Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2002-06-17
2004-08-31
Deb, Anjan (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S691000
Reexamination Certificate
active
06784672
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus and method for detecting the density of logs, cants, timbers, poles or trees. More particularly, the present invention relates to the detection of anomalies such as knots in wood.
2. Discussion of the Background
Lumber is typically sorted and classified primarily on the basis of the number of knots or other defects or anomalies therein. Lumber value may be increased by theoretical detection of internal log characteristics followed by orientation of the log on the carriage. In addition, cants sawn from logs are then sent to a resaw for processing into lumber.
Bowyer and Haygreen in
Forest Products and Wood Science
(1982) note that the characteristics of certain abnormal wood types such as compression wood, tension wood and juvenile wood can result in inferior performance of the wood products they contain. Compression wood is formed on the ground side of boles leaning softwood trees; tension wood is formed on the side opposite the ground on leaning hardwood trees. Juvenile wood formed near tree pith in the first 10 to 15 years of tree growth. Compression wood may exhibit longitudinal shrinkage up to 10 times more than that of normal wood. Wood products containing both normal and compression wood exhibit differential shrinkage when dried. Warpage is the result of this differential shrinkage.
Tension wood also shrinks abnormally longitudinally with the same warpage problems resulting. When machined, tension wood often has a fuzzy surface making furniture finishes substandard. Cell collapse during drying also frequently occurs resulting in a lumber grade-reducing drying defect.
Juvenile wood has thinner cell walls with resultant lower strength properties. Lumber with low strength properties may be assigned to a lower lumber grade. For this reason restrictions on purchases of young timber have been imposed in recent years as plantation timber growth rates have accelerated.
Differential orientation of the log or cant can change the location of the defects in the lumber sawn from the log and thereby change lumber grade and resultant value. To date, research on log positioning has focused on angular orientation of the logs about their central axes. Most defects in both logs and lumber are knot defects so that most of the influence on value change results from changing knot location in lumber by rotating the log. Peter et al.,
Forest Prod. J
. 2(11):47-50 (1962); Peter,
Forest Prod. J
. 17(11):19-24 (1967); Tsolakides,
Forest Prod. J
. 19(7):21-26 (1969); Wagner et al.,
Forest Prod. J
. 25(10):24-28 (1975); Richards et al., Res. Pap. FPL-356, USDA Forest Serv., Forest Prod. Lab. (1980); Steele et al.,
Forest Prod. J
. 44(3):69-72 (1994) have all conducted studies relating to the influence of angular orientation on increased lumber value and have indicated increases ranging from 9 percent to 21 percent for hardwood and 7.5 percent for southern yellow pine. All of these referenced studies, however, involved some form of computer simulation of the sawing process to determine increased lumber value.
Application of various technologies to perform internal log scanning have been pursued. For example, Szymani,
Scanning Technology and Process Optimization: Advances in the Wood Industry
, Miller Freeman Books (1999), discloses attempts at X-ray, NMR and ultrasound log scanning. A basic presumption for the application of internal log scanning to log sawing is that the knowledge of internal defects will lead to choosing the best sawing position and method and, therefore, will allow sawmills to realize potential gain. Development of devices for internal log scanning, however, requires solving numerous technical and cost problems before industrial application is feasible.
Shafer and Ross (2000) have disclosed, in U.S. Pat. No. 6,029,522, an ultrasonic device that allows detection of localized anomalies such as knots, decay and voids in logs. Multiple measurements allow generation of maps of anomaly location such that sawing decisions can position sawlines to produce lumber with maximum value. Haddox,
Wood Technology
127(2):22-27 (2000), reports a commercial installation of an ultrasound cant scanner.
A number of patents and publications, for example, U.S. Pat. No. 3,549,986 to Prine, U.S. Pat. No. 4,123,702 to Kinanen et al., U.S. Pat. No. 4,500,835 to Heikkila et al., British Patent Specification No. 1,489,554 and Finnish Patent Publication No. 53,365, disclose the use of microwaves to detect knots or slope of grain. Other patents such as, for example, U.S. Pat. No. 4,972,154 to Bechtel et al., U.S. Pat. No. 3,805,156 to Norton et al. and U.S. Pat. No. 5,585,732 to Steele and Kumar, disclose devices that employ radio frequency waves to detect knots or slope of grain in lumber. Neither the microwave nor the radio frequency lumber scanning devices describe the ability to detect knots or other types of density differences in logs, cants, timber, poles or trees.
Kaestner et al.,
Microwave Polarimetry
-
Based Wood Scanning
, Proceedings of the 12
th
International Symposium on Non-Destructive Testing of Wood, September 13-15, University of Western Hungary (2000), describe a device that employs a waveguide that both transmits microwaves and receives the reflected waves in the range of 4 to 8 GHz. The researchers employed analysis of the polarized signal because attenuated signals from surfaces within the log were so weak as to be difficult to identify. Internal knots and other density-related areas in scanned log sections were able to be delineated in the tomographic slices produced by this microwave scanning device. This Kaestner et al. device differs from the TLDD in that microwaves rather than radio frequency signals are employed to detect density-based anomalies. Wave guides are employed as sending and receiving transducers by the Kaestner et al. device while the TLDD employs electrodes as sending and receiving transducers.
A number of references disclose the use of computer tomography imaging in combination with technology such as X-ray technology to detect anomalies in logs. For example, U.S. Pat. No. 6,026,173 to Svenson et al. discloses a microwave tomographic device to detect dielectric property differences within biologic tissue. Multiple receiving and transmitting waveguides are arranged in a ring, and the object to be scanned is placed within the circular array. Multiple frequencies are transmitted through the tissue in frequencies ranging from 0.1 to 300 GHz by opposing transmitting and receiving waveguides. Signal analysis of the multiple frequency response to dielectric differences within the tissue allows imaging of the structures responsible for these differences. As with the Kaestner et al. device, the Svenson device employs microwaves transmitted and received with wave guides. This differs from the TLDD in that radio frequency signals are transmitted and received with electrodes.
Huang et al.,
Tomographic Imaging of Two
-
Component Flow using Capacitance Sensors
, Institute of Physics Publishing Co. (1989), and U.S. Pat. No. 5,130,661 to Beck et al. describe the development of a laboratory prototype of a capacitance electrode scanner for performing application of Electrical Capacitance Tomography (ECT) to obtain images of two-component fluids flowing through pipes. The device consists of an eight-electrode capacitance sensor in which the 8 electrodes are arranged equidistant from each other on the external periphery of the circular pipe through which the fluid flows. The capacitance of a 2 MHz radio frequency signal is measured between all possible pairs of the 8 electrodes. An image of the respective area occupied in the internal cross section of the pipe by each component of the two-component fluid flow is developed. This is accomplished by computer reconstruction of the measured capacitance values with a linear back-projection algorithm.
Plaskowski et al. in their book
Imaging Industrial Flows: Applications of Electrical Process Tomography
(1995) describe ECT technology in con
Cooper Jerome
Lionheart William
Steele Philip
Benson Walter
Deb Anjan
Kelber Steven B.
Mississippi State University
Piper Rudnick LLP
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