Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
1999-03-03
2001-08-21
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C324S640000
Reexamination Certificate
active
06278412
ABSTRACT:
This invention relates to a method and means for measuring characteristics of a materials by using microwaves transmitted through the materials.
Use of such a technique in general terms has been well known for a number of years, and as an example, U.S. Pat. No. 2,659,860 describes the use of attenuation of microwaves as a useful technique for the detection of an extent of moisture in material of known density.
There have however been a number of technical and cost difficulties with this technique which has prevented this technique from revolutionising the industry and some of these have been appropriately described in U.S. Pat. No. 5,621,330.
A major application for this technique is the measurement of moisture in packed materials and in particular cotton so that a total quantity of moisture can be assessed.
Cotton, subsequent to processing which includes removal of seeds and other unwanted materials, is packed into bales and it is the moisture content of the cotton in each bale that is of some importance. This can be in the form typically of processed cotton bales or raw(seed) cotton in incoming module form.
The features of this invention have particular application to cotton and to cotton bales but are not specifically limited in their broadest application to simply cotton, and can in a broadest sense apply to any organic material.
A characteristic of a cotton bale is that it is made by tramping individual charges of cotton into a holding means after which they are pressed and then bound by straps or wires and held thereafter in a bale shape.
Each charge of cotton however is easily separable from adjacent charges and in practice, each charge forms a layer in the bale so that the bale is then made up from a number of these layers which are easily separable if the bale is eventually opened out or broken down.
Further however, each charge of cotton forming a layer tends to have more consistent characteristics within the charge or layer than might occur across the layer or in adjacent charges forming other layers.
Using a microwave transmission and reception system then with respect to such bales has a number of significant problems unless the bale when being measured is aligned so that the microwave energy from transmitter to receiver whether this is so as to pass fully through the bale or to be passed through and back again through the bale, passes substantially in the alignment direction of the individual layers. In other words, most of the microwave energy then would be expected to pass through a single individual layer and it is therefore the measurement of the characteristics of that layer which will be measured.
It has been previously considered not practicable to use what might be termed an orthogonal measurement technique for reasons some of which will now be explained.
A first of these reasons is that when the bale is constructed, and recalling that the all up mass of a bale can be very large indeed, the so-called height of the bale is not accurately defined.
It is understandable as to why this would be the case, but this does not help the situation when the bale is to be laid on a conveyer belt and a transmitter and receiver for microwave energy is to be located as close as feasible to the sides of the bale. This is done In order to minimise stray reflections or losses occasioned by passing microwave energy through the air a variable distance from the side of the bale.
If the bale therefore is not entirely accurately placed on a conveyer belt or its height (it is height when it is manufactured but it is laid over when it is on a conveyer belt so that the height is in fact a reference to the effective width for purposes of measurement of characteristics) can be such that the bale itself can impinge on a part of the microwave transmission or receiving equipment and the moment that this occurs then this destroys the accuracy of the system and substantial and urgent repairs with existing equipment may be necessary.
Further, while it has been considered that if it was possible it would provide a more uniform measurement if a measurement could be taken orthogonally, nonetheless, there appears to be internal reflections caused by boundaries between the layers that interferes with the microwave that has been previously attempted to be transmitted through these making any results difficult to interpret or not sufficiently accurate for commercial purposes.
To the applicant's knowledge therefore measurement of characteristics of a cotton bale using microwave attenuation or change has always occurred by passing the microwave energy substantially in the direction along layers within a bale.
We have found that we can now effectively measure characteristics of a cotton bale by directing microwave energy orthogonally to the previously accepted direction.
In other words, we can now effect a commercial system for assessment of characteristics of a cotton bale where the predominant direction of the microwave energy is from layer to layer so that the microwave energy passes through all or substantially all of the layers during a measurement.
There is one significant advantage in doing this which is that such a reading will be affected by the degree of moisture in each of the layers so that the one reading becomes implicitly a reading effected by the total measure of moisture in the bale or at least a reasonable sample of the moisture in each layer.
How have we overcome the implicit problems however.
In accordance with this invention then this can be said to reside in a microwave transmission antenna arrangement for transmission of microwave signals from a position located in the adjacent vicinity of a bale transfer apparatus for transporting bales past the antenna for assessment purposes characterized in that the antenna is supported so as to be a forgiving support by being relatively movable with respect to a support base.
In preference, the antenna is supported with means to restore to a transmission and/or receiving position the position of the antenna subsequent to any relative dislodgment movement.
Further, there are means to detect such displacement.
In a production facility however, it is not good enough simply to know that the equipment has been displaced but it is also a preferred feature that the antenna shall be supported so that subsequent to any dislodgment, it will be restored to an accurate transmission and/or receiving position.
In a preferred arrangement, there is a spring loaded mounting holding an antenna in position against matching faces.
A next problem however is that because the bale when it is being positioned with its indeterminate height now determining the width, it becomes preferable even with forgiving mounts to allow for a larger air gap between the transmission and receiving antenna and the side of the bale.
This introduces the problem that if the antenna is in the form of a horn in which the larger end of the horn then is adjacent an expected side of the bale, then the horn itself becomes accessible to incoming microwave signals which can be coming from a diverse number of directions.
In preference, there is then provided microwave absorption means positioned in the vicinity of the entry location of signals into the receiving antenna.
In preference, such microwave absorbing surface surrounds and is positioned to be more likely to absorb microwaves which are being directed other than directly into the antenna.
In preference, the antenna is in the shape of a horn and there is microwave absorption material located and of a shape such as a collar surrounding an end of the horn the position of the internal surfaces of the collar being such as to define a passageway of approximately rectangular dimensions matching an outer rectangular dimension of the horn and having parallel sides aligned so as to be also parallel to a main access of the horn.
In preference, the microwave absorption surfaces exhibit absorption at the appropriate frequency of at least 5 dB.
In preference, in accordance with a further feature, the frequency has been found to be a significan
Kelly Richard Kingswood
Kuchar Krzysztof Marian
Clinger James
Ho Tan
Senterfitt Akerman
Vomax Pty Ltd.
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