| 摘要 |
<p>A log harvesting system is disclosed in which the log is graded automatically in the field by ultrasonic testing of the log. Pulses of utlrasonic waves are transmitted into the log to detect internal defects within the log by measuring changes in the transient time of the ultrasonic wave pulses through at least a portion of the log. A computer is used to determine the grade of the log and produce a grade output signal from transient time data and signals related to the length and diameter of the log. The log is marked with a different colored paint to indicate its grade by an automatic marking device in response to the receipt of the grade output signal. Ultrasonic testing apparatus may be added to a tree harvesting head with a saw for felling the tree and cutting the log to the proper length and delimber knives for removing limbs, in order to test the log for defects as the log is conveyed through such head. In one embodiment, a pair of ultrasonic transducer wheels are mounted on opposite sides of the log and pairs of transmitting and receiving transducers are selectively coupled to the log through liquid coupling chambers provided on the outer surface of such wheels as the wheels rotate along the length of the log.</p> |
