It is preferred to having the cutting edge on the slitting arms straight for convenience of manufacture of the carbide inserts 64, and to have each cutting edge 62 on a straight line passing through the swing axis 80 of the respective slitting arm. The other end of each cylinder is vented. It is preferred to provide the hub 24b with a gusset plate 59 braced by a flange 60 Tea Bag Packing Machine to resist flexing of the slitting arm in the outfeed direction. 6A-6C wherein progressively larger logs are shown each being advanced 12 inches, for example, during each rotation of the ring. Also, although conversion of a Nicholson A5A debarker to a bark splitting machine has been used as an example, it will be appreciated that other ring-type debarkers can be readily converted, as for example, those disclosed in U. This is illustrated in FIGS. Each insert holder 64 is secured by a pair of cap screws 66 to the slitting arm and has a sloped face 64a facing toward the incoming logs. This outward force is countered by pressurizing the air cylinders 32 so that their piston rods 34 extend and swing the levers 38 such as to rotate the pivot shafts 25 in the direction swinging the slitting arms inwardly toward the center of the rings 20, 22. This bumper limits inward swing of the respective slitter arm to a set distance from the center axis of the rings 20, 22, as for example, a distance of 1. This face has an outer recess in which a sharpened carbide is mounted. The swing arm 24 is given a rearward sweep for the cutting edge of 13 degrees for purposes of example. The forks 38a, 38b are joined by Shrinking Machine a stop element 42 arranged to engage a bumper 44 which is mounted on a stationary flange 45 fixed to the outer ring., may be modified by substituting the slitting arms of the present invention, The slitting arm units 24 are swing mounted on pivot shafts 25 mounted by a pair of central sealed bearings 26-27 on the outer ring 20. 6B. The fork 38b at the outfeed side is connected to the pivot pin 36 by a bolt 40 passing through the pivot pin 36 and through ring 41 projecting from the outfeed side of the fork 38b.

As indicated by slitting arm 124 in FIGS.

Basic to the present invention is providing each slitting arm 24a with a rearwardly sweeping cutting portion which is bent at 61 adjacent the gusset 60 in the rearward direction toward the outfeed side of the ring.

From the foregoing it will be slitting machine appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention.

Preferably the rings 20, 22 provide therebetween an annular air plenum 28 having a compressed air supply whose pressure is operator controlled by valves at a control station. 3,190,327 and 4,566,371. Preferably a stainless steel rod 68 is welded in position on the slitting arm to extend from the carbide inserts 63 past the bend 61 in the slitting arm and is sharpened to an edge 68a facing the incoming logs. 8A-8C. 8A-8C, the slitting arms may be articulated so that the outer part 124a of the arms containing the cutting slitting machine edge is free to swing about a hinge axis 126 relative to the hub portion 124b of the slitting arm 124.

The split hub 38c of each lever 38 is clamped by bolts 46 on the outfeed end of a respective pivot shaft 25. This edge assists in giving the swing arm a self-opening characteristic when a log of relatively large diameter is being processed. 9, by lines 62a and 62b, the cutting edge can also be made convex or concave, respectively. Stops 128-129 are provided at the hinge axis 126 to limit swinging movement of the outer slitting part 124a of the arms. The air plenum is connected by air lines 30 to one end of cylinders 32 which are pivotally mounted at that end to the outer ring at 33. Nos. A piston rod 34 extends from the vented end of each cylinder 32 and is journaled on a respective pivot pin 36 between the forks 38a-38b of a forked lever 38 having a split hub 38c at its other end. The central bearings 26-27 on this shaft are mounted in a boss 48 projecting in the outfeed direction from a mounting plate 50 bolted at 51 to the outer ring 20.
In accordance with the present invention a commercially available ring-type debarker, such for example, as a Nicholson A5A debarker with an air seal ring manufactured by the Nicholson Manufacturing Company, Seattle, Wash. When in operation the articulated slitting arms 124 tend to articulate to a bend angle at the articulation 126 which is equal to the lead angle of the helical slit generated for the log being processed. 6A, when a small log 6 inches in diameter is passing through the ring the lead angle increases to 32 degrees. The hub 24b is split and is keyed at 56 to the shaft.

When the slitting machine is in operation the slitting arm units 24 are initially positioned in front of the oncoming log to be processed by adjusting at the control station the air pressure in the air plenum 28 between the rings 20,22 while the outer ring 20 is driven at a preselected rotational speed. Accordingly, the invention is not limited except as by the appended claims. The slitting arm 24a is secured by bolts 53 and a dowel 54 to the hub. FIG. The pressure in the plenum 28 connected to the air cylinders 32 by the lines 30 is selected to provide an inward cutting force on the slitting arms adequate to force the cutting edges 62 through the bark of the log being processed, and still not sufficient to prevent self-opening of the arms or objectionable scoring of the wood beneath the bark.

Centrifugal force urges each swing arm 24a to swing outwardly responsive to rotation of the outer ring 20.

. For a given log advancing speed and ring rotational speed, the lead angle increases as log diameter decreases. As shown in FIG. If the cutting edge is concave, the radius of curvature of the concave edge 62b should be at least as great as the radius of the largest log to be processed. Pat. 6A-6C, respectively, and the corresponding slitting position of the slitting arms. This is slitting machine illustrated in FIGS. This corresponds to the lead angle of the helical path of the cutting edge of each swing arm as an intermediate sized log 16 inches in diameter passes through the ring as indicated in FIG. The forward end of the advancing log strikes the arms and the resulting impact forces cause the slitting arms to self-open until the cutting edge 62 of each arm reaches the bark, whereupon the cutting edge slits the bark in a helical path having a lead angle determined by the lineal speed of the advancing log, the rotational speed of the outer ring and the diameter of the log. FIGS.

Ideally the bend in the swing arms is selected to have an angle corresponding to the lead angle of the helical slit being cut into the log. Since this lead angle varies with log diameter, for a given log feed speed and ring rotational speed, it is preferred to select a lead angle corresponding to the lead angle for the helical cut on a log having a lead angle approximating the lead angle for the diameter of the average sized log being processed.5 inches. A cutting edge 62 is provided on the cutting portion of each slitting arm, preferably by carbide inserts 63 mounted in holders 64 seated end on end in a recess 65 formed in the arm 24a. 7A-7C show an end view of the oncoming logs shown in FIGS.S. Bolts 58 clamp the hub 24b in position on the shaft 25. However, as indicated in FIG. 6C illustrates passage of a relatively large log which is 32 inches in diameter giving a lead angle of 7 degrees. Each pivot shaft 25 projects at the infeed side of the machine to receive the hub of a respective slitting arm unit 24 comprising a slitting arm 24a and a hub 24b