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A Text-book of Paper-making cover

A Text-book of Paper-making

Chapter 88: Sorting.
By C. F. Cross
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About This Book

This work provides a comprehensive examination of the principles and processes involved in paper-making, emphasizing the scientific understanding necessary for effective practice. It covers the chemical properties of cellulose, the physical structure of fibers, and the analysis of plant substances, detailing methods for isolating cellulose from various raw materials. The text discusses specialized treatments for different fibers, bleaching, and the mechanical processes involved in paper production. Additionally, it addresses the testing and quality control of paper, along with considerations for site selection and water purification in paper mills. The authors aim to enhance the reader's grasp of the scientific foundations essential for modern paper-making.

FIG. 63.
FIG. 64.

Single-sheet Cutter.

—It is sometimes necessary, as in the case of paper having a water-mark, that the sheet should be cut with great exactness, so that the device shall come exactly in the centre. The ordinary cutter cannot be relied on for this purpose, and, in its place, a machine called a “single-sheet cutter” is used (Fig. 65). It consists essentially of a large wooden drum A, fixed on a horizontal axis, over which the paper is led by a pair of drawing-in rolls B. The paper is held against the drum by a clamp worked by the arm C. The paper is cut by the knife E moving against the stationary knife D. After the cut, the drum describes part of a circle, the paper being still held, so that it cannot go back with the drum. As soon as it has gone far enough, the clamp is removed, and the drum returns, bringing the paper with it. The length of the arc through which the drum moves, and therefore the size of sheet, is regulated by the length of the crank-arm F. If from any cause the cut should not take {174} place at the right time, the man in charge can, by pressing against the clamp, retard the motion of the paper, and thus bring back the cut to the right place. The small roller G is for the purpose of keeping the paper always tight.
FIG. 65.

Guillotine Cutter.

—It is sometimes necessary to trim the edges of sheets of paper or to divide them into smaller sheets. This is done by means of a guillotine cutter, an improved form of which, as manufactured by Salmon of Manchester, and called the “Victory” cutter, is shown in Fig. 66.

The paper to be cut is placed on the table F, touching the back gauge G, which can be brought backwards or forwards by means of the handle H, thus regulating the size of sheet.

The machine is set in motion by means of the lever A, which acts upon a friction-clutch connected with the driving-gear. This causes the knife-bar B and the clamp C to descend. {175} When the latter meets the paper its progress is arrested. The knife D, however, continues to descend, and passes through the sheets of paper. By means of slots placed at the back, the knife is made to take a diagonal course. The pressure of the clamp is maintained upon the paper during the cutting operation by means of a powerful spring contained in the tube E.

FIG. 66.

Sorting.

—The sheets of paper are now ready to be examined before being finally sent away from the mill. This is done in the “Finishing-house,” or “Salle” as it is sometimes called. This sorting is usually performed by women, who reject the inferior or damaged sheets. These are sold at a reduced price under the name of “retree.”

Paper is sold in sheets of definite sizes, and is made up into reams containing from 480 to 516 sheets. These sizes {176} correspond to different trade names—such, for example, as crown, demy, royal, imperial, &c. The weight per ream is usually expressed in addition to the name, thus: 14-lb. demy, 18-lb. double crown, &c. In this way the consumer is enabled to make a rough comparison of the thickness of the different kinds of paper.

In making paper it is the duty of the machineman to examine and weigh from time to time a sheet of the desired size, in order to ensure uniformity. Special lever balances can be obtained, showing at a glance the weight per ream of different numbers of sheets.