The greatest difficulty formerly experienced in the paper manufacture upon the continuous system of Fourdrinier, was to remove the moisture from the pulp, and condense it with sufficient rapidity, so as to prevent its becoming what is called water-galled, and to permit the web to proceed directly to the drying cylinders. Hitherto no invention has answered so well in practice to remove this difficulty as the channelled and perforated pulp rollers or dandies of Mr. John Wilks, the ingenious partner of Mr. Donkin; for which a patent was obtained in 1830. Suppose one of these rollers (see L, in [fig. 788.], and M, M, in [fig. 793.],) is required for a machine which is to make paper 54 inches wide, it must be about 60 inches long, so that its extremities (see [figs. 789.] and [790.]) may extend over or beyond each edge of the sheet of paper upon which it is laid. Its diameter may be 7 inches. About 8 grooves, each 1-16th of an inch wide, are made in every inch of the tube; and they are cut to half the thickness of the copper, with a rectangularly shaped tool. A succession of ribs and grooves are thus formed throughout the whole length of the tube. A similar succession is then made across the former, but of 24 in the inch, and on the opposite surface of the metal, which by a peculiar mode of management had been prepared for that purpose. As the latter grooves are cut as deep as the former, those on the inside meet those on the outside, crossing each other at right angles, and thereby producing so many square holes; leaving a series of straight copper ribs on the interior surface of the said tube, traversed by another series of ribs coiled round them on the outside, forming a cylindrical sieve made of one piece of metal. The rough edges of all the ribs must be rounded off with a smooth file into a semicircular form. [Figs. 789.] and [790.], A A, are portions of the ribbed copper tube. [Fig. 789.] shows the exterior, and [fig. 790.] the interior surface; b, b and b, b show the plain part at each of the ends, where it is made fast to the brass rings by rivets or screws; C, C are the rings with arms, and a centre piece in each, for fixing the iron pivot or shaft B; one such pivot is fixed by riveting it in each of the centre pieces of the rings, as shown at c, [fig. 790.]; so that both the said pieces shall be concentric with the rings, and have one common axis with each other, and with the roller. At a, a, a groove is turned in each of the pivots, for the purpose of suspending a weight by a hook, in order to increase the pressure upon the paper, whenever it may be found necessary.
[Fig. 791.] is an end view, showing the copper tube and its internal ribs A, A; the brass rings C, C; arm D, D, D; centre piece E, and pivot B. [Fig. 792.] is a section of the said ring, with the arms, &c.
The roller is shown at L, [fig. 788.], as lying upon the surface of the wire-web. The relative position of that perforated roller, and the little roller b, over which it lies, is such that the axis of L is a little to one side of the axis of b, and not in the same vertical plane, the latter being about an inch nearer the vat end. Hence, whenever the wire-web is set in progressive motion, it will cause the roller L to revolve upon its surface; and as the paper is progressively made, it will pass onwards with the web under the surface of the roller. Thus the pulpy layer of paper is condensed by compression under the ribbed roller; while it transmits its moisture through the perforations, it becomes sufficiently compact to endure the action of the wet press rollers H, H, and also acquires the appearance of parallel lines, as if made by hand in a laid mould.
Mr. Wilks occasionally employs a second perforated roller in the same paper machine, which is then placed at the dotted lines i, i, i.
The patentee has described in the same specification a most ingenious modification of the said roller, by which he can exhaust the air from a hollowed portion of its periphery, and cause the paper in its passage over the roller to undergo the sucking operation of the partial void, so as to be remarkably condensed; but he has not been called upon to apply this second invention, in consequence of the perfect success which he has experienced in the working of the first.
The following is a more detailed illustration of Mr. Wilks’ improved roller.