Patent GB-1492958-A (GB)
Title: Chipping apparatus
IPC: B27L11/02
Filed: 1974-11-29
Abstract: 1492958 Wood chip producing apparatus BLACK CLAWSON CO 29 Nov 1974 [30 Nov 1973] 51905/74 Heading B5L In an apparatus for producing wood chip from charges of oversize chips, waste wood or whole logs, for use in the pulp and paper industry, comprising a rotor provided with knife means and an anvil across which a charge is fed to the rotor so as to be cut into chips by the knife means, the latter comprises a plurality of sets of pairs of cutting edges equi-spaced about the rotor axis with each set effectively forming a knife profile stepped in a plane including the rotor axis, the anvil has a stepped profile substantially complementary to that of the knife profile, and the sets of cutting edges are respectively mounted on the leading edges of contiguous rotor segments presenting chip passage openings at their trailing edges and each being formed with a set of substantially spirally disposed arcuate knife back-up lands forming, with connecting surfaces, a stepped profile conforming with the knife profile, the lands having their maximum and minimum radii adjacent the cutting edges and the chip passage openings respectively, and the arrangement being such that during rotation of the rotor the rotor/anvil gaps adjacent the substantially spirally disposed lands gradually increase from a small dimension behind the cutting edges to a larger, chip size determining, dimension in front of said cutting edges. Thus, by use of the apparatus, the wood chips of acceptable length and width are produced, there is a reduction in tendency for charge pieces to upend since the anvil edge is not straight, and the substantially spiral rotor land configuration dissipates suction tending to draw in oversize sticks and splinters. As shown, a rotor 13 is journalled in a housing 12 defining a charge feeding shoot 19 having a bottom formed by an anvil 20. Chip discharge is by a horizontal tangential shoot (23, Fig. 1, not shown) or, as shown, upwardly converging shoots 21. The rotor 13 comprises two substantially frusto-conical assemblies secured together and each comprising three segments 30, 31 supporting sets of cutting blades 50 at their leading edges, having chip passage openings 33 at their trailing edges, and formed with substantially spirally disposed knife back-up lands 40a-40f and connecting surfaces 42a- 42e conforming with blade cutting edges 53, 54. The segments support fan blades 27 for propulsion of chips through the discharge shoots. Each blade 50 is of V-section and is clamped to its segment by way of a bolt 56 and clamp member 65, a bolt slot 55 in the blade providing for adjustment. Blade setting in the motor is effected using a gauge 111 comprising a stepped plate which is held by a bolt 112 on a housing bracket 110 so as to be radially disposed with respect to the rotor, and is removed before operation of the apparatus. The blades project slightly, e.g. 1/32 inch, beyond the leading edges of their associated back-up lands. The anvil 20 comprises a base 75 mounted on a housing plate 70 for adjustment tangentially towards and away from the rotor by way of a key and keyway 77, 72, positioning being effected by a bolt and locknut 78, 79. The base 75 carries, in stepped arrangement, wear plates 85 and a filler plate 88. The clearance between blade cutting edges 53, 54 and the anvil wear plates 85 may be, e.g. 0À010-0À027 inch. For handling whole logs, a V-groove centring guide may be provided at the entrance to the shoot 19. The charge may be gravity induced across the anvil by tilting the apparatus. In Fig. 20 (not shown), the rotor is a disc provided with conical lands and connecting surfaces, and the charge is fed in a direction inclined to the rotor axis.