991-12-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-11-30 | 1995-06-01 | 1995-12-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-11-30 | 1999-06-01 | 1999-12-01 | $7700.00 | Window Closed / Lapsed |