Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
2002-04-16
2003-01-07
Shah, Kamini (Department: 2856)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S097000, C073S849000
Reexamination Certificate
active
06505129
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to nondestructive testing of composite materials or panels, particularly wood based materials, such as plywood, oriented strand board, wafer board, particle board, and the like, to determine the strength and stiffness of such panels.
BACKGROUND OF THE INVENTION
The use and acceptance of composite materials and panels for various applications, such as, building constructions, continues to increase in the market place. As a result, it is becoming increasingly desirable to monitor the strength and stiffness of the panels being produced. This is so because the strength and stiffness of composite materials varies greatly due to the composite nature of the products and the difficulty in achieving uniform strength in the bonding materials used to join the composites together. Moreover, variations in feedstocks and other factors make manufacture of uniformly strong and elastic structures from composite elements difficult and costly.
Nondestructive inspection and testing of materials of all sorts is known. Many of the known methods for performing certain standards tests are manual or static methods. For example, to conduct a concentrated load test, it is known to build a frame with beams simulating joists in a building construction. The beams are spaced apart depending upon the end use and span rating of the panel to be tested. A hydraulically-actuated load is applied to the stationary panel at a specified distance from a non-secured edge and the deflection of the panel is measured by placing a dial-micrometer under the panel at a position opposite the load and reading the deflection on the micrometer scale.
U.S. Pat. No. 4,708,020 to Lau et al., which is incorporated herein by reference, relates to another form of nondestructive inspection and testing of composite panels to determine the strength and stiffness of the panels. More particularly, Lau et al. provide an apparatus and process for correlating end-use strength and stiffness values when the testing is carried out on hot panels. The panels may be tested at one temperature, approaching the press temperature, and the strength and stiffness determined for the end products at another temperature, generally ambient or end-use temperature. Lau et al. also provide a testing machine suitable for in-line testing for determining the strength and stiffness of panel products having different thicknesses. The testing machine of Lau et al. also enables panels to be graded so that rejects can be identified and panels can be separated into grade groups representing different strength and stiffness ranges.
The continuous panel tester of Lau et al. imposes a double reverse bend or “S” shaped configuration on the panels as they pass through the conveyor at line speed. The device of Lau et al. is configured and operated such that either the deflection of each panel may be measured for a specific load, or the load is measured for a particular deflection of each panel.
As set forth in Lau et al., there is provided a first in-feed roll and a last out-feed roll to direct each panel to be tested into and out of the overall continuous panel tester and grader. As also described in Lau et al., a plurality of photo switches along the conveyor line have the function of informing the microprocessor when a panel is in the tester. The photo switches of Lau et al. determine when one panel ends and a second panel commences to pass through the tester so as to ensure that readings from the load cells and temperature sensor represent strength and stiffness figures for one panel. Another feature of Lau et al. is the ability of the panel grader to test panels having different thicknesses by merely selecting the required nominal panel thickness. The microprocessor is programmed to control the necessary equipment to position the rolls of the apparatus to process the panels of the selected nominal thickness. Based on the selected nominal thickness which is inputted to the microprocessor, the microprocessor utilizes information received from the load cells and temperature sensor to calculate the hot strength and stiffness values for each panel and then the microprocessor uses a preprogrammed algorithm to determine the ambient or cold end-use strength and stiffness value for each of the tested panels. Lau et al. do provide that it may be desirable to use a thickness measuring sensor such as a laser sensor or an ultrasonic sensor, which is placed near the in-feed rolls of the panel tester, to obtain a more actual thickness measurement of each panel, as compared to using the selected nominal thickness for each panel, thereby providing for a more accurate calculation of the strength and stiffness properties for each panel.
Despite the increased use of composite materials for all sorts of building constructions and other uses, and the general desire to test the composite materials for strength and stiffness, a need still exists for an improved panel tester and grader which is efficient and economical in its manufacture and use and which also provides improved accuracy in terms of measuring and grading panel like products according to desired strength and stiffness values.
As can be appreciated by those skilled in the art, the many known manual methods for performing certain standard tests for panels or the like are generally labor intensive, slow processing, somewhat costly procedures that can readily lead to error or operator mistakes when trying to determine the strength and stiffness values for panels. Moreover, the known static testing machines do not allow a panel to continually move along the production line during testing, thereby limiting the usefulness of such testing equipment.
Although Lau et al. describe an automatic, continuous panel tester and grader which is in many aspects an improvement over the known manual or static methods, the device of Lau et al. also exhibits several problems. One problem with Lau et al. concerns the bending forces that are applied to the panels as they are fed to and passed out of the panel tester. Although Lau et al. recognize that no significant forces should be applied to the panels that would distort the loading forces of the panels in the “S” shaped path, it has actually been determined according to the present invention that the first in-feed roller (
40
) and the last out-feed roller (
70
) of Lau et al. (see
FIG. 2
thereof) do in fact apply undesirable bending forces or moments to the panels as they travel thereover, thereby resulting in significantly less than accurate strength and stiffness values for the tested panels. It has been determined according to the present invention that if the panels are subjected to a bending force outside the critical load zone or path, the deflection for a specific load or the load applied for a particular deflection may be greater than or less than what the actual deflection or load would be absent the undesirable bending force, depending on the direction the panels are caused to bend outside the load zone.
Another problem with Lau et al. concerns the location of the photo switches (
1
)-(
4
) (see
FIG. 1
thereof) which communicate with the microprocessor (
22
) so that the microprocessor knows when to begin and when to end taking and recording loading and temperature readings for a specific panel traveling through the panel tester. Lau et al. disclose that a composite panel (
10
) moves in an “S” shaped path through the tester. The first deflector roll (
14
) is positioned midway between a first pair of spaced positioning rolls (
13
) each of which cooperates with its respective reaction roll (
50
) to clamp the panel (
10
) therebetween, all of which function to bend the panel in a first direction in the first curved portion of the “S” shaped path. The second deflection roll (
16
) is positioned substantially midway between a second pair of positioning rolls (
13
) each of which cooperates with its respective reaction roll (
60
) to clamp the panel (
10
) therebetween, all of which function to bend the panel in a second dire
Janisch Justin M.
Starostovic Edward J.
Michael & Best & Friedrich LLP
Reynolds, II Thomas S.
Shah Kamini
Timberco, Inc.
Welch Teresa J.
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