US3639834A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Microwave moisture measurement apparatus having movable mirror scanning means
Assignee: Individual
•
Filing: 1970-04-17
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Granted: 1972-02-01
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Expires: 1990-04-17
Abstract
Abstract A microwave apparatus for measuring the moisture content of sheet material by producing a moisture signal proportional to the amount of microwaves absorbed by the water therein is described which employs a movable mirror scanning means for scanning the sheet material with a microwave beam transmitted between fixed transmitting and receiving antennas. A fixed mirror is positioned on the opposite side of the sheet from such scanning means for receiving the microwave beam reflected from a first movable mirror and reflecting the beam back through the sheet material to a second movable mirror. The movable mirrors are mounted on a carriage which is reciprocated back and forth across the moving sheet by a reversible motor coupled to a potentiometer for producing a position signal proportional to the position of such carriage. This position signal and the moisture signal are applied to the inputs of a computer for indicating the percentage moisture content of a sheet portion and its position on the sheet. The microwave beam passes through the sheet at an acute angle, in the range of 40* to 65*, to prevent standing wave interference distortion of the microwave beam. A telescope and light source are employed for optical alignment of the antennas and the movable mirrors.
Inventors
- 👤 Charles W E Walker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 03:04
CPC Classifications
G; G01; G01N; G01N22/00; G01N22/04
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
168 words
Microwave apparatus for measuring the moisture content of sheet material, comprising: microwave transmitter means including an output antenna mounted in a fixed position for generating a beam of microwave signals of a frequency so that when said beam is transmitted through said sheet material a portion of the beam is absorbed by the moisture in the sheet material; mirror means including at least one movable mirror for reflecting the microwave beam to cause said beam to be transmitted through a sheet portion of said sheet material; scanner means for moving the movable mirror relative to the sheet material to scan the beam of microwaves across the sheet material and cause said beam to be transmitted through different sheet portions; and microwave receiver means including an input antenna mounted in a fixed position for receiving the microwave beam after it is transmitted through the sheet material, and for converting the received microwaves into an electrical signal proportional to the moisture content of the sheet portion traversed by said beam.
Claim 2
Dependent Claim
168 words
Microwave apparatus for measuring the moisture content of sheet material, comprising: microwave transmitter means including an output antenna mounted in a fixed position for generating a beam of microwave signals of a frequency so that when said beam is transmitted through said sheet material a portion of the beam is absorbed by the moisture in the sheet material; mirror means including at least one movable mirror for reflecting the microwave beam to cause said beam to be transmitted through a sheet portion of said sheet material; scanner means for moving the movable mirror relative to the sheet material to scan the beam of microwaves across the sheet material and cause said beam to be transmitted through different sheet portions; and microwave receiver means including an input antenna mounted in a fixed position for receiving the microwave beam after it is transmitted through the sheet material, and for converting the received microwaves into an electrical signal proportional to the moisture content of the sheet portion traversed by said beam.
Claim 3
Dependent Claim
32 words
Microwave apparatus in accordance with claim 1 which also includes a position signal generator means for producing an electrical signal corresponding to the position of the microwave beam on the sheet material.
Claim 4
Dependent Claim
58 words
Microwave apparatus in accordance with claim 2 which also includes signal processing means having inputs connected to the outputs of the position signal generator means and the microwave receiver means for combining the moisture signal and the position signal to indicate the moisture content of the sheet portion and the position of said sheet portion on said sheet.
Claim 5
Dependent Claim
34 words
Microwave apparatus in accordance with claim 1 which also includes feeder means for moving the sheet material longitudinally and in which the scanner means moves the microwave beam laterally across the moving sheet material.
Claim 6
Dependent Claim
35 words
Microwave apparatus in accordance with claim 4 in which the mirror means includes two movable mirrors and a fixed mirror fixedly mounted on the opposite side of the sheet material from the two movable mirrors.
Claim 7
Dependent Claim
29 words
Microwave apparatus in accordance with claim 1 in which the scanner means includes a movable carriage on which the movable mirror is supported for movement across the sheet material.
Claim 8
Dependent Claim
33 words
Microwave apparatus in accordance with claim 6 in which the wheels of the carriage are supported on a track by guide roller means for enabling said carriage to be mounted in any position.
Claim 9
Dependent Claim
31 words
Microwave apparatus in accordance with claim 6 in which the scanner means includes a reversible motor means for reciprocating the carriage back and forth across the width of the sheet material.
Claim 10
Dependent Claim
89 words
Microwave apparatus in accordance with claim 6 in which the transmitter means directs the microwave beam in a first direction substantially parallel to the sheet material onto a first movable mirror which reflects the beam in a second direction through the sheet material onto a fixed mirror, the fixed mirror reflects the beam in a third direction through the sheet material again onto a second movable mirror, and the second movable mirror reflects the beam to the receiver means in a fourth direction substantially parallel to the sheet material.
Claim 11
Dependent Claim
65 words
Microwave apparatus in accordance with claim 8 which also includes optical alignment means for aligning the microwave antenna of the transmitter means with the microwave antenna of the receiver means and for aligning the movable mirrors with said antenna, said alignment means including a telescope and a light source attached to different ones of the antennas, and sighting holes provided through the two movable mirrors.
Claim 12
Dependent Claim
52 words
Microwave apparatus in accordance with claim 1 in which the microwave beam is free of frequency modulation and the beam strikes the sheet material at an acute angle to prevent the microwaves reflected by said sheet material from producing standing wave patterns which tend to cause interference distortion of the microwave beam.
Claim 13
Dependent Claim
21 words
Microwave apparatus in accordance with claim 11 in which the acute angle is in the range of 40* to 65* .
Claim 14
Dependent Claim
16 words
Microwave apparatus in accordance with claim 11 in which the acute angle is approximately 53* .
Claim 15
Dependent Claim
37 words
Microwave apparatus in accordance with claim 6 which also includes a microwave absorber member mounted on said carriage for movement with said movable mirror to position said absorber member between said sheet portion and said output antenna.
Claim 16
Dependent Claim
54 words
Microwave apparatus in accordance with claim 9 which also includes a pair of microwave absorber members mounted on said carriage for movement with said movable mirrors to position one absorber member between said sheet portion and said output antenna and to position the other absorber member between said sheet portion and said input antenna.
References Cited (Backward Citations)
US3278841A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-31 | 1975-08-02 | 1976-02-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-31 | 1979-08-02 | 1980-02-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-31 | 1983-08-02 | 1984-02-01 | $7700.00 | Window Closed / Lapsed |