Mr. Davy states that it has been found that the parallel sides of a cylinder are not adapted for the smooth extension of a skin upon them; and that the consequence of compressing it between such surfaces is to form little wrinkles, which the straight knife cuts through, and thereby produces holes. To obviate this defect, and also that of the ridges produced by the reciprocating action of the knife, a variety of machines has been projected, in which the cutters partook of a rotatory motion; but the mechanical difficulties attending the application of the principle have led to their abandonment. Mr Duxbury has, however, by a novel position of the cutters, and a peculiar form of the bed over which the skin is laid, overcome all those difficulties, and the skins are cut by one continuous smooth slice over the whole surface. The machine, as shown in the subjoined engravings, Figs. 1 and 2, essentially consist of a great vertical wheel A, 17 feet in diameter, composed of wood, strengthened by iron arms; the axle of which turns in plummer blocks, upon a strong framing II. Onthe periphery of this wheel are fixed twenty-five thin plates of steel, ground to a fine edge, and so closely fitted as to form a complete circular knife, projecting a short distance horizontally from the side of the wheel.
The skin to be split passes over the drum E, which instead of being straight sided longitudinally, has a curved concavity of the same radius as the curve described by the revolving knives, or continued circular knife before mentioned; his drum is made of wood externally, fitted upon an iron frame, and turned to the true curve. A slit is cut longitudinally on the surface of the drum, wherein the edges of the skin are secured; and the skin is kept distended during the operation by means of a cast-iron frame F, called by the patentee the governor, and shown in the following figure (3), on a larger scale. The ends slide in guides in the upright posts of the framing, to which it may be adjusted and fixed; and it is provided at K with a lever and chain for raising or lowering it from its position, as may be required. The skin as it is split passes through the opening H, and thence on to the roller G, whereon it is wound. Motion is given to the machine by a band passing round the pulley B, which actuates the pulley C on the same axis; and this, by means of an endless band, turns the pulley D; on the axis of the latter is an endless screw M, which turns the wheel L on the axis of the drum; thus motion is communicated to the whole.
In splitting small skins, several drums, such as that described, are arranged under the lower side of the great cutting wheel. The patentee also employs occasionally Fig. 3 a "governor" of a different kind, to compensate any irregularity that there may be in the surface of the drum; it consists, as shown in the annexed figure (4), of a series of pieces of metal hanging loosely on a bar, so that they may, simply by their gravity, press with a uniform force upon an irregular surface.