After leaving the dry kilns, the loaded car is transferred to the unstacker (see [Fig. 47]). Here it is placed on the unstacker car which, by means of a tension device, holds the load of lumber tight against the vertical frame of the unstacker. The frame of the unstacker is triangular and has a series of chains. Each chain has two special links with projecting lugs. The chains all travel in unison. The lug links engage a layer of boards, sliding the entire layer vertically, and the boards, one at a time, fall over the top of the unstacker frame onto the inclined table, and from there onto conveyor chains from which they may be delivered to any point desired, depending upon the length and direction of the chain conveyor.
With these unstackers one man can easily unload a kiln car in twenty minutes or less.
Fig. 47. The Lumber Unstacker Car, used for unloading cars of Lumber loaded by the Automatic Stacker.
Fig. 48. The Lumber Unstacker Car and Unstacker, used for unloading Lumber loaded by the Automatic Stacker.
The experience of many users prove that these edge stacking machines are not alike. This is important, because there is one feature of edge stacking that must not be overlooked. Unless each layer of boards is forced into place by power and held under a strong pressure, much slack will accumulate in an entire load, and the subsequent handling of the kiln cars, and the effect of the kiln-drying will loosen up the load until there is a tendency for the layers to telescope. And unless the boards are held in place rigidly and with strong pressure they will have a tendency to warp.