Not applicable.
Not applicable.
The present invention relates to conveyors in general and to conveyors for moving logs in particular.
Oriented chips or wafers of wood are used to construct oriented strandboard which has several structural and cost advantages over plywood. The strandboard is a truly modern composite material where the orientation of wood fibers in the wafers making up the board can be engineered to give the board desired properties of stiffness and strength. As compared to plywood, strandboard is more efficient at utilizing all the wood fiber present in relatively small diameter logs, and thus is lower cost them plywood. Moreover, strandboard is without the voids typically present in lower grades of plywood. Strandboard is manufactured from wood wafers cut by a flaker from debarked logs. The debarked logs are advanced along the long axes of the logs approximately 30 inches into the flaker. The logs are held fixed while the blades of the flaker, which extend parallel to the axes of the logs, are caused to rotate about a line parallel to the axis of the logs but displaced from the logs, to thereby reduce a 30-inch portion of the logs to wafers. The wafers are thin veneer-like wood chips or flakes which are used to form the oriented strandboard. Existing feed mechanisms between a debarker, in which the bark is removed from the logs, and the flaker typically employ two separate chain conveyors which operate by indexing the logs forward than pausing while the flaker makes its cutting stroke and then retracts.
Chain drives, while widely used for conveying logs, have several disadvantages, particularly where used to feed a flaker. Maintenance costs are higher than is desirable, as the weight and force with which logs can impact the drive systems results in the expenses of down time for repairs. Further, the cycle of advancing, pausing while the flaker makes its cutting stroke, and advancing again is less than ideally suited to the chain drive with the result that energy costs are higher than necessary.
What is needed is a conveying system of greater reliability, lower cost, and greater efficiency for feeding logs between a debarker and a flaker
The conveyor system of this invention extends between a log debarker and a flaker. The conveyor has five plates that are arranged within a conveying trough. The plates are continuous and extend the length of the conveyor. Three plates line the bottom of the conveyor trough and are supported on rollers, and two plates are positioned vertically on either side of the trough bottom to form approximately the lower half of the trough sides. The vertical plates forming the sides rest within C-channels lined with ultra high molecular weight plastic. Each of the five plates is driven with a hydraulic piston. In operation, all five plates together move forward approximately 30 inches at a constant velocity, and then each plate is retracted separately. The motion of the plates is such that the static coefficient of friction holds the logs against the plates during the forward stroke, but the dynamic coefficient of friction, which is lower than the static coefficient of friction, allows the plates to slide with respect to the logs resting thereon. The effect is a stepwise advance of the logs from the inlet to the outlet of the conveyor. Also, because the logs typically are held in contact with other logs when a single plate is retracted, the logs resting on or against the plate are held from reverse motion by the other logs which are engaged with the non moving plates. Because the plates are moved by simple hydraulic pistons which are ideally suited for discontinuous motion, energy usage as compared to a chain drive conveyor is reduced and the required drive power is substantially reduced to approximately 40 percent, of the installed horsepower of a comparable chain drive conveyor. The stroke and timing of the piston movements are easily controlled by a hydraulic control system which, for optimum reconfiguration, may be controlled by a programmable logic controller, or may use simple cam driven timing mechanisms.
It is an feature of the present invention to provide a conveying system between a log debarker and a flaker which is more reliable and of lower cost.
It is a further feature of the present invention to provide a conveying system between a log debarker and a flaker which has lower operating costs, and lower energy usage.
It is another feature of the present invention to provide a conveying system optimized for moving logs between a debarker and a flaker.
Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.