This invention pertains generally to what is known in the wood products industry as the secondary breakdown of logs or lumber, and more specifically, to a lumber workpiece charger system that offers significantly improved feeding and handling of workpieces to an edger.
In the wood products field, market conditions in recent years have riveted attention on the need for increasingly precise processing control to maximize yield and to minimize waste. In addition, the same market conditions have focused concern on increasing the speed with which usable output can occur.
One area in which precision processing advances have certainly been seen in recent years is in the area of so-called edging of flitches, cants or boards preparatory to the making, for example, of dimensioned lumber. The edging process generally falls within what is referred to above as secondary breakdown activity.
In the past, there has been a somewhat unhappy mutual exclusivity between speed of handling in the edging process and precision in maximizing yield. For example, it is typical that, say, a board which is to be edged is transported laterally (normal to its longitudinal axis) beneath a scanning system which takes a look at the board's outline, taking into account wane where such exists, with scanning data then produced and used, as by a computer system, to determine how the edges of this board should be trimmed for maximum ultimate yield. A trimming decision might, for example, involve taking more wood off one long edge than off the other of the board, might require that the board be slightly angulated before feeding through an edger, as well as other things.
The so-called trimming decision regarding edging is realized in a variety of conventional pre-positioning or cuing devices, such as adjustable pins which rise into the travel path of a board to define what might be thought of as the proper "leading edge" orientation that should be used in shifting the board into the feed-intake station in an edger.
Maintenance of proper position, from this point forward, requires careful positive handling of the board as the same as transported from its pre-positioned and angularly cued condition into the intake station of an edger, all to assure that when the board is "taken" by the edger, it will be guided along the edger's working axis with the proper predetermined angular and lateral orientation. However, equipment available in the past capable of accomplishing appropriate precision handling is relatively slow in operation. For example, prior art equipment is typically capable of handling successive work pieces at a rate approximating about 25- to about 30-pieces-per-minute under circumstances producing relatively gentle, non-damaging handling.
Equipment offering high-speed transfer of a board from a pre-positioned cued condition to a handed-off condition to an edger typically has involved fairly violent jolting action which often offsets precision through failure to maintain proper board orientation.
A general object of the present invention is to provide an improved edger charger system which offers the best of both worlds and the worst of neither. More specifically, an edger charger system is proposed herein which is capable of high-speed, anti-jolting, highly-precise handling of a board, or like workpiece, as the same is moved from a pre-positioned laterally and angularly cued condition toward ultimate hand-off for processing by an edger.
According to a preferred embodiment of the invention, the proposed charger system includes a precharge station which is laterally offset from the intake station of an associated charger, which precharge station is adapted for receiving and holding, in succession, workpieces which are, based upon prescanning data, laterally and angularly cued for proper transport through the edger. The system further includes a positive-action pinch-roll mechanism which facially grips opposite faces of a workpiece held in the precharge station. This pinch-roll mechanism, moved under the influence of a computer-controlled, hydraulic, linear positioner, shuttles a gripped workpiece rapidly (i.e., with rapid acceleration, high speed, and rapid deceleration) to the intake station in the charger. This movement is accomplished without jolting, and as a consequence with little likelihood for disorientation of the properly pre-cued board.
While the pinch-roll mechanism of the charger system continues to grip the board in the intake station, the usual clamp-roll mechanism in the edger closes upon the board, gripping the same, thus receiving a hand-off of the board before release of the latter by the charger's pinch-roll mechanism.
Again under the influence of the linear positioner, the pinch-roll mechanism is return-shuttled to the precharge station for similar handling of the next successive workpiece.
Positive-action gripping of a workpiece from a pre-cued condition through gripped hand-off to an edger strongly promotes precision handling performance. Transfer motion produced under the influence of a computer-controlled hydraulic linear positioner enables rapid, anti-jolting handling, and thus adds significant handling speed without jeopardizing precision positioning.
These and other advantages which are offered by the system of the present invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.