University of California

Other

Frank Carroll Beall

Richard Len Lemaster

Jacek Marek Biernacki

Li-Heng Chen

Disclosed are an apparatus and a monitoring system and various methods for use in the drying of lumber that use disclosed apparatus. During drying lumber is arranged in multiple courses stacked one on top of the other with multiple wooden stickers substantially evenly spaced from each other between courses and extending across the full width of said stack. The present invention includes a special sticker for inclusion in place of one of the wooden stickers to monitor the AE from the stack and to ultrasonically excite the stack for other measurements. The special sticker in the simplest form, includes a body portion and an acoustic sensor with the body portion constructed of an acoustically conductive material that is sized similarly to a wooden sticker. Also disclosed is a monitoring system which includes a special sticker and signal processing and control electronics coupled to receive an AE signal from the special sticker for monitoring and controlling the drying cycle of the lumber. Additionally, an ultrasonic signal can be applied to the special sticker to excite the stack and then monitor the stack response from the special sticker. By inclusion of an acoustic sensor at both ends of a special sticker the point across the load at which the AE occurs can be determined by linear interplation of the signals received from both sensors. By applying an ultrasonic signal to a special sticker and comparing a response signal received from the special sticker, various characteristics and control features can be obtained to predict the end-point of the drying cycle, the contact integrity of the special sticker with the lumber, and the moisture content of the lumber.

Special sticker and procedure for detecting acoustic emission (AE) or ultrasonic transmission during drying of lumber

The technology used in the present invention is acousto-ultrasonics (AU), in which a transmitted signal, at a controlled frequency is injected into a specimen with one transducer and received at another location by another transducer, permitting evaluation of the condition of the material in the signal path. In the experiments that were made using the present invention, the material within the press was a particleboard mat having the signal injected into the edge of one platen and received at the edge of the second platen. The AU signal received at the second platen is initially in response to pressure changes in the mat and subsequently follows the progression of internal bonding of the material. Since the propagated wave through the mat reacts to resin curing during the last phase of pressing, changes in material or press variables are reflected directly in shifts of the curve received at the second platen. By monitoring the AU response curve, the press can be manually or automatically controlled to open within a specific range of board properties, such as IB. Not only does the technology of the present invention permit the shortest possible press cycle, it also permits control over the desired internal bond of the boards. The technology can be used in many types of presses and can serve as a supervisory system for press performance to determine if any openings are degrading in heat transfer. Additionally, shifts in the AU response curve can alert the press operator to both trends and abrupt changes as they occur.

Ultrasonic monitoring of resin curing in a press for the production of

A method and apparatus for detecting internal bio-deterioration in round wood used in various applications (e.g. utility poles, pier pilings, round wood beams, posts and poles in structures, and living trees). The method includes the steps of securing a pulsing transducer adjacent one point on the surface of the round wood and securing a receiving transducer substantially diametrically opposite to the pulsing transducer. The pulsing transducer transmits ultrasonic signals through the round wood, which propagate through possibly deteriorated areas within the round wood. The receiving transducer receives the propagating ultrasonic signals, and a plurality of acousto-ultrasonic parameters contained in the received ultrasonic signals are processed and analyzed. The processing step includes the step of storing the averaged signals, and processing the stored signals on a real time basis to determine the acousto-ultrasonic parameters in the time and frequency domains. Optionally, the averaged signals are windowed and then stored before the AU parameters are processed and analyzed. The processing step further includes the step of generating at least one fixed frequency to cause the pulsing transducer to resonate and to inject ultrasonic signals at fixed frequencies. The pulsing and receiving transducers are secured to the round wood with a variety of coupling apparatus.

Growing community of inventors

El Sobrante, CA, United States of America

Frank Carroll Beall