In processing a log for producing lumber, it is common to clamp the log on or in a saw carriage or overhead conveyor so that the log length is aligned with a saw or saw array. The carriage or conveyor then conveys the log in one or more passes through the saw to cut the log into flitches or slabs, and generally a center cant of desired dimensions. There are a number of variations to the process and a number of different apparatus that make up the various components, at least in part dictated by the size of the log being processed and the type of lumber being produced.
A major concern of the lumber producing process in general is that the process maximize utilization of the log. It has long been recognized that small angular shifting of the log axis relative to the saw's cutting line can dramatically impact this utilization. (Hereafter this angular positioning of the log axis is referred to as skew positioning to differentiate it from rotative positioning of the log to be described hereafter.)
To achieve the desired skew positioning, it has been common to measure the lateral dimension of the log at spaced positions along the log length. This enables the development of a model of the log for computer analysis. A computer computes the potential lumber production from the log at various skew positions within the log model and selects a preferred skew position for the log. Positioning apparatus then repositions the log axis to achieve the desired skew position. Such repositioning apparatus may be a part of the carriage mechanism or it may be a separate apparatus that repositions the log prior to the log being clamped, e.g. in the overhead conveyor. A process and apparatus for skew positioning of a log for lumber processing is disclosed in U.S. Pat. No. 3,786,968 issued to Mason, et al on June 5, 1973.
Whereas establishing a preferred skew position for a log is unquestionably beneficial to log utilization, it has been determined that log utilization can be further improved by establishing a preferred rotative position for the log. It is believed that no one, prior to this invention, has suggested the benefits of analyzing a log for rotative positioning or provided the method or means for accomplishing a desired rotative positioning of the log.